Deficient iNOS in inflammatory bowel disease intestinal microvascular endothelial cells results in increased leukocyte adhesion.

Microvascular endothelial cells play a key role in inflammation by undergoing activation and recruiting circulating immune cells into tissues and foci of inflammation, an early and rate-limiting step in the inflammatory process. We have previously [Binion et al., Gastroenterology112:1898-1907, 1997] shown that human intestinal microvascular endothelial cells (HIMEC) isolated from surgically resected inflammatory bowel disease (IBD) patient tissue demonstrate significantly increased leukocyte binding in vitro compared to normal HIMEC. Our studies [Binion et al., Am. J. Physiol.275 (Gastrointest. Liver Physiol. 38):G592-G603, 1998] have also demonstrated that nitric oxide (NO) production by inducible nitric oxide synthase (iNOS) normally plays a key role in downregulating HIMEC activation and leukocyte adhesion. Using primary cultures of HIMEC derived from normal and IBD patient tissues, we sought to determine whether alterations in iNOS-derived NO production underlies leukocyte hyperadhesion in IBD. Both nonselective (N(G)-monomethyl-L-arginine) and specific (N-Iminoethyl-L-lysine) inhibitors of iNOS significantly increased leukocyte binding by normal HIMEC activated with cytokines and lipopolysaccharide (LPS), but had no effect on leukocyte adhesion by similarly activated IBD HIMEC. When compared to normal HIMEC, IBD endothelial cells had significantly decreased levels of iNOS mRNA, protein, and NO production following activation. Addition of exogenous NO by co-culture with normal HIMEC or by pharmacologic delivery with the long-acting NO donor detaNONOate restored a normal leukocyte binding pattern in the IBD HIMEC. These data suggest that loss of iNOS expression is a feature of chronically inflamed microvascular endothelial cells, which leads to enhanced leukocyte binding, potentially contributing to chronic, destructive inflammation in IBD.

Expression of mRNA for vasoactive intestinal peptide in rat small intestine.

Transplantation of small intestine is a neural model that permits studies of expression of the neuropeptide, vasoactive intestinal peptide, following extrinsic denervation, transection of intrinsic neural pathways, and an ischemic interval. Tissue levels of vasoactive intestinal peptide were examined at 3 months in ileum from a sham operation, in ileum after resection of proximal small intestine, in ileum after resection of proximal small intestine and extrinsic denervation, in ileum after resection of proximal small intestine and 30 min of ischemia, and in ileum obtained 3 months after ileal isografting in Lewis-to-Lewis combinations. Vasoactive intestinal peptide levels were increased in transplanted rat ileum, resection controls, denervation controls, and ischemic controls compared to sham-operated ileum (pANOVA < 0.01). The increased levels of this peptide were highest in denervation controls and lowest in ischemic controls. Northern blot analysis using rat vasoactive intestinal peptide cDNA identified a single 1.7-kb transcript in normal and transplanted rat ileum. The density of vasoactive intestinal peptide transcripts was increased in transplanted ileum (8450 +/- 540) compared to normal ileum (5790 +/- 620) (P < 0.01), and the ratio of this transcript to glyceraldehyde-3-phosphate dehydrogenase density units was also increased in transplanted ileum (0.81 +/- 0.08) compared to normal ileum (0.40 +/- 0.07; P < 0.01). Enhanced transcriptional regulation was the likely mechanism for increased tissue vasoactive intestinal peptide. The increased tissue levels appeared to be a response to extrinsic denervation and transection of intrinsic neural pathways, while an ischemic interval appeared to decrease tissue levels of the peptide.

Assessing the risk of blood exposure in the operating room.

During the past 3 years, a great deal of new information has been published on the risk of blood exposure and injury in the operating room. In addition, detailed information about the effectiveness of barrier materials, operating room garments, and gloves has also become available. On the basis of this information, it has become possible to recommend strategies, barrier materials, and garments that should reduce the risk of contracting a blood-borne infection in the operating room. Further attempts to decrease the risk of blood exposure and injury require thorough evaluation of all risk-reduction strategies and careful selection of protective apparel and barriers on the basis of well-designed studies performed in the operating room environment.

Effects of intestinal transplantation on postprandial motility and regulation of intestinal transit.

BACKGROUND: The effects of intestinal transplantation on gut motility have not been completely defined. In this study we examine the effects of ileal transplantation on ileal smooth muscle contractility, together with gastroduodenal emptying, intestinal flow, and transit rates in a canine model of short-gut syndrome. METHODS: Animals (n = 22) were instrumented with strain gauge transducers, collection cannulae, and infusion catheters to assess motility, intestinal flow and transit rates, and gastroduodenal emptying. Ten animals served to define normal parameters. Six animals underwent a 70% resection of the proximal small intestine to serve as short-gut controls. Six animals underwent removal of a 100-cm segment of the ileum, with cold storage, and autotransplantation the following day combined with a 70% resection of proximal bowel. RESULTS: Transplant animals exhibited delayed gastroduodenal emptying, reduced intestinal flow rates, and postprandial phasic contractions that were similar to short-gut controls. However, transplant animals experienced rapid intestinal transit compared with short-gut controls (4.8 +/- 0.4 cm/min vs 2.0 +/- 0.3 cm/min; mean +/- SEM; P <.05). CONCLUSIONS: The transplanted intestine, even with 18 hours of cold storage, exhibits a relatively normal postprandial motor response. However, adaptive responses of the transplanted intestine, such as regulation of intestine transit, may be impaired by neuromuscular injury associated with denervation or ischemia.

Postprandial motor activity and its relationship to transit in the canine ileum.

BACKGROUND: The purpose of this study was to elucidate the mechanism of reduced intestinal transit rate in the ileum as compared with the jejunum. METHODS: Twenty-one dogs were each instrumented with 12 strain gauge transducers, 2 collection cannulas, and an infusion catheter defining a 100 cm study in the midjejunum (n = 11) and midileum (n = 10). Postprandial motor activity and intestinal transit were measured 1 hour after ingestion of a 650 kcal solid meal. Contractile activity was analyzed by means of computer programs that determine frequency, amplitude, and propagation behavior of circular smooth muscle contractions. RESULTS: Postprandial ileal contractions occurred with greater frequency (13.7 +/- 2.5 versus 11.5 +/- 0.4; p = 0.04) and displayed a higher incidence of propagation (61% +/- 2% versus 44% +/- 3%; p = 0.0001) than jejunal contractions, but traveled at significantly slower rates (1.0 +/- 0.7 cm/sec vs 3.7 +/- 0.9 cm/sec; p = 0.0001). The net result was significantly slower transit in the ileum compared with the jejunum (4.7 +/- 0.7 cm/min versus 13.1 +/- 1.5 cm/min; p = 0.0006). Within each region, transit correlated with parameters of propagating contractions. Stepwise regression of the combined data revealed that contraction velocity was the most important variable determining intestinal transit rate (r = 0.64; p < 0.001). CONCLUSIONS: Contrary to previous thinking, postprandial ileal contractions display a high degree of temporal and spatial organization. Slow ileal transit is mainly due to reduced propagation velocity, which is intrinsic to the circular smooth muscle.

Immunological enhancement of rat small intestinal allografts.

In an attempt to evaluate whether survival of rat intestinal allografts could be extended by the administration of enhancing serum, Lewis-Brown Norway small intestine was transplanted to Lewis recipients, using microsurgical techniques. Only multiple injections of serum, administered on alternate days, resulted in a prolongation of survival by a few days. Neither graft irradiation nor a single injection of antiserum was effective in increasing survival time of the transplanted intestine. Clinical trials of intestinal transplantation from cadaver donors will probably have to await a clearer understanding of various methods of altering host responsiveness to foreign tissue. At the present time, central venous nutrition offers the best solution to the patient with an insufficient length of small intestine.

Double gloving. Protecting surgeons from blood contamination in the operating room.

Health care workers, particularly surgeons, understand the importance of preventing contamination from blood of patients infected with deadly viruses. One of the most common areas of contamination is the hands and fingers due to the failure of glove protection. There are varying opinions regarding the frequency of glove failure, the necessity of wearing two gloves for added protection, and the ability to operate when wearing two gloves. We performed a prospective, randomized, trial of 143 procedures involving 284 persons to answer these questions for surgeons and first assistants. Overall, the glove failure rate (blood contamination of the fingers) was 51% when one glove was worn and 7% when two gloves were worn. Acceptability was 88% in the group who agreed to wear two gloves, and 88% of these did not perceive that tactile sense was significantly impaired. We believe that double gloving should be, and can be, used routinely during major surgical procedures to protect surgeons from blood contamination.

The efficacy of oral antimicrobials in reducing aerobic and anaerobic colonic mucosal flora.

We investigated the impact of intestinal antisepsis on the colonic mucosa-associated flora. Four groups of dogs were studied: group A received no bowel preparation, group B received a three-day clear-liquid diet, group C underwent mechanical cleansing of the bowel, and group D had mechanical cleansing followed by oral neomycin and erythromycin. Mucosal biopsy specimens were obtained for bacteriologic and scanning electron microscopic (SEM) studies. No significant difference in recovery of mucosal bacteria was observed between groups A and B. A significant decrease in recovery of aerobes was observed in group C, and a significant decrease in both aerobes and anaerobes was observed in group D compared with group A; Enterobacteriaceae and Bacteroides were either eliminated or greatly reduced. The SEM analysis of group D revealed a marked decrease in mucosa-associated microflora compared with groups B and C. Oral neomycin-erythromycin produced a significant quantitative reduction in the colonic mucosa-associated bacterial population, including the potentially pathogenic Escherichia coli and Bacteroides fragilis group isolates. These mucosa-associated bacteria are a likely source of contamination of the abdominal cavity and wound at the time of colon surgery.

Acquired megacolon is associated with alteration of vasoactive intestinal peptide levels and acetylcholinesterase activity.

Based upon previous morphologic studies, we hypothesized that the development of acquired megacolon was associated with abnormalities of enteric neurotransmitter concentrations and enzymatic activities. Specimens were obtained at surgery from patients with normal descending-sigmoid colon (n = 13) and patients with sigmoid megacolon (n = 6; defined by radiologic measurement). Radioimmunoassays were used to measure the non-adrenergic, non-cholinergic inhibitory neuropeptide, vasoactive intestinal peptide, and the non-adrenergic, non-cholinergic excitatory neuropeptide, substance P, while spectrophotometric assays were used to quantitate acetylcholinesterase activity and choline acetyltransferase activity. There were significantly decreased concentrations of vasoactive intestinal peptide and decreased acetylcholinesterase activity in muscularis externa from patients with acquired megacolon. In megacolon, vasoactive intestinal peptide-containing nerve fibers appeared to be diminished in circular and longitudinal smooth muscle, and immunostaining of nerve cell bodies in the plexus submucosus externus appeared diminished. These results suggest the hypothesis that production of vasoactive intestinal peptide is altered allowing secondary colonic hypertrophy to develop from prolonged cholinergic nerve-mediated contractions of circular smooth muscle. As a corollary to this hypothesis, colonic dilatation might result from prolonged contraction of longitudinal smooth muscle.

Nitric oxide synthase is increased following small intestinal transplantation in the rat.

Transplantation of the small intestine is a neural model that could include extrinsic denervation, loss of intrinsic enteric neurons, or loss of intrinsic neural pathways. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity was measured in normal rat ileum, ileum 3 months after resection of the jejunum, and ileum 3 months after isotransplantation of the ileum. The distribution of NADPH diaphorase activity and immunoreactive neuronal nitric oxide synthase were examined. Nicotinamide adenine dinucleotide phosphate diaphorase activity was increased in transplanted ileum (16.5+/-3.5 mU/mg protein) compared to normal controls (6.6+/-0.7) and resection controls (6.8+/-0.6) (P < 0.05, ANOVA). Histologically, NADPH diaphorase activity and immunoreactive nitric oxide synthase appeared increased within nerve cell bodies following transplantation. These findings may represent an adaptive response of the enteric nervous system to extrinsic denervation. Loss of intrinsic neural pathways was not supported as a mechanism.

Gene expression and transcript size of the prepro-peptide VIP/PHM-27 in normal human tissue.

The transcript size of VIP/PHM-27 mRNA (vasoactive intestinal peptide/peptide histidine methionine) and the relative distribution of VIP/PHM-27 gene expression in 10 normal human tissues was examined. After mRNA extraction from tissue, VIP/PHM-27 transcript size and relative abundance of mRNA was determined by Northern blot analysis and densitometry of the autoradiograms. VIP/PHM-27 mRNA was detectable in brain, pancreas, colon, ileum and striated muscle while no hybridization signal was observed in liver, kidney, lung, heart, prostate and placental tissue. VIP/PHM-27 transcript in human brain and gut was a single band of 1.7 kb; by contrast, a 7.0-kb transcript was detected in striated skeletal muscle. The highest relative levels of mRNA were observed in brain and pancreas.

Pancreaticogastrostomy: clinical experience with a direct pancreatic-duct-to-gastric-mucosa anastomosis.

The propensity for leakage and disruption at the site of the pancreaticojejunostomy is a major reason for morbidity and death after pancreaticoduodenal resection. Because it is less prone to leakage and disruption, pancreaticogastrostomy has been reintroduced as a possible alternative to pancreaticojejunostomy. Of four patients in whom the pancreas was simply implanted into the stomach and five patients in whom a direct pancreatic-duct-to-gastric-mucosa anastomosis was constructed, there was no morbidity or death related to the pancreatic anastomosis. Because of evidence that a direct pancreatic-duct-to-gastric-mucosa anastomosis has an increased incidence of patency and because it was successful in a clinical setting, it is recommended.

Neural control of the canine pylorus.

After atropine administration the anesthetized dog exhibits significant spontaneous pyloric contractile activity and an inhibition-relaxation response upon electrical vagal stimulation. This inhibition-relaxation response was completely blocked by tetrodotoxin administration and by transection of the intraabdominal vagal nerves. In addition, tetrodotoxin administration caused a dramatic increase in spontaneous pyloric motor activity. The histaminergic receptor antagonists diphenhydramine and cimetidine did not block the inhibition-relaxation response. The octapeptide of cholecystokinin (CCK-OP) caused a dose-dependent increase in antral and pyloric motor activity which was significantly decreased by atropine administration. Therefore, histamine and CCK do not appear to play a significant role in the vagally mediated inhibition-relaxation response of the canine pylorus or in the atropine-resistant spontaneous pyloric motor activity.

Delayed gastroduodenal emptying is an important mechanism for control of intestinal transit in short-gut syndrome.

PURPOSE: To understand the relative importance of changes in ileal smooth muscle contractility versus alteration of intestinal flow rate as control mechanisms for regulating intestinal transit in a surgical model of short-gut syndrome. METHODS: A model of short-gut syndrome was created by performing a 70% proximal small-bowel resection in dogs. Ten control and 6 animals with short-gut syndrome were instrumented with strain gauge transducers, steel collection cannulas, and a Silastic intraluminal infusion catheter in the midileum. Motor activity was analyzed by computer programs that determine frequency, amplitude, and propagation behavior of postprandial contractions. Perfusions of 14C-polyethylene glycol and bolus injection of 3H-polyethylene glycol were used to determine intestinal flow and transit rates. Total gastroduodenal emptying was determined using a 14C-polyethylene glycol-labelled meal. RESULTS: Postprandial contraction frequency was decreased in animals with short-gut syndrome, but other significant changes in amplitude, mean area, and propagation behavior of postprandial ileal contractions were not seen. Gastroduodenal emptying and mean intestinal flow rates were markedly slower in animals with short-gut syndrome, as were intestinal transit rates. CONCLUSIONS: In this model of short-gut syndrome, the major adaptive change is decreased intestinal flow rate, related to delayed gastroduodenal emptying. The spatial organization of ileal contractions does not change substantially aside from a change in frequency which can be accounted for by transection of the intestinal wall.

Motor activity and transit in the autonomically denervated jejunum.

The role of extrinsic (autonomic) innervation in postprandial contractile activity of the small intestine is unknown. Using a canine model, we investigated the effects of complete extrinsic denervation on the parameters of fasting and postprandial jejunal contractions and their relationship to intestinal transit. Individual contractions were recorded using strain gauge transducers. Spatial and temporal parameters of contractions were analyzed by computer methods. Bolus injection of 14C-polyethylene glycol was used to calculate intestinal transit rates. Statistical comparisons of control and denervated animals were made by nonparametric tests. Extrinsic denervation did not abolish fasting or fed motor activity, but the following effects were observed: (1) the frequency of migrating motor complexes (MMCs) increased; (2) the onset of fed motor activity was delayed, and the duration of fed activity was shortened; (3) frequency, mean amplitude, and mean area of postprandial contractions were decreased; (4) fewer contractions propagated distally, and mean propagation distance was shortened; and (5) intestinal transit was slower for solids, but not for liquids. In the small intestine, extrinsic nerves modulate motor activity, which is under primary control of the intrinsic (enteric) nervous system.

Pathophysiology of small intestinal motility.

Only in the last few years have we begun to understand the effects of surgical procedures on contractile activity of the small intestine. Although most patients readily adapt to the procedures that are performed, operations such as small intestinal transplantation make it imperative that we pursue a more thorough understanding of the effects of surgery on the motility of the small intestine.

Bloodborne pathogen transmission from healthcare worker to patients. Legal issues and provider perspectives.

Health-care providers have an obvious, primary obligation to patients. Yet providers also have obligations to the public health (society), their institutional or individual self-interests, and their employees (fellow health-care workers). These obligations contain inherent conflicts, and attempts to reconcile the conflicts often perpetuate contradictions. This article identifies and discusses some of the moral and legal bases of these conflicts.

Prevention of blood exposure. Body and facial protection.

Regardless of the specific clinical setting in the operating room, it is clear that better protection of all personnel is an appropriate objective in the current environment. Better protection through improved PPE and modification of operational practices is essential. A prompt response to blood contact when it does occur is likewise appropriate. With conscientious applications of methods to reduce blood exposure, it is hoped that the operating room can become a safer place with respect to occupational infections from bloodborne pathogens.

Effect of surgical alteration of the rat gastrointestinal tract on the growth and development of Hymenolepis diminuta.

Eight groups of rats were used to study the involvement of the enteric (ENS) and central (CNS) nervous systems in the development of Hymenolepis diminuta using surgical intestinal transection, or CNS denervation, or both procedures. The transection procedure was used to isolate the ENS of the small intestine from either orad and/or caudal portions of the alimentary system, while the CNS denervation was used to eliminate direct visceral efferent inputs from the CNS. Nine days after the surgical procedures, all rats were infected with 35 cysticercoids of H. diminuta. On 20 days postinfection, the infection intensity, tapeworm dry weight, tapeworm morphology, intestine length, and intestinal wet weight were recorded. Only the combination of the duodenal and ileal transections with a CNS denervation reduced infection intensity and prevented the increased intestinal length normally observed in infected rats. In contrast, none of the various intestinal transection procedures alone or CNS denervation alone had any effect on the survival, ability to produce oncospheres or morphology of the tapeworms. In conclusion, tapeworm survival is decreased when both CNS and ENS inputs into the small intestine are altered or absent.