424 URIST, MAfDONALD, MOSS, AND SKOOG 



severity of the radiographic changes had no relation to the length 

 of time following the menopause (Moon and Urist, 1962). 



The relation between the time-dependent process of aging and 

 osteoporosis was obscure. Groen et al. ( 1960 ) described alveolar 

 atrophy in osteoporotic subjects and concluded that senilitv was 

 not the cause. Berglund and Lindquist ( 1960 ) described osteo- 

 porosis or osteopenia in adolescents. The appearance of the dis- 

 order in rare instances in young men, the so-called idiopathic oste- 

 oporosis (Hall and Kennedy, 1962), also suggested that a specific 

 factor, in addition to physiologic aging, endocrinopathy, and nutri- 

 tion, had to be taken into consideration. 



Degradation of the Collagen of Bone 



An interesting theory appeared in 1962 to propose that osteoporo- 

 sis is primarily a degenerative disease, rather than an endocrine 

 or metabolic disorder. Little et al. ( 1962 ) examined normal and 

 osteoporotic bone tissue bv electron microscopv and x-rav diffrac- 

 tion of the fibrous proteins. Bone was defatted with alkali and 

 decalcified with citric acid in order to enhance the solul:)ilitv of 

 collagen in acid buffer, and, thereby, separate soluble eucollagen. 

 This was reprecipitated in pure form by dialysis. The nonsoluble 

 collagen and ground substance were analyzed together as solid 

 residue. The x-rav diffraction pattern of the solid residue suggested 

 that the crystal structure of the collagen was altered or degraded. 

 Since these alterations were not seen in bone from nonosteoporotic 

 aged individuals, or in dead bone, and resembled degradation pro- 

 duced bv irradiation damage, it was suggested that an active degrad- 

 ing agent may be involved. The patterns also included the lines of 

 a fatty acid, possibly myristic acid. Electron micrographs of bone 

 showed loss of the normal architecture and fibrillar form of the 

 collagen in various areas of osteoporotic bone. Little et al. (1962) 

 suggested that osteoporosis was the result of a local agent emanat- 

 ing from osteocytes rather than a general chemical effect. The com- 

 position of the mineral phase of bone was the same in osteoporotic 

 and nonosteoporotic individuals of comparable age, and the apatite 

 crystallites probably played only a passive role (Holdeway et ah, 

 1962). The degradation of collagen by irradiation and starvation. 



