The Effect of Low-Level Prenatal X-Irradiation on Postnatal Development in the Wistar Rat

Abstract

The objective of this investigation was to determine the effect of low-dose prenatal X-irradiation on postnatal growth and neurobehavioral development, and whether alterations would manifest at dosages lower than those which produce anatomic malformations from exposure at the most sensitive period of organogenesis. Ninety-eight Wistar strain rats were exposed to 0.1 , 0.2, or 0.4 Gy X-radiation of were sham irradiated on the 9th or 17th day of gestation. A conventional teratologic evaluation was completed on half of the animals (572 fetuses). The age of appearance of four physiologic markers and of acquistion of six reflexes was observed in 372 offspring. Exposure during early organogenesis at these levels had no effect on any of these parameters. Prenatal exposure to X-radiation on the 17th day of gestation at dosage levels greater than 0.1 Gy resulted in alterations in the appearance of three postnatal neurophysiologic parameters. Growth retardation throughout the postpartum period also was observed in the offspring. The induction of developmental and reflex alterations had a comparable threshold to the known threshold for anatomic malformations on the 9th day. These results indicate that all of the parameters studied had thresholds either at or above 0.2 Gy acute radiation, and that the postpartum developmental and reflex acquisition measures were not more sensitive indicators of exposure to X-radiation than growth parameters. 0 1987 Society for Experimental Biology and Medicine. 256

Severity of Histopathologic Abnormalities and In Vivo Epileptogenicity in the In Utero Radiation Model of Rats Is Dose Dependent

“…We found a positive correlation between the radiation doses the rats received in utero and the severity of the cortical and hippocampal disorganization. This confirms previous animal studies that reported on the radiation dose dependence of brain damage (20,21,22,23). These studies suggested a nearly linear dose–response curve regarding the extent of histologic abnormalities seen in the postnatal brain.…”

“…EEG seizures were defined as rhythmic spiking or paroxysmal fast activity (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) Hz) that evolved in amplitude and/or frequency and lasted for ≥10 s. The rates of occurrence of ictal activity was calculated and expressed as seizures per day. The seizure-onset zone was mapped to the electrode(s) of maximal amplitude and phase reversal of the first spike.…”

Utilization of juvenile animal studies to determine the human effects and risks of environmental toxicants during postnatal developmental stages

“…From the perspective of biological plausibility and the results of animal studies, it would seem that the data favor the viewpoint that mental retardation is a deterministic effect with a threshold above 0.2 Sv (Brent et al, 1986, 1987; Jensh and Brent, 1986, 1987, 1988; Jensh et al, 1986, 1987; Brent, 1999; Miller, 1999). Histological examination of the irradiated brain exposed to 0.01 Sv shows no pathological consequences that could account for severe mental retardation (Jensh et al, 1995).…”

Protection of the Gametes Embryo/Fetus From Prenatal Radiation Exposure

“…phenomena that can only be evaluated at later life stages (Cowen and Geller 1960;Murphree and Pace 1960;Brent and Bolden 1961;Furchtgott 1963;Wohlfromm 1964a, 1964b;Hicks and D'Amato 1966;Wood et al 1967aWood et al , 1967bWood et al , 1967cMiller 1969;Brent 1970;Brent and Gorson, 1972;, 1988a, 1988bKamayana and Inouye 1994;Preston et al 2008). …”

“…During later stages, the fetus is not grossly deformed by radiation but can exhibit permanent cell depletion of various organs and tissues if the dose is high enough (Brent and Gorson 1972;Brent 1977;, 1988a, 1988bKameyama and Inouye 1994) (Table 3).…”