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Annals of Biomedical Engineering 2002Similarities between photoreceptor Kx channels and EAG and KCNQ channels suggest that the Kx channel may be related to one or both of these families of potassium...
Similarities between photoreceptor Kx channels and EAG and KCNQ channels suggest that the Kx channel may be related to one or both of these families of potassium channels. To provide a basis for further comparison of these channels, as well as to reveal the role of zinc (endogenously present in photoreceptors) in Kx channel modulation, we studied the effects of divalent cations on activation and kinetic properties of the noninactivating potassium current, I(Kx), in salamander rod photoreceptors. We found that divalent cations slowed the activation of I(Kx) and shifted its activation curve to positive potentials, effects attributable to surface charge screening. The effect of zinc on I(Kx) kinetics was considerably stronger than that expected from the activation curve shift alone. None of the divalent ions studied changed the monoexponential nature of I(Kx) activation. A simple model of a rod photoreceptor was created using NEURON software. In the model, zinc accelerated and sharpened the light response, broadening the frequency response of rod photoreceptors. Our results show that although the overall effects of divalent cations are in part due to surface charge screening effects, zinc also induced a specific change in I(Kx) activation kinetics, and this action profoundly alters rod response properties.
Topics: Ambystoma; Animals; Biomedical Engineering; Cations, Divalent; Computer Simulation; In Vitro Techniques; Kinetics; Light; Magnesium; Models, Biological; Potassium Channels; Retinal Rod Photoreceptor Cells; Zinc
PubMed: 12502230
DOI: 10.1114/1.1521415 -
Methods in Cell Biology 2015Retina is a neurosensory tissue lining the back of the eye and is responsible for light detection and relaying the signal to the visual cortex in the brain. Mammalian...
Retina is a neurosensory tissue lining the back of the eye and is responsible for light detection and relaying the signal to the visual cortex in the brain. Mammalian retina consists of six major types of neurons (including photoreceptors; rods and cones) and one type of glial cells arranged in distinct layers. Photoreceptors are the most abundant cell types accounting for approximately 60% of all cells in the retina. Owing to their unique structure and function as ciliated neurons and their vast majority, dysfunction and degeneration of photoreceptors is associated with several inherited blindness disorders, such as retinitis pigmentosa, cone-rod degeneration, and age-related macular degeneration. Therefore, it is imperative to examine the structure and function of photoreceptors so that better understanding of the pathogenesis of associated diseases can be obtained for designing therapeutic modalities. In this chapter, we will provide detailed methods for analyzing photoreceptor function (electroretinography), structure, and biochemical analysis of sensory cilia of photoreceptors using mammalian retina as model system. These methods are widely used to assess photoreceptor development and degeneration during disease.
Topics: Animals; Cilia; Electrophysiological Phenomena; Electroretinography; Mice; Mice, Inbred C57BL; Microscopy, Electron, Transmission; Retina; Retinal Cone Photoreceptor Cells; Retinal Rod Photoreceptor Cells; Staining and Labeling
PubMed: 25837387
DOI: 10.1016/bs.mcb.2014.12.005 -
Investigative Ophthalmology & Visual... Mar 2000All-trans retinoic acid (ATRA) or 9-cis retinoic acid (9CRA), added to dissociated developing neural retinal cells, induces progenitor cells to adopt the rod cell's...
PURPOSE
All-trans retinoic acid (ATRA) or 9-cis retinoic acid (9CRA), added to dissociated developing neural retinal cells, induces progenitor cells to adopt the rod cell's fate. Retinoic acid (RA) also produces apoptotic cell death in developing tissues. The effects of retinoids on mouse retinal development were examined.
METHODS
Retinas were explanted on postnatal day (PN)1 and cultured with or without the retinal pigment epithelium (RPE) attached. Retinas were cultured for 3 weeks in the absence or presence of 100 or 500 nM ATRA or 9CRA. Morphologic development and apoptotic cell death were examined using cell-specific immunocytochemical markers, the TdT-dUTP terminal nick-end labeling (TUNEL) method, and a caspase assay.
RESULTS
Retinal explants, with and without RPE, had similar age-dependent increases in opsin expression. In contrast, explants with RPE had less apoptosis during the first week than retinas without RPE. In explants with RPE, ATRA or 9CRA produced rod-selective apoptotic cell death in which 20% to 25% were lost by PN7 with no further loss by PN21. 9CRA-treated explants without RPE had a decreased number of apoptotic cells and a higher number of (rhod)opsin-positive cells at PN3.
CONCLUSIONS
Factors in RPE appear to regulate rod apoptosis in developing retina. Retinoids produce rod-selective apoptotic cell death during normal rod differentiation. In contrast, retinoids accelerate the expression of opsin in retinas without RPE. These differential effects of RA on rod photoreceptors-apoptosis and differentiation-are similar to those observed in other developing tissues and play an important role in both normal and pathologic development.
Topics: Animals; Apoptosis; Caspases; Cell Count; Cell Differentiation; Fluorescent Antibody Technique, Indirect; Glial Fibrillary Acidic Protein; Immunoenzyme Techniques; In Situ Nick-End Labeling; Mice; Mice, Inbred C3H; Organ Culture Techniques; Pigment Epithelium of Eye; Retina; Retinal Rod Photoreceptor Cells; Rod Opsins; Tretinoin
PubMed: 10711716
DOI: No ID Found -
Cell Apr 2009We show that the nuclear architecture of rod photoreceptor cells differs fundamentally in nocturnal and diurnal mammals. The rods of diurnal retinas possess the...
We show that the nuclear architecture of rod photoreceptor cells differs fundamentally in nocturnal and diurnal mammals. The rods of diurnal retinas possess the conventional architecture found in nearly all eukaryotic cells, with most heterochromatin situated at the nuclear periphery and euchromatin residing toward the nuclear interior. The rods of nocturnal retinas have a unique inverted pattern, where heterochromatin localizes in the nuclear center, whereas euchromatin, as well as nascent transcripts and splicing machinery, line the nuclear border. The inverted pattern forms by remodeling of the conventional one during terminal differentiation of rods. The inverted rod nuclei act as collecting lenses, and computer simulations indicate that columns of such nuclei channel light efficiently toward the light-sensing rod outer segments. Comparison of the two patterns suggests that the conventional architecture prevails in eukaryotic nuclei because it results in more flexible chromosome arrangements, facilitating positional regulation of nuclear functions.
Topics: Animals; Animals, Outbred Strains; Biological Evolution; Cell Differentiation; Cell Nucleus; Euchromatin; Heterochromatin; Histones; Mammals; Mice; Mice, Inbred C57BL; Retina; Retinal Rod Photoreceptor Cells; Vision, Ocular
PubMed: 19379699
DOI: 10.1016/j.cell.2009.01.052 -
The Journal of Veterinary Medical... Mar 2018Owl monkeys are the only one species possessing the nocturnal lifestyles among the simian monkeys. Their eyes and retinas have been interested associating with the...
Owl monkeys are the only one species possessing the nocturnal lifestyles among the simian monkeys. Their eyes and retinas have been interested associating with the nocturnal adaptation. We examined the cellular specificity and electroretinogram (ERG) reactivity in the retina of the owl monkeys by comparison with the squirrel monkeys, taxonomically close-species and expressing diurnal behavior. Owl monkeys did not have clear structure of the foveal pit by the funduscope, whereas the retinal wholemount specimens indicated a small-condensed spot of the ganglion cells. There were abundant numbers of the rod photoreceptor cells in owl monkeys than those of the squirrel monkeys. However, the owl monkeys' retina did not possess superiority for rod cell-reactivity in the scotopic ERG responses. Scanning electron microscopic observation revealed that the rod cells in owl monkeys' retina had very small-sized inner and outer segments as compared with squirrel monkeys. Owl monkeys showed typical nocturnal traits such as rod-cell dominance. However, the individual photoreceptor cells seemed to be functionally weak for visual capacity, caused from the morphological immaturity at the inner and outer segments.
Topics: Animals; Aotidae; Electroretinography; Female; Male; Microscopy, Electron, Scanning; Night Vision; Ophthalmoscopes; Photoreceptor Cells, Vertebrate; Retina; Retinal Rod Photoreceptor Cells; Saimiri
PubMed: 29375079
DOI: 10.1292/jvms.17-0418 -
Perception 2008
Topics: Animals; Color Perception; Humans; Retina; Retinal Pigments; Retinal Rod Photoreceptor Cells
PubMed: 19065851
DOI: 10.1068/p3710ed -
Investigative Ophthalmology & Visual... Oct 2003Retinal circadian signals may have a role in maintaining the normal function and health of photoreceptors. Melatonin is an output of the retinal circadian oscillator and...
PURPOSE
Retinal circadian signals may have a role in maintaining the normal function and health of photoreceptors. Melatonin is an output of the retinal circadian oscillator and provides nocturnal signaling that is mediated through specific G-protein-coupled receptors. Melatonin receptors are expressed in retinal photoreceptor cells, and this study was undertaken to test the hypothesis that melatonin directly increases photoreceptor responses through melatonin receptors.
METHODS
Transgenic Xenopus laevis frogs were generated using a DNA construct containing a Xenopus opsin promoter driving expression of a melatonin Mel(1c) receptor-green fluorescent protein (GFP) fusion protein (XOP-MEL(1c)-GFP). Electroretinogram (ERG) analysis on transgenic and normal tadpole eyes was performed in response to melatonin treatment, and the eyes were subsequently examined by confocal microscopy and GFP immunocytochemistry.
RESULTS
XOP-MEL(1c)-GFP transgenic frogs demonstrated GFP immunoreactivity in rod photoreceptor inner segments throughout the retina, indicating the rod-specific expression of the Mel(1c)-GFP fusion protein. ERG analysis of transgenic tadpole eyes showed that 1 to 100 nM melatonin increased the a- and b-wave amplitudes. Control transgenic (XOP-GFP) and normal frogs exhibited only modest ERG responses to 100-nM melatonin treatment. The effect of melatonin on a- and b-wave amplitudes in XOP-MEL(1c)-GFP transgenic frogs was dose dependent, with ERG responses occurring at physiological concentrations.
CONCLUSIONS
The results suggest that melatonin, acting through Mel(1c) receptors on rod photoreceptor membranes, directly stimulates the responsiveness of rod photoreceptors to light. This supports the hypothesis that melatonin acts both as an intracrine and paracrine circadian signal of darkness, and binds to specific receptors in photoreceptors and other retinal cells to increase visual sensitivity.
Topics: Animals; Animals, Genetically Modified; Circadian Rhythm; Dose-Response Relationship, Drug; Electroretinography; Fluorescent Antibody Technique, Indirect; Green Fluorescent Proteins; Luminescent Proteins; Melatonin; Microscopy, Confocal; Photic Stimulation; Receptors, Cell Surface; Receptors, Cytoplasmic and Nuclear; Receptors, Melatonin; Recombinant Fusion Proteins; Retinal Rod Photoreceptor Cells; Xenopus laevis
PubMed: 14507901
DOI: 10.1167/iovs.03-0329 -
Scientific Reports Jul 2020The intrinsic and extrinsic factors that regulate vertebrate photoreceptor specification and differentiation are complex, and our understanding of all the players is far...
The intrinsic and extrinsic factors that regulate vertebrate photoreceptor specification and differentiation are complex, and our understanding of all the players is far from complete. Her9, the zebrafish ortholog of human HES4, is a basic helix-loop-helix-orange transcriptional repressor that regulates neurogenesis in several developmental contexts. We have previously shown that her9 is upregulated during chronic rod photoreceptor degeneration and regeneration in adult zebrafish, but little is known about the role of her9 during retinal development. To better understand the function of Her9 in the retina, we generated zebrafish her9 CRISPR mutants. Her9 homozygous mutants displayed striking retinal phenotypes, including decreased numbers of rods and red/green cones, whereas blue and UV cones were relatively unaffected. The reduction in rods and red/green cones correlated with defects in photoreceptor subtype lineage specification. The remaining rods and double cones displayed abnormal outer segments, and elevated levels of apoptosis. In addition to the photoreceptor defects, her9 mutants also possessed a reduced proliferative ciliary marginal zone, and decreased and disorganized Müller glia. Mutation of her9 was larval lethal, with no mutants surviving past 13 days post fertilization. Our results reveal a previously undescribed role for Her9/Hes4 in photoreceptor differentiation, maintenance, and survival.
Topics: Animals; Animals, Genetically Modified; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; Cell Proliferation; Neurogenesis; Retinal Cone Photoreceptor Cells; Retinal Rod Photoreceptor Cells; Zebrafish; Zebrafish Proteins
PubMed: 32647335
DOI: 10.1038/s41598-020-68172-2 -
Vision Research May 2009The bandpass filtering properties of a rod network were studied via computer simulations. Sinusoidal current stimuli were applied to a single rod model to characterize...
The bandpass filtering properties of a rod network were studied via computer simulations. Sinusoidal current stimuli were applied to a single rod model to characterize its temporal filtering properties. The simulated frequency response revealed that a single rod behaves as a bandpass filter whose characteristics are affected by the stimulus strength and frequency. We analyzed the contribution of individual ionic currents to bandpass filtering and found that the filtering of small signals is largely regulated by the calcium-dependent currents I(K(Ca)) and I(Cl(Ca)), whereas the filtering of large signals is regulated by the hyperpolarization-activated current, I(h). Furthermore, rod network modeling by electrically interconnecting the single rod models revealed that the acceleration of signals that spread laterally through the rod network is attributed to I(K(Ca)) and not I(h).
Topics: Animals; Computer Simulation; Ion Channels; Membrane Potentials; Models, Neurological; Nerve Net; Photic Stimulation; Retinal Rod Photoreceptor Cells
PubMed: 19281836
DOI: 10.1016/j.visres.2009.03.003 -
Biochimica Et Biophysica Acta.... Oct 2017The light-sensing rod photoreceptor cell exhibits several adaptations in response to the lighting environment. While adaptations to short-term changes in lighting...
The light-sensing rod photoreceptor cell exhibits several adaptations in response to the lighting environment. While adaptations to short-term changes in lighting conditions have been examined in depth, adaptations to long-term changes in lighting conditions are less understood. Atomic force microscopy was used to characterize the structure of rod outer segment disc membranes, the site of photon absorption by the pigment rhodopsin, to better understand how photoreceptor cells respond to long-term lighting changes. Structural properties of the disc membrane changed in response to housing mice in constant dark or light conditions and these adaptive changes required output from the phototransduction cascade initiated by rhodopsin. Among these were changes in the packing density of rhodopsin in the membrane, which was independent of rhodopsin synthesis and specifically affected scotopic visual function as assessed by electroretinography. Studies here support the concept of photostasis, which maintains optimal photoreceptor cell function with implications in retinal degenerations.
Topics: Animals; Cell Membrane; Environment; Light; Membranes; Mice; Microscopy, Atomic Force; Retinal Degeneration; Retinal Rod Photoreceptor Cells; Rhodopsin; Rod Cell Outer Segment
PubMed: 28645515
DOI: 10.1016/j.bbamcr.2017.06.013