44 J. S. Grkfnsi'AN, H. J. J. Blackwood: Histochemical Studies 



Glycogen appeared in increasing amounts in maturing chondrocytes and was at a 

 maximum in cells of the hypertrophic zone at some distance from the mineralising 

 front, but disappeared from these cells before mineralisation actually commenced 

 (Fig. 3 and 4). This suggests that glycogen is probably not directly involved in the 

 calcification process but it would seem more likely, as suggested by Weatherall et al. 

 (1964), that it is concerned with mucopolysaccharide synthesis and matrix production. 



Weak sudanophilia was present in the cartilage matrix of the hypertrophic zone 

 prior to its mineralisation but somewhat stronger sudan staining occurred in the 

 mineralising matrix. The reaction was completely abolished, however, by prior 

 extraction of the sections in a methanol/alcohol mixture. The latter procedure also 

 resulted in a reduction in alcian blue staining at these sites. The substance or sub- 

 stances responsible for these findings could well be the same as that described by 

 Irving at sites of calcification in long bones and in teeth (Irving, 1959; Wuthier 

 and Irving, 1964; Irving, 1965). A likely explanation for these staining reactions is 

 that a lipid/acidic carbohydrate complex is involved and this possibility is being 

 investigated further. 



In general the histochemical activity of the surface articular zone of the cartilage 

 was low which is in keeping with its structure and the purely mechanical function 

 which this zone appears to fulfil. No significant differences in histochemical activity 

 was observed between animals of different ages and sex. 



Summary 



Histochemical changes coincident with cell differentiation and endochondral 

 ossification were studied in the condylar cartilages of the mandible of young Wistar 

 rats. Undemineralised cryostat sections were subjected to a range of functional and 

 analytical histochemical procedures. 



The results indicate that the metabolic activity of chondrocytes is roughly pro- 

 portional to matrix production. The presence of glycogen is correlated with this 

 metabolic activity rather than with mineralisation, whereas the presence of alkaline 

 phosphatase is strictly correlated with actual or impending mineralisation. Lysosomal 

 enzymes are present in chondrocytes. A sudanophilic substance which may not be 

 lipid in nature is also associated with sites of mineralisation. 



References 



Cabrini, R. L.: Histochemistry of ossification. In International Review of Cytology. No. XI. 



Bourne, G. H., and J. H. Danielli (eds.). 1961, p. 283. 

 DuvE, C. de: The Lysosome Concept. In Lysosomes. de Reuck, A. S. A., and M. P. Cameron 



(eds.). London: Churchill 1963, p. 1. 

 Fell, H. B.: Organ culture and the physiology of skeletal tissues. In Bone and Tooth. 



Blackwood, H. J. J. (ed.). Oxford: Pergamon Press 1964, p. 311. 

 Irving, J. T.: A histological staining method for sites of calcification in teeth and bone. 



Arch." oral Biol. 1, 89 (1959). 

 — Bone matrix lipids and calcification. In Calcified Tissues. Richelle, L. J., and M. j. 



Dallemagne (eds.). Liege: Universite de Liege 1965, p. 313. 

 Sledge, C. B., and J. T. Dingle: Oxygen induced resorption of cartilage in organ culture. 



Nature (Lond.) 205, 140 (1965). 



