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Stem cells capable of long-term proliferation and differentiation into different cell types may be a promising source of cells for regenerative medicine. Recently, much attention has been paid to fetal stem cells, among which are cells from amniotic fluid (AF). We have isolated amniotic stem cells from 3 AF samples. Flow cytometry, RT -PCR and immunohistochemistry have shown that these cells express mesenchymal (CD90, CD73, CD105, CD13, CD29, CD44, and CD146), neural (≤3-tubulin, Nestin, and Pax6), epithelial (keratin 19 and p63) markers and also markers of pluripotency (Oct4, Nanog, and Rex-1). Transplantation of the cells to nude mice does not lead to tumor formation. Thus, putative stem/progenitor cells from AF are capable of long-term proliferation in vitro and the profile of gene expression led us to speculate that they have greater differentiation potential than mesenchymal stem cells and may be useful for cell therapy.

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Influenza A virus matrix M1 protein is membrane associated and plays a crucial role in virus assembly and budding. The N-terminal two thirds of M1 protein was resolved by X-ray crystallography. The overall 3D structure as well as arrangement of the molecule in relation to the viral membrane remains obscure. Now a proteolytic digestion of virions with bromelain was used as an instrument for the in situ assessment of the M1 protein structure. The lipid bilayer around the subviral particles lacking glycoprotein spikes was partially disrupted as was shown by transmission electron microscopy. A phenomenon of M1 protein fragmentation inside the subviral particles was revealed by SDS-PAGE analysis followed by in-gel trypsin hydrolysis and MALDI-TOF mass spectrometry analysis of the additional bands. Putative bromelain-digestion sites appeared to be located at the surface of the M1 protein globule and could be used as landmarks for 3D molecular modeling.

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