Most anti-cancer agents induce apoptosis, however, a development of multidrug resistance in cancer cells and defects in apoptosis contribute often to treatment failure. Here, the mechanism of curcumin-induced apoptosis was investigated in human leukemia HL60 cells and their HL60/VCR multidrug-resistant counterparts. In both cell lines curcumin induced a bi-phasic ceramide generation with a slow phase until 6 h followed by a more rapid one. The level of the ceramide accumulation correlated inversely with the cell viability. We found that the ceramide elevation resulted from multifarious changes of the activity of sphingolipid-modifying enzymes. In both cell lines curcumin induced relatively fast activation of neutral sphingomyelinase (nSMase), which peaked at 3 h, and was followed by inhibition of sphingomyelin synthase activity. In addition, in HL60/VCR cells the glucosylceramide synthase activity was diminished by curcumin. This process was probably due to curcumin-induced down-regulation of P-gp drug transporter, since cyclosporine A, a P-gp blocker, also inhibited the glucosylceramide synthase activity. Inhibition of nSMase activity with GW4869 or silencing of SMPD3 gene encoding nSMase2 reversed the curcumin-induced inhibition of sphingomyelin synthase without affecting the glucosylceramide synthase activity. The early ceramide generation by nSMase was indispensable for the later lipid accumulation, modulation of Bax, Bcl-2 and caspase 3 levels, and for reduction of cell viability in curcumin-treated cells, as all these events were inhibited byGW4869 or nSMase2 depletion. These data indicate that the early ceramide generation by nSMase2 induced by curcumin intensifies the later ceramide accumulation via inhibition of sphingomyelin synthase, and controls pro-apoptotic signaling.

Lupinus albus plants , 22 day old, were exposed to wide range of soil water osmotic potential (Ys = 0 to –1.0 MPa) induced by Na Cl and CaCl2 treatments in combination with roots maintained under aerobic (drained at field capacity) or anaerobic (flooded) conditions in the soil, and sprayed with 5 mg l-1 salicylic acid (SA) solution. In drained plants salt stress negatively affected shoot and root growth, leaf relative water content (RWC), chlorophyll (Chl), soluble sugars (SS), soluble proteins (SP), and K+ contents. On the contrary, salinity significantly increased membranes injury by either heat (51 oC ) or dehydration (40% polyethylene glycol, PEG) stress and enhanced the accumulation of total free amino acids (TAA) , Na+, Ca+2 and Cl-. Waterlogging caused an additive reduction in growth, Chl content and leaf RWC but enhanced leaf membranes injury. Both salinity and waterlogging synergize to increase Na+, Ca2+ and Cl- accumulation. Plants treated with salicylic acid often had greater shoot and root dry matter, Chl content as well as higher K+ content. The effects of SA were more pronounced in salt-stressed plants grown under soil oxygen deprivation. Statistical analysis showed that the effects of single factors (soil salinity (Ys), soil waterlogging, (WL) and salicylic acid (SA) and their interactions (Ys × WL, Ys × SA, WL × SA and Ys × WL × SA) were significant for most parameters tested. Calculation of the coefficient of determination (h2) led to three important findings: (1) – salinity (Ys) was dominant in affecting stability of membranes to heat, Chl b stability, soluble proteins, total free amino acids, dry matter, Ca2+, Cl– and Na+ contents. (2) – Salicylic acid had dominant effects on stability of leaf membranes to dehydration stress, Chl a and Chl b, SS, SP, and HS contents. (3) – The share of waterlogging (WL) was dominant for K+ content. Finally it can be concluded that salicylic acid application had an ameliorative effect and helped lupine plants to grow successfully in the areas subjected to combined effects of salinity and oxygen deprivation, such as in salt marshes.

Effects of shoot and root supplementation with silicon on the response of Zea mays L. plants to matric water potential (Ψm) and oxygen deficiency (waterlogging) stresses were studied. The soil water limitation (Ψm) and oxygen deprivation significantly reduced shoot dry weight, chlorophyll (Chl) content, ascorbic acid content, as well as leaf relative water content. Both soil drying and waterlogging caused a significant increase in the leaf membrane injury by heat (51°C) and dehydration (40% PEG) stresses. The levels of lipid peroxidation (POL) and hydrogen peroxide (H2O2) content were increased by excess soil drying and oxygen deficiency. Supplementary silicon at 1.0 mM significantly increased Chl content and improved water status. Concentrations of H2O2, MDA, and proline and leaf membrane injury were significantly reduced by Si application. The reverse helds true for ascorbic acid. The results of this study indicate that application of silicon might improve growth attributes, effectively mitigate the adverse effect of drought and waterlogging, and increase tolerance of maize plants. The silicon-induced improvement of drought and anoxia tolerance was associated with the increase in oxidative defense abilities.

Effects of shoot and root supplementation with silicon on the response of Zea mays L. plants to matric water potential (Ψm) and oxygen deficiency (waterlogging) stresses were studied. The soil water limitation (Ψm) and oxygen deprivation significantly reduced shoot dry weight, chlorophyll (Chl) content, ascorbic acid content, as well as leaf relative water content. Both soil drying and waterlogging caused a significant increase in the leaf membrane injury by heat (51°C) and dehydration (40% PEG) stresses. The levels of lipid peroxidation (POL) and hydrogen peroxide (H2O2) content were increased by excess soil drying and oxygen deficiency. Supplementary silicon at 1.0 mM significantly increased Chl content and improved water status. Concentrations of H2O2, MDA, and proline and leaf membrane injury were significantly reduced by Si application. The reverse helds true for ascorbic acid. The results of this study indicate that application of silicon might improve growth attributes, effectively mitigate the adverse effect of drought and waterlogging, and increase tolerance of maize plants. The silicon-induced improvement of drought and anoxia tolerance was associated with the increase in oxidative defense abilities.

Coating nonmetallic-chalcogenide film material is developed to avoid oxidation and corrosion of the thin films. The chalcogenide part consists of a thin film of Se60Te30S10 prepared by the thermal evaporation technique. On the other hand, the nonmetallic carbon thin film is applied onto the as-plated chalcogenide surface by deposition from an electrically heated carbon rod (arc discharge). The products obtained are characterized with X-ray diffraction and Scanning Electron Microscopy. It is observed an enhancement in crystallinity upon annealing for the as prepared uncoated and coated carbon films is observed. Optical studies reveal that carbon coating influences the optical energy gap, absorption coefficient and refractive index of the Se60Te30S10 thin film.

Th e t he rm al d egr ad at ion b eh av io rs of p oly (v in yl al coh ol ) ( PV A) a nd P VA /z in c ox id e ( Zn O) c om pos it e ar e in ve st ig at ed u sin g d if fer en tia l th er ma l an al ys is ( DT A) . Th e d egr ad at ion ac tivation en er gy (Ed), frequency factor (ko) and Avrami exponent (n) as thermal kinetic parameters are calculated from the DTA results. The calculated values of Ed are 80.94 and 148.58 kJ mol 1 for PVA and PVA/ZnO composite, respectively, indicating the enhancement of the PVA thermal stability as ZnO nanoparticles are filled in PVA matrix. The n values are evaluated from the shape analyses of degradation peaks. From estimated n values, the degradation mechanisms are determined for both the complexes under investigation.

The structure of the as-prepared and thermal annealed Ag10As30S60 chalcogenide glass is characterized using the X-ray diffraction (XRD) and scanning electron microscopy (SEM). Differential scanning calorimetry (DSC) curves recorded at four different heating rates are analyzed to determine the glass and crystallization transition temperatures, thermal stability and enthalpy release. Two separated crystallization peaks are observed in the DSC curves. XRD results indicate the precipitation of AgAsS4 crystal phase is responsible for the first peak. Numerous phases with S8 dominant phase are accountable for the second peak. The crystallization kinetics such as the activation energy for the crystallization (Ec), the frequency factor (Ko) and the crystallization rate constant K are determined for each crystallization stage. The results show that the crystallization rate constant for the first crystallization stage is about six times larger than that of the second crystallization step.