Seasonal variations in antibiotic resistance gene transport in the Almendares River, Havana, Cuba

Numerous studies have quantified antibiotic resistance genes (ARG) in rivers and streams around the world, and significant relationships have been shown that relate different pollutant outputs and increased local ARG levels. However, most studies have not considered ambient flow conditions, which can vary dramatically especially in tropical countries. Here, ARG were quantified in water column and sediment samples during the dry- and wet-seasons to assess how seasonal and other factors influence ARG transport down the Almendares River (Havana, Cuba). Eight locations were sampled and stream flow estimated during both seasons; qPCR was used to quantify four tetracycline, two erythromycin, and three beta-lactam resistance genes. ARG concentrations were higher in wet-season versus dry-season samples, which combined with higher flows, indicated much greater ARG transport downstream during the wet-season. However, water column ARG levels were more spatially variable in the dry-season than the wet-season, with the proximity of waste outfalls strongly influencing local ARG levels. Results confirm that dry-season sampling provides a useful picture of the impact of individual waste inputs on local stream ARG levels, whereas the majority of ARGs in this tropical river were transported downstream during the wet-season, possibly due to re-entrainment of ARG from sediments

The decrease in growth hormone (GH) response after repeated stimulation with GH-Releasing hormone is partly caused by an elevation of somatostatin tonus.

Repeated injection of GHRH leads to a decrease in the GH response in normal subjects. Arginine (Arg) stimulates GH secretion by suppression of hypothalamic somatostatin. To confirm these findings, eight normal men were examined in a series of five settings: test 1 (GHRH/GHRH-TRH), 100 micrograms GHRH injected iv, followed by 100 micrograms GHRH, iv, after 120 min and 200 micrograms TRH, iv, after 150 min; test 2 (GHRH/Arg-TRH), like test 1, but instead of the second GHRH injection, a 30 g Arg infusion over 30 min; test 3 (GHRH/GHRH-Arg-TRH), like test 1, but additionally a 30 g Arg infusion after 120 min; test 4 (GHRH-Arg-TRH), iv GHRH and Arg infusion initially, followed by iv TRH after 30 min; and test 5 (TRH), 200 micrograms TRH, iv, at 0 min. For statistical evaluation, the area under the GH curve (AUC) from 0-120 min was compared with the AUC from 120-240 min. The GH response to the second administration of GHRH was significantly lower (P < 0.02) than the first increase [AUC, 0.5 +/- 0.01 min.mg/L (mean +/- SE) vs. 1.2 +/- 0.3]. No significant differences were found between the GH responses to either GHRH or Arg alone (AUC, 0.9 +/- 0.2 min.mg/L vs. 0.9 +/- 0.2). A larger GH increase (P < 0.02) was seen after GHRH-Arg compared to GHRH alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 1.2 +/- 0.3). The GH response (P < 0.02) to GHRH-Arg stimulation was lower after previous GHRH injection than after GHRH-Arg stimulation alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 3.5 +/- 0.9). There was a statistically significant difference between the TRH-stimulated TSH response in test 4 compared to that in test 5. We could show that decreasing GH responses to repeated GHRH can be avoided by a combined stimulation with GHRH/Arg. These findings suggest that the decreased GH response to a second GHRH bolus may be partly due to an elevated hypothalamic somatostatin secretion, which can be suppressed by Arg. The lower GH response to GHRH-Arg stimulation after a previous GHRH bolus suggests, furthermore, that the readily available GH pool in the human pituitary may be limited

Peptide synthesis by recombinant Fasciola hepatica cathepsin L1

Synthesis of the tripeptide Z-Phe-Arg-SerNH2 has been accomplished by a recombinant cysteine protease, cathepsin L1 from liver fluke (Fasciola hepatica), using Z-Phe-Arg-OMe as acyl acceptor and SerNH2 as nucleophile in 0.1 M ammonium acetate pH 9.0–12.5% v/v acetonitrile at 37 °C. LC–MS detection indicated tripeptide formation after 10 min, continuing up to 5.5 h. The ester Z-Phe-Arg-OMe was detected throughout the experiment but the hydrolysis product Z-Phe-Arg-OH appeared early and in quite large amounts. We believe that this is the first application of a parasite protease in enzymatic peptide synthesis

Effects of arginine and ornithine supplementation to a high‐protein diet on selected cellular immune variables in adult cats

Background: Dietary protein and amino acid intake and composition can modulate immune function. Objectives: To evaluate the effects of high‐protein intake and arginine and ornithine supplementation on feline immune cells. Animals: Ten healthy cats. Methods: Experimental study. Cats received a high‐protein basal diet as a single daily meal. A crossover design was applied with treatments being basal diet (w/o); basal diet with arginine supplementation (+50, 75, 100% compared to the arginine provision by the basal diet; Arg 1‐3); and basal diet with ornithine supplementation (+100, 150, 200% compared to the arginine provision by the basal diet; Orn 1‐3). Blood samples were collected at the end of each 11‐day treatment period. Results: Mitogen‐stimulated proliferative activity of blood leukocytes revealed a quadratic effect for the dietary supplementation of arginine (P = .02) and ornithine (P = .03) (means for ConA‐stimulation: w/o = 6.96; Arg 1 = 9.31; Arg 2 = 11.4; Arg 3 = 8.04; Orn 1 = 15.4; Orn 2 = 9.43; Orn 3 = 9.28; pooled SEM: 0.96). The number (% gated) of phagocytic granulocytes linearly decreased with increasing dietary concentrations of arginine (P = .05) and ornithine (P = .03) (means: w/o = 95.5; Arg 1 = 93.0; Arg 2 = 92.5; Arg 3 = 92.6; Orn 1 = 92.6; Orn 2 = 92.6; Orn 3 = 91.5; pooled SEM = 0.44). Conclusions and Clinical Importance: This study could demonstrate immunomodulating properties of dietary arginine and ornithine in cats

The Conformational Space of a Flexible Amino Acid at Metallic Surfaces

In interfaces between inorganic and biological materials relevant for technological applications, the general challenge of structure determination is exacerbated by the high flexibility of bioorganic components, chemical bonding, and charge rearrangement at the interface. In this paper, we investigate a chemically complex building block, namely, the arginine (Arg) amino-acid interfaced with Cu, Ag and Au (111) surfaces. We investigate how the environment changes the accessible conformational space of this amino acid, by building and analyzing a database of thousands of structures optimized with the PBE functional including screened pairwise van der Waals interactions. When in contact with metallic surfaces, the accessible space for Arg is dramatically reduced, while the one for Arg-H$^+$ is instead increased if compared to the gas-phase. This is explained by the formation of strong bonds between Arg and the surfaces and by their absence and charge screening on Arg-H$^+$ upon adsorption. We also observe protonation-dependent stereoselective binding of the amino acid to the metal surfaces: Arg adsorbs with its chiral C$_\alpha$H center pointing H away from the surfaces while Arg-H$^+$ adsorbs with H pointing toward the surface

Genome-wide inference of ancestral recombination graphs

The complex correlation structure of a collection of orthologous DNA sequences is uniquely captured by the "ancestral recombination graph" (ARG), a complete record of coalescence and recombination events in the history of the sample. However, existing methods for ARG inference are computationally intensive, highly approximate, or limited to small numbers of sequences, and, as a consequence, explicit ARG inference is rarely used in applied population genomics. Here, we introduce a new algorithm for ARG inference that is efficient enough to apply to dozens of complete mammalian genomes. The key idea of our approach is to sample an ARG of n chromosomes conditional on an ARG of n-1 chromosomes, an operation we call "threading." Using techniques based on hidden Markov models, we can perform this threading operation exactly, up to the assumptions of the sequentially Markov coalescent and a discretization of time. An extension allows for threading of subtrees instead of individual sequences. Repeated application of these threading operations results in highly efficient Markov chain Monte Carlo samplers for ARGs. We have implemented these methods in a computer program called ARGweaver. Experiments with simulated data indicate that ARGweaver converges rapidly to the true posterior distribution and is effective in recovering various features of the ARG for dozens of sequences generated under realistic parameters for human populations. In applications of ARGweaver to 54 human genome sequences from Complete Genomics, we find clear signatures of natural selection, including regions of unusually ancient ancestry associated with balancing selection and reductions in allele age in sites under directional selection. Preliminary results also indicate that our methods can be used to gain insight into complex features of human population structure, even with a noninformative prior distribution.Comment: 88 pages, 7 main figures, 22 supplementary figures. This version contains a substantially expanded genomic data analysi

A first checklist of the lichen-forming fungi of the Venezuelan Andes

Basing on an evaluation of the literature and some unpublished collections, 745 taxa of lichen forming-fungi are reported from the Venezuelan Andes, including 10 infraspecific taxa. Of these taxa 37 are new records for Venezuela: Actinoplaca vulgaris (Müll. Arg.) Vezda & Poelt, Asterothyrium decipiens (Rehm) R. Sant., Calopadia foliicola (Fée) Vezda, C. fusca (Müll. Arg.) Vezda, C. phyllogena (Müll. Arg.) Vezda, Chrysothrix chlorina (Ach.) J. R. Laundon, Cystocoleus ebeneus (Dillwyn) Thwaites, Diploschistes scruposus (Schreb.) Norm., Echinoplacaleucotrichoides (Vain.) R. Sant., Fellhanerabouteillei (Desm.) Vezda, F.dominicana (Vain.) Vezda, F. fuscatula (Müll. Arg.) Vezda, F. sublecanorina (Nyl.) Vezda, Gyalectidium filicinum Müll. Arg., Lecidea limosa Ach., Lepraria neglecta Auct., Ochrolechia africana Vain., Peltigera vainioi Gyelnik, Phyllobathelium nigrum R. Sant. & Tibell, Phyllophialealba R. Sant., Polymeridiumalbidum (Müll. Arg.) R. C. Harris, Porina epiphylla (Fée) Fée, Racodium rupestre Pers., Ramalina asahinae W. Culb. & C. Culb., R. calcarata Krog & Swinsc., R. puiggarii Müll Arg., R. rectangularis Nyl., Rhizoplaca melanophthalma (DC.) Leuckert & Poelt, Strigula antillarum (Fée) Müll. Arg., S. platypoda (Müll. Arg.) R. C. Harris, Tapellaria epiphylla (Müll. Arg.) R. Sant., T.nana (Fée) R. Sant., Tephromela aglaea (Sommerf.) Hertel & Rambold, Tricharia vainioi R. Sant., Trichothelium epiphyllum Müll. Arg., T. bipindense F. Schill. and Vezdaea foliicola Sérusiaux. Another 4 species are new records only for the Venezuelan Andes: Dimerellaepiphylla (Müll. Arg.) Malme, Porinaatrocoerulea Müll. Arg., Ramalina peruviana Ach. and Woessia apiahica (Müll. Arg.) Sérus. A list of synonyms used in the consulted literature is added. Four new combinations are proposed: Dictyonema zahlbruckneri (Schiffn.) V. Marcano, Heterodermia tropica (Kurok.) Sipman, Parmelinopsis cleefii (Sipman) V. Marcano & Sipman and Phyllobaeislinearis (De Vries) V. Marcano & Sipman