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Biomedical subjects

M A Glasby

Publications and source records attributed to M A Glasby.

At least 19 recordsLinked to original sources
PubMed2006

The use of ciliary neurotrophic factor to promote recovery after peripheral nerve injury by delivering it at the site of the cell body.

Despite a body of evidence showing that various neurotrophic factors support the survival of nerve cells and stimulate axonal outgrowth, doubt remains about their optimal site of application as well as the more compelling question of what clinical benefit, if any, they would confer. Ciliary neurotrophic factor (CNTF) supports the survival of motorneurons in vitro and in vivo. Direct delivery of CNTF to the cell bodies may help reduce the side effects and overcome the problem of rapid systemic clearance. The aim of this study was to establish whether nerve regeneration may be improved upon by the controlled addition of a specific humoral neurotrophic substance (CNTF) at the level of the cell body. Three groups of five adult sheep were used. The first group acted as normal controls. In the second and third groups, the median nerve was divided and repaired using an epineurial suture technique. In the second group, CNTF was supplied into the CSF at the level of C6 by an implanted osmotic pump. In the third group physiological saline was placed in the osmotic pump. The animals underwent comprehensive electrophysiological and isometric tension experiments at six months. All of the animals had reduced electrophysiological, morphometric and isometric tension indices after surgery compared to normal. The CNTF group had better results than the saline group in the following; (1) area and amplitude of the muscle action potential (2) the percentage of tetanus and muscle mass preserved after repair. These differences were only statistically significant for amplitude of the muscle action potential. No statistical difference was found in the morphological indices (fibre diameter, axon diameter, myelin thickness and internodal length) between the CNTF and saline groups. CNTF does not confer a functional benefit when applied at the level of the cell body.

Animals↗
PubMed2002

Assessment of the method and timing of repair of a brachial plexus traction injury in an animal model for obstetric brachial plexus palsy.

A Sunderland type IV traction injury to the C6 root of adult sheep or newborn lamb brachial plexus was used as a model for obstetric traction injury to the C5 root in humans. In one experimental cohort the injury was created and repaired using interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in a group of adult sheep and in a group of newborn lambs. In a second cohort a similar injury was created and repaired either immediately or after a delay of 30 days, using either interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in four groups of six newborn lambs. In all cases both functional and morphometric indices of nerve regeneration were poorer in the injured and repaired nerves than in normal nerves. In lambs the method of repair made no difference and no significant differences were found for any of the indices of nerve function or morphology. In sheep the use of muscle grafts was associated with a poorer outcome than the use of nerve autografts. Where a delay of 30 days had elapsed between injury and repair, the results using nerve autografts were not significantly different. Where freeze-thawed muscle autografts had been used, the maturation of the regenerated nerve fibres after delay was significantly poorer than after immediate repair. The electrophysiological variables CV(max) and jitter, which may be applied clinically, were found to be good discriminators of recovery in all of the animals and in respect of all procedures.

Analysis of Variance↗
PubMed2001

The use of conventional and invaginated autologous vein grafts for nerve repair by means of entubulation.

Nerve repair by entubulation has re-emerged recently as a possible means of enhancing the microenvironment at the site of repair by inclusion within the tube of various trophic factors. To this end, a modification of the vein-graft technique has been used by turning it inside out before repair, to expose the adventitial surface to the regenerating axons. A comparative study of standard vein grafting versus the inside-out technique was carried out in two equal-sized groups of inbred Lewis rats. Jugular vein isografts were derived from litter mates. The sciatic nerve was transected and repaired by entubulation using the standard vein graft in one group and the inside-out graft in the other group. Morpho-metric and electrophysiological assessment were carried out 3 months after repair. When the animals were assessed it was found that both the standard-vein-graft group and the inside-out group exhibited a reduction in all of the morphometric and electrophysiological variables when compared to normal nerves. The mean axon diameter, fibre diameter and myelin sheath thickness were, however, found to be greater in the group that underwent the inside-out repair. The superior morphometric results seen in the inside-out group were not matched by improved electrophysiological performance. It is concluded that the use of the inside-out technique confers no functional benefit over standard vein grafting.

Animals↗
PubMed2001

Obstetric brachial plexus palsy: a comparison of the degree of recovery after repair of a C6 ventral root avulsion in newborn and adult sheep.

The C6 motor rootlets were avulsed from the spinal cord in six newborn lambs to simulate a birth lesion of the upper root of the brachial plexus. Six 1-year-old sheep were used for comparison, and treated in a similar manner. The injury was repaired immediately in each group using an autologous coaxial freeze-thawed skeletal muscle graft. The animals were allowed to recover for 1 year after the surgery. The C6 root was then examined electrophysiologically and morphologically. The results were compared with those obtained from a group of untreated intact 1-year-old sheep. The fibre and axon diameters and myelin sheath thickness were significantly different in the group repaired as lambs when compared with the group repaired at the age of 1 year. There was also a significantly increased maximum conduction velocity and a greater range of conduction velocities within the nerve in the lambs. Central motor latency was significantly slower in the sheep than in the lambs. These findings would suggest a greater potential for recovery in the lambs after brachial plexus root avulsion injuries.

Age Factors↗
PubMed2000

Obstetric brachial plexus palsy: a large animal model for traction injury and its repair. Part 1: age of the recipient.

A Sunderland type IV traction injury to the C6 root of the sheep or lamb brachial plexus was used as a model for obstetric traction injury to the C5 root in humans. The injury was created and immediately repaired using interfascicular nerve autografts in a group of adult sheep and a group of newborn lambs. The animals were examined using electrophysiological and morphometric techniques 1 year after operation. It was found that the recovery of neuromuscular function was superior in the lambs. The implication is that nerves in newborn animals have a better potential for regeneration than that seen in older individuals. This is discussed with reference to the management of obstetric brachial plexus palsy.

Age Factors↗
PubMed1998

The use of absolute refractory period in the estimation of early postmortem interval.

The estimation of the time since death (postmortem interval) is one of the most difficult problems in forensic pathology. Most methods currently employed use temperature-based algorithms intended to model the cooling of the body after death and thus estimate the postmortem interval. These methods are subject to considerable inaccuracy but their reliability can be improved if a range of other observed criteria such as lividity and rigor are also taken into consideration. The aim of the present study was to investigate the feasibility of using the absolute refractory period as an adjunct to the estimation of postmortem interval. The relationship between the 'postmortem interval' and the 'duration of absolute refractory period' was investigated using the rat sciatic nerve. A strong correlation between the duration of the absolute refractory period and the postmortem interval was observed. When both absolute refractory period and temperature were used in conjunction, the strength of this correlation was increased.

Animals↗
PubMed1998

Biodegradable controlled release glass in the repair of peripheral nerve injuries.

The experiments in this paper were concerned with the recovery of function and ease of application of an entubulation technique using a biodegradable, controlled release glass tube (CRG) for the repair of a transected peripheral nerve. The peroneal nerves of 15 New Zealand White rabbits were repaired with either a CRG tube filled with freeze-thawed muscle, or a conventional freeze thawed muscle graft (FTMG). These were compared with controls in which a CRG was used to enclose the cut ends of a nerve separated by a 1 cm gap. Electrophysiological and morphometric assessment was carried out 6 months after repair. No statistical difference was found in any test between the FTMG and the CRG tube filled with freeze thawed muscle. The CRG tube and 1 cm gap produced inferior levels of recovery of function when compared with the other two repair groups.

Action Potentials↗
PubMed1998

Immediate and delayed nerve repair using freeze-thawed muscle autografts in complex nerve injuries. Associated arterial injury.

Five sheep underwent repair of the median nerve along with the establishment and repair of a brachial artery defect adjacent to the site of nerve injury. The defect in the brachial artery was of similar length to the nerve defect and lay in parallel with it. It was repaired using a reversed vein autograft harvested from one of the superficial veins of the arm. A further five sheep underwent similar treatment with the repair of the nerve delayed for 30 days after the establishment of the complicating vascular injury. Six months after the nerve repair, each group of sheep was assessed using electrophysiological and morphometric methods in order to establish objective indices of nerve recovery and regeneration. These results were compared with those from other sheep which had undergone nerve repair both immediate and delayed with no complicating injury and groups in which the complicating injury consisted of a cavity, fibrosis and haematoma. It was found that delay in the nerve repair and the presence of a complicating arterial injury, both separately and additively, contributed to a poorer outcome in recovery of nerve function and maturation. The effect of an arterial injury, in both of these respects, was to produce a worse outcome than the presence of a cavity with fibrosis and haematoma.

Animals↗
PubMed1998

Immediate and delayed nerve repair using freeze-thawed muscle allografts. Associated long-bone fracture.

Six sheep underwent repair of the median nerve in the forearm using freeze-thawed muscle autografts, along with the establishment and repair of a "fracture" adjacent to the site of nerve injury. The "fracture" was created by making a transverse osteotomy of the radius. It was repaired using an 8-hole dynamic compression plate. A further six sheep underwent similar treatment with the repair of the nerve delayed for 30 days after the establishment of the long-bone injury. Six months after the nerve repair, each group of sheep was assessed using electrophysiological and morphometric methods in order to establish objective indices of nerve recovery and regeneration. It was found that delay of the nerve repair and the presence of a complicating long-bone injury, both separately and additively, contributed to a poorer outcome in recovery of nerve function and maturation.

Animals↗
PubMed1998

Changes in muscle cytoarchitecture after peripheral nerve injury and repair. A quantitative and qualitative study.

The aim of this study was to assess the changes which occurred in the rat in target muscles after the injury and repair of a specific peripheral nerve, using several clinically-appropriate surgical techniques. There were alterations in the size, shape, morphology and cytochemical architecture of the fibres of the target muscles. These changes were marked when transection and repair of the nerve was compared with the less-severe crush injury. The method of repair did not correlate significantly with the occurrence of changes in muscle cytoarchitecture. The results suggest that the extent of cell loss and the changes in muscle fibre architecture were influenced by the type of injury, rather than by the method of repair.

Animals↗
PubMed1998

Stimulated jitter measurement in the assessment of recovery after different methods of peripheral nerve repair.

The recording of stimulated jitter offers a quantitative method for following the recovery of neuromuscular function after peripheral nerve repair. In groups of rats, electrophysiological recording of jitter was carried out on control animals and on animals 90 days after sciatic nerve division and subsequent repair with either direct end-to-end suture (NS), nerve graft (NG) or freeze thawed muscle graft (FTMG). It was found that values for jitter were highest in the FTMG group. The NS and NG groups demonstrated statistically similar jitter values when compared with each other and with the normal. It was concluded that the speed of nerve regeneration is slower in the FTMG group, at least initially, and that 90 days after sciatic nerve repair the FMTG group had an increase in the number of immature neuromuscular junctions when compared with the NS or NG groups. Jitter measurement would appear to offer a means of detecting small differences in nerve regeneration. The value of this in future developments in nerve repair is discussed.

Anastomosis, Surgical↗
PubMed1998

An electrophysiological and morphological comparison of the microwave muscle graft and the freeze-thawed muscle graft.

The purpose of this study was to assess the feasibility of using a microwave oven to produce denatured muscle grafts for the repair of 1 cm deficits in the rabbit peroneal nerve. Recovery of function was assessed after 6 months by electrophysiological and histological examination of the peroneal nerve and target muscles. The results were compared to normal rabbits and to a group whose nerves were repaired with freeze-thawed muscle grafts (FTMG). The results of this study showed that heating muscle in a microwave oven does produce a graft which may be used as an alternative to the FTMG. However, the technical difficulties in preparing a microwave muscle graft make the use of this technique in the clinical setting unlikely.

Animals↗
PubMed1998

In vitro nerve repair--in vivo. The reconstruction of peripheral nerves by entubulation with biodegradeable glass tubes--a preliminary report.

Biodegradeable "controlled release" inorganic polymer glass tubes can be manufactured to fit the dimensions of any nerve and their rate of solubility can be adjusted to encompass the time taken for nerve regeneration. They have been used in a number of biological applications. The facial nerve was repaired in a group of five sheep by entubulation with biodegradeable glass tubes. The sheep were assessed 10 months after repair and compared with a similar sized group of normal sheep. It was found that while there was a reduction in the peak velocity of conduction in the repaired nerves and in the range of conduction velocities, the minimum conduction velocity was within normal limits. There was a diminution in all of the measured variables of nerve morphometry but in no case did this reach statistical significance. These findings are consistent with the view that regeneration of the nerves had taken place to a degree at least as effective as that seen in nerves of a similar size repaired by conventional means.

Animals↗
PubMed1998

Peripheral nerve reconstruction using freeze-thawed muscle grafts: a comparison with group fascicular nerve grafts in a large animal model.

There is evidence to suggest that the 'freeze-thawed muscle graft' may function as an alternative to established methods of nerve reconstruction. Using a large animal model we compared this method with group fascicular nerve grafting in peripheral nerve reconstruction. We excised a 3 cm segment of right median nerve in 10 anaesthetized sheep. The resulting gaps were repaired with either group fascicular cable grafts (GFCGs) or freeze-thawed muscle grafts (FTMGs). After six months the right (grafted) and left (control) median nerves of each sheep were exposed and assessed for nerve blood flow, nerve conduction velocity and morphological indices of recovery. Nerve blood flow was reduced by 40% in those repaired with FTMGs. All the repaired nerves contained a population of significantly smaller nerve fibres and displayed a reduced peak nerve conduction velocity. Those repaired with FTMGs (mean velocity 30.96 m/s) had a peak velocity significantly faster than the GFCG group (mean 13.16 m/s). This study shows that peripheral nerve reconstruction with freeze-thawed muscle grafts compares well with repair using nerve grafts.

Animals↗
PubMed1997

Stimulated jitter measurements in the assessment of recovery after peripheral nerve repair.

The recording of stimulated jitter may offer a highly sensitive, quantitative method for following the recovery of neuromuscular function after peripheral nerve repair. In groups of rats, electrophysiological recording of jitter was carried out on control animals and animals which had had the sciatic nerves divided and repaired 14, 30, 60 and 90 days previously. It was found that values for jitter were highest in the early stages of regeneration and declined with time so that they were within normal limits by 90 days after repair. It is concluded that jitter measurement may be helpful as a test for the postoperative recovery of function in repaired nerves.

Animals↗
PubMed1995

Repair of the facial nerve in the cerebellopontine angle using freeze-thawed skeletal muscle autografts. An experimental surgical study in the sheep.

Six adult blackface sheep underwent repair of the transected facial nerve in the cerebellopontine angle using short freeze-thawed muscle autografts. A typical facial palsy was observed on the side of the intervention immediately after operation. The sheep were allowed to recover for one year by which time clinical observation showed a complete recovery of the facial palsy in 5 sheep and a partial recovery in the remaining sheep. Under general anaesthesia function of the repaired VIIth nerve and the normal contralateral facial nerve were assessed using electrophysiological stimulating and recording techniques. These studies showed restoration of facial nerve continuity to have taken place with functional reinnervation of target facial muscles. Electrophysiological indices of nerve function were consistent with those expected after repair of any peripheral nerve. Morphometric study of the nerves after their removal showed structural changes which though quantitatively different from those of normal nerve were consistent with those seen in other sites and studies where nerves have been repaired. This technique is discussed as a possible treatment for facial nerves whose continuity is disrupted during the removal of cerebellopontine angle tumours.

Animals↗
PubMed1995

A comparison of immediate and delayed nerve repair using autologous freeze-thawed muscle grafts in a large animal model. The simple injury.

Freeze-thawed muscle grafts (FTMG) have been suggested as an alternative to nerve grafts in reconstruction of peripheral nerve defects. This study compares the results of immediate and delayed nerve repair with freeze-thawed muscle graft in a large animal model. Under general anaesthesia, ten adult sheep underwent excision of 3 cm of the right median nerve. Five had immediate nerve reconstruction with FTMGs (Group A) and five were repaired after 4 weeks (Group B). At 6 months, both the right (repaired) and left ("control") median nerves of each sheep were assessed. Nerve blood flow distal to the graft in both groups of repaired nerves was approximately 60% of that in their respective control nerves. Peak nerve conduction velocities were significantly slower in the repaired nerves. The mean fibre diameters of the immediate and delayed repairs were 5.06 and 3.90 mu respectively compared to a control mean of 8.58 mu. G-ratios confirmed that the repaired nerves in both groups were well myelinated. The authors conclude that the FTMG can be used in delayed as well as immediate nerve reconstruction with minimal impairment of final results.

Animals↗