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P M van Haard

Publications and source records attributed to P M van Haard.

13 recordsLinked to original sources
PubMed1992

Gastrointestinal blood loss after non-steroidal anti-inflammatory drugs. Measurement by selective determination of faecal porphyrins.

1. A method for the detection of gastrointestinal blood loss based upon the selective measurement of faecal porphyrins was tested in two studies in healthy volunteers. 2. In the first study subjects (n = 6) received intragastric autologous blood (saline, 2 and 6 ml as a single dose) resulting in a dose dependent increase in faecal porphyrins. 3. In a subsequent placebo controlled cross over study in 12 subjects acetylsalicylic acid (ASA), nabumetone (a new NSAID) or placebo were administered for 5 days with a washout period of 9 days. They were no dietary restrictions. 4. All faeces were collected during the treatment period and both the full faecal homogenate and a random faecal sample were analyzed for deutero- and pemptoporphyrin content by h.p.l.c. Additionally a benzidine reaction was performed. 5. There was a highly significant correlation (r = 0.95) between the values obtained from random samples and the full homogenate. ASA increased the faecal porphyrin excretion (P less than 0.001) compared with placebo in contrast to nabumetone. Complaints of dyspepsia were most common after ASA. 6. Measurement of faecal porphyrins is useful for monitoring NSAID induced upper gastrointestinal blood loss and lacks some of the practical constraints of other methods.

Adult↗
PubMed1990

Vitamin K1 levels and K1-dependent coagulation factors II and X in preterm and small-for-date neonates.

In 17 preterm neonates and 7 small-for-date neonates, all formula-fed, vitamin K-dependent coagulation factors II and X remained near 45% of adult values from the moment of birth until 28 days postnatally. Vitamin K1 levels, however, showed a remarkable rise from below the detection limit of 0.022 ng/ml in umbilical cord blood, to serum levels with a range of 0.99-7.29 ng/ml vitamin K1 on day 3, with a further rise on days 7 and 28 postnatally. Vitamin K1 (Konakion) parenterally given to a third group of four preterm neonates as a 1 mg dose resulted in very high serum levels of vitamin K1 (64.08-157.10 ng/ml), but without any significant increase in plasma levels of vitamin K-dependent coagulation factors II and X, compared to the group without any extra vitamin K1. It is concluded that in healthy preterm and small-for-date neonates no correlation is seen between serum levels of vitamin K1 and plasma levels of coagulation factors II and X. After administration of 1 mg Konakion no accelerated increase is seen in coagulation factor activities.

Factor X↗
PubMed1990

Vitamin K1 levels and coagulation factors in healthy term newborns till 4 weeks after birth.

Vitamin K1 serum levels were assessed by means of an off-line multidimensional liquid chromatography in 18 mothers, shortly after delivery, and in their healthy term infants. Umbilical cord and venous blood samples were assayed up to 4 weeks of life. Concurrently, levels of coagulation factors II and X, antithrombin III and platelets were established. Although the detection limit of the assay was as low as 22 pg/ml, vitamin K1 concentration appeared to be still beyond that level in cord blood or in newborn serum within 30 min after birth, whereas vitamin-K-dependent coagulation factors are already at a level of 40%, without evidence for the presence of descarboxy prothrombin, in any of the investigated neonates. After 3 days, breast-fed neonates had lower vitamin K1 levels than formula-fed infants (0.76 and 1.44 ng/ml, respectively). The levels of the vitamin-K-dependent coagulation factors II and X, however, were comparable, regardless of the kind of feeding. After 28 days, breast-fed neonates had even lower vitamin K1 levels (0.49 ng/ml, while the formula-fed infants showed higher vitamin K1 levels (4.45 ng/ml). But even then, the levels of vitamin-K-dependent coagulation factors II and X were comparable, regardless of the kind of feeding. From this we conclude that the serum levels of vitamin K1 in formula-fed neonates exceed those of breast-fed infants from the moment of feeding (24 h and later) without a concomitant rise in vitamin-K-dependent coagulation factors. A relationship between vitamin K1 levels and vitamin-K-dependent coagulation factors could not be established in healthy term breast-fed or formula-fed infants.

Breast Feeding↗
PubMed1988

Chromatography of urinary indole derivatives.

Latest strategies are discussed for the routine chromatographic analysis of clinically important indole derivatives in urine. Analysis of 5-hydroxyindoleacetic acid and, perhaps more importantly, serotonin and 5-hydroxytryptophan remains attractive in the screening for carcinoid tumours and their differentiation. Analyses of two precursors of the skin pigment eumelanin seem to be promising in the monitoring of treatment of malignant melanoma and screening for pigmentation disorders and gallstone formation. Studies on the clinical relevance of the determination of tetrahydro-beta-carbolines and melatonin-related indoles await routine application of chromatographic methods designed to take into consideration the relative instability of these compounds. Application of GC-MS, although confined to larger and/or governmental laboratories remains attractive as a way of improving the specificity of analyses and in establishing reference methods. As for HPLC, the recent development of chromatographic and detection methods for the concurrent determination of different clinically important and metabolically related compounds from the same sample, preferably by direct injection techniques, seems to be fruitful and should be continued.

Animals↗
PubMed1987

Direct concurrent measurement of urinary vanillylmandelic acid, 5-hydroxyindoleacetic acid and homovanillic acid by HPLC. Three methodologies compared.

Three different direct HPLC methods for the determination of 3-methoxy-4-hydroxymandelic acid (VMA, vanillylmandelic acid), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylacetic acid (HVA, homovanillic acid) in urine were compared: two spectrofluorometric methods, applying discontinuous gradients, and one serial coulometric linear gradient method. The imprecision study (n = 6) revealed comparable coefficients of variation (CV), intra-assay ranging 1.4-11.1%, and inter-assay ranging 5.9-11.8% for physiological and moderately elevated levels of VMA, 5-HIAA and HVA. All methods showed good linearities up to 100 mumol/L for each of the three compounds studied. Analytical recoveries were 97-114% for VMA, 87-103% for 5-HIAA, and 80-95% for HVA. Recoveries were not dependent on urinary relative densities in the range 1.010-1.030 kg/L or on protein content (prior to acidification) in the range 0.1-3 g/L, or on the pH of conservation in the range 2-5 or on storage temperature in the range -20 - +22 degrees C for three weeks. The distributed-sample comparison revealed acceptable correlations and clinically unimportant accuracy differences between the methods. It is concluded that direct fluorometric and electrochemical HPLC methods can be used in the determination of major catecholamine and serotonin metabolites in human urine for clinical diagnosis and follow-up of neural crest and carcinoid tumours.

Chromatography, High Pressure Liquid↗
PubMed1986

Assay of urinary 5-hydroxyindole-3-acetic acid: two methodologies compared.

Udenfriend's (Sjoerdsma A, Weissbach H, Udenfriend S. J Am Med Assoc 1955; 159: 397) classical screening method for urinary 5-hydroxyindole-3-acetic acid (5-HIAA) is known to be subject to error due to food and drug interferences. Goldenberg (Goldenberg H. Clin Chem 1973; 19: 38-44) introduced a more specific and sensitive method, which has recently been modified by Zouheir Habbal (Zouheir Habbal M. Clin Chim Acta 1983; 130: 251-256). The latter method is shown to correlate fairly well with a high-pressure liquid chromatography (HPLC) method in the 0-100 mumol/24 h range (reference values up to 34 mumol/24 h). It is suggested that elevated values in Udenfriend's screening method can be reliably checked by applying either method.

Chromatography, High Pressure Liquid↗
PubMed1986

Quantitation of trans-vitamin K1 in small serum samples by off-line multidimensional liquid chromatography.

A sensitive high-performance liquid chromatography method for vitamin K1 using normal-phase fractionation was updated in order to cope with the limited volume of blood samples obtained from newborns. The method combines sample clean-up, normal-phase fractionation with reversed-phase chromatography using post-column electrochemical reduction and fluorescence detection. It was possible to measure vitamin K1 concentration in at least 0.2 ml of (potentially lipemic) serum even at a level of 0.3 nmol/l. The normal-phase method was compared to the updated method. The updated method shows about a twenty-fold lower limit of detectability than the previously described method.

Chromatography, High Pressure Liquid↗
PubMed1985

Vitamin K1 in the newborn.

By a sensitive high-performance liquid chromatography method it was possible to measure vitamin K1 concentrations in mothers and their newborn children, even at a level of 0.5 nmol/l. All neonates were born after an uncomplicated and full-term pregnancy. The vitamin K1 concentration in neonates proved to be about half the value of their mothers, which is consistent with earlier studies of vitamin K1 dependent clotting factors. One may assume the existence of a partial placental barrier to vitamin K1. Venous, arterial and mixed cord blood did not differ significantly, so puncturing the vena umbilicalis is sufficient to measure vitamin K1 concentrations in cord blood.

Adult↗
PubMed1982

Two serum pancreatic isoamylase determinations compared.

Serum pancreatic isoamylase activity was measured by a method involving inhibition of salivary isoamylase and by a well-known agarose electrophoretic method, modified by us. We saw changes in electrophoretic patterns of pancreatic isoamylase fractions after storage of serum samples for three weeks at 4-8 degrees C, but with the inhibition method no alterations in activities were found. Within-assay and between-assay imprecisions of both methods were about the same. Serum pancreatic amylase activities as measured by the inhibition method exceeded by about 10% those obtained by the electrophoretic method. The inhibition method seems to be a reasonable candidate for routine application, whereas the electrophoretic method is still time-consuming and requires special skill to perform. Some suggestions are given for improving the calibration of the inhibition method recommended by the manufacturer.

Blood Preservation↗
PubMed1980

Studies on (Na+ + K+)-activated ATPase. XLVI. Effect of cation-induced conformational changes on sulfhydryl group modification.

(1) (Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.1.6.3) contains 34 sulfhydryl groups on the catalytic subunit, and two on the glycoprotein subunit. Under native conditions, only sulfhydryl groups on the catalytic subunit are accessible to modifying reagents. (2) The degree of inhibition of (Na+ + K+)-ATPase activity by N-ethylmaleimide and 5,5'-dithiobis(2-nitrobenzoic acid) depends on the cations present in the reaction medium. Mg2+ strongly enchances the inhibitory effects of both sulfhydryl reagents. The effects of Mg2+ on the inhibition by 5,5'-dithiobis(2-nitrobenzoic acid) are counteracted by the addition of Na+ or K+. Na+ has no more effect than choline on the inhibition by 5,5'-dithiobis(2-nitrobenzoic acid), but it enhances the inhibitory effect of N-ethylmaleimide at low Na+ concentrations (less than 10 mM). Low concentrations of K+ (less than 10 mM) slightly protect the enzyme against modification. (3) Titration of residual sulfhydryl groups reveals that these ions do not only influence modification of essential sulfhydryl groups, but also that of sulfhydryl groups which are not essential for the enzyme activity. (4) These results indicate that Na+, K+ and Mg2+ have marked effects on the conformation of the catalytic subunit of (Na+ + K+)-ATPase. Various enzyme conformations can be induced, depending on the concentration and the kind of cation added. The largest effects are observed after addition of Mg2+.

Animals↗
PubMed1980

Pyrolysis mass spectra, sulfhydryl and tryptophan content of the embryonic nuclei from adult human normal and nuclear-cataractous lenses.

Cataractous state-related alterations were studied by Curie-point pyrolysis low voltage mass spectrometry performed on the embryonic nuclei from adult normal and nuclear-cataractous human lenses. It was shown that the relative intensities of ion signals assigned to sulfur dioxide and tentatively, to other sulfur oxidation products correlate with the increase in lens nuclear color. Since these ion signals may represent pyrolysis fragments from methionine sulfoxide, methionine sulfone, cysteic acid and disulfide compounds present in the parent material, it is concluded that progressive oxidation of sulfur compounds appears to take place during nuclear cataractogenesis. Automated pyrolysis mass spectrometry coupled with multivariate analysis of the spectral data by computer turned out to be a rapid method of characterizing sub-milligram samples of lens material. The results were supported by data obtained by conventional determination of sulfhydryl and tryptophan groups.

Cataract↗