Spatial and temporal patterns in the aquatic insect community of a high altitude Andean stream (Mendoza,Argentina)

Benthic invertebrate communities have been poorly studied in Andean streams apart from the Patagonian region. The primary objective of this work was to analyse the faunal composition at three different altitudes and to observe whether there were differences in aquatic insect community structure at spatial and temporal scales. Physicochemical variables were measured on a monthly basis. Sixteen families were found, the most frequent and abundant taxa being Massartellopsis (Ephemeroptera), Andesiops (Ephemeroptera), Metrichia neotropicalis (Trichoptera), Cailloma lucidula (Trichoptera), Austrelmis (Coleoptera), and the Chironomidae (Diptera). There was a change in benthic composition associated with land use and with the diminution of water quality from the headwaters to the mouth of the system. The middle reach was a transitional area where headwater species coexisted with species characteristic of the lower reach, with Austrelmis and the family Chironomidae being the most abundant elements.     

Forecasting the fate of high mountain ponds in the Andean region under future climate change

The aims of this study are (i) to identify areas in the Andean region where the climate will remain stable enough for the survival of the study species; (ii) to analyze how climate change will affect these areas under different climate scenarios; (iii) to generate spatially explicit predictive maps of the expansion or retraction of these areas; and (iv) based on this information, to identify areas with priority for conservation. The analysis was performed using presence‐only data for 14 Heteroptera and Odonata species. Current and future models were developed to identify areas where the climate would be suitable for small ponds, using Maxent v3.3.3k, with future models based on three different Global Climate Models for the 2050 period (scenarios A2a and B2a). Model performance was evaluated using the jackknife approach. Climatic niche breadth and climatic niche similarities were calculated through Levin's concentration metrics and the I statistic index (implemented in ENMTools), respectively. Maxent logistic outputs were converted into binary presence/absence maps, based on the ‘minimum training presence logistic threshold’, and used to build species richness maps for each condition considered (present and future). Current and future models with areas climatically suitable for small ponds were developed. All the study species proved to be narrow specialists and share similar climatic spaces. Our projections suggest that four of the species would not find suitable climate conditions for survival in the future. The priority area for conservation, where most species would find suitable climate conditions, is located between 33–47°S and 73–70°W. We identified future loss of the priority area towards the east and a small gain towards the north and south. The most probable situation for the year 2050 is a negative precipitation–evapotranspiration balance, and small ponds will probably be very short‐lived or dry completely during summer, suggesting a drastic change in species assemblages and species richness of the region, which could become a hotspot of extinction.     

Identification of a contact domain between echistatin and the integrin alpha(v)beta(3) by photoaffinity cross-linking.

The integrin alpha(v)beta(3) is the major receptor mediating the attachment of osteoclasts to the extracellular matrix in bone and plays a critical role in bone resorption and bone remodeling. Most of the ligands interacting with the alpha(v)beta(3) receptor contain an Arg-Gly-Asp (RGD) motif. Recently, we have identified two small RGD peptides, containing a benzophenone moiety at either the carboxyl or amino terminus, that photo-cross-linked within the beta(3)[99-118] [Bitan, G., et al. (1999) Biochemistry 38, 3414-3420] or the beta(3)[167-171] [Bitan, G., et al. (2000) Biochemistry 39, 11014-11023] sequence, respectively, of the alpha(v)beta(3) receptor in a selective fashion. Here, we report the synthesis of a photoreactive analogue of echistatin (a 49-amino acid peptide), a potent RGD-containing antagonist of the alpha(v)beta(3) receptor both in vitro and in vivo. This bioactive analogue is substituted at position 45 with a p-benzoyl moiety (pBz(2)), located within the flexible C-terminal domain and removed 20 amino acid residues from the R(24)GD(26) triad. This C-terminal domain was reported to contribute to receptor binding affinity by acting as an auxiliary binding site. The radiolabeled (125)I-[Arg(35),Lys(45)(N(epsilon)-pBz(2))]-echistatin photo-cross-links effectively to a site within the beta(3)[209-220] sequence. Residues in this domain have been reported to be part of the metal ion-dependent adhesion site (MIDAS). Receptor fragments overlapping this domain were reported to bind to fibrinogen and block fibrinogen binding to alpha(IIb)beta(3), the platelet integrin receptor. Taken together, position 45 in echistatin, located within an auxiliary binding site in echistatin, cross-links to a site distinct from the two previously reported sites, beta(3)[99-118] and beta(3)[167-171], which cross-link to photophores flanking the RGD triad. These cross-linking data support the hypothesis that the ligand-bound conformation of the integrin beta(3) subunit differs from the known conformation of I domains.     

Ligand-integrin alpha v beta 3 interaction determined by photoaffinity cross-linking: a challenge to the prevailing model

Integrin alpha(V)beta(3) plays a crucial role in angiogenesis, apoptosis, and bone remodeling, mainly by interacting with matrix proteins through recognition of an Arg-Gly-Asp (RGD) motif. Recently, a small cyclic RGD-containing alpha(V)beta(3)-ligand possessing a C-terminal photoreactive group was photo-cross-linked within beta(3)[99-118], in the N-terminus of the beta(3) chain [Bitan G et al. (1999) Biochemistry 38, 3414-3420]. In this paper, a photoreactive group at the N-terminus of the RGD-ligand is shown to interact within beta(3)[167-171], approximately 60 residues C-terminal to the previously identified domain. On the basis of these findings, a model of the putative I-like domain of the beta(3) subunit, homologous to alpha(M)-, alpha(L)-, and alpha(2)-I-domains, reveals that the beta(3)[99-118] and beta(3)[167-171] contact sites are close to each other and are on the opposite side relative to the metal ion-dependent adhesion site (MIDAS) motif. These observations contradict the prevailing model that proposes proximity between metal- and RGD-binding sites on the I-like domain. Our data suggest that either the I-like domain structure predicted for beta(3) is incorrect, or there is no spatial proximity between the RGD-binding site and the MIDAS motif in the I-like domain. Our results indicate that the current models for ligand-receptor interaction should be revisited.     

All Nations Depend on the Global Knowledge Pool – Analysis of Country of Origin of Studies Used for Health Technology Assessments in Germany

Background

Health Technology Assessments (HTAs) are used to inform decision-making and their usefulness depends on the quality and relevance of research and specific studies for health-policy decisions. Little is known about the country of origin of studies used for HTAs.

Objective

To investigate which countries have made the largest contributions to inform health policy decisions through studies included in HTAs in Germany.

Methods

The country of origin was extracted from all studies included in HTAs of the German Institute for Quality and Efficiency in Health Care, (IQWiG), published from 2/2006 to 9/2010. Studies were ranked according to the total number of studies per country, adjusted for population size, gross domestic product (GDP), and total health expenditure.

Results

1087 studies were included in 54 HTA reports. Studies were assigned to 45 countries. Most of the studies (27%) originated from the United States (USA), 18% were multinational, followed by 7% from the United Kingdom (UK) and 5% from Germany. Nordic countries led the ranking when adjusting for population size/million (ranks 1-3,6,9/45 countries), GDP/billion US$ (1,2,5,9,14/45), or health expenditure/billion US$ (1,3,5,12,13/45). The relative contribution of the UK was stable in the analyses when adjusted for population size (7/45), GDP (7/45), and health expenditure (9/45), whereas the USA (13, 18, and 30/45) and Germany (17, 19, and 21/45) dropped in the ranking.

Conclusions

More than half of the studies relevant for evidence-informed decision-making in Germany originated from the USA, followed by multinational research and the UK. Only 5% of the studies originated from Germany. According to our findings, there appears to be some discrepancy between the use of globally generated evidence and the contribution to the knowledge pool by individual countries.     

8-Mercaptoguanine-based inhibitors of Mycobacterium tuberculosis dihydroneopterin aldolase: synthesis,in vitro inhibition and docking studies

The dihydroneopterin aldolase (DHNA, EC 4.1.2.25) activity of FolB protein is required for the conversion of 7,8-dihydroneopterin (DHNP) to 6-hydroxymethyl-7,8-dihydropterin (HP) and glycolaldehyde (GA) in the folate pathway. FolB protein from Mycobacterium tuberculosis (MtFolB) is essential for bacilli survival and represents an important molecular target for drug development. S8-functionalized 8-mercaptoguanine derivatives were synthesised and evaluated for inhibitory activity against MtFolB. The compounds showed IC₅₀ values in the submicromolar range. The inhibition mode and inhibition constants were determined for compounds that exhibited the strongest inhibition. Additionally, molecular docking analyses were performed to suggest enzyme-inhibitor interactions and ligand conformations. To the best of our knowledge, this study describes the first class of MtFolB inhibitors.     

Design and evaluation of benzophenone-containing conformationally constrained ligands as tools for photoaffinity scanning of the integrin alphaVbeta3-ligand bimolecular interaction.

Integrins are cell-surface adhesion molecules involved in mediating cell-extracellular matrix interactions. High-resolution structural data are not available for these heterodimeric receptors. In order to generate tools for photoaffinity scanning of the RGD-binding site of human integrin alphaVbeta3. new conformationally constrained ligands were designed. The ligands were based on five different cyclic peptidic or peptidomimetic scaffolds with high affinity for alphaVbeta3. A single photoreactive group (a benzophenone moiety) was introduced at different positions relative to the RGD triad. In addition, an 125I or a biotin group was introduced as a reporting tag. Twenty-four cyclic ligands were prepared and their binding affinity for alphaVbeta3 was determined. In most cases, the modifications resulted in a 5- to 500-fold decrease in affinity relative to the unmodified scaffold. Analogs representing three of the five families were screened for their cross-linking efficiency. Ligands with submicromolar affinities cross-linked efficiently and specifically to the integrin receptor, whereas ligands with weaker affinities gave specific cross-linking, but with lower efficiency. Almost all of the screened ligands cross-linked predominantly to the beta3 subunit.