The influence of particle clustering on the rheological properties of highly concentrated magnetic nanofluids.

In this paper the particle volume fraction and temperature dependence of the dynamic viscosity of highly concentrated transformer oil based magnetic nanofluids was investigated in the absence of an external magnetic field. The solid particle volume fraction dependence of the relative viscosity was found to be very well fitted by the Krieger-Dougherty formula, whence the mean ellipticity of the colloidal particles and the effective surfactant layer thickness were obtained. Using the information on the particles' size and shape statistics obtained from TEM, DLS and magnetogranulometry investigations, it was concluded that the magnetite nanoparticles agglomerate in small clusters of about 1.3 particles/cluster, due to the van der Waals interactions. The effective thickness of the oleic acid surfactant layer was estimated as about 1.4 nm, in very good agreement with the value resulted from previous SANS investigations.

Erythropoiesis-stimulating agent withdrawal and oxidative stress in hemodialysis.

AIMS: Variation of the action of erythropoiesis-stimulating agent (ESA) may modify oxidative stress in hemodialyzed (HD) patients. Our aim was to follow changes of oxidative stress during withdrawal and subsequent resumption of ESA therapy. PATIENTS AND METHODS: After a 14-day suspension of epoietin-beta treatment, 11 HD patients received epoietin-beta and 10 patients darbepoietin-alpha. The whole blood oxidized and reduced glutathione (GSSG, GSH) and erythrocyte malondialdehyde (E-MDA) concentrations and the erythrocyte superoxide dismutase (E-SOD) and catalase (E-CAT) activities were determined before the ESA-free interval (baseline) and at Weeks 2, 6, 10 and 14. RESULTS: In both groups, the ratios GSSG/ GSH were increased at Weeks 2 and 6 (p < 0.001). The E-MDA levels were elevated (p < 0.01) and the E-SOD activities were decreased (p < 0.001) at Week 6. By Week 14, these markers had returned to the baseline, whereas the GSH (p < 0.001) and E-CAT activity levels (p < 0.001) had increased. CONCLUSIONS: An increase in oxidative stress was revealed by the ratio GSSG/GSH directly after the short-term withdrawal of epoietin-b therapy in HD. This new finding may have implications in conditions involving transiently depressed ESA action. For both ESAs, the early phase of readministration was associated with similarly increased oxidative stress, with a subsequent return to the baseline level.

Use of metabolic pathway flux information in anticancer drug design.

The metabolic phenotype of tumor cells promote the proliferative state, which indicates that (a) cell transformation is associated with the activation of specific metabolic substrate channels toward nucleic acid synthesis and (b) increased expression phosphorylation, allosteric or transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate unlimited growth. It is evident that cell transformation due to various K-ras point mutations is associated with the activation of specific metabolic substrate channels that increase glucose channeling toward nucleic acid synthesis. Therefore, phosphorylation, allosteric and transcriptional regulation of intermediary metabolic enzymes and their substrate availability together mediate cell transformation and growth. In this review, we summarize opposite changes in metabolic phenotypes induced by various cell-transforming agents, and tumor growth-inhibiting drugs or phytochemicals, or novel synthetic antileukemic drugs such as imatinib mesylate (Gleevec). Metabolic enzymes that further incite growth signaling pathways and thus promote malignant cell transformation serve as high-efficacy nongenetic novel targets for cancer therapies.