Biomedical subjects

Gines Escolar

Publications and source records attributed to Gines Escolar.

8 recordsLinked to original sources

PubMed2006

Effects on primary haemostasis of an anti-inflammatory agent with 5-lipoxygenase and cyclooxygenase inhibitory activity.

OBJECTIVE: Licofelone ([2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2,3-dihydro-1H-pyrrolizine-5-yl]-acetic acid) has been demonstrated to inhibit cyclooxygenase (COX)-1, COX-2, and 5-lipoxygenase. The aim of this study was to investigate the in-vitro effects of licofelone on platelet function. Effects observed were compared with those produced by the classic COX-1 inhibitor aspirin (ASA). METHODS: Platelet aggregation was assessed by a turbidimetric method. Platelet haemostatic performance was studied with the platelet function analyser (PFA-100), using collagen epinephrine and collagen ADP cartridges. Interaction of platelets with thrombogenic surfaces was analysed by perfusion experiments performed under flow conditions using both parallel and annular chambers. RESULTS: Licofelone prolonged the lag time of platelet aggregation induced by arachidonic acid and reduced maximal platelet aggregation induced by ADP or collagen. Studies using PFA-100 demonstrated that licofelone (0.1, 1 and 10 muM) significantly prolonged closure times (P < 0.05) with both types of cartridges. In studies with the parallel chamber exposing purified collagen, both licofelone and ASA significantly reduced (P < 0.05) overall platelet interaction with the thrombogenic surface. In studies performed in annular chamber exposing a highly thrombogenic vessel surface, licofelone reduced height and area of the platelet masses deposited (7.0 +/- 0.5 mum; P < 0.005 and 80.2 +/- 17.3 mum; P < 0.05 vs. control 10.6 +/- 0.9 mum and 194.8 +/- 44.7 mum, respectively). ASA also impaired thrombus formation but differences did not reach the levels of statistical significance. CONCLUSIONS: Under our experimental in-vitro conditions, licofelone interfered with platelet function as demonstrated by a diminished platelet aggregation, being more powerful than ASA and reducing the interaction of platelets with thrombogenic surfaces.

Acetates↗

PubMed2005

Efficient tyrosine phosphorylation of proteins after activation of platelets with thrombin depends on intact glycoprotein Ib.

The role of platelet glycoprotein Ib as a thrombin receptor has been often a subject of controversy. We have investigated the role of the thrombin receptors, GPIb and protease-activated receptor (PAR)-1. Tyrosine phosphorylation in whole platelet lysates and in cytoskeletal extracts was evaluated after activation with thrombin and with the thrombin receptor-activating peptide (TRAP). Different experimental approaches were applied including: (i) congenital deficiency of platelet GPIb (Bernard Soulier syndrome, BSS), (ii) antibody to GPIb (AP1), (iii) selective protease cleavage (metalloprotease), and (iv) antibody to (PAR)-1. After activation of control platelets with thrombin or TRAP, multiple proteins became tyrosine phosphorylated in platelet lysates and some of them associated with the cytoskeletal fraction. These effects were absent in BSS platelets. Presence of AP1 or metalloprotease treatment showed an inhibitory effect when platelets were activated with a low concentration of thrombin or TRAP. Blockade of PAR-1 with a specific antibody, SPAN 12, inhibited platelet response to both agonists. This study reinforces the hypothesis that GPIb is the high-affinity receptor for thrombin. The signaling mechanisms occurring through tyrosine phosphorylation of proteins triggered by thrombin seem to be dependent on intact GPIb. Moreover, our results indicate that both receptors, GPIb and PAR-1, are necessary to achieve a full platelet response to thrombin.

Bernard-Soulier Syndrome↗

PubMed2005

Uremic platelet dysfunction: past and present.

Uremic patients develop an acquired platelet dysfunction that results in bleeding complications. The pathogenesis of this hemostatic dysfunction is multifactorial and includes effects of circulating toxins, alterations of the vessel wall, anemia, and other factors, complicated by unwanted effects of hemodialysis procedures. This review seeks to place in perspective the evolution of knowledge on uremic platelet dysfunction. It examines how investigations of the altered hemostasis in these patients have led to a better understanding of the mechanisms involved and how these advances have contributed to the development of effective therapeutic strategies. It also comments upon the fact that elevated rates of thrombotic complications are apparently emerging as the bleeding tendency is better controlled. Emphasized is the delicate balance of hemostasis in the uremic condition, in which deficient hemostasis paradoxically coexists with accelerated atherosclerosis and an enhanced risk of thrombosis.

Blood Platelet Disorders↗

PubMed2004

Biocompatibility of cellulosic and synthetic membranes assessed by leukocyte activation.

BACKGROUND/AIMS: The contact of blood with artificial surfaces may activate blood leukocytes and platelets and initiate the leukocyte inflammatory response. We have investigated the effect of a hemodialysis (HD) with a cellulosic- and a synthetic-based membrane on circulating leukocyte activation. METHODS: Samples were obtained from patients with ESRD at baseline, and at 15 and 120 min of a hemodialysis session from both the arterial and venous lines. Leukocyte respiratory burst was analyzed by luminol chemiluminescence. Actin polymerization, expression of CD11b, and heterotypic aggregation were studied by flow cytometry, leukocyte labeling with NBD phallacidin and monoclonal antibodies, respectively. RESULTS: HD with a cellulosic membrane induced a transient fall in neutrophil (1.2 +/- 0.5 x 10(9) vs. 3.6 +/- 0.6 x 10(9) cells/l; p < 0.05) and monocyte counts (0.2 +/- 0.1 x 10(9) vs. 0.7 +/- 0.1 x 10(9) cells/l; p < 0.05). There was also an increase in respiratory burst in the venous line during a HD with a cellulosic membrane, at 15 and 120 min (100 +/- 41 and 143.2 +/- 45.3 vs. 23.8 +/- 15.7; p < 0.05). Polymerized actin, expressed as fluorescence arbitrary units, was increased in baseline samples from uremic patients versus control subjects (327.8 +/- 60.8 for a cellulosic membrane, p < 0.005, and 205 +/- 26.5 for a synthetic one, p < 0.05 vs. 97.8 +/- 27.6 in controls). The percentage of CD11b+ cells increased in samples during a HD with a cellulosic membrane at the venous line at 15 and 120 min (9.6 +/- 4.5 and 18.4 +/- 7.1% vs. 3.3 +/- 1.9%; p < 0.05%). Changes in heterotypic aggregation during HD did not reach statistical significance, but levels were higher in patients treated with a cellulosic membrane at all points than in patients dialyzed with a synthetic one. CONCLUSION: There is evidence of a priming state of leukocytes from uremic patients, which is more evident in patients dialyzed with a cellulosic membrane. Cellulosic membranes also induce greater leukocyte activation than synthetic membranes during hemodialysis.

Adult↗

PubMed2004

Induction of microparticle- and cell-associated intravascular tissue factor in human endotoxemia.

The precise role of intravascular tissue factor (TF) remains poorly defined, due to the limited availability of assays capable of measuring circulating TF procoagulant activity (PCA). As a model of inflammation-associated intravascular thrombin generation, we studied 18 volunteers receiving an infusion of endotoxin. A novel assay that measures microparticle (MP)-associated TF PCA from a number of cellular sources (but not platelets) demonstrated an 8-fold increase in activity at 3 to 4 hours after endotoxin administration (P <.001), with a return to baseline by 8 hours. TF antigen-positive MPs isolated from plasma were visualized by electron microscopy. Interindividual MP-associated TF response to lipopolysaccharide (LPS) was highly variable. In contrast, a previously described assay that measures total (cell and MP-borne) whole-blood TF PCA demonstrated a more modest increase, with a peak in activity (1.3-fold over baseline; P <.000 01) at 3 to 4 hours, and persistence for more than 24 hours. This surprisingly modest increase in whole-blood TF activity is likely explained by a profound although transient LPS-induced monocytopenia. MP-associated TF PCA was highly correlated with whole-blood TF PCA and total number of circulating MPs, and whole-blood TF PCA was highly correlated with TF mRNA levels.

Adult↗

PubMed2004

Isoform-specific quantification of endothelins in HUVEC culture supernatants by on-line high-performance liquid chromatography/electrospray mass spectrometry.

A method for the quantitative analysis of endothelin peptides in human umbilical vein endothelial cell (HUVEC) culture supernatants is reported. The analysis is isoform-specific and employs solid-phase extraction and subsequent HPLC fractionation followed by HPLC-ESIMS analysis. The peptide vasoactive-intestinal-contractor (VIC) was used as internal standard for the HPLC-ESIMS analysis. Linearity of calibration curves was from 50 fmol to 25 pmol. The limit of detection of the HPLC-ESIMS step using a buffer matrix was estimated at 50 fmol (S/N > 3). The overall limit of detection for supernatants of HUVEC was 500 fmol/mL. In HUVEC culture supernatants only ions of endothelin-1 (ET1) were observed. Basal levels were determined to be 1.8 +/- 0.3 pmol/mL. Quantitative results obtained for ET1 were in agreement with those obtained by using a standard addition method and by an ELISA method.

Amino Acid Sequence↗

PubMed2004

G-CSF increases the expression of VCAM-1 on stromal cells promoting the adhesion of CD34+ hematopoietic cells: studies under flow conditions.

OBJECTIVE AND METHODS: The knowledge of the mechanisms underlying the adhesive processes that lead to homing and/or mobilization of hematopoietic progenitor cells, and the influence of blood rheology, is still limited. We analyzed the impact of flow conditions on the adhesion of CD34+ peripheral blood progenitor cell (PBPC) to the adhesive proteins fibronectin, laminin, and collagen, and to stromal cells. RESULTS: Under static conditions, all the adhesive substrata assayed promoted adhesion of CD34+ PBPC, being higher on the stromal cells. Under flow conditions, adhesion of CD34+ PBPC was remarkable on stromal cells while insignificant onto the purified proteins. Exposure of stromal cell monolayers to granulocyte colony-stimulating factor (G-CSF) further enhanced PBPC adhesion. This effect correlated with the activation of p38 MAPK and with an increase in the expression of VCAM-1 on stromal cells exposed to G-CSF. In inhibitory assays, both an antibody to the G-CSFR and a specific inhibitor of the p38 MAPK blocked the effects induced by the cytokine. CONCLUSION: Our results provide direct evidence that in stromal cells G-CSF activates the signaling protein p38 MAPK, inducing expression of the adhesion receptor VCAM-1. This mechanism seems to promote adhesion of CD34+ cells on stromal cells and could play a potential role in homing events.

Antigens, CD34↗

PubMed2004

New insights into the management of bleeding disorders.

The Novo Nordisk European Symposium on New Insights into the Management of Bleeding Disorders was held April 23-24, 2004, in Madrid, Spain. More than 200 specialists in the management of congenital and acquired bleeding disorders attended the different sessions. During the symposium, new medical indications for the use of human recombinant activated factor VII (rFVIIa, eptacog alfa activated) were presented. Rationale for new clinical trials and updates on registry for emerging indications were also discussed.

Blood Coagulation Disorders↗