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1.
Endothelial dysfunction contributes to the development of ungulate's laminitis. Although extensively studied in equines, the endothelial function is not fully examined in bovine digital veins (BDVs). BDVs were studied under isometric conditions to describe the acetylcholine (ACh) endothelium‐dependent relaxation. Concentration–response curves were constructed to phenylephrine, ACh, and sodium nitroprusside (SNP). Relaxation responses were evaluated using either phenylephrine or depolarizing high‐potassium Krebs solution (DKS) as precontraction agents. Endothelium denudation and incubation with L‐NAME (300 μM), indomethacin (10 μM) or both were used to explore endothelial‐mediated mechanisms. Endothelium denudation did not modify phenylephrine and SNP responses, however, significantly (p < 0.05) converted a relaxation (63.2 ± 5%) response to ACh into a contraction (30.3±9%). The ACh‐evoked relaxation was significantly (p < 0.05) reduced in the presence of indomethacin (37.5 ± 6%) and L‐NAME (6.40 ± 2%). The presence of both inhibitors abolished the ACh‐evoked relaxation. Although DKS caused a higher precontraction than phenylephrine, ACh‐evoked relaxation (22.4 ± 3.4%) was still observed and was reduced by the combination of inhibitors (7.0 ± 1.0%). The ACh endothelium‐dependent relaxation in BDVs is essentially mediated by nitric oxide and endothelium‐derived prostanoids. The BDV endothelium function is a dynamic component in the control of the bovine digital blood flow, particularly under endothelial dysfunction conditions when venoconstriction might lead to postcapillary resistance increase.  相似文献   

2.
The underlying pathophysiological triggers for equine acute laminitis are unknown, although digital vasoconstriction, ischaemia, hypoxia and reperfusion injury may be involved. The contractile responses of isolated equine digital arteries (EDAs), harvested from the hindlimbs of normal horses postmortem at an abattoir, were studied acutely (up to 3 h) under hyperoxic (95% oxygen, 5% CO2) and hypoxic (95% nitrogen, 5% CO2) conditions in organ baths. Phenylephrine (PHE; 10?6 m ), 5‐hydroxytryptamine (5‐HT; 10?7 m ) and high potassium (K+; 118 mm ) caused contraction in EDAs which was significantly (P < 0.0001) enhanced under hypoxic conditions. In contrast, contraction stimulated by 9,11‐dideoxy‐9α,11α‐epoxymethanoprostaglandin F2α (U44069; 3 × 10?8 m ) was not significantly enhanced by hypoxia (P = 0.75). Hypoxia‐enhanced contraction in response to K+ was greater (P < 0.03) in vessels with a functional endothelium than in vessels in which the endothelium was removed by rubbing. Fasudil (10?6 to 10?5 m ), a Rho kinase inhibitor, and apocynin (10?3 to 3 × 10?3 m ), an NADPH oxidase inhibitor, significantly (P ≤ 0.05) inhibited hypoxia‐enhanced contraction in response to PHE and 5‐HT. In conclusion, hypoxia‐enhanced contraction occurred in EDAs. This appears to be partially mediated by reactive oxygen species produced by NAPDH oxidase, which activate Rho kinase to increase calcium sensitisation and enhance smooth muscle contraction.  相似文献   

3.
本研究选用了前列腺素类化合物(Prostaglandin E2（PGE2）、Prostaglandin F2α（PGF2α）、Prostaglandin D2（PGD2)）和受体选择性激动剂（Butaprost、U-46619）,用多道生理信号采集系统测定其对体外分离的奶牛输卵管峡部及壶腹部平滑肌收缩的影响,以此初步揭示受体的种类。结果发现,PGE2和Butaprost均抑制了奶牛输卵管峡部、壶腹部的自发性收缩运动,呈现明显的浓度依存性舒张反应;PGF2α在高浓度(1～10 μmol/L)下,使峡部和壶腹部的自发性收缩运动有了显著增强;PGD2在低浓度时轻微抑制了壶腹部平滑肌的收缩,但在高浓度(1～10 μmol/L)时加强了峡部和壶腹部平滑肌的收缩;U-46619从低浓度便引起了输卵管峡部和壶腹部平滑肌的强烈收缩。结果表明,EP4、EP2、FP、DP和TP受体同时存在于奶牛输卵管平滑肌上,能与内源性前列腺素类结合并参与调节输卵管平滑肌的自发性收缩。  相似文献   

4.
对牛卵巢卵泡内卵母细胞在不同浓度的CO2培养箱内体外成熟、体外受精后的卵裂率及胚胎体外发育进行了研究。结果显示,含5%小牛血清(CS)的TCM-199内的卵母细胞在2%CO2条件下培养20h后,达到第二次减数分裂期(MⅡ期)的卵子数明显高于在5%CO2条件下培养的卵母细胞数(P<0.05)。两种浓度的CO2条件下培养的牛卵母细胞体外受精后的卵裂率无明显差异,2%CO2浓度下培养的卵母细胞的囊胚发育率高于5%CO2浓度下培养的卵母细胞。  相似文献   

5.
A method for the isolation of an enriched population (greater than 60%) of bovine eosinophils was developed, using density gradient centrifugation. Eosinophils were isolated from peripheral blood by centrifugation on a density gradient medium of sp gr 1.092. Viability was greater than or equal to 95%, and the isolated eosinophils were found to be functional in chemokinetic and antibody-dependent cellular-cytotoxicity assays. This method represents a simple, rapid method for obtaining bovine eosinophils that can be used in a variety of assays of eosinophil function.  相似文献   

6.
The vasomotor effects of histamine on isolated bovine and equine basilar arteries were examined. Histamine induced contractions in both these preparations. The maximal response to and pEC50 value for histamine of the equine artery were larger than those of bovine tissue. Similar results were obtained with endothelium-denuded basilar arteries. Diphenhydramine (H1-receptor antagonist) inhibited histamine-induced contractions of the basilar arteries from both species in a concentration-dependent manner and its pA 2 values (with 95% confidence limits) were 7.61 (7.39–7.83) and 8.15 (8.01–8.29) for the bovine and equine preparations, respectively. Cimetidine (H2-receptor antagonist) slightly potentiated histamine-induced contractions of bovine, but not equine, basilar arteries. 2-Thiazolylethylamine (H1-receptor agonist) induced contractions in both preparations, whereas impromidine (H2-receptor agonist) induced weak relaxation of the bovine, but not the equine, tissue. These findings indicate that bovine basilar arterial smooth muscle cells possess H1- and H2-receptors. Stimulation of the former results in contraction, whereas stimulation of the latter results in weak relaxation. Equine basilar arterial smooth muscle cells possess H1-receptors, stimulation of which results in contraction.Abbreviations CR concentration ratio - EC50 concentration producing 50% maximal response - pA 2 negative logarithm of the molar concentration of antagonist that produces a twofold rightward shift of a concentration-response curve - pEC50 negative logarithm of EC50 - PGF2 prostaglandin F2 - PGI2 prostaglandin I2  相似文献   

7.
The effects of 5-hydroxytryptamine (5-HT) on the longitudinal smooth muscle from the rumen and reticulum of the bovine forestomach were investigated. 5-HT (0.25–490 μM) caused a contraction and a relaxation of the ruminal strips while it produced only an excitatory effect on the reticular strips. These effects were not affected by tetrodotoxin, hexamethonium, atropine or morphine, but were blocked by methysergide, LSD-25 or phenoxybenzamine. 5-HT potentiated the contraction evoked by stimulation of the intramural cholinergic nerves but did not show any effect on the relaxation produced by the non-adrenergic inhibitory nerves' excitation. The 5-HT-induced potentiation was not affected by morphine, LSD-25, methysergide and hexamethonium or high concentration of nicotine. Nicotine and dimethylphenylpiperazinium also caused a transient augmentation of the nerve-mediated contraction, but these effects were abolished by the competitive ganglionic blockers. The evoked contraction was depressed in high-Mg2+ solution, but this depression was antagonized partly by 5-HT. The affinity of the cholinomimetics to post-synaptic muscarinic receptor was not affected by 5-HT. It is concluded that contractions or relaxations of bovine forestomach strips induced by 5-HT are mediated through activation of D-receptors in the smooth muscle, and the 5-HT-induced potentiation of the evoked contraction may be elicited through presynaptic neural effects of 5-HT on the cholinergic nerves.  相似文献   

8.
The effects of endotoxin on β-adrenergic-mediated relaxation were investigated in the equine digital artery (EDA). Possible involvement of cyclooxygenase-2 (COX-2) in endotoxin-induced effects and basal EDA β-adrenoceptor functionality was also evaluated. Endothelium-intact (e(+)) and/or -denuded (e(-)) EDA rings were incubated overnight with lipopolysaccharide (LPS), LPS+NS398 (selective COX-2 inhibitor) or NS398 alone. Vessel rings were then mounted in organ baths and relaxant responses to isoproterenol (ISOP) recorded on U44069-induced pre-contraction. Response to ISOP was further evaluated in either incubated or freshly isolated (e(-)) rings acutely exposed to NS398. Fresh and incubated (e(-)) EDAs were also analysed for COX-2 expression by Western blotting. LPS caused endothelium-dependent enhancement of β-adrenergic mediated relaxation. NS398 did not reverse endotoxin effects, suggesting that COX-2 did not have a mediating role. In the absence of LPS, NS398 significantly increased ISOP-induced relaxation. This finding, together with immunoblot detection of COX-2 in both fresh and incubated (e(-)) vessels, revealed the existence of a constitutive COX-2 exerting tonic inhibitory modulation on EDA β-adrenergic-mediated relaxation. The results support the possible role of endotoxin in the vascular disturbances associated with equine laminitis. Moreover, the involvement of COX-2 in the physiological regulation of EDA tone warrants further clinical investigation into the efficacy and safety of selective COX-2 inhibitors on digital circulation in horses.  相似文献   

9.
旨在探讨线粒体钙单向转运体（mitochondrial calcium uniporter,MCU）介导线粒体Ca2+转运是否参与低氧诱导的肉鸡心肌细胞线粒体损伤。试验通过分离白羽肉鸡鸡胚原代心肌细胞,在低氧条件下（3% O2,5% CO2,92% N2）培养24、48、72 h,同时使用RU360抑制MCU的表达并在低氧条件下处理72 h后,使用流式细胞术检测细胞内Ca2+浓度、线粒体Ca2+浓度、线粒体活性氧水平和线粒体膜电位,检测MCU及其调节因子的mRNA和蛋白表达。结果显示,通过差速贴壁方法培养的心肌细胞纯度可达90%以上;低氧培养24 h,诱导心肌细胞MCU、MICU1 mRNA表达增加（P<0.05）,胞浆和线粒体内Ca2+浓度显著上升（P<0.05）,线粒体膜电位增加（P<0.05）;低氧培养48 h,诱导MCUR1和MICU1 mRNA表达减少（P<0.05）,细胞Ca2+浓度上升（P<0.05）;低氧培养72 h,诱导MCU mRNA表达增加（P<0.01）,细胞和线粒体内Ca2+增加（P<0.01）,线粒体膜电位下降（P<0.01）,活性氧增加（P<0.01）。低氧处理72 h后,与低氧组相比,RU360预处理组细胞和线粒体内Ca2+减少,线粒体膜电位上升,活性氧生成减少（P<0.01）,MCU mRNA表达减少（P<0.01）。结果表明：低氧诱导MCU上调导致线粒体钙超载,促使线粒体功能降低并发生损伤,进而心肌细胞发生损伤;抑制MCU表达可以减轻低氧诱导的心肌细胞线粒体钙超载,保护线粒体。  相似文献   

10.
This study investigated the effects of cortisol and insulin, hormones that affect both glycaemic status and vascular function, on the in vitro contractility of isolated healthy equine small laminar veins. Small veins (150–500 μm) draining the digital laminae from healthy horses or ponies were investigated by wire myography. Concentration response curves were constructed for noradrenaline (NA), phenylephrine (PE), endothelin‐1 (ET‐1) and 5‐hydroxytryptamine (5‐HT) in the presence of either cortisol (10?6 m ) or insulin (1000 μIU/mL). Cortisol significantly increased the maximum contractility of laminar veins to the vasoconstrictors NA and 5‐HT but decreased the maximal contraction to ET‐1. Insulin decreased the contractility of vessels to PE and ET‐1. It is possible that short‐term cortisol excess could enhance venoconstrictor responses to 5‐HT and NA in laminar veins in vivo, thereby predisposing to laminitis. Additionally, a reduction in the ability of insulin to counteract alpha‐adrenoreceptor and ET‐1‐mediated contraction, likely to occur in subjects with insulin resistance, may further exacerbate venoconstriction in animals prone to laminitis. These mechanisms may also predispose horses with disorders such as equine Cushing's disease and equine metabolic syndrome to laminitis.  相似文献   

11.
The effects of IV administered amiodarone, a class-III antiarrhythmic agent, on myocardial contractility, early myocardial relaxation, and hemodynamic variables were evaluated in normal canine hearts and those with infarcts. In the normal canine heart, amiodarone had important, but relatively mild, depressant effects on left ventricular contractility (assessed by maximal positive first derivative of left ventricular pressure (+dP/dtmax) and maximal elastance (Emax)) and heart rate when given IV at a dose of 10 mg/kg of body weight. An effect on contractility or active relaxation (assessed by maximal negative first derivative of left ventricular pressure (-dP/dtmax) and the time constant of isovolumic pressure decrease) was not identified with smaller doses. Myocardial infarction itself caused a predictable and marked depressant effect on myocardial contractility, as indicated by decreases in +dP/dtmax, ejection fraction, Emax, and -dP/dtmax, and elevation in end diastolic pressure. Additional depressive effects on contractility and active relaxation resulted when 10 mg of amiodarone/kg was administered to dogs with myocardial infarction and these effects were sufficient to worsen acute myocardial infarction-induced heart failure. Significant changes attributable to heart rate alone could not be identified. On the basis of our findings, we suggest that amiodarone administered IV should be used with caution in dogs with compromised ventricular function.  相似文献   

12.
Sheets of mucosa from the jejunum of healthy horses were mounted in incubation chambers and bathed with Krebs-Ringer bicarbonate solution. Changes in tissue function and histologic appearance were compared after the following conditions: (1) control conditions for 30 minutes with 95% O2/5% CO2 in the gas phase; (2) same conditions as control, except incubation with superoxide dismutase (300 U/ml) during the last 18 minutes; (3) anoxia for 15 minutes with 95% N2/5% CO2, followed by reoxygenation for 15 minutes; (4) same conditions as 3, except incubation with superoxide dismutase during reoxygenation; and (5) anoxia for 30 minutes. Anoxia reduced the accumulation of radiolabeled L-alanine and caused cell swelling, as indicated by an increase in tissue water and tissue Na contents. Reoxygenation improved the tissue's ability to accumulate L-alanine, but tissue swelling continued after this treatment. Tissue Na content and L-alanine accumulation were restored to control values by reoxygenation with superoxide dismutase in the bathing medium. The grade of structural damage, as indicated by separation of epithelial cells from villi, was equally severe after all, but control, conditions. Superoxide dismutase had no effect on the tissue control conditions. Results of this study suggest that superoxide radicals are involved in the pathogenesis of reperfusion injury in equine jejunal mucosa and that this may be of clinical importance in cases of small intestinal strangulation obstruction.  相似文献   

13.
Low doses of endotoxin cause vasoconstriction and hypoperfusion of the digit, small intestine, and cecum in horses. To determine the potential cause of these vascular alterations, in vitro vascular responses of palmar digital arteries and veins were determined in 8 horses after intravenous (IV) infusion of 1 L 0.9% NaCl (control) and 0.1 μg/kg Escherichia coli 055:B5 endotoxin in 1 L of 0.9% NaCl (endotoxin-treated). Vessels were surgically removed under general anesthesia, cut into 4-mm vascular rings, suspended in tissue baths, and attached to force displacement transducers for measurement of vascular tension. Cumulative concentration response curves to acetylcholine, bradykinin, nitroprusside, norepinephrine, 5-hydroxytryptamine (serotonin), and endothelin were determined. Maximal relaxation or contraction and the concentrations needed to produce 50% maximal relaxation or contraction were determined. Palmar digital arteries from endotoxin-treated horses relaxed significantly less in response to acetylcholine and bradykinin (endothelium-dependent), but not to nitroprusside (endothelium-independent) when compared with arteries from control horses. Digital arteries from endotoxin-treated horses also contracted significantly more with norepinephrine but less with serotonin. Digital veins responded less than digital arteries. In another study, vascular reactivity experiments documented that acetylcholine and bradykinin were endothelium-dependent vasodilators (endothelium-denuded vessels relaxed less than control vessels) in palmar digital vessels. Additionally, maximal relaxations for both vasodilators were significantly inhibited by N-nitro-L-arginine methyl ester (L-NAME), a nitric oxide antagonist, suggesting that acetylcholine and bradykinin cause relaxation through the nitric oxide pathway. The data from these studies indicate that low dose endotoxin impairs endothelium-dependent relaxation and augments adrenergic contraction of palmar digital arteries in horses.  相似文献   

14.
A method for the isolation of an enriched population (greater than 95%) of bovine polymorphonuclear leukocytes (PMNs) was developed using density gradient centrifugation. Leukocytes were isolated from peripheral blood by centrifugation in a density gradient medium (Percoll) of specific gravity 1.092. Viability was greater than or equal to 95% and the isolated PMNs were functional in migration inhibition and chemiluminescence assays. This has proved to be a simple effective method for obtaining bovine PMNs and yields cell populations that can be utilized for a variety of measures of PMN function.  相似文献   

15.
近年来低氧细胞培养逐渐成为研究热点，低氧条件下可提高细胞体外扩增的生长动力学、细胞的增殖率及干细胞分化等功能。缺氧诱导因子-1α(hypoxia inducible factor-1α，HIF-1α)是应答低氧应激的关键因子，也是介导低氧信号的转导中枢，与其相关的血管内皮生长因(vascular endothelia growthfactor，VEGF)、低氧促有丝分裂因子(hypoxia-induced mitogenic factor，HIMF)及促红细胞生成素(erythropoietin，EPO)等是其重要的靶基因，它们之间的相互作用对低氧条件下细胞的发生、发展有重要作用。笔者对低氧培养细胞的研究现状及低氧相关细胞因子的调控机制及作用进行概述，以期为探索细胞低氧机理提供理论依据，为低氧适应性及高原疾病治疗提供更多的研究思路。  相似文献   

16.
Strains of the suspensory ligament and deep digital flexor, superficial digital flexor, and long digital extensor tendons in the equine (pony) hind limb were recorded in vivo, using implanted strain gauges consisting of silicone rubber tubes filled with mercury. The relationship between strain gauge signals and tendon strains was obtained from tension-strain tests performed on isolated tendons after death of the ponies. During normal walking, maximal tendon strain (elongation over initial length, relative to the length of the structures at first ground contact) was 3.1% in the suspensory ligament and 3.4%, 2.3%, and 0.3% in the deep digital flexor, the superficial digital flexor, and the long digital extensor tendons, respectively. Changes (that occurred during walking) in the distance from origin to insertion of these musculotendinous structures were computed from limb geometric configuration and limb conformation. Maximal increase in origin to insertion length was 3.1% in the suspensory ligament and 2%, 1.6%, and 1.5% in the deep digital flexor, superficial digital flexor, and long digital extensor musculotendinous structures, respectively. The differences in strain, comparing the entire musculotendinous structure and its tendon, were explained by muscular contraction or relaxation.  相似文献   

17.
The effects of various selective phosphodiesterase (PDE) inhibitors on carbachol (CCh)-induced contraction in the bovine abomasum were investigated. Various selective PDE inhibitors, vinpocetine (type 1), erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA, type 2), milrinone (type 3), Ro20-1724 (type 4), vardenafil (type 5), BRL-50481 (type 7) and BAY73-6691 (type 9), inhibited CCh-induced contractions in a concentration-dependent manner. Among the PDE inhibitors, Ro20-1724 and vardenafil induced more relaxation than the other inhibitors based on the data for the IC50 or maximum relaxation. In smooth muscle of the bovine abomasum, we showed the expression of PDE4B, 4C, 4D and 5 by RT-PCR analysis. In the presence of CCh, Ro20-1724 increased the cAMP content, but not the cGMP content. By contrast, vardenafil increased the cGMP content, but not the cAMP content. These results suggest that Ro20-1724-induced relaxation was correlated with cAMP and that vardenafil-induced relaxation was correlated with cGMP in the bovine abomasum. In conclusion, PDE4 and PDE5 are the enzymes involved in regulation of the relaxation associated with cAMP and cGMP, respectively, in the bovine abomasum.  相似文献   

18.
The contractile response of intestinal strips in rainbow trout (Oncorhynchus mykiss Walbaum, 1792) to the administration of histamine was assessed by means of the organ bath technique. Intestinal strips were isolated from 16 clinically healthy fish and mounted in organ baths. Histamine was compared with the full agonist serotonin, to evaluate their contractile efficacy and potency. Serotonin elicited a concentration-related contraction in all examined intestinal strips, whereas histamine induced the contraction only in 14 exemplars. Of these, seven exhibited a concentration-related response. A sigmoidal curve was fitted from data (R(2) = 0.55) and its best fit values were compared with those of serotonin. Interestingly, histamine exhibited the same efficacy (E(max)) as serotonin (F-test, p > 0.05), but showed lower potency (by an order of magnitude) (F-test, p < 0.01). Moreover, the effect of the H1 antagonist, pyrilamine, has been tested to exclude aspecific contraction due to other agonists eventually released in situ following histamine administration. Pyrilamine showed a marked concentration-related antagonist action on the contractility induced by histamine with complete contractility antagonism at 10(-4)M. The authors suggest that the responses to histamine measured in the present study reflect a less sensitive response to an exogenous source of histamine, possibly due to bacterial metabolism.  相似文献   

19.
本试验旨在研究紫菀乙醇提物对豚鼠离体气管平滑肌收缩功能的影响。采用离体气管恒温灌流的方法,将豚鼠气管制成气管螺旋条,通过 BL-420F 生物机能实验系统测定其张力的变化,观察紫菀乙醇提物对离体气管平滑肌静息状态下的舒张作用,以及在氯化乙酰胆碱(Ach)、磷酸组胺(His)、CaCl2条件下和无钙下Ach诱导细胞内钙释放和外钙内流所致两种收缩条件下对离体气管平滑肌张力变化的影响。试验结果显示,低浓度紫菀乙醇提取物(0.002~0.008 g/mL)对静息状态下豚鼠离体气管平滑肌具有一定的收缩作用,高浓度(0.008~0.196 g/mL)时具有舒张作用;低、中、高3个剂量组均可抑制Ach、His和CaCl2引起的气管平滑肌收缩强度,使各致痉剂的量效曲线非平行右移并降低最大效应。紫菀乙醇提取物对His的抑制作用强度最大,其次为Ach,最后是CaCl2,且均呈剂量依赖性。以上结果表明紫菀乙醇提物具有舒张气管平滑肌的作用,其机制可能与抑制豚鼠气管平滑肌M受体、H1受体和阻断Ca2+通道从而抑制细胞Ca2+内流有关。  相似文献   

20.
The aim of the experiment was to study the effect of alcohol extract of Aster tataricus L.f.on the contraction of isolated guinea pig tracheal smooth muscle.The guinea pig tracheal smooth muscle was prepared by isolated tracheal thermostatic perfusion method.The effects of Aster tataricus L.f.on tracheal smooth muscle under the resting state and contraction stimulated by acetylcholine (Ach),histamine (His),CaCl2,Ca2+ release and influx in cells without calcium were measured by BL-420F biological function experiment systems.The results showed that Aster tataricus L.f.could induce the contraction of isolated trachea at resting state at a low concentrations of 0.002 to 0.008 g/mL and exerted a relaxation on the isolated trachea when at the higher concentrations of 0.008 to 0.196 g/mL.All of the three concentrations of Aster tataricus L.f.could inhibit the tension stimulated by Ach,His and CaCl2 which were antispasmodic agents,led to the non-parallelled rightward moving of cumulative concentration-response curve and the decline of maximal responses.The suppressive effect on His was the strongest,followed by Ach and CaCl2,and the suppression could counteract the contraction induced by extracellular Ca2+influx significantly,and they were all expressed concentration-dependent manner.These results indicated the alcohol extract of Aster tataricus L.f.could relax tracheal smooth muscle by acting on M-receptor and histamine receptor and blocking Ca2+ passage,thus inhibiting extracellular Ca2+influx.  相似文献   

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