Several types of 3-D autonomous sources of  autowaves   were
    predicted in excitable media. These  are  vortex-like 
    structures    whose filaments (rotation axes) can have
    complex  spatial    configurations (curved, knotted, twisted
    or closed  into  rings).    Up to very recently, only simple
    vortices and vortex  rings  were    observed  experimentally
    in  the   Belousov-Zhabotinskii   (B-Z)    reaction   and in
    cardiac tissue . We obtained  twisted  vortices    in a 3-D
    gelled B-Z reaction immobilized in agarose gel.    A
    twisted vortex at a cross-section looks as a  rotating 
    spiral,    whose rotation phase changes along  the  filament.
    The  filament    transpires the entire medium and terminates
    at its free surfaces.    The wave length of a twisted vortex
    proved  to  be  shorter  than    that of a simple one and
    decreased with twist ,  in  accord  with    theory   . The
    period, however, was little  dependent  on  twist,    this 
    being  inconsistent  with  computer  experiments.   Twisted 
    vortices  degraded  into  simple  ones.   Their   twist  
    decayed    exponentially, the time constant  increasing  with
    the  filament    length. The dynamics observed  fits  the 
    theory  of  diffusional    untwisting    rather than of shock
    waves.