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Biomedical subjects

H Steen

Publications and source records attributed to H Steen.

At least 37 records · Page 2Linked to original sources
PubMed2000

Minimal influence of facet joint anesthesia on isokinetic muscle performance in patients with chronic degenerative low back disorders.

STUDY DESIGN: Experimental design. OBJECTIVES: To examine the influence of pain reduction after facet joint injections on isokinetic back muscle performance. SUMMARY OF BACKGROUND DATA: Methods for evaluating the effect of facet joint injections vary. Recent studies base their results solely on the patient's subjective opinion and suggest a need for more objective, concrete, and reliable measurements. METHODS: Eighty-seven patients with a degenerative low back disorder (49 women and 38 men; mean age, 48 years; range, 22-79) who had facet joint injections as a part of preoperative evaluation participated. The mean duration of symptoms was 12.3 years (range, 1-45). The patients underwent isokinetic trunk flexor and extensor muscle strength testing at angular velocities of 60 deg/sec and 120 deg/sec. They performed two tests before the facet joint injections (to eliminate learning effect). All patients had bilateral facet joint injections at L5-S1. Those who did not report pain relief had additional injections at L4-L5. The flexion-extension test was repeated 15 minutes after each injection. Pain and fear were registered on visual analog scales. RESULTS: All 87 patients could perform the isokinetic tests. For extension at 60 deg/sec, a significant improvement was found between the two pretests (P < 0.05). Pain increased significantly from the first to the second pretest (P = 0.02), and a significant decrease in pain was found after the first injection (P = 0.0001). Fear decreased between each test, with a significant decrease after the first injection. No significant change was found for the muscle strength measurements after facet joint anesthesia. There were only weak correlations between decrease in pain and alteration in muscle performance, ranging from 0.06 to 0.37. CONCLUSION: Pain reduction after facet joint injections did not influence isokinetic muscle performance in patients with degenerative low back disorders.

Adult↗
PubMed2000

Detection and quantification of neurotensin in human brain tissue by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

A method was developed for mass spectrometric detection of neurotensin (NT)-like immunoreactivity and quantification of NT in human brain tissue. The method is based on immunoprecipitation followed by analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The identity of the major component of the immunoprecipitates as neurotensin was confirmed by fragment ion analysis on an electrospray ionization quadrupole time-of-flight instrument. MALDI-TOF-MS quantification of NT was achieved using stable-isotope-labeled NT as the internal standard, yielding an error of less than 5%. The method allowed detection of low-femtomole amounts of NT, staring from low-milligram amounts of lyophilized brain tissue. In addition to NT, several other peptides were detected in the purified samples, most of which, according to their molecular masses, corresponded to fragments of NT. The method is demonstrated with quantification of NT from human hypothalamus tissue, and a comparison is made with results obtained from competitive radioimmunoassay.

Brain Chemistry↗
PubMed2000

Reliability of goniometric measurements and visual estimates of hip ROM in patients with osteoarthrosis.

BACKGROUND AND PURPOSE: Range of motion (ROM) measurements have been included in several hip scores evaluating the results after hip surgery. The clinical procedures of performing these measurements vary and disagreement exists about the accuracy of visual estimatess compared to goniometer measurements. The purpose of this study was to study the reliability of goniometric measurements and visual estimates of hip ROM in patients with osteoarthrosis. METHOD: Hip ROM measurements (abduction, adduction, extension, flexion and internal/external rotation) were recorded by four different teams on the same day and were repeated one week later. Teams 1, 2 and 3 consisted of physiotherapists using standardized goniometric measurements. Team 4 involved an experienced orthopaedic surgeon making the assessments from visual estimates only. Twenty-five patients (6 M, 19 F; mean age 68.5 years, range 46-76 years) with osteoarthrosis of the hip, verified both clinically and radiologically, participated in the study. RESULTS: With the exception of abduction (p = 0.03), there were no significant differences between the measurements recorded on the first and the second occasions for the same teams. The coefficient of variance was 5.5% for flexion (lowest) and 26.1% for extension (highest). Reproducibility was best for flexion. There was also high reliability when all the arcs of motion were summed up (abuction + adduction + extension + flexion + internal/external rotation). With the exception of internal rotation, there were highly significant differences between the teams when two people performed the measurements compared to the values measured by a single individual. Concordance, expressed as the standardized agreement index, between visual estimates made by one individual (the orthopaedic surgeon) and goniometric measurements made by two experienced physiotherapists, were 0.77-0.83 which indicates good agreement. CONCLUSION: The reproducibility of hip ROM measurements was highest for flexion. There was also high reliability when all the six arcs of motion were summed up. Concordance between visual estimates and goniometric measurements indicates good agreement.

Aged↗
PubMed2000

Treatment of scoliosis with spinal bracing in quadriplegic cerebral palsy.

To evaluate the clinical results of the treatment and to assess the factors that influenced the rate of scoliosis progression, a retrospective study of spinal orthosis in 86 patients with spastic quadriplegic cerebral palsy was performed. The mean age of the patients was 13.8 years (range 5 to 33 years). Their scoliotic deformities were treated with custom-moulded, polypropylene thoraco-lumbar-sacral orthoses. Cobb angles were measured on radiographs taken in a sitting position before treatment, in orthosis, and during follow-up. The mean initial Cobb angle was 68.4 degrees (range 25 to 131 degrees). The mean correction in orthosis was 25 degrees (range 3 to 60 degrees). Seventy-two patients had a follow-up period of more than 2 years. At the latest follow-up, average 6.3 years (range 2 to 14 years) after the start of treatment, the mean Cobb angle without orthosis was 93.1 degrees (range 40 to 145 degrees). The mean progression per year was 4.2 degrees (range -3 to 21 degrees). Linear multiple regression revealed that age and initial correction in orthosis were the only variables that significantly influenced the rate of progression. Twenty-two patients had no progression or progression <1.0 degrees per year. Correction in orthosis was the only variable that predicted progression <1.0 degrees per year in both age groups (<15 years and > or =15 years). Of the 57 patients who were still alive and had not undergone surgical fusion, 72% used their orthoses at a mean age of 22 years. Parents and caregivers expressed satisfaction with the use of orthosis, mainly because of improved sitting stability which gave better overall function.

Adolescent↗
PubMed1999

Sensitivity to changes over time for the IKDC form, the Lysholm score, and the Cincinnati knee score. A prospective study of 120 ACL reconstructed patients with a 2-year follow-up.

The purpose of this study was to determine: (1) the sensitivity to changes over time for the IKDC form, the Lysholm score, and the Cincinnati knee score, (2) the relationship between the IKDC form, the Lysholm score and the Cincinnati knee score, (3) the criterion validity of each graded variable included in the IKDC form, and (4) if a functional knee test should be included as a graded variable and part of the final result of the IKDC form. We included in this prospective study 120 subjects who underwent ACL reconstruction with follow-up times of 3 and 6 months, and 1 and 2 years after surgery. Outcome measurements were the graded variables of the IKDC form (IKDC1-4 and IKDC-final), the Lysholm score, the Cincinnati knee score, a visual analogue scale for patient's satisfaction, knee joint laxity measurement (KT-1000 knee arthrometer), and two functional knee tests (the triple jump and stairs hopple tests). The IKDC1, IKDC2, IKDC-final, and the Lysholm score were not sensitive to changes over time. The Cincinnati knee score was highly sensitive to changes over time and showed significantly improved outcome between each follow-up. IKDC1-4 showed high criterion validity, indicating that the IKDC1-4 is a good means of documenting clinical examination at one follow-up, but not of detecting changes over time. The functional knee tests were significant outcome measurements after ACL reconstruction, and should be reported separately.

Adolescent↗
PubMed1999

Harvest of patellar tendon (bone-tendon-bone) autograft for ACL reconstruction significantly alters surface strain in the human patella.

The purpose of this study was to measure the effect of bone-patellar tendon-bone autograft harvest for anterior cruciate ligament (ACL) reconstruction on the surface strain of the human patella. Through progressive removal of bone from the patella, three different defect shapes as well as the intact patella were tested in each of seven knees. Maximum principal strain and corresponding principal direction were determined from each of three gages around the defect for the four conditions (intact plus three defect shapes). There were no statistically significant differences in overall average surface strain between any of the defect shapes. Following graft harvest, overall average strain (all three defects combined) increased in the patella both medial (15 percent increase) and lateral (34 percent increase) to the defect, while decreasing in the region directly proximal (22 percent decrease) to the harvest site compared to the intact patella. A statistically significant 7.5 deg shift of principal direction from longitudinal toward a more transverse (lateral-superior to medial-inferior) direction was observed in the medial region when a shallow-dome defect was made. We conclude that removal of a bone block from the anterior, inferior part of the patella induces a significant redistribution of the surface strain. This results in greater local strain adjacent to the upper border of the bone block increasing the risk for patella fracture. This effect may be of importance in various complications known to occur after ACL reconstruction.

Aged↗
PubMed1999

Lengthening of the tibia over an intramedullary nail, using the Ilizarov external fixator. Major complications and slow consolidation in 9 lengthenings.

We lengthened 9 tibial segments over a nail to reduce the time in the external fixator in 5 patients with constitutional shortness. The median lengthening was 7 (5.5-7.3) cm and the external Ilizarov frame was removed after median 99 (63-125) days. In spite of a short time in the external fixator, consolidation was slow, with a median lengthening index of 4.4 (2.4-6.1) months/cm. The procedure resulted in 3 fatigue fractures of the intramedullary nail or interlocking screws that needed revision and bone grafting. In 1 patient, a deep intramedullary infection occurred. After the experience of these major complications we have returned to the traditional callotasis lengthening method described by Ilizarov.

Achilles Tendon↗
PubMed1999

Reduced acetabular depth in hip instability in the newborn.

This study assessed the frequency of ultrasonographic hip instability and compared the results with clinical and morphological ultrasonographic evaluations of the hip in the newborn infant. Hip stability in 2016 consecutive births (1074 boys and 942 girls) was assessed clinically and ultrasonographically. Ultrasonography included dynamic stability testing and morphologic evaluations. Compared with ultrasonography, clinical stability testing had a specificity of 0.998 and a sensitivity of 0.667. The incidence of instability was 0.007 for hips and 0.010 for babies. Acetabular depth in 3994 normal hips was 8.3 +/- 0.9 mm, femoral head diameter was 15.4 +/- 1.3 mm, and acetabular bony coverage of the femoral head was 54 +/- 4.3%. Hip instability was significantly associated with a reduced acetabular depth. As the femoral head diameter was within normal in the unstable hips, coverage was significantly reduced.

Acetabulum↗
PubMed1998

Interactions between P-glycoprotein substrates and other cationic drugs at the hepatic excretory level.

1. In the present study it was tested whether known P-glycoprotein (P-gp) substrates/MDR reversal agents interact with small (type 1) and bulky (type 2) cationic drugs at the level of biliary excretion in the rat isolated perfused liver model (IPRL). The studies were performed with model compounds tri-n-butylmethylammonium (TBuMA) (a relatively small type 1 organic cation), rocuronium (Roc) (a bulky type 2 organic cation) and the classical P-gp substrate doxorubicin (Dox). 2. Inhibitors were given in a 4 fold molar excess to the substrate studied. To minimize an interaction of the substrates at the hepatic uptake level, the competing compounds were added when over 55% to 85% of the administered dose of the model compounds had been removed from the perfusate and taken up by the liver. 3. We found a mutual interaction between TBuMA and procainamidethobromide (PAEB), both type 1 cationic compounds during biliary excretion. Interestingly, type 2 compounds, such as rocuronium, clearly inhibited type 1 cationic drugs as well as Dox secretion into bile, whereas type 1 compounds did not significantly inhibit type 2 drug excretion into bile. The type 1 cations PAEB and TBuMA only moderately inhibited Dox biliary excretion. Dox did not inhibit the biliary excretion of the type 2 agent rocuronium whereas rocuronium reduced Dox biliary excretion by 50% compared to controls. 4. MDR substrates/reversal agents like verapamil, quinine, quinidine and vinblastine strongly reduced both type 1 and type 2 organic cation excretion into bile. Dox secretion into bile was also profoundly reduced by these drugs, vinblastine being the most potent inhibitor in general. 5. The lack of mutual inhibition observed in some combinations of substrates may indicate that major differences in affinity of the substrates for a single excretory system exist. Alternatively, multiple organic cation transport systems with separate substrate specificities may be involved in the biliary excretion of amphiphilic drugs. Furthermore, the present study revealed a clear positive correlation between the lipophilicity of the potential inhibitors studied and their respective inhibitory activity on the biliary excretion of the model drugs investigated. 6. Our data are compatible with a potential involvement of P-glycoprotein in the hepatobiliary excretion of doxorubicin as well as of some type 1 and type 2 organic cations. Furthermore we postulate that the hydrophobic properties of the amphiphilic cationic drugs studied play a crucial role in the accommodation of these agents by P-glycoprotein and/or other potential cationic drug carrier proteins in the canalicular membrane.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Evaluation of the mechanical environment during distraction osteogenesis.

Physical forces have been hypothesized to direct the process of bone regeneration during distraction osteogenesis. However, despite significant clinical experience, relatively little is known about how the mechanics of distraction influence bone formation. This study investigated net fixator forces and strains in the distraction callus during bilateral lengthening of tibiae in New Zealand White rabbits. Distractions yielded a classic viscoelastic response with a sharp increase in fixator force, followed immediately by significant relaxation. Tension acting on mesenchymal gap tissue caused by distraction was estimated to reach more than 30 N by the time full lengthening was achieved. Average maximum cyclic strains within the distraction zone during ambulation were estimated to be 14% to 15% and supported by the results of fluoroscopic imaging. Paradigms for fracture healing have hypothesized that such strains are incompatible with new bone formation. The documented clinical success of distraction osteogenesis at stimulating large volumes of new bone suggests that other mechanisms that warrant additional investigation may be at work during distraction.

Animals↗
PubMed1998

Effects of theophylline on tolerance to the bronchoprotective actions of salmeterol in asthmatics in vivo.

Long-term treatment with salmeterol produces tolerance for its protective effects against bronchoconstrictor stimuli in patients with asthma. There is human in vitro evidence that theophylline may prevent beta2-adrenoceptor downregulation. Therefore, we investigated the effect of theophylline on the tolerance to the protective effect of salmeterol against histamine challenge in asthma in vivo. In a parallel 6-wk study, 25 asthmatics were treated with theophylline (mean serum level +/- SEM: 9.9 +/- 1.1 mg/L, Days 1 to 40) or placebo, combined with inhaled salmeterol (50 microgram twice daily, Days 8 to 36). Histamine challenges were carried out by tidal breathing method at entry, and at Days 4, 8, 22, 36, and 40. The response was measured by PC20. There was no significant change in PC20 after 4 d monotherapy with theophylline or placebo (mean difference +/- SEM: 0.54 +/- 0.39 and -0.02 +/- 0.41 doubling dose [DD], respectively; p > 0.15). One hour after the first dose, salmeterol afforded significant protection against histamine, as shown by an increase in PC20 in both the theophylline and placebo group (by 3.49 +/- 0.28 and 3.36 +/- 0.32 DD, respectively; p < 0. 001). However, after 2 and 4 wk salmeterol treatment, the improvements in PC20 by salmeterol were significantly reduced to 1. 80 +/- 0.35 and 1.69 +/- 0.36 DD, respectively, in the theophylline group (p < 0.001), and to 1.55 +/- 0.47 and 1.52 +/- 0.56 DD, respectively, in the placebo group (p < 0.002). These changes were not significantly different between the groups (p > 0.80). After cessation of salmeterol treatment, PC20 was not significantly different from the values at entry in either group (p > 0.90). We conclude that regular theophylline treatment neither prevents, nor worsens, the development of tolerance to the bronchoprotective effect of salmeterol in asthmatics in vivo.

Administration, Inhalation↗
PubMed1997

Cross-cascade activation of ERKs and ternary complex factors by Rho family proteins.

Mitogens promote cell growth through integrated signal transduction networks that alter cellular metabolism, gene expression and cytoskeletal organization. Many such signals are propagated through activation of MAP kinase cascades partly regulated by upstream small GTP-binding proteins. Interactions among cascades are suspected but not defined. Here we show that Rho family small G proteins such as Rac1 and Cdc42hs, which activate the JNK/SAPK pathway, cooperate with Raf-1 to activate the ERK pathway. This causes activation of ternary complex factors (TCFs), which regulate c-fos gene expression through the serum response element. Examination of ERK pathway kinases shows that neither MEK1 nor Ras will synergize with Rho-type proteins, and that only MEK1 is fully activated, indicating that MEKs are a focal point for cross-cascade regulation. Rho family proteins utilize PAKs for this effect, as expression of an active PAK1 mutant can substitute for Rho family small G proteins, and expression of an interfering PAK1 mutant blocks Rho-type protein stimulation of ERKs. PAK1 phosphorylates MEK1 on Ser298, a site important for binding of Raf-1 to MEK1 in vivo. Expression of interfering PAK1 also reduces stimulation of TCF function by serum growth factors, while expression of active PAK1 enhances EGF-stimulated MEK1 activity. This demonstrates interaction among MAP kinase pathway elements not previously recognized and suggests an explanation for the cooperative effect of Raf-1 and Rho family proteins on cellular transformation.

3T3 Cells↗
PubMed1997

[Anisomelia. Clinical consequences and treatment].

The hypothesis that a causal relationship exists between unequal leg length and disorders in the back or lower extremities has been hard to prove. However, at the present time there is scientific documentation of an association between a difference in length of more than 1 cm and low back pain. Thus, in children with one leg one centimetre or more longer than the other, and in adults with symptoms, the discrepancy should be adjusted, especially if a lumbar scoliosis in the standing position has been documented radiographically. A difference in length of less than 2 cm should be treated by raising the shoe. An established or estimated difference of more than this is usually corrected by surgery, either by epiphysiodesis or by shortening or lengthening osteotomy. In adults with a moderate difference in leg length, a raised shoe test is recommended in order to evaluate the effect of a correction in practice before osteotomy is performed.

Adult↗
PubMed1997

Lack of concordance between mtDNA gene flow and population density fluctuations in the bank vole.

The genetic structure of bank voles Clethrionomys glareolus was determined from analyses of mitochondrial DNA (mtDNA) sequences, and compared with previous data on geographical synchrony in population density fluctuations. From 31 sample sites evenly spaced out along a 256-km transect in SE Norway a total of 39 distinct mtDNA haplotypes were found. The geographical distribution of the haplotypes was significantly non-random, and a cladistic analysis of the evolutionary relationship among haplotypes shows that descendant types were typically limited to a single site, whereas the ancestral types were more widely distributed geographically. This geographical distribution pattern of mtDNA haplotypes strongly indicates that the range and amount of female dispersal is severely restricted and insufficient to account for the previously observed synchrony in population density fluctuations. We conclude that geographical synchrony in this species must be caused by factors that are external to the local population, such as e.g. mobile predators.

Animals↗
PubMed1996

[The Ilizarov external fixator and method. Treatment of congenital and acquired deformities].

The Ilizarov method, with external fixation by means of rings, rods and wires, has been used at the Norwegian National Hospital, Orthopaedic Centre, since 1992. The method is unique in correcting multiplanar deformities in one surgical procedure. We have treated 70 patients with a wide variety of orthopaedic etiologies. Soft tissue and bone deformities in the lower extremity have been corrected separately or combined. The frequency of complications has been relatively high, but we still think that the Ilizarov method is useful to correct complex deformities in children and adults alike.

Adolescent↗
PubMed1996

Erythropoietic protoporphyria: two populations of reticulocytes, with and without protoporphyrin.

Erythrocytes from patients with erythropoietic protoporphyria contain large amounts of protoporphyrin. The photosensitivity experienced by these patients is assumed to be due to a leakage of protoporphyrin from the erythrocytes and transfer to the skin, where protoporphyrin acts as a photosensitizer. The leakage of protoporphyrin from the erythrocytes has been offered as an explanation for the great variety in protoporphyrin content observed among erythrocytes in this disease. Based on density gradient separation of red cells, it has been concluded that all reticulocytes and young erythrocytes contain large amounts of protoporphyrin. From our results, density gradient centrifugation is not suitable for age separation of red cells from patients with erythropoietic protoporphyria. By developing a new method for isolation of reticulocytes and applying flow cytometry to determine protoporphyrin content in individual cells, it was observed that two populations of reticulocytes were present in patients with erythropoietic protoporphyria, one with and the other without protoporphyrin. The half-life of protoporphyrin in red cells was found to be 12-14 days, in contrast to 1-2 days described previously, suggesting a slower release of protoporphyrin from the red cells than previously anticipated.

Cell Separation↗
PubMed1996

Negative regulation of Raf-1 by phosphorylation of serine 621.

The elevation of cyclic AMP (cAMP) levels in the cell downregulates the activity of the Raf-1 kinase. It has been suggested that this effect is due to the activation of cAMP-dependent protein kinase (PKA), which can directly phosphorylate Raf-1 in vitro. In this study, we confirmed this hypothesis by coexpressing Raf-1 with the constitutively active catalytic subunit of PKA, which could fully reproduce the inhibition previously achieved by cAMP. PKA-phosphorylated Raf-1 exhibits a reduced affinity for GTP-loaded Ras as well as impaired catalytic activity. As the binding to GTP-loaded Ras induces Raf-1 activation in the cell, we examined which mechanism is required for PKA-mediated Raf-1 inhibition in vivo. A Raf-1 point mutant (RafR89L), which is unable to bind Ras, as well as the isolated Raf-1 kinase domain were still fully susceptible to inhibition by PKA, demonstrating that the phosphorylation of the Raf-1 kinase suffices for inhibition. By the use of mass spectroscopy and point mutants, PKA phosphorylation site was mapped to a single site in the Raf-1 kinase domain, serine 621. Replacement of serine 621 by alanine or cysteine or destruction of the PKA consensus motif by changing arginine 618 resulted in the loss of catalytic activity. Notably, a mutation of serine 619 to alanine did not significantly affect kinase activity or regulation by activators or PKA. Changing serine 621 to aspartic acid yielded a Raf-1 protein which, when expressed to high levels in Sf-9 insect cells, retained a very low inducible kinase activity that was resistant to PKA downregulation. The purified Raf-1 kinase domain displayed slow autophosphorylation of serine 621, which correlated with a decrease in catalytic function. The Raf-1 kinase domain activated by tyrosine phosphorylation could be downregulated by PKA. Specific removal of the phosphate residue at serine 621 reactivated the catalytic activity. These results are most consistent with a dual role of serine 621. On the one hand, serine 621 appears essential for catalytic activity; on the other hand, it serves as a phosphorylation site which confers negative regulation.

Alanine↗