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1.
在麻醉的32只猫记录了电刺激颌下腺神经支引起的上涎核平均场电位和单位放电。逆行电刺激颌下腺神经支引起的上涎核平均场电位分布在同侧脑干背面闩部头端5.5—8mm处,与过去的组织学结果大致符合。用微电极在上涎核记录了68个对刺激颌下腺神经支有反应的单位,其中33个单位作了碰撞试验。有9个单位符合逆向反应标准,它们是真正的颌下腺节前神经元,逆行反应的潜伏期为14.4±2.5ms,其轴突传导速度为2.9±0.1m/s。其他不符合逆向反应标准的单位,对刺激颌下腺神经支仍能发生反应,估计多为中间神经元。在一部分单位观察了电刺激舌神经或味觉刺激舌引起的反应。根据这些观察对上涎核内存在复杂神经元回路的可能性作了讨论。 相似文献
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We ask under what circumstances two methods of dispersal-for-distance should be combined, given that the second method may carry the diaspore back towards its point of origin. The combination is made possible when the morphological adaptations of the diaspore are compatible. It is advantageous when the return on investment in the first method of dispersal declines sharply beyond some level of investment. The median seed achieves the best net distance when the two methods achieve similar distances; the upper decile of seeds achieve nearly a simple sum of the two distances. The first two conditions apply to the combination of ballistic with ant-dispersal, which is widespread in Australian sclerophyll shrubs. Mother plants’fitnesses could well be determined by the upper decile of distances their seeds achieve. It remains an open question whether the addition of ant-dispersal to ballistic dispersal achieves the selective advantage of distance or of placement. 相似文献
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WINSTON D. EDWARDS JULES J. BERMAN JERRY M. RICE MARK W. TOWNSEND 《Development, growth & differentiation》1979,21(6):519-525
The differentiation in organ culture of a rat nephroblastoma is compared with differentiation of normal rat metanephric tissue under the same conditions. The nephroblastoma arose in a 19 week old female Fischer F344 rat given a single intraperitoneal injection of 4.0 μmole methyl(methoxymethy1)nitrosamine (DMN-OMe)/g body weight at one day of age. The tumor consisted almost entirely of spindle cells although a few well-differentiated tubules were scattered throughout the tumor mass. No primitive tubules were seen, but focal aggregates of tumor cells suggestive of nascent epithelial differentiation were frequent. Fragments of the nephroblastoma were cultured on gelfoam sponge in Williams Medium E supplemented with hydrocortisone, insulin, and fetal bovine serum. Within one day extensive tubulogenesis was observed. High mitotic activity resulted in a steady increase in the size of cultured explants over a period of 6 days. By day six, differentiating tubules filled the explant tissue. Cultured fragments were nearly indistinguishable histologically from normal F344 rat fetal kidney explanted to organ culture on day 15 of gestation and grown in vitro for the same period. 相似文献
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Background
The incidence and prevalence of diabetes are increasing all over the world. Complications of diabetes constitute a burden for the individuals and the whole society. 相似文献10.