Effects of 0.6-Gy Prenatal X Irradiation on Postnatal Neurophysiologic Development in the Wistar Rat

Abstract

Forty-one pregnant Wistar strain rats were irradiated with 0.6-Gy X rays or were sham irradiated on the 9th or 17th days of gestation to determine if this dosage level would result in alterations in postnatal neurophysiologic development. Half of the mothers were sacrificed at term, and the developmental status of 221 newborns was evaluated. The remaining mothers delivered and raised their litters. The 16 1 offspring were observed for the age of attainment of the following physiologic parameters: pinna detachment, eye opening, testes descent, and vaginal opening. Offspring were also tested for the acquisition of the following selected reflexes: surface righting, negative geotaxis, auditory startle, air righting, and visual placing. Term fetal weight was lower than the controls in the group irradiated on the 9th day but was recuperable postnatally. None of the 9 developmental tests performed postnatally were abnormal in the animals irradiated on the 9th day. Thus, at least with regard to these measures, the surviving embryos exposed during the all-or-none period could not be differentiated from the controls. Offspring irradiated on the 17th day exhibited retarded growth which persisted during neonatal life. The three-day-mean neonatal weight was significantly lower in the group irradiated on the 17th day compared to controls. There were no significant maternal body weight or organ/weight differences between the groups. Rats exposed in utero on the 17th day had a significantly delayed acquisition of air righting. These results demonstrate that 0.6-Gy in utero irradiation on the 17th day of gestation can cause subtle alterations in growth and development of the Wistar strain rat during postnatal life. 0 1986 Society for Experimental Biology and Medicine. 61 1

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

“…The results of a previous study (35) in which a similar protocol was used to determine the effect of 0.6 Gy prenatal X-radiation are included in the tables. Although the study was completed at a different time, the methodology was the same, and the inclusion of these data will aid in the understanding of the effects of prenatal low-dose X-radiation on postnatal growth and development.…”

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).…”

“…Even if there was a linear relationship between the dose and IQ reduction, one could predict that 0.01 Sv could not account for a doubling of the incidence of mental retardation because a linear extrapolation of Otake and Schull's data (1999) would only represent a maximum reduction of 0.3 of an IQ point at 0.01 Gray (Gy). Behavioral studies in animals were unable to demonstrate neurobehavioral effects below 0.02 Gy (Jensh et al, 1986, 1987; Jensh and Brent, 1986) (Table 4). Although one has to be careful in extrapolating animal data to humans, the lack of neurobehavioral effects from in utero irradiation supports the other findings that indicate that mental retardation is a threshold (deterministic) effect (Table 3).…”

Urolithiasis in pregnancy. I: pathophysiology, fetal considerations and diagnosis

“…Schull and Otake [20] estimated that there is an ≈0.03 point IQ loss per mGy arising from in utero exposure to ionizing radiation during the most sensitive period of human brain development. In animal experiments, at 10 mGy there was no observable histological effect in the developing brain, and behavioural studies were unable to show neurobehavioural changes at < 200 mGy [21]. In animal models, doses as low as 100–250 mGy induced a variety of potentially relevant cellular effects (induction of apoptosis, p53 and nerve growth factors) in the brain.…”