Localization of glycogen synthetase during differentiation of presumptive cell types in Dictyostelium discoideum.

Ultramicrochemical techniques were utilized to assay glycogen synthetase (EC 2.4.1.11) activity in cell samples of Dictyostelium discoideum as small as 0.01 mug (dry weight) in reaction volumes of 0.1 mul. The activity was assayed by an amplification procedure employing the enzymatic cycling of pyridine nucleotides. These techniques were used to determine the extent of localization of glycogen synthetase in the two cell types during differentiation of D. discoideum. Localization studies in developing spore cells revealed decreasing enzyme activity to the culmination stage. During this phase of development, the enzyme required the presence of soluble glycogen for activity. From culmination to sorocarp stage, enzyme activity increased and was independent of the soluble glycogen. In developing stalk cells, synthetase showed a decreasing gradient of activity. In sorocarps, the cells in the stalk apex showed synthetase activity similar to that of the spores. The cells at the bottom of the stalk had no detectable activity.     

Cell sheet technology: a promising strategy in regenerative medicine

Regenerative medicine is a burgeoning field that is important to combat challenging diseases and functional impairments. Compared with traditional cell therapies with evident shortcomings (e.g., cell suspension injection or tissue engineering with scaffolds), scaffold-free cell sheet technology enables transplanted cells to be grafted and fully maintain their viability on target sites. Clinical and experimental studies have advanced the application of cell sheet technology to numerous tissues and organs (e.g., liver, cornea and bone). However, previous reviews have failed to discuss vital aspects of this rapidly developing technology, and many new challenges are gradually emerging. This review aims to provide a comprehensive introduction to cell sheet technology from cell selection to the ultimate applications of cell sheets, and challenges and future visions are also described.     

基于InVEST模型的疏勒河流域碳储量时空变化研究

研究区域土地利用方式与生态系统服务碳储量的关系，对于区域生态系统保护及经济社会可持续发展具有重要意义。利用InVEST模型碳储量模块和CA-Markov模型，探究并预测疏勒河流域1990-2015及2015-2040年流域生态系统碳储量时空变化特征及其与土地利用方式之间的关系。结果表明：疏勒河流域1990、1995、2000、2005、2010、2015年碳储量分别为7.994×10⁸、7.996×10⁸、7.998×10⁸、8.038×10⁸、8.064×10⁸、8.071×10⁸t，呈逐年增加趋势，累计增加7.7×10⁶t。土地利用类型变化是导致生态系统碳储量变化的主要因素，未利用地向耕地和草地转化有利于碳储量增加，而草地向耕地和未利用地的转化则导致碳储量减少。疏勒河流域碳储量存在显著的空间格局，碳储量较高区域呈现"北部点状-中部带状-南部点状片状"特征，这种分布格局与流域土地利用类型紧密联系。预测表明至2040年疏勒河流域碳储量为9.128×10⁸t，较2015年增加13.1%，主要原因是草地、耕地和林地面积较大幅度增长，提高了流域内的碳储量。     

Organic,inorganic, and caloric composition of eggs,pentaculae, and adults of the brooding sea cucumber Cucumaria curata cowles (Echinodermata: Holothuroidea)

Levels (percentage composition) of water, ash, carbohydrate, lipid, protein, and calories were determined for eggs, pentaculae, and adults of the sea cucumber Cucumaria curata Cowles. Component contents (μg/individual) were calculated for eggs and pentaculae. During the 28 days of development to hatching, the large yolky eggs gain water and ash, the total dry weight increasing from 169 to 190 μg/egg during embryogenesis. There were no statistically significant changes in lipid, protein, and caloric contents during embryogenesis, but carbohydrate decreased by 0.82 μg/egg.The decrease in carbohydrate is sufficient to account for estimated embryonic energy requirements. Based on the utilization of carbohydrate, embryos of C. curata show a nutritional pattern similar to that of the planktonic embryos of sea urchins and different from that of embryos developing from terrestrial eggs, freshwater eggs, and planktonic and demersal marine eggs.Although broods varied widely in egg number and mean egg dry weight, C. curata gives eggs which contain a constant proportion of organic components.Levels of ash, water, and protein in the adults exceeded those in the pentacula, and lipid comprises a much smaller proportion of the adult body than it did of the pentacula.