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Biomedical subjects

D A Hunter

Publications and source records attributed to D A Hunter.

69 records · Page 4Linked to original sources
PubMed1986

Effect of submuscular versus intramuscular placement of ulnar nerve: experimental model in the primate.

A primate model was developed to study the effect of submuscular versus intramuscular placement upon the development of ulnar nerve fibrosis. No significant adherence was found in either location between the ulnar nerve and the flexor-pronator muscle mass. There was no significant difference in the mean nerve fibre diameter or in the percent neural tissue between the ulnar nerves in the two different locations. It is suggested that it is the interaction of the transposed ulnar nerve with other fibrous anatomical structures proximal to, across, and distal to the elbow that causes failure in ulnar nerve transposition procedures, rather than an adverse reaction between the incised flexor-pronator muscle mass and the ulnar nerve.

Animals↗
PubMed1986

Histopathology of compression of the superficial radial nerve in the forearm.

A histologic assessment of the radial sensory nerve from a patient with nerve compression is reported. Histologic changes were confined to the region of the nerve compression. Connective tissue changes consisted of an increased thickness of the epineurium and perineurium. Nerve fiber changes consisted of Schwann cell pathology with marked thinning of the myelin noted in the myelinated fibers and evidence of degeneration and regeneration noted in the unmyelinated fiber population. Nerve fiber pathology was not uniform but varied from fascicle to fascicle in the compressed area.

Forearm↗
PubMed1986

A study of neurotrophism in a primate model.

This study investigated the existence of neurotrophism in a primate model. In eight adult cynomolgus monkeys the sensory component of the femoral nerve was sectioned and introduced into the proximal channel of a silicone Y chamber. The proximal stump was given distal choices of various tissues inserted into the remaining arms of the silicone Y chamber. The targets presented were combinations of tendon, muscle, intact distal nerve, distal nerve graft, or an empty silicone channel. After 6 weeks, ultrastructural analysis confirmed axonal growth toward distal nerve tissue, while minimal or no nerve regeneration was directed toward tendon, muscle, or the empty silicone channel. The results showed that either a distal nerve stump or a nerve graft will act as a specific target to the regenerating primate proximal nerve stump.

Animals↗
PubMed1985

A primate model for chronic nerve compression.

Peripheral compression neuropathy is a common clinical entity but little human nerve material has been available for study. It has been difficult to develop an experimental model of chronic nerve compression which is reliable and reproducible, making it difficult to assess the various treatment modalities currently in use to manage this problem. In a recent study using a rat model, connective tissue and nerve fiber changes associated with chronic nerve compression were described by the authors. The present study expands this same model of chronic nerve compression to the multifascicular median nerve of the cynomolgus monkey, using this model to test whether or not current surgical treatment modalities for nerve entrapment will alter the course of chronic nerve compression. Using histologic and morphometric parameters, there did not appear to be a difference between nerves treated by decompression alone or by decompression and internal neurolysis. Total number of nerve fibers remained constant, as did axon size, but a demyelinating process was demonstrated which is a significant component of chronic nerve compression. Although the small number of experimental animals (7) makes precise evaluation of the clinical modalities impossible, the authors expect that further study of the multifascicular median nerve of the cynomolgus monkey will prove to be a useful source of future experimental evidence and will help to interpret the diverse therapeutic and operative techniques currently in use.

Animals↗
PubMed1985

The nerve allograft response--an experimental model in the rat.

The nerve allograft response in a rat model is presented. The Lewis rat (RTI1) served as the recipient animal while Fischer rats (RTI1) and ACI rats (RTIa) provided the donor nerve allografts. A Lewis/Lewis autograft group was used as the control group. Histological and electrophysiological measurements of nerve regeneration were assessed at five months. While good regeneration was noted in the autograft and matched allograft groups, regeneration across the unmatched allograft was poor. The degree of nerve regeneration (as measured with histological and electrophysiological values) correlated well with previous immunological studies and would support the use of this model for future investigation of the nerve allograft response in the rat.

Animals↗
PubMed1985

Peripheral nerve injection injury with purified bovine collagen--an experimental model in the rat.

This study investigated the effect of purified bovine collagen (Zyderm collagen implant) on peripheral nerve tissue in rats. Zyderm was injected extrafascicularly and intrafascicularly into the sciatic nerve of adult Wistar rats. The nerves were examined by light and electron microscopy and the integrity of the blood-nerve barrier assessed by protein tracer technique. With light microscopy the precise anatomical location of the injected material could be identified. The purified bovine collagen did not appear to be neurotoxic. After extrafascicular injection, only minimal nerve fiber damage was seen. Intrafascicular injection produced a histological picture compatible with compression neuropathy and was associated with a breakdown in the blood-nerve barrier.

Animals↗
PubMed1985

Histologic assessment of nerve regeneration in the rat.

This study reports the degree of spontaneous regeneration that will occur in the sciatic nerve of a rat 5 months after complete resection of the nerve. In 30 animals, the sciatic nerve was excised. Histological assessment at 5 months revealed evidence of regeneration for a variable distance (mean 23.7 mm +/- 6.4 mm). Histological sections were studied at 1-cm intervals along the length of the nerve. Evidence of compartmentation with "minifascicle" formation was noted. The orientation of the nerve fibers was parallel to the long axis of the nerve. This study assessing spontaneous regeneration is meant to serve as a control for other studies evaluating the effect of factors that may influence nerve regeneration in the rat model.

Animals↗
PubMed1985

Nerve regeneration through a pseudosynovial sheath in a primate model.

This study investigated nerve regeneration through a pseudosynovial sheath in a primate. After resecting a 3-cm segment of the ulnar nerve at the elbow, the two ends of the divided nerve were placed at either end of the pseudosynovial tube, positioning the nerve ends such that they were separated by a 3-cm gap. Histologic evaluation at 3, 5, 7, and 9 months demonstrated evidence of nerve regeneration across this gap. Nerve fiber diameter and density assessment demonstrated a maturation of the fiber pattern with time. The overall morphologic pattern of the regenerating nerve within the pseudosheath was that of multiple small fascicles, each within its own perineurial compartment. This pattern resembled neither the proximal nor distal nerve fascicular pattern.

Animals↗
PubMed1985

Alteration of neuroma formation by manipulation of its microenvironment.

In a primate model a histologic assessment of neuroma formation is reported. Three experimental groups were defined. Transected sensory nerves left adjacent to the incisional wound in an area of movement (wrist) were considered the control group. In the "proximally cut" group the same sensory nerves were positioned well proximal to the incisional wound. In the "muscle-implantation" group these nerves were placed in adjacent muscles. At 6 months a histologic assessment of the neuroma formation in the three experimental groups was carried out. Implantation of the sensory nerve into muscle significantly altered the regenerative potential of that nerve. The muscle completely surrounded the sensory nerve. The minimal neuroma that formed had significantly less scar tissue and contained nerve fibers that were of a smaller diameter and decreased density than either the control or the proximally cut group. There were no histologic differences between these latter two groups. However, regeneration into the overlying skin that was noted in the control neuromas was not seen in those nerves which had been proximally cut.

Animals↗
PubMed1984

Chronic nerve compression--an experimental model in the rat.

This study reports a rat model of chronic nerve compression. The sciatic nerves of adult male Sprague Dawley rats were bonded with 1-cm lengths of tubing with varying internal diameters. Histological and electrical studies as well as studies to assess the blood-nerve barrier function were carried out at one through six months. With marked compression of the sciatic nerve, profound electrical changes were noted as early as one month, and histological findings were those of degeneration and regeneration. In the rats with minimal compression, nerve conduction studies remained normal. The earliest findings were alterations in the blood-nerve barrier, followed by histological changes in the large myelinated fibers at the periphery of the fascicles and changes about the nodes of Ranvier. This model appears to be a valid one with which to study other aspects of both the pathophysiology and treatment of chronic nerve compression.

Animals↗
PubMed1984

Peripheral nerve injury by chymopapain injection.

Chymopapain injected into the intervertebral disc space (chemonucleolysis) has been used clinically in patients with disc disease with success. Neurosurgical complications secondary to the procedure have, however, been reported. In this study, the authors have investigated the possible neurotoxic effect of chymopapain on the peripheral nerve in rat and primate models. While the extrafascicular injection caused no nerve fiber damage, the intrafascicular injection caused dose-related nerve fiber damage in both species.

Animals↗
PubMedDate not supplied

Intrafascicular injection of ammonium sulfate and bupivacaine in peripheral nerves of neonatal and juvenile rats.

BACKGROUND AND OBJECTIVES: Regional nerve blocks are often used for the treatment of postoperative pain in children. Ammonium sulfate is a non-narcotic anesthetic agent, which has been reported to provide pain relief lasting days to weeks, with few reported side effects in adult studies. Prior to considering clinical use in children, the neurotoxicity of ammonium sulfate in 4-day and 3-week old rats was assessed and compared with that of bupivacaine. METHODS: Each rat received a posterior tibial nerve intrafascicular injection (0.01 mL in 4-day-old and 0.02 mL in 3-week-old rats) using either 10% ammonium sulfate (n = 24 per age group), 0.5% bupivacaine (n = 18 per age group), 0.9% saline (n = 18 per age group), or 5% phenol (n = 18 per age group). A functional assessment by serial walking track analysis and a morphologic assessment by neurohistology were made. RESULTS: No abnormalities in serial walking track analysis and no structural nerve damage were detected after ammonium sulfate, bupivacaine, or saline injection. Bupivacaine caused mild focal changes in both age groups, which recovered by 8 weeks. CONCLUSIONS: Intrafascicular injection of ammonium sulfate was as safe as bupivacaine in this animal model. Further animal studies must be made before human trials are initiated.

Aging↗
PubMedDate not supplied

Chronic human nerve compression--a histological assessment.

While compression neuropathy is a common clinical problem, the opportunity to study human nerve material is rare. A histological assessment of the superficial radial nerve of four human cases with entrapment syndrome is reported. Changes in the perineurium and the endoneurial microvessels as well as the presence of Renaut bodies were the earliest histological abnormalities noted. Connective tissue changes included epineurial and perineurial fibrosis. Nerve fibre pathology varied from fascicle to fascicle. The myelinated and unmyelinated fibre populations responded differently to this compression. In the myelinated fibre population, marked thinning of the myelin was noted. In the unmyelinated fibre population, a shift in the fibre histogram due to a new population of very small fibres was observed suggesting degeneration with subsequent regeneration of this fibre population.

Adult↗