Daniel H Turnbull, Ph.D.

In utero phenotyping of mouse embryonic vasculature with MRI
Berrios-Otero, Cesar A; Nieman, Brian J; Parasoglou, Prodromos; Turnbull, Daniel H
2012 Jan;67(1):251-257, Magnetic resonance in medicine
The vasculature is the earliest developing organ in mammals and its proper formation is critical for embryonic survival. MRI approaches have been used previously to analyze complex three-dimensional vascular patterns and defects in fixed mouse embryos. Extending vascular imaging to an in utero setting with potential for longitudinal studies would enable dynamic analysis of the vasculature in normal and genetically engineered mouse embryos, in vivo. In this study, we employed an in utero MRI approach that corrects for motion, using a combination of interleaved gated acquisition and serial coregistration of rapidly acquired three-dimensional images. We tested the potential of this method by acquiring and analyzing images from wildtype and Gli2 mutant embryos, demonstrating a number of Gli2 phenotypes in the brain and cerebral vasculature. These results show that in utero MRI can be used for in vivo phenotype analysis of a variety of mutant mouse embryos. Magn Reson Med, 2011. (c) 2011 Wiley-Liss, Inc
— id: 147676, year: 2012, vol: 67, page: 251, stat: Journal Article,

Morphological and functional midbrain phenotypes in Fibroblast Growth Factor 17 mutant mice detected by Mn-enhanced MRI
Yu, Xin; Nieman, Brian J; Sudarov, Anamaria; Szulc, Kamila U; Abdollahian, Davood J; Bhatia, Nitin; Lalwani, Anil K; Joyner, Alexandra L; Turnbull, Daniel H
2011 Jun 1;56(3):1251-1258, Neuroimage
With increasing efforts to develop and utilize mouse models of a variety of neuro-developmental diseases, there is an urgent need for sensitive neuroimaging methods that enable in vivo analysis of subtle alterations in brain anatomy and function in mice. Previous studies have shown that the brains of Fibroblast Growth Factor 17 null mutants (Fgf17(-/-)) have anatomical abnormalities in the inferior colliculus (IC)-the auditory midbrain-and minor foliation defects in the cerebellum. In addition, changes in the expression domains of several cortical patterning genes were detected, without overt changes in forebrain morphology. Recently, it has also been reported that Fgf17(-/-) mutants have abnormal vocalization and social behaviors, phenotypes that could reflect molecular changes in the cortex and/or altered auditory processing / perception in these mice. We used manganese (Mn)-enhanced magnetic resonance imaging (MEMRI) to analyze the anatomical phenotype of Fgf17(-/-) mutants in more detail than achieved previously, detecting changes in IC, cerebellum, olfactory bulb, hypothalamus and frontal cortex. We also used MEMRI to characterize sound-evoked activity patterns, demonstrating a significant reduction of the active IC volume in Fgf17(-/-) mice. Furthermore, tone-specific (16- and 40-kHz) activity patterns in the IC of Fgf17(-/-) mice were observed to be largely overlapping, in contrast to the normal pattern, separated along the dorsal-ventral axis. These results demonstrate that Fgf17 plays important roles in both the anatomical and functional development of the auditory midbrain, and show the utility of MEMRI for in vivo analyses of mutant mice with subtle brain defects
— id: 131957, year: 2011, vol: 56, page: 1251, stat: Journal Article,

The Engrailed homeobox genes determine the different foliation patterns in the vermis and hemispheres of the mammalian cerebellum
Cheng, Yulan; Sudarov, Anamaria; Szulc, Kamila U; Sgaier, Sema K; Stephen, Daniel; Turnbull, Daniel H; Joyner, Alexandra L
2010 Feb;137(3):519-529, Development
Little is known about the genetic pathways and cellular processes responsible for regional differences in cerebellum foliation, which interestingly are accompanied by regionally distinct afferent circuitry. We have identified the Engrailed (En) homeobox genes as being crucial to producing the distinct medial vermis and lateral hemisphere foliation patterns in mammalian cerebella. By producing a series of temporal conditional mutants in En1 and/or En2, we demonstrate that both En genes are required to ensure that folia exclusive to the vermis or hemispheres form in the appropriate mediolateral position. Furthermore, En1/En2 continue to regulate foliation after embryonic day 14, at which time Fgf8 isthmic organizer activity is complete and the major output cells of the cerebellar cortex have been specified. Changes in spatially restricted gene expression occur prior to foliation in mutants, and foliation is altered from the onset and is accompanied by changes in the thickness of the layer of proliferating granule cell precursors. In addition, the positioning and timing of fissure formation are altered. Thus, the En genes represent a new class of genes that are fundamental to patterning cerebellum foliation throughout the mediolateral axis and that act late in development
— id: 112032, year: 2010, vol: 137, page: 519, stat: Journal Article,

In vivo MRI of neural cell migration dynamics in the mouse brain
Nieman, Brian J; Shyu, Jeffrey Y; Rodriguez, Joe J; Garcia, A Denise; Joyner, Alexandra L; Turnbull, Daniel H
2010 Apr 1;50(2):456-464, Neuroimage
Multipotent neuroblasts (NBs) are produced throughout life by neural stem cells in the forebrain subventricular zone (SVZ), and are able to travel long distances to the olfactory bulb. On arrival in the bulb, migrating NBs normally replace olfactory neurons, raising interest in their potential for novel cell replacement therapies in various disease conditions. An understanding of the migratory capabilities of NBs is therefore important, but as yet quantitative in vivo measurement of cell migration has not been possible. In this study, targeted intracerebral injections of iron-oxide particles to the mouse SVZ were used to label resident NBs in situ, and their migration was tracked noninvasively over time with magnetic resonance imaging (MRI). Quantitative intensity metrics were employed to identify labeled cells and to show that cells are able to travel at speeds up to 100 microm/h en route to the olfactory bulb, but that distribution through the olfactory bulb occurs at a much slower rate. In addition, comparison of histological and MRI measures of iron-oxide particle distribution were in excellent agreement. Immunohistochemistry analysis 1-3 weeks after labeling revealed that the majority of labeled cells in the olfactory bulb were immature neurons, although iron-oxide particles were also found in astrocytes and microglia. This work indicates that dynamic measurements of endogenous cell migration can be made with MRI and represents the first in vivo measurement of NB migration rates. The use of MRI in future studies tracking endogenous NB cells will permit a more complete evaluation of their role during homeostasis at various developmental stages and during disease progression
— id: 107770, year: 2010, vol: 50, page: 456, stat: Journal Article,

Ultrasound and magnetic resonance microimaging of mouse development
Nieman, Brian J; Turnbull, Daniel H
2010 ;476:379-400, Methods in enzymology
Ultrasound biomicroscopy (UBM) and magnetic resonance microimaging (micro-MRI) provide noninvasive, high-resolution images in mouse embryos and neonates, enabling volumetric and functional analyses of phenotypes, including longitudinal imaging of individual mice over critical stages of in utero and early-postnatal development. In this chapter, we describe the underlying principles of UBM and micro-MRI, including the advantages and limitations of these approaches for studies of mouse development, and providing a number of examples to illustrate their use. To date, most imaging studies have focused on the developing nervous and cardiovascular systems, which are also reflected in the examples shown in this chapter, but we also discuss the future application of these methods to other organ systems
— id: 112031, year: 2010, vol: 476, page: 379, stat: Journal Article,

Doppler-derived trigger signals for high-frame-rate mouse cardiovascular imaging
Aristizabal, Orlando; Mamou, Jonathan; Turnbull, Daniel H; Ketterling, Jeffrey A
2009 ;1:1987-1990, Conference Proceedings (IEEE Engineering in Medicine & Biology Society)
The availability of an electrocardiogram (ECG) waveform in the adult mouse has permitted the measurement of fast, dynamic cardiac events where data acquisition is synchronized to the R-wave of the ECG waveform. These methods can easily attain one thousand frames/s at ultrasound frequencies greater than 20 MHz. With the heart being the first organ to develop, normal cardiovascular function is crucial to the viability of the developing embryo. Thus, translating such methodologies to analyze embryonic cardiovascular development would add crucial information in mouse models of congenital heart disease which are embryonic lethal. Obtaining an ECG signal from mouse embryos is impractical. Therefore, in this study, preliminary results are presented which derive a cardiac-trigger signal from Doppler blood-flow waveforms. A continuous wave 40 MHz Doppler ultrasound system was used to acquire the Doppler waveforms and a real-time algorithm was developed to process the Doppler waveforms and generate a trigger. Validation studies revealed that a heart rate can be reliably measured and that the Doppler trigger algorithm was robust enough to follow changes in the blood flow. Preliminary data showed that Doppler-derived triggers can be used for highframe-rate prospective imaging of the early embryonic mouse heart
— id: 105672, year: 2009, vol: 1, page: 1987, stat: Journal Article,

Three-dimensional micro-MRI analysis of cerebral artery development in mouse embryos
Berrios-Otero, Cesar A; Wadghiri, Youssef Zaim; Nieman, Brian J; Joyner, Alexandra L; Turnbull, Daniel H
2009 Dec;62(6):1431-1439, Magnetic resonance in medicine
Vascular system development involves a complex, three-dimensional branching process that is critical for normal embryogenesis. In the brain, the arterial systems appear to develop in a stereotyped fashion, but no detailed quantitative analyses of the mouse embryonic cerebral arteries have been described. In this study, a gadolinium-based contrast perfusion method was developed to selectively enhance the cerebral arteries in fixed mouse embryos. Three-dimensional magnetic resonance micro-imaging (micro-MRI) data were acquired simultaneously from multiple embryos staged between 10 and 17 days of gestation, and a variety of image analysis methods was used to extract and analyze the cerebral arterial patterns. The results show that the primary arterial branches in the mouse brain are very similar between individuals, with the patterns established early and growth occurring by extension of the segments, while maintaining the underlying vascular geometry. To investigate the utility of this method for mutant mouse phenotype analysis, contrast-enhanced micro-MRI data were acquired from Gli2(-/-) mutant embryos and their wild-type littermates, showing several previously unreported vascular phenotypes in Gli2(-/-) embryos, including the complete absence of the basilar artery. These results demonstrate that contrast-enhanced micro-MRI provides a powerful tool for analyzing vascular phenotypes in a variety of genetically engineered mice
— id: 105501, year: 2009, vol: 62, page: 1431, stat: Journal Article,

High-frequency chirp ultrasound imaging with an annular array for ophthalmologic and small-animal imaging
Mamou, Jonathan; Aristizabal, Orlando; Silverman, Ronald H; Ketterling, Jeffrey A; Turnbull, Daniel H
2009 Jul;35(7):1198-1208, Ultrasound in medicine & biology
High-frequency ultrasound (HFU, >20 MHz) is an attractive means of obtaining fine-resolution images of biological tissues for ophthalmologic, dermatological and small-animal imaging applications. Even with current improvements in circuit designs and high-frequency equipment, HFU has two inherent limitations. First, HFU images have a limited depth-of-field (DOF) because of the short wavelength and the low fixed F-number of conventional HFU transducers. Second, HFU is usually limited to shallow imaging because of the significant attenuation in most tissues. In a previous study, a five-element annular array with a 17-MHz center frequency was excited using chirp-coded signals, and a synthetic-focusing algorithm was used to extend the DOF and increase penetration depth. In the present study, a similar approach with two different five-element annular arrays operating near a center frequency of 35 MHz is implemented and validated. Following validation studies, the chirp-imaging methods were applied to imaging vitreous-hemorrhage-mimicking phantoms and mouse embryos. Images of the vitreous phantom showed increased sensitivity using the chirp method compared with a standard monocycle imaging method, and blood droplets could be visualized 4mm deeper into the phantom. Three-dimensional datasets of 12.5-day-old mouse embryo heads were acquired in utero using chirp and conventional excitations. Images were formed and brain ventricles were segmented and reconstructed in three dimensions. The brain ventricle volumes for the monocycle excitation exhibited artifacts that were not apparent on the chirp-based dataset reconstruction
— id: 106212, year: 2009, vol: 35, page: 1198, stat: Journal Article,

Three-dimensional, in vivo MRI with self-gating and image coregistration in the mouse
Nieman, Brian J; Szulc, Kamila U; Turnbull, Daniel H
2009 Feb 27;61(5):1148-1157, Magnetic resonance in medicine
Motion during magnetic resonance imaging (MRI) scans routinely results in undesirable image artifact or blurring. Since high-resolution, three-dimensional (3D) imaging of the mouse requires long scan times for satisfactory signal-to-noise ratio (SNR) and image quality, motion-related artifacts are likely over much of the body and limit applications of mouse MRI. In this investigation, we explored the use of self-gated imaging methods and image coregistration for improving image quality in the presence of motion. Self-gated signal results from a modified 3D gradient-echo sequence showed detection of periodic respiratory and cardiac motion in the adult mouse-with excellent comparison to traditional measurements, sensitivity to respiration-induced tissue changes in the brain, and even detection of embryonic cardiac motion in utero. Serial image coregistration with rapidly-acquired, low-SNR volumes further enabled detection and correction of bulk changes in embryo location during in utero imaging sessions and subsequent reconstruction of high-quality images. These methods, in combination, are shown to expand the range of applications for 3D mouse MRI, enabling late-stage embryonic heart imaging and introducing the possibility of longitudinal developmental studies from embryonic stages through adulthood. Magn Reson Med, 2009. (c) 2009 Wiley-Liss, Inc
— id: 95051, year: 2009, vol: 61, page: 1148, stat: Journal Article,

Mn enhancement and respiratory gating for in utero MRI of the embryonic mouse central nervous system
Deans, Abby E; Wadghiri, Youssef Zaim; Berrios-Otero, Cesar A; Turnbull, Daniel H
2008 Jun;59(6):1320-1328, Magnetic resonance in medicine
The mouse is the preferred model organism for genetic studies of mammalian brain development. MRI has potential for in utero studies of mouse brain development, but has been limited previously by challenges of maximizing image resolution and contrast while minimizing artifacts due to physiological motion. Manganese (Mn)-enhanced MRI (MEMRI) studies have demonstrated central nervous system (CNS) contrast enhancement in mice from the earliest postnatal stages. The purpose of this study was to expand MEMRI to in utero studies of the embryonic CNS in combination with respiratory gating to decrease motion artifacts. We investigated MEMRI-facilitated CNS segmentation and three-dimensional (3D) analysis in wild-type mouse embryos from midgestation, and explored effects of Mn on embryonic survival and image contrast. Motivated by observations that MEMRI provided an effective method for visualization and volumetric analysis of embryonic CNS structures, especially in ventral regions, we used MEMRI to examine Nkx2.1 mutant mice that were previously reported to have ventral forebrain defects. Quantitative MEMRI analysis of Nkx2.1 knockout mice demonstrated volumetric changes in septum (SE) and basal ganglia (BG), as well as alterations in hypothalamic structures. This method may provide an effective means for in utero analysis of CNS phenotypes in a variety of mouse mutants
— id: 95052, year: 2008, vol: 59, page: 1320, stat: Journal Article,

A non-toxic ligand for voxel-based MRI analysis of plaques in AD transgenic mice
Sigurdsson, Einar M; Wadghiri, Youssef Z; Mosconi, Lisa; Blind, Jeffrey A; Knudsen, Elin; Asuni, Ayodeji; Scholtzova, Henrieta; Tsui, Wai H; Li, Yongsheng; Sadowski, Martin; Turnbull, Daniel H; de Leon, Mony J; Wisniewski, Thomas
2008 Jun;29(6):836-847, Neurobiology of aging
Amyloid plaques are a characteristic feature in Alzheimer's disease (AD). A novel non-toxic contrast agent is presented, Gd-DTPA-K6Abeta1-30, which is homologous to Abeta, and allows plaque detection in vivo. muMRI was performed on AD model mice and controls prior to and following intracarotid injection with Gd-DTPA-K6Abeta1-30 in mannitol solution, to transiently open the blood-brain barrier. A gradient echo T2(*)-weighted sequence was used to provide 100mum isotropic resolution with imaging times of 115min. The scans were examined with voxel-based analysis (VBA) using statistical parametric mapping, for un-biased quantitative comparison of ligand-injected mice and controls. The results indicate that: (1) Gd-DTPA-K6Abeta1-30 is an effective, non-toxic, ligand for plaque detection when combined with VBA (p</=0.01-0.001), comparing pre and post-ligand injection scans. (2) Large plaques can be detected without the use of a contrast agent and this detection co-localizes with iron deposition. (3) Smaller, earlier plaques require contrast ligand for MRI visualization. Our ligand when combined with VBA may be useful for following therapeutic approaches targeting amyloid in transgenic mouse models
— id: 71031, year: 2008, vol: 29, page: 836, stat: Journal Article,

Statistical mapping of sound-evoked activity in the mouse auditory midbrain using Mn-enhanced MRI
Yu, Xin; Zou, Jing; Babb, James S; Johnson, Glyn; Sanes, Dan H; Turnbull, Daniel H
2008 Jan 1;39(1):223-230, Neuroimage
Manganese-enhanced MRI (MEMRI) has been developed to image brain activity in small animals, including normal and genetically modified mice. Here, we report the use of a MEMRI-based statistical parametric mapping method to analyze sound-evoked activity in the mouse auditory midbrain, the inferior colliculus (IC). Acoustic stimuli with defined frequency and amplitude components were shown to activate and enhance neuronal ensembles in the IC. These IC activity patterns were analyzed quantitatively using voxel-based statistical comparisons between groups of mice with or without sound stimulation. Repetitive 40-kHz pure tone stimulation significantly enhanced ventral IC regions, which was confirmed in the statistical maps showing active regions whose volumes increased in direct proportion to the amplitude of the sound stimuli (65 dB, 77 dB, and 89 dB peak sound pressure level). The peak values of the activity-dependent MEMRI signal enhancement also increased from 7% to 20% for the sound amplitudes employed. These results demonstrate that MEMRI statistical mapping can be used to analyze both the 3D spatial patterns and the magnitude of activity evoked by sound stimuli carrying different energy. This represents a significant advance in the development of MEMRI for quantitative and unbiased analysis of brain function in the deep brain nuclei of mice
— id: 74214, year: 2008, vol: 39, page: 223, stat: Journal Article,

Excitation of polymer-shelled contrast agents with high-frequency ultrasound
Ketterling, Jeffrey A; Mamou, Jonathan; Allen, John S 3rd; Aristizabal, Orlando; Williamson, Rene G; Turnbull, Daniel H
2007 Jan;121(1):EL48-EL53, Journal of the Acoustical Society of America
Few experimental and complementary theoretical studies have investigated high-frequency (>20 MHz) nonlinear responses from polymer-shelled ultrasound contrast agents. Three polymer agents with different shell properties were examined for their single-bubble backscatter when excited with a 40 MHz tone burst. Higher-order harmonic responses were observed for the three agents; however, their occurrence was at least partly due to nonlinear propagation. Only one of the agents (1.1 microm mean diameter) showed a subharmonic response for longer excitations (approximately 10-15 cycles) and midlevel pressure excitations ( 2.5 MPa). Theoretical calculations of the backscattered spectrum revealed behavior similar to the experimental results in specific parameter regimes
— id: 95053, year: 2007, vol: 121, page: EL48, stat: Journal Article,

MRI in mouse developmental biology
Turnbull, Daniel H; Mori, Susumu
2007 May;20(3):265-274, NMR in biomedicine
Mice are used in many studies to determine the role of genetic and molecular factors in mammalian development and human congenital diseases. MRI has emerged as a major method for analyzing mutant and transgenic phenotypes in developing mice, at both embryonic and neonatal stages. Progress in this area is reviewed, with emphasis on the use of MRI to analyze cardiovascular and neural development in mice. Comparisons are made with other imaging technologies, including optical and ultrasound imaging, discussing the potential strengths and weaknesses of MRI and identifying the future challenges for MRI in mouse developmental biology.
— id: 72868, year: 2007, vol: 20, page: 265, stat: Journal Article,

Contrast-enhanced MRI of right ventricular abnormalities in Cx43 mutant mouse embryos
Wadghiri, Youssef Zaim; Schneider, Amanda E; Gray, Emily N; Aristizabal, Orlando; Berrios, Cesar; Turnbull, Daniel H; Gutstein, David E
2007 May;20(3):366-374, NMR in biomedicine
Imaging of the mammalian cardiac right ventricle (RV) is particularly challenging, especially when a two-dimensional method such as conventional histology is used to evaluate the morphology of this asymmetric, crescent-shaped chamber. MRI may improve the characterization of mutants with RV phenotypes by allowing analysis of the samples in any plane and by facilitating three-dimensional image reconstruction. MRI was used to examine the conditional knockout Cx43-PCKO mouse line known to have RV malformations. To help delineate the cardiovascular system and facilitate identification of the right ventricular outflow tract (RVOT), embryonic day (E) 17.5 embryos were perfusion fixed through the umbilical vein followed by a gadolinium-based contrast agent mixed in 7% gelatin. Micro-MRI experiments were performed at 7 T and followed by paraffin embedding of specimens, histological sectioning and hematoxylin and eosin (H&E) staining. Imaging of up to four embryos simultaneously allowed for higher throughput than traditional individual imaging techniques, while intravascular contrast afforded excellent signal-to-noise characteristics. All control embryos (n = 4) and heterozygous Cx43 knockout embryos (n = 4) had normal-appearing right ventricular outflow tract contours by MRI. Obvious abnormalities in the RVOT, including abnormal bulging and infiltration of contrast into the wall of the RV, were seen in three out of four Cx43-PCKO mutants with MRI. Furthermore, three-dimensional reconstruction of MR images with orthogonal projections as well as maximum-intensity projection allowed for visualization of the relationship of infundibular bulging segments to the pulmonary trunk in Cx43-PCKO mutant hearts. The addition of MRI to standard histology in the characterization of RV malformations in mutant mouse embryos aids in the assessment and understanding of morphologic abnormalities. Flexibility in the viewing of MR images, which can be retrospectively sectioned in any desired orientation, is particularly useful in the investigation of the RV, an asymmetric chamber that is difficult to analyze with two-dimensional techniques.
— id: 72869, year: 2007, vol: 20, page: 366, stat: Journal Article,

Large-scale reorganization of the tonotopic map in mouse auditory midbrain revealed by MRI
Yu, Xin; Sanes, Dan H; Aristizabal, Orlando; Wadghiri, Youssef Zaim; Turnbull, Daniel H
2007 Jul 17;104(29):12193-12198, Proceedings of the National Academy of Sciences of the United States of America
The cortex is thought to be the primary site of sensory plasticity, particularly during development. Here, we report that large-scale reorganization of the mouse auditory midbrain tonotopic map is induced by a specific sound-rearing environment consisting of paired low- (16 kHz) and high-frequency (40 kHz) tones. To determine the potential for plasticity in the mouse auditory midbrain, we used manganese-enhanced MRI to analyze the midbrain tonotopic maps of control mice during normal development and mice reared in the two-tone (16 + 40 kHz) environment. We found that the tonotopic map emerged during the third postnatal week in normal mice. Before 3 weeks, a larger percentage of auditory midbrain responded to each of the suprathreshold test frequencies, despite the fact that the primary afferent projections are in place even before hearing onset. By 3 weeks, the midbrain tonotopic map of control mice was established, and manganese-enhanced MRI showed a clear separation between the 16- and 40-kHz responses. Two-tone rearing dramatically altered the appearance of these discrete frequency-specific responses. A significant volume of the auditory midbrain became responsive to both rearing frequencies, resulting in a large-scale reorganization of the tonotopic map. These results indicate that developmental plasticity occurs on a much greater scale than previously appreciated in the mammalian auditory midbrain
— id: 73703, year: 2007, vol: 104, page: 12193, stat: Journal Article,

Analysis of 40 MHz Annular Array Imaging Performance In Mouse Embryos
Aristizabal, O; Turnbull, DH; Ketterling, JA
2006 NOV ;26(9):872-875, Proceedings (IEEE Ultrasonics Symposium)
Current high frequency ultrasound imaging,or ultrasound biomicroscopy (UBM) systems have the capability of imaging mouse embryos with a frame rate of up to 200 frames per second. 3D datasets can also be acquired with the appropriate hardware. Because of the limited depth of field (DOF), effective volumetric analysis is limited to approximately 2 mm about the passive focus for a fixed-focus transducer operating at 40 MHz. This shortcoming imposes a size limit which the current technology can effectively be used to segment out accurate volumetric anatomy of the embryonic mouse. Previously we reported the fabrication a five-element 40-MHz annular array and an array imaging system. Wire phantom measurements with this array reveals an increase in DOF from 1-2 mm (fixed-focus) to more than 10 mm with array focusing. When imaging attenuating media such as mouse embryos, it is expected that the figures of merit for the array images, such as the signal to noise ratio (SNR) and the depth of field (DOF) will be reduce. Images from mouse embryos from at gestational ages 11 (E11.5) and 13 (E13.5) were acquired with this annular array system, and show the superior image definition and quality over the fixed-focus images. Quantitative estimates of the SNR and DOF were calculated, and segmentation of the brain ventricles was accomplished for both gestational ages
— id: 90782, year: 2006, vol: 26, page: 872, stat: Journal Article,

40-MHz annular array imaging of mouse embryos
Aristizabal, Orlando; Ketterling, Jeffrey A; Turnbull, Daniel H
2006 Nov;32(11):1631-1637, Ultrasound in medicine & biology
Ultrasound biomicroscopy (UBM) has emerged as an important in vivo imaging approach for analyzing normal and genetically engineered mouse embryos. Current UBM systems use fixed-focus transducers, which are limited in depth-of-focus. Depending on the gestational age of the embryo, regions-of-interest in the image can extend well beyond the depth-of-focus for a fixed-focus transducer. This shortcoming makes it particularly problematic to analyze 3-D data sets and to generate accurate volumetric renderings of the mouse embryonic anatomy. To address this problem, we have developed a five-element, 40-MHz annular array transducer and a computer-controlled system to acquire and reconstruct fixed- and array-focused images of mouse embryos. Both qualitative and quantitative comparisons showed significant improvement with array-focusing, including an increase of 3 to 9 dB in signal-to-noise ratio and an increase of at least 2.5 mm in depth-of-focus. Volumetric-rendered images of brain ventricles demonstrated the clear superiority of array-focusing for 3-D analysis of mouse embryonic anatomy
— id: 71144, year: 2006, vol: 32, page: 1631, stat: Journal Article,

Cellular MRI contrast via coexpression of transferrin receptor and ferritin
Deans, Abby E; Wadghiri, Youssef Zaim; Bernas, Lisa M; Yu, Xin; Rutt, Brian K; Turnbull, Daniel H
2006 Jul;56(1):51-59, Magnetic resonance in medicine
Recently there has been growing interest in the development and use of iron-based contrast agents for cellular imaging with MRI. In this study we investigated coexpression of the transferrin receptor and ferritin genes to induce cellular contrast in a biological system. Expression of transgenic human transferrin receptor and human ferritin H-subunit was induced in a stably transfected mouse neural stem cell line. When grown in iron-rich medium, the transgenic cells accumulated significantly more iron than control cells, with a trend toward an increase in reactive oxygen species, but no detrimental effects on cell viability. This cellular iron significantly increased the transverse relaxivities, R2 and R2*, at 1.5 T and 7 T. By comparing measurements in the same cell samples at 1.5 T and 7 T, we confirmed the expected increase in relaxivity with increasing field strength. Finally, supplemented transgenic cells transplanted into mouse brain demonstrated increased contrast with surrounding neural tissue on T2*-weighted MR brain images compared to controls. These results indicate that dual expression of proteins at different critical points in the iron metabolism pathway may improve cellular contrast without compromising cell viability
— id: 69238, year: 2006, vol: 56, page: 51, stat: Journal Article,

High-frequency piezopolymer transducers with a copper-clad polyimide backing layer
Ketterling, Jeffrey A; Aristizabal, Orlando; Turnbull, Daniel H
2006 Jul;53(7):1376-1380, IEEE transactions on ultrasonics, ferroelectrics, & frequency control
The effect of a copper-clad polyimide (CCP) backing layer on piezopolymer transducer performance is evaluated. High-frequency, spherically curved polyvinylidene fluoride (PVDF) transducers with and without a CCP backing layer are electrically and acoustically tested. The results showed very similar operating characteristics. B-mode in vivo images of a mouse embryo also showed no qualitative differences, indicating that the CCP backing layer does not affect transducer performance
— id: 95054, year: 2006, vol: 53, page: 1376, stat: Journal Article,

Reduced Ptc or Gli3 function enhances tumorigenicity of Shh-induced medulloblastomas in mice
Weiner, HL; Pompeiano, M; Mohan, A; Bakst, R; Piedimonte, L; Stephen, D; Babb, JS; Zagzag, D; Turnbull, DH; Joyner, AL
2006 OCT ;8(4):470-470, Neuro-oncology
— id: 70328, year: 2006, vol: 8, page: 470, stat: Journal Article,

Design and fabrication of a 40-MHz annular array transducer
Ketterling, Jeffrey A; Aristizabal, Orlando; Turnbull, Daniel H; Lizzi, Frederic L
2005 Apr;52(4):672-681, IEEE transactions on ultrasonics, ferroelectrics, & frequency control
This paper investigates the feasibility of fabricating a five-ring, focused annular array transducer operating at 40 MHz. The active piezoelectric material of the transducer was a 9-microm thick polyvinylidene fluoride (PVDF) film. One side of the PVDF was metallized with gold and forms the ground plane of the transducer. The array pattern of the transducer and electrical traces to each annulus were formed on a copper-clad polyimide film. The PVDF and polyimide were bonded with a thin layer of epoxy, pressed into a spherically curved shape, then back filled with epoxy. A five-ring transducer with equal area elements and 100-microm kerfs between annuli was fabricated and tested. The transducer had a total aperture of 6 mm and a geometric focus of 12 mm. The pulse/echo response from a quartz plate located at the geometric focus, two-way insertion loss (IL), complex impedance, electrical crosstalk, and lateral beamwidth all were measured for each annulus. The complex impedance data from each element were used to perform electrical matching, and the measurements were repeated. After impedance matching; fc approximately equal to 36 MHz and -6-dB bandwidths ranged from 31 to 39%. The ILs for the matched annuli ranged from -28 to -38 dB
— id: 95055, year: 2005, vol: 52, page: 672, stat: Journal Article,

MRI approaches for specific targeting of PrPSc in the spleen of prion infected presymptomatic subjects
Sadowski, M; Wadghiri, ZY; Brown, D; Scholtzova, H; Pankiewicz, J; Turnbull, DH; Wisniewski, T
2005 ;64(6):A409-A410, Neurology
— id: 97607, year: 2005, vol: 64, page: A409, stat: Journal Article,

In vivo microimaging of mouse development and disease with ultrasound and MRI
Turnbull, DH
2005 MAR 4 ;19(4):A218-A218, FASEB journal
— id: 55692, year: 2005, vol: 19, page: A218, stat: Journal Article,

Magnetic resonance imaging of amyloid plaques in transgenic mice
Wadghiri, Youssef Zaim; Sigurdsson, Einar M; Wisniewski, Thomas; Turnbull, Daniel H
2005 ;299:365-379, Methods in molecular biology
Transgenic mice are used increasingly to model brain amyloidosis, mimicking the pathogenic processes involved in Alzheimer's disease (AD). In this chapter, a strategy is described that has been successfully used to map amyloid deposits in transgenic mouse models of AD with magnetic resonance imaging (MRI), utilizing molecular targeting vectors labeled with MRI contrast agents to enhance selectively the signal from amyloid plaques. To obtain sufficient spatial resolution for effective and sensitive mouse brain imaging, magnetic fields of 7-Tesla (T) or more are required. These are higher than the 1.5-T field strength routinely used for human brain imaging. The higher magnetic fields affect contrast agent efficiency, and determine the choice of pulse sequence parameters for in vivo MRI, all addressed in this chapter. Ex vivo imaging is also described as an important step to test and optimize protocols prior to in vivo studies. The experimental setup required for mouse brain imaging is explained in detail, including anesthesia, immobilization of the mouse head to reduce motion artifacts, and anatomical landmarks to use for the slice alignment procedure to improve image co-registration during longitudinal studies, and for subsequent matching of MRI with histology
— id: 56371, year: 2005, vol: 299, page: 365, stat: Journal Article,

In vivo auditory brain mapping in mice with Mn-enhanced MRI
Yu, Xin; Wadghiri, Youssef Zaim; Sanes, Dan H; Turnbull, Daniel H
2005 Jul;8(7):961-968, Nature neuroscience
There are currently no noninvasive imaging methods available for auditory brain mapping in mice, despite the increasing use of genetically engineered mice to study auditory brain development and hearing loss. We developed a manganese-enhanced MRI (MEMRI) method to map regions of accumulated sound-evoked activity in awake, normally behaving mice. To demonstrate its utility for high-resolution (100-mum) brain mapping, we used MEMRI to show the tonotopic organization of the mouse inferior colliculus. To test its efficacy in an experimental setting, we acquired data from mice experiencing unilateral conductive hearing loss at different ages. Larger and persistent changes in auditory brainstem activity resulted when hearing loss occurred before the onset of hearing, showing that early hearing loss biases the response toward the functional ear. Thus, MEMRI provides a sensitive and effective method for mapping the mouse auditory brainstem and has great potential for a range of functional neuroimaging studies in normal and mutant mice
— id: 56181, year: 2005, vol: 8, page: 961, stat: Journal Article,

Loss of connexin 43 in the cardiac neural crest results in outflow tract anomalies
Liu, S; Liu, FY; Shah, B; St Amend, T; Wadghiri, YZ; Turnbull, DH; Gutstein, DE
2004 OCT 26 ;110(17):59-60, Circulation
— id: 55934, year: 2004, vol: 110, page: 59, stat: Journal Article,

Embryonic heart failure in NFATc1-/- mice: novel mechanistic insights from in utero ultrasound biomicroscopy
Phoon, Colin K L; Ji, Rui Ping; Aristizabal, Orlando; Worrad, Diane M; Zhou, Bin; Baldwin, H Scott; Turnbull, Daniel H
2004 Jul 9;95(1):92-99, Circulation research
Gene targeting in the mouse has become a standard approach, yielding important new insights into the genetic factors underlying cardiovascular development and disease. However, we still have very limited understanding of how mutations affect developing cardiovascular function, and few studies have been performed to measure altered physiological parameters in mouse mutant embryos. Indeed, although in utero lethality due to embryonic heart failure is one of the most common results of gene targeting experiments in the mouse, the underlying physiological mechanisms responsible for embryonic demise remain elusive. Using in utero ultrasound biomicroscopy (UBM), we studied embryonic day (E) 10.5 to 14.5 NFATc1-/- embryos and control littermates. NFATc1-/- mice, which lack outflow valves, die at mid-late gestation from presumed defects in forward blood flow with resultant heart failure. UBM showed increasing abnormal regurgitant flow in the aorta and extending into the embryonal-placental circulation, which was evident after E12.5 when outflow valves normally first develop. Reduced NFATc1-/- net volume flow and diastolic dysfunction contributed to heart failure, but contractile function remained unexpectedly normal. Among 107 NFATc1-/- embryos imaged, only 2 were observed to be in acute decline with progressive bradyarrhythmia, indicating that heart failure occurs rapidly in individual NFATc1-/- embryos. This study is among the first linking a specific physiological phenotype with a defined genotype, and demonstrates that NFATc1-/- embryonic heart failure is a complex phenomenon not simply attributable to contractile dysfunction
— id: 43624, year: 2004, vol: 95, page: 92, stat: Journal Article,

Specific detection of PrPSc in the spleens of prion infected, presymptomatic mice by MRI
Sadowski, M; Wadghiri, YZ; Brown, D; Pankiewicz, J; Scholtzova, H; Tang, CY; Turnbull, DH
2004 JUL ;25(10):S465-S465, Neurobiology of aging
— id: 47741, year: 2004, vol: 25, page: S465, stat: Journal Article,

In vivo magnetic resonance of amyloid plaques in Alzheimer's disease model mice
Sigurdsson, E; Wadghiri, YZ; Sadowski, M; Elliott, JI; Li, YS; Scholtzova, H; Tang, CY; Aguinaldo, G; Duff, K; Turnbull, DH; Wisniewski, T
The living brain and Alzheimer's disease Berlin : Springer, 2004,
A key feature of Alzheimer's disease (AD) is the deposition of the amyloid beta (Abeta) as neuritic plaques in the brain. Transgenic mice overexpressing mutant amyloid precursor protein (APP), or both mutant APP and presenilin-1 (APP-PS1), develop Abeta plaques similar to AD patients and are currently the most widely used models of AD. The definitive diagnosis of AD still requires post-mortem examination. We have developed a novel method for the detection of Abeta plaques in the brains of AD model transgenic mice using magnetic resonance micro-imaging (muMRI). Our method is dependent on ligands that bind to AD amyloid lesions, allowing their detection by muMRI. These ligands are Abeta1-40 peptides, magnetically labeled with either gadolinium (Gd) or monocrystalline iron oxide nanoparticles (MION). When these are systemically injected with mannitol to transiently open the blood-brain barrier, we are able to detect the majority of amyloid lesions. The number of lesions detected by muMRI showed a statistically significant correlation with the Abeta burden determined by histology. This approach, with additional development, may be used to detect amyloid lesions in humans. Similar methods may also be used to image other conformational neurodegenerative disorders
— id: 4970, year: 2004, vol: , page: 47, stat: Chapter,

In vivo magnetic resonance imaging of amyloid plaques in mice with a non-toxic A beta derivative
Sigurdsson, EM; Wadghiri, YZ; Blind, JA; Knudsen, E; Asuni, A; Sadowski, M; Turnbull, DH; Wisniewski, T
2004 JUL ;25(10):S57-S57, Neurobiology of aging
— id: 47715, year: 2004, vol: 25, page: S57, stat: Journal Article,

Detection of Alzheimer's amyloid lesions in transgenic mice by magnetic resonance imaging
Sigurdsson, EM; Wadghiri, YZ; Li, YS; Elliott, JI; Tang, CY; Aguilnaldo, G; Duff, K; Pappolla, M; Watanabe, M; Scholtzova, H; Turnbull, DH; Wisniewski, T
2004 FEB ;25(2):251-251, Neurobiology of aging
— id: 42486, year: 2004, vol: 25, page: 251, stat: Journal Article,

Manganese-enhanced magnetic resonance imaging (MEMRI) of mouse brain development
Wadghiri, Youssef Zaim; Blind, Jeffrey A; Duan, Xiaohong; Moreno, Clement; Yu, Xin; Joyner, Alexandra L; Turnbull, Daniel H
2004 Dec;17(8):613-619, NMR in biomedicine
Given the importance of genetically modified mice in studies of mammalian brain development and human congenital brain diseases, MRI has the potential to provide an efficient in vivo approach for analyzing mutant phenotypes in the early postnatal mouse brain. The combination of reduced tissue contrast at the high magnetic fields required for mice, and the changing cellular composition of the developing mouse brain make it difficult to optimize MRI contrast in neonatal mouse imaging. We have explored an easily implemented approach for contrast-enhanced imaging, using systemically administered manganese (Mn) to reveal fine anatomical detail in T1-weighted MR images of neonatal mouse brains. In particular, we demonstrate the utility of this Mn-enhanced MRI (MEMRI) method for analyzing early postnatal patterning of the mouse cerebellum. Through comparisons with matched histological sections, we further show that MEMRI enhancement correlates qualitatively with granule cell density in the developing cerebellum, suggesting that the cerebellar enhancement is due to uptake of Mn in the granule neurons. Finally, variable cerebellar defects in mice with a conditional mutation in the Gbx2 gene were analyzed with MEMRI to demonstrate the utility of this method for mutant mouse phenotyping. Taken together, our results indicate that MEMRI provides an efficient and powerful in vivo method for analyzing neonatal brain development in normal and genetically engineered mice
— id: 52631, year: 2004, vol: 17, page: 613, stat: Journal Article,

Mutations in the sonic hedgehog pathway: Enhancement of medulloblastoma induction
Weiner, HL; Pompeiano, M; Mohan, A; Turnbull, DH; Joyner, AL
2004 ;100(4):780-780, Journal of neurosurgery
— id: 104594, year: 2004, vol: 100, page: 780, stat: Journal Article,

Imaging and therapeutic approaches for beta-sheet structures in prion and Alzheimer's diseases
Wisniewski, T; Pankiewicz, J; Scholtzova, H; Fernando, G; Chabalgoity, JA; Ji, Y; Wadghiri, YZ; Gan, WB; Tang, CY; Turnbull, DH; Mathis, CA; Kascsak, R; Klunk, WE; Carp, RI; Frangione, B; Sigurdsson, EM; Sadowski, M
2004 ;25(2):S30-S31, Neurobiology of aging
— id: 97595, year: 2004, vol: 25, page: S30, stat: Journal Article,

In vivo imaging of amyloid plaques in AD and prion disease model mice
Wisniewski, T; Sigurdsson, EM; Wadghiri, YZ; Carp, R; Tang, CY; Turnbull, DH; Mathis, C; Klunk, WE; Gan, WB; Sadowski, M
2004 APR ;25(12):S29-S29, Neurobiology of aging
— id: 42446, year: 2004, vol: 25, page: S29, stat: Journal Article,

44-MHz LiNbO3 transducers for UBM-guided Doppler ultrasound
Aristizabal, Orlando; Turnbull, Daniel H
2003 Jun;50(6):623-630, IEEE transactions on ultrasonics, ferroelectrics, & frequency control
In the post genome-sequencing era, physiological phenotyping of genetically engineered mice is critical to further our understanding of the functional consequences of specific genetic defects. We have developed a 40-50 MHz ultrasound biomicroscopy-(UBM) guided, pulsed Doppler system for the sensitive detection of in vivo blood velocity waveforms in the mouse embryonic cardiovascular system. Our approach uses separate transducers for simultaneous imaging and Doppler blood flow measurements. To this end, unfocused, air-backed lithium niobate (LiNbO3) transducers provide sensitive Doppler detection and the flexibility of adjusting the axial position of the pulsed Doppler sample volume over many millimeters depth range of the collimated ultrasound beam. In this paper we describe the fabrication and characterization of the electromechanical and ultrasonic beam properties of 44-MHz LiNbO3 Doppler transducers. We further demonstrate the utility of these Doppler transducers for interrogating blood vessels such as the dorsal aorta over a range of mouse embryonic stages and axial range-gate depths
— id: 39166, year: 2003, vol: 50, page: 623, stat: Journal Article,

Dynamic, contrast-enhanced perfusion MRI in mouse gliomas: Correlation with histopathology
Cha, Soonmee; Johnson, Glyn; Wadghiri, Youssef Zaim; Jin, Olivier; Babb, Jim; Zagzag, David; Turnbull, Daniel H
2003 May;49(5):848-855, Magnetic resonance in medicine
The aim of this study was to develop an MRI protocol to evaluate the growth and vascularity of implanted GL261 mouse gliomas on a 7T microimaging system. Both conventional T(1)- and T(2)-weighted imaging and dynamic, contrast-enhanced T(2)*-weighted imaging were performed on 34 mice at different stages of tumor development. MRI measurements of relative cerebral blood volume (rCBV) were compared to histological assessments of microvascular density (MVD). Enhancement on postcontrast T(1)-weighted images was compared to histological assessments of Evan's blue extravasation. Conventional T(2)-weighted and postcontrast T(1)-weighted images demonstrated tumor growth characteristics consistent with previous descriptions of GL261 glioma. Furthermore, measurements of rCBV from MRI data were in good agreement with histological measurements of MVD from the same tumors. Postcontrast enhancement on T(1)-weighted images was observed at all stages of GL261 glioma progression, even before evidence of angiogenesis, indicating that the mechanism of conventional contrast enhancement in MRI does not require neovascularization. These results provide quantitative support for MRI approaches currently used to assess human brain tumors, and form the basis for future studies of angiogenesis in genetically engineered mouse brain tumor models. Magn Reson Med 49:848-855, 2003
— id: 34729, year: 2003, vol: 49, page: 848, stat: Journal Article,

Onset of cardiac function during early mouse embryogenesis coincides with entry of primitive erythroblasts into the embryo proper
Ji, Rui Ping; Phoon, Colin K L; Aristizabal, Orlando; McGrath, Kathleen E; Palis, James; Turnbull, Daniel H
2003 Feb 7;92(2):133-135, Circulation research
When cardiac function and blood flow are first established are fundamental questions in mammalian embryogenesis. The earliest erythroblasts arise in yolk sac blood islands and subsequently enter the embryo proper to initiate circulation. Embryos staged 0 to 30 somites (S) were examined in utero with 40- to 50-MHz ultrasound biomicroscopy (UBM)-Doppler, to determine onset of embryonic heartbeat and blood flow and to characterize basic physiology of the very early mouse embryonic circulation. A heartbeat was first detected at 5 S, and blood vascular flow at 7 S. Heart rate, peak arterial velocity, and velocity-time integral showed progressive increases that indicated a dramatically increasing cardiac output from even the earliest stages. In situ hybridization revealed an onset of the heartbeat coincident with the appearance of yolk sac-derived erythroblasts in the embryo proper at 5 S. Early maturation of the circulation follows a tightly coordinated program
— id: 39310, year: 2003, vol: 92, page: 133, stat: Journal Article,

Ultrasound biomicroscopy-Doppler in mouse cardiovascular development
Phoon, Colin K L; Turnbull, Daniel H
2003 Jun 24;14(1):3-15, Physiological genomics
The ability to modify the mouse genome has yielded new insights into the genetic control of mammalian cardiovascular development. However, it is far less understood how genetic factors and their consequent structural changes alter cardiovascular function, a void largely due to the lack of effective noninvasive techniques to assess function in the developing mouse cardiovascular system. In this review, we discuss the recent advances in ultrasound biomicroscopy (UBM)-Doppler echocardiography for analyzing cardiovascular function in the embryonic mouse in utero. 'Cardiovascular function' encompasses broad aspects of physiology, including systolic and diastolic cardiac function, distribution of blood flow among various embryonic vascular beds, and vascular bed properties (impedance). A wide range of physiological measurements is possible using UBM-Doppler, but it is clear that the limitations of any single measurement warrant a multi-parameter approach to characterizing cardiovascular function. We further discuss the prospects for UBM-Doppler analysis of alternative vertebrate systems increasingly studied in developmental biology. The ability to correlate cardiovascular physiological phenotypes with their corresponding genotypes should lead to the elucidation of mechanisms underlying normal development, as well as embryonic disease and death
— id: 39181, year: 2003, vol: 14, page: 3, stat: Journal Article,

MRI approaches for the detection of prion disease pathology
Sadowski, Marcin; Tang, Cheuk Ying; Aguinaldo, Gilbert; Carp, Richard; Wadghiri, Youssef Zaim; Turnbull, Daniel H.; Wisniewski, Thomas
2003 ;60(5 Supplement 1):A250-118, Neurology
— id: 97614, year: 2003, vol: 60, page: A250, stat: Journal Article,

Detection of Alzheimer's amyloid in transgenic mice using magnetic resonance microimaging
Wadghiri, Youssef Zaim; Sigurdsson, Einar M; Sadowski, Marcin; Elliott, James I; Li, Yongsheng; Scholtzova, Henrieta; Tang, Cheuk Ying; Aguinaldo, Gilbert; Pappolla, Miguel; Duff, Karen; Wisniewski, Thomas; Turnbull, Daniel H
2003 Aug;50(2):293-302, Magnetic resonance in medicine
The presence of amyloid-beta (Abeta) plaques in the brain is a hallmark pathological feature of Alzheimer's disease (AD). Transgenic mice overexpressing mutant amyloid precursor protein (APP), or both mutant APP and presenilin-1 (APP/PS1), develop Abeta plaques similar to those in AD patients, and have been proposed as animal models in which to test experimental therapeutic approaches for the clearance of Abeta. However, at present there is no in vivo whole-brain imaging method to detect Abeta plaques in mice or men. A novel method is presented to detect Abeta plaques in the brains of transgenic mice by magnetic resonance microimaging (muMRI). This method uses Abeta1-40 peptide, known for its high binding affinity to Abeta, magnetically labeled with either gadolinium (Gd) or monocrystalline iron oxide nanoparticles (MION). Intraarterial injection of magnetically labeled Abeta1-40, with mannitol to transiently open the blood-brain barrier (BBB), enabled the detection of many Abeta plaques. Furthermore, the numerical density of Abeta plaques detected by muMRI and by immunohistochemistry showed excellent correlation. This approach provides an in vivo method to detect Abeta in AD transgenic mice, and suggests that diagnostic MRI methods to detect Abeta in AD patients may ultimately be feasible
— id: 38795, year: 2003, vol: 50, page: 293, stat: Journal Article,

in vivo magnetic resonance imaging of amyloid plaques in AD model mice
Wisniewski, T.; Sigurdsson, E. M.; Wadghiri, Y. Z.; Sadowski, M.; Scholtzova, H.; Tang, C. Y.; Aguilnaldo, G.; Duff, K.; Turnbull, D. H.
2003 ;2003(2):Abstract No. 203.7-302, Society for Neuroscience Abstract Viewer & Itinerary Planner
Amyloid deposition in Alzheimer's disease (AD) occurs many years before cognitive impairment. Brain imaging techniques targeting plaques will have an important diagnostic value and may help in identifying individuals in preclinical stages of AD. Magnetic resonance imaging (MRI) has a much higher resolution than positron enhanced tomography (PET) imaging and, therefore, is a more sensitive method to detect amyloid plaques. In our initial proof-of-concept studies (Magnetic Resonance in Medicine, in press), we utilized Abeta1-40 peptide, labeled with gadolinium or monocrystalline iron oxide nanoparticles (MION). When either of these ligands is injected in vivo systemically with mannitol to transiently open the blood-brain-barrier, we are able to image ex vivo the majority of Abeta plaques in Tg mice. Using Gd labeled Abeta1-40 and in vivo muMRI, we can also detect a substantial percentage of amyloid lesions. There is a high correlation between the numerical density of Abeta plaques detected by muMRI and by immunohistochemistry. Clinical use of Abeta1-40 is not feasible because it may add to the plaque burden. As a safer approach, we are using gadolinium labeled K6Abeta1-30, a non-toxic Abeta derivative with low propensity to form beta-sheet, while maintaining high affinity for Abeta. Our initial findings indicate that this compound has a similar effect as gadolinium labeled Abeta1-40 in allowing in vivo detection of amyloid plaques in Tg mice. We are currently exploring various ways to enhance the uptake of this compound into the brain. This approach may lead to a diagnostic MRI method to detect Abetaplaques in AD patients
— id: 97618, year: 2003, vol: 2003, page: Abstract No. 203.7, stat: Journal Article,

Transcriptional regulation of the endocardium as a unique endothelial cell population
Baldwin, HS; Robson, P; Zhou, B; Song, DC; Maschhoff, K; Pichal, S; Aristizabal, O; Phoon, C; Turnbull, D
2002 Mar 22;16(5):A1088-A1088, FASEB journal
— id: 27479, year: 2002, vol: 16, page: A1088, stat: Journal Article,

Establishment of cardiac function during early mouse embryogenesis
Ji, RP; Phoon, CK; Aristizabal, O; Palis, J; Turnbull, DH
2002 Apr;51(4):196-, Pediatric research
— id: 27456, year: 2002, vol: 51, page: 196, stat: Journal Article,

Complexity of embryonic heart failure: First insights from NFATc-l deficient mice
Phoon, CKL; Ji, RP; Aristizabal, O; Worrad, DM; Wu, BR; Baldwin, HS; Turnbull, DH
2002 NOV 5 ;106(19):286-287, Circulation
— id: 37202, year: 2002, vol: 106, page: 286, stat: Journal Article,

Spatial velocity profile in mouse embryonic aorta and Doppler-derived volumetric flow: a preliminary model
Phoon, Colin K L; Aristizabal, Orlando; Turnbull, Daniel H
2002 Sep;283(3):H908-H916, American journal of physiology. Heart & circulatory physiology
Characterizing embryonic circulatory physiology requires accurate cardiac output and flow data. Despite recent applications of high-frequency ultrasound Doppler to the study of embryonic circulation, current Doppler analysis of volumetric flow is relatively crude. To improve Doppler derivation of volumetric flow, we sought a preliminary model of the spatial velocity profile in the mouse embryonic dorsal aorta using ultrasound biomicroscopy (UBM)-Doppler data. Embryonic hematocrit is 0.05-0.10 so rheologic properties must be insignificant. Low Reynolds numbers (<500) and Womersley parameters (<0.76) suggest laminar flow. UBM demonstrated a circular dorsal aortic cross section with no significant tapering. Low Dean numbers (<100) suggest the presence of minimal skewing of the spatial velocity profile. The inlet length allows for fully developed flow. There is no apparent aortic wall pulsatility. Extrapolation of prior studies to these vessel diameters (300-350 microm) and flow velocities (~50-200 mm/s) suggests parabolic spatial velocity profiles. Therefore, mouse embryonic dorsal aortic blood flow may correspond to Poiseuille flow in a straight rigid tube with parabolic spatial velocity profiles. As a first approximation, these results are an important step toward precise in utero ultrasound characterization of blood flow within the developing mammalian circulation
— id: 39607, year: 2002, vol: 283, page: H908, stat: Journal Article,

In vivo detection of Alzheimer's amyloid by magnetic resonance imaging
Sigurdsson, EM; Wadghiri, YZ; Li, Q; Scholtzova, H; Tang, CY; Aguilnaldo, JG; Duff, K; Pappolla, M; Elliott, JI; Watanabe, M; Turnbull, DH; Wisniewski, T
2002 Jul-Aug;23(1):1307-, Neurobiology of aging
— id: 32425, year: 2002, vol: 23, page: 1307, stat: Journal Article,

Induction of medulloblastomas in mice, in the absence of Gli1
Weiner HL; Joyner A; Turnbull DH
2002 ;96:450-450, Journal of neurosurgery
— id: 34019, year: 2002, vol: 96, page: 450, stat: Journal Article,

Induction of medulloblastomas in mice by sonic hedgehog, independent of Gli1
Weiner, Howard L; Bakst, Richard; Hurlbert, Marc S; Ruggiero, Jason; Ahn, Esther; Lee, Wing Shing; Stephen, Daniel; Zagzag, David; Joyner, Alexandra L; Turnbull, Daniel H
2002 Nov 15;62(22):6385-6389, Cancer research
The Sonic hedgehog (Shh) signaling pathway plays a critical role in normal cerebellar development and has been implicated in medulloblastomas, common malignant childhood tumors of the cerebellum. To test whether Shh mis-expression is sufficient for medulloblastoma formation, we used ultrasound biomicroscopy-guided in utero injection of a Shh-expressing retrovirus into the cerebellum of 13.5-day mouse embryos to show that direct activation of the Shh pathway can lead to tumor formation. Significantly, medulloblastomas were observed in 76% of the mice infected with Shh-expressing retrovirus. Furthermore, contrary to recent suggestions that the Shh transcriptional target Gli1 plays a critical role in Shh-induced tumorigenesis, we found that medulloblastomas form in Gli1 null mutant mice. We have developed an efficient mouse model of medulloblastoma and shown that Gli1 is not required for tumorigenesis when Shh signaling is activated upstream in the pathway
— id: 34734, year: 2002, vol: 62, page: 6385, stat: Journal Article,

The HD mutation causes progressive lethal neurological disease in mice expressing reduced levels of huntingtin
Auerbach W; Hurlbert MS; Hilditch-Maguire P; Wadghiri YZ; Wheeler VC; Cohen SI; Joyner AL; MacDonald ME; Turnbull DH
2001 Oct 15;10(22):2515-2523, Human molecular genetics
Huntingtin is an essential protein that with mutant polyglutamine tracts initiates dominant striatal neurodegeneration in Huntington's disease (HD). To assess the consequences of mutant protein when huntingtin is limiting, we have studied three lines of compound heterozygous mice in which both copies of the HD gene homolog (Hdh) were altered, resulting in greatly reduced levels of huntingtin with a normal human polyglutamine length (Q20) and/or an expanded disease-associated segment (Q111): Hdh(neoQ20)/Hdh(neoQ20), Hdh(neoQ20)/Hdh(null) and Hdh(neoQ20)/Hdh(neoQ111). All surviving mice in each of the three lines were small from birth, and had variable movement abnormalities. Magnetic resonance micro-imaging and histological evaluation showed enlarged ventricles in approximately 50% of the Hdh(neoQ20)/Hdh(neoQ111) and Hdh(neoQ20)/Hdh(null) mice, revealing a developmental defect that does not worsen with age. Only Hdh(neoQ20)/Hdh(neoQ111) mice exhibited a rapidly progressive movement disorder that, in the absence of striatal pathology, begins with hind-limb clasping during tail suspension and tail stiffness during walking by 3-4 months of age, and then progresses to paralysis of the limbs and tail, hypokinesis and premature death, usually by 12 months of age. Thus, dramatically reduced huntingtin levels fail to support normal development in mice, resulting in reduced body size, movement abnormalities and a variable increase in ventricle volume. On this sensitized background, mutant huntingtin causes a rapid neurological disease, distinct from the HD-pathogenic process. These results raise the possibility that therapeutic elimination of huntingtin in HD patients could lead to unintended neurological, as well as developmental side-effects
— id: 35033, year: 2001, vol: 10, page: 2515, stat: Journal Article,

Telencephalic neural progenitors appear to be restricted to regional and glial fates before the onset of neurogenesis
McCarthy M; Turnbull DH; Walsh CA; Fishell G
2001 Sep 1;21(17):6772-6781, Journal of neuroscience
The contribution of early cell lineage to regional fate in the mammalian forebrain remains poorly understood. Previous lineage-tracing studies using retroviral methods were only begun at mid-neurogenesis and have suffered from region-specific retroviral silencing. We have been able to study cell lineage in the telencephalon from the onset of neurogenesis by using ultrasound backscatter microscopy to label the forebrain neuroepithelium and a modified retroviral lineage library to overcome regional silencing. Our studies suggest that by embryonic day 9.5, forebrain clones are primarily restricted to territories within anatomically demarcated regional boundaries, such as the cortex, striatum and hypothalamus. In addition, we observed a subset of clones that appeared to be composed entirely of glia. These observations suggest that both regional and cell-type restrictions exist within progenitor populations before the first forebrain cells become postmitotic
— id: 26687, year: 2001, vol: 21, page: 6772, stat: Journal Article,

In utero ultrasound micro-imaging of mouse embryos
Turnbull, DH
2001 MAR 8 ;15(5):A1068-A1068, FASEB journal
— id: 55094, year: 2001, vol: 15, page: A1068, stat: Journal Article,

Sensitivity and performance time in MRI dephasing artifact reduction methods
Wadghiri YZ; Johnson G; Turnbull DH
2001 Mar;45(3):470-476, Magnetic resonance in medicine
Although shimming can improve static field inhomogeneity, local field imperfections induced by tissue susceptibility differences cannot be completely corrected and can cause substantial signal loss in gradient echo images through intravoxel dephasing. Dephasing increases with voxel size so that one simple method of reducing the effect is to use thin slices. Signal-to-noise ratio (SNR) can then be increased by averaging over the subslices to form the final, thick slice. We call this method subslice averaging or SSAVE. Alternatively, a range of different amplitude slice select rephase gradients can be used to compensate for different susceptibility induced gradient offsets. The final image can then be formed by combining individual images in a variety of ways: summation, summation of the squares of the images, forming the maximum intensity projection of the image set, and Fourier transformation followed by summation. We show here that, contrary to previous claims, the theoretical sensitivity (i.e., SNR divided by the square root of the imaging time) of all these alternative methods is very similar. However, performance time (i.e., minimum-imaging time) of the simplest method, SSAVE, is much shorter than that of alternatives. This is confirmed experimentally on phantoms and anesthetized mice. Magn Reson Med 45:470-476, 2001.
— id: 21239, year: 2001, vol: 45, page: 470, stat: Journal Article,

Retrovirus-sonic hedgehog infection of murine embryonic cerebellar granule cells leads to tumor formation
Weiner HL; Joyaner AL; Turnbull D
2001 ;3:311-311, Neuro-oncology
— id: 34025, year: 2001, vol: 3, page: 311, stat: Journal Article,

In utero fate mapping reveals distinct migratory pathways and fates of neurons born in the mammalian basal forebrain
Wichterle H; Turnbull DH; Nery S; Fishell G; Alvarez-Buylla A
2001 Oct;128(19):3759-3771, Development
Recent studies suggest that neurons born in the developing basal forebrain migrate long distances perpendicularly to radial glia and that many of these cells reach the developing neocortex. This form of tangential migration, however, has not been demonstrated in vivo, and the sites of origin, pathways of migration and final destinations of these neurons in the postnatal brain are not fully understood. Using ultrasound-guided transplantation in utero, we have mapped the migratory pathways and fates of cells born in the lateral and medial ganglionic eminences (LGE and MGE) in 13.5-day-old mouse embryos. We demonstrate that LGE and MGE cells migrate along different routes to populate distinct regions in the developing brain. We show that LGE cells migrate ventrally and anteriorly, and give rise to the projecting medium spiny neurons in the striatum, nucleus accumbens and olfactory tubercle, and to granule and periglomerular cells in the olfactory bulb. By contrast, we show that the MGE is a major source of neurons migrating dorsally and invading the developing neocortex. MGE cells migrate into the neocortex via the neocortical subventricular zone and differentiate into the transient subpial granule neurons in the marginal zone and into a stable population of GABA-, parvalbumin- or somatostatin-expressing interneurons throughout the cortical plate
— id: 44324, year: 2001, vol: 128, page: 3759, stat: Journal Article,

In utero high-frequency (40 Mhz) echocardiographic analysis of murine embryonic heart development
Artman M; Srinivasan S; Phoon C; Aristizabal O; Turnbull DH
Etiology and morphogenesis of congential heart disease Armonk NY : Futura Pub., 2000,
— id: 2801, year: 2000, vol: , page: 285, stat: Chapter,

Progressive neurological disease in mice expressing reduced amounts of huntingtin with 20 and 111 glutamine repeat
Auerbach, W; Hurlbert, MS; Hilditch-Maguire, P; Wadghiri, YZ; Wheeler, VC; Cohen, SI; Joyner, AL; MacDonald, ME; Turnbull, DH
2000 OCT ;67(4):364-364, American journal of human genetics
— id: 54432, year: 2000, vol: 67, page: 364, stat: Journal Article,

Advances in ultrasound biomicroscopy
Foster FS; Pavlin CJ; Harasiewicz KA; Christopher DA; Turnbull DH
2000 Jan;26(1):1-27, Ultrasound in medicine & biology
The visualisation of living tissues at microscopic resolution is attracting attention in several fields. In medicine, the goals are to image healthy and diseased tissue with the aim of providing information previously only available from biopsy samples. In basic biology, the goal may be to image biological models of human disease or to conduct longitudinal studies of small-animal development. High-frequency ultrasonic imaging (ultrasound biomicroscopy) offers unique advantages for these applications. In this paper, the development of ultrasound biomicroscopy is reviewed. Aspects of transducer development, systems design and tissue properties are presented to provide a foundation for medical and biological applications. The majority of applications appear to be developing in the 40-60-MHz frequency range, where resolution on the order of 50 microm can be achieved. Doppler processing in this frequency range is beginning to emerge and some examples of current achievements will be highlighted. The current state of the art is reviewed for medical applications in ophthalmology, intravascular ultrasound, dermatology, and cartilage imaging. Ultrasound biomicroscopic studies of mouse embryonic development and tumour biology are presented. Speculation on the continuing evolution of ultrasound biomicroscopy will be discussed
— id: 44325, year: 2000, vol: 26, page: 1, stat: Journal Article,

Two lineage boundaries coordinate vertebrate apical ectodermal ridge formation
Kimmel RA; Turnbull DH; Blanquet V; Wurst W; Loomis CA; Joyner AL
2000 Jun 1;14(11):1377-1389, Genes & development
Proximal-distal outgrowth of the vertebrate limb bud is regulated by the apical ectodermal ridge (AER), which forms at an invariant position along the dorsal-ventral (D/V) axis of the embryo. We have studied the genetic and cellular events that regulate AER formation in the mouse. In contrast to implications from previous studies in chick, we identified two distinct lineage boundaries in mouse ectoderm prior to limb bud outgrowth using a Cre/loxP-based fate-mapping approach and a novel retroviral cell-labeling technique. One border is transient and at the limit of expression of the ventral gene En1, which corresponds to the D/V midline of the AER, and the second border corresponds to the dorsal AER margin. Labeling of AER precursors using an inducible Cre showed that not all cells that initially express AER genes form the AER, indicating that signaling is required to maintain an AER phenotype. Misexpression of En1 at moderate levels specifically in the dorsal AER of transgenic mice was found to produce dorsally shifted AER fragments, whereas high levels of En1 abolished AER formation. In both cases, the dorsal gene Wnt7a was repressed in cells adjacent to the En1-expressing cells, demonstrating that signaling regulated by EN1 occurs across the D/V border. Finally, fate mapping of AER domains in these mutants showed that En1 plays a part in positioning and maintaining the two lineage borders
— id: 11671, year: 2000, vol: 14, page: 1377, stat: Journal Article,

Two lineage boundaries and EN1 coordinate AER formation
Kimmel, RA; Turnbull, DH; Blanquet, V; Wurst, W; Loomis, CA; Joyner, AL
2000 JUN 1 ;222(1):227-227, Developmental biology (Orlando)
— id: 54559, year: 2000, vol: 222, page: 227, stat: Journal Article,

40 MHz Doppler characterization of umbilical and dorsal aortic blood flow in the early mouse embryo
Phoon CK; Aristizabal O; Turnbull DH
2000 Oct;26(8):1275-1283, Ultrasound in medicine & biology
Physiological study of the developing mouse circulation has lagged behind advances in molecular cardiology. Using an innovative high-frequency Doppler system, we noninvasively characterized circulatory hemodynamics in early mouse embryos. We used image-guided 43 MHz pulsed-wave (PW) Doppler ultrasound to study the umbilical artery and vein, or dorsal aorta in 109 embryos. Studies were conducted on embryonic days (E) 9.5-14.5. Heart rate, peak blood flow velocities, and velocity time integrals in all vessels increased from E9.5-14.5, indicating increasing stroke volume and cardiac output. Heart rate, ranging from 192 bpm (E9.5) to 261 bpm (E14.5), was higher than previously reported. Placental impedance, assessed by the time delay between the peaks of the umbilical arterial and venous waveforms and by venous pulsatility, decreased with gestation. Acceleration time, a load-independent Doppler index of cardiac contractility, remained constant but seemed sensitive to heart rate. High-frequency PW Doppler is a powerful tool for the quantitative, noninvasive investigation of early mouse circulatory development
— id: 17987, year: 2000, vol: 26, page: 1275, stat: Journal Article,

"Semi-invasive" Doppler imaging of early mouse embryonic aorta
Phoon, CK; Aristizabal, O; Turnbull, DH
2000 APR ;47(4):47A-47A, Pediatric research
— id: 54669, year: 2000, vol: 47, page: 47A, stat: Journal Article,

Abnormal cardiovascular physiology detected by in utero high-frequency Doppler precedes morphological defects in NF-ATc1 deficient mouse embryos
Phoon, CK; Aristizabal, O; Zhou, B; Wu, B; Baldwin, HS; Turnbull, DH
2000 OCT 31 ;102(18):109-109, Circulation
— id: 55244, year: 2000, vol: 102, page: 109, stat: Journal Article,

Ultrasound backscatter microscopy of mouse embryos
Turnbull DH
2000 ;135:235-243, Methods in molecular biology
— id: 11725, year: 2000, vol: 135, page: 235, stat: Journal Article,

Investigation of the role of BMP's in mammalian forebrain development
Corbin, Joshua G; Turnbull, Daniel H; Joyner, Alex; Fishell, Gord
1999 Oct 23-28;25(1-2):525-525, Abstracts (Society for Neuroscience)
— id: 15868, year: 1999, vol: 25, page: 525, stat: Journal Article,

Neonatal cardiomyopathy in mice homozygous for the Arg403Gln mutation in the alpha cardiac myosin heavy chain gene
Fatkin D; Christe ME; Aristizabal O; McConnell BK; Srinivasan S; Schoen FJ; Seidman CE; Turnbull DH; Seidman JG
1999 Jan;103(1):147-153, Journal of clinical investigation
Heterozygous mice bearing an Arg403Gln missense mutation in the alpha cardiac myosin heavy chain gene (alpha-MHC403/+) exhibit the histopathologic features of human familial hypertrophic cardiomyopathy. Surprisingly, homozygous alpha-MHC403/403 mice die by postnatal day 8. Here we report that neonatal lethality is caused by a fulminant dilated cardiomyopathy characterized by myocyte dysfunction and loss. Heart tissues from neonatal wild-type and alpha-MHC403/403 mice demonstrate equivalent switching of MHC isoforms; alpha isoforms in each increase from 30% at birth to 70% by day 6. Cardiac dimensions and function, studied for the first time in neonatal mice by high frequency (45 MHz) echocardiography, were normal at birth. Between days 4 and 6, alpha-MHC403/403 mice developed a rapidly progressive cardiomyopathy with left ventricular dilation, wall thinning, and reduced systolic contraction. Histopathology revealed myocardial necrosis with dystrophic calcification. Electron microscopy showed normal architecture intermixed with focal myofibrillar disarray. We conclude that 45-MHz echocardiography is an excellent tool for assessing cardiac physiology in neonatal mice and that the concentration of Gln403 alpha cardiac MHC in myocytes influences both cell function and cell viability. We speculate that variable incorporation of mutant and normal MHC into sarcomeres of heterozygotes may account for focal myocyte death in familial hypertrophic cardiomyopathy
— id: 7328, year: 1999, vol: 103, page: 147, stat: Journal Article,

A method for rapid gain-of-function studies in the mouse embryonic nervous system [see comments]
Gaiano N; Kohtz JD; Turnbull DH; Fishell G
1999 Sep;2(9):812-819, Nature neuroscience
We used ultrasound image-guided injections of high-titer retroviral vectors to obtain widespread introduction of genes into the mouse nervous system in utero as early as embryonic day 8.5 (E8.5). The vectors used included internal promoters that substantially improved proviral gene expression in the ventricular zone of the brain. To demonstrate the utility of this system, we extended our previous work in vitro by infecting the telencephalon in vivo as early as E8. 5 with a virus expressing Sonic Hedgehog. Infected embryos showed gross morphological brain defects, as well as ectopic expression of ventral telencephalic markers characteristic of either the medial or lateral ganglionic eminences
— id: 8484, year: 1999, vol: 2, page: 812, stat: Journal Article,

Notch/Delta signaling influences cell fate in the mouse telecephalon
Gaiano, Nicholas; Nye, Jeffrey S; Turnbull, Daniel H; Fishell, Gord
1999 Oct 23-28;25(1-2):2038-2038, Abstracts (Society for Neuroscience)
— id: 15841, year: 1999, vol: 25, page: 2038, stat: Journal Article,

2D multislice and 3D MRI sequences are often equally sensitive
Johnson G; Wadghiri YZ; Turnbull DH
1999 Apr;41(4):824-828, Magnetic resonance in medicine
A simple theoretical model was developed to compare the sensitivities (i.e., signal-to-noise ratios per unit imaging time) of two-dimensional (2D) multislice and 3D imaging sequences. The model shows that the sensitivities of 3D and 2D multislice MRI sequences are usually similar. Sensitivities are identical in T2-weighted sequences when the T(R)s of the two sequences are the same. In T1-weighted gradient-echo sequences, sensitivities are very similar when Ernst angle excitation is used and the T(R) of the 2D sequence is less than T1. The predictions of the model are confirmed in phantom and animal experiments
— id: 6119, year: 1999, vol: 41, page: 824, stat: Journal Article,

En1 plays multiple roles in vertebrate limb development
Kimmel, R; Loomis, C; Losos, K; Turnbull, D; Joyner, A
1999 JUN 1 ;210(1):228-228, Developmental biology (Orlando)
— id: 54019, year: 1999, vol: 210, page: 228, stat: Journal Article,

Lineage analysis during the emergence of regional patterning in the forebrain
McCarthy, Maria; Turnbull, Daniel; Walsh, Chris; Fishell, Gord
1999 Oct 23-28;25(1-2):1545-1545, Abstracts (Society for Neuroscience)
— id: 15843, year: 1999, vol: 25, page: 1545, stat: Journal Article,

Dilated cardiomyopathy in homozygous myosin-binding protein-C mutant mice
McConnell BK; Jones KA; Fatkin D; Arroyo LH; Lee RT; Aristizabal O; Turnbull DH; Georgakopoulos D; Kass D; Bond M; Niimura H; Schoen FJ; Conner D; Fischman DA; Seidman CE; Seidman JG
1999 Dec;104(12):1771-1771, Journal of clinical investigation
— id: 57577, year: 1999, vol: 104, page: 1771, stat: Journal Article,

Dilated cardiomyopathy in homozygous myosin-binding protein-C mutant mice
McConnell BK; Jones KA; Fatkin D; Arroyo LH; Lee RT; Aristizabal O; Turnbull DH; Georgakopoulos D; Kass D; Bond M; Niimura H; Schoen FJ; Conner D; Fischman DA; Seidman CE; Seidman JG; Fischman DH
1999 Nov;104(9):1235-1244, Journal of clinical investigation
To elucidate the role of cardiac myosin-binding protein-C (MyBP-C) in myocardial structure and function, we have produced mice expressing altered forms of this sarcomere protein. The engineered mutations encode truncated forms of MyBP-C in which the cardiac myosin heavy chain-binding and titin-binding domain has been replaced with novel amino acid residues. Analogous heterozygous defects in humans cause hypertrophic cardiomyopathy. Mice that are homozygous for the mutated MyBP-C alleles express less than 10% of truncated protein in M-bands of otherwise normal sarcomeres. Homozygous mice bearing mutated MyBP-C alleles are viable but exhibit neonatal onset of a progressive dilated cardiomyopathy with prominent histopathology of myocyte hypertrophy, myofibrillar disarray, fibrosis, and dystrophic calcification. Echocardiography of homozygous mutant mice showed left ventricular dilation and reduced contractile function at birth; myocardial hypertrophy increased as the animals matured. Left-ventricular pressure-volume analyses in adult homozygous mutant mice demonstrated depressed systolic contractility with diastolic dysfunction. These data revise our understanding of the role that MyBP-C plays in myofibrillogenesis during cardiac development and indicate the importance of this protein for long-term sarcomere function and normal cardiac morphology. We also propose that mice bearing homozygous familial hypertrophic cardiomyopathy-causing mutations may provide useful tools for predicting the severity of disease that these mutations will cause in humans
— id: 44326, year: 1999, vol: 104, page: 1235, stat: Journal Article,

Early steps in patterning of the embryonic mammalian hippocampus
Nery, Susana; Gaiano, Nicholas; Turnbull, Daniel H; Matise, Michael P; Fishell, Gord
1999 Oct 23-28;25(1-2):527-527, Abstracts (Society for Neuroscience)
— id: 15867, year: 1999, vol: 25, page: 527, stat: Journal Article,

Doppler characterization murine embryonic umbilical blood flow: Insights into developing embryonic-placental circulation and cardiac function
Phoon, CK; Aristizabal, O; Turnbull, DH
1999 APR ;45(4):28A-28A, Pediatric research
— id: 54064, year: 1999, vol: 45, page: 28A, stat: Journal Article,

Doppler characterization of dorsal aortic blood flow in the mouse embryo: Insights into the early developing circulation
Phoon, CK; Aristizabal, O; Turnbull, DH
1999 SEP ;104(3):660-660, Pediatrics
— id: 53835, year: 1999, vol: 104, page: 660, stat: Journal Article,

In utero ultrasound backscatter microscopy of early stage mouse embryos
Turnbull DH
1999 Jan-Feb;23(1):25-31, Computerized medical imaging & graphics
A high resolution ultrasound imaging technique, ultrasound backscatter microscopy (UBM), has previously been shown to be useful for in utero imaging of mouse embryos, and for direct manipulation of mouse embryos through UBM-guided injections. UBM images from mouse embryos staged between 8.5 and 10.5 days of gestation are presented to demonstrate the range of anatomical structures which can be studied with this approach. Ultrasound contrast agents have been injected into the forebrain ventricle of 10.5 day embryos to characterize the resulting three-dimensional distribution of the injected agents. These studies provide important background data relevant to future use of this technique for in utero analysis of early brain and heart development, and for in utero manipulation of mouse embryos through UBM-guided injections
— id: 7459, year: 1999, vol: 23, page: 25, stat: Journal Article,

In utero ultrasound microscopy of mouse embryos
Turnbull, DH
1999 JUN 1 ;210(1):222-222, Developmental biology (Orlando)
— id: 54015, year: 1999, vol: 210, page: 222, stat: Journal Article,

40-MHZ echocardiography scanner for cardiovascular assessment of mouse embryos
Aristizabal O; Christopher DA; Foster FS; Turnbull DH
1998 Nov;24(9):1407-1417, Ultrasound in medicine & biology
Congenital heart disease results from genetic defects that are manifested at early stages of embryogenesis. The mouse is the preferred animal model for studies of mammalian embryonic development and for an increasing number of human disease models. A number of genes identified in the mouse are critical for normal cardiovascular development, but an understanding of the underlying mechanisms regulating heart development is still incomplete, in part because of the lack of methods to measure hemodynamics in live mouse embryos. We describe the development of a 40-MHz ultrasound scanner, which allows image-guided continuous-wave and pulsed Doppler blood flow measurements in mouse embryos, in utero, at the critical early developmental stages. Doppler waveforms acquired from mouse embryonic umbilical vessels, descending aorta, and cardiac ventricles are presented to demonstrate the utility of the method. By combining image-guided ultrasound Doppler with the many available mouse mutants, this approach should lead to new insights into embryonic cardiovascular structure-function relationships
— id: 7489, year: 1998, vol: 24, page: 1407, stat: Journal Article,

Viral-mediated expression of delta-1 suggests that glial precursors are among the first neural cells specified during cortical development
Gaiano, Nicholas; Turnbull, Daniel H; Fishell, Gord
1998 Nov 7-12;24(1-2):1770-1770, Abstracts (Society for Neuroscience)
— id: 15922, year: 1998, vol: 24, page: 1770, stat: Journal Article,

Essential iris atrophy, pigment dispersion, and glaucoma in DBA/2J mice
John SW; Smith RS; Savinova OV; Hawes NL; Chang B; Turnbull D; Davisson M; Roderick TH; Heckenlively JR
1998 May;39(6):951-962, Investigative ophthalmology & visual science. IOVS
PURPOSE: To characterize ocular abnormalities associated with iris atrophy in DBA/2J mice and to determine whether mice of this strain develop elevated intraocular pressure (IOP) and glaucoma. METHODS: Different approaches, including slit-lamp biomicroscopy, ophthalmoscopic examination, ultrasound backscatter microscopy, and histology were used to examine the eyes of DBA/2J mice ranging from 2 to 30 months old. IOP was measured in DBA/2J mice of different ages. RESULTS: DBA/2J mice were found to develop pigment dispersion, iris transillumination, iris atrophy, anterior synechias, and elevated IOP. IOP was elevated in most mice by the age of 9 months. These changes were followed by the death of retinal ganglion cells, optic nerve atrophy, and optic nerve cupping. The prevalence and severity of these lesions increased with age. Optic nerve atrophy and optic nerve cupping was present in the majority of mice by the age of 22 months. CONCLUSIONS: DBA/2J mice develop a progressive form of secondary angle-closure glaucoma that appears to be initiated by iris atrophy and the associated formation of synechias. This mouse strain represents a useful model to evaluate mechanisms of pressure-related ganglion cell death and optic nerve atrophy, and to evaluate strategies for neuroprotection
— id: 57333, year: 1998, vol: 39, page: 951, stat: Journal Article,

Alteration of limb and brain patterning in early mouse embryos by ultrasound-guided injection of Shh-expressing cells
Liu A; Joyner AL; Turnbull DH
1998 Jul;75(1-2):107-115, Mechanisms of development
A basic limitation of the study of development in the mouse is the inaccessibility of the embryos, which are encased in the maternal uterus. We demonstrate the first use of ultrasound backscatter microscopy for guiding injections of cells and other agents into early stage mouse embryos. Cells were injected into the mouse neural tube cavity as early as 9.5 days post coitus (E9.5), and into the developing limb buds as early as E10.5. Furthermore, a cell-line engineered to express the secreted factor Sonic Hedgehog (Shh) was injected into early developing mouse brains or limbs. The Shh-expressing cells were found to induce ectopic expression of the Shh target genes Patched and Hnf3beta in the dorsal brain, and to alter digit patterning in the anterior limb bud. These results show that gene misexpression studies can be performed in mouse embryos using ultrasound-guided injection of transfected cells or retroviruses. In combination with the many available mouse mutants, this method offers a new approach for analyzing genetic interactions through gain-of-function studies performed in mutant mouse backgrounds
— id: 57334, year: 1998, vol: 75, page: 107, stat: Journal Article,

Noninvasive, in utero imaging of mouse embryonic heart development with 40-MHz echocardiography
Srinivasan S; Baldwin HS; Aristizabal O; Kwee L; Labow M; Artman M; Turnbull DH
1998 Sep 1;98(9):912-918, Circulation
BACKGROUND: The increasing number of transgenic and targeted mutant mice with embryonic cardiac defects has resulted in the need for noninvasive techniques to examine cardiac structure and function in early mouse embryos. We report the first use of a novel 40-MHz ultrasound imaging system in the study of mouse cardiac development in utero. METHODS AND RESULTS: Transabdominal scans of mouse embryos staged between 8.5 and 13.5 days of gestation (E8.5 to E13.5) were obtained in anesthetized mice. Atrial and ventricular contractions could be discerned from E9.5, and changes in cardiac morphology were observed from E9.5 to E13.5. Hyperechoic streaming patterns delineated flow through the umbilical, vitelline, and other major blood vessels. Diastolic and systolic ventricular areas were determined by planimetry of the epicardial borders, and fractional area change was measured as an index of contractile function. Significant increases in ventricular size were documented at each stage between E10.5 and E13.5, and the ability to perform serial imaging studies over 3 days of embryonic development is described. Finally, the detection of vascular cell adhesion molecule 1 (VCAM-1) homozygous null mutant embryos demonstrates the first example of noninvasive, in utero analysis of cardiac structure and function in a targeted mouse mutant. CONCLUSIONS: We used 40-MHz echocardiography to identify key elements of the early mouse embryonic cardiovascular system and for noninvasive dimensional analysis of developing cardiac ventricles. The ability to perform serial measurements and to detect mutant embryos with cardiac defects highlights the usefulness of the technique for investigating normal and abnormal cardiovascular development
— id: 7805, year: 1998, vol: 98, page: 912, stat: Journal Article,

Specification of mouse telencephalic and mid-hindbrain progenitors following heterotopic ultrasound-guided embryonic transplantation
Olsson M; Campbell K; Turnbull DH
1997 Oct;19(4):761-772, Neuron
We have demonstrated the utility of ultrasound backscatter microscopy for targeted intraparenchymal injections into embryonic day (E) 13.5 mouse embryos. This system has been used to test the degree of commitment present in neural progenitors from the embryonic ventral telencephalon and mid-hindbrain region. Many E13.5 ventral telencephalic progenitors were observed to integrate and adopt local phenotypes following heterotopic transplantation into telencephalic or mid-hindbrain targets, whereas mid-hindbrain cells of the same stage were unable to integrate and change fate in the telencephalon. In contrast, many mid-hindbrain cells from an earlier developmental stage (E10.5) were capable of integrating and adopting a forebrain phenotype after grafting into the telencephalon, suggesting that mouse mid-hindbrain progenitors become restricted in their developmental potential between E10.5 and E13.5
— id: 7230, year: 1997, vol: 19, page: 761, stat: Journal Article,

Ultrasound-guided injections into the mouse embryonic brain
Turnbull, DH; Olsson, M; Fishell, G; Joyner, AL
1997 ;62(2):1485-1488, Proceedings (IEEE Ultrasonics Symposium)
The authors have modified a 40-50 MHz ultrasound imaging system to allow image-guided injections into targeted brain regions of living mouse embryos. The injection technique is described, and example injections are shown. The significance of this research in basic biological science and the potential impact on future attempts at in utero therapy are described
— id: 104604, year: 1997, vol: 62, page: 1485, stat: Journal Article,

High frequency 40-MHz ultrasound. A possible noninvasive method for the assessment of the boundary of basal cell carcinomas
Gupta AK; Turnbull DH; Foster FS; Harasiewicz KA; Shum DT; Prussick R; Watteel GN; Hurst LN; Sauder DN
1996 Feb;22(2):131-136, Dermatologic surgery
BACKGROUND. Ultrasound imaging systems operating close to 20 MHz in frequency have been used to image skin tumors. Ultrasound imaging at 20 MHz has been used to determine the boundaries of basal cell carcinomas (BCCs). An inherent shortcoming of imaging systems operating at these frequencies is their limited resolution. OBJECTIVE. We investigated whether 40-MHz ultrasound imaging could provide higher resolution compared with the lower frequency systems and thus be a superior, noninvasive method of assessing the boundaries of BCCs. METHODS. Nine BCCs from six individuals were examined clinically and ultrasonographically, and then biopsied to confirm diagnosis. The depth of BCCs measured on histological sections was compared with the corresponding value obtained using ultrasound. For this study we required a nonsurgical, nondestructive means of treating BCCs that would allow repeated ultrasound imaging, and therefore topical 5-flurouracil (5-FU) was chosen. Following 5-FU therapy a biopsy was obtained from the site of the treated BCC after ultrasound imaging had been performed. Clinical, ultrasonic and histopathologic evaluation of each BCC was carried out independently by different individuals. At the end of the study all the BCC sites were treated surgically be electrodesiccation and curettage or completely excised. RESULTS. High resolution ultrasound images of BCCs were obtained with agreement between histology and ultrasound findings in all none lesions prior to therapy and in eight of none lesions posttherapy. There was a significant correlation between the depth of BCCs measured histologically and using ultrasound (P = 0.0004, r = 0.92). CONCLUSIONS. This study suggests that 40-MHz ultrasound may provide an estimate of the boundary of a BCC in vivo. High frequency 40-MHz ultrasound imaging may be an adjunct to clinical and histologic evaluation but does not replace the need to obtain tissue for microscopic examination
— id: 44328, year: 1996, vol: 22, page: 131, stat: Journal Article,

The use of high-frequency ultrasound as a method of assessing the severity of a plaque of psoriasis
Gupta AK; Turnbull DH; Harasiewicz KA; Shum DT; Watteel GN; Foster FS; Sauder DN
1996 Jun;132(6):658-662, Archives of dermatology
BACKGROUND AND DESIGN: Ultrasound imaging, while initially developed to visualize internal organs, is now being applied to image the skin. In this preliminary study, we used a high-frequency, 40-MHz ultrasound imaging system to provide high-resolution images in psoriasis and examined the relationship between clinical and ultrasound ratings in plaque-type psoriasis. The ultrasound image of a psoriatic plaque demonstrates a superficial echogenic band (band A), followed by a nonchogenic band (band B), and a deeper echogenic band (band C). RESULTS: In psoriatic plaques (N = 145), the severity of the psoriasis as assessed according to the degree of scaling, erythema, and thickness (SET score) correlated best with the width of band B (P < .001, r = 0.86) and less well with the width of bands A (P < .001, r = 0.59) and C (P < .001, r = 0.44). For the treated psoriatic plaques (n = 64), for which paired readings were available before and after therapy, changes in the SET scores correlated best with the change in the width of band B (P < .001, r = 0.96) and less well with the change in the width of bands A (P < .001, r = 0.61) and C (P < .001, r = 0.45). Ultrasound analyses and clinical evaluation were performed by independent raters. CONCLUSIONS: The data suggest that high-frequency ultrasound imaging may prove to be a noninvasive technique that can be used as an adjunct to the clinical evaluation of the lesional severity of psoriatic plaques
— id: 44327, year: 1996, vol: 132, page: 658, stat: Journal Article,

Ultrasound backscatter microscope analysis of mouse melanoma progression
Turnbull DH; Ramsay JA; Shivji GS; Bloomfield TS; From L; Sauder DN; Foster FS
1996 ;22(7):845-853, Ultrasound in medicine & biology
The incidence and mortality rate of cutaneous melanoma continue to increase throughout the world, making the study of melanoma biology an important area of current research. While recent breakthroughs in transgenic mouse technology have led to promising mouse skin models of melanoma, there is presently no technique available for quantitatively studying subsurface melanoma progression, in vivo. We demonstrate the first application of an imaging method called ultrasound backscatter microscopy (UBM) for imaging early murine melanomas with spatial resolution of 30 microns axial and 60 microns lateral. Murine B16 F10 melanomas have been imaged from their earliest detection, over several days, until they are 2 to 5 mm in diameter. Melanoma dimensions measured by UBM were found to be in excellent agreement with those determined histopathologically on the excised tumours. The relative rms errors in UBM-determined melanoma height and width were found to be 8.7% and 4.2%, respectively. The mean rate of increase in tumour height of early murine melanoma was found to be 0.37 +/- 0.06 mm/day. Computer-generated volumetric renderings of melanomas have been produced from three-dimensional image data, allowing quantitative comparisons of tumour volumes to be made. Using a priori assumptions of ellipsoid tumour shape, the relative error in UBM-determined volume was shown to be less than 17%. These results should be of considerable interest to investigators studying melanoma biology using mouse skin models, and have implications in the use of high frequency ultrasound imaging for the clinical assessment of cutaneous melanoma
— id: 8222, year: 1996, vol: 22, page: 845, stat: Journal Article,

Does high-frequency (40-60 MHz) ultrasound imaging play a role in the clinical management of cutaneous melanoma?
Semple JL; Gupta AK; From L; Harasiewicz KA; Sauder DN; Foster FS; Turnbull DH
1995 Jun;34(6):599-605, Annals of plastic surgery
The assessment of cutaneous melanoma in the clinical setting is often difficult, and important features such as depth and width remain unknown until the pathology report is received. Access to prognostic features such as vertical height before excisional biopsy would offer a basis for guidance in defining surgical margins and early planning of treatment options. Recently developed high-frequency ultrasound imaging in the 40-to 60-MHz range is a noninvasive method that provides in vivo information about cutaneous lesions. Imaging at these frequencies provides high-resolution data within the range of the epidermis and dermis (3-4 mm in depth). Ten cutaneous melanomas and seven pigmented lesions were assessed in this fashion. Vertical height was documented and compared to histopathological findings. High-frequency ultrasound imaging determination of vertical height correlated well with the standard measurement of Breslow's thickness on histological sections only in midrange (1.0-3.0 mm) lesions. Inflammatory cells at the base of three melanomas provoked an overestimation of the depth measurement with ultrasonography. Thick keratin layers such as those found on the feet acted as a virtual block to the high-frequency scanner. The application of this new advance in noninvasive imaging technology to the clinical assessment of cutaneous melanoma provides interesting in vivo data but in its present state does not replace the need for the biopsy of pigmented lesions and histopathological diagnosis
— id: 44329, year: 1995, vol: 34, page: 599, stat: Journal Article,

Ultrasound backscatter microscope analysis of early mouse embryonic brain development
Turnbull DH; Bloomfield TS; Baldwin HS; Foster FS; Joyner AL
1995 Mar 14;92(6):2239-2243, Proceedings of the National Academy of Sciences of the United States of America
The history of developmental and genetic analysis in the mouse has made it the model of choice for studying mammalian embryogenesis. Presently lacking is a simple technique for efficiently analyzing early mouse mutant phenotypes in utero. We demonstrate application of a real-time imaging method called ultrasound backscatter microscopy for visualizing mouse early embryonic neural tubes and hearts. This method was used to study live embryos in utero between 9.5 and 11.5 days of embryogenesis, with a spatial resolution close to 50 microns. Ultrasound backscatter microscope images of cultured embryos made it possible to visualize the heart chambers. This noninvasive imaging method was also used for analyzing a neural tube defect. The midhindbrain deletion associated with a null mutation of the Wnt-1 protooncogene was easily recognizable on ultrasound backscatter microscope images of 10.5- and 11.5-day embryos. Computer-generated volumetric renderings of the neural tube cavities were made from three-dimensional image data. This allowed a much clearer definition of the Wnt-1 mutant phenotype. These imaging techniques should be of considerable use in studying mouse development in utero
— id: 56723, year: 1995, vol: 92, page: 2239, stat: Journal Article,

A 40-100 MHz B-scan ultrasound backscatter microscope for skin imaging
Turnbull DH; Starkoski BG; Harasiewicz KA; Semple JL; From L; Gupta AK; Sauder DN; Foster FS
1995 ;21(1):79-88, Ultrasound in medicine & biology
There is a growing interest in high resolution, subsurface imaging of cutaneous tissues using higher frequency ultrasound, and several commercial systems have been developed recently which operate at 20 MHz. Some of the possible applications of higher frequency skin imaging include tumour staging, boundary definition, and studies of the response of tumours to therapy, investigations of inflammatory skin conditions such as psoriasis and eczema, and basic studies of skin aging, sun damage and the effects of irritants. Investigation of these areas is quite new, and the role of ultrasound skin imaging is continuing to evolve. Lateral resolution in the 20 MHz imaging systems ranges from 200 to 300 microns, which limits imaging applications to cutaneous structures which are relatively large in size. In this paper, a real-time ultrasound backscatter microscope (UBM) for skin imaging is described which operates in the 40-100 MHz range, providing axial resolution between 17 and 30 microns and lateral resolution between 33 and 94 microns. This improvement in resolution over current skin ultrasound systems should prove useful in determining the margins of small skin lesions, and in obtaining more precise, in vivo skin thickness measurements to characterize nonmalignant skin disease. Example images of normal skin, seborrhoeic keratosis and malignant melanoma illustrate the imaging potential of this system
— id: 6766, year: 1995, vol: 21, page: 79, stat: Journal Article,

Simulation of B-scan images from two-dimensional transducer arrays: Part II--Comparisons between linear and two-dimensional phased arrays
Turnbull DH; Foster FS
1992 Oct;14(4):344-353, Ultrasonic imaging
Two-dimensional (2-D) arrays have been proposed as a solution to the degradation in medical ultrasound image quality occurring as a result of asymmetric focusing properties of linear phased array transducers. The 2-D phased transducer array is also capable of electronically steering the symmetrically focused ultrasound beam throughout a three-dimensional volume. In a companion paper the potential of 2-D transducer arrays for medical imaging has been investigated using simulated B-scan images. In this paper, the advantages of 2-D over linear transducer arrays is demonstrated by simulating images of spherical cysts embedded in a large scattering volume. The large elevation beamwidth in the nearfield of a 5 MHz linear phased transducer array results in a severe reduction in the image contrast measured between a 4 mm diameter cyst and the surrounding scattering media. By employing a 2-D array with symmetric focusing, the contrast between the cyst and surrounding scatterers is significantly improved. The use of additional elements in the elevation direction of a linear array is also investigated. In this case the additional elements are included only to focus, but not to steer the ultrasound beam. Using the contrast characteristics of a 4 mm diameter cyst, it is shown that relatively few elevation elements are required to significantly improve the nearfield imaging capability of the linear array
— id: 44330, year: 1992, vol: 14, page: 344, stat: Journal Article,

Simulation of B-scan images from two-dimensional transducer arrays: Part I--Methods and quantitative contrast measurements
Turnbull DH; Lum PK; Kerr AT; Foster FS
1992 Oct;14(4):323-343, Ultrasonic imaging
Recently, theoretical investigations of the beamforming capability of two-dimensional (2-D) transducer arrays have characterized the array parameters required to steer a symmetrically focused ultrasound beam up to 45 degrees off-axis. These investigations have also shown that the number of elements in a steered 2-D array can be dramatically reduced by using a sparse set of elements, randomly distributed throughout the aperture of the transducer. The penalty paid for the use of a sparse array is the development of a 'pedestal' sidelobe in the beam profile, the amplitude of which increases as the number of elements in the array decreases. In this paper the potential of 2-D arrays for medical imaging is assessed by simulating B-scan images of spherical lesions, both cystic and scattering, embedded in a large random scattering volume. Similar contrast characteristics over a range of cyst sizes are demonstrated for a dense 2-D array and a sparse array with 1/8th the number of elements, both operating at 5 MHz. A 32nd order sparse array is shown to perform at a reduced level, producing unacceptable artifactual echoes within images of cysts. The 8th order sparse array pattern has been fabricated on a fixed-focus poly(vinylidene difluoride) transducer using photolithographic techniques. Experimental images from this transducer are used to verify some of the theoretical predictions made in this paper. Comparisons between simulated B-scan images from linear and 2-D phased arrays are presented in a companion paper
— id: 44331, year: 1992, vol: 14, page: 323, stat: Journal Article,

Ultrasonic characterization of selected renal tissues
Turnbull DH; Wilson SR; Hine AL; Foster FS
1989 ;15(3):241-253, Ultrasound in medicine & biology
Velocity, attenuation, and backscatter of ultrasound were measured in human renal tissues over a frequency range relevant to clinical imaging (3.5-7 MHz). Normal renal tissues, as well as three types of mass (angiomyolipoma, renal cell carcinoma, and oncocytoma) were studied, and comparisons made of the appearance of the tissues in clinical images to their ultrasonic and pathological properties. The results showed angiomyolipoma had high attenuation and backscatter coefficients due to acoustic impedance differences between fat and smooth muscle components of the tumour. The renal cell carcinomas were indistinguishable from normal kidney tissue, except in one case where infiltration by fatlike macrophages led to high attenuation and backscatter coefficients. This finding also supports the conclusion that fat/nonfat interfaces are a dominant scatter mechanism in renal tissues
— id: 44332, year: 1989, vol: 15, page: 241, stat: Journal Article,