Geochemical analyses of metal(loid) fractions do not predict plant uptake behavior: Are plant bioassays better tools to predict mine rehabilitation success?

Management of metal(loid) tailings at historic sites presents environmental hazards usually requiring rehabilitation to mitigate pollution risks. Strategies employed include capping or establishing vegetation directly, which requires tailings assessments to determine suitable rehabilitation approaches. Assessments are typically geochemical analyses, but plant based approaches may provide a more accurate measure of revegetation success although they are often limited to germination indices. This study uses the plant bioassay (Rhizotest™) with common geochemical assessment to predict plant uptake of metal(loid)s and the subsequent likely rehabilitation success. Pb/Zn tailings from five legacy sites within the UK and Ireland were characterized for pH, EC, water soluble and CaCl2-extractable content and aqua regia extractable content. Uptake of Sb, As, Cd, Cu, Ca, Mg, Mn, Zn, Pb was determined in shoots and roots of Lolium perenne. Total Zn, Pb, Sb, Cd and As in tailings ranged from 694 to 2683 mg kg-1, 1252 to 8072 mg kg-1, 14 to 148 mg kg-1, 1.3 to 44 mg kg-1 and 1.3 to 45 mg kg-1, respectively. The only correlation found between total and water soluble or CaCl2-extractable metal(loid) contents was for Cd, where r = 0.8 for total and CaCl2-extractable fractions. Limited uptake and translocation risk was identified for major contaminants Zn and Pb in most tailings samples but in some cases exceedance of phytotoxic threshold values occurred that was not reflected in geochemical analysis. Crucially, although total Cd and Sb content was relatively low (< 20 mg kg-1) in some tailings, elevated plant content for some samples highlights phytotoxic risk from minor elements. Results indicate that screening based on geochemical content is not sufficiently predictive of metal(loid) phytoavailability to reliably inform mine rehabilitation strategies. We therefore strongly recommend that geochemical analyses are supplemented with plant based bioassay to plan mine tailings revegetation and reduce risk of wider ecosystem metal(loid) transfer.

The estimation of absorbed dose rates for non-human biota: an extended intercomparison.

An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of ±20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota.

A QSAR study of the toxicity of amines to the fathead minnow.

Simple and multiple linear regressions were applied to the development of fish toxicity QSAR models for the 96-h LC50 to the fathead minnow, Pimephales promelas. The data on unbranched saturated primary alkylamines as well as the complete data set were well-fitted to linear QSAR models using log P or the valence first-order connectivity index (1XV) as descriptors. Although adding data on other subclasses of amines in this data set yield acceptable QSARs, only the tertiary amine subclass provided a poor fit with both of these descriptors. The amines include both acyclic and cyclic derivatives, either with no additional functional groups, or with the hydroxyl, keto, methoxy, and propargyl moieties. The molecular mechanism for fish toxicity of these amines as well as the outliers in the study were investigated. Based upon the calculated log P value of -1.40, tripropargylamine has an apparent excess toxicity of 84 times; in contrast, the measured shake-flask log P for this compound was subsequently found to be 1.26, giving a predicted LC50 consistent with the observed value. An upward curvature of the QSAR plot for the most hydrophilic compounds suggests a shift in mechanism for the lowest members of the series.

Sufentanil and succinylcholine for rapid-sequence anesthetic induction and tracheal intubation: hemodynamic and hormonal responses.

Rapid-sequence induction and tracheal intubation are used in the management of patients at risk of aspiration. Patients with coronary artery disease (CAD) are at additional risk of adverse hemodynamic responses to intubation. The hemodynamic and hormonal responses to intubation with sufentanil, 7 micrograms/kg, and succinylcholine, 1.5 mg/kg, were studied in patients with CAD and good left ventricular function (ejection fraction greater than or equal to 0.4) who were undergoing elective coronary artery bypass grafting. Tracheal intubation occurred 60 seconds after administration of sufentanil and succinylcholine. Heart rate, systemic and pulmonary arterial pressures, pulmonary artery occlusion and central venous pressures, and cardiac outputs were measured at various time intervals before and after induction of anesthesia. Systemic vascular resistance and cardiac index were calculated. Arterial blood samples were drawn before and after anesthetic induction for the determination of catecholamine concentrations in serum. Rapid-sequence administration of sufentanil and succinylcholine resulted in a moderate decrease (24%) in mean arterial pressure from 95 to 72 mm Hg, and the mean arterial pressure remained less than the control value at 1, 3, and 5 minutes after intubation. Systemic vascular resistance also decreased (23%) after administration of sufentanil and returned to control values 5 minutes after intubation. There were no changes in cardiac index until 5 minutes after intubation, at which time it decreased (18%) from 2.8 to 2.3 L/min/m2.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of chronic posttraumatic hand edema: a comparison of high voltage pulsed current, intermittent pneumatic compression, and placebo treatments.

The purpose of this study was to compare the efficacy of intermittent pneumatic compression (IPC) and high voltage pulsed current (HVPC) in reducing chronic posttraumatic hand edema. Thirty patients with posttraumatic hand edema were randomly assigned to IPC, HVPC, or placebo-HVPC groups (10 patients in each group). Patients received a single application of the respective treatment for 30 minutes. Measurements were made before and after a 10-minute rest period and after the 30-minute treatment. A volumetric method was used to quantify edema reduction. Reduction in hand edema was significant between the IPC and placebo-HVPC groups (p = .01). Differences in edema reduction between the HVPC and placebo-HVPC groups did not reach statistical significance (p = .04), but were considered clinically significant. There was no significant difference between the IPC and HVPC groups. A single 30-minute administration of IPC produced a significant reduction in hand edema. Additional clinical studies are needed to delineate maximally effective treatment protocols for reduction of chronic posttraumatic hand edema. [Griffin JW, Newsome LS, Stralka SW, et al: Reduction of chronic posttraumatic hand edema: A comparison of high voltage pulsed current, intermittent pneumatic compression, and placebo treatments.

Phonological process usage by young EMR children and nonretarded preschool children.

Phonological skills of 20 mentally retarded children (IQs 50 to 75) were compared with those of 10 communication handicapped, nonretarded children and 10 normally speaking nonretarded children. All groups were matched on mean length of utterance scores obtained in a spontaneous speech sample. The Weiner Phonological Process Analysis Tool was administered to reveal phonological process usage. Retarded and communication handicapped children used a significantly greater total number of phonological processes more frequently than did nonhandicapped preschool children, but all the children used the processes in a specific order. Certain processes predicted the existence of others in children's speech patterns.

Esmolol attenuates hemodynamic responses during fentanyl-pancuronium anesthesia for aortocoronary bypass surgery.

We evaluated the effects of esmolol, a short acting (t1/2 beta = 9 min) beta-blocker on hemodynamics during noxious stimulation associated with aortocoronary bypass surgery. Group E (n = 10) and P (n = 10) patients had their morning dose of beta- or calcium blockers withheld except for nifedipine, and were given infusions of esmolol (E) or placebo (P) beginning prior to anesthetic induction and continuing until mediastinal dissection. Group S (n = 10) patients received their usual medication the morning of surgery and received neither esmolol nor placebo. All patients received fentanyl infusions for anesthesia and pancuronium for relaxation. Esmolol patients had no changes in heart rate throughout the study. In contrast, significant increases in heart rate occurred during induction, intubation, and surgical stimulation in Groups P and S. Esmolol patients had a statistically significant but transient increase in pulmonary capillary wedge pressure (PCWP) after intubation, which did not require treatment. There were no significant changes in PCWP in Group S and a decrease in PCWP in Group P patients. We conclude that esmolol was effective in attenuating potentially deleterious responses to noxious stimulation during fentanyl-pancuronium anesthesia.

Severe preeclampsia: hemodynamic effects of lumbar epidural anesthesia.

The hemodynamic effects of lumbar epidural anesthesia (LEA) were evaluated in 11 patients with severe preeclampsia. All patients were receiving magnesium sulfate upon entry into the study. Hemodynamic measurements were obtained before and after LEA, at delivery, and 2 hr postpartum. Lumbar epidural anesthesia significantly reduced mean arterial pressure from 121.4 mm Hg to 97.7 mm Hg, without altering cardiac index, pulmonary vascular resistance, central venous pressure (CVP), or pulmonary capillary wedge pressure (PCWP). There was a slight but statistically insignificant decrease in systemic vascular resistance from 1078 to 900.7 dynes X sec X cm-5. Cardiac index and left ventricular stroke work index were elevated in these patients, suggesting hyperdynamic left ventricular function. There was poor correlation between PCWP and CVP in several patients. We conclude that LEA may be used safely in severe preeclamptic patients and that pulmonary arterial catheters may help guide appropriate therapy in preeclamptic patients with cardiac failure or oliguria refractory to modest fluid challenges.

Direct inhibition of gastrointestinal carbonic anhydrase by ethanol.

Carbonic anhydrase (CA) was found to be equally susceptible to direct inhibition by ethanol, whether the enzyme originated from homogenates of rabbit gastric, duodenal, or ileal mucosa. When gastric mucosa was separated into a soluble (cytoplasmic) and a membrane fraction, the membrane CA was more susceptible to ethanol inhibition, but less susceptible to acetazolamide inhibition, than the soluble enzyme. Male rat liver CA is relatively insensitive to acetazolamide inhibition, while female rat liver CA shows a sensitivity similar to that of other tissues. We found ethanol inhibited male and female rat liver CA equally, indicating a different site, or mode, of inhibition for ethanol and acetazolamide.