用2DNMR鉴定倍半萜多元酯的结构

利用2DNMR结合其他波谱方法从苦皮藤种子油中鉴定了2个新倍半萜多元酯,它们分别是1α-苯甲酰氧-8β-烟酰氧-9α、11β-2乙酰氧-β-二氢沉香呋喃,1β-苯甲酰氧-2α、8β、9α、11β-4乙酰氧-β-二氢沉香呋喃,命名为苦皮藤酯2和3。     

对冷适应大鼠棕色脂肪和肝脏在非寒颤产热机制中作用的评价

本实验主要观察并比较了大鼠冷适应前后直肠温度(RT)、血清游离脂肪酸(SFFA)浓度、肩胛间棕色脂肪组织(IBAT)和肝脏cAMP含量的变化及其对去甲肾上腺素(NE)反应性的改变。结果表明:①冷适应28d大鼠在冷环境中RT稳定,NE刺激后RT上升幅度大于常温对照组(P<0.005);②冷适应1d组SFFA升高,冷适应28d组SFFA接近对照组,且对NE刺激无反应,对照组给NE后SFFA与RT一致性升高;③冷适应28d组IBAT的cAMP升高,而肝脏的cAMP含量三组间无显著性差异。NE刺激后,冷适应28d组IBAT和肝脏cAMP均升高,与RT反应一致,而对照组不变。结果提示,在5±3℃适应28d的大鼠已建立冷适应机制,非寒颤产热(NST)容量增加,在冷适应的不同时期,肝脏和IBAT调节NST的机制不同。     

森林土壤氮转化的微生物功能研究

本文研究了不同林型下土壤(A+6层和A_1层)微生物、土壤酶活性在森林土壤氮转化中的作用。结果表明不同林型下土壤具有不同的固氮作用、反硝化作用、氨化作用和硝化作用速率,即阔叶林>针阔混交林>针叶林。已经证明,固氮作用主要存在于森林土壤的A_1层,反硝化作用主要存在于A_0层。森林土壤存在2种硝化作用过程,即由自养微生物所引起的自养硝化作用过程和异养微生物所引起的异养硝化作用过程。它的存在与林型有关,某些森林土壤中这2种硝化作用过程都存在,如针阔混交林下的A_0层和A_1层。有些林型下土壤,则以异养硝化作用过程为主,如针叶林的A_0层。     

Transformation of trichloroethylene by sulfate-reducing cultures enriched from a contaminated subsurface soil

Summary Trichloroethylene (TCE) was reductively dechlorinated to cis-1,2-dichloroethylene (cDCE) by sulfate-reducing cultures enriched from a contaminated subsurface soil. The highest observed transformation rate of TCE was 213 mol l^–1 per day at 35° C. The predominant biotransformation product was cDCE. However, further dechlorination of cDCE was not observed in most of the cultures. Methane production was insignificant and active sulfate reduction was achieved by maintaining excess sulfate. A comparison of sodium sulfide and sodium dithionite for their effect on the transformation of TCE revealed that the latter is a better reducing agent. The extent of TCE transformation in 25 days was ca. 20% higher in the dithionite-amended cultures. A decrease in the rate and extent of TCE transformation was observed with an increase in the concentration of bromoethanesulfonate up to 50 mabetm. Offprint requests to: S. G. Pavlostathis     

Structure of phenylalanine-accepting transfer ribonucleic acid and of its environment in aqueous solvents with different salts

Yeast tRNA(Phe) was studied in different salt-containing solvents by UV absorbance and small-angle neutron scattering (SANS). This extends results obtained previously in NaCl and KCl solutions [Li, Z.-Q., Giegé, R., Jacrot, B., Oberthür, R., Thierry, J. C., & Zaccai, G. (1983) Biochemistry 22, 4380-4388]. As expected, at low concentrations of all salts studied, the tRNA molecule is unfolded. The importance of specific counterion interactions and the flexibility of the macromolecule are emphasized by the observation that it cannot take up its folded structure in N(CH3)4Cl solvents, even when that salt concentration is increased to 1 M, in the absence of Mg ions. In CsCl solvents, on the other hand, the folded conformation is obtained in salt concentrations above about 0.2 M, similar to NaCl or KCl. By a comparison of SANS results in CsCl H2O and CsCl 2H2O solvents with the data from NaCl and KCl solvents, thermodynamic and structural parameters were derived for the solvated macromolecule. All the data are accounted for, quantitatively, by a model for the particle in NaCl, KCl, or CsCl solution made up of tRNA76-, closely associated with 76 positive hydrated counterions, surrounded by an aqueous solvent layer that excludes salt (and, therefore, of density different from that of bulk solvent). The mass of water in that layer depends on salt concentration, and the values found are consistent with those predicted by the Donnan effect.     

The effects of a known family-size distribution on the estimation of genetic parameters.

We consider the question: In a segregation analysis, can knowledge of the family-size distribution (FSD) in the population from which a sample is drawn improve the estimators of genetic parameters? In other words, should one incorporate the population FSD into a segregation analysis if one knows it? If so, then under what circumstances? And how much improvement may result? We examine the variance and bias of the maximum likelihood estimators both asymptotically and in finite samples. We consider Poisson and geometric FSDs, as well as a simple two-valued FSD in which all families in the population have either one or two children. We limit our study to a simple genetic model with truncate selection. We find that if the FSD is completely specified, then the asymptotic variance of the estimator may be reduced by as much as 5%-10%, especially when the FSD is heavily skewed toward small families. Results in small samples are less clear-cut. For some of the simple two-valued FSDs, the variance of the estimator in small samples of one- and two-child families may actually be increased slightly when the FSD is included in the analysis. If one knows only the statistical form of the FSD, but not its parameter, then the estimator is improved only minutely. Our study also underlines the fact that results derived from asymptotic maximum likelihood theory do not necessarily hold in small samples. We conclude that in most practical applications it is not worth incorporating the FSD into a segregation analysis. However, this practice may be justified under special circumstances where the FSD is completely specified, without error, and the population consists overwhelmingly of small families.     

血友病患者血清中淋巴腺病病毒/人T细胞Ⅲ型病毒抗体检测

对浙江省1982～1984年注射了美国产浓缩Ⅶ因子制剂的18例血友病患者,用酶联免疫吸附法(ELTSA)检测了血清中淋巴腺病病毒/人T细胞Ⅲ型病毒(LAV/HTLV-Ⅲ)抗体,发现4例阳性,并经免疫荧光试验和Western印迹法证实。2例应用了国产浓缩Ⅷ因子者抗体阴性。一例从美国来华旅游死于艾滋病者,LAV/HTLV-Ⅲ抗体阳性。本研究证明,LAV/HTLVⅢ病毒巳通过美国生产的Ⅷ因子制剂传入中国。     

青海贵德、共和两盆地晚新生代哺乳动物

本文记述了青海省贵德及共和两盆地的几个含晚新生代哺乳动物化石地点的地层剖面及采自18个地点的26种(代表20个属)哺乳动物化石.对其中的 Myospalax arvicolinus, Microtus, Anancus, Leptobos crassus gonghenensis subsp. nov., L. vallisarni, Bison (Superbison) crassicornis, Boopsis breviceps作了较详细的描述和讨论.通过对动物群的分析初步确定了盆地主要堆积物的时代——贵德盆地:上新世—早更新世;共和盆地:早—中更新世,并简略探讨了两盆地的发育历史.     

土壤中含EB病毒诱导物的检测

从广西壮族自治区梧州市、苍梧县、罗城县和北京市收集的土壤标本中发现有EB病毒诱导物。梧州市和苍梧县沿公路和江河两旁桐油树下的土壤标本,对EB病毒早期抗原诱导的阳性率为40～58％。在其他大戟科植物下的土壤标本中,也发现有EB病毒诱导物。对桐油树下土壤中EB病毒诱导物与鼻咽癌发生的可能关系进行了讨论。