The aim of the present work was to develop optimal protocols for immunocytochemical reactions for nuclear protein NeuN for light and laser confocal microscopy which avoid the thermal antigen demasking procedure, which degrades the state of the tissue and requires use of expensive adhesive-coated slices. Maximal antigen retention was obtained after fixation in zinc-formalin and Bouin's fluid (maximum one day). Two protocols are proposed allowing the thermal demasking procedure to be avoided during detection of neuron marker NeuN on paraffin sections examined by light and confocal microscopy.

The possibility of mesenchymal stem cell differentiation in the cardiomyocyte direction was studied on Wistar-Kyoto rats with myocardial infarction induced by ligation of the left coronary artery. In vitro treatment of mesenchymal stem cells with 5-azacitidine led to spontaneous contractions of about 15% cells in culture. Analysis of the expression of matrix RNA showed expression of fetal and functional markers of the myocardium in this cell culture. In vivo on day 21 after myocardial infarction and intravenous transplantation of mesenchymal stem cells into the periinfarction area, myocardial cells carrying donor label were detected. Immunohistochemical analysis showed that these cells were cardiomyocytes integrated into the myocardium. These cells can be a result of differentiation of transplanted mesenchymal stem cells or fusion of endogenous cardiomyocytes with exogenous mesenchymal stem cells.

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