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Biomedical subjects

A Zapata

Publications and source records attributed to A Zapata.

At least 19 recordsLinked to original sources
PubMed1992

Building blocks for the synthesis of glycosyl-myo-inositols involved in the insulin intracellular signalling process.

Glycosylation of (+/- )-1-O-benzyl-2,3:5,6-di-O-isopropylidene-myo-inositol (4) with 6-O-acetyl-4-O-allyl-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranosyl trichloroacetimidate (6) gave the 4-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)- myo-inositol derivative (9) as a mixture of diastereoisomers which could be resolved by chromatography. Likewise alpha-glycosylation of 4 with 6-O-acetyl-2-azido-3-O-benzoyl-2-deoxy-4-O-(2,3,4,6-tetra-O-acetyl-beta- D- galactopyranosyl)-D-glucopyranosyl trichloroacetimidate (10) gave the corresponding pseudotrisaccharide derivative 16 as a mixture of diastereomers which could be resolved partially by chromatography. alpha-Glycosylation of enantiomerically pure 2,3:5,6- (18) and 2,3:4,5-di-O-isopropylidene-1-O-menthoxycarbonyl-myo-inositol (19) with 3,4,6-tri-O-acetyl-2-azido-2-deoxy-D-glucopyranosyl trichloroacetimidate (20) gave the pseudodisaccharide derivatives 21 and 22, respectively. Likewise, alpha-glycosylation of 18 with 10 afforded a pseudotrisaccharide derivative (23).

Carbohydrate Sequence↗
PubMed1992

Infantile stimulation and the role of the benzodiazepine receptor system in adult acquisition of two-way avoidance behavior.

The present study shows that postnatal "consistent" handling (CH) of rats had long-lasting improving effects on coping with an stressful task (i.e. two-way active avoidance), and that such effects were partially prevented by acute Ro 15-1788 (antagonist of benzodiazepine receptor-BZR; 5 mg/kg) administration. Long-lasting detrimental effects in the same task were also observed in rats which received postnatal "inconsistent" handling (INCH), effects that were slightly increased by acute Ro 15-1788 treatment. Finally, Ro 15-1788 tended to increase avoidance acquisition in non-handled (NH) animals. The observed effects of Ro 15-1788 could be partially attributed to a differential modulation of the process of avoidance acquisition depending on postnatal treatments producing different levels of emotionality.

Adaptation, Psychological↗
PubMed1992

Transplantation of cultured thymic fragments in congenitally athymic and euthymic rats. Culture with deoxyguanosine or cyclosporin A does not influence the histologic characteristics and outcome after transplantation in syngeneic and allogeneic combinations.

Cultured thymic fragments (CTF) from WAG/CPB (RT1u) and DA/01a (RT1a) rats were prepared in the presence or absence of 2'deoxyguanosine or cyclosporin A, and subsequently transplanted under the kidney capsule of congenitally athymic and euthymic WAG/CPB recipients. The rationale of the culture supplements was that these may affect the disappearance of medullary dendritic cells, with subsequent induction of allotolerance. However, the immunohistology of the CTF showed more RT1 class II-positive cells than keratin-positive cells, indicative of the maintenance of dendritic cells. Grafts in athymic animals showed the recovery of the original thymic architecture within 6 weeks after transplantation. The influx of host-derived lymphocytes was accompanied by an influx of dendritic cells in the medulla-like area and macrophages in the cortex. A similar recovery was observed for syngeneic CTF in euthymic recipients. In addition lymphocytic infiltration was seen in the connective tissue surrounding the epithelial areas. Allogeneic grafts in euthymic animals were rejected within 3 weeks after transplantation. This outcome of the transplanted CTF under different conditions was not affected by the supplementation of the thymic culture before transplantation with 2'deoxyguanosine or cyclosporin A. We conclude that there is no tolerance induction after transplantation in euthymic allogeneic rats of CTF prepared in the presence of 2'deoxyguanosine. This conclusion is in contrast to data in the mouse, which may be explained by the maintenance of dendritic cells during culture. A chimaeric state of donor-derived epithelium and host-derived dendritic cells is obtained by transplantation of allografts in athymic rats.

Analysis of Variance↗
PubMed1992

Reptilian thymus gland: an ultrastructural overview.

Like in higher vertebrates, the thymus gland of reptiles consists of lymphoid cells within epithelial framework and characteristic myoid cells. Mammalian-like Hassall's corpuscles are absent. Secretory cells, secretory and degenerative cysts as well as phagocytic cells, and plasma cells can be observed. Interdigitating cells and some characteristic features of thymic innervation and vascular system are also described in the reptilian thymus gland.

Animals↗
PubMed1991

Beneficial effects of infantile stimulation on coping (avoidance) behavior in rats are prevented by perinatal blockade of benzodiazepine receptors with Ro 15-1788.

The present study shows that postnatal 'consistent' handling (CH; which consisted of removing the pups from the nest and placing them individually in plastic cages lined with paper towel for a period of 15 min daily between 1 and 22 postnatal days) of rats had long-lasting improving effects on coping with a stressful task (i.e. enhancement on the early acquisition of two-way active avoidance), but such effects were completely prevented when CH treatment was combined with chronic perinatal Ro 15-1788 (7 mg/kg/day, between prenatal day 19 and postnatal day 22) administration (i.e. blockade of benzodiazepine receptor (BZR)). A long-lasting decremental effect was also observed in the same task in rats which received postnatal 'inconsistent' handling (INCH; in which stimulation of pups was changed every day between 1 and 22 postnatal days), without being affected by the concomitant perinatal Ro 15-1788 treatment. These results suggest that intact ontogeny of BZRs is necessary to obtain the enduring positive effects of CH on emotional behavior (i.e. early acquisition of two-way active avoidance).

Adaptation, Psychological↗
PubMed1991

Post-hatching development of the thymic epithelial cells in the rainbow trout Salmo gairdneri: an ultrastructural study.

This study reports the ultrastructure of subpopulations of epithelial cells of the thymic parenchyma during the post-hatching development of the rainbow trout, Salmo gairdner, kept at 14 degrees C. At hatching, the thymus contained a small number of medium and large thymocytes interspersed among three different types of epithelial cells: (1) epithelial cells adjacent to the connective tissue capsule; (2) ramified dark epithelial cells with electron-dense cytoplasm; and (3) pale electron-lucent epithelial cells displaying secretory-like features. All these cells types were anchored to one another by desmosomes and had apparently differentiated from the pharyngeal epithelium. At 4 days after hatching, the thymus enlarged, and numerous gaps occurred between the cell processes of contiguous epithelial cells adjacent to the capsular connective tissue. In 21-day-old trout, thymic trabeculae developed carrying blood vessels, and a subcapsular zone became evident containing lymphoblasts and large subcapsular epithelial cells. In 30-day-old trout, an outer thymic zone developed consisting of spindle-shaped epithelial cells which formed a dense network. At this stage, scattered cystic cells, which apparently differentiated from the pale epithelial cells, were present.

Animals↗
PubMed1991

Testosterone induces lymphopenia in turtles.

Owing to the possible role of sex steroids in the immune-neuroendocrine interactions found in lower vertebrates, we attempted to delineate the effect of testosterone propionate on peripheral blood (PB) and the lymphoid organs of the turtle Mauremys caspica. A single intraperitoneal injection of 200 micrograms/g body weight produced thymic involution and intense lymphopenia in the spleen and, less severely, in the PB compartment. It is suggested that lymphocyte redistribution may occur among the various compartments of the body as the main effect of hormone-induced lymphocyte redistribution, although the mechanism in reptiles and mammals is not yet understood.

Animals↗
PubMed1991

The early acquisition of two-way (shuttle-box) avoidance as an anxiety-mediated behavior: psychopharmacological validation.

Several lines of evidence have established that performance during the initial steps of acquisition on a shuttle-box avoidance task is an anxiety-mediated behavior (i.e., the differences between strains selectivity bred for emotionality; the effects of postnatal handling; the course of the corticosterone response and behavioral measures of fear during acquisition). The present study was carried out to add pharmacological evidence to that view by testing the action of anxiogenic and anxiolytic drugs. Single 40-trial sessions with mild shocks (0.4 mA-0.6 mA) were used. In the first experiments the action of sodium pentobarbital (1.25, 2.5 and 5 mg/kg) and three benzodiazepines (diazepam, 2 and 4 mg/kg; alprazolam, 1, 1.25 and 1.5 mg/kg and adinazolam, 1, 2, 4 and 6 mg/kg) were tested. The last two experiments tested a possible proanxiety action of Ro 15-4513 (2, 5 and 10 mg/kg) and FG 7142 (5, 10 and 15 mg/kg), two partial inverse agonists of benzodiazepine receptors, which previous data had suggested to be anxiogenic. The results showed that the measure of acquisition of a two-way active avoidance is a sensitive mean for detecting either anxiolytic or anxiogenic effects of drugs, independently of their effects on locomotor activity, thus suggesting that such test could be a valid model of anxiety in animals.

Animals↗
PubMed1991

In vitro characterization of rat thymic macrophages.

Thymic macrophages have been isolated from Wistar rats and maintained in long-term culture. Day 1-isolated thymic macrophages expressed MHC class I and II antigens, Thy-1, CR3, CD4, ED1, ED2, as well as acid phosphatase and non-specific esterase activities. Whereas cultured macrophages were positive for the activation antigen recognized by the mAb OX48, which was not expressed after isolation, MHC class II and Thy-1 expression were down-regulated during the culture, but could be induced with human rIL-2 or with Con A-SCM, which are also inducers of IL-2R, a cell-surface marker not expressed on Day 1 or on cultured macrophages.

Animals↗
PubMed1991

Rat thymic cultures: morphological and phenotypical characterization.

Rat thymic cultures have been established in order to analyse the morpho-functional characteristics of thymic epithelial and non-epithelial cells in vitro. Stromal cultures, originating from implanted thymic fragments, consist of fibroblasts occupying most of the culture surface, epithelial cells forming discrete colonies, thymocytes and bone marrow-derived cells. Epithelial cells show a low class II MHC antigen expression, which is highly increased in semi-adherent cells, and do not interact with thymocytes. Thymocytes proliferate extensively at the beginning of the culture, but almost disappear at the end of the first week; however, restarting of thymocyte proliferation occurs during the second week of culture. Bone marrow-derived cells include ED- Ia+ CR3- IL-2R- dendritic cells (DC), ED+ Ia+ CR3+ IL-2R+ non-adherent thymic phagocytic cells (PTR) and ED+ Ia- CR3- IL-2R- adherent type 1 and 2 macrophages, derived from PTR. Both PTR and DC establish lympho-stromatic complexes with thymocytes present in the cultures. These results suggest that PTR and DC present in rat thymic cultures belong to different cell lineages, and that they are, respectively, the in vitro equivalents of intrathymic macrophages and interdigitating cells.

Animals↗
PubMed1990

Enzyme- and immuno-histochemical study of the thymic stroma in the rainbow trout, Salmo gairdneri, Richardson.

Owing to the lack of data about thymic non-lymphoid cells in fish we decided to perform a histochemical characterization of these cells in order to ascertain their relationships to other thymic components. In the present study we analyze the enzyme-histochemical patterns for acid phosphatase, alkaline phosphatase, non-specific sigma-naphthyl acetate esterase and 5' nucleotidase activities, as well as the presence of keratin demonstrated by immunoperoxidase staining, in the non-lymphoid cell populations of the thymus of the rainbow trout, Salmo gairdneri. According to their location in the organ, morphology and histochemical reactivities, we were able to define seven different subpopulations of keratin-positive epithelial cells: 1) Epithelial cells limiting with the capsular and septal connective tissues; 2) Subcapsular epithelial cells; 3) Stellate epithelial cells of the inner thymic zone; 4) Large, ovoid epithelial cells of the inner thymic zone; 5) Acidophilic epithelial cells of the outer thymic zone; 6) Cystic cells; and 7) Goblet cells. The significance of the heterogeneity of the epithelial cell (EC) population, its specific distribution in the organ, which apparently conforms distinct cell microenvironments, as well as the possible phylogenetical relationships between these microenvironments and the classical cortex and medulla of the mammalian thymus, are discussed.

5'-Nucleotidase↗
PubMed1989

Different sensitivity to the dexamethasone treatment of the lymphoid organs of Rana perezi in two different seasons.

Adult female frogs (Rana perezi) have been used to analyze structural and morphometrical changes which affect lymphoid organs after treatment with a single dose of dexamethasone (DX). Special attention was given to the distinct sensitivity observed during two different periods of the year. Morphological differences were found between adult control frogs sacrificed in November and February. In February, frogs showed degenerated thymic reticular epithelial cells but lesser numbers of cortical pycnotic and mitotic thymocytes than in November. Splenic lymphoid tissue was clearly less well developed in February. No significant variations were found in the morphometrical parameters of jugular bodies whereas the number of lymphocytes of both peripheral blood and bone marrow was significantly higher in February than in November. In contrast, frogs sacrificed in February exhibited less drastic variations as well as a more delayed response to DX-treatment than those of November. The reported differential changes could be attributed to possible distinct levels of circulating sexual and nonsexual steroids during both seasonal periods.

Animals↗
PubMed1989

Pulmonary phospholipids in amniotic fluid of pathologic pregnancies: relationship with clinical status of the newborn.

We evaluated phospholipids, C-peptide and cortisol levels in amniotic fluid of 203 pathologic pregnancies (63, class A, B and C diabetics; 11 class D, F and H diabetics; 44 preclampsia and 85 Rh-isoimmunization); the control group was 82 normal pregnant women. There was an acceleration of fetal pulmonary maturation in women with preclampsia and severe Rh-isoimmunization in class D, F and H diabetics (at 34 weeks gestation the incidence of mature surfactant (lecithin/sphingomyelin greater than or equal to 2.7 and presence of phosphatidyl-glycerol) in these groups was 30%, 50% and 100%, respectively, while it was zero in the control group). At 37 and 38 weeks only 44.4% of the class A, B and C diabetics had mature surfactant and there was a significant difference with respect to the control group (x2 = 4.9; p less than 0.05); C-peptide levels in these diabetics (class A, B and C) were higher than in controls (p less than 0.001); in pregnant women with accelerated fetal lung maturation they were lower. We demonstrated a close relationship between fetal pulmonary maturity and the type of surfactant in amniotic fluid, which was independent of gestational age.

Amniotic Fluid↗
PubMed1988

Effects of neonatal treatment with estrogens on the development of the thymus in rats.

In order to study the effects of sex hormones administered during the neonatal period on the thymic development we have injected 5 days old female rats with a single dose (0.1mg) of estradiol benzoate. The evolution of the thymus gland after treatment was morphometrically analyzed. The thymus of the estrogen-injected animals diminished in size between the 7th and the 15th day, increasing afterwards. The cortex was the most sensitive compartment in the thymus to estrogenic treatment. Both thymic involution and enlargement were associated to changes in the frequency of large lymphoid cells in the subcapsular region and variations in the thymic cortex weights. The observed effects are tentatively attributed to alterations in the thymocyte differentiation probably due to modifications in the secretion of thymic hormones.

Animals↗
PubMed1988

Alterations in the peripheral lymphoid organs and differential leukocyte counts in Saprolegnia-infected brown trout, Salmo trutta fario.

The number of circulating leukocytes and the structure of splenic and renal lymphoid tissue were comparatively analysed in healthy and Saprolegnia-infected wild brown trout, Salmo trutta fario. Sick trout showed lymphopenia, mainly due to decreased numbers of circulating small lymphocytes, and heterophilia. The splenic and renal lymphoid tissue of infected trout exhibited similar changes, consisting of cellular depletion, lymphoid cell degeneration, and vascular alterations with blood vessel enlargement and hypertrophy of sinusoidal endothelial cells. Furthermore, the endothelial cells in the spleen and kidney of the infected trout contained cytoplasmic vesicles filled with material of possible fungal origin. The absence of a reticular sheath was also evident in the splenic ellipsoids. These results suggest some immunodepression in Saprolegnia-infected trout which might favour the course of the disease.

Animals↗
PubMed1988

Amniotic fluid phospholipids and foetal lung maturation.

An analysis was made of samples of amniotic fluid from 82 pregnant women with normal pregnancies, ranging from 29 to 40 weeks of amenorrhoea. Lipid extraction was quantitative and individual phospholipids were isolated by two-dimensional chromatography. The lecithin/sphingomyelin ratio (L/S) increased significantly (t = 2.17; p less than 0.05) between 35 and 36 weeks of amenorrhoea (from 2.9 +/- 1.0 to 4.3 +/- 1.7). Phosphatidyl-glycerol (PG) was detected from 35 weeks of pregnancy, the time at which the incidence of amniotic samples with mature surfactant (L/S greater than or equal to 2.7 and presence of PG) was 9%; mature surfactant incidence increased to 55.5% at 36 weeks and 100% at 37 or more weeks. There was a good correlation between surfactant levels in amniotic fluid and new-born respiratory function.

Amniotic Fluid↗
PubMed1988

Detection of Thy-1+ cells in the developing thymus of the lizard, Chalcides ocellatus.

The ontogenic appearance of Thy-1+ cells was studied in the thymus of the lizard, Chalcides ocellatus, by indirect immunofluorescence using a rabbit antibrain antiserum produced against surface determinants shared by both the thymus and the brain lizards. Thymic Thy-1+ cells were first detected at stage 37. They increased rapidly reaching adult numbers by stage 41. Apparently Thy-1+ cells differentiate from lymphoid precursors arriving at the thymus analage before stage 37. The results are compared to those found during the differentiation of Thy-1+ thymocyte in murine thymus and agree with former reports on the thymic development in Chalcides using rabbit antisera against adult thymocyte marker(s).

Animals↗