Brain-derived neurotrophic factor modulation of Kv1.3 channel is disregulated by adaptor proteins Grb10 and nShc

Background

Developmental dyslexia is a specific cognitive disorder in reading acquisition that has genetic and neurological origins. Despite histological evidence for brain differences in dyslexia, we recently demonstrated that in large cohort of subjects, no differences between control and dyslexic readers can be found at the macroscopic level (MRI voxel), because of large variances in brain local volumes. In the present study, we aimed at finding brain areas that most discriminate dyslexic from control normal readers despite the large variance across subjects. After segmenting brain grey matter, normalizing brain size and shape and modulating the voxels' content, normal readers' brains were used to build a 'typical' brain via bootstrapped confidence intervals. Each dyslexic reader's brain was then classified independently at each voxel as being within or outside the normal range. We used this simple strategy to build a brain map showing regional percentages of differences between groups. The significance of this map was then assessed using a randomization technique.

Results

The right cerebellar declive and the right lentiform nucleus were the two areas that significantly differed the most between groups with 100% of the dyslexic subjects (N = 38) falling outside of the control group (N = 39) 95% confidence interval boundaries. The clinical relevance of this result was assessed by inquiring cognitive brain-based differences among dyslexic brain subgroups in comparison to normal readers' performances. The strongest difference between dyslexic subgroups was observed between subjects with lower cerebellar declive (LCD) grey matter volumes than controls and subjects with higher cerebellar declive (HCD) grey matter volumes than controls. Dyslexic subjects with LCD volumes performed worse than subjects with HCD volumes in phonologically and lexicon related tasks. Furthermore, cerebellar and lentiform grey matter volumes interacted in dyslexic subjects, so that lower and higher lentiform grey matter volumes compared to controls differently modulated the phonological and lexical performances. Best performances (observed in controls) corresponded to an optimal value of grey matter and they dropped for higher or lower volumes.

Conclusion

These results provide evidence for the existence of various subtypes of dyslexia characterized by different brain phenotypes. In addition, behavioural analyses suggest that these brain phenotypes relate to different deficits of automatization of language-based processes such as grapheme/phoneme correspondence and/or rapid access to lexicon entries.     

Direct modulation and optical confinement factor modulation of semiconductor lasers

A method for modulation of semiconductor lasers is demonstrated. The method is based on the modulation of the optical confinement factor. Using this method an enhanced—3-dB bandwidth is observed in agreement with the small signal rate equation analysis. A modulation response that drops at high frequencies slower than the conventional direct current modulation response is achieved. This supports the theoretical predictions, showing an intrinsic 1/f decay rate for the optical confinement factor modulation scheme versus an intrinsic 1/f² decay for direct modulation.     

Difference in trafficking of brain-derived neurotrophic factor between axons and dendrites of cortical neurons,revealed by live-cell imaging

Background  

Brain-derived neurotrophic factor (BDNF), which is sorted into a regulated secretory pathway of neurons, is supposed to act retrogradely through dendrites on presynaptic neurons or anterogradely through axons on postsynaptic neurons. Depending on which is the case, the pattern and direction of trafficking of BDNF in dendrites and axons are expected to be different. To address this issue, we analyzed movements of green fluorescent protein (GFP)-tagged BDNF in axons and dendrites of living cortical neurons by time-lapse imaging. In part of the experiments, the expression of BDNF tagged with cyan fluorescent protein (CFP) was compared with that of nerve growth factor (NGF) tagged with yellow fluorescent protein (YFP), to see whether fluorescent protein-tagged BDNF is expressed in a manner specific to this neurotrophin.     

Enhancement of the thermoelectric power factor of MnSi1.7 film by modulation doping of Al and Cu

It is well known that aluminum (Al) and copper (Cu) are acceptor impurities with shallow- and deep-energy levels in silicon (Si), respectively. The thermoelectric power factor of Al and Cu codoped Si film is larger than that of only Al-doped Si film. In this report, the Al and Cu codoped Si layer, Si: (Al + Cu), is used as a barrier layer, while a higher manganese silicide (HMS, MnSi_1.7) layer is used as a well layer to enhance the power factor of MnSi_1.7 film. It is found that the Al and Cu modulation doped MnSi_1.7 film, Si: (Al + Cu)/MnSi_1.7, has a power factor almost two times larger than that of only Al modulation doped MnSi_1.7 film, Si: Al/MnSi_1.7. It is also found that an undoped Si spacer layer between the Si: (Al + Cu) barrier layer and the MnSi_1.7 well layer can enhance the power factor further. Finally, it is demonstrated that the MnSi_1.7 film with double Si barrier layers, Si: (Al + Cu)/MnSi_1.7/Si: (Al + Cu), has the highest power factor, 1423×10^?6 W/m?K² at 783 K, which is very close to that of MnSi_1.7 bulk material.     

Performance enhancement of 10 Gb/s direct modulation optical OFDM by external optical injection

We show experimentally and by simulation a performance enhancement of a directly modulated 10 Gb/s optical Orthogonal Frequency Division Multiplexing (OFDM) system due to external optical injection. The experiment is performed back to back and over 12 km of single mode fiber. The injection extends the range of linear operation of the laser and therefore extends the usable bandwidth for direct modulation formats which are susceptible to nonlinearity, such as OFDM. Nonlinearity in the system and its reduction due to injection are estimated by means of a two tone test. Additionally the performance enhancement on OFDM systems was verified in both simulation and experimentally by the comparisons of the average Bit Error Rate (BER) and Error Vector Magnitude (EVM).     

Exercise-induced motor improvement after complete spinal cord transection and its relation to expression of brain-derived neurotrophic factor and presynaptic markers

Background  

It has been postulated that exercise-induced activation of brain-derived neurotrophic factor (BDNF) may account for improvement of stepping ability in animals after complete spinal cord transection. As we have shown previously, treadmill locomotor exercise leads to up-regulation of BDNF protein and mRNA in the entire neuronal network of intact spinal cord. The questions arise: (i) how the treadmill locomotor training, supplemented with tail stimulation, affects the expression of molecular correlates of synaptic plasticity in spinal rats, and (ii) if a response is related to BDNF protein level and distribution.     

Tuning and modulation of a laser by acoustic wave

The possibility is suggested of tuning and modulation of an ordinary (not DFB) laser by the acoustic wave of relatively low frequency. The results of a calculation for the simplest case are presented and corresponding estimates are made for the laser of GaAlAs type.     

Enhancement and modulation of terahertz radiation by multi-color laser pulses

We study theoretically intense terahertz radiation from multi-color laser pulse with uncommon frequency ratios. Comparing the two-color laser scheme, of which the uncommon frequency ratio should be set to be a specific value, we show that by using multi-color harmonic laser pulses as the first pump component, the lasers as the second pump component can be adjusted in a continuous frequency range. Moreover, these multi-color laser pulses can effectively modulate and enhance the terahertz radiation, and the terahertz yield increases with the increase of the wavelength of the uncommon pump component and is stable to the laser relative phase. Finally, we utilize the electron densities and velocities of ionization events to illustrate the physical mechanism of the intense terahertz generation.     

Pump-probe analysis of the cross-phase modulation degradation induced by 10 Gbit/s amplitude-shift-keyed signals on 40 Gbit/s DPSK signals

A study of the cross-phase modulation (XPM) degradation of differential-phase-shift-keyed (DPSK) signals due to amplitude-shift-keyed signals is performed using pump-probe simulation. Approximate expressions for the contributions of the XPM-induced intensity and phase modulation to the electrical current fluctuations at the differential-phase-exchange-keyed receiver are presented. It is shown that, unlike prior works and similar to intensity-modulated signals, the contribution of XPM-induced intensity modulation is dominant in systems using standard fiber or high residual dispersion.     

Heat transfer and friction factor characteristic of spherical and inclined teardrop dimple channel subjected to forced convection

An experimental and numerical investigation is performed in order to determine the outcome of dimple geometries on the heat transfer and friction factor in a dimple cooling channel subjected to turbulent flow. Two geometries taken into consideration are spherical and inclined teardrop. In order to have a better comparison between the two different dimple channel, the dimple depth, total wetted area of dimple, and dimple pitch have been kept constant. In case of spherical and inclined teardrop dimple channels, heat transfer augmentation, friction losses, and flow pattern have been obtained for a Reynolds Number range from 14,000 to 65,000. The investigation shows that the dimple geometry has a significant contribution to increasing the heat transfer augmentation and determining the flow pattern. The inclined teardrop dimple arrangement shows the maximum heat transfer that is 17% higher than the spherical dimple channel, whereas inclined teardrop dimple results in the rise of friction factor of about 5.93–16.14% times as compared to the spherical dimple within the specified Reynolds number. The inclined teardrop and spherical dimple channel show the heat transfer enhancement of 2.74 to 3.20 times and 2.38 to 2.68 times than that of smooth channels provided thermal boundary conditions and flow conditions are kept same. The numerical study has been performed, which provided a detailed insight into the flow structures and vortex formations in spherical and inclined teardrop dimple channel.     

Spectral modulation of third-harmonic generation by molecular alignment and preformed plasma

We demonstrate spectral modulation of third-harmonic generation from molecular alignment effects. The third harmonic spectrum is broadened or narrowed under different influences of cross-phase modulations originating from various molecular alignment revivals. Furthermore, the spectrum and spatial distribution of the generated third harmonic pulse change dramatically in the presence of a preformed plasma. Under the influence of a preformed plasma, a narrower third harmonic spectrum is observed, and the conical third-harmonic pulse increases while the axial part decreases. The investigation provides an effective method to modulate the spectral characteristic and spatial distribution of third-harmonic generation from intense femtosecond filament.     

Suppression and feedback control of anomalous induced backscattering by pump-frequency modulation

The possibility of induced backscattering parametric decay instability resonant suppression by harmonic pump-frequency modulation is demonstrated experimentally. It is shown that the pump anomalous reflection is strongly reduced at the modulation frequency equal to the difference of the decay instability eigenfrequencies. The parametric instability feedback control method is proposed based on this effect.     

Binding of ciguatera toxins to the voltage‐gated Kv1.5 potassium channel in the open state. Docking of gambierol and molecular dynamics simulations of a homology model

Ciguatera poisoning is a toxinological syndrome from ingestion of seafood contaminated by dinoflagellate toxins which has serious social and economic consequences from the Indo‐Pacific to the Caribbean. These polyannealed ethereal‐ring toxins, which comprise ciguatoxins, maitotoxin, and gambierol, are known to affect ion channels. Reported here are the first indications at molecular level as to the mode of interaction of these toxins with ion channels. The study concerns gambierol, an eight‐ring ladder polyether which is known to affect TRPV1‐type of thermal and pain sensation channels, as well as to inhibit voltage‐gated currents in K⁺ channels of mouse taste cells. Automated docking of gambierol on a homology model of the voltage‐gated Kv1.5 potassium ion channel in implicit solvent is followed by molecular dynamics (MD) simulation of the complex in a POPC membrane solvated with water. It is found that gambierol binds to the internal helices of the channel, unequally to the different subunits of the tetramer. Such unequal binding is a novel observation that should stimulate and aid developing a much demanded medical treatment of ciguatera poisoning. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative aes: the problems of the energy dependent phase shift and modulation amplitude and of the non-ideal behaviour of the channel electron multiplier

In pursuit of the objective to obtain identical Auger electron spectra from different types of instruments, the Varian 10 keV CMA system has been studied. On one particular unit it is shown that the high frequency of 17 kHz, chosen for modulating the spectrometer to produce differential spectra, causes two major errors, each of which affects the relative intensities of peaks in the spectrum. Firstly, it is shown that the phase of the AC signal changes by 56° through the spectrum to 2000 eV, and secondly the amplitude of the AC modulation varies by 100% over the same range. The latter causes low energy peaks to be reduced to half of their true intensity, but the former can cause intensities at either high or low energy to be reduced even more strongly. It is recommended that instruments should be tested and operated, if necessary, at a lower frequency such as 1.7 kHz at which the problems should disappear. A further factor affecting intensities in both the direct and differentiated spectra is the operation of the bias control for the cone of the channel electron multiplier. Field penetration of the cone causes an unwanted behaviour. It is recommended that the cone be fitted with a transparent wire mesh to remove this field penetration and then the bias may be operated at the required potential of at least 200V.     

RF spectral modulation caused by delayed interference and photodetection of optical noise

We demonstrate that an RF spectral fringe appears when a nonpolarized optical noise and its delayed replica are combined and photo-detected without any polarization control. A theoretical analysis explains the visibility of the fringe and its insensitivity to polarization.     

Public channel cryptography by synchronization of neural networks and chaotic maps

Two different kinds of synchronization have been applied to cryptography: synchronization of chaotic maps by one common external signal and synchronization of neural networks by mutual learning. By combining these two mechanisms, where the external signal to the chaotic maps is synchronized by the nets, we construct a hybrid network which allows a secure generation of secret encryption keys over a public channel. The security with respect to attacks, recently proposed by Shamir et al., is increased by chaotic synchronization.     

High-resolution spectroscopy of gases by density modulation and UV spectrum of UF6

The spectrum of UF₆ vapor between 430-200nm has been measured with the aid of a specially constructed recording spectrophotometer employing a 1.5m spectrograph and the technique of pressure (optical density) modulation. Details of the apparatus are described.