508 HEART F lELD OPERAT IONS 



HETEROPLASTIC TRANSPLANTATION OF HEART RUDIMENTS 



Copenhaver (1950 to 1959) has successfully transplanted Ambly stoma punctatum, 

 Amblystoma tlgrlnum, Amblystoma mexicanum and Triton taenlatus hearts and heart parts' 

 reciprocally. In such transplants it is important to realize that there are intrinsic 

 differences in growth rate and in final pulse rate, in consequence of which the chimeric 

 heart attains functional interest. Specific parts of the heart, such as the ventricle, 

 the sinus venosus, etc. may he interposed between the other parts of the host heart. These 

 are, of course, orthotopic transplants. 



Variations in this procedure include: 



a. Eeveraing of the axis of the transplant hut placing it In the otherwise 

 orthotopic position, in order to determine the direction of pulsation 



in the transplant, and the control of the transplant over the host organ. 



b. Transplantation heteroplastically to an heterotopic position, such as in 

 place of somites #7 to #10. 



OBSERVATIONS AMP TABULATION OF DATA : 



In all instances comparable stage embryos should be carried along simultaneously with 

 the experimentals in order to allow direct comparison of the results of heart field ex- 

 periments. Most of the experiments can be terminated about 8 days after the operation, 

 and the host may be anesthetized in l/5,000 MS 222 emd be dissected (along with the con- 

 trols) to determine the degree of development. In heteroplastic transplants the pulse 

 rates of controls, experimentals, and parts of experimental transplants should be deter- 

 mined. Photographs and drawings will constitute the record of these operations, and his- 

 tological analysis is generally very instructive, providing comparable controls are avail- 

 able. 



DISCUSSION: 



lyplcal vertebrates have hearts of bilateral origin. In both the Urodeles and the 

 Anura the prospective heart forming material is derived from the two lateral mesenchymal 

 plates. E^ the time these mesenchymal anlagen have migrated to the ventral position, they 

 have acquired self-differentiating capacities of heart so that if transplanted to an heter- 

 otopic position or explanted into a culture medium they will each give rise to a chambered, 

 primitive heart, often with sinus, auricle, ventricle, and arterial bulb, all of which may 

 exhibit typical rhythmic pulsations. 



Heart anlagen may be split to give multiple hearts or an extra heart anlage may be 

 superimposed on the host heart material to produce a larger but normal heart, providing 

 the axes of the host and the donor heart anlagen are the same. 



The heart area of the amphibian is considered as an equi- potential system In that as 

 little as half of the area possesses the requirements for the development of an entire and 

 normal heart. Anterior and posterior portions of the heart area, transplanted to a foreign 

 species (Copenhaver, 1930) will give rise to corresponding specific portions of the ulti- 

 mate heart. The posterior transplant combines with the anterior portion from the host and 

 generally acts as a pacemaker, giving the host the rhythmical control similar to that 

 normally found in the donor species. 



