Model reactions for abiotic mercury(II) methylation: Kinetics of methylation of mercury(II) by mono-, di-, and tri-methyltin in seawater

The usual presence of mercury(II) with monodi-, and tri-methyltin in water, sediments, and plants in estuarine environments suggests possible abiotic formation of methylmercury via methyl transfer from methyltin compounds. Kinetics studies of reactions between mercury(II) and methyltin compounds under pseudo-first-order conditions in seawater show that relative rate of methylmercury formation under the same conditions are: monomethyltin <trimethyltin> dimethyltin. This order is explainable mainly by the speciation and charge of methyltin compounds in seawater and by the existence of mercury(II) as a tetrachloro anion. A factorial experiment with the variables pH and salinity (seawater diluted with deionized water) showed that pH, but not salinity, is significant at the 95% confidence level; and that reaction rates increase as pH increases. These results suggest the possibility of abiotic methylation of mercury(II) in seawater. Additional experiments in seawater demonstrated an absence of methylation of mercury(II) (14 days) and mercury(0) (35 days) by methyl iodide.     

Synthesis of 7-methyl-4,6,6a,7,10,10a-hexa-hydroindolo[4,3-fg]quinazoline derivatives

The synthesis of a series of compounds indolo[4,3-fg]quinazoline related to ergoline (indolo[4,3-fg]quinoline) is reported. The key step of the synthetic sequence is the ring cleavage of the ketone IV. The stereochemistry of the chiral centers is established by the chirality of dihydrolysergic acid I.     

Effects of mobile phone exposure on time frequency fine structure of transiently evoked otoacoustic emissions

Mobile phones have become very commonly used worldwide within a short period of time. To date there is only limited knowledge about interaction between electromagnetic fields (EMFs) emitted by mobile phones and the auditory function. Moreover, there is widespread concern that there may be potential for harm. The aim of this study was to assess potential subtle changes in cochlear function by measuring the temporal and spectral fine structure of transiently evoked otoacoustic emissions (TEOAE) in normal hearing subjects after exposure to EMFs emitted by Global System for Mobile Communication (GSM) mobile phones. TEOAEs were recorded in 27 healthy young adults before and after 10 min of real or sham exposure in a double-blind design. TEOAE data were analyzed both globally (broadband analysis) and using the Wavelet Transform (analysis of the time-frequency fine structure). The broadband analysis revealed no significant effect on TEOAEs related to exposure, confirming results of previous studies; in addition, no significant change was detected in the analysis of the elementary wavelet components, suggesting that the temporal and spectral fine structure of TEOAEs is not affected by 10 min exposure to low-intensity EMFs emitted by GSM mobile phones.     

The Hungarian periconceptional service as a model for community genetics

OBJECTIVES: This review describes the methods and results of the Hungarian periconceptional service consisting of counselling, examinations and medical interventions. (The term periconceptional is used instead of preconceptional because the early postconceptional period is also involved to this service.) METHODS: The service was based on three steps: check-up examination of reproductive health (i.e., preconceptional screenings), a 3-month preparation for conception, dispensed and/or supervised by qualified nurses, and a better protection in early pregnancy for the most sensitive early development of the embryo for voluntary and eligible couples. RESULTS: Experiences from the coordinating centre of the Hungarian periconceptional service are summarized between February 1, 1984, and January 31, 1999, thus 15 years. Participants with positive family histories, case histories and subjects with genito-urinary infections had a more effective flow towards secondary care. Infertile couples were diagnosed and treated sooner. The periconceptional service is effective for the introduction of periconceptional folic acid-containing multivitamin supplementation and for the reduction of smoking and alcohol consumption in females in the preconceptional period. The rate of major congenital abnormalities (20.6 per 1,000) was significantly lower than expected. CONCLUSIONS: The periconceptional service is feasible and has many benefits. Thus, proper preparation for conception is the earliest and probably the most important effort to prevent genetic diseases.     

Cyclodextrin complexation improves aqueous solubility of the antiepileptic drug,rufinamide: solution and solid state characterization of compound-cyclodextrin binary systems

Rufinamide (RUF) was characterized in terms of cyclodextrin (CD) complexation in order to improve its aqueous solubility. Binary systems of RUF with three CDs—β-cyclodextrin (β-CD), randomly methylated-β-cyclodextrin (RAMEB) and sulfobutylether-β-cyclodextrin (SBE-β-CD)—were characterized with a wide variety of analytical techniques. Liquid state characterization was carried out by complementary techniques such as nuclear magnetic resonance spectroscopy (NMR), capillary electrophoresis (CE), mass spectrometry (MS) and phase solubility studies. The latter revealed that the stability of the complexes decreased in the order of RAMEB?>?β-CD?>?SBE-β-CD. A_L-type diagrams were obtained in all cases, characteristic of 1:1 stoichiometry, with a maximum of over 15-fold increase in RUF solubility, when complexed with RAMEB. NMR Job plot and MS studies confirmed phase solubility results, regarding the binding stoichiometry. ¹H NMR and 2D ROESY investigations revealed the inclusion of the triazole moiety of RUF, confirmed by molecular modeling. Solid state complexation in 1:1 molar ratio was carried out by kneading method and investigated by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). Comparative dissolution studies indicated an over two-fold improvement in dissolution efficacy of the kneaded products, when compared to the pure drug. Results of the present study might pave the way for a drug formulation with improved bioavailability.     

Third-Order Differential Subordinations for Analytic Functions Associated with Generalized Mittag-Leffler Functions

In this paper, third-order differential subordination results are obtained for analytic functions associated with an operator defined by the normalized form of the generalized Mittag-Leffler functions. Some particular cases involving Mittag-Leffler and hyperbolic functions are also considered.     

On the turbulent couette flow of an incompressible fluid with temperature-dependent viscosity

Summary Starting from energy and Navier-Stokes equations with temperature-dependent viscosity, we have obtained the Reynolds equations for the mean values of velocity, temperature and pressure. We have then applied these equations to the Couette flow; on the well-known hypothesis of mixing-length and Prandtl turbulent number, the above mentioned relations have been written in a more amenable form.Some general considerations concerning the reciprocal dependence between temperature and velocity gradients at wall have been deduced.Finally some solutions numerically obtained for several values of Reynolds number are given and discussed in some detail to point out the influence of the temperature-dependent viscosity.

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Sommario Introducendo nelle equazioni dell'energia e di Navier-Stokes le parti medie e fluttuanti della velocità, temperatura, pressione e viscosità, vengono ricavate le cosiddette equazioni di Reynolds, ossia le equazioni che descrivono i campi di velocità e temperatura medi. Dal confronto di quest'ultime, in cui la viscosità è considerata dipendente dalla temperatura, con quelle originarie di Reynolds si deduce la forma che nel caso in esame assumono gli sforzi apparenti.Successivamente le equazioni ottenute vengono applicate al moto a Couette e discusse, dopo aver introdotto in esse le ipotesi della lunghezza di miscelamento e del numero di Prandtl turbolento; da questa analisi vengono tratte alcune conclusioni di carattere generale riguardanti i legami tra il campo dinamico e quello termico. Infine vengono date alcune soluzioni ottenute per via numerica, le quali illustrano l'influenza che sulle distribuzioni di temperatura e velocità viene esercitata dalla dipendenza della viscosità dalla temperatura.

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Synthesis and aggregation behaviour of a new sultaine surfactant

The aggregation properties of a new sultaine surfactant have been studied in buffered aqueous solution at pH 7.4 under controlled condition of osmolarity. Spontaneously formed sultaine vesicles with a mean diameter of about 1 μm can be observed by optical microscopy. The phase behaviour of the surfactant has been investigated by differential scanning calorimetry (DSC) and Nile Red fluorescence. Two critical vesicular concentrations (CVC(1) and CVC(2)) have been fluorimetrically measured, by using pyrene and Nile Red as the fluorescent probes. The two populations of vesicles behave differently as a consequence of their size. The stability of extruded large unilamellar vesicles (LUV) formed slightly above the CVC(1) has been evaluated in the temperature range 25-75°C by following the rate of spontaneous release of entrapped 5(6)-carboxyfluorescein (CF). The stability of the same vesicles at 70°C has also been investigated under osmotic stress obtained by adding NaCl or sucrose to the bulk solution. At a sultaine concentration above the CVC(2) LUV tend to associate and form stable larger closely packed aggregates as suggested by Dynamic Laser Light Scattering and rheological measurements.     

In vitro anti-HMPV activity of meroditerpenoids from marine alga Stypopodium zonale (Dictyotales)

In this paper, we evaluated the antiviral activity against HMPV replication of crude extract of the marine algae Stypopodium zonale and of two meroditerpenoids obtained from it, atomaric acid and epitaondiol, and a methyl ester derivative of atomaric acid. Their selectivity indexes were 20.78, >56.81, 49.26 and 12.82, respectively. Compared to ribavirin, the substances showed a relatively low cytotoxicity on LLC-MK2 cells, with a significant antiviral activity, inhibiting at least 90% of viral replication in vitro, which demonstrates the potential of these marine natural products to combat infections caused by HMPV in vitro.