Growth factors, heat-shock proteins and regeneration in echinoderms.  The study of regeneration in armed echinoderm species, including crinoids, ophiuroids and asteroids, is attracting increasing attention. Recent interest has focused on the presence and potential role of growth factors, including members of the nerve growth factor (NGF) and transforming growth factor-beta (TGF-beta) families, in the regenerative process and their possible relationship to the normal developmental (ontogenetic) regulatory cascade. In addition, the expression patterns of the heat-shock family of stress proteins (Hsps) during regeneration are also important. Their role forms part of a normal stress response to the trauma of autotomy in combination with a putative function in tissue remodelling and associated protein turnover during regeneration. The temporal dynamics of the stress response may also be strongly indicative of environmentally adaptive pressures operating on these systems.