3,167 research outputs found
Target-derived neurotrophic factors regulate the death of developing forebrain neurons after a change in their trophic requirements
Many neurons die as the normal brain develops. How this is regulated and whether the mechanism involves neurotrophic molecules from target cells are unknown. We found that cultured neurons from a key forebrain structure, the dorsal thalamus, develop a need for survival factors including brain-derived neurotrophic factor (BDNF) from their major target, the cerebral cortex, at the age at which they innervate it. Experiments in vivo have shown that rates of dorsal thalamic cell death are reduced by increasing cortical levels of BDNF and are increased in mutant mice lacking functional BDNF receptors or thalamocortical projections; these experiments have also shown that an increase in the rates of dorsal thalamic cell death can be achieved by blocking BDNF in the cortex. We suggest that the onset of a requirement for cortex-derived neurotrophic factors initiates a competitive mechanism regulating programmed cell death among dorsal thalamic neurons
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Parental investment and child health in a Yanomamö village suffering short-term food stress
The 1998 El Niño significantly reduced garden productivity in the
Upper Orinoco region in Venezuela. Consequently, parents were forced to
allocate food carefully to their children. Nutrition data collected from village
children combined with genealogical data allowed the determination of which
children suffered most, and whether the patterns of food distribution
accorded with predictions from parental investment theory. For boys, three
social variables accounted for over 70% of the variance in subcutaneous fat
after controlling for age: number of siblings, age of the mother’s youngest
child, and whether the mother was the senior or junior co-wife, or was
married monogamously. These results accord well with parental investment
theory. Parents experiencing food stress faced a trade-off between quantity
and quality, and between investing in younger versus older offspring. In
addition, boys with access to more paternal investment (i.e. no stepmother)
were better nourished. These variables did not account for any of the
variance in female nutrition. Girls’ nutrition was associated with the size of
their patrilineage and the number of non-relatives in the village, suggesting
that lineage politics may have played a role. An apparent lack of relationship
between orphan status and nutrition is also interesting, given that orphans
suffered high rates of skin flea infections. The large number of orphans being
cared for by only two grandparents suggests that grooming time may have
been the resource in short supply.
Introductio
Optimal Configuration of Proton-Therapy Accelerators for Relative-Stopping-Power Resolution in Proton Computed Tomography
SUCI02 inhibits the erbB-2 tyrosine kinase receptor signaling pathway and arrests the cell cycle in G 1 phase in breast cancer cells
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73321/1/j.1349-7006.2006.00143.x.pd
Evaluation of Eye Protection Filters Used with Broad-Spectrum and Conventional LED Curing Lights
Exploring 4D Quantum Hall Physics with a 2D Topological Charge Pump
The discovery of topological states of matter has profoundly augmented our
understanding of phase transitions in physical systems. Instead of local order
parameters, topological phases are described by global topological invariants
and are therefore robust against perturbations. A prominent example thereof is
the two-dimensional integer quantum Hall effect. It is characterized by the
first Chern number which manifests in the quantized Hall response induced by an
external electric field. Generalizing the quantum Hall effect to
four-dimensional systems leads to the appearance of a novel non-linear Hall
response that is quantized as well, but described by a 4D topological invariant
- the second Chern number. Here, we report on the first observation of a bulk
response with intrinsic 4D topology and the measurement of the associated
second Chern number. By implementing a 2D topological charge pump with
ultracold bosonic atoms in an angled optical superlattice, we realize a
dynamical version of the 4D integer quantum Hall effect. Using a small atom
cloud as a local probe, we fully characterize the non-linear response of the
system by in-situ imaging and site-resolved band mapping. Our findings pave the
way to experimentally probe higher-dimensional quantum Hall systems, where new
topological phases with exotic excitations are predicted
p70 S6 kinase and actin dynamics: A perspective
p70 S6 kinase (p70S6K), a member of the AGC serine/threonine kinase family, was initially identified as a key player, together with its downstream effector S6, in the regulation of cellular growth and survival. The p70S6K protein has emerged in recent years as a multifunctional protein which also regulates the actin cytoskeleton and thus plays a role in cell migration. This new function is through two important activities of p70S6K, namely actin cross-linking and Rac1 and Cdc42 activation. The testis is critically dependent on an intricate balance of fundamental cellular processes such as adhesion, migration, and differentiation. It is increasingly evident that Rho GTPases and actin binding proteins play fundamental roles in regulating spermatogenesis within the testis. In this review, we will discuss current findings of p70S6K in the control of actin cytoskeleton dynamics. In addition, the potential role of p70S6K in spermatogenesis and testicular function will be highlighted
Surface structure and frictional properties of the skin of the Amazon tree boa Corallus hortulanus (Squamata, Boidae)
The legless locomotion of snakes requires specific adaptations of their ventral scales to maintain friction force in different directions. The skin microornamentation of the snake Corallus hortulanus was studied by means of scanning electron microscopy and the friction properties of the skin were tested on substrates of different roughness. Skin samples from various parts of the body (dorsal, lateral, ventral) were compared. Dorsal and lateral scales showed similar, net-like microornamentation and similar friction coefficients. Average friction coefficients for dorsal and lateral scales on the epoxy resin surfaces were 0.331 and 0.323, respectively. In contrast, ventral scales possess ridges running parallel to the longitudinal body axis. They demonstrated a significantly lower friction coefficient compared to both dorsal and lateral scales (0.191 on average). In addition, ventral scales showed frictional anisotropy comparing longitudinal and perpendicular direction of the ridges. This study clearly demonstrates that different skin microstructure is responsible for different frictional properties in different body regions
A Bayesian Framework to Account for Complex Non-Genetic Factors in Gene Expression Levels Greatly Increases Power in eQTL Studies
Gene expression measurements are influenced by a wide range of factors, such as the state of the cell, experimental conditions and variants in the sequence of regulatory regions. To understand the effect of a variable of interest, such as the genotype of a locus, it is important to account for variation that is due to confounding causes. Here, we present VBQTL, a probabilistic approach for mapping expression quantitative trait loci (eQTLs) that jointly models contributions from genotype as well as known and hidden confounding factors. VBQTL is implemented within an efficient and flexible inference framework, making it fast and tractable on large-scale problems. We compare the performance of VBQTL with alternative methods for dealing with confounding variability on eQTL mapping datasets from simulations, yeast, mouse, and human. Employing Bayesian complexity control and joint modelling is shown to result in more precise estimates of the contribution of different confounding factors resulting in additional associations to measured transcript levels compared to alternative approaches. We present a threefold larger collection of cis eQTLs than previously found in a whole-genome eQTL scan of an outbred human population. Altogether, 27% of the tested probes show a significant genetic association in cis, and we validate that the additional eQTLs are likely to be real by replicating them in different sets of individuals. Our method is the next step in the analysis of high-dimensional phenotype data, and its application has revealed insights into genetic regulation of gene expression by demonstrating more abundant cis-acting eQTLs in human than previously shown. Our software is freely available online at http://www.sanger.ac.uk/resources/software/peer/
Why I tense up when you watch me: inferior parietal cortex mediates an audience’s influence on motor performance
The presence of an evaluative audience can alter skilled motor performance through changes in force output. To investigate how this is mediated within the brain, we emulated real-time social monitoring of participants’ performance of a fine grip task during functional magnetic resonance neuroimaging. We observed an increase in force output during social evaluation that was accompanied by focal reductions in activity within bilateral inferior parietal cortex. Moreover, deactivation of the left inferior parietal cortex predicted both inter- and intra-individual differences in socially-induced change in grip force. Social evaluation also enhanced activation within the posterior superior temporal sulcus, which conveys visual information about others’ actions to the inferior parietal cortex. Interestingly, functional connectivity between these two regions was attenuated by social evaluation. Our data suggest that social evaluation can vary force output through the altered engagement of inferior parietal cortex; a region implicated in sensorimotor integration necessary for object manipulation, and a component of the action-observation network which integrates and facilitates performance of observed actions. Social-evaluative situations may induce high-level representational incoherence between one’s own intentioned action and the perceived intention of others which, by uncoupling the dynamics of sensorimotor facilitation, could ultimately perturbe motor output
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