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Biomedical subjects

E H Mosbach

Publications and source records attributed to E H Mosbach.

At least 91 records · Page 5Linked to original sources
PubMed1981

Dehydroxylation of 16 alpha-hydroxyprogesterone by fecal flora of man and rat.

16 alpha-Hydroxyprogesterone, precursor of biliary 16 alpha-hydroxypregnanolone, was incubated with mixed fecal flora of humans and rats. The major steroid metabolite formed in both systems was 3 alpha-hydroxy-17 alpha-pregnan-20-one. These results demonstrated that the fecal flora reduced the delta 4-3 keto structure, removed the hydroxy group at C-16 and isomerized the side chain from the beta to the alpha configuration. Ring-A reduction of the substrate resulted in a 5 beta-compound with human flora and a 5 alpha-product with rat bacteria. The prevalence of 16 alpha-dehydroxylating organisms varied considerably in human fecal flora and was approximately 10(5)/g of feces in the three rats tested. Rat fecal flora dehydroxylated 16 alpha-hydroxyprogesterone after 4-5 days incubation at 37 degrees C, at pH 6.5-7.5, and with a substrate concentration of 20-80 microgram/ml (optimal condition). Preliminary evidence suggests that 16 alpha-dehydroxylase is exclusively of bacterial origin and is synthesized by an obligate anaerobe.

Adult↗
PubMed1981

Cofactor requiremets for 7 alpha-dehydroxylation of cholic and chenodeoxycholic acid in cell extracts of the intestinal anaerobic bacterium, Eubacterium species V.P.I. 13708.

The characteristics of 7 alpha-dehydroxylase, a bile acid-biotransforming enzyme, were determined using dialyzed cell extracts of Eubacterium sp. V.P.I. 12708. 7 alpha-Dehydroxylase was induced by cholic acid in this organism. Induction by cholic acid resulted in the differential synthesis of at least five new polypeptides with molecular weights of 77,000, two at 56,000, 27,000 and 23,500, as determined by both one and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis. The relative molecular weight of 7 alphs-dehydroxylase activity was estimated by anaerobic Bio-Gel A 1.5 M gel filtration chromatography to be 114,000. NAD+ was the only cofactor to consistently stimulate 7 alpha-dehydroxylase activity in dialyzed cell extracts. The specific activity increased 4- to 6-fold with either cholic or chenodeoxycholic acid as a substrate in the presence of NAD+. NAD+ was also required for the reduction of the delta 6-intermediate to deoxycholic acid. Other pyridine or flavin nucleotides were ineffective cofactors when added alone. Saturation kinetics for NAD+ with cholic or chenodeoxycholic acid as substrates were hyperbolic, and Lineweaver-Burk plots yielded apparent Km values of 0.13 mM and 0.006 mM, respectively. Similar kinetics were obtained with cholic acid giving an apparent Km of 25 microM. The substrate saturation curve for chenodeoxycholic acid 7 alpha-dehydroxylation indicated substrate inhibition at high concentrations of chenodeoxycholic acid (greater than 50 microM). These studies show that 7 alpha-dehydroxylase is an inducible enzyme and requires NAD+ as a cofactor in this bacterium.

Bile Acids and Salts↗
PubMed1979

Metabolism of potential precursors of chenodeoxycholic acid in cerebrotendinous xanthomatosis (CTX).

In patients with cerebrotendinous xanthomatosis (CTX), diminished cholic acid production is associated with incomplete oxidation of the cholesterol side chain and the excretion of C(25)-hydroxy bile alcohols. The aims of this investigation were 1) to provide quantitative information on the pool size and production rate of chenodeoxycholic acid by the isotope dilution technique; and 2) to investigate the possible existence of a block in chenodeoxycholic acid synthesis and explain the absence of chenodeoxycholic acid precursors in CTX. After the injection of [24-(14)C]chenodeoxycholic acid, measurements of chenodeoxycholic acid pool size and production rate in a CTX subject were, respectively, 1/20 and 1/6 as great as controls. Further, three potential precursors of chenodeoxycholic acid, namely [G-(3)H]7alpha-hydroxy-4-cholesten-3-one, [G-(3)H]5beta-cholestane-3alpha,7alpha,25-triol, and [G-(3)H]5beta-cholestane-3alpha,7alpha,26-triol, were administered to the CTX and control subjects and the specific activity curves of [G-(3)H]cholic acid and [G-(3)H]chenodeoxycholic acid were constructed and compared. In the control subjects, the two bile acids decayed exponentially, but in the CTX patient maximum specific activities were abnormally delayed, indicating the hindered transformation of precursor into bile acid. These results show that chenodeoxycholic acid synthesis is small in CTX and that the conversion of 7alpha-hydroxy-4-cholesten-3-one, 5beta-cholestane-3alpha,7alpha,25-triol, and 5beta-cholestane-3alpha,7alpha,26-triol to both chenodeoxycholic acid and cholic acid were similarly impaired.

Adult↗
PubMed1979

Reverse cross-coupling in the synthesis 3 alpha, 7 alpha-dihydroxy-5 beta-cholestanoic acid.

The present report describes the characterization of (24R and 24S)-27-nor-24-methyl-3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acids obtained in considerable amounts during the synthesis of (25RS)-3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acid by the electrolytic coupling of chenodeoxycholic acid and the half ester of methylsuccinic acid. The mixture of 24R and 24S diastereomers was resolved by analytical and preparative thin-layer chromatography and characterized by gas-liquid chromatography, proton magnetic resonance, and molecular rotation differences. For reference, the model compound, 27-nor-3 alpha, 7 alpha-dihydroxy-5 beta-cholestan-26-oic acid, was synthesized by electrolytic coupling of chenodeoxycholic acid and the half ester of succinic acid.

Cholestanols↗
PubMed1978

Chemical synthesis of 5beta-cholestane-3alpha, 7alpha, 24, 25-tetrol and its metabolism in the perfused rabbit liver.

5beta-[G-3H]Cholestane-3alpha, 7alpha, 24xi, 25-tetrol (IV) was synthesized via dehydration and peroxidation of 5beta-[G-3H]cholestane-3alpha, 7alpha, 25-triol. Following perfusion of the labeled compound in the isolated rabbit liver, the bile alcohol and bile acid metabolites secreted into the bile were identified by a combination of thin layer chromatography, gas-liquid chromatography, and gas-liquid chromatography/mass spectrometry. The following bile alcohols were tentatively identified: 5beta-cholest-23-ene-3alpha, 7alpha, 25-triol, 5beta-cholest-25-ene-3alpha, 7alpha, 12alpha, 24xi-tetrol, and 5beta-cholestane-3alpha, 7alpha, 12alpha, 24xi, 25-pentol. The amount of administered tetrol recovered unchanged ranged from 1 to 88%. Cholic acid was the major product, but limited amounts of chemodeoxycholic acid were also formed. The 24-hydroxyl group in the steroid side chain did not prevent 12alpha-hydroxylation.

Animals↗
PubMed1978

Biosynthesis of chenodeoxycholic acid: side-chain hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha-diol by subcellular fractions of guinea pig liver.

Side-chain hydroxylation of 5 beta-cholestane-3 alpha, 7 alpha diol was studied in subcellular fractions of guinea pig liver. The purity of the microsomal and the mitochrondrial fractions was determined with marker enzymes, and relatively little cross contamination between the particulate fractions was detected. Methods for the analysis of the incubation mixture by thin-layer chromatography and gas-chromatography-mass spectrometry were developed. Optimal assay conditons were established for the major hydroxylation reactions, namely the mitochondrial 26-hydroxylation and the microsomal 25-hydroxylation, It was found that the most active side-chain hydroxylation in the guinea pig was the microsomal 25-hydroxylation. The mitochondrial omega-hydroxylation was stereospecific, in that the rate of formation of (25R)-5 beta-cholestane-3 alpha, 7 alpha, 26-triol was 8 times greater than that of the 25S isomer. The microsomal "25" hydroxylation was not stereospecific under the conditions employed. It is concluded that the mitochondrial "26" hydroxylation (leading to the formation of (25R)-5 beta-cholestane-3 alpha, 7 alpha, 26-triol) plays an important role in the biosynthesis of chenodeoxycholic acid. The participation of microsomal 25-hydroxylation in the formation of chenodeoxycholic acids requires further investigation.

Animals↗
PubMed1978

Preparation and characterization of (24R and 24S)-5beta-cholestane-3alpha,7alpha,24,25-tetrols and (24R and 24S)-5beta-cholestane-3alpha,24,25-triols.

(24R and 24S)-5beta-cholestane-3alpha,7alpha,24,25-tetrols were prepared by osmium tetroxide oxidation of 5beta-cholest-24-ene-3alpha,7alpha-diol. The resulting diastereomeric tetrols were separated by thin-layer chromatography, their purity ascertained by melting point, gas-liquid chromatography and mass spectra and their structural configurations were assigned by molecular rotation measurement and circular dichroism studies. In a similar fashion, the (24R and 24S)-5beta-cholestane-3alpha,24,25-triols were prepared and their structures identified.

Cholestanols↗
PubMed1978

Metabolism of (24R and 24S)-27-nor-24-methyl-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acids and 27-nor-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid in guinea pigs.

[7beta-3H]-(24R and 24S)-27-nor-24-methyl-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acids and [7beta-3H]-27-nor-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid (C27 and C26 bile acids having the same nuclear configuration as cheno-deoxycholic acid and its precursor, 3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic-acid) were synthesized and administered intraperitoneally to bile fistula guinea pigs. The biliary bile acids formed were hydrolyzed and analyzed by thin layer chromatography, and the metabolites were identified by the inverse isotope dilution method. The results showed that both (24R and 24S)-27-nor-24-methyl-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acids were not metabolized by the liver and were excreted unchanged as their taurine and glycine conjugates whereas 27-nor-3alpha,7alpha-dihydroxy-5beta-cholestan-26-oic acid was converted to chenodeoxycholic acid.

Animals↗
PubMed1978

Intrahepatic pigment and crystal forms in patients with cerebrotendinous xanthomatosis (CTX).

Liver specimens from two patients with cerebrotendinous xanthomatosis revealed intracellular inclusions that appeared either as amorphous pigment or in a crystalloid form. The pigment was usually found in assoication with the smooth endoplasmic reticulum and occasionally free floating in the cytosol. The chemical nature of these inclusions has not yet been determined. However, the accumulation of such material may indicate the presence of nonmetabolizable bile alcohols resulting from a defect in bile acid synthesis.

Adult↗
PubMed1978

Absolute configuration of pentahydroxy bile alcohols excreted by patients with cerebrotendinous xanthomatosis: a circular dichroism study.

The absolute configurations of the C27 pentahydroxy bile alcohols present in bile and feces of two patients with cerebrotendinous xanthomatosis (CTX) were determined by circular dichroism (CD) spectroscopy. The CD spectra of 5beta-cholestane-3alpha,7alpha,12alpha,24alpha,25-pentol in the presence of Eu(fod)3 [tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyloctane-4,6-dionato) europium (III)] exhibited a negative Cotton effect and was assigned to 24R absolute configuration. Conversely, 5beta-cholestane-3alpha,7alpha,12alpha,24beta,25-pentol showed a strong positive Cotton effect and was assigned the 24S configuration. These assignments were based upon comparison with a model compound, 5-cholestene-3beta,24(R),25-triol, whose single-crystal X-ray structure has been determined. The importance of these data is to establish a structural mechanism for the conversion of 5beta-cholestane-3alpha,7alpha,12alpha,24S,25-pentol rather than 5beta-cholestane-3alpha,7alpha,12alpha,24R,25-pentol into cholic acid in man as well as in animals.

Bile↗
PubMed1978

Preparation of 24(R)- and 24(S)-5beta-cholestane-3alpha,7alpha,24-triols and 25(R)- and 25(S)-5beta-cholestane-3alpha,7alpha,26-triols by a hydroboration procedure.

This report describes a new and convenient method for the preparation of 5beta-cholestane-3alpha,7alpha,24-triol (24R and 24S) and 5beta-cholestane-3alpha,7alpha,26-triol (25R and 25S) starting from 5beta-cholestane-3alpha,7alpha,25-triol. Dehydration of the latter with acetic anhydride and glacial acetic acid yielded a mixture of 5beta-cholest-24ene-3alpha,7alpha-diol and the corresponding delta25 compound. Hydroboration and oxidation of the delta24 unsaturated bile alcohol resulted in the formation of 5beta-cholestane-3alpha,7alpha,24-triol. 5beta-Cholestane-3alpha,7alpha,26-triol and 5beta-cholestane-3alpha,7alpha-diol were obtained from the delta25 bile alcohol. In each case the bile alcohols epimeric at C-24 and C-25 were resolved by analytical and preparative thin-layer chromatography and characterized by gas-liquid chromatography, infrared-, proton magnetic resonance-, and mass spectrometry. Tentative assignment of the 24R, 24S and 25R, 25S configurations was made on the basis of molecular rotation differences. These epimeric bile alcohols will be useful for biological studies of chenodeoxycholic acid biosynthesis.

Borohydrides↗
PubMed1978

Gas-liquid chromatography-mass spectrometry of trimethylsilyl ethers of bile alcohols.

This report describes the gas-liquid chromatography-mass spectrometry (GLC-MS) of the trimethylsilyl ethers of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha-triol with mono- or dihydroxy substitution in the side chain. Compounds with 24- and 25-unsaturation in the side chain were also studied. The gas-liquid chromatographic separation of the different bile alcohols was carried out using 3% QF-1 and 1% HI-EFF 8BP as column packings. Both columns were useful in that the retention times of the trimethyl-silyl ethers of the various 5 beta-cholestanetetrols varied linearly with the position of the side-chain trimethylsiloxyl substituent. The major fragmentations in the GLC-MS of all bile alcohols tested were due to the trimethylsiloxyl side-chain substituent(s). A trimethylsiloxyl group at C-22 was the most effective in promoting side-chain fragmentation, followed, in order of decreasing effectiveness, by substituents at carbons 25, 23, 24, and 26. The side-chain fragments generally gave rise to one or two intense mass peaks and a series of weaker peaks, 90 mass units apart, owing to the loss of successive molecules of trimethylsilanol. Most 5 beta-cholestane-triols, -tetrols, and -pentols can be unequivocally identified by their strong side-chain fragmentation peaks, except for 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol, the trimethylsilyl ether of which exhibited very low intensity side-chain fragments.

Cholestanols↗
PubMed1977

Metabolism of bile alcohols in the perfused rabbit liver - C26 bile alcohols.

The metabolism of a C26 bile alcohol (I, 24-nor-5beta-cho-lestane-3alpha, 7alpha,25-triol) was studied in the isolated perfused rabbit liver. The new bile alcohol and bile acid metabolites secreted into the bile were isolated and identified by a combination of TLC, GLC and GLC-MS. The following bile alcohols were found: II, 24-nor-5beta-cholestane-3alpha,7alpha,12alpha,25-tetrol, III, 24-nor-5beta-cholestane-3alpha,7alpha,12alpha,25,26-pentol; IV, 24-nor-5beta-cholest-23-ene-3alpha,7alpha,12alpha-triol; and V, 24-nor-5beta-cholest-23-ene-3alpha,7alpha-diol. In the bile acid fraction, 24-nor-cholic acid and 3alpha,7alpha,12alpha-trihydroxy-24-nor-5beta-cholest-23-en-26-oic acid were present. The perfused nor-triol was not resistant to 12alpha-hydroxylation.

Animals↗