By means of a histofluorescence technique (FGS method), a post-natal ontogeny of dopaminergic neurons (DA-cells) in the retina was studied in rats which had been born and reared under diurnal lighting (LD), reversed lighting (DL), constant lighting (LL), or continuous dark conditions (DD). The time of first appearance of DA-cells was not altered by any of the above conditions; weakly fluorescent cell bodies were visible at about the 10th postnatal day. After the eyes were open the DA fluorescence of the cell body was gradually increased in intensity in all LD, DL, and LL rats, but not for DD rats. At the 16-17th day the processes of the cell first became visible, extending laterally to the inner plexiform layer. The somata and their processes appeared to be well developed at the postnatal 4-6th week, and they resembled those of the adult rat. On the other hand, the DA-cells in the DD rats showed a weak fluorescence in both the somata and their processes. When the DD rats were transferred and reared under LD conditions for 1-3 days, the DA fluorescence was increased. These results strongly suggest that the initiation of retinal DA synthesis is independent of environmental lighting condition, but an adequate light stimulus is required for continued normal development of DA-cells. Unlike in the rat, fluorescent cells in the guinea pig and chick retinas were observed to be fairly mature at birth or hatching. The developmental pattern of DA-cells in the three species examined coincides with the maturation of visual function.

Aging↗

PubMed1980

Drug-induced changes in catecholaminergic cells of the fish retina.

The changes in fluorescence intensity and number of visible catecholaminergic cells (CA-cells), as revealed by means of a histofluorescence technique, were used as indicators of the effects of various pharmacological agents upon CA-cells in the retina of fishes (Cyprinus carpio and Eugerres plumieri). The study includes in vivo and in vitro experiments. In the in vivo experiments, intravitreal injection, two or three hours before eye enucleation, of 10 microgram L-DOPA, dopamine, or noradrenaline accentuated CA-cell fluorescence and increased the number of visible cells, whereas 10 microgram of tyramine, octopamine, synephrine, or adrenaline reduced the endogenous fluorescence. Intramuscular injection of reserpine (3 mg/kg) abolished CA-cell fluorescence. In the in vitro experiments, pieces of isolated retinas were incubated for three or 30 minutes in media containing different drugs. Only minor changes in fluorescence were detected after three minutes of incubation, but after 30 minutes, dopamine (20 microM) markedly enhanced CA-cell fluorescence. Carbachol (20 mM), acetylcholine (10 mM) plus BW-anticholinesterase (1 mM) or substance P(1.6 x 10(-2) mM), all reduced CA-cell fluorescence. Kainic acid (20 mM) abolished fluorescence from CA-cell somata, while fluorescent fiber networks remain unchanged. L-aspartate (5 mM) and GABA (10 mM) in the incubation medium did not influence fluorescence intensity. The results are relevant to, and consistent with, electrophysiological observations of dopamine-mediated spatial effects on horizontal cell potentials.

Acetylcholine↗

PubMed1980

Spatial distribution of catecholaminergic cells in the fish retina.

The cell density, distribution pattern, and morphology of catecholaminergic (CA) cells have been studied by fluorescence microscopy of retinal flat-mounted preparations from various species of fresh water, estuary, and marine is lowest in the central region surrounding the optic disc, slightly higher in the intermediate region, and highest in the periphery. The size of CA-cells is smaller the higher their density. Following administration of L-Dopa, dompamine, or noradrenaline, the density of CA-cells approximately doubled, due to the appearance of small fluorescent cells. CA-cells are arranged in rows along radial lines which fan out from the optic disc. In large cells of the central and intermediate regions three to five processes arise from the some and extend and ramify irregularly in the inner plexiform layer, while in small cells from the intermediate and peripheral regions two processes arise from opposite poles and extend regularly in a direction perpendicular to the rows of cells and parallel to the retinal margin. In the retina of the marine fish Holocentrus sp CA-cells are fewer in number compared to other fish studied and their processes extend without any regular pattern. In the toad their size and density are homogenous throughout the retina, and their processes show a regular arrangement.

Animals↗

PubMed1980

Spatial density of catecholaminergic cells in the carp retina.

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Animals↗

PubMed1980

DNA damage induced with near-ultraviolet light irradiation in the presence of quinoxaline-1,4-dioxide.

When Bacillus subtilis transforming DNA was irradiated with near-ultraviolet light in the presence of quinoxaline-1,4-dioxide, the activity of DNA decreased rapidly. This loss of activity was ascribed to damages on DNA that lead to chain cleavages of the molecule. A feature of this phototoxic action of the reagent is that it takes place in nitrogen atmosphere and is inhibited by oxygen.

Bacillus subtilis↗

PubMed1979

Suppression of retinal spike discharge by dipropylacetate (Depakene): a possible involvement of GABA.

Effects of dipropylacetate (DPA) were studied on spike discharges in the isolated carp retina. (1) DPA, applied electrophoretically or by pressure-microinjection in the vicinity of the recording electrode at the inner plexiform layer, consistently activated spike discharges. (2) DPA introduced into the perfusate produced complex actions; some units responded to DPA with an initial activation followed by suppression of spike discharges. (3) When gamma-aminobutyric acid (GABA) was applied electrophoretically together with perfusion of DPA, the depressing effect was greater than that obtained with each of these compounds alone. Bicuculline in the perfusate markedly attenuated the depressing actions of GABA or DPA singly, or in combination. (4) It is concluded that the delayed suppression of spike discharges by perfused DPA appears to be mediated by GABA-receptors on ganglion cells in the carp retina.

Animals↗

PubMed1979

Effects of catecholamines and related compounds on horizontal cells in the fish retina.

The effects of catecholamines (CA) and certain related compounds in the superfusate were examined on the intracellularly recorded potential from horizontal cells in the fish (Eugerres plumieri) retina. The stimulated retinal area consisted of a central spot 1.0 mm in diameter and an annulus 2.0 mm in inner diameter and 4.0 mm in outer diameter; both forms of monochromatic stimuli were centered relative to the recording microelectrode. Each of the CA (dopamine, noradrenaline, and adrenaline) produced an analogous effect on the hyperpolarizing response of all types of horizontal cells. The depolarizing response of the C (R/G)-type cells was found to change variably with the CA. The effect of dopamine (DA) among the CA was most pronounced when they were used at an equivalent amount. With 10--50 microM, the action of DA was variable but in general its effect was to increase slightly both center and surround responses. In some cases, however, DA initially augmented the surround and reduced the center response. Large amounts of the CA (100--200 microM) augmented the center response and attenuated the surround response considerably; these reciprocal changes usually were associated with moderate depolarization of the cells (5--10 mV). Recovery then occurred in 15--20 minutes. These results indicate that the CA, up to a certain amount, do not directly affect the transmission from photoreceptors to horizontal cells, since the center response became larger. At the same time, the lateral propagation of an S-potential appears to be selectively affected by the CA, suggesting that the adrenergic system participates in this phenomenon. When an excess of these compounds (200-500 microM) was given, the cells were rapidly depolarized to near 0 MV and eventually the light-induced responses were abolished. Large amounts (5--10 mM) of metabolic products of the CA (DOPAC and VMA) were found to reduce the center response slightly more than the surround. alpha-Methylnoradrenaline, 5-hydroxydopamine, and serotonin also caused the same but less effect on horizontal cells as did DA. Reserpine and clonidine mimicked the CA effect only if these compounds had been preceded by repeated applications of one of the CA or if the retina had been pretreated with Marplan. Propranolol, haloperidol, and apomorphine affected neither the horizontal cell membrane potential nor the CA effect. However, phentolamine in large amounts (500 microM) markedly diminished the DA action. Therefore, alpha-adrenergic receptors appear to be involved in the CA-induced changes observed in the horizontal cell response.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1979

Similarities in effects of acetylcholine and dopamine on horizontal cells in the fish retina.

The effect of acetylcholine (ACh) on cone- and rod-connected horizontal cells (generating photopic and scotopic L-type S-potentials, respectively) in the fish (Eugerres plumieri) retina was compared with that of dopamine (DA), and some similarities were found in the effects. About two-thirds of the L-type horizontal cells examined were sensitive to a test solution containing ACh (10 mM in concentration) and BW-anticholinesterase (BW; 1.0 mM). ACh with BW augmented a center response and attenuated a surround response as did DA (0.2 mM), although the latter effect was more pronounced and longer-lasting. ACh with BW frequently produced oscillations of the horizontal cell membrane potential, as did DA with clonidine (alpha-adrenergic stimulant). Phentolamine (alpha-adrenergic blocker) interrupted both the effects of DA and ACh on the center and surround responses, while hexamethonium (cholinergic antagonist) appeared to interfere selectively with the effect of ACh. Therefore, the ACh-induced changes observed in the horizontal cell membrane potential are assumed to be mediated by the adrenergic system in the fish retina.

Acetylcholine↗

PubMed1979

Effects of some amino acids on horizontal cells in the fish retina.

Effects of some amino acids on horizontal cells were examined in the fish (Eugerres plumieri) retina. L-aspartate (5 mM in concentration) and L-glutamate (10 mM) consistently depolarized all types of horizontal cells, although the effect of L-aspartate was more pronounced. gamma-Aminobutyric acid (GABA; 10 mM) consistently hyperpolarized the cone-connected L- and C-type horizontal cells, whereas the effect on the rod-connected cells was slight or nonexistent. The hyperpolarizing effect of GABA on the cone-horizontal cells was markedly diminished by picrotoxin (0.1 mM). Usually, glycine (10 mM) showed slight and variable effects. It merely depolarized some cone-horizontal cells but weakly hyperpolarized some rod-horizontal cells. In a few cases, however, glycine began to drastically hyperpolarize the cone-horizontal cells in retinas that had been repeatedly treated with certain agents used. Taurine and beta-alanine (10 mM each) had negligible effects, although the former slightly depolarized and the latter merely hyperpolarized both cone- and rod-horizontal cells.

Amino Acids↗

PubMed1979

Reciprocal changes in center and surrounding S potentials of fish retina in response to dopamine.

Effects of dopamine (DA) were examined on the intracellularly recorded potential from horizontal cells in the fish (Eugerres plumieri) rentina. DA (100 micron in the perfusate) augmented the center S potential in a response to a spot illumination and attenuated the surrounding S potential to an annular light by approximately 40%. These reciprocal changes in the S potentials were associated with a slight depolarization (2.5 mV) of the horizontal cell, and were reversible in 10-15 min. The results indicate that DA at this concentration does not affect directly the synaptic transmission from photoreceptors to horizontal cells, while it appears to interfere selectively with the lateral propagation of an S potential. The effects of DA observed may represent an aspect of function of DA-containing interplexiform cells in the retina.

Animals↗

PubMed1979

Histochemical studies on catecholaminergic cells in the carp retina.

Histochemical studies on catecholaminergic cells were conducted with the carp (Cyprinus carpio) retina. Catecholamine (CA)-containing cell bodies appear sparsely distributed among amacrine cells in the innermost cellular row of the inner nuclear layer (INL) and occasionally in the outer half part of the inner plexiform layer (IPL); only exceptionally are they found among ganglion cells. The fluorescent cells interspersed with the amacrine cells and in the IPL send their fiber processes toward both the outer plexiform layer (OPL) and the IPL; the fine fibers form dense networks in the INL and IPL. Pretreatment of the fish with intramuscular injection of reserpine (20 hr prior to enucleation) completely depleted CA from the retina. The fluorescence of catecholaminergic cells was enhanced, and the number of fluorescent cells visible was increased, by intravitreous injection of L-DOPA, DA, and NA (3 prior to enucleation). A combination of pretreatment with intramuscular reserpine and intravitreous NA was particularly effective. These results indicate that catecholamines may play an important role in the modulation of the membrane potential of horizontal cells.

Animals↗

PubMed1979

Rod- and cone-bipolar cell responses in the carp retina.

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Animals↗

PubMed1979

Chemical modification study of aminoacyl-tRNA conformation.

Chemical reactivity of cytosines in 32P-labeled E. coli tRNA1Leu, E. coli tRNAPhe and yeast tRNAPhe before and after aminoacylation was examined by use of a cytosine-specific reagent, semicarbazide-bisulfite mixture. In all the three tRNA species examined, the cytosine residues that were susceptible to the modification were the same in the aminoacylated tRNA and the unacylated tRNA. Only a limited number of the cytosine residues were modifiable: those that occur in the anticodon, the 3'-CCA terminus, the D-loop, and the extra loop. The sites accessible by the reagent are in good agreement with the general three-dimensional structure of tRNA proposed in literature. These results indicate that the gross conformation of these tRNAs does not change on aminoacylation, and consequently favor the view that the T psi C(G) sequence could become exposed in later steps of protein synthesis in order to achieve the binding of aminoacyl tRNA to ribosomes.

Anticodon↗