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PubMed1994

Intraperitoneal thermochemotherapy for prevention of peritoneal recurrence of gastric cancer. Final results of a randomized controlled study.

BACKGROUND: Continuous hyperthermic peritoneal perfusion (CHPP) with a solution that contained 10 micrograms/ml mitomycin C was devised initially as a method for intraperitoneal thermochemotherapy. The authors conducted a randomized clinical trial to evaluate the efficacy of CHPP as a prophylactic treatment for prevention of peritoneal recurrence of gastric cancer with serosal invasion. METHODS: Between January 1983 and October 1986, 82 patients with gross serosal invasion but no gross peritoneal metastasis were divided by random sampling into two groups before undergoing potentially curative surgery for gastric cancer: 42 patients were scheduled to receive CHPP, whereas 40 were not scheduled to receive this treatment. CHPP was administered immediately after closing the abdomen after gastric resections while the patients were still on the operating table under general anesthesia. RESULTS: The 5-year survival rate (64.2%) of patients in the CHPP group was higher than that (52.5%) of patients in the control group although the difference was not significant. Of several patterns of cancer recurrence, peritoneal recurrence was more frequent in the control group than in the CHPP group. The mortality rate from peritoneal recurrence in the case of patients in the CHPP group was much lower than that of patients in the control group (P = 0.0854). CHPP did not induce anastomotic breakdown or chemical peritonitis after surgery. CONCLUSIONS: The results indicate that CHPP is effective in preventing peritoneal recurrence of gastric cancer with serosal invasion, which is highly likely to reappear in the peritoneum.

Aged↗
PubMed1985

Secretory hormones of Entamoeba histolytica.

Watery diarrhoea as distinct from dysentery is occasionally seen in intestinal amoebiasis, suggesting a component of intestinal secretion. To study the pathogenesis of this watery diarrhoea, we evaluated the effect of lysates of Entamoeba histolytica on active intestinal electrolyte transport using rabbit ileum and rat colon studied by the Ussing chamber-voltage clamp technique. Amoebic lysates added to the ileal and colonic mucosal surfaces did not alter electrolyte transport; in contrast, addition to the ideal and colonic serosal surfaces caused an increase in short-circuit current which was transient in the ileum but more prolonged in the colon. This increase in current corresponded to inhibition of active Na+ and Cl- absorption and apparent stimulation of Cl- secretion in rat colon. In rabbit ileum, the short-circuit current response was: (1) dependent on serosal Ca2+, (2) inhibited by serosally applied verapamil, (3) associated with reversible desensitization, and (4) only partially inhibited by heating. These characteristics were similar to those of a series of neurohumoral substances present in mammalian intestinal mucosa which affect active electrolyte transport by increasing the permeability of the basolateral membrane to Ca2+. Substances with these properties identified include serotonin, substance P and neurotensin. All three substances were shown to be present in amoebic lysates by radioimmunoassay. Serotonin was also present by high performance liquid chromatography (HPLC) and thin layer chromatography, and neurotensin by HPLC. Prostaglandins were not present by radioimmunoassay. Attempts were made to determine which of these neurohumoral substances contributed to the changes in intestinal transport caused by amoebic lysates. Serotonin was thought to be involved, from the inhibition of the transport effect of amoebic lysate on rat colon by anti-serotonin antibody and by bufotenine, which inhibits the effect of serotonin on ion transport. Prostaglandins also appeared to be involved, since pretreatment with PGE2 or indomethacin inhibited the effects of amoebic lysate on transport. We conclude that amoebae contain neurohumoral substances, including serotonin, neurotensin and substance P, which may be important in the intestinal secretion caused by amoebae. Serotonin appears partially responsible for the intestinal secretion. In addition, amoebae may induce prostaglandin synthesis by the intestinal mucosa which could also contribute to the secretory response. The relation between the neurohumoral substances which act by Ca2+ and the prostaglandins presumably caused to be synthesized in the intestinal mucosa is not known.

Animals↗
PubMed1993

Intraoperative enteroscopy in Crohn's disease.

Intraoperative small bowel endoscopy was performed on 33 occasions in 31 patients with Crohn's disease. The extent of mucosal inflammation was compared with that of changes in the external bowel wall: serositis, fat-wrapping and mural thickening. The influence of endoscopic findings on surgical management was evaluated. Mucosal inflammation was generally more extensive than serositis (P < 0.01), but less so than mural thickening (P < 0.001). The extent of fat-wrapping did not differ from that of mucositis. Of 23 patients undergoing reoperation or with fistula or abscess, however, eight had serositis and/or fat-wrapping in bowel segments without mucosal inflammation. Endoscopic findings influenced surgical decisions on 20 of the 33 occasions, limiting planned resection in 14, identifying strictures for repair in one, and deciding against resection in two cases and for extended resection in three. These results suggest that external inflammatory changes are unreliable guides to the extent of intestinal mucositis and requirements for resection in Crohn's disease. By visualizing the mucosa, intraoperative enteroscopy can provide information for more precise surgery, thereby limiting resection.

Adolescent↗
PubMed1996

Port-site metastases in patients undergoing laparoscopy for gastrointestinal malignancy.

Laparoscopic colonic resection and laparoscopy for the assessment of malignant disease have been advocated. Metastatic deposits at port sites are recognized but the incidence of these is poorly defined. Forty-six patients, of median age 65 (range 19-90) years, with gastrointestinal malignancy underwent laparoscopy. Eighteen patients died a median of 4 (range 1-28) months after laparoscopy, four following colonic resection and 14 with gastro-oesophageal malignancy; ten had undergone resection. Median follow-up of the 28 survivors is 8 (range 2-39) months. Five of the 46 patients developed port-site recurrence giving an early incidence of port-site recurrence in this cohort of patients of 11 per cent. Five of 20 patients with tumour involving serosal surfaces developed port-site recurrence compared with none of 26 without serosal involvement (P = 0.022, Fisher's exact test). Port-site recurrence may be related to serosal involvement with tumour.

Adult↗
PubMed2004

Increased vascular endothelial growth factor production in fibroblasts isolated from strictures in patients with Crohn's disease.

BACKGROUND: Vascular endothelial growth factor (VEGF) is a potent angiogenic factor that is implicated in early wound healing and fibrosis. Fibroblasts may initiate stricture formation in Crohn's disease through overexpression of VEGF. The aim of this study was to examine VEGF expression and regulation in fibroblasts isolated from patients with Crohn's disease. METHODS: Fibroblasts were isolated by a primary explant technique from serosal biopsies of non-strictured and strictured segments of bowel from eight patients undergoing resection for Crohn's disease, and normal colon from six patients undergoing resection for benign and malignant colorectal disease. Fibroblasts were cultured with transforming growth factor (TGF) beta and corticosteroids. After 24 h the culture supernatant was collected for VEGF assay by enzyme-linked immunosorbent assay. RESULTS: VEGF production was significantly higher in fibroblasts isolated from strictures (mean(s.e.m.) 1980(260) pg/ml) than from non-strictured segments (1116(165) pg/ml) in patients with Crohn's disease or control fibroblasts (898(93) pg/ml). TGF-beta increased VEGF production in normal and non-strictured Crohn's fibroblasts. Corticosteroids suppressed unstimulated VEGF production in all groups. CONCLUSION: Enhanced serosal fibroblast VEGF production might play a role in initiating stricture formation in Crohn's disease. VEGF production in serosal fibroblasts is sensitive to stimulation with TGF-beta. Corticosteroids may reduce stricturing through suppression of VEGF.

Adult↗
PubMed2003

Analysis of colorectal tumor progression by microdissection and comparative genomic hybridization.

This investigation aimed to identify patterns of copy number change in colorectal tumor progression from adenoma to liver metastasis. Fifty-three microdissected sub-regions from 17 cases of colorectal cancer were assigned to one of six histopathologically defined categories: coexisting adenoma, tumor above the muscularis layer, tumor within the muscularis layer, tumor extending through the bowel wall to serosal fat, lymph node metastasis, and liver metastasis. Microdissected samples were treated by a microwave processing step and then used as templates for universal PCR amplification. PCR products were fluorophore labeled and subjected to comparative genomic hybridization. Copy number changes were found in all samples, and every chromosome arm (excluding acrocentric short arms) was affected. More losses than gains were detected, but there were no significant differences between the numbers of changes seen in each category. Each individual sample revealed unique changes, additional to those shared within each case. The most frequently observed gains were of X and 12q. The most common losses were of 8p, 16p, 9p, 15q, 18q, and 10q. Nominally significant associations were observed between metastatic tumor and loss of 12q24.1 or 10p13-14, non-metastatic tumor and loss of 8q24.1, tumor extending to serosal fat and loss of 6q24-25 or gain of 4q11-13, tumor extending to serosal fat and metastatic lesions and loss of 4q32-34 or 22q11-12, and adenoma and loss of 15q24. Loss of 4q32-34 remained highly significant after correction for multiple testing. Adenoma was the only category not to show loss of 17p. These data reveal a genetically heterogeneous picture of tumor progression, with a small number of changes associated with advanced disease.

Adenocarcinoma↗
PubMed2003

Endoscopic sonographic evaluation of the thickened gallbladder wall in patients with acute hepatitis.

PURPOSE: Thickening of the gallbladder wall is often observed during abdominal sonographic examination in patients with acute hepatitis. However, there is rarely an opportunity for a histopathologic analysis of these structural changes. Endoscopic sonography (EUS) can accurately delineate the structure of the gallbladder wall and therefore may be useful for visualizing changes in the gallbladder wall in patients with acute hepatitis. Hence, we prospectively studied the ability of EUS to detect specific structural changes in the gallbladder wall in patients with acute hepatitis and examined the effect of high elevation of serum liver enzyme levels on the gallbladder wall. METHODS: A study group of patients diagnosed with acute hepatitis who had gallbladder wall thickening and a control group of patients without acute hepatitis or gallbladder disease underwent EUS between May 1, 1999, and June 1, 2002. EUS was used to measure the thickness of the gallbladder wall and to visualize each of its layers. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels of the patients with acute hepatitis were measured at the time of the EUS examination. Statistically significant differences were determined using an independent t test and the chi-squared test. A p value of less than 0.05 was considered statistically significant. RESULTS: The acute hepatitis group comprised 28 men and 24 women with a mean age of 40.8 years. The control group comprised 25 men and 25 women with a mean age of 45.1 years. The mean gallbladder wall thickness +/- standard deviation in the acute hepatitis group (6.3 +/- 2.6 mm) was significantly greater than that in the control group (1.6 +/- 0.4 mm; p < 0.01). The mean thickness of the gallbladder wall for patients in whom both the AST and the ALT levels were 500 U/l or higher (7.0 +/- 2.6 mm) was significantly greater than that for patients with levels below 500 U/l (5.4 +/- 2.3 mm; p < 0.05). In the acute hepatitis group, EUS showed thickened, well-defined muscular and serosal layers of the gallbladder wall in 24 of the patients and a diffusely thickened gallbladder wall, in which each layer was ill defined, in the other 28 patients. The mean thickness of the gallbladder wall for patients with the pattern of ill-defined layers was significantly greater than that for the patients with the pattern of well-defined layers (p < 0.05). The pattern of ill-defined layers was more common among patients in whom the serum AST and ALT levels were at least 500 U/l than among patients with levels below 500 U/l (p < 0.05). CONCLUSIONS: We propose that gallbladder wall thickening in patients with acute hepatitis is associated with prominent changes in the muscular and serosal layers. Patients with highly elevated serum liver enzyme levels are more likely to have gallbladder wall thickening and disruption of planes between the muscular and serosal layers than are patients with normal liver enzyme levels.

Acute Disease↗
PubMed1984

The sodium and chloride dependence of chloride secretion by the opercular epithelium.

The effects of ion substitutions on the Cl- secretion rate and tissue conductance of isolated short-circuited opercular epithelia from sea-water-adapted Fundulus heteroclitus were investigated. Serosal Na+ substitution had the same effect on the Cl- secretion rate that serosal Cl- substitution had on the active component of the Cl- efflux. This similarity indicated a 1:1 Na-Cl requirement for active Cl- secretion across this epithelium, which supports the proposal of a coupled NaCl uptake mechanism at the serosal membrane of Cl- secretory epithelia. Mucosal Na+ and Cl- substitutions appeared to inhibit completely the active Cl- secretory flux. The reductions in the tissue conductance with mucosal ion substitutions suggested that this effect can be attributed to a blocking of the apical membrane Cl- conductance. These mucosal ion effects suggested a possible direct regulatory influence of the external salinity on the Cl- secretion rate and tissue conductance, which provide alternative explanations for observations with the teleost gill epithelium.

Animals↗
PubMed2004

Modulation of intestinal P-glycoprotein function by cremophor EL and other surfactants by an in vitro diffusion chamber method using the isolated rat intestinal membranes.

Effects of various surfactants on the transport of rhodamine123, a P-glycoprotein (P-gp) substrate, across the isolated rat intestinal membranes were examined by an in vitro diffusion chamber system. The jejunal serosal-to-mucosal transport (Jsm) of rhodamine123 was more than threefold greater than its mucosal-to-serosal transport (Jms), suggesting that the net movement of rhodamine123 across the rat jejunum was preferentially secretory direction. There exists a regional difference in the intestinal transport of rhodamine123 and the secretory directed transport was remarkably observed in the jejunum. The Jsm/Jms ratio of rhodamine123 decreased in the presence of 0.3 mM verapamil and 10 mM sodium azide (NaN3) + 1 mM sodium fluoride (NaF), confirming that rhodamine123 might be secreted from the intestinal tissue into the lumen by a P-gp-mediated efflux system. Nonionic surfactants [0.1% Cremophor EL, Tween 80 and n-dodecyl-beta-D-maltopyranoside (LM)] reduced the Jsm/Jms ratio of rhodamine123, whereas its ratio was not influenced in the presence of 0.1% cationic surfactant (hexadecyltrimethylammonium bromide, C16TAB) and anionic surfactant (sodium dodecyl sulfate, SDS). Therefore, these findings suggested that charge of surfactants was possibly related to the action of these surfactants on the intestinal absorption of P-gp substrates. On the other hand, the transfer of rhodamine123 was not affected by the addition of Cremophor EL to the serosal side. Because the c.m.c. of Cremophor EL is 0.0095 w/v%, interactions between rhodamine123 and the micellar form of Cremophor EL may decrease the P-gp-mediated efflux of rhodamine123 at higher concentrations. In the kinetic analysis, the Vmax value (nmol/min/g wet tissue) of rhodamine123 decreased, although the Km value (mM) was constant in the presence of Cremophor EL. Therefore, Cremophor EL inhibited the efflux transport of rhodamine123 in a noncompetitive manner. Cremophor EL did not affect the transport of [14C]Gly-Sar and [3H]3-O-methyl-D-glucose, suggesting that the action of Cremophor EL might be P-gp specific. These findings indicated that nonionic surfactants including Cremophor EL and Tween 80 may be useful pharmaceutical excipients for inhibiting the function of P-gp, thereby increasing the intestinal absorption of various drugs, which are secreted by a P-gp-mediated efflux system in the intestine.

3-O-Methylglucose↗
PubMed2005

Dose dependency in the oral bioavailability of an organic cation model, tributylmethyl ammonium (TBuMA), in rats: association with the saturation of efflux by the P-gp system on the apical membrane of the intestinal epithelium.

The oral bioavailability of tributylmethyl ammonium (TBuMA), an organic cation (OC), exhibited a dose-dependency (i.e., 17, 27, and 35% at doses of 0.4, 4, or 12 micromol/kg, respectively) in the rat. Relevant mechanisms were investigated in the present study by estimating the mucosal to serosal (m-s) and serosal to mucosal (s-m) transport of TBuMA across the rat ileum in an Ussing chamber experiment. The m-s permeability rapidly increased with TBuMA concentration in the mucosal side, and then becoming constant at high TBuMA concentrations. Various studies, including temperature- and potential-dependency and inhibition experiments, revealed that carrier-mediated transport mechanisms (most likely OCT1, OCT3, and P-gp) are involved in the s-m transport of TBuMA, and the saturation of the transport at higher concentrations is responsible for the concentration-dependency in the m-s permeability or dose-dependency of the bioavailability of TBuMA. A nonlinear regression of the m-s transport, based on the assumption of a mixed process of linear diffusion and saturable efflux, exhibited a clearance (CLlinear) of 0.343 microL/min/cm2 for the passive diffusion, and an apparent Km of 241 microM for the saturable process. The Km value is consistent with the concentration range in the intestine which is expected to be achieved after the oral dosing of TBuMA at a dose of 0.4 micromol/kg (i.e., 68 approximately 185 microM). Interestingly, the m-s transport of TBuMA was increased by the presence of P-gp substrates or inhibitors in the mucosal side, but not by the mucosal presence of OCT substrates or inhibitors, suggesting that only efflux transport systems on the apical membrane (e.g., P-gp), but not those on the serosal membrane (e.g., OCT1 and OCT3), of the intestinal epithelial cells, are involved in the dose-dependency or concentration dependency. A similar relationship seems likely for drugs that are substrates of efflux transporters on the apical membrane of the intestinal epithelium.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed2007

Impact of cremophor-EL and polysorbate-80 on digoxin permeability across rat jejunum: delineation of thermodynamic and transporter related events using the reciprocal permeability approach.

The effect of Cremophor-EL (Cr-EL) and polysorbate-80 (PS-80) on the transepithelial permeability of digoxin (DIG) has been evaluated using the reciprocal permeability approach to delineate thermodynamic and transporter related events. Permeability data were corrected for solubilization using the micellar association constant (Ka) obtained from Papp data generated in the presence of the nonspecific ATPase inhibitor sodium orthovanadate. In the presence of mucosal Cr-EL, a concentration dependent decrease in serosal-mucosal (S-M) and increase in M-S transport was observed. Whilst serosal Cr-EL resulted in a reduction in S-M DIG transport, no impact on M-S transport was apparent. For PS-80, the presence of either serosal or mucosal surfactant led to a decrease in secretory (S-M) DIG transport, however no effect on absorptive transport was evident. The data confirm the potential P-gp inhibitory effects of Cr-EL, but suggest that in contrast to Cr-EL, PS-80 is not a potent inhibitor of P-gp and is incapable of increasing absorptive drug transport, at least in excised rat intestinal tissue and at the concentrations tested. The data are also consistent with the involvement of additional transporters (both apical and basolateral) in the intestinal permeability of DIG, although more definitive data is required to confirm this possibility.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Prevention of tissue injury and postsurgical adhesions by precoating tissues with hyaluronic acid solutions.

The effectiveness of inhibiting serosal tissue damage and preventing surgical adhesions by precoating tissues with dilute solutions of hyaluronic acid (HA) was evaluated in a rat cecal abrasion model. This study was performed at three independent laboratories using the same protocol. Three hundred and seventy-five adult rats were divided into five treatment groups (125 animals at each study site): 0.1% HA, 0.25% HA, 0.4% HA, phosphate-buffered saline solution (PBS), and no solution. The abdominal cavity of each animal was precoated with 4 ml of test solution or no solution, prior to a controlled abrasion of the cecum. One week later, the animals were sacrificed and adhesions were scored on a 0-4 scale. The data were pooled because no statistical difference was found in the trends at the three study sites. The PBS precoating and no tissue precoating treatment groups had the same high incidence of cecal adhesions, which was significantly higher than the incidence of adhesions in the HA treatment groups. As the HA concentration in the precoating solution increased from 0% (PBS group) to 0.4% HA, the mean incidence of cecal adhesions decreased in a concentration-dependent manner from 1.6 +/- 0.11 to 0.7 +/- 0.09 (P < 0.001). The percentage of animals with no cecal adhesions increased from 11% in the PBS group to 50% in the 0.4% HA treatment group (P < 0.001). In a separate histological study employing 150 rats, HA solutions significantly inhibited serosal tissue damage and ameliorated the inflammatory response due to abrasion and desiccation compared to that with no coating or precoating with buffered saline. Together, these studies demonstrate that tissue precoating with dilute HA solutions reduces damage to serosal tissues during surgery and thereby limits formation of postsurgical adhesions.

Administration, Topical↗
PubMed2000

Aggregation substance promotes colonic mucosal invasion of Enterococcus faecalis in an ex vivo model.

BACKGROUND: Bacterial translocation through the gastrointestinal tract is the crucial step in the pathogenesis of intraabdominal infections. We assessed whether aggregation substance (AS), a bacterial adhesin and virulence factor of Enterococcus faecalis, promotes bacterial translocation and colonic mucosal invasion in an ex vivo experiment. METHODS: Colonic mucosa of male Wistar rats was placed in a modified Ussing system. The mucosal side of the chamber was filled with a suspension of E. faecalis OG1X:pAM721 (AS-positive) or E. faecalis OG1X (AS-negative). The serosal side was filled with sterile Dulbecco's modified Eagle's medium. For assessment of colonic mucosal invasion the mucosal side was incubated for 2.5 h with a suspension of AS-positive or AS-negative enterococci. After being washed, a solution of gentamicin and penicillin G in tissue culture medium was added on both sides in order to kill extracellular bacteria. Subsequently, the mucosa was removed from the system, washed, lysed with Triton X-100, and homogenized. Viable intramural bacteria were quantified by plating serial dilutions of the homogenate on Todd-Hewitt broth agar plates. To quantify bacterial translocation samples which were taken at various time points from the serosal side were plated on Todd-Hewitt broth agar plates and colony forming units (CFU) were determined. RESULTS: Invasion of the AS-positive E. faecalis strain OG1X:pAM721 into the colonic mucosa was significantly higher than invasion rates of the AS-negative strain OG1X (2.88 log(10) CFU/ml vs 1.73 log(10) CFU/ml; P = 0.02). However, none of the tested strains was found to translocate from the mucosal to the serosal side within the incubation time of 4 h. CONCLUSIONS: The aggregation substance promotes invasion of E. faecalis into colonic mucosa.

Animals↗
PubMed1995

Modulation of noradrenaline release in rat isolated stomach by prostanoids, but not by histaminergic mechanisms.

Several gastric functions are modulated by the sympathetic nervous system, but local mechanisms involved in the control of noradrenaline release are largely unknown. Overflow of endogenous noradrenaline was studied from isolated rat stomach incubated in Ussing chambers allowing the separate determination of mucosal and serosal overflow. Spontaneous noradrenaline overflow was similar at the mucosal and serosal side, but electrical field stimulation caused a frequency-dependent increase in noradrenaline overflow selectively at the serosal side. Evoked noradrenaline overflow was blocked by tetrodotoxin, not affected by indometacin and markedly enhanced (by about 250%) by yohimbine. In the presence of indometacin and yohimbine, sulprostone (an agonist at EP1/EP3 receptors) and misoprostol (an agonist at EP2/EP3 receptors) reduced the noradrenaline overflow evoked by stimulation at 3 Hz maximally by about 80% (EC50: 6 nmol/l and 11 nmol/l, respectively). The EP1 receptor selective antagonist AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid) did not antagonize the inhibition by sulprostone. Noradrenaline overflow evoked by stimulation at 1 Hz and 3 Hz was increased by scopolamine by about 50% and almost completely inhibited by oxotremorine. Neither, histamine nor the H3 receptor selective agonist (R)-alpha-methyl-histamine, nor the H1, H2 and H3 selective receptor antagonists mepyramine, cimetidine and thioperamide significantly affected noradrenaline overflow evoked by stimulation at 1 Hz or 3 Hz. In conclusion, impulse-induced noradrenaline release in the rat stomach is controlled by multiple presynaptic mechanisms involving alpha 2-adrenergic autoreceptors, EP3 prostanoid and muscarine heteroreceptors, whereas histaminergic mechanisms do not appear to be significant.

Abortifacient Agents, Nonsteroidal↗
PubMed1994

Basolateral potassium membrane permeability of A6 cells and cell volume regulation.

The K+ permeabilities (86Rb(K) transport) of the basolateral membranes (JbK) of a renal cell line (A6) were compared under isosmotic and hypo-osmotic conditions (serosal side) to identify the various components involved in cell volume regulation. Changing the serosal solution to a hypo-osmotic one (165 mOsm) induced a fast transient increase in Cai (max < 1 min) and cell swelling (max at 3-5 min) followed by a regulatory volume decrease (5-30 min) and rise in the SCC (stabilization at 30 min). In isosmotic conditions (247 mOsm), the 86Rb(K) transport and the SCC were partially blocked by Ba2+, quinidine, TEA and glibenclamide, the latter being the least effective. Changing the osmolarity from isosmotic to hypo-osmotic resulted in an immediate (within the first 3-6 min) stimulation of the 86Rb(K) transport followed by a progressive decline to a stable value higher than that found in isosmotic conditions. A serosal Ca(2+)-free media or quinidine addition did not affect the initial osmotic stimulation of JbK but prevented its "secondary regulation", whereas TEA, glibenclamide and DIDS completely blocked the initial JbK increase. Under hypo-osmotic conditions, the initial JbK increase was enhanced by the presence of 1 mM of barium and delayed with higher concentrations (5 mM). In addition, cell volume regulation was fully blocked by quinidine, DIDS, NPPB and glibenclamide, while partly inhibited by TEA and calcium-free media. We propose that a TEA- and glibenclamide-sensitive but quinidine-insensitive increase in K+ permeability is involved in the very first phase of volume regulation of A6 cells submitted to hypo-osmotic media. In achieving cell volume regulation, it would play a complementary role to the quinidine-sensitive K+ permeability mediated by the observed calcium rise.

Animals↗
PubMed1995

Water pathways across a reconstituted epithelial barrier formed by Caco-2 cells: effects of medium hypertonicity.

Caco-2 cells, originated in a human colonic cancer, are currently used as model systems to study transepithelial transports. To further characterize their water permeability properties, clone P1 Caco-2 cells were cultured on permeable supports. At confluence, the transepithelial net water movement (Jw), mannitol permeability (Ps), and electrical resistance (R) were simultaneously measured. The observed results were correlated with transmission and freeze-fracture electron microscopy studies and compared with those obtained, in similar experimental conditions, in a typical mammalian epithelial barrier: the rabbit rectum. When the serosal solution was made hypertonic (50 mM polyethylene glycol-PEG), the spontaneously observed secretory Jw rapidly reversed, became absorptive and then stabilized. Simultaneously, the R values dropped and Ps went up. In the case of the rabbit rectal epithelium, a similar treatment did not elicit significant changes in the water permeability during the first 20 min following the osmotic challenge while there was a significant increase in the transepithelial resistance. After exposure to serosal hypertonicity, several morphological modifications developed in the Caco-2 cells: Localized dilations in the intercellular spaces and vacuoles in the cytoplasm appeared. Nevertheless, most cells remained in contact and no evidence of cell shrinking was observed. Simultaneously, the tight-junction structure was more or less disorganized. The filament network lost its sharpness and "omega" figures appeared, bordering the intercellular spaces. In some cases the tight-junction network was completely disrupted. In the case of the rabbit rectum the structural modifications were completely different: Serosal hypertonicity rapidly induced cell shrinking and the opening of the intercellular spaces, with no noticeable change in the tight-junction structure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Unidirectional fluxes of short-chain fatty acids across segments of the large intestine in pig, sheep and pony compared with guinea pig.

Unidirectional fluxes of short-chain fatty acids across pig, sheep and pony caecum, proximal and distal colon were studied under short-circuit current conditions in Ussing chambers. Findings are compared with results from guinea pig. Marked species differences are apparent; highest mucosal-to-serosal fluxes of acetate, propionate and butyrate were seen in guinea pig, lower values in pig and smallest fluxes in sheep and pony. Segmental differences between caecum, proximal and distal colon exist mainly in guinea pig and are less developed in pig, sheep and pony. Inhibition of Na+/H+ exchange by amiloride added to the mucosal solution decreased the mucosal-to-serosal fluxes of short-chain fatty acids clearly in guinea pig caecum and proximal colon, and very little in distal colon. This effect was somewhat less pronounced in pig caecum and distal colon, in caecum and distal colon of sheep and caecum of the pony. In pig, sheep and pony proximal colon and pony distal colon no significant inhibition was observed. Inhibition of the K(+)-H+ ATPase by addition of ouabain to the mucosal solution diminished mucosal-to-serosal fluxes of short-chain fatty acids in the guinea pig distal colon extensively. No comparable inhibition was seen in any of the other segments in the animals studied.

Amiloride↗
PubMed1990

Construction of a stable nipple valve with processed dermal sheep collagen for continent ileostomy and urostomy.

Complications of the nipple valve system used for continent urostomy and ileostomy basically consist of incomplete (or complete lack of) adhesion of the invaginated serosal surfaces of the valve. A novel concept in fixation of the valve by means of the intussusception of a newly developed biomaterial (processed dermal sheep collagen; PDSC) was tested. The implanted PDSC is characterized by induction of fibroblast invasion and formation of new collagen fibers, initial high tensile strength, bio-inertion and (slow) biodegradation. It was implanted between the serosal surfaces of the invagination in 14 dogs without the application of the commonly used staples and synthetic mesh. Good permanent fixation was obtained in all cases after the PDSC had been sutured in place. As the observation time advanced up to 2 years, an increased amount of newly formed collagen was seen anchoring the serosal surfaces firmly together via the implanted PDSC with apparent slow degradation. In none of the test animals did complications occur. The first clinical trial was successful.

Animals↗