Mechanistic studies of anti-hyperpigmentary compounds: elucidating their inhibitory and regulatory actions.

Searching for depigmenting agents from natural sources has become a new direction in the cosmetic industry as natural products are generally perceived as relatively safer. In our previous study, selected Chinese medicines traditionally used to treat hyperpigmentation were tested for anti-hyperpigmentary effects using a melan-a cell culture model. Among the tested chemical compounds, 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were found to possess hypopigmentary effects. Western blot analysis, reverse transcriptase polymerase chain reaction (RT-PCR), cyclic adenosine monophosphate (cAMP) assay, protein kinase A (PKA) activity assay, tyrosinase inhibition assay and lipid peroxidation inhibition assay were performed to reveal the underlying cellular and molecular mechanisms of the hypopigmentary effects. 4-Ethylresorcinol and 4-ethylphenol attenuated mRNA and protein expression of tyrosinase-related protein (TRP)-2, and possessed antioxidative effect by inhibiting lipid peroxidation. 1-Tetradecanol was able to attenuate protein expression of tyrosinase. The hypopigmentary actions of 4-ethylresorcinol, 4-ethylphenol and 1-tetradecanol were associated with regulating downstream proteins along the PKA pathway. 4-Ethylresorcinol was more effective in inhibiting melanin synthesis when compared to 4-ethylphenol and 1-tetradecanol

Large-Eddy Simulation of Flow and Pollutant Transports in and Above Two-Dimensional Idealized Street Canyons

A large-eddy simulation (LES) model, using the one-equation subgrid-scale (SGS) parametrization, was developed to study the flow and pollutant transport in and above urban street canyons. Three identical two-dimensional (2D) street canyons of unity aspect ratio, each consisting of a ground-level area source of constant pollutant concentration, are evenly aligned in a cross-flow in the streamwise direction x. The flow falls into the skimming flow regime. A larger computational domain is adopted to accurately resolve the turbulence above roof level and its influence on the flow characteristics in the street canyons. The LES calculated statistics of wind and pollutant transports agree well with other field, laboratory and modelling results available in the literature. The maximum wind velocity standard deviations σi in the streamwise (σu), spanwise (σv) and vertical (σw) directions are located near the roof-level windward corners. Moreover, a second σw peak is found at z ≈ 1.5h (h is the building height) over the street canyons. Normalizing σi by the local friction velocity u*, it is found that σu/u* ≈ 1.8, σv/u* ≈ 1.3 and σw/u* ≈ 1.25 exhibiting rather uniform values in the urban roughness sublayer. Quadrant analysis of the vertical momentum flux u′′w′′ shows that, while the inward and outward interactions are small, the sweeps and ejections dominate the momentum transport over the street canyons. In the x direction, the two-point correlations of velocity Rv,x and Rw,x drop to zero at a separation larger than h but Ru,x (= 0.2) persists even at a separation of half the domain size. Partitioning the convective transfer coefficient ΩT of pollutant into its removal and re-entry components, an increasing pollutant re-entrainment from 26.3 to 43.3% in the x direction is revealed, suggesting the impact of background pollutant on the air quality in street canyons. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Flow pattern and pollutant removal behavior for idealized 2D urban street canyons in different thermal stratifications using large-eddy simulation

postprintThe 2011 General Assembly of the European Geosciences Union (EGU), Vienna, Austria, 3-8 April 2011. In Geophysical Research Abstracts, 2011, v. 13, EGU2011-293

Analysis of the momentum and pollutant transport at the roof level of 2D idealized street canyons: a large-eddy simulation solution

To investigate the detailed momentum and pollutant transports between urban street canyons and the shear layer, a large-eddy simulation (LES) model was developed to calculate the flow and pollutant dispersion in isothermal conditions. The computational domain consisted of three identical two-dimensional (2D) idealized street canyons of unity aspect ratio. The flow field was assumed to be periodic in the horizontal domain boundaries. The subgrid-scale (SGS) stress was calculated by solving the SGS turbulent kinetic energy (TKE) conservation. An area pollutant source with constant pollutant concentration was prescribed on the ground of all streets. Zero pollutant concentration and an open boundary were applied at the domain inflow and outflow, respectively. The quadrant and budget analyses were employed to examine the …published_or_final_versionThe 7th General Assembly of the European Geosciences Union (EGU2010), Vienna, Austria, 2-7 May 2010. In Geophysical Research Abstracts, 2010, v. 12, EGU2010-1486-

Large-eddy simulation of turbulent transports in urban street canyons in different thermal stabilities

Three scenarios of large-eddy simulation (LES) were performed to examine the characteristic flow and pollutant dispersion in urban street canyons under neutral, unstable and stable thermal stratifications. Street canyons of unity aspect ratio with ground-heating or –cooling are considered. In the LESs of the thermal stabilities tested, a large primary recirculation is developed in the center core and the turbulence production is dominated at the roof level of the street canyon. The current LES results demonstrate that unstable stratification enhances the mean wind, turbulence and pollutant removal of street canyons. On the other hand, in stable stratification, which has been less investigated in the past, the ground-level mean wind and turbulence are substantially suppressed by the large temperature inversion. Whereas, the weakened recirculating wind in the street canyon results in a larger velocity gradient that increases the turbulence production at the roof level. It also slows down the turbulence being carried from the roof down to the lower street canyon. Therefore, a higher level of turbulent kinetic energy (TKE) is retained at the mid-level of the windward side in the stably stratified street canyon.postprintThe 5th International Symposium on Computational Wind Engineering (CWE2010), Chapel Hill, N.C., 23-27 May 2010

Large-eddy simulation of street canyon flow and pollutant transport in neutral and unstable stratifications

Session 15 - Urban Dispersion II: 15.1postprintThe 90th Annual Meeting of the American Meteorological Society (AMS), Atlanta, GA., 17-21 January 2010

Transition temperature in QCD with physical light and strange quark masses

We present results from a calculation of the transition temperature in QCD with two light and one heavier (strange) quark mass on lattices with temporal extent N_t =4 and 6. Calculations with improved staggered fermions have been performed with a strange quark mass fixed close to its physical value and for various light to strange quark mass ratios that correspond to light pseudo-scalar masses in the range (150-500) MeV. From a combined extrapolation to the chiral (m_l -> 0) and continuum (aT -> 0) limits we obtain for the transition temperature at the physical point T_c = 192(7)(4) MeV. We also present first results from an ongoing calculation of the QCD equation of state with almost realistic light and strange quark masses.Comment: 4 pages, 4 figures, to appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Shanghai, Nov. 200

Sertoli-germ cell anchoring junction dynamics in the testis are regulated by an interplay of lipid and protein kinases

When Sertoli and germ cells were co-cultured in vitro in serum-free chemically defined medium, functional anchoring junctions such as cell-cell intermediate filament-based desmosome-like junctions and cell-cell actin-based adherens junctions (e.g. ectoplasmic specialization (ES)) were formed within 1-2 days. This event was marked by the induction of several protein kinases such as phosphatidylinositol 3-kinase (PI3K), phosphorylated protein kinase B (PKB; also known as Akt), p21-activated kinase-2 (PAK-2), and their downstream effector (ERK) as well as an increase in PKB intrinsic activity. PI3K, phospho (p)-PKB, and PAK were co-localized to the site of apical ES in the seminiferous epithelium of the rat testis in immunohistochemistry studies. Furthermore, PI3K also co-localized with p-PKB to the same site in the epithelium as determined by fluorescence microscopy, consistent with their localization at the ES. These kinases were shown to associate with ES-associated proteins such as β1-integrin, phosphorylated focal adhesion kinase, and c-Src by co-immunoprecipitation, suggesting that the integrin-laminin protein complex at the apical ES likely utilizes these protein kinases as regulatory proteins to modulate Sertoli-germ cell adherens junction dynamics via the ERK signaling pathway. To validate this hypothesis further, an in vivo model using AF-2364 (1-(2,4-dichlorobenzyl)-1H-indazole-3-carbohydrazide) to perturb Sertoli-germ cell anchoring junction function, inducing germ cell loss from the epithelium in adult rats, was used in conjunction with specific inhibitors. Interestingly, the event of germ cell loss induced by AF-2364 in vivo was also associated with induction of PI3K, p-PKB, PAK-2, and p-ERK as well as a surge in intrinsic PKB activity. Perhaps the most important of all, pretreatment of rats with wortmannin (a PI3K inhibitor) or anti-β1-integrin antibody via intratesticular injection indeed delayed AF-2364-induced spermatid loss from the epithelium. In summary, these results illustrate that Sertoli-germ cell anchoring junction dynamics in the testis are regulated, at least in part, via the β1-integrin/PI3K/PKB/ERK signaling pathway. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.postprin