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61.
Biochemical and phenotypical correction of an envelope mutant of Salmonella typhimurium 总被引:1,自引:0,他引:1
R A Pizarro G O Boselli L V Orce 《Archives internationales de physiologie et de biochimie》1984,92(5):333-337
Salmonella typhimurium DA 361 bears an env D1 mutation with the following abnormal phenotypical and biochemical characteristics: a) it autolyses at stationary phase in nutrient broth; b) it grows in chains of short rods; c) it is a poor maltose fermenter and d) it has a diphosphatidylglycerol (DPG) content twice as high than its isogenic non-lytic pair DA 362 (env D+) and LT2, of which both are derivatives. Growth of DA 361 in the presence of 400 mM ethanol leads on a 50% decrease of DPG level, thereby equalling its PG/DPG ratio with those of the control strain. Consequently, a correction on the other phenotypical and biochemical anomalies are induced since the DA 361 strain decreases its autolytic activity, ferments normally maltose and appear as rods undifferentiated from DA 362. 相似文献
62.
Carbon and nitrogen stable isotope analyses have improved our understanding of food webs and movement patterns of aquatic
organisms. These techniques have recently been applied to diet studies of elasmobranch fishes, but isotope turnover rates
and isotope diet–tissue discrimination are still poorly understood for this group. We performed a diet switch experiment on
captive sandbar sharks (Carcharhinus plumbeus) as a model shark species to determine tissue turnover rates for liver, whole blood, and white muscle. In a second experiment,
we subjected captive coastal skates (Leucoraja spp.) to serial salinity reductions to measure possible impacts of tissue urea content on nitrogen stable isotope values.
We extracted urea from spiny dogfish (Squalus acanthias) white muscle to test for effects on nitrogen stable isotopes. Isotope turnover was slow for shark tissues and similar to
previously published estimates for stingrays and teleost fishes with low growth rates. Muscle isotope data would likely fail
to capture seasonal migrations or diet switches in sharks, while liver and whole blood would more closely reflect shorter
term movement or shifts in diet. Nitrogen stable isotope values of skate blood and skate and dogfish white muscle were not
affected by tissue urea content, suggesting that available diet–tissue discrimination estimates for teleost fishes with similar
physiologies would provide accurate estimates for elasmobranchs. 相似文献
63.
Postural sway was compared for humans touching an external object while standing on an immobile or slowly moving posturographic platform. When the platform moves, the central nervous system may interpret the movement of the point of the contact with the external object as the movement of the body relative to the support or as the movement of the support itself. Thus, the information concerning the body position that is provided by the touch becomes ambiguous. It was demonstrated that contact with an external object during standing on an unstable support leads to a decrease in support sway. When a subject stands on a moving platform, this decrease is smaller than in the case of an immobile platform. Contact with an external object causes a decrease in postural responses to shank muscle vibrations on an immobile platform. On a moving platform, this decrease is nonsignificant. The change in postural sway depending on the unambiguity of afferent information is discussed in terms of the interaction between afferent signals of different modalities on the basis of the body scheme in subjects maintaining balance.Translated from Fiziologiya Cheloveka, Vol. 31, No. 1, 2005, pp. 59–65.Original Russian Text Copyright © 2005 by Kazennikov, Shlykov, Levik. 相似文献
64.
We have studied the effect of parathyroid hormone (PTH) on adenylate cyclase of microvessels isolated from rat cerebral cortex. Native bovine (b) PTH-(1–84), the synthetic amino-terminal fragment bPTH-(1–34) and the synthetic analog [Nle8, Nle18, Tyr34]-bPTH- (1–34) amide stimulated adenylate cyclase in a dose-dependent manner with apparent ED50 values of 16 nM, 6.3 nM and 15 nM respectively. The stimulation by bPTH was greatly enhanced by guanosine triphosphate. The PTH antagonist, [Nle8, Nle18, Tyr34]-bPTH-(3–34) amide inhibited the action of bPTH-(1–84) and bPTH-(1–34). In summary, PTH stimulated adenylate cyclase in rat cerebral microvessels in a very similar manner to its stimulation in the renal cortex. 相似文献
65.
A newborn child was noted to have an ulcerated lesion on the vertex of her scalp, which was diagnosed as aplasia cutis congenita. As this disorder is relatively rare and frequently misdiagnosed, this case is reported and the relevant literature reviewed. 相似文献
66.
Responses in pigmentation and anti-oxidant expression in Arctic Daphnia along gradients of DOC and UV exposure 总被引:1,自引:0,他引:1
Responses in carapace melanization and expression of the majoranti-oxidant catalase (CAT) and glutathione transferase (GST)in Arctic Daphnia were assessed in enclosures along a gradientof dissolved organic carbon (DOC). This gradient was createdby adding freeze-dried humic matter to 2 m3 UV-transparent enclosures,yielding final nominal concentrations of 1, 2.5, 5 and 10 mgC l-1. The UV attenuation was strongly affected by additionsof DOC, and attenuation coefficients at 320 nm increased from3.0 in the control to approximately 3.5 and 11.0 m-1 in the1 and 10 mg DOC treatments respectively. Most Daphnia showedpronounced carapace melanization, and the absorbance of short-waveradiation through the carapace was strongly related to the degreeof melanization. Nevertheless, the different UV climate in theenclosures did not cause any short-term adaptation in Daphniapigmentation over a 3 week period. The levels of CAT and GSTwere assessed over time in the control and at 10 mg DOC. Theseenzymes displayed opposite patterns, with somewhat lower activitiesof CAT at low DOC (control) relative to 10 mg DOC, while theopposite was found for GST. There was also a significant negativecorrelation between CAT and solar irradiation for GST in bothbags, while no effects were found for GST. 相似文献
67.
Walking speed is a fundamental indicator for human well-being. In a clinical setting, walking speed is typically measured by means of walking tests using different protocols. However, walking speed obtained in this way is unlikely to be representative of the conditions in a free-living environment. Recently, mobile accelerometry has opened up the possibility to extract walking speed from long-time observations in free-living individuals, but the validity of these measurements needs to be determined. In this investigation, we have developed algorithms for walking speed prediction based on 3D accelerometry data (actibelt®) and created a framework using a standardized data set with gold standard annotations to facilitate the validation and comparison of these algorithms. For this purpose 17 healthy subjects operated a newly developed mobile gold standard while walking/running on an indoor track. Subsequently, the validity of 12 candidate algorithms for walking speed prediction ranging from well-known simple approaches like combining step length with frequency to more sophisticated algorithms such as linear and non-linear models was assessed using statistical measures. As a result, a novel algorithm employing support vector regression was found to perform best with a concordance correlation coefficient of 0.93 (95%CI 0.92–0.94) and a coverage probability CP1 of 0.46 (95%CI 0.12–0.70) for a deviation of 0.1 m/s (CP2 0.78, CP3 0.94) when compared to the mobile gold standard while walking indoors. A smaller outdoor experiment confirmed those results with even better coverage probability. We conclude that walking speed thus obtained has the potential to help establish walking speed in free-living environments as a patient-oriented outcome measure. 相似文献
68.
69.
E A Rybnikova V G Shaliapina O N Zamuruev 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1999,49(1):77-83
The effects of corticotropin-releasing hormone (CRH) injected into the dorsal neostriatum on the open-field and shuttle-box behavior were studied in rats with high (Koltushi high avoidance, KHA) and low (Koltushi low avoidance, KLA) capability for avoidance learning. The effects of this hormone on the behavior of these rat strains were different. In KLA rats with passive strategy of behavior the CRH injection led to a rapid locomotor activation in the open field, while the rats with active behavioral strategy (KHA) reacted to the injection by a significant decrease in locomotion and change for the passive mode of behavior. The same CRH effects on locomotion were obtained in the shuttle-box experiments. Moreover, in the KLA rats the neurohormone injection resulted in an improvement of avoidance learning in contrast to the KHA rats, in which CRH substantially impaired avoidance learning. The obtained evidence is discussed in terms of the important role of striatal CRH in the choice of behavioral strategy in stress. 相似文献
70.
X-IRRADIATION of mammalian cells in culture yields a survival curve of the threshold type (for review see ref. 1). It isjnter-esting to ask how one can enhance the radiation response by small changes of the physical environment of the cells, as can be done chemically, for example, by incorporation of 5-bromo-deoxyuridine into DNA1,2. Elevation of the temperature is a likely prospect for enhancement of radiosensitivity for the following reasons. It is known that proteins are heat labile and that temperature sensitive mutants of bacteria and phage can be obtained for many different enzymes3 which are operative at 37° C but not at 42° or 43°C. For example4, DNA polymerase is reversibly temperature sensitive; it is rendered inoperative above 42°C, but will be functional again when the temperature is lowered. It is not unreasonable to expect that temperature sensitive mutations for many enzymes occur frequently and that the use of temperatures somewhat higher than the normal range at which the cells grow might disclose sensitivities for specific enzymes in normal cells of higher organisms. 相似文献