A SERIAL AUTORADIOGRAPHIC ANALYSIS OF Hsup3sup 3-GLYCINE UTILIZATION AND DISTRIBUTION IN THE FEMORA OF GROWING MICE

The amino acid composition of collagen and the role of collagen in bone formation are reviewed. It is pointed out that glycine is the predominant amino acid of collagen. Results are reported from a serial, autoradiographic study of the localization and distribution of H/sup 3/ in the femora of young mice following the administration of H/sup 3/-glycine. The functional behavior and capacity of different skeletal cells in matrix production are discussed. (26 references.) (C.H.

Autoradiographic investigation of circadian rhythms in alveolar bone periosteum and cementum in young mice

This report presents circadian rhythms in cell proliferation of alveolar bone periosteum and cementum of the maxillary first molars of male 5-week-old BNL, Swiss albino mice which were maintained on a 12 hr light1 dark cycle. Mice were injected with 3H-TDR (lucilgm. body wt.) 1 hr prior to sacrifice and killed every 3 hrs for 24 hrs starting at 9 a.m. Maxillae were decalcified, routinely processed histologically and autoradiographs prepared. Cell labeling indices of alveolar bone and cementum mesial to the first molar were determined. Alveolar bone periosteal and cemental cells show circadian rhythm in their DNA synthetic processes. Peaks in percent labeling exhibit higher values than previously reported for nontraumatized, normal dental periosteum and cementum. While the outer periosteum reveals a single 24 hr peak (6 p.m.), inner periosteum and cementum reveal two ultradian peaks 9 to 12 hrs apart involving both light and dark periods. Rodents are nocturnal, but high peaks are also evident in the light periods, consequently, not all peaks are synonymous with the period of animal activity and feeding. Although the single daylight peak of the outer periosteum may indicate growth of that surface at night to about noon, the double peaks exhibited by inner periosteum and cementum indicate lightldark, continuously active surfaces in terms of DNA synthesis and growt