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Zusammenfassung Zur vollständigen Ausschaltung des Sauerstoff-Effektes bei der Bestrahlung vonDrosophila-Embryonen genügt eine 15 Sekunden dauernde Vorbehandlung mit Stickstoff. 相似文献
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Activities of superoxide dismutase (SOD), catalase (CAT), and peroxidases (PER) were examined at 24-h intervals during Drosophila development. SOD activities show a U-shaped curve from egg to adult stages whereas CAT and PER are consistently low in egg through larval stages. Male and female larvae have similar activities of SOD, CAT, and PER whereas male adults have elevated activities of these enzymes. Larvae are more sensitive to H2O2 and 3-amino-1,2,4-triazole (an inhibitor of CAT) than adults. 相似文献
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S. Dolfini A. M. Courgeon L. Tiepolo 《Cellular and molecular life sciences : CMLS》1970,26(9):1020-1021
Riassunto La durata media delle fasi del ciclo cellulare (G1, S e G2) e del tempo di generazione totale (G
T
) in una linea stabilizzata di cellule diDrosophila melanogaster risulta essere rispettivamente di 1.8, 10.0, 7.2 e 18.8 ore. 相似文献
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It is widely accepted that phosphorylation of the retinoblastoma (Rb) protein during the G1 phase of the mammalian division
cycle is a major control element regulating passage of cells into S phase and through the division cycle. The experiments
supporting G1-phase-specific Rb phosphorylation and the historical development of this idea are reviewed. By making a rigorous
distinction between 'growth cessation' and the phenomena of 'cell cycle exit' or 'G1-phase arrest', the evidence for the G1-phase-specific
phosphorylation of Rb protein is reinterpreted. We show that the evidence for G1-phase phosphorylation of Rb rests on few
experiments and a chain of reasoning with some weak links. Evidence is reviewed that growth conditions regulate the phosphorylation
of Rb. A growth-regulated control system that is independent of the cell cycle explains much of the evidence adduced to support
cycle-specific phosphorylation of Rb. We propose that additional experimental evidence is needed to decide whether there is
a G1-phase-specific phosphorylation of Rb protein.
Received 16 October 2000; received after revision 13 November 2000; accepted 15 November 2000 相似文献
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M. Krishna Rao J. V. Pantulu K. Jayalakshmi 《Cellular and molecular life sciences : CMLS》1979,35(9):1154-1155
Summary Effect of B-chromosomes on the duration of the mitotic cycle was studied by a colchicine shock method in the root-tip cells of pearl millet (Pennisetum typhoides). 3 B-chromosomes were found to have very little effect, whereas 5 B-chromosomes resulted in an increase of the duration by about 39%.This investigation was financed by the University Grants Commission, New Delhi. 相似文献
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H. Moser 《Cellular and molecular life sciences : CMLS》1967,23(11):916-917
Zusammenfassung Im mitotischen Zyklus vollständig asynchroner, exponentiell proliferierender neoplastischer Manusmastzellen des Stamms P815Y ist dieG1-Phase vollständig abwesend. DNA-Synthese (S-Phase) beansprucht 84%,G2-Phase 14% und Mitose 4% der vollen Dauer des Zell-Zyklus.
This investigation was supported by the Office of Naval Research under contract No. Nonr-266(76) and by the Health Research Council of the City of New York under contract No. I-428, and carried out at Columbia University (Department of Biochemistry).
Recipient of Career Scientist Award of the Health Research Council of the City of New York under Contract No. I-428. 相似文献
This investigation was supported by the Office of Naval Research under contract No. Nonr-266(76) and by the Health Research Council of the City of New York under contract No. I-428, and carried out at Columbia University (Department of Biochemistry).
Recipient of Career Scientist Award of the Health Research Council of the City of New York under Contract No. I-428. 相似文献
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Summary Chloroplastic and cytoplasmic ribosomal RNA syntheses were analyzed in synchromous culteres. All 4 rRNA species are simultaneously accumulated during the light period of the cell cycle. Cytoplasmic rRNA synthesis is repressed only during the later part of the S phase. 相似文献
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M. H. Goyns 《Cellular and molecular life sciences : CMLS》1981,37(1):34-35
Summary Polyamine accumulation was related to RNA biosynthesis and content during the cell cycle of CHO-K1 and HeLa cells. The highest correlations were observed between polyamine accumulation and RNA content. Feeding, serumstarved cultures of embryonic chick fibroblasts, which exhibit a 3-fold increase in RNA content, demonstrated that RNA content was most closely paralleled by spermidine content.I acknowledge the receipt of a Medical Research Council studentship. 相似文献
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M H Goyns 《Experientia》1981,37(1):34-35
Polyamine accumulation was related to RNA biosynthesis and content during the cell cycle of CHO-K1 and HeLa cells. The highest correlations were observed between polyamine accumulation and RNA content. Feeding, serum-starved cultures of embryonic chick fibroblasts, which exhibit a 3-fold increase in RNA content, demonstrated that RNA content was most closely paralleled by spermidine content. 相似文献
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Ras proteins in the control of the cell cycle and cell differentiation 总被引:12,自引:0,他引:12
The Ras family of small GTPases includes three closely related proteins: H-, K-, and N-Ras. Ras proteins are involved in
the transduction of signals elicited by activated surface receptors, acting as key components by relaying signals downstream
through diverse pathways. Mutant, constitutively activated forms of Ras proteins are frequently found in cancer. While constitutive
Ras activation induces oncogenic-like transformation in immortalized fibroblasts, it causes growth arrest in primary vertebrate
cells. Induction of p53 and cyclin-dependent kinase inhibitors such as p15INK4b, p16INK4a, p19ARF, and p21WAF1 accounts for this response. Interestingly, while ras has usually been regarded as a transforming oncogene, the analysis of Ras function in most of the cellular systems studied
so far indicates that the promotion of differentiation is the most prominent effect of Ras. While in some cell types, particularly
muscle, Ras inhibits differentiation, in others such as neuronal, adipocytic, or myeloid cells, Ras induces differentiation,
in some cases accompanied by growth arrest. Several possible mechanisms for the pleiotropic effects of Ras in animal cells
are discussed.
Received 8 March 2000; received after revision 24 May 2000; accepted 24 May 2000 相似文献
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Changes in olfactory perception during the menstrual cycle 总被引:8,自引:0,他引:8
The aim of the study was to find correlations between changes in olfactory sensitivity and the menstrual cycle. 14 young, healthy volunteers participated in the experiments. Subjects menstruated regularly and did not use oral contraceptives. Three odorants were investigated: phenylethyl alcohol, androstenone, and nicotine. Dilution series of the odorants were prepared, and presented to the subjects in order to determine the detection thresholds (triple forced choice). Additionally, the subjects' hedonic estimates of the odorants were measured, and mood states as well as hormonal levels of LH and estrogen were determined. Before the actual experiments started, subjects participated in three training sessions. One experiment was subdivided into 5 phases (two pre- and two postovulatory phases; one ovulatory phase). Only with regard to androstenone did trend analyses reveal a significant quadratic relationship between hedonic estimates and phases of the menstrual cycle, peaking at ovulation. Olfactory sensitivity was not significantly influenced by the menstrual cycle. 相似文献
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T. Hummel R. Gollisch G. Wildt G. Kobal 《Cellular and molecular life sciences : CMLS》1991,47(7):712-715
Summary The aim of the study was to find correlations between changes in olfactory sensitivity and the menstrual cycle. 14 young, healthy volunteers participated in the experiments. Subjects menstruated regularly and did not use oral contraceptives. Three odorants were investigated: phenylethyl alcohol, androstenone, and nicotine. Dilution series of the odorants were prepared, and presented to the subjects in order to determine the detection thresholds (triple forced choice). Additionally, the subjects' hedonic estimates of the odorants were measured, and mood states as well as hormonal levels of LH and estrogen were determined. Before the actual experiments started, subjects participated in three training sessions.One experiment was subdivided into 5 phases (two pre- and two postovulatory phases; one ovulatory phase). Only with regard to androstenone did trend analyses reveal a significant quadratic relationship between hedonic estimates and phases of the menstrual cycle, peaking at ovulation. Olfactory sensitivity was not significantly influenced by the menstrual cycle. 相似文献