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A Zapata

Publications and source records attributed to A Zapata.

At least 55 records · Page 3Linked to original sources
PubMed1994

Influence of metabolic control of pregnant diabetics on fetal lung maturity.

We studied the relationship between the metabolic control of pregnant diabetics and fetal lung maturity. In 31 diabetic and 20 normal pregnancies we analysed phospholipids in amniotic fluid and glycaemic control parameters. There were no differences in amniotic fluid lecithin/sphingomyelin (L/S) and phosphatidylinositol/sphingomyelin (PI/S) ratios between pregnant diabetics with strict metabolic control and the control group. Pregnant diabetics with poor metabolic control had significantly different L/S and PI/S ratios than the normal pregnant women. Six women in this group of poorly controlled diabetics had mature surfactant in amniotic fluid (L/S > or = 2.7 and presence of phosphatidylglycerol) at 32-34 weeks of amenorrhea; the difference was significant (p < 0.05) with respect to the control group. These six women had recurrent hypoglycaemic episodes (6.4 +/- 1.3 episodes/week) at 14-27 weeks of amenorrhea. Our findings suggest that hypoglycaemic stress on the fetus could disturb fetal synthesis of pulmonary phospholipids.

Adult↗
PubMed1994

In vitro effects of deoxyguanosine (dGuo) on thymic stromal cells. A discussion.

Different in vitro approaches have been used to enrich thymic epithelial cells for the analysis of their role in inducing tolerance. One widely used approach consists of the organ culture of mouse fetal thymic lobes (FTOCs) in the presence of 2'-deoxyguanosine (dGuo), that is thought to selectively eliminate both thymocytes and interdigitating cells/dendritic cells (IDCs/DCs) from the thymic cultured tissue. The dGuo-induced effects on rat thymic stromal cells appear to differ from those described in mouse. In this paper we present evidence supporting the presence of rat DCs in both thymic cultured fragments and thymic stromal cell primary cultures after dGuo treatment. Possible explanations for these contradictory results are discussed.

Animals↗
PubMed1994

Role of thymic stromal cells in thymocyte education: a comparitive analysis of different models.

The thymus is the privileged lymphoid organ for T-cell differentiation, including clonal selection. Precursor thymocytes are selected on the basis of their ability to recognize self-major histocompatibility complex molecules (MHC) that are expressed on thymic stromal cells, including epithelial cells, macrophages, and interdigitating cells/dendritic cells (IDCs/DCs). Epithelial cells have been associated with positive selection, and dendritic cells with negative selection, but the exact role played by these stromal elements is still unresolved. This review focuses on the different in vitro and in vivo approaches that have been used to elucidate the role of thymic stromal cell types in thymic function, and on a critical evaluation of these approaches.

Animals↗
PubMed1993

Characterization of distal lymphoid nodules in the chicken caecum.

In this report, we describe lymphoid nodules consistently found in the distal region of each chicken caecum at approximately 3 cm from the ileo-cecal junction. These structures were studied by light microscopy both in normal and Eimeria tenella-infected chickens. They were observed with the naked eye in infected birds but not in normal chickens. In these latter the region of the caecal lamina propria corresponding to that in which the lymphoid aggregates were visible revealed a light infiltration by diffuse lymphoid tissue as well as a few germinal centers. The distal lymphoid nodules were studied using a panel of monoclonal antibodies which are specific for chicken Ig-containing cells, macrophages, Ia-like positive cells, and interdigitating cells, as well as a policlonal antiserum reactive with S-100 protein to stain both interdigitating cells and follicular dendritic cells. The immunohistochemical study demonstrated the resemblance of these aggregates to the caecal tonsils, suggesting that they represent specialized mucosa-associated lymphoid tissue that respond to antigens in the caecal lumen, their function being to enhance the mucosal defense provided by the caecal tonsils against antigens in the lumen of the caeca.

Animals↗
PubMed1993

The neuro-endocrine component of the rat thymus: studies on cultured thymic fragments before and after transplantation in congenitally athymic and euthymic rats.

An immunohistochemical study was done for the presence of tyrosine hydroxylase (noradrenergic innervation), neuron-specific protein PGP9.5, and anterior pituitary hormones (beta-subunit of follicle-stimulating hormone, growth hormone, beta-subunit of luteinizing hormone, prolactin, and beta-subunit of thyroid-stimulating hormone) in cultured thymic fragments before and after transplantation in congenitally athymic and euthymic rats. The cultured thymic fragments consisted of epithelial cells and were depleted of lymphocytes. After implantation in syngeneic and allogeneic athymic recipients and in syngeneic euthymic recipients, a recovery of the original architecture was found within 6 weeks; rejection occurred within 3 weeks for allogeneic transplantation in euthymic rats. During culture nerve-like profiles almost disappeared from the tissue, and reappeared simultaneously with the influx of host-derived cells and the restoration of the original thymic architecture. A high immunoreactivity for hormones and PGP9.5 was found in epithelial cells after culture and in the first phase after transplantation. These epithelial cells may represent precursor-epithelial cells, based on their unusual ultrastructure and combined expression of markers that in the normal thymus occur only on subcapsular/medullary epithelium or on cortex epithelium. These data indicate a potential role of the neuroendocrine function of the thymus during restoration of the thymus architecture starting from precursor-like epithelial cells.

Adrenergic Fibers↗
PubMed1993

Limits of habituation and extinction: implications for relapse prevention programs in addictions.

Problems in the application of exposure techniques to the management of long term dishabituation in addicts are discussed in the light of human and animal evidence. Extinction and habituation of responses to drug cues or drug aftereffects are unstable and strongly dependent on context, thus limiting the effectiveness of cue exposure treatments in the prevention of relapse. Several strategies are suggested to improve the stability of extinction and habituation in order to enduringly prevent relapse in addictions. (i) Warning patients about the episodic resurgence of unexpected urges or cravings precipitated by conditioned contexts and exposing them to such contexts. (ii) To obtain a maximum protection against relapse, extinction should 'recreate' all the original learning contexts (i.e. all possible drug cues). (iii) The behavioral chains involved in self administering drugs ought to be incorporated into cue exposure treatments (without permitting consummatory responses) in order to decrease their signal value as cues for drugs.

Animals↗
PubMed1993

Cell-surface marker analysis of rat thymic dendritic cells.

Rat thymic dendritic cells have been isolated by collagenase digestion, separation of the low-density cell fraction by centrifugation on metrizamide, and differential adherence. The resulting dendritic cell preparation had a purity of > 90%, and has been analysed by flow cytometry (FCM) using a large panel of monoclonal antibodies (mAb). Dendritic cells expressed major histocompatibility (MHC) class I and class II molecules, the leucocyte common antigen CD45, the rat leucocyte antigen OX44, the rat macrophage marker ED1, and the adhesion molecules Mac-1, LFA-1 and ICAM-1. They were negative for the T- and B-cell-specific forms of CD45, CD45R and B220, and the B-cell marker OX12. Concerning T-cell marker expression, they were negative for T-cell receptor (TcR) and OX40, but they expressed CD2, CD4 and CD8, and interestingly, 50% of DC were CD5+, 50% expressed the alpha-chain of interleukin-2 receptor (IL-2R), and 80% were positive for the T-cell activation antigen recognized by the mAb OX48. Moreover, 60% of DC expressed high levels of Thy-1, whereas 40% displayed intermediate levels of this T-cell marker.

Animals↗
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↗