ABSTRACT
We examined the spatial dynamics of in vitro clot growth in human blood and plasma and found that initially, a clot grows at a constant speed, then abruptly stops and becomes surrounded by an 'inhibition zone' in which coagulation is strongly suppressed. We also observed the formation of 'stratified structures' (target patterns) in which solid layers alternated with liquid plasma. These and other spatial regimes of clotting are explained in terms of two interacting concentration waves propagating without attenuation. The experimental results are consistent with a hypothesis that blood is a bi-excitable medium, a new type of excitable medium.
Subject(s)
Blood Coagulation/physiology , Blood Platelets/physiology , Fibrin/biosynthesis , Fibrin/chemistry , Fluorescence , Humans , In Vitro Techniques , Light , Plasma/physiology , Scattering, Radiation , Thrombin/biosynthesis , Time FactorsABSTRACT
The mechanisms of autowaves propagation through local non-homogeneities in active media relevant to diverse class of physiological systems were studied by means of a computer simulation. The model proposed by Zel'dovich and Frank-Kamenetsky and that of FitzHugh-Nagumo were used for studying autowave tunneling, which in a broad sense implies underbarrier passing. It was shown that for every fixed parameter value corresponding to the degree of non-excitability of local area a critical value for non-excitable zone latitude exists. An autowave overcomes the barrier and continues to propagate when the value of zone latitude is less than critical. Critical conditions for origination of a source of periodical sequence of impulses in excitable medium were found. The source properties, as shown, can be modified by regulation of size of a non-excitable zone and a zone of higher excitability. In particular, the conditions when spatial irregularity behaves as a source of unidirectional and/or asynchronous sequence of impulses were explored.
