Tribological and material properties for cartilage of and throughout the bovine stifle: support for the altered joint kinematics hypothesis of osteoarthritis

SummaryObjectivePrior studies suggest that ligament and meniscus tears cause osteoarthritis (OA) when changes in joint kinematics bring underused and underprepared regions of cartilage into contact. This study aims to test the hypothesis that material and tribological properties vary throughout the joint according to the local mechanical environment.MethodThe local tribological and material properties of bovine stifle cartilage (N = 10 joints with 20 samples per joint) were characterized under physiologically consistent contact stress and fluid pressure conditions.ResultsOverall, cartilage from the bovine stifle had an equilibrium contact modulus of Ec0 = 0.62 ± 0.10 MPa, a tensile modulus of Et = 4.3 ± 0.7 MPa, and a permeability of k = 2.8 ± 0.9 × 10−3 mm4/Ns. During sliding, the cartilage had an effective friction coefficient of μeff = 0.024 ± 0.004, an effective contact modulus of Ec = 3.9 ± 0.7 MPa and a fluid load fraction of F′ = 0.81 ± 0.03. Tibial cartilage exhibited significantly poorer material and tribological properties than femoral cartilage. Statistically significant differences were also detected across the femoral condyle and tibial plateau. The central femoral condyle exhibited the most favorable properties while the uncovered tibial plateau exhibited the least favorable properties.ConclusionsOur findings support a previous hypothesis that altered loading patterns can cause OA by overloading underprepared regions. They also help explain why damage to the tibial plateau often precedes damage to the mating femoral condyle following joint injury in animal models. Because the variations are driven by fundamental biological processes, we anticipate similar variations in the human knee, which could explain the OA risk associated with ligament and meniscus tears

Phase I clinical and pharmacology study of the novel epothilone analog BMS-247550 given weekly in patients advanced solid tumors

0info:eu-repo/semantics/publishe

Efeitos da nutrição mineral sobre o crescimento, aspecto, composição elementar e fixação de nitrogênio em Azolla

Azolla filiculoides Lam foi cultivado em solução nutritiva arejada, sempre desprovida de N combinado, sendo submetida aos seguintes tratamentos: omissão de P, K, Ca, Mg, S, Fe e Mo, excesso de Mn e Al. As plantas foram colhidas depois de 3 semanas da inoculação. Verificou-se que as deficiências de P, K, Ca e Mg provocaram diminuição na produção de matéria seca e na atividade de nitrogenase. A análise mineral mostrou que: a falta de um elemento provoca redução no seu teor; grande acumulo de Mo; diminuição no teor de Al (do inóculo ou contaminação) no tratamento menos S que garantiu o maior crescimento; efeitos inibitórios ou sinergísticos semelhantes aos descritos no caso de plantas superiores. A toxidez de Al e Mn causou, principalmente a primeira, redução no crescimento e na atividade da nitrogenase. Houve correlações positivas entre: N total e crescimento, atividade de nitrogenase e N total.The mineral nutrition of Azolla feliculoides Lam was studied in solutions deficient in phosphorus, potassium, calcium, magnesium, sulfur, iron and molybdenum, and in excess of Mn and Al. Dry weight, N2 fixation and mineral composition of Azolla were determined after 3 weeks. Phosphorus, potassium, calcium and magnesium deficiencies and excess of manganese and aluminium decressed growth severely and also depressed the activity of nitrogenase. Phosphorus deficiency improved the uptake of iron and zinc. Potassium deficiency increased the levels of phosphorus in dry matter. Magnesium deficiency caused lower uptake of K and better uptake of Ca, Fe and Mn. Sulfur deficiency reduced aluminium uptake and promoted the best growth. Positive correlations were found between: N content and dry matter, nitrogenase activity and N content