Axonal quantification of the white matter association fasciculi in cerebral hemispheres of cow (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus).

BACKGROUND: Cerebral white matter consists mainly of axons surrounded by myelin sheaths, which are grouped to form association, commissural, and projection fasciculi. The aim of our work was to quantify and compare under the microscope the axons of the white matter association fasciculi in the cerebral hemispheres of cow (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus) indirectly by identification of their myelin sheaths. MATERIALS AND METHODS: The samples were taken from 30 cerebral hemispheres: 10 cow, 10 pig and 10 rabbit (15 right and 15 left). They were obtained following a protocol based on the Talairach-Tournoux coordinate system for human and primate brains. The slides were stained with Luxol Fast Blue, observed by optical microscopy, and photographed at 600×. Samples were also prepared for observation in scanning transmission electron microscopy with osmium tetroxide. The myelin sheaths/axons were counted with the ImageJ software. RESULTS: Statistically significant differences in the number of myelin sheaths per 410 µm² were found in the inferior and superior longitudinal fasciculi between the left and right hemispheres of cows, with predominance of the right hemisphere; and in the inferior occipitofrontal fasciculus of the rabbit with predominance of the left hemisphere. CONCLUSIONS: The use of animal models for experiments in the cerebral fasciculi, especially pig, could give us a greater understanding of the behaviour of demyelinating and neurodegenerative diseases in humans.

The effects of early positive parenting and developmental delay status on child emotion dysregulation.

BACKGROUND: Emotion regulation has been identified as a robust predictor of adaptive functioning across a variety of domains (Aldao et al. ). Furthermore, research examining early predictors of competence and deficits in ER suggests that factors internal to the individual (e.g. neuroregulatory reactivity, behavioural traits and cognitive ability) and external to the individual (e.g. caregiving styles and explicit ER training) contribute to the development of ER (Calkins ). Many studies have focused on internal sources or external sources; however, few have studied them simultaneously within one model, especially in studies examining children with developmental delays (DD). Here, we addressed this specific research gap and examined the contributions of one internal factor and one external factor on emotion dysregulation outcomes in middle childhood. Specifically, our current study used structural equation modelling (SEM) to examine prospective, predictive relationships between DD status, positive parenting at age 4 years and child emotion dysregulation at age 7 years. METHOD: Participants were 151 families in the Collaborative Family Study, a longitudinal study of young children with and without DD. A positive parenting factor was composed of sensitivity and scaffolding scores from mother-child interactions at home and in the research centre at child age 4 years. A child dysregulation factor was composed of a dysregulation code from mother-child interactions and a parent-report measure of ER and lability/negativity at age 7 years. Finally, we tested the hypothesis that positive parenting would mediate the relationship between DD and child dysregulation. RESULTS: Mothers of children with DD exhibited fewer sensitive and scaffolding behaviours compared with mothers of typically developing children, and children with DD were more dysregulated on all measures of ER. SEM revealed that both DD status and early positive parenting predicted emotion dysregulation in middle childhood. Furthermore, findings provided support for our hypothesis that early positive parenting mediated the relationship between DD and dysregulation. CONCLUSIONS: This work enhances our understanding of the development of ER across childhood and how endogenous child factors (DD status) and exogenous family factors (positive parenting) affect this process. Our findings provide clear implications for early intervention programmes for children with DD. Because of the predictive relationships between (a) developmental status and ER and (b) parenting and ER, the results imply that sensitive parenting behaviours should be specifically targeted in parent interventions for children with DD.