自杀意念者产生自杀行动的双系统模型

自杀一直以来是全球非自然死亡的主要原因之一,目前已有大量用于解释自杀行为的理论,但缺乏对自杀意念到自杀行动产生的内部机制的完善解释。自杀可以看作是自我控制失败的结果,借助于自我控制的双系统模型理论,分别从冲动系统和控制系统展开了对自杀意念者产生自杀行动的内部机制的分析。基于自杀意念者的负性情绪、高自我损耗、低认知灵活性三种心理特征,冲动系统能够引起自杀行动的自动化加工;控制系统对自杀行动的产生既有抑制作用,也有一定的促进作用;状态和特质边界条件影响冲动系统和控制系统的强弱关系。通过对自杀行动产生的内部机制进行探讨,为自杀理论的相关理论研究提供新的方向。未来可对自杀行动产生的双系统模型进行实证检验,识别出不同类型自杀者的控制系统差异,探究冲动系统内外部影响因素的交互作用。

Bifunctional chimeric SuperCD suicide gene -YCD: YUPRT fusion is highly effective in a rat hepatoma model

AIM： To investigate the effects of catalytically superior gene-directed enzyme prodrug therapy systems on a rat hepatoma model. METHODS： To increase hepatoma cell chemosensitivity for the prodrug 5-fluorocytosine （5-FC）, we generated a chimeric bifunctional SuperCD suicide gene, a fusion of the yeast cytosine deaminase （YCD） and the yeast uracil phosphoribosyltransferase （YUPRT） gene. RESULTS： In vitro stably transduced Morris rat hepatoma cells （MH） expressing the bifunctional SuperCD suicide gene （MH SuperCD） showed a clearly marked enhancement in cell killing when incubated with 5-FC as compared with MH cells stably expressing YCD solely （MH YCD） or the cytosine deaminase gene of bacterial origin （MH BCD）, respectively. In vivo, MH SuperCD tumors implanted both subcutaneously as well as orthotopically into the livers of syngeneic ACI rats demonstrated significant tumor regressions （P〈0.01） under both high dose as well as low dose systemic 5-FC application, whereas MH tumors without transgene expression （MH naive） showed rapid progression. For the first time, an order of in vivo suicide gene effectiveness （SuperCD〉〉 YCD〉〉BCD〉〉〉negative control） was defined as a result of a direct in vivo comparison of all three suicide genes. CONCLUSION： Bifunctional SuperCD suicide gene expression is highly effective in a rat hepatoma model, thereby significantly improving both the therapeutic index and the efficacy of hepatocellular carcinoma killing by fluorocytosine.

Novel function of perforin in negatively regulating CD4^＋ T cell activation by affecting calcium signaling

Perforin is a pore-forming protein engaged mainly in mediating target T cell death and is employed by cytotoxic T lymphocytes （CTLs） and natural killer cells. However, whether it also plays a role in conventional CD4^＋ T cell function remains unclear. Here we report that in perforin-deficient （PKO） mice, CD4^＋ T cells are hyperproliferative in response to T cell receptor （TCR） stimulation. This feature of hyperproliferation is accompanied by the enhancement both in cell division and in IL-2 secretion. It seems that the perforin deficiency does not influence T cell development in thymus spleen and lymph node. In vivo, perforin deficiency results in increased antigen-specific T cell proliferation and antibody production. Furthermore, PKO mice are more susceptible to experimental autoimmune uveitis. To address the molecular mechanism, we found that after TCR stimulation, CD4^＋ T cells from PKO mice display an increased intracellular calcium flux and subsequently enhance activation of transcription factor NFAT1. Our results indicate that perforin plays a negative role in regulating CD4^＋ T cell activation and immune response by affecting TCR-dependent Ca^2＋ signaling.

Time to feed： How diet, competition, and experience may influence feeding behaviour and cannibalism in wood frog tadpoles Lithobates sylvaticus

Wood frog Lithobates sylvaticus tadpoles develop in temporary wetlands where high population densities can force tadpoles into aggregations that intensify competition and can lead to cannibalism. However, chemical alarm cues released from injured conspecifics could also dissuade cannibalism. The purpose of this study was to test mechanisms that may influence can- nibalistic behaviour. We tested whether the tendency of tadpoles to consume conspecifics would increase with the presence of competition and/or cues of profitable diets. Tadpoles placed in 1L experimental containers were tested for feeding initiation times of multiple diets, including conspecific tissues and conspecific tissues combined with chemical cues from the alternative diets （brine shrimp and comrneal）. Tadpoles were tested in the presence and absence of a competitor, and at multiple times over the course of the study. Tadpoles exhibited an altered response to diets over time; however the presence of a competitor reduced re- sponse times to all diets including conspecific tissues. Similarly, the presence of specific diets also reduced the response time of tadpoles to conspecific tissues. These results suggest competition among feeding tadpoles could result in aggressive behaviour leading to indiscriminate predation and cannibalism [Current Zoology 60 （5）： 571-580, 2014 ].

时事聚焦：国际（4月24日-4月30日）

中国(7月3日-7月9日) 全国1.5万干部学历学位有假。4日,中组部等部门联合发布的《关于干部学历、学位检查清理工作的报告》指出,各地、各部门对全国党政机关、事业单位县处级以上干部和中管企业领导人员共67万多人的学历、学位重新进行了审核,并对15000多例误填、错填或虚填、假填的学历、学位进行了纠正和规范。