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941.
Electron microscope study of the structures of the Bacillus subtilis prophages, SPO2 and phi105 总被引:14,自引:0,他引:14
Circular duplex structures of the correct length are observed in the electron microscope in hybridization mixtures of lysogen DNA and mature phage DNA for the case of the temperate Bacillus subtilis bacteriophage SPO2. This result shows that the sequence order of the prophage is a circular permutation of that of the mature phage. By making heteroduplexes of prophage DNA with that of the SPO2 deletion mutants, R90 and S25, the att site of the phage has been mapped at 61.2 ± 0.6% from one end of the mature phage DNA, which has a length of 38,600 base pairs. In the same co-ordinate system, the R90 deletion extends from 58.9 ± 0.7 to 66.8 ± 0.8% on the SPO2 chromosome, whereas the S25 deletion extends from 63.2 ± 0.6 to 66.9 ± 0.7%. In similar experiments with lysogen and mature phage DNA's of the temperate B. subtilis phage, φ105, no circular structures were seen. This result shows that the sequence order in the prophage and the phage are colinear, without circular permutation. 相似文献
942.
RNA and DNA in developing retinae: comparison of a normal with the degenerating retinae of C3H mice 总被引:4,自引:2,他引:2
R N Lolley 《Journal of neurochemistry》1973,20(1):175-182
Abstract— The Nucleic acids were measured in developing retinae of normal (DBA) mice and those afflicted with an inherited degenerative disease (C3H). The content of RNA in normal and C3H retinae increased to a maximum at 5 days of postnatal age. Thereafter, that of C3H retinae declined to a value lower than the normal. The content of DNA in normal and C3H retinae was maximal at 10 and 5 days of postnatal age, respectively. By 20 days, it declined in both retinae to nearly adult values. The DNA/RNA ratio of normal adult retinae was about 3, while that of C3H adult retinae was nearly 1–5. It is proposed that the photoreceptor cells possess a smaller cytoplasmic volume and a larger DNA/RNA ratio than the cells of the inner retina. The loss of DNA in developing normal and C3H retinae appears to result from cellular death. It was calculated that approximately 1 million cells in normal and 6 million cells in C3H retinae disappear during development. Cellular death in C3H retinae may not be restricted to the photoreceptor population. 相似文献
943.
During an ultrastructural study of small-intestinal mucosa from a patient suffering from alpha-chain disease organisms were identified within the epithelial cytoplasm which showed the fine structural features of the coccidian group. Though coccidiosis is well recognized as causing a diarrhoeal and often lethal illness in animals it has been neglected as a cause of disease in man. Thus this finding may be significant and warrants further investigation into its possible role in the pathogenesis of alpha-chain disease. 相似文献
944.
M Hall D K Parker P L Grover J Y Lu N E Hopkins W L Alworth 《Chemico-biological interactions》1990,76(2):181-192
The effects of three aryl acetylenes, 1-ethynylpyrene (EP), 2-ethynylnaphthalene (EN) and 3-ethynylperylene (EPE), upon the metabolism of benzo[a]pyrene (BaP) by microsomes isolated from rat liver were investigated. These aryl acetylenes all inhibited the total metabolism of BaP. Formation of BaP 7,8-dihydrodiol and BaP tetrol products by microsomal preparations from rats that had been pretreated with 3-methylcholanthrene (3MC) were preferentially inhibited. The effects of EP upon the metabolism of BaP 7,8-dihydrodiol by microsomes from rat liver were also studied. This aryl acetylene strongly inhibited the formation of BaP tetrols from BaP 7,8-dihydrodiol by liver microsomes both from untreated rats and from rats pretreated with 3MC, but enhanced the conversion of the BaP dihydrodiol into other metabolites. 相似文献
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G C Randall 《Journal of developmental physiology》1988,10(1):77-83
The role of cortisol as a factor controlling the deposition of glycogen in the pig fetus was examined by infusing either a low dose (1 mg/day) or a high dose (3 mg/day) of cortisol into chronically-catheterized hypophysectomized fetal pigs for five days beginning on day 100-104 of gestation. After infusion, liver glycogen was significantly higher (P less than 0.05) and lung glycogen significantly lower (P less than 0.05) than in uninfused hypophysectomized litter mates although concentrations were significantly different from intact litter mates (P less than 0.05). Although skeletal and cardiac muscle content increased after infusion this difference was not significant. Changes in tissue glycogen content were similar for both the low and high rates of infusion. These observations indicate that exogenous cortisol alone is able to stimulate liver glycogen deposition and reverse the effect of hypophysectomy. Although other factors may be necessary for maximal response this suggests that cortisol is an important stimulant for liver glycogen deposition in the fetal pig. The effect of cortisol on muscle glycogen was equivocal suggesting that other hormones may play a more important role in this tissue. 相似文献