Assessing the toxicity of lead in sediments to Hyalella azteca: the significance of bioaccumulation and dissolved metal

1999 ◽  
Vol 56 (8) ◽  
pp. 1494-1503 ◽  
Author(s):  
Uwe Borgmann ◽  
Warren P Norwood
Keyword(s):  
Screening Tool ◽  
Water Concentration ◽  
Dry Mass ◽  
Overlying Water ◽  
Organic C ◽  
Complexing Capacity ◽  
Large Water ◽  
The Relationship ◽  
Pb Concentration ◽  
Body Concentration

The relationship between bioaccumulation and toxicity of Pb to Hyalella was the same for animals exposed to Pb in water alone and for those exposed to Pb-spiked sediments, provided that the animals were gut cleared before Pb analysis. The same critical body concentration (about 126 nmol·g dry mass-1) can be used to predict Pb toxicity in both water-only and sediment exposures. Furthermore, Pb bioavailability in Pb-spiked sediments was due primarily to dissolved metal: animals caged above the sediments accumulated the same amount of Pb and had the same mortality as animals exposed directly to sediment. Increasing the water to sediment ratio from 4:1 to 67:1 resulted in a lower dissolved organic C and lower total dissolved Pb concentration in the water but no change in bioavailable Pb (i.e., bioavailable Pb was not proportional to total dissolved Pb). The overlying water concentration may be a useful indicator of bioavailable Pb in sediment tests, provided a large water to sediment ratio is used to reduce the effect of sediment on overlying water quality (i.e., Pb-complexing capacity). Although less reliable than body concentration measurements, this could provide a useful screening tool for possible Pb-induced toxicity because it can be measured without test animals present.

scholarly journals Nutritional and biochemical changes induced by lead in sunflower (Helianthus annuus L.)

2016 ◽  
Vol 37 (3) ◽  
pp. 1229 ◽  
Author(s):  
Claudia Brito de Abreu ◽  
Bárbara Lima do Sacramento ◽  
Andréia Teixeira Alves ◽  
Silvany Cardim Moura ◽  
Milena Santos Pinelli ◽  
...  
Keyword(s):  
Helianthus Annuus ◽  
Cell Metabolism ◽  
Dry Mass ◽  
Soluble Carbohydrate ◽  
Mass Yield ◽  
Growth Reduction ◽  
Biochemical Indicator ◽  
Organic Solute ◽  
Induced Changes ◽  
Pb Concentration

The aim of this study was to evaluate the effects of increasing concentrations of lead (Pb) in the nutrient solution on growth and macronutrient and organic solute contents of Helianthus annuus plants. The experimental design was completely randomized with four replications. The dry mass yield was not affected by the treatments up to a Pb concentration of 0.6 mM, indicating that H. annuus was tolerant to this Pb concentration in the growth medium. The reductions in leaf, stem and root dry masses at a Pb concentration of 0.8 mM were 74, 84 and 85%, respectively. Lead stress did not reduce the levels of nitrogen (N), phosphorus (P) and potassium (K), indicating that the growth reduction observed at 0.8 mM Pb could not be attributed to deficiencies of these nutrients. On the other hand, Pb significantly reduced calcium (Ca) and magnesium (Mg) contents in leaves, stems and roots, which might, at least in part, explain the Pb-induced growth reduction in the H. annuus plants. Pb increased soluble carbohydrate, free amino acid and proline contents in leaves, and soluble protein and proline contents in roots, showing stress-induced changes in cell metabolism. The data also suggest that Ca and Mg concentrations may be used as nutritional indicators and the proline content may be used as a biochemical indicator of Pb toxicity in H. annuus.

scholarly journals Linking the lithogenic, atmospheric, and biogenic cycles of silicate, carbonate, and organic carbon in the ocean

2009 ◽  
Vol 6 (4) ◽  
pp. 6579-6599
Author(s):  
S. V. Smith ◽  
J.-P. Gattuso
Keyword(s):  
Carbon Storage ◽  
Chemical Weathering ◽  
Dissolved Inorganic Carbon ◽  
North Pacific Ocean ◽  
Atmospheric Co2 ◽  
Molar Ratio ◽  
Co2 Uptake ◽  
Organic C ◽  
Co2 Gas ◽  
The Relationship

Abstract. Geochemical theory describes long term cycling of atmospheric CO2 between the atmosphere and rocks at the Earth surface in terms of rock weathering and precipitation of sedimentary minerals. Chemical weathering of silicate rocks takes up atmospheric CO2, releases cations and HCO3− to water, and precipitates SiO2, while CaCO3 precipitation consumes Ca2+ and HCO3− and releases one mole of CO2 to the atmosphere for each mole of CaCO3 precipitated. At steady state, according to this theory, the CO2 uptake and release should equal one another. In contradiction to this theory, carbonate precipitation in the present surface ocean releases only about 0.6 mol of CO2 per mole of carbonate precipitated. This is a result of the buffer effect described by Ψ, the molar ratio of net CO2 gas evasion to net CaCO3 precipitation from seawater in pCO2 equilibrium with the atmosphere. This asymmetry in CO2 flux between weathering and precipitation would quickly exhaust atmospheric CO2, posing a conundrum in the classical weathering and precipitation cycle. While often treated as a constant, Ψ actually varies as a function of salinity, pCO2, and temperature. Introduction of organic C reactions into the weathering-precipitation couplet largely reconciles the relationship. ψ in the North Pacific Ocean central gyre rises from 0.6 to 0.9, as a consequence of organic matter oxidation in the water column. ψ records the combined effect of CaCO3 and organic reactions and storage of dissolved inorganic carbon in the ocean, as well as CO2 gas exchange between the ocean and atmosphere. Further, in the absence of CaCO3 reactions, Ψ would rise to 1.0. Similarly, increasing atmospheric pCO2 over time, which leads to ocean acidification, alters the relationship between organic and inorganic C reactions and carbon storage in the ocean. Thus, the carbon reactions and ψ can cause large variations in oceanic carbon storage with little exchange with the atmosphere.

scholarly journals Irrigation management strategies for reducing verticillium wilt severity in eggplants

2020 ◽  
Vol 46 (1) ◽  
pp. 9-13
Author(s):  
Ricardo Nunes Cabral ◽  
Waldir Aparecido Marouelli ◽  
Adalberto C. Café-Filho
Keyword(s):  
Verticillium Wilt ◽  
Water Availability ◽  
Management Strategy ◽  
Irrigation Management ◽  
Management Strategies ◽  
Dry Mass ◽  
Infested Soil ◽  
Irrigation Strategy ◽  
Available Soil Moisture ◽  
The Relationship

ABSTRACT Verticillium wilt in eggplants is a root disease of difficult control. In this study, we report the relationship between soil water availability and the disease intensity in order to identify management strategies that are unfavourable to the pathogen and capable of reducing the disease progression and the damage caused by it. Four irrigation management strategies were compared in soil infested or not infested with Verticillium dahliae, which consisted of: irrigating when the available soil moisture was maintained at 90% (WA90%), 55% (WA55%) and 20% (WA20%) during the entire growing cycle, and kept at 20% in the vegetative stage, and at 90% in the production stage (WA20-90%). Experimental design was in randomized blocks, including eight treatments in factorial arrangement (4x2) and three replicates. The management strategy WA20-90% led to a significant reduction in the disease severity and in the extent of xylem colonization by the pathogen. The dry mass of plants in infested soil was 12% lower than that of control treatments and was higher with the irrigation strategy WA90% than with WA55% or WA20%. The strategy WA20-90% was efficient in reducing the disease with no significant reduction in dry mass.

Estimated Placental Volume and Gestational Age

2017 ◽  
Vol 35 (08) ◽  
pp. 748-757
Author(s):  
Kimberly Isakov ◽  
John Emerson ◽  
Katherine Campbell ◽  
France Galerneau ◽  
Amber Anders ◽  
...  
Keyword(s):  
Birth Weight ◽  
Confidence Interval ◽  
Clinical Utility ◽  
Screening Tool ◽  
Placental Pathology ◽  
Parabolic Curve ◽  
Microscopic Evaluation ◽  
The Relationship ◽  
Placental Volume ◽  
Best Fit

Objective The objective of this study was to validate estimated placental volume (EPV) across a range of gestational ages (GAs). Study Design Three hundred sixty-six patients from 2009 to 2011 received ultrasound scans between 11 + 0 and 38 + 6 weeks GA to assess EPV. An EPV versus GA best fit curve was generated and compared with published normative curves of EPV versus GA in a different population. A subanalysis was performed to explore the relationship between EPV and birth weight (BW). Results Analysis of EPV versus GA revealed a parabolic curve with the following best fit equation: EPV = (0.372 GA − 0.00364 GA2)3. EPV was weakly correlated with BW, and patients with an EPV in the bottom 50th percentile had 2.42 times the odds of having a newborn with a BW in the bottom 50th percentile (95% confidence interval: 1.27–4.68). Microscopic evaluation of two placentas corresponding to the smallest EPV outliers revealed significant placental pathology. Conclusion Placental volume increases throughout gestation and follows a predictable parabolic curve, in agreement with the existing literature. Further validation is required, but EPV may have the potential for clinical utility as a screening tool in a variety of settings.

Monitoring plasma concentrations of psychotropic drugs

1974 ◽  
Vol 12 (2) ◽  
pp. 6-8
Keyword(s):  
Steady State ◽  
Plasma Concentration ◽  
Tissue Concentration ◽  
Plasma Concentrations ◽  
Water Concentration ◽  
Plasma Samples ◽  
Active Metabolites ◽  
The Relationship ◽  
The Brain ◽  
Reliable Methods

Techniques are now available for estimating the plasma concentration of several drugs used in psychiatry. These techniques are clearly important for research but they can hardly be expected to improve the clinical management of patients unless the estimation is sensitive, reliable and reasonably quick; the method should be specific for the particular drug but should also specifically estimate any active metabolites. Even when reliable figures have been obtained, much more information is needed before they can be interpreted. The relationship between plasma (or plasma water) concentration and relevant tissue concentration (e. g. in the brain) must be known. Plasma samples should be taken at appropriate times, e. g. after the attainment of ‘steady-state’ conditions: plasma and tissue levels will then be in equilibrium. Diagnoses must be soundly based if inferences are to be drawn. Reliable methods of assessing clinical response must be available. These requirements pose difficult problems in psychiatry.

scholarly journals A deeper look at the relationship between root carbon pools and the vertical distribution of the soil carbon pool

2017 ◽  
Author(s):  
Ranae Dietzel ◽  
Matt Liebman ◽  
Sotirios Archontoulis
Keyword(s):  
Soil Carbon ◽  
Plant Root ◽  
Substantial Contribution ◽  
Root Turnover ◽  
Soil Organic C ◽  
Organic C ◽  
Native Prairie ◽  
Perennial Plant ◽  
Root Carbon ◽  
The Relationship

Abstract. Plant root material makes a substantial contribution to the soil organic carbon (C) pool, but this contribution is disproportionate below 20 cm, where 30 % of root mass and 50 % of soil organic C is found. Root carbon inputs changed drastically when native perennial plant systems were shifted to cultivated annual plant systems. We used the reconstruction of a native prairie and a continuous maize field to examine both the relationship between root carbon and soil carbon and the fundamental rooting system differences between the vegetation under which the soils developed versus the vegetation under which the soils continue to change. In all treatments we found that root C : N ratios increased with depth, which may help explain why an unexpectedly large proportion of soil organic C is found below 20 cm. Measured root C : N ratios and turnover times along with modeled root turnover dynamics showed that in moving from prairie to maize, a large, structural-tissue dominated root C pool with slow turnover, concentrated at shallow depths was replaced by a small, non-structural-tissue dominated root C pool with fast turnover evenly distributed in the soil profile. These differences in rooting systems suggest that while prairie roots contribute more C to the soil than maize at shallow depths, maize may contribute more C to the soil than prairies at deeper depths.

scholarly journals PSXI-24 Rumen temperature, fermentation and microbial signatures are poorly associated with steer feed-efficiency profiles

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 382-382
Author(s):  
Obioha N Durunna ◽  
Daalkhaijav Damiran ◽  
John R Campbell ◽  
Jeffery A Carroll ◽  
Bart Lardner
Keyword(s):  
Feed Intake ◽  
Feed Efficiency ◽  
Screening Tool ◽  
Rumen Fluid ◽  
Microbial Populations ◽  
Environmental Footprint ◽  
Rumen Temperature ◽  
Potential Applications ◽  
Cost Implications ◽  
The Relationship

Abstract Breeding feed-efficient cattle can reduce the environmental footprint of beef operations but assessing all replacement candidates for feed-intake is not practical due to cost implications. The main objectives of this study were to evaluate if rumen temperature (RumT), measured with wireless rumen Thermobolus® can distinguish steers with different feed-efficiency profiles and whether steers with divergent efficiency profiles have different nutrient fermentation signatures. The study also validated the relationship between rectal temperature (RecT) and RumT measured with automatic thermistors. Residual feed intake (RFI) profiles of 160 steers were measured over two years. All steers were assessed for RFI profiles using high and moderate forage diets, respectively, over two successive periods each year. Each steer was fitted with a rumen Thermobolus® throughout each ~80-d test period while half of the steers wore an automatic temperature-logger rectal device for ~30d. The devices recorded the RumT and RecT every 5 minutes, respectively. Rumen fluid samples were collected from high-RFI (n = 5) and low-RFI (n = 5) steers to assess if differences in rumen fermentation and microbial profiles exist. Circadian-adjusted RumT and RecT for each steer were used for analysis. The within-period correlations between RumT and RecT ranged between 49 and 77%. There was a trend (P = 0.08) that differences exist for rhythm-adjusted temperatures among different RFI profiles with low-RFI steers (39.72±0.01oC) having lower average RumT than those in high (39.75±0.01oC) or medium (39.74±0.01oC) classes. The correlation between the two test-periods for rhythm-adjusted RumT was 65% while the correlation between RFI from both periods was 47%. There was no difference (P > 0.30) between high- and low-RFI animals for the total or individual volatile fatty acid fractions or microbial populations. The narrow temperature variation among RFI classes limits its use as screening tool but the higher across-period correlation encourages the need for further studies into alternative potential applications.

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