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Biomedical subjects

C Nordborg

Publications and source records attributed to C Nordborg.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1979

The ratio between thickness of media and internal radius in cerebral, mesenteric and renal arterial vessels in spontaneously hypertensive rats.

1. Larger arterial vessels of 15-day-old spontaneously hypertensive (SH) rats showed significantly greater media/internal radius ratio than those of Wistar-Kyoto rats in the brain, kidney and mesentery. 2. Since larger cerebral and renal arteries of adult SH rats did not differ from controls the above results indicate the presence of a non-pressure-dependent vascular abnormality in young SH rats. 3. There were marked differences between the vascular beds of adult SH rats in the increase of media/radius ratio. Thus the changes were evident in all sizes of mesenteric arteries but only in the smallest cerebral arteries.

Aging↗
PubMed1979

Local anesthetics: importance of mode of application, concentration and adrenaline for the appearance of nerve lesions. An experimental study of axonal degeneration and barrier damage after intrafascicular injection or topical application of bupivacaine (Marcain).

Local anesthetics are designed for application in or close to nerve tissue. In spite of their wide clinical use, surprisingly few investigations deal with the neural toxicity of modern local anesthetics. In this experimental study, the effects were investigated of intrafascicular or topical application of the long-acting local anesthetic bupivacaine on the rabbit sciatic nerve. Axonal degeneration was histologically evaluated and a fluorescence-microscopic technique used to detect lesions in the blood-nerve barrier. Topical application of bupivacaine in clinically recommended concentrations around the nerve caused no detectable nerve injury, while intrafascicular injections caused considerable axonal degeneration and damaged the blood nerve barrier. Axonal degeneration was the same after injection of physiologic saline solution and bupivacaine 0.5%, but it increased with increasing bupivacaine concentration and especially with the addition of adrenaline. On the other hand, the acute effects of intrafascicular injection, as visualized in the barrier experiments, changed little with the addition of adrenaline, indicating that it is the injection trauma itself which is deleterious. It is concluded that intraneural injections should be avoided and that plain bupivacaine solutions should be routinely used.

Administration, Topical↗
PubMed1978

The influence of protein-calorie malnutrition on the development of internodal segments. A study on peripheral nerve and spinal roots in rats.

The current investigation comprised normal young rats as well as rats submitted to a 50% food reduction or severe protein restriction. Isolated nerve fibres from lumbar spinal roots and sciatic nerves were investigated with reference to the relation between length and diameter of internodes as well as variation of internodal length along single nerve fibres. The present results do not support the view that protein-calorie malnutrition should cause neuropathy. Internodal segments were, on an average, shorter in relation to their thickness in young rats submitted to severe protein restriction or a 50% food reduction. The deviation was most marked in low-protein animals and particularly among coarser internodal segments. An inhibition of longitudinal growth was considered to be the main factor behind the difference between malnourished and normal rats.

Animals↗
PubMed1977

Paranodal myelin retraction in protein deficient and normal rats: a morphometric study.

Young rats, submitted to severe protein restriction were studied concerning the width of inter-myelin gaps at the nodes of Ranvier in peripheral nerve fibres. The results gave no proof of increased paranodal myelin retraction in lumbar spinal roots or the sciatic nerves of low-protein rats. Malnourished rats as well as controls showed great interindividual differences as to the presence of nodes with wide inter-myelin gaps.

Animals↗
PubMed1977

The influence of protein-calorie malnutrition on the development of paranodal regions in spinal roots. A study with the OTAN method on rat.

During the early postnatal development of spinal roots in rats paranodal regions were often found, containing OTAN-positive inclusions in the Schwann cell cytoplasm. The presence of OTAN-positive paranodal regions showed variations in time, which were synchronous for ventral and dorsal roots. Dorsal roots, however, showed a more marked presence during development than ventral roots. Spinal roots of animals submitted to a 50% food restriction, were shown to contain more OTAN-positive paranodal regions than controls. This was true for ventral as well as dorsal roots. It is suggested that crowding of internodal segments could be one factor, determining the presence of paranodal, OTAN-positive material.

Animals↗
PubMed1976

Intraneural tissue reactions induced by internal neurolysis. An experimental study on the blood-nerve barrier, connective tissues and nerve fibres of rabbit tibial nerve.

Surgical treatment of peripheral nerve lesions associated with intraneural fibrosis is sometimes extended to include internal neurolysis. This procedure is performed in order to release the individual nerve fascicles from interfascicular scar tissue which is believed to constrict nerve fibres and thereby interfere with their function and regenerative capacity. However, an internal neurolysis per se implies a significant trauma to the nerve and may induce microvascular damage and formation of new intraneural scar tissue. Considering this, such a procedure appears justified only when the preoperative intraneural fibrosis is more severe than the scarring which might be induced by the surgical procedure as such. In order to evaluate the tissue reactions following internal neurolysis an experimental investigation was carried out: internal neurolysis was performed on normal rabbit tibial nerve. After varying postoperative periods up to 6 months specimens of nerves were analysed. Reactive changes of connective tissue and myelin sheath lesions, indicating nerve fibre damage, were investigated in histological sections studied by light microscopy. Barrier function of perineurial membrane and endoneurial vessels was investigated by fluorescent microscopic tracing of locally applied or intravenously injected albumin labelled with Evans' blue. The results indicate that an experimental internal neurolysis per se may induce fibrosis in all layers of the nerve and may cause some nerve fibre damage. However, the barrier function of the perineurium and the endoneurial vessels seems to be generally well preserved. The findings are discussed in relation to indications for internal neurolysis.

Animals↗
PubMedDate not supplied

Amino acids in the neuronal microenvironment of focal human epileptic lesions.

Extracellular fluid was topically sampled with a dialysis probe during electrocorticography from the exposed cerebral cortex in 23 patients undergoing epilepsy surgery. Sampling was done in parallel from epileptiform regions and from non-epileptic areas. The former were classified according to the histopathology, into neoplastic, non-tumoral or 'special cases'. The epileptiform regions had significantly higher extracellular concentrations of alanine, glycine and phosphoethanolamine in the majority of the cases. The excised epileptic lesions were analyzed to provide the corresponding intracellular concentrations of amino acids. Several of the non-tumoral group showed high concentrations of GABA, ethanolamine and alanine. The intra- to extracellular concentration ratio for amino acids was low for phosphoethanolamine, glycine, serine and glutamine in most of the samples of epileptiform cortex, while the intracellular accumulative ability for ethanolamine apparently was stronger in epileptiform than in normal cortex.

Adolescent↗
PubMedDate not supplied

Effects of collagenase on nerve tissue. An experimental study on acute and long-term effects in rabbits.

Intradiscal injection of proteolytic enzymes implies a potential risk for exposure of nervous tissue to the enzyme solution. In the present study, the effects on peripheral nerve tissue of application of a solution containing a clinically recommended concentration of collagenase have been evaluated. Acute experiments showed that the enzyme induces transient swelling at the site of application and edema in the epineurium. There were, however, no detectable effects on the permeability of the perineurium or the endoneurial microvascular bed. Four and 8 weeks later, there was a slight fibrosis in the epineurium, but neurophysiologic tests did not reveal any impairment of the nerve function. The results are discussed in terms of the clinical use of collagenase for dissolution of herniated intervertebral discs.

Animals↗
PubMedDate not supplied

Effect of metoprolol on diet-induced atherosclerosis in rabbits.

The effect of metoprolol, a beta 1-blocker, on atherogenesis was evaluated in rabbits fed a diet supplemented with 0.25% cholesterol and 3% coconut oil for 21 weeks. After 7 weeks on the diet, the rabbits were randomly divided into treated (n = 22) and untreated (n = 22) groups. Treated animals received metoprolol subcutaneously by an osmotic pump for 14 weeks, resulting in a plasma level of 774 +/- 69 nM during the investigation. Plasma concentrations of cholesterol, triglycerides, and phospholipids did not differ between the two groups. Nor were there any significant differences between the two groups in plasma concentrations of apolipoprotein A-I, apolipoprotein B, apolipoprotein C-III, and apolipoprotein E measured by electroimmunoassay. At the end of the study, the aortas were cut into three portions and the extent of atherosclerosis was determined by morphometry. The group that had received metoprolol had significantly (p less than 0.015) less atherosclerosis in the aorta (ascending plus arch 37.8 +/- 6.8%, thoracic 32.9 +/- 6.1%, abdominal 19.8 +/- 6.1% of total intimal area; mean +/- SEM) than the controls (ascending plus arch 54.9 +/- 7.1%, thoracic 48.0 +/- 6.2%, abdominal 25.9 +/- 5.5%).

Animals↗
PubMedDate not supplied

Morphometric study on cerebral vessels in spontaneously hypertensive rats.

The ratio between media thickenss and lumen radius was determined in cerebral arterial vessels of 15- and 200-day-old spontaneously hypertensive (SHR) and normotensive rats (Kyoto Wistar and local Wistar rats). A modification of Furuyama's morphometrical method was used. There was a statistically significant increase of media/radius ratio among medium size and large vessels in 15-day-old SHR. Furthermore, the media cross section area and lumen radius was increased in the internal carotid arteries of young SHR. These early vascular aberrations could be caused by the slight increase of blood pressure at this age or be due to other genetically determined mechanisms in SHR. In 200-day-old SHR a significantly increased media/radius ratio was seen in arterial vessels with a radius less than 80 microns when compared to local Wistar rats but only in the smaller arterioles (r less than 20 microns) when compared to Kyoto Wistar rats. The present results offer a likely explantation for the increased cerebrovascular resistance during maximum vasodilatation in SHR.

Animals↗
PubMedDate not supplied

The morphometry of consecutive segments in cerebral arteries of normotensive and spontaneously hypertensive rats.

The media cross-sectional area, the media thickness, the internal radius and the ratio between media thickness and internal radius were determined in consecutive sections of extraparenchymal cerebral arteries of 7- and 12-month-old normotensive and spontaneously hypertensive rats. The study included intracranial pial and basal arteries as well as extracranial cervical arteries. In the chronically hypertensive rats the media to radius ratio was consistently higher than in normotensive rats over the entire calibre spectrum investigated (radius 5-400 micron). The increase of the ratio in the extracranial arteries of the hypertensive rats was exclusively due to a thicker media. In the basal intracranial arteries the increase of ratio was due to a thicker media and/or a smaller internal radius in 7- and 12-month-old rats with moderate hypertension (mean arterial pressure, MAP 171 +/- 8 and 177 +/- 7 mm Hg respectively). In 7-month-old rats with severe hypertension (MAP 204 +/- 11 mm Hg) the increase of ratio was mainly due to a smaller internal radius. The observed structural alterations are likely to be of hemodynamic importance.

Aging↗
PubMedDate not supplied

Estrogen receptors in giant cell arteritis. An immunocytochemical, western blot and RT-PCR study.

OBJECTIVE: Giant cell arteritis (GCA) is a chronic form of vasculitis which predominantly affects women over 50 years of age. The aim of this study was to analyse the presence of estrogen receptor alpha (ER) in the temporal arteries of patients with GCA. METHODS: Inflamed temporal artery biopsies from 43 GCA patients were stained with monoclonal antibodies to two different segments of the ER and compared with non-inflamed arteries from age- and sex-matched controls who had not received a clinical diagnosis of GCA. The protein that was extracted from 4 GCA-positive biopsies and 4 non-GCA controls was analysed using the Western blot method with a monoclonal antibody to ER. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis using primer pairs specific to ER-cDNA was performed on the total RNA from 4 GCA-positive biopsies and 4 non-GCA controls. RESULTS: The inflamed arteries expressed distinct cytoplasmic immunoreactivity to ER in activated mononuclear inflammatory cells and in giant cells. Biopsies from GCA patients and controls displayed cytoplasmic ER positivity in smooth muscle cells. Western blot analysis revealed two bands corresponding to approximately 64 and 54 kDa, respectively, in the inflamed arteries and controls. In the inflamed biopsies and non-GCA controls, RT-PCR analysis revealed a strong band corresponding to approximately 670 bp, as expected, and a weaker band corresponding to approximately 440 bp. CONCLUSION: In inflamed arteries from GCA patients, smooth muscle cells, activated mononuclear inflammatory cells and giant cells express cytoplasmic ER. Non-inflamed control arteries also express cytoplasmic ER in smooth muscle cells. The accumulation of cytoplasmic ER may suggest the involvement of estrogen not only in GCA but also in normal vascular aging. The results justify further investigations into the pathogenetic roles of estrogen metabolism in GCA.

Aged↗