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ETUDE DE QUELQUES PROPRIETES STRUCTURALES ET HISTOCHIMIQUES DU MESOBLASTE MARGINAL DES BOURGEONS DE MEMBRES DE L'EMBRYON DE POULET (STADES 20 A 26)

par Milaire, Jean ;Duchesnes, Christiane
Référence Archives d'Anatomie Microscopique et de Morphologie Experimentale, 68, 3, page (169-193)
Publication Publié, 1979

Article révisé par les pairs

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Résumé :

Two different kinds of topographical heterogeneities have been detected in the marginal mesoderm of developing chick fore-and hindlimb buds during the period extending from stage 20 to stage 26. The first one results from the early individuation, in this particular area, of two cellular layers of different density: a subectodermal layer of loose mesoderm and a deep layer of compact mesoderm which surrounds the marginal venous network. Each contains large and stellate mesodermal cells with a high count of cytoplasmic and nucleolar RNA. The proximodistal thickness of the compact layer increases in the postaxial half of the marginal zone. A number of facts indicate that the perivascular dense layer represents the undifferentiated mesoderm of the basi-metapod, and that the presumptive skeletal and musculo-tendinous materials are still undistinctly mingled in this layer. On stage 24 in the leg buds and on stage 25 in the wing buds, a dispersion occurring in the dense mesodermal layer releases its more proximal cells which take part in the organization of new subectodermal cellular layers, one dorsal and the other ventral. The second heterogeneity demonstrated in the marginal mesoderm results from the existence in the subectodermal (subridge) cell layers, of very selective dephosphorylating activities toward ATP and AMP at pH 7.2. Whereas these two enzymatic reactions were shown to be present in the whole mesodermal field of younger limb buds, from stages 20-21 on, both of them become confined to the outer cell layer interposed between the apical ectodermal ridge and the distal aspect of the marginal venous network; the reactive area thus includes the outer layer of loose mesoderm as well as the distal part of the deep compact layer. In addition, the intensity of both enzymatic reactions is obviously stronger in the same postaxial zone where the thickness of the compact layer is higher. The ATP-phosphohydrolase reaction remains strong up to stage 26, that of the AMP-phosphohydrolase (5'-nucleotidase) shows a drastic, though unexplained decrease at stage 24.