THE INDIRECT EFFECT OF IRRADIATION ON EMBRYONIC DEVELOPMENT. II. IRRADIATION OF THE PLACENTA
A method of irradiating placental tissue separate from embryonic tissue is described. Rat embryos and placental tissue were selectively irradiated on the l2th gestational day and examined on the l6th gestational day for growth retardation, fetal mortality, and congenital malformations. The maternal organism received no irradiation in this ex periment; only the placenta, embryo, or both. This is in sharp contradistinction to the previous paper in which the embryo and placenta were simultaneously shielded, while only the maternal organism was irradiated. The data indicate that irradiation of the placenta (while shielding the embryo and mother) did not alter fetal growth or fetal mortality. This was demonstrated by two separate results within this experiment, namely, irradiation of the placenta resulted in the same fetal mortality and fetal weight as the control embryos, and, secondly, irradiation of the entire embryonic site and the embryo alone resulted in embryos with fetal weights which could not be distinguished statistically. On the other hand, if only the mother was irradiated, fetal death resulted; and the incidence of resorptions increased with the dose rate. Thus, fetal mortality was increased by maternal irradiation and not affected by placental irradiation. These data lend further support to the conclusion that malformations prodruced by irradiating pregnant mammals are due primarily to the direct effect of ionizing radiation on the embryo and are not a result of placental injury (on the l2th day at least) or metabolic abnormalities induced in the mother by irradiation of the maternal organism. This is more apparent when one realizes that malformations can be produced with as little as 25 to 200 r (whole-body irradiation to pregnant mammals); yet in the two indirect experiments herein described doses of 400 r were used in the placental irradiation experiment and 400 to 1400 r, in the maternal irradiation experiment without obvious congenital malformations. Because of the nature of the experimental conditions, one cannot be certain of platental radioresistance at earlier stages of gestation. Furthermore, no broad general conclusions can be drawn regarding the responsibility of the placenta in the over-all picture of comgenital malformations. (auth)
- Research Organization:
- Jefferson Medical Coll., Philadelphia
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-15-023304
- OSTI ID:
- 4041230
- Journal Information:
- A.M.A. J. Diseases Children, Journal Name: A.M.A. J. Diseases Children Vol. Vol: 100
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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