A lymphocytopenic virus was isolated from a cell culture derived from a strain of Ehrlich ascites carcinoma and from the mouse passage strain of Ehrlich ascites carcinoma. The virus was not cytopathic in tissue culture but was infective in adult mice in the several strains tested. The major pathologic changes were in the spleen, lymph nodes, and thymus and resulted in a marked diminution of lymphocytes, accompanied by degenerative hepatitis and the development of peritoneal and pleural fluid. The infection was of short duration and was followed by morphologic and functional regeneration of tissue. In the period post infection, the Swiss and C3H mice developed a fibrous encapsulation of the visceral organs. The pathologic changes associated with this virus are different from those known to be associated with mouse hepatitis, and Reo III and murine leukemia viruses.
Summary DBA/1 (audiogenic seizure-susceptible) and A/Jax (seizure-resistant) mice were subjected to bell-ringing sound and an approximate 80–90 per cent effective carcinogenic dose of 20-methylcholanthrene and observed for time of tumor induction and ultimate fate. There was a delay in the time of tumor induction (latent period) in DBA/1 mice subjected to audio stimulus as compared with DBA/1 controls, whereas A/Jax mice were unaffected. Despite the delayed tumor induction in sound-stimulated DBA/1 mice, their survival time was the same as comparable controls. It is believed that, once induced, the tumor cell growth was stimulated by the sound stress exposure. No significant differences in carcinogenesis were noted when cortisone was administered in lieu of sound stress. The addition of cortisone to sound stress exposure significantly reduced the tumor induction in the DBA/1 mice (58 per cent), whereas tumor induction in A/Jax mice was 100 per cent, a slight increase over A/Jax controls.
Based on present data, the M-P virus appears antigenically and morphologically to be a strain of the lymphocytic choriomeningitis virus, with some different biological properties.
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