A rigorous homogenization theory is derived to describe the effective admittivity of cell suspensions. A new formula is reported for dilute cases that gives the frequency-dependent effective admittivity with respect to the membrane polarization. Different microstructures are shown to be distinguishable via spectroscopic measurements of the overall admittivity using the spectral properties of the membrane polarization. The Debye relaxation times associated with the membrane polarization tensor are shown to be able to give the microscopic structure of the medium. A natural measure of the admittivity anisotropy is introduced and its dependence on the frequency of applied current is derived. A Maxwell-Wagner-Fricke formula is given for concentric circular cells, and the results can be extended to the random cases. A randomly deformed periodic medium is also considered and a new formula is derived for the overall admittivity of a dilute suspension of randomly deformed cells.Mathematics Subject Classification (MSC2000): 35R30, 35B30.

The progression of cancers and neurodegenerative disorders is largely defined by a set of molecular determinants that are either complementarily deregulated, or share remarkably overlapping functional pathways. A large number of such molecules have been demonstrated to be involved in the progression of both diseases. In this review, we particularly discuss our current knowledge on p53, cyclin D, cyclin E, cyclin F, Pin1 and protein phosphatase 2A, and their implications in the shared or distinct pathways that lead to cancers or neurodegenerative diseases. In addition, we focus on the interdependent regulation of brain cancers and neurodegeneration, mediated by intercellular communication between tumor and neuronal cells in the brain through the extracellular microenvironment. Finally, we shed light on the therapeutic perspectives for the treatment of both cancer and neurodegenerative disorders. Keywords Age-related diseases • Cell death • Cell survival • Redox system • Glioma • Neurotoxicity Abbreviations Aβ Amyloid-β AD Alzheimer's disease ALS Amyotrophic lateral sclerosis AMPA α-Amino-3-hydroxy-5-methyl-4isoxazolepropionate APC/C Anaphase promoting complex/ cyclosome APP Amyloid precursor protein ATRA All-trans retinoic acid APL Acute promyelocytic leukemia Bax Bcl-2 associated X BH3 Bcl-2 homology 3 Bim Bcl-2-interacting mediator of cell death BimEL Bim-extra long CDK Cyclin-dependent kinase Cellular and Molecular Life Sciences

This paper provides an analysis of the linearized inverse problem in multifrequency electrical impedance tomography. We consider an isotropic conductivity distribution with a finite number of unknown inclusions with different frequency dependence, as is often seen in biological tissues. We discuss reconstruction methods for both fully known and partially known spectral profiles, and demonstrate in the latter case the successful employment of difference imaging. We also study the reconstruction with an imperfectly known boundary, and show that the multifrequency approach can eliminate modeling errors and recover almost all inclusions. In addition, we develop an efficient group sparse recovery algorithm for the robust solution of related linear inverse problems. Several numerical simulations are presented to illustrate and validate the approach.

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Quantum dots (QDs) are novel tools with multiple biological and medical applications because of their superior photoemission and photostability characteristics. However, leaching of toxic metals from QDs is of great concern. Therefore, for the successful application of QDs in bioscience, it is essential to understand their biological fate and toxicity. We investigated toxicological effects and tissue distribution of mercaptopropionic acid‐conjugated cadmium selenide/cadmium sulfide (CdSe/CdS‐MPA) QDs after repeated intraperitoneal injection into BALB/c mice. The mice were injected every 3 days with various doses of QDs (0, 5, 10 and 25 mg kg−1). The subsequent effects of QDs on plasma levels of various biomarkers were evaluated at different time points (at 0, 1, 4, 7, 10, 13 and 15 days). Various tissue samples (spleen, liver, lung, kidneys, brain, heart and thymus) were collected for toxicity analysis, distribution testing, histopathological examination and inflammation assessment. No abnormal clinical signs or behaviors were recorded but the body weight of mice treated with 25 mg kg−1 QDs was significantly decreased from day 7 compared with control mice. QDs were observed in the liver, spleen, lung and kidneys, but not in brain or heart. Significantly higher levels of lactate dehydrogenase and nicotinamide adenine dinucleotide phosphate oxidase were found in the plasma, liver and spleen. Histopathological examination did not show any tissue toxicity but the levels of interleukin‐6, a pro‐inflammatory marker, were increased in the plasma, liver and spleen. All of these findings provide insight into the observed toxicological effect levels and tissue‐specific distribution of CdSe/CdS‐MPA QDs. Copyright © 2012 John Wiley & Sons, Ltd.

The objective of this study was to evaluate the permeation of paraben derivatives - methylparaben (MP), propylparaben (PP), and butylparaben (BP) - in hairless mouse full skin and human cadaver epidermis using a Franz diffusion cell method, which is proposed as a reliable alternative method to an skin absorption test. Parabens, esterified hydroxybenzoic acid compounds, are widely used as preservatives in food, cosmetics, and pharmaceutical products. The skin permeation rate showed dose dependency, and the hairless mouse full skin showed a higher flux value than human cadaver epidermis. Among the permeability coefficient (K) values of three parabens, MP showed a higher K value than PP or BP. Hence, according to the definitions of Marzulli et al., parabens would be classified as "moderate" penetrants.

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