Reactivation and Dedifferentiation of Differentiated Murine Erythroleukemic Cell Nuclei

A murine erythroleukemic cell line, 745 A4-TG, deficient in hypoxanthine-guanine-phosphoribosyl transferase, can be induced with 3 mM hexamethylene bisacetamide to yield at least 50% of cells undergoing irreversible erythroid differentiation and finally losing capacity for cell divisions. The effects of such induced differentiation of 745 A4-TG on its ability to form viable and proliferating hybrids when fused with 3T3 1T22 fibroblasts were investigated. We found that when the induced 745 A4-TG cells were used, more continuously proliferating hybrids were obtained than could be accounted for by the residual uninduced cells which remained in these induced preparations. This suggests that some of the induced 745 A4-TG cells, when fused with 3T3 1T22 reverted from the induced phenotype of a limited capacity for cell proliferation to an uninduced state of continuous proliferation. This observation was further confirmed with the use of fully differentiated 745 A4-TG cells, which were obtained after selection with a bromodeoxyuridine suicide treatment to eliminate the uninduced and the partially differentiated cells in the preparations. When these selected, fully differentiated cells, as characterized by their lack of proliferation capacity and thymidine kinase activity, were fused with 3T3 1T22 (also deficient in thymidine kinase), it was found that not only were viable hybrid colonies obtained in a selection medium, which precluded the proliferation of either parental cells, but these hybrids continued to proliferate for more than two months in selection medium. These data thus confirmed that some fully differentiated erythroleukemic nucleus components in the hybrids were reactivated to regain capacity for cell proliferation and to dedifferentiate to synthesize thymidine kinase for survival in the selection medium. The lack of hemoglobin synthesis by these hybrids also indicates dedifferention of these murine erythroleukemic components in the hybrids.     

Preparation of base-modified nucleosides suitable for non-radioactive label attachment and their incorporation into synthetic oligodeoxyribonucleotides.

A very mild and efficient procedure has been developed for the preparation of C-5 substituted deoxyuridines. The substituent carries a masked primary aliphatic amino group. These compounds are readily converted into their phosphoramidites and can be used to prepare oligonucleotides carrying one or more aliphatic amino groups. Fluorescein isothiocyanate coupled to these compounds gives oligonucleotide probes carrying multiple fluorescein labels. These compounds have a free 5'-hydroxy group enabling additional 5'- end radioactive labelling for evaluation of their hybridization characteristics. It was found that oligonucleotides carrying a long (11 atom) linker arm to the fluorescein hybridize more efficiently to mRNA than those carrying a short (4 atom) arm. The long linker arm derivatives are comparable to underivatized oligonucleotides in hybridizing to mRNA.     

大鼠脑室注射P物质引起的血压升高与脑啡肽和β-内啡肽有关

给乌拉坦麻醉大鼠侧脑室注射P物质(SP)10μg 引起的升压效应,可被脑室注射纳洺酮15μg 部分阻断。将抗β-内啡肽抗血清、抗甲啡肽抗血清及抗亮啡肽抗血清各10μl 分别注入侧脑室预处理60min 后,再注入 SP,其升压效应明显减弱;而抗强啡肽抗血清则对其无影响。上述结果提示:大鼠脑室注射 SP 引起的升压效应,可能是通过释放β-内啡肽和脑啡肽实现的。     

脊髓苯环立啶受体的心血管效应与去甲肾上腺素能系统

本文应用受体阻断、高效液相,6-OHDA 化学损毁神经末梢和放射自显影等多学科技术方法,探讨脊髓苯环立啶受体的心血管效应与去甲肾上腺素能神经系统的关系。结果表明,哌唑嗪、育亨宾均可对抗 ith PCP 的降压和减慢心率作用,ith PCP 产生降压和减慢心率作用时,脊髓脑脊液内 MHPG 的含量升高;用6-OHDA 损毁脊髓 NA 能神经末梢后,ith PCP的降压和减慢心率作用大为减弱,脊髓 PCP 受体密度亦同时大为降低。可以认为,脊髓内有 PCP 受体分布于 NA 能神经末梢上,促进 NA 释放或抑制 NA 重摄取,可能是脊髓 PCP 受体产生心血管抑制效应的重要机理。     

龟鳖类寄生血簇虫六新种

血簇虫(Haemogregarina Danilewsky,1885)属真球虫目(Eucoccidia)血簇虫科(Haemogregarinidae),这一属的寄生虫,其寄主以爬行动物为主,两栖动物和鱼类也有寄生。至今已记载有300余种。龟鳖类的血簇虫研究,国内尚无报道。作者在1984年3月—1985年3月,对我国龟鳖类寄生的血簇虫进行了调查研究,共解剖检查了中华     

Chromosomes and their relationship to nuclear components during the cell cycle in Chinese hamster cells

Summary Chromosomes and their relationship to nuclear components during various phases of the cell cycle were studied with different fixation, embedding, and enzyme techniques. The results showed that interphase chromosomes may have oriented in such a way that a given locus became associated with the nuclear membrane. Some chromosomes also appeared to interact with the nucleolus. The nuclear matrix materials, however, were distributed between the chromosomes and formed a delineating boundary for the chromosomes. These matrix materials, furthermore, formed channel-like structures within the nucleus and towards the cytoplasm through their interaction with nuclear pore complexes. During mitosis, chromosomes were encapsulated with material that appeared to be derived from the matrix, disintegrated residues and fragments of the nuclear envelope, the lamina, and nucleolar material. These chromosome-associated materials seen in mitosis appeared to serve as foci for formation of new nuclear components in subsequent interphase.