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Biomedical subjects

O Svensson

Publications and source records attributed to O Svensson.

At least 73 records · Page 4Linked to original sources
PubMed1994

Fibromodulin distribution and association with collagen.

Fibromodulin, an acidic 59-kDa proteoglycan, binds to collagen and inhibits collagen fibril formation in vitro. To determine whether fibromodulin is also bound to collagen in vivo, we used immunocytochemical methods to study the spatial relation of the proteoglycan to collagen fibrils in cartilage and tendon. We also studied the quantitative distribution of fibromodulin among compartments in articular cartilage at the ultrastructural level. Fibromodulin was identified with polyclonal antibodies raised in rabbits, and immunoreactivity was detected with protein-A gold. As the major proportion of fibromodulin immunoreactivity was localized along the periphery of the collagen fibrils, the relationship to the banding pattern of the collagen fibrils was mapped. The proteoglycan showed a non-random distribution, with preference to the gap region, axially within the D-period. Reactivity differed among the tissue compartments, with the lowest degree of labelling pericellularly, increasing with distance from the cell, the highest levels being observed in the interterritorial matrix. Labelling density was highest at the articular surface, gradually decreasing towards the cartilage-bone junction. The correlation between collagen fibril diameter and fibromodulin concentration also varied among compartments. Thus, the ratio of fibromodulin to collagen surface density was highest at the surface of the joint cartilage, exhibiting a gradient with higher values in the territorial matrix, decreasing towards the cell in all layers. These findings indicate that fibromodulin represents a factor used by chondrocytes to regulate assembly and function of collagen fibrils.

Animals↗
PubMed1994

Comparison of threshold values between steroid and nonsteroid unipolar membrane leads.

The aim of this study was to evaluate whether steroid membrane leads can reduce pacing thresholds and thereby save energy as compared to nonsteroid membrane leads. The study was a random sample, double blind test consisting of 90 patients between 49-94 years of age admitted to seven hospitals in Europe for pacemaker implantation. The two leads compared in this study had contoured activated carbon tips covered with ion exchange membranes. The leads were identical except that 30 micrograms of dexamethasone was dissolved in the ion exchange membrane of one of the leads. Normal lead implant procedures were used. Follow-up procedures were conducted at 2 weeks and 1, 3, 6, and 12 months after lead implantation. The pulse generator was programmed to an amplitude of 2.5 or 5 V and a duration of 0.5 msec. The stimulation threshold was measured using the VARIO function. The threshold was measured a total of three times in order to determine the presence of microdislocations. At the 2- and 4-week follow-ups, the stimulation threshold was significantly lower for the steroid leads than for the membrane leads without steroid (0.54 +/- 0.19 vs 0.76 +/- 0.25 V, P = 0.0005; and 0.59 +/- 0.19 vs 0.74 +/- 0.26 V, P = 0.005), but after 3 months, the threshold values were almost the same for both leads.

Aged↗
PubMed1993

Long-term results of Boston brace treatment on vertebral rotation in idiopathic scoliosis.

The long-term effect of Boston brace treatment was investigated by computed tomography measurements before treatment, after bracing, and at mean follow-up at 8.5 years in 25 patients with idiopathic scoliosis. At follow-up, the pretreatment Cobb angle, the vertebral rotation, the rib hump, and the translation of the apical vertebra were not significantly changed. The sagittal diameter of the thoracic cage was significantly decreased at follow-up. The current study demonstrates that the Boston brace does not improve, but prevents progression of vertebral rotation, translation, rib hump, and Cobb angle in idiopathic scoliosis. The reduced sagittal diameter is noteworthy and may be of importance for cosmesis and pulmonary function.

Adolescent↗
PubMed1993

A qualitative and quantitative study of retrieved femoral heads in three different types of resurface hip arthroplasties.

Tissue reactions and percentage of mineralized bone in three different types of retrieved femoral head hip resurface prostheses were studied in undecalcified ground sections without removing the metal. All of the prostheses demonstrated soft tissue between the cement-implant and bone. There were some areas without soft tissue between bone and cement. This bone was often not normally stained, indicating a disturbed mineralization. The soft tissue layer in the cemented prostheses was observed in different stages of necrosis, while the uncemented prostheses demonstrated a thick collagen membrane. One of the cemented groups demonstrated a gradual decrease of mineralized bone towards the cement. The uncemented implants revealed normal bone qualitatively and quantitatively when the bone bordering the prosthesis was excluded. Too high interfacial stresses were probably a major failure mechanism, especially in the rapidly failed noncemented prostheses. Negative long-term effects of the cement on the bone may have contributed to failure in the cemented resurface arthroplasties.

Adult↗
PubMed1993

Tracking of changes in latency and amplitude of the evoked potential by using adaptive LMS filters and exponential averagers.

The adaptive LMS algorithm in combination with exponential averagers are compared to the use of exponential averagers only in tracking latency and amplitude changes in the evoked potential. The estimator is intended for use in applications where neurologic functions are monitored by detecting changes in the evoked potential. Two different structures of the estimator are evaluated and it is found that averaging before filtering is to be preferred. It is shown that the desired signal to the LMS-filter can have a rather low SNR with only mirror influence on the estimator performance. The estimator which combines an LMS-filter and an exponential averager was shown to detect changes in latency faster than the estimator which uses a nonfiltered average. The LMS-filter is shown to exhibit bias in the estimate of the evoked potential due to the fact that response and background spectra has overlapping frequency ranges. The bias seems not to affect the latency estimation while amplitude estimation was clearly affected. Simulations are performed with both white noise and EEG background.

Computer Simulation↗
PubMed1993

Stereologic studies on collagen in bovine articular cartilage.

In an ultrastructural stereologic study on bovine articular cartilage we found that collagen volume density increased with increasing distance from the joint surface and from the chondrocyte. These results not only corroborate previous biomechanical data of a vertical stiffness gradient, but they also suggest that the mechanical forces are unevenly distributed horizontally. On the other hand, although mean collagen fibril diameter showed large differences between the interterritorial compartments of the three zones, there was a population of slender fibrils in all zones and compartments. Since the coarser fibrils provide the high tensile strength (Nimni 1988), the role of the slender fibrils may be to enhance the deformability of the tissue. Moreover, in spite of substantial differences in mean fibril diameter, collagen surface densities were in the same order of magnitude in the territorial and interterritorial compartments, and only slightly lower in the pericellular compartments. The surface parameter may be important for specific molecular interactions. The collagen fibrils have different polarity, i.e. the direction of the fibrils appears to be parallel and antiparallel, about 50% running in each direction. This, together with the very high length/diameter ratio (Clark 1985), may indicate that each fibril is assembled by the concerted action of many cells. The characteristic properties of articular cartilage depend on interactions between its macromolecular components, and the present quantitative data form a basis for discussions on the specificity and regulation of such interactions.

Animals↗
PubMed1991

Parathyroid cell number and size in hypocalcemic young rats.

Weanling rats were fed diets with normal (1%) or low (0.08% or 0.02%, respectively) Ca content for 28 days prior to sacrifice. The total volume of the parathyroids was estimated from serial sections. Volume density of secretory cells was calculated according to conventional stereological techniques, whereas cell number and cell size were estimated by the dissector method. Compared with controls the animals of the experimental groups developed moderate and severe hypocalcemia and their parathyroids were enlarged with a proportional growth of parenchyma and interstitium. Related to the body weight, secretory cell volume was highest in animals with severe hypocalcemia. In the enlarged glands the size of parathyroid secretory cells was increased by 30-40%, whereas total cell number was unaltered. Thus, the increased parathyroid size was due to cell hypertrophy rather than hyperplasia.

Animals↗
PubMed1991

Anaerobic osteomyelitis--treatment with metronidazole in an experimental rabbit model.

Anaerobic micro-organisms are important agents in chronic bone infections. Their pathogenic role, however, is still unclear partly because of methodological reasons. In this paper an experimental model of osteomyelitis is used for studies of metronidazole treatment of bone infections induced by Bacteroides fragilis. The proximal tibial metaphyses of ten New Zealand white rabbits were excavated and filled with sheets of polyvinyl alcohol, into which a suspension of B. fragilis cells was injected on the right side, while saline was used on the left side. Within a month the animals showed immunological and radiological signs of an established bone infection. After 25 weeks of observation, four animals were treated with subcutaneous injections of metronidazole at a dosage of 10 mg/kg body weight twice daily for three weeks and five animals received saline. After 37 weeks the animals were killed. Radiological, histological and microbiological evaluation showed bilateral osteomyelitis in all animals. Prolonged raised titres of antibodies suggested an established infection, and not merely a colonization. There were no differences between the animals treated with metronidazole and the animals not treated.

Animals↗
PubMed1991

Anaerobic osteomyelitis. A new experimental rabbit model.

Experimental studies of osteomyelitis have been hampered by methodologic problems. For inducing experimental anaerobic osteomyelitis, the medullary cavity of the proximal tibial metaphysis of five New Zealand white rabbits was excavated and filled with a polyvinyl alcohol sponge. On the right side, 1 ml of a suspension containing Bacteroides fragilis (10(7) colony-forming units/ml) was injected, while on the left side, Ringer's solution was used as a control substance. Within five weeks, all animals developed clinical signs of osteomyelitis. The findings were verified by roentgenograms and bone scans. There was a significant rise in titers against the inoculated B. fragilis strain in every rabbit, and when killed at 18 weeks after the bacterial inoculation cultures containing the inoculated strain were obtained from all animals. No other bacterial strains were isolated. With one exception, cultures were positive in samples from both the inoculated and the control side, indicating hematogenous seeding. In one animal, the cultures from the inoculated side were negative, whereas on the control side, there was significant growth of the inoculated strain. Histologic examination of the infection sites showed low-grade chronic osteitis. In contrast to previous studies, which have indicated severe difficulty in obtaining a single-strain anaerobic osteomyelitis, the present method gives a high infection rate with reproducible immunologic, roentgenographic, and histologic reactions.

Animals↗
PubMed1990

Integrity of the gluteus medius after the transgluteal approach in total hip arthroplasty.

The postoperative integrity of the conjoined aponeurosis of the gluteus medius and vastus lateralis was studied in 97 consecutive total hip arthroplasties in 95 patients performed via a transgluteal approach. Metal markers were placed in the gluteal/vastus aponeurosis, one on each side of the suture line, and the integrity of the repair was assessed on radiographs taken immediately after surgery and 2 weeks, 2 months, and 1 year after operation. Separation between the markers occurred in about half of the patients, but gross separations were rare. Since most separations showed a progressive increment, elongation of the sutured aponeurosis might be a more common mechanism than perioperative injury to the neurovascular pedicle. Moreover, the degree of separation did not correlate with pain, and Trendelenburg gait was significantly increased only in the group of patients with a separation greater than 2.5 cm, indicating that a moderate gluteal elongation may be readily compensated for.

Buttocks↗
PubMed1990

Rickets induced by calcium or phosphate depletion.

We studied the effects of calciopenia and phosphopenia on longitudinal growth, skeletal mineralization, and development of rickets in young Sprague-Dawley rats. At an age of 21 days, two experimental groups were given diets containing 0.02% calcium or 0.02% phosphorus; otherwise the diets were nutritionally adequate. After 7, 14, and 21 days, five animals from each group were randomly chosen. The animals were anaesthetized and blood samples were drawn for analysis of calcium, phosphorus, and immunoreactive parathyroid hormone, whereupon the animals were killed. Length, weight, and specific weight of the left femur were measured. After 28 days on the respective diet the remaining animals were killed and one proximal tibia from each animal was processed for light microscopy and subjected to stereological analysis. Both experimental groups developed progressive growth retardation, more so the phosphate-depleted group. The calciopenic animals developed severe hypocalcaemia and secondary hyperparathyroidism, whereas the phosphate-depleted animals, in spite of marked secondary hypercalcaemia, had unaltered levels of immunoreactive parathyroid hormone. By 28 days both experimental groups displayed rachitic changes, more pronounced in the phosphate-depleted animals. This paper provides quantitative data demonstrating that calciopenia per se may cause rickets in young rats, but that the rachitic changes in this condition are less severe, and the growth pattern different from those in phosphate depletion.

Animals↗
PubMed1989

Parathyroid cell number and size in hypercalcemic rats: a stereologic study employing modern unbiased estimators.

Recently developed stereologic methods for unbiased estimations of particle number and size were employed to study parathyroid growth in normal and hypercalcemic young rats. Thus, the parathyroid cell number and size of parathyroid secretory cells were estimated by both the disector method and the volume-weighted mean volume method. The glandular volume was calculated from serial sections, and the volume density of secretory cells was estimated by conventional stereologic techniques. Three groups of animals were studied: normal rats at 3 weeks of age, hypercalcemic rats at 7 weeks of age, and age-matched controls. Hypercalcemia was induced by feeding the animals a purified diet that was nutritionally adequate except for low amounts of phosphate (0.02%) from 3 weeks of age. During the period from 3 to 7 weeks of age, the number of parathyroid secretory cells increased by 100%, whereas the mean cell volume increased by 20%. However, when calculated per gram body weight the volume and number of cells were larger in the younger animals. The phosphate-depleted animals grew slowly and developed severe hypercalcemia. Their parathyroid secretory cells were smaller, and each gland contained fewer cells than in age-matched controls. The lower cell number and cell volume, however, were proportional to the reduced body weight. Data from the 3-week-old animals indicate that the reduced cell number and size in hypercalcemic rats reflected growth arrest rather than atrophy.

Animals↗