Reactive derivatives for affinity labeling in the ifenprodil site of NMDA receptors

To prepare thiol-reactive ifenprodil derivatives designed as potential probes for cysteine-substituted NR2B containing NMDA receptors, electrophilic centers were introduced in different areas of the ifenprodil structure. Intermediates and final compounds were evaluated by binding studies and by electrophysiology to determine the structural requirements for their selectivity. The reactive compounds were further tested for their stability and for their reactivity in model reactions; some were found suitable as structural probes to investigate the binding site and the docking mode of ifenprodil in the NR2B subunit.     

Albumin Mexico (Al Me ) in the Guatemalan highlands

The examination of the sera of two samples of Guatemalans (total n = 386) revealed the presence of albumin Mexico (Al^Me) among unrelated individuals from the western highlands near the Mexican border. The frequency in the putatively less admixed sample, from Quiché, was 0.008. This is the first report of albumin polymorphism among American Indians south of Mexico. The presence of the Al^Me allele among Indians of the Guatemalan highlands argues for a zone of gene flow between contiguous groups of Mexico and Guatemala. The failure to detect albumin polymorphism among lowland populations of the Yucatan peninsula may likewise be significant, but more testing of samples is required before definitive statements can be made with respect to contacts among and within highland and lowland groups.     

From forest to cropland and pasture systems: a critical review of soil organic carbon stocks changes in Amazonia

The impact of deforestation on soil organic carbon (SOC) stocks is important in the context of climate change and agricultural soil use. Trends of SOC stock changes after agroecosystem establishment vary according to the spatial scale considered, and factors explaining these trends may differ sometimes according to meta‐analyses. We have reviewed the knowledge about changes in SOC stocks in Amazonia after the establishment of pasture or cropland, sought relationships between observed changes and soil, climatic variables and management practices, and synthesized the δ¹³C measured in pastures. Our dataset consisted of 21 studies mostly synchronic, across 52 sites (Brazil, Colombia, French Guiana, Suriname), totalling 70 forest–agroecosystem comparisons. We found that pastures (n = 52, mean age = 17.6 years) had slightly higher SOC stocks than forest (+6.8 ± 3.1 %), whereas croplands (n = 18, mean age = 8.7 years) had lower SOC stocks than forest (?8.5 ± 2.9 %). Annual precipitation and SOC stocks under forest had no effect on the SOC changes in the agroecosystems. For croplands, we found a lower SOC loss than other meta‐analyses, but the short time period after deforestation here could have reduced this loss. There was no clear effect of tillage on the SOC response. Management of pastures, whether they were degraded/nominal/improved, had no significant effect on SOC response. δ¹³C measurements on 16 pasture chronosequences showed that decay of forest‐derived SOC was variable, whereas pasture‐derived SOC was less so and was characterized by an accumulation plateau of 20 Mg SOC ha^?1 after 20 years. The large uncertainties in SOC response observed could be derived from the chronosequence approach, sensitive to natural soil variability and to human management practices. This study emphasizes the need for diachronic and long‐term studies, associated with better knowledge of agroecosystem management.     

Social structure of killer whales (Orcinus orca) in a variable low-latitude environment,the Galápagos Archipelago

Killer whales (Orcinus orca) have strong social matrilineal bonds and form groups and long-lasting associations, but little is known about their population or social structure in an equatorial setting such as the waters around the Galápagos Islands. Using 91 encounters and identification photographs from 1991 to 2017, we identified 64 killer whales of which 18 individuals were locals with high resighting rates. Group size was small, ranging from 1 to 15 animals, with 69% of the groups containing four or fewer animals. Using social network analysis (SOCPROG 2.7) whales grouped into three distinct units and one loose association with frequent exchange between different groups. One male–male unit showed a strong association (association strength = 0.55). Overall, associations lasted over at least 3 years. Our data give first evidence of a loose social organization of Galápagos killer whales, similar to fission-fusion societies.     

Direct classification of related species of fungal endophytes (Epichlo? spp.) using visible and near-infrared spectroscopy and multivariate analysis.

The aim of this work was to investigate the potential of visible and near-infrared (Vis-NIR) reflectance spectroscopy for the classification of three morphologically similar species of fungal endophytes of grasses. Vis-NIR spectra (400-2498 nm) from 34 isolates of Epichlo? sylvatica, 32 of Epichlo? typhina and 38 of Epichlo? festucae were recorded directly from fresh mycelium growing in potato dextrose agar plates. Multivariate procedures applied to the spectral data were discriminant modified partial least squares regression, soft independent modelling of class analogy and discriminant partial least squares regressions (PLS1, PLS2). Several types of data pretreatments were tested to develop the classification models. The best predictive models were achieved with PLS2 analysis; with this method, 90% of E. typhina and 100% of E. festucae and E. sylvatica external validation samples were successfully classified. These results show the potential of Vis-NIR spectroscopy combined with multivariate analysis as a rapid method for classifying morphologically similar species of filamentous fungi.     

Probenecid inhibits the human bitter taste receptor TAS2R16 and suppresses bitter perception of salicin

Bitter taste stimuli are detected by a diverse family of G protein-coupled receptors (GPCRs) expressed in gustatory cells. Each bitter taste receptor (TAS2R) responds to an array of compounds, many of which are toxic and can be found in nature. For example, human TAS2R16 (hTAS2R16) responds to β-glucosides such as salicin, and hTAS2R38 responds to thiourea-containing molecules such as glucosinolates and phenylthiocarbamide (PTC). While many substances are known to activate TAS2Rs, only one inhibitor that specifically blocks bitter receptor activation has been described. Here, we describe a new inhibitor of bitter taste receptors, p-(dipropylsulfamoyl)benzoic acid (probenecid), that acts on a subset of TAS2Rs and inhibits through a novel, allosteric mechanism of action. Probenecid is an FDA-approved inhibitor of the Multidrug Resistance Protein 1 (MRP1) transporter and is clinically used to treat gout in humans. Probenecid is also commonly used to enhance cellular signals in GPCR calcium mobilization assays. We show that probenecid specifically inhibits the cellular response mediated by the bitter taste receptor hTAS2R16 and provide molecular and pharmacological evidence for direct interaction with this GPCR using a non-competitive (allosteric) mechanism. Through a comprehensive analysis of hTAS2R16 point mutants, we define amino acid residues involved in the probenecid interaction that result in decreased sensitivity to probenecid while maintaining normal responses to salicin. Probenecid inhibits hTAS2R16, hTAS2R38, and hTAS2R43, but does not inhibit the bitter receptor hTAS2R31 or non-TAS2R GPCRs. Additionally, structurally unrelated MRP1 inhibitors, such as indomethacin, fail to inhibit hTAS2R16 function. Finally, we demonstrate that the inhibitory activity of probenecid in cellular experiments translates to inhibition of bitter taste perception of salicin in humans. This work identifies probenecid as a pharmacological tool for understanding the cell biology of bitter taste and as a lead for the development of broad specificity bitter blockers to improve nutrition and medical compliance.     

First Colombian multicentric newborn screening for congenital toxoplasmosis

Aims

To determine the incidence of congenital toxoplasmosis in Colombian newborns from 19 hospital or maternal child health services from seven different cities of five natural geographic regions (Caribbean, Central, Andean, Amazonia and Eastern).

Materials and Methods

We collected 15,333 samples from umbilical cord blood between the period of March 2009 to May 2010 in 19 different hospitals and maternal-child health services from seven different cities. We applied an IgM ELISA assay (Vircell, Spain) to determine the frequency of IgM anti Toxoplasma. The results in blood cord samples were confirmed either by western blot and repeated ELISA IgM assay. In a sub-sample of 1,613 children that were negative by the anti-Toxoplasma IgM assay, the frequency of specific anti-Toxoplasma IgA by the ISAGA assay was determined. All children with positive samples by IgM, IgA, clinical diagnosis or treatment during pregnancy were recalled for confirmatory tests after day 10 of life.

Results

61 positive samples for specific IgM (0.39%) and 9 positives for IgA (0.5%) were found. 143 questionnaires were positive for a clinical diagnosis or treatment for toxoplasmosis during pregnancy. 109 out of the 218 children that had some of the criteria for postnatal confirmatory tests were followed. Congenital toxoplasmosis infection was confirmed in 15 children: 7 were symptomatic, and three of them died before the first month of life (20% of lethality). A significant correlation was found between a high incidence of markers for congenital toxoplasmosis and higher mean annual rainfall for the city.

Conclusions

Incidence for congenital toxoplasmosis is significantly different between hospitals or maternal child health services from different cities in Colombia. Mean annual rainfall was correlated with incidence of congenital toxoplasmosis.     

The Ras-like protein R-Ras2/TC21 is important for proper mammary gland development

R-Ras2/TC21 is a GTPase with high sequence and signaling similarity with Ras subfamily members. Although it has been extensively studied using overexpression studies in cell lines, its physiological role remains poorly characterized. Here we used RRas2-knockout mice expressing β-galactosidase under the regulation of the endogenous RRas2 promoter to investigate the function of this GTPase in vivo. Despite its expression in tissues critical for organismal viability, RRas2(-/-) mice show no major alterations in viability, growth rates, cardiovascular parameters, or fertility. By contrast, they display a marked and specific defect in the development of the mammary gland during puberty. In the absence of R-Ras2/TC21, this gland forms reduced numbers of terminal end buds (TEBs) and ductal branches, leading to a temporal delay in the extension and arborization of the gland tree in mammary fat pads. This phenotype is linked to cell-autonomous proliferative defects of epithelial cells present in TEBs. These cells also show reduced Erk activation but wild type-like levels of phosphorylated Akt. Using compound RRas2-, HRas-, and NRas-knockout mice, we demonstrate that these GTPases act in a nonsynergistic and nonadditive manner during this morphogenic process.     

Cooperativity between the preproinsulin mRNA untranslated regions is necessary for glucose-stimulated translation

Glucose regulates proinsulin biosynthesis via stimulation of the translation of the preproinsulin mRNA in pancreatic beta-cells. However, the mechanism by which this occurs has remained unclear. Using recombinant adenoviruses that express the preproinsulin mRNA with defined alterations, the untranslated regions (UTRs) of the preproinsulin mRNA were examined for elements that specifically control translation of the mRNA in rat pancreatic islets. These studies revealed that the preproinsulin 5'-UTR was necessary for glucose stimulation of preproinsulin mRNA translation, whereas the 3'-UTR appeared to suppress translation. However, together the 5'- and 3'-UTRs acted cooperatively to markedly increase glucose-induced proinsulin biosynthesis. In primary hepatocytes the presence of the preproinsulin 3'-UTR led to reduced mRNA levels compared with the presence of the SV40 3'-UTR, consistent with the presence of mRNA stability determinants in the 3'-UTR that stabilize the preproinsulin mRNA in a pancreatic beta-cell-specific manner. Translation of these mRNAs in primary hepatocytes was not stimulated by glucose, indicating that regulated translation of the preproinsulin mRNA occurs in a pancreatic beta-cell-specific manner. Thus, the untranslated regions of the preproinsulin mRNA play crucial roles in regulating insulin production and therefore glucose homeostasis by regulating the translation and the stability of the preproinsulin mRNA.