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M Nishimura

Publications and source records attributed to M Nishimura.

At least 19 recordsLinked to original sources
PubMed1979

Effect of surface potential on the intramembrane electrical field measured with carotenoid spectral shift in chromatophores from Rhodopseudomonas sphaeroides.

Changes in the surface potential, the electrical potential difference between the membrane surface and the bulk aqueous phase were measured with the carotenoid spectral shift which indicates the change of electrical field in the membrane. Chromatophores were prepared from a non-sulfur purple bacterium, Rhodopseudomonas sphaeroides, in a low-salt buffer. Surface potential was changed by addition of salt or by pH jump as predicted by the Gouy-Chapman diffuse double layer theory. When a salf was added at neutral pH, the shift of carotenoid spectrum to shorter wavelength, corresponding to an increase in electrical potential at the outside surface, was observed. The salts of divalent cations (MgSO4, MgCl-2, CaCl2) were effective at concentrations lower than those of monovalent cation salts (NACl, KCl, Na2SO4) by a factor of about 50. Among the salts of monoor divalent cation used, little ionic species-dependent difference was observed in the low-concentration range except that due to the valence of cations. The pH dependence of the salt-induced carotenoid change was explained in terms of the change in surface charge density, which was about 0 at pH 5--5.5 and had negative values at higher pH values. The dependence of the pH jump-induced absorbance change on the salt concentration was also consistent with the change in the charge density. The surface potential change by the salt addition, which was calibrated by H+ diffusion potential, was about 90 mV at the maximum. From the difference between the effective concentrations with salts of mono- and divalent cations at pH 7.8, the surface charge density of (-1.9 +/- 0.5) . 10(-3) elementary charge per A2, and the surface potential of about -100 mV in the presence of about 0.1 mM divalent cation of 5 mM monovalent cation were calculated.

Bacterial Chromatophores↗
PubMed1979

Inducibility of chromosomal aberrations by metal compounds in cultured mammalian cells.

Metal compounds were tested for their ability to induce chromosomal aberrations in cultured mammalian cells. Chromosomal aberrations were induced by the application of some Cr, Mn and Ni compounds. Among 6-valent Cr compounds, K2Cr2O7 and CrO3 induced high levels of aberrations, at rates which were similar for Cr-equivalent doses. The perchromate compounds were more efficient in producing chromosomal aberrations than was a chromate compound, K2CrO4. A 3-valent Cr compound, Cr2(SO4)3, was less toxic and failed to induce a demonstrable increase in chromosomal aberrations. KMnO4 induced aberrations, but at a low rate. As to Ni compounds, NiCl2 and (CH3COO)2Ni induced few aberrations. Administration of K2Ni(CN)4 induced only gaps. NiS induced a low but definite increase in chromosomal aberrations. The rate of these aberrations increased with an increase in treatment time from 24 to 48 h, indicating a time-dependent increase in the hereditable toxicity of metal compounds. CdCl2 and HgCl2 were somewhat toxic, but failed to induce chromosomal aberrations in the present study.

Animals↗
PubMed1979

Inducation of chromosomal aberrations in cultured mammalian cells by nickel compounds.

The effects of 4 Ni compounds, nickel chloride, nickel acetate, potassium cyanonickelate, and nickel sulfide were studied in a line of mammary carcinoma cells from the C3H mouse. All 4 were easily taken up by the cells and reacted with protein, RNA, and possibly DNA. Measurements of leucine, uridine, and thymidine uptake during exposure showed that the syntheses of protein and DNA were more sensitive than RNA. Chromosomal aberrations were observed during the recovery period following the end of the treament with Ni. The implications of these results were discussed with respect to the carcinogenicity of the compounds and to the recommended protocols for mutagenicity testing by chromosomal aberrations.

Animals↗
PubMed1979

Energetic coupling in the primary processes of photosynthesis in Chromatium. pH dependence of delayed fluorescence, electron transfer and degree of coupling.

The effects of pH on the thermodynamic properties of the proton-translocating cyclic electron transfer system in a purple photosynthetic bacterium Chromatium vinosum were studied. Two thermodynamic parameters, the flux (Je) and force (deltamue) of the electron transfer process, were analyzed. The rate of electron transfer in the re-reduction of photooxidized reaction-center bacteriochlorophyll was used as Je. deltamue was determined from the intensity of the delayed fluorescence from bacteriochlorophyll. deltamue is composed of the redox potential difference and the electrical potential difference between two electron transfer components. In the steady state under illumination, the flux-to-force ratio is determined by the following relationship: Je = (1--q2)Lee deltamue where q is the "degree of coupling" of electron transfer to proton translocation and Lee is the value of Je/delta-approximately similar e when there is no back pressure by formation of delta approximately muH+ (electrochemical potential difference of H+). The value of (1--q2) Lee increased with increasing pH in the neutral pH range. Uncouplers and ionophores that dissipate delta-approximately muH+ increased Je and decreased deltamue. The effects were more prominent in the lower pH range. Therefore, q must be smaller at higher pH. The coupling is probably tight when redox components are saturated with protons. The experimental results agreed with the theoretical predictions for a system where a hydrogen-translocating component functions as an electron-proton symport carrier.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗
PubMed1979

Pigmentary degeneration of the retina in heredodegenerative neurological diseases.

Frequency of pigmentary degeneration of the retina (PDR) among patients with degenerative and heredodegenerative neurological diseases (HDNDs) was estimated based on the hospital statistics. PDR was detected in 3% of 176 inpatients with HDNDs by careful ophthalmologic examination. On the other hand, out of 30 consecutive cases of PDR seen in our Department of Neurology, 15 patients were associated with some form of HDNDs. Atypical PDR were more frequently associated with HDNDs than typical PDR. Among neurological manifestations in those 15 cases of PDR associated with HDNDs, mental deficiency, hearing disturbance, spasticity, progressive ophthalmoplegia and ataxia were most frequently encountered. Four cases with unusual symptomatology were presented. Clinical analysis of cases of PDR associated with HDNDs in the present series as well as in the relevant literature revealed an extreme variety of clinical manifestations and underlying metabolic disorders, suggesting a possible participation of multiple factors in the pathogenesis of PDR. Importance of careful ophthalmologic examination in HDNDs was stressed from the prognostic point of view.

Adolescent↗
PubMed1979

Changes in pancreatic somatostatin content in spontaneously diabetic mice, as determined by radioimmunoassay and immunohistochemical methods.

A specific RIA for somatostatin (SRIF) was used to determine the SRIF content of the pancreas and hypothalamus in spontaneously diabetic C57BL/KsJ dbdb and C57BL/6J obob mice. In addition, SRIF- and glucagon-containing cells were examined in the pancreatic islets with an immunohistochemical technique. In dbdb mice, immunoassayable pancreatic SRIF content was increased, as was the number of SRIF- or glucagon-containing cells. In obob mice, immunoassayable pancreatic SRIF content was also increased, but no increase was noted in the number of SRIF- or glucagon-containing cells. The hypothalamic SRIF content of either strain was not different from that of controls. These results regarding pancreatic SRIF content were in accord with some but not all previous reports. These differences may be related to the age of the mice or to the conditions in which they were bred. The pancreatic SRIF increase in both dbdb and obob mice may be attributable to hyperglucagonemia, hyperglycemia, or a decrease in insulin action. Further work is necessary to clearly delineate the mechanism.

Animals↗
PubMed1979

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Action Potentials↗
PubMed1978

Studies on electron transfer systems in the marine diatom Phaeodactylum tricornutum. I. Isolation and characterization of cytochromes.

Two cytochromes of the C type, c-550 and c-553, were isolated from the marine diatom, Phaeodactylum tricornutum, and purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. The cytochrome c-550 had absorption maxima at 550, 522, and 417 nm in the reduced form and at 524, 407, 351, and 277 nm in the oxidized form. It was an autoxidizable acidic protein with an isoelectric point of 5.1 and had a low redox potential of about -0.20 V at pH 7.0. The molecular weight of this cytochrome was close to 17,000. This cytochrome combined with CO and CN-. The CO complex was dissociated reversibly by light. The cytochrome c-553 had absorption maxima at 553, 522.5, and 417 nm in the reduced form and at 528, 410, and 356 nm in the oxidized form. The protein had an acidic isoelectric point of 3.7 and had a high mid-point redox potential of +0.36 V at pH 7.0. Its molecular weight was approximately 10,500. The cytochrome may be considered to be a photosynthetic cytochrome of the f type. Cytochromes of the B type were also found in Phaeodactylum tricornutum; one in soluble form, and the other in bound form. The soluble form had absorption maxima at 560, 529, and 427 nm in the reduced state and at 413 nm in the oxidized state.

Animals↗