Biomedical subjects

Bernard Weiss

Publications and source records attributed to Bernard Weiss.

21 records · Page 2Linked to original sources

PubMedDate not supplied

Sex-specific alterations of cerebral cortical cell size in rats exposed prenatally to dioxin.

Sex-specific patterns of cerebral cortical lateralization have been documented consistently in both the human and animal brain. Male rats tend to exhibit pronounced right hemisphere dominance compared with females, while females typically exhibit more diffuse lateralization patterns and greater left hemisphere bias compared with males. Prenatal TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin) exposure produces demasculinization of male offspring sexual behavior, suggesting interference with sexual differentiation of the brain. In previous studies, a reversal of cortical thickness patterns in rats was shown after prenatal TCDD exposure on gestational day 8 (GD 8). The current study, based on the same brain sections, attempted to define changes in the number of cortical cells and cell size distributions in brains of offspring from TCDD-treated dams. Pregnant females were given a single oral dose of 0 or 180 ng kg(-1) TCDD on GD 8. Cell counts and sizes were determined in 3-month-old offspring. Areas 17 and 18a at bregma -3.8 were analysed using digitized, enhanced images of brain sections produced by a photomicroscope fitted with a high-resolution digital camera. Prenatal TCDD exposure altered the relative proportions of smaller and larger cell sizes in male, but not in female offspring. Both exposed males and females, however, exhibited a significant reversal of hemispheric dominance based on cell number. These findings demonstrate that prenatal exposure to TCDD alters the normal patterns of cortical cell asymmetry in a manner consistent with our previous data on thickness patterns.

Animals↗

PubMedDate not supplied

Sexually dimorphic alterations of brain cortical dominance in rats prenatally exposed to TCDD.

Sexually dimorphic patterns of cortical lateralization are documented extensively in both human and animal brains. Male rats tend to exhibit pronounced right hemisphere dominance compared with females, whereas females typically exhibit more diffuse lateralization patterns and greater left hemisphere bias compared with males. Prenatal TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin) exposure produces demasculinization of male offspring sexual behavior. In previous studies, we showed a reversal of cortical dominance in rats after prenatal TCDD exposure on gestational day 18 (GD 18). The current study aimed to determine the nature of changes observed in rats exposed to TCDD on GD 8. In addition, locomotor activity was measured in male and female offspring on postnatal day (PND) 30, 60 and 90. Pregnant females were given, via gavage, a single dose of 0, 20, 60 or 180 ng kg(-1) TCDD on GD 8. Cortical depth measurements were taken in selected brain regions in offspring 3 months old that had been exposed to the 180 ng kg(-1) dose. Areas 2, 3, 17, 18a and 39 at bregmas -1.8, -3.8 and -5.8 were analyzed by quantifying digitized, enhanced images produced by a photomicroscope fitted with a special color camera. In both male and female offspring, cortical thicknesses in control brains exceeded those of exposed brains. In several brain areas of male offspring exposed to TCDD, right hemispheric dominance reversed to left hemispheric dominance. Female offspring brains showed a contrary move towards right hemisphere dominance. Motor activity in juvenile and mature animals did not differ among dose groups. These data demonstrate that prenatal exposure to TCDD reduces cortical thickness and alters the normal pattern of cortical asymmetry, a finding consistent with the sexually dimorphic behavioral effects induced by this agent.

Animals↗

PubMedDate not supplied

Impaired cued delayed alternation behavior in adult rat offspring following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on gestation day 15.

This investigation used random ratio (RR) and cued delayed alternation procedures to examine the operant behavior of adult male and female rats following prenatal 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Offspring were exposed to a single maternal dose of 0.0, 0.06, 0.18 or 0.54 microg/kg po of TCDD on gestation day (GD) 15. For RR, adult subjects were trained to respond on one lever in a two-lever chamber for food reinforcement. The response requirement was increased across sessions. Male offspring responded at higher rates than females regardless of RR value and prenatal exposure history. For delayed alternation, animals were required to alternate responses on both apparatus levers and to inhibit responding during randomly interpolated delay intervals. The performance of male and female offspring exposed to 0.18-microg/kg TCDD was significantly less accurate and this group committed more errors by responding during the delay intervals than the other exposure groups. A similar trend was observed in the 0.54- microg/kg group. Overall, response accuracy during the delayed alternation procedure was inversely related to delay length and tended to improve with experience. Interpretations of these outcomes include the possibility that TCDD interfered with the development of attentional processes, impaired response inhibition or promoted response perseveration despite the presence of cues, indicating changes in reinforcement contingencies.

Administration, Oral↗