Atmospheric sources,transport and deposition of mercury in Michigan: Two years of event precipitation

To assess the sources, transport and deposition of atmospheric mercury (Hg) in Michigan, a multi-site network was implemented in which Hg concentrations in event precipitation and ambient samples (vapor and participate phases) were determined. Results from the analysis of 2 years of event precipitation samples for Hg are reported here. The volume-weighted average Hg concentration in precipitation was 7.9, 10.8 and 10.2 ng/L for the Pellston, South Haven and Dexter sites, respectively. Yearly wet deposition of Hg for 1992–93 and 1993–94 was 5.8 and 5.5 μg/m² at Pellston, 9.5 and 12.7 μg/m² at South Haven and 8.7 and 9.1 μg/m at Dexter. A spatial gradient in both the Hg concentration and wet deposition was observed. Northern Michigan received almost half the deposition of Hg recorded at the southern Michigan sites. The concentration of Hg in precipitation exhibited a strong seasonal behavior with low values of 1.0 to 2.0 ng/L in winter and maximum values greater than 40 ng/L in summer. The spring, summer and autumn precipitation accounted for 89 to 91% of the total yearly Hg deposition. Mixed-layer back trajectories were calculated for each precipitation event to investigate the meteorological history and transport from potential Hg source regions. Elevated Hg concentrations were observed with air mass transport from the west, southwest, south, and southeast. At each of the sites precipitation events for which the Hg concentration was in the 90th and 10th percentile were-analyzed for trace elements by ICP-MS to investigate source impacts.     

A method of inoculating barley seedlings with Ramularia collo‐cygni

A method of inoculating seedlings with the fungus Ramularia collo-cygni, the causal agent of ramularia leaf spot (RLS), an increasingly important problem in barley in Europe and elsewhere, is described. Symptoms of RLS similar to those found in the field were reproduced on seedlings and the fungus was re-isolated from them, fulfilling the third and fourth of Koch's postulates. The method was similar to one used for the related fungus, Mycosphaerella graminicola (anamorph Septoria tritici), a pathogen of wheat. Briefly, plants were sprayed with a suspension of R. collo-cygni mycelium fragments, incubated at 15°C, first in darkness for 48 h then in a 16-h-light/8-h-dark cycle. Disease levels reached saturation when plants were sprayed to runoff with a suspension of 480 cm² of mycelium, scraped from the entire surface of 7·5 Petri dishes (9 cm diameter) and sieved, in 50 mL water. Growth of seedlings in high light intensity (900 µmol m⁻² s⁻¹, 16-h daylength) before inoculation increased disease symptoms, but reduced disease when applied after inoculation. In contrast to M. graminicola, near-ultraviolet light after inoculation reduced symptom development. It is proposed that for the full development of RLS, plants should be grown in a stressful environment before inoculation. Nine barley lines were assessed for their resistance to RLS as seedlings and a subset were tested in field trials with natural infection by R. collo-cygni. There was cultivar-by-isolate interaction in the amount of RLS symptoms on seedlings. RLS levels on adult plants in field plots were correlated with RLS scores on seedlings formed by one isolate but not the other.     

Evidence for cross-adaptation between s-triazine herbicides resulting in reduced efficacy under field conditions

BACKGROUND: Enhanced atrazine degradation has been observed in agricultural soils from around the globe. Soils exhibiting enhanced atrazine degradation may be cross-adapted with other s-triazine herbicides, thereby reducing their control of sensitive weed species. The aims of this study were (1) to determine the field persistence of simazine in atrazine-adapted and non-adapted soils, (2) to compare mineralization of ring-labeled (14)C-simazine and (14)C-atrazine between atrazine-adapted and non-adapted soils and (3) to evaluate prickly sida control with simazine in atrazine-adapted and non-adapted soils.RESULTS: Pooled over two pre-emergent (PRE) application dates, simazine field persistence was 1.4-fold lower in atrazine-adapted than in non-adapted soils. For both simazine and atrazine, the mineralization lag phase was 4.3-fold shorter and the mineralization rate constant was 3.5-fold higher in atrazine-adapted than in non-adapted soils. Collectively, the persistence and mineralization data confirm cross-adaptation between these s-triazine herbicides. In non-adapted soils, simazine PRE at the 15 March and 17 April planting dates reduced prickly sida density at least 5.4-fold compared with the no simazine PRE treatment. Conversely, in atrazine-adapted soils, prickly sida densities were not statistically different between simazine PRE and no simazine PRE at either planting date, thereby indicating reduced simazine efficacy in atrazine-adapted soils.CONCLUSIONS: Results demonstrate the potential for cross-adaptation among s-triazine herbicides and the subsequent reduction in the control of otherwise sensitive weed species. Copyright (c) 2008 Society of Chemical Industry.     

Evaluating the demographic history of the Seychelles kestrel (Falco araea): Genetic evidence for recovery from a population bottleneck following minimal conservation management

An important requirement for biologists conserving vulnerable species of wildlife and managing genetic problems associated with small population size is to evaluate existing evidence regarding what is known of a species’ recent population history. For endemic island species in particular, current genetic impoverishment could be due to either a recent population crash or a consequence of an evolutionary history of sustained isolation and small effective population size. Interpreting any given case can often be further complicated by incomplete or contradictory evidence from historical field surveys that might suggest a very different demographic history. Here, we use the case of the Seychelles kestrel (Falco araea), an island endemic previously listed as critically-endangered but now relatively common, to illustrate how genetic data from microsatellite genotypes of 100–150-year-old museum specimens reveals a recent and severe population crash since the 1940s to approximately eight individuals, before the population recovered. We re-interpret the historical population trajectory of the Seychelles kestrel in the light of the minimal intervention required for this species to recover. We examine different ecological explanations for the decline and apparently unassisted recovery of the Seychelles kestrel, review the evidence for similarly unaided recoveries elsewhere and discuss the implications of unaided population recoveries for future species conservation programmes. Demographic profiles from historical genetic signatures can provide highly informative evidence when evaluating past and future recovery efforts for endangered species.     

Induction of precocious puberty in heifers II: advanced ovarian follicular development

Precocious puberty can be induced in a majority of heifers weaned early and fed a high-concentrate diet. The objective of this experiment was to determine whether induction of precocious puberty is associated with an acceleration of ovarian maturation in heifers. Crossbred Angus and Simmental heifer calves were weaned at 104 +/- 2 (n = 18; early weaned) or 208 +/- 3 (n = 10; normal-weaned, NW) d of age. The early weaned heifers were fed a high-concentrate (60% corn; EWH, n = 9) or control diet (30% corn; EWC, n = 9). The NW heifers were also fed the control diet after weaning. Daily transrectal ultrasonography was performed to characterize a complete follicular wave beginning at a mean age of 126, 161, 196, 224, and 252 (EWH and EWC), or 224 and 252 (NW) d. Blood samples were collected daily during periods of ultrasonography to determine estradiol concentrations and weekly beginning at mean ages of 153 (EWH and EWC) or 216 (NW) d to be analyzed for progesterone concentrations. Heifers in the EWH treatment were heavier (P < 0.01) than EWC heifers from a mean age of 175 d through the end of the study (treatment x age; P < 0.05). Body weights did not differ between EWC and NW. At mean ages of 196 and 224 d, the maximum diameter of the dominant follicle (MaxDF) was greater (P < 0.05) in EWH than EWC heifers. At a mean age of 224 d, MaxDF was greater (P < 0.05) in EWC than NW heifers but was not different by a mean age of 252 d. All EWH, 5 of 9 EWC, and 5 of 10 NW heifers attained puberty at less than 300 d of age (precocious puberty). Age at puberty was less (P < 0.05) in EWH (252 +/- 9 d) than in EWC and NW (308 +/- 26 and 330 +/- 25 d, respectively) treatments. Across all heifers, MaxDF and duration of follicular waves increased with age (P < 0.05), mean number of follicles during follicular waves decreased with age (P < 0.05), and peak concentrations of estradiol during follicular waves increased until a mean age of 224 d. To further characterize aspects of precocious puberty, heifers were compared across treatments between those that experienced precocious puberty and those that did not. In heifers that experienced precocious puberty, BW at puberty was less (P < 0.01) and MaxDF, follicular wave duration, and peak estradiol concentrations were greater (P < 0.05) compared with heifers that did not experience precocious puberty. Ovarian maturation was accelerated in heifers that were weaned early and fed a high-concentrate diet and was associated with precocious onset of puberty.     

The genome of the sea urchin Strongylocentrotus purpuratus

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.     

A review of zoonotic disease surveillance supported by the Armed Forces Health Surveillance Center

The Armed Forces Health Surveillance Center (AFHSC), Division of Global Emerging Infections Surveillance and Response System conducts disease surveillance through a global network of US Department of Defense research laboratories and partnerships with foreign ministries of agriculture, health and livestock development in over 90 countries worldwide. In 2010, AFHSC supported zoonosis survey efforts were organized into four main categories: (i) development of field assays for animal disease surveillance during deployments and in resource limited environments, (ii) determining zoonotic disease prevalence in high-contact species which may serve as important reservoirs of diseases and sources of transmission, (iii) surveillance in high-risk human populations which are more likely to become exposed and subsequently infected with zoonotic pathogens and (iv) surveillance at the human-animal interface examining zoonotic disease prevalence and transmission within and between human and animal populations. These efforts have aided in the detection, identification and quantification of the burden of zoonotic diseases such as anthrax, brucellosis, Crimean Congo haemorrhagic fever, dengue fever, Hantaan virus, influenza, Lassa fever, leptospirosis, melioidosis, Q fever, Rift Valley fever, sandfly fever Sicilian virus, sandfly fever Naples virus, tuberculosis and West Nile virus, which are of military and public health importance. Future zoonotic surveillance efforts will seek to develop local capacity for zoonotic surveillance focusing on high risk populations at the human-animal interface.     

Development and analytical validation of an enzyme-linked immunosorbent assay (ELISA) for the measurement of alpha(1)-proteinase inhibitor in serum and faeces from cats

The objective of this study was to develop and analytically validate an ELISA for the measurement of alpha(1)-proteinase inhibitor (α(1)-PI) in serum and faeces from cats. Lower detection limit, linearity, accuracy, precision, reproducibility, and reference intervals were determined. The lower detection limits were 0.02 g/L for serum and 0.04 μg/g for faeces. The observed-to-expected (O/E) ratios for serial dilutions of serum and faecal samples ranged from 100.0 to 129.7% (mean±SD: 112.2±9.9%) and 103.5 to 141.6% (115.6±12.8%), respectively. The O/E ratios for samples spiked with seven known concentrations of α(1)-PI ranged from 82.3 to 107.8% (94.7±7.6%) for serum, and 78.5 to 148.7% (96.8±18.2%) for faeces. The coefficients of variation for intra-assay and inter-assay variability were <7.9% and <12.1% for serum, and 5.3%, 11.8%, 14.2%, and 7.7%, 10.2%, 20.4% for faeces, respectively. Reference intervals were 0.6-1.4 g/L for serum and upto 1.6 μg/g for faeces. We conclude that this ELISA is sufficiently linear, accurate, precise, and reproducible for clinical evaluation.     

Female access to fertile land and other inputs in Zambia: why women get lower yields

Throughout the developing world, it is a well-documented fact that women farmers tend to get lower yields than their male counterparts. Typically this is attributed to disproportionate access to high-quality inputs and labor, with some even arguing there could be a skills-gap stemming from unbalanced access to training and education. This article examines the gender-based yield gap in the context of Zambian maize producers. In addition to the usual drivers, we argue that Zambia’s patriarchal and multi-tiered land distribution system could disfavor women with respect to accessing quality soils. We are uniquely able to control for soil characteristics using farm data from a sample of 1573 fields with accompanying soil analysis. We find an expected difference in yields, but no evidence of a gap in unobserved characteristics, like skill, after controlling for access to inputs, especially quality soil, suggesting women are indeed disproportionately disadvantaged. We discuss how our findings could be used to develop self-targeting policy interventions that could empower women and would be consistent with the government’s stated equity goals.