The quaternionic generalization of the Dirac equation is investigated. From elementary considerations of unitarity and Lorentz invariance it is demonstrated that potentials with quaternionic parts are not consistent with representation independence. This result leads to the conclusion that either quaternionic quantum mechanics singles out a special class of Dirac representations, or that allowed potentials appearing in the problem have no j or k components. If the latter alternative is the case, consideration of nonrelativistic wave mechanics casts doubt on the existence of simple experimental tests of quaternionic quantum mechanics.
. Growth of the eel trypanosome, Trypanosoma granulosum, was attempted in five semi‐defined and three defined media. Growth was poor in four semi‐defined and two defined media, but one semi‐defined medium, a modified version of SDM‐79 without MEM F‐14, supported good growth of the trypanosome. In this medium, doubling time was between 1 and 2 days, over 90% of organisms seen in culture after 6 days were trypomastigotes, and 1.8 × 0.1 × 107 trypanosomes ml−1 was achieved in 7 days. When foetal calf serum from the modified SDM‐79 was substituted with insulin to create a fully defined medium, a modest but significant increase in cell numbers occurred compared with controls. In vitro experiments with D, L‐alpha‐difluoromethylomithine (DFMO) showed morphological changes leading to destruction of the trypanosome with increasing concentrations of the drug. A 50‐mM concentration of DFMO inhibited growth by more than 90%, and the IC50 was found to be 16 × 2 mM.
To study the function of different lymphocyte populations in the Moloney strain of murine sarcoma virus (M-MuSV) tumorigenesis, we gave M-MuSV injections to CBA mice selectively deprived of thymus (T) lymphocytes by thymectomy, X-rradiation, and syngeneic bone marrow injection. Although no tumors appeared in the control group, 80% of the derived mice had tumors that grew progressively and ultimately killed them. In deprived mice, grafted with a syngeneic thymus (reconstituted mice) before or after an M-MuSV injection, tumors regressed or did not develop. Histologically, the lymph nodes and spleens of reconstituted mice, compared to those of deprived animals, showed repopulation of the thymus-dependent areas and prominent follicles in the cortex. Moreover, tumor tissue of reconstituted mice was extensively infiltrated by lymphocytes. To evaluate the number of lymphoid cells needed to prevent or regress M-MuSV tumors, we injected varying amounts of lymphoid cells into deprived mice. Even low lymphocyte numbers (10(6) cells) were sufficient to exert, in some cases, protection against M-MuSV tumorigenesis. This effect was not abolished by subsequent splenectomy or antilymphocyte serum treatment. Finally, deprived mice, given repeated injections of antiserum (hyperimmune) against M-MuSV, had tumors which appeared only after a prolonged latency. From these results, it is concluded that T-cell population integrity is important in affording total host protection against the M-MuSV tumors.
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