Effective swimmer’s action during the grab start technique

The external forces applied in swimming starts have been often studied, but using direct analysis and simple interpretation data processes. This study aimed to develop a tool for vertical and horizontal force assessment based on the swimmers' propulsive and structural forces (passive forces due to dead weight) applied during the block phase. Four methodological pathways were followed: the experimented fall of a rigid body, the swimmers' inertia effect, the development of a mathematical model to describe the outcome of the rigid body fall and its generalization to include the effects of the inertia, and the experimental swimmers' starting protocol analysed with the inclusion of the developed mathematical tool. The first three methodological steps resulted in the description and computation of the passive force components. At the fourth step, six well-trained swimmers performed three 15 m maximal grab start trials and three-dimensional (3D) kinetic data were obtained using a six degrees of freedom force plate. The passive force contribution to the start performance obtained from the model was subtracted from the experimental force due to the swimmers resulting in the swimmers' active forces. As expected, the swimmers' vertical and horizontal active forces accounted for the maximum variability contribution of the experimental forces. It was found that the active force profile for the vertical and horizontal components resembled one another. These findings should be considered in clarifying the active swimmers' force variability and the respective geometrical profile as indicators to redefine steering strategies.

La concepció clàssica de la monarquia egípcia a partir de la documentació literària del Regne Mitjà i la seva pervivència en Època Grecorromana. El cas paradigmàtic d'Alexandre el Gran

Aquest estudi s’insereix en un projecte de tesi. L’estudi versa sobre l’ideal egipci de monarquia durant el Regne Mitjà, a partir de l’anàlisi directa de quatre fonts literàries del període. S’ha constatat que la concepció de monarquia resultant, concebuda com a clàssica o modèlica, és la que es transmet en essència fins a l’etapa final de la història antiga egípcia, encara que readaptant-se a les noves realitats polítiques i culturals. L’anàlisi d’aquest ideal teòric de monarquia ha estat fonamental per afrontar l’objectiu essencial del projecte de tesi: l’estudi de la legitimació d’Alexandre el Gran com a faraó d’Egipte, és a dir, l’examen en profunditat del conjunt de mecanismes mitjançant els quals el macedoni va assumir el rol clàssic dels monarques egipcis i que expliciten el procés segons el qual un nou sobirà, que a més era d’origen estranger, fou inserit en la ideologia faraònica tradicional. Per tal de determinar com això es va produir, es fa necessari l’estudi del període en què Alexandre és el titular del tron del país (332-323 aC), és a dir, del moment de gènesi, formulació i desenvolupament de l’entramat ideològic que proporcionarà base teològica al nou govern i l’adequarà a la tradició. Per a l’examen d’aquest període cronològic, la documentació egípcia s’erigeix com la principal font d’informació, i per tant, durant el projecte s’ha compilat i analitzat el conjunt de la documentació de procedència egípcia disponible fins al moment que, datada o no, s’adscriu cronològicament a aquest període.

High-throughput hydrophilic interaction chromatography coupled to tandem mass spectrometry for the optimized quantification of the anti-Gram-negatives antibiotic colistin A/B and its pro-drug colistimethate.

Colistin is a last resort's antibacterial treatment in critically ill patients with multi-drug resistant Gram-negative infections. As appropriate colistin exposure is the key for maximizing efficacy while minimizing toxicity, individualized dosing optimization guided by therapeutic drug monitoring is a top clinical priority. Objective of the present work was to develop a rapid and robust HPLC-MS/MS assay for quantification of colistin plasma concentrations. This novel methodology validated according to international standards simultaneously quantifies the microbiologically active compounds colistin A and B, plus the pro-drug colistin methanesulfonate (colistimethate, CMS). 96-well micro-Elution SPE on Oasis Hydrophilic-Lipophilic-Balanced (HLB) followed by direct analysis by Hydrophilic Interaction Liquid Chromatography (HILIC) with Ethylene Bridged Hybrid - BEH - Amide phase column coupled to tandem mass spectrometry allows a high-throughput with no significant matrix effect. The technique is highly sensitive (limit of quantification 0.014 and 0.006μg/mL for colistin A and B), precise (intra-/inter-assay CV 0.6-8.4%) and accurate (intra-/inter-assay deviation from nominal concentrations -4.4 to +6.3%) over the clinically relevant analytical range 0.05-20μg/mL. Colistin A and B in plasma and whole blood samples are reliably quantified over 48h at room temperature and at +4°C (<6% deviation from nominal values) and after three freeze-thaw cycles. Colistimethate acidic hydrolysis (1M H2SO4) to colistin A and B in plasma was completed in vitro after 15min of sonication while the pro-drug hydrolyzed spontaneously in plasma ex vivo after 4h at room temperature: this information is of utmost importance for interpretation of analytical results. Quantification is precise and accurate when using serum, citrated or EDTA plasma as biological matrix, while use of heparin plasma is not appropriate. This new analytical technique providing optimized quantification in real-life conditions of the microbiologically active compounds colistin A and B offers a highly efficient tool for routine therapeutic drug monitoring aimed at individualizing drug dosing against life-threatening infections.

Immuno-monitoring of CD8+ T cells in whole blood versus PBMC samples.

The study of natural T cell responses against pathogens or tumors, as well as the assessment of new immunotherapy strategies aimed at boosting these responses, requires increasingly precise ex vivo analysis of blood samples. For practical reasons, studies are often performed using purified PBMC samples, usually cryopreserved. Here, we report on FACS analyses of peripheral blood T cells, performed by direct antibody staining of non-purified total blood. For comparison, fresh PBMC, purified by Ficoll, were analysed. Our results show that the latter method can induce a bias in subpopulation distribution, in particular of CD8+ T cells, and sometimes lead to inaccurate measurement of antigen specific CD8+ T cell responses. Direct analysis of total blood can be applied to longitudinal immuno-monitoring of T cell-based therapy. While the need to purify and cryopreserve PBMC for subsequent studies is obvious, the use of whole blood has the advantage of providing unbiased results and only small amounts of blood are used.

Quantification of glucuronidated and sulfated steroids in human urine by ultra-high pressure liquid chromatography quadrupole time-of-flight mass spectrometry.

The urinary steroid profile is constituted by anabolic androgenic steroids, including testosterone and its relatives, that are extensively metabolized into phase II sulfated or glucuronidated steroids. The use of liquid chromatography coupled to mass spectrometry (LC-MS) is an issue for the direct analysis of conjugated steroids, which can be used as urinary markers of exogenous steroid administration in doping analysis, without hydrolysis of the conjugated moiety. In this study, a sensitive and selective ultra high-pressure liquid chromatography coupled to quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS) method was developed to quantify major urinary metabolites simultaneously after testosterone intake. The sample preparation of the urine (1 mL) was performed by solid-phase extraction on Oasis HLB sorbent using a 96-well plate format. The conjugated steroids were analyzed by UHPLC-QTOF-MS(E) with a single-gradient elution of 36 min (including re-equilibration time) in the negative electrospray ionization mode. MS(E) analysis involved parallel alternating acquisitions of both low- and high-collision energy functions. The method was validated and applied to samples collected from a clinical study performed with a group of healthy human volunteers who had taken testosterone, which were compared with samples from a placebo group. Quantitative results were also compared to GC-MS and LC-MS/MS measurements, and the correlations between data were found appropriate. The acquisition of full mass spectra over the entire mass range with QTOF mass analyzers gives promise of the opportunity to extend the steroid profile to a higher number of conjugated steroids.

Quantify this! Report on a round table discussion on quantitative mass spectrometry in proteomics.

Following the success of the first round table in 2001, the Swiss Proteomic Society has organized two additional specific events during its last two meetings: a proteomic application exercise in 2002 and a round table in 2003. Such events have as their main objective to bring together, around a challenging topic in mass spectrometry, two groups of specialists, those who develop and commercialize mass spectrometry equipment and software, and expert MS users for peptidomics and proteomics studies. The first round table (Geneva, 2001) entitled "Challenges in Mass Spectrometry" was supported by brief oral presentations that stressed critical questions in the field of MS development or applications (Stöcklin and Binz, Proteomics 2002, 2, 825-827). Topics such as (i) direct analysis of complex biological samples, (ii) status and perspectives for MS investigations of noncovalent peptide-ligant interactions; (iii) is it more appropriate to have complementary instruments rather than a universal equipment, (iv) standardization and improvement of the MS signals for protein identification, (v) what would be the new generation of equipment and finally (vi) how to keep hardware and software adapted to MS up-to-date and accessible to all. For the SPS'02 meeting (Lausanne, 2002), a full session alternative event "Proteomic Application Exercise" was proposed. Two different samples were prepared and sent to the different participants: 100 micro g of snake venom (a complex mixture of peptides and proteins) and 10-20 micro g of almost pure recombinant polypeptide derived from the shrimp Penaeus vannamei carrying an heterogeneous post-translational modification (PTM). Among the 15 participants that received the samples blind, eight returned results and most of them were asked to present their results emphasizing the strategy, the manpower and the instrumentation used during the congress (Binz et. al., Proteomics 2003, 3, 1562-1566). It appeared that for the snake venom extract, the quality of the results was not particularly dependant on the strategy used, as all approaches allowed Lication of identification of a certain number of protein families. The genus of the snake was identified in most cases, but the species was ambiguous. Surprisingly, the precise identification of the recombinant almost pure polypeptides appeared to be much more complicated than expected as only one group reported the full sequence. Finally the SPS'03 meeting reported here included a round table on the difficult and challenging task of "Quantification by Mass Spectrometry", a discussion sustained by four selected oral presentations on the use of stable isotopes, electrospray ionization versus matrix-assisted laser desorption/ionization approaches to quantify peptides and proteins in biological fluids, the handling of differential two-dimensional liquid chromatography tandem mass spectrometry data resulting from high throughput experiments, and the quantitative analysis of PTMs. During these three events at the SPS meetings, the impressive quality and quantity of exchanges between the developers and providers of mass spectrometry equipment and software, expert users and the audience, were a key element for the success of these fruitful events and will have definitively paved the way for future round tables and challenging exercises at SPS meetings.

Degeneracy of antigen recognition as the molecular basis for the high frequency of naive A2/Melan-a peptide multimer(+) CD8(+) T cells in humans.

In contrast with the low frequency of most single epitope reactive T cells in the preimmune repertoire, up to 1 of 1,000 naive CD8(+) T cells from A2(+) individuals specifically bind fluorescent A2/peptide multimers incorporating the A27L analogue of the immunodominant 26-35 peptide from the melanocyte differentiation and melanoma associated antigen Melan-A. This represents the only naive antigen-specific T cell repertoire accessible to direct analysis in humans up to date. To get insight into the molecular basis for the selection and maintenance of such an abundant repertoire, we analyzed the functional diversity of T cells composing this repertoire ex vivo at the clonal level. Surprisingly, we found a significant proportion of multimer(+) clonotypes that failed to recognize both Melan-A analogue and parental peptides in a functional assay but efficiently recognized peptides from proteins of self- or pathogen origin selected for their potential functional cross-reactivity with Melan-A. Consistent with these data, multimers incorporating some of the most frequently recognized peptides specifically stained a proportion of naive CD8(+) T cells similar to that observed with Melan-A multimers. Altogether these results indicate that the high frequency of Melan-A multimer(+) T cells can be explained by the existence of largely cross-reactive subsets of naive CD8(+) T cells displaying multiple specificities.

Photographic rectification of the graphic documentation of historical and archaeological heritage: The case of the southern facade of the Praetorium tower in Tarragona (Tarraco, Hispania Citerior)

This article details the use of photographic rectification as support for the graphic documentation of historical and archaeological heritage and specifically the southern facade of the Torre del Pretori (Praetorium Tower) in Tarragona. The Praetorium Tower is part of a larger monumental complex and one of the towers that connected different parts of the Tarraco Provincial Forum, the politic-administrative centre of the ancient capital of Hispania Citerioris. It is therefore a valuable example of the evolution of Roman urban architecture. The aim of this project is to provide accurate graphic documentation of the structure to facilitate the restoration and conservation of the tower, as well as to provide a more profound architectural and archaeological understanding of the Roman forum. The use of photographic rectification enabled us to overcome the spatial and time difficulties involved in collecting data caused by the size and location of the building. Specific software made it easier to obtain accurate two-dimensional images. For this reason, in our case, photographic rectification helped us to make a direct analysis of the monument and facilitated interpretation of the architectural stratigraphy. We currently separate the line of research into two concepts: the construction processes and the architecture of the building. The documentation collected permitted various analyses: the characterisation of the building modules, identification of the tools used to work the building materials, etc. In conclusion, the use of orthoimages is a powerful tool that permits the systematic study of a Roman building that has evolved over the centuries and is now in a modern urban context.

People favour imperfect catching by assuming a stable world

The visual angle that is projected by an object (e.g. a ball) on the retina depends on the object's size and distance. Without further information, however, the visual angle is ambiguous with respect to size and distance, because equal visual angles can be obtained from a big ball at a longer distance and a smaller one at a correspondingly shorter distance. Failure to recover the true 3D structure of the object (e.g. a ball's physical size) causing the ambiguous retinal image can lead to a timing error when catching the ball. Two opposing views are currently prevailing on how people resolve this ambiguity when estimating time to contact. One explanation challenges any inference about what causes the retinal image (i.e. the necessity to recover this 3D structure), and instead favors a direct analysis of optic flow. In contrast, the second view suggests that action timing could be rather based on obtaining an estimate of the 3D structure of the scene. With the latter, systematic errors will be predicted if our inference of the 3D structure fails to reveal the underlying cause of the retinal image. Here we show that hand closure in catching virtual balls is triggered by visual angle, using an assumption of a constant ball size. As a consequence of this assumption, hand closure starts when the ball is at similar distance across trials. From that distance on, the remaining arrival time, therefore, depends on ball's speed. In order to time the catch successfully, closing time was coupled with ball's speed during the motor phase. This strategy led to an increased precision in catching but at the cost of committing systematic errors.

Amostragem de suspensões: Emprego da técnica na análise direta de amostras

This review presents some characteristics related to slurry sampling in trace analysis in terms of its advantages, limitations and applications, as well as the latest advance in this area, such as mechanization, chemical modifiers, stabilization agents and others. The reviewed applications include foods, biological and geological materials.

Análise direta de sólidos por espectrometria de absorção atômica com atomização em forno de grafite: uma revisão

This is a review of direct analysis using solid sampling graphite furnace atomic absorption spectrometry. Greater emphasis is dedicated to sample preparation, sample homogeneity, calibration and its application to microanalysis and micro-homogeneity studies. The main advantages and some difficulties related to the applicability of this technique are discussed. A literature search on the application of solid sampling graphite furnace atomic absorption spectrometry in trace element determination in many kinds of samples, including biological, clinical, technological and environmental ones, is also presented.

Développement de méthodes d’analyse directe de polluants organiques volatils à l’état de traces dans l’air et les biogaz

Il est reconnu que le benzène, le toluène, l’éthylbenzène et les isomères du xylène, composés organiques volatils (COVs) communément désignés BTEX, produisent des effets nocifs sur la santé humaine et sur les végétaux dépendamment de la durée et des niveaux d’exposition. Le benzène en particulier est classé cancérogène et une exposition à des concentrations supérieures à 64 g/m3 de benzène peut être fatale en 5–10 minutes. Par conséquent, la mesure en temps réel des BTEX dans l’air ambiant est essentielle pour détecter rapidement un danger associé à leur émission dans l’air et pour estimer les risques potentiels pour les êtres vivants et pour l’environnement. Dans cette thèse, une méthode d’analyse en temps réel des BTEX dans l’air ambiant a été développée et validée. La méthode est basée sur la technique d’échantillonnage direct de l’air couplée avec la spectrométrie de masse en tandem utilisant une source d’ionisation chimique à pression atmosphérique (APCI-MS/MS directe). La validation analytique a démontré la sensibilité (limite de détection LDM 1–2 μg/m3), la précision (coefficient de variation CV < 10%), l’exactitude (exactitude > 95%) et la sélectivité de la méthode. Des échantillons d’air ambiant provenant d’un site d’enfouissement de déchets industriels et de divers garages d’entretien automobile ont été analysés par la méthode développée. La comparaison des résultats avec ceux obtenus par la technique de chromatographie gazeuse on-line couplée avec un détecteur à ionisation de flamme (GC-FID) a donné des résultats similaires. La capacité de la méthode pour l’évaluation rapide des risques potentiels associés à une exposition aux BTEX a été prouvée à travers une étude de terrain avec analyse de risque pour la santé des travailleurs dans trois garages d’entretien automobile et par des expériences sous atmosphères simulées. Les concentrations mesurées dans l’air ambiant des garages étaient de 8,9–25 µg/m3 pour le benzène, 119–1156 µg/m3 pour le toluène, 9–70 µg/m3 pour l’éthylbenzène et 45–347 µg/m3 pour les xylènes. Une dose quotidienne environnementale totale entre 1,46 10-3 et 2,52 10-3 mg/kg/jour a été déterminée pour le benzène. Le risque de cancer lié à l’exposition environnementale totale au benzène estimé pour les travailleurs étudiés se situait entre 1,1 10-5 et 1,8 10-5. Une nouvelle méthode APCI-MS/MS a été également développée et validée pour l’analyse directe de l’octaméthylcyclotétrasiloxane (D4) et le décaméthylcyclopentasiloxane (D5) dans l’air et les biogaz. Le D4 et le D5 sont des siloxanes cycliques volatils largement utilisés comme solvants dans les processus industriels et les produits de consommation à la place des COVs précurseurs d’ozone troposphérique tels que les BTEX. Leur présence ubiquitaire dans les échantillons d’air ambiant, due à l’utilisation massive, suscite un besoin d’études de toxicité. De telles études requièrent des analyses qualitatives et quantitatives de traces de ces composés. Par ailleurs, la présence de traces de ces substances dans un biogaz entrave son utilisation comme source d’énergie renouvelable en causant des dommages coûteux à l’équipement. L’analyse des siloxanes dans un biogaz s’avère donc essentielle pour déterminer si le biogaz nécessite une purification avant son utilisation pour la production d’énergie. La méthode développée dans cette étude possède une bonne sensibilité (LDM 4–6 μg/m3), une bonne précision (CV < 10%), une bonne exactitude (> 93%) et une grande sélectivité. Il a été également démontré qu’en utilisant cette méthode avec l’hexaméthyl-d18-disiloxane comme étalon interne, la détection et la quantification du D4 et du D5 dans des échantillons réels de biogaz peuvent être accomplies avec une meilleure sensibilité (LDM ~ 2 μg/m3), une grande précision (CV < 5%) et une grande exactitude (> 97%). Une variété d’échantillons de biogaz prélevés au site d’enfouissement sanitaire du Complexe Environnemental de Saint-Michel à Montréal a été analysée avec succès par cette nouvelle méthode. Les concentrations mesurées étaient de 131–1275 µg/m3 pour le D4 et 250–6226 µg/m3 pour le D5. Ces résultats représentent les premières données rapportées dans la littérature sur la concentration des siloxanes D4 et D5 dans les biogaz d’enfouissement en fonction de l’âge des déchets.

Nouvelles stratégies pour l’analyse des cyanotoxines par spectrométrie de masse

Les cyanobactéries ont une place très importante dans les écosystèmes aquatiques et un nombre important d’espèces considéré comme nuisible de par leur production de métabolites toxiques. Ces cyanotoxines possèdent des propriétés très variées et ont souvent été associées à des épisodes d’empoisonnement. L’augmentation des épisodes d’efflorescence d’origine cyanobactériennes et le potentiel qu’ils augmentent avec les changements climatiques a renchéri l’intérêt de l’étude des cyanobactéries et de leurs toxines. Considérant la complexité chimique des cyanotoxines, le développement de méthodes de détection simples, sensibles et rapides est toujours considéré comme étant un défi analytique. Considérant ces défis, le développement de nouvelles approches analytiques pour la détection de cyanotoxines dans l’eau et les poissons ayant été contaminés par des efflorescences cyanobactériennes nuisibles a été proposé. Une première approche consiste en l’utilisation d’une extraction sur phase solide en ligne couplée à une chromatographie liquide et à une détection en spectrométrie de masse en tandem (SPE-LC-MS/MS) permettant l’analyse de six analogues de microcystines (MC), de l’anatoxine (ANA-a) et de la cylindrospermopsine (CYN). La méthode permet une analyse simple et rapide et ainsi que la séparation chromatographique d’ANA-a et de son interférence isobare, la phénylalanine. Les limites de détection obtenues se trouvaient entre 0,01 et 0,02 μg L-1 et des concentrations retrouvées dans des eaux de lacs du Québec se trouvaient entre 0,024 et 36 μg L-1. Une deuxième méthode a permis l’analyse du b-N-méthylamino-L-alanine (BMAA), d’ANA-a, de CYN et de la saxitoxine (STX) dans les eaux de lac contaminés. L’analyse de deux isomères de conformation du BMAA a été effectuée afin d’améliorer la sélectivité de la détection. L’utilisation d’une SPE manuelle permet la purification et préconcentration des échantillons et une dérivatisation à base de chlorure de dansyle permet une chromatographie simplifiée. L’analyse effectuée par LC couplée à la spectrométrie de masse à haute résolution (HRMS) et des limites de détections ont été obtenues entre 0,007 et 0,01 µg L-1. Des échantillons réels ont été analysés avec des concentrations entre 0,01 et 0,3 µg L-1 permettant ainsi la confirmation de la présence du BMAA dans les efflorescences de cyanobactéries au Québec. Un deuxième volet du projet consiste en l’utilisation d’une technologie d’introduction d’échantillon permettant des analyses ultra-rapides (< 15 secondes/échantillons) sans étape chromatographique, la désorption thermique à diode laser (LDTD) couplée à l’ionisation chimique à pression atmosphérique (APCI) et à la spectrométrie de masse (MS). Un premier projet consiste en l’analyse des MC totales par l’intermédiaire d’une oxydation de Lemieux permettant un bris de la molécule et obtenant une fraction commune aux multiples congénères existants des MC. Cette fraction, le MMPB, est analysée, après une extraction liquide-liquide, par LDTD-APCI-MS/MS. Une limite de détection de 0,2 µg L-1 a été obtenue et des concentrations entre 1 et 425 µg L-1 ont été trouvées dans des échantillons d’eau de lac contaminés du Québec. De plus, une analyse en parallèle avec des étalons pour divers congénères des MC a permis de suggérer la possible présence de congénères ou d’isomères non détectés. Un deuxième projet consiste en l’analyse directe d’ANA-a par LDTD-APCI-HRMS pour résoudre son interférence isobare, la phénylalanine, grâce à la détection à haute résolution. La LDTD n’offre pas de séparation chromatographique et l’utilisation de la HRMS permet de distinguer les signaux d’ANA-a de ceux de la phénylalanine. Une limite de détection de 0,2 µg L-1 a été obtenue et la méthode a été appliquée sur des échantillons réels d’eau avec un échantillon positif en ANA-a avec une concentration de 0,21 µg L-1. Finalement, à l’aide de la LDTD-APCI-HRMS, l’analyse des MC totales a été adaptée pour la chair de poisson afin de déterminer la fraction libre et liée des MC et comparer les résultats avec des analyses conventionnelles. L’utilisation d’une digestion par hydroxyde de sodium précédant l’oxydation de Lemieux suivi d’une purification par SPE a permis d’obtenir une limite de détection de 2,7 µg kg-1. Des échantillons de poissons contaminés ont été analysés, on a retrouvé des concentrations en MC totales de 2,9 et 13,2 µg kg-1 comparativement aux analyses usuelles qui avaient démontré un seul échantillon positif à 2 µg kg-1, indiquant la possible présence de MC non détectés en utilisant les méthodes conventionnelles.

G protein ss gamma subunits mediate presynaptic inhibition of transmitter release from rat superior cervical ganglion neurones in culture

The activation of presynaptic G protein-coupled receptors (GPCRs) is widely reported to inhibit transmitter release; however, the lack of accessibility of many presynaptic terminals has limited direct analysis of signalling mediators. We studied GPCR-mediated inhibition of fast cholinergic transmission between superior cervical ganglion neurones (SCGNs) in culture. The adrenoceptor agonist noradrenaline (NA) caused a dose-related reduction in evoked excitatory postsynaptic potentials (EPSPs). NA-induced EPSP decrease was accompanied by effects on the presynaptic action potential (AP), reducing AP duration and amplitude of the after-hyperpolarization (AHP), without affecting the pre- and postsynaptic membrane potential. All effects of NA were blocked by yohimbine and synaptic transmission was reduced by clonidine, consistent with an action at presynaptic alpha 2-adrenoceptors. NA-induced inhibition of transmission was sensitive to pre-incubation of SCGNs with pertussis toxin (PTX), implicating the involvement of G alpha(i)/(o)beta y subunits. Expression of G alpha transducin, an agent which sequesters G protein beta gamma (G beta y) subunits, in the presynaptic neurone caused a time-dependent attenuation of NA-induced inhibition. Injection of purified G beta gamma subunits into the presynaptic neurone inhibited transmission, and also reduced the AHP amplitude. Furthermore, NA-induced inhibition was occluded by pre-injection of G beta gamma subunits. The Ca2+ channel blocker Cd2+ mimicked NA effects on transmitter release. Cd2+, NA and G beta gamma subunits also inhibited somatic Ca2+ current. In contrast to effects on AP-evoked transmitter release, NA had no clear action on AP-independent EPSPs induced by hypertonic solutions. These results demonstrate that G beta gamma subunits functionally mediate inhibition of transmitter release by alpha 2-adrenoceptors and represent important regulators of synaptic transmission at mammalian presynaptic terminals.

Breast, colorectal, and prostate cancer risk in the European Prospective Investigation into Cancer and Nutrition–Norfolk in relation to phytoestrogen intake derived from an improved database

Background: The characterization of phytoestrogen intake and cancer risk has been hindered by the absence of accurate dietary phytoestrogen values. Objective: We examined the risk of breast, colorectal, and prostate cancers relative to phytoestrogen intake on the basis of a comprehensive database. Design: Demographic and anthropometric characteristics, a medical history, and 7-d records of diet were collected prospectively from participants (aged 40–79 y) in the European Prospective Investigation into Cancer and Nutrition–Norfolk (EPIC-Norfolk). Five hundred nine food items were analyzed by liquid chromatography–mass spectrometry/mass spectrometry, and 13C3-labeled internal standards were analyzed for isoflavones (genistein, daidzein, glycitein, biochanin A, and formononetin), lignans (secoisolariciresinol and matairesinol), and enterolignans from gut microbial metabolism in animal food sources (equol and enterolactone). From the direct analysis, values for 10,708 foods were calculated. Odds ratios (ORs) for breast (244 cases, 941 controls), colorectal (221 cases, 886 controls), and prostate (204 cases, 812 controls) cancers were calculated relative to phytoestrogen intake. Results: Phytoestrogen intake was not associated with breast cancer among women or colorectal cancer among men. Among women, colorectal cancer risk was inversely associated with enterolactone (OR: 0.33; 95% CI: 0.14, 0.74) and total enterolignans (OR: 0.32; 95% CI: 0.13, 0.79), with a positive trend detected for secoisolariciresinol (OR: 1.60; 95% CI: 0.96, 2.69). A positive trend between enterolignan intake and prostate cancer risk (OR: 1.27; 95% CI: 0.97, 1.66) was attenuated after adjustment for dairy intake (OR: 1.19; 95% CI: 0.77, 1.82). Conclusion: Dietary phytoestrogens may contribute to the risk of colorectal cancer among women and prostate cancer among men.