Target-specific nerve regeneration through a nerve guide in the rat

Nerve regeneration across a gap in peripheral nerve has been achieved through various nonneural nerve guides in both lower and primate species. This technique can only be useful if the regenerated nerve cable grows specifically to and reinnervates the appropriate distal target. In this study, the proximal peroneal fascicle of rat sciatic nerve was inserted into the proximal limb of a Y-shaped nerve guide. Distal peroneal and tibial fascicles were placed within the two distal limbs of the same Y. The proximal peroneal nerve grew preferentially by a 2:1 ratio to the appropriate distal peroneal fascicle suggesting that target-specific reinnervation is possible through a nerve guide.     

Inferior alveolar nerve reconstruction with a polyglycolic acid bioabsorbable nerve conduit.

A custom-designed polyglycolic acid (PGA) bioabsorbable nerve conduit was used to reconstruct a 25-mm defect in the right inferior alveolar nerve. The initial nerve injury, following a dental extraction, resulted in loss of lower lip sensation and severe facial pain. Sixteen months after tooth extraction, with no improvement in symptomatology, the alveolar canal was enlarged in diameter by means of mandibular osteotomy to accommodate a 2-mm-diameter polyglycolic acid tube. The proximal end of the inferior alveolar nerve was sutured into the polyglycolic acid tube. The mental nerve was sutured into the distal end of the tube. Pain of neural origin was relieved in the early postoperative period. Two years following nerve reconstruction, pain relief remains excellent and perception of pressure and vibration is similar to the thresholds for these perceptions on the contralateral lip.     

Modulation of peripheral nerve regeneration: a tissue-engineering approach. The role of amnion tube nerve conduit across a 1-centimeter nerve gap

A new type of a biodegradable nerve graft conduit material, the amnion tube, has been developed in our laboratory. To test the tube in the peripheral nerve regeneration process, it was initially applied across a 1-cm sciatic nerve gap in rats and was compared with other nerve conduit materials. We used male Sprague-Dawley rats as our animal model. The experiment included 66 rats that were randomly assigned into five groups: autograft (n = 17), amnion tube (n = 19), silicone tube (n = 20), no repair (n = 7), and sham group (n = 3). The process of peripheral nerve regeneration was evaluated at 2, 4, 10, and 17 weeks following injury and repair by using morphologic and functional assessments of the outcome of nerve regeneration in each animal. Nerve regeneration across the amnion tube nerve conduit was comparable with that seen in autograft and superior to that of the silicone group. A uniform nerve tissue was seen filling and crossing the amnion conduit, and the regenerated nerve from the proximal stump reached the distal end and was undifferentiated from the normal nerve tissues. At 4 months, the amnion tube biodegraded and no longer could be identified and differentiated from the nerve tissues. The amnion tube animal group showed a number of axons very close to that in the nerve autograft group (37,157 versus 33,054). Functional recovery at a 2- to 4-week interval was significantly statistically higher only in the amnion tube animal group (p = 0.01). However, the improvement disappeared between 10 and 17 weeks. In conclusion, the amnion tube is a potential ideal nerve conduit material secondary to its unique characteristics: it contains important neurotropic factors, is biodegradable, provokes a very weak immune response, is semiflexible, is readily available, and is easily manufactured into different sizes and diameters.     

Effects of nerve growth factor on nerve regeneration through a vein graft across a gap.

The limited availability of donor sites for nerve grafts and their inherent associated morbidity continue to stimulate research toward finding suitable alternatives. In the following study, the effect of direct administration of nerve growth factor (NGF) into a nerve conduit across a gap was tested in a rat sciatic nerve model. A 1-cm segment of the right sciatic nerve in Sprague-Dawley rats was resected, and the gap was then bridged using one of three methods: group I (NGF-treated group, n = 12), a vein graft filled with NGF (100 ng in 0.3-ml phosphate buffered saline); group II (control group, n = 12), a vein graft filled with phosphate buffered saline only; group III (standard nerve graft, n = 11), a resected segment of the sciatic nerve. All animals were evaluated at 3 and 5 weeks by behavioral testing and at 5 weeks by electrophysiologic testing. At 3 weeks, sensory testing showed that the latency to a noxious stimulus in group I animals (8.0 +/- 5.4 sec, mean +/- SD) was significantly lower than that of group II animals (13.2 +/- 6.5 sec), indicating that sensory recovery was superior in the animals receiving NGF. The mean latency of animals in group III was 12.9 +/- 6.5 sec, but the difference between the latencies of group I and group III did not reach statistical significance. At 5 weeks, there was no difference in sensory testing between groups. Motor function in groups I and III as measured by walk pattern analysis was superior to that of group II at 5 weeks (toe spread ratios 0.66 +/- 0.09, 0.48 +/- 0.07, and 0.69 +/- 0.09 for groups I, II, and III, respectively). Mean motor conduction velocities across the 1-cm gap were 8.6 +/- 4.7 m/sec, 2.5 +/- 0.7 m/sec, and 6.9 +/- 2.9 m/sec in groups I, II, and III respectively. The difference between groups I and III was not statistically significant, but the motor conduction velocity of group II was significantly slower than that of either group I or III (p < 0.002). The positive effects of NGF on regeneration of nerves across a gap seen in this study suggest that it may be useful for treating peripheral nerve injuries in combination with autogenous vein grafts.     

Electrodiffusion model of a nerve impulse

Electrodiffusion equations are deduced which describe the formation of the action potential in the axone. It is suggested that the membrane dividing internal and external axone electrolytes after being stimulated with an electric impulse returns after some time to the initial "closed" state. It is shown that the overshut of the action potential takes place due to non-linear profile distortion of the shock wave of electrical field tension vector created by the movement of sodium and potassium ions through the membrane of the axone.     

ATP as a nerve transmitter substance

The ubiquitous biochemical adenosine triphosphate (ATP) has been postulated to fill yet another role, and one conceptually unrelated to those already accepted for it. Burnstock, Campbell, Satchell &; Smythe (1970) have proposed that ATP functions as a chemical transmitter substance for certain peripheral nerves. In this paper, an examination of the characteristics of a molecular model of ATP built according to accepted structures is made. It is seen that this molecule shares with others already known to function as neurotransmitters, certain fundamental characteristics of charge distribution. It is suggested that although definite proof of a neurotransmitter role for ATP will have to await further understanding of the molecular mechanisms of synaptic transmission, there is no reason why it should not be considered in this light.     

Outcome following implantation of a peripheral nerve stimulator in patients with chronic nerve pain

This study evaluated the usefulness of the implanted peripheral nerve stimulator in patients with pain following injury to a peripheral nerve. The patient sample (n = 17) consisted of 7 men and 10 women with a mean age of 48 years (SD = 18 years). The mean follow-up time since implantation of the stimulator was 21 months (SD = 15 months). Workers' compensation and/or litigation were involved in 11 cases. Peripheral nerve stimulators were placed in the upper extremity in 12 patients and in the lower extremity in 5 patients. Pain relief following implantation was rated as excellent by five patients, good by six patients, fair by four patients, and poor by two patients. A statistically significant decrease in reported pain level was found postoperatively (p < 0.0003). There was no statistically significant difference in postoperative pain level between men and women (p = 0.30), between cases involving workers' compensation or litigation and those not involving these issues (p = 1.0), or between patients who received an upper-extremity implant and those who received a lower-extremity implant (p = 0.56). Of the 12 patients who were unable to work before the operation, 6 returned to work after the operation. In conclusion, peripheral nerve stimulators can be useful in decreasing pain in carefully selected patients with severe neurogenic pain.     

Entropy changes associated with a nerve impulse

In this paper the problem of entropy changes in a nerve fibre when an action potential is taking place is analysed. A probability field associated with the ionic distribution in the axoplasma and the extracellular space is defined. The total variation of its entropy can be computed on the basis of Gibbs' distribution of ions in the system. The final formula deduced for the entropy variation allows computations based on experimental data for the giant axon and the myelinated fibre. It represents at the same time a derivation of Brillouin's neguentropy principle of information in the particular case of the nerve.     

Studies of nerve proteins; isolation and physicochemical characterization of a protein from lobster nerve

1. A procedure is described by which several protein constituents may be obtained from extracts of lobster claw nerves. One of these fractions, designated fraction A, representing 10 per cent of the total non-dialyzable material of the extracts, has been obtained in relatively (85 per cent) pure form. 2. This component has been characterized with respect to its physicochemical properties, particle shape, dimensions, and absorption spectrum.