Anesthesia as an effective agent against the production of congenital anomalies in mouse fetuses exposed to electromagnetic radiation.

A total of 130 female mice pregnant at 8 days were exposed singly to a 7.3 watt microwave waveguide at 2,450 MHz wave length while being monitored for total obsorbed dose, the exposure being four minutes. Among the 1,328 offspirng examined (327 of which were controls) those not anesthetized but irradiated showed greater fetal damage than those that were anesthetized and placed in one of the three positions with respect to the radiation beam. Immobilization with anesthesia and restraint in the broadside position provided the greatest protection to the fetus against any teratologic effects. Anesthesia reduces the body temperature to a degree equivalent to the rise in temperature expected from the radiation conditions used, hence the protection against the primary thermal effect of microwave irradiation.

The relation of dose rate of microwave radiation to the time of death and total absorbed dose in the mouse.

This experiment demonstrates that for microwave radiation, absorbed dose determination alone is not dosimetrically sufficient. The average absorbed dose to death in this experiment increases as the rate of absorption decreases. This observation is not surprising since microwave energy produces heating of the biological tissues. Hence, with a higher rate of heating the body of an animal, the less it is able to retain homeostasis through metabolic regulation than with a lower rate of heating. The absorbed dose rate and the duration of exposure must both be determined in any microwave biological effects experiments.

The relation of sex, age, and weight of mice to microwave radiation sensitivity.

It is of interest to determine whether the weanling mouse, the sexually mature mouse, or the aged mouse of both sexes are similarly sensitive to microwave radiation. This study included 114 male and female mice irradiated to death with 2450 MHZ microwave radiation at 7.5 watts forward power, a minimum of 14 mice being used for any single set of variables. Weanling mice of 1 month of age are fully developed with respect to most organ systems except the reproductive. Two month old mice are sexually and otherwise mature, fully capable of survival and reproduction. The age mice of both sexes were ex-breeders which had been used for constant litter production for at least 12 months, and had waning reproductive potential. They were therefore about 14 months of age. It was found that the male mice on the average weighed more than the females (least difference at weaning) and both showed considerable weight increase with age; that weanling males irradiated to death absorbed slightly more radiant energy than did the weanling females, but they were also slightly heavier; that time to death under constant exposure from the beam increased with age for both sexes, indicating increasing microwave resistance with age and/or weight; that the mean absorbed dose at death did not show significant differences related to age or weight within the same sex; that the males showed slight increase in radio-tolerance with age and/or weight as measured by the absorbed dose at death when compared with the females which showed a decline in radio-tolerance with age and/or weight; that in all cases sex seemed to be somewhat more important than did age or weight in determining the lethal absorbed dose at death; and that it took longer longer for the older mice to die due probably to the fact that the rate of absorption of radiation was slower with their increased weight. It is the absorbed dose in joules per gram that is biologically significant and the data shows that the mean absorbed dose to death within either sex shows no significant difference with respect to age or weight, but that the difference between the sexes are significant, particularly among the aged ex-breeders.

Does x-radiation of the preconceptional mammalian ovum lead to sterility and/or congenital anomalies?

Sexually mature CF1 female mice were x-radiated with 10 to 500 R prior to mating with normal males of the same strain, and no exposure rendered the mice sterile immediately; estrous was not altered, so that normal matings occurred; the litter size of females exposed to the 500-R dose was reduced, possibly due to induction of dominant lethal genes. The second and third meiotic maturations following x-radiation gave rise to fertilizable ova which resulted in offspring that did not show any increase in the incidence of congenital anomalies. With increasing levels of exposure to x-rays, there was a decrease in the reproductive live-span. If the interval between x-radiation and mating was lengthened to 60 days, none of those exposed to 300 R or more was fertile; those exposed to 100 R showed variable fertility, evidenced by reduced litter sizes, but there were no anomalies. None of the offspring of the x-radiated females showed a significant weight loss, even to 2 months of age. Thus, when ova were x-rayed before fertilization with normal sperm, normal fertilization occurred and normal offspring were produced from at least the first three successive estrous cycles; after that, various degrees of sterility were evident, depending upon the dose level of the original exposure. Since resorptions (but not anomalies) were increased with the higher doses, dominant lethal and recessive mutatuions may have been obscured by the normal alleles of the unirradiated male mates. The ovarian ovum could not readily be sterilized by x-rays, nor could it be so damaged as to cause congenital anomalies. Nevertheless, one must be aware that all x-rayed ova may carry recessive mutatuions which might be phenotypically evident if they are on the female sex (X) chromosome, unmasked by an allelomorph on the male (Y) chromosome, or might even surface in future generations, if chance combines them with similar genes.