Anticoagulant and fibrinogenolytic properties of the venom of Polybia occidentalis social wasp

Previous studies have shown that venoms of social wasps and bees exhibit strong anticoagulant activity. The present study describes the anticoagulant and fibrinogen-degrading pharmacological properties of the venom of Polybia occidentalis social wasp. The results demonstrated that this venom presented anticoagulant effect, inhibiting the coagulation at different steps of the clotting pathway (intrinsic, extrinsic and common pathway). The venom inhibited platelet aggregation and degraded plasma fibrinogen, possibly containing metal-dependent metalloproteases that specifically cleave the B beta-chain of fibrinogen. In conclusion, fibrinogenolytic and anticoagulant properties of this wasp venom find a potential application in drug development for the treatment of thrombotic disorders. For that, further studies should be carried out in order to identify and isolate the active compounds responsible for these effects. Blood Coagul Fibrinolysis 21: 653-659 (c) 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Essential role of platelet-activating factor receptor in the pathogenesis of Dengue virus infection

Severe dengue infection in humans causes a disease characterized by thrombocytopenia, increased levels of cytokines, increased vascular permeability, hemorrhage, and shock. Treatment is supportive. Activation of platelet-activating factor (PAF) receptor (PAFR) on endothelial cells and leukocytes induces increase in vascular permeability, hypotension, and production of cytokines. We hypothesized that activation of PAFR could account for the major systemic manifestations of dengue infection. Inoculation of adult mice with an adapted strain of Dengue virus caused a systemic disease, with several features of the infection in humans. In PAFR(-/-) mice, there was decreased thrombocytopenia, hemoconcentration, decreased systemic levels of cytokines, and delay of lethality, when compared with WT infected mice. Treatment with UK-74,505, an orally active PAFR antagonist, prevented the above-mentioned manifestations, as well as hypotension and increased vascular permeability, and decreased lethality, even when started 5 days after virus inoculation. Similar results were obtained with a distinct PAFR antagonist, PCA-4246. Despite decreased disease manifestation, viral loads were similar (PAFR(-/-)) or lower (PAFR antagonist) than in WT mice. Thus, activation of PAFR plays a major role in the pathogenesis of experimental dengue infection, and its blockade prevents more severe disease manifestation after infection with no increase in systemic viral titers, suggesting that there is no interference in the ability of the murine host to deal with the infection. PAFR antagonists are disease-modifying agents in experimental dengue infection.

Comparisons of the release of vasodilator substances from left and right cardiac chambers of the isolated perfused rabbit heart: Implications for intraventricular thrombus formation

Prostacyclin (PgI(2)) and endothelium-derived nitric oxide (EDNO) are produced by the arterial and venous endothelium. In addition to their vasodilator action on vascular smooth muscle, both act together to inhibit platelet aggregation and promote platelet disaggregation. EDNO also inhibits platelet adhesion to the endothelium. EDNO and PgI(2) have been shown to be released from the cultured endocardial cells. In this study, we examined the release of vasoactive substances from the intact endocardium by using isolated rabbit hearts perfused with physiological salt solution (95% O(2)/5% CO(2), T = 37 degrees C). The right and left cardiac chambers were perfused through separate constant-flow perfusion loops (physiological salt solution, 8 ml min(-1)). Effluent from left and right cardiac, separately, was bioassayed on canine coronary artery smooth muscle, which had been contracted with prostaglandin F(2 alpha_)(2 x 10(-6) M) and no change in tension was exhibit. However, addition of calcium ionophore A23187 (10(-6) M) to the cardiac chambers` perfusion line induced vasodilation of the bioassay coronary ring, 61.4 +/- 7.4% versus 70.49 +/- 6.1% of initial prostaglandin F(2 alpha) contraction for the left and right cardiac chambers perfusate, respectively (mean +/- SEM, n = 10, p > 0.05). Production of vasodilator was blocked totally in the left heart but, only partially blocked in the right heart by adding indomethacin (10(-5) M) to the perfusate, respectively, 95.2 +/- 2.2% versus 41.5 +/- 4.8% (mean +/- SEM, n = 10, p < 0.05). 6-Keto prostaglandin F(1 alpha), measured in the endocardial superfusion effluent was also higher for the left cardiac chambers than for the right at the time of stimulation with the A23187, respectively, 25385.88 +/- 5495 pg/ml (n = 8) versus 13,132.45 +/- 1839.82 pg/ml (n = 8), (p < 0.05). These results showed that cyclooxygenase pathway plays major role in generating vasoactive substances for the left cardiac chamber endocardium; while it is not the main pathway for the right ventricular endocardium at which EDNO and PgI(2) Could act together and potentiate their antithrombogenic activities in isolated perfused rabbit heart. This may be an explanation for the intraventricular thrombus mostly seen in left ventricle rather than in right ventricle as a complication of myocardial infarction. (C) 2009 Elsevier Inc. All rights reserved.

Antitumoural effect of an L-amino acid oxidase isolated from Bothrops jararaca snake venom

An L-amino acid oxidase (BjarLAAO-I) from Bothrops jararaca snake venom was highly purified using a stepwise sequential chromatography on Sephadex G-75, Benzamidine Sepharose and Phenyl Sepharose. Purified BjarLAAO-I showed a molecular weight around 60,000 under reducing conditions and about 125,000 in the native form, when analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively. BjarLAAO-I is a homodimeric acidic glycoprotein, pI similar to 5.0, and N-terminal sequence showing close structural homology with other snake venom LAAOs. The purified enzyme catalysed the oxidative deamination of L-amino acids, the most specific substrate being L-Phe. Five amino acids, L-Ser, L-Pro, L-Gly, L-Thr and L-Cys were not oxidized, clearly indicating a significant specificity. BjarLAAO-I significantly inhibited Ehrlich ascites tumour growth and induced an influx of polymorphonuclear cells, as well as spontaneous liberation of H(2)O(2) from peritoneal macrophages. Later, BjarLAAO-I induced mononuclear influx and peritoneal macrophage spreading. Animals treated with BjarLAAO-I showed higher survival time.

Evaluation of platelet count by automatic blood counter QBC Vet Autoread (R) compared with blood smear estimative and count by hemocytometer

The platelet blood count in laboratorial routine provides to the clinician important information about the hemostasis of the patient. There are many techniques described, however the gold standard techniques realized in hemocytometer spent a lot of time, making this technique impracticable in great routines. This research had the intent to evaluate if the automatic veterinary blood counter QBC Vet Autoread (R), whose results get five minutes to be ready, is capable to offer a trustworthy platelet count number. To this end, were evaluated the correlations among three different forms of platelets count in dogs: count in automatic blood counter QBC Vet Autoread (R), estimative in blood smear and the gold standard method by manual count in hemocytometer. The viability and confidence use of automatic blood counters of the medicine veterinary routine. Seventeen dogs were chosen randomly way, in the medical and surgical routine of HOVET-USP. The analysis revel high correlation between the hemocytometer and the estimative in blood smear (r=0,875) and between the hemocytometer and automatic blood count by QBC Vet Autoread (R) (r=0,939). Conclude that the platelet blood cont by QBC Vet Autoread (R), in addition to be fast, it`s more truthful when compared with estimative in blood smear, although the latter one also had elevated correlation. However, morphological analysis through the smears cannot be dismissed because none of the other two techniques evaluated have the ability to assess platelet morphological changes.

Influence of Antiplatelet Drugs in the Pathogenesis of Experimental Periodontitis and Periodontal Repair in Rats

Background: Platelets contain an array of biologic mediators that can modulate inflammation and repair processes including proinflammatory mediators and growth factors. Previous studies have shown that periodontitis and periodontal repair are associated with platelet activation. We hypothesized that drug-induced platelet inactivation may interfere in the processes of inflammation and repair in experimental periodontitis in rats by suppressing the release of biologic mediators from platelets to the site of injury. Methods: To measure the effects on periodontitis, ligatures were placed around first molars, and aspirin (Asp, 30 mg/kg) or clopidogrel (Clo, 75 mg/kg) was given intragastrically once daily for 15 days. Interleukin-6 (IL-6), tumor necrosis factor-a (TNF-alpha), and thromboxane A(2) levels were measured by enzyme-linked immunosorbent assay. To evaluate the effects of antiplatelet drugs on periodontal repair, ligatures were removed after 15 days of periodontitis induction, and Asp or Clo were administered beginning the following day for 15 days. Periodontal repair was assessed by microcomputed tomography. Results: On periodontitis phase, Asp and Clo significantly reduced levels of TNF-alpha and II-6 (P < 0.05), but only Asp decreased thromboxane A(2) (P < 0.05). Asp and Clo decreased inflammatory infiltration; however, this reduction was more pronounced with Clo treatment (P < 0.05). Histometric analysis showed that Asp and Clo impaired alveolar bone resorption. During the repair phase and after removal of the ligatures, microcomputed tomography analysis demonstrated that treatment with Asp and Clo did not impair alveolar bone repair. Conclusion: Systemic administration of Asp and Clo attenuates the inflammation associated with periodontitis without affecting the repair process when stimulus is removed. J Periodontol 2011;82:767-777.

The effect of resource aggregation at different scales: Optimal foraging behavior of Cotesia rubecula

Resources can be aggregated both within and between patches. In this article, we examine how aggregation at these different scales influences the behavior and performance of foragers. We developed an optimal foraging model of the foraging behavior of the parasitoid wasp Cotesia rubecula parasitizing the larvae of the cabbage butterfly Pieris rapae. The optimal behavior was found using stochastic dynamic programming. The most interesting and novel result is that the effect of resource aggregation within and between patches depends on the degree of aggregation both within and between patches as well as on the local host density in the occupied patch, but lifetime reproductive success depends only on aggregation within patches. Our findings have profound implications for the way in which we measure heterogeneity at different scales and model the response of organisms to spatial heterogeneity.

Clinical trials with glycoprotein IIB/IIIA antagonists - No benefit without bleeding?

As the glycoprotein GPIIb/IIIa receptor is the final common pathway in platelet aggregation, antagonists of this receptor cause a profound inhibition of aggregation induced by any agonist. The short-term efficacy and safety of GPIIb/IIIa antagonists in patients undergoing coronary angioplasty was demonstrated with murine 7E3 Fab, but this antibody was immunogenic. Abciximab is a chimeric human-mouse monoclonal antibody that is less immunogenic. The first major trial with a GPIIb/IIIa antagonist was the EPIC trial with abciximab, which showed that abciximab reduced the ischemic complications of coronary balloon angioplasty and atherectomy in high-risk patients, but increased the risk of bleeding. Subsequent studies showed that using less concurrent heparin reduced bleeding. Abciximab also reduced the rate of revascularization. Further studies have shown that the benefits of abciximab extended to all patients undergoing angioplasty (EPILOG), including patients with unstable angina (CAPTURE) and acute myocardial infarction (RAPPORT). Clinical trials with eptifibatide and tirofiban have failed to demonstrate benefit, at the doses used, in angioplasty. Abciximab and eptifibatide, but not oral xemilofiban, improve the safety of the coronary stenting procedure. Shortterm intravenous treatment with lamifiban, eptifibatide or tirofiban is beneficial in acute coronary syndromes (unstable angina, non-Q wave myocardial infarction). Orally active GPIIb/IIIa antagonists are being developed for use in acute coronary syndromes and myocardial infarction. However, no benefit has been shown with lefradafiban in acute coronary syndromes and sibrafiban and orbofiban are harmful. Eptifibatide, lamifiban and abciximab improve coronary patency in myocardial infarction, and long-term trials of GPIIb/IIIa antagonists are being conducted in acute myocardial infarction. Abciximab can cause thrombocytopenia, and all the GPIIb/IIIa antagonists increase the incidence of bleeding, but there is no excess of intracranial hemorrhage. (C) 2001 Prous Science. All rights reserved.

Pharmacotherapy of intermittent claudication

Intermittent claudication (IC) is leg muscle pain, cramping and fatigue brought on by exercise and is the primary symptom of peripheral arterial disease. The goals of pharmacotherapy for IC are to increase the walking capacity/quality of life and to decrease rates of amputation. In 1988, pentoxifylline was the only drug that had reasonable supportive clinical trial evidence for being beneficial in IC. Since then a number of drugs have shown benefit or potential in IC. Cilostazol, a specific inhibitor of phosphodiesterase 3 and activator of lipoprotein lipase, clearly increases pain-free and absolute walking distances in claudicants. However, cilostazol does cause minor side effects including headache, diarrhoea, loose stools and flatulence. Naftidrofuryl, a serotonin (5-HT2) receptor antagonist and antiplatelet drug, is beneficial in claudicants. Inhibitors of platelet aggregation (including nitric oxide from L-arginine or glyceryl trinitrate) and anticoagulants (low molecular weight heparin, defibrotide) probably have both short and long-term benefits in IC. In addition, intravenous infusions of prostaglandins (PGs) PGE1 and PGI2 have an established role in severe peripheral arterial disease and the recent introduction of longer lasting and/or oral forms of the PGs makes them more likely to be useful in the IC associated with less severe forms of the disease. There are some exciting new approaches to the treatment of IC, including propionyl-L-carnitine and basic fibroblast growth factor (bFGF).

Clopidogrel: A CURE in acute coronary syndromes? (A Key Paper Evaluation)

The standard approach to preventing acute coronary syndromes (ACSs)has been to inhibit platelet aggregation with aspirin and to inhibit blood coagulation with low molecular-weight heparin (LMWH). Even with this combination there is still a substantial short and long-term cardiovascular risk. The Clopidogrel in Unstable angina to prevent Recurrent Events (CURE) trial [1] compared clopidogrel plus aspirin against aspirin alone in patients with ACSs. The clopidogrel regimen was a loading dose of 300 mg p.o. followed by 75 mg/day and the recommended dose of aspirin was 75 - 325 mg/day. The first primary outcome was a composite of death from cardiovascular causes, non-fatal myocardial infarction (MI) or stroke and this occurred significantly less often in the clopidogrel than the placebo group (9.3 vs. 11.4%). Although there were more clopidogrel patients with life-threatening bleeding (clopidogrel 2.2%, placebo 1.8%), this represented GI haemorrhages and bleeding at sites of arterial puncture rather than fatal bleeding. This trial suggests a role for clopidogrel in the long-term treatment of ACSs

Prolonged retention after aggregation into secretory granules of human R183H-growth hormone (GH), a mutant that causes autosomal dominant GH deficiency type II

Human R183H-GH causes autosomal dominant GH deficiency type II. Because we show here that the mutant hormone is fully bioactive, we have sought to locate an impairment in its progress through the secretory pathway as assessed by pulse chase experiments. Newly synthesized wild-type and R183H-GH were stable when expressed transiently in AtT20 cells, and both formed equivalent amounts of Lubrol-insoluble aggregates within 40 min after synthesis. There was no evidence for intermolecular disulfide bond formation in aggregates of wild-type hormone or the R183H mutant. Both wildtype and R183H-GH were packaged into secretory granules, assessed by the ability of 1 mm BaCl2 to stimulate release and by immunocytochemistry. The mutant differed from wildtype hormone in its retention in the cells after packaging into secretory granules; 50% more R183H-GH than wild-type aggregates were retained in AtT20 cells 120 min after synthesis, and stimulated release of R183H-GH or a mixture of R183H-GH and wild-type that had been retained in the cell was reduced. The longer retention of R183H-GH aggregates indicates that a single point mutation in a protein contained in secretory granules affects the rate of secretory granule release.

Comparison of the in vitro neuromuscular activity of venom from three Australian snakes (Hoplocephalus stephensi, Austrelaps superbus and Notechis scutatus): Efficacy of tiger snake antivenom

1. Tiger snake antivenom, raised against Notechis scutatus venom, is indicated not only for the treatment of envenomation by this snake, but also that of the copperhead (Austrelaps superbus ) and Stephen's banded snake (Hoplocephalus stephensi ). The present study compared the neuromuscular pharmacology of venom from these snakes and the in vitro efficacy of tiger snake antivenom. 2. In chick biventer cervicis muscle and mouse phrenic nerve diaphragm preparations, all venoms (3-10 mug/mL) produced inhibition of indirect twitches. In the biventer muscle, venoms (10 mug/mL) inhibited responses to acetylcholine (1 mmol/L) and carbachol (20 mumol/L), but not KCl (40 mmol/L). The prior (10 min) administration of 1 unit/mL antivenom markedly attenuated the neurotoxic effects of A. superbus and N. scutatus venoms (10 mug/mL), but was less effective against H. stephensi venom (10 mug/mL); 5 units/mL antivenom attenuated the neurotoxic activity of all venoms. 3. Administration of 5 units/mL antivenom at t(90) partially reversed, over a period of 3 h, the inhibition of twitches produced by N. scutatus (10 mug/mL; 41% recovery), A. superbus (10 mug/mL; 25% recovery) and H. stephensi (10 mug/mL; 50% recovery) venoms. All venoms (10-100 mug/mL) also displayed signs of in vitro myotoxicity. 4. The results of the present study indicate that all three venoms contain neurotoxic activity that is effectively attenuated by tiger snake antivenom.

Effect of cylindrical filler aggregation on the electrical conductivity of composites

This work reports on the effect of carbon nanotube aggregation on the electrical conductivity and other network properties of polymer/carbon nanotube composites by modeling the carbon nanotubes as hard-core cylinders. It is shown that the conductivity decreases for increasing filler aggregation, and that this effect is more significant for higher cylinder volume fractions. It is also demonstrated, for volume fractions at which the giant component is present, that increasing the fraction of cylinders within clusters leads to a break of the giant component and the formation of a set of finite clusters. The decrease of the giant component with the increase of the fraction of cylinders within the cluster can be related to a decrease of the spanning probability due to a decrease of the number of cylinders between the clusters. Finally, it is demonstrated that the effect of aggregation can be understood by employing the network theory.

Pseudomonas aeruginosa amidase: Aggregation in recombinant Escherichia coli

The effect of cultivation parameters such as temperature incubation, IPTG induction and ethanol shock on the production of Pseudomonasaeruginosa amidase (E.C.3.5.1.4) in a recombinant Escherichia coli strain in LB ampicillin culture medium was investigated. The highest yield of solubleamidase, relatively to other proteins, was obtained in the condition at 37 degrees C using 0.40 mM IPTG to induce growth, with ethanol. Our results demonstrate the formation of insoluble aggregates containing amidase, which was biologically active, in all tested growth conditions. Addition of ethanol at 25 degrees C in the culture medium improved amidase yield, which quantitatively aggregated in a biologically active form and exhibited in all conditions an increased specific activity relatively to the soluble form of the enzyme. Non-denaturing solubilization of the aggregated amidase was successfully achieved using L-arginine. The aggregates obtained from conditions at 37 degrees C by Furier transform infrared spectroscopy (FTIR) analysis demonstrated a lower content of intermolecular interactions, which facilitated the solubilization step applying non-denaturing conditions. The higher interactions exhibited in aggregates obtained at suboptimal conditions compromised the solubilization yield. This work provides an approach for the characterization and solubilization of novel reported biologically active aggregates of this amidase.