220 



GROWTH PRINCIPLES AND THEORY 



20r 



'15 — 



10 



4 8 12 16 20 24 28 

 Days after administration 



f 



Fig. 24. Growth of pituitary dwarf mice without and with administration of growth 

 hormone. After Smith and McDowell from Bertalanffy, 1951a. 



A classic example of hormonal control of growth are the pituitary dwarf mice whose 

 growth is inhibited by a recessive gene. This leads to lack of eosinophilic cells in the 

 anterior lobe, and consequent lack of growth hormone; injection of growth hormones 

 stimulates growth so that the dwarfs reach almost normal weight (Fig. 24). The fundamental 

 metabolic aberrations caused by the dwarf gene and the lack of growth hormone is indicated 

 by the reduction of basal as well as tissue metabolism (Bertalanffy and Estwick, 1954) and 

 the absence of higher nuclear classes in the dwarfs (Leuchtenberger et al., 1954). Similar 

 changes are found in hypophysectomized animals with respect to changes in basal and 

 tissue metabolism (Bertalanffy and Estwick, 1954), decrease of kathepsin activity (Mathies, 

 Palm and Gaebler, 1 95 1 ) , and in RNA content of cells (Leslie, 1 955) . Further investigation 

 is needed to determine to what extent such effects are due to the absence of the somato- 



450 



400 



350 



■^300 

 c 



.■g>250 



i 



200 

 150 

 100 

 50 



100 



200 300 400 

 Time in days 



500 



Fig. 25. Growth of hypophysectomized rats (9). A Daily injections of growth hormone 

 (o. I mg, from the 140th day 0.2 mg daily) ; B Control. After Li and Evans from Harms, 1955. 



