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Biomedical subjects

Lars Carlsson

Publications and source records attributed to Lars Carlsson.

7 recordsLinked to original sources

Circular fingerprints: flexible molecular descriptors with applications from physical chemistry to ADME.

Circular fingerprints -- the representation of molecular structures by atom neighborhoods -- have been applied to a wide range of applications, such as similarity searching and the prediction of absorption, distribution, metabolism, excretion and toxicity properties. In recent years there has been a surge in applications resulting from the superior performance of circular fingerprints in comparative studies. This feature examines the nature of circular fingerprints as well as their applications, including virtual screening, metabolism prediction and the estimation of pK((a)) constants.

Algorithms↗

Proliferation and differentiation potential of chondrocytes from osteoarthritic patients.

Autologous chondrocyte transplantation (ACT) has been shown, in long-term follow-up studies, to be a promising treatment for the repair of isolated cartilage lesions. The method is based on an implantation of in vitro expanded chondrocytes originating from a small cartilage biopsy harvested from a non-weight-bearing area within the joint. In patients with osteoarthritis (OA), there is a need for the resurfacing of large areas, which could potentially be made by using a scaffold in combination with culture-expanded cells. As a first step towards a cell-based therapy for OA, we therefore investigated the expansion and redifferentiation potential in vitro of chondrocytes isolated from patients undergoing total knee replacement. The results demonstrate that OA chondrocytes have a good proliferation potential and are able to redifferentiate in a three-dimensional pellet model. During the redifferentiation, the OA cells expressed increasing amounts of DNA and proteoglycans, and at day 14 the cells from all donors contained type II collagen-rich matrix. The accumulation of proteoglycans was in comparable amounts to those from ACT donors, whereas total collagen was significantly lower in all of the redifferentiated OA chondrocytes. When the OA chondrocytes were loaded into a scaffold based on hyaluronic acid, they bound to the scaffold and produced cartilage-specific matrix proteins. Thus, autologous chondrocytes are a potential source for the biological treatment of OA patients but the limited collagen synthesis of the OA chondrocytes needs to be further explained.

Aged↗

Knee kinematics in medial arthrosis. Dynamic radiostereometry during active extension and weight-bearing.

We studied the kinematics of the knee during weight-bearing active extension in 14 patients with medial osteoarthrosis (OA) and in 10 controls using dynamic radiostereometry. Between 50 degrees and 20 degrees of extension the OA knees showed decreased internal tibial rotation corresponding to less posterior displacement of the lateral femoral flexion facet center. The midpoint between the two tips of the tibial intercondylar eminence occupied a more posterior position within the range of motion analyzed. The observed changes were similar to those previously recorded in chronic tear of the anterior cruciate ligament. Patients with medial arthrosis of the knee joint show a specific and abnormal pattern of joint motion.

Adolescent↗

Co-management: concepts and methodological implications.

Co-management, or the joint management of the commons, is often formulated in terms of some arrangement of power sharing between the State and a community of resource users. In reality, there often are multiple local interests and multiple government agencies at play, and co-management can hardly be understood as the interaction of a unitary State and a homogeneous community. An approach focusing on the legal aspects of co-management, and emphasizing the formal structure of arrangements (how governance is configured) runs the risk of neglecting the functional side of co-management. An alternative approach is to start from the assumption that co-management is a continuous problem-solving process, rather than a fixed state, involving extensive deliberation, negotiation and joint learning within problem-solving networks. This presumption implies that co-management research should preferably focus on how different management tasks are organized and distributed concentrating on the function, rather than the structure, of the system. Such an approach has the effect of highlighting that power sharing is the result, and not the starting point, of the process. This kind of research approach might employ the steps of (1) defining the social-ecological system under focus; (2) mapping the essential management tasks and problems to be solved; (3) clarifying the participants in the problem-solving processes; (4) analyzing linkages in the system, in particular across levels of organization and across geographical space; (5) evaluating capacity-building needs for enhancing the skills and capabilities of people and institutions at various levels; and (6) prescribing ways to improve policy making and problem-solving.

Community Participation↗

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 1. Horizontally cemented components: AP better fixated than MB.

BACKGROUND: Controversy still exists as to whether to mount the tibial bearing on a metal baseplate or not. Furthermore, the tibial component can be either horizontally or completely cemented. We evaluated metal backing versus all-polyethylene using horizontal cementing technique. PATIENTS AND METHODS: We randomized 40 patients with knee arthrosis (40 knees) to 2 groups: cemented total knee arthroplasty (AGC, Biomet) using either all-polyethylene (AP) or metal-backed (MB) tibial components (n = 20 for each group). All tibial implants had a total thickness of 8 mm. We used proximal cement-ing, including only the horizontal part of the tibia with avoidance of the stem-bone interface. RESULTS: The positioning of the implants, as judged by the HKA angle, showed an average neutral alignment in both groups. Preoperatively and after 2 years, there was no statistically significant difference between the HSS scores in both groups (p = 0.6 and 0.4). After 2 years, the metal-backed components had rotated more around the longitudinal axis, median 0.5 degrees vs. 0.2 degrees (internal or external rotation, p = 0.002), and showed increased maximum total point motion, median 1.0 vs. 0.4 mm (maximum migration or MTPM, p = 0.003). INTERPRETATION: Our study indicates that better fixation can be obtained with the all-polyethylene design if proximally cemented thin components are used.

Aged↗

All-polyethylene vs. metal-backed tibial component in total knee arthroplasty-a randomized RSA study comparing early fixation of horizontally and completely cemented tibial components: part 2. Completely cemented components: MB not superior to AP components.

BACKGROUND: Uncertainty exists as to whether metal backing (MB) of the tibial component is better than an all-polyethylene component (AP). This is valid for both horizontally and completely cemented components. We evaluated completely cemented MB vs. AP (Part 2). PATIENTS AND METHODS: In a randomized study, 39 patients (40 knees) with knee arthrosis were operated with cemented low-conforming total knee arthroplasty (AGC, Biomet) with a tibial component of uniform thickness (8 mm), cemented both beneath the tibial tray and around the stem. 20 patients had an all-polyethylene (AP) tibial component and 20 patients had an identical but metal-backed (MB) tibial component. We used clinical examination and radiostereometric analysis (RSA) to evaluate the hypothesis that MB improves component fixation. Fixation was evaluated using RSA up to 2 years after surgery. Clinical assessment was performed preoperatively and after 2 years using the Hospital for Special Surgeons (HSS) score. RESULTS: We found no differences in micromotion, and no differences in clinical scores could be detected between the groups at any time point. INTERPRETATION: Our findings indicate that there was equal initial fixation of the AP and MB stemmed monobloc components when they were cemented beneath the tibial plateau and around the stem.

Aged↗

Institutional frameworks for sustainability? A comparative analysis of the forest sectors of Russia and the Baltic States.

After the break-up of the Soviet system, the divergence in forest management among Soviet republics became obvious. While the forest sectors of the Baltic States have been fundamentally changed, Russia has not been able to develop an institutional framework that would fit the prerequisites for social-ecological resilience. It is argued that sustainable development requires institutional frameworks that have the capacity to adapt and learn, and thus to treat policies as experiments that are constantly assessed and readjusted. This, however, requires a participatory approach and in this respect the Baltic States are believed to be on a more promising track. Finally, it is concluded that only to the extent that suitable institutional frameworks will be developed will social-ecological resilience be a significant feature of the natural resources management in the former communist countries.

Baltic States↗