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We studied the dynamic of proliferative activity of cultured mouse transformed fibroblast-like L-929 cells in the logarithmic growth phase. During a long period (December 5-23, 2020), we revealed a 4-day rhythm of daily increase in the number of L-929 cells with an amplitude not lower than in a culture of embryonic fibroblast-like cells. Hence, the formation of the 4-day rhythm is not associated with the molecular mechanisms of inhibition of proliferation, which are absent in transformed cells. Daily thawing of samples of one culture over 17 days showed the presence of a 4-day rhythm synchronous between all thawed samples and the control cell culture. As deep freezing leads to the cessation of all life processes in cells, the formation of a 4-day rhythm of proliferative activity of cell culture is determined by an exogenous mechanism. [ABSTRACT FROM AUTHOR]

There are individual differences in the tolerance to hypoxia and stress. Stress can contribute to the development of various diseases, including inflammatory bowel disease. It was found that inflammatory bowel diseases in animals susceptible to hypoxia runs more severe course than in tolerant animals. We studied morphofunctional changes in the colon under conditions of modeled cold stress in male C57BL/6 mice susceptible and tolerant to hypoxia. The animals were daily subjected to cold stress (20 min at -20°C) for 2 weeks. Cold stress was followed by an increase in the volume fraction of goblet cells in the colon and production of mucins by these cells in mice tolerant to hypoxia and an increase in cell content in the lamina propria of the colon mucous membrane in animals susceptible to hypoxia. The number of serotoninproducing endocrine cells increased in both groups, but these changes were more pronounced in mice susceptible to hypoxia. [ABSTRACT FROM AUTHOR]

The features of B16 melanoma progression in male C57BL/6 mice with initially high and low resistance to hypoxia were studied. To assess the resistance to hypoxia, the mice were placed in a low-pressure chamber at a simulated altitude of 10,000 m. One month after testing, B16 melanoma was inoculated to high- and low-resistant animals. In 19 days after melanoma transplantation, the severity of melanoma progression was assessed by morphological and immunofluorescent methods. The expression of vegf-a and hif-1a in the liver of melanomabearing and control mice was evaluated by real-time PCR. Tumor growth progression was more pronounced in low-resistant mice, which was seen from high weight of the primary tumor node, relative necrosis area, proliferation rates (mitotic index and number of Ki-67+ cells), and expression of vegf-a gene in the liver. In high-resistant to hypoxia animals, the number of caspase-3+ cells dying by apoptosis was higher. The data on more rapid melanoma progression in mice with low resistance to hypoxia should be considered during the search of new prognostic markers and methods for therapy of malignant neoplasms. [ABSTRACT FROM AUTHOR]