Cancer et Hérédité

Sans résumé     

Génétique moléculaire des dysgénésies testiculaires

The first step of male differentiation is the testis determination which is genetically controled. The key role of SRY gene is now established. However, a number of clinical and genetic data favoured the role of other genes taking place upstream or downstream SRY. Most of 46, XX males possess a translocated SRY gene and thus develop testis, but SRY gene is not found in 10% of such patients. Likewise, the molecular study of 46, XY females participated in the identification of SRY as testis determining factor, but 80% of XY gonadal dysgenesis are not explained by an abnormality of SRY gene. Several clinical situations permitted to suspect the role of autosomal (chromosome 1, 9, 10 17 …) and X chromosome loci in the pathology of sex determination. Some recent works concern, in particular, the testis determining factor of the X chromosome (TDF-X) that could act as a repressor of the testis differentiation. In conclusion, molecular mechanisms of sexual determination appear to be much complex, involving probably several genes in a pathway that remain to be elucidated.     

Chromosomes et hétérochromosomes de ténébrionidés

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Systématique moléculaire des Mélitées

The holarctic subfamily Melitaeinae of Nymphalid butterflies (old genus Melitaea Hbn.) has been split into various genera by morphological systematics, but this division has been debated. This work presents the results of a preliminary survey of European taxa using two types of molecular criteria: analysis of enzyme variation by electrophoresis (19 loci) and sequencing of a mtDNA fragment (ND1 gene). The information provided by both kinds of markers are largely congruent. The division of the subfamily into two monophyletic lines corresponding to the genera Euphyryas s. 1. and Melitaea s. l. is validated. The subsequent division of the former genus into two units, Eurodryas and Hypodryas is also confirmed by molecular criteria. Inside rhe old genus Melitaea, a monophyletic assemblage, corresponding to the ‘Mellicta group’ is disclosed, but the phylogeny of the other species of the group is confused. Uniting them in a ‘Didymaeformia group’ or in a genus Melitaea s. str. risks rhe generation of a paraphyletic assemblage. It remains to be determined whether or not these results are due to insufficient resolution, or whether they reflecr a real evolutionary pattern     

Perspectives nouvelles de la cartographie biogéographique végétale intégrée

Résumé Après avoir indiqué les objectifs et les concepts généraux de la cartographie biogéographique intégrée de la végétation et de son écologie, l'auteur expose, avec plus de détails, les conceptions de forme dans l'expression cartographique, ainsi que les conceptions sur le contenu scientifique des cartes biogéographiques.A ce propos, il décrit un modèle général de la perception des faits et de leurs relations réciproques au'il désigne par l'expression: pyramide de perception. Ce modèle comprend 5 niveaux, des petites aux très grandes échelles. Une application à l'écologie végétale et à la phytogégraphie est développée. De nouveaux types de cartes sont décrits (carte de l'occupation des terres, cartes phyto-écologiques).

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Summary The author, first of all, shows the objectives and the main concepts of the biogeographical integrated cartography of the vegetation and of its ecology, he exposes after that, in a more circumstantial way, the conception of the form in the cartographical expression as well as the conceptions bearing on the scientific content of biogeographical maps.In this connection he describes a general model of the perception of facts and of their reciprocal relations, he terms this model: pyramid of perception. This latter comprises 5 levels from the small to the largest scales. An application to plant ecology and to plant geography is developed. New map types (certain forms of land-use maps, phytoecological maps) are described.

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Zusammenfassung Einleitend bespricht der Verfasser das Ziel und die allgemeinen Begriffe der integrierten biogeographischen Vegetationskartierung und deren Ökologie. Dann behandelt er eingehend die Formenbegriffe in der kartographischen Darstellung, sowie die den wissen-schaftlichen Inhalt der biogcographischen Karten betreffenden Begriffe.In dieser Beziehung beschreibt er ein allgemeines Modell der gegenseitigen Beziehungen und der Wahrnehmung der Tatsachen. Das Modell wird durch den Ausdruck Wahrnehmungspyramide bezeichnet und besteht aus 5 Stufen, von den kleinen bis zu den großen Maßstäben. Eine Anwendung zur Vegetationsökologie und zur Phytogeographie wird erörtert. Es werden neue Kartentype beschrieben (einige Formen von Bodennutzungskarten, phytoökologische Karten).

     

Métastase splénique isolée métachrone d’un adénocarcinome colique

Isolated splenic metastases of colorectal cancers are very rare but possible even after several years of remission. We report the case of a 74-year-old man who developed isolated metachronous splenic metastasis of left colon cancer 5 years after the treatment of the primary tumor. Splenic metastasis was found by imaging examinations. The patient underwent splenectomy and the histological examination confirmed the metastatic nature of the splenic lesion. 18F-FDG PET allows both staging and resectability of these isolated metachronous splenic metastasis because a long-term survival can be achieved by splenectomy.     

Les BIMEs: un exemple de séquences répétées chez les entérobactéries

Bacterial interspersed mosaic elements (or BIMEs) are repeated sequences identified in several enterobacterial genomes. BIMEs are a mosaic combination of small sequence motifs. It has been estimated that 500 BIMEs are scattered over the bacterial genome. BIMEs have been identified in several enterobacteria: Escherichia coli, Salmonella typhimurium, Klebsiella sp. and relatives of these bacteria. BIME function is not known, but their interactions with specific proteins (DNA polymerase I, gyrase and integration host factor) suggest that they could be involved in functional organization of bacterial chromosomes. Four other families of interspersed repetitive sequences have been shown to exist in a variety of bacterial genomes. Like BIMEs, these sequences are rather small, contain a region of dyad symmetry, and are found in extragenic locations. Unlike BIMEs, IRU (or ERIC), box C sequences and RSA sequences occur in enterobacteria but also in other Gram-negative bacteria.     

Données synchorologiques sur la végétation littorale européenne

Four aspects of the synchorology of plant communites along the European coastline are treated: (1) with examples from sand dunes (Agropyreta and Ammophileta) and salt marshes (Puccinellieta maritimae) synvicariance is elucidated; (2) The increase in synvicariance towards the inner sand dunes is discussed as a result of an increasing effect of autochthonous climatic features; (3) with examples from sand dunes and cliffs the concept of synendemism is elucidated; (4) synvicariance at the landscape (geosigmetum) is discussed with examples from the French coastline.

     

Absence de corrélation génotype-phénotype dans les absences de canaux déférents

Absence of the vas deferens is a rare cause of male infertility, associated with mutations in the cystic fibrosis transmembrane regulator (CFTR) gene in about 80% of cases. Only limited published data are available concerning the correlation between genotype and reproductive tract abnormalities observed in this disease: presence or absence of seminal vesicles and parts of the epididymis, symmetrical or asymmetrical lesions, testicular volumes. We screened 47 patients for the 13 most common CFTR mutations on the cystic fibrosis gene and for the 5-thymidine variant of the polythymidine tract of intron 8. Renal, scrotal and transrectal ultrasonography was performed in each patient to explore the testes and reproductive tract. All patients presented absence of the ampullae of the vas deferens. Forty patients presented bilateral absence of the vas deferens and 7 presented unilateral absence of the vas deferens. At least one mutation of the cystic fibrosis gene was present in 64% of cases: 47% had the ΔF 508 mutation and 63% had the 5T allele. No mutation was detected in seventeen patients, including 3 patients with unilateral renal agenesis and 3 patients with unilateral absence of the vas deferens. No differences were observed for seminal vesicles and symmetry of vesicular and epididymal abnormalities between patients with or without CFTR gene mutations, but epididymal abnormalities were significantly more frequent in the group without mutation (p=0.01). Testicular volumes were significantly lower in the patients without mutation or with the 5T allele only, than in the patients with at least one CFTR gene mutation: 10.7±4.1 ml versus 15.1±4.5 ml, respectively (p<0.001). In conclusion, in cases of isolated absence of the vas deferens, there is no difference in sperm duct abnormalities between patients with or without CFTR gene mutation. These results suggest that other genetic or environmental determinants are required to explain a common pathogenesis for these malformations. The decreased testicular volume of patients without CFTR gene mutation or with the 5T allele only suggests the existence of an unidentified secretory or mixed factor involved in these forms of absence of the vas deferens.