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PubMed2000

Morphometry of Macaca mulatta forelimb. I. Shoulder and elbow muscles and segment inertial parameters.

The present study examined the morphometric properties of the forelimb, including the inertial properties of the body segments and the morphometric parameters of 21 muscles spanning the shoulder and/or elbow joints of six Macaca mulatta and three M. fascicularis. Five muscle parameters are presented: optimal fascicle length (L(0)(M)), tendon slack length (L(S)(T)), physiological cross-sectional area (PCSA), pennation angle (alpha(0)), and muscle mass (m). Linear regressions indicate that muscle mass, and to a lesser extent PCSA, correlated with total body weight. Segment mass, center-of-mass, and the moment of inertia of the upper arm, forearm, and hand are also presented. Our data indicate that for some segments, radius of gyration (rho) predicts segment moment of inertia better than linear regressions based on total body weight. Key differences between the monkey and human forelimb are highlighted.

Animals↗
PubMed1988

Migration of Schwann cells and axons into developing chick forelimb muscles following removal of either the neural tube or the neural crest.

A study has been made of the effects of neural crest and neural tube removal at the brachial level on the migration of Schwann cells and axons into the flexor digitorum profundus (fdp) and flexor carpi ulnaris (fcu) muscles of the avian forelimb. The identification of Schwann cells was based on the assumption that antibody HNK-1 uniquely labels these cells at the growing end of limb nerves. Myotubes and nerves were identified by using antibodies to myosin and to neurofilament protein, respectively. The removal of neural crest cells at stage 13 gave a complete Schwann cell-free embryo at the brachial level. Motor axons only grew to the base of the forelimb, forming a rudimentary plexus by stage 27, and failed to penetrate the limb. Removal of the neural tube at stage 13 did not prevent sensory axons from forming a plexus at the base of the limb; these axons subsequently developed into the brachialis longus inferior (bli n) and superior (bls n) nerves. By stage 27 the bli n had branched into the interosseus nerve (in n) and the medial-ulnar nerve (m-u n) trunks. However, unlike the result in control embryos, no nerves were detected amongst the developing fdp and fcu muscles, thus indicating that sensory axons do not grow into the muscles in the absence of motor axons. In contrast, Schwann cells were observed amongst the myotubes at the level of the in n and m-u nerve trunks. The present observations show that motor axons do not enter the limb bud and innervate limb muscles in the absence of Schwann cells. Furthermore, in the absence of motor axons (neural-tube-removed embryos) sensory axons still enter the limb (behind migrating Schwann cells) but fail to innervate developing muscles even though Schwann cells are present among the developing myotubes.

Animals↗
PubMed1983

Electron-microscopical study of the operculum in anuran tadpole after extirpation of the right forelimb during metamorphosis.

The process of histolysis and fenestration of the skin of the prospective opercular perforation region of Rana japonica after extirpation of the right forelimb was observed during metamorphosis by transmission and scanning electron microscopy. Epidermal cells of the belly of the tadpole, including the operculum, are extremely similar in their ultrastructure. Epidermal cells of the prospective opercular perforation region during metamorphosis become thin and vacuolated especially around the nucleus perhaps by autolysis, associated with lysosomal activity. The histolysis and formation of the perforation of the operculum occurs in the complete absence of forelimb. Macrophages containing phagosomes and lymphocytes or other blood cells are almost always found in the intercellular epidermis. Necrotic epidermal cells progressively separate by cleft formation and slough off without cornification.

Animals↗
PubMed1996

Bone mineral density and turnover following forelimb immobilization and recovery in young adult dogs.

The purpose of this experiment was to study changes in bone mass, structure, and turnover in the canine forelimb after unilateral immobilization and recovery. The right forelimbs of 14 adult mongrel dogs were immobilized for 16 weeks. Six dogs served as controls. Seven immobilized and three control dogs were euthanized at the end of the immobilization period. Recovery consisted of 16 weeks of kennel confinement followed by 16 weeks of treadmill exercise. Seven once-immobilized and three control dogs were euthanized at the end of the recovery period. Bone mineral density of both the proximal (PBMD) and central (CBMD) radius was determined by dual X-ray absorptiometry. Standard histomorphometric endpoints for bone mass and turnover were determined in the cancellous bone of the proximal radius. After immobilization, PBMD, CBMD, and trabecular thickness were lower in the immobilized limb than in either the contralateral or control limbs (P < 0.05). Only CBMD remained significantly lower (P < 0.05) after recovery. At the end of immobilization, bone formation endpoints were significantly higher in the immobilized limb than both the contralateral and control limbs. Bone turnover was also significantly lower in the contralateral limb than in the immobilized and control limbs. After recovery, all differences in bone turnover had resolved. Immobilization of 16 weeks duration caused an elevation in cancellous bone formation rate and reduced bone density in both cortical and cancellous bone. After 32 weeks of recovery, turnover abnormalities disappeared, cancellous bone normalized, but cortical bone mass remained low. Recovery of cortical bone from immobilization takes longer than recovery of cancellous bone.

Animals↗
PubMed1985

Ascending and descending effects of joint afferent discharge on forelimb and hindlimb flexion reflex excitability in decerebrate cats.

In decerebrate cats with intact innervation of the fore- and hindlimbs, flexion reflexes are most easily elicited in forelimb muscles when the hindlimb is extended, and hindlimb flexion reflexes are most easily elicited when the forelimbs are extended. After intra-articular injection of local anaesthetic, this modulation of reflex excitability is abolished. Thus, in addition to their known segmental effects, joint afferents also exert significant ascending and descending effects on motoneurone excitability.

Animals↗
PubMed1999

The prevalence and risk factors associated with forelimb skin abrasions and sole bruising in preweaning piglets.

The presence of skin abrasions and sole bruising in 264 preweaning piglets (1-30 days old) from 13 breeding units in south west England was investigated in 1995. The mean prevalence of forelimb skin abrasions among the pigs on the study farms was 36% (range 0-59%) and sole bruising was 50% (range 0-95%). Skin abrasions were located on three aspects on the front limbs: the carpus, the metacarpus and the digit. Lesions occurred early in a piglet's life; the modal ages for sole bruising was 4 days and for skin abrasions were 5 and 10 days. The presence of skin abrasions on the front limbs was significantly associated with the presence of sole bruising on the front feet. Logistic regression indicated that part-concrete, part-round-mesh (OR 56.4) and part-concrete, part-metal-rods floors (OR 15.9) and exposed aggregate (OR 4.6) were associated with an increased odds of sole bruising while the presence of sparse straw (OR 0.12) or deep straw (OR 0.12) in the pen was associated with lower odds of sole bruising. The same floor type (part-concrete, part-round-mesh) was associated with increased odds of forelimb skin abrasions (OR 2.2). A worn floor surface where the solid adjoined the perforated area (OR 4.6) and the presence of sparse shavings (OR 1.7) were also associated with an increased risk of skin abrasions.

Animals↗
PubMed1990

A new rodent model for neuroleptic-induced pseudo-parkinsonism: low doses of haloperidol increase forelimb tremor in the rat.

Rats were trained to use the right forelimb to exert continuous downward pressure on a force transducer and simultaneously to drink sweetened milk from a dipper controlled by the emitted force. Oscillations in forelimb force during this performance were spectrally analyzed to describe the tremorogenic effects of haloperidol (0.04, 0.08, or 0.16 mg/kg). Haloperidol reduced time-on-task and increased the variance of force oscillations in the 10.0-25.0-Hz frequency band. When atropine sulfate (5 mg/kg) was given along with haloperidol, time-on-task was partially restored, and the effects of haloperidol on the 10.0-25.0-Hz band were diminished. These data suggest that the behavioral deficits produced by relatively low doses of haloperidol in rats are analogous (and possibly homologous) to neuroleptic-induced Parkinsonian symptoms in humans.

Animals↗
PubMed1990

Efferent Pattern of Fictive Locomotion in the Cat Forelimb: with Special Reference to Radial Motor Nuclei.

In immobilized decerebrate cats fictive locomotion was evoked by midbrain stimulation to analyse the efferent pattern to elbow and to distal forelimb muscles innervated by the deep radial nerve. The locomotor activity was assessed by recording nerve discharges and motoneuronal membrane potential changes. The elbow flexor and extensor motoneurons showed a reciprocal activity; the membranes were correspondingly depolarized and hyperpolarized. In the motor nuclei to the wrist and digit extensors the active phases changed systematically according to the radio-ulnar order of the muscles: the extensor carpi radialis (ECR) was flexor-coupled, the ulnaris (ECU) extensor-coupled, the digitorum communis (EDC), the lateralis (EDL) and the indicis proprius (EIP) displayed intermediate patterns. Intracellular recordings from these motoneurons revealed in all motor nuclei, except ECR, a double depolarization. The first occurred early and the second later in the flexor phase; a hyperpolarization was interposed. The second depolarization mainly determined the active phase. According to the radio-ulnar order of the muscles the onset and termination of the second depolarization were delayed. This was presumably due to the interposed hyperpolarization, which progressively increased in amplitude. The ECR exhibited a single depolarization, into which the double depolarization apparently merged. The other radial motor nuclei, supinator (Sup) and Abductor pollicis longus (APL) displayed complex patterns. Sup showed tonic discharges, flexor-type discharges or discharges extending both into the flexor and extensor phase, APL showed discharges similar to either EIP or Sup. Membrane potential changes were small in APL and Sup. Thus, the central locomotor network generates differentiated efferent activities in the distal forelimb muscles, the radio-ulnar order of the muscles being important for the generated pattern.

Journal Article↗
PubMed2006

Habitual use of the primate forelimb is reflected in the material properties of subchondral bone in the distal radius.

Bone mineral density is directly proportional to compressive strength, which affords an opportunity to estimate in vivo joint load history from the subchondral cortical plate of articular surfaces in isolated skeletal elements. Subchondral bone experiencing greater compressive loads should be of relatively greater density than subchondral bone experiencing less compressive loading. Distribution of the densest areas, either concentrated or diffuse, also may be influenced by the extent of habitual compressive loading. We evaluated subchondral bone in the distal radius of several primates whose locomotion could be characterized in one of three general ways (quadrupedal, suspensory or bipedal), each exemplifying a different manner of habitual forelimb loading (i.e. compression, tension or non-weight-bearing, respectively). We employed computed tomography osteoabsorptiometry (CT-OAM) to acquire optical densities from which false-colour maps were constructed. The false-colour maps were used to evaluate patterns in subchondral density (i.e. apparent density). Suspensory apes and bipedal humans had both smaller percentage areas and less well-defined concentrations of regions of high apparent density relative to quadrupedal primates. Quadrupedal primates exhibited a positive allometric effect of articular surface size on high-density area, whereas suspensory primates exhibited an isometric effect and bipedal humans exhibited no significant relationship between the two. A significant difference between groups characterized by predominantly compressive forelimb loading regimes vs. tensile or non-weight-bearing regimes indicates that subchondral apparent density in the distal radial articular surface distinguishes modes of habitually supporting of body mass.

Absorptiometry, Photon↗
PubMed2006

Forelimb postischaemic reactive hyperaemia is impaired by hypotensive low body negative pressure in healthy subjects.

Local metabolic conditions adapt blood supply to metabolic requirement by a direct effect on vascular smooth muscles and indirectly by modulating sympathetic vasoconstrictor effectiveness. During exercise, sympathetic nervous activity could in turn interfere on local metabolic control of vascular tone and restrain blood flow to active muscles. In order to investigate that interaction non-invasively, we measured postischaemic reactive hyperaemia (RH) in the forelimb of eight healthy young men (22.7 +/- 2.1 years) at rest and during two levels of sympathetic stimulation using low body negative pressure (LBNP -15 and -30 mmHg). During every stages, RH was measured after 40, 60, 90 and 180 s of arterial occlusion, respectively. In control conditions, RH rose with duration of ischaemia (18.9, 24.2, 30.4, 33.1 ml min(-1) per 100 ml(-1) for 40, 60, 90 and 180 s of ischaemia, respectively). During non-hypotensive LBNP (-15 mmHg) sympathetic activation was associated with decreased forelimb blood flow (6.4 +/- 0.9 versus 3.9 +/- 0.6 ml min(-1) per 100 ml(-1), P<0.01), but RH were not significantly different from control conditions. During hypotensive tachycardia LBNP (-30 mmHg), RH were significantly lower than under the previous LBNP stage. This fall in RH was greater after the shortest gap of ischaemia and tapered off as arterial occlusion gap increased (-22.3, -13.1, -10.5 and -8.7% for 40, 60, 90 and 180 s of ischaemia, respectively). These results suggested that vascular tone adaptation to local metabolic conditions was modified by sympathetic nervous activation. This was particularly marked when an hypotensive-mediated sympathetic stimulation was opposed to short gaps of ischaemia.

Adult↗
PubMed1968

Conduction velocity in proximal and distal portions of forelimb axons in the baboon.

1. Peripheral nerves of the baboon's forelimb were stimulated at different sites, and the latencies of antidromic action potentials were measured in intracellular records from forelimb motoneurones.2. The conduction velocity of single motor axons was slower in the brachial plexus than in the nerves of the arm and forearm. This proximal slowing of conduction velocity was more marked for rapidly conducting axons than for the more slowly conducting ones.3. Gross recordings from dorsal and ventral roots showed that the conduction velocity was slower in the brachial plexus than in the arm for fast afferent as well as efferent nerve fibres.4. The proximal slowing of conduction velocity was shown to be due neither to errors of measurement nor to proximo-distal differences of temperature.

Journal Article↗
PubMed1973

Behavioral development after forelimb deafferentation on day of birth in monkeys with and without blinding.

Four infant monkeys underwent somatosensory deafferentation of both forelimbs within hours after birth. Ambulation, climbing, and reaching toward objects developed spontaneously in each case. Thumb-forefinger prehension could be trained by operant shaping methods. Two infants deafferented at birth and blinded by eyelid closure were retarded in motor development by only 1 to 2 weeks. Results indicate that topographic sensory feedback and autogenetic spinal reflexes are not necessary after birth for the development of most types of movement performed by the forelimb musculature in monkeys.

Animals↗
PubMed1980

Telemetered electromyography of forelimb muscle chains in gibbons (Hylobates lar).

Electromyographic studies of brachiation in the gibbon controvert deductions, based on dissection, about the purported functions of muscle chains in the hylobatid forelimb. Neither force conduction distally along the components of the chains nor simultaneity of muscular contraction occurs in brachiation. Rather, the unique structure of the forelimb is probably the result of evolved changes in the short head of biceps brachii to enhance its role as a forearm flexor.

Action Potentials↗
PubMedDate not supplied

Activities of acetylcholinesterase, choline acetyltransferase, and catecholamine production in the spinal cord of the axolotl Ambystoma mexicanum during forelimb regeneration.

Amputation of an axolotl limb causes severance of the brachial nerves, followed by their regeneration into a blastema. It is known that these nerves provide a neurotrophic factor to blastemal cells. To approach the problem of the response of spinal cord nerve centers to forelimb amputation, we have studied biosynthetic activities in the nerve centers involved in axonal injury during limb regeneration. We report that the acetylcholinesterase (AChE) activity in the spinal cord is elevated 2 days (+69%) and 7 days (+28%) after limb amputation compared with levels in unamputated control animals, but is not significantly elevated at 3 h or 15 days. The percentages of slow (3.6S and 6.0S) and fast (18S) sedimenting forms of AChE progressively decrease 2 and 7 days after amputation, while those of intermediate sedimenting forms (10.5S and 14.0S) increase. Fifteen days after amputation, lower molecular weight forms return to the control level, but the heavy molecular weight form of AChE is absent as at 7 days; consequently intermediate molecular weight forms are in a greater proportion than the other two forms. Choline acetyltransferase activity was measured only 2 days after amputation (when AChE was at its highest level). It increases by about 34% with regard to the controls. Adrenaline is higher than controls 2 days after amputation, while noradrenaline is not significantly modified. The metabolic changes observed in the spinal cord during limb regeneration probably are the result of a general reaction to the stress of amputation (transection of brachial nerves) and regeneration of nerve fibers, since similar metabolic activities were observed after a simple denervation of the two unamputated forelimbs.

Acetylcholinesterase↗
PubMed1991

Two movement-related foci in the primate cingulate cortex observed in signal-triggered and self-paced forelimb movements.

1. Single-unit activity in the cingulate cortex of the monkey was recorded during the performance of sensorially (visual, auditory, or tactile) triggered or self-paced forelimb key press movements. 2. Microelectrodes were inserted into the broad rostrocaudal expanse of the cingulate cortex, including the upper and lower banks of the cingulate sulcus and the hemispheric medial wall of the cingulate gyrus. 3. A total of 1,042 task-related neurons were examined, the majority of which were related to the execution of the key press movements. In greater than 60% of them, the movement-related activity preceded the activity in the distal flexor muscles. 4. The movement-related neurons were distributed, in two foci, in the posterior and anterior parts of the cingulate cortex, both including the upper and lower banks of the cingulate sulcus. The posterior focus was found to largely overlap the area projecting to the forelimb area of the primary motor cortex by the use of the horseradish peroxidase (HRP) method. 5. About 40% of the cingulate cortical neurons showed equimagnitude responses during the signal-triggered and self-paced movements. The neurons exhibiting a selective or differential response to the self-paced motor task were more frequently observed in the anterior than in the posterior cingulate cortex. 6. The long-lead type of changes in activity, ranging from 500 ms to 2 s, were observed mainly before the self-paced and, much less frequently, before the triggered movements. They were particularly abundant in the anterior cingulate cortex. 7. Only a few of the neurons showed activity time-locked to the onset of the sensory signals. 8. These observations indicate that the anterior and posterior parts of the cingulate cortex are distinct entities participating in the performance of limb movements, even if the movements are simple, such as those in this study.

Animals↗
PubMed1990

Morphological basis of arm-swinging: multivariate analyses of the forelimbs of Hylobates and Ateles.

Field and laboratory studies of arm-swinging in gibbons reveal its singularity even compared to spider monkeys. On the basis of principal components and discriminant analyses of size-corrected forelimb variables, this study confirms their morphological uniqueness and the more generalized nature of the spider monkey forelimb. Long forearms, well-developed scapular spines, and sagittally thicker radial shafts are features associated strictly with gibbon arm-swinging. On the other hand, large humeral heads, projecting medial epicondyles, and axially elongated scapulae, traditionally regarded as arm-swinging traits, are probably more important for climbing.

Animals↗
PubMed1968

Vascular responses after alpha adrenergic receptor blockade: II. Responses of venous and arterial segments to adrenergic stimulation in the forelimb of dog.

The effects of nerve stimulation and of intraarterial injections of norepinephrine on arterial and venous resistances were studied in the perfused forelimb of dog before and after administration of the alpha adrenergic receptor blocker phenoxybenzamine.Pressures were recorded from the perfused brachial artery and a small metacarpal vein in the forepaw. Blood flow to the whole forelimb was maintained constant. Changes in perfusion pressure in the brachial artery reflected primarily changes in arterial resistance and changes in small vein pressure reflected changes in resistance of venous segments downstream from the point of pressure measurement.Alpha receptor blockade reduced vasoconstrictor responses to both nerve stimulation and norepinephrine. Responses to angiotensin, used in these experiments as an internal control, were not blocked consistently in a dose-related manner indicating that the effects of phenoxybenzamine were specific to adrenergic stimuli.Increases in venous pressure in response to norepinephrine and to nerve stimulation were blocked almost completely whereas increases in arterial pressure were reduced only in part by the blocker. The more effective reduction of pressor responses in the small vein was not caused by a passive reduction in blood flow through the paw nor was it caused by a reduction in the concentration of norepinephrine in the venous effluent reaching the venous segments.This differential effect of alpha receptor blockade on increases in venous and arterial resistances may account for the beneficial effect of phenoxybenzamine in shock.

Journal Article↗
PubMed2003

Electromyographic activity in the Rhesus monkey forelimb muscles during a goal directed movement and locomotion before, during and after spaceflight.

The aim of the present study was to analyse the effects of microgravity on i) the achievement of goal-directed arm movements and ii) the quadrupedal non-human primate locomotion. A reaching movement in weightlessness would require less muscle contraction since there is no need to oppose gravity. Consequently the electromyographic (EMG) activity of the monkey forelimb muscles should be changed during or after spaceflight. EMG activity of the biceps and triceps muscles during goal-directed arm movements were studied in Rhesus monkeys before, during and after 14 days of spaceflight and flight simulation at normal gravity. The EMG activity was also recorded during treadmill locomotion before and after spaceflight. When performing arm motor tasks, the delay values of the EMG bursts were unchanged during the flight. On the contrary, mean EMG was significantly decreased during the flight comparatively to the pre- and post-flight values, which were very similar. Compared with flight animals, the control ground monkey showed no change in the burst durations and mean EMG. After spaceflight, quadrupedal locomotion was modified. The animals had some difficulty in moving, and abnormal steps were numerous. The integrated area of triceps bursts was increased for the stance phase during locomotion. Taken together these data showed that spaceflight induces a dual adaptative process: first, the discharge of the motor pools of the forelimb musculature was modified during exposure to microgravity, and then upon return to Earth, monkeys changed their new motor strategy and re-adapt to normal gravity.

Adaptation, Physiological↗