Zeitschrift fur medizinische Laboratoriumsdiagnostik最新文献

Enzymopathies of pyruvate kinase are caused by defects of structural genes forming stable and unstable mutants, respectively. Stable mutants of PK are characterized by high S0,5 PEP and nearly unchanged Vmax. A decrease of PEP affinity can be the result from a very high allosteric constant L0 or from an increased KPEP. From the pattern of PAGE can be concluded that stable PK mutants are tetraheteromers composed of two normal and two shortened polypeptide chains. We suppose that this is the result of a mutation of a codon which stops the polypeptide synthesis of PK earlier. Most PK mutants are unstable. They are characterized by low catalytic activity and high PEP affinity. The kinetic properties of unstable mutants are changed posttranslational by proteolytic modifications. Furthermore low S0,5 PEP values result from a persistence of the isoenzyme PK-K in reticulocytes and erythrocytes, respectively. A prenatal diagnosis of PK enzymopathies can be carried out with a very small blood volume by using the method of isoelectrophoretic focussing.

Two modifications of a double antibody enzyme immunoassay for the determination of urinary albumin content are described. The method is simple, rapid and precise and can be carried out in test tubes and on microtiter plates as well. In 1:10 diluted urine samples albumin concentrations of 1.25 to 20 mg/l (corresponding to the normal range) can be determined. For a control sample with 0.3 mg/l albumin the intra- and interassay coefficients of variation were 4.9% (n = 11) and 10.4% (n = 21), respectively, on microtiter plates.

The hyperexcretion of urinary enzymes with systemic Lupus Erythematosus (SLE) was assayed. 31 patients with confirmed SLE (30 women, and 1 man, age 16-33 years) were studied. Patients were divided into two groups according to the degree of kidney damage: 21 patients with proteinuria, and 10 patients without proteinuria. 12 patients of the first group had nephrotic syndrome (NS). 30 practically healthy subjects served as a control group. In patients with Lupus-nephritis (LN) the increase of activities of urinary GGT, AP, BGRS, NAG, and CHE was observed, the increase was especially clearly shown in LN-patients with NS. The increase of activity of urinary GGT and NAG was shown in the group of SLE patients who did not have clinical and laboratory signs of LN, which can be used as early index for the damage of tubular epithelium.

Rat liver microsomes were microencapsulated in a pure aqueous medium by means of a new technique. The wall of the microcapsules consists of a semipermeable simplex membrane which is stabilized mainly by electrostatic interactions between a polymeric polyanion (sodium cellulose sulphate) and a polymeric polycation (polydimethyldiallylammonium chloride). The metabolic as well as the mechanic parameters of the microcapsules could be markedly improved by separating the metabolic (liver microsomes) from the membrane component (sodium cellulose sulphate) in such a way that two distinct compartments are formed during the preparation of the microcapsules.

The clinical usefulness of the fructosamine assay is reviewed. Problems of external standardization are discussed and possibilities to circumvent these problems are considered.

Clinical signs and the determination of thyroid autoantibodies are usually used for the classification of hyperthyroidism. We examined the usefulness of two ELISA for the determination of membrane and thyroglobulin autoantibodies. 117 patients with Graves' disease, 53 patients with toxic goitre and 47 patients with unclear hyperthyroidism were inspected. The best classification into immunogenic and nonimmunogenic hyperthyroidism were achieved with the membrane antibodies at a borderline titre of greater than 1:400. The thyroglobulin antibodies were also useful and increased the security of the classification. We conclude that both tests are suitable for the classification of patients with hyperthyroidism and should be applied to the first diagnostic step in the immunological diagnostic of the thyroid.

A modification of the original method of R.A. Johnson et al. for nonenzymatically glycated serum proteins (fructosamine test) is described. Problems of performance and optimization of the method as well as of calibration and the influence of protein composition on the results are discussed. Measuring is manually performed after a 8 min preincubation interval over a 1 min's period using the spectrophotometer "Spekol 220". Interserial precision was 3.2%. First clinical results demonstrate the possibility to assess glycemic control in type 1 diabetic patients over a integrated time interval.

A new method is described for determining the prognosis of acute myocardial infarction (AMI) progress due to temporal increase in the isoenzyme, i.e. malic dehydrogenase (MDH), aspartate aminotransferase (ASAT), lactic dehydrogenase (LDH), and the increase in the creatine kinase (CK). It is shown that the time of enzymatic activity is an essential factor. If 25 hours of increase in enzymatic activity of MDH and CK are exceeded, AMI deteriorates dramatically.