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The effect of compressive loading magnitude on in situ chondrocyte calcium signaling
Madden, Ryan M. J.,Han, Sang-Kuy,Herzog, Walter Springer Berlin Heidelberg 2015 Biomechanics and modeling in mechanobiology Vol.14 No.1
<P>Chondrocyte metabolism is stimulated by deformation and is associated with structural changes in the cartilage extracellular matrix (ECM), suggesting that these cells are involved in maintaining tissue health and integrity. Calcium signaling is an initial step in chondrocyte mechanotransduction that has been linked to many cellular processes. Previous studies using isolated chondrocytes proposed loading magnitude as an important factor regulating this response. However, calcium signaling in the intact cartilage differs compared to isolated cells. The purpose of this study was to investigate the effect of loading magnitude on chondrocyte calcium signaling in intact cartilage. We hypothesized that the percentage of cells exhibiting at least one calcium signal increases with increasing load. Fully intact rabbit femoral condyle and patellar bone/cartilage samples were incubated in calcium-sensitive dyes and imaged continuously under compressive loads of 10–40 % strain. Calcium signaling was primarily associated with the dynamic loading phase and greatly increased beyond a threshold deformation of about 10 % nominal tissue strain. There was a trend toward more cells exhibiting calcium signaling as loading magnitude increased ([FORMULA OMISSION] = 0.133). These results provide novel information toward identifying mechanisms underlying calcium-dependent signaling pathways related to cartilage homeostasis and possibly the onset and progression of osteoarthritis.</P>
Nanda Poddar,Kajal Kumar Mondal,Niall Madden 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.1
This paper describes the longitudinal dispersion of passive tracer molecules injected in a steady, fully developed, viscous, incompressible, laminar flow through an annular pipe with a first order heterogeneous boundary absorption at the outer wall, numerically using layer-adapted meshes. The model is based on steady advection-diffusion equation with Dirichlet and Robin boundary conditions. The solutions are discussed in the form of iso-concentration contours of the tracer molecules in the vertical plane. An artanh transformation is used to convert the infinite domain into a finite one. A combination of central finite difference and 2-point upwind scheme is adopted to solve the governing advection-diffusion equation. It is shown that how the mixing of tracers is affected by the shear flow, aspect ratio and the first-order boundary absorption. When the flow becomes convection dominated, the monotone finite difference on a uniform mesh does not work properly, so a layer-adapted mesh, namely a “Shishkin” mesh, is used to capture the layer phenomena at the different downstream stations. The present results are compared with existing experimental and numerical data and we have earned an excellent agreement with them. It is observed that, due to the use of layer adapted mesh, we have achieved a better agreement with the experimental data than some other previous results available in the literature, especially in the closest downstream location. The results of this study are likely to be of interest to understand the basic mechanism of dispersion process of solute in blood through a catheterized artery with an absorptive arterial wall.
Maria Azrad,Robin T. Vollmer,John Madden,Mark Dewhirst,Thomas J. Polascik,Denise C. Snyder,Mack T. Ruffin,Judd W. Moul,Dean E. Brenner,Wendy Demark-Wahnefried 한국식품영양과학회 2013 Journal of medicinal food Vol.16 No.4
Enterolactone and enterodiol, mammalian lignans derived from dietary sources such as flaxseed, sesame seeds, kale, broccoli, and apricots, may impede tumor proliferation by inhibiting activation of nuclear factor kappa B (NFκB) and vascular endothelial growth factor (VEGF). We examined the associations between urinary enterolactone and enterodiol with prostatic tumor expression of NFκB, VEGF, and Ki67 among 147 patients with prostate cancer who participated in a presurgical trial of flaxseed supplementation (30 g/day) for 30 days. Urinary enterolignans and tissue biomarkers were determined by high-performance liquid chromatography and immunohistochemistry, respectively. After supplementation, we observed significant correlations between intakes of plant lignan and urinary concentrations of total enterolignans (ρ=0.677, P<.0001), enterolactone (ρ=0.676, P<.0001), and enterodiol (ρ=0.628, P<.0001). Importantly, we observed that total urinary enterolignans and enterolactone were significantly and inversely correlated with Ki67 in the tumor tissue (ρ=−0.217, P=.011, and ρ=−0.230, P=.007, respectively), and a near-significant inverse association was observed for enterodiol (ρ=−0.159, P=.064). An inverse association was observed between enterolactone and VEGF (ρ=−0.143, P=.141), although this did not reach statistical significance. We did not observe an association between enterolignans and NFκB. In conclusion, flaxseed-derived enterolignans may hinder cancer cell proliferation via VEGF-associated pathways.
주영지,Anastasia M. Soreghan,Megan E. Elwood Madden,Gerilyn S. Soreghan 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.4
Sediment particle shape and microtexture are key parameters utilized for characterizing sediment transport and weathering (both physical and chemical) processes, which in turn are governed by environmental conditions such as climate. Assessing particle shape often involves either qualitative descriptors or time-consuming measurements of shape parameters by a human operator. This study employs a state-of-the-art, quantitative shape analysis instrument known as the “Morphologi G3” from Malvern Instruments, an automated microscope system capable of determining quantitative shape parameters via static image analysis of > 1000 particles in less than two hours. This instrument captures 2D projected images of particles and provides information on grain size measurements such as circle-equivalent diameter, length, width, perimeter, and area, as well as shape parameters such as circularity and convexity. As a case study, we conducted analyses on mud- and sand-sized particles collected from fluvial/alluvial systems of end-member climates to assess variations in sediment particle morphology potentially related to climate and/or transport distance and processes. Sediment samples were collected from fluvial systems in four contrasting climates: hot-arid (southeastern California, USA), hot-humid (eastern Puerto Rico), glacial-arid (proglacial stream of the Dry Valleys, Antarctica), and glacial-humid (Austerdalen proglacial stream, Norway). Results provide quantitative constraints on shape differences that relate to climate and transport, even for very fine-grained sand and mud size fractions. Comparison of the circularity of sediment particles from the four end-member climates indicates that the very fine sand fractions reflect differential physical abrasion and transport processes, whereas the morphology of the mud fraction seemingly imprints chemical weathering processes. We conclude that this new technique has great potential to further document impacts of climate on particle shape with applications to both modern and deep-time depositional systems.
Makela, J.T.A.,Rezaeian, Z.S.,Mikkonen, S.,Madden, R.,Han, S.K.,Jurvelin, J.S.,Herzog, W.,Korhonen, R.K. Published for the Society by Baillère Tinda 2014 OSTEOARTHRITIS AND CARTILAGE Vol.22 No.6
Objective: The aim of this study was to investigate the site-dependent changes in the structure and function of articular cartilage in the lapine knee joint at a very early stage of osteoarthritis (OA), created experimentally by anterior cruciate ligament transection (ACLT). Methods: Unilateral ACLT was performed in eight mature New Zealand white rabbits. ACL transected and contralateral (C-L) joints were prepared for analysis at 4 weeks after ACLT. Three rabbits with intact joints were used as a control group (CNTRL). Femoral groove, medial and lateral femoral condyles, and tibial plateaus were harvested and used in the analysis. Biomechanical tests, microscopy and spectroscopy were used to determine the biomechanical properties, composition and structure of the samples. A linear mixed model was chosen for statistical comparisons between the groups. Results: As a result of ACLT, the equilibrium and dynamic moduli were decreased primarily in the femoral condyle cartilage. Up to three times lower moduli (P < 0.05) were observed in the ACLT group compared to the control group. Significant (P < 0.05) proteoglycan (PG) loss in the ACLT joint cartilage was observed up to a depth of 20-30% from the cartilage surface in femoral condyles, while significant PG loss was confined to more superficial regions in tibial plateaus and femoral groove. The collagen orientation angle was increased (P < 0.05) up to a cartilage depth of 60% by ACLT in the lateral femoral condyle, while smaller effects, but still significant, were observed at other locations. The collagen content was increased (P < 0.05) in the middle and deep zones of the ACLT group compared to the control group samples, especially in the lateral femoral condyle. Conclusion: Femoral condyle cartilage experienced the greatest structural and mechanical alterations in very early OA, as produced by ACLT. Degenerative alterations were observed especially in the superficial collagen fiber organization and PG content, while the collagen content was increased in the deep tissue of femoral condyle cartilage. The current findings provide novel information of the early stages of OA in different locations of the knee joint.