内吞作用与胚胎诱导

在两柄类胚胎初级诱导的研究中,诱导物质如何进入反应细胞是一个受到重视(Grunzand Staubach,1979;Toivonen,1979)、但是仍未能解决的问题。为了对这一问题有所阐明,进行了离体诱导实验和电镜的观察。东方蝾螈(Cynops orientalis)早期原肠胚的外胚层块用豚鼠骨髓粗提液(BME)——有效的中胚层诱导物(Toivonen,1953)——处     

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。     

三七中达马烷型皂甙的热不稳定性及酸水解产物

前人已证明人参和三七中富含的达马烷型人参皂甙在通常酸性水解下甙元即发生变化,而在弱酸(如50％醋酸,0.1N盐酸)条件下则形成次级皂甙。本文报道人参甙(ginseno-sides)和三七甙(notoginsenosides)的水溶液在水浴上加热亦分别形成相应的C-20位去糖基的次级皂甙。联系到人参和三七均有在蒸煮加工后C-20位去糖基皂甙收率增大的趋势,似可认为人参和三七中的这类皂甙有相当一部分是在生药的加工泡制以及提取过程中形成的次级皂甙,而不一定是植物体的原生成分。将人参甙Rb_1单体以酸水解,不仅得到主产物人参二醇(3),还分离到异去氢原人参二醇(5)、达马烷-20(22)-烯-3β,12β,26-三醇(6)、20(R)-达马烷-3β,12β,20,25-四醇(7)以及20(S)-和20(R)-原人参二醇(1、2)的混合物,从而认为这些微量成分与人参二醇一样均为达马烷型人参皂甙在酸性水解条件下C-20位糖基断裂后由真甙元的侧链转化形成的工作产物。     

Analysis of cell-growth-phase-related variations in hyaluronate synthase activity of isolated plasma-membrane fractions of cultured human skin fibroblasts.

Hyaluronate synthase activity is localized exclusively in plasma-membrane fractions of cultured human skin fibroblasts. The enzyme activity of plasma membranes prepared from exponential-growth-phase cells was about 6.5 times that of stationary-growth-phase cells. Hyaluronate synthase from exponential-growth-phase cells exhibited lower Km and higher Vmax. values for both UDP-N-acetylglucosamine and UDP-glucuronic acid and higher rate of elongation of hyaluronate chains compared with the enzyme from stationary-growth-phase cells. Hyaluronate synthase exhibited an extremely short half-life, 2.2 h and 3.8 h respectively when cells were treated with cycloheximide and actinomycin D. The cell-growth-phase-dependent variations in hyaluronate synthase activity appear to be due to its high turnover rate as well as due to some post-translational modification of the enzyme protein as cells progress from early exponential to stationary growth phase. The isolated plasma membranes contained a protein (Mr approx. 450,000) that was selectively autophosphorylated from [gamma-32P]ATP in vitro in the presence of hyaluronate precursors in the reaction mixture and that also exhibited some hyaluronate-synthesis-related properties. The 32P-labelled protein isolated from plasma membranes of exponentially growing cells expressed an efficient UDP-[14C]glucuronic acid- and UDP-N-acetyl[3H]glucosamine-binding activity and was able to synthesize oligosaccharides (Mr 5000) of [14C]glucuronic acid and N-acetyl[3H]glucosamine residues. The corresponding protein of stationary-growth-phase cells, which expressed much higher nucleotide-sugar-precursor-binding activity, appeared to have lost its oligosaccharide-synthesizing activity.     

The effect of 1-β-d-arabinofuranosyl-cytosine on the expression of the common fragile site at 3p14

Summary The effect of the G₂-treatment of 1--d-arabino-furanosyl-cytosine (araC) on the expression of the common fragile site at 3p14 (FRA3B) was studied. A significantly increased frequency of FRA3B induced by G₂ treatment of araC was found in the lymphocytes grown in folate-deficient medium (positive rate 100%). A relatively low frequency of FRA3B was also induced in the cultures with folate in four of the seven subjects. These is a synergistic effect between araC and growth in folate-deficient medium on the induction of FRA3B. The results suggest that the DNA lesions related to the expression of FRA3B induce the long-patch repair and that the low DNA polymerase activity and inefficient repair process during G₂ phase is involved in the expression of FRA3B.     

Preliminary crystallographic studies of lobster D-glyceraldehyde-3-phosphate dehydrogenase and the modified enzyme carrying the fluorescent derivative

When the active-site carboxymethylated D-glyceraldehyde-3-phosphate dehydrogenase is irradiated with ultraviolet light in the presence of NAD+, a fluorescent NAD derivative that is covalently linked to the enzyme is obtained. A preliminary crystallographic study of this fluorescent derivative, as well as of the native and the carboxymethylated enzymes from Palinurus versicolor, showed that they are isomorphous and belong to space group C2 as reported for the native enzyme from Palinurus vulgaris. The three forms of the enzyme, although they have identical unit cell parameters, differ considerably in their diffraction patterns, indicating marked differences in conformation in spite of the fact that they differ chemically only in a restricted region around the active site.     

三乙醇胺基强碱性聚苯乙烯树脂共价固定胰酶的研究

用多孔强碱型三乙醇胺基聚苯乙烯阴离子交换树脂做为载体,用CNBr与载体上的多羟基作用共价偶联了胰酶。红外光谱表明:其共价偶联反应机理与用CNBr活化多糖类载体并接酶的机理相类似。最适偶联条件研究表明:CNBr用量增多,酶蛋白载量增加。但比活下降。偶联pH为10时,固定化酶有适宜的载量和较高的比活。由于胰酶水解蛋白反应释放出H~+质子,这些质子在载体内积累,使微环境内H~+质子浓度增加,进而使得固定化胰酶的pH—活性曲线在pH9～11范围内未出现下降。在变温和60℃恒温下对固定化酶的热稳定性测试表明:固相酶的热稳定性比天然酶的热稳定性有所提高。     

鱼类染色体G—显带的Brd U—BSG方法及白鲢G—带模式图的初步建立

本文报道了一种显示鱼类染色体G-带的BrdU-BsG方法。采用肾细胞短期培养,收获前12小时加入BrdU,使终浓度为10μg/ml。制片经HCl、Ba(OH)_2处理,4×SSC温育。Giemsa染色,显示出白鲢的G-带。其带纹细致清晰,一个细胞的单倍染色体上显示带纹达200条以上,是目前已报道的鱼类多重带中带纹最多的,且反差明显,带纹有特征性,结果较稳定。根据实验结果初步建立了白鲢的G-带模式图。