Electron cytochemistry of peroxidase activity in neutrophils of the bone marrow of the frog Rana temporaria.

The bone marrow of the frog was studied during the spring and winter periods. During the winter period, one type of large granules in the neutrophils of the frog proved to be peroxidase-positive. The remaining, smaller granules are peroxidase-negative. In the spring, immature and mature neutrophils are encountered in the frog. The mature neutrophils of the frog in the spring and winter periods are analogous. The immature neutrophils contain peroxidase activity in the perinuclear space, the endoplasmic reticulum and some of the granules. Some of the peroxidase-containing granules are directly associated with the canals of the endoplasmic reticulum. In the immature neutrophils, during the formation of the peroxidase-containing granules, peroxidase-negative granules smaller in size are already present in the cytoplasm. Thus, the sequence of granule formation usual for mammals is apparently not observed in the neutrophils of certain amphibia. "Annular" mitochondria, encompassing part of the cytoplasm were detected in the neutrophils. These apparently represent a section through a spherical mitochondrion enveloping and isolating a certain zone of the cell. It is proposed that the mitochondria in this way, differing from the lysosomal mode, participate in the catabolism of the cytoplasm.