Biomedical subjects

A Mlakar

Publications and source records attributed to A Mlakar.

5 recordsLinked to original sources

PubMed1997

2-Hydroxy-succinaldehyde, a lipid peroxidation product proving that polyunsaturated fatty acids are able to react with three molecules of oxygen.

2-Hydroxy-succinaldehyde was detected by a GC/MS analysis of trapped aldehydic compounds obtained after Fe2+/ascorbate lipid peroxidation of arachidonic acid. Precursor molecules of aldehydes are hydroperoxy compounds. Thus the generation of the two aldehydic groups in 2-hydroxysuccinaldehyde requires a precursor molecule with two hydroperoxy groups. The hydroxy group in 2-position is generated by a third hydroperoxidation reaction. The detection of 2-hydroxysuccinaldehyde--although found only in traces--is the first example for triple dioxigenation of unsaturated fatty acid. Linolenic acid produces 2-hydroxysuccinaldehyde in much lower amounts than arachidonic acid. A similar oxidation of linoleic acid was not observed.

Aldehydes↗

PubMed1996

Previously unknown aldehydic lipid peroxidation compounds of arachidonic acid.

Arachidonic acid was oxidized by iron ascorbate. Samples were withdrawn in time intervals. The aldehydic oxidation products were trapped by preparation of pentafluorbenzyloximes. Their trimethylsilylated derivatives were subjected to analysis by GC/MS. The main aldehydic lipid peroxidation product was found to be the well-known 4-hydroxy-2-nonenal (HNE), but 2-hydroxy heptanal (HH) -- a previously unknown lipid peroxidation product of arachidonic acid -- was detected to be nearly equally abundant. Malondialdehyde (MDA), glyoxal and 2-hydroxy-4-decenal (HDE) were detected to be produced in up to 100 times lower amounts compared to HNE. The amounts of aldehydes increased steadily with time. In addition, n-l-hydroxy-n-oxo acids were detected. Similar aldehydes were obtained by iron ascorbate-induced oxidation of hydroxy acids derived by NaBH4-reduction of 13-hydroperoxy-9-cis-11-trans-octadecadienoic acid. Since this and analogous hydroxy acids (LOHs) are the main biological degradation products of hydroperoxides of unsaturated acids (LOOHs) their further peroxidation seems to be a main source of toxic aldehydes.

Acetamides↗

PubMed1996

Iron (II) ions induced oxidation of ascorbic acid and glucose.

Lipid peroxidation (LPO) of polyunsaturated fatty acids (PUFAs) is suspected to be involved in the generation of chronic diseases. A model reaction for LPO is the air oxidation of PUFAs initiated by Fe2+ and ascorbic acid. In the course of such model reactions glycolaldehyde (GLA) was detected as main aldehydic product. Since it is difficult to explain the generat on of GLA by oxidation of PUFAs, it was suspected that GLA might be derived by oxidation of ascorbic acid. This assumption was verified by treatment of ascorbic acid with Fe2+. Produced aldehydic compounds were trapped by addition of pentafluorobenzylhydroxylamine hydrochloride (PFBHA-HCl), trimethylsilylated and finally identified by gas chromatography/mass spectronetry (GC/MS). Oxidation of ascorbic acid with O2 in presence of iron ions produced not only glycolaldehyde (GLA), but also glyceraldehyde (GA), dihydroxyacetone (DA) and formaldehyde. Glyoxal (GO) and malondialdehyde (MDA) were detected as trace compounds. The yield of the aldehydic compounds was increased by addition of lipid hydroperoxides (LOOH) or H2O2. The buffer influenced the reaction considerably: Iron ions react with Tris buffer by producing dihydroxyacetone (DA). Since ascorbic acid is present in biological systems and Fe2+ ions are obviously generated by cell damaging processes, the production of GLA and other aldehydic components might add to the damaging effects of LPO. Glucose suffers also oxidation to short-chain aldehydic compounds in aqueous solution, but this reaction requires addition of equimolar amounts of Fe2+ together with equimolar amounts of H2O2 or 13-hydroperoxy -9-cis-11-trans-octadecadienoic acid (13-HPODE). Therefore this reaction, also influenced by the buffer system, seems to be not of biological relevance.

Aldehydes↗

PubMed1994

Reinvestigation of lipid peroxidation of linolenic acid.

Recently, we deduced a mechanism for lipid peroxidation of linoleic acid [1]. This mechanism was now applied to predict the occurrence of previously unknown lipid peroxidation products of linolenic acid. The proposed structures of peroxidation products allowed to search for these predicted compounds in reaction mixtures with the aid of 'ion trace' by mass spectrometry. Thus, a great number of previously unknown lipid peroxidation products was detected. It is assumed that these compounds also occur--at least as intermediates--in lipid peroxidation processes in mammalian tissue.

Gas Chromatography-Mass Spectrometry↗

PubMed1982

[Massive transfusion].

Data about the definition of massive transfusion are given. The physiological changes during conservation of blood are reviewed and the effects of stored blood transfusion are stressed. The massive transfusion cases in 1979 are presented (in materials of five surgical departments) and the patient's condition during and after the massive transfusion analyzed. There was no correlation between volume of massive transfusion and frequency of complications during intensive therapy treatment. The group of patients transfused with transfusion pump showed better results.

Adult↗