Effects of dried longan seed (Euphoria longana Lam.) extract on VEGF secretion and expression in colon cancer cells and angiogenesis in human umbilical vein endothelial cells

Angiogenesis is a critical event in cancer metastasis, via delivery of needed oxygen and nutrients to tumor cells. Anti-angiogenesis is one strategy for controlling cancer progression. We herein report anti-angiogenesis activity of dried longan seeds using colon adenocarcinoma cells (SW480 cells) and human umbilical vein endothelial cells (HUVECs). Sephadex LH-20 column chromatography was used for separate three dried longan seed fractions. We firstly evaluated vascular endothelial cell growth factor (VEGF) secretion, expression and colony formation of SW480 cells, using enzyme-linked immunosorbent assay (ELISA), Western blot analysis and soft agar assays. Meanwhile cell proliferation, gelatinase activity and tube formation of HUVECs were determined via proliferation assay, gelatin zymography and in vitro tube formation assay, respectively. The results suggest that dried longan seed fractions could be potential angiogenic inhibitors not only interruption of VEGF secretion and expression in SW480 cells but also abrogation of cell proliferation, the activity of gelatinase and tube formation of HUVECs.     

VULCAN-SUPPORTED Pt ELECTROCATALYSTS FOR PEMFCs PREPARED USING SUPERCRITICAL CARBON DIOXIDE DEPOSITION

In this study, supercritical carbon dioxide (scCO₂) deposition was used to prepare vulcan-supported Pt (Pt/Vulcan) electrocatalysts for proton exchange membrane fuel cells (PEMFCs), and the effects of process variables on the properties of the electrocatalysts were investigated. The two different methods used to reduce the organometallic precursor were thermal reduction in nitrogen at atmospheric pressure and thermal reduction in scCO₂. In the former method, the maximum Pt loading achieved was 9%, and this was governed by the adsorption isotherm of the Pt precursor between the scCO₂ phase and the Vulcan phase. By using the latter method, higher Pt loadings of 15% and 35% could be achieved. The Pt/Vulcan catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). The average particle sizes for Pt/Vulcan 9%, 15%, and 35% catalysts were 1.2, 1.3, and 2 nm, respectively. Electrochemical surface areas obtained from CV data were found to vary with the Pt loading.     

Inhibitory effects of lemon grass (Cymbopogon citratus Stapf) on formation of azoxymethane-induced DNA adducts and aberrant crypt foci in the rat colon

The 80%-ethanol extract of lemon grass (Cymbopogon citratus Stapf), a medicinal plant in Thailand, has been reported to be antimutagenic against various known mutagens in the Salmonella mutation assay. To investigate chemoprevention in an animal carcinogenesis model, we examined inhibitory effects of the lemon grass extract on the formation of azoxymethane (AOM)-induced DNA adducts and aberrant crypt foci (ACF) in the rat colon. One week after the start of the treatment with lemon grass extract at doses of 0.5 or 5 g/kg body wt by gavage, F344 rats received two s.c. injections of 15 mg of AOM per kg body weight at 1 week apart. For DNA adduct analysis of the colon and liver, the rats were killed 12 h after the second AOM injection. The DNA from the liver and colon were used for O6-methylguanine and N7-methylguanine analysis. For ACF analysis in the initiation stage, AOM-injected rats were continuously treated with lemon grass extract and were killed 3 weeks after the second AOM injection. For analysis in the promotion stage the treatment with the lemon grass extract (0.5 g/kg) started 2 weeks after the second AOM injection and continued for 12 weeks until the animals were killed. Lemon grass treatment significantly inhibited DNA adduct formation in both the colonic mucosa and the muscular layer but not in the liver. In addition, lemon grass extract treatment significantly inhibited ACF formation in both the initiation stage and the promotion stage. Especially in the promotion stage, lemon grass treatment inhibited the formation of larger ACF (with four or more crypts per focus), which was predictive of tumor incidence. Furthermore, lemon grass extract inhibited fecal beta-glucuronidase competitively and had antioxidant activity. These results suggest that the lemon grass extract inhibits the release of activated aglycon, methylazoxymethanol, from a glucuronide conjugate in the colon, and decreases the DNA adducts and ACF formation in the rat colon.     

Pt-based electrocatalysts for polymer electrolyte membrane fuel cells prepared by supercritical deposition technique

Pt-based electrocatalysts were prepared on different carbon supports which are multiwall carbon nanotubes (MWCNTs), Vulcan XC 72R (VXR) and black pearl 2000 (BP2000) using a supercritical carbon dioxide (scCO₂) deposition technique. These catalysts were characterized by using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and cyclic voltammetry (CV). XRD and HRTEM results demonstrated that the scCO₂ deposition technique enables a high surface area metal phase to be deposited, with the size of the Pt particles ranging from 1 to 2 nm. The electrochemical surface areas (ESAs) of the prepared electrocatalysts were compared to the surface areas of commercial ETEK Pt/C (10 wt% Pt) and Tanaka Pt/C (46.5 wt% Pt) catalysts. The CV data indicate that the ESAs of the prepared Pt/VXR and Pt/MWCNT catalysts are about three times larger than that of the commercial ETEK catalyst for similar (10 wt% Pt) loadings. Oxygen reduction activity was investigated by hydrodynamic voltammetry. From the slope of Koutecky–Levich plots, the average number of electrons transferred in the oxygen reduction reaction (ORR) was 3.5, 3.6 and 3.7 for Pt/BP2000, Pt/VXR and Pt/MWCNT, correspondingly, which indicated almost complete reduction of oxygen to water.     

Development of a PM2.5 sampler with inertial impaction for sampling airborne particulate matter

A simple and low cost PM_2.5 impactor for sampling airborne particulate matter was developed, designed and evaluated. The design was an assembly of an acceleration nozzle and an impaction plate. Particles with sufficient inertia were unable to follow air streamlines and impacted on the plate. Smaller particles followed the streamlines, avoided being captured by the plate and could then be collected on a downstream filter. Analytical and numerical models were formulated to predict collection efficiency, flow fields and vectors, and particle trajectories in the impactor. The modeling suggested that an optimal operational domain exists for the PM_2.5 impactor. A prototype was then built and tested. The collected particles on the impaction plate and downstream of the PM_2.5 impactor were analyzed by using scanning electron microscopy. Experimental results agreed well with the theoretical predictions. Testing of the PM_2.5 impactor prototype showed promising results for this airborne particulate matter sampler.