Brane world corrections to Newton's law

We discuss possible variations of the effective gravitational constant with length scale, predicted by most of alternative theories of gravity and unified models of physical interactions. After a brief general exposition, we review in more detail the predicted corrections to Newton's law of gravity in diverse brane world models. We consider various configurations in 5 dimensions (flat, de Sitter and AdS branes in Einstein and Einstein-Gauss-Bonnet theories, with and without induced gravity and possible incomplete graviton localization), 5D multi-brane systems and some models in higher dimensions. A common feature of all models considered is the existence of corrections to Newton's law at small radii comparable with the bulk characteristic length: at such radii, gravity on the brane becomes effectively multidimensional. Many models contain superlight perturbation modes, which modify gravity at large scale and may be important for astrophysics and cosmology.Comment: Brief review, 16 pages, 92 references. Some description and references adde

Platelet activating factor stimulates arachidonic acid release in differentiated keratinocytes via arachidonyl non-selective phospholipase A2

Platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is known to be present in excess in psoriatic skin, but its exact role is uncertain. In the present study we demonstrate for the first time the role of group VI PLA2 in PAF-induced arachidonic acid release in highly differentiated human keratinocytes. The group IVα PLA2 also participates in the release, while secretory PLA2s play a minor role. Two anti-inflammatory synthetic fatty acids, tetradecylthioacetic acid and tetradecylselenoacetic acid, are shown to interfere with signalling events upstream of group IVα PLA2 activation. In summary, our major novel finding is the involvement of the arachidonyl non-selective group VI PLA2 in PAF-induced inflammatory responses

Induction of Cellular Senescence by Secretory Phospholipase A2 in Human Dermal Fibroblasts through an ROS-Mediated p53 Pathway

Secretory phospholipase A2 (sPLA2) is involved in various cellular physiological and pathological responses, especially in inflammatory responses. Accumulating evidence suggests that inflammation is an underlying basis for the molecular alterations that link aging and age-related pathological processes. However, the involvement of sPLA2 in cellular senescence is not clear. In this study, we found that sPLA2 treatment induces cellular senescence in human dermal fibroblasts (HDFs), as confirmed by increases in senescence-associated β-galactosidase activity, changes in cell morphology, and upregulation of p53/p21 protein levels. sPLA2-induced senescence was observed in p16-knockdown HDFs and p16-null mouse fibroblasts, but not in p53-knockdown HDFs and p53-null mouse fibroblasts. Treatment with sPLA2 increases reactive oxygen species (ROS) production, and an antioxidant, N-acetylcysteine, inhibits sPLA2-induced cellular senescence. These results suggest that sPLA2 has a role in cellular senescence in HDFs during inflammatory response by promoting ROS-dependent p53 activation and might therefore contribute to inflammatory disorders associated with aging