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At least 1,135 records · Page 63Linked to original sources
PubMed1988

Effect of pentoses and pentitols on fermentation of hay by mixed populations of ruminal microorganisms.

Consecutive batch culture, a technique which involves sequential transfer of cultures to fresh medium at regular intervals, was used to establish mixed ruminal-microbial populations in an anaerobic medium containing highly digestible hay. Once volatile fatty acid production was stable, perturbations were imposed in consecutive cultures by the addition of one of each of the following pentoses or analogous pentitols: l-arabinose, d-lyxose, d-ribose, d-xylose, l-arabitol, d-arabitol (lyxitol), ribitol, and xylitol. With the exception of d-lyxose, the addition of pentoses caused marked increases in propionate and valerate production, and except for d-arabitol, pentitol addition caused increases in butyrate and valerate production. On transfer to and continued incubation in the control medium, volatile fatty acid production reverted to preperturbed levels. The presence of pentitols and pentoses significantly reduced the endpoint pH of cultures and the proportion of hay that was fermented. With all added substrates, the response to the perturbation was at its maximum within one incubation (i.e., within 48 h). Similarly, the variables being monitored all returned to control levels within one incubation. On the basis of these results, it is suggested that changes were related to the need to maintain a redox balance within anaerobic cultures rather than any significant changes in the microbial population that was present.

Journal Article↗
PubMed1988

[Experimental and clinical demonstration of the antiproliferative effect of a highly purified coal tar fraction in a special gel vehicle].

In this study a combination of clinical and experimental investigations demonstrates the antiproliferative effect of the coal tar-containing preparation Berniter. From a concentration of 70 micrograms/ml onwards (= 0.35 micrograms coal tar/ml) Berniter inhibits DNA synthesis of transformed human keratinocytes in vitro. The growth inhibiting effect is reversible up to the ED50 concentration (257 micrograms Berniter/ml = 1.3 micrograms coal tar/ml). The tar-free vehicle has no identifiable effect on the proliferation of the cells at a concentration of 260 micrograms/ml. However, at higher concentrations (ED50 = 1023 micrograms/ml) the vehicle also inhibits cell growth, this inhibition being irreversible. The effect of Berniter and the tar-free vehicle on amino acid metabolism corresponds with the reduced growth rate. The ED50 concentrations (331 micrograms/ml for Berniter and 1445 micrograms/ml for the tar-free vehicle) are higher than those in the investigation of the proliferation. The clinical trial was performed in two groups of 12 and 11 patients, respectively, suffering from Psoriasis capillitii. After 3 days' topical treatment of both groups with salicylic acid for scaling, one group was treated for 4 weeks with betamethasone-17-valerate (in the following briefly called Bet-17-v), as a commercial lotion. The other group received Bet-17-v initially for 3 days and was then treated for 4 weeks with Berniter. The 4 parameters used for evaluation (erythema, scaling, infiltration and itching) showed a more significant improvement in the Berniter group than in the Bet-17-v group. Subjectively, treatment with Berniter was assessed to be preferable.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Contraluminal para-aminohippurate transport in the proximal tubule of the rat kidney. III. Specificity: monocarboxylic acids.

In order to study the specificity of the contraluminal para-aminohippurate (PAH) transport system, the inhibitory potency of monocarboxylates on the 3H-PAH influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: if a homologous series of fatty acids with increasing chain length is tested, inhibition of contraluminal PAH influx is first seen with valerate (app. Ki 1.4 mmol/l), increasing up to nonanoate (app. Ki 0.06 mmol/l) and remaining in this range up to duodecanoate, the last compound of this series which is sufficiently water-soluble. Similarly, the inhibitory potency of aromatic monocarboxylates increases with increasing hydrophobicity. If the fatty acids are esterified, their inhibitory potency is lost. If they are transformed to the respective aldehydes their inhibitory potency is preserved at a reduced degree. Introduction of a hydrophobic methyl-, ethyl-, or propyl-group increases the inhibitory potency. A beta-, but not an alpha-oxo-group augments the inhibitory potency of phenylpropionate analogs, an OH group diminishes it, and a NH2 group abolishes it. Among phenyl-fatty acids an increase in affinity is observed from phenyl- less than benzoylamine- less than phenoxy- less than benzoyl-acetate and -propionate. All monocarboxylate compounds, so far tested, do not inhibit contraluminal sulfate and Na+/succinate influx. The data indicate that the PAH transporter interacts with monocarboxylates and also with aldehydes which have a hydrophobic moiety. An additional oxo-group facilitates the interaction. Thus, the benzoyl compounds show the highest affinity observed.

Aminohippuric Acids↗
PubMed1991

Production of poly-D(-)-3-hydroxybutyrate and poly-D(-)-3-hydroxyvalerate by strains of Alcaligenes latus.

Alcaligenes latus strains can accumulate poly-D(-)-3-hydroxybutyrate (PHB) up to about 85% of cell dry weight. The abilities to store poly-D(-)-3-hydroxyvalerate (PHV) of three strains of A. latus were investigated. With Na-propionate as PHV precursor, strain A. latusDSM 1122 had better PHV accumulation ability than strains A. latus DSM 1123 and 1124. Strain A. latus DSM 1123 could store PHV when Na-valerate but not Na-propionate served as the PHV precursor. PHB and PHV accumulation by A. latus DSM 1124 rapidly increased when propionic acid and acetic acid were together added to the fermentor. This increase was not obtained in the culture shaker flask and fermentor growing the same strain when Na-propionate alone served as a PHV precursor.

Acetates↗
PubMed1975

Effect of methoxyindole 2-carboxylic acid and 4-pentenoic acid on adipose tissue metabolism.

1. Administration of methoxyindole 2-carboxylic acid to rats caused an increase in circulating free fatty acids which was associated with rapid hypoglycemia in fasted rats and liver glycogenolysis without hypoglycemia in fed rats. 2. The incorporation of labeled glucose, pyruvate and acetate carbons into triacylglycerol-glycerol, triacylglycerol-fatty acids and CO2 was inhibited in epididymal fat pads from methoxyindole 2-carboxylic acid-treated rats and by the addition of methoxyindole 2-carboxylic acid in vitro. In contrast, palmitate esterification and oxidation were enhanced by methoxyindole 2-carboxylic acid. 3. The activity of enzymes associated with fatty acid synthesis was reduced to a varying degree in the presence of methoxyindole 2-carboxylic acid in the reaction mixture in concentrations lower than those used to inhibit glucose and pyruvate metabolism in the intact tissue in vitro. 4. 4-Pentenoic acid, a potent inhibitor of pyruvate and palmitate metabolism in the liver, was considerably less effective in adipose tissue. 5. The effect of the two hypoglycemic substances investigated on adipose tissue metabolism seems to be different.

Acetates↗
PubMed1983

A new biosynthetic route of porphyrin precursors in common between animals and plants.

An additional enzyme, 4-oxo-5-hydroxyvalerate (OHV) dehydrogenase was identified and characterized. This enzyme catalyzes the conversion of OHV to 4,5-dioxovalerate, a direct precursor of 5-aminolevulinate. The enzyme was partially purified from rat liver supernatant as two isoenzyme (ca. 40,000 and 70,000 dalton). 5-Aminolevulinate was formed from OHV via 4,5-dioxovalerate by this dehydrogenase and alanine-4,5-dioxovalerate aminotransferase (EC 2.6.1.43). This dehydrogenase required NADP or NAD as a hydrogen acceptor. The enzyme was heat sensitive and catalyzed the reaction reversibly. The dehydrogenase was present in the high speed supernatants of liver and kidney of rat, rabbit and human, and that of spinach leaf.

Alcohol Oxidoreductases↗
PubMed1987

Nonenzymatic synthesis of delta-aminolevulinate (ALA) by cobalt (Co++).

Cobalt, a metal known to modulate the heme biosynthetic enzymes, is shown to be capable of catalysing the formation of ALA through a transamination reaction. The transamination reaction follows a double-displacement reaction kinetics. Further, it has also been shown that the product of the reaction catalysed by cobalt can be used by the enzyme ALA dehydratase as the substrate in the formation of porphobilinogen. The formation of ALA by cobalt can be inhibited by the intermediates of the heme biosynthetic pathway, mainly protoporphyrin. Heme, on the other hand, does not have any effect on the reaction at all concentrations tested.

Alanine↗
PubMed1989

Glutathione conjugation of the alpha-bromoisovaleric acid enantiomers in the rat in vivo and its stereoselectivity. Pharmacokinetics of biliary and urinary excretion of the glutathione conjugate and the mercapturate.

The glutathione (GSH) conjugation of (R)-and (S)-alpha-bromoisovaleric acid (BI) in the rat in vivo, and its stereoselectivity, have been characterized. After administration of racemic [1-14C]BI two radioactive metabolites were found in bile: only one of the possible diastereomeric BI-GSH conjugates, (R)-I-S-G (35 +/- 2% of the dose), and an unidentified metabolite "X" (6 +/- 1%). In urine, only one of the possible BI-mercapturates, (R)-I-S-MA (14 +/- 1%), minor unidentified polar metabolites (5 +/- 1%) and unchanged BI (13 +/- 2%) were excreted. When (R) or (S)-BI were administered separately, the same metabolites were found. However, a ten-fold difference in excretion half lives of the biliary metabolites was observed following (S)-and (R)-BI administration, (S)-BI being more rapidly excreted. The excretion of the mercapturate in urine shows the same difference in excretion rate: its half life after administration of (R)-BI was more than 10 times longer than after a dose of (S)-BI. More of the dose of (S)-BI was excreted after 5 hr in bile and urine: 58% and 23% respectively for (S)- and (R)-BI. Therefore, a pronounced stereoselectivity in GSH conjugation exists for the (R) and (S) enantiomers of BI in the rat in vivo, which is a major determinant of their pharmacokinetics. The results suggest that (slow) inversion of the chiral centre of BI occurred in the rat in vivo.

Acetylcysteine↗
PubMed1976

Microdetermination of methylmalonic acid and other short chain dicarboxylic acids by gas chromatography: use in prenatal diagnosis of methylmalonic acidemia and in studies of isovaleric acidemia.

We have developed a sensitive gas-chromatographic method for the determination of methylmalonic acid and other short chain dircarboxylic acids in biological samples. The method is based on the isolation of the short chain dicarboxylic acid fraction by Dowex 3 X 4 column chromatography followed by gas-chromatography analysis of these acids as methyl esters. 2-n-Pentyl-malonic acid is used as an internal standard. With this method, methylmalonic, succinic and methylsuccinic acids were consistently detected and accurately measured in urine and serum from normal subjects; the identity of these acids being verified by mass spectroscopy. The method's sensitivity permitted its used in the prenatal diagnosis of methylmalonic acidemia by measuring methylmalonic acid in urine and amniotic fluid from three pregnant heterozygous women at risk. One affected (vitamin B-12 responsive type) and two unaffected fetuses were correctly diagnosed prenatally as judged by postnatal investigations. The amount of methylmalonic acid in urine and amniotic fluid was distinctly increased (2 to 14 times normal) in the former and consistently normal in the latter two cases during the third trimester of pregnancy. Effect of prenatal therapy with large doses of vitamin B-12 was closely followed in the first case using analyses of multiple maternal urine specimens. Urinary methylsuccinic acid excretion was studied in two cases with isovaleric acidemia. It was normal in a sample from a patient in remission but was increased seven fold over control during an episode of ketoacidosis.

Adult↗
PubMed1982

Increased excretion of lactate, glutarate, 3-hydroxyisovalerate and 3-methylglutaconate during clinical episodes of propionic acidemia.

Metabolic changes dependent upon clinical conditions were studied in an eight-month-old girl with propionyl CoA carboxylase deficiency. Only methylcitric acid and 2-methyl-3-oxovaleric acid were detected in the urine of the patient under clinically favorable conditions. During episodes of clinical decompensation, she excreted increased amounts of all the metabolites associated with this disorder. Four acetyl CoA precursors increased during clinical episodes: glutaric acid, a catabolic intermediate of lysine; 3-hydroxyisovaleric acid and 3-methylglutaconic acid, catabolic intermediates of leucine; and lactic acid. This suggests that under clinically favorable conditions the patient has an altered propionate metabolism which proceeds via normal acetyl CoA metabolism with sufficient capacity for acetyl CoA plus propionyl CoA metabolism. When the production of propionyl CoA exceeds the metabolic capacity, however, the catabolism of potent ketogenic amino acids is effectively suppressed in order to reduce acetyl CoA production.

Amino Acid Metabolism, Inborn Errors↗