Response of the canine internal intercostal muscles to chest wall vibration.

Although high-frequency mechanical vibration of the rib cage reduces dyspnea, its effects on the respiratory muscles are largely unknown. We have previously shown that in anesthetized dogs, vibrating the rib cage during inspiration elicits a marked increase in the inspiratory electromyographic (EMG) activity recorded from the external intercostal muscles but does not affect tidal volume (VT). In the present studies, we have tested the hypothesis that the maintenance of VT results from the concomitant contraction of the internal interosseous (expiratory) intercostals.

Response of the canine inspiratory intercostal muscles to chest wall vibration.

High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and external intercostal muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent external intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal intercostal activity was recorded in only four animals.

Reflex inhibition of canine inspiratory intercostals by diaphragmatic tension receptors.

1. Electrical stimulation of phrenic afferent fibres in the dog elicits a reflex inhibition of efferent activity to the inspiratory intercostal muscles. However, electrical stimulation has a poor selectivity, so the sensory receptors responsible for this inhibition were not identified.

Effects of vigabatrin on motor potentials evoked with magnetic stimulation.

We studied the effect of an acute loading dose of vigabatrin on threshold of motor responses and duration of silent period elicited with cortical magnetic stimulation in normal subjects. In contrast to phenytoin, vigabatrin does not increase the motor threshold of first dorsal interosseus muscle. We also show that, although vigabatrin increases GABA concentrations in the central nervous system, duration of silent period studied at various stimulus intensities is not modified after vigabatrin administration.

Abnormal motor evoked responses to transcranial magnetic stimulation in focal dystonia.

We evaluated motor responses evoked after magnetic cortical stimulation in dystonia, emphasizing the relationship between resting and facilitation state. We studied 15 normal controls (mean age, 37.9 years; range, 23 to 63) and 13 dystonic patients (mean age, 43.

Effects of diphenylhydantoin on motor potentials evoked with magnetic stimulation.

We studied the effect of an acute loading dose of diphenylhydantoin (DPH) on motor responses elicited with cortical magnetic stimulation in normal subjects. DPH increased significantly the motor threshold activation of ADM, APB, FDI and biceps. The motor threshold increase was of greater magnitude for the proximal muscle.

Somatosensory central conduction time after sural and tibial nerve stimulation.

We recorded spinal and cortical somatosensory evoked potentials (SEPs) after sural and tibial nerve stimulation at the ankle in 34 normal subjects. Spinal SEPs were reproducible with sural nerve stimulation in only 65% of normal subjects. The spinal amplitudes were significantly smaller after sural nerve stimulation.

Spinal and brain-stem SEPs and H reflex during enflurane anesthesia.

Whereas cortical SEPs are altered by halogenated anesthetics, spinal and subcortical SEPs are thought to be hardly affected. In this study the spinal N13 potential (recorded with anterior neck reference) showed a significant delay with enflurane anesthesia. The P13 and P14 far-field potentials, however, remained unchanged.

Dissociation of P13-P14 far-field potentials: clinical and MRI correlation.

P13 and P14 far-field potentials are recorded over the scalp with median nerve stimulation when non-cephalic reference is used to measure somatosensory evoked potentials. The dissociation of these 2 potentials is exceptional. Only 2 cases subsequent to pontine lesions have been described hitherto.

Topographic analysis of the effects of isoflurane anesthesia on SEP.

Isoflurane anesthesia induces a striking increase in the P22 potential recorded over the precentral scalp whereas the amplitude of the N20 is reduced. It is not known whether the increased "P22" enhanced by isoflurane arises from the same generator as the small precentral P22 potential recorded in the normal awake subject. Multi-channel recordings of SEP before and during isoflurane anesthesia were performed in 13 normal subjects.

Inhibitory effects of ATP and other nucleotides on atrial natriuretic peptide (ANP) binding to R1-type ANP receptors in human neuroblastoma NB-OK-1 cell membranes.

ATP dose-dependently inhibited rat 125I-ANP-(99-126) binding to membranes from the human neuroblastoma cell line NB-OK-1 by increasing the KD value for the hormone without altering the Bmax value. After a 20 min preincubation with 37.5 pM 125I-ANP-(99-126) and 0.

Synaptic effects of halogenated anesthetics on short-latency SEP.

We evaluated the effects of different stable end-tidal concentrations of isoflurane, enflurane, or halothane on short-latency somatosensory evoked potentials recorded during general anesthesia. Isoflurane and enflurane significantly enhanced the P22 over the pre-central scalp, whereas the parietal N20 amplitude did not increase. The P22 increase did not occur with halothane, which indicates that the P22 changes are a specific effect of certain anesthetics, probably related to their influence on synaptic events.

Acute effects of diphenylhydantoin on peripheral and central somatosensory conduction.

We studied the acute effects of an intravenous loading dose of DPH (16 mg/kg body weight) on peripheral and central somatosensory conduction in 10 normal volunteers. Somatosensory evoked potentials were recorded before and at regular intervals after DPH infusion. There was no effect on peripheral conduction.

[Course of central somatosensory conduction in a case of vitamin B12 deficiency].

We report clinical and neurophysiological data of a 58 year-old man with vitamin B12 deficiency and a 6 years follow-up. The initial clinical disorders did not permit a clear distinction between peripheral and central nervous system disease. Detailed analysis of the somatosensory central conduction time (measured from onset latencies of N11 and N20) showed clear evidence of slowed down conduction at spinal cervical level (reflected by the N11-P14 interval) whereas supraspinal conduction (as shown by the P14-N20 interval) was normal.

The effect of stimulus frequency on post- and pre-central short-latency somatosensory evoked potentials (SEPs).

We assessed the influence of the stimulus frequency on short-latency SEPs recorded over the parietal and frontal scalp of 26 subjects to median nerve stimulation and 16 subjects to digital nerve stimulation. When the stimulus frequency is increased from 1.6 Hz to 5.

Differential effects of isoflurane on SEP recorded over parietal and frontal scalp.

We evaluated the effects of different concentrations of isoflurane on short-latency somatosensory evoked potentials recorded over the parietal and frontal scalp in 14 patients during general anesthesia at stable end-tidal concentrations between 0% and 2.5%. At concentrations between 0% and 1%, there was a marked discrepancy between the amplitude of the parietal N20, which remained stable, and the striking increase of the frontal P22.

The effect of acute hemiplegia on intercostal muscle activity.

We recorded the EMG of parasternal intercostal muscles in 25 patients with flaccid hemiplegia during quiet spontaneous breathing, voluntary hyperventilation, and CO2-induced hyperventilation. The respiratory drive was abnormal on the hemiplegic side and the function of the intercostal muscles was affected specifically during voluntary hyperventilation.

Selective unilateral absence or attenuation of wave V of brain-stem auditory evoked potentials with intrinsic brain-stem lesions.

The contribution of ipsilateral and contralateral auditory brain-stem structures to the generation of wave V of brain-stem auditory evoked potentials is a controversial subject. We describe two cases with an intrinsic brain-stem lesion that involved the lateral lemniscus unilaterally in the middle and upper pons. The focal nature of the auditory structures was confirmed by detailed neuropathologic data in one case and by magnetic resonance scans in the other one.

Somatosensory conduction in vitamin B12 deficiency.

We tested the hypothesis that the somatosensory central conduction time (CCT) can reveal central nervous system involvement in vitamin B12-deficient patients when this cannot be established on clinical grounds alone. Three patients with pernicious anemia and without clinical signs of upper motor neuron lesion had a striking increase of CCT. This increase was shown to be reversible in 1 patient who improved over 3 years of treatment.

The somatosensory central conduction time: physiological considerations and normative data.

The somatosensory central conduction time (CCT) can be measured from the peak of N13 to the peak of N20 (peak CCT) or from the onset of N11 to the onset of N20 (onset CCT). The onset and peak CCT were measured concomitantly in 40 normal subjects and the mean peak CCT was significantly shorter than the mean onset CCT. Records with different reference electrodes (linked earlobes, F3, over the ipsilateral parietal scalp, non-cephalic reference in some subjects) showed no significant latency change of the N11 onset, the N20 onset, the peak and onset CCT in contrast with the significant latency changes of the N13 and N20 peak with different montages.

Femoral versus peroneal neuropathy in diabetic children and adolescents--relationships to clinical status, metabolic control and retinopathy.

In order to estimate the prevalence of diabetic neuropathy in proximal and distal peripheral nerves, femoral and peroneal motor conduction was evaluated in 61 diabetic children, adolescents and young adults whose type 1 diabetes had become clinically apparent before the age of 14 years. Femoral motor nerve conduction velocity (FMNCV) in diabetic patients (63.8 +/- 10.

Prognostic value of early cortical somatosensory evoked potentials after resuscitation from cardiac arrest.

Short-latency somatosensory evoked potentials (SEPs) were evaluated in patients after cardiorespiratory arrest to study their pattern of recovery in the acute stage of anoxic-ischaemic coma. Fifty consecutive comatose patients were investigated within 8 h after cardiorespiratory resuscitation. In 30 patients no cortical SEPs were recorded and none of the patients recovered cognition.