应用显微放射自显影技术对辐射诱发的微核合成DNA研究——Ⅰ.不同照射量的效应

本试验用放射性比度为5μCi/ml的~3H-胸腺嘧啶核苷(~3H-TdR)标记经不同照射量辐照的蚕豆根尖细胞,应用显微放射自显影技术,研究微核的DNA合成。试验结果表明,不同照射量的γ射线对细胞及微核合成DNA的影响是明显的。微核细胞及微核的标记率随着照射量的增大而减少,呈线性递减关系。本文还根据微核细胞的标记类型,对微核在细胞遗传工程研究方面的应用价值进行了探讨。     

克山病是一种“心肌线粒体病(Mitochondrial Cardiomyopathy)”

亚急克病人心肌线粒体内膜电子传递链的琥珀酸氧化酶系,琥珀酸脱氢酶和细胞色素氧化酶活性明显低于对照。H~ -ATP酶的活性及其对寡霉素的敏感性都明显下降。ATP能量化后线粒体膜电位的变化也比对照明显降低。膜脂流动性低于对照。亚急克病人心肌线粒体内观察到较多的电子致密无定形物质,经电镜X射线微区等方法分析,认为这些物质不是Ca_3(PO_4)_2,而可能是一种蛋白质凝聚物。此外,心肌线粒体的硒含量远低于对照,而Ca含量明显高于对照。上述结果都反映亚急克病人心肌线粒体明显损伤。根据克山病患者心肌细胞线粒体结构与功能方面呈现的如此广泛与明显的异常,可将克山病称为“心肌线粒体病(Mitochondrial Cardiomyopathy)”。     

贵州宽叶缬草油的化学成分

贵州产宽叶缬草(Valeriana officinalis L.var.latifolia Miq.)油,用Finnigan4510型毛细管气相色谱/质谱/计算机联用方法进行了化学成分分析,共检出了29个成分鉴定了其中21个成分,占全精油的92.33%,主要成分为乙酸龙脑酯,α-蒎烯,莰烯,β-蒎烯,柠檬烯,乙酸葛缕酯,二氢乙酸葛缕酯等。该油芬芳,适于调配烟用香精,亦用于调节器配食用香精和化妆品香精。     

Iodoazomycin riboside (1-(5'-iodo-5'-deoxyribofuranosyl)-2-nitroimidazole), a hypoxic cell marker. I. Synthesis and in vitro characterization

Misonidazole (MISO), a selective radiosensitizer of hypoxic cells, forms adducts with cellular biomolecules with rates which are 30-50 X higher under hypoxic as compared to aerobic conditions of incubation. This technique of sensitizer adduct formation was proposed as a possible means of measuring the hypoxic fraction of solid tumors by noninvasive procedures. Iodoazomycin riboside (5'-IAZR) and 5'-[125I]AZR were synthesized and chemically characterized. Measurements of in vitro cytotoxicity and radiosensitizing ability with EMT-6 tumor cells in vitro indicated that 5'-IAZR is approximately 3 X more toxic and effective than is azomycin riboside (AZR) and approximately 10 X more toxic and effective than is MISO. 5'-[125I]AZR was shown to selectively bind to hypoxic EMT-6 cells at rates which were 2.5-3 X faster than those of MISO. The absolute rates of binding of 5'-IAZR to hypoxic cells at concentrations of 10-100 microM are the highest observed in this laboratory for any hypoxic cell radiosensitizer tested to date. These data suggest that 5'-IAZR, when labeled with an appropriate radioisotope (e.g., 131I), might be a useful marker for hypoxic cells in solid tumors amenable to noninvasive detection. Additional studies with animal tumor models appear to be warranted.     

A simple purification of calmodulin by reversed phase chromatography with hydrophobic polymer 3520

A new adsorption chromatography procedure for the purification of calmodulin from bovine brain was developed using polymeric adsorbent 3520. Calmodulin was first isolated by DEAE-Cellulose column chromatography and further purified to apparent homogeneity following elution with 50% ethanol from the adsorbent column. Polyacrylamide gel electrophoresis showed one band either in the presence of Ca2+ or EGTA. The polymeric adsorbent 3520 is a non-polar polymer lacking exchangeable groups. The selective adsorption of calmodulin is based on hydrophobic interaction within the matrix, and is Ca2+ independent. Neither high salt (0.5 M NaC1) nor EGTA (5 mM) was able to elute the CaM from the adsorption column whereas ethanol (50%) eluted it completely. This method is simple to use and it provides highly purified calmodulin with high yield.     

High-speed preparative-scale separation and purification of ribosomal 5S and 5.8S RNA's via Sephacryl S-300 gel filtration chromatography

In this work we present a rapid and economical alternative to Sephadex and high performance size exclusion chromatography (HPSEC) for preparative-scale separation and purification of low molecular weight RNA's: 5.8S RNA, 5S RNA, and tRNA's. These three RNA species can be well resolved from each other and from higher molecular weight RNA species via Sephacryl S-300 gel filtration chromatography under mild eluting conditions: 10 mM Tris-HCl buffer, pH 7.5, containing 1.0 M NaCl. For a sample load of about 250 mg, the resolving power of a Sephacryl S-300 column (78 X 3.2 cm) is comparable to that of a 4.5 times larger Sephadex G-75 column (144 X 5 cm). Moreover, the total separation period is 2.5 times shorter for the Sephacryl method. Up to 500 mg or more of crude ribosomal RNA mixtures could be separated via two Sephacryl S-300 columns operated in tandem.     

Mutants of Pachysolen tannophilus with Improved Production of Ethanol from d-Xylose

The conversion of d-xylose to ethanol by the yeast Pachysolen tannophilus is relatively inefficient in batch culture. The inefficiency has been attributed in part to concurrent utilization of ethanol in the presence of appreciable concentrations of d-xylose and to the formation of xylitol and other by-products. To increase the concentration of ethanol accumulated in batch cultures, UV-induced mutants of P. tannophilus were selected on the basis of diminished growth on ethanol. Eleven independent mutant loci that conferred the ethanol-defective phenotype were identified. Three led to a greater yield and volumetric rate of production of ethanol than the wild type. One also produced less xylitol and was characterized by a deficiency in activity for malate dehydrogenase.     

In vitro regeneration of plantlets in Fagraea fragrans Roxb. — a tropical tree

Different vegetative parts of Fagraea fragrans Roxb., a valuable timber tree of South East Asia, were used as explants in in vitro studies.Nodal segments showed the best growth response as numerous adventitious shoots were regenerated in MS medium supplemented with Benzyl adenine (BA, 8.8 um) and 2,4-dichlorophenoxyacetic acid (2,4-D, 0.5 um). Shoot buds also developed from the leaf and root segments that were subcultured. The detailed process of callus growth and differentiation leading to the formation of whole plantlets is described. Uniform plantlets obtained could be transplanted successfully in soil.