共查询到20条相似文献,搜索用时 15 毫秒
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The distribution of cyclic AMP-dependent protein kinase activity in porcine thyroid glands has been studied. Enzyme activity catalyzing phosphorylation of exogenous substrate (protamine) from ATP, and cyclic AMP binding were determined in parallel in subcellular fractions purified by differential centrifugation and flotation on sucrose density layers. Both activities were found in all the studied fractions; they were quantitatively the highest in the cytosol but particles showed the highest specific activities.Latent protein-kinase activity was unmasked by action of detergents on microsomes (× 5–10 fold) and solubilized (85 to 99 p. cent of the initial total activity). Cyclic AMP binding capacity was also recovered in detergent-treated microsomal extracts in spite of reduced cyclic AMP binding in the presence of detergent.Protein kinase activity and cyclic AMP-binding proteins were less represented in purified nuclei than in microsomes. Again both activities were unmasked by detergent.Preparations highly enriched in Golgi membranes were compared to rough microsomal preparations. Higher protein kinase activity was detected in rough microsomes as compared to Golgi membranes, whereas the reverse was true for cyclic AMP binding. Both activities were equalized after detergent treatment. Since unmasking of protein kinase activity was the highest in Golgi membranes, this fraction contains more enzyme activity and cyclic AMP binding capacity than rough microsomes.The localization of endogeneous protein substrates of cyclic AMP-dependent protein kinases was investigated using purified soluble protein kinase subcellular fractions. The better endogeneous substrates seemed to be localized in the rough microsomal and in the nuclear fractions. 相似文献
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Camille J. Francois 《Biochemical Systematics and Ecology》1973,1(4):231-236
In every species other than mammals xanthine oxidoreductase behaves as a dehydrogenase, never as an oxidase. In three mammalian species, the enzyme acts intracellularly as a dehydrogenase, but its class-specific ambivalence allows its extracellular conversion into an oxidase.
Résumé
En dehors de la classe des Mammifères, l'oxydoréductase de la xanthine ne se comporte jamais comme une oxydase. Chez les Mammifères, une ambivalence de la molécule permet l'expression d'une activité déshydrogénasique (NAD) dans la cellule, et d'une activité oxydasique en dehors de la cellule. 相似文献
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A. Roques 《Entomologia Experimentalis et Applicata》1986,40(2):177-187
La réponse visuelle des adultes de Lasiomma melania Ackl. (Diptera, Anthomyiidae) à des carrés englués de diverses couleurs ou combinaisons de couleurs a été étudiée durant 5 années consécutives dans plusieurs mélèzins (Larix decidua) des Hautes-Alpes. Une préférence pour le jaune et le jaune à bandes pourpres a été mise en évidence chez ce ravageur dont la femelle pond sur les cônes de mélèze. L'attractivité de chaque type de piège est fonction à la fois du sexe et du stade de maturation sexuelle des individus. La couleur jaune attire en majorité des insectes émergents immatures. Elle semble représenter, selon le plan dans lequel elle est située, un signal nutritionnel de type fleur (plan horizontal) ou un signal de reconnaissance du feuillage de mélèze (plan vertical). Les individus mûrs sexuellement, recherchant les arbres produisant des cônes, sont en revanche capturés essentiellement sur les pièges verticaux jaunes à bandes pourpres. Ceux-ci miment, en l'amplifiant, le contraste de réflectance existant entre le feuillage des mélèzes et les cônes. Ce contraste paraît correspondre à un signal permettant la reconnaisance des arbres possédant des cônes. La ponte est cependant limitée à un stade particulier de développment de ces derniers alors que le contraste est à peu près stable dans le temps. D'autres signaux émis par les cônes, vraisemblablement d'ordre olfactif, doivent guider le vol d'approche et l'atterrissage des femelles. 相似文献
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B. R. Berland D. J. Bonin S. Y. Maestrini J. P. Pointier 《International Review of Hydrobiology》1972,57(6):933-944
Several methods of growth potential estimation of marine productivity are discussed: (1) simultaneous measurements of nutrient content and organic production, (2) chemical composition of algal cells, (3) bioassay with algal cultures. This last method appears to be the most convenient; it allows to study the role of a nutrient component both when utilized alone and when combined in a pool of nutrients. Several aspects of bioassay technology are discussed: test species, chemical enrichments and growth estimation of test cultures. 相似文献
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This paper is an attempt to describe and analyze in formal terms a genetic circuit which is rather complex and reasonably well disentangled: the control of immunity in lambdoid bacteriophages. Known models are expressed as logic equations, which relate the stade of activity of genes to variables of three kinds: genetic variables which describe the genotype of the organism, environmental variables like temperature and memorization variables. The value of each memorization variable (presence or absence of a gene product) is related to the value of the corresponding function (operation or not of the gene) by two characteristic time delays, an «establishment delay and a «decay delay.From the equations, one can derive matrices which facilitate comparison between models by showing which stable states are predicted by each model. Implications of current models, which had apparently remained cryptic, have been realized and experimentally tested.From the matrices, one can derive graphs which show the pathways (sequences of states) consistent with each model. These graphs are frequently branched and in these cases one has to analyze which conditions determine that one pathway rather than another one, is followed. 相似文献
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A Golgi-rich fraction is prepared from cat hepatocytes by the means of a four-step sucrose density gradient. The material applied to this gradient is composed either of smooth microsomes prepared from healthy animals, or of total microsomes prepared from cat treated by 50 per cent ethanol (0.6 g/100 g body weight, administered by stomach tube).A light fraction (d : 1.10) is obtained by the two procedures. It does not show any glucose-6-phosphatase activity, but is enriched in sialyltransferase, known as a marker enzyme for Golgi apparatus. It also contains the three enzymes implicated in the biosynthetic pathway for UDP-glucose (glucokinase, phosphoglucomutase and UTP : glucose-1-phosphate uridylyltransferase).UDP-glucose being the ultimate substrate in membranous glucosylation reactions, these results could support the hypothesis that sugar-nucleotides necessary for the glycoprotein biosynthesis are produced in the Golgi vesicles directly. 相似文献
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Using synchrotron radiation as the excitation light, we studied the fluorescence parameters of perylene incubated with pigeon erythrocyte membranes and with an isotropic viscous medium, the Primol 342 oil.From 4 to 37°C, we observed a single lifetime of 4.5 ns in the oil and two with the membrane (τ1 = 1−1.4 ns and τ2 = 5.4−6.1 ns). The dependence upon temperature of the rotation correlation time of perylene () in the oil was characteristic of an isotropic medium, whereas the limiting value of anitropy (r ∞) was zero. With the membrane, γ ∞ decreased from 0.14 to 0.06 and from 2.9 to 0.5 ns, indicating a greater amplitude and frequency of molecular motions.The addition of chlorpromazine, indomethacine, tetracaine, n-octylamine, octanol or octanoic acid to the membrane decreased the τ1 and τ2 values. This would stem from the desorganization of the membrane induced by the drugs. 相似文献
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B. R. Berland D. J. Bonin S. Y. Maestrini J. P. Pointier 《International Review of Hydrobiology》1973,58(2):203-220
Ten cultures of phytoplankters, including four strains of Skeletonema costatum from different origins, were used to improve some aspects of the bioassay technology. Special attention was paid to the preliminary nutrient limitation of the inocula. When the cells are maintained in nutrient starvation, their carbon, nitrogen, carbohydrates, proteins and above all chlorophyll a contents decrease. The minimum appears after a range of 2–7 days, according to species. The survival of these limited cells and their capacity to give rise to active growing cultures when sub-cultured are different with species, but efficiency in the inocula they provide usually can occur only until the minimum content in cellular components appears. Starved cells and enriched cultures of Chaetoceros lauderi and Skeletonema costatum were used to inoculate several samples of sea water, in order to test the effect of the starvation on the experimental results. It appears that the starved cells increase the sensitivity of the method, but they are more susceptible to substances limiting their growth. In the opinion of the authors the best way would be to use both starved and enriched cells as inocula, but, when this is impossible, cautiously starved cells should be used with unpolluted sea waters. 相似文献
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Matthieu Manceny Chafika Chettaoui Michel Malo Georgia Barlovatz-Meimon Franck Delaplace 《Comptes rendus biologies》2006,329(12):938
We present a method to model biological systems, the theory of games networks. It extends game theory by multiplying the number of games, and by allowing agents to play several games simultaneously. Some important notions of biological systems, such as locality of interactions and modularity, can then be modelled. To cite this article: M. Manceny et al., C. R. Biologies 329 (2006). 相似文献