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      Anatomía del Cuerpo Calloso en Ratas Sometidas a Estrés Prenatal Crónico Translated title: Anatomy of Corpus Callosum in Rats Submitted to Chronic Prenatal Stress

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          Abstract

          RESUMEN: El cuerpo calloso (CC), es la mayor comisura de sustancia blanca del encéfalo de los mamíferos placentados, constituida por numerosos haces de fibras transversales que conectan áreas corticales de ambos hemisferios cerebrales. Por otro lado, el estrés se define como una respuesta general del organismo ante demandas externas o internas, inicialmente amenazantes, que consiste en movilizar recursos fisiológicos y psicológicos para poderlas afrontar. Dada la importancia del cuerpo calloso en las conexiones cortico-corticales, el objetivo del presente estudio, fue evaluar el efecto en ratas, de un estrés prenatal crónico por inmovilización, sobre la anatomía macroscópica del CC. Se utilizaron seis ratas preñadas de la cepa Wistar de 250 g, de las cuales tres fueron sometidas, a partir del octavo día postconcepción, a una restricción de movimiento por diez días (2h/día). Posteriormente, las madres prosiguieron su gestación, parto y lactancia. Al nacimiento, las camadas fueron ajustadas a seis crías machos por madre (n=36), destetadas a los 21 días y sacrificadas a los 45-52 días de edad. Los encéfalos fueron seccionados a través de la cisura interhemisférica y ambos hemisferios fotografiados por su cara medial. Las imágenes fueron digitalizadas y analizadas mediante el programa Scion Image®, para la medición del área total, parciales (tercio anterior, medio, posterior y quinto posterior) y perímetro callosal. Es así como, el estrés prenatal por inmovilización, afectó significativamente (p<0,01), la morfología macroscópica del cuerpo calloso. Evidenciándose una disminución del área total, áreas parciales y perímetro callosal, en los animales sometidos a restricción prenatal. Estableciendo una relación directa entre número de axones y área callosal e inversa entre diámetro y densidad axonal; lo observado podría tener incidencia en la transferencia interhemisférica.

          Translated abstract

          SUMMARY: The Corpus Callosum (CC) is the largest white matter commissure in the brain of placental mammals, consisting of numerous transverse fiber bundles that connect cortical areas of both cerebral hemispheres. On the other hand, stress is defined as a general response of the organism to external or internal demands, initially threatening, which consists of mobilizing physiological and psychological resources to be able to face them. Given the importance of CC in cortico-cortical connections, the aim of the present study, was to evaluate the effect of chronic pre-natal immobilization stress on the macroscopic anatomy of CC in rats. Six 250g pregnant rats of the Wistar strain were used, of which three were subjected, starting on the eighth post-conception day, to movement restriction for ten days (2h/day). Subsequently, the mothers continued their gestation, delivery and lactation. At birth, litters were adjusted to six male offspring per mother (n=36), which were weaned at 21 days and slaughtered at 45-52 days of age. The brains were fixed, and later sectioned through the interhemispheric fissure and both hemispheres photographed by their medial aspect. The images were digitized and analyzed using the Scion Image® program, for the measurement of the total area, partial area (ante- rior, middle and posterior thirds, as well as posterior fifth) and callosal perimeter. Thus, prenatal stress due to immobilization significantly affected (p<0.01), the macroscopic morphology of the CC. Evidence shows a decrease in the total area, partial areas and callosal perimeter in the animals subjected to prenatal restraint, as compared to normal animals. Establishing a direct relationship between number of axons and callosal area and an inverse relationship between diameter and axonal density, what was observed may have an impact on interhemispheric transfer.

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          Most cited references25

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          Chronic Stress Induces Contrasting Patterns of Dendritic Remodeling in Hippocampal and Amygdaloid Neurons

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            Prenatal stress and brain development.

            Prenatal stress (PS) has been linked to abnormal cognitive, behavioral and psychosocial outcomes in both animals and humans. Animal studies have clearly demonstrated PS effects on the offspring's brain, however, while it has been speculated that PS most likely affects the brains of exposed human fetuses as well, no study has to date examined this possibility prospectively using an independent stressor (i.e., a stressful event that the pregnant woman has no control over, such as a natural disaster). The aim of this review is to summarize the existing animal literature by focusing on specific brain regions that have been shown to be affected by PS both macroscopically and microscopically. These regions include the hippocampus, amygdala, corpus callosum, anterior commissure, cerebral cortex, cerebellum and hypothalamus. We first discuss the mechanisms by which the effects of PS might occur. In particular, we show that maternal and fetal hypothalamic-pituitary-adrenal (HPA) axes, and the placenta, are the most likely candidates for these mechanisms. We see that, although animal studies have obvious advantages over human studies, the integration of findings in animals and the transfer of these findings to human populations remains a complex issue. Finally, we show how it is possible to circumvent these challenges by studying the effects of PS on brain development directly in humans, by taking advantage of natural or man-made disasters and assessing the impact and consequences of such stressful events on pregnant women and their offspring prospectively. Copyright © 2010 Elsevier B.V. All rights reserved.
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              Fiber composition of the human corpus callosum.

              The densities of fibers of different sizes were calculated in ten regions of the corpus callosum of twenty human brains (ten females, ten males). Light microscopic examination revealed a consistent pattern of regional differentiation of fiber types in the corpus callosum. Thin fibers are most dense in the anterior corpus callosum (genu), and decrease in density posteriorly towards the posterior midbody, where they reach a minimum. Towards the posterior corpus callosum (splenium), the density of thin fibers increases again, but in the posterior pole of the callosum the density decreases locally. Large-diameter fibers show a pattern complementary to that of thin fibers, having a peak of density in the posterior midbody and a local increase of density in the posterior pole of the corpus callosum. Across subjects, the overall density of callosal fibers had no significant correlation with callosal area and an increased callosal area indicated an increased total number of fibers crossing through. Considering different fiber sizes, this was only true for small diameter fibers, whose large majority is believed to interconnect association cortex. No sex differences in fiber composition of the corpus callosum were found.
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                Author and article information

                Journal
                ijmorphol
                International Journal of Morphology
                Int. J. Morphol.
                Sociedad Chilena de Anatomía (Temuco, , Chile )
                0717-9502
                2022
                : 40
                : 2
                : 343-347
                Affiliations
                [1] Santiago de Chile orgnameUniversidad de Chile orgdiv1Facultad Ciencias Veterinarias y Pecuarias orgdiv2Departamento de Patología Animal Chile
                Article
                S0717-95022022000200343 S0717-9502(22)04000200343
                1051be68-7656-4350-abde-04e5c79ed506

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

                History
                : 10 January 2022
                : 16 February 2022
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 25, Pages: 5
                Product

                SciELO Chile

                Categories
                ARTÍCULOS

                Prenatal Stress,Rata,Estrés prenatal,Cuerpo calloso,Rat,Corpus Callosum

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