HEART FIELD OPERATION 303 



Variations in this procedure include: 



a. Reversing of the axis of the transplant but 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 AND 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 experi- 

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

 the host may be anesthetized in 1/3, 000 MS 222 and be dissected (along with the controls) 

 to determine the degree of development. In heteroplastic transplants the pulse rates of 

 controls, experimentals, and parts of experimental transplants should be determined. 

 Photographs and drawings will constitute the record of these operations, and histological 

 analysis is generally very instructive, providing comparable controls are available. 



DISCUSSION: 



Typical 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. By 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 

 heterotopic 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 super- 

 imposed 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 ultimate 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. 



REFERENCES 



BACON, R. L. , 1945 - "Self-differentiation and induction in the heart of Amblystoma". Jour, Exp. Zool 98:87. 



COPENHAVER, W. M., 1955 - "Heart, Bloodvessels, Blood and Entodermal Derivatives" . Chap, in Willier, Weiss, Hamburger 

 "Analysis of Development" . Saunders, Philadelphia. 



COPENHAVER, W. M. , 1958 - "Distribution of radioactive sulfate in the heart of fetal, newborn, and adult rabbits". Anot. 

 Rec. 131:669-680. 



COPENHAVER, W. M. , R. .van DYKE, R. RUGH, 1960 - "Effects of x-irradiation on embryos at critical stages of heart devel- 

 opment." Yale Jour. Biol. G Med. 32:421-430. 



EKMAN, G. , 1925 - "Experimentelle Beitrage 2ur Hertzenwicklung der Amphibien. " Arch. f. Ent. Mech. 106:320. 



EKMAN, G. , 1929 - "Experimentelle Untersuchungen uber die fruheste Herzentwicklung bei Rana fusca". Arch. f. Ent. Mech. 

 116:327. 



FALES, D. E. , 1946 - "A study of double hearts produced experimentally in embryos of Amblystoma punctatum". Jour. Exp. 

 Zool. 101:281. 



GIRGIS, A., 1930 - "The development of the heart in the rabbit. " Proc. Zool. Soc. London 3:755-782. 



GOERTTLER, K. , 1928 - "Die Bedeutung der ventrolateralen Mesodermbezirke fur die Herzenlage der Amphibienkeim. " Anat. 

 Anz. Erg. Heft. 66:132. 



