Distal Segments Of Small Intestine Research Articles

Carbohydrase activity in proximal and distal segments of small intestine in health, irritated bowel syndrome and enteropathy with membrane digestion disturbance

Diagnostics of enteropathy with membrane digestion disturbance (EMDD) is based on the evaluation of carbohydrase activity in duodenal mucosa (DM). There is no information about diagnostic value of ileum mucosa (IM) carbohydrases.
 Aim. Assess the diagnostic value of carbohydrases activity in mucous membrane of duodenum and distal ileum in patients with EMDD and irritable bowel syndrome (IBS).
 Materials and methods. The study includes 12 patients with EMDD, 16 patients with IBS and 12 relatively healthy persons (control group). Study design included analysis of food tolerance and evaluation of activity of sucrase, glucoamylase, maltase and lactase in mucous membrane of duodenum and ileum based on the method of Dahlquist with N.I. Belostotsky modification. Microsoft Office Excel and Statistica 10.0 were used for statistical evaluation of material. Mann–Whitney criterion was used to evaluate the differences between quantitative parameters. The differences were considered to be significant at p0.05. Control group was used for comparison.
 Results. In control group the carbohydrases activity in duodenum mucosa was not significantly statistically different from the one in IM. In patients of the IBS group, the activity of glucoamylase and maltase in the IM was significantly higher than in the duodenum: glucoamylase by 2.2 times, maltase by 2 times. In patients with EMDD the activity of glucoamylase, maltase and sucrase in IM is higher than in DM by 5.2, 3.8 and 2 times respectively, which signifies the formation of compensatory reaction of adaptive shift, initially described by A.M. Ugolev in 1985.
 Conclusion. The evaluation of carbohydrase activity in IM provides more information about pathogenesis of EMDD and its differential diagnosis with IBS.

Maternal protein restriction during pregnancy affects gene expression and immunolocalization of intestinal nutrient transporters in rats

Intrauterine dietary restriction may cause changes in the functioning of offspring organs and systems later in life, an effect known as fetal programming. The present study evaluated mRNA abundance and immunolocalization of nutrient transporters as well as enterocytes proliferation in the proximal, median and distal segments of small intestine of rats born to protein-restricted dams. Pregnant rats were fed hypoproteic (6% protein) or control (17% protein) diets, and offspring rats were evaluated at 3 and 16 weeks of age. The presence of SGLT1 (sodium-glucose co-transporter 1), GLUT2 (glucose transporter 2), PEPT1 (peptide transporter 1) and the intestinal proliferation were evaluated by immunohistochemical techniques and the abundance of specific mRNA for SGLT1, GLUT2 and PEPT1 was assessed by the real-time PCR technique. Rats born to protein-restricted dams showed higher cell proliferation in all intestinal segments and higher gene expression of SGLT1 and PEPT1 in the duodenum. Moreover, in adult animals born to protein-restricted dams the immunoreactivity of SGLT1, GLUT2 and PEPT1 in the duodenum was more intense than in control rats. Taken together, the results indicate that changes in the small intestine observed in adulthood can be programmed during the gestation. In addition, they show that this response is caused by both up-regulation in transporter gene expression, a specific adaptation mechanism, and intestinal proliferation, an unspecific adaptation mechanism.

Investigation of drug metabolism in various segments of small intestine in the rat

In the extrahepatic drug metabolism the intestinal tract can play an important role. These experiments were designed to study the biotransformation of p-nitrophenol (PNP) in the small intestine in the rat. Various segments of the small intestine (proximal and distal jejunum, terminal ileum) were perfused with isotonic solution in vivo containing different concentrations of PNP (20-100-500-1000 μM) and the concentrations of metabolites (PNP-G: p-nitrophenol glucuronide, PNP-S: p-nitrophenol sulfate) were determined in the perfusion medium. It was found a decreasing tendency in the glucuronidation from the proximal to distal segment of the small intestine: e.g. 430 nmol, 240 nmol, and 100 nmol PNP-G appeared in the perfusion medium in the proximal, distal jejunum and in the terminal ileum, respectively, when 500 μM PNP was luminally perfused for 90 minutes. Similar ratio was found at the luminal perfusion of other PNP-concentrations, too. Luminal appearance of sulfoconjugate of PNP was considerably lower and no clear gradient tendency in the formation of PNP-S could be detected in the small intestine from the proximal to distal segment. Our results show that there are considerable differences in drug metabolism in various segments of the small intestine. We have found a gradient conjugating activity from proximal to distal segment of small intestine in the glucuronidation of PNP.

Characterization of Expression in Mice of a Transgene Containing 3.3 kb of the Human Lactase-Phlorizin Hydrolase (LPH) 5′ Flanking Sequence

The regulation of human intestinal lactase-phlorizin hydrolase remains incompletely understood. One kb of pig and 2kb of rat 5'-flanking sequence controls correct tissue, cell, topographic, and villus LCT expression. To gain insight into human LCT expression, transgenic mouse lines were generated from 3.3kb of human LPH 5' flanking sequence from a lactase persistent individual fused to a human growth hormone (hGH) reporter bounded by an insulator. Four lines were identified in which reporter expression was specifically detectable in the intestine and no other organ, two of which demonstrated hGH expression specific to small and large intestine. Quantitative RT-PCR was carried out on proximal to distal segments of small intestine at fetal days 16.5 and 18.5 and at birth, postnatal days 7 and 28 in line 22. In fetal intestine, hGH expression demonstrated a proximal to distal gradient similar to that in native intestine. There was no significant difference between hGH expression levels at 7 and 28days in segment 3, the midpoint of the small intestine, where expression of endogenous lactase is maximal at 7days and declines significantly by 28days. Distal small intestine displayed high levels of hGH expression in enteroendocrine cells, which were shown to be a subset of the PYY cells. Thus, a 3.3-kb LPH 5' flanking sequence construct from a lactase persistent individual is able to maintain postnatal expression in transgenic mice post weaning.

Effect of Vilon and Epithalon on glucose and glycine absorption in various regions of small intestine in aged rats.

Vilon (Lys-Glu) and Epithalon (Ala-Glu-Asp-Gly) administered orally for 1 month improved transport characteristics of the small intestine in aged rats. Vilon enhanced passive glucose accumulation in the serous fluid in inverted sac made from the distal region of the small intestine, while Epithalon enhanced this process in the medial region. Vilon stimulated active glucose accumulation in the serous sac of the medial small intestine, Epithalon - in the proximal and distal small intestinal segments. Glycine absorption increased only in the proximal intestinal segment under the effect of Epithalon.

Uptake of Mycobacterium avium subsp. paratuberculosis through the distal small intestinal mucosa in goats: an ultrastructural study.

Various pathogens gain access to the intestinal wall via specialized cells, the M cells, found among the follicle-associated epithelial cells overlying the domes of the Peyer's patches. The present study was undertaken to examine the uptake of live Mycobacterium avium subsp. paratuberculosis in the distal small intestine of goat kids. Following laparotomy, distal small intestinal segments of five goats were ligated and injected with bacterial suspension. After 1 hour, the intestinal segments were excised and fixed for light and electron microscopic studies. M. a. paratuberculosis organisms were observed by transmission electron microscopy at locations in the intestinal wall, suggesting transcellular transportation through the M cells. The organisms were present both in the cytoplasm of the M cells and in the cytoplasm of intraepithelial leukocytes found in M-cell pockets. Intercellular bacteria between M cells were occasionally seen. Bacteria were not observed in association with the absorptive epithelium. This study indicates that in goat kids, M. a. paratuberculosis enters the intestinal wall primarily through the M cells in the follicle-associated epithelium of the Peyer's patches.

Premicellar taurocholate enhances calcium uptake from all regions of rat small intestine

Background/Aims: The specific components of bile, which is necessary for normal calcium absorption, are unknown. We have previously shown that Ca2+ is bound with high affinity by premicellar taurocholate. The current studies examined the effects of taurocholate on intestinal calcium transport. Methods: Intestinal Ca2+ uptakes were measured from proximal, mid, and distal small intestinal segments perfused with solutions containing 45 CaCl2 (0.1–1 mmol/L), taurocholate (0–10 mmol/L), trihydroxymethylaminomethane buffer (pH 7), phenolsulfonpthalein (nonabsorbable marker), and NaCl (total ionic strength, 0.16 mol/L) for four randomized perfusion periods. In other studies, the proximal small intestine was divided into two equal segments and perfused with either 45CaCl2 or 45CaCl2 plus taurocholate (2.5–5 mmol/L). Calcium absorption was measured from the difference in uptake and calcium concentration retained in mucosa. Finally, effects of taurocholate on Ca2+ uptake across isolated brush border membrane vesicles were measured. Results: Premicellar taurocholate produced an approximately 1.7–2-fold enhancement (P < 0.01) in Ca2+ uptake in all regions, with lesser contributions from micellar taurocholate. These effects resulted in a net increase in calcium absorption. Premicellar taurocholate also significantly increased calcium uptake across brush border vesicles. Conclusions: Premicellar taurocholate significantly enhances calcium uptake into, and absorption across, enterocytes. The mechanisms remain to be experimentally verified.

Bidirectional small-intestinal permeability in the rat to some common marker molecules in vitro.

The barrier properties of the small intestine were investigated by studying the bidirectional permeability to five commonly used marker molecules. Proximal and distal small-intestinal segments from rats were mounted in diffusion chambers, and the permeation of the markers 3H-mannitol (Mw 182), 51Cr-ethylenediamineteraacetic acid (Mw 341), [mercaptopropionic acid], D-arginine8]-vasopressin (Mw 1069), fluorescein isothiocyanate (FITC)-dextran (mean Mw 3000), and inulin (Mw 5200) was measured across the mucosa in both directions. A generally increased inward (mucosa to serosa) and a decreased outward (serosa to mucosa) permeation of the markers was found in the proximal to distal direction. The inward permeability showed increasing regional differences with decreasing size of the markers. In the absence of the villous epithelium, removed by scraping the intestinal wall, 86% to 62% of the proximal and distal barrier was lost in the inward direction but only 14% to 26% in the outward direction. The intestinal epithelial barrier is more permeable in the outward than in the inward direction, and regional permeability differences exist in a size-dependent fashion. The results suggest two passage routes, one for the smallest molecule, mannitol, and a second for the larger markers in the present size range, both apparently different from the route for macromolecules such as intact proteins.

Detection of Rotavirus Infection in Calves Employing Immunofluorescence

Abstract The rotavirus fluoresceing antigen (FA) was demonstrated in mucosal cells of the intestinal smears of proximal, mid and distal segments of small intestine in experimentally infected calves examined on day 2 and 4 post infection. However, on day 6 post infection, the FA could be detected only in the distal segment of small intestine. The intestinal cells from all the control calves and those sacrificed on day 8 and 10 post infection and from colon of all the calves were found negative for the presence of rotavirus antigen.

Hyperosmolal Formula in Neonatal Piglets

SummaryIngestion of hyperosmolal formula (HOF) by neonatal piglets has been shown to cause significant time‐dependent reduction in phase 3 myoclectric activity, which persists in the terminal ileum. To determine whether a single hyperosmolal meal leads to elevated concentrations of gastrointestinal (GI) hormones that inhibit intestinal motility and/or promote bacterial proliferation and disruption of intestinal mucosa, we studied 20 healthy neonatal piglets following feeding with an increased HOF (872 ± 32 mOsmol/kg, n = 10) and commercial pig milk formula (481 ± 41 mOsmol/kg, n = 10). Gastrin, secretin, cholecystokinin, and motilin concentrations were determined by radioimmunoassay during fasting and postprandial periods (15, 30, 45, 120, 180, and 240 min). Gastrin concentrations were significantly increased at 15 and 30 min following a hyperosmolal meal (p &lt; 0.01), but there were no statistical differences in GI hormone concentrations between groups. These transient elevations of gastrin concentrations are associated with significant postprandial reductions in phase 3 small intestinal myoelectric activity (SIMEA) that we have observed. Aerobic bacterial titers were not significantly different between proximal and distal small intestinal segments or between experimental groups, and anaerobic bacteria were seldom recovered. Thus, SIMEA was not sufficiently altered to produce significant bacterial proliferation. Small intestinal histology, assessed by light microscopy, showed normal proximal and distal small intestinal mucosa in 8 of 10 piglets from each group. Therefore, orogastric instillation of a single hyperosmolal feed does not result in intestinal mucosal damage. Further studies are warranted to determine the effects of hyperosmolal feeds when additional risk factors exist in the neonate.

Hyperosmolal Formula in Neonatal Piglets

Ingestion of hyperosmolal formula (HOF) by neonatal piglets has been shown to cause significant time-dependent reduction in phase 3 myoelectric activity, which persists in the terminal ileum. To determine whether a single hyperosmolal meal leads to elevated concentrations of gastrointestinal (GI) hormones that inhibit intestinal motility and/or promote bacterial proliferation and disruption of intestinal mucosa, we studied 20 healthy neonatal piglets following feeding with an increased HOF (872 +/- 32 mOsmol/kg, n = 10) and commercial pig milk formula (481 +/- 41 mOsmol/kg, n = 10). Gastrin, secretin, cholecystokinin, and motilin concentrations were determined by radioimmunoassay during fasting and postprandial periods (15, 30, 45, 120, 180, and 240 min). Gastrin concentrations were significantly increased at 15 and 30 min following a hyperosmolal meal (p less than 0.01), but there were no statistical differences in GI hormone concentrations between groups. These transient elevations of gastrin concentrations are associated with significant postprandial reductions in phase 3 small intestinal myoelectric activity (SIMEA) that we have observed. Aerobic bacterial titers were not significantly different between proximal and distal small intestinal segments or between experimental groups, and anaerobic bacteria were seldom recovered. Thus, SIMEA was not sufficiently altered to produce significant bacterial proliferation. Small intestinal histology, assessed by light microscopy, showed normal proximal and distal small intestinal mucosa in 8 of 10 piglets from each group. Therefore, orogastric instillation of a single hyperosmolal feed does not result in intestinal mucosal damage. Further studies are warranted to determine the effects of hyperosmolal feeds when additional risk factors exist in the neonate.

Differential stimulation of S-adenosylmethionine decarboxylase by difluoromethylornithine in the rat colon and small intestine

The effects of chronic inhibition of ornithine decarboxylase (ODC) by the specific inhibitor difluoromethylornithine (DFMO) in the rat colon and small intestine on mucosal contents of polyamines, decarboxylated S-adenosylmethionine (decarboxylated AdoMet) and S-adenosylmethionine decarboxylase (AdoMet decarboxylase) activity were studied. Administration of 1% DFMO in the drinking water for 10 or 15 weeks resulted in inhibition of ODC and decreases in intracellular putrescine and spermidine contents in both proximal and distal segments of small intestine and colon. At both time points DFMO administration resulted in a dramatic stimulation of AdoMet decarboxylase activity and a rise in decarboxylated AdoMet content in the proximal and distal small-intestinal segments compared with controls, which was not seen in either colonic segment of DFMO-treated animals. This differential stimulation of AdoMet decarboxylase by DFMO in the small intestine and colon could not be entirely explained on the basis of differences in polyamine contents, which are known to regulate this enzyme activity. Kinetic and inhibition studies of AdoMet decarboxylase in control small and large intestine revealed that: (1) there was no difference in Vmax. values between the tissues; (2) the Km for AdoMet was higher in the small intestine than in the colon; and (3) the Ki for product inhibition by decarboxylated AdoMet was higher in the small intestine than in the colon. These results suggest that the differential stimulation of AdoMet decarboxylase by DFMO in the small intestine and colon may be due to different isoenzymes and could play a significant role in the regulation of polyamine contents throughout the gut.

EFFECT OF MALNUTRITION ON THE ADHERENCE OF SALMONELLA TYPHIMURIUM (ST) TO RAT ENTEROCYTE

The adherence of bacteria to intestinal mucosa is an important initial event in the pathogenesis of enteric infections. Such infections occur frequently in association with undernutrition. We investigated the adherence of two strains of ST to enterocytes from ad-libitum fed and nutrient restricted rats in order to study the effects of nutrient restriction on the adherence of ST to enterocytes. An animal model of malnutrition was produced by feeding young male adult rats 50% of the daily intake in control ad-libitum fed rats. Enterocytes were isolated from proximal and distal small intestinal segments by agitation in isolation medium. Adherence was studied using fimbriated (S7471F) and non-fimbriated (S7471N) strains of ST labelled with 3H-adenine. Labelled bacteria were incubated with freshly isolated enterocytes for 30 min. at 37 C. and the free bacteria were separated from those bound to enterocytes by membrane filtration and washing. The bound bacteria was quantitated by liquid scintillation. Adherence was significantly higher with S7471F both with proximal and distal intestinal enterocytes. There was no significant difference between the malnourished and control rats with respect to degree of adherence despite significant differences in body and organ weights and serum albumin. Prolongation of the period of nutrient restriction (to 12 wks) did not produce any change in pattern of adherence. We conclude that the adherence patterns of these strains of ST to enterocytes are not significantly altered by malnutrition.

Intestinal Maturation: in Vivo Zinc Transport

Summary: We investigated with an in vivo single pass perfusion technique net absorption and the lumen to mucosa flux of zinc in the proximal and distal small intestine and in the colon segments of suckling (2-wk-old), weanling (3-wk-old) and adolescent (6-wk-old) rats. The concentration of zinc in the isotonic sodium chloride solution perfused through the intestinal segments was either below (10 μM) or above (25, 50, and 100 μM) serum zinc level. In suckling rats, the relationship between luminal zinc concentration and net absorption and lumen to mucosa flux was curvilinear in the proximal segment only; however, the relationship was linear in the distal small intestine and colon. In weanling rats, the relationship between luminal zinc concentration and net absorption and lumen to mucosa flux was curvilinear in the proximal and distal small intestinal segments and linear in the colon segments. In the adolescent rats, the relationship between luminal zinc concentration, net absorption and lumen to mucosa flux was curvilinear in all intestinal segments studied. The curvilinear relationships noted fits a Michaelis-Menten kinetics. Analysis of the kinetic data indicate a progressive rise in mean Km values with age in the proximal segments of all age groups. Similarly, there was a rise in mean Km values in the distal segments of the weanling and adolescent rats. These findings suggest that intestinal zinc transport is characterized by a maturational pattern which evolves with age.

Intestinal maturation: effect of luminal osmolality on net mineral secretion.

We investigated with an in vivo single-pass perfusion technique net secretion of calcium, magnesium, and zinc from proximal and distal small intestinal segments and from the cecum plus colon segments of suckling, weanling, and adolescent rats during perfusion with either isotonic (300 mOsm/kg) or hypertonic (500 mOsm/kg) mineral-free solutions. There was not secretion of calcium, magnesium, and zinc in all segments perfused at all age periods. During isotonic perfusion, rates of net secretion of calcium and zinc were severalfold greater in the proximal and distal segments of the suckling rats compared with the corresponding segments of the adolescent rats. Net magnesium secretion was similar in the sucking and adolescent rats. Net secretion rates for the weanling rats tended to be intermediate. During hypertonic perfusion, net secretion rates for calcium, magnesium, and zinc were severalfold greater from all segments of the suckling rats compared with the corresponding segments of the adolescent rats. During either isotonic or hypertonic perfusions, rates of net secretion of calcium and magnesium in general were greater from the proximal and distal segments than from the cecum plus colon in the suckling and weanling rats. In contrast, for the adolescent rats, net secretions from all segments in general were similar. For zinc, rates of net secretion were somewhat greater in the cecum plus colon of rats in all age groups. Our findings suggest a greater permeability of the intestinal epithelium, not only to water and electrolytes but also to certain minerals (calcium and magnesium) and trace elements (Zn) in suckling rats compared with adolescent rats. The implication is that during periods of osmotic diarrhea, infant animals appear to be at risk for losing excessive amounts of minerals and trace elements. These findings may have clinical relevance to human infants suffering from recurrent diarrheal diseases.

Effect of chronic malnutrition on intestinal structure, epithelial renewal, and enzymes in suckling rats.

Summary: To evaluate the impact of malnutrition on the developing gut, we studied small bowel structure, epithelial renewal, and enzymes in suckling rats deprived of adequate nutrient from birth. Rat pups were suckled by foster dams fed ad libitum one of three isocaloric, semipurified diets containing 6,9, or 25% (control) protein throughout gestation and lactation. An additional control group consisted of pups raised with their natural, chow-fed mothers. Although survival of the pups, 98% in the chow-fed and 25% protein groups, decreased to 83% in the 9% groups and 53% in the 6% protein groups, body and gut weights were remarkably uniform within each study group. Mean body weight, gut weight, villus height, and crypt depth were markedly and significantly less in the 6 and 9% pups when compared with those in the chow and 25% control groups, the 6% group being significantly more affected was than the 9% group (P < 0.001). Pups raised by chow-fed mothers also weighed significantly less (P < 0.001) than did those raised by dams fed the 25% protein diet. Total small intestinal protein and DNA content of mucosal scrapings were less in 6 than 9% rat pups (P < 0.001), which in turn were less than those in the 25% group (P < 0.05). The protein/DNA ratio in the small intestine of the 6% animals only was reduced when compared with the 25% group (P < 0.05). Epithelial cell migration assessed by autoradiography with [3H]thymidine was significantly slower in both proximal and distal intestinal segments of the 6% animals when compared with those from the 25% group (P < 0.001). Incorporation of the 3H, seen by autoradiography after 1 hr, was also signficantly decreased in the 6% group (P < 0.001). Calculated for the total small intestine, lactase, sucrase, alkaline phosphatase, and thymidine kinase activities were significantly diminished (P ≤ 0.001) in the 6% animals compared with 25% controls. Calculated in relation to mucosal protein content and compared with 25% controls, sucrase and alkaline phosphatase activities were significantly decreased (P < 0.001) in both proximal and distal small intestinal segments of the 6% animals, but thymidine kinase activity was decreased only in the distal segment (P < 0.001). However, lactase specific activity was increased in both proximal and distal segments from the 6% group (P < 0.001). Further studies of this phenomenon demonstrated a significant increase in intracellular acid β-galac-tosidase (P < 0.001), particularly in the distal intestinal segment, but also a marked increase in brush border β-galactosidase. Our data demonstrate that in the small intestinal mucosa of the suckling rat, chronic malnutrition causes a decreased number of cells and impaired epithelial proliferation. These abnormalities reflect a profound direct impact of malnutrition on the gut of the young animal and demonstrate a delay in the normal pattern of postnatal maturation of the small intestinal epithelium.

Small intestinal glucose transport. Proximal-distal kinetic gradients.

Proximal and distal small intestinal segments of the rat were perfused in situ at two different rates with isotonic solutions containing glucose in concentrations ranging from 25 to 600 mg/100 ml. Absorption was measured as glucose disappearance rate from the lumen. Glucose absorption had not previously been studied at intraluminal concentrations above and below blood glucose. Absorption was more rapid from the proximal segment. In both segments absorption was independent of perfusion rate and of whether glucose was analyzed by counting (14)C or by the Somogyi method. The latter finding suggests that of the unidirectional fluxes, flux out of the bowel is much greater than flux into the bowel. In contrast to the findings in previous studies neither segment showed rate-limiting kinetics, and the Michaelis-Menten analysis was not applicable. The form of the curve depicting absorption rate in relation to concentration differed between the two segments. At the higher concentrations absorption rate continued to increase much more rapidly in the proximal than in the distal segment. The observations could not be explained by known mechanisms of glucose transport and illustrate the difficulties of achieving biochemically and physiologically meaningful in vivo studies of intestinal absorption.

DEGRADATION OF ALBUMIN BY ISOLATED SEGMENTS OF THE GASTROINTESTINAL TRACT IN RATS.

Summary1. Studies of NaI131 absorption from and I131-albumin catabolism in isolated segments of gastrointestinal tract of rats are described. 2. One hour following the simultaneous injection of NaI131 into stomach, proximal, middle, and distal small intestinal segments, there was net gain of radioactivity in the gastric lumen, and a mean loss of 13.3 to 15.3% of the injected dose per cm2 of serosal surface in the small bowel segments. 3. After injection of 1.7-2.6 mg of I131-albu-min into stomach, proximal middle, and distal small bowel segments mean percentages catabolized per cm2 in one hour in respective segments were 6.4, 10.2, 13.3, and 13.0. 4. Diversion of pancreatic and biliary secretions for 24 hours prior to study lowered these means to 4.0, 5.1, 2.9, and 4.9 respectively. 5. These studies indicate that the stomach and all levels of the small bowel possess significant potential for degrading serum albumin entering the lumen, and that pancreatico-biliary secretions make a significant, but not the...