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Biomedical subjects

T Räsänen

Publications and source records attributed to T Räsänen.

At least 19 recordsLinked to original sources
PubMed2000

Estrogen-dependent tensile properties of the rabbit knee medial collateral ligament.

The influence of oophorectomy or continuous administration of estradiol on the tensile properties of the rabbit knee medial collateral ligament was investigated. Young postpubertal female New Zealand white rabbits were either oophorectomized or underwent a sham operation. The sham-operated animals received in addition a daily dosage of 4 mg 17beta-estradiol. After 5 months the animals were killed, and the material properties of the bone-ligament-bone complex in one knee were determined using a material testing machine and video system, and compared to non-treated control animals. There was no difference in elastic modulus between the groups. However, the ligaments from low-dose estrogen-treated animals had a smaller cross-sectional area and a higher ultimate tensile strength than those from controls or oophorectomized rabbits (P<0.04-0.0003).

Animals↗
PubMed1999

Rat model of Achilles tendon disorder. A pilot study.

Three-month-old male rats were subjected 3 times weekly for 1 h to eccentric exercise of one triceps surae muscle (30 stimulations/min) under general anesthesia in order to induce Achilles tendon disorder corresponding to paratenonitis and tendinosis in man. Net muscle work during the sessions ranged between 0.67 and 4.37 mJ (mean 1.72, SD 0.77). After 9 and 13 sessions, respectively, 2 rats started to show gait alterations during the functional test which was performed 2-3 times weekly. These rats were killed after additional sessions which showed a worsening of the limp. The other trained rats and controls did not limp and were killed after 7-11 weeks. Histologic evaluation of the Achilles tendons from the exercised limb showed in the majority of the cases hypervascularization, increased number of nerve filaments and increased immunoreactivity for substance P and calcitonin gene-related peptide. The tendons from the nonstimulated limb looked normal. The distribution of collagen types I and II appeared normal in the tendon and its insertion to the calcaneus. Inflammation of the epi- and paratenon could be provoked in the rat, but tendon changes corresponding to chronic tendinosis did not develop within 11 weeks with the used training regime. The clinical relevance of this model for chronic tendon disease needs to be evaluated further.

Achilles Tendon↗
PubMed1999

Do more highly organized collagen fibrils increase bone mechanical strength in loss of mineral density after one-year running training?

The aim of this study was to evaluate the effects of long-term running training on the structural properties of bone. Ten beagle dogs ran according to a strenuous progressive program (up to 40 km/day) for 1 year. At the end of the training program, there was a significant reduction in bone mineral density (up to 9.7%) in the vertebrae of the runner dogs as compared with 10 sedentary control dogs. Polarized light microscopy of the vertebral trabecular bone, however, displayed proportionally higher retardation values of the collagen network of the runner dogs than of the sedentary dogs, suggesting a reorganization in a more parallel manner in the collagen fibrils. The concentration and cross-linking of collagen in the bones remained similar in both groups. No differences were observed in the force to failure of bones of the two groups nor in the histomorphometric analysis of the bones. We suggest that the collagen network in the bones accounted for the maintenance of the strength properties in the bones of the runner dogs despite the loss of mineral density.

Animals↗
PubMed1999

Articular cartilage compressive stiffness following oophorectomy or treatment with 17beta-estradiol in young postpubertal rabbits.

BACKGROUND: Changes in estrogen concentrations during adolescence (contraceptives, secondary amenorrhea) may influence cartilage mechanics and therefore its capacity to respond adequately to physical demands. The purpose of this study was to investigate the influence of oophorectomy or continuous administration of estradiol on cartilage compressive properties in an immature animal model. METHODS: Young postpubertal female New Zealand white rabbits were either oophorectomized (n=9) or underwent a sham-operation (n=8). The sham-operated animals received in addition a daily dosage of 4 mg 17beta-estradiol orally starting 3 weeks after surgery until death. After 5 months the animals were killed, and cartilage compressive properties (ramp and creep moduli) were determined at 4 defined knee joint regions by in situ indentation tests. Five age-matched rabbits were used as controls. RESULTS: Femoral cartilage stiffness (ramp and 15-s creep moduli) and thickness in oophorectomized animals were significantly higher than those in controls or estradiol-treated animals (p<0.05 and less), but there was no difference between the latter groups. Tibial cartilage showed less obvious treatment-dependent differences. The cartilage in the medial compartment was thicker than in the lateral one, and femoral cartilage was thinner than tibial cartilage (p<0.00005), irrespective of the treatment. CONCLUSIONS: Oophorectomy during adolescence led to increased femoral cartilage thickness and stiffness. The relevance of these findings for the development of cartilage disease has to be elucidated in the future.

Age Factors↗
PubMed1998

Maturation-related compressive properties of rabbit knee articular cartilage and volume fraction of subchondral tissue.

OBJECTIVE: Knowledge about the physiologic change in cartilage biomechanics, accompanying the structural remodeling of the cartilage bone unit during maturation, may have relevance to understand the development of joint disease. The purpose of this study was to investigate maturation-dependent changes of compressive properties of articular cartilage and volume fraction of subchondral tissue in healthy rabbit knees. METHODS: Cartilage compressive properties (instantaneous and creep moduli) were tested at seven defined knee joint regions of five young (ten weeks), five adolescent (eighteen weeks) and five adult (above thirty-one weeks) healthy rabbits with in-situ indentation tests. Morphometric analysis of volume fraction of subchondral tissue was carried out at four regions. RESULTS: Cartilage stiffness (instantaneous modulus) decreased between infancy and adolescence (P < 0.009), and stayed then the same. A simultaneous significant change in (50-second) creep modulus was only observed at one region, but both moduli correlated to each other. Subchondral tissue consisted of cancellous bone in the young, and formed a more solid bone plate not before adolescence. Its volume fraction increased from infancy to adolescence (P < 0.001), but stayed then the same. There was a significant inverse correlation between the volume fraction of subchondral tissue and cartilage stiffness at the four measured regions (R2 = -0.59). The arrangement of collagen fiber bundles in the deeper cartilage layers changed from a mesh-like structure in the young to a more perpendicular alignment in the adolescent and adult. CONCLUSION: The maturation-related change in compressive properties coincided with a conspicuous change in volume fraction of the subchondral tissue. The main change appeared around puberty.

Animals↗
PubMed1996

Regional variations of indentation stiffness and thickness of normal rabbit knee articular cartilage.

The rabbit knee is frequently used as an experimental model for cartilage repair, but the choice of different joint regions for such studies makes comparisons between methods difficult. Furthermore, there is only limited information available about the regional variations of the biomechanical properties in normal rabbit knee articular cartilage. In the present study in situ indentation tests were used to map the short-term stiffness and thickness of articular cartilage at seven locations (anterior and posterior areas of the medial and lateral femoral condyles, the patellar groove, and the central areas of the medial and lateral tibial plateaus) in nine normal rabbit knee joints. Short-term cartilage stiffness was described by elastic moduli under ramp loading and 15-s creep conditions. The moduli were calculated according to Hayes' single-phase elastic model. A moderate positive correlation (r = 0.54) between cartilage stiffness and thickness was found for rabbit femoral cartilage, but was not confirmed for tibial cartilage, which had the thickest, but also the softest cartilage of all areas. The cartilage in the patellar groove and the medial compartments of both femoral condyles and tibial plateaus was stiffer and thicker than that in the lateral components, similar to previous findings in dogs. However, the dog femoral cartilage was found to be stiffer at the anterior than at the posterior regions, but we found the opposite in the rabbit. These dissimilarities between animal models may be caused by different joint loading characteristics. Accordingly, in rabbits repair processes in the more anterior femoral areas with less stiff cartilage may not be comparable to repairs in more posterior areas where cartilage is stiffer.

Animals↗
PubMed1996

Neck injuries from skate blades in ice hockey: a report of three cases.

This article describes three neck slash injuries in amateur ice hockey players, with a fatal outcome in two. One player died of asphyxation secondary to hemorrhage into the respiratory passage, but the other died of hemorrhage from the main blood vessels in the neck, severed by the skate blade. All three were not wearing any neck protecting device. Neck slash injury from skate blades, as a preventable sports-related injury, and the need for neck protective equipment in preventing such injuries are discussed.

Adolescent↗
PubMed1996

The morphology of ligament insertions after failure at low strain velocity: an evaluation of ligament entheses in the rabbit knee.

The morphology of failed rabbit knee entheses is described after in vitro load to failure testing at low strain velocity. Avulsion fracture was the dominant failure mode both for the cruciate ligaments and the medial collateral ligament. The patellar ligament became avulsed in most cases from the patellar insertion. The ligamentous anterior attachment of the medial meniscus failed by a midsubstance rupture and the posterior fibrocartilaginous attachment by a rupture near to the meniscal horn. On histological inspection the failure characteristics usually appeared more elaborate, involving to different degrees all portions of the bone-ligament-bone complexes. Avulsion fracture through subchondral bone was often combined with a partial ligament midsubstance rupture. In few cases avulsion from the cement line was combined with a rupture between the uncalcified fibrocartilage and the ligament. The medial collateral ligament failed in one case entirely at the cement line of its femoral insertion. Horizontal rupture through the calcified fibrocartilage and a vertical cleavage crossing the tidemark were also observed. The superficial portion of the patellar ligament failed with a midsubstance rupture, and the deeper part with an avulsion through the calcified fibrocartilage or an avulsion fracture. The complex failure characteristics may be attributed to uneven loading, nonuniformity of the structure, and specific anatomical location. Subchondral bone beneath femoral and tibial insertions seems to be weaker than the transitional zone between soft tissue and hard bone at the enthesis. The overall inferior structural quality of a ruptured ligament has to be taken into account when parts of the original structure are used for suturing or reconstruction.

Animals↗
PubMed1995

Comparison of optical, needle probe and ultrasonic techniques for the measurement of articular cartilage thickness.

Analysis of the mechanical properties of articular cartilage necessitates determination of thickness of the tested tissue. To evaluate the suitability of different methods for thickness measurements, the thickness of bovine and canine knee articular cartilage was determined with optical (stereomicroscopic), needle probe and ultrasonic techniques. The results obtained with the stereomicroscope and the needle probe showed high, linear correlations (r = 0.97, n = 80). The mean thickness obtained with the needle was slightly higher than the optical thickness (0.88 +/- 0.36 mm vs 0.85 +/- 0.34 mm, mean +/- S.D., n = 80, p < 0.01, matched-pairs Student t-test) or the ultrasonic thickness (0.93 +/- 0.42 mm vs 0.87 +/- 0.36 mm, n = 45, p < 0.05). The high scatter between optical and ultrasonic thickness, considered to be due to complex measurement geometry of canine knee articular cartilage, invalidated the use of the A-mode, 10 MHz-ultrasonic device for thickness measurements. Based on the results of uncertainty analysis it is concluded that optical and needle probe methods can be used interchangeably when determining shear modulus of articular cartilage with indentation tests. However, if high area-aspect ratios (indenter radius-to-cartilage thickness ratios) are used in the indentation measurements uncertainty in shear modulus may be markedly increased due to possible errors in the measurement of cartilage thickness.

Animals↗
PubMed1993

Organizational factors influencing serious occupational accidents.

The aim of this article is to examine organizational factors influencing serious occupational accidents. The study was part of a larger project investigating 99 serious occupational accidents in southern Finland. A workplace analysis and an accident analysis were done at accident sites. In connection with this investigation, 73 victims, 91 foremen, and 83 co-workers were interviewed with a structured questionnaire. The results showed that the need to save time, tight schedules, and a lack of caution had a greater influence on accidents than did the foremen, co-workers, customers, professional pride, curiosity, or the wage system. Big companies had the lowest risk of serious occupational accidents. Accident risk was significantly greater for subcontractors than for main contractors.

Accidents, Occupational↗
PubMed1992

Chromium supplementation in impaired glucose tolerance of elderly: effects on blood glucose, plasma insulin, C-peptide and lipid levels.

Altogether twenty-six elderly subjects (aged 65-74 years) with persistent impaired glucose tolerance (World Health Organization (1985) criteria) identified in a population-based study, were randomly treated either with chromium-rich yeast (160 micrograms Cr/d) or with placebo for 6 months. The 24 h urinary Cr increased from 0.13 (SE 0.03) to 0.40 (SE 0.06) micrograms/d in the Cr group (n 13) but no change was found in the placebo group (n 11) (0.13 (SE 0.02) v. 0.11 (SE 0.02) micrograms/d). No significant change was observed in the oral glucose tolerance test (glucose dose 75 g; 0, 1 and 2 h blood glucose respectively): 5.3 (SE 0.1), 9.3 (SE 0.3), 8.2 (SE 0.3) mmol/l v. 5.0 (SE 0.1), 8.5 (SE 0.4), 7.3(SE 0.5) mmol/l in the Cr group; 4.9 (SE 0.2), 9.2 (SE 0.6), 8.1 (SE 0.3) mmol/l v. 4.8 (SE 0.2), 8.5 (SE 0.5), 7.0 (SE 0.6) mmol/l in the placebo group (baseline v. 6 months). Glycosylated haemoglobin, plasma insulin, C-peptide and apolipoprotein A1 and B levels remained unchanged, and no improvement was seen in serum total cholesterol (6.2 (SE 0.3) v. 6.4 (SE 0.3) mmol/l for the Cr group, 6.2 (SE 0.4) v. 6.5 (SE 0.3) mmol/l for the placebo group), high-density-lipoprotein-cholesterol (1.1 (SE 0.1) v. 1.2 (SE 0.1) mmol/l for the Cr group, 1.0 (SE 0.1) v. 1.1 (SE 0.1) mmol/l for the placebo group) or triacylglycerols (2.5 (SE 0.4) v. 2.0 (SE 0.4) mmol/l for the Cr group, 2.4 (SE 0.2) v. 2.5 (SE 0.2) mmol/l for the placebo group). The present results indicate that Cr supplementation does not improve glucose tolerance or serum lipid levels in elderly subjects with stable impaired glucose tolerance.

Aged↗
PubMed1985

Triggering infections in reactive arthritis.

Certain microbes like yersinia, salmonella, shigella, campylobacter, chlamydia, and possibly gonococcus can trigger reactive arthritis especially in patients of the HLA-B27 type. In the present study we have used serological and culture methods to identify the probable triggering infection in 50 consecutive HLA-B27 positive patients diagnosed as having reactive arthritis. The two most common triggering agents thus identified were Yersinia enterocolitica (12 patients) and Chlamydia trachomatis (11 patients). In addition six patients had high antistreptolysin O titres and two high teichoic acid antibody titres suggesting group A streptococci and Staphylococcus aureus as triggering agents. In 13 patients no preceding infection could be identified. The identity of the infective agent seems to have very little effect on the clinical picture of the reactive arthritis - the only difference between the various aetiological groups in the present material was absence of fever in the patients with a preceding C. trachomatis infection, of whom only one out of 11 had a temperature greater than or equal to 38 degrees C, whereas 13 of 16 patients with a preceding enterobacterial, and five of the eight patients with a streptococcal or staphylococcal infection had raised temperatures.

Arthritis, Infectious↗
PubMed1983

Occurrence of antibodies to teichoic acid in patients with diseases other than staphylococcal infection.

To determine the usefulness of the teichoic acid antibody (TAA) test in conditions where unspecific viral and bacterial antibodies are often encountered, we measured TAA by the gel-diffusion method in 475 patients without known staphylococcal disease; they included 213 patients with arthritis, 108 with liver diseases, 100 with gastro-intestinal disorders and 54 with acute pharyngitis. Positive controls were 104 patients with Staphylococcus aureus bacteraemia and 203 healthy adults were negative controls. Thirteen (6%) of the healthy adults had positive TAA titres (greater than or equal to 4), and the highest titre was 8 in two people (1%). Positive titres were found in 38% of patients with S. aureus bacteraemia and high titres (greater than or equal to 8) were seen in 24%. Among the patients with arthritis, positive TAA titres were found significantly more often than in healthy controls in patients with Yersinia arthritis (p less than 0.01) and systemic lupus erythematosus (SLE; p less than 0.02). In other patient groups, the percentage of positive TAA titres did not differ significantly from that in healthy adults. Eight (2%) of the 475 patients without known staphylococcal infection had TAA titres greater than or equal to 8 but these high titres were not associated with any particular disease group. Only two of these eight patients had slightly raised antibody to staphylococcal alpha-haemolysin. We conclude that the TAA test cannot be used as a reliable indicator of septic staphylococcal disease in patients with Yersinia arthritis or SLE, but that in general, TAA titres greater than or equal to 8 point strongly to S. aureus infection even in patients with autoimmune or liver diseases.

Adolescent↗
PubMed1981

Occurrence and specificity of antibodies against group-specific polysaccharides in beta-hemolytic streptococcal infections.

We studied the possibility of detecting beta-hemolytic streptococcal infections by determining antibodies against the group specific polysaccharides from streptococci of groups A, A-variant, C and G. The methods used were radio-immunoassay with these four polysaccharides and hemagglutination of group A polysaccharide sensitized erythrocytes. Significant increases in these antibodies were rare in tonsillitis patients, whereas high concentrations of antibodies could often be observed in association with severe systemic infections or rheumatic fever. Both strictly immunogen-restricted and crossreactive antibodies could be demonstrated by isoelectric focusing and inhibition of antigen-binding. Although previously considered nonexistent, group specific carbohydrate antibodies of IgM class could also be demonstrated.

Adolescent↗
PubMed1980

Mast cells and eosinophils as regulators of functional homeostasis in the gastric mucosa.

The numerous mast cells of the interstitial tissue of the gastric mucosa are the sites of histamine synthesis and storage. If this biogenic amine is liberated from these cells it transmits simulation of gastric acid secretion to the epithelial cells. However, the effect of this released histamine is limited by the eosinophilic leukocytes, which find their way to the origin of histamine and decompose it. The functional level of these two kinds of cells is controlled by the neuroendocrine system.

Animals↗