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101.
Elena Kosenko Yuri Kaminsky Eugenio Grau María-Dolores Miñana Goizane Marcaida Santiago Grisolía Vicente Felipo 《Journal of neurochemistry》1994,63(6):2172-2178
Abstract: Injection of large doses of ammonia into rats leads to depletion of brain ATP. However, the molecular mechanism leading to ATP depletion is not clear. The aim of the present work was to assess whether ammonium-induced depletion of ATP is mediated by activation of the NMDA receptor. It is shown that injection of MK-801, an antagonist of the NMDA receptor, prevented ammonia-induced ATP depletion but did not prevent changes in glutamine, glutamate, glycogen, glucose, and ketone bodies. Ammonia injection increased Na+ ,K+ -ATPase activity by 76%. This increase was also prevented by previous injection of MK-801. The molecular mechanism leading to activation of the ATPase was further studied. Na+ ,K+ -ATPase activity in samples from ammonia-injected rats was normalized by "in vitro" incubation with phorbol 12-myristate 13-acetate, an activator of protein kinase C. The results obtained suggest that ammonia-induced ATP depletion is mediated by activation of the NMDA receptor, which results in decreased protein kinase C-mediated phosphorylation of Na+ ,K+ -ATPase and, therefore, increased activity of the ATPase and increased consumption of ATP. 相似文献
102.
Seema Mathur 《Biological trace element research》1994,41(3):201-215
An ayurvedic medicine, Liv-52, was studied as a prophylactic agent against beryllium-induced toxicity in rats. Administration
of berylliumper se caused severe degenerative and necrotic changes in kidneys, liver, and uterus. Beryllium exposure also reduced glycogen content,
activities of alkaline phosphatase, succinate-dehydrogenase, and adenosine-triphosphatase in these organs. On the contrary,
activities of acid phosphatase and glucose-6-phosphatase showed marginal increase. Liv-52-primed rats exhibited comparatively
less marked toxic effects. 相似文献
103.
Sulfate reduction in methanogenic bioreactors 总被引:9,自引:0,他引:9
Stefanie J.W.H. Oude Elferink ré Visser Look W. Hulshoff Pol Alfons J.M. Stams 《FEMS microbiology reviews》1994,15(2-3):119-136
Abstract: In the anaerobic treatment of sulfate-containing wastewater, sulfate reduction interferes with methanogenesis. Both mutualistic and competitive interactions between sulfate-reducing bacteria and methanogenic bacteria have been observed. Sulfate reducers will compete with methanogens for the common substrates hydrogen, formate and acetate. In general, sulfate reducers have better growth kinetic properties than methanogens, but additional factors which may be of importance in the competition are adherence properties, mixed substrate utilization, affinity for sulfate of sulfate reducers, relative numbers of bacteria, and reactor conditions such as pH, temperature and sulfide concentration. Sulfate reducers also compete with syntrophic methanogenic consortia involved in the degradation of substrates like propionate and butyrate. In the absence of sulfate these methanogenic consortia are very important, but in the presence of sulfate they are thought to be easily outcompeted by sulfate reducers. However, at relatively low sulfate concentrations, syntrophic degradation of propionate and butyrate coupled to HZ removal via sulfate reduction rather than via methanogenesis may become important. A remarkable feature of some sulfate reducers is their ability to grow fermentatively or to grow in syntrophic association with methanogens in the absence of sulfate. 相似文献
104.
105.
Jörg Brunet 《Plant and Soil》1994,161(2):157-166
The influence of base cation concentrations on pH and aluminium sensitivity of the woodland grasses Bromus benekenii and Hordelymus europaeus was studied in flowing solution culture experiments. Plants were exposed to low pH (3.9, experiment 1) and Al concentrations of 19 and 37 M (experiment 2) at two base cation (Ca+Mg+K) levels, all within the ranges measured in natural forest soil solutions. Elevated base cation concentrations ameliorated both H and Al toxicity, as indicated by increased root and shoot growth. In the third experiment, interactions between pH (4.3 and 4.0) and Al (0 and 19 M) were investigated. It was shown that the combined toxicity effects of H and Al were not greater than the separate H or Al effects. Tissue concentrations of base cations and Al increased with increasing concentrations in the solution, but were also influenced by the base cation : Al ratio. Relating the experimental evidence with the composition of forest soil solutions suggests an important role of soil pH and Al in controlling the distribution of the two species. Growth conditions also differ at various soil depths. Concentrations of free cationic Al were higher and base cation concentrations lower at 5–10 cm than at 0–5 cm soil depth. Increasing base cation concentrations may protect roots from both H and Al injury during periods of drought when concentrations of most elements increase in the soil solution, whereas molar ratios between base cations, H and Al remain unchanged. 相似文献
106.
Iron toxicity and other chemical soil constraints to rice in highland swamps of Burundi 总被引:1,自引:0,他引:1
Iron toxicity is suspected to be a major nutritional disorder in rice cropping systems established on flooded organic soils that contain reductible iron. A pot trial was carried out to assess Fe toxicity to rice in flooded Burundi highland swamp soils with a wide range of organic carbon contents. Soil and leaf analyses were performed and total grain weight was determined. Clear Fe toxicity was diagnosed, based on leaf Fe content at panicle differentiation. Leaf Fe contents higher than 250 g g–1 dry matter induced lower Mg (and probably Mn) uptake, and a 50% total grain weight reduction. These features were associated with exchangeable Fe equivalent fractions higher than 86%. Besides, several non-Fe toxic soils exhibited an Mg-Mn imbalance. 相似文献
107.
Effect of shock-loading of heavy metals on total organic carbon and phosphate removal in an anaerobic-aerobic activated sludge process 总被引:1,自引:0,他引:1
The effect of shock-loading of zinc, copper and cadmium ions on the removal of total organic carbon (TOC) and phosphate in an anaerobic-aerobic activated sludge process was investigated. TOC removal was not sensitive to shock-loading of Zn2+ and Cd2+ ions, and complete removal was achieved even at 20 mg Zn2+/l and 20 mg Cd2+/l. However, with over 1 mg Cu2+/1 TOC removal efficiency decreased. PO
inf4
sup3-
removal, in contrast, was extremely sensitive to these metal ions, with the threshold being 1 mg Zn2+/l and 1 mg Cd2+/l. Higher concentrations adversely affected PO
inf4
sup3-
removal. Copper again proved detrimental; no PO
inf4
sup3-
removal was achieved even at 1 mg Cu/l. These results highlight the sensitivity of the removal efficiencies of TOC and PO
inf4
sup3-
to shock loadings of these heavy metals.Y.P. Ting is with the Department of Chemical Engineering, National University of Singapore, Kent Ridge, 0511, Singapore; H. Imai and S. Kinoshita are with the Department of Chemical Process Engineering, Hokkaido University, Sapporo 060, Japan. 相似文献
108.
Prabha Modi Professor B. Sadasivudu U. Lakshminarayana C. R. K. Murthy 《Neurochemical research》1994,19(3):353-358
The functional significance of ammonia production in brain under physiological or pathological conditions is not clearly known. NH4
+ stimulates Na+, K+ activated ATPase causing stabilization of neuronal membranes of which gangliosides are major structural components. Moreover ammonia is known to inhibit lysosomal enzymes which include enzymes degrading gangliosides. Gangliosides have been shown to stimulate neuritogenesis in neuronal cultures and prevent the damage of the neurons from glutamate toxicity particularly in areas of brain ischemia. Hyperammonemia without any behavioural changes was induced in experimental rats by intraperitoneal administration of either a single dose (0.8 mmol/100 g wt.) or by six hourly doses (0.6 mmol/100 g wt.) of ammonium acetate. An increase in the content of gangliosides along with a rise in the content of GD1A and GD1B without any change in -galactosidase and N-acetylhexosaminidase was observed in cerebral cortex, cerebellum, and brain stem, following the administration of single dose of ammonium acetate. Gangliosides, after extraction from the different brain regions, were estimated by the thiobarbituric acid method and expressed in terms of sialic acid. Individual gangliosides were separated and estimated by thin layer chromatography using resorcinol as the staining agent. These results suggest that ammonia production in the neuronal pathways in brain either as a result of repeated stimulation under physiological conditions or as a result of focal ischemia or injury, may likewise cause an increase in the content of gangliosides which may help in neuritic growth (physiological conditions facilitating synaptic plasticity) and may exert a protective effect on the neurons in the ischemic area against glutamate toxicity.Former Professor of Biochemistry, OMC, Hyderabad. 相似文献
109.
Celery (Apium graveolens L. var Dulce) is a high value crop affected at different growth stages by a variety of nutrient disorders. Each nutrient concentration can be corrected for its dependence on concentrations of other nutrients by recognizing plant composition as a closed system whose components add up to one. New variables z
i are computed as logratioed values of individual nutrients, where each nutrient concentration is corrected for the geometric mean of all nutrient concentrations. The z
i are used together with principal component analysis (PCA) to relate celery composition to yield, deficiency symptoms and quality parameters. A survey of commercial celery fields suggested that (1) celery growth is most often limited by P and N deficiencies associated with Fe toxicity; (2) K uptake is most likely to become limiting when the crop reaches 15 cm in height; (3) blackheart incidence can be traced to low levels of K and Mg in external petioles, and (4) cracked stem incidence is related to low B when the crop is 30 cm in height. 相似文献
110.
Ring S. M. Fisher R. P. Poile G. J. Helyar K. R. Conyers M. K. Morris S. G. 《Plant and Soil》1993,155(1):521-524
The major phytotoxins in acid soils are aluminium and manganese. Tolerances to Al and to excessive Mn are independently inherited and Al and Mn solubilities in soils vary. In this work, the response of pasture grasses and legumes to soil acidity was studied on three soils with different Al and Mn concentrations. One provides moderate concentrations of Al with little Mn; one provides high concentrations of both Al and Mn and another provides a very high concentration of Mn at relatively low concentrations of Al. The response of a plant cultivar to changes in the soil acidity induced by lime or acid additions reflects the degree of Al and/or Mn stress provided by a particular soil, and the ability of the cultivar to tolerate those stresses. Examples are given of the way cultivars with different tolerances to Al and Mn toxicity respond to changes in acidity on the soils with different Al and Mn solubility characteristics. The utility of this screening technique to define the tolerance of cultivars to acidity on classically different soils is highlighted. 相似文献