Biomedical subjects

M Cernadas

Publications and source records attributed to M Cernadas.

10 recordsLinked to original sources

PubMed2001

Integrin alpha E(CD103)beta 7 mediates adhesion to intestinal microvascular endothelial cell lines via an E-cadherin-independent interaction.

Integrins are important for T cell interactions with endothelial cells. Because the integrin alpha(E)beta(7) is expressed on some circulating gut-homing T cells and as T cell numbers are reduced in the intestinal lamina propria of alpha(E)-deficient mice, we evaluated whether alpha(E)beta(7) mediates binding to intestinal endothelial cells. We found that anti-alpha(E)beta(7) mAbs partially blocked the binding of cultured intraepithelial T cells to human intestinal microvascular endothelial cells (HIMEC). Furthermore, alpha(E)beta(7)-transfected K562 cells bound more efficiently than vector-transfected K562 cells to HIMEC. Finally, HIMEC bound directly to an alpha(E)beta(7)-Fc fusion protein. These interactions were partially blocked by anti-alpha(E)beta(7) mAbs, and endothelial cell binding to the alpha(E)beta(7)-Fc was dependent upon the metal ion-dependent adhesion site within the alpha(E) A domain. Of note, the HIMEC lacked expression of E-cadherin, the only known alpha(E)beta(7) counterreceptor as assessed by functional studies, flow cytometry, and RT-PCR. Thus, HIMEC/alpha(E)beta(7) binding was independent of E-cadherin. In addition, this interaction appeared to be tissue selective, as HIMEC bound to the alpha(E)beta(7)-Fc, whereas microvascular endothelial cells from the skin did not. Finally, there was evidence for an alpha(E)beta(7) ligand on intestinal endothelial cells in vivo, as alpha(E)beta(7) expression enhanced lymphocyte binding around vessels in the lamina propria in tissue sections. Thus, we have defined a novel interaction for alpha(E)beta(7) at a nonepithelial location. These studies suggest a role for alpha(E)beta(7) in interactions with the intestinal endothelium that may have implications for intestinal T cell homing or functional responses.

Antibodies, Blocking↗

PubMed2000

The role of alpha and beta chains in ligand recognition by beta 7 integrins.

Integrins alpha(E)beta(7) and alpha(4)beta(7) are involved in localization of leukocytes at mucosal sites. Although both alpha(E)beta(7) and alpha(4)beta(7) utilize the beta(7) chain, they have distinct binding specificities for E-cadherin and mucosal addressin cell adhesion molecule-1 (MAdCAM-1), respectively. We found that mutation of the metal ion-dependent adhesion site (MIDAS) in the alpha(E) A-domain (D190A) abolished E-cadherin binding, as did mutation F298A on the A-domain surface near the MIDAS cleft. A docking model of the A-domain with E-cadherin domain 1 indicates that coordination of the alpha(E) MIDAS metal ion by E-cadherin Glu(31) and a novel projection of Phe(298) into a hydrophobic pocket on E-cadherin provide the basis for the interaction. The location of the binding site on the alpha(E) A-domain resembles that on other integrins, but its structure appears distinctive and particularly adapted to recognize the tip of E-cadherin, a unique integrin ligand. Additionally, mutation of the beta(7) MIDAS motif (D140A) abolished alpha(E)beta(7) binding to E-cadherin and alpha(4)beta(7)-mediated adhesion to MAdCAM-1, and alpha(4) chain mutations that abrogated binding of alpha(4)beta(1) to vascular cell adhesion molecule-1 and fibronectin similarly reduced alpha(4)beta(7) interaction with MAdCAM-1. Thus, although specificity can be determined by the integrin alpha or beta chain, common structural features of both subunits are required for recognition of dissimilar ligands.

Amino Acid Sequence↗

PubMed2000

B7-1 (CD80) and B7-2 (CD86) have complementary roles in mediating allergic pulmonary inflammation and airway hyperresponsiveness.

We examined the roles of B7-1 (CD80) and B7-2 (CD86) in a model of allergic pulmonary inflammation and airway hyperresponsiveness (AHR) by using mice with germline deletions of the B7-1 and/or B7-2 molecules. Multiple parameters of the allergic response were affected to varying degrees by the absence of B7-1 and/or B7-2. Mice lacking both B7-1 and B7-2 had no elevation of serum immunoglobulin E, lack of airway eosinophilia, and no AHR. These same disease parameters were also reduced in mice lacking either B7-1 or B7-2. Lack of B7-1 and/or B7-2 resulted in an increase in T-helper 1 cytokine production. Our observations suggest that whereas B7-2 is quantitatively more significant in the induction of this response, B7-1 and B7-2 may have complementary roles in mediating the development of allergic pulmonary inflammation.

Animals↗

PubMed1999

CD23 and allergic pulmonary inflammation: potential role as an inhibitor.

CD23, a receptor for immunoglobulin E, is expressed at increased levels in asthmatic and atopic individuals and has been associated with disorders characterized by chronic inflammation. Using an established murine model, we employed several complementary strategies to investigate the role of CD23 in allergic pulmonary inflammation and airway hyperresponsiveness (AHR). Specifically, these approaches included the modulation of CD23 function in vivo by administration of anti-CD23 monoclonal antibody (mAb) or Fab fragments to wild-type mice and the analysis of CD23-deficient mice. Administration of anti-CD23 mAb, but not anti-CD23 Fab fragments, produced attenuation of pulmonary inflammation, AHR, and CD8(+) T-cell activation. On the basis of a model that the anti-CD23 mAb transduces, whereas the Fab fragment inhibits, CD23 signaling, these results suggest that CD23 negatively regulates pulmonary inflammation and AHR. This hypothesis is supported by our observation that CD23-deficient mice developed increased inflammation and AHR after sensitization and challenge with allergen. Together, these results indicate that CD23 negatively regulates pulmonary inflammation and airway hyperreactivity.

Animals↗

PubMed1996

Inhibition of T cell costimulation abrogates airway hyperresponsiveness in a murine model.

Activation of naive T cells requires at least two signals. In addition to the well characterized interaction of the T cell antigen receptor with the antigen/MHC expressed on an antigen-presenting cell, T cell activation also requires costimulation by a second set of signals. The best characterized costimulatory receptor is CD28, which binds to a family of B7 ligands expressed on antigen-presenting cells. In asthma, although activated T cells play a role in the initiation and maintenance of airway inflammation, the importance of T cell costimulation in bronchial hyperresponsiveness had not been characterized. Therefore, we tested the hypothesis that inhibition of the CD28:B7 costimulatory pathway would abrogate airway hyperresponsiveness. Our results show that blockade of costimulation with CTLA4-Ig, a fusion protein known to prevent costimulation by blocking CD28:B7 interactions, inhibits airway hyperresponsiveness, inflammatory infiltration, expansion of thoracic lymphocytes, and allergen-specific responsiveness of thoracic T cells in this murine model of allergic asthma.

Airway Resistance↗

PubMed1996

T cell activation in a murine model of asthma.

To determine the mechanisms by which inhaled antigens produce pulmonary inflammation and bronchial hyperreactivity, we have developed a murine model of asthma. BALB/c mice are sensitized and challenged with ovalbumin (OVA). Compared with mice treated with phosphate-buffered saline (PBS), OVA-treated mice developed increased lung resistance, decreased dynamic compliance, and greater methacholine reactivity. Bronchoalveolar lavage fluid revealed significant increases in the proportion of neutrophils and eosinophils. Tissue sections of OVA-treated mice demonstrated goblet cell metaplasia and focal perivascular and peribronchial infiltrates composed of lymphocytes, neutrophils, and eosinophils. Analysis of thoracic lymphocytes via flow cytometry revealed an expansion of both CD4+ and B cell populations, with increased expression of interleukin-2 receptor on CD4+ T cells, indicated increased activation. There was also increased expression of CD44 on CD4+ and CD8+ lymphocytes, suggesting an expansion of the local memory cell population. These findings support the hypothesis that activation of T lymphocytes mediates allergic pulmonary inflammation and bronchial reactivity in asthma.

Animals↗

PubMed1995

Comparison of the effects of meperidine and nalbuphine on intrapartum fetal heart rate tracings.

OBJECTIVE: To examine the effects of meperidine and nalbuphine on intrapartum fetal heart rate (FHR) tracings using computer analysis. METHODS: We studied 28 women with uncomplicated pregnancies in early labor at term with reactive FHR tracings. The women were randomized to receive either meperidine 50 mg or nalbuphine 10 mg intravenously on request. One-hour FHR recordings were obtained before and immediately after administration of the medications. RESULTS: There were no significant differences in the FHR characteristics of the two groups during the pre-treatment period. Nalbuphine significantly decreased the number of accelerations of 10 beats per minute (17 versus 4, P = .003) and 15 beats per minute (10 versus 1.5, P = .001), time spent in episodes of high variation (35.5 versus 10 minutes, P = .004), long-term variation (47 versus 29.8 milliseconds, P = .002), and short-term variation (8.4 versus 6.4 milliseconds, P = .03). Meperidine had no significant effect on any FHR characteristic. CONCLUSION: In the early intrapartum period of normal term pregnancies and at commonly used dosages, nalbuphine had a significant effect on FHR tracings, whereas meperidine had no effect, as determined by computer analysis.

Adolescent↗

PubMed1992

Glycation alters collagen fibril organization.

Incubation of rat tail tendon in 0.2M ribose results in accelerated non-enzymatic glycosylation of collagen, with the formation of fluorescent cross-links between molecules and decreased solubility. Electron micrographs of tendon cross-sections show an increased fibril packing density with increasing degrees of glycation. After a one-week incubation in ribose, every fibril appears in close contact with all of its neighbors, and the packing density has increased to 76%, from a value of 62% in controls. Irregular diameters and fusion of fibrils also are seen. All of the fibrils in a bundle appear to become cross-linked together, creating a larger stress bearing unit. This model is consistent with stress-strain curves showing a large increase in tensile stress and stiffness after a one-week incubation period in ribose. The diameters of the collagen fibrils increase in size in glycated tendon. We hypothesize larger diameters result from an increased resistance to shrinkage during the specimen preparation process, as a result of the rigid sugar derived cross-links. Closer fibril packing, increased fibril diameters, and irregular diameters have been reported in diabetic tissues, and may result from decades of glycation induced cross-link accumulation.

Animals↗

PubMedDate not supplied

Effects of placental delivery method and intraoperative glove changing on postcesarean febrile morbidity.

This study was designed to evaluate the effects of the placental delivery methods and intraoperative glove changing on postcesarean febrile morbidity. In this randomized controlled trial, consenting patients were randomized to one of four management protocols: Group A (n = 26)--no glove change with manual placental delivery; Group B (n = 27)--no glove change with expressed placental delivery; Group C (n = 27)--glove change with manual placental delivery; and Group D (n = 28)--glove change with expressed placental delivery. Glove change was performed by removal of a second glove after delivery of the fetal head. Variables examined included febrile morbidity, endometritis, maximums and durations of elevated temperatures, as well as other demographic, intrapartum, and postpartum variables. Febrile morbidity and endometritis rates were not significantly different between the four groups. When the groups were combined so as to compare no glove change versus glove change (Groups A and B vs. C and D) and manual versus expressed placental delivery (Groups A and C vs. B and D), there were no significant differences in either febrile morbidity (relative risk: 0.7, 95% CI: 0.3-1.4 and relative risk: 1.4, 95% CI: 0.6-3.5) or endometritis (relative risk: 1.2, 95% CI: 0.5-2.8 and relative risk: 1.5, 95% CI: 0.6-3.6), respectively. There were no statistically significant differences in measures of postcesarean febrile morbidity based on placental delivery method or intraoperative glove change.

Cesarean Section↗

PubMedDate not supplied

Direct regulation of Na(+)-dependent myo-inositol transport by sugars in retinal pigment epithelium: role of phorbol ester and staurosporin.

An Na(+)-dependent active process for myo-inositol (MI) uptake, sharing a common carrier system with glucose and sensitive to phlorizin, was previously established in primary cultures of bovine retinal pigment epithelial (RPE) cells (26, 32). The present report further examines the nature of glucose-induced inhibition of MI transport in primary cultures of RPE cells. RPE cells were grown in supplemented Dulbecco's modification of Eagle's medium (DMEM) containing 5 mM D-glucose (basic growth media) or 40 mM D-glucose or its nonmetabolizable analogue, alpha-methyl-D-glucoside (alpha MG); 1-5 mM nonradioactive MI, pyruvate, or lactate; or 0.2-20 microM phorbol 12-myristate 13-acetate (TPA) or straurosporin (modified growth media), for up to 4 weeks. The capacity of RPE cells to accumulate 3H-MI (ratios of intracellular transported radioactive MI, [MI]i, to external free MI concentration, [MI]i/[MI]o) decreased by up to 41% or 34% when cells were grown for 10 days or longer with 40 mM D-glucose or 40 mM alpha MG, respectively, compared to cells grown in basic growth media. The rate of uptake of 3H-MI also was reduced to 63 +/- 15% or 48 +/- 8% of the control values when cells were fed 1 or 5 mM nonradioactive MI, respectively. In addition, cellular capacity to bind to [3H]phlorizin was reduced to 52 +/- 7%, 61 +/- 5%, or 38 +/- 6% of the controls when RPE cells were fed 40 mM D-glucose, 40 mM alpha MG, or 5 mM nonradioactive MI, respectively. Growth media containing either pyruvate or lactate, the glucose metabolites, did not suppress the ability of RPE cells to accumulate MI. An 18 +/- 8% reduction in [3H]thymidine incorporation into DNA occurred when cells were grown in 40 mM glucose for 12-14 days, compared to cells grown with 5 mM glucose. Chronic treatment (12-14 days) of the cells with phorbol ester, an activator of protein kinase C, caused up to twofold increase in MI uptake, [3H]phlorizin binding, cell number, and DNA synthesis. However, when the rates of MI uptake into cells grown in basic growth media or TPA-treated media were normalized to cell number, no significant difference in MI uptake was found between the treated and untreated cells. Addition of staurosporin, a protein kinase C inhibitor, together with TPA, in the growth media reversed the phorbol-induced increase of MI uptake.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkaloids↗