Bromocriptine/SKF38393 ameliorates islet dysfunction in the diabetic (db/db) mouse

Dysfunction of pancreatic islets plays a crucial role in the etiology of type II diabetes. Chronic hyperglycaemia or hyperlipidaemia may impair islet function. Previous studies by our laboratory have demonstrated that dopaminergic agonists ameliorated hyperglycaemia and hyperlipidaemia in obese and diabetic rodents. In the present study, we investigated the effect of a treatment with the dopamine D₂ /D₁ receptor agonists (bromocriptine/SKF38393, BC/SKF) on islet dysfunction in db/db mice. Our results show that a 2-week BC/SKF treatment markedly reduced hyperglycaemia and hyperlipidaemia, and significantly improved islet dysfunction demonstrated by an increase of secretagogue-stimulated insulin release from islets of db/db mice to levels observed in islets from lean mice. There was also a fourfold increase of insulin content in the pancreas of BC/SKF-treated db/db mice compared with that in untreated controls. The effect of BC/SKF on islet function cannot be mimicked in pair-fed animals. BC/SKF had no direct stimulatory effect on islet insulin secretion, suggesting BC/SKF treatment improved islet function via an indirect mechanism. This treatment markedly improved the abnormally elevated daily levels of corticosterone, blood glucose and plasma lipids, supporting the view that BC/SKF may affect the neuroendocrine system that in turn regulates peripheral metabolism and thereby improves islet function. Received 3 April 1998; accepted 27 April 1998     

红树植物白骨壤对盐度的某些生理反应

红树植物白骨壤叶片的泌盐作用随着盐度的增加而增强，２０‰和４０‰盐度处理白骨壤叶片的泌盐作用比对照处理分别增加了２．７倍和４．７倍．叶片蒸腾作用和气孔导度则不同，当盐度由对照升高到４０‰时，蒸腾作用和气孔导度分别下降了５５％和４８％．叶和茎的膜脂质过氧化作用在盐度存在下都有所升高，根却有所降低．对超氧化物歧化酶的测定显示：在根中，超氧化物歧化酶较好地抑制了膜脂质过氧化作用的发生，而在叶和茎中，超氧化物歧化酶对脂质过氧化作用的抑制并不明显，两者之间可能存在更为复杂的相互关系．     

胃粘膜HCO_3~－分泌的细胞机制和调节

正常的胃粘膜上皮细胞依赖新陈代谢的过程分泌ＧＣＯ－３。它依赖于跨膜Ｎａ＋梯度和Ｎａ＋－Ｋ＋－ＡＴＰ酶的活性；也可伴随ＮａＨＣＯ３协同转运。粘膜损伤时，紧密连结被损害或上皮脱落，可增加粘膜渗透性，使ＨＣＯ－３被动转运进入胃腔。酸可刺激依赖新陈代谢的ＨＣＯ－３分泌，也可造成其被动转运．中枢神经系统参与调节胃ＨＣＯ－３分泌，迷走神经促进其分泌，而交感神经抑制其分泌。ＨＣＯ－３参与组成一个胃粘液－ＨＣＯ－３屏障，保护胃粘膜免受损伤，促进粘膜自身修复和再生。     

植物病原细菌的细菌素与细菌性病害的防冶

本文介绍了细菌素的一般性状,化学性质、遗传学基础及其在植物细菌性病害防治中的应用,探讨了细菌素在防病实践中存在的问题及解决途径。     

A simple method for in vivo testing of glandular enzymatic activity on potential precursors of larval defensive compounds inPhratora species (Coleoptera: Chrysomelinae)

The presence of glandular -glucosidase and oxidase-specific activities, and the possible role of phenolglucosides and related compounds as precursors for larval defensive compounds, were directly demonstrated by introducing salicin, saligenin and helicin into the defensive glands ofPhratora species.Ph. tibialis andPh. laticollis that normally secrete endogenously-produced iridoid monoterpenes and do not use phenolglucosides from their food sources as precursors, were able to produce salicyladehyde from helicin when the latter was introduced into the defensive glands.     

一种高效、稳定的分泌型原核表达载体的构建及应用

以本室构建的原核表达载体pTO-T7为基础载体，PCR合成ompT引导序列，插入该载体多克隆位点上游，构建了分泌型原核表达载体pTO-OT．将2个外源基因克隆至pTO-OT，2个重组质粒在大肠杆菌中均得以高效表达．表达产量在25％～34％之间．Western blot分析证实了融合蛋白可被大肠杆菌信号肽酶有效地切割。并具有良好的免疫学活性．对重组表达菌株的连续传代实验证实了该表达载体具有良好的表达稳定性，显示了其在基因工程中的应用价值．     

U73122和三氟吡啦嗪对柴胡皂甙(I)促胰腺腺泡酶分泌的影响

应用碘淀粉比色法检测淀粉酶活性技术 ,以卡巴可 ( CCh)及八肽胆囊收缩素 ( CCk-8)为阳性对照药 ,研究了磷脂酶 C( PLC)抑制剂 U731 2 2和钙调素 ( Ca M)抑制剂三氟吡啦嗪 ( trifluoperazine)影响柴胡皂甙 ( I) [SA( I) ]刺激大鼠胰腺腺泡酶分泌的剂量依赖性和分泌动力学特征 .U731 2 2抑制 SA( I)和 CCh促酶分泌有相似的剂量依赖性 ,1 0 - 5mol·L- 1 U731 2 2分别抑制了相同浓度 SA( I)和 CCh作用的 5 7.4 %和 6 1 .5 % .U731 2 2抑制 SA( I)促酶分泌动力学较对 CCh的抑制缓慢且持续时间较长 .trifluoperazine抑制 SA( I)促酶分泌与对 CCk-8的抑制有相似的剂量依赖性 ,高浓度对 SA( I)作用的抑制更显著 .结果表明 ,SA( I)活化 PLC和 Ca M包括在其促酶分泌的细胞信号传导通路中     

葡萄糖供应速率对大肠杆菌表达及分泌人表皮生长因子的影响

采用一株大肠杆菌BL 21(DE 3)[pBLMVL 2EGF]生产人表皮生长因子(hEGF),其中hEGF表达由PL启动子控制并通过phoA信号肽分泌到胞外。实验结果表明:诱导阶段以恒定比供应速率流加葡萄糖时,流加速率对hEGF的表达和分泌有很大影响。当葡萄糖比供应速率为0.122g/(g.h)时,hEGF表达水平最低,分泌效率最差,只有37.5%;随着葡萄糖比供应速率的增加,胞外和胞内hEGF比生产速率明显增加,当葡萄糖比供应速率为0.196 g/(g.h)时,单位菌体产生的hEGF水平最高(121.6 m g/g),其中分泌至胞外的hEGF占42%。此外,诱导前补充有机氮源有利于提高诱导初始hEGF的生产速率。     

Hedgehog signaling in pancreas development and disease

Since its discovery, numerous studies have shown that the Hedgehog (Hh) signaling pathway plays an instrumental role during diverse processes of cell differentiation and organ development. More recently, it has become evident that Hh signaling is not restricted to developmental events, but retains some of its activity during adult life. In mature tissues, Hh signaling has been implicated in the maintenance of stem cell niches in the brain, renewal of the gut epithelium and differentiation of hematopoietic cells. In addition to the basal function in adult tissue, deregulated signaling has been implicated in a variety of cancers, including basal cell carcinoma, glioma and small cell lung cancer. Here, we will focus on the role of Hh signaling in pancreas development and pancreatic diseases, including diabetes mellitus, chronic pancreatitis and pancreatic cancer. Received 5 August 2005; received after revision 4 November 2005; accepted 22 November 2005