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At least 1,099 records · Page 61Linked to original sources
PubMed1987

Glucuronidation of 6 alpha-hydroxy bile acids by human liver microsomes.

The glucuronidation of 6-hydroxylated bile acids by human liver microsomes has been studied in vitro; for comparison, several major bile acids lacking a 6-hydroxyl group were also investigated. Glucuronidation rates for 6 alpha-hydroxylated bile acids were 10-20 times higher than those of substrates lacking a hydroxyl group in position 6. The highest rates measured were for hyodeoxy- and hyocholic acids, and kinetic analyses were carried out using these substrates. Rigorous product identification by high-field proton nuclear magnetic resonance and by electron impact mass spectrometry of methyl ester/peracetate derivatives revealed that 6-O-beta-D-glucuronides were the exclusive products formed in these enzymatic reactions. These results, together with literature data, indicate that 6 alpha-hydroxylation followed by 6-O-glucuronidation constitutes an alternative route of excretion of toxic hydrophobic bile acids.

Adult↗
PubMed1982

Enzymatic determination of total 3 alpha-hydroxy bile acids in faeces. Validation in healthy subjects of a rapid method suitable for clinical routine purpose.

A method for determining faecal bile acids, suitable for clinical purposes, is introduced. The analysis uses a 0.2-g stool specimen, a simple extraction procedure, and 3 alpha-steroid dehydrogenase determination. The method, which is rapid, has been validated by gas-liquid chromatography and by recovery of internal standards. Stool examination was done in 16 healthy volunteers on free diet and in 25 patients with non-gastrointestinal diseases who were on a fat- and fibre-fixed diet. No difference was found between the two groups, so the data were pooled, and the normal reference interval (mean +/- S.D.) for faecal bile acid output was calculated to be 0-975 mumol/24h.

3-Hydroxysteroid Dehydrogenases↗
PubMedDate not supplied

[Effect of cultivation conditions on the accumulation of poly-beta-hydroxy-butyric acid in Rhizobium lupini].

The influence of the age of the culture and nitrogen source on the accumulation of poly-beta-hydroxybutyric acid by different strains of Rhizobium lupini was studied. The accumulation depended on the age of the culture and reached maximum at the end of the logarithmic and at the beginning of the stationary phase of the bacterial growth (about 50-60% dry weight). The accumulation varied in relation to the nitrogen source used: it was the highest in the glutamate medium and the lowest on nitrate nitrogen; the culture grown on ammonium phosphate was intermediate.

Ammonia↗
PubMed1976

Studies on the in vivo formation of acrolein: 3-hydroxy-propylmercapturic acid as an index of cyclophosphamide (NSC-26271) activation.

3-Hydroxypropylmercapturic acid (MCA) has been quantitatively determined in the urine of rats given cyclophosphamide (CP), related antineoplastic agents, allyl alcohol, or acrolein, with a simple procedure involving the use of an amino-acid analyzer. Male rats (300-400 g) injected with CP (50mg [179.1 mumols]/kg of body weight) excreted 16.7 mumols of MCA/kg in their 24-hour urine. Equivalent amounts of isophosphamide produced 9.0; triphosphamide, 16.1; ASTA-5607, 7.2; ASTA-5122, 4.1; and cytoxyl alcohol, 0.4mumols of MCA/kg. From allyl alcohol and acrolein, 26.3 and 19.7 mumols of MCA/kg were obtained respectively. MCA values were directly proportional to drug dose levels. Since acrolein and phosphorodiamidic acid mustard are the toxic decomposition products of aldophosphamide, and acrolein conjugation appears to be the first step for MCA formation values for MCA would reflect active CP levels. The in vitro interaction of acrolein with glutathione, other sulfhydryl compounds, and a few amino acids at concentrations of 0.15 mumols/ml was also studied. The decrease of acrolein's main absorption peak at 209 nm was used to follow its reaction rate. The faster interactions observed were with the sulfhydryl compounds, where a 50% decrease of absorption in interactions with glutathione and cysteine (at pH 7.4 and 23 degrees C) took place in 111 and 30 seconds respectively. Incubation of these adducts at 37 degrees C and 100 degrees C generated acrolein with a maximum recovery yield of 83% at 100 degrees C. Five patients given 1 g of CP iv excreted 6.4-50 mumols of MCA in their urine in 6 hours.

Acetylcysteine↗
PubMed1975

Studies on the metabolism of beta-hydroxy- aspartic acid.

The content of beta-hydroxyaspartic acid was measured in the urine of man and several species of animals. The configuration of urinary beta-hydroxyaspartic acid was deduced to be L-erythro in form by chromatographic comparisons with authentic samples. An increased excretion of urinary beta-hydroxyaspartic acid was observed in cats when serine or thiamine was administered with glycine. Glycine-1-14C administered to rats was incorporated into the urinary beta-hydroxyaspartic acid. The formation of beta-hydroxyaspartic acid in pig-liver homogenate increased in the presence of glutamate and thiamine pyrophosphate. These results were discussed in relation to the author's working hypothesis on the biosynthesis of beta-hydroxyaspartic acid.

Animals↗