778 research outputs found

    Amylin in the periphery II: An updated mini-review

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    Amylin is a polypeptide that is cosecreted with insulin from the beta cells of the pancreas. Therefore, in states of diabetes in which the beta-cell mass is largely depleted or dysfunctional, insulin and amylin secretion are also lost or dysregulated. While the soluble monomeric form of amylin acts as a hormone that alters physiological responses related to feeding and acts as a specific growth factor, there has been renewed interest in the less-soluble oligomeric and insoluble polymeric forms of human (also monkey and cat) amylin that may contribute to the establishment of a pathophysiological pathway to overt diabetes. With this discovery has grown the hope of minimizing, with appropriate therapy, these toxic forms to preserve the functional (c) not-cell mass. Human beta cells may also be more vulnerable to these forms and one risk factor, a higher fat diet, may promote toxic forms. The generation and utilities of transgenic rodent models, which express enhanced levels of human amylin, have been accompanied by strategies that may lead to the reduction of toxic forms and associated risk factors. The successful definition and faithful expression of the physiological receptors (and complexes) for amylin that may differ for each target organ is an important development in the field of amylin research generally. Besides the heuristic value for the understanding of the molecular biology of receptors, the opportunity to screen and identify nonpeptide analogues that bind the physiological receptors has important implications for biomedicine and clinical practice in relation to treatments for diabetic complications, bone diseases, and eating disorders. In particular, in their capacities to mimic the effects of amylin as a growth factor, amylin analogues may prove useful in the stimulation of beta-cell mass (in conjunction with other factors), reduce the activity of the osteoclast population, and stimulate the regeneration of proximal tubules following toxic insult (and thus avoid the development of renal insufficiency)

    On the origin of the λ\lambda-transition in liquid Sulphur

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    Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid Sulphur around TλT_\lambda, i.e. in the temperature range where an abrupt increase in viscosity by four orders of magnitude is observed upon heating within few degrees. This allowed us - overcoming photo-induced and absorption effects at visible wavelengths - to reveal a chain relaxation process with characteristic time in the ms range. These results do rehabilitate the validity of the Maxwell relation in Sulphur from an apparent failure, allowing rationalizing the mechanical and thermodynamic behavior of this system within a viscoelastic scenario.Comment: 5 pages, 4 eps figures, accepted in Phys. Rev. Let

    Association of the 894G>T polymorphism in the endothelial nitric oxide synthase gene with risk of acute myocardial infarction

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    Background: This study was designed to investigate the association of the 894G>T polymorphism in the eNOS gene with risk of acute myocardial infarction (AMI), extent of coronary artery disease (CAD) on coronary angiography, and in-hospital mortality after AMI. Methods: We studied 1602 consecutive patients who were enrolled in the GEMIG study. The control group was comprised by 727 individuals, who were randomly selected from the general adult population. Results: The prevalence of the Asp298 variant of eNOS was not found to be significantly and independently associated with risk of AMI (RR = 1.08, 95%CI = 0.77–1.51, P = 0.663), extent of CAD on angiography (OR = 1.18, 95%CI = 0.63–2.23, P = 0.605) and in-hospital mortality (RR = 1.08, 95%CI = 0.29–4.04, P = 0.908). Conclusion: In contrast to previous reports, homozygosity for the Asp298 variant of the 894G>T polymorphism in the eNOS gene was not found to be associated with risk of AMI, extent of CAD and in-hospital mortality after AM

    Pressure screening in the interior of primary shells in double-wall carbon nanotubes

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    The pressure response of double-wall carbon nanotubes has been investigated by means of Raman spectroscopy up to 10 GPa. The intensity of the radial breathing modes of the outer tubes decreases rapidly but remain observable up to 9 GPa, exhibiting a behavior similar (but less pronounced) to that of single-wall carbon nanotubes, which undergo a shape distortion at higher pressures. In addition, the tangential band of the external tubes broadens and decreases in amplitude. The corresponding Raman features of the internal tubes appear to be considerably less sensitive to pressure. All findings lead to the conclusion that the outer tubes act as a protection shield for the inner tubes whereas the latter increase the structural stability of the outer tubes upon pressure application.Comment: PDF with 15 pages, 3 figures, 1 table; submitted to Physical Review
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