Wound debridement potential of glycosidases of the wound-healing maggot, Lucilia sericata.

The wound-healing maggot, Lucilia sericata Meigen (Diptera: Calliphoridae), degrades extracellular matrix components by releasing enzymes. The purpose of this study was to investigate the glycosylation profiles of wound slough/eschar from chronic venous leg ulcers and the complementary presence of glycosidase activities in first-instar excretions/secretions (ES1) and to define their specificities. The predominant carbohydrate moieties present in wound slough/eschar were determined by probing one-dimensional Western blots with conjugated lectins of known specificities. The presence of specific glycosidase activities in ES1 was determined using chromogenic and fluorogenic substrates. The removal of carbohydrate moieties from slough/eschar proteins by glycosidases in ES1 was determined by two-dimensional electrophoresis and Emerald 300 glycoprotein staining. α-D-glucosyl, α-D-mannosyl and N-acetylglucosamine residues were detected on slough/eschar-derived proteins. Furthermore, it was demonstrated that the treatment of slough/eschar with ES1 significantly reduced uptake of the carbohydrate-specific stain. Subsequently, α-D-glucosidase, α-D-mannosidase and N-acetylglucosaminidase activities were identified in ES1. Specific chromogenic and fluorogenic substrates and gel filtration chromatography showed that these activities result from distinct enzymes. These activities were mirrored in the removal of α-D-glucosyl, α-D-mannosyl and N-acetylglucosamine residues from proteins of slough/eschar from maggot-treated wounds. These data suggest that maggot glycosidases remove sugars from slough/eschar proteins. This may contribute to debridement, which is ultimately accomplished by a suite of biochemically distinct enzymes present in ES1.

Maggot chymotrypsin I from Lucilia sericata is resistant to endogenous wound protease inhibitors.

BACKGROUND: A chymotrypsin found in the secretions of Lucilia sericata and manufactured as a recombinant enzyme degrades chronic wound eschar ex vivo. OBJECTIVES: To characterize the inhibition profile of the L. sericata recombinant chymotrypsin I. METHODS: Activity of recombinant chymotrypsin I and its sensitivity to endogenous inhibitors were determined enzymatically using the fluorogenic substrate succinyl-alanyl-alanyl-prolyl-phenylalanyl-aminomethyl coumarin. RESULTS: We report the presence of high concentrations of two endogenous inhibitors, α1-antichymotrypsin and α1-antitrypsin, in wound eschar and a trace of a third, α2-macroglobulin, with the potential to inhibit this debridement process. However, the addition of a soluble and inhibitor-containing extract of chronic wound eschar to chymotrypsin I did not affect activity of the enzyme, neither did the addition of purified native α1-antichymotrypsin or α1-antitrypsin, although chymotrypsin I was inhibited by α2-macroglobulin. Conversely, the mammalian equivalent, α-chymotrypsin, was inhibited by the purified native α1-antichymotrypsin, α1-antitrypsin and α2-macroglobulin and by the soluble extract of wound eschar. CONCLUSIONS: The data suggest that the maggot-derived chymotrypsin I is biochemically distinct from human α-chymotrypsin and the lack of inhibition by wound eschar suggests a means by which chymotrypsin I activity survives within the wound to contribute towards debridement during maggot biotherapy.

Degradation of eschar from venous leg ulcers using a recombinant chymotrypsin from Lucilia sericata.

BACKGROUND: Larvae of the greenbottle Lucilia sericata are used to debride nonhealing wounds and stimulate the production of fresh granulation tissue. Previous publications have shown that secretions from L. sericata contain a number of proteolytic activities including a chymotrypsin that degrades a number of extracellular matrix components such as fibronectin, laminin and collagen. OBJECTIVES: To produce a recombinant L. sericata chymotrypsin (chymotrypsin I) and determine its effects on the degradation of patient wound eschar. METHODS: An active recombinant chymotrypsin I from L. sericata was cloned and expressed in Sf9 cells and its subsequent effects ex vivo on eschar from venous leg ulcers were determined by two-dimensional electrophoresis. RESULTS: The recombinant enzyme had the attributes of a chymotrypsin, possessing sequence homology with other chymotrypsins and demonstrating attributes of the native enzyme including cleavage of the chymotrypsin substrate succinyl-alanyl-alanyl-prolyl-phenylalanyl-7-amino-4-methyl coumarin, inhibition by phenylmethylsulphonyl fluoride and lack of inhibition by amidinophenylmethylsulphonyl fluoride. Importantly, the recombinant chymotrypsin cleaved the majority of proteins from slough/eschar from venous leg ulcers in a superior manner to chymotrypsins from human and bovine sources. CONCLUSIONS: The ex vivo degradation of eschar from venous leg ulcers indicates the potential value of recombinant chymotrypsin I as a novel, stand-alone debridement agent.

Reduced helminth burden increases allergen skin sensitization but not clinical allergy: a randomized, double-blind, placebo-controlled trial in Vietnam.

BACKGROUND: Observational evidence suggests that infection with helminths protects against allergic disease and allergen skin sensitization. It is postulated that such effects are mediated by helminth-induced cytokine responses, in particular IL-10. OBJECTIVE: We tested this hypothesis in a rural area of central Vietnam where hookworm infection is endemic. METHODS: One thousand five hundred and sixty-six schoolchildren aged 6-17 were randomly allocated to receive either anti-helminthic therapy or a placebo at 0, 3, 6, and 9 months. We compared changes in the prevalence of exercise-induced bronchoconstriction, allergen skin sensitization, flexural eczema on skin examination, questionnaire-reported allergic disease (wheeze and rhinitis symptoms), and immunological parameters (hookworm-induced IFN-gamma, IL-5, IL-10) between 0 and 12 months. RESULTS: One thousand four hundred and eighty-seven children (95% of these randomized) completed the study. The most common helminth infections were hookworm (65%) and Ascaris lumbricoides (7%). There was no effect of the therapy on the primary outcome, exercise-induced bronchoconstriction (within-participant mean percent fall in peak flow from baseline after anti-helminthic treatment 2.25 (SD 7.3) vs. placebo 2.19 (SD 7.8, P=0.9), or on the prevalence of questionnaire-reported wheeze [adjusted odds ratio (OR)=1.16, 95% confidence interval (CI) 0.35-3.82, P=0.8] and rhinitis (adjusted OR=1.39, 0.89-2.15, P=0.1), or flexural dermatitis on skin examination (adjusted OR=1.15, 0.39-3.45, P=0.8). However, anti-helminthic therapy was associated with a significantly higher allergen skin sensitization risk (adjusted OR=1.31, 1.02-1.67, P=0.03). This effect was particularly strong for children infected with A. lumbricoides at baseline (adjusted OR=4.90, 1.48-16.19, P=0.009). Allergen skin sensitization was inversely related to hookworm-specific IL-10 at baseline (adjusted OR=0.76, 0.59-0.99, P=0.04). No cytokine tested, including IL-10, changed significantly after the anti-helminthic therapy compared with the placebo. CONCLUSION: A significant reduction in worm burden over a 12-month period in helminth-infected children increases the risk of allergen skin sensitization but not of clinical allergic disease. The effect on skin sensitization could not be fully explained by any of the immunological parameters tested.

Relative importance of Ixodes ricinus and Ixodes trianguliceps as vectors for Anaplasma phagocytophilum and Babesia microti in field vole (Microtus agrestis) populations.

The importance of Ixodes ricinus in the transmission of tick-borne pathogens is well recognized in the United Kingdom and across Europe. However, the role of coexisting Ixodes species, such as the widely distributed species Ixodes trianguliceps, as alternative vectors for these pathogens has received little attention. This study aimed to assess the relative importance of I. ricinus and I. trianguliceps in the transmission of Anaplasma phagocytophilum and Babesia microti among United Kingdom field voles (Microtus agrestis), which serve as reservoir hosts for both pathogens. While all instars of I. trianguliceps feed exclusively on small mammals, I. ricinus adults feed primarily on larger hosts such as deer. The abundance of both tick species and pathogen infection prevalence in field voles were monitored at sites surrounded with fencing that excluded deer and at sites where deer were free to roam. As expected, fencing significantly reduced the larval burden of I. ricinus on field voles and the abundance of questing nymphs, but the larval burden of I. trianguliceps was not significantly affected. The prevalence of A. phagocytophilum and B. microti infections was not significantly affected by the presence of fencing, suggesting that I. trianguliceps is their principal vector. The prevalence of nymphal and adult ticks on field voles was also unaffected, indicating that relatively few non-larval I. ricinus ticks feed upon field voles. This study provides compelling evidence for the importance of I. trianguliceps in maintaining these enzootic tick-borne infections, while highlighting the potential for such infections to escape into alternative hosts via I. ricinus.

Contrasting dynamics of Bartonella spp. in cyclic field vole populations: the impact of vector and host dynamics.

Many zoonotic disease agents are transmitted between hosts by arthropod vectors, including fleas, but few empirical studies of host-vector-microparasite dynamics have investigated the relative importance of hosts and vectors. This study investigates the dynamics of 4 closely related Bartonella species and their flea vectors in cyclic populations of field voles (Microtus agrestis) over 3 years. The probability of flea infestation was positively related to field vole density 12 months previously in autumn, but negatively related to more recent host densities, suggesting a dilution effect. The 4 Bartonella species exhibited contrasting dynamics. Only B. grahamii, showed a distinct seasonal pattern. Infection probability increased with field vole density for B. doshiae, B. taylorii and BGA (a previously unidentified species) and with density of coexisting wood mice for B. doshiae and B. grahamii. However, only the infection probability of BGA in spring was related to flea prevalence. B. doshiae and BGA were most common in older animals, but the other 2 were most common in non-reproductive hosts. Generally, host density rather than vector abundance appears most important for the dynamics of flea-transmitted Bartonella spp., possibly reflecting the importance of flea exchange between hosts. However, even closely related species showed quite different dynamics, emphasising that other factors such as population age structure can impact on zoonotic risk.

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.

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.

Determination of body composition in conscious adult female Wistar utilising total body electrical conductivity.

Total body electrical conductivity (TOBEC) is a noninvasive method for estimating fat free mass (FFM) in live animals. In this study, we have evaluated the use of the Em-Scan SA-3000, which is claimed by the manufacturers to perform better than earlier analysers. Previous studies in rats using these earlier versions of the TOBEC analyser have always used anaesthesia to minimise movement artefacts. As repeated anaesthesia also has the potential to induce artefacts by disrupting food intake, for example, we have also attempted to determine if this TOBEC analyser can be used to predict body composition in conscious adult weight-stable female Wistar rats. A simplified cafeteria diet was used to produce large variations in body composition (40-350 g fat/carcass) and a full chemical body composition analysis was performed to generate a TOBEC calibration equation. The TOBEC parameter was more strongly correlated to FFM (r(2)=.785) than it was to body weight (r(2)=.669) or other body composition parameters. Using the TOBEC calibration equation to predict fat mass on these data, there was an excellent correlation with the value obtained by chemical analyses (r(2)=.952, slope=0.958). To determine if the TOBEC calibration equation derived from this calibration study would then be useful for the routine estimation of body composition an additional, validation study was performed. This validation study was performed 6 months later, used an independent group of obese female Wistar rats and was undertaken by different TOBEC operators. This validation study, again, showed a good correlation between the TOBEC- and chemical-derived fat mass (r(2)=.918, slope=1.003) indicating stability of the calibration equation with time and independence from operator. We therefore conclude that it is possible to meaningfully estimate body fat changes in conscious rats using this TOBEC analysis system.

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.

Total antioxidant capacity of colon in patients with chronic ulcerative colitis.

It has been proposed that oxidative stress is involved in the pathophysiology of ulcerative colitis. We have reported the depletion of the nonenzymatic antioxidant, glutathione, in colon from active and inactive ulcerative colitis. The colon contains several biochemically linked antioxidant systems. We hypothesized that diminished total antioxidant capacity in active ulcerative colitis would be associated with increased colonic lipid peroxidation. This study was designed to determine total antioxidant capacity and lipid hydroperoxide levels using colon obtained at surgery from controls (N = 16; 4 females, 12 males; mean age 70 years), and active and inactive ulcerative colitis (N = 15; 3 females, 12 males; mean age 39). Total antioxidant capacity of control colon was higher in muscularis externa compared to the mucosal-submucosal layer (P < 0.05). There were no differences in colonic total antioxidant capacity or lipid hydroperoxide levels comparing control colon to inactive and active ulcerative colitis. The results did not support depletion of tissue total antioxidant capacity by free radicals. Depletion of glutathione in ulcerative colitis may be a specific disorder rather than a secondary defect attributable to global oxidative stress. Nonspecific antioxidant supplements appear unlikely to be beneficial in the treatment of ulcerative colitis.

Nitric oxide production is diminished in colonic circular muscle from acquired megacolon.

PURPOSE: Nitric oxide modulates human colonic smooth muscle function. To determine whether nitric oxide production is altered in colon from acquired megacolon, we measured cholinergic nerve-mediated contractions in vitro before and after inhibition of nitric oxide synthase. METHODS: Intramural nerves in circular smooth muscle from histologically normal colon (n = 12) and acquired megacolon (n = 3) were activated by electrical field stimulation. RESULTS: In controls blockade of nitric oxide synthase by N(G)-Nitro-L-Arginine induced increases (P < 0.05) in amplitude of contractions; these increases in amplitudes were blocked by L-Arginine (analysis of variance; P < 0.05). By contrast, blockade of nitric oxide synthase did not increase amplitudes of contractions with circular smooth muscle from acquired megacolon. An immediate phasic contraction was blocked by atropine sulfate. CONCLUSIONS: The results support the concept that nitric oxide production modulates cholinergic nerve-mediated contractions in normal colonic circular muscle, whereas acquired megacolon is associated with altered release of this inhibitory neurochemical. Potential explanations include depletion of tissue L-Arginine, decreased capacity to recycle citrulline to arginine, or decreased release of vasoactive intestinal peptide from circular smooth muscle in acquired megacolon.

Effect of barium sulfate on wound healing in the gastrointestinal tract of the rat.

PURPOSE: To study the effect of barium sulfate on wound healing in the gastrointestinal tract of the rat. MATERIALS AND METHODS: Sixty rats weighing approximately 320 g were divided into four groups: Fifteen control rats had gastric, small-bowel, and colonic incisions; 15 rats had gastric incision; 15 rats had small-bowel incision; and 15 rats had colonic incision. Barium sulfate was placed into the incision before closure in all rats except those in the control group, and the effects were documented clinically and histopathologically for 3 months. Autopsy was performed in five rats from each group at 1, 4, and 12 weeks. The incisions in the rats receiving barium sulfate were compared with those in the control rats. RESULTS: There was no difference in the clinical course (weight gain, activity, and viability) between the control and experimental groups. Early and late autopsy findings and histopathologic grading of healing and inflammatory response were similar for both the control and experimental groups. CONCLUSION: Under the conditions of this study, the effect of barium sulfate on visceral transmural wound healing in the gastrointestinal tract of the rat was minimal.

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.

The Pseudomonas aeruginosa quorum-sensing signal molecule N-(3-oxododecanoyl)-L-homoserine lactone has immunomodulatory activity.

Diverse gram-negative bacterial cells communicate with each other by using diffusible N-acyl homoserine lactone (AHL) signal molecules to coordinate gene expression with cell population density. Accumulation of AHLs above a threshold concentration renders the population "quorate," and the appropriate target gene is activated. In pathogenic bacteria, such as Pseudomonas aeruginosa, AHL-mediated quorum sensing is involved in the regulation of multiple virulence determinants. We therefore sought to determine whether the immune system is capable of responding to these bacterial signal molecules. Consequently the immunomodulatory properties of the AHLs N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) and N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) were evaluated in murine and human leukocyte immunoassays in vitro. OdDHL, but not OHHL, inhibited lymphocyte proliferation and tumor necrosis factor alpha production by lipopolysaccharide-stimulated macrophages. Furthermore, OdDHL simultaneously and potently down-regulated the production of IL-12, a Th-1-supportive cytokine. At high concentrations (>7 x 10(-5) M) OdDHL inhibited antibody production by keyhole limpet hemocyanin-stimulated spleen cells, but at lower concentrations (<7 x 10(-5) M), antibody production was stimulated, apparently by increasing the proportion of the immunoglobulin G1 (IgG1) isotype. OdDHL also promoted IgE production by interleukin-4-stimulated human peripheral blood mononuclear cells. These data indicate that OdDHL may influence the Th-1-Th-2 balance in the infected host and suggest that, in addition to regulating the expression of virulence determinants, OdDHL may contribute to the pathogenesis of P. aeruginosa infections by functioning as a virulence determinant per se.

Heligmosomoides polygyrus immunomodulatory factor (IMF), targets T-lymphocytes.

Experiments were performed to investigate the immunological site of action of an immunomodulatory factor (IMF), isolated from the gastrointestinal nematode Heligmosomoides polygyrus. IMF inhibited antibody production in murine and human 'T-helper (Th-2) driven' immunoassays. The effects were mediated via T lymphocytes as T cell-depleted cultures failed to respond to IMF, a result confirmed by prepulsing discrete cell subsets with the immunomodulant. Although the molecular nature and mode of action of IMF has yet to be determined, it would appear to be a relatively small non-proteinaceous molecule. From this data, we suggest that H. polygyrus secretes a systemically-active IMF from the intestinal lumen, to down-regulate Th-2 cell development in order to promote its survival in a potentially immunologically hostile environment.

Distribution of muscarinic receptor subtypes in rat small intestine.

Despite its great promise, small intestinal transplantation in some patients is complicated by difficult postoperative management. The reasons for this are complex. In a rat model of small intestinal transplantation, frequencies of migrating myoelectric complexes during fasting are reduced in ileal isografts and muscarinic receptor density is decreased. We hypothesized that the distribution of muscarinic 1 receptors localized to enteric neurons is altered after small intestinal transplantation. Distal small intestine was orthotopically transplanted in Lewis-to-Lewis donor-recipient combinations. At 3 months, transplanted and normal ileum was obtained to prepare membrane fractions. [N-methyl-3H]Scopolamine served as ligand, while scopolamine methylbromide, pirenzepine, and methoctramine were used in competitive homologous and heterologous displacement experiments. Receptor subtype models were examined by nonlinear regression analysis. In normal and transplanted ileum, heterologous displacement was consistent with three site models (P < 0.05). In normals, the muscarinic 1 receptor subtype was most abundant, with a relative distribution of 69 to 78%. There was a relative distribution of 13 to 16% for muscarinic 3 receptor subtype. After transplantation, the muscarinic 1 subtype decreased to a mean of 45% but the muscarinic 3 subtype increased to a mean of 42%. Using pirenzepine, mean pKD values were not different between the two groups. It is concluded that the decrease in muscarinic 1 receptor subtype after transplantation could be related to neuronal cell loss or to downregulation of the expression of muscarinic 1 receptors. The results did not support defective posttranslational processing of receptor proteins.

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.

Inflammation modulates in vitro colonic myoelectric and contractile activity and interstitial cells of Cajal.

Inflammation suppresses phasic contractile activity in vivo. We investigated whether inflammation also suppresses in vitro phasic contractile activity and, if so, whether this could in part be due to the alteration of specific slow wave characteristics and morphology of the interstitial cells of Cajal (ICC). Circular muscle strips were obtained from normal and inflamed distal canine colon. Inflammation was induced by mucosal exposure to ethanol and acetic acid. The amplitudes of spontaneous, methacholine-induced, substance P-induced, and electrical field stimulation-induced contractions were smaller in inflamed muscle strips than in normal muscle strips. Inflammation reduced the resting membrane potential and the amplitude and duration of slow waves in circular muscle cells. Inflammation did not affect the amplitude of inhibitory junction potentials but did decrease their duration. Ultrastructural studies showed expansion of the extracellular space between circular muscle cells, reduction in the density of ICC and associated neural structures, damage to ICC processes, vacuolization of their cytoplasm, and blebbings of the plasma membrane. We conclude that inflammation-induced alterations of slow wave characteristics contribute to the suppression of phasic contractions. These alterations may, in part, be due to the damage to ICC. Inflammation impairs both the myogenic and neural regulation of phasic contractions.