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.     

Les néoblastes dans la régénération antérieure deDendrocoelum lacteum,Turbellarié triclade

Résumé Les néoblastes de la région postérieure du corps de la PlanaireD. lacteum ont les mêmes propriétés migratrices et histogénétiques que les néoblastes de la région prépharyngienne. En cas de section transversale à quelque niveau que ce soit, les néoblastes du fragment postérieur se déplacent d'arrière en avant pour s'accumuler en un bourgeon de régénération normal. Mais la différenciation de ces cellules ne se produit qu'en cas de section nettement antérieure à la racine du pharynx (alors il y a régénération). Après une section postérieure à la racine du pharynx, les néoblastes dégénèrent.

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Neoblasts in the anterior regeneration ofDendrocoelum lacteum, Turbellaria tricladida

Summary Neoblasts of the posterior region of the body in the PlanarianD. lacteum have the same migratory and histogenetic properties as neoblasts of the prepharyngeal region. With transverse cuts at whatever level, neoblasts of the posterior fragment migrate forward to accumulate as a normal regeneration bud. But differentiation of these cells only occurs in ease of a section clearly anterior to the root of the pharynx (regeneration then follows). After a transection posterior to this level, the neoblasts degenerate.

     

Sahelian woody vegetation in Sénégal

Structure and composition of woody vegetation in Sahelian forest types (not including riparian and riverine types) were studied in Sénégal. The application of classification and ordination resulted in the recognition of seven distinctive woody community types, related to soil and precipitation gradients. The described vegetation types only contained four strictly Saharan species, the rest being of Sahelian and Soudanean affinity, so a floristic change from savanna to desert vegetation after two decades of drought could not be confirmed. Tree density was lower in the northern part than earlier, possibly an indication of degradation. Rejuvenation was greatest at the northernmost arenosolic stations, but low in the southern, ferrouginous areas. This presumably demonstrates the resilience of North-Sahelian vegetation, at the moment being in a dynamic rejuvenation phase, after a period of adverse conditions.     

Spermatogénèse et Paraplégie

In this article, the paraplegics’ possibilities for procreation will be examined. A first chapter will deal with the testicle functioning along with the study of hormonal measuring and testicle histology (study involving 100 patients). As a result, it appears that, after a testicle biopsy, there is a testicle lesion of neurological origin that is sometimes irreversible. On the contrary, the endocrinal testicle lesions have proved reversible under stimulation or spontaneously. A second chapter will deal with the different techniques to obtain an ejaculation and the semen analysis. The techniques that were used being: massage by vibrator, electroejaculation, ejaculation through pharmacological stimulation. The study focuses on 124 ejaculatory tests among which 64 forward ejaculations (52%) and 4 bachward ejaculations (3%) were obtained. The resulting semen analysis revealed a spermatozoon count greater than 20 millions per millilitre (that is 51,5%) and smaller than 5 millions in 11 cases (16%).     

Chromosomes et hétérochromosomes de ténébrionidés

Sans résumé Avec 81 figures dans le texte