Search

Equilibrium, creep, and dynamic behaviors of agarose gels (2.0–14.8%) in confined compression were investigated in this study. The hydraulic permeabilities of gels were determined by curve-fitting creep data to the biphasic model (J. Biomech. Eng. 102 (1980) 73) and found to be similar in value to those published in the literature (AIChE J. 42 (1996) 1220). A new relationship between intrinsic permeability and volume fraction of water was found for agarose gel, capable of predicting deformation-dependent permeabilities of bovine articular cartilage and 2% agarose gel published in literature. This relationship is accurate for gels and cartilage over a wide range of permeabilities (four orders of magnitude variation). The dynamic stiffness of the gels increases with gel concentration and loading frequency (0.01–1.0 Hz). The increase in dynamic stiffness with loading frequency is less pronounced for gels with higher concentrations. The results of this study provide a new insight into deformation-dependent permeability behavior of agarose gel and cartilage, and are important for understanding biological responses of cells to interstitial fluid flow in gel or in cartilage under dynamic mechanical loading. [Copyright &y& Elsevier]

Aim: To investigate whether apparent diffusion coefficient (ADC) histogram parameters based on whole solid tumour volume could differentiate high-grade (HGSOC) from low-grade serous ovarian carcinoma (LGSOC) and to correlate those parameters with the Ki-67 proliferation index.Materials and Methods: One hundred and seven patients with HGSOCs and 19 patients with LGSOCs confirmed at surgery and histology who underwent conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) were analysed retrospectively. ADC histogram parameters (including the mean, standard deviation [SD], 10th, 25th, 50th, 75th, and 90th percentiles, kurtosis, and skewness) were obtained using the whole solid tumour volume region of interest (ROI). The Mann-Whitney U test, Pearson's chi-square test, Fisher's exact test, kappa test, Spearman's correlation, and receiver operating characteristic (ROC) curves were used for statistical analyses.Results: For ADC histogram parameters, the mean (p<0.001), SD (p=0.003), and all percentiles (10th, 25th, 50th, 75th, and 90th percentile; all p<0.001) were significantly lower in HGSOC than in LGSOC, and the area under the ROC curve (AUC) was 0.717-0.807. Skewness was significantly higher in HGSOC than in LGSOC (p<0.001, AUC = 0.773); however, kurtosis was not significantly different between HGSOC and LGSOC (p=0.140). The 25th and 75th percentiles, SD and 10th percentile, and 75th percentile showed the highest sensitivity of 91.6%, specificity of 79.0%, and accuracy of 88.1%, respectively. All histogram parameters (except for kurtosis) were poorly correlated with the Ki-67 index (|r| = 0.191-0.274, p<0.05).Conclusion: ADC histogram parameters based on whole solid tumour volume can be helpful for differentiating between HGSOC and LGSOC. [ABSTRACT FROM AUTHOR]

Abstract: Exogenous administration of IGF-1 has been proposed as a therapy for disc degeneration. The objectives of this study were to develop a numerical model for quantitatively analysing exogenous administration of IGF-1 into the intervertebral disc (IVD) via intradiscal injection and to investigate the effects of IGF-1 administration on distribution of glucose and oxygen in the IVD. In this study, the reversible binding reaction between IGF-1 and IGF binding proteins was incorporated into the mechano-electrochemical mixture model. The model was used to numerically analyse transport of IGF-1, glucose, oxygen and lactate in the IVD after IGF-1 administration. The enhancement of IGF-1 on lactate production was also taken into account in the theoretical model. The numerical analyses using finite element method demonstrated that the binding reactions significantly affect the time-dependent distribution of IGF-1 in the IVD. It was found that the region affected by IGF-1 was smaller and the duration of the therapeutic IGF-1 level was longer in the degenerated disc with a higher concentration of IGF binding proteins. It was also found that the IGF-1 injection can reduce glucose concentration and increase lactate accumulation (i.e., lower pH) in the IVD and these influences were regulated by the IGF-1 binding reactions. This study indicated the complexity of intradiscal administration of growth factors, which needs to be fully analysed in order to achieve a successful outcome. The new theoretical model developed in this study can serve as a powerful tool in analysing and designing the optimal treatments of growth factors for disc degeneration. [Copyright &y& Elsevier]