Changes In Signal Strength Research Articles

Tune It Down to Live It Up? Rapid, Nongenomic Effects of Cortisol on the Human Brain

The stress hormone cortisol acts on the brain, supporting adaptation and time-adjusted coping processes. Whereas previous research has focused on slow emerging, genomic effects of cortisol, we addressed the rapid, nongenomic cortisol effects on in vivo neuronal activity in humans. Three independent placebo-controlled studies in healthy men were conducted. We observed changes in CNS activity within 15 min after intravenous administration of a physiological dose of 4 mg of cortisol (hydrocortisone). Two of the studies demonstrated a rapid bilateral thalamic perfusion decrement using continuous arterial spin labeling. The third study revealed rapid, cortisol-induced changes in global signal strength and map dissimilarity of the electroencephalogram. Our data demonstrate that a physiological concentration of cortisol profoundly affects the functioning and perfusion of the human brain in vivo via a rapid, nongenomic mechanism. The changes in neuronal functioning suggest that cortisol acts on the thalamic relay of background as well as on task-specific sensory information, allowing focus and facilitation of adaptation to challenges.

Astigmatism and optical coherence tomography measurements

To evaluate the effect of astigmatism change on measurement of retinal nerve fiber layer (RNFL) and macular thickness by Cirrus HD spectral-domain optical coherence tomography (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, CA, USA). A total of 30 right eyes from 30 healthy young subjects underwent RNFL and macular thickness measurements using Cirrus HD OCT. Measurements were performed at the baseline state and induced with-the-rule (WTR) and against-the-rule (ATR) astigmatism states by wearing toric soft contact lenses (+1.50 -3.25 diopter × 90° and +1.50 -3.25 diopter × 180° respectively). Differences in RNFL and macular thickness between the baseline state and induced astigmatism states were analyzed. Wearing toric soft contact lenses induced a mean 2.92 diopter WTR and 3.18 diopter ATR astigmatism respectively. After signal strength change adjustment, RNFL thicknesses of average, superior quadrant, 12 and 6 o'clock hour sectors decreased after induction of a WTR astigmatism (mean difference range, 1.58 to 6.88 μm); RNFL thicknesses of average, nasal, temporal quadrants, 2, 3, and 9 o'clock hour sectors decreased after induction of an ATR astigmatism (mean difference range, 0.75 to 5.11 μm) (all P values <0.05). Macular thickness was not significantly affected by astigmatism changes (all P values ≥ 0.250). Although the amount of change was not substantial, RNFL thickness measured by Cirrus HD OCT was affected by astigmatism changes induced by contact lenses. It may be warranted to consider the effect of astigmatism on RNFL thickness measured by OCT in eyes with higher degrees of astigmatism.

Dealing with sample aneuploidy and mosaicsm using the ASCAT algorithm on different SNP array platforms

Cancer samples pose a challenging problem for analysis using microarray technology. The basic array CGH (aCGH) approach can confidently detect changes in copy number when a sample is measured against a normal control. However, the necessary normalization pre-processing step will essentially wash away the information associated with hyperdiploid samples. This can be an issue especially with cancer samples. Additionally, mosaic samples, due to different mixture of cells in the sample, can also severely complicate the analysis and interoperation of samples with microarray technology. One of the recently proposed approaches to simultaneously deal with these issues is called the Allele Specific Copy Number Analysis of Tumors (ASCAT) algorithm (1). The approach takes advantage of the SNP information from SNP microarrays to combine the change in total signal strength (log-R value) with the B-Allele Frequency (BAF) to create an optimization function that has local minimas at values corresponding to possible sample ploidy and percent normal contamination. Here we demonstrate an efficient implementation of the ASCAT algorithm on processing cancer samples generated by The Cancer Genome Atlas (TCGA) project. Using Affymetrix and Illumina SNP array data, results are compared between the different platforms as well as with and without application of the ASCAT algorithm. Characterization of a percentage of the cells as normal contaminants within the samples using the ASCAT algorithm reveals many more gains and losses in the aberration profile of the tumors than in samples processed without ASCAT. ASCAT also identified that a large percentage of samples contain high ploidy numbers. With the sample ploidy and extent of normal contamination identified using ASCAT, clearer and more accurate calls can be made for cancer samples. 1. Van Loo P, Nordgard SH, Lingjaerde OC, et al. Allele-specific copy number analysis of tumors. Proc Natl Acad Sci USA 2010;107:16910-16915.

I Agree: Binocular Rivalry Stimuli are Common but Rivalry is Not

I Agree: Binocular Rivalry Stimuli are Common but Rivalry is Not

Solar eclipse effects of 22 July, 2009 on the propagation of radio signals

The results of investigation of the variation of radio signal strengths during the solar eclipse on July 22, 2009 are reported in this paper. Observations of the radio signals transmitted from different radio stations at different frequencies and received at a particular observing site indicate a distinct change in signal strength around the time the eclipse umbra passes the propagation paths. The three types of variations in the eclipse day and particularly during its peak period are different from propagation under normal condition. The phenomena of signal variations, the noted “Inverted U-shape“ at one of the frequencies before the occurrence of the eclipse and 13 to 15 minutes time difference between the enhancement of the signal strength and the onset of eclipse are some interesting characteristics. The results are interpreted by ionospheric D-layer behavior at such times.

Strength violation effect on soft-error detection in sub-micron technology

In nanometer technologies, circuits are increasingly sensitive to various kinds of perturbations. Alpha particles and atmospheric neutrons induce single-event upsets (SEU), affecting memory cells, latches, and flip-flops. In addition, single-event transients (SET) can be initiated in the combinational logic and captured by the latches and flip-flop associated with the logic outputs. Designers cannot control the sources of soft-errors, but their effects can be mitigated through soft-error detection techniques. This paper proposes an algorithm to detect soft-errors at the switch-level caused by current spikes which can affect the driving strength. The offered approach uses a novel coding system to be applied in certain functions that are sensitive to strength variations. It is able to detect even the slight changes in signal strength caused by both cosmic rays and alpha particle from package contamination. Most soft-error detection techniques sense the logic changes in the circuit while this paper proves that a wide range of soft-errors are the result of strength violation in switch-level. Experimental results illustrate the importance of accurate simulation methods and stress the effect of driving strength changes in switch-level for soft-error detection in today’s technology.

Endothelial cell activation in a VEGF-A gradient: Relevance to cell fate decisions

Distribution of vascular endothelial cell growth factor A (VEGF-A) as a gradient determines microvascular endothelial cell (EC) fate during organogenesis. While much is understood about mechanisms of differential distribution, less is known about how EC perceive and interpret a graded VEGF-A signal to generate positional target gene activation. Using microvascular EC, we analyzed the effect of time and graded VEGF-A input on VEGFR2 autophosphorylation, signal kinase activation and induction of immediate-early genes. The threshold and time to peak activation of VEGFR2 were dependent on signal strength over a 50-fold range in concentration with 3-fold concentration differences readily distinguished. Longer duration of exposure did not compensate for low concentration of VEGF-A, suggesting intensity and duration of signal were not interpreted equivalently. With the same conditions, graded and time-sensitive information was transduced through the PLCγ/p44/p42MAPK signal pathway but not the parallel AKT pathway. Analysis of MAPK-induced angiogenic immediate-early genes determined that EGR-1, EGR-3, and NR4A1 were dependent on graded input while NR4A2 and DSCR1 were independent with ‘switch-like’ induction. These data demonstrate rapid, linear integration of VEGF-A levels but independent interpretation of duration of signal and identify potential nodes for segregation of gradient-dependent and -independent responses. These results describe how microvascular EC fate decisions can be determined by comparatively moderate changes in VEGF signal strength, resulting in combinatorial changes in the repertoire of immediate-early genes for transcription effectors.

Attention Improves Object Representation in Visual Cortical Field Potentials

Selective attention improves perception and modulates neuronal responses, but how attention-dependent changes of cortical activity improve the processing of attended objects is an open question. Changes in total signal strength or enhancements in signal-to-noise ratio have been proposed as putative mechanisms. However, it is still not clear whether, and to what extent, these processes contribute to the large perceptual improvements. We studied the ability to discriminate states of activity in visual cortex evoked by differently shaped objects depending on selective attention in monkeys. We found that gamma-band activity from V4 and V1 contains a high amount of information about stimulus shape, which increases for V4 recordings considerably with attention in successful trials, but not in case of behavioral errors. This effect resulted from enhanced differences between the stimulus-specific distributions of power spectral amplitudes. It could be explained neither by enhancements of signal-to-noise ratios, nor by changes in total signal power. Instead our results indicate that attention causes underlying cortical network states to become more distinct for different stimuli, providing a new neurophysiological explanation for improvements of behavioral performance by attention. The absence of the enhancement in discriminability in trials with behavioral errors demonstrates the relevance of this novel neural mechanism for perception.

Phenotypic integration and independence: Hormones, performance, and response to environmental change

Hormones coordinate the co-expression of behavioral, physiological, and morphological traits, giving rise to correlations among traits and organisms whose parts work well together. This article considers the implications of these hormonal correlations with respect to the evolution of hormone-mediated traits. Such traits can evolve owing to changes in hormone secretion, hormonal affinity for carrier proteins, rates of degradation and conversion, and interaction with target tissues to name a few. Critically, however, we know very little about whether these changes occur independently or in tandem, and thus whether hormones promote the evolution of tight phenotypic integration or readily allow the parts of the phenotype to evolve independently. For example, when selection favors a change in expression of hormonally mediated characters, is that alteration likely to come about through changes in hormone secretion (signal strength), changes in response to a fixed level of secretion (sensitivity of target tissues), or both? At one extreme, if the phenotype is tightly integrated and only the signal responds via selection's action on one or more hormonally mediated traits, adaptive modification may be constrained by past selection for phenotypic integration. Alternatively, response to selection may be facilitated if multivariate selection favors new combinations that can be easily achieved by a change in signal strength. On the other hand, if individual target tissues readily "unplug" from a hormone signal in response to selection, then the phenotype may be seen as a loose confederation that responds on a trait-by-trait basis, easily allowing adaptive modification, although perhaps more slowly than if signal variation were the primary mode of evolutionary response. Studies reviewed here and questions for future research address the relative importance of integration and independence by comparing sexes, individuals, and populations. Most attention is devoted to the hormone testosterone (T) and a songbird species, the dark-eyed junco (Junco hyemalis).

The effect of lubricating eye drops on optical coherence tomography imaging of the retina.

The goal of this study was to examine the potential value of corneal lubrication in improving the quality of optical coherence tomography (OCT) imaging of the retina. This study is a consecutive series of 13 eyes of 11 patients in whom repeated attempts at OCT imaging failed to yield a good quality study despite the absence of significant media opacity or inadequate pupil dilation. Immediately following several poor quality scans, each eye received lubricating eye drops. The quality of images before and after the administration of drops was assessed. A statistically significant improvement in OCT image quality was observed following the administration of eye drops in each case. The change in mean signal strength (SS) was from 4.35 to 6.26 (p=0.0002). The proportion of scans with erroneous edge detection decreased from 41 to 13 percent. Lubricating drops appear to improve the quality and feasibility of OCT imaging in selected cases.

Exploring GSM data in pervasive environments

PurposeA cell phone that behaves in a manner reflective of the current context has been a goal for the pervasive and ubiquitous research communities for a long time. This paper aims to demonstrate how two aspects of context – location and activity – can be inferred using GSM data present on standard cell phones.Design/methodology/approachA background knowledge of GSM networks is provided, followed by an assessment of the stability of signal strength levels in order to establish their usefulness in inferring aspects of context. A qualitative location system using GSM signals is presented and how to infer the current activity of the cell phone carrier is demonstrated.FindingsThe paper shows that by using the patterns of signal strength fluctuations and changes to the current serving cell and monitored neighbouring cells it is possible to distinguish between various states of movement such as walking, driving a car and remaining stationary.Originality/valueThe paper focuses on the practical aspects of deploying and managing location based services in dynamic outdoor environments.

A Statistical View of the Transient Signals That Support a Wireless Call

A wireless call in a cellular network requires the cooperation of a wireless enabled device such as a cell phone and a dynamic set of base stations, antennas, and other network elements, with control of the call changing in response to changes in signal strength and the location of the mobile. The signaling between the network and mobile needed to manage the call generates a huge amount of signal strength data, some of which is seen only by the mobile placing the call and some of which is seen only by the network. This article describes some of the complexities of the signal strength data and provides a statistical model of the signals from the network to the wireless device that takes the time-dependent, spatial, and multivariate nature of the call into account. An approach to estimating the model parameters online as network data are collected, which would be useful for network monitoring, is also described and applied to a set of call data obtained from an active commercial CDMA (code division multiple access) network.

Developmental and genetic mechanisms for evolutionary diversification of serial repeats: eyespot size in Bicyclus anynana butterflies

Serially repeated pattern elements on butterfly wings offer the opportunity for integrating genetic, developmental, and functional aspects towards understanding morphological diversification and the evolution of individuality. We use captive populations of Bicyclus anynana butterflies, an emerging model in evolutionary developmental biology, to explore the genetic and developmental basis of compartmentalized changes in eyespot patterns. There is much variation for different aspects of eyespot morphology, and knowledge about the genetic pathways and developmental processes involved in eyespot formation. Also, despite the strong correlations across all eyespots in one butterfly, B. anynana shows great potential for independent changes in the size of individual eyespots. It is, however, unclear to what extent the genetic and developmental processes underlying eyespot formation change in a localized manner to enable such individualization. We use micromanipulations of developing wings to dissect the contribution of different components of eyespot development to quantitative differences in eyespot size on one wing surface. Reciprocal transplants of presumptive eyespot foci between artificial selection lines and controls suggest that while localized antagonistic changes in eyespot size rely mostly on localized changes in focal signal strength, concerted changes depend greatly on epidermal response sensitivities. This potentially reflects differences between the signal-response components of eyespot formation in the degrees of compartmentalization and/or the temporal pattern of selection. We also report on the phenotypic analysis of a number of mutant stocks demonstrating how single alleles can affect different eyespots in concert or independently, and thus contribute to the individualization of serially repeated traits.

E-Cadherin Adhesion Activates c-Src Signaling at Cell–Cell Contacts

Cadherin-based cell-cell contacts are prominent sites for phosphotyrosine signaling, being enriched in tyrosine-phosphorylated proteins and tyrosine kinases and phosphatases. The functional interplay between cadherin adhesion and tyrosine kinase signaling, however, is complex and incompletely understood. In this report we tested the hypothesis that cadherin adhesion activates c-Src signaling and sought to assess its impact on cadherin function. We identified c-Src as part of a cadherin-activated cell signaling pathway that is stimulated by ligation of the adhesion receptor. However, c-Src has a biphasic impact on cadherin function, exerting a positive supportive role at lower signal strengths, but inhibiting function at high signal strengths. Inhibiting c-Src under circumstances when it is activated by cadherin adhesion decreased several measures of cadherin function. This suggests that the cadherin-activated c-Src signaling pathway serves positively to support cadherin function. Finally, our data implicate PI3-kinase signaling as a target for cadherin-activated c-Src signaling that contributes to its positive impact on cadherin function. We conclude that E-cadherin signaling is an important activator of c-Src at cell-cell contacts, providing a key input into a signaling pathway where quantitative changes in signal strength may result in qualitative differences in functional outcome.

Exorcising the `segment length curse': summer temperature reconstruction since AD 1640 using non-detrended stable carbon isotope ratios from pine trees in northern Finland

Stable carbon isotope ratios from the latewood cellulose of 12 trees from two sites in northern Finland are used to construct an isotope chronology covering AD 1640 to 2002. By measuring isotopic ratios of every sample independently it is possible to identify and remove the juvenile portion of each δ 13C series, correct the individual series for anthropogenic changes in atmospheric carbon dioxide isotopic ratios and concentrations, and to quantify changes in signal strength through time. Most importantly, it is possible to demonstrate that there are no long-term trends in the carbon isotope series that are related to tree age. This means that it is not necessary to detrend the series and so they have the potential to retain climate information at all temporal frequencies. The correlation between the non-detrended carbon isotope series and July/August mean temperature is high ( r=0.72) and comparison with meteorological records suggests that the dominant control over tree ring δ13C at these high latitude, moist sites is photosynthetic rate rather than stomatal conductance. Summer temperature reconstructions based on three different calibrations are presented, with verification based on a mixture of jacknife and split period designs, providing robust and near identical results. Reconstructed late summer temperatures in the early 1900s are very low but the years centred around AD 1660 and 1760 appear to have experienced warmer summers than the late twentieth century, thus our late summer reconstruction does not show a recent warming trend. Our results are in agreement with other palaeoclimate reconstructions for northern Fennoscandia, which show late twentieth-century warming occurring predominantly in the winter. Our results suggest that, where replication and common signal strength are sufficiently high, stable carbon isotope dendroclimatology may provide high resolution proxy time series that also record climate information at lower temporal frequencies, thus avoiding the `segment length curse' that can apply to palaeoclimate reconstructions based on other tree ring parameters such as ring widths and density.

Monitoring the setting and hardening of early-age mortar using a pulse-echo ultrasonic guided wave approach

A pulse-echo ultrasonic guided wave approach that monitors the setting and hardening of early-age mortar during the first twenty-four hours ofhydration is presented. The method transmits a torsional wave mode on one end of a cylindrical steel rod embedded in mortar and then receives the reflected signals. Both the reflection from the end of the rod and the reflection from the point where the waveguide enters the mortar are monitored. The development of the mortar's mechanical properties is related to both the energy leaked into the surrounding mortar and the energy reflected at the entry point. Experiments were performed on mixtures with varying water-cement ratios (w/c = 0.40, 0.50, and 0.60), chemical admixtures (accelerant and retardant), and mineral admixtures (silica fume and fly ash). The time of setting and compressive strength of the different mortar mixtures was determined in accordance with ASTM standards. The change in signal strength of the end- and entry-reflection of the guided wave appears to be correlated to the setting times and compressive strength of the mortar. The ability of this method to only require access to one side of the specimen makes it attractive for the development of a portable system that monitors early-age cementitious materials in the field.

Functional Imaging: Is the Resting Brain Resting?

It is often assumed that the human brain only becomes active to support overt behaviour. A new study challenges this concept by showing that multiple neural circuits are engaged even at rest. We highlight two complementary hypotheses which seek to explain the function of this resting activity.

Renin Enhancer Is Critical for Control of Renin Gene Expression and Cardiovascular Function

Renin Enhancer Is Critical for Control of Renin Gene Expression and Cardiovascular Function

Presynaptic Unsilencing: Searching for a Mechanism

Nascent synaptic networks have a high incidence of silent synapses. In this issue of Neuron, Shen et al. show that a brief burst of action potentials rapidly awaken silent synapses by increasing the availability of synaptic vesicles for fusion through BDNF-triggered presynaptic actin remodeling mediated by the small GTPase Cdc42.

MLPA: a rapid, reliable, and sensitive method for detection and analysis of abnormalities of 22q

In this study, essential test characteristics of the recently described multiplex ligation-dependent probe amplification (MLPA) method are presented, using chromosome 22 as a model. This novel method allows the relative quantification of approximately 40-45 different target DNA sequences in a single reaction. For the purpose of this study, MLPA was performed in a blinded manner on a training set containing over 50 samples, including typical 22q11.2 deletions, various atypical deletions, duplications (trisomy and tetrasomy), and unbalanced translocations. All samples in the training set have been previously characterized by fluorescence in situ hybridization (FISH) with cosmid or BAC clones and/or cytogenetic studies. MLPA findings were consistent with cytogenetic and FISH studies, no rearrangement went undetected and repeated tests gave consistent results. At a relative change in comparative signal strength of 30% or more, sensitivity and specificity values were 0.95 and 0.99, respectively. Given that MLPA is likely to be used as an initial screening method, a higher sensitivity, at the cost of a lower specificity, was deemed more appropriate. A receiver operator characteristic (ROC) curve analysis was performed to calculate the most optimal threshold range, with associated sensitivity and specificity values of 0.99 and 0.97, respectively. Finally, performance of each individual probe was analyzed, providing further useful information for the interpretation of MLPA results. In conclusion, MLPA has proven to be a highly sensitive and accurate tool for detecting copy number changes in the 22q11.2 region, making it a fast and economic alternative to currently used methods. The current study provides valuable and detailed information on the characteristics of this novel method.