The modification of molybdenum nitrides: the effect of the second metal component

A set of Mo2N-based bimetallic catalysts with high surface area around 140 m 2 /g have been successfully prepared from precursors obtained using the coprecipitation method. Both the precursors and the end-catalysts were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The nitriding processes were monitored by differential thermal analysis (TDA). The catalytic properties of Co-Mo bimetallic catalyst under mediumpressure (3.0 MPa) are much better for the hydrodenitrogenation of pyridine than those of pure γ-Mo2N and a commercially used sulfided CoMo/Al2O3 catalyst. The introduction of the second metal component has been shown to disrupt the morphology of the nitride phase with a greater concentration of (111) planes being present compared to (200) planes, a situation that is reversed compared to γ-Mo2N. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contributing authors

Contributing authors     

Effects of the novel antimigraine agent, frovatriptan, on coronary and cardiac function in dogs

The effects of frovatriptan (VML 251/SB-209509) on coronary artery function were investigated in isolated coronary arteries from beagle dogs. Low concentrations of frovatriptan produced contraction with -logEC50 7.55 +/- 0.08 (n = 11). The maximal observed contraction attained was 56 +/- 7% of the control 5-hydroxytryptamine (5-HT; 10 microM) response. At high concentrations of frovatriptan (>6 microM), reversal of sumatriptan (10 microM)-induced contractions was noted. In arteries precontracted with the thromboxane mimetic, U46619, frovatriptan produced a bell-shaped concentration-response relation with a maximal response at 600 nM. Concentrations of frovatriptan >2 microM produced marked reversal of tone, with full relaxation of precontracted tissues at 200 microM. In anesthetized, open-chest mongrel dogs, intravenous (n = 5) or intracoronary (n = 5) artery administration of frovatriptan (0.0001-1 mg/kg) had no consistent effect on left ventricular end-diastolic pressure, left end-systolic pressure, cardiac contractility, aortic blood flow, systemic peripheral resistance, coronary blood flow, coronary vascular resistance, mean arterial blood pressure, or heart rate when compared with vehicle (n = 3). Intravenous sumatriptan produced minor effects on blood pressure and heart rate. Intracoronary artery administration of sumatriptan (0.0003 mg/kg) produced an increase in systemic peripheral resistance to 120.5 +/- 8.2% compared with vehicle (97.8 +/- 5.4%; p < 0.05). This dose of sumatriptan also produced a significant increase in coronary blood flow and decrease in coronary vascular resistance. Intravenous administration of sumatriptan produced a dose-related reduction in left ventricular diastolic pressure with a reduction to 58.3 +/- 8.3% and 41.7 +/- 25% of control values observed at 0.3 and 1 mg/kg, respectively; however, administration of sumatriptan by an intracoronary route had no effect. In a model of myocardial infarction, comparable doses of sumatriptan (1.0 mg/kg) or frovatriptan (0.1 mg/kg), in terms of their effect on carotid vascular resistance, had no significant effect on infarct size. Frovatriptan had no effect on coronary blood flow after reperfusion; however, sumatriptan produced a significant reduction in coronary blood flow for < or =3 h. These studies show that frovatriptan has the capability of relaxing coronary arteries in vitro, has no overall effect on cardiac function at rest with no effect on coronary hemodynamics after myocardial infarction, and has a profile superior to that of sumatriptan.     

Zinc oxide nanoparticle induced genotoxicity in primary human epidermal keratinocytes

Zinc oxide (ZnO) nanoparticles are widely used in cosmetics and sunscreens. Human epidermal keratinocytes may serve as the first portal of entry for these nanoparticles either directly through topically applied cosmetics or indirectly through any breaches in the skin integrity. Therefore, the objective of the present study was to assess the biological interactions of ZnO nanoparticles in primary human epidermal keratinocytes (HEK) as they are the most abundant cell type in the human epidermis. Cellular uptake of nanoparticles was investigated by scanning electron microscopy using back scattered electrons imaging as well as transmission electron microscopy. The electron microscopy revealed the internalization of ZnO nanoparticles in primary HEK after 6 h exposure at 14 microg/ml concentration. ZnO nanoparticles exhibited a time (6-24 h) as well as concentration (8-20 microg/ml) dependent inhibition of mitochondrial activity as evident by the MTT assay. A significant (p < 0.05) induction in DNA damage was observed in cells exposed to ZnO nanoparticles for 6 h at 8 and 14 microg/ml concentrations compared to control as evident in the Comet assay. This is the first study providing information on biological interactions of ZnO nanoparticles with primary human epidermal keratinocytes. Our findings demonstrate that ZnO nanoparticles are internalized by the human epidermal keratinocytes and elicit a cytotoxic and genotoxic response. Therefore, caution should be taken while using consumer products containing nanoparticles as any perturbation in the skin barrier could expose the underlying cells to nanoparticles.     

Perspective Study of Vinyl Grafting onto Leucaena glauca Seed Gum and Guar Gum by Hydrogen Peroxide Initiation

Graft copolymerization of various vinyl monomers onto Leucaena glauca seed gum has been performed using hydrogen peroxide as the initiator in aqueous slurry. Guar gum grafts also have been prepared to compare graftability of both the gums as they are structurally related to each other. To study the grafting behaviour of vinylic monomers towards the polygalactomannans the reaction conditions were kept constant for all the sets. The choosen monomers were acrylonitrile, methylmethacrylate, acrylamide, styrene, methacrylic acid and acrylic acid. The reaction products were characterized by grafting parameters like percent grafting, grafting frequency, grafting efficiency along with thermogravimetric and infra-red spectroscopic analysis.