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31.
Summary Ethidium was found to be taken up by yeast cells in a process that, at certain concentrations has the main following characteristics: a) a substrate is required; b) it presents cooperative kinetics, withn, according to the Hill equation 3; c) ethidium can be concentrated more than 100-fold; d) the uptake is inhibited by Ca2+; e) the uptake of the dye is inhibited by monovalent cations with a selectivity pattern similar to that observed in their transport by yeast; f) ethidium inhibits the uptake of K+, and, at concentrations up to about 250 m produces a competitive inhibition on the uptake of Rb+; and g) ethidium produces the same effects as K+ on respiration and the extrusion of H+. It is concluded that ethidium is taken up by yeast cells in a selective way by the same transport system normally employed for monovalent cation uptake. 相似文献
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Water consumption related to the life cycle of metals is seldom reported, even though mines are often situated in very dry regions. In this study we quantified the life cycle consumption of groundwater and fresh surface water (blue water footprint [WFblue]) for the extraction and production of high‐grade copper refined from both a copper sulfide ore and a copper oxide ore in the Atacama Desert of northern Chile. Where possible, we used company‐specific data. The processes for extracting copper from the two types of ore are quite different from each other, and the WFblue of the sulfide ore refining process is 2.4 times higher than that of the oxide ore refining process (i.e., 96 cubic meters per metric ton [tonne] of copper versus 40 cubic meters per tonne of copper). Most of the water consumption (59% of WFblue) in the sulfide ore process occurred at the concentrator plant, via seepage, accumulation, and also by evaporation. In the oxide ore process, the main user of water is the heap‐leaching process, with 45% of WFblue. The crushing and agglomeration operations, electrowinning cells, and solution pools are also significant contributors to the total consumption of water in the oxide ore process. Most of the water consumed in the oxide ore process was lost to evaporation. The WFblue of the oxide ore process can be reduced by preventing water evaporation and using more sophisticated devices during irrigation of the leaching heaps. The WFblue of the sulfide ore refining process can be reduced by improving water recovery (i.e., reducing seepage, accumulation, and evaporation) from the tailings dam at the concentrator plant. Using seawater in the production of copper is also a promising option to reduce the WFblue by up to 62%. 相似文献
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X-Irradiation of rat hippocampus in vitro with low doses accelerated spontaneous impulse passage without concomitant changes in synaptic activity. There was a negative correlation between the original frequency of neuron discharges and the degree of quickening the impulses in response to the effect of radiation. Perfusion of slices by a noncalcium solution blocked the synaptic transmission but did not influence the response to the effect of ionizing radiation. 相似文献
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D Jerusalinsky C Cerve?asky C Pe?a S Raskovsky F Dajas 《Neurochemistry international》1992,20(2):237-246
Two new polypeptides were isolated and purified from the venom of the snake Dendroaspis angusticeps, which also contains other neuroactive peptides such as Dendrotoxins and Fasciculins. The amino acid composition of the peptides was determined and the first 10 amino acids from the MTX2 N-terminal fragment were sequenced. The so-called muscarinic toxins (MTX1 and MTX2) have been shown to inhibit the specific binding of [3H]QNB (0.15 nM), [3H]PZ (2.5 nM) and [3H]oxoM (2 nM) to bovine cerebral cortex membranes by 60, 88 and 82% respectively. In contrast, they caused only a 30% blockade of the [3H]QNB specific binding to similar membrane preparations from the brainstem. The Hill number for the [3H]PZ binding inhibition by the putative muscarinic toxin MTX2 was 0.95 suggesting homogeneity in the behaviour of the sites involved. The data from [3H]oxoM binding gave a Hill number of 0.83. The decreases in the specific binding involved increases in KD for the three different ligands (8-fold for [3H]QNB, 4-fold for [3H]PZ and 3.5-fold for [3H]oxoM) without significant changes in Bmax, except for a slight decrease in the [3H]oxoM binding sites (-19%); such results suggest that there may be a competitive inhibition between the MTXs and these ligands. The Ki for MTX2/[3H]PZ was 22.58 +/- 3.52 nM; for MTX2/[3H]oxoM, 144.9 +/- 21.07 nM and for MTX2/[3H]QNB, 134.98 +/- 18.35 nM. The labelling of MTX2 with 125I allowed direct demonstration of specific and saturable binding to bovine cerebral cortex synaptosomal membranes. In conclusion, the results reported in this study strongly support the hypotheses that the two polypeptides isolated from D. angusticeps venom selectively inhibit specific ligand binding to central muscarinic receptors, in a competitive manner at least for the antagonist [3H]PZ and that the MTX2 specifically binds to a central site that is suggested to be a muscarinic receptor of the M1 subtype. 相似文献
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Rakić Tamara Pešić Mila Kostić Nikola Andrejić Gordana Fira Djordje Dželetović Željko Stanković Slaviša Lozo Jelena 《Plant and Soil》2021,462(1-2):349-363
Plant and Soil - Flotation tailings represent an extremely unfriendly substrate for plant colonization due to toxic metal concentrations and marked macronutrient deficiencies. The perennial grass... 相似文献
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Kamal Laina Zarisa Mohd Adam Mowaffaq Adam Ahmed Shahpudin Siti Nurfatimah Mohd. Shuib Ahmad Naqeeb Sandai Rosline Hassan Norazian Mohd Tabana Yasser Basri Dayang Fredalina Than Leslie Thian Lung Sandai Doblin 《Mycopathologia》2021,186(2):221-236
Mycopathologia - Candida albicans has been reported globally as the most widespread pathogenic species contributing candidiasis from superficial to systemic infections in immunocompromised... 相似文献
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Delgado Naranjo Juan Martin Jiménez Callejón Maria José Peñuela Vásquez Mariana Rios Luis Alberto Robles Medina Alfonso 《Journal of applied phycology》2021,33(4):2031-2045
Journal of Applied Phycology - The thraustochytrid Aurantiochytrium limacinum SR21 is a promising source of docosahexaenoic acid (DHA) for human consumption as dietary supplement, replacing... 相似文献