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Biomedical subjects

F A Muskiet

Publications and source records attributed to F A Muskiet.

At least 73 records · Page 4Linked to original sources
PubMed1995

Vitamin C and glycohemoglobin.

Three groups of 10 age- and sex-matched nondiabetic volunteers took 0, 750, or 1500 mg of vitamin C each day for 12 weeks. Glycohemoglobin (GHb) was measured by HPLC, electrophoresis, affinity chromatography, and immunoassay at baseline (-4 weeks and -1 day), during supplementation (6 weeks and 12 weeks), and after supplementation ended (6 and 12 weeks). Plasma vitamin C increased twofold during supplementation but, in contrast with the results of Davie et al. (Diabetes 1992; 41:167-73), there were no between-group differences in GHb, glucose, and fructosamine concentrations. Fructosamine may have increased with storage time. The net effects of vitamin C on absolute GHb at 12 weeks vs -1 day (and at 12 weeks vs 12 weeks after) in % GHb amounted to: HPLC -0.035 (-0.050); electrophoresis +0.005 (+0.035); affinity chromatography -0.070 (+0.015); and immunoassay -0.110 (+0.025). We conclude that supplementation of nondiabetics with 750 or 1500 mg of vitamin C daily for 12 weeks does not cause interference in GHb determinations by HPLC, electrophoresis, affinity chromatography, or immunoassay, and does not reduce in vivo Hb glycation.

Adult↗
PubMed1995

Standardization of glycohemoglobin results and reference values in whole blood studied in 103 laboratories using 20 methods.

We investigated the effect of calibration with lyophilized calibrators on whole-blood glycohemoglobin (glyHb) results. One hundred three laboratories, using 20 different methods, determined glyHb in two lyophilized calibrators and two whole-blood samples. For whole-blood samples with low (5%) and high (9%) glyHb percentages, respectively, calibration decreased overall interlaboratory variation (CV) from 16% to 9% and from 11% to 6% and decreased intermethod variation from 14% to 6% and from 12% to 5%. Forty-seven laboratories, using 14 different methods, determined mean glyHb percentages in self-selected groups of 10 nondiabetic volunteers each. With calibration their overall mean (2SD) was 5.0% (0.5%), very close to the 5.0% (0.3%) derived from the reference method used in the Diabetes Control and Complications Trial. In both experiments the Abbott IMx and Vision showed deviating results. We conclude that, irrespective of the analytical method used, calibration enables standardization of glyHb results, reference values, and interpretation criteria.

Calibration↗
PubMed1994

Hemoglobins S and C: reference values for glycohemoglobin in heterozygous, double-heterozygous and homozygous subjects, as established by 13 methods.

Glycohemoglobin (gly-Hb) reference ranges of non-diabetic adults with HbAA (n = 17), HbAS (n = 37), HbAC (n = 22), HbSC (n = 8), HbSS (n = 6) and HbCC (n = 3) were determined by 13 methods, based on affinity chromatography, HPLC, electrophoresis and immunoassay. Gly-Hb of subjects with HbAS and HbAC can be measured without major difficulties by most methods. Some give rise to absolute gly-Hb differences > or = 1% compared with subjects with HbAA. Measurement of HbA1c/total Hb cannot be recommended. Some HPLC and immunoassay methods cannot measure gly-Hb in subjects with HbSC, HbSS and HbCC, whereas others may suffer from interference. Most methods showed low gly-Hb, reflecting increased erythrocyte turnover. Use of special reference ranges requires previous knowledge of the condition (affinity chromatography and immunoassay) or separation of gly-Hb and its precursor Hb (HPLC and electrophoresis). Interpretation is, however, not recommended because of the numerous factors that determine erythrocyte turnover.

Adult↗
PubMed1994

Effects of supplemental dietary calcium on quantitative and qualitative fecal fat excretion in man.

Oral calcium supplementation is thought to be a useful interventional agent to decrease colon cancer risk. This is supposedly due, at least in part, to the binding of bile acids and fatty acids by calcium in the colon, thus prohibiting the damaging effects of these substances to the epithelium. To determine the effects of calcium supplementation on fecal fat excretion, 24 subjects kept a fat and calcium constant diet for one week and were supplemented with either 0, 2 or 4 g elemental calcium as calcium carbonate in a double-blind fashion. At the end of the week 72-hour feces was collected, and total fat, neutral fat, fatty acids and the ratio of polyunsaturated and saturated fatty acids (P/S ratio) were measured. Calcium dose-dependently increased the percentual excretion of total fat as related to fat intake: 6.8 +/- 0.9% during 0 g, 7.4 +/- 1.0% during 2 g and 10.2 +/- 1.4% during 4 g, r = 0.44, p = 0.03. This was due to increased fatty acid excretion, excretion of neutral fat was not affected, nor was the P/S ratio. It is concluded that calcium supplementation modestly increases fecal fatty acid excretion. No adverse metabolic effects are to be expected from this in case of long-term calcium supplementation in subjects at increased risk for colon cancer.

Adult↗
PubMed1994

Serotonin, catecholamines, histamine, and their metabolites in urine, platelets, and tumor tissue of patients with carcinoid tumors.

We monitored long-term (median 11 months) concentrations of platelet serotonin and urinary serotonin, 5-hydroxyindoleacetic acid, and seven catecholamine metabolites in 44 patients with carcinoid tumors. Tumor serotonin and catecholamine contents (11 patients) and urinary histamine and N-methylhistamine (15 patients) were determined. Consistently increased concentrations of indoles, notably platelet serotonin, were observed in 96%, 43%, and 0% of patients with mid-, fore-, and hindgut carcinoids, respectively. Urinary dopamine metabolites, notably 3-methoxytyramine, were consistently increased in 38%, 20%, and 7% of patients with mid-, hind-, and foregut carcinoids, respectively. For urinary norepinephrine/epinephrine metabolites, notably normetanephrine and metanephrine, these data were 33%, 20%, and 14%, respectively. Midgut carcinoid tumors had the highest serotonin contents, whereas concentrations of catecholamines were independent of primary localization. There was no consistent relation between biogenic amine contents in tumors and urinary excretion of the amine metabolites. Occurrence of carcinoid syndrome was related to increased serotonin production rate. Increased histamine production is not an important feature in patients with lung carcinoids or liver-metastasized ileum carcinoids.

Adolescent↗
PubMed1994

Gestational age dependency of essential fatty acids in cord plasma cholesterol esters and triglycerides.

Plasma cholesterol ester and triglyceride fatty acid compositions of 38 singleton deliveries (23-42 wk), three twins (32, 39, and 40 wk), and their mothers were investigated. No gestational age-dependent changes occurred in maternal fatty acid compositions. Long-chain polyunsaturated fatty acids in fetal cholesterol esters and triglycerides were higher, and their precursors (18:2c,omega 6 and 18:3c,omega 3) were lower than those in corresponding maternal lipid classes. Except for 22:6c,omega 3,20:2c,omega 6, and 22:5c,omega 6, all long-chain polyunsaturated fatty acids in fetal triglycerides increased with advancing gestation. Fetal triglyceride 22:6c,omega 3/22:5c,omega 3 ratio decreased, whereas 22:5c,omega 6/22:4c,omega 6 remained constant. Fetal cholesterol ester and triglyceride 20:3c,omega 9 contents were higher than those of corresponding maternal fractions and did not change with gestation. Triglyceride 18:2c,omega 6 contents of babies with gestational ages of more than 34 wk were linearly related to those of their mothers. The data suggest that increasing triglyceride long-chain polyunsaturated fatty acid content with advancing gestation is partially caused by delta 6- and delta 5-desaturase maturation in the liver. Constancy of 22:6c,omega 3 and 22:5c,omega 6/22:4c,omega 6 and decrease of 22:6c,omega 3/22:5c,omega 3 in triglycerides may point to low hepatic delta 4-desaturation. Transplacental transport of 20:3c,omega 9, following by fetal conservation, should be considered. High 18:2c,omega 6 and low 18:3,omega 3 intakes by the mother may unfavorably influence fetal production of 22:6c,omega 3 in the liver. Because of low hepatic delta 4-desaturation capacity the influence may be small, however.

Cholesterol↗
PubMed1994

Effect of calibration on dispersion of glycohemoglobin values determined by 111 laboratories using 21 methods.

One hundred eleven laboratories, using 21 different methods based on five different principles, determined glycohemoglobin (GHb) percentages in two identical series of six lyophilized hemolysates and three similarly processed calibrators, distributed 3 months apart. To assign GHb percentages to calibrators, we used HbA1c results from nine participants who used the Bio-Rad Diamat high-performance liquid chromatographic method. Three-point calibration with assigned values improved mean intralaboratory variation (CV) from 6.6% to 3.5%. For samples with low (5.5%) and high (14.1%) GHb percentages, respectively, calibration decreased interlaboratory variation per method (from 10% to 4% and from 6% to 3%), inter-method variation (from 18% to 4% and from 16% to 3%), and overall interlaboratory variation (from 25% to 7% and from 15% to 4%). Without calibration, 71% of the laboratories did not meet the clinically desirable intralaboratory CV of 3.5%; calibration reduced this proportion to 39%. We conclude that, irrespective of the analytical method used, calibration greatly reduces all sources of GHb variation.

Calibration↗
PubMed1993

High performance liquid chromatographic profiling of tryptophan and related indoles in body fluids and tissues of carcinoid patients.

A high performance liquid chromatographic method with quaternary gradient elution and fluorometric detection was developed for profiling of tryptophan (TRP), 5-hydroxytryptophan, serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) in urine, platelet-rich plasma and (tumour) tissue of patients with carcinoid tumours. Prior to injection, urine samples were diluted and filtered. Platelet-rich plasma and tissue homogenates were prepurified by C18 solid phase extraction. Detection limits were approx. 2 pmol. Results of urinary 5-HT and 5-HIAA compared favourably with those of single component analyses. No consistent diurnal variations were found for TRP, 5-HT and 5-HIAA in 12-h urine samples from 15 healthy adults. Abstinence of 5-HT-rich foods reduced urinary levels of 5-HT and 5-HIAA. C18 extraction of indoles from protein-containing matrices was studied in platelet-rich plasma. Although time-consuming and complicated for daily routine use, the present approach offers particular advantages over single component analyses in the study of TRP metabolism in patients with carcinoid tumours.

5-Hydroxytryptophan↗
PubMed1993

Isotope dilution ammonia chemical ionization mass fragmentographic analysis of urinary 3-O-methylated catecholamine metabolites. Rapid sample clean-up by derivatization and extraction of lyophilized samples.

We developed a method for simultaneous quantification of the urinary 3-O-methylated catecholamine metabolites 3-methoxytyramine, normetanephrine and metanephrine by stable isotope-dilution ammonia chemical ionization mass fragmentography. Prepurification of lyophilized samples was done by simultaneous deconjugation and pentafluoropropionylation, followed by extraction and rederivatization. Compared with our previously described method, based on acid hydrolysis, alkaline extraction, derivatization and electron-impact mass fragmentography, the present method was found to be less laborious, more sensitive and presumably more accurate. New urinary excretion values were established for apparently healthy adults. The present prepurification method may prove applicable for profiling of a variety of naturally occurring mono-, di- and polyamines in biological samples.

Adult↗
PubMed1993

Fatty acid composition of human milk triglyceride species. Possible consequences for optimal structures of infant formula triglycerides.

Human milk triglycerides (TGs) were separated into 14 fractions by silver ion high-performance liquid chromatography (HPLC) with light-scattering detection (LSD). Subsequent fractionation by reversed-phase HPLC-LSD resulted in 75 subfractions. The major 48 were analysed by gas chromatography for their intact TG and fatty acid (FA) compositions. Using a constrained non-linear optimization computer program, the FA compositions and abundances of 170 different TG combinations were calculated. The major two, 16:0/18:1/18:1 (11.8 mol%) and 16:0/18:1/18:2 (10.0 mol%), were almost twice as abundant as expected from random FA distribution. The apolarities of 16:0 and 18:0 seem to be modulated by unsaturated FAs (18:1, 18:2) or medium-chain FAs (MCFAs; 8:0-12:0). MCFAs were present in 19 mol%. Of these, 7.2 mol% are likely to harbour stereospecific structures with an MCFA at sn-3, 16:0 or 14:0 at sn-2, and 18:1 or 18:2 at sn-1. These structures are excellent substrates for lingual and gastric lipases, producing products that assist in duodenal TG lipolysis.

Chromatography, Gas↗
PubMed1993

Indicators of long chain polyunsaturated fatty acid status of exclusively breastfed infants at delivery and after 20-22 days.

The fatty acid composition of plasma cholesterol esters (CE), erythrocytes (RBC) and mature milk from seven lactating/women and their exclusively breastfed newborns, living on Dominica, were studied. Blood samples were taken from umbilical cord and mother at birth. A sample of breastmilk was collected on day 20-22 postpartum, together with a blood sample from the baby. At birth, cord blood plasma CE and RBC total long chain polyunsaturated fatty acid (LC-PUFA) contents were higher, and linoleic (18:2c, omega 6) and alpha-linolenic (18:3c, omega 3) acid contents lower, than in corresponding maternal compartments. Cord blood RBC LC-PUFA omega 3 content was lower and LC-PUFA omega 6 content higher than in maternal RBC. After birth, feeding with human milk led to a drop in LC-PUFA content in the plasma CE fraction, whereas RBC LC-PUFA content remained virtually constant. Current understanding of the origin and relative affinity of fatty acids incorporated in plasma CE and RBC suggests that RBC LC-PUFA content is a more reliable parameter for LC-PUFA status than plasma CE LC-PUFA content. The RBC LC-PUFA data suggest therefore that at birth the newborn has a lower LC-PUFA omega 3 status than the mother, and that this does not change during three weeks of exclusive breastfeeding.

Breast Feeding↗
PubMed1993

Milk of patients with tightly controlled insulin-dependent diabetes mellitus has normal macronutrient and fatty acid composition.

The composition of macro- and micronutrients in milk from six patients with tightly controlled insulin-dependent diabetes mellitus [median glycosylated hemoglobin concentrations at parturition of 5.2% (range 4.9-5.3%, reference range 4.9-6.6%) and 6 wk thereafter of 6.1% (range 5.0-6.3%, reference range 5.0-6.4%) was compared with that from five control subjects. Milk samples were collected halfway through a single breast-feeding at days 3-5 (colostrum); 7, 9, and 10 (transitional milk); and 12, 15, 17, 21, 25, 29, and 35 (mature milk). We found no abnormalities in macronutrient (triglycerides, lactose, and protein), cholesterol, glucose, and myoinositol concentrations or fatty acid composition. Two of three longitudinally studied patients showed rather constant ratios between glucose concentrations in milk and capillary blood. The present data suggest that tight control corrects a multitude of milk abnormalities associated with moderate and poor control.

Adult↗
PubMed1993

Age-dependent vitamin D status and vertebral condition of white women living in Curaçao (The Netherlands Antilles) as compared with their counterparts in The Netherlands.

Plasma vitamin D metabolites and parathyroid hormone concentrations of two groups of white women, aged 26-46 and 63-83 y, in Curaçao were studied to evaluate the effect of yearlong abundant sunlight on frequency of vertebral compression fractures in elderly women. 25-Hydroxyvitamin D of the younger group (median, 116 nmol/L) was higher than that of the older group (75 nmol/L). Both groups had higher 25-hydroxyvitamin D compared with approximately age-matched counterparts in The Netherlands during autumn and winter (50 and 25 nmol/L, respectively). Similar differences were found for 1,25-dihydroxyvitamin D, although to a lesser extent. Parathyroid hormone concentrations of older women in Curaçao (4.3 pmol/L) were higher than those of the younger women (2.3 pmol/L). Roentgenographic analyses of the spines of the older women did not show vertebral compression fractures commonly encountered in women living at higher latitudes. Uninterrupted high plasma concentrations of vitamin D metabolites may reduce vertebral compression fractures in postmenopausal white women.

Adult↗
PubMed1993

Glycohaemoglobin: comparison of 12 analytical methods, applied to lyophilized haemolysates by 101 laboratories in an external quality assurance programme.

Stable lyophilized ethylenediaminetetra-acetic acid (EDTA)-blood haemolysates were applied in an external quality assurance programme (SKZL, The Netherlands) for glycohaemoglobin assays in 101 laboratories using 12 methods. The mean intralaboratory day-to-day coefficient of variation (CV), calculated from the assay of 12 unidentified pairs over a period of 1 year, was 5.2% (range: 0.2-28.7). Forty-seven per cent of laboratories did not meet the criterion of CV < 5%, whereas 68% did not meet the clinically more desirable 3.3-3.6%. Linearity, as derived from the analysis of five combinations of two haemolysates with low and high glycohaemoglobin percentages over 6 months, was excellent (mean correlation coefficient 0.9953; range: 0.9188-0.9999). Analysis of two samples with high and low glycohaemoglobin percentages gave mean interlaboratory coefficients of variation of 10% for one method performed by several laboratories and 22% for all methods performed by all laboratories. It is concluded that the majority of laboratories do not meet the clinically desirable intralaboratory precision and that an unacceptably high interlaboratory precision exists.

Edetic Acid↗
PubMed1993

Influence of hemoglobin variants and derivatives on glycohemoglobin determinations, as investigated by 102 laboratories using 16 methods.

Influences of hemoglobin (Hb) variants (HbSS, HbCC, beta-thalassemia, HbAE, HbAS, HbAC, hereditary persistent HbF) and Hb derivatives (carbamylated- and acetylated-Hbs, Schiff base, and those formed in stored blood) on results of glyco-Hb assays by 102 laboratories using 16 different methods were investigated. Affinity chromatography shows deviating results only with homozygous Hb S and C. Correct interpretation of results from patients with decreased erythrocyte half-lives requires previous knowledge on this condition. Measurements of HbA1c by HPLC and electrophoresis are obviously unsuitable for homozygous hemoglobinopathies; for heterozygous hemoglobinopathies and Hb synthesis variants, HbA1c should be expressed as percentage of HbA0 + HbA1c; abnormal Hbs are usually recognized; both carbamylated- and acetylated-Hbs interfere and Schiff base must be eliminated. Except for stored blood, all Hb variants and derivatives gave erroneous results with disposable ion-exchange columns. Dako's immunoassay is not affected by Hb derivatives; glycated Hb variants are not recognized as glyco-Hb and percentages are consequently too low. Glyco-Hb by the immunoassay of Bayer (performed by one laboratory) is not affected by Hb variants and derivatives.

Chemistry, Clinical↗
PubMed1993

Beta-N-terminal glycohemoglobins in subjects with common hemoglobinopathies: relation with fructosamine and mean erythrocyte age.

Amounts of beta-N-terminal glycohemoglobins (HbX1c), serum fructosamine, and erythrocyte polyamines were determined in nondiabetic adults with HbAA, HbAC, HbAS, HbCC, HbSC, HbSS, and HbS/hereditary persistent HbF (HPFH). The groups did not differ in fructosamine concentrations. Mean (95% confidence limits) HbX1c percentages were: 4.4 (4.1-4.8) for HbA1c in HbAA, 4.3 (3.9-4.8) for HbA1c in HbAC, 4.1 (3.6-4.6) for HbC1c in HbAC, 4.4 (4.0-4.7) for HbA1c in HbAS, 2.6 (range: 2.3-3.8) for HbC1c in HbCC, 2.0 (1.5-2.4) for HbS1c in HbSC, 0.9 (0.6-1.3) for HbS1c in HbSS, and 1.3 (range: 0.8-2.4) for HbS1c in HbS/HPFH. There was a nonlinear inverse relation between HbX1c and erythrocyte polyamines, indicating that HbX1c percentage decreases with decreasing mean erythrocyte age. We conclude that amounts of HbX1c in subjects with heterozygous hemoglobinopathies should be expressed as a percentage of HbX0 + HbX1c, not total hemoglobin. Interpretation of HbX1c in subjects with a decreased erythrocyte half-life is difficult; measurement of fructosamine seems a suitable alternative.

Adolescent↗
PubMed1993

Interference of carbamylated and acetylated hemoglobins in assays of glycohemoglobin by HPLC, electrophoresis, affinity chromatography, and enzyme immunoassay.

In vitro-synthesized carbamylated and acetylated hemoglobins interfered in assays of glycohemoglobin by HPLC and electrophoresis but had no effects on results obtained by affinity chromatography and enzyme immunoassay. Correlations between long-term serum urea concentrations and glycohemoglobin percentages revealed that, in vivo, carbamylated hemoglobin equivalent to 0.063% of total hemoglobin is formed for every 1 mmol/L of serum urea. The use of acetylsalicylate, either chronically in small doses (200-300 mg/day) or for 1 week at 2000 mg/day, did not cause significant interference from acetylhemoglobin, formed in vivo. We conclude that interference from carbamylated hemoglobin explains only a small part of existing discrepancies between results of glycohemoglobin assays in current use. The interfering effect of acetylhemoglobin formed in vivo with acetyl-CoA as substrate is as yet unknown.

Acetylation↗