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Biomedical subjects

K Negishi

Publications and source records attributed to K Negishi.

At least 199 records · Page 11Linked to original sources
PubMed1983

Development of retinal monoamine neurons in larval goldfish: a histofluorescence study.

The emergence of retinal monoamine neurons was explored in embryonic and larval goldfish (Carassius auratus) by means of a histofluorescence technique. The high-affinity uptake capacity of dopamine (DA) and indoleamine-accumulating (IA) neurons for exogenously applied DA and 5,6-dihydroxytryptamine began to occur simultaneously on the hatching day (stage 25/26). Endogenous DA neurons were first detected on the third postnatal day (stage 26/27). The appearance of DA and IA neurons was found to begin in the central part and to extend to the peripheral part of individual retinas. The first DA and IA neurons to be detected were situated in the inner nuclear layer and migrated proximally to the innermost level of the inner nuclear layer 5-7 days after hatching. The developmental process of monoamine neurons observed represents an aspect of cellular differentiation and maturation in the goldfish retina.

5,6-Dihydroxytryptamine↗
PubMed1983

Effect of sodium fluorescein on neurite outgrowth from the retinal explant culture: an in vitro model for retinal toxicity.

Effect of sodium fluorescein was examined on neurite outgrowth from the retinal explants of chick embryos cultured with chicken gizzard extract, containing macromolecules which promote neurite outgrowth. A dose more than 0.5 mg/ml of fluorescein completely prevented the neurite outgrowth from the retinal explants. The minimum dose of toxic effect of fluorescein on the neurite outgrowth was about 0.2 mg/ml. The fluorescein also caused lysis of pre-existing neurites which had been fully extended by gizzard extract.

Animals↗
PubMed1983

N4-aminocytidine: formation, reactivity, and mutagenicity.

N4-Aminocytidine was readily formed on treatment of cytidine with hydrazine-bisulfite under mild conditions. This reaction can be carried out for cytosines in polynucleotids as well. The nucleoside N4-aminocytidine was strongly mutagenic to bacteria and phage. The transformation of cytosines in polynucleotides into N4-aminocytosines is a convenient method for generating reactive groups in the polymer.

Chemical Phenomena↗
PubMed1982

N-Sulfomethylation of guanine, adenine and cytosine with formaldehyde-bisulfite. A selective modification of guanine in DNA.

When guanine-, adenine- and cytosine-nucleosides and nucleotides were treated with formaldehyde and then with bisulfite, stable N-sulfomethyl compounds were formed. N2-Sulfomethylguanine, N6-sulfomethyladenine, N4-sulfomthylcytosine and N6-sulfomethyl-9-beta-D-arabinofuranosyladenine were isolated as crystals and characterized. A guanine-specific sulfomethylation was brought about by treatment and denatured single-stranded DNA with formaldehyde and then with bisulfite at pH 7 and 4 degrees C. Since native double-stranded DNA was not modified by this treatment, this new method of modification is expected to be useful as a conformational probe for polynucleotides.

Adenine↗
PubMed1982

New dopaminergic and indoleamine-accumulating cells in the growth zone of goldfish retinas after neurotoxic destruction.

Juvenile goldfish were allowed to grow for 3 months after dopaminergic or indoleamine-accumulating cells in their retinas had been destroyed by intravitreal injection of 6-hydroxydopamine or 5,7-dihydroxytryptamine, respectively. New cells of each type were found growing in concentric rings at the margin of the retina. To compensate for the loss of dopaminergic innervation in retinas treated with 6-hydroxydopamine, cells in the growth zone appeared to proliferate at a higher rate than those in untreated retinas and long processes were extended into the retina by the first dopaminergic cells to appear.

5,6-Dihydroxytryptamine↗
PubMed1982

The choice of opiate receptor subtype by neo-endorphins.

The choice of opiate receptor subtype by alpha- and beta-neo-endorphin was studied in isolated preparations. Neo-endorphins had significant inhibitory actions on the electrically evoked contractions of guinea-pig ileum, mouse vas deferens and rabbit ileum as well as on the rabbit vas deferens which had been shown to contain kappa-receptors exclusively. Mr 2266, a relatively specific kappa-receptor antagonist, was more effective than naloxone, a relatively mu-receptor antagonist, to antagonize the agonist actions of neo-endorphins in either the guinea-pig and rabbit ileum or in the rabbit vas deferens. By contrast, in the mouse vas deferens, the effectiveness of Mr 2266 to antagonize the agonist actions of neo-endorphins was low and similar to that of naloxone. The potencies of neo-endorphins relative to that of ethylketocyclazocine, a representative kappa-receptor agonist, in the guinea-pig ileum were similar to those in the rabbit ileum but were significant different from those in the mouse vas deferens. The data indicate that neo-endorphins act as kappa-receptor agonists in either the guinea-pig and rabbit ileum or in the rabbit vas deferens while in the mouse vas deferens they act on opiate receptor subtypes other than kappa- and mu-receptors.

Animals↗
PubMed1982

Evidence that dynorphin-(1-13) acts as an agonist on opioid kappa-receptors.

The study concerned the opioid-receptor subtype on which dynorphin-(1-13) acts in in vitro isolated preparations. The potency of dynorphin-(1-13) relative to that of ethylketocyclazocine (Mr 2266), a representative kappa-receptor agonist, in inhibiting the electrically evoked contractions of the guinea-pig ileum was found to be similar to that found with either mouse was deferens or rabbit ileum. Moreover, Mr 2266 was found to be several-fold more effective than naloxone to antagonize the agonist actions of both kappa-receptor agonists such as ethylketocyclazocine, ketocyclazocine and bremazocine, and dynorphin-(1-13) either in the guinea-pig ileum, mouse vas deferens, or in rabbit ileum. Additionally, dynorphin-(1-13) was found to have a significant inhibitory action on the rabbit vas deferens which had been shown to contain kappa-receptors exclusively. The data indicate that dynorphin-(1-13) acts as an endogenous agonist on kappa-receptors.

Animals↗
PubMed1982

Growth zone of the juvenile goldfish retina revealed by fluorescent flat mounts.

The retinas of juvenile goldfish (Carassius auratus) were processed for fluorescence microscope studies with flat mounts. The fish were reared in a laboratory aquarium for 1-3 months after either one class of retinal dopaminergic (DA) cells or indoleamine-accumulating (IA) cells had been destroyed by intravitreal injection of 6-hydroxydopamine (6-OHDA; 2.5 micrograms) or 5,7-dihydroxytryptamine (5,7-DHT; 2.5 micrograms). The fish grew 10-12 cm in body length on the average for 3 months. The retinas were isolated at various survival times after pretreatment with 6-OHDA or 5,7-DHT. To improve detection of the cells, a mixture of noradrenaline (NA; 0.5 microgram) and 5,6-DHT (0.5 microgram) was intravitreally injected into the eyes 2 hr before enucleation. Retinal growth occurred by cell proliferation at the circumferential margin distal to the retinal center. In this process, DA and IA cells were added in concentric rings, with a rate of cell accretion of approximately 12 cells per day, estimated from the mean cell density in the growth zone (about 252 micrograms width) over a 3-month period. In order to compensate for loss of dopaminergic innervation induced by intravitreal 6-OHDA, the proliferation rate appeared to be facilitated significantly compared to that in normal retinas, and long and centrally extending processes were found to emerge from the DA cells formed earliest after intravitreal injection of 6-OHDA.

5,7-Dihydroxytryptamine↗
PubMed1982

5-hydroxytryptamine stimulates [3H]dopamine release from the fish retina.

Serotonin (5-hydroxytryptamine, 5-HT; 0.5 micro M and above) stimulated the release of [3H]dopamine ([3H]DA) from particulate fractions of the carp (Cyprinus carpio) retina. The 5-HT effect was dose- and Ca2+-dependent, and was structurally specific. A similar response was not elicited by the other indoles (5,6-dihydroxytryptamine, 5,7-dihydroxytryptamine, 5-hydroxytryptophan, or 5-hydroxyindoleacetic acid) examined. An increase in [3H]DA release was elicited by addition of 5-HT agonists (5-methoxytryptamine, 5-methoxy-N,N-dimethyltryptamine, and tryptamine), but not antagonized by three 5-HT antagonists (metergolin, methysergide, and spiperone). Either DA alone or noradrenaline (0.5 mM) produced a large increase in [3H]DA release from the particulate fractions, but this action was Ca2+-independent. Further, no significant release of [3H] gamma-aminobutyric acid could be evoked by 5-HT (0.5 mM) under similar experimental conditions. Taken together, the present data suggest that 5-HT stimulates [3H]DA release from the fish retina through a specific receptor-mediated mechanism on dopaminergic terminals, but not through an exchange or nonspecific phenomenon.

5-Methoxytryptamine↗
PubMed1981

Indoleamine-accumulating cells and dopaminergic cells are distributed similarly in carp retina.

Carp (Cyprinus carpio) retinas were processed for simultaneous visualization of dopaminergic (DA) and indoleamine-accumulating (ID) cells in flat-mounts under fluorescence microscope. A mixture of 5 micrograms noradrenaline (NA) and 5 micrograms 5,6-dihydroxytryptamine (5,6-DHT) was injected intravitreally into the eyes 2 h before enucleation. The spatial distribution and density were compared between NA-loaded DA-cells (greenish fluorescence) and 5,6-DHT-loaded ID-cells (yellowish). The two classes of cells were found to distribute similarly in a mixed fashion. Their densities were higher in the peripheral region than in the rest and extremely high at the retinal margin. Where the densities were higher, the size of cell bodies tended to be smaller. DA-cells were generally larger than ID-cells. Those cells, located in the intermediate and peripheral regions, appeared to be arranged in radial rows originating at the optic disc.

5,6-Dihydroxytryptamine↗