Chlorophyll fluorescence as a marker for herbicide mechanisms of action

Photosynthesis is the single most important source of 02 and organic chemical energy necessary to support all non-autotrophic life forms. Plants compartmentalize this elaborate biochemical process within chloroplasts in order to safely harness the power of solar energy and convert it into usable chemical units. Stresses (biotic or abiotic) that challenge the integrity of the plant cell are likely to affect photosynthesis and alter chlorophyll fluorescence. A simple three-step assay was developed to test selected herbicides representative of the known herbicide mechanisms of action and a number of natural phytotoxins to determine their effect on photosynthesis as measured by chlorophyll fluorescence. The most active compounds were those interacting directly with photosynthesis (inhibitors of photosystem I and II), those inhibiting carotenoid synthesis, and those with mechanisms of action generating reactive oxygen species and lipid peroxidation (uncouplers and inhibitors of protoporphyrinogen oxidase). Other active compounds targeted lipids (very-long-chain fatty acid synthase and removal of cuticular waxes). Therefore, induced chlorophyll fluorescence is a good biomarker to help identify certain herbicide modes of action and their dependence on light for bioactivity. Published by Elsevier B.V.

Karyotype Conservation in 2 Populations of the Parthenogenetic Scorpion Tityus serrulatus (Buthidae): rDNA and Its Associated Heterochromatin Are Concentrated on Only One Chromosome

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Identification of a molecular marker linked to apomixis in Brachiaria humidicola (Poaceae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Viral infections in workers in hospital and research laboratory settings: a comparative review of infection modes and respective biosafety aspects

Objectives: To compare modes and sources of infection and clinical and biosafety aspects of accidental viral infections in hospital workers and research laboratory staff reported in scientific articles. Methods: PubMed, Google Scholar, ISI Web of Knowledge, Scirus, and Scielo were searched (to December 2008) for reports of accidental viral infections, written in English, Portuguese, Spanish, or German; the authors' personal file of scientific articles and references from the articles retrieved in the initial search were also used. Systematic review was carried out with inclusion criteria of presence of accidental viral infection's cases information, and exclusion criteria of absence of information about the viral etiology, and at least probable mode of infection.Results: One hundred and forty-one scientific articles were obtained, 66 of which were included in the analysis. For arboviruses, 84% of the laboratory infections had aerosol as the source; for alphaviruses alone, aerosol exposure accounted for 94% of accidental infections. of laboratory arboviral infections, 15.7% were acquired percutaneously, whereas 41.6% of hospital infections were percutaneous. For airborne viruses, 81% of the infections occurred in laboratories, with hantavirus the leading causative agent. Aerosol inhalation was implicated in 96% of lymphocytic choriomeningitis virus infections, 99% of hantavirus infections, and 50% of coxsackievirus infections, but infective droplet inhalation was the leading mode of infection for severe acute respiratory syndrome coronavirus and the mucocutaneous mode of infection was involved in the case of infection with influenza B. For blood-borne viruses, 92% of infections occurred in hospitals and 93% of these had percutaneous mode of infection, while among laboratory infections 77% were due to infective aerosol inhalation. Among blood-borne virus infections there were six cases of particular note: three cases of acute hepatitis following hepatitis C virus infection with a short period of incubation, one laboratory case of human immunodeficiency virus infection through aerosol inhalation, one case of hepatitis following hepatitis G virus infection, and one case of fulminant hepatitis with hepatitis B virus infection following exposure of the worker's conjunctiva to hepatitis B virus e antigen-negative patient saliva. of the 12 infections with viruses with preferential mucocutaneous transmission, seven occurred percutaneously, aerosol was implicated as a possible source of infection in two cases, and one atypical infection with Macacine herpesvirus 1 with fatal encephalitis as the outcome occurred through a louse bite. One outbreak of norovirus infection among hospital staff had as its probable mode of infection the ingestion of inocula spread in the environment by fomites.Conclusions: The currently accepted and practiced risk analysis of accidental viral infections based on the conventional dynamics of infection of the etiological agents is insufficient to cope with accidental viral infections in laboratories and to a lesser extent in hospitals, where unconventional modes of infection are less frequently present but still have relevant clinical and potential epidemiological consequences. Unconventional modes of infection, atypical clinical development, or extremely severe cases are frequently present together with high viral loads and high virulence of the agents manipulated in laboratories. In hospitals by contrast, the only possible association of atypical cases is with the individual resistance of the worker. Current standard precaution practices are insufficient to prevent most of the unconventional infections in hospitals analyzed in this study; it is recommended that special attention be given to flaviviruses in these settings. (C) 2011 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Studies on the activation of the pre-kininogenin-kininogenin (pre-kallikrein-kallikrein) system by sulfated polysaccharides and kaolin

The activation of pre-kininogenin to kininogenin (pre-kallikrein to kallikrein) is one of the steps in the series of reactions of a complex system, linked also to fibrinolysis and coagulation, that leads to kinin release in plasma (See Cochrane et al., 1976; Wuepper, 1976; Kaplan et al., 1976; Kaplan et al., 1976). For human plasma, a test using kaolin as activator and measuring kallikrein activity with the chromogenic substrate Chromozym PK (Nα-benzoyl-prolyl-phenylalanyl-arginyl-nitroanilide, Pentapharm, Basle) is routinely employed. The purpose of this paper is to further study the mechanism of this activation, by means of different activators and using as inhibitor hexadimethrine bromide (Polybrene). Besides kaolin, sulfated polysaccharides, such as heparin and cellulose sulfate are able to activate pre-kininogenin to kininogenin. Hexadimethrine as expected, inhibited the activation by heparin and also that by cellulose sulfate. The activation by kaolin however followed a different pattern suggesting, at least partially, a different mode of action of this activator. © 1979.

Structure and catalytic mechanism of glucosamine 6-phosphate deaminase from Escherichia coli at 2.1 Å resolution

Background: Glucosamine 6-phosphate deaminase from Escherichia coli is an allosteric hexameric enzyme which catalyzes the reversible conversion of D-glucosamine 6-phosphate into D-fructose 6-phosphate and ammonium ion and is activated by N-acetyl-D-glucosamine 6-phosphate. Mechanistically, it belongs to the group of aldose-ketose isomerases, but its reaction also accomplishes a simultaneous amination/deamination. The determination of the structure of this protein provides fundamental knowledge for understanding its mode of action and the nature of allosteric conformational changes that regulate its function. Results: The crystal structure of glucosamine 6-phosphate deaminase with bound phosphate ions is presented at 2.1 Å resolution together with the refined structures of the enzyme in complexes with its allosteric activator and with a competitive inhibitor. The protein fold can be described as a modified NAD-binding domain. Conclusions: From the similarities between the three presented structures, it is concluded that these represent the enzymatically active R state conformer. A mechanism for the deaminase reaction is proposed. It comprises steps to open the pyranose ring of the substrate and a sequence of general base-catalyzed reactions to bring about isomerization and deamination, with Asp72 playing a key role as a proton exchanger.

Increased B chromosome frequency and absence of drive in the fish Prochilodus lineatus

The neotropical freshwater fish species Prochilodus lineatus (Pisces, Prochilodontidae) shows 2n = 54 chromosomes plus supernumerary microchromosomes ranging in number from zero to seven among different animals. The transmission rates of B chromosomes were studied by the analysis of the parental and F1 generations in 10 controlled crosses performed with specimens from a natural population. The mean transmission rate observed for B chromosomes (k(B) = 0.511) was consistent with that expected from a regular meiotic behaviour orbs in both sexes and with the theoretical value under a Mendelian mode of transmission (0.5). Possible explanations for the dramatic increase in B frequency observed in this population during the last 10 years are discussed, bearing in mind the current absence of drive.

On the picture dependence of Ramond-Ramond cohomology

Closed string physical states are BRST cohomology classes computed on the space of states annihilated by b- 0. Since b- 0 does not commute with the operations of picture changing, BRST cohomologies at different pictures need not agree. We show explicitly that Ramond-Ramond (RR) zero-momentum physical states are inequivalent at different pictures, and prove that non-zero-momentum physical states are equivalent in all pictures. We find that D-brane states represent BRST classes that are non-polynomial on the superghost zero-modes, while RR gauge fields appear as polynomial BRST classes. We also prove that in x-cohomology, the cohomology where the zero-mode of the spatial coordinates is included, there is a unique ghost-number one BRST class responsible for the Green-Schwarz anomaly, and a unique ghost number minus one BRST class associated with RR charge. © 1998 Elsevier Science B.V.

Tensile bond strengths of hard chairside reline resins as influenced by water storage

Due to gradual resorption of the edentulous ridge bone, removable prostheses often require denture base relines to improve fit and stability. This research evaluated the bond strength between one heat-cured acrylic resin (Lucitone 550®) and two hard chairside reline resins, after two different periods of storage in water (50 h and 30 days). The bond strength was evaluated using a tensile test. The mode of failure, adhesive or cohesive, was also recorded. The results submitted to the Kruskal-Wallis test indicated that the highest tensile strengths were achieved with intact Lucitone 550® denture base resin in both periods of storage in water. After 50 h of storage in water, Duraliner II® reline material exhibited the highest bond strength to the denture base resin. After 30 days of storage in water, Duraliner II® reline resin demonstrated a significant reduction in adhesion, showing lower tensile bond strength than Kooliner® material. Both hard chairside reline materials failed adhesively across Lucitone 550® denture base resin, in both periods of time. © 1999 Blackwell Science Ltd.

Raman scattering study of zincblende InxGa1-xN alloys

We report on first-order micro-Raman and resonant micro-Raman scattering measurements on c-InxGa1-xN (0 ≤ x ≤ 0.31) epitaxial layers. We have found that both, the transverse-optical (TO) and longitudinal-optical (LO) phonons of InxGa1-xN alloy exhibit a one-mode-type behavior. Their frequencies at Γ lie on straight lines connecting the corresponding values obtained for the c-GaN and c-InN binary compounds. Evidence for phase separation is shown in the sample with the alloy composition x = 0.31. The Raman spectra, with excitation energy close to 2.4 eV, show an enhanced additional peak, with frequency between the values found for the LO and TO phonon modes of the C-In0.31Ga0.69N epitaxial layer. We ascribed this peak to the LO phonon mode of a minority phase with In content of ≈0.80.

Effect of barium titanate seed particles on the sintering and lattice parameters in PbMg1/3Nb2/3O3 ceramics

PbMg1/3Nb2/3O3 (PMN) powder was prepared by citrate organic solution, and barium titanate (BT) seed particles were added to encourage the perovskite phase formation. Sintering was followed using the constant heating rate mode of a dilatometer, and it was observed that the seed concentration affected the PMN shrinkage rate and crystal structure. The study of the lattice parameters of the samples after the sintering process indicates that the diffusion of the titanium and of the barium inside perovskite and pyrochlore PMN phases occurs. Moreover, this substitution provoked a decrease of the lattice parameters as showed by the Rietveld refinement.

Can one cure the nonunitarity of three-dimensional quadratic gravity using a topological Chern-Simons term?

Quadratic gravity in (2+1)D is nonunitarity at the tree level. When a topological Chern-Simons term is added to this theory, the harmless massive scalar mode of the former gives rise to a troublesome massive spin-0 ghost, while the massive spin-2 ghost is replaced by two massive physical particles both of spin-2. Therefore, unlike what it is claimed in the literature, quadratic Chern-Simons gravity in (2+1)D is nonunitary at the tree level. © 2004 Published by Elsevier B.V.

Effect of microwave disinfection procedures on torsional bond strengths of two hard chairside denture reline materials

Purpose: This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). Materials and Methods: Cylindrical (30 x 3.9 mm) denture base specimens (n = 160) were stored in water at 37°C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n = 10): Group 1 (G1) - tests performed after bonding; Group 2 (G2) - specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3) - specimens irradiated daily until seven cycles of disinfection; Group 4 (G4) - specimens immersed in water (37°C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p = 0.05). Results: For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days - 138 MPa; 30 days - 132 MPa), G3 (2 days - 126 MPa; 30 days - 130 MPa), and G4 (2 days - 130 MPa; 30 days - 137 MPa) were significantly higher (p < 0.05) than G1 (2 days - 108 MPa; 30 days - 115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days - 73 MPa; 30 days - 71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day - 86 MPa; 30 days - 90 MPa), G3 (2 days - 82 MPa; 30 days - 82 MPa), and G4 specimens (2 days - 78 MPa; 30 days - 79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. Conclusions: Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study. Copyright © 2006 by The American College of Prosthodontists.

Shear bond strength fatigue limit of rest seats made with dental restoratives

Purpose: This study compared the shear bond strength (SBS) to enamel of rest seats made with a glass-ionomer cement (Fuji IX GP Fast), a resin-modified glass-ionomer cement (Fuji II LC), and a composite resin (Z100 MP) under monotonic and cyclic loading. Materials and Methods: Rest seats were built up onto the lingual surfaces of 80 intact human mandibular incisors. Specimens (n=10) were stored in distilled water at 37°C for 30 days and subjected to shear forces in a universal testing machine (0.5 mm/min) until fracture. The SBS values were calculated (MPa) using the bonding area (9.62 mm2) delimited by adhesive tags. A staircase approach was used to determine the SBS fatigue limit of each material. Specimens were submitted to either 10,000 cycles (5 Hz) or until specimen fracture. A minimum of 15 specimens was tested for each material. Scanning electron microscopy was used to examine the mode of failure. Data were statistically analyzed with one-way ANOVA and Tukey HSD tests (α = 0.05). Results: Z100 MP yielded higher (p < 0.05) SBS (12.25 MPa) than Fuji IX GP Fast (7.21 MPa). No differences were found between Fuji II LC (10.29 MPa) and the other two materials (p > 0.05). Fuji II LC (6.54 MPa) and Z100 MP (6.26 MPa) had a similar SBS limit. Fuji IX GP Fast promoted the lowest (p < 0.05) SBS fatigue limit (2.33 MPa). All samples showed cohesive failure patterns. Conclusion: Fatigue testing can provide a better means of estimating the performance of rest seats made with dental restoratives.

Dispersal of the delayed action insecticide sulfluramid in colonies of the leaf-cutting ant Atta sexdens rubropilosa (Hymenoptera: Formicidae)

Toxic baits are the most used control method for leaf-cutting ants due to their high effectiveness and because they are considered the safest for humans. Taking into account that the importance of leaf-cutting ants as pests, knowing the process by which dispersal and worker contamination is achieved becomes essential to understand several aspects about the functioning of a bait-borne AI (active ingredient) used in toxic baits. It has been established that an effective toxic bait should have a delayed- action AI, but its dispersion among the different sizes of workers is unknown. Workers of different sizes are involved in quite different tasks such foraging, cultivation of symbiotic macrofungus or control of deleterious microfungi. Therefore, we prepared a toxic bait containing the delayed-action AI sulfluramid and a dye (Rhodamine B) as an AI tracer in order to study dispersal and contamination in colonies, evaluated at different periods and in relation to different workers' sizes. Both field and laboratory colonies were evaluated. The great level of contamination, about 50% at 24 hours, in all sizes of workers demonstrates that worker contact with toxic bait is intense within this period. The distribution in field and laboratory colonies was similar. This contamination pattern is probably enough to cause the colony to die because of contamination of smaller workers, leading to the loss of control of the aggressive microfungi, which can quickly overgrow the symbiotic fungus culture. The dispersal dynamics of AI in leaf-cutting ant workers is important for investigations on the mode of action of this insecticide in the colony, and as a reference in future studies, such as those attempting to reduce the concentration of AIs in baits to reduce their environmental impact, or for facilitation of new AI screening.