PI3K/Akt通路在丙泊酚减轻大鼠脑缺血性损伤中的作用

目的研究PI3K/Akt信号通路在丙泊酚减轻大鼠缺血性脑损伤中的作用。方法制备大鼠脑缺血模型,随机分为对照组、溶媒组、丙泊酚治疗组和LY294002干预组,丙泊酚腹腔注射给药,LY294002脑室内给药。对大鼠神经功能损伤进行评分,测量大鼠脑梗死体积;分析大鼠缺血性脑水肿程度;检测脑组织髓过氧化物酶(MPO)的含量;Western blot法检测信号通路关键蛋白p-Akt、Akt的表达变化;ELISA法检测血浆TNF-α和IL-1β的分泌。结果丙泊酚能明显减轻大鼠神经功能障碍、脑梗死体积、脑水肿、MPO活性、TNF-α和IL-1β含量,丙泊酚的抗炎作用和神经保护作用被LY294002抑制。丙泊酚上调p-Akt的表达,这种作用也被LY294002抑制。结论 PI3K/Akt信号通路在丙泊酚减轻脑缺血诱导的脑损伤过程中起重要的调节作用。     

PI3K/Akt信号通路在外源性硫化氢后处理大鼠离体心肌中的作用

目的探讨PI3K/Akt信号通路是否参与硫化氢后处理减轻离体大鼠心肌缺血/再灌注损伤。方法 70只♂Sprague Dawley(SD)大鼠随机分为5组(n=14):缺血/再灌注组(I/R组),硫化氢后处理组(N组),溶媒组(D组),LY294002组(L组),硫化氢后处理+LY294002组(N+L组)。采用离体心脏Langendorff灌注模型,平衡灌注20min后停灌40min复灌60min。记录平衡末及灌注结束时的左室舒张末期压(LVEDP)、左室发展压(LVDP)、左室内压上升最大速率(+dp/dt)、左室内压下降最大速率(-dp/dt)、心率(HR)、冠脉血流量(CF);灌注结束时,TTC法染色心肌切片并计算心肌梗死面积百分比,TUNEL法检测心肌细胞凋亡计算凋亡指数(AI),Western blot半定量p-Akt和总的Akt表达水平。结果平衡灌注末各组间心功能指标(基础值)差异未见统计学意义(P>0.05)。灌注结束时,与I/R组比较,N组可改善再灌注损伤心功能的各项指标(P<0.05),使心肌梗死面积缩小和凋亡指数降低(P<0.05),p-Akt表达水平升高(P<0.05)。LY294002逆转了硫化氢后处理的心功能指标、心肌梗死面积、凋亡指数及p-Akt表达水平(P<0.05),使L组和N+L组p-Akt蛋白表达明显低于N组(P<0.05)。结论外源性硫化氢后处理通过PI3K/Akt信号通路减轻离体大鼠心肌缺血/再灌注损伤。     

Urantide对大鼠心肌缺血/再灌注后心肌细胞凋亡的作用及机制研究

目的观察urantide对大鼠缺血/再灌注心肌组织氧化应激损伤的作用和心肌细胞凋亡的影响及其与PI3K/Akt及PKC信号通路的关系。方法可逆性冠脉左前降支结扎造成心肌缺血/再灌注模型,给予大鼠心脏缺血30 min再灌注90 min。80只大鼠随机分为假手术组、缺血/再灌注(I/R)组、urantide低、中、高剂量组(3,10,30μg.kg-1)、维拉帕米对照组(1.6 mg.kg-1)、urantide+CHE组(30μg.kg-1+1 mg.kg-1)、urantide+LY294002组(30μg.kg-1+0.3 mg.kg-1)。Urantide低、中、高剂量组中urantide于缺血前5 min舌下静脉1 min内一次性推注,urantide+CHE组与urantide+LY294002组中,在穿线稳定后舌下静脉分别快速推注CHE与LY294002,5 min后舌下静脉快速推注uran-tide 30μg.kg-1,稳定10 min后再行缺血/再灌注操作。实验结束后测定大鼠血清中超氧化物歧化酶(SOD)、一氧化氮合酶(NOS)活力和丙二醛(MDA)含量以及一氧化氮(NO)含量。TUNEL法检测凋亡细胞指数(AI),免疫组化法检测心肌组织Bcl-2、Bax的蛋白表达。结果与I/R组相比,urantide 30μg.kg-1能明显升高SOD活性(P<0.01),明显减少血清中MDA的含量(P<0.05),明显提高NOS活力(P<0.01),使NO含量增加(P<0.01);Bax蛋白表达和心肌细胞凋亡指数降低(P<0.01),Bcl-2蛋白表达增加(P<0.05);urantide+CHE组与urantide+LY294002组与urantide30μg.kg-1组相比,SOD活力和NO含量下降,MDA含量上升,心肌组织中Bax蛋白表达和心肌细胞凋亡指数上升,而Bcl-2蛋白表达下降,与I/R组比较差异无统计学意义(P>0.01)。结论 Urantide能够通过激活PKC和PI3K/Akt信号转导通路,减少心肌组织氧自由基的含量,进一步调控Bcl-2和Bax蛋白的表达,抑制心肌缺血/再灌注大鼠心肌细胞的凋亡,从而对大鼠心肌缺血/再灌注具有一定保护作用。     

PI3K/Akt信号传导通路在右美托咪定抗大鼠肢端缺血/再灌注致急性肺损伤中的作用

目的:探讨PI3K/Akt信号传导通路在右美托咪定对大鼠肢体缺血/再灌注致急性肺损伤中的作用.方法:通过止血带捆扎大鼠双后肢根部从而建立大鼠缺血/再灌注肺损伤模型,通过随机数字表法分为对照组、缺血/再灌注组(I/R组)、I/R+右美托咪定组(D组)和I/R+右美托咪定组+LY294002(DL组),通过ELISA和Western blot检测细胞炎症因子及PI3K/Akt信号传导通路蛋白的表达.结果:I/R组中MDA和MPO含量、细胞炎症因子表达及p-Akt蛋白含量较对照组均明显升高;D组中上述肺损伤指标较I/R组均显著下调;与D组相比,DL组中MDA和MPO含量、细胞炎症因子表达及p-Akt蛋白含量均上调.     

丹参对脑缺血再灌注损伤脑组织中p-Akt、Caspase-3和HIF-1α蛋白的影响

目的 探讨丹参对脑缺血再灌注损伤脑组织中磷酸化AKT蛋白(p-AKT)、半胱氨酸蛋白酶-3(Caspase-3)和缺氧诱导因子-1α(HIF-1α)蛋白的影响。方法 2020年3—5月,48只健康SD大鼠随机分为假手术组、模型组、丹参组和LY294002组,每组12只。丹参组灌胃给予丹参水提物灌胃,LY294002组肌内注射PI3K/AKT抑制剂LY294002,假手术组和模型组给予同体积生理盐水灌胃。采用线栓法建立局灶性脑缺血再灌注损伤模型。观察脑缺血再灌注后大鼠神经功能缺损情况及脑梗死体积,检测缺血脑组织中p-Akt、HIF-1α和Caspase-3蛋白水平的表达。结果 造模后,假手术组神经功能评分、脑梗死体积均为0;LY294002组神经功能评分最高,脑梗死体积最大,其次为模型组,丹参组最低,组间比较差异有统计学意义(P 0.05)。造模后,丹参组HIF-1α水平最高,其次为模型组与LY294002组,均显著高于假手术组,差异有统计学意义(P 0.05);造模后,丹参组p-Akt水平最高,其次为模型组,LY294002组次之,均显著高于假手术组,差异有统计学意义(P 0.05);造模后,LY294002组Caspase3水平最高,其次为模型组,丹参组次之,均显著高于假手术组,差异有统计学意义(P 0.05)。结论 丹参对脑缺血再灌注损伤具有保护作用,其机制可能与激活PI3K/Akt信号通路,上调p-Akt和HIF-1α蛋白表达,降低Caspase-3表达有关。     

蛇床子素通过PI3K/Akt通路诱导外阴鳞癌SW962细胞凋亡

目的探讨蛇床子素(osthole或osthol)能否通过PI3K/Akt通路诱导细胞凋亡,抑制细胞增殖。方法体外培养外阴鳞癌SW962细胞,加入不同浓度蛇床子素,MTT法检测细胞存活情况,DAPI染色观察细胞形态学变化;流式细胞术检测SW962细胞凋亡情况; Western blot检测Bcl-2、Bax、cleaved caspase-3、PI3K和p-Akt蛋白表达,及蛇床子素和IGF-1共作用下PI3K/Akt通路蛋白的变化。结果 MTT结果显示,蛇床子素呈浓度依赖性地抑制SW962细胞增殖;DAPI染色和流式细胞术结果显示,蛇床子素呈浓度依赖性诱导细胞凋亡。Western blot结果显示,蛇床子素能上调Bax和cleaved caspase-3蛋白表达,下调PI3K、p-Akt和Bcl-2蛋白表达。IGF-1诱导PI3K、p-Akt和Bcl-2蛋白表达增加,蛇床子素逆转IGF-1作用,3种蛋白表达下调。结论蛇床子素通过抑制PI3K/Akt通路,诱导外阴鳞癌SW962细胞凋亡,抑制细胞增殖。     

Akt通路与丙泊酚后处理大鼠的脑保护作用

目的:观察丙泊酚后处理对局灶性脑缺血再灌注大鼠神经元凋亡的影响及其与PI3K-Akt信号转导通路的关系.方法:采用Longa法建立局灶性脑缺血再灌注模型.60只雄性SD大鼠随机分成4组,每组15只.假手术组(S组)、缺血再灌注组(I/R组)、缺血再灌注+丙泊酚后处理组(P组)、缺血再灌注+丙泊酚后处理+LY294002(LY组).分别进行神经功能评分、脑梗死体积测定、TUNEL凋亡计数、western-blotting检测Akt与p-Akt的水平.结果:与I/R组比较,P组脑梗死体积减小,细胞凋亡减少,磷酸化Akt的表达增加.而这种保护作用会被PI3K-Akt信号通路阻断剂LY294002所抑制.结论:丙泊酚后处理抑制缺血再灌注所致的神经元细胞凋亡,这种保护作用由生存信号通路PI3K-Akt的活化所介导.     

表没食子儿茶素没食子酸酯通过抑制心肌细胞凋亡缓解心肌缺血再灌注损伤的机制研究

目的:探讨表没食子儿茶素没食子酸酯(EGCG)对心肌缺血再灌注损伤的保护作用及其可能机制。方法:以叔丁基过氧化氢(TBHP)处理H9C2心肌细胞构建缺血再灌注细胞模型,采用MTS法考察经不同剂量(3.125、6.25、12.5、25、50、100、200μmol/L)EGCG预处理后细胞的存活情况,并计算细胞存活率;采用Western blotting法检测经不同剂量(100、200μmol/L)EGCG预处理后细胞中凋亡蛋白(Bcl-2、Bax)的表达情况。将雄性C57BL/6小鼠随机分为假手术组、模型组和EGCG组(5 mg/g),每组15只。假手术组和模型组小鼠均灌胃等体积生理盐水,EGCG组小鼠灌胃相应药物,每日1次,连续7 d。末次给药12 h后,采用前降支结扎法复制心肌缺血再灌注损伤小鼠模型。采用伊文思蓝和TTC双染色法观察各组小鼠的心肌梗死面积,并计算梗死面积占横截面积百分比,采用WST-1法检测其血清超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量,采用Western blotting法检测其心肌组织中凋亡蛋白的表达(Bcl-2、Bax)以及通路相关蛋白[磷脂酰肌醇3激酶(PI3K)、磷酸化PI3K(p-PI3K)、蛋白激酶B(Akt)、磷酸化Akt(p-Akt)]的磷酸化水平。结果:细胞试验结果显示,与对照组比较,模型组细胞存活率、Bcl-2的相对表达量均显著降低,Bax的相对表达量显著升高(P<0.05);与模型组比较,25、50、100、200μmol/L EGCG组细胞存活率以及100、200μmol/L EGCG组细胞Bcl-2的相对表达量均显著升高,100、200μmol/L EGCG组细胞Bax的相对表达量均显著降低(P<0.05)。动物实验结果显示,假手术组小鼠未见心肌组织缺血、心腔扩大等现象;模型组小鼠可见明显的心肌梗死现象,其梗死面积占横截面积百分比、血清MDA含量、心肌组织Bax的相对表达量和p-PI3K/PI3K、p-Akt/Akt值均较假手术组显著升高,SOD活性和Bcl-2的相对表达量均较假手术组显著降低(P<0.05);与模型组比较,EGCG组小鼠心肌梗死面积有所缩小,其梗死面积占横截面积百分比、血清MDA含量、心肌组织Bax的相对表达量和p-PI3K/PI3K、p-Akt/Akt值均显著降低,SOD活性和Bcl-2的相对表达量均显著升高(P<0.05)。结论:EGCG对心肌缺血再灌注损伤具有一定的保护作用,这种作用可能与抑制心肌细胞凋亡、改善机体氧化应激状态、调控凋亡蛋白表达、降低PI3K/Akt通路相关蛋白的磷酸化水平有关。     

PI3K-Akt信号转导通路在舒芬太尼后处理减轻大鼠心肌缺血再灌注损伤中的作用

目的探讨磷脂酰肌醇-3-激酶/丝氨酸-苏氨酸激酶(PI3K-Akt)信号转导通路在舒芬太尼后处理减轻大鼠心肌缺血再灌注损伤中的作用。方法健康雄性SD大鼠50只,体质量230²80 g,2280 g,2³月龄,采用随机数字表法,将其随机分为5组(n=10):假手术组(S组)、心肌缺血再灌注损伤组(I/R组)、舒芬太尼后处理组(PO组)、舒芬太尼后处理组+PI3K特异性抑制剂LY294002组(PO+L组)、PI3K特异性抑制剂LY294002组(L组)。I/R组,PO组,PO+L组,L组采用结扎左冠状动脉前降支30 min,再灌注120 min的方法来建造心肌缺血再灌注的模型。I/R组在再灌注前5 min时尾静脉注射0.9%氯化钠注射液1 ml,PO组在再灌注前5 min时尾静脉注射1ml舒芬太尼稀释液1μg/kg,PO+L组尾静脉注射1 ml舒芬太尼稀释液1μg/kg+LY2940020抑制剂0.3mg/kg,L组尾静脉注射1 ml LY2940020抑制剂0.3 mg/kg。于再灌注120 min时处死大鼠,取缺血部位心肌组织,用10%甲醛固定,常规石蜡包埋,切片。光镜下观察病理学结果,采用免疫组织化学方法测定心肌细胞Akt及磷酸化Akt(p-Akt)的表达,计算p-Akt平均吸光度值与Akt平均吸光度值的比值(p-Akt/Akt),采用TUNEL染色法检测心肌细胞凋亡,计算心肌细胞凋亡指数(AI)。结果与S组比较,其余4组AI、p-Akt/Akt的表达均升高(P<0.05);PO组比I/R组、PO+L组、L组AI降低,p-Akt/Akt的表达升高(P<0.05);PO+L组比L组AI降低,p-Akt/Akt的表达升高(P<0.05);I/R组与PO+L组及L组上述指标比较差异无统计学意义(P>0.05)。结论 PI3K-Akt信号转导通路参与了舒芬太尼后处理减轻大鼠心肌缺血再灌注损伤的作用。     

PI3K/Akt调节线粒体Cx43蛋白表达在H_2S后处理离体大鼠心肌中的保护作用

目的探讨PI3K/Akt信号通路是否通过调节线粒体缝隙连接蛋白Cx43而在硫化氢(H2S)后处理中减轻离体大鼠心脏缺血/再灌注(I/R)损伤。方法 56只♂SpragueDawley(SD)大鼠随机分为4组(n=14):缺血/再灌注组(I/R组),PI3K/Akt信号通路抑制剂LY294002组(LY组),硫化氢后处理组(NP组),硫化氢后处理+PI3K/Akt信号通路抑制剂LY294002组(N+L组)。采用离体心脏Langen-dorff灌注模型,平衡灌注20 min后停灌30 min复灌60 min。记录平衡末及灌注结束时的心率(HR)、左室舒张末期压(LVEDP)、左室发展压(LVDP)、左室内压上升最大速率(+dp/dtmax)、左室内压下降最大速率(-dp/dtmax);灌注结束时,TTC法染色心肌切片并计算心肌梗死面积百分比;TUNEL法检测心肌细胞凋亡,计算凋亡指数(AI);Westernblot半定量线粒体总的Cx43(total connexin 43,tCx43)和磷酸化Cx43(phosphorylated connexin 43,pCx43)表达水平。结果平衡灌注末各组间心功能指标差异无统计学意义。再灌注后,与I/R组比较,NP组心功能的各项指标明显改善(P<0.05);心肌梗死面积减少(26.5±4.2)%vs(44.5±5.3)%(P<0.05);凋亡指数降低(25.9±3.0)%vs(43.1±1.9)%(P<0.05);线粒体tCx43和pCx43蛋白表达水平明显升高。LY294002逆转了H2S后处理产生的心肌保护效应,使N+L组心功能指标及线粒体中tCx43和pCx43的表达水平降低(P<0.05),心肌梗死面积及凋亡指数均增加(P<0.05)。结论 PI3K/Akt信号通路通过上调线粒体缝隙连接蛋白Cx43蛋白的表达而在硫化氢(H2S)后处理中减轻离体大鼠I/R损伤。     

Cerebral metabolism of [3H]-p-chloroamphetamine

The time-dependent metabolism of intraventricularly administered $\text{[}{}^3\text{H}\text{]-p-}\text{chloroamphetamine}$ was followed. The parent compound and its metabolites were recovered by high pressure liquid chromatography and characterized by high pressure liquid chromatography, thin-layer chromatography, and gas chromatography-mass spectrometry. By 4 hr after injection, two major toluene-soluble metabolites were present in brain. Their biological half-lives were different from the parent compound. On the basis of their analyses, one of the metabolites is p-chloronorephedrine, the other (P₃) is as yet unidentified. Pretreatment with Lilly 110140 prevented or markedly reduced the synthesis of both p-chloronorephedrine and P₃. Iprindole prevented the synthesis of p-chloronorephedrine. The P₃ appeared first in the brain then in the liver, suggesting that both of these organs can metabolize p-chloroamphetamine to this compound. The metabolites were recovered primarily from the nuclear and microsomal fractions following subcellular fractionation of the brain, with small quantities present in the synaptosomal fraction. The level of metabolites was higher in the brainstem than in the neocortex. Glutathione, administered simultaneously with p-chloroamphetamine either intraventricularly or intraperitoneally failed to alter the toxicity of p-chloroamphetamine.     

Clevudine University of Georgia/Abbott/Bukwang/Triangle/Yale University

The pyrimidine analog, clevudine (L-FMAU: 2'-fluoro-5-methyl-beta-L-arabinofuranosyluridine) is a potent antihepatitis B virus (HBV) and anti-Epstein-Barr virus (EBV) agent, discovered by researchers at the University of Georgia, in collaboration with Yale University and Bukwang. Bukwang transferred its technology to Triangle Pharmaceuticals in 1998 together with a license to develop clevudine worldwide except Korea [279649], [281942]. In June 1999, Triangle and Abbott Laboratories entered into a strategic alliance to copromote antiviral products including L-FMAU [326798]. In September 2000, Triangle Pharmaceuticals Inc initiated a 30-day phase I/II evaluation of clevudine in HBV-infected patients [381755]. Clevudine is a much less toxic derivative of the toxic agent P-D-FMAU. The mechanism of action of clevudine is not yet clear, but the agent induces a rapid decrease in HBV nucleic acid as doses increase from 0.3 to 10 mg/kg [319145]. It is believed that the target for clevudine lies in the viral replication mechanism. Clevudine is phosphorylated to the triphosphate form intracellularly. This is removed slowly from the cells, thus exerting a sustained inhibitory antiviral activity [178173], [320720], [320721].     

Spotlight from the American Society for Preventive Cardiology on Key Features of the 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guidelines on the Management of Blood Cholesterol

The 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol retains focus on recommendations for statin treatment in the original four statin-eligible groups [those with atherosclerotic cardiovascular disease (ASCVD), diabetes, low-density lipoprotein cholesterol (LDL-C) ≥ 190 mg/dL, and higher risk primary prevention] without the use of treatment initiation or target LDL-C levels from the earlier 2013 American College of Cardiology/American Heart Association (ACC/AHA) guideline, but has several new features. First, patients with primary prevention are divided into those who are at low (< 5%), borderline (5% to < 7.5%), intermediate (7.5% to < 20%), and high (≥ 20%) risk based on the ASCVD risk estimator. Moreover, the new guideline goes further to consider a wider range of factors [now called “risk enhancers”—premature family history of ASCVD, persistently high LDL-C, chronic kidney disease (CKD), metabolic syndrome, conditions specific to women, inflammatory diseases, and high-risk ethnicities] that can be used to better inform the treatment decision. Moreover, more detailed recommendations on how the results of coronary calcium scanning can be used to inform the treatment decision are provided, including how it may be used to “de-risk” certain patients for delaying or avoiding the use of statin therapy. There are also specific sections for cholesterol management in other patient subgroups including women, children, certain ethnic groups, those with CKD, chronic inflammatory disorders and HIV, as well as discussion on the management of hypertriglyceridemia. Importantly, for persons with known ASCVD, a distinction is made for those who are at “very high risk” based on having had two major ASCVD events or one major event and two or more other high risk conditions, such as diabetes or other major risk factors, or bypass surgery or percutaneous intervention. Finally, the concept of a threshold LDL-C for initiating a non-statin therapy (after considering highest tolerated statin dosage) is provided, with ezetimibe recommended as the key non-statin to be added if the LDL-C still remains ≥ 70 mg/dL for all ASCVD patients, and in those who are at “very high risk”, further consideration for using a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor. While the new guideline does have greater detail (and arguably, complexity), the refinements provide a strategy for guiding the clinician to target both statin and non-statin therapy to those most likely to derive benefit.     

Pitavastatin Nissan/Kowa Yakuhin/Novartis/Sankyo

Pitavastatin (nisvastatin) is an HMG CoA reductase inhibitor being developed jointly by Nissan, Kowa Kogyo, Novartis and Sankyo for the potential treatment of atherosclerosis and hyperlipidemia.     

Amlodipine/Valsartan/Hydrochlorothiazide

Amlodipine/valsartan/hydrochlorothiazide (HCTZ) is a fixed-dose combination of the well established antihypertensive agents amlodipine (a calcium channel antagonist), valsartan (an angiotensin II receptor antagonist), and HCTZ (a thiazide diuretic). In patients with moderate or severe hypertension, triple combination therapy with amlodipine + valsartan + HCTZ produced significantly greater reductions from baseline in mean sitting systolic and diastolic BP (msSBP and msDBP) than either valsartan + HCTZ, amlodipine + HCTZ, or amlodipine + valsartan in a large, 8-week, randomized, double-blind, multinational, phase III trial. Furthermore, the proportion of patients achieving overall BP control at endpoint was significantly greater with the triple combination regimen than with any of the dual regimens, with significantly more triple combination recipients achieving msSBP and msDBP control at each assessment throughout the trial. Subgroup analyses of this study suggested that amlodipine + valsartan + HCTZ was generally more effective in reducing BP and providing overall BP control than the dual combination therapies, irrespective of age, race, gender, ethnicity, or hypertension severity. Several smaller studies provide data that support the efficacy of amlodipine + valsartan + HCTZ in patients whose BP is inadequately controlled with amlodipine + valsartan, amlodipine + HCTZ, or valsartan + HCTZ dual combination therapy. Treatment with amlodipine + valsartan + HCTZ for up to 8 weeks was generally well tolerated in the large, phase III trial, with most adverse events being transient and of mild to moderate severity.     

N-Nitroso-N-Methyldodecylamine and N-Nitroso-N-Methyltetradecylamine in household dishwashing liquids

Eleven household dishwashing liquids and four household surface cleaners were analysed for N-nitroso-N-methyldodecylamine and N-nitroso-N-methyltetradecylamine by gas chromatography with detection using a Thermal Energy Analyzer. Both nitrosamines were found in three of the dishwashing detergents and one of the surface cleaners. [1-¹⁴C]-N-Nitroso-N-methyldodecylamine was used to determine recoveries, which were between 65 and 88%. Levels of N-nitroso-N-methyldodecylamine ranged from 112 to 661 ppb and those of N-nitroso-N-methyltetradecylamine from 46 to 151 ppb. A simple method was developed to screen the products for N,N-dimethyldodecylamine-N-oxide, a surfactant ingredient suspected of being the source of these nitrosamines. By application of this method it was established that all of the products formulated with this amine oxide contained these two nitrosamines, whereas in products that did not contain this ingredient, these nitrosamines were not detected.     

PROTON AND POTASSIUM TRANSPORT BY H+/K+-ATPases

1. H⁺/K⁺-ATPases are members of the P-type ATPase multigene family. The prototypical H⁺/K⁺-ATPase is the protein that acidifies gastric luminal contents. The physiological and pharmacological significance of this pump has led to a detailed investigation of its biochemistry and molecular and cell biology. 2. Recently, a number of closely related H⁺/K⁺-ATPase isoforms have been discovered. These isoforms are present in organs other than the stomach, including the colon and kidney, where they contribute to acid—base and potassium homeostasis. The structure, expression and physiological roles of the gastric H⁺/K⁺-ATPase and other isoforms are reviewed.     

INTERACTIONS OF Na+, H2O2 AND THE Na+-Ca2+ EXCHANGER STIMULATE Ca2+ RELEASE IN CK1.4 CELLS

1. The present study aimed to demonstrate that interactions of cations, hydrogen peroxide (H₂O₂) and the Na⁺-Ca²⁺exchanger stimulate Ca²⁺ release and oscillations of cytosolic Ca²⁺ [Ca²⁺]i in non-transfected Chinese Hamster Ovary (CHO) C1 cells and in transfected CHO (CK1.4) cells that contained an expression vector coding the Na⁺-Ca²⁺ exchanger sequence. 2. The [⁴⁵Ca²⁺] uptake assay, fura-2 fluorescence imaging and 2² and 2³ factorial orthogonal statistics provide comparative, direct, efficient, quantitative and transient methods to delineate the effects of such interactions on Ca²⁺ influx, Ca²⁺release and [Ca²⁺]i in C1 and CK1.4 cells. 3. In contrast to the control of either Na⁺-, Ca²⁺- or H₂O₂-free or CI cells, an elevated [⁴⁵Ca²⁺] uptake was induced by Ca²⁺, Na⁺ and H₂O₂ individually and in combination, intracellular Ca²⁺ release was activated by H₂O₂ and by combinations of either H₂O₂ and Na⁺, H₂O₂ and the Na⁺-Ca²⁺ exchanger, Na⁺ and the Na⁺-Ca²⁺ exchanger or by H₂O₂, Na⁺ and the Na⁺-Ca²⁺ exchanger and a rise in [Ca²⁺]i was triggered by H₂O₂, Na⁺ and a combination of Na⁺ and the Na⁺-Ca²⁺exchanger. 4. These results indicate that interactions between H₂O₂, Na⁺ and the Na⁺-Ca²⁺ exchanger stimulate intracellular Ca²⁺mobilization via Ca²⁺-induced Ca²⁺ release mechanisms, ATP-activated G-protein coupled P_2y-purinoceptor-sensitive pathways, Na⁺-Ca²⁺ exchanger-mediated Ca²⁺ influx and cation-π interaction (a strong non-covalent force between the cation and the π face of an aromatic structure in the transmembrane protein). 5. The present findings provide important clues for understanding Ca²⁺ signal transduction mechanisms from the plasma membrane to the endoplasmic reticulum.     

EFFECTS OF THE OPIOID PEPTIDES [MET5]ENKEPHALIN-ARG6-PHE7 AND [MET5]ENKEPHALIN-ARG6-GLY7-LEU8 ON CHOLINERGIC NEUROTRANSMISSION IN THE RABBIT ISOLATED ATRIA

1. The effect of the opioid peptides [Met5]enkephalin-Arg6-Phe7 (MEAP) and [Met5]enkephalin-Arg6-Gly7-Leu8 (MEAGL) were compared with those of [Leu5]enkephalin and [D-Ala2,Met5]enkephalinamide (DAME) on cholinergic neurotransmission in the rabbit isolated atria. 2. Rabbit isolated atria had a resting rate of 190 beats/min. In the presence of the beta-adrenoceptor antagonist propranolol (0.3 mumol/l), atria responded to electrical field stimulation with a cholinergically mediated negative chronotropic response. The opioid peptides had no effect on the resting rate, but inhibited the negative chronotropic response to field stimulation. The IC50 values for inhibiting the cholinergic responses were 1.4 mumol/l for [Leu5]enkephalin (LE), 1.4 mumol/l for MEAP, 1.3 mumol/l for MEAGL and 0.2 mumol/l for DAME. Responses of a similar magnitude to exogenous acetylcholine were unaffected. 3. Thus, MEAP, MEAGL and LE had similar potencies but DAME was about seven times more potent in inhibiting cholinergic neurotransmission in the rabbit isolated atria. The site of inhibition appears to be prejunctional.