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Biomedical subjects

A Gramsbergen

Publications and source records attributed to A Gramsbergen.

At least 37 records · Page 2Linked to original sources
PubMed2000

Sciatic nerve transection in the adult rat: abnormal EMG patterns during locomotion by aberrant innervation of hindleg muscles.

The effects of lesions in the sciatic nerve were studied in adult rats. In the left hindleg, a segment 12 mm long was resected from the proximal part of the nerve, before the bifurcation into the peroneal and tibial nerves. This segment in a reversed orientation was used as a nerve graft. EMG patterns in the tibialis anterior and the gastrocnemius muscles at both sides were recorded during locomotion in six rats after recovery periods varying from 15 to 21 weeks. The specificity of axonal outgrowth was studied in nine rats by retrogradely labeling the motoneurons with unconjugated Cholera Toxin subunit B (CTB) after injections into the gastrocnemius, the soleus, and the tibialis anterior muscles at both sides. EMG patterns at the operated side were irregular and we often observed coactivation of the gastrocnemius and tibialis anterior muscle. Moreover, burst activity was badly adjusted to the phases of the stepcycle. Retrogradely labeling indicated that the pools of motoneurons innervating the respective muscles at the left side had increased in volume. Neuronal diameters were slightly decreased but a considerable decrease was observed in dendritic branching and dendrite bundles in the pools of the SOL and in the GC were absent. No consistent trends in neuronal numbers at the affected side in comparison to the right side were detected. We conclude that axons, sprouting from the proximal stump of the sciatic nerve, innervate the muscles aselectively and that the motoneurons of origin maintain their original activation pattern.

Animals↗
PubMed2000

Vestibular deprivation and the development of dendrite bundles in the rat.

Motoneuronal pools of muscles that subserve postural tasks contain dendrite bundles. We investigated in the rat the development of these bundles in the pools of the long back muscles and related this to postural development. Motoneurons and their dendrites were retrogradely labeled by injecting unconjugated cholera toxin subunit B (CTB) into the muscles of 54 normal rats from birth until adulthood and into 18 rats that were vestibularly deprived from the 5th postnatal day (P5). Dendrite bundles coursing in a transverse direction already occurred at P1. From P4, the first longitudinal bundles could be observed, but the major spurt in development occurred between P6 and P9, when conspicuous bundles developed coursing in rostro-caudal and transverse directions. This is the age when rats become able to stand freely and walk a few steps. Around P20, the dendrite bundles attained their adult characteristics. Vestibular deprivation by plugging both semicircular horizontal canals did not lead to a retarded development of dendrite bundles nor to a changed morphology. This finding is remarkable, as behavioral analysis showed a delay in postural development by about 3 days. We hypothesize that dendrite bundles in the pools of the long back muscles function to synchronize the motoneurons in different spinal cord segments.

Acoustic Stimulation↗
PubMed1999

The activation of back muscles during locomotion in the developing rat.

The development of posture during locomotion was studied in rats from the 11th day until adulthood. The EMGs were recorded and analyzed of the left and right longissimus muscles at caudal, intermediate and rostral levels as well as of the gastrocnemius, the tibialis and the vastus medialis muscles and movements were simultaneously recorded on videotape. Results indicate that from the 12th day of life, burst activity occurs in the longissimus muscles which is phase-related to the stepcycle. Until the 21st day these muscles are most strongly activated during burst activity in the gastrocnemius muscle in the contralateral hindleg but thereafter this activation coincides with bursts in the ipsilateral gastrocnemius muscle. At adult age such activation in the LL is restricted to fast walking or to accelerations. Latencies between bursts in the longissimus muscles and the gastrocnemius muscles vary around 100 ms until the 25th day, but thereafter they decrease to adult values of less than 10 ms. The large variations in these phase-relations at all ages suggest that supraspinal influences and afferent input are important factors in this coupling. The shift from a contra- to an ipsilateral coupling between bursts in the longissimus and in the gastrocnemius muscles might indicate that an ontogenetically older pattern of locomotion with the trunk muscles playing a major role in propulsion, is replaced by a newer pattern, mainly effected by extremity movements.

Aging↗
PubMed1999

Functional assessment of sciatic nerve reconstruction: biodegradable poly (DLLA-epsilon-CL) nerve guides versus autologous nerve grafts.

The aim of this study was to compare functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with modified denatured muscle tissue (MDMT), or an autologous nerve graft. We evaluated nerve recovery using walking track analysis (measurement of the sciatic function index [SFI]) and electrostimulation tests. Functional nerve recovery after reconstruction with a biodegradable p(DLLA-epsilon-CL) nerve guide filled with MDMT was faster when compared with nerve reconstruction using an autologous nerve graft. We conclude that in case of a short nerve gap in the rat, reconstruction can best be carried out using a p(DLLA-epsilon-CL) biodegradable nerve guide filled with MDMT.

Absorbable Implants↗
PubMed1998

Dendro-dendritic connections between motoneurons in the rat spinal cord: an electron microscopic investigation.

The ultrastructural characteristics of identified dendrite bundles in the rat spinal cord were analyzed following retrograde tracing from the soleus muscles. Dendrite bundles are arranged in networks that are heavily interconnected by means of gap junctions. The bundles are formed by at least 10 crossing dendrites travelling in different focal planes. In between dendrites, elongated gap junctional complexes are frequently found. Dendrite lamellar bodies, recently described to occur in relation with gap junctions in the central nervous system were not observed in the present study.

Animals↗
PubMed1998

Polyneural innervation in the psoas muscle of the developing rat.

Polyneural innervation was studied in the psoas muscle in developing rats from P4 till P25 and at adult age, with the combined silver-acetylcholinesterase technique. Nerve endings were counted, and end-plates were measured. These data were compared with such data in the human. The end of polyneural innervation in the rat (around P20) and in the human (around 12 weeks postterm age) in both cases coincides with a transformation in motor behavior and postural control. The rat's psoas muscle at early stages is less heavily innervated than this muscle in the human. Up to three axons per motor end-plate were counted at P4, but in the human up to five axons at 25 weeks of post menstrual age. This difference might be related to the lower percentage of type I muscle fibers in the rat.

Animals↗
PubMed1998

Motor development after vestibular deprivation in rats.

This review summarizes the postural development in the rat and the influences of vestibular deprivation from the 5th postnatal day on this development. Vestibular deprivation leads to a delay in motor development. Most probably this delay is caused by a delay in the development of postural control, which is characterized by a retarded EMG development in postural muscles. Our results indicate that the developing nervous system cannot compensate for a vestibular deficit during the early phase of ontogeny.

Animals↗
PubMed1998

The influence of betamethasone and dexamethasone on motor development in young rats.

Synthetic corticosteroids such as dexamethasone and betamethasone are widely used in clinical practice of the perinatal period to enhance lung maturation. However, indications emerged both on the basis of investigations in humans and in experimental animals that such treatment leads to abnormal brain development. In the present study, the neurologic development and the development of locomotion were studied in two groups of rats injected either with dexamethasone or with betamethasone on their 3rd and 4th d, and this was compared with development in a group of control rats injected with saline. Each group consisted of 12 rats. Neurologic reflexes were tested daily and the rat's physical development (body weight and age at eye opening) was noted from the 4th until the 21 st d. Locomotion was recorded on videotape and analyzed during playback runs. Results indicated a growth retardation in both groups of rats treated with corticosteroids, but remarkably, the opening of the eyes was advanced by about 1 d in the dexamethasone group compared with control rats and rats treated with betamethasone. Several reflexes showed normal development, but the negative geotaxis and free-fall righting responses developed retarded. Locomotion in both experimental groups was characterized by a postural tremor and an abnormal posture during walking from the 9th until the 15th d. Although the walking pattern after this age became fluent, the gait width remained abnormally increased until the 20th d. Our results indicate that both dexamethasone and betamethasone interfere with the development of vestibular and cerebellar functions involved in complex motor patterns.

Aging↗
PubMed1998

Posture and locomotion in the rat: independent or interdependent development?

In this essay, recent research into the relation between postural control and the development of walking in the rat is reviewed. The adult-like walking pattern develops at the 15th to 16th day (P15-P16). Until this age, postural control, as indicated by EMG activity in the longissimus muscle in the trunk, is poorly phased in relation to the stepcycle. After P15-P16, accuracy increases but only after P21 is the adult pattern of EMG activity in the trunk muscles in relation to locomotor activity in the hindpaw muscles established. Neuroanatomical research revealed that those muscles in trunk and extremities which fulfil important postural tasks are innervated by motoneuronal pools containing conspicuous dendrite bundles. These bundles emerge at about the age when the adult type of postural control starts to develop. As spinal transsection at P10 abolishes their development, we hypothesize that the development of dendrite bundles is dependent on the ingrowth or the becoming functional of descending projections. On the basis of the neurophysiological and neuroanatomical results we conclude that the development of postural control, which reaches its final stage 5-6 days after the adult-like pattern of walking has developed, is dependent on the maturation of suprasegmental structures and their spinal projections.

Adult↗
PubMed1997

Regression of polyneural innervation in the human psoas muscle.

During the early stages of mammalian ontogeny muscle fibres are innervated by more than one axon. This polyneural innervation is replaced by mononeural innervation in the course of development. The regression of polyneural innervation in the psoas muscle in the human is the topic of the present study. Innervation patterns were studied in fetuses from 15 1/2 weeks of post menstrual age (PMA) and in babies until 80 weeks PMA (40 weeks after term age) and compared to data from two adults. Motor endplates were stained by a combined acetylcholinesterase stain. Innervation patterns and motor endplate morphology were studied and the sizes of endplates were measured. As a main result of our study polyneural innervation of the psoas muscle remains at a level of about 2 endings per endplate (range 1-5 terminals) until 18-25 weeks PMA and decreases thereafter. From 52 weeks PMA (12 weeks post term) onwards, muscle fibres are predominantly mononeurally innervated. During development the morphology of the terminal patterns of the nerve endings becomes more complex and the size of endplates increases, implying that the adult pattern of muscle innervation is reached at the age at which a major functional transformation in the neurobehavioural repertoire occurs (i.e. the end of the second and the beginning of the third month.

Acetylcholinesterase↗
PubMed1997

The effects of early vestibular deprivation on the motor development in the rat.

The motor development after uni- or bilateral vestibular deprivation from the 5th or 16th postnatal day was studied in 23 rats between the 6th and the 60th day. Their motor behaviour was compared to that of 17 normal rats. Vestibular deprivation from the 5th day causes a marked retardation in motor development. Our results suggest that this retardation is caused by non-optimal stabilization of the trunk during development. Vestibular deprivation from the 16th day causes only short lasting disturbances of motor behaviour for one or two days. The main permanent effect of bilateral vestibular deprivation is head oscillation during locomotion. The temporal organization of the motor behaviour of rats bilaterally deprived from the 5th day was disturbed as well. These rats show more bouts of locomotion, rearing and pivoting.

Aging↗
PubMed1997

Aspects of postural development in the rat.

The activation patterns in the longissimus and gastrocnemius muscles during the development of the mature type of locomotion were studied in rats from the 11th day until maturity. The EMG's of these muscles were recorded and movements were simultaneously recorded on videotape. Results indicate that during locomotion at early ages, the longissimus muscles are activated irregularly. From the 16th day, the bursts in the longissimus muscle become more pronounced. During locomotion, they are activated differentially and often a simultaneous activation of the longissimus and the contralateral gastrocnemius muscle was observed. From the 20th day, bursts in the gastrocnemius muscle during walking coincide with bursts in the ipsilateral longissimus muscle. Our results demonstrate that the mature type of postural control (from the 20th day) develops a few days after the development of the mature type of fluent walking (around the 15th-16th day).

Animals↗
PubMed1996

Dendrite bundles in motoneuronal pools of trunk and extremity muscles in the rat.

The anatomical distribution and the content of dendrite bundles were studied in the spinal cord of adult rats. We injected retrogradely transported Cholera Toxin subunit B into muscles in order to label motoneurons and their dendrites. Twenty-one muscles in the trunk and in extremities were selected which are involved in a variety of motor tasks. Reconstructions were made from consecutive sections and the organization of dendrites was studied. In addition, the distributions of fiber types in the muscles were estimated on the basis of ATPase and succinic dehydrogenase-stained sections. Dendrite bundles are confined to pools of muscles which have postural tasks. Two different types can be distinguished. In the first type, longitudinal dendrite bundles extend over the length of the pool and also transversal bundles occur. Such pools innervate the axial musculature, and the soleus and flexor carpi ulnaris muscles in the extremities. These muscles contain relatively high percentages of slow twitch type I muscle fibers. In the second type, the occurrence of bundles is confined to a few zones within the pool. Such pools innervate muscles which are involved in postural tasks but in addition they also subserve other movement tasks. Distinct regions within these muscles are characterized by high percentages of type I muscle fibers.

Animals↗
PubMed1996

The function of the long back muscles during postural development in the rat.

The development of the EMG of the multifidus (MM) and longissimus lateralis (LL) muscles was studied in 16 rats between the 6th day (P6) and P45 and related to behavioural development. The EMG changes gradually from irregular and spiky towards a regular interference pattern and simultaneously, the general activity level increases. From P11, tonic background activity occurs with phasic activity superimposed. During locomotion, a relation between increasing activity in the long back muscles and the swing phase of both hind paws develops, but only from P15 the activity modulates consistently with the step cycle. From the end of the second week of life, the activity in the long back muscles precedes hind paw movements. The development of the EMG of the LL and MM is closely followed by the development of adult and fluent motor patterns. This suggests that the stabilisation of the trunk is essential for the development of these patterns.

Animals↗
PubMed1994

Development of the EMG of the soleus muscle in the rat.

The EMG of the soleus muscle was recorded with bipolar electrodes chronically implanted in rats aged 10-30 days. Changes in the activity pattern were studied in relation to motor development. The firing pattern and shape of motor units were studied at higher resolution. EMG activity was closely related to motor behaviour and posture. At P11, soleus was only phasically active during movements. Tonic EMG activity appeared with age, and by P16 the activity pattern was similar to that of the adult. The activity level also increased markedly with age. This was paralleled by a change in hindlimb posture. The development of tonic activity precedes the development of dendrite bundles in the motoneuron pool of the soleus muscle, which does not support the hypothesis that bundle formation is causally related to tonic activity in postural muscles. At young ages, the tonic EMG was characterized by a clear oscillation pattern with a frequency ranging from 7 to 20 Hz, the higher frequencies occurring at older ages. This oscillation disappeared around P16, which suggests that it is related to functional development of the stretch reflex. Periods of high frequency firing were observed in the EMG; the highest firing frequencies occurred during locomotion. The maximum firing frequency increased steeply to about 80 Hz at P18. It is suggested that bursts of high frequency firing are related to the development of monoaminergic innervation of the spinal cord. During the first three weeks, motor unit action potentials often showed complex shapes of long duration and considerable spike-to-spike variability. Computer simulation of the summation process of fibre potentials at the electrode showed that the small fibre diameters and high variability in diameter at young ages are major factors with respect to the generation of complex potentials.

Action Potentials↗
PubMed1993

The effect of early movement restriction: an EMG study in the rat.

The effect of early immobilization upon the adult locomotor pattern was studied. One hindlimb of neonatal rats was immobilized during 20 days and the EMG pattern was studied 3-8 weeks after termination of movement restriction. All rats showed a fluent locomotion pattern at these ages, but the EMG pattern revealed differences in the timing of flexor and extensor activity between the previously immobilized and the contralateral side. We suggest that interference with movement related afferent feedback at young ages has subtle but long-lasting effects upon the locomotion generating neural circuits.

Animals↗
PubMed1993

Early cerebellar hemispherectomy in the rat. Effects on the maturation of two hindlimb muscles and on lumbar motoneurones.

Cerebellar hemispherectomy before the 10th day in rats leads to extensive neuronal remodelling. In the present study the problem was studied whether such early lesions also have effects on the maturation of the soleus and the extensor digitorum longus muscles in the hindleg as well as on the formation of dendrite bundles from motoneurons innervating the soleus muscle. Results indicate consistent left-to-right differences in the numbers of muscle fibres but no differences in muscle differentiation. Dendritic bundles of soleus motoneurons, at the side ipsilateral to the cerebellar lesion are absent or less conspicuous in comparison to the contralateral side or to those bundles in normal rats. Cerebellar lesioning at the 30th day does not affect dendritic bundles.

Animals↗