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Biomedical subjects

K Messner

Publications and source records attributed to K Messner.

At least 37 records · Page 2Linked to original sources
PubMed1998

Oxidation of phenanthrene by a fungal laccase in the presence of 1-hydroxybenzotriazole and unsaturated lipids.

Phenanthrene, a polycyclic aromatic hydrocarbon, was efficiently oxidized by laccase in the presence of both 1-hydroxybenzotriazole and unsaturated lipids. 73% of initially added phenanthrene was degraded within 182 hours to give phenanthrene-9,10-quinone and 2,2'-diphenic acid as the major products. The system was also able to peroxidize linoleic acid to its corresponding hydroperoxides suggesting the involvement of lipid peroxidation in laccase catalyzed phenanthrene oxidation. Lipid peroxidation by laccase required 1-hydroxybenzotriazole and did not depend on Mn2+ and H2O2 suggesting that the chemical reactions involved differ from those previously reported for manganese peroxidase.

Basidiomycota↗
PubMed1998

The menisci of the knee joint. Anatomical and functional characteristics, and a rationale for clinical treatment.

The menisci and their insertions into bone (entheses) represent a functional unit. Thanks to their firm entheses, the menisci are able to distribute loads and therefore reduce the stresses on the tibia, a function which is regarded essential for cartilage protection and prevention of osteoarthrosis. The tissue of the hypocellular meniscal body consists mainly of water and a dense elaborate type I collagen network with a predominantly circumferential alignment. The content of different collagens, proteoglycans and nonproteoglycan proteins shows significant regional variations probably reflecting functional adaptation. The meniscal horns are attached via meniscal insertional ligaments mainly to tibial bone. At the enthesis, the fibres of the insertional ligaments attach to bone via uncalcified and calcified fibrocartilages. This anatomical configuration of gradual transition from soft to hard tissue, which is identical to other ligament entheses, is certainly essential for normal mechanical function and probably protects this vulnerable transition between 2 biomechanically different tissues from failure. Clinical treatment of meniscal tears needs to be based on these special anatomical and functional characteristics. Partial meniscectomy will preserve some of the load distribution function of the meniscus only when the meniscal body enthesis entity is preserved. Repair of peripheral longitudinal tears will heal and probably preserve the load distribution function of the meniscus, whereas radial tears through the whole meniscal periphery or more central and complex tears may be induced to heal, but probably do not preserve the load distribution function. There is no proof that replacement of the meniscus with an allograft can reestablish some of the important meniscal functions, and thereby prevent or reduce the development of osteoarthrosis which is common after meniscectomy. After implantation, major problems are the remodelling of the graft to inferior structural, biochemical and mechanical properties and its insufficient fixation to bone which fails to duplicate a normal anatomical configuration and therefore a functional meniscal enthesis.

Animals↗
PubMed1998

Regional differences in cell shape and gap junction expression in rat Achilles tendon: relation to fibrocartilage differentiation.

Tendon cells have complex shapes, with many cell processes and an intimate association with collagen fibre bundles in their extracellular matrix. Where cells and their processes contact one another, they form gap junctions. In the present study, we have examined the distribution of gap junction components in phenotypically different regions of rat Achilles tendon. This tendon contains a prominent enthesial fibrocartilage at its calcaneal attachment and a sesamoid fibrocartilage where it is pressed against the calcaneus just proximal to the attachment. Studies using DiI staining demonstrated typical stellate cell shape in transverse sections of pure tendon, with cells withdrawing their cell processes and rounding up in the fibrocartilaginous zones. Coincident with change in shape, cells stopped expressing the gap junction proteins connexins 32 and 43, with connexin 43 disappearing earlier in the transition than connexin 32. Thus, there are major differences in the ability of cells to communicate with one another in the phenotypically distinct regions of tendon. Individual fibrocartilage cells must sense alterations in the extracellular matrix by cell/matrix interactions, but can only coordinate their behaviour via indirect cytokine and growth factor signalling. The tendon cells have additional possibilities--in addition to the above, they have the potential to communicate direct cytoplasmic signals via gap junctions. The formation of fibrocartilage in tendons occurs because of the presence of compressive as well as tensile forces. It may be that different systems are used to sense and respond to such forces in fibrous and cartilaginous tissues.

Achilles Tendon↗
PubMed1998

Age- and injury-dependent concentrations of transforming growth factor-beta 1 and proteoglycan fragments in rabbit knee joint fluid.

OBJECTIVE: The purpose of the study was to characterize maturation-related changes of TGF-beta 1 and proteoglycan fragment (PG) concentrations in joint fluid of healthy rabbit knees, and to investigate changes associated with osteochondral injury and spontaneous repair. METHODS: In 26 young (age range: 12-15 weeks), 26 adolescent (18-25 weeks), and 26 adult (33-44 weeks) New Zealand white rabbits, TGF-beta 1 and PG concentrations were analyzed in joint fluid samples which were taken before, and at several time intervals (max. 1 year) after creation of a osteochondral defect in the knee medial femoral condyle. At death, the characteristics of the regenerated tissue in the defect and any signs of degeneration of adjacent cartilage were recorded and graded. RESULTS: In preoperative samples, TGF-beta 1 and PG concentrations decreased with maturation (P < 0.01), and were moderately correlated (r = 0.51, P < 0.001). Shortly after trauma, the concentrations of both substances were found increased, which was followed by a decrease up to 3 months, and then again an increase up to 1 year. However, meanwhile PG concentrations had similar magnitude irrespective of age, TGF-beta 1 concentrations never reached similarly high levels in adulthood as in infancy or adolescence. The cartilage adjacent to the defect had more signs for degeneration in younger rabbits, and also osteophytes were more common in young than adult animals. CONCLUSION: The similar pattern for TGF-beta 1 and PG concentrations during postnatal maturation may reflect the stimulatory effect of TGF-beta 1 on proteoglycan synthesis. The higher TGF-beta 1 concentrations in younger animals may be a reason for their better healing capacity, but also for their higher susceptibility to osteoarthritic change compared to adult animals.

Aging↗
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↗
PubMed1998

Barriers to implementing a quality improvement program.

Critical barriers can prevent the implementation of an effective quality improvement (QI) program in the health care setting, including organizational culture, restructuring, quality assurance/quality control functions, QI teams and costs. Common pitfalls encountered that cause QI programs to falter--or worse, to fail--are discussed.

Costs and Cost Analysis↗
PubMed1998

Healing of the anterior attachment of the rabbit meniscus to bone.

In a rabbit model the healing process of the anterior attachment of the medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel. Evaluations of the healing tissue were histologic analysis, application of immunohistochemical methods to show collagen types and nerve regeneration, and mechanical load to failure tests. Secondary changes to knee joint cartilage, as signs of eventual dysfunction of the refixed meniscus, were evaluated by analysis of proteoglycan fragment concentration in joint fluid and histologic analysis of knee joint articular cartilage and synovium. The healing tissue between the refixed attachment and bone matured from highly cellular, nonspecific granulation tissue at 1 week, to bone, fibrocartilaginous, and fibrous tissues, which at some sites developed an insertion specific tissue arrangement within a 12-week period. However, the irregular interface between the fibrocartilaginous tissue and the underlying bone, which is typical for a normal insertion, was not reestablished. Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a few collagen fibers connected the refixed attachment tissue to bone. New bone formation turned the initially cancellous bone tunnel walls into more solid cortical bone. However, new bone formation did not fill the distal part of the channel. The refixed meniscal attachment underwent necrosis and was revitalized by cell ingrowth from the periphery. Nerve fibers were found in the newly formed insertion by 12 weeks. The failure load at tensile testing never reached more than 20% that of a normal attachment. Degeneration of articular cartilage and increased proteoglycan fragment in the joint fluid were common after this procedure. These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architecture of a normal meniscal insertion and a normal meniscal joint protective function were not reestablished.

Animals↗
PubMed1997

Maturation-dependent repair of untreated osteochondral defects in the rabbit knee joint.

Repair of untreated full-thickness cartilage defects in the medial femoral knee condyle was studied in 17 young, 21 adolescent, and 19 adult rabbits. At 6 weeks, the defect was completely filled by tissue regeneration in all young and adolescent animals, but in only few of the adults (p < 0.05). The morphology of all repairs improved from fibrous tissue to hyaline-like cartilage over time (p < 0.05), but at 3 and 6 weeks, the repair tissue in young and adolescent rabbits was more cartilage-like than in the adults (p < 0.05). In addition, bonding of the repair tissue to the adjacent cartilage was better in the young and adolescent than in the adult animals (p < 0.05). At 12 weeks, subchondral bone had formed in some young and adolescent repairs, but in no case in the adults. None of the repairs showed normal cartilage appearance, but formation of hyaline-like cartilage was common at 12 weeks. Irrespective of age or observation time, the repair site showed decreased stiffness and larger strain values compared to adjacent or control cartilage (p < 0.001) with no tendency for improvement over time. Younger animals showed a faster filling of the defect and an earlier specialization of the repair tissue than adult animals, but the mechanical quality of the regenerated tissue remained inferior to normal.

Aging↗
PubMed1997

Sequential scintigraphy and orthoradiographic measurement of femoral shortening after femoral neck fracture.

The objective of the study was to assess scintigraphic patterns and femoral shortening after femoral neck fracture in order to select predictive parameters for late complications. Eighty-eight patients with osteosynthesized femoral neck fractures were followed for 2 years with regular scintigraphic evaluations and orthoradiographic measurements of femoral length shortening. Four different patient categories were identified with regard to the late outcome two different groups with uneventful healing and two different groups with late complications. Accordingly, a high scintigraphic uptake at 1 month may either point to an uneventful healing if combined with minor femoral shortening or indicate failure if combined with a high degree of femoral shortening. In contrast, low scintigraphic uptake may either reflect primary fracture healing if accompanied by minor femoral shortening or predict failure if a high degree of femoral shortening is present. Compared with using scintigraphy alone, combined scintigraphic evaluation and assessment of femoral shortening increased the accuracy for prediction of late failures from 80% to 93%. Early scintigraphic patterns after osteosynthesis of femoral neck fractures have to be validated with care. Radiographic assessment of femoral shortening, which is less invasive, gives better prognostic accuracy and should therefore be preferred for this purpose.

Adult↗
PubMed1997

Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid.

PURPOSE: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. MATERIAL AND METHODS: Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographs and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid. RESULTS: The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injured knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p < 0.01). There were no changes in the controls. CONCLUSION: MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis.

Adolescent↗
PubMed1997

Postnatal development of the cruciate ligament insertions in the rat knee. morphological evaluation and immunohistochemical study of collagens types I and II.

The postnatal structural remodelling and calcification patterns in the insertions (entheses) of both cruciate ligaments were studied in a rat model with histology and immunohistochemical analysis of collagens types I and II. In the neonate, both ligaments which labelled only for type I collagen attached to epiphyseal cartilage which solely labelled for collagen type II. The entheses calcified between days 20 and 35, and a subchondral bone plate formed under the entheses between days 30 and 55. Thus, within a period of 35 days the tissue to which the ligaments attached increased multifold in stiffness. Interestingly, the process of enthesial calcification and formation of compact bone did not happen simultaneously in both ligaments, not even synchronous at both ends of the same ligament or within a single insertion. This asynchronous calcification of the different knee ligament insertions may make the sudden change in mechanical environment at the entheses less dramatic for the ligaments and knee joint surfaces as anticipated from mechanical models. In addition, a fibrocartilaginous tissue, rich in collagen type II, formed in the ligament at a time when the epiphyseal cartilage was replaced by bone, and grew wider with time. The interposition of a fibrocartilaginous zone in the insertion may diminish the sudden change in stiffness between ligament soft tissue and hard bone.

Animals↗
PubMed1996

Tensile strength of the tibial meniscal attachments in the rabbit.

The rabbit knee is a common model for meniscus replacement, but data on the failure load of its meniscal attachments are not available. Therefore we determined the tensile failure load of the normal attachment of the rabbit meniscus. Both knee joints of five adolescent New Zealand white rabbits were dissected, leaving only the menisci intact on the tibia. Both menisci were sectioned at the midpoint along the circumference, and the anterior attachment of the lateral meniscus and the anterior and posterior attachments of the medial meniscus were tested on a MTS 858 machine. In the rabbit, the posterior attachment of the lateral meniscus inserts on the femur and thus was not tested. All failures occurred within the soft tissue of the attachment. The anterior attachments had significantly different failure loads (lateral, 158 +/- 28N; medial, 108 +/- 25N), and both were stronger than the posterior attachment of the medial meniscus (75 +/- 23N, p < 0.05). There were no differences between left and right knees. The relatively high failure loads in the meniscus attachments may be indicative of the normal tensile loads developed in these structures and the demands on the fixation of a meniscal substitute.

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

The postnatal development of the insertions of the medial collateral ligament in the rat knee.

Bone soft tissue remodelling at the femoral and tibial insertions of the medial collateral ligament (MCL) of the rat knee was monitored at regular intervals from birth to 120 days of age in 40 Sprague Dawley rats. At birth the femoral insertion originated from the perichondrium of the epiphysis. By day 8 the perichondrium within the insertion had turned into fibrocartilage. Secondary ossification of the femoral epiphysis had progressed in the region near to the insertion site by day 15. The epiphyseal cartilage was entirely replaced by bone by day 40 except for the fibrocartilage within the insertion. After that stage, no qualitative change in zonal insertion characteristics was observed, but only increase in size and decrease in cellularity. At birth, the tibial ligament inserted onto the thin cortical bone of the metaphysis via periosteum. At day 8, osteoclasts started to resorb the thin cortical bone at the ligament insertion, thus forming a metaphyseal depression between days 10 and 20. From days 20 to 120, the insertion remained qualitatively unchanged, showing three zones, the ligament, periosteum, and metaphyseal trabecular bone. The deep periosteal layer showed osteoclastic activity in the proximal part and osteoblastic activity in the distal part. The migration-mechanism of the ligament insertion during growth seems to be caused by this growth-related osteoclastic resorption of the proximal metaphyseal bone and by simultaneous osteogenic activity, which successively cements the distal part of the ligament to bone. The persistence of the periosteal layer and the metaphyseal depression for up to 120 days may be regarded as a sign of continuing growth in this animal model. This is the first investigation showing that the formation of the metaphyseal depression is a purely postnatal event, and suggests that this process might be initiated by the change in mode of growth and joint biomechanics after birth, enabling ligament development and migration in a growing and increasingly loaded weight-bearing joint. The mainly resorptive process, which takes place during development of the tibial MCL insertion, may account for the tensile failure of this ligament that commonly occurs at this site during growth. The pronounced morphological differences between the chondral femoral and the periosteal tibial attachment of the adult MCL are apparently caused by the different postnatal development processes at epiphyses and metaphyses.

Animals↗
PubMed1996

An immunohistochemical study of enthesis development in the medial collateral ligament of the rat knee joint.

The changing distributions of collagens and glycosaminoglycans have been studied at the attachments of the medial collateral ligament during postnatal development. The ligament is of particular interest because it has a fibrocartilaginous attachment to the femoral epiphysis, but a fibrous one to the tibial metaphysis. Ligaments were examined in rats killed at birth and at 2, 4, 6, 8, 10, 20, 30, 45, 60, 90 and 120 days after birth. Cryosections were immunolabelled with monoclonal and polyclonal antibodies against types I and II collagen, chondroitin 4 and 6 sulfate, dermatan and keratan sulfate. Although the ligament is attached at both ends to bones that develop from cartilage, there was a striking difference in collagen labelling. Type II collagen was only found in spicules of calcified cartilage in bone beneath the tibial enthesis after ossification had commenced, but there was a continuous band of labelling at all stages of development at the femoral enthesis. Initially, the cartilage at the femoral attachment lacked type I collagen, but by 45 days labelling was continuous from ligament to bone. Continuity of labelling was seen much earlier at the tibial enthesis, as soon as bone had formed. There were also marked changes in glycosaminoglycan distribution. Keratan sulfate was present at both entheses up to 45 days, but only at the femoral enthesis thereafter. Both attachments labelled throughout life for dermatan sulfate, but chondroitin 4 and 6 sulfate were only found at the femoral end. The results suggest that enthesial cartilage at the femoral attachment was initially derived from the cartilaginous bone rudiment but was quickly eroded on its deep surface by endochondral ossification as bone formed at the attachment site. It was replaced by fibrocartilage developing in the ligament. This mechanism allows enthesis cartilage/fibrocartilage to contribute to the growth of a bone at a secondary centre of ossification in addition to dissipating stress at the ligament-bone junction.

Age Factors↗
PubMed1996

Rigid osteosynthesis decreases the late complication rate after femoral neck fracture. The influence of three different osteosynthesis devices evaluated in 369 patients.

The influence of three different fixation devices on late healing complications after femoral neck fractures was studied in a large patient group from three different hospitals. Except for the choice of device, which was unique to each hospital, all other factors having a potential influence on the late outcome, such as sex and age of the patients, initial degree of fracture dislocation and quality of surgical reduction were similar among the three groups. Within a 2-year observation period the incidence of late segmental collapses (14%-19%) was not related to choice of device, but a higher number of non-unions (27%-30%) occurred after adaptive non-rigid methods using screws (von Bahr) or a flanged nail (Rydell) than after a more rigid osteosynthesis (8%, Deyerle). Using such a rigid fixation, the complication rate could be reduced by one-third and the need for revision surgery halved. A device providing stable fixation should be preferred for treatment of femoral neck fractures in the elderly to prevent the healing complications related to insufficient stabilization.

Adult↗
PubMed1996

Chondral damage and age depress the long-term prognosis after partial meniscectomy. A 12- to 15-year follow-up study.

The effect of chondral damage and age on the long-term prognosis after partial meniscectomy was investigated in two matched groups of patients (n = 40), one with intact and the other with severely disrupted cartilage at the time of operation. Twelve to 15 years after meniscectomy a clinical and radiographic examination was done. Significantly more patients with intact cartilage (85%) than with chondral damage at operation (50%) had excellent or good knee function (P < 0.05). The activity levels decreased from active individual sports to physical fitness activities (P < 0.001), equally in both groups. Joint space reduction on roentgenograms was seen in 16 patients (80%) with chondral damage and in 6 patients (30%) with intact cartilage (P < 0.001). In addition to chondral damage, age over 30 years (P < 0.04) at the time of operation was associated with a worse functional (P < 0.03) and radiographic (P < 0.01) outcome.

Adolescent↗