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排序方式: 共有195条查询结果,搜索用时 15 毫秒
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M J Olszewska H Kuran B Damsz K Marciniak 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1987,25(1):69-77
Experimental model consisted in blocking cells in G1 phase by cold treatment (12 h, 10 degrees C); following 3 h of postincubation at 20 degrees C, cells initiated S phase. In the present studies it has been shown that 2 h postincubation at 20 degrees C of cold-treated young seedlings of Helianthus annuus L. results in transformation of inactive meristematic nucleoli, characterized by small sizes, reduced amount of dry mass and granular component and by the presence of few and large fibrillar centres into large active nucleoli displaying high dry mass and granular component contents, numerous and small fibrillar centres. After 3 h of postincubation at 20 degrees C, nucleoli lose their granular component, decrease in size and dry mass content. At this moment cytoplasm enriches in ribosomes and its dry mass increases. Maximum of nucleolar activity is preceded by an accumulation of proteins in nucleoli. It is concluded that an enhanced transport of ribosomes is one of the conditions of S phase initiation. 相似文献
3.
K Marciniak A Bilecka 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1985,23(4):231-245
Using cytophotometric method, after staining preparations with gallocyanin RNA content was examined in nucleus, nucleolus and cytoplasm of six species of angiospermal plants in successive (1-7 mm) segments of root representing successive zones of differentiation. During the cell cycle, RNA content duplicates in the nucleus, nucleolus and cytoplasm of meristematic cells. On the other hand, during growth and differentiation of parenchyma cells in species with endoreplication the content of nucleolar RNA does not increase in proportion with DNA content. High level of endoreplication is connected with high nucleolar RNA content and low cytoplasmic RNA content. In species without endoreplication at low nucleolar RNA content, a considerable growth of cytoplasmic RNA content takes place. 相似文献
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In a variety of tumour systems, individuals carrying progressively growing neoplasms have lymphoid cells with a specific cytotoxic effect on cultured tumour cells from the same individual1–4. Since the sera of tumour-bearing individuals have been shown to prevent tumour cell destruction by immune lymphocytes in vitro2,5–8 and since this serum blocking activity appears early in primary and transplant tumour development5,7, it has been suggested that the appearance of this serum blocking activity might be responsible for the progressive growth of tumours in individuals having cytotoxic lymphocytes. Counteraction of this blocking activity would thus be of primary importance in facilitating the function of an already existing or bolstered cell-mediated immunity. The serum blocking activity might be inhibited in various ways, by preventing the formation of blocking antibody or by interfering with its action (“unblocking”), as demonstrated in Moloney sarcoma regressor sera9. This type of serum also has a therapeutic effect on Moloney sarcomas in vivo10,11, which has been tentatively attributed to its unblocking activity8,9 or, possibly, to a complement-dependent cytotoxicity10. Tumour growth in the Moloney sarcoma system, however, might be due in part to continuous recruitment of neoplastic cells by virus-induced transformation and so the therapeutic effect could be due to a virus-neutralizing serum activity9,10. 相似文献
6.
On the mechanism of ATP-induced shape changes in the human erythrocyte membranes: the role of ATP 下载免费PDF全文
In the preceding paper (Sheetz, M. and S.J. Singer. 1977. J Cell Biol. 73:638-646) it was shown that erythrocyte ghosts undergo pronounced shape changes in the presence of mg-ATP. The biochemical effects of the action of ATP are herein examined. The biochemical effects of the action of ATP are herein examined. Phosphorylation by ATP of spectrin component 2 of the erythrocyte membrane is known to occur. We have shown that it is only membrane protein that is significantly phosphorylated under the conditions where the shape changes are produced. The extent of this phosphorylation rises with increasing ATP concentration, reaching nearly 1 mol phosphoryle group per mole of component 2 at 8mM ATP. Most of this phosphorylation appears to occur at a single site on the protein molecule, according to cyanogen bromide peptide cleavage experiments. The degree of phosphorylation of component 2 is apparently also regulated by a membrane-bound protein phosphatase. This activity can be demonstrated in erythrocyte ghosts prepared from intact cells prelabeled with [(32)P]phosphate. In addition to the phosphorylation of component 2, some phosphorylation of lipids, mainly of phosphatidylinositol, is also known to occur. The ghost shape changes are, however, shown to be correlated with the degree of phosphorylation of component 2. In such experiment, the incorporation of exogenous phosphatases into ghosts reversed the shape changes produced by ATP, or by the membrane-intercalating drug chlorpromazine. The results obtained in this and the preceding paper are consistent with the proposal that the erythrocyte membrane possesses kinase and phosphates activities which produce phosphorylation and dephosphorylation of a specific site on spectrin component 2 molecules; the steady-state level of this phosphorylation regulates the structural state of the spectrin complex on the cytoplasmic surface of the membrane, which in turn exerts an important control on the shape of the cell. 相似文献
7.
Gold salts and phenylbutazone selectively inhibit the synthesis of PGF2α and PGE2 respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE2 and PGF2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action
and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function. 相似文献
8.
M J Olszewska A Bilecka H Kuran K Marciniak R Osiecka 《Folia histochemica et cytobiologica / Polish Academy of Sciences, Polish Histochemical and Cytochemical Society》1989,27(2):107-112
In root meristems of 3 species (Secale cereale L., Vicia faba L. subsp. minor, Allium cepa L.) the durations of cell cycles and their phases were calculated using 3H-thymidine labelling. In the above species and in Helianthus annuus L. (parameters of the cell cycle determined earlier) the G1 and G2 phase durations were different: G1 + 1/2 M from 3 h to 6.1 h, G2 + 1/2 M from 1.1. h to 8.3 h, depending on the species. The rate of rRNA transport from nucleoli into cytoplasm during recovery after cold treatment was calculated from our data presented earlier. The results indicate that in 4 species studied there is no correlation (at P = 0.05) between the rate of rRNA transport and the duration of G1 and G2 phases. 相似文献
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10.
Sally E. Thomas Elke Malzer Adriana Ordó?ez Lucy E. Dalton Emily F. A. van ′t Wout Elizabeth Liniker Damian C. Crowther David A. Lomas Stefan J. Marciniak 《The Journal of biological chemistry》2013,288(11):7606-7617
Cell cycle checkpoints ensure that proliferation occurs only under permissive conditions, but their role in linking nutrient availability to cell division is incompletely understood. Protein folding within the endoplasmic reticulum (ER) is exquisitely sensitive to energy supply and amino acid sources because deficiencies impair luminal protein folding and consequently trigger ER stress signaling. Following ER stress, many cell types arrest within the G1 phase, although recent studies have identified a novel ER stress G2 checkpoint. Here, we report that ER stress affects cell cycle progression via two classes of signal: an early inhibition of protein synthesis leading to G2 delay involving CHK1 and a later induction of G1 arrest associated both with the induction of p53 target genes and loss of cyclin D1. We show that substitution of p53/47 for p53 impairs the ER stress G1 checkpoint, attenuates the recovery of protein translation, and impairs induction of NOXA, a mediator of cell death. We propose that cell cycle regulation in response to ER stress comprises redundant pathways invoked sequentially first to impair G2 progression prior to ultimate G1 arrest. 相似文献