High performance liquid chromatography as a tool in the definition of abnormalities in monoamine and tryptophan metabolites in cerebrospinal fluid from patients with neurological disorders

In this study we report the levels of 3-methoxy-4-hydroxyphenylglycol, 3,4-dihydroxyphenylacetic acid, homovallinic acid, tryptophan, 5-hydroxyindole-3-acetic acid and serotonin in lumbar cerebrospinal fluid (CSF) from patients with multiple sclerosis, cerebrovascular disease and muscular tension headache the later, as healthy controls. The separation of these substances was performed on a reversed phase column by ion pair high performance liquid chromatography and detection was made by a glassy carbon electrode set at +900 mV vs Ag+/AgCl. The whole separation was achieved within 25 min. Concentrations of all substances (10-1000 pmole/L) were linearly proportional to areas obtained. The system is sensitive, stable and reproducible. The significance of CSF levels of these metabolites from patients groups compared with healthy controls are discussed.     

Trace element concentration in head hair of the inhabitans of the Rawalpindi-Islamabad area

Instrumental neutron activation analysis technique has been used to determine the concentration levels of 12 trace elements in human head hair samples collected from 105 individuals living in various areas of Rawalpindi-Islamabad. The data show that the average concentrations of Mn, Co, Ag and Au are higher in the female group as compared to the male group. Four individuals were found to have elevated levels of Se due to the use of anti-dandruff shampoos, whereas two individials had elevated levels of Hg.     

INAA of toxic elements in coal and their transfer into environments

An instrumental neutron activation analytical (INAA) technique is described for the determination of 26 toxic and other trace elements in Eastern Coal (NBS SRM-1632a), local coal and its ash. The coal ash was produced by heating coal at 750°C in a muffled furnace. The transfer of these elements to the environment on the complete compustion of coal is estimated from the difference between the elemental concentration of coal and its ash.     

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.     

Separation of potential flavoring compounds by high-performance liquid chromatography

High-performance liquid chromatography separated successively and quantitatively the food flavoring agents pyrimidines, purines and nucleosides, followed by nucleotides, then by polyphenols and finally by pyrazines with a reversed-phase octadecylsilica (μBondapak C₁₈) column and various proportions of methanol, water, acetic acid and tetrabutylammonium phosphate (PIC A). The polar solvent (solvent A) was water—acetic acid—PIC A (97.5:1.5:1.0) and the relatively non-polar solvent (solvent B) was methanol—acetic acid—PIC A (97.5:1.5:1.0). Purines, pyrimidines, and nucleosides were eluted with solvent A. Nucleotides were eluted with a mixture of solvents A and B (9:1). Polyphenols were separated with a gradient starting at 10% solvent B and finishing at 25% solvent B, and finally the pyrazines were removed successively from the column with a gradient starting at 25% solvent B and finishing at 45% solvent B. The resolution and reproducibility were excellent for more than 50 compounds. By this method beverages could be analyzed directly, without solvent extraction, for flavoring compounds.     

HPLC determination of piperine in pepper and in pepper extracts

Summary HPCL quantitation of piperine in pepper and in pepper extracts is described. This is optimised on nitratedsulphonated phenyl silica gel with phloracetophenone as internal standard.     

Dynamic molecular recognition in the generation of a new crystal-engineering motif: a unique case study of a dicarboxylic acid with a ditopic receptor favouring a polymeric over a dimeric hydrogen-bonded supramolecular complex

A new crystal-engineering motif has been developed where a ditopic receptor 1 shows a novel syn-syn hydrogen-bonded polymeric supramolecular complex (Fig. 4b) (instead of a 1:1 dimeric syn-syn or polymeric syn-anti complex) giving rise to a hydrogen-bonded stair-like polymeric ribbon structure between the binding groups of the receptor pyridine amide and the carboxyl groups of the guest substrate.     

Radiochemical analysis of toxic elements in biological materials

A radiochemical method for simultaneous determination of toxic elements (Hg, Cd and Sb) in biological materials has been developed. The procedure involves the irradiation of samples with thermal neutrons and quantitative one-step separation in 0.1M 4-(5-nonyl)pyridine/benzene from 2.0M hydrochloric acid followed by gamma-ray spectrometry. The procedure is applied for the analysis and to the studies of distribution of these elements in IAEA-RMs, human serum and hair samples. Results obtained are found to be in good agreement with those reported in the literature.