共查询到20条相似文献,搜索用时 31 毫秒
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Growth and ploidy of rat ventricular myocytes were studied during development in situ and in grafts (1 day old rat ventricle transplanted under kidney capsule of syngenic adult animals). Both in situ and in the transplants polyploidization occurred on days 4-14 of postnatal life, and the modal group of myocytes was represented by binucleate diploid (2c x 2) cells. Minor quantities of 4c, 4c x 2, 8c and 2c x 4 myocytes were detected as well. In ventricles of 14 and 28 days old rats and in the transplants of the corresponding age the portion of polyploid myocytes was 90-96% and 32-63% respectively. The intensity of postmitotic myocyte transplants was decreased as compared with in situ development, and cells that exit proliferation cycle did not grow until day 14. The data on thymidine label dilution suggest that diploid myocytes of the transplant can divide two or three times but the majority of labeled diploids divided only once. Labeled 2c x 2 myocytes originated from the first, and less frequently, the second cell generation or resulted from initial acytokinetic mitosis. Mononucleate tetraploids 4c originated from 2c x 2 and mostly from 2c cells. Octaploids were formed after 3d or 4th labeled mitosis. The conclusion about cardiac myocyte polyploidization as an intrinsic developmental program is supported, implying the programming of onset, mode, duration and termination of polyploidization and its prolongation during early postnatal life.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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G I Mchedlishvili M N Varazashvili 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(10):387-388
The experiments in adult rabbits revealed that in the blood flowing in cerebral veins the red cell concentration and hematocrit are much greater than in the veins of hind legs of the same animals. In blood samples taken from the heart these values are higher than in those taken from the hind leg, but usually lower than in blood samples taken from the brain. Under conditions of reduced cerebral blood flow (ischemia) the red cell concentration and hematocrit in the brain vessels decrease significantly as compared to the control conditions. Thus, the red cell distribution in arterial branching sequence is irregular, depending both on the localization of the vascular bed and the blood flow rate in it. 相似文献
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Romanov SP Aleksanian ZA Manoĭlov VV 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2002,88(10):1356-1368
With the aid of tensotremorography, a voluntary effort was recorded and characteristics of involuntary and voluntary components of the hands' isometrically recorded efforts were studied. The revealed frequency ranges of the oscillations spectral density's changes corroborate existence of two suprasegmental systems of movements control, the systems being related to voluntary control and a current control of the efforts maintaining or preserving a posture. Results of cross-correlation analysis of the hands' efforts maintained under conditions of a visual feedback are demonstrated in norm and in central disorders of the movement control system. 相似文献
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本文简要介绍了植物基因组领域主要的组织和计划,简单分析了国际植物基因组计划的特点和我国存在的问题,并初步提出我国的应对策略。 相似文献
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Marc Yudkoff 《Neurochemical research》2017,42(1):10-18
Glutamatergic neurotransmission entails a tonic loss of glutamate from nerve endings into the synapse. Replacement of neuronal glutamate is essential in order to avoid depletion of the internal pool. In brain this occurs primarily via the glutamate-glutamine cycle, which invokes astrocytic synthesis of glutamine and hydrolysis of this amino acid via neuronal phosphate-dependent glutaminase. This cycle maintains constancy of internal pools, but it does not provide a mechanism for inevitable losses of glutamate N from brain. Import of glutamine or glutamate from blood does not occur to any appreciable extent. However, the branched-chain amino acids (BCAA) cross the blood–brain barrier swiftly. The brain possesses abundant branched-chain amino acid transaminase activity which replenishes brain glutamate and also generates branched-chain ketoacids. It seems probable that the branched-chain amino acids and ketoacids participate in a “glutamate-BCAA cycle” which involves shuttling of branched-chain amino acids and ketoacids between astrocytes and neurons. This mechanism not only supports the synthesis of glutamate, it also may constitute a mechanism by which high (and potentially toxic) concentrations of glutamate can be avoided by the re-amination of branched-chain ketoacids. 相似文献
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Neural induction and patterning in the mouse in the absence of the node and its derivatives 总被引:2,自引:0,他引:2
The signals which induce vertebrate neural tissue and pattern it along the anterior-posterior (A-P) axis have been proposed to emanate from Spemann's organizer, which in mammals is a structure termed the node. However, mouse embryos mutant for HNF3 beta lack a morphological node and node derivatives yet undergo neural induction. Gene expression domains occur at their normal A-P axial positions along the mutant neural tubes in an apparently normal temporal manner, including the most anterior and posterior markers. This neural patterning occurs in the absence of expression of known organizer genes, including the neural inducers chordin and noggin. Other potential signaling centers in gastrulating mutant embryos appear to express their normal constellation of putative secreted factors, consistent with the possibility that neural-inducing and -patterning signals emanate from elsewhere or at an earlier time. Nevertheless, we find that the node and the anterior primitive streak, from which the node derives, are direct sources of neural-inducing signals, as judged by expression of the early midbrain marker Engrailed, in explant-recombination experiments. Similar experiments showed the neural-inducing activity in HNF3 beta mutants to be diffusely distributed. Our results indicate that the mammalian organizer is capable of neural induction and patterning of the neural plate, but that maintenance of an organizer-like signaling center is not necessary for either process. 相似文献
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