Surface flow profiles for dry and wet granular materials by Particle Tracking Velocimetry; the effect of wall roughness

Two-dimensional Particle Tracking Velocimetry (PTV) is a promising technique to study the behaviour of granular flows. The aim is to experimentally determine the free surface width and position of the shear band from the velocity profile to validate simulations in a split-bottom shear cell geometry. The position and velocities of scattered tracer particles are tracked as they move with the bulk flow by analyzing images. We then use a new technique to extract the continuum velocity field, applying coarse-graining with the postprocessing toolbox MercuryCG on the discrete experimental PTV data. For intermediate filling heights, the dependence of the shear (or angular) velocity on the radial coordinate at the free surface is well fitted by an error function. From the error function, we get the width and the centre position of the shear band. We investigate the dependence of these shear band properties on filling height and rotation frequencies of the shear cell for dry glass beads for rough and smooth wall surfaces. For rough surfaces, the data agrees with the existing experimental results and theoretical scaling predictions. For smooth surfaces, particle-wall slippage is significant and the data deviates from the predictions. We further study the effect of cohesion on the shear band properties by using small amount of silicon oil and glycerol as interstitial liquids with the glass beads. While silicon oil does not lead to big changes, glycerol changes the shear band properties considerably. The shear band gets wider and is situated further inward with increasing liquid saturation, due to the correspondingly increasing trend of particles to stick together

Functional detection of MDR1/P170 and MRP/P190-mediated multidrug resistance in tumour cells by flow cytometry.

Multidrug resistance (MDR) in tumour cells is often caused by the overexpression of the plasma membrane drug transporter P-glycoprotein (P-gp) or the recently discovered multidrug resistance-associated protein (MRP). In this study we investigated the specificity and sensitivity of the fluorescent probes rhodamine 123 (R123), daunorubicin (DNR) and calcein acetoxymethyl ester (calcein-AM) in order to detect the function of the drug transporters P-gp and MRP, using flow cytometry. The effects of modulators on the accumulation and retention of these probes were compared in several pairs of sensitive and P-gp- as well as MRP-overexpressing cell lines. R123, in combination with the modulator PSC833, provided the most sensitive test for detecting P-gp-mediated resistance. Moreover, in a 60 min drug accumulation assay R123 can be regarded as a P-gp-specific probe, since R123 is not very efficiently effluxed by MRP. In contrast to R123, a 60 min DNR or calcein-AM accumulation test could be used to detect MRP-mediated resistance. The MRP-specific modulator genistein could be used in combination with DNR, but not with calcein-AM. Vincristine (VCR) can be used to increase the cellular uptake of calcein-AM in MDR cells, but is not specific for MRP. Thus, although the combination of DNR with genistein appeared to be as sensitive as the combination of calcein-AM with VCR, the former may be used to probe specific MRP activity whereas the latter provides a combined (P-gp + MRP) functional MDR parameter. With these functional assays the role and relative importance of P-gp and MRP can be studied in, for example, haematological malignancies

Characterization of a clonal human colon adenocarcinoma line intrinsically resistant to doxorubicin.

Intrinsic low-level resistance to anti-cancer drugs is a major problem in the treatment of gastrointestinal malignancies. To address the problem presented by intrinsically resistant tumours, we have isolated two monoclonal lines from LoVo human colon adenocarcinoma cells: LoVo/C7, which is intrinsically resistant to doxorubicin (DOX); and LoVo/C5, which shows the same resistance index for DOX as the mixed parental cell population. For comparison, we have included in the study a LoVo-resistant line selected by continuous exposure to DOX and expressing a typical multidrug resistant (MDR) phenotype. In these cell lines we have studied the expression and/or activity of a number of proteins, including P-glycoprotein 170 (P-gp), multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), glutathione (GSH)-dependent enzymes and protein kinase C (PKC) isoforms, which have been implicated in anti-cancer drug resistance. Intracellular DOX distribution has been assessed by confocal microscopy. The results of the present study indicate that resistance in LoVo/C7 cells cannot be attributed to alterations in P-gp, LRP or GSH/GSH-dependent enzyme levels. Increased expression of MRP, accompanied by alterations in the subcellular distribution of DOX, has been observed in LoVo/C7 cells; changes in PKC isoform pattern have been detected in both intrinsically and pharmacologically resistant cells