Ionotropic Glutamate Receptors Show Unique Distribution and Localization in the Dorsal Cochlear Nucleus of the Rhesus Monkey

The dorsal cochlear nucleus (DCN) receives auditory information via the auditory nerve coming from the cochlea. It is responsible for much of the integration of auditory information, and it projects this auditory information to higher auditory brain centers for further processing. This study focuses on the DCN of adult Rhesus monkeys to characterize two specific cell types, the fusiform and cartwheel cell, based on morphometric parameters and type of glutamate receptor they express. The fusiform cell is the main projection neuron, while the cartwheel cell is the main inhibitory interneuron. Expression of AMPA glutamate receptor subunits is localized to certain cell types. The activity of the CN depends on the AMPA receptor subunit composition and expression. Immunocytochemistry, using specific antibodies for AMPA glutamate receptor subunits GluR1, GluR2/3 and GluR4, was used in conjunction with morphometry to determine the location, morphological characteristics and expression of AMPA receptor subunits in fusiform and cartwheel cells in the primate DCN. Qualitative as well as quantitative data indicates that there are important morphological differences in cell location and expression of AMPA glutamate receptor subunits between the rodent DCN and that of primates. GluR2/3 is widely expressed in the primate DCN. GluR1 is also widely expressed in the primate DCN. GluR4 is diffusely expressed. Expression of GluR2/3 and GluR4 in the primate is similar to that of the rodent. However, expression of GluR1 is different. GluR1 is only expressed by cartwheel cells in the rodent DCN, but is expressed by a variety of cells, including fusiform cells, in the DCN of the primate.

Stochastic beamforming for cochlear implant coding

Cochlear implants are prosthetic devices used to provide hearing to people who would otherwise be profoundly deaf. The deliberate addition of noise to the electrode signals could increase the amount of information transmitted, but standard cochlear implants do not replicate the noise characteristic of normal hearing because if noise is added in an uncontrolled manner with a limited number of electrodes then it will almost certainly lead to worse performance. Only if partially independent stochastic activity can be achieved in each nerve fibre can mechanisms like suprathreshold stochastic resonance be effective. We are investigating the use of stochastic beamforming to achieve greater independence. The strategy involves presenting each electrode with a linear combination of independent Gaussian noise sources. Because the cochlea is filled with conductive salt solutions, the noise currents from the electrodes interact and the effective stimulus for each nerve fibre will therefore be a different weighted sum of the noise sources. To some extent therefore, the effective stimulus for a nerve fibre will be independent of the effective stimulus of neighbouring fibres. For a particular patient, the electrode position and the amount of current spread are fixed. The objective is therefore to find the linear combination of noise sources that leads to the greatest independence between nerve discharges. In this theoretical study we show that it is possible to get one independent point of excitation (one null) for each electrode and that stochastic beamforming can greatly decrease the correlation between the noise exciting different regions of the cochlea. © 2007 Copyright SPIE - The International Society for Optical Engineering.

Changes In The Connective Tissue Sheath Of Wistar Rat Nerve With Aging.

The alterations due to aging in the peripheral nerves can affect the physiology of these structures. Thus, the purpose of the present study was to describe the activity of the MMP-2 and MMP-9, as well as the structure and composition of the extracellular matrix of the rat sciatic nerve during maturation and aging. Our results have shown that the extracellular matrix of the sciatic nerve of 30-, 180- and 730-day-old Wistar rats present ultrastructural, morphometrical and biochemical changes during aging. The perineurium was the structure most affected by age, as evidenced by a decrease in thickness and in collagen fibril content. Cytochemical analysis detected proteoglycans in the basal membrane of Schwann cells and around perineural cells, as well as on the collagen fibrils of the perineurium and endoneurium at all ages. Biochemical analyses showed that the quantity of non-collagenous proteins was higher in 730-day-old animals compared to other ages, while the uronic acid content was higher in 30-day-old animals. Morphometrical analysis detected greater numbers of myelinated fibers and increased myelin thickness in 180-day-old animals. Zymography analysis detected greater amounts and activity of MMP-2 and MMP-9 in 180- and 730-day-old animals compared to younger rats. In conclusion, our results showed changes in the structural organization and composition of extracellular matrix of the sciatic nerve during aging, such as increase in the non-collagenous protein content and higher MMP-2 and MMP-9 activity, decrease in uronic acid concentration and in collagen fibril content in the perineurium, as well as degeneration of nerve fibers.

Granulocyte Colony-stimulating Factor (g-csf) Positive Effects On Muscle Fiber Degeneration And Gait Recovery After Nerve Lesion In Mdx Mice.

G-CSF has been shown to decrease inflammatory processes and to act positively on the process of peripheral nerve regeneration during the course of muscular dystrophy. The aims of this study were to investigate the effects of treatment of G-CSF during sciatic nerve regeneration and histological analysis in the soleus muscle in MDX mice. Six-week-old male MDX mice underwent left sciatic nerve crush and were G-CSF treated at 7 days prior to and 21 days after crush. Ten and twenty-one days after surgery, the mice were euthanized, and the sciatic nerves were processed for immunohistochemistry (anti-p75(NTR) and anti-neurofilament) and transmission electron microscopy. The soleus muscles were dissected out and processed for H&E staining and subsequent morphologic analysis. Motor function analyses were performed at 7 days prior to and 21 days after sciatic crush using the CatWalk system and the sciatic nerve index. Both groups treated with G-CSF showed increased p75(NTR) and neurofilament expression after sciatic crush. G-CSF treatment decreased the number of degenerated and regenerated muscle fibers, thereby increasing the number of normal muscle fibers. The reduction in p75(NTR) and neurofilament indicates a decreased regenerative capacity in MDX mice following a lesion to a peripheral nerve. The reduction in motor function in the crushed group compared with the control groups may reflect the cycles of muscle degeneration/regeneration that occur postnatally. Thus, G-CSF treatment increases motor function in MDX mice. Nevertheless, the decrease in baseline motor function in these mice is not reversed completely by G-CSF.

Fracture Of Distal Humerus: Mipo Technique With Visualization Of The Radial Nerve.

To evaluate the outcomes in patients treated for humerus distal third fractures with MIPO technique and visualization of the radial nerve by an accessory approach, in those without radial palsy before surgery. The patients were treated with MIPO technique. The visualization and isolation of the radial nerve was done by an approach between the brachialis and the brachiorradialis, with an oblique incision, in the lateral side of the arm. MEPS was used to evaluate the elbow function. Seven patients were evaluated with a mean age of 29.8 years old. The average follow up was 29.85 months. The radial neuropraxis after surgery occurred in three patients. The sensorial recovery occurred after 3.16 months on average and also of the motor function, after 5.33 months on average, in all patients. We achieved fracture consolidation in all patients (M=4.22 months). The averages for flexion-extension and prono-supination were 112.85° and 145°, respectively. The MEPS average score was 86.42. There was no case of infection. This approach allowed excluding a radial nerve interposition on site of the fracture and/or under the plate, showing a high level of consolidation of the fracture and a good evolution of the range of movement of the elbow. Level of Evidence IV, Case Series.

Effects Of Misalignments In The Retinal Nerve Fiber Layer Thickness Measurements With Spectral Domain Optical Coherence Tomography.

Purpose. To investigate misalignments (MAs) on retinal nerve fiber layer thickness (RNFLT) measurements obtained with Cirrus(©) SD-OCT. Methods. This was a retrospective, observational, cross-sectional study. Twenty-seven healthy and 29 glaucomatous eyes of 56 individuals with one normal exam and another showing MA were included. MAs were defined as an improper alignment of vertical vessels in the en face image. MAs were classified in complete MA (CMA) and partial MA (PMA), according to their site: 1 (superior, outside the measurement ring (MR)), 2 (superior, within MR), 3 (inferior, within MR), and 4 (inferior, outside MR). We compared RNFLT measurements of aligned versus misaligned exams in all 4 sectors, in the superior area (sectors 1 + 2), inferior area (sectors 3 + 4), and within the measurement ring (sectors 2 + 3). Results. RNFLT measurements at 12 clock-hour of eyes with MAs in the superior area (sectors 1 + 2) were significantly lower than those obtained in the same eyes without MAs (P = 0.043). No significant difference was found in other areas (sectors 1 + 2 + 3 + 4, sectors 3 + 4, and sectors 2 + 3). Conclusion. SD-OCT scans with superior MAs may present lower superior RNFLT measurements compared to aligned exams.

Hearing Preservation And Cochlear Implants According To Inner Ear Approach: Multicentric Evaluation.

Electroacoustic stimulation is an excellent option for people with residual hearing in the low frequencies, who obtain insufficient benefit with hearing aids. To be effective, the subject's residual hearing should be preserved during cochlear implant surgery. To evaluate the hearing preservation in patients that underwent implant placement and to compare the results in accordance with the approach to the inner ear. 19 subjects underwent a soft surgical technique, and the electrode MED-EL FLEX™ EAS, designed to be atraumatic, was used. We evaluated pre- and postoperative tonal audiometric tests with an average of 18.4 months after implantation, to measure the rate of hearing preservation. 17 patients had total or partial preservation of residual hearing; 5 had total hearing preservation and two individuals had no preservation of hearing. The insertion of the electrode occurred through a cochleostomy in 3 patients, and in 2 of these there was no hearing preservation; the other 16 patients experienced electrode insertion through a round window approach. All patients benefited from the cochlear implant, even those who are only using electrical stimulation. The hearing preservation occurred in 89.4% of cases. There was no significant difference between the forms of inner ear approach.

Transcutaneous Tibial Nerve Stimulation In The Treatment Of Lower Urinary Tract Symptoms And Its Impact On Health-related Quality Of Life In Patients With Parkinson Disease: A Randomized Controlled Trial.

A randomized controlled trial study was performed to evaluate the efficacy of transcutaneous tibial nerve stimulation (TTNS) and sham TTNS, in patients with Parkinson disease (PD) with lower urinary tract symptoms (LUTS). Randomized controlled trial. Thirteen patients with a diagnosis of PD and bothersome LUTS were randomly allocated to one of the following groups: Group I: TTNS group (n = 8) and group II: Sham group (n = 5). Both groups attended twice a week during 5 weeks; each session lasted 30 minutes. Eight patients received TTNS treatment and 5 subjects allocated to group II were managed with sham surface electrodes that delivered no electrical stimulation. Assessments were performed before and after the treatment; they included a 3-day bladder diary, Overactive Bladder Questionnaire (OAB-V8), and the International Consultation on Incontinence Quality of Life Questionnaire Short Form (ICIQ-SF), and urodynamic evaluation. Following 5 weeks of treatment, patients allocated to TTNS demonstrated statistically significant reductions in the number of urgency episodes (P = .004) and reductions in nocturia episodes (P < .01). Participants allocated to active treatment also showed better results after treatment in the OAB-V8 and ICIQ-SF scores (P < .01, respectively). Urodynamic testing revealed that patients in the active treatment group showed improvements in intravesical volume at strong desire to void (P < .05) and volume at urgency (P < .01) when compared to subjects in the sham treatment group. These findings suggest that TTNS is effective in the treatment of LUTS in patients with PD, reducing urgency and nocturia episodes and improving urodynamic parameters as well as symptom scores measured by the OAB-V8 and health-related quality-of-life scores measured by the ICIQ-SF.

The Neuromuscular Activity Of Bothriopsis Bilineata Smaragdina (forest Viper) Venom And Its Toxin Bbil-tx (asp49 Phospholipase A2) On Isolated Mouse Nerve-muscle Preparations.

The presynaptic action of Bothriopsis bilineata smaragdina (forest viper) venom and Bbil-TX, an Asp49 PLA2 from this venom, was examined in detail in mouse phrenic nerve-muscle (PND) preparations in vitro and in a neuroblastoma cell line (SK-N-SH) in order to gain a better insight into the mechanism of action of the venom and associated Asp49 PLA2. In low Ca(2+) solution, venom (3μg/ml) caused a quadriphasic response in PND twitch height whilst at 10μg/ml the venom additionally induced an abrupt and marked initial contracture followed by neuromuscular facilitation, rhythmic oscillations of nerve-evoked twitches, alterations in baseline and progressive blockade. The venom slowed the relaxation phase of muscle twitches. In low Ca(2+), Bbil-TX [210nM (3μg/ml)] caused a progressive increase in PND twitch amplitude but no change in the decay time constant. Venom (10μg/ml) and Bbil-TX (210nM) caused minor changes in the compound action potential (CAP) amplitude recorded from sciatic nerve preparations, with no significant effect on rise time and latency; tetrodotoxin (3.1nM) blocked the CAP at the end of the experiments. In mouse triangularis sterni nerve-muscle (TSn-m) preparations, venom (10μg/ml) and Bbil-TX (210nM) significantly reduced the perineural waveform associated with the outward K(+) current while the amplitude of the inward Na(+) current was not significantly affected. Bbil-TX (210nM) caused a progressive increase in the quantal content of TSn-m preparations maintained in low Ca(2+) solution. Venom (3μg/ml) and toxin (210nM) increased the calcium fluorescence in SK-N-SH neuroblastoma cells loaded with Fluo3 AM and maintained in low or normal Ca(2+) solution. In normal Ca(2+), the increase in fluorescence amplitude was accompanied by irregular and frequent calcium transients. In TSn-m preparations loaded with Fluo4 AM, venom (10μg/ml) caused an immediate increase in intracellular Ca(2+) followed by oscillations in fluorescence and muscle contracture; Bbil-TX did not change the calcium fluorescence in TSn-m preparations. Immunohistochemical analysis of toxin-treated PND preparations revealed labeling of junctional ACh receptors but a loss of the presynaptic proteins synaptophysin and SNAP25. Together, these data confirm the presynaptic action of Bbil-TX and show that it involves modulation of K(+) channel activity and presynaptic protein expression.

Mesenchymal Stem Cells Engrafted In A Fibrin Scaffold Stimulate Schwann Cell Reactivity And Axonal Regeneration Following Sciatic Nerve Tubulization.

The present study investigated the effectiveness of mesenchymal stem cells (MSCs) associated with a fibrin scaffold (FS) for the peripheral regenerative process after nerve tubulization. Adult female Lewis rats received a unilateral sciatic nerve transection followed by repair with a polycaprolactone (PCL)-based tubular prosthesis. Sixty days after injury, the regenerated nerves were studied by immunohistochemistry. Anti-p75NTR immunostaining was used to investigate the reactivity of the MSCs. Basal labeling, which was upregulated during the regenerative process, was detected in uninjured nerves and was significantly greater in the MSC-treated group. The presence of GFP-positive MSCs was detected in the nerves, indicating the long term survival of such cells. Moreover, there was co-localization between MSCs and BNDF immunoreactivity, showing a possible mechanism by which MSCs improve the reactivity of SCs. Myelinated axon counting and morphometric analyses showed that MSC engrafting led to a higher degree of fiber compaction combined with a trend of increased myelin sheath thickness, when compared with other groups. The functional result of MSC engrafting was that the animals showed higher motor function recovery at the seventh and eighth week after lesion. The findings herein show that MSC+FS therapy improves the nerve regeneration process by positively modulating the reactivity of SCs.

Effect Of Low-level Laser Therapy (lllt) On Peripheral Nerve Regeneration Using Fibrin Glue Derived From Snake Venom.

The purpose of this study was to assess whether the adhesive permits the collateral repair of axons originating from a vagus nerve to the interior of a sural nerve graft, and whether low-level laser therapy (LLLT) assists in the regeneration process. Study sample consisted of 32 rats randomly separated into three groups: Control Group (CG; n=8), from which the intact sural nerve was collected; Experimental Group (EG; n=12), in which one of the ends of the sural nerve graft was coapted to the vagus nerve using the fibrin glue; and Experimental Group Laser (EGL; n=12), in which the animals underwent the same procedures as those in EG with the addition of LLLT. Ten weeks after surgery, the animals were euthanized. Morphological analysis by means of optical and electron microscopy, and morphometry of the regenerated fibers were employed to evaluate the results. Collateral regeneration of axons was observed from the vagus nerve to the interior of the autologous graft in EG and EGL, and in CG all dimensions measured were greater and presented a significant difference in relation to EG and EGL, except for the area and thickness of the myelin sheath, that showed significant difference only in relation to the EG. The present study demonstrated that the fibrin glue makes axonal regeneration feasible and is an efficient method to recover injured peripheral nerves, and the use of low-level laser therapy enhances nerve regeneration.

Contribution of skin immunohistochemistry in the evaluation of nerve fibers in diabetes mellitus type 2

175

Operant measurement of auditory threshold in prelingually deaf users of cochlear implants: II

Two experiments evaluated an operant procedure for establishing stimulus control using auditory and electrical stimuli as a baseline for measuring the electrical current threshold of electrodes implanted in the cochlea. Twenty-one prelingually deaf children, users of cochlear implants, learned a Go/No Go auditory discrimination task (i.e., pressing a button in the presence of the stimulus but not in its absence). When the simple discrimination baseline became stable, the electrical current was manipulated in descending and ascending series according to an adapted staircase method. Thresholds were determined for three electrodes, one in each location in the cochlea (basal, medial, and apical). Stimulus control was maintained within a certain range of decreasing electrical current but was eventually disrupted. Increasing the current recovered stimulus control, thus allowing the determination of a range of electrical currents that could be defined as the threshold. The present study demonstrated the feasibility of the operant procedure combined with a psychophysical method for threshold assessment, thus contributing to the routine fitting and maintenance of cochlear implants within the limitations of a hospital setting.

Nerve endings of filliform, fungiform and vallate papillae of dorsal tongue mucosa of White-lipped peccary (Tayassu pecari): Neurohistological observations

The neurohistologic observations were performed using the specimens prepared by Winkelmann and Schmitt silver impregnation method. The tissues were fixed in 10% formalin solution and sections of 40µm thickness were obtained by Leica Cryostat at -30ºC. The sections of dorsal mucosa of White-lipped peccary tongue showed numerous filliform and fungiform papillae, and two vallate papillae on the caudal part. The epithelial layer revealed queratinized epithelial cells and the connective tissue papillae of different sizes and shapes. Thick nerve fiber bundles are noted into the subepithelial connective tissue of the papillae. The connective tissue of fungiform and vallate papillae contained numerous sensitive nerves fibers bundles forming a complex nerve plexus.

Participation of neuronal nitric oxide synthase in experimental neuropathic pain induced by sciatic nerve transection

Nerve injury leads to a neuropathic pain state that results from central sensitization. This phenomenom is mediated by NMDA receptors and may involve the production of nitric oxide (NO). In this study, we investigated the expression of the neuronal isoform of NO synthase (nNOS) in the spinal cord of 3-month-old male, Wistar rats after sciatic nerve transection (SNT). Our attention was focused on the dorsal part of L3-L5 segments receiving sensory inputs from the sciatic nerve. SNT resulted in the development of neuropathic pain symptoms confirmed by evaluating mechanical hyperalgesia (Randall and Selitto test) and allodynia (von Frey hair test). Control animals did not present any alteration (sham-animals). The selective inhibitor of nNOS, 7-nitroindazole (0.2 and 2 µg in 50 µL), blocked hyperalgesia and allodynia induced by SNT. Immunohistochemical analysis showed that nNOS was increased (48% by day 30) in the lumbar spinal cord after SNT. This increase was observed near the central canal (Rexed’s lamina X) and also in lamina I-IV of the dorsal horn. Real-time PCR results indicated an increase of nNOS mRNA detected from 1 to 30 days after SNT, with the highest increase observed 1 day after injury (1469%). Immunoblotting confirmed the increase of nNOS in the spinal cord between 1 and 15 days post-lesion (20%), reaching the greatest increase (60%) 30 days after surgery. The present findings demonstrate an increase of nNOS after peripheral nerve injury that may contribute to the increase of NO production observed after peripheral neuropathy.