Effects of Na-Ca exchange on cartilage swelling and fluid transport

The generalized triphasic theory has been developed for describing mechanoelectrical behaviors of charged-hydrated-soft tissues containing multi-electrolytes. In the present work, this theory is used to study the problem Na super(+)-Ca super(++) exchange in cartilage. In particular, the effects of Na super(+)-Ca super(++) exchange on the one-dimensional swelling behavior of the tissues is investigated by determining the transport of Na super(+) and Ca super(++) across the throughout the layer of tissue, and by calculating the stresses, strains and fluid velocities within the tissue induced by the Na super(+)-Ca super(++) exchange. The stresses strains and fluid velocities within the tissue were calculated using a finite-difference method. Calculation results showed that the strain distribution within the specimen was non-monotonic and nonlinearly dependent on the local concentrations of Na super(+) and Ca super(++) present

Electrical potentials associated with passive ion transport across chondrocyte membranes

Previous studies on cartilage metabolism have focused on how mechanical signals are transmitted from the extracellular matrix into the cell to influence its synthesis activities as well as on mRNA expression. Mechanical loading on cartilage causes interstitial fluid flow, solid matrix deformation, streaming potential and other electrochemical effects which in turn cause passive ion transport across the cell membranes. This study determines the mechano-electrochemical events associated with the passive ion transport and fluid flow across a chondrocyte membrane. The passive ion transport across the thin membrane is described using a one-dimensional model. Several equations which provide the quantitative relationships between mechanical signals and electrochemical signals across the membrane are presented

Determination of Heavy Metals in Alpinia oxyphylla Miq. Collected from Different Cultivation Regions

20 batches of Alpinia oxyphylla Miq. were collected from Yunnan, Guangdong, Guangxi, and Hainan province in China. The contents of heavy metals of As, Hg, Pb, Cd, and Cu were determined and compared. The results indicated that geographical source might be a major factor to influence the contents of heavy metals of arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu) in Alpinia oxyphylla Miq. Compared to the criteria of heavy metals, the contents of As, Hg, Pb, and Cd in almost all the samples were in accordance with The Green Trade Standards. The contents of Cu were higher than the criteria for heavy metals except the samples from Changxing town, Qiongzhong county, Maoyang town, Qiongzhong county, Wupo town, Tunchang county, and Nanlv town, Tunchang county, in Hainan province. The best cultivation regions of Alpinia oxyphylla Miq. were from Changxing town, Qiongzhong county, Maoyang town, Qiongzhong county, Wupo town, Tunchang county, and Nanlv town, Tunchang county, in Hainan province. This research would provide the scientific basis for quality control and standardization of Alpinia oxyphylla Miq

Determination of Heavy Metals in Alpinia oxyphylla Miq. Collected from Different Cultivation Regions

20 batches of Alpinia oxyphylla Miq. were collected from Yunnan, Guangdong, Guangxi, and Hainan province in China. The contents of heavy metals of As, Hg, Pb, Cd, and Cu were determined and compared. The results indicated that geographical source might be a major factor to influence the contents of heavy metals of arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), and copper (Cu) in Alpinia oxyphylla Miq. Compared to the criteria of heavy metals, the contents of As, Hg, Pb, and Cd in almost all the samples were in accordance with The Green Trade Standards. The contents of Cu were higher than the criteria for heavy metals except the samples from Changxing town, Qiongzhong county, Maoyang town, Qiongzhong county, Wupo town, Tunchang county, and Nanlv town, Tunchang county, in Hainan province. The best cultivation regions of Alpinia oxyphylla Miq. were from Changxing town, Qiongzhong county, Maoyang town, Qiongzhong county, Wupo town, Tunchang county, and Nanlv town, Tunchang county, in Hainan province. This research would provide the scientific basis for quality control and standardization of Alpinia oxyphylla Miq

Conditional equivalence of chemical loading and mechanical loading on articular cartilage

The objective of this paper is to ascertain the conditions for equivalence between chemical or osmotic loading and mechanical loading on articular cartilage. Constitutive equations for a charged-hydrated-soft tissue are given and chemical potentials are derived. Equivalence between chemical vs. mechanical load is discussed. Using the triphasic constitutive equations, it is shown that for every chemical load generated by a given concentration of polyethylene glycol (PEG) in a NaCl solution there corresponds an isotropic mechanical load, P sub(A), which imparts to the tissue an identical equilibrium deformation. However, the mechanical load must be delivered in an isotropic manner via rigid-porous, free-draining loading platens

Predictions of the Swelling-Induced Pre-Stress in Articular Cartilage

Due to the presence of fixed charges in articular cartilage, the tissue in situ is in a swollen state with its associated pre-stresses. In this paper, the triphasic theory, which models the tissue as a mixture of three phases (solid, fluid and ions), is used to predict the swelling-induced stresses and strains in a geometrically simplified (spherical layer) model of articular cartilage on the femoral or humoral head. The model predictions indicate that the residual stresses and strains depend strongly on the magnitude and distribution of the fixed charged density, matrix stiffness and the curvature of the layer of the tissue. This study indicates that specific models for each diarthrodial joint and cartilage layer must be developed in order to assess the relative importance of these three factors on influencing the residual-stress states within the tissue

A new constitutive model for hydration-dependent mechanical properties in biological soft tissues and hydrogels

It is challenging to noninvasively determine the mechanical properties of biological soft tissues in vivo. In this study, based on the biphasic theory and the transport models, a new constitutive model for hydration-dependent mechanical properties in hydrated soft materials was derived: [Formula: see text] , where H(A) = λ + 2μ is the aggregate modulus, ϕ(f) is the volume fraction of fluid (i.e., hydration), A and n (>2) are two parameters related to the transport properties of the biphasic materials. A linear model for hydration-dependent shear modulus in the literature was verified for hydrogels. The effects of tissue hydration on mechanical properties (aggregate modulus and Poisson’s ratio) were investigated. It was found that the value of Poisson’s ratio was very sensitive to the tissue hydration in soft materials with high water content. The predictions of the aggregate modulus and shear modulus for hydrogels by the model compared well with those from experimental results. This study is important for developing new techniques for noninvasively assessing the mechanical properties of biological soft tissues using quantitative MRI methods as well as for designing scaffolds with proper mechanical properties for tissue engineering applications