Comparative biochemical responses and antioxidant activities of the rabbit urinary bladder to whole grapes versus resveratrol

Molecular and Cellular Biochemistry - The objective of this study is to compare the antioxidant activity of a whole-grape suspension with the antioxidant activity or pure resveratrol on the effect...     

大亚湾冬季不同粒级浮游生物的氮稳定同位素特征及其与生物量的关系

生物量在营养级上的分布作为一种生态系统的指示指标,可以指示因人类干扰和环境变化导致的生态系统的改变,揭示生态系统功能的差异性。调查了冬季大亚湾不同区域各粒级浮游生物的生物量大小及其氮稳定同位素丰度比值(δ¹⁵N)与环境因子的关系,通过构建营养级谱比较了大亚湾不同区域浮游食物网结构的差异。研究结果显示,浮游生物的δ¹⁵N值基本随着粒径的增大而增加,但100-212 μm粒级的δ¹⁵N值为5.08‰,略低于1.2-100 μm粒级的5.58‰。> 500 μm 粒级的δ¹⁵N值最大,平均为8.16‰。在湾口和敞水带的S1、S9站各粒级的δ¹⁵N都要小于其他站位,而各粒级δ¹⁵N的最大值一般都出现在湾底的S8站。在各粒级颗粒物中,1.2-100 μm粒级的δ¹⁵N最适合用来指示水体的环境状况,受陆源输入影响较小的海域的δ¹⁵N值小。生物量与氮稳定同位素构建的营养级谱的斜率与总溶解氮的浓度和氮磷比呈显著负相关关系。处于湾口的站位的营养级谱的谱线要更陡峭一些,表明该处捕食者/被捕食者的比率更低。     

白色污染的治理及其展望

针对白色污染的危害及其严重性,综述了治理白色污染的重要技术,并对社会上使用的纸餐具以及相关可降解产品进行了探讨,最后提出要想彻底解决白色污染问题,就必须政策和技术并重。     

Multiplicity of infection does not accelerate infectivity evolution of viral parasites in laboratory microcosms

Coinfection with multiple parasite genotypes [multiplicity of infection (MOI)] creates within-host competition and opportunities for parasite recombination and is therefore predicted to be important for both parasite and host evolution. We tested for a difference in the infectivity of viral parasites (lytic phage Φ2) and resistance of their bacterial hosts (Pseudomonas fluorescens SBW25) under both high and low MOI during coevolution in laboratory microcosms. Results show that MOI has no effect on infectivity and resistance evolution during coevolution over ～80 generations of host growth, and this is true when the experiment is initiated with wild-type viruses and hosts, or with viruses and hosts that have already been coevolving for ～330 generations. This suggests that MOI does not have a net effect of accelerating parasite adaptation to hosts through recombination, or slowing adaptation to hosts through between-parasite conflict in this system.     

Diversity-disturbance relationships: frequency and intensity interact

An influential ecological theory, the intermediate disturbance hypothesis (IDH), predicts that intermediate levels of disturbance will maximize species diversity. Empirical studies, however, have described a wide variety of diversity-disturbance relationships (DDRs). Using experimental populations of microbes, we show that the form of the DDR depends on an interaction between disturbance frequency and intensity. We find that diversity shows a monotonically increasing, unimodal or flat relationship with disturbance, depending on the values of the disturbance aspects considered. These results confirm recent theoretical predictions, and potentially reconcile the conflicting body of empirical evidence on DDRs.     

Discrimination of the closely related A and B genomes in AABB tetraploid species of Avena

Fluorescent in situ (FISH) and Southern hybridization procedures were used to investigate the chromosomal distribution and genomic organization of the satellite DNA sequence As120a (specific to the A-genome chromosomes of hexaploid oats) in two tetraploid species, Avena barbata and Avena vaviloviana. These species have AB genomes. In situ hybridization of pAs120a to tetraploid oat species revealed elements of this repeated family to be distributed over both arms of 14 of the 28 chromosomes of these species. Genomes A and B were subsequently distinguished, indicating an allopolyploid origin for A. barbata. This was confirmed by assigning the satellited chromosomes to individual genomes, using the satellite itself and two ribosomal probes in simultaneous and sequential in situ hybridization analyses. Differences between A. barbata and A. vaviloviana genomes were also revealed by both FISH and Southern techniques using pAs120a probes. Whereas two B-genome chromosome pairs were found to be involved in intergenomic translocations in A. vaviloviana, FISH detected no intergenomic rearrangements in A. barbata. When using pAs120a as a probe, Southern hybridization also revealed differences in the hybridization patterns of the two genomes. A 1300-bp EcoRV fragment was present in A. barbata but absent in A. vaviloviana. This fragment was also detected in Southern analyses of A-genome diploid and hexaploid oat species. Received: 27 November 2000 / Accepted: 28 February 2001     

Portable oxygen and exercise tolerance in patients with chronic hypoxic cor pulmonale.

Breathing 30% oxygen during exercise alleviated arterial hypoxaemia and reduced minute ventilation in patients with severe chronic bronchitis. A similar level of oxygen (2 or 4 litres of oxygen/minute) from nasal prongs also increased their exercise tolerance, as assessed by the distance that they could walk on the level in 12 minutes. Nevertheless, a single-blind controlled study showed that the effort of carrying their portable supply of liquid oxygen, in the Union Carbide Oxygen Walker, abolished this gain in exercise tolerance. The improvement in walking distance was restored when oxygen on exercise was provided by wheeling the oxygen walker on a light-weight shopping trolley.