Electron microscopic study of erythroblastic islands obtained by 'tissue-stamp culture' method

Analyzing the Formation, Morphology, and Integrity of Erythroblastic Islands

The bone marrow is the primary site of erythropoiesis in healthy adult mammals. In the bone marrow, erythroid cells mature within specialized microenvironments termed erythroblastic islands (EBIs). EBIs are multi-cellular clusters comprised of a central macrophage surrounded by red blood cell (erythroid) progenitors. It has been proposed that the central macrophage functions as a "nurse-cell" providing iron, cytokines, and growth factors for the developing erythroid cells. The central macrophage also engulfs and destroys extruded erythroid nuclei. EBIs have recently been shown to play clinically important roles during human hematological disease. The molecular mechanisms regulating this hematopoietic niche are largely unknown. In this chapter, we detail protocols to study isolated EBIs using multiple microscopy platforms. Adhesion molecules regulate cell-cell interactions within the EBI and maintain the integrity of the niche. To improve our understanding of the molecular regulation of erythroid cells in EBIs, we have developed protocols for immuno-gold labeling of erythroid surface antigens to combine with scanning electron microscopy. These protocols have allowed imaging of EBIs at the nanometer scale, offering novel insights into the processes regulating red blood cell production.

Mechanisms of regulation of erythropoiesis during hemolytic anemia

We studied changes in the erythroid hemopoietic stem during phenylhydrazine-induced hemolytic anemia. Stimulation of erythropoiesis was associated with increased functional activity of erythroid precursors, which resulted from changes in feeder capacity of hemopoiesis-inducing microenvironmental cells and erythropoietic activity of the plasma. The development of encephalopathy induced by a hemolytic poison was accompanied by a decrease in hyperplasia of bone marrow erythropoiesis. It was related to a decrease in the number of proliferating erythroid precursor cells. These changes accompanied the increase in the secretory function of adherent myelokaryocytes, rise in erythropoietic activity of the plasma, enhanced formation of erythroid hemopoietic islets, and accelerated maturation of hemopoietic cells.

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.