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51.
The tannins, delphinidin and procyanidin were isolated from flowers of white clover (Trifolium repens) and the leaves of Arnot Bristly Locust (Robina fertilis) respectively, and tested for mutagenic properties in a range of systems. There was no evidence for either compound causing significant levels of frameshift or base-pair mutagenesis in bacterial mutagenicity assays, although both were weakly positive in a bacterial DNA-repair test. Both compounds very slightly increased the frequency of petite mutagenesis in Saccharomyces cerevisiae strain D5. In V79 Chinese hamster cells, both were efficient inducers of micronuclei. In each of these test systems, increasing the potential of the compound for metabolic activation by addition of 'S9' mix had little effect on toxicity or mutagenicity of either tannin. It would seem that potential chromosome-breaking activity of condensed tannins could represent a carcinogenic hazard for animals grazing on pastures of white clover in flower. It may also have wider implications for human carcinogenesis by some, if not all, condensed tannins. 相似文献
52.
Tyrosine-311 of a beta chain is the essential residue specifically modified by 4-chloro-7-nitrobenzofurazan in bovine heart mitochondrial ATPase 总被引:1,自引:0,他引:1
A peptide containing an essential tyrosine residue, modified with the nitrobenzofurazan group, has been purified from bovine heart mitochondrial ATPase. The composition of the peptide indicates that this tyrosine is residue 311 in the sequence of a beta chain. The problem of the instability of the tyrosyl-nitrobenzofurazan bond was overcome by working throughout at relatively acidic pH and using pepsin digestion of the enzyme. 相似文献
53.
Abstract Proton translocation associated with electron flow to oxygen has been observed with cells of Nitrobacter winogradskyi in the presence of either potassium ferrocyanide or isoascorbate plus N , N , N ', N ' tetramethyl- p -phenylenediamine. The data are consistent with a proton pumping function for the terminal oxidase, cytochrome aa 3 , in this organism as the mechanism for generating a protonmotive force. The failure of previous work with Nitrobacter [4] to detect proton translocation linked to oxidation of nitrite, the physiological substrate, is discussed. 相似文献
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55.
C J Gordon J H Ferguson 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1984,46(4):387-397
We have demonstrated that a comparative analysis of the physiological effects of exposure of laboratory mammals to radiofrequency electromagnetic radiation (RFR) may be useful in predicting exposure thresholds for humans if the effect is assumed to be due only to heating of tissue. The threshold specific absorption rate (SAR) necessary to affect a thermoregulatory parameter shows an inverse and linear relationship to body mass. The inverse relationship between threshold SAR and body mass is attributed to a surface area: body mass relationship. In comparison to small mammals, relatively large mammals have a reduced capacity to dissipate an internal heat load passively, and are therefore physiologically more sensitive to RFR exposure. The threshold for a thermoregulatory response depends on the type of response measured, species, ambient temperature, etc. By extrapolation, it can be shown that a SAR of only 0.2-0.4 W/kg is required to promote a thermoregulatory response in a mammal with a body mass of 70 kg (e.g. weight of adult human). The specific absorption rate bioeffects data collected from laboratory mammals can be related by means of a simple power formula: threshold SAR (W/kg) = aMb, where M is body mass in kg, a is a constant and b is equal to approximately -0.5. Through this equation we have illustrated that a threshold SAR measured in a species weighing 100 g would be 10 times greater than that of a species weighing 10 000 g. Accordingly, a relatively low SAR that is physiologically ineffective in small mammals may be stressful to larger species. 相似文献
56.
Walter W. Ferguson 《Primates; journal of primatology》1986,27(4):485-492
The taxonPraeanthropus africanus (Weinert, 1950), represented by the Garusi maxilla, is valid and reinstated. The morphological pattern of the Garusi maxilla is not
that of a primitive hominid, but of a relatively generalized pongid. Since the apelike lectotype L.H.-4 and paralectotype
A.L.200-1a ofAustralopithecus afarensis
Johanson et al. 1978 are conspecific withP. africanus, and originate from the same formation, they are reassigned toPraeanthropus africanus. 相似文献
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59.
Inhibition by calcium of senescence of detached cucumber cotyledons: effect on ethylene and hydroperoxide production 总被引:4,自引:0,他引:4 下载免费PDF全文
The effect of Ca on senescence was followed in detached cucumber (Cucumis sativus L.) cotyledons floating on various solutions in the dark. Compared with those in water, cotyledons in 10−4 molar CaCl2 exhibited reduced chlorophyll loss and H2O2 production, reduced and delayed ethylene production, and did not undergo a burst in CO2 production. In contrast, Mg had little effect on cotyledon senescence, whereas K stimulated chlorophyll loss but did not increase H2O2 accumulation of ethylene and CO2 production. This reduction in the rate of senescence by Ca could also be achieved by increasing the endogenous levels of Ca in the cotyledons before excision, although the reduction was less than that with Ca in the external solution. The addition of H2O2 to the solutions on which cotyledons were floated stimulated chlorophyll breakdown, but effects on ethylene and CO2 were not consistent. 相似文献