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S Minamikawa

Publications and source records attributed to S Minamikawa.

4 recordsLinked to original sources
PubMed2000

Maintenance of neutral buoyancy by depth selection in the loggerhead turtle Caretta caretta.

Time-series data of swimming speed and dive depth were recorded in six female loggerhead turtles Caretta caretta during the internesting period. The dive profiles of all animals indicated that they stayed at particular depths without swimming and that these depths were correlated with dive duration. These results support the hypothesis that lung air is used to achieve neutral buoyancy in the loggerhead turtle. To test this hypothesis, female turtles were equipped with lead weights and time/depth recorders. The residence depth of the turtles increased when their specific gravity was artificially decreased. This indicates that they control depth rather than lung volume, suggesting that the residence depth of loggerhead turtles during the internesting period is not determined actively. They presumably remain at a particular depth exclusively to save energy for egg maturation during the internesting period. Lung volume was estimated from the change in depth of weighted animals to be 50-150 ml kg(-1). The resulting residence depth of all turtles was within the range at which they maintained the neutral buoyancy.

Air↗
PubMed1997

Histone deacetylase inhibitor activates the WAF1/Cip1 gene promoter through the Sp1 sites.

Treatment of cultured cells with trichostatin A (TSA), a specific histone deacetylase inhibitor, induces the histone hyperacetylation and modulates expression of some mammalian genes. We examined the effects of TSA on cell growth arrest, and its relation to expression of the WAF1/Cip1 gene, a potent inhibitor of cyclin-dependent kinases, in a p53-mutated human osteosarcoma cell line MG63. TSA at 500 ng/ml induced growth arrest at both G1 and G2/M phases, and the expressions of the WAF1/Cip1 mRNA and protein. We also examined the changes of acetylated isoforms of histone H4. Dose-response and kinetic analysis suggest a close correlation between the level of histone acetylation and the induction of the WAF1/Cip1 expressions. Using several mutant WAF1/Cip1 promoter fragments, we found that the TSA responsive elements are two Sp1 sites at -82 and -69 relative to the transcription start site. These findings indicate that TSA induces the WAF1/Cip1 promoter through the typical Sp1 sites, in a p53-independent fashion. Furthermore, the Sp1-luc plasmid, containing SV40 promoter-derived three consensus Sp1 binding sites, was markedly activated by TSA, compared to the mutant Sp1-luc plasmid. These results demonstrate that transcriptional activation through the Sp1 sites of the WAF1/Cip1 promoter by TSA coincides with induced hyperacetylation of histone H4.

Animals↗
PubMed1970

Elimination of sex factors in Escherichia coli by urea.

Eliminatory action of urea on the sex factor (F) in Escherichia coli K-12 strains is reported. Growth of E. coli harboring F or F'8 (F-gal) factors in Penassay Broth containing urea led to the loss of these genetic elements and yielded F(-) cells. Appearance of F(-) cells among survivors was already observed when the culture was in the very early stage of exponential phase. However, frequencies of F(-) cells formed did not increase much as a function of the incubation time. Unusual F(+) or F'8 cells which retained the ability of genetic transfer but showed resistance to M12 phage were also isolated. Addition of sucrose to broth with urea led to the favorable growth of cells in the culture and the increase, if little, of elimination frequencies of F factors by urea. These findings, coupled with other observations, suggest that urea has two separate actions in enhancing the frequency of F(-) bacteria, namely, (i) to inactivate F by direct action, such as mutation, and (ii) to select the F(-) variants by differentially inhibiting the growth of F(+).

Bacteriological Techniques↗