Serum concentration of D-dimers as a marker of the activation of the fibrinolytic system in patients undergoing bronchoscopic and thoracoscopic investigations. (65/402)

BACKGROUND: Hypercoagulability is common even after minimally invasive surgical techniques and is pathogenetically linked to postoperative thrombotic and cardiac complications. The activation of the coagulation and fibrinolytic systems after bronchoscopic and thoracoscopic investigations has not yet been elucidated. OBJECTIVE: The aim of our study was to evaluate whether bronchoscopic and thoracoscopic investigations activate the fibrinolytic system. METHODS: This study assessed cross-linked fibrinogen degradation products (D-dimer) in 120 patients after bronchoscopy with and without biopsies and/or bronchoalveolar lavage and after thoracoscopy with biopsies of the parietal pleura. RESULTS: Both bronchoscopy and thoracoscopy induced a minor but significant increase in D-dimers in most patients, reversible mostly within 24 h. In rare cases, distinct increases lasting at least 24 h occurred. CONCLUSIONS: The slight and temporary increase in serum D-dimers induced by bronchoscopy and thoracoscopy is nonsignificant in most patients; however, in some cases, the coagulation/fibrinolytic systems may become markedly activated.  (+info)

Polyglutamine protein aggregation and toxicity are linked to the cellular stress response. (66/402)

Chronic exposure of cells to expanded polyglutamine proteins results in eventual cell demise. We constructed mouse cell lines expressing either the full-length androgen receptor (AR), or truncated forms of AR containing 25 or 65 glutamines to study the cellular consequences of chronic low-level exposure to these proteins. Expression of the polyglutamine-expanded truncated AR protein, but not the full-length expanded protein, resulted in the formation of cytoplasmic and nuclear aggregates and eventual cell death. Nuclear aggregates preferentially stained positive for heat shock protein (hsp)72, a sensitive indicator of a cellular stress response. Biochemical studies revealed that the presence of nuclear aggregates correlated with activation of the c-jun NH2-terminal kinase (JNK). Different metabolic insults, including heat shock treatment, and exposure to sodium arsenite or menadione, proved more toxic to those cells expressing the polyglutamine-expanded truncated protein than to cells expressing the non-expanded form. Cells containing cytoplasmic polyglutamine-protein aggregates exhibited a delayed expression of hsp72 after heat shock. Once expressed, hsp72 failed to localize normally and instead was sequestered within the protein aggregates. This was accompanied by an inability of the aggregate-containing cells to cease their stress response as evidenced by the continued presence of activated JNK. Finally, activation of the cellular stress response increased the overall extent of polyglutamine protein aggregation, especially within the nucleus. Inclusion of a JNK inhibitor reduced this stress-dependent increase in nuclear aggregates. Abnormal stress responses may contribute to enhanced cell vulnerability in cells expressing polyglutamine-expanded proteins and may increase the propensity of such cells to form cytoplasmic and nuclear inclusions.  (+info)

Menadione causes endothelial barrier failure by a direct effect on intracellular thiols, independent of reactive oxidant production. (67/402)

Menadione (MQ), a quinone used with cancer chemotherapeutic agents, causes cytotoxicity to endothelial cells (EC). Previous studies have suggested that MQ induces an oxidative stress and dysfunction in EC by either increasing hydrogen peroxide (H(2)O(2)) production or depleting intracellular glutathione (GSH), the main intracellular antioxidant. Since a primary function of EC is to form a barrier to fluid movement into tissues, protecting organs from edema formation and dysfunction, our aim was to see if MQ would cause a barrier dysfunction and to ascertain the mechanism. Using diffusional permeability to fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) as a measure of barrier function, we found that 15 micro M MQ incubated with a bovine pulmonary artery EC (BPAEC) monolayer for 4 h produced a profound barrier failure ( approximately 7-fold increase in permeability) with a parallel fall in glutathione, almost to depletion. These two events were highly correlated. Immunofluorescent imaging showed formation of paracellular holes consistent with a loss or rearrangement of cell-cell and cell-matrix adhesion molecules. H(2)O(2) (100 micro M), a concentration which gave about the same increase in permeability as MQ, only slightly decreased GSH concentration. Antioxidants, such as catalase (CAT) and dimethylthiourea (DMTU), which were able to block the H(2)O(2)-induced changes, had no effect on the MQ-induced permeability and GSH changes, suggesting that H(2)O(2) was not involved in MQ-induced effects. MQ caused a severe EC cytotoxicity as judged by lactate dehydrogenase (LDH) leakage from the EC, whereas H(2)O(2) caused only a minor increase. Also, MQ profoundly inhibited the activities of glucose-6-phosphate dehydrogenase (G6PDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), key thiol enzymes involved in glutathione and ATP metabolism, whereas H(2)O(2) produced only a slight decrease in these activities. We conclude that the cytotoxicity of MQ and resulting barrier dysfunction correlate with GSH depletion and inactivation of key metabolic enzymes, compromising antioxidant defenses, rather than being consistent with H(2)O(2)-mediated oxidative stress.  (+info)

Tranexamic acid is beneficial as adjunctive therapy in treating major upper gastrointestinal bleeding in dialysis patients. (68/402)

BACKGROUND: In a pilot, non-randomized trial we tested the efficacy of tranexamic acid (TXA), a potent fibrinolytic inhibitor, as adjunctive therapy in standard treatment of major upper gastrointestinal bleeding in dialysis patients. METHODS: Twenty consecutive patients (12 male, eight female; 63+/-8 years) with 36 episodes of major upper gastrointestinal bleeding were included in the study. In 16 episodes of bleeding TXA was used (in a dosage of 20 mg intravenously, followed for the next 4 weeks by 10 mg/kg/48 h orally), whereas in 20 other cases of bleeding, TXA was not used. The decision to use TXA was left to the attending physician's clinical judgement, resulting in all the more severe cases of bleeding being treated with TXA. RESULTS: Treatment including TXA was shown to be beneficial (relative to cases not treated with TXA) in terms of decreasing the rate of early re-bleeding (in the first week, 0 vs 6, P<0.05), the rate of early and late re-bleeding (in the first month, 1 vs 8, P<0.05), the rate of repeated endoscopic procedures (in the first month, 1 vs 8, P<0.05) and the number of blood transfusions needed (in the first month, 1.4+/-1.3 vs 2.6+/-1.5 units, P<0.05). CONCLUSIONS: The results of this pilot study suggest that TXA can be beneficial in the treatment of major upper gastrointestinal bleeding in dialysis patients. This remains to be definitely confirmed in a randomized study.  (+info)

Selectin-mucin interactions as a probable molecular explanation for the association of Trousseau syndrome with mucinous adenocarcinomas. (69/402)

Trousseau described spontaneous, recurrent superficial migratory thrombophlebitis associated with occult cancers, and this was later correlated with disseminated microangiopathy (platelet-rich clots in small blood vessels). Trousseau syndrome often occurs with mucinous adenocarcinomas, which secrete abnormally glycosylated mucins and mucin fragments into the bloodstream. Since carcinoma mucins can have binding sites for selectins, we hypothesized that selectin-mucin interactions might trigger this syndrome. When highly purified, tissue-factor free carcinoma mucin preparations were intravenously injected into mice, platelet-rich microthrombi were rapidly generated. This pathology was markedly diminished in P- or L-selectin-deficient mice. Heparin (an antithrombin-potentiating agent that can also block P- and L-selectin recognition of ligands) ameliorated this platelet aggregation, but had no additional effect in P- or L-selectin-deficient mice. Inhibition of endogenous thrombin by recombinant hirudin also did not block platelet aggregation. Mucins generated platelet aggregation in vitro in hirudinized whole blood, but not in platelet-rich leukocyte-free plasma nor in whole blood from L-selectin-deficient mice. Thus, Trousseau syndrome is likely triggered by interactions of circulating carcinoma mucins with leukocyte L-selectin and platelet P-selectin without requiring accompanying thrombin generation. These data may also explain why heparin ameliorates Trousseau syndrome, while vitamin K antagonists that merely depress thrombin production do not.  (+info)

Effects of epsilon-aminocaproic acid and aprotinin on leukocyte-platelet adhesion in patients undergoing cardiac surgery. (70/402)

BACKGROUND: The administration of aprotinin during cardiopulmonary bypass (CPB) is hypothesized to decrease activation of leukocytes and platelets and possibly reduce their adhesion. Although epsilon-aminocaproic acid (EACA) shares the ability of aprotinin to inhibit excessive plasmin activity after CPB, its effect on leukocyte and platelet activation and leukocyte-platelet (heterotypic) adhesion is largely unknown. This study was performed to determine the relative effectiveness of the antifibrinolytics, aprotinin and EACA, at reducing leukocyte and platelet activation and leukocyte-platelet conjugate formation in patients undergoing CPB. METHODS: Thirty-six patients scheduled to undergo cardiac surgery with CPB were randomized in a double-blind fashion to receive EACA, aprotinin, or saline (placebo). Markers of plasmin activity (D-dimer concentrations), platelet activation (CD62P), leukocyte activation (CD11b), and leukocyte-platelet adhesion (monocyte- and neutrophil-platelet conjugates) were measured before, during, and after CPB. RESULTS: Platelet CD62P (P-selectin), monocyte CD11b, and monocyte-platelet conjugates were all significantly increased (compared with baseline) in the saline group during and after CPB. Despite equivalent reductions in D-dimer formation in patients receiving EACA (P < 0.0001) and aprotinin (P < 0.0001), decreases in platelet CD62P and monocyte CD11b expression were incomplete (not significantly different from saline control). In contrast, peak monocyte-platelet conjugate formation was significantly reduced by both EACA (P = 0.026) and aprotinin (P = 0.039) immediately after CPB. CONCLUSIONS: EACA seems to be as effective as aprotinin at reducing peak monocyte-platelet adhesion after CPB. Furthermore, inhibition of excessive plasmin activity seems to influence monocyte-platelet adhesion. The findings suggest that monocyte-platelet conjugate formation may be a useful marker of monocyte and platelet activation in this clinical setting.  (+info)

Quantitative assessment of fibrinogen cross-linking by epsilon aminocaproic acid in patients with end-stage liver disease. (71/402)

Analysis of the effectiveness of antifibrinolytic therapy for liver transplant recipients is hampered by lack of quantitative assays for assessing drug effects. We adapted chemical engineering tools used in polymerization studies to quantify fibrinogen cross-linking by plasma from liver transplant patients obtained before and after epsilon aminocaproic acid (EACA) therapy. A target fluorescein isothiocyanate-fibrinogen (FITC-fibrinogen) molecule was constructed; it fluoresces in a quantifiable pattern when in solution, and undergoes cross-linking in the presence of plasmin inhibitors. Cross-linking quenches the fluorescent signal, and the quenching is a quantifiable endpoint. Thus fluorescence from this reporter molecule can be used to assess functional improvement in fibrinogen cross-linking as a result of antifibrinolytic therapies, and it is sensitive to picomolar amounts of plasmin inhibitors and activators. Cross-linking of FITC-fibrinogen by patient plasma, before and after EACA therapy, was assessed using fluorescence spectrometry. Fluorescence patterns from FITC-fibrinogen indicated no significant cross-linking of the target fibrinogen as a consequence of EACA in posttreatment plasma. When the fibrinogen-FITC target was assayed without plasma in the presence of EACA at concentrations that bracket therapeutic levels (100 and 400 microg/ml), significant fluorescence quenching (target FITC-fibrinogen cross-linking) was achieved. These results suggest that fibrinogen-FITC fluorescence is sensitive enough to detect EACA activity in clinically relevant ranges, but that EACA given in usual doses is insufficient to promote fibrinogen cross-linking in patients with end-stage liver disease.  (+info)

The prophylactic use of tranexamic acid and aprotinin in orthotopic liver transplantation: a comparative study. (72/402)

The efficacy of tranexamic acid (TA) and aprotinin (AP) in reducing blood product requirements in orthotopic liver transplantation (OLT) was compared in a prospective, randomized and double-blind study. One hundred and twenty seven consecutive patients undergoing OLT were enrolled; TA was administered to 64 OLT patients at a dose of 10mg /kg/h and aprotinin was administered to 63 OLT patients at a loading dose of 2 x 10(6) KIU followed by an infusion of 500,000 KIU/h. The portocaval shunt could not be performed in 14 OLT patients in the TA group and in 13 OLT patients in the AP group. However, all OLT patients that received either drug were included in the analysis. Perioperative management was standardized. Hemogram, coagulation tests, and blood product requirements were recorded during OLT and during the first 24 hours. No differences in diagnosis, Child score, preoperative coagulation tests, and intraoperative data were found between groups. No significant differences were observed in hemogram and intraoperative coagulation tests with the exception of activated partial thromboplastin time (aPTT). Similarly, there were no intergroup differences in transfusion requirements. Thromboembolic events, reoperations and mortality were similar in both groups. In conclusion, administration of regular doses of TA and AP during OLT did not result in large differences between the two groups.  (+info)