Comparative properties of ferredoxins from a marine and freshwater species of Porphyridium

Ferredoxins were isolated from the freshwater red alga Porphyridium aerugineut, and from Porphyridium cruentum, a related marine species. A sin     

Effects of metabolic inhibitors on cell lethality and mutation induction in Chinese hamster cells. I. Inhibitors of de novo purine synthesis and a comparison with the effects of caffeine

The effect of pre- and posttreatment incubation of UV-irradiated and ethyl methanesulphonate (EMS) treated cells with non-toxic concentrations of inhibitors of de novo purine synthesis (dnPS) on expression of potentially lethal and premutational damage at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 cells has been examined. The concentrations of inhibitors used were shown to profoundly perturb de novo DNA synthesis, by measurements of [¹⁴C]formate uptake, and cell cycle progression by flow cytofluorimetry. Postincubation in 6-methyl mercaptopurine ribonucleoside (MMPR) usually but not invariably potentiated the cytotoxic effects of UV and EMS but azaserine (AZS) and methotrexate (MTX) were without effect. No effects on mutant frequencies were observed on posttreatment with any of these agents. Caffeine produced the least effect on dnPS, but invariably potentiated lethal damage. This potentiation of lethal damage is not mediated by dnPS inhibition as has been suggested for Chinese hamster ovary (CHO) cells.     

Developpement,Croissance et fecondite de cladoceres en fonction de la temperature et du niveau trophique. Elevage experimental in situ dans deux etangs

Samples of Daphnia longispina, Ceriodaphnia quadrangula and Bosmina longirostris have been simultaneously reared in cages immersed in two fish ponds differing principally by their trophic status.Vital parameters such as duration of postembryonic stage, rate of growth of young and adults as well as fecundity were studied against environmental factors.The importance of food quantity, temperature and of their interaction on size, rate of growth and fecundity was investigated.The magnitude of the discrepancies between these parameters as measured under natural and laboratory conditions is stressed.

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Developpement, Croissance et fecondite de cladoceres en fonction de la temperature et du niveau trophique. Elevage experimental in situ dans deux etangs

Institut Royal des Sciences Naturelles de Belgique et Service de Biologie, Université de l'Etat à Mons     

The structure of cyanobacterial phycobilisomes: a model

Phycobilisomes, supramolecular complexes of water-soluble accessory pigments, serve as the major light-harvesting antennae in cyanobacteria and red algae. Regular arrays of these organelles are found on the surface of the thylakoid membranes of these organisms. In the present study, the hemi-discoidal phycobilisomes of several species of cyanobacteria were examined in thin sections of cells and by negative staining after isolation and fixation. Their fundamental structures were found to be the same. Isolated phycobilisomes possessed a triangular core assembled from three stacks of disc-shaped subunits. Each stack contained two discs which were 12 nm in diameter and 6–7 nm thick. Each of these discs was probably subdivided into halves 3–3.5 nm thick. Radiating from each of two sides of the triangular core were three rods 12 nm in diameter. Each rod consisted of stacks of 2 to 6 disc-shaped subunits 6 nm thick. These discs were subdivided into halves 3 nm thick.The average number of discs of 6 nm thickness forming the peripheral rods varied among the strains studied. For certain chromatically adapting strains, the average rod length was dependent upon the wavelength of light to which cells were exposed during growth. Analyses of phycobilisomes by spectroscopic techniques, polyacrylamide gel electrophoresis, and electron microscopy were compared. These analyses suggested that the triangular core was composed of allophycocyanin and that the peripheral rods contained phycocyanin and phycoerythrin (when present). A detailed model of the hemi-discoidal phycobilisome is proposed. This model can account for many aspects of phycobiliprotein assembly and energy transfer.Abbreviations PBS phycobilisome(s) - PBP phycobiliprotein(s) - AP allophycocyanin - PC phycocyanin - PE phycoerythrin - PEC phycoerythrocyanin - AP-B allophycocyanin B - C- cyanobacterial - R- rhodophytan - B- Bangiophycean - SDS sodium dodecyl sulfate - LPP Lyngbya-Plectonema-Phormidium group - Na-KPO₄ buffers NaH₂PO₄ titrated with a solution of KH₂PO₄ of equivalent molarity to a given pH     

Environmental filtering rather than dispersal limitation dominated plant community assembly in the Zoige Plateau

Identifying the mechanisms that underlie the assembly of plant communities is critical to the conservation of terrestrial biodiversity. However, it is seldom measured or quantified how much deterministic versus stochastic processes contribute to community assembly in alpine meadows. Here, we measured the decay in community similarity with spatial and environmental distance in the Zoige Plateau. Furthermore, we used redundancy analysis (RDA) to divide the variations in the relative abundance of plant families into four components to assess the effects of environmental and spatial. Species assemblage similarity liner declined with geographical distance (p < .001, R ² = .6388), and it decreased significantly with increasing distance of total phosphorus (TP), alkali‐hydrolyzable nitrogen (AN), available potassium (AK), nitrate nitrogen (NO₃ ⁺–N), and ammonia nitrogen (NH₄ ⁺–N). Environmental and spatial variables jointly explained a large proportion (55.2%) of the variation in the relative abundance of plant families. Environmental variables accounted for 13.1% of the total variation, whereas spatial variables accounted for 11.4%, perhaps due to the pronounced abiotic gradients in the alpine areas. Our study highlights the mechanism of plant community assembly in the alpine ecosystem, where environmental filtering plays a more important role than dispersal limitation. In addition, a reasonably controlled abundance of Compositae (the family with the highest niche breadth and large niche overlap value with Gramineae and Cyperaceae) was expected to maintain sustainable development in pastoral production. These results suggest that management measures should be developed with the goal of improving or maintaining suitable local environmental conditions.     

梨小食心虫化学感受蛋白cDNA的克隆、序列分析及原核表达

为了研究梨小食心虫Grapholita molesta化学感受蛋白（chemosensory proteins, CSPs）在化学感受系统中的作用, 本研究利用RT-PCR和RACE技术克隆到一条梨小食心虫化学感受蛋白的全长cDNA序列, 命名为GmolCSP （GenBank 登录号： JQ821389）。序列分析表明, GmolCSP开放阅读框序列为384 bp, 编码127个氨基酸残基, 预测N末端含有18个氨基酸组成的信号肽序列, 其成熟蛋白的预测分子量为12.80 kD, 等电点为8.33。该基因编码的氨基酸序列与其他鳞翅目昆虫化学感受蛋白的氨基酸序列具有较高同源性。RT-PCR结果显示, GmolCSP在梨小食心虫成虫触角、 去触角的头、 胸、 腹、 足和翅中都有表达。将GmolCSP重组到表达载体pET-32a中, 转入大肠杆菌Escherichia coli BL21（DE3）进行表达。SDS-PAGE和Western 印迹检测结果显示, 梨小食心虫化学感受蛋白基因在大肠杆菌中成功地表达出一个分子量约为29 kD的融合蛋白, 与预测的融合蛋白分子量大小一致。本研究结果为进一步研究该蛋白的分子结构和功能奠定了良好基础。