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Biomedical subjects

K Takamiya

Publications and source records attributed to K Takamiya.

120 records · Page 7Linked 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↗
PubMed1977

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores.

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores was studied at room temperature and under intermittent illuminations. The decay of delayed fluorescence was constituted of two components; a fast component decayed with a half time of about 8 ms, a slow one decayed in parallel with the reduction of photooxidized bacteriochlorophyll (P+) with a half time of 100-200 ms. The biphasic decay of delayed fluorescence indicated that a rapid equilibrium was established between the primary electron acceptor and the secondary acceptor. In the presence of o-phenanthroline, the time course of the decay of delayed fluorescence was identical with that of the reduction of P+ in reaction center-rich subchromatophore particles, although they did not necessarily coincide with each other in "intact" chromatophores. The intensity of the slow component was increased and the decay was accelerated at basic pH values. Reagents that dissipate the proton gradient across the chromatophore membranes such as carbonylcyanide m-chlorophenylhydrazone (CCCP) and nigericin accelerated the decay of the slow component. These effects are probably resulting from changes in internal pH of chromatophore vesicles. Reagents that dissipate the membrane potential such as CCCP and valinomycin decreased the intensity.

Bacterial Chromatophores↗
PubMed1977

Delayed fluorescence from bacteriochlorophyll in Chromatium vinosum chromatophores: characteristics in the presence of o-phenanthroline.

Delayed fluorescence from bacteriochlorophyll in the chromatophores of Chromatium vinosum, a photosynthetic purple sulfur bacterium, was studied in the presence of o-phenanthroline (o-phen) under intermittent illumination. Re-reduction of the photooxidized reaction center bacteriochlorophyll (P+) in the dark interval was accelerated by o-phen. This effect was attributed to the return of electrons trapped in the primary electron acceptor (A) to P+. In the presence of o-phen, the time course of the decay of delayed fluorescence was not coincident with that of the re-reduction of P+. The delayed fluorescence was somewhat intensified at the early stage (within 30 ms) of relaxation in the dark period. Prolonged illumination (longer than 20 ms) or uncouplers such as carbonylcyanide m-chlorophenylhydrazone (CCCP) or valinomycin plus nigericin decreased the intensity of delayed fluorescence and suppressed the stimulation of delayed fluorescence at the early stage. Delayed fluorescence from reaction center-rich subchromatophore particles decayed with a time course identical to that of the reduction of P+ and was not affected by CCCP, in the presence of o-phen. The intensification at the early stage in the chromatophores can be interpreted in terms of charge separation between pairs of P and A, primary electron donor and acceptor molecules, oriented perpendicular to the intact chromatophore membrane, the effect decreasing in parallel with the recombination of P+ and A-.

Bacterial Chromatophores↗
PubMed1976

Isolation and some properties of NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii.

NAD+ reductase of the green photosynthetic bacterium Prosthecochloris aestuarii was isolated and purified by ammonium sulfate fractionation, DEAE-cellulose column chromatography, and Sephadex G-200 gel filtration. This enzyme is an FAD-containing flavoprotein and has absorption maxima at 485 (shoulder0 452, 411, and 385 nm (the 411 nm band is due to cytochrome). The molecular weight of the enzyme as determined by gel filtration using Sephadex G-200 is 119,000. The enzyme catalyzes the reduction of NAD+ and NADP+ by photoreduced spinach ferredoxin or reduced benzyl viologen...

2,6-Dichloroindophenol↗
PubMed1976

Light-induced oxidation-reduction reactions of cytochromes in the green sulfur photosynthetic bacterium Prosthecochloris aesturarii.

The light-induced oxidation-reduction reactions of cytochromes in intact cells, starved cells, and chlorobium vesicle fractions of the green sulfur photosynthetic bacterium Prosthecochloris aesturarii were studied under anaerobic conditions. On the basis of both kinetic and spectral properties, at least three cytochrome species were found to be involved in the light-induced oxidation-reduction reactions of intact cells. These cytochromes were designated according to the positions of alpha-band maxima as C555 (rapid and slow components) and C552 (intermediate). By comparing the light-minus-dark difference spectra with the reduced-minus-oxidized difference spectra of purified cytochromes of this organism, rapid component C555 and intermediate component C552 are suggested to correspond to the purified cytochromes c-555(550) and c-551.5, respectively. Although the identity of the slow-phase component is uncertain, one possibility is that the slow phase is due to the bound form of c-555(550). In substrate-depleted (starved) cells, only one cytochrome species, C555 remained in the reduced state in the dark and oxidized upon actinic illumination. This corresponds to the rapid C555 component in intact cells. In the case of chlorobium vesicle fractions, one cytochrome species having an alpha-band maximum at 554 nm was oxidized by actinic light. The effects of several inhibitors on the absorbance changes of intact cells were studied. Antimycin A decreased the rate of the dark reduction of rapid C555 component. The complex effects of CCCP (carbonyl cyanide m-chlorophenylhydrazone) on the oxidation-reduction reactions of cytochromes were interpreted as the results of inhibition of the electron donation to oxidized C552 and C555 (slow), and a shift of the dark steady-state redox levels of cytochromes. Based on these findings, it is suggested that the rapid C555 component is located in a cyclic electron transfer pathway. The other two cytochromes, C552 and C555 (slow), may be located in non-cyclic electron transfer pathways and receive electrons from exogenous substrates such as sodium sulfide. A tentative scheme for the electron transfer system in Prosthecochloris aestuarii is presented and its nature is discussed.

Antimycin A↗
PubMedDate not supplied

Central nervous system magnetic resonance imaging findings in neuro-Behçet syndrome.

In a patient with neuro-Behçet (N-B) syndrome, MRI images obtained with TR 2000 msec, and TE 80 msec showed an increased signal intensity in the brain stem corresponding to the neurological symptoms. In N-B syndrome, the brain stem has been documented as a main site of the lesion, and MRI shows promise as a useful technique in the diagnosis of this disease.

Behcet Syndrome↗