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Biomedical subjects

B Rydevik

Publications and source records attributed to B Rydevik.

At least 73 records · Page 4Linked to original sources
PubMed1989

Microvascular response to locally injected collagenase. An experimental investigation in hamsters and rabbits.

Collagenase was injected into the ears of rabbits and the cheek-pouches of hamsters. The acute and long-term microvascular effects were studied by vital microscopy and microangiography. The enzyme was injected at three different concentrations: 120 units/ml, 600 units/ml and 3,000 units/ml. The medium (600 units/ml) and high (3,000 units/ml) concentrations induced effects on the microcirculation such as blood flow impairment and microbleedings. The magnitude of these effects was related to the concentration of the enzyme. Generally, these microvascular effects were of low magnitude as compared with other substances tested using the same experimental models.

Animals↗
PubMed1989

Edema formation in spinal nerve roots induced by experimental, graded compression. An experimental study on the pig cauda equina with special reference to differences in effects between rapid and slow onset of compression.

Edema formation in spinal nerve roots of the pig cauda equina was studied following experimental compression at various pressure levels, durations, and rates of onset, using a fluorescence microscopic technique. The time-pressure thresholds for the occurrence of edema in the nerve roots were: following rapid onset of compression (0.05-0.1 seconds), 2 minutes at both 50 mm Hg and 200 mm Hg, and following slow onset of compression (the pressure was slowly increased during 15-20 seconds), 2 hours at 50 mm Hg and 2 minutes at 200 mm Hg. Generally, the edema formation was more pronounced after rapid than after slow onset of compression. The data in this study also indicate that intraneural edema might be more easily formed in nerve roots than in peripheral nerves after compression injury.

Animals↗
PubMed1988

The history of carpal tunnel syndrome.

Carpal tunnel syndrome is the most frequently diagnosed, best understood and most easily treated entrapment neuropathy. During the first half of the 20th century, however, most patients with carpal tunnel syndrome were diagnosed as having compression of either the brachial plexus or thenar nerve motor branch of the median nerve. As late as 1950, only twelve patients with operative release of the transverse carpal ligament for idiopathic carpal tunnel syndrome had been reported. The delay in accurate anatomical localization of this compressive neuropathy can be attributed both to the confusion caused by the diverse manifestations of median nerve compression in the carpal tunnel, and to some interesting developments that altered early investigations in this area.

Carpal Tunnel Syndrome↗
PubMed1988

Chemonucleolysis for sciatica. A critical review.

Intradiscal injection of chymopapain for the treatment of sciatica due to disc herniation has been used for more than 25 years, but is still under debate. We review the indications, complications, and clinical results, and discuss the tissue effects of chymopapain. The results following surgical disc removal versus chymopapain injection indicate that surgery with removal of the disc hernia through a small laminotomy remains the documented treatment of choice for patients with proven disc herniation and sciatica in whom conservative treatment has failed.

Chymopapain↗
PubMed1988

Wide tourniquet cuffs more effective at lower inflation pressures.

Longitudinal and radial tissue-fluid pressure distributions were determined beneath and adjacent to wide (12 and 18 cm) pneumatic tourniquet cuffs placed on intact human cadaveric arms and legs, respectively. Tissue fluid pressures exhibited relatively broad maxima at midcuff, and in most cases showed no differences at the various depths studied. Limb circumference was not a determining factor in the transmission of pressure to deeper tissue. We also investigated the effect of four cuff sizes (4.5, 8, 12, and 18 cm) on eliminating blood flow to the lower legs of normal subjects. The cuff pressure required to eliminate blood flow decreased as cuff width increased; thigh circumference was a determining factor in the pressure required to eliminate blood flow while using the smaller cuffs, but not while using the 18-cm cuff. Thus, wide cuffs transmit a greater percentage of the applied tourniquet pressure to deeper tissues than conventional cuffs; accordingly, lower cuff pressures are required, which may minimize soft-tissue damage during extremity surgery.

Arm↗
PubMed1987

Effects of epidural and intrathecal application of collagenase in the lumbar spine: an experimental study in rabbits.

An experimental model is described in which collagenase in different concentrations and volumes were applied epidurally or intrathecally in the rabbit lumbar spine. This made it possible to study the tissue effects in a situation similar to that of collagenase leaking from a disc or accidental epidural or intrathecal injection at chemonucleolysis. Epidurally applied collagenase, in higher concentration, caused a local thinning of the dura. This effect was reduced at lower concentrations and volumes. Intrathecally injected collagenase, even in small amounts, caused intrathecal hemorrhage and acute paraplegia in the hind limbs. Therefore, in the clinical situation, intrathecal injection of collagenase must be avoided.

Animals↗
PubMed1987

Results of treatment of severe carpal-tunnel syndrome without internal neurolysis of the median nerve.

Thirty-three hands (twenty-nine patients) had a release of the carpal tunnel without internal neurolysis for severe carpal-tunnel syndrome. All of the hands had increased values for two-point discrimination or thenar atrophy, or both. Twenty-three (89 per cent) of the twenty-six hands that had increased values for two-point discrimination and twenty-six (87 per cent) of the thirty hands that had an elevated result on Semmes-Weinstein testing had normal values at follow-up. Nine (90 per cent) of the ten hands that had weakness of the thenar muscles (grade-3 strength or less) regained grade-4 or 5 strength. Thirteen (65 per cent) of the twenty hands that had thenar atrophy regained normal muscle bulk. Eighteen (62 per cent) of the twenty-nine patients had complete resolution of symptoms and signs of compression of the median nerve. No significant difference was found between the results in this series of patients and those in a previously reported similar group of patients who were treated by release of the carpal tunnel combined with internal neurolysis of the median nerve.

Adult↗
PubMed1986

Effects of nerve compression on fast axonal transport in streptozotocin-induced diabetes mellitus. An experimental study in the sciatic nerve of rats.

The hypothesis that nerves in diabetes mellitus exhibit an increased susceptibility to compression was experimentally tested. Inhibition of fast axonal transport was induced by local compression in sciatic nerves of rats with streptozotocin-induced diabetes mellitus. Fast anterograde axonal transport was measured after application of 3H-leucine to the motor neurone cell bodies in the spinal cord. The sciatic nerve was subjected to local, graded compression in vivo by a small compression chamber. The amount of accumulation of proteins was quantified by calculation of a transport block ratio. Compression at 30 mm Hg for 3 h induced a significantly greater (p less than 0.05) accumulation of axonally transported proteins at the site of compression in nerves of diabetic animals (transport block ratio: 1.01 +/- 0.35; n = 7) than in nerves of controls (0.67 +/- 0.16; n = 7). Accumulation was significantly higher in ligature experiments of both control (1.34 +/- 0.44; n = 8; p less than 0.01) and diabetic animals (1.45 +/- 0.30; n = 8; p less than 0.05), indicating that the block of transport in compressed nerves was incomplete. Neither sham compressed diabetic (0.50 +/- 0.09; n = 6) nor control (0.49 +/- 0.11; n = 6) nerves showed any block of axonal transport. The possible causes of the increased inhibition of fast axonal transport in diabetic rats are discussed. The results indicate that diabetes may lead to an increased susceptibility of peripheral nerves to compression.

Animals↗
PubMed1986

Mechanical effects of compression of peripheral nerves.

Effects of graded compression on nerve function were analyzed in order to evaluate the relative importance of pressure level and duration of compression for functional deterioration. The pressure was applied by means of a small inflatable cuff. The effects of two pressure levels, i.e., 80 mm Hg applied for 2 hr or 400 mm Hg applied for 15 min, were studied in rabbit tibial nerves. The lower pressure tested, which is known to induce ischemia of the compressed nerve segment, also causes some degree of mechanical deformation of the nerve trunk, which leads to incomplete recovery following pressure release. The duration of compression is of importance for the degree of nerve injury even at the higher pressure level tested.

Animals↗
PubMed1984

Changes in fast axonal transport during experimental nerve compression at low pressures.

The minimal pressure for impairment of fast anterograde axonal transport was determined in rabbit vagus nerve. Proteins, transported by fast anterograde axonal transport, were labeled by a microinjection of [3H]leucine into the nodose ganglion, and a small compression chamber was applied around the cervical vagus nerve. In this way the nerve was subjected to acute, graded compression. Compression at 20 mm Hg for 2 h as well as sham compression did not induce accumulation of axonally transported proteins at the level of compression. However, a pressure of 30 mm Hg for 2 h induced a block of axonal transport at the site of compression. The causes of the axonal transport block are discussed as well as the minimal pressure level in relation to pressures found in clinical nerve compression lesions.

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↗
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

Changes in nerve function and nerve fibre structure induced by acute, graded compression.

Rabbit tibial nerves were subjected to direct, acute graded compression by means of an inflatable compression chamber. The acute and long term effects of 50, 200 and 400 mmHg applied for two hours on nerve function and nerve fibre structure were investigated. A pressure of 50 mmHg applied for two hours induced only minimal or no acute deterioration of maximal conduction velocity and nerve fibre structure. Conduction velocity was gradually reduced during compression at 200-400 mmHg pressure for two hours and in those cases the recovery of nerve conduction after pressure release was incomplete. Ultrastructural analysis revealed pronounced, early nerve fibre damage in these nerves. Three weeks after compression, nerves compressed at 50 mmHg for two hours had normal afferent and motor conduction velocity, although there were morphological signs of slight nerve fibre damage. Nerves compressed at 200 mmHg for two hours exhibited reduction of conduction velocity only at the level of compression, in contrast to the nerves compressed at 400 mmHg for two hours in which conduction velocity was reduced both at the level of compression and distal to the compressed segment. Morphologically, the nerves compressed at 200-400 mmHg for two hours showed varying degrees of demyelination and axonal degeneration three weeks after compression.

Action Potentials↗
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

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↗