Rayleigh wave propagation in centrosymmetric materials with micro-stiffness, flexoelectric and micro-inertia effects

A theoretical investigation of Rayleigh waves propagation in polarized media has been carried out using a reformulated flexoelectric theory for isotropic dielectrics with micro-inertia effect. Within this non-classical theory, the internal energy density is the functional of the strain tensor, dilatation gradient, deviatoric part of stretch gradient and rotation gradient tensors, polarization vector, and polarization gradient. The obtained system of governing equations additionally contains three material length-scale parameters to account the micro-stiffness effect, one material constant to capture the micro-inertia effect, two flexoelectric constants to describe the flexoelectric effect and three length scale parameters related to the polarization gradient. To solve the coupled governing equations, the method of Lamé-type potentials for mechanical displacement and electric polarization vectors is used. The influences of various factors such as micro-stiffness, flexoelectricity, electric quadrupoles and micro-inertia effects on the phase velocity of the Rayleigh waves in a homogeneous isotropic half-space are studied. It is found that above effects become significant with the increase of the wavenumber. This study can be important for the investigation of high frequency surface acoustic waves in dielectric materials.

Electrical activation of vagal efferent or afferent neurons elicits two distinct mechanisms of anti-inflammatory actions

Inhibition of inflammation by reducing macrophage activation and pro-inflammatory cytokine production by electrical vagal nerve stimulation is well documented. Despite this ability to regulate inflammation, the mechanisms and intermediaries in this process are not completely understood. Vagal efferent neurons are thought to be the primary source of anti-inflammatory activity, despite the composition of the vagus nerve, which is predominantly vagal afferent neurons. Activation of vagal efferent neurons ameliorates lipopolysaccharide (LPS)-induced sepsis and is dependent on acetylcholine (ACh) derived from choline acetyltransferase (ChAT+) T-cells. Recent studies have identified vagal afferent fibers as anti-inflammatory as well, however the circuitry, including whether these vagal-mediated anti-inflammatory mechanisms converge, is unknown. Here, we show that VNS is capable of eliciting two distinct, anti-inflammatory mechanisms orchestrated by vagal efferent or afferent neurons. Using ChAT+ T-cell conditional KO mice, we show that afferent VNS reduced LPS-induced inflammation independently of T-cell derived ACh by measuring serum and lymphatic organ TNF-α and IL-6 levels. Using a highly selective β2-adrenergic receptor (β2-AR) antagonist, we show that intact, efferent, and notably afferent VNS regulates immunity in a β2-AR-dependent fashion. Together, these findings demonstrate that VNS is capable of eliciting two unique neuro-immune circuits with distinct mechanistic elements. Continued development of these circuits will inform the design of future vagal nerve stimulators, that may improve the efficacy of these devices in the regulation of immunity.

Sensory Nociceptive Neurons Contribute to Host Protection During Enteric Infection With Citrobacter rodentium

BACKGROUND

Neurons are an integral component of the immune system that functions to coordinate responses to bacterial pathogens. Sensory nociceptive neurons that can detect bacterial pathogens are found throughout the body with dense innervation of the intestinal tract.

METHODS

In this study, we assessed the role of these nerves in the coordination of host defenses to Citrobacter rodentium. Selective ablation of nociceptive neurons significantly increased bacterial burden 10 days postinfection and delayed pathogen clearance.

RESULTS

Because the sensory neuropeptide CGRP (calcitonin gene-related peptide) regulates host responses during infection of the skin, lung, and small intestine, we assessed the role of CGRP receptor signaling during C rodentium infection. Although CGRP receptor blockade reduced certain proinflammatory gene expression, bacterial burden and Il-22 expression was unaffected.

CONCLUSIONS

Our data highlight that sensory nociceptive neurons exert a significant host protective role during C rodentium infection, independent of CGRP receptor signaling.

Divergence of neuroimmune circuits activated by afferent and efferent vagal nerve stimulation in the regulation of inflammation

KEY POINTS

It has previously been shown that afferent and efferent vagal nerve stimulation potently inhibits lipopolysaccharide (LPS)-induced inflammation Our data show inhibition of inflammation by efferent but not afferent vagal nerve stimulation requires T-cell derived acetylcholine We show that afferent and efferent neuroimmune circuits require β₂ -adrenergic receptor signalling ABSTRACT: Chronic inflammation due to inappropriate immune cell activation can have significant effects on a variety of organ systems, reducing lifespan and quality of life. As such, highly targeted control of immune cell activation is a major therapeutic goal. Vagus nerve stimulation (VNS) has emerged as a therapeutic modality that exploits neuroimmune communication to reduce immune cell activation and consequently inflammation. Although vagal efferent fibres were originally identified as the primary driver of anti-inflammatory actions, the vagus nerve in most species of animals predominantly comprises afferent fibres. Stimulation of vagal afferent fibres can also reduce inflammation; it is, however, uncertain how these two neuroimmune circuits diverge. Here we show that afferent VNS induces a mechanism distinct from efferent VNS, ameliorating lipopolysaccharide (LPS)-induced inflammation independently of T-cell derived acetylcholine (ACh) which is required by efferent VNS. Using a β₂ -adrenergic receptor antagonist (β₂ -AR), we find that immune regulation induced by intact, afferent, or efferent VNS occurs in a β_2- AR-dependent manner. Together, our findings indicate that intact VNS activates at least two distinct neuroimmune circuits each with unique mechanisms of action. Selective targeting of either the vagal efferent or afferent fibres may provide more personalized, robust and effective control over inappropriate immune responses.

Sensory afferent neurons coordinate in host immune responses to Citrobacter rodentium

Background

Neuro-immune communication is a vital component of regulating host immune responses to pathogens. Specialized sensory neurons have recently been described to detect bacterial pathogens in the skin, lung, and small intestine, inducing either maladaptive or host-protective responses. Here we assessed the role of sensory nociceptive neurons in the host response to the enteric pathogen Citrobacter rodentium.

Methods

Selective ablation of nociceptive neurons was accomplished using the Trpv1 agonist Resiniferatoxin (RTX) 10 days prior to C. rodentium infection of mice (C57BL/6).

Results

RTX-treated mice exhibited significantly increased bacterial burden 10 days post infection and delayed pathogen clearance compared to vehicle control mice. This reduced host-protective immune response was due to significantly reduced expression of IL-22, and recruitment of CD3+ T-cells into the colonic mucosa. This process appears to be TRPV1 dependent as TRPV1 KO mice experienced a similar delay in T-cell recruitment. Expression of pro-inflammatory cytokines in RTX-treated mice was significantly enhanced, and was associated with increased numbers of colonic T-cells 29 days p.i.. As previous studies identified the sensory neuropeptide CGRP as a regulator of host immune responses, we assessed the role of CGRP receptor signaling during C. rodentium infection. Antagonism of the CGRP receptor reduced expression of Il6, and Ifng, while bacterial burden and Il22 expression was not reduced compared to C. rodentium-infected vehicle-treated control mice.

Conclusions

Our data indicate that sensory nociceptive neurons exert a significant host protective role during C. rodentium infection that is independent of CGRP.

Immunoenzymatic quantification of low concentrations of thyrotropin

We evaluated an immunoenzymatic assay (Abbott HTSH EIA) for thyrotropin (TSH) as a tool for detecting hyperthyroidism and for monitoring thyroid hormone suppressive therapy in patients with nodular goiter, thyroid carcinoma, and hypopituitarism. We also tested with thyroliberin (TRH), to determine the correlation between peak and basal TSH in suppressed patients. For comparison, we used a nonequilibrium radioimmunoassay optimized for maximum sensitivity (J Clin Endocrinol Metab 1975;41:676). Hyperthyroid patients with values for either or both triiodothyronine and thyroxin above the normal reference interval had Abbott assay values less than or equal to 0.2 milli-int. unit/L, clearly below the Abbott assay normal range, as determined in 116 euthyroid subjects. We detected one-third of the suppressed patients (greater than or equal to 0.3 milli-int. unit/L) with RIA, 69% with the Abbott assay (TSH greater than or equal to 0.04 milli-int. unit/L). Only 20% of patients with undetectable basal TSH values in the Abbott assay responded to TRH with a detectable peak TSH value; the peak TSH value after TRH was proportional to the basal TSH value. A single basal TSH measurement by the Abbott HTSH EIA should be adequate for monitoring the degree of thyroidal suppression in thyroid-hormone-treated patients.

Immunoenzymatic quantification of low concentrations of thyrotropin

We evaluated an immunoenzymatic assay (Abbott HTSH EIA) for thyrotropin (TSH) as a tool for detecting hyperthyroidism and for monitoring thyroid hormone suppressive therapy in patients with nodular goiter, thyroid carcinoma, and hypopituitarism. We also tested with thyroliberin (TRH), to determine the correlation between peak and basal TSH in suppressed patients. For comparison, we used a nonequilibrium radioimmunoassay optimized for maximum sensitivity (J Clin Endocrinol Metab 1975;41:676). Hyperthyroid patients with values for either or both triiodothyronine and thyroxin above the normal reference interval had Abbott assay values less than or equal to 0.2 milli-int. unit/L, clearly below the Abbott assay normal range, as determined in 116 euthyroid subjects. We detected one-third of the suppressed patients (greater than or equal to 0.3 milli-int. unit/L) with RIA, 69% with the Abbott assay (TSH greater than or equal to 0.04 milli-int. unit/L). Only 20% of patients with undetectable basal TSH values in the Abbott assay responded to TRH with a detectable peak TSH value; the peak TSH value after TRH was proportional to the basal TSH value. A single basal TSH measurement by the Abbott HTSH EIA should be adequate for monitoring the degree of thyroidal suppression in thyroid-hormone-treated patients.

Stimulation of LH fragments with reduced bioactivity following GnRH agonist administration in women

In eumenorrheic women with endometriosis and in oligo-amenorrheic women with polycystic ovarian disease (PCO), chronic administration of a long-acting GnRH agonist (GnRH-a) reduced the circulating concentrations of estrogens and androgens to levels similar to those of castrated women. The concommittant elevation of LH in both groups suggested that the measured immunoreactive LH had reduced bioactivity. In seven women with endometriosis, bioactive LH (BA LH) measured as the in-vitro secretion of testosterone by dispersed Leydig cells, was significantly (p less than 0.001) reduced from 10.8 +/- 1.2 (SEM) to 4.4 +/- 0.2 mIU/ml at the end of 28 days of GnRH-a therapy. In five women with PCO, BA LH decreased from 44.2 +/- 15.5 to 5.7 +/- 0.6 mIU/ml (p = 0.06). These changes of BA LH appeared to be responsible for the suppression of ovarian androgen secretion during GnRH-a treatment and in turn may have contributed to the profound decreases of estrogen production by reducing the amount of precursor androgen available for aromatization. Free alpha subunit levels increased simultaneously with the decrease of BA LH at the end of therapy, suggesting a post-receptor effect of GnRH-a. Beta subunit levels became undetectable. Cross-reaction of alpha subunit in the RIA for LH was sufficient to only partially account for the LH levels measured. On sephadex G-100 chromatography the excess immunoreactive material was detected at and immediately following the alpha subunit tracer. Further studies will be necessary to elucidate the chemical nature of the immunoreactive LH secreted during GnRH-a therapy.

Histochemical fluorescence after application of neurochemicals to caudate nucleus and septal area in vivo

The movement of carbachol, norepinephrine, and dopamine from cannula sites in caudate nucleus and septal area of freely moving rats was traced by means of biogenic amine fluorescence. Fluorescent patterns seen after application of carbachol and norepinephrine to brain tissue did not appear to differ from controls. Three types of movement from the cannula site after administration of dopamine were observed. There was a spherical distribution approximately 2 millimeters in diameter. Fluorescence also followed axonal pathways in the orthodromic direction, suggesting that dopamine may have been transported by " axonal streaming " or by some other unknown mechanism in periaxonal spaces. Because fluorescence was present in both the ependymal lining and the choroid plexus, it was inferred that the cerebral ventricles were also involved in the movement of chemical. Any attempt to ascribe anatomical localization to behavioral effects resulting from chemical stimulation of the brain should take into account the widespread movement of chemicals after their local application to brain tissue.