In-Situ Study on the Tensile Deformation and Fracture Mechanism of a Bimodal-Structured Mg-Gd-Y Alloy.

The as-extruded (EX) Mg-Gd-Y alloy studied here exhibited a bimodal structure, composed of fine dynamic recrystallized (DRXed) grains with random orientations and longitudinal coarse hot-worked grains. The slip analysis showed the DRXed grains exhibited mainly basal slips, while the hot-worked grains exhibited mainly prismatic slips during the tensile deformation. The distribution of geometrically necessary dislocations (GNDs) showed that there was strain partitioning between the fine and coarse grain regions. The hetero-deformation induced (HDI) hardening occurred between the two domains. It improves the strength and strain hardening capability of the alloy, leading to good strength-ductility synergy. Microcracks tended to nucleate at the DRXed grain boundaries, as well as at the interface between the two domains. The calculation of geometric compatibility parameter (m') indicated that strain incompatibility between the adjacent grains induced the crack nucleation. The toughening effect of the fine DRXed grains hindered the crack propagation. However, the major crack formed at the interface between the two domains propagated unstably, due to the high stress concentration and the large crack size, causing the final failure.

Evaluating the Effects of Tetrachloro-1,4-benzoquinone, an Active Metabolite of Pentachlorophenol, on the Growth of Human Breast Cancer Cells.

Tetrachloro-1,4-benzoquinone (TCBQ), an active metabolite of pentachlorophenol (PCP), is genotoxic and potentially carcinogenic. As an electrophilic and oxidative molecule, TCBQ can conjugate with deoxyguanosine in DNA molecules and/or impose oxidative stress in cells. In the current study, we investigated the effects of TCBQ on intracellular ROS production, apoptosis, and cytotoxicity against three different subtypes of human breast cancer cells. Luminal A subtype MCF7 (ER(+), PR(+), HER2(-)) cells maintained the highest intracellular ROS level and were subjected to TCBQ-induced ROS reduction, apoptosis, and cytotoxicity. HER2 subtype Sk-Br-3 (ER(-), PR(-), HER2(+)) cells possessed the lowest intracellular ROS level. TCBQ promoted ROS production, inhibited apoptosis, and elevated cytotoxicity (due to necrosis) against Sk-Br-3 cells. Triple-negative/basal-like subtype MDA-MB-231 cells were less sensitive towards TCBQ treatment. Therefore, the effect of prolonged exposure to PCP and its active metabolites on cancer growth is highly cancer-cell-type specific.

Hedyotis diffusa water extract diminished the cytotoxic effects of chemotherapy drugs against human breast cancer MCF7 cells.

Hedyotis diffusa is a Chinese herbal medicine widely used in combination with other herbal medicines such as Scutellaria barbata to treat various types of cancer. Late-stage and recurrent cancer patients usually use H. diffusa during chemotherapy in expecting to achieve additive or synergistic therapeutic effects. Several classes of active ingredients, including anthraquinones, iridoid glucosides and stigmasterols. have been isolated and characterized from H. diffusa. In the current study, we isolated alkaloid/flavonoid from H diffusa and showed that the crude alkaloid/flavonoid extract rather than its three major components possessed antitumor activity against human breast cancer cell line MCF7. Co-administration of H. diffusa water extract diminished the cytotoxicities of chemotherapy drugs doxorubicin, cyclophosphamide and docetaxel towards the MCF7 cells, implicating that H. diffusa should not be used during breast cancer chemotherapy.