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R E Marc

Publications and source records attributed to R E Marc.

33 records · Page 2Linked to original sources
PubMed1985

(3H) glycine-accumulating neurons of the human retina.

Isolated human retinas were incubated in physiological saline containing micromolar (3H) glycine. The types, distributions, and synaptologies of glycine-accumulating neurons were determined by light and electron microscope autoradiography. Two types of amacrine cells were discriminated on the bases of number of processes descending into the inner plexiform layer, density of label in light-microscope autoradiographs, size, and synaptic features: (1) Gly1 amacrine cells have moderate labeling, several oblique dendrites arising from the soma, and electron lucent synaptic terminals containing large presynaptic specializations, nd (2) Gly2 amacrine cells have dense labeling, a single proximal dendrite, and moderately electron-dense terminals with small presynaptic specializations. Gly1 amacrine cells constitute approximately 15% and Gly2 amacrine cells approximately 38% of all cells in the amacrine cell layer. The laminar distribution of label in the inner plexiform layer was measured by scanning microdensitometry, which provided a format for categorizing types of synaptic contacts. Many features of glycine-accumulating amacrine cell contacts were similar to those of cat AII/Gly2 amacrine cells: a diffuse yet bisublaminar distribution of label, concentration of synaptic output in sublamina a, rod bipolar cell input in sublamina b and gap junctions in mid-inner plexiform layer involving labeled cells. The evidence seems to indicate that human Gly2 amacrine cells and cat AII/Gly2 amacrine cells are homologous cell types. finally, some cone bipolar cells were labeled.

Autoradiography↗
PubMed1984

Three distinct morphological classes of receptors in fish olfactory organs.

Three morphologically distinct classes of receptor-neurons are proposed: (1) type I ciliar cells, (2) microvillar cells and (3) type II ciliar cells. Retrograde transport of horseradish peroxidase by axons in the olfactory nerve to the olfactory organs of goldfish (Carassius auratus) and channel catfish (Ictalurus punctatus) provided evidence that these axon-bearing cells are present in the organs of both species. Goldfish olfactory organs were also studied with scanning electron microscopy, dissociated with papain for isolated cell preparations, and processed for ultrastructural localization of acid phosphatase activity. Type I ciliar cells are similar to ciliar olfactory receptors found in all vertebrate classes. Microvillar cells are present in the olfactory organs of most fishes and in the tetrapod vomeronasal organ. In goldfish and catfish, type I ciliar and microvillar cells are concentrated on the inner third of each lamella, nearest to the median raphe. Type II ciliar cells have often been described as respiratory-type or ciliated nonsensory cells. They are structurally similar to respiratory epithelial cells in the nasal cavities of tetrapods and have motile cilia that beat synchronously, indicative of their role in mediating fluid flow over the olfactory epithelium. In goldfish they occur singly and in aggregates throughout the organ. In catfish they are segregated from type I ciliar and microvillar cells on the outer two-thirds of each lamella. In goldfish and catfish they have axons that pass through the olfactory nerve to the olfactory bulb; hence, they are receptor-neurons as well as analogous to respiratory epithelium. In addition to the three receptor types described above, cells resembling receptors with rodlike distal processes were seen filled with horseradish peroxidase and observed with scanning and transmission electron microscopy. Cells of similar structure have been documented elsewhere, often called "rod cells," and sometimes considered a separate receptor type in fishes. In this study, a number of rodlike processes were found with their ciliar or microvillar components partially fused. High levels of acid phosphatase activity were localized to these processes, and examples were found that corresponded to each of the three receptor types. Olfactory receptor turnover is believed to persist through life. The evidence presented supports the hypothesis that fusion of their dendritic apical processes marks an early stage of receptor cell senescence.

Acid Phosphatase↗
PubMed1982

Spatial organization of neurochemically classified interneurons of the goldfish retina-I. Local patterns.

Certain interneurons in the goldfish retina are uniquely specifiable by their abilities to take up exogenously supplied [3H]gamma-aminobutyric acid (GABA), [3H]glycine, [3H]dopamine of [3H]serotonin al low micromolar concentrations. Each ligand labels one or two unique populations of interneurons yielding six cell types characterized by soma location, soma size, level and form of dendritic arborization, and local spatial patterning. This report summarizes these qualitative features and provides quantitative evidence on the size and spatial distributions of : (1) GABA-ergic horizontal cells, (2) GABA-ergic amacrine cells, (3) glycinergic amacrine cells; (4) glycinergic interplexiform cells; (5) dopaminergic interplexiform cells; and (6) indoleaminergic amacrine cells.

Animals↗
PubMed1981

Uptake of aspartic and glutamic acid by photoreceptors in goldfish retina.

The uptake of acidic amino acids by goldfish photoreceptors was investigated by light microscope autoradiography. Isolated retinas were incubated in media containing micromolar amounts of L-[3H]aspartate, L-[3H]glutamate, and D-[3H]aspartate. We have four major observations. (i) Rods accumulate L-[3H]glutamate with a high-affinity transport system; they exhibit a glutamate-to-aspartate selectivity ratio of 30:1. When incubated in 1-10 microM L-[3H]glutamate, rods label more densely than cones. A unit area of rod membrane transports glutamate 30 times better than a unit area of cone membrane. (ii) Red-sensitive and green-sensitive cones show accumulation of L-[3H]aspartate, D-[3H]aspartate, and L-[3H]glutamate, apparently with high affinity, but with little selectivity. Because rods have poor aspartate uptake, red-sensitive and green-sensitive cones may be preferentially labeled with L-[3H]aspartate or D-[3H]aspartate, (iii) Blue-sensitive cones show no uptake of L-[3H]aspartate, D-[3H]aspartate, or L-[3H]glutamate other than that attributable to low-affinity transport. (iv) Various cell types in the goldfish retina can clearly discriminate between glutamate and aspartate, unlike acidic amino acid transport systems described in mammalian brain.

Animals↗
PubMed1981

Glycinergic pathways in the goldfish retina.

Autoradiographic localization of high affinity [3H]glycine uptake in the retina of the goldfish has been used to study some anatomical and physiological properties of potentially glycinergic neurons. There are two classes of retinal cells exhibiting high affinity glycine uptake: Aa amacrine cells and I2 interplexiform cells. Aa amacrine cells constitute about 20% of the somas in the amacrine cell layer and send their dendrites to the middle of the inner plexiform layer. There they are both pre- and postsynaptic primarily to other amacrine cells. Photic modulation of glycine uptake indicates that they are probably red-hyperpolarizing/green-depolarizing neurons. I2 interplexiform cells are a newly discovered type of interplexiform cell; in the outer plexiform layer, they receive direct synaptic input from the somas of red-dominated GABAergic H1 horizontal cells and are apparently presynaptic to dendrites of unidentified types of horizontal cells. The connections of I2 interplexiform cells have not been successfully characterized in the inner plexiform layer. These findings extend our knowledge of neurochemically specific pathways in the cyprinid retina and indicate that glycine, like GABA, is a neurotransmitter primarily involved with circuits coding "red" information.

Animals↗
PubMed1978

GABA-ergic pathways in the goldfish retina.

A high-affinity uptake mechanism for [3H]-gamma-aminobutyric acid (GABA) has been localized to type H1 cone horizontal cells and type Ab pyriform amacrine cells in the retina of the goldfish by light and electron microscopy autoradiography. By stimulating isolated retinas with colored lights during incubation we have been able to use [3H]-GABA uptake as a probe of light-evoked changes in membrane potential. All colors of lights increase and darkness decreases [3H]-GABA uptake by H1 cone horizontal cells. Our model of voltage dependence of GABA uptake predicts that all colors of light should hyperpolarize H1 cone horizontal cells and other investigators have shown by intracellular recording and dye-marking that type H1 cone horizontal cells hyperpolarize to all wavelengths of light. We have also obtained evidence that dark-induced depolarization of cone horizontal cells leads to release of GABA. Type Ab pyriform amacrine cells show maximal [3H]-GABA uptake in darkness and when exposed to green or blue lights, but red lights dramatically suppress uptake. We predict these neurons to be red-depolarizing, and recent intracellular recordings and dye-marking by Famiglietti et al. ('77) support our conclusions. Synaptic relations of apparently GABA-ergic neurons were investigated in the electron microscope. We propose type H1 cone horizontal cells to be both pre- and post-synaptic to red-sensitive cones and type Ab pyriform amacrine cells to be both pre- and post-synaptic to red-sensitive center-depolarizing bipolar cells.

Animals↗
PubMed1977

Chromatic organization of primate cones.

The distribution of baboon retinal cones were mapped histochemically by light-stimulated reduction of nitroblue tetrazolium chloride. Blue cones were distributed regularly in the periphery: red and green cones were distributed randomly everywhere. The ordering of cone densities was green > red > blue.

Animals↗
PubMed1977

Chromatic patterns of cone photoreceptors. 1976 Glenn A. Fry Award Lecture.

The operations of vertebrate visual neurons must eventually be expressed in terms of the spectral classes and spatial distributions of photoreceptors that constitute inputs to those neurons. By using a cytochemical probe that permits visualization of the responses of cone photoreceptors to light stimulation, it has been possible to describe the spectral classes and spatial patterns of cones in a lower vertebrate, the goldfish, and in a primate, the baboon. This information is an important first step in analyzing the connections between cones and retinal neurons.

Animals↗
PubMed1976

Color receptor identities of goldfish cones.

Goldfish retinas were exposed to spectral lights, then incubated with nitroblue tetrazolium chloride. Diformazan deposits revealed that five morphologically distinct cone types were segregated into three color classes: red long double and long single cones, green short double and long single cones, and blue short single and miniature short single cones.

Animals↗
PubMedDate not supplied

Neurochemical signatures revealed by glutamine labeling in the chicken retina.

Postembedding immunocytochemistry was used to determine the retinal distribution of the amino acid glutamine, and characterize amino acid signatures in the avian retinal ganglion cell layer. Glutamine is a potential precursor of glutamate and some glutamatergic neurons may use this amino acid to sustain production of glutamate for neurotransmission. Ganglion cells, cells in the inner nuclear layer, and some photoreceptors exhibited glutamine immunoreactivity of varying intensity. Ganglion cells demonstrated the highest level of immunoreactivity which indicates either slow glutamine turnover or active maintenance of a large standing glutamine pool relative to other glutamatergic neurons. Müller's cells in the avian retina are involved in glutamate uptake and carbon recycling by the rapid conversion of glutamate to glutamine, thus explaining the low glutamate and high glutamine immunoreactivity found throughout Müller's cells. Most chicken retinal ganglion cells are glutamate (E) and glutamine (Q) immunoreactive but display diverse signatures with presumed functional subsets of cells displaying admixtures of E and Q with GABA (gamma) and/or glycine (G). The four major ganglion cell signatures are (1) EQ; (2) EQ gamma; (3) EQG; and (4) EQ gamma G.

Animals↗
PubMedDate not supplied

Glutamate antagonists that block hyperpolarizing bipolar cells increase the release of dopamine from turtle retina.

Some neurochemical features of the neuronal circuitry regulating dopamine release were examined in the retina of the turtle, Pseudemys scripta elegans. Glutamate antagonists that block hyperpolarizing bipolar cells, such as 2,3 piperidine dicarboxylic acid (PDA), produced dose-dependent dopamine release. In contrast, the glutamate agonist 2-amino-4-phosphonobutyric acid (APB), which blocks depolarizing bipolar cell responses with high specificity, had no effect on the release of dopamine. The gamma-aminobutyric acid (GABA) antagonist, bicuculline, also produced potent dose-dependent release of dopamine. The release of dopamine produced by PDA was blocked by exogenous GABA and muscimol, suggesting that the PDA-mediated release process was polysynaptic and involved a GABAergic synapse interposed between the bipolar and dopaminergic amacrine cells. The only other agents that produced dopamine release were chloride-free media and high extracellular K+; in particular, kainic acid and glutamate itself were ineffective. These results suggest that the primary neuronal chain mediating dopamine release in the turtle retina is: cone----hyperpolarizing bipolar cell----GABAergic amacrine cell----dopaminergic amacrine cell.

Aminobutyrates↗
PubMedDate not supplied

Horizontal cell synapses onto glycine-accumulating interplexiform cells.

Horizontal cells mediate lateral transmission of signals in the outer plexiform layer of the vertebrate retina, and are presumed to contribute to surround properties of photoreceptors and bipolar cells by chemical transmission. The cell bodies and dendrites of fish horizontal cells possess presynaptic specializations characteristic of conventional chemical synapses. Horizontal cell axon terminals have not so far been shown to contain presynaptic specializations nor have the targets of the somatic and dendritic synapses been fully characterized. Using electron microscope autoradiography of retinas labelled by high-affinity 3H-glycine uptake, we show here that goldfish horizontal cells make somatodendritic and axodendritic synapses on glycinergic interplexiform cells (Gly-IPCs) as apposed to dopaminergic interplexiform cells. Thus, horizontal cells have at least three postsynaptic targets: photoreceptors, bipolar cells and Gly-IPCs. Gly-IPCs may constitute a major alternative pathway for horizontal cell signals to reach the inner plexiform layer.

Animals↗