Small intestine and small colon neuropathy in equine dysautonomia (grass sickness)

The number of neurons in the coeliacomesenteric ganglia and the myenteric and submucosal plexuses of the jejunum, ileum and small colon, and the pathological changes induced in them, were studied in various types of equine dysautonomia. In all forms of dysautonomia, severe and extensive neuron loss and damage occurred in the ileum. In acute and subacute dysautonomia, jejunal neuron loss and damage were severe, but in chronic cases significantly less loss or damage occurred. The damage followed the same pattern in the small colon but it was always less obvious than in the jejunum. The distribution of the damage was uniform within a segment of the intestine. In fatal cases of dysautonomia, the clinical severity and duration of illness seems, in most instances, to be related to the amount of neuronal disruption occurring in the jejunum. Severe disruption results in acute/subacute dysautonomia, while milder damage leads to the chronic form.No case of dysautonomia was encountered in which enteric neuron loss and damage occurred without significant neuronal disruption also occurring in the coeliacomesenteric ganglia.Ileal neuronal damage and loss are not invariably worse than that in the jejunum, and the possible reasons for this, together with the relationship between neuronal damage and possible causes of dysautonomia, are discussed.Abbreviations H&E haematoxylin and eosin Deceased. Formerly of the Moredun Research Institute, 408 Gilmerton Road, Edinburgh, EH17 7JH, UK     

Digestion of soybean meal proteinin the equine small and large intestine at various levels of intake

Four mature pony geldings weighing an average of 134 kg and fitted with ileal cannulas were used in a 4×4 Latin square experiment to determine the digestibility of soybean meal (SBM) protein in different segments of the equine digestive tract at various levels of protein intake. A complete basal corn-based diet was supplemented with SBM to formulate four diets with increasing crude protein. The diets, labeled A (basal), B, C and D, contained 4.9%, 9.5%, 14% and 16.5% crude protein (as fed), and provided nitrogen, per feeding, at approximately 44.8, 84.3, 123.9 and 146.3 mg/kg of body weight, respectively. Chromic oxide was fed to measure ileal flow and fecal excretion. Digestion and absorption of nitrogen was determined from changes in nitrogen: chromium ratios, and true digestion of nitrogen was computed by regression analysis. True total tract digestion of nitrogen was 95.7%. True digestibility of nitrogen in the small intestine over the range of linearity was 72.2%, while true digestibility of nitrogen reaching the large intestine was 89.8%. These data indicate that the protein in SBM was almost completely digested in the equine digestive tract. Furthermore, approximately 75% of the digestible protein was digested prececally when nitrogen intake was less than approximately 125 mg/kg of body weight per feeding.     

Vascular anatomy of the equine small colon

The vasculature of 22 small colons from dead adult ponies was perfused with latex or barium sulphate solution. The vascular anatomy was studied by use of dissection and alkali digestion of the latex specimens and microangiography of the barium sulphate-perfused specimens. The small colon is supplied by the caudal mesenteric artery. The left colic artery arises from the caudal mesenteric artery, which then becomes the cranial rectal artery. Branches from the left colic and cranial rectal arteries form anastomosing arcades that become narrower distally along the length of the small colon. From these arcades arise terminal arteries, which enter the small colon wall and give rise to a subserosal, an intermuscular, and a large submucosal plexus, with frequent anastomoses between them. The venous drainage closely parallels the arterial supply, except near to its origin from the portal vein, when the left colic vein and caudal mesenteric vein are separate from the corresponding arteries.     

Molecular characterisation of fructose transport in equine small intestine

REASONS FOR PERFORMING STUDY: Fructose can be a suitable carbohydrate supplement for horses before and/or during endurance exercise. In comparison to glucose, the ingestion of fructose results in a lower insulin peak and less marked fluctuations in blood glucose during exercise, potentially avoiding hypoglycaemia-induced exhaustion. OBJECTIVES: To assess the capacity of the equine small intestine to absorb fructose and to determine the mechanism, molecular structure and properties of equine intestinal fructose transport. METHODS: Using PCR-based strategies, RNA isolated from equine small intestine and primers designed to homologous regions of the fructose transporter, GLUT5, cDNA of other species, we cloned and sequenced equine GLUT5 (eGLUT5). Northern and western blot analyses, in conjunction with immunohistochemistry, utilising eGLUT5 cDNA and antibodies, assessed expression of eGLUT5 along the longitudinal and radial axes of the small intestine. Functional properties of fructose transport in intestinal brush-border membrane vesicles were measured using the rapid-filtration technique. RESULTS: eGLUT5 is expressed in the villus enterocytes with highest levels in duodenum>jejunum and lowest in the ileum. Kinetic studies indicate eGLUT5 is a low affinity, high capacity transporter. CONCLUSIONS: Equine small intestine has the capacity to absorb fructose. POTENTIAL RELEVANCE: The molecular probes produced in these studies can be used as diagnostic aids to determine equine intestinal monosaccharide malabsorption.     

Molecular characterisation of carbohydrate digestion and absorption in equine small intestine

Dietary carbohydrates, when digested and absorbed in the small intestine of the horse, provide a substantial fraction of metabolisable energy. However, if levels in diets exceed the capacity of the equine small intestine to digest and absorb them, they reach the hindgut, cause alterations in microbial populations and the metabolite products and predispose the horse to gastrointestinal diseases. We set out to determine, at the molecular level, the mechanisms, properties and the site of expression of carbohydrate digestive and absorptive functions of the equine small intestinal brush-border membrane. We have demonstrated that the disaccharidases sucrase, lactase and maltase are expressed diversely along the length of the intestine and D-glucose is transported across the equine intestinal brush-border membrane by a high affinity, low capacity, Na+/glucose cotransporter type 1 isoform (SGLT1). The highest rate of transport is in duodenum > jejunum > ileum. We have cloned and sequenced the cDNA encoding equine SGLT1 and alignment with SGLT1 of other species indicates 85-89% homology at the nucleotide and 84-87% identity at the amino acid levels. We have shown that there is a good correlation between levels of functional SGLT1 protein and SGLT1 mRNA abundance along the length of the small intestine. This indicates that the major site of glucose absorption in horses maintained on conventional grass-based diets is in the proximal intestine, and the expression of equine intestinal SGLT1 along the proximal to distal axis of the intestine is regulated at the level of mRNA abundance. The data presented in this paper are the first to provide information on the capacity of the equine intestine to digest and absorb soluble carbohydrates and has implications for a better feed management, pharmaceutical intervention and for dietary supplementation in horses following intestinal resection.     

Post operative neutrophilic inflammation in equine small intestine after manipulation and ischaemia

REASONS FOR PERFORMING STUDY: Post operative ileus (POI) remains an important cause of post operative morbidity and mortality in the horse. However, clinical progression of naturally occurring cases of POI in both horse and man does not entirely support the 'neurogenic' hypothesis as the sole mechanism of POI; and the hypothesis that inflammation plays a major role at 12-24 h after surgery requires validation. HYPOTHESIS: An inflammatory infiltrate in the muscularis externa and myenteric plexus of equine jejunum is present 18 h following a period of ischaemia. METHODS: Samples of normal jejunum, jejunum from the proximal resection margins of clinical cases and jejunum obtained 18 h after 1 or 2 h ischaemia or manipulation alone were evaluated for neutrophil infiltration. Samples obtained 18 h after surgery were additionally evaluated for leucocyte activation using calprotectin immunohistochemistry. Results were evaluated by ANOVA and P < 0.05 was considered significant. RESULTS: Significant neutrophilic inflammation was identified in the samples from the proximal resection margins of clinical cases compared to uninjured jejunum. In experimental cases, neutrophilic inflammation appeared to be increased further by 18 h and was identified through all intestinal layers, particularly in the serosa, fascial planes around circular and longitudinal muscle fibres, and myenteric plexus. This elevated level of neutrophilic inflammation was mirrored by an increased number of calprotectin-positive cells in these intestinal layers, indicating leucocyte activation. CONCLUSIONS: Significant neutrophilic inflammation occurs in equine jejunal myenteric layers 18 h after surgery. POTENTIAL RELEVANCE: This neutrophilic inflammation coincides with the clinical time point at which POI is identified and may indicate that inflammatory pathways, rather than solely neurogenic pathways, are responsible for POI in the horse.     

Eimeria organisms develop in the epithelial cells of equine small intestine

Histopathologic and immunohistochemical examinations were performed to determine the origin of host cells parasitized by Eimeria in the small intestines collected from five foals. Eimeria organisms at various stages (mainly microgametes and macrogametes) were frequently found in the cytoplasm of hypertrophied host cells in the lamina propria at the tips of villi of the jejunum and ileum. The cytoplasm of the host cell was immunohistochemically positive for cytokeratin AE1/AE3 and cytokeratin 13 and was negative for vimentin, desmin, alpha-smooth muscle actin, chromogranin A, neuron-specific enolase, and factor VIII. The host cells parasitized by Eimeria species had the immunostaining characteristics of epithelial cells but not of mesenchymal cells, endothelial cells of lacteals or capillaries, smooth muscle cells or neuroendocrine cells. These results suggest that the host cell of Eimeria species is possibly derived from intestinal epithelial cells and then displaced into the lamina propria of the small intestine.     

Effect of intraluminal distention on microvascular perfusion in the equine small colon

OBJECTIVE: To determine the effect of experimental intraluminal distention on microvascular perfusion of the small colon in horses. ANIMALS: 6 mixed-breed healthy horses (mean age [+/- SDI, 9.1 +/- 2 years). PROCEDURE: Under general anesthesia, the small colon was exposed by celiotomy and 3 segments were demarcated. In 1 of these segments, intraluminal obstruction was created by placement of a latex balloon inflated to a pressure of 40 mm Hg (obstructed segment). The other segments were the sham-operated segment and the control segment. Microvascular perfusion was evaluated in the mucosal, submucosal, muscular, and serosal layers by injection of 15 microm-diameter colored microspheres into branches of the caudal mesenteric artery. Recovery of microspheres was performed by tissue digestion, washing, and centrifugation. Distribution of microspheres in the intestinal layers was evaluated by direct observation of stained frozen sections by light microscopy. RESULTS: A significant reduction was observed in total microvascular perfusion of obstructed segments, which was 26.4% of that of control segments. This reduction was not evident in the mucosal layer. CONCLUSIONS AND CLINICAL RELEVANCE: Intraluminal distention of the equine small colon wall can promote ischemia by a reduction in microvascular perfusion in the intestinal wall. Intestinal layers do not seem to be affected to the same extent, because the absolute value for mucosal perfusion did not decrease in the obstructed segment.     

Colopexy of the equine large colon: comparison of two techniques

A study was designed to evaluate 2 colopexy techniques (A and B) in 8 clinically normal horses to determine which technique would prevent recurrence of large-colon displacement and/or volvulus. For technique A, 35 cm of the lateral free band of the left ventral colon was sutured to the abdominal wall, 6 cm to the left of ventral midline. For technique B, the medial free band of the left ventral colon was sutured to the medial free band of the right ventral colon, and 8 cm of the lateral free band of the left ventral colon was sutured to the abdominal wall, 6 cm to the left of ventral midline. One horse from each group was euthanatized at 6 months, and another at 12 months after surgery. The position of the large colon, the integrity of the colopexy, and other adhesions within the abdominal cavity were evaluated. At necropsy, attempts were made to manually create displacement and volvulus of the large colon. The remaining horses in each group were anesthetized 6 months or 12 months after surgery, and the integrity of the colopexy was evaluated. After a 60-day recovery period, these horses were exercised for 2 months. Although each horse initially lost weight, the weight of all but 2 was acceptable at the conclusion of the study. Two horses that had technique-B colopexies had progressive weight loss serious enough to warrant euthanasia. Both colopexy techniques prevented manual creation of large-colon displacement and large-colon volvulus centered at the sternal and diaphragmatic flexures. Technique-A colopexy also prevented manual creation of volvulus of the large colon centered at its base.(ABSTRACT TRUNCATED AT 250 WORDS)     

Morphologic alterations observed during experimental ischemia of the equine large colon

Morphologic changes that develop sequentially in the large colon during experimentally induced ischemia were documented in 14 halothane-anesthetized horses. Colonic ischemia was induced by 4 types of vascular occlusion, 24 cm proximal and distal to the pelvic flexure. The effect of transmural (colonic wall) vascular compression combined with either venous occlusion (3 horses, group A) or venous and arterial occlusion (3 horses, group B) of the colonic vessels was studied for 1, 2, and 6 hours of occlusion. Also observed was the effect of reperfusion for 0.5 hour after release of the clamps for the 1- and 2-hour occlusions and for 1 hour after release of the clamps for the 6-hour occlusion. Effects of occluding only the colonic veins (4 horses, group C), or the colonic veins and arteries (4 horses, group D) were studied for 0.5, 1, 1.5, and 2 hours of occlusion and during reperfusion for 0.5 hour. Full-thickness intestinal biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 0.75, 1, 1.5, and 2 hours during occlusion and at 0.5 hour after release of vascular occlusion. Biopsy specimens were obtained at hourly intervals from the 2 horses in which 6-hour occlusion was performed and at 1 hour after release of vascular occlusion. Macroscopic changes (serosal color, mucosal color, serum leakage) in the colon were recorded.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrasonographic examination of the small intestine, large intestine and greater omentum in 30 Saanen goats

The small and large intestine of 30 healthy Saanen goats were examined ultrasonographically using a 5.0 MHz-linear transducer. The goats were examined on the right side, from the eighth rib to the caudal aspect of the flank. The small and large intestine could be easily differentiated. The descending duodenum could be imaged in 19 goats, and the jejunum and ileum seen in all goats. The jejunum and ileum were most often seen in cross-section and rarely in longitudinal section in the ventral region of the right flank. The intestinal contents were usually homogenously echoic, and active motility was observed in all the goats. The diameter of the small intestine was 0.8–2.7 cm (1.6 [0.33] cm). The spiral ansa of the colon was imaged in all the goats, and in 21 the caecum was also seen. Both these sections of large intestine were most commonly seen in the dorsal region of the right flank. The spiral ansa of the colon was easily identified by its spiral arrangement of centripetal and centrifugal gyri, which had a garland-like appearance. Because of intraluminal gas, only the wall of the colon closest to the transducer could be imaged. The diameter of the spiral colon ranged from 0.8 to 2.0 cm (1.1 [0.24] cm). Usually only the wall of the caecum closest to the transducer could be imaged and it appeared as a thick, echoic, slightly undulating line. The greater omentum could be seen in all the goats.     

Xanthine oxidase formation during experimental ischemia of the equine small intestine.

We hypothesized that xanthine oxidase plays a role in the postischemic reperfusion injury in the equine small intestine. Under anesthesia, four horses and two ponies underwent ischemic strangulating obstructions of segments of the proximal jejunum, mid-jejunum and ileum. Prior to vascular occlusion, and at 1 h and 2 h of ischemia, full-thickness intestinal biopsies were collected for histopathological evaluation and for determination of combined xanthine dehydrogenase (XDH) plus xanthine oxidase (XO) activity, and XO activity alone. The level of XO activity was expressed in percentage according to the ratio of XO/(XDH + XO). We found a nearly threefold increase in the combined level of XDH plus XO activity from ileum to duodenum (p less than 0.04). However, the preischemic level of % XO activity did not vary significantly (p = 0.61) between segments of jejuno-ileum. Likewise, no significant difference was noted between intestinal segments after ischemia. Therefore, the data from all intestinal segments were pooled for each time and analyzed using Wilcoxon's signed rank test (one-tailed). Compared to the pre-ischemic level of % XO activity (median 27%), the % XO activity increased after 1 h of ischemia (median 37.0%), reaching statistical significance (p = 0.016). There were no statistical differences between the preischemic % XO activity and the % XO activity in non-ischemic bowel at the end of the anesthetic period. During ischemia, % XO activity increased, which lends credence to the importance of xanthine oxidase in previously-documented reperfusion injury in the equine small intestine.     

A comparison of three methods of end-to-end anastomosis in the equine small colon

Six animals were used to compare simple interrupted, simple continuous, and stapled techniques for end-to-end rotated small colon anastomoses. Three ponies were evaluated three days after surgery for adhesion formation and luminal diameter at each anastomosis site. Two ponies and one horse were evaluated 14 days after surgery for adhesion formation. All anastomosis sites were examined histologically for alignment of tissue planes, and evidence of inflammation. No single technique was superior in all areas examined. While only three of the nine anastomoses had mild fibrinous adhesions at three days after surgery, all anastomoses had varying degrees of well-organized adhesions by 14 days after surgery. Three days after surgery luminal diameter was most comprised by the simple continuous technique. Although the simple interrupted technique was most consistent in its alignment of tissue planes, it was only slightly better than the simple continuous pattern. Stapled anastomoses were inverted or everted at all sites examined. Adhesion formation was less extensive, and histologic evidence of inflammation was less severe, in stapled anastomoses. The average times required to complete the simple interrupted, simple continuous, and stapled anastomoses were 22, 14, and 8 minutes, respectively.     

Effects of dietary fructo-oligosaccharide on villous height and disaccharidase activity of the small intestine,pH, VFA and ammonia concentrations in the large intestine of weaned pigs

Abstract

An experiment was conducted to investigate changes in the lumen and wall of the intestinal tract of weaned pigs caused by fructo-oligosaccharides (FOS) and consequences for growth. Twelve male pigs weaned at 24 days were individually housed and fed either control, 0.25% FOS, or 3% FOS diets for 21 days after weaning. The pH of chyme in the caecum and proximal colon were lower (p<0.001) in 3% FOS compared to other treatments. Mean molar proportions (%) of total SCFA values along the large intestine were significantly affected by FOS diet. Acetic acid was significantly higher in control compared with other treatments. Butyric acid and isobutyric acid were significantly increased in 0.25 and 3% FOS compared to the control. Feed intake, empty body weight gain, disaccharidase activities and villous height in the small intestine were not significantly affected by FOS. It was concluded that dietary FOS stimulates fermentation in the large intestine, but does not significantly affect enzyme activity, ammonia content, villous height and growth.     

Myeloperoxidase activity of the large intestine in an equine model of acute colitis.

OBJECTIVE: To determine whether quantification of myeloperoxidase (MPO) activity could be a useful laboratory technique to detect granulocyte infiltration in equine intestinal tissues. SAMPLE POPULATION: Intestinal tissue (inflamed or healthy) collected from 16 age- and sex-matched Shetland Ponies. PROCEDURE: Intestinal tissue MPO activity was determined, and histologic assessment of adjacent specimens from healthy and inflamed intestine was done. RESULTS: Intestinal tissue MPO activity and histopathologic score increased with time after castor oil challenge and peaked at 16 hours in an equine diarrhea model in which individual ponies provided their own control tissues. CONCLUSIONS: Intestinal tissue inflammation scores correlated positively with tissue MPO activity in adjacent specimens. CLINICAL RELEVANCE: Tissue MPO assay may be a useful laboratory tool to quantify intestinal mucosal inflammation in ponies.