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1
Content available remote Variability and plasticity of motor unit properties in mammalian skeletal muscle
100%
Celichowski J. , Krutki P.
Biocybernetics and Biomedical Engineering
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2012
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tom Vol. 32, no. 4
33-45
EN
In the majority of mammalian skeletal muscles, contractile properties of motor units are variable and three main types of these units can be distinguished. The present review summarizes: results of studies of motor unit properties in the medial gastrocnemius muscle and their variability in two species, cats and rats, and studies on differences of motor unit properties in two genders. Moreover, plasticity of motor unit properties in rat medial gastrocnemius evoked by two kinds of spinal cord injury, total transection and hemisection, is reviewed, and effects of two types of training, treadmill locomotor and whole-body vibration training, are summarized. Finally, changes in the motor unit properties during the aging process are presented.
2
Content available remote The tetanic depression in unfused tetani of fast motor units in mammalian muscle
100%
Celichowski J.
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tom Vol. 25, no. 4
27-35
EN
Tetanic depression is a phenomenon that limits the force of unfused tetani in contractions evoked at unstable stimulation frequencies. In our experiments this phenomenon was visible in tetani evoked at two frequencies of stimulation: the lower immediately followed by the higher one. The force at the higher stimulation frequency was evidently depressed in relation to the force achieved during the control constant-frequency stimulations. This depression concerned the fast motor units and it was not observed in the slow units. The tetanic depression was initially found in the rat medial gastrocnemius muscle. However, it is not clear whether this phenomenon is specific only to the rat muscle or it concerns all mammals. Therefore, in the subsequent series of experiments, the tetanic depression was investigated in the motor units of the feline medial gastrocnemius, and the effect was also observed in all fast units. The maximum evoked depression exceeded 50% of the control values. Moreover, the analysis of the relationship between the amplitude of the tetanic depression and the degree of the tetanic fusion revealed that the strongest amplitude of depression was observed in the middle-fused tetani (with the fusion index in the range 0.5-0.7). The third experimental series proved that the tetanic depression could be visible in tetani evoked at a progressively increasing frequency of stimulation. Moreover, it was found that the effect of the force decrease could result from the prolongation of only one, the first interpulse interval. The amplitude of this decrease exceeded 20% of the control values. Summarizing, the tetanic depression is a phenomenon influencing the force of unfused tetani of the fast motor units at an increasing stimulation frequency. The depressive effect is present in various species of mammals, probably, including human. The amplitude of the depression depends on the fusion of the tetanic contraction. The physiological significance of tetanic depression is closely related to reduction of the importance of the motoneuronal firing rate.
3
Content available remote Motor unit contractions evoked by stimulation with variable interpulse intervals
100%
Krutki P. , Celichowski J. , Raikova R.
Biocybernetics and Biomedical Engineering
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2012
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tom Vol. 32, no. 3
29-42
EN
During natural contractions motor units (MUs) are activated by variable frequency discharge patterns of motoneurones. The aim of this review was (1) to discuss differences between tetanic contractions developed at constant and random frequencies of pulses; (2) to show results of mathematical decomposition of these tetani into series of twitch-shaped responses to individual pulses; (3) to indicate that it is possible to predict the tetanic force of a MU with high accuracy by using regression equations derived on a basis of the relationships between the parameters of the decomposed twitches and the force level at which the next response begins.
4
Content available The influence of increasing and decreasing frequency of stimulation on the contraction of motor units in rat medial gastrocnemius muscle
100%
Celichowski J. , Bichler E.
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2000
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tom 51
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nr 4,2
5
Changes in fusion index during the fatigue test of fast motor units in the medial gastrocnemius muscle of the rat
100%
Celichowski J. , Grottel K. , Bichler E.
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nr 4
6
Content available remote Interspecies differences in the force-frequency relationship of the medial gastrocnemius motor units
100%
Mrowczynski W. , Celichowski J. , Krutki P.
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nr 3
EN
Single, functionally isolated motor units were studied in the medial gastrocnemius (MG) muscle of cats and rats. Axons of their motoneurons were stimulated with trains of pulses at frequencies increasing from 1 to 150 Hz and forces developed by muscle fibers were measured and force-frequency curves were compared between species. The following observations were made: (1) the most steep parts of curves (related to unfused tetani of motor units) begun at lower frequencies of stimulations in all types of feline motor units, (2) for fast motor units, the same relative values of force of unfused tetani were achieved at significantly lower frequencies of stimulations in the cat than in the rat. Twitch time parameters of both species influenced the course of force-frequency curves. It was showed that the contraction times of feline units varied in the wide range (21-81 ms), and these units reached 60% of the maximum force at stimulation frequencies between 10 and 38 Hz. On the other hand, contraction times of rat units ranged from 10 to 34 ms, whereas stimulation frequencies necessary to reach 60% of the maximum force varied considerably, from 12 to 65 Hz. The correlations between the above parameters were found for motor units of each species. However, the regression lines drown for the collected population of cat and rat units did not form linear continuity. Thus it seems that interspecies differences in the twitch contraction times do not fully explain different force-frequency relationships in mammalian skeletal muscles.
7
Fatigability of motor units estimated by changes in work performed during their repetitive stimulation during the fatigue test
100%
Celichowski J. , Grottel K. , Bichler E.
Acta Neurobiologiae Experimentalis
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1999
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tom 59
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nr 1
8
The time course of the last contractions during incompletely fused tetani of motor units in rat skeletal muscle
100%
Celichowski J. , Bichler E.
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nr 1
9
Content available remote Differences between properties of male and female motor units in the rat medial gastrocnemius muscle
100%
Celichowski J. , Drzymala H.
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nr 1
EN
Differences between motor units in hindlimb locomotor muscles of male and female Wistar rats were studied. The contractile and action potential properties of various types of motor units as well as proportions of these units in the medial gastrocnemius muscle were analyzed. Experiments were based on functional isolation and electrical stimulation of axons of single motor units. Composition of motor units was different for male and female subjects, with higher number of the fast fatigable and lower number of slow type units in male animals. The contraction and the half-relaxation times were significantly longer in male motor units, what might be due to differences in muscle size. Slower contraction of male motor units likely corresponds to lower firing rates of their motoneurons. On the other hand, no significant differences between sexes were observed with respect to force parameters of motor units (the twitch and the maximum tetanus forces), except the fast resistant units (higher force values in male muscles). The mass of the muscle was approximately 1.5 time bigger in male rats. However, the mean ratio of motor unit tetanus force to the muscle mass was almost twice smaller in this group, what indirectly suggests that muscles of male rats are composed of higher number of motor units. Finally, female muscles appeared to have higher fatigue resistance as the effect of higher proportion of resistant units (slow and fast resistant) and higher values of the fatigue index in respective motor unit types. The motor unit action potentials in female rats had slightly lower amplitudes and shorter time parameters although this difference was significant only for fast resistant units.
10
Content available Relationship between the tension-time area and the frequency of stimulation in motor units of the rat medial gastrocnemius muscle
100%
Celichowski J. , Grottel K. , Bichler E.
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2000
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tom 51
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nr 2
11
Content available remote Computer system for identification and analysis of motor unit potential trains
84%
Mazurkiewicz Ł. , Piotrkiewicz M.
Biocybernetics and Biomedical Engineering
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2004
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tom Vol. 24, no. 3
15-23
EN
The paper presents a computerized system for identification and analysis of electromyographic signals recorded from muscle by needle electrodes. The system provides information on human motoneuron activity as time sequences of identified single motor unit potentials. This information can afterwards be statistically processed to obtain data on motoneuron properties in healthy subjects and in some neuromuscular diseases. A special attention has been paid to the description of the methods of spike identification, including extraction of spikes from the signal and automatic classification, which is based on the statistical pattern recognition approach. The system described is also an example of adaptation of modern computer technology for biomedical research.
12
Content available remote Diagnozowanie schorzeń nerwowo-mięśniowych za pomocą sieci neuronowych w oparciu o skalogramy potencjałów czynnościowych
84%
Dobrowolski A. , Wierzbowski M. , Tomczykiewicz K.
Przegląd Elektrotechniczny
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2009
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tom R. 85, nr 11
99-104
PL
W artykule przedstawiono nową metodę diagnozowania chorób nerwowo-mięśniowych opartą na analizie skalogramów wyznaczonych za pomocą falek Symlet 4. Z otrzymanych skalogramów wyekstrahowano 5 cech, umożliwiających klasyfikację do grupy miogennej, neurogennej lub prawidłowej za pomocą sztucznych sieci neuronowych różnych typów. Zastosowano perceptron progowy, perceptron wielowarstwowy oraz sieć SVM w wersji liniowej.
EN
The paper presents a new method of diagnosis of neural-muscle disorders based on analysis of scalograms of action potentials determined by using the ‘Symlet 4’ wavelet technique. The scalograms provide 5 features that allow artificial neural network classifier to distinguish between three classes: myogenic, neurogenic or normal. The neural networks utilized were single-layer perceptron, multilayer perceptron and linear support vector machine.
13
Content available remote Force generated by fast motor units of the rat medial gastrocnemius muscle during stimulation with pulses at variable intervals
84%
Krutki P. , Pogrzebna M. , Drzymala H. , Raikova R. , Celichowski J.
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tom 59
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nr 1
EN
During natural contractions of a muscle, motor units (MUs) are activated by irregular discharge patterns of motoneurones. The aim of this study was to analyze changes in contractile forces of MUs following patterns of stimulation at variable frequency. Experiments were performed on 33 functionally isolated MUs of the fast-type in the medial gastrocnemius (MG) muscle of adult Wistar rats, under pentobarbital anaesthesia. The MUs forces evoked at five different regular stimulation patterns of constant frequencies were compared to forces generated during five random patterns of irregular stimulation with the same mean values of interpulse intervals, between 10 and 75 ms, and variability of these intervals of ± 50% in each case. These values cover the natural range of the preferred firing rates of the MG motoneurones from unfused to nearly fused tetanic contractions. Analysis of changes in tetanic forces indicated a linear relationship between the interpulse interval as well as the initial level of the force and the amplitude of the force increase of the next contraction. It was demonstrated that variability of the instantaneous tetanic force during the irregular discharge pattern depends on the level of tetanic fusion. Moreover, it was demonstrated that for low and moderately-fused tetani, effectiveness of a MU contraction (expressed as the force-time area) is considerably higher for contractions evoked by irregular stimulation patterns. On the basis of the results of this study it was supposed that during voluntary contractions, the influence of changes in the motoneuronal firing rate on the motor unit force depends on the initial level of force.
14
Tetanic depression: a phenomenon influencing the production of tension in fast-twitch motor units in rat medial gastrocnemius
84%
Celichowski J.
|
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nr 2
15
Content available remote Tetanic depression in fast motor units of the cat gastrocnemius muscle
84%
Celichowski J. , Krutki P. , Lochynski D. , Grottel K. , Mrowczynski W.
Journal of Physiology and Pharmacology
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2004
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tom 55
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nr 2
EN
Ability of muscle fibers to generate force is decreased when higher frequency of stimulation of motor units immediately follows lower frequency. This phenomenon called tetanic depression was found in rat medial gastrocnemius. However, it was not clear whether tetanic depression occurred only in rat muscle or it concerns all mammals. This study was conducted on motor units of cat medial gastrocnemius. Analyses were made at three successive trains of stimulation: 30 Hz, 20 and 30 Hz and again 30 Hz (the first pattern) or 40 Hz, 25 and 40 Hz and 40 Hz (the second pattern). In all fast units force generated within the middle tetanus was lower than force generated at the same, but constant frequency of stimulation applied earlier or later. The mean tetanic depression in 30 Hz tetani amounted to 10.9% for fast fatigable (FF) and 15.9% for fast resistant (FR) motor units, whereas in 40 Hz tetani mean values were 5.6% and 7.3% for FF and FR motor units, respectively. In slow motor units tetanic depression was not observed. These results proved the existence of tetanic depression in the feline muscle and indicated that its intensity depends on the fusion of tetanus. It has been concluded, that the tetanic depression is a general property of fast motor units in mammals.
16
Motor units of medial gastrocnemius muscle in the rat during the fatigue test. II. Changes in the time course of sequential tetani of fatigue test
84%
Celichowski J.
Acta Neurobiologiae Experimentalis
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1992
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tom 52
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nr 2
17
The influence of a doublet of stimuli at the beginning of the tetanus on its time course
84%
Celichowski J. , Grottel K.
Acta Neurobiologiae Experimentalis
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1998
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tom 58
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nr 1
18
Content available remote Method of automatic recognition and other solutions used in new computer program for full decomposition of EMG signals
67%
Młoźniak D. , Piotrkiewicz M.
Biocybernetics and Biomedical Engineering
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2015
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tom Vol. 35, no. 1
22--29
EN
The analysis of electromyographic signals can be very time consuming. In designing a program for EMG signal analysis, there are two competing factors: the accuracy of the final result and its speed. In scientific work, accuracy is the most important factor. All of the existing decomposition programs used in neurophysiology require a final phase of manual corrections, if reliable results are to be obtained. This phase is considerably longer than the phase of automatic recognition. The solutions presented below, used in our new MUR program, allow for the accurate decomposition of complex EMG signals in a reasonable amount of time. The decomposition is performed interactively with optimal time division between automatic and manual tasks. All of this is achieved through a simple method of automatic recognition with the use of the modified coefficient of determination and the method of multiple subtractions of potentials.
19
Motor units of medial gastrocnemius muscle in the rat during the fatigue test. I. Time course of unfused tetanus
67%
Celichowski J.
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nr 1
20
The age dependent effect of partial denervation of rat fast muscles on their activity
67%
Tyc F. , Slawinska U. , Vrbova G.
Acta Neurobiologiae Experimentalis
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1999
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tom 59
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nr 2
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