Hypoxia-induced modulation of apoptosis and BCL-2 family proteins in different cancer cell types

Hypoxia plays an important role in the resistance of tumour cells to chemotherapy. However, the exact mechanisms underlying this process are not well understood. Moreover, according to the cell lines, hypoxia differently influences cell death. The study of the effects of hypoxia on the apoptosis induced by 5 chemotherapeutic drugs in 7 cancer cell types showed that hypoxia generally inhibited the drug-induced apoptosis. In most cases, the effect of hypoxia was the same for all the drugs in one cell type. The expression profile of 93 genes involved in apoptosis as well as the protein level of BCL-2 family proteins were then investigated. In HepG2 cells that are strongly protected against cell death by hypoxia, hypoxia decreased the abundance of nearly all the pro-apoptotic BCL-2 family proteins while none of them are decreased in A549 cells that are not protected against cell death by hypoxia. In HepG2 cells, hypoxia decreased NOXA and BAD abundance and modified the electrophoretic mobility of BIM(EL). BIM and NOXA are important mediators of etoposide-induced cell death in HepG2 cells and the hypoxia-induced modification of these proteins abundance or post-translational modifications partly account for chemoresistance. Finally, the modulation of the abundance and/or of the post-translational modifications of most proteins of the BCL-2 family by hypoxia involves p53-dependent and -independent pathways and is cell type-dependent. A better understanding of these cell-to-cell variations is crucial in order to overcome hypoxia-induced resistance and to ameliorate cancer therapy

A new occurrence of samuelsonite in the Buranga Pegmatite, Rwanda

A new occurrence of the rare mineral species, samuelsonite, is reported from the Buranga pegmatite, Rwanda, in close association with gatumbaite and burangaite, as aggregates of bladed crystals imbedded in trolleite and in bertossaite. Its crystallographic properties, determined both by the rotation and Wassenberg techniques and by the powder method, are: a= 18.621(3), b = 6.842(1), c = 14.066(2)Å, ß = 112°30'(1’), C2/m, Z = 2.Gmeas = 3.24(5) and Gcalc =3.22. A wet chemical analysis gives: 43.79 P2O5, 6.18 Al2O3, 0.07 Fe2O3, 7.92 FeO, 8.91 MnO, 0.07 MgO, 28.41 CaO, 2.31 BaO, 0.43 Li2O, 0.35 Na2O, 1.85 H2O+, total 100,29%. Because of some structural similarities with the apatite structure, a few assigments of the infrared absorption bands are tentatively proposed. A discussion on the crystal chemistry shows that Li resides in the octahedral M sites, whereas Na is sequestred with the excess of Mn and Ca in the X sites of the structure

Analysis of gas holdup in bubble columns with non-Newtonian fluid using electrical resistance tomography and dynamic gas disengagement technique

This paper presents an experimental analysis of the influence of the liquid rheology on the gas flow pattern in a bubble column reactor. Aqueous solutions of xanthan are selected as an example of non-Newtonian shear thinning fluid. Averaged gas holdup is determined by two experimental techniques: parietal pressure probes and electrical resistance tomography (ERT). ERT is also used to provide 2D images of the gas phase distribution in a column cross-section. Bubble size distributions are evaluated by a gas disengagement technique using the parietal pressure probes. All these techniques clearly show the gas flow pattern is different in Newtonian and non-Newtonian fluids. Gas holdup values decrease when increasing the liquid viscosity and reach a minimum or a plateau. Homogeneous flow regime, observed in water at low gas velocities, tends to disappear when viscosity increases. This evolution is visualized by a much less isotropic distribution of the gas phase within cross-section of the column and by the appearance of much larger bubbles due to an increased coalescence phenomenon. (c) 2005 Elsevier Ltd. All rights reserved.MESURES HYDRODYNAMIQUES ET MODÉLISATION STOCHASTIQUE DANS LES SYSTÈMES POLYPHASIQUES DU GÉNIE DES PROCÉDÉ

The mineralogical status of "cavolinite" from Vesuvius, Italy, and crystallochemical data on the davyne subgroup

Since its description in 1825 as a new mineral species from the Monte Somma caldera, Vesuvius, “cavolinite” has been a source for debate and confusion. Now, “cavolinite” is simply considered as an obsolete name for nepheline, (Na3K)[Al4Si4O16]. In order to shed some light on the status of this mineral, 12 specimens labelled as “cavolinite” were revisited by X-ray diffraction, micro-Raman spectroscopy, and electron microprobe chemical analyses. First, the X-ray powder method shows that all the specimens belong to the davyne subgroup of the cancrinite group. However, among the investigated samples, two populations of “cavolinite” are distinguishable. “Cavolinite” crystals lining small vugs exhibit a prismatic habit, have a chemical composition with about 3.3 Cl per formula unit, and are poor in sulphate (0.01 to 0.08 SO4 2- pfu). Moreover, they show superstructure reflections doubling the parameter a of the hexagonal unit cell (a = 25.8 and c = 5.4 Å). These crystals correspond to quadridavyne, [(Na,K)6Cl2](Ca2Cl2)[Si6Al6024]. “Cavolinite” filling up large geodes of the second population occurs as entangled platelets or fibrous masses. Their chemical compositions reveal about 2.3 Cl pfu and are richer in sulphate (0.4 to 0.7 SO4 2- pfu). As no superstructure reflections were observed along the a axis, the cell parameters (a = 12.75 and c = 5.35 Å) correspond to those of davyne [(Na,K)6(SO4)0.5-1Cl1-0(CO3)0-1](Ca2Cl2)[Si6Al6024]. The two populations are also qualitatively distinguishable by micro- Raman spectroscopy, by comparing the relative intensity of the vibration peaks of SO4 at about 990 cm-1.Moreover, the presence of CO3 groups is clearly detected in a few samples. The vibration peak for CO3 (at about 1050 cm-1) is particularly intense in one of the samples, in agreement with the results of the crystal structure refinement, which points to about 0.9 CO3 2- groups pfu. Owing to 160 point analyses performed on the whole collection of samples by electron microprobe, a plot of the alkali contents pfu, Na versus K, shows a complete solid solution between two channel contents, Na3.6K2 and Na5.4K0.4. The two populations can be recognized here again. All the “cavolinite” samples identified as quadridavyne show a broader range of the Na↔K substitution than those identified as davyne in which the replacement of Na by Ca in the channels can be more significant