Experimental Homograft Aortic Valve Replacement

In dogs, single non‐coronary cusp homograft aortic valves were transplanted with the aid of cardio‐pulmonary bypass. A high incidence of Dirofilaria immitis infestation was observed and may have contributed to the mortality observed. Short‐term survivors only were obtained, and the acute histological changes in the transplanted valves consisted of œdema and infiltration with erythrocytes, which resulted in an increase in thickness of the valve cusp. Copyrigh

The Martin Titanline arterial clamp. A new lightweight alternative.

When haemostatic clamps are applied, evidence of injury at the site of clamp application may be seen when the clamp is removed. Rarely, the intima may be disrupted. When a new arterial clamp became available, a study was designed to compare the Martin Titanline arterial clamp (13-143-35, curved arterial clamp) with several other arterial clamps already in use. The Martin clamp is a modified pivot-point, preset-tension, spring-controlled arterial clamp. The closing pressures of several clamps were measured objectively. The injury produced when the clamps were applied to occlude the blood flow on the carotid artery of a dog was assessed by histological study of the excised segments of the arterial wall. Histological cross-sections were prepared from canine carotid artery which had been perfused for 1 h after the clamp had been applied for 1 h. Histological evidence of injury was limited to disruption of the intimal layer and compression of the medial layer. No significant difference between the amount of damage caused by the DeBakey, Satinsky or Martin clamp was identified. When compared to the other varieties of clamp listed above, the Martin clamp had a significantly lower closing pressure (304 g) compared with 580g (Bulldog), 580 g (Satinsky), and 686 g (DeBakey). The Martin clamp was easier to apply, did not obstruct the operative field as readily and had good clamp-retention characteristics throughout the procedure

Another look at rejection in pig liver homografts

Orthotopic liver homografting in 59 pigs was successful in producing survival beyond the immediate operative period in 29 animals. Survivors without immunosuppression were subjected to serial biopsy from 3 days to more than one year after transplantation. A composite picture of progressive histological changes in the group as well as in individuals has been built up. About 3 days after transplantation, there appeared in homografts (but not in autografts) progressive infiltration of the portal tracts by round cells, which was well established by the second postoperative week, and which was accompanied in severely affected animals by round-cell infiltration of the parenchyma, extensive death of hepatocytes by apoptosis, and canalicular bile stasis. The heavy round-cell infiltration coincided with the appearance of jaundice in about half the animals, and subsided spontaneously with the jaundice. By 4 weeks the lymphocytic infiltration was much less marked, but there developed a progressive fibrosis with disruption of the lobules and the appearance of regenerative nodules. This appeared to vary in speed of development and severity from animal to animal, but was present in most long-term survivors, despite apparent clinical and biochemical evidence of well being. Two long-term survivors died with biochemical and pathological evidence of progressive hepatocellular insufficiency. While acute rejection rarely causes death in this species, changes suggestive of chronic rejection occur in most animals and may cause death from liver failure

An electron microscopic study of the mode of donor cell death in unmodified rejection of pig liver allografts

The only type of cell death found in pig liver allografts 1 week after technically successful operation was apoptosis. Its extent paralleled the degree of mononuclear cell infiltration of the liver parenchyma, and mononuclear cells were found applied to the surfaces of hepatocytes showing early stages of the process. The results suggest that cellular immune attack induces apoptosis of donor cells, and that the action is a direct one. However, implication of other factors such as vascular damage in the induction of apoptosis in the grafts could not be excluded