BONE RESORPTION IN TISSUE CULTURE 611 



changing to roller tubes it was found that good bone resorption 

 took place with hitherto ineffective concentrations of ox\gen, 

 whereas high concentrations of ox\gen were toxic. Of interest was 

 the finding that \ariation in extent of bone resorption (from slight 

 to marked) could be obtained in roller tubes bv utilizing a relatively 

 small spectrum of oxygen concentrations. From Figs. 1 to 6 it may 

 be seen that after 7 davs of culture, whereas gassing with 10 per 

 cent oxvgen resulted in onlv slight resorption in the median suture 

 area of the frontal bone, 20 per cent oxygen resulted in almost com- 

 plete resorption of this region. In both instances, however, the parie- 

 tal bone was relatively unaffected. On the other hand, cultures 

 gassed with 30 per cent O- rcNcaled widespread resorption in the 

 median suture area, occasionalh' affecting the parietal bones as well. 

 It seems clear, therefore, that in this culture svstem bone resorption 

 not onlv is oxygen dependent but can be regulated bv alterations in 

 the oxvgen concentration. 



Observations of Bone Resorption with 

 Time-Lapse Microcinematographij 



Attempts to visualize the resorptive process with time-lapse micro- 

 ciiiematographv at magnifications up to 660 times have revealed 



Fig. 1. Seven-day roller-tube culture gassed with 10 per cent oxygen 

 (balance nitrogen). Note slight resorption (R) in sagittal suture of frontal bone 

 area, (x 14.) 



Fig. 2. Seven-dav roller-tube culture gassed with 20 per cent oxygen 

 (balance nitrogen). Note moderate amount of resorption (R) in sagittal suture 

 area of frontal bone. (X 14.) 



Fig. 3. Seven-day roller-tube culture gassed with 80 per cent oxygen 

 (balance nitrogen) . Note marked resorption (R) in sagittal suture area of frontal 

 bone. (X 14.) 



Fig. 4. Parietal bone of same calvarium as Fig. 1. Culture gassed with 10 

 per cent oxvgen (balance nitrogen). Note absence of resorption. (X 14.) 



Fig. 5. Parietal bone of same calvarium as Fig. 2. Culture gassed with 20 

 per cent oxygen (balance nitrogen). Slight resorption (R) evident. (X 14.) 



Fig. 6. Parietal bone of same calvarium as Fig. 3. Culture gassed with 30 

 per cent oxygen (balance nitrogen). Note marked resorption (R). (X 14.) 



(Figures 1 to 6 were reproduced by permission from the author's paper in 

 Ciucmicrogiaphy in Cell Biology, edited by George G. Rose and published by 

 the Academic Press, Inc., New York, 1963.) 



