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When sheets of mucosa from the cecum of clinically normal horses were incubated in vitro with radiolabeled L-alanine, they could accumulate this amino acid against an apparent concentration gradient after 60 to 150 minutes of incubation. The active transport system for L-alanine was on the serosal surface of the mucosal sheet only. L-Alanine accumulation at 60 minutes was partly inhibited by 20 mM glycine (P less than 0.01), 0.5 mM ouabain (P less than 0.05), and Na deprivation (P less than 0.02). Anoxia for 60 minutes increased L-alanine accumulation, but had adverse effects on cell structure and intracellular cation distributions. Transmucosal fluxes induced a small, but significant (P less than 0.05), net secretion of L-alanine, and the mean (+/- SEM) transmucosal potential difference was 7.3 +/- 0.7 mV over the period of flux measurement. It was concluded that L-alanine was accumulated by the serosal surface of the cecal mucosa, possibly to provide substrate for tissue metabolism. There was no evidence that the cecal mucosa could actively transport this amino acid from the luminal bathing medium.

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Two experiments were conducted to assess differences in fermentative activities of digesta obtained from various regions of the pig gastrointestinal tract. In experiment 1, the contents of small intestines, ceca, and colons of 110-kg pigs were collected, diluted twofold, and incubated for 2 h at 37 degrees C. In experiment 2, colonic samples from 16,100-kg pigs were similarly treated, except that the incubation period was 5 h. Total gas (gas pressure), CH4, H2, lactate, formate, acetate, propionate, butyrate, valerate, and isovalerate were measured in experiment 1. Only the gas variables were measured in experiment 2. Statistically significant differences (P greater than 0.05) were not observed among the gas production rate estimates across the small-intestinal, cecal, and colonic regions in experiment 1. Furthermore, all the small-intestinal samples and half the cecal samples assayed in experiment 1 were nonmethanogenic. The mean methanogenic and total-gas production rate estimates for the colonic samples in experiment 1 were 0.052 ml g of wet contents-1 h-1 and 1.7 ml of total gas g of wet contents-1 h-1, respectively. No differences in the methanogenic rate estimates were detected between the proximal, middle, and distal thirds of the pig colons (P greater than 0.05). The volatile fatty acid and lactate molar percentages measured in experiment 1 were consistent with previously published observations. Hydrogen accumulated to the greatest extent (7 microM on average) in the in vitro incubations of small-intestinal contents, whereas the H2 concentrations ranged from 0.5 to 1 microM for the incubated cecal and colonic samples in experiment 1.(ABSTRACT TRUNCATED AT 250 WORDS)

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Two bile acid extraction procedures were compared using endogenously radiolabeled tissues and feces. The method of Setchell et al. (J. Lipid Res. 24, 1085-1100, 1983) resulted in essential complete extraction, whereas that of Manes and Schneider (J. Lipid Res. 6, 376-377, 1971) gave recoveries between 56-82%. The time requirement for the method of Setchell et al. could be drastically reduced with no loss in extraction efficiency. Using extracts from endogenously labeled material, a purification procedure using C18 solid-phase extraction cartridges was developed that recovers greater than 90% of bile acids. The distribution of bile acids within the intestinal tract and liver of the rat was determined.

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1. Stomach and pyloric caeca homogenates from the crown-of-thorns starfish hydrolysed p-nitrophenyl esters, alpha-naphthyl esters, cholesteryl oleate and tributyrin. The pyloric caeca contained the highest activities. 2. The p-nitrophenyl acetate hydrolytic activity eluted at 0.23 M NaCl on ion exchange chromatography while the p-nitrophenyl palmitate hydrolytic activity eluted between 0.2 and 1.0 M NaCl. 3. Polyacrylamide gel zymograms for alpha-naphthyl acetate hydrolytic activity revealed one major band and several minor bands of activity for both tissues. 4. Isoelectric focusing zymograms revealed one major band with a pI = 4.2 for both tissues, with an additional band at pI = 3.5 for pyloric caeca. 5. The pyloric caeca contained twice as much lipid as the stomach. Lipid extracts contained mixtures of steroids and steroid-esters; a cholesterol-like sterol was tentatively identified.

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Samples from the duodenum, jejunum, and ileum, as well as from the cecum and colon, were obtained from 11 mature grass-fed horses. Viable counts of total culturable and proteolytic bacteria were made on habitat-simulating media containing 40% clarified ruminal fluid. The mean pHs in the duodenum, jejunum, and ileum were 6.32, 7.10, and 7.47, respectively; the mean pH decreased to 6.7 in the hindgut. The acetate concentration increased along the length of the small intestine and was the only volatile fatty acid present in this gut segment. Molar proportions of acetate, propionate, and butyrate in the hindgut were 85:10:3. Differences in bacterial counts on habitat-simulating media containing equine cecal fluid or clarified ruminal fluid were negligible. Bacterial counts showed a substantial population in the duodenum (ca. 2.9 x 10(6) per g [wet weight] of sample), and this increased to 29.0 x 10(6) in the jejunum and 38.4 x 10(6) in the ileum. Proteolytic bacteria formed a high proportion of the total culturable bacteria, especially in duodenal samples. Counts of proteolytic bacteria per gram (wet weight) of sample were 3.0 x 10(6), 15.6 x 10(6), and 22.0 x 10(6) in the duodenum, jejunum, and ileum, respectively. There was a close relationship between lumenal and mucosal bacterial counts, although actual values were lower in mucosal samples. The mucosal bacterial population in the duodenum was high relative to the lumenal population. Although the comparison of bacterial populations in the hindgut of the horse and white rhino was limited to a single animal, the results were of interest. Counts were higher in the cecum than in the colon for both the horse and the white rhino.(ABSTRACT TRUNCATED AT 250 WORDS)

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The fecapentaenes are potent mutagens found in the stool of some humans and pigs. These compounds are produced by Bacteroides species in the gut from an uncharacterized family of precursor compounds, and have been postulated to pose a risk of human colorectal cancer. To better understand fecapentaene production in vivo, and to determine if excreted levels measured in epidemiologic studies are representative of the entire colon, fecapentaenes were assayed from multiple sites in the bowel in an autopsy study of 16 humans and 2 pigs. An indirect measurement of fecapentaene precursors was also made. Colonic concentrations of fecapentaenes and precursors varied widely between individuals, but were consistent for each individual throughout the colon. In addition, the measurements of rectal contents, assumed to approximate values in excreted stool, were equivalent to measurements from the colon.

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Enterosiderosis in both SPF Hartley guinea pigs and vitamin C-deficient animals of the same strain were studied by light and electron microscopy. Enterosiderosis was detected in all animals in the present study. Macrophages, inclosing yellowish-brown pigments and erythrocytes, appeared in the lamina propria of the intestinal mucosa, mainly in the cecum. These pigments in the macrophages were positive for Prussian blue, PAS and the Nile blue reaction. Residual bodies containing highly electron-dense ferritin-like particles, lipofuscin granules and debris of phagocytized erythrocytes were found by electron microscopy in the macrophages. In vitamin C-deficient guinea pigs, the number of macrophages, including the same above pigments, appeared in the lamina propria of the intestinal mucosa, and there was severe enterosiderosis. In the absorptive cells of the intestinal mucous membrane, granules positive for the Prussian blue reaction appeared only in the duodenum. These findings strongly suggest that the pigments in the macrophages in enterosiderosis of the guinea pigs were mixtures of iron and lipofuscin granules and that the iron is derived from erythrocytes phagocytized by macrophages in the lamina propria, but not from iron absorbed by epithelial cells.

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A total of 260 New Zealand White growing rabbits were used to study the effect of diet on chemical composition of cecal contents and on production and composition of soft and hard feces. Eight diets varying in their acid detergent fiber (9.8% to 32.7%) and starch (13% to 30%) levels were evaluated. The diet affected (P less than .01) all the variables studied, except dry matter (DM) and molar proportions of volatile fatty acids on cecal contents. An increase of dietary crude fiber increased crude fiber level in cecal contents (from 11.58% to 26.53%). However, a relatively lower proportion of fibrous material was found in the cecal contents when rabbits were fed the more fibrous diets. This suggests that dietary fiber has a direct influence on the efficiency of particle separation in the digestive tract. Crude protein and volatile fatty acid concentrations of cecal contents decreased (from 30.14% to 19.65% and from 47.8 to 36.7 mmol/liter, respectively) when dietary crude fiber increased. This could be related to availability of energy to cecal microorganisms. Ammonia concentration of cecal contents was not affected by dietary crude fiber. Daily production of soft feces varied from 14.98 to 29.59 g DM/d, and the contribution of soft feces to total DM and to crude protein intake ranged from 10.6% to 15.0% and from 12.8% to 20.5%, respectively; these values were the smallest and the largest for the least and the most fibrous diets, respectively. From this study we conclude that dietary fiber has a major effect on the digestive processes in the rabbit and that dietary starch level has no influence on any of the variables studied.

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Electrolyte transport across rabbit caecal epithelium was investigated in vitro using conventional short-circuiting and radioisotope techniques. In standard saline the caecum exhibited a relatively high short-circuit current (Isc = 4.4 microEq.cm-2.h-1) and conductance (6.43 mS.cm-2). Both sodium and chloride were absorbed (JNa(net) = 6.40 and JCl(net) = 3.40 microEq.cm-2.h-1) and potassium was secreted (JK(net) = -0.5 microEq.cm-2.h-1). Removal of Na+ abolished Isc and JCl(net) whereas removal of Cl- reduced JNa(net) to 2.92 microEq.cm-2.h-1 but did not alter Isc. In HCO3(-)-free salines containing 10(-4) M acetazolamide JCl(net) was abolished and JNa(net) and Isc were reduced to 2.3 and 2.5 microEq.cm-2.h-1 respectively. A positive residual ion flux (approximately 1 microEq.cm-2.h-1) was detected in standard and Cl(-)-free salines but not in Na+-free or HCO3- buffers. Mucosal amiloride (10(-3) M) decreased net Na+ and Cl- absorption but did not decrease Isc. Mucosal DIDS (10(-4) M) decreased JCl(net) while mucosal bumetanide (10(-4) M) did not affect any of the measured parameters. Finally, addition of theophylline (8 mM) stimulated Cl- secretion and increased Isc. It is concluded that net sodium absorption by caecal epithelia occurs by both electrogenic and electroneutral mechanisms whereas net chloride absorption occurs only by an electroneutral process. Coupling of the absorptive fluxes of Na+ and Cl- may result from Na+/H+ and Cl-/HCO3- antiport systems in this tissue. Finally, it is proposed that up to half of the Isc is due to a Na+-dependent secretion of bicarbonate ion.

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Little is known about the distribution of glycoproteins in the digestive tube of birds. In the present study, the localization and distribution of mucins in the digestive tract of the chicken are reported. Sialo- and sulpho-mucins were widely distributed throughout the chicken digestive tube. Some of the mucous cells of the proximal segment of the proventriculus presented neutral glycoproteins; in the medial segment, surface cells containing only sialo-mucins were observed. Surface cells of the gizzard contained both sialo- and sulpho-mucins while PAS-positive material was localized in the lumen of the glands. 2 types of mucous cells were observed in the small intestine; 1 type contained only sialo-mucins and the other contained both sialo- and sulpho-mucins. In the large intestine and caecum, both types of acid mucins were present in the mucous cells. In conclusion, the distribution of glycoproteins in the chicken reported in the present study show marked differences with that reported in other avian species.

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In the cecal epithelium of the chicken, glycoconjugates were studied by light microscopy with lectin-peroxidase and correlated procedures, and by electron microscopy with high iron diamine-thiocarbohydrazide-silver proteinate (HID-TCH-SP) and periodic acid (PA)-TCH-SP methods. Mucous granules of goblet cells and striated border of columnar cells at the basal cecum contained acidic and neutral glycoconjugates with sulfate ester, vicinal diol groupings and alpha-D-mannose, alpha-D-glucose, beta-D-galactose, N-acetyl-D-glucosamine, and sialic acid-galactose dimers. In addition, terminal galactose-(1-3)N-acetylgalactosamine disaccharides were detected. In the apical cecum, similar glycoconjugates involved in the mucous granules of goblet cells and the striated border of columnar cells were found to be smaller in amount. Terminal galactose-(1-3)N-acetylgalactosamine disaccharides together with glycogen particles were also visualized in columnar cells of the basal and apical cecum. The histophysiological significance of glycoconjugates involved in the chicken cecal epithelium was discussed.

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Each of nine different toxigenic strains of Clostridium difficile was administered orally to groups of hamsters pre-treated with clindamycin and housed individually in sterile isolator boxes. Faecal pellets and caecal contents from well, diarrhoeic, moribund and freshly dead animals were analysed for C. difficile and toxins A (enterotoxin) and B (cytotoxin), and tissue obtained when animals were killed was examined histologically. Not all strains were equally virulent in this model. Four strains of C. difficile killed all animals within 48 h and are designated as highly virulent for hamsters. These strains were clinical isolates from three cases of disease in man and one case in a hamster. Five strains caused death of some animals but only after 5 and upt to 13 days and are designated as less virulent for hamsters. These strains were isolated from asymptomatic infants (2) and household pets (2), and from the environment (1). The surviving test hamsters were killed after 14 days and, in most cases, were colonised by C. difficile, though levels of toxins A and B in caecal contents were low. None of the cultures used for challenge was capsulate or hydrophobic. There was no correlation between virulence and production of toxins A and B in vitro in tryptic-nitrate broth. With two strains examined, there was a correlation between virulence and toxin A (but not toxin B) production in caecal emulsions derived from clindamycin pre-treated hamsters. Caecal contents from the majority of moribund and freshly dead animals had quantities of toxin A sufficient to cause disease or death if given orogastrically. Toxin B was not produced in a fixed ratio with toxin A. The data support the view that high virulence of C. difficile is determined by efficient disease-inducing colonisation of the gut and the ability to generate, rapidly, high levels of toxin A in vivo.

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Free glucose was assayed in the caecal contents of rats. Whereas control animals had less than 60 nmol glucose per g of caecal contents, 230 nmol glucose/g caecal contents were determined 3 hours after the administration of 300 mg Palatinit by gastric intubation. In contrast to an earlier report (8), caecal fluid thus contained less than 3% of the glucose concentration of 11 mumol/ml claimed to occur after Palatinit administration by these authors (8). Since the anaerobic fermentation capacity for glucose by the caecal contents of rats amounted to at least 630 nmol glucose/min X g fresh weight at 37 degrees C, only the low glucose concentrations reported above are plausible.

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The intramural distribution of Met5-enkephalin-Arg6-Gly7-Leu8 (MERGL) was studied in the oesophago-cardiac, pyloric, ileo-caecal and sigmoid-recto-anal regions of the human digestive tract. Serial samples encompassing each area were separated into mucosa, submucosa and muscularis externa and extracted for radioimmunoassay. Comparatively low levels of MERGL immunoreactivity were measured throughout the cardiac junction. Conversely, a remarkable peak of MERGL concentration was detected at the pyloric junction, in both submucosa and muscularis. A progressive decrease in tissue levels of the same peptide, most evident in the submucosa, was detected on the proximal side of the ileo-caecal region. In the distal sigmoid colon and rectum MERGL concentrations showed a rapid decline, down to very low levels in the anal canal. The results may suggest the involvement of an enkephalinergic mechanism in the control of the human pylorus.

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1. Digesta samples were collected from five West Indian manatees, Trichechus manatus, for volatile fatty acid (VFA) analysis. 2. Mean total VFA concentrations were low in the stomach and duodenum (18.6 and 12.3 mM/l, respectively). Mean VFA concentrations were considerably higher in the cecum and colon (220.6 and 307.3 mM/l, respectively). 3. The relative proportions of the individual VFA's shifted from predominantly acetic acid in the foregut to a mixture of acetic, butyric and propionic acids in the hindgut. 4. The VFA concentrations in the manatee are similar to those in the dugong, Dugong dugon, and the green sea turtle, Chelonia mydas. 5. The mean total VFA concentrations indicate that the cecum and colon of the manatee are sites of microbial cellulose fermentation. The contribution of VFAs to the manatees' total energy requirements could not be calculated, but it is probably considerable.

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Short-chain fatty acid concentrations were measured in the cecal contents of 9 healthy rabbits and 20 rabbits with experimentally induced mucoid enteropathy. In control rabbits, cecal concentration of acetate was the most abundant, followed by that of butyrate and propionate--a feature distinguishing rabbits from most other mammals. In mucoid enteropathy, cecal acetate and butyrate concentrations were lower, whereas propionate, isobutyrate, valerate, and isovalerate were increased. The results indicated that there were abnormal fermentation and cecal maldigestion in rabbits with mucoid enteropathy.

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The distribution of peptide YY (PYY)-like immunoreactivity (IR) in rat tissues was determined by specific RIA after extraction with boiled 1 N acetic acid. The high concentration of PYY-IR was observed in the gastrointestinal tract, with concentrations gradually increasing from the duodenum to the end of colon. The concentration of PYY-IR in the colon was 298.7-449.5 pmol/g tissue (approximately 100-200 times more than that in the duodenum). Pituitary and pancreas contained measurable amounts of PYY-IR (6.8 and 6.3 pmol/g tissue). The concentration of PYY-IR in the mucosa was higher than that in the muscular layer in the small intestine, cecum, colon, and rectum. The ratio of the mucosal PYY-IR to the muscular PYY-IR was highest in the distal small intestine (4.7-6.8). Sephadex G-50 gel chromatography of the colon extracts revealed the one PYY-IR peak which corresponds to [125I]PYY. The gradual increase of PYY-IR from the duodenum to the end of the colon is different from the distribution of other known gut peptides.

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1. The time-course of metabolic adaptation by rats to diets containing either wheat bran or gum arabic was studied during a 12-week period. 2. Stool weight was increased with wheat bran but not with gum arabic, and had stabilized after 4 weeks. 3. Bacterial mass as measured by diaminopimelic acid content had stabilized by week 4. Bacterial mass increased on feeding gum arabic but was unchanged with wheat bran. 4. There was increased caecal short-chain fatty acid, hydrogen and methane production with gum arabic but not with wheat bran. The change in caecal metabolic activity was slow to stabilize (8-12 weeks at least). 5. The faecal excretion of bile acids increased twofold with the wheat-bran-supplemented diet compared with the gum-arabic-supplemented and unsupplemented diets. Relatively greater amounts of muricholic acids were present in the caeca and faeces of gum-arabic-fed rats compared with the other groups.

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