Improved method for the routine determination of acetylcholine and choline in brain microdialysate using a horseradish peroxidase column as the immobilized enzyme reactor

A modified microbore high-performance liquid chromatography-immobilized enzyme reactor-electrochemical detection system for acetylcholine (ACh) and choline (Ch) was developed. The system used the horseradish peroxidase and a solution mediator ferrocene to convert the analyte into an oxidized ferrocene species which was detected electrochemically by reduction at 0 mV. There was an excellent linear relationship between the concentration of ACh/Ch and the peak height over the range of 1-5000 nmol/l. The limit of detection for ACh was 2 fmol/5 microl (S/N=3:1). Compared with the common method recommended by Bioanalytical System Inc. (BAS), this method exhibits a 200-fold improvement in the detection limit. The ACh and Ch levels in rat brain microdialysate were examined.     

FGF-10 induces SP-C and Bmp4 and regulates proximal-distal patterning in embryonic tracheal epithelium

The induction, growth, and differentiation of epithelial lung buds are regulated by the interaction of signals between the lung epithelium and its surrounding mesenchyme. Fibroblast growth factor-10 (FGF-10), which is expressed in the mesenchyme near the distal tips, and bone morphogenetic protein 4 (BMP4), which is expressed in the most distal regions of the epithelium, are important molecules in lung morphogenesis. In the present study, we used two in vitro systems to examine the induction, growth, and differentiation of lung epithelium. Transfilter cultures were used to determine the effect of diffusible factors from the distal lung mesenchyme (LgM) on epithelial branching, and FGF-10 bead cultures were used to ascertain the effect of a high local concentration of a single diffusible molecule on the epithelium. Embryonic tracheal epithelium (TrE) was induced to grow in both culture systems and to express the distal epithelial marker surfactant protein C at the tips nearest the diffusible protein source. TrE cultured on the opposite side of a filter to LgM branched in a pattern resembling intact lungs, whereas TrE cultured in apposition to an FGF-10 bead resembled a single elongating epithelial bud. Examination of the role of BMP4 on lung bud morphogenesis revealed that BMP4 signaling suppressed expression of the proximal epithelial genes Ccsp and Foxj1 in both types of culture and upregulated the expression of Sprouty 2 in TrE cultured with an FGF-10 bead. Antagonizing BMP signaling with Noggin, however, increased expression of both Ccsp and Foxj1.     

Analysis of glucose and lactate in hippocampal dialysates of rats during the operant conditioned reflex using microdialysis

Changes of extracellular glucose and lactate in hippocampus for freely moving rats during the operant conditioned reflex were examined simultaneously. Samples of the dialysate were assayed for both glucose and lactate using in vivo microdialysis and a microbore flow injection analysis-immobilized enzyme reactor-electrochemical detection (FIA-IMER-ECD) system. Microdialysis samplings were conducted in a Skinner box where lights were delivered as conditioned stimuli (CS) paired with foot shocks as unconditioned stimuli (US). In the treatment group the concentration of glucose and lactate showed no fluctuations during the whole process. However, in the control group in which the rats were exposed to many foot shocks, lactate levels decreased by 19% below baseline during the behavioral session and glucose showed a delayed decrease (by 18%). Compared with glucose, lactate can immediately indicate the dynamic changes in brain.     

Sera from patients with type 2 diabetes and neuropathy induce autophagy and colocalization with mitochondria in SY5Y cells

The etiology of diabetic neuropathy is multifactorial and not fully elucidated, although oxidative stress and mitochondrial dysfunction are major factors. We reported previously that complement-inactivated sera from type 2 diabetic patients with neuropathy induce apoptosis in cultured neuronal cells, possibly through an autoimmune immunoglobulin-mediated pathway. Recent evidence supports an emerging role for autophagy in a variety of diseases. Here we report that exposure of human neuroblastoma SH-SY5Y cells to sera from type 2 diabetic patients with neuropathy is associated with increased levels of autophagosomes that is likely mediated by increased titers of IgM or IgG autoimmune immunoglobulins. The increased presence of macroautophagic vesicles was monitored using a specific immunohistochemical marker for autophagosomes, anti-LC3-II immunoreactivity, as well as the immunohistochemical signal for beclin-1, and was associated with increased co-localization with mitochondria in the cells exposed to diabetic neuropathic sera. We also report that dorsal root ganglia removed from streptozotocin-induced diabetic rats exhibit increased levels of autophagosomes and co-localization with mitochondria in neuronal soma, concurrent with enhanced binding of IgG and IgM autoimmune immunoglobulins. To our knowledge, this is the first evidence that the presence of autophagosomes is increased by a serum factor, likely autoantibody(ies) in a pathological condition. Stimulation of autophagy by an autoantibody-mediated pathway can provide a critical link between the immune system and the loss of function and eventual demise of neuronal tissue in type 2 diabetes.     

山西云蒙山油松种群的年龄结构和动态特征

本文用样方法研究了山西云蒙山油松种群的年龄结构、存活曲线和数量动态规律,并且讨论了油松种群数量动态和群落演替的关系,结果表明:油松种群具有增长型和衰退型的动态特征,影响油松种群数量的内在机制主要是种内光资源的竞争。尽管大多数油松种群处于不断衰减状态,但其群落结构及性质在较长时期内将不会发生显著的变化。     

黄土区次降雨条件下林地径流和侵蚀产沙形成机制——以人工油松林和次生山杨林为例

以黄土区两种常见森林植被(次生山杨林和人工油松林)长期定位观测试验为基础,从水量平衡和径流产沙机理出发,分析了次降雨条件下两种林地和荒地坡面产流产沙过程.结果表明,次降雨量在5.0～50.0 mm范围内,油松林和山杨林的林冠和枯枝落叶层总截留率分别为15.45%～56.80%和20.56%～47.81%,且随降雨量的增大而减小.与荒坡地相比,林地土壤入渗性能显著增强,尤其是0～20cm土层.分析表明,在一般降水条件下林地无径流产生;而在降雨雨强为2.5 mm·min^-1和历时30 min条件下,山杨林地无地表径流产生,荒坡地的径流流速和径流挟沙浓度均为油松林地的23.5倍,而其径流剪切力和径流能量均为后者的8倍;油松林地的径流量和产沙量比荒地分别减少了87.6%和99.4%,与径流小区多年(1988～2000)观测平均值(分别为87.0%和99.9%)相近.     

逐步聚类法及其应用

本文介绍了一种非等级分类方法——逐步聚类法,并将其应用于翅果油树灌丛的数量分类研究,结果表明：逐步聚类法实现最优分类的目标过程,是依样方组内具有最小的离差平方和。样方组间具有最大的离差平方和为标准,使样方组内具有最大的同质性,样方组间具有最大的异质性,其分类结果与实际情况吻合度较高;其次,逐步聚类法只需计算每个样方到该样方形心的距离,可缩短计算时间和节省计算机内存单元,提高工作效率。 与模糊c—均值聚类和TWINSPAN结果相比,逐步聚类的结果类似于模糊c—均值聚类,即样方组内具有较高的同质性;在不要求分类结果具有明显上下级关系的前提下,逐步聚类结果要优于TWINSPAN。