scholarly journals Characterization of motor units in behaving adult mice shows a wide primary range

2014 ◽  
Vol 112 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Laura K. Ritter ◽  
Matthew C. Tresch ◽  
C. J. Heckman ◽  
Marin Manuel ◽  
Vicki M. Tysseling
Keyword(s):  
Human Subjects ◽  
Motor Units ◽  
Quiet Standing ◽  
Striking Difference ◽  
Firing Patterns ◽  
Adult Mice ◽  
Firing Range ◽  
Synaptic Noise ◽  
Wide Range ◽  
Fast Twitch

The mouse is essential for genetic studies of motor function in both normal and pathological states. Thus it is important to consider whether the structure of motor output from the mouse is in fact analogous to that recorded in other animals. There is a striking difference in the basic electrical properties of mouse motoneurons compared with those in rats, cats, and humans. The firing evoked by injected currents produces a unique frequency-current (F-I) function that emphasizes recruitment of motor units at their maximum force. These F-I functions, however, were measured in anesthetized preparations that lacked two key components of normal synaptic input: high levels of synaptic noise and neuromodulatory inputs. Recent studies suggest that the alterations in the F-I function due to these two components are essential for recreating firing behavior of motor units in human subjects. In this study we provide the first data on firing patterns of motor units in the awake mouse, focusing on steady output in quiet stance. The resulting firing patterns did not match the predictions from the mouse F-I behaviors but instead revealed rate modulation across a remarkably wide range (10–60 Hz). The low end of the firing range may be due to changes in the F-I relation induced by synaptic noise and neuromodulatory inputs. The high end of the range may indicate that, unlike other species, quiet standing in the mouse involves recruitment of relatively fast-twitch motor units.

Motor-unit stimulation patterns during fatiguing contractions of constant tension

1988 ◽  
Vol 60 (4) ◽  
pp. 1198-1214 ◽  
Author(s):  
B. R. Botterman ◽  
T. C. Cope
Keyword(s):  
Motor Units ◽  
Medial Gastrocnemius ◽  
Fatigue Properties ◽  
Endurance Time ◽  
Stimulation Rate ◽  
Wide Range ◽  
Constant Tension ◽  
Slow Twitch ◽  
Fast Twitch ◽  
Tetanic Tension

1. Through computer feedback control, muscle-unit tension was maintained by altering the stimulation rate of a functionally isolated motor axon. The required stimulation patterns and fatigue properties of motor units from the flexor carpi radialis (FCR), flexor digitorum longus (FDL), and medial gastrocnemius (MG) muscles of the cat were studied when tension was maintained or "clamped" at a constant average level (25% of maximum tetanic tension). 2. In each muscle, two distinct stimulation patterns were observed during constant-tension contractions, one associated with slow-twitch units and the other with fast-twitch units. Once target tension was reached, slow-twitch units required fairly constant rates in order to maintain a constant force, whereas fast-twitch units displayed a marked decline in rate during the early phases of the contraction, averaging between 42 and 54% for the three muscles. The decline in rate most likely represented potentiation of the contractile response and slowing of contractile speed. In general, slow-twitch units responded with lower mean rates (approximately 14 pps less), averaged over the course of the contraction, than fast-twitch units. 3. For fast-twitch units of each muscle, resistance to fatigue varied continuously and over a wide range. The duration that tension could be maintained at 25% of maximum, defined as endurance time, ranged between 16 and 2063 s. No categorization of fast-twitch units into groups could be made on the basis of endurance time. Of the 5 slow-twitch units followed beyond 2700 s, only one failed to maintain tension during the observation period. 4. For hindlimb fast-twitch units, endurance was independent of the stimulation rate needed to maintain tension during the contraction. By contrast, there was a significant tendency for an inverse relation between endurance time and mean stimulation rate for FCR fast-twitch units. 5. Recovery of maximum tension was evaluated at 30 s, 1 min, 2 min, and 5 min following a constant-tension contraction. After a 5-min rest, fast-twitch units were able to produce an average of 80-85% of their maximum tetanic tension. By using the median endurance time (approximately 100 s) to divide the fast-twitch population into "low" and "high" endurance groups, recovery of tension was found not to be uniform among the two groups. High endurance units were able to recover a greater percentage of their original maximum tetanic tension. No difference was found between force recovery for low and high endurance units at 30 s.(ABSTRACT TRUNCATED AT 400 WORDS)

Krypton 85 myocardial blood flow: precordial scintillation versus coronary sinus sampling

1965 ◽  
Vol 209 (4) ◽  
pp. 705-710 ◽  
Author(s):  
Michael D. Klein ◽  
Lawrence S. Cohen ◽  
Richard Gorlin
Keyword(s):  
Blood Flow ◽  
Myocardial Blood Flow ◽  
Coronary Sinus ◽  
Human Subjects ◽  
Radioactive Decay ◽  
Empirical Correction ◽  
Wide Range ◽  
Actual Flow ◽  
Flow Through ◽  
High Degree

Myocardial blood flow in human subjects was assessed by comparative simultaneous measurement of krypton 85 radioactive decay from coronary sinus and precordial scintillation. Empirical correction of postclearance background from precordial curves yielded a high degree of correlation between flows derived from the two sampling sites (r = .889, P < .001). Comparison of left and right coronary flows in nine subjects revealed similarity in flow through the two vessels over a wide range of actual flow values (r = .945, P < .001).

Ensemble discharge from Golgi tendon organs of cat peroneus tertius muscle

1990 ◽  
Vol 64 (3) ◽  
pp. 813-821 ◽  
Author(s):  
G. Horcholle-Bossavit ◽  
L. Jami ◽  
J. Petit ◽  
R. Vejsada ◽  
D. Zytnicki
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Good Correspondence ◽  
Golgi Tendon Organs ◽  
Afferent Fibers ◽  
Slow Type ◽  
Tendon Organs ◽  
Fast Twitch ◽  
Force Profiles ◽  
Tendon Organ

1. The responses of individual tendon organs of the cat peroneus tertius muscle to motor-unit contractions were recorded in anesthetized cats during experiments in which all the Ib-afferent fibers from the muscle had been prepared for recording in dorsal root filaments. This was possible because the cat peroneus tertius only contains a relatively small complement of approximately 10 tendon organs. 2. Motor units of different physiological types were tested for their effects on the whole population of tendon organs in the muscle. Effects of unfused tetanic contractions were tested under both isometric and anisometric conditions. Each motor unit activated at least one tendon organ, and each tendon organ was activated by at least one motor unit. Individual slow-type units were found to act on a single or two receptors, whereas a fast-type unit could activate up to six tendon organs. 3. In one experiment, the effects of 8 motor units on 10 tendon organs were examined. One fast-twitch, fatigue resistant (FR)-type unit acted on six tendon organs, of which four were also activated by another FR unit. The contraction of each unit, on its own, elicited a range of individual responses, from weak to strong. The discharge frequencies of individual responses displayed no clear relation with the strength of contraction, nor did they accurately represent the shape of force profiles. But when all the discharges were pooled, a fairly good correspondence appeared between variations of contractile force and variations of averaged discharge frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of type II adenylyl cyclase mRNA in rabbit skeletal muscle by chronic motor nerve pacing

1996 ◽  
Vol 271 (2) ◽  
pp. E253-E260 ◽  
Author(s):  
C. E. Torgan ◽  
W. E. Kraus
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Protein Kinase ◽  
Adenylyl Cyclase ◽  
Regulation Of Gene Expression ◽  
Rabbit Skeletal Muscle ◽  
Type Ii ◽  
Wide Range ◽  
Electrical Pacing ◽  
Fast Twitch

Skeletal muscle exhibits a wide range in functional phenotype in response to changes in physiological demands. We have observed that, in response to changes in work patterns, alterations in gene expression of some proteins coincide with changes in adenylyl cyclase (AC) activity [Kraus, W.E., J.P. Longabaugh, and S. B. Liggett. Am. J. Physiol 263 (Endocrinol. Metab. 26): E266-E230, 1992]. We now examine AC isoform transcript prevalence in various rabbit skeletal muscles and in response to changing work demands. Using reverse transcriptase-polymerase chain reaction, we detected type II AC isoform transcripts in rabbit skeletal muscle. Ribonuclease protection analyses revealed that expression of the type II isoform significantly correlated with the percentage of fast-twitch type IIb/IId fibers (r2 = 0.765, P < 0.01). When a fast-twitch muscle was converted to a slow-twitch muscle via chronic electrical pacing, expression of type II AC mRNA significantly decreased. This response occurred 3 days after the onset of stimulation (78% decrease) and was still present after 21 days of stimulation (76% decrease). As type II AC is relatively insensitive to calcium regulation while sensitive to protein kinase C (PKC) signaling, these data provide further impetus for investigations of protein kinase A and PKC cross-talk signaling mechanisms in the regulation of gene expression.

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.

Changes in diaphragm motor unit EMG during fatigue

1990 ◽  
Vol 68 (5) ◽  
pp. 1917-1926 ◽  
Author(s):  
G. C. Sieck ◽  
M. Fournier
Keyword(s):  
Motor Unit ◽  
Fatigue Test ◽  
Motor Units ◽  
Evoked Force ◽  
Slow Twitch ◽  
The Right ◽  
Fast Twitch ◽  
Multiple Units ◽  
Motor Unit Emg ◽  
Stimulation Of

Fatigue-related changes in the waveform and root-mean-square (rms) values of evoked motor unit electromyographic (EMG) responses were studied in the right sternocostal region of the cat diaphragm. Motor units were isolated by microdissection and stimulation of C5 ventral root filaments and then classified as fast-twitch fatigable (FF), fast-twitch fatigue intermediate (FInt), fast-twitch fatigue resistant (FR), or slow-twitch (S) based on standard physiological criteria. The evoked EMG responses of S and FR units showed very little change during the fatigue test. The evoked EMG waveform and rms values of FF and FInt units displayed variable changes during the fatigue test. When changes were observed, they typically included a prolongation of the EMG waveform, a decrease in peak amplitude, and a decrease in rms value. The changes in EMG amplitude and rms values were not correlated. In more fatigable units, the decrease in force during the fatigue test generally exceeded the decrease in EMG rms values. Changes in the evoked force and EMG responses of multiple units innervated by C5 or C6 ventral roots were also examined during the fatigue test. The decrease in diaphragm force during the fatigue test closely matched the force decline predicted by the proportionate contribution of different motor unit types. However, the observed reduction in diaphragm EMG rms values during the fatigue test exceeded that predicted based on the aggregate contribution of different motor unit types. It was concluded that changes in EMG do not reflect the extent of diaphragm fatigue.

scholarly journals Brain-wide quantification of the supraspinal connectome

2021 ◽  
Author(s):  
Zimei Wang ◽  
Adam Romanski ◽  
Vatsal Mehra ◽  
Yunfang Wang ◽  
Benjamin C. Campbell ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Web Based ◽  
Locomotor Recovery ◽  
Adult Mice ◽  
Comprehensive Information ◽  
Normal Behavior ◽  
Wide Range ◽  
Cord Injury ◽  
Functional Consequences ◽  
Intuitive Manner

The supraspinal connectome is essential for normal behavior and homeostasis and consists of a wide range of sensory, motor, and autonomic projections from brain to spinal cord. Extensive work spanning a century has largely mapped the cell bodies of origin, yet their broad distribution and complex spatial relationships present significant challenges to the dissemination and application of this knowledge. Fields that study disruptions of supraspinal projections, for example spinal cord injury, have focused mostly on a handful of major populations that carry motor commands, with only limited consideration of dozens more that provide autonomic or crucial motor modulation. More comprehensive information is essential to understand the functional consequences of different injuries and to better evaluate the efficacy of treatments. Using viral retrograde labeling, 3D imaging, and registration to standard neuro-anatomical atlases we now provide a platform to profile the entire supraspinal connectome by rapidly visualizing and quantifying tens of thousands of supraspinal neurons, each assigned to more than 60 identified regions and nuclei throughout the brains of adult mice. We then use this tool to compare the lumbar versus cervically-projecting connectomes, to profile brain-wide the sensitivity of supraspinal populations to graded spinal injuries, and to correlate locomotor recovery with connectome measurements. To share these insights in an intuitive manner, we present an interactive web-based resource, which aims to spur progress by broadening understanding and analyses of essential but understudied supraspinal populations.

scholarly journals Bursting Rate Variability

2021 ◽  
Vol 12 ◽  
Author(s):  
Roberto Martin del Campo Vera ◽  
Edmond Jonckheere
Keyword(s):  
Wavelet Decomposition ◽  
Empirical Distribution ◽  
Human Subjects ◽  
Muscle Relaxation ◽  
Wavelet Packets ◽  
Striking Difference ◽  
Semg Signal ◽  
Return Times ◽  
High Incidence ◽  
Semg Activity

In this paper, a new electromyographic phenomenon, referred to as Bursting Rate Variability (BRV), is reported. Not only does it manifest itself visually as a train of short periods of accrued surface electromyographic (sEMG) activity in the traces, but it has a deeper underpinning because the sEMG bursts are synchronous with wavelet packets in the D8 subband of the Daubechies 3 (db3) wavelet decomposition of the raw signal referred to as “D8 doublets”—which are absent during muscle relaxation. Moreover, the db3 wavelet decomposition reconstructs the entire sEMG bursts with two contiguous relatively high detail coefficients at level 8, suggesting a high incidence of two consecutive neuronal discharges. Most importantly, the timing between successive bursts shows some variability, hence the BRV acronym. Contrary to Heart Rate Variability (HRV), where the R-wave is easily identified, here, time-localization of the burst requires a statistical waveform matching between the “D8 doublet” and the burst in the raw sEMG signal. Furthermore, statistical fitting of the empirical distribution of return times shows a striking difference between control and quadriplegic subjects. Finally, the BRV rate appears to be within 60–88 bursts per minute on average among 9 human subjects, suggesting a possible connection between BRV and HRV.

scholarly journals Iron absorption from rice meals cooked with fortified salt containing ferrous sulphate and ascorbic acid

1974 ◽  
Vol 31 (3) ◽  
pp. 367-375 ◽  
Author(s):  
M. H. Sayers ◽  
S. R. Lynch ◽  
R. W. Charlton ◽  
T. H. Bothwell ◽  
R. B. Walker ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Iron Absorption ◽  
Ferrous Sulphate ◽  
Striking Difference ◽  
Red Cell ◽  
Indian Women ◽  
Threefold Increase ◽  
Cooking Process ◽  
Wide Range ◽  
The Mean

1. Iron absorption from rice-containing meals was measured by red cell utilization of radioactive Fe in sixty-six volunteer multiparous Indian women.2. In all the studies salt added during the cooking process was used as the carrier for supplemental inorganic Fe and ascorbic acid.3. Intrinsic Fe in the rice and supplementary inorganic Fe were absorbed to the same extent, with a wide range of absorption values.4. There was a striking difference between the mean absorption of a 3 mg dose of ferrous Fe given to fasting subjects in a solution containing 30 mg ascorbic acid and that of Fe in a rice meal (48.7 and 3.5% respectively).5. When ascorbic acid was added during cooking there was a threefold increase in the absorption of both intrinsic Fe and supplementary Fe when a sufficient quantity (60 mg) was present.6. It is concluded that the Fe nutrition of rice-eating communities could be improved significantly by the addition of ascorbic acid to the diet.

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