bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vector short‐latency somatosensory‐evoked potentials after median nerve stimulation
Authors: Kaji Ryuji , Sumner Austin J. 
Published: January 2005

AbstractA new method has been developed for recording short‐latency somatosensory‐evoked potentials after median nerve stimulation. Negative electrical forces recorded with three orthodiagonal bipolar electrodes in the neck had a direction opposite to that of impulse conduction in the proximal peripheral and cervical somatosensory pathway. Sequential tracings of vectors opposite the electrical forces were made in three‐dimensional display, thus reproducing the actual time sequence of electrical events in those structures. Fixed generators such as the subcortical nuclei were also analyzed with this technique, and multiple generators of N13 potential (N13a and N13b) were visualized. This technique may be useful in the functional evaluation of the somatosensory pathway in the cervical cord.
Effects of short spaceflights on mechanical characteristics of rat muscles
Authors: Holy Xavier , Mounier Yvonne 
Published: January 2005

AbstractThe aim of this study was to investigate the contractile protein characteristics after 5‐day (Cosmos 1514) and 7‐day (Cosmos 1667) spaceflights. The experiments were performed on skinned fibers from the soleus, gastrocnemius lateralis, and plantaris muscles isolated from Wistar rats. A reduction in fiber diameter might explain the decrease in the maximal tension in the soleus, whereas this tension was unaltered in the gastrocnemius and the plantaris. Moreover the calcium sensitivity of the myofilament appeared modified in the soleus and in the gastrocnemius: The tension/pCa relationships were shifted toward higher calcium concentrations, indicating a decrease in the appearent calcium binding constant of the tropinin C. The tension/pCa relationship appeared unaltered in the plantaris after spaceflight. Finally, the studies of the time to reach a steady tension indicated an increase in the rate of force development in the soleus and, on the contrary, a slowing down in the plantaris. No change in the gastrocnemius was found. The results were analyzed with references to the different muscle functions in disuse atrophy.
Abnormal M‐wave responses during exercise in myotonic muscular dystrophy: A Na+‐K+ pump defect?
Authors: Fenton John , Garner Scott , McComas Alan J. 
Published: January 2005

AbstractMaximum M‐waves (muscle compound action potentials) were studied in the abductor pollicis brevis (APB), extensor digitorum brevis (EDB), and tibialis anterior (TA) muscles of 12 patients with myotonic muscular dystrophy (MMD) and in the same number of control subjects, matched for age and sex. The peak‐to‐peak amplitudes and voltage‐time areas of the responses were measured at rest, between 40 maximum voluntary contractions (each lasting 3 s) and also during a 2‐min recovery period. In 34 of the 36 control muscles the M‐waves potentiated during the period of intermittent voluntary contractions. In the MMD patients, however, the M waves exhibited initial declines in 25 of 30 muscles. In the APB and EDB muscles the normalized mean values for the smallest M‐waves, recorded during the 350 s total observation periods, differed significantly between the 2 groups of subjects. It is suggested that the sarcolemmal Na+‐K+ pump has a raised threshold for activation in MMD patients.
Quantitation of axon loss and conduction block in peroneal nerve palsies
Authors: Brown William F. , Watson Brad V. 
Published: January 2005

AbstractWe compared conduction in motor fibers supplying the extensor digitorum brevis (EDB) and anterior lateral compartment (AL) muscles. The object was to determine whether there were any differences in the relative proportions of degenerated and blocked nerve fibers between the longer EDB and shorter AL fibers. In almost every case the percentage of motor fibers undergoing axonal degeneration was greatest in EDB fibers. Conversely, the percentage of conduction block was greatest in the AL motor fibers. As clinical recovery is dependent on AL muscles rather than EDB, electrophysiological study of the relative proportions of degenerated and blocked fibers in the former should provide a more reliable measure of outcome than similar studies of EDB. Conduction velocity distal to the fibular head was not slowed despite the large loss of EDB motor fibers. Evidence for selective involvement of the larger myelinated fibers is, therefore, lacking. The location of the major conduction abnormalities was in almost every case between the mid‐fibular head and popliteal fossa.
AAEM minimonograph #3: Motor unit recruitment
Authors: Petajan Jack H. 
Published: January 2005

AbstractMotor unit recruitment is the process by which different motor units are activated to produce a given level and type of muscle contraction. At minimal levels of muscle contraction (innervation), muscle force is graded by changes in firing rate (rate coding) of individual motoneurons (MNs). At higher levels of innervation, recruitment is accomplished by the addition of different motor units firing at or above physiologic tremor rate. During slowly graded and ballistic increases in force, motor units are recruited in rank order of their size. In addition to MN soma diameter, other factors contribute to the selectivity of MN activation. For la afferent MN activation in the cat, synaptic density and efficacy as well as specific membrane resistance are also rank ordered for slow, fatigue resistant, and fast fatigue motor units with slow motor units recruited first. The central drive for motor unit activation is distributed to all the MNs of the pool serving a given muscle. Size‐structure organization of the MN pool determines the order of recruitment and how MNs interact with each other. Disorders of the motor unit affect recruitment. A method for the clinical electromyographic assessment of recruitment is suggested. Assessment is made at three levels of innervation: minimal contraction for onset and recruitment firing rates; moderate contraction required to maintain the limb against gravity for the maximum number of motor units, their firing rates, and motor unit spikes/s; maximal voluntary contraction (MVC) for detection of high threshold enlarged motor units characteristic of reinnervation and completeness of the interference pattern (IP). Loss of muscle fibers results in early and excessive recruitment at minimal and moderate levels of innervation. Loss of motor units can result in both an increased rate and range of single motor unit firing at all levels of innervation. With reinnervation and enlargement of motor units, firing rates increase significantly and the interference pattern during MVC is incomplete.
Tea‐sensitive potassium channels and inward rectification in regenerated rat sciatic nerve
Authors: Gardon Thomas R. , Kocsis Jeffery D. , Waxman Stephen G. 
Published: January 2005

AbstractSucrose gap and intra‐axonal recording technques were used to identify the types of ion channels and inward rectification that are present in regenerated axons of adult (>8 weeks) rat sciatic nerve after crush injury. In sucrose gap recordings, 4‐aminopyridine (4‐AP) led to slight broadening of the compound action potential (CAP) in normal nerve, and a greater broadening in regenerated nerves. By 12 days after sciatic nerve crush, regenerated nerves manifested an afterhyperpolarization (AHP) lasting up to 250 ms that was sensitive to tetraethylammonium (TEA). A similar TEA‐sensitive AHP could be elicited with repetitive stimulation. Hyperpolarizing constant current steps (0.1 to 0.5 mA; 600–900 ms duration) applied across the sucrose gap through regenerated axons evoked membrane hyperpolarizations with a depolarizing, Cs+‐sensitive relazation in the response to hyperpolarization, which is characteristic of inward rectification, occuring after about 70 ms. The relaxation was present as early as 21 days after nerve crush. Intra‐axonal recordings showed burst firing in 4‐AP that was terminated by an AHP that temporally correlated with the TEA‐sensitive AHP, and a relaxation in the respones to hyperpolazing current, similar to that of whole nerve recordings. The results demonstrate that in addition to voltagesensitive sodium channels and 4‐AP‐sensitive potassium channels, there are TEA‐sensitive and inwardly rectifying channels on mammalian regenerated peripheral nerve axons.
Normal maximal and minimal motor nerve conduction velocities in adults determined by a collision method
Authors: Arasaki Keisuke , Iijima Masakazu , Nakanishi Tokao 
Published: January 2005

AbstractUsing a new collision method, we measured motor nerve conduction velocities of the ulnar nerve in the forearm and the action potential amplitude of the abductor digit minimi muscle on 60 adults, ages 20 to 82 years and apparently free from diseases of the peripheral nervous system. Both maximal and minimal motor nerve conduction velocities were linear functions of age; 64.42 – 0.05 age and 60.45 – 0.12 age, respectively. The percentage of the minimal to the maximal motor nerve conduction velocities was expressed as 94.45 – 0.13 age. The maximum amplitude of evoked muscle action potentials was also correlated with age. This novel method may be useful in detecting pathology of motor nerve fibers which results in a decrease in submaximal conduction velocities.
Somatosensory evoked potentials of the medial and lateral plantar and calcaneal nerves
Authors: Dumitru Daniel , Kalantri Ananthlal , Dierschke Brenda 
Published: January 2005

AbstractThe ideal electrodiagnostic procedure to assess possible plantar neuropathies continues to elude investigators. Motor studies are rarely abnormal, pure sensory studies may be difficult to obtain, needle electromyography can demonstrate membrane instability in normal feet. Mixed nerve plantar studies may be more diagnostically valuable than the other techniques but they also have shortcomings. In this report, a technique utilizing somatosensory evoked potentials to assess the medial and lateral plantar and calcaneal nerves is demonstrated. Normative data with respect to latencies, amplitudes, and side‐to‐side differences are presented. Two illustrative cases are also discussed in which the more standard techniques to evaluate plantar neuropathies fail to do so, but the SEP methodology suggests compromise of the intrinsic foot nerves.
Magnetic stimulation of muscle evokes cerebral potentials
Authors: Zhu Yu , Starr Arnold 
Published: January 2005

AbstractSomatosensory evoked potentials (SEPs) were recorded from the scalp in man to magnetic stimulation of various skeletal muscles. The potentials consisted of several components, the earliest of which decreased in latency as the stimulated site moved rostrally, ranging from 46 msec for stimulation of the gastrocnemius, to 14 msec for stimulation of the deltoid. Experiments were performed to distinguish the mechanisms by which magnetic stimulation of the muscle was effective in evoking these cerebral potentials. For the gastrocnemius, the intensity of the magnetic stimulus needed for evoking cerebral potentials was less than that required for activating mixed or sensory nerves in proximity to the muscle belly (eg, posterior tibial nerve in the popliteal fossa, sural nerve at the ankle). Vibration of the muscle or passive lengthening of the muscle, procedures which activate muscle spindles, were accompanied by a significant attenuation of the potentials evoked by magnetic stimulation of the muscle. Anesthesia of the skin underlying the stimulating coil had no effect on the latency or amplitude of the early components of the magnetically evoked potentials, whereas electrically evoked potentials from skin electrodes were abolished. Thus, the cerebral potentials accompanying magnetic stimulation of the muscle appear to be due to activation of muscle afferents. We suggest that magnetic stimulation of muscle can provide a relatively simple method for quantifying the function of muscle afferents originating from a wide variety of skeletal musculature.
Altered Na+ channel activity and reduced Cl− conductance cause hyperexcitability in recessive generalized myotonia (becker)
Authors: Franke Christian , Iaizzo Paul A. , Hatt Hanns , Spittelmeister Wolfgang , Ricker Kenneth , Lehmann‐Horn Franke 
Published: January 2005

AbstractIntact muscle fibers or resealed fiber segments from 7 patients with recessive generalized myotonia were studied in vitro. All fibers had normal resting membrane potentials and normal resting [Ca2+]i several hours after removal. Contractions were characterized by slowed relaxation which was due to electrical after‐activity. Often spontaneous depolarizations were recorded intracellularly. In all fibers, the steady state voltage‐current relationship was abnormal, due to a reduced Cl2+ conductance. However, this conductance ranged from 0% to 66% of the total membrane conductance, whereas, in normal muscle, it was 80%. Theoretically, myotonic after‐discharges would not appear until the Cl− conductance is below 20%. Thus, the membrane hyperexcitability must be due to another defect, at least in the preparations in which the Cl− conductance was only slightly reduced. In all patches from all patients investigated with the patch clamp technique, we observed reopenings of the Na+ channels throughout depolarizing pulses (such behavior was absent in normal muscle). If a patch was polarized to potentials less negative than the resting potential, the duration of the reopenings increased. We conclude that a combination of reduced Cl− conductance and the reopenings of Na+ channels underlie the electrical afteractivity in recessive generalized myotonia.
Myotonia and neuromuscular transmission in the mouse
Authors: Költgen Dirk , Brinkmeier Heinrich , Jockusch Harald 
Published: January 2005

AbstractThe role of neuromuscular transmission and acetylcholine receptors in the phenotypic expression of hereditary myotonia was reinvestigated in two mutants of the mouse, ADR (adr/adr) and MTO (adrmto/adrmto). Three neuromuscular blockers, curare, flaxedil, and α‐bungarotoxin, did not prevent mechanical myotonia of EDL and soleus muscles from the two mutants. Furthermore, electrical myotonia was demonstrated in isolated ADR muscle fibers devoid of nerve endings. We conclude that neither release nor reception of acetylcholine are important for the mechanism of myotonia in mouse mutants. The previously described suppression of myotonic aftercontractions by high concentrations of curare (Muscle & Nerve 1987;10:293–298) could not be reproduced; rather, a prolongation of aftercontractions was found. The other drugs had no significant effect on myotonic aftercontractions. Because neuromuscular transmission is not involved in human myotonias, this result supports the use of myotonic mice as a model, at least for recessive generalized myotonia (Becker).
Chronic multifocal demyelinating neuropathy associated with central nervous system demyelination
Authors: Naganuma Mutsuo , Shima Kohji , Matsumoto Akihisa , Tashiro Kunio 
Published: January 2005

AbstractWe have carried out a long‐term study of lesions found in a man who had a demyelinating disease of both central and peripheral nervous systems. During the 10 years of his clinical course, he suffered from optic neuritis, multifocal myelitis, and chronic multifocal demyelinating neuropathy, with persistent conduction block. Our study revealed that both central and peripheral nervous system demyelination occurred repeatedly and simultaneously.
The silent period produced by electrical stimulation of mixed peripheral nerves
Authors: Leis A. Arturo , Ross Mark A. , Emori Takumi , Matsue Yoshihiko , Saito Takanori 
Published: January 2005

AbstractThe electromyographic silent period (SP) produced by electrical stimulation of the median and ulnar nerve, before and after lidocaine block of the ulnar nerve at the elbow, was recorded in the voluntarily contracting abductor pollicis brevis (APB) muscle of 4 normal subjects. Prior to block, stimulation of the corresponding segment in either nerve (e.g., wrist and elbow) elicited SPs with similar end points. With more proximal stimulation, the SPs consistently ended earlier. Following the block, ulnar nerve stimulation below the elbow failed to elicit a SP in any subject, despite a mechanical twitch caused by the antagonistic contraction of adductor pollicis muscle. Ulnar nerve stimulation above the block elicited a SP in all subjects similar to the preblock SP. In all 4 subjects, submaximal median nerve stimulation at the wrist produced an H‐reflex, followed by a SP in the absence of the direct M‐response. This SP, due to selective activation of sensory fibers, lacked a collision component, but, was otherwise similar to the SP elicited by supramaximal wrist stimulation. These findings indicate that the ascending volley following electrical stimulation of a mixed peripheral nerve produces the SP without apparent contribution from the descending motor volley.
Ca‐, Sr‐tension relationships and contraction velocities of human muscle fibers
Authors: Ruff Robert L. , Whittlesey Diana 
Published: January 2005

AbstractMuscle fibers from the lateral gastrocnemius or intercostal muscles of 7 normal adult males were chemically skinned (sarcolemma disrupted) and isolated fibers were divided into two parts for histochemical determination of fiber type and physiologic studies. The Ca‐ and Sr‐induced tension relationships and maximum contraction velocities were measured. Slow twitch fibers developed tension at lower concentrations of Ca or Sr than fast twitch fibers. The difference between fast and slow twitch fibers was greatest when Sr was the activating cation. Fast and slow twitch fibers generated similar maximum tensions. The contraction velocities of fast twitch fibers were more than two‐fold greater than slow twitch fibers. Fast‐oxidative‐glycolytic (FOG, type IIA) and fast‐glycolytic (FG, type IIB) fibers had similar Ca‐ and Sr‐tension relationships and contraction velocities.
Electrophysiologic studies in the Guillain–Barré syndrome: Effects of plasma exchange and antibody rebound
Authors: Rudnicki S. , Vriesendorp F. , Koski C. L. , Mayer R. F. 
Published: January 2005

AbstractNerve conduction studies (NCS) and antiperipheral nerve myelin antibody (A‐PNM Ab) titers were measured serially in 29 patients with Guillain‐Barré syndrome (GBS), of whom 21 were treated with plasmapheresis. Data were obtained from 3 to 6 days until 1 to 2 years after onset of symptoms. Within 3 to 6 days, mean NCS were abnormal. They improved some by 1 week and became maximally abnormal by 4 to 8 weeks, during which time A‐PNM Ab fell to low levels. In 5 patients plasmapheresed, A‐PNM Ab fell and then increased at 4 to 8 weeks, followed by significant deterioration of NCS (P = 0.01) compared with those without antibody rebound at 18 weeks. These results suggest that, in monophasic GBS, there may be two mechanisms of conduction dysfunction such as early paranodal retraction and later demyelination. In some patients plasmapheresed, A‐PNM Ab may rebound associated with further conduction dysfunction. These patients may benefit from further plasmapheresis.
The neuromuscular basis of hereditary kyphoscoliosis in the mouse
Authors: Bridges Leslie R. , Coulton Gary R. , Howard Gillian , Moss Jill , Mason Roger M. 
Published: January 2005

AbstractWe describe a new neuromuscular disorder in the kyphoscoliotic mouse mutant (ky). Mice were killed at ages from birth to 210 days, and tissues were taken for standard light microscopy, histochemistry, nerve ending studies, and electron microscopy. At birth a few myofibers showed phagocytosis ultrastructurally. Between 6 and 25 days there was prominent necrosis and regeneration in soleus, gracilis, paraspinal, and back muscles. At 47 days, these muscles were atrophic and necrosis and regeneration were rare. At 136 days, all muscle groups, including head muscles, showed some degree of myofiber atrophy and gracilis was fibrotic. Prominent intramuscular axonal sprouting was present from 31 days. Peripheral nerves and anterior horn cells were normal. The findings indicate a neuromuscular basis of hereditary kyphoscoliosis in the mouse. The animal may be useful as a model of human muscle disease and scoliosis.
Myosin isoforms in hindlimb muscles of normal and dystrophic (ReJ129 dy/sol;dy) mice
Authors: Reggiani Carlo , Brocks Lenny , Wirtz Peter , Loermans Helene , te Kronnie Geertruy 
Published: January 2005

AbstractMyosin isoform expression was studied in hindlimb muscles of control (Dy/Dy) and dystrophic (dy/dy) mice of the ReJ129 strain during postnatal development. Three myosin heavy chain isoforms (fast II‐B MHC, neonatal MHC, and slow or I MHC) were identified using monoclonal antibodies. Only original fibers, i.e., fibers formed during fetal life, were studied. Necrotic and regenerating fibers were excluded. The disappearance of neonatal MHC was found to be delayed in all muscles of dystrophic mice, except the soleus. The fraction of fibers containing I MHC was similar in control and dystrophic animals at all ages, except during the third postnatal week. The developmental increase in the fraction of fibers expressing II‐B MHC was interrupted in dystrophic mice by two marked declines. The first occurred during the second postnatal week at the beginning of the main wave of fiber necrosis, and the second occurred at between 30 and 90 postnatal days.
Conduction velocities of α‐motor fibers innervating human thenar muscles and order of recruitment upon voluntary contraction
Authors: Kakuda Naoyuki , Nagaoka Masanori , Tanaka Reisaku 
Published: January 2005

AbstractConduction velocity (CV) of single α‐motor fibers was measured using a combination of microneurogrphic and spike‐triggered averaging techniques on 7 healthy subjects (aged 25 to 42). Two tungsten microelectrodes were inserted percutaneously into the median nerve at the wrist and 4 to 6 cm more proximally. Motor unit activities recorded from thenar muscles during voluntary isometric contraction with a third microelectrode, were isolated with a window discriminator, and used to trigger an averager. CVs were calculated by dividing the interelectrode distance by the conduction time between unitary activities in the proximally and distally averaged neurograms. The CVs of 100 units ranged between 34 and 66 m/s, with the peak at around 50 m/s. The relationship between CVs and recruitment orders was compared within sets of 2 or 3 units recorded simultaneously. Statistical analysis using a χ2 test revealed that slower motor units tended to be recruited earlier than faster units (P < 0.001).
Conduction studies of the normal sural nerve
Authors: Horowitz Steven H. , Krarup Christian 
Published: January 2005

AbstractThe sural nerve was studied orthodromically using the near‐nerve technique in 273 normal subjects (155 females, 118 males) aged 5 to 90 years. The sensory action potential (SAP), evoked at the dorsum of the foot, was recorded at the lateral malleolus and midcalf, and at the midcalf when evoked at the lateral malleolus. In addition, the SAP was recorded at intermediate distal sites and at proximal sites at the popliteal fossa, the gluteal fold, and the S‐1 root. The amplitude of the SAP recorded at midcalf was 32% higher in females than in males. This was probably due to volumeconduction properties, as differences between genders were less noticeable at more distal recording sites. The amplitude decreased steeply and exponentially with age. Conduction distance had a strong influence on the amplitude of the SAP, which decreased with increasing distance following a power relationship with an exponent of 1.4 to 1.7. This decrease was due to temporal dispersion with decreased summation and increased phase cancellation. The conduction velocity was slightly lower along the very distal course of the nerve than along more proximal segments.