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Radioactive 2-deoxy-D-glucose incorporation into the prefrontal and premotor cortex of the monkey performing a forelimb movement.

Radioactive 2-deoxy-D-glucose (2-DG) incorporation into the monkey prefrontal and premotor cortex was studied in relation to extention-flexion movement at the wrist joint in two experimental and two control monkeys. With 2-DG injection and 45 min' intensive task performance thereafter, the following areas showed increased accumulations of radioactive glucose: the dorsomedial and dorsolateral prefrontal areas, including the lateral and medial banks of the principle sulcus; the ventral prefrontal and orbitofrontal areas; the cingulate gyrus, and the premotor cortex. In these areas, patch- or strip-like patterns were observed in the accumulation of 2-DG.

Animals↗

Monosynaptic raphespinal and reticulospinal projection to forelimb motoneurones in cats.

Wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) was injected in the nerve branches to the spino- and acromiodeltoid muscles. After injection, the cats were awake for a period of 100 h during which they performed target-reaching and/or walking movements. Transneuronally labelled neurones were found in the nucleus raphe pallidus, in the magno- and gigantocellular parts of the medial reticular formation. All neurones were located between the level of the obex and 6 mm rostrally of the obex. These results demonstrate that medullary raphespinal and reticulospinal neurones have monosynaptic connexions with deltoid motoneurones. The raphespinal projection is partly from neurones with large cell bodies assumed to be non-monoaminergic.

Animals↗

The projection of low-threshold muscle afferents of the forelimb to the main and external cuneate nuclei of the monkey.

The bulbar relay subserved by primary muscle afferents from the monkey's deep radial nerve was investigated by means of transganglionic labeling with wheatgerm agglutinin conjugated with horseradish peroxidase as well as by electrophysiological techniques. It was found that the "deep" input was confined to the pars triangularis of the main cuneate nucleus and to the ventromedial segment of the external cuneate nucleus. On the other hand, labeling occurring following incubation of the superficial (cutaneous) branch of the radial nerve was limited to the pars rotunda of the main cuneate nucleus. The cytoarchitectonic differentiation of the medullary relays is thus met by a clear-cut submodality segregation.

Afferent Pathways↗

Cervical root repair in adult rats after transection: recovery of forelimb motor function.

Functional recovery was achieved in rats after repairing the transected left sixth and seventh cervical roots. Intercostal nerves were used for reanastomosis between the transected roots and the spinal cord, and acidic fibroblast growth factor with fibrin glue was applied. Experimental rats showed relevant functional recovery of gait and grooming reflexes. Electromyography demonstrated less denervation and more regeneration. Horseradish peroxidase retrograde axonal tracing disclosed a statistically significant increase of motor neuron survival, suggesting that motor neuron survival was significantly correlated with functional recovery. It is our belief that this novel treatment strategy may help patients with similar injuries in the future.

Animals↗

Chronic recording of EMG activity from large numbers of forelimb muscles in awake macaque monkeys.

Studies of the neural control of movement often require or benefit from long-term recording of EMG activity from large numbers of muscles involved in a particular motor task. While chronic recording of EMG activity has been described in a number of previous monkey studies, the number of muscles recorded has been somewhat limited and the implantation approach has been highly invasive procedures. This paper presents two EMG implant fabrication and surgical implantation methods that are suitable for use in monkeys, relatively non-traumatic and capable of simultaneous recording from 24 or more muscles.

Animals↗

Olfaction directs skilled forelimb reaching in the rat.

Rats were trained to reach for food pellets, which varied in size from 20 to 300 mg, from one of 21 locations on a shelf located just outside a test cage. After a barrier was lifted, giving access to a food pellet, latency to contact the food was timed, number of reaches to contact the food were counted, the distance of each misplaced reach from the food was measured and the success or failure of each attempt was noted. Control rats walked along the front of the cage sniffing to locate the food. Once they located a food pellet, they inserted their nose between the bars of the cage, sniffed the food for one to three respiratory cycles, raised their snout slightly, and then inserted a forepaw to grasp the food. They seldom required more than three reaches to contact the food and on about half of all trials they were successful in grasping the food. They were more successful in grasping medium-sized food pellets. Performance was unchanged on all measures after vision was occluded with eye patches. Following olfactory bulb removal, however, the rats no longer sniffed to locate the food or sniffed the food prior to initiating a reach. Rather they systematically moved along the length of the cage inserting their snout between the bars at each possible food location and without sniffing reached for the food 'as if blind'. Latency, number of reaches to contact the food and the distance of misplaced reaches increased whereas success rate remained unchanged. Substantial additional impairments were not produced when the bulbectomized rats were given visual occlusion. The study demonstrates that rats locate food and direct reaching using olfaction. The results are discussed in terms of the sensory control of skilled limb use and their relevance to the evolution of the sensory guidance of limb use.

Animals↗

Increase of self-mutilation behavior in forelimb deafferented rats, following stimulation of the dorsal raphe nucleus.

The role of dorsal raphe nucleus (DRN) was studied in rats which develop scratching or/and self-mutilation after deafferentation of brachial plexus. The extent of the lesions was measured in four groups of deafferented rats. Two control groups: implanted and not implanted, a group of animals in which DRN was stimulated, and a group in which it was electrolytically destroyed. We observed an increase of scratching and self-mutilation in the implanted group but overall in the stimulated group, and no change in the abnormal behavior was provoked by DRN lesion.

Animals↗

Protein synthesis in isolated rabbit forelimb muscles. The possible role of metabolites of arachidonic acid in the response to intermittent stretching.

Protein synthesis was measured in isolated intact rabbit muscles by the incorporation of [3H]phenylalanine added at a high concentration (2.5 mM) to the incubation medium. Intermittent mechanical stretching substantially increased the rate of protein synthesis relative to that in control muscles incubated under a constant tension. Indomethacin and meclofenamic acid, inhibitors of the enzyme cyclo-oxygenase, which converts free arachidonic acid into the prostaglandins, prostacyclins and thromboxanes, decreased the rate of protein synthesis in intermittently stretched muscles, but had no effect on synthesis rates in the unstimulated controls. Arachidonic acid at concentrations of 0.2 and 1.0 microM gave a highly significant increase in the rate of protein synthesis in muscles incubated under a constant tension. The ability of arachidonic acid to increase protein-synthesis rates was abolished by the addition of indomethacin. Activation of protein synthesis by intermittent stretching persisted for 10-20 min after the stretch stimulation had ceased. Indomethacin, added either during the initial incubation with intermittent stretching or during the subsequent period when protein synthesis was measured after stimulation had ceased, decreased protein-synthesis rates. This decrease was similar whether indomethacin was present during the initial, final or entire incubation period. In experiments analogous with those in (4) above, when Ca2+ was withheld and EGTA added for the entire incubation, rates of protein synthesis were again decreased. The rates of protein synthesis observed when Ca2+ was present during either an initial stimulation phase or a final, unstimulated, measurement phase were similar, and were intermediate between control rates and those in muscles incubated without Ca2+ for the whole experiment. Two prostaglandins, F2 alpha (2.8 microM) and A1 (28 microM), increased rates of protein synthesis in unstimulated muscles, but prostaglandins E2 and D2 and the leukotrienes C4 and D4 failed to do so. It is concluded that the stretch-stimulated increase in protein synthesis may be caused by activation of membrane phospholipases, release of arachidonic acid and a consequent increase in prostaglandin synthesis.

Animals↗

Forelimb proportions and the evolutionary radiation of Neornithes.

Analysis of a comprehensive dataset demonstrates that the brachial index (BI = humerus length/ulna length) of modern birds (Neornithes) varies significantly between clades at all taxonomic levels, yet is strongly correlated with recent phylogenetic hypotheses. Variance in BI at the infraclass level is low, but increases rapidly during the proposed major radiation of neornithines in the Palaeocene and Eocene. Although a BI of greater than 1 is primitive for Neornithes, more basal groups of Mesozoic birds (Confuciusornithidae and some members of the diverse Enantiornithidae) had BIs comparable with those of 'higher' modern clades. It is possible that occupation of ecological niches by these Mesozoic clades precluded the divergence of some groups of neornithines until after the Cretaceous-Tertiary boundary. We suggest that with further analysis and data collection the relationships between flight behaviour, ecology and BI can be determined. Hence, BI may provide a useful tool for characterizing the ecology of fossil birds.

Analysis of Variance↗