Determinants of cardiac Na(+)/Ca(2+) exchanger temperature dependence: NH(2)-terminal transmembrane segments

The cardiacNa⁺/Ca²⁺ exchanger (NCX) in troutexhibits profoundly lower temperature sensitivity in comparison to themammalian NCX. In this study, we attempt to characterize the regions of the NCX molecule that are responsible for its temperature sensitivity. Chimeric NCX molecules were constructed using wild-type trout andcanine NCX cDNA and expressed in Xenopus oocytes.NCX-mediated currents were measured at 7, 14, and 30°C using thegiant excised-patch technique. By using this approach, the differentialtemperature dependence of NCX was found to reside within theNH₂-terminal region of the molecule. Specifically, we foundthat ~75% of the Na⁺/Ca²⁺ exchangedifferential energy of activation is attributable to sequencedifferences in the region that include the first four transmembranesegments, and the remainder is attributable to transmembrane segmentfive and the exchanger inhibitory peptide site.

     

Synthesis,semipreparative HPLC separation,biological evaluation,and 3D-QSAR of hydrazothiazole derivatives as human monoamine oxidase B inhibitors

The present study reports on synthesis in high yields (70–99%), HPLC enantioseparation, inhibitory activity against human monoamino oxidases, and molecular modeling including 3D-QSAR studies, of a large series of (4-aryl-thiazol-2-yl)hydrazones (1–45). Most of the synthesized compounds proved to be potent and selective inhibitors of hMAO-B isoform in the micromolar or nanomolar range, thus demonstrating that hydrazothiazole could be considered a good pharmacophore to design new hMAO-B inhibitors. Due to the presence in some derivatives of a chiral center, we also performed a semipreparative chromatographic enantioseparation of these compounds obtained by a stereoconservative pattern. The separated enantiomers were submitted to in vitro biological evaluation to point out the stereorecognition of the active site of the enzyme towards these structures. Finally, a 3D-QSAR study was carried out using Comparative Molecular Field Analysis (CoMFA), aiming to deduce rational guidelines for the further structural modification of these lead compounds.     

Integration of clinical and gene expression endpoints to explore furan-mediated hepatotoxicity

Molecular techniques, such as cDNA microarrays, are being used to aid in the elucidation of the mechanisms of toxicity of a variety of compounds. In this study, we evaluate the molecular effects of furan in the rat liver. Sprague-Dawley rats were exposed to 4 or 40 mg/kg furan for up to 14 days. Furan induced an initial degenerative and necrotic phenotype that was followed by inflammation and fibrosis, consistent with previous observations for this compound. RNA was harvested from each lobe of the liver at several time points to observe whether lobe-specific gene expression effects occurred. Similar gene expression changes were observed in all lobes, however the magnitude of gene expression change was more pronounced in the right lobe. Finally, to help determine the correlation between gene expression changes and liver pathology, we applied traditional microarray visualization tools to the assessment of clinical chemistry and pathology parameters.     

Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin

doi:10.1111/j.1741‐2358.2009.00292.x
Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin Objective: In this study, the effect of relining and surface treatment on the impact strength (IS) of a heat‐polymerising denture base acrylic resin (Lucitone 550‐L) was evaluated. Materials and methods: Rectangular bars of L were made (60 × 6 × 2 mm) and relined (2 mm) with the relining resins Ufi Gel Hard (UH) and Tokuso Rebase Fast (TR). Specimens relined with L and intact L, TR and UH specimens were also made (60 × 6 × 4 mm), for comparison. Before relining, the L surface was left untreated or wetted with methyl methacrylate monomer and/or the bonding agents (BA) supplied by manufacturers of the reline resins. V‐notches were machined at the midpoint of the length of all specimens. The notches were made either across the width (Nw) or across the thickness of the specimens (Nth). The Charpy impact test was performed using a 0.5‐J pendulum, which had been specially designed and constructed. Data were analysed separately for each notch position using one‐way analysis of variance and Tukey honestly significant difference post‐hoc test (p = 0.05). Results: The IS of L was similar to that of L/L. For the Nw notch, treating the denture base L with TR BA and relining with TR reline material produced the highest IS. Conclusion: The IS of specimens made from heat polymerising acrylic resin Lucitone 550 was increased after relining using the hard chairside reline resin TR with its proprietary BA.     

Functional genomics of brain aging and Alzheimer's disease: focus on selective neuronal vulnerability

Pivotal brain functions, such as neurotransmission, cognition, and memory, decline with advancing age and, especially, in neurodegenerative conditions associated with aging, such as Alzheimer's disease (AD). Yet, deterioration in structure and function of the nervous system during aging or in AD is not uniform throughout the brain. Selective neuronal vulnerability (SNV) is a general but sometimes overlooked characteristic of brain aging and AD. There is little known at the molecular level to account for the phenomenon of SNV. Functional genomic analyses, through unbiased whole genome expression studies, could lead to new insights into a complex process such as SNV. Genomic data generated using both human brain tissue and brains from animal models of aging and AD were analyzed in this review. Convergent trends that have emerged from these data sets were considered in identifying possible molecular and cellular pathways involved in SNV. It appears that during normal brain aging and in AD, neurons vulnerable to injury or cell death are characterized by significant decreases in the expression of genes related to mitochondrial metabolism and energy production. In AD, vulnerable neurons also exhibit down-regulation of genes related to synaptic neurotransmission and vesicular transport, cytoskeletal structure and function, and neurotrophic factor activity. A prominent category of genes that are up-regulated in AD are those related to inflammatory response and some components of calcium signaling. These genomic differences between sensitive and resistant neurons can now be used to explore the molecular underpinnings of previously suggested mechanisms of cell injury in aging and AD.     

Development of a Rapid Agglutination Latex Test for Diagnosis of Enteropathogenic and Enterohemorrhagic Escherichia coli Infection in Developing World: Defining the Biomarker,Antibody and Method

Background

Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC/EHEC) are human intestinal pathogens responsible for diarrhea in both developing and industrialized countries. In research laboratories, EPEC and EHEC are defined on the basis of their pathogenic features; nevertheless, their identification in routine laboratories is expensive and laborious. Therefore, the aim of the present work was to develop a rapid and simple assay for EPEC/EHEC detection. Accordingly, the EPEC/EHEC-secreted proteins EspA and EspB were chosen as target antigens.

Methodology

First, we investigated the ideal conditions for EspA/EspB production/secretion by ELISA in a collection of EPEC/EHEC strains after cultivating bacterial isolates in Dulbecco’s modified Eagle’s medium (DMEM) or DMEM containing 1% tryptone or HEp-2 cells-preconditioned DMEM, employing either anti-EspA/anti-EspB polyclonal or monoclonal antibodies developed and characterized herein. Subsequently, a rapid agglutination latex test (RALT) was developed and tested with the same collection of bacterial isolates.

Principal findings

EspB was defined as a biomarker and its corresponding monoclonal antibody as the tool for EPEC/EHEC diagnosis; the production of EspB was better in DMEM medium. RALT assay has the sensitivity and specificity required for high-impact diagnosis of neglected diseases in the developing world.

Conclusion

RALT assay described herein can be considered an alternative assay for diarrhea diagnosis in low-income countries since it achieved 97% sensitivity, 98% specificity and 97% efficiency.     

Ants as egg predators of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Australian cotton crops

Abstract Helicoverpa armigera is a major pest of Australian cotton crops. To assess the impact of ant predation on H. armigera populations, the behaviour of four common ant taxa was observed in cotton crops in northern New South Wales over the 1999−2000 and 2001−02 seasons. Areas of cotton were artificially stocked with H. armigera eggs prior to observation. Pheidole spp. were the most frequently observed ants within the crop canopy in 1999−2000 and took the most H. armigera eggs. Iridomyrmex spp. were more frequently observed than Pheidole spp. in 2001−02 and also took some H. armigera eggs. Neither Paratrechina spp. nor Rhytidoponera metallica (Smith) took any H. armigera eggs, although both were seen in the crop canopy. Irrigation, cultivation and insecticide application disrupted foraging ants and limited their impact on H. armigera populations.     

Using pedigree reconstruction to estimate population size: genotypes are more than individually unique marks

Estimates of population size are critical for conservation and management, but accurate estimates are difficult to obtain for many species. Noninvasive genetic methods are increasingly used to estimate population size, particularly in elusive species such as large carnivores, which are difficult to count by most other methods. In most such studies, genotypes are treated simply as unique individual identifiers. Here, we develop a new estimator of population size based on pedigree reconstruction. The estimator accounts for individuals that were directly sampled, individuals that were not sampled but whose genotype could be inferred by pedigree reconstruction, and individuals that were not detected by either of these methods. Monte Carlo simulations show that the population estimate is unbiased and precise if sampling is of sufficient intensity and duration. Simulations also identified sampling conditions that can cause the method to overestimate or underestimate true population size; we present and discuss methods to correct these potential biases. The method detected 2–21% more individuals than were directly sampled across a broad range of simulated sampling schemes. Genotypes are more than unique identifiers, and the information about relationships in a set of genotypes can improve estimates of population size.     

A Neutron Scattering Study of the Ternary Complex EF-Tu•GTP-valy1-tRNAVal 1A

Abstract

The complex formation between elongation factor Tu (EF-Tu), GTP, and valyl-tRNA^Val _1A has been investigated in a hepes buffer of “pH” 7.4 and 0.2 M ionic strength using the small-angle neutron scattering method at concentrations of D₂O where EF-Tu (42% D₂O) and tRNA (71% D₂O) are successively matched by the solvents. The results indicate that EF-Tu undergoes a conformational change and contracts as a result of the complex formation, since the radius of gyration decreases by 15% from 2.82 to 2.39 nm. tRNA^Val _1A, on the other hand, seems to mainly retain its conformation within the complex, since the radii of gyration for the free (after correction for interparticular scattering) and complexed form are essentially the same. 2.38 and 2.47 nm, respectively.