scholarly journals The Excitability of Human Corticospinal Neurons is Depressed by Thiopental

1995 ◽  
Vol 22 (3) ◽  
pp. 218-222
Author(s):  
K. Kong ◽  
C. Ukachoke ◽  
G. McGuire ◽  
D. Wong ◽  
P. Ashby
Keyword(s):  
Cortical Neurons ◽  
Magnetic Stimulation ◽  
Human Subjects ◽  
Motor Units ◽  
Normal Subjects ◽  
Spinal Motoneurons ◽  
Corticospinal Pathway ◽  
First Dorsal Interosseous Muscle ◽  
Normal Human ◽  
Dorsal Interosseous Muscle

AbstractBackgroundWe tested the effect of thiopental on the excitability of the corticospinal-motoneuron axis in normal human subjects.MethodsMagnetic stimulation was used to excite the neurons in the motor cortex which give rise to the fast conducting corticospinal pathway. The characteristics of the composite excitatory post-synaptic potentials (EPSPs) produced in individual spinal motoneurons by cortical stimulation were derived from changes in the firing probability of voluntarily activated motor units of the first dorsal interosseous muscle.ResultsIn 5 normal subjects, we found that thiopental, in incremental doses sufficient to sustain drowsiness (total dose 75 to 175 mg), significantly reduced the amplitude of these composite EPSPs.ConclusionsThiopental reduced the facilitation of motoneurons from the cortex most likely by depressing cortical neurons.

Excitability of human motor cortex during hyperventilation and hypercapnia

1994 ◽  
Vol 72 (8) ◽  
pp. 909-913 ◽  
Author(s):  
K. Kong ◽  
C. Ukachoke ◽  
P. Ashby ◽  
K. R. Chapman
Keyword(s):  
Motor Cortex ◽  
Cortical Neurons ◽  
Healthy Subjects ◽  
Magnetic Stimulation ◽  
Motor Units ◽  
Spinal Motoneurons ◽  
Human Motor Cortex ◽  
Corticospinal Pathway ◽  
Human Motor ◽  
End Tidal

We tested the hypothesis that the excitability of corticospinal neurons was altered by changes in [Formula: see text]. Magnetic stimulation was used to excite the neurons in the human motor cortex that give rise to the fast-conducting corticospinal pathway. The characteristics of the composite excitatory postsynaptic potentials (EPSPs) produced in individual spinal motoneurons by cortical stimulation were derived from changes in the firing probability of voluntarily activated motor units. The amplitudes of these composite EPSPs in response to a constant cortical stimulus were assumed to reflect the excitability of cortical neurons. In 10 healthy subjects, we found no statistically significant changes in the excitability of the cortical neurons during normocapnic conditions (mean end-tidal [Formula: see text] 5.1 kPa), during hyperventilation-induced hypocapnia (mean end-tidal [Formula: see text] 2.9 kPa), and during hyperoxic hypercapnia induced by a rebreathing technique (mean end-tidal [Formula: see text] 6.9 kPa). We conclude that the excitability of corticospinal neurons activated by magnetic stimulation is not significantly affected by changes in [Formula: see text].Key words: corticospinal neurons, [Formula: see text], magnetic stimulation.

Functional magnetic stimulation of expiratory muscles: a noninvasive and new method for restoring cough

1998 ◽  
Vol 84 (4) ◽  
pp. 1144-1150 ◽  
Author(s):  
Vernon W. H. Lin ◽  
Caleb Hsieh ◽  
Ian N. Hsiao ◽  
James Canfield
Keyword(s):  
Critical Care ◽  
Neurological Disorders ◽  
Magnetic Stimulation ◽  
Human Subjects ◽  
Normal Subjects ◽  
Stimulation Parameters ◽  
Normal Human ◽  
Lower Thoracic Spine ◽  
Expiratory Muscles ◽  
Stimulation Of

The purpose of this study was to assess the effectiveness of functional magnetic stimulation (FMS) for producing expiratory function in normal human subjects. Twelve able-bodied normal subjects were recruited for this study. FMS of the expiratory muscles was performed by using a magnetic stimulator and placing the magnetic coil along the lower thoracic spine. Results showed that peak expired pressure, volume, and flow rate generated by FMS at the end of normal inspiration (102.5 ± 13.62 cmH2O, 1.6 ± 0.16 liters, and 4.8 ± 0.35 l/s, respectively) were comparable to their voluntary maximal levels ( P > 0.1). The optimal coil placement was between T7 and T11, and the optimal stimulation parameters were a frequency of 25 Hz and 70–80% of maximal intensity. We conclude that 1) FMS of the lower thoracic nerves in normal subjects resulted in a significant expiratory function comparable to their voluntary maximum; 2) FMS was noninvasive and was well tolerated by all subjects; and 3) FMS may be useful to produce cough in patients in critical care or perioperative settings, or in patients with neurological disorders.

scholarly journals The innervation and organization of motor units in a series-fibered human muscle: the brachioradialis

2010 ◽  
Vol 108 (6) ◽  
pp. 1530-1541 ◽  
Author(s):  
Zoia C. Lateva ◽  
Kevin C. McGill ◽  
M. Elise Johanson
Keyword(s):  
Human Subjects ◽  
Standing Waves ◽  
Motor Units ◽  
Human Muscle ◽  
Motor Unit Action Potential ◽  
Distal Muscle ◽  
Normal Human ◽  
Motor Unit Action ◽  
Unit Action ◽  
Individual Motor

We studied the innervation and organization of motor units in the brachioradialis muscle of 25 normal human subjects. We recorded intramuscular EMG signals at points separated by 15 mm along the proximodistal muscle axis during moderate isometric contractions, identified from 27 to 61 (mean 39) individual motor units per subject using EMG decomposition, and estimated the locations of the endplates and distal muscle/tendon junctions from the motor-unit action potential (MUAP) propagation patterns and terminal standing waves. In three subjects all the motor units were innervated in a single endplate zone. In the other 22 subjects, the motor units were innervated in 3–6 (mean 4) distinct endplate zones separated by 15–55 mm along the proximodistal axis. One-third of the motor units had fibers innervated in more than one zone. The more distally innervated motor units had distinct terminal waves indicating tendonous termination, while the more proximal motor units lacked terminal waves, indicating intrafascicular termination. Analysis of blocked MUAP components revealed that 19% of the motor units had at least one doubly innervated fiber, i.e., a fiber innervated in two different endplate zones by two different motoneurons, and thus belonging to two different motor units. These results are consistent with the brachioradialis muscle having a series-fibered architecture consisting of multiple, overlapping bands of muscle fibers in most individuals and a simple parallel-fibered architecture in some individuals.

Platelet catecholamines and platelet function in normal human subjects

1987 ◽  
Vol 73 (1) ◽  
pp. 99-103 ◽  
Author(s):  
A. P. Wilson ◽  
C. C. T. Smith ◽  
B. N. C. Prichard ◽  
D. J. Betteridge
Keyword(s):  
Platelet Function ◽  
High Performance ◽  
Human Subjects ◽  
Normal Subjects ◽  
Noradrenaline Content ◽  
Collagen Concentration ◽  
Normal Human ◽  
Wall Interaction ◽  
Local Release

1. We have used high-performance liquid chromatography with electrochemical detection to measure plasma and platelet catecholamines in 24 normal subjects. 2. In the same subjects platelet function was assessed by measuring platelet aggregation in response to adenosine 5′-pyrophosphate, thrombin, adrenaline and collagen. Platelet sensitivity to prostacyclin was also examined. 3. Platelet noradrenaline showed a positive correlation with extent of aggregation induced by ‘low-dose’ collagen (1 μg/ml). No correlation was seen at the higher collagen concentration. 4. Platelet noradrenaline content also correlated with sensitivity of platelets to prostacyclin. High platelet noradrenaline concentrations appeared to result in decreased sensitivity to prostacyclin. 5. No other correlations were observed. 6. These data suggest that platelet noradrenaline rather than plasma levels may be involved in modifying platelet function in vivo. Local release of platelet catecholamines may affect the platelet/vessel wall interaction, the primary physiological step in platelet activation.

Catechol O-Methyltransferase in Red Blood Cells of Schizophrenic, Depressed, and Normal Human Subjects

1976 ◽  
Vol 128 (2) ◽  
pp. 184-187 ◽  
Author(s):  
Helen L. White ◽  
Malcolm N. McLeod ◽  
Jonathan R. T. Davidson
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Subjects ◽  
Normal Subjects ◽  
Enzyme Preparations ◽  
Human Red Blood Cells ◽  
Schizophrenic Patients ◽  
Normal Human ◽  
The Mean ◽  
Isoelectric Ph

SummaryCatechol O-methyltransferase of lysed human red blood cells was assayed under optimal conditions, using saturating concentrations of the substrates, S-adenosyl-L-methionine and 3,4-dihydroxybenzoic acid. The mean enzyme activity found in 24 normal subjects was 29.2 nmol/hr/ml RBC. The mean activity in blood of 33 female unipolar depressives was not significantly different from normal. However, higher enzyme activities were observed in the blood of 11 schizophrenic patients (38.9 nmol/hr/ml RBC). Partially purified enzyme preparations from blood of normal and schizophrenic individuals were indistinguishable with respect to substrate specificities, isoelectric pH values, and ratios of the two O-methylated products. Therefore it is unlikely that any defect in O-methylation which may occur in schizophrenia can be attributed to a change in the intrinsic properties of erythrocyte catechol O-methyltransferase.

Lithium and erythrocyte membrane cation carrier studies in normal and manic depressive subjects

1977 ◽  
Vol 7 (2) ◽  
pp. 229-233 ◽  
Author(s):  
G. J. Naylor ◽  
A. Smith ◽  
L. J. Boardman ◽  
D. A. T. Dick ◽  
E. G. Dick ◽  
...  
Keyword(s):  
Erythrocyte Membrane ◽  
Human Subjects ◽  
Normal Subjects ◽  
Sodium Concentration ◽  
Manic Depressive Psychosis ◽  
Manic Depressive ◽  
Normal Human ◽  
Potassium Influx ◽  
Erythrocyte Sodium

synopsisChanges in the erythrocyte membrane cation carrier following lithium ingestion in normal human subjects were studied; ouabain sensitive potassium influx fell significantly during the lithium treated phase. Lithium was fed to rats and no change in erythrocyte Na-K ATPase was shown. These findings contrast with studies of lithium in manic depressive psychosis. The fluctuations in the erythrocyte membrane cation carrier were studied in 5 normal subjects over 12 weeks and the correlations between the parameters calculated. The erythrocyte sodium concentration correlated positively with the ouabain sensitive potassium influx. This too contrasts with findings in manic depressive psychosis.

Aminophylline and human diaphragm strength in vivo

1990 ◽  
Vol 68 (6) ◽  
pp. 2591-2596 ◽  
Author(s):  
R. D. Levy ◽  
S. Nava ◽  
L. Gibbons ◽  
F. Bellemare
Keyword(s):  
Motor Units ◽  
Normal Subjects ◽  
Acute Administration ◽  
Transdiaphragmatic Pressure ◽  
Gastric Pressure ◽  
Significant Difference ◽  
Before And After ◽  
Normal Human ◽  
Twitch Characteristics

The transdiaphragmatic pressure (Pdi) twitch response to single shocks from supramaximal bilateral phrenic nerve stimulation was studied before and after acute intravenous infusions of aminophylline [14.9 +/- 3.1 (SD) micrograms/ml] in nine normal subjects. Stimulation was performed with subjects in the sitting position against an occluded airway from end expiration. Baseline gastric pressure and abdominal and rib cage configuration were kept constant. There was no significant difference in peak twitch Pdi from the relaxed diaphragm between control (38.8 +/- 3.3 cmH2O) and aminophylline (40.2 +/- 5.2 cmH2O) experiments. Other twitch characteristics including contraction time, half-relaxation time, and maximum relaxation rate were also unchanged. The Pdi-twitch amplitude at different levels of voluntary Pdi was measured with the twitch occlusion technique, and this relationship was found to be similar under control conditions and after aminophylline. With this technique, maximum Pdi (Pdimax) was calculated as the Pdi at which stimulation would result in no Pdi twitch because all motor units are already maximally activated. No significant change was found in mean calculated Pdimax between control (146.9 +/- 27.0 cmH2O) and aminophylline (149.2 +/- 26.0 cmH2O) experiments. We conclude from this study that the acute administration of aminophylline at therapeutic concentrations does not significantly affect contractility or maximum strength of the normal human diaphragm in vivo.

Relationship Between Simulated Common Synaptic Input and Discharge Synchrony in Cat Spinal Motoneurons

2001 ◽  
Vol 86 (5) ◽  
pp. 2266-2275 ◽  
Author(s):  
Marc D. Binder ◽  
Randall K. Powers
Keyword(s):  
Synaptic Input ◽  
Human Subjects ◽  
Motor Units ◽  
Human Hand ◽  
Spinal Motoneurons ◽  
Common Input ◽  
Voluntary Contractions ◽  
High Degree ◽  
The Relationship ◽  
Repetitive Discharge

Synchronized discharge of individual motor units is commonly observed in the muscles of human subjects performing voluntary contractions. The amount of this synchronization is thought to reflect the extent to which motoneurons in the same and related pools share common synaptic input. However, the relationship between the proportion of shared synaptic input and the strength of synchronization has never been measured directly. In this study, we simulated common shared synaptic input to cat spinal motoneurons by driving their discharge with noisy, injected current waveforms. Each motoneuron was stimulated with a number of different injected current waveforms, and a given pair of waveforms were either completely different or else shared a variable percentage of common elements. Cross-correlation histograms were then compiled between the discharge of motoneurons stimulated with noise waveforms with variable degrees of similarity. The strength of synchronization increased with the amount of simulated “common” input in a nonlinear fashion. Moreover, even when motoneurons had >90% of their simulated synaptic inputs in common, only ∼25–45% of their spikes were synchronized. We used a simple neuron model to explore how variations in neuron properties during repetitive discharge may lead to the low levels of synchronization we observed experimentally. We found that small variations in spike threshold and firing rate during repetitive discharge lead to large decreases in synchrony, particularly when neurons have a high degree of common input. Our results may aid in the interpretation of studies of motor unit synchrony in human hand muscles during voluntary contractions.

Cerebral metabolism of isotopic glucose in chronic mental disease

1959 ◽  
Vol 14 (5) ◽  
pp. 849-854 ◽  
Author(s):  
William Sacks
Keyword(s):  
Mental Disease ◽  
Cerebral Metabolism ◽  
Human Subjects ◽  
Psychiatric Patients ◽  
Normal Subjects ◽  
Main Site ◽  
Significant Difference ◽  
Normal Human ◽  
Average Activity ◽  
Theoretical Considerations

A previous investigation of cerebral metabolism of isotopic glucose in normal human subjects was extended and similar studies performed upon chronic psychiatric patients. With variously labeled glucose-C14 as substrates, average activity-time curves and values for cumulative C14O2 resulting from cerebral oxidation of labeled glucose showed no significant variations between normal and psychotic subjects. A significant difference (P < 0.02) between the two groups did occur in comparing the fraction of brain CO2 derived from glucose. Calculations using individual glucose-U-C14 experiments gave averages of 56% for normal subjects and 36% for mental patients. These values agreed with those derived from composite curves of variously labeled glucose. That less brain CO2 was derived from glucose in psychotic subjects seemed to indicate a greater dilution of some carbohydrate intermediate(s) by protein and/or lipid intermediate(s); and, possibly, a decreased cerebral oxidation of carbohydrate. Theoretical considerations suggested that pyruvate and/or lactate might be the main site(s) of dilution. Submitted on January 28, 1959

Change in recruitment order of motor units in human parasternal intercostal muscles with sleep state

1993 ◽  
Vol 74 (6) ◽  
pp. 2718-2723 ◽  
Author(s):  
W. A. Whitelaw ◽  
K. P. Rimmer ◽  
H. S. Sun
Keyword(s):  
Sleep Stage ◽  
Human Subjects ◽  
Motor Units ◽  
Excitatory Input ◽  
Sleep State ◽  
Intercostal Muscles ◽  
Intramuscular Electrodes ◽  
Normal Human ◽  
Low Threshold ◽  
Recruitment Order

Recruitment order of individual motor units in the early part of inspiration in parasternal intercostal muscles was observed in normal human subjects during wakefulness and non-rapid-eye-movement sleep. Electromyograms from bipolar fine wire intramuscular electrodes were recorded while the subjects lay supine in a sleep laboratory, and sleep stage was determined by polysomnography. From wakefulness to sleep there were numerous examples of shifts in order of recruitment among the low threshold units of early inspiration. There were corresponding shifts in the order of derecruitment of these units. Analysis of frequency of firing of units also suggested that the levels of excitatory input to one unit of a pair could be altered relative to the level of input of the other one. The data imply that there are at least minor differences in distribution of excitatory inputs from various sources among motoneurons of this muscle pool.

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