Étude en microscopie électronique et par cytophotométrie à balayage de la structure et de la distribution de la chromatine dans les noyaux des cellules cartilagineuses deTriturus cristatus âgés au cours de la régénération

Résumé Les cellules cartilagineuses des membres postérieurs deTriturus cristatus en régénération après amputation, ont été étudiées en microscopie électronique et par cytophotométrie à balayage. Nous nous sommes intéressés à la structure et à la distribution de la chromatine mais aussi à différents organites cytoplasmiques. Dans l'étude de cytophotométrie à balayage, la chromatine a été considérée à travers son constituant majeur, l'ADN, coloré par la réaction de Feulgen. Au cours de la régénération du membre, l'hétérochromatine initialement condensée, essentiellement accolée à la membrane nucléaire se décondense. Les vacuoles du cytoplasme, caractéristiques des animaux âgés par rapport aux animaux jeunes, disparaissent, les mitochondries et le reticulum endoplasmique rugueux deviennent plus abondants. Les caractéristiques nucléaires de l'activation cellulaire apparaissent précocement, précédent les modifications cytoplasmiques et conduisent à des cellules en tous points identiques aux cellules d'animaux jeunes en dehors de tout processus régénératif. Cette phase d'euchromatisation et de restructuration cytoplasmique est peut-être nécessaire à l'accroissement d'activité métabolique et à la division cellulaire qui suivent. Son déroulement peut expliquer tout au moins le ralentissement de la régénération observé chez les animaux âgés par rapport aux animaux jeunes.

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Electron microscopic and scanning cytophotometric study of chromatin structure and distribution in nuclei of cartilaginous cells of agedTriturus cristatus during regeneration

Summary Cartilaginous cells of aged newts (Triturus cristatus) were studied during hind limb regeneration. The electron microscope was used to study the structure and distribution of chromatin in the cell nuclei, while the DNA content of the chromatin was measured by means of a scanning cytophotometer.Changes in the ultrastructure of the cytoplasm during regeneration were also studied.It was observed that the structure and distribution of chromatin in the activated cell is greatly modified. In the non-activated cell of the aged newt, the chromatin is found highly condensed and distributed peripherally close to the nuclear membrane. In contrast, in the activated cells, the chromatin is much less condensed and is distributed throughout the nucleus. Moreover, cytoplasmic vacuoles, found only in the non-activated aged cells, disappear and an increase in the mitochondria and rough endoplasmic reticulum is also observed.Changes in the nuclear structure are observed prior to the cytoplasmic modifications.It is interesting to note that the process of activation induces structural changes in the aged cells which make these cells appear to be structurally identical to the young cells. This process of rejuvenation takes 3–5 days in the newt.We suggest that these structural changes of the chromatin and cytoplasm in the aged cells are necessary to increase the metabolic activity which precedes cell division. It may also explain why regeneration takes a longer time in the aged animals than in the young ones.

     

Essai d'une théorie de la stabilité de la structure des sols

Sans résumé     

Traumatisme de la verge et des organes génitaux

The most frequent cause of testicular injuries is blunt trauma (following sports injuries or road accidents). Penetrating injuries are rare. Increased scrotal volume and a painful testis are the main symptoms and require scrotal ultrasonography. Scrotal ultrasonography is very sensitive and specific for testicular rupture or intratesticular haematoma. Two out of three patients with testicular injuries require surgical exploration. Secondary complications due to delayed management of trauma are testicular atrophy, sterility or impotence. Penile fracture (rupture of corpus cavernosum) is due to direct trauma by an excessive force applied to an erect penis. Swelling, penile ecchymosis, penile curvature and pain are the usual symptoms of rupture of the tunica albuginea. Urethral injury must be ruled out. Cavernosography, ultrasonography or MRI are not considered mandatory to establish a diagnosis but can be prescribed in the absence of typical signs or symptoms. Early surgical exploration and repair ensure a better outcome. Secondary complications are penile curvature, chronic pain and impotence.     

Un estimateur de distributions ajusté pour une aide à la décision de la neutralité génétique des populations

The estimate of the neutrality of a population is often made from a single measurement based on simulations of random patterns. Disputed cases pose a problem regarding the decision-making about the neutrality of the study population. We propose in this paper to provide assistance to the decision of this problem by coupling a genetically neutral populations simulator to a fast adjusted non-parametric estimator of simulated distributions. The choice of the Epanechnikov kernel for the non-parametric method of estimating the kernel allows an analytical approach of the optimal bandwidth, which leads to an improvement in the complexity and therefore a gain in computing time. The fast and reliable estimation of simulated distributions allows to assess the credibility of the decisions about the neutrality of these populations. These results are illustrated by two Tunisian populations whose neutrality is not genetically determined.     

Etude sur la végétation des dunes et des landes de la bretagne

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Relations entre la tolérance ou la sensibilité à la salinité lors de la germination des semences et les composantes de la nutrition en sodium

Adsorption, absorption and translocation of sodium were compared in three species showing an ascending degree in tolerance to salinity: red cabbage (tolerant) shows higher Root Cationic Exchange Capacity than tomato (sensitive) or radish (intermediate). At low NaCl concentrations, tomato accumulates the greatest quantities of sodium; but Na⁺ translocation remains proportional to the quantity absorbed in the three plants. At high salt concentrations, diffusive phenomena explain similar accumulation in every plant, but red cabbage quickly localises 50% of Na⁺ amount in cotyledons, while this element stays stored in tomato roots. The consequence of these three nutrition phases was discussed in relation to the behaviour observed at the germination time of these same plants.      

Kyste du tractus thyréoglosse dégénéré révélant un microcarcinome papillaire multifocal de la thyroïde

The malignant degeneration of thyroglossal duct cyst (TDC) is a very rare phenomenon. It occurs 1% of operated cysts where papillary carcinoma represents the most frequent pathological type. The authors report a clinical observation of a papillary carcinoma of thyroid occurring in a thyroglossal duct cyst concomitant to a multifocal micropapillary thyroid discovered in a 21-year-old woman. A total thyroidectomy was performed. A complementary treatment by radioactive iodine 131 (3,7 GBq) was undertaken. Two years later, the patient is doing well and does not present any sign of recurrence. In the light of this observation, the authors propose to report the diagnosis and therapeutic aspects of degenerated thyroglossal duct cyst.     

Action de l'actinomycine D sur la différenciation cellulaire au cours de la régénération de Planaires qui viennent d'éclore

Résumé L'utilisation de l'actinomycine D, au cours de la régénération de Planaires à l'éclosion ou de celle d'adultes, montre que ces deux groupes d'animaux réagissent différemment à l'antibiotique.La régénération se produit en présence de l'antibiotique chez les jeunes Planaires, alors que, pour la même concentration (50 g/cm³), elle est totalement bloquée chez les adultes. Elle débute dès la décapitation des animaux; le retour dans l'eau, après un traitement par l'antibiotique qui va de 1 à 4 jours, ne modifie pas son déroulement morphologique.L'examen ultrastructural montre que les cellules différenciées présentent le plus souvent des dissociations nucléolaires importantes.Les lésions s'étendent progressivement à toute la cellule qui dégénère fréquemment. Les cellules morphologiquement indifférenciées ne sont que faiblement altérées (raréfaction du composant granulaire du nucléole), et récupèrent une structure normale après retour dans l'eau.Ces résultats conduisent à envisager l'étude des synthèses d'ARN, au cours de ces expériences, au niveau des organismes entiers et au niveau cellulaire.

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On the action of actinomycin D on the cellular differentiation during the regeneration in PlanariansI. Morphological, histological and ultrastructural studies on the regeneration capacity in presence of the antibiotic

Summary The utilization of actinomycin D during the regeneration of young and adult Planarians shows that the two groups of animals react differently to the antibiotic.Regeneration takes place in the presence of the antibiotic in young Planarians, whereas it is entirely inhibited in adult ones, applying the same concentration (50 g/cm³). In the young animals it begins immediately after decapitation. Their return into the water, after a treatment with the antibiotic lasting from 1 to 4 days, does not interfere with the morphological differentiation. The ultrastructural investigation exhibits that in the majority of the undifferentiated cells the nucleolus is largely dissociated.The lesions gradually extend to the whole cell which frequently degenerates. The morphologically undifferentiated cells are weakly impaired (depletion of the granular component of the nucleolus), and they recover a normal structure after their return into water.These results lead us to study the RNA synthesis, during these experimentations, on the whole organism as well as the cellular level.