Contaminant Loading in Drainage and Fresh Water Used for Wetland Management at Stillwater National Wildlife Refuge

Throughout the western United States, studies have identified various detrimental effects of contaminants to aquatic biota from the use of agricultural drainage water for management of arid wetlands. However, little is known about the relative contributions of contaminant loading from pollutants dissolved in water compared with those carried by drifting material (e.g., detritus) associated with drainage water. Consequently, we determined loading rates for contaminants dissolved in water and those incorporated by drifting material for drainage (Diagonal Drain) as well as fresh (S-Line Canal) water used for wetland management at Stillwater National Wildlife Refuge (SNWR), Nevada during the early, middle, and late periods of the irrigation season (June through mid-November) in 1993. We found loading rates for trace elements throughout the irrigation season were almost entirely (> 98%) associated with contaminants dissolved in the water rather than incorporated by drift. Although drift contributed little to the total loading for trace elements to SNWR wetlands, contaminant concentrations were much greater in drift compared with those dissolved in water. Loading rates for dissolved As, B, Hg, and total dissolved solids (TDS) differed among periods for the Diagonal Drain. Along the Diagonal Drain, loading rates for dissolved As, B, Hg, Mo, unionized ammonia (NH₃-N), TDS, and Zn differed among its three sampling sites. B was the only trace element with differences in loading rates for drift among periods from the Diagonal Drain. In contrast, loading rates for As, B, Cr, Cu, Hg, Se, and Zn in drift differed among periods for the S-Line Canal. Along Diagonal Drain, loading rates in drift for B (middle and late periods), Cr, Cu, and Zn differed among sites. Hg (xˉ ≥ 12.0 ng/L) and NH₃-N (xˉ ≥ 0.985 mg/L) dissolved in water as well as B (xˉ ≥ 97.4 μg/g DW) and Hg (xˉ ≥ 0.461 μg/g DW) in drift from the Diagonal Drain and S-Line Canal exceeded screening levels (SLs) for protection of aquatic biota throughout the irrigation season. Dissolved As (xˉ ≥ 0.0426 mg/L) in water from the Diagonal Drain during all periods exceeded the SL for protection of aquatic biota. Dissolved B (xˉ = 1.03 mg/L) in water from the Diagonal Drain during the early period exceeded the SL for protection of aquatic biota. Received: 18 September 1997/Accepted: 5 February 1998     

Bupropion and paroxetine differentially influence cardiovascular and neuroendocrine responses to stress in depressed patients

BACKGROUND: There exists a need to identify safe and effective treatments for depression in patients with coronary heart disease (CHD). METHODS: Using a cross-sectional design, 17 depressed patients being treated with bupropion (200-450 mg/day) were compared with 17 depressed patients being treated with paroxetine (10-50 mg/day) and with a group of 15 unmedicated, non-depressed controls for cardiovascular, neuroendocrine and heart rate variability (HRV) measures at rest and in response to mental and physical stressors. RESULTS: Regardless of treatment, both treated groups exhibited blunted plasma cortisol, plasma epinephrine, systolic blood pressure, cardiac output, and pre-ejection period responses to mental stressors relative to controls. Bupropion treated individuals exhibited greater total peripheral resistance (TPR) increases than either the paroxetine or control groups, and greater plasma norepinephrine (NE) increases to mental stressors than the paroxetine group. The bupropion group also displayed reduced HRV at rest relative to the controls and during orthostatic challenge relative to both the control and paroxetine groups. LIMITATIONS: Despite the fact that the treated groups were well matched for depression and other psychiatric histories, lack of randomization into treatment arms may be associated with a selection bias in the two treated groups. CONCLUSIONS: Although both pharmacological treatments were associated with a blunting of some cardiovascular and neuroendocrine responses to stress relative to controls, which may be reflective of their therapeutic mechanisms of action, the results of our study also suggest that bupropion is associated with a more detrimental autonomic profile than paroxetine, as reflected in increased TPR and NE, and reduced HRV. The results of this study may have implications for the pharmacological treatment of depression in CHD patients.     

'Late onset' ornithine transcarbamylase deficiency: function of three purified recombinant mutant enzymes

Although many mutations in the ornithine transcarbamylase gene have been correlated with 'late onset' of hyperammonemia in patients, the effects of these mutations on enzyme function are largely unknown. Three recurrent mutations (R40H, R277W and R277Q) found in patients with 'late onset' disease were incorporated into 'mature' human ornithine transcarbamylase cDNA and overexpressed in Escherichia coli. The three recombinant mutant enzymes were purified to homogeneity on an affinity column and their biochemical characteristics were compared to the wild type enzyme. The R277W and R277Q mutants display markedly reduced affinity for L-ornithine, loss of substrate inhibition, alkaline shift of pH optimum, and reduced thermal stability compared to the wild type enzyme. These differences, particularly the reduced affinity for L-ornithine, are sufficient to account for their biochemical effects. In contrast, the 'mature' R40H mutant was biochemically indistinguishable from the wild type enzyme in vitro.      

The ability of active versus passive coping tasks to predict future blood pressure levels in normotensive men and women

Casual blood pressure (BP) after a 2-year follow-up interval was determined in 40 normotensive men and women (20 Blacks and 20 Whites), who had been initially tested for cardiovascular responses to a variety of active and passive coping tasks, including active speech, passive speech, reaction time, and forehead cold pressor tasks. Stepwise multiple regression analyses were used to identify the best model for predicting follow-up BP. Average systolic blood pressure (SBP) level during cold pressor stress was the single most powerful predictor of casual SBP over 2 years even after controlling for initial resting SBP. Other predictors of follow-up SBP were initial SBP, parental history of hypertension, and heart rate and SBP during passive speech (final model R(2) = .78). For follow-up diastolic blood pressure (DBP), the only significant predictors were initial DBP and male gender. These results contribute to a growing body of literature that suggests that cardiovascular measures observed during stressors have predictive validity above and beyond that of traditional predictor variables.     

Non surgical management of pseudoaneurysms

Background: The incidence of pseudoaneurysm has increased due to the large number of vascular procedures performed and the widespread use of anticoagulation therapy during procedures. Non-invasive methods for management of pseudoaneurysms comprise of ultrasound guided compression (USGC), thrombin therapy, arterial embolisation and endovascular stent graft insertion. We discuss our experience in the management of fourteen cases of pseudoaneurysms using non surgical techniques.     

The emergency drugs box--time for action?

Many GDPs are confused about which emergency drugs they should stock. There is a lack of uniform advice on this topic. Most recommended lists of emergency drugs contain superfluous medications which GDPs would never be expected to use. This paper rationalises the content of the emergency drugs box and provides clear, standardised guidance. A list of ten essential emergency drugs is presented, all of which can be administered by simple routes. Every GDP should be trained and competent to use these essential emergency drugs.