For this purpose a technique of cervical heterotopic heart transplantation in mice has been developed and is described as follows. Mice. Male mice from CBA and BALB/c strains, weighing 20–25 g, were from Harlan Olac Ltd., UK The CBA was used as the donor and recipient in isogeneic transplant groups, and the BALB/c was used as the donor and CBA as the recipient in allotransplant groups.

The operating microscope was manufactured by DF Vas-concellos SA, São Paulo, Brazil. Sutures were 1 1/0 Ethilon and 14-um Ethilon. A 3-mm curved round-bodied needle, diameter 30 um, cord length 2.30 mm, was used with monofilament (polyamide 66), Ethicon Ltd.) UK Two fine microsurgical clamps and an applicator forceps were used (John Weiss & Son, UK), as well as a fine-tip cautery (Edward Weck & Company). Both donor and recipient operations were done under clean conditions. Benzyl penicillin (10,000 units) was administered im at the time of surgery. Donor operation. Under ether or Hypnorm plus Hypnovel anesthesia, 20 units of heparin was injected via the penile vein. The anterior chest wall was then separated from the diaphragm, and the anterior rib cage was divided with a pair of scissors on both sides of the sternum from the lower rib margin to the clavicle. Under the microscope (16X) the right superior vena cava and the inferior vena cava were ligated with 6-0 silk suture near the atrium and divided distally to the ligatures. The ascending aorta and a segment of the innominate artery were mobilized, the aorta was ligated and cut close to the innominate artery, and a 1-mm length of the innominate artery was left attached to the aorta for late revascularization (Fig. 1, C and D). The main pulmonary artery was mobilized and transected at the point of bifurcation. The left superior vena cava and pulmonary veins were ligated en masse and divided distally. The left atrium was ligated to reduce its size. The heart was then excised and immersed in cold saline (2–4" C). Cervical heterotopic transplantation. Under Hypnorm plus Hypnovel anesthesia, the recipient was placed in a supine position, with the head facing the operator. The head was stretched and immobilized with a piece of rubber band holding the upper incisor teeth of the animal to the operating board. After shaving, a vertical incision about 1.5 cm long was made in the neck from the midpoint of the chin to the right midclavicle). This provided excellent exposure of the operative site without the need for a retractor. Under the microscope (16X) the external jugular vein was mobilized from the clavicle to its first major bifurcation. All the small branches of this segment were cut with the fine-tip cautery. The jugular vein was proximally clamped with the fine clamp close to the clavicle and then transected distally at the point of bifurcation. The sternomastoid muscle was transected to expose the right common carotid artery. The vessel was mobilized and clamped proximally with the fine clamp and ligated and transected distally. Under 25X magnification the donor heart was transplanted into the anterior neck of the recipient by using the end-to-end suture technique for both artery and vein anastomoses. The innominate artery of the donor heart and the right common carotid artery of the recipient were anastomosed first using 11/