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211.
Two components of the venom of the predatory wasp Philanthus triangulum F. significantly reduce--to a greater or less extent--the high affinity uptake of glutamate in rat hippocampus. A concentration of 10 microM delta-PTX caused a reduction of 74%, while the other component, beta-PTX, at the same concentration, caused a reduction of 18%. Hence the effect of delta-PTX on high affinity glutamate uptake in the hippocampus is comparable with its effect on high affinity glutamate uptake in insect neuromuscular junctions. Contrary to our previous findings that beta-PTX has no effect on high affinity glutamate uptake in insect glutamatergic terminal axons, however, beta-PTX significantly reduces high affinity glutamate uptake in the hippocampus, albeit less effectively than delta-PTX. 相似文献
212.
Three-dimensional chromatin distribution in neuroblastoma nuclei shown by confocal scanning laser microscopy 总被引:3,自引:0,他引:3
G J Brakenhoff H T van der Voort E A van Spronsen W A Linnemans N Nanninga 《Nature》1985,317(6039):748-749
The relationship between cell shape and function has long been of interest. However, although the behaviour of the cytoskeleton during the cell cycle has been studied extensively variations in the shape and three-dimensional substructure of the nucleus are less well documented. The spatial distribution of chromatin has previously been studied by a mathematical analysis of the optical densities of stained nuclei, allowing an indirect derivation of the three-dimensional distribution of chromatin. More direct information on chromatin organization can be obtained from electron-microscopic serial sections, although this is very laborious. Using an iterative deconvolution algorithm, Agard and Sedat achieved a degree of optical sectioning in conventional fluorescence microscopy and reconstructed the three-dimensional arrangement of polytene chromosomes. We report here on the three-dimensional structure of cultured mammalian cells as visualized by confocal scanning laser microscopy (CSLM). The exceptionally short depth of field of this imaging technique provides direct optical sectioning which, together with its higher resolution, makes CSLM extremely useful for studying the three-dimensional morphology of biological structures. 相似文献
213.
E J van der Molen G J de Graaf T J Spierenburg M J Nabuurs A J Baars L P Jager 《Experientia》1986,42(11-12):1247-1249
An exploratory study was made of the mechanisms underlying the toxic action of carbadox in young pigs: dehydration, loss of appetite and at autopsy seemingly specific and selective structural alterations of the glomerular zone of the adrenal cortex. Administration of carbadox in the feed, in dosages of 150 ppm (approximately 6 mg X kg-1 b. wt X day-1) caused a rapid decline in the plasma aldosterone levels (to 10% of control) followed by significant changes in the sodium and potassium levels in blood. Characteristic for the toxic action of carbadox are the rapid and seemingly selective and specific alterations in the aldosterone-releasing zona glomerulosa of the adrenals. Our results indicate that with carbadox a functional and possibly reversible extirpation of the adrenal zona glomerulosa can be achieved in pigs. 相似文献
214.
G. M. Cronin P. R. Wiepkema J. M. van Ree 《Cellular and molecular life sciences : CMLS》1986,42(2):198-199
Summary The study presents evidence that the stereotypies of tethered sows are associated with the release of endorphins. This is the first indication that stereotypies may be an effective coping strategy. 相似文献
215.
216.
The hepatitis delta (delta) virus possesses a circular RNA 总被引:33,自引:0,他引:33
Hepatitis delta (delta) virus (HDV), a satellite virus of the hepatitis B virus (HBV), causes a severe form of viral hepatitis in humans. Here we present evidence based on electron microscopy and electrophoretic behaviour that HDV contains a single stranded circular RNA molecule. This is the first animal virus identified with a circular RNA genome. Circular RNAs have only been found in plant viruses. We have obtained a partial complementary DNA clone representing approximately 25% of the total genome of HDV. Analysis of this cDNA revealed similarity to two plant viruses that may explain the origin of the virus. 相似文献
217.
B. L. van der Waerden 《Archive for History of Exact Sciences》1988,38(1):13-22
Summary In the astronomical treatise ryabhatya of ryabhata several verses are interpolated, namely all those verses in which either Brahman was mentioned or extremely large periods were introduced. The interpolator was known to AlBrn as ryabhata of Kusumapura, who belongs to the school of the elder ryabhata. The aim of the interpolator was to bring the teaching of the elder ryabhata into accordance with the revelation of Svayambh. Svayambh is another name for Brahm. 相似文献
218.
219.
A. S. van Jaarsveld 《Cellular and molecular life sciences : CMLS》1992,48(8):774-778
This investigation of the socio-ecological development and endocrine variance in the spotted hyaena,Crocuta crocuta, illustrates that the complexity of a multivariate endocrine system cannot fully be understood using the concept of a class mean (). Any comprehensive investigation of a multivariate endocrine system should also include an analysis of variance (), as it may provide additional insights into the dynamics of an endocrine hypervolume. Mean cortisol concentrations could not differentiate between various social and reproductive categories (MANOVA); however, in males an analysis of variance (principal component analysis) indicated that the contrast between cortisol and androstenedione was the principle axis of variance once the androgen secreting ability had been accounted for. On the other hand, the same contrast was found to be the principal axis of variance in the female sub-sample, suggesting that cortisol may play a significant role in regulating the endocrine dynamics of this species, despite showing little variance in mean values among various social and reproductive categories. 相似文献
220.
In crustaceans, all the steps in the assimilation of food take place in the hepatopancreas. To facilitate the study of this organ, a method for the dissociation of cell types was developed. The hepatopancreas of the prawn Palaemon serratus was mechanically dissociated and the cells separated by Percoll density-gradient centrifugation. The E and R cells had similar densities of around 1.05 g/ml. The F cells were separated into two distinct fractions with densities of 1.075 and 1.082 g/ml. The B cells sedimented at a density of 1.12 g/ml. The ratio between the two populations of F cells was found to vary during the intermolt cycle while B cells disappeared after the molt. When the density gradient fractions were incubated with 3H-leucine, incorporation was highest in the F cell fractions. Measurements of alpha-amylase activity, indicated that the two populations of F cells may be derived from the same cell type. 相似文献