Turnover of cell surface-bound capsular polysaccharide in Staphylococcus aureus

The capsular polysaccharide (CPS) of Staphylococcus aureus strain Smith was labelled by growth of bacteria in the presence of radioactive N-acetylglucosamine and was separated from labelled cell wall components by affinity chromatography on wheat germ agglutinin following dissolution of the cells by lysostaphin. The products were partially characterised chemically and immunochemically. Similar labelled components were found in the culture fluid during growth. In a pulse-chase experiment, cell-bound CPS was released continuously into the culture fluid at the same rate as cell wall turnover and there was no evidence of direct excretion of CPS.     

Cub growth and maternal care in cheetahs

Using cub growth as an index, I examine the influence of maternalnutrition, litter size, and cub sex on maternal care in cheetahs(Acinonyx jubatus) and compare cub and litter growth rates withthose of other large feilds. Seventy-nine free-living cheetahcubs in 21 litters from 15 mothers were weighed at least oncebetween 6 and 48 days of age. Eleven litters were weighed atthe beginning and end of a 5-day observation of their mothers.The mean cub growth rate varied significantly between litters,due primarily to differences in maternal food intake. Growthdeclined sharply when maternal food intake was less than 1.5kg/ day, but did not increase with greater levels of food intake.Lower limits of growth rates may therefore have been set bythe mother's food intake, whereas upper limits may be set bythe intrinsic physiological ability of cubs to grow. Althoughmale cubs were heavier than female cubs in the same litter whenfirst weighed, major differences in growth rate between thesexes were not apparent at this stage. Both cheetah cubs andlitters grow fast relative to other large felids, and I arguethat this may be an adaptation to the high rate of cheetah juvenilemortality from predation.     

A living environment. Objectives and measures in the Swedish Government Bill on environmental policy 1990/91, pertaining to waters and the seas

Increased international cooperation to limit transboundary and global environmental problems, increased sectoral responsibility and decentralization, and improved information and statistics on the state of the environment are the main lines for the development of future environmental policy. For lakes, watercourses, and the seas the overall objective is to maintain viable, balanced populations of naturally occurring species. Pollution is not to limit the use of water for fishing, recreation, or water supply. Foreign species or organisms subjected to genetic mutation are only to be introduced with great restriction. Measures are suggested that will reduce environmental disturbances from agriculture and forestry, traffic, energy production, industry, goods, chemical products, and waste.Paper presented at Seminar on Ecosystems Approach to To Water Management (Oslo, Norway, 27–31 May 1991).     

Temperature gradient gel electrophoresis: detection of a single base substitution in the cattle β-lactoglobulin gene

An A in equilibrium with G transition in exon III is known to differentiate alleles A and B of the cattle beta-lactoglobulin (BLG) gene. A BLG exon III fragment containing the transition site was amplified by the polymerase chain reaction. Temperature gradient gel electrophoresis (TGGE) was then used to detect this transition and hence to genotype cattle: the AT base-pair in allele A was readily distinguished from the GC base-pair of allele B. TGGE can be used to detect any single base-pair substitution, and thus is a powerful method of detecting genetic variability.     

濒危植物永瓣藤叶片功能性状对环境因子的响应

植物叶片功能性状能够响应环境条件的变化，反应了植物对环境的适应策略。当前，针对藤本植物叶片功能性状地理格局及其环境驱动力的研究较少。以国家重点保护植物永瓣藤（Monimopetalum chinense）为研究对象，对其分布区内11个种群的15个叶片功能性状进行测量，并结合气候、土壤因子来解释叶性状变异。比较叶片性状在局域和区域尺度上的种内变异程度，利用多元逐步回归分析环境因子对叶性状的影响。结果表明，在局域尺度上，永瓣藤叶功能性状变异系数介于3.0%-22.5%，其中，叶面积变异程度最大，叶片碳含量变异最小。永瓣藤叶片形状随纬度上升而变得宽且圆。叶片磷含量相对较低，永瓣藤的生长可能受到了磷限制。土壤与气候因子是叶片性状的重要驱动因素，解释了25%-97%的叶片性状变异。在温度和水分充足的情况下，永瓣藤叶片趋向于的慢速生长的保守策略。总体来说，永瓣藤叶片功能性状通过一定的种内变异和性状组合，并与气候、土壤因子相互作用，适应当前的环境条件。     

Ant assemblage composition explains high predation pressure on artificial caterpillars during early night

1. Predator–prey interactions, especially those involving herbivorous insects, are of great importance in maintaining biodiversity. Predation pressure varies temporally in response to prey availability and activity. However, little is known about the patterns and drivers of fluctuations in predation pressure at fine temporal scales. 2. Artificial caterpillars (placed on plant leaves at breast height) were used to assess changes in predation pressure across four time intervals of the day in a monsoonal tropical rainforest in south-west China. The study examined how assemblage composition of arboreal ants, the dominant predators, changed across the same time intervals. The potential linkages between biotic (arboreal ants) and abiotic (temperature and light intensity) factors with predation rate were evaluated. 3. Predation rate on caterpillars during the early part of the night (19.00–01.00 hours) was significantly higher than in the morning, afternoon, or late night. Ant assemblage composition, rather than species richness or total abundance, best explained the variations in predation rate on artificial caterpillars. 4. The results help to strengthen understanding of trophic interactions by demonstrating that predation pressure fluctuates at finer timescales than previously tested, and that a particular set of ant species may play major roles in predation on caterpillars and possibly other organisms.