Separating Convective from Diffusive Mass Transport Mechanisms in Ionic Liquids by Redox Pro-fluorescence Microscopy

The study of electrochemical reactivity requires analytical techniques capable of probing the diffusion of reactants and products to and from electrified interfaces. Information on diffusion coefficients is often obtained indirectly by modeling current transients and cyclic voltammetry data, but such measurements lack spatial resolution and are accurate only if mass transport by convection is negligible. Detecting and accounting for adventitious convection in viscous and wet solvents, such as ionic liquids, is technically challenging. We have developed a direct, spatiotemporally resolved optical tracking of diffusion fronts which can detect and resolve convective disturbances to linear diffusion. By tracking the movement of an electrode-generated fluorophore, we demonstrate that parasitic gas evolving reactions lead to 10-fold overestimates of macroscopic diffusion coefficients. A hypothesis is put forward linking large barriers to inner-sphere redox reactions, such as hydrogen gas evolution, to the formation of cation-rich overscreening and crowding double layer structures in imidazolium-based ionic liquids.

Luciferase-free Luciferin Electrochemiluminescence

Luciferin is one of Nature's most widespread luminophores, and enzymes that catalyze luciferin luminescence are the basis of successful commercial "glow" assays for gene expression and metabolic ATP formation. Herein we report an electrochemical method to promote firefly's luciferin luminescence in the absence of its natural biocatalyst-luciferase. We have gained experimental and computational insights on the mechanism of the enzyme-free luciferin electrochemiluminescence, demonstrated its spectral tuning from green to red by means of electrolyte engineering, proven that the colour change does not require, as still debated, a keto/enol isomerization of the light emitter, and gained evidence of the electrostatic-assisted stabilization of the charge-transfer excited state by double layer electric fields. Luciferin's electrochemiluminescence, as well as the in situ generation of fluorescent oxyluciferin, are applied towards an optical measurement of diffusion coefficients.

Experimental Evidence of Long-Lived Electric Fields of Ionic Liquid Bilayers

Herein we demonstrate that ionic liquids can form long-lived double layers, generating electric fields detectable by straightforward open circuit potential (OCP) measurements. In imidazolium-based ionic liquids an external negative voltage pulse leads to an exceedingly stable near-surface dipolar layer, whose field manifests as long-lived (∼1-100 h) discrete plateaus in OCP versus time traces. These plateaus occur within an ionic liquid-specific and sharp potential window, defining a simple experimental method to probe the onset of interfacial ordering phenomena, such as overscreening and crowding. Molecular dynamics modeling reveals that the OCP arises from the alignment of the individual ion dipoles to the external electric field pulse, with the magnitude of the resulting OCP correlating with the product of the projected dipole moment of the cation and the ratio between the cation diffusion coefficient and its volume. Our findings also reveal that a stable overscreened structure is more likely to form if the interface is first forced through crowding, possibly accounting for the scattered literature data on relaxation kinetics of near-surface structures in ionic liquids.

The corona of a surface bubble promotes electrochemical reactions

The evolution of gaseous products is a feature common to several electrochemical processes, often resulting in bubbles adhering to the electrode’s surface. Adherent bubbles reduce the electrode active area, and are therefore generally treated as electrochemically inert entities. Here, we show that this general assumption does not hold for gas bubbles masking anodes operating in water. By means of imaging electrochemiluminescent systems, and by studying the anisotropy of polymer growth around bubbles, we demonstrate that gas cavities adhering to an electrode surface initiate the oxidation of water-soluble species more effectively than electrode areas free of bubbles. The corona of a bubble accumulates hydroxide anions, unbalanced by cations, a phenomenon which causes the oxidation of hydroxide ions to hydroxyl radicals to occur at potentials at least 0.7 V below redox tabled values. The downhill shift of the hydroxide oxidation at the corona of the bubble is likely to be a general mechanism involved in the initiation of heterogeneous electrochemical reactions in water, and could be harnessed in chemical synthesis.

Gas bubbles forming on the surface of an electrode, a phenomenon common to several industrial electrolytic processes, are usually perceived as inert, passivating entities. Here, the authors show that that this general assumption does not hold for gas bubbles masking anodes operating in water.

Association of PHB 1630 C>T and MTHFR 677 C>T polymorphisms with breast and ovarian cancer risk in BRCA1/2 mutation carriers: results from a multicenter study

BACKGROUND

The variable penetrance of breast cancer in BRCA1/2 mutation carriers suggests that other genetic or environmental factors modify breast cancer risk. Two genes of special interest are prohibitin (PHB) and methylene-tetrahydrofolate reductase (MTHFR), both of which are important either directly or indirectly in maintaining genomic integrity.

METHODS

To evaluate the potential role of genetic variants within PHB and MTHFR in breast and ovarian cancer risk, 4102 BRCA1 and 2093 BRCA2 mutation carriers, and 6211 BRCA1 and 2902 BRCA2 carriers from the Consortium of Investigators of Modifiers of BRCA1 and BRCA2 (CIMBA) were genotyped for the PHB 1630 C>T (rs6917) polymorphism and the MTHFR 677 C>T (rs1801133) polymorphism, respectively.

RESULTS

There was no evidence of association between the PHB 1630 C>T and MTHFR 677 C>T polymorphisms with either disease for BRCA1 or BRCA2 mutation carriers when breast and ovarian cancer associations were evaluated separately. Analysis that evaluated associations for breast and ovarian cancer simultaneously showed some evidence that BRCA1 mutation carriers who had the rare homozygote genotype (TT) of the PHB 1630 C>T polymorphism were at increased risk of both breast and ovarian cancer (HR 1.50, 95%CI 1.10-2.04 and HR 2.16, 95%CI 1.24-3.76, respectively). However, there was no evidence of association under a multiplicative model for the effect of each minor allele.

CONCLUSION

The PHB 1630TT genotype may modify breast and ovarian cancer risks in BRCA1 mutation carriers. This association need to be evaluated in larger series of BRCA1 mutation carriers.

Low levels of endogenous estradiol protect bone mineral density in young postmenopausal women

OBJECTIVE

Low levels of endogenous estrogens may play a role in the protection of bone mineral density (BMD) in healthy postmenopausal women. The aim of this study was to evaluate the effect of endogenous estradiol and testosterone on bone mass in young and older healthy postmenopausal women.

METHODS

The study involved 99 postmenopausal women aged 55-75 years. The BMDs of the lumbar spine, proximal femur and total skeleton were determined. Measurements were taken of serum calcium, bone alkaline phosphatase, Crosslaps, estradiol, estrone, sex hormone binding globulin, testosterone, bioavailable testosterone and urine calcium. Estradiol was measured using a sensitive assay with a lower detection limit at 5 pg/ml.

RESULTS

A multivariate analysis showed that the BMD of the lumbar spine was significantly predicted by estradiol (p < 0.05), and testosterone (p < 0.0001). Likewise, testosterone was found to be an independent predictor of the BMD of the total femur (p < 0.001) and the total skeleton (p < 0.001). The population was divided into two groups: < or = 65 (Group 1) and > 65 years (Group 2) of age and also stratified according to estradiol levels: > 10 and < or = 10 pg/ml. Significant differences in BMD were found in women in Group 1 in whom estradiol levels higher than 10 pg/ml were associated with a higher BMD of the lumbar spine (+ 14%, p < 0.01), proximal femur (+ 6%, p < 0.05) and total skeleton (+ 7%, p < 0.05) compared with women with estradiol levels below 10 pg/ml. Bone alkaline phosphatase levels (p < 0.05) and serum Crosslaps (not significant) were lower in women in Group 1 with a level of estradiol more than 10 pg/ ml.

CONCLUSION

Endogenous estradiol levels higher than 10 pg/ml and testosterone protected bone mass in healthy postmenopausal women under 65 years of age. These results were not observed in the group of older women.

Working memory interference control deficit in children referred by teachers for ADHD symptoms

It has been hypothesised that children with Attention Deficit/Hyperactivity Disorder (ADHD) present memory problems, including working memory deficits. This research is aimed at finding clearer evidence of a working memory deficit in these children. In the first study 22 children that had been referred by teachers as having ADHD symptoms were compared with a control group. Their performance on a listening span test, drawn up by De Beni, Palladino, Pazzaglia, and Cornoldi (1998), was investigated. In this task the subjects were asked to select the names of animals in word strings and to remember the last word in each string. In a second study, 34 children with ADHD symptoms and 50 control children were presented with a visuospatial working memory task mirroring the verbal task used in Study 1. In both studies, the children with ADHD symptoms had difficulty in remembering the last item in the string and had a higher number of intrusions when memorising items that were not in the final position. The results were interpreted that children with ADHD symptoms have working memory problems because they are not capable of suppressing information that initially has to be processed, and subsequently excluded from memory. This particular difficulty can be interpreted as an inhibitory processing deficit. The implications of the results in understanding learning difficulties in children with ADHD are discussed.

Modulation of spatial alternation and anxiety by septal scopolamine systemic diazepam in mice

To investigate the behavioral consequences of benzodiazepines in subjects whose septo-hippocampal cholinergic (ACh) activity was impaired, C57BL/6 mice received an injection of 2.5 microg/0.2 microl of scopolamine into the medial septal area with an i.p. injection of 0.5 mg/kg of diazepam. The consequences of these treatments administered in combination or alone were evaluated on anxiety measured in an elevated plus-maze and on spontaneous alternation carried out in a T-maze, using two different intertrial intervals (ITI: 5s or 30s). In these conditions, only the combined treatment provoked a decrease of the anxiety level, which was associated with an impairment of spontaneous alternation restricted to the 5s ITI. Because mice were not impaired during the sequential 30s ITI, this seems to rule out the possibility that this alternation deficit resulted from a working memory loss. These results suggest an involvement of a septal ACh-GABA-A/BDZ interaction in the exaggeration of cognitive deficits produced by benzodiazepines in patients characterized by a cholinergic hypofunction.

Consequences of selective blockade of septal noradrenergic afferents on anxiety and spatial working memory performance in mice

This experiment was designed to investigate the role of septal noradrenergic (NA) afferents in the control of anxiety and spatial working memory. To this end, C57Bl/6 mice were infused bilaterally into the lateral septal nuclei with 500 ng/0.2 microliter of BE 2254, a selective alpha 1 postsynaptic adrenoceptor antagonist. The consequences of this reversible treatment were evaluated 20 min later on the anxiety level measured in an elevated plus-maze and on spatial working memory, evaluated under four different conditions via the learning of a delayed nonmatching to place (DNMTP) rule achieved in an eight-arm radial maze. In these conditions, the BE 2254, as well as the saline-injected control group, showed an elevation of the anxiety level that may be the indirect expression of a nonspecific septal dysfunction induced by the vehicle injection rather than the normal behavioral response produced by the decrease of septal NA activity. This septal dysfunction also impaired spatial working memory but only when mnesic difficulty of the task is increased, suggesting that this impairment expresses a general memory deficit rather than a working memory deficit per se. A lack of spatial working memory deficits in BE 2254 or saline-injected animals was also observed in two other conditions of the behavioral protocol. However, when treatments were applied before the first exposure of animals to the radial maze (exploration session), only the group which received BE 2254 was impaired during the acquisition session for the rule performed 24 h later. This delayed perturbation seems to be linked, at this stage of the learning procedure, to the lack of NA-dependent processes taking place during the exploration session. Taken together, these data suggest that septal NA mechanisms are more essential at initial stage of this learning, when animals process new features of the situation, than during the expression of spatial working memory per se.

[Effects of bicarbonated-alkaline water (Uliveto) on gastric and gallbladder emptying in normal subjects. Ultrasonic evaluation]

In 10 healthy patients gastric and gallbladder emptying after a standard meal (800 cal, 60% glucides, 20% protides, 20 lipids) associated with 400 ml alkaline bicarbonated water or tap water were evaluated by ultrasonography. An increase of gastric emptying was noted after alkaline bicarbonated water versus tap water with significant differences at 30' (p less than 0.05), 60' (p less than 0.01) and 120' (p less than 0.05). No significant differences exist in final gastric emptying time. Alkaline bicarbonated water induced less intensive gallbladder emptying with statistical difference versus tap water at 60' and 120' from the standard meal (p less than 0.01).