1,617 research outputs found
Piecewise Linear Identification for the Rate-Independent and Rate-Dependent Duhem Hysteresis Models
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57843/1/HysteresisIDTACMarch2007.pd
Semilinear Duhem Model for Rate-Independent and Rate-Dependent Hysteresis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57865/1/HysteresisSemilinearDuhemTAC2005.pd
A GABAergic projection from the centromedial nuclei of the amygdala to ventromedial prefrontal cortex modulates reward behavior
The neural circuitry underlying mammalian reward behaviors involves several distinct nuclei throughout the brain. It is widely accepted that the midbrain dopamine (DA) neurons are critical for the reward-related behaviors. Recent studies have shown that the centromedial nucleus of the amygdala (CeMA) has a distinct role in regulating reward-related behaviors. However, the CeMA and ventromedial PFC (vmPFC) interaction in reward regulation remains poorly understood. Here, we identify and dissect a GABAergic projection that originates in the CeMA and terminates in the vmPFC (VGat-Cre(CeMA-vmPFC)) using viral-vector-mediated, cell-type-specific optogenetic techniques in mice. Pathway-specific optogenetic activation of the VGat-Cre(CeMA-vmPFC) circuit in awake, behaving animals produced a positive, reward-like phenotype in real-time place preference and increased locomotor activity in open-field testing. In sucrose operant conditioning, the photoactivation of these terminals increased nose-poking effort with no effect on licking behavior and robustly facilitated the extinction of operant behavior. However, photoactivation of these terminals did not induce self-stimulation in the absence of an external reward. The results described here suggest that the VGat-Cre(CeMA-vmPFC) projection acts to modulate existing reward-related behaviors. SIGNIFICANCE STATEMENT Many studies have shown that the interactions between the centromedial nucleus of the amygdala (CeMA) and ventromedial PFC (vmPFC) have critical roles for emotional regulation. However, most studies have associated this circuit with fear and anxiety behaviors and emphasized top-down processing from vmPFC to CeMA. Here, we provide new evidence for bottom-up CeMA to vmPFC influence on reward-related behaviors. Although previous work implicated the CeMA in incentive salience, our results isolate the investigation to a specific CeMA GABAergic projection to the vmPFC. This long-range GABAergic interaction between amygdala and frontal cortex adds a new dimension to the complex regulation of reward-related behaviors
Shaken and stirred: conduction and turbulence in clusters of galaxies
(abridged) Uninhibited radiative cooling in clusters of galaxies would lead
to excessive mass accretion rates contrary to observations. One of the key
proposals to offset radiative energy losses is thermal conduction from outer,
hotter layers of cool core clusters to their centers. However, conduction is
sensitive to magnetic field topology. In cool-core clusters the heat buoyancy
instability (HBI) leads to B-fields ordered preferentially in the direction
perpendicular to that of gravity, which significantly reduces the level of
conduction below the classical Spitzer-Braginskii value. However, the cluster
cool cores are rarely in perfect hydrostatic equilibrium. Sloshing motions due
to minor mergers, galaxy motions or AGN can significantly perturb the gas and
affect the level of thermal conduction. We perform 3D AMR MHD simulations of
the effect of turbulence on the properties of the anisotropic thermal
conduction in cool core clusters. We show that very weak subsonic motions, well
within observational constraints, can randomize the magnetic field and
significantly boost effective thermal conduction beyond the saturated values
expected in the pure unperturbed HBI case. We find that the turbulent motions
can essentially restore the conductive heat flow to the cool core to level
comparable to the theoretical maximum of 1/3 Spitzer for a highly tangled
field. Runs with radiative cooling show that the cooling catastrophe can be
averted and the cluster core stabilized. Above a critical Froude number, these
same turbulent motions also eliminate the tangential bias in the velocity and
magnetic field that is otherwise induced by the trapped g-modes. Our results
can be tested with future radio polarization measurements, and have
implications for efficient metal dispersal in clusters.Comment: submitted to ApJ, references added, expanded Section
Galaxy Motions, Turbulence and Conduction in Clusters of Galaxies
Unopposed radiative cooling in clusters of galaxies results in excessive mass
deposition rates. However, the cool cores of galaxy clusters are continuously
heated by thermal conduction and turbulent heat diffusion due to minor mergers
or the galaxies orbiting the cluster center. These processes can either reduce
the energy requirements for AGN heating of cool cores, or they can prevent
overcooling altogether. We perform 3D MHD simulations including field-aligned
thermal conduction and self-gravitating particles to model this in detail.
Turbulence is not confined to the wakes of galaxies but is instead
volume-filling, due to the excitation of large-scale g-modes. We systematically
probe the parameter space of galaxy masses and numbers. For a wide range of
observationally motivated galaxy parameters, the magnetic field is randomized
by stirring motions, restoring the conductive heat flow to the core. The
cooling catastrophe either does not occur or it is sufficiently delayed to
allow the cluster to experience a major merger that could reset conditions in
the intracluster medium. Whilst dissipation of turbulent motions is negligible
as a heat source, turbulent heat diffusion is extremely important; it
predominates in the cluster center. However, thermal conduction becomes
important at larger radii, and simulations without thermal conduction suffer a
cooling catastrophe. Conduction is important both as a heat source and to
reduce stabilizing buoyancy forces, enabling more efficient diffusion.
Turbulence enables conduction, and conduction enables turbulence. In these
simulations, the gas vorticity---which is a good indicator of trapped
g-modes--increases with time. The vorticity growth is approximately mirrored by
the growth of the magnetic field, which is amplified by turbulence.Comment: Submitted to MNRA
Phenotypic covariance of longevity, immunity and stress resistance in the Caenorhabditis nematodes
Background \ud
Ageing, immunity and stresstolerance are inherent characteristics of all organisms. In animals, these traits are regulated, at least in part, by forkhead transcription factors in response to upstream signals from the Insulin/Insulin– like growth factor signalling (IIS) pathway. In the nematode Caenorhabditis elegans, these phenotypes are molecularly linked such that activation of the forkhead transcription factor DAF-16 both extends lifespan and simultaneously increases immunity and stress resistance. It is known that lifespan varies significantly among the Caenorhabditis species but, although DAF-16 signalling is highly conserved, it is unclear whether this phenotypic linkage occurs in other species. Here we investigate this phenotypic covariance by comparing longevity, stress resistance and immunity in four \ud
Caenorhabditis species. \ud
\ud
Methodology/Principal Findings \ud
We show using phenotypic analysis of DAF-16 influenced phenotypes that among four closely related Caenorhabditis nematodes, the gonochoristic species (Caenorhabditis remanei and Caenorhabditis brenneri) have diverged \ud
significantly with a longer lifespan, improved stress resistance and higher immunity than the hermaphroditic species (C. elegans and Caenorhabditis briggsae). Interestingly, we also observe significant differences in expression levels between the daf-16 homologues in these species using Real-Time PCR, which positively correlate with the observed phenotypes. Finally, we provide additional evidence in support of a role for DAF-16 in regulating phenotypic coupling by using a combination of wildtype isolates, constitutively active daf-16 mutants and bioinformatic analysis. \ud
\ud
Conclusions \ud
The gonochoristic species display a significantly longer lifespan (p < 0.0001)and more robust immune and stress response (p<0.0001, thermal stress; p<0.01, heavy metal stress; p<0.0001, pathogenic stress) than the hermaphroditic species. Our data suggests that divergence in DAF-16 mediated phenotypes may underlie many of the differences observed between these four species of Caenorhabditis nematodes. These findings are further supported by the correlative higher daf-16 expression levels among the gonochoristic species and significantly higher lifespan, immunity and stress tolerance in the constitutively active daf-16 hermaphroditic mutants
Phenotypic covariance of Longevity, Immunity and Stress Resistance in the Caenorhabditis Nematodes
Background: Ageing, immunity and stresstolerance are inherent characteristics of all organisms. In animals, these traits are regulated, at least in part, by forkhead transcription factors in response to upstream signals from the Insulin/Insulin–like growth factor signalling (IIS) pathway. In the nematode Caenorhabditis elegans, these phenotypes are molecularly linked such that activation of the forkhead transcription factor DAF-16 both extends lifespan and simultaneously increases immunity and stress resistance. It is known that lifespan varies significantly among the Caenorhabditis species but, although DAF-16 signalling is highly conserved, it is unclear whether this phenotypic linkage occurs in other species. Here we investigate this phenotypic covariance by comparing longevity, stress resistance and immunity in four Caenorhabditis species. \ud
\ud
Methodology/Principal Findings: We show using phenotypic analysis of DAF-16 influenced phenotypes that among four closely related Caenorhabditis nematodes, the gonochoristic species (Caenorhabditis remanei and Caenorhabditis brenneri) have diverged significantly with a longer lifespan, improved stress resistance and higher immunity than the hermaphroditic species (C. elegans and Caenorhabditis briggsae). Interestingly, we also observe significant differences in expression levels between the daf-16 homologues in these species using Real-Time PCR, which positively correlate with the observed phenotypes. Finally, we provide additional evidence in support of a role for DAF-16 in regulating phenotypic coupling by using a combination of wildtype isolates, constitutively active daf-16 mutants and bioinformatic analysis. \ud
\ud
Conclusions: The gonochoristic species display a significantly longer lifespan (p<0.0001) and more robust immune and stress response (p<0.0001, thermal stress; p<0.01, heavy metal stress; p<0.0001, pathogenic stress) than the hermaphroditic species. Our data suggests that divergence in DAF-16 mediated phenotypes may underlie many of the differences observed between these four species of Caenorhabditis nematodes. These findings are further supported by the correlative higher daf-16 expression levels among the gonochoristic species and significantly higher lifespan, immunity and stress tolerance in the constitutively active daf-16 hermaphroditic mutants
NCoR Repression of LXRs Restricts Macrophage Biosynthesis of Insulin-Sensitizing Omega 3 Fatty Acids
SummaryMacrophage-mediated inflammation is a major contributor to obesity-associated insulin resistance. The corepressor NCoR interacts with inflammatory pathway genes in macrophages, suggesting that its removal would result in increased activity of inflammatory responses. Surprisingly, we find that macrophage-specific deletion of NCoR instead results in an anti-inflammatory phenotype along with robust systemic insulin sensitization in obese mice. We present evidence that derepression of LXRs contributes to this paradoxical anti-inflammatory phenotype by causing increased expression of genes that direct biosynthesis of palmitoleic acid and ω3 fatty acids. Remarkably, the increased ω3 fatty acid levels primarily inhibit NF-κB-dependent inflammatory responses by uncoupling NF-κB binding and enhancer/promoter histone acetylation from subsequent steps required for proinflammatory gene activation. This provides a mechanism for the in vivo anti-inflammatory insulin-sensitive phenotype observed in mice with macrophage-specific deletion of NCoR. Therapeutic methods to harness this mechanism could lead to a new approach to insulin-sensitizing therapies
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