The Effect of Roentgen Rays on the Time of the First Cleavage in Marine Invertebrate Eggs

Partial Additivity of the Mitotic Delays Induced by Separate γ-irradiation of Sea-urchin Eggs and Sperm

“…The present experiments confirm the observation of Henshaw and Francis (1936) that the mean mitotic delay is greater when both the egg and sperm are irradiated than when only one gamete is irradiated . However, both their experiments and the present ones show that the mean mitotic delay when both of the gametes are irradiated is less than the arithmetic sum of the delays when only the egg or only the sperm is irradiated .…”

“…The amount of mitotic delay is approximately proportional to the logarithm of the dose of X-radiation administered to Arbacia sperm (Henshaw 1940) and eggs also exhibit a logarithmic response to low doses (Henshaw, Henshaw andFrancis 1933, Henshaw andFrancis 1936) . Carlson (1954) discussed calculations indicating that a large part of the apparent additivity of the mean mitotic delays arising from radiation damage administered separately to eggs and sperm by Henshaw and Francis (1936) might be explained by random mixing of the two populations . Carlson proposed that the mitotic delay might be governed by the more heavily damaged gamete without any actual interaction of the separate damages .…”

“…Nonetheless, many fundamental questions concerning the relationships between the site and time of radiation damage and the resulting mitotic delay remain unanswered . Henshaw and Francis (1936) found that, when both sperm and eggs received a given dose of X-radiation, the mean division delay was greater than that arising from irradiation of just one gamete . However, the total delay was not as great as the arithmetic sum of the mean delays induced by irradiation of either eggs or sperm .…”

The Loci of Action of Ultraviolet and X-Radiation and of Photorecovery in the Egg and Sperm of the Sea Urchin Arbacia Punctulata

“…They find no recovery in the dark in the unfertilized egg of Strongylocentrotus, but we have not done the comparable experiments with Arbacia. Henshaw (1932) has, however, shown that unfertilized eggs of Arbacia recover from x-ray (see below). (Experiments 7,17,20) If sea urchin sperm is exposed to ultraviolet radiation and then used to fertilize normal eggs (Experiment 7), these eggs cleave later than do eggs fertilized with normal sperm (e.g., Giese, 1939Giese, , 1946Marshak, 1949 b).…”

Dosage-rate in Radiotherapy

“…It was shown long ago by Henshaw andFrancis (1933, 1936) that when sea urchin sperm or ova are irradiated the time between insemination and first cleavage is prolonged.f This delay in first cleavage increases with the dose, but if an interval is allowed between irradiation and insemination the effect of a given dose is decreased. The cells appear to recover in the interval.…”