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Biomedical subjects

M Nishimura

Publications and source records attributed to M Nishimura.

At least 1,351 records · Page 75Linked to original sources
PubMed1981

Cytomorphological study of cultured mammalian cells treated with benzaldehyde, catechol and their derivatives with special reference to inhibition of DNA synthesis.

Cytotoxicity and cytomorphological changes induced in cultured mammalian cells by the application of benzaldehyde, pyrocatechol and their derivatives were examined. Among the compounds tested, 3,4-dihydroxybenzaldehyde (protocatechualdehyde) and 1,2-dihydroxybenzene (pyrocatechol) produced cytomorphological changes characteristic of specific inhibitors of DNA synthesis in V79 cells and EJ-1 cells. However, they did not induce such changes in HeLa cells. 2,3-Dihydroxybenzaldehyde and catecholamines did not produce such characteristic changes in V79 cells. The cytological effects of protocatechualdehyde and pyrocatechol were confirmed by a study on the incorporation of 3H-precursors of DNA, RNA and protein into 3 cell lines.

Animals↗
PubMed1981

[Toxic and metabolic liver injury (author's transl)].

Water soluble exogenous compounds are commonly excreted by the kidneys, but most of the exogenous substances are lipid soluble and have therefore first to be metabolized in the liver to water soluble compounds. Depending upon the nature of the chemical compound, the metabolism in the liver leads either to detoxification or toxification. Alcohol belongs to the most important substances which may cause severe liver injury. Alterations of the liver due to hydrocarbons as well as carcinogens, mycotoxins and thorium dioxide are relatively rare. Compounds such as analgesic and antiarrhythmic drugs, antibiotics, oral antidiabetic agents, antihypertensive and antirheumatic agents, chemotherapeutic drugs, hormones, laxatives, psychotropic drugs, thyreostatic and antineoplastic agents may also cause liver injury. For establishing the diagnosis, a detailed past history is required especially with respect to alcohol and drug consumption as well as regarding occupational exposure towards toxic compounds. Although the determination of liver enzyme activities in the serum may give some indication for liver cell injury, the histological examination of the liver by needle biopsy is required for the diagnosis. The therapy consists of the exclusion of the toxic compound and, if possible, of an increased elimination of the ingested toxins.

Alcoholic Intoxication↗
PubMed1981

Antiproliferative activity of protocatechualdehyde on Chinese hamster cells grown in culture.

The mode of cytotoxic action of protocatechualdehyde on V79 cells was examined. The cytotoxicity of protocatechualdehyde on V79 cells was time- and cell cycle-dependent. The lethal action is selective for the cells at S phase only. The cells lethally damaged at S phase seemed to complete their DNA synthesis, although the rate of DNA synthesis became lower and the duration of S phase was prolonged. Some cells arriving at G2 phase directly entered the next S phase without cell division and died of karyorrhexis or karyolysis. Cells treated at stages of the cell cycle other than S showed normal progression of their cell cycle to the G1/S boundary. The block point of the cell cycle seemed to lie a little behind that with hydroxyurea. When the cells at phases other than S were blocked with protocatechualdehyde for 14 hr, elongation of the next S phase occurred after removal of protocatechualdehyde. On alkaline sucrose gradient analysis, little scission of parental DNA was observed in the cells treated with protocatechualdehyde.

Animals↗
PubMed1980

Salt-induced pH changes in spinach chloroplast suspension. Changes in surface potential and surface pH of thylakoid membranes.

A pH decrease in chloroplast suspension in media of low salt concentration was observed when a salt was added at pH values higher than 4.4, while at lower pH values a pH increase was observed. The salt-induced pH changes depended on the valence and concentration of cations of added salts at neutral pH values (higher than 4.4) and on those of anions at acidic pH values (lower than 4.4). The order of effectiveness was trivalent greater than divalent greater than monovalent. The pH value change by salt addition was affected by the presence of ionic detergents depending on the sign of their charges. These characteristics agreed with those expected from the Gouy-Chapman theory on diffuse electrical double layers. The results were interpreted in terms of the changes in surface potential, surface pH and the ionization of surface groups which result in the release (or binding) of H+ to (or grom) the outer medium. The analysis of the data of KCl-induced pH change suggests that the change in the surface charge density of thylakoid membranes depends mainly on the ionization of carboxyl groups, which is determined by the surface pH. When the carboxyl groups are fully dissociated, the surface charge density reaches -1.0 +/- 0.1 . 10(-3) elementary charge/square A. Dependence of the estimated surface potential on the bulk pH was similar to that of electrophoretic mobility of thylakoid membrane vesicles.

Cations↗
PubMed1980

Correlation of membrane-potential-sensing carotenoid to pigment-protein complex II in Rhodopseudomonas sphaeroides.

The changes in carotenoid absorbance induced by illumination or by a diffusion potential were larger in chromatophores from cells cultured under low light intensity than those in chromatophores from high-light culture in a photosynthetic bacterium, Rhodopseudomonas sphaeroides. The carotenoid molecules which are associated with the pigment-protein complex (with the infrared bacteriochlorophyll peaks at 800 and 850 nm) (complex II) probably respond to the electrical field changes in the chromatophore membrane.

Bacterial Chromatophores↗
PubMed1980

Thermodynamics of electron transfer and its coupling to vectorial processes in biological membranes.

A method is developed to express the flux of an electron transfer reaction as a function of the conjugate force, the redox potential difference, throughout the nonlinear region. The flux can be expressed by a product of the hyperbolic sine of the force, a factor ("redox-poising parameter") determined by the redox potentials of subsystem (in certain cases by local pH's and pK's of subsystems), and some constants. This is analogous to the expression of the flux of a diffusion process by the product of its force and the concentration of the diffusing species. The redox-poising parameter corresponds to the concentration term. The expression is applied to redox chains in which electron transfers are coupled to vectorial processes such as proton translocation or electric current.

Electron Transport↗
PubMed1980

Effects of surface potential on the equilibrium and kinetics of redox reactions of membrane components with external reagents in chromatophores from Rhodopseudomonas sphaeroides.

The characteristics of the salt and pH dependences of the redox levels of cytochrome c2 and reaction center bacteriochlorophyll were studied in chromatophores from Rhodopseudomonas sphaeroides. They could be explained in terms of the difference of redox potential in the membrane from that in the bulk aqueous phase due to the electrostatic potential difference arising from charges fixed on the membrane surface. The midpoint potentials (Em) became lower when the surface potential (the electrostatic potential at the surface with reference to the bulk aqueous phase) had large negative values at lower salt concentrations at neutral pH, as predicted by the Gouy-Chapman theory. The rate of oxidation of cytochrome c2 in chromatophores by ferricyanide also depended on salt and pH levels. The rate was low at low salt concentrations, probably because of the lower surface concentration of ferricyanide compared with the bulk concentration, due to the surface potential.

Bacterial Chromatophores↗
PubMed1980

Cytotoxicity of methyl bromide: effect of methyl bromide on cultured mammalian cells.

Cytotoxicity of methyl bromide on cultured mammalian cells was examined. Acute toxic action was induced by methyl bromide itself and its cytotoxicity was reduced in the presence of glutathione. Its hydrolysis products or its reaction products with organic compounds in the medium was extremely low in toxicity. Although methyl bromide is known to be a methylating agent, morphological changes induced on HeLa cells were different from the changes characteristic of chemotherapeutic alkylating agents. Lethal concentration of methyl bromide on HeLa cells and primary cultured muscle, kidney and brain cells was similar (10 microgram/ml). In a detailed survey, however, there was a slight difference in the susceptibility among the cells from primary culture of brain.

Animals↗
PubMed1980

The spontaneous action potential of rabbit atrioventricular node cells.

The rabbit atrioventricular (A-V) node, with dimensions of approximately 5 X 3 mm was dissected into 15 small specimens (0.5 X 0.5 mm). A majority of the specimens continued to discharge spontaneous action potentials, the action potential configuration being almost identical in different specimens. The amplitude (98 mV) and the maximum rate of rise of the action potential (11 V/sec) were similar to those recorded from the intact A-V node (amplitude 98 mV, maximum rate of rise of action potential 12 V/sec). In these small specimens, the "resting membrane potential (-44 mV)" was approximately 20 mV less negative than that in the intact A-V node preparation (-62 mV) before the dissecting procedure. The spontaneous discharge in these small A-V node specimens was attributed to the low resting membrane potential. The small specimen became inexcitable under the effects of blockers of is, though TTX had no significant effect on the action potential. The after-hyperpolarization was observed after cessation of the depolarizing current pulse. It is concluded that the slow inward current and the slow kinetics of the outward current contribute to the generation of the spontaneous A-V node action potentials as in the sinoatrial node.

Action Potentials↗
PubMed1980

Effect of an intravenous infusion of ethanol on serum enzymes and lipids in patients with alcoholic liver disease.

Administration of ethanol to healthy subjects as well as those with alcoholic fatty livers has been noted to cause mild elevation of serum enzyme activities and alcoholic hyperlipemia. To see whether this effect is also manifested in alcoholics with advanced liver damage, the serum enzyme activities and lipid content after administration of i.v. ethanol (1.2 g/kg of body wt) over 90 min were compared in 5 alcoholics with hepatic fibrosis and/or alcoholic fatty liver and in 9 patients with alcoholic hepatitis with or without cirrhosis. Disappearance rate of ethanol from the serum was nearly the same in both groups. Serum activities of asparate aminotransferase, mitochondrial isoenzyme of asparate aminotransferase, and ornithine carbamyl transferase, measured at 9 and 12 hr after termination of the i.v. ethanol, were significantly elevated in alcoholics with alcoholic hepatitis (P less than 0.05). They were not elevated in alcoholics with fatty liver. By contrast, hyperlipemic responses, measured as the serum content of triacylglycerol 3 hr after ethanol were significantly greater in alcoholics with fatty liver than in alcoholics with alcoholic hepatitis (P less than 0.05). The observed difference in responses of serum enzyme activities and lipid content after ethanol represents an enhanced susceptibility of patients with alcoholic hepatitis and cirrhosis towards alcohol-induced injury.

Adult↗