Min Post-stimulation Research Articles

Gender-specific modulation of short-term neuroplasticity in the visual cortex induced by transcranial direct current stimulation

Transcranial direct current stimulation (tDCS) is a non-invasive method of modulating levels of cortical excitability. In this study, data gathered over a number of previously conducted experiments before and after tDCS, has been re-analyzed to investigate correlations between sex differences with respect to neuroplastic effects. Visual evoked potentials (VEPs), phosphene thresholds (PTs), and contrast sensitivity measurements (CSs) are used as indicators of the excitability of the primary visual cortex. The data revealed that cathodally induced excitability effects 10 min post stimulation with tDCS, showed no significant difference between genders. However, stimulation in the anodal direction revealed sex-specific effects: in women, anodal stimulation heightened cortical excitability significantly when compared to the age-matched male subject group. There was no significant difference between male and female subjects immediately after stimulation. These results indicate that sex differences exist within the visual cortex of humans, and may be subject to the influences of modulatory neurotransmitters or gonadal hormones which mirror short-term neuroplastic effects.

Effects of transcranial random noise stimulation (tRNS) on the cortical excitability

Event Abstract Back to Event Effects of transcranial random noise stimulation (tRNS) on the cortical excitability Vera Moliadze1*, L. Chaieb1, D. Terney1, A. Antal1 and W. Paulus1 1 Georg-August University, Germany Transcranial application of weak random noise may appear to be a promising tool for clinical neuroplasticity research, for it allows a painless, selective, focal, non-invasive and reversible excitability modulation of the cortex without an adaptation effect. The “random noise” signal contains all frequencies up to half of the sampling rate, i.e. a maximum of 640 Hz. This random level of current generated for every sample (sampling rate 1280 sps) and is normally distributed; the probability density function follows a bell-shaped curve. Methods: Stimulation was delivered by a battery-driven electrical stimulator (NeuroConn GmbH, Ilmenau, Germany) through conductive-rubber electrodes, placed in two saline-soaked sponges. To detect these current-driven changes of excitability we used single-pulse TMS, frequently employed in these kind of studies. The intensity of the TMS pulse is calibrated before the experiment to induce a motor evoked potential (MEP) amplitude of about 1 mV in the resting first dorsal interosseus muscle. MEP size increases or decreases after an external stimulation of the brain reflecting excitability enhancement or reduction of the motor cortex. Following stimulation, 40 single test-pulse MEPs were recorded at a time constant of 4 +/- 0.04s eight times, i.e. approximately 0 min, 5 min, 10 min post-stimulation and then every 10 minutes up to 60 min. Results: Applying 10 min random noise stimulation over the primary motor cortex induces excitability changes of up to 20-50 %, as revealed by TMS, which lasts for 60 minutes post-stimulation. However, RNS over the premotor cortex did not induce any significant excitability changes. The observed increase in MEP post-stimulation indicates that tRNS application has the ability to modulate levels of cortical excitability. Conference: Bernstein Symposium 2008, Munich, Germany, 8 Oct - 10 Oct, 2008. Presentation Type: Poster Presentation Topic: All Abstracts Citation: Moliadze V, Chaieb L, Terney D, Antal A and Paulus W (2008). Effects of transcranial random noise stimulation (tRNS) on the cortical excitability. Front. Comput. Neurosci. Conference Abstract: Bernstein Symposium 2008. doi: 10.3389/conf.neuro.10.2008.01.091 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Nov 2008; Published Online: 17 Nov 2008. * Correspondence: Vera Moliadze, Georg-August University, Göttingen, Germany, vmoliadze@med.uni-goettingen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vera Moliadze L. Chaieb D. Terney A. Antal W. Paulus Google Vera Moliadze L. Chaieb D. Terney A. Antal W. Paulus Google Scholar Vera Moliadze L. Chaieb D. Terney A. Antal W. Paulus PubMed Vera Moliadze L. Chaieb D. Terney A. Antal W. Paulus Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Analysis of Lipolytic Protein Trafficking and Interactions in Adipocytes

This work examined the colocalization, trafficking, and interactions of key proteins involved in lipolysis during brief cAMP-dependent protein kinase A (PKA) activation. Double label immunofluorescence analysis of 3T3-L1 adipocytes indicated that PKA activation increases the translocation of hormonesensitive lipase (HSL) to perilipin A (Plin)-containing droplets and increases the colocalization of adipose tissue triglyceride lipase (Atgl) with its coactivator, Abhd5. Imaging of live 3T3-L1 preadipocytes transfected with Aquorea victoria-based fluorescent reporters demonstrated that HSL rapidly and specifically translocates to lipid droplets (LDs) containing Plin, and that this translocation is partially dependent on Plin phosphorylation. HSL closely, if not directly, interacts with Plin, as indicated by fluorescence resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) experiments. In contrast, tagged Atgl did not support FRET or BiFC with Plin, although it did modestly translocate to LDs upon stimulation. Abhd5 strongly interacted with Plin in the basal state, as indicated by FRET and BiFC. PKA activation rapidly (within minutes) decreased FRET between Abhd5 and Plin, and this decrease depended upon Plin phosphorylation. Together, these results indicate that Plin mediates hormone-stimulated lipolysis via direct and indirect mechanisms. Plin indirectly controls Atgl activity by regulating accessibility to its coactivator, Abhd5. In contrast, Plin directly regulates the access of HSL to substrate via close, if not direct, interactions. The differential interactions of HSL and Atgl with Plin and Abhd5 also explain the findings that following stimulation, HSL and Atgl are differentially enriched at specific LDs.

Prolactin-Induced Activation of Nuclear Factor κB in Bovine Mammary Epithelial Cells: Role in Chronic Mastitis

We sought to determine whether prolactin (PRL) could influence the neutrophilic inflammation that characterizes chronic mastitis. Most of the genes encoding inflammatory proteins depend on the nuclear factor κB (NF-κB) for their expression. We addressed the hypothesis that immunomodulatory activities of PRL might arise from an increase in NF-κB activity. MAC-T cells, a bovine mammary epithelial cell line, were stimulated with increasing concentrations of bovine PRL (1, 5, 25, 125, and 1,000 ng/mL). Level of NF-κB binding activity was measured and mRNA was evaluated for IL-1β, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GMCSF), IFN-γ, and tumor necrosis factor (TNF)-α, cytokines known to require NF-κB for their maximal transcription. Prolactin activated NF-κB; maximal NF-κB activation was weaker with PRL than with TNF-α at 30 or 180min poststimulation. In addition, PRL significantly amplified, in a dose-dependent manner, mRNA expression of IL-1β, IL-6, IL-8, GMCSF, and TNF-α. We measured PRL concentrations in blood and milk from healthy and chronic mastitis-infected cows, and studied the relationship between the PRL concentration and the degree of inflammation in the mammary gland as indirectly assessed by somatic cell counts (SCC). Plasma PRL did not differ significantly between healthy and chronic mastitis-affected cows (63.7 and 67.5 ng/mL, respectively). Milk PRL concentration was significantly increased in chronic mastitis-affected quarters with the highest SCC, and had a positive significant correlation between SCC, as well as between the number of neutrophils present in milk samples. The present findings show that PRL promotes an inflammatory response in bovine mammary epithelial cells via NF-κB activation, and suggest a role for PRL in the pathogenesis of chronic mastitis.

Monocytes infected withMycobacterium tuberculosisregulate MAP kinase-dependent astrocyte MMP-9 secretion

Tuberculosis (TB) of the CNS (CNS-TB) carries a high mortality. Disease pathology is characterized by widespread destruction of CNS tissues. Matrix metalloproteinase-9 (MMP-9) is able to catabolyze specific components of the CNS tissue matrix and blood-brain barrier. Increased cerebrospinal fluid MMP-9 concentrations are associated with tissue damage, leukocyte infiltration, and death in CNS-TB. Using zymography, Western analysis, and transcription factor assays, we investigated mechanisms regulating MMP-9 activity in CNS-TB. We demonstrate that conditioned media from monocytes infected with Mycobacterium tuberculosis (CoMTB) induce MMP-9 secretion from astrocytes (U373-MG). IL-1beta and TNF-alpha are necessary but not sufficient for such induction of astrocyte MMP-9 secretion. CoMTB up-regulates AP-1 DNA-binding activity, and the c-Jun, FosB, and JunB subunits are particularly increased. MMP-9 secretion from CoMTB-stimulated astrocytes is dependent on the activity of p38, Erk, and Jnk MAPKs. Phosphorylation of p38, Erk, and Jnk is activated rapidly, peaking 30 min poststimulation with CoMTB. Inhibition of IL-1beta but not TNF-alpha in CoMTB decreases p38, Erk, and Jnk activity in astrocytes. Consistently, IL-1beta signals through the MAPK cascade at physiological levels, whereas TNF-alpha, IL-6, IL-10, CCL-2, CCL-5, and CXCL-8 (all present in CoMTB) do not. In summary, the data suggest that monocyte-dependent cytokine networks may play a key role in the development of a matrix-degrading environment during CNS-TB.

The effect of treating infected skin grafts with Acticoat™ on immune cells

A study was conducted to determine the effect of Acticoat™ placed on an infected skin graft on parameters of immunity. Two partial thickness wounds (2 cm × 4 cm) were created on the dorsal midline of Hartley guinea pigs ( n = 28). Wounds were covered with autologous skin graft and maintained either aseptically (Noninoculated, n = 8), inoculated with Staphylococcus aureus (Surgery-Inoculated, n = 8) with or without Acticoat™ bandage (Surgery-Inoculated-Acticoat, n = 6). Five days later, splenocytes and blood were collected to estimate natural killer cell (NK) cytotoxicity, proliferative response to T and B cell mitogens and neutrophil oxidative burst. Animals that did not undergo surgery were included as a nonsurgery control group. [ 3H]-thymidine incorporation in response to a variety of T and B cell mitogens was significantly lower for all groups undergoing surgery compared to the nonsurgery control group ( p < 0.0001) and no additional effect was observed on this immune measure by applying the Acticoat bandage. The Surgery-Inoculated-Acticoat group exhibited greater NK cytotoxic activity (as assessed as the ability to lyse K562 tumor cells) compared to the Surgery-Inoculated group ( p < 0.006). The Surgery-Inoculated-Acticoat group had higher neutrophil oxidative burst at 5 min post stimulation, but was not different from controls after 15 min. In conclusion, the application of an Acticoat™ bandage to an inoculated surgery wound did not alter the low cell-mediated immune response that followed surgery, but appeared to increase parameters (NK cytotoxic activity and neutrophil function) of innate immunity.

Relationship between Cortisol Increment and Basal Cortisol: Implications for the Low-Dose Short Adrenocorticotropic Hormone Stimulation Test

We analyzed the low-dose (1 microg) rapid adrenocorticotropic hormone test (LDST) in 17 patients with a normal hypothalamic-pituitary-adrenal axis to determine reference intervals for the LDST on the basis of poststimulation cortisol increments. We analyzed test results for 17 patients (14 females and 3 males; age range, 18-46 years) who had received a 2-mL aliquot of low-dose (1 microg) adrenocorticotropic hormone prepared from one 250-microg vial of Synacthen diluted in 500 mL of sterile normal saline solution. Sampling took place at 0, 20, 30, and 60 min post stimulation. The cortisol increment was plotted against basal cortisol. We observed a marked interdependence of the basal cortisol concentration with the increase in cortisol concentration. The relationship was inverse and linear with the best fit observed at 30 min post stimulation. The lower 95% prediction limit for basal cortisol at the zero increment was 400 nmol/L with a mean concentration of 600 nmol/L. We propose that a peak cortisol concentration <400 nmol/L is a sufficient single criterion for abnormal adrenal function as assessed by the LDST. Concentrations of 400-600 nmol/L are in the gray area, and those >600 nmol/L confirm normal adrenal function. Repeat analyses with larger sample sizes are warranted to confirm these observations.

IgE-dependent Activation of Sphingosine Kinases 1 and 2 and Secretion of Sphingosine 1-Phosphate Requires Fyn Kinase and Contributes to Mast Cell Responses

Engagement of the high affinity receptor for IgE (FcepsilonRI) on mast cells results in the production and secretion of sphingosine 1-phosphate (S1P), a lipid metabolite present in the lungs of allergen-challenged asthmatics. Herein we report that two isoforms of sphingosine kinase (SphK1 and SphK2) are expressed and activated upon FcepsilonRI engagement of bone marrow-derived mast cells (BMMC). Fyn kinase is required for FcepsilonRI coupling to SphK1 and -2 and for subsequent S1P production. Normal activation of SphK1 and -2 was restored by expression of wild type Fyn but only partly with a kinase-defective Fyn, indicating that induction of SphK1 and SphK2 depended on both catalytic and noncatalytic properties of Fyn. Downstream of Fyn, the requirements for SphK1 activation differed from that of SphK2. Whereas SphK1 was considerably dependent on the adapter Grb2-associated binder 2 and phosphatidylinositol 3-OH kinase, SphK2 showed minimal dependence on these molecules. Fyn-deficient BMMC were defective in chemotaxis and, as previously reported, in degranulation. These functional responses were partly reconstituted by the addition of exogenous S1P to FcepsilonRI-stimulated cells. Taken together with our previous study, which demonstrated delayed SphK activation in Lyn-deficient BMMC, we propose a cooperative role between Fyn and Lyn kinases in the activation of SphKs, which contributes to mast cell responses.

Increased Proliferation and Altered Growth Factor Dependence of Human Mammary Epithelial Cells Overexpressing the Gab2 Docking Protein

The docking protein Gab2 is a proto-oncogene product that is overexpressed in primary breast cancers. To determine the functional consequences of Gab2 overexpression, we utilized the immortalized human mammary epithelial cell line MCF-10A. In monolayer culture, expression of Gab2 at levels comparable with those detected in human breast cancer cells accelerated epidermal growth factor (EGF)-induced cell cycle progression and was associated with increased basal Stat5 tyrosine phosphorylation and enhanced and/or more sustained EGF-induced Erk and Akt activation. Three-dimensional Matrigel culture of MCF-10A cells resulted in the formation of polarized, growth-arrested acini with hollow lumina. Under these conditions, Gab2 increased cell proliferation during morphogenesis, leading to significantly larger acini, an effect dependent on Gab2 binding to Grb2 and Shp2 and enhanced by recruitment of the p85 subunit of phosphatidylinositol 3-kinase. Pharmacological inhibition of MEK revealed that, in addition to direct activation of phosphatidylinositol 3-kinase, increased Erk signaling also contributed to Gab2-mediated enhancement of acinar size. In addition, Gab2 overcame the proliferative suppression that normally occurs in late stage cultures and conferred independence of the morphogenetic program from exogenous EGF. Finally, higher levels of Gab2 expression led to the formation of large disorganized structures with defective luminal clearance. These findings support a role for Gab2 in mammary tumorigenesis.

Epidermal Growth Factor Induces Tyrosine Phosphorylation, Membrane Insertion, and Activation of Transient Receptor Potential Channel 4

Various members of the canonical family of transient receptor potential channels (TRPCs) exhibit increased cation influx following receptor stimulation or Ca(2+) store depletion. Tyrosine phosphorylation of TRP family members also results in increased channel activity; however, the link between the two events is unclear. We report that two tyrosine residues in the C terminus of human TRPC4 (hTRPC4), Tyr-959 and Tyr-972, are phosphorylated following epidermal growth factor (EGF) receptor stimulation of COS-7 cells. This phosphorylation was mediated by Src family tyrosine kinases (STKs), with Fyn appearing to be the dominant kinase. In addition, EGF receptor stimulation induced the exocytotic insertion of hTRPC4 into the plasma membrane dependent on the activity of STKs and was accompanied by a phosphorylation-dependent increase in the association of hTRPC4 with Na(+)/H(+) exchanger regulatory factor. Furthermore, this translocation and association was defective upon mutation of Tyr-959 and Tyr-972 to phenylalanine. Significantly, inhibition of STKs was concomitant with a reduction in Ca(2+) influx in both native COS-7 cells and hTRPC4-expressing HEK293 cells, with cells expressing the Y959F/Y972F mutant exhibiting a reduced EGF response. These findings represent the first demonstration of a mechanism for phosphorylation to modulate TRPC channel function.

Thyrotropin-releasing hormone (protirelin) inhibits potassium-stimulated glutamate and aspartate release from hippocampal slices in vitro

Excess excitatory amino acid release is involved in pathways associated with seizures and neurodegeneration. Thyrotropin-releasing hormone (TRH; protirelin), a brain-derived tripeptide, has shown efficacy in the treatment of such disorders, yet its mechanism of neuroprotection is poorly understood. Using superfused hippocampal slices, we tested the hypothesis that TRH could inhibit evoked glutamate/aspartate release in vitro. Rat hippocampal slices were first equilibrated in oxygenated Krebs buffer (KRB) (120 min) then superfused for 10 min with KRB (control), or KRB containing 0.1, 1, or 10 μM TRH respectively, prior to and during 5 min depolarization with high potassium KRB (50 mM [K +] ± TRH). Fractions (1 min) were collected during the 5 min stimulation and for an additional 10 min thereafter and analyzed for glutamate and aspartate by HPLC. TRH had no effect on baseline glutamate/aspartate release, while all three TRH doses significantly ( P < 0.05) inhibited peak 50 mM [K +]-stimulated glutamate/aspartate release, and glutamate remained below control ( P < 0.05) at 15 min post stimulation. A 5 min pulse of TRH (10 μM) had no affect on basal glutamate/aspartate release, whereas the TRH pre-pulsed slices failed to release glutamate/aspartate by [K +]-stimulation given 15 min later. These results are the first to show a potent and prolonged inhibitory effect of TRH on evoked glutamate/aspartate release in vitro. These initial studies suggest that exogenous and/or endogenous TRH may function, in part, to modulate excess glutamate release in specific CNS loci. Additional studies are in progress to fully understand the mechanism of this potent effect of TRH and its implication in various CNS disorders.

Co-release of noradrenaline and dopamine in the cerebral cortex elicited by single train and repeated train stimulation of the locus coeruleus

BackgroundPrevious studies by our group suggest that extracellular dopamine (DA) and noradrenaline (NA) may be co-released from noradrenergic nerve terminals in the cerebral cortex. We recently demonstrated that the concomitant release of DA and NA could be elicited in the cerebral cortex by electrical stimulation of the locus coeruleus (LC). This study analyses the effect of both single train and repeated electrical stimulation of LC on NA and DA release in the medial prefrontal cortex (mPFC), occipital cortex (Occ), and caudate nucleus. To rule out possible stressful effects of electrical stimulation, experiments were performed on chloral hydrate anaesthetised rats.ResultsTwenty min electrical stimulation of the LC, with burst type pattern of pulses, increased NA and DA both in the mPFC and in the Occ. NA in both cortices and DA in the mPFC returned to baseline within 20 min after the end of the stimulation period, while DA in the Occ reached a maximum increase during 20 min post-stimulation and remained higher than baseline values at 220 min post-stimulation. Local perfusion with tetrodotoxin (TTX, 10 μM) markedly reduced baseline NA and DA in the mPFC and Occ and totally suppressed the effect of electrical stimulation in both areas.A sequence of five 20 min stimulations at 20 min intervals were delivered to the LC. Each stimulus increased NA to the same extent and duration as the first stimulus, whereas DA remained elevated at the time next stimulus was delivered, so that baseline DA progressively increased in the mPFC and Occ to reach about 130 and 200% the initial level, respectively.In the presence of the NA transport (NAT) blocker desipramine (DMI, 100 μM), multiple LC stimulation still increased extracellular NA and DA levels.Electrical stimulation of the LC increased NA levels in the homolateral caudate nucleus, but failed to modify DA level.ConclusionThe results confirm and extend that LC stimulation induces a concomitant release of DA and NA in the mPFC and Occ.The different time-course of LC-induced elevation of DA and NA suggests that their co-release may be differentially controlled.

Different patterns of blood flow response in the trapezius muscle following needle stimulation (acupuncture) between healthy subjects and patients with fibromyalgia and work-related trapezius myalgia

Needle stimulation (acupuncture) has recently been shown to increase blood flow in the tibialis anterior muscle and overlying skin in healthy subjects (HS) and patients with fibromyalgia (FM). The aim of the present study was to examine the effect of needle stimulation on local blood flow in the trapezius muscle and overlying skin in HS and two groups of patients suffering from chronic pain in the trapezius muscle, i.e., FM and work-related trapezius myalgia (TM) patients. Two modes of needling, deep muscle stimulation (Deep) and subcutaneous needle insertion (SC), were performed at the upper part of the shoulder and blood flow was monitored for 60 min post-stimulation. Blood flow changes were measured non-invasively by using a new application of photoplethysmography. Increased blood flow in the trapezius muscle and overlying skin was found in all three groups following both Deep and SC. In HS, Deep was superior to SC in increasing skin and muscle blood flow, whereas in FM, SC was as effective as, or even more effective, than Deep. In the severely affected TM patients, no differences were found between the stimuli, and generally, a lesser blood flow response to the stimuli was found. At Deep, the muscle blood flow increase was significantly larger in HS, compared to the two patient groups. Positive correlations were found between muscle blood flow at Deep and pressure pain threshold in the trapezius muscle, neck movement and pain experienced at the stimulation, and negative correlations were found with spontaneous pain-related variables, symptom duration and age, pointing to less favorable results with worsening of symptoms, and to the importance of nociceptor activation in blood flow increase. It was hypothesized that the different patterns of muscle blood flow response to the needling may mirror a state of increased sympathetic activity and a generalized hypersensitivity in the patients. The intensity of stimulation should be taken into consideration when applying local needle stimulation (acupuncture) in order to increase the trapezius muscle blood flow in chronic pain conditions.

Sphingosine 1-phosphate effect on endothelial cell PAF synthesis: role in cellular migration.

Sphingosine 1-phosphate (S1P) and vascular endothelial growth factor (VEGF) are two inflammatory mediators capable of promoting endothelial cell (EC) migration and angiogenesis. As VEGF inflammatory effect is mediated by the synthesis of endothelial platelet-activating factor (PAF) which is also contributing to VEGF chemotactic activity, we wanted to assess if S1P can trigger PAF synthesis in EC and if S1P-induced migration is PAF-dependent. Treatment of bovine aortic EC (BAEC) with S1P (10(-10)-10(-6) M) increased dose- and time-dependently the synthesis of PAF by up to 3.3-fold above the basal level, with a maximal amount of PAF detected at 20 min post-stimulation. This biological response was attenuated by inhibiting p38 mitogen-activated protein kinase (MAPK), cytosolic or secreted phospholipase A(2) (cPLA(2), sPLA(2)) activity, suggesting that p38 MAPK activation by S1P promotes the conversion of membrane phospholipids into PAF through the combined activation of cPLA(2) and sPLA(2). Interestingly, pretreatment of BAEC with extracellular PAF receptor antagonists (BN52021, 10(-5) M and CV3988, 10(-6) M) reduced by up to 42% the cellular migration induced by S1P (10(-6) M). These data demonstrate the capacity of S1P to induce PAF synthesis, which contributes in part to S1P chemotactic activity.

The Protein-tyrosine Phosphatase SHP-1 Associates with the Phosphorylated Immunoreceptor Tyrosine-based Activation Motif of FcγRIIa to Modulate Signaling Events in Myeloid Cells

Fc gamma RIIa is a low affinity IgG receptor uniquely expressed in human cells that promotes phagocytosis of immune complexes and induces inflammatory cytokine gene transcription. Recent studies have revealed that phagocytosis initiated by Fc gamma RIIa is tightly controlled by the inositol phosphatase SHIP-1, and the protein-tyrosine phosphatase SHP-1. Whereas the molecular nature of SHIP-1 involvement with Fc gamma RIIa has been well studied, it is not clear how SHP-1 is activated by Fc gamma RIIa to mediate its regulatory effect. Here we report that Fc gamma RIIa clustering induces SHP-1 phosphatase activity in THP-1 cells. Using synthetic phosphopeptides, and stable transfectants expressing immunoreceptor tyrosine-based activation motif (ITAM) tyrosine mutants of Fc gamma RIIa, we demonstrate that SHP-1 associates with the phosphorylated amino-terminal ITAM tyrosine of Fc gamma RIIa, whereas the tyrosine kinase Syk associates with the carboxyl-terminal ITAM tyrosine. Association of SHP-1 with Fc gamma RIIa ITAM appears to suppress total cellular tyrosine phosphorylation. Furthermore, Fc gamma RIIa clustering results in the association of SHP-1 with key signaling molecules such as Syk, p85 subunit of PtdIns 3-kinase, and p62dok, suggesting that these molecules may be substrates of SHP-1 in this system. Finally, overexpression of wild-type SHP-1 but not catalytically deficient SHP-1 led to a down-regulation of NF kappa B-dependent gene transcription in THP-1 cells activated by clustering Fc gamma RIIa.

Effects of TENS frequency, intensity and stimulation site parameter manipulation on pressure pain thresholds in healthy human subjects

This study evaluated the effects of varying frequency, intensity and stimulation site, of transcutaneous electrical nerve stimulation (TENS) in an experimental model of pain. In a double-blind design 240 volunteers were randomised to one of six experimental TENS groups, a sham TENS or control ( n=30 per group; gender balanced). Two TENS frequencies (110 or 4 Hz) and two intensities (strong but comfortable or highest tolerable) at a fixed pulse duration (200 μs) were applied at three sites relative to the measurement site (segmentally, extrasegmentally or a combination of these), for 30 min. Pressure pain thresholds (PPT) were measured using a pressure algometer, in the first dorsal interosseous muscle, every 10 min, during stimulation and for a further 30 min. The high frequency, high intensity segmental, and combined stimulation groups, showed rapid onset and significant hypoalgesic effects. This effect was sustained for 20 min post-stimulation in the high frequency segmental group. All other TENS intervention groups showed hypoalgesic responses similar to the sham TENS group, and none of these groups reached a clinically significant hypoalgesic level. Conclusions: The role of TENS frequency, intensity and site are pivotal to achieving optimal hypoalgesic effects, during and after stimulation. Clinical applications of these parameter combinations require further investigations.

Prenatal morphine exposure suppresses mineralocorticoid receptor-dependent basal synaptic transmission and synaptic plasticity in the lateral perforant path in adult male rats

The effects of prenatal morphine exposure (E11–18) on mineralocorticoid receptor (MR) modulation of synaptic plasticity were investigated in the lateral perforant path (LPP)-dentate gyrus granule cell synaptic system. Hippocampal slices were prepared from adult, prenatally saline- or morphine-exposed male rats. One hour prior to decapitation, some adult male rats were injected subcutaneously with saline or the MR antagonist, canrenoic acid (50 mg/kg). LPP was stimulated with high-frequency (2×100 Hz/0.5 s) and short-term plasticity (STP) and long-term potentiation (LTP) were evaluated at 5 and 30 min poststimulation, respectively. Prenatally saline-exposed male rats injected with saline 1 h prior to decapitation showed significantly higher levels of baseline, STP, and LTP than prenatally saline-exposed, canrenoic acid-treated males. In contrast, prenatally morphine-exposed male rats regardless of saline or canrenoic acid injection 1 h prior to decapitation were comparable in their baseline, STP, and LTP activities. Thus, the results demonstrate that canrenoic acid decreases the efficacy of the basal synaptic transmission in the LPP as well as suppresses synaptic plasticity in saline-exposed males. However, in adult morphine-exposed male rats, canrenoic acid has no other or further effects than a saline treatment suggesting that prenatal morphine exposure suppresses MR-dependent basal synaptic transmission as well as synaptic plasticity.

Increased cortical excitability induced by transcranial DC and peripheral nerve stimulation

This study investigated the effect of short periods of simultaneous weak anodal direct current (DC) stimulation and peripheral ulnar nerve (ES) stimulation on corticospinal excitability. The experiments involved repeated testing of ten normal subjects with four different protocols: (1) No Stimulation; (2) DC only; (3) ES only; (4) DC plus ES. Motor evoked potentials (MEP) were recorded from the First Dorsal Interosseous (FDI); Abductor Digiti Minimi (ADM) and Flexor Carpi Ulnaris (FCU). The baseline MEP amplitude was compared with that obtained immediately after the first set of stimulation, after the second set of stimulation, 15 min post stimulation and 30 min after stimulation. No significant change was seen with the No Stimulation and ES Only protocols. FDI showed a significant change in the DC protocol after the second set of stimulation but the changes were not present 15 or 30 min after. The DC plus ES protocol showed FDI changes that were significant after the second set of stimulation with the elevations persisting when tested 15 and 30 min post intervention. These observations show that a period of anodal DC stimulation preceding a period of ulnar nerve stimulation resulted in significant and persistent elevations in cortical excitability.

Trigeminal modulation of gustatory neurons in the nucleus of the solitary tract

Electrophysiological methods were used to investigate the effects of trigeminal nerve stimulation or transection on responses of single gustatory neurons in the nucleus of the solitary tract (NTS) to tastants (NaCl, sucrose, citric acid, monosodium glutamate) in pentobarbital-anesthetized rats. Unilateral transection of the lingual nerve, or the mandibular branch of the trigeminal nerve, resulted in significant reductions (by 21 and 29%, respectively; P<0.01) in tastant-evoked responses, with no further effect following bilateral transection. Electrical stimulation of the central cut end of the mandibular nerve directly excited nine of 14 gustatory NTS units. For these units, central mandibular stimulation facilitated the tastant-evoked responses in six, depressed responses in three, and had no effect in five. Facilitation of tastant-evoked responses peaked 4 min after mandibular stimulation and recovered within 8 min. Electrical stimulation of the peripheral cut end of the mandibular nerve significantly reduced tastant-evoked responses in nine other NTS units, with a maximal reduction at 4 min post-stimulation followed by recovery. Stimulation of the superior cervical sympathetic ganglion did not affect NTS tastant-evoked responses. These results suggest the presence of complex central modulation of NTS neurons by trigeminal afferents, as well as a peripheral depressant effect on gustatory processing possibly mediated via neuropeptide release from trigeminal nerve endings in the tongue.

Adrenal suppression from high-dose inhaled fluticasone propionate in children with asthma.

This cross-sectional study was designed to examine the prevalence of adrenocortical suppression in children with asthma treated with high-dose inhaled fluticasone propionate (FP). Children and adolescents (n=50) with asthma, treated with inhaled FP at a dose of > or = 1,000 mg a day for > or = 6 months, were enrolled. Early morning serum cortisol was performed. Subjects with a serum cortisol of < 400 nmol x L(-1) had a tetracosactrin stimulation test. Fifty subjects of mean age 13.1 yrs were treated with a mean dose of 924.7 microg x m(-2) x day(-1) FP for a mean duration of 2 yrs. Of the 50 subjects, 36 (72%) had serum cortisol levels of < 400 nmol x L(-1) and underwent tetracosactrin stimulation test. Of these, 6 (17%) demonstrated a less than two-fold increase in serum cortisol from baseline and peak cortisol level of < or = 550 nmol x L(-1) at 30 or 60 min poststimulation. There was a significant negative correlation between the dose of FP x m(-2) and stimulated peak cortisol level. Biochemical evidence of adrenocortical insufficiency was demonstrated in 12% of the subjects, indicating that high-dose fluticasone propionate use may be associated with dose-dependent adrenocortical suppression.