3-Methylindole (skatole) and indole production by mixed populations of pig fecal bacteria

Pig fecal slurries converted added L-tryptophan either to indole without detectable intermediates or to 3-methylindole (skatole) via indole-3-acetate. The initial rate of production of 3-methylindole was greatest at pH 6.5 and less at pH 5.0 and 8.0; the initial rates of indole production were similar at pH 6.5 and 8.0. More than 80% of the tryptophan added was converted to 3-methylindole at pH 5.0; at pH 8.0 85% was converted to indole. Both pathways had similar Km values for tryptophan and similar maximum rates. Indole-3-carbinol and indole-3-acetonitrile completely inhibited the production of 3-methylindole from indole-3-acetate but had no effect on the reactions involving L-tryptophan.

Does oxybutynin add to the effectiveness of prompted voiding for urinary incontinence among nursing home residents? A placebo-controlled trial

OBJECTIVE

To determine if oxybutynin, a bladder relaxant medication, adds to the effectiveness of prompted voiding (PV) in the management of urinary incontinence among nursing home residents.

DESIGN

Randomized, placebo-controlled, double-blinded, dose-adjusted, crossover trial of oxybutynin added along with PV.

SETTING

Seven nursing homes in Los Angeles County, California.

PARTICIPANTS

Seventy-five nursing home residents with predominantly urge incontinence, whose incontinence did not respond well to a trial of PV.

MAIN OUTCOME MEASURES

The frequency of incontinence, measured as the percentage of hourly (7 AM to 7 PM) physical checks over a 3-day period at which the resident was found wet.

RESULTS

Sixty-three (84%) of the residents completed the study. Among those completing the trial, the percent of checks wet went from 26.5% to 23.7% on placebo to 20.2% on active drug. These changes were statistically significant but not clinically meaningful. A clinically significant decrease in the frequency of incontinence, which we defined as a relative reduction in the percent of checks wet of > 33%, occurred in 20 subjects (32%) while on active drug and in 12 subjects (19%) while on placebo (P = .48 by chi-square). Twenty-five subjects (40%) met our "continence criteria" of an average of one or less wet per day while on active drug, and 11 subjects (18%) achieved this goal on placebo (P = .005 by chi-square).

CONCLUSION

Oxybutynin does not add to the clinical effectiveness of PV in the majority of nursing home residents with urge type urinary incontinence. Selected residents may, however, become more responsive to PV while on oxybutynin. Our data are consistent with other studies of bladder relaxant medications in functionally impaired populations. New drugs and/or other interventions are needed for the large number of incontinent nursing home residents who do not respond well to PV.

Effect of dietary fiber on microbial activity and microbial gas production in various regions of the gastrointestinal tract of pigs

The microbial activity, composition of the gas phase, and gas production rates in the gastrointestinal tract of pigs fed either a low- or a high-fiber diet were investigated. Dense populations of culturable anaerobic bacteria, high ATP concentrations, and high adenylate energy charges were found for the last third of the small intestine, indicating that substantial microbial activity takes place in that portion of the gut. The highest microbial activity (highest bacterium counts, highest ATP concentration, high adenylate energy charge, and low pH) was found in the cecum and proximal colon. Greater microbial activity was found in the stomach and all segments of the hindgut in the pigs fed the high-fiber diet than in the pigs fed the low-fiber diet. Considerable amounts of O2 were found in the stomach (around 5%), while the content of O2 in gas samples taken from all other parts of the gastrointestinal tract was < 1%. The highest concentrations and highest production rates for H2 were found in the last third of the small intestine. No methane could be detected in the stomach or the small intestine. The rate of production and concentration of methane in the cecum and the proximal colon were low, followed by a steady increase in the successive segments of the hindgut. A very good correlation between in vivo and in vitro measurements of methane production was found. The amount of CH4 produced by pigs fed the low-fiber diet was 1.4 liters/day per animal. Substantially larger amounts of CH4 were produced by pigs fed the high-fiber diet (12.5 liters/day)(ABSTRACT TRUNCATED AT 250 WORDS)

Gas chromatographic determination of indole and 3-methylindole (skatole) in bacterial culture media, intestinal contents and faeces

A simple, rapid and inexpensive gas chromatographic method was developed for the determination of indole and 3-methylindole (skatole) in faeces, intestinal contents and bacterial cultures. It involves a simple homogenization and extraction with chloroform. The extract is injected onto a gas chromatograph equipped with a 12.5-m fused-silica capillary column coated with BP20 and a film thickness of 0.5 micron. To simplify the chromatograms and to get a higher sensitivity a nitrogen-phosphorus-sensitive detector is applied. The detection limit for indole and 3-methylindole under the conditions employed is 20 micrograms/kg, which is well below the values typically found in intestinal contents (up to 100 mg/kg). Recovery for both compounds was close to 100%, and the mean coefficients of variation were 3.5% for indole and 3.0% for 3-methylindole. The method has demonstrated its practical value in the analysis of more than 50,000 samples in our laboratory. More than 100 samples can be analyzed per day.

Metastatic or locally advanced colorectal cancer treated with 5-fluorouracil and low dose leucovorin

Eighty-one patients with metastatic or locally advanced colorectal cancer were treated at four oncological centers in Denmark with a regimen consisting of 5-fluorouracil 400 mg/m2 and leucovorin 20 mg/m2 for 5 consecutive days every 4 weeks. The response rate was 21% among all 81 patients (CR 3, PR 14). The median survival was 10 months regardless of measurability, sex and location of disease. Toxicity was mild, 6 (7%) patients were excluded from the study due to gastrointestinal side-effects and 15 (19%) patients had the 5-FU dose reduced due to side-effects. The results are comparable to those of other studies using different doses of leucovorin.

Digestion of polysaccharides and other major components in the small and large intestine of pigs fed on diets consisting of oat fractions rich in beta-D-glucan

The digestibility of polysaccharides and other major components and the metabolic response of the microflora in the small and large intestines to oat diets varying in mixed linked beta(1-->3; 1-->4)-D-glucan (beta-glucan) were studied in experiments with ileum-cannulated pigs. The oat fractions for diets were prepared in a dry milling process in which oat groats were milled into two endosperm fractions (oat flour 1 and oat flour 2) and oat bran. The digestibility of polysaccharides and the metabolic response of the microflora were followed for the two contrasting diets, oat flour 1 and oat bran, from ingestion to excretion while the digestibility of oat groats and oat flour 2 were estimated only at the ileum and in faeces. There was no degradation of beta-glucan from either oat flour 1 or bran in the stomach and the first, middle and distal thirds of the small intestine (average digestibility approximately 0), while in the terminal ileum digestibility increased to 0.30 to 0.17 respectively. The digestion of starch in the first third of the small intestine was lower for the high-beta-glucan oat-bran diet (0.49) than for the low-beta-glucan flour diet (0.64). However, digestibility differences between the two diets levelled out as the digesta moved aborally in the small intestine and the digestibility at the terminal ileum was almost complete (0.970-0.995) for all diets. Oat non-starch polysaccharides (NSP) were an easily digestible energy source for the microflora in the large intestine less than 13% of dietary NSP being recovered in faeces. The bulk of beta-glucan which survived the small intestine was degraded in the caecum and proximal colon while arabinoxylan was more slowly degraded. The amount of residues passing the ileo-caecal junction has little impact on the density of micro-organisms in the large intestine, which on the flour and bran diets were in the range of 10(10)-10(11) viable counts/g digesta, but a high impact on the activity of the flora in colon. Oat bran resulted in a higher proportion of butyric acid in large intestinal content compared with the flour diet. The faecal bulking effect of oat bran was mainly caused by an increased excretion of protein and fat, presumably of bacterial origin. Of all the diets tested the oat-bran diets had the lowest digestibilities of protein and fat at the terminal ileum and in the faeces.

Oat bran but not a beta-glucan-enriched oat fraction enhances butyrate production in the large intestine of pigs

Digestibility of polysaccharides and other macronutrients and the metabolic response of the microflora in the large intestine to a low dietary fiber wheat flour diet and three enriched diets with equal amounts of added dietary fiber (oat bran, a beta-glucan-enriched oat fraction and insoluble oat residues) were studied in ileal-cannulated pigs. The digestibility of starch was high in the small intestine (98-100%). At this site of the gastrointestinal tract there was also a significant degradation of mixed linked beta (1 --> 3; 1 --> 4)-D-glucan (beta-glucan) (45-54%), whereas arabinoxylan was quantitatively recovered in ileal effluent. Type and amount of polysaccharides passing the ileal-cecal junction had little effect of the density of microorganism in the large intestine (approximately 10(10) viable counts/g digesta) but did have a high impact on the activity of the flora in colon as measured by the concentration of ATP in digesta. The relative proportion of butyrate in the short-chain fatty acids in the luminal contents of the large intestine was 6.6-8.4% when the low dietary fiber wheat flour diet was fed. However, when either oat bran or insoluble residues were included in the diet, the level was raised to 9.3-11.2%. No effect was seen after the addition of the beta-glucan-enriched fraction. This study showed that arabinoxylan and not beta-glucan in the cell walls of oat bran was responsible for the enhanced butyrate production of oat bran.

Gastrointestinal implications in pigs of wheat and oat fractions. 2. Microbial activity in the gastrointestinal tract

The present work was undertaken to study the microbial activity in various segments of the gastrointestinal (GI) tract of pigs as influenced by the source and level of wheat and oat dietary fibre (DF). Eight experimental diets were prepared from wheat and oat fractions and studied in a series of two experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets comprising fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series included further diets based on rolled oats and rolled oats plus oat bran. The eight diets were given to thirty-two ileal-cannulated pigs, with sixteen pigs in each experiment. After a total period of 34 d (Expt 1) and 42 d (Expt 2), the pigs were slaughtered 4 h post-feeding and samples taken for adenine nucleotides (adenosine 5'-triphosphate (ATP); adenylate energy charge (AEC)), organic acids (lactic acid (LA); short chain fatty acids (SCFA)) and pH at twelve sites of the GI tract. The microbial activity as measured by the ATP concentration was low in the stomach and the cranial two-thirds of the small intestine, but tended to increase in the distal third. In the caecum a sharp rise in microbial activity was observed; the highest level was found for the diet providing most fermentable substrates. In all the diets but the rolled oats + oat bran diets, microbial activity showed a descending pattern as the digesta moved through the colon. In the large intestine source and level of residues had a marked influence on microbial activity. LA was the chief organic acid in the stomach and small intestine (10-40 mmol/l) while LA relative to SCFA was a minor component in the caecum and colon (10-20 mmol/l). The contribution of SCFA to total organic acids was reciprocal to LA, i.e. low in the stomach and small intestine (less than 20 mmol/l) and high in the caecum and colon. In the large intestine the concentration of SCFA decreased from 100-140 mmol/l in the caecum and proximal colon to 40-80 mmol/l in the distal colon. The acetic: propionic acid ratio increased from the caecum to the distal colon. With the diets based on oat alone (rolled oats; rolled oats + oat bran) the increase was less significant.(ABSTRACT TRUNCATED AT 400 WORDS)

Isolation of cyanobacterial heterocysts with high and sustained dinitrogen-fixation capacity supported by endogenous reductants

A method is described for the preparation of cyanobacterial heterocysts with high nitrogen-fixation (acetylene-reduction) activity supported by endogenous reductants. The starting material was Anabaena variabilis ATCC 29413 grown in the light in the presence of fructose. Heterocysts produced from such cyanobacteria were more active than those from photoautotrophically-grown A. variabilis, presumably because higher reserves of carbohydrate were stored within the heterocysts. It proved important to avoid subjecting the cyanobacteria to low temperatures under aerobic conditions, as inhibition of respiration appeared to lead to inactivation of nitrogenase. Low temperatures were not harmful in the absence of O2. A number of potential osmoregulators at various concentrations were tested for use in heterocyst isolation. The optimal concentration (0.2 M sucrose) proved to be a compromise between adequate osmotic protection for isolated heterocysts and avoidance of inhibition of nitrogenase by high osmotic strength. Isolated heterocysts without added reductants such as H2 had about half the nitrogen-fixation activity expected on the basis of intact filaments. H2 did not increase the rate of acetylene reduction, suggesting that the supply of reductant from heterocyst metabolism did not limit nitrogen fixation under these conditions. Such heterocysts had linear rates of acetylene reduction for at least 2 h, and retained their full potential for at least 12 h when stored at 0 degree C under N2.

N2O as a substrate and as a competitive inhibitor of nitrogenase

We have investigated the inhibitory effect of N2O on NH3 formation by purified component proteins from Klebsiella pneumoniae and have confirmed that the inhibition is competitive with respect to N2 and that N2O is reduced to N2, which in turn is further reduced to NH3. In addition, we have shown that N2O is unable to support HD formation from D2 and H2O. N2-supported HD formation from D2 and H2O was found to be inhibited by N2O. In contrast to N2, N2O was found to suppress nitrogenase-mediated H2 evolution completely at infinitely high pN2O. H2 was found to inhibit N2O-supported NH3 production but not N2O-supported N2 production. The steady-state kinetics of N2O reduction showed a good fit to Michaelis-Menten kinetics with a Km for N2O of 5 mM at 30 degrees C, corresponding to 24 kPa of N2O. A model is proposed that fits the observed results.

Effect of high pN2 and high pD2 on NH3 production, H2 evolution, and HD formation by nitrogenases

We have investigated the effect of the partial pressure of N2 and D2 on HD formation, H2 evolution, and NH3 production by nitrogenase from Klebsiella pneumoniae and Clostridium pasteurianum. By using pressures up to 4 atm, we have been able to extend the concentration range of N2 and D2 in our investigations beyond that used in previous studies. The pN2 dependence of HD formation with constant pD2 ideally shows no HD formation under zero pN2, reaches a peak which depends on the pD2, and then decreases to zero at very high pN2. K. pneumoniae and C. pasteurianum nitrogenases differ in their Ki(D2) for nitrogen fixation. C. pasteurianum nitrogenase had the lower activity for formation of HD. With K. pneumoniae nitrogenase, D2 enhanced H2 evolution from 31% of the electron flux partitioned to H2 in the absence of D2 to 51% of the electron flux partitioned to H2 at 400 kPa of D2. With C. pasteurianum nitrogenase, the equivalent values were 33% and 48% of the total electron flux. Our results support the mechanism for nitrogenase-catalyzed reductions proposed by W. W. Cleland [Guth, J., & Burris, R. H. (1983) Biochemistry 22, 5111-5122].