Paw preference in mice with callosal defects induced by prenatal gamma irradiation

The development of the corpus callosum of male Swiss mice was perturbed by exposure to gamma radiation at embryonic day 16 with total doses of 2 Gy (N = 48) or 3 Gy (N = 26). At adulthood paw preference was studied in these callosal defective animals and in 93 control nonirradiated male Swiss mice. The analysis of directional laterality indicated a populational tendency for right paw use in the 2 Gy group (60 per cent ) that was markedly increased in the 3 Gy group (95 per cent ). In the 3 Gy group, directional laterality was significantly different from chance in contrast to that observed in normal controls (49 per cent ). In the three groups most mice presented a significant individual paw preference. These data are consistent with our hypothesis that the early absence of the corpus callosum disrupts the normal pattern of directional asymmetries

Absence of populational cerebral asymmetries in mice with callosal defects induced by prenatal gamma irradiation

The development of the corpus callosum of 19 male Swiss mice was disturved by exposure to a 60Co gamma source on embryonic day 16 with a total dose of 2 Gy (dose rate of 56 to 59 rads/min). At adulthood the animals were perfused with saline followed by formaldehyde and the cerebral hemispheres were weighed and phtographed in dorsal, lateral and medial views. Brain asymmetries were evaluated by measurements of hemisphere weight, as well as dorsal and lateral areas. From the measurements of the midsagittal callosal areas, performed on the medial views, 2 subgroups could be identified: one with a small callosal remnant (N=9) and another with a non-measurable callosal area (N=10). In spite of a pronounced individual asymmetry, the irradiated mice (N=19) did not show a populational asymmetry toward any side. A slight tendency favoring the left hemisphere was found in the small remmant subgroup. These results are consistent with our previous data for a strain of mice in which some animals present callosal defects. We conclude that the present data support the hypothesis that the corpus callosum may play a role in directing morphological hemispheric asymmetries