1. Articles in category: Developmental Biology

    217-240 of 249 « 1 2 ... 7 8 9 10 11 »
    1. 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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    2. 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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    3. 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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    4. 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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    5. 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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    6. 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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    7. 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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    8. 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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    9. 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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    10. 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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    11. 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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    12. 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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    13. Hemodynamic measurements from individual blood cells in early mammalian embryos with Doppler swept source OCT

      Hemodynamic measurements from individual blood cells in early mammalian embryos with Doppler swept source OCT
      The most common and lethal birth defects affect the cardiovascular (CV) system. The mouse is a superior model for identifying and understanding mammalian CV birth defects, but there is a great need for tools that can detect early and subtle deficiencies in cardiac function in mouse embryos. We combined swept source optical coherence tomography (SS-OCT) with live mouse embryo culture protocols to generate structural two-dimensional and three-dimensional imaging and hemodynamic measurements in a live 8.5 day embryo just a few hours after the beginning of a heartbeat. Our data show that individual circulating blood cells can be visualized with ...
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    14. Quantitative Measurement of Blood Flow Dynamics in Embryonic Vasculature Using Spectral Doppler Velocimetry

      The biophysical effects of blood flow are known to influence the structure and function of adult cardiovascular systems. Similar effects on the maturation of the cardiovascular system have been difficult to directly and non-invasively measure due to the small size of the embryo. Optical coherence tomography (OCT) has been shown to provide high spatial and temporal structural imaging of the early embryonic chicken heart. We have developed an extension of Doppler OCT, called spectral Doppler velocimetry (SDV), that will enable direct, non-invasive quantification of blood flow and shear rate from the early embryonic cardiovascular system. Using this technique, we calculated ...
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    15. Optical coherence tomography captures embryonic heart dynamics

      Optical coherence tomography captures embryonic heart dynamics
      An advanced imaging technique has both the spatial and temporal resolution to investigate the developing heart in important animal models such as chicks and mice. In studying the mechanisms that drive early heart formation, researchers rely primarily on static methods such as histology and immunohistochemistry. During cardiac looping, the minuscule heart transforms from a tubular form to a four-chambered heart, a complex process which relies upon mechanical stresses from the functioning heart for feedback. Optical coherence tomography (OCT) imaging emdash a sophisticated, noninvasive technique that can capture detailed images of biological tissue by measuring optical scattering emdash offers the ability ...
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    16. Sequential en-face optical coherence tomography imaging and monitoring of Drosophila Melanogaster larval heart

      This article demonstrates two modalities to acquire information on cardiac function in larval Drosophila Melanogaster: in-vivo imaging and heartbeat monitoring. To achieve these goals a dedicated imaging instrument able to provide simultaneous en-face Optical Coherence Tomography (OCT) and Laser Sca ... [Proc. SPIE 7168, 71680G (2009)] published Thu Feb 19, 2009.
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    17. Imaging of cardiovascular dynamics in early mouse embryos with swept source optical coherence tomography

      Imaging of cardiovascular dynamics in early mouse embryos with swept source optical coherence tomography
      Congenital cardiovascular defects are very common, occurring in 1% of live births, and cardiovascular failures are the leading cause of birth defect-related deaths in infants. To improve diagnostics, prevention and treatment of cardiovascular abnormalities, we need to understand not only how cells f ... [Proc. SPIE 7168, 71680E (2009)] published Thu Feb 19, 2009.
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    18. A new method for detection and quantification of heartbeat parameters in Drosophila, zebrafish, and embryonic mouse hearts

      The genetic basis of heart development is remarkably conserved from Drosophila to mammals, and insights from flies have greatly informed our understanding of vertebrate heart development. Recent evidence suggests that many aspects of heart function are also conserved and the genes involved in heart development also play roles in adult heart function. We have developed a Drosophila heart preparation and movement analysis algorithm that allows quantification of functional parameters. Our methodology combines high-speed optical recording of beating hearts with a robust, semi-automated analysis to accurately detect and quantify, on a beat-to-beat basis, not only heart rate but also diastolic and ...
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    19. Real-time in vivo imaging of adult Zebrafish brain using optical coherence tomography

      Real-time in vivo imaging of adult Zebrafish brain using optical coherence tomography

      We report noninvasive imaging of the brain of adult Zebrafish (Danio rerio) using real time optical coherence tomography (OCT) capable of acquiring cross sectional 2D OCT images @ 8 frames/sec. Anatomic features such as telencephalon, tectum opticum, eminentia Granularis and cerebellum were clearly resolved in the OCT images. A 3D model of Zebrafish brain was reconstructed, for the first time to our knowledge, using these 2D OCT images.

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    20. Live imaging of blood flow in mammalian embryos using Doppler swept-source optical coherence tomography

      Live imaging of blood flow in mammalian embryos using Doppler swept-source optical coherence tomography

      Studying hemodynamic changes during early mammalian embryonic development is critical for further advances in prevention, diagnostics, and treatment of congenital cardiovascular (CV) birth defects and diseases. Doppler optical coherence tomography (OCT) has been shown to provide sensitive measurements of blood flow in avian and amphibian embryos. We combined Doppler swept-source optical coherence tomography (DSS-OCT) and live mouse embryo culture to analyze blood flow dynamics in early embryos. SS-OCT structural imaging was used for the reconstruction of embryo morphology and the orientation of blood vessels, which is required for calculating flow velocity from the Doppler measurements. Spatially and temporally resolved blood ...

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    21. Repeated, noninvasive, high resolution spectral domain optical coherence tomography imaging of zebrafish embryos

      Repeated, noninvasive, high resolution spectral domain optical coherence tomography imaging of zebrafish embryos
      Abstract Purpose: To demonstrate a new imaging method for high resolution spectral domain optical coherence tomography (SD-OCT) for small animal developmental imaging. Methods: Wildtype zebrafish that were 24, 48, 72, and 120 h post fertilization (hpf) and nok gene mutant (48 hpf) embryos were imaged in vivo. Three additional embryos were imaged twice, once at 72 hpf and again at 120 hpf. Images of the developing eye, brain, heart, whole body, proximal yolk sac, distal yolk sac, and tail were acquired. Three-dimensional OCT data sets (501×180 axial scans) were obtained as well as oversampled frames (8,100 axial scans ...
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    22. Michelson Diagnostics Diversifies into Non-Medical Market

      Michelson Diagnostics Diversifies into Non-Medical Market
      Reacting to strong customer demand, Michelson Diagnostics Ltd (MDL) is broadening the commercial application of its unique 'multibeam' Optical Coherence Tomography (OCT) technology into markets outside its core target of cancer diagnosis. These include such diverse areas as industrial metrology, product inspection, tissue engineering and developmental biology. "We are reacting to customers who have realised that the superior image definition provided by our patented multi-beam OCT technology is very advantageous in their applications", said MDL CEO Jon Holmes. "For a given depth of focus, you get twice the resolution, (or, for a given resolution, four times the focal depth), compared ...
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    23. Dynamic variation of hemodynamic shear stress on the walls of developing chick hearts: computational models of the heart outflow tract

      Abstract  Heart morphogenesis and growth are influenced by hemodynamic forces (wall shear stress and blood pressure) acting on the walls of the heart. Mechanisms by which hemodynamic forces affect heart development are not well understood, in part because of difficulties involved in measuring these forces in vivo. In this paper, we show how wall shear stress in the heart outflow tract (OFT) of chick embryos at an early developmental stage (HH18) are affected by changes in the geometry and motion of the OFT wall. In particular, we were interested in the effects of cardiac cushions, which are protrusions of the ...
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    24. Dual-beam Fourier domain optical Doppler tomography of zebrafish

      Dual-beam Fourier domain optical Doppler tomography of zebrafish

      We have developed a dual-beam Fourier domain optical Doppler tomography (FD-ODT) system to image zebrafish (Danio rerio) larvae. Two beams incident on the zebrafish with a fixed angular separation allow absolute blood flow velocity measurement to be made regardless of vessel orientation in a ... [Opt. Express 16, 13624-13636 (2008)]

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    217-240 of 249 « 1 2 ... 7 8 9 10 11 »
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