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S Yazulla

Publications and source records attributed to S Yazulla.

At least 55 records · Page 3Linked to original sources
PubMed1988

Synaptic organization of dopaminergic interplexiform cells in the goldfish retina.

The synaptic organization of dopaminergic interplexiform cells (DA-IPC) in the goldfish retina was studied by a combined double-label electron-microscopical (EM) immunocytochemical/autoradiographical study. DA-IPCs were labeled with antisera against tyrosine hydroxylase. The possibility of synaptic contact with GABAergic amacrine cells in the proximal inner plexiform layer (IPL) was studied by using 3H-GABA uptake. Most synaptic input and output from DA-IPC processes involved amacrine cell processes. In addition, synaptic interactions were observed between DA-IPC processes and bipolar cell terminals, other DA-IPC processes, very small dendrites in the IPL, ganglion cell and optic fiber layers (OFL), and cell bodies in the ganglion cell layer (GCL). Input and output synapses with GABAergic amacrine processes also were observed. Two-thirds of the DA-IPC boutons in the proximal IPL were involved in "junctional appositions," that is, the junctions appeared to be specialized but they were different than classical chemical synapses. The synaptic organization of DA-IPCs in the goldfish IPL appears to be far more complex than previously thought. Although earlier studies have attempted to explain the action of dopamine in terms of interaction only with amacrine cells, the present study shows that effects involving bipolar cells, other DA-IPCs, unidentified processes and cell bodies in the GCL and OFL must be considered as well.

Animals↗
PubMed1987

Ultracytochemical distribution of ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase in the synaptic layers of goldfish retina.

Ouabain-sensitive, K+-dependent p-nitrophenylphosphatase (K+-pNPPase) activity, which represents the second dephosphorylation step of Na+,K+-ATPase, was localized histochemically at the light and electron microscopical levels in the goldfish retina. K+-pNPPase staining was most intense in the outer and inner plexiform layers and less intense over the photoreceptor inner segments. K+-pNPPase staining was observed on the membranes of horizontal cell dendrites and presynaptic membrane of all cone pedicles but only rarely over rod spherules. Bipolar cell dendrites in the outer plexiform layer were not stained for K+-pNPPase. In the inner plexiform layer (IPL), K+-pNPPase staining was observed at 90% of the bipolar cell ribbon synapses but only at 40% of amacrine cell synapses. The proportion of K+-pNPPase staining at amacrine cell synapses increased from 26 to 49% as one progressed from the outer to inner layers of the IPL, while staining at bipolar cell synapses showed no such trend. Only 16% of the amacrine synapses onto mixed, rod-cone (mb) bipolar cell synaptic terminals were positive for K+-pNPPase. We suggest that the differential distribution of K+-pNPPase staining at retinal synapses can be explained, in part, by the ionic conductances gated at the postsynaptic sites. In addition, the presence of K+-pNPPase on lateral horizontal cell dendrites in cone pedicles is consistent with the hypothesis that the sodium pump is involved in the release of GABA at feedback synapses from horizontal cells to cone photoreceptors.

4-Nitrophenylphosphatase↗
PubMed1987

GABAergic input to the synaptic terminals of mb1 bipolar cells in the goldfish retina.

An EM-autoradiographical/immunocytochemical technique was used to study amacrine cell synapses onto mb1 bipolar cell terminals in goldfish retina. Tissue was double labeled for [3H]GABA uptake and glutamate decarboxylase (GAD) immunolocalization. Nearly 90% of the amacrine cell synaptic processes onto both proximal and distal halves of mb1 terminals were labeled with either [3H]GABA or GAD-immunoreactivity (IR). Proximal half: 73% of the amacrine synapses were labeled with [3H]GABA uptake and 82% with GAD-IR; 88% of [3H]GABA labeled contacts were double labeled. Distal half: 17% of the amacrine synapses were labeled with [3H]GABA uptake and 67% with GAD-IR; 63% of [3H]GABA labeled contacts were double labeled. After consideration of the possible sources of [3H]GABA labeled synapses onto mb1 terminals, we concluded that the synaptic terminals of pyriform Ab amacrine cells double label for [3H]GABA and GAD-IR despite our previous report that Ab cell bodies do not stain for anti-catfish brain GAD antiserum. We suggest that Ab cells contain isoenzymes of GAD which differ in subcellular distribution, thereby accounting for the differential staining of the cell bodies and dendrites obtained with the GAD antiserum we used.

Animals↗
PubMed1987

Double-label analysis of GAD- and GABA-like immunoreactivity in the rabbit retina.

Rabbits were injected intravitreally with colchicine and the retinas were subsequently processed for simultaneous visualization of GAD-like and GABA-like immunoreactivity (LIR) at the light microscopical level. The use of specific antisera from unrelated species minimized the possibility of crossreactivity between the two markers. Colocalization of GABA-LIR and GAD-LIR was observed in approximately 32% of somata on the inner border of the inner nuclear layer (INL) and roughly 15% of the somata in the ganglion cell layer (GCL). All GAD-positive cells were double labeled whereas 15% of the GABA-LIR cells in the INL and 52% of those in the GCL were negative for GAD-LIR. Both markers were seen throughout the inner plexiform layer. In addition, processes coursing through the OPL, perhaps from interplexiform cells, and horizontal cell bodies were double-labeled with these GABAergic probes.

Animals↗
PubMed1987

Interspecific comparisons of immunohistochemical localization of retinal neurotransmitters in four species of bats.

Four ecologically distinctive Neotropical bat species of the family Phyllostomidae were collected and their retinae surveyed immunohistochemically for the presence of neurotransmitter candidates: glucagon, somatostatin, vasoactive intestinal peptide, substance P (SP), methionine enkephalin, serotonin (5-HT) and two enzymes, glutamic acid decarboxylase (GAD) and tyrosine hydroxylase (TOH). In all four species immunoreactivity (IR) to GAD, TOH and SP was found. GAD-IR and SP-IR showed little interspecies variation whereas TOH-IR differed interspecifically in a pattern that matched the systematic relationships and the ecological characteristics of the bats. 5-HT-IR, which has not previously been reported from mammalian retinae, was found in fibers in the inner nuclear layer and in the outer and inner plexiform layers of Macrotus waterhousii, which is a relatively underived insectivorous phyllostomid bat, but was not found in the retinae from frugivorous or nectarivorous species.

Animals↗
PubMed1986

Neurotoxic action of kainic acid in the isolated toad and goldfish retina: I. Description of effects.

The neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). KA caused vacuolization of proximal and distal segments of horizontal cell dendrites in the OPL as well as perikaryal vacuolization and/or chromatin clumping in selected classes of neurons in the inner nuclear layer. Further, KA caused vacuolization and swelling in the inner plexiform layer. These effects were very similar in the retinae of goldfish and toad. The extent of vacuolization in the OPL was graded with KA concentration and with length of incubation. For 15-minute incubations, half-maximal vacuolization was found at 10-20 microM KA. At 25 microM KA, OPL vacuolization was evident within 1-2 minutes of application of KA. In goldfish, but not in toad, rod-connecting dendrites were less sensitive to KA than cone-connecting dendrites.

Animals↗
PubMed1986

Neurotoxic action of kainic acid in the isolated toad and goldfish retina: II. Mechanism of action.

The specificity and mechanism of the neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). Of 21 compounds tested as potential mimics of KA neurotoxicity in the OPL, only the enantiomers of glutamate and aspartate mimicked KA, inducing a low-level neurotoxic effect at concentrations 5,000-10,000-fold higher than concentrations of KA giving comparable effects. Further, of 22 compounds tested as potential blockers of KA neurotoxicity in the OPL, only D-gamma-glutamylglycine, D,L-alpha-amino pimelic acid, sodium pentobarbital, D,L-alpha-amino adipic acid, L-glutamate, and L-aspartate blocked KA neurotoxicity (IC50 values of 0.1, 0.3, 0.3, 2, 5, and 15 mM, respectively). In ionic substitution experiments, KA-induced vacuolization was found to require sodium and chloride ions but not calcium ions in the extracellular medium. These findings support the hypothesis that KA combines with specific receptors in the membrane of susceptible neurons in the retinal OPL, leading to prolonged opening of membrane channels permeable to sodium and potassium ions. An accompanying equilibrating chloride influx may result in intracellular ion excess, leading to osmotic swelling and vacuolization. The membrane receptors involved in mediating the action of KA in the OPL are likely to be a class of postsynaptic or extrasynaptic glutamate receptor.

Amino Acids↗
PubMed1986

Neuropeptide-like immunoreactive cells in the retina of the larval tiger salamander: attention to the symmetry of dendritic projections.

Light microscopic immunocytochemistry was used to study the morphology of cells that showed immunoreactivity (IR) to antisera against substance P (SP), glucagon (GLU), met enkephalin (ENK), and somatostatin (SS) in the retina of the larval tiger salamander. Both vertical sections and retinal whole mounts were studied. All four antisera labeled amacrine cells in the inner nuclear layer and cells in the ganglion cell layer (GCL). GLU-IR cells had processes stratified throughout the inner plexiform layer (IPL), whereas the other three types had bistratified projections in laminae 1 and 5, with lamina 5 being broader and more dense. Two types of SS-IR amacrine cell were observed. As seen in retinal whole mount, most GLU-IR and ENK-IR amacrine cells had processes that were symmetrically distributed about the soma, whereas processes of SS- and SP-IR amacrine cells were markedly asymmetrical. The dendritic fields of SP-IR amacrine cells were selectively oriented toward the periphery of the retina in the nasal, temporal, and dorsal areas. Immunoreactive cells in the GCL had fine projections into the IPL and in addition gave rise to two large oriented processes proximal to the soma that projected in opposite directions for 100-200 microns. The oriented processes often showed further branching; they appeared to be along the radiated lines from the optic disc but did not enter it. The implications of the selectively oriented processes of SP-IR amacrine cells and cells in the GCL are discussed.

Ambystoma↗
PubMed1986

Comparative distribution of 3H-GABA uptake and GAD immunoreactivity in goldfish retinal amacrine cells: a double-label analysis.

The comparative distribution of 3H-GABA uptake and glutamic acid decarboxylase immunoreactivity (GAD-IR) in amacrine cells of goldfish retina was studied simultaneously by using a combined autoradiographic/immunocytochemical technique in order to determine the degree of colocalization of these two markers of GABAergic neurons; 3H-GABA was taken up most intensely by large pyriform Ab amacrine cells (3% of inner nuclear layer (INL) somata), and less intensely by smaller, polyform amacrine cells (12% of INL somata), cell bodies in the ganglion cell layer (one-half as common as Ab cells), and cell bodies in the inner plexiform layer (very rare). GAD-IR was observed in 25% of amacrine cells in the INL, the vast majority of which were polyform in shape, and cell bodies in the ganglion cell layer. Twice as many cells were labeled for GAD-IR as for 3H-GABA uptake. Of the cells that took up 3H-GABA, colocalization of 3H-GABA uptake and GAD-IR was observed in 90% of the polyform amacrine cells, 80% of the cells in the ganglion cell layer, and none of the pyriform Ab amacrine cells or cells in the inner plexiform layer. We suggest that the polyform cells compose the major population of GABAergic amacrine cells in the goldfish retina, rather than the pyriform Ab cells. GABAergic displaced amacrine cells or ganglion cells are also indicated by our data. The implications of these data with regard to the physiology of the goldfish retina are discussed as well.

Animals↗
PubMed1986

GABA-like immunoreactivity in the vertebrate retina: a species comparison.

Rabbit antisera directed against gamma-amino butyric acid (GABA) conjugated to bovine serum albumin was used to localize neurons containing GABA-like immunoreactivity in the retinas of nine species of animals: human, cat, rabbit, rat, chicken, turtle, frog, mudpuppy and goldfish. The retinas of all species contained GABA-like labeling in several populations of amacrine cells in the inner nuclear layer, cells in the ganglion-cell layer that may include displaced amacrine cells and in fibers in the inner plexiform layer and in the optic nerve fiber layer. Labeled horizontal cells were found in cat and in all non-mammalian retinas. Labeled interplexiform cells were found in rat, rabbit, cat and human retinas. Labeled bipolar cells were restricted to frog and mudpuppy retinas. The distribution of anti-GABA is usually similar to that of anti-glutamic acid decarboxylase and neuronal [3H]GABA uptake, indicating good correspondence between these 'GABAergic' markers. However, several significant differences among these markers are discussed.

Animals↗
PubMed1986

Separation and light adaptation of rod and cone signals in the retina of the goldfish.

The aspartate-isolated fast P III response was used to monitor the responses of goldfish photoreceptors at varying intensities of steady background illumination. When the retina contained the normal complement of rods and cones, light adaptation consisted of response compression, a shift of the response curve to more intense stimuli (cellular adaptation), and responses to decrements as well as increments of light. Rod and cone contributions to the fast P III response were separated by taking advantage of photomechanical movements of the photoreceptors to produce "all-rod" and "all-cone" retinae. Rods employ response compression as their primary adaptation mechanism. Rods show little cellular adaptation or responses to decremental flashes. However, cones do not show response compression, but continue to respond at bright backgrounds due to cellular adaptation.

Adaptation, Ocular↗
PubMed1985

Colocalization of GAD-like immunoreactivity and 3H-GABA uptake in amacrine cells of rabbit retina.

Rabbit retinas were double labeled to determine the degree of colocalization of glutamic-acid-decarboxylase-like immunoreactivity (GAD-like IR) and 3H-GABA uptake using light (LM) and electron microscopic (EM) autoradiography. Both GAD-like IR and 3H-GABA uptake were found in amacrine cell bodies in the inner nuclear layer (INL) as well as in cell bodies in the ganglion cell layer (GCL), and throughout the inner plexiform layer. GAD-like IR was found in 32% of the amacrine cells in the INL, 86% of which also showed 3H-GABA uptake; 3H-GABA uptake was observed in 38% of the amacrine cells. However, only 72% of these cells showed GAD-like IR. Labeled cells in the GCL were only 10-15% as common as similarly labeled cells in the INL. As in the INL, all GAD-positive cells in the GCL were double labeled, but only 53% of the cells taking up 3H-GABA were double labeled. We suggest that labeled cells in the GCL were ganglion cells rather than displaced amacrine cells. Cells, in both the INL and GCL, that showed 3H-GABA uptake but no GAD-like IR had a higher average grain density than double-labeled cells, indicating that uptake by these cells was specific. The relevance to GABAergic function of 3H-GABA uptake without an indication of GAD-like IR is yet to be determined. Statistical analysis at the EM level showed that one-third of the GAD-positive synaptic terminals of amacrine cells were double labeled after a 4-month exposure. Longer exposures at the EM level should reveal a higher percentage of GAD-positive terminals because at the LM level, one-half of the double-labeled cell bodies were "lightly" labeled with grains. The high degree of colocalization of GAD-like IR and 3H-GABA uptake suggests that both markers may be useful for labeling GABAergic neurons in the rabbit retina.

Animals↗
PubMed1985

Stimulated release of endogenous GABA and glycine from the goldfish retina.

The release of endogenous gamma-aminobutyric acid (GABA) and glycine from the isolated goldfish retina, measured by high-pressure liquid chromatography (HPLC), was Ca2+-independent when evoked by L-glutamate or L-aspartate and partially Ca2+-dependent when evoked by 50 mM K+. D-Aspartate potentiated GABA and glycine release evoked by L-glutamate and inhibited that evoked by L-aspartate. These data are similar to those reported for radiolabeled GABA and glycine. However, the relative amount released compared to the total amino acid content in the retina was much less (10%) for the endogenous compounds. We suggest that results obtained with [3H]GABA and [3H]glycine can be generalized in a qualitative manner to their endogenous counterparts in goldfish retina.

Animals↗
PubMed1985

Evoked efflux of [3H]GABA from goldfish retina in the dark.

H1 horizontal cells of goldfish retina probably are GABAergic and receive synaptic excitation from red cone photoreceptors in the dark. This study was designed to detect efflux of [3H]GABA from H1 cells by a physiological stimulus in order to obtain information regarding the identity of the red cone transmitter and obtain information on the role of dopaminergic interplexiform cells (DA-IPCs), the other synaptic input to H1 cells. Efflux of [3H]GABA was studied by biochemical analysis of perfused isolated retinas. Retinas were incubated in dim red light for 15 min in 0.72 microM [3H]GABA, rinsed for 30 min in red light and subjected to darkness under a variety of conditions. Radioactivity in the perfusate was determined by liquid scintillation spectroscopy. The findings are: 1. both L-glutamate and L-aspartate cause a dose-dependent efflux of [3H]GABA from H1 cells, 2. inclusion of 3.2 mM D-aspartate in the perfusion medium potentiates L-glutamate and totally inhibits L-aspartate, 3. retinas perfused in the standard Ringer do not show increased [3H]GABA efflux when placed in the dark, 4. when 3.2 mM D-aspartate is in the perfusion medium, there is significant dark-induced [3H]GABA efflux which is reduced with light onset, 5. 100 microM dopamine inhibits the dark-induced efflux of [3H]GABA. These results show that efflux of [3H]GABA from H1 cells can be detected under physiological conditions strongly suggesting that the H1 cell is GABAergic and, in addition, is subject to antagonistic inputs from red cones and DA-IPCs. Furthermore, since D-aspartate potentiates L-glutamate and inhibits L-aspartate, and is required for the detection of dark-induced efflux of [3H]GABA, it is unlikely that the transmitter for red cones is L-aspartate but more likely is L-glutamate.

Animals↗
PubMed1985

Synaptic organization of substance P-like immunoreactive amacrine cells in goldfish retina.

A class of amacrine cells in the goldfish retina displays substance P-like immunoreactivity (SPIR). We studied the synaptic organization of SPIR amacrine cells by electron microscopical immunocytochemistry. Amacrine cells showing SPIR have processes which ramify in a very narrow band in layer 3 of the inner plexiform layer. SPIR is restricted to large dense-cored vesicles (DCVs), which are distributed throughout the dendrites. Processes labeled with SPIR contain a mixture of DCVs and numerous small agranular vesicles. Of 88 synaptic contracts analyzed, SPIR processes occurred as the presynaptic element 57 times and as the postsynaptic element 31 times. SPIR processes made synapses upon amacrine and ganglion cell dendrites with equal frequency and received synaptic input from both amacrine and bipolar cells. The stratification of SPIR amacrine cells in proximal sublamina a suggests that their synaptic interactions are restricted to "off" and "on-off" neurons. However, this is in contrast to published electrophysiological data. Possible explanations for this discrepancy are discussed in detail.

Animals↗
PubMed1984

Uptake of 3H-glycine in the outer plexiform layer of the retina of the toad, Bufo marinus.

The uptake of 3H-glycine in the retina of the toad, Bufo marinus, was investigated by light and electron microscopical autoradiography. Uptake of 3H-glycine was very prominent in large cell bodies in the inner nuclear layer as well as in discrete clusters in both the outer plexiform layer (OPL) and the inner plexiform layer. This pattern in similar to that described for 3H-glycine-accumulating putative interplexiform cells in goldfish, frog, and Xenopus retinas. Electron microscopical autoradiography of the OPL revealed large, grain-containing varicosities which had electron-lucent cytoplasm and contained both small, agranular and large, dense-core vesicles. The varicosities made extensive en passant and spine synapses in the OPL. Definitive identification of their postsynaptic targets was not achieved. However, autoradiographic analysis with 3H-GABA uptake as well as electrophysiological evidence suggests that axons but not cell bodies or dendrites of 3H-GABA-accumulating horizontal cells (H1 cells) are postsynaptic targets of the varicosities. The presence of dense-core vesicles in the varicosities suggested co-occurrence of glycine and a biogenic amine or neuropeptide. The indirect immunofluorescence technique was used to determine whether any such substances were present in the OPL of the toad retina. However, no specific labeling was found in the OPL for any of 19 substances tested. The extensive synaptic output provided by glycine-accumulating varicosities in the toad OPL may indicate an important role of glycine in the synaptic function of the distal toad retina. We suggest that these varicosities derive from a presumably glycinergic interplexiform cell.

Animals↗
PubMed1984

Two types of pyriform Ab amacrine cells in the goldfish retina: an EM analysis of [3H]GABA uptake and somatostatin-like immunoreactivity.

Pyriform Ab amacrine cells in the goldfish retina take up [3H]GABA and show somatostatin-like immunoreactivity (SLIR), leading to the question of whether these two markers are labeling the same or different types of Ab amacrine cells. We used a double-label radio/immuno-technique at the electron microscopical level to visualize the comparative location of [3H]GABA uptake and SLIR in Ab amacrine cells and their processes. SLIR was restricted to large dense-cored vesicles in processes of Ab amacrine cells. In no case were processes labeled with SLIR observed to take up [3H]GABA. Thus, there are at least two types of pyriform Ab amacrine cells: one that takes up [3H]GABA and one that shows SLIR. These may correspond to the two types of Ab amacrine cells described by Cajal in his classic studies on the retina.

Animals↗