Autophagy and other vacuolar protein degradation mechanisms

Autophagic degradation of cytoplasm (including protein, RNA etc.) is a non-selective bulk process, as indicated by ultrastructural evidence and by the similarity in autophagic sequestration rates of various cytosolic enzymes with different half-lives. The initial autophagic sequestration step, performed by a poorly-characterized organelle called a phagophore, is subject tofeedback inhibition by purines and amino acids, the effect of the latter being potentiated by insulin and antagonized by glucagon. Epinephrine and other adrenergic agonists inhibit autophagic sequestration through a prazosin-sensitive ₁-adrenergic mechanism. The sequestration is also inhibited by cAMP and by protein phosphorylation as indicated by the effects of cyclic nucleotide analogues, phosphodiesterase inhibitors and okadaic acid.Asparagine specifically inhibits autophagic-lysosomal fusion without having any significant effects on autophagic sequestration, on intralysosomal degradation or on the endocytic pathway. Autophaged material that accumulates in prelysosomal vacuoles in the presence of asparagine is accessible to endocytosed enzymes, revealing the existence of an amphifunctional organelle, the amphisome. Evidence from several cell types suggests that endocytosis may be coupled to autophagy to a variable extent, and that the amphisome may play a central role as a collecting station for material destined for lysosomal degradation.Protein degradation can also take place in a salvage compartment closely associated with the endoplasmic reticulum (ER). In this compartment unassembled protein chains are degraded by uncharacterized proteinases, while resident proteins roturn to the ER and assembled secretory and membrane proteins proceed through the Golgi apparatus. In thetrans-Golgi network some proteins are proteolytically processed by Ca²⁺-dependent proteinases; furthermore, this compartment sorts proteins to lysosomes, various membrane domains, endosomes or secretory vesicles/granules. Processing of both endogenous and exogenous proteins can occurr in endosomes, which may play a particularly important role in antigen processing and presentation. Proteins in endosomes or secretory compartments can either be exocytosed, or channeled to lysosomes for degradation. The switch mechanisms which decide between these options are subject to bioregulation by external agents (hormones and growth factors), and may play an important role in the control of protein uptake and secretion.     

Cholecystokinin is not a major regulator in the digestive system in the chicken

To find out whether physiological concentrations of cholecystokinin (CCK), a gastrointestinal hormone in mammals, are also active in chickens, the pancreatic amylase secretory response to CCK-8 was investigated in vitro. Rat pancreatic acini responded to the physiological concentration of CCK-8, but in chickens amylase release was induced at a concentration of CCK-8 1000 times higher than that observed in rats. In another experiment, biliary flow was tested with several doses of CCK-8. The bile flow was stimulated in a dose-dependent fashion, but a significant enhancement was not obtained at a concentration of 0.5 g CCK-8/kg body weight, which was considerably higher than physiological ones. It is concluded that endogeneous CCK does not have an important role in the digestive system in the chicken.     

胰腺腺泡细胞胞浆游离钙浓度的测定及药物作用的研究

本文建立了用荧光指示利Fura－2测定胰腺腺泡细胞胞浆游离Ca2＋浓度（［Ca2＋］i）的实验技术,包括：胰腺腺泡的分离制备;Fura—2／AM的负载;腺泡悬液的荧光光谱测量等．测定了胰腺腺泡细胞［Ca2＋］i。的静息值和卡巴可促腺泡细胞［Ca2＋］i升高的剂量—效应关系及动力学过程,并研究了柴胡总皂甙对胰腺腺泡细胞［Ca2＋i］的影响．发现0．01mg／ml浓度的柴胡总皂甙使胰腺腺泡细胞［Ca2＋］。明显升高,0．1mg／ml浓度时可使［Ca2＋］。升高到静息值的3倍,提示柴胡总皂甙的促酶分泌作用是通过胞内［Ca2＋］i升高介导的．     

GABA促进小鼠离体胃胃酸分泌活动的机制探讨

为了探讨γ-氨基丁酸(GABA)对小鼠离体胃胃酸分泌(GAS)的调节作用和机制,在体外37℃缓冲溶液中培育小鼠全胃标本,测定灌流液的pH值。结果表明:丙谷胺(2、6×10-7mol/L),可显著地抑制胃酸分泌。GABA(2～10×10-7mol/L)则以一种浓度依赖的方式显著地促进胃酸分泌,若用丙谷胺(6×10-7mol/L)和不同浓度的GABA共同灌流胃,则显著阻断GABA的促进效应,逻辑斯谛曲线(Logisticcurve)显示这种阻断是不完全的。西咪替丁(Cim,10×10-7mol/L)明显抑制胃酸分泌,并不完全阻断GABA对胃酸分泌的促进效应。若用丙谷胺(6×10-7mol/L)和西米替丁(Cim,10×10-7mol/L)与GABA(4～10×10-7mol/L)共同灌流胃,对GABA促进胃酸分泌的效应仍显示不完全阻断作用。结果提示:GABA可能通过G细胞或/和ECL细胞间接促进壁细胞泌酸;GABA也可能直接激活壁细胞,促进胃酸分泌。     

Molecular mechanisms in therapy of acid-related diseases

Inhibition of gastric acid secretion is the mainstay of the treatment of gastroesophageal reflux disease and peptic ulceration; therapies to inhibit acid are among the best-selling drugs worldwide. Highly effective agents targeting the histamine H2 receptor were first identified in the 1970s. These were followed by the development of irreversible inhibitors of the parietal cell hydrogen-potassium ATPase (the proton pump inhibitors) that inhibit acid secretion much more effectively. Reviewed here are the chemistry, biological targets and pharmacology of these drugs, with reference to their current and evolving clinical utilities. Future directions in the development of acid inhibitory drugs include modifications of current agents and the emergence of a novel class of agents, the acid pump antagonists. Received 30 May 2007; received after revision 15 August 2007; accepted 13 September 2007     

Cholera toxin structure, gene regulation and pathophysiological and immunological aspects

Many notions regarding the function, structure and regulation of cholera toxin expression have remained essentially unaltered in the last 15 years. At the same time, recent findings have generated additional perspectives. For example, the cholera toxin genes are now known to be carried by a non-lytic bacteriophage, a previously unsuspected condition. Understanding of how the expression of cholera toxin genes is controlled by the bacterium at the molecular level has advanced significantly and relationships with cell-density-associated (quorum-sensing) responses have recently been discovered. Regarding the cell intoxication process, the mode of entry and intracellular transport of cholera toxin are becoming clearer. In the immunological field, the strong oral immunogenicity of the non-toxic B subunit of cholera toxin (CTB) has been exploited in the development of a now widely licensed oral cholera vaccine. Additionally, CTB has been shown to induce tolerance against co-administered (linked) foreign antigens in some autoimmune and allergic diseases. Received 25 October 2007; accepted 12 December 2007     

Family I.3 lipase: bacterial lipases secreted by the type I secretion system

Based on the classification of bacterial lipolytic enzymes, family I.3 lipase is a member of the large group of Gram-negative bacterial true lipases. This lipase family is distinguished from other families not only by the amino acid sequence, but also by the secretion mechanism. Lipases of family I.3 are secreted via the well-known type I secretion system. Like most of proteins secreted via this system, family I.3 lipases are composed of two domains with distinct yet related functions. Recent years have seen an increasing amount of research on this lipase family, in terms of isolation, secretion mechanism, as well as biochemical and biophysical studies. This review describes our current knowledge on the structure-function relationships of family I.3 lipase, with an emphasis on its secretion mechanism. Received 18 April 2006; received after revision 3 July 2006; accepted 24 August 2006     

普林格尔治疗仪促进产后乳汁分泌的疗效观察

目的：观察普林格式治疗仪促进产后乳汁分泌的疗效。方法各选取100例产后30 d乳汁量少的产妇，一组接受普林格尔治疗仪治疗，称为观察组，一组只接受传统方法治疗，称为对照组，观察两组产妇乳汁量的变化。结果经过普林格尔治疗仪治疗和指导的观察组效果明显优于只接受传统方法治疗的对照组，差异具有显著性（p〈0.05）。结论普林格尔治疗仪有利于促进产妇产后的乳汁分泌，且操作简单、风险小、无副作用，值得推广。     

下丘脑-垂体-肾上腺轴激素分泌的周期震荡及混沌现象

结合生理学内分泌调节理论,采用了变步长龙格-库塔法,以Matlab软件为计算平台,对改进的下丘脑-垂体-肾上腺轴激素脉冲分泌的非线性动力学进行了参变量数据模拟,求出了下丘脑-垂体-肾上腺轴激素脉冲分泌的周期振荡解及混沌解.结果显示,此分泌系统中激素浓度变化与实验事实相符,其混沌模型是合理的.     

INO1基因在粟酒裂殖酵母中的表达及对蔗糖酶分泌和磷脂合成的影响

分别用含有INO1基因的两个质粒pADH-INO和pSPIN-22对天然肌醇营养缺陷型的粟酒裂殖酵母（Schizosaccharomyces pombe）进行转化，得到的转化子分别命名为Sch.P944和Sch.P1025.通过对Sch.P944和Sch.P1025的研究，发现两个质粒均能在粟酒裂殖酵母中自主复制并使其变成肌醇原养型，但肌醇分泌的速度和数量Sch.P944均高于Sch.P1025。用该两菌株研究肌醇合成与细胞生长及可分泌蔗糖酶比活的关系，结果显示：细胞的生长与肌醇的合成紧密相关；而蔗糖酶的比活，当葡萄糖含量小于1％时，菌株Sch.P944的蔗糖酶分泌是解葡萄糖阻遏的，而Sch.P1025在实验范围内，蔗糖酶的比活都受到葡萄糖的阻遏作用。对Sch.P944和Sch.P1025膜磷脂的组成进行分析比较发现，膜磷脂中磷脂酰肌醇（PI）的含量Sch.P944比Sch.P1025高，而磷脂酰丝氨酸（PS）的含量Sch.P944比Sch.P1025低。这意味着肌醇通过磷脂酰肌醇参与了蔗糖酶分泌的解阻遏作用。