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Biomedical subjects

E Egger

Publications and source records attributed to E Egger.

At least 163 records · Page 9Linked to original sources
PubMed1977

Suitability of commercial enzyme control sera for the quality control of activity determinations of L-aspartate aminotransferase and L-alanine aminotransferase in human serum.

Details of a systematic approach to suitability testing of commercial control sera are given for substrate optimized L-aspartate aminotransferase and L-alanine aminotransferase methods at 37 degrees C. Their acceptability for control purposes of standardized methods depends on: (1) the range of control values in relation to borderline values, (2) stability, (3) aspect, clarity, (4) NADH consumption in preincubation time, (5) blank activities, (6) kinetic data as half saturation constants and saturation curves, (7) influence of effectors, (8) isoenzyme pattern. These evaluation criteria are proposed for suitability testing. The term "representativeness" should be introduced as a special criterion for main characteristics of control materials. The authors want to point out the close connection with standardization of methods.

Absorption↗
PubMed1977

Pyridoxal 5'-phosphate as an activator of the apoenzyme of alanine aminotransferase in human serum.

The relationship between reaction conditions and the stimulation of alanine aminotransferase by pyridoxal 5'-phosphate was investigated. Reaction conditions given for optimized alanine aminotransferase measurements are also optimal for measurements in the presence of pyridoxal 5'-phosphate taking into consideration the inhibitory effect of phosphate buffer. Addition of 150 mumol/1 pyridoxal 5'-phosphate to the reaction mixture guarantees a maximal stimulation after a pre-incubation period of 10 min. Factors influencing the magnitude of stimulation rates of both aminotransferases in different patient groups by pyridoxal 5'-phosphate are discussed.

Alanine Transaminase↗
PubMed1976

Influence of auxiliary enzymes on the spectrophotometric measurement of alanine aminotransferase and aspartate aminotransferase activities.

We investigated the enzyme activity of the blank in the spectrophotometric determination of the aminotransferase activities and aspartate aminotransferase activity. 6 lactate dehydrogenase and 3 malate dehydrogenase preparations from different manufactures and from different organs showed additional and contaminating activity. The additional activity depends upon the 2-oxoglutarate concentration. The contaminating activity is caused by alanine aminotransferase and aspartate aminotransferase in the auxiliary enzymes. We propose that exact definitions must be given for the auxiliary enzymes in the recommendations of standard determinations for enzyme activities.

Alanine Transaminase↗
PubMed1976

[A simple method for the synthesis of phosphatidylcholine with the fatty acid substituted in the 2-position].

The preparation of PC with the 14C-fatty acids palmitic, stearic, oleic and linoleic acid at OH-group in position 2 is described. The starting material is egg yolk lecithin. By the attack of snake venom phospholiphase lyso-PC is produced which is reacylated by the appropriate fatty acid anhydride. In comparison with the methods published up to now this preparation has the advantage of higher yields and greater simplicity. By means of in vivo synthesis it is impossible to get PC species with only one fatty acid in a defined position. Working with radioactive fatty acids the specific radioactivity can be adapted to the requirements. The procedure can be made on a semi-technical scale.

Carbon Radioisotopes↗
PubMed1975

Fatty acid pattern of lipids in normal and dystrophic human muscle.

The fatty acid distribution of the main lipid fractions: triglycerides (TG), phosphatidylcholine (PCh), phosphatidylethanolamine (PE), and sphingomyelin (Sph) of muscle from 6 patients with progressive muscular dystrophy (p.m.d.), Duchenne, 8 to 12 years old was estimated and compared with normal controls of different age. In view of the results of several authors about varied fatty acid distribution in immature muscle a third group comprising samples of neonatal muscle was studied. 1. The fatty acid pattern of the lipid fractions TG, Sph, and PE from muscle of patients with p.m.d. shows no important variation in comparison to normal controls. In contrast to this the fatty acid distribution in PCh is extremely varied: the percentage of 18:2 is decreased and corrrespondingly the content of 18:1 is increased. In view of the high percentage (nearly 10%) in which linoleic acid is substituted by oleic acid in PCh, effects on the plasma membrane are to be expected. 2. The fatty acid pattern in neonatal muscle shows in narly all positions of the fractions TG, Sph, PE, and PCh a different distribution from normal or dystrophic muscle. In view of the most important variation in dystrophic muscle it must be stated that generally 18:2 is decreased. This deficit was replaced by an increase of all other fatty acids (not only at a substitution by 18:1 as given in p.m.d.). Therefore the diminished content of linoleic acid in PCh of neonatal and dystrophic muscle cannot be interpreted as expression of a corresponding or similar lipid metabolism in both tissues. The results were seen as signs of significant qualitative alterations especially of PCh in p.m.d. They were discussed as proof of our thesis that the basic defect in p.m.d. concerns the specific acylation of PCh with linoleic acid.

Adult↗
PubMed1975

[The influence of pyridoxal 5'-phosphate on the temperature relationships of aspartate aminotransferase isoenzymes].

The relationship between temperature and the behaviour of aspartate aminotransferase was investigated in the presence of pyridoxal 5'-phosphate. The addition in vitro of pyridoxal 5'-phosphate caused an increase in the activity and altered the thermal behaviour of aspartate aminotransferase. In choosing the temperature for the determination of enzymic activity, the concentration of the coenzyme must therefore also be considered.

Aspartate Aminotransferases↗
PubMed1975

[Influence of temperature on enzyme activity determination in serum : L-aspartate aminotransferase isoenzymes].

The influence of temperature on activity assays of the isoenzymes of L-aspartic aminotransferase in described. For this purpose, isolated human isoenzymes were added to inactivated serum. Half-saturation constants were determined at 17.8 degrees C, 25 degrees C, 30 degrees C, and 37 degrees C, and the substrate saturation and pH curves were recorded. The cytoplasmatic (c) and mitochondrial (m) GOT showed temperature-dependent differences in the half-saturation constants for the substrates L-aspartate and 2-oxoglutarate. For both isoenzymes pH 7.4 is considered the optimum regardless of the temperature of measurement, and Tris-HCl is the optimal buffer. In the Arrhenius plot there is a bent at 27 degrees C for both isoenzymes. Thermal denaturation as a possible reason for this deviation from the linearity in the Arrhenius plot could be ruled out.

Aspartate Aminotransferases↗
PubMed1975

[Phosphatidylcholine transfer between liposomes and mitochondria. Testing system for the study of specific phospholipid exchange].

A system consisting of liposomes and mitochondria for studying the exchange of specific phospholipids is described. The liposomes were prepared from phosphatidylcholine labelled with 14C-palmitic acid. The transfer of liposomes to the mitochondria is specifically stimulated 2- to 3fold by the pH 5.1 supernatant, and proceeds in a linear fashion for 90 min.

Animals↗