Volatile compounds in shoulder gland secretions of male flying foxes, genus Pteropus (Pteropodidae, Chiroptera)

The shoulder gland secretions of captive males of the Indian flying fox (Pteropus giganteus), the little golden-mantled flying fox (P. pumilus), the island flying fox (P. hypomelanus), and the large flying fox (P. vampyrus) were examined by gas chromatography-mass spectrometry. Sixty-five compounds, including hydrocarbons, carboxylic acids, alcohols, aldehydes, ketones, esters, and amides, were identified among the four species. Many of these compounds, such as squalene, cholesterol, and C5-C16 straight- and branched-chain carboxylic acids, are typical of tetrapod epidermal products. Aldehydes, which were detected in all four Pteropus species, and some straight- and branched-chain ketones, which were detected in P. hypomelanus and P. pumilus, are known from other mammalian skin glands. Acetophenone, 4-acetoxyacetophenone, and 4-hydroxyacetophenone were observed in P. pumilus; the last compound comprised 37.1% of the total ion current. 2,3-Butanediol, a prominent component (5.2-19.3%) in the secretions of P. giganteus, P. hypomelanus, and P. pumilus, and C10 and C12 isopropyl esters and C10-C14 1-methylbutyl esters, observed in P. hypomelanus and P. vampyrus, have not previously been reported from vertebrates. alpha-Methyl-4-methoxybenzyl alcohol and dihydro-5-phenyl-2(3H)-furanone, from P. giganteus and P. pumilus, are new natural products. 1-Chloro-3-methyl-2-butene, another new natural product, and five C5 compounds exhibiting a similar isoprenoid structure were observed in P. giganteus. Striking contrasts were observed in the chemical profiles of the species we examined, with even general chemical classes differentially represented among them.     

Quantitative measurement of Batrachochytrium dendrobatidis in amphibian skin

The ability to quantify infections provides a tool with which to perform comparative pathological research. The need exists for a simplistic standard method to compare infection levels of Batrachochytrium dendrobatidis, a major cause of global amphibian declines. Through examination of skin sloughs of the Cape river frog Afrana fuscigula, we present an accessible method that not only provides quantitative measurements of B. dendrobatidis, but also provides information that increases the confidence of detection through histological surveys. The method relies on the availability of live animals that are actively shedding skin. By employing a direct microscopic count of sporangia, it is possible to express infection in terms of density. Micro-spatial infection in the skin of A. fuscigula is characterised by significant differences in sporangium density among the different components of the foot, and by similar differences in site infection frequency. Notably, toe tips and tubercles contain higher infection densities and are more often infected than webbing or the base of the foot. This pattern of infection might facilitate disease transmission due to the increased exposure of these components to abrasion. Density data can be used with the Poisson frequency function to approximate binomial probabilities of detecting B. dendrobatidis through histology. The probability matrix produced for A. fuscigula indicated that foot-site selection for histology markedly influenced the number of sections required to detect B. dendrobatidis at a specific level of probability. Thus, examination of a test sample of skin tissue with direct-count quantification can help in planning the sampling of tissues for histological surveys.     

Antiestrogenic activity of flavonoid phytochemicals mediated via the c-Jun N-terminal protein kinase pathway. Cell-type specific regulation of estrogen receptor alpha

Flavonoid phytochemicals act as both agonists and antagonists of the human estrogen receptors (ERs). While a number of these compounds act by directly binding to the ER, certain phytochemicals, such as the flavonoid compounds chalcone and flavone, elicit antagonistic effects on estrogen signaling independent of direct receptor binding. Here we demonstrate both chalcone and flavone function as cell type-specific selective ER modulators. In MCF-7 breast carcinoma cells chalcone and flavone suppress ERα activity through stimulation of the stress-activated members of the mitogen-activated protein kinase (MAPK) family: c-Jun N-terminal kinase (JNK)1 and JNK2. The use of dominant-negative mutants of JNK1 or JNK2 in stable transfected cells established that the antiestrogenic effects of chalcone and flavone required intact JNK signaling. We further show that constitutive activation of the JNK pathway partially suppresses estrogen (E2)-mediated gene expression in breast, but not endometrial carcinoma cells. Our results demonstrate a role for stress-activated MAPKs in the cell type-specific regulation of ERα function.     

Spatial and temporal patterns of neutral and adaptive genetic variation in the endangered African wild dog (Lycaon pictus)

Deciphering patterns of genetic variation within a species is essential for understanding population structure, local adaptation and differences in diversity between populations. Whilst neutrally evolving genetic markers can be used to elucidate demographic processes and genetic structure, they are not subject to selection and therefore are not informative about patterns of adaptive variation. As such, assessments of pertinent adaptive loci, such as the immunity genes of the major histocompatibility complex (MHC), are increasingly being incorporated into genetic studies. In this study, we combined neutral (microsatellite, mtDNA) and adaptive (MHC class II DLA‐DRB1 locus) markers to elucidate the factors influencing patterns of genetic variation in the African wild dog (Lycaon pictus); an endangered canid that has suffered extensive declines in distribution and abundance. Our genetic analyses found all extant wild dog populations to be relatively small (N_e < 30). Furthermore, through coalescent modelling, we detected a genetic signature of a recent and substantial demographic decline, which correlates with human expansion, but contrasts with findings in some other African mammals. We found strong structuring of wild dog populations, indicating the negative influence of extensive habitat fragmentation and loss of gene flow between habitat patches. Across populations, we found that the spatial and temporal structure of microsatellite diversity and MHC diversity were correlated and strongly influenced by demographic stability and population size, indicating the effects of genetic drift in these small populations. Despite this correlation, we detected signatures of selection at the MHC, implying that selection has not been completely overwhelmed by genetic drift.     

High-throughput comparison of gene fitness among related bacteria

ABSTRACT: BACKGROUND: The contribution of a gene to the fitness of a bacterium can be assayed by whether and to what degree the bacterium tolerates transposon insertions in that gene. We use this fact to compare the fitness of syntenic homologous genes among related Salmonella strains to reveal differences not apparent at the gene sequence level. RESULTS: A transposon Tn5 derivative was used to construct mutants in Salmonella Typhimurium ATCC14028 (STM1) and Salmonella Typhi Ty2 (STY1), which were then grown in rich media. The locations of 234,152 and 53,556 integration sites, respectively, were mapped by sequencing. These data were compared to similar data available for a different Ty2 strain (STY2) and essential genes identified in E. coli K-12 (ECO). Of 277 genes considered essential in ECO, all had syntenic homologs in STM1, STY1, and STY2, and all but nine genes were either devoid of Tn insertions or had very few. For three of these nine genes, part of the annotated gene lacked Tn integrations (yejM, ftsN and murB). At least one of the other six genes, trpS, had a potentially functionally redundant gene encoded elsewhere in Salmonella but not in ECO. An additional 165 genes were almost entirely devoid of transposon integrations in all three Salmonella strains examined, including many genes associated with protein and DNA synthesis. Four of these genes (STM14_1498.L, STM14_2872, STM14_3360.RJ, and STM14_5442) are not found in E. coli. Notable differences in the extent of gene selection were also observed among the three different Salmonella isolates. Mutations in hns, for example, were selected against in STM1 but not in the two STY strains, which have a defect in rpoS rendering hns nonessential. CONCLUSIONS: Comparisons among transposon integration profiles from different members of a species and among related species, all grown in similar conditions, identify differences in gene fitness among syntenic homologous genes. Further differences in fitness profiles among shared genes can be expected in other selective environments, with potential relevance for comparative systems biology.     

Nitrite oxidation in the Namibian oxygen minimum zone

Nitrite oxidation is the second step of nitrification. It is the primary source of oceanic nitrate, the predominant form of bioavailable nitrogen in the ocean. Despite its obvious importance, nitrite oxidation has rarely been investigated in marine settings. We determined nitrite oxidation rates directly in ¹⁵N-incubation experiments and compared the rates with those of nitrate reduction to nitrite, ammonia oxidation, anammox, denitrification, as well as dissimilatory nitrate/nitrite reduction to ammonium in the Namibian oxygen minimum zone (OMZ). Nitrite oxidation (⩽372 nM NO₂⁻ d⁻¹) was detected throughout the OMZ even when in situ oxygen concentrations were low to non-detectable. Nitrite oxidation rates often exceeded ammonia oxidation rates, whereas nitrate reduction served as an alternative and significant source of nitrite. Nitrite oxidation and anammox co-occurred in these oxygen-deficient waters, suggesting that nitrite-oxidizing bacteria (NOB) likely compete with anammox bacteria for nitrite when substrate availability became low. Among all of the known NOB genera targeted via catalyzed reporter deposition fluorescence in situ hybridization, only Nitrospina and Nitrococcus were detectable in the Namibian OMZ samples investigated. These NOB were abundant throughout the OMZ and contributed up to ∼9% of total microbial community. Our combined results reveal that a considerable fraction of the recently recycled nitrogen or reduced NO₃⁻ was re-oxidized back to NO₃⁻ via nitrite oxidation, instead of being lost from the system through the anammox or denitrification pathways.     

Near-infrared fluorescence detection permits accurate imaging of loading controls for Western blot analysis

Housekeeping proteins are typically chosen as internal loading controls for Western blot analysis because of their high, relatively constant expression. It was previously reported that antibodies against beta-actin did not reliably identify differences in sample loading, and extended antibody incubations caused a failure to discriminate differences in target protein levels. Here, beta-actin and GAPDH were evaluated as loading controls using near-infrared fluorescence. A load-dependent response in signal intensity was observed over a 250-fold range of sample concentrations, with R(2) values as high as 0.9939. Longer antibody incubations continued to detect differences in protein level and load-dependent responses became more linear.     

Influence of male aggregation size on female visitation in Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Abstract  The importance of male aggregation size for female visitation and initiation of male pheromone-calling was investigated in Bactrocera tryoni (Froggatt) (Diptera: Tephritidae) using artificial male aggregations in large laboratory cages. Female B. tryoni visited the largest aggregation more frequently than single males in association with a higher proportion of calling males, but there was no correlation between aggregation size and female visitation. Female B. tryoni had a limited capacity to perceive a difference between the number of calling males. Calling propensity of male B. tryoni was increased by the presence of conspecific males. Increased calling propensity in larger groups of male B. tryoni may be due to social facilitation of male calling behaviour. Female visitation at aggregations was only weakly associated with male calling, suggesting that aggregation size and the number of pheromone-calling males are not the only factors important in locating mates in B. tryoni , and it is possible that low-density populations could persist so long as females can encounter single males.     

NVP-DPP728 (1-[[[2-[(5-cyanopyridin-2-yl)amino]ethyl]amino]acetyl]-2-cyano-(S)- pyrrolidine), a slow-binding inhibitor of dipeptidyl peptidase IV.

Inhibition of dipeptidyl peptidase IV (DPP-IV) has been proposed recently as a therapeutic approach to the treatment of type 2 diabetes. N-Substituted-glycyl-2-cyanopyrrolidide compounds, typified by NVP-DPP728 (1-[[[2-[(5-cyanopyridin-2-yl)amino]ethyl]amino]acetyl]-2-cyano-(S )-p yrrolidine), inhibit degradation of glucagon-like peptide-1 (GLP-1) and thereby potentiate insulin release in response to glucose-containing meals. In the present study NVP-DPP728 was found to inhibit human DPP-IV amidolytic activity with a K(i) of 11 nM, a k(on) value of 1.3 x 10(5) M(-)(1) s(-)(1), and a k(off) of 1.3 x 10(-)(3) s(-)(1). Purified bovine kidney DPP-IV bound 1 mol/mol [(14)C]-NVP-DPP728 with high affinity (12 nM K(d)). The dissociation constant, k(off), was 1.0 x 10(-)(3) and 1.6 x 10(-)(3) s(-)(1) in the presence of 0 and 200 microM H-Gly-Pro-AMC, respectively (dissociation t(1/2) approximately 10 min). Through kinetic evaluation of DPP-IV inhibition by the D-antipode, des-cyano, and amide analogues of NVP-DPP728, it was determined that the nitrile functionality at the 2-pyrrolidine position is required, in the L-configuration, for maximal activity (K(i) of 11 nM vs K(i) values of 5.6 to >300 microM for the other analogues tested). Surprisingly, it was found that the D-antipode, despite being approximately 500-fold less potent than NVP-DPP728, displayed identical dissociation kinetics (k(off) of 1.5 x 10(-)(3) s(-)(1)). NVP-DPP728 inhibited DPP-IV in a manner consistent with a two-step inhibition mechanism. Taken together, these data suggest that NVP-DPP728 inhibits DPP-IV through formation of a novel, reversible, nitrile-dependent complex with transition state characteristics.