Modeling of post-stroke stimulation of cortical tissue.

Following a stroke, cortical networks in the penumbra area become fragmented and partly deactivated. We develop a model to study the propagation of waves of electric potential in the cortical tissue with integro-differential equations arising in neural field models. The wave speed is characterized by the tissue excitability and connectivity determined through parameters of the model. Post-stroke tissue damage in the penumbra area creates a hypoconnectivity and decreases the speed of wave propagation. It is proposed that external stimulation could restore the wave speed in the penumbra area under certain conditions of the parameters. Model guided cortical stimulation could be used to improve the functioning of cortical networks.

Interplay between reaction and diffusion processes in governing the dynamics of virus infections.

Spreading of viral infection in the tissues such as lymph nodes or spleen depends on virus multiplication in the host cells, their transport and on the immune response. Reaction-diffusion systems of equations with delays in cell proliferation and death by apoptosis represent an appropriate model to study this process. The properties of the cells of the immune system and the initial viral load determine the spatiotemporal regimes of infection spreading. Infection can be completely eliminated or it can persist at some level together with a certain chronic immune response in a spatially uniform or oscillatory mode. Finally, the immune cells can be completely exhausted leading to a high viral load persistence in the tissue. It has been found experimentally, that virus proteins can affect the immune cell migration. Our study shows that both the motility of immune cells and the virus infection spreading represented by the diffusion rate coefficients are relevant control parameters determining the fate of virus-host interaction.

[Resistance of BCG-vaccinated body to tumor growth after administration of cyclophosphamide and desensitization]. / Soprotivliaemost' vaktsinirovannogo BTsZh organizma rostu opukholi posle primeneniia tsiklofosfana i desensibilizatsii.

It was shown that tumor growth is intensifying as a result of tumor cell implantation not only in early sensitization of BCG-vaccinated organism (see previously published data) but at the later period as well. Cyclophosphan removed this effect whereas desensitization carried out against the background of cyclophosphan action restored it. The data on the relationship between tuberculin allergy and the state of immunological defence reactions of the body suggest the possibility of stimulation of tumor growth as well as of its inhibition.