The C-terminal domain of the antiamyloid chaperone DNAJB6 binds to amyloid-ß peptide fibrils and inhibits secondary nucleation.

The DNAJB6 chaperone inhibits fibril formation of aggregation-prone client peptides through interaction with aggregated and oligomeric forms of the amyloid peptides. Here, we studied the role of its C-terminal domain (CTD) using constructs comprising either the entire CTD or the first two or all four of the CTD ß-strands grafted onto a scaffold protein. Each construct was expressed as WT and as a variant with alanines replacing five highly conserved and functionally important serine and threonine residues in the first ß-strand. We investigated the stability, oligomerization, antiamyloid activity, and affinity for amyloid-ß (Aß42) species using optical spectroscopy, native mass spectrometry, chemical crosslinking, and surface plasmon resonance technology. While DNAJB6 forms large and polydisperse oligomers, CTD was found to form only monomers, dimers, and tetramers of low affinity. Kinetic analyses showed a shift in inhibition mechanism. Whereas full-length DNAJB6 activity is dependent on the serine and threonine residues and efficiently inhibits primary and secondary nucleation, all CTD constructs inhibit secondary nucleation only, independently of the serine and threonine residues, although their dimerization and thermal stabilities are reduced by alanine substitution. While the full-length DNAJB6 inhibition of primary nucleation is related to its propensity to form coaggregates with Aß, the CTD constructs instead bind to Aß42 fibrils, which affects the nucleation events at the fibril surface. The retardation of secondary nucleation by DNAJB6 can thus be ascribed to the first two ß-strands of its CTD, whereas the inhibition of primary nucleation is dependent on the entire protein or regions outside the CTD.

Caught between HIV exceptionalism and health service integration: Making visible the role of public health policy in the scale-up of novel sexual health services.

The role of contextual factors for program implementation is well-documented; however, their changing function throughout implementation phases is less established. We conducted an institutional ethnography to understand how structural conditions for scaling up initiatives are shaped by public health policy. We conducted 25 interviews with implementers of a comprehensive sexual health testing service in Canada, 21 meeting observations, and textual analyses of key policies and reports. Our analysis revealed a disjuncture between implementers' task of scaling up programming and the actualities of working within the discursive and material confines of policies premised on HIV exceptionalism and underfunded integrated health services.

Novel Approach for Characterizing pH-Dependent Uptake of Ionizable Chemicals in Aquatic Organisms.

Here, we present and evaluate a combined experimental and modeling approach for characterizing the uptake of ionizable chemicals from water and sediments into aquatic organisms under different pH conditions. We illustrate and evaluate the approach for two pharmaceuticals (diclofenac and fluoxetine) and one personal care product ingredient (triclosan) for the oligochaete Lumbriculus variegatus. Initially, experimental data on the uptake of the three chemicals at two pH values were fitted using a toxicokinetic model to derive uptake and depuration constants for the neutral and ionized species of each molecule. The derived constants were then used to predict uptake from water and sediment for other pH conditions. Evaluation of predictions against corresponding experimental data showed good predictions of uptake for all test chemicals from water for different pH conditions and reasonable predictions of uptake of fluoxetine and diclofenac from a sediment. Predictions demonstrated that the level of uptake of the study chemicals, across pH ranges in European streams, could differ by up to a factor of 3035. Overall, the approach could be extremely useful for assessing internal exposure of aquatic organisms across landscapes with differing pH. This could help support better characterization of the risks of ionizable chemicals in the aquatic environment.

Routes of uptake of diclofenac, fluoxetine, and triclosan into sediment-dwelling worms.

The present study investigated the route and degree of uptake of 2 ionizable pharmaceuticals (diclofenac and fluoxetine) and 1 ionizable compound used in personal care products (triclosan) into the sediment-dwelling worm Lumbriculus variegatus. Studies were done on complete worms ("feeding") and worms where the head was absent ("nonfeeding") using (14) C-labeled ingredients. Biota sediment accumulation factors (BSAF), based on uptake of (14) C, for feeding worms increased in the order fluoxetine (0.3) < diclofenac (0.5) < triclosan (9), which is correlated with a corresponding increase in log octanol-water partition coefficient. Biota sediment accumulation factor estimates are representative of maximum values because the degree of biotransformation in the worms was not quantified. Although no significant differences were seen between the uptake of diclofenac and that of fluoxetine in feeding and nonfeeding worms, uptake of the more hydrophobic antimicrobial, triclosan, into the feeding worms was significantly greater than that in the nonfeeding worms, with the 48-h BSAF for feeding worms being 36% higher than that for the nonfeeding worms. The results imply that dietary uptake contributes to the uptake of triclosan, which may be a result of the high hydrophobicity of the compound. Models that estimate exposure of ionizable substances may need to consider uptake from both the water column and food, particularly when assessing risks from dynamic exposures to organic contaminants.

Screening level mixture risk assessment of pharmaceuticals in STP effluents.

We modeled the ecotoxicological risks of the pharmaceutical mixtures emitted from STP effluents into the environment. The classic mixture toxicity concept of Concentration Addition was used to calculate the total expected risk of the analytically determined mixtures, compare the expected impact of seven effluent streams and pinpoint the most sensitive group of species. The risk quotient of a single, randomly selected pharmaceutical is often more than a factor of 1000 lower than the mixture risk, clearly indicating the need to systematically analyse the overall risk of all pharmaceuticals present. The MCR, which is the ratio between the most risky compound and the total mixture risk, varies between 1.2 and 4.2, depending on the actual scenario and species group under consideration. The mixture risk quotients, based on acute data and an assessment factor of 1000, regularly exceed 1, indicating a potential risk for the environment, depending on the dilution in the recipient stream. The top 10 mixture components explain more than 95% of the mixture risk in all cases. A mixture toxicity assessment cannot go beyond the underlying single substance data. The lack of data on the chronic toxicity of most pharmaceuticals as well as the very few data available for in vivo fish toxicity has to be regarded as a major knowledge gap in this context. On the other hand, ignoring Independent Action or even using the sum of individual risk quotients as a rough approximation of Concentration Addition does not have a major impact on the final risk estimate.

Pharmaceuticals and personal care products in the environment: what are the big questions?

BACKGROUND: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. OBJECTIVE: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. DATA SOURCES: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. DATA SYNTHESIS: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f ) antibiotic resistance, and g) risk management. CONCLUSIONS: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.