Instability analysis of spin-electron-acoustic waves and the appearance of separated spin electron cyclotron mode in spin-polarized magnetized quantum plasma.

Linear and nonlinear characteristics of electrostatic waves are studied in a magnetized plasma consisting of spin-up (n_{↑}) and spin-down (n_{↓}) state populations with uniformly distributed static ions in the background. The linear analysis shows the existence of four modes. One of these modes, termed the separated spin electron cyclotron wave, is found to be due to the separated spin populations. The Zakharov-Kuznetsov equation is derived by the reductive perturbation technique. The instability growth rate γ is obtained from the same equation. It is observed that the magnetized spin quantum plasma admits rarefactive soliton with constant amplitude but increasing width with the increasing strength of the applied magnetic field. It has also been observed that the amplitude of soliton decreases and its width increases with the increasing values of polarization ratio κ. The unstable region expands with the increase in polarization ratio and contracts with the increased plasma number density and magnetic-field strength. The (growth rate) γ of instability reduces by increasing the κ and is increasing when the density of the plasma and the strength of the magnetic field increasing. The model developed in this work finds its scope in studying degenerate electron gas and astrophysical systems such as pulsar magnetosphere and neutron stars.

Heterogeneous Cell Types in Single-cell-derived Clones of MCF7 and MDA-MB-231 Cells.

BACKGROUND/AIM: Variations in cell phenotype in a single-cell-derived clone may result from asymmetric cell divisions that lead to different cell fate in a homogenous microenvironment. The aim of this study was to demonstrate the extent of cell variety in single-cell-derived clones and propose a different strategy in treating cancer by observed phenotypic heterogeneity in cellular types. Additionally, the role of metabolic enzyme and housekeeping gene, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), in cellular phenotype was evaluated in two breast cancer cell lines. MATERIALS AND METHODS: Two GAPDH-overexpressing breast cancer cell lines, MCF7-GAPDH-RFP (MCF7-RFP) and MDA-MB-231-GAPDH-RFP (MDA-RFP), were established. Microscopic recordings were made at 12-h intervals in single-cell-derived clones of both cell lines up to 8-10 days. Crystal violet and Hoechst 33342 (Hoechst), as well as specific cell-type (epithelial and mesenchymal) antibodies, were used for cytochemical and immunohistochemical staining analyses, respectively, at 3, 6 and 9 days during cell growth. RESULTS: Three types of clones with distinct morphologies were identified as holo-, mero- and paraclones. The rates of colony survival during cell growth were 8.3 and 41.7% in MCF7-RFP and MDA-RFP, respectively. Although no significant difference was found in the colony forming efficiency (CFE) of both MCF7 and MDA-MD-231 wild-type cells, a markedly significant difference was seen in the CFE of MCF7-RFP and MDA-RFP cells (p=0.001). Wild-type cell-derived holoclones of both cell lines showed drug resistance to doxorubicin (Dox). However, levels of proliferating cell nuclear antigen (PCNA) and vimentin (VIM) marginally decreased in Dox-treated clones. Furthermore, high level of intraclonal heterogeneity was found for CD44, CD140a, VIM, fibronectin (FN), focal adhesion kinase (FAK), paxillin (PXN) and vinculin (VCL) in MCF7 and MDA clones during different stages of clonal development. Expressions of CD140a, FN, VIM and FAK were induced in GAPDH-red fluorescent protein (RFP)-tagged clones of both cell lines. CONCLUSION: The GAPDH-RFP recombinant protein played an important role in morphological heterogeneity detection in early stages of clonal development. Moreover, phenotypic heterogeneity in clones, caused by the cells expressing specific antigens, such as CD44, CD140a, FN, VIM, FAK and VCL, can be the right target for therapeutic drugs.

Azacytidine-induced Chemosensitivity to Doxorubicin in Human Breast Cancer MCF7 Cells.

BACKGROUND/AIM: It is necessary to select an appropriate strategy that makes cancer cells more sensitive to chemotherapeutic drug(s). The aim of this study was to further explore the mechanism(s) behind drug sensitization in the breast cancer MCF7 cell line using 5-azacytidine (AzaC) pretreatment in doxorubicin (Dox) chemotherapy. MATERIALS AND METHODS: Cells were treated with either AzaC or Dox alone or in combination (AzaC+Dox) for 24 and 48 h. Cells were also pretreated with AzaC for a week before replacement with Dox at varying concentrations in another group of experiments (AzaC/Dox) for 24 and 48 h. The cells in the groups were subjected to cytochemical analyses, including 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT), intracellular reactive oxygen species (ROS) and cell death by dual staining with Hoechst33342 (Hoechst) and propidium iodide (PI). Cells were also analyzed for determining specific alterations of possible target proteins by western blot. RESULTS: Compared to a single (AzaC and Dox) or simultaneous drug exposure (AzaC+Dox), cellular activity was significantly reduced in AzaC/Dox group of cells in a dose- and time-dependent manner (p<0.05). The clonogenic potential of cells was also significantly inhibited in AzaC/Dox compared to Dox and AzaC group after 7 days (p<0.05). The rates of ROS-generated and PI-stained cells were significantly higher in the AzaC+Dox and AzaC/Dox groups compared to those of individual drug groups at 48 h (p<0.05). These observations were accompanied by activation of ERK1/2 and p38MAPK, as well as up-regulation of BAX and P53 in the AzaC/Dox group. However, the levels of BCL-2 were down-regulated in Dox and AzaC+Dox among a different group of cells. Elevated levels of activated caspase-3 were observed only in AzaC/Dox group of cells. The levels of phospho-nuclear factor-kappa B (pNF-ĸB)(Thr) decreased with increasing dosage of Dox in different groups, while down-regulation of heat shock protein 70 (HSP70) was observed only in the AzaC+Dox group of cells. CONCLUSION: AzaC significantly increases the sensitivity of MCF7 cells to Dox via activation of ERK1/2, P53, BAX and caspase-3. Moreover, the inhibition of pNF-ĸB(Thr) and HSP70 might also contribute to an increase in the sensitivity of MCF7 cells to Dox.