Mobility of the ankle mortise. A roentgen stereophotogrammetric analysis

In 7 adult volunteers, a roentgen stereophotogrammetric technique was used to analyze the tibiofibular relationship during active unloaded movements of the ankle. The greatest movements were observed during plantar to dorsiflexion with an average widening of the ankle mortise of 1.0 mm and an average dorsal translation of the fibula of 0.9 mm. No significant rotation of the fibula could be revealed.

Long C3-C5 propriospinal neurones in the cat

Intracellular recording was made in the C3-C5 segments of cats from cells identified as long propriospinal neurones (PNs) by antidromic activation from the lower thoracic segments. The cell bodies were in laminae VII and VIII and their ventrally located axons were either uncrossed or crossed. Stimulation of higher motor centres revealed monosynaptic excitatory postsynaptic potentials (EPSPs) from cortico-, rubro-, tecto-, reticulo-, interstitio-, fastigio- and trigeminospinal fibres. Monosynaptic inhibitory postsynaptic potentials (IPSPs) were evoked from reticulospinal fibres. These PSPs were in addition to the separately described effects from the vestibular nuclei. Monosynaptic EPSPs were also evoked in some cells from neck or forelimb afferents and disynaptic EPSPs or IPSPs from forelimb afferents.

Vestibular effects in long C3-C5 propriospinal neurones

The effects of stimulation of the vestibular nerve and of regions in and around the vestibular nuclei on long C3-C5 propriospinal neurones (PNs) were investigated with intracellular recording. Disynaptic excitatory postsynaptic potentials were evoked from the contralateral (co) or ipsilateral (i) vestibular nerve in many long PNs but mainly in crossed PNs from the co and in uncrossed from the i nerve. Disynaptic inhibitory postsynaptic potentials were evoked more rarely, mainly from the i vestibular nerve. Threshold mapping revealed an excitatory relay from the co nerve in the medial vestibular nucleus (MVN) and also that the excitatory MVN neurones projecting to the long PNs send collaterals to the abducens and interstitial nucleus of Cajal. Excitation from the i vestibular nerve was relayed in the lateral vestibular nucleus (LVN) and in the MVN. Also, non-second order LVN neurones project to the long PNs. Monosynaptic IPSPs were evoked from the i MVN and i LVN.

Subpopulations and functions of long C3-C5 propriospinal neurones

Long C3-C5 propriospinal neurones (PNs) are classified in 3 types depending on their pyramidal and vestibular input. The first type of PNs received pyramidal excitation but lacked vestibular effects. The second type of PNs was excited from the medial vestibular nucleus but not from the pyramid. The third type of PNs was excited from the lateral vestibular nucleus either from second order neurones or from non-second order neurones. Monosynaptic excitatory postsynaptic potentials from neck afferents and/or oligosynaptic postsynaptic potentials from forelimb afferents were found in some of the PNs of the second and third type but not in those of the first type. Collision experiments revealed that cortico- and rubrospinal fibres to the long C3-C5 PNs terminate in the rostral spinal cord, presumably in the forelimb segments. Vestibular and reticular effects on the PNs are partly from fibres terminating in the rostral spinal cord and partly from fibres projecting to the lumbar cord. It is postulated that the different types of PNs contribute to the adjustment of hindlimb posture which is required during different movements of the forebody. It is suggested that the basic tonus is maintained mainly by the direct projection to the hindlimb segments from lateral vestibulospinal and reticulospinal neurones which excite antigravity muscles via lumbar interneurones and that the long C3-C5 PNs converge onto the same interneurones so that they act by modulation of the basic tonus.

Reflex pathways from group II muscle afferents. 2. Functional characteristics of reflex pathways to alpha-motoneurones

The convergence of group II muscle afferents on interneurones in reflex pathways has been elucidated by investigating interaction in transmission to motoneurones. Recording was also made from interneurones activated from group II afferents. Maximal group II EPSPs evoked in motoneurones from different muscles (extensors or flexors and extensors) did not summate linearly but with a deficit of 35-40%. The corresponding deficit in summation with Ia EPSPs was 7%. It is suggested that the difference in deficit is caused largely by occlusion due to shared interneuronal discharge zones and that it gives an approximate minimal measure of the convergence of group II afferents from different muscles on the interneurones. Tests with weak group II volleys from different muscles gave no or little evidence for spatial facilitation in the disynaptic excitatory pathway to flexor motoneurones, and there was no or little temporal facilitation of transmission in this pathway. It is suggested that group II excitation of the interneurones in this pathway depends on few afferents giving large unitary EPSPs. Convergence of cutaneous afferents and joint afferents on the interneurones was evidenced by spatial facilitation from these afferents of group II transmission to motoneurones. Convergence on interneurones in the trisynaptic inhibitory pathway from group II afferents to extensor motoneurones was also investigated with the spatial facilitation technique. There was convergence on common interneurones of group II afferents from different muscles (extensors or flexors and extensors) and from cutaneous afferents as well as joint afferents. Trisynaptic group II IPSPs, including those depending on spatial facilitation from different muscles were resistant to recurrent depression from motor axon collaterals and are therefore not mediated by the reciprocal Ia inhibitory pathway. Interneurones with monosynaptic group II EPSPs were recorded from in the dorsal horn and intermediate region. Graded stimulation revealed large unitary EPSPs from few group II afferents. The EPSP evoked by a single group II afferent may produce firing (extracellular recording). Convergence of monosynaptic group II EPSPs from different muscles was rather limited but could be from flexors and extensors. Extensive multisensory convergence onto some of these interneurones was indicated by di- or polysynaptic EPSPs from group II and III muscle afferents, from joint afferents and from cutaneous afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Reflex pathways from group II muscle afferents. 3. Secondary spindle afferents and the FRA: a new hypothesis

A hypothesis is forwarded regarding the role of secondary spindle afferents and the FRA (flexor reflex afferents) in motor control. The hypothesis is based on evidence (cf. Lundberg et al. 1987a, b) summarized in 9 introductory paragraphs. Group II excitation. It is postulated that subsets of excitatory group II interneurones (transmitting disynaptic group II excitation to motoneurones) may be used by the brain to mediate motor commands. It is assumed that the brain selects subsets of interneurones with convergence of secondary afferents from muscles whose activity is required for the movement. During movements depending on coactivation of static gamma-motoneurones impulses in secondary afferents may servo-control transmission to alpha-motoneurones at an interneuronal level. The large group II unitary EPSPs in interneurones are taken to indicate that, given an adequate interneuronal excitability, impulses in single secondary afferents may fire the interneurone and produce EPSPs in motoneurones; interneuronal transmission would then be equivalent to that in a monosynaptic pathway but with impulses from different muscles combining into one line. It is postulated that impulses in the FRA are evoked by the active movements and that the role of the multisensory convergence from the FRA onto the group II interneurones is to provide the high background excitability which allows the secondary spindle afferents to operate as outlined above. The working hypothesis is put forward that a movement governed by the excitatory group II interneurones is initiated by descending activation of these interneurones, but is maintained in a later phase by the combined effect of FRA activity evoked by the movement and by spindle secondaries activated by descending activation of static gamma-motoneurones. As in the original "follow up length servo" hypothesis (Rossi 1927; Merton 1953), we assume that a movement at least in a certain phase can be governed from the brain solely or mainly via static gamma-motoneurones. However, our hypothesis implies that the excitatory group II reflex connexions have a strength which does not allow transmission to motoneurones at rest and that the increase in the gain of transmission during an active movement is supplied by the movement itself. Group II inhibition. It is suggested that the inhibitory reflex pathways like the excitatory ones have subsets of interneurones with limited group II convergence. When higher centres utilize a subset of excitatory group II interneurones to evoke a given movement, there may mobilize inhibitory subsets to inhibit muscles not required in the movement.(ABSTRACT TRUNCATED AT 400 WORDS)

Reflex pathways from group II muscle afferents. 1. Distribution and linkage of reflex actions to alpha-motoneurones

The interneuronally mediated reflex actions evoked by electrical stimulation of group II muscle afferents in low spinal cats have been reinvestigated with intracellular recording with motoneurones to knee flexors and ankle extensors. The results of Eccles and Lundberg (1959) have been confirmed and extended. There was wide convergence from flexors and extensors of group II excitation to flexor and group II inhibition to extensor motoneurones. Some quantitative differences in the effect from the different nerves are described. Latency measurements suggest that the minimal linkage is disynaptic in the excitatory interneuronal pathways and trisynaptic in the inhibitory pathways. Disynaptic group II EPSPs were found in 14% of the ankle extensor motoneurones but were much more common in unanaesthetized high spinal cats (Wilson and Kato 1965). From these results and corresponding ones on flexors (Holmqvist and Lundberg 1961) it is postulated that secondary afferents in addition to the weak monosynaptic connexions (Kirkwood and Sears 1975) have disynaptic excitatory pathways and trisynaptic inhibitory pathways to both flexor and extensor motoneurones. It is proposed that the group II actions of the flexor reflex pattern characterizing the anaesthetized low spinal cat are due to suppression of the inhibitory pathway to flexor motoneurones and the excitatory pathway to extensor motoneurones. In some ankle extensor motoneurones the disynaptic group II EPSPs occurred in combination with IPSPs from the FRA (including group II and III muscle afferents). The possibility is considered that these group II EPSPs are mediated by an interneuronal group II pathway with little or no input from group III muscle afferents but probably from extramuscular receptors. In other ankle extensor motoneurones group II EPSPs were combined with EPSPs from group III muscle afferents, cutaneous afferents and joint afferents. It is postulated that these group II EPSPs are mediated by an interneuronal pathway from the FRA which also supply interneuronal pathways giving inhibition to extensor or/and flexor motoneurones and excitation to flexors as postulated by Eccles and Lundberg (1959) and Holmqvist and Lundberg (1961).

Hypermetria in forelimb target-reaching after interruption of the inhibitory pathway from forelimb afferents to C3-C4 propriospinal neurones

Forelimb target-reaching in cats with a transection at C5/6 of the cortico- and rubrospinal tracts is known to depend on C3-C4 propriospinal neurones (PNs). An additional lesion transecting the dorsal column (DC) in C5/6, caudal to the C3-C4 PNs, gave pronounced hypermetria in lifting and protraction during target-reaching. If the additional DC lesion instead was made in C2, rostral to the C3-C4 PNs, there was only small hypermetria in lifting and none in protraction. It is postulated that the hypermetria after the C5/6 DC lesion is due to interruption of the inhibitory pathway from the forelimb to the C3-C4 PNs. It is suggested that feedback control from the forelimb of the premotoneurones is an integral part of the control of normal target-reaching.

Effects of dorsal column transection in the upper cervical segments on visually guided forelimb movements

Complete transection of the dorsal column in C2 in cat gave severe defects in forelimb target-reaching and food-taking tested with retrieval of food from a cylinder. Among the symptoms were marked dysmetria in all directions and dyscoordination of movements in different joints, with only slow recovery over weeks and months. It is postulated that normal visual guidance of forelimb movements to a stationary target depends on somatosensory information to the brain via the dorsal column.

The inhibitory feedback pathway from the forelimb to C3-C4 propriospinal neurones investigated with natural stimulation

Light mechanical stimulation of the skin and passive joint movements in the forelimb gave effective activation of interneurones located medially in the C3-C4 segments. Such interneurones may be inhibitory to C3-C4 propriospinal neurones (PNs) and recording from PNs revealed that the stimuli which activated the interneurones evoked inhibition in the PNs. It is postulated that a movement commanded via the C3-C4 PNs evoke impulses in forelimb afferents which by negative feedback control transmission in the C3-C4 PNs and thus govern the execution of the movements.

Integration in descending motor pathways controlling the forelimb in the cat. 11. Inhibitory pathways from higher motor centres and forelimb afferents to C3-C4 propriospinal neurones

Intracellular recording was made in the C3-C4 segments from cell bodies of a previously described system of propriospinal neurones (PNs), which receive convergent monosynaptic excitation from different higher motor centres and mediate disynaptic excitation and inhibition from them to forelimb motoneurones. Inhibitory effects in these PNs have now been investigated with electrical stimulation of higher motor centres and forelimb nerves. Short-latency IPSPs were evoked by volleys in the cortico-, rubro- and tectospinal tracts and from the reticular formation. Latency measurements showed that those IPSPs which required temporal summation were disynaptically mediated. After transection of the corticospinal tract in C2, only small and infrequent disynaptic IPSPs were evoked from the pyramid. It is postulated that disynaptic pyramidal IPSPs only to a small extent are evoked by monosynaptic excitation of reticulospinal inhibitory neurones known to project directly to the PNs, and that they are mainly mediated by inhibitory interneurones in the C3-C4 segments. Tests with spatial facilitation revealed monosynaptic excitatory convergence from tecto-, rubro- and probably also from reticulospinal fibres on inhibitory interneurones monosynaptically excited from corticospinal fibres (interneuronal system I). Disynaptic IPSPs were also evoked in the great majority of the PNs by volleys in forelimb muscle and skin nerves. A short train of volleys was usually required to evoke these IPSPs from group I muscle afferents. In the case of cutaneous nerves and mixed nerves single volleys were often effective, and the lack of temporal facilitation of IPSPs produced by a train of volleys showed strong linkage from these nerves. The results obtained after transection of the dorsal column at different levels show that the relay is almost entirely rostral to the forelimb segments. Test with spatial facilitation revealed that interneurones monosynaptically activated from forelimb afferents receive convergent excitation from corticospinal but not or only weakly so from tecto- or rubrospinal fibres. There was also convergence from group I muscle afferents and low threshold cutaneous afferents on common interneurones. It is postulated that the disynaptic IPSPs from forelimb afferents are mediated by inhibitory interneurones (interneuronal system II) other than those receiving convergent descending excitation. Volleys in corticospinal fibres, in addition to the disynaptic IPSPs, evoke late IPSPs in the PNs. Similar late IPSPs were evoked from the ipsilateral forelimb by stimulation of the FRA.(ABSTRACT TRUNCATED AT 400 WORDS)

Integration in descending motor pathways controlling the forelimb in the cat. 10. Inhibitory pathways to forelimb motoneurones via C3-C4 propriospinal neurones

A further analysis has been made of inhibitory pathways to motoneurones via C3-C4 propriospinal neurones (PNs). Intracellular recording was made from triceps brachi motoneurones and effects from higher centres and forelimb afferents on corticospinal IPSPs were investigated after transection of the corticospinal tract at the C5/C6 border. The shortest latencies of the IPSPs evoked by stimulation of the pyramid were as brief as those of the pyramidal EPSPs (Illert et al. 1977). It is postulated that the minimal linkage of the pyramidal IPSPs is disynaptic via inhibitory C3-C4 PNs projecting directly to motoneurones. It was confirmed that pyramidal IPSPs usually are depressed by volleys in forelimb motor axon collaterals (Illert and Tanaka 1978). A quantitative comparison was made of the recurrent depression of pyramidal IPSPs and of IPSPs caused by activation of the Ia inhibitory interneurones. The result support the hypothesis of two parallel inhibitory cortico-motoneuronal pathways via C3-C4 PNs, one disynaptic via the inhibitory PNs and the other trisynaptic via excitatory PNs and Ia inhibitory interneurones. Pyramidal volleys also evoked late IPSPs which in some cases were not depressed from forelimb motor axon collaterals. It is postulated that the late IPSPs are partly due to activation of inhibitory C3-C4 PNs. Disynaptic pyramidal IPSPs were effectively facilitated by volleys in rubro-, tecto- and reticulospinal fibres - but not from vestibulospinal fibres - showing a convergence from the former descending tracts on common inhibitory C3-C4 PNs. Projection from forelimb afferents and corticospinal fibres on common inhibitory C3-C4 PNs was revealed by strong facilitation of disynaptic pyramidal IPSPs from cutaneous forelimb afferents. No corresponding effect was evoked from C2 neck afferents. Stimulation in the lateral reticular nucleus (LRN) evoked monosynaptic IPSPs in some motoneurones. The results of threshold mapping in and around the LRN suggest that the IPSPs are caused by antidromic stimulation of ascending collaterals of inhibitory neurones also projecting to motoneurones, possibly the inhibitory C3-C4 PNs.

Integration in descending motor pathways controlling the forelimb in the cat. 12. Interneurones which may mediate descending feed-forward inhibition and feed-back inhibition from the forelimb to C3-C4 propriospinal neurones

Extra- and intracellular recording was made from cells in the C3-C4 segments with the aim of finding interneurones of previously described inhibitory pathways to the C3-C4 propriospinal neurones, which may mediate descending feed-forward inhibition and feed-back inhibition from the forelimb, respectively. The lateral interneurones were found in the lateral part of lamina VII interspersed among the C3-C4 PNs and like them they receive convergent monosynaptic EPSPs and disynaptic IPSPs from the cortico-, rubro-, tecto- and reticulospinal tracts. Disynaptic IPSPs, but only rarely monosynaptic EPSPs, are evoked in them from forelimb nerves. The lateral interneurones do not project to the lateral reticular nucleus (LRN). The medial interneurones were found medially in laminae V and VI in a region where volleys in forelimb nerves evoke extracellular monosynaptic focal potentials (Rosén 1969). There is somatotopic organization of the projection from the forelimb to this region. Many neurones are strongly monosynaptically excited from group I muscle or/and cutaneous forelimb afferents. In addition, late discharges are evoked in many cells from cutaneous afferents and high threshold muscle afferents. Corticospinal volleys evoked monosynaptic excitation in the great majority of these cells and usually also late EPSPs or IPSPs. Typically, rubrospinal and tectospinal volleys evoked neither monosynaptic excitation nor late effects as those elicited from corticospinal fibres. In some of the interneurones, IPSPs were evoked from forelimb nerves. About 20% of the medial "interneurones" have an ascending projection to the caudal brain stem. Threshold mapping for antidromic stimulation revealed termination in the main cuneate nucleus, the external cuneate nucleus and/or the LRN and also a branch projecting to more rostral levels in the brain. A few of the neurones in the medial region are PNs projecting to the forelimb segments. It is postulated that interneurones both of the lateral and medial type are inhibitory and project to the C3-C4 PNs. It is further postulated that the former are intercalated in the descending feed-forward inhibitory pathway to the C3-C4 PNs and the latter in the feed-back inhibitory pathway from the forelimb to these PNs. The role of feed-forward and feed-back inhibition of transmission from the brain to forelimb motoneurones via the C3-C4 PNs is discussed.

Longitudinal study of physical working capacity of young people with spastic cerebral palsy

Nineteen adolescents with spastic diplegia and 12 able-bodied controls took part in a longitudinal study of aerobic capacity and physical working capacity during their teens. Absolute values for aerobic capacity and physical working capacity increased during the teens for both groups, which appears to contradict earlier descriptions of prematurely decreased physical working capacity among cerebral-palsied adolescents. On the other hand, net mechanical efficiency during submaximal bicycle ergometer tests decreased significantly in the diplegic group during their teens, and especially among those with severe motor handicap. This is of interest because these children are at risk of insufficient physical activity at school, partly because of the unsatisfactory design of physical education programmes for motor-handicapped children.

The pattern of monosynaptic Ia-connections to hindlimb motor nuclei in the baboon: a comparison with the cat

The pattern of Ia-connections to motor nuclei of 17 hindlimb muscles (or groups of muscles) has been investigated in baboons by intracellular recording of Ia-e.ps.p.s evoked in motoneurons from different muscle nerves. The amplitudes are normalized to 70 mV resting potential and compared with similarly normalized Ia-e.ps.p.s in cats. As in the cat, Ia-excitation is drawn from a restricted number of muscles and the homonymous effect is usually dominating. Heteronymous connections to many motor nuclei are different in the two species. For example, hip extensors are generally more Ia-isolated from each other in baboons than in cats, and also knee flexors have fewer Ia-interconnections than in cats. A unidirectional Ia-synergism between some hip extensors and knee flexors in cats has changed to a bidirectional one in baboons, with a tendency to lateralization of the connections. Among ankle extensors, soleus has smaller heteronymous Ia-connections from its synergic ankle extensors than in cats. In baboons, plantaris is heteronymously Ia-excited from gastrocnemius-soleus but not from the intrinsic plantar muscles; whereas in cats there exists a considerable Ia-projection from the intrinsic plantar muscles but not from gastrocnemius-soleus. There is a corresponding difference in the insertion of the plantaris tendon, which shows that this muscle acts as toe extensor in cats but as ankle extensor in baboons. For most of the motor nuclei, the homonymous as well as the total aggregate of Ia-e.ps.p.s is smaller in the baboon than in the cat; but the amplitude range between different motor nuclei is larger in the baboon. Reciprocal Ia-i.ps.p.s are evoked only after spinal transection or when brain function is depressed. It is postulated that baboons, contrary to cats, have descending tonic inhibition of transmission in the reciprocal Ia-inhibitory pathway. The phylogenetic flexibility of Ia-connections is discussed and contrasted with their ontogenetic stability.

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.

Paroxysmal atrial tachycardia in infancy: long-term follow-up study of 49 subjects

A follow-up study of 49 individuals with paroxysmal atrial tachycardia in infancy is reported. Forty subjects had supraventricular tachycardia and nine had atrial flutter/fibrillation. The mean follow-up period was 24 years. Males whose ECGs showed preexcitation displayed the highest rate of recurrences (approximately 60%) in the long-term follow-up. Approximately 30% of the subjects without preexcitation in the ECG displayed episodes of supraventricular tachycardia in their third decade. Eight-six percent of the children of the subjects in the present series were males. The prognosis is good in the absence of congenital heart disease.

Electrophysiological evidence against the hypothesis that corticospinal fibres send collaterals to the lateral reticular nucleus

Extracellular focal synaptic potentials (FSPs) were recorded in forelimb segments of cats in the region where corticospinal volleys (pyramidal stimulation) gave a maximal FSP. No FSP was recorded in this region on stimulation of the medial part of the lateral reticular nucleus (LRN), provided that ventral spinal pathways through which FSPs can be evoked from the LRN region were transected. It is postulated that the projection from the cerebral cortex to the LRN is not by collaterals from corticospinal neurones but rather by separate corticofugal neurones.

Effects of 4-aminopyridine on synaptic transmission in the cat spinal cord

An analysis was made of effects of 0.1-1.0 mg/kg 4-aminopyridine (4-AP) i.v. on excitatory and inhibitory spinal reflex pathways in lightly anaesthetized or decerebrated cats. The effects appeared within the first minutes of the injection, reached maximum after about 10-15 min and remained stable during at least several hours. 4-AP enhanced the following synaptic actions on motoneurones: monosynaptic excitation from Ia afferents and descending tracts, disynaptic and polysynaptic excitation from group Ib, group II, cutaneous and high threshold muscle afferents, disynaptic inhibition from Ia and Ib afferents and recurrent and polysynaptic inhibition from different afferents. 4-AP also increased primary afferent depolarization and excitation of ascending tract cells by peripheral stimuli. In the case of the disynaptic inhibitory pathways it has been shown that 4-AP may enhance the excitation of the interposed interneurones but it also increases the action of these interneurones on the motoneurones; monosynaptic inhibition evoked in motoneurones by electrical stimulation of the axons of the inhibitory interneurones was used as a test response in these experiments. No indications were found of direct effects of 4-AP on excitability of afferent fibres or motoneurones to electrical stimuli. No systematic changes were either found in the membrane potential of motoneurones or in the duration of action potentials of these neurones or primary afferents. It is therefore concluded that small doses of 4-AP enhance synaptic transmission in the spinal cord by an action at a presynaptic level.

Integration in descending motor pathways controlling the forelimb in the cat. 7. Effects from the reticular formation on C3-C4 propriospinal neurones

Effects of stimulation in the medullary reticular formation (RF) on C3-C4 propriospinal neurones (PNs) were investigated in two series of experiments: (1) indirectly by analyzing how propriospinal transmission to forelimb motoneurones is modified by reticular stimuli; (2) directly by intracellular recording from C3-C4 neurones, which were identified as propriospinal by their antidromic activation from the C6 segment. Propriospinally mediated disynaptic EPSPs evoked in motoneurones from the pyramid (Pyr) and the red nucleus (NR) were effectively facilitated by conditioning stimulation in the RF with a time course of facilitation indicating monosynaptic linkage to the PNs. Propriospinally mediated trisynaptic IPSPs were facilitated less regularly and sometimes instead depressed by conditioning stimulation in the RF. The depression is at least partly due to inhibition of the first order PNs. Recording from C3-C4 PNs revealed that many of them were excited or inhibited by single stimuli in the RF. The brief latency of the EPSPs evoked in these neurones shows monosynaptic linkage from fast reticulospinal fibres. Some IPSPs were similarly monosynaptically evoked from fast fibres and observations are presented suggesting that longer latency IPSPs are monosynaptically mediated by slower fibres. Facilitation of propriospinal transmission to motoneurones as well as the EPSPs and IPSPs in PNs were evoked from a region within or close to the nucleus reticularis gigantocellularis. Convergence of monosynaptic EPSPs from Pyr, NR, tectum, and RF was common in C3-C4 PNs. Linear summation of the EPSPs from RF with those evoked from cortico-, rubro-, or tectospinal tracts shows that the former are not due to stimulation of collaterals which the latter tracts may have in RF. Mediation of the EPSPs and IPSPs by descending, rather than by antidromically activated ascending fibres, was indicated by temporal facilitation produced by RF stimuli, subliminal for evoking monosynaptic PSPs in the PNs. Stimulation of the labyrinth did not evoke disynaptic PSPs in any of the PNs investigated. It is concluded that the C3-C4 PNs projecting to forelimb motoneurones can be excited not only from the cortico-, rubro-, and tectospinal tracts (Illert et at. 1977, 1978) but also by reticulospinal fibres.

Kjel-Foss Automatic Analysis Using an Antimony-Based Catalyst: Collaborative Study

Collaborators in 7 Kjel-Foss laboratories and 1 manual Kjeldahl laboratory performed protein determinations on fishmeal: 10 with traditional mercury catalyst and 10 with a new antimonybased catalyst. Repeatability, interlaboratory variation, and variation vs. manual Kjeldahl were equal to or better with the new catalyst than with the mercury catalyst. In addition, 48 different products were analyzed: 5-10 determinations were made on each product with the mercury catalyst and 5–10 were made with the new catalyst. After the Kjel-Foss procedure was modified slightly with higher acid settings, the differences in recovery and repeatability of the 2 procedures were not more than ±1%.

Dissociated motor development--developmental patterns, clinical characteristics, causal factors and outcome, with special reference to late walking children

Dissociated motor development, defined as marked gross motor delay without any abnormal neurological signs and contrasting to a normal fine motor-adaptive performance, was studied prospectively in a consecutive in a consecutive series of 78 children, 48 girls and 30 boys, aged 7-23 months at first examination. When 17 months of age, 10 of them had become normalized, and in further three a disability explaining their gross motor delay had been diagnosed. At an average age of 4.2 years, the remaining 65 late walkers were, regardless of cause and developmental and neurological findings at final follow-up, characterized by a number of deviating clinical features as muscular hypotonia (71%), shuffling (51%) and dissociated or late pattern of learning to sit (79%). In 30 out of 65 late walkers (46%) a defined clinical condition of probable pathogenetic implication was found. In 35 out of 65 late walkers (54%), no explaining clinical condition was found. They have been designed to be idiopathic late walkers. Except for muscular hypotonia, present in 77%, conventional neurology was normal in this group. Minor neurological signs such as a positive Foerster sign, defect balance reactions in standing, or asymmetry in prewalking locomotion were, however, occasionally and temporarily observed. Girls were overrepresented among idiopathic late walkers, 69% compared to 43% among the symptomatic late walkers. Complete normalization was more common in the idiopathic group (66%) than in the symptomatic group (27%). Early differentiation between the late walkers who were normalized and those who developed mild mental retardation or neurological handicaps was difficult but not quite impossible. Heredity for shuffling, a non-revealing pre- and perinatal history, a developmental pattern of late learning to sit, and shuffling favoured a normal outcome. Creepers with a dissociated pattern of learning to sit and crawlers with muscular hypotonia were found to have an increased risk for later handicap.

Muscle abnormalities in coeliac disease: studies on gross motor development and muscle fibre composition, size and metabolic substrates

In 11 children with coeliac disease gross motor development was assessed before and during diet treatment using the gross motor subscale of the Denver developmental screening test. ATP, creatine phosphate (CP), glycogen and lactate concentrations, muscle fibre size and fibre composition were measured in specimens obtained by needle biopsy from the vastus lateralis muscle. Before treatment, gross motor development was delayed. ATP, and to a lesser extent, CP and glycogen concentrations were lowered compared to a control group. After treatment, gross motor development was normal and no differences in ATP, CP or glycogen concentrations were found compared to the control group. Fibre size seemed unaffected by the disease. The percentage of type 1 fibres was significantly lower before treatment, compared to values obtained during treatment and from the control group. Whether these metabolic changes were due to the coeliac disease per se or the inactivity which it causes was not possible to establish. In humans, only altered neurogenic influence on the muscles has been previously shown to give changes in fibre composition.

Metabolic substrates, muscle fibre composition and fibre size in late walking and normal children

In 10 children with delayed walking, muscle specimens were obtained by needle biopsy from the vastus lateralis muscle for determination of ATP, creatine phosphate (CP), glycogen and lactate concentration, as well as fibre composition and fibre size. The values obtained are compared with corresponding results for a control group of 25 children aged 2 months--11 years. Details of the control series are given and its validity as a reference group is discussed. Six children (group I) who showed minor gross motor delay but otherwise normal development at follow-up were found to have lowered ATP, CP and glycogen concentrations, compared to 4 children (group II) who had general developmental delay, and to the control group. The children in group I were shown to have smaller fibre size and a greater difference between type 1 and 2 fibres than the children in group II and in the control group. No differences in the concentrations of metabolic substrates or the morphometric values could be detected between group II and the control group.

The drawing test -- a tool for assessment of arm-hand function in children of 1--3 years of age

The construction and evaluation of a simple drawing test for assessment of arm-hand function in children of 1--3 years of age are described. A thick crayon (1.2 x 10 cm) and a piece of white paper (20 x 30 cm) are the only equipment needed. The need, when assessing fine motor development, of a test for evaluation of arm-hand function and the advantages of the test described are discussed. It is concluded that the method is of diagnostic value in children with CNS and neuromuscular disorders and is a useful tool for clinical studies and for routine developmental examination.

Gross and fine motor performance in healthy Swedish children aged fifteen and eighteen months

Gross and fine motor performance have been assessed in thirtynine 15-month-old and thirtynine 18-month-old children selected through systematic sampling from a population of healthy newborns. The performance was estimated with corresponding subscales of Denver Developmental Screening Test and Motor age test. In addition fine motor performance was assessed by the "Drawing test" for which the expected performance at 15 and 18 months is given. Of the 78 children, 83% had crawled on hand and knees, 9% crept on their tummy and 8% shuffled on their bottom before walking. Median age for walking was 11.8 months, the 97th percentile 16.0 months. Of the 15-month-old children, 90% walked with ability to stop and start, and 90% of the 18-month-old were in addition able to walk backwards, run stiffly, climb up and down a standard staircase and seat themselves in an armchair of suitable size. Of the 15-month-old, 90% were able to build a tower of two cubes or more, and 90% of the 18-month-old were able to build a tower of three cubes or more (size 1 1/2 inch). Almost 90% of the 15-month-old and all of the 18-month-old had the cognitive ability to coordinate a crayon and paper. In drawing attempts of the 15 month-old, the weak unstable combination with a top-tong/tong grasp and 1/2 pronated forearm was the dominating hand-grasp fore-arm position. In the 18 month-old a more mature grasp and forearm combination, mainly palmar grasp with or without stablizing index finger + overpronated forearm, was found.

Reciprocal inhibition during the tonic stretch reflex in the decerebrate cat

1. The aim of this study was to investigate post-synaptic reciprocal Ia inhibition during the stretch reflex; particularly the extent to which an increased Ia excitation of the Ia inhibitory interneurones will be counteracted by recurrent inhibition from motor axon collaterals. For this purpose we investigated depression of monosynaptic test reflexes antagonist flexors (reciprocal inhibition) during static stretch of quadriceps or triceps surae in unanaesthetized decerebrate cats. 3. With increasing stretch of the extensor muscle there was first a linear augmentation of reciprocal inhibition, but along with the stretch reflex in the extensor a plateau appeared in the inhibition of the flexors, although the extensor stretch reflex (judged by the e.m.g.) increased with further stretching. Within the range of stretching of triceps surae which gave increased stretch reflexes the plateau in the reciprocal inhibition was usually maintained, while during stretching of quadriceps a second phase of augmenting reciprocal inhibition often appeared. Stretch beyond the level which increased the stretch reflex activity gave augmenting reciprocal inhibition both in case of quadriceps and triceps surae. 3. Excitability measurements from central terminals of Ia afferents revealed that the increasing reciprocal inhibition during increasing stretch reflex activity in quadriceps was associated with a primary afferent depolarization in knee flexor Ia afferents; there was no corresponding effect in ankle flexor Ia afferents during stretch reflexes in triceps surae. 4. The primary afferent depolarization evoked in knee flexor Ia afferents by electrical nerve stimulation was then compared with the presynaptic inhibition of knee flexor monosynaptic test reflexes produced by the same stimuli. The results suggest that the second phase of increasing reciprocal inhibition in knee flexors is due to presynaptic inhibition and accordingly that the depth of post-synaptic reciprocal inhibition remains constant at different degrees of stretch reflex activity in both knee and ankle extensors. 5. It is postulated that during increasing stretch reflex activity the increment in Ia excitation and recurrent inhibitio; on to the Ia inhibitory interneurones almost exactly balance each other. It is suggested that recurrent inhibition of Ia inhibitory interneurones may serve as a segmental autoregulatory mechanism to keep 'alpha-gamma-linked reciprocal inhibition' at a constant depth during different levels of agonist activity.

Role of joint afferents in motor control exemplified by effects on reflex pathways from Ib afferents

1. Intracellular recording from motoneurones to hind limb muscles in the cat was used to investigate the effect of volleys in the posterior nerve to the knee joint on motoneurones and on transmission from Ib afferents. 2. Volleys in the joint nerve facilitate transmission in disynaptic and trisynaptic inhibitory and excitatory reflex pathways from Ib afferents. It is postulated that facilitation, which appears at a strength of 1.5 times threshold, is evoked, not by Ib afferents which 'contaminate' the joint nerve, but by afferents from joints receptors. 3. T;e time course of facilitation of the disynaptic Ib i.p.s.p.s in motoneurones indicates that these joint afferents have disynaptic connexions with the interneurones of the Ib inhibitory pathway. 4. A brief description is given of synaptic effects evoked in motoneurones by graded electrical stimulation of the posterior nerve to the knee joint. At low stimulus strength the effects may be evoked via interneurones of Ib reflex pathways, but some results suggest that other interneuronal paths are utilized as well. Somewhat higher strengths, but occasionally less than 2 times threshold, produce later synaptic effects presumably mediated by reflex paths from the flexor reflex afferents; it does not seem likely that the contributory afferents in the joint nerve have nociceptive function. 5. It is suggested that impulses from impulses from joint receptors can influence tension regulation from Golgi tendon organs; if these receptors are activated in the terminal phase of the movement they may contribute a purposeful decrease of tension. It is pointed out that joint receptors may have an important role in motor regulation by their effects on interneurones of the different neuronal systems controlling motoneurones.

Integration in descending motor pathways controlling the forelimb in the cat. 5. Properties of and monosynaptic excitatory convergence on C3--C4 propriospinal neurones

Recording was made in the C3--C4 segments from cell bodies of propriospinal neurones identified by their antidromic activation from more caudal segments. Monosynaptic excitatory effects from descending motor pathways and primary afferents were investigated by electrical stimulation of higher motor centres and peripheral nerves in the forelimb and neck. The cell bodies were located mainly laterally in Rexed's layer VII. Threshold mapping for single axons showed that they descend in the lateroventral part of the lateral funicle. Antidromic stimulation at different spinal cord levels showed that some neurones terminated in the forelimb segments, others in the thoracic cord or in the lumbar segments. Terminal slowing of the conduction velocity suggested axonal branching over some segments. Monosynaptic EPSPs were evoked in the neurons by stimulation of the contralateral pyramid, red nucleus and dorsal tegmentum-superior colliculus. It is concluded that corticospinal, rubrospinal and tectospinal fibres project directly to both short and long propriospinal neurones. There was marked frequency potentiation in tectospinal synapses. Convergence from two descending tracts was common and in half of the tested cells all three tracts contributed monosynaptic excitation. Experiments with collision of descending volleys and antidromic volleys from the brachial segments demonstrated that the corticospinal and rubrospinal monosynaptic projection to the propriospinal neurones is by collaterals from fibres continuing to the forelimb segments.

Maximal aerobic capacity of young people with spastic cerebral palsy

Maximal aerobic capacity in bicycle ergometer tests was studied in nine children (aged 11 to 12 years) and five young men (aged 19 to 23 years), all with a spastic form of cerebral palsy, and compared with non-handicapped control groups. Results showed somewhat lower values for heart rate, oxygen uptake/kg, ventilation/kg and blood lactate concentrations for the majority of the spastic group. The physical work capacity of the handicapped group amounted to about 50 per cent of the corresponding values for the non-handicapped controls. Poor mechanical efficiency in the spastic group is the consequence of high oxygen uptake in relation to the work performed. The poor mechanical performance is mainly caused by the extra amount of energy required for qualitative changes in the muscle (constant hypertonia), involuntary movements and stabilizing movements during exercise on the bicycle ergometer.

Cutaneous facilitation of transmission in reflex pathways from Ib afferents to motoneurones

1. The effect of volleys in low threshold cutaneous afferents upon transmission of synaptic action from Ib afferents to motoneurones has been investigated with intracellular recording from alpha motoneurones to hind limb muscles. 2. There was facilitation from cutaneous afferents of transmission in excitatory and inhibitory reflex pathways from Ib afferents without any evidence for difference in effect on di- and trisynaptic pathways. It is postulated that volleys in cutaneous afferents evoke excitatory action in interneurones of these reflex pathways. 3. The time course of the facilitation suggest that cutaneous afferents have disynaptic excitatory connexions with the interneurones intercalated in the disynaptic Ib inhibitory pathways to motoneurones. 4. Some observations are reported suggesting that interneuronal transmission in Ib inhibitory pathways to motoneurones might be facilitated from Ia afferents. 5. The findings are discussed in relation to the presumed role of Ib reflex action in regulating muscle tension.

Integration in descending motor pathways controlling the forelimb in the cat. 2. Convergence on neurones mediating disynaptic cortico-motoneuronal excitation

With intracellular recording from forelimb motoneurones the spatial facilitation technique has been used to investigate interaction between descending pathways and forelimb afferents. As previously shown for the hindlimb, pyramidal volleys effectively facilitate interneuronal transmission in reflex pathways from different primary afferents. Evidence is presented suggesting disynaptic excitation from corticospinal fibres of interneurones in the reciprocal Ia inhibitory pathway. Interneurones of other reflex pathways from group I muscle afferents recieve monosynaptic pyramidal excitation. During pyramidal facilitation volleys in cutaneous afferents may evoke PSPs in motoneurones after a central delay of 1.3 ms suggesting that the minimal linkage is disynaptic. Information regarding convergence on the neurones intercalated in the disynaptic cortico-motoneuronal pathway was obtained by investigating the effect from primary afferents and from other descending pathways on the disynaptic pyramidal EPSPs. Volleys in cutaneous and group I muscle affferents facilitate transmission in the disynaptic cortico-motoneuronal transmission with a time course showing oligosynaptic (probably monosynaptic) action the intercalated neurone. Rubrospinal volleys likewise effectively facilitate disynaptic cortico-motoneuronal pathway with a time course showing oligosynaptic (probably monosynaptic) action on the intercalated neurone. Rubrospinal volleys likewise effectively facilitate disynaptic cortico-motoneuronal transmission with a time course showing monosynaptic action on the intercalated neurone. Spatial facilitation experiments involving three tests revealed that those intercalated neurones which receive convergent monosynaptic excitation from corticospinal and rubrospinal fibres are excited also from cutaneous forelimb afferents. Disynaptic cortico-motoneuronal transmission was also monosynaptically facilitated by stimuli in the dorsal mesencephalic tegmentum probably activating tectospinal fibres. Disynaptic, presumed tectospinal EPSPs were facilitated from cutaneous forelimb afferents. The convergence onto the neurones intercalated in the disynaptic excitatory cortico-motoneuronal pathway suggests that these neurones integrate the activity in different descending pathways and primary forelimb afferents.

Integration in descending motor pathways controlling the forelimb in the cat. 1. Pyramidal effects on motoneurones

Stimulation of the contralateral pyramid and intracellular recording from forelimb motoneurones was used to investigate corticimotoneuronal pathways in the cat. A train of pyramidal volleys evokes short-latency EPSPS in flexor motoneurones and in many extensor motoneurones. The latency for the onset after the effective pyramidal volley-usually the third - strongly indicates a disynaptic linkage. These disynaptic EPSPs were common in triceps motoneurones to fast heads but rare in those to slow heads. Pyramidal IPSPs with a slightly longer latency, suggesting a trisynaptic linkage, were found in both flexor and extensor motoneurones. They were common in motoneurones to slow heads of triceps. Disynaptic pyramidal IPSPs were found only occasionally. In addition pyramidal volleys may evoke late large EPSPs and/or IPSPs in any combination with the short-latency PSPs.

Oxygen consumption in relation to work load in students with cerebral palsy

Eighteen adolescents with various forms of cerebral palsy performed tests on a mechanically braked ergometer bicycle. VO2 was measured at different loads and net mechanical efficiency calculated. It was found that efficiency was poor at light loads for most of the students but that there were significant intergroup differences in mechanical efficiency at higher loads. The leveling-off plateau demonstrated by healthy adolescents was only attained by a few of the disabled students. It was concluded that the muscle hypertonia and involuntary movements were responsible for the high level of energy expended in the mechanical work performed.