In order to evaluate the importance of gestational age and the dose-incidence relationship by gamma radiation, pregnant ICR @entity19 at gestational days from 2.5 to 15.5 days post-coitus (p.c.) were exposed to a single dose of 2.0 Gy and also at day 11.5 after conception, which was the most sensitive stage for the induction of major @entity600 . The animals were sacrificed on day 18 of gestation and the fetuses were examined for mortality, @entity851 , changes in head size and other @entity154 . The only demonstrable effect of irradiation during the pre-implantation period was an increase in prenatal mortality. Resorptions were maximal on exposure at day 2.5 after conception. The pre-implantation irradiated embryos which survived did not show any major @entity2241 . A small head, @entity851 , a @entity2419 , dilatation of the cerebral ventricle, a @entity8 , and @entity2526 and tail after exposure were prominent during the organogenesis period, especially on day 11.5 of gestation. As for the dose-incidence relationship, the incidence of a small head, @entity851 fetuses, a @entity2419 , dilatation of cerebral ventricle and @entity2526 in live fetuses rose as the radiation dose increased. The result indicated that the late period of organogenesis in the development of the brain, skull and extremities of a @entity19 was a particularly sensitive phase. The threshold doses of radiation that induced a @entity2419 and dilatation of the cerebral ventricle, and abnormal extremities were between 1.0 and 2.0 Gy, and between 0.5 and 1.0 Gy, respectively.

Dependence of XXXX upon gestational age and exposed dose of gamma radiation.

@entity154 :: ('MESH:D000013', 'Disease') :: ['morphological abnormalities'] @entity8 :: ('MESH:D007674', 'Disease') :: ['renal pelvis'] @entity851 :: ('MESH:D006130', 'Disease') :: ['growth-retarded', 'growth retardation'] @entity19 :: ('10090', 'Species') :: ['mice', 'mouse'] @entity600 :: ('MESH:D000014', 'Disease') :: ['congenital malformations'] @entity2526 :: ('MESH:D025063', 'Disease') :: ['abnormalities of the extremities'] @entity2419 :: ('MESH:D002972', 'Disease') :: ['cleft palate'] @entity2241 :: ('MESH:D005315', 'Disease') :: ['fetal abnormalities']
@entity600 :: (MESH:D000014,Disease) :: ['malformation']
