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At least 19 recordsLinked to original sources

PubMed1978

Integration in descending motor pathways controlling the forelimb in the cat. 4. Corticospinal inhibition of forelimb motoneurones mediated by short propriospinal neurones.

A previously described inhibitory trisynaptic cortico-motoneuronal pathway (Illert et al., 1976a) was analysed in order to identify the two relay stations. Intracellular recording was made from motoneurones to elbow muscles. Corticospinal fibres were stimulated in the contralateral medullary pyramid. Pyramidal IPSPs were abolished by a transection of the corticospinal tract in C2 but remained after a corresponding lesion in C5. After a C5 lesion pyramidal volleys facilitated transmission in the Ia inhibitory pathway with a time course suggesting disynaptic excitatory action on the Ia inhibitory interneurones. The trisynaptic pyramidal IPSPs were depressed by volleys in the appropriate recurrent motor axon collaterals as would be expected if these IPSPs were mediated by Ia inhibitory interneurones. It is concluded that trisynaptic cortico-motoneuronal inhibition is evoked by consecutive activation of propriospinal neurones in C3--C4 and segmental Ia inhibitory interneurones.

Animals↗

PubMed1977

Functional organization of vestibular and visual inputs to neck and forelimb motoneurons in the frog.

1. Intracellular responses in neck and forelimb motoneurons to electrical stimulation of the vestibular nerve, the optic tectum, and the optic nerve were studied in frog. 2. Stimulation of the anterior branch of the vestibular nerve typically produced EPSPs, bilaterally, in neck, shoulder (DOR), and forelimb extensor (TRI, RAD) motoneurons, and bilateral IPSPs in forelimb adductor (PED) and flexor (ULN, COR) motoneurons. 3. Latencies of PSPs recorded in neck, shoulder, and proximal extensor motoneurons (TRI) were mostly in the disynaptic range, whereas many of those recorded in distal extensor (RAD) and in adductor and flexor motoneurons involved three synapses. 4. Lesion of the vestibulospinal fibers greatly reduced the vestibular nerve-evoked field potentials in the spinal cord and the occurrence of PSPs in forelimb motoneurons. These results as well as the latency measurements suggest that the pathway linking vestibular nerve and forelimb motoneurons mainly consists of vestibulospinal fibers, though involvement of other structures for production of later PSPs could not be completely ruled out. Hemisection of the brain stem at its most caudal level showed that the pathway to the contralateral motoneurons crosses at the level of brain stem as well as in the spinal cord. 5. Stimulation of the optic tectum produced EPSPs, IPSPs, and a mixture of EPSPs and IPSPs in neck, shoulder, and forelimb motoneurons, bilaterally. Most frequently, a combination of an excitation and inhibition was observed. The pathway from the optic tectum to neck and limb motoneurons is at least dysnaptic in nature. 6. Stimulation of the optic nerve produced IPSPs and a mixture of EPSPs and IPSPs in neck and forelimb motoneurons. Impulses originating from the optic nerve descend as far as to lumbar motoneurons producing EPSP-IPSP sequences bilaterally. 7. Interaction studies suggested that the vestibular and optic pathways to neck and forelimb motoneurons are separate from each other so that the site of integration of vestibular and visual input occurs at the level of motoneurons. 8. Evidence for electronic coupling among forelimb motoneurons and electrical synaptic transmission in th pathway linking vestibular nerve and forelimb motoneurons is presented.

Animals↗

PubMed1977

Interaction of transcapillary Starling forces in the isolated dog forelimb.

Three of the four Starling forces were measured in the intact dog forelimb after anesthetization and all four of the Starling forces were measured in the same forelimb which was surgically isolated yet innervated. In the isolated forelimb, isogravimetric capillary pressure (Pci) averaged 15.6 mmHg; colloid osmotic pressure of the plasma proteins (IIp) averaged 19.9 mmHg; mean interstitial fluid pressure (Pif) was +0.4 mmHg, and the average value of interstitial colloid osmotic pressure (IIif) was 4.9 mmHg. Thus the net imbalance in the Starling forces, i.e., (Pci - Pif) - (IIp - IIif), averaged 0.3 mmHg. Furthermore, the value of IIif was consistently decreased after isolation (average decrease of 1.2 mmHg) while Pif was always increased following isolation (average increase of 4.3 mmHg). In addition, it was found that if the forelimb was denervated during isolation, then Pif was increased by an average of 2 mmHg above Pif in the innervated, isolated forelimb. In summary, these studies show that the differences between the intact and isolated forelimb are that Pci averages 10-11 mmHg in the intact forelimb and 15-16 mmHg in the isolated innervated forelimb while interstitial fluid pressure is negative in the intact limb and positive in the isolated limb.

Animals↗

PubMed1978

Functional morphology of forelimb joints in the woolly monkey Lagothrix lagothricha.

This gross anatomical study of embalmed forelimb joints of the South American woolly monkey Lagothrix lagothricha focuses on the problem of determining in osteoligamentous preparations how the disposition of the capsular apparatus and the geometry of the articular surfaces govern the amount and types of movement permitted at a joint, and then correlates these findings with the use of the forelimb in the positional capabilities of captive wooly monkeys observed by this author. Data collection was by dissection, quantitative range of motion studies on osteoligamentous preparations, and by qualitative manipulations of these preparations and of disarticulated bones. Supplemental evidence was obtained from radiographs and from an estimate of angular values of articular surfaces. Presented for the shoulder, elbow, radioulnar, and hand joint complexes are the functional anatomy of the capsular apparatus and articular surfaces, the quantitative range of motion data, and proposed mechanisms of movement that combine the functional morphology with the observed use of the forelimb in activities by the animal. The structurofunctional framework of MacConaill is the basis for the joint analysis. The evidence suggests that the functional anatomy of these joints correlates well with the possible positional capabilities of Lagothrix. The morphology of the capsular apparatus and joint surfaces reflect both the arboreal quadrupedalism and forelimb suspension of the woolly monkey. The positions of maximum congruency and close-pack approximate the forelimb's weight-bearing stance during palmigrade arboreal quadrupedalism. During forelimb suspension, the taut and twisted capsular apparatus of close-packed joints maintains the integrity of forelimb links in tension. This is the first known report of the internal band of the collateral ligament of the proximal interphalangeal joints of the second through fifth digits being incorporated into the terminal tendon of the extensor assembly. This author believes this is a mechanism not only for maintaining the integrity of these joints during forelimb suspensory activities when the body is supported by the middle phalanges, but also for helping to coordinate the flexion-extension actions of the phalanges for smooth grasping and release maneuvers in an arboreal environment. When sufficient comparative data have been collected, such correlations of the functional morphology of joints with positional behavior may be used to postulate positional capabilities of fossil primates.

Acromioclavicular Joint↗

PubMed1978

The failure of double-half forelimbs to undergo distal transformation following amputation in the axolotl, Ambystoma mexicanum.

Although capable of initiating early regenerative responses, axolotl forelimb stumps which are composed of double-half limb tissues fail to undergo the events that normally lead to the replacement of missing parts. In the present study, the posterior halves of right forelimbs were exchanged with the anterior halves of left forelimbs, or the dorsal halves of right forelimbs were exchanged with the ventral halves of left forelimbs. Forelimbs were amputated through the graft region 30 days after grafting. Limb stumps bearing double-dorsal, double-ventral or double-posterior tissues either produced hypomorphic regenerates or failed to form any externally visible outgrowth. When the limb stump bore double-anterior tissues, no externally visible structures were formed. Normal and multiple regenerates were never formed by double-half limbs. These results are discussed in terms of the polar coordinate model and suggest that the regeneration blastema requires a complete circumference of positional values in order to complete distal transformation.

Ambystoma↗

PubMed1976

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.

Animals↗

PubMed1977

Structural correlates of forelimb function in fur seals and sea lions.

Dissections, manipulation of ligamentary preparations, analysis of limb proportions, and quantitative aspects of forelimb myology are used to correlate forelimb morphology in fur seals and sea lions (sub-family Otariinae) with previously published data as to their locomotor function (English, '76a). Comparisons to structure and function in generalized fissiped carnivores are then used to elucidate locomotor adaptations in fur seals and sea lions. Unique features of forelimb function during swimming in these pinnipeds include the amounts of abduction-adduction and rotary movements used. Modifications of the size, attachments and fasicle architecture of the muscles and the structure and range of possible movement of the joints suggest that in fur seals and sea lions these movements (1) take place about the glenohumeral (shoulder) joints, (2) that the movements are probably finely controlled, and (3) that they contribute to the generation of massive forward thrust via the cooperative activity of muscles capable of generating large amounts of force throughout the range of movement. Recovery movements occur through a similarly large range, and modifications of forelimb anatomy either to minimize or overcome water resistance are noted. The adaptive significance of these modifications is interpreted as allowing fur seals and sea lions to swim at speeds necessary to feed on the fast swimming prey presumably abundant in their adaptive zone.

Animals↗

PubMed1978

Comparison of forelimb and hindlimb motor deficits following dorsal column section in monkeys.

Macaca speciosa monkeys were trained to acquire food reinforcement with motor responses that were defined by 4 different tasks. The effects of dorsal column lesions on the speed of these responses were compared for the forelimbs vs. the hindlimbs. Enduring impairments were not seen for any limb when the animal was required to accurately project a limb to different points in space, even with exclusion of visual guidance and with random variation of the start and stop points for each movement. Similarly, when the task required that the animals emit rapid response sequences, the forelimbs were impaired temporarily, but no long-term deficits were seen for the forelimbs or the hindlimbs. Although these impositions of spatial and temporal demands did not reveal striking disruptions of whole-limb movements, hindlimb grasp responses were shown to be impaired over long periods of postoperative testing. This corroborates previous findings for the forelimb and indicates that facility of distal extremity movement depends crucially on dorsal column-lemniscal input.

Animals↗

PubMed1978

Effects of locally and systemically infused bradykinin on transvascular fluid and protein transfer in the canine forelimb.

Local intra-arterial infusions of bradykinin into canine forelimbs perfused either naturally or at constant inflow markedly increase skin lymph protein concentration promoting edema formation. However, prolonged systemic infusions of this agent either intravenously or into the left ventricular chamber, in blood concentrations calculated to exceed those that produce massive protein and fluid efflux on local administration, causes only minimal increases in lymph protein concentration, and in naturally perfused forelimbs promotes extravascular fluid reabsorption rather than net fluid filtration. Local infusions of bradykinin fail to alter aortic pressure whereas systemic infusions produce a profound but transient decrease in this variable. Moreover, the local intra-arterial infusion of bradykinin into forelimbs perfused at constant inflow fails to increase skin lymph protein concentration after 60 minutes of systemic hypotension. In contrast to bradykinin alone, the simultaneous infusion of bradykinin and norepinephrine or bradykinin and isoproterenol fails to increase skin lymph protein concentration. The antagonism of the bradykinin protein efflux by both norepinephrine and isoproterenol can be prevented by prior treatment with propranolol. These data suggest that the liberation of catecholamines may account, in part, for the minimal increases in forelimb protein efflux during systemic infusions of bradykinin relative to that produced by local intra-arterial infusions of this agent.

Animals↗

PubMed1978

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.

Action Potentials↗

PubMed1979

Comparison of dynamic properties of canal-evoked vestibulospinal reflexes of the neck and forelimb in the decerebrate cat.

The responses of neck and forelimb muscles to sinusoidal polarization of the horizontal canal nerve were compared by recording from these muscles simultaneously. Contrary to results on the vestibulocollic reflex, the central phase lag in the vestibulo-forelimb reflex increases with increasing frequencies up to 3 Hz. This demonstrates a difference in the organization of vestibular-driven pathways to neck and forelimb muscles.

Animals↗

PubMed1978

Forelimb reflexes modulated by tonic neck positions in cats.

The modulation of monosynaptic forelimb reflexes by tonic neck positions was investigated in cats with the head fixed. Lateral flexion of the body in a horizontal plane markedly facilitates reflexes of the deep radial nerve (DR) in the ipsilateral forelimb, while the antagonistic ulnar nerve (ULN) reflexes are strongly inhibited. Opposite effects are seen after contralaternal body movement. Dorsiflexion of the body clearly increases DR-reflexes and exerts a reciprocal although more pronounced inhibition on ULN reflexes. Opposite effects appear after ventriflexion. The reflex modulation starts with head-body displacements of approximately 5 degrees and increases with increasing angles. Furthermore reflex modulation does not depend on the intact cerebrum and cerebellum. The comparison of forelimb and hindlimb reflexes shows a decrease of the neck influences along the spinal cord.

Animals↗

PubMed1979

Neuronal activity in the cortical supplementary motor area related with distal and proximal forelimb movements.

Monkeys were trained to perform two different motor acts, one involving muscle activity in distal forelimb muscles and the other in proximal forelimb and shoulder girdle muscles. After confirming spatial and temporal dissociation of muscle activity in the two motor acts, single unit activity in the supplementary motor area (SMA) was recorded. SMA neurons related with the distal and proximal forelimb movements were found to be arranged rostrocaudally with a considerable overlap. In the overlapping region, neurons related with the distal movement were located more deeply.

Animals↗

PubMed1979

Development of the segmental innervation of the chick forelimb.

A number of recent studies have shown that during embryonic development the initial innervation of a target structure may be made up, in part, by axons which do not form part of the mature innervation of that structure. In the present study we have examined the motor innervation of the major muscles of the chick forelimb at different stages of development using HRP-uptake-labelling of motoneurons, electrophysiological recording and measurement of muscle contraction. In the mature White Leghorn chick the major contribution to the motor innervation of the forelimb is from spinal segments 14, 15 and 16. Using the HRP-labelling technique we have shown that at stages 26-29 of development motoneurons in segments 12-17 have axon terminals in the presumptive biceps muscle. Between stages 30 and 35, however, the axon terminals arising from segments 12, 13, 16 and 17 are lost, leaving the mature innervation from segments 14 and 15. We have also observed the loss of innervation of the biceps muscle by segment 16 using electrophysiological recording of compound action potentials in the biceps nerve and by measurement of the local contraction of the biceps muscle in response to stimulation of the segmental nerves. Similar changes in the innervation of the triceps, extensor metacarpi radialis, flexor carpi ulnaris and flexor digitorum profundus muscles have also been observed. These results are discussed in relation to the hypothesis that (i) the motoneuron pools and muscles in the developing spinal cord and forelimb are matched, (ii) that some axons which arrive in a particular muscle during early development are unable to form a stable connexion and (iii) that the inability of an axon terminal to form a stable connexion in a muscle results in the death of the motoneuron. Intracellular recording from muscle cells at stage 35 shows that the synaptic site on each cell is innervated by about three separate axons. Over the next few stages, however, all but one of the innervating axons is lost. From our contraction studies it is clear that the removal of the excess axon terminals after stage 35 is not associated with the establishment of the mature segmental innervation pattern of the muscle.

Action Potentials↗

PubMed1977

The effects of thalidomide and two analogues on the regenerating forelimb of the newt.

Oral administration (3 mg/day) of thalidomide during the dedifferentiation and early limb-bud stages of newt forelimb regeneration produced a variety of specific limb deformities. Proximal and preaxial skeletal elements were the most severely malformed, e.g. preaxial hemimelia, severe proximal deformities, and preaxial polydactyly. Likewise, oral, daily doses (3 mg) of the teratogenic analogue, EM12, on days 7 and 8 following bilateral amputation caused the same incidence and type of forelimb abnormalities as did thalidomide. Conversely, the non-teratogenic analogue, EM87, when orally administered (3 mg/day) on days 7 and 8 post-amputation resulted in a low rate of limb deformities, similar in type to those seen in control regenerates. The type of limb deformities observed in the regenerating newt forelimb following thalidomide treatment nearly mimic those seen in the human and monkey syndromes. Therefore, the newt represents a possible model for investigating some of the problems associated with thalidomide teratogenesis.

Amputation, Surgical↗

PubMed1978

Effect of endotoxin on glucose uptake by the isolated forelimb of the dog.

Recent research has demonstrated that an increase in glucose utilization by skeletal muscle occurs in hemorrhagic shock. It is conceivable that the hypoglycemia of gram-negative septic shock is, in part, due to increased glucose utilization by peripheral tissues. The hypothesis tested in this study was that there is an increase in glucose uptake by the isolated innervated and/or denervated forelimb of the dog subjected to endotoxin shock. Results indicate that endotoxin does not affect a net increase of glucose uptake by the isolated forelimb. No increase in uptake occurred when blood glucose concentration was normal. However, when endotoxin hypotension induced a significant hyperglycemia or when arterial glucose concentration was elevated by glucose administration an apparent increase in forelimb glucose uptake occurred. It is concluded that endotoxin does not increase the uptake of glucose by skin and muscle except that it causes hyperglycemia secondary to increased sympathoadrenal discharge in the shock state. Thus, if the dog becomes sufficiently hyperglycemic, an apparent increase in glucose uptake occurs, probably because of accumulation of glucose in the interstititial space of skin and muscle.

Animals↗

PubMed1976

[Descending long-loop reflexes in the human spinal cord I. Facilitation of the triceps surae H reflex following stimulation of forelimb afferences (author's transl)].

The H reflex in the triceps surae muscle was elicited by just supraliminal stimulation of the tibial nerve. It was conditioned by paired impulses to the brachial plexus or the forelimb nerves and in some cases to other sites of the body. With a conditioning test interval of 32-47 msec a facilitation occurred which reached its maximum at about 80 msec and lasted for about 400 msec. The facilitation evoked by ipsilateral conditioning had a shorter latency than that from contralateral (ipsilateral: 32-42 msec, contralateral; 37-47 msec). The facilitation at the optimum interval (about 80 msec) ranged between 1;5 and 11.3 times of the control values. Ipsilateral conditioning was slightly more effective than the contralateral one (Fig. 1, 2). Stimulation of different forelimb nerves at an interval of 80 msec showed only insignificant differences in the amount of facilitation but was more effective than skin stimulation in the most cases (Fig. 3). Varying the intensity of the conditioning stimulus showed that facilitation occurred with just perceptable stimuli but it became more pronounced as soon as pain threshold (2-3 time of perception threshold) was exceeded (Fig. 3). This suggests that facilitation was mainly due to activation of nociceptor afferents. From the onset of facilitation and the conduction velocities of the respective forelimb and hindlimb afferents (cf. 6) a central reflex lantency of about 43 msec was calculated. To get further insight into the central connections of the reflex loop the H reflex was conditioned by paravertebral stimulation at C5 and L1 level. Both stimuli caused a distinct facilitation. However, the latency of the onset was 10-15 msec shorter with lumbar stimulation than with cervical stimulation. This and the similar time course of facilitation seen in animal experiments (12) suggest that an early part of facilitation is mediated via a descending propriospinal pathway. The major part, however, is supposed to be mediated via supraspinal pathways and seems to be related to a startle response.

Animals↗

PubMed1979

The interaction of nerves of opposite regenerating polarity in fused newt forelimbs.

Previous studies involving nerve interactions and limb regenerative processes were carried out on adult newts after their forelimbs were amputated through the distal radius and ulna and fused end-to-end. On the basis of limb regeneration results at the junction of the fused limbs, it was postulated that regenerating nerves from each limb (i.e., nerves of opposite polarity) would not invade the foreign territory of the contralateral limb if it were already normally innervated. A direct study of this nerve interaction, however, was not made in this earlier study. The present investigation was designed to obtain direct histological and electrophysiological evidence for the interaction of nerves of opposite regenerating polarity in fused newt forelimbs. The primary objective was to determine how the regenerating nerves would interact in the establishment of innervation territories-first, at the fusion zone, which represents the junction of the normal innervation territories of the nerves of each limb; and secondly, half way up one of the limbs, where interaction would occur in a territory normally innervated by only one of the regenerating nerves. The results showed that when nerves of opposite regenerating polarity approached one another at the junction of the fused limbs a discontinuation of axonal growth occurred; no indication of overlap of nerves into foreign territory was seen. When the nerves were allowed to interact within one of the fused limbs, however, an overlap of nerve fibers and a functional "double innervation" of that limb was demonstrated. These results are discussed in terms of possible mechanisms for the establishment of innervation territories in salamander limbs. The question of nerve-muscle reinnervation specificity is also raised.

Animals↗