Hematopoetic stem cells (HSC) are the progenitors for the lympho‐hematopoietic system, with long lifespan and high proliferation potential. Transplantation of HSC from bone marrow or peripheral blood represents a standard therapy in severe hematological conditions. A possible alternative source of HSC is the umbilical cord blood, prepared by various separation procedures followed by expansion in cultures supplemented with hematopoietic growth factors. In order to check the effects of placental conditioned medium (PCM) from placental cells culture upon viability of HSC, we added plasma, PCM, dimetil sulfoxyde or hemin in HSC cultures. Flow cytometry or direct scoring of solid cultures using CD45+, CD34+, CD71+ and CD14+ fluorescent‐labeled monoclonal antibodies evaluated the effects upon cell proliferation and colony forming ability of HSC cultures, versus controls. PCM produced the highest proliferation, followed by plasma, DMSO and hemin. PCM improved the survival time and maintained a higher proportion of immature cells. PCM stimulates the differentiation towards myeloid lineage progenitor cells (>90% being CD45+), increasing the percentage of CD14+, granulocites /monocytes precursors. It is highly suggestive that PCM contains growth factors or cytokines, which regulate the development of HSC. Characterization of these factors is in progress.
Following hibernation, most salamander liver cells undergo alterations. The liver cells containing the structure of their active period present a normal nucleus, glycogen granules disseminated throughout the entire cytoplasm and granular mitochondria with several peripheral cristae. Most cells, however, possess altered mitochondria, transformed into electron-dense masses, or clear vesicles with the possibility of digesting the ambient organelles. Other cells have clear vacuoles with similar digestive possibilities. The endoplasmic reticulum is poorly represented in the liver cells that have suffered advanced alteration. The nucleus of these cells is homogeneously granular. The cytoplasm is populated by electron-dense bodies and lipid vacuoles. The nucleolemma and plasmalemma are thickened. The pigmented cells, altered concomitantly with the liver cells, contain granular aggregates. Some of the pigmented cells exhibit electron-clear formations similar to the reflecting platelets of the iridocytes of the integument of lower vertebrates.
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