Formation Of Organic Matrix Research Articles

Total protein, collagen, nucleic acids and calcium ions during rabbit odontogenesis

The accurate quantitation of biochemical patterns during embryogenesis in a specific organ system involves calculating, not merely values for quantities of substrate, but distribution, i.e., concentration per unit tissue space. Embryonic, neonatal and early postnatal tooth germs possess cell populations of unequal size, type and function. Studying a specific molecular species in the “total organ” can be extremely misleading if one assumes the organ system to be homogeneous. The mammalian tooth germ is heterogeneous in most aspects; specifically when considering dynamic alterations associated with development. Therefore, to adjust for some of these factors, this study related morphology to a series of biochemical events. Histological examinations of rabbit deciduous posterior tooth germs representative of the twentieth and twenty-fifth days of gestation, birth, and fifth day postnatal were correlated with chemical parameters. Wet and dry weight determinations indirectly evaluate water content and relationships between intra and extracellular spaces. DNA values establish qualitative values for cell number per tooth germ and related substrate concentration to cell number. Biochemical observations indicated that during initial extracellular organic matrix formation, non-collagenous protein concentrations decreased, whereas collagen and calcium values significantly increased. Since mineralization occurs during latter periods of our experimentation, calcium ion content was related with collagen synthesis and odontogenic extracellular matrices (enamel and dentine). Such base line studies serve as a primary step to understanding mechanisms of differentiation during odontogenesis and suggested stages during development for further research.

Healing bone fractures and simultaneous administration of radioisotopes of sulfur, calcium and yttrium.

A mixture of carrier-free radioisotopes, Ca45, S35 and Y91, was injected into rats bearing left tibial fractures, in states of repair varying from 3–18 days. Twenty-four hours after injection, both tibias were removed and analyzed for content of each radioisotope. At all intervals up to 18 days, postfracture, the injured bone contained more of all three isotopes than the intact, contralateral mate. A maximum in 24 hour retention of radiosulfate in tissue at the fracture site, was reached by the 7th to 10th day, after which retentions of a dose of S35 declined rapidly. Retentions of a dose of Ca45 in the fractured bone also rose rapidly during the first 3–10 days of healing. Thereafter, 24 hour retention values continued to rise but at a reduced pace. The avidity of healing bone for yttrium increased sharply during the same 3–10 day interval during which radiosulfate deposition became most effective. After this time 24-hour retention values for Y91 increased only slightly, if at all. The data suggest that formation of the sulfated mucopolysaccharides of osteoid matrix and fibrocartilaginous callus began by at least the 3rd day, if not earlier. The healing fracture made its greatest demands for plasma sulfate during the 7th to 10th day, postfracture. New calcium was laid down at the fracture site just as early as new sulfate, but the demands for plasma Ca continued throughout the 18 days of observation, as might be expected for a mineralizing callus. Yttrium fixation in the healing bone appeared to be more closely related to events leading to organic matrix formation than to mineralization of the new tissue.