Using stressor gradients to determine reference expectations for great river fish assemblages

We describe a simple empirical modeling approach for determining least-disturbed conditions for the great rivers of the Upper Mississippi River basin: Missouri, Upper Mississippi, and Ohio Rivers. We used multivariate analysis to identify reference strata (reaches for which a single reference expectation was appropriate) on each river. Strata included the Upper Missouri, Lower Missouri, impounded Upper Mississippi, unimpounded Upper Mississippi, and the Ohio River. We created a multimetric stressor gradient for each stratum using a suite of site- and landscape-scale metrics. Site-scale metrics included water chemistry, aquatic and riparian habitat, and human disturbance metrics. Landscape-scale metrics included land use, land cover, and proximity to human disturbance. The gradient was scaled from 0 (least stressed) to 1 (most stressed). Multimetric indices of condition based on fish assemblages for the Lower Missouri and Upper Mississippi River were responsive to stressor gradients based on 18–24 abiotic stressor metrics. Ohio River fish assemblages were responsive to a hand-picked three-metric gradient. We used the y-intercept of quantile regression to predict the fish index value for a stressor gradient value of 0 (the fish index value at a site with the lowest mean stressor gradient score in the reference stratum) which we designated as least-disturbed condition for the fish index for that stratum. We trisected the difference between predicted least-disturbed condition (ceiling value) and a floor value set at the 5th percentile of the sample to create thresholds for three condition classes: least-disturbed, intermediate, and most-disturbed. Based on the derived condition class thresholds for the fish index, 10% (by length) of the Lower Missouri was in least-disturbed condition, compared to 14% of the Ohio River and 19% of the impounded Upper Mississippi River. The index of condition exhibited longitudinal variation that was associated with the location of major urban areas along each river. We conclude that empirical modeling based on an abiotic stressor gradient can provide an alternative approach for deriving internal reference expectations for great rivers with few, if any, minimally disturbed sites.     

Dengue Virus Infections among Haitian and Expatriate Non-governmental Organization Workers — Léogane and Port-au-Prince,Haiti, 2012

In October 2012, the Haitian Ministry of Health and the US CDC were notified of 25 recent dengue cases, confirmed by rapid diagnostic tests (RDTs), among non-governmental organization (NGO) workers. We conducted a serosurvey among NGO workers in Léogane and Port-au-Prince to determine the extent of and risk factors for dengue virus infection. Of the total 776 staff from targeted NGOs in Léogane and Port-au-Prince, 173 (22%; 52 expatriates and 121 Haitians) participated. Anti-dengue virus (DENV) IgM antibody was detected in 8 (15%) expatriates and 9 (7%) Haitians, and DENV non-structural protein 1 in one expatriate. Anti-DENV IgG antibody was detected in 162 (94%) participants (79% of expatriates; 100% of Haitians), and confirmed by microneutralization testing as DENV-specific in 17/34 (50%) expatriates and 42/42 (100%) Haitians. Of 254 pupae collected from 68 containers, 65% were Aedes aegypti; 27% were Ae. albopictus. Few NGO workers reported undertaking mosquito-avoidance action. Our findings underscore the risk of dengue in expatriate workers in Haiti and Haitians themselves.     

Barium modifies the concentration dependence of active potassium transport by insect midgut

Summary The rate of active K⁺ transport by the isolated lepidopteran midgut shows a rectangular hyperbolic relation to [K⁺] over the range 20 to 70mm K⁺ in the absence of any divalent cation. Addition of Ba⁺⁺ to the hemolymph (K⁺ uptake) side introduces a linear component to the concentration dependence, such that active K^– transport is decreased at [K⁺] of 55mm or less, but increased transiently at higher [K⁺]. As [Ba⁺⁺] is increased over the range 2 to 8mm the linear component increases and the saturating component decreases; in 8mm Ba⁺⁺ the concentration dependence is dominated by the linear component. The effect of Ba⁺⁺ cannot easily be accounted for by simple competition with K⁺ for basal membrane uptake sites. Similar effects might be exercised by other alkali earth cations, since the concentration dependence of active K⁺ transport possesses a substantial linear component in solutions containing 5mm Ca⁺⁺ and 5mm Mg⁺⁺ (the alkali earth metal concentrations of standard lepidopteran saline).     

Cereals from a Bronze Age storage vessel at Torralba D'En Salort,Menorca, Spain

Charred cereals were recovered from a Bronze Age storage vessel excavated from a settlement in Menorca. The cereals may have been charred by accident or connected with some ceremony or ritual. Most of the cereal was hulled and naked barley, although a small amount of wheat representing a wide range of different morphologies was also present.     

Mesozooplankton of the Kosi Bay lakes,South Africa

The Kosi coastal lake system, a chain of four interconnected basins, is located in the subtropical north-eastern corner of South Africa. Little information is available on zooplankton of the system and the main aim of this study is to report on zooplankton samples collected during 2002 and 2003. The set of samples consists of seasonal, subsurface mesozooplankton samples that were collected during nighttime in each of the lakes. A well-developed salinity gradient was evident along the interconnected lakes in the subsurface water during all seasons, ranging from freshwater in the upper lake Amanzamnyama to a maximum of 22 recorded in Lake Makhawulani. The zooplankton community structures of the lakes reflected the salinity gradient of the system, with some coastal marine taxa recorded in the lakes closer to the mouth and only freshwater taxa recorded in Lake Amanzamnyama. Mesozooplankton diversity and abundance were relatively low compared to other estuarine systems along the eastern coast of South Africa. The dominant taxa were calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the mysid Mesopodopsis africana in the lower lakes, whereas cyclopoids Mesocyclops sp. and Thermocyclops sp. dominated the freshwater lake Amanzamnyama.     

Redox state of respiratory chain enzymes and potassium transport in silkworm mid-gut

The midgut of Hyalophora cecropia actively transports potassium from hemolymph to lumen and the energy for this process appears to be intimately linked to oxidative metabolism. In the present investigation, we monitored concurrently the rate of active transport and the redox levels of the components of the respiratory chain in the intact tissue under a variety of experimental conditions. Approximately equal concentrations of cytochromes a₃, a, c and b-557 were found. Other investigators (Pappenheimer, Jr, A. M. and Williams, C. M. (1954) J. Biol. Chem. 209, 915, Shappirio, D. G. and Williams, C. M. (1957) Proc. R. Soc. Lond. Ser. B 147, 233 and Chance, B. and Pappenheimer, Jr, A. M. (1954) J. Biol. Chem. 209, 931) have identified cytochrome b-557 with b₅ and found that it exists primarily in an extramitochondrial location.Steady-state experiments demonstrated that all these cytochromes were approximately 50% reduced while active transport proceeded at a high rate in regular cecropia Ringer containing 32 mM KCl. When the potassium concentration was reduced, the active transport decreased and all the cytochromes became more oxidized. Addition of 1 mM cyanide inhibited active transport by 90% and caused a 100% reduction of all cytochromes. Redox state and short circuit current (I_sc) kinetics measured as the tissue was made anoxic showed that all the respiratory enzymes, except cytochrome b-557, became fully reduced at a faster rate than the rate of inhibition of the I_sc. The rate of cytochrome b-557 reduction followed kinetically the I_sc.These observations are interpreted in a scheme where cytochrome b-557 (possibly b₅) branches off cytochrome c from the conventional respiratory chain, utilizing cytochrome a₃ as the terminal oxidase for both branches. Cytochrome b-557 may be involved in providing a direct link between oxidative metabolism and active transport in the midgut of the silkworm.     

Atrial natriuretic peptide levels during development of chronic heart failure after myocardial infarction in rats

Serum levels of atrial natriuretic peptide (ANP) are elevated in chronic heart failure presumably due to dilatation of the left atrium resulting from increases in intracardiac pressures. To define the time course of changes in serum ANP levels and to determine the relationship to left ventricular end-diastolic pressure, rats were subjected to coronary artery ligation to produce myocardial infarction and left ventricular failure. Atrial natriuretic peptide levels were measured weekly for four weeks thereafter. In rats with myocardial infarction and elevation of left ventricular end-diastolic pressure there was no change in ANP levels at 7 and 14 days. However, at day 21 and 28, ANP levels were elevated more than 3 fold. There was a correlation between ANP levels and left ventricular end-diastolic pressures. There was no correlation between ANP levels and right atrial pressures or serum sodium concentrations. We conclude that the chronic elevation of left ventricular end-diastolic pressure is required to produce an increase in ANP after myocardial infarction which results in chronic heart failure.     

Amount and distribution of biochemical-genetic variation among wild populations and a hatchery stock of Atlantic salmon, Salmo salar L., from north-east Ireland

The effects of tributyltin (TBT) compounds on gill morphology were examined in the mummichog, Fundulus heteroclitus , in 96-h LC50 and 6-week sublethal exposures. Morphometry was used for the identification and quantification of effects with the light microscope. A 96-h LC50 of 17.2 μg 1 ¹ was determined. Morphometric analysis of gill tissues revealed hypertrophy of the lamellar epithelium in fish exposed to 17.2 μg 1–1. Relative diffusing capacity was significantly decreased (−41 %); ( P <0.05, ANOVA, Bonferroni t -test). At 35.6 μg 1⁻¹, TBT exposure resulted in a significant reduction (− 40%) in the volume of the lamellar blood channels. Both of these observations occurred in fish that showed signs of acute poisoning including loss of equilibrium. In fish exposed to sublethal concentrations of 0.105–2.000 μg TBT 1⁻¹ for 6 weeks, there were no pathological changes in the gill. There were no treatment-related changes in the surface morphology of the gills of fish from both experiments upon scanning electron microscopic examination. Although gill pathology was observed in acutely toxic exposures, it does not appear to be a major mechanism of TBT toxicity.