Scientists have found that if the planarians immediately after irradiation to cut off the head or cause other damage in the area of injury they can still stem cells, but in whole worms all the stem cells die. The reason is not in dividing cells (after irradiation it was blocked for two weeks) and in the inhibition of apoptosis. The signal about the damage to the stem cells pass cells that die due to injury. Article published in the journal Current Biology.
Stem cells — the main resource regeneration in damaged tissues. They are vulnerable to damaging environmental influences, including radiation. Therefore, for example, planarians (flat worms known model to study regeneration) after exposure the most stem cells die, and recovery from them is difficult.
As the damaged tissue stem cells signal about the necessity of individual regeneration and stem cells of planarians, in turn, react to the injury is unknown: the fate of individual cells is difficult to track because of their weight. After irradiation, however, leaving relatively few stem cells, and their reaction to various injuries it is convenient to study.
Carolyn Adler (Carolyn Adler) College of veterinary medicine Cornell University, and her colleagues irradiated planarian Schmidtea mediterranea 2000 rad (a third of the lethal dose). Immediately after that, the animals head was cut off or cause other damage, and then tracking the distribution of stem cells using cytogenetic methods (polymerase chain reaction real-time fluorescence hybridization in situ).
One day after irradiation, the planarian without further damage, markers of stem cells is practically not expressed, and the removal of the head immediately prior to or immediately after irradiation slowed the loss of stem cells. Even after irradiation with a lethal dose of 6000 rad of the headless planarians preserved part of the stem cells. Cutting head a day after the exposure did not help stem cells survive.