Effects of a hybrid maternal environment on brain growth and corpus callosum defects of inbred BALBc mice: A study using ovarian grafting

Abstract

The corpus callosum of many but not all BALB/c mice is either abnormally small or absent. The basis for the defect is hereditary, but the proportion of mice expressing the anomaly can be modified by changing the early environment. The present study investigated the effects of an F1 hybrid maternal environment, which is known to promote better fetal development than an inbred environment, on body and brain growth in BALB/c and on the incidence of the corpus callosal defect. Ovarian follicle cells from BALB/cWah (albino) mice were grafted into pigmented F1 hybrid, BALB/cWah, and pigmented BALB female hosts of comparable age which were subsequently mated to BALB/cWah males. Groups of unoperated BALB/cWah and pigmented BALB dams were included as controls. Data from 111 litters were analyzed. Results showed that BALB mice with F1 mothers had heavier bodies at birth, weaning, and 100 days of age and heavier brains at 100 days than those with either grafted or ungrafted BALB mothers. The effects at birth were evident across all litter sizes (2 to 11), but those at weaning and 100 days were seen only in litters of more than 5 or 6. Neither the F1 hybrid maternal environment nor the grafting procedure itself appeared to influence the incidence or expression of the corpus callosal defect. About 22% of the offspring from each of the three groups (ungrafted BALB, grafted BALB, and grafted F1) showed a defective corpus callosum.

The effects of intrauterine position on the degree of corpus callosum deficiency in two substrains of BALB/c mice

“…Recently, the technique of ovarian grafting was employed to test the hypothesis that the BALB maternal environment was somehow exacerbating an already unfavorable situation with respect to callosal development. The results of that study showed conclusively that, notwithstanding the fact that the brains and bodies of animals nurtured preand postnatally by F, hybrid mothers were significantly larger than those whose mothers were BALB, the proportion of animals showing defective callosa did not differ between the groups (Bulman-Fleming & Wahlsten, 1988). Yet, this result does not preclude the possibility of prenatal microenvironmental differences for animals within a litter which result from the differential placement of fetuses within the uterine horns.…”

Tests of Genetic Allelism between Four Inbred Mouse Strains with Absent Corpus Callosum

“…Owing to their extremely poor breeding characteristics, the eight I/LnJ mice were all adults. Most reciprocal crosses were not performed because maternal effects have been shown not to be involved in the CC defect (Bulman-Fleming and Wahlsten 1988) and because of doubt about the breeding efficiency of some of the strains. BALB mice are noted poor breeders.…”

Genetically Defined Animal Models of Neurobehavioral Dysfunctions

“…Any sex difference in the CC must be exceedingly small, and links to possible sex differences in hemispheric specialization must be tenuous, especially in view of recent challenges to the interpretation of studies of lateralization of neural function (Efron, 1990). Small sex differences are sometimes reported in rats (e.g., Berrebi et al, 1988), but they do not always appear in mice (Bulman- Fleming and Wahlsten, 1988;Cassells et al, 1990;Lipp et al, submitted for publication).…”

“…Whether their visual system shows the same anomalously crossed optic axons as observed in other albino rodents (Jeffery, 1989) remains to be determined. Behaviorally, BALB/c mice have two features that may pose problemso They are albino and thus highly sensitive to variable levels of illumination, probably being handicapperl in tasks requiring visual acuity (Upchurch and Wehner, 1988)0 In this regard, a pigmented BALB/c strain produced by more than 25 generations of backcrossing may prove useful in future research (Bulman- Fleming and Wahlsten, 1988)0 Also, many BALB/c substrains show behavioral immobility ("freezing") when exposed to stressful environmentso For example, in Zürichwehave been unable to conduct studies in swimming navigation with these mice, because many animals showed motionless floating (with high-frequency defecation) during many trialso Similar swimming behavior has been observed elsewhere (Schwegler and Buselmaier, 1981)0 Others have had some success in swimming tasks with BALB/c, although the animals tend to swim rather poorly compared with C57BL/6 mice (Lassalle etal., 1979)0…”