Determination of basal bone mineral density in the femur bones of male and female Wistar rats.

Changes in bone mineral content of calcium (Ca), phosphorous (P), magnesium and potassium for male and female Wistar rats during their development from 3 weeks old to adulthood (27 weeks old) were measured. Bone mineral content was related to areal bone mineral density (BMD) which was measured in vivo at the femoral neck using a calibrated X-ray transmission system to obtain basal curves as a function of the age of the specimen. Diagnostic curves were built to determine low BMD (osteopaenia) and osteoporosis in female rats fed a Ca-depleted diet (50%) based on the obtained data and the criteria established by the World Health Organization. Bone mineral content is directly related to sex and age, but P did not change throughout the experimental period. P content did not exhibit significant changes with growing, while Ca was greatest in male rats, producing significant differences in the Ca:P ratio. Male rats reach the Ca:P ratio peak before female rats. However, areal BMD does not follow the same trend. On the other hand, osteoporosis produced a 45% decrease in this parameter for young and mature adults. These results make Z-score values available to diagnose bone-mass losses and hence the possibility of improving the conditions of non-contact measurement of BMD in vivo. This technique can be used for future experiments with Wistar rats.

Early undernourishment interferes with the maternal aggressive response triggered by an intruder entering the homing cage.

The maternal aggressive response (MAR) against intruders is temporarily expressed during lactation in association with the rearing and protection of offspring to promote their survival and growth in the nest. This normal component of maternal behaviour requires both the hormonal changes occurring at the end of pregnancy and the presence of pups for its establishment. Because early food restriction in the rat results in long-term maternal deficiencies, we analysed in Wistar rats the effects of perinatal undernutrition on the MAR to an intruder at days 1, 4, and 8 postpartum. The data showed that undernourished dams exhibited significant reductions of sniffing frequency on days 4 and 8 and significant increases of biting on day 4 and of lateral attacks on postpartum days 4 and 8. The finding of an altered MAR during the lactating period may be relevant for the survival and long-term behavioural development of the progeny.

Efectos del estrés prenatal sobre la ramificación neuronal en la corteza visual de ratas neonatas / Prenatal stress of effects on neuronal branching in the visual cortex of the pup rats

Se evaluó el efecto del estrés por inmovilización aplicado a ratas gestantes, sobre la morfología de las neuronas piramidales en la corteza visual de machos descendientes de dichas hembras, a los 14 y 21 días posnatales. Ratas hembra de la cepa Wistar fueron sometidas a estrés por inmovilización forzada durante toda la gestación, en periodos que variaron entre 2 y 6 horas por día. En neuronas del área visual, impregnadas con el método de Golgi se cuatificó el grado de ramificación dendrítica. Los resultados muestran disminución de ramificaciones dendríticas sobre todo en ratas de 21 días. Las deficiencias en la capacidad de aprendizaje y comportamiento adaptativo observadas en animales descendientes de madres sometidas a estrés durante la gestación podrían explicarse con base a estos resultados