Faecal Residues Research Articles

Studies on the re-establishment of the intestinal microflora in germ-free rats with special reference to the metabolism of N-isopropyl-alpha-chloroacetanilide (propachlor).

Conventional rats metabolize 2-chloro-N-isopropylacetanilide (propachlor) mainly to various 2-methylsulphonylacetanilides and to residues in the faeces that are unextractable. Mercapturic acid pathway (MAP) metabolites of propachlor are the source of the methylsulphonyl sulphur and the insoluble faecal residues. Germ-free and antibiotic-treated rats quantitatively metabolized propachlor only to MAP metabolites, which were excreted in the urine and faeces (all water-soluble). Germ-free rats given enemas of caecal contents from conventional rats were qualitatively similar to conventional rats with respect to the metabolism of propachlor within 56 days of the inoculations i.e. they excreted 2-methylsulphonyl acetanilides in the urine and insoluble residues in the faeces. They approached quantitative similarity within 180 days. Antibiotic-treated rats spontaneously recovered the ability to metabolize propachlor as conventional rats, qualitatively within 6 days and quantitatively within 21 days. While differences occurred in the faecal metabolites of propachlor, biliary secretion of metabolites by germ-free rats was not different from that of conventional or antibiotic-treated rats.

Enterohepatic circulation in formation of propachlor (2-chloro-N-isopropylacetanilide) metabolites in the rat

1. Bile secreted from rats given single oral doses of 2-chloro-N-isopropylacetanilide (propachlor) contained 58% dose as metabolites from the mercapturic acid pathway (glutathione, mercapturate, cysteine conjugates, and a sulphoxide of the mercapturate). 2. Bile secreted from rats given single oral doses of the cysteine conjugate of propachlor contained glucuronide conjugates of hydroxylated 2-methylsulphonyl-N-isopropylacetanilides. 3. In contrast, when the intestinal microflora were bypassed by intravenous administration of the cysteine conjugate of propachlor, the bile contained only the mercapturate and the sulphoxide of the mercapturate. 4. Rats fed an antibiotic-containing diet and given single oral doses of either propachlor or the cysteine conjugate of propachlor excreted only mercapturic acid pathway metabolites in the urine, bile, and faeces, and no methylsulphonyl-containing metabolites. Faecal 14C from the antibiotic-fed rats given either propachlor or the cysteine conjugate of propachlor was extractable, in contrast to previously reported unextractable faecal 14C residues from untreated rats given propachlor orally. 5. From these results, we conclude that metabolism by the microflora was necessary for production of the methylsulphonyl-containing metabolites excreted by the rat. Enterohepatic circulation of the xenobiotic moiety of these mercapturic acid pathway metabolites is influenced by the presence of a microbial C-S lyase.

The microbial contribution to human faecal mass.

A method has been developed, based on techniques used for isolating bacteria from the rumen, that enables human faeces to be fractionated into three major components. The method requires repeated, vigorous agitation of a suspension of faecal solids with detergent, the use of a stomacher, and high-speed centrifugation. By this means the faecal microflora are separated from faecal dietary-fibre residues. These two components, with water-soluble material in the stool, comprise 98.3 +/- 0.9% of faecal solids. The purity of the microbial fraction was demonstrated by Gram and plant stains and by scanning electron microscopy. Microscopic counts of the bacteria in each fraction of the stool showed that the microbial fraction contained 95% of the total bacteria. Chemical analysis of the component sugars indicated 6-7% possible contamination by non-bacterial polysaccharides. The bacterial pellet was 6% nitrogen, and accounted for 60% of the total faecal nitrogen. When faeces from nine healthy subjects on a metabolically controlled British-type diet were studied, bacteria comprised 54.7 +/- 1.7% of the total solids, fibre 16.7 +/- 0.8% and soluble material 24.0 +/- 1.3%. Bacteria therefore represent a much larger proportion of the faecal mass than was previously thought.

Cobalt, copper, and zinc in yellow-hrown pumice soils under grazed, permanent pastures

Abstract The 0–7.5 cm depth of soil from 29 pastures on yellow-brown pumice soils contains more H+/H2O2- and EDTA/NH4Cl-extractable Co, Cu, and Zn than the corresponding 7.5–15 cm depth. The differences in H+/H2O2-extractable quantities between the two depths ranges from. 0.1 to 2.3 ppm Co, 0.1 to 2.2 ppm Cu, and 0.5 to 9.8 ppm Zn. H+/H2O2 is known to dissolve orgamc matter, any manganese oXides, and some Al and Fe in these soils and the above increments in extractable Co, Cu, and Zn are shown to be consistent with their accumulation from fertiliser additions and plant and faecal deposition. Fertiliser addition is the major contnbutor to changes in soil Co, and Cu in plant and faecal residues is the major contributor to changes in soil Cu. For Zn, both factors make significant contributions. Laboratory experiments support the conclusion that these elements derived from fertiliser, accumulate in the surface 7.5 cm of soil. At a solution concentration of 10−5 M the percentages of divalent Co, Cu, and Zn, sorbed from 0.01M NaNO3 are greater than 90% at pH 5 to 6, which 18 the normal field pH range. The similarity of the sorption reactions of hydrolysable divalent cations is examined for Co and Cd, where the amounts sorbed at pH 3.7 are highly correlated (r = 0.97*** for 0–7.5 cm and 0.94*** for 7.5–15 cm samples) . The amounts sorbed appear to depend on the organic matter content of the soil as well as the pH, but the influence of manganese oxides is probably small.