STRUCTURAL AND FUNCTIONAL (ELECTROENCEPHALOGRAPHIC) CHANGES IN THE POSTNATAL MAMMALIAN BRAIN RESULTING FROM X IRRADIATION OF THE EMBRYO
Electroencephalography was used to follow the effect of relatively low levels of exposure to x rays of rat embryos as the effects persisted and changed throughout the critical maturation period of life. It was hoped that such a study might reveal how the electroencephalogram (EEG), at an early stage in life, could indicate the presence of a functional congenital anomaly caused by embryonic x irradiation. Irradiation of the rat embryo at gestational age of 9.5 days with 100 r caused the death of some in utero and of others within the first two weeks after birth, but in the same litters some lived at least for 24 weeks. Rats which survived the first two weeks of postnatal life, but died shortly thereafter showed marked deviations from the normal in their EEG's, independently of the presence of overt congenital anomalies. Rats, similarly exposed in utero but surviving for 24 weeks showed consecutive maturation EEG tracings which were similar to those of controls. Those photic responses which could be elicited were less in xirradiated than in control rats. Irregularities in the EEG seen in young rats, previously x-irradiated in utero, were usually associated with early or impending death, while tdentically x-irradiated litter mates, with essentially normal ECG's survived and continued to give almost normal tracings. Electroencephalography may provide, therefore, a supplemental check on the function of a brain previously subjected to x irradiation in utero and be of prognostic significance as to impending death. Congenital anomalies were also observed, especially eye defects and hydrocephalus. A survey of the authors' earlier results in mouse embryos and fetuses shows that the central nervous system in the developing mammalian embryo is particularly radiovulnerable. As neurogenesis begins, the sensitivity of the embryo as a whole rises abruptly, and gross congenital anomalies, usually involving the central nervous system, result from irradiation. Since neuroblasts are present from that time on, through intrauterine life, and for some days after birth, these neural elements make the embryo, fetus, and newborn particularly radiosensitive. It was found that in the embryo or fetus the LD/sub 50/ fluctuates between 95 and 800 r, sometimes showing a 3- or 4-fold change within a 24-hr developmental period. In both mouse and rat it has been established that at the time when neurogenesis is initiated there is the highest probability of producing central nervous system congenital anomalies. (BBB)
- Research Organization:
- Columbia Univ., New York
- NSA Number:
- NSA-17-038813
- OSTI ID:
- 4657557
- Journal Information:
- Military Med., Vol. Vol: 128; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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