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Biomedical subjects

M Miyamoto

Publications and source records attributed to M Miyamoto.

At least 595 records · Page 33Linked to original sources
PubMed1980

In vitro antimicrobial activity of cefotaxime, a new cephalosporin.

Cefotaxime, a new semisynthetic cephalosporin derivative, showed a broad spectrum of antibacterial activity against clinically isolated strains of gram-positive and gram-negative bacteria. This cephalosporin was slightly less active than cefazolin against Staphylococcus aureus but 4 to 300 times as active as carbenicillin against gram-negative organisms, including Pseudomonas aeruginosa, Pseudomonas cepacia, Enterobacter cloacae, and Serratia marcescens. Cefotaxime was the most active compound against members of the Enterobacteriaceae and 20- to 100-fold more active than cefoxitin against the indole-positive Proteus group. The minimal bactericidal concentrations of the compound were identical to, or two times higher than, the minimal inhibitory concentrations against Escherichia coli and P. aeruginosa and four times higher against S. marcescens. A reduction of inoculum size decreased greatly the minimal inhibitory and bactericidal concentrations of cefotaxime against E. coli P. aeruginosa, and S. marcescens. The antibiotic was very stable to penicillinase and cephalosporinase produced by gram-negative bacteria, including Proteus vulgaris.

Anti-Bacterial Agents↗
PubMed1980

[Behavioral changes following lesioning of the nucleus accumbens (ACB) and effects of centrally acting drugs in rats (author's transl)].

ACB is one of the sites containing nerve terminals of the mesolimbic dopamine system. We have found that all the male Sprague-Dawley rats with electrolytic lesions of bilateral ACB showed locomotor hyperactivity and hyperemotionality. Muricide was also observed in about 40% of these lesioned rats. Hyperemotionality and muricide were maximum during the first 2-3 days after the lesioning, then gradually declined. Locomotor hyperactivity lasted invariably for over 30 days. Hyperemotionality and muricide were both inhibited by the following drugs given i.p., chlorpromazine; haloperidol; diazepam; estazolam; aminooxyacetic acid (GABA transaminase inhibitor); phenoxybenzamine. However, imipramine, atropine and L-5-hydroxytryptophan inhibited selectively the muricidal behavior. Lesioning of the catecholaminergic (CA) system by administration of 6-hydroxydopamine into bilateral ACB-produced only moderate hyperemotionality with no evidence of locomotor hyperactivity and muricide. These results suggest that lesioning of the CA system plus other neural mechanisms in ACB are required for development of these three forms off hyperemotional behavior. Cholinergic, serotonergic, GABAergic and CA mechanisms may also be involved in hyperemotionality and muricide in ACB lesioned rats.

5-Hydroxytryptophan↗
PubMed1980

[Different effects of the replacement of extracellular sodium with lithium on the abnormal spike discharges caused by 2 convulsants, Metrazol and strychnine, on an identifiable giant neuron of the mollusc Achatina fulica Ferussac].

The influences of the replacement of sodium with lithium in the extracellular medium on the abnormal spike discharges, caused by two convulsants, metrazol and strychnine, of a giant neurone (TAN, tonically autoactive neurone) identified in the suboesophageal ganglia of the African giant snail (Achatina fulica Férussac) were examined. The slow oscillations of potential caused by metrazol disappeared after this replacement. On the other hand, the abnormal action potentials caused by strychnine, as well as the normal action potentials, still remained after the removal of sodium in the medium.

Action Potentials↗
PubMed1980

[Effects of clavines, ergot alkaloids, on the membrane potential of an identifiable giant neuron of the African giant snail Achatina fulica Ferussac].

The effects of seven clavines, alkaloids of ergot, on the electrical activity of an identifiable giant neurone (TAN, tonically autoactive neurone) of the African giant snail were examined. All the substances examined, lysergine, agroclavine, elymoclavine, festuclavine, chanoclavine, rugulovasine A and rugulovasine B, at 2 X 10(-4) kg/l have no constant effect on TAN, indicating that they have no direct effect on this neurone. However, the substances examined, except for chanoclavine, in the same concentration occasionally caused the transient depression with an augmentation of trans-synaptic influences. This depression may be due to the trans-synaptic influences. The four substances examined, lysergine, agroclavine, elymoclavine and festuclavine, in the same concentration produced TAN abnormal spike discharges, doublet or triplet spikes.

Animals↗
PubMed1980

Inhibitory effects of ergot alkaloids and their derivatives on the excitability of an identifiable giant neurone of the African giant snail (Achatina fulica Férussac).

The effects of ergot alkaloids and their derivatives on the excitability of an identifiable giant neurone, TAN (tonically autoactive neurone), found in the suboesophageal ganglia of the African giant snail (Achatina fulica Férussac) were examined. Ergometrine and methylergometrine had the strongest inhibitory effects. The critical concentrations were 3 X 10(-5) approximately 10(-4) kg/l. The three hydrogenated ergot derivatives, 9, 10-dihydroergocristine, 9, 10-dihydroergocryptine and 9, 10-dihydroergocornine, had weaker inhibitory effects than those of ergometrine and methylergometrine. The other substances examined, including D-lysergic acid, D-lysergic acid amide, D-lysergic acid piperidinamide, had no effect. Some of the substances examined, for example, lysergine, agroclavine, elymoclavine, nicergoline, ergotamine, bromocriptine and lergotrile, at high concentrations occasionally caused transient inhibition immediately after their application. This inhibition may be due to the synaptic influences produced by the excitation of other neurones. Some of the substances examined, lysergine, agroclavine, elymoclavine, festuclavine, nicergoline and lergotrile, at high concentrations caused abnormal spike discharges of TAN such as doublet or triplet spikes.

Animals↗
PubMed1979

[The high pressure liquid chromatography of corticoids. II. Analysis of synthetic corticoids in blood and urine (author's transl)].

The high pressure liquid chromatographic (HPLC) technique was developed to separate and quantitate the synthetic corticosteroids (s-CS) which are widely used clinically. 1) 12 kinds of s-CS in alcoholic solvent and 2) some of their metabolites in the plasma and urine of healthy subjects with oral administration of s-CS were investigated for the preliminary work. The results are summarized as follows: 1) Cortisol sodium phosphate, Dexamethasone 21, disodium phosphate, Paramethasone acetate, Cortisol acetate, Cortisone acetate, Methylprednisolone acetate, Prednisone, Dexamethasone, 9 alpha-fluorocortisol, Betamethasone, Triamcinolone, and Prednisolone in ethanol were clearly separated by HPLC from Cortisol (F). In the suitable condition of the HPLC (LC-2 type) with a Zorbax SIL column, organic solvent (cyclohexane:dichloromethane:ethanol = 9:4:1)-carrier mobile phases and UV detector, the retention time of each s-CS was obviously different from that of F. The calibration curve was obtained in a linear line with regards to each s-CS. The mean recovery was 97.6% and the coefficient of variation were 1.6 (intraassay) and 7.2 (interassay)%. The sensitivity of the steroid determination was 200pg order. 2) The serial changes in plasma concentrations of s-CS; CS-metabolites and endogenous F were shown in 3 healthy males and 2 females following oral administration of the s-CS. The separated metabolites in number and quality depended on the kind of s-CS. Prednisone and other kinds of the acidified products were separated from prednisolone in the plasma and urinary samples of the healthy subjects as well as Addisonian patients. In conclusion, the HPLC method is useful for the separation and quantitation of the UV-absorbing CS of human plasma and urine. The obtained chromatograms may be an indication of the metabolic state of the subject with treatment of s-CS.

Adrenal Cortex Hormones↗
PubMed1979

[Thyrotropin-releasing hormone (TRH): Enhancement of dopamine dependent circling behavior and its own circling-inducing effect in unilateral striatal lesioned animals (author's transl)].

Enhancement by TRH of the dopamine(DA) agonist-induced circling behavior and effect of TRH itself on circling behavior were investigated. TRH(2.5--20 mg/kg, i.p.) remarkably enhanced the circling behavior induced by apomorphine or-L-DOPA in the mice lesioned unilaterally in the caudate nucleus by injection of 6-hydroxydopamine (60OHDA) or by tissue aspiration with subsequent reserpinization. TRH also enhanced the apomorphine-induced stereotypy in reserpinized normal mice. The above TRH-enhancing action of the circling behavior was potentiated, suppressed or unaffected by alpha-methyl-para-tyrosine (alpha-MT) or GABA-ergic drugs. In the 6-OHDA lesioned mice treated with TRH, the cyclic AMP formation by DA or apomorphine was clearly enhanced in the triatal slices taken from the lesioned side but not from the intact side. In the rats lesioned unilaterally in the nigrostriatal DA pathway by 6-OHDA, high doses of TRH injected i.p. (100 mg/kg) or into the non-lesioned caudate nucleus (50 micrograms) produced circling toward the lesioned side, which was suppressed by haloperidol or alpha-MT. TRH(10(-5)--10(-3)M) increased the 14C-DA release from the rat striatal slices in vitro. These results suggest that TRH at low doses facilitates the DA postsynaptic transmission in association with an increase of DA-stimulated cyclic AMP formation in the striatum under supersensitization of the DA receptors, and also at high doses enhances the DA neuronal activity by increasing the DA release from the striatal nerve terminals.

Animals↗
PubMed1979

Suppression of graft-versus-host reaction by preincubation of the graft with an antitumor protein, neocarzinostatin.

The immunosuppressive activity of neocarzinostatin, an antitumor antibiotic with a high molecular weight, was demonstrated, as measured by the local and systemic graft-versus-host reaction in rats. The preincubation of parental strain lymphocytes with doses more than 1 micrograms/ml of neocarzinostatin for at least 10 min at 37 degrees C resulted in the marked suppression of the popliteal lymph node enlargement, when injected subcutaneously into the hind footpads of F1 hybrid rats. The suppressive effect was temperature-dependent and irreversible, because the neocarzinostatin (1 microgram/ml) pretreatment of parental lymphocytes at 4 degrees C was not effective in the suppressive activity, and the reincubation of cells after the removal of the drug from the culture did not result in demonstrable changes in the degree of suppression. The neocarzinostatin pretreatment does not result in visible changes in the oxygen consumption rate and viability of cells in vitro or in the distribution pattern within a regional lymph node, indicating that treated cells may retain the same viability and migration capacity in vivo as do untreated cells. Furthermore, the drug pretreatment resulted in the complete prevention of runting syndrome, when treated parental lymphocytes were injected intravenously into F1 hybrid rats.

Animals↗
PubMed1979

Changes in 2,3-DPG content and oxygen affinity in erythrocytes stored at 4 degrees C.

The 2,3-DPG content of red blood cells increased within the first 24 h when fresh erythrocytes or whole blood were stored 4 degrees C. This phenomenon was strongly pH dependent. The temporary increase in 2,3-DPG was scarcely observed below pH 7.4 or above pH 7.8. In the case of whole blood, the increase was observed in CPD blood out not in ACD blood. Similar results were obtained with erythrocytes suspended in saline, when its pH was adjusted to approximately 7.6. Plasma proteins were not essential for the increase in 2,3-DPG content. Extracellular oxygen levels were continually measured in erythrocytes suspensions in order to check the changes in oxygen affinity of hemoglobin without damaging the cells. Both extracellular oxygen levels and 2,3-DPG contents were simultaneously increased by keeping fresh erythrocytes at 4 degrees C. Inhibition of glycolysis with sodium fluoride and monoidoacetic acid indicated that the in vivo steady state of glycosis in erythrocytes might be altered by chilling to make the rate of 2,3-DPG synthesis faster than that of 2,3-DPG decomposition.

Citrates↗
PubMed1979

Reduced response of plasma aldosterone to acute ACTH stimulation during long-term treatment with spironolactone in essential hypertension.

The response of plasma aldosterone (PA) to ACTH administration (250 micrograms alpha 1-24 ACTH i.m.) before and during treatment with spironolactone (Sp, 75--100 mg/day) for at least 8 months was studied in 11 patients with essential hypertension. These responses were compared with those before and during prolonged treatment with hydrochlorothiazide (Th, 50--75 mg/day), with or without potassium supplement, in 14 hypertensives. PA and plasma cortisol (PC) were determined by radioimmunoassay in which Sp showed minimal cross-reactivity. Both Sp and Th treatments caused similar increases in plasma renin activity accompanied by nearly identical decreases in blood pressure and body weight. PA was also increased by both treatments, but to a significantly greater extent in the Sp-treated group. Serum potassium concentration was increased only by Sp treatment. The response of PA, but not of PC, to acute ACTH stimulation was blunted in the Sp-treated group. That is, the maximal increment of PA above the baseline level was significantly lower during Sp treatment than either before Sp treatment of during Th treatment. These results demonstrate that long-term treatment with Sp can inhibit aldosterone production by acute ACTH stimulation in patients with essential hypertension.

Adrenocorticotropic Hormone↗
PubMed1979

Thyrotropin-releasing hormone: hyperactivity and mesolimbic dopamine system in rats.

The mechanism of stimulatory action of thyrotropin-releasing hormone (TRH) on spontaneous motor activity was investigated in rats. TRH produced a significant hyperactivity with intraperitoneal administration of 20 mg/kg or bilateral injection of 10 micrograms into the nucleus accumbens septi (NAS). Following bilateral injection of 6-hydroxydopamine into the mesolimbic dopamine (DA) pathway, the hyperactivity induced by TRH was not altered, whereas the response to apomorphine given intraperitoneally or DA injected into the NAS was clearly enhanced. The TRH-induced hyperactivity was remarkably suppressed by alpha-methyltyrosine and in contrast, augmented by pargyline. Systemic injection of aminooxyacetic acid in a dose producing behavioral depression reduced markedly the TRH-induced hyperactivity. Bilateral injection of ethanolamine O-sulphate (100 micrograms) into the NAS produced no behavioral depression per se, but remarkably attenuated the hyperactivity response to TRH or DA (20 micrograms) given intraperitoneally or into the NAS. Both TRH (10(-5) and 10(-4) M) and methamphetamine (10(-6)--10(-4) M increased the spontaneous release of 14C-DA from rat NAS slices. These findings suggest that TRH induces hyperactivity by enhancing DA release from nerve terminals in the NAS without a direct stimulation of the post-synaptic DA recptors. TRH and GABA, independently or via interaction between them, may play a reciprocal regulatory role in the activity of the mesolimbic DA system.

Animals↗
PubMed1979

Prolonged pseudoaldosteronism induced by glycyrrhizin.

We describe the natural recovery from the aggravated hypertension, hypokalemia and suppression of the renin-aldosterone axis after the glycyrrhizin discontinuation in two mild hypertensive women aged 71 and 68 years, who had been administered 273 to 546 mg glycyrrhizin daily for 1.5 and 6 months, respectively, for the treatment of liver disease. About one month after the glycyrrhizin discontinuation, acceleration of hypertension, hypokalemia and suppression of the renin-aldosterone system still continued in both patients. At this stage, sodium restriction resulted in the normalization of blood pressure with weight loss and the subsequent sodium repletion produced a rapid increase in blood pressure to hypertensive levels observed before sodium restriction, with weight gain. Plasma renin activity and plasma aldosterone were low and did not respond to sodium restriction. Inappropriately excessive amounts of potassium were also excreted in the presence of hypokalemia. About one and a half months later, the improvements of aggravated hypertension, hypokalemia and suppressed renin-aldosterone system gradually occurred in both patients. Sodium restriction performed about three months later in case 2 no longer produced the changes in blood pressure and body weight. Plasma renin activity and plasma aldosterone responded subnormally to sodium restriction. These results demonstrate that both patients had a prolongation of the syndrome resembling primary aldosteronism except the low plasma aldosterone level about one month after the glycyrrhizin discontinuation. The possible mechanisms by which this prolongation was caused are discussed.

Aged↗