17 



Histophysical Studies on Bone Cells 

 and Bone Resorption 



RICHARD W. YOUNG, Department of Anatomy. School of Medicine, 

 Center for the Health Sciences, University of California, Los Angeles, 

 California 



ONE approach to the study of the mechanisms of hard tissue de- 

 struction directs attention to possible variations in the tissues them- 

 selves in regions preferentiallv disposed to such destructive processes. 

 In regard to bone, this relationship has frequently been investigated 

 in systemically accelerated resorptive states induced by parathyroid 

 stimulation, or by injection of parathvroid extract. The results of 

 these studies have led, however, to contradictorv conclusions. 



Under such circinnstances, "stable" rather than "labile" bone is 

 said to be preferentiallv resorbed. "Stable" bone apparently cor- 

 responds to older, more heavilv mineralized bone, while "labile" 

 bone refers to newer, less completely calcified bone" (McLean and 

 Urist, 1961). 



A number of studies indicate, in fact, that under parathyroid 

 stimulation there is selective resorption of older, fully mineralized 

 bone (Woods and Armstrong, 1956; Clark and Geoffrov, 1958; 

 Elliott and Talmage, 1958; Talmage et al, 1959, 1960, 1961) . Other 

 data, however, suggest that it is actuallv newly formed bone, in 



" Stable bone has also been referred to as "nonexchangeablc," "unavailable," 

 "deeper," "well established," and "structural" bone. Labile bone has also been 

 designated "reactive," "exchangeable," and "metabolic" bone. 



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