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Biomedical subjects

G Lundborg

Publications and source records attributed to G Lundborg.

At least 19 recordsLinked to original sources
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↗
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

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↗
PubMed1992

The pathophysiology of nerve compression.

The basic pathophysiology of an acute and chronic nerve compression lesion is complex. Compression of a peripheral nerve induces marked changes in intraneural microcirculation and nerve fiber structure, impairment of axonal transport, and alterations in vascular permeability, with edema formation and deterioration of nerve function. The peripheral nerves of subjects with underlying neuropathies are more susceptible to compression injury.

Humans↗
PubMed1991

Does insulin-like growth factor I (IGF-1) trigger the cell body reaction in the rat sciatic nerve?

Regeneration was measured after the infliction of a crush lesion on rat sciatic nerves which 4 days earlier had been subjected to a distal conditioning transection. Such nerves exhibited an increased outgrowth of nerve fibers as compared to nerves subjected to a single crush lesion. This increased outgrowth could be prevented, if the nerve was locally perfused around the site of the transection during the 4 days conditioning interval, with cycloheximide, actinomycin D and vinblastine, inhibitors of protein-, RNA-synthesis and retrograde axonal transport, respectively. The inhibitory effect of cycloheximide could be overcome by simultaneous perfusion with insulin-like growth factor I (IGF-1). The results suggest that proteins including IGF-1 which are synthesised locally around a nerve lesion and then transported retrogradely could trigger regenerative events in the neuronal cell body.

Animals↗
PubMed1991

Recombinant human insulin-like growth factor-I stimulates in vitro matrix synthesis and cell proliferation in rabbit flexor tendon.

Flexor tendons have an intrinsic ability for repair, with a capacity to metabolize matrix components and to proliferate. To identify factors with the potential of affecting those abilities, the effects of recombinant human insulin-like growth factor (rhIGF-I), insulin and fetal calf serum (FCS) on the synthesis of proteoglycan, collagen, and non-collagen protein and cell proliferation were investigated in short-term explant cultures of the deep flexor tendon of the rabbit. Matrix synthesis and cell proliferation were stimulated dose dependently by rhIGF-I at doses between 10 and 250 and at 10-100 ng/ml, respectively, by insulin at 250-5,000 ng/ml, and by FCS at 2-15%. Estimated maximal stimulation (Emax) of up to three times the control value was observed with rhIGF-I at 250 ng/ml. Maximal stimulation was observed at 5,000 ng/ml with insulin, and FCS at 15%. rhIGF-I was more potent than insulin in stimulating protein synthesis and cell proliferation. The Emax of stimulation of proteoglycan and collagen synthesis by rhIGF-I were two times that of FCS, and the Emax of cell proliferation by FCS was twice that of rhIGF-I. Growth factors thus have the ability to stimulate matrix synthesis and cell proliferation in rabbit flexor tendon. This provides a rationale for further studies on the role of growth factors in flexor tendon healing in humans.

Animals↗
PubMed1991

Long-term explant culture of rabbit flexor tendon: effects of recombinant human insulin-like growth factor-I and serum on matrix metabolism.

The effects of human recombinant insulin-like growth factor-I (rhIGF-I, 50 ng/ml) on matrix metabolism in the deep flexor tendon from the tendon sheath region of the rabbit were studied in explants cultured for 3 weeks. Tendon segments cultured in medium supplemented with fetal calf serum (FCS) exhibited proliferation of the superficial cell layers. Synthesis of proteoglycan and non-collagen protein (NCP) increased threefold during the first week and remained elevated during the next 2 weeks of culture in medium supplemented with rhIGF-I or FCS, but not in medium without supplements (bovine serum albumin, BSA). The estimated halflife (t1/2) for elimination of newly labeled proteoglycans from the tendon explants ranged from 5.1 to 8.5 days and from 4.9 to 6.8 days for NCP in supplemented medium. Presence of rhIGF-I or FCS did not affect degradation of matrix as compared with BSA. The total hexosamine content per tendon segment was stable during the culture period, but the non-collagen protein content decreased by 25%. Collagen synthesis decreased to 10% of the initial level after 3 weeks in supplemented medium, but to 3% in unsupplemented medium. There was no measurable turnover of collagen in explants cultured in either medium, and the collagen content remained unchanged. Our results suggest that rhIGF-I, as well as FCS, stimulates matrix synthesis but does not influence matrix turnover in rabbit flexor tendon explants in long-term culture as compared with medium without supplements. We conclude that rhIGF-I may be used as a defined growth-promoting factor in serum-free media and may be of importance in tendon healing.

Animals↗
PubMed1991

Neurotropism, frozen muscle grafts and other conduits.

Axonal regeneration following nerve transection requires a number of cellular and biochemical phenomena in the axons as well as the nerve cell bodies. The nerve cells must survive the trauma. Since axonal severance means amputation of a large axoplasmic volume from the remaining parts of the nerve cell, the cell body must prepare for increased synthesis of axoplasm to replace the missing parts. A sprouting process must be initiated at the level of transection. Regenerating axonal processes are to regenerate towards peripheral targets, a process regulated by an interaction between genetic mechanisms in the nerve cell body and biochemical information at the molecular level along the pathway.

Animals↗
PubMed1991

Effect of drying on regenerating rat sciatic nerve.

To study the effects of drying on regeneration, crush lesions were made on the sciatic nerve of 38 rats and the injured area was then air-dried for various periods of time (0-60 min). The regeneration distance of sensory nerve fibres was measured by the pinch reflex test three or six days later. Regeneration was significantly impaired by drying the nerve for 30 or 60 min, but shorter periods (10 min) also seemed to affect axonal outgrowth. Regeneration distances were increased in nerves that were subjected to drying and then allowed to recover for a week (conditioning interval) before the nerve was crushed. The results show that drying of a peripheral nerve is detrimental to nerve regeneration, and we suggest that nerves should not be exposed to air for more than a few minutes during operation without irrigation.

Animals↗
PubMed1991

Reconstruction of flexor tendon pulley with expanded polytetrafluoroethylene (E-PTFE). An experimental study in rabbits.

Gore-Tex (expanded Polytetrafluoroethylene, E-PTFE) was used to replace the distal pulleys on the proximal phalanges of 20 rabbits. Morphology and function of the reconstructed pulleys were evaluated at 12-20 weeks. The breaking strength of the E-PTFE pulley equalled that of a normal pulley. Range of motion, tendon excursion, and force of flexion were no different from those of normal pulleys. No adhesions between flexor tendons and synovial tendon sheaths or the E-PTFE pulleys could be detected. No adverse tissue reactions were seen. Fibroblast-like cells from the surrounding tissues had grown into the membrane. In other experiments, where the pulleys had been either removed or detached, local fibrosis and adhesions were seen, and the deep flexor tendons had ruptured. The results of the present study indicate that E-PTFE can be used as a biosynthetic replacement for damaged pulleys.

Animals↗
PubMed1991

Abductor pollicis longus tendon arthroplasty for treatment of arthrosis in the first carpometacarpal joint.

A retrospective study of 21 hands in 19 patients was carried out to show the results after excision of the os trapezium for the treatment of arthrosis of the first carpometacarpal joint. A technically easy procedure was used that was based on a tendon plasty using the abductor pollicis longus (APL) tendon. Special attention was paid to the effects of compressive load on the stability of the thumb. The mean follow-up time was 25 months (range 11-38) and all patients achieved good mobility. Pain was reduced in all cases but one. In operated hands grip strength was 84% of estimated normal strength and pinch strength 83%. On radiographs of the hands the mean distance between the base of the metacarpal bone and the scaphoid bone was 4.6 mm, this was reduced by 1.9 mm during compression. When radiographs were taken during a compressive load, two dislocations of the thumb base were found that had otherwise been missed.

Aged↗