科学家“实验室培育肾”移植老鼠

　　美国科研人员说，一个在实验室“培育”的老鼠肾已经移植到一只老鼠身上并开始产生尿液。

　　英国广播公司４月１４日报道，《自然—医学》杂志刊登的一篇研究文章说，“改造肾”虽不如“天然肾”效用高，但研究人员认为这一领域前景广阔。按照设想，研究人员把一个老化肾中的细胞剥离，剩下蜂巢状“支架”，再移入接受移植患者的细胞。

　　马萨诸塞综合医院研究人员已经完成第一道步骤，除去一个老鼠肾里的细胞。接下来１２天，他们把这个肾放置在一个模拟老鼠体内环境的特殊烘箱中。“改造肾”在实验室接受测试时，产尿效能达到天然肾的２３％。不过，植入一只老鼠体内后，这一指标下降至５％。

　　研究小组主管哈拉尔德·奥特对研究成果满意，说“改造肾”如果能有天然肾１０％至１５％的效能，患者将不再需要血液透析。

　　研究人员说，“改造肾”技术有两个主要优点：“改造肾”与患者匹配，患者接受移植后不需要终身服用抗排异药物；这将大幅增加可移植器官的数量，缘由是大部分可移植器官因与患者不匹配而无法移植，却可以在接受“改造”后移植。

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Molecular Cloning of Novel Antimicrobial Peptide Genes from the Skin of the Chinese Brown Frog, Rana chensinensis
Abstract
One species of the Chinese brown frog, Rana chensinensis, is widely distributed in north-central China. In this study, a cDNA library was constructed to clone the antimicrobial peptides' genes from the skin of R. chensinensis. Twenty-three prepropeptide cDNA sequences encoding twelve novel mature antimicrobial peptides were isolated and characterized. Six peptides belonged to three known families previously identified from other Ranid frogs: temporin (4 peptides), brevinin-2 (1 peptide), and palustrin-2 (1 peptide). The other six peptides showed little similarity to known antimicrobial peptides. According to the amino acid sequences, with or without α-helix structure, and either hydrophilic or hydrophobic, these were organized into four new families: chensinin-1 (3 peptides), chensinin-2 (1 peptide), chensinin-3 (1 peptide), and chensinin-4 (1 peptide). Five peptides from different families were chemically synthesized, and their antimicrobial, cytolytic, and hemolytic activities were evaluated. Of these, brevinin-2CE showed strongest antimicrobial activities against both the Gram-positive and Gram-negative bacteria with a slight hemolysis. Temporin-1CEe and palustrin-2CE also displayed a slight hemolysis, but they had different activities to prokaryotic cells. Temporin-1CEe showed higher antimicrobial activity against Gram-positive bacteria than Gram-negative bacteria, whereas it was contrary to palustrin-2CE. Chensinin-1 CEb and chensinin-3CE only had moderate antimicrobial activity against microorganisms. In addition, the brevinin-2 peptides from different brown frogs were analyzed to reveal the taxonomy and phylogenetic relationships of R. chensinensis.