632 REGENERATION AND GROWTH 7 



TABLE 14 



PROMOTION OF REGENERATION BY THYROID HORMONE 



Tissue or organ Reference 



A/T r 1 • I Arey, 1036; Nettleship, iqa.'x; 



Mammalian skin _ ', ^-^ , if ^^^' 



' Barclay et al., 1944; Carlson, 1952 



■Klt^■u I Steinlin, 1900; Bayon, 190":?; Fontaine 



Mammalian bone , / ' j j ' 



t et al., 1952 



Mammalian liver Canzanelli et al., 1949 



Mammalian muscle Kovalenko, 1954 



^r ^ , ^ 1 Wolff, 1891^; Walter, 191 1; Diaz-Guerrero, 



Vertebrate nerve ■> ^j^ > j ■> 1 



' '947 



Bird, feather Belkin, 1946 



Tri turns, limb Richardson, 1945 



Triturus, tail Kambara, 1953 



Axolotl, limb Belkin, 1946 



Axolotl, tail Jaques, 1950; Hess and Kopf, 1951 



Rana, tadpole, limb Peadon, 1953 



In the R-phase of limb-regeneration in the newt, ACTH induces de-differen- 

 tiation and the essential mobihsation of old collagen (pp. 619, 626) and of epider- 

 mis (Hall and Schotte, 1951). In the rabbit the same solution of dermal collagen 

 and thinning of the epidermis is caused by cortisone (Gillman et al., 1955). Corti- 

 sone depresses P-phase activities in connective tissues (Zoger, 1952; Kent and 

 Whitehouse, 1955, p. SSff), inhibiting the uptake of sulphur in the synthesis of 

 mucoproteins. Extra ACTH administered to an animal with intact adrenals 

 inhibits regeneration in the newt (Schotte and Chamberlain, 1955), possibly by 

 increasing abnormally, or differentially, the activity of the S-corticoids. 



The action of the N-group and of the mineralocorticoids needs further, more 

 specific study. DOCS has been found to depress bone-healing (Fontaine et al., 

 1952). On the other hand the androgens promote the regeneration of bone (Prin- 

 cipe and Bellucci, 1952) and of somatic tissues generally (Arey, 1936; Hopper, 

 1949) as they do somatic growth (Burrows, 1949; Roberts and Szego, 1953; 

 Gaunt, 1954)- However the evidence is not unequivocal; Baxter et al. (1944), 

 Guerner and Wrba (1953), and Brauchardt (1953) found no favourable effect on 

 regeneration under various conditions {cf. Korschelt, 1927, p. 665). Androgens 

 improve nitrogen-retention in regenerating animals (Cuthbertson, 1944) as in 

 normal animals, which shows that any favourable effect must be in the P-phase. 

 With exceptions (Callan, 1939), the gonadal hormones control the seasonal 

 "regeneration" of male accessory and secondary sexual structures (Hopper, 1949) 

 but this is a more specific effect. Oestrogens similarly control the regeneration of 

 the corresponding female structures, but they tend to inhibit genera) somatic 

 growth (Burrows, 1949; Roberts and Szego, 1953; Fishman, 1951), and probably 

 somatic regeneration also (Read, 1954; Brauchard, 1953), though a positive ac- 

 tion on pancreatic islet-regeneration has been claimed (Foglia et al., 1954). 

 According to Lauber (1933) both male and female gonadal hormones promote 

 somatic regeneration, but only (or particularly) in the appropriate sex. This 



