玉米8个栽培亚种（类型）的核型和C—带带型的比较研究

本文首次报道了玉米8个亚种、2个亚型和2个杂交品种的核型和Giemsa C-带带型。所有材料的根尖细胞染色体数目均为2n=20。主要由中部和亚中部着丝点染色体组成。第6染色体短臂均具随体,但大小不同。所有材料均显示有亚端带和端带,在第6染色体的短臂上显示有NOR或/和随体带。C-带的分布、总数目和总长度各不相同。其总带数变异于6至18之间,C-带总长度为5.65—11.40％之间。在核型中,具中部着丝点的染色体数目及C-带总数,罕见栽培或原始的类型通常多于广泛栽培的类型。此外,有关核型和C-帝的变异和进化也进行了简略的讨论。     

大麦染色体银带的研究

本文以六棱、四棱和二棱大麦为材料,用去壁低渗火焰干燥法制备染色体标本,标本在60℃恒温下经70—80％AgNO_3水溶液处理12—14小时,可在核仁组成区、着丝粒和端粒出现黑色银染区。细胞化学反应说明这些不同区域的银染物质具有相同的性质。银染带型与C带型和N带型迥然不同,3种大麦的银染带型也有差别。试验还证明染色体标本制备技术对银染效果影响极大,只有合适的酶解和火焰干燥处理才能促使着丝粒和端粒显示出银染正反应。     

异育淇鲫及其双亲同工酶的比较研究

用4.5％聚丙烯酰胺凝胶平板电泳研究了异育淇鲫及其母本淇鲫和父本兴国红鲤的肌可溶性蛋白以及肾、肝、眼、背白肌和心等五种组织的乳酸脱氢酶(LDH)、苹果酸脱氢酶(MDH)和酯酶(EST)。结果发现:异育淇鲫的肌可溶性蛋白以及同工酶的电泳图谱与母本淇鲫相同而与父本兴国红鲤显著不同,因而认为异育淇鲫是淇鲫雌核发育的产物,父本基因对子代基本无影响。在此基础上,本文对异源精子在雌核发育中所起的生物学作用进行了初步探讨。     

猕猴属五个种mtDNA多态性研究

本文以10种限制性内切酶研究猕猴属5个种(Macaca mulatta.M.nemestrina.M.assemensis.M.thibetana,M arctoides)线粒体DNA进化。在13个个体中,共检出8种限制性类型。恒河猴种内存在广泛的线粒休DNA限制性片段长度多态性(RFLP)。结合日本猴(M.fuscata)的有关资料,构建了猕猴属6个种的分子系统树,并给出各个种的分化时间。结果表明,这6个种可分成4个类群,熊猴和藏酋猴、恒河猴和日本猴之间的遗传距离较近,可分别划为同一类群,红面猴与其他5种猴的遗传距离最远,在系统发生上分离最早。     

长江三角洲石荠苧属群体水平变异式样的研究

本文应用数量分类学方法对长江三角洲地区5种石荠苧属植物的群体进行了表征变异式样的分析,并参照繁育方式、生态适应和染色体数目等证据,来揭示种内群体间变异式样的差异及其与环境条件的关系,并探讨了这些种可能的种系发生关系。笔者认为石荠苧属Mosla在进化的早期就已经分化为两个大支,在分类上即表现为两个组——唇萼组和石荠苧组的分化。     

Kinetics of the inhibition of plasminogen activators by the plasminogen-activator inhibitor. Evidence for ''second-site'' interactions.

The reactions between plasminogen-activator inhibitor (PAI) and different plasminogen activators were studied in the presence of chromogenic peptide substrates for the enzymes. Our findings suggest that the rate constants for the reactions of PAI with single-chain tissue plasminogen activator (tPA), two-chain tPA, high-Mr urokinase and low-Mr urokinase are high and quite similar (1.6 X 10(7)-3.9 X 10(7) M-1.s-1). A free active site in the enzymes seems to be necessary for their reaction with PAI. Amino acids with antifibrinolytic properties did not interfere with the reactions. However, di-isopropyl phosphorofluoridate-inactivated tPA inhibited the reaction between PAI and all plasminogen activators in a similar way. These findings clearly demonstrated that a 'second-site' interaction, in addition to that between the enzyme active site and the inhibitor 'bait' peptide bond, is of importance for the high reaction rate. The reaction rate between PAI and single-chain tPA in the presence of an activator substrate (D-Ile-Pro-Arg p-nitroanilide) was decreased in the presence of fibrin. Fibrin caused a decrease in the Km for the single-chain tPA-substrate reaction. As a consequence, the 'free' concentration of single-chain tPA in the system decreased in the presence of fibrin, affecting the reaction rate between PAI and single-chain tPA. The phenomenon might be of physiological relevance, in the sense that single-chain tPA bound to fibrin in the presence of plasminogen would be protected against inactivation by PAI.     

Purification of phosphate-dependent glutaminase from isolated mitochondria of Ehrlich ascites-tumour cells.

Phosphate-dependent glutaminase was purified to homogeneity from isolated mitochondria of Ehrlich ascites-tumour cells. The enzyme had an Mr of 135,000 as judged by chromatography on Sephacryl S-300. SDS/polyacrylamide-gel electrophoresis displayed two protein bands, with Mr values of 64,000 and 56,000. Two major immunoreactive peptides of Mr values of 65,000 and 57,000 were found by immunoblot analysis using anti-(rat kidney glutaminase) antibodies. The concentration-dependences for both glutamine and phosphate were sigmoidal, with S0.5 values of 7.6 mM and 48 mM, and Hill coefficients of 1.5 and 1.6, respectively. The glutaminase pH optimum was 9. The activation energy of the enzymic reaction was 58 kJ/mol. The enzyme showed a high specificity towards glutamine. A possible explanation for the different kinetic behaviour found for purified enzyme and for isolated mitochondria [Kovacević (1974) Cancer Res. 34, 3403-3407] should be that a conformational change occurs when the enzyme is extracted from the mitochondrial inner membrane.     

ADP-ribosylation in isolated nuclei of Physarum polycephalum.

ADP-ribosylation of histones and non-histone nuclear proteins was studied in isolated nuclei during the naturally synchronous cell cycle of Physarum polycephalum. Aside from ADP-ribosyltransferase (ADPRT) itself, histones and high mobility group-like proteins are the main acceptors for ADP-ribose. The majority of these ADP-ribose residues is NH2OH-labile. ADP-ribosylation of the nuclear proteins is periodic during the cell cycle with maximum incorporation in early to mid G2-phase. In activity gels two enzyme forms with Mr of 115,000 and 75,000 can be identified. Both enzyme forms are present at a constant ratio of 3:1 during the cell cycle. The higher molecular mass form cannot be converted in vitro to the low molecular mass form, excluding an artificial degradation during isolation of nuclei. The ADPRT forms were purified and separated by h.p.l.c. The low molecular mass form is inhibited by different ADPRT inhibitors to a stronger extent and is the main acceptor for auto-ADP-ribosylation. The high molecular mass form is only moderately auto-ADP-ribosylated.     

25-Hydroxylation of vitamin D3 by a cytochrome P-450 from rabbit liver mitochondria.

A cytochrome P-450 catalysing 25-hydroxylation of vitamin D3 was purified from liver mitochondria of untreated rabbits. The enzyme fraction contained 9 nmol of cytochrome P-450/mg of protein and showed only one protein band with an apparent Mr of 52,000 upon SDS/polyacrylamide-gel electrophoresis. The preparation showed a single protein spot with an apparent isoelectric point of 7.8 and an Mr of approx. 52,000 upon two-dimensional isoelectric-focusing-polyacrylamide-gel electrophoresis. The purified cytochrome P-450 catalysed 25-hydroxylation of vitamin D3 up to 5000 times more efficiently than did the mitochondria. The cytochrome P-450 required both ferredoxin and ferredoxin reductase for catalytic activity. Microsomal NADPH-cytochrome P-450 reductase could not replace ferredoxin and ferredoxin reductase. The cytochrome P-450 catalysed, in addition to 25-hydroxylation of vitamin D3, the 25-hydroxylation of 1 alpha-hydroxyvitamin D3 and the 26-hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol. The enzyme did not catalyse side-chain cleavage of cholesterol, 11 beta-hydroxylation of deoxycorticosterone, 1 alpha-hydroxylation of 25-hydroxyvitamin D3, hydroxylations of lauric acid and testosterone or demethylation of benzphetamine. The results raise the possibility that the 25-hydroxylation of vitamin D3 and the 26-hydroxylation of C27 steroids are catalysed by the same species of cytochrome P-450 in liver mitochondria. The possible role of the liver mitochondrial cytochrome P-450 in the metabolism of vitamin D3 is discussed.     

Activation and inhibition of microsomal glutathione transferase from mouse liver.

Mouse liver microsomal glutathione transferase was purified in an N-ethylmaleimide-activated as well as an unactivated form. The enzyme had a molecular mass of 17 kDa and a pI of 8.8. It showed cross-reactivity with antibodies raised against rat liver microsomal glutathione transferase, but not with any of the available antisera raised against cytosolic glutathione transferases. The fully N-ethylmaleimide-activated enzyme could be further activated 1.5-fold by inclusion of 1 microM-bromosulphophthalein in the assay system. The latter effect was reversible, which was not the case for the N-ethylmaleimide activation. At 20 microM-bromosulphophthalein the activated microsomal glutathione transferase was strongly inhibited, while the unactivated form was activated 2.5-fold. Inhibitors of the microsomal glutathione transferase from mouse liver showed either about the same I50 values for the activated and the unactivated form of the enzyme, or significantly lower I50 values for the activated form compared with the unactivated form. The low I50 values and the steep slope of the activity-versus-inhibitor-concentration curves for the latter group of inhibitors tested on the activated enzyme indicate a co-operative effect involving conversion of activated enzyme into the unactivated form, as well as conventional inhibition of the enzyme.