Search PubMed⌕ Search

Biomedical subjects

Y Seki

Publications and source records attributed to Y Seki.

At least 235 records · Page 13Linked to original sources
PubMed1981

Siroheme as an active catalyst in sulfite reduction.

Siroheme extracted by acetone/HCl treatment of sulfite reductase from yeast and purified by column chromatography catalyzed the reduction of sulfite to thiosulfate and sulfide when coupled with a hydrogen-hydrogenase-methyl viologen system. The activity increased with decrease in pH from 7 to 4, and an apparent Km value of 50 mM for sulfite was obtained. In contrast to sirohydrochlorin plus Fe2+, addition of inorganic iron or 2,2'-bipyridine prior to the reduction reaction had scarcely any effect on the sulfite-reducing activity of siroheme. Hydroxylamine was reduced by siroheme at a much faster rate than sulfite, and the rate increased with increase in pH from 6 to 9. Siroheme extracted from Chromatium vinosum strain D sulfite reductase also reduced sulfite to thiosulfate and sulfide.

Catalysis↗
PubMed1981

An immunohistochemical study of lens development in a mutant small eye and cataractous mouse.

The immunohistochemical method was used to study lens formation in a new dominant mouse strain with a small eye and lens cataract (gene symbol Cs). Antisera to pure alpha- and gamma-crystallins were used. In the homozygotes, the eyes have cataractous lenses about half the size of normal lenses. In the heterozygotes, the eyes show opacities of the lens but the lens itself is normal in size. The mouse strain has two genes in the same autosome which cause the phenogenetical characteristics of small eyes and cataracts. One reflects the defect of the gamma-crystallin synthesis in the secondary lens fibers in the equatorial zone. This is a recessive gene and it may cause the small lens. The other gene is responsible for the swollen, granular and misshaped fiber cells. This is a dominant gene like that in the Fraser's cataract and it may cause the cataract lens.

Animals↗
PubMed1980

Peripheral nervous system functions of workers exposed to n-hexane at a low level.

In order to assess the effects on the peripheral nervous system of n-hexane at a low level, an epidemiological study using a questionnaire, neurological examinations, and neurophysiological studies was carried out on two age-matched groups; one, consisting of 14 exposed workers and the other, of 14 control workers. The 8 h time weighted average of n-hexane concentration in the exposure environment was 58 +/- 41 (mean +/- SD) ppm. In the individual worker, no obvious signs could be found indicating damage to the nervous system that were referable to the n-hexane exposure. On the other hand, when the subjects were taken in groups, the results obtained from the exposed group showed a minor partiality for functional impairment of the peripheral nervous system in many test items. In particular, statistically significant differences between the two groups were detected in the following items: (1) inquiries by questionnaire for persistent or transient symptoms regarding muscle weaknesses and dyesthesia of limbs; (2) the jump test on one foot; (3) the tuning fork test for vibration sensation on the radial processes; (4) the maximal velocity and the residual latency of motor nerve conduction of the posterior tibial nerve. In conclusion, it is not likely that at exposure levels less than the current threshold limit value of 100 ppm proposed by ACGIH, n-hexane may induce clinically overt polyneurophathy. However, there is no gainsaying the possibility that in the exposed workers as a whole, small cumulative effects in the peripheral nervous system may be brought about by long-term n-hexane exposure less than 100 ppm.

Adult↗
PubMed1979

A possible intraneuronal site of action of thymoleptics.

The uptake of catecholamines (CAs) into crude mitochondria preparations (P2 fractions) and vesicle preparations from rat hypothalamus and striatum were compared in terms of the inhibition by thymoleptics and other drugs. Thymoleptics preferentially inhibited the uptake of CAs into hypothalamic P2 fractions, while ATPase inhibitors preferentially inhibited the uptake of dopamine into striatal P2 fractions. When the preparation obtained from rats pretreated with reserpine was used, the preferential inhibition of hypothalamic uptake by thymoleptics was entirely abolished. When P2 fractions from both regions were incubated with 10(-6) M 14C-imipramine, the intrasynaptosomal distribution of labeled imipramine revealed its affinity not only to the synaptosomal membrane, but also to the synaptic vesicles. Accumulated 3H-norepinephrine (NE) could be released by a hypoosomotic shock from striatal P2 fractions, but not from hypothalamic P2 fractions. The ATP-Mg2+-dependent uptake of 3H-NE into the synaptic vesicles from rat brain stem was inhibited by desipramine. These results indicate that the inhibition of CA uptake by thymoleptics in the hypothalamus is predominantly due to the inhibition at the synpatic vesicle, while in the striatum the uptake at the synaptosomal membrane is predominantly inhibited.

Adenosine Triphosphate↗
PubMed1979

Biochemical studies on sulfate-reducing bacteria. XV. Separation and comparison of two forms of desulfoviridin.

Desulfoviridin from Desulfovibrio vulgaris was separated into two forms by DEAE-Sephadex column chromatography. The major form had a pI of 4.4 and the minor form one of 4.5-4.6. Both forms produced mainly trithionate, besides thiosulfate and sulfide, in methylviologen-linked sulfite reduction. The specific activities of sulfite reduction, as well as of hydroxylamine reduction, were virtually identical in both forms. There were no great differences in their absorption spectra, CD spectra, molecular weights, subunit compositions, labile sulfide, and iron contents, and amino acid compositions. The N-terminal amino acid was alanine in both forms.

Amino Acids↗