A B S T R A C TA new technique for the cultivation of living tissues in the multipurpose culture chamber is described. This procedure employs strips of cellophane as the agent for anchoring tissue explants to the coverslip walls of the chamber and disposes of the time-honored plasma-clot technique. The primary advance embodied in this procedure lies in the fact that cells emigrating from so-cultured explants manifest themselves in a highly differentiated manner comparable to the cells of origin, whereas the outgrowth from the same types of tissue in plasma clots results in a more undifferentiated type of growth. Comparisons of outgrowths from embryonic thyroid, bone, and muscle (chicken) are photographically documented, and attention is called to certain cytochemica] methods which further corroborate the differentiated quality obtained with the cellophane-strlp technique.

The detito-epithelial janctions (DEJ) of Rhesus monkeys were examined by electron microscopy. Various fixation procedures were employed in this study. It was revealed that the basal lamina between the junctionai epithelium and the tooth surfaces was composed of three layers: the lamina lucida, the lamina densa and the sub-lamina lucida. Fine filaments often coursed through the lamina densa,, lamina lucida and hemidesmosomes and combined them into a stroctural unit. An electron-dense linear border, presumably derived from tissue fluid, was generally observed on the tooth surface at the DEJ except that cotnposed of the fibrillar cementum. This border was helpful in distinguishing the afibrillar cementtim from the dental cuticle. The existence of a sub-lamina lucida hetween Hit lamina densa and the tooth surfaces is a newly defined layer. It is hypothetically CODsidered to be an area of competetive electrostatic forces of repulsion and London Van der Waals forces of attraction.

Specimens from 2 cases of gingival hyperplasia resulting from the treatment with the immnosuppressant cyclosporin A (CSGH) and 4 cases of inflamed gingiva (non‐CSGH) were examined by electron microscopy with particular interest in the fibroblasts. In general, the fibroblasts in CSGH revealed the ultrastructural characteristics of active protein synthesis and secretion and less cytotoxic or degenerative changes. Some fibroblasts in the CSGH (23.8%) displayed cytological modifications comparable to so‐called myofibroblasts, i.e., microfilament bands with semi‐periodic dense nodes, nuclear indentations, and basal‐lamina associated, cell‐lo‐stromal junctions. Conversely, 5.9% of the fibroblasts in the non‐CSGH showed these modifications. The modified fibroblasts were found most predominantly in the transitional area between inflamed and fibrous connective tissues. From these findings, it is suggested that the myofibroblastic modification in CSGH is regarded as a common morphological sign in actively proliferating fibrous tissue and may participate in the host‐tissue response to the plaque‐associated irritants.