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Biomedical subjects

R Kock

Publications and source records attributed to R Kock.

28 records · Page 2Linked to original sources
PubMed1993

A high-performance liquid chromatographic method for the determination of hypoxanthine, xanthine, uric acid and allantoin in serum.

A method was developed for the simultaneous determination of hypoxanthine, xanthine, uric acid and allantoin based on isocratic reversed-phase chromatography. This HPLC-method additionally allows the direct determination with UV-detection of inosine-5'-phosphate, uridine, thymine, orotic acid, allopurinol and oxipurinol, besides hypoxanthine, xanthine and uric acid in the same chromatographic run. Allantoin elutes in this system near the void volume and a fraction is collected covering the retention time range for this substance. After hydrolysis allantoin is converted to glyoxylate-2,4-dinitrophenylhydrazone, rechromatographed and detected at 360 nm. The coefficient of variation for this method does not exceed 5.0% for a serum concentration of 0.3 mumol/l hypoxanthine and is not greater than 5.3% for a xanthine concentration of 0.3 mumol/l serum. Recoveries were 90-110% for both hypoxanthine and xanthine. The determination of uric acid had an imprecision and inaccuracy not exceeding 1.45% in the concentration range of 103-568 mumol/l. Due to the more complex procedure required for the determination of allantoin, the coefficient of variation between days was 13.6% for a sample containing 0.8 mumol/l allantoin and the recoveries for this analyte were in the range of 86-93%. Reference ranges (mean +/- SD) determined on 171 serum samples from healthy adults were 12.7 +/- 6.6 mumol/l for hypoxanthine, 3.3 +/- 1.4 mumol/l for xanthine, and 15.7 +/- 7.9 mumol/l for allantoin. No significant age or sex dependence was observed. Uric acid concentrations were 320 +/- 55 mumol/l serum for men and 206 +/- 55 mumol/l for women.

Adolescent↗
PubMed1993

[Glucose homeostasis in cystic fibrosis. Oral glucose tolerance test in comparison with formula administration].

BACKGROUND: Glucose tolerance is often impaired in Cystic Fibrosis. The impact of this condition on enteral nutritional support in case of malnourishment remains to be studied. METHOD: In this study the glucose-, C-peptide- and insulin-responses to an OGTT and a standard enteral formula load were investigated in 19 non-diabetic CF-patients. Each test was performed with a carbohydrate load of 1.75 g/kg bodyweight. RESULTS: 11 patients had a normal OGTT (Group I) and 8 had an impaired glucose tolerance (Group II). After the formula load the glucose concentrations were significantly lower than after the OGTT at 30, 60, and 90 min in both groups and at 120 min in group II only. In group II the glucose values exceeded 6.7 mmol/l at 120 min after both OGTT and formula load and were significantly higher than in group I. The food glycaemic index, a parameter for comparison of glucose response to different diets was calculated. It ranged from 30 to 80% in both groups. An increased C-peptide- and insulin-secretion was found in patients with impaired glucose tolerance. CONCLUSIONS: The condition of impaired glucose tolerance must be considered for enteral hyperalimentation of Cystic Fibrosis-patients. The selection of formulas for nutritional support should be based on the calculation of the Food Glycemic Index because of its high interindividual variability.

Adolescent↗
PubMed1992

Sonographic evaluation of gallbladder motility in patients with end-stage renal disease on haemodialysis.

Thirty nine patients with end-stage renal disease on haemodialysis therapy with upper gastrointestinal symptoms were investigated for gallbladder motor function as the cause of their symptoms using cholecystosonography in fasting state, after a cholecystokinetic agent (BILOPTIN fatty meal) and after a smooth muscle relaxant (BUSCOPAN). Forty healthy individuals served as a control group. No significant difference was found between dialysis patients and healthy controls regarding the gallbladder area during fasting state, or the variation in the area of gallbladder during maximal contraction and dilatation. However, the patients on dialysis therapy of longer duration had stronger gallbladder contraction in response to a cholecystokinetic agent. Serum gastrin concentrations were increased in haemodialysis patients, but there was no consistent relationship between serum gastrin and gallbladder motility. The upper gastrointestinal symptoms of dialysis patients are unlikely to be due to disturbed gallbladder motility.

Adult↗
PubMed1991

The determination of thyroxine and thyroxine uptake with new homogeneous enzyme immunoassays using Boehringer Mannheim/Hitachi analysis systems.

New homogeneous enzyme immunoassays for the determination of thyroxine and thyroxine uptake have been developed. The CEDIA assays are based on the cloned enzyme donor immunoassay technology, which involves fragments of beta-galactosidase prepared by genetic engineering. The assays have been adapted for Boehringer Mannheim/Hitachi analysers. The CEDIA T4/T Uptake assays were evaluated in eleven clinical chemistry laboratories on various Boehringer Mannheim/Hitachi analysis systems, using a 2-point calibration. The analytical range of the T4 test was 10 to 258 nmol/l thyroxine. The T uptake test had a measuring range between 20-50%. Depending on the concentration of the analyte (samples from hypo-, eu- or hyperthyroid patients), mean coefficients of variation ranged from 1.8 to 4.8% within-run and from 4.1 to 6.5% between-run for the T4 assay. Even better coefficients of variation were obtained for the T uptake assay (1.4 to 2.3% within-run, 2.8 to 3.3% between run). The relative inaccuracy of the CEDIA assays with respect to values assigned by other tests was satisfactory in various control sera. The T4 assay was compared with one radioimmunoassay, one enzyme immunoassay and one fluorescence polarisation immunoassay. Slopes ranging from 0.9 to 1.1 and intercepts ranging from -10 to +10 nmol/l thyroxine were obtained with two exceptions. The results of the T uptake test correlated reasonably with those of other thyroxine-binding methods. No interference was observed with icteric and lipaemic sera. Haemoglobin up to 4 g/l had no significant influence. Results of the CEDIA T Uptake test are mainly used for calculation of the free thyroxine index, in which the thyroxine value is corrected for variations of thyroxine-binding protein concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoanalysis↗
PubMed1989

A candidate reference method for the determination of uric acid in serum based on high performance liquid chromatography, compared with an isotope dilution-gas chromatography-mass spectrometer method.

A method based on isocratic high performance liquid chromatography (HPLC) with UV detection at 292 nm is proposed as a candidate reference method for the determination of uric acid. Data obtained by this method are compared with those from an isotope dilution-gas chromatography-mass spectrometric method (ID-GC-MS), using [1,3-15N2]uric acid as internal standard and selected mass detection at m/z = 456 and m/z = 458. The inaccuracy of the ID-GC-MS method is maximally 0.4% for NBS-SRM-909 control sera with a concentration of 483 mumol/l. The coefficient of variation between days is 0.26%-0.80% and 0.37-0.90% for 14 control sera from other suppliers. The maximum bias of the HPLC method is 0.6%, and the coefficient of variation between days is 0.31%-0.65% for NBS-SRM-909 control sera. The coefficient of variation between days for the other 14 control sera tested is 0.35%-0.66%. Comparison of the HPLC method with the reference ID-GC-MS method resulted in a coefficient of correlation of r = 0.9998 (n = 14). The concentration of uric acid in the tested control sera ranged from 160 to 624 mumol/l.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Allozyme variation and differentiation in African and Indian rhinoceroses.

We studied variation at 25 to 31 allozymic loci in African and Asian rhinoceroses. Four taxa in three genera were examined: African Ceratotherium simum simum (northern white rhinoceros), C. s. cottoni (southern white rhinoceros), Diceros bicornis (black rhinoceros), and Rhinoceros unicornis (Indian rhinoceros). Extremely small amounts of intraspecific variation were observed in sample sizes of 2 to 10 presumably unrelated individuals per taxon: P = .00-.10, H = 0.00-0.02. We examined demographic bottlenecks and sampling errors as possible reasons for the low levels of detectable variation. The very small intraspecific genetic distance (D = 0.005) between the two living white rhinoceros subspecies is far less than the distance that has been reported for other mammal subspecies. The mean D value of 0.32 +/- 0.11 between the two African genera was also less than expected given the divergence time of greater than 7 million years suggested by the fossil record. Rhinoceroses may be evolving more slowly at the structural gene loci than are some other mammal groups. The estimate of D = 1.05 +/- 0.24 for the African-Indian split supports this idea, as the lineage diverged at least 26 million years ago. Our results contribute to the currently available scientific information on which management decisions aimed toward saving endangered rhinoceroses should be based.

Animals↗