Social aversive stimuli presented to the mother produce the precocious expression of fear in rat pups.

During the stress hypo-responsive period, rat pups do not display fear responses toward adult males, yet they exhibit distress behavior in isolation. Since the mother modulates her offspring's affective development, we hypothesized that by altering the mother's behavior, a prolonged stressful situation would modify the ontogeny of the fear responses and distress behaviors in pups. Therefore, we repeatedly exposed the mother-litter dyad to different socially stressful stimuli and subsequently evaluated in 8-day-old pups their fear responses toward an anesthetized male, as well as their distress behavior in isolation. Our results show that repeated exposure to unfamiliar males and females, which altered maternal behavior by eliciting aggression in the mother, was associated with the precocious fear responses in pups, though without altering their distress behavior in isolation. We propose that the mother, as the principal mediator of environmental influences, provokes the precocious expression of fear in pups through alterations in her maternal behavior.

Características estereológicas del hígado de rata (Rattus norvergicus) sometidas a menopausia inducida por ovariectomía / Stereologic characteristics of the liver of rats (Rattus norvergicus) submitted to ovariectomy-induced menopause

Durante la menopausia ocurren cambios hormonales, como disminución de estradiol y aumento de las hormonas folículo estimulante y luteinizante. En mujeres premenopáusicas la fibrosis y esteatosis hepática es menor que en mujeres postmenopáusicas, mejorando cuando se administra terapia hormonal de reemplazo. El objetivo del estudio fue determinar aspectos cuantitativos del hígado de ratas sometidas a un modelo experimental de menopausia inducida por ovariectomía. Utilizamos 10 ratas Sprague-Dawley (Rattus norvergicus) adultas, sanas. Las ratas fueron pesadas y divididas en dos grupos (ovariectomía bilateral=Grupo Ovx y control=Grupo Sham). A los 60 días fueron sacrificadas y retirado el hígado, obteniéndose un trozo de cada hígado. Se realizaron 5 cortes de 4 um y se tiñeron con HE. Se analizaron 5 campos por lámina. Se usó el test M42. Los parámetros estereológicos considerados fueron: Nv, Vv, Sv y número total (Nt) de hepatocitos y sinusoides hepáticos. El peso promedio del grupo Ovx y Sham fue 300,8 g y 285,8 g respectivamente. La Nv de hepatocitos de ratas sometidas a cirugías Sham (CS) y Ovx (CO) fue de 6,89 x105/mm3 y 7,70 x105/mm3, respectivamente. La Vv de hepatocitos CS y CO fue de 71,92 por ciento y 80,48 por ciento, respectivamente. La Sv de hepatocitos CS y CO fue de 260,61 mm2/mm3 y 273,64 mm2/mm3, respectivamente. El volumen promedio de hígados CS fue de 8,40 mm3 y el Nt de hepatocitos promedio fue 5,79 x 106. El volumen promedio de los hígados CO fue 9,28 mm3 y el Nt de 7,15 x 106. Respecto a los sinusoides, la Nv en el hígado CS y CO fue de 2,81 x105/mm3 y 2,64 x105/mm3, respectivamente. La Vv de sinusoides en CS y CO fue de 16,74 por ciento y 16,46 por ciento, respectivamente. La Sv de sinusoides en ratas CS y CO fue de 49,40 mm2/mm3 y 45,21 mm2/mm3, respectivamente. El Nt de sinusoides CS y CO fue en promedio 2,37 x 106 y 2,45 x 106, respectivamente. La ausencia de estrógeno puede generar fibrosis y esteatosis hepática como lo señala...

During menopause, hormonal changes such as decreased estradiol and increased follicle stimulating and luteinizing hormones occur. In premenopausal women fibrosis and hepatic steatosis is less than in postmenopausal women and improves when hormone replacement therapy is administered. The aim of this study was to determine quantitative aspects of the liver of rats undergoing an experimental model of ovariectomy-induced menopause. We used 10 Sprague-Dawley (Rattus norvergicus) healthy adults. The rats were weighed and divided into two groups (bilateral oophorectomy = Group Ovx and control = Group Sham). The animals were sacrificed at 60 days and the liver removed, obtaining a piece of each liver. Five cuts were made of 4 microns and stained with HE. We analyzed five fields per slide. M42 test was used. Stereological parameters considered were as follows: Nv, Vv, Sv and total number (Tn) of hepatocytes and sinusoids. The average weight of Ovx and Sham group was 300.8 g and 285.8 g, respectively. The Nv of hepatocytes of rats subjected to sham surgery (CS) and Ovx (CO) was 6.89 and 7.70 x105/mm3 x105/mm3, respectively. The Vv of CS and CO hepatocytes was 71.92 percent and 80.48 percent, respectively. SV and CO, CS hepatocytes was 260.61mm2/mm3 and 273.64 mm2/mm3 , respectively. The average volume of CS livers was 8.40 mm3 and hepatocyte Tn averaged 5.79 x 106. The average volume was 9.28 mm3 CO livers and Tn of 7.15 x 106. Regarding the sinusoids, the Nv in the liver CS and CO was 2.81 x105/mm3 and 2.64 x105/mm3, respectively. The Vv of sinusoids in CS and CO was 16.74 percent and 16.46 percent, respectively. The sinusoids in rats Sv CS and CO was 49.40 mm2/mm3 and 45.21 mm2/mm3, respectively. The sinusoids Tn CS and CO averaged 2.37 x 106 and 2.45 x 106, respectively. The lack of estrogen can cause fibrosis and hepatic steatosis as noted by other authors, but also changes in the organization and the proportion of the components of the liver, factors to ...