We have employed the orthograde transport of wheat germ agglutinin conjugated to horseradish peroxidase to study the organization of rubrospinal connections in adult and pouch young opossums. Our results suggest that: (1) in the adult opossum rubrospinal axons are distributed more widely than suggested by previous studies; (2) rubrospinal projections are formed postnatally in the opossum, but much earlier than corticospinal connections; (3) rubrospinal axons do not grow synchronously, as a massive bundle following a few leading axons, but by addition of axons over a protracted period of time; and (4) the growth of rubral axons into the spinal gray matter follows a predictable rostral to caudal gradient as well as a proximal to distal one relative to the tract. Rubrospinal development is discussed in light of the growth of cerebellar and cortical axons into the red nucleus and the development of motor function.

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Thesis (M. Sc.)--Queen's University, 2001. / Includes bibliographical references (leaves 78-93).

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A glândula pineal deve ser analisada e estudada em animais da fauna brasileira, para que dados da pesquisa básica possam ser aplicados em novas técnicas de manejo reprodutivo destes animais, inclusive em cativeiro, face à íntima relação deste órgão fotorreceptor com o ciclo reprodutivo. Para este estudo, foram utilizados 10 gambás (Didelphis sp), provenientes do Departamento de Anatomia da USP e UNIFEOB, já mortos e fixados. Nenhum animal foi submetido a situações de dor/sofrimento e ao sacrifício de sua vida. A glândula pineal foi encontrada em todos animais estudados e apresentou-se de diminutas dimensões, não sendo possível, portanto descrever-lhe características macroscópicas. Através da análise microscópica pudemos localizar a glândula no espaço correspondente ao plano mediano, em relação ao encéfalo, rostral e dorsalmente aos colículos rostrais, ventralmente aos hemisférios cerebrais e caudalmente à comissura habenular. Consiste de uma evaginação do teto do diencéfalo e mostra-se em forma de "U" invertido. Comparativamente a características de glândulas pineais de outras espécies animais, a do Didelphis genus, que estudamos, revela peculiaridades tanto em relação ao seu tamanho, apenas perceptível microscopicamente, quanto ao fato de apresentar suas células secretoras dispersas também em áreas vizinhas. Tais peculiaridades motivam reflexões sobre o papel funcional da glândula, na espécie considerada. / The pineal gland must to be analyzed and studied in animals of the Brazilian fauna, to apply the data obtained in the basic research of new techniques at reproductive handling of these animals, including in captivity, in view of the close relation between this photoreceptor organ with the circadian and reproductive cycle. For this study, 10 opossums (Didelphis sp), had been used, already died and fixed, proceeding from the Department of Anatomy of USP and UNIFEOB. None animals were submitted to pain/suffering situations and their no life sacrifice. The pineal gland was found in all studied animals with and smaller dimention, not possessing, therefore goss features. By microscopy analysis we could found the gland in the correspondent space to median plan in relation to the encephalon, rostral and dorsally to the rostral coliculli, ventrally to the brain hemispheres and caudally to the habenular comissure. That consistes like an evagination of the diencephalons tectum showing the "U" shape. Considering other pineal glands and its features in different species, we note the gland is extremely small for it specie, possessing dispersed secretory cells in the nervous parenchyma whose form, sufficiently irregular, suggests a small hormonal performance to them in the Didelphis genus. Comparativelly of the pineal gland feactures in different animals, the Didelphis genus, that was our aim, shows pecualirity as in size relation, only microscopically visible, than the fact to prossessing dispased secretory cells, with irregular surrounding shape. All pecualiarites suggest refletion about the function action of the gland at the studied specie.