Search PubMed⌕ Search

Biomedical subjects

G Lundborg

Publications and source records attributed to G Lundborg.

At least 109 records · Page 6Linked to original sources
PubMed1994

Can sensory and motor collateral sprouting be induced from intact peripheral nerve by end-to-side anastomosis?

The possibility that collateral sprouting could occur from intact axons in an undamaged sciatic nerve was studied in the rat by suturing either a 7-day predegenerated or a fresh nerve segment in an end-to-side fashion to the sciatic nerve proper. Following a 14- or 35-day recovery period, the pinch reflex test was performed on the transplanted segment to demonstrate the presence of sensory axons. The majority of cases, using a predegenerated nerve segment but not a fresh segment, responded positively. Neurofilament staining and histological examination confirmed the presence of axons in the attached nerve segment. In another series of experiments, the proximal peroneal fascicle was ligated and cut. Following a 7-day predegeneration period the distal stump was sutured end-to-side to the ipsilateral tibial fascicle. After 90 days, stimulation of the tibial nerve proximal to the attached site induced substantial contraction in both the native gastrocnemius muscle and the foreign tibialis anterior muscle. These findings suggest that collateral sprouting may occur from intact axons, perhaps induced by factors emanating from the attached nerve segment, and subsequently make functional peripheral connections.

Anastomosis, Surgical↗
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

Trophism, tropism, and specificity in nerve regeneration.

Target-derived neurotrophic factors are of basic importance for survival of neurons. In the normal state, such neurotrophic factors, synthesized by the target tissues, are taken up by nerve terminals and transported by retrograde axonal transport in axons to the nerve-cell bodies to maintain their viability. After nerve injury, neurotrophic factors are synthesized by non-neuronal cells (Schwann cells and fibroblasts) in the nerve trunk, thereby supporting the outgrowth of axons. Neurite-outgrowth-promoting factors on cell surfaces (cell adhesion molecules, "recognition molecules") or in the extracellular matrix promote extension of the axons by providing an appropriate "adhesiveness" in the substrate. Both neurotrophic and neurite-outgrowth-promoting factors are essential for axonal growth after injury. Specificity in end-organ reinnervation is a complex phenomenon which may be based on physical factors at the zone of injury, as well as on molecular interaction between axons and substrate cells along the pathways and at the target level. Such processes may include molecular recognition of appropriate axons and maintenance of such axons by trophic mechanisms, as well as the pruning of inappropriate axons. The ultimate errors in target reinnervation are reflected in a cortical re-organization in the somatosensory cortex. The capacity of the brain to "reprogram" itself and adapt to this functional re-organization is critical for the ultimate recovery of functional sensory/motor function after nerve injuries.

Animals↗
PubMed1994

Long-term results of fracture of the scaphoid. A follow-up study of more than thirty years.

Fifty-six patients who had had a fracture of the scaphoid from January 1950 through December 1959 were interviewed, re-examined, and had radiographs made of both hands an average of thirty-six years (range, thirty-one to forty years) later. The average age at the time of the treatment was twenty-eight years (range, fifteen to forty-five years). Fifty-two of the fifty-six patients were treated at the time of the fracture; the other four had a non-union when first seen. The rate of non-union for the fresh fractures at the most recent follow-up examination was 10 per cent (five of fifty-two). Dorsal intercalated-segment instability was found in three of the fifty-six patients; all three had a pseudarthrosis and manifest radiocarpal osteoarthrosis. Marked radiocarpal osteoarthrosis developed in only one (2 per cent) of the forty-seven patients who had a healed fracture; it was far more common in the group that had a pseudarthrosis, in which the prevalence was five of nine patients. Manifest osteoarthrosis also seemed to be associated with pain or weakness: it had developed in only three (6 per cent) of the forty-nine patients who did not have any symptoms at the re-examination, compared with three of the seven who had symptoms.

Adolescent↗
PubMed1993

Pretreatment of rats with pulsed electromagnetic fields enhances regeneration of the sciatic nerve.

Regeneration of the sciatic nerve was studied in rats pretreated in a pulsed electromagnetic field (PEMF). The rats were exposed between a pair of Helmholtz coils at a pulse repetition rate of 2 pps at a field density of 60 or 300 microT. The PEMF treatment was then discontinued. After an interval of recovery, regeneration of the sciatic nerve was initiated by a crush lesion. Regeneration of sensory fibers was measured by the "pinch test" after an additional 3-6 days. A variety of PEMF pretreatments including 4 h/day for 1-4 days or exposure for 15 min/day during 2 days resulted in an increased regeneration distance, measured 3 days after the crush lesion. This effect could be demonstrated even after a 14-day recovery period. In contrast, pretreatment for 4 h/day for 2 days at 60 microT did not affect the regeneration distance. The results showed that PEMF pretreatment conditioned the rat sciatic nerve in a manner similar to that which occurs after a crush lesion, which indicates that PEMF affects the neuronal cell body. However, the mechanism of this effect remains obscure.

Animals↗
PubMed1993

The influence of predegeneration on regeneration through peripheral nerve grafts in the rat.

Nerve regeneration through predegenerated (PNG) or fresh (FNG) autografts in either fresh or delayed recipient nerve beds were studied in the rat sciatic nerve. Grafts 10 mm in length were excised either immediately or following a 7-day period of predegeneration. They were sutured into gaps on the contralateral side which were either freshly made or had been made 7 days previously. The early recovery (10 days at 2-day intervals) was evaluated by the sensory pinch test to measure the rate of regeneration and the delay period. The PNG group had an improvement in axonal regeneration as evidenced by a reduced delay period, a reduced number of regeneration failures, and less variability in regeneration distances compared to the FNG group. Conditioning the host site blocked some of the delay reduction in the PNG group, but had no effect on regeneration rate or delay in the FNG group. The presence of axons in the graft was confirmed by immunocytochemistry for neurofilament protein and by electron microscopy. The results suggest that proliferated cells, primarily Schwann cells, promote regeneration through the suture line and graft into the distal segment.

Animals↗
PubMed1993

Metacarpophalangeal joint arthroplasty based on the osseointegration concept.

The osseointegration concept has been used for fixation of 68 MP joint endoprostheses in 31 patients operated on at the Department of Hand Surgery, Malmö General Hospital during the period 1988-1992. The indications were rheumatoid arthritis (50 joints), primary osteoarthrosis (three joints), post-traumatic osteoarthrosis (three joints), post-traumatic osteoarthrosis (five joints), post-infectious osteoarthrosis (seven joints) and joint deformities secondary to spastic conditions (three joints). The average follow-up time was 2.5 years (6-54 months). The surgical procedure included resection of the joint followed by introduction of screw-shaped titanium fixtures into the bone marrow cavities of the metacarpal and the phalangeal base. Rheumatoid cases usually required grafting of cancellous bone and marrow from the iliac crest. At the same time a flexible constrained silicone spacer was connected to the titanium fixtures in such a way as to allow later replacement of the spacer if accessory. The average active range of motion (ROM) was 57 degrees in the rheumatoid cases and 50 degrees in all cases. Radiological and clinical osseointegration occurred in every case, and there were no clinical signs of loosening. In four cases (6%) there was a fracture of the joint mechanism. Patient satisfaction was high, with pain relief, increased range of motion, improved hand function and good cosmetic appearance.

Adult↗
PubMed1993

Neurophysiological investigation of hands damaged by vibration: comparison with idiopathic carpal tunnel syndrome.

Forty-seven men with numbness and paresthesiae in their hands after long-term occupational exposure to vibrating hand-held tools were examined neurophysiologically and clinically. The vibration thresholds of the finger tips were assessed and fractionated neurography of the median nerve motor and sensory fibres carried out. They were compared with control groups of healthy subjects and patients with idiopathic carpal tunnel syndrome. The patients exposed to vibration had major increases in their finger vibration thresholds, shown with both the Goldberg-Lindblom vibrameter and the Lundborg vibrogram. They also had a moderately increased motor distal latency at the wrist, but significantly less than patients with idiopathic carpal tunnel syndrome. Similar changes were seen in the sensory conduction velocities from finger to wrist. Measurement of fractionated conduction velocity across the carpal tunnel showed a bimodal distribution; one group of patients exposed to vibration had a significant reduction in conduction velocity similar to that in the genuine carpal tunnel syndrome, and one group had no localised affection at the carpal tunnel, suggesting more distal dysfunction at the level of palm or finger, or at the receptor level. A careful neurophysiological assessment of these cases is necessary before treatment is planned. It is particularly important to confirm median nerve damage at the wrist level if the carpal tunnel ligament is to be sectioned.

Adult↗
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

Vibrotactile perception threshold measurements for diagnosis of sensory neuropathy. Description of a reference population.

Recognition of the fact that impairment of the tactile sense may occur independently of other disturbances in the vibration syndrome has rekindled an interest in developing a diagnostic method for early detection of vibration-induced neuropathy. There is also evidence suggesting that vibrotactile measurements represent a valuable diagnostic tool in compressive neuropathies, such as the carpal tunnel syndrome. The method may also become useful for diagnosing sensory neuropathies caused by other factors, such as solvents, pesticides, heavy metals, alcoholism, and diabetes. However, before vibrotactile measurement can be accepted and established as a tool for clinical diagnostic purposes, for screening, and in research, the level and the shape of the normal threshold curve have to be specified. With the purpose of assembling normative data, the vibrotactile perception thresholds (8-500 Hz) of the right index fingertip were measured in 171 healthy males (19-75 years) not exposed to vibration. A Békésy audiometer was modified to operate in combination with a vibration exciter, instead of headphones, at frequencies lower than usual (8-500 Hz). The results showed that the perception thresholds increased from about 100 dB to about 140 dB (rel. 10(-6) m/s2rms) as a function of frequency and age. The frequency-dependent changes were not linear, however, but displayed a peak in sensitivity at 125 Hz. Threshold changes due to aging were most pronounced at the highest frequencies. It is of the utmost importance that these natural changes are taken into account when making comparisons between groups or individuals.

Adult↗
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

The utility of portable nerve conduction testing for patients with carpal tunnel syndrome: a prospective clinical study.

The usefulness and accuracy of a portable instrument, the electroneurometer, for measuring distal motor latencies was determined in a prospective study of 28 patients (51 hands) with carpal tunnel syndrome and 10 controls (18 hands). There was a close correlation of distal motor latencies from the electroneurometer with those from formal electrodiagnostic testing. The average distal motor latency of controls was 3.3 +/- 0.4 msec, compared with a mean value of 5.2 +/- 1.8 msec in symptomatic hands. The sensitivity of the neurometer test alone was 69% (9 false-negatives); when combined with quantitative sensibility testing, sensitivity increased to 84%. Specificity of the neurometer test alone was 100% (no false-positives). The portable electroneurometer is a convenient, painless, inexpensive device for screening patients with carpal tunnel syndrome. Formal electrodiagnostic testing is indicated for differentiation of lesions present at different levels, for detection of subtle sensory changes, and for use in those patients in whom surface electrode usage is ineffective.

Adult↗
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

Restoration of the injured flexor tendon surface: a possible role for endotenon cells. A morphological study of the rabbit tendon in vivo.

The ability of rabbit deep flexor tendons to restore the gliding surface and to heal, without the normal contribution of the superficial epitenon layer of the tendons, was studied by light and scanning electron microscopy. The epitenon layer was carefully removed from defined segments of the tendons. The remaining central tendon tissue was divided, sutured and placed in diffusion chambers subcutaneously in the back of the rabbits. After two weeks of culture, most of the sutured gaps were bridged and the tendons were encapsulated by flattened and spindle-shaped cells which covered a random network of thin collagen fibres. After five and 11 weeks, fibroblast-like cells in multiple layers formed a cobblestone-like surface. Thus, a tendon deprived of its epitenon layer still contains cells which can produce collagen, bridge the gap and restore the injured tendon surface.

Animals↗