Specificities of heparan sulphate proteoglycans in developmental processes

Heparan sulphate proteoglycans are abundant cell-surface molecules that consist of a protein core to which heparan sulphate glycosaminoglycan chains are attached. The functions of these molecules have remained mostly underappreciated by developmental biologists; however, the actions of important signalling molecules, for example Wnt and Hedgehog, depend on them. To understand both the mechanisms by which ligands involved in development interact with their receptors and how morphogens pattern tissues, biologists need to consider the functions of heparan sulphate proteoglycans in signalling and developmental patterning.     

Heparan sulphate bound growth factors: a mechanism for stromal cell mediated haemopoiesis

The proliferation and development of haemopoietic stem cells takes place in close association with marrow stromal cells. This intimate cell contact presumably enables the stem cells and their progeny to respond to stimuli present on the stromal cell surface. While the nature of these stimuli has not been determined, it is likely that growth factors play some role. Recently, it was demonstrated that the natural and the recombinant haemopoietic growth factor, granulocyte/macrophage colony stimulating factor (GM-CSF), could be adsorbed out of solution by an extract of human marrow stromal extracellular matrix (ECM) with retention of biological activity. However, the precise ECM molecules involved were not identified. Here, we clearly demonstrate that the major sulphated glycosaminoglycan of mouse marrow stroma, heparan sulphate, possesses the ability to adsorb both GM-CSF and the multilineage haemopoietic growth factor, Interleukin 3 (IL-3). Furthermore, these growth factors, once bound, can be presented in the biologically active form to haemopoietic cells.     

集中参数模型模拟近生理压力波形

为了更好的研究细胞在近生理环境下的力学响应,本文利用集中参数模型,通过数值模拟的结果来指导实验.在平行平板流动腔前后添加必要的元件构成三元件三单元的集中参数模型,通过改变参数来模拟各种近生理压力波形.     

十二烷基硫酸钠的纯化

为得到满足表面化学实验研究规格的十二烷基硫酸钠（以下简称ＳＤＳ），用水结晶、泡沫分离、乙醇三次重结晶、乙醚抽提等方法，对市售的一种Ｃ．Ｐ．级试剂进行纯化处理．就所得结果对各种纯化方法的特点进行比较、分析和讨论，据此提出了一种纯化市售Ｃ．Ｐ．级试剂的方案，并用于另一种市售Ｃ．Ｐ．级试剂的纯化，获得满意的结果．     

酸性KMnO4-HCHO化学发光体系检测硫酸庆大霉素注射液中硫酸庆大霉素的含量

在酸性条件下,高锰酸钾氧化硫酸庆大霉素(Gentamicin sulphate)产生微弱化学发光,而甲醛的存在可以对该化学发光有增敏作用。该化学发光强度随硫酸庆大霉素浓度的增加而增强,并由此建立一种甲醛-酸性高锰酸钾化学发光体系快速测定硫酸庆大霉素的方法。在优化条件下,硫酸庆大霉素在5.0×10~(-5)～5.0×10~(-4 )g/mL的浓度范围内呈良好的线性关系,ΔI=3.338 24 c-7.379 34(R~2=0.995 3),方法检测限为1.5×10~(-5 )g/mL(S/N=3),并对3.0×10~(-4 )g/mL的硫酸庆大霉素10次平行测定,其相对标准偏差(RSD)为1.4%。并将建立的流动注射化学发光分析方法应用于硫酸庆大霉素注射液中硫酸庆大霉素的含量测定,方法简单,结果令人满意。     

紧密联系日常生活和临床提高生理学教学质量

探讨如何联系日常生活和临床实际上好生理课,提高生理学教学质量.教师要拓宽知识面,在教学中联系身边熟悉的事例,提高学生的学习兴趣和主动性;同时紧密联系临床病例突出生理学的临床实用性,笔者在教学中采取导入式和汇聚式教学方法,将生理学知识与临床相互渗透,即可加强基础理论知识的学习,同时可培养学生运用生理知识分析问题和解决问题的能力,从而有效地提高生理学理论教学效果.     

Seasonal bone growth and physiology in endotherms shed light on dinosaur physiology

Cyclical growth leaves marks in bone tissue that are in the forefront of discussions about physiologies of extinct vertebrates. Ectotherms show pronounced annual cycles of growth arrest that correlate with a decrease in body temperature and metabolic rate; endotherms are assumed to grow continuously until they attain maturity because of their constant high body temperature and sustained metabolic rate. This apparent dichotomy has driven the argument that zonal bone denotes ectotherm-like physiologies, thus fuelling the controversy on dinosaur thermophysiology and the evolution of endothermy in birds and mammal-like reptiles. Here we show, from a comprehensive global study of wild ruminants from tropical to polar environments, that cyclical growth is a universal trait of homoeothermic endotherms. Growth is arrested during the unfavourable season concurrently with decreases in body temperature, metabolic rate and bone-growth-mediating plasma insulin-like growth factor-1 levels, forming part of a plesiomorphic thermometabolic strategy for energy conservation. Conversely, bouts of intense tissue growth coincide with peak metabolic rates and correlated hormonal changes at the beginning of the favourable season, indicating an increased efficiency in acquiring and using seasonal resources. Our study supplies the strongest evidence so far that homeothermic endotherms arrest growth seasonally, which precludes the use of lines of arrested growth as an argument in support of ectothermy. However, high growth rates are a distinctive trait of mammals, suggesting the capacity for endogenous heat generation. The ruminant annual cycle provides an extant model on which to base inferences regarding the thermophysiology of dinosaurs and other extinct taxa.     

紧密联系日常生活和临床提高生理学教学质量

探讨如何联系日常生活和临床实际上好生理课,提高生理学教学质量.教师要拓宽知识面,在教学中联系身边熟悉的事例,提高学生的学习兴趣和主动性;同时紧密联系临床病例突出生理学的临床实用性,笔者在教学中采取导入式和汇聚式教学方法,将生理学知识与临床相互渗透,即可加强基础理论知识的学习,同时可培养学生运用生理知识分析问题和解决问题的能力,从而有效地提高生理学理论教学效果.     

Chondroitin proteoglycans are involved in cell division of Caenorhabditis elegans

Glycosaminoglycans such as heparan sulphate and chondroitin sulphate are extracellular sugar chains involved in intercellular signalling. Disruptions of genes encoding enzymes that mediate glycosaminoglycan biosynthesis have severe consequences in Drosophila and mice. Mutations in the Drosophila gene sugarless, which encodes a UDP-glucose dehydrogenase, impairs developmental signalling through the Wnt family member Wingless, and signalling by the fibroblast growth factor and Hedgehog pathways. Heparan sulphate is involved in these pathways, but little is known about the involvement of chondroitin. Undersulphated and oversulphated chondroitin sulphate chains have been implicated in other biological processes, however, including adhesion of erythrocytes infected with malaria parasite to human placenta and regulation of neural development. To investigate chondroitin functions, we cloned a chondroitin synthase homologue of Caenorhabditis elegans and depleted expression of its product by RNA-mediated interference and deletion mutagenesis. Here we report that blocking chondroitin synthesis results in cytokinesis defects in early embryogenesis. Reversion of cytokinesis is often observed in chondroitin-depleted embryos, and cell division eventually stops, resulting in early embryonic death. Our findings show that chondroitin is required for embryonic cytokinesis and cell division.     

氯化钾和硫酸铵复分解制备硫酸钾相图分析

氯化钾与硫酸铵复分解制备硫酸钾工艺具有工艺过程简单等优点,但其反应转化率较低。通过计算确定了氯化钾和硫酸铵水溶液体系相图,并对水溶液体系和甲醇溶液体系的相图进行分析比较,计算了反应转化率。结果表明,在反应过程中添加甲醇后,相际关系并未改变,但反应转化率显著提高。基于甲醇溶液体系的相图,可进一步研究新的生产工艺。