Search results for "Photoreceptor Cells"
showing 10 items of 99 documents
The cGMP-gated channel of the rod photoreceptor — a new type of channel structure?
1990
Recents findings from Numa's laboratory reveal that there might exist a wider variety in channel protein structure than originally anticipated. Recently, the cloning has been reported of the first cGMP-gated ion channel, the vertebrate rod photoreceptor which is activated by cGMP acting from the inside of the rod outer segment membrane
Deletion of myosin VI causes slow retinal optic neuropathy and age-related macular degeneration (AMD)-relevant retinal phenotype
2015
The unconventional myosin VI, a member of the actin-based motor protein family of myosins, is expressed in the retina. Its deletion was previously shown to reduce amplitudes of the a- and b-waves of the electroretinogram. Analyzing wild-type and myosin VI-deficient Snell’s Waltzer mice in more detail, the expression pattern of myosin VI in retinal pigment epithelium, outer limiting membrane, and outer plexiform layer could be linked with differential progressing ocular deficits. These encompassed reduced a-waves and b-waves and disturbed oscillatory potentials in the electroretinogram, photoreceptor cell death, retinal microglia infiltration, and formation of basal laminar deposits. A pheno…
Analysis of the human a-wave ERG component
2006
The a-wave is one of the main issues of research in the field of ocular electrophysiology, since it is strictly connected with early photoreceptoral activities. The present study proposes mathematical methods that analyse this component in human subjects, and supports experimental evidence relating to possible correlations among the responses of photoreceptoral units under a light stimulus. The investigation is organized in two parts: the first part concerns the onset and the initial slope, up to the first minimum (about 10-15 ms), the second part deals with the main portion of the wave, up to about 30 ms. In both cases, the a-waves, recorded at various levels of luminance, have been fitted…
Calcium-Dependent Assembly of Centrin-G-Protein Complex in Photoreceptor Cells
2002
Photoexcitation of rhodopsin activates a heterotrimeric G-protein cascade leading to cyclic GMP hydrolysis in vertebrate photoreceptors. Light-induced exchanges of the visual G-protein transducin between the outer and inner segment of rod photoreceptors occur through the narrow connecting cilium. Here we demonstrate that transducin colocalizes with the Ca(2+)-binding protein centrin 1 in a specific domain of this cilium. Coimmunoprecipitation, centrifugation, centrin overlay, size exclusion chromatography, and kinetic light-scattering experiments indicate that Ca(2+)-activated centrin 1 binds with high affinity and specificity to transducin. The assembly of centrin-G-protein complex is medi…
Photoreceptors, lightness constancy and color vision.
1986
Rod-cone based color vision in seals under photopic conditions
2016
Marine mammals have lost the ability to express S-cone opsin, and possess only one type of M/L-cone in addition to numerous rods. As they are cone monochromats they should be color blind. However, early behavioral experiments with fur seals and sea lions indicated discrimination ability between many shades of grey and blue or green. On the other hand, most recent training experiments with harbor seals under "mesopic" conditions demonstrated rod based color blindness (Scholtyssek et al., 2015). In our experiments we trained two harbor seals (Phoca vitulina) and two South African fur seals (Arctocephalus pusillus) with surface colors under photopic conditions. The seals had to detect a triang…
Melanocortin receptor agonists MCR1-5protect photoreceptors from high-glucose damage and restore antioxidant enzymes in primary retinal cell culture
2016
Retinal photoreceptors are particularly vulnerable to local high-glucose concentrations. Oxidative stress is a risk factor for diabetic retinopathy development. Melanocortin receptors represent a family of G-protein-coupled receptors classified in five subtypes and are expressed in retina. Our previous data indicate that subtypes 1 and 5 receptor agonists exert a protective role on experimental diabetic retinopathy. This study focuses on their role in primary retinal cell cultures in high-glucose concentrations. After eye enucleation from wild-type male C57BL/6 mice, retinal cells were isolated, plated in high-glucose concentration and treated with melanocortin receptors 1 and 5 agonists an…
Effects of Presynaptic Mutations on a Postsynaptic Cacna1s Calcium Channel Colocalized with mGluR6 at Mouse Photoreceptor Ribbon Synapses
2008
Purpose Photoreceptor ribbon synapses translate light-dependent changes of membrane potential into graded transmitter release via L-type voltage-dependent calcium channel (VDCC) activity. Functional abnormalities (e.g., a reduced electroretinogram b-wave), arising from mutations of presynaptic proteins, such as Bassoon and the VDCCalpha1 subunit Cacna1f, have been shown to altered transmitter release. L-type VDCCalpha1 subtype expression in wild-type and mutant mice was examined, to investigate the underlying pathologic mechanism. Methods Two antisera against Cacna1f, and a Cacna1f mouse mutant (Cacna1fDeltaEx14-17) were generated. Immunocytochemistry for L-type VDCCalpha1 subunits and addi…
Ribbon synapses of the mammalian retina contain two types of synaptic bodies--ribbons and spheres.
1989
The present paper reports that the synaptic bodies of the retinal ribbon synapses in rat, guinea pig, golden hamster and mouse are a heterogeneous population of organelles. In addition to the well-known synaptic ribbons sensu stricto which consist of a platelike electron-dense central structure surrounded by electron-lucent synaptic vesicles, there are what is termed synaptic spheres, in which the core is not platelike, but round to oval. In rat retinae procured at day, ribbons outnumbered spheres by a factor of 4. At night spheres were not seen in photoreceptor cells. Spheres, like ribbons, may lie some distance from the synaptic site, perhaps indicating transit from their site of origin t…
Strain differences in the ratio of synaptic body types in photoreceptors of the rat retina.
1993
In the retinal outer plexiform layer of seven different rat strains, synaptic bodies (SB) were counted and, according to their morphology, characterized as synaptic ribbons (SR), synaptic spheres (SS) or intermediate structures. It was found that absolute SB numbers showed relatively small variations while SR/SS ratios differed considerably between the strains investigated. These results are discussed with respect to retinal pigmentation and to formation and degradation, respectively, of synaptic ribbons.