Seasonal Mass Migration of Water Boatmen (Hemiptera: Corixidae) as a Wetland–River Linkage and Dietary Subsidy to Riverine Fish

Ecosystems - Cross-boundary movements of organisms can act as important ecosystem linkages by subsidizing food webs. We investigated the magnitude and implications of a little understood food web...     

Dryland Salinity and Ecosystem Distress Syndrome: Human Health Implications

Clearing of native vegetation for agriculture has left 1.047 million hectares of southwest Western Australia affected by dryland salinity, and this area may expand up to a further 1.7–3.4 million hectares if trends continue. Ecosystems in saline-affected regions display many of the classic characteristics of Ecosystem Distress Syndrome, one outcome of which has not yet been investigated in relation to dryland salinity: adverse human health implications. This article seeks to review existing information and identify potential adverse human health effects. Three key potential impacts on human health resulting from dryland salinity are identified: wind-borne dust and respiratory health; altered ecology of the mosquito-borne disease Ross River virus; and mental health consequences of salinity-induced environmental degradation. Given the predicted increase in extent and severity of dryland salinity over coming decades, adverse outcomes of salinity are likely to be further exacerbated, including those related to human health. There is a clear need to investigate the issues discussed in this review and also to identify other potential adverse health effects of dryland salinity. Investigations must be multidisciplinary to sufficiently examine the broad scope of these issues. The relationship between human health and salinity may also be relevant beyond Australia in other countries where secondary soil salinization is occurring.     

Antimicrobial resistance in Escherichia coli isolates from raccoons (Procyon lotor) in Southern Ontario, Canada

We conducted a cross-sectional study to determine the prevalence of antimicrobial resistance (AMR) in fecal Escherichia coli isolates from raccoons (Procyon lotor) living in Ontario, Canada. From June to October 2007, we trapped raccoons in three areas: one primarily urban site around Niagara, one primarily rural site north of Guelph, and one at the Toronto Zoo. In addition, we conducted a longitudinal study at the Toronto Zoo site to investigate the temporal dynamics of fecal E. coli and AMR in raccoons. Reduced susceptibility to ≥1 antimicrobial agent was detected in E. coli isolates from 19% of 16 raccoons at the urban site, 17% of 29 raccoons from the rural site, and 42% of 130 samples collected from 59 raccoons at the zoo site. Raccoons from the zoo site were significantly more likely to shed E. coli with reduced susceptibility to ≥1 antimicrobial agent than animals from the rural site (odds ratio [OR], 3.41; 95% confidence interval [CI], 1.17 to 12.09; P = 0.02). Resistance to expanded-spectrum cephalosporins (and the associated bla(CMY-2) gene) was detected in two animals from the zoo site and one animal from the rural site. Serotyping and pulsed-field gel electrophoresis analysis show that raccoons on the zoo grounds harbor a diverse assemblage of E. coli, with rapid bacterial turnover within individuals over time. Our study indicates that raccoons may shed resistant bacteria of public health significance and that raccoons have the potential to disseminate these bacteria throughout their environment.     

Calls,colours, shape,and genes: a multi‐trait approach to the study of geographic variation in the Amazonian frog Allobates femoralis

Evolutionary divergence in behavioural traits related to mating may represent the initial stage of speciation. Direct selective forces are usually invoked to explain divergence in mate‐recognition traits, often neglecting a role for neutral processes or concomitant differentiation in ecological traits. We adopted a multi‐trait approach to obtain a deeper understanding of the mechanisms behind allopatric divergence in the Amazonian frog, Allobates femoralis. We tested the null hypothesis that geographic distance between populations correlates with genetic and phenotypic divergence, and compared divergence between mate‐recognition (acoustic) and ecological (coloration, body‐shape) traits. We quantified geographic variation in 39 phenotypic traits and a mitochondrial DNA marker among 125 individuals representing eight populations. Geographic variation in acoustic traits was pronounced and tracked the spatial genetic variation, which appeared to be neutral. Thus, the evolution of acoustic traits tracked the shared history of the populations, which is unexpected for pan‐Amazonian taxa or for mate‐recognition traits. Divergence in coloration appeared uncorrelated with genetic distance, and might be partly attributed to local selective pressures, and perhaps to Batesian mimicry. Divergence in body‐shape traits was low. The results obtained depict a complex evolutionary scenario and emphasize the importance of considering multiple traits when disentangling the forces behind allopatric divergence. ©2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 826–838.     

Inhibition of mammalian ribonucleases by endogenous adenosine dinucleotides

The most potent low molecular weight inhibitors of pancreatic RNase superfamily enzymes reported to date are synthetic derivatives of adenosine 5(')-pyrophosphate. Here we have investigated the effects of six natural nucleotides that also incorporate this moiety (NADP(+), NADPH, ATP, Ap(3)A, Ap(4)A, and Ap(5)A) on the activities of RNase A and two of its homologues, eosinophil-derived neurotoxin and angiogenin. With eosinophil-derived neurotoxin and angiogenin, Ap(5)A is comparable to the tightest binding inhibitors identified previously (K(i) values at pH 5.9 are 370 nM and 100 microM, respectively); it ranks among the strongest small antagonists of RNase A as well (K(i)=230 nM). The K(i) for NADPH with angiogenin is similar to that of Ap(5)A. These findings suggest that Ap(5)A and NADPH may serve as useful new leads for inhibitor design. Examination of inhibition under physiological conditions indicates that NADPH, ATP, and Ap(5)A may suppress intracellular RNase activity significantly in vivo.     

The absence of SIR2alpha protein has no effect on global gene silencing in mouse embryonic stem cells

The yeast sir2 gene plays a central role in mediating gene silencing and DNA repair in this organism. The mouse sir2alpha gene is closely related to its yeast homologue and encodes a nuclear protein expressed at particularly high levels in embryonic stem (ES) cells. We used homologous recombination to create ES cells null for sir2alpha and found that these cells did not have elevated levels of acetylated histones and did not ectopically express silent genes. Unlike yeast sir2 mutants, our sir2alpha null ES cells had normal sensitivity to insults such as ionizing radiation and heat shock, and they were able to silence invading retroviruses normally. These sir2alpha null cells were able to differentiate in culture normally. Our results failed to provide evidence that the mammalian SIR2alpha protein plays a role in gene silencing and suggest that the physiological substrate(s) for the SIR2alpha deacetylase may be nuclear proteins other than histones.     

Synthesis of mycothiol, 1D-1-O-(2-[N-acetyl-L-cysteinyl]amino-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol, principal low molecular mass thiol in the actinomycetes

Members of the actinomycetes produce 1D-1-O-(2-[N-acetyl-L-cysteinyl]amino-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol or mycothiol 1 as principal low molecular mass thiol. Chemical synthesis of a biosynthetic precursor of mycothiol, the pseudodisaccharide 1D-1-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol 13 was achieved by the following steps: (1) Enantioselective synthesis gave the glycosyl acceptors (-)-2,3,4,5,6-penta-O-acetyl-D-myo-inositol D-7 and the corresponding L-isomer L-7. (2) Condensation of D-7 and L-7 with the glycosyl donor 3,4,6-tri-O-acetyl-2-deoxy-2-(2,4-dinitrophenylamino)-alpha-D-glucopyranosylbromide afforded the corresponding alpha and beta anomeric products, which could be resolved by silica gel chromatography. (3) Deprotection of these by hydrolysis using an anion exchange resin gave 1D- and 1L-1-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-myo-inositol 13 and 15 and the corresponding beta-coupled anomers 14 and 16. Only 13, and to a much lesser extent 15, were used by enzymes present in an ammonium sulphate fraction of a cellfree extract of Mycobacterium smegmatis for the enzymatic synthesis of mycothiol. In the absence of acetyl-SCoA, the immediate biosynthetic precursor of 1, desacetylmycothiol, was the major product.     

Evolution of base composition in the insulin and insulin-like growth factor genes

The genomes of homeothermic (warm-blooded) vertebrates are mosaic interspersions of homogeneously GC-rich and GC-poor regions (isochores). Evolution of genome compartmentalization and GC-rich isochores is hypothesized to reflect either selective advantages of an elevated GC content or chromosome location and mutational pressure associated with the timing of DNA replication in germ cells. To address the present controversy regarding the origins and maintenance of isochores in homeothermic vertebrates, newly obtained as well as published nucleotide sequences of the insulin and insulin-like growth factor (IGF) genes, members of a well-characterized gene family believed to have evolved by repeated duplication and divergence, were utilized to examine the evolution of base composition in nonconstrained (flanking) and weakly constrained (introns and fourfold degenerate sites) regions. A phylogeny derived from amino acid sequences supports a common evolutionary history for the insulin/IGF family genes. In cold- blooded vertebrates, insulin and the IGFs were similar in base composition. In contrast, insulin and IGF-II demonstrate dramatic increases in GC richness in mammals, but no such trend occurred in IGF- I. Base composition of the coding portions of the insulin and IGF genes across vertebrates correlated (r = 0.90) with that of the introns and flanking regions. The GC content of homologous introns differed dramatically between insulin/IGF-II and IGF-I genes in mammals but was similar to the GC level of noncoding regions in neighboring genes. Our findings suggest that the base composition of introns and flanking regions is determined by chromosomal location and the mutational pressure of the isochore in which the sequences are embedded. An elevated GC content at codon third positions in the insulin and the IGF genes may reflect selective constraints on the usage of synonymous codons.      

Sources of error in neurotransmitter analysis

A compound having fluorescence characteristics similar to those of 5-hydroxytryptamine (5-HT), when reacted with ninhydrin, is present in several invertebrates (Fasciola hepatica, Aplysia californica, Tritonia diomedia, and Hirudo medicinalis). However, this substance is not identical with 5-HT [ Andreini, G. C., Beretta, C., Faustini, R., and Gallina, G. (1970)Experientia26, 166–167]. We confirmed these findings for Fasciola and also observed this substance in Spirometra mansonoides and mouse brain. Using chromatography and amino acid analysis we identified this substance as lysine. While 5-HT is also demonstrable in Spirometra, no 5-HT is present in Fasciola. Although epinephrine and dopamine seem to be present in Spirometra when the hydroxyindole technique of Laverty and Taylor [ Laverty, R., and Taylor, K. M. (1968)Anal. Biochem.22, 269–279] is used, neither amine is detectable in adult Spirometra by mass spectrometric analysis. A relatively high concentration of tyrosine in Spirometra could account for the apparent presence of dopamine. Therefore, lysine, tyrosine, and possibly other substances can be sources of error in the detection of biogenic amines in invertebrates.