1. Articles in category: Developmental Biology

    193-216 of 246 « 1 2 ... 6 7 8 9 10 11 »
    1. SMAD signaling drives heart and muscle dysfunction in a Drosophila model of muscular dystrophy

      SMAD signaling drives heart and muscle dysfunction in a Drosophila model of muscular dystrophy
      Loss-of-function mutations in the genes encoding dystrophin and the associated membrane proteins, the sarcoglycans, produce muscular dystrophy and cardiomyopathy. The dystrophin complex provides stability to the plasma membrane of striated muscle during muscle contraction. Increased SMAD signaling due to activation of the transforming growth factor-β (TGFβ) pathway has been described in muscular dystrophy; however, it is not known whether this canonical TGFβ signaling is pathogenic in the muscle itself. Drosophila deleted for the γ/δ-sarcoglycan gene (Sgcd) develop progressive muscle and heart dysfunction and serve as a model for the human disorder. We used dad-lacZ flies to demonstrate the signature ...
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    2. Optical Coherence Tomography Imaging of Early Quail Embryos

      Optical Coherence Tomography Imaging of Early Quail Embryos
      Congenital heart defects (CHDs) affect thousands of newborns each year in the United States. Recent research using animal model systems indicates that the abnormal function of the early tubular heart precedes structural defects such as septal defects. Optical coherence tomography (OCT) is an imaging modality that can provide high spatial and temporal resolution to study both the structure and the function of the tubular heart. With technical advances in OCT imaging speed, especially with frequency domain OCT and image-based retrospective gating, it is now possible to image a beating avian embryonic heart in three dimensions under physiological conditions and follow ...
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    3. High-Speed Optical Coherence Tomography Imaging of the Beating Avian Embryonic Heart

      High-Speed Optical Coherence Tomography Imaging of the Beating Avian Embryonic Heart
      Congenital heart defects (CHDs) affect thousands of newborns each year in the United States. Recent research using animal model systems indicates that the abnormal function of the early tubular heart precedes structural defects such as septal defects. Optical coherence tomography (OCT) is an imaging modality that can provide high spatial and temporal resolution to study both the structure and the function of the tubular heart. With technical advances in OCT imaging speed, especially with frequency domain OCT and image-based retrospective gating, it is now possible to image a beating avian embryonic heart in three dimensions under physiological conditions and follow ...
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    4. Speckle variance OCT imaging of the vasculature in live mammalian embryos

      Speckle variance OCT imaging of the vasculature in live mammalian embryos

      Live imaging of normal and abnormal vascular development in mammalian embryos is important tool in embryonic research, which can potentially contribute to understanding, prevention and treatment of cardiovascular birth defects. Here, we used speckle variance analysis of swept source optical coherence tomography (OCT) data sets acquired from live mouse embryos to reconstruct the 3-D structure of the embryonic vasculature. Both Doppler OCT and speckle variance algorithms were used to reconstruct the vascular structure. The results demonstrates that speckle variance imaging provides more accurate representation of the vascular structure, as it is not sensitive to the blood flow direction, while the ...

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    5. Physiological homology between Drosophila melanogaster and vertebrate cardiovascular systems

      Physiological homology between Drosophila melanogaster and vertebrate cardiovascular systems
      The physiology of the Drosophila melanogaster cardiovascular system remains poorly characterized compared with its vertebrate counterparts. Basic measures of physiological performance remain unknown. It also is unclear whether subtle physiological defects observed in the human cardiovascular system can be reproduced in D. melanogaster. Here we characterize the cardiovascular physiology of D. melanogaster in its pre-pupal stage by using high-speed dye angiography and optical coherence tomography. The heart has vigorous pulsatile contractions that drive intracardiac, aortic and extracellular-extravascular hemolymph flow. Several physiological measures, including weight-adjusted cardiac output, body-length-adjusted aortic velocities and intracardiac shear forces, are similar to those in the closed ...
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    6. Arrhythmia Caused by a Drosophila Tropomyosin Mutation Is Revealed Using a Novel Optical Coherence Tomography Instrument

      Arrhythmia Caused by a Drosophila Tropomyosin Mutation Is Revealed Using a Novel Optical Coherence Tomography Instrument
      Background Dilated cardiomyopathy (DCM) is a severe cardiac condition that causes high mortality. Many genes have been confirmed to be involved in this disease. An ideal system with which to uncover disease mechanisms would be one that can measure the changes in a wide range of cardiac activities associated with mutations in specific, diversely functional cardiac genes. Such a system needs a genetically manipulable model organism that allows in vivo measurement of cardiac phenotypes and a detecting instrument capable of recording multiple phenotype parameters. Methodology and Principal Findings With a simple heart, a transparent body surface at larval stages and ...
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    7. Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

      Measuring hemodynamics in the developing heart tube with four-dimensional gated Doppler optical coherence tomography

      Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at ...

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    8. Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography

      Heart wall velocimetry and exogenous contrast-based cardiac flow imaging in Drosophila melanogaster using Doppler optical coherence tomography
      Drosophila melanogaster (fruit fly) is a central organism in biology and is becoming increasingly important in the cardiovascular sciences. Prior work in optical imaging of the D. melanogaster heart has focused on static and dynamic structural anatomy. In the study, it is demonstrated that Doppler optical coherence tomography can quantify dynamic heart wall velocity and hemolymph flow in adult D. melanogaster. Since hemolymph is optically transparent, a novel exogenous contrast technique is demonstrated to increase the backscatter-based intracardiac Doppler flow signal. The results presented here open up new possibilities for functional cardiovascular phenotyping of normal and mutant D. melanogaster.
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    9. Mechanics of head fold formation: investigating tissue-level forces forces during early development

      Mechanics of head fold formation: investigating tissue-level forces forces during early development
      During its earliest stages, the avian embryo is approximately planar. Through a complex series of folds, this flat geometry is transformed into the intricate three-dimensional structure of the developing organism. Formation of the head fold (HF) is the first step in this cascading sequence of out-of-plane tissue folds. The HF establishes the anterior extent of the embryo and initiates heart, foregut and brain development. Here, we use a combination of computational modeling and experiments to determine the physical forces that drive HF formation. Using chick embryos cultured ex ovo, we measured: (1) changes in tissue morphology in living embryos using ...
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    10. Imaging modalities to assess structural birth defects in mutant mouse models

      Imaging modalities to assess structural birth defects in mutant mouse models
      Assessment of structural birth defects (SBDs) in animal models usually entails conducting detailed necropsy for anatomical defects followed by histological analysis for tissue defects. Recent advances in new imaging technologies have provided the means for rapid phenotyping of SBDs, such as using ultra-high frequency ultrasound biomicroscopy, optical coherence tomography, micro-CT, and micro-MRI. These imaging modalities allow the detailed assessment of organ/tissue structure, and with ultrasound biomicroscopy, structure and function of the cardiovascular system also can be assessed noninvasively, allowing the longitudinal tracking of the fetus in utero. In this review, we briefly discuss the application of these state-of-the-art imaging ...
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    11. Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral domain optical coherence tomography

      Measurement of absolute blood flow velocity in outflow tract of HH18 chicken embryo based on 4D reconstruction using spectral domain optical coherence tomography

      The measurement of blood-plasma absolute velocity distributions with high spatial and temporal resolution in vivo is important for the investigation of embryonic heart at its early stage of development. We introduce a novel method to measure absolute blood flow velocity based on high speed spectral domain optical coherence tomography (OCT) and apply it to measure velocities across the heart outflow tract (OFT) of a chicken embryo (stage HH18). First, we use the OCT system to acquire 4D 
[(x,y,z) + t] images of the OFT in vivo. Second, we reconstruct the 4D microstructural images and obtain the orientation of the ...

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    12. Optical coherence tomography as approach for the minimal invasive localization of the germinal disc in ovo before chicken sexing

      Optical coherence tomography as approach for the minimal invasive localization of the germinal disc in ovo before chicken sexing
      In most industrial states a huge amount of newly hatched male layer chickens are usually killed immediately after hatching by maceration or gassing. The reason for killing most of the male chickens of egg producing races is their slow growth rate compared to races specialized on meat production. When the egg has been laid, the egg contains already a small disc of cells on the surface of the yolk known as the blastoderm. This region is about 4 - 5 mm in diameter and contains the information whether the chick becomes male or female and hence allows sexing of the chicks ...
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    13. The Embryonic Heart: Imaging Life as it Happens - University of Houston Professor Captures Video of Heart Before it Begins to Beat (Video Snippet)

      The Embryonic Heart: Imaging Life as it Happens - University of Houston Professor Captures Video of Heart Before it Begins to Beat (Video Snippet)
      Imagine being able to image life as it happens by capturing video of the embryonic heart before it begins beating. A professor at the University of Houston, in collaboration with scientists at Baylor College of Medicine, is doing just that. Kirill Larin, assistant professor of biomedical engineering in the Cullen College of Engineering at UH, and his colleagues in the Texas Medical Center are documenting the formation of the mammalian heart through a high-resolution, non-invasive imaging device, providing perhaps the best live imagery taken of the vital organ. “Everything we know about early development of the heart and formation of ...
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    14. Gene Deletion Screen for Cardiomyopathy in Adult Drosophila Identifies a New Notch Ligand

      Gene Deletion Screen for Cardiomyopathy in Adult Drosophila Identifies a New Notch Ligand
      Rationale: Drosophila has been recognized as a model to study human cardiac diseases. Objective: Despite these findings, and the wealth of tools that are available to the fly community, forward genetic screens for adult heart phenotypes have been rarely performed because of the difficulty in accurately measuring cardiac function in adult Drosophila. Methods and Results: Using optical coherence tomography to obtain real-time analysis of cardiac function in awake Drosophila, we performed a genomic deficiency screen in adult flies. Based on multiple complementary approaches, we identified CG31665 as a novel gene causing dilated cardiomyopathy. CG31665, which we name weary (wry), has ...
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    15. Imaging of mouse embryonic eye development using optical coherence tomography

      Imaging of mouse embryonic eye development using optical coherence tomography
      Congenital abnormalities are often caused by genetic disorders which alter the normal development of the eye. Embryonic eye imaging in mouse model is important for understanding of normal and abnormal eye development and can contribute to prevention and treatment of eye defects in humans. In this study, we used Swept Source Optical Coherence Tomography (SS-OCT) to image eye structure in mouse embryos at 12.5 to 17.5 days post coitus (dpc). The imaging depth of the OCT allowed us to visualize the whole eye globe at these stages. Different ocular tissues including lens, cornea, eyelids, and hyaloid vasculature were ...
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    16. Focusing light through living tissue

      Focusing light through living tissue
      Tissues such as skin, fat or cuticle are non-transparent because inhomogeneities in the tissue scatter light. We demonstrate experimentally that light can be focused through turbid layers of living tissue, in spite of scattering. Our method is based on the fact that coherent light forms an interference pattern, even after hundreds of scattering events. By spatially shaping the wavefront of the incident laser beam, this interference pattern was modified to make the scattered light converge to a focus. In contrast to earlier experiments, where light was focused through solid objects, we focused light through living pupae of Drosophila melanogaster. We ...
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    17. Minimal invasive localization of the germinal disc in ovo for subsequent chicken sexing using optical coherence tomography

      Minimal invasive localization of the germinal disc in ovo for subsequent chicken sexing using optical coherence tomography

      Reason for using optical coherence tomography (OCT) to locate the germinal disc is the questionable and ethically alarming killing of male layer chickens because for the layer line only the females are necessary. To avoid this and to protect the animal rights, the sex of the fertilized chicken egg has to be determined as early as possible in the unincubated state. Because the information whether the chick becomes male or female can be found in the germinal disc an accurate localization for sexing is essential. The germinal disc is located somewhere on top of the yolk and has a diameter ...

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    18. Gabor-based fusion technique for Optical Coherence Microscopy

      Gabor-based fusion technique for Optical Coherence Microscopy
      We recently reported on an Optical Coherence Microscopy technique, whose innovation intrinsically builds on a recently reported - 2 μm invariant lateral resolution by design throughout a 2 mm cubic full-field of view - liquid-lens-based dynamic focusing optical probe [Murali et al.,Optics Letters 34, 145-147, 2009]. We shall report in this paper on the image acquisition enabled by this optical probe when combined with an automatic data fusion method developed and described here to produce an in-focus high resolution image throughout the imaging depth of the sample. An African frog tadpole (Xenopus laevis) was imaged with the novel probe and the ...
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    19. Sub-cellular resolution imaging with Gabor domain optical coherence microscopy

      Sub-cellular resolution imaging with Gabor domain optical coherence microscopy
      Optical Coherence Microscopy (OCM) utilizes a high NA microscope objective in the sample arm to achieve an axially and laterally high resolution OCT image. An increase in NA, however, leads to a dramatically decreased depth of focus (DOF), and hence shortens the imaging depth range so that high lateral resolution is maintained only within a small depth region around the focal plane. One solution to increase the depth of imaging while keeping a high lateral resolution is dynamic-focusing. Utilizing the voltage controlled refocus capability of a liquid lens, we have recently presented a solution for invariant high resolution imaging using ...
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    20. Fourier Domain Optical Coherence Tomography as a Noninvasive Means for In Vivo Detection of Retinal Degeneration in Xenopus laevis Tadpoles

      ose. To determine the efficacy of Fourier domain optical coherence tomography (FD-OCT) as a noninvasive, nonlethal method for detecting in vivo, pathologic signs of retinal degeneration in Xenopus laevis larvae. Methods. A prototype OCT system using FD detection customized for tadpole imaging was used to noninvasively obtain retinal scans in two different transgenic X. laevis models of retinal degeneration. FD-OCT retinal scans were compared with laser scanning confocal micrographs of histologic sections of the same eye. Retinal thickness was measured in the histologic micrographs and compared with in vivo measurements acquired with FD-OCT. Results. In vivo retinal images of X ...
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    21. Development of a high speed spectral domain optical coherence tomography system at 835 nm

      We develop a high speed multi-functional spectral domain (SD-OCT) system, using a broadband light source centered at 835nm and a custom-built spectrometer with a spectral resolution of 0.0674nm. After precise spectral calibration of the spectrometer, non-uniform discrete Fourier transform (NDFT) of the acquired spectral data is adopted for image reconstruction. In vivo imaging of human finger from volunteer at A-scan rate of 29 kHz with different reconstruction methods reveal that with the NDFT method, improved sensitivity fall-off especially at large depth is achieved in contrast to the conventional discrete Fourier transform (DFT) with interpolation method. And the phase information ...

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    22. Multiple-cardiac-cycle noise reduction in dynamic optical coherence tomography of the embryonic heart and vasculature

      Multiple-cardiac-cycle noise reduction in dynamic optical coherence tomography of the embryonic heart and vasculature
      Recent progress in optical coherence tomography (OCT) allows imaging dynamic structures and fluid flow within scattering tissue, such as the beating heart and blood flow in mouse embryos. Accurate representation and analysis of these dynamic behaviors require reducing the noise of the acquired data. Although noise can be reduced by averaging multiple neighboring pixels in space or time, such operations reduce the effective spatial or temporal resolution that can be achieved. We have developed a computational postprocessing technique to restore image sequences of cyclically moving structures that preserves frame rate and spatial resolution. The signal-to-noise ratio (SNR) is improved by ...
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    23. In vivo imaging of the cyclic changes in cross-sectional shape of the ventricular segment of pulsating embryonic chick hearts at stages 14 to 17: A contribution to the understanding of the ontogenesis of cardiac pumping function

      The cardiac cycle-related deformations of tubular embryonic hearts were traditionally described as concentric narrowing and widening of a tube of circular cross-section. Using optical coherence tomography (OCT), we have recently shown that, during the cardiac cycle, only the myocardial tube undergoes concentric narrowing and widening while the endocardial tube undergoes eccentric narrowing and widening, having an elliptic cross-section at end-diastole and a slit-shaped cross-section at end-systole. Due to technical limitations, these analyses were confined to early stages of ventricular development (chick embryos, stages 10-13). Using a modified OCT-system, we now document, for the first time, the cyclic changes in cross-sectional ...
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    24. Manual-scanning optical coherence tomography probe based on position tracking

      Manual-scanning optical coherence tomography probe based on position tracking
      A method based on position tracking to reconstruct images for a manual-scanning optical coherence tomography (OCT) probe is proposed and implemented. The method employs several feature points on a hand-held probe and a camera to track the device’s pose. The continuous device poses tracking, and the collected OCT depth scans can then be combined to render OCT images. The tracking accuracy of the system was characterized to be about 6 um along two axes and 19 um along the third. A phantom target was used to validate the method. In addition, we report OCT images of a 54-stage Xenopus ...
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    193-216 of 246 « 1 2 ... 6 7 8 9 10 11 »
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