西双版纳热带雨林地栖小兽群落的初步研究

西双版纳热带雨林地栖小兽群落的初步研究ＡＰＲＥＬＩＭＩＮＡＲＹＳＴＵＤＹＯＮＧＲＯＵＮＤ┐ＤＷＥＬＬＩＮＧＳＭＡＬＬＭＡＭＭＡＬＣＯＭＭＵＮＩＴＹＩＮＴＲＯＰＩＣＡＬＲＡＩＮＦＯＲＥＳＴＯＦＸＩＳＨＵＡＮＧＢＡＮＮＡ西双版纳热带森林地处热带东南亚北...     

中华姬鼠巢区的研究

中华姬鼠是亚热带山地常绿阔叶林内的优势种。本文报道了用标志重捕流放法,研究该鼠不同个体的巢区大小、相互关系以及在样地上的分布等一些生态学资料。     

Brain Amino Acids Measured by Intracerebral Dialysis in Portacaval Shunted Rats

Changes in brain amino acid uptake and metabolism have been proposed as a possible etiological factor in hepatic encephalopathy. By use of a brain dialysis technique (a thin tube implanted in the brain of the living animal), the extracellular amino acid concentrations in the striatum of portacaval (PC)-shunted and sham-operated rats were measured. Leucine, phenylalanine, methionine, and glutamine were increased two- to sixfold in the PC-shunted rats, whilst no changes were seen for GABA, valine, glutamate, or isoleucine, confirming previous reports. Aspartate levels were 350% higher in the PC-shunted rats, and this rise, as well as that of phenylalanine, was significantly correlated with the lower motor activity observed in the PC-shunted rats, suggesting a possible importance of these amino acids in the etiology of hepatic encephalopathy. The amino acid concentrations measured in whole blood demonstrated the well-known pattern of low levels of branched-chain amino acids and increased concentrations of phenylalanine, glutamine, and histidine.     

Molecular identification of Chinese cultivated Porphyra (Bangiaceae, Rhodophyta) based on the rDNA internal transcribed spacer-1 sequence and random amplified polymorphic DNA markers

Porphyra yezoensis Ueda and P. tenera Kjellman are two common commercial seaweeds cultivated in China, but it is difficult to identify them routinely because they are morphologically and systematically very close. The nuclear ribosomal internal transcribed spacer-1 (ITS-1) region of nine selected Porphyra cultivars from China were sequenced and determined. Combined with some ITS-1 data from GenBank, the phylogenetic analysis inferred from the neighbour-joining method indicated that the Porphyra species in this study exhibited clear taxonomic relationships and could be identified clearly to species. Based on the results, the random amplified polymorphic DNA (RAPD) technique was applied to distinguish 12 Porphyra cultivars, some of which turn out to be different lineages of the same Porphyra species. Eight specific RAPD markers were scored and used to construct a fingerprint that could distinctly identify different Porphyra cultivars. The results suggest that both the rDNA ITS-1 sequence and RAPD markers are useful methods to identify Porphyra cultivars, and may also be valid for phylogenetic and taxonomic studies.     

A novel host-specific restriction system associated with DNA backbone S-modification in Salmonella

A novel, site-specific, DNA backbone S-modification (phosphorothioation) has been discovered, but its in vivo function(s) have remained obscure. Here, we report that the enteropathogenic Salmonella enterica serovar Cerro 87, which possesses S-modified DNA, restricts DNA isolated from Escherichia coli, while protecting its own DNA by site-specific phosphorothioation. A cloned 15-kb gene cluster from S. enterica conferred both host-specific restriction and DNA S-modification on E. coli. Mutational analysis of the gene cluster proved unambiguously that the S-modification prevented host-specific restriction specified by the same gene cluster. Restriction activity required three genes in addition to at least four contiguous genes necessary for DNA S-modification. This functional overlap ensures that restriction of heterologous DNA occurs only when the host DNA is protected by phosphorothioation. Meanwhile, this novel type of host-specific restriction and modification system was identified in many diverse bacteria. As in the case of methylation-specific restriction systems, targeted inactivation of this gene cluster should facilitate genetic manipulation of these bacteria, as we demonstrate in Salmonella.     

The amino-terminal domain of bovine viral diarrhea virus Npro protein is necessary for alpha/beta interferon antagonism

The alpha/beta interferon (IFN-alpha/beta) system is the first line of defense against viral infection and a critical link between the innate and adaptive immune responses. IFN-alpha/beta secretion is the hallmark of cellular responses to acute RNA virus infections. As part of their survival strategy, many viruses have evolved mechanisms to counteract the host IFN-alpha/beta response. Bovine viral diarrhea virus (BVDV) (genus Pestivirus) was reported to trigger interferon production in infected cultured cells under certain circumstances or to suppress it under others. Our studies with various cultured fibroblasts and epithelial bovine cells indicated that cytopathic (cp) BVDV induces IFN-alpha/beta very inefficiently. Using a set of engineered cp BVDVs expressing mutant Npro and appropriate controls, we found that the IFN-alpha/beta response to infection was dependent on Npro expression and independent of viral replication efficiency. In order to investigate whether the protease activity of Npro is required for IFN-alpha/beta antagonism, we engineered Npro mutants lacking protease activity by replacement of amino acid E22, H49, or C69. We found that E22 and H49 substitutions abolished the ability of Npro to suppress IFN, whereas C69 had no effect, suggesting that the structural integrity of the N terminus of Npro was more important than its catalytic activity for IFN-alpha/beta suppression. A catalytically active mutant with a change at a conserved Npro region near the N terminus (L8P) in both BVDV biotypes did not antagonize IFN-alpha/beta production, confirming its involvement in this process. Taken together, these results not only provide direct evidence for the role of Npro in blocking IFN-alpha/beta induction, but also implicate the amino-terminal domain of the protein in this function.