Ultrastructural megakaryocyte modifications after vanadium inhalation in spleen and bone marrow.

Previous reports from our laboratory informed in mice an increase in platelets in blood, and megakaryocytes in spleen and bone marrow after vanadium inhalation. This element has become important in recent years because of its increased presence as an air pollutant. With this precedent, we evaluate the ultrastructural modifications in MKs from the spleen and bone marrow in our mouse experimental model. Mice inhaled 0.02 M V(2)O(5) 1 h twice a week for 12 weeks. Tissues were processed for transmission electron microscopy. Results indicate an increase in the size and cytoplasmic granular content, as well as nuclear changes in MKs of exposed mice, changes which correlate with the time of exposure. Modifications in MKs described here suggest that inhaled vanadium induce megakaryocytic maturation, a raise in its granules content and demarcation membrane systems, which may lead to a rise in circulating platelet production and an increased risk for thromboembolic events.

Spleen of Dasypus hybridus (Mammalia, dasypodidae): a light and electron microscopic study.

Armadillos are relictual mammals important as models for biomedical studies. They contain adaptative and primitive characteristics in both anatomical and physiological aspects. In this study we describe the splenic histology and cytology of the "mulita," Dasypus hybridus. Organ samples were processed for light and electron microscopy study. The microanatomy of the organ samples as well as their different cell types are described. The spleen is non-sinusoidal, with the typical arrangement for storage functions. White pulp is lightly diffuse. Red pulp is a meshwork of circulating, immunocompetent and hemopoietic cells. Differences with other studied members of the group are discussed. The general structure of the organ agrees with the semi-fossorial habit of the species. Persistence of myeloid activity in the adult suggests the existence of specific inductive functions of the stroma. Better knowledge of this fact may give further insight on the phylogeny of hemopoiesis.