槟榔碱和氯硝柳胺联合应用对钉螺足跖平滑肌收缩活动的增效作用

目的进一步研究槟榔碱和氯硝柳胺联合应用的增效作用。方法采用离体钉螺足跖平滑肌收缩活动的实验方法,从功能上研究增效作用。结果曾用浸泡实验表明槟榔碱与氯硝柳胺合用时,可降低氯硝柳胺的浓度,抑制钉螺上爬,增强氯硝柳胺灭螺效果。现用钉螺足跖平滑肌实验以收缩张力作指标,进一步证实两药在无效浓度下联合应用,确有增效作用。结论由于槟榔碱在浸泡实验中用量大于平滑肌实验42和85倍,此时槟榔碱抑制慢通道阻Ca2 内流,而使足跖平滑肌松驰发挥灭螺增效作用。     

甘草提取物与氯硝柳胺联合灭螺机制研究

目的 探索甘草提取物与氯硝柳胺联合用药的灭螺机制。方法 采用室内浸杀法,以氯硝柳胺（Nic）、甘草提取物（GE）、GE+Nic浸泡钉螺24、48 h后,以水养法检测存活情况后,选活螺解剖,分离肝脏后观察不同药物对钉螺肝脏蛋白质、糖原水平的影响。利用离体钉螺平滑肌实验方法观察上述不同药物对钉螺足跖平滑肌收缩活动的影响。结果 甘草提取物对钉螺肝脏的蛋白质及糖原水平并无显著影响（P均 > 0.05）,但能显著抑制钉螺足跖平滑肌的收缩,降低收缩频率（P均 < 0.05）;氯硝柳胺能显著降低钉螺肝脏的蛋白质及糖原水平（P均 < 0.05）,且可增强钉螺足跖平滑肌的收缩强度和收缩频率（P均 < 0.05）;甘草提取物与氯硝柳胺联用后能进一步降低钉螺肝脏的蛋白质及糖原水平,且能够抑制钉螺足跖平滑肌的收缩,降低收缩频率（P均 < 0.05）。结论 甘草提取物与氯硝柳胺联用能加速对钉螺肝脏的损伤,同时可抑制其足跖平滑肌的活动,增加药物接触时间,达到灭螺增效作用。     

乙酸β-哌啶乙酯的灭螺作用与钙离子的关系

目的研究乙酸β-哌啶乙酯(Ape)的杀螺作用与Ca2+的关系. 方法采用完全浸泡和离体钉螺足平滑肌的实验方法,研究Ape杀螺效果及其对Ca2+的影响.结果0.1 mg/L和0.5 mg/LApe均有杀螺作用(P均＜0.05),且呈浓度依赖性.不同浓度的Ape对钉螺足平滑肌的收缩效应曲线呈双相性.低浓度时(10-7～3×10-6mol/L)可增强其收缩幅度,且能被钙通道阻滞剂维拉帕米所拮抗;高浓度时(10-5～10-4mol/L)则能拮抗钙通道激动剂Bay K 8644增强钉螺足平滑肌的收缩幅度.结论Ape具有一定的杀螺作用,其影响平滑肌收缩的结果表明,高浓度有阻Ca2+作用.     

槟榔碱对大鼠门静脉和钙通道电流的剂量与效应关系

目的探讨槟榔碱(Arecoline,Are)对大鼠门静脉和钙通道电流(Ica)的剂量与效应的关系,阐明Are灭螺增效的作用机制.方法采用离体大鼠门静脉自发性收缩活动的实验方法和全细胞膜片钳记录技术,研究Are的剂量与效应关系,及其对Ca2+和Ic.的影响.结果不同浓度的Are对大鼠门静脉的收缩力呈双相反应.10-7～3×10-7mol/LAre使门静脉的收缩力增强;10-5～10-4mol/L则使收缩力逐渐抑制,均呈浓度依赖性.Are3×10-8～10-4mol/L对单个心室肌细胞钙通道电流的作用与门静脉一致,亦呈浓度依赖性的双相反应.门静脉收缩活动和全细胞记录钙通道电流的结果证明,不同浓度的Are对Ca2+和Ica均显示有剂量与效应关系,低浓度有促Ca2+及增加Ica作用,高浓度有阻Ca2+内流及降低Ica作用.结论阻钙作用可能是Are降低钉螺上爬附壁率、灭螺增效作用的理论依据.     

槟榔碱与灭螺药物合用的增效作用研究

目的证明槟榔碱与灭螺药物合用的增效作用。方法采用WHO公布的“杀螺剂实验室终筛法”中的浸泡法。结果在0．125mg／L氯硝柳胺和1．25mg／L五氯酚钠的药液中,分别加入槟榔碱100mg／L,其24h钉螺开厣率由47．8％和13．3％,升至66．7％和83．3％;1h上爬附壁率,由81．1％和92．2％,下降至35．0％和30．0％;死亡率由1．1％和3．3％,增加到66．7％和100％（P＜0．01）。结论槟榔碱与化学灭螺药合用后,降低了钉螺对药物刺激的敏感性,钉螺上爬率明显降低,灭螺效果显著增强,从而证明了槟榔碱具有降低化学灭螺药的剂量,抑制钉螺上爬,增强灭螺效果的作用。     

低浓度槟榔碱对钉螺足跖平滑肌收缩和对豚鼠恼室肌细胞 …

目的 研究槟碱对钉螺足平滑肌影响及其机制。方法 采用离体钉螺足跖平滑肌收缩活动的实验方法和全细胞膜处钳技术，探讨槟碱的作用特点和对Ｃａ＾２＋通道的影响。结果 ３μｍｏｌ／Ｌ槟榔碱可增加足跖平滑肌的收缩力和收缩频率。３０ｎｍｏｌ／Ｌ～１μｍｏｌ／Ｌ槟碱直接开放豚鼠单个心室肌细胞钙通道，使１～５曲线峰值增大，激活曲线左移。结论较低浓度的槟碱可增加钉螺足跖平滑肌的收缩活动，此作用可能与该药直接开放该通道     

低浓度槟榔碱对钉螺足跖平滑肌收缩和对豚鼠心室肌细胞钙内流作用的实验研究

目的研究槟榔碱对钉螺足跖平滑肌影响及其机制。方法采用离体钉螺足跖平滑肌收缩活动的实验方法和全细胞膜片钳技术，探讨槟榔碱的作用特点和对Ｃａ~(２＋)通道的影响。结果３μｍｏｌ／Ｌ槟榔碱可增加足跖平滑肌的收缩力和收缩频率。 ３０ ｎｍｏｌ／Ｌ～１μｍｏｌ／Ｌ摈榔碱直接开放豚鼠单个心室肌细胞钙通道，使Ｉ～Ｖ曲线峰值增大，激活曲线左移。结论较低浓度的槟榔碱可增加钉螺足跖平滑肌的收缩活动，此作用可能与该药直接开放该通道，促使Ｃａ~(２＋)内流有关。     

血水草生物碱杀螺、灭蚴作用的研究

目的研究血水草生物碱(ECA)杀灭钉螺及日本血吸虫尾蚴的作用。方法观察实验室及现场浸泡杀螺效果;钉螺接触药物上爬情况;浸泡杀螺卵效果;浸杀尾蚴防护血吸虫感染的作用。结果浸泡72h钉螺死亡率100％的血水草生物碱溶液的浓度及温度分别为:1.25mg/L,30℃;2.5 mg/L、5 mg/L、10 mg/L均为25℃。水温 26℃～28℃现场灭螺10mg/L,72h钉螺死亡率84％;20 mg/L,72h死亡率达92％。5mg/L溶液螺卵浸泡72h孵出率为0％～10％。5mg/L ECA溶液明显抑制钉螺上爬,20mg/L时钉螺静止不动。结论血水草有杀灭钉螺、螺卵及日本血吸虫尾蚴的作用,是一种有研究前景的植物杀螺、灭蚴剂。     

槟榔碱与杀螺药物合用对钉螺足跖肌及神经节细胞影响的透射电镜观察

为研究槟榔碱(Arecoline,ARE)与杀螺药物合用对钉螺足跖肌和神经节细胞超微结构的影响,探索其灭螺增效的作用机制.用加入和未加入ARE的灭螺药物分别浸泡钉螺24 h后,运用透射电镜观察25 mg/L ARE单用或与杀螺药合用对钉螺足跖肌及神经节细胞超微结构的影响.结果25 mg/L ARE、0.625 mg/L五氯酚钠(NAPCP)、0.0625 mg/L氯硝柳胺(NIC)单用时,用药组钉螺足跖肌及神经节细胞超微结构与正常钉螺基本相同.而25 mg/L ARE分别与0.625 mg/L NAPCP、0.0625 mg/L NIC合用时,钉螺足跖肌及神经节细胞均发生明显改变.足跖肌纤维的肌丝被破坏,细胞器消失,核膜残缺,染色质凝集成团;神经节细胞高度变性坏死,成为一团低电子密度与高电子密度均匀混合的物质.结果表明,ARE能增强灭螺药对钉螺足跖肌和神经节细胞的破坏作用.     

槟榔碱与杀螺药合用对钉螺头足部影响的扫描电镜观察

目的：研究槟槟榔碱（Arecoline,ARE)灭螺增效的作用机制,方法：用加入和未加入ARE的灭螺药分别浸泡钉螺24h,运用扫描电镜观察一定浓度的ARE单用或与杀螺药合用对钉螺头部及触角,足跖肌,壳轴肌形态结构的影响,结果：25mg/LARE,0.625mg/L五氮酚钠（NaPCP),0.0625mg/L氮硝柳胺（NC）单用时,钉螺的头部及触角,足跖肌、壳轴肌的形态与正常钉螺形态结构相近,而5mg/LARE分别与0．625mg/LNaPCP,0.625mg/LNIC合用时,钉螺的触角,足跖肌和壳轴肌的表面皱褶变平坦,形态结构完全破坏,与单用5mg/LNaPCP,1mg/LNIC的结构相同,结论：ARE能增强灭螺药对钉螺软体结构的破坏作用。     

低浓度槟榔碱杀螺作用的实验观察

采用WHO推荐的"杀螺剂实验室终筛法"中的浸泡法,将受试钉螺分为6组,分别投入浓度为0.5、1.0、1.5、2.0 mg/L的槟榔碱溶液中,对照组溶液分别为2.0 mg/L的氯硝柳胺以及去氯自来水。经上述浓度槟榔碱作用1 h,钉螺的开厣率依次为55.6%、90.0%、92.2%、95.6%,附壁率均为0,氯硝柳胺对照组开厣率为13.3%,附壁率为1.1%,去氯水组开厣率及附壁率均为77.8%;槟榔碱作用24 h钉螺死亡率依次为91.2%、95.6%、84.4%、73.3%,氯硝柳胺对照组为100%,去氯水组为0。24 h内不同浓度槟榔碱组钉螺头足部软体均肿胀明显,对照组无肿胀。表明槟榔碱在极低浓度时即具有显著的杀灭钉螺作用,且能够抑止钉螺上爬附壁。     

Effects of metabolic blockade on intracellular calcium concentration in isolated ferret ventricular muscle

Tension and intracellular free calcium concentration [( Ca2+]i) were measured in isolated ferret papillary muscles. When both anaerobic glycolysis and oxidative phosphorylation were prevented (metabolic blockade), there was a rapid decline of both developed tension and systolic [Ca2+]i signals. Subsequently, resting tension increased, and after a further delay, resting [Ca2+]i also rose. When oxidative metabolism was restarted after a period of metabolic blockade that was sufficient to elevate both resting tension and [Ca2+]i, a variable recovery of mechanical function occurred. In preparations that showed recovery, resting tension declined toward control level, and there was considerable recovery of developed tension. [Ca2+]i initially fell, but it then rose to a level similar to that at the end of the preceding period of metabolic blockade and exhibited large variations in amplitude with frequency components in the range 0.2-1 Hz. This elevated [Ca2+]i gradually declined. Arrhythmias were often present during this recovery period and appeared to be triggered by the spontaneous increases in [Ca2+]i. In preparations that failed to recover, resting tension remained elevated or increased, and developed tension showed little recovery. Such preparations showed larger rises in [Ca2+]i both during and after metabolic blockade, and [Ca2+]i continued to rise when oxidative metabolism was restarted. In experiments in which Na-Ca exchange was inhibited (by replacement of sodium by lithium or by the application of nickel), the rise of [Ca2+]i when oxidative metabolism was restarted was reduced, but recovery of mechanical function was improved. The correlation between elevated [Ca2+]i on reactivation of oxidative metabolism and failure of recovery of mechanical function suggests that elevated [Ca2+]i has a direct role in preventing the recovery of mechanical function.     

Calcium induced reversible alterations in excitation-contraction coupling in verapamil treated rat myocardium

We studied the effects of a calcium channel blocking agent, verapamil (V) (2 to 10 micrograms/ml), in the presence of increasing external calcium on simultaneously recorded transmembrane electrophysiological properties and mechanical function of rat myocardium. Left ventricular papillary muscles from male Fischer 344 rats were studied electrically, by standard microelectrode techniques, and mechanically in an isolated tissue bath at 30 degrees C. Control (0 micrograms/ml V + 2.4 mM Ca2+) = C, action potential duration at 50% and 75% repolarization (D50ap and D75ap) recorded from papillary muscles were short (14.1 +/- 0.75 ms; 33.3 +/- 2.7 ms) compared with recordings from papillary muscles subjected to increasing doses of verapamil (2, 4, 6, 8, or 10 micrograms/ml) + 2.4 mM Ca2+ = V, (17.3 +/- 0.77 ms; 121.4 +/- 8.9 ms: 10 micrograms/ml) (P less than 0.001). Upon augmentation of external calcium [10 micrograms/ml Verapamil + augmented Ca2+ (4.8, 7.2, or 9.6 mM] = VCa, D50ap and D75ap decreased but still remained significantly longer than control D50ap and D75ap (15.1 +/- 0.77 ms; 110.1 +/- 7.9 ms). Developed tension (Td), time to peak developed tension (TPT), time to one-half relaxation (T1/2R) and resting tension (Tr) decreased as a function of verapamil concentration. Although TPT and T1/2R returned toward C values when external calcium was increased, Tr continued to decrease while Td increased above control levels. A significant correlation was found between measured parameters of contraction and transmembrane action potential for C and VCa muscles. However, in V muscles no significant correlation was observed between these same mechanical and electrical parameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

The interrelationship of calcium-mediated action potentials and tension development in cat ventricular myocardium.

Studies of Ca-mediated action potentials and mechanical activity of cat papillary muscles and trabeculae partially depolarized and Na-inactivated by K-rich (13.7 mm) solution were performed. Variation in strength of muscle stimulation resulted in gradation of rate of rise, overshoot and duration of Ca-mediated action potentials, peak tension and time to peak tension. At constant stimulus strength the rate of rise, overshoot and duration of the Ca-mediated action potentials were markedly depressed when the frequency of stimulation was increased. Two/second was maximum driving frequency. Within this range the frequency: tension relationship was similar to, although less than, the control. When steady state peak tension was low the Ca inflow was high—as indicated by $\text{d}\text{V}\text{d}\text{t}{}_{\mathrm{<mtext>max</mtext>}}$, overshoot and plateau positivity—and action potential prolonged. Following frequency change, $\text{d}\text{V}\text{d}\text{t}{}_{\mathrm{<mtext>max</mtext>}}$ of the rising phase and overshoot decreased (increased) during the initial positive (negative) inotropic effect, and then tapered to steady-state by the end of the 1–2 min inotropic change. Hence, during staircase, as well as in steady state, the tension development was intimately interrelated to the Ca inflow, the underlying mechanism being discussed. Reducing [Ca]_o to 0.25 mm completely inhibited Ca-mediated excitation as well as contraction within 15–20 min. Inhibitors of the slow Ca inward current (Verapamil, D 600) similarly inhibited Ca-mediated action potentials, but left resting state excitation and contraction (1/min) essentially unaltered.     

Frequency-dependent myosin light chain phosphorylation in isolated myocardium

A specific light chain subunit (P-light chain) of myosin from striated and smooth muscles is phosphorylated by Ca2+ calmodulin-dependent myosin light chain kinase. Phosphorylation of cardiac P-light chain was examined in isolated perfused rabbit ventricular septae to determine the effect of contraction frequency on this Ca2+-dependent reaction. Muscles stimulated at 42 beats/min had 0.23 mol phosphate/mol P-light chain which decreased to 0.12 mol phosphate/mol P-light chain when the muscles were made quiescent (0 beats/min in the presence of 22 mM K+ for 30 min). Rephosphorylation of P-light chain to 0.24 mol phosphate/mol P-light chain occurred in muscles stimulated at 84 beats/min for 90 min but not in muscles stimulated at 42 beats/min for 30 min (0.15 mol phosphate/mol P-light chain). Stimulation at frequencies ranging from 0 to 126 beats/min for 30 min produced a frequency-dependent increase in P-light chain phosphorylation from 0.1 to 0.4 mol phosphate/mol P-light chain. Increased inotropy for 30 s with isoproterenol was not associated with significant increases in P-light chain phosphorylation in muscles stimulated at 42 beats/min. The rates of myosin P-light chain phosphorylation and dephosphorylation in ventricular muscle are much slower than the reported rates of phosphorylation in either fast-twitch skeletal or smooth muscles. The extent of cardiac P-light chain phosphorylation appears dependent upon the steady-state frequency of contraction.     

Effects of trifluoperazine on the contraction kinetics of the isolated intact tracheal and pulmonary artery smooth muscle

BACKGROUND: We studied the effect of the calmodulin antagonist trifluoperazine (TFP) on isolated intact rat tracheal and pulmonary artery smooth muscle contractile behaviour. METHODS: Experimental series: 1) TFP-dose-response curves for TFP's effect on force generation were constructed using rat tracheal smooth muscles and rat pulmonary artery preparations (n = 8). A concentration of 1 micromol/l TFP was chosen for the subsequent experimental series. 2) Tracheas and pulmonary arteries (n = 14) were dissected in three segments. One of them was used immediately for experiments ("native"), the other two were treated for 12 h in 4 degrees C Tyrode solution without ("12 h cold storage") or with 1 micromol/l TFP ("12 h cold storage + TFP"). These preparations contracted after supramaximal effective electrical field stimulation. The force-clamping technique was used to analyse kinetic and mechanical parameters of smooth-muscle contraction in both types of preparation (measurement conditions: resting tension 2 mN, 37 degrees C, modified Krebs-Henseleit solution). RESULTS: 1) TFP decreased developed force dose-dependently in pulmonary artery and tracheal smooth muscle. 2) During sustained tonic activation, the contraction kinetics become slower both with and without TFP treatment (p < 0.0001). 3) TFP caused a dramatic retardation of the velocity of force generation in both types of preparation for any given time interval during the course of a tonic activation (p < 0.0005). 4) The dramatic effects of TFP on the contraction kinetics were not associated with effects on the extent of force generation. CONCLUSIONS: These results support the assumption that tracheal and pulmonary artery smooth muscle cross-bridge rates are controlled by a calcium-calmodulin-dependent myosin light chain kinase. This finding suggests the involvement of a calmodulin-independent regulator process responsible for the changes observed in the cross-bridge cycling rates during sustained tonic activation. A direct intervention on the contractile apparatus level is a measure for reduction of smooth-muscle tone without negative inotropic side effects.     

Calcium hypersensitivity in airways smooth muscle. Isometric tension responses following anaphylaxis

The isometric tension of anaphylactic guinea pig trachealis muscle preparation was examined at subphysiologic extracellular calcium concentrations, in vitro. Paired observations of control to passively sensitized (egg albumin antiserum) and antigen-challenged muscles (anaphylaxis) were made to exposure to trace Ca++ followed by cumulative Ca++ replacement. Following anaphylaxis, a leftward shift of the Ca++ concentration-tension responses was found at 0.25--0.5 mM Ca++ (p less than 0.001); EC50 was 1.5 x greater than control. A greater maximal tension was also noted at 2.52 mM Ca++. Passively sensitized muscles did not exhibit this heightened response. Subthreshold tissue chemical mediators are tentatively excluded as causative. An increased sensitivity to extracellular Ca++ exists in resting smooth muscle following anaphylaxis.     

Ca2+-recruitment in tachykinin-induced contractions of gut smooth muscle from African clawed frog,Xenopus laevis and rainbow trout,Oncorhynchus mykiss

Changes in intracellular Ca(2+) concentration control many essential cellular functions like the contraction of smooth muscle cells. The aim of this study was to investigate if the tachykinin substance P (SP) engages external Ca(2+)-sources, internal Ca(2+)-sources, or both in the contraction of the gastrointestinal smooth muscle of rainbow trout (Oncorhynchus mykiss) and the African clawed frog (Xenopus laevis). Strip preparations made of either longitudinal smooth muscle of proximal intestine or circular smooth muscle of cardiac stomach were mounted in organ baths and the tension was recorded via force transducers. Ca(2+)-free Ringer's solution containing the Ca(2+) chelating agent EGTA (2mM) abolished all spontaneous contractions. Exposure to SP in Ca(2+)-free solution decreased the response. Preparations were also treated with the Ca(2+)-ATPase inhibitor thapsigargin (10 microM) during 30 min. Thapsigargin reduced the effect of SP on intestinal longitudinal smooth muscle in rainbow trout and on stomach circular smooth muscle in the African clawed frog and to a less extent in the intestinal longitudinal smooth muscle. The results show that external Ca(2+) is of great importance, but is not the only source of Ca(2+) recruitment in SP-activation of gastrointestinal smooth muscle in rainbow trout and the African clawed frog.