55^ BELANGER, ROBICHON, MIGICOVSKY, COPP, VINCENT 



These combined facts lead to the concept of a dual role for the 

 osteocytes. While the young and small osteocyte probably continues 

 at a slower pace the accretion initiated by the osteoblast, the mature, 

 hypertrophic osteocyte presides over salt removal through changes 

 induced in the organic matrix ( osteolysis ) . 



A Variety of Factors Which Induce Osteolysis 



Pregnancy in the rat, as observed by Ruth ( 1954 ) and now con- 

 firmed, accelerates osteolysis. Para-Thor-Mone, vitamin D, and nor- 

 ethandrolone are all acceleration factors. We have also observed that 

 toxic substances such as lathyric seed and fluoride promote this 

 phenomenon. A few samples of human bone neoplasms recently 

 obtained, and also specimens from two children afflicted with osteo- 

 genesis imperfecta, have revealed exaggerated osteolysis. 



Under any one or a combination of these factors, the maturation 

 of the osteocyte has been accelerated (Figs. 14 to 16) and the secre- 

 tory mechanism has been stepped up. Metachromatic material has 

 been deposited sometimes homogCxieously, in a decreasing gradient 

 around the lacunae, sometimes as irregular granular clumps. 



Hyperactive large osteocytes in our experimental material have 

 oftentimes become depleted ( Fig. 12 ) and died. Death of the osteo- 

 cytes has been reported by several investigators. It has been related 

 to a variety of injuries: rickets, osteomalacia, chronic phosphorus 

 and thallium intoxication, fluorosis (Rutishauser and Majno, 1951); 

 osteolathyrism (Selye, 1957); berylHum intoxication (Kelly et al., 

 1961); circulatory insufficiency (Sherman and Selakovitch, 1957); 

 old age (Frost, 1960). 



X-ray microradiography of mineralized sections and alpharadiog- 

 raphy of comparable demineralized matrix have revealed that con- 

 comitant accelerated loss of mineral and organic density occurred in 

 the immediate vicinity of the hypertrophic lacunae (Figs. 6 to 10, 

 18 to 20, and 23 to 26). Some of these records indicate that the 

 osteolytic phenomenon is related to single cells or to small groups 

 of adjacent enlarged osteocytes (Figs. 22, 27, and 28). 



The fact that mineralization of the lacunae appears as "subsequent 

 to cell death" (Kelly et al, 1961) or as "characteristic of aging" 



