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Biomedical subjects

E Jankowska

Publications and source records attributed to E Jankowska.

At least 109 records · Page 6Linked to original sources
PubMed1988

[Reaction time to single and double stimuli in operators of mining equipment].

The study was aimed at a comparison of the results of the reaction time for single (light or sound) and double stimuli (simultaneous emission of light and sound) in machine operators. The studies were carried out under laboratory conditions and in the working environment. The obtained data proved that underground, under specific copper mine conditions, similar to laboratory conditions, the theory of "intersensory facilitation" should be applied. The results of our studies can be useful for ergonomic practice.

Adult↗
PubMed1987

Field potentials generated by group II muscle afferents in the middle lumbar segments of the cat spinal cord.

1. A powerful projection from group II muscle afferents of hind-limb muscles to the 3rd, 4th and 5th segments of the lumbar spinal cord has been demonstrated by focal synaptic field potential recording. 2. Field potentials were found at two locations: one in the dorsal horn (Rexed's laminae IV and V) and the other in the intermediate zone and ventral horn (Rexed's laminae VII and VIII). In the dorsal horn the field potentials were exceptionally large and were evoked only by group II afferents. At more ventral locations, they were smaller and were sometimes preceded by small field potentials evoked by group I afferents. 3. At both locations field potentials could be evoked by stimulation of a number of hind-limb muscle nerves at strengths sufficient to activate group II afferents. However, some nerves consistently evoked more powerful effects than others and the largest potentials were from the nerves to quadriceps, sartorius and to the pretibial flexor muscles (tibialis anterior and extensor digitorum longus). Activation of articular afferents (from the knee joint nerve) or Pacinian corpuscle afferents (from the interosseous nerve) evoked small field potentials at some locations. 4. In the dorsal horn the latency of the field potentials was so short that they must have been generated monosynaptically. Field potentials in the ventral horn had longer latencies, by 0.5-1.0 ms, but they also appear to have been monosynaptically evoked by slowly conducting intraspinal collaterals. This conclusion is based primarily on the effects of intraspinal stimulation which was found to antidromically activate afferents with the appropriate latencies and thresholds. 5. Evidence is presented that the dorsal and ventral field potentials are generated by afferents whose receptors can be activated by small (less than 100 micron) muscle stretches.

Action Potentials↗
PubMed1987

An interneuronal relay for group I and II muscle afferents in the midlumbar segments of the cat spinal cord.

1. The properties of interneurones located in the 4th lumbar segment of the cat spinal cord (L4 interneurones) have been investigated by intracellular and extracellular recording from individual neurones. The study focused on interneurones projecting to hind-limb motor nuclei and/or interposed in pathways from group II muscle afferents. The projection to motor nuclei was assessed from antidromic activation of the neurones by stimuli applied in the motor nuclei of the 7th lumbar (L7) segment. 2. Interneurones which projected to gastrocnemius-soleus or hamstring motor nuclei were found in laminae VI and VII and at the border between laminae VII and VIII. The dominant peripheral input to most of them was from group II muscle afferents, but they were also influenced by group I muscle afferents and by afferents in cutaneous, joint and interosseous nerves. Both excitatory post-synaptic potentials (e.p.s.p.s) and inhibitory post-synaptic potentials (i.p.s.p.s) were evoked from all of these fibre systems. 3. The same kind of multimodal input was also found in other interneurones in laminae VI and VII. However, their axonal projections were not identified and they might have included neurones projecting to motor nuclei (though outside the areas which were stimulated) as well as neurones with more local actions. 4. Interneurones located in laminae IV and V of the dorsal horn appeared to constitute a separate functional population since both their projections and their input differed from those of the more ventrally located interneurones; none of the dorsal horn interneurones were found to project to motor nuclei and none had input from group I afferents, although they were influenced by group II muscle afferents and by afferents in cutaneous, joint and interosseous nerves. 5. Many of the excitatory actions from group I and II afferents upon L4 interneurones were found to be evoked monosynaptically. A high proportion of L4 neurones synapsing upon motoneurones would thus be interposed in disynaptic reflex pathways from these afferents. In comparison to actions evoked via interneurones of the caudal lumbar segments, any post-synaptic potentials (p.s.p.s) evoked via L4 interneurones would be delayed. These delays would amount to 0.4-0.9 ms for p.s.p.s. from group I afferents and by 0.5-2.5 ms for group II p.s.p.s. 6. In many interneurones, particularly those located ventrally, i.p.s.p.s. were evoked by group I and II muscle afferents at latencies which indicated that they were evoked disynaptically. They may therefore reflect inhibitory interactions between subpopulations of L4 interneurones.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1987

Post-synaptic actions of midlumbar interneurones on motoneurones of hind-limb muscles in the cat.

1. The hypothesis that interneurones in the 4th lumbar segment (L4) are interposed between group I and group II afferents and hind-limb motoneurones has been tested. Action potentials of single interneurones were induced by ionophoretically applied homocysteate and recorded in parallel with post-synaptic potentials in motoneurones; the latter were recorded from motor axons in the ventral root of the first sacral segment as population potentials, using the sucrose gap technique. 2. The action potentials of twenty-four L4 interneurones were found to be followed by either e.p.s.p.s. or i.p.s.p.s in motoneurones. The latencies of the majority of these p.s.p.s were consistent with monosynaptically evoked excitation or inhibition of motoneurones since they exceeded the latencies of antidromic activation of the interneurones from the S1 motor nuclei by only a fraction of a millisecond. 3. The dominant input to both the excitatory and the inhibitory interneurones was from group II muscle afferents, in particular from the quadriceps nerve. The latencies of excitation of the interneurones by these afferents indicated a monosynaptic coupling between them. The same interneurones were co-excited by group I and cutaneous afferents and by descending fibres. 4. We conclude that not only excitation but also inhibition of hind-limb motoneurones from group II afferents may be mediated disynaptically and that interneurones in the 4th lumbar segment contribute to both.

Action Potentials↗
PubMed1986

Labelling of midlumbar neurones projecting to cat hindlimb motoneurones by transneuronal transport of a horseradish peroxidase conjugate.

When wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) is injected into a hindlimb nerve it is first transported to motoneuronal somata and then, transneuronally, to interneurones in several spinal segments. However, the distribution of the labelled interneurones has been found to be dependent on the experimental conditions. Interneurones of the S1, L7, L6 and L5 segments were labelled in all the preparations used in this study while interneurones of the L4 and L3 segments were labelled only in some of them. The labelling of the L3-L4 interneurones was found when the animals were awake and active (after injection of WGA-HRP under short lasting anaesthesia) or when the contralateral pyramid was stimulated in animals which remained anaesthetized during the whole survival period. Since the transneuronal transport of WGA-HRP is enhanced by synaptic activity, these results are taken to indicate that L3 and L4 interneurones operate as last order neurones of neuronal pathways which subserve centrally initiated movements, in particular those activated by the corticospinal tract fibres.

Animals↗
PubMed1986

Lamina VIII interneurones interposed in crossed reflex pathways in the cat.

The location of a group of interneurones projecting to contralateral motor nuclei has been established using retrograde transneuronal transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP). After labelling the motoneurones of semitendinosus, medial gastrocnemius or quadriceps muscles, interneurones which were secondarily labelled were found in lamina VIII and in the neighbouring narrow strip of lamina VII. They were found to be distributed from the 4th lumbar to the 1st sacral segments, with the highest concentration in the 6th and 7th lumbar segments and at the border between the 4th and 5th lumbar segments. The electrophysiological properties of lamina VIII interneurones of the 6th lumbar segment have been investigated using both extracellular and intracellular recording. Many of these interneurones could be antidromically activated following weak stimuli applied in contralateral motor nuclei. Post-synaptic potentials were evoked from a variety of primary afferents including group I muscle afferents. However, when present, the post-synaptic potentials (p.s.p.s) of group I origin were of considerably smaller amplitudes than p.s.p.s. evoked from higher threshold muscle or cutaneous afferents and smaller than p.s.p.s. which followed stimulation of the spinal cord at the thoracic level. P.s.p.s. from the latter two sources appear to constitute the main input to lamina VIII interneurones. Group I input has been found in forty lamina VIII interneurones. These were usually affected by either ipsilateral or contralateral group I afferents and only exceptionally by both. Excitatory post-synaptic potentials (e.p.s.p.s) from ipsilateral afferents were evoked in about twice as many neurones as e.p.s.p.s from the contralateral afferents. E.p.s.p.s were often accompanied by inhibitory post-synaptic potentials (i.p.s.p.s). Group Ia afferents appeared to contribute to both e.p.s.p.s and i.p.s.p.s, whether these were evoked from ipsilateral or from contralateral afferents. In several cases Ia afferents were as effective as all group I afferents while in other cases Ib afferents appeared to be an important or even the exclusive source of the p.s.p.s. The latencies of e.p.s.p.s indicated that they were evoked mono-, di- or trisynaptically from ipsilateral group I afferents and di- or trisynaptically from contralateral afferents, I.p.s.p.s appeared to be evoked via pathways with only one additional interneurone. About one-third of all the intracellularly investigated lamina VIII interneurones were both affected by group I afferents and antidromically activated from the contralateral motor nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1985

Further indications for enhancement of retrograde transneuronal transport of WGA-HRP by synaptic activity.

Factors affecting the retrograde transneuronal transport of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP), from spinal motoneurones to interneurones, have been studied in the cat. To this end, the location of transneuronally labelled interneurones was compared in animals which were awake or remained anaesthetized after WGA-HRP had been injected into the semitendinosus or the medial gastrocnemius nerve. In the anaesthetized animals motor axons of the injected nerves were stimulated selectively, to activate only Renshaw cells, or together with group I afferents, to activate also laminae V-VI interneurones with input from these muscles. The interneurones labelled in this study were distributed in different spinal cord regions than the interneurones labelled in preparations in which group I afferents of antagonist muscles were stimulated, as described in a previous study. The reported observations extend evidence of Harrison et al. that the retrograde transneuronal transport of WGA-HRP is facilitated by synaptic activity.

Animals↗
PubMed1985

Sources of input to interneurones mediating group I non-reciprocal inhibition of motoneurones in the cat.

Intracellular recordings have been made from laminae V-VI interneurones interposed in pathways of non-reciprocal inhibition of motoneurones from group I afferents of triceps surae and/or plantaris. A comparison of actions of brief stretches of triceps surae and plantaris with actions of electrical stimulation of nerves of these muscles revealed that I a afferents influenced about a half of the interneurones excited by I b afferents. Electrical stimulation of seven muscles nerves, three cutaneous nerves, posterior knee joint and interosseous nerves, the red nucleus and the pyramidal tract, evoked excitatory post-synaptic potentials (e.p.s.p.s) in various proportions of interneurones. Most of the interneurones were excited monosynaptically, or both monosynaptically and disynaptically by group I afferents. This, together with a very small proportion of interneurones in which e.p.s.p.s were evoked only disynaptically, indicates that the same last-order interneurones may subserve di- and trisynaptically evoked inhibition of motoneurones. Other fibre systems excited these interneurones monosynaptically (interosseal, rubro- and corticospinal), disynaptically (cutaneous, rubro- and corticospinal) and polysynaptically. The coupling of the earliest e.p.s.p.s from group II and joint afferents could not be established, but was consistent with their mediation by only one or two interposed interneurones. Inhibition was evoked from all fibre systems with excitatory input to the same or to other interneurones of the sample, except from group II afferents, the effects of which were found in a much smaller number of cells and may not be fully representative.

Action Potentials↗
PubMed1985

Organization of input to the interneurones mediating group I non-reciprocal inhibition of motoneurones in the cat.

Patterns of convergence of different presynaptic fibre types onto interneurones mediating non-reciprocal inhibition of motoneurones have been studied in order to investigate to what extent the population of these interneurones is homogeneous or can be divided into subgroups on the basis of their input. In a sample of interneurones, all of which were interposed in pathways from the group I afferents of one group of muscles (triceps surae and plantaris), individual interneurones exhibited a wide variety of convergence patterns. Some interneurones were influenced by only a few types of afferent or descending fibre systems whereas others were influenced by many. Furthermore, various fibre systems excited and/or inhibited individual interneurones in different combinations. While there appeared to be too many patterns of convergence to allow any simple classification into a few distinct groups of interneurones, two possibilities were considered. One was that certain presynaptic fibre types influence individual interneurones in preferred combinations. The other was that they converge entirely at random. To investigate this, the frequencies of convergence of various pairs of fibre types were predicted assuming that each of them influences a proportion of the interneurones independently of other sources. Generally, there was close correspondence between such predicted and observed frequencies of occurrence of tested combinations of input. These findings are thus compatible with an organization whereby individual presynaptic fibres innervate a random sample of the population of interneurones. Deviations from the predicted incidence of convergence patterns were found primarily for synaptic actions mediated di- or oligosynaptically and are attributed to a consequence of convergence at the pre-interneuronal level. A particular consequence of such an organization is that interneurones in pathways of non-reciprocal inhibition are shared by afferents of different muscles in a continuum of combinations. The functional implications of this arrangement are discussed.

Action Potentials↗
PubMed1984

On the origin of presynaptic depolarization of group I muscle afferents in Clarke's column in the cat.

The origin of presynaptic depolarization of group I afferents in Clarke's column has been re-investigated, using changes in excitability of single fibres as a measure of their depolarization. In contrast to the previously reported lack of effects following conditioning stimulation of group Ia afferents, these afferents have been found to increase the excitability of other group Ia afferent terminals in Clarke's column. Flexor Ia and Ib afferents were found to be more effective than extensor afferents. The group I origin of the presynaptic depolarization of group I afferents in Clarke's column thus appears to be as of other terminals of these afferents. In order to define the location of interneurones mediating primary afferent depolarization in Clarke's column, changes in the excitability of afferents in Clarke's column were measured after isolating L4 and more rostral segments from the sacral and caudal lumbar segments, except for the dorsal columns, or after transection of ipsilateral lateral and ventral funiculi. Primary afferent depolarization of group Ia, or unspecified group I origin, was also found after such lesions and its effectiveness appeared to be as in intact preparations. It may thus be evoked primarily by interneurones located in the same segments as Clarke's column.

Afferent Pathways↗
PubMed1984

Do interneurones in lower lumbar segments contribute to the presynaptic depolarization of group I muscle afferents in Clarke's column?

Intersegmentally evoked primary afferent depolarization (PAD) was analysed to investigate whether any lower lumbar propriospinal neurones are involved in mediating PAD from group I afferents to group I afferents both in the same segments and in Clarke's column. The intersegmental PAD of lower lumbar afferents, as judged by recording dorsal root potentials, was evoked by stimuli applied in the grey matter of L3 and L4 segments. With intraspinal stimuli of 10 microA or less PAD was evoked from two foci: from within the middle part of the dorsal columns and from the dorsal part of the dorsal horn. Dorsal root potentials evoked from the dorsal horn focus appeared with longer latencies. When the dorsal columns were transected PAD was evoked only from the dorsal horn focus. No PAD appeared upon stimulation of Clarke's column after transection of the dorsal columns even with stronger (20 microA) stimuli. Interactions between the actions of the intraspinal stimuli and of different groups of afferents were analysed to define the neuronal pathways via which the intersegmental PAD was evoked. Neurones located within both the lower and the upper lumbar segments were found to be involved. Indications have only been found for a contribution of neurones mediating PAD from afferents other than group I afferents. Lesions of the ipsilateral and contralateral, lateral and ventral funiculi (in addition to the dorsal columns) were made in order to define which of these funiculi are required for the appearance of the intersegmental PAD. The intersegmental PAD could be evoked from the dorsal horn when either the contralateral or the ipsilateral funiculi were left intact.

Afferent Pathways↗
PubMed1984

Labelling of interneurones by retrograde transsynaptic transport of horseradish peroxidase from motoneurones in rats and cats.

Transsynaptic transport of conjugates of wheat germ agglutinin with horseradish peroxidase (WGA-HRP) has been studied in rats and cats. WGA-HRP was injected into a muscle nerve from which it was first transported to motoneurones and along sensory fibres, and secondarily to interneurones. More extensive labelling of interneurones occurred in preparations with only relevant ventral roots intact than in preparations with only dorsal roots intact, which indicates that the transsynaptic transport of WGA-HRP is primarily in the retrograde direction, i.e. from motoneurones to interneurones. Such a transport appeared to be considerably enhanced by neuronal activity.

Animals↗
PubMed1984

On re-excitation of feline motoneurones: its mechanism and consequences.

Conditions required for re-excitation of lumbosacral motoneurones, i.e. for double impulses in the motor axons associated with a single soma-dendritic action potential, were examined in cats anaesthetized with pentobarbitone and paralysed with gallamine triethiodide. Simultaneous recording from a motoneurone (intracellular, and in some experiments also extracellular), and from its axon in a ventral root, was used to assess the relations between the soma and the double axonal action potentials. Action potentials (greater than 70 mV) evoked by brief depolarizing current pulses applied intracellularly were never observed to cause re-excitation. Re-excitation could, however, be regularly induced by procedures which increased the delay between the initial segment and soma-dendritic components of these potentials. Re-excitation could be evoked (i) when brief hyperpolarizing pulses were applied before the onset of the soma-dendritic spikes, (ii) when the depolarizing pulses were applied on a background of long hyperpolarizing pulses or (iii) when two action potentials were evoked in a quick succession (by two brief depolarizing pulses). No relationship was found between the presence of re-excitation of motor axons and the presence of the delayed depolarization which follows the soma-dendritic spikes. Neither re-excitation nor delayed depolarization were found to be dependent upon re-excitation of the initial segment. These observations are thus at variance with previous suggestions that the initial segment spikes induce the re-excitation of motor axons and that the initial segment spikes cause the delayed depolarization following soma-dendritic spikes. Since re-excitation of a motor axon occurred without any signs of a second initial segment spike, it is concluded that it is initiated at the level of the axon, most likely at the first node of Ranvier. Re-excitation of motor axons was also observed during repetitive firing induced by intracellular current injection. However, it occurred then only occasionally, and only under strong depolarizing drive. It is thus not expected to be a common phenomenon under natural conditions of repetitive firing.

Action Potentials↗
PubMed1984

An intracellular study of descending and non-cutaneous afferent input to spinocervical tract neurones in the cat.

Previous studies of input on to spinocervical tract neurones have been extended by investigating the post-synaptic actions of non-cutaneous afferent fibres and of descending tracts on to these neurones, using intracellular recording. In particular, actions of group II muscle, joint and Pacinian afferent fibres and rubro- and corticospinal tract fibres were investigated. Group II muscle afferent fibres evoked excitation and inhibition at a minimal latency compatible with a disynaptic linkage. Increasing the stimulus strength to include group III afferent fibres enhanced these post-synaptic actions only modestly. Inhibition was evoked less frequently and/or required trains of stimuli. Weak stimulation of the interosseous nerve evoked short latency (disynaptic) inhibition or excitation, the latter less frequently. Post-synaptic potentials evoked below threshold for group III afferent fibres of the interosseous nerve are attributed to the actions of Pacinian corpuscles. Low threshold joint afferent fibres evoked excitation at short latency. Higher threshold joint afferent fibres usually evoked inhibition at longer latency, although high threshold excitation was sometimes observed. Stimulation of the pyramidal tract evoked constant latency, unitary e.p.s.p.s which followed high frequencies. The evidence suggests that such e.p.s.p.s are evoked monosynaptically. Polysynaptic excitation and inhibition were also observed. No convincing evidence could be found of actions evoked directly by the rubrospinal tract, although actions mediated via other descending systems could be induced from the red nucleus. A large degree of convergence was seen from different peripheral and descending systems on to individual neurones.

Action Potentials↗
PubMed1984

Convergence onto interneurons subserving primary afferent depolarization of group I afferents.

The aim of the study was to investigate whether common or independent neuronal pathways are used to evoke primary afferent depolarization (PAD) from selectively activated group Ia and Ib afferents of different muscles. To this end, the spatial facilitation of effects of various afferents, indicating convergence on the same interneurons, was used as a test. Its occurrence was assessed on dorsal root potentials (DRPs) evoked in unspecified fibers or using intra-axonal recording from identified group Ia muscle spindle afferents or group Ib tendon organ afferents. Spatial facilitation has been found in PAD pathways a) from various Ia-afferents, whether of flexors or extensors; b) from various Ib-afferents, whether of flexors or extensors; and c) from flexor Ib-afferents and flexor or extensor Ia-afferents. In contrast, no indications have been found for common pathways from extensor Ib- and any Ia-afferents under conditions that proved effective in other combinations. Latencies of those components of PAD that appeared as a result of the spatial facilitation ranged from 2 to more than 7 ms, indicating that the convergence occurred in the shortest (trisynaptic) as well as longer pathways. The same patterns of convergence have been found in PAD pathways to extensor and flexor Ia-afferents (in experiments with intraaxonal recording from these afferents). The possibility might thus be considered that some neuronal pathways are used to modulate transmission via Ia-afferents independently of their muscle origin. The same might hold true for extensor and flexor Ib-afferents. Generally, it is concluded that the minimal number of distinct neuronal populations subserving PAD of group I afferents may be two to six. Additionally, actions of cutaneous, joint, and interosseous afferents on DRPs from Ia-afferents were reexamined to further the comparison between neurons mediating PAD and those mediating postsynaptic excitation or inhibition of motoneurons. Only depression of Ia DRPs followed stimulation of these afferents at intensities of 1.5-2.0 times threshold and higher; lower threshold afferents were apparently ineffective. On the basis of lack of convergence of extensor Ib and Ia muscle afferents and of low-threshold cutaneous afferents, interneurons mediating PAD may thus be distinguished from the interneurons subserving Ib and Ia-like-Ib postsynaptic actions in motoneurons. The latter are coexcited by these three groups of afferents.

Animals↗
PubMed1983

Propriospinal control of interneurons in spinal reflex pathways from tendon organs in the cat.

After chronic hemisection at C3, stimulation of propriospinal fibers in the dorsal quadrant at Th 10 facilitated disynaptic PSPs from Ib afferents in hindlimb motoneurons. Recording from interneurons monosynaptically activated from group I muscle afferents, and of extracellular focal synaptic potentials around them, revealed monosynaptic EPSPs from long propriospinal neurons. It is suggested that propriospinal neurons originating in the forelimb segments have direct excitatory connexions with inter-neurons of Ib reflex pathways to hindlimb motoneurons.

Animals↗