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Biomedical subjects

B Fontaine

Publications and source records attributed to B Fontaine.

At least 19 recordsLinked to original sources
PubMed2001

Use of the Kleihauer test to detect fetal erythroblasts in the maternal circulation.

Non-invasive prenatal diagnosis of aneuploidies on fetal nucleated erythrocytes present in the maternal circulation is hampered by the extremely small cell number of uncertain origin (70% of erythroblasts circulating during pregnancy have a maternal origin). Therefore, a method allowing selection of the fetal cells among the maternal cells is indispensable after the erythroblast enrichment step. In the present study, after an erythroblast enrichment step on a ficoll gradient followed by a positive immuno-magnetic selection with anti-CD71 or anti-GPA antibodies, a rapid, simple and direct chemical staining method adapted from the classical Kleihauer test was developed to select fetal cells. Precise differentiation between fetal and maternal erythroblasts is based on the constitutional difference between fetal and adult haemoglobin (Hb). The fetal cells appear with an intense pink cytoplasmic staining while maternal cells with adult haemoglobin are colourless. Preservation of the cytoplasmic integrity allows one to distinguish morphological characteristics and to visualize simultaneously nuclear hybridization signal by FISH (fluorescent in situ hybridization). This approach was tested by FISH analysis using dual-colour X- and Y-specific DNA probes on blood samples from 15 pregnant women, with the results being compared to cytogenetic or sonographic sex determination. For 12 pregnancies fetal sex was determined successfully (5 XY/7 XX), in two cases in situ hybridization failed, and in one case no fetal erythroblast was observed after the Kleihauer test. The selection method was applied to a pregnancy at risk for cystic fibrosis (CF). After a Kleihauer test, fetal erythroblasts were collected by microdissection, whole genomic DNA was amplified by primer extension pre-amplification (PEP) followed by a nested CF PCR. The fetal genotype was successfully characterized and confirmed by conventional prenatal diagnosis.

Antibodies↗
PubMed2001

Correlating multiple MRI parameters with clinical features: an attempt to define a new strategy in multiple sclerosis.

MRI is the most powerful imaging technique in managing patients with suspected or confirmed multiple sclerosis (MS). However, conventional MRI variables show nonspecific abnormalities weakly correlated with clinical progression of the disease. New techniques, now routinely available, offer better characterisation of the pathophysiology. We combined conventional MRI, including lesion load, contrast enhancement and "black holes" with magnetisation transfer and diffusion-weighted imaging and localised proton MR spectroscopy (MRS) to study their relationship with disability, course and duration of MS. The variables that were the most significantly linked to the course of the disease (relapsing remitting versus secondary progressive) were lesion load, mean overall magnetisation transfer ratio and apparent diffusion coefficient (MGADC), the percentage of ADC in (PADCIMD), and out of (PAD-COMD) modal distribution, and the ratio N-acetylaspartate and creatine-containing compounds on MRS of the centrum semiovale. MGADC and PADCIMD were the independent factors most related to disability and duration of disease. Combining MRI techniques is clinically relevant and feasible for studies of MS and may be applied to other diseases of the central nervous system.

Adult↗
PubMed2001

Occupational and environmental risk factors of the myelodysplastic syndromes in the North of France.

Aetiological factors of the myelodysplastic syndromes (MDS) are largely unknown, with the exception of alkylating agents, ionizing radiation and benzene. Some other risk factors have been suggested by the few epidemiological studies reported (solvents, ammonia, exhaust gases, metals, pesticides, alcohol). We performed a case-control study to assess the relationship between occupational or environmental factors and MDS. Two hundred and four patients with newly diagnosed MDS, and 204 sex- and age-matched controls were included. Medical history, demographic data, lifetime exposure and hobbies were obtained. Qualitative and quantitative exposure to chemical and physical hazards were evaluated with the patients and reviewed by a group of experts in occupational exposure. The median age was 70 years and 62% of the patients were men. In univariate analyses, we found relationships between MDS and smoking habits, gardening, occupations such as health professionals, technical and sale representatives, machine operators, agricultural workers, textile workers, qualitative occupational exposures (exposed/non-exposed) to oil, solvents, ammonia, pesticides, fertilizers, cereal dusts, contact with poultry or livestock and infective risk, and lifetime cumulative exposure to solvents, oil, textile dust and infective risk. The main risk factors of MDS determined by multivariate analyses (conditional logistic regression) were, being an agricultural worker [odds ratio (OR) = 3.66; 95% confidence interval (CI) 1.9-7.0], textile operator (OR = 3.66; 95% CI 1.9-7.9), health professional (OR = 10.0; 95% CI 2.1-48.7), commercial and technical sale representative (OR = 4.45; 95% CI 1.4-14.6), machine operator (OR = 2.69; 95% CI 1.2-6.0), living next to an industrial plant (OR = 2.45; 95% CI 1.5-4.1), smoking (OR = 1.74; 95% CI 1.1-2.7) and lifetime cumulative exposure to oil (OR = 1.1; 95% CI 1.0-1.2). Further studies should be performed to assess specific exposures more precisely and it would be of interest to develop a map of haematological malignancies according to industrial background.

Aged↗
PubMed2001

Could capillary zone electrophoresis of tryptic peptides be used for the characterization of hemoglobin variants?

The present article describes a simple and rapid new peptide mapping procedure that could be used to assist identification of rare hemoglobin variants in clinical laboratories. Four hemoglobin variants were taken as example, namely Hb D-Ouled Rabah, Hb Marseille, Hb G-Philadelphia, and Hb Ube-2, and isolated by electrophoresis at alkaline pH. The globin chains were aminoethylated and, after tryptic digestion, the peptides were separated by a capillary zone electrophoresis method. Highly reproducible migration times of the peptides were obtained with intra-assay and inter-assay coefficients of variation of less than 1 and 2%, respectively.

Amino Acid Sequence↗
PubMed2001

Hypokalaemic periodic paralysis type 2 caused by mutations at codon 672 in the muscle sodium channel gene SCN4A.

Hypokalaemic periodic paralysis (hypoPP) is an autosomal dominant muscle disorder characterized by episodic attacks of muscle weakness associated with a decrease in blood potassium levels. Mutations in the gene encoding the skeletal muscle voltage-gated calcium channel alpha-1 subunit (CACNL1A3) account for the majority of cases. Recently, mutations in the gene coding for the skeletal muscle voltage-gated sodium channel alpha subunit (SCN4A) have been reported in a small number of hypoPP families. In order to determine the relative frequency of the CANCL1A3 and SCN4A mutations in a large population of hypoPP patients, and to specify the clinical and pathological features associated with each of them, we searched for mutations in 58 independent hypoPP index cases. We detected the causative mutation in 45 cases: 40 were linked to the CACNL1A3 gene and five to the SCN4A gene. One mutation has not been described before. Some remarkable clinical features were observed in a large hypoPP family carrying an SCN4A mutation: a complete penetrance in men and women, an early age at onset, postcritic myalgias and an increased number and severity of attacks induced by acetazolamide. A muscle biopsy, performed in two members of this family, revealed a peculiar myopathy characterized by tubular aggregates. In contrast, vacuoles were predominant in muscles from hypoPP patients carrying CACNL1A3 mutations. Our findings point to the usefulness of a molecular characterization of hypoPP patients in clinical practice. They also provide new clues for understanding the mechanisms behind functional and structural alterations of the skeletal muscle in hypoPP.

Adolescent↗
PubMed2001

Congenital myopathies and congenital muscular dystrophies.

Congenital myopathies and congenital myopathic dystrophies are distinct groups of inherited diseases of muscle, genetically heterogeneous, that manifest in early life or infancy. Congenital myopathic dystrophy is characterized by a dystrophic pattern, whereas no necrotic or degenerative changes are present in congenital myopathies. Much progress has been made in recent years in clarifying the classification of the congenital myopathies. This is a clinically and genetically heterogeneous group of conditions originally classified according to unique morphological changes seen in muscle. Not unlike the later-onset muscular dystrophies, the discovery of the genetic aetiology of many of the congenital myopathies has led to a revamping of how these conditions can now be diagnosed and this should enable physicians to give a more accurate prognosis to patients and their families. New mutations in the ryanodine receptor, slow tropomyosin, troponin T1, actin, and nebulin genes have been described in the last 2 years. Clinical and genetic guidelines for conditions like nemaline rod myopathy and central core disease have been suggested. The notion of minus and surplus protein myopathies has been developed. Several groups of congenital myopathic dystrophy have been identified. In the first category, without intellectual impairment or major structural brain abnormalities, half of the cases are merosin deficient due to mutations of the laminin alpha 2 chain gene. If generally the muscular phenotype is severe, mild allelic variants have been reported with early onset dystrophies and partial merosin deficiency. Among other pure congenital myopathic dystrophies unlinked to the laminin alpha 2 gene, one form has been assigned to chromosome 1q42. In the group of congenital myopathic dystrophies associated with mental retardation and structural brain abnormalities, two main entities are genetically characterized: (1) Fukuyama congenital myopathic dystrophy, affecting the Japanese population, is due to fukutin gene mutations, and (2) the muscle eye brain syndrome assigned to chromosome 1p32-34. In several cases, the gene localization remains unknown.

Humans↗
PubMed2001

[Familial orthochromatic leukodystrophy: clinicopathological study of two cases].

This paper reports the clinico-pathological data in a French family with orthochromatic leukodystrophy. The parents were first cousins and had seven children. Among those, two sisters and one brother presented with neurological signs, with onset around the 5(th) decade, including a dementing syndrome of frontal type, a tetrapyramidal syndrome, seizures, and, in one sibling, a cerebellar syndrome. CT scan or MRI showed diffuse involvement of the white matter. The neurological signs worsened progressively leading to death within 11 and 22 months. Neuropathological examination was performed in two cases. It revealed characteristic orthochromatic leukodystrophy. In one case, the presence of pigmented macrophages and astrocytes was suggestive of Van Bogaert and Nyssen disease. However there were some atypical features including the absence of pigmented cells in the second case whose clinical course was shorter, and the cavitary appearance of the white matter changes with a relative increase in the number of oligodendrocytes raising the issue of a possible link between this condition and cavitary orthochromatic leukodystrophies.

Aged↗
PubMed2001

Web-based surgical educational tools.

This paper describes work being undertaken as part of the WebSET (Web-based Standard Educational Tools) project. The project is producing a standardised suite of interactive three-dimensional educational tools, delivered across the WWW. The major focus will be the use of open technology and standards, and the production of learning components that can be used as building blocks for further development in a wide range of application areas. Two learning disciplines have been selected for the development of the WebSET tools: surgical training, and physiological education. A high quality consortium from across Europe has been assembled with complementary skills in the technologies needed by the project. The project is partly funded by the European Commission.

Curriculum↗
PubMed2001

[A case of mitochondrial cytopathy (MERFF) without ragged red fibers at the onset].

We report a case of a mitochondrial cytopathy (MERRF) with a late diagnosis because of the absence of Ragged-Red Fibers (RRF) in the first muscular biopsy performed in childhood. Eight years after the onset of the disease the familial history and the clinical manifestations were very suggestive of a mitochondrial cytopathy and a second biopsy was performed confirming the diagnosis of MERRF. The authors discuss several hypotheses to explain the negativity of the first muscular biopsy. The absence of ragged-red fibers does not exclude the diagnosis of a mitochondrial cytopathy and other investigations are justified such as the biochemical study of the respiratory chain and the molecular analysis of mitochondrial DNA.

Adult↗
PubMed2000

Voltage-sensor sodium channel mutations cause hypokalemic periodic paralysis type 2 by enhanced inactivation and reduced current.

The pathomechanism of familial hypokalemic periodic paralysis (HypoPP) is a mystery, despite knowledge of the underlying dominant point mutations in the dihydropyridine receptor (DHPR) voltage sensor. In five HypoPP families without DHPR gene defects, we identified two mutations, Arg-672-->His and -->Gly, in the voltage sensor of domain 2 of a different protein: the skeletal muscle sodium channel alpha subunit, known to be responsible for hereditary muscle diseases associated with myotonia. Excised skeletal muscle fibers from a patient heterozygous for Arg-672-->Gly displayed depolarization and weakness in low-potassium extracellular solution. Slowing and smaller size of action potentials were suggestive of excitability of the wild-type channel population only. Heterologous expression of the two sodium channel mutations revealed a 10-mV left shift of the steady-state fast inactivation curve enhancing inactivation and a sodium current density that was reduced even at potentials at which inactivation was removed. Decreased current and small action potentials suggested a low channel protein density. The alterations are decisive for the pathogenesis of episodic muscle weakness by reducing the number of excitable sodium channels particularly at sustained membrane depolarization. The results prove that SCN4A, the gene encoding the sodium channel alpha subunit of skeletal muscle is responsible for HypoPP-2 which does not differ clinically from DHPR-HypoPP. HypoPP-2 represents a disease caused by enhanced channel inactivation and current reduction showing no myotonia.

Action Potentials↗
PubMed2000

Spectrum of SPG4 mutations in autosomal dominant spastic paraplegia.

Autosomal dominant hereditary spastic paraplegia (AD-HSP) is a group of genetically heterogeneous neurodegenerative disorders characterized by pro- gressive spasticity of the lower limbs. Five AD-HSP loci have been mapped to chromosomes 14q, 2p, 15q, 8q and 12q. The SPG4 locus at 2p21-p22 has been shown to account for approximately 40% of all AD-HSP families. SPG4 encoding spastin, a putative nuclear AAA protein, has recently been identified. Here, sequence analysis of the 17 exons of SPG4 in 87 unrelated AD-HSP patients has resulted in the detection of 34 novel mutations. These SPG4 mutations are scattered along the coding region of the gene and include all types of DNA modification including missense (28%), nonsense (15%) and splice site point (26.5%) mutations as well as deletions (23%) and insertions (7.5%). The clinical analysis of the 238 mutation carriers revealed a high proportion of both asymptomatic carriers (14/238) and patients unaware of symptoms (45/238), and permitted the redefinition of this frequent form of AD-HSP.

Adenosine Triphosphatases↗
PubMed2000

No evidence for long CAG/CTG repeats in families with spastic paraplegia linked to chromosome 2p21-24.

Autosomal dominant familial spastic paraplegia (AD-FSP) is a genetically heterogeneous, neurodegenerative disorder characterized by spasticity and progressive weakness in the lower limbs. Anticipation has been suggested to occur and an association between expanded CAG/CTG repeats and AD-FSP linked to the SPG4 locus (2p21-p24) has been described. In this study, 42 affected individuals from six SPG4 families were screened for expanded CAG/CTG repeats using the repeat expansion detection (RED) method. Large RED products (range 180-240 nucleotides) corresponding in size to repeats at the ERDA1 locus were detected in eight patients and at the CTG 18.1 locus in one patient. The large ERDA1 repeats did not segregate with the disorder within families. Mean age at onset and index of severity were not significantly different between patients with or without expanded RED products. Furthermore, no abnormal proteins were found by Western blot in 15 selected patient samples as compared with controls, using the 1C2 antibody, which detects long polyglutamine stretches. Thus, in contrast to previous reports, our study provides evidence against the hypothesis that a large translated CAG repeat expansion is the basis of SPG4. We propose that mechanisms other than large pathogenic CAG/CTG repeats may account for the disease in the SPG4 families tested here.

Adolescent↗
PubMed2000

Cytokines in genetic susceptibility to multiple sclerosis: a candidate gene approach. French Multiple Sclerosis Genetics Group.

The immune system is involved in the pathophysiology of multiple sclerosis (MS) but the initiating antigen(s) is not yet identified. Since cytokines control both the intensity and the quality of the immune response they may be relevant candidates for the genetic susceptibility to MS. To analyze the contribution of type 1 and type 2 cytokine and cytokine receptor genes in the genetic susceptibility to MS, we have examined, in 116 French MS sibpairs, whether there is significant linkage between MS and 15 cytokine or cytokine receptor genes using 31 highly polymorphic genetic markers. The data were analyzed using the maximum likelihood score and the transmission disequilibrium approaches. None of the candidate genes tested was significantly linked to MS on the whole population. However, after stratification of the analysis on the basis of sharing (or not) of the HLA-DRB1*1501 allele, indication of linkage was found for the IL2-RB gene. These findings suggest that the IL2-RB locus contributes to the genetic susceptibility in a subgroup of MS patients.

Cytokines↗
PubMed2000

Perlecan, the major proteoglycan of basement membranes, is altered in patients with Schwartz-Jampel syndrome (chondrodystrophic myotonia).

Schwartz-Jampel syndrome (SJS1) is a rare autosomal recessive disorder characterized by permanent myotonia (prolonged failure of muscle relaxation) and skeletal dysplasia, resulting in reduced stature, kyphoscoliosis, bowing of the diaphyses and irregular epiphyses. Electromyographic investigations reveal repetitive muscle discharges, which may originate from both neurogenic and myogenic alterations. We previously localized the SJS1 locus to chromosome 1p34-p36.1 and found no evidence of genetic heterogeneity. Here we describe mutations, including missense and splicing mutations, of the gene encoding perlecan (HSPG2) in three SJS1 families. In so doing, we have identified the first human mutations in HSPG2, which underscore the importance of perlecan not only in maintaining cartilage integrity but also in regulating muscle excitability.

Amino Acid Sequence↗