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Biomedical subjects

L B Dahlin

Publications and source records attributed to L B Dahlin.

At least 55 records · Page 3Linked to original sources
PubMed1995

Prevention of macrophage invasion impairs regeneration in nerve grafts.

The importance of cell invasion for regeneration in nerve segments was investigated in rats. The regeneration distance of axons in predegenerated nerve segments was compared to the outgrowth in nerve segments where cell invasion had been prevented. A 10 mm long nerve segment, which was predegenerated (preserved or impaired blood circulation) or kept in a Millipore chamber (pore size 0.22 microns), was sutured as a nerve graft at the contralateral side three days or two weeks after the initial procedure. At two weeks immunocytochemical staining and routine histologic analysis revealed pronounced myelin breakdown and presence of ED1 and ED2 positive macrophages in the predegenerated nerve segment. Nerve segments, which were kept in the Millipore chamber, showed no invasion of macrophages and the myelin sheaths were preserved. The regeneration distances of axons in the nerve segments, evaluated with the pinch reflex test, were significantly longer in the predegenerated nerve segments compared to the nerve segments kept in Millipore chambers. Nerve grafts, which were taken from predegenerated nerves with intact blood circulation, showed the longest regeneration distances. It is suggested that the regeneration process can be impaired in nerve segments where cell and macrophage invasion as well as myelin breakdown are prevented and that preservation of the blood circulation during the degeneration process is important.

Animals↗
PubMed1994

Nerve repair: correlation of restitution of functional sensibility with specific cognitive capacities.

To test the hypothesis that cognitive capacity is correlated with the outcome of functional sensibility after nerve repair, 19 patients were evaluated 2 to 5 years after median or ulnar nerve repair at the distal forearm level. The sensory evaluation included tests for functional sensibility as well as assessments addressing perception thresholds for touch/pressure and vibration. Psychometric tests for cognitive capacity were also carried out. Multiple regression analysis, correcting for the effect of age and the ability to perceive touch/vibration, was used to investigate the relationship between functional sensibility and cognitive capacity, and to determine which of the tested central nervous factors had the greatest influence on the outcome of recovery of functional sensibility. On a ranking list of such factors verbal learning and visuo-spatial logic capacity were the most important ones, indicating significant correlations with functional sensibility. It is concluded that cognitive capacity factors may play an important role for the functional outcome following nerve repair and that variations in such factors may help to explain the variability in the outcome of nerve repair.

Adolescent↗
PubMed1994

Diabetes mellitus but not impaired glucose tolerance is associated with dysfunction in peripheral nerves.

To clarify whether long-term impaired glucose tolerance (IGT) is associated with dysfunction of peripheral and autonomic nerves, age-matched men with IGT and diabetes mellitus were followed prospectively for 12-15 years, when peripheral and autonomic nerve function was assessed. The patients comprised four subgroups: (1) 51 IGT subjects (duration of IGT at least 12-15 years); (2) 35 diabetic patients, with IGT 12-15 years ago, who later developed diabetes; (3) 34 diabetic patients, duration of diabetes at least 12-15 years; and (4) 62 age-matched non-diabetic control subjects. Mean age of the whole study population was 61 +/- 2 years (mean +/- SD), not different in the four groups. Peripheral nerve function tests included nerve conduction velocities, amplitudes, distal latencies, F-reflexes, and sensory perception thresholds for heat, cold, and vibration. Autonomic nerve function tests included the heart rate reaction during deep breathing (expiration to inspiration ratio) and to tilt (acceleration and brake indices). Despite 12-15 years of IGT, peripheral nerve function did not differ between IGT and control subjects, whereas autonomic nerve function deviated; an abnormal expiration to inspiration ratio (a sign of vagal nerve dysfunction) was significantly more common (15/51 versus 5/62; p < 0.01) in IGT than in control subjects. Diabetic patients (groups 2 and 3) showed lower conduction velocities (in general 2-4 m s-1 lower) than IGT and control subjects in all tested nerves. In conclusion, diabetes but not IGT, is associated with peripheral nerve dysfunction.

Age Factors↗
PubMed1994

Changes in slow axonal transport of tubulin induced by local application of colchicine to rabbit vagus nerve.

The biochemical and morphological responses of the rabbit vagus nerve to local application of colchicine and to nerve crush were investigated. Fourteen days after the cervical vagus nerve had been crushed or subjected to local application of colchicine for 2 h, nodose ganglia of anaesthetized rabbits were either injected with [35S]methionine or [3H]leucine for studies of slow and fast axonal transport, respectively, or prepared for light microscopical examination. The radio-labelled proteins of the faster of the two slow transport groups (SCb; 25-30 mm day-1) were separated by one- or two-dimensional polyacrylamide gel electrophoresis and both radio-labelled tubulin and actin were quantified by densitometry from resulting fluorographs of gels. A relative increase in radio-labelled tubulin was found in SCb in the crushed and colchicine-treated nerves; this increase persisted for up to 50 days after nerve crush. Morphological changes in nerve cell bodies induced by colchicine were similar, but smaller in magnitude than those in crushed nerves. It is concluded that a temporary arrest of axonal transport produced by colchicine can lead to a redistribution of tubulin transport comparable with that found in regenerating nerve.

Animals↗
PubMed1993

Inflammatory cells and mediators in the silicone chamber model for nerve regeneration.

In the present study the inflammatory response was quantitatively evaluated during peripheral nerve regeneration. The fluid from silicone nerve regeneration chambers, inserted in rats, was collected during the early period of regeneration of transected sciatic nerves (6 h-7 d) and analysed with respect to inflammatory cells and mediators (leukotriene B4, LTB4, and interleukin-1 alpha, IL-1 alpha). Leucocytes were detected during the entire period (up to 7 d after implantation). The highest concentration was detected after 24 h. PMNG (polymorphonuclear granulocyte) was the predominant cell type in the chamber fluid during the initial 5d of regeneration. Analysis of the concentration of LTB4 demonstrated two peaks (at 24 h and 5 d). The IL-1 alpha concentration displayed an early and relatively smaller peak after 24 h and a second and much larger peak after 7 d, concomitant with an increase of the number of mononuclear cells.

Animals↗
PubMed1993

Axonal transport and morphological changes following nerve compression. An experimental study in the rabbit vagus nerve.

Axonal transport and morphological changes were studied in the rabbit vagus nerve after the nerves had been subjected to compression at either 0, 50 or 200 mmHg for two hours. Slow axonally transported proteins, tubulin and actin, were radiolabelled with 35S-methionine two, seven or 14 days after the injury and the distribution of radiolabelled tubulin and actin within component b of slow transport was measured three days later by densitometric analysis of fluorographs of polyacrylamide gel. No significant differences were found in the distribution of tubulin two (50 and 200 mmHg) or seven (200 mmHg) days after injury, but at 14 days (200 mmHg) there was significantly increased radiolabelling of tubulin relative to actin in the nerve 60 to 70 mm from the nodose ganglion. Morphometric measurements of the nerve cell bodies two days after the compression injury at 200 mmHg revealed no significant changes. Previous work has shown that morphological changes, similar to those found after axotomy, were present in nerve cell bodies seven days after a compression injury. This, taken together with the present results, indicates that compression can induce both morphological and biochemical changes in the neurone. The altered axonal transport of tubulin associated with nerve injury follows a slower time course and does not precede the morphological changes. The findings may be of relevance when discussing the double crush syndrome.

Actins↗
PubMed1993

Acute nerve compression at low pressures has a conditioning lesion effect on rat sciatic nerves.

Effects of acute compression for 2 hours around the sciatic nerve trunk at 30 or 80 mmHg on the regeneration potential in rat sciatic nerves were studied. Sham compression or mobilization was performed contralaterally. A week later a crush injury was inflicted proximal to the compressed segment. After another 3 or 6 days the length of axonal outgrowth was measured, using the pinch test technique. We found that compression at either level caused an increased length of axonal outgrowth compared to the mobilized or sham-compressed nerves. The results show that an acute compression at low pressures does have a conditioning lesion effect on peripheral nerves.

Animals↗
PubMed1992

The formation of a 'pseudo-nerve' in silicone chambers in the absence of regenerating axons.

The formation of a regenerate between sciatic nerve segments or stumps inserted into Y-tunnelled silicone chambers was studied under conditions where regenerating axons were prevented from entering the chamber. This was accomplished by using an isolated segment of the nerve as a proximal insert. After one week, a cellular regenerate spanned the proximal and distal inserts. The size of the regenerate increased if circulation was preserved in the distal inserts. At four weeks, a perineurium-like sheath surrounded the regenerate and longitudinally oriented Schwann cell columns could be observed throughout the regenerate. A similar 'pseudo-nerve' formed towards a piece of distally inserted tendon. Thus, the information required for the formation of a nerve-like structure is inherent to the non-neuronal cells entering the chamber. Schwann cells, in contrast to regenerating axons, do not exhibit preferential growth towards nervous tissue.

Animals↗
PubMed1992

Specificity of muscle reinnervation following repair of the transected sciatic nerve. A comparative study of different repair techniques in the rat.

Specificity of muscle reinnervation and the recovery of muscle contractility were studied after repair of the transected rat sciatic nerve. Six different techniques were compared: epineurial suture, perineural suture, whole nerve graft, interfascicular grafts, skeletal muscle bridge and tubulization. Muscle tetanic force and specificity of reinnervation were evaluated 12 weeks after nerve repair. Recovery of tetanic force was superior after repair with epineurial sutures. There was no statistical significance between the other methods in respect of tetanic force. The specificity of muscle reinnervation was best after tubulization, repair with interfascicular grafts and perineurial suture.

Animals↗
PubMed1992

Vibration-induced muscle injury. An experimental model and preliminary findings.

The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.

Animals↗
PubMed1992

Vibration exposure and conditioning lesion effect in nerves: an experimental study in rats.

The effects of controlled vibrations of defined frequency (80 Hz), acceleration (32 m/s2 root mean square), and duration (5 hours daily, 2 or 5 days) induced to the hind limb of rats on the regeneration potential in the sciatic nerve after a test crush lesion were determined. Exposure to vibration induced a marked and significant increase in outgrowth length of axons from the crush injury as evaluated after 3 and 6 days with the pinch reflex test. This effect was still observed 1 month but not 3 months after exposure to vibration. Even such a short duration of vibration exposure as 2 days induced an increased length of outgrowth. Such a conditioning effect may be due to local changes in the environment of the axons or to changes in the nerve cell bodies in the dorsal root ganglion. The results indicate that an alarm reaction exists in the nerve at a time point where no structural changes are observed in the nerve. By inducing such a conditioning lesion to nerve tissue, vibration represents a trauma corresponding to a crush lesion or transection of the nerve.

Animals↗
PubMed1992

Reinnervation of muscles in rats after repair of transsected sciatic nerves with Y-shaped and X-shaped silicone tubes. Muscle reinnervation after nerve repair.

Reinnervation of the gastrocnemius and anterior tibial muscles was assessed by measurements of tetanic force after repair of sciatic nerves with Y-shaped or X-shaped silicone tubes in rats. The transsected proximal stump of either the tibial or the peroneal fascicle was introduced into the opening of a Y-shaped silicone tube, or both fascicles were introduced into an X-shaped tube. The distal tibial and peroneal fascicles were inserted into the distal outlets of the tubes leaving a gap of 4 mm between proximal and distal stumps. In the X-shaped tubes the proximal inserts were placed opposite or adjacent to their respective distal parts. Sixteen weeks later reinnervation was evaluated by measurements of tetanic force of the gastrocnemius and anterior tibial muscles after electrical stimulation of the fascicles. There was preferential reinnervation in both types of tubes. In Y-shaped tubes about 90% of the tetanic force could be recorded from both muscles after stimulation of the peroneal and tibial fascicles, respectively. Recovery was lower in the X-shaped tubes, amounting to about 75%. Contractions evoked by misrouted fibres were similar (roughly 40%) in both models. We conclude that motor axons preferentially, but not exclusively, selected a path to reinnervate their original target muscle.

Animals↗
PubMed1992

Vibrotactile function of the hand in compression and vibration-induced neuropathy. Sensibility index--a new measure.

The perception thresholds for vibration stimuli of the hand at seven frequencies (8-500 Hz) were evaluated in 300 patients referred to the Department of Hand Surgery in Malmö during the years 1985-1990 for various types of neuropathy (carpal tunnel syndrome, vibration-induced neuropathy, cervical rhizopathy, brachialgia, ulnar neuropathy, radial tunnel syndrome, and polyneuropathy). A sensibility index was calculated by dividing the integrated area under the obtained vibrogram curve of each object tested (areaT) by that of the corresponding area under a superimposed and age matched reference curve (areaR). Sensibility index of less than 0.8 was regarded as the cut off value. The index and little fingers bilaterally were tested to reflect median and ulnar nerve function. There were considerable variations in patterns of pathology among the various groups of patients. In patients with unilateral carpal tunnel syndrome only 10 patients (23%) had abnormalities limited to one recording, while 21 patients (47%) showed abnormalities in all four recordings. This indicates that an isolated carpal tunnel syndrome may reflect more generalised disease of the peripheral nervous system.

Carpal Tunnel Syndrome↗
PubMed1992

Stimulation of regeneration of the sciatic nerve by experimentally induced inflammation in rats.

The effects of application of a chromic catgut suture (conditioning lesion) placed close to the sciatic or tibial nerves on regeneration of the sciatic nerve after a crush lesion (test lesion), that had been induced after an appropriate conditioning interval (two or four weeks) were assessed. The catgut suture induced an inflammatory reaction around the nerve during the four weeks after application of the catgut suture (conditioning interval) but no signs of degeneration of nerve fibres were seen. There was a significant increase in length of outgrowth of sensory nerve fibres as measured by the pinch reflex test when the test lesion was applied after two and four weeks' exposure to the catgut suture. The rate of regeneration was increased by about 11% when the catgut suture had been applied for four weeks before the test lesion was made. The findings indicate that an inflammatory reaction around a peripheral nerve may act as a conditioning lesion, thereby stimulating regeneration of the nerve.

Animals↗
PubMed1992

Conditioning effect induced by chronic nerve compression. An experimental study of the sciatic and tibial nerves of rats.

To find out if chronic nerve compression could affect the peripheral nerve by acting as a "conditioning lesion", silicone tubes (internal diameter 0.8-1.6 mm) were placed round the sciatic or tibial nerves of adult rats for different time periods. After the period of compression the tubes were removed and a test crush lesion was made on the sciatic nerve in the thigh. Regeneration distances of the sensory nerve fibres were analysed by the pinch reflex test after a further three or six days. Compression of sciatic or tibial nerves induced a significant increase in outgrowth length compared with nerves subjected to mobilisation and crush lesion alone. All the tubes tested had a conditioning effect, but only tubes with a small internal diameter seemed to induce nerve fibre degeneration as assessed by immunocytochemistry. The results showed that chronic compression induced a regenerative response in the peripheral nerve. The mechanism by which this was accomplished remains obscure but it may involve both the neurons and the non-neuronal cells.

Animals↗
PubMed1992

Reconstruction of ligaments with expanded polytetrafluoroethylene. An experimental study in rabbits.

The medial collateral ligaments in the knee joints of 15 rabbits were replaced with expanded polytetrafluoroethylene (E-PTFE). The joints were not immobilised postoperatively, and their structure and function were evaluated after 12 months. Range of motion was equal in all groups. Stability of the knee joints and breaking strength of the ligaments were similar in the group in which the ligament had been reconstructed and in the sham operated control group (n = 8). The group in which the ligament had been severed and left to heal by formation of scar tissue (n = 7) had significantly reduced joint stability and the breaking strength of the medial collateral ligament was significantly less. The E-PTFE ligaments were well incorporated into the surrounding tissues. There were no adverse tissue reactions and the articular cartilage looked normal both macroscopically and microscopically. These results indicate that E-PTFE might be a useful substitute for damaged ligaments, at least in smaller joints like metacarpophalangeal and interphalangeal joints.

Animals↗