Effect of antifungal agents on indwelling voice prosthetic biofilms

Rehabilitating the lost voice of laryngectomy patients by insertion of a silicone rubber voice prosthesis is now generally considered to be superior to any other form of substitute voice production. However, a drawback of these implants is the rapid colonization by a mixed biofilm of bacteria and yeasts, mainly Candida species, leading to failure and frequent exchange of the implant. A strategy frequently applied by otolaryngologists is oropharyngeal yeast decontamination by using antifungal agents, despite the fact that there is no compelling evidence that prescription of antifungal agents will prolong the lifetime of voice prostheses. Moreover, the prophylactic use of antifungal agents contributes to the development of resistant strains. Alternative approaches to prolonging the lifetime of silicone rubber voice prostheses may be found in modification of the silicone rubber surface of the implant, diet supplementation with active, probiotic bacteria, or salivary substitutes with synthetic antimicrobial peptides.</p

Polarographic reduction of uranium(VI) under complexing and noncomplexing conditions nature of the uranium(V) sulphate complex

The polarographic reduction of U(VI) to U(V) in acid solution is sensitive to both type and concentration of anion present. Consequently, the reduction was studied using perchlorate as a non-complexing anion and sulphate as a complexing anion.In HClO4 solution, increasing the perchlorate concentration shifts to more positive potentials, which seem to correspond to junction potential effects. Increasing either HClO4 or perchlorate concentrations increases the limiting current slightly, which can be attributed to a higher rate of disproportionation of U(V); other factors, e.g., viscosity of the solution, tend to counteract the effect of the disproportionation.In sulphate media, UO2+ is not strongly complexed, the asociation constant for the U(V)-sulphate complex being ca. 0[middle dot]13, if UO2SO4 is the most stable uranyl sulphate complex present. The effect of acid on the stability of the latter complex confirms its existence as an uncharged species. Limiting currents are pseudo diffusion-controlled, e.g., increasing the solution viscosity by increasing the electrolyte content decreases the current; this is due to the maximum disproportionation rate of U(V) having been reached at even the lowest sulphuric acid level investigated; increasing the anion concentration consequently slows down diffusion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32451/1/0000534.pd

Molecular Epidemiology and Evolutionary Trajectory of Emerging Echovirus 30, Europe

In 2018, an upsurge in echovirus 30 (E30) infections was reported in Europe. We conducted a large-scale epidemiologic and evolutionary study of 1,329 E30 strains collected in 22 countries in Europe during 2016-2018. Most E30 cases affected persons 0-4 years of age (29%) and 25-34 years of age (27%). Sequences were divided into 6 genetic clades (G1-G6). Most (53%) sequences belonged to G1, followed by G6 (23%), G2 (17%), G4 (4%), G3 (0.3%), and G5 (0.2%). Each clade encompassed unique individual recombinant forms; G1 and G4 displayed >= 2 unique recombinant forms. Rapid turnover of new clades and recombinant forms occurred over time. Clades G1 and G6 dominated in 2018, suggesting the E30 upsurge was caused by emergence of 2 distinct clades circulating in Europe. Investigation into the mechanisms behind the rapid turnover of E30 is crucial for clarifying the epidemiology and evolution of these enterovirus infections.Peer reviewe

Molecular epidemiology and evolutionary trajectory of emerging echovirus 30, Europe

In 2018, an upsurge in echovirus 30 (E30) infections was reported in Europe. We conducted a large-scale epidemiologic and evolutionary study of 1,329 E30 strains collected in 22 countries in Europe during 2016-2018. Most E30 cases affected persons 0-4 years of age (29%) and 25-34 years of age (27%). Sequences were divided into 6 genetic clades (G1-G6). Most (53%) sequences belonged to G1, followed by G6 (23%), G2 (17%), G4 (4%), G3 (0.3%), and G5 (0.2%). Each clade encompassed unique individual recombinant forms; G1 and G4 displayed >= 2 unique recombinant forms. Rapid turnover of new clades and recombinant forms occurred over time. Clades G1 and G6 dominated in 2018, suggesting the E30 upsurge was caused by emergence of 2 distinct clades circulating in Europe. Investigation into the mechanisms behind the rapid turnover of E30 is crucial for clarifying the epidemiology and evolution of these enterovirus infections.Molecular basis of virus replication, viral pathogenesis and antiviral strategie

RECENT TRENDS IN ORGANIC POLAROGRAPHY

INTRODUCTION The present paper does not attempt to be exhaustive in listing all of the current trends in the polarography of organic compounds. Rather, an attempt has been made to focus attention on those trends, which seem of major importance for future studies in organic polarography, with particular reference to some of the unsolved problems which still confront us. Significant recent activity in organic polarography has been distinguished by attempts to define more precisely the paths followed by the electrode process, including the nature of the phenomena which occur in the electrical double layer preceding, accompanying and following the electron-transfer process. This has involved, among other features, the development of theoretical equations and practical approaches for (a) characterizing the interrelationship of the chemical and electrochemical steps involved, (b) defining the role of adsorption as a necessary or accompanying phenomenon, and (c) explaining the actual energy level and the actual concentrations in the interfacial region of the participants in the electrode reaction. The roles of protons and of the solvent in organic electrode reactions have received considerable attention, e.g., in reference to the identification of initial oneelectron steps in multielectron processes. Techniques such as cyclic voltammetry and electron spin resonance have been useful in some cases in characterizing the free radicals produced in initial one-electron steps. Availability of satisfactory graphite indicating electrodes has extended the variety of organic electrochemical oxidations which can be studied. Literature coverage Reference to the literature in the present paper is not exhaustive; selected reviews and comprehensive studies are cited, which summarize and exemplify the trends discussed. The December 1965 issue of Talanta, honouring the 75th birthday of Professor Jaroslav Heyrovsky, contains a number of useful summaries of the polarographic behaviour of different types of organic compounds&apos;6, of the application of polarography in certain areas7, and of the effect of the solvent on the behaviour of organic compounds8&apos;°. Reference should also be made to the very useful reviews on organic polarography and allied areas which appear in the biennial review issues of Analytical Chemistry by Wawzonek, Stock, Bard, Hume and others. INVESTIGATIVE TECHNIQUES Since chemistry is, basically, an experimental science, it seems proper to consider first several developments in techniques, which seem particularly 297 PHILIP J. ELVING relevant for the future investigation and utilization of organic electrode processes. For example, the development of three-electrode configurations, largely involving operational amplifier control systems, has minimized the problems associated with the large iR drop experienced with polarography in organic solvent solutions of high resistance&quot;. Electrodes for electrooxidation Until relatively recently, systematic study of the electrochemical behaviour of organic compounds was largely confined to the investigation of their reduction at the dropping mercury electrode, except for the rather limited number which were sufficiently reversible to be studied polarographically or potentiometrically at platinum electrodes&apos;2. Study of electrochemical oxidation was limited by the unavailability of an electrode, which would not itself be oxidized at the relatively positive potential necessary for investigating organic compounds, whose oxidation usually involves a high activation overpotential. Consequently, although the polarographic reduction of many types of organic compounds has been investigated, only a relatively small amount of work has been done on their oxidation. The situation has been changed in recent years by the development of reliable indicating electrodes, based on various types of graphite13&apos;14. These have included wax-impregnated spectroscopic carbon rods, mixtures of graphite paste with various organic solvents, pyrolytic graphite and glassy graphite. The negative potential range available at graphite is less than that at mercury, although greater than that at platinum; however, the extended positive range available at graphite, e.g., up to l5 volt vs. S.C.E., is a decided advantage. Mercury electrodes are at times far from ideal for studying organic reductions due to a variety of phenomena, e.g., mercury electrodes are apt to be unsuitable for studying electrode processes involving heterocyclic compounds containing divalent sulphur substituents because of the possible interfering effects of adsorption and surface activity, of catalytic hydrogen evolution, and of reaction between mercury and sulphur. Cyclic voltammetry The importance of cyclic voltammetry at constant area electrodes as a tool for mechanistic studies of electrode processes has been amply demonstrated. For example, it facilitates the identification of reversible redox couples and frequently of electroactive intermediates which may be formed either chemically or electrolytically. Recent papers by Sham, Nicholson, and others&apos;5&apos;8, on the theory of stationary electrode polarography have provided the means of quantitatively resolving the electrochemical and associated chemical steps in such electrode processes. Alternating current polarography In view of the fact that Drs. B. Breyer and G. C. Barker have presented papers on alternating current polarography and tensammetry at the symposium (cf. pages 313 and 239), for which the current paper was prepared, the reader is referred to their papers for an indication of the utility of a.c. polarography in studying organic electrode processes. RECENT TRENDS IN ORGANIC POLAROGRAPHY Controlled potential electrolysis Electrolysis at controlled electrode potential&apos;9&apos;20 is a relatively old technique which the author and his collaborators still generally find to be essential in studying organic electrode processes. Such electrolysis permits the preparation of sufficiently large amounts of products to permit their isolation, characterization, identification and determination. The products of transitory electrolysis at micro electrodes and of exhaustive electrolysis at massive electrodes are generally similar except in some cases where chemical rate phenomena can cause differences. Controlled potential electrolyses have permitted the elucidation of complex electrode processes with unexpected products, e.g., the reduction of acetylenedicarboxylic acid to rac-a, a &apos;-dimethylsuccinic acid via reactions involving decarboxylation and dimerization, and the intermediate formation of fulgenic and dimethylmaleic acids, and some interesting stereochemistry21. It should be noted that the detailed examination of an electrolyzed solution provides excellent training in analytical chemistry for graduate students. The characterization of all of the solution components and the striking of a material balance between reactants and products usually involves considerable skill in the use of a variety of separation and measurement approaches. The use of controlled potential electrolysis in organic synthesis will be briefly considered later. Optical and magnetic resonance spectroscopy An interesting development in recent years has been the use of optical and magnetic resonance spectroscopic techniques for identifying electrode reaction products and intermediates. In particular, electron spin resonance has been used to detect transitory intermediates. Probably the most extensive use of this approach has been by Adams and his collaborators22&apos;23. However, the technique must be used with caution since, as Adams22 recently pointed out, there are frequent failures to detect free radical formation and even to obtain patterns which are interpretable. In general, it would seem that electron spin resonance will detect free radical intermediates where the halflives of these species are sufficiently long. However, where the free radical rapidly reacts either chemically or electrochemically, it may not be feasible to detect its presence. Infrared analysis by attenuated total reflection and allied reflectance techniques are beginning to be used in an attempt to detect and identify intermediates in electrode processes by spectrum scanning of the solutionelectrode interfacial region during electrolysis. The introduction of optically transparent electrodes may permit the concurrent examination of solutions during electrolysis by absorption spectrophotometry or internal reflectance spectroscopy24&apos; 25 Mention should be made of the considerable interest shown in recent years in the examination of the luminescence phenomena which accompany the electrolytic generation of certain free radicals. ROLE OF THE CHEMICAL ENVIRONMENT It is obviously not possible to explain completely or even satisfactorily the course of many electrochemical processes unless the relevant environment, 299 PHILIPJ. ELVING that is, the electrode-solution system, is sufficiently well characterized. Composition of the test solution, which is probably the critically decisive factor in determining the observed polarographic behaviour of organic compounds, is subsequently discussed. First, however, attention will be focussed on the locus of the electrode reaction, the solution-electrode interface or the electrical double layer. Solution-electrode interface The structure of the double layer is well known to be of importance in electrochemical kinetics and therefore in determination of the potentials of irreversible processes, which include most organic electrode reactions, for at least two reasons: (i) it influences the effective potential difference which favours the electrochemical reaction, and (ii) it causes the effective concentration of electroactive species to differ from the bulk concentration. The situation is well summarized in Delahay&apos;s recent book26. The question as to whether the organic species must be adsorbed on the electrode in a type of chemisorption prior to electron transfer would seem now to be answered in the negative, although there are many cases in which adsorption of organic reactant, products or both seems to be an essential feature of the overall electrode reaction. It is likely that an orientation of the organic species in the interphase is necessary before electron transfer occurs; the energy for such a process would be likely to vary similarly to that for an adsorption process. Thus, Streitweiser27 recently pointed out that the variation in potential for carbon-halogen bond fission in certain alkyl halides is explicable on the basis of the carbon-halogen bond being parallel to the electrode surface during electron transfer rather than normal as customarily postulated for carbon-halogen fission28&apos;29. Many investigators have considered the energy of adsorption, if involved, to be negligible compared to the other energies acting, although the possibility has been considered that adsorption energy may be the significant factor in the variation of half-wave potential for an aliphatic homologous series28. The all-important topic of adsorption will not be discussed further since the recognized authority on the subject, Dr. A. N. Frumkin, has discussed the adsorption of organic compounds at the mercury-solution interface in the present symposium (cf. page 263). Reference should be made at this point to the assumption explicit in much discussion of organic polarography that the electrode is simply an inert imaginary plane through which electrons can pass in one direction or the other. Little attention is yet being given to the actual situation, as has been at least partially revealed by the extensive studies of Frumkin, Parsons, Mairanovskii and others3032, on the effects of adsorption on the electrode and of the potential variation in the double layer. There is little doubt that, in the future, the definition of the potential variation in the double layer as developed so largely from the work of Professor Frumkin and his collaborators -will be a dominant factor in obtaining a more detailed picture of electrode processes. At present, there is an unfortunate tendency by some polarographers to use psi and related potentials as a deus ex machina in explaining phenomena as being due to such potentials, 300 RECENT TRENDS IN ORGANIC POLAROGRAPHY when their values either are not known or have been guessed at from other studies, whose relevancy may or may not be sufficient. The treatment of the influence of the double layer structure on electrode processes on the basis of the Frumkin approach has been succinctly summarized by Koryta33; Mairanovskii32 has considered the approach as applied to the polarographic reduction of organic compounds. Parsons3&apos; has recently considered the form of the isotherm for the adsorption of organic compounds at electrodes, while general phenomena associated with adsorption at electrodes has been reviewed by Kastening and Holleck34, and by Reilley and In view of the fact that Drs. H. A. Laitinen and K. Schwabe discussed polarography in solvents other than water at the present symposium (cf. page 227), mention will only be made of two or three points of primary im portance for organic polarography. The first concerns the desirability of investigating solvents which are in themselves reactive. For example, pyridine is a non-proton releasing solvent of a type sufficiently different from those commonly used to warrant its investigation. Chemically, pyridine is a strong Lewis base, is apparently resistant to normal oxidation, and forms adducts with many carbonium ions, which are quite stable N-substituted pyridinium compounds. Consequently, since the oxidation of organic compounds frequently involves the removal of protons and/or the formation of carbonium ions, pyridine would greatly facilitate such reaction by acting as a proton acceptor and a carbonium ion stabilizer. This is illustrated by the behaviour of the quinone-hydroquinone system in pyridine41. A second point involves the need for better evaluation of the purity of solvents, particularly in. respect to the effect of small amounts of impurity. Thus, practically all commercially available pyridine contains material in the millimolar or lower concentration range, which show a variety of electrochemical behaviour, including appearance of a pre-wave to background discharge, formation of Lewis acid-base adducts more readily reducible than those of pyridine, and surface activity. PHILIP J. ELVING The possibly important effect of minute amounts of water in organic solvents needs to be more carefully considered than it usually is. The presence o f 001 per cent water in a typical solvent corresponds to a 4 or 5 millimolar water solution, which is many times the concentration of the electroactive species. At the present time, the effect of such residual amounts of water is commonly overlooked except when the author requires the presence of a hydrogen ion source to complete a postulated reaction scheme. Of major importance for future work in non-aqueous media is the establishment of potential scales which will permit correlation of the data obtained in aqueous and non-aqueous media. The problems involved and some possible solutions have been explored by Kolthoff39 in a recent comprehensive paper on polarography in organic solvents

Variation of the Half-Wave Potential of Organic Compounds With pH. Report No. 78

From 19th International Union of Pure and Applied Chemistry Congress, London. A systematic introduction is presented to the subject of the variation with pH of the polarographic half-wave potential, which is probably the most readily measured electrochemical energetic parameter of organic compounds. Emphasis is placed on (a) the types of relationships observed for both reversible and irreversible electrode processes, (b) the mathematical formulation of these relationships, (c) the structural, mechanistic, kinetic, and environmental factors influencing such relationships, and (d) the presumptive physical causes for such relationships, e.g., the effect of pH on the electrochemical kinetics. Although the discussion is primarily concerned with behavior in aqueous solution, the conclusions drawn are equally valid for nonaqueous media in which hydrogen ion or some other Lewis acid can play a significant role. The half-wave potential for an organic electrode process may be independent of pH, or may vary lineanly or sigmoidally; other types of relationships observed are likely to be combinations of such effects. These variations may be due (a) to direct participation of hydrogen ion in the transition state involving the electroactive site in the organic molecule and the electron source, e.g., polarization of the bond to be broken, (b) to control of the state of reactants and/or products via participation in pre- and postequilibria, e.g., acid-base equilibria affecting the nature of the reactant or (c) to the effects of other kinetic, adsorption, steric, hydrogen-bonding and electrical double layer phenomena, as well as to combinations and variations of these effects. Solution composition factors influencing the observed variation of half-wave potential with pH include the ionic strength, the nature of the solvent, the specific identity of buffer components, and nonspecific salt effects. The implications of the experimentally observed half-wave potential-pH relations are considered in respect to the development of analytical procedures and the correlation of half-wave potential data. (auth