Research on arbuscular mycorrhizae in Mexico: an historical synthesis and future prospects

This review analyzes the historical development and advances of the research on arbuscular mycorrhizal fungi (AMF) in Mexico, as well as the prospects for future research. AMF-research has been focused on studying both diversity and functionality in several ecosystems of Mexico, but mainly in the tropical dry and rainy ecosystems, and the agricultural systems. In Mexico, 95 species of AMF have been recorded, representing 41% of the known species worldwide. The functional effects of AMF colonization have been examined in approximately 10% of the known host plants, but greenhouse studies continue to dominate over those conducted under field conditions. Even though research to date has been at the organismic level, further effort is needed due to the high plant diversity in Mexico. Studies on AMF biomass under field conditions and more taxonomic determination are required based on morphological features, biochemical determinations (fatty acids) and molecular tools. In addition, ecophysiological and ecological in situ studies would help in understanding the relationships among AMF, soil fauna, nutrients, and host plants. The contribution of AMF to ecosystemic processes is a priority line of research that requires an integrated approach (inter- and multidisciplinary) in order to define the role of AM symbioses for biogeochemical models. The creation of a Mexican mycorrhizal research network has and will help to identify the main challenges. Generating similar research protocols, and sharing databases and experience will assist mycorrhizologists working under the diverse financial and ecological contexts that is to be found in Mexico and Latin America.     

Dietary oxidized n-3 PUFA induce oxidative stress and inflammation: role of intestinal absorption of 4-HHE and reactivity in intestinal cells

Dietary intake of long-chain n-3 PUFA is now widely advised for public health and in medical practice. However, PUFA are highly prone to oxidation, producing potentially deleterious 4-hydroxy-2-alkenals. Even so, the impact of consuming oxidized n-3 PUFA on metabolic oxidative stress and inflammation is poorly described. We therefore studied such effects and hypothesized the involvement of the intestinal absorption of 4-hydroxy-2-hexenal (4-HHE), an oxidized n-3 PUFA end-product. In vivo, four groups of mice were fed for 8 weeks high-fat diets containing moderately oxidized or unoxidized n-3 PUFA. Other mice were orally administered 4-HHE and euthanized postprandially versus baseline mice. In vitro, human intestinal Caco-2/TC7 cells were incubated with 4-hydroxy-2-alkenals. Oxidized diets increased 4-HHE plasma levels in mice (up to 5-fold, P < 0.01) compared with unoxidized diets. Oxidized diets enhanced plasma inflammatory markers and activation of nuclear factor kappaB (NF-κB) in the small intestine along with decreasing Paneth cell number (up to -19% in the duodenum). Both in vivo and in vitro, intestinal absorption of 4-HHE was associated with formation of 4-HHE-protein adducts and increased expression of glutathione peroxidase 2 (GPx2) and glucose-regulated protein 78 (GRP78). Consumption of oxidized n-3 PUFA results in 4-HHE accumulation in blood after its intestinal absorption and triggers oxidative stress and inflammation in the upper intestine.     

Calculating kinetics and pathways of protein-ligand association

While studies of protein-ligand association have mostly focused on the native complex and its stability (binding affinity), relatively little attention has been paid to the association process that precedes the formation of the complex. Here we review approaches to study the kinetics of association and association mechanisms, i.e. the probability distribution of association pathways. Selected methods are described that allow these properties to be calculated quantitatively from simulation models. We summarize some applications of these methods and finally propose a model mechanism by which proteins may efficiently screen potential ligands for those that can be natively bound.     

Human intestinal epithelial cell line SK-CO15 is a new model system to study Na(+)/H(+) exchanger 3

The Caco-2 cell line represents absorptive polarized intestinal epithelial cells that express multiple forms of Na(+)/H(+) exchanger (NHE) in their plasma membranes. Caco-2 cells express the major apical NHE isoform NHE3, but low NHE3 expression together with inefficient transfection often hamper intended studies. In this study, we examined whether SK-CO15 cells could be used to study NHE3 regulation. SK-CO15 cells grown on Transwell inserts developed polarized epithelial cells with microvilli. The transfection efficiency of SK-CO15 cells was markedly higher compared with Caco-2 cells, an advantage in gene transfer and knockout. SK-CO15 cells expressed NHE1, NHE2, and NHE3. NHE3 expression was significantly greater in these cells than Caco-2, and NHE3 comprised more than half of total NHE activity. Apical expression of NHE3 in SK-CO15 cells was confirmed by confocal immunofluorescence and surface biotinylation. NHE regulatory factors NHERF1 and NHERF2, which are important for regulation of NHE3 activity, were expressed in these cells. Stimulatory response of NHE3 in SK-CO15 cells was assessed by dexamethasone and lysophosphatidic acid (LPA). Treatment with dexamethasone for 24-48 h increased NHE3 expression and activity. Similarly to Caco-2 cells, SK-CO15 cells lacked the expression of the LPA receptor LPA(5,) but exogenous expression of LPA(5) resulted in acute stimulation of NHE3. Forskolin acutely inhibited NHE3 activity in SK-CO15 cells, further attesting the validity of these cells. We conclude that SK-CO15 cells with the amenity for transfection and high endogenous NHE3 expression are a new and better cell model for NHE3 regulatory investigation than widely used Caco-2 cells.     

Subjective estimations of thermal environment in recreational urban spaces—Part 2: international comparison

The present paper is the second part of our study in which we compare the results obtained in Szeged (Hungary) with those achieved through earlier outdoor thermal comfort projects based on simultaneous questionnaire surveys and on-site meteorological measurements. The main characteristics of the selected studies—conducted in Hungary, Sweden, Portugal, Canada, Taiwan and across Europe in the frame of project RUROS—are reviewed, emphasizing the common features and also the discrepancies in the applied methodology. We discuss their potential effects on the evolution and interpretation of the results concerning the subjective assessment of the thermal environment. Another aspect of the comparison focuses on the regional climatic differences naturally ensuing from the various locations, which left their marks on the results related to both physiological acclimatization and mental adaptation. The compared results of different studies include correlation coefficients expressing interrelationships between the different aspects of subjective estimations (thermal sensation, perceptions, preferences) and also between subjective assessments and the corresponding meteorological parameters. We compare neutral temperatures (expressed in physiological equivalent temperature, PET) which arose for Taiwan and Hungary, as well as thermal sensation zones for local inhabitants. Subjectively assessed temperature values of Sweden and Hungarians are analyzed according to the measured air temperature. According to our experiences the methodology should be standardized for the level of field surveys and also for the level of data processing in order to make the data collected in different locations comparable.     

Multivariate analysis to discriminate yeast strains with technological applications in table olive processing

This survey uses a multivariate classification analysis to discriminate yeast strains with interesting biochemical activities for the processing of table olives among a collection of 32 isolates belonging to 16 different yeast species. Lipase, esterase and β-glucosidase activities (desirable characteristics) were quantitatively evaluated in both extracellular and cellular fractions for all isolates in different types of culture media. The study of the quantitative data by cluster and principal component analyses led to the identification of several Wickerhamomyces anomalus, Candida boidinii and Candida diddensiae isolates with promising characteristics (the best global activity levels), clearly differentiated from the rest of the yeasts. The results obtained in this work open up new alternatives to this methodology for the study, classification and selection of the most suitable yeasts to be used as starters, alone or in combination with lactic acid bacteria, during table olive processing.     

The amphibians of the relict Betampona low-elevation rainforest,eastern Madagascar: an application of the integrative taxonomy approach to biodiversity assessments

The Strict Nature Reserve of Betampona protects one of the last remaining relicts (about 2,228 ha) of low elevation rainforests in eastern Madagascar. Yet little has been previously published about the amphibian fauna of this rainforest. During 2004 and 2007, Betampona was surveyed over a total period of 102 days. Frogs were searched by opportunistic searching, pitfall trapping and acoustic surveys. The survey work confirmed the occurrence of 76 taxa, of which 36 are currently candidate species and about 30% were first considered as undescribed species. The identification of species included a multidimensional and integrative approach that links morphology, bioacoustics, ecology and genetics. Of these taxa, 24 species are potentially endemic to this low elevation eastern region. Considering the relatively small area of the Betampona forest, and its narrow elevational range, 76 amphibian species represents an unusually high richness compared to other sites in Madagascar. Although the eastern region is now largely deforested, our results reveal the importance of this relict forest, which is protecting a diverse amphibian fauna that includes many potentially endemic species.     

Discovery of 3,4-dihydropyrimidin-2(1H)-ones with inhibitory activity against HIV-1 replication

3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) were selected and derivatized through a HIV-1 replication assay based on GFP reporter cells. Compounds 14, 25, 31, and 36 exhibited significant inhibition of HIV-1 replication with a good safety profile. Chiral separation of each enantiomer by fractional crystallization showed that only the S enantiomer retained anti-HIV activity. Compound (S)-40, a novel and potent DHPM analog, could serve as an advanced lead for further development and the determination of the mechanism of action.