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The structure and function of the immune system of pigs are the main subjects of interest to numerous research centers, which is undoubtedly related to the potential of using pig organs in xenotransplantation. Another reason for intensive studies on this subject is the need for secure and effective immunoprophylaxis of pigs and the improvement of their immunological status. The present paper presents the current knowledge on the prenatal ontogeny of lymphocytes in pigs. The ontogeny of pigs’ immune system starts in early gestation. During the prenatal period the system undergoes numerous changes which ultimately result in its achievement of immunological competence. Although the immune system in pigs is physiologically developed already on the 35th day of pregnancy, only a small numbers of lymphocytes and other lymphatic elements can be detected in fetal organs. The hematopoiesis in bone morrow starts around the 45th day of pregnancy. Lymph nodes, including mesenteric lymph nodes, are devoid of their defense function until the 70th day of prenatal life. The most dynamic development of the immune system of pigs takes place between the 60th and 90th day of gestation. To a greater extent, the diffusion of lymphocytes in secondary lymphatic organs occurs after birth, and the intensity of this process seems to be related to the colonization of the gut and enhanced by the contact of newborns with environmental antigens.
The aim of this research was the development and maturation of neurons in the baso-lateral group of corpus amygdaloideum in pigs during the ontogenesis process. The brains of domestic pigs of both sexes (taken during the following periods of their lives: from 7th to 15th week of intrauterine life, newborn animals, one-month and one-year-old animals) were used as the material for the examination. The brains were removed and processed conventionally by the microscope. The basolateral group of corpus amygdaloideum in domestic pigs consists of nucleus amygdaloideum lateralis and nucleus amygdaloideum basalis-lateralis. In the 7th, 8th and 9th weeks of intrauterine life the primary corpus amygdaloideum is made up of a very large quantity of thickly arranged neuroblasts. Their nuclei are of spherical shape and the cell nucleus is surrounded by a very small quantity of cytoplasm. In the 10th, 11th and 12th weeks of intrauterine life the differentiation of the formerly homogenous cells takes place. The group, dorsally situated, is corpus amygdaloideum lateralis, while lying beneath it is corpus amygdaloideum basalislateralis. In the next period of intrauterine life and in newborn animals the appearance of nervous cells forming nucleus amygdaloideum lateralis and nucleus amygdaloideum basalis-lateralis does not change. One can say that the cells forming the above mentioned nuclei of corpus amygdaloideum in domestic pigs are already morphologically mature in newborn animals.
At the initial stage of ontogeny, in Caryophylliidae (Miocene Caryophyllia salinaria, C. depauperata, Recent C. berteriana) and Flabellidae (Miocene Flabellum roissyanum Recent Jauania cailleti), wall and septa are formed simultaneously, and their trabecular structure is coalesced (marginothecal wall). At subsequent juvenile stage in Caryophylliidae the presence of the extensive exosarc enables formation of costo-septa and, in consequence, formation of trabeculotheca. Trabeculotheca consists of fragments of primordial wall located between the costosepta. The trabeculothecal segments vanish in the adult stage in the majority of corals when the septothecal wall is formed by thickening of the costo-septa. In others, however, marginotheca can be present throughout the whole ontogenetic sequence (C. salinaria). Most Flabellidae are characterized by limited expression of exosarc and the presence of marginothecal wall up to the adult stage. The origin of 'flabellid' organization in Caryophylliina may result from a simple modification of ontogeny - extention of initial morphology to later ontogenetic stages. Such corals could develop several times, and the Flabellidae may be polyphyletic
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