Maternal investment, sex-differential prospects, and the sex ratio in wild house mice

In a population of first-generation offspring from wild-caught house mice (Mus musculus domesticus), previous evidence suggested that male fitness is more strongly affected by an increase in body weight than female fitness. This paper shows that in these mice the young are weaned at heavier weights the smaller the litter and the better the maternal body condition. These effects persisted into adulthood and were less pronounced in female young. However, contrary to expectation from conventional sex ratio theory, maternal condition and litter size had no detectable effect on sex ratios. Also, litter size did not affect sex ratios in two populations of laboratory-kept, wild-caught western (M. m. domesticus) and eastern house mice (M. m. musculus). Wild house mice, therefore, appear not to adaptively manipulate the sex ratio of offspring. It is argued that this absence of sex ratio trends might not be maladaptive, but rather that models currently used to predict sex ratio trends in rodents may not be valid. Received: 13 March 1997 / Accepted after revision: 9 August 1997     

Women infected with parasite Toxoplasma have more sons

The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings and the socioeconomic status of the parents. As parasite infection affects many immunological and physiological parameters of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born from 1996 to 2004 contained information regarding the mother’s age, concentration of anti-Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I.₉₅ = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable.     

VR1+细胞模型的构建和Nielsen假说的验证

为研究类香草素受体(vanilloid receptortype 1,VR1)作为刺激性室内空气污染物的触发性生物靶分子的生理作用,在VR1-cDNA质粒基础上,应用分子克隆和细胞转染技术构建了体外培养的VR1 -HEK293细胞模型,应用此细胞模型进行辣椒素和甲醛致VR1 -HEK293细胞死亡实验.结果表明,VR1 -HEK293细胞模型构建成功,VR1 细胞死亡实验是一种简便有效的鉴定VR1体外表达的实验方法;甲醛能够激活VR1,且激活反应能被VR1特异性拮抗剂capsazepine所阻断,从而推断甲醛对气道的刺激作用也是通过VR1所介导的.用体外细胞学实验证实了VR1是甲醛作用的生物靶分子,以实验证实了Nielsen假说的正确性.     

Chlorinated dioxins and furans as trace products of combustion: Some theoretical aspects

Recent advances in combustion theories are reviewed, especially the detailed mechanisms of hydrocarbon oxidation, formation of polynuclear aromatic hydrocarbon from aliphatic fuels, and the behavior of halogens in flames. Experimental observations of polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) formation in combustion of aliphatic fuels such as acetylene, ethylene and methane in the presence of hydrogen chloride are summarized. Then, from combustion chemistry considerations a reaction mechanism for T₄CDD/F formation in the CH₄/ HCl/O₂ system is developed. This mechanism consists of elementary reactions describing the main oxidation steps, formation of chlorinated C₁‐ to C₄‐species, formation of the first aromatic ring, and T₄CDD/F formation. The mechanism may be extended to other hydrocarbon fuels and higher PCDD/F homologues. Possible relevance of the mechanism to the “trace chemistries of fire hypothesis”; is discussed.     

碳排放权交易试点是否促进了对外直接投资?

环境规制与跨国投资之间的关系一直是学术界关注的焦点。作为重要的环境规制手段,碳排放权交易试点的推进标志着我国环境规制强度的增强。对外直接投资(OFDI)作为最典型的跨国经济活动之一,是中国"走出去"战略的重要组成部分。近年来,中国对外直接投资存量与净额都呈现稳定的上升趋势,与此同时,环境规制强度也在不断提升。中国对外直接投资是否受到国内环境规制加强的影响值得探讨,而2013年正式启动碳排放权交易试点为解决此问题提供了一个准自然实验场景。基于此,文章使用中国30个省级行政单位2010—2019年的面板数据,以北京、上海、广东、天津、湖北、重庆和福建开展的碳排放权交易试点作为准自然实验,运用双重差分法(DID)研究碳排放权交易试点的开展是否提升了对外直接投资水平。研究结论表明,碳排放权交易试点能够显著提升我国对外直接投资水平。且该结论在平行趋势检验、合成控制法(SCM)、安慰剂检验等检验后依旧稳健。此外,潜在机制的研究发现碳排放权交易试点满足"污染避难所假说"和"波特假说",进而促进了对外直接投资水平的提升。通过净效应的初步讨论,文章发现"污染避难所假说"仍旧在目前占据主导地位。研究结论意味着:(1)未来要继续推进全国统一的碳排放权交易市场建设;(2)持续探索激发碳排放权交易试点对创新产生的激励效应;(3)完善投资便利化的制度与措施,搭建国际技术交易或信息平台等。一方面促进我国生态环境的改善,另一方面促进对外投资水平的增质提量。