Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 6

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

The influence of a doublet of stimuli at the beginning of the tetanus on its time course

100%
Celichowski J., Grottel K.
|
|
vol. 58
|
issue 1
47-53
EN
The influence of a pair of stimuli generated in a short time sequence (doublet) at the beginning of stimulation on the time course of the following tetanus was investigated. Experiments were performed on single motor units in rat's medial gastrocnemius. The doublet evoked an increase in tetanic tension, tetanic fusion and the area under tension record. These effects were measured in tetani fused to varying degrees. It was found that for all types of motor units the strongest influence of the doublet was observed in half-fused tetani. Moreover, the doublet influenced the first part of tetanus significantly more as compared to the second. Slow motor units showed greater sensitivity of the tension and the tetanus area to the doublet than fast units. The results show that slow units are characterized by better summation of their tension at the beginning of a tetanus. a tetan
2
Content available remote

Fatigability of motor units estimated by changes in work performed during their repetitive stimulation during the fatigue test

81%
Celichowski J., Grottel K., Bichler E.
Acta Neurobiologiae Experimentalis
|
1999
|
vol. 59
|
issue 1
37-43
EN
In numerous studies resistance to fatigue is evaluated by measuring the peak tension of motor units in muscle. In the present study, the work performed within successive tetani during the fatigue test of rat medial gastrocnemius motor units was estimated by assessing of the area under the tension record. Resistance to fatigue was evaluated by a modified fatigue index which is expressed as the ratio of the area under a tetanus recorded two minutes after maximal potentiation of tension has been reached to the area under this maximally potentiated tetanus. The values of this modified fatigue index were compared to the standard fatigue index which was taken as the ratio of peak tensions for corresponding tetani. For fast fatigable units, values of the modified fatigue index were significantly lower than those of the standard index. This observation resulted from changes in the shape of unfused tetani accompanying developing fatigue. These changes strongly influenced the area under the tension record whereas the peak tension of these tetani diminished less significantly. For slow and a part of fast resistant to fatigue units (with the standard fatigue index above 0.85) the modified fatigue index was slightly higher than the standard one although the difference was not significant. This phenomenon was due to the prolongation of relaxation which was visible in the last part of the fatigue test. It is being concluded that the modified fatigue index describes more precisely the fatigue-induced changes in tetani during the fatigue test than the standard fatigue index, especially in fast fatigable units.
3
Content available remote

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

81%
Celichowski J., Grottel K., Bichler E.
|
|
issue 2
165-168
EN
The area under twitch tension records was measured for motor units in rat medial gastrocnemius. These measures were compared to measures of tension. The tension varied in significantly larger range than the area. The area of slow motor units was similar to the area of fast resistant units, whereas their tensions differed significantly. The area depended mainly on the amplitude of contraction and to a smaller degree on its time course. The measure of area under the tension record gives a more exact evaluation of the work performed by contracting motor units than the measure of tension alone. The obtained results show that motor units in mammalian muscle are less variable in their ability to perform contractile work and moreover, that slow motor units play a more significant role during contractions than was supposed based on tension measures.
4
Content available remote

Branching neurones in the cervical spinal cord with axons that reach sacral segments and the lateral reticular nucleus. An electrophysiological study in the cat

81%
Krutki P., Grottel K., Mrowczynski W.
Acta Neurobiologiae Experimentalis
|
1999
|
vol. 59
|
issue 4
279-285
EN
Branching neurones in the cervical enlargement of the spinal cord were electrophysiologically studied in alpha-chloralose anaesthetized cats with the method of antidromic activation of axons. Stimulating electrodes were placed bilaterally at levels of lower thoracic and sacral segments and in the lateral reticular nucleus (LRN), ipsilaterally to the recording sites in C6/C7 segments. Thirty-nine out of a total one hundred neurones could be classified as bidirectional neurones with both descending and ascending collaterals. In the remaining cases only long descending projections to spinal segments were found. Comparison of conduction velocities measured in descending branches revealed no significant differences between individual neurones. On the other hand, descending collaterals of double direction neurones conducted impulses considerably faster than their axonal branches ascending to LRN. Our results suggest that parallel transmission of information to various, spinal or supraspinal centres of the nervous system is more common than reported before.
5
Content available remote

Projections of laminae IV-VI neurones located in the S2 segment of the spinal cord to the C6 segment and the cerebellum in the cat

81%
Mrowczynski K., Grottel K., Krutki P.
|
|
issue 2
103-111
EN
Ascending projections of neurones of the second sacral segment (S2) of the spinal cord to the sixth cervical segment (C6) and to the cerebellum were electrophysiologically investigated in eight adult cats under alpha-chloralose anaesthesia. Antidromic potentials recorded from 44 neurones following stimulation of their axons in the grey matter of the C6 segment as well as in the contralateral restiform body (coRB) showed evidence of both supraspinal and propriospinal projections. About one third of neurones (15) ascended to the cerebellum through the coRB and gave off collaterals to the C6 segment, while the rest (29) terminated exclusively at the level of the C6 segment. The cell bodies were found mainly in central parts of Rexed's laminae IV, V and VI while axons ran in lateral funiculi. Axonal conduction velocities measured between S2 and C6 segments were in the range of 42-78 m/s. A decrease of conduction velocity above the Th13 and C6 segments was found in most axons suggesting that they give some collaterals at spinal as well as supraspinal levels.
6
Content available remote

Changes in fusion index during the fatigue test of fast motor units in the medial gastrocnemius muscle of the rat

81%
Celichowski J., Grottel K., Bichler E.
Acta Neurobiologiae Experimentalis
|
1996
|
vol. 56
|
issue 4
881-887
EN
Changes in the fusion of tetani were investigated in fatigue tests of 50 fast motor units of the rat medial gastrocnemius muscle. Fusion of the tetani was measured using the fusion index, being the ratio of the tension to which motor unit relaxed before the last of tetanus to the peak tension of the last component. In both types of fast units (fast fatigable and fast resistant ) the changes in the fusion index were similar to those in tetanic tension: first they increased and then decreased. However, the increase of the fusion index was longer than that of tension and the subsequent decrease in the fusion index was smaller than that of tetanic tension. Furthermore, the initial increase in the fusion index of fast fatigable motor units was greater than in the tension. The dependence of the fusion index on twitch time enables the analysis of the influence of changes in the twitch time on changes in tension of unfused tetani observed during activity of fast motor units.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.