Degeneration and regeneration in rabbit peripheral nerve with long-term nerve cuff electrode implant: a stereological study of myelinated and unmyelinated axons

Spatio-temporal patterns of neuronal activity after the induction of long-term potentiation (LTP) in mouse hippocampal slices were studied with the use of a real-time high-resolution optical recording system. The slices were stained with voltage-sensitive dye and then high-frequency pulses (tetanus) were delivered to Schaffer collaterals of CA3 at the stratum radiatum of CA1. Optical signals as well as field potential in response to test pulses were potentiated after tetanus. The area of response measured by optical recording was slightly but significantly enlarged after tetanus, suggesting that the propagation of optical responses from CA1 towards the subiculum was enlarged. It was suggested that a great increase in neuronal activity was elicited at CA1 and the subiculum after LTP. These changes of spatio-temporal patterns of neuronal activity may contribute to learning and memory. The effect of trichloroethylene (TCE) on LTP was studied with the use of both electrical and optical and recording. The hippocampus from mice injected with 300 mg/kg or 1000 mg/kg TCE was sliced 24 hours after TCE-administration. Test pulses were delivered to Schaffer collaterals every 30 sec and the field potential from the stratum pyramidale of CA1 was recorded. At 40 min after the application of tetanus, population spikes (PS) were potentiated in all groups, but the post/pre ratio of PS was smaller in TCE groups than in the control. Optical recording was also carried out in 1000 mg/kg TCE-injected mice. At 40 min after tetanus, the optical signal response to the test pulse was potentiated in both TCE and control groups, but the post/pre ratio of the optical signals was smaller in TCE than in the control. No significant difference was detected in the increase in the neuronal response area between TCE and the control. It was suggested that TCE depressed the LTP, whereas the increase in the area after tetanus meant that a good amount of neuronal activity was still potentiated.     

Bipolar electrode implantation for myoelectrical recordings of rat bowel

This report describes a technique to implant bipolar electrodes into the rat bowel. We implanted a total of 129 pairs of bipolar electrodes into the bowel of rats. 124 pairs of electrodes (96.3%) have continuously functioned allowing repeated myoelectrical readings. Of these, 69 electrodes functioned over 8 weeks. Only 5 electrodes (3.7%) failed. The advantage of our technique includes: (1) high success rate in implantation, (2) long term durability, and (3) less technical difficulty.     

Neuromagnetic recordings of the human peripheral nerve with planar SQUID gradiometers

Magnetic fields produced by a travelling volley in the human ulnar nerve have been successfully measured in a lightly shielded environment. Recordings of the tangential component of the magnetic field were made using a planar second-order gradiometer integrated with a first-order gradiometric superconducting quantum interference device (SQUID). Devices were fabricated in our clean-room facility at the University of Strathclyde and measurements taken in an eddy-current shielded room at the Wellcome Biomagnetism Unit. We use no additional shielding and no electronic differencing or field-nulling techniques. Evoked magnetic fields of 60 fT peak-to-peak were obtained after 1536 averages but they could be seen easily as early as 512 averages. Measurements were made over four points above the ulnar nerve on the upper arm and from these the conduction velocity was calculated as 60 m s(-1).     

Suprascapular nerve block for persistent rotator cuff lesions

The suprascapular nerve supplies sensory nerves to the posterosuperior aspect of the shoulder, including major portions of the rotator cuff. Suprascapular nerve block using steroid/bupivacaine is temporarily effective in reducing pain in rotator cuff tendinitis and tears, improving movement range in tendinitis and is possible in an outpatient setting with little or no complication risk.     

Suprascapular nerve rotator cuff compression syndrome in volleyball players

OBJECTIVE AND DESIGN: Eighteen active acromegalics entered a prospective open study with cabergoline (CAB), a dopaminergic drug much more potent than bromocriptine (Br). METHODS: CAB was administered for 6 months at doses ranging between 0.5 mg twice weekly and 0.5 mg/day. Clinical-anamnestic characteristics of the patients were: (i) sensitivity to dopamine agonist drugs (10 patients); (ii) resistance to somatostatin analogs (SAs) (8 patients): (iii) intolerance to SA (3 patients). In 2 patients marked hyperprolactinemia was present. RESULTS: Basal GH was 6.6 microg/l (2.2-50) (median (range)), and on treatment it was 3.5 microg/l (1.2-34) (P=0.013). The corresponding IGF-I values were 720 microg/l (410-1438) and 375 microg/l (167-1260) respectively (P=0.00001). Individual GH levels decreased below 2 microg/l in 5 patients, and between 2 and 5 microg/l in another 5 patients. IGF-I levels were suppressed below 50% of baseline in 8 patients and normal age-adjusted IGF-I values were reached in 5 patients (27% of the series). The retrospective comparison with previous chronic treatment with Br in the 10 suitable patients showed a greater effectiveness of CAB (IGF-I decrease on CAB treatment, 46.8%, on Br treatment, 31%, P=0.02). Adenoma shrank in the 3 patients whose pituitary imaging was repeated during CAB. CONCLUSIONS: These results envisage that CAB may represent a worthy therapeutic tool in acromegalic patients, inducing a degree of IGF-I and GH suppression comparable to SAs, administered by the oral route and much less expensive.     

Patch-clamp recordings of membrane currents evoked during natural synaptic activity in sympathetic neurons

BACKGROUND: Cationic streptococcal proteinase (erythrotoxin B) and its precursor, zymogen, are putative nephritogenic antigens. The present study was designed to test whether serum titers to these antigens were good markers of streptococcal infection associated with glomerulonephritis. METHODS: We studied 153 patients (male/female = 104/49, age range, 2 to 23 years old) with acute poststreptococcal glomerulonephritis (APSGN) from three countries (Venezuela, Chile and Argentina). The site of the initial infection was the skin in 84 patients, the throat in 55 patients and was unknown in 14 patients. In addition, we studied 23 patients (1 to 24 years old) with streptococcal infection not associated with glomerulonephritis (14 patients with impetigo and 9 patients with pharyngitis). As control group, 93 healthy individuals (54 males, 2 to 19 years old) were studied. Anti-zymogen and anti-proteinase titers were determined in a single laboratory by ELISA, and the intra- and interassay coefficients of variation were 5.3% and 8.5%, respectively. ASO titers and anti-DNAse B titers were also done. RESULTS: Anti-zymogen titers of 1:800 to 1:3200 had likelihood ratios (sensitivity/1-specificity) for detection of streptococcal infection in APSGN patients ranging from 2.00 to 44.2 in Argentina, Chile and Venezuela. Anti-zymogen titers decreased one to two months after APSGN and they were 1 to 3 log2 dilutions higher that anti-proteinase titers. Receiver operating characteristic (ROC) curves showed that anti-zymogen titers were consistently superior to anti-streptolysin O and anti-DNAse B titers as markers for streptococcal infection in APSGN. CONCLUSIONS: These results suggest that increased anti-zymogen antibody titers are the best available marker for streptococcal infection associated with acute glomerulonephritis.     

Altered subthreshold sodium currents and disrupted firing patterns in Purkinje neurons of Scn8a mutant mice

Sodium currents and action potentials were characterized in Purkinje neurons from ataxic mice lacking expression of the sodium channel Scn8a. Peak transient sodium current was approximately 60% of that in normal mice, but subthreshold sodium current was affected much more. Steady-state current elicited by voltage ramps was reduced to approximately 30%, and resurgent sodium current, an unusual transient current elicited on repolarization following strong depolarizations, was reduced to 8%-18%. In jolting mice, with a missense mutation in Scn8a, steady-state and resurgent current were also reduced, with altered voltage dependence and kinetics. Both spontaneous firing and evoked bursts of spikes were diminished in cells from null and jolting mice. Evidently Scn8a channels carry most subthreshold sodium current and are crucial for repetitive firing.     

Opioid-activated postsynaptic, inward rectifying potassium currents in whole cell recordings in substantia gelatinosa neurons

Opioid-activated postsynaptic, inward rectifying potassium currents in whole cell recordings in substantia gelatinosa neurons. J. Neurophysiol. 80: 2954-2962, 1998. Using tight-seal, whole cell recordings from isolated transverse slices of hamster and rat spinal cord, we investigated the effects of the mu-opioid agonist (-Ala2, N-Me-Phe4,Gly5-ol)-enkephalin (DAMGO) on the membrane potential and conductance of substantia gelatinosa (SG) neurons. We observed that bath application of 1-5 microM DAMGO caused a robust and repeatable hyperpolarization in membrane potential (Vm) and decrease in neuronal input resistance (RN) in 60% (27/45) of hamster neurons and 39% (9/23) of rat neurons, but significantly only when ATP (2 mM) and guanosine 5'-triphosphate (GTP; 100 microM) were included in the patch pipette internal solution. An ED50 of 50 nM was observed for the hyperpolarization in rat SG neurons. Because G-protein mediation of opioid effects has been shown in other systems, we tested if the nucleotide requirement for opioid hyperpolarization in SG neurons was due to G-protein activation. GTP was replaced with the nonhydrolyzable GTP analogue guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S; 100 microM), which enabled DAMGO to activate a nonreversible membrane hyperpolarization. Further, intracellular application of guanosine-5'-O-(2-thiodiphosphate) (GDP-beta-S; 500 microM), which blocks G-protein activation, abolished the effects of DAMGO. We conclude that spinal SG neurons are particularly susceptible to dialysis of GTP by whole cell recording techniques. Moreover, the depletion of GTP leads to the inactivation of G-proteins that mediate mu-opioid activation of an inward-rectifying, potassium conductance in these neurons. These results explain the discrepancy between the opioid-activated hyperpolarization in SG neurons observed in previous sharp electrode experiments and the more recent failures to observe these effects with whole cell patch techniques.     

钯(Ⅱ)-丁二酮肟络合物在碳糊电极上的阳极吸附伏安法研究

报道了在碳糊电极上络合吸附阳极伏安法测定钯的新方法。在pH 4.2的HAc-NaAc缓冲溶液中,钯(Ⅱ)与丁二酮肟(DMG)形成的络合物在0.20 V(vs.SCE)搅拌富集60s,静止10 s,然后在0.20~1.20 V范围内以300 mV/s的扫描速度线性扫描,在0.90 V处产生灵敏的阳极吸附伏安峰。其二阶导数峰电流与钯(Ⅱ)的浓度在3.0×10-9~8.0×10-7mol/L范围内呈线性关系,富集120 s,检出限达5.0×10-10mol/L。本方法应用于催化剂中钯的测定,相对标准偏差为3.6%~4.7%,加标回收率在94%以上,结果与火焰原子吸收光谱法测定结果一致。     

Comparison of single-fiber and macro electrode recordings: relationship to motor unit action potential duration

The factors contributing to the duration of a motor unit action potential (MUAP) are believed to be well known, with both manual measurements and computer simulations agreeing with respect to MUAP durations approaching 10 ms. In this investigation, it is clearly demonstrated that use of a wide-open amplifier bandpass combined with signal-to-noise ratio enhancement results in MUAP durations approaching 30 ms recorded with either a macro or single-fiber electrode. Why the clinically recorded MUAP duration differs significantly from these physiologic durations is discussed. A hypothesis is presented whereby the major contributing factor toward MUAP duration is the total time of action potential transmembrane current flow along the muscle fiber from end-plate zone to musculotendinous junction.     

Simultaneous multisite recordings and stimulation of single isolated leech neurons using planar extracellular electrode arrays

Planar extracellular electrode arrays provide a non-toxic, non-invasive method of making long-term, multisite recordings with moderately high spatial frequency (recording sites per unit area). This paper reports advances in the use of this approach to record from and stimulate single identified leech neurons in vitro. A modified enzyme treatment allowed identified neurons to be extracted with very long processes. Multisite extracellular recordings from the processes of such isolated neurons revealed both the velocity and direction of action potential propagation. Propagation in two cell types examined was from the broken stump towards the cell body (antidromic). This was true for spontaneous action potentials, action potentials produced by injecting current into the cell body and extracellular stimulation of the extracted process via a planar extracellular electrode. These results extend previous findings which have shown that the tip of the broken stump of extracted neurons has a high density of voltage-activated sodium channels. Moreover they demonstrate the applicability of extracellular electrode arrays for recording the electrical excitability of single cells.     

Effect of phenol on the ion currents of frog nerve ending

The morphology of livers of Wistar rats treated with beta-carotene (BC), vitamin A (VA, retinol acetate) or corn oil (CO, controls) and submitted to the resistant hepatocyte model of carcinogenesis was studied. Preneoplastic lesions (PNL) were smaller and less numerous in the BC group. The latter group also presented fewer placental glutathione-S-transferase (GST-P) positive and hematoxylin and eosin (H&E) distinguishable PNL, with smaller mean areas and smaller mean areas of the liver occupied by PNL. Clear cell foci predominated in BC livers. In picrosirius-stained liver sections, fibrosis, whether or not accompanying the bile ductular cells, surrounded only 16.67% of PNL in the BC group, as compared to 35.71% in the VA group and 87.72% in the CO group. Moreover, the ductular cell reaction was smaller in the BC group. Smooth muscle actin-positive cells surrounded some PNL, mostly in CO rats, and less frequently in the VA and BC groups. Examination by transmission electron microscopy (TEM) showed that cells with nuclei similar to those of perisinusoidal cells, devoid of cytoplasmic fat globules, probably represented myofibroblasts derived from Ito cells and accompanied the ductular cell reaction. On the basis of these results, we suggest that BC reduced not only the PNL but also the ductular (oval) cell reaction in this experimental model.     

Neural conduction velocity of the human auditory nerve: bipolar recordings from the exposed intracranial portion of the eighth nerve during vestibular nerve section

We measured the conduction velocity of the intracranial portion of the auditory nerve in 3 patients undergoing vestibular nerve section to treat Ménière's disease. The conduction velocity varied from patient to patient, with an average value of 15.1 m/sec. The latency of peak III of the brain-stem auditory evoked potentials (BAEPs) increased by an average of 0.5 msec as a result of exposure of the eighth nerve, and if that increase is assumed to affect the entire length of the auditory nerve (2.6 cm) evenly, then the corrected estimate of conduction velocity would be 22.0 m/sec. Estimates of conduction velocity based on the interpeak latencies of peaks I and II of the BAEP, assuming that peak II is generated by the mid-portion of the intracranial segment of the auditory nerve, yielded similar values of conduction velocities (about 20 m/sec).     

Executive function in individuals with subthreshold autism traits.

Objective: Recent research has documented increased psychosocial difficulties in individuals who report higher-than-typical autistic traits but without an Autism Spectrum Disorder (ASD) diagnosis. Less is known, however, regarding the cognitive profile of individuals with subthreshold autism symptomatology. The objective of the present study was to provide additional insight into this issue and examine whether young adults who report higher degrees of autism traits also report experiencing increased difficulties with executive control. Method: The Behavior Rating Inventory of Executive Function was utilized to evaluate behavioral aspects of executive functioning in 66 and 28 individuals who endorsed high and low subthreshold levels of autism symptomatology, respectively. Results: After accounting for Attention Deficit/Hyperactivity Disorder (ADHD) symptomatology at both the group and individual participant levels, we found that autism traits continued to explain a significant amount of variance in participants' overall level of executive function (Global Executive Composite) as well as within most individual executive domains. Interestingly, the high and low trait groups did not differ on the inhibitory control and organization of materials scales, areas of functioning that appears to be largely spared in individuals with ASD as well. Conclusions: Findings from the present study are consistent with past research linking ASD and executive control impairment. In addition, ASD and ADHD traits were associated with unique contributions to the executive control profile of individuals with subthreshold autism symptomatology. This finding underscores the importance of accounting for ADHD symptomatology in studying ASD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability of the input-output properties of chronically implanted multiple contact nerve cuff stimulating electrodes

The objective of this investigation was to measure the input-output (I-O) properties of chronically implanted nerve cuff electrodes. Silicone rubber spiral nerve cuff electrodes, containing 12 individual platinum electrode contacts, were implanted on the sciatic nerve of seven adult cats for 28-34 weeks. Measurements of the torque generated at the ankle joint by electrical stimulation of the sciatic nerve were made every 1-2 weeks for the first 6 weeks post-implant and every 3-5 weeks between 6 weeks and 32 weeks post-implant. In three implants the percutaneous lead cable was irreparably damaged by the animal within 4 weeks after implant and further testing was not possible. One additional lead cable was irreparably damaged by the animal at 17 weeks post-implant. The three remaining implants functioned for 28, 31, and 32 weeks. Input-output curves of ankle joint torque as a function of stimulus current amplitude were repeatable within an experimental session, but there were changes in I-O curves between sessions. The degree of variability in I-O properties differed between implants and between different contacts within the same implant. After 8 weeks, the session to session changes in the stimulus amplitude required to generate 50% of the maximum torque (I50) were smaller (15+/-19%, mean +/- s.d.) than the changes in I50 measured between 1 week and 8 weeks post-implant (34+/-42%). Furthermore, the I-O properties were more stable across changes in limb position in the late post-implant period than in acutely implanted cuff electrodes. These results suggest that tissue encapsulation acted to stabilize chronically implanted cuff electrodes. Electrode movement relative to the nerve, de- and regeneration of nerve fibers, and the inability to precisely reproduce limb position in the measurement apparatus all may have contributed to the variability in I-O properties.     

Digital simulation of the membrane voltages and currents in nerve and muscle fibers

This paper describes digital computer simulations of the membrane voltages and currents in axons and muscle fibers. The simulations, which allow calculations ona nonuniform fiber, are based on the discrete Hodgkin-Huxley and Falk-Fatt equations. An efficient algorithm is used to solve the set of equations generated. Calculations are made of the voltage and current at the natural end of a muscle fiber and the results are compared with measurements by other investigators.     

Mechanical environment associated with rotator cuff tears

The patient is a 12-year-old boy with acute mixed lineage leukemia (AMLL) and with a rare karyotype of trisomy 6. He was referred to our hospital with gingival swelling, bleeding at the conjunctiva and huge hepatosplenomegaly. Complete blood count revealed leukocytosis with 79% blasts, anemia and thrombocytopenia. Bone marrow examination revealed 82.5% blasts which were morphologically judged as M1 according to the French-American-British classification. Immunophenotyping of leukemic cells showed the presence of CD2, CD7, CD19 and CD13 antigens, suggesting the diagnosis of AMLL. Cytogenetic analysis revealed a single abnormal karyotype of 47,XY,+6,add(15)(q22) which was successfully detected by fluorescence in situ hybridization (FISH) with the probe mapping at the alpha-satellite region of chromosome 6. Although the patient was treated with several chemotherapy regimens, he could not achieve complete remission and he died of progressive disease 11 months after admission. Fluorescence in situ hybridization analysis was very informative in assessing the residual leukemic cells in interphase during his clinical course.