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排序方式: 共有218条查询结果,搜索用时 38 毫秒
211.
Cultural Transmission Among Aka Pygmies 总被引:2,自引:0,他引:2
212.
Cerapeplus siamensis gen.n., sp.n. from Thailand is described and illustrated. The new genus is characterized by filament-based lamellar secretions arising from the lateral body margin, a feature observed for the first time in Coleoptera. Possible autapomorphies for the micropeplid genera are discussed. It is concluded that Cerapeplus and Kalissus are monophyletic; Micropeplus and/Or Peplomicrus are probably polyphyletic but both genera together form a monophyletic group. A number of characters support the family status of the micropeplids recently proposed by some authors. A revised family diagnosis is provided. 相似文献
213.
Studies in our laboratories involved the placing of argon-filled hand-sealed glass ampoules (tip-, balloon-, or draw-sealed) containing biological materials dried by sublimation of ice in vacuo in water baths at elevated temperatures. Although these ampoules tested negative for “leakers,” many ampoules upon removal from the water bath contained beads of moisture. To determine if the water within the ampoules entered through openings in the closed ends, we used a laser imaging apparatus to examine the sealed ends. We carried out studies also on machine-sealed ampoules.Two modes of laser imaging were used: dark-field imaging and interference imaging. In tip-sealed ampoules, uniform, long channels were found in the gatherings of glass at the ends of the ampoules; the lengths of the channels were approximately ten times their diameters. In balloon-sealed ampoules, pore-like openings were found; the lengths of the pores were approximately four times their diameters. In draw-sealed ampoules, channels of small diameters were observed; the lengths of the open pathways were approximately 30 times their diameters. Based on the sizes of the images obtained with laser imaging, the magnifications used for photographic reproductions and the original measurements of the sealed ampoules we estimated the openings in tip-sealed and balloon-sealed ampoules to range from 5 to 8 μm and the channels in draw-sealed ampoules to be less than 3 μm in diameter, The diameters of the helix-like openings in machine-sealed ampoules were less than 5 μm.To prevent the migration of molecules into and out of ampoules, we sought for a barrier that could be interposed between the external environments of the ampoules. Many liquid formulations of natural and man-made elastomers were tested; neoprene dissolved in toluol was found best. 相似文献
214.
J Moss S J Stanley P A Watkins D L Burns C R Manclark H R Kaslow E L Hewlett 《Biochemistry》1986,25(9):2720-2725
Pertussis toxin catalyzed ADP-ribosylation of the guanyl nucleotide binding protein transducin was stimulated by adenine nucleotide and either phospholipids or detergents. To determine the sites of action of these agents, their effects were examined on the transducin-independent NAD glycohydrolase activity. Toxin-catalyzed NAD hydrolysis was increased synergistically by ATP and detergents or phospholipids; the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS) was more effective than the nonionic detergent Triton X-100 greater than lysophosphatidylcholine greater than phosphatidylcholine. The A0.5 for ATP in the presence of CHAPS was 2.6 microM; significantly higher concentrations of ATP were required for maximal activation in the presence of cholate or lysophosphatidylcholine. In CHAPS, NAD hydrolysis was enhanced by ATP greater than ADP greater than AMP greater than adenosine; ATP was more effective than MgATP or the nonhydrolyzable analogue adenyl-5'-yl imidodiphosphate. GTP and guanyl-5'-yl imidodiphosphate were less active than the corresponding adenine nucleotides. Activity in the presence of CHAPS and ATP was almost completely dependent on dithiothreitol; the A0.5 for dithiothreitol was significantly decreased by CHAPS alone and, to a greater extent, by CHAPS and ATP. To determine the site of action of ATP, CHAPS, and dithiothreitol, the enzymatic (S1) and binding components (B oligomer) were resolved by chromatography. The purified S1 subunit catalyzed the dithiothreitol-dependent hydrolysis of NAD; activity was enhanced by CHAPS but not ATP. The studies are consistent with the conclusion that adenine nucleotides, dithiothreitol, and CHAPS act on the toxin itself rather than on the substrate; adenine nucleotides appear to be involved in the activation of toxin but not the isolated catalytic unit. 相似文献
215.
The simple preparation of an ethidium-bromide-based nucleic acid affinity medium is described. The medium is composed of an acrylamide matrix to which ethidium bromide is attached. Its use in preparative purification and fractionation of nucleic acids in solution and in electrophoretic elution of nucleic acids from gels is reported. Nucleic acids can be eluted from this medium with a buffered salt solution and concentrated by ethanol precipitation without persistent contamination with undesirable impurities. 相似文献
216.
Construction and characterization of Bordetella pertussis mutants lacking the vir-regulated P.69 outer membrane protein 总被引:10,自引:0,他引:10
M. Roberts N. F. Fairweather E. Leininger D. Pickard E. L. Hewlett A. Robinson C. Hayward G. Dougan L. G. Charles 《Molecular microbiology》1991,5(6):1393-1404
The Bordetella pertussis P.69 protein is an immunogen with vaccine potential. The role of this protein in pathogenesis is unclear; it has been associated with the toxic adenylate cyclase and adhesion to eukaryotic cells. For further analysis of the role of P.69 in the biology of B. pertussis, we have constructed strains which specifically lack P.69. The cloned P.69 (prn) gene of B. pertussis was insertionally inactivated with a kanamycin-resistance cassette. This inactivated gene was used to construct P.69- mutants of B. pertussis by allelic exchange using plasmid pRTP1. B. pertussis P.69- strains produced normal levels of other vir-regulated factors, including adenylate cyclase. The serotype of B. pertussis, determined by Eldering and Preston typing sera and monoclonal antibodies, was also unaffected by the presence or absence of P.69. The ability of a prn mutant to adhere to and invade HEp2 cells was not significantly different from that of its parent strain. A strain containing a mutation in fhaB was significantly less adhesive and invasive than its parent, and a prn fhaB double mutant exhibited an even greater reduction in adhesiveness and invasiveness down to levels comparable with a Vir- strain. However, strains harbouring mutations in FHA and/or P.69 were able to colonize or multiply in the murine respiratory tract, although a Vir- strain was unable to survive and proliferate in the same infection model. 相似文献
217.
Nicole Hess Courtney Helfrecht Edward Hagen Aaron Sell Barry Hewlett 《Human nature (Hawthorne, N.Y.)》2010,21(3):330-354
Sex differences in physical and indirect aggression have been found in many societies but, to our knowledge, have not been
studied in a population of hunter-gatherers. Among Aka foragers of the Central African Republic we tested whether males physically
aggressed more than females, and whether females indirectly aggressed more than males, as has been seen in other societies.
We also tested predictions of an evolutionary theory of physical strength, anger, and physical aggression. We found a large
male bias in physical aggression. Controlling for anger, we found an adult female bias in indirect aggression. Physical strength
predicted anger, which predicted hitting, although results were sensitive to the inclusion or exclusion of traditional healers,
who were physically and emotionally distinct from other Aka. With some important caveats, our results generally support the
predicted sex differences in physical aggression and indirect aggression, and the predicted relationships among anger, strength,
and aggression. 相似文献
218.