Effect of long-term water immersion on the fracture toughness of denture base and reline resins

doi: 10.1111/j.1741‐2358.2011.00573.x
Effect of long‐term water immersion on the fracture toughness of denture base and reline resins purpose: This study evaluated the fracture toughness (FT) of one denture base (Lucitone 550 – L) and four hard reline resins [Ufi Gel Hard (UH), Tokuyama Rebase II (TR), New Truliner (NT) and Kooliner (K)], and the effect of long‐term water storage on this property. Materials and methods: Forty specimens (40 × 8 × 4 mm) of each material were made, and FT was assessed after polymerisation (control of reliners), after 48 ± 2 h in water at 37°C (control of denture base resin) and after storage in water at 37°C for 7, 90 or 180 days (all materials). Data (MPa.m^1/2) were analysed by two‐way anova and Games–Howell test (p = 0.05). Results: Resin L exhibited the highest FT mean values. After 180 days of storage, FT mean values of L (3.37), UH (1.53) and K (1.20) were higher than those of the other periods. FT mean values of NT decreased from control (1.63) to 7 days (1.30) and then remained constant. FT mean values of TR (1.13) were similar in all periods of analysis. Conclusion: The denture base resin L showed higher FT mean values than the reline resins. Long‐term water storage increased the FT of L, UH and K, reduced the FT of NT and did not influence the FT of TR.     

Parameters of Metabolic Syndrome and Its Relationship with Zincemia and Activities of Superoxide Dismutase and Glutathione Peroxidase in Obese Women

Alterations in antioxidant defense in obese people with metabolic syndrome can contribute to oxidative stress. This study assessed the relationship between the parameters of metabolic syndrome and the zincemia, activity of superoxide dismutase, and glutathione peroxidase enzymes in obese women. Seventy-three premenopausal women, aged between 20 and 50 years, were divided into two groups: case group, composed of obese (n = 37), and control group, composed of no obese (n = 36). Analyses of zinc intake, parameters of metabolic syndrome, plasma, and erythrocyte zinc, and activities of superoxide dismutase and glutathione peroxidase were carried out. The mean values of body mass index of obese women and control group were 34.5 ± 3.4 and 21.7 ± 1.9 kg/m², respectively (p < 0.05). In the study, body mass index, waist circumference, and zinc intake were higher in obese women than control group (p < 0.05). The plasma zinc and activity of superoxide dismutase did not show significant differences between obese and controls (p > 0.05). The values of erythrocyte zinc was 36.4 ± 15.0 μg/gHb and 45.4 ± 14.3 μg/gHb and of glutathione peroxidase was 46.4 ± 19.4 U/gHb and 36.7 ± 13.6 U/gHb in obese women and controls, respectively (p < 0.05). The study shows that there are alterations in biochemical parameters of zinc in obese women, with low zinc concentrations in erythrocytes. Regression analysis demonstrates that the erythrocyte zinc and activity of superoxide dismutase enzyme is influenced by components of the metabolic syndrome, and the plasmatic glucose, body mass index, and waist circumference have a negative correlation with this enzyme.     

Effect of coffee alkaloids and phenolics on egg-laying by the coffee leaf miner Leucoptera coffeella

The recognized importance of coffee alkaloids and phenolics mediating insect-plant interactions led to the present investigation aiming to test the hypothesis that the phenolics chlorogenic and caffeic acids and the alkaloid caffeine and some of its derivatives present in coffee leaves affect egg-laying by the coffee leaf miner Leucoptera (=Perileucoptera) coffeella (Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae), one of the main coffee pests in the Neotropical region. These phytochemicals were, therefore, quantified in leaves from 12 coffee genotypes and their effect on the egg-laying preference by the coffee leaf miner was assessed. Canonical variate analysis and partial canonical correlation provided evidence that increased leaf levels of caffeine favour egg-laying by the coffee leaf miner. An egg-laying preference bioassay was, therefore, carried out to specifically test this hypothesis using increasing caffeine concentrations sprayed on leaves of one of the coffee genotypes with the lowest level of this compound (i.e. Hybrid UFV 557-04 generated from a cross between Coffea racemosa Lour. and C. arabica L.). The results obtained allowed the recognition of a significant concentration-response relationship, providing support for the hypothesis that caffeine stimulates egg-laying by the coffee leaf miner in coffee leaves.     

Biology of the first generation of a laboratory colony of Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae)

The phlebotomine sand flies Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) are very close and may be involved in the transmission of Leishmania spp. Ross, 1903 in Brazil. The biology of the first laboratory-reared generations of these species, descended from insects captured in Além Paraíba (N. intermedia) and Corinto (N. neivai) in the Brazilian state of Minas Gerais, is described here. The captured females were fed on hamsters and maintained individually in rearing pots. Laboratory temperature and relative humidity were maintained at 25-26 masculineC and 80% respectively. The productivity of the first generation of N. intermedia was greater than that of N. neivai, and its development time clearly shorter, particularly for the second and third larval instars.     

Fine‐scale habitat heterogeneity explains the local distribution of two Amazonian frog species of concern for conservation

To test the hypothesis that subtle differences in abiotic requirements can result in almost total spatial segregation, we sampled two species of diurnal frogs, Atelopus spumarius and Allobates sumtuosus, in a primary forest reserve in central Brazilian Amazonia. We conducted visual and acoustic surveys on three occasions over 2 months, in 40 streamside (riparian) plots distributed throughout the reserve's two major drainage basins, using a grid system that covers 64 km². On average, drainages differed in the pH of stream water and the number of connected and isolated streamside pools. Differences in abiotic characteristics of drainages were associated with the spatial distribution of frog species. The occurrence and density of Allobates sumtuosus was negatively related to stream pH and discharge and positively related to the number of isolated pools in plots. The occurrence and density of Atelopus spumarius was associated with streams with high discharge and pH near neutral. These results indicate that although very large reserves will probably contain sufficient landscape heterogeneity to accommodate different species of diurnal frogs, due to strongly patchy distributions, in situ studies using fine‐scale species‐distribution models will be necessary to assess the adequacy of small reserves in Amazonia that cover hundreds of square kilometers or less for the conservation of some anuran species.     

Planning for optimal conservation of geographical genetic variability within species

Systematic Conservation Planning (SCP) involves a series of steps that should be accomplished to determine the most cost-effective way to invest in conservation action. Although SCP has been usually applied at the species level (or hierarchically higher), it is possible to use alleles from molecular analyses at the population level as basic units for analyses. Here we demonstrate how SCP procedures can be used to establish optimum strategies for in situ and ex situ conservation of a single species, using Dipteryx alata (a Fabaceae tree species widely distributed and endemics to Brazilian Cerrado) as a case study. Data for the analyses consisted in 52 alleles from eight microsatellite loci coded for a total of 644 individual trees sampled in 25 local populations throughout species’ geographic range. We found optimal solutions in which seven local populations are the smallest set of local populations of D. alata that should be conserved to represent the known genetic diversity. Combining these several solutions allowed estimating the relative importance of the local populations for conserving all known alleles, taking into account the current land-use patterns in the region. A germplasm collection for this species already exists, so we also used SCP approach to identify the smallest number of populations that should be further collected in the field to complement the existing collection, showing that only four local populations should be sampled for optimizing the species ex situ representation. The initial application of the SCP methods to genetic data showed here can be a useful starting point for methodological and conceptual improvements and may be a first important step towards a comprehensive and balanced quantitative definition of conservation goals, shedding light to new possibilities for in situ and ex situ designs within species.     

Structural and Molecular Basis of the Peroxynitrite-mediated Nitration and Inactivation of Trypanosoma cruzi Iron-Superoxide Dismutases (Fe-SODs) A and B: DISPARATE SUSCEPTIBILITIES DUE TO THE REPAIR OF TYR35 RADICAL BY CYS83 IN Fe-SODB THROUGH INTRAMOLECULAR ELECTRON TRANSFER*

Trypanosoma cruzi, the causative agent of Chagas disease, contains exclusively iron-dependent superoxide dismutases (Fe-SODs) located in different subcellular compartments. Peroxynitrite, a key cytotoxic and oxidizing effector biomolecule, reacted with T. cruzi mitochondrial (Fe-SODA) and cytosolic (Fe-SODB) SODs with second order rate constants of 4.6 ± 0.2 × 10⁴ m⁻¹ s⁻¹ and 4.3 ± 0.4 × 10⁴ m⁻¹ s⁻¹ at pH 7.4 and 37 °C, respectively. Both isoforms are dose-dependently nitrated and inactivated by peroxynitrite. Susceptibility of T. cruzi Fe-SODA toward peroxynitrite was similar to that reported previously for Escherichia coli Mn- and Fe-SODs and mammalian Mn-SOD, whereas Fe-SODB was exceptionally resistant to oxidant-mediated inactivation. We report mass spectrometry analysis indicating that peroxynitrite-mediated inactivation of T. cruzi Fe-SODs is due to the site-specific nitration of the critical and universally conserved Tyr³⁵. Searching for structural differences, the crystal structure of Fe-SODA was solved at 2.2 Å resolution. Structural analysis comparing both Fe-SOD isoforms reveals differences in key cysteines and tryptophan residues. Thiol alkylation of Fe-SODB cysteines made the enzyme more susceptible to peroxynitrite. In particular, Cys⁸³ mutation (C83S, absent in Fe-SODA) increased the Fe-SODB sensitivity toward peroxynitrite. Molecular dynamics, electron paramagnetic resonance, and immunospin trapping analysis revealed that Cys⁸³ present in Fe-SODB acts as an electron donor that repairs Tyr³⁵ radical via intramolecular electron transfer, preventing peroxynitrite-dependent nitration and consequent inactivation of Fe-SODB. Parasites exposed to exogenous or endogenous sources of peroxynitrite resulted in nitration and inactivation of Fe-SODA but not Fe-SODB, suggesting that these enzymes play distinctive biological roles during parasite infection of mammalian cells.     

Notch Signalling Is Required for the Formation of Structurally Stable Muscle Fibres in Zebrafish

Background

Accurate regulation of Notch signalling is central for developmental processes in a variety of tissues, but its function in pectoral fin development in zebrafish is still unknown.

Methodology/Principal Findings

Here we show that core elements necessary for a functional Notch pathway are expressed in developing pectoral fins in or near prospective muscle territories. Blocking Notch signalling at different levels of the pathway consistently leads to the formation of thin, wavy, fragmented and mechanically weak muscles fibres and loss of stress fibres in endoskeletal disc cells in pectoral fins. Although the structural muscle genes encoding Desmin and Vinculin are normally transcribed in Notch-disrupted pectoral fins, their proteins levels are severely reduced, suggesting that weak mechanical forces produced by the muscle fibres are unable to stabilize/localize these proteins. Moreover, in Notch signalling disrupted pectoral fins there is a decrease in the number of Pax7-positive cells indicative of a defect in myogenesis.

Conclusions/Significance

We propose that by controlling the differentiation of myogenic progenitor cells, Notch signalling might secure the formation of structurally stable muscle fibres in the zebrafish pectoral fin.     

Sequence-dependent in vivo importation of tRNAs into the mitochondrion of Leishmania tarentolae.

Sequence determinants for the importation of tRNAs into the mitochondrion of Leishmania tarentolae in vivo were investigated. tRNA(Ile)(UAU) is exclusively localized within the mitochondrion and tRNA(Gln)(CUG) exclusively in the cytosol (Lye LF, Chen DHT, Suyama Y, 1993, Mol Biochem Parasitol 58:233-246; Shi X, Chen DHT, Suyama Y, 1994, Mol Biochem Parasitol 65:23-37). L. tarentolae cells were transfected with plasmids encoding either tRNA(Ile) or tRNA (Gln) that were tagged with altered sequences in the D loop, permitting discrimination from the endogenous tRNAs. Primer extension analysis was used to show that the plasmid-encoded genes were expressed and that the tagged tRNAs showed a similar intracellular localization as the endogenous tRNAs. Exchange or deletion of the 5'-flanking genomic sequences had no effect on the expression or mitochondrial localization of the tagged tRNA(Ile) or on the expression or cytosolic localization of the tagged tRNA(Gln), suggesting that the signals for importation are localized within the tRNA itself. Swapping the D loop+stem from the exclusively cytosolic tRNA(Gln) with that from the tRNA(Ile) produced a partial mitochondrial localization of the plasmid-expressed mutated tRNA(Gln). However, D loop exchange did not eliminate the mitochondrial localization of the plasmid-expressed mutated tRNA(Ile), suggesting that tertiary structure or additional sequence elements may be involved in the importation signal.