Forskolin supresses seizures induced by pentylenetrazol in mice

Summary Forskolin, an adenylate cyclase activator when injected s.c. (1 mg/kg) in mice, caused an elevation of cAMP in the forebrain and cerebellum of up to 170% and 130%, respectively. The treatment was found to prevent seizures induced by pentylenetetrazol. This suppression had subsided 30 min after the injection, when cAMP level was again normal in the cerebellum but still elevated in the forebrain.     

三氯乙酸沉淀蛋白法辅助提取牛奶中环腺苷酸工艺

以牛奶为原料,通过离心去除乳中脂肪,采用不同质量分数不同用量TCA沉淀乳中蛋白质,再浓缩乳糖,分离提取环腺苷酸（cAMP）,选用最佳高效液相色谱条件测定牛奶中cAMP含量.结果表明,不同质量分数TCA处理组之间比较,质量分数为10%TCA处理组cAMP含量显著高于其他2组（P〈0.05）;不同用量TCA处理组之间比较,8 mL相同质量分数TCA处理组cAMP含量较其他2组显著降低（P〈0.05）.选用TCA沉淀乳蛋白方法提取cAMP时最佳工艺是TCA质量分数为10%,用量为4 mL,cAMP质量浓度为（29.02±1.58）μg/mL.研究通过建立牛奶中cAMP的提取工艺,可从奶酪副产物、乳清、不合格原料奶中提取cAMP,在降低cAMP提取成本、废物利用、增加牛奶附加值等方面具有重要意义.     

TNF-α upregulates adenosine 2b (A2b) receptor expression and signaling in intestinal epithelial cells: a basis for A2bR overexpression in colitis

Adenosine is an endogenous signaling molecule upregulated during inflammatory conditions. Acting through the A2b receptor (A2bR), the predominant adenosine receptor in human colonic epithelia, adenosine has been directly implicated in immune and inflammatory responses in the intestine. Little is known about expression and regulation of A2bR during inflammation. Tumor necrosis factor alpha (TNF-α) is highly upregulated during chronic and acute inflammatory diseases. This study examined the expression of A2bR during colitis and studied effects of TNF-α on A2bR expression, signaling and function. Results demonstrated that A2bR expression increases during active colitis. TNF-α pretreatment of intestinal epithelial cells increased A2bR messenger RNA and protein expression. TNF-α significantly increased adenosine-induced membrane recruitment of A2bR and cyclic adenosine monophosphate downstream signaling. Further, TNF-α potentiated adenosine-induced shortcircuit current and fibronectin secretion. In conclusion, we demonstrated that TNF-α is an important regulator of A2bR, and during inflammation, upregulation of TNF-α may potentiate adenosine-mediated responses. Received 21 July 2005; received after revision 22 August 2005; accepted 19 September 2005 †These authors contributed equally to this work.     

三七叶皂苷抗炎作用机理的实验研究

目的:研究三七叶皂苷(PnGL)对大鼠气囊滑膜炎的抗炎作用机理.方法:皮下注射角叉菜胶(Car)25mg/kg复制大鼠气囊滑膜炎模型,气囊灌洗液中白细胞数、蛋白含量、NO及TNF含量分别用试管稀释法、Lowry法、Rivanol法及酶联免疫吸附分析法进行.采用放免分析法进行气囊灌洗液中性粒细胞(Neu)内环磷酸腺苷(cAMP)含量的测定.结果:PnGL60,120,240mg.kg-1能剂量依赖性地升高中性粒细胞(Neu)内cAMP含量,抑制炎症介质肿瘤坏死因子(TNF)及一氧化氮(NO)水平的升高,显著降低灌洗液中白细胞数量及蛋白含量.相关分析显示,PnGL升高Neu内cAMP水平的作用与其降低TNF、NO含量的能力呈显著负相关.结论:升高Neu内cAMP水平及其抑制NO及TNF含量升高是PnGL发挥抗炎作用的重要分子机制.     

Signal transduction in axon guidance

Neurons establish specific connections by extending projections to contact their targets. Projections, such as axons, navigate to the target by sensing guidance cues in their environment and responding with directed movement and shape change. The recent identification of the molecular identities of many guidance cues and guidance receptors has demonstrated that axons are guided to their targets by combinations of cues that attract and repel them. The current challenge is to elucidate how these guidance cue/receptor interactions control navigation. This review focuses on recent progress in identifying the signaling pathways downstream of these receptors and in determining why an axon is attracted or repelled by a particular guidance cue.     

交通相关PM2.5对人外周血淋巴细胞凋亡的影响

为探讨交通相关PM2.5对人外周血淋巴细胞凋亡的诱导作用及可能机制,为交通相关PM2.5的免疫毒性提供实验依据,采用0、50、100、200μg/mL PM2.5对人外周血淋巴细胞进行24 h和48 h染毒,FITC-AnnexinV/PI染色,流式细胞仪检测淋巴细胞早期凋亡和坏死;采用0、20、80、320μg/mL PM2.5浓度分别染毒人外周血淋巴细胞24、48、72 h,Western blot法测定细胞内含半胱氨酸的天冬氨酸特异蛋白水解酶3(cysteinyl aspartate specific proteinase 3,Caspase-3)和cAMP反应元件结合蛋白(cAMP-response element binding protein,CREB)蛋白表达水平,ELISA法检测细胞内环磷酸腺苷(cyclic adenosine monophos-phate,cAMP)含量.结果表明,50、100、200μg/mL PM2.5染毒细胞24 h和48 h后,淋巴细胞早期凋亡和坏死均高于生理盐水组,差异有统计学意义(P<0.01),且具有一定的剂量-效应关系;20、80、320μg/mL PM2.5染毒细胞24、48、72 h后,各剂量组Caspase-3蛋白表达水平均高于对照组,除80μg/mL PM2.5染毒72 h外,差异均具有统计学意义(P<0.01).320μg/mL PM2.5染毒细胞24、48、72 h后,细胞内cAMP含量均比生理盐水组升高(P<0.05).PM2.5染毒72 h后,CREB表达水平随PM2.5浓度的升高而降低(P<0.01).可见,交通相关PM2.5可诱导人外周血淋巴细胞产生凋亡,且细胞内cAMP和CREB参与了凋亡的调控.     

EP2 receptor stimulation promotes calcium responses in astrocytes via activation of the adenylyl cyclase pathway

Astrocytes are a heterogeneous population of cells that are endowed with a great variety of receptors for neurotransmitters and neuromodulators. Recently prostaglandin E₂ has attracted great interest since it is not only released by astrocytes but also activates receptors coupled to either phospholipase C or adenylyl cyclase. We report that EP₂ receptor stimulation triggers cAMP production but also causes release of Ca²⁺ from intracellular stores. This effect is shared by other receptors similarly coupled to adenylyl cyclase and elicited by direct stimulation of the enzyme or application of cAMP analogues. However, the stimulation of the Ca²⁺ response by cAMP is not mediated by protein kinase A, since a specific antagonist of this kinase had no effect. Such a cross-talk between cAMP and Ca²⁺ was not observed in all astrocytes. It might therefore reflect a specific resource of either a subpopulation or astrocytes in a specific functional state. Received 6 June 2006; received after revision 25 July 2006; accepted 31 August 2006     

Suppression of chaos by periodic oscillations in a model for cyclic AMP signalling inDictyostelium cells

We investigate how the introduction of cells oscillating periodically affects the behaviour of a suspension ofDictyostelium discoideum amoebae undergoing chaotic oscillations of cyclic AMP. The analysis of a model indicates that a tiny proportion of periodic cells suffices to transform chaos into periodic oscillations in such suspensions. A similar result is obtained by forcing the aperiodic oscillations by a small-amplitude, periodic input of cyclic AMP. The results provide an explanation for the observation of regular oscillations in suspensions of a putatively chaotic mutant ofDictyostelium discoideum ¹². More generally, the results show how chaos in biological systems may disappear through the coupling with periodic oscillations.     

沙棘提取物对癌细胞DNA、蛋白质合成及体内血浆中cAMP含量的影响

采用同位素示踪技术和蛋白质结合法研究了沙棘汁和沙棘油的抗癌机理。结果显示：沙棘汁对Ｌ＿（７７１２）白血病、Ｓ＿（１８０）肉瘤、腹水型肝癌等细胞的ＤＮＡ、蛋白质合成均无抑制作用。沙棘油浓度在０．００５～１．０ｍｇ／Ｌ时对Ｌ＿（７７１２）白血病细胞ＤＮＡ合成有抑制作用，且此时抑制率与浓度呈负相关。沙棘汁ｉｐ注射剂量为１／５ＬＤ＿（５０）时，沙棘汁对小鼠血浆ｃＡＭＰ含量略有提高。