Co-activation of Gi and Gq proteins exerts synergistic effect on human platelet aggregation through activation of phospholipase C and Ca2+ signalling pathways

Our previous studies have shown that subthreshold concentrations of two platelet agonists exert synergistic effects on platelet aggregation. Here we studied the mechanism of synergistic interaction of 5-hydroxytryptamine (5-HT) and epinephrine mediated platelet aggregation. We show that 5-HT had no or little effect on aggregation but it did potentiate the aggregation response of epinephrine. The synergistic interaction of 5-HT (1-5 microM) and epinephrine (0.5-2 microM) was inhibited by alpha2-adrenoceptor blocker (yohimbine; IC50= 0.4 microM), calcium channel blockers (verapamil and diltiazem with IC50 of 10 and 48 mM, respectively), PLC inhibitor (U73122; IC50=6 microM) and nitric oxide (NO) donor, SNAP (IC50=1.6 microM)). The data suggest that synergistic effects of platelet agonists are receptor-mediated and occur through multiple signalling pathways including the activation PLC/Ca2+ signalling cascades.     

A novel and expeditious approach to unusual spirolactam building blocks

A rapid access to 7-azaspiro[4.5]decan-6-ones 1 involving three regio- and chemoselective reactions starting from tetrabromonorbornyl derivatives is described. The alkaline H(2)O(2) cleavage reaction of monosubstituted alpha-diketones 9 furnished the potential bridged bicyclic lactones 10in a highly regio- and stereoselective manner. The radical-mediated, intermolecular bridgehead C-C bond formation of the versatile bridged lactones 10 with acrylonitrile followed by LAH reduction of the adduct 13 intriguingly leads to the formation of novel spirolactam building blocks 1.     

XRF estimation of Cd,Hf, Hg,and Gd in uranium solution

A new curriculum in radiochemistry for undergraduate chemistry is described.     

Electrode Kinetics and Ternary Complex Formation of Cd2+‐Antibiotics‐Vitamin‐B5 System. A Polarographic Study

Cd²⁺ complexes with antibiotics viz. neomycin, chlortetracycline, oxytetracycline, tetracycline, penicillin‐V and penicillin‐G as primary ligands and vitamin‐B₅ as secondary ligand have been reported at pH = 7.30 ± 0.01 and μ = 1.0 M KNO₃ at 298 K by polarographic technique.¹ Cd²⁺ formed 1:1:1, 1:1:2, and 1:2:1 complexes with a stability constants trend of neomycin < chlortetracycline < oxytetracycline < tetracycline < penicillin‐V < penicillin‐G can be explained on the basis of the nature of ligands, bonding, and steric hindrance of these drugs. The nature of electrode processes were reversible and diffusion controlled. The values of stability constants showed that these drugs can be used to reduce the toxicity of Cd.     

Kinetics of anation of chromium(III) by L-phenylalanine

Summary The kinetics of anation of chromium(III) species, [Cr(H₂O)₆]⁴⁺ and [Cr(H₂O)₅OH]²⁺, by L-phenylalanine in aqueous acid has been studied spectrophotometrically. Effects of varying [substrate], [ligand], [H⁺], , % ethanol and temperature were investigated. The kinetic data suggest a mechanism where outersphere-associations [between chromium(III) species and phenylalanine in the zwitterionic form] precede anation. Comparison of the results with published data suggest an I_a path for the [Cr(H₂O)₆]³⁺ reaction and I_d path for the [Cr(H₂O)₅OH]²⁺ reaction.     

Terpenoids of the oleoresin ofPinus kochiana

The chemical composition of the oleoresin of Koch's pine growing in the Caucasus has been studied. It has been shown that, with respect to the composition of the monoterpenes and the resin acids, the oleoresin of this species does not differ from oleoresins of the subgenusDiploxylon studied previously. Predominating among the sesquiterpenes is germacrene D, which has not previously been found in the resins of the conifers of the USSR. The diterpenoids are represented by tricyclic compounds (pimarinol, isopimarinol, and methyl 15-hydroxydehydroabietate and the hydrocarbons corresponding to them).     

Stannyl radical-mediated cleavage of pi-deficient heterocyclic sulfones. Synthesis Of alpha-fluoro esters

Treatment of ethyl 2-(pyridin-2-ylsulfonyl)hexanoate with tributylstannane and azobis(2-methyl-2-propanitrile) (AIBN) in benzene at reflux for 36 h resulted in hydrogenolysis to give ethyl hexanoate (60%), whereas no reaction was observed after 48 h at reflux with ethyl 2-(phenylsulfonyl)hexanoate. Ethyl 2-(pyrimidin-2-ylsulfonyl)hexanoate underwent quantitative hydrogenolysis within 1 h under these conditions. This represents a mild new methodology for removal of the synthetically useful sulfone moiety. Substitution of Bu(3)SnD for Bu(3)SnH gave access to alpha-deuterium-labeled esters. Treatment of the alpha-(pyrimidin-2-ylsulfonyl) enolates derived from several esters with Selectfluor gave high yields of the 2-fluoro-2-(pyrimidin-2-ylsulfonyl)alkanoates, which were smoothly desulfonylated [Bu(3)SnH (2 equiv)/AIBN/benzene/Delta] to give 2-fluoroalkanoates. "Catalytic" tin hydride, generated from tribuytltin chloride (0.15 equiv) and excess polymethylhydrosiloxane in the presence of potassium fluoride, also effected removal of the pi-deficient alpha-(pyrimidin-2-ylsulfonyl) moiety from acid derivatives in high yields. Desulfonylation is suggested to proceed via alkoxy ketyl-type radicals and tin enolates.     

Direct conversion of N-methoxy-N-methylamides (Weinreb amides) to ketones via a nonclassical Wittig reaction

[reaction: see text] N-Methoxy-N-methylamides (Weinreb amides) are converted efficiently into ketones by reaction with alkylidenetriphenylphosphoranes and in situ hydrolysis of the product.     

Separation and Determination of Ephedrine Enantiomers and Synephrine by High Performance Capillary Electrophoresis in Dietary Supplements

The chiral separation of ephedrine alkaloids by high performance capillary electrophoresis is of great interest since the enantiomers exhibit quantitative and qualitative differences in pharmacological activity. The isomers of (–)-ephedrine, (+)-pseudoephedrine, (–)-N-methylephedrine, (+)-N-methylpseudoephedrine, (+)-norpseudoephedrine and (–)-norephedrine are the major bioactive components of E. sinica (Ma-Huang) which is a Chinese herb used for weight loss and as an energy booster in the US. However, the compounds stereoisomers are not present in the plant material. The electrophoretic separation was performed using a 110 cm × 50 m I.D. (101.5 cm effective length) fused silica capillary. The samples were injected by pressure for 5 s at 50 mbar and the running voltage was 30 kV at the injector end of the capillary. Within 23 min, nine ephedrine compounds and synephrine were separated at 210 nm. The method was successively applied to the determination of the ephedrine compounds in dietary supplement products. Parameters affecting the resolution between (+) and (–)-enantiomers, such as pH, cyclodextrin concentration, temperature, organic modifier, buffer concentration and capillary dimensions were reported.