Nitric oxide production in host-versus-graft and graft-versus-host reactions in the rat.

The present study was designed to determine whether .N = O produced in vivo during the rejection of histoincompatible tissues might permit serum NO2-/NO3- levels to serve as markers of a rejection reaction. Rat syngeneic and allogeneic liver, heart, bone marrow/spleen cell, small bowel, skin, and sponge matrix grafts were performed and the stable end-products of .N = O, NO2-/NO3-, were serially assayed in the serum of the grafted animals. A significant rise of serum NO2-/NO3- levels in the allografted animals preceded the onset of clinical signs of rejection or graft-versus-host disease, with the exception of the skin and sponge matrix graft models, where elevated serum NO2-/NO3- levels were never observed. In all transplant models, normal serum NO2-/NO3- levels were observed at all times in animals that received syngeneic grafts. Furthermore, treatment of allograft recipients with the immunosuppressive agents FK 506 or cyclosporine A inhibited .N = O production. Determination of serum creatinine levels demonstrated that the elevated serum NO2-/NO3- levels were not caused by kidney dysfunction. Serum NO2-/NO3- levels might be useful early serum markers of the initiation of a rejection reaction or graft-versus-host disease when functional markers of graft dysfunction are not apparent.

Meta-analyses of studies on bone marrow micrometastases: an independent prognostic impact remains to be substantiated.

PURPOSE: In 1997, the immunocytologic detection of isolated tumor cells in bone marrow, termed micrometastasis, will be optionally included in the tumor-node-metastasis (TNM) classification indicated M1(i). In the present meta-analyses, 20 studies, which included 2,494 patients, regarding the prognostic influence of a positive bone marrow micrometastases (BMM) status on relapse-free and/or overall survival were analyzed. MATERIALS AND METHODS: The literature search included the Medline and Current Contents bibliographic data bases from August 1980 to June 1997. The statistical evaluation considered the prognostic influence of the prevalence of micrometastatic cells in bone marrow on relapse-free and/or overall survival. The comparable effect estimate and its corresponding 95% confidence interval (CI) were calculated with the Mantel-Haenszel method using the originally published data of the retrieved studies. RESULTS: The presence of epithelial cells in bone marrow was detectable in all carcinoma types, with a median prevalence of approximately 35%. Fourteen of 20 studies found a positive correlation between positive BMM status and reduced relapse-free survival by univariate analysis, but only five of 11 studies confirmed positive BMM status as an independent predictor of short disease-free survival. Regarding overall survival, positive BMM status was identified univariately in five of 12 studies, but multivariately in only two studies, as an independent factor of poor survival. Despite the heterogeneity of the studies, calculation of the relative risk (RR) for reduced relapse-free survival was possible for breast cancer, which resulted in a Mantel-Haenszel RR (RR(MH)) of 1.34 (95% CI, 1.27 to 1.42). CONCLUSION: In conclusion, the results suggest that the prognostic impact of epithelial cells in bone marrow remains to be substantiated by further studies using standardized methodic protocols before its entrance in the TNM classification.

Leukocytes of the intestinal muscularis: their phenotype and isolation.

The basal presence of immunologically potent cells within the intestinal muscularis externa and their functional significance is unclear. Our aim was to investigate the basal distribution of various leukocyte populations within the rat jejunal muscularis. In addition, we sought to immunohistochemically phenotype the muscularis macrophage in jejunal whole-mounts, isolate these cells in primary culture, and investigate their ontogenesis. Macrophages form a regularly distributed network that expresses major histocompatibility complex class II, CD14 receptors, and a low level of CD11/CD18. The macrophages are activated by dissection and are present in fetal animals. Enriched macrophage cultures show a normal resident phenotype and remain present for weeks in dissociated muscularis cultures. The results also demonstrate the presence of neutrophils, monocytes, mast cells, and lymphocytes within the muscularis and suggest that the dense network of muscularis macrophages may be a potent resident trigger for inflammation in response to tissue injury or bacterial translocation.

Distinct patterns of differentiation induced in the monocytic cell line Mono Mac 6.

The human Mono Mac 6 cell line exhibits many characteristics of mature blood monocytes including expression of the CD14 molecule and production of cytokines, such as interleukin-1 (IL-1), IL-6, and tumor necrosis factor. To determine whether these cells can be further differentiated, we treated the cells for up to 3 days with either prostaglandin E2 (PGE2; 10(-5) or 10(-6) M), lipopolysaccharide (LPS; 10-20 ng/ml), or tetradecanoylphorbol-13-acetate (TPA; 10-50 ng/ml). All three reagents reduced proliferation and expression of the early myelomonocytic antigen CD33, and all increased phagocytosis of staphylococci and constitutive expression of mRNA for the macrophage colony-stimulating factor (M-CSF) receptor. By contrast, with respect to CD23 (Fc epsilon RII) expression, CD14 expression, and production of O2-, the three reagents induced distinct responses. Expression of CD23 (Fc epsilon RII) on Mono Mac 6 cells (36%) was not increased by LPS and TPA but was increased by PGE2 treatment to 48%, with a 50% increase of fluorescence intensity. The CD14 antibody My4 stained more than 75% of untreated Mono Mac 6 cells with a specific mean fluorescence intensity of 87.5 channels. This staining was increased more than twofold by both PGE2 and LPS. Staining with the CD14 antibody UCHM1 (6%) was increased to 43% by PGE2 and to 43% by LPS. This increase in CD14 cell surface expression was accompanied by a rise in soluble CD14 and enhancement of CD14 mRNA. By contrast, TPA treatment resulted in a twofold decrease of CD14 cell surface staining with no significant change in sCD14, while CD14 mRNA was transiently down-regulated. Secretion of O2- (stimulated by TPA) was already detectable in untreated Mono Mac 6 cells (6.1 mmol/10(6) cells/30 min), and this response was enhanced 10-fold by pretreatment with LPS but not with PGE2 or TPA. The kinetics of M-CSF receptor mRNA, CD14 expression, and O2- production revealed that these monocytic features started to increase at 6-24 h and were maximal at 2 days. These data suggest that the three reagents induce maturation of the Mono Mac 6 cells to different levels or into different branches of the monocyte system with the notable differences that PGE2 enhances CD23 expression, LPS enhances O2- secretion, and TPA down-regulates CD14.

Rejection of ileal versus jejunal allografts.

Small-bowel allografts are replete with lymphocytes, which may be the main stimulus for the recipient's immune system, thereby inducing rejection. Since most of the lymphoid tissue is located in the ileum, one would expect ileal grafts to be rejected more rapidly than are jejunal grafts. To test this theory, we transplanted a jejunal (n = 13) or an ileal segment (n = 9) or the entire small bowel (n = 6) orthotopically in the BN----LEW rat strain combination. Jejunal grafts included a short segment of the mesentery, whereas ileal and whole small-bowel grafts included the entire mesentery with its lymph nodes. Segmental as well as entire-bowel grafts induced peak anti-BN titers on the 6th to 7th postoperative day. In rats with entire-bowel grafts, rejection culminated in the recipient's death after an average of 9.5 +/- 1 days from graft necrosis and peritonitis; the rejection of jejunal (13.1 +/- 2.1 days) and ileal grafts (12.9 +/- 1.3 days) was less rapid. Segmental grafts were often encapsulated, and the causes of death were inanition and intestinal obstruction. Thus, despite their high lymphocyte content, ileal grafts were not rejected more quickly than were jejunal grafts; they should, therefore, be preferred because of their greater specialized absorptive capacity. Histologically, entire-bowel grafts were found to be rejected as rapidly as were segmental grafts; however, the toxic effects of the larger grafts that are undergoing rejection lead to earlier death of the recipient.

Clinical course, morphology, and treatment of chronically rejecting small bowel allografts.

As acute rejection episodes are most frequently prevented or controlled in clinical organ transplantation, chronic rejection processes have become the major reason for late dysfunction and eventual loss of the allograft. The recent reports on successful clinical intestinal transplantation prompted us to investigate chronic rejection processes that may arise after the initial control of acute rejection. Using the strongly histoincompatible ACI-->LEW rat strain combination and serial graft biopsies after limited initial immunosuppressive therapy with cyclosporine, we defined the clinical and pathomorphologic course of chronic rejection of orthotopic small bowel allografts. Differing from acute rejection, the bowel wall (especially the mucosa and submucosa) was not the primary target of chronic rejection. We observed progressive destruction of the Peyer's patches and the mesenteric lymph nodes of the graft--a process which began during the 4-week course of CsA--and infiltration and destruction of graft mesenteric vessels. Testing the immunosuppressive drugs FK506 and CsA for their efficacy to ameliorate ongoing chronic rejection, we found that a short course (5 days) of FK506 was more effective than a second 4-week course of CsA. However, while allograft function recovered sufficiently to allow a temporary improvement of the recipient's global nutritional state, pathomorphologic graft changes failed to reverse substantially. Eventually all grafts failed due to progressive chronic rejection.

Hyaluronic acid and purine nucleoside phosphorylase in vascular and luminal effluents of small bowel grafts as parameters of preservation injury.

Reliable parameters reflecting the degree of graft injury after small bowel preservation are currently not established. We investigated hyaluronic acid (HA) and purine nucleoside phosphorylase (PNP) as indicators of preservation injury before small bowel transplantation. In the first part of the study, intestinal grafts were harvested, perfused with saline, and flushed either immediately or after 1, 6, 12, 24, and 48 hr of cold storage (n = 6/group). HA and PNP were assayed in vascular and luminal effluents. In the second part of the study, 24 grafts were transplanted after preservation periods of 1, 6, 9, and 12 hr (n = 6/group) to assess if HA and PNP are predictors of postoperative graft survival. HA levels in vascular effluents and PNP activities in luminal effluents correlated with duration of preservation time and predicted graft survival. Utilizing both parameters significantly increased the predictive accuracy.

Graft-versus-host disease induced by small bowel allografts. Clinical course and pathology.

The histopathological changes and the course of graft-versus-host (GVH) disease were studied in the rat model of small-bowel transplantation using the Lewis----LBN-F1 strain combination. Allograft-induced GVH disease led to the recipients' death from enteritis, dermatitis and emaciation after 14.4 +/- 2.9 days (heterotopic grafts) and 14.0 +/- 0.7 days (orthotopic grafts). Histologic evidence of dermatitis (epidermal hyperkeratosis and cutaneous infiltration by mononuclear and polymorphonuclear cells) and enteritis (villous blunting and sloughing, inflammatory infiltrate of the recipient's own intestine) appeared on the 9th to 13th postoperative days, and these changes became fulminant within 2-3 days. The lymphatic tissues of the Lewis grafts and the LBN-F1 host underwent a course of progressive lymphoid depletion and loss of follicular architecture beginning on the 5th postoperative day. Throughout the postoperative course, the small-bowel graft remained intact. The relative spleen weight progressively increased until shortly before death, when a marked reduction was observed. The clinical triad of diarrhea, diffuse dermatitis, and hypertrophy of the lymphoid organs followed by their atrophy suggests a diagnosis of GVH disease rather than rejection of the small-bowel allograft. The diagnosis can be confirmed by biopsy of a recipient lymph node or the intestinal allograft (cave perforation) if it is accessible.

Functional impairment of enteric smooth muscle and nerves caused by chronic intestinal allograft rejection regresses after FK506 rescue.

We have previously demonstrated that subclinical chronic rejection (CR) induces structural and functional alterations in enteric smooth muscle and nerves in a rat model of small intestinal transplantation. This study was designed to investigate the effect of prolonged FK506 rescue therapy on these sequelae of CR. Immunohistochemistry of BrdU-labeled muscle cells demonstrated that active proliferation of intestinal smooth muscle caused by CR was successfully aborted by FK506 rescue therapy after a period of 30 days (control = 0.14 +/- 0.09; CR = 30.4 +/- 1.73; rescue = 2.4 +/- 0.63 cells/jejunal cross-section, P < 0.01). However, FK506 did not reverse the already established increase in muscular thickness (control = 92 +/- 2.4; CR = 193 +/- 10.6; rescue = 188 +/- 8.1 microns) due to CR. Bethanechol stimulated circular muscle contractility was improved markedly with rescue therapy (maximal contractile force reached 39.5% of control values in CR grafts and 68.8% after rescue). Rescue therapy did not reverse the loss of NADPH-diaphorase positive myenteric ganglia (control = 37 +/- 1.4; CR = 28 +/- 2.9; rescue = 23 +/- 1.7 ganglia/cross-section). Despite the persistent loss of ganglia, inhibitory junction potentials (IJPs) improved significantly returning to control values with FK506 (control = 10 +/- 0.5; CR = 5 +/- 0.3; CR rescue = 10 +/- 0.7 mV; IJPs recorded at 1 pulse/150V/0.75 ms). Although structural changes in enteric smooth muscle and myenteric neurons induced by CR were not reversed, the progression of subclinical CR can be effectively curbed by FK506 rescue therapy. The improvement in muscular mechanics and inhibitory neural innervation is probably due to the cessation of infiltrating immunocytes and sprouting of remaining myenteric nerves.

Oxygen free radical content and neutrophil infiltration are important determinants in mucosal injury after rat small bowel transplantation.

Mucosal injury is an immediate event following revascularization of small intestinal grafts in the context of transplantation (SBTx). The generation of oxygen free radicals (OFR) and tissue infiltration by activated neutrophils are consequences of ischemia and reperfusion and known causative factors of tissue injury; to delineate their role in the reperfusion injury occurring after cold preservation of the intestine and subsequent transplantation was the aim of this study. Prior to orthotopic SBTx in Sprague-Dawley rats, grafts were stored in cold (4 degrees C) Ringer's lactate solution for 1 (n=6), 2 (n=7), and 4 hr (n=7). Small bowel biopsy specimens were obtained before harvesting, at the end of the (cold) ischemic period and immediately before unclamping (i.e., before revascularization) and 30, 60, 120 min, and 24 hr after transplantation to evaluate tissue injury by histology, OFR production, (measured by luminol-enhanced chemiluminescence [LCL]), and the degree of neutrophil infiltration by myeloperoxidase staining. Reperfusion of the graft significantly worsened the histologically graded mucosal injury compared with that seen before unclamping. However, 24 hr after engraftment, mucosal morphology was restored almost completely. OFR production increased significantly during the early phases of reperfusion (30, 60, and 120 min) and returned to control values after 24 hr. Reperfusion of the graft was associated with a marked increase in the number of mucosal neutrophils. The present study indicates that OFR production and neutrophilic infiltration commence and progressively increase with graft reperfusion. These changes parallel the mucosal injury. Ischemic intervals of 4 hr were not associated with a statistically significant greater ischemic-injury patterns compared with 1- and 2-hr intervals. The profound changes associated with reperfusion probably overshadow the minor, yet likely, progressive injury patterns associated with longer ischemia times.

Evidence that nitric oxide production by in vivo allosensitized cells inhibits the development of allospecific CTL.

The oxidative metabolism of L-arginine to its bioactive product, nitric oxide (.N = O) has been shown to inhibit rat splenocyte mixed lymphocyte reactions. To determine if alloantigen-induced .N = O production might be operative in vivo, cells that had infiltrated a rat sponge matrix allograft were tested for de novo .N = O production as well as .N = O production upon restimulation with the sensitizing alloantigen. When graft-infiltrating cells were placed in culture, a peak in de novo .N = O production was observed by day 6 graft-infiltrating cells, the time when donor-specific CTL activity by the graft-infiltrating cells was first observed. Upon restimulation with alloantigen, allograft-infiltrating cells produced greatly increased levels of .N = O, and this production was associated with inhibition of lymphocyte cytolytic function. The addition of NG-monomethyl-L-arginine (NMA), the competitive inhibitor of oxidative L-arginine metabolism, inhibited .N = O production and promoted allospecific CTL development. Both observed effects of NMA were reversed by addition of excess L-arginine. Cytokine(s) able to induce proliferation of the IL-2-dependent T cell line CTLL-2 could be detected in alloantigen-stimulated cultures in both the presence and absence of NMA. However, proliferation of the graft-infiltrating cells in response to these cytokines was observed only in the presence of NMA. The immunosuppressive macrolide FK506 was a potent inhibitor of .N = O production in these cultures, presumably acting by inhibiting the production of those cytokines that induce the oxidative L-arginine pathway.

Evidence that small bowel preservation causes primarily basement membrane and endothelial rather than epithelial cell injury.

The main site of injury induced during small bowel preservation is perceived to be the basement membrane and the endothelium of the highly vascularized mucosa, an aspect evaluated here in further detail. The effects of preservation were studied using a specific basement membrane stain (laminin antibody), an endothelial cell stain (factor 8 antibody) and standard histology. In addition, mucosal glutaminase activity reflecting enterocyte integrity was measured as monitor of the extent of preservation injury. Using a rat model, small bowel grafts were harvested, the vascular bed and bowel lumen were flushed, and the grafts were stored (4 degrees C) for 1, 6, 9, and 12 hr and transplanted into syngeneic hosts. After cold storage prior to transplantation, full-thickness small bowel biopsies were obtained for the various tissue preparations. Histologic evaluation at the end of the preservation period revealed separation of the villous epithelium from the lamina propria that increased with extending preservation time. Tissue staining with the laminin antibody disclosed progressive changes with increasing preservation intervals. Staining with the factor 8 antibody demonstrated also progressive changes, but failed to reflect in a gradual fashion increasing endothelial cell injury. Histologic injury became more pronounced after transplantation and reperfusion, then showing destruction of epithelial cells; the extent of injury correlated with the duration of preservation. Glutaminase activity was maintained after cold storage, indicating that the enterocytes remained intact during this period, but when assayed after reperfusion, glutaminase decreased with increasing preservation intervals and increasing histologic mucosal damage. We conclude that cold ischemic injury involves primarily the endothelium and the basement membrane, which progresses to global mucosal impairment with reperfusion.

Evaluation of preservation conditions and various solutions for small bowel preservation.

The aim of the study was to delineate the most optimal preservation conditions for small bowel grafts. Established preservation solutions such as EuroCollins, University of Wisconsin, histidine-tryptophane-ketoglutarate-Brettschneider, phosphate-buffered sucrose (PBS 140), and 3 new solutions--extracellular fluid (ECF), lactobionate fructose, and a modified lactobionate fructose solution--were compared with saline to determine the most optimal solution for the intestine. Recipient survival, standard histology, and glutaminase activity were used to assess the degree of injury encountered after 12 hr of preservation followed by transplantation. To evaluate the various preservation conditions, ECF was used at pH 6.8 (original ECF). Grafts were preserved most optimally when a vascular washout after the cold storage period was omitted and when topical rewarming of the graft with 37 degrees C saline before reperfusion was performed. Graft survival was not significantly different after preservation with any solution tested (50-83%). Highest graft survival (83%) was achieved with lactobionate fructose and PBS140. Histologic evaluation 20 min after reperfusion revealed minor differences between most groups; a slight advantage was observed for PBS140-preserved grafts. Mucosal glutaminase activity of PBS140-preserved grafts was significantly higher 20 min after reperfusion compared with any other solution evaluated, indicating a superior graft function. These data indicate that different preservation conditions have a great impact on postoperative graft survival and that PBS140 might be preferable to any of the other preservation solutions tested.

Induction of graft-versus-host disease and rejection by sensitized small bowel allografts.

This study was undertaken to investigate under which circumstances graft versus host disease occurs following fully allogenic small bowel transplantation in the rat. To facilitate the development of GVHD, Brown-Norway donors were specifically sensitized against the Lewis hosts prior to transplantation. Additionally, the Lewis recipients were immunocompromised before transplantation using splenectomy, cyclosporine, and antilymphocyte serum. No further immunosuppressive therapy was administered after transplantation. When all pretreatment regimens were used, acute lethal GVHD arose in two of nine animals (22%), whereas in two animals (22%) signs of acute GVHD and rejection were observed concurrently. When recipients of sensitized grafts were pretreated with CsA alone, one of eight animals (12.5%) showed signs of GVHD and rejection. All other animals died of acute rejection without clinical signs of acute GVHD. However, histological signs of GVHD were observed frequently in hosts grafted with a sensitized small bowel transplant. These data show that acute lethal GVHD can occur when an immunocompromised host is grafted with a sensitized intestinal transplant.

Evidence that indefinite survival of small bowel allografts achieved by a brief course of cyclosporine or FK506 is not due to systemic hyporesponsiveness.

The immunological status of Lewis (LEW) recipients of indefinitely surviving (greater than 400 days) orthotopic Brown-Norway (BN) small bowel allografts was investigated 1 to 1 1/2 years after cessation of immunosuppressive therapy with either cyclosporine or FK506 and compared with recipients of syngeneic grafts. A normal proliferative response (as measured by a mixed lymphocyte culture) of recipient peripheral lymph node lymphocytes in response to the donor-specific (BN) and the third-party (ACI) antigen, was observed in all experimental groups. Cytolytic T cell generation (as measured by a standard 51Cr-release cytotoxicity assay) in response to the donor-specific (BN) and the third-party (ACI) antigen was observed also in all groups. A FACS analysis of allograft-recipient splenocytes showed no evidence for systemic lymphoid chimerism. BN or ACI skin grafts transplanted onto recipients of allogeneic and syngeneic small bowel grafts were rejected completely in 12-17 days, while the intestinal grafts remained functional. Immunohistologic evaluation of the allografts, using anti-BN class I and anti-Lewis class II monoclonal antibodies showed anti-BN staining on the epithelial and endothelial structures, whereas the mononuclear cells in the lamina propria stained positively with the anti-LEW monoclonal antibody. However, lymphoid depletion and scarring of Peyer's patches and mesenteric lymph nodes as well as focal obliterative mesenteric arteriopathy, indicative of an indolent chronic rejection, were observed. These data demonstrate that recipients of indefinitely surviving small bowel allografts remain immune competent and do not retain the intestinal graft on the basis of specific hyporesponsiveness to the donor antigens.

Heterotopic intestinal transplantation aggravates the insult of chronic rejection.

BACKGROUND: Intestinal grafts are placed either heterotopically (out of continuity) or orthotopically (in continuity); the latter is believed to be advantageous, as intraluminal nutrients and intestinal secretions might modulate the intestinal immune status and possibly delay rejection. METHODS: This study was designed to delineate the effects of heterotopic versus orthotopic allograft position on the morphology and function of intestinal smooth muscle in our rat model of chronic rejection. Syngeneic orthotopic grafts were evaluated to control for changes due to the transplantation process. RESULTS: Histochemistry of the graft's muscularis externa showed a significant thickening due to hyperplasia and hypertrophy, which was most pronounced in heterotopic grafts (control = 92+/-2.4 microm, syngeneic grafts = 140+/-6.7 microm, orthotopic allografts = 278+/-26.6 microm, heterotopic allografts = 456+/-50 microm). In terms of function, muscle strips from allografts only generated 23% of the total bethanechol-induced contractile force in vitro compared to unoperated controls and syngeneic grafts. The mean resting membrane potential of control and isograft muscle cells was -69 +/- 0.9 mV with a slow-wave amplitude of 20+/-0.5 mV. Chronic rejection hyperpolarized the resting membrane potential of orthotopic allografts (-66 +/- 0.5 mV) and even more so of heterotopic allografts (-58 +/- 3.4 mV). Slow-wave amplitudes were decreased in orthotopic (14+/-0.9 mV) and nearly abolished in heterotopic allografts (2+/-1.2 mV). CONCLUSIONS: Our data indicate that allografts in heterotopic position are most susceptible to the insult of chronic rejection exemplified by increased proliferative and hypertrophic transformation of intestinal smooth muscle and a marked decrease in mechanical and electrical activity.

The effects of administration of nitric oxide inhibitors during small bowel preservation and reperfusion.

The effects of nitric oxide (NO) during small bowel preservation and reperfusion were studied in a rat model of heterotopic, syngeneic LEW-->LEW transplantation. A 6-hr preservation interval was chosen, which leads consistently to moderate graft injury permitting graft and recipient survival. To evaluate the function of NO during preservation and reperfusion, two inhibitors (NitroG-L-arginine methyl ester [L-NAME] and NG-monomethyl-L-arginine [NMA]) were administered and compared with a transplanted group receiving no treatment. The extent of preservation and reperfusion injury were delineated by histologic study and by the measurement of mucosal glutaminase on tissue specimens obtained 20 min after revascularization and 24 hr and 4 weeks postoperatively. Serum and mucosal NO(2-)+NO3- levels were determined at the same time points. Graft function and survival was inferior in all cases where NO production was inhibited. When recipients were treated with NO inhibitors, graft function and survival was more impaired when L-NAME was administered compared with NMA administration. Donor and graft pretreatment with NO inhibitors impaired graft function but not survival, and was less detrimental than recipient treatment. Mucosal NO(2-)+NO3- levels significantly increased in untreated transplanted animals 20 min after reperfusion. This increase was abolished in groups treated with NO inhibitors. Serum NO(2-)+NO3- levels increased significantly after 24 hr, and this increase was even more pronounced when NO inhibitors were administered. Furthermore, liver function deteriorated after inhibition of NO, indicating a more severe inflammatory response of the recipient after NO inhibition. These data indicate that mucosal NO production within the graft during preservation, and especially during reperfusion, has beneficial effects, but increased serum NO(2-)+NO3- levels coincided with inferior graft condition due to preservation and reperfusion injury.

Review article: effects of the 5-HT3 receptor antagonist alosetron on neuromuscular transmission in canine and human intestinal muscle.

BACKGROUND: Currently, therapeutic treatments for irritable bowel syndrome fail to produce significant clinical results. We hypothesized that alosetron, a selective 5-HT3 antagonist, may provide symptomatic relief in irritable bowel syndrome patients through a decrease in the amplitude of gastrointestinal contractions. AIM: To determine the in vitro effect of alosetron on neuromuscular transmission in the canine and human jejunal and colonic muscularis externa. RESULTS: Alosetron diminished electrical field-stimulated (EFS) contractions recorded from muscles of the canine and human small and large intestines. Mechanistically, the diminished EFS response could be explained by the ability of alosetron to decrease the fractional release of 14C-choline radiolabelled acetylcholine evoked by EFS from human jejunal muscle. The inhibition of EFS contractions was not limited to atropine-sensitive events, as non-cholinergic excitatory EFS evoked contractions were also inhibited. Additionally, alosetron at high concentrations (> 30 microM) directly altered bethanechol stimulated contractions. CONCLUSION: Caution must be used in the interpretation of these data because significant alterations in EFS-induced contractions were only observed with large pharmacological concentrations of alosetron, and the response was not selective for cholinergically-mediated excitatory neuromuscular transmission.

Ileoanal anastomosis with proximal ileal reservoir: an experimental study.

Endorectal ileoanal anastomosis with proximal interposition of an ileal reservoir was evaluated experimentally in dogs as an approach to retain sphincteric control of defecation after proctocolectomy. Two months after the operative procedure, eight animals with a reservoir had four to eight semisolid stools per day and were continent. In contrast, six animals with straight ileoanal anastomosis were incontinent with 10 to 14 evacuations per day. Motility studies demonstrated a reduction of propulsive peristalsis within the undistended reservoir, which is considered the responsible factor for increased intestinal transit time and reduced stool frequency. Filling of the reservoir to capacity elicited strong peristaltic contractions, which may assure a more complete evacuation of the reservoir during defecation. Reservoir capacity increased substantially (150% to 200%) within 2 months but only to a minor degree thereafter, indicating that the reservoir does not dilate progressively into an atonic viscus. Motility patterns remained unaltered as the reservoir became more complaint with time. Mucosal alterations (flattening of villi, submucosal inflammation) were detected in the reservoir but did not result in nutritional defects within an observation period of 1 year.

Portal versus caval venous drainage of small bowel allografts: technical and metabolic consequences.

The potential metabolic and technical consequences of systemic (portacaval anastomosis [PC-A]) as opposed to portal venous drainage (portaportal anastomosis [PP-A]) of orthotopic small bowel isografts was evaluated in a rat model. Rats with portacaval (PC) shunts were studied for comparison. During the study period of 6 months, rats with small bowel grafts (PP-A or PC-A) gained weight at rates equal to that of normal age-matched rats (+40% of the preoperative weight) whereas rats with PC shunts lost 20% of their weight. At autopsy 6 months after operation, rats with PC shunts had significant liver atrophy (2.0% of total body weight) in comparison with rats with orthotopic isografts. Moderate liver atrophy was detected in rats with grafts and PC-A in comparison with those with PP-A (2.6% versus 2.8% of total body weight, statistically not significant). Serum ammonia levels were significantly elevated for PC shunts (560 +/- 148 micrograms/dl) and PC-A (140 +/- 22 micrograms/dl) when compared with PP-A (83 +/- 10 micrograms/dl). In terms of technical difficulties, both PC-A and PP-A could be achieved with the same success rate. Systemic venous drainage for small bowel grafts is followed by metabolic alterations that are similar, although much less pronounced, to those seen after a PC shunt. Thus our findings do not offer compelling reasons to prefer PP-A over PC-A. However, with longer follow-up and the use of hepatotoxic immunosuppressive drugs, these minimal alterations may progress and induce metabolic sequelae of clinical significance. Under these circumstances it would be advisable to use the physiologic portal drainage rather than systemic venous drainage in small bowel transplantation.