Hartmut M. Liebich

Upregulation of cholesterol synthesis after acute myocardial infarction—is cholesterol a positive acute phase reactant?

Acute myocardial infarction is associated with profound alterations in the plasma lipoprotein profile. The mechanism of these alterations is not clear, and both cholesterol biosynthesis up- and downregulation could possibly be a consequence of acute myocardial infarction. We determined plasma lipids, lipoproteins, apolipoproteins, and lathosterol-which is regarded as an estimate of whole body cholesterol biosynthesis in humans-concentrations in 34 patients (age 68+/-10 years, 24 male, 10 female) admitted to our hospital with acute MI and with onset of symptoms within the last 12 h. Samples were taken immediately after admission to the hospital, and 1, 2, and 10 days after admission. On the first day after admission there was a decrease in total cholesterol (C) by 14.1%, (P = 0.01), in LDL-C by 14.4% (P = 0.03), in HDL-C by 9.3% (NS), and in triglycerides by 19.5% (NS). Apolipoprotein B100 was reduced by 18.3% (P = 0.008), and apolipoprotein AI by 12.3% (NS). The lathosterol/cholesterol ratio was increased by 23.1% after 1 day, and by 28.7% after 2 days (P = 0.05). After 10 days, all variables except the apolipoproteins had essentially returned to baseline values. In conclusion, the changes in the plasma lipid profile after acute myocardial infarction are associated with a profound increase of whole body cholesterol biosynthesis as judged by the lathosterol/cholesterol ratio. These changes may possibly enhance the delivery of cholesterol to cells involved in tissue repair mechanisms after acute myocardial infarction.

Identification of plasticizers in medical products by a combined direct thermodesorption–cooled injection system and gas chromatography–mass spectrometry

The combination of a new thermodesorption module with a cooled injection system now provides a powerful system for direct analysis of volatile trace compounds in gaseous, liquid and solid samples by gas chromatography-mass spectrometry (GC-MS). As a cooled injection system is used for the cryofocusing of the desorbed volatiles the GC-MC system still can be used for the regular analysis of liquid samples. Although plasticizers usually are analyzed by GC-MS after solvent extraction, contaminated solvents and glassware are very well known problems. Analysis of plasticizers in plastic materials by direct thermodesorption instead saves time and avoids cross contaminations. Many medical products are made of plasticized polyvinyl chloride. Extraction of the common plasticizer di(2-ethylhexyl) phthalate (DEHP) into blood will occur, and harmful effects of DEHP in the human body have been suggested. We therefore analyzed 21 different plastic devices which are used for various invasive techniques in medicine by direct thermodesorption GC-MS. In some of the plastics up to 30 different components were identified. By far the most common plasticizer found was DEHP, followed by diethyl and dibutyl phthalates.

Gas chromatographic and gas chromatographic-mass spectrometric analysis of organic acids in plasma of patients with chronic renal failure

Apart from increased concentrations of aliphatic dicarboxylic acids and phenolic aromatic acids in plasma from patients with chronic renal failure, there is large elevation of a furanoid acid, 3-carboxy-4-methyl-5-propyl-2- furanpropionic acid, and of hippuric acid. The levels of 3-hydroxy- and 4- hydroxyhippuric acid are also raised. The quantitative results are as follows: furanoid acid in hemodialysis patients, 1.4 +/- 0.6 mg/dl; in healthy individuals, 0.2 +/- 0.1 mg/dl; hippuric acid in hemodialysis patients, 9.8 +/- 6.5 mg/dl; in health individuals, 0.4 +/- 0.5 mg/dl. Both compounds are dialysable, but less effectively than creatinine and urea. The mean elimination rate of the furanoid acid is only 21%.

Excretion pattern investigation of urinary normal and modified nucleosides of breast cancer patients by RP‐HPLC and factor analysis method

Modified nucleosides, formed post-transcriptionally in RNA by a number of modification enzymes, are excreted in abnormal levels in the urine of patients with malignant tumors. To test their usefulness as tumor markers, and to compare them with the conventional tumor markers, a reversed-phase high-performance liquid chromatographic (RP-HPLC) method and a factor analysis method have been used to study the excretion pattern of nucleosides of breast cancer patients. A clear cut differentiation of the breast cancer group and the healthy individuals in two clusters without overlapping was obtained.

Capillary electrophoresis in clinical chemistry

Since its introduction, capillary electrophoresis has diversified, spreading out into different specialized fields covering solutions for almost any analytical questions arising in research laboratories. In the context of clinical chemistry, results must be provided at low costs and in a clinically relevant time frame; however, the attributes which have made capillary electrophoresis such a successful tool in basic research are identical to those attracting clinical laboratories: speed (more efficient, less labor-intensive), low costs (minimal buffer consumption), small sample volume (reduced blood collection volume from patient), increased selectivity (determination of multiple solutes in one run), and versatility (detection of analytes over the wide range of molecular masses and chemical composition). Nevertheless, it should be mentioned that there are still some drawbacks at this stage to be solved in the near future, such as lack of sensitivity for many clinical applications or the constraint to measure in a sequential mode. The aim of this survey is to familiarize clinical chemists, as well as chemists, with a short introduction to capillary electrophoresis, followed by chapters reviewing prominent fields of applications and the latest developments in clinical chemistry.

Concentration and anlalysis of organic volatiles in skylab 4

Abstract The volatile components in the cabin atomosphere of Skylab 4 at various times during the mission were concentrated and analysed. More than 300 compounds could be detected by high-resolution gas chromatography with differences in concentration of as much as six orders of magnitude. 107 substances were identified by mass spectromety, covering a molecular-weight range of approximately 60 to more than 500. The concetration of 80 compounds were determined for three samples taken on days 11·47 and 77 of the mission. The compositionof the volatiles in the spacecrafts atmosphere differs significantly from other environments. A wide variety of various silicon compounds, mostly methylated siloxanes of molecular weight up to 584, was detected. Fluorocarbons (Freons) were also present.

Application of capillary electrophoresis in clinical chemistry: the clinical value of urinary modified nucleosides.

Urinary modified nucleosides were determined by capillary electrophoresis using a 300 mM SDS-25 mM sodium tetraborate-50 mM sodium dihydrogenphosphate buffer. The nucleosides were extracted from urine by phenylboronate affinity gel chromatography. In cancer patients the levels of the modified nucleosides are generally elevated. By an artificial neural network method breast cancer patients were differentiated from normal individuals, which indicates that the modified nucleosides could be of clinical value as tumor markers.

Analysis of trace volatile metabolites in serum and plasma

Abstract A method is described for analyzing volatile constituents in 5- to 10-ml samples of human serum and plasma. A headspace sampling technique was employed by which volatile sample constituents are carried in a stream of ultra-pure nitrogen and adsorbed onto a porous polymer with subsequent heat desorption. The concentrated volatiles were separated on highly efficient capillary columns. Mass spectrometric identifications were made with 55 ml of serum. Characteristic components in normal serum are: ethanol, 4-methyl-2-pentanone, hexanal, 1-butanol, 2-hexanol, 2-heptanone, and benzaldehyde.

Analysis of normal and modified nucleosides in urine by capillary electrophoresisa)

SummaryModified nucleosides excreted in urine have been studied as potential diagnostic markers for cancer and AIDS, and as indicators for the whole-body turnover of RNA. Until now, reversed-phase (RP) HPLC and, to some extent, immunoassays are the preferred analytical methods for urinary nucleosides. A new capillary electrophoretic method for the analysis of normal and modified nucleosides in urine has been developed and optimized in our laboratory. The separation of nucleosides extracted from normal human urine on phenyl boronic acid affinity chromatography columns was performed in uncoated 565 mm (500 mm to detection window) × 50 μm i.d. capillary tubing using a 300 mM SDS—25 mM borate—50 mM phosphate buffer (pH 6.7), a 45-s load, a voltage of 7.5 kV (41 μA) and UV detection at 260 and 210 nm. The average recovery of the nucleosides was 91 %. The calibration curves were linear over all physiological and pathophysiological concentration ranges and the limits of detection were at micromolar levels. Reproducibility of migration times were better than 1 % (coefficient of variation,CV), and the reproducibilities of the determined concentrations were better than 5 % for standards and 6–15 % for extracted urine. The developed method was used to quantify 15 normal and modified nucleosides in 25 normal urines to establish reference ranges. The analysis time was less than 45 min.

Hydroxycarboxylic and oxocarboxylic acids in urine:products from branched-chain amino acid degradation and from ketogenesis

Hydroxy- and oxomonocarboxylic acids in urine of healthy individuals and of patients with diabetic ketoacidosis are analysed as methyl esters and methyl esters/O-methyloximes, respectively, by gas chromatography and gas chromatography-mass spectrometry. The derivatives are pre-fractionated by thin-layer chromatography. The acids originate mainly from ketogenesis and from the metabolism of valine, leucine and isoleucine. The amino acid metabolites fall into three groups: the 2-oxocarboxylic acids (2-oxoisovaleric acid, 2-oxoisocaproic acid and 2-oxo-3-methylvaleric acid); the 2-hydroxycarboxylic acids (2-hydroxyisovaleric acid, 2-hydroxyisocaproic acid and 2-hydroxy-3-methylvaleric acid); and the 3-hydroxycarboxylic acids (3-hydroxyisobutyric acid, 3-hydroxyisovaleric acid, 3-hydroxy-2-ethylpropionic acid, threo-3-hydroxy-2-methylbutyric acid and erythro-3-hydroxy-2-methylbutyric acid). The threo form of 3-hydroxy-2-methylbutyric acid is the major constituent within the diastereomeric pair. Of the three groups of amino acid metabolites, the 3-hydroxycarboxylic acids in particular are elevated during ketoacidosis. The characteristic general features of the mass spectrometric fragmentation of the derivatives of the identified components are systematically described. The discussion of the fragmentation includes constituents of low concentrations, such as 3-oxocaproic acid, 4-oxobutyric acid and 5-oxocaproic acid, which can be detected only when the pre-fractionation technique is applied.