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Biomedical subjects

M Nishimura

Publications and source records attributed to M Nishimura.

At least 1,387 records · Page 77Linked to original sources
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↗
PubMed1978

Studies on electron transfer systems in the marine diatom Phaeodactylum tricornutum. II. Identification and determination of quinones, cytochromes, and flavins.

Quinones constituting the electron transfer systems in a marine unicellular diatom, Phaeodactylum tricornutum, were isolated and identified chromatographically. The alga contained five quinones, i.e., plastoquinone A, plastoquinone C, plastoquinone D, alpha-tocopherylquinone, and ubiquinone-9. Other types of quinones, such as vitamin K1, were not detected. The contents of plastoquinone A, plastoquinone C, plastoquinone D, ubiquinone-9, and alpha-tocopherylquinone were 25.5, 4.95, 1.99, 4.78, and 0.28 mmol per mol of chlorophyll, respectively. The contents of the soluble C-type cytochromes, cytochrome c-550 and cytochrome c-553, were 2.15 and 4.34 mmol (heme basis) per mol of chlorophyll, respectively. The amount of B-type cytochrome in the bound form was estimated to be 3.24 mmol (heme basis) per mol of chlorophyll. The acid-soluble flavins, FAD and FMN, were present in amounts of 0.68 and 0.41 mmol per mol of chlorophyll, respectively.

Animals↗
PubMed1978

Diffusion-potential-induced oxidation and reduction of cytochromes in chromatophores from Rhodopseudomonas sphaeroides.

A membrane potential jump was induced by the addition of valinomycin in the presence of a KCl concentration gradient across the membrane of Rhodopseudomonas sphaeroides chromatophores. As well as a carotenoid band shift, which is known to be an indicator of membrane potential, absorbance changes due to the oxidation-reduction reactions of cytochromes accompanied the jump. Under aerobic conditions with no reductant added, a part of cytochrome c2 was reduced by an inside-positive potential jump of about 100 mV in the time range of tens of seconds. This can be explained by the location of the cytochrome on the inner side of the chromatophore membrane and electrophoretic flow of electrons across the membrane. On the other hand, in the presence of 1 mM ascorbate, a similar jump of membrane potential induced a rapid oxidation of cytochrome c2 and a subsequent reduction. A rapid reduction of b-type cytochrome was also observed. Antimycin A inhibited the c2 oxidation, but did not inhibit the b reduction. The oxidation of cytochrome c2 may be explained by a diffusion-potential-induced electron flow to cytochrome b and a simultaneous electron donation by cytochrome b and cytochrome c2 to a common electron acceptor, possibly a quinone.

Anaerobiosis↗
PubMed1978

Isolation of intact plastids from protoplasts from castor bean endosperm.

Protoplasts were prepared from castor bean (Ricinus communis) endosperm by treatment with a mixture of the commercial enzymes Macerozyme R-10 and Cellulose "Onozuka" R-10. The protoplasts were gently ruptured by forcing the suspension through a hypodermic needle and the homogenate centrifuged on a linear sucrose gradient. From such a homogenate the mitochondria are recovered at their typical isopycnic density of 1.18 g/ml, but the glyoxysomes are retained, with other membranes, at a density of 1.13. The plastids reach their typical density of 1.22 on the gradient and are thus clearly separated from other organelles. Moreover, since essentially all of the ribulose bisphosphate carboxylase activity on the gradient is present in this fraction it can be concluded that the plastids are intact and have been recovered in high yield.

Journal Article↗
PubMed1978

Hydrolases in vacuoles from castor bean endosperm.

Vacuoles were prepared from endosperm tissue of 4-day-old castor bean seedlings (Ricinus communis var. Hale) and purified on a stepped sucrose gradient. It was shown by assays of marker enzymes that there was only trace contamination of the final preparation by other organelles (mitochondria, glyoxysomes, nuclei, spherosomes, and plastids) and by cytoplasmic components. Hydrolytic enzymes (acid protease, carboxypeptidase, phosphodiesterase, RNAase, phytase and beta-glucosidase) were present in the isolated vacuoles in amounts indicating a primarily vacuolar localization in vivo. The vacuoles also contained storage protein and high concentrations of sucrose. The over-all results indicate that the vacuoles from castor bean endosperm are the site of hydrolysis of the constituents of the protein bodies and are a temporary storage compartment for the sucrose produced from fat and protein reserves.

Journal Article↗
PubMed1978

Biosynthesis of ribulose-1,5-bisphosphate carboxylase in spinach leaf protoplasts.

Spinach leaf (Spinacia oleracea L. var. Kyoho) protoplasts sustain protein-synthesizing activity as measured by the incorporation of [(14)C]-leucine into the protein fraction both in the light and in the dark. By the immunoprecipitation of ribulose-1,5-bisphosphate (RuP(2)) carboxylase with rabbit antibody raised against the purified spinach enzyme preparation, it was found that approximately 7% of the total radiocarbon incorporated into the protein fraction in the light was in the carboxylase molecules. However, there was no measurable net increase observed in the content of the enzyme protein in the experimental conditions employed. It was found that both chloramphenicol and cycloheximide inhibited the incorporation of [(14)C]leucine into RuP(2) carboxylase and its constituent subunits, as measured by the immunoprecipitation of the enzyme molecule and its subunits, A and B.

Journal Article↗
PubMed1978

Effect of ultraviolet or laser light irradiation on the growth of Micrasterias thomasiana.

The effect of ultraviolet on laser light on growth of lobes in a green alga, Micrasterias thomasiana was investigated. During plasmolysis, the cell wall and the outermost region of the cytoplasm were separately irradiated with an ultraviolet or laser microbeam. Growth of the lobes was more effectively inhibited by irradiation of the cytoplasm than of the cell wall when the dose of irradiation was weak. Growth inhibition was observed in the irradiated cytoplasm where no apparent decrease in velocity of plasma streaming was seen, which suggested that irradiation caused more damage to the mechanism of exocytosis than to the migration of secretion vesicles. Strong irradiation resulted in gelatinization of the cytoplasm. With strong doses of irradiation on both the cytoplasm and cell wall, growth was completely inhibited.

Cell Wall↗
PubMed1978

Experimental neurogenic pulmonary edema in cats.

Hemorrhagic pulmonary edema was produced consistently in 19 of 20 anesthetized, paralyzed, ventilated cats when intracranial pressure (ICP) was raised for 30 minutes by intraventricular infusion of mock CSF to 150 mm Hg in 14, or 200 mm Hg in six. However, under identical conditions, except that ICP was raised to only 100 mm Hg, three of seven animals did not develop hemorrhagic edema of the lungs and the remaining four had spotty hemorrhage. Thirteen control animals with normal ICP had normal lungs. Gravimetric lung water analysis by Pearce's method confirmed gross and microscopic appearance of hemorrhagic pulmonary edema. Extravascular lung water (p less than 0.05) and lung blood (p less than 0.05) were significantly greater than control values when ICP was raised to or exceeded 150 mm Hg. Despite hemorrhagic edema, pulmonary gas exchange (O2, CO2) remained unaffected. This animal model allows quantitative measurement of neurogenically-mediated hemorrhagic edema of the lungs before gas exchange is impaired. The model may facilitate clarification of the pathogenesis of neurogenic pulmonary edema and, consequently, refine evaluation of therapy.

Animals↗
PubMed1978

Immunological studies on myasthenia gravis: operative indication and cell-mediated immunity.

An important aspect of the management of patients with myasthenia gravis is the decision to recommend thymectomy. Hitherto, many investigators have reported the relationship between the operative effects and such factors as age, sex, duration of symptoms, or degree of germinal center proliferation in the myasthenic thymus. However, these reports are not practical aids in deciding the indication for thymectomy in an individual myasthenic patient. The currently accepted indications of thymectomy for myasthenic patients are (1) the thymomatous patient, especially those with malignancy, and (2) the nonthymomatous patients who are resistant to medical treatment. From our present data we would add the following as an indication of the operation: (3) patients who have high T-cell subpopulation levels with highly blastogenic activities and strong skin test reactivities. In order to assure good operative results in myasthenic patients, surgeons should examine their patients' preoperative immunological states.

Adolescent↗