Diuretic drug binding to human glutathione transferase P1‐1: potential role of Cys‐101 revealed in the double mutant C47S/Y108V

The diuretic drug ethacrynic acid (EA), both an inhibitor and substrate of pi class glutathione S‐transferase (GST P1‐1), has been tested in clinical trials as an adjuvant in chemotherapy. We recently studied the role of the active site residue Tyr‐108 in binding EA to the enzyme and found that the analysis was complicated by covalent binding of this drug to the highly reactive Cys‐47. Previous attempts to eliminate this binding by chemical modification yielded ambiguous results and therefore we decided here to produce a double mutant C47S/Y108V by site directed mutagenesis and further expression in Escherichia coli and the interaction of EA and its GSH conjugate (EASG) examined by calorimetric studies and X‐ray diffraction. Surprisingly, in the absence of Cys‐47, Cys‐101 (located at the dimer interface) becomes a target for modification by EA, albeit at a lower conjugation rate than Cys‐47. The Cys‐47 → Ser mutation in the double mutant enzyme induces a positive cooperativity between the two subunits when ligands with affinity to G‐site bind to enzyme. However, this mutation does not seem to affect the thermodynamic properties of ligand binding to the electrophilic binding site (H‐site) and the thermal or chemical stability of this double mutant does not significantly affect the unfolding mechanism in either the absence or presence of ligand. Crystal structures of apo and an EASG complex are essentially identical with a few exceptions in the H‐site and in the water network at the dimer interface. Copyright © 2010 John Wiley & Sons, Ltd.     

Nocturnal heart rate variability parameters as potential fibromyalgia biomarker: correlation with symptoms severity

Introduction  

At present, there is neither a laboratory test nor an imaging technique able to differentiate people with fibromyalgia (FM) from healthy controls. This lack of an objective biomarker has hampered FM recognition and research. Heart rate variability (HRV) analyses provide a quantitative marker of autonomic nervous system activity. Nighttime is a stable period in which most people are resting. Sleep is modulated by autonomic activity. Sleeping problems are prominent in FM. The objectives of this study are: 1) to explore different nocturnal HRV parameters as potential FM biomarkers and 2) to seek correlation between such HRV parameters and diverse FM symptoms.     

A new species of alucita L. (Lepidoptera: alucitidae) from northern Chile

Male and female adults of a new species of Alucita L. (Lepidoptera: Alucitidae) are described and illustrated from the Azapa Valley, northern Chile. Immature stages are associated with fruit of "chuve", Tecoma fulva (Cav.) D. Don. (Bignoniaceae). This is the first species of Alucitidae described from Chile.     

First host plant record for Pero obtusaria Prout (Lepidoptera: Geometridae)

The shrub Pluchea chingoyo is mentioned as the first host plant record for larvae of the little known moth Pero obtusaria Prout.     

Diverse coactivator recruitment through differential PPARγ nuclear receptor agonism

The PPARγ nuclear receptor regulates the expression of genes involved in lipid and carbohydrate metabolism, and it has protective effects in some patients with type 2 diabetes. Nevertheless, the therapeutic value of the PPARγ nuclear receptor protein is limited due to the secondary effects of some PPARγ ligands. Because the downstream effects of PPARγ are determined by the binding of specific cofactors that are mediated by ligand-induced conformational changes, we evaluated the differential effects of various ligands on the binding of certain cofactors associated with PPARγ. The ligands used were rosiglitazone for treating type 2 diabetes and telmisartan for treating arterial hypertension. Functional, phenotypic, and molecular studies were conducted on pre-adipocyte 3T3-L1 and functional studies in U2OS cells. The moderating influence of various cofactor families was evaluated using transient transfection assays. Our findings confirm that telmisartan has a partial modulating effect on PPARγ activity compared to rosiglitazone. The cofactors SRC1 and GRIP1 mediate the activity of telmisartan and rosiglitazone and partially determine the difference in their effects. Studying the modulating activity of these cofactors can provide interesting insights for developing new therapeutic approaches for certain metabolic diseases.     

Diversity,Ecology and Biogeochemistry of Cyst-Forming Acantharia (Radiolaria) in the Oceans

Marine planktonic organisms that undertake active vertical migrations over their life cycle are important contributors to downward particle flux in the oceans. Acantharia, globally distributed heterotrophic protists that are unique in building skeletons of celestite (strontium sulfate), can produce reproductive cysts covered by a heavy mineral shell that sink rapidly from surface to deep waters. We combined phylogenetic and biogeochemical analyses to explore the ecological and biogeochemical significance of this reproductive strategy. Phylogenetic analysis of the 18S and 28S rRNA genes of different cyst morphotypes collected in different oceans indicated that cyst-forming Acantharia belong to three early diverging and essentially non symbiotic clades from the orders Chaunacanthida and Holacanthida. Environmental high-throughput V9 tag sequences and clone libraries of the 18S rRNA showed that the three clades are widely distributed in the Indian, Atlantic and Pacific Oceans at different latitudes, but appear prominent in regions of higher primary productivity. Moreover, sequences of cyst-forming Acantharia were distributed evenly in both the photic and mesopelagic zone, a vertical distribution that we attribute to their life cycle where flagellated swarmers are released in deep waters from sinking cysts. Bathypelagic sediment traps in the subantarctic and oligotrophic subtropical Atlantic Ocean showed that downward flux of Acantharia was only large at high-latitudes and during a phytoplankton bloom. Their contribution to the total monthly particulate organic matter flux can represent up to 3%. High organic carbon export in cold waters would be a putative nutritional source for juveniles ascending in the water column. This study improves our understanding of the life cycle and biogeochemical contribution of Acantharia, and brings new insights into a remarkable reproductive strategy in marine protists.     

Structural Analysis of Intermolecular Interactions in the Kinesin Adaptor Complex Fasciculation and Elongation Protein Zeta 1/ Short Coiled-Coil Protein (FEZ1/SCOCO)

Cytoskeleton and protein trafficking processes, including vesicle transport to synapses, are key processes in neuronal differentiation and axon outgrowth. The human protein FEZ1 (fasciculation and elongation protein zeta 1 / UNC-76, in C. elegans), SCOCO (short coiled-coil protein / UNC-69) and kinesins (e.g. kinesin heavy chain / UNC116) are involved in these processes. Exploiting the feature of FEZ1 protein as a bivalent adapter of transport mediated by kinesins and FEZ1 protein interaction with SCOCO (proteins involved in the same path of axonal growth), we investigated the structural aspects of intermolecular interactions involved in this complex formation by NMR (Nuclear Magnetic Resonance), cross-linking coupled with mass spectrometry (MS), SAXS (Small Angle X-ray Scattering) and molecular modelling. The topology of homodimerization was accessed through NMR (Nuclear Magnetic Resonance) studies of the region involved in this process, corresponding to FEZ1 (92-194). Through studies involving the protein in its monomeric configuration (reduced) and dimeric state, we propose that homodimerization occurs with FEZ1 chains oriented in an anti-parallel topology. We demonstrate that the interaction interface of FEZ1 and SCOCO defined by MS and computational modelling is in accordance with that previously demonstrated for UNC-76 and UNC-69. SAXS and literature data support a heterotetrameric complex model. These data provide details about the interaction interfaces probably involved in the transport machinery assembly and open perspectives to understand and interfere in this assembly and its involvement in neuronal differentiation and axon outgrowth.     

Nest-site selection and reproductive success of a critically endangered parrot,the Great Green Macaw (Ara ambiguus), in an anthropogenic landscape

Nest-site selection is the principal way in which secondary cavity-nesting species mitigate the negative effects of factors such as predation, parasitism and exposure on reproductive success. Large-bodied secondary cavity-nesting birds rely on large cavities in mature trees that are often absent or reduced in anthropogenically disturbed forests. Hence, the availability of high-quality nest-sites may be limited for these species, potentially reducing reproductive success. The aim of this study was to investigate nest-site selection and the effect of nest-site features on reproductive success in the critically endangered Great Green Macaw Ara ambiguus in northern Costa Rica. We show that Great Green Macaws select nest-sites according to the characteristics of the cavity and the tree in which they are located. Moreover, reproductive success is a function of certain cavity features. However, the availability of high-quality cavities, those with features associated with higher reproductive success, is potentially limited. By studying nest-site selection and productivity together, we have identified that the availability of high-quality cavities could potentially limit the future recovery of the critically endangered Great Green Macaw.     

Cost Effectiveness of Daclatasvir/Asunaprevir Versus Peginterferon/Ribavirin and Protease Inhibitors for the Treatment of Hepatitis c Genotype 1b Na?ve Patients in Chile

Introduction

Daclatasvir and Asunaprevir (DCV/ASV) have recently been approved for the treatment of chronic hepatitis C virus infection. In association, they are more effective and safer than previous available treatments, but more expensive. It is unclear if paying for the additional costs is an efficient strategy considering limited resources.

Methods

A Markov model was built to estimate the expected costs in Chilean pesos (CL$) and converted to US dollars (US$) and benefits in quality adjusted life years (QALYs) in a hypothetic cohort of naive patients receiving DCV/ASV compared to protease inhibitors (PIs) and Peginterferon plus Ribavirin (PR). Efficacy was obtained from a mixed-treatment comparison study and costs were estimated from local sources. Utilities were obtained applying the EQ-5D survey to local patients and then valued with the Chilean tariff. A time horizon of 46 years and a discount rate of 3% for costs and outcomes was considered. The ICERs were estimated for a range of DCV/ASV prices. Deterministic and probabilistic sensitivity analyses were performed.

Results

PIs were extendedly dominated by DCV/ASV. The ICER of DCV/ASV compared to PR was US$ 16,635/QALY at a total treatment price of US$ 77,419; US$11,581 /QALY at a price of US$ 58,065; US$ 6,375/QALY at a price of US$ 38,710; and US$ 1,364 /QALY at a price of US$ 19,355. The probability of cost-effectiveness at a price of US$ 38,710 was 91.6% while there is a 21.43% probability that DCV/ASV dominates PR if the total treatment price was US$ 19,355. Although the results are sensitive to certain parameters, the ICER did not increase above the suggested threshold of 1 GDP per capita.

Conclusions

DCV/ASV can be considered cost-effective at any price of the range studied. These results provide decision makers useful information about the value of incorporating these drugs into the public Chilean healthcare system.