科尔沁沙地不同密度小叶锦鸡儿灌丛水量平衡研究

根据沙地水分平衡理论推算了不同栽植密度下小叶锦鸡儿灌丛的蒸散量.结果表明,小叶锦鸡儿灌丛生长期土壤水分含量随着植被密度增加而降低,0.5 m×1 m、1 m×2 m密度植被区平均土壤含水量低于凋萎湿度(1.55%),2 m×2 m密度植被和天然小叶锦鸡儿植被平均土壤含水量保持在1.60%以上,能够满足植被生存和生长的水分需求.蒸散量随着植被密度增加而增大,以0.5 m×1 m密度灌丛区最高,为297.81 mm,占同期降水量的97.90%;2 m×2 m密度灌丛区最低,为279.71 mm,生长期末期土壤水分节余为24.49 mm.依据生长期土壤水分状况和水分平衡要求,科尔沁沙地小叶锦鸡儿灌丛适宜密度应为2 m×2 m.     

一种提取动物基因组总DNA的野外样品保存方法

为了确定一种方便的野外动物样品保存方法,以新鲜材料作对照,从-20℃冰箱、70%乙醇、含50mmol/L EDTA的70%乙醇、95%乙醇、液氮处理的高原鼠肌肉和肝脏组织中提取基因组总DNA。通过琼脂糖凝胶电泳和紫外分光光度计对提取的基因组总DNA质量进行检测。结果显示:相同处理的肝脏DNA产量大,肌肉组织提取的DNA质量好;各种保存方法提取的DNA降解程度依次为,-20℃冰箱、70%乙醇>含50mmol/L EDTA的70%乙醇、95%乙醇>液氮>新鲜。选择新鲜肌肉和95%酒精处理的肌肉样品提取的总DNA作模板,进行微卫星PCR扩增,均可获得清晰的电泳带。将该方法用于高原鼢鼠,进行线粒体12S rRNA、Cytb和D-loop区测序,结果显示该方法保存的样品与新鲜样品没有差别。因此,在野外用95%乙醇固定肌肉样品是一种可行的样品保存方法。     

Maintenance and Distribution of Epithelial Stem/Progenitor Cells after Corneal Reconstruction Using Oral Mucosal Epithelial Cell Sheets

We assessed the maintenance and distribution of epithelial stem/progenitor cells after corneal reconstruction using tissue-engineered oral mucosal cell sheets in a rat model. Oral mucosal biopsy specimens were excised from green fluorescent protein (GFP) rats and enzymatically treated with Dispase II. These cells were cultured on inserts with mitomycin C-treated NIH/3T3 cells, and the resulting cell sheets were harvested. These tissue-engineered cell sheets from GFP rats were transplanted onto the eyes of a nude rat limbal stem cell deficiency model. Eight weeks after surgery, ocular surfaces were completely covered by the epithelium with GFP-positive cells. Transplanted corneas expressed p63 in the basal layers and K14 in all epithelial layers. Epithelial cells harvested from the central and peripheral areas of reconstructed corneas were isolated for a colony-forming assay, which showed that the colony-forming efficiency of the peripheral epithelial cells was significantly higher than that of the central epithelial cells 8 weeks after corneal reconstruction. Thus, in this rat model, the peripheral cornea could maintain more stem/progenitor cells than the central cornea after corneal reconstruction using oral mucosal epithelial cell sheets.     

西藏乃东县发现豆雁

正2016年1月6日,在西藏自治区乃东县泽当镇羌哉村(29°16′29.634″N,95°49′44.202″E,海拔3 557 m)观察到2只雁,该雁全身以灰褐色为主,尾下覆羽为白色,脚为橙黄色,喙黑色、喙端有黄斑,嘴甲和鼻孔间有白色斑点,两胁具灰褐色黄斑。经鉴定为豆雁(Anser fabalis)(约翰·马敬能等2000,Mark 2009,曲利明2014)。查阅相关文献(中国科学院青藏高原综合科学考察队1983,赵正阶2001,郑光美2011,刘迺发等2013),确认     

Role of lysine in the replication of reovirus: I. Synthesis of complete and empty virions

Lysine is essential for the replication of infectious reovirus. Omission of lysine from the extracellular medium not only permitted the continued synthesis of structural viral proteins and viral double-stranded ribonucleic acid (RNA), but also caused an enhanced formation of viral structures which were separable by isopycnic sedimentation of CsCl into a top band consisting of empty particles with a buoyant density of 1.29 g/cm³ and essentially free of viral RNA, and two lower bands which were difficult to resolve and had an average buoyant density of 1.37 g/cm³. The lower bands contained most of the viral nucleic acid. The above effects were reversed when lysine was restored early after infection. In contrast, a single band with a buoyant density of 1.38 g/cm³ was obtained from lysine-plus infected cells.     

Contamination and survival of Pseudomonas aeruginosa in hospital used sponges.

The microbial contamination of in-use sponges was investigated. Of the sixty sponges examined, 51 (85%) were contaminated with 10(3)-10(9) colony forming units (CFU) per sponge. Pseudomonas aeruginosa was isolated from sixteen (26.7%) of the sixty sponges. P. aeruginosa survived for 2 months in contaminated sponges which were left at room temperature and became dry to the touch. The susceptibility of sponges to P. aeruginosa contamination should be recognized. Once sponges are contaminated with P. aeruginosa, eradication of this organism is difficult even if the sponges are dried.     

Positive selection driving the evolution of a gene of male reproduction, Acp26Aa, of Drosophila: II. Divergence versus polymorphism

The evolution of the gene for a male ejaculatory protein, Acp26Aa, has been shown to be driven by positive selection when nonsibling species in the Drosophila melanogaster subgroup are compared. To know if selection has been operating in the recent past and to understand the details of its dynamics, we obtained DNA sequences of Acp26Aa and the nearby Acp26Ab gene from 39 D. melanogaster chromosomes. Together with the 10 published sequences, we analyzed 49 sequences from five populations in four continents. The southern African population is somewhat differentiated from all other populations, but its nucleotide diversity is lower at these two loci. We find the following results for Acp26Aa: (1) The R: S (replacement : silent changes) ratio is significantly higher in the between-species comparisons than in the within-species data by the McDonald and Kreitman test. Positive selection is probably responsible for the excess of amino acid replacements between species. (2) However, within-species nucleotide diversity is high. Neither the Tajima test nor the Fu and Li test indicates a reduction in nucleotide diversity due to positive selection in the recent past. (3) The newly derived nucleotides in D. melanogaster are at high frequency significantly more often than predicted by the neutral equilibrium. Since the nearby Acp26Ab gene does not show these patterns, these observations cannot be attributed to the characteristics of this chromosomal region. We suggest that positive selection is active, but may be weak, for each amino acid change in the Acp26Aa gene.