Experimental Study and Detailed Modeling of Toluene Degradation in a Low-Pressure Stoichiometric Premixed CH4/O2/N2 Flame

Temperature and mole fraction profiles have been measured in laminar stoichiometric premixed CH4/O2/N2 and CH4/1.5%C6H5CH3/O2/N2 flames at low pressure (0.0519 bar) by using thermocouple, molecular beam/mass spectrometry (MB/MS), and gas chromatography/mass spectrometry (GC/MS) techniques. The present study completes our previous work performed on the thermal degradation of benzene in CH4/O2/N2 operating at similar conditions. Mole fraction profiles of reactants, final products, and reactive and stable intermediate species have been analyzed. The main intermediate aromatic species analyzed in the methane-toluene flame were benzene, phenol, ethylbenzene, benzylalcohol, styrene, and benzaldehyde. These new experimental results have been modeled with our previous model including submechanisms for aromatics (benzene up to p-xylene) and aliphatic (C1 up to C7) oxidation. Good agreement has been observed for the main species analyzed. The main reaction paths governing the degradation of toluene in the methane flame were identified, and it occurs mainly via the formation of benzene (C6H5CH3 + H = C6H6 + CH3) and benzyl radical (C6H5CH3 + H = C6H5CH2 + H2). Due to the abundance of methyl radicals, it was observed that recombination of benzyl and methyl is responsible for main monosubstitute aromatic species analyzed in the methane-toluene flame. The oxidation of these substitute species led to cyclopentadienyl radical as observed in a methane-benzene flame.

Bilateral lobar lung transplantation--the first two cases in Belgium

In the last twenty years lung transplantation has become an established treatment for end-stage lung failure refractory to medical management. Over this time, better short and long-term results have been achieved due to improvements in organ procurement, perfusion and preservation strategies, newer immunosuppressant regimes and better post-transplant care. The limiting factor for the number of lung transplantation procedures performed is the shortage of available donor organs. This results in longer waiting times for listed patients, with a substantially increased risk of dying prior to transplantation, especially in the paediatric population. Several surgical strategies have evolved to overcome the donor shortage, with lobar transplantation becoming a viable alternative. We describe our initial experience with two young patients with end-stage cystic fibrosis (CF) who required lung transplantation. Given their small size it was not possible to transplant an entire lung from an adult donor in each hemithorax. We describe lobar transplantation as a technique used to overcome this, in the first such operation in Belgium.

Nano-polymer-dispersed liquid crystal as phase modulator for a tunable vertical-cavity surface-emitting laser at 1.55 mum

We demonstrate what we believe is the first nonmechanical tunable vertical-cavity surface-emitting laser operating in the C band. This was achieved as a result of the combination of an InGaAs quantum well structure with a 6lambda thickness tunable index nano-polymer-dispersed liquid-crystal material. Experimental results exhibited a potential tunable range close to 10 nm, in the preliminary version, and excellent single mode locking due to the side-mode suppression ratio (more than 20 dB) over the whole spectral range. Another decisive advantage, compared to mechanical solutions, was the tuning response time of a few tens of microseconds (>30 micros) to scan the full spectral range (10 nm), making this device appropriate for some access network functions, as well as being robust and low cost. The voltage values are the main limitation to wavelength range extension. We present a first version of the device optically pumped. The next version will be electrically pumped as required for the access network applications targeted here.

Explosion characteristics of synthesised biogas at various temperatures

Biogas is considered as a valuable source of renewable energy. Indeed, it can be turned into useful energy (heat, electricity, fuel) and can contribute to reduce greenhouse gas emissions. Knowledge of its safety characteristics is a very important practical issue. Experimental investigation of synthesised biogas explosion characteristics was conducted in a 20-L sphere at various temperatures (30-70 degrees C) and at atmospheric pressure. The studied biogas was made of 50% methane (CH(4)) and 50% carbon dioxide (CO(2)). It was also saturated with humidity: this composition is frequently met in digesters during waste methanisation. There are two inert gases in biogas: water vapour and carbon dioxide. Its vapour water content rises along with temperature. The presence of these inert gases modifies considerably biogas characteristics compared to the ones of pure methane: explosion limits are lowered and beyond 70 degrees C, water vapour content is sufficient to inert the mixture. Furthermore, explosion violence (estimated with the maximum rate of pressure rise values, (dp/dt)(max)) is three times lower for biogas than for pure methane at ambient temperature.

Listeria pleuritis 1 week after lung transplantation

Listeria monocytogenes is an important bacterial pathogen in immunocompromised patients, the elderly, pregnant women and transplant patients, but until now it has not been reported in lung transplants. We report the first case of listeriosis in a lung transplant recipient who presented with a pleural effusion 8 days after transplantation. After the introduction of a thorax drain and the administration of intravenous antibiotics during 3 weeks, the patient recovered completely. This case highlights the increased risk for uncommon respiratory infections in lung transplant patients and examines the specific management of listeria pleuritis.

Gregariousness and protandry promote reproductive insurance in the invasive gastropod Crepidula fornicata: evidence from assignment of larval paternity

According to the size-advantage hypothesis, protandric sequential hermaphroditism is expected when the increase in reproductive success with age or size is small for males but large for females. Interestingly, some protandrous molluscs have developed gregarious strategies that might enhance male reproductive success but at the cost of intraspecific competition. The gastropod Crepidula fornicata, a European invading species, is ideal for investigating mating patterns in a sequential hermaphrodite in relation to grouping behaviour because individuals of different size (age) live in perennial stacks, fertilization is internal and embryos are brooded. Paternity analyses were undertaken in stacks sampled in three close and recently invaded sites in Brittany, France. Paternity assignment of 239 larvae, sampled from a set of 18 brooding females and carried out using five microsatellite loci, revealed that 92% of the crosses occurred between individuals located in the same stack. These stacks thus function as independent mating groups in which individuals may reproduce consecutively as male and female over a short time period, a pattern explained by sperm storage capacity. Gregariousness and sex reversal are promoting reproductive insurance in this species. In addition, females are usually fertilized by several males (78% of the broods were multiply sired) occupying any position within the stack, a result reinforcing the hypothesis of sperm competition. Our study pointed out that mating behaviours and patterns of gender allocation varied in concert across sites suggesting that multiple paternities might enhance sex reversal depending on sperm competition intensity.

Evaluating the “Leeds criteria” forPseudomonas aeruginosainfection in a cystic fibrosis centre

Four separate categories of chronic Pseudomonas aeruginosa (Pa) infection in children with cystic fibrosis (CF) have been previously defined, based on airway cultures taken over the previous year. The aim of the present study was to evaluate this definition in the current authors' paediatric and adult CF clinic using clinical, immunological and lung function parameters. During follow-up, out of 193 patients, 55 (34%) CF patients had never been infected with Pa, 27 (17%) were free of Pa, 29 (18%) were intermittently infected and 51 (31%) were chronically infected. Disease severity markers, such as lung function, were significantly worse in the chronic group, especially in the paediatric population. Differences in adult patients were smaller and no longer significant. Pa antibodies differed strongly between the groups, and were very high (mean+/-sd 55.4+/-5.5) and highly statistically significant from all other groups in the chronic group. They were low and different from all other groups in the never group (1.8+/-0.6). Pa antibodies did not differ between the free of Pa and the intermittent group. In conclusion, the current authors confirmed an agreement between Pseudomonas aeruginosa status according to the new definition and clinical status, as well as with the level of Pseudomonas aeruginosa antibodies.

Rapid screening of DOM's metal-binding ability using a fluorescence-based microplate assay

This note describes the development of a method to rapidly quantify the metal-binding ability of low-volume DOM samples based on their fluorescence properties. The method uses 96-well microplates to screen the fluorescence quenching observed when increasing concentrations of various metals are added to the pH-buffered DOM sample. Only 1.6 mL of DOM sample is required to quantify the binding affinity for each metal and the result is obtained in a few minutes. This study presents results for a surface soil DOM sample for which binding was assessed for Cu2+, Fe2+, Ni2+ at pH 5 and 9.

Weakly acidic reflux in patients with chronic unexplained cough during 24 hour pressure, pH, and impedance monitoring

BACKGROUND AND AIMS

Acid gastro-oesophageal reflux is one of the most important causes of chronic cough. The response to acid suppression in these patients is not as good as in patients with heartburn but improvement with antireflux surgery has been reported, suggesting the involvement of a non-acidic gastric component in the refluxate. Less acidic reflux may produce symptoms such as regurgitation or chest pain. We investigated whether chronic cough might be associated with weakly acidic reflux.

METHODS

We studied 28 patients with chronic cough using 24 hour ambulatory pressure-pH-impedance monitoring. Manometry was used for precise recognition of cough and impedance-pHmetry to detect acid (pH <4), weakly acidic (pH 7-4), and weakly alkaline (impedance drops, pH >/=7) reflux. A symptom association probability (SAP) analysis was performed for each type of reflux.

RESULTS

Analysis was completed in 22 patients with 24 cough events (5-92)/patient. The majority of cough events (69.4%) were considered "independent" of reflux whereas 30.6% occurred within two minutes of a reflux episode. Half of these (49%) were "reflux cough" sequences, involving acid (65%), weakly acidic (29%), and weakly alkaline (6%) reflux. Ten patients (45%) had a positive SAP between reflux and cough: five with acid, two with acid and weakly acidic, and three only with weakly acidic reflux.

CONCLUSIONS

Ambulatory pressure-pH-impedance monitoring with SAP analysis allowed precise determination of the temporal association between cough and gastro-oesophageal reflux (acid, weakly acidic, and weakly alkaline) and identification of a subgroup of patients with chronic cough clearly associated with weakly acidic gastro-oesophageal reflux.

Effects of spontaneously chosen crank rate variations on electromyographic responses in sub-maximal arm exercise in inexperienced subjects

The aim of the present study was to compare electromyographic responses during arm exercises with a crank rate chosen spontaneously ( T(S)) or set at 20% below or above ( T(-20), T(+20)) the spontaneously chosen crank rate (SCCR). Ten male physical education students performed arm exercises with intensities ranging from 20% to 80% of maximal power. Muscular activity levels were analysed for the biceps brachii and the triceps brachii muscles using integrated rectified surface electromyography (iEMG). All values were presented as the mean and standard deviation. During T(S), the sum of iEMG for the two muscles studied was significantly ( P<0.05) lower than during T(+20) for each power output. No significant differences were observed in iEMG values between T(S) and T(-20). The hypothesis that SCCR relates to a minimisation of muscle activation during an upper body exercise was not confirmed. Variations superior or inferior to a 20% increase of the iEMG responses do not influence it. Moreover, the selection of crank rates depends on the power output and the SCCR increased significantly ( P<0.05) with increasing power output.

Crystal structure of bis(8-chloro-5-(4-methylpiperazinium-1-yl)pyrido- [2,3-b][1,5]benzoxazepine) fumarate – fumaric acid solvate (1:1), (C17H18ClN4O)2(C4H2O4) · C4H4O4

C42H42Cl2N8O10, triclinic, P1̅ (no. 2), a = 9.625(1) Å, b = 9.929(3) Å, c = 11.860(2) Å, α = 108.12(2)°, β = 73.24(1)°, γ = 87.38(1)°, V = 1019.9 Å3, Z = 1, Rgt(F) = 0.043, wRref(F2) = 0.131, T = 293 K.

Maximal lactate steady state does not correspond to a complete physiological steady state

The purpose of this study was to verify whether the maximal lactate steady state (MLSS) corresponds to a physiological steady state. Eight male trained subjects performed a 30-min test on a cycle ergometer at a constant power corresponding to their own MLSS which had been previously determined. No significant variation was observed between the 10th and the 30th min for arterial lactate concentration, redox state, arterial oxygen pressure, arterial oxygen saturation, bicarbonates concentration, base excess, hematocrit, hemoglobin concentration, plasma volume, oxygen uptake, carbon dioxide output, gas exchange ratio, minute ventilation, ventilatory equivalents for oxygen and carbon dioxide, and arterial systolic blood pressure values. However, arterial carbon dioxide pressure and pH values were significantly different between the 10th and the 30th min (p < 0.01). Respiratory rate values and heart rate significantly increased (p < 0.01). These results indicate that MLSS does not correspond to a complete physiological steady state.

A reversible copper extrusion-insertion electrode for rechargeable Li batteries

Although widely used, the most promising Li-based technologies still suffer from a lack of suitable electrodes. There is therefore a need to seek new materials concepts to satisfy the increasing demands for energy storage worldwide. Here we report on a new layered electrode material, Cu(2.33)V(4)O(11), which shows a sustainable reversible capacity of 270 mA h g(-1) at a voltage of about 2.7 V, and electrochemically reacts with Li in an unusual and spectacular way. The reaction entails a reversible Li-driven displacement process leading to the growth and disappearance of Cu dendrites with a concomitant reversible decomposition and recrystallization of the initial electrode material. We show from structural considerations that the uniqueness of Cu(2.33)V(4)O(11) is rooted in the peculiar flexibility of the stacked [V(4)O(11)](n) layers, which is due to the presence of pivot oxygen atoms. Fully reversible displacement reactions could provide a new direction for developing an alternative class of higher energy density Li storage electrodes.

Removal of hexavalent chromium with a lignocellulosic substrate extracted from wheat bran

In this paper, a new recovery system of the toxic hexavalent chromium Cr(VI) is proposed that uses a lignocellulosic substrate derived from the industrial treatment process of wheat bran. We studied the adsorption mechanism of Cr(VI) onto the lignocellulosic substrate and showed that the adsorption reaction consumes a large amount of protons goes along the reduction of Cr(VI) into Cr(III). The oxidation of lignin moieties takes place concurrently to the chromium reduction and leads to the formation of hydroxyl and carboxyl functions. The latter contribute to an increase in the number of ion-exchange sites for the reduced chromium. The maximum adsorption capacity for hexavalent chromium was found at about 35 mg g(-1) in an acidic medium. This is comparable to other natural substrates and ordinary adsorbents.

Metal ions binding onto a lignocellulosic substrate extracted from wheat bran: a NICA-Donnan approach

In this study ion binding to solid organic matter was investigated. We used the NICA-Donnan model to describe the interaction between Cu(II), Pb(II), and Cd(II) ions and a lignocellulosic substrate extracted from wheat bran. Such a material represents a very cheap and flexible substrate, which can be used as a natural filter to remove toxic metal ions from industrial effluents or applied in the decontamination and rehabilitation of abandoned industrial sites. Moreover, such a material also represents a very simple model of natural organic matter derived from lignin and cellulose, for which there is now a lack of thermodynamic data as far as their interaction with toxic metal ions is concerned. Experimental results were obtained in various conditions of pH and ionic strength. In our modeling, we used the acidity constants and the concentration of sites that were determined in a previous work. The parameters deduced from the NICA-Donnan model were also compared to thermodynamic data available for other cases of natural organic matter, mainly humic substances.

Maximal lactate steady state, respiratory compensation threshold and critical power

Critical power (CP) and the second ventilatory threshold (VT(2)) are presumed to indicate the power corresponding to maximal lactate steady state (MLSS). The aim of this study was to investigate the use of CP and VT(2) as indicators of MLSS. Eleven male trained subjects [mean (SD) age 23 (2.9) years] performed an incremental test (25 W.min(-1)) to determine maximal oxygen uptake (.VO(2max)), maximal aerobic power (MAP) and the first and second ventilatory thresholds (VT(1) and VT(2)) associated with break points in minute ventilation (.V(E)), carbon dioxide production (.VCO(2)), .V(E)/.VCO(2) and .V(E)/.VO(2) relationships. Exhaustion tests at 90%, 95%, 100% and 110% of .VO(2max), and several 30-min constant work rates were performed in order to determine CP and MLSS, respectively. MAP and .VO(2max) values were 344 (29) W and 53.4 (3.7) ml.min(-1).kg(-1), respectively. CP [278 (22) W; 85.4 (4.8)% .VO(2max)] and VT(2) power output [286 (28) W; 85.3 (5.6)% .VO(2max)] were not significantly different (p=0.96) but were higher (p<0.05) than the MLSS work rate [239 (21) W; 74.3 (4.0)% .VO(2max)] and VT(1) power output [159 (23) W; 52.9 (6.9)% .VO(2max)]. MLSS work rate was significantly correlated (p<0.05) with those noted at VT(1) and VT(2) (r=0.74 and r=0.93, respectively). VT(2) overestimated MLSS by 10.9 (6.3)% .VO(2max), which was significantly higher than VT(1) [+21.4 (5.6)% .VO(2max); p<0.01]. CP calculated from a given range of exhaustion times does not correspond to MLSS.

Use of a NICA-Donnan approach for analysis of proton binding to a lignocellulosic substrate extracted from wheat bran

The acid-base properties of a lignocellulosic substrate extracted from wheat bran have been investigated. The lignocellulosic substrate was first studied by use of FTIR, XPS, and solid-state 13C NMR to characterize the surface-active groups. Major contributions arise from the presence of carboxylic and phenolic sites. The former are associated with long-chain fatty acids and the latter are constituent units of lignin. All ionizable sites were quantified by use of the Ca-acetate method and by potentiometric titrations in non-aqueous media. Results were compared with those from conductimetric titrations in water and in the presence of barium ions. Protometric titration curves for the lignocellulosic substrate were obtained at several ionic strengths. Data were also treated with the NICA-Donnan model to determine the intrinsic ionization parameters.

Characterization and comparison of two ligno-cellulosic substrates by (13)C CP/MAS NMR, XPS, conventional pyrolysis and thermochemolysis

Ligno-cellulosic substrates (LCSs) isolated from wheat straw and bran exhibit high complexing capacities and may have important applications for metal removal from industrial effluents. These two LCSs were examined in the present work by spectroscopic and pyrolytic methods (solid state cross polarization magic angle spinning (CP/MAS) (13)C NMR, XPS, conventional Curie pyrolysis (Cupy)/GC/MS, and TMAH thermochemolysis/GC/MS). This combined study highlighted the limitation of some of the above methods when applied to ligno-cellulosic materials and the resulting biases and the usefulness of TMAH thermochemolysis. A large difference in composition was observed between bran- and straw-LCS due to a much higher contribution of alkyl moieties in the former. These moieties correspond to fatty acids esterified to the ligno-cellulosic macromolecular structure and such carboxylic functions should play an important role for metal complexation.

Spontaneously chosen crank rate variations in submaximal arm exercise with inexperienced subjects. Effects on cardiorespiratory and efficiency parameters

The aim of the present study was to compare the physiological responses during arm exercises when the crank rate was chosen spontaneously (TS) or set at +/- 20 % (T-20, T+ 20) of the spontaneously chosen crank rate (SCCR). Eight physical education male students, aged 22 +/- 3.2 years, performed an upper body exercise in which intensities ranged from unload to 80 % of maximal power. No significant difference was observed in oxygen uptake, ventilation, gross and net efficiency values between TS and T+ 20 or T-20. Nevertheless, oxygen uptake and ventilation were significantly (p < 0.05) lower and gross and net efficiencies higher (p < 0.05) during T-20 than T+ 20. No significant difference was noticed for heart rate, delta and work efficiency between TS, T-20 and T+ 20. The hypothesis that SCCR is the most economical one according to the efficiency parameters was not quite verified. However, crank rates lower than SCCR could be interesting because they increase gross efficiency compared to higher crank rates. Moreover, the selection of crank rates depends on power output. Indeed, SCCR increased significantly (p < 0.05) with power output. In the physical reconditioning of injured or handicapped subjects, the latter are very sensitive to the power output, and the crank rate could be another constraint.

Original 2-alkylamino-6-halogenoquinazolin-4(3H)-ones and K(ATP) channel activity

A series of 6-substituted 2-alkylaminoquinazolin-4(3H)-ones structurally related to 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides were synthesized and tested as putative K(ATP) channel openers on isolated pancreatic endocrine tissue as well as on isolated vascular, intestinal, and uterine smooth muscle. Most of the 6-halogeno-2-alkylaminoquinazolin-4(3H)-ones were found to inhibit insulin release from pancreatic B-cells and to exhibit vasorelaxant properties. In contrast to their pyridothiadiazine dioxide isosteres previously described as more active on the endocrine than on the smooth muscle tissue, quinazolinones cannot be considered as tissue selective compounds. Biological investigations, including measurements of (86)Rb, (45)Ca efflux from pancreatic islet cells and measurements of vasodilator potency in rat aortic rings exposed to 30 or 80 mM KCl in the presence or the absence of glibenclamide, were carried out with 6-chloro- and 6-iodo-3-isopropylaminoquinazolin-4(3H)-ones. Such experiments showed that, depending on the tissue, these new compounds did not always express the pharmacological profile of pure K(ATP) channel openers. Analyzed by X-ray crystallography, one example of quinazolinones appeared to adopt a double conformation. This only suggests a partial analogy between the 2-alkylaminoquinazolin-4(3H)-ones and the 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxides. In conclusion, the newly synthesized quinazolinones interfere with insulin secretion and smooth muscle contractile activity. Most of the compounds lack tissue selectivity, and further investigations are required to fully elucidate their mechanism(s) of action.

RPE responses during arm and leg exercises: effect of variations in spontaneously chosen crank rate

The aim of this study was two-fold. First, the rating of perceived exertion (RPE) was compared between two different upper and lower body exercises. Subjects (n = 12) performed with spontaneously chosen crank or pedal rates: (i) incremental maximum power tests (Test 1), with an initial work rate of 50% of maximal power followed by increases of 10% at each 120-sec. work stage and (ii) tests (Test 2) with exercise bouts set at 20, 40, 60, and 80% of maximal power separated by passive recovery periods. Second, the effects of variations in spontaneously chosen crank rate on RPE was analysed using the second test performed only with upper body. Subjects performed Test 2 three times with crank rates spontaneously chosen by the subjects, set at plus or minus 20% of spontaneously chosen crank rate. During both Tests 1 and 2 for upper or lower body, RPE increased linearly (p<.01) with power output. No significant difference was noticed between upper and lower body tests; however, RPE was significantly different (p<.05) between Test 1 results for upper and lower body at 70, 80, 90, and 100% of maximal power. The greater RPE at high power output could be linked to the important effect of fatigue during upper body exercise. Among the three crank-rate conditions, no significant difference in RPE was noticed. The choice of crank rate does not seem to influence the perception of exertion in upper body cycling exercise.

Nano-sized transition-metal oxides as negative-electrode materials for lithium-ion batteries

Rechargeable solid-state batteries have long been considered an attractive power source for a wide variety of applications, and in particular, lithium-ion batteries are emerging as the technology of choice for portable electronics. One of the main challenges in the design of these batteries is to ensure that the electrodes maintain their integrity over many discharge-recharge cycles. Although promising electrode systems have recently been proposed, their lifespans are limited by Li-alloying agglomeration or the growth of passivation layers, which prevent the fully reversible insertion of Li ions into the negative electrodes. Here we report that electrodes made of nanoparticles of transition-metal oxides (MO, where M is Co, Ni, Cu or Fe) demonstrate electrochemical capacities of 700 mA h g(-1), with 100% capacity retention for up to 100 cycles and high recharging rates. The mechanism of Li reactivity differs from the classical Li insertion/deinsertion or Li-alloying processes, and involves the formation and decomposition of Li2O, accompanying the reduction and oxidation of metal nanoparticles (in the range 1-5 nanometres) respectively. We expect that the use of transition-metal nanoparticles to enhance surface electrochemical reactivity will lead to further improvements in the performance of lithium-ion batteries.

Motor unit recruitment and EMG power spectra during ramp contractions of a bifunctional muscle

Surface electromyograms (EMGs) were analysed on the short and long head of the biceps brachii (BBSH and BBLH) during single (F and S) or dual (F+S) flexion and supination tasks. It was confirmed, by the analysis of EMG root-mean-square (RMS) values, that the highest activations of BBSH and BBLH were obtained during a maximal dual task. This study was essentially concerned with the analysis of power spectra data obtained during progressive or ramp contractions (RCs). The shape of the power spectra established during the first second of the RCs differs between F, S and F+S tasks. Differences in mean power frequency (MPF) calculated during RCs would be representative of a recruitment of motor units (MUs) that is, at least partly, task-dependent. In order to compare MPF values calculated from RCs performed under different mechanical conditions (F, S and F+S), MPF-RMS(PSD) relationships have been established (RMS(PSD) being defined as the power spectrum density RMS). Both BBSH and BBLH exhibited initial MPF values higher in supination RC than in flexion RC. Because of plateau values reached at the same level of muscle activation whatever the task performed, the slope of the MPF-RMS(PSD) relationship was lower in S than in F. These results are in favour of MU recruitment that is, at least partly, different in F and in S conditions. Dual submaximal tasks seem to mix the activation of the F and S subpopulations of MUs as revealed by the spectral parameters obtained during F+S ramp contractions. This study could find some implication in the field of muscle rehabilitation or reinforcement.

Characterization of a Snorhizobium meliloti ATP-binding cassette histidine transporter also involved in betaine and proline uptake

The symbiotic soil bacterium Sinorhizobium meliloti uses the compatible solutes glycine betaine and proline betaine for both protection against osmotic stress and, at low osmolarities, as an energy source. A PCR strategy based on conserved domains in components of the glycine betaine uptake systems from Escherichia coli (ProU) and Bacillus subtilis (OpuA and OpuC) allowed us to identify a highly homologous ATP-binding cassette (ABC) binding protein-dependent transporter in S. meliloti. This system was encoded by three genes (hutXWV) of an operon which also contained a fourth gene (hutH2) encoding a putative histidase, which is an enzyme involved in the first step of histidine catabolism. Site-directed mutagenesis of the gene encoding the periplasmic binding protein (hutX) and of the gene encoding the cytoplasmic ATPase (hutV) was done to study the substrate specificity of this transporter and its contribution in betaine uptake. These mutants showed a 50% reduction in high-affinity uptake of histidine, proline, and proline betaine and about a 30% reduction in low-affinity glycine betaine transport. When histidine was used as a nitrogen source, a 30% inhibition of growth was observed in hut mutants (hutX and hutH2). Expression analysis of the hut operon determined using a hutX-lacZ fusion revealed induction by histidine, but not by salt stress, suggesting this uptake system has a catabolic role rather than being involved in osmoprotection. To our knowledge, Hut is the first characterized histidine ABC transporter also involved in proline and betaine uptake.

3-Alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1,1-dioxides structurally related to diazoxide and pinacidil as potassium channel openers acting on vascular smooth muscle cells: design, synthesis, and pharmacological evaluation

A series of 3-alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides structurally related to diazoxide and pinacidil were synthesized and tested as possible K(ATP) channel openers on isolated pancreatic endocrine tissue as well as on isolated vascular, intestinal, and uterine smooth muscle. In contrast to previously described 3-alkylamino-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1, 1-dioxides, most of the new compounds were found to be poorly active on B-cells but exhibited clear vasorelaxant properties. 3-(3, 3-Dimethyl-2-butylamino)-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxide (4d) and 7-chloro-3-(3, 3-dimethyl-2-butylamino)-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxide (5d), two compounds bearing the alkyl side chain of pinacidil, were found to be the most active representatives of their respective series on rat aorta rings. 3-Cycloalkylalkylamino- and 3-aralkylamino-7-chloro-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides also expressed myorelaxant activity on electrically stimulated guinea pig ileum and on oxytocin-induced contractions of the rat uterus. Further biological investigations ((86)Rb efflux measurements, vasodilator potency on 30 and 80 mM KCl-induced contractions in the absence and presence of glibenclamide) revealed that compounds 4d and 5d, but not compound 5f, expressed the pharmacological profile of classical K(ATP) channel openers. In conclusion, by changing the position of the nitrogen atom in the pyridine ring, we now have obtained a family of drugs expressing an opposite tissue selectivity. Taken as a whole, the present findings also suggest that 3-alkylamino-4H-pyrido[2,3-e]-1,2,4-thiadiazine 1, 1-dioxides such as 4c, 4d, 5c, and 5d may be considered as new examples of K(ATP) channel openers expressing a pharmacological profile similar to that of pinacidil and diazoxide.

Preparation and pharmacological evaluation of the R- and S-enantiomers of 3-(2-butylamino)-4H- and 3-(3-methyl-2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide, two tissue selective ATP-sensitive potassium channel openers

The preparation and the pharmacological evaluation of the R- and S-isomers of 3-(2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide (BPDZ 42) and 3-(3-methyl-2-butylamino)-4H-pyrido[4,3-e]-1,2,4-thiadiazine 1,1-dioxide (BPDZ 44), two potassium channel openers, is described. Their optical purity was estimated by means of capillary electrophoresis (R- and S-BPDZ 42) and chiral HPLC (R- and S-BPDZ 44). The absolute configuration of each isomer of BPDZ 44 was deduced from crystallographic data. Pharmacological assays performed with the R- and S-isomers of BPDZ 44 revealed only slight differences in their activity on pancreatic B-cells but significant differences in their activity on vascular smooth muscle cells: the R-isomer being sixfold more potent than its corresponding S-isomer. The R-isomer of BPDZ 42 was shown to be more potent than its corresponding S-isomer on the endocrine pancreas. S-BPDZ 44 as well as R- and S-BPDZ 42 were found to exhibit tissue selectivity for the pancreatic versus the vascular smooth muscle tissue.

4H-1,2,4-Pyridothiadiazine 1,1-dioxides and 2,3-dihydro-4H-1,2, 4-pyridothiadiazine 1,1-dioxides chemically related to diazoxide and cyclothiazide as powerful positive allosteric modulators of (R/S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid receptors: design, synthesis, pharmacology, and structure-activity relationships

A series of 4H-1,2,4-pyridothiadiazine 1,1-dioxides and 2, 3-dihydro-4H-1,2,4-pyridothiadiazine 1,1-dioxides bearing various alkyl and aryl substituents on the 2-, 3-, and 4-positions was synthesized and tested as possible positive allosteric modulators of the (R/S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors. Many compounds were found to be more potent than the reference compounds diazoxide and aniracetam as potentiators of the AMPA current in rat cortex mRNA-injected Xenopus oocytes. The most active compound, 4-ethyl-2,3-dihydro-4H-pyrido[3,2-e]-1,2, 4-thiadiazine 1,1-dioxide (31b), revealed an in vitro activity on Xenopus oocytes not far from that of cyclothiazide, the most potent allosteric modulator of AMPA receptors reported to date. Moreover, 31b, but not cyclothiazide, was found to potentiate the duration and the amplitude of the excitatory postsynaptic field potentials induced by electric stimulation in rat hippocampal slices. Such an effect could indicate, for 31b, but not for cyclothiazide, a possible interaction with postsynaptic AMPA receptor binding sites located on hippocampal CA1 neurons. Structure-activity relationships indicated that the structural requirements responsible for a biological activity on AMPA receptors are different from those responsible for an inhibitory activity on the insulin releasing process (putative ATP-sensitive K+-channel openers). For instance, 31b and other related dihydropyridothiadiazines were found to be ineffective as inhibitors of insulin release from rat pancreatic B-cells, in contrast to diazoxide and known pyridothiadiazines reported as ATP-sensitive K+-channel openers. Conversely, the pyridothiadiazines active on B-cells were found to be ineffective as potentiators of the AMPA currents in Xenopus oocytes. Thus, 31b appeared to be more specific than diazoxide as an AMPA receptor modulator. This compound may be considered as a new pharmacological tool, different from diazoxide and cyclothiazide, for studying AMPA receptors. Moreover, 31b can also constitute a new therapeutic agent for the treatment of cognitive disorders.