L'evolution des theories phytosociologiques en Russie

Sans résumé     

Etude cytologique de la prehypophyse du pigeon pendant la couvaison et la lactation

Résumé Les hypophyses de 22 Pigeons des deux sexes sacrifiés soit pendant la couvaison, soit pendant la période de soins aux jeunes, ou lactation, ont été comparées à celles de 43 Pigeons des deux sexes, adultes non lactants ou prépubères, normaux ou soumis à divers traitements (lumière permanente, métopirone, thyroxine). Elles ont toutes été examinées en microscopie optique et 13 d'entre elles ont été en outre étudiées au microscope électronique.Sur la base de leurs affinités tinctoriales et de leurs caractères histochimiques, 6 types cellulaires ont pu être identifiés (Tableau 2). Seuls trois d'entre eux, tous localisés dans le lobe céphalique de l'adénohypophyse, sont intensément modifiés pendant la couvaison et la lactation. D'une part, la cellule eta, érythrosinophile, et la cellule kappa, cyanophile mais PAS négative, sont fortement stimulées. D'autre part, la cellule delta, cyanophile et PAS positive, est déprimée.Les caractères ultrastructuraux de ces six types cellulaires sont décrits et plus particulièrement ceux des cellules sollicitées pendant la couvaison et la lactation.La confrontation de l'évolution respective de ces trois types cellulaires avec celle de la paroi du jabot montre que la cellule eta érythrosinophile élabore la prolactine. La signification fonctionnelle de la cellule kappa demeure hypothétique: elle élaborerait l'hormone mélanophorotrope, MSH. La valeur thyréotrope des cellules delta est démontrée par les modifications déclenchées à leur niveau par des injections de thyroxine; ces modifications sont identiques à celles observées pendant la lactation.

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Summary The pituitaries of 22 pigeons of both sexes fixed either during incubation or lactation (care for the young) were compared with those of 43 adult pigeons that were either adult but non-lactating, or prepuberal; these were either normal or variously treated (permanent illumination, administration of metopirone or thyroxin). All were studied with the light microscope and 13 among them were also examined with the electron microscope. On the basis of their staining properties and histochemical characteristics, six cellular types were identified. Only three among these, all located in the cephalic lobe of the adenohypophysis are intensively modified during incubation and lactation On the one hand, the eosinophilic eta cell and the cyanophilic but PAS-negative kappa cell are strongly stimulated. On the other hand, the cyanophilic and PAS-positive delta cell is depressed. The ultrastructural characteristics of these six cell types are described, in particular of those involved in incubation and lactation. Comparison of the development of these three cell types and of the crop shows that the eta cell furnishes prolactine. The functional significance of the kappa cell remains hypothetical; it may produce the melanophorotropic hormone (MSH). The thyrotropic nature of the delta cell is demonstrated by its modification in response to thyroxin administration; these changes are identical with those observed during lactation.

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Ce travail est dédié à M. le Prof. Bargmann à l'occasion de son 60^e anniversaire et en témoignage de notre respectueuse admiration.

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Avec la collaboration technique de Mmes Denise Lescanne, et Renée Picart et de M. Claude Pennarun pour les photos.     

Relation entre poids frais et poids sec chez quelques invertébrés d'eau douce

Resume La relation entre le poids frais et le poids sec, établie pour 10 espèces différentes, varie nettement de l'une à l'autre. Le premier représente 6 à 9 fois le second chez les Mollusques, 3 à 5 fois chez les Arthropodes, et 4 à 7 fois chez les Planaires étudiés.

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Summary The relation between live weight and dry weight, which was investigated for 10 different species, often differs significantly from one species to another. The values determined for the ratio of the live weight to the dry weight were of the magnitude 6 – 9 : 1 for the Molluscs, 3 – 5 : 1 for the Arthropods, and 4 – 7 : 1 for the Planarians.

     

Évaluation du contenu surrénalien en androstènedione et effets de la castration chez le lapin domestique (Oryctolagus cuniculus)

DHEA, DHEA sulphate and androstenedione are C19 steroïds secreted by the adrenal cortex. These hormones with a weak androgen activity are precursors of estrogens and androgens. In human and other primates these hormones are produced in important quantities, even though, in domestic and laboratory animals, a few secretion is measured. In this survey, the androstenedione is quantified both in plasma and adrenal gland of young, prepubertal and adult rabbits and the castration effects on adrenal cortex histology are noted too. The absolute weight (AW) of the left adrenal gland is slightly higher than the right (p > 0.05) for all animals and the gland absolute weight (AW) for the adult rabbit is superior to the young and prepubertal rabitts (p < 0.05). The castration effect in adult increases the adrenal weight (p < 0.001). A zonation of adrenal cortex for young rabbits is observed. The zona fasciculata is important for young and prepubertal rabbits whereas, the zona reticularis is thicker for the adults. Thickness of glomerulosa, fasciculata and reticularis zonas increased with 6.55% (p > 0.05), 15.9% (p < 0.01) and 79.21% (p < 0.001) for the castred adult rabbits and histological modifications were observed in the zona reticularis. The plasma androstenedione is negligible for the young (0.060 ± 0.01 ng/mL), weak for the prepubertal (0.152 ± 0.03 ng/mL) and reaches (0.263 ± 0.03 ng/mL) for the adult. The androstenedione relative content (ng/100 mg of adrenal weight) is 2.90 ± 0.30; 4.54 ± 0.82 and 1.34 ± 0.36 for the young, prepubertal and adult rabbits. In this work, an increase of the androstenedione adrenal content is observed for the prepubertal rabbits, which could intervene in the process of puberty.