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Biomedical subjects

H Nitta

Publications and source records attributed to H Nitta.

At least 127 records · Page 7Linked to original sources
PubMed1980

Inhibitory action of lanthanum(La) on PGF2 alpha - induced contraction of guinea-pig stomach muscle.

The effects of lanthanum(La) on contractions induced by prostaglandin F2 alpha(PGF2 alpha) or isotonic K+ were investigated in the isolated stomach muscle of guinea-pig. Low concentrations of La( 0.1-1 microM) inhibited the contraction to PGF2 alpha 1 microM in a dose-dependent manner, without affecting the tonic contraction to isotonic K+. 0.1 and 1 microM La shifted the dose-response curve for PGF2 alpha( 0.001 - 1 microM) to the right and reduced the maximum response. The IC50 of La against PGF2 alpha and K+ were 0.6 microM and 30 microM, respectively. These results support the suggestion that PGF2 alpha -induced contraction in the stomach muscle depends mainly on the intracellular release of sequestered Ca, which would be depleted or immobilized by La.

Animals↗
PubMed1980

Endogenous prostaglandins and spontaneous contractions in the circular muscle of the guinea-pig stomach.

The physiological significance of endogenous prostaglandin (PG) on spontaneous contractions in isolated circular muscles of the guinea-pig stomach was investigated. Contents of the E and F types of PG were measured by radioimmunoassay as PGE2 and PGF2 alpha. The isolated circular muscles contained 17.04 +/- 2.12 ng PGE2/g tissue (n = 12) and 9.38 +/- 0.62 ng PGF2 alpha/g tissue (n = 12), and released 0.36 +/- 0.04 ng PGE2/g tissue/min (n = 10) and 0.14 +/- 0.01 ng PGF2 alpha/g tissue/min (n = 12) into the solution. These contents and releases of PGs were reduced by treatment with indomethacin (ID50 = 0.3 microgram/ml). Indomethacin (0.1-6 microgram/ml) increased the amplitude of spontaneous contractions dose-dependently, while high concentrations (20 microgram/ml) conversely depressed it. Physiological concentrations of exogenously applied PGE2 (0.03-0.35 ng/ml) markedly suppressed spontaneous contractions in the presence and absence of indomethacin (3 microgram/ml), while PGF2 alpha in concentrations of 0.35-3.54 ng/ml slightly increased them. Therefore, these results suggested that spontaneous contractions in circular muscles were largely influenced by the E type of endogenous PG, not by the F type. The indomethacin-induced increase in the amplitude of spontaneous contractions was not affected by intrinsic nerves and was accompanied by an increase in spike discharges on the slow wave and 45Ca uptake in the muscle cells. These observations suggested that the E type of endogenous PG in circular muscles might play a suppressive role in spontaneous contractions by inhibiting spike generation on the slow wave.

Animals↗
PubMed1979

Study on trace impurity elements in highly purified iron and aluminum by neutron activation analysis.

Activation analysis was carried out on the purified iron and aluminum to study the behavior of trace impurities on purification process, and to estimate the purity of the purified samples. Thermal neutrons with high Cd ratio through D2O column or graphite column were used for the activation of samples to reduce the interference effects by fast neutrons, the reactions, (n, p) or (n, a), from matrix elements. On the zone refined aluminum, the segregation of impurity elements was cleary observed. In the case of iron, decrease of impurity content was confirmed on superposing the various purification processes.

Aluminum↗