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Biomedical subjects

M Vekemans

Publications and source records attributed to M Vekemans.

At least 127 records · Page 7Linked to original sources
PubMed1997

Postpartum contraception: the lactational amenorrhea method.

Breastfeeding still accounts for a significant proportion of all fertility reduction, the average birth interval being longer among populations that breastfeed. However, per se it is not reliable for individual fertility suppression. The lactational amenorrhea method (LAM) is a highly efficient tool for the individual woman to utilize physiology to space births. Suckling induces a reduction in gonadotropin releasing hormone, luteinizing hormone and follicle stimulating hormone release, resulting in amenorrhea, through an intracerebral opioid pathway: beta-endorphins inhibit gonadotropin releasing hormone and dopamine secretions, which, in turn stimulates prolactin secretion and milk production. Reduced suckling precipitates the return of ovulation. During lactation, menses before 6 months are mostly anovulatory, and fertility remains low. The lactational amenorrhea method is based on three simultaneous conditions: (1) the baby is under 6 months; (2) the mother is still amenorrheic; and (3) she practises exclusive or quasi-exclusive breastfeeding on demand, day and night. Experiments with LAM extended to 9-12 months are ongoing. We use a standardized algorithm to present LAM. The lactational amenorrhea method is a way both to space births and to support breastfeeding, which should be replaced by a contraceptive method in due course. A 'Breastfeeding-LAM-Family Planning' team is very helpful in maternity wards for promoting modern breastfeeding, LAM, and contraception, and for alleviating barriers and misconceptions. The lactational amenorrhea method is at least 98% effective, comparing favorably with other contraceptive methods. Acceptability and continuity are not very well known; as with other 'natural' methods the figures are probably low in a general population but high for motivated couples. The lactational amenorrhea method avoids double protection, and thus saves resources, is especially (but not exclusively) suitable for couples interested in natural family planning and is accepted by religious authorities. The lactational amenorrhea method gives time to decide upon a long-term method of contraception. Unwanted pregnancies, although infrequent, conceived while using LAM result in very short, high-risk birth intervals. Introduction of LAM in family planning programs demands training, attention to be given to working mothers, positive attitudes of health personnel, close links between postpartum and family planning teams, situation analysis, budgets, evaluations, follow-up activities, modifications of record keeping systems and computing programs, and of national family planning guidelines. In conclusion, LAM is an efficient family planning method which should be promoted. The lactational amenorrhea method should always include the shift to another method when its criteria are no longer implemented.

Algorithms↗
PubMed1997

Trisomy for the distal segment of the short arm of chromosome 17 in a boy with mild mental retardation and some dysmorphic features.

The authors describe a boy with a triangular face, wide forehead, telecanthus, large ears, prominent root of the nose, long and bulging philtrum, thin upper lip, everted lower lip, high arched palate, micrognathism, pointed chin, overriding toes, joint laxity, and mild mental retardation. Cytogenetic investigation disclosed the presence of an added chromosome, a very small acrocentric, consisting in the presence of the last band of the short arm of chromosome 17. This anomaly results from a 3:1 mal segregation of a balanced (13q17p) reciprocal maternal translocation leading to a trisomy 17pter. This is a previously undescribed chromosome anomaly.

Abnormalities, Multiple↗
PubMed1997

[Detection of chromosome anomalies using in situ hybridization on fetal tissue sections].

The use of in situ hybridization to detect and characterize chromosome anomalies on cytogenetic preparations is now largely applied in clinical laboratories. Its use in embryofetopathology on formalin-fixed and paraffin-embedded tissues, when an aneuploid condition is suspected but a routine chromosomal analysis is not possible was assessed in the present study. Control values of hybridization signals obtained after different enzymatic digestion protocols have been established on normal fetal tissues. Tissue conservation and fetal age as well as other parameters have also been analysed. A successful hybridization has been achieved in most cases. Failure of hybridization was observed in specimens associated with extensive tissular lysis. In conclusion, the application of in situ hybridization on fetal tissues is very useful to detect chromosome anomalies in embryofetopathology.

Aneuploidy↗
PubMed1996

Possible new variant of Nijmegen breakage syndrome.

We report on a child with microcephaly, small facial and body size, and immune deficiency. The phenotype is consistent with Nijmegen breakage syndrome (NBS), with additional clinical manifestations and laboratory findings not reported heretofore. Most investigations, including the results of radiation-resistant DNA synthesis, concurred with the diagnosis of NBS. Cytogenetic analysis documented abnormalities in virtually all cells examined. Along with the high frequency of breaks and rearrangements of chromosomes 7 and 14, we found breakage and monosomies involving numerous other chromosomes. Because of some variation in the clinical presentation and some unusual cytogenetic findings, we suggest that our patient may represent a new variant of Nijmegen breakage syndrome.

Cells, Cultured↗
PubMed1996

A case report of Down syndrome and centroblastic lymphoma.

We describe a case of left cervical stage I centroblastic lymphoma in a 29-year old male patient with Down's syndrome due to a (14; 21) Robertsonian translocation. The disease presented as extensive lymph node necrosis leaving rare areas of tumor cells, accounting for the diagnostic difficulties. According to our review of the literature, lymphoma is one of the most common neoplasms in DS patients and may represent the second most common malignancy in this condition, far behind leukemia.

Adult↗
PubMed1996

Translocation between chromosomes 6 and 15 (45,XX,t(6;15)(q25;q11.2)) with further evidence for lack of imprinting of the insulin-like growth factor II/mannose-6-phosphate receptor in humans.

We report a 24 year old female with growth retardation, microcephaly, and congenital abnormalities who has an unbalanced de novo translocation between chromosomes 16 and 6: 45,XX,t(6;15)(q25;q11.2). FISH analysis confirmed that the deletion on chromosome 15 is proximal to the Prader-Willi locus. Several genes have been assigned to the 6q25-qter region including the insulin-like growth factor II/mannose-6-phosphate (IGF-II/M6P) receptor. DNA analysis from our patient documented the loss of one IGF2R gene copy. These data confirm the localisation of the IGF2R receptor to distal 6q25. We also showed reduced expression of the soluble and membrane bound IGF-II receptor, a gene dosage effect incompatible with imprinting. The IGF2R gene has been shown to be imprinted in the mouse but not in humans. Our data provide further evidence for lack of imprinting of this gene in humans.

Adult↗
PubMed1996

Confined placental mosaicism.

In most pregnancies the chromosomal complement detected in the fetus is also present in the placenta. The detection of an identical chromosomal complement in both the fetus and its placenta has always been expected as both develop from the same zygote. However, in approximately 2% of viable pregnancies studied by chorionic villus sampling (CVS) at 9 to 11 weeks of gestation, the cytogenetic abnormality, most often trisomy, is confined to the placenta. This phenomenon is known as confined placental mosaicism (CPM). It was first described by Kalousek and Dill in term placentas of infants born with unexplained intrauterine growth restriction (IUGR). Contrary to generalised mosaicism, which is characterised by the presence of two or more karyotypically different cell lines within both the fetus and its placenta, CPM represents tissue specific chromosomal mosaicism affecting the placenta only. The diagnosis of CPM is most commonly made when, after the diagnosis of chromosomal mosaicism in a CVS sample, the second prenatal testing (amniotic fluid culture or fetal blood culture analysis) shows a normal diploid karyotype.

Chorionic Villi Sampling↗
PubMed1996

[Continuity of utilization of a levonorgestrel releasing contraceptive implant: prospective study in Belgium].

Since 1988 we inserted 760 sets of a subcutaneous hormonal contraceptive releasing levonorgestrel active for 5 years. The aim of the study was to investigate the continuation rates. We considered our first 612 insertions. The 5-year cumulative pregnancy rate was 3.7%. The continuation rates were high (50% of the implants remained in situ after 3 1/2 years). These rates increased with age, and were better with European than with non-European subjects (mainly Moroccan and Turkish women). Parity didn't influence. The rates increased over time, because more unhappy women soon came back compared to satisfied users. Removals were related to pregnancy wish, irregular blood loss, end of action, and various side effects. In a few cases untrained physicians removed the implants.

Adult↗
PubMed1996

[Waardenburg's syndrome].

Waardenburg syndrome is an autosomal dominant disorder characterised by sensorineural hearing loss, pigmentary abnormalities of iris, hair and skin and dystopia canthorum. The expression of clinical findings of Waardenburg syndrome is extremely variable. The potential sources of this variability include allelic variation, genetic heterogeneity, epistatic modifying genes and stochastic effects. This type of multifactorial inheritance based on oligogenic epistasis is very different from the model based on polygenic inheritance. Indeed in the first model, knowledge of the genotype at relevant modifier loci may allow prediction and possibly treatment of clinically relevant aspects of the phenotype. Therefore a more complete understanding of gene expression in Waardenburg could provide insights that are relevant to many other multifactorial diseases.

Animals↗
PubMed1995

The rat phospholipase C beta 4 gene is expressed at high abundance in cerebellar Purkinje cells.

Inositol phospholipid-specific phospholipase C (PLC) generates two important second messengers, inositol triphosphate and diacylglycerol. The recently cloned rat PLC beta 4 cDNA is highly homologous to the norpA cDNA of Drosophila melanogaster. We have mapped the PLC beta 4 gene expression in rat brain tissue sections by in situ hybridization. The PLC beta 4 gene is expressed at high abundance in cerebellar Purkinje cells and neurones of the substantia nigra, the median geniculate bodies and the thalamic nuclei. PLC beta 4 transcripts are also detected in the mammillary nuclei, the neocortex, the habenula and the olfactory bulbs. The specific pattern of gene expression we have observed should help to clarify the relationships between the PLC beta 4 and various constituents of second-messenger systems involved in transduction mechanisms triggered by the stimulation of seven transmembrane domain receptors. The strong gene expression in Purkinje cells and retinal neurones suggests that PLC beta 4 may be involved in the pathogenesis of mouse and human neurological diseases characterized by ataxia and retinal degeneration.

Animals↗
PubMed1995

Upper limb malformations in DiGeorge syndrome.

We report on upper limb anomalies in two children with a complete DiGeorge sequence: conotruncal defects, hypocalcemia, thymic aplasia, and facial anomalies. One child had preaxial polydactyly, and the other had club hands with hypoplastic first metacarpal. In both patients, molecular analysis documented a 22q11 deletion. To our knowledge, limb anomalies have rarely been reported in DiGeorge syndrome, and they illustrate the variable clinical expression of chromosome 22q11 deletions.

Chromosome Deletion↗
PubMed1995

Dysembryoplastic neuroepithelial tumors in two children with neurofibromatosis type 1.

Dysembryoplastic neuroepithelial tumors (DNT) occur mainly in children and are always clinically associated with intractable complex partial seizures. In the first report, which included 39 cases, the patients had no neurological deficit and no stigmata of phacomatosis. In contrast, we observed a DNT in 2 children with a neurofibromatosis type 1. The first patient developed intractable complex partial seizures at age 9 years and was operated at the age of 13 years. Neuroimaging study showed multifocal involvement with three separated lesions in the frontal, parietal and temporal lobes. The second patient was a 16-year-old boy with 5-year history of severe and refractory epilepsy. Magnetic resonance imaging identified a right temporal lesion and the patient underwent a right temporal lobectomy. This unusual association of two cases of DNT with neurofibromatosis type 1 raises the question of whether this association is specific or fortuitous.

Adolescent↗
PubMed1995

PAX-genes expression during human embryonic development, a preliminary report.

PAX-genes encode important transcriptional factors during embryogenesis. They are also involved in human diseases, Waardenburg syndrome, Aniridia and tumors. We report in the present paper a preliminary in situ hybridization study of PAX3-, PAX5- and PAX6-gene expression during human embryonic development. PAX3-gene is expressed in the neural groove before closure, and in the closed neural tube. Afterwards, its expression is observed in the mesencephalon, the rhombencephalon and the spinal cord. PAX5-gene expression is restricted to the mesencephalon-rhombencephalon boundary and the spinal cord. PAX6-gene is expressed early in the neural tube, just after its closure. Afterwards, its expression is observed in the forebrain, the rhombencephalon, the somites and the spinal cord. These patterns of expression are observed early during human embryonic development and are specific in time and space. This preliminary report shows the feasibility of in situ hybridization methodology for studying the expression of developmental genes during the early stages of human embryogenesis. It opens the way to study the pathogenesis of polymalformative syndromes and tumorigenesis.

Chromosome Mapping↗
PubMed1994

U-type exchange in a paracentric inversion as a possible mechanism of origin of an inverted tandem duplication of chromosome 8.

A mentally retarded male with dysmorphic features was found to have a de novo 46,XY,inv dup(8) (p.23.1-->12). Confirmation of the segments duplicated in the rearrangement was achieved by biochemical analysis of glutathione reductase, which maps to 8p21.1, and DNA studies using the chromosome specific probe y-19-1D (D85131), which maps to 8p21. Assay of cathepsin B, which has been localised to 8p22, did not differ from controls with normal chromosomal constitution. DNA studies using the Defensin 1 gene probe, which maps to 8p23, showed a previously undetected deletion of that segment. We propose that the inverted tandem duplication/deletion arose as a single U-type exchange within an inversion loop.

Abnormalities, Multiple↗