BONE DESTRUCTION BY MULTINUCLEATED GIANT CELLS 529 



of the animals failed to influence the resorption of the implants. A 

 possible explanation is that vital osteoblasts and osteocytes are 

 necessary for this hormone to stimulate bone resorption. 



Summary 



1. Devitalized autogenous subcutaneous bone implants in rats 

 have been studied with respect to osteoclasis. 



2. Decalcified implants from normal rats began, after 2 weeks, 

 to be resorbed by multinucleated giant cells. These cells had vir- 

 tually the same enzyme activity as osteoclasts and were capable of 

 resorbing uncalcified bone matrix. 



3. The osteoid of devitalized autogenous implants from rachitic 

 rats was not resorbed by giant cells until it had become calcified 

 after implantation. 



4. Parathyroid extract or parathyroidectomy did not affect the 

 time of appearance or number of giant cells appearing around im- 

 plants. 



5. It is considered that the giant cells studied are comparable 

 to osteoclasts. There appears to be a type of tropism influencing 

 their appearance which is exerted by bone matrix that is or has been 

 calcified, but not by matrix such as rachitic osteoid which has not 

 been calcified. 



Acknowledgments. This project was supported in part by Research 

 Grants D-876 and D-1592 from the National Institute of Dental Research, 

 National Institutes of Health, United States Public Health Service. Dr. 

 Handelman holds a postdoctoral fellowship awarded by the National In- 

 stitute of Dental Research. 



References 



Bailie, J. M., and Irving, J. T. 1955. Development and healing of rickets 

 in intramembranous bone. Acta Med. Scand., 152, Suppl. 36, 1-14. 



Baker, B. L., and Klapper, Z. F. 1961. Oxidative enzymes in the foreign 

 body giant cell. /. Histochem. and Cytochem., 9, 713-714. 



Bujard, E. 1946. Osteoclastes et cellules geantes. Rev. med. Suisse 

 romande, 66, 475-482. 



Burstone, M. S. 1961a. Modifications of histochemical techniques for the 



