PubMed Health⌕ Search

Biomedical subjects

L J Spaapen

Publications and source records attributed to L J Spaapen.

At least 19 recordsLinked to original sources
PubMed2001

Tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency in Dutch neonates.

Four neonates with a positive phenylalanine screening test (Phe concentrations between 258 and 1250 micromol/L) were investigated further to differentiate between phenylalanine hydroxylase (PAH) deficiency and variant hyperphenylalaninaemia (HPA) forms. In patients 1 and 2 a tetrahydrobiopterin (BH4) load caused a significant decrease of the plasma Phe levels. A combined phenylalanine/BH4 loading test was performed in patients 2, 3 and 4. In the latter two patients, plasma Phe concentrations completely normalized within 8 h after the BH4 load (20 mg/kg). Basal urinary pterins were normal in all four patients. The activity of dihydropteridine reductase (DHPR) was normal in patients 1, 2 and 3 and 50% of control values in patient 4 (not in the range of DHPR-deficient patients). In patient 3 a subsequent phenylalanine loading test with concomitant analysis of plasma biopterins revealed a normal increase of biopterin, excluding a BH4 biosynthesis defect. Pterins and neurotransmitter metabolites in CSF of patients 1, 3 and 4 were normal. DNA mutations detected in the PAH gene of patients 1-4 were A313T, and L367fsinsC; V190A and R243X; A300S and A403V; R241C and A403V. The results are suggestive for mutant PAH enzymes with decreased affinity for the cofactor BH4.

Biopterins↗
PubMed2001

Are children with cystic fibrosis who are treated with a proton-pump inhibitor at risk for vitamin B(12) deficiency?

BACKGROUND: In a recent study, the authors demonstrated the beneficial effect of proton-pump inhibitors (PPI) on fat malabsorption and bone mineral content in children with cystic fibrosis (CF). Prolonged use of PPI could result in vitamin B(12) deficiency as a consequence of impaired release of vitamin B(12) from food in a nonacid environment. The aim of this study was to evaluate the vitamin B 12 status of CF patients either treated with a PPI or not by measuring vitamin B(12) and homocysteine blood levels, the latter being a sensitive indicator of vitamin B(12) deficiency. METHODS: The study population consisted of 20 CF patients, 11 patients treated with a PPI for at least 2 years and 9 patients not treated with a PPI, and 10 healthy, age-matched control participants. Homocysteine blood levels were measured by high-performance liquid chromatography, and vitamin B(12) levels were measured by a competitive protein-binding assay. RESULTS: Vitamin B(12) levels were significantly higher in both CF groups compared with the control participants (PPI+, P = 0.02; PPI-, P = 0.009). There was no significant difference in vitamin B(12) levels between both CF groups. Homocysteine levels were normal and similar in all groups. CONCLUSIONS: Cystic fibrosis patients treated with a PPI for at least 2 years show no signs of vitamin B(12) deficiency.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1993

RFLP haplotyping and mutation analysis of the phenylalanine hydroxylase gene in Dutch phenylketonuria families.

Restriction fragment length polymorphism haplotyping of mutated and normal phenylalanine hydroxylase (PAH) alleles in 49 Dutch phenylketonuria (PKU) families was performed. All mutant PAH chromosomes identified by haplotyping (n = 98) were screened for eight of the most predominant mutations. Compound heterozygosity was proven in 40 kindreds. Homozygosity was found for the IVS/2nt1 mutation in 5 families, and for the R158Q and IVS10nt546 mutations in one family each. All patients from these families suffer from severe PKU, providing additional proof that these mutations are deleterious for the PAH gene. Genotypical heterogeneity was evident for mutant haplotype 1 (n = 27) carrying the mutations R261Q (n = 12), E280K (n = 4, P281L (n = 1) and unknown (n = 10), and likewise for mutant haplotype 4 (n = 30) carrying the mutations R158Q (n = 13), Y414C (n = 1) and unknown (n = 16). Mutant haplotype 3 (n = 20), in tight association with mutation IVS12nt1, appeared to be in strong linkage disequilibrium (LDE) with its normal counterpart allele (n = 4). Mutant haplotype 6 (n = 4), in tight association with the IVS10nt546 mutation, showed moderate LDE with its counterpart allele (n = 1). The distribution of the mutant PAH haplotypes 1, 3 and 4 among the Dutch PKU population resembles that in other Northern and Western European countries, but it is striking that mutant haplotype 2 and its associated mutation R408W is nearly absent in The Netherlands, in strong contrast to its neighbouring countries.

Base Sequence↗
PubMed1991

Gas chromatography method for the separation of amino acids enantiomers in plasma and urine. Application in a case of short bowel syndrome.

Urinary amino acids were isolated from the urine of healthy controls and a patient with a short bowel syndrome. Following derivatization with isopropyl alcohol/HCl and trifluoroacetic anhydride the amino acid enantiomers were separated by gas chromatography on a Chirasil-L-Val column. All subjects excreted D-alanine (10-30% of total Ala). The percentage D-alanine was higher in the patient with the short bowel syndrome. The excretion of D-alanine did not correlate with the D-lactate excretion. An intestinal origin for the D-amino acids is the most probable explanation.

Adolescent↗
PubMed1991

Accumulation of odd-numbered long-chain fatty acids in fetuses and neonates with inherited disorders of propionate metabolism.

Fetuses affected with propionic acidemia incorporate great amounts of odd-numbered long-chain fatty acids (OLCFA) into their body lipids. This is due to abundant supply with precursor amino acids of propionyl-CoA throughout pregnancy. After birth, the lower provision of precursor amino acids during dietary treatment compared with fetal life results in a decline of propionyl-CoA production and therefore OLCFA synthesis. However, the observed decrease of OLCFA may also partly reflect the recovery from acute ketoacidotic episodes that the patients experienced soon after birth as long as they were undiagnosed. In a patient with vitamin B12-responsive methylmalonic aciduria treated prenatally with large doses of vitamin B12 given to the mother, the cord plasma lipids contained normal amounts of OLCFA. This indicates that prenatal therapy led to an increased flux of propionyl-CoA through the defective methylmalonyl-CoA mutase step. Thus, in addition to the quantification of a decline in methylmalonic acid in maternal urine, OLCFA in cord blood lipids might be a further parameter for evaluating prenatal treatment in patients with vitamin B12-responsive methylmalonic aciduria.

Acyl Coenzyme A↗
PubMed1989

Recurrence of nephrocalcinosis after renal transplantation in an adult patient with primary hyperoxaluria type I.

The medical history of a 42-year-old patient with primary hyperoxaluria type I is presented. Primary hyperoxaluria was suspected after renal transplantation, when oxalate deposits were found in a biopsy of the kidney graft. Diagnosis of type I hyperoxaluria was confirmed by the finding that significantly increased amounts of glycolic acid and oxalic acid were excreted. Treatment of the patient with 500 mg pyridoxine daily resulted in a decrease of the excretion of oxalate to normal values.

Adult↗
PubMed1988

Different pathways for deoxyguanosine toxicity in T-lymphocytes of various developmental stages.

The basis of the selective cellular immunodeficiency which occurs in patients with purine nucleoside phosphorylase (PNP) deficiency still is not completely understood. We studied the mechanism of deoxyguanosine (dGuo) toxicity in proliferating lymphoid T-cells of different maturation stage, i.e. in T-cells of adult peripheral blood and cord blood and in CD3+ and CD3- subfractions of thymocytes. The mitogen-induced proliferation of T-cells from peripheral blood and cord blood and of CD3+ and CD3- subfractions of thymocytes. The mitogen-induced proliferation of T-cells from peripheral blood and cord blood and of CD3+ thymocytes, as well as the spontaneous proliferation of CD3- thymocytes, are inhibited by dGuo. CD3+ and CD3- thymocytes are significantly more sensitive to dGuo than T-cells from peripheral blood or cord blood. Among the thymocyte subfractions CD3- thymocytes appeared to be extremely sensitive. In all cell types studied, inhibition of proliferation is accompanied by intracellular increases in both guanosine triphosphate (GTP) and deoxyguanosine triphosphate (dGTP) concentrations. By use of the PNP inhibitor 8-aminoguanosine, or the metabolites hypoxanthine or deoxycytidine, the metabolism of dGuo could be selectively directed to the formation of GTP or to dGTP. Based on the pattern of rescue from dGuo intoxication under these different metabolic conditions we conclude that in CD3- thymocytes dGuo toxicity is mediated by dGTP. In all other cell types studied GTP mediates dGuo intoxication. Altogether the results show that during the maturation from immature thymocytes to mature peripheral blood T-cells a shift occurs in the pattern of dGuo toxicity since dGuo toxicity in the former is primarily caused via the dCyd kinase pathway, and in the latter mainly the degradation route is involved. Since in PNP deficiency mature T-cells do occur in the peripheral blood, we must conclude that some cells escape the stage of T-cell maturation in the thymus which is extremely sensitive to dGuo. Furthermore, the results imply that as far as T-cell development in the normal thymus is concerned, survival and death of cells might be regulated by local (deoxy) nucleoside availability.

Adult↗
PubMed1987

Urinary D-4-hydroxyphenyllactate, D-phenyllactate and D-2-hydroxyisocaproate, abnormalities of bacterial origin.

Analysis of urinary organic acids in patients admitted for screening for inborn errors of metabolism incidentally revealed the presence of abnormal amounts of 4-hydroxyphenyllactate (4-HPLA) and phenyllactate (PLA). These compounds are found in tyrosinaemia and phenylketonuria but in our patients such disorders could not be established. By means of configuration analysis it was shown that these 2-hydroxyacids consisted partly of the D-enantiomers, pointing to a bacterial origin. Endogenously formed urinary 2-hydroxyacids in tyrosinaemia or phenylketonuria consisted of only the L-enantiomers. Furthermore, the urine of a patient with an established short bowel syndrome contained a wide variety of bacterial amino acid metabolites, including 2-hydroxyisocaproic acid (2-HICA). In this case 2-HICA occurred predominantly in the D-form whereas in the urine of a patient with maple syrup urine disease this compound appeared to have the L-configuration.

Amino Acid Metabolism, Inborn Errors↗
PubMed1987

A new case of purine nucleoside phosphorylase deficiency: enzymologic, clinical, and immunologic characteristics.

Deficiency of purine nucleoside phosphorylase (PNP) was detected in a 3-yr-old boy who was admitted for investigation of a behavior disorder and spastic diplegia. The urinary excretion of purines, analyzed by high-performance liquid chromatography, showed the presence of large amounts of (deoxy)inosine and (deoxy)guanosine and low uric acid levels. Analysis of the (deoxy)nucleotide pools of erythrocytes showed elevated levels of deoxyguanine nucleotides and NAD and decreased guanine nucleotides. PNP activity in red blood cells was 0.1-0.5% of normal on two occasions and undetectable on four later measurements. Furthermore no immunoreactive material could be detected in his red cell lysate using an anti-PNP antiserum. PNP activities in the red cells of the patient's parents were 35 and 50% of normal. The presence of (minor) residual PNP activity in the patient enabled the investigation of some enzyme properties after partial purification. No abnormalities could be detected in substrate affinity for inosine, heat stability, and electrophoretic properties. In the heterozygous parents no signs of a mutant enzyme could be found. The molecular specific activities of the parental enzymes were also normal, indicating that no immunoreactive material attributable to inactive-mutant enzyme subunits was present. A striking feature of the patient is the prevailing neurologic abnormalities presumably caused by the metabolic disorder. A severe lymphopenia exists; however, clinical symptoms of an immune deficiency did not become apparent until the age of 4 yr.

Attention Deficit Disorder with Hyperactivity↗
PubMed1986

Functional and mechanistic studies on the toxicity of deoxyguanosine for the in vitro proliferation and differentiation of human peripheral blood B lymphocytes.

Deoxyguanosine (dGuo) has been implicated as the toxic metabolite causing a severe impairment of cellular immunity in children with a genetic deficiency of purine nucleoside phosphorylase (PNP). In peripheral blood T cells of normal donors both the pathway which leads to phosphorylation of dGuo (ultimately resulting in deoxyguanosine triphosphate, dGTP) and the salvage pathway which starts with degradation of dGuo by PNP (resulting in the formation of guanosine triphosphate, GTP) contribute to the inhibition of proliferation. In normal peripheral blood B cells, addition of dGuo leads to an inhibition of proliferation and differentiation. The concentrations of dGuo needed to cause a 50% inhibition are equivalent for peripheral blood T cells and B cells. Inhibition of B cell differentiation can be observed at the level of intracytoplasmic as well as secreted Ig and concerns all Ig isotypes. The early phase of B cell activation which takes place during a 24-h preculture with formalinized Cowan I Staphylococci is not affected by dGuo; it is not until proliferation and differentiation of B cells, brought about by culturing in the presence of crude concanavalin A supernatant, occurs that inhibitory effects of dGuo become evident. Addition of dGuo to B cell cultures results in an intracellular accumulation of GTP and dGTP. Addition of 8-aminoguanosine, a PNP inhibitor, next to dGuo, completely prevents the dGuo-mediated inhibition. Under these circumstances the dGuo-mediated increase in intracellular GTP is abrogated while dGTP accumulation still occurs. This indicates that the inhibitory effect of dGuo on the proliferation and differentiation of peripheral blood B lymphocytes of normal donors is independent of dGTP accumulation.

Adenine↗