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71.
H. Notbohm 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,696(2):223-225
A DNA-protein complex isolated from Thermoplasma acidophilum has been examined using low-angle X-ray scattering measurements. In agreement with the results of electron-microscopic studies a diamter of 5.5 nm is deduced. Finally, a simplified model of the DNA-protein particles is discussed postulating a kinked DNA. 相似文献
72.
Data are presented which were collected in the course of the past ten years and bear on the correlation of absorbance at 800 nm and the EPR signal at g = 2 (‘copper signal’) of cytochrome c oxidase in various states of oxidation and ligation. Both EPR and optical reflectance spectra were obtained at low temperature (?170 to ?190°C). For some sets of samples spectra were recorded in the range 500–1100 nm. A particular effort was made to study this correlation with what are called ‘mixed valence’ states (Greenwood, C., Wilson, M.T. and Brunori, M. (1974) Biochem. J. 137, 205–215), when cytochrome a and the EPR-detectable copper are thought to be oxidized and the other components reduced and vice versa. These data show no evidence that the copper component of cytochrome oxidase which has so far not been detected by EPR makes a contribution to the absorption between 800 and 900 nm exceeding 10–15% of the total, which is close to or within the error of the respective measurements. For the various states of the oxidase examined in this work the 700–800 nm region did not appear to be more useful than the 800–900 nm region for determining the state of the EPR-undetectable copper in a reliable way. These conclusions are in agreement with results presented previously from other laboratories concerning the relationship of optical (approx. 800 nm) and EPR spectroscopic (g = 2) data obtained with the enzyme. 相似文献
73.
F W Jennings D D Whitelaw P H Holmes H G Chizyuka G M Urquhart 《International journal for parasitology》1979,9(4):381-384
During the aparasitaemic period following chemotherapy of all three strains of T. brucei infections in mice, successful transmission as shown by subsequent parasitaemia, was regularly achieved following the inoculation of homogenates of brain tissue into recipient mice. Transmission with blood obtained at the same time was consistently negative and in the case of T. brucei TREU 667, homogenates of other organs were non-infective. The implications of this central nervous system involvement are discussed with particular reference to its use as a model for relapsing infections after therapy in man. 相似文献
74.
75.
Rajagopalan Sridhar Eric C. Stroude W. Rodger Inch 《In vitro cellular & developmental biology. Plant》1979,15(9):685-690
Summary 2-Deoxy-d-glucose (2DG) and 5-thio-d-glucose (5TG) are glucose antimetabolites that are known to be selectively toxic to hypoxic cells grown as single cells or
as monolayer cultures. These analogues were toxic to Chinese hamster V79 cells grown as multicell spheroids even under aerobic
conditions. When spheroids, 500- to 600-μm diameter, were exposed to 7.5mm of these chemicals for 3 days, the number of clonogenic cells per spheroid dropped to 50% for 5-thio-d-glucose and 20% for 2-deoxy-d-glucose, relative to control values. Survivals were reduced to less than 1% when the experiment was repeated in glucose-free
medium. Scanning electron photomicrographs of spheroids treated with 7.5mm of either analogue showed extensive damage to the outer cells. The cell killing observed was much more than could be predicted
on the basis of the hypoxic fraction known to be present in these spheroids. The crowded tumor-like environment may make the
cells vulnerable to the cytotoxic action of glucose analogues and other glycolytic inhibitors.
Supported by the Ontario Cancer Treatment and Research Foundation, London Clinic. 相似文献
76.
BACKGROUNDS: Recently, potential liver toxicity was discussed with the intake of kava extract preparations (Piper methysticum) as anxiolytic drugs. The aim of this study was to test chronic toxicity in rats by oral application of an ethanolic kava full extract. METHODS: Wistar rats of both sexes were fed 7.3 or 73 mg/kg body weight of ethanolic kava extract for 3 and 6 months. The animals were examined for changes in body weight, hematological and liver parameters, and macroscopical and microscopical histological changes in the major organs. RESULTS: No signs of toxicity could be found. CONCLUSIONS: The results are in accordance with the medical experience regarding the use of kava preparations and the long tradition of kava drinking in the South Pacific island states. Specifically, the results do not back the suspicion of potential liver toxicity. 相似文献
77.
Comparison of the Virulence of Methicillin-Resistant and Methicillin-Sensitive Staphylococcus aureus
Sadao Mizobuchi Junzaburo Minami Fu Jin Osamu Matsushita Akinobu Okabe 《Microbiology and immunology》1994,38(8):599-605
The virulence of methicillin-resistant Staphylococcus aureus (MRSA) was compared with that of methicillin-sensitive S. aureus (MSSA), using 13 MRSA and 7 MSSA strains isolated from clinical specimens. The infectivity and lethality of the two groups were examined as to the inoculum required to infect 50% of guinea pigs (ID50) and to kill 50% of mice (LD50), respectively. The mean ID50 [log10 colony forming units (CFU)] for MRSA strains was 7.1 ± 0.60 standard deviation, which was 1.5 higher than that for MSSA strains (P < 0.001). The mean LD50 (log10 CFU) for MRSA strains was 9.0 ± 0.42, being 1.1 higher than that for MSSA strains (P = 0.001). Pretreatment of mice with cyclophosphamide decreased the mean LD50 for MRSA strains more than that for MSSA strains, resulting in the difference in the mean LD50 being insignificant (P = 0.502). These results indicate that MRSA is less virulent than MSSA in normal hosts, but that they are equally virulent in immunocompromised hosts. The growth of MRSA strains was much slower than that of MSSA strains in the lag phase, although their growth rates were almost the same in the exponential growth phase, suggesting that the difference in virulence between them may be at least partly due to such a difference in growth. 相似文献
78.
《Electromagnetic biology and medicine》2013,32(2):132-142
Non thermal (NT) effect of direct radiation 4 Hz-modulated 90–160 GHz of Millimeter Waves (MMW) and preliminary MMW-treated physiological solution (PS) influence were studied on snail isolated neuron, rat's brain tissue hydration and skin penetration. It was shown that the 4 Hz-modulated low intensity 90–160 GHz MMW direct radiation and MMW-treated PS leads to on single neuron shrinkage, skin and brain tissue dehydration. On the basis of obtained data it was suggested that the cell bathing aqua medium serve as a target through which the NT effect of MMW on cell hydration is realized. The MMW-induced brain tissue dehydration can considering as consequence of MMW-induced skin water structural changes leading to unknown messenger formation able to modulate the brain cell hydration. The extrasensitivity of cell hydration to low intensity of MMW radiation allow to recommend cell hydration as a cellular marker for estimation of the NT biological effect of MMW on cells and organisms. 相似文献
79.