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991.
Basic electrophysiological parameters and frequency sensitivity of the ventricular myocardium of human embryos 总被引:1,自引:0,他引:1
The basic electrophysiological manifestations of the ventricular myocardium of twelve 7- to 12-week human embryos were measured with a glass electrode and a programmed stimulation technique. The resting membrane potential value was 79.37 +/- 0.34 mV and the overshoot 32.7 +/- 0.57 mV; the action potential (AP) duration at 1 Hz stimulation frequency was 120.0 +/- 5.7 ms at AP plateau phase levels and 258 +/- 17 ms at the level corresponding to 95% repolarization. The duration of the AP was a function of the stimulation frequency. i.e. it altered in correlation to the stimulation programme fully developed frequency sensitivity). In stimulation with different frequencies the duration of the steady state AP was in an inverse relation to the stimulation frequency, the maximum changes being found in the terminal repolarization zone. An interpolated extrasystole mainly affected the duration of the plateau phase. 相似文献
992.
In the present work the effects of the hypophysis hormones on oviduct mucoprotein components distribution patterns were studied. Remarkable changes after treating the toad with hypophysis injections were apparent. The distribution pattern for hexose, sialic acid, hexosamine and phosphate from 18 hours hypophysis treated toads were found to be identical with those obtained from preovulatory period animals. On the other hand, the levels for mucoprotein components from hypophysis treated animals were found to be approximately one-half or more higher than those obtained from postovulatory period toads. Otherwise, hypophysis treatment of the toads in preovulatory period had not effect on the levels and distribution patterns of mucoprotein components. These results suggest that hypophysis hormones are involved in the increase of the oviduct secretory activity. 相似文献
993.
Phosphatidylcholine is one of the most frequent phospholipid components of the inner mitochondrial membrane ofNeurospora crassa. Quantitative analysis of phospholipids of the wild strain ofNeurospora crassa and of its twocho mutants showed that these strains did not significantly differ in the content of phosphatidylcholine. Mutants cultivated
in a medium without choline contained, as compared with the wild strain, an increased amount of phosphatidylserine and a decreased
quantity of phosphatidic acid. Respiratory activity increased and sensitivity to inhibitors of respiration changed. It is
likely that the presence of choline in the growth medium exerts a regulatory effect on the cell metabolism of these mutants. 相似文献
994.
995.
Incubation of cell-free extracts ofC. utilis and its ethionine-resistant mutants with methionine, aspartate and alanine, and with various acceptor oxo-acids showed the
presence of several transamination activities (Glu-Asp, Ala-Glu, Met-Glu, Met-Ala, Ala-Asp, but not Met-Asp). The lack of
utilization of methionine by mec mutants appears to be due to a transport lesion. 相似文献
996.
Cultivation ofAspergillus niger 97A in baffled flasks on a shaker brings about metabolic changes demonstrated in increased citric acid biosynthesis, morphological
changes and alterations in the mycelial cell wall. 相似文献
997.
K. Lívanský 《Folia microbiologica》1982,27(6):455-459
The buffering capacity of solutions of KH2PO4 and NaHCO3 increases with their concentration, the behaviour being describable by mathematical expressions. Solutions of KH2PO4 prepared from tap water exhibit a buffering capacity higher by an order of magnitude than those prepared from distilled water.
However, there is no difference between the buffering capacities of solutions of NaHCO3 prepared from tap and distilled water. Urea and NH4NO3 have almost no effect on the buffering capacities of sol utions. 相似文献
998.
999.
Dagmar Jičínská Eduard Brabec Marcel Rejmánek Jan Jeník Joří Haager Josef Holub Věroslav Samek Hana Rambousková Josef Holub Marie Naděžda Končalová Robert Neuhäusl Josev Kyncl František Krahuleo Jaroslav Dobrý Blanka Úlehlová Jiří Úlehla Eliška Rybníčková Kamil Rybníček 《Folia Geobotanica》1982,17(4):431-448
1000.
Characterization of a Manganese Superoxide Dismutase from the Higher Plant Pisum sativum 总被引:1,自引:1,他引:0 下载免费PDF全文
A manganese-containing superoxide dismutase (EC 1.15.1.1) was fully characterized from leaves of the higher plant Pisum sativum L., var. Lincoln. The amino acid composition determined for the enzyme was compared with that of a wide spectrum of superoxide dismutases and found to have a highest degree of homology with the mitochondrial manganese superoxide dismutases from rat liver and yeast. The enzyme showed an apparent pH optimum of 8.6 and at 25°C had a maximum stability at alkaline pH values. By kinetic competition experiments, the rate constant for the disproportionation of superoxide radicals by pea leaf manganese superoxide dismutase was found to be 1.61 × 109 molar−1·second−1 at pH 7.8 and 25°C. The enzyme was not sensitive to NaCN or to H2O2, but was inhibited by N3−. The sulfhydryl reagent p-hydroxymercuribenzoate at 1 mm concentration produced a nearly complete inhibition of the manganese superoxide dismutase activity. The metal chelators o-phenanthroline, EDTA, and diethyldithiocarbamate all inhibited activity slightly in decreasing order of intensity. A comparative study between this higher plant manganese superoxide dismutase and other dismutases from different origins is presented. 相似文献