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The discovery of the double helix structure of DNA 50 years ago by J.D. Watson and F.H.C. Crick laid the foundation for modern molecular biology. This opened the way of 50 years of research resulting in the elucidation of gene expression mechanisms, in the development of molecular biology tools allowing analyzing and manipulating genes and in medical and forensic applications now routinely used. The discovery of the double helix structure allowed to evidence the DNA property of molecular hybridization on which are based most of the molecular biology tools, from the old Southern blot method to the recently developed microarrays. [Copyright &y& Elsevier]

Hypophosphatasia is characterized by defective bone mineralization associated with impaired activity of the tissue non-specific alkaline phosphatase (TNSALP) due to mutations in the TNSALP gene. We describe a child with a mutation that has not been described up to now.Case report. – A 4-year-old child presented with clinical symptoms of rickets and premature loss of decideous teeth. Reduced serum alkaline phosphatase activity and radiographic features led to the diagnosis of hypophosphatasia, which was confirmed by genetic investigation. The molecular study showed two missense mutations, of which one is a novel mutation.Conclusion. – Hypophosphatasia is suspected in a child with rickets and premature loss of decideous teeth. Such symptoms should prompt the search of a reduced serum alkaline phosphatase activity. The clinical and molecular diagnosis of the disease is important for the genetic counseling but also for a proper determination of prognosis, as it is related to the type of mutation. [Copyright &y& Elsevier]

The evolution of a patient suffering from a serious head injury can require the placement of a tracheotomy. This helps with respirator weaning and usually enables the patient to be moved from the neurosurgical intensive care ward to the neurosurgery ward. Patients fitted with a tracheotomy will therefore be cared for by post-intensive care neurological rehabilitation departments.

Purpose of the Study: Congenital cholesteatoma is a well-described anatomical and clinical entity. Adult forms are rare. We describe a posterosuperior encapsulated cholesteatoma and compare this case to other infantile and adult forms described in the literature., Material and Methods: A 25-year-old patient with no medical history consulted for left conductive hearing loss. A flat tympanogram was obtained. The temporal bone computed tomographic scan showed a soft tissue density lesion of the middle ear and anterior stapes erosion. A congenital cholesteatoma was discovered during surgical exploration. The lesion was removed and the ossicular chain was reconstructed with a Shea piston., Results: The patient showed approximately 20dB conductive hearing improvement., Discussion: Existence of congenital cholesteatoma is well established. Adult forms are exceptional and often diffuse. A localized, encapsulated form is described in this article. The specificity remains unknown. It is uncertain whether the adult and infantile forms have the same origin. A multifactorial or metaplastic mechanism could explain adult congenital cholesteatoma., Conclusion: Pathogenic hypothesis for adult forms of congenital cholesteatoma are different from infantile forms.

Background: Hypophosphatasia is a rare inherited disorder characterized by defective bone and teeth mineralization and deficiency of serum and bone alkaline phosphatase activity. Several mutations in the TNSALP gene are identified., Aim: The authors describe a Tunisian case having a mutation that has not been described up to now., Case: It is about an infant, in the antecedents of recurring disease of the lungs in child since the age of seven months, which presents clinical and radiological signs of rickets. The diagnosis of hypophosphatasia is strongly suspected in front of Reduced serum alkaline phosphatase activity and confirmed by the genetic study. The child is homozygous for a new mutation L282P in the ninth exon of the gene. The parents and two brother and sister are heterozygous for the same mutation.

The recent progress in cloning and sequencing the genes responsible for genetic diseases and the use of Polymerase Chain Reaction (PCR) allow to test genetic diseases with a few quantity of DNA. Amniotic cells are easily sampled by using amniocentesis. When abnormal ultrasound allows to suspect a genetic disease, PCR on DNA from amniotic cells is a very efficient test to confirm or exclude the presence of the disease. Microsatellites sequences can be used on amniotic cells as a rapid test for chromosomal aneuploidies.

Unlabelled: Among the many acquired or constitutional causes of chondrodysplasia punctata, the X-linked recessive form is well individualized., Case Report: A male newborn presented a dysmorphic syndrome with a marked nasal hypoplasia, a macroglossia and a short neck. The diagnosis of chondrodysplasia punctata was made by radiography whereas the chromosomal chart revealed the existence of an additional Y fragment in Xpter, effectuating a partial disomy Yp and a monosomy Xpter. Molecular biology showed a deletion of very small size, isolated and located between the gene missing aryl sulfatase E and the microsatellite DXS 1233, sping gene MRX2 (non-specific gene of mental retardation), and making it possible to give the reassuring elements as regards the psychomotor prognosis, sometimes compromised in this disorder., Conclusion: In case of chondrodysplasia punctata with dysmorphy, it is important to execute a chromosomal chart in the search for a chromosomal reorganization on the X and a study in molecular biology.

Fragile X syndrome is the most common cause of inherited mental retardation. Since the identification of the mutation, a Cytosine-Guanine-Guanine repeat in the Fragile X Mental Retardation (FMR1) gene, the genetic counselling and the diagnosis of the disease have been dramatically improved. The nature of the mutation and its size must be integrated in the calculation of the risk of transmission of mental retardation and in the genetic counselling in the family. Out of 245 patients affected with mental retardation referred to our laboratory, we found 37 (15%) fragile X patients, allowing to screen for the mutation in the family and to propose prenatal diagnosis in carrier females.

High molecular weight DNA extracted from 50 unrelated parisian individuals constitutes a "DNA-thèque" which can be used at the population level. This procedure allows preparation from a variety of tissues such as liver, placenta and leucocytes. The "quality" of the DNA obtained (about 50 Kb, RNA and protein free) and the efficiency of the method (in terms of the yield of DNA obtained) are considered. Blood is the easiest material to obtain and permits the obtaining of a reasonable amount of human and primate DNA, particularly when familial investigation is planned for polymorphism studies. One of the objects of this article is to encourage others to make use of our bank, for studies in population and evolutionary genetics.

We develop here several models concerning strategies for detection of restriction polymorphisms in humans. These different strategies concern the numbers of individuals to test in a DNA collection, the nature of restriction enzyme to utilize, and the length of the probes. For enzyme utilization different strategies are based on (i) the nature of the restriction site; (ii) the mean length of restriction fragments obtained; (iii) the methylated cytosine characteristics in the CG doublets. Each of these approaches are tested in experimental situations.

21-deoxycortisol is a steroid produced mainly by the adrenal gland. Its normal plasma baseline concentrations (0.03 to 0.30 n/ml) and its concentrations after tetracosactide injection (0.15 to 0.76 ng/ml) do not significantly vary with age, sex and phases of the menstrual cycle. 21-deoxycortisol was assayed in plasma by a specific radioimmunological method and its values were compared with those of 17-OH progesterone in heterozygous subjects with the classical and non-classical forms of 21-hydroxylase deficiency, and in the amniotic fluid of foetuses with this deficiency. Baseline concentrations of 21-deoxycortisol in the classical forms of 21-hydroxylase deficiency (n = 12; 55.36 to 186.6 ng/ml) and post-tetracosactide concentrations in non-classical late onset forms (n = 31; 4.04 to 47 ng/ml) were much higher than in normal subjects, thus making this steroid as sensitive as, or even more sensitive than 17-OH progesterone in diagnosing 21-hydroxylase deficiency. Post-tetracosactide assays of 21-deoxycortisol in 84 heterozygous subjects with 21-hydroxylase deficiency (0.70 to 5.40 ng/ml) enabled these subjects to be detected with a more than 90 percent sensitivity, which cannot be obtained with 17-OH progesterone assays. 21-deoxycortisol concentrations in the amniotic fluid of foetuses with 21-hydroxylase deficiency (n = 11; 0.391 to 0.930 ng/ml) were constantly superior to those observed in normal foetuses (n = 38; 0.034 to 0.221 ng/ml), so that the deficiency can be diagnosed with the steroid as easily as with 17-OH progesterone.

Incidence of congenital adrenal hyperplasia due to 21 hydroxylase deficiency was studied in France. Five hundred and twenty six patients born during the period 1963-1979 were found. Assuming complete ascertainment in females, the incidence of the disease is 0.43 X 10(-4) or 1: 23,044. The frequency of the carriers is 0.013 (1/76). The birth places of patients show an unequal geographic distribution. The mean inbreeding coefficient is 270 X 10(-5), a figure higher than the mean coefficient of France. The frequency of marriages between first cousins is slightly raised, 0.3%.