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Dive into the research topics where Maarten F. C. M. Knapen is active.

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Featured researches published by Maarten F. C. M. Knapen.


European Journal of Obstetrics & Gynecology and Reproductive Biology | 1999

Glutathione and glutathione-related enzymes in reproduction : A review

Maarten F. C. M. Knapen; Petra L.M. Zusterzeel; Wilbert H.M. Peters; Eric A.P. Steegers

Glutathione and glutathione-related enzymes are pivotal for the normal functioning of several important biological processes in humans. Glutathione and glutathione-related enzymes are involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species. The role of reactive oxygen species in reproduction was the subject of many investigations, and there is compelling evidence for the involvement of these species in the physiology and pathology of both male and female reproductive systems. The glutathione/glutathione-related enzyme system was extensively studied in gynaecological oncology, but to a lesser extent in other topics related to reproduction. In this paper a review is provided on the glutathione/glutathione-related enzyme system in reproduction. Attention is given to its role as a detoxicating system, and as an early marker for disease.


Obstetrics & Gynecology | 1999

Glutathione S-transferase isoenzymes in decidua and placenta of preeclamptic pregnancies

Petra L.M. Zusterzeel; Wilbert H.M. Peters; Marion A.H De Bruyn; Maarten F. C. M. Knapen; Hans M.W.M. Merkus; Eric A.P. Steegers

OBJECTIVE To investigate a possible involvement of glutathione S-transferases, major detoxificating enzymes, in the pathophysiology of preeclampsia. METHODS Levels of glutathione S-transferase isoforms and enzyme activity were assessed in placental and decidual tissues in 22 preeclamptic and 21 normotensive women. Measured values were analyzed statistically using the Mann-Whitney U test for comparison between groups, and the signed-rank test for comparison within groups. RESULTS Glutathione S-transferase pi is the main glutathione S-transferase isoform in normal placental and decidual tissue. Lower median placental and decidual glutathione S-transferase pi levels were found in preeclamptic women compared with controls: 1268 (range: 524-3925) and 2185 (range: 503-6578), P = .05, for placenta; 1543 (range: 681-2967) and 2169 (range: 893-3929), P = .02, for decidua. The total amount of glutathione S-transferases in control and preeclamptic pregnancies was higher in decidua than in placenta. CONCLUSION Reduced levels of glutathione S-transferase class pi in preeclampsia might indicate a decreased capacity of the glutathione/glutathione S-transferase detoxification system. A higher total amount of glutathione S-transferases in decidual tissue might point to a more pronounced protective role of decidua compared with placenta.


Molecular Cytogenetics | 2012

Genomic SNP array as a gold standard for prenatal diagnosis of foetal ultrasound abnormalities

Malgorzata I. Srebniak; Marjan Boter; Grétel Oudesluijs; Titia E. Cohen-Overbeek; Lutgarde C. P. Govaerts; Karin E. M. Diderich; Renske Oegema; Maarten F. C. M. Knapen; Ingrid van de Laar; Marieke Joosten; Diane Van Opstal; Robert-Jan H. Galjaard

BackgroundWe have investigated whether replacing conventional karyotyping by SNP array analysis in cases of foetal ultrasound abnormalities would increase the diagnostic yield and speed of prenatal diagnosis in clinical practice.Findings/resultsFrom May 2009 till June 2011 we performed HumanCytoSNP-12 array (HCS) (http://www.Illumina.com) analysis in 207 cases of foetal structural abnormalities. HCS allows detecting unbalanced genomic abnormalities with a resolution of about 150/200 kb. All cases were selected by a clinical geneticist after excluding the most common aneuploidies by RAD (rapid aneuploidy detection). Pre-test genetic counselling was offered in all cases.In 24/207 (11,6%) foetuses a clinically relevant genetic abnormality was detected. Only 8/24 abnormalities would have been detected if only routine karyotyping was performed. Submicroscopic abnormalities were found in 16/207 (7,7%) cases. The array results were achieved within 1-2 weeks after amniocentesis.ConclusionsPrenatal SNP array testing is faster than karyotyping and allows detecting much smaller aberrations (~0.15 Mb) in addition to the microscopic unbalanced chromosome abnormalities detectable with karyotyping (~ > 5 Mb). Since karyotyping would have missed 66% (16/24) of genomic abnormalities in our cohort, we propose to perform genomic high resolution array testing assisted by pre-test counselling as a primary prenatal diagnostic test in cases of foetal ultrasound abnormalities.


Obstetrics & Gynecology | 1998

Low whole blood glutathione levels in pregnancies complicated by preeclampsia or the hemolysis, elevated liver enzymes, low platelets syndrome

Maarten F. C. M. Knapen; Theo P.J. Mulder; Iris A.L.M van Rooij; Wilbert H.M. Peters; Eric A.P. Steegers

Objective To investigate the pathophysiologic involvement of glutathione in pregnancies complicated by preeclampsia or the hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome. Methods Total whole blood glutathione levels were measured by high performance liquid chromatography in 23 women with pregnancies complicated by preeclampsia or the HELLP syndrome and in 22 normotensive gravidas. Total glutathione levels and the total glutathione/hemoglobin ratios of patients were compared with those of controls by the Mann-Whitney U test. Results Median total glutathione levels were lower in preeclamptic pregnancies or those complicated by the HELLP syndrome than in normotensive pregnancies (647 [range 268–986] and 750 [range 495–1572] μmol/L, P = .05). The median total glutathione/hemoglobin ratios were significantly lower in preeclamptic pregnancies or in those complicated by the HELLP syndrome than in normotensive pregnancies (0.079 [range 0.033–0.122] and 0.101 [range 0.073–0.210], P = .02). Conclusion Decreased total glutathione levels in maternal whole blood might indicate decreased detoxificating or free radical scavenging capacity in pregnancies complicated by preeclampsia or the HELLP syndrome.


Fertility and Sterility | 2003

Glutathione and glutathione S-transferases A1-1 and P1-1 in seminal plasma may play a role in protecting against oxidative damage to spermatozoa

Maarten T.M. Raijmakers; Hennie M.J. Roelofs; Eric A.P. Steegers; R.égine P.M Steegers-Theunissen; Theo P.J. Mulder; Maarten F. C. M. Knapen; Wai Yee Wong; Wilbert H.M. Peters

OBJECTIVE To study the levels of glutathione, glutathione S-transferase A1-1, and glutathione S-transferase P1-1 in seminal fluid of fertile and subfertile men. DESIGN Retrospective case-control study. SETTING Departments of gastroenterology, obstetrics and gynecology, and epidemiology and biostatistics in a university medical center. PATIENT(S) Twenty-five subfertile men visiting the fertility clinic and 25 fertile men from midwife practices were recruited. INTERVENTION(S) Collection of semen of subfertile and fertile men. MAIN OUTCOME MEASURE(S) Plasma levels of glutathione and glutathione S-transferases A1-1 and P1-1 in relation to seminal characteristics. RESULT(S) Glutathione, glutathione S-transferase A1-1, as well as glutathione S-transferase P1-1 were found in considerable amounts in seminal fluid of subfertile and fertile men. No differences between groups were found for glutathione S-transferases A1-1 and P1-1. Also, no associations with sperm count, motility, or morphology could be detected. Fertile men had significantly higher glutathione levels as compared with the case of subfertile men. Associations of glutathione with sperm motility quality (r(s) = 0.321) and abnormal sperm morphology (r(s) = -0.496) were found. CONCLUSION(S) The presence of glutathione S-transferases A1-1 and P1-1 in seminal fluid suggests a role in the protection against (oxidative) damage of spermatozoa, whereas glutathione may play a role in male fertility.


American Journal of Obstetrics and Gynecology | 1998

Plasma glutathione S-transferase Alpha 1-1: A more sensitive marker for hepatocellular damage than serum alanine aminotransferase in hypertensive disorders of pregnancy

Maarten F. C. M. Knapen; Theo P.J. Mulder; Jan G.A. Bisseling; Renate H.M.J. Penders; Wilbert H.M. Peters; Eric A.P. Steegers

OBJECTIVE Our purpose was to investigate the value of plasma glutathione S-transferase Alpha 1-1 measurements in the assessment of hepatocellular damage in hypertensive disorders of pregnancy. STUDY DESIGN Patients were recruited at the Department of Obstetrics and Gynecology of the University Hospital, Nijmegen, The Netherlands. Five groups of patients were studied: normotensive pregnancy (n = 87), pregnancy-induced hypertension (n = 48), preeclampsia (n = 79), the syndrome of hemolysis, elevated liver enzymes, and low platelets (n = 39), and serially studied normotensive pregnancy (n = 21). Blood was collected for assessment of plasma glutathione S-transferase Alpha 1-1 levels and serum alanine aminotransferase activity. Levels in hypertensive pregnancies were compared with levels in normotensive pregnancy by the Mann-Whitney U test. Patients were categorized according as to whether their values are below (normal) or above (elevated) the upper normal reference level. The difference in relative magnitude of elevation between the two factors was determined by the Wilcoxon matched-pairs signed-rank test. RESULTS Plasma levels in the longitudinally studied normotensive pregnancy group did not differ between gestational ages and were not significantly different from those of the normotensive control group. Median levels of glutathione S-transferase Alpha 1-1 and alanine aminotransferase were significantly increased (p < 0.01, p < 0.0001, respectively) in all subgroups of hypertensive pregnancies compared with normotensive pregnancies. When both levels were elevated, the relative magnitude of the increase of glutathione S-transferase Alpha 1-1 levels was significantly higher than that of alanine aminotransferase activity in preeclampsia (p < 0.01) and the syndrome of hemolysis, elevated liver enzymes, and low platelets (p < 0.0001). Almost half the patients with preeclampsia showed elevated levels of alanine aminotransferase and/or glutathione S-transferase Alpha 1-1. CONCLUSION Plasma glutathione S-transferase Alpha 1-1 measurements may provide a more sensitive indicator of acute hepatic damage in preeclampsia and the syndrome of hemolysis, elevated liver enzymes, and low platelets compared with the assessment of aminotransferase activity and therefore may allow earlier recognition of these syndromes. The clinical benefits of plasma measurements of glutathione S-transferase Alpha 1-1 for monitoring the hepatic condition in the management of these patients need to be elucidated in further studies.


European Journal of Human Genetics | 2016

Prenatal SNP array testing in 1000 fetuses with ultrasound anomalies: causative, unexpected and susceptibility CNVs

Malgorzata I. Srebniak; Karin E. M. Diderich; Marieke Joosten; Lutgarde C. P. Govaerts; Jeroen Knijnenburg; Femke de Vries; Marjan Boter; Debora Lont; Maarten F. C. M. Knapen; Merel C. de Wit; A. T. J. I. Go; Robert-Jan H. Galjaard; Diane Van Opstal

To evaluate the diagnostic value of single-nucleotide polymorphism (SNP) array testing in 1033 fetuses with ultrasound anomalies we investigated the prevalence and genetic nature of pathogenic findings. We reclassified all pathogenic findings into three categories: causative findings; unexpected diagnoses (UD); and susceptibility loci (SL) for neurodevelopmental disorders. After exclusion of trisomy 13, 18, 21, sex-chromosomal aneuploidy and triploidies, in 76/1033 (7.4%) fetuses a pathogenic chromosome abnormality was detected by genomic SNP array: in 19/1033 cases (1.8%) a microscopically detectable abnormality was found and in 57/1033 (5.5%) fetuses a pathogenic submicroscopic chromosome abnormality was detected. 58% (n=44) of all these pathogenic chromosome abnormalities involved a causative finding, 35% (n=27) a SL for neurodevelopmental disorder, and 6% (n=5) a UD of an early-onset untreatable disease. In 0.3% of parental samples an incidental pathogenic finding was encountered. Our results confirm that a genomic array should be the preferred first-tier technique in fetuses with ultrasound anomalies. All UDs involved early-onset diseases, which is beneficial for the patients to know. It also seems that UDs occur at a comparable frequency among microscopic and submicroscopic pathogenic findings. SL were more often detected than in pregnancies without ultrasound anomalies.


British Journal of Obstetrics and Gynaecology | 1998

Liver function following pregnancy complicated by the HELLP syndrome

Maarten F. C. M. Knapen; Anne M. van Altena; Wilbert H.M. Peters; Hans M.W.M. Merkus; Jan B.M.J. Jansen; Eric A.P. Steegers

Serum levels of aminotransferases, lactate dehydrogenase, gammaglutamyl transferase, alkaline phosphatase, albumin and conjugated bilirubin, measured in 54 women at a median of 31 months (range 3–101) after pregnancies complicated by the HELLP syndrome, were not elevated. Total bilirubin levels, however, were elevated in 20′1/0 of these women; this represents a significant difference from the prevalence in 151 women with a previous normal pregnancy (χ2= 12.23, P < 0.001), or in the normal female population (χ2= 22.34, P < 0.00001). This raises the possibility that a dysfunction of the bilirubin‐conjugating mechanism represents a risk factor for the development of the HELLP syndrome.


American Journal of Medical Genetics Part A | 2013

A de novo GLI3 mutation in a patient with acrocallosal syndrome

Leonie Speksnijder; Titia E. Cohen-Overbeek; Maarten F. C. M. Knapen; Simone M. Lunshof; A. Jeannette M. Hoogeboom; Ans M. van den Ouwenland; Irenaneus F.M. de Coo; Maarten H. Lequin; Hanno J. Bolz; Carsten Bergmann; Leslie G. Biesecker; Patrick J. Willems; Marja W. Wessels

Acrocallosal syndrome is characterized by postaxial polydactyly, macrocephaly, agenesis of the corpus callosum, and severe developmental delay. In a few patients with this disorder, a mutation in the KIF7 gene has been reported, which was associated with impaired GLI3 processing and dysregulaton of GLI3 transcription factors. A single patient with acrocallosal syndrome and a de novo p.Ala934Pro mutation in GLI3 has been reported, whereas diverse and numerous GLI3 mutations have also been described in syndromes with overlapping clinical manifestations, including Greig cephalopolysyndactyly syndrome, Pallister–Hall syndrome, trigonocephaly with craniosynostosis and polydactyly, oral–facial‐digital syndrome, and non‐syndromic polydactyly. Here, we describe a second patient with acrocallosal syndrome, who has a de novo, novel c.2786T > C mutation in GLI3, which predicts p.Leu929Pro. This mutation is in the same domain as the mutation in the previously reported patient. These data confirm that mutations in GLI3 are a cause of the acrocallosal phenotype.


American Journal of Obstetrics and Gynecology | 2014

The effectiveness of multifetal pregnancy reduction in trichorionic triplet gestation

Lidewij van de Mheen; Sheila Everwijn; Maarten F. C. M. Knapen; Dick Oepkes; Melanie Engels; G. Manten; Hans A. Zondervan; Soetinah A.M. Wirjosoekarto; John M. G. van Vugt; Jan Jaap Erwich; Sebastiaan W. Nij Bijvank; Anita Ravelli; Steffie Heemelaar; Maria G. van Pampus; Christianne J.M. de Groot; Ben Willem J. Mol; Eva Pajkrt

OBJECTIVE The objective of the study was to assess in trichorionic triplet pregnancies the effectiveness of elective reduction to twins. STUDY DESIGN This was a nationwide retrospective cohort study. We compared the time to delivery and perinatal mortality in trichorionic triplet pregnancies electively reduced to twins with ongoing trichorionic triplets and primary dichorionic twins. RESULTS We identified 86 women with reduced trichorionic triplet pregnancies, 44 with ongoing trichorionic triplets, and 824 with primary twins. Reduced triplets had a median gestational age at delivery of 36.1 weeks (interquartile range [IQR], 33.3-37.5 weeks) vs 33.3 (IQR, 28.1-35.2) weeks for ongoing triplets and 37.1 (IQR, 35.3-38.1) weeks for primary twins (P < .001). The total number of surviving children in the reduced group was 155 (90%) vs 114 (86%) in the ongoing triplet group. After reduction, 75 of women (87%) had all their fetuses surviving, compared with 36 (82%) (relative risk [RR], 1.3; 95% confidence interval [CI], 0.72-2.3) for ongoing triplets and 770 (93%) (RR, 0.91; 95% CI, 0.82-1) for primary twins. There were 6 women without any surviving children (7%) after reduction vs 5 (11.4%) (RR, 0.81; 95% CI, 0.47-1.4) among women with ongoing triplets and 32 (3.9%) (RR, 1.7; 95% CI, 0.8-3.7) in women with primary twins. CONCLUSION In women with a triplet pregnancy, fetal reduction increases gestational age at birth with 3 weeks as compared with ongoing triplets. However, there the impact on neonatal survival is limited.

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Marieke Joosten

Erasmus University Rotterdam

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Eric A.P. Steegers

Erasmus University Rotterdam

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A. T. J. I. Go

Erasmus University Rotterdam

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Karin E. M. Diderich

Erasmus University Rotterdam

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Diane Van Opstal

Erasmus University Rotterdam

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D. Van Opstal

Erasmus University Rotterdam

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