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111.
D. Francis Nanette D. Davies J. A. Bryant S. G. Hughes D. R. Sibson P. N. Fitchett 《Experimental cell research》1985,158(2)
We have examined by fibre autoradiography the spacing of replicons in pea root meristems during synchronized entry into S phase from arrest at the G1/S boundary. Pretreatment with the DNA cross-linking agent, psoralen, produces a marked shortening of replicon spacing, suggesting that premature arrest of the replication fork results in the recruitment of additional initiation points within a given replicon family. This is discussed in relation to models for the control of DNA replication. 相似文献
112.
Kay LE 《Journal of the history of biology》1985,18(2):207-246
Journal of the History of Biology - 相似文献
113.
Summary The enzyme protochlorophyllide (pchlide) reductase has been identified amongst the peptides, resolved by sodium dodecyl sulphate
polyacrylamide gel electrophoresis (SDS-PAGE), of chloroplast membranes from oat and barley plants. In support of this identification
the enzymic activity associated with the enzyme has also been measured in the same preparations. A higher level of enzyme
was found in plants which had been darkened prior to extraction. Based on this data, mechanisms for the light regulated diurnal
variation of the reductase are discussed. 相似文献
114.
The selectivity of action of the aspartic-proteinase inhibitor IA3 from yeast (Saccharomyces cerevisiae). 总被引:1,自引:0,他引:1 下载免费PDF全文
The ability of the aspartic-proteinase inhibitor IA3 from yeast (Saccharomyces cerevisiae) to affect the activities of a range of mammalian and microbial aspartic proteinases was examined. The inhibitor appeared to be completely selective in that only the aspartic proteinase A from yeast was inhibited to any significant extent. IA3 thus represents the first example of a totally specific, naturally occurring, aspartic-proteinase inhibitor. 相似文献
115.
The mechanism of guanosine triphosphate depletion in the liver after a fructose load. The role of fructokinase. 总被引:1,自引:0,他引:1 下载免费PDF全文
A Sephadex G-25 filtrate of a 100 000g supernatant of rat liver homogenate was shown to be able to phosphorylate fructose, with GTP as the phosphate donor. Attempts to separate ATP- and GTP-dependent fructokinase activities failed, indicating that there is a single enzyme able to use both nucleotides. With a partially purified enzyme, Km values for fructose of 0.83 and 0.56 mM were found with ATP and GTP as substrates respectively. Km values of 1.53 and 1.43 mM were found for GTP and ATP respectively. Both ADP and GDP inhibited the GTP- and ATP-dependent fructokinase activity. We conclude that the depletion of hepatic GTP caused by intravenous administration of fructose to mice and rats can be explained simply by the utilization of the nucleotide by fructokinase. 相似文献
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Kaiser K. G.; Davies N. J.; Rodriguez-Roisin R.; Bencowitz H. Z.; Wagner P. D. 《Journal of applied physiology》1985,58(3):996-1004
Ten anesthetized normal dogs were each given two methacholine inhalational challenges to produce large amounts of low ventilation-perfusion (VA/Q) regions but little shunt. After one challenge, high-frequency ventilation (HFV) was applied, whereas after the other conventional mechanical ventilation (MV) was used, the order being randomized. Levels of both ventilatory modes were selected prior to challenge so as to result in similar and normal mean airway pressures and arterial PCO2 levels during control conditions. Gas exchange was assessed by both respiratory and multiple inert-gas transfer. Comparing the effect of HFV and MV, no statistically significant differences were found for lung resistance, pulmonary hemodynamic indices, arterial and mixed venous PO2, expired-arterial PO2 differences, or inert-gas data expressed as retention-excretion differences. The only variables that were different were mean airway pressure (2 cm higher during HFV, P less than 0.04) and arterial PCO2 (10 Torr higher during HFV, P less than 0.002). These results suggest that in this canine model of lung disease characterized by large amounts of low VA/Q regions, HFV is no more effective in delivering fresh gas to such regions than is MV. 相似文献
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