RESUMO
Thermotoga maritima, a thermophilic eubacterium, is motile at temperatures ranging from 50 to 105 degrees C. The cells are propelled by a single flagellum which most of the time spins clockwise. Changes in the swimming direction ("tumbles") are achieved by short reversals of the direction of filament rotation. The average speed of swimming cells depends on the temperature, reaching a maximum value of about 60 microns/s at 85 degrees C. The cells show a thermotactic response to temporal temperature changes. When the temperature is raised, the rate of tumbles is increased, while decreasing temperature decreases the tumbling rate.
Assuntos
Bactérias Anaeróbias Gram-Negativas/citologia , Flagelos/ultraestrutura , Bactérias Anaeróbias Gram-Negativas/fisiologia , Temperatura Alta , Processamento de Imagem Assistida por Computador , Microscopia de Vídeo , MovimentoRESUMO
Flagellated envelopes of Halobacterium salinarium cells were prepared by lysis with taurodeoxycholate. After solubilization of the envelopes with Triton X-100 at high ionic strength, flagella and round patches from which numerous flagella emerged were isolated by gel filtration chromatography. We conclude that the flagellar bundle of H. salinarium is inserted into a differentiated polar cap structure.
Assuntos
Flagelos/ultraestrutura , Halobacterium salinarum/ultraestrutura , Fracionamento Celular , Halobacterium salinarum/química , Microscopia Eletrônica , Polietilenoglicóis/química , Ácido Taurodesoxicólico/químicaRESUMO
Use of vitamin and mineral supplements was assessed in a population-based case-control study of oral and pharyngeal cancer, conducted during 1984-1985 in four areas of the United States. There was no association with intake of multivitamin products, but users of supplements of individual vitamins, including vitamins A, B, C, and E, were at lower risk after controlling for the effects of tobacco, alcohol, and other risk factors for these cancers. After further adjustment for use of other supplements, vitamin E was the only supplement that remained associated with a significantly reduced cancer risk. The adjusted odds ratio of oral and pharyngeal cancer for "ever regularly used" vitamin E was 0.5 (95% confidence interval 0.4-0.6). To the authors' knowledge, this is the first epidemiologic study to show a reduced oral cancer risk with vitamin E use. Although it is not clear that the lower risk among consumers of vitamin E supplements is due to the vitamin per se, the findings are consistent with experimental evidence and should prompt further research on the role of vitamin E and other micronutrients as inhibitors of oral and pharyngeal cancer.
