Amphibians 



269 



DIFFERENCES IN INDUCTIVITY OF 

 ADULT TISSUES 



The phenomenon that some adult tissues 

 imitate the action of normal head inductors 

 and others that of trvmk-tail inductors was 

 investigated further by Chviang ('38, '39), 

 who used mouse kidney and Triturus liver 

 as indvictors, testing their effects both on 

 whole Tritvirus gastrulae and on isolated 

 gastrvila ectoderm which served as a jacket 

 for the grafts (Figs. 93-96, 103, 104). 



Table 14 shows that, whereas Triturus 

 liver induced head as well as trunk-tail 

 structures in both experimental series, mouse 



into two groups: liver, thymus and kidney of 

 certain animals induced almost exclusively 

 "archencephalic" strvictures* (tel- and dien- 

 cephalon with eyes, nose, balancers), where- 

 as the kidneys of other animals acted as 

 "deuterencephalic" (rhombencephalon, oto- 

 cysts) and spinocaudal inductors. Undoubt- 

 edly, regional influences of the host com- 

 plicate the situation. However, even if due 

 allowance is made for this factor, differ- 

 ences of different organs with respect to 

 their archencephalic and spinocaudal induc- 

 tivities are uncontestable. Yet no relationship 

 of a general kind can be established between 

 the histological type of certain adult organs 



Table 14. Inductive Specificity of Fresh Mouse Kidney and Triturus Liver {from Chuang, '39) 



kidney would do so only when grafted into 

 a whole gastrula but confined itself to purely 

 ectodermal cephalic structures when enclosed 

 in isolated ectoderm. This difference can be 

 explained by assuming that mouse kidney 

 is unable to induce mesodermal structures 

 out of ectoderm, but can induce them from 

 the mesoderm which is available in whole 

 embryos. Triturus liver, on the other hand, 

 can induce mesodermal trunk structures from 

 either ectoderm or mesoderm. These results 

 show that differences do exist in the effect- 

 specificity of adult organs. In agreement with 

 the data on heat-treated embryonic tissues, 

 Chuang ('39, '40) found that in both kidney 

 and liver the mesodermizing capacity is 

 much more readily abolished by boiling 

 water (within two seconds) than is the 

 neuralizing capacity (still present after one 

 hour of boiling. Fig. 103). This indicates 

 the presence of different inducing factors 

 which are possibly similar to those present 

 in embryonic inductors. 



Inductor-specific differences were brought 

 out even more strikingly in the experiments 

 of Toivonen ('40), who tested various adult 

 vertebrate tissues which were first treated 

 with 70 per cent alcohol and then implanted 

 in whole Triturus gastrulae. The tissues fall 



(such as liver or kidney) and the type of 

 their inductions. For instance, the alcohol- 

 treated kidney of the viper induced archen- 

 cephalic structures, that of the guinea pig 

 spinocaudal structures and that of the beef 

 induced both (Toivonen, '40; Toivonen and 

 Kuusi, '48). If one compares these results 

 with those of Holtfreter ('34b), Chuang ('39) 

 and Hama ('44) on the inductivity of liver 

 and kidney from various species, it becomes 

 even more difficvilt to draw general conclu- 

 sions as to the inductive specificity of adult 

 tissues. In addition to species differences, 

 such factors as age (Rotmann, '42) and star- 

 vation (Toivonen, '51) of the donor animal, 

 as well as pretreatment of the inducing 

 material and the competence condition of 

 the reacting tissue, influence the results. This 

 applies not only to such complex inductions 

 as head and trunk structures but also to 

 single tissues such as a free lens, which can 

 be induced by a variety of fresh or killed 

 embryonic and adult tissues. 



* A terminological inconsistency should be 

 pointed out: Lehmann ('42b) introduced the terms 

 "archencephalic" and "deuterencephalic" as des- 

 ignations of parts of the brain, whereas Toivonen 

 and others use them to designate different regions 

 of the head, including non-neural structures. 



