利用泽兰实蝇控制紫茎泽兰的生防策略研究

本文根据野外泽兰实蝇种群15个世代的调查资料,利用契贝谢夫正交多项式拟合了泽兰实蝇、紫茎泽兰的空间格局。阐明了泽兰实蝇空间格局的序列变化及紫茎泽兰空间格局的特点;揭示了泽兰实蝇空间格局的特点受当地主风及寄主紫茎泽兰空间格局特点的影响;并从最优控制系统的角度对泽兰实蝇-紫茎泽兰系统作了初步探讨。首次提出了最佳释放虫量指标为每条虫占有10条枝条。这些结果为多点释放及定点多次释放泽兰实蝇防治紫茎泽兰这一生防策略提供了理论基础。     

山莨菪碱对经有限蛋白水解后的脑突触膜Ca~(2+)-ATPase的影响

 从猪脑中提取钙调蛋白和突触质膜,我们研究了山莨菪碱对经有限蛋白水解和磷脂酶A_2处理后的突触膜Ca~(2+)-ATPase活性影响。发现药物对不同预处理后的Ca~(2+)-ATPase表现出不同影响并调节钙调蛋白对它的激活作用。     

多羟基苯衍生物对逆转录酶抑制动力学的研究

 一些多羟基苯衍生物对逆转录酶呈现竞争性抑制作用,它们对M-MLV逆转录酶的抑制作用比AMV逆转录酶要强。     

高温厌氧条件下纤维素的直接乙醇发酵

本文介绍了出分解纤维素的嗜热厌氧菌Clostridium celluloflavus sp.nov.直接发酵纤维素产乙醇的初步研究、发酵于60℃下进仃,其主要产物为乙醇、乙酸、氢气和二氧化碳。文中介绍了间歇发酵的若干特征与影响发酵的因素,1％纤维素发酵至120小时,大约有70％纤维素被分解;乙醇的转化率约为0.36g/g降解纤维素;发酵液中乙醇浓度达到56至61mM。发酵中乙醇与乙酸浓度的比值因发酵时间与其它发酵条件的不同而不同。     

Recombinant adenoviruses with large deletions generated by Cre-mediated excision exhibit different biological properties compared with first-generation vectors in vitro and in vivo.

In vivo gene transfer of recombinant E1-deficient adenoviruses results in early and late viral gene expression that elicits a host immune response, limiting the duration of transgene expression and the use of adenoviruses for gene therapy. The prokaryotic Cre-lox P recombination system was adapted to generate recombinant adenoviruses with extended deletions in the viral genome (referred to here as deleted viruses) in order to minimize expression of immunogenic and/or cytotoxic viral proteins. As an example, an adenovirus with a 25-kb deletion that lacked E1, E2, E3, and late gene expression with viral titers similar to those achieved with first-generation vectors and less than 0.5% contamination with E1-deficient virus was produced. Gene transfer was similar in HeLa cells, mouse hepatoma cells, and primary mouse hepatocytes in vitro and in vivo as determined by measuring reporter gene expression and DNA transfer. However, transgene expression and deleted viral DNA concentrations were not stable and declined to undetectable levels much more rapidly than those found for first-generation vectors. Intravenous administration of deleted vectors in mice resulted in no hepatocellular injury relative to that seen with first-generation vectors. The mechanism for stability of first-generation adenovirus vectors (E1a deleted) appeared to be linked in part to their ability to replicate in transduced cells in vivo and in vitro. Furthermore, the deleted vectors were stabilized in the presence of undeleted first-generation adenovirus vectors. These results have important consequences for the development of these and other nonintegrating vectors for gene therapy.     

Sequencing, distribution, and inactivation of the dipeptidase A gene (pepDA) from Lactobacillus helveticus CNRZ32.

Previously, the gene for a general dipeptidase (pepDA) was isolated from a gene bank of Lactobacillus helveticus CNRZ32. The pepDA gene consists of a 1,422-bp open reading frame which could encode a polypeptide of 53.5 kDa. No significant identity was found between the deduced amino acid sequence of the pepDA product and the sequence for other polypeptides reported in GenBank. Southern hybridization studies with a pepDA probe indicated that the nucleotide sequence for pepDA is not well conserved among a variety of lactic acid bacteria. Growth studies indicated that a pepDA deletion had no detectable effect on growth rate or acid production by L. helveticus CNRZ32 in milk. Furthermore, no difference in total cellular dipeptidase activity was detected between the mutant and wild-type strains during logarithmic growth in MRS medium.     

Purification and characterization of an oxygen-sensitive, reversible 3,4-dihydroxybenzoate decarboxylase from Clostridium hydroxybenzoicum.

A 3,4-dihydroxybenzoate decarboxylase (EC 4.1.1.63) from Clostridium hydroxybenzoicum JW/Z-1T was purified and partially characterized. The estimated molecular mass of the enzyme was 270 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave a single band of 57 kDa, suggesting that the enzyme consists of five identical subunits. The temperature and pH optima were 50 degrees C and pH 7.0, respectively. The Arrhenius energy for decarboxylation of 3,4-dihydroxybenzoate was 32.5 kJ . mol(-1) for the temperature range from 22 to 50 degrees C. The Km and kcat for 3,4-dihydroxybenzoate were 0.6 mM and 5.4 x 10(3) min(-1), respectively, at pH 7.0 and 25 degrees C. The enzyme optimally catalyzed the reverse reaction, that is, the carboxylation of catechol to 3,4-dihydroxybenzoate, at pH 7.0. The enzyme did not decarboxylate 2-hydroxybenzoate, 3-hydroxybenzoate, 4-hydroxybenzoate, 2,3-dihydroxybenzoate, 2,4-dihydroxybenzoate, 2,5-dihydroxybenzoate, 2,3,4-trihydroxybenzoate, 3,4,5-trihydroxybenzoate, 3-F-4-hydroxybenzoate, or vanillate. The decarboxylase activity was inhibited by 25 and 20%, respectively, by 2,3,4- and 3,4,5-trihydroxybenzoate. Thiamine PPi and pyridoxal 5'-phosphate did not stimulate and hydroxylamine and sodium borohydride did not inhibit the enzyme activity, indicating that the 3,4-dihydroxybenzoate decarboxylase is not a thiamine PPi-, pyridoxal 5'-phosphate-, or pyruvoyl-dependent enzyme.     

Longitudinal studies of viral sequence, viral phenotype, and immunologic parameters of human immunodeficiency virus type 1 infection in perinatally infected twins with discordant disease courses.

Perinatal human immunodeficiency virus type 1 (HIV-1) infections cause a broad spectrum of clinical disease and are variable in both the age of the patient at onset of serious disease and the progression of the clinical course. Heterozygotic perinatally infected twins with a marked difference in their clinical courses were monitored during the first 2 years of life. Twin B, the second-born twin, developed AIDS by 6 months of age and died at 22 months of age, while twin A remained minimally symptomatic through the first 2 years. Sequential blood specimens were obtained from the twins in order to characterize the immunologic properties of the children and the phenotypes and genotypes of the HIV-1 isolates at various times. Twin A developed neutralizing antibodies and a high-level antibody-mediated cellular cytotoxicity (ADCC) response, while twin B had no neutralizing antibody and a much lower ADCC response. The virus isolates obtained from the two children at various time points proliferated equally well in peripheral blood mononuclear cells, were nonsyncytium inducing, and could not infect established T-cell lines. They differed in their ability to infect primary macrophages. In parallel to the biological studies, the HIV-1 tat and part of the env gene sequences of the longitudinal isolates at four time points were determined. Sequences of virus from both twins at different time points were highly conserved; the viruses evolved at a similar rate until the last analyzed time point, at which there was a dramatic increase in sequence diversity for the sicker child, especially in the tat gene. Our results show that the viruses isolated at different times do not have significant changes in growth properties. The absence or low levels of neutralizing antibodies may correlate with disease progression in the twins.