The nature of variations in the radioresistance of sea urchin eggs in the early embryogenesis

The synchronously developing sea urchin eggs (Strongylocentrotus nudus) have been used for the experiment. Radioprotective efficiency of cysteamine (applied in the concentrations ranging from 1.10-5 to 5.10-3M) has been studied at two stages of mitosis: metaphase and telophase. Cysteamine (5.10-3M) has been found to level the variations in radiosensitivity of these phases producing the strongest effect in the radiosensitive phase (telophase) and the slightest effect in the radioresistant phase (metaphase). Determination of the relative protective effectiveness of cysteamine in relation to the original radiosensitivity of a cell, and, hence, to its thiol content, has demonstrated that the higher the radiosensitivity of a cell at the time of the exposure the higher the relative protective efficiency of cysteamine. The data obtained evidence of the idea that thiols play an essential role in the determination of radioresistance of different stages of mitosis of the developing sea urchin eggs