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At least 793 records · Page 44Linked to original sources
PubMed2001

The v-Src SH3 domain facilitates a cell adhesion-independent association with focal adhesion kinase.

Integrins facilitate cell attachment to the extracellular matrix, and these interactions generate cell survival, proliferation, and motility signals. Integrin signals are relayed in part by focal adhesion kinase (FAK) activation and the formation of a transient signaling complex initiated by Src homology 2 (SH2)-dependent binding of Src family protein-tyrosine kinases to the FAK Tyr-397 autophosphorylation site. Here we show that in viral Src (v-Src)-transformed NIH3T3 fibroblasts, an adhesion-independent FAK-Src signaling complex occurs. Co-expression studies in human 293T cells showed that v-Src could associate with and phosphorylate a Phe-397 FAK mutant at Tyr-925 promoting Grb2 binding to FAK in suspended cells. In vitro, glutathione S-transferase fusion proteins of the v-Src SH3 but not c-Src SH3 domain bound to FAK in lysates of NIH3T3 fibroblasts. The v-Src SH3-binding sites were mapped to known proline-X-X-proline (PXXP) SH3-binding motifs in the FAK N- (residues 371-377) and C-terminal domains (residues 712-718 and 871-882) by in vitro pull-down assays, and these sites are composed of a PXXPXXPhi (where Phi is a hydrophobic residue) v-Src SH3 binding consensus. Sequence comparisons show that residues in the RT loop region of the c-Src and v-Src SH3 domains differ. Substitution of c-Src RT loop residues (Arg-97 and Thr-98) for those found in the v-Src SH3 domain (Trp-97 and Ile-98) enhanced the binding of distinct NIH3T3 cellular proteins to a glutathione S-transferase fusion protein of the c-Src (Trp-97 + Ile-98) SH3 domain. FAK was identified as a c-Src (Trp-97 + Ile-98) SH3 domain target in fibroblasts, and co-expression studies in 293T cells showed that full-length c-Src (Trp-97 + Ile-98) could associate in vivo with Phe-397 FAK in an SH2-independent manner. These studies establish a functional role for the v-Src SH3 domain in stabilizing an adhesion-independent signaling complex with FAK.

3T3 Cells↗
PubMed2003

Myofibroblast differentiation by transforming growth factor-beta1 is dependent on cell adhesion and integrin signaling via focal adhesion kinase.

Myofibroblast differentiation and activation by transforming growth factor-beta1 (TGF-beta1) is a critical event in the pathogenesis of human fibrotic diseases, but regulatory mechanisms for this effect are unclear. In this report, we demonstrate that stable expression of the myofibroblast phenotype requires both TGF-beta1 and adhesion-dependent signals. TGF-beta1-induced myofibroblast differentiation of lung fibroblasts is blocked in non-adherent cells despite the preservation of TGF-beta receptor(s)-mediated signaling of Smad2 phosphorylation. TGF-beta1 induces tyrosine phosphorylation of focal adhesion kinase (FAK) including that of its autophosphorylation site, Tyr-397, an effect that is dependent on cell adhesion and is delayed relative to early Smad signaling. Pharmacologic inhibition of FAK or expression of kinase-deficient FAK, mutated by substituting Tyr-397 with Phe, inhibit TGF-beta1-induced alpha-smooth muscle actin expression, stress fiber formation, and cellular hypertrophy. Basal expression of alpha-smooth muscle actin is elevated in cells grown on fibronectin-coated dishes but is decreased on laminin and poly-d-lysine, a non-integrin binding polypeptide. TGF-beta1 up-regulates expression of integrins and fibronectin, an effect that is associated with autophosphorylation/activation of FAK. Thus, a safer and more effective therapeutic strategy for fibrotic diseases characterized by persistent myofibroblast activation may be to target this integrin/FAK pathway while not interfering with tumor-suppressive functions of TGF-beta1/Smad signaling.

Cell Adhesion↗
PubMed2003

Beta1 integrin/focal adhesion kinase-mediated signaling induces intercellular adhesion molecule 1 and receptor activator of nuclear factor kappaB ligand on osteoblasts and osteoclast maturation.

We have assessed characteristics of primary human osteoblasts, shedding light on signaling mediated by beta1 integrin. beta1 integrins are major receptors for these matrix glycoproteins. 1) Integrins beta1, alpha2, alpha3, alpha4, alpha5, alpha6, and alphav were highly expressed on primary osteoblasts. 2) Engagement of beta1 integrins on osteoblasts by cross-linking with specific antibody or ligand matrices, such as fibronectin or collagen, augmented expression of intercellular adhesion molecule 1 (ICAM-1) and receptor activator of nuclear factor kappaB ligand (RANKL) on the surface. 3) Up-regulation of ICAM-1 and RANKL on osteoblasts by beta1 stimulation was completely abrogated by pretreatment with herbimycin A and genistein, tyrosine kinase inhibitors, or transfection of dominant negative truncations of focal adhesion kinase (FAK). 4) Engagement of beta1 integrins on osteoblasts induced tartrate-resistant acid phosphatase-positive multinuclear cell formation in the coculture system of osteoblasts and peripheral monocytes. 5) Up-regulation of tartrate-resistant acid phosphatase-positive multinuclear cell formation by beta1 stimulation was completely abrogated by transfection of dominant negative truncations of FAK. Our results indicate that beta1 integrin-dependent adhesion of osteoblasts to bone matrices induces ICAM-1 and RANKL expression and osteoclast formation via tyrosine kinase, especially FAK. We here propose that beta1 integrin/FAK-mediated signaling on osteoblasts could be involved in ICAM-1- and RANKL-dependent osteoclast maturation.

Antibodies, Monoclonal↗
PubMed1994

Structural requirements for adhesion of soluble recombinant murine vascular cell adhesion molecule-1 to alpha 4 beta 1.

This study describes the identification of seven amino acid residues of the vascular cell adhesion molecule (VCAM-1) that influence binding to the alpha 4 beta 1 receptor. Using recombinant murine VCAM-1-IgG, which is bound by both mouse (WEHI 231) and human (Ramos) lymphoid cells, two approaches demonstrated the crucial role of the first two NH2-terminal Ig-like domains in binding: (a) blocking monoclonal anti-mouse VCAM-1 antibodies bound to only truncation variants that included the first two domains; (b) site-direct mutagenesis of the first NH2-terminal domain showed that alanine substitution of the amino acid residues R36, D40, K46, S54, N65, T72, and E81 partially or completely reduced adherence by human and/or mouse cells. Of these D40, when mutated to A, N, or K (but not E), showed complete abrogation of adherence by mouse and human cells, as well as inability to bind blocking anti-murine VCAM-1 antibody MVCAM.A429, while not inducing gross structural perturbations in VCAM-1. By molecular modeling, the D40 residue was located on a beta turn connecting two beta strands defined as C and D. The residues R36, K46, S54, N65, T72, and E81, which perturb cell adherence and caused small changes to gross structure, are conformationally near or adjacent to D40. Although these residues, identified as crucial for cell adhesion, are all located in domain 1, it is evident that there is a structural requirement for domains 1 and 2 to be intact so that cell adhesive function can occur.

Amino Acid Sequence↗
PubMed1994

Role of vascular cell adhesion molecule 1/very late activation antigen 4 and intercellular adhesion molecule 1/lymphocyte function-associated antigen 1 interactions in antigen-induced eosinophil and T cell recruitment into the tissue.

To determine the role of vascular cell adhesion molecule 1 (VCAM-1)/very late activation antigen 4 (VLA-4) and intercellular adhesion molecule 1 (ICAM-1)/lymphocyte function-associated antigen 1 (LFA-1) interactions in causing antigen-induced eosinophil and T cell recruitment into the tissue, we studied the effect of the in vivo blocking of VCAM-1, ICAM-1, VLA-4, and LFA-1 by pretreatment with monoclonal antibodies (mAb) to these four adhesion molecules on the eosinophil and T cell infiltration of the trachea induced by antigen inhalation in mice. The in vivo blocking of VCAM-1 and VLA-4, but not of ICAM-1 and LFA-1, prevented antigen-induced eosinophil infiltration into the mouse trachea. On the contrary, the in vivo blocking of VCAM-1 and VLA-4, but not of ICAM-1 and LFA-1, increased blood eosinophil counts after antigen challenge, but did not affect blood eosinophil counts without antigen challenge in sensitized mice. Furthermore, the expression of VCAM-1 but not ICAM-1 was strongly induced on the endothelium of the trachea after antigen challenge. In addition, pretreatment with anti-IL-4 mAb decreased the antigen-induced VCAM-1 expression only by 27% and had no significant effect on antigen-induced eosinophil infiltration into the trachea. The in vivo blocking of VCAM-1 and VLA-4 inhibited antigen-induced CD4+ and CD8+ T cell infiltration into the trachea more potently than that of ICAM-1 and LFA-1. In contrast, regardless of antigen challenge, the in vivo blocking of LFA-1, but not of ICAM-1, increased blood lymphocyte counts more than that of VCAM-1 and VLA-4. These results indicate that VCAM-1/VLA-4 interaction plays a predominant role in controlling antigen-induced eosinophil and T cell recruitment into the tissue and that the induction of VCAM-1 expression on the endothelium at the site of allergic inflammation regulates this eosinophil and T cell recruitment.

Administration, Inhalation↗
PubMed1995

Levels of circulating intercellular adhesion molecule-1 and -3 but not circulating endothelial leucocyte adhesion molecule are increased in patients with rheumatoid vasculitis.

The aim of this study was to investigate whether levels of circulating adhesion molecules reflect vascular inflammation in rheumatoid vasculitis (RV). Levels of circulating intercellular adhesion molecule-1 (cICAM-1), c-ICAM-3 and circulating endothelial leucocyte adhesion molecule (cE-selectin) were determined in 14 patients with RV and compared to 47 patients with rheumatoid arthritis (RA) and 100 healthy donors (HD). Enzyme-linked immunosorbent assays were used to quantify cICAM-1, cICAM-3 and cE-selectin. We found that in RV significantly (P < 0.0001) elevated levels of cICAM-1 and cICAM3, but not cE-selectin, were found when compared with RA patients. Levels > 2 S.D. above the mean level of HD were present for cICAM-1, cICAM-3 and cE-selectin in 57, 71 and 21%, respectively of patients with RV and 2, 21 and 44%, respectively of the RA patients. Increased levels of both cICAM-1 and cICAM-3 were found in 43% of the RV patients and in none of the RA patients. Comparison of the serum levels of patients studied in an active and inactive phase of RV revealed significantly lower levels of cICAM-3 levels in the inactive phase. In conclusion we find that determination of cICAM-1 and cICAM-3 may be useful as a marker of vascular inflammation in patients with RV.

Aged↗
PubMed2000

Y-27632, an inhibitor of rho-associated protein kinase, suppresses tumor cell invasion via regulation of focal adhesion and focal adhesion kinase.

Migration of rat ascites hepatoma (MM1) cells, invasion and phagokinetic movement were induced by the combination of lysophosphatidic acid (LPA) and fibronectin (FN). Induction of migratory activity was tightly correlated with morphological change of MM1 cells from spherical or polygonal-shaped cells to fusiform-shaped ones with pseudopodia. MM1 cells were mobile in a fusiform shape, whereas those of a spherical or polygonal shape were not. A small GTPase Rho and one of its downstream effectors ROCK (Rho-associated coiled-coil forming protein kinase), play essential roles in these processes, as evidenced by suppression of migration and morphological change of MM1 cells by Clostridium botulinum C3 exoenzyme, an inhibitor of Rho, or by Y-27632, an inhibitor of ROCK. Y-27632 also suppressed the formation of fusiform-shaped pseudopodia-carrying MM1 cells that was induced by stimulation with the combination of LPA and FN. LPA and FN also evoked the formation of focal adhesions and actin bundles, and tyrosine phosphorylation of focal adhesion kinase (FAK) and paxillin. The inhibitory effect of Y-27632 on LPA-induced migration and morphological change of MM1 cells was considered to be mediated, at least in part, by impaired formation of focal adhesions and actin bundles. Y-27632 suppressed LPA-induced tyrosine phosphorylation of FAK and paxillin, suggesting that ROCK regulates these molecules and Y-27632 inhibits cellular migration and morphological change, at least in part, through this regulation.

Actins↗
PubMed2002

Increased monocyte adhesion to aortic endothelium in rats with hyperhomocysteinemia: role of chemokine and adhesion molecules.

OBJECTIVE: The stimulatory effect of homocysteine (Hcy) on monocyte chemoattractant protein (MCP)-1 expression in vitro has been suggested to play an important role in Hcy-mediated atherosclerosis. We investigated whether such a stimulatory effect occurs in vivo, leading to monocyte adhesion to the endothelium. METHODS AND RESULTS: Sprague-Dawley rats were divided into 4 groups. Hyperhomocysteinemia was induced in 1 group of rats after 4 weeks of a high-methionine diet (serum Hcy levels were 4- to 5-fold higher than levels in control rats). The number of ED-1-positive cells present on the surface of aortic endothelium was significantly elevated in hyperhomocysteinemic rats. There was a significant increase in the expression of MCP-1, vascular cell adhesion molecule-1 (VCAM-1), and E-selectin in the endothelium. Antibodies recognizing MCP-1, VCAM-1, or E-selectin could abolish the enhanced monocyte binding to the aortic endothelium of hyperhomocysteinemic rats. Endothelium-dependent aortic relaxation was impaired in hyperhomocysteinemic rats. CONCLUSIONS: These results suggest that in the absence of other known risk factors, hyperhomocysteinemia stimulates the expression of MCP-1, VCAM-1, and E-selectin in vivo, leading to increased monocyte adhesion to the aortic endothelium. Such an effect may contribute significantly to the development of atherosclerosis by facilitating monocyte/macrophage infiltration into the arterial wall.

Animals↗
PubMed1992

Increased binding of synovial T lymphocytes from rheumatoid arthritis to endothelial-leukocyte adhesion molecule-1 (ELAM-1) and vascular cell adhesion molecule-1 (VCAM-1).

The infiltration of the synovial membrane (SM) by mononuclear cells, mostly T cells, is a typical histopathological feature associated with rheumatoid arthritis (RA). The entry of T lymphocytes into the SM is believed to be mediated by a number of molecules in the endothelium that are induced in response to a series of inflammatory mediators. In this study, we have investigated the adhesion of synovial T cells from RA patients to two endothelial ligands: endothelial-leukocyte adhesion molecule-1 (ELAM-1), the only selectin known to function as a vascular addressin for T cells, and vascular cell adhesion molecule-1 (VCAM-1), the cellular ligand of VLA-4. Our results clearly demonstrate that synovial T cells isolated from both SM and synovial fluid (SF), bearing an activated and memory phenotype, displayed an enhanced capacity to interact with these two endothelial molecules as compared with T cells from peripheral blood (PB) either of the same RA patients or healthy donors. A further enhancement of VLA-4-mediated T cell binding to VCAM-1 and fibronectin could be observed when already in vivo-activated synovial T cells were stimulated in vitro with phorbol esters, suggesting the existence of several cellular affinity levels for both very late activation-4 (VLA-4) ligands. Moreover, both PB and synovial T cells from RA patients exhibited strong proliferative responses when they were cultured with either fibronectin or VCAM-1 in combination with submitogenic doses of anti-CD3 mAb. This increased endothelial binding ability of synovial T lymphocytes together with their proliferation in response to the interaction with VCAM-1 and fibronectin may represent important mechanisms in the regulation of T cell penetration and persistence in the chronically inflamed SM of RA.

Antigens, CD↗
PubMed1992

Adhesion to vascular cell adhesion molecule 1 and fibronectin. Comparison of alpha 4 beta 1 (VLA-4) and alpha 4 beta 7 on the human B cell line JY.

Most mononuclear leukocytes and cell lines express the integrin alpha 4 beta 1 (VLA-4) heterodimer. In this study we have used Northern blotting and immunoprecipitation experiments to demonstrate that a B lymphoblastoid cell line (JY) expressed the integrin beta 7 subunit in association with alpha 4. These alpha 4 beta 7-positive JY cells bound poorly or not at all to VLA-4 ligands (soluble form of vascular cell adhesion molecule 1 (sVCAM-1) and the CS1 region of fibronectin). In contrast, a beta 1-positive variant of JY cells (selected to express a mixture of alpha 4 beta 1 and alpha 4 beta 7) bound avidly to VLA-4 ligands, and this binding was completely inhibitable by anti-alpha 4 and anti-beta 1 monoclonal antibodies. Thus, beta 1 expression appears to be a critically important component of VLA-4-mediated binding to its ligands. After either JY or JY-beta 1 cells were stimulated for 15 min with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, the majority of adhesion to VCAM or fibronectin remained alpha 4- and beta 1-dependent, but a low amount of adhesion to sVCAM-1 or fibronectin became alpha 4-dependent, beta 1-independent, thus suggesting a role for alpha 4 beta 7. In summary, we have found (i) that alpha 4 beta 7 makes little or no contribution to fibronectin or VCAM-1 binding on unstimulated JY cells, (ii) that alpha 4 beta 7 perhaps makes a minor contribution to ligand binding on 12-O-tetradecanoyl-phorbol-13-acetate-stimulated cells, and (iii) that alpha 4 beta 1 is the functionally dominant VCAM-1 and fibronectin receptor even when expressed in relatively low amounts compared to alpha 4 beta 7.

Antibodies, Monoclonal↗
PubMed1995

Differential patterns of circulating intercellular adhesion molecule-1 (cICAM-1) and vascular cell adhesion molecule-1 (cVCAM-1) during liver allograft rejection.

During allograft rejection, adhesion molecules play an integral role in infiltration, activation, and binding of effector cells to target tissue. Some adhesion molecules, including ICAM-1 and VCAM-1, exist in soluble, circulating forms that retain ligand-binding activity. In the present study the levels of circulating ICAM-1 (cICAM-1) and VCAM-1 (cVCAM-1) were compared in the serum and bile of pediatric liver recipients. The cICAM-1 was significantly elevated in the serum during allograft rejection and infection relative to periods when no rejection was apparent. Biliary cICAM-1, however, was specifically elevated during rejection and not during infection or when no rejection was apparent. The cVCAM-1 levels were elevated in the serum during rejection compared with levels when no rejection was evident. In contrast, cVCAM-1 was not detected in the bile. Serum levels of both cICAM-1 and cVCAM-1 decreased rapidly following successful treatment for rejection, whereas elevated levels persisted, or increased, in ongoing rejection. The differential patterns of the circulating forms of ICAM-1 and cVCAM-1 were consistent with the membrane expression of these molecules during graft rejection. ICAM-1 expression was extensive on bile duct epithelium, endothelium, hepatocytes, and infiltrating leukocytes during rejection, while VCAM-1 was restricted to endothelium. These findings indicate that the release of circulating adhesion molecules is a prominent feature of liver allograft rejection. Measurement of these markers may be useful in distinguishing rejection from infection and in determining the efficacy of treatment for rejection.

Adolescent↗
PubMed1993

Costimulation with integrin ligands intercellular adhesion molecule-1 or vascular cell adhesion molecule-1 augments activation-induced death of antigen-specific CD4+ T lymphocytes.

Integrin ligands intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) can efficiently costimulate proliferation of resting T cells but not that of Ag-specific T cells. In contrast, CD28 ligand B7 and CD2 ligand leukocyte function-associated Ag (LFA-3) can support IL-2 synthesis and proliferation of Ag-specific T cells more efficiently than that of resting T cells. The molecular basis for this differential costimulation of T cells is poorly understood. In this study, using mAb and soluble IgC gamma 1 chimeras of these adhesion molecules, we demonstrate that coligation of the TCR and CD11a/CD18 (LFA-1/beta 2 integrin) or CD29/CD49d (very late activation Ag-4/beta 1 integrin) using anti-TCR mAb and either ICAM-1 or VCAM-1 induces activation-dependent death of DRw6-specific CD4+ T cells. Similar coligation of the TCR with CD2 or CD28 using either mAb or ligands LFA-3 or B7 not only lacked the ability to induce death but also failed to reverse or inhibit integrin-facilitated death of DRw6-specific T cells. Each of these ligands augmented anti-TCR mAb-induced transcription of IL-2 and IL-4 genes. Exogenous addition of IL-2 and IL-4 did not reverse the integrin-supported T cell death. The death-promoting costimulatory effects of ICAM-1 and VCAM-1 were observed with Ag-specific chronically stimulated T cells but not with either resting T cells or those activated in short-term cultures. Treatment of T cells with cyclosporin A or a protein tyrosine kinase inhibitor herbimycin A inhibited ICAM-1 or VCAM-1-promoted activation-induced T cell death. The Ag-specific T cells that survived death-promoting effects of ICAM-1 or VCAM-1 proliferated efficiently upon restimulation with these ligands. Exposure of DRw6-specific T cells to DRw6+ B7+ ICAM-1+ LFA-3+ VCAM-1+ APC but not DR3+ B7+ ICAM-1+ LFA-3+ VCAM-1+ APC induced death of these T cells. This effect was blocked by pretreatment of T cells with mAb directed at CD18 or CD29 but not with those against CD2 or CD28. Taken together, these results suggest that TCR-directed engagement of integrins by their ligands ICAM-1 or VCAM-1 induces activation-dependent death of some perhaps more differentiated Ag-specific T cells and this may be an important homeostatic mechanism by which functional expression of Ag-specific T cells is regulated during an ongoing immune response.

Antigen-Presenting Cells↗
PubMed1999

Protein adhesion force dynamics and single adhesion events.

Using the manipulation force microscope, a novel atomic force microscope, the adhesion forces of bovine serum albumin, myoglobin, ferritin, and lysozyme proteins to glass and polystyrene substrates were characterized by following the force necessary to displace an adsorbed protein-covered microsphere over several orders of magnitude in time. This force was consistent with a power law with exponent a = 0.37 +/- 0.03 on polystyrene, indicating that there is no typical time scale for adhesion on this substrate. On glass, the rate of adhesion depended strongly on protein charge. Forces corresponding to single protein adhesion events were identified. The typical rupture force of a single lysozyme, ferritin, bovine serum albumin, and myoglobin protein adhering to glass was estimated to be 90 +/- 10 pN, 115 +/- 13 pN, 277 +/- 44 pN, and 277 +/- 44 pN, respectively, using a model of the experimental system. These forces, as well as the force amplitudes on hydrophobic polystyrene, correlate with protein stiffness.

Animals↗
PubMed1990

Development of an Adhesion Assay and Characterization of an Adhesion-Deficient Mutant of Pseudomonas fluorescens.

A sand column adhesion assay was developed which distinguishes the adhesion abilities of a number of pseudomonads isolated from fine sandy loam. Pseudomonas fluorescens Pf0-1 which adhered at >90% of the total cells added was subjected to transposon Tn5 insertion mutagenesis. From 2,500 Pf0-1::Tn5 mutants examined in the sand column assay, two adhesion-deficient Pf0-1 mutants showing <50% attachment were isolated. Marker exchange analysis of one of these mutants, Pf0-5, confirmed that the decreased adhesion was linked to the Tn5 insertion in the chromosome. The growth rate of Pf0-5 in enriched media and sterile soil was similar to that of the wild type; in minimal medium, however, Pf0-5 grew faster. In a soil column assay, less Pf0-5 than wild-type bacteria were recovered, suggesting a decreased ability to persist in soil. A 34-kilodalton major outer membrane protein present in the wild type was missing in Pf0-5. Transmission electron microscopy of the cell surface revealed that the wild-type possessed polar flagella which were absent in the mutant.

Journal Article↗
PubMed1968

Platelet adhesiveness: the effect of centrifugation on the measurement of adhesiveness in platelet-rich plasma.

Platelet adhesiveness has been measured in citrated whole blood and in platelet-rich plasma obtained from normal subjects, splenectomized patients, and from patients in whom the diagnosis of recurrent venous thrombosis had been made. The duration of centrifugation used in the preparation of platelet-rich plasma was found to have a profound effect on the measurement of platelet adhesiveness because the figure for platelet adhesiveness measured in platelet-rich plasma obtained by centrifugation was considerably lower than that found in citrated whole blood. This effect was particularly marked when platelet-rich plasma was obtained from subjects in whom platelet adhesiveness measured in whole blood was increased.

Blood Cell Count↗
PubMed1997

Regulation of leukocyte adhesion molecules CD11b/CD18 and leukocyte adhesion molecule-1 on phagocytic cells activated by malaria pigment.

There is increasing evidence that inappropriate immune activation induced by parasite products occurs in malaria disease. To further elucidate the role of Plasmodium falciparum-derived products on host immune activation, we studied the expression of leukocyte adhesion molecules (CD11b/CD18 and LAM-1) on neutrophils and monocytes in response to malaria pigment using flow cytometry. Exposure of leukocytes to isolated malaria pigment derived from ruptured schizonts resulted in significant up-regulation of CD11b/CD18 expression and down-regulation of LAM-1 on both neutrophils and monocytes. In contrast, culture supernatants (pigment free) from ruptured schizonts did not alter the expression of CD11b/CD18 and LAM-1. The increase of CD11b/CD18 and the loss of LAM-1 expression occurred simultaneously with the earliest response detected at 10 min and a plateau reached by 60 min. The effect of malaria pigment on leukocyte adhesion molecules was inhibited by EDTA in a dose-dependent manner. Phagocytosis of malaria pigment was also suppressed by EDTA. This observation suggests that phagocytosis of malaria pigment may be a prerequisite for the effect of malaria pigment on the regulation of CD11b/CD18 and LAM-1 expression. Regulation of leukocyte adhesion molecules through up-regulation of CD11b/CD18 and down-regulation of LAM-1 by malaria pigment could promote leukocyte adherence to endothelium in vivo. This increased adherence of malaria pigment-activated leukocytes might induce cytokine (tumor necrosis factor alpha and interleukin-1beta)-mediated increases in capillary permeability resulting in local tissue edema, and a cytokine-mediated increase in adhesion molecule expression causing vascular clogging by adherent red blood cells, and in severe disease by adherent leukocytes.

Animals↗
PubMed1993

[Adhesion of calcium oxalate crystal to Madin-Darby canine kidney cells: quantitative determination and effects of glycosaminoglycans (GAG) and cell injuries on adhesion].

The present investigation was designed to study adhesion of calcium oxalate crystals on the surface of intact MDCK cells quantitatively, and to estimate the effects of glycosaminoglycans (GAGs) and cell injuries on these adhesions. Calcium oxalate monohydrate (COM) crystals adhere to the cell surface by an active force, and the attachment is in a time and concentration dependency with plateau. Pre-treatments with low concentration of GAGs (chondroitin sulphate C, hyaluronic acid, heparan sulphate, heparin and sodium pentosan polysulphate) produce significant reductions of the adhesion. There are significant decreases of the adhesions with pre-treatments of Triton-X100, 0.1 N HCl and gentamicin. These phenomena might be induced by some alterations of cell surface structures or characters. The current quantitative system on MDCK cells should serve as a useful model for the investigations of interactions with crystals and tubular cells. Our studies may also support the hypothesis of attachment of microcrystals to the cellular membrane, which is one of the most important and the earliest process of the pathophysiology of kidney stone.

Animals↗
PubMed2004

In vitro shear bond strength of self-etching adhesives in comparison to 4th and 5th generation adhesives.

PURPOSE: To determine the shear bond strength (SBS) of different established (Resulcin Aqua Prime & Monobond N: RA, Prompt L-Pop III: PLP) and experimental (AC-Bond: AC, AC-Bond + Desensitizer: ACD) self-etching adhesives in comparison to fourth (Optibond FL: FL) and fifth generation (Excite: EX, Gluma Comfort Bond: CB) adhesives. MATERIALS AND METHODS: All adhesives were applied on flat enamel and dentin surfaces and light cured following manufacturers' directions. Tetric Ceram A2 composite cylinders 3.5 mm in diameter and 2.0 mm in height were sheared off (1 mm/min) after thermocycling (5 to 55 degrees C, 5000x). The t-test (5% level, Bonferroni-correction) was used for statistical analysis. RESULTS: SBS in enamel: RA: 27.0+/-5.8 MPa, PLP: 15.9+/-3.4 MPa, AC: 28.1+/-4.4 MPa, ACD: 22.2+/-4.1 MPa, FL: 33.2+/-3.2 MPa, EX: 30.5+/-5.1 MPa, CB: 30.1+/-3.7 MPa. SBS in dentin: RA: 25.8+/-5.7 MPa, PLP: 20.7+/-2.9 MPa, AC: 27.0+/-4.5 MPa, ACD: 20.7+/-3.7 MPa, FL: 34.4+/-3.8 MPa, EX: 30.0+/-4.6 MPa, CB: 27.9+/-2.6 MPa. FL resulted in significantly (p < 0.002) higher SBS in enamel and dentin than RA, AC, ACD, and PLP, and in higher SBS to dentin than CB. In enamel and dentin, RA performed significantly superior to PLP, but was not different from AC and ACD. EX and CB were both on the same level of significance as AC and RA, but showed superior results to ACD and PLP (enamel and dentin). PLP resulted in significantly lower SBS values in enamel and dentin than all the other materials investigated, except ACD in dentin, to which it was equivalent. CONCLUSION: Resulcin Aqua Prime & Monobond N and AC-Bond were not significantly different than established 5th generation products. AC-Bond + Desensitizer and Prompt L-Pop have significantly different SBS from established 4th and 5th generation products. Future studies are required to investigate marginal integrity to determine if self-etching adhesives are an adequate alternative to one- and multi-bottle systems.

Dental Etching↗