Choice of tracers for the evaluation of spray deposits

Tracer substances, used to evaluate spraying effectiveness, ordinarily modify the surface tension of aqueous solutions. This study aimed to establish a method of using tracers to evaluate distribution and amount of spray deposits, adjusted to the surface tension of the spraying solution. The following products were tested: 0.15% Brilliant Blue, 0.15% Saturn Yellow in 0.015% Vixilperse lignosulfonate, and 0.005% sodium fluorescein, and mixtures of Brilliant Blue plus Saturn Yellow and Brilliant Blue plus sodium fluorescein at the same concentrations. Solutions were deposited on citrus leaves and stability was determined by measuring fluorescence and optical density of solutions without drying, dried in the dark and exposed to sunlight for 2, 4 and 8 h. These values were compared to those obtained directly in water. The static surface tension of the tracer solution was determined by weighing droplets formed during a period of 20 to 40 seconds. The Brilliant Blue and Saturn Yellow mixture at 0.15% was stable under all conditions tested. It was not absorbed by the leaves and maintained the same surface tension as that of water, thus permitting concentration adjustment to the same levels used for agrochemical products, and allowing the development of a qualitative method based on visual evaluation of the distribution of the pigment under ultraviolet light and of a quantitative method based on the determination of the amount of the dye deposited in the same solution. Spray deposition could be evaluated at different surface tensions of the spraying solution, simulating the effect of agrochemical formulations

Functional Evolution of Duplicated Odorant-Binding Protein Genes, Obp57d and Obp57e, in Drosophila

Odorant-binding proteins (OBPs) are extracellular proteins found in insect chemosensilla, where they participate in the sensing of odors, tastes, and pheromones. Although a large number of OBP genes have been identified in insect genomes, their molecular functions and biological roles have been clarified in limited cases. Two OBP genes, Obp57d and Obp57e, were involved in the evolution of host-plant preference in Drosophila sechellia. Comparative analyses of the Obp57d/e genomic sequences from 27 closely related species suggested that the two genes arose by tandem gene duplication and functionally diverged from each other. In this study, the functional evolution of Obp57d and Obp57e was examined by in vitro binding assays using recombinant proteins synthesized in a bacterial system. Compared to the ancestral Dpse\OBP57de, Dmel\OBP57d was more specialized to tridecanoic acid while Dmel\OBP57e was generalized regarding their binding affinity, suggesting that the two OBP genes underwent subfunctionalization and neofunctionalization. A behavioral analysis using knockout flies supported that the biological role is different between OBP57d and OBP57e in vivo. Site-directed mutagenesis of the evolutionarily conserved amino acids revealed that these residues play an important role in protein folding. These findings provide a clue to understanding how the repertoire of OBP genes is maintained in a genome under natural selection

Balanços energéticos agropecuários: uma importante ferramenta como indicativo de sustentabilidade de agroecossistemas.

No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distribuem nos sistemas produtivos. Na agropecuária, a atenção tem sido voltada a novas fontes de energia (biomassa) ou em tecnologia alternativa, visando a racionalização do uso de energia fóssil ou elétrica. Entretanto, a agricultura tem se desenvolvido baseada fortemente na utilização intensiva de máquinas agrícolas, com conseqüente uso de combustíveis fósseis. Um fator de estrangulamento muito forte no consumo energético geral tem sido a utilização massiva de fertilizantes derivados do petróleo nos agroecossistemas. Estudos de Balanços Energéticos visam determinar os pontos de estrangulamento energético fundamentando a busca por tecnologias poupadoras de energia, especialmente aquelas de origem fóssil (combustível, fertilizante, agrotóxicos, energia despendida na fabricação das máquinas e implementos, etc.). No Brasil, a Região Sul, é onde se encontram vários trabalhos buscando uma agricultura mais auto-sustentável, do ponto de vista da utilização da energia. Em vista da possibilidade de eventuais futuras crises energéticas, o presente trabalho procura analisar o estado-da-arte dos estudos em Balanço Energético, no Brasil e no Mundo, como uma ferramenta de indicação da sustentabilidade dos sistemas agropecuários

Checkpoint Signaling, Base Excision Repair, and PARP Promote Survival of Colon Cancer Cells Treated with 5-Fluorodeoxyuridine but Not 5-Fluorouracil

The fluoropyrimidines 5-fluorouracil (5-FU) and FdUrd (5-fluorodeoxyuridine; floxuridine) are the backbone of chemotherapy regimens for colon cancer and other tumors. Despite their widespread use, it remains unclear how these agents kill tumor cells. Here, we have analyzed the checkpoint and DNA repair pathways that affect colon tumor responses to 5-FU and FdUrd. These studies demonstrate that both FdUrd and 5-FU activate the ATR and ATM checkpoint signaling pathways, indicating that they cause genotoxic damage. Notably, however, depletion of ATM or ATR does not sensitize colon cancer cells to 5-FU, whereas these checkpoint pathways promote the survival of cells treated with FdUrd, suggesting that FdUrd exerts cytotoxicity by disrupting DNA replication and/or inducing DNA damage, whereas 5-FU does not. We also found that disabling the base excision (BER) repair pathway by depleting XRCC1 or APE1 sensitized colon cancer cells to FdUrd but not 5-FU. Consistent with a role for the BER pathway, we show that small molecule poly(ADP-ribose) polymerase 1/2 (PARP) inhibitors, AZD2281 and ABT-888, remarkably sensitized both mismatch repair (MMR)-proficient and -deficient colon cancer cell lines to FdUrd but not to 5-FU. Taken together, these studies demonstrate that the roles of genotoxin-induced checkpoint signaling and DNA repair differ significantly for these agents and also suggest a novel approach to colon cancer therapy in which FdUrd is combined with a small molecule PARP inhibitor