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Biomedical subjects

K Obara

Publications and source records attributed to K Obara.

At least 181 records · Page 10Linked to original sources
PubMed1980

Presence of binding component(s) for testosterone in rat liver cytosol.

The existence of testosterone-binding component in the cytosol fraction of the male rat liver was shown. The binding ability of the component with testosterone was decreased by the addition of excess unlabeled steroids, but the steroid binding activity of the serum was not affected. The Scatchard plot indicated that the component has a moderate binding affinity with testosterone and the number of the binding sites of the component is limited.

Animals↗
PubMed1980

Effect of ruthenium red on excitation-contraction coupling in frog skeletal muscle.

The effects of ruthenium red (RR) on electrical and mechanical responses, and on Ca fluxes at rest and during potassium contracture (K contracture) in frog skeletal muscle were examined. By the treatment of single fibers with RR, the peak tensions of twitch and K contracture were inhibited, the degree of inhibition being dependent on the concentration of RR and on the duration of pretreatment. The inhibitory effect of RR on K contracture was pronounced at lower concentrations of K. The recovery of twitch tension from complete inhibition was observed several minutes after removal of RR by washing the fiber in normal Ringer solution, and was accelerated by brief exposure to 190 mM K solution. Caffeine contracture was not affected by RR. Moreover, resting and action potentials were not changed by RR except for an enhancement of a negative afterpotential. From these results, it is concluded that RR blocks excitation-contraction coupling (E-C coupling) in frog skeletal muscle. In addition, Ca influx, especially early rapid Ca influx, was markedly inhibited by RR, although the amount of self-exchangeable Ca was not significantly decreased. On the basis of these results, the sites and mechanism of RR action were discussed.

Action Potentials↗
PubMed1979

Information transmission in multi-input-output stochastic neuron models.

The Shannon's information theory in multi-way channels (Shannon, 1961) is applied to multi-input-output relations of the stochastic automaton models for interaction of excitatory and inhibitory impulse sequences proposed in the previous papers (Tsukada et al., 1977). In these models, the output spike train depends upon several statistical characteristics (mean frequency, standard deviation, form, order-dependence or order-independence, etc.) of the excitatory and inhibitory input spike trains. By the use of the multiple-access channel in information theory, some stochastic properties of temporal pattern discrimination in neurons are analyzed and discussed with biological systems.

Action Potentials↗
PubMed1979

Effect of transverse tubule-disruption on 14C-caffeine influx in frog skeletal muscle.

Effect of transverse tubule-disruption (T-disruption) on 14C-caffeine influx was studied using small bundles, consisting of 40 to 50 fibers, of frog semitendinosus muscle. The peak tension of caffeine contracture was inhibited by about 69% at 5 mM caffeine and by about 31% at 7 mM caffeine by T-disruption. In addition, the amount of caffeine influx in a small bundle was inhibited by about 52% at 5 mM caffeine and by about 28% at 7 mM caffeine by T-disruption, corresponding to the inhibition of the peak tension of caffeine contracture by T-disruption. These findings support our previous suggestion that caffeine enters the muscle fibers through the surface membrane and transverse tubuler membrane (T-membrane), and that the T-membrane contributes to the entry of caffeine more greatly at 5 mM caffeine than at 7 mM caffeine. Moreover, at 5 mM caffeine it was noted that there is a slight difference between the extent of inhibition of the caffeine influx and that of the peak contracture tension. From these results, it could be concluded that the inhibition of peak tension of caffeine contracture by T-disruption is mainly due to the inhibition of caffeine influx which occurs through the T-membrane and is partly due to the functional disturbance of the sarcoplasmic reticulum which is probably induced by T-disruption.

Animals↗
PubMed1979

Induction of the FAD synthetase system in rat liver by phenobarbital administration.

FMN and FAD synthesizing activities in rat liver were investigated when drug metabolizing enzymes were induced by phenobarbital. The FAD content of the liver mitochondrial and microsomal fractions were increased by either one shot administration or three successive daily administrations of phenobarbital. Similarly the flavokinase and FAD pyrophosphorylase activities also increased in the mitochondrial, microsomal and cytosol fractions. The authors have verified that activation of the FAD synthesizing system is induced by phenobarbital and suggest that the FMN and FAD contents are regulated not only by variations of flavin enzyme apoprotein, but also by changes in flavokinase and FAD pyrophosphorylase activities.

Adenosine Triphosphate↗
PubMed1979

Inhibition of testicular androgenesis by urinary antigonadotropins and melatonin in rats.

Comparative in vitro and in vivo studies of the effects of urinary gonadotropin-inhibiting substances and melatonin on the androgenesis in rat testicular homogenates were performed. When the urinary extract containing the inhibiting substances or melatonin was added directly to the incubation medium, and was also injected into rats 24 and 48 hrs prior to sacrifice, either one was effective in suppressing the conversion of pregnenolone to testosterone and/or androstenedione in testicular tissues. The urinary extract exerted the inhibitory effect on the conversion of cholesterol to pregnenolone in vitro and in vivo, whereas melatonin did not have this effect in vitro and in vivo. These findings suggest that the antigonadotropic substances are different from melatonin in their action on androgenesis in the rat testes.

Androstenedione↗
PubMed1978

Effect of actinomycin D or puromycin on microsomal testosterone hydroxylase activity enhanced by testosterone in female rat liver.

The injection of testosterone propionate for 4 successive days into female rats resulted in an increase of the in vitro conversion of the hydroxylated testosterones from testosterone by the hepatic microsomal fraction, but no change in the content of microsomal cytochrome P-450 occurred. Actinomycin D or puromycin, which was administered for 4 days with injections of testosterone propionate, prevented the enzyme induction.

Animals↗
PubMed1978

Serum vitamin B12 levels of patients with rheumatoid arthritis.

To elucidate the role of vitamin B12 in the formation of anemia in patients with rheumatoid arthritis serum B12 levels were investigated in patients with rheumatoid arthritis, patients with osteoarthritis and normal subject. Serum B12 level in patients with rheumatoid arthritis was significantly higher than that in patients with osteoarthritis and normal subjects. Serum B12 level increased in proportion to Steinbrocker's stages, and was related more closely to hemoglobin concentration than to erythrocyte count and had a high correlation with alpha1- and alpha2-globulin.

Adult↗