Expression profiling of senescent-associated genes in human dermis from young and old donors. Proof-of-concept study.

It is often described that it is difficult to really discriminate the cause of intrinsic skin aging. The aim of this study was to compare the profiles of expression of senescence-associated genes in biopsies of dermis from young and old human donors. TGF-beta1 was up-regulated in the dermis of old donors as well as the TGF-beta1-regulated genes. The anti-oxidant enzymes Selenium-dependent Glutathione peroxidase and Glutatione S-Transferase Theta 1 were also up-regulated in old dermis as well as Tumor Necrosis Factor Receptor Superfamily 1A. None of these genes had altered expression level in skin fibroblasts embedded in a collagen matrix and exposed to sublethal doses of UVB, suggesting their involvement in intrinsic aging. This study represents a proof-of-concept of larger whole transcriptome studies where all avenues should be used to subtract changes in gene expression due to extrinsic aging from changes potentially due to intrinsic aging

A fluorescence probe study on effects of surfactants on cloud points in aqueous poly(N-isopropylacrylamide) solutions.

Fluorescence probe methods were applied to investigate micelle formation of poly(N-isopropylacrylamide) (PNIPA) with two kinds of surfactants, anionic sodium n-dodecyl sulfate (SDS) or cationic n-dodecyltrimethylammonium chloride (DTAC), in aqueous solutions using pyrene or 1-pyrenecarboxaldehyde as fluorescence probes. Two PNIPA samples, one having a hydrophobic chain-end group and the other having a negatively-charged hydrophilic chain-end group, were used to investigate effects of the chain-end group on formation of the micelles. It was found that the critical aggregation concentration, at which the surfactant molecules start to bind to the PNIPA chains to form the micelles, is much lower for the PNIPA solutions containing SDS than for the solutions containing DTAC. This is consistent with the previous result that the cloud point in the PNIPA solutions containing SDS starts to increase from its value in the surfactant-free solutions at much lower concentration of added surfactant than that in the solutions containing DTAC. It was also found that there is a discrepancy in emission spectra for the solutions containing SDS between the two PNIPA samples but not for the solutions containing DTAC, indicating that the chain-end group of PNIPA may affect the microenvironmental polarity in the micelles composed of PNIPA and the surfactants