CHANGES IN THE BONE AND CARTILAGE OF THE SYMPHYSIS PUBIS OF THE MOUSE DURING PREGNANCY AND AFTER PARTURITION, AS REVEALED BY METACHROMATIC STAINING AND THE PERIODIC ACID-SCHIFF TECHNIQUE

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Abstract
SUMMARY: A re-investigation has been made of the histological changes in the tissues of the symphysis pubis of the mouse during the first pregnancy and after parturition, using the techniques of metachromatic staining with toluidine blue, the McManus-Hotchkiss periodic acid-Schiff (p.a.s.) reaction, and basophilic staining with haematoxylin. During the last week of pregnancy two maj or changes take place: (1) resorption of the anteromedial bony walls of the innominates leading to shortening of the symphysis, and (2) transformation of the symphysial cartilage, manifested by loss of metachromasia and basophilia and ability to react with p.a.s., leading to ultimate disappearance of stainable chondroid matrix and its replacement first by argyrophil and then by collagenous connective tissue. Further resorption of bone from the symphysial walls of the innominates and, probably, retention of fluid in the newly formed connective tissue helps to widen the interpubic gap. After parturition, the collagenous connective tissue which had replaced the cartilage and resorbed bone reverts to a mesenchyme-like tissue, the cells of which differentiate into osteoblasts or chondroblasts or haemopoietic cells. Cartilage differentiates by deposition of metachromatic chondroid matrix around chondroblasts, the matrix becoming more and more metachromatic, p.a.s.-positive and basophilic. Bone differentiates, first in connective tissue, later by endochondral ossification. Marrow begins to differentiate even before the bone which will confine it is laid down. The effect of hyaluronidase on metachromasia, basophilia and reaction to p.a.s. of the symphysial tissues is described, and its significance discussed in relation to the pregnancy and post-partum changes.