HEART FIELD OPERATION 



301 



CULTURE OF HEART TISSUE IN ISOLATION 



After the bilateral heart rudiments have fused ventrally it is possible to remove the 

 mesodermal mass and the overlying ectoderm, and to have it differentiate in isolation in 

 the appropriate medium. In general (see "Isolation Culture" exercise) the culture medi- 

 um should consist of the normal culture medium which contains some (coelomic) body 

 fluids from adults of the same species. In addition, it is now known that 0. 5% sodium 

 sulfadiazine will retard the development of bacteria and hence prolong the life of the 

 isolate. 



^ 1% 

 75Hrs. 84Hrs 

 B 



26 Hrs. 



a o 



I Hr. 



23 Hrs. 

 C 



50 Hrs. 



Self-differentiation of presumptive heart material cultured in modified Holt- 

 freter's solution. A, Amblystoma punctatum, stage 11. Explant of gastrula 

 wall from outlined area lateral to the blastopore differentiates as shown in B. 

 Arrows show direction of contraction wave at 84 hours after explantation. 

 C, differentiation of presumptive mesoderm explanted from an embryo of 

 stage 15, late medullary plate stage. (Redrawn after Bacon, '45. ) 



(Courtesy of W. M. Copenhaver and W. B. Saunders Pub. Co. , from 

 Willier, Weiss, Hamburger "Analysis of Development" 1955.) 



The explanted heart may be cultured in a hanging drop of medium, on the underside of a 

 coverslip sealed over a depression slide; in Standard Solution in a depression slide; or 

 over an agar-embryonic fluid base. If the medium is changed every 3 to 4 days, the ex- 

 plant may be carried to quite an advanced stage of differentiation. 



HETEROPLASTIC TRANSPLANTATION OF HEART RUDIMENTS 



Copenhaver (1930 to 1939) has successfully transplanted Amblystoma punctatum, Ambly- 

 stoma tigrinufn, Amblystoma mexicanum and Triton taeniatus hearts and heart parts 

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

 ferences 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 be interposed between the other parts of the host heart. These 

 are, of course, orthotopic transplants. 



