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Biomedical subjects

T Hidaka

Publications and source records attributed to T Hidaka.

306 records · Page 17Linked to original sources
PubMed1969

Responses of the smooth muscle membrane of guinea pig jejunum elicited by field stimulation.

Field stimulation of the jejunum elicited successively an action potential of spike form, a slow excitatory depolarization, a slow inhibitory hyperpolarization, and a postinhibitory depolarization as a rebound excitation. The slow depolarization often triggered the spike. The inhibitory potential showed lower threshold than did the excitatory potential. Both the excitatory potentials were abolished by atropine and tetrodotoxin. Effective membrane resistance measured by the intracellular polarizing method was reduced during the peak of the excitatory potential, but the degree of reduction was smaller than that evoked by iontophoretic application of acetylcholine. Conditioning hyperpolarization of the muscle membrane modified the amplitude of the excitatory potential. The estimated reversal potential level for the excitatory potenialt was about 0 mv. No changes could be observed in the amplitude of the inhibitory potential when hyperpolarization was induced with intracellularly applied current. Low [K](o) and [Ca](o) blocked the generation of the excitatory potential but the amplitude of the inhibitory potential was enhanced in low [K](o). Low [Ca](o) and high [Mg](o) had no effect on the inhibitory potential.

Acetylcholine↗
PubMed1969

Biophysical and mechanical properties of red and white muscle fibres in fish.

1. The electrical properties of red muscle fibres of the silver carp (Carassius auratus (Linné)) were investigated and compared with those of white fibres. The resting membrane potential of red muscle was -73.1 mV, and of white muscle -82.4 mV. The effective resistance of fibre, time constant and space constant were 1.43 MOmega, 26.6 msec and 2.1 mm for red muscle and 1.0 MOmega, 48.4 msec and 1.9 mm for white muscle.2. The membrane capacitance in red muscle was 2.55 muF/cm(2) and in white muscle was 7.23 muF/cm(2), though the sarcoplasmic reticulum and the transverse tubular system were developed equally in both tissues.3. No rectification could be observed in the current-voltage relation in both the muscles. However, in excess potassium solutions, both types of muscle showed anomalous rectification.4. In red muscle it was rare to trigger a spike by nerve stimulation or by field stimulation of the tissue. However, in white muscle, there appeared graded responses and occasionally spikes were generated with overshoot potentials.5. Excess potassium concentration produced contracture in the red muscle, but even forty times of normal potassium never produced contracture in the white muscle.

Animals↗
PubMed1969

Effects of catecholamines on the cholinergic neuromuscular transmission in fish red muscle.

1. The effects of adrenaline and noradrenaline on neuromuscular transmission and the question of whether these catecholamines act on the presynaptic nerve terminal or on the post-synaptic membrane were investigated using the fin muscles of the silver carp.2. Noradrenaline (10(-8)-10(-6) g/ml.) had no effect on membrane potential or input resistance of the membrane. In contrast, adrenaline (10(-8)-10(-6) g/ml.) hyperpolarized the membrane and increased the input resistance.3. Noradrenaline had no effect on the amplitude of the miniature junction potentials but caused them to become more frequent.4. Adrenaline enhanced the amplitude of the miniature junction potentials and slightly increased their frequency. These effects of adrenaline were partly due to the increased input resistance of the post-synaptic membrane, and probably did not involve the presynaptic terminals.5. Both noradrenaline and adrenaline increased the amplitude and prolonged the falling phase of the excitatory junction potentials (e.j.p.s).6. Noradrenaline enhanced the amplitude and prolonged the duration of the extracellularly recorded excitatory junction current. No such effect was observed with adrenaline.7. Adrenaline but not noradrenaline enhanced the amplitudes of acetylcholine potentials evoked by iontophoretic application of acetylcholine.8. Noradrenaline and adrenaline had no effect on the compound action potentials of the nerve supplying the red muscle, recorded by the sucrose gap method.

Acetylcholine↗
PubMed1967

The action of 5-hydroxytryptamine on Mytilus smooth muscle.

1. In the nerve-muscle preparation, where catch was characteristically minimal, 5-hydroxytryptamine (5-HT) had no effect on resting membrane potential, junction potentials, spikes or contraction.2. In muscle bundles, where catch was prominent, 5-HT did not change membrane potentials, but prolonged junction potentials and lowered the threshold for spike discharge and contraction.3. In muscle bundles, exposed to high concentrations of 5-HT, depolarization evoked repetitive spikes, while in low 5-HT, spikes were seldom fired even with much greater depolarization.4. In muscle bundles, the effective membrane resistance, R(eff.), decreased from 45-60 to 23-35 MOmega as 5-HT concentration was increased.5. It is suggested that 5-HT may facilitate spike discharge by lowering the internal free Ca(2+) concentration.

Animals↗
PubMedDate not supplied

Reduction in the incidence of Helicobacter pylori-associated carcinoma in Japanese young adults.

Helicobacter pylori (Hp) is a major risk factor for gastric carcinogenesis. In Japan, the incidence of Hp infection in young adults has declined markedly. The purpose of this study was to clarify this trend in the incidence of Hp-associated gastric carcinoma (GCa) in young (under 30 years of age) Japanese patients. We enrolled 53 such patients who underwent surgical resection of GCa in one of 18 hospitals in the Hiroshima prefecture between 1976 and 1999. The patients were classified into groups based on three 8-year periods (1976-83, 1984-91, and 1992-1999) in which their cases occurred. We compared the numbers of patients and estimated the histology of carcinomas, grades of gastritis and Hp infection histologically. Of the 53 patients, 49 (92%) showed Hp infection. The frequency of GCa in young adults has decreased gradually (21, 18, and 14 patients in 1976-83, 1984-91 and 1992-99, respectively). The numbers of Hp-positive carcinomas decreased radically (21, 17 and 11 patients, respectively). This trend was associated with improvement in the degree of gastritis in non-neoplastic mucosa. Of the four Hp-negative patients, three had signet ring cell carcinoma. Moreover, the numbers of patients with non-signet ring cell carcinoma also decreased (18, 12 and 7 patients in each period, respectively). These results suggest that Hp-associated carcinoma has declined gradually in young Japanese.

Adolescent↗
PubMedDate not supplied

Membrane fluidity in Ehrlich ascites tumor cells treated with adriamycin.

The incubation of Ehrlich ascites tumor cells with adriamycin resulted in an increase in lipid peroxide content and a decrease in membrane fluidity as measured by electron spin resonance using the paramagnetic probe 5-doxylstearic acid. Coincidently, the incorporation of [3H]thymidine into tumor cells was progressively inhibited as the concentration of adriamycin was increased. The results indicate that adriamycin induces changes in the plasma membrane of Ehrlich ascites tumor cells after exposure to a low, but cytotoxic, level of this agent.

Animals↗