An effect of parasite-encoded arginase on the outcome of murine cutaneous leishmaniasis

Classical activation of macrophages infected with Leishmania species results in expression and activation of inducible NO synthase (iNOS) leading to intracellular parasite killing. Macrophages can contrastingly undergo alternative activation with increased arginase activity, metabolism of arginine along the polyamine pathway, and consequent parasite survival. An active role for parasite-encoded arginase in host microbicidal responses has not previously been documented. To test the hypothesis that parasite-encoded arginase can influence macrophage responses to intracellular Leishmania, a comparative genetic approach featuring arginase-deficient mutants of L. mexicana lacking both alleles of the gene encoding arginase (Deltaarg), as well as wild-type and complemented Deltaarg controls (Deltaarg[pArg]), was implemented. The studies showed: 1) the absence of parasite arginase resulted in a significantly attenuated infection of mice (p<0.05); 2) poorer survival of Deltaarg in mouse macrophages than controls correlated with greater NO generation; 3) the difference between Deltaarg or control intracellular survival was abrogated in iNOS-deficient macrophages, suggesting iNOS activity was responsible for increased Deltaarg killing; 4) consistently, immunohistochemistry showed enhanced nitrotyrosine modifications in tissues of mice infected with Deltaarg compared with control parasites. Furthermore, 5) in the face of decreased parasite survival, lymph node cells draining cutaneous lesions of Deltaarg parasites produced more IFN-gamma and less IL-4 and IL-10 than controls. These data intimate that parasite-encoded arginase of Leishmania mexicana subverts macrophage microbicidal activity by diverting arginine away from iNOS.     

Diet-dependent depletion of queuosine in tRNAs in Caenorhabditis elegans does not lead to a developmental block

Queuosine (Q), a hypermodified nucleoside, occurs at the wobble position of transfer RNAs (tRNAs) with GUN anticodons. In eubacteria, absence of Q affects messenger RNA (mRNA) translation and reduces the virulence of certain pathogenic strains. In animal cells, changes in the abundance of Q have been shown to correlate with diverse phenomena including stress tolerance, cell proliferation and tumour growth but the function of Q in animals is poorly understood. Animals are thought to obtain Q (or its analogues) as a micronutrient from dietary sources such as gut microflora. However, the difficulty of maintaining animals under bacteria-free conditions on Q-deficient diets has severely hampered the study of Q metabolism and function in animals. In this study, we show that as in higher animals, tRNAs in the nematode Caenorhabditis elegans are modified by Q and its sugar derivatives. When the worms were fed on Q-deficient Escherichia coli, Q modification was absent from the worm tRNAs suggesting that C. elegans lacks a de novo pathway of Q biosynthesis. The inherent advantages of C. elegans as a model organism, and the simplicity of conferring a Q-deficient phenotype on it make it an ideal system to investigate the function of Q modification in tRNA.     

Synthesis, antimalarial, antileishmanial, antimicrobial, cytotoxicity, and methemoglobin (MetHB) formation activities of new 8-quinolinamines

We report the synthesis, in vitro antiprotozoal (against Plasmodium and Leishmania), antimicrobial, cytotoxicity (Vero and MetHb-producing properties), and in vivo antimalarial activities of two series of 8-quinolinamines. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pentyl}-(2S/2R)-2-aminosubstitutedamides (21-33) and N1-[4-(4-ethyl-6-methoxy-5-pentyloxy-8-quinolylamino)pentyl]-(2S/2R)-2-aminosubstitutedamides (51-63) were synthesized in six steps from 6-methoxy-8-nitroquinoline and 4-methoxy-2-nitro-5-pentyloxyaniline, respectively. Several analogs displayed promising antimalarial activity in vitro against Plasmodium falciparum D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) clones with high selectivity indices versus mammalian cells. The most promising analogs (21-24) also displayed potent antimalarial activity in vivo in a Plasmodium berghei-infected mouse model. Most interestingly, many analogs exhibited promising in vitro antileishmanial activity against Leishmania donovani promastigotes, and antimicrobial activities against a panel of pathogenic bacteria and fungi. Several analogs, notably 21-24, 26-32, and 60, showed less MetHb formation compared to primaquine indicating the potential of these compounds in 8-quinolinamine-based antimalarial drug development.     

The role of organic matter and microbial community controlling nitrate reduction under elevated ferrous iron concentrations in boreal lake sediments

Hydrobiologia - The nitrogen availability, that affects the greenhouse gas emission and the trophic level of lakes, is controlled mainly by microbial processes. We measured in a boreal nitrate and...     

AFD-Net: Apple Foliar Disease multi classification using deep learning on plant pathology dataset

Plant and Soil - Plant diseases significantly affect the crop, so their identification is very important. Correct identification of these diseases is crucial for establishing a good disease control...     

Nitrification Inhibitor and Plant Growth Regulators Improve Wheat Yield and Nitrogen Use Efficiency

Journal of Plant Growth Regulation - The field experiment was conducted to investigate the effects of applying urea with nitrification inhibitor (NI) (Nitrapyrine) alone or in combination with...     

Crystal structure of aspartyl dipeptidase from Xenopus laevis revealed ligand binding induced loop ordering and catalytic triad assembly

Gene encoding aspartyl dipeptidase from Xenopus levies (PepExl) is upregulated by thyroid hormone and is proposed to play a significant role in resorption of tadpole tail during metamorphosis. However, the importance of peptidase activity for the resorption of the tail remain elusive. Here we report the crystal structures of first eukaryotic S51 peptidase, PepExl, in its ligand-free and Asp-bound states at 1.4 and 1.8 Å resolutions, respectively. The active site is located at dimeric interface and the catalytic triad is found to be dissembled in ligand-free and assembled in Asp-bound state. Structural comparison and molecular dynamic simulations of ligand-free and Asp-bound states shows that distinct loop (loop-A) plays an important role in active site shielding, substrate binding and enzyme activation. This study illuminates the Asp-X dipeptide binding in PepExl is associated with ordering of the loop-A and assembly of residues of catalytic triad in active conformation for enzymatic activity.