Sex and seasonal differences in the spatial terrestrial distribution of gray treefrog (Hyla versicolor) populations

Fragmentation of terrestrial landscapes has exacerbated the need to understand the spatial requirements of organisms, especially those that undergo seasonal migrations, such as pond-breeding amphibians. Pond-breeding amphibians spend much of their lives in terrestrial habitat at some distance from aquatic breeding sites. The terrestrial habitat required by a particular individual encompasses the area adjacent to a breeding pond that is used for activities such as foraging or overwintering, as well as the expanses of habitat through which it moves. To elucidate amphibian spatial habitat requirements, we monitored gray treefrog (Hyla versicolor) movements through terrestrial habitat adjacent to breeding ponds using radiotelemetry and mark–recapture along transects of artificial refugia. Results indicate that gray treefrogs frequently make migrations between foraging grounds, overwintering sites, and breeding ponds of 200 m or more, with a maximum-recorded movement distance of 330 m. Additionally, females travel farther than males for reasons independent of body size, and the distribution of males during the breeding season is biased towards breeding ponds relative to the non-breeding season. The data illustrate the importance of habitat directly adjacent to breeding sites for males, and indicate that habitat loss resulting in small patches may have a greater negative impact on females than males, and consequently may have disproportionately large effects on population persistence. These results emphasize that effective management of amphibian breeding locations via protection of both aquatic and adjacent upland terrestrial resources likely requires detailed information regarding variation in movements between the sexes and among seasonal activity periods.     

Functional expression in pichia pastoris of an acidic pectin methylesterase from jelly fig (Ficus awkeotsang)

A cDNA fragment encoding an acidic pectin methylesterase (PME) of jelly fig achene was successfully expressed in Pichia pastoris under the control of the glyceraldehydes-3-phosphate dehydrogenase promoter. The recombinant PME was produced as a secretory protein by N-terminal fusion of a cleavable prepropeptide for signal trafficking, and thus easily harvested from the culture medium. Compared with native N-glycosylated PME (38 kDa) purified from jelly fig achenes, this recombinant PME (45 kDa) appeared to be hyperglycosylated. Activity staining indicated that the recombinant PME was functionally active. Yet the hyperglycosylated recombinant PME possessed thermostability and enzymatic capability over a broad pH range equivalent to those of the native PME. The success of functional production of this acidic jelly fig PME in P. pastoris has significantly broadened its applications in industry.     

Analyzing highly variable potency data using a linear mixed-effects measurement error model

A house standard lot is tested along with experimental samples in a variable TCID₅₀ assay in order to monitor and control assay performance. Instead of being simply a control, it is proposed to use this lot as a calibration standard to reduce the systematic variability in the assay caused by acknowledged sources of variability such as the age of the cells used in the assay and interlaboratory differences. Because of this new proposal, the consistency of the relationship between the test sample and the house standard is assessed within the acceptance range of the house standard. A linear mixed-effects measurement error model is proposed for the data. The slope curve is then used to assess the dynamic relationship between the sample and the house standard within the house standard range. It is shown with these analyses that the sample and the house standard have uniformly good agreement within the house standard range.     

Seasonal variability of platinum, palladium and rhodium (PGE) levels in road dusts and roadside soils, perth, western australia

The emission of Platinum–group elements (PGE) from automobile catalytic converters has led to rapid increases in Pt, Pd and Rh concentrations in roadside media. This paper examines the temporal variability of PGE levels in road dusts and roadside soils on a seasonal basis over a 12 month period. Road dust and roadside soil samples were analysed by ICP–MS following microwave digestion and cation exchange. Concentrations of PGE in all road dust and roadside soil samples are elevated above local background concentrations with maximum levels of Pt?440 ng g^?1, Rh?91 ng g^?1 and Pd?440 ng g^?1. Systematic seasonal variations in PGE levels are observed in both sample types and the temporal distribution of PGE levels is affected by a number of factors including surface morphology and rainfall. PGE ratios in road dusts and soils are consistent with known catalytic converter composition throughout the sampling period indicating the PGE remain associated during mobilisation and transport.     

Lethal critical body residues as measures of Cd,Pb, and Zn bioavailability and toxicity in the earthworm<Emphasis Type="Italic">Eisenia fetida</Emphasis>

Background. Earthworm heavy metal concentrations (critical body residues, CBRs) may be the most relevant measures of heavy metal bioavailability in soils and may be linkable to toxic effects in order to better assess soil ecotoxicity. However, as earthworms possess physiological mechanisms to secrete and/or sequester absorbed metals as toxicologically inactive forms, total earthworm metal concentrations may not relate well with toxicity. Objective  The objectives of this research were to: i) develop LD₅₀s (total earthworm metal concentration associated with 50% mortality) for Cd, Pb, and Zn; ii) evaluate the LD₅₀ for Zn in a lethal Zn-smelter soil; iii) evaluate the lethal mixture toxicity of Cd, Pb, and Zn using earthworm metal concentrations and the toxic unit (TU) approach; and iv) evaluate total and fractionated earthworm concentrations as indicators of sublethal exposure. Methods  Earthworms (Eisenia fetida (Savigny)) were exposed to artificial soils spiked with Cd, Pb, Zn, and a Cd-Pb-Zn equitoxic mixture to estimate lethal CBRs and mixture toxicity. To evaluate the CBR developed for Zn, earthworms were also exposed to Zn-contaminated field soils receiving three different remediation treatments. Earthworm metal concentrations were measured using a procedure devised to isolate toxicologically active metal burdens via separation into cytosolic and pellet fractions. Results and Discussion  Lethal CBRs inducing 50% mortality (LD₅₀, 95% CI) were calculated to be 5.72 (3.54-7.31), 3.33 (2.97-3.69), and 8.19 (4.78-11.6) mmol/kg for Cd, Pb, and Zn, respectively. Zn concentrations of dead earthworms exposed to a lethal remediated Zn-smelter soil were 3-fold above the LD₅₀ for Zn and comparable to earthworm concentrations in lethal Zn-spiked artificial soils, despite a 14-fold difference in total soil Zn concentration between lethal field and artificial soils. An evaluation of the acute mixture toxicity of Cd, Pb, and Zn in artificial soils using the Toxic Unit (TU) approach revealed an LD₅₀ (95% CI) of 0.99 (0.57-1.41) TU, indicating additive toxicity. Conclusions  Total Cd, Pb, and Zn concentrations in earthworms were good indicators of lethal metal exposure, and enabled the calculation at LD₅₀s for lethality. The Zn-LD₅₀ developed in artificial soil was applicable to earthworms exposed to remediated Zn-smelter soil, despite a 14-fold difference in total soil Zn concentrations. Mixture toxicity evaluated using LD₅₀s from each single metal test indicated additive mixture toxicity among Cd, Pb, and Zn. Fractionation of earth worm tissues into cytosolic and pellet digests yielded mixed results for detecting differences in exposure at the sublethal level Recommendation and Outlook  CBRs are useful in describing acute Cd, Pb, and Zn toxicity in earthworms, but linking sublethal exposure to total and/or fractionated residues may be more difficult. More research on detoxification, regulation, and tissue and subcellular partitioning of heavy metals in earthworms and other invertebrates is needed to establish the link between body residue and sublethal exposure and toxicity. Keywords: Bioavailability; Cd; critical body residues; earthworms; metals; Pb; soil; Zn An erratum to this article is available at .     

Oxygen and carbon isotopic composition of limestones and dolomites, bikini and eniwetok atolls

Aragonitic, unconsolidated sediments from the borings on the Eniwetok and Bikini atolls are isotopically identical with unaltered skeletal fragments, whereas the recrystallized limestones exhibit isotopic variations resulting from alteration in meteoric waters during periods of emergence. Dolomites and associated calcites are enriched in O(18), perhaps because of interaction with hypersaline brines.     

A microdomain for protein secretion in Gram-positive bacteria

Gram-positive bacteria face unique challenges in generating biologically active conformations for their exported proteins because they lack a dedicated compartment for folding secreted polypeptides. We have discovered that protein secretion by way of the general secretory (Sec) pathway in the important human pathogen Streptococcus pyogenes proceeds through a single microdomain. Unlike other mechanisms for asymmetry involving the Sec pathway, proteins destined for secretion are targeted to a single locus distal to either cell pole that has specialized to contain the Sec translocons. This subcellular organization may represent a paradigm for secretion common to other Gram-positive pathogens with profound implications for pathogenesis.     

Mutational analysis of the tyrosine phosphatome in colorectal cancers

Tyrosine phosphorylation, regulated by protein tyrosine phosphatases (PTPs) and kinases (PTKs), is important in signaling pathways underlying tumorigenesis. A mutational analysis of the tyrosine phosphatase gene superfamily in human cancers identified 83 somatic mutations in six PTPs (PTPRF, PTPRG, PTPRT, PTPN3, PTPN13, PTPN14), affecting 26% of colorectal cancers and a smaller fraction of lung, breast, and gastric cancers. Fifteen mutations were nonsense, frameshift, or splice-site alterations predicted to result in truncated proteins lacking phosphatase activity. Five missense mutations in the most commonly altered PTP (PTPRT) were biochemically examined and found to reduce phosphatase activity. Expression of wild-type but not a mutant PTPRT in human cancer cells inhibited cell growth. These observations suggest that the mutated tyrosine phosphatases are tumor suppressor genes, regulating cellular pathways that may be amenable to therapeutic intervention.