Cat hindlimb motoneurons during locomotion. I. Destination, axonal conduction velocity, and recruitment threshold

1987 ◽  
Vol 57 (2) ◽  
pp. 510-529 ◽  
Author(s):  
J. A. Hoffer ◽  
G. E. Loeb ◽  
W. B. Marks ◽  
M. J. O'Donovan ◽  
C. A. Pratt ◽  
...  
Keyword(s):  
Conduction Velocity ◽  
Femoral Nerve ◽  
Mean Value ◽  
Thigh Muscle ◽  
Recruitment Threshold ◽  
Axonal Conduction ◽  
Anterior Thigh ◽  
Spike Triggered Averaging ◽  
Conduction Velocities ◽  
The Mean

Fine flexible wire microelectrodes chronically implanted in the fifth lumbar ventral root (L5 VR) of 17 cats rendered stable records of the natural discharge patterns of 164 individual axons during locomotion on a treadmill. Fifty-one out of 164 axons were identified as motoneurons projecting to the anterior thigh muscle group. For these axons, the centrifugal propagation of action potentials was demonstrated by the technique of spike-triggered averaging using signals recorded from cuff electrodes implanted around the femoral nerve. The axonal conduction velocity was measured from the femoral nerve cuff records. For 43/51 motoneurons, the corresponding target muscle was identified by spike-triggered averaging of signals recorded from bipolar EMG electrodes implanted in each of the anterior thigh muscles: vastus intermedius, medialis and lateralis, sartorius anterior and medialis, and rectus femoris. For 32/51 motoneurons, the recruitment threshold during locomotion was determined from the mean value of the rectified digitally smoothed EMG of the target muscle measured at the time when the motoneuron fired its first spike for each step. The recruitment threshold of every motoneuron was relatively constant for a given speed of walking, but for some units there were small systematic variations as a function of treadmill speed (range: 0.1-1.3 m/s). Recruitment thresholds were standardized with respect to the mean value of peak EMG activity of the target muscle during 16 s of walking at 0.5 m/s. For 28/51 motoneurons recorded in nine cats, recruitment thresholds (range: 3-93% of peak target muscle EMG) were linearly correlated (r = 0.51, P less than 0.02) to axonal conduction velocities (range: 57-117 m/s). In addition, for seven recorded pairs of motoneurons that projected to the same muscle in the same cat, the recruitment thresholds were ordered by relative conduction velocities. Taken together, these results are consistent with the notion that, in normal cat locomotion up to a medium trot, anterior thigh motoneurons are progressively recruited in an orderly fashion.

Mechanical Properties and Behaviour of Motor Units in the Tibialis Anterior During Voluntary Contractions

1997 ◽  
Vol 22 (6) ◽  
pp. 585-597 ◽  
Author(s):  
Michaël Van Cutsem ◽  
Patrick Feiereisen ◽  
Jacques Duchateau ◽  
Karl Hainaut
Keyword(s):  
Mechanical Properties ◽  
Tibialis Anterior ◽  
Motor Units ◽  
Voluntary Contraction ◽  
Recruitment Threshold ◽  
Time To Peak ◽  
Spike Triggered Averaging ◽  
The Mean ◽  
Voluntary Contractions ◽  
Mean Time

The present work was carried out to analyse the properties and behaviour of Tibialis anterior motor units (MUs) during voluntary contractions in humans. A total of 528 single MU mechanical properties was recorded in 10 subjects by means of the spike-triggered averaging (STA) technique. MU recruitment thresholds and discharge frequencies were recorded during linearly increasing maximal voluntary contraction (MVC). The results indicate a mean (±SD) MU torque of 25.5 ± 21.5 mN•m. and a mean time-to-peak of 45.6 ± 13.6 ms. A comparison of the average MU twitch torque with that of the muscle allowed an estimate of about 300 MUs in the Tibialis anterior. A positive linear relationship was recorded between the MU twitch torque and the recruitment threshold. The mean minimal and maximal discharge frequencies of MUs were 8.4 ± 3.0 Hz and 33.2 ± 14.7 Hz, respectively. The results of the present work indicate that MU behaviour during voluntary contractions is different in the tibialis anterior and in the adductor pollicis. Key words: discharge frequency, recruitment threshold, motor unit count

Activity of spindle afferents from cat anterior thigh muscles. I. Identification and patterns during normal locomotion

1985 ◽  
Vol 54 (3) ◽  
pp. 549-564 ◽  
Author(s):  
G. E. Loeb ◽  
J. A. Hoffer ◽  
C. A. Pratt
Keyword(s):  
Activity Patterns ◽  
Muscle Length ◽  
Knee Extensor ◽  
Muscle Spindles ◽  
Swing Phase ◽  
Thigh Muscle ◽  
Knee Extensors ◽  
Nerve Cuff ◽  
Anterior Thigh ◽  
Spike Triggered Averaging

The naturally occurring activity patterns of anterior thigh muscle spindle afferents were recorded during unrestrained treadmill locomotion by means of floating microelectrodes chronically implanted in the fifth lumbar dorsal root ganglion. Conduction velocity of units from primary and secondary endings was determined by spike-triggered averaging of the signals from a chronically implanted nerve cuff. Activity from knee extensor muscle spindles generally occurred during periods of muscle lengthening, but was often greater for small stretches when the muscle was active (during stance phase of walking) than for larger stretches when the muscle was passive (swing phase), indicating fusimotor enhancement of spindle sensitivity in phase with extrafusal muscle recruitment. Activity from spindles in biarticular muscles acting across the knee and hip was more variable and complex than that seen in the pure knee extensors, and frequently included activity during rapid muscle shortening (swing phase) indicative of strong static fusimotor input. Changes in speed of gait caused changes in the range and velocity of muscle length excursions monitored by chronically implanted length gauges, but such changes were accompanied by only modest changes in spindle afferent activity, suggesting concurrent and compensatory changes in fusimotor influence on spindles. Activity from spindle secondary endings was generally lower, more regular, and less velocity dependent than that from primary endings, consistent with their lack of input from the dynamic fusimotor apparatus. The activity of all spindle afferents studied was similarly well modulated during extrafusal activity of the parent muscles, regardless of the kinematic conditions of muscle length and velocity during which this muscle work occurred. This suggests that the fusimotor apparatus is well orchestrated to regulate the static and dynamic sensitivity of primary spindle afferents at levels appropriate to the anticipated motion.

Electrophysiological properties of developing phrenic motoneurons in the cat

1991 ◽  
Vol 65 (3) ◽  
pp. 671-679 ◽  
Author(s):  
W. E. Cameron ◽  
J. S. Jodkowski ◽  
H. Fang ◽  
R. D. Guthrie
Keyword(s):  
Action Potential ◽  
Conduction Velocity ◽  
Age Groups ◽  
Mean Amplitude ◽  
Significant Negative Correlation ◽  
Spontaneous Discharge ◽  
Electrophysiological Properties ◽  
Axonal Conduction ◽  
Phrenic Motoneurons ◽  
The Mean

1. Intracellular recordings were made in 427 phrenic motoneurons from kittens (in four stages of postnatal development, ranging from 2 to 14 wk) and in 72 motoneurons from adult cats. These experiments were performed to determine how the pattern of spontaneous discharge changes in phrenic motoneurons during development and how these changes might be influenced by alterations in the electrophysiological properties of these neurons. 2. The mean axonal conduction velocity increased significantly (P less than 0.0001) throughout this period of development, with the most rapid increase occurring between weeks 2 and 5 (18.5 +/- 5.4 and 32.4 +/- 5.6 m/s, respectively, mean +/- SD). 3. There was no change in the magnitude of the membrane potential, antidromic action potential, or positive overshoot; whereas there was a decrease in the half-width of the action potential from 2 (652 +/- 184 ms) to 14 (525 +/- 116 ms) wk postnatal. 4. The mean duration of the afterhyperpolarization (AHPdur) decreased from 69 +/- 20 ms at 2 wk to 60 +/- 16 ms by 9 wk, then increased to 66 +/- 18 ms by 14 wk of age and to 75 +/- 21 ms in the adult. The mean amplitude of the afterhyperpolarization (AHPamp) in the 2-wk-old group (4.9 +/- 1.8 mV) was larger than that at weeks 5 (3.9 +/- 1.7 mV) and 9 (3.9 +/- 1.6 mV), whereas the mean AHPamp of the adult (3.1 +/- 1.2 mV) was significantly smaller than the mean of any younger group. A significant negative correlation was found between AHPdur and axonal conduction velocity in all age groups studied, including the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Recruitment order of motoneurons in stretch reflexes is highly correlated with their axonal conduction velocity

1984 ◽  
Vol 52 (3) ◽  
pp. 410-420 ◽  
Author(s):  
P. Bawa ◽  
M. D. Binder ◽  
P. Ruenzel ◽  
E. Henneman
Keyword(s):  
Motor Unit ◽  
Conduction Velocity ◽  
Motor Units ◽  
Medial Gastrocnemius ◽  
Stretch Reflexes ◽  
Decerebrate Cat ◽  
Unit Type ◽  
Axonal Conduction ◽  
Conduction Velocities ◽  
Recruitment Order

Motor units of soleus and medial gastrocnemius (MG) muscles were studied in pairs during stretch reflexes in the decerebrate cat to determine the relation between their recruitment orders and axonal conduction velocities. In 97% of soleus pairs, the motor unit with the lower axonal conduction velocity was recruited first. Since the soleus is a homogeneous muscle in the cat, differences in motor-unit type are, therefore, not a sine qua non for orderly recruitment nor is recruitment random within homogeneous populations of motor units, as recently proposed (28). In the medial gastrocnemius, a heterogeneous muscle, the same high correlation (97%) between recruitment sequence and conduction velocity was observed. Thus, the factors that determine recruitment order in heterogeneous muscles are as closely correlated with axonal diameter as they are in homogeneous muscles. Comparison of axonal conduction velocities in our sample of MG units with those in three samples of type-identified MG units studied by other investigators also suggests that motor-unit type is not the critical factor controlling the sequence of activation in heterogeneous muscles. It is concluded that the combined effects of all presynaptic and postsynaptic factors that determine susceptibility to discharge in motoneurons during stretch reflexes are strictly correlated with their axonal conduction velocities, as predicted by the size principle.

Classification and response characteristics of muscle spindle afferents in the primate

1976 ◽  
Vol 39 (1) ◽  
pp. 1-8 ◽  
Author(s):  
P. D. Cheney ◽  
J. B. Preston
Keyword(s):  
Conduction Velocity ◽  
Muscle Afferents ◽  
Primary Afferents ◽  
The Other ◽  
Intermediate Region ◽  
Muscle Spindle Afferents ◽  
Muscle Stretch ◽  
Response Characteristics ◽  
Conduction Velocities ◽  
The Mean

A study was made of the response characteristics of spindle afferents in the baboon soleus muscle. Afferents were isolated from the dorsal roots, their conduction velocities were determined, and their responses were recorded to muscle stretch at rates of 2.5-45 mm/s and amplitudes of 2-10 mm. Spindle afferents could be classified as primary or secondary on the basis of two criteria. The first criterion was conduction velocity. The conduction velocity histogram was bimodal, with peaks at about 45 and 80 m/s and an intermediate region from 55 to 70 m/s. The second criterion was the pattern of adaptation following the peak of ramp stretch. This latter criterion has the advantage of allowing units with intermediate conduction velocities also to be confidently classified as primary or secondary. The velocity and position sensitivities of primate spindle afferents were determined. The mean dynamic index and mean dynamic sensitivity of secondary afferents were about 45% of the corresponding values for primary afferents. On the other hand, the position sensitivities of primary and secondary spindle afferents in the baboon were not significantly different.

Long-period modulated superstructures in Pd-12.5 at.%Ce and Pd-15 at.%Ce alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 164-165
Author(s):  
Noriyuki Kuwano ◽  
Masaru Itakura ◽  
Kensuke Oki
Keyword(s):  
Electron Microscopy ◽  
Mean Value ◽  
Heavy Elements ◽  
Arc Furnace ◽  
X Ray ◽  
Long Period ◽  
Ultra High Purity ◽  
Heat Treated ◽  
Atomic Scattering ◽  
The Mean

Pd-Ce alloys exhibit various anomalies in physical properties due to mixed valences of Ce, and the anomalies are thought to be strongly related with the crystal structures. Since Pd and Ce are both heavy elements, relative magnitudes of (fcc-fpd) are so small compared with <f> that superlattice reflections, even if any, sometimes cannot be detected in conventional x-ray powder patterns, where fee and fpd are atomic scattering factors of Ce and Pd, and <f> the mean value in the crystal. However, superlattices in Pd-Ce alloys can be analyzed by electron microscopy, thanks to the high detectability of electron diffraction. In this work, we investigated modulated superstructures in alloys with 12.5 and 15.0 at.%Ce.Ingots of Pd-Ce alloys were prepared in an arc furnace under atmosphere of ultra high purity argon. The disc specimens cut out from the ingots were heat-treated in vacuum and electrothinned to electron transparency by a jet method.

Partition Coefficient Ratios and Tumour Perfusion Studied with 85mKr and 133Xe

1987 ◽  
Vol 26 (06) ◽  
pp. 253-257
Author(s):  
M. Mäntylä ◽  
J. Perkkiö ◽  
J. Heikkonen
Keyword(s):  
Partition Coefficient ◽  
Partition Coefficients ◽  
Regional Blood Flow ◽  
Blood Perfusion ◽  
Compartmental Analysis ◽  
Malignant Tumour ◽  
Mean Value ◽  
Perfusion Rate ◽  
Biological Variables ◽  
The Mean

The relative partition coefficients of krypton and xenon, and the regional blood flow in 27 superficial malignant tumour nodules in 22 patients with diagnosed tumours were measured using the 85mKr- and 133Xe-clearance method. In order to minimize the effect of biological variables on the measurements the radionuclides were injected simultaneously into the tumour. The distribution of the radiotracers was assumed to be in equilibrium at the beginning of the experiment. The blood perfusion was calculated by fitting a two-exponential function to the measuring points. The mean value of the perfusion rate calculated from the xenon results was 13 ± 10 ml/(100 g-min) [range 3 to 38 ml/(100 g-min)] and from the krypton results 19 ± 11 ml/(100 g-min) [range 5 to 45 ml/(100 g-min)]. These values were obtained, if the partition coefficients are equal to one. The equations obtained by using compartmental analysis were used for the calculation of the relative partition coefficient of krypton and xenon. The partition coefficient of krypton was found to be slightly smaller than that of xenon, which may be due to its smaller molecular weight.

Detection of Soluble Fibrin Monomer Complexes in Blood by Means of Protamine Sulphate Test

1968 ◽  
Vol 20 (01/02) ◽  
pp. 044-049 ◽  
Author(s):  
B Lipiński ◽  
K Worowski
Keyword(s):  
Human Subjects ◽  
Coronary Thrombosis ◽  
Mean Value ◽  
Healthy Human ◽  
Protamine Sulphate ◽  
Soluble Fibrin ◽  
Fibrin Monomer ◽  
Dog Plasma ◽  
The Mean ◽  
Precipitable Protein

SummaryIn the present paper described is a simple test for detecting soluble fibrin monomer complexes (SFMC) in blood. The test consists in mixing 1% protamine sulphate with diluted oxalated plasma or serum and reading the optical density at 6190 Å. In experiments with dog plasma, enriched with soluble fibrin complexes, it was shown that OD read in PS test is proportional to the amount of fibrin recovered from the precipitate. It was found that SFMC level in plasma increases in rabbits infused intravenously with thrombin and decreases after injection of plasmin with streptokinase. In both cases PS precipitable protein in serum is elevated indicating enhanced fibrinolysis. In healthy human subjects the mean value of OD readings in plasma and sera were found to be 0.30 and 0.11, while in patients with coronary thrombosis they are 0.64 and 0.05 respectively. The origin of SFMC in circulation under physiological and pathological conditions is discussed.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

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