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Biomedical subjects

G Lundborg

Publications and source records attributed to G Lundborg.

At least 199 records · Page 11Linked to original sources
PubMed1982

Nerve regeneration across an extended gap: a neurobiological view of nerve repair and the possible involvement of neuronotrophic factors.

We have compared the anatomic and functional regeneration of a transected sciatic nerve following regrowth from its proximal stump through either preformed empty mesothelial chambers or autologous nerve grafts bridging a 10 mm gap. Within the mesothelial chambers an organized multifascicular nerve trunk forms between the proximal and distal stumps. After 3 months, distal segment cross sections from the mesothelial chamber and nerve graft groups did not differ with respect to axonal density or distribution of axonal diameters. Mean conduction velocities across the gaps were also similar, although the nerve graft group had a wider distribution of velocities. Little or no regeneration was evident when the gap between the nerve stumps was left empty. These results suggest that if the regrowing proximal stump is in an appropriate environment, it can form a well organized and oriented nerve trunk. In the mesothelial chambers, the regenerating nerve is surrounded by a loose cellular stroma and a small amount of interstitial fluid, which was found to contain trophic activity for cultured rodent sensory neurons. Such factors may also support nerve regeneration in vivo.

Animals↗
PubMed1982

Median nerve compression in the carpal tunnel--functional response to experimentally induced controlled pressure.

Controlled external compression was applied to the medium nerve of 16 volunteer subjects. Tissue fluid pressure in the carpal canal was monitored with a wick catheter and pressures of 30, 60 and 90 mm Hg were induced for periods varying from 30 to 90 minutes.l Sensory and motor conduction and two-point discrimination were continuously monitored. Tissue compression at 30 mm Hg caused mild neurophysiological changes and symptoms of hand paresthesias. Compression at both 60 and 90 mm Hg induced a rapid, complete sensory conduction block which consistently preceded a motor block by 10 to 30 minutes. Frequently, two-point discrimination remained normal until the last stages of preserved sensory fiber conduction. In three cases, a modification of the model utilizing an arm tourniquet, demonstrated that ischemia rather than mechanical deformation was the primary cause of the functional deterioration. It was concluded that there is a critical pressure level between 30 and 60 mm Hg where nerve fiber viability is acutely jeopardized.

Adult↗
PubMed1982

In vivo regeneration of cut nerves encased in silicone tubes: growth across a six-millimeter gap.

We describe an experimental in vivo system for studying peripheral nerve regeneration, in which the proximal stump of a transected nerve regrows through a transparent silicone chamber toward the distal stump. Physical separation permits examination of the effects of the humoral and/or cellular influences from the distal stump on regenerating fibers before they invade the distal segment itself. A small segment of the rat sciatic nerve was resected, leaving a 6 mm gap which was then encased by a cylindrical silicone chamber. Within the first weeks, a nerve trunk regenerated along the central axis of the chamber bridged the gap between the proximal and distal stumps. When the distal nerve stump was omitted from the distal opening of the chamber, only a thin structure with a few small-caliber fibers extended across the gap. In each instance regenerating nerve appeared as a cord-like structure completely surrounded by clear fluid, a feature which permits easy collection of the extracellular fluid for analysis of its chemical properties and biological activity. This feature also allows in vivo manipulation of the humoral environment in which nerve regeneration occurs.

Animals↗
PubMed1981

Reorganization and orientation of regenerating nerve fibres, perineurium, and epineurium in preformed mesothelial tubes - an experimental study on the sciatic nerve of rats.

Regeneration of severed peripheral nerves is unfortunately often incomplete, due to loss of nerve fibers and neuroma formation. A new approach is presented with the intention of improving the conditions for nerve repair. In the first of the two stages, a pseudosynovial tube is formed around a silicone rubber rod, surrounded by a stainless steel spiral, which was placed in the backs of rats. This tube, in the second stage, is used as a free "tube graft" to bridge gaps of about 10-12 mm lengths in the severed sciatic nerve. The tube was kept open by the metal spiral. Regenerating nerve fibers with their sprouts grew into the initially open space in the tube. A new nerve trunk was formed, comprised of closely packed myelinated and unmyelinated axons, organized into fascicles. Demonstration by electron microscopy and by EMG recording of reinnervation of foot muscles supported successful long-term results. The fascicles were delimited by perineurial and epineurial sheaths and, furthermore, showed signs of maturation. It was also demonstrated that the nerve-fiber regeneration ceased after a few weeks if there was no distal nerve inserted into the tube. The importance of optimizing the interaction between local factors and regenerating nerve fibers for reestablishment of functionally valuable motor units is discussed.

Animals↗
PubMed1981

Effects of graded compression on intraneural blood blow. An in vivo study on rabbit tibial nerve.

Compression applied to a peripheral nerve may easily interfere with intraneural blood flow. In the present experimental study, a vital microscopic technique was used to observe changes in intraneural microcirculation (intrafascicularly and extrafascicularly) when graded compression was applied to a rabbit's tibial nerve by a specially designed minicompression device. Interference with venular flow was observed already at a pressure of 20 to 30 mm Hg while arteriolar and intrafascicular capillary flow was impaired at about 40 to 50 mm Hg. At 60 to 80 mm Hg no blood flow could be observed in the nerve. Nerves observed 3 or 7 days after 2 hours of compression at 400 mm Hg showed no or very slow stagnant blood flow within the previously compressed segment. It is concluded that acute compression of nerve may cause persistent impairment of intraneural microcirculation due to mechanical injury to blood vessels.

Acute Disease↗
PubMed1981

A case of forearm amputation with additional multilevel partial amputations.

A right-handed 4 1/2-year old boy had a sharp amputation 3 cm proximal to his left wrist joint in a hay-cutting machine accident. In addition, he sustained 5 incisions on the anterior and ulnar aspects of the same forearm, the proximal and deepest including radius, ulna and the deep branch of the radial nerve. In a 19 1/2 hours operation, his left hand was replanted and the mainly cold anoxaemia time was 16 hours. Despite several reoperations, the hand could not be saved but the proximal portion of the amputated part did survive. On the 21st day the hand was reamputated at the radiocarpal joint level and the stump closed with viable skin from the proximal 2/3 of the dorsum of the hand. On a 1 year follow-up, the length growth was found to be close to normal. A myoelectric prosthesis is functioning well not only from impulses in the reinnervated extensor muscles but also from the flexor muscles which have been denervated and anatomically divided at least at two levels. Partial replantation success and perfect revascularization and reinnervation in the forearm was gained, thanks to extensive surgery. These results in an extremely complicated injury like this do show that every surgical effort should be made in pediatric extremity trauma.

Amputation, Traumatic↗
PubMed1980

Experimental studies on cellular mechanisms involved in healing of animal and human flexor tendon in synovial environment.

An experimental model is presented to study superficial healing of animal and human flexor tendon in a synovial environment. The results indicate that in a synovial environment a cut and resutured flexor tendon may heal in its superficial parts without adhesion formation. When cell seeding via the synovial fluid is prevented by a dialysing membrane the picture, as revealed by light microscopy, is little changed. When the model is modified so that the central cells of the tendon are exposed to the synovial fluid, these cells become activated. The results indicate that superficial as well as deep cells of the tendon possess a potential for repair if they are adequately nourished, and that cell seeding plays no major role in the process of proliferation and repair. The picture of intrinsic repair potential in a synovial environment seems to be valid also for human flexor tendons.

Animals↗
PubMed1980

Nerve regeneration through preformed pseudosynovial tubes. A preliminary report of a new experimental model for studying the regeneration and reorganization capacity of peripheral nerve tissue.

In a two-stage procedure the pseudosynovial sheath, formed around a silicone rubber rod placed in the back of rats, was used as a free "tube-graft" to bridge freshly cut gaps of 12 mm length in the sciatic nerve. The tube was kept open by a thin metal spiral, originally implanted around the silicone rubber rod. In this model the regenerating nerve fibers grew into an "open" space formed inside the pseudosynovial tube. The tissue formed in the tube was analyzed after 3 months by light and electron microscopy. Within the tube a new nerve trunk was formed, comprising closely packed myelinated and nonmyelinated fibers organized in fascilcles. The fascicles were surrounded by regenerated perineurim, and the new nerve was surrounded by an epineurium-like sheath. An electromyogram recorded from the flexor muscles of the foot confirmed motor reinnervation. The findings are discussed in view of current concepts of nerve regeneration.

Animals↗
PubMed1980

Superficial repair of severed flexor tendons in synovial environment. An experimental, ultrastructural study on cellular mechanisms.

Severed and subsequently sutured rabbit flexor tendons were kept free and isolated in the synovial cavity of the knee joint. In one series the tendon specimens were surrounded by a dialyzing membrane to avoid cell seeding from the synovial fluid. At different intervals of time over a period of 3 weeks, the tendons were studied morphologically with special reference to scanning electron microscopy. Adhesions were not observed and, with synovial fluid as the nutrient medium, the tendons showed an intrinsic ability to repair in the superficial layers, also bridging the suture gap. Moreover, cell seeding, mainly of macrophages, from the synovial fluid could be demonstrated on the very surface of the tendon. When this cell seeding was prevented, the fibroplasia in the superficial layer of the tendon did decrease slightly, but tendon cell morphology was that of active fibroblasts. The results support the concept that flexor tendons may show intrinsic fibroplasia when nourished by synovial fluid, while macrophages, mainly of extrinsic origin, contribute to restoration of the tendon surface.

Animals↗
PubMed1980

Blockage of axonal transport induced by acute, graded compression of the rabbit vagus nerve.

Rapid axonal transport in rabbit vagus nerve was studied during and after graded nerve compression. Proteins of the rapid axonal transport were labelled by micro-injection of 3H-leucine into the nodose ganglion and the cervical vagus nerve was subjected to graded compression by a small "mini-cuff" applied directly to the exposed nerve trunk. The results showed that even slight trauma to the nerve, in this model represented by a pressure at 50 mmHg applied for two hours, may induce accumulation of axonally transported proteins at the level of compression. This transport block was, however, reversible within one day. 200 mmHg and 400 mmHg applied for two hours similarly induced a block of axonal transport persisting up to at least one and three days respectively after the compression. Time for recovery of normal transport was correlated with the magnitude of the pressure applied to the nerve. The results indicate that axons may survive, that is not undergo Wallerian degeneration, after blockage of rapid axonal transport persisting at least one day after the compression trauma.

Animals↗
PubMed1980

The role of the synovial fluid and tendon sheath for flexor tendon nutrition. An experimental tracer study on diffusional pathways in dogs.

Radioactive tracers were used to analyse nutritional mechanisms of flexor tendons of dogs during various experimental conditions. The transport and distribution of methyl glucose in the tendon was analysed 15 min after intravenous injection during the following experimental conditions: (1) normal state--rest; (2) passive mobilization of the tendon; (3) active mobilization of the tendon; (4) exclusion of exposure to synovial fluid-preservation of vascular supply; (5) exclusion of vascular supply--preservation of exposure to synovial fluid. The results indicate that active mobilization gives a significant increase in tracer concentration in the volar part of the tendon, while passive mobilization has no such effect. Diffusional pathways from the synovial fluid plays a major role for transport of tracer into the tendon, while the intrinsic vascular system apparently is of no or minor importance in this respect. The main mechanism for solute transport within the tendon is passive diffusion. Transport of sulphate in the volar part follows a similar pattern as in other avascular tissues and the incorporation of sulphate by the cells is low and comparable to that in articular cartilage. The results support our previous hypothesis that the flexor tendon system physiologically corresponds to a joint, and that the synovial fluid plays an important role for flexor tendon nutrition.

Animals↗
PubMed1980

Restoration of superficially damaged flexor tendons in synovial environment. An experimental ultrastructural study in rabbits.

Flexor tendon from the synovial sheath region of rabbits was resected and placed as a free body in a synovial knee joint recess. Structural changes of the surface of the graft caused by the instruments used to handle the tendon during the surgery (jewellers microforceps), was analysed by electron microscopy at various time intervals up to 6 weeks. The superficial coat of amorphous material, i.e. ground substance, on the surface of the tendon was dishevelled by the instruments. The injured areas were crowded with monocytes and macrophages during the first days. An increasing number of fibroblasts and mesothelial-like cells covered the damaged area in less than two weeks. The superficial coat of ground substance was not completely restored until after 3 weeks or more. The results obtained are discussed in relation to functional aspects.

Animals↗
PubMed1980

Flexor tendon specimens in organ cultures.

The healing process of sectioned and subsequently sutured rabbit tendon segments was studied over a period of 3 weeks, using an organ culture technique. In one series, the tendon specimens were exposed to a chemically defined culture medium for nutrition. In two control series, the specimens were kept in the synovial cavity of the knee joint for varying periods of time, before being transferred to the culture medium. The tendons remained viable in the medium. The superficial tendon cells demonstrated the morphological characteristics of fibroblasts, but cellular fibroplasia could not be detected. The two control series subjected to synovia prior to transfer into the culture medium showed superficial repair similar to the findings in previous studies on healing capacity of tendon nourished by synovia. The investigation supports the hypothesis that superficial tendon cells are fibroblasts with a potential for repair and that synovia is an efficient nutrient medium. Thus, the beneficial effects on repair exercised by the tendon sheath function should be utilized in flexor tendon surgery.

Animals↗