Biomedical subjects

J Losada

Publications and source records attributed to J Losada.

18 recordsLinked to original sources

PubMed2002

Cell proliferation, nuclear ploidy, and EGFr and HER2/neu tyrosine kinase oncoproteins in infiltrating ductal breast carcinoma.

The purpose of this work was to study if the variations in the nuclear DNA content and the expression of EGFr and HER2/neu transmembrane oncoproteins were related and if this influences the rate of cell proliferation modifying, in each case, the potential aggressivity of the neoplasia. Thirty-four ductal breast carcinoma tissue samples of tumors of up to 2 cm in diameter were analyzed by flow cytometry. HER2/neu and EGFr were measured by immunohistochemical methods. Twenty cases were diploid (DNA index of 1) and 14 cases were aneuploid (DNA index other than 1). The expression of EGFr and HER2/neu was significantly higher in aneuploid tumors compared with diploid tumors. The cell proliferation rate was significantly higher in tumors with an aneuploid pattern. The expression of EGFr was associated with a higher rate of cell proliferation. The higher expression of EGFr and HER 2/neu oncoproteins in aneuploid tumors suggests that the increased proliferative activity of aneuploid carcinomas is influenced by the activity of such oncoproteins, which favors a more aggressive biological behavior.

Breast Neoplasms↗

PubMed2002

Rat neonatal intestinal wall-free graft.

An experimental study was carried out in order to evaluate the regeneration capacity of the neonatal intestinal wall in ischaemia and its repercussion over organs of the immune system such as the spleen. We isolated a reservoir of small intestine in adult Sprague-Dawley rats that, after having been everted and placed at a subcutaneous level, was grafted with a free small intestine segment of neonatal Sprague-Dawley rats and analysed 3, 15 and 30 days after grafting. Samples obtained were stained with Martin's trichromic stain and studied at the light microscopic level. A total regeneration of the crypt architecture, formed by absorptive enterocytes, was observed in the interior of the reservoirs. A quantitative immunohistochemical study with monoclonal antibodies against CD4, CD8, MHC I and MHC II was carried out in the spleen of these animals. An additional immunohistochemical study was also performed in the small intestine reservoirs and spleen of transplanted animals using nitric oxide synthase (NOS) antibodies. Three days after transplantation NOS immunoreactive cells were observed in the reservoirs with transplanted neonatal small intestine. Antigenic stimulation produced, in the spleen red pulp of transplanted animals, a significant increase (P < 0.001) in the percentage of NOS, CD8 and MHC I immunoreactive cells in relation with values observed in control animals. These morphometric changes could be related with the stimulation that nitric oxide produces in the proliferation of the cytotoxic T cells.

Animals↗

PubMed2001

Cobaltocenium-functionalized poly(propylene imine) dendrimers: redox and electromicrogravimetric studies and AFM imaging.

The first four generations of cobaltocenium-functionalized, diaminobutane-based poly(propylene imine) dendrimers DAB-dend-Cb,(PFb)x (x = 4, 8, 16, and 32; Cb=[Co(eta5-C5H4CONH)(eta5-C5H5)] (1-4) have been synthesized and characterized. The redox activity of the cobaltocenium centers in 1-4 has been characterized by using cyclic voltammetry and the electrochemical quartz-crystal microbalance (EQCM). All of the dendrimers exhibit reversible redox chemistry associated with the cobaltocenium/cobaltocene redox couple. Upon reduction. the dendrimers exhibit a tendency to electrodeposit onto the electrode surface, which is more pronounced for the higher generations. Pt and glassy carbon electrodes could be modified with films derived from 1-4,exhibiting a well-defined and persistent electrochemical response. EQCM measurements show that the dendrimers adsorb, at open circuit, onto platinum surfaces at monolayer or submonolayer coverage. Cathodic potential scanning past -0.75 V at which the cobaltocenium sites are reduced, gave rise to the electrodeposition of multilayer equivalents of the dendrimers. The additional material gradually desorbs upon re-oxidation so that only a monolayer equivalent remains on the electrode surface. Changes in film morphology as a function of dendrimer generation and surface coverage were studied by using admittance measurements of the quartz-crystal resonator on the basis of its electrical equivalent circuit, especially in terms of its resistance parameter. In general, we find that films of the lower dendrimer generation 1 behave rigidly, whereas those of the higher generation 4 exhibit viscoelastic behavior with an intermediate behavior being exhibited by 2 and 3. Using tapping-mode atomic force microscopy (AFM). we have been able to obtain molecularly resolved images of dendrimer 4 adsorbed on a Pt(111) electrode.

Journal Article↗

PubMed2000

Mixed Ferrocene-Cobaltocenium Dendrimers: The Most Stable Organometallic Redox Systems Combined in a Dendritic Molecule This work was supported by the Dirección General de Enseñanza Superior e Investigación Científica (PB-97-0001). We are grateful to M. J. Vicente and Dr. M. T. Alonso for valuable discussions on ESI-MS.

Explore the source record for details and available documents.

Journal Article↗

PubMed1999

Distribution of the group II metabotropic glutamate receptors (mGluR2/3) in the enteric nervous system of the rat.

We used affinity purified antisera specific for group II metabotropic glutamate receptors in combination with a pre-embedding immunocytochemical method for light microscopy to investigate the localization of mGluR2/3 receptors in the enteric nervous system of the rat small intestine. In the submucosal plexuses of the jejunum and ileum, strongly mGluR2/3 immunoreactive cells were distributed between the circular muscular layer and the muscularis mucosa. In addition, oval or rounded immunostained ganglion cells appeared located in the myenteric plexuses of both intestinal regions. Nerve fibers intensely stained were observed extending between adjacent myenteric ganglia. The localization of mGluR2/3 receptors in enteric neurons might have functional implications in the physiology and pathology of the gut.

Animals↗

PubMed1998

Immunocytochemical localization of the mGluR1b metabotropic glutamate receptor in the rat hypothalamus.

The mGluR1 metabotropic glutamate receptor is a G-protein-coupled receptor that exists as different C-terminal splice variants. When expressed in mammalian cells, the mGluR1 splice variants exhibit diverse transduction mechanisms and also slightly differ in their apparent agonist affinities. In the present study, we used an affinity-purified antiserum, specifically reactive to the mGluRlb splice variant, in combination with a highly sensitive preembedding immunocytochemical method for light microscopy to investigate the distribution of this receptor in the rat hypothalamus. An intense immunoreactivity for mGluRlb was observed in distinct hypothalamic nuclei. Thus, neuronal cell bodies and dendrites were stained in the preoptic area, suprachiasmatic nucleus, dorsal hypothalamus, lateral hypothalamus, dorsomedial nucleus, tuberomammilary nucleus, and lateral mammilary body. The ventromedial nucleus exhibited neuropil immunostaining but neuronal cell bodies were not labeled. Strong mGluRlb immunoreactivity was observed in magnocellular neurons of the neuroendocrine supraoptic, paraventricular, and arcuate nuclei. Also, neuronal cell bodies were heavily labeled in the retrochiasmatic nucleus, anterior commissural nucleus, and periventricular nucleus. These immunocytochemical observations, together with previous studies, suggest that mGluRlb is coexpressed with other class I mGluRs in some nuclei throughout the hypothalamus. However, mGluRlb is so far the only receptor of this class strongly expressed in the supraoptic, paraventricular, and arcuate nuclei, which might have relevant implications in the physiological control of the neuroendocrine hypothalamic-pituitary system.

Amino Acid Sequence↗

PubMed1995

DNA ploidy and PCNA index in pancreatic lesions producing hyperinsulinemic hypoglycemia.

DNA nuclear content and PCNA index (proportion of PCNA reactive cells) have been studied by flow cytometry in eight pancreatic lesions producing hyperinsulinemic hypoglycemia to assess DNA ploidy and tumoral growth fraction. Adult nesidioblastosis had a diploid DNA index, two adenomas were near diploid, and four of the adenomas and the carcinoma were aneuploid. The median value of PCNA index (6.056% +/- 6.76) was significantly correlated (P < 0.05) with the mean tumor diameter (2.43 cm +/- 1.96). Tumors with a PCNA index < 6.056% showed a diameter less than the mean tumoral diameter and a benign clinical course. Tumors with PCNA index > 6.056% generally displayed a diameter bigger than the mean tumoral diameter, being associated with lymph node metastases in one case. The authors conclude that nuclear DNA and PCNA index cytometric studies are useful parameters to assess the biological behavior of pancreatic lesions producing hyperinsulinemic hypoglycemia.

Adenoma↗

PubMed1995

Study of ACTH-immunoreactive cells after transplantation of neonatal adrenal glands into adult adrenalectomized rats.

The morphological and morphometrical features of the ACTH-immunoreactive cells of the anterior pituitary gland were compared between adult rats with intact adrenals, adult rats without adrenals, and adult rats with regenerated adrenocortical nodules. The removal of the adrenal glands produced a great increase in the number and size of the cytoplasmic processes of the ACTH-immunoreactive cells that sometimes establish contact with those of the neighbouring immunoreactive cells. In addition, in this experimental group, the ACTH-cell percentage and the mean cell, cytoplasmic, and nuclear areas were greatly increased in comparison with those found in control animals. Several regenerated adrenocortical nodules were observed in the small-bowel segment of rats transplanted with neonatal adrenal glands. The percentage and morphometrical values of the pituitary ACTH-reactive cells of this experimental group, although slightly increased relative to the rats with intact adrenals, were greatly decreased in relation to those of the adrenalectomized animals. It is concluded that the neonatal adrenal tissue regenerated after its transplantation into adult rats, a process that modified the percentage, the morphological characteristics, and the morphometrical values of the ACTH-immunoreactive cells of the adrenalectomized rats.

Adrenal Glands↗

PubMed1995

Immunohistochemical analysis of adrenal proliferation and corticosterone expression in experimental adrenal regeneration.

The proliferative activity, the organization and the corticosterone expression of adrenocortical cells in an experimental adrenal regeneration process after the transplantation of neonatal adrenal glands to adult hosts was investigated. Three days after transplantation, the medullar and the innermost adrenocortical cells of the neonatal adrenal glands showed degenerative and necrotic changes due to the lack of vascular supply. The remaining outermost adrenocortical cells did not display any PCNA immunoreaction. The first PCNA expression, pointing out the beginning of the proliferative cycle, was observed in a 45.4% of the adrenocortical cells, one week after transplantation. After three weeks, several regenerated adrenocortical nodules with a bigger size than the one observed in the previous periods were seen. In these nodules, while the outermost adrenocortical cells were disposed in parallel to the capsule or in rounded groups, the bulk of the regenerated mass width was composed of cells forming longitudinal cords. PCNA immunoreaction was almost exclusively restricted to subcapsular cells (62.5%) and to cells of the outermost portion of the cords (32.5%), the global percentage of PCNA immunopositive cells being 18.4%. Twelve weeks after transplantation, regenerated adrenocortical cells were arranged in three layers: glomerulosa, fasciculata and reticularis. Only 1.85% of the adrenocortical cells were PCNA immunopositive. Although in the early stages of the regeneration process, all the adrenocortical cells, both proliferating and non proliferating cells expressed corticosterone, a restriction of this immunoreactivity to the zonae fasciculata and reticularis was observed when cell zonation was apparent.

Adrenal Cortex↗

PubMed1994

Analysis of the pituitary-thyroid axis in bilaterally adrenalectomized or adrenal transplanted rats.

The percentage, distribution, shape, intensity of staining and morphometrical parameters of the pituitary TSH immunoreactive cells and the histological features of the thyroid glands, were compared between adult rats with intact adrenals, without adrenals and biadrenalectomized animals with neonatal adrenal grafts. After the removal of the adrenal glands, TSH immunoreactive cells increased in percentage and exhibited a higher complexity of the cellular outline, than that of the intact animals. The nuclear, cytoplasmic and cell areas were significantly increased. However the bigger enhancement of the cytoplasmic area relative to the nuclear area, produced a decrease in the nuclear/cell area ratio. The thyroid glands showed some histological evidences of activation. After the transplantation of neonatal adrenal glands to adult rats, several adrenocortical nodules were present in the lumen of the small bowel segment. These adrenal masses induced a great decrease in the TSH cell area, which coupled with a smaller but significant variation of the nuclear area, led to an increase in the nuclear/cell area ratio relative to that observed in adrenalectomized animals. In addition, the distribution, shape and intensity of the immunoreactive material was similar to that observed in intact animals. In this experimental group, thyroid histology was observed to be similar to that of the intact animals.

Adrenal Glands↗

PubMed1994

Utility of an excluded and everted segment of small intestine placed under the skin of the abdominal wall as an adrenal transplant site in rats.

The feasibility of excluded and everted small intestine segments as reservoirs for adrenal tissue transplantation was compared between biadrenalectomized adult rats with isogenic transplants of adrenal quarters or allogenic transplants of neonatal adrenal glands. Small clusters of adrenocortical cells, located between the adipocytes and the mesenteric vessels of the segments' lumen, were observed following isogenic transplantation. Several large regenerated adrenocortical nodules, surrounded by a connective capsule, were present in each of the rats transplanted with neonatal adrenal glands. Medullary tissue did not regenerate. It was concluded that the excluded and everted segments of small intestine were optimal sites for adrenal tissue transplantation and that the regeneration process of the adrenocortical tissue takes place more quickly after the transplantation of neonatal adrenal glands than after the transplantation of adrenal quarters.

Abdominal Muscles↗

PubMed1992

[Gastric metastasis of melanoma].

The authors report a case of gastric metastases from a melanoma three years after the removal of the original tumour located at the front side of the left leg. The metastases was diagnosed because of asymptomatic iron deficiency anemia.

Gastrectomy↗

PubMed1989