[Dynamic instabilities in microtubule cytoskeleton. A phase diagram].

Instabilities in the growth and depolymerization of microtubules are considered in the framework of self-organization theory. An extended reaction-diffusion model for the microtubule dynamics has been formulated. A phase diagram of microtubule cytoskeleton has been constructed, which determines the regions of stability for steady and nonstationary solutions of the model. It is shown that the instabilities in microtubule dynamics result from kinetic nonequilibrium phase transitions. On the basis of phase diagram structure, a general classification of the microtubule cytostatic regulatory factors is suggested. The problem of mutual amplification of the activity of cytostatic agents is discussed.

[Tunneling of autowaves through unexcitable parts of active media]. / Tunnelirovanie avtovoln cherez nevozbudimye uchastki aktivnykh sred.

The mechanisms of propagation of autowaves through local heterogeneities in active media were studied by computer simulation. The model proposed by Zel'dovich and Frank-Kamenetsky and that of FitzHugh-Nagumo were used for studying autowave tunneling. It was shown that the underbarrier passage of an autowave through a nonexcitable area is limited by threshold values. It was shown that, for every fixed parameter value corresponding to the degree of nonexcitability of a local area, there exists a critical value for nonexcitable zone latitude. An autowave overcomes the barrier and continues to propagate when the value of zone latitude is less than the critical. Critical conditions for the origination of sources of secondary periodical sequences of impulses in excitable medium were found. It was shown that the properties of sources of secondary autowaves can be modified by regulating the size of the nonexcitable zone and the zone of increased excitability. In particular, the conditions were explored under which spatial irregularity behaves as a source of a unidirectional and/or an asynchronous sequence of impulses.

[Spatial aspects of blood coagulation dynamics. III. Growth of clots in vitro]. / Prostranstvennye aspekty dinamiki svertyvaniia krovi. III. Rost tromba in vitro.

The growth of fibrin clots in thin blood plasma layers was studied. It was found that the clot growth stops or is strongly retarded if its thickness approaches 0.5 mm. Polymer clots growing toward each other fuse together at distances between the coagulation activation centers less than 1 mm, whereas at distances of about 1.5 mm, the clots are separated by ungrowing flat gaps. In some experiments, successive formation of concentric ring-shaped structures was observed. Around the centers of coagulation initiation, up to 3 fibrin rings separated by areas of uncoagulated plasma were formed. The data agree well with the hypothesis advanced by the authors earlier that blood coagulation is regulated by auto-wave mechanism.

[Spatial aspects of the dynamics of blood coagulation. I. Hypothesis]. / Prostranstvennye aspekty dinamiki svertyvaniia krovi. I. Gipoteza.

General physical requirements concerning spatial development of a clot as well as modern biochemical kinetic data on blood coagulation system have been analyzed. The hypothesis assuming an autowave mechanism of blood clotting process is proposed. It is suggested that the thrombin autowave propagates in blood starting from the site of vessel injury. Behind the front of this wave the conditions necessary for appearance of the anticoagulation autowave (which inhibits the clotting process) are being created. The second wave starts later and propagates with greater speed catching up the first one at the definite distance; the clotting process is stopped at this moment. The crucial experiment to verify the hypothesis is proposed.

[Spatial aspects of the dynamics of blood coagulation. II. Phenomenological model]. / Prostranstvennye aspekty dinamiki svertyvaniia krovi. II. Fenomenologicheskaia model'.

Pattern formation dynamics of the blood clotting system was investigated using a reaction-diffusion model based on modern biochemical concepts. It is shown through analysis of the model that the pattern formation mechanism in the blood significantly differs from the well known fundamental Turing's mechanism. Within the mechanism discovered the human blood is treated as the specific new-type active medium, in which the pattern formation is determined by the interplay of two autowaves.