Immunohistochemical identification and localization of orexin A and orexin type 2 receptor in the horse gastrointestinal tract

The aim of the present study was to investigate the presence and the distribution of cells containing orexin A and orexin type 2 receptor in the horse stomach and gut, by means of immunohistochemical techniques.Orexin A was identified in the stomach fundic and pyloric regions and in the duodenum. In the same stomach regions, a large subset of orexin A-positive cells also showed orexin type 2 receptor-like immunoreactivity. Moreover, in the duodenum, many of them, seemed to store serotonin.Characteristically, enteric neurons or ganglia also displayed orexin A and, sometimes, orexin type 2 receptor immunoreaction.Orexin A and orexin type 2 receptor immunoreactivity was also found in the nerve fibers in the enteric submucosal layer.Our results, together with data present in the literature, could contribute to the understanding of complex mechanisms regulating the horse gut functionality that are depending very likely on the consequence of the co-operation of both a central and a peripheral control.     

Eosinophilic intestinal diseases of the horse

Eosinophilic intestinal diseases of the horse are not commonly reported. Similar diseases are reported in man, but for either species, these eosinophilic diseases, are poorly understood. Eosinophilic intestinal disease may be accompanied by eosinophilic disease of other organs, or eosinophilia may be restricted to the intestine. When infiltration of eosinophils is restricted to the intestine, horses have a good prognosis for resolution of clinical signs, even though the treatment may include celiotomy with intestinal decompression or resection and administration of a corticosteroid. When eosinophilic intestinal disease is accompanied by infiltration of other organs, such as skin, pancreas, lungs or liver, the horse's prognosis for survival is very poor.     

Small intestinal adenocarcinoma in a horse

A 21-year-old mare was evaluated for intermittent episodes of apparent abdominal pain of 6 month's duration. Abdominal palpation per rectum revealed distended small intestine in the caudal portion of the abdomen. Ventral midline celiotomy revealed a mass in the midjejunal region. The mass was resected, and a side-to-side anastomosis performed. The histologic diagnosis was tubular adenocarcinoma of the small intestine. The mare was still alive 13 months after surgery.     

Simulated small intestinal volvulus in the anesthetized horse

Experimental closed loop small intestinal volvulus was studied in the anesthetized horse. Volvulus was simulated by ligation of the mesenterial veins to a segment of small intestine. Physical signs and hemodynamic, hematologic, clinical chemical, bacteriologic and peritoneal fluid values were examined. Compared to conscious horses anesthesia highly delayed and modified the clinical signs of shock (changes in mucosal colour, dehydration, decreased skin temperature, elevated pulse rate, low blood pressures) and of small intestinal volvulus (altered peristalsis, gastric dilation). Plasma glucose response to shock was also modified by unconsciousness. However, a dose response relationship was indicated between the extent of small intestinal damage and clinical symptoms. The same was applicable to changes in blood pressures, blood acid-base balance, lactate, potassium, chloride, glucose, inorganic phosphorus, creatinine, creatine kinase, red blood cell and total white blood cell counts and serum total protein. The relationship was also indicated in the following peritoneal fluid values: volume, lactate, pH, total white cell counts, alkaline phosphatase and bacteriology. Changes related to shock (insufficient tissue perfusion) were low blood pressures and metabolic acidosis due to anaerobic glycolysis with accumulation of lactic acid. Also low plasma glucose and elevated plasma potassium, creatinine, inorganic phosphorus and creatine kinase were regarded as consequences of shock.     

Polymorphism of the acetylcholine receptor in the horse

A cDNA probe to the alpha subunit of the murine acetylcholine receptor was used to demonstrate restriction fragment length polymorphism in an acetylcholine receptor gene in the horse. Three different patterns of polymorphism have been observed with fragment sizes of 4.3 and 2.9 kilobases (kb) (pattern 1), 4.3 and 2.5 kb (pattern 2) and 4.3, 2.9 and 2.5 kb (pattern 1,2). Analysis of a three generation pedigree has suggested that patterns 1 and 2 represent two allelic forms of the gene encoding the alpha subunit of the acetylcholine receptor. These data provide a basis for the examination of the genetic control of neuromuscular function in the horse.     

Quantification of immunoglobulins in respiratory tract secretions of the horse

Lavage techniques were used to obtain secretions from the nasal cavity, trachea and bronchi of conscious horses. The techniques, which utilised fibreoptic endoscopy for recovery of tracheal and bronchial secretions, were well tolerated by the horses. The recovery rates of the lavaged fluids were acceptable, but were lowest for bronchial secretions, and there was minimal contamination by blood. The fluids were analysed for IgG and IgM by single radial immunodiffusion, and for IgA and albumin by rocket immunoelectrophoresis. Relative to albumin there was significantly more IgA and IgM, and significantly less IgG, in the nasal cavity than the trachea. IgA and IgM levels were greatest in the nasal cavity and decreased progressively to the bronchi, whereas IgG levels showed the reverse trend. The immunoglobulin: albumin ratios of secretions taken from many levels of the tract were significantly higher than those of serum, suggesting local production of immunoglobulin in the respiratory tract.     

Abdominal adhesions after small intestinal surgery in the horse

One hundred thirteen of 172 horses (66%) undergoing exploratory celiotomy for a small intestinal lesion survived 4 or more days after surgery. Intra-abdominal adhesions causing clinical problems requiring additional surgery or euthanasia were documented in 25 horses (22.1%). Problems developed in significantly more males than females. The most common initial small bowel lesion was ileal impaction (12 horses); 21 horses underwent small intestinal resection or bypass. However, there was no significant difference in the incidence of intra-abdominal adhesions between horses that underwent intestinal resection or bypass and those that did not. Only 4 of the 25 horses (16%) with problems associated with postoperative adhesions survived. The mean interval between surgical procedures or between the initial procedure and euthanasia for all horses was 84 days (range, 7-512 days; median, 25 days). However, 70% of the subsequent celiotomies were performed within 60 days of the previous surgery. The mean interval between celiotomies was 221 days (range, 9-512 days) for the survivors and 61 days (range, 7-358 days) for the nonsurvivors. These results indicated that most of the problems related to postoperative intra-abdominal adhesions occurred within 2 months of the initial small intestinal surgery. Furthermore, the earlier development of postoperative adhesions was associated with a poorer prognosis for survival.     

Ovarian and intestinal angiomatosis in a horse

Dozens of red, raised nodules scattered along the serosal surface of the small intestine and the right and left ovaries were observed as incidental findings on gross examination in a 21-year-old Thoroughbred mare euthanatized for severe lameness. Histologically, these nodules were composed of numerous, variably sized, redundant vascular profiles filled with red blood cells and fibrin thrombi. Based on the presence of multiple nodules composed of benign vascular channels scattered within the small intestine and ovary, a diagnosis of angiomatosis is proposed. To the authors' knowledge, this is the first report of small intestinal and ovarian angiomatosis in a horse.     

Hypereosinophilia in a horse with intestinal lymphosarcoma.

Paraneoplastic eosinophilia is reported in dogs, cats, and humans. Hypereosinophilia (an eosinophil count greater than 1.5 x 10(9) L) is often associated with metastasis and a poor prognosis. This report describes a case of paraneoplastic hypereosinophilia in a pony. Neoplasia should be included in the differential diagnoses in a horse with eosinophilia.     

Immunocytochemical distribution of endocrine cells in the gastrointestinal tract of the horse

Endocrine cells immunoreactive for somatostatin, gastrin, glicentin, glucagon, secretin, cholecystokinin, motilin and neurotensin were identified immunocytochemically in the gastrointestinal mucosa of the horse. Somatostatin-, glicentin- and glucagon-immunoreactive cells were very numerous in the cardiac and fundic regions of the stomach, whereas most gastrin-immunoreactive cells were confined to the pyloric region. Somatostatin-immunoreactive cells also were detected in all portions of the small intestine while gastrin-immunoreactive cells were confined exclusively to the upper portion and glicentin-immunoreactive cells were limited to the lower portions of the small intestine. Secretin-, cholecystokinin- and motilin-immunoreactive cells were observed only in the duodenum, while neurotensin-immunoreactive cells were confined primarily to the ileum. In the large intestine, somatostatin- and glicentin-immunoreactive cells were detected in the colon and rectum. The preferential location of endocrine cells provides additional information for future studies on the physiological roles of gastrointestinal peptides in the gastrointestinal tract of the horse.     

Diagnosis of upper respiratory tract diseases in the performance horse.

Wastage of performance horses because of respiratory dysfunction is common. Appropriate identification of the disease is paramount for treatment recommendations. Diagnostic modalities for upper respiratory tract dysfunction include a thorough physical examination, radiographic evaluation when appropriate, and upper respiratory tract endoscopy. Anatomical deviations or structural are easily identified during resting evaluation, while exercise testing is often necessary to assess thedynamic properties of the upper airway. Utilizing the many diagnostic tools available allows the clinician to make an accurate diagnosis and recommend appropriate treatment.     

Fluorometric evaluation of large and small intestinal ischaemia in the horse

Arteriovenous (ischaemic strangulating obstruction, ISO) and venous obstructions (haemorrhagic strangulating obstruction, HSO) were created for 70 min in the small intestine of eight anaesthetised horses, and ISO was created in four horses for 2 h and four horses for 3 h at the sternal and diaphragmatic flexures of the large colon. Five minutes following release of the occlusions, sodium fluorescein 20 per cent (0.5 mg/kg bodyweight intravenously) was administered. Serial quantitative measurements of serosal surface fluorescence of the injured segments and a control segment were made at 2, 10, 15, 20 and 30 mins using a fibreoptic perfusion fluorometer. Significant differences in fluorescence were seen in small intestine segments between HSO vs control, ISO vs HSO, but not ISO vs control segments. In the large colon, significant differences were seen between the fluorescence in the ischaemic 3 h ventral colon and control segments, and a trend for difference in fluorescence between the 2 and 3 h ischaemic segments. Differences in fluorescence between 2 vs 3 h dorsal colon segments and 2 or 3 h dorsal colon vs control segments were not significant.     

Diagnostic value of intestinal alkaline phosphatase in horse serum

Antiserum directed against equine intestinal Alkaline Phosphatase (ALP) was produced in rabbits and used to develop a sensitive and quantitative assay for the detection of intestinal ALP in equine serum. This assay was then used to measure the half-life of intravenously injected intestinal ALP and to determine if the intestinal ALP was present in normal horse sera, sera from horses presented for lesions not involving the gastrointestinal tract and sera from horses presented with lesions involving the gastrointestinal tract. The results suggest that intestinal ALP is not likely to appear in equine serum even when gastrointestinal disease is present and, therefore, appears to be of no diagnostic value.     

Review of large intestinal motility and mechanisms of impaction in the horse

The large intestine has distinct motility patterns which include non-rhythmic haustral kneading of ingesta and stronger rhythmic retropulsive and propulsive contractions which move ingesta along the tract. A variable site electrical pacemaker exists at the pelvic flexure where the strong rhythmic contractions begin. The large intestine can contract adequately with only the intrinsic nerve supply intact. Neurotransmitters have profound effects on large intestinal activity.     

Primary epitheliotropic intestinal T-cell lymphoma in a horse.

A 17-year-old Quarterhorse gelding with a clinical diagnosis of protein-losing enteropathy was submitted for necropsy following a 4-5-month duration of weight loss, decreased appetite, and hypoproteinemia. Gross findings included multiple 1-2-cm diameter ulcers on the luminal surfaces of the duodenum and ileum. Histologic examination revealed individual large, round cells infiltrating much of the mucosal epithelium of the duodenum, jejunum, ileum, and colon in addition to multifocal areas of ulceration. Similar round cells infiltrated Brunner's glands and expanded the submucosa beneath the foci of ulceration. Immunohistochemical staining indicated the round cell population was of T-lymphocyte origin. Several features of this equine neoplasm bear similarities to enteropathy-associated T-cell lymphoma in humans.     

Models for estimating digesta passage kinetics in the gastrointestinal tract of the horse

Fecal samples were collected to evaluate mathematical models to describe the kinetics of digesta passage in the segments of the equine gastrointestinal tract and to compare the passage kinetics of hay and oats. Four Norwegian Cold-blooded trotters (cecally cannulated, approximately 500 kg of BW) were fed Cr-mordanted hay and Yb-marked oats with their morning meal. The meal consisted of 2 kg of hay and 1 kg of oats processed as ground, pelleted, extruded, or micronized. Each horse was fed each type of oats on different days of collection, after a 5-d adaptation period, in a 4 x 4 Latin square design. Fecal samples were collected 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 48, and 52 h after administration of the marker dose. The samples were analyzed for Cr and Yb, and values were plotted using 1- and 2-compartment nonlinear passage models and an algebraic model. The 1-compartment G4 model and the 2-compartment G4G1 model showed an equally good fit to the observed excretion curves, based on low mean square error and SE. The excretion curves for hay (Cr) and oats (Yb) showed a striking similarity, and there seemed to be no difference in retention time between hay and oats in the horse. The mixing compartments in the horse are believed to be the cecum or both the cecum and the right ventral and dorsal segments of the colon, but further research in this area is needed to make a final conclusion.