title: The pig synovium. I. The intact synovium in vivo and in organ culture.
abstract: 1. The normal synovium of the metacarpophalangeal joints of young pigs was examined by light and electron microscopy with special reference to the superficial layer (intima). 2. Cells of the macrophage-like or A-type (Barland et al. 1962) constituted only a small proportion of the intimal synoviocytes; the majority were of the intermediate and B-types. 3. Synovial villi were explanted on Millipore filters and maintained as organ cultures. The intimal cells in contact with the Millipore formed long branched processes which penetrated deeply into the substrate; these cells, which had a very well-developed endoplasmic reticulum, resembled those of the B-type. The synoviocytes at the upper (free) surface of the villus withdrew their long processes, acquired lamelliform pseudopodia, and their endoplasmic reticulum regressed; they were similar in appearance to the A-type. 4. In the organ cultures the highly branched cells (B-type) next to the Millipore were less phagocytic than the rounded cells (A-type) at the free surface of the villus.
mesh_terms: D000818:Animals; D008854:Microscopy, Electron; D009924:Organ Culture Techniques; D010587:Phagocytosis; D013552:Swine / Q000033:anatomy & histology*; D013583:Synovial Membrane / Q000166:cytology / Q000648:ultrastructure*