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S M Maas

Publications and source records attributed to S M Maas.

At least 19 recordsLinked to original sources
PubMed2001

Increased tumour risk for BWS patients correlates with aberrant H19 and not KCNQ1OT1 methylation: occurrence of KCNQ1OT1 hypomethylation in familial cases of BWS.

Beckwith-Wiedemann syndrome (BWS) is an overgrowth malformation syndrome that maps to human chromosome 11p15.5, a region that harbours a number of imprinted genes. We studied the methylation status of H19 and KCNQ1OT1 (LIT1/KvDMR1) in a large series of BWS patients. Different patient groups were identified: group I patients (20%) with uniparental disomy and hence aberrant methylation of H19 and KCNQ1OT1; group II patients (7%) with a BWS imprinting centre 1 (BWSIC1) defect causing aberrant methylation of H19 only; group III patients (55%) with a BWS imprinting centre 2 (BWSIC2) defect causing aberrant methylation of KCNQ1OT1 only; and group IV patients (18%) with normal methylation patterns for both H19 and KCNQ1OT1. BWS patients have an increased risk of developing childhood tumours. In our patient group, out of 31 patients (group III) with KCNQ1OT1 demethylation only, none developed a tumour. However, tumours were found in 33% of patients with H19 hypermethylation (group I and II) and in 20% of patients with no detectable genetic defect (group IV). All four familial cases of BWS showed reduced methylation of KCNQ1OT1, suggesting that in these cases the imprinting switch mechanism is disturbed.

Alleles↗
PubMed2000

RET and GDNF gene scanning in Hirschsprung patients using two dual denaturing gel systems.

Hirschsprung disease (HSCR) is a congenital disorder characterised by intestinal obstruction due to an absence of intramural ganglia along variable lengths of the intestine. RET is the major gene involved in HSCR. Mutations in the GDNF gene, and encoding one of the RET ligands, either alone or in combination with RET mutations, can also cause HSCR, as can mutations in four other genes (EDN3, EDNRB, ECE1, and SOX10). The rare mutations in the latter four genes, however, are more or less restricted to HSCR associated with specific phenotypes. We have developed a novel comprehensive mutation detection system to analyse all but three amplicons of the RET and GDNF genes, based on denaturing gradient gel electrophoresis. We make use of two urea-formamide gradients on top of each other, allowing mutation detection over a broad range of melting temperatures. For the three remaining (GC-rich) PCR fragments we use a combination of DGGE and constant denaturing gel electrophoresis (CDGE). These two dual gel systems substantially facilitate mutation scanning of RET and GDNF, and may also serve as a model to develop mutation detection systems for other disease genes. In a screening of 95 HSCR patients, RET mutations were found in nine out of 17 familial cases (53%), all containing long segment HSCR. In 11 of 78 sporadic cases (14%), none had long segment HSCR. Only one GDNF mutation was found, in a sporadic case.

Amino Acid Substitution↗
PubMed2000

Interstitial deletion of the long arm of chromosome 2: a clinically recognizable microdeletion syndrome?

We report on a boy with an interstitial deletion of the long arm of chromosome 2 with breakpoints in chromosome bands q23 and q24.3. Main features were low-set and malformed ears, digital anomalies and congenital heart defects, which have also been reported in most of the previously described cases. A comparison of the features of the present patient with those in previously reported cases suggests the deletion 2q23q24 to be a clinically recognizable syndrome.

Abnormalities, Multiple↗
PubMed1999

[Genes and genetics in Hirschsprung's disease].

Hirschsprung's disease (HSCR) is a congenital disorder characterized by intestinal obstruction due to the absence of intramural ganglia along variable lengths of the colon. Occurrence among family members and recurrence risks among siblings are indications for involvement of genetic predispositions. Mutations have been discovered in five different susceptibility genes. One of the most important findings is the detection of specific mutations in the so-called RET gene, which can also be responsible for the multiple endocrine neoplasia type 2A (MEN2A) syndrome. HSCR patients with such specific mutations run an increased risk of developing MEN type 2A related tumours.

Drosophila Proteins↗
PubMed1999

Laparoscopic rectosigmoid colpopoiesis: does it benefit our transsexual patients?

When inversion of the combined penile and scrotal skin flaps for vaginoplasty in male-to-female transsexuals has not led to functional results, rectosigmoid colpopoiesis offers an immediate solution to a complicated and difficult problem. However, open colocolpopoiesis involves major surgery, and it may be associated with substantial extended morbidity and hospitalization, short- and long-term unfavorable results, and extensive scarring of the abdomen. To reduce this associated morbidity, we employ a laparoscopically assisted approach and a total laparoscopic rectosigmoid colpopoiesis. This procedure has been performed safely in the series presented herein, with no apparent compromise in the adequacy of the dissections. We conclude that our patients benefited from this procedure, and we advocate considering a total or partial laparoscopic approach whenever secondary rectosigmoid colpopoiesis is indicated in male-to-female transsexuals.

Adult↗
PubMed1998

Oncological implications of RET gene mutations in Hirschsprung's disease.

BACKGROUND: Germline mutations of the RET proto-oncogene identical to those found in the tumour predisposition syndrome multiple endocrine neoplasia type 2A (MEN2A), were detected in 2.5-5% of sporadic and familial cases of Hirschsprung's disease. Some patients with Hirschsprung's disease may therefore be exposed to a highly increased risk of tumours. AIMS: To define clinical use of RET gene testing in Hirschsprung's disease and related patient management from an oncological point of view. METHODS: Sixty patients with Hirschsprung's disease were screened for RET mutations. In three, MEN2A type RET mutations were detected. Case reports for these three patients are presented. RESULTS AND CONCLUSIONS: Only 22 families or sporadic patients with Hirschsprung's disease and MEN2A type RET mutations have been reported. Therefore, it is difficult to predict tumour risk for patients with familial or sporadic Hirschsprung's disease, and their relatives, who carry these mutations. For these mutation carriers, periodic screening for tumours as in MEN2A is advised, but prophylactic thyroidectomy is offered hesitantly. RET gene testing in familial or sporadic Hirschsprung's disease is not recommended at present outside a complete clinical research setting. In combined MEN2A/Hirschsprung's disease families RET gene testing, tumour screening, and prophylactic thyroidectomy are indicated as in MEN2A.

Adult↗
PubMed1996

EEC syndrome and genitourinary anomalies: an update.

We report on a large family with the ectrodactyly, ectodermal dysplasia, clefting (EEC) syndrome. The clinical manifestations in this family show great variability. Specific genitourinary anomalies were found. The propositus with micturition problems is discussed in detail. A dysplastic bladder epithelium might be the cause of these problems. A remarkable improvement of the complaints was achieved upon treatment with synthetic sulfonated glycosaminoglycans.

Abnormalities, Multiple↗
PubMed1996

[Consensus inflammatory intestinal diseases in children: ulcerative colitis and Crohn disease. Work Group Academic Medical Center, Amsterdam].

Members of different societies, including Paediatrics, Gastroenterology, Clinical Chemistry, Radiology and Pathology, involved in the treatment of children with inflammatory bowel disease (IBD) reached consensus during 12 meetings about definition, clinical and diagnostic work-up as well as initial treatment options in paediatric IBD. On the basis of history and physical examination a distinction is made between colitis-like or Crohn-like appearance. Further laboratory investigations are required in the presence of malnutrition, extraintestinal manifestations or growth retardation. Pathology plays an important part in the final diagnosis. Special attention is given to pubertal staging and height measurements as routine aspects of the treatment of children with IBD.

Algorithms↗
PubMed1995

Further characterization of the 5'-flanking region of the rat lactase-phlorizin hydrolase gene.

The lactase-phlorizin hydrolase gene is widely used as a marker of intestinal differentiation. Recent evidence demonstrating that transcription plays a major role in the regulation of this gene suggests that study of the 5'-flanking region will allow an understanding of how the expression of this gene is controlled. However, sequence, restriction, and primer extension analysis of a rat genomic clone has revealed that previously published data are incomplete. In the present study, we used a directed sequencing strategy to carefully analyze this region. Our expanded analysis of the 5'-flanking region of the lactase-phlorizin hydrolase gene should facilitate future studies of its structure and function.

Animals↗
PubMed1992

[Pregnancy during residency].

The number of female residents in the Netherlands has steadily increased in recent years. Due to the increased time on waiting lists to enter residency programmes and to the increased duration of training, female residents will be older during their residencies. This will probably result in an increased number of pregnancies during residencies. A questionnaire regarding pregnancy during residency was sent to 191 residents in two university hospitals in the Netherlands. The response rate was 74.3%. Fifty percent of the male and only 19% of the female residents had children. No negative effects of a pregnancy on their training were experienced or anticipated by the residents. However, a negative effect on the functioning of the department was expected. No formal provisions, like replacements were available and many solutions to replace pregnant colleagues depended on the flexibility of the colleagues. The wish to have children was high and equally distributed among male and female residents, 92% and 96%, resp. Given the difficulty to seek a permanent position and to have children after residency, the choice of many female residents will be to have their children during residency. This increase in number of pregnancies requires anticipation of the residency programme directors. They should take the lead in proposing adequate regulations.

Adult↗
PubMed1991

A method for analysis of the local atrial evoked response for determination of atrial capture in permanent pacing systems.

We developed a method for detection and analysis of the local atrial evoked response. Eleven patients undergoing permanent dual chamber pacemaker implantations for standard clinical indications were included in the study. Using a pacing system emulator, charge balancing using a variable triphasic stimulus waveform to reduce polarization artifact amplitude was performed first. This could not be completed in one patient because of a poor signal-to-noise ratio. Subsequent analysis of the local atrial evoked response in the remaining ten patients showed the typical signal to be a biphasic waveform with an initial negative deflection followed by a positive deflection nearly equal in amplitude. The mean amplitude of the atrial evoked response was 3.1 +/- 1.4 mV, while the intrinsic P wave amplitude in these same patients averaged 5.6 +/- 3.0 mV. The summed evoked response, a parameter that is directly proportional to the area of the signal, was used to determine atrial pacing threshold. The median atrial pacing threshold determined by the algorithm was 1.00 V. There was no instance of failure to detect loss of capture, nor was loss of capture inaccurately determined when there was still successful atrial pacing. Atrial capture in permanent pacing systems can thus be determined using an algorithm to record and analyze the local atrial evoked response. This method could potentially be useful in the automatic determination of atrial pacing threshold.

Algorithms↗