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Biomedical subjects

W Gerhardt

Publications and source records attributed to W Gerhardt.

At least 73 records · Page 4Linked to original sources
PubMed1979

EDTA effect on creatine kinase (CK) and on the SCE reagent.

The inclusion of EDTA in the creatine kinase reagent recommended by the Scandinavian Committee on Enzymes was shown to increase reagent stability from less than 24 h to 5 days. Part of this effect can be explained by the fact that EDTA delays the formation of inhibitory products formed when N-acetyl cysteine is oxidized. The addition of EDTA to the reagent also results in increased measured CK activity. This effect is more pronounced for CK-BB than for CK-MM. Calcium and ferric ions are shown to inhibit the enzyme and the chelation of these ions can partly explain the observed increase of CK acitivity.

Acetylcysteine↗
PubMed1979

Creatine kinase B-subunit activity in serum after immunoinhibition of M-subunit activity.

Creatine kinase (EC 2.7.3.2) B-subunit activity in serum may be routinely measured as residual activity after specific immunoinhibition of the M-subunit. We assessed the inhibition kinetics, specificity, completeness of inhibition, and inhibitory capacity of three different anti-M preparations, with use of isolated human BB, MM, and MB isoenzymes. The Scandinavian-recommended reaction system was used. We suggest a set of tentative quality requirements for anti-M for use in diagnosing acute myocardial infarction. The need to measure and subtract sample residual adenylate kinase activity was demosntrated. We describe a routine photometric method for determining B-subunit activity in serum. With the Scandinavian CK method the upper reference value for total creatine kinase in serum was found to be 150 U/L for women, 270 U/L for men. By bioluminescence, we found the upper reference value for B-subunit activity to be 6 U/L for both sexes. We discuss three different modes for applying B-subunit determinations to the diagnosis of acute myocardial infarction.

Adenylate Kinase↗
PubMed1978

Creatine kinase isoenzyme variants in human serum.

In serum from about 800 patients, total creatine kinase and its subunit B activities were determined by the recommended Scandinavian creatine kinase method in the absence and presence of a creatine kinase M subunit inhibitory antibody. Eight patients had supranormal subunit B activities, but normal or near-normal values for total creatine kinase activity. Electrophoresis of sera from these eight patients showed, in addition to the normally migrating isoenzyme MM, one or two abnormally migrating creatine kinase isoenzyme bands, located between normally migrating isoenzymes MM and MB. Experimental data suggest that these abnormal bands may be isoenzyme BB with changed electrophoretic mobility. The eight patients had no particular disorder in common.

Adult↗
PubMed1978

Creatine kinase in serum: 5. Effect of thiols on isoenzyme activity during storage at various temperatures.

We studied changes in the activity of human creatine kinase isoenzymes (native MM in serum, MM, MB, and BB preparations in serum matrix) on storage in the presence of 0, 10, 20, and 50 mmol of N-acetyl cysteine, 2-mercaptoethanol, and 1-thioglycerol per liter of serum at 37, 30, 25, 4, and -20 degrees C. We also assessed the stability of the thiols under the same conditions. We generally confirmed increasing stability in the sequence: BB, MB, and MM isoenzyme. Above 30 degrees C irreversible inactivation is very rapid, even in the presence of thiols. At lower temperatures endogenous MM is sufficiently stable; thus, the use of protective thiols can be restricted to sera expected to contain isoenzymes MB or BB. Our studies lead us to prefer use of 50 mmol of N-acetyl cysteine per liter of serum. The other thiols cause turbidity to develop earlier and their decomposittion products diminish the activity more. The initial activity of the MB and BB preparations increased by as much as 2.3- and 1.8-fold on storage with thiols. This effect was not observed with either endogenous MB and MM or with the MM prepartion.

Creatine Kinase↗
PubMed1977

Creatine kinase B-subunit activity in human serum. II. Evaluation of s-ck b-subunit activity in the diagnosis of acute myocardial infarction.

In a group of 113 consecutive patients taken into a coronary care unit on suspicion of acute myocardial infarction, blood samples were taken every 6 h and the following enzyme activities were measured: creatine kinase (S-CK), aspartate aminotransferase (S-ASAT), alanine aminotransferase (S-ALAT) and lactate dehydrogenase (S-LD). All measurements were made according to the Recommendations of the Scandinavian Committee on Enzymes. On all patients S-CK B subunit activity was determined by immunoinhibition with a specific anti CK M-subunit inhibitory antibody. At peak values of the respective total enzyme activities CK and LD isoenzymes were further qualitatively estimated by electrophoresis. The data indicate that even serial determinations of total CK, ASAT, ALAT and LD activities in serum do not provide the information required for a conclusive diagnosis of myocardial infarction in the individual case. In contrast, the positive predictive value (PV) of S-CK B was found to be 1.0 and the negative predictive value was 0.98. S-CK MB showed a PV pos. of 1.0 and also a PV neg. of 1.0. Electrophoretic determination of S-LD isoenzymes was slightly poorer with a PV pos. of 0.96 and PV neg. of 0.98. S-CK, total activity with nearly 9 per cent false positives had a positive predictive value of only 0.91, but a negative one of 1.0.

Acute Disease↗
PubMed1977

Creatine kinase in serum: 3. Further study of adenylate kinase inhibitors.

In search of an appropriate inhibitor to suppress the interference of adenylate kinase with the creatine kinase assay, we found that the combination diadenosine pentaphosphate (10 mumol/liter) and AMP (5 mmol/liter) is a better inhibitor than is fluoride (25 mmol/liter). The latter inhibits adenylate kinase uncompetitively and weakly (Ki = 2.5 mmol/liter), and must be incorporated in the starting reagent, and at 30 degrees C it becoms fully effective only after a lag phase of 6 min. In this concentration, fluoride inhibits adenylate kinase from erythrocytes, muscle, liver or platelets by 94, 92, 88, and 87%, respectively, and creatine kinase by 8%. Bromide and chloride also inhibit creatine kinase. Attempts to replace AMP by a specific inhibitor of liver adenylate kinase failed. Homologs of diadenosine pentaphosphate with either fewer or more phosphoryl groups in the polyphosphate bridge inhibited even more weakly than did the pentaphosphate. Platelets can significantly contribute to adenylate kinase activity in serum. The inhibitor combination inhibited adenylate kinase from platelets by 90%.

Adenine Nucleotides↗
PubMed1976

[Experiences in short-term dialyses with 2 capillary dialyzers in parallel and serial circuit in 2 and 3 shift operations].

It is reported on experiences made in 200 short-term dialyses with every 2 capillary dialysators. 167 dialyses of which 112 were performed by means of parallel arrangement and 55 by means of serial arrangement of the dialysators are analysed in detail. In their effectivity of dialysis the two variants proved to be nearly equivalent, in which cases the series-connection is of practical advantage. In two shifts of nurses up to 3 shifts of patients could be treated. In the large area dialysis an adaptation of the dialysate and a more intensive control of the patients must be performed. Advantages and disadvantages of this method are discussed.

Blood Pressure↗
PubMed1976

Creatine kinase in serum: 2. Interference of adenylate kinase with the assay.

Interference of adenylate kinase with Oliver's method [Biochem. J. 61, 116 (1955)] for creatine kinase is usually suppressed by including an adenylate kinase inhibitor, AMP. We studied the kinetics and compared the inhibition capacities of AMP and diadenosine pentaphosphate. Both are competitive inhibitors, AMP being markedly weaker, with a Ki of about 300 mumol/liter for adenylate kinase from erythrocyte, muscle, and liver. AMP also weakly inhibitis creatine kinase. Diadenosine pentaphosphate inhibits erythrocyte and muscle adenylate kinase strongly (Ki about 0.03 mumol/liter), the liver isoenzyme less strongly (Ki about 3 mumol/liter), and has no effect on creatine kinase up to 100 mumol/liter. All three adenylate kinases may be present in a patinet's serum, causing sample blanks to be high in a creatine kinase assay that lacks inhibitors. In acute hepatic damage, liver adenylate kinase activity in serum can be grossly increased. Use of sufficient diadenosine pentaphosphate alone for complete inhibition is relatively expensive. Consequently, we recommend a combination of both inhibitors. Diadenosine pentaphosphate, 10 mumol, combined with 5 mmol of AMP per liter inhibits adenylate kinase from erythrocytes and muscle by 97% and from liver by 95%.

Acute Disease↗