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11.
Summary Cell surface gamma-glutamyl transpeptidese activity in cultured neoplastic astrocytes was significantly increased upon treatment of the cells with the hepatoprotective disulfide, cystamine. The cystamine effect was sensitive to cycloheximide and could be significantly depressed by exogenous glutathione. Surface gamma-glutamyl transpeptidase activity was also modulated by the presence in the culture medium of the unsaturated fatty acids, linoleic acid and arachidonic acid. Metabolism of the fatty acids via the cyclooxygenase pathway was not a prerequisite for their modulation of the glycoprotein ectoenzyme. Lipoxygenase, however, was found to potentiate the unsaturated fatty acid effect in neoplastic astrocytes. Lipoxygenase is reported to catalyze the conversion of unsaturated fatty acids to their corresponding peroxides. The data indicate an oxidative influence on the control of gamma-glutamyl transpeptidase activity. 相似文献
12.
This study is based on a sample of 9,134 children ranging in age from 2 to 17 years from which the excessively lean and fat children by skinfold thickness were excluded. This sample was derived from the combined data sets of the first and second National Health and Nutrition Examination Surveys (NHANES I and II) of 1971-1974 and 1976-1980. Means and percentiles of upper arm muscle area were calculated for 3 cm increments in stature from 84 to 184 cm for boys and from 84 to 176 cm for girls. Based on means, Z-score units, and percentile ranges of upper arm muscle area by stature, five operational categories of nutritional status have been established. It is recommended that these standards and this classification system be used to supplement current standards of weight for age and weight for height in order to obtain a more complete assessment of body composition and nutritional status. 相似文献
13.
Angeles Alonso-Moraga Antonio Bocanegra Juan M. Torres Juan López-Barea Carmen Pueyo 《Molecular and cellular biochemistry》1987,73(1):61-68
The intracellular concentrations of total glutathione, GSSG and protein · S-SG, the total excreted glutathione concentration, and the susceptibility towards GSH-reacting compounds were assayed in strains of Escherichia coli deficient in biosynthesis and/or reduction of glutathione. A deficiency in glutathione reductase displaced the glutathione status towards the oxidized forms. This displacement was more clearly appreciated in strains additionally deficient in glutathione biosynthesis. A deficiency in catalase activity also produced an increase in the oxidation of glutathione. The most severe changes were observed in the concentrations of protein-glutathione mixed disulfides and in the amount of glutathione excreted to the medium. Increased sensitivities towards compounds known to interact with cellular GSH were observed in glutathione reductase deficient strains, although these effects were enhanced in strains additionally deficient in GSH biosynthesis 相似文献
14.
Near a hen house (50–600 m), vitality ofPinus sylvestris, N-, P-, K-, Ca-, Mg-contents of the needles, N-, Mg-, K-, Ca- and Al-contents in soil extracts and NH3/NH
4
+
-contents of the air were determined. Damage symptoms occurred when N-immissions hit the canopy directly. In contrast no visible decline of the above ground plant could be observed if N was mainly deposited on the soil. 相似文献
15.
The debated identity of a small forest bushbaby in Malawi is resolved by a short-term field study of the animals’ behavior.
Locomotor styles, calling patterns, and the structure of advertising calls confirm that the species is Galago zanzibaricusrather than G. demidoffor G. thomasi.A detailed comparison of acoustic structure between the Malawi animals and G. zanzibaricusin Kenya demonstrates a degree of between-population variation, although the calls remain conservative in those parameters
expected to aid recognition of conspecifics. Distribution records extend the known geographical range of G. zanzibaricusover most of the northern half of Malawi. Further studies are required to link the animals from this region with either of
the previously recognized subspecies: G. z. zanzibaricusfrom East Africa or G. z. grantifrom southern Malawi, Mozambique, and Zimbabwe. 相似文献
16.
Effect of High Doses of Dietary Vitamin E on the Concentrations of Vitamin E in Several Brain Regions, Plasma, Liver, and Adipose Tissue of Rats 总被引:1,自引:0,他引:1
G. T. Vatassery M. F. Brin S. Fahn H. J. Kayden M. G. Traber 《Journal of neurochemistry》1988,51(2):621-623
The object of this study was to assess the influence of high levels of dietary vitamin E on vitamin E concentrations in specific areas of the brain. Four-week-old male rats were fed vitamin E-deficient, control, and high-vitamin E (1,000 IU/kg) diets for 4 months. Concentrations of alpha-tocopherol in serum, adipose tissue, liver, cerebrum, cerebellum, and striatum were determined by liquid chromatography with fluorescence detection. In the high-vitamin E group, alpha-tocopherol concentrations in cerebrum, cerebellum, and striatum increased uniformly to 1.4-fold of values in controls; serum, adipose tissue, and liver attained even higher concentrations: 2.2-, 2.2-, and 4.6-fold, respectively, of control values. As observed before, brain levels of alpha-tocopherol were somewhat resistant to vitamin E deficiency, in contrast to the peripheral tissues. 相似文献
17.
The host suitability of five of the most common weed species occurring in maize (Zea mays L.) fields in South Africa to Pratylenchus zeae was tested. Based on the number of nematodes per root unit, mealie crotalaria (Crotalaria sphaerocarpa) was a good host; goose grass (Eleusine indica), common pigweed (Amaranthus hybridus), and thorn apple (Datura stramonium) were moderate hosts; and khaki weed (Tagetes minuta) was a poor host. Only the root residues of khaki weed suppressed the P. zeae infestation of subsequently grown maize. When goose grass, khaki weed, and mealie crotalaria were grown in association with maize in soil infested with P. zeae, goose grass and khaki weed severely suppressed maize root development; this resulted in a low number of nematodes per maize root system and a high number of nematodes per maize root unit. Mealie crotalaria did not restrict maize root growth and did not affect nematode densities per maize root system or maize root unit. Special attention should be given to the control of mealie crotalaria, which is a good host for P. zeae, and goose grass, which, in addition to its ability to compete with maize, is also a suitable host for P. zeae. 相似文献
18.
Richard C. Leegood Carlos A. Labate Steven C. Huber H. Ekkehard Neuhaus Mark Stitt 《Planta》1988,176(1):117-126
Glycerol induced a limitation on photosynthetic carbon assimilation by phosphate when supplied to leaves of barley (Hordeum vulgare L.) and spinach (Spinacia oleracea L.). This limitation by phosphate was evidenced by (i) reversibility of the inhibition of photosynthesis by glycerol by feeding orthophosphate (ii) a decrease in light-saturated rates of photosynthesis and saturation at a lower irradiance, (iii) the promotion of oscillations in photosynthetic CO2 assimilation and in chlorophyll fluorescence, (iv) decreases in the pools of hexose monophosphates and triose phosphates and increases in the ratio of glycerate-3-phosphate to triose phosphate, (v) decreased photochemical quenching of chlorophyll fluorescence, and increased non-photochemical quenching, specifically of the component which relaxed rapidly, indicating that thylakoid energisation had increased. In barley there was a massive accumulation of glycerol-3-phosphate and an increase in the period of the oscillations, but in spinach the accumulation of glycerol-3-phosphate was comparatively slight. The mechanism(s) by which glycerol feeding affects photosynthetic carbon assimilation are discussed in the light of these results.Abbreviations Chl
chlorophyll
- C
i
intercellular concentration of CO2
- P
phosphate
- PGA
glycerate-3-phosphate
- Pi
orthophosphate
- triose-P
sum of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate 相似文献
19.
Glutathione reductase fromSaccharomyces cerevisiae undergoes redox interconversionin situ andin vivo
José Peinado Javier Florindo J. López-Barea 《Molecular and cellular biochemistry》1992,110(2):135-143
Redox interconversion of glutathione reductase was studiedin situ withS. cerevisiae. The enzyme was more sensitive to redox inactivation in 24 hour-starved cells than in freshly-grown ones. While 5 μM NADPH
or 100 μM NADH caused 50% inactivation in normal cells in 30 min, 0.75 μM NADPH or 50 μM NADH promoted a similar effect in
starved cells. GSSG reactivated the enzyme previously inactivated by NADPH, ascertaining that the enzyme was subjected to
redox interconversion. Low EDTA concentrations fully protected the enzyme from NADPH inactivation, thus confirming the participation
of metals in such a process. Extensive inactivation was obtained in permeabilized cells incubated with glucose-6-phosphate
or 6-phosphogluconate, in agreement with the very high specific activities of the corresponding dehydrogenases. Some inactivation
was also observed with malate, L-lactate, gluconate or isocitrate in the presence of low NADP+ concentrations.
The inactivation of yeast glutathione reductase has also been studiedin vivo. The activity decreased to 75% after 2 hours of growth with glucono-δ-lactone as carbon source, while NADPH rose to 144%
and NADP+ fell to 86% of their initial values. Greater changes were observed in the presence of 1.5 μM rotenone: enzymatic activity
descended to 23% of the control value, while the NADH/NAD+ and NADPH/NADP+ ratios rose to 171% and 262% of their initial values, respectively. Such results indicate that the lowered redox potential
of the pyridine nucleotide pool existing when glucono-δ-lactone is oxidized promotesin vivo inactivation of glutathione reductase. 相似文献
20.
Osamu Katano 《Environmental Biology of Fishes》1992,35(4):343-350
Synopsis Paired males of the dark chub, Zacco temmincki, buried released eggs by vibrating their anal fin, but this behavior was prevented and eggs were cannibalized when many satellites (males and females) were present. A number of satellite males also caused a loss to paired males in sperm competition on spawning grounds far from shelters. Paired males followed repeating tactics, which were defined as successive spawning acts at the same redd, in most cases, but occasionally did shifting tactics which refer to spawning acts conducted successively at different redds. The proportion of the shifting tactic was not correlated with the dominance status of paired males. The shifting tactic was not advantageous in performing spawnings frequently. The calculation of the total advantage of both tactics indicated that the shifting tactic itself was not more beneficial than the repeating tactic at any density of satellites. Since a number of satellites stayed around the redd when no spawning pair was present, or pursued a pair or a single dominant male moving between spawning grounds, the occasional shifting tactics of paired males functioned to confuse and disperse satellites. The spawning tactics of paired males apparently reflected potential fitness costs of satellites. Paired males mainly spawned at the redds near shelters, despite the fact that more satellites were present to devour eggs, presumably because they could obtain many females and monopolize fertilizations. 相似文献