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M Nieto

Publications and source records attributed to M Nieto.

At least 37 records · Page 2Linked to original sources
PubMed1998

CD43 interacts with moesin and ezrin and regulates its redistribution to the uropods of T lymphocytes at the cell-cell contacts.

Chemokines as well as the signaling through the adhesion molecules intercellular adhesion molecule (ICAM)-3 and CD43 are able to induce in T lymphocytes their switching from a spherical to a polarized motile morphology, with the formation of a uropod at the rear of the cell. We investigated here the role of CD43 in the regulation of T-cell polarity, CD43-cytoskeletal interactions, and lymphocyte aggregation. Pro-activatory anti-CD43 monoclonal antibody (MoAb) induced polarization of T lymphocytes with redistribution of CD43 to the uropod and the CCR2 chemokine receptor to the leading edge of the cell. Immunofluorescence analysis showed that all three ezrin-radixin-moesin (ERM) actin-binding proteins localized in the uropod of both human T lymphoblasts stimulated with anti-CD43 MoAb and tumor-infiltrating T lymphocytes. Radixin localized at the uropod neck, whereas ezrin and moesin colocalized with CD43 in the uropod. Biochemical analyses showed that ezrin and moesin coimmunoprecipitated with CD43 in T lymphoblasts. Furthermore, in these cells, the CD43-associated moesin increased after stimulation through CD43. The interaction of moesin and ezrin with CD43 was specifically mediated by the cytoplasmic domain of CD43, as shown by precipitation of both ERM proteins with a GST-fusion protein containing the CD43 cytoplasmic tail. Videomicroscopy analysis of homotypic cell aggregation induced through CD43 showed that cellular uropods mediate cell-cell contacts and lymphocyte recruitment. Immunofluorescence microscopy performed in parallel showed that uropods enriched in CD43 and moesin localized at the cell-cell contact areas of cell aggregates. The polarization and homotypic cell aggregation induced through CD43 was prevented by butanedione monoxime, indicating the involvement of myosin cytoskeleton in these phenomena. Altogether, these data indicate that CD43 plays an important regulatory role in remodeling T-cell morphology, likely through its interaction with actin-binding proteins ezrin and moesin. In addition, the redistribution of CD43 to the uropod region of migrating lymphocytes and during the formation of cell aggregates together with the enhancing effect of anti-CD43 antibodies on lymphocyte cell recruitment suggest that CD43 plays a key role in the regulation of cell-cell interactions during lymphocyte traffic.

Antigens, CD↗
PubMed1998

The chemokine SDF-1alpha triggers a chemotactic response and induces cell polarization in human B lymphocytes.

We studied the expression and possible functional role of chemokine receptors CXCR3, CXCR4 and CCR5 in normal human B lymphocytes. B cells from both peripheral blood and tonsils expressed high levels of CXCR4 but not the other chemokine receptors tested. CXCR4 ligand, stromal cell-derived factor (SDF)-1alpha, elicited a potent chemotactic response and induced a polarized motile phenotype in B cells, resulting in redistribution of the adhesion molecule ICAM-3 to a posterior appendage of the cell, termed uropod, and of CXCR4 receptor to the leading edge of migrating B cells. Time-lapse videomicroscopy studies revealed that SDF-1alpha-treated cells recruited additional bystander B cells through the uropod. SDF-1alpha induced levels of cellular recruitment comparable to those elicited by polarization-inducing anti-ICAM-3 monoclonal antibody, in an LFA-1/ICAM-1, -3-dependent fashion. Moreover, this chemokine increased intracellular Ca2+ levels in B lymphocytes, and induced a rapid CXCR4 receptor down-regulation on the cell surface membrane. These results provide new insight into the important biological role of SDF-1alpha in physiological processes in which B cells participate, and suggest a key role for chemokines in normal B cell trafficking and recirculation.

Antigens, CD↗
PubMed1998

Effect of miglitol administration to non-insulin-dependent diabetic rats.

1. The effect of the acute or chronic oral administration of miglitol (Bay M 1099 alpha-glucosidase inhibitor) to non-insulin-dependent diabetic rats was studied. 2. The acute oral administration of miglitol (10 mg/kg b.w.) reduced significantly the increment of blood glucose after oral maltose (2 g/kg b.w.) overload (364 +/- 58 and 205 +/- 12 mmol/90 min, without and with miglitol respectively; P < 0.05). 3. Under chronic oral administration of miglitol (10 mg/kg b.w.), two days after the start of treatment the blood glucose dropped from 7.53 +/- 9.59 to 4.40 +/- 5.50 mmol/l. The plasma insulin, cholesterol, or triglycerides levels were not modified. 4. A significant reduction (P < 0.01) in water and food intake was observed. Normal rats values were not affected by miglitol treatment.

1-Deoxynojirimycin↗
PubMed1998

Mode of action of sulfanilyl fluoroquinolones.

The mode of action of sulfanilyl fluoroquinolones (NSFQs) was investigated with NSFQ-104, NSFQ-105, and some structurally related compounds. Evidence arising from interactions with p-aminobenzoic acid and trimethoprim suggested that a sulfonamidelike mechanism of action makes little or no contribution to the in vitro activity of NSFQs. NSFQ-105 showed an activity that inhibits gyrase-catalyzed DNA supercoiling that is similar to the activity of other fluoroquinolones. Also, NSFQ-105 uptake was decreased by the presence of Mg2+ and increased by a lower pH. These results indicate that NSFQs having only one ionizable group could exhibit more favorable kinetics of access to the bacterial cell than zwitterionic fluoroquinolones.

Anti-Infective Agents↗
PubMed1998

Differential effects of antibodies to vascular cell adhesion molecule-1 and distinct epitopes of the alpha4 integrin in HgCl2-induced nephritis in Brown Norway rats.

Four distinct epitopes (A, B1, B2, and C) have been functionally defined on the human alpha4 integrin. In this study, two cross-reactive antihuman alpha4 monoclonal antibodies (mAb) (HP2/1 and HP2/4 specific for epitopes B1 and B2, respectively) were used to functionally characterize the rat VLA-4 subunit and to define similar functional epitopes in this rodent species. It was found that B1 and B2 anti-alpha4 mAb completely block adhesion to fibronectin, but the inhibition of adhesion to vascular cell adhesion molecule-1 (VCAM-1) with HP2/1 mAb was lower than with HP2/4 mAb. It was also observed that epitope B2 HP2/4 mAb induced homotypic aggregation in rat lymphocytes, whereas epitope B1 HP2/1 mAb did not. Using the HgCl2 model of nephritis, this study shows the protective effect of both anti-alpha4 mAb against infiltration of the renal interstitium by leukocytes. Nevertheless, HP2/1 mAb, but not HP2/4 mAb, virtually abolished the anti-glomerular basement membrane antibody synthesis and glomerular deposits. These findings indicate the dual but independent role played by alpha4 integrins in both extravasation of leukocytes and in the production of antibodies. Finally, this study demonstrates that anti-rat VCAM-1 mAb showed a positive reactivity of the renal vascular endothelium and, most importantly, that administration of anti-VCAM-1 antibodies completely abrogated the interstitial cell infiltrates without affecting anti-glomerular basement membrane antibody production. These results confirm the important role played by VLA-4/VCAM-1 pathway in leukocyte infiltration, and further support the dual and independent role of alpha4 integrins in both renal infiltration and autoantibody synthesis in this model of renal disease.

Analysis of Variance↗
PubMed1998

The two poles of the lymphocyte: specialized cell compartments for migration and recruitment.

Chemotaxis, the directed migration of leukocytes towards a chemoattractant gradient, is a key phenomenon in the immune response. During lymphocyte-endothelial and -extracellular matrix interactions, chemokines induce the polarization of T lymphocytes, with generation of specialized cell compartments. The chemokine receptors involved in detection of the chemoattractant gradients concentrate at the leading edge (advancing front or anterior pole) of the cell. The adhesion molecules ICAM-1, -3, CD44 and CD43 redistribute to the uropod, an appendage at the posterior pole of migrating T lymphocyte that protrudes from the contact area with endothelial or extracellular matrix substrates. Whereas chemokine receptors sense the direction of migration, the uropod is involved in the recruitment of bystander leukocytes through LFA-1/ICAM-dependent cell-cell interactions. While beta-actin concentrates preferentially at the cell's leading edge, the motor protein myosin II and a microtubule organizing center (MTOC) are packed in the uropod. The actin-binding protein moesin, which belongs to the ERM family of ezrin, radixin and moesin, redistributes to the distal portion of uropods and physically interacts with ICAM-3, CD44 and CD43, thus acting as a physical link between the membrane molecules and the actin cytoskeleton. Moreover, the moesin-ICAM-3 association correlates with the degree of cell polarity. The redistribution of the chemokine receptors and adhesion molecules to opposite poles of the cell in response to a chemoattractant gradient may guide cell migration and cell-cell interactions during lymphoid cell trafficking in immune and inflammatory responses.

Animals↗
PubMed1997

A novel region of the alpha4 integrin subunit with a modulatory role in VLA-4-mediated cell adhesion to fibronectin.

The integrin VLA-4 (alpha4 beta1) is a receptor for fibronectin and vascular cell-adhesion molecule 1 (VCAM-1). Four functionally different epitopes, designated A, B1, B2 and C, have previously been defined on the alpha4 subunit. Using K562 alpha4 mutant transfectants we found that alpha4 amino acids Tyr151, Gln152, Asp153, Tyr154 and Val155 are important for the structure of the epitope B2. Mutations at alpha4 Gln152 substantially impaired the transfectant adhesion to a CS-1-containing fragment of fibronectin (FN-H89), whereas this adhesion was not affected on the other alpha4 mutant transfectants. None of the alpha4 mutations significantly altered the adhesion of the different alpha4 transfectants to VCAM-1. In addition, we have identified residues Gln152, Asp153 and Tyr154 as part of the alpha4 epitope B2 involved in homotypic cell aggregation. The decrease in adhesion to FN-H89 shown by Gln152 alpha4 mutant transfectants was the result of an inefficient binding of FN-H89 by VLA-4 mutated at this residue. Also, mutant VLA-4 displayed an altered reactivity with HUTS-21, an anti-beta1 monoclonal antibody that reacts with functionally active VLA integrins. Adhesion to FN-H89 was not restored unless stimuli that increase the ligand-binding affinity of VLA heterodimers were added, suggesting that cell adhesion was affected in the initial phases. These results indicate that alpha4 Gln152 modulates cell adhesion to FN-H89 by playing important roles in the maintenance and/or the acquisition of an active state of VLA-4, an integrin that is normally expressed on the cell surface in a range of multiple activation states. The location of the alpha4 Gln152 residue on a loop of the upper surface of the proposed beta-propeller structure suggests a close association with potential ligand-binding sites.

Antibodies, Monoclonal↗
PubMed1997

Polarization of chemokine receptors to the leading edge during lymphocyte chemotaxis.

Leukocyte migration in response to cell attractant gradients or chemotaxis is a key phenomenon both in cell movement and in the inflammatory response. Chemokines are quite likely to be the key molecules directing migration of leukocytes that involve cell polarization with generation of specialized cell compartments. The precise mechanism of leukocyte chemoattraction is not known, however. In this study, we demonstrate that the CC chemokine receptors CCR2 and CCR5, but not cytokine receptors such as interleukin (IL)-2Ralpha, IL-2Rbeta, tumor necrosis factor receptor 1, or transforming growth factor betaR, are redistributed to a pole in T cells that are migrating in response to chemokines. Immunofluorescence and confocal microscopy studies show that the chemokine receptors concentrate at the leading edge of the cell on the flattened cell-substratum contact area, induced specifically by the signals that trigger cell polarization. The redistribution of chemokine receptors is blocked by pertussis toxin and is dependent on cell adhesion through integrin receptors, which mediate cell migration. Chemokine receptor expression on the leading edge of migrating polarized lymphocytes appears to act as a sensor mechanism for the directed migration of leukocytes through a chemoattractant gradient.

Cells, Cultured↗
PubMed1996

Interleukin-15 induces adhesion receptor redistribution in T lymphocytes.

Chemotactic factors such as cytokines and chemokines direct the migration of leukocytes into inflammatory sites. Chemokines play a role regulating both the expression and adhesive properties of leukocyte integrins. We have recently described an additional function of chemokines in the induction of cell polarization and adhesion receptor redistribution during the initial step of leukocyte locomotion. We herein report that interleukin (IL)-15, a newly described cytokine with chemotactic properties, is able to induce uropod formation on T lymphoblasts to which intercellular adhesion molecule (ICAM)-3, a leukocyte-restricted counter-receptor for the lymphocyte function-associated antigen (LFA)-1 integrin, is redistributed. Other adhesion molecules, such as ICAM-1, ICAM-2, CD43 and CD44, also redistributed to the uropod, although in a lower proportion of the cells. The induction of uropod formation by IL-15 was observed on T lymphoblasts adhering to the integrin ligands fibronectin, vascular cell adhesion molecule (VCAM)-1 and ICAM-1, but not to bovine serum albumin or poly-L-lysine. The effect of IL-15 was dose dependent and specifically inhibited by a monoclonal antibody (mAb) against this cytokine. Blocking experiments with anti-IL-2 receptor beta chain mAb showed an inhibitory effect on IL-15-mediated redistribution of ICAM-3, whereas no effect was observed in the presence of anti-IL-2 receptor alpha chain mAb. The uropod induced by IL-15 is enriched in many different adhesion receptors and, being well exposed to the external milieu, is likely to modulate the adhesive properties of lymphocytes.

Antigens, CD↗
PubMed1996

Expression of functionally active alpha 4 beta 1 integrin by thymic epithelial cells.

We have investigated the expression and function of the VLA-4 heterodimer alpha 4 beta 1, a member of the beta 1 integrin subfamily, on human thymic epithelial cells (TEC) derived from cortical epithelium. The expression of the alpha 4 integrin chain was studied in four different cloned TEC lines derived from either fetal or post-natal human thymus by both flow cytometry and immunoprecipitation techniques with anti-alpha 4 MoAbs. All different cell lines assayed expressed significant levels of alpha 4, as revealed by their reactivity with MoAbs specific for distinct alpha 4 epitopes. The alpha 4 subunit expressed by TEC was associated to beta 1 but not to beta 1 chain, and displayed the characteristic 80/ 70 kD pattern of proteolytic cleavage. The VLA-4 integrin in these cells was constitutively active in terms of adhesiveness to both fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In addition, this heterodimer localized to punctate regions of the cell in the area of contact with the substratum, named point contacts assessed by staining with the anti-beta 1 activation epitope 15/7 MoAb. According to the cortical origin of the TEC lines expressing VLA-4, human thymus sections stained with different anti-alpha 4 antibodies revealed the presence of cortical, and in smaller numbers medullary epithelial cells bearing alpha 4 integrin. The expression of alpha 4 in the thymus was also found in both adult and fetal rats, in which epithelial cells were also specifically stained. Altogether, our data show that VLA-4 is an additional component of the integrin repertoire of TEC, and suggest that it could have an important role in thymus epithelial cell-thymocyte interactions.

Animals↗
PubMed1996

In vitro study of the effect of miglitol on carbohydrate digestion and intestinal metabolism in normal and non-insulin-dependent diabetic rats.

The effect of miglitol was studied (20 mg/kg body weight), administered intraduodenally alone or together with maltose, on the absorption and intestinal metabolism of glucose during its translocation from the lumen of the intestine to the blood, using in vitro perfused preparations of complete small intestine-pancreas, proximal small intestine alone, or distal small intestine alone, isolated from normal and non-insulin-dependent diabetic rats. In the absence of a luminal administration of maltose in normal rats, the glucose uptake from the vascular perfusate was greater in the presence (0.52 +/- 0.04 mmol/h) than in the absence (0.39 +/- 0.02 mmol/h) of miglitol (p < 0.05). In diabetic rats, no significant variations were observed in glucose uptake from the vascular perfusate as an effect of miglitol, but the glucose uptake in the presence of this drug was significantly less (p < 0.05) than that observed in normal rats. Portal lactate was significantly greater (p < 0.05) in diabetic than in normal rats and, after administration of miglitol, rose in both normal and diabetic rats, the rise being significantly greater in normal than in diabetic rats (p < 0.01). When maltose was administered luminally (2 g/kg body weight), the values of portal glucose in both normal and diabetic rats were significantly less in the presence of miglitol in the complete as well as in the distal and proximal small intestine preparations (p < 0.05); the glucose uptake from luminal administered maltose was greater in the presence of miglitol in diabetic (p < 0.05) and in normal (p < 0.05) rats except in the complete small intestine of normal rats; and no significant differences were observed in portal lactate levels between normal and diabetic rats in the presence of miglitol. In conclusion, our results show that miglitol administered luminally at the doses employed here, as well as reducing the transport of glucose from the lumen of the intestine into the blood supply, significantly stimulate intestinal glucose metabolism.

1-Deoxynojirimycin↗
PubMed1996

[The presentation form of headache in children].

The purpose of the present study was to assess an retrospective analysis on 167 children with chronic or severe headache, ranged in age from 2 to 14 years (7.19 +/- 2.36 years old) who were referred to the pediatric neurology service of Virgen del Rocio Hospital of Sevilla from december 1992 to december 1994. The most common type of headache was migraine which constituted 43.91% of all these cases. Tension headache accounted for 27.71%. A family history of headache, primarily maternal, was found in 114 patients in whom it could be evaluated. Children with migraine had a greater proportion of mothers with a history of migraine than those with tension headache. No significant variations were observed between chronic evolution and acute. We conclude that headache is not uncommon in children and it treatment must be individualized and requires more than just the use of pharmacotherapy.

Adolescent↗
PubMed1996

[Cranioencephalic cutaneous angiofibromatosis].

A nine year old girl with no significant prenatal or perinatal history had presented, at the age of four months, with infantile spasms and later with partial crises with or without secondary generalization. On examination there was left hemiparesis and various skin lesions: a pink plaque in the frontal region with hair loss, fibrous plaques on the right side of the face and hypomelanic spots on the trunk and thighs and some cafe-au-lait spots on the thorax and abdomen. On neuroimaging by CT and MR right cerebral hemiatrophy, periventricular calcifications and lesions in the right hemisphere were seen. On AMR an angioma was seen on the anterior communicating artery. A skin biopsy of the frontal plaque showed perifollicular fibromatosis with marked vascular proliferation. We discuss whether the presentation of this case of encephalocraneo-cutaneous angiofibromatosis is a new phenotype of tuberose sclerosis or a new neurocutaneous syndrome.

Age of Onset↗
PubMed1995

Chemokines regulate cellular polarization and adhesion receptor redistribution during lymphocyte interaction with endothelium and extracellular matrix. Involvement of cAMP signaling pathway.

Leukocyte recruitment is a key step in the inflammatory reaction. Several changes in the cell morphology take place during lymphocyte activation and migration: spheric-shaped resting T cells become polarized during activation, developing a well defined cytoplasmic projection designated as cellular uropod. We found that the chemotactic and proinflammatory chemokines RANTES, MCP-1, and, to a lower extent, MIP-1 alpha, MIP-1 beta, and IL-8, were able to induce uropod formation and ICAM-3 redistribution in T lymphoblasts adhered to ICAM-1 or VCAM-1. A similar chemokine-mediated effect was observed during T cells binding to the fibronectin fragments of 38- and 80-kD, that contain the binding sites for the integrins VLA-4 and VLA-5, respectively. The uropod structure concentrated the ICAM-3 adhesion molecule (a ligand for LFA-1), and emerged to the outer milieu from the area of contact between lymphocyte and protein ligands. In addition, we found that other adhesion molecules such as ICAM-1, CD43, and CD44, also redistributed to the lymphocyte uropod upon RANTES stimulation, whereas a wide number of other cell surface receptors did not redistribute. Chemokines displayed a selective effect among different T cell subsets; MIP-1 beta had more potent action on CD8+ T cells and tumor infiltrating lymphocytes (TIL), whereas RANTES and MIP-1 alpha targeted selectively CD4+ T cells. We have also examined the involvement of cAMP signaling pathway in uropod formation. Interestingly, several cAMP agonists were able to induce uropod formation and ICAM-3 redistribution, whereas H-89, a specific inhibitor of the cAMP-dependent protein kinase, abrogated the chemokine-mediated uropod formation, thus pointing out a role for cAMP-dependent signaling in the development of this cytoplasmic projection. Since the lymphocyte uropod induced by chemokines was completely abrogated by Bordetella pertussis toxin, the formation of this membrane projection appears to be dependent on G proteins signaling pathways. In addition, the involvement of myosin-based cytoskeleton in uropod formation and ICAM-3 redistribution in response to chemokines was suggested by the prevention of this phenomenon with the myosin-disrupting agent butanedione monoxime. Interestingly, this agent also inhibited the ICAM-3-mediated cell aggregation, but not the cell adhesion to substrata. Altogether, these results demonstrate that uropod formation and adhesion receptor redistribution is a novel function mediated by chemokines; this phenomenon may represent a mechanism that significantly contributes to the recruitment of circulating leukocytes to inflammatory foci.

Antigens, CD↗
PubMed1995

[Graphic presentation in the displacement and approbation of nature in botanical expeditions in the 18th century].

My purpose, on this work, is to illustrate the central role that plays the visual representations on the botanical exploration. I used documents (graphics and written) from the school of painting of José Celestinno Mutis in Santa Fe de Bogotá, that informs us about artists' training and the process of elaboration of sheets; the same as in the newspapers of Ruiz and Pavón during the publication of the Flora Peruviana. The artist's in the process of classification (construction) of new species active function stands out.

Botany↗
PubMed1994

Site-directed mutagenesis of cysteine residues of hepatitis B surface antigen. Analysis of two single mutants and the double mutant.

The structure of hepatitis B surface antigen (HBsAg) is mainly maintained by an intricate disulfide network responsible for most of its structural and antigenic properties. Characterization of three cysteine-replacement mutants of HBsAg has been performed by both structural and immunological methods. Replacement of Cys121 or Cys124 with serine results in mutant proteins that show diminished binding titres to both monoclonal antibodies and to a polyclonal serum, indicating that a structural change has taken place. Circular dichroism analysis shows that the substitution of either of these two residues also diminishes the helical content of the protein. However, the double mutant, in which both cysteine residues have been simultaneously changed, reverts the properties of the single mutations, and shows similar behaviour to the wild-type protein. Both the single and double cysteine mutants are efficiently glycosylated and secreted from Chinese hamster ovary cells and, in all cases, the mutant proteins assemble into spherical particles of similar buoyant density to both the wild-type and serum derived HBsAg.

Animals↗