Search PubMed⌕ Search

Biomedical subjects

K Ohsawa

Publications and source records attributed to K Ohsawa.

At least 127 records · Page 7Linked to original sources
PubMed1981

Surface potential and surface charge density of the cerebral-cortex synaptic vesicle and stability of vesicle suspension.

Using a microelectrophoresis instrument employing the Lazer-Zee system, the electrophoretic mobility of synaptic vesicles isolated from Guinea-pig brain cortex was measured under conditions. The mobility was found to depend on both pH and ionic concentration of the solution. The surface of the synaptic vesicle was shown to be negatively charged under physiological conditions. The isoelectric point was observed at pH 4.0 in 0.01 M NaCl solution. Effects of divalent cations were examined and reversal of surface charge was observed in 0.1 M CaCl2 solution. Interaction of vesicles was also considered on the basis of the DLVO theory of colloid stability by using calculated values of surface charge density and surface potential of the synaptic vesicle.

Animals↗
PubMed1980

Excitatory effects of dihydrocapsaicin on nociceptive neurons in the medial thalamus.

Effects of capsaicin and dihydrocapsaicin, which are pungent substances contained in Capsicum annuum L., were studied in 32 gallamine triethiodide immobilized cats. Single units were recorded from the medial thalamus using stainless steel microelectrodes. Of the 56 neurons recorded, 28 were responsive to both noxious (pinching) and non-noxious (hair and/or tapping) stimuli, while 16 were activated only by non-noxious stimuli. The remaining 12 neurons did not respond to any natural stimulus. Somatic receptive fields of nociceptive and non-nociceptive neurons were found to be widely distributed over the whole body. Twenty-six of 28 nociceptive neurons were activated by an intra-arterial administration of bradykinin, capsaicin and dihydrocapsaicin. Fourteen of 16 non-nociceptive neurons were not activated by these substances. The mean latency and duration of bradykinin were 8.7 and 12.5 sec, those of capsaicin were 1.2 and 6.1 sec and those of dihydrocapsaicin were 1.3 and 5.0 sec, respectively. The increase of firing frequency produced by capsaicin and dihydrocapsaicin was inhibited by morphine and this inhibition was antagonized by naloxone. However, the activity of medial thalamic neurons with non-noxious stimuli was not affected by these drugs. These results suggest that the pain-conducting fibers were selectively activated by capsaicinoids as well as by bradykinin.

Action Potentials↗
PubMed1979

The lipid and protein content of cholinergic synaptic vesicles from the electric organ of Torpedo marmorata purified to constant composition: implications for vesicle structure.

The lipid, protein, acetylcholine and ATP content of cholinergic synaptic vesicles isolated from the richly innervated electric organ of Torpedo marmorata and purified to constant composition has been determined. The number of vesicles present in the preparations has been estimated by quantitative electron microscopy and the mean composition of the vesicle deduced. The acetylcholine content of the purest preparations was considerably greater than that previously attained and reached a mean of 6.10 mmole/g of protein and 2.6 X 10(5) molecules/vesicle; the mean values, for all determinations, were 4.1 +/- S.E.M. 0.6 and 2.6 X 10(5) +/- S.E.M. 0.6 X 10(5) respectively. The lipid and protein content of the vesicle (about 140 and 80 ag/vesicle respectively) is relatively low, indicating a thin, lipid-rich membrane and a highly hydrated core of which not more than 1-2% can be occupied by protein. These findings are consistent with conclusions drawn from recent density determinations made at different osmotic pressures using penetrating and non-penetrating gradients.

Acetylcholine↗
PubMed1977

A newly designed decantation for purified synaptic vesicle.

A new decanting device of fine stainless steel needles has been developed, which can remove a layer from a gradient with little contamination from the adjacent upper or lower layers. This new apparatus can be used for removal of a very narrow band from a density gradient and has been successfully used in the fractionation of synaptic vesicles from brain homogenates.

Cell Separation↗
PubMedDate not supplied

Mutagenicities of xanthone derivatives in Salmonella typhimurium TA100, TA98, TA97, and TA2637.

The mutagenicities of naturally occurring xanthones were tested in Salmonella typhimurium TA100, TA98, TA97, and TA2637 by the preincubation method. Xanthydrol, gentisein, gentisin, isogentisin, 1-hydroxy-3,7-dimethoxyxanthone, 1,3,7-trimethoxyxanthone, desmethylbellidifolin, bellidifolin and dimethylbellidifolin were mutagenic, but unsubstituted xanthone was not mutagenic to TA100, TA98, TA97 and TA2637 with or without a metabolic activation system. The beta-O-glucosides, norswertianolin and swertianolin, were only mutagenic when a metabolic activation system containing beta-glucosidase was used, and the C-glucoside mangiferin was not mutagenic even with this system.

Animals↗