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C A Maldonado

Publications and source records attributed to C A Maldonado.

15 recordsLinked to original sources
PubMed2001

Sexual dimorphism of apoptosis in lactotrophs induced by bromocryptine.

Interruption of lactation provokes a massive degeneration of surplus lactotrophs in the rat pituitary gland. This process was determined to be non-apoptotic in nature, and this observation raised many questions as cell death by apoptosis has been described in several tissues after withdrawal of trophic hormones. In this study we explored various experimental conditions and gathered new information leading to a comprehensive interpretation of the factors involved in the induction of apoptosis in lactotrophs. With this aim, we investigated the apoptogenic role of bromocryptine on lactotrophs in several experimental models involving male and female rats. Even though bromocryptine increased the expression of P53 in all experimental models, apoptosis was only triggered in male and ovariectomised females. In both conditions the oestrogen stimulation is low or nil, and the occurrence of apoptosis can be correlated with the appearance of atypical lactotrophs and the level of P53 expression. The existence of apoptosis was validated with the observation of DNA laddering in electrophoresis. By contrast, in intact females the majority of lactotrophs present signs of an increased prolactin secretion and no DNA fragmentation was found. Endogenous oestrogens probably prevent the deep inhibitory effect of a dopamine agonist and thus block apoptosis. Besides, the morphological analysis of regressing pituitary revealed the coexistence of lactotrophs to be an important factor responsible for tissue remodelling in functional pituitary glands undergoing apoptotic and non-apoptotic cell deaths. The non-apoptotic cell death appeared to be an important factor responsible for tissue remodelling in functional pituitary glands. The present results suggest that the occurrence of apoptosis in regressing lactotrophs caused by bromocryptine is sexually dimorphic and probably associated with the survival effect of endogenous oestrogens in intact females.

Animals↗
PubMed2001

Expression of galectins-1 and -3 correlates with defective mononuclear cell apoptosis in patients with juvenile idiopathic arthritis.

OBJECTIVE: Juvenile idiopathic arthritis (JIA) is characterized by hyperplasia of synovial cells and accumulation of mononuclear inflammatory infiltrates, which are locally maintained through a balance between cell proliferation and apoptosis. Although defective clearance of activated T cells in RA joints has been explained by alterations of the Fas-Fas ligand system, this has not been confirmed in synovial tissue of patients with JIA. We evaluated the relation between expression of galectin-1 (Gal-1) and galectin-3 (Gal-3) (beta-galactoside-binding proteins with pro- and anti-apoptotic properties, respectively) and the apoptosis and proliferation rates of infiltrative lymphocytes in synovial tissue of patients with JIA. METHODS: Using slide cytometry and in situ end labeling we observed dysregulated apoptosis of infiltrating mononuclear cells within the synovial tissue of patients with JIA. RESULTS: Patients with pauciarticular JIA showed minimal apoptosis, high Bcl-2 expression, and high or normal proliferation rates, while patients with polyarticular disease showed the lowest apoptotic indexes, accompanied by low Bcl-2 expression and low proliferation rates. We found that Gal-1 expression is downregulated and Gal-3 expression is upregulated in synovial tissue from patients with JIA. CONCLUSION: In patients with polyarticular JIA, accumulation of inflammatory cells is mainly due to downregulated apoptosis, whereas in patients with pauciarticular disease the process results from increased proliferation. Defective mononuclear apoptosis in synovial inflammatory infiltrates from patients with JIA could be explained in part by decreased Gal-1 and increased Gal-3 expression.

Antigens, Differentiation↗
PubMed2000

Response of bronchiolar Clara cells induced by a domestic insecticide. Analysis of CC10 kDa protein content.

Clara cells are the most reactive to xenobiotics among the mammalian respiratory tract cells. In this report, the response of Clara cells to acute or repetitive exposure to a commercial insecticide was studied, correlating the changes in the cell ultrastructure with the intracellular content of CC10 kDa protein as quantified by immunocytochemical morphometry. After a single exposure to insecticide, Clara cells reveal great expansion of their volume which is accompanied by a remarkable proliferation of smooth endoplasmic reticulum, swelling of the mitochondria, and changes in the nucleus. Morphometric analysis of CC10 bronchiolar content showed significant increases in both the number of Clara cells and the immunostained areas in individual cells. By western blot, CC10 immunoreactive bands strongly increased in lungs after insecticide treatment, but they were only slightly higher than the control when the vehicle of the insecticide was tested. By repetitive exposure to the insecticide, the rat bronchiolar epithelium undergoes extensive alterations, particularly on Clara cells, the number of which is considerably reduced. The remaining Clara cells shrink in size and the typical dome-like cytoplasm is lost. Secretory granule release is no longer seen and the changes of their shape and secretory content reflect a marked degradation and condensation process. Repetitive exposures to the insecticide produced a severe blockage of the proteinopoietic activity, particularly on the synthesis of CC10. Results reported here reveal that the acute inhalation of a commercial insecticide produces hypertrophy of Clara cells, a significant augmentation of CC10 synthesis, and probably differentiation de novo of Clara cells, and morphological changes compatible with a detoxification process. By contrast, exposure for 5 days provoked a general inhibitory effect on Clara cell activity with the loss of cell capability to synthesize and secrete CC10 kDa protein.

Animals↗
PubMed1999

Immunocytochemical study of the distribution of a 16-kDa galectin in the chicken retina.

PURPOSE: To compare the distribution of a developmentally regulated 16-kDa galectin in the chicken retina at two different developmental stages: embryonic day 13 (ED13) and postnatal day 10 (PD10) retinas, by immunocytochemical analysis using light and transmission electron microscopy. METHODS: Semi-thin and thin sections from ED13 and PD10 retinas were incubated with the IgG fraction purified from a rabbit antiserum raised against the 16-kDa chicken galectin. After incubation with colloidal gold particle-labeled goat anti-rabbit IgGs, tissue sections were analyzed by light and transmission electron microscopy. To improve the observation by light microscopy, semi-thin immunostained sections were intensified by silver enhancement. RESULTS: In ED13 retinas a specific galectin labeling was detected in the region corresponding to the outer limiting membrane by light microscopy. This labeling seemed to be associated with the apical villi of Muller glial cells and their specialized junctions, as judged by transmission electron microscopy. In PD10 retinas, the more relevant finding revealed by light microscopy was the detection of a widespread immunostaining at the level of all retinal layers. The ultrastructural analysis indicated that the galectin labeling was detected at the cytoplasmic and nuclear compartments of Muller cells throughout the different retinal layers. Moreover, the labeling was detected in the inner limiting membrane in structures that resemble the end feet of Muller cells. The apical villi, and the specialized junctions of these glial cells, appeared more strongly stained in PD10 retinas than in ED13 retinas. Finally, highly intense labeling in a group of mitochondria localized in the inner segments of cone cells was observed. CONCLUSIONS: The present study clearly supports the idea that the subcellular distribution of the 16-kDa galectin changes during the development of the chicken retina. Morphologic changes associated with developmentally regulated expression and subcellular compartmentalization of the retinal galectin suggest that this lectin may be involved in the modulation of several processes in the visual system. Its presence in the apical villi of Miller cells may be related by modulatory functions between retina and pigment epithelium, but its presence in the cytoplasm and nucleus of these glial cells suggests a potential immunomodulatory role and its involvement in different metabolic processes between Muller and the other retinal cells. Finally, although the presence of galectins inside mitochondria has not been described before, this localization gives rise to the idea that this lectin may be involved in the modulation of mitochondrial processes.

Animals↗
PubMed1998

Apoptotic and non-apoptotic cell death in hormone-dependent glands.

The proliferation of cells and cell death are involved in the maintenance of appropriate tissue homeostasis. In the present study, two different mechanisms of cell death were identified in the prostate and pituitary glands when morphological data, fragmentation of DNA, and TUNEL labelling of apoptotic nuclei were compared. Typical cell death by apoptosis was identified by morphological and molecular approaches in the prostate after orchidectomy. By contrast, neither DNA fragmentation nor TUNEL labelling were found in dead cells occurring in the pituitary gland after interruption of lactation. Regressing lactotrophs were characterised by condensation and disruption of the cytoplasmic matrix, but preserved intact nuclei until advanced stages of regression. Degenerating "dark" cells comparable to those described in the pituitary were also seen coexisting with typical apoptosis in the prostate epithelial lining of orchidectomised rats. Both forms of cell death could be clearly differentiated, because dark cells suffer severe alterations of cytoplasmic organelles while maintaining the integrity of the nucleus. In contrast, apoptotic cells present well-preserved cytoplasmic organelles, but grossly disrupted nuclei with fragmentation and condensation of chromatin.

Animals↗
PubMed1996

Influence of L-triiodothyronine on rat somatotroph cells.

The L-Triiodothyronine (L-T3) has a direct influence on the population of somatotrophs in rat pituitary gland. This effect is dose-dependent and induces both proliferation of somatotrophs and striking changes in the synthesis and secretion of growth hormone (GH). Daily injections of 5 micrograms L-T3 for 7 days increased significantly the synthesis and storage of GH in pituitary gland, but the GH release was partially blocked. By contrast, injections of 10 micrograms L-T3 promote rapid synthesis and secretion of GH with removal of the cytoplasmic stores of the hormone and a consequent rise of serum levels. A close correlation was found between levels of stimulation and proliferation or retrogression of lactotroph cell population.

Animals↗
PubMed1995

Changes in thyrotroph and somatotroph cell populations induced by stimulation and inhibition of their secretory activity.

The populations of cells which produce immunoreactive growth hormone (GH) and thyroid stimulating hormone (TSH) in the rat pituitary gland do not occur in fixed percentages but vary greatly under different physiological and experimental conditions. These variations can be directly correlated to the levels of stimulation and/or inhibition of the specific secretory activity. In both types of cell, sustained stimulation with trophic hormones or blockage of the feedback mechanisms induces remarkable growth in the specific cell population. Conversely, the interruption or inhibition of the stimulus thwarted the hormonal secretion and caused a massive degeneration of redundant cells. The stimulation of both GH and TSH cells is accompanied by an enhanced secretory activity as judged by their higher concentrations in serum and hypertrophy of the cytoplasmic organelles involved in synthesis and intracellular processing of the hormones. By contrast, interruption of the stimulus is followed by a variable degree of disruption of the cytoplasmic organization, including a sizable degeneration of cells. In stimulated rats, the concentrations of both GH and TSH decreased significantly in pituitary tissue due to mobilization of the hormonal stores contained in secretory granules. On the other hand, the withdrawal of stimuli blocked the hormonal release; this is reflected by the accumulation of both hormones and secretory granules in pituitary tissue. The strict correlation between the size of the GH and TSH populations with stimulation and inhibition of hormonal secretory activity reported in this investigation further supports the critical role played by the cell renewal process in endocrine secretion.

Animals↗
PubMed1993

Fate of degenerating lactotrophs in rat pituitary gland after interruption of lactation: a histochemical and immunocytochemical study.

In the pituitary gland of pregnant and lactating rats a striking proliferation of lactotrophs occurs to meet the increased demands for prolactin. Following interruption of lactation the redundant lactotrophs undergo a massive degeneration until pre-pregnant proportions are re-established. Immunocytochemical detection of prolactin allows the recognition of degenerating lactotrophs until advanced stages of degeneration and leads to the conclusion that this process is autolytic in nature. Histochemistry of acid phosphatase reveals a remarkable accumulation of this enzyme in Golgi cisternae and lysosomes. At later stages of degeneration the acid phosphatase spreads throughout the entire cell. The presence of increased numbers of necrotic cells appears to activate phagocytosis of stellate cells and, to a lesser extent, of follicular cells. Stellate cells responsible for the secondary processing of cell residues are isolated cells characterized by a prominent oval nucleus and an electron-lucent cytoplasm with scarce organelles and extensive cytoplasmic processes. They appear as scavenger cells engulfing cell remnants and debris. Immunocytochemistry of S-100 protein discloses differential staining of two types of cell, one forming clusters of 2-4 cells with faint immunoreactivity, while the other type consists of isolated cells with a stellate profile and stronger labelling to S-100 protein.

Acid Phosphatase↗
PubMed1986

Cardiodilatin-immunoreactivity in specific atrial granules of human heart revealed by the immunogold stain.

The immunogold technique was applied to detect cardiodilatin-immunoreactivity (CDD-IR) in human heart. Using antibodies directed against C-terminal regions of CDD, we could identify colloidal gold label in specific atrial granules of human heart. The granules in all areas of the myoendocrine cells were homogeneously labelled and all right atrial biopsy specimen of patients with different heart diseases reacted positively and had the same distribution of label. The Golgi-apparatus and ergastoplasma exhibited and extremely weak CDD-IR. The results indicate a predominant storage of CDD in specific granules.

Atrial Natriuretic Factor↗
PubMed1986

Influence of embedding media in prolactin labelling with immunogold techniques.

Immunogold labelling of prolactin in three different embedding media was compared. The polymeric prolactin in secretory granules was labelled in the three media, however, acrylic monomers (Lowicryl K4M and LR White) provided a more intense labelling with higher dilutions of the primary antibody, compared to the labelling in the epoxy resin (araldite). An intense labelling of monomeric prolactin in Golgi complex was detected only in acrylic embedments, and the labelling on the rough endoplasmic reticulum was significant only in LR White embedded tissues.

Acrylic Resins↗
PubMed1986

Long-term expression of isomyosins and myoendocrine functions in ectopic grafts of atrial tissue.

Tissue fragments of newborn rat atria were transplanted under the dorsal skin or into the bed of the anterior tibial muscle of nude mice. After 5-11 weeks, the grafts, which had reorganized into beating atrium-like structures, were analyzed and compared to ventricular tissue transplanted the same way. As revealed by monoclonal antibodies against alpha- and beta-type myosin heavy chains, atrial grafts retained a typical pattern of myosin expression distinct from that of ventricular grafts. The majority of ectopic atrial myocytes contained specific atrial granules in which cardiodilatin-immunoreactive material has been localized. Specific granules and cardiodilatin immunoreactivity were not found in myocytes of ventricular grafts. We conclude that the long-term maintenance of isomyosin expression and of the myoendocrine function of atrial tissue is largely independent of the anatomical environment.

Animals↗
PubMed1986

Regression of redundant lactotrophs in rat pituitary gland after cessation of lactation.

Regressive changes occurring in the pituitary gland of the rat after removal of litters were studied. Pituitary glands of lactating rats were characterized by the presence of numerous hypertrophied lactotrophs. Interruption of lactation caused a blockade of prolactin synthesis and secretion, followed by degeneration of lactotrophs. Morphometric analysis of pituitary glands revealed that lactotrophs accounted for about 50% of the total hypophysial cell count in lactating rats. This percentage decreased progressively and reached pre-pregnant levels 7 days after removal of litters; the decrease was inversely correlated with an increase in the number of degenerating lactotrophs which comprised 30% of all lactotrophs 72 h after removal of litters. The morphological changes found in lactotrophs were closely related to changes in the prolactin content of serum and the pituitary gland. Regression of lactotrophs appeared to be the most important cause inducing the reversal of hypophysial lactotrophic activity to pre-pregnant conditions.

Animals↗
PubMed1986

Improvement of prolactin immunolabelling in osmium-fixed acrylic-embedded pituitary gland.

Immunolabelling of prolactin (PRL) with protein A-colloidal gold complex and tissue fine structure were enhanced after postfixation of pituitary gland with osmium tetroxide and embedment in acrylic momers (LR White). Thin sections were treated with sodium metaperiodate before immunocytochemistry. An intense PRL labelling was detected in secretory granules, Golgi complexes and extracellular accumulation of the hormone. The use of osmium greatly improved the fine structure of the tissue and its stability during acrylic embedment.

Acrylates↗