Both experimental and clinical data indicate that the sympathetic nervous system may affect the development of certain tumors. To test this, in the present study we combined in vivo and in vitro approaches to study the effect of the sympathetic nervous system on proliferation of BP6-TU2 fibrosarcoma cells. First, we investigated the effect of 6-hydroxydopamine-induced sympathectomy on tumor development and survival of tumor-bearing rats. One week after chemical sympathectomy, we injected the BP6-TU2 fibrosarcoma cells intraperitoneally into male Wistar rats. The sympathectomy significantly reduced the incidence of intraperitoneal tumors and resulted in significantly improved survival of tumor-bearing rats compared to those with intact sympathetic innervation. Using immunohistochemical methods, we found neuron-specific enolase immunopositive structures within fibrosarcoma tissue, indicating innervation of tumors. Finally, an in vitro study showed elevated proliferation of BP6-TU2 fibrosarcoma cells in response to adding norepinephrine to the culture medium. Our findings indicate that sympathetic nerves directly potentiate the proliferation of BP6-TU2 fibrosarcoma cells in rats.
Our data indicate that feeding of male Wistar rats with a high carbohydrate normocaloric diet results in a substantial development of obesity. Moreover, exposure of juvenile individuals to obesogenic environment leads, after a certain "latent period", to the development of obesity that may reflect low protein content of used liquid diet or higher resistance of juvenile organism to the obesogenic factors. Finally, based on the data obtained we suggest that Fresubin, with respect to its properties, may serve as a diet for the development of obesity which may exemplify an "obesity model" applicable in small laboratory animals.
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