Analysis of growth kinetics and proliferative heterogeneity of Lewis lung carcinoma cells growing as unfed culture.

AIM: To analyze the growth kinetics and proliferative heterogeneity of Lewis lung carcinoma (LLC) cells during their growth in monolayer for 5 days without replacement of culture medium (unfed culture). METHODS: Cell biology methods, sandwich enzyme-linked immunosorbent assay for vascular endothelial growth factor (VEGF) detection (ELISA), enzymatic glucose-oxidase method for glucose measurements, mathematical modeling. RESULTS: Created mathematical model showed good fit to experimental data; that allowed to determine kinetic (model) parameters of LLC cells and predict the changes in number of proliferating and quiescent cells (proliferative heterogeneity) during their growth. It was shown that growth kinetics of viable LLC cells possesses non-monotonous character - during first three days of growth the number of cells raised exponentially, with following decrease after the maximal level was achieved. At the same time the decrease of number of viable cells/increase of number of dead cells has been observed upon complete depletion of culture medium by glucose content. Glucose dependence of cell transition rate from proliferation to resting state predicted by mathematical model possessed a pronounced two-phase character. At a wide range of relatively high glucose concentrations (> 1.0 mg/ml) the transition rate was close to zero. At concentrations lower than 0.7 mg/ml, the rate of transition swiftly increased resulting in sharp change in cellular composition. At an interval from 70 to 90 h, practically all proliferating cells transited to a resting state. The rate of quiescent cell death was relatively low, and this was in part caused by too low level of glucose consumption compared to proliferating cells. It was shown that during LLC cells growth VEGF production rate decreased monotonously in spite of the fact that the level of VEGF in incubation medium increased monotonously. Observed monotonous decrease of VEGF production rate could not be explained by VEGF degradation in incubation medium (our results displayed the stability of VEGF molecule during investigations). CONCLUSIONS: Weak dependence of cell transition rate from proliferating to resting state from glucose level (> 0.7 mg/ml) and low rate of cell death provided slow decrease of the pool of quiescent cells in the population, thus significantly increasing their chance to survive upon nutritional deficiency.

Basic studies of local adsorption in burn treatment.

The model of a full-thickness thermal burn in rats was used to demonstrate that the application of adsorptive dressings made of a fibrous activated carbon material (ACFM) after early excision of a burn crust exerts a considerable influence on the development of both local and general symptoms of burn disease. Three days after the excision a water content in underlying tissues falls from 84.81 +/- 0.62% to 54.47 +/- 4.2%, the wound surface area decreases by 10%, while this surface area under gauze bandages increases by 6.3%. The local adsorption results in lower activity of proteolytic serum enzymes and toxicity of blood serum in burned animals as well as in the positive dynamics of changes in functional activity of the immune system. By the 14th day the T-cell activity in animals with adsorptive carbon dressings was by 3.2 times higher than that in the animals with gauze bandages. The level of B-cell response if ACFM is applied exceeds normal values to a great extent, starting from the first days after the excision of a burn crust.