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991.
Adult rats with normal or X-irradiated testes were used in an experiment to test the possible existence of a chalone in the testis. On the 11th day following irradiation, i.e. as the type A spermatogonia proliferated actively to restore the partially destroyed spermatogonial population, the animals with irradiated testes were subdivided into three groups. Rats of the first group were injected intraperitoneally with a saline extract of normal adult rat testes. Animals of the second group were injected with an equal amount of physiological saline while the rats of the third group received equivalent injections of a saline liver extract. Two additional groups of rats with non-irradiated testes, injected with the testicular extract or saline solution, served as controls. Following the last injection all animals were injected with 3H-thymidine and sacrificed. From each animal one testis was used to determine the specific radioactivity of its DNA, the other testis was processed for radioautography. The testicular extract produced a significant decrease in uptake of radioactivity by the irradiated testes. There was no difference in the radioactivity uptake by the testes of non-irradiated rats. Correspondingly the labeling index of type A spermatogonia was significantly lower in animals of the first group than in the other two groups of animals with irradiated testes. However, there was no difference in the labeling indices of Intermediate and type B spermatogonia or of preleptotene spermatocytes in the animals receiving the extracts or the saline solution. In animals with non-irradiated testes there was no difference in the labeling indices of type A or other types of spermatogonia or of spermatocytes. These data were taken to indicate that a saline extract of normal adult testes contains a substance that can inhibit specifically the proliferation of type A spermatogonia during the repair phase of the spermatogonial population following irradiation. This substance was tentatively considered as a spermatogonial chalone. 相似文献
992.
Yves Nubar 《Biophysical journal》1971,11(3):252-264
The viscosity of blood, measured by the usual viscometers in which slip is not considered, is found to be flow dependent, varying markedly with shear rate, pressure gradient, and vessel diameter in the lower ranges of these factors. The study postulates, on grounds thought reasonable, that slip may be present in blood flow, as a function of the nature of the wall surfaces, shear stress at the wall, and relative cell volume (RCV) adjacent to the wall. It presumes that blood possesses a specific, flow-independent viscosity, and determines theoretically the viscosity indications of viscometers if blood slipped in the instruments. The study shows that if the slip function is of a certain plausible form, these viscosity indications would exhibit a flow dependence of much the same pattern as the actual indications supplied by the usual viscometers. The slip postulate permits, therefore, an interpretation of the “anomalous” flow behavior of blood, dispensing with the prevailing assumption of an ad hoc variability of its viscosity with flow factors. To the extent that viscometric data for blood may be representative of other non-newtonian fluids, the slip postulate may be applicable to these fluids. 相似文献
993.
Genetic analysis of mannityl opine catabolism in octopine-type Agrobacterium tumefaciens strain 15955 总被引:11,自引:0,他引:11
Yves Dessaux Jacques Tempé Stephen K. Farrand 《Molecular & general genetics : MGG》1987,208(1-2):301-308
Summary The genetic organization of functions responsible for mannityl opine catabolism of the Ti plasmid of Agrobacterium tumefaciens strain 15955 was investigated. A partial HindIII digest of pTi15955 was cloned into a broad host range cosmid and the clones obtained were tested for ability to confer mannityl opine degradation upon Agrobacterium. Inserts containing genes for catabolism of mannopinic acid, mannopine, agropine, and agropinic acid were obtained, spanning a segment of 43 kb on the Ti plasmid. Two clones conferring upon Agrobacterium the ability to catabolize the mannityl opines were mobilized to several Rhizobium sp., to Pseudomonas putida and P. fluorescens and to Escherichia coli. The catabolic functions were phenotypically expressed in all Rhizobium sp. tested, and in P. fluorescens, but not in P. putida or in E. coli. 相似文献
994.
Yves Tourneur Raman Mitra Martin Morad Oger Rougier 《The Journal of membrane biology》1987,97(2):127-135
Summary The early phase of activation of the inward-rectifying potassium channel is studied on single cells from guinea-pig heart. The current is quasi-instantaneous when it is outward, but activates with time when it is inward. This relaxation is exponential and its time-constant decreases with hyperpolarization. TheI/V curve reflects a strong inward rectification and has a negative slope conductance on depolarization. Similar results were recorded in the absence of sodium, calcium, chloride ions and in isotonic potassium. Cesium slows down the phase of activation, and eventually appears to block the channels by suppression of the activation. Barium, conversely, does not affect the activation, but promotes an inactivation of this current, which blocks it. These results are independent on the cells' dissociation method. They suggest that this current is the inward rectifier, calledI
K1 on heart. Its activation curve suggests that the inward and outward currents are flowing through the same channels. The inward rectifier is time-and voltage-dependent on heart as on other tissues. The effects of cesium and barium are also similar. The importance of its negative slope conductance is discussed. 相似文献
995.
A technique for forming protoplasts from Frankia cells and regenerating them to the normal hyphal mode of growth is described. Electron microscopy proved that protoplasts were studied and not spores or small hyphae. Regenerated colonies were investigated for genetic markers. One ArI3 colony had been cured of its plasmids without being affected in its symbiotic properties. 相似文献
996.
Ann C. Andersen Georges Pelletier Alex N. Eberle Philippe Leroux Sylvie Jegou Hubert Vaudry 《Peptides》1986,7(6):941-951
The distribution of melanin-concentrating hormone (MCH) in the central nervous system of the frog Rana ridibunda was determined by the indirect immunofluorescence technique using antibodies against synthetic salmon MCH, generated in rabbits. The most prominent group of MCH-like containing perikarya was detected in the preoptic nucleus. Comparatively, a moderate number of cell bodies was observed in the dorsal infundibular nucleus and in the ventral thalamic area. Brightly immunofluorescent nerve bundles were found in the preoptic nucleus and in the ventral infundibular nucleus, coursing towards the internal zone of the median eminence and the pituitary stalk. An intense network of immunofluorescent fibers was localized in the neural lobe of the pituitary. The subcellular localization of MCH-like material was studied in the neurohypophysis using the immunogold technique. It was demonstrated that MCH-like material was contained in dense core vesicles (80–90 mm in diameter) within specific nerve terminals. The present findings indicate that, in amphibians, MCH-like peptide is located in specific hypothalamic neurons. Our data suggest that MCH may be released by neurohypophyseal nerve endings as a typical neurohormone. 相似文献
997.
998.
The norepinephrine (NE) concentration of 14 discrete brain nuclei of rats fed with either purina rat chow or highly palatable foods, given or in a restricted quantity isocaloric with the Purina rat chow diet, was measured by high performance liquid chromatography with electrochemical detection. The NE level was significantly increased in the n. suprachiasmaticus, n. paraventricularis, n. arcuatus and n. amygdaloideus (medialis, corticalis, centralis, basalis pars lateralis, lateralis pars posterior) of rats fed with palatable foods given in restricted amount. The increased NE level seems to be associated with the limitation of access to highly palatable food whilst the regimen composition and the palatability of foods are not implicated in this phenomenon. Some hypothalamic and amygdaloid NE-containing neurones can be affected by food-restriction stress, suggesting a role of this neuronal system in feeding activity. 相似文献
999.
This study was undertaken to evaluate the combined effects of sucrose feeding and exercise training on serum insulin, triglycerides, as well as cholesterol and its distribution into lipoproteins of female Wistar rats. The animals were fed ad libitum either laboratory chow alone, or chow and a 32% aqueous sucrose solution. Half of each dietary group was submitted to an exercise-training program. Both sucrose feeding and exercise training elicited greater energy intake. Sucrose feeding produced a marked elevation in triglyceridemia that was prevented by exercise training. Insulin levels paralleled those of triglycerides. The sucrose-fed animals had higher total cholesterol levels than the animals given chow. Although exercise training did not affect total cholesterol in the chow-fed animals, it partly prevented the sucrose-induced elevation in total cholesterol. Cholesterol in the lipoproteins of lower densities was increased significantly with sucrose feeding, and exercise training totally prevented this augmentation. The amount of cholesterol carried by high-density lipoprotein (HDL) was not affected by exercise training in the chow-fed animals. In contrast, sucrose feeding increased HDL-cholesterol in sedentary animals, whereas exercise training partly prevented this increase. The HDL/total cholesterol ratio was similar in all groups. Changes in insulin concentration underline the importance of this hormone in the regulation of blood lipid levels. 相似文献
1000.
Mhamed Saīd El Kebbaj Norbert Latruffe Yves Gaudemer 《Biochemical and biophysical research communications》1980,96(4):1569-1578
D-β-hydroxybutyrate dehydrogenase, a lipid requiring enzyme, is rapidly and completely inactivated by phenylglyoxal, 2,3-butanedione and 1,2-cyclohexanedione. Inactivation, which occurs at the millimolar range, depends on the nature of buffer, borate ions are required to get enzyme inactivation by 2,3-butanedione. Most of the inactivation follows a pseudo first order kinetics, the stoichiometry being of one to one. Presence of NAD+ or methylmalonate (a substrate-like compound) prior addition of inhibitor does not affect inactivation, while methylmalonate in presence of NAD+ strongly protects against inactivation. Chemical modification of the enzyme does not affect KD of NAD while KM of β-hydroxybutyrate and Ki of methylmalonate (protecting agent) increase. In view of the high specificity of these inhibitors for arginyl residues of proteins, these results are in favour of the presence of at least one arginyl residue essential for enzyme activity and located in, or near the substrate binding site. 相似文献