Biomedical subjects
Publications and source records attributed to J Kawada.
Nadilidixic acid at 5 x 10(-6) M produced a substantial increase in thermal susceptibility of Ts-7, suggesting either that the thermal and nalidixic acid targets are identical or closely interdependent.
The interaction between [131I]-thyroglobulin liposomes and thyroidal lysosomes was used as an in vitro model system for analyzing the relation of colloid droplets to lysosomes in follicular cells. The rates of hydrolysis of [131I]-thyroglobulin in a liposome-lysosome system (Lipo-Lyso system) and a thyroglobulin-lysosome system (TG-Lyso system) were compared. Hydrolysis of thyroglobulin in the Lipo-Lyso system increased hyperbolically and was greater than that in the TG-Lyso system for about 10 h. Liposomal thyroglobulin was not degraded by the 20,000 X g supernatant obtained on disruption of the lysosomal fraction. On varying the pH of the incubation medium, the highest activity was observed under acidic conditions in both systems. Under neutral or weakly alkaline conditions, the Lipo-Lyso system still showed 50% of the maximal hydrolytic activity, while the TG-Lyso system showed no activity. ATP and anaerobic conditions had no effect on either system. Cysteine (5 X 10-2M) and p-chloromercuribenzene sulfonic acid (PCMBS, 10-3 M) had not influence on hydrolysis in the Lipo-Lyso system, but in the TG-Lyso system cysteine greatly increased, and PCMBS significantly reduced the rate of hydrolysis. Dibutyryl cyclic AMP had no effect. Chlorpromazine (Cpz) decreased liposomal thyroglobulin hydrolysis in a concentration-dependent manner. In the TG-Lyso system, concentrations of 10-4M Cpz had no effect. These results strongly suggest that liposomes rapidly fused with lysosomes, providing optimal conditions for hydrolysis of thyroglobulin.
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Electrolyte-induced myelinolysis was produced in rats to evaluate electrophysiological derangement in the brainstem. Auditory brainstem responses (ABRs) were used to assess the brainstem function. Rats treated with hypertonic saline for 2 days had normal interpeak latencies in ABRs. Rats treated with vasopressin-induced hyponatremia alone and those with hypertonic saline after 3 days of hyponatremia had significantly prolonged interpeak latencies between waves II-III and III-IV in ABRs. These prolongations indicate electrophysiological derangement of the upper pons and mesencephalon in hyponatremic rats as well as in rats with hyponatremia followed by hypernatremic myelinolysis. In view of these data, hyponatremia may be a prerequisite for electrolyte-induced myelinolysis and electrolyte derangements such as hyponatremia, and rapidly correcting hypernatremia may be the cause of electrolyte-induced myelinolysis in rats.