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A Zapata

Publications and source records attributed to A Zapata.

At least 91 records · Page 5Linked to original sources
PubMed1985

Evidence of non-early ultrastructural regionalization in the neural epithelium of the chick by stereological methods.

Cell populations of the anterior, medial and posterior regions of the neural epithelium of chick embryo were analyzed by ultrastructural morphometrical and stereological methods. No morphological subcellular differences appear to occur between the cells of these distinct areas, demonstrable by morphometrical and stereological conventional methods. The homogeneity of this cell population in each stage during neurulation is discussed in relation to the induction process.

Age Factors↗
PubMed1984

Interdigitating cells in the thymus of the turtle Mauremys caspica. Possible relationships to macrophages.

Interdigitating cells are non-lymphoid elements in the thymus and peripheral, secondary lymphoid organs of higher vertebrates. Their origin and functional significance are a matter of controversy. In the present investigation we analyze, for the first time, the nature of presumptive interdigitating cells of the thymus of an ectothermic vertebrate, the turtle Mauremys caspica. This model is specially useful because of the seasonal variations that affect the reptilian lymphoid organs. Immature pro-interdigitating cells and phagocytosing mature interdigitating cells are described with special emphasis on their ultrastructural characteristics and possible relationships with monocytes and macrophages.

Animals↗
PubMed1984

Plasma cells in adult Atlantic hagfish, Myxine glutinosa.

Hagfishes, the most primitive vertebrates, are of special interest for the evolution of immune responses. Eptatretus stoutii, the Pacific hagfish, is able to mount cellular and humoral immune responses but all attempts to demonstrate in them the presence of plasma cells have failed. In the present study we demonstrate for the first time plasma cells identifiable by ultrastructural criteria in the pronephros, a primitive lymphohaemopoietic organ, of Myxine glutinosa, the Atlantic hagfish.

Animals↗
PubMed1983

Non-lymphoid cells of the anuran spleen: an ultrastructural study in the natterjack, Bufo calamita.

The present study is concerned with the ultrastructure of the spleen in the natterjack, Bufo calamita (Anura, Bufonidae), with special emphasis on the structure and function of the non-lymphoid elements occurring in the red and white pulp. The organ consists of two clearly distinguishable areas, the white and the red pulp, separated by a prominent marginal zone. Thus, the pattern of lymphocytic arrangement in the spleen of Bufo calamita corresponds to a follicular model and is similar to that reported in the primitive anurans of the Pipidae family, such as Xenopus laevis. The white pulp presents a reticular network consisting of two different cell types and free cells, such as lymphocytes, plasma cells, and macrophages. The red pulp is formed by cell cords, where reticular cells and fibers, macrophages and lymphocytes occur, and blood sinuses which sometimes contain developing erythroid elements. Colloidal carbon particles injected via the lymph sac are trapped exclusively by free macrophages in the red pulp which then move through the marginal zone to the white pulp. Giant, ramified, non-phagocytic cells appear in both white and red pulp. They have been functionally related with the trapping of antigen-antibody complexes on their surface, and a possible dendritic significance is discussed on the basis of their morphologic characteristics.

Animals↗
PubMed1983

Erythropoiesis in the thymus of the spotless starling, Sturnus unicolor.

Although previously described in other avian species, intrathymic erythropoiesis is a remarkable feature of the thymus of Sturnus unicolor. In discrete stages of the life cycle of this species, erythroblasts and mature erythrocytes occupy large areas of the thymic cortex and cortico-medullary border. Simultaneously, degenerated thymocytes and epithelial-reticular cells occur in the same areas. The relationship between intrathymic erythropoiesis, degeneration of cortical lymphocytes and epithelial-reticular cells, and macrophage activity is discussed and related to a possible functional role of sex hormones in this phenomenon.

Animals↗
PubMed1983

Structure of the non-lymphoid cells during the postnatal development of the rat lymph nodes. Fibroblastic reticulum cells and interdigitating cells.

This study describes the postnatal development of the nonlymphoid cells with special reference to the fibroblastic reticulum cells (FRCs) and interdigitating cells (IDCs). The first lymphocytes of the neonatal lymph nodes are located in the developing deep cortex units (DCUs) identified by the Gomori's technique for reticulin fibres. Ultrastructural studies demonstrate that FRCs form the stroma of the DCUs. By light and electron microscopy, it is demonstrated that FRCs occupy the outer cortex in the following stages of development of the lymph nodes. Thus, FRCs form the stroma of the primary follicles and, later, are transformed in follicular dendritic cells (FDCs) of the germinal centres. Immature or pro-IDCs appear as migrating elements in the deep cortex of lymph nodes of the neonatal rats. The ultrastructure of the pro-IDCs resembles that of the mature IDCs but not that of the phagocytic cells. Pro-IDCs are transformed into mature IDCs whose cytoplasmic expansions contact lymphocytes via tight junctions. Some of these lymphocytes are likely apposed to FRCs of the DCUs. No cells containing Birbeck granules were found in the parenchyma of the lymph nodes during the postnatal development. The role of these nonlymphoid cells is discussed with respect to the immunologic function of mammalian lymph nodes.

Animals↗
PubMed1983

Postnatal development of the non-lymphoid elements in the rat lymph node. Connective reticulum cells, macrophages and postcapillary venules.

The present study analyzes ultrastructurally the non-lymphoid elements occurring in the diffuse deep cortex and medulla of the postnatal developing lymph nodes of the rat. The supporting meshwork of the organ consist of connective reticulum cells joined together themselves by intercellular junctions. Two morphologically different macrophage cell types can be described in the developing lymph nodes. The first one consists of free-migrating macrophages homing the cortical parenchyma, apparently related with phagocytosis of necrotic cells. In contrast, macrophages located in the lumen of the medullary lymphatic sinuses are anchored to connective reticulum cell processes. They form lymphocyte-macrophage clusters and are involved also in erythrophagocytosis phenomena. Postcapillary venules lined by a low cuboidal endothelium, which allow lymphocyte diapedesis, appear in the diffuse deep cortex of the neonatal lymph nodes. The possible significance of all these cellular elements is discussed with respect to their role as constituents of the local lymph node microenvironments.

Animals↗
PubMed1983

Aging changes in lymphopoietic and myelopoietic organs of the annual cyprinodont fish, Nothobranchius guentheri.

The thymus of aging annual, cyprinodont fish, Nothobranchius guentheri and Cynolebias adloffi begins to undergo senescent changes at approximately four months. At this time, the histopathology reveals increased amounts of connective tissue, epithelial cysts and myoid cells, but decreased numbers of thymocytes. At 12 months, of the 50 fish observed at 10 stages from day 15 and 1, 2, 4, 6, 8, 9, 10, 11, 12 months the maximum time of senescence, there was an increased incidence of tumors in the oral cavity, connective tissue, kidney and liver in all 5 fish. At least in the kidney, the malignant transformation was classified as nodular-type histiocytic lymphoma. It is of interest that development of these tumors occurs during peak senescent changes in the thymus, supporting the view that as fish age, accompanied by atrophy of the thymus, the immune system is less vigorous and there is an increase in the incidence of cancer.

Aging↗
PubMed1982

Ultrastructure of gut-associated lymphoid tissue (GALT) in the amphibian urodele, Pleurodeles waltlii.

The ultrastructure of gut-associated lymphoid tissue (GALT) has been studied in the salamander, Pleurodeles waltlii. Lymphoid accumulations appear as true infiltrates scattered throughout the lamina propria cell elements. The most important components of these infiltrates are small and medium sized lymphocytes, and, in lesser amounts, developing and mature plasma cells, macrophages and granulocytes. Migrating lymphoid cells massively invade the intestinal epithelium inducing noticeable modifications, such as the disappearance of the basement membrane and decreased numbers of mucous cells. Thus, in its organization and cell composition, the GALT of P. waltlii appears to represent a primitive phylogenetic precursor of the mammalian "intestinal-immunologic" barrier.

Animals↗
PubMed1982

Ultrastructural study of interdigitating cells in the thymus of the spotless starling, Sturnus unicolor.

Interdigitating cells (IDC) in the thymus of the spotless starling, Sturnus unicolor, were examined by electron microscopy. They occur principally in the thymic medulla and corticomedullary border. They possess an irregular nucleus and a perinuclear area of cytoplasm, containing most of the membranous organelles, surrounded by a peripheral electron-lucent zone. Clusters of smooth Golgi vesicles and complicated labyrinthine membrane-membrane contacts are the most characteristic cytological features. Birbeck granules are absent. Lymphocytes, plasma cells and even myoid cells can be found embedded in the cytoplasm. Immature elements, intermediate between epithelial-reticular cells and interdigitating cells, are tentatively identified as prointerdigitating cells. The functional significance of IDCs, and their phylogenetic significance in the vertebrate immune system, is discussed.

Animals↗
PubMed1982

Lymphoid organs of teleost fish. III. Splenic lymphoid tissue of Rutilus rutilus and Gobio gobio.

The ultrastructure of splenic lymphoid tissue of two teleost fish, Rutilus rutilus and Gobio gobio, constitutes discrete foci around the small arteries and "melano-macrophage" centres. It contains small and medium lymphocytes, lymphoblasts, macrophages and plasma cells. Plasmacytopoiesis and macrophage-lymphocyte clusters have been described and the significance of "melano-macrophage" centres and macrophage-lymphocyte clusters is discussed.

Animals↗
PubMed1981

Ultrastructure of splenic white pulp of the turtle, Mauremys caspica.

The ultrastructure of splenic tissue of non-immunized turtles, Mauremys cas[pica, shows two areas, namely, the white pulp which is lymphoid in nature, and the red pulp which is formed by cell cords and sinusoids, Between both areas there is always a marginal zone with gaps through which cells leak. In the white pulp, there are two blood vessel types; one with muscled walls, and the other showing thinner walls sheathed by reticular cells, Reticular cells constitute a network where there occur dendritic macrophages, lymphoblasts and small and medium lymphocytes. Mature plasma cells are scare in the white pulp.

Animals↗
PubMed1981

Ultrastructure of the jugular body of Rana pipiens.

The jugular bodies in adult Rana pipiens, are surrounded by a capsule of mesothelium and connective tissue, and their parenchyma consists of cell cords arranged in a sinusoidal network. The cell cords are formed by irregular reticular cells, showing numerous filaments and joined together by zonulae adherents. The intercellular spaces are filled by reticular fibres and free cells. These latter are small and medium lymphocytes, lymphoblasts, and developing and mature plasma cells. Additionally, free macrophages, neutrophils and acidophils also occur. Sinusoidal blood vessels show thin walls with numerous filaments and pinocytotic vesicles. They exhibit a discontinuous basement membrane, and tight junctions frequently occur between endothelial cells. Occasionally, lymphatic vessels are found and the innervation is principally vasomotor, although nerve endings appear remarkably near reticular cells and lymphocytes. The jugular bodies of adult R. pipiens are plasma cell and antibody-forming organs, whose functional significance is discussed in relation to their ultrastructural organization.

Animals↗
PubMed1981

Plasma cells in the ammocoete of Petromyzon marinus.

This study demonstrates for the first time the presence of mature and developing plasma cells in the spleen of non-immunized ammocoetes of Petromyzon marinus. Plasmocytes occur as electron-dense cells with much condensed chromatin and an extensively large developed and dilated rough endoplasmic reticulum. The importance of this finding is emphasized in relation to the evolution of the immune system.

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