Remarkably, three studies that followed rats from birth until 18 months [26] and 24 months of age [24]; [25] revealed that early stimulation has a permanent effect on spatial learning, even though such experience involved no more than ∼15 min of daily separation from the dam and exposure to a non-home environment along with necessary experimenter handling.
The models were formulated with the individuals' post-trial status (survivor/immobilised) as the binary response, family as random intercept, and the rest of the explanatory variables: experimental group, gender, sire, dam and exposure time, as fixed effects (Table 4).
This suggests that any stress experienced by the dams following exposure to the CPS schedule was of insufficient intensity to affect neurobehavioural development in the offspring.
Milk from dams contained exposure concentration-related amounts of Hg.
Because chemical treatment of a dam during prenatal exposure results in a single exposure group per treatment, one offspring in each litter was treated as a single observation.
LEC culture on intact (iAM) or devitalised and/or denuded (dAM) AM and exposure of cultivated LEC to the air liquid interface (air-lifting) are also studied to develop methods that maintain LEC stemness and stratification, respectively [5].
These two markers have been used to evaluate the effects of chlorpyrifos on ACh systems in adult rats (Liu and Pope 1996, 1998) and to characterize the immediate and delayed effects of postnatal chlorpyrifos or diazinon exposure (Dam et al. 1999; Rhodes et al. 2004; Richardson and Chambers 2005; Slotkin et al. 2001, 2006a, 2008a).
These markers have been used previously to characterize effects of chlorpyrifos on cholinergic systems in adult rats (Liu and Pope 1996, 1998) and to evaluate the immediate and delayed effects of postnatal chlorpyrifos exposure (Dam et al. 1999; Rhodes et al. 2004; Richardson and Chambers 2005; Slotkin et al. 2001).
These markers have been used previously to characterize effects of chlorpyrifos on ACh systems in adult rats (Liu and Pope 1996, 1998) and to evaluate the immediate and delayed effects of postnatal chlorpyrifos exposure (Dam et al. 1999; Rhodes et al. 2004; Richardson and Chambers 2005; Slotkin et al. 2001).
These latter factors promoted stream piracy, breaching of dune dams, and aerial exposure and forestation of infilled lakebeds.
Maternal NOAELs were determined to be ≥1000 mg/kg/day for all studies except Hatakenaka (1991) (Table 3), which reported loose stools in a few dams at that exposure.
