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Biomedical subjects

H Hirata

Publications and source records attributed to H Hirata.

At least 325 records · Page 18Linked to original sources
PubMed1973

Role of an electrical potential in the coupling of metabolic energy to active transport by membrane vesicles of Escherichia coli.

Membrane vesicles from E. coli can oxidize D-lactate and other substrates and couple respiration to the active transport of sugars and amino acids. The present experiments bear on the nature of the link between respiration and transport. Respiring vesicles were found to accumulate dibenzyldimethylammonium ion, a synthetic lipid-soluble cation that serves as an indicator of an electrical potential. The results suggest that oxidation of D-lactate generates a membrane potential, vesicle interior negative, of the order of -100 mV. In vesicles lacking substrate, an electrical potential was created by induction of electrogenic efflux of K(+) with the aid of the K(+) ionophores, valinomycin and monactin. These conditions induced transient accumulation by the vesicles of [(14)C]proline and other metabolites. Experiments with inhibitors and ionophores indicate that neither ATP nor the respiratory chain is involved; the electrical potential generated by K(+) efflux is coupled directly to the transport systems. The results verify two predictions derived from Mitchell's chemiosmotic hypothesis: respiring vesicles generate an electrical potential of the proper polarity and magnitude; and a membrane potential is in itself sufficient to drive the active transport of amino acids and other metabolites.

Ammonium Chloride↗
PubMedDate not supplied

Artificial metastases and decrease of fibrinolysis in the nude mouse lung after hemithoracic irradiation.

X-irradiation to the nude mouse lung and the ensuing pulmonary metastasis of the injected human cancer cells were investigated. Human cancer cells were injected intravenously into nude mice following 20 Gy right hemithoracic irradiation. The right lungs showed evidence of metastasis while metastasis was slight in the non-irradiated left lung. Platelet aggregation and fibrin deposition occurred around the arrested cancer cells in the capillaries of the right lung. The fibrinolytic activity of the irradiated right lung was lower than that of the non-irradiated contralateral lung. Natural killer cell activity was lower in the right-lung-irradiated mice than in the non-irradiated mice. We conclude that when the target organ is exposed to X-irradiation, there will be a decrease in fibrinolytic activity, a condition paving the way toward a metastasis.

Animals↗
PubMedDate not supplied

Calcium antagonist flunarizine hydrochloride affects striatal D2 dopamine receptors in the young adult and aged rat brain.

The calcium (Ca) antagonist flunarizine hydrochloride (FNZ) has been reported to induce parkinsonism, especially in the elderly. The effects of FNZ on dopamine receptors in rat striatal membranes, especially in aged rats, were studied using radiolabeled receptor assay. Similar displacing potencies in [(3)H]spiperone bindings were exhibited for FNZ and the Ca antagonists verapamil and nicardipine. FNZ was found to directly and competitively effect D2 receptors (D2-Rs) as an antagonist, without effecting D1 receptors. Furthermore, the washing of preoccupied membranes revealed that FNZ has a long-acting potent effect on D2-Rs. The comparative study of FNZ and sulpiride in young-adult and aged rats showed that the effect of FNZ on D2-Rs was more marked in aged rats. These results might be related to FNZ-induced parkinsonism and its high incidence in the elderly.

Journal Article↗