"Particle-filament complex" in tumor cells of northern pike, Esox lucius L.

Examination of the cells of lymphoreticular neoplasms of the northern pike (Esox lucius L.) by electron microscopy has demonstrated the presence of unusual cytoplasmic crystalloid inclusions in cells of a spontaneous trunk tumor. The ultra-structural analysis revealed that the inclusions are composed of parallel arrays of filaments associated with rows of particles. This is designated as "particle-filament complex". The filaments of the complex measured 90--120A in diameter and 0.6--2.8 micron in length. A row of dense particles measuring 250A in diameter was arranged in regular manner between the parallel filaments. It is of interest that the complex was always accompanied by an unusual structure of nucleus of the tumor cell. The nuclei were composed entirely of filaments which were distorted and closely packed. The significance of the particle-filament complex associated with altered nucleus remains to be determined.