BONE DESTRUCTION BY MULTINUCLEATED GIANT CELLS 523 



Groups 4 and 5 



No giant cells were seen around dead muscle or skin, or around 

 the foreign material introduced. The muscle was rapidly fragmented 

 and was invaded by a number of macrophages. The skin appeared 

 resistant to resorption and was walled off with connective tissue. 

 The inert foreign material likewise was walled off with a thin layer 

 of fibrous tissue, and no specific cell reaction was seen. 



Group 6 



Under the experimental conditions employed, no effect at all on 

 the number or time of appearance of giant cells was caused by para- 

 thvroid extract or by parathyroidectomy. Administration of parathy- 

 roid extract caused a large increase in the number of osteoclasts on 

 the tibia of the same animal, and parathyroidectomy was successful 

 as judged by the marked hypocalcemia found in the animals after 

 starvation for 24 hours. 



Discussion 



The first problem considered in this project was whether or not 

 the giant multinucleated cells were comparable to osteoclasts. 



Other workers have investigated the enzyme content of giant 

 cells. Baker and Klapper ( 1961 ) implanted polyvinyl sponges sub- 

 cutaneouslv into adult rats and carried out histochemical tests on 

 the giant cells that appeared. They found succinic dehydrogenase, 

 cytochrome c oxidase, diphosphopyridine nucleotide diaphorase, 

 and lactic and malic dehydrogenases, the enzymes being present in 



Fig. 4. Giant cells are seen at the end of the decalcified, devitalized bone. 

 Implant was removed after 2 weeks. Note the associated cellular reaction. For 

 comparison with Fig. 5. Hematoxylin and eosin. (X 350.) 



Fig. 5. Parallel section to Fig. 4 was reacted for succinic dehydrogenase. 

 Note intense activity in giant cells, which are larger than the osteoclasts seen 

 in Fig. 6. (X 350.) 



Fig. 6. Labial alveolar bone of a 3-day-old rat, taken from around the 

 upper incisor and reacted for succinic dehydrogenase. Note the positive re- 

 action in osteoclasts resorbing bone (B). Positive reaction also seen in basal 

 end of ameloblasts (A), (x 350.) 



