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PubMed1998

A Method for Immobilizing the Forelimbs of Rabbits.

Immobilizing the forelimbs of rabbits after surgical procedures is necessary to allow healing, yet it often can be difficult, because rabbits are often able to pull the repaired limb from its cast soon after surgery and well before adequate tissue repair has taken place. We describe here a method of immobilization that uses 3 layers of cast material combined with flexion of the radiocarpal and radiohumeral joints. This method resulted in successful immobilization in 97% of the rabbits on which it was used.

Journal Article↗
PubMed1998

Differential effects of GDNF treatment on rotational asymmetry, skilled forelimb use deficits and sensory neglect in unilateral 6-OHDA-lesioned rats.

The ability of a single intranigral infusion of glial cell line-derived neurotrophic factor (GDNF) to reverse deficits in skilled paw usage and sensorimotor orientation and to ameliorate apomorphine-induced rotational asymmetry in unilateral 6-hydroxydopamine-lesioned rats was examined. After lesioning, all rats developed sensory inattention on the side contralateral to the lesion, rotational asymmetry in response to apomorphine administration and significant deficits in successfully performing a forelimb reaching task dependent upon the use of somatosensory and proprioceptive feedback. A single intranigral injection of GDNF (300 micro g) made 4 wks. after the 6-OHDA lesion, significantly decreased the number of drug-induced rotations at 1 and 2 wks. after GDNF administration. At the same time however, no improvements were noted in performance of the paw reaching task or in sensorimotor orienting. Post mortem analyses showed that the GDNF treatment did not cause any increase in striatal dopamine levels but did increase tyrosine hydroxylase-positive immunohistochemical staining in the substantia nigra on the side of the GDNF infusion. These results demonstrate the need for multiple behavioral measures of efficacy when evaluating treatments for parkinsonism in the unilateral 6-hydroxydopamine lesion model in the rat.

Journal Article↗
PubMed1982

[Motor cortex control of fast and slow motoneurons innervating forelimb muscles of the cat].

Intracellular potentials of forelimb motoneurons of pyramidal cats were recorded by glass microelectrodes following repetitive stimulation of the contralateral pericruciate cortex, and patterns of the postsynaptic potentials (PSPs) evoked thereby were analysed. The motoneurons tested were identified by antidromic invasion from either of the following nerves: long (lo. T), lateral (la. T) and medial (med. T) heads of triceps, anconeus (Anc), biceps (Bi), deep radial (dR), median (M) and ulnar (U). The motoneurons were classified into fast and slow motoneurons on the basis of the duration of afterhyperpolarization (AHP) and the axonal conduction velocity. All of Anc and 65% of med. T motoneurons were classified into slow motoneurons. On the other hand, 35% of med. T, 84% of lo. T and la. T motoneurons were classified into fast motoneurons. About 70% of motoneurons innervating Bi and wrist controlling muscles (dR, M and U) were classified into fast motoneurons and the rest into slow motoneurons. Repetitive stimulation of the pericruciate cortex produced predominantly inhibitory PSPs (I-type) or mixed PSPs (M-type) in 67% of Anc and 56% of slow triceps motoneurons, while it evoked predominantly excitatory PSPs (E-type) in 97% of fast triceps motoneurons. Thus, patterns of PSPs in elbow extensor (Anc and triceps) motoneurons produced by cortical stimulation were in general excitatory to fast and inhibitory to slow motoneurons, similarly to the case in hindlimb motoneurons. In dR, M and U motoneurons, cortical stimulation produced E-type (84%) or M-type (16%) PSPs in fast motoneurons, while it evoked M-type (55%) or E-type (45%) PSPs in slow motoneurons. Patterns of PSPs in these motoneurons produced by cortical stimulation had a tendency similar to the case in triceps motoneurons; excitatory components of PSPs were predominant in fast motoneurons and inhibitory components were mainly observed in slow motoneurons. In most fast and slow Bi motoneurons, E-type or M-type PSPs were observed when the precruciate area was stimulated. With post-cruciate stimulation, however, excitatory components became smaller and inhibitory components were marked and changes in the pattern of PSPs were observed in 37% of motoneurons, as compared with precruciate stimulation. Thus, in Bi motoneurons, the qualitative difference of patterns of PSPs evoked by cortical stimulation in fast and slow motoneurons, as observed definitely in triceps motoneurons described avobe, was not clearly recognized.

Action Potentials↗
PubMed1986

Changes in the extracellular matrix and glycosaminoglycan synthesis during the initiation of regeneration in adult newt forelimbs.

The extracellular matrix (ECM) of the distal tissues in a newt limb stump is completely reorganized in the 2-3-week period following amputation. In view of numerous in vitro studies showing that extracellular material influences cellular migration and proliferation, it is likely that the changes in the limb's ECM are important activities in the process leading to regeneration of such limbs. Using biochemical, autoradiographic, and histochemical techniques we studied temporal and spatial differences in the synthesis of glycosaminoglycans (GAGs) during the early, nerve-dependent phase of limb regeneration. Hyaluronic acid synthesis began with the onset of tissue dedifferentiation, became maximal within 1 weeks, and continued throughout the period of active cell proliferation. Chondroitin sulfate synthesis began somewhat later, increased steadily, and reached very high levels during chondrogenesis. During the first 10 days after amputation, distributions of sulfated and nonsulfated GAGs were both uniform throughout dedifferentiating tissues, except for a heavier localization near the bone. Since nerves are necessary to promote the regenerative process, we examined the neural influence on synthesis and accumulation of extracellular GAGs. Denervation decreased GAG production in all parts of the limb stump by approximately 50%. Newt dorsal root ganglia and brain-derived fibroblast growth factor each produced twofold stimulation of GAG synthesis in cultured 7-day regenerates. The latter effect was primarily on synthesis of hyaluronic acid. The results indicate that the trophic action of nerves on amphibian limb regeneration includes a positive influence on synthesis and extracellular accumulation of GAGs. Since the ECM exerts a major influence on cellular proliferation and migration, the effect of nerves on GAG metabolism may have considerable importance for growth and development of the early regenerate.

Acetates↗
PubMed1980

The growth of segmental nerves from the brachial myotomes into the proximal muscles of the chick forelimb during development.

A study has been made of the growth of segmental nerves 13 to 16 (SN13 to SN16) into the chick limb bud, from the time when they have just reached the ends to the brachial myotomes (stage 21: Hamburger and Hamilton, '51), until they enter the newly formed ventral (stage 24) and dorsal (stage 25) pre-muscle cell masses in the limb bud. At stage 22 axon bundles of SN13 to SN16 have grown off the ends of their respective myotomes, and converge towards the most densely packed mesenchyme in the limb bud at segmental level 15. As a consequence, the first axon bundles of SN14 and SN16 have almost joined those of SN15, whereas the further removed SN13 axon bundles have not yet reached the level of SN15. By stage 23 the first axon bundles from SN14 to SN16 have joined at segmental level 15 to form a nerve which grows toward the ventral pre-muscle cell mass. At stage 24 axon bundles from SN13 have joined those from SN14 to SN16 to form the brachialis longus inferior nerve, which enters the densest region of the ventral pre-muscle. Other axons from SN13 to SN15 grow along the pathways provided by the early arriving axon bundles towards the ventral pre-muscle, but diverge from those at segmental level 14 to grow to the dorsal pre-muscle. By stage 25 axon bundles from SN13 to SN15 have joined to form the brachialis longus superior nerve which enters the densest region of the dorsal pre-muscle. At stage 26 a plexus has formed due to this pattern of growth of the segmental nerves between stages 22 and 25. It is suggested that pre-muscle cells synthesize a nerve growth factor which directs the growth of axons into the limb bud.

Animals↗