Clinical trials have demonstrated that kilohertz-frequency transcutaneous spinal cord stimulation (TSCS) can be used to facilitate the recovery of sensory-motor function for patients with spinal cord injury, whereas the neural mechanism of TSCS is still undetermined so that the choice of stimulation parameters is largely dependent on the clinical experience. In this paper, a finite element model of transcutaneous spinal cord stimulation was used to calculate the electric field distribution of human spinal cord segments T ₁₂ to L ₂, whereas the activation thresholds of spinal fibers were determined by using a double-cable neuron model. Then the variation of activation thresholds was obtained by varying the carrier waveform, the interphase delay, the modulating frequency, and the modulating pulse width. Compared with the sinusoidal carrier, the usage of square carrier could significantly reduce the activation threshold of dorsal root (DR) fibers. Moreover, the variation of activation thresholds was no more than 1 V due to the varied modulating frequency and decreases with the increased modulating pulse width. For a square carrier at 10 kHz modulated by rectangular pulse with the frequency of 50 Hz and the pulse width of 1 ms, the lowest activation thresholds of DR fibers and dorsal column fibers were 27.6 V and 55.8 V, respectively. An interphase delay of 5 μs was able to reduce the activation thresholds of the DR fibers to 20.1 V. The simulation results can lay a theoretical foundation on the selection of TSCS parameters in clinical trials.
Humans ; Spinal Cord Stimulation/methods* ; Nerve Fibers/physiology* ; Finite Element Analysis ; Spinal Cord/physiology* ; Computer Simulation ; Spinal Cord Injuries/physiopathology* ; Lumbosacral Region ; Lumbar Vertebrae ; Transcutaneous Electric Nerve Stimulation/methods* ; Models, Neurological

PURPOSE: Though there are many reports regarding the structure-function relationship in glaucoma, they are too complicated to apply to the routine clinical setting. The aim of this study was to investigate the direct relationship between peripapillary retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and visual field (VF) severity indices computed by standard automated perimetry. METHODS: This cross-sectional comparative study included 104 glaucomatous patients and 59 healthy subjects. Peripapillary RNFL thickness was measured by spectral domain (SD) and time domain (TD) OCTs. Four glaucoma VF severity indices, including mean deviation (MD), pattern standard deviation (PSD), Collaborative Initial Glaucoma Treatment Study (CIGTS) VF score, and Advanced Glaucoma Intervention Study (AGIS) VF score, were calculated using standard automated perimetry. The Pearson's correlation coefficients (r) between the average and quadrants of peripapillary RNFL thicknesses and the four VF severity indices were calculated. RESULTS: In glaucomatous eyes, the r value between the average RNFL thickness measured by SD OCT and each VF severity index were 0.562, -0.514, -0.577, and -0.567 for the MD, PSD, CIGTS VF score, and AGIS VF score, respectively (all p < 0.001). Among each quadrant, the inferior RNFL thickness showed the largest r value; 0.587, -0.552, -0.613, and -0.598 for the MD, PSD, CIGTS VF score, and AGIS VF score, respectively (all p < 0.001). Measurements by TD OCT showed similar strengths of association with SD OCT. CONCLUSIONS: Moderate correlation was identified between peripapillary RNFL thicknesses measured by SD/TD OCT and glaucoma VF severity indices. Among each quadrant, the inferior RNFL thickness showed the greatest association with glaucoma VF severity indices. There was no significant difference according to the type of VF severity index or the type of OCTs.
Adult ; Aged ; Cross-Sectional Studies ; Female ; Humans ; Male ; Middle Aged ; Nerve Fibers/*pathology ; Optic Nerve/*pathology ; Optic Nerve Diseases/*diagnostic imaging/physiopathology ; Retinal Ganglion Cells/*pathology ; Severity of Illness Index ; Tomography, Optical Coherence/*methods ; Visual Field Tests/methods ; Visual Fields/*physiology ; Young Adult

OBJECTIVETo explore the value of the application of oil red O staining in spinal cord injury (SCI) of rats.

METHODSWith simple randomization, 24 Spargue-Dawley male rats were divided into normal control group including 6, and SCI group including 18. Spinal cord was transected at spinal lever T10 to build SCI model. Six rats of SCI group were sacrificed randomly at 1, 2, 4 weeks after surgery. After the spinal cord tissue sections were made, oil red O staining methods were used to observe the changes at the end of transected spinal cord. Images were analyzed by Image-Pro Plus 6.0 and SPSS 20.0 software.

RESULTSThe oil red O staining of normal control group showed that white matter surrounded by myelin sheath was clear and obviously distinctive from grey matter. Uneven and strengthened staining in oil O was observed in grey matter of SCI group at 1, 2, 4 weeks post-SCI.

CONCLUSIONIt is a good method to label the myelin sheath in spinal cord and distinct white matter from grey matter by oil red O staining. Analysis of the images showed that lipid may become another target for drugs, which needs more researches.

Animals ; Azo Compounds ; Gray Matter ; pathology ; Male ; Nerve Fibers ; physiology ; Nerve Regeneration ; Rats ; Rats, Sprague-Dawley ; Spinal Cord Injuries ; pathology ; Staining and Labeling

PURPOSE: To evaluate the effect of pattern scan laser (PASCAL) photocoagulation on peripapillary retinal nerve fiber layer (RNFL) thickness, central macular thickness (CMT), and optic nerve morphology in patients with diabetic retinopathy. METHODS: Subjects included 35 eyes for the PASCAL group and 49 eyes for a control group. Peripapillary RNFL thickness, cup-disc area ratio and CMT were measured before PASCAL photocoagulation and at 2 and 6 months after PASCAL photocoagulation in the PASCAL or control groups. RESULTS: The average RNFL thickness had increased by 0.84 microm two months after and decreased by 0.4 microm six months after PASCAL photocoagulation compared to baseline, but these changes were not significant (p = 0.83, 0.39). The cup-disc area ratio was unchanged after PASCAL photocoagulation. CMT increased by 18.11 microm (p = 0.048) at two months compared to baseline thickness, and partially recovered to 11.82 microm (p = 0.11) at six months in the PASCAL group. CONCLUSIONS: PASCAL photocoagulation may not cause significant change in the peripapillary RNFL thickness, CMT, and optic nerve morphology in patients with diabetic retinopathy.
Adult ; Aged ; Aged, 80 and over ; Diabetic Retinopathy/physiopathology/*surgery ; Female ; Fluorescein Angiography ; Follow-Up Studies ; Humans ; Laser Coagulation/*methods ; Lasers, Solid-State/*therapeutic use ; Macula Lutea/*pathology ; Male ; Middle Aged ; Nerve Fibers/*pathology ; Optic Nerve/*pathology ; Prospective Studies ; Retinal Ganglion Cells/*pathology ; Tomography, Optical Coherence ; Visual Acuity/physiology

PURPOSE: To investigate patterns of subsequent progression of localized retinal nerve fiber layer (RNFL) defects and to quantify the extent of progression in normal-tension glaucoma (NTG) patients. METHODS: Thirty-three eyes of 33 consecutive NTG patients who had shown continuous progression of localized RNFL defect on serial red-free fundus photographs were selected for the study. Patterns of subsequent progression of localized RNFL defects were categorized, and extents of progression were quantified. Serial evaluations of disc stereophotographs and visual fields were also performed to detect progression. RESULTS: The most common pattern was continuous widening of the defect towards the macula (n = 11, 33.3%) followed by sharpening of the defect border after widening of the defect towards the macula (n = 5, 15.2%), continuous widening of the defect away from the macula (n = 2, 6.1%), and deepening of the defect after appearance of a new defect (n = 2, 6.1%). Four eyes (12.1%) simultaneously showed two patterns of subsequent progression. In 13 eyes that showed continuous widening of the defect, subsequent angular widening towards the macula and away from the macula were 9.2 ± 6.0degrees (range, 1.1degrees to 24.4degrees; n = 11) and 5.2 ± 4.9degrees (range, 0.3degrees to 11.3degrees; n = 2), respectively. Thirty-two eyes showed no progression of optic disc cupping. Out of the 21 eyes in which Humphrey central 30-2 threshold visual field tests were performed after progression of RNFL defects, 15 eyes showed no deterioration in the visual field. CONCLUSIONS: There were nine patterns of subsequent progression of localized RNFL defects. Among them, continuous RNFL loss proceeding temporally was the most common one. Initial progression of the defect proceeded temporally, especially in the defect located at the inferior fundus, might be at a risk of further RNFL loss temporally.
Adult ; Aged ; Disease Progression ; Female ; Follow-Up Studies ; Humans ; Intraocular Pressure/physiology ; Low Tension Glaucoma/*diagnosis/physiopathology ; Male ; Middle Aged ; Nerve Fibers/*pathology ; Optic Disk/pathology ; Photography ; Retinal Ganglion Cells/*pathology ; Tonometry, Ocular ; Visual Fields/physiology

PURPOSE: To evaluate the relationship between the structural damage as assessed by time-domain optical coherence tomography (OCT) and functional changes in glaucoma. METHODS: In total, 190 patients with normal tension glaucoma or primary open angle glaucoma were included in this study. The thickness of retinal nerve fiber layer (RNFL) around the optic disc and the area of RNFL defect were determined using OCT scans. The relationships between the RNFL thickness or area of the defect and visual field (VF) indices were assessed using the Lowess function, regression analysis and partial Spearman correlation. The differences between these associations depending on the stage of VF damage were further analyzed. Age, optic disc size, refraction, central corneal thickness and the presence of systemic disease were corrected for in order to exclude confounding factors. RESULTS: A logarithmic scale of RNFL thickness showed a negative linear relationship with VF indices. The area of the RNFL defect showed a weak correlation with the pattern of standard deviation, whereas the remnant RNFL thickness was moderately correlated with the pattern of standard deviation (partial Spearman correlation coefficient, 0.39, -0.47, respectively; p < 0.0001). Many outliers were detected in the Lowess-plotted graphs. Multiplication of the area and the inverted RNFL thickness showed a moderately correlated logarithmic relationship with the VF indices (partial Spearman correlation coefficient, 0.46; 95% confidence interval, 0.34 to 0.57; p < 0.0001). In the severe stage of VF damage, correlation between the area of the RNFL defect and mean deviation was significantly greater than in other stages (partial Spearman correlation coefficient, -0.66; p = 0.02). CONCLUSIONS: The thickness of the RNFL had a negative logarithmic correlation with the VF indices and was more relevant to the VF indices than the area of the RNFL defect, as measured by OCT.
Aged ; Female ; Glaucoma, Open-Angle/*physiopathology ; Humans ; Low Tension Glaucoma/*physiopathology ; Male ; Middle Aged ; Nerve Fibers/*pathology ; Optic Nerve Diseases/*physiopathology ; Retinal Ganglion Cells/*pathology ; Tomography, Optical Coherence ; Visual Field Tests ; Visual Fields/*physiology

BACKGROUNDIndirect traumatic optic neuropathy (TON) is an acute injury of the optic nerve associated with severe visual dysfunction, which may be a result of secondary mechanical injury and vascular disorder of the optic nerve due to trauma. We analyzed the natural course of axonal loss and blood flow disturbances in patients with indirect TON to find a possible therapeutic window.

METHODSA cohort of 54 patients with indirect TON recruited between October 2008 and October 2010 at Beijing Tongren Hospital was retrospectively analyzed. The patients were divided into no light perception group (NLP) and better than NLP (btNLP) group. Specifically, the thickness of the retinal nerve fiber layer (RNFL) measured by spectral domain optical coherence tomography (SD-OCT), and hemodynamic parameters of the ophthalmic artery (OA), central retinal artery (CRA) and posterior ciliary artery (PCA) were determined.

RESULTSTwo weeks after injury, there was a statistically significant decrease in the thickness of RNFL in the btNLP group as compared with the fellow control eyes (P < 0.05). In contrast, in the NLP group, RNFL thickness slightly increased for 2 weeks following injury, then overtly reduced after 4 weeks (P < 0.05). Peak systolic velocity (PSV) of CRA was significantly decreased 4 weeks after injury (P < 0.05) in both the NLP group and btNLP group (P < 0.05). The thickness of RNFL in the NLP group was negatively correlated with PSV of CRA after 1 week of injury (P < 0.05, r = -0.962).

CONCLUSIONSSD-OCT is a useful supplement in detecting the axonal loss in TON. The dynamic change of the thickness of RNFL appears to correlate with the hemodynamic disturbances in the natural course of TON. The first 2 weeks following an injury is critical and should be considered as the therapeutic window for TON patients.

Adult ; Female ; Humans ; Male ; Middle Aged ; Nerve Fibers ; physiology ; Optic Nerve ; physiology ; Optic Nerve Injuries ; physiopathology ; Retinal Neurons ; physiology ; Retrospective Studies ; Tomography, Optical Coherence

OBJECTIVETo develop a system for automatically controlling carotid sinus pressure in the study on baroreceptors.

METHODSThe preparation containing carotid sinus with parts of the connected vessels and carotid sinus nerve (CS-CSN) were isolated and perfused. A critical pressure controlling component (PRE-U, Hoerbiger, Deutschland) dictated by a computer was integrated into the system to clamp the intrasinus pressure. The pressure command and the relevant intrasinus pressure were compared to evaluate the validity of the pressure controlling system.

RESULTSA variety of sinus pressure-controlling patterns, including pulsation, ramp and step pressures, could be achieved accurately by using the system, and the pressure-dependent discharge activities of sinus nerve were confirmed.

CONCLUSIONThis system for clamping carotid sinus pressure could realize multiple pressure-controlling patterns and is a useful and flexible pressure controlling method that could applied in the study on mechano-electric transduction of baroreceptors.

Animals ; Blood Pressure ; Carotid Sinus ; innervation ; physiology ; Nerve Fibers ; physiology ; Pressoreceptors ; physiology ; Rabbits

Spinal cord injury (SCI) is frequently companied by necrosis and apoptosis of oligodendrocytes (OLs), which contributes to demyelination of myelinated nerve fibers and their electrophysiological defects. This pathological demyelination often results in sensory or motor deficits. Here, we first focus on the microenvironment changes after SCI that cause OLs' death, then discuss the major mechanism of endogenous oligodendrocytogenesis and axonal remyelination, and finally summarize current therapies targeting OLs protection and replacement.
Animals ; Apoptosis ; physiology ; Cell Death ; physiology ; Humans ; Necrosis ; pathology ; Nerve Fibers, Myelinated ; pathology ; Nerve Regeneration ; physiology ; Oligodendroglia ; pathology ; Spinal Cord ; physiopathology ; Spinal Cord Injuries ; pathology ; physiopathology ; therapy

OBJECTIVETo discuss the electrophysiologic effects of regenerative nerve fibres affected by control releasing of FK506.

METHODSFrom Mar. to Sep. in 2008, the body weigh of 32 Sprague-Dawley rats which was 200 to 250 g,anesthesia was performed with an intraperitoneal injection of 30 mg/kg 1% continal. The sciatic nerve was transected in each rat by the excision of a 10 mm gap just proximal to the trifurcation of the nerve. The 10 mm gap of sciatic nerve had been bridged with the new double channel nerve conduit of fusiform shape, which were randomly divided into two groups basing on the different drug in the channel, each group contained 16 animals. In group A,100 microl of chitin for medical use was injected into the conduit,in group B the two branches of the conduit respectively contained 100 microl of the chitin and 10 microl FK506 (group B2) or physiologic saline (group B1). At 8 and 12 week after operation, the morphology in regenerative nerve and electrophysiologic effects by detect compound muscle active potential (CMAP) and cortical somatosensory evoked potential (CSEP) were evaluated.

RESULTSThere were not significant differences of the regenerative nerve fibres between two channels in group A, but in group B2, the number of the regenerative fibres was much more than that in group B1. The latency of CMAP and CSEP in group B2 was shorter than that in group B1. But its amplitude was higher. There were highly significant difference between the groups (P < 0.01).

CONCLUSIONThe electrophysiologic effects of regenerative nerve fibres can be significantly promoted by FK506, which provide theory base for immunosuppressive treatment of peripheral nerve.

Animals ; Chitin ; administration & dosage ; Delayed-Action Preparations ; Female ; Immunosuppressive Agents ; administration & dosage ; pharmacology ; Male ; Nerve Fibers ; drug effects ; physiology ; Nerve Regeneration ; Rats ; Rats, Sprague-Dawley ; Tacrolimus ; administration & dosage ; pharmacology