26 



Animal Gollagenase 

 and Collagen Metabolism 



CHARLES M. LAPIERE* and JEROME GROSS, Department of 

 Medicine, Harvard Medical School at the Massachusetts General Hos- 

 pital, Boston, Massachusetts 



TISSUE remodeling during growth and development requires that 

 synthesis and removal of structural elements be precisely synchro- 

 nized in time and space. Cell migration, aggregation, differential 

 multiplication, and selectively timed and placed cell death are 

 major features of the process. The resultant complexities of the com- 

 plete tissues have made it difficult to dissect and analyze the relevant 

 mechanisms involved in these processes. 



Because of the ubiquitous distribution of the extracellular struc- 

 tural element collagen, because of the singular and specific char- 

 acteristics of this protein, and because of the large body of knowl- 

 edge concerning its structure, chemistry, and metabolism, we have 

 chosen to follow its fate in a controllable remodeling system, the 

 metamorphosing tadpole. Metamorphosis can be initiated by thy- 

 roid compoimds, producing rapid resorption of large collagen-con- 

 taining structures sucli as tail fin and gill (Gudernatsch, 1912; Allen, 

 1929; Frieden, 1961). Simultaneously, there is hypertrophy of other 

 collagenous tissues such as the skin of the back. Local intricate 

 changes are induced in the shape of specialized structures such as 

 the mouth parts, opercular areas, limbs, eye positions, etc. 



* Permanent address: Institut de Medecine, Hopital de Baviere, Liege, Belgimn. 



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