Does egg competition occur in marine broadcast‐spawners?

When the availability of sperm limits female reproductive success, competition for sperm, may be an important broker of sexual selection. This is because sperm limitation can increase the variance in female reproductive success, resulting in strong selection on females to compete for limited fertilization opportunities. Sperm limitation is probably common in broadcast-spawning marine invertebrates, making these excellent candidates for investigating scramble competition between broods of eggs and its consequences for female reproductive success. Here, we report our findings from a series of experiments that investigate egg competition in the sessile, broadcast-spawning polychaete Galeolaria caespitosa. We initially tested whether the order in which eggs encounter sperm affects their fertilization success at two ecologically relevant current regimes. We used a split-clutch-split--ejaculate technique to compare the fertilization success of eggs from individual females that had either first access (competition-free treatment) or second access (egg competition treatment) to a batch of sperm. We found that fertilization success depended on the order in which eggs accessed sperm; eggs that were assigned to the competition-free treatment exhibited significantly higher fertilization rates than those assigned to the egg competition treatment at both current speeds. In subsequent experiments we found that prior exposure of sperm to eggs significantly reduced both the quantity and quality of sperm available to fertilize a second clutch of eggs, resulting in reductions in fertilization success at high and low sperm concentrations. These findings suggest that female traits that increase the likelihood of sperm-egg interactions (e.g. egg size) will respond to selection imposed by egg competition.     

关于最大信息熵原理与群体遗传平衡一致性的探讨

汪小龙等建立了用最大信息熵原理推导一个基因座上群体遗传平衡的统一数学模型,并给出了模型的最大值解,此解正是Hardy-Weinberg平衡定律所给出的基因型频率。这说明当群体基因型信息熵最大时,群体基因型频率不再变化,达到平衡状态,从而证明了最大信息熵原理与Hardy-Weinberg平衡定律具有一致性,同时指出这一结论可以推广至有迁移、突变、选择、遗传漂变、近亲交配的群体以及多个基因座情形。概括地说就是：最大信息熵原理与群体遗传平衡具有一致性。但是,他们仅仅证明了最大信息熵原理与一个基因座上Hardy-Weinberg平衡定律具有一致性,本文在这个范围内将其推广至多个基因座,且每一个基因座均为复等位基因情形。至于最大信息熵原理是否与其它的群体遗传平衡具有一致性,他们的结论仅仅是猜想,并未严格推导。事实上,要想将这种一致性推广到迁移、突变、随机漂变和近亲交配等群体,则不见得正确。      

Optimal allocation between nutrient uptake and growth in a microbial trichome

 A microbial trichome grows by assimilating nutrients from its environment, and converting these into catalytic macro-molecular machinery. This machinery may be divided into assimilatory machinery and proliferative machinery. The former type is involved in nutrient uptake, whereas the latter type enables the trichome to grow. The cells in the trichome are faced with an allocation problem: given the availability of nutrients in the environment, how many macro-molecular building blocks should be allocated to the synthesis of assimilatory machinery, and how many to the synthesis of proliferative machinery? We answer this question for a particular model, which is a generalization of the Droop quota model. We formulate a two-dimensional non-linear optimal control problem, corresponding to this model. An optimal allocation regime with a singular segment is derived, based on Pontryagin’s maximum principle. We give a direct proof of optimality. We discuss how actual biological cells might implement this optimal regime. Received: 16 December 1996 / Revised version: 14 September 1997     

甜瓜不同变种及其杂交后代的香气特征研究

对4个甜瓜变种亲本及其相互间的4个杂交组合F1成熟果实中的香气组成特征及遗传表现进行了研究。结果显示:(1)甜瓜不同变种亲本成熟果实的香气组成特征差异很大,硬皮甜瓜(var.cantalupensis)变种(Charentais)香气成分主要以酯类物质为主,与呼吸跃变性状紧密相连;九碳醛类化合物是影响越瓜(var.conomon)变种八棱脆(Balengcui)的重要化合物;非呼吸跃变类型的冬甜瓜(var.inodorus)变种皇后(Queen)的特征性物质是九碳醇类化合物;其它类物质含量(OASPC)是香瓜变种(var.makuwa)甜宝(Tianbao)的一个主要特征。(2)对11个香气组成等性状进行主成分分析结果显示,前3个主成分累积贡献率达77.80%,PC1主要与酯类物质含量、香气种类数、醇类含量及醛类物质含量等呈显著相关关系,PC2则主要与其他类物质含量及乙烯释放速率显著相关,据此可将不同变种及组合区分开。(3)不同类型的香气类物质在不同变种的杂交组合中表现趋势不同,大部分的酯类化合物含量在F1代果实中居于双亲之间,且偏向于高亲值,而醛类、醇类以及其它类化合物在F1代均表现为接近低亲值。     

Sex differences in host defence interfere with parasite‐mediated selection for outcrossing during host–parasite coevolution

The Red Queen hypothesis proposes that coevolving parasites select for outcrossing in the host. Outcrossing relies on males, which often show lower immune investment due to, for example, sexual selection. Here, we demonstrate that such sex differences in immunity interfere with parasite‐mediated selection for outcrossing. Two independent coevolution experiments with Caenorhabditis elegans and its microparasite Bacillus thuringiensis produced decreased yet stable frequencies of outcrossing male hosts. A subsequent systematic analysis verified that male C. elegans suffered from a direct selective disadvantage under parasite pressure (i.e. lower resistance, decreased sexual activity, increased escape behaviour), which can reduce outcrossing and thus male frequencies. At the same time, males offered an indirect selective benefit, because male‐mediated outcrossing increased offspring resistance, thus favouring male persistence in the evolving populations. As sex differences in immunity are widespread, such interference of opposing selective constraints is likely of central importance during host adaptation to a coevolving parasite.     

肿瘤旋磁治疗机的基本原理与临床初步应用

ZCX-Ⅱ型旋磁治疗机由上下两对磁头组成,下磁头由电动马达驱动,而上磁头则是在下磁头耦合力的作用下而发生同步旋转,以达到人体组织纤维与磁力线发生相对运动,从而产生磁生物学效应的目的,属国际首创。随机选择的32例临床放弃治疗的晚期恶性肿瘤患者,使用ZCX-Ⅱ型肿瘤旋磁治疗机,采用不同的治疗参数进行治疗。结果观察,症状完全缓解率达28.1%,部分缓解率达65.6%,总有效率为93.8%1,年生存率为28.1%。治疗后所有患者的临床症状和体征均可得到不同程度的改善和缓解,且无任何严重地毒副作用。文中介绍了该设备的基本原理、使用方法和临床疗效,并对其临床相关问题进行简要讨论。     

一类Kolmogorov＇s系统的动力学性质

用定性分析的方法对一类Kolmogorov＇s系统进行了研究,讨论了系统平衡点的性态,给出了系统无闭轨的充分条件以及存在唯一稳定极限环的条件.改进了李万同（1992）和颜向平（2004）等人的工作.获得了一些新结果.     

我国实验动物福利发展战略与十二五生命科技发展需求及对策的探讨

实验动物福利越来越受到社会各方面的重视.欧美等发达国家已经建立起了一套比较完善的实验动物福利法规体系,而我国还没有专门的实验动物福利立法,与国外发达国家相比存在较大差距,但是不断出现的与实验动物福利有关的经贸技术壁垒以及十二五发展的需要使得实验动物福利成为我国目前亟待解决的战略问题.