title: Age-dependent mitogenesis in normal connective tissue cells.
abstract: We have previously described ways to use the mesentery for studies of proliferation in intact tissue. Here we have studied a weak and a strong mitogenic response in the mesentery of rats aged 6--42 weeks, induced by a single intraperitoneal injection of saline or the mast-cell-degranulating drug 48/80. Proliferation was measured by the specific DNA activity, the fraction of fibroblast- and mesothelial-like cells in the S+G2 cell-cycle-phases, and the mitotic index. We also counted the relative number of mast cells in the tissue (normalized to 5,000 fibroblast-like and mesothelial-like cells), since this might influence 48/80-induced mast-cell-mediated proliferation. In old animals there was a decline in the proliferative response and the time required to initiate DNA synthesis was prolonged. This appears to be the first report of such an age-dependent proliferation characteristic in the mesentery, and probably in any connective tissue. The normalized number of mast cells in the mesentery also declined with increasing age.
mesh_terms: D000367:Age Factors; D000818:Animals; D002452:Cell Count; D003239:Connective Tissue Cells; D004247:DNA / Q000096:biosynthesis; D005347:Fibroblasts / Q000166:cytology; D008297:Male; D008407:Mast Cells / Q000166:cytology; D008643:Mesentery / Q000166:cytology; D008938:Mitosis; D051381:Rats
chemical_list: D004247:DNA