The toe-spreading reflex of the rabbit revisited--functional evaluation of complete peroneal nerve lesions.

Although a variety of electrophysiological and morphological tests are available for studying nerve regeneration in animals, these endpoints do not necessarily correlate with the return of muscle function. Recent efforts have focused on the assessment of function as the endpoint of nerve regeneration. One of the best known of these tests is the sciatic function index in rats. For rabbits, the toe-spreading reflex has been suggested as a valuable index of peroneal function. We examined the reliability and sensitivity of the toe-spreading reflex in a study of nerve regeneration of the peroneal nerve in 10 New Zealand White rabbits. Eleven weeks after the transection and immediate suturing of the peroneal nerve in both hind legs (at two slightly different sites), a toe-spreading reflex could always be elicited on that side where the level of the severed nerve was closer to the dependent muscles. Also on this hind leg the muscle weight of the peroneal target muscles was significantly higher (P = 0.031) than on the contralateral side, which corresponds well to the results of the toe-spreading reflex. The toe-spreading reflex is an excellent and sensitive indicator of the onset of motor recovery in the peroneal nerve-dependent muscles of rabbits. Even small differences in the localization of lesions in both hind legs can be differentiated with this test.     

Regeneration of the rat sciatic nerve after various experimental lesions (morphologic and morphometric analysis)

Dynamics of structural restoration of the peripheral nerve (n. ischiadicus) have been studied in the noninbred rats in 3 series of experiments: after local freezing, pinching and cutting with a subsequent connection of the nerve ends by means of an implanted arterial vessel. As demonstrate the methods of light and electron microscopy, myelinization of the nervous fibers in the distal part of the nerve begins between the 10th-20th days after the effect. Further, amount of the myelinated nerve fibers (NF) significantly increases, they become essentially thicker. However, even in the later time of the observation (9 months) most of NF remain thinner than in the control nerve; this demonstrates that the reparative processes take a longer time than it was supposed before. The comparative analysis makes it possible to recommend the cryogenic lesion of the nerve as the most perspective model to study processes of the reparative histogenesis. Certain positive signs of sutureless connection of the cut nerve by means of the implanted arterial vessel are noted for clinical substitution of vast diastases of the nerve.     

Axoplasmic transport of microtubule-associated proteins in the rat sciatic nerve

32P-ATP was injected into the L5 dorsal root ganglion and axoplasmic transport of the phosphorylate MA proteins 2, microtubule-associated proteins 2, was observed. After the injection of 32P-ATP, the nerve was dissected out at prescribed time intervals and sliced into 5-mm pieces. Each segment was electrophoresed on an SDS-polyacrylamide slab gel and subjected to autoradiography. A protein of 310,000 dalton was transported at a velocity of 6.6-10.6 mm/day in the axon with the electrophoretic mobility identical to that of MA proteins 2, one of the key components associated with the microtubules.     

Presence of monogalactosyl diglyceride in the rat nerve sciatic]

We present a pattern of fractionation of total lipids, leading to the isolation of individual glycolipids, MGDG contains as sugars, a high quantity of galactose and a low level of glucose. The study of the fatty acids distribution shows: a) a high level of saturated short chains fatty acids, b) a high level of palmitic acid (C 16:0, 68% of the total).     

Treatment of diabetic neuropathy by decompression of the posterior tibial nerve

A series of 58 operations on 36 patients were performed for decompression of the posterior tibial nerve for the treatment of diabetic neuropathy. Preoperative symptoms included lack of sensation, pain, or both. Eleven of the 36 patients had neurotrophic ulcers, which were treated simultaneously. The operation was found to be effective for relief of pain in 24 of the 28 patients with that complaint (86 percent). Restoration of sensation was less consistent with improvement noted in 18 of the 36 patients (50 percent). The follow-up period ranged from 12 to 84 months (mean, 32 months) and five patients had some degree of recurrent symptoms. No patient has developed a new ulcer after nerve decompression. Wound complications were minimal (12 percent), even though ulcers were treated simultaneously. No patient required surgical treatment for the decompression incision, although one did require hospital admission for treatment of a wound infection. In general, the procedure seemed to be a worthwhile treatment, which should be considered ill selected diabetics with symptomatic neuropathy.     

Microtubules in myelinated and unmyelinated axons of rat sciatic nerve

Summary Tannic acid in glutaraldehyde was used to stain microtubules in myelinated and unmyelinated axons of rat sciatic nerve. In the majority of areas the tannic acid failed to penetrate the unmyelinated axons whilst penetrating neighbouring myelinated axons, suggesting a difference in the ability of the two types of nerves to exclude tannic acid. Where tannic acid had penetrated the unmyelinated axons the 13 protofilament substructure and size of the microtubules appeared identical to those seen in the myelinated axons.     

Evaluation of fibrin glue in rat sciatic nerve repairs

Using the rat sciatic nerve model, we evaluated the merits of homologous fibrin glue in the repair of peripheral nerve transections as compared to standard epineural suture repairs. A total of four study groups were used, with 10 animals assigned to each group. In group I, the transected sciatic nerve was repaired with six interrupted 10-0 nylon sutures; in group II, only two interrupted sutures were used; in group III, a two-suture repair was reinforced with fibrin glue; and in group IV, only fibrin glue was used. All animals were sacrificed at 8 weeks, and histologic sections evaluated. When fibrin alone was used, dehiscence occurred in 80 percent of the animals, and as reinforcement of a two-suture repair, it only increased the inflammatory reaction.     

Transport of muscarinic cholinergic receptors in the sciatic nerve of rat

On the basis of the specific [³H]quinuclidinyl-benzilate binding, the transport of muscarinic cholinergic receptors has been demonstrated in the ventral horn, sciatic nerve and in the 3 mm segments proximal and distal to the ligature of rat sciatic nerves ligated for 24 h (a) without electrolytic lesion, (b) six days after lesion of the spinal ganglia, (c) six days after lesion of the motoric axons, and (d) six days after transection of the sciatic nerve. The distribution of these receptors was also studied in the ventral spinal horn, dorsal root sensory axons, spinal ganglia and sciatic nerve of rabbit.Our results suggest that the receptors are transported in the sciatic nerve of rat. This transport consists of a large anterograde, and a discrete retrograde flow of muscarinic cholinergic receptors. Most of the receptors are possibly synthesized in the motoneuron cell bodies and migrate in the motoric axons; to a lesser extent they may also be synthesized in the cell bodies of the dorsal root ganglia and migrate in the sensory axons of the sciatic nerve.     

Substance P-, CGRP- and NPY-immunoreactive nerve fibers in rat sciatic nerve-end neuromas

Substance P (SP)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-immunoreactive nerve fibers were examined in experimental sciatic nerve-end neuromas in the rat with immunohistochemical techniques. At 1-3 days after nerve ligation and section of the sciatic nerve there was an accumulation of SP-like immunoreactivity (SP-LI). Six days after the lesion there was, however, a marked reduction and the neuromas remained virtually depleted from SP-LI at survival times between 8 days and 3 months. CGRP-LI was strong at 1-5 days post-operatively. By 8 days, CGRP-LI was reduced, but a large number of axons were still immunoreactive, and remained immunolabelled up to 3 months. CGRP-LI nerve fibers formed endbulbs, and appeared to grow in both anterograde and retrograde directions. Fine fibers sprouts were first observed at 8 days, but preterminal branching in neuromas aged less than a month was uncommon. At early stages (1-3 days) after ligation, there was a marked accumulation of NPY-LI proximal to the nerve constriction. NPY-LI was reduced from 5 days and on, but many fibers remained NPY-positive and their growth pattern through proximal and distal neuroma segments could be determined. The present results thus may indicate a differential effect of nerve injury on neuropeptide expression: immunohistochemically detectable SP-LI rapidly disappears from sciatic nerve fibers trapped in nerve-end neuromas, but CGRP-LI and NPY-LI remain and are useful as neuroanatomical markers for two subclasses of sprouting axons. Furthermore, the findings suggest that both CGRP and NPY, but not SP, could be involved in ectopic electrical activity in experimental neuromas.     

Fatty acid distribution of the normal sciatic nerve lipids in the rat

We isolated and purified the main lipids of the rat sciatic nerve. After methanolysis, fatty acids were isolated and purified by thin layer chromatography, and studied by gas chromatography. C 16 and C 18 fatty acids are the most abundant. Among the long-chain fatty acids, arachidonic acid (20:4) is present in some lipids; highly desaturated fatty acids in C 22 and C 24 are also present. In general, the fatty acids are highly saturated; cholesterol esters and ethanolamine phosphoglyceride fatty acids are highly unsaturated.     

Histotopography and composition of the microcirculatory bed of the sciatic nerve in the rat

By means of macro-microscopical preparation methods, horseradish peroxidase injection, semithin sections, electron microscopy histotopography and composition of microvessels of the sciatic nerve have been studied in 20 mature male white rats. The perineural membrane has been stated to have no its own vascular network. In composition of the sciatic nerve and its large branches muscular venules are revealed; they run longitudinally along the whole length of the endoneural space and are tributaries of the epineural veins. A suggestion is made that presence of the contractile apparatus in the venular wall can play an important role in formation of the postcapillary resistance, regulating the hydrostatic pressure value in the lumen of endoneural capillaries ad intensity of liquor filtration into the interstitial space.     

Chemical and structural changes of neurofilaments in transected rat sciatic nerve

The sequence of changes occurring in transected rat sciatic nerve was examined by electron microscopy and by sodium dodecyl sulfate (SDS) polyacrylamide disc gel electrophoresis. Representative segments of transected nerves were processed for ultrastructural examinations between 0 and 34 days after the transection of sciatic nerves immediately below the sacro-sciatic notch. The remainder of the transected nerves and the intact portions of sciatic nerves were desheathed and immediately homogenized in 1 percent SDS containing 8 M urea and 50 mM dithioerythritol. Solubilized proteins were analyzed on 12 percent gels at pH 8.3 in a discontinuous electrophoretic system. Initial changes were limited to the axons of transected nerve fibers and were characterized by the loss of microtubules and neurofilaments and their replacement by an amorphous floccular material. These changes became widespread between 24 and 48 h after transection. The disruption of neurofilaments during this interval occurred in parallel with a selective loss of 69,000, 150,000 and 200,000 mol wt proteins from nerve homogenates, thus corroborating the view that these proteins represent component subunits of mammalian neurofilaments. Furthermore, the selective changes of neurofilament proteins in transected nerves indicate their inherent lability and suggest their susceptibility to calcium-mediated alterations. Electrophoretic profiles of nerve proteins during the 4-34-day interval after nerve transection reflected the breakdown and removal of myelin, the proliferation of Schwann cells and the deposition of endoneurial collagen. A marked increase of intermediate-sized filaments within proliferating Schwann cell processes was not accompanied by the appearance of neurofilamentlike proteins in gels of nerve homogenates.