David L. Sigalet

FK506 increases permeability in rat intestine by inhibiting mitochondrial function.

BACKGROUND & AIMS Under normal physiological conditions, the intestine presents an adenosine triphosphate (ATP)-dependent barrier to luminal contents. Disruption of this barrier function can occur when cellular metabolism is compromised. This study examined the effects of FK506 on intestinal permeability and enterocyte metabolic function in Lewis rats. METHODS Rats were administered FK506 at a dose of 0.1, 0.5, or 2 mg/kg on alternate days for 6 weeks. Intestinal permeability was assessed by measuring urinary recovery of 99mTc-diethylenetriamine pentacetate, and electrophysiological conductance measurements were performed in Ussing chambers. Metabolic function was assessed in isolated enterocytes by measuring total ATP and CO2 release from [14C]pyruvate and [14C]glucose. RESULTS Rats treated with FK506 showed a dose-dependent reduction in weight gain as well as increased in vivo and in vitro intestinal permeability. There was no difference in plasma creatinine or urinary output. Changes in permeability correlated with reduced ATP levels and CO2 release because of diminished mitochondrial function. Lactate production, as a measure of glycolytic activity, was not altered by FK506. CONCLUSIONS In a dose-dependent manner, FK506 treatment in rats reduces weight gain, increases intestinal permeability, and decreases the ability of the small intestine to use glucose as an energy source.

The physiology of adaptation to small bowel resection in the pig: An integrated study of morphological and functional changes

This study examined the adaptive response to extensive small intestinal resection in the juvenile domestic pig. Control animals underwent an ileal transection with end-to-end anastomosis, whereas resected pigs had a resection of the mid-75% of the total small bowel length. Animals were followed for 16 weeks. Resected animals gained less weight than controls, with no significant difference in feed intake per unit animal weight. In vivo fat, protein, carbohydrate, and total energy absorption were reduced in resected animals. Resected pigs had increased in vitro passive ileal uptake of fatty acids, cholesterol, and L-glucose, but no change in active D-glucose uptake. Microscopic morphology was altered, with an increase in the size of villi, a decrease in villous density, and no net change in mucosal surface area per unit of serosal surface area. Gross bowel length and diameter increased proportionately more in the resected than the control groups. This study demonstrated that massive resection results in a significant change in nutritional status in the growing pig. Functional and morphological changes occur, demonstrating intestinal adaptation. These findings suggest that this model would be suitable for the study of therapeutic modalities for the short-bowel syndrome in humans.

Atypical tuberculosis in the pediatric patient: Implications for the pediatric surgeon☆

Atypical species of mycobacteria (AMB) are now the most common cause of granulomatous lymphadenopathy. It is important for pediatric surgeons to be aware of this disease, because excision is the mainstay of therapy. We have reviewed the experience with this disease in Alberta by reviewing the records of the Provincial Laboratory of Public Health from 1979 to 1990. This facility reviews all tuberculosis cultures for the province. A total of 74 cases of infection caused by AMB were identified in patients under the age of 15. Complete records were available for 53 of these cases. These infections were characterized by a short history (11.2 weeks) of remarkably nontender regional lymphadenopathy (usually cervicofacial, 45/50) in young (average age, 13.6 months), caucasian (48/53) children. Attempts to treat these lesions by incision and drainage or drug therapy were unsuccessful (12/12 failed), whereas primary excision was successful in 33 of 37 cases. Secondary excisions were also successful in 16 of 16 cases where required. The annual rate of AMB over the study period was 1.21 cases per 100,000 children; the rate of M tuberculosis lymphadenopathy was 0.3 per 100,000. In the absence of specific risk factors for human tuberculosis (family history, native Indian or Asian ethnic origin) AMB is the most likely cause of prolonged painless lymphadenopathy and should be treated early by complete excision.

Intestinal function following allogeneic small intestinal transplantation in the rat.

This study tests the hypothesis that small bowel transplantation alters the function of the intestine. The function of the small intestine was investigated after syngeneic (BN----BN or Lew----Lew) and fully allogeneic (BN----Lew) orthotopic total small intestinal transplantation (SIT) using a two-stage model. All animals were treated with cyclosporine A throughout the 60-day study period. Syngeneic transplantation reduced weight gain in the (BN----BN) rats, but not in the (Lew----Lew) animals. Allogeneic transplantation caused a reduction in weight gain for the first 30 days posttransplantation, which may have been associated with graft-versus-host disease. Thereafter, the rate of growth of allogeneic SIT animals was normal. Dietary fat absorption was reduced in all groups of transplanted animals. Intestinal permeability to mannitol and polyethylene glycol 400 (PEG-400) was increased by syngeneic transplantation in all groups, with further permeability increases to mannitol, lactulose, PEG-400, and 51Cr-EDTA after allogeneic SIT. The glucose-stimulated intestinal short circuit current was reduced by both syngeneic and allogeneic SIT, but the maximal active transport rate for glucose uptake was increased, as was the passive uptake of fatty acids. These functional alterations were not associated with changes in intestinal morphology or evidence of rejection. These findings demonstrate that: (1) SIT results in significant changes in the transport characteristics of the bowel, but these have a minimal impact on the well-being of the animal overall; (2) SIT induces an increase in intestinal permeability to mannitol and PEG-400, with a further increase in permeability to all markers following allogeneic SIT; (3) following SIT, and the immune events associated with allogeneic SIT, significant adaptation of the transplanted intestine occurs. We suggest that denervation of the small intestine after SIT is the underlying cause of the changes observed.

Reduction of nutrient absorption in normal rats by cyclosporine.

The indications for using cyclosporine are expanding rapidly beyond immune suppression for transplantation. We have previously described reduced active glucose uptake by small bowel following CsA treatment in rats. This study examined the effect of varying the dose and route of administration of CsA on bowel function. Male Lewis rats were given CsA via subcutaneous injection at doses of 5 mg/kg or 30 mg/kg on alternate days, or orally via gavage at 0 (control solvent oil), 7.5 mg/kg, or 30 mg/kg daily. Weight gain and feed intake were followed for 1 month when a balance study was performed to quantify in vivo nutrient absorption from the feed. In vitro studies of glucose and fatty acid uptake studies were then performed. Weight gain was reduced by high-dose CsA whether given orally or by subcutaneous injection. Oral CsA reduced in vivo fat and energy absorption from the diet, and all doses and routes of administration of CsA caused a reduction in both active glucose uptake and passive fatty acid absorption by the bowel in vitro. Thus, CsA has significant effects on bowel function in the normal rat. We suggest that further studies are indicated to determine the effects of CsA in man, especially in conditions with already-impaired bowel function.

Small bowel transplantation: past, present and future.

As techniques for immune suppression improve, the clinical utility of small bowel transplantation will increase. Recent reports of long-term (over 1 year) survival with totally enteral nutrition following bowel transplantation have increased interest in this area and prompted the present review of the state of the art of small bowel transplantation. Background methodology is emphasized, in order to allow for more critical review of reported models, and to provide a framework for comparing results. The functional capacity of bowel following transplantation, and the effects of immune suppression on bowel function are reviewed in detail. Prospects for future direction in basic and clinical research are discussed.

The impact of surgical technique on the development of graft versus host disease in a rat small intestinal transplant model.

The small intestine and its mesentery contain a large amount of lymphoid tissue that can mediate graft-versus-host disease (GVHD) in small intestinal transplant recipients. To assess the impact of surgical technique and the retention of the recipients small intestine on GVHD intensity, 12 adult Lewis rats received heterotopic small bowel transplants and 12 received orthotopic small bowel transplants from Brown Norway donors. Twelve Lewis to Lewis heterotopic small-bowel-transplanted animals served as the control group. All recipients were given cyclosporine (10 mg/kg/alternate days) subcutaneously. The parameters followed were: weight gain and feed intake; clinical signs of GVHD; relative spleen weight; popliteal lymph node enlargement assay; and histological evaluation of spleen, liver, skin, native intestine, and transplanted intestine. According to the clinical scoring system, heterotopically transplanted animals were found to have a more severe GVHD than the orthotopic group. There were statistically significant differences between the relative spleen weights of the heterotopic transplant group and the control group (P = 0.001, 0.004, and 0.007 on days 7, 14, and 21, respectively) and between the heterotopic and orthotopic groups at 7 days (P=0.037). Lymph node enlargement assays were statistically different between heterotopic and orthotopic groups (P = 0.019, 0.020, and 0.007 on days 7, 14, and 21, respectively). Histological evaluation of skin biopsy specimens also demonstrated that GVHD was indeed more severe in the heterotopic transplanted group when compared with orthotopically transplanted animals. These findings confirm that retention of the native small intestine in the heterotopic intestinal transplant model significantly increases the severity of GVHD following transplantation.