Summary
An electron microscopic study of cellular modifications in mammary tissue from post-lactating mice, rats, and rabbits was undertaken. The modifications are due to resorption of previously elaborated and stored secretory material and to degeneration of a number of isolated gland cells.
Stored secretory material, in particular protein granules, are apparently digested in the cytoplasm without participation of lysosomes. Liquified homogenous material is found in the acinar lumen and in the enlarged inter-cellular spaces. It is probably carried to the still well developed capillaries of the interstitium.
The decrease of cytoplasmic volume in surviving cells and the degeneration process of dying cells involve the participation of lysosomes. The amount of ergastoplasm and Golgi elements decrease rapidly whereas free ribosomes appear. In surviving cells the autolytic process is limited to small areas of cytoplasm. Dying cells become vacuolated and are either eliminated as colostrum bodies in the acinar lumen or lysed and eliminated in the interstitium.
During this process myoepithelial cells do not undergo degeneration and play apparently an important rôle in maintaining the surviving cells together. Equally, the junctional complex ofFarquhar andPalade appears well preserved between most of the gland cells. It should be supposed that this structure is rapidly restored after elimination of dying cells.
Résumé
Des fragments de glande mammaire prélevés chez des souris, des rates et des lapines à différents stades de la régression ont été étudiés au microscope électronique.
Les modifications ultrastructurales qui accompagnent la régression traduisent soit le retour au repos soit la dégénérescence de cellules glandulaires. Les produits sécrétoires maintenus en stase sont lysés directement dans le cytoplasme sans l'intervention de lysosomes et réabsorbés à travers les espaces inter-cellulaires élargis. Au contraire, la lyse cellulaire implique la présence de lysosomes. Cette autolyse peut rester partielle et aboutir à une réduction du volume cytoplasmique, ou frapper massivement la cellule entière qui est vouée à la mort. Le matériel lysé est éliminé à travers les espaces inter-cellulaires vers les vaisseaux qui en assurent la résorption finale.
Durant ce processus, deux systèmes assurent la cohésion des cellules entre elles et la continuité de l'arbre glandulaire: les complexes de jonction et les cellules myoépithéliales qui restent logtemps préservées.
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Hollmann, K.H., Verley, J.M. La régression de la glande mammaire à l'arrêt de la lactation. Z.Zellforsch 82, 222–238 (1967). https://doi.org/10.1007/BF01901703
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DOI: https://doi.org/10.1007/BF01901703