Search results for "conduction velocity"

Transient hypothyroidism during lactation alters the development of the corpus callosum in rats. An in vivo magnetic resonance image and electron mic…

2020

Magnetic resonance imaging (MRI) data of children with late diagnosed congenital hypothyroidism and cognitive alterations such as abnormal verbal memory processing suggest altered telencephalic commissural connections. The corpus callosum (CC) is the major inter-hemispheric commissure that contra-laterally connects neocortical areas. However, in late diagnosed neonates with congenital hypothyroidism, the possible effect of early transient and chronic postnatal hypothyroidism still remains unknown. We have studied the development of the anterior, middle and posterior CC, using in vivo MRI and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated r…

2019

AbstractDuring early postnatal life, speed up of signal propagation through many central and peripheral neurons has been associated with an increase in axon diameter or/and myelination. Especially in unmyelinated axons postnatal adjustments of axonal membrane conductances is potentially a third mechanism but solid evidence is lacking. Here, we show that axonal action potential (AP) conduction velocity in theDrosophilagiant fiber (GF) interneuron, which is required for fast long-distance signal conduction through the escape circuit, is increased by 80% during the first day of adult life. Genetic manipulations indicate that this postnatal increase in AP conduction velocity in the unmyelinated…

C- and Aδ-fiber components of heat-evoked cerebral potentials in healthy human subjects

1999

Feedback-controlled laser heat was used to stimulate the hairy skin of the hand dorsum and forearm, and heat-evoked cerebral potentials were recorded at midline (Fz, Cz, Pz) and temporal (T3, T4) scalp positions. Based on data from primary afferent electrophysiology a stimulus level (40 degrees C) was chosen, which is above C-fiber heat threshold, but clearly below A delta-nociceptor heat threshold in order to excite selectively C-fibers without concomitant excitation of A delta-fibers. Feedback-controlled stepped heat stimuli to 40 degrees C elicited ultralate laser evoked potentials (LEPs) at the vertex in a high proportion of experiments (90%). Estimates of conduction velocity calculated…

Conduction times of cortical projections to paravertebral muscles in controls and in patients with multiple sclerosis

1994

Tuberculoid leprosy and Type 1 lepra reaction.

2008

Summary A patient is described with tuberculoid leprosy and Type 1 (lepra) reaction from Sicily a non-endemic region, who lived previously in Manila from 2000 to 2005. The skin lesions became acutely inflamed and edematous. The plaques were painless to touch or pinprick, and there was swelling of the nerves in the fibro-osseous tunnels under the surface of the skin, including both the ulnar nerve at the elbow, and the posterior tibial nerve (medial malleolus). During the course of electro-neurographic studies, conduction velocity in the motory nerves indicated a slowing-down. The diagnosis of leprosy was confirmed by residence in an endemic area for about 5 years, by simultaneous skin lesio…

Effect of electrode location on surface electromyography changes due to eccentric elbow flexor exercise.

2009

Experiments were carried out to determine whether the location of electrodes has an effect on eccentric exercise–induced changes in surface electromyography (sEMG) variables in the biceps brachii muscle. sEMG signals were recorded with a grid of 64 electrodes before and up to 4 days post-exercise. Root mean square (RMS) and mean power frequency (MNF) were calculated for: (1) each channel; (2) as an average of all channels; and (3) as an average of individual channel rows and columns. Mean muscle-fiber conduction velocity (CV) was estimated similarly but was based on double-differential channels. Maximal isometric voluntary torque decreased 21.3 ± 5.6% post-exercise. The average sEMG variabl…

F-Wave study in patients with chronic renal failure on regular haemodialysis

1986

Motor nerve conduction along the entire length of ulnar and tibialis posterior nerves was studied in 30 uraemic patients and in 20 control subjects. The M and F latencies, MNCV (between the stimulus sites), FWCV (between the spinal cord and the stimulus sites) and F-ratio (conduction time ratio of proximal to distal segment) were assessed to evaluate the conduction in the proximal versus the distal nerve segment. In the uraemic patients, the slowing of nerve conduction involved both segments of the tested nerves to the same extent. In fact, the F-ratio did not show any significant difference between the two groups; in only one patient was its value lower than the normal limit in the tibiali…

Induction of vascular endothelial growth factor release by transcutaneous frequency modulated neural stimulation in diabetic polyneuropathy

2008

Background: Pharmacological treatment for diabetic polyneuropathy (DP) has shown limited benefit; frequency-modulated electrical stimulation (FREMS) has shown positive results in pain control and nerve conduction velocity in DP. Objective: To investigate the effects of FREMS vs transcutaneous electrical nerve stimulation (TENS) on the release of vascular endothelial growth factor (VEGF) in Type 2 diabetic and in non-diabetic subjects. Methods: 10 non-diabetic [mean age 37±5 yr; females (F)/males (M): 6/4] and 10 Type 2 diabetic subjects (mean age 52±6 yr; F/M: 5/5) with DP underwent TENS (for 10 min) followed by 30 min interval without electrical stimulation, and then FREMS (for 10 min) ove…

EMG power spectrum and features of the superimposed M-wave during voluntary eccentric and concentric actions at different activation levels.

2001

Muscle fiber conduction velocity (CV) may be affected by the level of voluntary activation and by the diameter of the fiber. Both the frequency component of the electromyography (EMG) power spectrum, such the as median frequency (MF) or mean power frequency, and the duration of muscle compound action potential to single supramaximal electrical impulse (maximal M-wave) may be related to CV. The aim of the present study was to examine how changes in the activation level in lengthening and in shortening conditions would affect the EMG power spectrum during voluntary effort, and compare them to changes in M-wave shape in similar conditions. Ten male subjects performed eccentric and concentric k…

Increased risk of sensory neuropathy in workers with chloracne after exposure to 2,3,7,8-polychlorinated dioxins and furans

1999

Objective - The existence of a peripheral neuropathy after exposure to polychlorinated dioxins (PCDD) is still discussed, as studies concerning dioxin effects on the peripheral nervous system are rare and contradictory. Material and methods - Clinical and neurophysiological examinations (motor conduction velocity of the peroneal nerve, sensory conduction velocities of the sural and ulnar nerves) were made in 156 dioxin exposed workers (42 with, 114 without cloracne) from one pesticide producing plant. Because of known risk factors for peripheral neuropathy, 7 workers with and 28 without cloracne were excluded from further analysis. Results - Workers with chloracne had a significantly higher…