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Biomedical subjects

J Leceta

Publications and source records attributed to J Leceta.

46 records · Page 3Linked to original sources
PubMed1987

Effects of dexamethasone on the lymphoid organs of Rana perezi.

Owing to the possible importance of steroids in the mutual neuroendocrine-immune influences found in lower vertebrates, we study the structural and morphometrical changes induced by a single dose of dexamethasone, a synthetic corticosteroid, on the lymphoid organs of the frog Rana perezi. The dexamethasone treatment produces thymic involution with massive destruction of cortical lymphocytes, intense peripheral lymphopenia with lymphocyte redistribution to the bone marrow from peripheral blood and spleen. The effects on the spleen were less dramatic than in the thymus, but, the proportion of white pulp underwent a significant decrease and the size of splenic lymphoid follicles diminished. Our results demonstrate that Rana perezi is a corticosensitive species although the induced corticosteroid effects were less drastic than those described in other vertebrates, mainly mammals.

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PubMed1986

Seasonal variations in the immune response of the tortoise Mauremys caspica.

The primary and secondary immune responses to sheep erythrocytes (SRBC) have been characterized in the tortoise Mauremys caspica in terms of circulating antibodies and PFC response in two different seasons: summer and autumn. Primary immunization is followed by the appearance of both 2ME-sensitive antibodies and splenic PFCs in autumn but not in summer. During the secondary response, 2ME-resistant antibodies were found in both seasons, but the number of PFCs was significantly reduced during summer. The results are discussed from the perspective of the role played by glucocorticosteroids in the seasonal variations affecting reptilian immunoreactivity.

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PubMed1985

Dendritic immune complex trapping cells in the spleen of the snake, Python reticulatus.

The spleen of the snake Python reticulatus, was investigated as to its general histology as well as the presence of immune complex trapping cells both at the light and electron microscopical level. Histological examination revealed that the spleen of this reptile was encapsulated and contained some trabeculae. In the splenic parenchyma two different regions could be distinguished: viz. red and white pulp. The white pulp appeared to be arranged around "central arterioles" and their smaller branches extending towards the periphery of the white pulp. The red pulp was composed of blood sinusoids and cell cords. Electron microscopy revealed at least three types of non-lymphoid cells in the white pulp of the spleen of python: reticulum cells, forming the framework; some macrophages and dendritic cells predominantly located in the periphery of the white pulp. Of these types of non-lymphoid cells, only dendritic cells were able to trap and to retain intravenously injected horseradish peroxidase (HRP)-rabbit-anti-HRP immune complexes on their cell surface as determined by enzymehistochemistry at the light and electron microscopical level. These dendritic cells were frequently found in association with collagen fibres and did not engulf large quantities of carbon particles. These data suggest that dendritic cells in the spleen of the python might be the phylogenetic precursors of the mammalian follicular dendritic cells.

Animals↗
PubMed1985

Seasonal changes in the thymus and spleen of the turtle, Mauremys caspica. A morphometrical, light microscopical study.

Mauremys caspica has been used to analyze morphological changes which affect lymphoid organs (thymus and spleen) throughout the year related to annual variations of circulating steroid hormones. Both organs undergo seasonal variations which, however, differentially affect their distinct compartments (cortex and medulla in the thymus; PALS and PELS in the splenic white pulp). The greatest thymic involution occurs in summer, with some recovery at the beginning of autumn and a slow decrease throughout the winter. At the beginning of spring, although the gland increases somewhat in size, the thymic cortex is only slightly developed. Only at the end of spring does the thymus reach a large size, with a well developed cortex and medulla. In the same season, the splenic lymphoid tissue reaches its maximum development, but in the summer it undergoes a dramatic decrease. These results are confronted with the activity of steroid hormones measured by radio-immune assay, confirming possible relationships between the development of lymphoid organs during summer and spring, and levels of circulating corticosterone and testosterone. The decrease in lymphoid tissue during winter could be related to temperature-dependent membrane homeoviscosity.

Animals↗
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↗
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↗
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

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.

Animals↗
PubMedDate not supplied

Vasoactive intestinal peptide in thymus: synthesis, receptors and biological actions.

Evidence summarized in this report indicates that thymocytes produce and secrete VIP. Moreover, different stimuli such as Con A, LPS and anti-TCR antibody induce a significant increase in VIP production by thymocytes. In addition, proinflammatory cytokines such as IL-1, IL-6 and TNF-alpha, but not IL-2, stimulate in a similar time-dependent manner VIP production by lymphocytes. We also describe the expression of VIP1 receptor and VIP2 receptor mRNA in murine thymocytes. Thus, VIP released in thymus microenvironment may modulate immune functions through direct binding to VIP receptors on thymocytes. Our functional data support that VIP through the interaction with their specific receptors affect three important aspects of thymocytes function: cytokine production, mobility and apoptosis.

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