Short chain fatty acid rectal irrigation for left-sided ulcerative colitis: a randomised, placebo controlled trial.

BACKGROUND: Short chain fatty acid (SCFA) deficiency is associated with colitis in animals and humans, and the mucosal metabolism of these compounds is decreased in ulcerative colitis. AIMS: To assess the efficacy of topical SCFA treatment in ulcerative colitis. PATIENTS AND METHODS: 103 patients with distal ulcerative colitis were entered into a six week, double-blind, placebo controlled trial of rectal SCFA twice daily; patients who were unchanged on placebo were offered SCFA in an open-label extension trial. RESULTS: Of the 91 patients completing the trial, more patients in the SCFA treated than in the placebo treated group improved (33% v 20%, p = 0.14, NS). Those on SCFA also had larger, but statistically non-significant, reductions in every component of their clinical and histological activity scores. In patients with a relatively short current episode of colitis (< 6 months, n = 42), more responded to SCFA than to placebo (48% v 18%, p = 0.03). These patients also had larger, but statistically non-significant, decreases in their clinical activity index (p = 0.08 v placebo). Every patient who improved used at least five of six of the prescribed rectal SCFA irrigations, whereas only 37% who did not improve were as compliant. In the open-label extension trial, 65% improved on SCFA; these patients also had significant reductions (p < 0.02) in their clinical and histological activity scores. CONCLUSIONS: Although SCFA enemas were not of therapeutic value in this controlled trial, the results suggest efficacy in subsets of patients with distal ulcerative colitis including those with short active episodes. Prolonged contact with rectal mucosa seems to be necessary for therapeutic benefit.

Assessment of technical competence during ERCP training.

BACKGROUND: Successful performance of diagnostic and therapeutic ERCP requires skillful manipulation of the duodenoscope and accessories. The evaluation process for assessing competency is still in evolution. Recommendations for the number of examinations has ranged from 35 to 200, made without the benefit of prospective data. METHODS: Pancreatic and common bile duct cannulation rates were prospectively recorded for 21 trainees and 9 proctors over 6 years in a large university-based training program. Trainee success rates were compared to those of the proctor and learning curves were constructed. RESULTS: Trainees performed 641 examinations over 6 years. Each did an average of 31 examinations (range, 10 to 96). For both pancreatic duct and common bile duct cannulation, there was a rapid linear rise of the success curve extending up to the fortieth procedure. Pancreatic duct cannulation rates exceeded those of the common bile duct. CONCLUSIONS: This is the first prospective evaluation of acquisition of skills in ERCP. Although the rapid rise of the learning curve ends at the fortieth examination, the 85% level of selective cannulation is not reached for the pancreas duct until the seventieth procedure and is not reached for the common bile duct even at 100 procedures. These data suggest a threshold of at least 100 procedures.

Transport of n-butyrate into human colonic luminal membrane vesicles.

Human colonic short-chain fatty acid (SCFA) absorption is associated with increased luminal pH and HCO3- and enhanced Na+ absorption. Therefore, the mechanism of colonic SCFA transport, its dependence on Na+ and HCO3- and interactions with Cl-/HCO3- and Na+/H+ exchangers were characterized. Luminal membrane vesicles (LMV) isolated by divalent cation precipitation from organ donor colons were used for n-butyrate transport. Uptake of n-butyrate into the human colonic LMV was minimal even in the presence of an inward pH gradient, but an outward HCO3- gradient significantly increased uptake rates. HCO3(-)-stimulated butyrate uptake was saturable with an apparent Michaelis constant of 1.5 +/- 0.2 mM and maximal velocity of 105 +/- 3 nmol.mg protein-1.3 s-1. Intravesicular butyrate resulted in trans-stimulation of n-[1-14C]butyrate uptake. Butyrate uptake was inhibited approximately 25-40% by C2-C5 SCFAs and approximately 40% by niflumic acid. Butyrate uptake was not affected by extravesicular Na+, and 22Na uptake was unaltered by extravesicular butyrate. Butyrate uptake was independent of extra- or intravesicular CI-, and butyrate loading produced no changes in 36Cl uptake. We conclude that the predominant mechanism of n-butyrate transport across the human colonic luminal membrane appears to be via a HCO3-/SCFA antiport system independent of Cl-/HCO3- exchange and Na+ transport.

Intestinal distribution of human Na+/H+ exchanger isoforms NHE-1, NHE-2, and NHE-3 mRNA.

The identity of Na+/H+ exchanger (NHE) isoforms in the human small intestine and colon and their role in vectorial Na+ absorption are not known. The present studies were undertaken to examine the regional and vertical axis distribution of NHE-1, NHE-2, and NHE-3 mRNA in the human intestine. Ribonuclease protection assays were used to quantitate the levels of mRNA of these isoforms in various regions of the human intestine. In situ hybridization technique was used to localize NHE-2 and NHE-3 mRNA in the colon. The NHE-1 isoform message was present uniformly throughout the length of the human intestine. In contrast, mRNA levels for human NHE-2 and NHE-3 isoforms demonstrated significant regional differences. The NHE-3 abundance was found in decreasing order: ileum > jejunum > proximal colon = distal colon. The NHE-2 message level in the distal colon was significantly higher than in the proximal colon but was evenly distributed in the small intestine. In addition, NHE-2 mRNA was present in surface epithelial cells as well as in cells of the crypt region, suggesting the presence of NHE-2 message throughout the vertical axis of the colonic crypts. In contrast, NHE-3 mRNA was localized to surface colonocytes in the proximal colon. On the basis of this tissue-specific localization of NHE-2 and NHE-3 mRNA, it can be speculated that the relative contribution of NHE-2 and NHE-3 isoforms in Na+ absorption in the human intestine may be region specific, and these putative apical isoforms may be differentially regulated.

Chloride transport in human proximal colonic apical membrane vesicles.

The mechanism(s) of Cl- transport across the human colonic apical membranes are not well understood. Apical membrane vesicles (AMV) purified from organ donor proximal colonic mucosa and a rapid millipore filtration technique were utilized to study 36Cl- uptake into these vesicles. Outwardly directed OH- and HCO3- gradient stimulated 36Cl- uptake into these vesicles demonstrating a transient accumulation over equilibrium uptake. Voltage clamping the membrane potential of the vesicles or making them inside positive with K+/valinomycin failed to influence chloride uptake, indicating that the conductive Cl- uptake pathway is minimal in proximal colonic AMV. Anion exchange inhibitors, DIDS and SITS (1 mM) inhibited OH- and HCO3- stimulated 36Cl- uptake by approximately 60%. Furosemide also demonstrated a small but significant inhibition of chloride uptake. Amiloride, bumetanide and acetazolamide (1 mM) failed to inhibit 36Cl uptake. HCO3- and pH gradient stimulated 36Cl- uptake exhibited saturation kinetics with an apparent Km for chloride of 4.0 +/- 0.7 mM and Vmax of 17.8 +/- 3.9 nmol/mg per min. Bromide, chloride, nitrate and acetate (50 mM each) inhibited 5 mM 36Cl uptake. Inwardly directed gradients of Na+, K+, or Na+ and K+ did not stimulate 36Cl- uptake into these vesicles, indicating that uptake of Na+ and Cl- in human proximal colonic AMV does not involve Na-Cl or Na-K-2Cl cotransport. The above findings indicate that chloride transport in human proximal colonic AMV involves an electroneutral Cl-HCO3- (OH-) exchange process. In view of the previous demonstration of Na+-H+ antiporter in these vesicles, dual ion exchange mechanism of Na+-H+ and Cl-HCO3- in apical membrane domain of human colonocytes is postulated to be the primary mechanism for NaCl absorption in the human proximal colon.

Endoscopic findings and overtube-related complications associated with esophageal variceal ligation.

Esophageal variceal ligation (EVL) has emerged as a popular alternative to endoscopic sclerotherapy (ES), with equal efficacy as ES in control of active bleeding, rebleeding rate, and variceal eradication. The complication rate for EVL has been reported lower than for ES in several clinical trials. However, several unique complications inherent to EVL have been recognized. Overtube injury to the pharynx and proximal esophagus has been the most serious complication. Transient vocal cord paralysis, cricopharyngeal perforation, proximal esophageal laceration, varix rupture, and free esophageal perforation have also been reported. Direct banding-induced complications have been limited to rebleeding from banded ulcers, transient esophageal obstruction, and simple strictures. Pulmonary as well as serious systemic complications have yet to be reported. We report four complications of EVL, review the literature, and suggest strategies for the recognition, management, and prevention of EVL complications.

Calcium transport mechanism in human colonic apical membrane vesicles.

BACKGROUND & AIMS: Recent studies have shown the role of human colon in the absorption of calcium, especially in the presence of severe disease or resection of the small bowel. The aim of the current study was to explore the mechanism(s) of calcium uptake by the purified human colonic apical membrane vesicles. METHODS: Apical membrane vesicles were purified from mucosal scrapings of colons from organ donors, and 45Ca uptake was measured using a rapid filtration technique. RESULTS: The majority of the 45Ca associated with vesicles represented uptake into closed intravesicular space, whereas the remaining 45Ca uptake represented binding to the vesicles. Ca2+ uptake was found to be dependent on time, pH, temperature, and ionic strength of the incubation medium and inhibitable by ruthenium red, La3+, and ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid. Experiments of the effects of membrane potential generated by K+/valinomycin or anion substitutions on Ca2+ uptake showed that the Ca2+ uptake process was potential insensitive. Calcium uptake was unaffected by outwardly directed H+, K+, and Na+ gradients. Ca2+ uptake showed saturation kinetics with no significant differences in Michaelis constant and maximum velocity values of this transporter between proximal and distal colonic segments. CONCLUSIONS: The uptake of Ca2+ by human colonic apical membranes involves predominantly a carrier-mediated transport mechanism.

Endoscopic retrograde cholangiopancreatography and stent placement via gastrostomy: technical aspects and clinical application.

Significant advances in the field of enteral nutrition (1), combined with technical advances in percutaneous access, have increased the indications for, and safety of, enteral alimentation (2). A mature gastrostomy stoma not only provides access to the gastrointestinal lumen for nutrition, but in selected cases, provides access for the diagnostic and therapeutic endoscopist. In 1971, Wiendl first reported diagnostic fiberoptic stomal endoscopy (3). This has since been followed by reports of diagnostic endoscopic retrograde cholangiopancreatography (ERCP) (4), and more recently, the first case of therapeutic ERCP by Gray et al. (5). We report here on the second case of therapeutic ERCP in a patient with metastatic squamous-cell carcinoma of the head and neck, with liver metastasis. We discuss the technical aspects, indications, and future of therapeutic stomal endoscopy.

Mechanisms of Na+ transport in human distal colonic apical membrane vesicles.

Apical membrane vesicles purified from mucosal scrapings obtained from distal segments of organ donor colons and a 22Na-uptake technique were used to characterize the mechanism(s) of Na+ transport into these vesicles. An outwardly directed H+ gradient (pH 5.5in/7.5out) markedly increased uptake of 22Na into these vesicles. Osmolarity studies demonstrated that 22Na was taken up into the intravesicular space with minimal binding observed to the surface of the vesicles. Voltage clamping in the presence of K+/valinomycin reduced the H+ gradient-dependent 22Na uptake into these vesicles by approximately 45% and generation of an inside negative membrane potential significantly increased 22Na uptake. Under non voltage clamped conditions, H+ gradient-dependent 22Na uptake into these vesicles was significantly inhibited by specific inhibitors of Na(+)-H+ exchange (DMA, HMA and EIPA) as well as by inhibitor of epithelial Na+ channels (phenamil). Under voltage clamped conditions, H+ gradient-dependent 22Na uptake, however, was unaffected by phenamil (20 microM), but was almost completely inhibited by DMA, HMA and EIPA (20 microM each). The mechanism of amiloride inhibition of electroneutral Na(+)-H+ exchange was noncompetitive with a Ki for amiloride of 340 microM. Electroneutral 22Na uptake exhibited saturation kinetics with an apparent Km for Na+ of 8.7 +/- 1.7 mM and a Vmax of 2.02 +/- 0.45 nmol/mg per 5 s. The Na(+)-H+ exchange demonstrated cation specificity similar to the Na(+)-H+ exchangers described in other epithelia. These studies demonstrate for the first time that Na+ transport across the apical membranes of human distal colon involves both conductive Na+ uptake and an electroneutral Na(+)-H+ exchange process.

Neutrophil depletion attenuates human intestinal reperfusion injury.

Intestinal ischemia/reperfusion injury (I/R) results from reactive oxygen metabolites generated by the xanthine oxidase system and activated neutrophils (PMN). In animal models, removing PMN from initial reperfusate has consistently decreased tissue injury. This experiment was designed to test this potential clinical treatment in human bowel subjected to I/R. The extent of reperfusion injury was assessed by measuring the activity of mucosal alkaline phosphatase (A phi), which is a specific marker of reperfusion injury. Human small intestine (n = 13) obtained at the time of organ harvest for transplantation was perfused for 60 min on an ex vivo perfusion circuit. Reperfusate consisted of autologous blood passed through a leukocyte filter (n = 6) or unfiltered blood (n = 7). Control intestine was sampled at harvest, after transport to the lab on ice (cold ischemia), and after 60 min warm ischemia. Mucosa was homogenized and assayed for A phi activity by cleavage of p-nitrophenyl phosphate. A phi activity (nmole/mg/min) was not decreased after either cold (774 +/- 37) or warm (753 +/- 40) ischemia compared to freshly harvested bowel (770 +/- 51). Both reperfused segments showed a significant decrease in A phi activity compared to controls (P < 0.05); however, reperfusion with leukocyte-filtered blood attenuated the decrease in enzyme activity compared to unfiltered blood (327 +/- 30 vs 506 +/- 25, P < 0.05), constituting an apparent reduction in injury of 35%. The observation that the severity of reperfusion injury was decreased by removal of PMN from the reperfusate demonstrates the efficacy of this strategy in human intestine for the first time.

Na+ transport in human proximal colonic apical membrane vesicles.

BACKGROUND/AIMS: The mechanisms of Na+ movement across colonocyte plasma membranes in the human colon are not well understood. Current studies were undertaken to investigate Na+ transport pathways in apical membranes of proximal organ donor colons. METHODS: Purified apical membrane vesicles and rapid filtration 22Na-uptake techniques were used. RESULTS: An outwardly directed H(+)-gradient (pH 5.5 in/7.5 out) increased 22Na uptake into these vesicles. H+ gradient-driven 22Na uptake was significantly reduced by voltage clamping with K+/valinomycin, but was significantly stimulated by creation of an inside-negative potential. Potential sensitive 22Na uptake was inhibited by Na+ channel inhibitors phenamil and benzamil. Electroneutral 22Na uptake was insensitive to phenamil and benzamil, but was inhibited by amiloride, 5-(N,N-dimethyl)amiloride, 5-(N,N-hexamethylene)amiloride, and 5-(N-ethyl-N-isopropyl)amiloride. Electroneutral 22Na uptake showed saturation kinetics with an apparent Michaelis constant for Na+ of 11.8 +/- 2.4 mmol/L and a maximal velocity of 2.5 +/- 0.6 nmol.mg protein-1 x 5 s-1. The mechanism of amiloride inhibition was noncompetitive with an inhibitor constant for amiloride of 325 mumol/L. Acetazolamide, furosemide, bumetanide, 4-acetamido-4'-isothiocyano-2,2'-disulfonic acid stibene, and 4,4'-di-isothiocyanatostilbene-2,2'-disulfonic acid (1 mmol/L each) failed to inhibit 22Na uptake. Li+ and NH4+ (but not Cs+, K+, or choline+) inhibited H(+)-gradient driven 22Na uptake. CONCLUSIONS: Na+ transport in human proximal colonic apical membrane vesicles involves both conductive Na+ transport and an electroneutral Na(+)-H+ exchange.

Shape, volume, and content of the deglutitive pharyngeal chamber imaged by ultrafast computerized tomography.

BACKGROUND: Conventional radiographic techniques image only the silhouettes of the deglutitive pharyngeal chamber. This study aimed to accurately image the horizontal plane shape and content of the pharynx during swallowing. METHODS: Dynamic computerized tomography images of the pharynx were obtained at the rate of 17 per second during swallowing. Multiple adjacent levels were imaged in eight subjects and a single level was scanned in four subjects during swallows of varied volume. Images were analyzed for area, volume, and the bolus fraction of the deglutitive pharyngeal chamber. RESULTS: The deglutitive chamber enlarged to approximately 24 mL (during tongue loading) compared with a preswallow pharyngeal volume averaging 15 mL. Throughout the 10 mL swallows, the bolus occupied less than 30% of the lumen regardless of axial level. The bolus fraction of the deglutitive chamber increased with swallow volume, as did the dimensions of the upper esophageal sphincter and the bolus velocity through the upper esophageal sphincter. CONCLUSIONS: The deglutitive pharyngeal chamber was typically approximately 15 mL > the bolus volume, implying that an obligatory 15 mL of air was swallowed under these test conditions. Most swallowed air originated as air trapped within the pharynx and larynx as the oropharynx was sealed from above and below.

Placement of a feeding button ("one-step button") as the initial procedure.

The procedure of choice for enteral feeding access is now percutaneous endoscopic gastrostomy (PEG). Standard PEG tubes have the disadvantages of clogging, stomal enlargement, and external bulkiness. Button replacement tubes can covert the more cumbersome PEG tubes to low external profile devices. A procedure and an early experience is described for placement of a button as a single-step procedure. This procedure is an over-the-wire, "push" procedure. Sixty-nine buttons were placed, 47 (61%) for neurologic reasons and 22 (32%) for cancer and other reasons. In 49 of the 69 (71%), there was no difficulty at all with insertion, and in only two (3%) could the button not be placed. Complications were assessed at 48 h and at 3 wk. No complications were found in 61 (90%). In only two patients (3%) were there serious complications (gastro-colon-cutaneous fistula and "peritonitis"). The One-Step Button represents a rapid, safe procedure for the placement of a low-profile PEG with its attendant advantages.

Transport of propionate by human ileal brush-border membrane vesicles.

Human ileal brush-border membrane vesicles were employed to study the mechanisms of short-chain fatty acid (propionate) absorption especially to determine the effects of intravesicular HCO3- and the component of nonionic diffusion. Preloading the vesicles with HCO3- resulted in up to 20-fold "overshoots" of transport, and this effect was not seen with other intravesicular anions. This transport process was very fast (peak uptake 6 s) and was not due to intravesicular buffering by HCO3-. Radiolabeled propionate transport demonstrated transstimulation when the vesicles were preloaded with unlabeled propionate. An inward H+ gradient led to stimulation of propionate transport much smaller than in the presence of trans-HCO3-, whereas an inward Na+ gradient had no effect. Propionate transport was attenuated by the anion exchange inhibitors SITS and DIDS. Under HCO3- gradient conditions, propionate transport exhibited saturation kinetics with an apparent Km of 21 +/- 3 mM and a Vmax of 50 +/- 3 nmol.mg protein-1.3 s-1. Propionate transport was inhibited up to 40% by 2-5 carbon short-chain fatty acids (10 mM) but not by other organic anions. Short-chain fatty acid transport in the human ileum is Na+ independent and occurs mostly via a specific anion exchange mechanism with HCO3-. Our results also demonstrate a small component of nonionic diffusion of the protonated fatty acid (or anion exchange for OH-).