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101.
Glutathione peroxidase activity and release of glutathione from oxygen-deficient perfused rat heart.
C Guarnieri F Flamigni C Rossoni-Caldarera 《Biochemical and biophysical research communications》1979,89(2):678-684
The effect of cellular hypoxia on glutathione levels in rat hearts was determined. Hearts perfused with 95% N2–5% CO2 demonstrated a significant decrease in tissue reduced glutathione content when compared to control hearts perfused with 95% O2–5% CO2. The hypoxic perfusate contained reduced glutathione and its release was time dependent over a period of 60 minutes. The cellular depletion of oxidized glutathione and its release into coronary effluent were less evident with respect to reduced glutathione. Moreover during hypoxic perfusion we have observed a decrease of cytosol glutathione peroxidase activity. These results suggest that severe oxygen-deprivation causes in myocardial cells a significant perturbation of glutathione metabolism. 相似文献
102.
The structure of the iron bleomycin nitric oxide complex is altered in the presence of calf thymus DNA as determined from epr studies. This altered structure predominates for one iron bleomycin nitric oxide molecule per coil of the DNA helix. In the absence of nitric oxide, as the pH is lowered, iron bleomycin dissociates in two steps, supporting the hypothesis that in-plane nitrogens may be easily perturbed. 相似文献
103.
Kenneth Krell Elizabeth D. Jacobson Katherine Selby 《In vitro cellular & developmental biology. Plant》1979,15(5):326-328
Summary The mutation frequency of L5178Y mouse lymphoma cells to resistance to 5′-bromo-2′-deoxyuridine increased 6-to 14-fold after
growth in ethylene oxide-sterilized polycarbonate culture flasks compared to growth in glass flasks. No comparable increase
was observed when L5178Y cells were growth in identical polycarbonate culture flasks sterilized by autoclaving. 相似文献
104.
R.J. Šrám 《Mutation research》1976,41(1):25-42
The relationship between acute and chronic exposures in mutagenicity studies on mammals still lacks experimental data that might permit the decision whether or not the long-term exposures are of significance in mutagenicity testing.Fractional application of TEPA, THIOTEPA, EMS cyclophosphamide and sodium arsenite was made in experiments with mice, by using the dominant-lethal test and cytogenetic analysis of bone marrow. In most experiments the repeated application yielded the same or higher genetic injury than the same total dose at a single application. Negative results are discussed in relation to the threshold dose and the different sensitivity of the germ-cell stage.Possible interaction of mutagens was also studied by analyzing the combined effect of a long-term exposure to sodium arsenite, which probably affected the repair mechanism, and of a single dose of TEPA. It is concluded that the present stage of knowledge requires acceptance of the opinion that the genetic risk induced by chronic exposure to a chemical is as serious as that induced by an acute exposure. 相似文献
105.
G. U. Okereke 《Plant and Soil》1984,81(3):421-428
Summary A total of 81 strains isolated by T. N. Gamble from soils from eight countries, fresh water lake sediments and nitrified poultry
manure were examined for their ability to grow on N2O as their electron acceptor, as well as for their tendency to produce N2O from NO
3
−
in the absence and presence of acetylene. Seventy-seven of the 81 strains were confirmed as denitrifiers. Fifty-nine of the
77 strains grew on N2O, while 12 strains produced N2O but could not utilize it. Six strains reduced NO
3
−
to N2 but could not grow on N2O, suggesting that even if N2O is always an intermediate product of denitrification, it is not always a freely diffusible intermediate. The organisms,
however, would consume N2O that accumulated early in growth and accumulated N2O in the presence of acetylene. Thus the total number of N2O users was 65 strains or 83% of the total tested. This implies that the N2O reducing capacity of denitrifiers occur widely in nature. A high proportion ofPseudomonas fluorescens biotype II reduced N2O. The accumulation of N2O from NO
3
−
in the presence of acetylene provides strong evidence that N2O is generally an intermediate in denitrification as well as provides additional support for the usefulness of this chemical
as a general inhibitor of N2O reduction. 相似文献
106.
Microbial production and uptake of nitric oxide in soil 总被引:3,自引:0,他引:3
Abstract Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism. 相似文献
107.
Methods of preparing dried gelatin films containing purified reaction centers of Rhodopseudomonas sphaeroides are described. The spectral properties of reaction centers in solution are essentially maintained in dried gelatin films. These films are uniform and have excellent optical properties, showing little particulate scattering at temperatures down to about 4K. Film contraction on cooling to 90K is less than 1% in linear dimension. Linear dichroism spectra are reported for films at room and low temperature. Reaction centers show a moderate amount of linear dichroism in unstretched gelatin films; the magnitude of the linear dichroism becomes much greater when the films are stretched. In stretched films, linear dichroic ratios (; absorbance measured with electric vector parallel and perpendicular to stretching direction) between 1.7 and 2.2 were obtained for the 860 nm absorption band of the bacteriochlorophyll component that undergoes primary photooxidation. The relative polarizations of light-induced absorption changes of reaction centers in stretched films are similar to those reported by Vermeglio and Clayton ((1976) Biochim. Biophys. Acta 449, 500–515) and support their hypothesis that absorbance decreases, maximal near 860 and 810 nm, and an increase near 790 nm are associated with the respective disappearance and appearance of discrete bands characteristic of the reduced and oxidized bacteriochlorophyll dimer. This interpretation is also supported by the polarization of the absolute absorption spectrum near 810 and 860 nm. An absorption band near 540 nm, ascribed to the Qx transitions of two molecules of bacteriopheophytin in the reaction center, is split at low temperatures into two bands having similar polarizations. This splitting is probably not due to exciton coupling of the two molecules, since excition theory predicts different polarizations. 相似文献
108.
ALAN R. WELLBURN 《The New phytologist》1998,139(1):5-9
Air quality thresholds for O3 for the protection of human health and vegetation set by the European Union (EU) have been exceeded in Europe regularly in the 1990s. Because target reductions for oxides of nitrogen (NOx ) set for the year 2000 are unlikely to be achieved, these O3 exceedances are likely to continue into the next millenium. Improvements of plant tolerance towards O3 are being investigated but very little work has been done to explore NOx tolerance and plant acclimation to NO2 and NO. However, it is clear that within the populations of some plant species there is wide variation, and some individuals can fix NOx and use the nitrogen directly from the atmosphere, rather than rely upon, for example, root uptake of nitrate. It is possible that individuals capable of fixing NOx could be selected for a range of species, and genotypes with high rates of uptake could be of value as crops or for forestation in polluted areas (e.g. landscaping in the vicinity of motorways) to reduce tropospheric concentrations of NOx significantly and also to decrease the potential for O3 production. 相似文献
109.
110.