化学药物对家兔离体小肠平滑肌电生理特性的影响

观察各种化学药物对家兔离体小肠各段平滑肌的作用,采用常规离体灌流的十二指肠、空肠及回肠平滑肌标本作舒缩运动实验,记录用药前后各段小肠平滑肌的收缩活动特征及变化规律.结果显示：不同浓度的乙酰胆碱和磷酸组织胺能增强小肠各段平滑肌的收缩频率与幅度,其幅值变化与用药前有显著性差异（P＜0.01） ,并呈剂量依赖性;而不同浓度的肾上腺素和阿托品则抑制小肠各段平滑肌（P＜0.01） .不同肠段对各种化学药物的作用存在着差异,一般十二指肠作用最强,空肠次之,回肠最差.     

NaOH、HCl、BaCl_2对家兔小肠段平滑肌收缩的影响

平滑肌对一些酸碱等化学物质较为敏感,其可能会影响小肠的肌电活动,进而影响小肠的运动。本研究试图探讨氢氧化钠(Na OH)、盐酸(HCl)、氯化钡(Ba Cl_2)对离体家兔小肠段平滑肌收缩功能的影响,以期了解不同化学药物对小肠肌电活动的影响,为肠道疾病的诊断和治疗提供参考。本研究选取健康家兔,处死后取家兔的十二指肠、空肠、回肠离体后进行恒温灌流,分别给予1 mol/L的Na OH溶液、1 mol/LHCl溶液、1 mol/L Ba Cl_2溶液,并选择相对应肠段作为对照组,仅给予等量生理盐水恒温灌流,对比各组小肠平滑肌电活动变化。研究表明,Ba Cl_2干预下,十二指肠、空肠、回肠的收缩频率均高于对照组、Na OH组、HCl组,差异均具有统计学意义(p0.05);Ba Cl_2组、Na OH组、HCl组离体家兔小肠平滑肌的最大振幅均显著的高于对照组(p0.05),Ba Cl_2组离体家兔小肠平滑肌的最大振幅均显著的高于Na OH组、HCl组(p0.05);Ba Cl_2组、Na OH组离体家兔小肠平滑肌的负波最大振幅均显著的高于对照组、HCl组(p0.05),Ba Cl_2组离体家兔小肠平滑肌的负波最大振幅均显著的高于Na OH组(p0.05)。我们的研究初步表明:Ba Cl_2能显著的增强离体家兔小肠段平滑肌收缩功能,Na OH和HCl溶液会增强体家兔小肠平滑肌的最大振幅。研究显示Ba Cl_2的作用机制可能是促使平滑肌强直性收缩,而Na OH和HCl酸碱类物质的刺激可使肠壁内神经元兴奋,促进小肠平滑肌的运动。     

黄体酮对离体家兔气管平滑肌收缩活动的影响

目的：研究黄体酮对离体家兔气管平滑肌收缩活动的影响。方法：采用家兔离体气管平滑肌标本,观察黄体酮对ACh及Ca-Cl2量效曲线的影响,同时观察在无钙液中加入CaCl2时单剂量Ach诱发标本双时相收缩反应的影响。结果：黄体酮能使ACh及CaCl2量效曲线明显压低,最大反应降低,且能够抑制ACh引起的第1时相收缩,对第Ⅱ时相收缩作用无明显影响。且黄体酮对ACh量效曲线的影响是上皮依赖性的。结论：黄体酮对离体气管平滑肌的松弛作用与抑制电压依赖性钙通道(PDC)和ACh引起的细胞内Ca^2 释放及上皮细胞的作用有关。     

哌替啶对肠道平滑肌运动的抑制作用及其机制

目的：研究哌替啶对肠道平滑肌运动的影响及其作用机制。方法：制备家兔离体小肠,记录小肠平滑肌张力,观察哌替啶对肠肌运动的影响。并进一步测定哌替啶灌胃前后小鼠小肠推进运动的变化。结果：在不同浓度的哌替啶作用下家兔离体肠肌收缩活动减弱：哌替啶灌胃后小鼠小肠推进减慢。哌替啶对离体肠肌的抑制作用不能被纳洛酮所阻断。结论：哌替啶对肠肌运动有抑制作用,其肠道作用可能与阿片受体无关。     

氢溴酸高乌甲素对小肠平滑肌运动的作用

目的：研究氢溴酸高乌甲素对小肠平滑肌运动的影响并探讨其可能的作用机制。方法：记录氢溴酸高乌甲素对家兔离体小肠平滑肌运动的影响,并测定氢溴酸高乌甲素处理后小鼠小肠推进运动的变化。结果：氢溴酸高乌甲素抑制家兔离体小肠平滑肌收缩的发展张力。纳洛酮对氢溴酸高乌甲素的肠肌抑制作用无明显影响（P〉0.05）。乙酰胆碱（0.1 mg/L）可使家兔小肠舒张末张力明显增加。氢溴酸高乌甲素处理后,乙酰胆碱对肠肌舒张末张力的增加百分比降低（P〈0.05）。氢溴酸高乌甲素对小鼠小肠推进运动有显著抑制作用（P〈0.05）。结论：氢溴酸高乌甲素对小肠平滑肌收缩有抑制作用,并可以部分阻断乙酰胆碱的肠肌收缩作用,阿片受体可能不参与该抑制作用。     

银杏叶提取物对小鼠离体小肠平滑肌收缩特性的影响

目的观察不同浓度的银杏叶提取物(Extract of Ginkgo biloba, EGb)对小鼠离体小肠平滑肌活动的影响,探讨EGb对小肠平滑肌的作用机制.方法制备离体肠段标本,灌流给药后记录不同浓度EGb作用下小肠收缩变化.结果低浓度和中浓度的EGb对离体小肠平滑肌有兴奋作用,随浓度增加,低浓度EGb的兴奋程度呈降低趋势,中浓度EGb的兴奋程度呈升高趋势;高浓度EGb引发抑制效应,随浓度增加,抑制程度降低.结论不同浓度范围的EGb对离体小肠平滑肌有不同作用,可能通过对平滑肌的直接作用或调节激素释放,影响离子通道等途径发挥作用.     

黄芩苷对家兔离体子宫平滑肌的作用

目的:观察黄芩苷对家兔离体子宫平滑肌收缩的作用及其与Ca2+的关系.方法:制作常规离体家兔子宫平滑肌肌条,考察黄芩苷对子宫肌条反应的影响.结果:(1)黄芩苷(5-10mmol-L-1)剂量依赖抑制子宫平滑肌收缩;(2)黄芩苷对催产素及高K去极化液中Ca2+所致的离体子宫平滑肌收缩均呈剂量依赖性抑制;使CaC12累积量-效曲线非平行性右移,最大效应下降,呈非竞争性抑制;(3)且对子宫平滑肌依细胞内、外Ca2+两种收缩成分均呈抑制作用.结论:黄芩苷对家兔离体子宫平滑肌条的抑制作用,可能与其拮抗Ca2+有关.     

栀子对兔胃平滑肌体外运动的影响

目的：观察利胆药物-栀子对兔离体胃平滑肌的影响,并初步探讨其作用机制。方法：取兔胃肌条,安置在各恒温灌流肌槽中并用BL-310生物技能实验系统记录胃各部平滑肌条的收缩活动,结果：栀子显著升高兔胃底和胃体纵行肌条张力,增加其收缩频率,减小胃体收缩波平均振幅,并有剂量依赖关系。结论：栀子对胃肌条收缩活动具有明显的兴奋作用,这种兴奋作用部分经由M受体介导。     

膀胱平滑肌细胞自发性钙活动传递的在体观察和分析

目的:观察离体活膀胱肌条铺片中平滑肌细胞自发性钙活动,并分析平滑肌细胞自发性钙活动的特征.方法:制作离体膀胱肌条铺片,Physiological saline生理液灌流保持肌条铺片活性.待肌条自发性收缩活动出现后,Fluo-4负载肌条铺片激光扫描共聚焦显微镜观察并高速扫描记录平滑肌细胞自发性钙活动,随后利用Fluoview软件分析平滑肌细胞自发性钙活动肌束内纵向、横向及肌束间的传递情况.结果:成功记录到离体活膀胱肌条铺片中平滑肌细胞的节律性自发性钙活动.钙活动在肌束内纵向传递几乎无时间延迟,但在肌束内横向传递有一定的时间延迟;在相邻的膀胱平滑肌束间也记录到钙活动的传递.结论:平滑肌细胞的自发性钙活动起源于肌束的一侧,随后传导到肌束的另一侧;平滑肌细胞钙活动纵向传递和横向传递的途径和机制可能不同;膀胱平滑肌束之间的钙活动传递可能是通过ICCs细胞完成.     

胆汁对空肠平滑肌条运动影响的实验研究

目的:观察胆汁对兔离体小肠平滑肌的影响并初步探讨其作用机制.方法:取兔空肠纵行肌条,安置在各恒温灌流肌槽中并用BL-310生物技能实验系统记录空肠平滑肌条的收缩活动.结果:胆汁显著降低兔空肠肌条张力, 减小其收缩波平均振幅及收缩频率,并有剂量依赖关系.结论:胆汁对空肠肌条收缩活动具有明显的抑制作用,这种抑制作用部分经由肾上腺素能α受体及前列腺素介导,并有壁内神经节的参与.     

Ultrastructural changes in interneuron connections in intramural ganglia of the small intestine in suckling rabbits with experimental cholera]

Data, received in investigation of the small intestine intramural ganglia of 34 suckling rabbits show, that development of experimental cholera induce in the neurons reactive shifts, changed by dystrophic alterations. Prevaluation of cholinergic influences in autonomic ganglia in small intestine promotes enterocytes hypersecretion and accelerating of motor activity.     

Effects of external calcium, magnesium, and temperature on spontaneous contractions of pregnant human myometrium

Spontaneous isometric contractions of small isolated segments from the isthmic region of pregnant human myometrium were recorded to clarify the characteristics of and influences of experimental conditions on contractions. There is a spontaneous periodicity in membrane activity of human myometrium, and contractions evoked with a sustained electric stimulus were affected by spontaneous rhythmic contractions. The frequency of contractions increased markedly, but their duration decreased when temperature of the bathing fluid was increased from 26 degrees C to 39 degrees C. Both excess (7 mM) and low (0.5 mM) calcium levels suppressed the generation of spontaneous contraction. Frequency and half-duration gradually decreased when external magnesium was increased from 0 mM to 3.6 mM. These results indicate that the pattern of contraction depends on the frequency of and intervals between each action potential, and that spontaneous contractility-particularly its frequency-is extremely sensitive to external temperature and ionic conditions.     

Uptake of hexoses and lipids into rabbit jejunum and colon following ileal resection: effect of variations in the cholesterol and fat content of the diet

After 6 weeks feeding on either a high-cholesterol/fat (H) or a low-cholesterol/fat (L) diet, jejunal and colonic uptake was measured using a previously validated in vitro technique in control rabbits with an intact intestinal tract (C) and in animals submitted to the surgical removal of the distal half of the small intestine (R). The uptake of hexoses and fatty acids was influenced by ileal resection and by diet. Dietary manipulation altered the passive and active transport properties of the intestine and had a different effect on intestinal transport in animals with an ileal resection than in animals with an intact small intestine.     

兔急性肠道缺血再灌注损伤模型的建立

目的:建立小肠急性缺血再灌注损伤模型,确定合适的肠系膜上动脉阻断时间.方法:将70只新西兰兔随机按不同的肠系膜缺血时间(0、15、30、45、60min)分为A、B、C、D、E5组,每组14只,取8只用于恢复血供2h后留取各组兔下腔静脉血标本及肠组织,检测血清中MDA含量的变化,光镜下观察小肠组织形态学变化并对小肠黏膜损伤程度进行评分.另6只用于术后24h、 48h及72h生存率的观察.结果:A、B、C组的术后生存率均>83.3%.C、D、E组的MDA含量及肠黏膜损伤评分与A组比较,差异均有显著性(F=12.13～280.24,p<0.01).结论:肠系膜缺血30min,再灌注2h是建立兔小肠急性再灌注损伤的合适时间.     

Carboxylesterase in the liver and small intestine of experimental animals and human

Native polyacrylamide gel electrophoresis showed carboxylesterase (CES) to be the most abundant hydrolase in the liver and small intestine of humans, monkeys, dogs, rabbits and rats. The liver contains both CES1 and CES2 enzymes in all these species. The small intestine contains only enzymes from the CES2 family in humans and rats, while in rabbits and monkeys, enzymes from both CES1 and CES2 families are present. Interestingly, no hydrolase activity at all was found in dog small intestine. Flurbiprofen derivatives were R-preferentially hydrolyzed in the liver microsomes of all species, but hardly hydrolyzed in the small intestine microsomes of any species except rabbit. Propranolol derivatives were hydrolyzed in the small intestine and liver microsomes of all species except dog small intestine. Monkeys and rabbits showed R-preferential and non-enantio-selective hydrolysis, respectively, for propranolol derivatives in both organs. Human and rat liver showed R- and S-preferential hydrolysis, respectively, in spite of non-enantio-selective hydrolysis in their small intestines. The proximal-to-distal gradient of CES activity in human small intestine (1.1-1.5) was less steep than that of CYP 3A4 and 2C9 activity (three-fold difference). These findings indicate that human small intestine and liver show extensive hydrolase activity attributed to CES, which is different from that in species commonly used as experimental animals.     

Action of Escherichia coli heat-stable enterotoxin II on isolated sections of mouse ileum

When Escherichia coli STII was applied to the serosa of the ileum at a concentration of 40 micrograms/ml, an acceleration of the spontaneous motility and a weak contraction were induced 2-3 min later. The induction was not affected by the addition of atropine (10(-6) M), but was abolished by the addition of papaverine (10(-4) M). When STII was applied to the mucosa, the acceleration of the spontaneous motility appeared 7-8 min later, but a contraction was not induced. These results suggest that STII acts directly on muscle cell of the ileum and enhances the spontaneous motility of the intestine.     

Mechanisms of excitatory actions of neurotensin on canine small intestinal circular muscle in vivo and in vitro

We have shown previously that close intra-arterial injections of neurotensin in vivo inhibited phasic activity induced by field stimulation of the canine small intestine during anaesthesia but had little effect during quiescence. In contrast, in vitro in the present study, full thickness strips of the muscularis externa cut in the circular axis responded to the lowest effective neurotensin concentrations (10(-12) to 10(-9) M) with an increase in frequency and amplitude of spontaneous contractions; as the concentration was increased from 10(-8) to 10(-7) M, neurotensin inhibited spontaneous activity. A small tonic contraction also occurred; it was maximal at 10(-7) M. Since sufficient tetrodotoxin to block field-stimulated nerve responses did not significantly reduce any of these responses in vitro, the neurotensin responses in vitro did not appear to involve actions on nerves. Indomethacin did not alter the excitatory response to 10(-11) M neurotensin but 5,8,11,14-eicosatetraynoic acid inhibited the excitatory response in a reversible fashion, without altering the response to acetylcholine. Thus excitation in vitro may require the release of excitatory metabolites of arachidonic acid via the lipoxygenase pathway. The neurotensin response in vivo was further studied by evaluating its actions against repetitive submaximal contractions induced by intra-arterial injections of acetylcholine given every minute. Doses that produced a short inhibition of the field-stimulated activity (10(-11) to 10(-10) mol intra-arterially) did not produce inhibition but 10(-10) mol significantly increased the response to acetylcholine. Higher doses (10(-9) mol) produced a significant inhibition of the first subsequent acetylcholine dose but no enhancement of later doses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interactions of Giardia lamblia with human intestinal mucus: enhancement of trophozoite attachment to glass

Giardia lamblia trophozoites frequently are associated with mucus in vivo. We investigated the effects of human intestinal mucus on parasite attachment and survival in vitro. All samples of mucus from the duodenum and ileum (from four humans and two rabbits) enhanced attachment at 100 micrograms/ml. Attachment increased with mucus concentrations from 1 to 1000 micrograms/ml but declined toward the unstimulated level at concentrations above 1000 micrograms/ml. Mucus from the small intestine also promoted the survival of the parasites during the 2-h incubation. In contrast, colonic mucus promoted survival, but inhibited attachment. Fractionation of mucus from the human small intestine by cesium chloride equilibrium density gradient ultracentrifugation revealed that both attachment- and survival-promoting activities were in the low density, protein-rich fraction. The high density fractions containing the mucins were devoid of activity. Thus, a non-mucin fraction of mucus from the human small intestine may promote colonization by G. lamblia.     

The level of dietary protein and carbohydrate has a different effect on intestinal uptake of hexoses and lipids in rabbits with an ileal resection than in those with an intact intestinal tract

Either high protein, low carbohydrate (HP) or low protein, high carbohydrate (LP) diets were fed for 6 weeks to rabbits with or without resection of the distal half of the small intestine. Control and resected rabbits fed HP consumed more food and gained more weight than the animals fed LP. The level of dietary protein has a different effect on intestinal transport in animals with an ileal resection than in those with an intact small intestine. With 0.5 mM glucose, the in vitro uptake in control rabbits was greater for the LP than HP diet but was unchanged in resected rabbits; uptake of 0.5 mM galactose and 3-O-methyl glucose was unaffected by HP and LP, whereas in rabbit uptake was lower in LP than HP. The uptake of 40 mM glucose was greater with the LP than HP diet in control rabbits, but lower with LP than HP in resected rabbits. In control rabbits, the uptake of aluric acid was lower on the LP than HP diet; the uptake of octanoic acid, decanoic acid, and cholesterol was unchanged; and the uptake of each fatty acid and cholesterol was greater in resected rabbits fed LP than HP. Feeding a low protein diet to animals with an ileal resection is associated with lower jejunal uptake of high concentrations of glucose, but the higher uptake of galactose and enhanced permeability to fatty acids result in superior weight gain. Thus, recommendations for alterations in dietary protein and carbohydrate levels following ileal resection must be made with the knowledge that these changes may influence intestinal transport function as well as body weight gain.