Measurement of pitch perception as a function of cochlear implant electrode and its effect on speech perception with different frequency allocations.

OBJECTIVE: An experiment was conducted to investigate the possibility that speech perception could be improved for some cochlear implant (CI) users by adjustment of the frequency allocation to the electrodes, following assessment of pitch perception along the electrode array. STUDY SAMPLE: Thirteen adult CI users with MED-EL devices participated in the study. DESIGN: Pitch perception was assessed for individual CI electrode pairs using the Pitch Contour Test (PCT), giving information on pitch discrimination and pitch ranking for adjacent electrodes. Sentence perception in noise was also assessed with ten different frequency allocations, including the default. RESULTS: Pitch perception was found to be poorer for both discrimination and ranking scores at either end of the electrode array. A significant effect of frequency allocation was found for sentence scores [F(4.24,38.2) = 7.14, p < 0.001] and a significant interaction between sentence score and PCT ranking score for basal electrodes was found [F(4.24,38.2) = 2.95, p = 0.03]. Participants with poorer pitch perception at the basal end had poorer scores for some allocations with greater basal shift. CONCLUSIONS: The results suggest that speech perception could be improved for CI users by assessment of pitch perception using the PCT and subsequent adjustment of pitch-related stimulation parameters.

Potent and multiple regulatory actions of microglial glucocorticoid receptors during CNS inflammation.

In CNS, glucocorticoids (GCs) activate both GC receptor (GR) and mineralocorticoid receptor (MR), whereas GR is widely expressed, the expression of MR is restricted. However, both are present in the microglia, the resident macrophages of the brain and their activation can lead to pro- or anti-inflammatory effects. We have therefore addressed the specific functions of GR in microglia. In mice lacking GR in macrophages/microglia and in the absence of modifications in MR expression, intraparenchymal injection of lipopolysaccharide (LPS) activating Toll-like receptor 4 signaling pathway resulted in exacerbated cellular lesion, neuronal and axonal damage. Global inhibition of GR by RU486 pre-treatment revealed that microglial GR is the principal mediator preventing neuronal degeneration triggered by lipopolysaccharide (LPS) and contributes with GRs of other cell types to the protection of non-neuronal cells. In vivo and in vitro data show GR functions in microglial differentiation, proliferation and motility. Interestingly, microglial GR also abolishes the LPS-induced delayed outward rectifier currents by downregulating Kv1.3 expression known to control microglia proliferation and oxygen radical production. Analysis of GR transcriptional function revealed its powerful negative control of pro-inflammatory effectors as well as upstream inflammatory activators. Finally, we analyzed the role of GR in chronic unpredictable mild stress and aging, both known to prime or sensitize microglia in vivo. We found that microglial GR suppresses rather than mediates the deleterious effects of stress or aging on neuronal survival. Overall, the results show that microglial GR acts on several key processes limiting pro-inflammatory actions of activated microglia.

Expression of neuronal markers in the endometrium of women with and those without endometriosis.

STUDY QUESTION: How do the expression patterns of neuronal markers differ in the endometrium of women with and without endometriosis? SUMMARY ANSWER: The neuronal markers, PGP9.5, NGFp75 and VR1, are expressed in the endometrium at levels that do not differ between women with and without endometriosis. WHAT IS KNOWN ALREADY: Aberrant neuronal growth within the uterus may contribute to abnormal fertility and uterine dysfunction. However, controversy still exists as to whether aberrant innervation in the endometrium is associated with gynaecological pathology such as endometriosis. This may reflect the use of subjective methods such as histology to assess the innervation of the endometrium. We, therefore, employed a quantitative method, western blotting, to study markers of endometrial innervation in the presence and absence of endometriosis. STUDY DESIGN, SIZE, DURATION: This study included 45 women undergoing laparoscopic examination for the diagnosis of endometriosis. Endometrial samples were analysed by western blot for the expression of neuronal and neurotrophic markers, PGP9.5, VR1 and NGFp75. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: Endometrial pipelle biopsies were obtained from patients with (n = 20, study group) and without (n = 25, control group) endometriosis. Tissue was analysed by immunohistochemistry and western blot analysis for the expression of pan-neuronal marker, PGP9.5, sensory nociceptive marker, TPVR1, and low-affinity neurotrophic growth factor receptor, NGFRp75. MAIN RESULTS AND THE ROLE OF CHANCE: PGP9.5, NGFp75 and VR1 were expressed in the endometrium of women, independent of the presence of endometriosis. Furthermore, the expression level of PGP9.5, VR1 and NGFp75 did not alter between the two cohorts of women. LIMITATIONS, REASONS FOR CAUTION: Studies of this nature are subject to the heterogeneous nature of patient population and tissue samples despite attempts to standardize these parameters. Hence, further studies using similar methodology will be required to confirm our results. WIDER IMPLICATIONS OF THE FINDINGS: Our results highlight that sensory neuronal markers are present in women with and without endometriosis. Future work will assess what the targets of the endometrial nerves are and investigate their function, their impact on endometrial biology and, in particular, whether aberrant neuronal function, rather than the mere presence of neuronal function, could be the root cause of subfertility and/or pain affecting many endometriosis sufferers. Our results do not, however, confirm the previous paradigm of increased innervation in the endometrium of women with endometriosis, nor the use of nerve cell detection from pipelle biopsies to diagnose endometriosis.

Activation of TrkB receptors by NGFß mimetic peptide conjugated polymersome nanoparticles.

Activation of tyrosine kinase receptor B (TrkB), a neurotrophin receptor, has been shown to increase neuronal cell survival and promote regeneration. Stimulation of the TrkB receptor by neurotrophic growth factors has been identified as a possible therapeutic target for the treatment of neurodegenerative disorders. However, growth factor delivery is problematic because of a short half-life in vivo. We have conjugated hNgf-EE, a short peptide mimetic of NGFß to the surface of polymersome nanoparticles and shown that they are capable of activating the TrkB receptor in vitro in the SHSY-G7 cell line. We propose that polymersomes could act as a scaffold for the delivery of TrkB activating moieties and that the polymersome size and polyethylene glycol surface have been shown to increase in vivo retention time. These multifunctional nanoparticles have potential for the treatment of neurodegenerative disorders by TrkB activation. From the ClinicaL Editor: Tyrosine kinase receptor B activation has been shown to promote regeneration and survival of neurons. However, growth factor delivery to stimulate these receptors remains problematic. The authors demonstrate that a peptide mimetic of NGFß conjugated to the surface of polymersome nanoparticles is capable of activating the TrkB receptors. These nanoparticles may offer a novel treatment strategy for a variety of neurodegenerative disorders.

The effect of non-steroidal anti-inflammatory agents on behavioural changes and cytokine production following systemic inflammation: Implications for a role of COX-1.

Systemic inflammation gives rise to metabolic and behavioural changes, largely mediated by pro-inflammatory cytokines and prostaglandin production (PGE(2)) at the blood-brain barrier. Despite numerous studies, the exact biological pathways that give rise to these changes remains elusive. This study investigated the mechanisms underlying immune-to-brain communication following systemic inflammation using various anti-inflammatory agents. Mice were pre-treated with selective cyclo-oxygenase (COX) inhibitors, thromboxane synthase inhibitors or dexamethasone, followed by intra-peritoneal injection of lipopolysaccharide (LPS). Changes in body temperature, open-field activity, and burrowing were assessed and mRNA and/or protein levels of inflammatory mediators measured in serum and brain. LPS-induced systemic inflammation resulted in behavioural changes and increased production of IL-6, IL-1beta and TNF-alpha, as well as PGE(2) in serum and brain. Indomethacin and ibuprofen reversed the effect of LPS on behaviour without changing peripheral or central IL-6, IL-1beta and TNF-alpha mRNA levels. In contrast, dexamethasone did not alter LPS-induced behavioural changes, despite complete inhibition of cytokine production. A selective COX-1 inhibitor, piroxicam, but not the selective COX-2 inhibitor, nimesulide, reversed the LPS-induced behavioural changes without affecting IL-6, IL-1beta and TNF-alpha protein expression levels in the periphery or mRNA levels in the hippocampus. Our results suggest that the acute LPS-induced changes in burrowing and open-field activity depend on COX-1. We further show that COX-1 is not responsible for the induction of brain IL-6, IL-1beta and TNF-alpha synthesis or LPS-induced hypothermia. Our results may have implications for novel therapeutic strategies to treat or prevent neurological diseases with an inflammatory component.

Solutes, but not cells, drain from the brain parenchyma along basement membranes of capillaries and arteries: significance for cerebral amyloid angiopathy and neuroimmunology.

UNLABELLED: Elimination of interstitial fluid and solutes plays a role in homeostasis in the brain, but the pathways are unclear. Previous work suggests that interstitial fluid drains along the walls of arteries. AIMS: to define the pathways within the walls of capillaries and arteries for drainage of fluid and solutes out of the brain. METHODS: Fluorescent soluble tracers, dextran (3 kDa) and ovalbumin (40 kDa), and particulate fluospheres (0.02 microm and 1.0 microm in diameter) were injected into the corpus striatum of mice. Brains were examined from 5 min to 7 days by immunocytochemistry and confocal microscopy. RESULTS: soluble tracers initially spread diffusely through brain parenchyma and then drain out of the brain along basement membranes of capillaries and arteries. Some tracer is takenf up by vascular smooth muscle cells and by perivascular macrophages. No perivascular drainage was observed when dextran was injected into mouse brains following cardiac arrest. Fluospheres expand perivascular spaces between vessel walls and surrounding brain, are ingested by perivascular macrophages but do not appear to leave the brain even following an inflammatory challenge with lipopolysaccharide or kainate. CONCLUSIONS: capillary and artery basement membranes act as 'lymphatics of the brain' for drainage of fluid and solutes; such drainage appears to require continued cardiac output as it ceases following cardiac arrest. This drainage pathway does not permit migration of cells from brain parenchyma to the periphery. Amyloid-beta is deposited in basement membrane drainage pathways in cerebral amyloid angiopathy, and may impede elimination of amyloid-beta and interstitial fluid from the brain in Alzheimer's disease. Soluble antigens, but not cells, drain from the brain by perivascular pathways. This atypical pattern of drainage may contribute to partial immune privilege of the brain and play a role in neuroimmunological diseases such as multiple sclerosis.

Overexpression of tau results in defective synaptic transmission in Drosophila neuromuscular junctions.

Synaptic dysfunction is believed to be an early pathological change in neurodegenerative diseases and may cause the earliest clinical symptoms. We have used Drosophila to model a tauopathy in order to analyse the earliest neuronal and synaptic dysfunction. Our work has shown that overexpression of human tau (0N3R) in larval motor neurons causes a disruption of axonal transport and a morphological and functional disruption of NMJs (neuromuscular junctions). Tau-expressing NMJs are smaller with an abnormal structure. Despite abnormal morphology, tau-expressing NMJs retain synaptotagmin expression and can form active zones. Tau-expressing NMJs are functionally abnormal and exhibit disrupted vesicle cycling and synaptic transmission. At low-frequency stimulation (1 Hz), ESPs (evoked synaptic potentials) produced by tau-expressing motor neurons were indistinguishable from wild-type; however, following high-frequency stimulation (50 Hz), ESPs from tau-expressing NMJs were significantly decreased in amplitude. To investigate the mechanism underlying the change in ESPs, we analysed the relative numbers and distribution of mitochondria. This revealed that motor neurons expressing tau had a significant reduction in the number of detectable mitochondria in the pre-synaptic terminal. Our results demonstrate that tau overexpression results in synaptic dysfunction, associated with a reduced complement of functional mitochondria. These findings suggest that disruption of axonal transport and synaptic transmission may be key components of the pathogenic mechanism that underlie neuronal dysfunction in the early stages of tauopathies.

Cytokine-induced enhancement of autoimmune inflammation in the brain and spinal cord: implications for multiple sclerosis.

UNLABELLED: Multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) are autoimmune inflammatory diseases in which cytokines are intimately involved. Here we test the hypothesis that injection of pro-inflammatory cytokines, tumour necrosis factor-alpha (TNFalpha) and interferon gamma (IFNgamma) into the brain of animals in the prodromal phase of EAE significantly enhances inflammation in the central nervous system (CNS). We were particularly interested to learn whether a local increase in cytokines influenced the pathology locally, or more extensively, within the CNS. EAE was induced in female adult Lewis rats. Eight days post-inoculation, TNFalpha or INFgamma was injected into one cerebral hemisphere. Days 11 and 13 post-inoculation (3 and 5 days after the injection of cytokine) inflammation was quantified by the number of perivascular cuffs and the degree of major histocompatibility complex (MHC) class II expression by microglia. Normal animals injected with cytokines, and EAE animals with saline injection served as controls. RESULTS: microglial activation was increased three- to fourfold in the brain and eightfold in the spinal cord (P

GSK-3beta inhibition reverses axonal transport defects and behavioural phenotypes in Drosophila.

The tauopathies are a group of disorders characterised by aggregation of the microtubule-associated protein tau and include Alzheimer's disease (AD) and the fronto-temporal dementias (FTD). We have used Drosophila to analyse how tau abnormalities cause neurodegeneration. By selectively co-expressing wild-type human tau (0N3R isoform) and a GFP vesicle marker in motorneurons, we examined the consequences of tau overexpression on axonal transport in vivo. The results show that overexpression of tau disrupts axonal transport causing vesicle aggregation and this is associated with loss of locomotor function. All these effects occur without neuron death. Co-expression of constitutively active glycogen-synthase kinase-3beta (GSK-3beta) enhances and two GSK-3beta inhibitors, lithium and AR-A014418, reverse both the axon transport and locomotor phenotypes, suggesting that the pathological effects of tau are phosphorylation dependent. These data show that tau abnormalities significantly disrupt neuronal function, in a phosphorylation-dependent manner, before the classical pathological hallmarks are evident and also suggest that the inhibition of GSK-3beta might have potential therapeutic benefits in tauopathies.

T-cell- and macrophage-mediated axon damage in the absence of a CNS-specific immune response: involvement of metalloproteinases.

Recent evidence has highlighted the fact that axon injury is an important component of multiple sclerosis pathology. The issue of whether a CNS antigen-specific immune response is required to produce axon injury remains unresolved. We investigated the extent and time course of axon injury in a rodent model of a delayed-type hypersensitivity (DTH) reaction directed against the mycobacterium bacille Calmette-Guérin (BCG). Using MRI, we determined whether the ongoing axon injury is restricted to the period during which the blood-brain barrier is compromised. DTH lesions were initiated in adult rats by intracerebral injection of heat-killed BCG followed by a peripheral challenge with BCG. Our findings demonstrate that a DTH reaction to a non-CNS antigen within a CNS white matter tract leads to axon injury. Ongoing axon injury persisted throughout the 3-month period studied and was not restricted to the period of blood-brain barrier breakdown, as detected by MRI enhancing lesions. We have previously demonstrated that matrix metalloproteinases (MMPs) are upregulated in multiple sclerosis plaques and DTH lesions. In this study we demonstrated that microinjection of activated MMPs into the cortical white matter results in axon injury. Our results show that axon injury, possibly mediated by MMPs, is immunologically non-specific and may continue behind an intact blood-brain barrier.

Role of chemokines, neuronal projections, and the blood-brain barrier in the enhancement of cerebral EAE following focal brain damage.

The role of focal brain damage as a trigger for autoimmune inflammation in multiple sclerosis (MS) is unclear. In this study we examine mechanisms by which experimental autoimmune encephalomyelitis (EAE) is enhanced by focal brain damage. EAE was produced in Lewis rats by footpad inoculation; focal brain damage, in the form of a cortical cryolesion (cryolesion-EAE), was induced 8 days post-inoculation (d.p.i.). The distribution of inflammation and chemokine production in cryolesion-EAE and EAE-only were compared. Inflammation in the brain, measured by immunocytochemistry for T lymphocytes (W3/13) and microglial activation (MHC class II -OX6), was significantly enhanced in cryolesion-EAE 11-15 d.p.i. (p < 0.01-0.05) but by 20-40 d.p.i., equated with EAE-only. Inflammation in cryolesion-EAE related to breakdown of the blood-brain barrier (BBB) at the site of the cryolesion and also to the corticospinal tracts and thalamus, reflecting the afferent and efferent neuronal connections with the cryolesioned cortex. Semiquantitative RT/PCR dot-blot hybridization assay showed a 6-fold increase in mRNA for specific chemokines in the brain in cryolesion-EAE at 9 d.p.i. (MCP-1) and 11 d.p.i. (MCP-1 and MCP-5) with no significant increase in RANTES, GRO-alpha, or MIP-1alpha. By 14 d.p.i., the levels of MCP-1 and MCP-5 mRNA equated with EAE-only animals. These results suggest that enhancement and location of autoimmune inflammation in the brain following focal cortical injury initially involve chemokines such as the macrophage chemoattractants MCP-1 and MCP-5, and the activities of afferent and efferent neuronal connections with the site of damage. By analogy, similar factors may modulate or reactivate autoimmune inflammation in MS.

Simultaneous time-varying systemic appearance of oral and hepatic glucose in adults monitored with stable isotopes.

The rates (and extent) of appearance of glucose in arterialized plasma from an oral glucose load and from liver (RaO, RaH) can be estimated in humans using radioisotopes, but estimates vary among laboratories. We investigated the use of stable isotopes and undertook 22 primed intravenous infusions of D-[6,6-2H2]glucose with an oral load including D-[13C6]glucose in healthy humans. The effective glucose pool volume (VS) had a lower limit of 230 ml/kg body weight (cf. 130 ml/kg commonly assumed). This VS in Steele's one-compartment model of glucose kinetics gave a systemic appearance from a 50-g oral glucose load per 70 kg body weight of 96 +/- 3% of that ingested, which compared with a theoretical value of approximately 95%. Mari's two-compartment model gave 100 +/- 3%. The two models gave practically identical RaO and RaH at each point in time and a plateau in the cumulative RaO when absorption was complete. Less than 3% of 13C was recycled to [13C3]glucose, suggesting that recycling errors were practically negligible in this study. Causes of variation among laboratories are identified. We conclude that stable isotopes provide a reliable and safe alternative to radioactive isotopes in these studies.

Cerebral amyloid angiopathy: amyloid beta accumulates in putative interstitial fluid drainage pathways in Alzheimer's disease.

Cerebral amyloid angiopathy in Alzheimer's disease is characterized by deposition of amyloid beta (Abeta) in cortical and leptomeningeal vessel walls. Although it has been suggested that Abeta is derived from vascular smooth muscle, deposition of Abeta is not seen in larger cerebral vessel walls nor in extracranial vessels. In the present study, we examine evidence for the hypothesis that Abeta is deposited in periarterial interstitial fluid drainage pathways of the brain in Alzheimer's disease and that this contributes significantly to cerebral amyloid angiopathy. There is firm evidence in animals for drainage of interstitial fluid from the brain to cervical lymph nodes along periarterial spaces; similar periarterial channels exist in humans. Biochemical study of 6 brains without Alzheimer's disease revealed a pool of soluble Abeta in the cortex. Histology and immunocytochemistry of 17 brains with Alzheimer's disease showed that Abeta accumulates five times more frequently around arteries than around veins, with selective involvement of smaller arteries. Initial deposits of Abeta occur at the periphery of arteries at the site of the putative interstitial fluid drainage pathways. These observations support the hypothesis that Abeta is deposited in periarterial interstitial fluid drainage pathways of the brain and contributes significantly to cerebral amyloid angiopathy in Alzheimer's disease.