title: A radioautographic study of chondrocytic proliferation in nasal septal cartilage of the prenatal rat.
abstract: Six pregnant female Sprague-Dawley rats were labeled with tritiated thymidine and killed, one each day, during the terminal six days of pregnancy. Nasal septal cartilages of five pups from each litter (a total of pups in all) were monitored radioautographically for cellular proliferation. It was found that chondrocytes were moderately active mitotically on gestational day 16, showing 12.1 grains per microscopic field. Activity increased sharply the following day (16.5 grains/field) then declined slightly on day 18 to a 16.1 count. There was a marked drop on both the 19th and 20th days (13.1 and 10.3 grains/field respectively) followed by a leveling off on the 21st day (9.3 grains/field). No specific location in the septal cartilage could be identified as a growth center. The area of highest proliferative activity varied from day to day, being seen in the nasal tip on day 16, centered in the middle two-thirds of the cartilage twenty-four hours later, then moving caudally to the posterior one-half the following day (day 18). On day 19, a final shift back to the middle of the septum was observed. It was impossible to identify an active zone anywhere within the septum of either the 20- or the 21-day prenatal rat.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002356:Cartilage / Q000166:cytology* / Q000196:embryology; D002455:Cell Division; D005865:Gestational Age; D008938:Mitosis; D009300:Nasal Septum / Q000166:cytology* / Q000196:embryology; D051381:Rats