Roberts Rugh

Radiosensitivity with respect to the estrous cycle in the mouse.

lethality, carcinogenesis and cataractogenesis, shortening of life, sterility and a variety of other sequelae. The present study is made from another point of view, namely the effect of a physiological condition of the animal, i.e., estrus, on its response to whole-body X-irradiation. Ellinger (1) may have been one of the first to recognize the male as the more reliable sex in radiation lethality studies. It was natural to presume that the major difference was therefore related somehow to the estrous cycle. The present study is a report of the effect of X-irradiation of female mice near the LD50 level established for the male, but at each of the phases of the estrous cycle as determined by the vaginal smear method.

PITUITARY-INDUCED SEXUAL REACTIONS IN THE ANURA

Since the original work by Wolf (1929), ovulation has been success fully induced by anterior pituitary treatment in sixteen species of Anura and four species of the Urodela (Rugh, 1935). It is the purpose of this paper to present data on anterior pituitary-induced sexual reactions during the summer months. As a result of these observations it is now possible to say that anuran eggs and tadpoles are available at all seasons.

THE X-IRRADIATION OF MARINE GAMETES. A STUDY OF THE EFFECTS OF X-IRRADIATION AT DIFFERENT LEVELS ON THE GERM CELLS OF THE CLAM, SPISULA (FORMERLY MACTRA)

1. The spermatozoa of the clam Spisula are more radioresistant than are its eggs.2. The fertilizing power of Spisula sperm in the dry or concentrated state could not be affected by x-irradiation even to 264,000 r.3. Increasing x-irradiation of Spisula spermatozoa caused increasing delay in cleavage time of normal eggs fertilized by such sperm, but the curve was not linear and did not exceed 15 minutes. This delay represents the time interval between the first and the second normal cleavages.4. Trochophore production was at its lowest following 163,000 r x-irradiation of the spermatozoa, but with further x-irradiation trochophore production reached 95%. Such trochophores, while viable for a time, were not normal.5. Dilution of Spisula spermatozoa increased their radiosensitivity as determined by the effect on subsequent embryonic development.6. The demonstrated parthenogenetic stimulating ability of Spisula spermatozoa exposed to 189,000 r or more x-rays and used with Spisula eggs, could not be achieved wh...

THE SO-CALLED "RECOVERY" PHENOMENON AND "PROTECTION" AGAINST X-IRRADIATION AT THE CELLULAR LEVEL

The terms recovery and protection in radiobiology are specifically defined. As circumscribed, recovery at the cellular level does not occur following x irradiation damage. Protection simply refers to better survival and in no way implies saving the exposed cell from the sequelae of x irradiation insult. Data are presented from a study of the percentage cleavage and development of sea urchin (Arbacia) eggs at stated intervals following delayed fertilization and following irradiation in cysteinamine, as well as a combination of the two variables. It is concluded that recovery from x irradiation damage defined as restoration of the normal state does not oceur even with a delay in insemination. There may be some evidence of chemical nuclear protection to the extent that some eggs can develop to the early pluteus stages but no further. This is hardly protection in the common usage of the word. It is concluded, therefore, that nuclear damage by x irradiation is irrevocable and irreparable and that neither recovery nor protection, properly defined, occurs at the cellular level following x irradiation damage. (C.H.)

HYDRATION AND RADIOSENSITIVITY

Summary and Conclusions 1. Artemia “eggs,” essentially in the blastula stage in suspended development, can tolerate about 200,- 000 r more x-radiation in the dry than in the wet state, if criteria of hatching and motility after 48 hours hydration are considered. 2. The disparity between hatching and motility curves is greater in dry than in hydrated eggs following x-irradiation. Requirements for hatching must be less radiosensitive than those for motility, since there was always a disparity between these 2 steps in development. It is probable that hydrated eggs are so radiosensitive that only the hardiest survive, and these reach motility. 3. Hydrated eggs are variously radiosensitive, depending upon duration of hydration prior to x-irradiation. There is an immediate drop in radioresistance following hydration, with gradual recovery of this resistance so that after 7 hours of hydration eggs are quite radioresistant again. 4. Delay of one month between x-irradiation and hydration was detrimental to eggs, resulting in reduced values for hatching and motility. The greatest disparity was at 300,000 r.