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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.

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The paper presents the ultrastructural modifications occurring in uterine cervix epithelium in 10 patients with clinical susceptibility of HPV infections. The presence of viral HPV particles was identified in 5 cases and in 1 case the concomitant presence of both HPV and HSV2 particles was detected. The maximum amount of HPV virions is found in the spinous and superficial layer, particularly in the nucleus, but also in cytoplasm. In all the studied cases, cellular alterations were present in the whole depth of the epithelium. The degree of cellular alterations depends upon the epithelial layer to which they belong and to the stage of the disease as well. Cellular alterations are more pronounced at the level of the spinous and superficial layer being present both in nucleus (chromatin condensations, invaginations of the nuclear membrane, the occurrence of some pseudonuclei) and cytoplasm (intracytoplasmic vacuolizations, the presence of some inclusions). The presence of some giant mono- and binucleated cells as well as the formation of cellular syncytia in case of severe alterations are also reported.

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Imunotim, a polypeptidic extract from bovine thymus, induces the appearance of barrier cells in the spleen; these cells form a syncytial network and play an important role in blood cleaning. They are of fibroblastic origin. The cytoplasm of the cells in the network is dense and contains vesicles that seem to be detached from the nucleolemma. The nuclei are of small sizes. Cells (maybe lymphocytes) in different stages of disintegration can be seen in the network.

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Ten days after inoculation of sarcomatous homogenate in the leg muscle of chickens, the appearance of sarcomatous tumours was observed by electron microscopy. Viral replication and cell transformation strongly altered phospholipids and glycolipids content of the tissue: 6.12 +/- 0.23 micromoles phospholipid phosphorus/g tissue in normal tissue and 3.5 +/- 0.19 micromoles phosphorus/g tissue in sarcomatous tissue. The concentration of lipid-bound sialic acids in normal tissues was 10.5 +/- 0 nmoles/g tissue and 24.27 +/- 0.8 nmoles/g tissue in sarcomatous tissue.

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The hepatocytes of Rana esculenta exhibit hexagonal, probably icosahedral, viral particles disseminated in the cytoplasm among cellular organelles (mitochondria, cisternae of the endoplasmic reticulum, Golgi complex). The particles consist of an electron-dense core (nucleoid) and a less electron-dense envelope (capsid). Empty capsids (without nucleoid) or semilunar capsid fragments can be sometimes observed. The virus seems to be a cytoplasmic one, as it has not been found in the nucleus of hepatocytes.

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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 sytoplasm 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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