[Morphogenetic changes during newt tail regeneration under changed gravity conditions]

Gravity-dependent shape alterations in newt tail regenerates are described, which were previously noticed in experiments onboard satellites Foton M2, M3 and in corresponding laboratory controls. Laboratory conditions were developed that allow reproducing this phenomenon persistently in the adult newts Pleurodeles waltl (Michahelles, 1830). The newts kept in an aquarium (in partial weightlessness) after 1/3 tail amputation developed normal lanceolate regenerates, while those that stayed on a moist mat (exposed to greater gravity than in aquarium) developed curved tail regenerates. Dynamics of the shape alterations were described using computer morphometric analysis. The curve was shown to develop at stage III of regeneration and to be caused by bending of the developing axial structures: the ependymal tube and the cartilage rode. Cellular processes were described that accompany the tail shape changes, such as cell migration and formation of dense aggregates. Unequal proliferation throughout the wound epidermis and blastema was revealed using BrdU assay. Proliferation increased within dorsal and apical regions of the regenerates in the newts kept on the mat cell compared with the aquarian animals.