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B Hamel

Publications and source records attributed to B Hamel.

At least 37 records · Page 2Linked to original sources
PubMed1998

Björnstad syndrome in a patient with mental retardation.

Björnstad syndrome in a patient with mental retardation: Pili torti or twisted hair can appear as an isolated defect, in association with other ectodermal defects, in association with other clinical features or can be acquired. Björnstad syndrome is a rare condition with apparent autosomal recessive inheritance, characterized by hearing loss and twisted hairs (pili torti). All patients with Björnstad syndrome reported thusfar have normal intelligence. We report on a patient with severe mental retardation and review the literature.

Hair↗
PubMed1996

Genetic mapping of the human homologue (T) of mouse T(Brachyury) and a search for allele association between human T and spina bifida.

We describe a genetic analysis of the human homologue (T) of the mouse T (Brachyury) gene; human T was recently cloned in our laboratory. The protein product of the T gene is a transcription factor crucial in vertebrates for the formation of normal mesoderm. T mutant Brachyury mice die in midgestation with severe defects in posterior mesodermal tissues; heterozygous mice are viable but have posterior axial malformations. In addition to its importance in development, T has intrigued geneticists because of its association with the mouse t-haplotype; this haplotype is a variant form of the t-complex and is characterized by transmission ratio distortion, male sterility and recombination suppression. We have identified a common polymorphism of human T by single strand conformation polymorphism (SSCP) and used this in mapping studies and to re-investigate the idea that human T is involved in susceptibility to the multifactorial, neural tube defect, spina bifida. Our mapping data show that human T maps to 6q27 and lies between two other genes of the t-complex, TCP1 and TCP10. These data add to the evidence that in man the genes of the t-complex are split into two main locations on the short and long arms of chromosome 6. We have used an allele association test which is independent of mode of inheritance and penetrance to analyse data from the spina bifida families. Using this test we find evidence for a significant (p = 0.02) association between transmission of the TIVS7-2 allele of the human T gene and spina bifida.

Alleles↗
PubMed1994

Clinical and molecular studies in a large Dutch family with Noonan syndrome.

We describe the largest Noonan syndrome (NS) family reported to date. The manifestations of the affected relatives are discussed. In the absence of a biochemical marker NS is still a clinical diagnosis. The diagnostic criteria that were used are presented compared with other published criteria for diagnosing NS. The large size of this family enabled us to test the possible involvement of candidate regions by multipoint linkage analysis. Both the region surrounding the NF1 locus on chromosome 17 and the proximal part of chromosome 22 could be excluded. Since NS may well be heterogeneous, the use of such a large family in linkage studies of NS should prove indispensable.

Adult↗
PubMed1994

Prediction of mental status in carriers of the fragile X mutation using CGG repeat length.

For genetic counseling in fragile X (fra(X)) families, it is important to know the diagnostic impact of the CGG repeat length in carriers of the fragile X mutation. We have analyzed the CGG repeat length in 106 males and 73 females who had inherited the maternal fra(X) mutation. The sensitivity, specificity, and predictive value of the CGG repeat analyses, as measured on Southern blots of PstI/EcoRI digests, were calculated. In males the sensitivity, specificity and negative predictive value were 99%, 100% and 94%; respectively. In females the specificity (60%) and, consequently, the positive predictive value (82%) was reduced. Therefore, it remains impossible to predict accurately whether a female fetus demonstrating a full mutation will be affected. On the other hand, the negative predictive value of the CGG test in females was 100%. We have no evidence, as yet, that for female carriers with the full mutation, cytogenetic analysis is of additional value to predict the mental status. However, we have observed one mentally retarded fra(X) case with extreme mosaicism in which a typical premutation fragment was the predominant DNA species. Therefore, until more data and better DNA tests are available, we would like to advocate additional cytogenetic investigation if in a fetus a CGG repeat length in the premutation range is found.

Blotting, Southern↗
PubMed1993

The gene for spondyloepiphyseal dysplasia (SEDL) maps to Xp22 between DXS16 and DXS92.

Previous linkage studies in X-linked spondyloepiphyseal dysplasia (SEDL) placed the gene in the region Xp22.2-p22.1 by linkage to DXS41. Here we have extended our earlier studies by analyzing 15 families with 13 markers from the Xp22 region. Pairwise linkage analysis revealed significant linkage of the SEDL to 8 markers from the Xp22.2-Xp22.1 region. Maximum lod scores were obtained with DXS207, tau max = 9.16 at theta max = 0.021 with confidence limits of 0.00-0.09, and DXS197, tau max = 7.98 at theta max = 0.00 with confidence limits of 0.00-0.06. The study of one recombinant in family 4 indicated that DXS 41 is more likely proximal to DXS92 than distal. Multipoint linkage results and analysis of recombination events indicated that the mutation responsible for SEDL is located in Xp22 between DXS 16 and DXS 92.

Chromosome Mapping↗
PubMed1993

Marden-Walker syndrome: case report, literature review and nosologic discussion.

The Marden-Walker syndrome is characterized by psychomotor retardation, a mask-like face with blepharophimosis, micrognathia and a high-arched or cleft palate, low-set ears, kyphoscoliosis and joint contractures. We report on a male patient with the clinical features of the syndrome. In addition, he had a Dandy-Walker malformation with hydrocephalus and vertebral abnormalities. During pregnancy, there were feeble fetal movements and polyhydramnios. We propose that Marden-Walker syndrome is one of the etiologic possibilities in children with the heterogeneous fetal a(hypo)kinesia deformation sequence (FADS). Differential diagnosis is discussed. The etiology is probably heterogeneous.

Abnormalities, Multiple↗
PubMed1991

Cartilage hair hypoplasia, metaphyseal chondrodysplasia type McKusick: description of seven patients and review of the literature.

We describe 7 cases of cartilage hair hypoplasia (CHH) with emphasis on the clinical and immunological aspects. The literature on CHH is reviewed and symptoms in 63 non-Amish cases are summarized. In this autosomal recessive disorder the immunodeficiency, hair abnormalities, and severity of skeletal involvement show extremely variable expressivity, between and within families. Two of the 3 sib-pairs among our cases demonstrate the great difference in expression within one family. At adult age roentgenological abnormalities can be very mild, or even absent. An impairment in cell-mediated immunity is present in all of our cases and seems a consistent manifestation in CHH; however, sometimes it is very subtle and without clinical symptoms.

Abnormalities, Multiple↗
PubMed1991

Linkage analysis in X-linked adrenoleukodystrophy and application in post- and prenatal diagnosis.

We have performed linkage analysis with the DNA markers DXS52 and the clotting factor VIII gene (F8C), in several large families with X-linked adrenoleukodystrophy (ALD). The tight linkage to DXS52 could be extended giving a maximal LOD score of 22.5 at 1 cM. F8C was also tightly linked to ALD with a maximal LOD score of 7.8 without recombination. Multipoint linkage analysis with the markers DXS304, DXS52, and F8C indicated that both the gene for ALD and for F8C are distal to DXS52. In four patients with ALD, no major structural rearrangement in the Xqter region was observed; in particular, there were no abnormalities in the vision blindness genes. DNA analysis appeared to be of use in determination of the carrier status of females at risk, for the determination of the origin of the mutation in a particular family, and for prenatal diagnosis.

Adrenoleukodystrophy↗
PubMed1990

The effect of CaCl2 and verapamil on the binding of cisplatin to cultures of normal and transformed human fibroblasts.

Normal and transformed human fibroblasts were treated for either 1 sec or 1 h with the antitumor drug cis-dichlorodiamine platinum (cisplatin). The dose response of drug binding and cell survival was determined for cells treated with the drug in the presence or absence of 3.0 mM CaCl2. The levels of drug initially bound to both cell types was similar and was not affected by the presence of Ca2+. The dividing non-transformed cells were most sensitive to killing by short treatment with cisplatin compared to the transformed cells or the confluent non-transformed cultures. After 1 h of cisplatin treatment, the levels of drug bound to the cells were significantly less than that recovered after the shorter treatment. This time-dependent loss of cisplatin was inhibited both by CaCl2 and by the calcium channel blocking agent, verapamil. The higher levels of cisplatin bound after 1 h in the presence of these agents, however, did not in all cases result in decreased survival; the effects were dependent on cell type and on whether the cells were dividing or confluent. Analysis of cisplatin binding to cell cultures indicated that initially the cisplatin was weakly attached to the pericellular and substratum attached material but that with time, the drug bound to this material decreased. This time-dependent removal from the extracellular matrix was much less in the transformed cell cultures and was inhibited by calcium. We propose that the major site of interaction of cisplatin with these cells is in the extracellular matrix and with time the cultures alter their extracellular matrix to decrease this binding. This removal process appears to involve calcium or calcium transport since CaCl2 and verapamil both block these changes.

Calcium Channel Blockers↗
PubMed1989

Contiguous gene syndromes due to deletions in the distal short arm of the human X chromosome.

Mendelian inherited disorders due to deletions of adjacent genes on a chromosome have been described as "contiguous gene syndromes." Short stature, chondrodysplasia punctata, mental retardation, steroid sulfatase deficiency, and Kallmann syndrome have been found as isolated entities or associated in various combinations in 27 patients with interstitial and terminal deletions involving the distal short arm of the X chromosome. The use of cDNA and genomic probes from the Xp22-pter region allowed us to identify 12 different deletion intervals and to confirm, and further refine, the chromosomal assignment of X-linked recessive chondrodysplasia punctata and Kallmann syndrome genes. A putative pseudoautosomal gene affecting height and an X-linked non-specific mental retardation gene have been tentatively assigned to specific intervals. The deletion panel described is a useful tool for mapping new sequences and orienting chromosome walks in the region.

Chromosome Deletion↗
PubMed1982

Melnick-Needles syndrome: indication for an autosomal recessive form.

We describe three patients with bone changes and the facial characteristics of the Melnick-Needles syndrome (MNS). Associated anomalies (once bilateral glaucoma, twice congenital heart defect) were the reason for referral. The MNS literature also suggests a high frequency of associated anomalies, especially cardiopulmonary malformations. The distribution of the affected relatives, consanguinity of one pair of parents, and absence of similar symptoms in parents and other relatives makes autosomal recessive inheritance of the trait in this family a definite possibility. This is of great importance in genetic counseling, particularly of sporadic cases.

Abnormalities, Multiple↗
PubMed1982

[Comparative study of two microbiological assay methods of serum isoniazid].

Two microbiological assay techniques for estimation of biologically active isoniazid concentrations in human serum were compared : the vertical diffusion method and a large plate method similar to that commonly used for the antibiotics. Four hundred seventy four tests were carried out on the serum from 133 patients. Parallel titrations were determined by two biologists on the same serum samples, with the same standard solutions, by the two methods performed rapidly after the collection of specimens and after they have been stored in the frozen state during one week and were compared. It was found that the variability obtained in these conditions was 26 per cent for the vertical diffusion method and 14 per cent for the large plate method. The correlation coefficients were 0,87 and 0,95 respectively. Also it will be noted that the large plate method is faster, of lower cost and require smaller volumes of serum. However, it also failed to detect levels lower than 0,5 and upper than 2 micrograms/ml, the standard curve is not stable and must be run with each assay and it is also subject to interference by other antibiotics.

Anti-Bacterial Agents↗
PubMed1981

Evaluation of a syntactic pattern recognition approach to quantitative electroencephalographic analysis.

This paper reports an experiment designed to evaluate the usefulness of a syntactic pattern recognition approach to quantitative EEG analysis. This approach provides a systematic way of organizing and interpreting spatially and temporally distributed activity in an EEG record. Many automated scoring systems evaluate only background activity, ignoring the significant transient events that may occur in an EEG. In contrast, syntactic methods allow evaluation of background activity in combination with transient events. In this paper, 454 EEGs recorded from a population of renal patients are evaluated using (1) the syntactic approach, and (2) a method based on discriminant analysis. The main finding is that the syntactic approach outperforms the discriminant analysis method when each technique is compared to visual scoring.

Electroencephalography↗