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Myoglobin, muscle fibre diameter, and citrate synthase activity were measured in leg muscle of untrained and trained men and in the myocardium from the apex of the left ventricle and from papillary muscle in patients subjected to open heart surgery. The citrate synthase (CS) activity was 60% higher in trained than in untrained skeletal muscle. In the myocardium it was around four times greater than in untrained skeletal muscle but there was no difference between the apex of the left ventricle and papillary muscle. The fibre diameter varied almost threefold between the different groups of muscles with the largest diameter in untrained skeletal muscle and the with the largest diameter in untrained skeletal muscle and the smallest in papillary muscle. The myoglobin content in trained skeletal muscle did not differ from that of untrained muscle. In the left ventricle it was only 40% of that found in untrained muscle while papillary muscle had almost twice as high a myoglobin content as did the left ventricle. The ratio between myoglobin and fibre diameter, however, was of similar magnitude in skeletal muscle and the left ventricle while it was twice as high in papillary muscle as in the other muscles. In conclusion, the diffusion distance in terms of fibre diameter decreased with increased oxidative capacity (CS activity), when comparing the statistical means of the four different groups. The capacity for oxygen diffusion in relation to oxygen demand measured as the ratio of myoglobin to fibre diameter appeared to be of similar magnitude in skeletal muscle and left ventricle but was higher in papillary muscle.

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In 54 patients with lung and 14 with ovarian carcinomas the quantitative variations of the major histocompatibility complex (MHC)-determined class I and class II antigens of the tumor cells were related to their in vitro interaction with blood lymphocytes, to the lymphoid infiltration of the tumors, and to the metastatic state of the disease. The tumor cell-lymphocyte interaction was measured by the proliferative response in mixed lymphocyte tumor cell culture and by the cytotoxic activity of the lymphocytes. The results showed that (1) none of the 23 tumors from patients with disseminated disease were lysed; (2) class I-negative tumors were not damaged; (3) lymphoid infiltration was present in a higher proportion of class II-positive tumors; and (4) both MHC-positive and -negative tumors were found among the disseminated tumors. The requirement of class I expression in the lytic interaction substantiates our earlier conclusion concerning the cytotoxic T lymphocyte nature of lymphocyte-mediated auto-tumor lysis. The lack of auto-tumor lysis in patients with metastases suggests impairment of lymphocyte function in advanced stages of the disease.