Raman spectroscopic study of DNA photodamage sensitized by hypocrellin B and 5-brominated-hypocrellin B

Hypocrellin B (HB) is a highly effective photosensitizer. One of its derivatives, 5-brominated-hypocrellin B (5-Br-HB) has better photosensitive characterlstics than it. Using Raman spectroscopy, the microcosmic photodamage to DNA sensitized by HB and 5-Br-HB was studied at molecular level. The results showed that when HB and 5-Br-HB were added to the solution of DNA and irradiated, the characteristic Raman frequencies and intensities of DNA changed to various degrees. The photodamage occurred on the whole DNA molecule, including phosphate backbone, deoxyribose and four bases. Not only the conformation but also the configuration of DNA was photodamaged: breakage of some H-bonds, disappearance of B-form conformation, scission of double or single strand and serious damage of four bases. The damage to A-T pairs was stronger than that to C-G pairs and DNA became polynucleotides finally. The 5-Br-HB-photosensitized damage to DNA was stronger than HB, which suggested the better photosensitive characteristics of 5-Br-HB in bioactive environment. The molecular mechanisms of photodamage to DNA sensitized by 5-Br-HB and HB were also elucidated.     

Transgene for growth hormone in common carp（Cyprinus carpio L.） promotes thymus development

The transgenic carp were produced by micro-injection of CAgcGHc into the fertilized eggs. Observation of the thymus development between the transgenics and non- transgenic controls was carried out. The thymus of one-year- old transgenics F1 showed a great increase in both size and weight. The unilateral thymus of the transgenics weighed from 190 to 295 mg with average 218.6 mg, whereas the uni-lateral thymus of the controls weighed 20—81 mg with av-erage 42.5 mg; i.e. the thymus weight in the transgenics was 5.14 fold over that in the controls. The index of thymus/body weight in the transgenics was 2.97 fold over the controls. Light microscopy observation indicated that the thymus of the transgenics well developed with the thickened outer re-gion and compactly arranged thymocytes, while the thymus in the controls were degenerating with the thinned outer region, scattered thymocytes and groups of fatty cells. Fur-ther analysis with the electron microscopy revealed that pro-liferous cells in the transgenics were mainly small lympho-cytes and no pathological changes were found. The results confirmed that the 揂ll-fish?GH-transgene promotes thy-mus development and thymocyte proliferation, and retards thymus degeneration. The study has laid a foundation for further analysis of the immunobiological function in GH- transgenic carp.     

Immigration of lymphoid precursor cells into the thymic rudiment inXenopus

Summary The origin of thymic lymphocytes was investigated, using a new reliable method to mark cells inXenopus. It was easily observed that extraneous cells immigrated into the thymic rudiment 4 days after fertilization and differentiated into a cell population identified as thymic lymphocytes in a fully developed thymus. Clearly, lymphoid precursor cells are of extrinsic origin.This work was supported in part by a grant from the Ministry of Education, Science and culture of Japan (No. 59770026).     

A dioestrous increase in thymocyte proliferation during the oestrous cycle

Summary Coitus, which precedes internal fertilisation, is a unique physiological event which allows motile allogeneic spermatozoa to enter the female host and invade her tissues. The cyclic cellular proliferation observed in the thymus of the female rat may be an important preparation of her immune system for this event.     

DNA主链构象与脱氧鸟苷组分构象相关性的喇曼分析

对小牛胸腺ＤＮＡ纤维样品溶解３ｈ内的空间构象变化过程进行了喇曼光谱分析，结果显示了表征脱氧鸟苷糖环折迭不同类型的６７２ｃｍ＾－１与６８３ｃｍ＾－１峰的同时存在，与ＤＮＡ分子主链不同特征峰的同时出现之间有着明显的联系。     

6-位脂肪胺取代的萘酰亚胺衍生物与DNA的相互作用

利用紫外可见光谱、荧光光谱、圆二色谱和粘度测试,考察了8个6-位脂肪胺取代的萘酰亚胺衍生物与小牛胸腺DNA的相互作用.研究结果表明:小牛胸腺DNA对与其结合能力强的化合物3a～3d有荧光猝灭作用,对与其结合能力弱的3e～3h有荧光增强效应;圆二色谱显示这些萘酰亚胺化合物能引起DNA二级结构发生不同的变化.在紫外-可见吸收光谱和粘度测试中,这些化合物与DNA的相互作用没有差别.综合光谱学和粘度测试的结果,推断这些化合物是通过嵌插方式与DNA结合,由于结构不同,它们与DNA之间作用程度存在差异.     

Calf thymus ribonuclease H IIa activity lacks ribonuclease H specificity

Summary Less purified fractions of ribonuclease H IIa activity of calf thymus display divalent cation-dependent ribonuclease H activity and divalent cation-independent ribonuclease activity. Because the ratio of the two enzyme activities does not change during successive chromatographic procedures, we suggest that ribonuclease H IIa activity is indeed able to degrade both ssRNA and the RNA moiety of RNA·DNA-hybrids. Ribonuclease H IIa activity can therefore be differentiated from calf thymus ribonuclease H I and H IIb by its lack of ribonuclease H specificity. The native molecular mass of ribonuclease H IIa activity is between 23 and 28 kDa. Under denaturing conditions a 23 kDa-protein band copurifies with the enzyme activity suggesting that this enzyme is monomeric.     

酶性DNA（Ⅴ）──硫酸二甲酯对小牛胸腺DNA酯酶活性的抑制作用

实验表明，硫酸二甲酯显著抑制小牛（Ｂｏｓｔａｕｒｕｓ）胸腺ＤＮＡ的酯酶活性，提示鸟嘌呤（Ｎ７）基团与酶性ＤＮＡ的酯酶活性有关．     

Expression of multidrug resistance (mdr) gene(s) in primary lymphoid organs of chicken immune system during embryonic development

The presence of a multidrug resistance (MDR) related protein, P-170, in normal and pathological lymphoid cells has been described. The present report evaluates the expression of themdr 1 gene by using the reverse Polymerase Chain Reaction (PCR) on cells obtained from the thymus and bursa of chicken embryos starting from day 12 until hatching. Results show that the thymic cells are positive from day 12 to the end of the observation period. In contrast,mdr mRNA was detected in the bursa from day 14 to day 17 of embryonic life. Possible relationships between the expression ofmdr and the development of T and B lymphocytes are discussed.     

DNA具酯酶活性的酶动力学初步研究

在发现绿豆、蜘蛛和小牛胸腺ＤＮＡ有促进乙酸萘酯水解的酯酶活并建立ＤＮＡ酯活性测定方法的基础上，对具酯酶活性的ＤＮＡ进行了ＰＨ、酶反应速度、ＤＮＡ浓度以及各种金属离子影响的酶动力学实验。