Publications by authors named "Christopher D Saunter"

Human lens regeneration and the Bag-in-the-Lens (BIL) surgical treatment for cataract both depend upon lens capsule closure for their success. Our studies suggest that the first three days after surgery are critical to their long-term outcomes. Using a rat model of lens regeneration, we evidenced lens epithelial cell (LEC) proliferation increased some 50 fold in the first day before rapidly declining to rates observed in the germinative zone of the contra-lateral, un-operated lens.

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The feeling of hunger or satiety results from integration of the sensory nervous system with other physiological and metabolic cues. This regulates food intake, maintains homeostasis and prevents disease. In C.

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Organ and tissue development are highly coordinated processes; lens growth and functional integration into the eye (emmetropia) is a robust example. An epithelial monolayer covers the anterior hemisphere of the lens, and its organization is the key to lens formation and its optical properties throughout all life stages. To better understand how the epithelium supports lens function, we have developed a novel whole tissue imaging system using conventional confocal light microscopy and a specialized analysis software to produce three-dimensional maps for the epithelium of intact mouse lenses.

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Background And Purpose: The TRPV4 ion channels are Ca permeable, non-selective cation channels that mediate large, but highly localized, Ca signals in the endothelium. The mechanisms that permit highly localized Ca changes to evoke cell-wide activity are incompletely understood. Here, we tested the hypothesis that TRPV4-mediated Ca influx activates Ca release from internal Ca stores to generate widespread effects.

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Article Synopsis
  • Pressure myography is a key technique in vascular research that evaluates the diameter of pressurized arteries to study smooth muscle and endothelial cell activity.
  • The authors have developed VasoTracker, an open-source pressure myograph system and analysis software that can be set up for about 10% of the price of typical commercial systems.
  • VasoTracker includes a user-friendly website providing guidance on assembly and usage, making it an accessible and versatile tool for assessing vascular function.
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The adaptive optics scanning laser ophthalmoscope (AOSLO) was first developed in 2002 and since then the technology has been adopted in several laboratories around the world, for both clinical and psychophysical research. There have been a few major design implementations of the AOSLO. The first used on-axis tilted spherical mirrors in a planar arrangement, and the second minimized the build up of astigmatism present in the first design by using a non-planar arrangement.

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Blood flow, blood clotting, angiogenesis, vascular permeability, and vascular remodeling are each controlled by a large number of variable, noisy, and interacting chemical inputs to the vascular endothelium. The endothelium processes the entirety of the chemical composition to which the cardiovascular system is exposed, carrying out sophisticated computations that determine physiological output. Processing this enormous quantity of information is a major challenge facing the endothelium.

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Endothelial cells are reported to be glycolytic and to minimally rely on mitochondria for ATP generation. Rather than providing energy, mitochondria in endothelial cells may act as signaling organelles that control cytosolic Ca signaling or modify reactive oxygen species (ROS). To control Ca signaling, these organelles are often observed close to influx and release sites and may be tethered near Ca transporters.

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Graded refractive index lenses are inherent to advanced visual systems in animals. By understanding their formation and local optical properties, significant potential for improved ocular healthcare may be realized. We report a novel technique measuring the developing optical power of the eye lens, in a living animal, by exploiting the orthogonal imaging modality of a selective plane illumination microscope (SPIM).

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Aging is the summation of many subtle changes which result in altered cardiovascular function. Impaired endothelial function underlies several of these changes and precipitates plaque development in larger arteries. The endothelium transduces chemical and mechanical signals into changes in the cytoplasmic calcium concentration to control vascular function.

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Stereoscopic 3D (S3D) displays provide an additional sense of depth compared to non-stereoscopic displays by sending slightly different images to the two eyes. But conventional S3D displays do not reproduce all natural depth cues. In particular, focus cues are incorrect causing mismatches between accommodation and vergence: The eyes must accommodate to the display screen to create sharp retinal images even when binocular disparity drives the eyes to converge to other distances.

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Key Points: Age is proposed to be associated with altered structure and function of mitochondria; however, in fully-differentiated cells, determining the structure of more than a few mitochondria at a time is challenging. In the present study, the structures of the entire mitochondrial complements of cells were resolved from a pixel-by-pixel covariance analysis of fluctuations in potentiometric fluorophore intensity during 'flickers' of mitochondrial membrane potential. Mitochondria are larger in vascular myocytes from aged rats compared to those in younger adult rats.

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Agonist-mediated signaling by the endothelium controls virtually all vascular functions. Because of the large diversity of agonists, each with varying concentrations, background noise often obscures individual cellular signals. How the endothelium distinguishes low-level fluctuations from noise and decodes and integrates physiologically relevant information remains unclear.

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Article Synopsis
  • - Mitochondrial shape plays a crucial role in both normal bodily functions and the development of diseases, but measuring their morphology in living cells has been challenging due to their complex structures.
  • - The researchers developed a technique called Flicker-assisted Localization Microscopy (FaLM) to analyze individual mitochondria, allowing for clearer imaging and differentiation of their shapes by utilizing specific fluorophores and advanced camera technology.
  • - Their findings showed that in hypertensive situations, mitochondria tend to be larger and more clustered compared to normotensive conditions, suggesting that changes in mitochondrial architecture could be linked to hypertension.
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  • Increased pressure negatively impacts the endothelial control of vascular tone, but the mechanisms behind pressure sensing and vascular response inhibition are still unclear.
  • A novel imaging technique allows the observation of Ca(2+) signaling in a large number of interconnected endothelial cells within pressurized arteries, revealing that pressure not only alters their shape but also suppresses Ca(2+) signals.
  • The study suggests that the endothelium can sense pressure changes through mechanisms that do not rely on traditional mechanoreceptors, indicating a potential new understanding of vascular mechanotransduction.
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  • The OPT (ordered pull-through) model describes how cell density is distributed in the mammalian lens epithelium, using dimensionless parameters to allow comparisons across different species with varying lens sizes.
  • The model incorporates two key parameters: β/α, which indicates the relative proliferation rates in different lens regions, and γ(GZ), a factor reflecting cell transition from epithelium to lens body, and it validates best-fit values across several mammalian species.
  • The model successfully explains the higher cell density at the lens periphery where proliferation occurs, links the β/α ratio to a crucial survival factor (FGF-2), and predicts age-related changes in cell density, which were confirmed in studies of mouse and human
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In vivo bioluminescent imaging (BLI) is a sensitive and reliable technique for studying gene expression, although experiments must be controlled tightly to obtain reproducible and quantitative measurements. The luciferase reaction depends on the availability of the reaction substrate, oxygen, and ATP, the distribution of which can vary markedly in different tissues. Here we used in vivo fiber optic technology, combined with stereotaxis-assisted surgery, to assess luciferase reaction kinetics in response to 2 anesthetic regimens, isoflurane and ketamine-xylazine.

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We report on a single plane illumination microscope (SPIM) incorporating adaptive optics in the imaging arm. We show how aberrations can occur from the sample mounting tube and quantify the aberrations both experimentally and computationally. A wavefront sensorless approach was taken to imaging a green fluorescent protein (GFP) labelled transgenic zebrafish.

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We demonstrate real-time microscope image gating to an arbitrary position in the cycle of the beating heart of a zebrafish embryo. We show how this can be used for high-precision prospective gating of fluorescence image slices of the moving heart. We also present initial results demonstrating the application of this technique to 3-D structural imaging of the beating embryonic heart.

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The quantitative measurement of particle motion in optical tweezers is an important tool in the study of microrheology and can be used in a variety of scientific and industrial applications. Active microheology, in which the response of optically trapped particles to external driving forces is measured, is particularly useful in probing nonlinear viscoelastic behavior in complex fluids. Currently such experiments typically require independent measurements of the driving force and the trapped particle's response to be carefully synchronized, and therefore the experiments normally require analog equipment.

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Single-particle tracking (SPT) is a range of powerful analysis techniques that measure particle motion from video microscopy image sequences. SPT is used to study the behavior of motor proteins and associated organelle transport within a cell. Many SPT algorithms deliver subpixel accurate measurements with noisy data corresponding to sub-10-nm resolution.

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The apparently stationary phase of mitochondrial motion was investigated in epithelial cells by spinning disk confocal light microscopy combined with image correlation based single particle tracking using custom software producing sub-pixel accuracy measurements (approximately 5 nm) at 10-12 Hz frame-rates. The analysis of these data suggests that the previously described stationary, or anchored phase, in mitochondrial movement actually comprise Brownian diffusion, interspersed with frequent and brief motor-driven events whose duration are stochastically determined. We have therefore discovered a new aspect of mitochondrial behavior, which we call stochastically determined, directed movement.

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