Mitotic arrest by deuterium oxide

In marine invertebrate eggs, where cell divisions occur without growth, deuterium oxide produces arrest of, or serious delay in, mitosis and cytokinesis. All stages requiring assembly or operation of mechanical structures in the cytoplasm are sensitive to D.O. The block is reversible in some cells.     

Satellite deoxyribonucleic acid from Bacillus cereus strain T

DNA isolated from exponentially growing cultures of Bacillus cereus T has a single component (density 1.696 g cm(-3)) in a cesium chloride density gradient whereas DNA isolated from spores shortly after the initiation of germination has two components: a major one (density 1.696 g cm(-3)) and a satellite (density, 1.725 g cm(-3)). The DNA of both components is doublestranded. By the first cell division there is no satellite DNA.     

Antibodies to deoxyribonucleic acid irradiated with ultraviolet light: detection by precipitins and immunofluorescence

Two rabbits were immunized with a complex consisting of ultravioietirradiated DNA and methylated bovine serum albumin. Serum antibodies reacted only with irradiated DNA, and the serological reaction was shown by immuneprecipitation and immunofluorescence.     

杀鼠剂溴敌隆与小牛胸腺DNA的相互作用

利用紫外光谱和荧光光谱研究二代抗凝杀鼠剂溴敌隆(BRD)与小牛胸腺DNA(ct-DNA)的相互作用.结果表明:ct-DNA可使BRD的紫外吸收光谱发生增色,但试验中没有观察到明显的光谱红移及等吸收点的出现;ct-DNA对BRD的稳态荧光有明显的猝灭作用,属于静态猝灭方式;通过热力学分析判断BRD与ct-DNA之间的相互作用主要是氢键和范德华力作用.吸收光谱、竞争试验、阴离子猝灭试验以及离子强度影响试验一致表明,BRD与ct-DNA之间主要以沟区结合方式发生作用.     

X-rays affect the incorporation of 5-iododeoxyuridine into deoxyribonucleic acid

When labeled with iodine-131, 5-iododeoxyuridine, an analogue of thymidine, is useful in estimating the effect of x-radiation on deoxyribonucleic acid metabolism. Although this compound is readily incorporated into deoxyribonucleic acid in the absence of ionizing radiation, we find that whole-body exposure to as little as 10 r will significantly inhibit its incorporation.     

Incorporation of unnatural pyrimidine bases into deoxyribonucleic acid of mammalian cells

When a mammalian cell strain was incubated with 5-iododeoxyuridine and 5-bromodeoxyuridine, DNA thymine was partially replaced by the halogen-containing pyrimidines. The extent of incorporation of the unnatural bases increased when amethopterin and hypoxanthine were added to the medium. It is thus evident that the replacement of DNA thymine by selected structural analogs, a phenomenon previously reported for bacterial systems, is applicable to cells of higher organisms.     

Dynamic structure of membranes by deuterium NMR

Progress in our understanding of the dynamic structure of membrane lipids and proteins has recently been made possible by the advent of high-field "solid-state" nuclear magnetic resonance spectroscopic studies of specifically deuterium-labeled systems. Major features of lipid and protein dynamics have been deduced.     

Circadian activity rhythm of the deer mouse, Peromyscus: effect of deuterium oxide

Chemical modification of a vertebrate activity rhythm, the circadian (approximately 24-hour) rhythm of Peromyscus leucopus noveboracensis, has been demonstrated. Activity in a running wheel was used to measure the rhythms of mice kept individually in conditions of continuous darkness. Deuterium oxide was presented in the drinking water. The length of the periods of rhythm increased directly and linearly with the increase in concentration of deuterium oxide. There is no threshold for this effect, and the maximum concentration of deuterium oxide (30 percent) that was presented resulted in a 6 percent lengthening of the period of circadian rhythm. The mice reverted to rhythms similar in period length to control values after deuterium oxide was withdrawn from their drinking water.     

Deoxyribonucleic acid antibody: a method to detect its primary interaction with deoxyribonucleic acid

Antibody to DNA in human serums can be detected by the ammonium sulfate method. This sensitive and specific technique, which measures the primary interaction between DNA and antibody to DNA, is based on the observation that free DNA is soluble in 50-percent saturated ammonium sulfate whereas antibody-bound DNA is insoluble.     

Porphyrin-heme pathway: regulation by intermediates in bile acid synthesis

Dihydroxycoprostane and trihydroxycoprostane, intermediates in normal bile acid synthesis in the liver, enhanced the rate of porphyrin synthesis in cultured liver cells by induction of delta-aminolevulinate synthetase, the rate-limiting enzyme for this pathway. Other 5beta-cholestane derivatives and cholest-5-ene derivatives were ineffective. The selectivity of the induction may indicate that the above-mentioned coprostanes have a physiological role in porphyrin synthesis.     

Polyinosinic acid--polycytidylic acid: inhibition of DNA synthesis stimulated by isoproterenol

Polyinosinic acid * polycytidylic acid (poly I * poly C) inhibits isoproterenol-stimulated DNA synthesis in salivary glands of mice. A single intraperitoneal injection of 250 micrograms of poly I * poly C inhibits the stimulation of DNA synthesis when given 10 minutes before isoproterenol or at any time during the 20-hour lag period between the injection of isoproterenol and the subsequent DNA synthesis. The inhibition caused by poly I * poly C is not due to a generalized toxic action but seems to be exerted through a relatively selective mechanism. Polyuridylic acid and diethylaminoethyl dextran are less effective in inhibiting isoproterenol-stimulated DNA synthesis.     

脱氢松香酸的合成研究

采用优化路线以松香为原料合成脱氢松香酸,简化了合成步骤,产率达44.3%.