Utilization of 14 C-labeled E. coli by the rat cecum and after force-feeding

Intestinal bacterial origin of D-alanine in urine of mutant mice lacking D-amino-acid oxidase

Urine from mutant mice which lack D-amino-acid oxidase contained a large amount of D-alanine. The alanine content was not changed by changes in the dietary composition or by starvation. However, oral administration of an antibiotic, amoxicillin, decreased the urinary alanine to the normal level. These results suggest that the D-alanine is not of dietary origin but of intestinal bacterial origin.

[Absorption and use of amino acids infused into the cecum of growing pigs. 4. Comparative studies on oral or cecal administration of 15N-lysine and 15N-urea, respectively]

12 pigs were divided into 4 groups. All animals received an identical basal diet deficient in lysine and additional isonitrogenous amounts of 66.4 mmol N in the form of 15N-lysine and 15N-urea resp. orally or caecally. Caecal application was carried out as permanent infusion through caecal cannulae. N- and 15N-balances were ascertained of all animals and the remain of the labelled nitrogen was determined. From the comparison of the N-balances the conclusion can be drawn that though caecally applied N-compounds, whether they were infused as amino acids or as non-amino acid-N, disappear in the large intestine, i.e. are digested, do not, however, improve the N-balance but are excreted as additional urine-N. Subsequent to oral application, lysine or urea are almost quantitatively absorbed in the small intestine. Absorbed lysine is used in the synthesis of body protein, absorbed urea, however, is almost completely excreted in urine (83% of the 15N-amount absorbed). 15N-excretion in faeces after the oral application of 15N-lysine and 15N-urea resp. was less than 1% of the 15N-amount applied, after caecal infusion, however, it was approximately 6%, the biggest part of which (70-77%) was incorporated in bacteria protein. After caecal infusion the main quota of the infused 15N-amount (greater than or equal to 80%) was excreted in urine, most of it in the form of urea. After the oral application of 15N-lysine this could be detected in both the TCA-soluble fraction of the serum and the serum protein. After caecal infusion 15N in the TCA-soluble fraction of the serum could mainly be found as NPN, absorption and incorporation of intact 15N-lysine were considerably lower. An calculation showed that the maximum of the absorbed 15N-amount in the form of lysine was 3% and that of the infused amount was 1.8%. It can generally be doubted that the absorption of lysine in the large intestine is significant in the protein metabolism. The absorption of utilizable lysine is practically completed at the end of the ileum. In the large intestine mainly the ammonia by the catabolic activity of the intestinal flora is absorbed and subsequently excreted through the intestines.

Studies of the large intestine of sheep. 3. Nitrogen kinetics in sheep given chopped lucerne (medicago sativa) hay

A study was made of nitrogen kinetics in the large intestine of sheep given 800 g chopped lucerne (Medicago sativa) hay/d. Four sheep were continuously infused with (15NH4)2SO4 into the caecum and three other sheep were infused intravenously with [15N]urea. A digesta marker, 51Cr complexed with EDTA (51Cr-EDTA), was infused into the rumen of each sheep to allow estimation of the rates of digesta constituents. Infusions were continued until tracer concentrations reached plateaux in digesta and blood pools, after which the sheep were anaesthetized and slaughtered. Pre-infusion samples and samples on plateau were obtained before slaughter for subsequent analysis to give plasma urea and rumen ammonia-N concentration and enrichment. At slaughter, digesta were obtained from the ileum and segments of the large intestine. These were analysed for 51Cr-EDTA content and concentration and enrichment of ammonia-N, microbial N and non-urea non-ammonia-N (NU-NAN). N flows in segments of the large intestine were calculated and represented in a quantitative eight-pool model. Transfer of plasma urea across the wall of the caecum and proximal colon was negligible but there was an input of 0.8 g endogenous NU-NAN/d. Flow of urea plus ammonia-N in digesta from the ileum into the caecum contributed 1.0 g N/d to the caecal ammonia pool. Proteolysis and deamination produced a further 3.0 g ammonia-N/d in the caecum and proximal colon. The net absorption of N between the ileum and the rectum was 2.8 g N/d but 3.0 g ammonia-N/d was absorbed from the caecum and proximal colon and, in addition, at least 0.9 g ammonia-N/d from the distal colon and rectum. Ammonia-N was incorporated into caecal microbes (0.6 g N/d) and approximately 57% of the NU-NAN in caecal digesta was microbial N. The majority of the microbial N flowing from the caecum was excreted in faeces. The rate of irreversible loss of urea-N from plasma, measured by intravenous infusion of [15N]urea, was 13.6 g/d. On average 83 (SE 6.8)% of the 15NH3 apparently absorbed from the caecum was incorporated into plasma urea; caecal ammonia contributed 9-19% of the N in plasma urea and 0.2-3.1% of the N in rumen ammonia.

Effects of removal of the forestomach and caecum on the utilization of dietary urea in golden hamsters (Mesocricetus auratus) given two different diets

1. Surgical removal of the forestomach, the caecum or both the forestomach and the caecum, was performed on growing male golden hamsters (Mesocricetus auratus) given a low-or high-fibre diet. 2. In Expt 1, 18 d after surgery, the hamsters which were given a concentrate before surgery were given an experimental low-fibre diet containing urea or [15N] urea (10 g/kg diet) for 9 d. In Expt 2, 5 d after surgery, the hamsters which were given a forage diet before surgery were adopted to an experimental high-fibre diet containing urea (10 g/kg) and dried Italian ryegrass (Lolium italicum) powder (400 g/kg diet) for 5 d, and 10 d after surgery, given a diet containing [15N]urea (10 g/kg diet) for 9 d. 3. In both experiments, removal of the caecum resulted in a significant lowering of both weight-gain and the digestibility of the dry matter, and removal of the forestomach resulted in a significant decrease of both accumulation of 15N in the body protein and proportion of 15N retained in the body protein as a proportion of the administered dosage. 4. The effect of removal of the caecum on the utilization of [15N] urea was not apparent in Expt 1, but the utilization of [15N] urea was significantly lowered by removal of the caecum in Expt 2. 5. These results suggest that the caecum may play a more important role in food utilization than the forestomach. However, the forestomach of the golden hamster plays a significant role in the utilization of dietary urea. It is presumed that the role of the caecum in the utilization of urea may vary under different dietary conditions.

Glycoprotein degradation in the blind loop syndrome: identification of glycosidases in jejunal contents

Contents obtained from jejunum of normal controls, self-emptying and self-filling blind loop rats were analyzed for the presence of glycoprotein-degrading glycosidases. The blind loop syndrome was documented by the increased fat excretion and slower growth rate of self-filling blind loop rats 6 wk after surgery. With p-nitrophenylglycosides as substrate, the specific activity of alpha-N-acetylgalactosaminidase, a potential blood group A destroying glycosidase, was 0.90+/-0.40 mU/mg of protein. This level was 23-fold higher than the specific activity of normal controls. In partially purified self-filling blind loop contents, the activity of alpha-N-acetylgalactosaminidase was 9- to 70-fold higher than activities of self-emptying and normal controls. Antibiotic treatment with chloromycetin and polymyxin decreased 24-fold the glycosidase levels in self-filling blind loops. In experiments with natural substrate, the blood group A titer of a20,000g supernate from normal jejunal homogenates decreased 128-fold after 24-h incubation with blind loop contents. Normal contents failed to diminish the blood group reactivity of the natural substrate. Furthermore, blind loop contents markedly decreased the blood group A titer of isolated brush borders. Incubation between blind loop bacteria and mucosal homogenates or isolated brush borders labeled with d-[U-(14)C]glucosamine revealed increased production of labeled ether extractable organic acids. Likewise, intraperitoneal injection of d-[U-(14)C]glucosamine into self-filling blind loop rats resulted in incorporation of the label into luminal short chain fatty acids. These results suggest that glycosidases may provide a mechanism by which blind loop bacteria obtain sugars from intestinal glycoproteins. The released sugars are used and converted by bacteria into energy and organic acids. This use of the host's glycoproteins would allow blind loop bacteria to grow and survive within the lumen independent of exogenous sources.

[Protein digestability and amino acid absorption in various segments of the digestive tract of pigs. 1. Methods of animal experimentation, protein content and amino acid patterns of the digesta in the small intestine and in feces after feeding different feeds]

Re-entrance cannulae were applied by way of operations at the end of the small intestine of a larger number of growing pigs. After a post-operative phase these animals were fed with various rations (N-free diet, fattening feed for pigs, rations with dried skim milk resp. wheat gluten + lysine and wheat + wheat gluten + lysine). During the main experiment periods the ileum digesta (24 hour-periods of collecting) and the feces were quantitatively registered. The protein and amino acid content ascertained in the feed rations, the digesta and feces samples are reported, comparatively evaluated and discussed. The amount of amino acids (in mg per kg intake of dry matter) contained in the ileum digesta after N-free feeding were statistically calculated with regard to differences occuring between the animals and days. For most amino acids a significant decrease in the ileum digesta could be detected during the course of the N-free feeding period. Moreover, the amount of amino acids in the ileum digesta was compared with the metabolic fecal amino acids, from which conclusions could be drawn concerning the disappearance rate of the individual amino acids in large intestine.