Biomedical subjects

K Grottel

Publications and source records attributed to K Grottel.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cervical and reticular projections of neurones located in S1 and S2 segments of the cat's spinal cord.

Sacral neurones (S1 and S2 segments) projecting to the cervical cord (C6 segment) and to the contralateral gigantocellular reticular nucleus (coGRN) were electrophysiogically studied on 7 adult cats under alpha-chloralose anaesthesia. Antidromic action potentials were recorded from 48 neurones following stimulation of their axons in both the C6 segment and coGRN. Two groups of investigated cells were distinguished in the gray matter of sacral segments: one distributed in laminae V-VI (12 neurones), the other located in medial part of lamina VII and lamina VIII (36 neurones). All cells from the first group projected to C6. The latter group consisted of three types of neurones: projecting to C6 (n = 9), to coGRN (n = 1) as well as to both C6 and coGRN (n = 26). Axons of all identified neurones ran in lateral funiculi ipsilaterally, contralaterally or bilaterally. Conduction velocities were comprised in the ranges 35-81 m/s and 34-70 m/s for neurones projecting to the reticular formation and the cervical spinal cord, respectively. Decrease in conduction velocities was found in some axons in their distal parts suggesting more extensive divergence to various segments in the spinal cord or supraspinal centres.

Animals↗

PubMed1997

Cells in and outside the motor trigeminal nucleus projecting to the cerebellar paramedian lobule.

To investigate afferent projections to the cerebellar paramedian lobule (PML) from neurones in the motor trigeminal nucleus (Vmt) and the region around it, the method of retrograde transport of HRP, WGA-HRP and FG was employed in the rabbit. After tracer injection into various regions of PML, labelled neurones were observed mainly in the ventral and ventrolateral margins of the beta and gamma parts of Vmt, respectively. In the region just outside Vmt, neurones were labelled mainly in the lateral and dorsolateral parts of region 'h' and in the region adjacent to the root fibres of the facial nerve and even among them. Some neurones were recognized dorsally in region 'm' and in the pars alpha of the parvocellular reticular nucleus. The projection is sparse and bilateral with a slight ipsilateral predominance. Neurones in Vmt send axons to PML sublobules b-f. Projection from regions around Vmt reaches all PML sublobules with sublobules e-f receiving more fibres.

Animals↗

PubMed1997

Lamina VII and VIII neurons of the S2 segment bilaterally projecting to the C6 segment of the spinal cord in the cat.

Intracellular and extracellular recordings of antidromic action potentials were applied to investigate neurons of the S2 segment projecting to the C6 segment of the cat spinal cord. The cell bodies were located in laminae VII and VIII of the gray matter while axons ascended in lateral funiculi. Thirty-two out of the total 45 neurons were found to project to the C6 segment bilaterally, seven ipsilaterally and six contralaterally. The axonal conduction velocities were in the 42-96 m/s range and in some neurons were significantly lower in distal parts of axons, supposing that some neurons may give off collateral branches to various segments of the spinal cord. It is discussed if the investigated neurons form a part of the propriospinal system or if their cervical projections are only collaterals of long tracts ascending to supraspinal levels. The organisation of the presented connections between spinal enlargements indicates their contribution in complex mechanisms of co-ordination of movements of the limbs.

Action Potentials↗

PubMed1997

Secondary vestibular projection to the reticular formation of rabbit lower brainstem with reference to reciprocity.

The secondary vestibular projection to the RF of lower brainstem was studied in the rabbit by retrograde transport of HRP and WGA-HRP. The projection is rather strong and originates bilaterally in all the main vestibular nuclei. The majority of afferents to the RF arise in the ventrolateral and ventromedial regions of MV and IV, respectively, whereas projections from SV and the ventral region of LV are weaker. Although no clear-cut topographical relationship was noted between location of neurons in the VNC and projection sites in the RF, some degree of preferential connections was found. All four vestibular nuclei project to RGc, though SV and LV contribute less than the others. Rpc alpha is supplied by fibers from MV and IV. RPc and Rpc receive projections from MV and/or IV. A minute connection was traced from the interstitial nucleus of the VIII nerve to RGc. The RF nuclei relaying vestibular information may plan an important role in the control of eye and head movements as well as in the postural adjustments required during animal displacement. The present results are discussed in comparison with those of earlier studies and with reference to reciprocity.

Animals↗

PubMed1997

Changes in tension-frequency relationship of motor units induced by their activity in rat muscle.

In 57 motor units of rats' medial gastrocnemius muscle the influence of activity on the course of 10 successively repeated tension-frequency curves (T-f curves) was observed. In slow motor units the steep parts of successive T-f curves usually shifted slightly towards higher frequencies. However, in some slow units of relatively short contraction these T-f curves shifted towards lower frequencies. In fast units, especially those of the FF type, more marked changes were observed in T-f curves. At first, a shift of the second to third curve towards lower frequencies was observed. Curves then shifted progressively towards higher frequencies. In all motor units greater changes in tension could be observed in unfused tetani than in fused tetani. In some motor units the tension of fused tetani showed a progressive decrease. Changes in the course of T-f curves related to changes in contraction and relaxation times. The results presented here explain how the duration of the activity can change the sensitivity of motor unit tension to the frequency of stimuli. The importance of the changes observed in the T-f relation in the process of fatigue is discussed.

Animals↗

PubMed1996

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

Changes in the fusion of tetani were investigated in fatigue tests of 50 fast motor units of the rat medical 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 component 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 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.

Animals↗

PubMed1995

Changes in tension of slow motor units in rat medial gastrocnemius during constant-rate stimulation at different frequencies.

Changes in tension of slow motor units in the medial gastrocnemius muscle of the rat were measured and compared in three fatigue tests, each of 4 min duration. In one of these tests motor unit tetani were evoked by repeated trains of stimuli of the standard frequency, 40 Hz, while in other tests frequencies of 20 and 60 Hz were used. Tetanic tension initially decreased in the majority of units during these three tests, then potentiated and, in the last part of the fatigue test, the tension was normally stable. Initial changes in tension were greatest in the fatigue tests with the lowest stimulation frequency (20 Hz) and smallest or even absent during tests with the stimulation frequency of 60 Hz. Moreover, initial changes in tension occurred for the longest period of time when the lowest frequency of stimulation (20 Hz) was used. Some of the motor units showed a slow decrease in tension in the last part of tests, especially when frequencies of 60 and 40 Hz were used. These results show that the tension of repeated unfused tetani of a slow motor unit is not constant, even during constant frequency stimulation, and changes in tension are greater in less fused tetani.

Animals↗

PubMed1995

Non-reciprocal connections between the perihypoglossal nuclei and the cerebellar paramedian lobule in rabbits and their relationship to the climbing fiber zones.

Retrogradely transported horseradish peroxidase (HRP) was used to investigate the organization of projections from the perihypoglossal nuclei to the cerebellar paramedian lobule, and possible reciprocal corticoperihypoglossal connections in rabbits. The absence of labeled Purkinje cells in the paramedian lobule after HRP injections of the perihypoglossal nuclei, compared with labeling in the nodulus, ipsilateral flocculus and adjacent ventral paraflocculus, strongly suggests that corticoperihypoglossal projections do not originate in the paramedian lobule. Comparison of labeling patterns in the perihypoglossal nuclei following HRP injections into various sublobules of the paramedian lobule suggests that projections from the perihypoglossal nuclei to the paramedian lobule exist and that some degree of topographic organization is present exclusively in bilateral projections from the caudal part of nucleus prepositus hypoglossi. All perihypoglossal projections end in deep parts of sublobules e-b of zones C2 and D1 (as defined by inferior olivary labeling). It is significant that in the ipsilateral nucleus prepositus hypoglossi, two groups of cells projecting to zone C2 are arranged rostrocaudally between three other groups projecting to zone D1.

Animals↗

PubMed1995

The relationship between fusion index and stimulation frequency in tetani of motor units in rat medial gastrocnemius.

The relationship between tetanic fusion and frequency of stimulation was investigated in 81 motor units of the rat medial gastrocnemius. A fusion index was calculated for tetani evoked by trains with constant frequency stimuli. This index is expressed as the ratio of a/b, where a is the distance from a baseline to the maximal relaxation before the last component of tetanus and b is the peak amplitude of the last component. The fusion-frequency relation has a sigmoid shape. The steep portion of the relation corresponds to lower frequencies for slow motor units than for fast units. Among the fast units, FR motor units are fused at somewhat lower frequencies than FF ones. However, the increase in fusion index per 1 Hz change in frequency of stimulation for the three types of motor units is similar. This observation suggests a similar course of fusion within different motor units. The fusion index shows a correlation with the contraction time as well as with the half-relaxation time.

Animals↗

PubMed1994

Dual projections of the ventromedial lamina VI and the medial lamina VII neurones in the second sacral spinal cord segment to the thalamus and the cerebellum in the cat.

Neurons of origin of the crossed spinocerebellar and/or spinothalamic tracts giving off axon collaterals at supraspinal levels were antidromically identified and labeled with horseradish peroxidase in lower sacral spinal cord segments of cats. Their cell bodies were located mainly in the medial part of lamina VII and rarely in the ventromedial aspect of lamina VI. In the S2 segment 77 neurons with axons in the opposite dorsolateral funiculus were recorded; 36 of them were invaded from only the thoracic level, 21 from both the thoracic level and the restiform body, 3 from both the thoracic level and the thalamus, and 17 from both the thoracic level, the restiform body and the thalamus on the contralateral side. These termination areas suggest that the S2 neurons under study transmit peripheral signals of proprioceptive, exteroceptive and nociceptive sensations.

Animals↗

PubMed1994

Antidromic field potentials recorded from cell groups of S2 spinal cord segment with axons in the opposite Th13 dorsolateral funiculus in the cat.

Location of cell groups within gray matter of S2 spinal cord segment, whose axons are running in the opposite Th13 dorsolateral funiculus, were studied by means of antidromic field potentials recorded in chloralose anaesthetized cats. The cell bodies are forming six separate groups occupying medial laminae II and III, medial laminae IV and V, medial lamina VII, medial lamina VIII, lateral laminae V and VI and lateral laminae VIII and IX. Properties of main components in antidromic field potentials recorded in each of areas have been described. The presumable termination sites of axons of investigated cellular groups are considered.

Anesthesia↗

PubMed1993

Twitch/tetanus ratio and its relation to other properties of motor units.

The ratio of single twitch tension to maximal tetanic tension (Tw/Tet ratio) represents one of the physiological properties of single motor units. In our study, in agreement with the results of other studies, the mean Tw/Tet ratio of slow motor units was lower than that of fast motor units. But we found that the Tw/Tet ratios of the slow motor units with twitch tension between 0.75 and 1.5 g were higher than those of fast motor units with twitch tension in the same range. A significant linear relation between Tw/Tet ratio and twitch tension was obtained for the three types of motor units. This relationship could be due to the increasing number of muscle fibres within a motor unit with the twitch tension.

Animals↗

PubMed1993

The reticulovestibular projection in the rabbit: an experimental study with the retrograde horseradish peroxidase method.

The reticulovestibular projections of the brainstem in the rabbit were studied by the retrograde transport of horseradish peroxidase (HRP). After selective iontophoretic injections of the tracer into various subdivisions of the vestibular nuclear complex (VNC), labeled neurons were found in defined regions of the reticular formation (RF) of the caudal pons and the rostral medulla. The results indicate that all four vestibular nuclei receive projection from RF. This projection is bilateral with a contralateral predominance. The major projection originates from dorsal and dorsolateral regions of the caudal pontine reticular nucleus (RPc) and the gigantocellular reticular nucleus (RGc) at the transitional level between them. A modest projection originates from pars alpha of the caudal pontine reticular nucleus (RPc alpha), the parvocellular reticular nucleus (Rpc) and pars alpha of the parvocellular nucleus (Rpc alpha), mostly from their ventral regions. A small projection arises from pars alpha of the gigantocellular reticular nucleus (RGc alpha), as well as from the ventral reticular subnucleus (Rv) and cell group a in the caudal aspect of the medulla. No clear-cut topical relationship was noted between the location of neurons in RF and projection site in VNC. The superior vestibular nucleus (SV) and the medial vestibular nucleus (MV) receive projections exclusively from RPc and RGc, whereas the lateral reticular nucleus (LV) and the inferior vestibular nucleus (IV) receive additional projections from the remaining RF nuclei. The termination areas of reticular fibers within SV and IV seem to be diffuse but in MV and LV there is a clear preponderance to the regions located ventrally. The present study has established cells of origin for the reticulovestibular projections from the pontomedullary RF to individual VNC nuclei in the rabbit.

Animals↗

PubMed1992

The dependence of the twitch course of medial gastrocnemius muscle of the rat and its motor units on stretching of the muscle.

The relationship between the force of a single twitch of the medial gastrocnemius muscle of the rat and contraction and half-relaxation times, on one hand, and the load of the muscle on the other, was studied. Twitches of the whole muscle and its individual motor units were induced. The optimal load, at which the majority of motor units reached the greatest twitch force, was 10 G. Mean optimal loads for twitches of different types of motor units were very similar. Slow motor units reached a slightly greater twitch force at greater loads (12.5 G) than at 10 G. However, the optimal load for the twitch of the whole muscle was much greater. It was 47 G on the average. The contraction and half-relaxation times of motor units, as well as of the whole muscle, became longer as the force stretching the muscle increased. Half-relaxation time changed more rapidly than contraction time. Both parameters were undergoing the greatest changes in slow motor units.

Animals↗

PubMed1991

Functional properties of crossed spinocerebellar tract neurones with cell bodies in the S1 segment.

Functional properties of a crossed spinocerebellar tract with cell bodies located in laminae VII and IX of the S1 segment were investigated using intracellular recording. The neurones were found to be excited by group I and II muscle afferents and afferents of skin, joint and interosseus nerves. Volleys from group II muscle afferents and cutaneous afferents evoked inhibition in these cells. It is concluded that S1 spinocerebellar neurones convey a similar type of information to that of dorsal spinocerebellar tract and ventral spinocerebellar tract neurones but integrate it in a different way.

Animals↗

PubMed1991

Non-reciprocal connections between the vestibular nuclei and the cerebellar paramedian lobule, with special reference to the climbing fiber zones: an analysis in the rabbit using the retrograde horseradish peroxidase method.

The organization of the secondary vestibular projections onto the cerebellar paramedian lobule (PML) and possible reciprocal corticovestibular connections were investigated by the retrograde horseradish (HRP) technique in the rabbit. Following injections of the tracer into the vestibular nuclear complex (VNC), an ill-defined, sagittal band composed of numerous labelled Purkinje cells was found ipsilaterally throughout the length of the lateral portion of the vermis, the ventral paraflocculus and the flocculus. However, no labelled Purkinje cells were found in the cortex of the PML. The results indicate that zone B, considered to give rise to cerebellar corticovestibular projections, is not present in the rabbit PML. After injections of HRP into the PML, the retrograde labelling pattern in the VNC was analyzed, in relation to the climbing fiber zones identified by retrograde labelling in the inferior olive. No clear-cut correspondence could be found between the vestibular subdivisions and climbing fiber zones in the PML, except that only the interstitial nucleus of the vestibular nerve projects into zone D1 in sublobules e and d. There were no vestibular projections to zone D2. The only salient feature was that cells projecting onto zones C2, C1 and C3 of the PML were arranged rostrocaudally in the inferior vestibular nucleus and the caudal portion of the medial vestibular nucleus. In addition, a topical relationship was found between parts of the VNC and sublobules of the PML.

Animals↗

PubMed1991

Changes in motor unit action potentials during the fatigue test.

The studies were performed on medial gastrocnemius motor units of the rat. Changes in amplitude, duration and latency of motor unit action potentials were monitored in the course of fatigue test in the three types of motor unites: FF (fast twitch, fatigable), FR (fast twitch, resistant), and S (slow twitch, resistant) motor unit. In a majority of the motor units the amplitude of action potential decreased. The most pronounced decrease took place in FF units, less pronounced one in FR units, while in S type motor units the decrease was insignificant. However, in a part of investigated motor units the amplitude of their action potential transiently increased at the beginning of the fatigue test and, then decreased or was maintained at the same level till the end of the fatigue test. In a few motor units, particularly the slow ones, no changes in action potential amplitude were observed. In the studied material, a decrease in action potential amplitude was on the average less pronounced than a decrease in tetanus tension in the course of the fatigue test. In a majority of studied motor units the duration of action potential was becoming prolonged, which was most pronounced in FF type motor units and least pronounced in S type ones. In few slow motor units the duration showed no alterations. Changes in action potential duration were much more marked than changes in their amplitude. The changes in action potential in fast motor units were less pronounced than changes in their tetanus tension, while in the slow motor units they resembled each other in intensity. Comparison of motor unit action potential changes with changes in their tetanic tension in the course of fatigue test demonstrated no clear-cut relationship between the two phenomena.

Action Potentials↗

PubMed1990

Division of motor units in medial gastrocnemius muscle of the rat in the light of variability of their principal properties.

Ninety-seven motor units of medial gastrocnemius muscle of the rat were examined. Among the examined motor units, fast (F) and slow (S) units were distinguished on the base of the presence or absence of sag reflex in unfused tetanus, induced by stimulation at 40 Hz. The fatigue test, in turn, permitted to distinguish fast fatigable (FF) and fast resistant (FR) units. Fatigue index was calculated using two techniques, the results of which differed significantly from each other. The following basic features of motor units were examined: contraction time, half-relaxation time and twitch force. A more detailed analysis of all characteristics of the units disclosed that their classification into fast and slow units on the base of the sag test alone was unjustified. A more appropriate classification resulted when multiple properties of the units were considered. The distinguished types of the units differed significantly from each other in the examined properties. On the other hand, a significant individual variability in the properties was also shown to exist within each type of the units. Various characteristics of the motor units showed correlation with each other in the whole population of motor units and/or their individual types.

Animals↗