EXENCEPHALIA FOLLOWING X-IRRADIATION OF THE PRE-IMPLANTATION MAMMALIAN EMBRYO
If the mouse embryo is exposed to 50 r x rays at any time from fertilization of the egg through the 9th day of gestation, its probability of being killed or developing gros anomalies averages about 13%. If the exposure is to 200 r x rays, the probability is increased to 26%. The controls showed 5.7% death but no anomalies. The remaining litter mates that were similarly exposed, were questionably "normal" and generally stunted. The gross congenital anomaly known as exencephaly may result from x irradiation at any time from 0.5 to 9.0 days after conception. The idea of a critical period for this anomaly will have to be modified to include all stages of development prior to the differentiation of the nervous system. Execephaly raay be produced by damage to the newly fertilized egg before any cleavages or by darmage to neulroblasts at 8.5 days. It is probable that the irradated blastomers somehow interfere with the normal processes of gastrulation; this results in cephalic anomalies. Intreased x irradiation did not increase the incidence of exencephaly as much as it increased the incidence of resorption. Exencephaly, therefore, is a the incidence of resorption. Exencephnly, therefore, is a central nervous system anomaly which does not kill in utero, and is intermediate between apparent normality of some and death of others. Prior to the first cleavage the fertilized egg is highly susceptible to irradiation insult, with 42% being resorbed after 50 r and 64% after 200 r. This represents very high reproductive waste, which is due solely to embryonic x irradiation. On the basis of the development of such an anomaly as exencephnly, it is believed that the stunted litter raates which appear to be normal may not function normtally and that 50 r to any embryo prior to day 9.0 is permanently injurious, particularly to the central nervous system. The variations in the responses of litter mate embryos raay be due to genetic dif= ferences between individuals, commonly called normal biological variability. The minimal exposure to x rays width may cause permanent neurological damage to the erabryo or fetus has not been established. It is certainly less than 50 r x rays. 41 references. (auth)
- Research Organization:
- Columbia Univ., New York
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-14-022776
- OSTI ID:
- 4153707
- Journal Information:
- J. Neuropathol. Exptl. Neurol., Vol. Vol: 18; Other Information: Orig. Receipt Date: 31-DEC-60
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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