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Background: Inhibition of platelet responsiveness is important for controlling thrombosis. It is well established that platelet endothelial cell adhesion molecule-1 (PECAM-1) serves as a physiological negative regulator of platelet-collagen interactions. We recently demonstrated that leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a negative regulator of platelet production and reactivity. It is however not known if LAIR-1 and PECAM-1 function in the same or different inhibitory pathways. Objectives: In this study, we investigated the role of LAIR-1 alongside PECAM-1 in megakaryocyte development and platelet production and determined the functional redundancy through characterization of a LAIR-1/PECAM-1 double knockout (DKO) mouse model. Methods: LAIR-1 and PECAM-1 expression in megakaryocytes were evaluated by western blotting. Megakaryocyte ploidy and proplatelet formation were evaluated by flow cytometry and fluorescent microscopy. Platelet function and signalling were compared in wild-type, LAIR-1−/−, PECAM-1−/− and DKO mice using aggregometry, flow cytometry and western blotting. Thrombosis was evaluated using the FeCl3 carotid artery model. Results: We show that LAIR-1/PECAM-1 DKO mice exhibit a 17% increase in platelet count. Bone marrow-derived megakaryocytes from all 3 mouse models had normal ploidy in vitro, suggesting that neither LAIR-1 nor PECAM-1 regulates megakaryocyte development. Furthermore, relative to wild-type platelets, platelets derived from LAIR-1, PECAM-1, and DKO mice were equally hyperresponsive to collagen in vitro, indicating that LAIR-1 and PECAM-1 participate in the same inhibitory pathway. Interestingly, DKO mice exhibited normal thrombus formation in vivo due to DKO mouse platelets lacking the enhanced Src family kinase activation previously shown in platelets from LAIR-1-deficient mice. Conclusion: Findings from this study reveal that LAIR-1 and PECAM-1 act to inhibit GPVI-mediated platelet activation via the same signaling pathway. Mice lacking LAIR-1 and PECAM-1 do not however exhibit an increase in thrombus formation despite minor increase in platelet count and reactivity to collagen. This study adds to the growing evidence that immunoreceptor tyrosine-based inhibition motif–containing receptors are important regulators of platelet count and function.

Charge interactions play a critical role in the activation of the innate immune system by damage- and pathogen-associated molecular pattern receptors. The ability of these receptors to recognize a wide spectrum of ligands through a common mechanism is critical in host defense. In this article, we argue that platelet glycoprotein receptors that signal through conserved tyrosine-based motifs function as pattern recognition receptors (PRRs) for charged endogenous and exogenous ligands, including sulfated polysaccharides, charged proteins and nanoparticles. This is exemplified by GPVI, CLEC-2 and PEAR1 which are activated by a wide spectrum of endogenous and exogenous ligands, including diesel exhaust particles, sulfated polysaccharides and charged surfaces. We propose that this mechanism has evolved to drive rapid activation of platelets at sites of injury, but that under some conditions it can drive occlusive thrombosis, for example, when blood comes into contact with infectious agents or toxins. In this Opinion Article, we discuss mechanisms behind charge-mediated platelet activation and opportunities for designing nanoparticles and related agents such as dendrimers as novel antithrombotics.

BackgroundThe left atrial posterior wall (LAPW) is potentially an important area for the development and maintenance of atrial fibrillation. We assessed whether there are regional electrical differences throughout the murine left atrial myocardium that could underlie regional differences in arrhythmia susceptibility.MethodsWe used high-resolution optical mapping and sharp microelectrode recordings to quantify regional differences in electrical activation and repolarisation within the intact, superfused murine left atrium and quantified regional ion channel mRNA expression by Taqman Low Density Array. We also performed selected cellular electrophysiology experiments to validate regional differences in ion channel function.ResultsSpontaneous ectopic activity was observed during sustained 1Hz pacing in 10/19 intact LA and this was abolished following resection of LAPW (0/19 resected LA, PConclusionsThe murine LAPW myocardium has a different electrical phenotype and ion channel mRNA expression profile compared with other regions of the LA, and this is associated with increased ectopic activity. If similar regional electrical differences are present in the human LA, then the LAPW may be a potential future target for treatment of atrial fibrillation.

The present paper is an attempt to present the hydrobiological observation on Virla reservoir of Khargone district. The data revealed that 5 major algal groups i.e. Cyanophyceae, Bacillariophyceae, Chlorophyceae, Euglenophyceae and Chrysophyceae are present in Virla reservoirs.