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At least 19 recordsLinked to original sources
PubMed1975

Light dependence of osmium reactivity in mouse photoreceptor cells.

Mouse photoreceptor cells exhibit local accumulations of osmium deposits after prolonged osmic staining at slightly elevated temperatures. Deposits were evident along the membranes of outer segment lamellae, Golgi cisternae and vesicles, nuclear envelopes, and synaptic vesicles. Other membranes within the photoreceptor cells were unreactive. No osmium reactivity was seen in other cells of the retina except for osmiophilic outer segment material which had been phagocytized by the pigment epithelium. In the outer segments, inner segments, and synaptic regions of the photoreceptor cells, the amount of osmium reactivity was increased by light stimulation and decreased following extended dark adaptation. The possible significance of the localized osmium reactivity is discussed.

Animals↗
PubMed1978

Limulus ventral eye. Physiological properties of photoreceptor cells in an organ culture medium.

Ventral photoreceptor cells bathed in an organ culture medium typically have resting potentials of -85 mV and membrane resistances of 35 Momega and, when dark-adapted, exhibit large potential fluctuations (LPFs) of 60 mV and small potential fluctuations (SPFs) of less than 30 mV. LPFs appear to be regenerative events triggered by SPFs, the well-known quantum bumps. In the dark, SPFs and LPFs occur spontaneously. At intensities near threshold, the rate of occurrence is directly proportional to light intensity, indicating that SPFs and LPFs are elicited by single photon events. At higher intensities, SPFs and LPFs sum to produce a receptor potential that is graded over approximately a 9-log-unit range of light intensity. Amplitude histograms of the discrete potential waves are bimodal, reflecting the SPF and LPF populations. Histograms of current waves are unimodal. SPFs and LPFs are insensitive to 1 microgram tetrodotoxin. I-V characteristics show initial inward currents of approximately 15 nA for voltage clamps to -40 mV and steady-state outward currents for all clamp potentials. Photoreceptor cells bathed in organ culture medium retain these properties for periods of at least 75 days.

Animals↗
PubMed1976

Enzymic basis for cyclic GMP accumulation in degenerative photoreceptor cells of mouse retina.

The activities of guanylate cyclase, guanosine 3', 5'-monophosphate (cyclic GMP) phosphodiesterase and 5'-nucleotidase were measured during postnatal development in retinas of control and C3H/HeJ mice. In control retina, each of these enzyme activities increases in conjunction with photoreceptor cell differentiation and maturation. In C3H retina, guanylate cyclase and 5-nucleotidase activities increase with photoreceptor cell development and decrease with photoreceptor cell death. However, the activity of a class of cyclic GMP phosphodiesterase which distinguishes the photoreceptor cells of control mice and those of several other species is not demonstrable in retina of C3H mice at any age. It is suggested that the deficiency in cyclic GMP phosphodiesterase activity may account for the accumulation of cyclic GMP which has been shown to occur in the C3H photoreceptor cells before they degenerate.

Aging↗
PubMedDate not supplied

[Electron microscopic study of presumptive photoreceptor cells in the aboral organ of the ctenophore, Beroë cucumis].

Presumptive photoreceptor cells are located in the receptor epithelium of the aboral organ and exhibit some common morphological characters with flagellar photoreceptors of some invertebrates, as well as with photoreceptors of vertebrates. These cells are specifically distinguished by the presence of a special membrane structure in their epinuclear zone, this structure being the derivative of a cilium. Presumptive photoreceptor cells which have a short central projection and form in their basal part the synaptic contacts ("triads") with the adjacent nervous endings, may be classified as pseudosecondary receptor cells. Acetylcholinesterase was found in the synaptic regions. Cytoplasm of the presumptive photoreceptor cells is rich in granular vesicles which contain biogenic amines.

Animals↗
PubMed1979

Characteristics of phospholipids in microvillar membranes of octopus photoreceptor cells.

Characteristics of lipids in the microvillar membranes of octopus photoreceptor cells were studied in order to obtain some information on the membrane environment with rhodopsin in the invertebrate. (1) The membranes contain lipid and protein in almost equal proportion. The majority of lipids are phospholipids. Neutral lipids make up 16% of the total lipids, the major constituent of which is cholesterol. (2) Phosphatidylethanolamine and phosphatidylcholine are the major phospholipids. Phosphatidylserine, ceramide 2-aminoethylphosphonate and sphingomyelin occur as minor components. An unidentified alkaline and acid stable phospholipid was found. (3) The predominant fatty acids of phosphatidylethanolamine and phosphatidylcholine are highly unsaturated such as 22 : 6, 20 : 5 and 20 : 4. The 22 : 6 and 20 : 5 are exclusively linked at the 2-position, but the 20 : 4 is linked significantly at the 1-position of the phospholipids. (4) Major molecular species are 16 : 0/22 : 6 (48.4%) and 16 : 0/20 : 4 (19.6%) in phosphatidylcholine, and 20 : 4/22 : 6 (50.7%) and 16 : 0/22 : 6 (25.6%) in phosphatidylethanolamine.

Animals↗
PubMed1979

A comparison of receptive and non-receptive plasma membrane areas of photoreceptor cells in the leech, Hirudo medicinalis.

Microvillar (receptive) and external (non-receptive) portions of the plasmalemma of photoreceptor cells of Hirudo were compared electron microscopically in thin sections and freeze-fracture replicas. A morphometric approximation showed that the surface area of the microvillar membrane is about 19 times larger than that of the external membrane. The microvillar membrane most probably undergoes extensive membrane turnover. In both segments of the membrane the particles associated with the P- and the E-fracture faces are randomly distributed except at some specific sites. The particles adhere predominantly to the P-faces. The particle densities on the fracture faces of the microvillar membrane differ from those of the external membrane. The P-face particles of the external membrane appear to be larger than those of the microvillar membrane. It is suggested that the P-face particles of the microvillar membrane represent sites where the photopigment is incorporated into the membrane. The distinguishing structural features correspond to the functional differences postulated for both portions of the plasma membrane.

Animals↗
PubMed1978

The dynamic behaviour of photoreceptor cells in the fly in response to random (white noise) stimulation at a range of temperatures.

1. Photoreceptor cells in Calliphora stygia were stimulated with randomly fluctuating green light while the resulting fluctuations in membrane potential were recorded with intracellular micro-electrodes. 2. Fourier analysis was used to obtain the frequency response functions between the light intensity fluctuations and the membrane potential fluctuations at a range of different temperatures. 3. The results show that for small light fluctuations the transducer function can be modelled by a cascade of five identical linear exponential filters whose time constants decrease as the temperature of the cell is increased. 4. The time constants of the linear filters and their rate of change with temperature are similar to the electrical behaviour of cell membranes. However, a series of chemical reactions with similar activation energies could also explain the observed behaviour. 5. Evidence is presented that the total light response is a linear summation of discrete waves of depolarization (bumps), which become longer in duration but of constant area as the temperature is reduced.

Animals↗
PubMed1978

Horizontal cells of the turtle retina. II. Analysis of interconnections between photoreceptor cells and horizontal cells by light microscopy.

Criteria were established whereby the chief and accessory members of double cones, red-, green-, and blue-sensitive single cones, and rods could be distinguished from one another in 1-micrometer sections through the retinas of Pseudemys scripta elegans and Chelydra serpentina. Criteria included the presence of absence of an oil droplet, the size, color, and radial position of the oil droplet, the size and shape of the inner and outer segments, and the shape orientation of the connection between the perikaryon and synaptic terminal of each receptor cell. Using these criteria, the color-specific interconnections between horizontal cells and receptor cells were analyzed using 1-micrometer serial sections through Golgi-stained examples of horizontal cells of each type. The results of this analysis are: (a) H1 cells bodies contact both the red- and green-sensitive members of double cones, as well as red- and green-sensitive single cones. (b) H1 axon terminals contact only the red-sensitive chief members of double cones, red-sensitive single cones, and rods. (c) H2-type cells contact only green- and blue-sensitive single cones. (d) H3-type cells contact only blue-sensitive single cones. (e) H4-type cells contact only the green-sensitive accessory members of double cones. With the exception of H1 cell bodies, all horizontal cells generally contacted every appropriate receptor cell type within their receptive field. A model for the generation of complex horizontal cell light responses is proposed and discussed.

Animals↗
PubMed1977

Cyclic GMP accumulation causes degeneration of photoreceptor cells: simulation of an inherited disease.

Guanosine 3',5'-monophosphate (cyclic GMP) metabolism in developing eye rudiments of Xenopus laevis embryos in culture is disrupted by the phosphodiesterase inhibitor isobutylmethylxanthine. At low concentrations of inhibitor the rudiments develop normally, but at higher concentrations of the inhibitor, cyclic GMP accumulates in the rudiments and the retinal photoreceptor cells degenerate selectively. The isobutylmethylxanthine-induced photoreceptor degeneration is associated with an accumulation of cyclic GMP and, in this respect, it stimulates an early biochemical defect in the inherited degenerative disease of rd mice.

Animals↗
PubMed1979

Subcellular calcium localization and AT0-dependent Ca2+-uptake by smooth endoplasmic reticulum in an invertebrate photoreceptor cell. An ultrastrucutral, cytochemical and X-ray microanalytical study.

In Hirudo medicinalis an extensive and highly elaborate three dimensional network of smooth endoplasmic reticulum cisternae is found in very close structural relationship to the receptive (microvillar) membrane, as reported for many other invertebrates. A variant of the potassium pyroantimonate technique showed that these submicrovillar endoplasmic reticulum cisternae (SMC) and mitochondria are major intracellular calcium stores. Furthermore, using saponine-skinned photoreceptors for an in situ accumulation experiment, calcium oxalate precipitates in SMC demonstrate that this organelle is able to accumulate Ca2+ from a concentration of 2 x 10(-5) M, when ATP, Mg2+, and oxalate ions are present in the accumulation medium. This result provides direct evidence for the hypothesis that SMC may play a particularly important role in the regulation of intracellular ionized calcium in invertebrate photoreceptor cells. Morphological evidence supports this view.

Animals↗
PubMed1979

Renewal of opsin in the photoreceptor cells of the mosquito.

Mosquito rhodopsin is a digitonin-soluble membrane protein of molecular weight 39,000 daltons, as determined by sodium dodecyl sulfate gel electrophoresis. The rhodopsin undergoes a spectral transition from R515-520 to M480 after orange illumination. The visual pigment apoprotein, opsin, is the major membrane protein in the eye. Protein synthesis in the photoreceptor cells occurs in the perinuclear cytoplasm and the newly made protein is transported to the rhabdom. Light adaptation increases the rate of turnover of this rhabdomal protein. The turnover of electrophoretically isolated opsin is also stimulated by light adaptation. The changes observed in protein metabolism biochemically, are consistent with previous morphological observations of photoreceptor membrane turnover. The results agree with the hypothesis that the newly synthesized rhabdomal protein is opsin.

Adaptation, Physiological↗
PubMed1977

Localization of 5-hydroxytryptamine and protein(s) in the secretion granules of the rudimentary photoreceptor cells in the pineal of Lacerta.

In order to localize 5-hydroxytryptamine (5-HT) stores, the pineal organ of Lacerta was examined by electron microscopy following argentaffin and chromaffin reactions. The results obtained with these ultracytochemical reactions were correlated with those obtained previously using the Falck and Hillarp method and electron microscopic radioautography. The secretion granules (diameter: 60-340 nm) of the secretory rudimentary photoreceptor (SRP) cells are the locus of the argentaffin and chromaffin reactions. The reactivity of the granules disappeared after p-CPA or reserpine administration and increased after nialamide injection. From the previous and present results it can be concluded that 5-HT in the pineal organ of Lacerta is stored in the secretion granules of SRP cells and coexists with a proteinaceous and/or possibly a glycoproteinaceous component. Whether this secretion is neurohormonal in nature is still not clear.

Animals↗
PubMed1979

The first optic ganglion of the bee. III. Regional comparison of the morphology of photoreceptor-cell axons.

The nine receptor cells in each ommatidium of the worker bee end as six short visual fibres in the lamina and as three long visual fibres in the medulla. Behavioural and physiological evidence for regional variation in spectral sensitivity prompted observations on the morphology of the visual units. The distribution, branching pattern, diameter and the arrangement of axonal protusions of the characteristic receptor-cell axons were studied in various regions of the lamina. The six short visual fibres and two of the long visual fibres in each laminar cartridge are uniform over the total eye surface. Only the receptor axons of the ninth cell a UV and polarised light-sensitive cell, show obvious regional variation. In view of the regional constancy in morphology of eight of the nine receptor-cell axons, the regional variations in spectral sensitivity demand either functional subdivision of morphologically indistinguishable photoreceptors (e.g., content of different visual pigments) or a highly complex connectivity pattern of their axons in the first optic ganglion.

Animals↗
PubMed1978

Fine structure and radioautography of rabbit photoreceptor cells.

The retina of the adult rabbit contains two types of photoreceptors. Type I predominates and is a typical rod. The identity of the type II cell has been uncertain until now. This study demonstrates that the type II cell has certain conelike morphologic features including a pale nucleus, complex synaptic pedicel, and multiple wrappings of the outer segment by microvilli of the pigment epithelium. The type II outer segment is also conelike in that some intradisc spaces are patent to the extracellular space, that the pattern of renewal is diffuse as demonstrated radioautographically with sugar and amino acids as precursors, and that the few examples of distal tip shedding found in this study occur mainly in the early part of the dark cycle. The interior of the type II outer segment is labeled selectively with 3H-fucose, whereas the interior of the type I outer segment remains unlabeled with this sugar at all time intervals examined. The label probably reflects the presence of a fucose-containing glycoprotein in the conelike outer segment which is lacking in the rod outer segment and may represent a visual pigment or other intrinsic molecule(s). An amorphous material which forms a symmetric sleeve around the photoreceptor connecting cilium has been demonstrated after intravitreal injections of horeseradish peroxidase. This cilium-associated material is labeled specifically by 4 hr following intravitreal injection of 3H-fucose, before the interphotoreceptor matrix shows significant labeling, suggesting that it is composed of a sugar-containing material. Possible functions of the cilium-associated material, including structural support and ionic regulation, are discussed.

Animals↗