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Biomedical subjects

J C Hafkenscheid

Publications and source records attributed to J C Hafkenscheid.

At least 55 records · Page 3Linked to original sources
PubMed1984

Serum trypsin, alpha-amylase and lipase during bombesin stimulation in normal subjects and patients with pancreatic insufficiency.

The effect of infusion of bombesin (60 pmol/kg 20 min) on pancreatic enzymes in serum was studied in 13 normal subjects and 12 patients with pancreatic insufficiency. In normal subjects administration of bombesin induced large increases in serum trypsin (p less than 0.01), while serum total alpha-amylase and pancreatic alpha-amylase did not change and serum lipase showed only a modest rise (0.01 less than p less than 0.05). Patients with pancreatic insufficiency had significantly lower serum concentrations of all enzymes studied (p less than 0.01) and in such patients bombesin did not change the concentrations of pancreatic enzymes in serum. It is concluded that determination of the serum trypsin response to bombesin may be of help in the diagnosis of pancreatic insufficiency.

Adolescent↗
PubMed1984

Kits for enzyme determinations compared: relation between composition and quality.

Kits of five different suppliers, composed according to the Dutch recommendations for determination of the enzyme activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, gamma-glutamyltransferase, alkaline phosphatase, and creatine kinase, were intercompared. Activity concentrations of the enzymes in human sera were measured under defined conditions, evaluated, and related to the actual composition of the kits. Concentrations of all kit components were determined by various analytical techniques. The overall results of the activity measurements and the composition of at least three kits inter-agree well. We found deviations as great as 10% in our analytical evaluation of the kits of the other two suppliers, which can partly be accounted for.

Alanine Transaminase↗
PubMed1984

Influence of substrate concentration on the activation of transketolase, aspartate aminotransferase, and glutathione reductase by coenzymes.

We investigated the mechanism by which the three most commonly measured enzymes in erythrocytes are activated by their respective coenzymes by determining the catalytic activity concentrations of transketolase (EC 2.2.1.1), aspartate aminotransferase (EC 2.6.1.1), and glutathione reductase (EC 1.6.4.2) in relation to various substrate concentrations. We conclude that the underlying mechanisms by which the enzymes are activated are not the same.

Aspartate Aminotransferases↗
PubMed1983

Stability test of six enzymes for internal quality control.

The daily quality control for the determination of the catalytic activity concentrations of enzymes is an important aspect in clinical chemistry. Instead of the expensive, commercially available control sera, we have looked for a simple, reliable and cheap method for the quality control of enzyme determinations. Commercially available enzymes were suspended in an albumin solution and ampoules were filled with 1.0 ml of these various solutions. The ampoules were stored at 4 degrees C or -20 degrees C. Once a week, during 10 months, catalytic activities of these enzyme-albumin solutions were determined together with the same activities in freshly reconstituted control sera. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine kinase and gamma-glutamyltransferase were determined at 30 degrees C according to well-described methods. alpha-Amylase was determined with the Phadebas method at 37 degrees C. Except for creatine kinase, the stability and reliability of these enzyme solutions are fully comparable with control sera during the experimental period. The catalytic activity concentration of creatine kinase decreased slowly during the 10 months. The enzyme solutions react in the same manner as commercial test sera on changes in the reaction conditions for the enzyme determinations. The conclusion seems justified that these enzyme solutions can be used for the daily quality control of the enzyme determinations instead of control sera.

Alanine Transaminase↗
PubMed1983

Determination of alpha-amylase, trypsin and lipase in duodenal fluid: comparison of methods.

The three most important enzymes present in duodenal fluid, alpha-amylase, trypsin and lipase, were determined by two different methods. Various dilution fluids for these determinations were compared. Some kinetic data are described together with the reproducibility of the assays. For alpha-amylase the Phadebas method was compared with an UV method. Trypsin was determined using an immunoreactive trypsin test and a titrimetric method, while lipase was determined with a titrimetric method and a Cu-soap method. There was very good agreement between the two alpha-amylase methods and between the two trypsin determinations. There was also good agreement between both lipase methods. The advantages and disadvantages of all the methods are discussed.

Amylases↗
PubMed1983

Apoenzyme content of serum aminotransferases in relation to plasma pyridoxal-5'-phosphate concentration.

To investigate the considerable variation in stimulation of serum aminotransferase activities by pyridoxal-5'-phosphate added in vitro, we determined the pyridoxal-5'-phosphate content of plasma, using the tyrosine decarboxylase reaction together with the catalytic activities of alanine aminotransferase and aspartate aminotransferase, with and without pyridoxal-5'-phosphate supplementation, within a group of normal human individuals. We found a very significant inverse linear relationship between plasma pyridoxal-5'-phosphate concentration and stimulation of the activities of these enzymes in serum after supplementation with pyridoxal-5'-phosphate. We conclude that the degree of stimulation of the apoenzyme of the two serum aminotransferases clearly depends on the pyridoxal-5'-phosphate concentration in vivo.

Apoenzymes↗
PubMed1982

Influence of pyridoxal-5'-phosphate on temperature relationship of aspartate aminotransferase and alanine aminotransferase.

The influence of pyridoxal-5'-phosphate on the temperature relationship of aspartate aminotransferase and alanine aminotransferase has been determined. On varying the reaction temperature from 25 degrees to 45 degrees both enzymes showed small but significant deviations from a linear Arrhenius relationship. Supplementation with pyridoxal-5'-phosphate in general enhanced the catalytic activity to the same degree over the entire temperature range. Our results corroborate the findings of Rej but not those of Jung et al.

Alanine Transaminase↗
PubMed1981

Renal excretion of sulphamethoxazole and its metabolite N4-acetylsulphamethoxazole in patients with impaired kidney function.

Plasma and urine concentrations of creatinine, sulphamethoxazole and its metabolite N4-acetylsulphamethoxazole were measured in patients with varying degrees of kidney impairment. The plasma elimination half-life of sulphamethoxazole is not influenced by the kidney function, while the half-life of the metabolite is fully dependent on the kidney function. The renal clearances of the metabolites and that of the parent compound under alkaline urine conditions are linearly related to the creatinine clearance. Kidney impairment affects only the renal clearance of the metabolite, whereas sulphamethoxazole is metabolized (acetylated) independently of kidney function.

Acetylation↗
PubMed1981

Effect of starvation of the synthesis rate of albumin in vivo and its relation to the concentrations of amino acids in the peripheral blood, the portal circulation and in the liver cytosolic fraction.

The synthesis rate of albumin was measured in vivo by the 14C-carbonate method in fed control rabbits, in animals after a short-term fast (24-36h), and after starvation for 8 days. The albumin synthesis rate was significantly lower in animals after a short-term fast in comparison to the fed control group. A starvation for a longer period did not further decrease the synthesis rate of albumin. The serum concentrations of essential amino acids from the systemic circulation and from the portal blood after a short-term fast did not differ significantly nor were they higher in comparison to those of fed rabbits. Despite the increased serum levels of the most essential amino acids in the systemic venous blood after long-term starvation, there were no or little changes in concentrations of amino acids in portal blood and liver cytosolic fraction from fasted animals as compared to those of the fed group. These findings suggest that the reduction of albumin synthesis in fasting state is not primarily due to a reduction in the direct availability of these amino acids for albumin synthesis in the liver.

Albumins↗
PubMed1980

Temperature-converting factors for enzymes: comparison of methods.

Temperature-converting factors for six enzymes, which are determined very often in the clinical laboratory, are given. The determinations were carried out according to the recommendations of the German Society for Clinical Chemistry and of the Committee on Enzymes of the Dutch Society for Clinical Chemistry. These factors are described not only for human sera but also for some batches of commercial test sera and for the pure enzymes. There are two main conclusions. (1) Factors determined according to the German recommendations cannot be used in any simple way to convert enzymatic activities which have been determined according to the Dutch recommendations. (2) Factors determined using commercial test sera cannot be used for converting enzymatic activities of human origin.

Alanine Transaminase↗
PubMed1979

Determination of serum aminotransferases: activation by pyridoxal-5'-phosphate in relation to substrate concentration.

To investigate the activation of aspartate- and alanine aminotransferases by pyridoxal-5'-phosphate, we determined the enzymatic activity in serum in two different ways: (a) Preincubation of the serum alone or the serum with pyridoxal-5'-phosphate and starting the reaction by the addition of the serum sample or the serum sample + coenzyme, respectively. (b) Preincubation of the serum or the serum with pyridoxal-5'-phosphate in the reaction medium and starting the reaction by adding 2-oxoglutarate. There are only small differences in activities of both aminotransferases determined according to these two different methods. The stimulation by pyridoxal-5'-phosphate is also of the same order, when both methods are compared. Further, these enzymatic activities were measured with use of various concentrations of substrates. From our experiments we conclude that the degree of stimulation of the apoenzyme of the two enzymes is independent of which way the enzymatic reaction is carried out or the substrate concentration, except that aspartate aminotransferase activity is more stimulated by the coenzyme at higher 2-oxoglutarate concentrations.

Alanine Transaminase↗