Cyclodextrins inhibit replication of scrapie prion protein in cell culture

Prion diseases are fatal neurodegenerative disorders that are caused by the conversion of a normal host-encoded protein, PrP(C), to an abnormal, disease-causing form, PrP(Sc). This paper reports that cyclodextrins have the ability to reduce the pathogenic isoform of the prion protein PrP(Sc) to undetectable levels in scrapie-infected neuroblastoma cells. Beta-cyclodextrin removed PrP(Sc) from the cells at a concentration of 500 microM following 2 weeks of treatment. Structure activity studies revealed that antiprion activity was dependent on the size of the cyclodextrin. The half-maximal inhibitory concentration (IC(50)) for beta-cyclodextrin was 75 microM, whereas alpha-cyclodextrin, which possessed less antiprion activity, had an IC(50) of 750 microM. This report presents cyclodextrins as a new class of antiprion compound. For decades, the pharmaceutical industry has successfully used cyclodextrins for their complex-forming ability; this ability is due to the structural orientation of the glucopyranose units, which generate a hydrophobic cavity that can facilitate the encapsulation of hydrophobic moieties. Consequently, cyclodextrins could be ideal candidates for the treatment of prion diseases.     

Regulation of D-xylose metabolism in Caulobacter crescentus by a LacI-type repressor

In the oligotrophic freshwater bacterium Caulobacter crescentus, D-xylose induces expression of over 50 genes, including the xyl operon, which encodes key enzymes for xylose metabolism. The promoter (P(xylX)) controlling expression of the xyl operon is widely used as a tool for inducible heterologous gene expression in C. crescentus. We show here that P(xylX) and at least one other promoter in the xylose regulon (P(xylE)) are controlled by the CC3065 (xylR) gene product, a LacI-type repressor. Electrophoretic gel mobility shift assays showed that operator binding by XylR is greatly reduced in the presence of D-xylose. The data support the hypothesis that there is a simple regulatory mechanism in which XylR obstructs xylose-inducible promoters in the absence of the sugar; the repressor is induced to release DNA upon binding D-xylose, thereby freeing the promoter for productive interaction with RNA polymerase. XylR also has an effect on glucose metabolism, as xylR mutants exhibit reduced expression of the Entner-Doudoroff operon and their ability to utilize glucose as a sole carbon and energy source is compromised.     

Targeting the RAF/MEK/ERK, PI3K/AKT and P53 pathways in hematopoietic drug resistance

We have presented data which documents the importance of the Raf>MEK>ERK and PI3K>Akt pathways in the development of drug resistance in hematopoietic cells. Further understanding of how these pathways interact and induce drug resistance could result in the identification of novel approaches to treat drug resistance in leukemia. Furthermore, p53 played a role in drug resistance in these cells as introduction of a DN-p53 construct increased the resistance of the cells to chemotherapeutic drugs. The drug-sensitive and drug-resistant FL/ΔAkt:ER+ΔRaf-1:AR cells will allow us the ability to determine not only which downstream components are induced by either Raf>MEK>ERK or PI3K>Akt that are necessary for proliferation and prevention of apoptosis, but also which components are important in drug resistance and how these two pathways can interact to influence drug resistance.     

Prions: where do we stand 20 years after the appearance of bovine spongiform encephalopathy?

Bovine spongiform encephalopathy (BSE) is a transmissible spongiform encephalopathy (TSE) identified twenty years ago in the British cattle herds. Creutzfeldt-Jakob disease (CJD) is a TSE that occurs in humans. In 1996, scientists found a possible link between BSE and a new variant of CJD (vCJD). The fact that the non conventional infectious agent of TSE, named prions, could cross the species barrier from cattle to human through meat consumption, raised a tremendous concern for public safety in Europe. This led to the development in the following two decades of substantial and expensive measures to contain BSE and prevent its transmission to humans. In parallel, scientific programs have been funded to progress through the comprehension of the physiopathology of these fatal disorders. In Europe, the BSE epidemics is now ending and the number of cases is decreasing thanks to the strict control of animal foodstuff that was the main source of prion contamination. Only a small number of vCJD have been detected, however, additional concerns have been raised recently for public safety as secondary transmission of CJD through medical procedure and blood transfusion is possible. In addition, the possibility that the BSE was transmitted to other animals including small ruminants is also worrisome. Research efforts are now focussing on decontamination and ante mortem diagnosis of TSE to prevent animal and human transmission. However, needs for fundamental research are still important as many questions remain to be addressed to understand the mechanism of prion transmission, as well as its pathogenesis.     

Neutron imaging versus standard X-ray densitometry as method to measure tree-ring wood density

Neutron imaging is a new non-destructive testing method in wood science. It is similar to X-ray methods but with differing sensitivities for different elements. In this study, neutron imaging was used to ascertain the density profiles of thin spruce samples and compared with results generated with standard X-ray microdensitometry. Data obtained through neutron imaging were similar to those resulting from the X-ray method. The advantage of neutron imaging is its higher sensitivity to some elements such as hydrogen. Together with the high neutron-sensitivity of the applied detectors (imaging plates) this makes shorter exposure times possible, and yields more detailed information on the inner composition of wood. X-ray film, which is still most commonly used in X-ray densitometry, has the disadvantage that the relationship between the optical density of the film and the density of wood is non-linear. This means that corrections and calibration with step wedges are necessary, whereas with neutron imaging the digital values can be used directly to calculate the density at a certain point of the specimen. Thus neutron imaging appears to be an appropriate method, which can be used as complement to established X-ray methods for fast and straightforward investigations of tree rings, growth zones and wood density.     

Comparison of Echinacea alkylamide pharmacokinetics between liquid and tablet preparations

The relative oral bioavailability of alkylamides from two different Echinacea dosage forms (liquid and tablet) were compared in a small two-way crossover study in humans (n=3). The liquid preparation investigated contained a mixture of Echinacea purpurea root (300 mg/ml) and Echinacea angustifolia root (200 mg/ml) extracted in 60% ethanol. The tablet preparation investigated was also a mixture of E. purpurea root (675 mg/tablet) and E. angustifolia root (600 mg/tablet), but was prepared from the dried 60% ethanolic extracts of these two Echinacea species. Alkylamides were found to be rapidly absorbed and measurable in plasma from both preparations. No significant differences in the tetraene alkylamide pharmacokinetic parameters for T(1/2), AUC(t-lin) and C(max) in the two different preparations were found. T(max) increased from 20 min for the liquid to 30 min for the tablet, which is not unexpected as the tablet required time for disintegration before absorption could occur. These results suggested that there was no significant difference in the bioavailability of alkylamides from the liquid and tablet Echinacea formulations. Furthermore, the results also indicated that the absorption site and any alkylamide loss due to digestive processes were similar in both preparations.