Browsing by Subject "Eye"
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Item Complex eye formation in the squid Doryteuthis pealeii and its evolutionary implications(2015-12) Koenig, Kristen Marie; Gross, Jeffrey Martin; Marcotte, Edward M.; Juenger, Thomas; Zakon, Harold; Stein, DavidPhotoreception is a ubiquitous sensory ability found across the Metazoa, and photoreceptive organs are intricate and diverse in their structure. While the morphology of the compound eye in Drosophila and the single-chambered eye in vertebrates have elaborated independently, the amount of conservation within the “eye” gene regulatory network remains controversial with few taxa studied. To better understand the evolution of photoreceptive organs, we established the cephalopod, Doryteuthis pealeii, as a Lophotrochozoan model for eye development. Utilizing histological, transcriptomic and molecular assays we characterize eye formation in Doryteuthis pealeii. Through lineage tracing and gene expression analyses, we demonstrate that cells expressing Pax and Six genes incorporate into the lens, cornea and iris. Functional assays demonstrate that Notch signaling is required for photoreceptor cell formation and retina organization. This comparative approach places the canon of eye research in traditional models into perspective, highlighting complexity as a result of conserved or convergent mechanisms.Item Laser-induced heating, phase-shift, and damage : measurements and simulations(2011-05) Condit, Jonathan Christopher; Rylander, H. Grady (Henry Grady), 1948-; Milner, Thomas E.This research was a collaborative effort between the Air Force Research Laboratory (AFRL) and the University of Texas at Austin to study laser induced thermal lensing. Analysis with a high-frame rate thermal camera system in an optical cuvette determined rates of heating and cooling in water exposed to 1200, 1310 and 1318-nm wavelengths. Thermal modeling software (BTEC) developed at AFRL was used to simulate the beam parameters that were used experimentally. The simulation was also used to compute axial temperature for various power levels, beam diameters, and pulse durations. Laser-induced optical pathlength modulation or phase-shift was computed to study the thermal lensing effect. Power and irradiance damage thresholds were calculated for collimated and focused geometries to study the effect in a focusing eye on retinal damage thresholds.Item The roles of mab21l2 in development of the eye(2019-07-23) Gath, Natalie Nicole; Vokes, Steven Alexander; Gross, Jeffrey Martin; Agarwala, Seema; Matouschek, Andreas; Stein, DavidMutations in MAB21L2 result in severe ocular defects including microphthalmia, anophthalmia, coloboma, microcornea, and cataracts. The molecular and cellular underpinnings of these defects are unknown, as is the normal cellular function of MAB21L2. Zebrafish mab21l2 [superscript au10] mutants possess ocular defects resembling those in humans with MAB21L2 mutations, providing an excellent model to characterize mab21l2 functions during eye development. mab21l2 [superscript -/-] mutants possessed a host of ocular defects including microphthalmia and colobomas as well as small, disorganized lenses and cornea dysgenesis. Decreased proliferation, increased cell death, and defects in marker gene expression were detected in the lens. Cell death in the optic stalk was elevated in mab21l2 [superscript -/-] mutants and the basement membrane between the edges of the choroid fissure failed to break down. Neuronal differentiation in the retina was normal, however. mab21l2 [superscript -/-] mutant corneas were disorganized, possessed an increased number of cells, some of which proliferated ectopically, and failed to differentiate the corneal stroma. Human mutant MAB21L2 [superscript R51C] and MAB21L2 [superscript R51H] mRNAs possessed dominant negative function, inducing colobomas in wild type fish. Yeast-2-hybrid assays provided potential binding partners for the function of mab21l2, including transcription factors and actin/myosin related proteins. mab21l2 function is required for morphogenesis and cell survival in the lens and optic cup, and basement membrane breakdown in the choroid fissure. mab21l2 function also regulates proliferation in the lens and cornea; in its absence, the lens is small and mispatterned, and corneal morphogenesis and patterning are also disrupted. mab21l2 protein function may involve transcriptional regulation or control of cell shape and movement.Item Thermal lensing in ocular media(2009-05) Vincelette, Rebecca Lee; Welch, Ashley J., 1933-; Rockwell, Benjamin A.This research was a collaborative effort between the Air Force Research Laboratory (AFRL) and the University of Texas to examine the laser-tissue interaction of thermal lensing induced by continuous-wave, CW, near-infrared, NIR, laser radiation in the eye and its influence on the formation of a retinal lesion from said radiation. CW NIR laser radiation can lead to a thermal lesion induced on the retina given sufficient power and exposure duration as related to three basic parameters; the percent of transmitted energy to, the optical absorption of, and the size of the laser-beam created at the retina. Thermal lensing is a well-known phenomenon arising from the optical absorption, and subsequent temperature rise, along the path of the propagating beam through a medium. Thermal lensing causes the laser-beam profile delivered to the retina to be time dependent. Analysis of a dual-beam, multidimensional, high-frame rate, confocal imaging system in an artificial eye determined the rate of thermal lensing in aqueous media exposed to 1110, 1130, 1150 and 1318-nm wavelengths was related to the power density created along the optical axis and linear absorption coefficient of the medium. An adaptive optics imaging system was used to record the aberrations induced by the thermal lens at the retina in an artificial eye during steady-state. Though the laser-beam profiles changed over the exposure time, the CW NIR retinal damage thresholds between 1110-1319-nm were determined to follow conventional fitting algorithms which neglected thermal lensing. A first-order mathematical model of thermal lensing was developed by conjoining an ABCD beam propagation method, Beer's law of attenuation, and a solution to the heat-equation with respect to radial diffusion. The model predicted that thermal lensing would be strongest for small (< 4-mm) 1/e² laser-beam diameters input at the corneal plane and weakly transmitted wavelengths where less than 5% of the energy is delivered to the retina. The model predicted thermal lensing would cause the retinal damage threshold for wavelengths above 1300-nm to increase with decreasing beam-diameters delivered to the corneal plane, a behavior which was opposite of equivalent conditions simulated without thermal lensing.