Anatomical relationship between enkephalin-containing neurones and caecum-projecting neurones in the chicken intestinal nerve

The anatomical relationship between enkephalin-immunoreactive neurones and caecum-projecting neurones in the intestinal nerve of Remak (INR) of the chicken was investigated using retrograde transport of cholera toxin subunit B and immunohistochemistry with anti-enkephalin serum. After injection of cholera toxin into the base or body of the caecum, labelled neurones were mainly observed in the cranial part of the rectal INR. Enkephalin-immunoreactive neuronal cell bodies were found in the caudal part of the rectal INR and their fibres closely surrounded caecum-projecting neurones in the cranial part of the rectal INR. Diameters of caecum-projecting neurones surrounded with enkephalin-containing terminals were significantly larger than those of caecum- projecting neurones without enkephalin-terminals (P < 0.01). From these results, it is suggested that enkephalin-containing neurones are able to affect large-sized caecum-projecting neurones. This pathway may be involved with unique motility of the rectum and caeca that uric acid is retrogradely carried from the cloaca to the caeca.     

Adrenergic, cholinergic, and nonadrenergic-noncholinergic intrinsic innervation of the jejunum in horses.

OBJECTIVE: To determine the major neurotransmitters that regulate contractile activity in the jejunum of horses. SAMPLE POPULATION: Jejunal specimens from 65 horses without gastrointestinal tract lesions. PROCEDURE: Jejunal smooth muscle strips, oriented in the plane of the circular or longitudinal muscular layer, were suspended isometrically in muscle baths. Neurotransmitter release was induced by electrical field stimulation (EFS) delivered at 30 and 70 V intensities and at various frequencies on muscle strips maintained at low or high muscle tone. To detect residual nonadrenergic-noncholinergic neurotransmission, the response of muscle to EFS in the presence of adrenergic and cholinergic blockade was compared with the response in the presence of tetrodotoxin. RESULTS: Atropine (ATR) decreased the contractile response of muscle strips to EFS under most conditions. However, ATR increased the contractile response of high-tone circular muscle. Adrenergic blockade generally increased the muscle responses to 30 V EFS and in high-tone longitudinal muscle but decreased contractile responses in high-tone circular muscle. Tetrodotoxin significantly altered the responses to EFS, compared with adrenergic and cholinergic receptor blockade. CONCLUSIONS: Acetylcholine and norepinephrine appear to be important neurotransmitters regulating smooth muscle contractility in the equine jejunum. They induce contraction and relaxation, respectively, in most muscle preparations, although they may cause opposite effects under certain conditions. In addition, nonadrenergic-noncholinergic excitatory and inhibitory influences were detected. CLINICAL RELEVANCE: Acetylcholine or norepinephrine release within the myenteric plexus of horses may alter gastrointestinal motility.     

Effect of catecholamines on the smooth muscles of the esophageal groove of calves

The effect of noradrenaline and adrenaline on isolated smooth muscle from the reticular groove of calves was studied. Both catecholamines caused a concentration-dependent (1.1.10(-6) mol/l) contraction of the transversal muscle strips from the floor of the reticular groove. This excitatory effect was antagonized by prazosin (10(-7)) mol/l), and by high concentrations of yohimbine (10(-6) mol/l) and atropine (10(-5)) mol/l). Tetrodotoxin (3.10(-6) mol/l), an inhibitor of nerve conduction, did not change the contraction induced by catecholamines (55.10(-6)) mol/l). Catecholamines did not produce a contraction of the longitudinal muscle from the lips of the reticular groove. The beta-adrenergic agonist isoprenaline (55.10(-6) mol/l) even elicited a reduction of acetylcholine (55.10(-6)) mol/l) induced contraction of both the transversal and the longitudinal muscle from the reticular groove. The relaxing effect of isoprenaline was antagonized by propranolol (55.10(-6)) mol/l). According to these results the excitatory effect of catecholamines on the smooth muscle cells occurs through alpha-adrenergic receptors, whereas the relaxing effect is mediated by beta-adrenergic receptors of the muscle cell. The excitatory effect of catecholamines on the transversal muscle appears to be predominant. Atropine appears to be an unspecific blocking agent of alpha-adrenergic receptors.     

Dorsal Approach to the Caudal Pelvic Canal and Rectum Effect on Normal Dogs

A dorsal surgical approach to the perineal area and rectum was made on 10 healthy, adult dogs. The rectococcygeal muscle was incised and the levator ani and external sphincter muscles were separated to the level of the caudal rectal nerve. All dogs were clinically normal throughout a 3 week postoperative observation period.     

Intracellular microelectrode recording to characterize inhibitory neuromuscular transmission in jejunum of horses

OBJECTIVE: To evaluate electrical activity of jejunal circular muscle in horses and characterize electrical responses to stimulation by intrinsic inhibitory neurons. SAMPLE POPULATION: Portions of jejunum obtained from horses euthanatized for reasons other than gastrointestinal tract disease. PROCEDURE: Isolated circular muscle preparations were perfused with oxygenated modified Krebs solution. Glass microelectrodes were used for intracellular recording of membrane potentials from single smooth muscle cells. Electrical activity and responses to electrical field stimulation (EFS) of intrinsic neurons in the presence of guanethidine and atropine were recorded. Mediators of responses to nerve stimulation were also evaluated, using N-nitro-L-arginine methyl ester (L-NAME) and apamin. RESULTS: Mean resting membrane potential (RMP) was 41.5+/-1.8 mV. Small membrane potential oscillations were observed in muscle cells. Single or multiple action potentials were often superimposed on the peaks of these oscillations. Spontaneous oscillations and action potentials were blocked by nifedipine. Transient hyperpolarizations of smooth muscle cell membrane potentials (inhibitory junction potentials [IJP]) were observed in response to electrical field stimulation. The IJP evoked by stimulus trains consisted of an initial fast component followed by a slow component. The L-NAME did not have a significant effect on RMP and did not significantly affect the fast component of IJP at any stimulus frequency tested. In contrast, L-NAME abolished the slow component of IJP observed after trains of pulses. In the continued presence of L-NAME, apamin had no significant effect on RMP but effectively reduced the fast component of IJP. CONCLUSIONS AND CLINICAL RELEVANCE: Findings suggest that inhibitory neurotransmitters supplying equine jejunum act through different ionic mechanisms. Understanding these mechanisms may suggest new therapeutic targets for treatment of motility disorders.     

Influence of the autonomic nervous system in the horse urinary bladder

alpha and beta-adrenergic receptors in detrusor muscle and bladder base of horses were investigated by in vitro responses of smooth muscle strips to exogenous agonist and antagonist drugs. Noradrenaline, isoprenaline and salbutamol induced relaxation of detrusor muscle strips which was significantly inhibited by propranolol and butoxamine suggesting that the response is mediated by beta-2 adrenergic receptors. In the urinary bladder base noradrenaline, phenylephrine and B-HT 920 induced strong contractile effects. These contractile responses were inhibited by the alpha antagonist phenoxybenzamine, the alpha-1 selective antagonist prazosin and the alpha-2 selective antagonist yohimbine. The inhibitory action of prazosin was more potent than that observed with yohimbine suggesting that the response in the bladder base of horses is mediated predominantly by alpha-1 adrenergic receptors, although alpha-2 receptors also participate.     

Age-related changes in contractions of chicken aorta and ischiadic artery

The characteristics of the contraction of vascular smooth muscle were examined in thoracic aorta and ischiadic artery of chickens aged 3, 6, 10 and 18 weeks. High K⁺ solution induced a sustained contraction in smooth muscle preparations of aorta and ischiadic artery in vitro . The contraction of the ischiadic artery became greater with age, whereas the contraction of the aortic preparation did not. In the ischiadic artery, the magnitude of the contraction divided by the weight of the muscle preparation was constant at all ages studied. However, those in the aortic preparation decreased with age. These results suggest that the changes in the contractile responses of vascular smooth muscle owing to the age of chickens vary widely according to the preparations of blood vessels, and that the functional smooth muscle cells in the thoracic aorta of chicken do not increase with age.     

Transplanting the superficial gluteal muscle in the treatment of perineal hernia and flexure of the rectum in the dog

The authors distinguish between perineal hernia and flexure of the rectum. They describe in detail an operative procedure to treat these conditions using a transplanted superficial gluteal muscle to reinforce the ischio rectal fossa.     

Mechanisms of the Eimeria tenella growth inhibitory activity induced by concanavalin A and reticuloendotheliosis virus supernatants with interferon gamma activity in chicken macrophages and fibroblasts

Pretreatment of chicken bone marrow macrophages and embryo fibroblasts with supernatants containing chicken interferon gamma (IFN-gamma) for 24 hr prior to inoculation inhibited intracellular Eimeria tenella replication, measured by [3H] uracil incorporation. The supernatants (Sns) were obtained from culture of lymphoblastoid cells transformed by a reticuloendotheliosis virus (REV) and chicken splenocytes stimulated with concanavalin A (Con A). The mechanisms of the E. tenella growth inhibitory activity induced by Sn REV and Sn Con A in chicken macrophages and fibroblasts were studied. Addition of oxygen scavengers (superoxide dismutase, D-mannitol, DABCO, benzoic acid, L-histidine hydrochloride) was able to overcome the inhibition of E. tenella replication after pretreatment with Sn REV or Sn Con A in macrophage cultures but not in fibroblast cultures. Nitric oxide (NO) synthesis was induced in macrophage culture treated with Sn REV or Sn Con A but not in fibroblast culture. Addition of NG monomethyl-L-arginine, an NO synthase inhibitor together with the supernatants was also able to overcome inhibition of E. tenella replication in macrophage culture. On the other hand, addition of L-tryptophan to Sn REV- or Sn Con A-treated fibroblasts was able to reverse the inhibitory effect on E. tenella replication. In conclusion, production of inorganic NO or toxic oxygen intermediates may be involved in the E. tenella growth inhibitory activity of chicken macrophages pretreated with supernatants containing an IFN-gamma activity, and cellular tryptophan depletion may be involved for chicken fibroblasts, thus matching the mechanisms of the IFN-gamma-induced growth inhibitory activity for protozoans in mammals.     

Selective blockade of the responses of reticuloruminal muscle to 5-HT in sheep

The effects of intravenous administration of 5-HT on the patterns of reticulo-rumen contractions were studied in conscious sheep. Contractions were measured by strain gauges applied to the external wall of the reticulum and the ventral and/or dorsal sac of the rumen. The responses to 5-HT comprised (i) a short-lived contraction followed by (ii) a sustained increase in muscle tone and (iii) a concomitant inhibition of the extrinsic reticulo-rumen contractions. The corresponding blockades produced by (i) atropine, (ii) 5-HT antagonists and (iii) chemical sympathectomy suggest involvement of a peripheral cholinergic mechanism in the initial contractile response and a central adrenergic mechanism in the reflex inhibition of extrinsic reticulo-rumen contractions.     

Alterations of Endothelium-Dependent Digital Vascular Responses in Horses Given Low-Dose Endotoxin

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.     

Effect of azaperone on cardiovascular responsiveness in stress-sensitive pigs

The effect of intramuscular azaperone on the cardiovascular responses to stimulation of the sympathetic nervous system was examined in thiopentone-anaesthetized stress-sensitive pigs. Sympathetic stimulation was achieved with the Valsalva-like manoeuvre, and the intravenous tyramine, isoprenaline and phenylephrine tests. The responses were monitored as the changes in heart rate and blood pressure. Azaperone exerted an alpha adrenergic blocking action and possibly a mild beta adrenergic blocking effect. It also retarded pre-adrenoreceptor activation of heart rate. It is suggested that azaperone has peripheral actions which could contribute towards its prophylactic effect in preventing stress-induced deaths in pigs.     

Management and Outcome of a Non-iatrogenic,Nearly Circumferential,Full-thickness Retroperitoneal Rectal Tear in a Horse

An 8-year-old Quarter Horse stallion presented to the Veterinary Teaching Hospital for evaluation of acute colic and a suspected rectal tear. Clinical examination revealed a nearly circumferential retroperitoneal full-thickness rectal tear. Exploratory laparotomy was performed, and medical management of the tear continued for 6 weeks. Multiple attempts at direct suturing of the tear were unsuccessful. Despite intensive medical management, the horse was not able to defecate, and the tear did not heal adequately, so the horse was humanely euthanized. Necropsy revealed complete obliteration of the muscular layers of the rectum with only a small area of rectal mucosa intact dorsally. There is limited information available on the management of circumferential rectal tears. Based upon this experience and other historical reports, a poor prognosis may be expected for circumferential full-thickness retroperitoneal rectal tears involving the ventral aspect of the rectum.     

Histochemical study of the distribution of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)-positive neurons in the chicken caecum

The distribution of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)-positive neurones was investigated in the chicken caecum. Double staining combined NADPHd histochemistry with immunohistochemistry for neural nitric oxide synthase (nNOS) indicated that NADPHd-positive neurones also showed immunoreactivity for nNOS. NADPHd-positive nerve cell bodies were observed in both the myenteric and the submucous plexuses. Nerve fibres showing enzyme activity were mainly distributed in the circular muscle layer, but only a few fibres in the mucosal layer. Fine nerve fibres showing NADPHd activity were found running between germinal centres in the caecal tonsil. Quantitative analysis showed no significant differences in the number of enzyme-positive nerve cell bodies per ganglion of the myenteric and the submucous plexuses among three different caecal regions; proximal, middle and distal regions. Larger numbers of ganglia were detected in the submucous plexus than the myenteric plexus at all three regions. These data indicate that nitrergic neurones in the submucous plexus mainly project to the circular muscle layer in the chicken caecum. It is possible that nitrergic nerves regulate the motility of the chicken caecum.     

肉仔鸡日粮外源核苷酸营养作用初探

为研究日粮核苷酸 (NT) ,对肉仔鸡的营养作用 ,72只 1日龄AA肉仔鸡饲喂纯合日粮 5天以耗竭可能由母源带来的核苷酸 ,然后分成 4组 ,分别喂以添加 0 ,0 .1 % ,0 .2 %的核苷酸及 0 .5 %酵母培养物的纯合日粮。测定了 1 0日龄及 1 4日龄各组试鸡肠粘膜、肝脏中蛋白质及RNA含量 ,十二指肠绒毛高度、肠壁厚度、肠粘膜湿重等指标 ,用一次性注射大剂量3H -Tyr的方法测定了 1 2日龄各组试鸡肠粘膜蛋白质合成率。结果表明纯合日粮能显著耗竭雏鸡肠粘膜中的RNA ,纯合日粮中添加 0 .2 %NT使雏鸡肠道粘膜核酸及蛋白质含量及肝脏的核酸含量比对照皆有显著的增加 ,并能促进肠绒毛的生长及提高肠壁厚度。说明满足了氨基酸需要的肉仔鸡内源合成的NT不能满足生长发育的需要     

紫菀乙醇提取物对豚鼠离体气管平滑肌收缩功能的影响

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。     

Time-dependent changes in inhibitory action of lipopolysaccharide on intestinal motility in rat

Endotoxin causes gastrointestinal motility disorder. Aim of this study is to clarify inhibitory mechanisms of lipopolysaccharide (LPS) on smooth muscle contraction in rat ileum. Ileal tissues were isolated from control rat or from LPS-induced peritonitis model rat. Treatment with LPS inhibited carbachol (CCh)-mediated contraction in a time-dependent manner. Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) genes were also upregulated, but iNOS expression was preceded by a rising of COX-2. All subtypes of prostaglandin E₂ (PGE₂) receptors (EP1-EP4) were expressed in ileum, and PGE₂ and selective EP2 or EP4 agonist inhibited CCh-mediated contraction. Selective iNOS inhibitor did not reverse LPS-induced inhibition of contraction by CCh at 1 and 2 hr, but reduced the inhibitory action at 4 hr after the LPS treatment. COX-2 inhibitor reversed the inhibitory action by LPS in all exposure time. Finally, in ileal tissues isolated from peritonitis model rat, iNOS expression was upregulated only at 4 hr after LPS administration, resulting in enhanced inhibitory action of LPS against CCh-induced contraction. In conclusion, LPS induces COX-2 to produce PGE₂, which initially activates EP2 and/or EP4 on smooth muscle cells to inhibit the contractility in early phase of LPS exposure. Moreover, in late phase of LPS treatment, iNOS is expressed to produce NO, which in turn inhibited the contraction by CCh. The inhibitory cascade is similar in the ileum isolated from peritonitis model rat, indicating time-dependent changes of inhibitory action by LPS on intestinal motility in peritonitis.     

Effects of Alcohol Extract of Aster tataricus L.f.on the Contraction of Guinea Pig Tracheal Smooth Muscle in vitro

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.     

Effect of bombesin and substance P on the smooth muscle of the chicken crop

The effect of bombesin and of substance P was investigated in smooth muscle strips of the chicken crop. Bombesin in picomolar concentration (0.1×10^-12–5×10^-12mol/l) caused a concentration-related contraction of the muscle strips. Substance P in nanomolar concentration (0.1×10^-9–10×10^-9mol/l) was effective in the same manner. Tetrodotoxin (2×10^-7mol/l) did not influence the contraction responses to either bombesin or substance P. The excitatory effect of bombesin and of substance P did not follow activation of cholinergic receptors since their effect on the crop smooth muscle was not antagonized by atropine (10^-4mol/l) or by hexamethonium (10^-4mol/l). Strips stored for 24 hours in the Tyrode's solution at 4°C without a supply of oxygen maintained their full sensitivity to bombesin and to substance P. These results are consistent with a direct action of bombesin and substance P on the crop smooth muscle.     

Repeated manual evacuation for treatment of rectal tears in four horses

Horses with tears that involve all layers of the rectum except the mesocolon (grade IIIb) have a poor prognosis for survival because of the difficulty in treating these wounds and the propensity for them to progress to full perforations (grade IV). Most treatments for grade-IIIb rectal tears involve surgery of some kind, but not all grade-IIIb rectal tears require surgical intervention. We report on 4 horses with grade-IIIb rectal tears that were evaluated via palpation per rectum and endoscopy. Two of 4 horses were admitted with signs consistent with shock and endotoxemia, and evaluation of all peritoneal fluid samples was indicative of nonseptic peritonitis. Horses were treated via administration of antibiotics and anti-inflammatory drugs and repeated manual evacuation of the terminal portion of the small colon and rectum. Treatment centered on preventing further enlargement of the rectal tear by eliminating the storage function of the terminal portion of the small colon and rectum. None of our horses had worsening of the original injury, and horses were discharged within 2 weeks of admission with full resolution of the rectal tear. Outcomes in the horses of our report indicate that repeated manual evacuation can be successful for treatment of horses with grade-IIIb rectal tears.