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D van Leenen

Publications and source records attributed to D van Leenen.

8 recordsLinked to original sources
PubMed2001

Significantly higher number of fetal cells in the maternal circulation of women with pre-eclampsia.

Although the pathophysiology of pre-eclampsia is unknown, several studies have indicated that abnormal placentation early in pregnancy might play a key role. It has recently been suggested that this abnormal placentation may result in transfusion of fetal cells (feto-maternal transfusion) in women with pre-eclampsia. In the present study, fetal nucleated red blood cells were isolated from 20 women with pre-eclampsia and 20 controls using a very efficient magnetic activated cell sorting (MACS) protocol. The number of male cells was determined using two-color fluorescence in situ hybridization (FISH) for X and Y chromosomes. Significantly more XY cells could be detected in women with pre-eclampsia (0.61+/-1.2 XY cells/ml blood) compared to women with uncomplicated pregnancies (0.02+/-0.04 XY cells/ml blood) (Mann-Whitney U-test, p<0.001). These results suggest that fetal cell trafficking is enhanced in women with pre-eclampsia, and this finding may contribute to the understanding of the pathophysiology of the disease.

Adult↗
PubMed2000

How useful is the in vitro expansion of fetal CD34+ progenitor cells from maternal blood samples for diagnostic purposes?

Fetal cells present in the maternal circulation are a potential source of fetal DNA that can be used for the development of a prenatal diagnostic test. Since their numbers are very low, amplification of fetal cells has been discussed for a long time. So far, most studies have focused on culturing fetal erythroid cells. In this study, we evaluated whether limiting numbers of fetal haemopoietic progenitor cells present in an excess of maternal cells were able to overgrow the maternal component. Therefore, we used a model system in which limiting numbers of male CD34+ umbilical cord blood cells were diluted in 400 000 female CD34+ peripheral blood cells. The number of XY positive cells derived from umbilical cord blood was determined using two-colour in situ hybridization with X and Y chromosomal probes. We demonstrated a 1500-fold relative expansion of male umbilical cord blood cells over the peripheral blood component after three weeks of liquid culture, which also corresponded to the extent of expansion of CD34+ cells derived from 20-week fetal blood. However, application of the same culture protocol to maternal blood samples obtained at 7-16 weeks of gestation showed no preferential growth of fetal haemopoietic progenitor cells. This study, therefore, suggests that fetal primitive haemopoietic progenitor cells do either not circulate in maternal blood before 16 weeks of gestation, or require different combinations/concentrations of cytokines for their in vitro expansion.

Antigens, CD34↗
PubMed1999

Mammalian Cry1 and Cry2 are essential for maintenance of circadian rhythms.

Many biochemical, physiological and behavioural processes show circadian rhythms which are generated by an internal time-keeping mechanism referred to as the biological clock. According to rapidly developing models, the core oscillator driving this clock is composed of an autoregulatory transcription-(post) translation-based feedback loop involving a set of 'dock' genes. Molecular clocks do not oscillate with an exact 24-hour rhythmicity but are entrained to solar day/night rhythms by light. The mammalian proteins Cryl and Cry2, which are members of the family of plant blue-light receptors (cryptochromes) and photolyases, have been proposed as candidate light receptors for photoentrainment of the biological clock. Here we show that mice lacking the Cryl or Cry2 protein display accelerated and delayed free-running periodicity of locomotor activity, respectively. Strikingly, in the absence of both proteins, an instantaneous and complete loss of free-running rhythmicity is observed. This suggests that, in addition to a possible photoreceptor and antagonistic clock-adjusting function, both proteins are essential for the maintenance of circadian rhythmicity.

Animals↗
PubMed1998

Glycogen storage disease type II: identification of a dinucleotide deletion and a common missense mutation in the lysosomal alpha-glucosidase gene.

In nine Dutch patients with the infantile form of glycogen storage disease type II (GSDII), who were compound heterozygous for either 525delT or exon18del (1), sequence analysis was performed to search for the mutations in the second lysosomal alpha-glucosidase allele. One patient had a novel TG deletion at cDNA position 379 + 380. Surprisingly five of the nine patients had the same two base pair changes: A921 --> T and G925 --> A. The first change is a well-known polymorphism but the second one is a novel mutation and results in the substitution of Gly309 by Arg. By screening 43 other GSDII patients the same mutation was found in two other cases, one from The Netherlands and one from France. To verify its deleterious effect, the mutation was introduced in the wild type lysosomal alpha-glucosidase cDNA and expressed in COS cells.

Alleles↗
PubMed1997

Mutation detection in glycogen storage-disease type II by RT-PCR and automated sequencing.

A new method is described for detection of mutations in the lysosomal alpha-glucosidase gene (GAA) leading to Glycogen Storage Disease type II (GSDII). A key feature of the method is isolation and reverse transcription of mRNA followed by PCR amplification of lysosomal alpha-glucosidase cDNA with M13-extended primers. Dye labeled primers are used for cycle sequencing and an ABI PRISM 377 DNA sequencing system for analysis. The method is rapid and complementary to the automated sequencing of all the 19, PCR amplified, coding exons of the GAA gene. The advantages and pitfalls of this new method are discussed in the light of the results obtained with an infantile GSDII patient. A new splice site mutation in the GAA gene of this patient was identified, IVS16(+2T-->C), resulting in the deletion of 16 base pairs of exon 16.

DNA, Complementary↗
PubMed1993

Pentoxifylline attenuates neutrophil activation in experimental endotoxemia in chimpanzees.

Costimulation of neutrophils and cytokines may play an important role in organ injury in sepsis. Pentoxifylline inhibits various neutrophil functions in vitro, and attenuates endotoxin-induced production of TNF in both in vitro and in vivo models. To assess the effect of pentoxifylline on neutrophil activation in endotoxemia, nine adult chimpanzees (Pan troglodytes) were i.v. injected with saline (n = 2), Escherichia coli endotoxin (4 ng/kg; n = 4), or E. coli endotoxin (4 ng/kg) in combination with pentoxifylline (500 mg/3 h, starting 30 min before the endotoxin injection; n = 3). Serial blood samples were obtained for measurements of leukocyte counts and the granulocytic proteinases elastase complexed with alpha 1-antitrypsin and lactoferrin, and cytokines during the next 5 h. No changes were observed in the saline-treated chimpanzees. Endotoxin induced a marked leukocytosis and neutrophilia, which were slightly reduced by pentoxifylline. In contrast, pentoxifylline almost completely prevented endotoxin-induced neutrophil degranulation: peak elastase-alpha 1-antitrypsin was 164 +/- 21 ng/ml (mean +/- SE) after endotoxin alone, vs 71 +/- 7 ng/ml after endotoxin with pentoxifylline (t = 3 h; p < 0.05); peak lactoferrin was 329 +/- 15 and 182 +/- 5 ng/ml, respectively (t = 5 h; p < 0.05). Pentoxifylline also inhibited the endotoxin-induced release of TNF (271 +/- 26 vs 55 +/- 23 pg/ml at t = 1.5 h; p < 0.05) and IL-6 (225 +/- 42 vs 73 +/- 25 pg/ml at t = 2 h; p < 0.05). IL-8 release was not significantly inhibited by pentoxifylline. In none of the animals activation of the C system could be detected. We conclude that pentoxifylline attenuates neutrophil activation in endotoxemia in chimpanzees, probably in part by inhibiting the release of TNF.

Animals↗
PubMed1993

Release of soluble receptors for tumor necrosis factor in clinical sepsis and experimental endotoxemia.

To assess the role of tumor necrosis factor (TNF) in the appearance of soluble TNF receptors (sTNFRs), 20 consecutive patients with a clinical diagnosis of sepsis were studied as were 7 chimpanzees after administration of endotoxin (4 ng/kg) with or without pentoxifylline. The patients had markedly elevated serum levels of sTNFR-p55 and sTNFR-p75 compared with healthy controls (P < .0001 for both receptors). The levels of both soluble receptors correlated with simultaneously measured immunoreactive TNF concentrations (p55: r = .63, P < .01; p75: r = .69, P < .001). In the chimpanzees, endotoxin induced subsequent rises in the serum concentrations of TNF and sTNFRs. Although pentoxifylline reduced the TNF response to intravenous endotoxin to 20% (P < .05), the appearance of sTNFRs was only moderately inhibited (sTNFR-p55 to 79% on average, P < .05; sTNFR-p75 to 77%, P = .12). These results indicate that TNF either does not play an important role in the appearance of sTNFRs in systemic infection or that a small amount of TNF remaining in the circulation after some bacterial challenges is sufficient to preserve the secretion of its soluble receptors.

Adult↗