RAREFYING DISEASE OF THE SKELETON -i^O 



and the inhibition of conversion of sokible to insoluble collagen in 

 irradiated experimental animals (Gerber et ah, 1962), illustrated 

 some of the possible derangements that could occur in aging and 

 osteoporotic bone. 



The level of the urinary hydroxyproline has also been interpreted 

 to reflect either the process of degradation or turnover of bone 

 collagen. Bastomsky and Dull (1962) described hydroxyprolinuria 

 in rats treated with parathyroid hormone and triiodothyronine. Klein 

 et al. ( 1962 ) found a 60 per cent increase in a patient with hvper- 

 parathyroidism with bone disease, as compared with no increase in 

 two patients without bone disease. Raveni et al. (1962) measured 

 total and free urinary hydroxyproline in normal and osteoporotic 

 patients and concluded that an increase in the free fraction reflects 

 increased destruction or catabolism of bone in this disorder. Ibsen 

 et al. ( 1963 ) evaluated a proline tolerance in rabbits with healing 

 fractures and concluded that bone formation increased the rate of 

 proline utilization. Further investigations may establish proline 

 metabolism as a useful indicator of bone matrix metabolism in 

 health and disease. 



Alterations in the Mticoproteins of Bone 



Casuccio et al. ( 1962 ) described abnormalities of the osteocytes 

 in bone tissue and a decrease in several fractions of the mucopoly- 

 saccharides of bone matrix in the skeleton of aged and osteoporotic 

 subjects. The perilacunar sheath of Rouget-Neumann was accen- 

 tuated, metachromasia was absent, nuclei were pyknotic, the canalic- 

 uli were reduced in number and showed terminal club-shaped 

 thickenings. The osteocyte sheaths were shrunken, shriveled, or 

 absent. The mucoprotein cylinders that normally fill out the canalic- 

 uli were absorbed and the osteocytes retracted their cytoplasmic 

 processes. This suggests intralacunar resorption or osteocytolysis as 

 described by Heller et al. ( 1950 ) . Casuccio ( 1962 ) observed a 50 

 per cent decrease in protein nitrogen but only a 6 to 9 per cent de- 

 crease in inorganic mineral in bone tissue in osteoporotic patients; 

 the bones of aged individuals without osteoporosis were similarly 

 altered, although to a lesser degree. Four fractions of the mucopoly- 

 saccharides of bone were influenced by both aging and osteoporosis 



