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1.
The effects of cardiotoxin on the ATPase activity and Ca2+-transport of guinea pig erythrocyte and rabbit muscle sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase (E.C.3.6.1.3) were investigated. Erythrocyte (Ca2+ + Mg2+)-ATPase was inhibited by cardiotoxin in a time- and dose-dependent fashion and inhibition appears to be irreversible. Micromolar calcium prevented this inhibitory effect. Specificity for (Ca2+ + Mg2+)-ATPase inhibition by cardiotoxin was indicated since a homologous neurotoxin had no effect. Cardiotoxin did not affect (Ca2+ + Mg2+)-ATPase activity from sarcoplasmic reticulum, but Ca2+-transport was 50% inhibited. This inhibition was not due to an increased Ca2+-efflux and could be the result of an intramolecular uncoupling of ATPase activity from Ca2+-transport. Inhibition of Ca2+-transport by cardiotoxin could not be prevented by millimolar concentrations of Ca2+. It is suggested that the biological effects of cardiotoxin could be a consequence of inhibition of plasma membrane (Ca2+ + Mg2+)-ATPases. 相似文献
2.
3.
Louise Warnich Peter N. Meissner Richard J. Hift Jan H. Louw Carel J. van Heerden Andries E. Retief 《Human genetics》1996,97(5):690-692
The gene for variegate porphyria (VP), an autosomal dominant disease with a high prevalence in South Africa, evidently due
to a founder effect, was previously mapped to chromosome 14q32. In the current study this localization was evaluated by linkage
and haplotype analyses using microsatellite markers spanning a region of more than 20 cM on chromosome 14q32. In many recent
studies linkage disequilibrium between disease and marker loci has been utilized to map genes in founder populations, but
we could not find any association between VP and the markers used in this study. Our data suggest that the allocation of VP
to chromosome 14q32 may be incorrect.
Received: 1 September 1995 / Revised: 1 November 1995 相似文献
4.
Detecting non-neutral heterogeneity across a region of DNA sequence in the ratio of polymorphism to divergence 总被引:11,自引:4,他引:7
Natural selection, in the form of balancing selection or selective sweeps,
can result in a decoupling of the amounts of molecular polymorphism and
divergence. Thus natural selection can cause some areas of DNA sequence to
have greater silent polymorphism, relative to divergence between species,
than other areas. It would be useful to have a statistical test for
heterogeneity in the polymorphism to divergence ratio across a region of
DNA sequence, one that could identify heterogeneity greater than that
expected from the neutral processes of mutation, drift, and recombination.
The only currently available test requires that a region be arbitrarily
divided into sections that are compared with each other, and the
subjectivity of this division could be problematic. Here a test is proposed
in which runs of polymorphic and fixed sites are counted, where a "run" is
a set of one or more sites of one type preceded and followed by the other
type. The number of runs is smaller than otherwise expected if
polymorphisms are clumped together. By simulating neutral evolution and
comparing the observed number of runs to the simulations, a statistical
test is possible which does not require any a priori decisions about
subdivision.
相似文献
5.
The properties of progesterone-binding proteins in plasma of pregnant Cape porcupines were investigated using radiolabelled progesterone and either progesterone or cortisol as competing ligands as well as native plasma and heated (60 degrees C for 30 min) plasma. The results demonstrated that plasma from pregnant porcupines contains corticosteroid-binding globulin, but that it constitutes a significant portion of plasma progesterone-binding proteins only during the early stages of pregnancy. Corticosteroid-binding globulin of porcupines appears to be as heat labile as that of guinea-pigs. Concentrations of progesterone-binding proteins in plasma increased during pregnancy to reach concentrations at the eleventh week that were 25 times higher than those of progesterone; concentrations increased significantly (r2 = 0.88) with the increase in progesterone concentration. The results indicate that plasma progesterone-binding proteins in Cape porcupines (Old World hystricomorph) are similar in composition to those in guinea-pigs (New World hystricomorph). 相似文献
6.
7.
When varanid lizards, Varanus niloticus, were allowed to select their preferred body temperature (c. 34°C) they exhibited swifter growth, larger food intake and superior efficiency of conversion when compared with animals restricted to a maximum body temperature of 24°C. At the higher temperature the animals also exhibited a higher metabolic rate and increased thyroid activity, while those at the lower temperature lostproportionately more energy via respiration. A complete energy budget over a period of 6 weeks is presented. 相似文献
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9.
The synergistic effect of exogenous cobra phospholipase A2 on the hemolysis rate of guinea pig erythrocytes by highly purified snake venom cardiotoxins was investigated. In the presence of phospholipase A2 the reaction was not only faster and had a lower activation energy but followed a sigmoidal instead of a linear time course. Similar results were obtained using porcine pancreatic phospholipase A2. Significantly, addition of even a trace of cobra phospholipase A2 (approx. 0.1%, w/w) was sufficient to bring about the full synergistic effect, emphasizing the stringent purity requirements for any meaningful investigation of cardiotoxin's own action. The possibility that the action of cardiotoxin on its own may involve the stimulation of an endogenous phospholipase is discussed in the light of the results obtained with exogenous cobra enzyme. 相似文献
10.
Cleanthe D. Louw 《Mycopathologia》1976,58(3):169-176
Nuclear distribution and behaviour during vegetative growth and spore formation inAlternaria tenuis was studied utilising the HCl — Giemsa staining technique. The vegetative mycelium and conidia are predominantly monokaryotic. Anastomoses, followed by nuclear migrations, have been recorded. Intercellular nuclear migrations have only been observed in germinating conidia. Nuclear behaviour during conidial formation indicates that the conidia are homokaryotic. Cytological differences have been found in different monocoidal isolates of A. tenuis. 相似文献