[Organ and tissue regeneration in lower vertebrate animals during space flight and after its completion]

The most important data obtained in studies of the influence of space flight factors on the limb and lens regeneration in the newt Pleurodeles waltlii have been summarized. Regeneration of these organs under the conditions of space flight and after its termination proceeded just as on the ground. However after the 7th, 13th and 16th days of space flight, a trend was shown toward acceleration of the limb and lens regenerates development according to the regeneration stages and synchronization of the achieved stages, which was accompanied in some cases by an increased proliferative activity of the regenerate cells. It was shown that in two groups of animals operated before the 16-day space flight (I) and just after its termination (II) accelerated development of the limb and lens regenerates was observed. In group II, at the large bud stage, the index of 3H-thymidine labeled blastema cells was more than twice that in the control. The size of regenerates in groups I and II exceeded reliably those in the control. These results suggest a prolonged effect of space flight factors on the limb and lens regeneration. It was also shown that the capacity of the muscle minced 14 days before the flight for regeneration was not suppressed, although somewhat decreased. An electron microscopic study showed degenerative-atrophic changes in the intact hind limb muscle after the 16-day space flight. We believe that the phenomenon of synchronization and accelerated regeneration of the limb and lens observed in the most experiments are due to the effect of microgravity on the animals.