1. Articles in category: Developmental Biology

    193-216 of 237 « 1 2 3 4 5 6 7 8 9 10 »
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. 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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    14. 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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    15. 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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    16. A 3D Video of the Embryonic Heartbeat

      Researchers are using a new imaging technique to study the development of the mammalian heart. One percent of infants in the United States are born with cardiovascular abnormalities. The developmental processes that lead to these congenital problems aren't visible in ultrasound scans, and the lack of tools for imaging mammalian development non-invasively at high resolution has hindered researchers' attempts to understand these processes. In the hopes of providing insights into how these developmental problems might be prevented, researchers at the University of Houston have developed an imaging system they're using to take 3D video of the mammalian heart ...
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    17. Live imaging of rat embryos with Doppler swept-source optical coherence tomography

      Live imaging of rat embryos with Doppler swept-source optical coherence tomography
      The rat has long been considered an excellent system to study mammalian embryonic cardiovascular physiology, but has lacked the extensive genetic tools available in the mouse to be able to create single gene mutations. However, the recent establishment of rat embryonic stem cell lines facilitates the generation of new models in the rat embryo to link changes in physiology with altered gene function to define the underlying mechanisms behind congenital cardiovascular birth defects. Along with the ability to create new rat genotypes there is a strong need for tools to analyze phenotypes with high spatial and temporal resolution. Doppler OCT ...
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    18. Serial Examination of an Inducible and Reversible Dilated Cardiomyopathy in Individual Adult Drosophila

      Recent work has demonstrated that Drosophila can be used as a model of dilated cardiomyopathy, defined as an enlarged cardiac chamber at end-diastole when the heart is fully relaxed and having an impaired systolic function when the heart is fully contracted. Gene mutations that cause cardiac dysfunction in adult Drosophila can result from abnormalities in cardiac development or alterations in post-developmental heart function. To clarify the contribution of transgene expression to post-developmental cardiac abnormalities, we applied strategies to examine the temporal and spacial effects of transgene expression on cardiac function. We engineered transgenic Drosophila based on the well-characterized temperature-sensitive Gal80 ...
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    19. Doppler OCT imaging of cytoplasm shuttle flow in Physarum polycephalum

      The Doppler optical coherence tomography technique was applied to image the oscillatory dynamics of protoplasm in the strands of the plasmodium of slime mould Physarum polycephalum. Radial contractions of the gel-like walls of the strands and the velocity distributions in the sol-like endoplasm streaming along the plasmodial strands are imaged. The motility inhibitor effect of carbon dioxide on the cytoplasm shuttle flow and strand-wall contraction is shown. The optical attenuation coefficient of cytoplasm is estimated.
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    20. Fourier domain optical coherence tomography (FD-OCT) as a non-invasive means for in vivo detection of retinal degeneration in Xenopus laevis tadpoles.

      Purpose: To determine the efficacy of Fourier domain-optical coherence tomography (FD-OCT) as a non-invasive and non-sacrificial method for detecting in vivo, pathological signs of retinal degeneration in Xenopus laevis larvae. Methods: A prototype OCT system using Fourier domain detection customized for tadpole imaging was used to non-invasively 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 histological sections of the same eye. Retinal thickness was measured in the histological micrographs and compared with in vivo measurements acquired with FD-OCT. Results: We obtained in vivo retinal ...
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    21. Ultra-high-resolution full-field optical coherence tomography for imaging of a developing embryo

      Optical coherence tomography (OCT) is a new emerging technique for cross-sectional imaging with high spatial resolution of micrometer scale. It enables in vivo and non-invasive imaging with no need to contact the sample and is widely used in biological and clinic application. In this paper a white-light interference microscope is developed for ultrahigh-resolution full-field optical coherence tomography (Full-Field OCT) to implement 3D imaging of biological tissue. The experimental setup is based on a Linnik-type interferometer illuminated by a tungsten halogen lamp via a bundle of fiber. En-face tomographic images are obtained by demodulation of a combination of interferometric images recorded ...

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    22. Efficient postacquisition synchronization of 4-D nongated cardiac images obtained from optical coherence tomography: application to 4-D reconstruction of the chick embryonic heart

      Four-dimensional (4-D) imaging of the embryonic heart allows study of cardiac morphology and function in vivo during development. However, 4-D imaging of the embryonic heart using current techniques, including optical coherence tomography (OCT), is limited by the rate of image acquisition. Here, we present a nongated 4-D imaging strategy combined with an efficient postacquisition synchronization procedure that circumvents limitations on acquisition rate. The 4-D imaging strategy acquires a time series of images in B mode at several different locations along the heart, rendering out-of-phase image sequences. Then, our synchronization procedure uses similarity of local structures to find the phase shift ...
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    23. Feature Of The Week 7/11/09: High temporal resolution OCT using image-based retrospective gating

      Feature Of The Week 7/11/09: High temporal resolution OCT using image-based retrospective gating
      Feature Of The Week: 7/11/09: Studying abnormalities during heart development in the embryo is crucial for the understanding of congenital heart disease. Our group has been developing specialized OCT-based instruments and software and applying them to the study of the developing heart in avian and mouse models [1-5]. The developing morphology is of interest, but even more interesting is the development of cardiac function, the ability of the heart to contract and pump blood. Several groups have shown that mechanical forces influence the morphogenesis of the developing heart [6-9].
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    24. Real-Time Imaging of Circulating Individual Blood Cells in Mammalian Embryos with Doppler SS-OCT

      Real-Time Imaging of Circulating Individual Blood Cells in Mammalian Embryos with Doppler SS-OCT
      Congenital cardiovascular (CV) defects are present in approximately 1% of live births. Moreover, among deaths due to birth defects, cardiovascular failures are the most likely. Therefore, characterization of mammalian embryonic cardio dynamics and understanding of the hemodynamic changes that occur during embryonic development is crucial for improving diagnostics, prevention, and treatment of cardiovascular defects and diseases. In this work, we combined Swept Source Optical Coherence Tomography (SSOCT) with live mouse embryo culture protocols to generate structural 2-D and 3-D imaging and hemodynamic measurements in live 8.5 day embryos. Our data show that individual circulating blood cells can be visualized ...
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    193-216 of 237 « 1 2 3 4 5 6 7 8 9 10 »
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