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101.
Anne-Marie Gaben-Cogneville Yolande Aron Ginette Idriss Thérèse Jahchan Jean-Yves Pello Elisabeth Swierczewski 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1983,762(3):437-444
Using a density gradient medium (Percoll) we succeeded in isolating homogeneous cell populations from the stromal-vascular fraction of the inguinal tissue of 3-day-old rats. In primary culture, in medium 199 supplemented with 10% fetal calf serum and 5.5 mM glucose, almost complete differentiation (90%) of these fractions was obtained for the first time in presence of a physiological concentration of insulin (10?9 M). During the adipose conversion, insulin markedly enhanced the activities of glycerol-3-phosphate dehydrogenase and acid:CoA ligase. When VLDL and heparin were added with insulin to the medium, this effect was not potentiated. On the contrary, VLDL and heparin in presence of insulin increased the triglyceride content of the cells. With VLDL and heparin only, the biochemical and morphological characteristics of the cells were very similar to those observed in control culture. The heavier fraction was morphologically heterogeneous and did not undergo the adipose conversion to the same extent as the two lighter fractions. It was concluded that this model could be helpful in studying the proliferation and the differentiation of preadipocytes at an early stage of development. 相似文献
102.
Elisabeth Zindler-Frank 《Plant biology (Stuttgart, Germany)》1991,104(3):229-232
Young plants of Phaseolus and Canavalia were grown in nutrient solutions where calcium had been partially or totally replaced by either strontium or sodium. The deleterious effect of this replacement on growth and development was greater with strontium than with sodium. As the calcium content of the nutrient solution was decreased fewer calcium oxalate crystals were formed in leaf tissues. There were fewer crystals formed when calcium was replaced by strontium than by sodium. Changes in solubility characteristics of the crystals indicated that they had incorporated strontium. 相似文献
103.
Blom Gerard Van Duin Elisabeth H. S. Aalderink R. Hans Lijklema Lambertus Toet Christian 《Hydrobiologia》1992,(1):153-166
In shallow, wind exposed lakes, the light conditions, the cycling of nutrients, heavy metals and organic micro-pollutants and changes in the local composition of the sediment top layer can be dominated by resuspension/erosion of bottom sediment and sedimentation of suspended solids. A 2 dimensional model for Sediment Transport, Resuspension and Sedimentation in Shallow lakes (STRESS-2d), based on an existing transport model, is discussed. In the model, mass balance equations for the water compartment and the bottom sediment are solved numerically. Up to 7 sediment fractions can be taken into account, each having a specific set of resuspension/erosion and sedimentation parameter values. Several options for modelling the changes in the bottom sediment composition are available.A simulation experiment for Lake Veluwe (The Netherlands), in which model options with and without the distinction of sediment fractions were used, showed that using sediment fractions to account for the variability in the sediment composition leads to an improvement of the model results, particularly the simulated phosphorus sediment-water exchange fluxes. For Lake Ketel (The Netherlands) two options for modelling changes in the bottom sediment composition are compared. It is shown that an option in which a thin water-sediment layer on top of the more consolidated bottom sediment is simulated provides an improvement in the simulation of the suspended solids concentration. 相似文献
104.
The wide-ranging neuronal actions of excitatory amino acids, such as glutamate, are thought to be mediated mainly by postsynaptic N-methyl-D-aspartate (NMDA) and non-NMDA receptors. We now report the existence of presynaptic glutamate receptors in isolated nerve terminals (synaptosomes) prepared from hippocampus, olfactory bulb, and cerebral cortex. Activation of these receptors by NMDA or non-NMDA agonists, in a concentration-dependent manner, resulted in Ca(2+)-dependent release of noradrenaline from vesicular transmitter stores. The NMDA-stimulated release was potentiated by glycine and was blocked by Mg2+ and selective NMDA antagonists. In contrast, release stimulated by selective non-NMDA agonists was blocked by 6-cyano-7-nitroquinoxaline-2,3- dione, but not by Mg2+ or NMDA antagonists. Our data suggest that the presynaptic glutamate receptors can be classified pharmacologically as both the NMDA and non-NMDA types. These receptors, localized on nerve terminals of the locus ceruleus noradrenergic neurons, may play an important role in interactions between noradrenaline and glutamate. 相似文献
105.
106.
Pilar Galan Helene Thibault Paul Preziosi Serge Hercberg 《Biological trace element research》1992,32(1-3):421-426
The relationship between iron status and capacity for IL-2 production by lymphocytes was assessed in 81 children from 6 mo
to 3 yr of age selected at random from a population with low socioeconomic status, undergoing free systematic examination
in four children's health centers in the Paris area. Iron deficiency was defined by the existence of at least two abnormal
values among the three indicators of iron status: serum ferritin level ≤12 μg/L, transferrin saturation <12%, and erythrocyte
protoporphyrin concentration >3 μg/g hemoglobin. According to this definition, 53 children were classified as iron deficient
and 28 as iron sufficient. No differences were observed between the iron-deficient and iron-sufficient groups in terms of
the IL-2 concentration without stimulation by PHA. IL-2 production by lymphocytes stimulated with PHA, as well as the stimulation
index (ratio of IL-2 concentration following stimulation by PHA to that of IL-2 concentration without stimulation by PHA)
were significantly lower in iron-deficient children. The reduction in IL-2 production by activated lymphocytes observed in
our study of iron-deficient children may be responsible for impairments in immunity found by other authors, particularly in
cell-mediated immunity. 相似文献
107.
Elisabeth Tillberg Christian Dons May Haugstad Stein Nilsen 《Physiologia plantarum》1981,52(4):401-406
The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10−7 M and in a few experiments, 10−6 M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO2 uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [14 C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA. 相似文献
108.
109.
Interactions between normal human peripheral blood T lymphocytes and monocytes were investigated by measuring the in vitro cellular adherence of these cells in the presence and in the absence of mitogens. Concanavalin A (Con A), lentil lectin (Lc), and phytohemagglutinin (PHA) in mitogenic doses increased 15 to 20 times the binding of T lymphocytes to monocytes. The lectin-induced binding was similar to that produced by neuraminidase-gal-actose-oxidase treatment. A good correlation was found between the early cellular adherence induced by these lectins and by neuraminidase-galactose-oxidase and the blastogenesis of the T lymphocytes measured after 3 days of culture by [3H]thymidine uptake. However, wheat germ agglutinin (WGA), a nonmitogenic lectin, also increased the binding of T lymphocytes to monocytes. Addition of specific carbohydrates completely inhibited the cellular interactions induced by lectins. Peanut agglutinin (PNA) induced adherence of lymphocytes only after treatment of these cells with neuraminidase. Striking differences were not found between the lectin-induced adherence observed with autologous and heterologous cells. Killing of monocytes abolished entirely the lectin-induced adherence of lymphocytes, however killed T lymphocytes were still able to interact weakly with live monocytes. Dexamethasone was found to be a potent inhibitor of mitogen-induced cellular interactions. 相似文献
110.
avec la collaboration technique de DANIELLE RAPHEL Jocelyne Albertini-Berhaut Elisabeth Alliot 《Biochemical Systematics and Ecology》1979,7(4):317-321
Proteolytic activity in the stomach, pyloric caeca and intestine decreases with increasing size in the three fish species Mugil auratus, M. capito and M. saliens. Differences between these species are found mainly in the gastric proteolytic activity which appears to be related to diet. This activity is pronounced in M. saliens whose diet is mainly carnivorous. Comparison of regression lines relating gastric proteolytic activity to size reveals differences which distinguish M. auratus from both of the other species. Total proteolytic activity exhibits high variability depending on the types of diet. 相似文献