Alopecia induced in young mice by exposure to excess dietary zinc

Second generation mice were exposed to normal (50 ppm, Group I) or excess (2000 ppm, Group II) zinc in the maternal diet during gestation and lactation, then weaned and continued on the mother's diet until sacrifice at 8 weeks. Tibia zinc reflected dietary intake. Group II had reduced plasma copper, body weight, and hematocrit; the second coat of hair appeared late and was lighter in color than Group I, possibly as an effect of copper and pigmentation development and hair growth.     

Mechanism of origin of complete hydatidiform moles

Complete or 'true' hydatidiform mole, an abnormality of human gestation, is characterized by hydropic degeneraton of all placental villi, marked hypertrophy of the trophoblast, absence of a fetus and a propensity to become malignant. The chromosome constitution of complete moles is usually 46,XX, and Kajii et al. reported that the entire genome in seven out of seven cases was paternal in origin, with all centromere markers homozygous for paternal heteromorphisms. These observations, since confirmed, can be explained by the fertilization of an 'empty' egg--no effective genome--by either a haploid sperm that then duplicates without cytokinesis, to restore the diploid number, or by a diploid sperm resulting from failure of the second meiotic division. We report here a study of a series of complete moles that shows the first alternative to be correct in the majority of cases.     

Complex lipid determines tissue-specific replication of Mycobacterium tuberculosis in mice

Tuberculosis is the leading cause of death in the world resulting from a single bacterial infection. Despite its enormous burden on world health, little is known about the molecular mechanisms of pathogenesis of Mycobacterium tuberculosis. Bacterial multiplication and concomitant tissue damage within an infected host, including experimentally infected mice, occurs primarily in the lungs-the favoured niche of M. tuberculosis. Although it has been proposed that the distinctive cell wall of M. tuberculosis is important for virulence, rigorous genetic proof has been lacking. Here, using signature-tagged mutagenesis, we isolated three attenuated M. tuberculosis mutants that cannot synthesize or transport a complex, cell wall-associated lipid called phthiocerol dimycocerosate (PDIM) which is found only in pathogenic mycobacteria. Two mutants have transposon insertions affecting genes implicated in PDIM synthesis; the third has a disruption in a gene encoding a large transmembrane protein required for proper subcellular localization of PDIM. Synthesis and transport of this complex lipid is only required for growth in the lung; all three mutants are unaffected for growth in the liver and spleen. This clearly shows that a lipid is required for M. tuberculosis virulence.     

施普林格·自然：以多种出版模式满足研究人员的需求

 自21世纪初开放获取运动兴起以来,科学研究过程中的文献访问障碍在一定程度上被消除,学术出版传播的模式也不断革新。随着互联网、大数据、人工智能等现代技术发展日益成熟并广泛运用于学术出版与交流,科技期刊已经从传统的、印刷形式为主的静态单刊,演化为单刊数字平台、刊群平台、集团平台、纯数字平台。三大变革影响着科技出版的过去和未来。第一是印刷向数字出版的过渡,期刊出版已将近完成了这一转变,这一数字化转变可称为可及性的变革。第二是由订阅模式向开放获取的转变,这一进程大概已完成了1/4,这可称作读者/用户的变革,因为它扫除阻挡研究成果被人阅读、使用和再使用的剩余障碍,对科研的未来至关重要。目前,正在进入一个扩展阶段,即从内容服务扩展到解决方案服务。