Hierarchical analysis of variation in the mitochondrial 16S rRNA gene among Hymenoptera

Nucleotide sequences from a 434-bp region of the 16S rRNA gene were analyzed for 65 taxa of Hymenoptera (ants, bees, wasps, parasitoid wasps, sawflies) to examine the patterns of variation within the gene fragment and the taxonomic levels for which it shows maximum utility in phylogeny estimation. A hierarchical approach was adopted in the study through comparison of levels of sequence variation among taxa at different taxonomic levels. As previously reported for many holometabolous insects, the 16S data reported here for Hymenoptera are highly AT-rich and exhibit strong site-to-site variation in substitution rate. More precise estimates of the shape parameter (alpha) of the gamma distribution and the proportion of invariant sites were obtained in this study by employing a reference phylogeny and utilizing maximum-likelihood estimation. The effectiveness of this approach to recovering expected phylogenies of selected hymenopteran taxa has been tested against the use of maximum parsimony. This study finds that the 16S gene is most informative for phylogenetic analysis at two different levels: among closely related species or populations, and among tribes, subfamilies, and families. Maximization of the phylogenetic signal extracted from the 16S gene at higher taxonomic levels may require consideration of the base composition bias and the site-to-site rate variation in a maximum-likelihood framework.      

Mycotoxins of Alternaria alternata produced on ceiling tiles

The production of mycotoxins by Alternaria alternata in cellulosic ceiling tiles was examined with thin-layer chromatography and high-performance liquid chromatography procedures. Alternariol and alternariol monomethyl ether were found in ceiling tile extracts, whereas extracts of control rice cultures of all three isolates produced these mycotoxins plus altenuene and altertoxin I. Extensive fungal growth and mycotoxin production occurred in the ceiling tiles at relative humidities of 84–89% and 97%. Received 28 May 1997/ Accepted in revised form 06 October 1997     

Water Flow in Wheat Seedlings after Small Water Deficits

Cultures of Scenedesmus obliquus when grown heterotrophically for 10 or 30 days without addition of fresh medium showed 85 and 98% loss of their photosynthetic capacity respectively. This loss in photosynthetic capacity was accompanied by an increase in quantum requirement. No major changes in the pigment amounts or types were detected which would explain the decay in photosynthetic capacity. Partial reactions mediated by photosystem II or I showed a more or less constant decay over a period of 30 days. Photosystem II reactions appeared less stable than those of photosystem I, decaying by 95% as compared with 70%, over this time period. The results of comparative studies on aged cells for their potential of cytochrome f photooxidation, fluorescence kinetics, 520 nm absorbance change and the variable influence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone on the photosynthetic capacity of such cells, suggest that it is the inherent ability of the cells to photooxidize plastohydroquinone which is affected primarily. In addition, secondary changes were noted in the activity of reactions on the water-splitting side of photosystem II and in the P700 — plastocyanin — cytochrome f complex.     

Cellular and physiological upregulation of inducible nitric oxide synthase,arginase, and inducible cyclooxygenase in wound healing

Wound repair is regulated by overlapping cellular, physiological and biochemical events. Prostaglandins and nitric oxide have been a focus for inflammation research particularly since the discovery of their inducible isoforms nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Study of the cellular expression of iNOS and COX-2 and arginase which competes with iNOS for its substrate, in an in vivo model of wound healing could reveal important roles for these enzymes in the physiological progression of wound repair. Adult male rats received full thickness dermal wounds which were harvested at different times. Protein levels and activities of the enzymes were assessed by western blot and biochemical assays respectively. The cellular distribution and the colocalization were assessed by immunostaining. The protein levels and activities of iNOS, arginase, and COX-2 increased only during the inflammatory phase of wound. Immunocytochemistry showed that the three enzymes were coexpressed and the main cellular source was inflammatory cells mainly macrophages. iNOS was induced at the wound site and was the earliest to increase significantly (p < 0.05) for only up to 3 days postwounding. However, arginase and COX-2 significant ( p < 0.05) upregulation started at a later time points and continued for up to 14 days postwounding. Therefore iNOS, compared with arginase and COX-2, showed a temporal difference in expression during wound healing which could be explained by their products being required at different stages of the healing process. The coordinated expression of the three enzymes at different time points could account for the physiological progression of the healing process.     

The geographical region of origin determines the phagocytic vulnerability of Lichtheimia strains

Mucormycoses are life-threatening infections that affect patients suffering from immune deficiencies. We performed phagocytosis assays confronting various strains of Lichtheimia species with alveolar macrophages, which form the first line of defence of the innate immune system. To investigate 17 strains from four different continents in a comparative fashion, transmitted light and confocal fluorescence microscopy was applied in combination with automated image analysis. This interdisciplinary approach enabled the objective and quantitative processing of the big volume of image data. Applying machine-learning supported methods, a spontaneous clustering of the strains was revealed in the space of phagocytic measures. This clustering was not driven by measures of fungal morphology but rather by the geographical origin of the fungal strains. Our study illustrates the crucial contribution of machine-learning supported automated image analysis to the qualitative discovery and quantitative comparison of major factors affecting host–pathogen interactions. We found that the phagocytic vulnerability of Lichtheimia species depends on their geographical origin, where strains within each geographic region behaved similarly, but strongly differed amongst the regions. Based on this clustering, we were able to also classify clinical isolates with regard to their potential geographical origin.     

海洋浮游藻类细胞质膜氧化还原活性与细胞外CA活性的关系

海洋浮游藻类除通过吸收和释放分子与离子来改变其环境的化学成分外,还可通过细胞外表面一些酶的作用引起质膜外化学物质变化。在这方面,海洋浮游藻类一个主要的细胞外表面酶-碳酸酐酶(CA),在经胰蛋白酶处理从细胞质膜上释放出来后,仍保留其催化活性。当细胞外表面CA(简称细胞外CA)具活性时,可催化质膜外HCO_3~-与CO_2的相互转化,为Rubisco(磷酸核酮糖羧化酶)提供一稳定的CO_2流量环境,以维持正常的光合作用。     

Zerumbone induced apoptosis in liver cancer cells via modulation of Bax/Bcl-2 ratio

Background  

Zerumbone is a cytotoxic component isolated from Zingiber zerumbet Smith, a herbal plant which is also known as lempoyang. This new anticancer bioactive compound from Z. zerumbet was investigated for its activity and mechanism in human liver cancer cell lines.