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Basic principles have been developed for a discrete stochastic simulation model of an elementary proliferative unit of the intestinal epithelium, a "crypt-villus" system. The analysis of the results obtained after a single exposure of the animal's abdomen to 3 and 6 Gy radiation has demonstrated that the dynamics of the number of cells that synthesize DNA in a small intestine crypt of exposed mice depends on the rate of radiation damage repair (50 to 100 h following irradiation). The rate of repair after 6 Gy irradiation is 1.5 times lower that after 3 Gy. The changes in the shape of the labeled mitoses curve, followed up during the postirradiation recovery of the intestinal epithelium, may occur with the time parameters of the cell mitotic cycle being invariable. 相似文献
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D A Perumov V V Machkovski? D Iu Iakovlev E I Budovski? 《Bioorganicheskaia khimiia》1984,10(12):1695-1697
The action of methoxyamine (MA) on B. subtilis transforming DNA (50 degrees C, pH 4,5 and 6,0, 1 M MA) was studied. The rate of cytosine residues modification in DNA is 250 times less than in monomer (rate constants for DNA are 1,5 X 10(-1) min-1 at pH 4,5, and 2,5 X 10(-6) min-1 in the first 300 hours of treatment at pH 6,0). At pH 4,5 the rates of cytosine (I) conversion into N4-methoxycytosine (II) and into 6-methoxyamino-5,6-dihydro-N4-methoxycytosine (III) are constant (II/III ratio is about 2,1). At pH 6,0 the II/III ratio smoothly increases from 1,0 to 1,6 (200 and 900 hours of treatment) due to a decrease in the product III accumulation rate. The frequency of MA-induced mutations shows a bell-shaped dependence on time with maxima (approximately 10%) at 80 (pH 4,5) and 500 (pH 6,0) hours of treatment. In both cases approximately 10% of cytosine residues are modified. These results suggest that either compound III is efficiently removed from the transforming DNA, or its presence does not arrest the DNA replication. 相似文献
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Alekseeva I. V. Bakman A. S. Iakovlev D. A. Kuznetsov N. A. Fedorova O. S. 《Molecular Biology》2021,55(2):241-251
Molecular Biology - The human N-glycosylases SMUG1 and MBD4 catalyze the removal of uracil residues from DNA resulting from cytosine deamination or replication errors. For polymorphic variants of... 相似文献