Biomedical Engineering Reference
In-Depth Information
full-term infants (Fallang et al., 2003), and clinical studies have
indicated that the quality of reaching and grasping behavior in preterm
infants is generally less than that in full-term infants (Fallang et al.,
2003; Plantinga et al., 1997).
At 190-210 days of age, the Fagan test of infant intelligence was
conducted. This paradigm makes use of the infant's proclivity to direct
more visual attention to novel stimuli rather than familiar stimuli. The
test measures the time infants spend looking at familiar versus novel
items. Deficits in the Fagan task can qualitatively predict deficits in
intelligence quotient (IQ) measurements assessed in children at later
ages (Fagan and Singer, 1983). Control monkey infants in the
Burbacher et al. (1999b, 2004a) study spent more than 62% of their
time looking at novel versus familiar monkey faces, while none of the
treated monkeys displayed a preference for the novel faces. Results of
this test were not different among control and exposed groups. A cohort
effect appeared to reduce the statistical power of this analysis. Because
of the longer latency between birth and assessment, these results would
not be expected to be confounded by the postulated methanol-induced
decrease in gestation length of the exposed groups. Negative results
were obtained for the remaining seven tests that evaluated early
reflexes, gross motor development, spatial and concept learning and
memory, and social behavior.
5.3.4 Summary of Developmental Toxicity Findings in
Experimental Animals Exposed to Methanol by Inhalation
While the oral gavage and drinking water routes of exposure were used
in some of the studies described earlier, the most complete data sets in
terms of dose-response relationships that allow one to posit NOAELs
and LOAELs have used inhalation exposures. Findings from these
studies are summarized in Table 5.2. The lowest NOAEL from among
the tabulated inhalation studies is for effects of methanol on postnatal
brain weight in rats from the NEDO (1987) study. The NOAEL for this
effect was 500 ppm methanol. However, where studies were carried out
in a similar fashion (e.g., in the rat by Nelson et al. (1985) and in the
mouse by Rogers et al. (1993)), the mouse appears to be more sensitive
