“…We examined immunohistologically and by immunoelectron microscopy the time course of alterations of MK expression in fetal rat brains at the neurogenesis stage after injury by transplacental administration of ethylnitrosourea (ENU). One main effect of ENU is to block DNA synthesis (Swann and Magee, 1971), resulting in microcephalus or cortical and spinal cord dysgenesis in rats (Hallas and Das, 1978, 1979; Fujiwara, 1980; Houle and Das, 1984; Yoshida et al, 1984; Oyanagi et al, 1986, 1987, 1988, 1998, 2001) up to 48 hr after the administration, when repair of the injured NE is completed (Fujiwara, 1980; Yoshida et al, 1984; Oyanagi et al, 1986, 1987, 1988). A single intravenous injection of ENU (60 mg/kg body weight) does not disrupt the glial limitans over the cerebrum or tight junctions of NE cells, and does not induce hemorrhage, tissue laceration, or heterotopic mass (Yoshida et al, 1984; Oyanagi et al, 1986, 2001).…”