Dynamic Changes in Phase-Amplitude Coupling Facilitate Spatial Attention Control in Fronto-Parietal Cortex

Attention is a core cognitive mechanism that allows the brain to allocate limited resources depending on current task demands. A number of frontal and posterior parietal cortical areas, referred to collectively as the fronto-parietal attentional control network, are engaged during attentional allocation in both humans and non-human primates. Numerous studies have examined this network in the human brain using various neuroimaging and scalp electrophysiological techniques. However, little is known about how these frontal and parietal areas interact dynamically to produce behavior on a fine temporal (sub-second) and spatial (sub-centimeter) scale. We addressed how human fronto-parietal regions control visuospatial attention on a fine spatiotemporal scale by recording electrocorticography (ECoG) signals measured directly from subdural electrode arrays that were implanted in patients undergoing intracranial monitoring for localization of epileptic foci. Subjects (n = 8) performed a spatial-cuing task, in which they allocated visuospatial attention to either the right or left visual field and detected the appearance of a target. We found increases in high gamma (HG) power (70–250 Hz) time-locked to trial onset that remained elevated throughout the attentional allocation period over frontal, parietal, and visual areas. These HG power increases were modulated by the phase of the ongoing delta/theta (2–5 Hz) oscillation during attentional allocation. Critically, we found that the strength of this delta/theta phase-HG amplitude coupling predicted reaction times to detected targets on a trial-by-trial basis. These results highlight the role of delta/theta phase-HG amplitude coupling as a mechanism for sub-second facilitation and coordination within human fronto-parietal cortex that is guided by momentary attentional demands.     

Urinating Standing versus Sitting: Position Is of Influence in Men with Prostate Enlargement. A Systematic Review and Meta-Analysis

Background

It is suggested that the body posture during urination can influence urodynamic parameters in patients with Lower Urinary Tract Symptoms (LUTS) to an extent approaching pharmacological interventions. In this article, the influence of body position during micturition on maximum urinary flow rate (Qmax), voiding time (TQ) and post-void residual volume (PVR) in healthy males and patients with LUTS is analyzed by means of a systematic review and meta-analysis.

Evidence Acquisition

A systematic search was conducted in 14 medical databases. Studies comparing urodynamic parameters in standing versus sitting position were eligible for inclusion. Studies were stratified according to health status of included male participants: healthy individuals and patients with LUTS. Standardized mean differences for Qmax, TQ and PVR were pooled in a random effects model.

Results

Eleven articles were included. In men with LUTS, a significantly lower PVR (−24.96 ml; 95%CI −48.70 to −1.23) was shown in sitting position compared to standing. In accordance, Qmax was increased (1.23 ml/s; 95%CI −1.02 to 3.48), and TQ was decreased (−0.62 s; 95%CI −1.66 to 0.42) in sitting position, although these differences did not reach statistical significance. In healthy men, Qmax (0.18 ml/s; 95% CI −1.67 to 2.02), TQ (0.49 s; 95%CI −3.30 to 4.27) and PVR (0.43 ml; 95%CI −0.79 to 1,65) were similar in sitting and standing position.

Conclusion

For healthy men, no difference is found in any of the urodynamic parameters. In patients with LUTS, the sitting position is linked with an improved urodynamic profile.     

N-Carbamoyl-α-Amino Acids Rather than Free α-Amino Acids Formation in the Primitive Hydrosphere: A Novel Proposal for the Emergence of Prebiotic Peptides

Our previous kinetic and thermodynamic studies upon the reactional system HCHO/HCN/ NH₃ in aqueous solutions are completed. In the assumed prebiotic conditions of the primitive earth ([HCHO] and [HCN] near 1 g L^–1, T = 25 °C, pH = 8, [NH₃] very low), this system leads to 99.9% of -hydroxyacetonitrile and 0.1% of -aminoacetonitrile (precursor of the -amino acid). The classical base-catalyzed hydration of nitriles, slow and not selective, can not modify significantly this proportion. On the contrary, we found two specific and efficient reactions of -aminonitriles which shift the initial equilibrium in favor of the -aminonitrile pathway. The first reaction catalyzed by formaldehyde generates -aminoamides, precursors of -aminoacids. The second reaction catalyzed by carbon dioxide affords hydantoins, precursors of N-carbamoyl--aminoacids. In the primitive hydrosphere, where the concentration in carbon dioxide was estimated to be higher than that of formaldehyde, the formation of hydantoins was consequently more efficient. The rates of hydrolysis of the -aminoacetamide and of the hydantoin at pH 8 being very similar, the synthesis of the N-carbamoyl--amino acid seems then to be the fatal issue of the HCHO/HCN/NH₃ system that nature used to perform its evolution. These N-protected -amino acids offer new perspectives in prebiotic chemistry, in particular for the emergence of peptides on the prebiotic earth.     

Dissemination of rat cytomegalovirus through infected granulocytes and monocytes in vitro and in vivo

The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals.     

Scyllatoxin, a blocker of Ca(2+)-activated K+ channels: structure-function relationships and brain localization of the binding sites.

Chemical modifications of scyllatoxin (leiurustoxin I) have shown that two arginines in the sequence, Arg6 and Arg13, are essential both for binding to the Ca(2+)-activated K+ channel protein and for the functional effect of the toxin. His31 is important both for the binding activity of the toxin and for the induction of contractions on taenia coli. However, although its iodination drastically decreases the toxin activity, it does not abolish it. Chemical modification of lysine residues or of Glu27 does not significantly alter toxin binding, but it drastically decreases potency with respect to contraction of taenia coli. The same observation has been made after chemical modification of the lysine residues. The brain distribution of scyllatoxin binding sites has been analyzed by quantitative autoradiographic analysis. It indicates that apamin (a bee venom toxin) binding sites are colocalized with scyllatoxin binding sites. The results are consonant with the presence of apamin/scyllatoxin binding sites associated with Ca(2+)-activated K+ channels. High-affinity binding sites for apamin can be associated with very-high-affinity (less than 70 pM), high-affinity (approximately 100-500 pM), or moderate-affinity (greater than 800 pM) binding sites for scyllatoxin.     

Measurement of prostaglandin G/H synthase and lipoxygenase activity in the stomach wall by HPLC

A method for the determination of prostaglandin G/H synthase and lipoxygenase activities in tissues was developed and employed with rat gastric mucosa samples. Tissues and microsomes were incubated in a buffer containing nonionic detergent and 1.32 mM arachidonic acid for 10 min. Following extraction with ethyl acetate, the oxidation products of arachidonic acid were derivatized with panacyl bromide. A reversed-phase column and a quaternary mobile phase were used to separate and quantitate the panacyl bromide esters of prostaglandin E2 and leukotriene C4/D4. Prostaglandin G/H synthase and lipoxygenase activities were determined in gastric mucosa and were 371 +/- 66 and 173 +/- pg/mg/min, respectively.     

Multi‐modal acousto‐optic/ultrasound imaging of ex vivo liver tumors at 790 nm using a Sn2P2S6 wavefront adaptive holographic setup

Biological tissues are very strong light‐scattering media. As a consequence, current medical imaging devices do not allow deep optical imaging unless invasive techniques are used. Acousto‐optic imaging is a light‐ultrasound coupling technique that takes advantage of the ballistic propagation of ultrasound in biological tissues to access optical contrast with a millimeter resolution. We have developed a photorefractive‐crystal‐based system that performs self‐adaptive wavefront holography and works within the optical therapeutic window. As it works at an appropriate wavelength range for biological tissues imaging, it was tested on ex vivo liver samples containing tumors as a pre‐clinical study. Optical contrast was obtained even if acoustical one was not significant.

Ultrasound image (left) and acousto‐optic image (right) of a liver biopsy with tumors. Acousto‐optic imaging exhibits tumors that are not detected through ultrasound.