Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 18

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  motor unit
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
1

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.
Acta Neurobiologiae Experimentalis
|
1996
|
tom 56
|
nr 4
2

The time course of the last contractions during incompletely fused tetani of motor units in rat skeletal muscle

100%
Celichowski J., Bichler E.
Acta Neurobiologiae Experimentalis
|
2002
|
tom 62
|
nr 1
3
Content available remote

Differences between properties of male and female motor units in the rat medial gastrocnemius muscle

100%
Celichowski J., Drzymala H.
Journal of Physiology and Pharmacology
|
2006
|
tom 57
|
nr 1
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.
4
Content available remote

Interspecies differences in the force-frequency relationship of the medial gastrocnemius motor units

100%
Mrowczynski W., Celichowski J., Krutki P.
Journal of Physiology and Pharmacology
|
2006
|
tom 57
|
nr 3
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.
5
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
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.
Journal of Physiology and Pharmacology
|
2000
|
tom 51
|
nr 2
6

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
|
1999
|
tom 59
|
nr 1
7
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
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.
Journal of Physiology and Pharmacology
|
2000
|
tom 51
|
nr 4,2
8
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
|
2004
|
tom 55
|
nr 2
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.
9

The area under the record of contractile tension: estimation of work performed by a contracting motor unit

84%
Celichowski J., Grottel K., Bichler E.
Acta Neurobiologiae Experimentalis
|
1998
|
tom 58
|
nr 2
10
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.
Journal of Physiology and Pharmacology
|
2008
|
tom 59
|
nr 1
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.
11
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

The rate of changes in tension within fused tetani of single motor units in rat medial gastrocnemius muscle

84%
Celichowski J., Bichler E.
Journal of Physiology and Pharmacology
|
1998
|
tom 49
|
nr 4
12
Content available remote

The number of motor units in the medial gastrocnemius muscle of male and female rats

84%
Celichowski J., Drzymala-Celichowska H.
Journal of Physiology and Pharmacology
|
2007
|
tom 58
|
nr 4
The number of motor units in the hindlimb locomotor muscle - the medial gastrocnemius - was estimated in male and female Wistar rats by comparison of the whole muscle tetanic force to the mean tetanic force of its motor units. Functional isolation of motor units was achieved by electrical stimulation of single axons from ventral roots of L4 - L5 spinal nerves, while the whole muscle force was measured during stimulation of the sciatic nerve. The medial gastrocnemius muscle is approximately 1.5 times bigger by mass, and is innervated by 10% more motoneurones in males compared to females. Estimation of the force that can be generated by the three types of motor unit in the studied muscle revealed that in both sexes fast fatigable units are responsible for over 60% of the total force output whereas the percentage of the force output contributed by slow units in females is approximately twice that in males. Concluding, the motor innervation of hindlimb skeletal muscles is sexually dimorphic and in the rat male medial gastrocnemius muscle contains about 10% more motor units than in females.
13

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
|
1992
|
tom 52
|
nr 2
14

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
|
1998
|
tom 58
|
nr 1
15

Tetanic depression: a phenomenon influencing the production of tension in fast-twitch motor units in rat medial gastrocnemius

84%
Celichowski J.
Acta Neurobiologiae Experimentalis
|
2001
|
tom 61
|
nr 2
16

Motor units of medial gastrocnemius muscle in the rat during the fatigue test. I. Time course of unfused tetanus

67%
Celichowski J.
Acta Neurobiologiae Experimentalis
|
1992
|
tom 52
|
nr 1
17

The age dependent effect of partial denervation of rat fast muscles on their activity

67%
Tyc F., Slawinska U., Vrbova G.
Acta Neurobiologiae Experimentalis
|
1999
|
tom 59
|
nr 2
18

MU firing characteristics in human dystrophic muscle

67%
Piotrkiewicz M., Filipiuk M., Hausmanowa-Petrusewicz I.
Acta Neurobiologiae Experimentalis
|
1993
|
tom 53
|
nr 1
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.