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971.
972.
Ca2+ ions are thought to play important roles in processes underlying neuronal plasticity such as synapse stabilization. We employed the Fura-2 technique on brainstem slices of neonatal rats to measure changes in intracellular Ca2+ ([Ca2+]i) in neurons of the lateral superior olive (LSO) in order to analyse whether these cells have functional Ca2+ channels when synaptic maturation takes place. Rises in intracellular Ca2+ could be induced by KCl-evoked depolarizations or by glutamate, but not by glycine or GABA. These results show that Ca2+ channels are present in developing LSO neurones and that many of them, if not all, belong to the voltage-sensitive type. We speculate that these channels play a role during ontogeny by mediating Ca(2+)-dependent mechanisms of synapse stabilization. 相似文献
973.
H Logothetou-Rella 《Canadian Metallurgical Quarterly》1993,8(3):407-423
Spermatozoa-like cells (nuclear vlimata) have been identified in malignant cell cultures and embryonic cells, also common in the cytology and histology of all types of human neoplasia even after chemotherapy. A new mechanism of invasion of malignant cells has been described, according to which neoplastic cells behave and function as parasites using host-cells to divide, survive and eventually produce nuclear vlimata (bullets). Nuclear vlimata are the end cell products of incomplete, unequal, assymetrical division of neoplastic cells. The nuclear vlima exhibits similar morphology to spermatozoa and virus (head with, or without, tail) and invades the cytoplasm and/or nucleus of surrounding host-cells by a similar mechanism to sperm-oocyte interaction (fertilization) or viral cell infection, in the events of nuclear vlima-->tumor-->nuclear vlima-->tumor. The nuclear vlima head contains and transfers DNA, and when incorporated into the host-nucleus is indistinguishable from nucleoli and when in the cytoplasm is similar to sperm pronucleus, observed after sperm penetration of the oocyte. Function of nuclear vlimata is directly dependent on the specific extracellular matrix produced by malignant cells, consisting of glycosaminoglycans-protease-membranes. This mechanism of invasion constitutes the link of all scientific information concerning human neoplasia. 相似文献
974.
975.
To provide insight into the stream of Medicare payments over time, a sixteen-year longitudinal study examines three age cohorts of beneficiaries, looking separately at beneficiaries who died during the study period and those who survived. The common wisdom that a small minority of the population accounts for a large majority of health care expenditures is tempered when health care use is examined over an extended period of time. By putting high average costs in the final years of life in the context of a cohort's total lifetime experience, the study shows a leveling of spending over time, resulting in a lower concentration of health care resources on a small fraction of the population. 相似文献
976.
Zaleski A. Sinha S.P. Ioannou D.E. Campisi G.J. Hughes H.L. 《Electron Devices, IEEE Transactions on》1995,42(9):1697-1700
By operating one channel of a typical SOI MOSFET in avalanche while keeping the opposite channel accumulated, charge injection into the opposite gate takes place. Three independent experiments are described that demonstrate the occurrence of this opposite-channel based charge injection. The experimental results are in agreement with PISCES numerical simulations 相似文献
977.
978.
The photodegradation of seven carbamate pesticides (bendiocarb, isoprocarb, promecarb, ethiofencarb, furathiocarb, fenoxycarb and pirimicarb), in aqueous solution, has been examined by GC-MS. The most general result was formation of the corresponding phenols. Irradiation of isoprocarb and promecarb also resulted in photo-Fries rearrangement to ortho- and para-hydroxybenzamides. In the case of ethiofencarb photocleavage of the carbon-sulfur bond gave 2-methylphenyl methylcarbamate as main product. Likewise, N-S bond cleavage occurred upon irradiation of furathiocarb, to allow the formation of the carbamate insecticide carbofuran, butyl methylcarbamate and carbofuranphenol. Under similar conditions, fenoxycarb gave p-phenylphenol and 2-hydroxydibenzofuran, through primary homolysis of the aryloxy-methylene bond. Finally, pirimicarb gave rise to 2-formylamino-5,6-dimethylpyrimidin-4-yl dimethylcarbamate. 相似文献
979.
980.
G. Mestres F. Niefloud R. Fortune J. M. Devoisselle R. Marti H. Maillols 《Drug development and industrial pharmacy》1996,22(12):1193-1199
This paper reports a study undertaken using techniques of static and dynamic light scattering to investigate the influence of sodium salicylate and methyl salicylate on droplet size of oil-in-water emulsions. The rates of changes were measured by determining the size and distribution of the oil droplet in the material. All emulsions showed a bimodal size distribution; the mean diameters and polydispersity were calculated from intensity. These data were analyzed with nonlinear regressions and bootstrap methodology. An amount of methyl salicylate component induced a decrease of mean diameter and standard deviation. On the contrary, sodium salicylate entailed the growth of all droplet populations and coalescence for the highest concentration. 相似文献