Chiral separation of flurbiprofen enantiomers by preparative and simulated moving bed chromatography

This study presents the chiral resolution of flurbiprofen enantiomers by preparative liquid chromatography using the simulated moving bed (SMB) technology. Flurbiprofen enantiomers are widely used as nonsteroidal anti‐inflammatory drugs, and although demonstrate different therapeutic actions, they are still marketed as a racemic mixture. The results presented here clearly show the importance of the selection of the proper solvent composition for the preparative separation of flurbiprofen enantiomers. Chiral SMB separation is carried out using a laboratory‐scale unit (the FlexSMB‐LSRE®) with six columns, packed with the Chiralpak AD® stationary phase (20 μm). Results presented include the experimental measurement of equilibrium and kinetic data for two very different solvent compositions, a traditional high hydrocarbon content [10%ethanol/90%n‐hexane/0.01% trifluoroacetic acid (TFA)] and a strong polar organic composition (100%ethanol/0.01%TFA). Experimental data, obtained using the two mobile phase compositions, are used to predict and optimize the SMB operation. After selecting 10%ethanol/90%n‐hexane/0.01%TFA as the most appropriate solvent composition, three feed concentrations of racemic flurbiprofen were considered. Using 40 g/l of racemic flurbiprofen feed solution, the purities for both outlet streams were above 99.4%, the productivity was 13.1 g_feed/(L_bed h), and a solvent consumption of 0.41 L_solvent/g_feed was achieved. Chirality, 2011. © 2011 Wiley‐Liss, Inc.     

7-Ketocholesterol-induced apoptosis. Involvement of several pro-apoptotic but also anti-apoptotic calcium-dependent transduction pathways

Oxysterols, and particularly 7-ketocholesterol, appear to be strongly involved in the physiopathology of atherosclerosis. These molecules are suspected to be cytotoxic to the cells of the vascular wall and monocytes/macrophages, particularly by inducing apoptosis. Previous studies have demonstrated that 7-ketocholesterol-induced apoptosis is triggered by a sustained increase of cytosolic-free Ca2+, which elicits the mitochondrial pathway of apoptosis by activation of the calcium-dependent phosphatase calcineurin, leading to dephosphorylation of the 'BH3 only' protein BAD. However, thorough study of the results suggests that other pathways are implicated in 7-ketocholesterol-induced cytotoxicity. In this study, we demonstrate the involvement of two other calcium-dependent pathways during 7-ketocholesterol-induced apoptosis. The activation of the MEK-->ERK pathway by the calcium-dependent tyrosine kinase PYK 2, a survival pathway which delays apoptosis as shown by the use of the MEK inhibitor U0126, and a pathway involving another pro-apoptotic BH3 only protein, Bim. Indeed, 7-ketocholesterol treatment of human monocytic THP-1 cells induces the release of Bim-LC8 from the microtubule-associated dynein motor complex, and its association with Bcl-2. Therefore, it appears that 7-ketocholesterol-induced apoptosis is a complex phenomenon resulting from calcium-dependent activation of several pro-apoptotic pathways and also one survival pathway.     

An automated tube-type blood viscometer: validation studies

The technical complexity of previous rheometers has tended to limit the availability of blood viscosity data obtained over a wide range of shear rates. However, an automated tube-type viscometer, the Rheolog, has been developed; it employs a disposable flow assembly and less than five minutes are required to obtain blood viscosity results over a shear rate range of 1-1500 s(-1). We have carried out validation studies of the Rheolog using normal human blood and have compared these results with those obtained by cone-plate and Couette viscometers; storage time and temperature effects were also evaluated. Replicate measurements indicated mean CV levels less than 5%, and were independent of hematocrit and shear rate. Rheolog blood viscosity data agreed closely with those from other viscometers: average Rheolog differences from mean cone-plate and Couette values were -0.3% at 28% hematocrit, -1.4% at 41% hematocrit (i.e., native), and 1.0% at 56% hematocrit. Storage at room temperature up to 8 hours and at 4 degrees C up to 4 days had minimal effects whereas notable changes were observed when stored for 3 hours at 37 degrees C. Our results indicate that, within the hematocrit and shear rate limits employed herein, the Rheolog provides rapid, accurate and reproducible blood viscosity data, and suggest its usefulness for both basic science and clinical studies.     

Azido-containing diketo acid derivatives inhibit human immunodeficiency virus type 1 integrase in vivo and influence the frequency of deletions at two-long-terminal-repeat-circle junctions

We previously found that azido-containing beta-diketo acid derivatives (DKAs) are potent inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase (IN) (X. Zhang et al., Bioorg. Med. Chem. Lett., 13:1215-1219, 2003). To characterize the intracellular mechanisms of action of DKAs, we analyzed the antiviral activities of two potent azido-containing DKAs with either a monosubstitution or a disubstitution of azido groups, using single- and multiple-replication-cycle assays. Both azido-containing DKAs significantly inhibited HIV-1 infection in 293T, CEM-SS, and H9 cells (50% inhibitory concentration = 2 to 13 micro M) and exhibited low cytotoxicity (50% cytotoxic concentration = 60 to 600 micro M). Inhibition of HIV-1 IN in vivo was demonstrated by the observation that previously described L-708,906 resistance mutations in HIV-1 IN (T66I and T66I/S153Y) also conferred resistance to the azido-group-containing DKAs. In vitro assays and in vivo analysis indicated that the DKAs did not significantly inhibit the 3' processing and selectively inhibited the strand transfer reaction. In addition, quantitative PCR indicated that two-long-terminal-repeat (2-LTR) circles were elevated in the presence of the azido-containing DKAs, confirming that HIV-1 IN was the intracellular target of viral inhibition. To gain insight into the mechanism by which the DKAs increased 2-LTR-circle formation of 3'-processed viral DNAs, we performed extensive DNA sequencing analysis of 2-LTR-circle junctions. The results indicated that the frequency of deletions at the circle junctions was elevated from 19% for the untreated controls to 32 to 41% in the presence of monosubstituted (but not disubstituted) DKAs. These results indicate that the structure of the DKAs can influence the extent of degradation of viral DNA ends by host nucleases and the frequency of deletions at the 2-LTR-circle junctions. Thus, sequencing analysis of 2-LTR-circle junctions can elucidate the intracellular mechanisms of action of HIV-1 IN inhibitors.     

Nuclear DNA content of Vitis vinifera cultivars and ploidy level analyses of somatic embryo-derived plants obtained from anther culture

Flow cytometry was employed to determine the ploidy level of Vitis vinifera L. somatic embryo-derived plants obtained from anther culture. Only one among the 41 analysed plants (2.4%) presented somaclonal variation (tetraploidy); the other plants were diploid. No significant differences (P≤0.05) were detected between diploid and parental field plants. No haploid or aneuploid plants were observed. The nuclear DNA content of nine V. vinifera cultivars was also estimated using flow cytometry. A non-significant variation was found among the cultivars, with DNA content ranging from 1.17 pg/2C (cv. ‘Tinta Barroca’ and ‘Viosinho’) to 1.26 pg/2C (cv. ‘Cabernet Sauvignon’). These results and previous studies on other Vitis species suggest that Vitis genome is stable with regard to nuclear DNA content.     

Constitutive inhibition of plasma CETP by apolipoprotein C1 is blunted in dyslipidemic patients with coronary artery disease

Plasma cholesteryl ester transfer protein (CETP) promotes the cholesterol enrichment of apoB-containing lipoproteins (VLDL and LDL) at the expense of HDL. Recent studies demonstrated that apoC1 is a potent CETP inhibitor in plasma of healthy, normolipidemic subjects. Our goal was to establish whether the modulation of CETP activity by apoC1 is influenced by dyslipidemia in patients with documented coronary artery disease (CAD). In the total CAD population studied (n = 240), apoC1 levels correlated negatively with CETP activity, independently of apoE-epsilon, CETP-Taq1B, and apoC1-Hpa1 genotypes. In multivariate analysis, the negative relationship was observed only in normolipidemic patients, not in those with hypercholesterolemia, hypertriglyceridemia, or combined hyperlipidemia. In the normolipidemic subjects, apoC1 levels were positively associated with higher HDL- to LDL-cholesterol ratio (r = 0.359, P < 0.001). It is concluded that apoC1 as a CETP inhibitor no longer operates on cholesterol redistribution in high-risk patients with dyslipidemia, probably due to increasing amounts of VLDL-bound apoC1, which is inactive as a CETP inhibitor. Patients with dyslipidemia could experience major benefits from treatment with pharmacological CETP inhibitors, which might compensate for blunted endogenous inhibition.     

Mannosylglycerate stabilizes staphylococcal nuclease with restriction of slow β-sheet motions

Mannosylglycerate is a compatible solute typical of thermophilic marine microorganisms that has a remarkable ability to protect proteins from thermal denaturation. This ionic solute appears to be a universal stabilizing agent, but the extent of protection depends on the specific protein examined. To understand how mannosylglycerate confers protection, we have been studying its influence on the internal motions of a hyperstable staphylococcal nuclease (SNase). Previously, we found a correlation between the magnitude of protein stabilization and the restriction of fast backbone motions. We now report the effect of mannosylglycerate on the fast motions of side-chains and on the slower unfolding motions of the protein. Side-chain motions were assessed by (13)CH(3) relaxation measurements and model-free analysis while slower unfolding motions were probed by H/D exchange measurements at increasing concentrations of urea. Side-chain motions were little affected by the presence of different concentrations of mannosylglycerate or even by the presence of urea (0.25M), and show no correlation with changes in the thermodynamic stability of SNase. Native hydrogen exchange experiments showed that, contrary to reports on other stabilizing solutes, mannosylglycerate restricts local motions in addition to the global motions of the protein. The protein unfolding/folding pathway remained undisturbed in the presence of mannosylglycerate but the solute showed a specific effect on the local motions of β-sheet residues. This work reinforces the link between solute-induced stabilization and restriction of protein motions at different timescales, and shows that the solute preferentially affects specific structural elements of SNase.     

Morphological Changes in the Midgut of Aedes aegypti L. (Diptera: Culicidae) Larvae Following Exposure to an Annona coriacea (Magnoliales: Annonaceae) Extract

Bioinsecticides are important in the control of disease vectors, but data regarding their physiological effects on target insects are incomplete. This study describes morphological changes that occur in the midgut of third instar Aedes aegypti L. (Diptera: Culicidae) following treatment with a methanolic extract of Annona coriacea (Magnoliales: Annonaceae). Dissected midguts were subdivided into anterior and posterior regions and analyzed by light and scanning electron microscopy. Insects exposed to the extract displayed intense, destructive cytoplasmic vacuolization in columnar and regenerative midgut cells. The apical surfaces of columnar cells exhibited cytoplasmic protrusions oriented toward the lumen, suggesting that these cells could be involved in apocrine secretory processes and/or apoptosis. We report that A. coriacea extracts induced morphological alterations in the midgut of A. aegypti midgut larvae, supporting the use of plant extracts for control of the dengue vector.     

Cholesterol trafficking and raft-like membrane domain composition mediate scavenger receptor class B type 1-dependent lipid sensing in intestinal epithelial cells

Scavenger receptor Class B type 1 (SR-B1) is a lipid transporter and sensor. In intestinal epithelial cells, SR-B1-dependent lipid sensing is associated with SR-B1 recruitment in raft-like/ detergent-resistant membrane domains and interaction of its C-terminal transmembrane domain with plasma membrane cholesterol. To clarify the initiating events occurring during lipid sensing by SR-B1, we analyzed cholesterol trafficking and raft-like domain composition in intestinal epithelial cells expressing wild-type SR-B1 or the mutated form SR-B1-Q445A, defective in membrane cholesterol binding and signal initiation. These features of SR-B1 were found to influence both apical cholesterol efflux and intracellular cholesterol trafficking from plasma membrane to lipid droplets, and the lipid composition of raft-like domains. Lipidomic analysis revealed likely participation of d18:0/16:0 sphingomyelin and 16:0/0:0 lysophosphatidylethanolamine in lipid sensing by SR-B1. Proteomic analysis identified proteins, whose abundance changed in raft-like domains during lipid sensing, and these included molecules linked to lipid raft dynamics and signal transduction. These findings provide new insights into the role of SR-B1 in cellular cholesterol homeostasis and suggest molecular links between SR-B1-dependent lipid sensing and cell cholesterol and lipid droplet dynamics.     

Evidence for diet partitioning among three coexisting native freshwater fishes in South Africa's Cape Fold Ecoregion

The partitioning of limited resources commonly explains how different species can coexist within the same ecological community. In this 2010 study, the diets of three coexisting freshwater fishes (Cape galaxias Galaxias zebratus, n = 27; Cape kurper Sandelia capensis, n = 60; Breede River redfin Pseudobarbus burchelli, n = 77) were characterised and compared in three headwater streams in South Africa's Cape Fold Ecoregion using gut contents and stable isotope analyses. These data were analysed to ascertain whether the three species exploit distinct trophic niches. Both approaches provided evidence that these species occupy different trophic niches, though with some overlap. However, dietary differences among sites were not consistent and were probably influenced by site-specific factors like resource availability. Pseudobarbus burchelli had a broader niche breadth at Tierkloof Stream than the other two species, but not at Waaihoek or Tierstel Streams. Our results also suggest that P. burchelli consumed a more omnivorous diet than do the other two species, whereas S. capensis occupied a higher trophic position than the other two species and consumed vertebrates. Our findings suggest that these species occupy non-equivalent feeding niches in Cape Fold Ecoregion headwater streams, and that diet partitioning might facilitate their coexistence in these systems.