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Biomedical subjects

N Miki

Publications and source records attributed to N Miki.

At least 163 records · Page 9Linked to original sources
PubMed1984

Antiserum against neurite outgrowth factor in chick gizzard extract and its inhibitory effect on neuritic response in cultured ciliary neurons.

Antiserum against a neurite outgrowth factor (NOF) of gizzard extract that promotes neurite outgrowth from dissociated ciliary ganglionic neurons (CG neurons) of 8-day-old chick embryo was prepared to determine whether or not the antiserum inhibits neurite outgrowth from cultured neurons or explants of chick and murine tissues. When CG neurons were cultured on a polyornithine-coated well exposed to NOF (NOF-bound POR well), marked neurite outgrowth was observed. When NOF-bound POR wells were exposed to antiserum, neurite outgrowth from CG neurons was gradually inhibited with increasing amounts of antiserum, while exposure to preimmune serum did not prevent neurite outgrowth. Antiserum had no effect on neuronal survival during a 48-h incubation. The diluted antiserum, which produced nearly 100% inhibition of the NOF activity, was almost equally active in suppressing the activity of NOFs in conditioned media (CM) of various chick embryo tissues, but showed much less inhibitory effects on NOFs in CM of murine tissues. The appearance of neurites from explants of spinal cord, dorsal root ganglion, or retina of chick embryo was also inhibited by the antiserum. These results indicate that antiserum against NOF from gizzard extract suppressed the activity of NOFs from various sources, and that there are species differences in NOFs, at least between chick and murine.

Animals↗
PubMed1984

Evidence that opiatergic and alpha-adrenergic mechanisms stimulate rat growth hormone release via growth hormone-releasing factor (GRF).

An antiserum raised against human pancreatic growth hormone-releasing factor-(1-40) (hpGRF-40) was found to recognize the rat hypothalamic growth hormone-releasing factor (rhGRF): This antiserum, when given iv to adult male rats, completely abolished GH release induced by a synthetic rhGRF (0.2, 1 microgram/kg BW), and inhibited the physiological GH secretion over 2 days. After passive immunization with anti-hpGRF-40 serum, iv injection of either FK 33-824 (100 micrograms/kg BW), an enkephalin analogue, or clonidine (125 micrograms/kg BW), an alpha-adrenergic agent, failed to stimulate GH release in the unanesthetized rat. These results indicate that the GH-releasing actions of opiatergic and alpha-adrenergic mechanisms are mediated through stimulation of endogenous rhGRF release in the rat.

Animals↗
PubMed1984

A single class of neurotensin receptors with high affinity in neuroblastoma X glioma NG108-15 hybrid cells that mediate facilitation of synaptic transmission.

Receptor binding of [3H]neurotensin was examined on membrane preparations derived from neuroblastoma X glioma NG108-15 hybrid cells. The specific binding was saturable and reversible, and a dissociation constant (Kd) was calculated to be about 0.24 nM from the rate constants. Scatchard analysis of neurotensin binding at equilibrium revealed a single class of binding sites with a Kd of 0.86 nM and a maximal binding capacity (Bmax) of 250 fmol/mg of protein (7700 receptor sites/cell). [D-Arg9]-Neurotensin had a high affinity (IC50 = 0.5 nM) for the neurotensin receptors, but [D-Phe11]-neurotensin had a lower affinity (IC50 = 280 nM), while angiotensin II and bradykinin had almost no affinity for [3H]neurotensin-binding sites. Under similar conditions [3H]neurotensin binding to mouse and rat brain synaptosomal fractions showed two binding sites with high (0.86 and 0.44 nM) and low (13 and 19 nM) affinities. We have examined several possible physiological consequences of neurotensin receptor binding. Neurotensin (10 microM) exhibited no influence on adenylate cyclase activity, 45Ca uptake, or 32Pi incorporation into phosphatidylinositol fractions of NG108-15 cells. Electrophysiological study of isolated NG108-15 cells revealed neurotensin-induced transient hyperpolarization followed by sustained depolarization with enhanced membrane excitability. Application of neurotensin to NG108-15 cells that had formed synapses with cultured striated muscle cells caused a considerable increase in frequency of miniature endplate potentials from the muscle cells. These data show that NG108-15 cells possess a single class of neurotensin receptors similar to a high affinity site of synaptosomal membranes from the murine brains.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Seishin-renshi-in therapy for patients with discomforts on the lower urinary tract].

The clinical effect of Seishin-renshi-in was studied in 18 patients with prolonged discomfort in the lower urinary tract. Seishin-renshi-in was administered orally at doses of 7.5 g, for courses ranging from 2 weeks to more than 10 weeks. Except in 4 cases in which administration was stopped because of slight side effects on the gastrointestinal tract; the overall effective ratio was 81%. Our findings suggest that Seishin-renshi-in may be useful in the control of discomforts in the lower urinary tract.

Administration, Oral↗
PubMed1983

A prominent feature of the conversion of P-450 to P-420 of cytochrome P-450B1 among the cytochrome P-450 isozymes.

Conversion of cytochrome P-450 to P-420 was observed with the use of three isozymes of P-450, P-450PB, P-450MC and P-450B1. The last one, which was isolated and characterized in our laboratories, is the cytochrome P-450 with high affinity for cytochrome b5. Of these isozymes, cytochrome P-450B1 is predominantly fast in the rate of conversion from P-450 to P-420 in the reduced state under carbon monoxide. p-Nitroanisole, which is the substrate of P-450B1 for demethylation, accelerated the conversion, whereas the effects of the compound on the rate of conversion of the other P-450S were small. The effect of cholate on the conversion was distinct and rapid but not very selective among the isozymes. Stabilization with glycerol for prevention of the conversion was found to be effective, for any of these isozymes. No remarkable difference was observed in the stability of the oxidized state among these isozymes when detected in the CO-reduced form. The rates of the reaction from the oxidized to the CO-reduced form were measured with these isozymes. The rate of P-450B1 was the highest in both the medium with glycerol and that without glycerol. Circular dichroism was measured with respect to conversion of P-450 to P-420. The absorption at 450 nm was related to the significant circular dichroism, while the increased absorption at 420 nm due to the conversion was not accompanied by distinct circular dichroism. These data support the concept that the heme vicinity of cytochrome P-450B1 is more labile in the structure of the reduced form under carbon monoxide than those of the other isozymes.

Animals↗
PubMed1983

Tetanus toxin: a rapid and selective blockade of the calcium, but not sodium, component of action potentials in cultured neuroblastoma N1E-115 cells.

The slow action potential of mouse neuroblastoma N1E-115 cells, which was elicited in Na-free medium and whose amplitude was directly dependent on extracellular Ca concentrations, was blocked by tetanus toxin (TNTX) without change in resting membrane potential and resistance. The average value of action potential overshoot (peak potential level of spikes) in the absence and presence of TNTX was -1 and -11 mV, respectively. The concentration of TNTX required for 50% inhibition of Ca-dependent spikes (IC50) was about 65 ng/ml. The amplitude of spikes was decreased within 10-20 min after adding TNTX. The inhibition of Ca-dependent spikes was mimicked by 10 mM CoCl2 and MnCl2, but not by the boiled or neutralized toxin. The results indicate that TNTX inhibited electrogenesis of Ca, but not Na, components of action potentials of the neuroblastoma cells.

Animals↗
PubMed1983

Tetanus toxin blocks Ca spikes in neuroblastoma clone N1E-115 cells.

The effect of tetanus toxin on the Ca spike of the action potential evoked in neuroblastoma clone N1E-115 cells by constant current stimulation in Na+-free medium containing various concentrations of Ca2+(1.8-80 mM) was examined by intracellular recordings. Tetanus toxin (more than 140 ng/ml) blocked the Ca spikes. The resting membrane potentials and membrane input resistances of tetanus toxin-treated cells were similar to those of untreated cells. The blocking effect of tetanus toxin was evident in medium containing Ca2+ at concentrations of more than 30 mM. The difference between the peak levels of the action potentials of toxin-treated and untreated cells was statistically significant at Ca2+ concentrations of 7.2 mM and more.

Action Potentials↗
PubMed1983

Cytotoxic action of prostaglandin D2 on mouse neuroblastoma cells.

Addition to the culture medium of prostaglandin (PG) D2 resulted in the degeneration in a dose- and time-dependent manner of N18TG-2 cells cloned from mouse neuroblastoma. The ED50 for PGD2-induced cytotoxicity was about 10 microM. The degenerative changes were irreversible when the cells were exposed for more than 10 h. Scanning and transmission electron microscopic examination revealed that treatment with PGD2 resulted in appearance of numerous blebs of various sizes along the cell surface and also in destruction of surface membrane and of cytoplasmic organelles. Tumor weight of N18TG-2 neuroblastoma inoculated subcutaneously on the backs of A/J mice was about 35-70% less than that of controls after 14 days of single daily i.p. or s.c. injections of 0.5-1 mg/kg of PGD2. The results indicate that PGD2 has growth-inhibitory effects on mouse neuroblastoma cells in vitro and in vivo.

Animals↗
PubMed1983

Analysis of a distinctive protein in chick retina during development.

Soluble proteins from the chick retina were analyzed at various developmental stages by SDS-polyacrylamide gel electrophoresis. A peptide of about 24,000 daltons (24 Kd protein) appeared in the 14-day embryo and gradually increased with embryonic age, maintaining a fairly steady level after hatching. Polypeptides which correspond to actin and tubulin, however, remained almost unchanged during development. The 24 Kd protein was not detected in the cerebrum, tectum, pigment epithelium or vitreous body at any age. To characterize this protein, it was partially purified by gel filtration and ion exchange column chromatography, and its isoelectric point was measured. It was focused in a diffuse spot at about pH 5.5. In the bovine retina, a protein was observed at 24,000 daltons on SDS-polyacrylamide gel, but its isoelectric point was more basic than that of chick retina. It is suggested that the 24 Kd protein is one of the distinctive proteins that increase in concentration during the chick retinal development, and would be closely associated with retinal functions.

Animals↗
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

Failure of prolactin short loop feedback mechanism to operate in old as compared to young female rats.

The short loop feedback effect of PRL was studied in young (4-5 months of age) and old (24-26 months of age) ovariectomized rats after a single iv injection of bovine PRL (bPRL, 500 micrograms/100 g BW) or BSA (500 micrograms/100 g BW). Blood samples were collected via intraatrial cannula every 20 min for assay of PRL. Plasma PRL levels in both young and old ovariectomized rats were pulsatile in nature, and showed approximately one PRL pulse per hour. The magnitude of the PRL peaks and concentrations of plasma PRL, but not the number of PRL peaks, were significantly greater in the old than in the young rats. The effect of bPRL on in situ PRL release was studied after verifying that bPRL does not cross-react with rat PRL RIA, but does significantly increase the release of [3H] dopamine from the median eminence in vitro. This latter effect was dose dependent. In young rats, a single injection of bPRL minimally reduced the concentration of plasma PRL between 100 min and 5 h, but by 22-25 h it decreased plasma PRL to approximately one third of preinjection levels. The magnitude of the PRL pulses, but not the pulse frequency was significantly reduced after administration of bPRL treatment to young rats. Treatment with BSA did not alter the concentration of plasma PRL or the magnitude and frequency of the PRL pulses in young rats. In old rats, plasma PRL concentrations and the frequency and magnitude of the PRL pulses were not significantly decreased after injection of either bPRL or BSA. Thus, the feedback inhibition of PRL on PRL release may not be operative in old rats. The loss of the short loop feedback inhibition of PRL is believed to be due to the reduction in hypothalamic dopaminergic activity previously reported by our and other laboratories in old rats.

Aging↗
PubMed1983

Action of tetanus toxin on cholinergic neuroblastoma X glioma hybrid cells: selective blockade of Ca spikes.

We examined the effect of tetanus toxin on clonal neuroblastoma X glioma hybrid cells, NG108-15, by intracellular microelectrode studies of passive membrane electrical properties and action potentials generated under various conditions. Binding of tetanus toxin to the surface of the cells was demonstrated by indirect immunofluorescent staining but no morphological alteration was observed in tetanus toxin-treated cells under a phase contrast microscope. These is no significant difference between the tetanus toxin-treated and untreated cells in their passive electrical membrane properties, i.e. resting membrane potentials, input resistances, time constants and input capacities. Cells in 120 mM Na+, 2 mM Ca2+ salt solution showed Na spikes, and cells in high Ca2+ (30 mM), Na+-free salt solution showed Ca spikes in response to depolarizing current pulses. While the Na spike was not affected by tetanus toxin, the Ca spike was blocked by the toxin. The minimum dose of tetanus toxin for maximum suppression of the peak potential level of the Ca spike was 250 ng/ml. Addition of tetraethyl ammonium (TEA) to extracellular fluid enhanced the Ca spike in untreated cells. In toxin-treated cells, TEA did not alter the effect of tetanus toxin on the Ca spike. Blockade of the Ca spike by tetanus toxin could be detected even at low extracellular Ca2+ concentration (10 mM) by adding TEA to the extracellular fluid and adjusting the membrane potential to a steady hyperpolarized level (-80 mV) to ensure optimal and uniform electrical responses. The usefulness of NG108-15 hybrid cells for in vitro investigations on the mechanism of action of tetanus toxin was discussed.

Action Potentials↗
PubMed1982

Receptor-associated changes of the catecholamine-sensitive adenylate cyclase in glioma cells doubly transformed with Moloney sarcoma virus.

A doubly transformed rat glioma cell line, designated C6V-1, was obtained from rat glioma C6 cells by infection with a rat-adapted variant of Moloney sarcoma virus (MSV-M-os). The C6V-1 cells show karyotypic changes in chromosome number (43) and structure, while C6 cells possess a normal male karyotype. C6V-1 and C6 cells were employed for characterization of a receptor-adenylate cyclase system of the surface membrane. C6V-1 cells showed lower adenylate cyclase activity than that of C6 cells, though the apparent Km for ATP in both types of cells was the same. The maximal stimulation of adenylate cyclase by isoproterenol was significantly reduced, and Kact for isoproterenol was approximately 18-fold lower in C6V-1 cells. When the concentration of beta-adrenergic receptors was measured by various concentrations of [3H] dihydroalprenolol (DHA), the maximal binding sites of C6 and C6V-1 cells were 760 and 230 fmol/mg protein, respectively, without any changes in the association constant for DHA. The concentration of isoproterenol required for 50% displacement of the [3H] DHA binding (Kd) was the same (around 1.5 X 10(-6)M) in both cells, measured in the presence of GTP. Thus the 19-fold drop in the Kd/Kact ratio in C6V-1 cells suggests an incomplete coupling of beta-receptors to adenylate cyclase. Cyclic AMP phosphodiesterase activity and cAMP content in C6V-1 were lower than in C6 cells. Mitochondrial monoamine oxidase and cytosomal enolase activities, however, were somewhat higher in C6V-1 cells. The results indicate that a set of changes in the receptors and in the cyclic AMP system of C6V-1 is one of the specific alterations by transformation, even though those may not be the cause of cell transformation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1982

Effect of nitrogen dioxide exposure on cyclic GMP in rat lung.

In vivo exposure of rats to 10 ppm nitrogen dioxide (NO2) for 6 h caused approx. 5-fold increase in the content of cyclic GMP in lung tissue. This increased cyclic GMP level lasted up to 24 h but returned to the normal level within 2 days, even when the NO2 exposure continued. This increase in the content of cyclic GMP of lung tissue by NO2 exposure was observed in both young and aged rats. There were no statistically significant changes in the content of cyclic AMP in lung tissue.

Animals↗
PubMed1982

A spin trap study on anaerobic dehalogenation of halothane by a reconstituted liver microsomal cytochrome P-450 enzyme system.

In the presence of a spin trapping reagent, N-tert-butyl-alpha-phenylnitrone, anaerobic incubation of halothane (2-bromo-2-chloro-1,1,1-trifluoroethane) with a reconstituted cytochrome P-450 enzyme system of rabbit liver microsomes exhibited an electron spin resonance spectrum containing signals of a nitroxide radical, and all components of the reconstituted system were necessary to produce the nitroxide radical. Formation of 2-chloro-1,1,1-trifluoroethane, the product of anaerobic dehalogenation of halothane by the reconstituted system, was inhibited by N-tert-butyl-alpha-phenylnitrone. These results indicate that a radical intermediate of halothane is produced during the anaerobic dehalogenation reaction, and that the radical is trapped by N-tert-butyl-alpha-phenylnitrone to form a N-tert-butyl-alpha-phenylnitrone radical adduct.

Anaerobiosis↗