In vitro evaluation of an intraluminal solution to attenuate effects of ischemia and reperfusion in the small intestine of horses

OBJECTIVE: To evaluate the efficacy of intraluminal administration of a customized solution during low-flow ischemia and reperfusion in the jejunum of horses. SAMPLE POPULATION: Segments of jejunum obtained from 13 healthy adult horses. PROCEDURE: In isolated segments of jejunum maintained in an extracorporeal circuit, arterial flow was reduced to 20% of baseline for 40 minutes (ischemia) followed by 60 minutes of reperfusion. In 2 groups, a customized solution (concentrations, 12.5 and 25%, respectively) was placed in the lumen prior to low-flow ischemia and maintained during reperfusion. The control group received intraluminal lactated Ringer's solution for the same duration. Various metabolic, hemodynamic, histologic, and permeability variables were recorded. RESULTS: The 12.5% solution resulted in less histomorphologic injury and reduced mucosal permeability to albumin, compared with the 25% solution and the lactated Ringer's solution. Morphologic injury and permeability were reduced in tissues that received the 25% solution, compared with the control group, but this difference was not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Use of a 12.5% customized solution appeared to minimize injury in the isolated extracoporeal jejunal loop, which provides some indication that it might be useful in clinical situations.     

In vitro evaluation of a customized solution for use in attenuating effects of ischemia and reperfusion in the equine small intestine.

OBJECTIVE: To determine whether a customized solution could attenuate the effects of low-flow ischemia and reperfusion injury of the equine jejunum. SAMPLE POPULATION: A segment of jejunum obtained from 21 healthy adult horses. PROCEDURE: A segment of jejunum was maintained in an isolated extracorporeal circuit, and arterial flow was reduced to 20% of baseline for 40 minutes (ischemia) followed by 60 minutes of reperfusion. In 1 group, a customized solution was infused at a rate of 1 ml/min during low-flow ischemia and 3 ml/min during reperfusion. In a second group, the solution was infused at the same rate during low-flow ischemia, but it was infused at a rate of 7 ml/min during reperfusion. Control groups received lactated Ringer's solution administered at the same rates as for the customized solution. Various metabolic, hemodynamic, histologic, and permeability variables were recorded. RESULTS: A lower flow rate during reperfusion (3 ml/min) had a beneficial effect, compared with lactated Ringer's solution or the higher flow rate (7 ml/min). Use of the solution at this rate resulted in less histomorphologic injury and reduced mucosal permeability to albumin. CONCLUSIONS AND CLINICAL RELEVANCE: Use of a customized solution at a lower flow rate during repurfusion appeared to have a protective effect on equine jejunum when administered IV during low-flow ischemia and reperfusion.     

Effects of Carolina rinse solution, dimethyl sulfoxide, and the 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion

OBJECTIVE: To evaluate effects of Carolina rinse solution, dimethyl sulfoxide (DMSO), and 21-aminosteroid, U-74389G, on microvascular permeability and morphology of the equine jejunum after low-flow ischemia and reperfusion. ANIMALS: 20 healthy adult horses. PROCEDURE: Under anesthesia, full-thickness biopsy specimens of a distal portion of the jejunum were obtained for baseline measurements. In addition to a control segment, 2 jejunal segments were identified as sham-operated or experimental segments. Experimental segments underwent 60 minutes of low-flow ischemia and 3.5 hours of reperfusion. Treatments were as follows: U-74389G (3 mg/kg, IV; 6 horses), DMSO (20 mg/kg, IV; 6) diluted in 1 L of saline (0.9% NaCl) solution, local perfusion (via jejunal artery) of Carolina rinse solution (0.5 mL/kg; 4), and local perfusion of lactated Ringer's solution (0.5 mL/kg; 4). RESULTS: Jejunal microvascular permeability was significantly lower after treatment with Carolina rinse solution or DMSO, compared with U-74389G or lactated Ringer's solution treatments. After DMSO treatment, serosal- and submucosal-layer edema was significantly increased in experimental segments, compared with control or sham-operated segments; however, edema increases were significantly less than for lactated Ringer's solution or U-74389G treatments. Significant decreases in intestinal wet weight-to-dry weight ratio were found following Carolina rinse solution or DMSO treatments, compared with lactated Ringer's solution or U-74389G treatments. Edema formation and leukocyte infiltration in jejunal segments of horses treated with lactated Ringer's solution or U-74389G were increased, compared with Carolina rinse solution or DMSO treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Carolina rinse solution and DMSO may be protective against ischemia-reperfusion injury in the equine jejunum.     

Use of an isolated intestinal circuit to evaluate the effect of ischemia and reperfusion on mucosal permeability of the equine jejunum

OBJECTIVES: To evaluate the efficacy of an isolated perfusion circuit and the effect of ischemia-reperfusion on mucosal permeability of the jejunum. STUDY DESIGN: In vitro study of intestinal mucosal permeability. ANIMALS: Twelve healthy adult horses. METHODS: A control segment of jejunum was placed in an isolated perfusion circuit for 240 minutes and mucosal permeability was measured. After detecting no deleterious effects of the isolated system on the control intestine, low flow ischemia was created in experimental segments for 20, 40, 60 and 90 minutes followed by 60 minutes of reperfusion and mucosal permeability was evaluated. At the completion of the studies, histologic evaluation was used to determine mucosal grades, surface area, and volume. RESULTS: Control tissue was maintained in the isolated circuit for 240 minutes without effect on mucosal grade, surface area, or volume relative to intact tissue. After ischemia-reperfusion, mucosal grade increased, and volume and surface area decreased progressively with longer periods of ischemia. Mucosal clearance of albumin remained constant during 240 minutes of perfusion in control tissue and was elevated after ischemia-reperfusion. CONCLUSIONS: No deleterious changes were noted in jejunum perfused with this isolated circuit, whereas alterations in mucosal permeability were present after ischemia-reperfusion. CLINICAL RELEVANCE: The isolated perfusion circuit successfully maintained an isolated segment of jejunum within physiologic limits, and can be used to evaluate the effects of injury and the efficacy of pharmaceuticals to attenuate these changes.     

Serosal injury in the equine jejunum and ascending colon after ischemia-reperfusion or intraluminal distention and decompression

OBJECTIVE: To document morphologic changes that occur in equine intestinal serosa after experimentally induced ischemia and subsequent reperfusion (jejunum, ascending colon) or after intraluminal distention and decompression (jejunum). STUDY DESIGN: Morphologic effects of ischemia-reperfusion or intraluminal distention-decompression determined on the serosal layer of the equine jejunum. The large colon serosa was evaluated after ischemia-reperfusion injury. ANIMALS OR SAMPLE POPULATION: Seven adult horses. METHODS: After induction of general anesthesia and ventral median celiotomy, ischemia was created by arteriovenous (AVO) and lumen occlusion of a 20-cm segment of jejunum and ascending colon for 70 minutes, followed by a 60-minute reperfusion period. Intraluminal distention (25 cm H2O) was created in a second 20-cm jejunal segment and maintained within the abdomen for 120 minutes, followed by a 120-minute decompression period. Seromuscular biopsies were obtained upon entering the abdomen and after the ischemic and reperfusion periods, and after the distention and decompression periods along with corresponding control seromuscular biopsies. Samples were processed and examined by light microscopy, transmission electron, and scanning electron microscopy. RESULTS: Ischemia and reperfusion, and intraluminal distention and decompression, resulted in severe morphologic changes in the seromuscular layer of equine jejunum. A similar period of ischemia-reperfusion caused minimal changes in the ascending colon serosa. CONCLUSION: Adult equine jejunum sustains more serosal damage than the ascending colon after similar periods of ischemia-reperfusion injury. Intraluminal distention and subsequent decompression causes serosal damage in the equine jejunum. CLINICAL RELEVANCE: The small intestine is more susceptible to seromuscular layer damage than the ascending colon.     

Effects of ischemia and the cyclooxygenase inhibitor flunixin on in vitro passage of lipopolysaccharide across equine jejunum

OBJECTIVE: To determine whether ischemia and flunixin affect in vitro lipopolysaccharide (LPS) absorption in samples of the jejunum of horses. ANIMALS: 12 horses. PROCEDURE: Horses were anesthetized, a midline celiotomy was performed, and the jejunum was located. Two 30-cm sections of jejunum (60 cm apart) were selected. One segment was designated as control tissue; ischemia was induced in the other segment for 120 minutes. Horses were then euthanatized. Mucosa from each jejunal segment was mounted on Ussing chambers and treated with or without flunixin. Tissues from 6 horses were used to assess permeability to radiolabeled LPS; mucosal samples from the remaining 6 horses were incubated with fluorescent-labeled LPS (FITC-LPS) and examined histologically. Production of tumor necrosis factor-alpha (TNF-alpha) and production of LPS-binding protein (LBP) were assessed as indicators of mucosal response to LPS. RESULTS: Ischemia significantly increased mucosal permeability to LPS, but by 180 minutes, the mucosa was not more permeable than control tissue. Flunixin treatment adversely affected intestinal barrier function throughout the experiment but did not result in increased mucosal permeability to LPS. Compared with control tissues, LBP production was increased by ischemia and reduced by exposure to LPS. In ischemic tissue, FITC-LPS entered the lamina propria but TNF-alpha was produced on the mucosal side only, indicating little response to the absorbed LPS. CONCLUSIONS AND CLINICAL RELEVANCE: Ischemia increased LPS passage across equine jejunal mucosa. Flunixin delayed mucosal recovery but did not exacerbate LPS absorption. Evaluation of the clinical importance of flunixin-associated delayed mucosal recovery requires further in vivo investigation.     

Evaluation of Postoperative Peritoneal Lavage in Standing Horses for Prevention of Experimentally Induced Abdominal Adhesions

Objective —To evaluate the postoperative use of peritoneal lavage for prevention of experimentally induced intraabdominal adhesions in horses.
Study Design —Areas of serosal abrasion were created on the jejunum of 12 horses. Postoperatively, six horses had peritoneal lavage, and six horses did not (controls). The number of adhesions was determined at necropsy 2 weeks after surgery.
Animals or Sample Population—12 horses.
Methods —Five sites of jejunal serosal abrasion were created in each horse. A 32 French thoracic catheter was placed into the right ventral aspect of the abdomen before closure of the abdominal incision. Treated horses had abdominal lavage with 10 L of lactated Ringer's solution on four occasions, then catheters were removed from all horses 34 hours after celiotomy. Horses were necropsied at 2 weeks to quantify the number of intraabdominal adhesions.
Results —All control horses and one treated horse developed intraabdominal adhesions. The number of adhesions was significantly less ( P <.0293) in treated horses. No adverse inflammatory reactions appeared to be associated with repeated peritoneal lavage using lactated Ringer's solution or use of an abdominal drain.
Conclusions —Peritoneal lavage reduced the frequency of intraabdominal adhesions.
Clinical Relevance —When postoperative adhesions are likely to develop, postoperative peritoneal lavage may decrease the frequency of adhesion formation.     

Evaluation of a laparoscopic technique for collection of serial full-thickness small intestinal biopsy specimens in standing sedated horses

OBJECTIVE: To assess a technique for laparoscopic collection of serial full-thickness small intestinal biopsy specimens in horses. ANIMALS:13 healthy adult horses. PROCEDURES: In the ex vivo portion of the study, sections of duodenum and jejunum obtained from 6 horses immediately after euthanasia were divided into 3 segments. Each segment was randomly assigned to the control group, the double-layer hand-sewn closure group, or the endoscopic linear stapler (ELS) group. Bursting strength and bursting wall tension were measured and compared among groups; luminal diameter reduction at the biopsy site was compared between the biopsy groups. In the in vivo portion of the study, serial full-thickness small intestinal biopsy specimens were laparoscopically collected with an ELS from the descending duodenum and distal portion of the jejunum at monthly intervals in 7 sedated, standing horses. Biopsy specimens were evaluated for suitability for histologic examination. RESULTS: Mean bursting strength and bursting wall tension were significantly lower in the ELS group than in the hand-sewn and control groups in both the duodenal and jejunal segments. Use of the hand-sewn closure technique at the biopsy site reduced luminal diameter significantly more than use of the stapling technique. In the in vivo part of the study, all 52 biopsy specimens collected during 26 laparoscopic procedures were suitable for histologic examination and no clinically important perioperative complications developed. CONCLUSIONS AND CLINICAL RELEVANCE: Laparoscopic collection of serial full-thickness small intestinal biopsy specimens with a 45-mm ELS may be an effective and safe technique for use in healthy adult experimental horses.     

Use of an extracorporeal circuit to evaluate effects of intraluminal distention and decompression on the equine jejunum

OBJECTIVE: To use an extracorporeal circuit to evaluate effects of intraluminal distention on the jejunum of healthy horses. SAMPLE POPULATION: 2 jejunal segments from each of 5 horses. PROCEDURE: Jejunal segments were harvested and maintained in an extracorporeal circuit. One segment was subjected to distention (intraluminal pressure, 25 cm H2O) followed by decompression, and 1 segment was maintained without distention. The influence of distention-decompression on vascular resistance was calculated. Mucosal permeability was evaluated by measuring the clearance of albumin from blood to lumen. After distention and decompression, tissue specimens were collected for histomorphologic evaluation. In addition, the contractile response of the circular smooth muscle layer was determined following incubation with 3 prokinetic agents. RESULTS: Intestinal vascular resistance increased during intraluminal distention and returned to baseline values after decompression. Albumin clearance rate increased after distention, compared with baseline and control values. Histologic examination of the distended segments revealed grade-1 and -2 lesions of the mucosal villus. Edema and hemorrhage were evident in the submucosa and muscular layers. Mesothelial cell loss, edema, and hemorrhage were also evident in the serosa. Mucosal surface area and villus tip height decreased and submucosal volume increased in the distended tissue. Compared with responses in control specimens, distention decreased the contractile response induced by cisapride, erythromycin, and metoclopramide. CONCLUSIONS AND CLINICAL RELEVANCE: Intraluminal distention of the jejunum followed by decompression increased mucosal permeability and injury and decreased responses to prokinetic agents. Horses with intraluminal intestinal distention may have a decreased response to prokinetic agents.     

Induction of peritoneal adhesions with small intestinal ischaemia and distention in the foal

Twenty-two foals were divided into groups of intestinal distension and intestinal ischaemia as methods to induce peritoneal adhesions. In the first group, the lumen of a segment of distal small intestine was occluded without extramural vascular compromise and distended with lactated Ringer's solution to a constant pressure of 25 cm H2O for 2 h within the abdomen. The ischaemic group underwent 70 mins total vascular occlusion of identical segments of bowel. Serosal biopsies were obtained before and after each experimental procedure and following 60 mins of reperfusion. Similar biopsies were harvested from a control group of foals with no bowel occlusions. The foals were destroyed 10 days after surgery and tissues collected for histological and ultrastructural evaluation. Experimental and control mesothelial surfaces were denuded histologically immediately after experimental occlusions. Serosal oedema and cellular infiltration were observed following reperfusion of the ischaemic segments but were present immediately after 2 h of distension. All foals had developed bowel-to-bowel and bowel-to-mesentery adhesions of the experimental segments. Control foals under 30 days old exhibited mesenteric contraction and thickening of the isolated segment whereas those older than 30 days had little or no mesenteric thickening or contraction. Histologically, in the experimental segments, fibrous tissue had formed on the outer boundary of the original serosa, and new mesothelial-like cells were present on the surface of fibrous tissue in some areas. Some serosal fibrosis was also seen in most of the control segments.     

Effects of superoxide dismutase on injury induced by anoxia and reoxygenation in equine small intestine in vitro.

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.     

Preliminary study of capsule endoscopy in the small intestine of horses

Objective To evaluate the visibility of various portions of the small intestine in healthy horses using capsule endoscopy. Procedure Six healthy, conscious adult Thoroughbreds were restrained and an endoscopic capsule (PillCam® SB capsule) was inserted into the oesophagus using an intranasal catheter aided by a guide wire. Water (500 mL) flushed the capsule down the gastrointestinal tract. Data were collected and stored in the recorder of the endoscopic system for 6 hours after capsule insertion and the images were evaluated using an image reader and scored using a visual analogue scale. Results Capsule endoscopy enabled observation of the distinct mucosal shape, colour, and villus structure of the intestinal lumen from the duodenum through the proximal jejunum. At 4 h after passing the pylorus, the endoscopic capsule started transmitting increasingly dark images in the distal jejunum as the lumen circumference increased. Means of the visual analogue scale in the duodenum, proximal jejunum, and distal jejunum were 93.8 ± 1.3%, 86.2 ± 2.5% and 48.8 ± 6.3%, respectively. Differences among these values were statistically significant (P < 0.05). Conclusions and Clinical Relevance Capsule endoscopy enables observation of the distinct mucosal shape, colour and villus structure of the proximal and mid-small intestine in healthy horses.     

Effect of venous strangulation obstruction on length of equine jejunum and relevance to small-intestinal resection

OBJECTIVE--To determine if venous strangulation obstruction (VSO) of the distal half of the equine small intestine would increase length of that segment. STUDY DESIGN--Halothane-anesthetized horses were assigned randomly to 3 groups of 5 horses: Group 1 (controls)--the entire small intestine was measured and rubber-shod clamps were applied to mark each end of the most distal 50% of the small intestine; Group 2--same procedure, except that VSO was induced in the distal 50% of the small intestine for 180 minutes; and Group 3--same initial procedure, except that VSO was induced for 90 minutes and followed by reperfusion for 90 minutes. ANIMALS OR SAMPLE POPULATION--Fifteen horses. METHODS--The proximal and distal halves of the small intestine were measured before and at 180 minutes after clamps and ligatures were applied. At the end of the study, biopsies were taken to assess mucosal epithelial damage by light microscopy, and horses were euthanatized while under general anesthesia. RESULTS--Intestine subjected to VSO and VSO and reperfusion had marked hemorrhagic changes and thickening in the intestinal wall. Both groups had incurred a grade 2.8 of 5 mucosal injury by 180 minutes. Total length of small intestine and length of the distal 50% did not change in the control group, but intestine subjected to VSO only and VSO and reperfusion had increased in length by 29% (P <.05) and 36% (P <.05), respectively. CONCLUSIONS--Small intestine of horses subjected to VSO can increase in length, and this change could cause an overestimate of the amount of intestine involved in an extensive strangulating lesion. CLINICAL RELEVANCE--An overestimate of the amount of intestine involved in an extensive strangulating lesion could lead to an overly pessimistic assessment of a horse's risk for postresection malabsorption and maldigestion. Therefore, estimates of the proportion of small intestine that is strangulated should be corrected for this potential error and the risk of malabsorption determined accordingly.     

Effects of flunixin meglumine or etodolac treatment on mucosal recovery of equine jejunum after ischemia

OBJECTIVE: To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion. ANIMALS: 24 horses. PROCEDURE: Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithelial flux of tritium-labeled mannitol measured mucosal permeability. Denuded villous surface area and mean epithelial neutrophil count per mm2 were calculated. Western blot analysis for cyclooxygenase (COX)-1 and -2 was performed. Pharmacokinetics of flunixin and etodolac and eicosanoid concentrations were determined. RESULTS: Ischemic-injured tissue from horses treated with flunixin and etodolac had significantly lower TER and increased permeability to mannitol, compared with that from horses treated with saline solution. Epithelial denudation after ischemia and 18 hours after recovery was not significantly different among treatments. Both COX-1 and -2 were expressed in ischemic-injured and nonischemic tissues. Ischemia caused significant upregulation of both COX isoforms. Eicosanoid concentrations were significantly lower in tissues from flunixin and etodolac-treated horses, compared with that from horses treated with saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: Flunixin and etodolac treatment retarded recovery of intestinal barrier function in jejunal mucosa after 18 hours of reperfusion, whereas tissues from horses treated with saline solution recovered baseline values of TER and permeability to mannitol.     

The characteristics of intestinal injury peripheral to strangulating obstruction lesions in the equine small intestine.

Recent studies suggest that horses requiring surgical correction of strangulating intestinal obstruction may develop post operative complications as a result of ischaemia/reperfusion injury. Therefore, the mucosal and serosal margins of resected small intestine from 9 horses with small intestinal strangulating lesions were examined for evidence of ischaemia/reperfusion injury. Severe mucosal injury and marked elevations in myeloperoxidase activity were detected at ileal resection margins (n = 4), whereas the mucosa from proximal jejunal (n = 9) and distal jejunal (n = 5) resection margins was normal. However, the serosa from jejunal resection margins had evidence of haemorrhage and oedema, and the proximal jejunal serosa had significantly increased numbers of neutrophils. Histological injury in ileal stumps is indicative of the inability fully to resect the ileum in horses with distal small intestinal strangulations. One of 4 horses subjected to ileal resection was subjected to euthanasia and found to have a necrotic ileal stump. Evidence of serosal injury and neutrophil infiltration in the proximal jejunal resection margins may predispose horses to post operative adhesions. Four of 8 horses discharged from the hospital suffered from recurrent colic in the post operative period.     

Use of an extracorporeal circuit to evaluate effects of ischemia and reperfusion of the equine large colon

OBJECTIVE: To determine efficacy of an extracorporeal circuit to maintain a segment of equine large colon for 3.5 hours and to evaluate the effect of low arterial flow on histologic and metabolic variables. SAMPLE POPULATION: Segments of large colon from 15 healthy adult horses. PROCEDURE: The pelvic flexure was surgically removed and maintained in an isolated circuit. In the control group, tissue was evaluated for 3.5 hours, whereas in the low-flow group, arterial flow was reduced to 20% of baseline for 40 minutes followed by 2 hours of reperfusion. Various metabolic and hemodynamic variables were evaluated at 30-minute intervals. Effects of nitric oxide (NO) and L-N-nitro-arginine-methyl-ester (L-NAME) on contractile activity were determined, and histomorphologic evaluation was performed at the completion of the study. RESULTS: Low-flow ischemia with reperfusion caused significant histomorphologic differences, compared with the control group. In the low-flow group, significant differences included reduction in PaCO2, reduction in bicarbonate concentrations, increase in PaO2, and an increase in base deficit in arterial and venous blood samples. Other significant differences included increases in PCV, protein concentration, total WBC count, and albumin clearance for the low-flow group. Differences were not detected in inhibitory activity of the low-flow group relative to the control tissue with or without addition of NO and L-NAME. CONCLUSION: The extracorporeal circuit maintained a segment of equine intestine for 3.5 hours and can be used to simulate ischemic injury. The extracorporeal circuit provides the potential to investigate pharmaceutic agents that can minimize intestinal injury.     

Attenuation of ischaemic injury in the equine jejunum by administration of systemic lidocaine

REASONS FOR PERFORMING STUDY: Absorption of endotoxin across ischaemic-injured mucosa is a major cause of mortality after colic surgery. Recent studies have shown that flunixin meglumine retards mucosal repair. Systemic lidocaine has been used to treat post operative ileus, but it also has novel anti-inflammatory effects that could improve mucosal recovery after ischaemic injury. HYPOTHESIS: Systemic lidocaine ameliorates the deleterious negative effects of flunixin meglumine on recovery of mucosal barrier function. METHODS: Horses were treated i.v. immediately before anaesthesia with either 0.9% saline 1 ml/50 kg bwt, flunixin meglumine 1 mg/kg bwt every 12 h or lidocaine 1.3 mg/kg bwt loading dose followed by 0.05 mg/kg bwt/min constant rate infusion, or both flunixin meglumine and lidocaine, with 6 horses allocated randomly to each group. Two sections of jejunum were subjected to 2 h of ischaemia by temporary occlusion of the local blood supply, via a midline celiotomy. Horses were monitored with a behavioural pain score and were subjected to euthanasia 18 h after reversal of ischaemia. Ischaemic-injured and control jejunum was mounted in Ussing chambers for measurement of transepithelial electrical resistance (TER) and permeability to lipopolysaccharide (LPS). RESULTS: In ischaemic-injured jejunum TER was significantly higher in horses treated with saline, lidocaine or lidocaine and flunixin meglumine combined, compared to horses treated with flunixin meglumine. In ischaemic-injured jejunum LPS permeability was significantly increased in horses treated with flunixin meglumine alone. Behavioural pain scores did not increase significantly after surgery in horses treated with flunixin meglumine. CONCLUSIONS: Treatment with systemic lidocaine ameliorated the inhibitory effects of flunixin meglumine on recovery of the mucosal barrier from ischaemic injury, when the 2 treatments were combined. The mechanism of lidocaine in improving mucosal repair has not yet been elucidated.     

In vitro transport of cycloleucine by equine cecal mucosa

Mucosa obtained from the cecum of healthy horses and incubated in vitro with 0.1 mM cycloleucine could accumulate this amino acid against an apparent concentration gradient after 60 and 120 minutes. Accumulation by the serosal (antiluminal) surface of the tissue was 3 times greater than accumulation by the mucosal (luminal) surface after 120 minutes (P less than 0.001). Cycloleucine accumulation was significantly reduced by Na deprivation after 60 minutes (P less than 0.05) and 120 minutes (P less than 0.01) and by anoxic conditions after 120 minutes (P less than 0.05). Transmucosal flux from mucosal to serosal surface of the tissue was significantly (P less than 0.05) greater than the opposing flux, but both unidirectional fluxes were small and were largely attributed to passive processes. It was concluded that the most avid transport system for cycloleucine was on the serosal surface of the horse's cecal mucosa, and an active transport system was not evident on the mucosal surface. An active transport system for amino acids on the serosal surface could be explained by the need for crypt cells, the predominant epithelial cell type in the cecum, to obtain nutrients from blood, rather than from the intestinal lumen.     

Microvascular circulation of the ascending colon in horses

Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light microscopic observation, using standard histologic methods. In sections from 6 horses, injection replicas were made by perfusing the vessels with 2 types of plastics. The results of microangiography, light microscopy, and scanning electron microscopy of vascular replicas were correlated, providing a comprehensive documentation of the microvasculature of the ascending colon at the pelvic flexure. Arteries branched from mesenteric colic vessels approximately every 2 cm toward the colonic tissue. Immediately after branching, arterial vessels formed an anastomotic plexus, the colonic rete. However, each branch from the colic vessel eventually continued into the colonic tissue. A second set of vessels originated from the colonic tissue. A second set of vessels originated from the colonic rete and supplied the mesenteric lymph nodes. Arterial vessels penetrated the tunica muscularis into the submucosa 3 to 4 cm toward the antimesenteric border forming a submucosal vascular network. From the submucosal arterioles, branching took place at right angles to supply the mucosal capillaries. Capillaries surrounded the colonic glands and anastomosed at the luminal surface, forming a superficial luminal honeycomb-appearing vascular plexus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of small intestinal ischemia and reperfusion on expression of tumor necrosis factor-alpha and interleukin-6 messenger RNAs in the jejunum, liver, and lungs of dogs

OBJECTIVE: To determine the effects of intestinal ischemia and reperfusion on the expression of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 mRNAs in the jejunum, liver, and lungs of dogs. ANIMALS: 8 healthy adult Beagles. PROCEDURES: In each dog, the cranial mesenteric artery was occluded for 0 (control group; n=4) or 60 (I-R group; 4) minutes, followed by reperfusion for 480 minutes; serum TNF-alpha and IL-6 activities and expression levels of TNF-alpha and IL-6 mRNAs in jejunal, hepatic, and lung tissues were measured before and at the end of the ischemic period and at intervals during reperfusion. For each variable, values were compared between the control and I-R groups at each time point. RESULTS: Compared with the control group, serum IL-6 activity increased significantly after 180 minutes of reperfusion in the I-R group; also, jejunal TNF-alpha mRNA expression increased significantly after 60 (peak) and 180 minutes of reperfusion. In the I-R group, expressions of IL-6 mRNA in the liver and TNF-alpha and IL-6 mRNAs in the lungs increased significantly at 480 minutes of reperfusion, compared with the control group. Serum TNF-alpha activity, expression of IL-6 mRNA in the jejunum, and expression of TNF-alpha mRNA in the liver in the control and I-R groups did not differ. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that the liver, lungs, and jejunum contributed to the production of TNF-alpha and IL-6 after intestinal ischemia and reperfusion in dogs, suggesting that intestinal ischemia and reperfusion induce a systemic proinflammatory cytokine response in dogs.