RESUMEN
In motor nerve conduction studies, important diagnostic information is provided by the late-wave responses, comprised of F-waves, A-waves, and repeaters. Late-waves in addition to contamination from power line interference and baseline disturbance, are of low amplitude and random in nature. This makes computer-based analysis of late-wave activity very challenging, especially the computer-based F-wave onset latency assignment. Currently available algorithms assign latency independently on a trace-by-trace basis without considering the information present in an entire ensemble of traces. A novel algorithm that takes into account the ensemble information for segmenting and classifying regions of late-wave data is described in this paper, which in turn can be used to improve the performance of computer-based F-wave onset latency assignment.
Asunto(s)
Potenciales de Acción/fisiología , Algoritmos , Electrofisiología/métodos , Neuronas Motoras/clasificación , Neuronas Motoras/fisiología , Humanos , Procesamiento de Imagen Asistido por Computador , Conducción Nerviosa/fisiologíaRESUMEN
PURPOSE: F-wave studies are valuable tools in clinical neurophysiology. F-wave parameter estimation must be based on multiple F-wave traces due to their inherent variability. Repetitive supramaximal stimulation is uncomfortable for many patients. This study tested the hypothesis that submaximally stimulated nerves yield F-wave parameters equivalent to those obtained with supramaximal stimulation. METHODS: Thirty-five peroneal nerves from 27 subjects were stimulated both supramaximally and submaximally. CMAP and F-wave responses from the extensor digitorum brevis muscle were recorded and analyzed offline. Automated algorithms were used to determine F-wave parameters. RESULTS: Mean, minimum, maximum F-wave latencies, F-wave duration, and chronodispersion showed no statistically significant difference under the two stimulation conditions. F-wave persistence, amplitude, and subject's discomfort level, were lower with statistical significance. The correlation coefficient of submaximal and supramaximal mean F-wave latencies was 0.977 and their intraclass correlation coefficient was 0.976. The bias of the mean latencies was 0.21 ms and the 95% limits of agreement were less than 5% of the mean F-wave latency. CONCLUSIONS: F-waves acquired with submaximal stimulation possess characteristics statistically equivalent to those obtained under supramaximal stimulation, as measured by the latency and duration parameters. Persistence and amplitude were lower. Reduction in discomfort level was also achieved.
Asunto(s)
Electrodiagnóstico/métodos , Enfermedades del Sistema Nervioso/diagnóstico , Conducción Nerviosa/fisiología , Nervio Peroneo/fisiología , Adulto , Vías Aferentes/fisiología , Anciano , Estimulación Eléctrica/efectos adversos , Estimulación Eléctrica/métodos , Electrodiagnóstico/normas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neuronas Motoras/fisiología , Músculo Esquelético/inervación , Músculo Esquelético/fisiología , Satisfacción del Paciente , Valor Predictivo de las Pruebas , Tiempo de Reacción/fisiología , Reflejo/fisiología , Sensibilidad y Especificidad , Procesamiento de Señales Asistido por Computador , Factores de TiempoRESUMEN
Clinical findings have limited value in predicting electrophysiologically confirmed median neuropathy at the wrist (MNW). To determine the value of clinical findings and an automated electrophysiologic neurodiagnostic device (AEND) in diagnosing MNW, we studied two groups of 75 consecutive patients (an initial group and a validation group, 150 total) referred to an academic electrophysiology laboratory for upper extremity complaints. The definitive standard for MNW was the neurologist's diagnosis after formal clinical and electrodiagnostic evaluation. The neurologist was blinded to the results of the AEND (NC-Stat, NeuroMetrix, Inc). In the validation group, the AEND yielded a distal motor latency (DML) in 97% of hands with a conventional motor response, and the correlation of the AEND DML with the conventional DML was 0.94 (P < 0.001). Of 248 symptomatic hands, the neurologist diagnosed 117 (47%) with MNW. At 90% specificity, the AEND DML had a sensitivity of 86% for MNW. Age, body mass index, sensory symptoms in digits 1 to 3, and nocturnal awakening were independent clinical predictors of MNW. Each 1-msec increase in the adjusted AEND DML was independently associated with an OR of 298 (95% confidence interval, 40 to 2233) for MNW. Each 1-msec increase in the F-wave latency was independently associated with an OR of 2.6 (95% confidence interval, 1.3 to 4.9) for MNW. Compared with a model based solely on clinical variables, an algorithm including symptom variables plus the AEND DML had an odds ratio for correct diagnostic classification of 6.3 (95% confidence interval, 3.8 to 12.3). The sensitivity at 90% specificity improved from 40% for the clinical model to 86% for the model with DML. A practical method for integrating clinical and electrophysiologic findings to assess the risk of MNW was proposed. This method correctly stratified 79% of control and MNW patients into very low- and high-risk groups, respectively. We concluded that MNW diagnosis is significantly improved with an AEND.
Asunto(s)
Técnicas de Diagnóstico Neurológico , Electrofisiología/instrumentación , Neuropatía Mediana/diagnóstico , Síndromes de Compresión Nerviosa/diagnóstico , Articulación de la Muñeca , Adulto , Anciano , Algoritmos , Estudios de Casos y Controles , Potenciales Evocados Motores , Femenino , Humanos , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Curva ROC , Análisis de Regresión , Reproducibilidad de los ResultadosRESUMEN
Accurate, noninvasive determination of the distribution of conduction velocities (DCV) among fibers of a peripheral nerve has the potential to improve both clinical diagnoses of pathology and longitudinal studies of the progress of disease or the efficacy of treatments. Current techniques rely on long distances of propagation to increase the amount of temporal dispersion in the compound signals and reduce the relative effect of errors in the forward model. The method described in this paper attempts to reduce errors in DCV estimation through transfer function normalization and, thereby, eliminate the need for long segments of nerve. Compound action potential (CAP) signals are recorded from several, equally spaced electrodes in an array spanning only a 10-cm length of nerve. Relative nerve-to-electrode transfer functions (NETF's) between the nerve and each of the array electrodes are estimated by comparing discrete Fourier transforms of the array signals. NETF's are normalized along the array so that waveform differences can be attributed to the effects of temporal dispersion between recordings, and more accurate DCV estimates can be calculated from the short nerve segment. The method is tested using simulated and real CAP data. DCV estimates are improved for simulated signals. The normalization procedure results in DCV's that qualitatively match those from the literature when used on actual CAP recordings.
Asunto(s)
Potenciales de Acción/fisiología , Simulación por Computador , Modelos Neurológicos , Conducción Nerviosa/fisiología , Nervios Periféricos/fisiología , Adulto , Algoritmos , Electrodos , Humanos , Masculino , Nervio Mediano/fisiología , Tiempo de Reacción , Procesamiento de Señales Asistido por ComputadorRESUMEN
ARIA (for acetylcholine receptor-inducing activity), a protein purified on the basis of its ability to stimulate acetylcholine receptor (AChR) synthesis in cultured myotubes, is a member of the neuregulin family and is present at motor endplates. This suggests an important role for neuregulins in mediating the nerve-dependent accumulation of AChRs in the postsynaptic membrane. Nerve-muscle synapses have now been analyzed in neuregulin-deficient animals. Mice that are heterozygous for the deletion of neuregulin isoforms containing an immunoglobulin-like domain are myasthenic. Postsynaptic AChR density is significantly reduced, as judged by the decrease in the mean amplitude of spontaneous miniature endplate potentials and bungarotoxin binding. On the other hand, the mean amplitude of evoked endplate potentials was not decreased, due to an increase in the number of quanta released per impulse, a compensation that has been observed in other myasthenic states. Thus, the density of AChRs in the postsynaptic membrane depends on immunoglobulin-containing neuregulin isoforms throughout the life of the animal.
Asunto(s)
Glicoproteínas/fisiología , Proteínas del Tejido Nervioso/fisiología , Unión Neuromuscular/metabolismo , Receptores Colinérgicos/metabolismo , Acetilcolina/metabolismo , Animales , Bungarotoxinas/metabolismo , Glicoproteínas/genética , Heterocigoto , Inmunoglobulinas/análisis , Técnicas In Vitro , Potenciales de la Membrana , Ratones , Placa Motora/metabolismo , Placa Motora/fisiología , Debilidad Muscular/etiología , Proteínas del Tejido Nervioso/genética , Neurregulina-1 , Neurregulinas , Receptores Colinérgicos/genética , Transmisión SinápticaRESUMEN
We have determined the structure of a metastable disulphide isomer of human insulin. Although not observed for proinsulin folding or insulin-chain recombination, the isomer retains ordered secondary structure and a compact hydrophobic core. Comparison with native insulin reveals a global rearrangement in the orientation of A- and B-chains. One face of the protein's surface is nevertheless in common between native and non-native structures. This face contains receptor-binding determinants, rationalizing the partial biological activity of the isomer. Structures of native and non-native disulphide isomers also define alternative three-dimensional templates. Threading of insulin-like sequences provide an experimental realization of the inverse protein-folding problem.
Asunto(s)
Insulina/química , Modelos Moleculares , Conformación Proteica , Secuencia de Aminoácidos , Dicroismo Circular , Humanos , Insulina/metabolismo , Isomerismo , Cinética , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Proinsulina/química , Pliegue de Proteína , Estructura Secundaria de Proteína , Receptor de Insulina/metabolismo , Moldes Genéticos , TermodinámicaRESUMEN
We describe advanced protocols for the discrimination and classification of neuronal spike waveforms within multichannel electrophysiological recordings. The programs are capable of detecting and classifying the spikes from multiple, simultaneously active neurons, even in situations where there is a high degree of spike waveform superposition on the recording channels. The protocols are based on the derivation of an optimal linear filter for each individual neuron. Each filter is tuned to selectively respond to the spike waveform generated by the corresponding neuron, and to attenuate noise and the spike waveforms from all other neurons. The protocol is essentially an extension of earlier work [1], [13], [18]. However, the protocols extend the power and utility of the original implementations in two significant respects. First, a general single-pass automatic template estimation algorithm was derived and implemented. Second, the filters were implemented within a software environment providing a greatly enhanced functional organization and user interface. The utility of the analysis approach was demonstrated on samples of multiunit electrophysiological recordings from the cricket abdominal nerve cord.
Asunto(s)
Algoritmos , Artefactos , Neuronas/fisiología , Procesamiento de Señales Asistido por Computador , Validación de Programas de Computación , Potenciales de Acción , Animales , Protocolos Clínicos , Análisis Discriminante , Electrofisiología , Estudios de Evaluación como Asunto , Gryllidae , Sensibilidad y EspecificidadRESUMEN
Transcriptional elongation provides a key control point in the regulation of eukaryotic gene expression. Here we describe homonuclear and 15N-heteronuclear 3D NMR studies of the nucleic acid binding domain of human transcriptional elongation factor TFIIS. This domain contains a Cys4 Zn(2+)-binding site with no homology to previously characterized Cys4, Cys6, or Cys2-His2 Zn fingers. Complete 1H and 15N NMR resonance assignment of a 50-residue TFIIS peptide-Zn2+ complex is obtained. Its solution structure, as determined by distance geometry/simulated annealing (DG/SA) calculations, exhibits a novel three-stranded antiparallel beta-sheet (designated the Zn ribbon). Analogous sequence motifs occur in a wide class of proteins involved in RNA or DNA transactions, including human basal transcriptional initiation factor TFIIE. A three-dimensional model of the TFIIE Cys4 domain is obtained by DG-based homology modeling. The role of the TFIIS Zn ribbon in the control of eukaryotic transcriptional elongation is discussed.