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At least 469 records · Page 26Linked to original sources
PubMed1983

Isovalerylglucuronide, a new urinary metabolite in isovaleric acidemia. Identification problems due to rearrangement reactions.

Isovaleryl-beta-D-glucuronide, a new metabolite in the urine of patients with isovaleric acidemia, is described. Its gas chromatographic and mass spectrometric parameters are presented. In alkaline solution this glucuronide exhibited intramolecular rearrangements, resulting in isomers bearing the acyl moiety on C-2, C-3 and C-4. The isomers showed similar mass spectra but different positions on the gas chromatogram. In the index patient isovalerylglucuronide was a main metabolite, but the excretion was a transient phenomenon. Only traces of isovalerylglucuronide could also be detected in the urine of three other patients with isovaleric acidemia. The significance of this metabolite for the detoxication of isovalerate in isovaleric acidemia is discussed.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

A simple method of determining 4-hydroxyisovaleric acid and its level in a patient with isovaleric acidemia.

We developed a simple and rapid method for the quantitative determination of 4- hydroxyisovaleric acid using the conversion of this acid to the corresponding lactone,and measured its levels in the plasma of a patient with isovaleric acidemia during an episode of severe ketoacidosis. 4-Hydroxyisovaleric acid reached a peak two days after plasma isovaleric acid was at its highest level.

Acidosis↗
PubMed1996

Unusual dehydrations in anaerobic bacteria: considering ketyls (radical anions) as reactive intermediates in enzymatic reactions.

Dehydratases have been detected in anaerobic bacteria which use 2-, 4- or 5-hydroxyacyl-CoA as substrates and are involved in the removal of hydrogen atoms from the unactivated beta- or gamma-positions. In addition there are bacterial dehydratases acting on 1,2-diols which are substrates lacking any activating group. These enzymes contain either FAD, or flavins + iron-sulfur clusters or coenzyme B12. It has been proposed that the overall dehydrations are actually reductions followed by oxidations or vice versa mediated by these prosthetic groups. Whereas the gamma-hydrogen of 5-hydroxyvaleryl-CoA is activated by a transient two-election alpha, beta-oxidation, the other substrates are proposed to require either a transient one-electron reduction or an oxidation to a ketyl (radical anion).

Acyl Coenzyme A↗
PubMed1981

Gemfibrozil--the effect of biliary cholesterol saturation of a new lipid-lowering agent and its comparison with clofibrate.

Clofibrate is known to increase cholesterol saturation of bile and the prevalence of gallstones. We studied 10 healthy volunteer subjects to determine the effect of gemfibrozil (a new lipid-lowering agent) on biliary cholesterol saturation and to compare it with that of clofibrate. Biliary cholesterol saturation indices were calculated on fasting duodenal bile samples collected before and after administration of each drug for 4 weeks using a 4-week "washout" period between each preparation. There was a statistically significant rise in the cholesterol saturation index from a control value, taken as the mean of 2 samples, of 1.226 (0.785--1.526), median (range), to 1.547 (0.807--1.781) after clofibrate, P less than 0.05, but the rise to 1.352 (0.840--2.686) after gemfibrozil was not significant. However, direct comparison of the cholesterol saturation indices on clofibrate and gemfibrozil revealed no statistically significant difference. Only prospective clinical trials will establish definitively the risk of cholelithiasis on gemfibrozil but these results suggest that this drug is unlikely to have an advantage over clofibrate in this respect.

Bile↗
PubMed1982

Light and electron microscopy of liver in hyperlipoproteinemic patients under long-term gemfibrozil treatment.

The effects of long-term gemfibrozil (Lopid) therapy on human liver structure are not known. Studies of this nature are becoming essential in determining the risk/benefit ratio since gemfibrozil is an effective agent for the control of hyperlipoproteinemia types IIa, IIb, and IV. Particularly, gemfibrozil is effective when dietary management or available therapeutic control fail to reduce serum cholesterol and triglycerides as well as normalizing the lipoprotein pattern. Percutaneous liver biopsies of 9 patients on long-term gemfibrozil therapy were evaluated by light microscopy, interference contrast optics and transmission electron microscopy. The distribution of patients according to lipoprotein phenotype was 3 Type IIa, 3 Type IIb, and 3 Type IV. Their lipoprotein patterns approached normal and the serum lipids were controlled during gemfibrozil therapy. By light microscopy, the lobular architecture and other parameters were within normal limits. Varying degrees of fatty change were found as would be expected. No preferential lobular disposition of the fat globules was evident. Coalescence of fat droplets, nuclear displacement and fatty cysts were noted. Differential interference contrast microscopy revealed several degrees of contrast amplitude in these droplets suggesting a heterogeneous lipid deposition in hepatocytes. The subcellular analysis revealed a moderate degree of glycogen deposition, absence of nuclear abnormalities and unremarkable mitochondria; the rough endoplasmic reticulum was not significantly altered and smooth surfaced membranes appeared proliferated. Detailed analysis of the peroxisome population showed matrix rarefaction, marginal plate formation and spurious densities though no significant proliferation occurred. Distribution of peroxisomes in hepatocytes varied widely from cell to cell and in different lobular areas. This study confirmed the association of hepatic fatty change with hyperlipoproteinemia irrespective of the pattern observed in circulating lipoproteins. Peroxisome proliferation, as seen in rodents when receiving gemfibrozil, did not occur and the structure of these subcellular organelles was not compromised. It was concluded that the long-term administration of this compound did not show adverse effects on the hepatocyte in hyperlipoproteinemia.

Gemfibrozil↗
PubMed1993

Glutamatergic and non-glutamatergic responses evoked in neonatal rat lumbar motoneurons on stimulation of the lateroventral spinal cord surface.

The effects on lumbar motoneurons of thoracic cord stimulation were investigated in the neonatal rat hemisected spinal cord in vitro using intracellular recording. Four responses were evoked--a fast, excitatory postsynaptic potential, a second component to the fast excitatory postsynaptic potential, a fast inhibitory postsynaptic potential and a slow excitatory postsynaptic potential. The fast (CNQX-sensitive) excitatory postsynaptic potential was probably monosynaptic, was blocked by CNQX, (10 microM) and showed a frequency-dependent run-down at stimulation frequencies between 0.1 and 1 Hz. A slower component to the fast excitatory postsynaptic potential ((+-)-2-amino-5- phosphono-valeric acid-sensitive excitatory postsynaptic potential) was blocked by (+-)-2-amino-5-phosphonovaleric acid (50 microM). Following fast excitatory postsynaptic potential blockade with both CNQX and (+-)-2-amino-5-phosphonovaleric acid, a fast inhibitory postsynaptic potential was revealed. This reversed at a membrane potential close to resting and was incompletely blocked by either bicuculline (30 microM) or strychnine (10 microM). The slow excitatory postsynaptic potential was a delayed depolarization associated with a small increase in input resistance (20%) and was insensitive to block by CNQX and/or (+/-)-2-amino-5-phosphonovaleric acid. It increased in amplitude on membrane depolarization and decreased on hyperpolarization and was potentiated by cocaine (3 microM) and citalopram (0.1 microM), but not by desipramine (5 microM). The slow excitatory postsynaptic potential was blocked by ketanserin (1 microM) and by LY 53857 (1 microM). It is concluded that a non-glutamatergic transmitter is involved in generating the slow excitatory postsynaptic potential possibly 5-hydroxytryptamine acting at 5-hydroxytryptamine 2 receptors.

2-Amino-5-phosphonovalerate↗
PubMed2004

Synthesis and properties of methyl 5-(1'R,2'S)-(2-octadecylcycloprop-1-yl)pentanoate and other omega-19 chiral cyclopropane fatty acids and esters related to mycobacterial mycolic acids.

A 23-26-carbon chain length range of omega-19 (1'R,2'S) cyclopropane fatty acids, related to mycobacterial mycolic acids, has been prepared. The key cyclopropyl intermediate, (1'R,2'S)-(Z)-1-formyl-2-octadecylcyclopropane, underwent Wittig chemistry with various reagents to provide vinylic precursors, which were selectively reduced to the corresponding saturated omega-19 cyclopropane fatty acids or esters. The 24-carbon omega-19 cyclopropane ester was made by chain elongation of the 23-carbon ester. Saturated and unsaturated chiral cyclopropane acids and esters were assayed, using wall extracts of Mycobacterium smegmatis; the incorporation of 14C-acetate was used to measure inhibition or stimulation of mycolic acid synthesis. Minor inhibition (2-3%) was shown by the 23- and 24-carbon saturated esters; all the other compounds were stimulants. The most effective (38-55%) stimulators of mycolate synthesis were the unsaturated esters with 23- and 26-carbons and the saturated and unsaturated 25-carbon acids.

Carbon Isotopes↗
PubMed2000

Enantiomeric separation and discrimination of 2-hydroxy acids as O-trifluoroacetylated (S)-(+)-3-methyl-2-butyl esters by achiral dual-capillary column gas chromatography.

An efficient method is described for the simultaneous enantiomeric separation of 18 different racemic 2-hydroxy acids for the determination of their absolute configurations. It involves the conversion of each enantiomer into a diastereomeric O-trifluoroacetylated (S)-(+)-3-methyl-2-butyl ester for the direct separation by achiral dual-capillary column gas chromatography with subsequent identification and determination of its chirality by retention index (I) library matching. The enantiomers of each acid were well separated with high resolution values (R > or = 1.4) on DB-5 and DB-17 columns of different polarity. When temperature-programmed I values of 2-hydroxy acid enantiomers as their diastereomeric derivatives were measured on both columns, the I values were characteristic of each enantiomer. Simple I matching with the reference values was thus useful in cross-checking each acid enantiomer for the identification and chiral discrimination. When applied to urine samples, the present method allowed positive identification of most of the spiked 2-hydroxy acids from normal urine and for endogenous (S)-lactic acid and (S)-2-hydroxybutyric acid from a clinical urine specimen.

Chromatography, Gas↗