7,931 research outputs found
"'Painting of a Sorrow': Visual Culture and the Performance of Stasis in David Garrick's Hamlet"
Identifying functional populations among the interneurons in laminae I-III of the spinal dorsal horn
The spinal dorsal horn receives input from primary afferent axons, which terminate in a modality-specific fashion in different laminae. The incoming somatosensory information is processed through complex synaptic circuits involving excitatory and inhibitory interneurons, before being transmitted to the brain via projection neurons for conscious perception. The dorsal horn is important, firstly because changes in this region contribute to chronic pain states, and secondly because it contains potential targets for the development of new treatments for pain. However, at present, we have only a limited understanding of the neuronal circuitry within this region, and this is largely because of the difficulty in defining functional populations among the excitatory and inhibitory interneurons. The recent discovery of specific neurochemically defined interneuron populations, together with the development of molecular genetic techniques for altering neuronal function in vivo, are resulting in a dramatic improvement in our understanding of somatosensory processing at the spinal level
The Complexity Dilemma in Policy Market Design
Regulators are increasingly pursuing their policy objectives by creating markets. To create a policy market, regulators require firms to procure a product that is socially useful but that confers little direct private benefit to the acquiring party. Examples of policy markets include pollutant emissions trading programs, renewable energy credit markets, and electricity capacity markets. Existing scholarship has tended to analyze policy markets simply as market-based regulation. Although not inaccurate, such inquiries are necessarily incomplete because they do not focus on the distinctive traits of policy markets. Policy markets are neither typical regulations nor typical markets. Concentrating on policy markets as a distinctive type of market brings to light common characteristics of such markets, which in turn generates insights into how they can be used more effectively to implement policy. In particular, this Article focuses on a recurring fundamental challenge in policy market design: managing complexity. Typical markets manage complexity through market forces. As a regulatory creation, however, policy markets require regulators to manage their complexity. This poses what we call the complexity dilemma, which requires regulators to balance strong pressures both toward and away from complexity. The central argument of this Article is that although policy markets are an important part of a regulator’s toolkit, they are also subject to complexity that limits their usefulness. Understanding the complexity dilemma and its crucial role in policy market design forms an essential step toward progress in improving the design and function of these markets
Quantum critical response: from conformal perturbation theory to holography
We discuss dynamical response functions near quantum critical points,
allowing for both a finite temperature and detuning by a relevant operator.
When the quantum critical point is described by a conformal field theory (CFT),
conformal perturbation theory and the operator product expansion can be used to
fix the first few leading terms at high frequencies. Knowledge of the high
frequency response allows us then to derive non-perturbative sum rules. We
show, via explicit computations, how holography recovers the general results of
CFT, and the associated sum rules, for any holographic field theory with a
conformal UV completion -- regardless of any possible new ordering and/or
scaling physics in the IR. We numerically obtain holographic response functions
at all frequencies, allowing us to probe the breakdown of the asymptotic
high-frequency regime. Finally, we show that high frequency response functions
in holographic Lifshitz theories are quite similar to their conformal
counterparts, even though they are not strongly constrained by symmetry.Comment: 45+14 pages, 9 figures. v2: small clarifications, added reference
Spinal neurons that contain gastrin-releasing peptide seldom express Fos or phosphorylate extracellular signal-regulated kinases in response to intradermal chloroquine
Background: Gastrin-releasing peptide (GRP) is thought to play a role in the itch evoked by intradermal injection of chloroquine. Although some early studies suggested that GRP was expressed in pruriceptive primary afferents, it is now thought that GRP in the spinal cord is derived mainly from a population of excitatory interneurons in lamina II, and it has been suggested that these are involved in the itch pathway. To test this hypothesis, we used the transcription factor Fos and phosphorylation of extracellular signal-regulated kinases (ERK) to look for evidence that interneurons expressing GRP were activated following intradermal injection of chloroquine into the calf, in mice that express enhanced green fluorescent protein (EGFP) in these cells.
Results: Injection of chloroquine resulted in numerous Fos- or phospho-ERK (pERK) positive cells in the somatotopically appropriate part of the superficial dorsal horn. The proportion of all neurons in this region that showed Fos or pERK was 18% and 21%, respectively. However, among the GRP–EGFP, only 7% were Fos-positive and 3% were pERK-positive. As such, GRP–EGFP cells were significantly less likely than other neurons to express Fos or to phosphorylate ERK.
Conclusions: Both expression of Fos and phosphorylation of ERK can be used to identify dorsal horn neurons activated by chloroquine injection. However, these results do not support the hypothesis that interneurons expressing GRP are critical components in the itch pathway
Expression of gastrin-releasing peptide by excitatory interneurons in the mouse superficial dorsal horn
Background:
Gastrin-releasing peptide (GRP) and its receptor have been shown to play an important role in the sensation of itch. However, although GRP immunoreactivity has been detected in the spinal dorsal horn, there is debate about whether this originates from primary afferents or local excitatory interneurons. We therefore examined the relation of GRP immunoreactivity to that seen with antibodies that label primary afferent or excitatory interneuron terminals. We tested the specificity of the GRP antibody by preincubating with peptides with which it could potentially cross-react. We also examined tissue from a mouse line in which enhanced green fluorescent protein (EGFP) is expressed under control of the GRP promoter.<p></p>
Results:
GRP immunoreactivity was seen in both primary afferent and non-primary glutamatergic axon terminals in the superficial dorsal horn. However, immunostaining was blocked by pre-incubation of the antibody with substance P, which is present at high levels in many nociceptive primary afferents. EGFP+ cells in the GRP-EGFP mouse did not express Pax2, and their axons contained the vesicular glutamate transporter 2 (VGLUT2), indicating that they are excitatory interneurons. In most cases, their axons were also GRP-immunoreactive. Multiple-labelling immunocytochemical studies indicated that these cells did not express either of the preprotachykinin peptides, and that they generally lacked protein kinase Cγ, which is expressed by a subset of the excitatory interneurons in this region.<p></p>
Conclusions:
These results show that GRP is expressed by a distinct population of excitatory interneurons in laminae I-II that are likely to be involved in the itch pathway. They also suggest that the GRP immunoreactivity seen in primary afferents in previous studies may have resulted from cross-reaction of the GRP antibody with substance P or the closely related peptide neurokinin A
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