Acute toxicity of six freshwater mussel species (Glochidia) to six chemicals: implications for Daphnids and Utterbackia imbecillis as surrogates for protection of freshwater mussels (Unionidae).

Acute (24-h) toxicity tests were used in this study to compare lethality responses in early life stages (glochidia) of six freshwater mussel species, Leptodea fragilis, U. imbecillis, Lampsilis cardium, Lampsilis siliquoidea, Megalonaias nervosa, and Ligumia subrostrata, and two standard test organisms, Ceriodaphnia dubia and Daphnia magna. Concentrations of carbaryl, copper, 4-nonylphenol, pentachlorophenol, permethrin, and 2,4-D were used in acute exposures to represent different chemical classes and modes of action. The relative sensitivities of species were evaluated by ranking their LC50 values for each chemical. We used these ranks to determine the extent to which U. imbecillis (one of the most commonly used unionids in toxicity tests) was representative of the tolerances of other mussels. We also calculated geometric mean LC50s for the families Unionidae and Daphnidae. Rankings of these data were used to assess the extent to which Daphnidae can be used as surrogates for freshwater mussels relative to chemical sensitivity. While no single chemical elicited consistently high or low toxicity estimates, carbaryl and 2,4-D were generally the least toxic to all species tested. No species was always the most sensitive, and Daphnidae were generally protective of Unionidae. Utterbackia imbecillis, while often proposed as a standard unionid mussel test species, did not always qualify as a sufficient surrogate (i.e., a substitute organism that often elicits similar sensitivity responses to the same contaminant exposure) for other species of mussels, since it was usually one of the more tolerant species in our rankings. U. imbecillis should be used as a surrogate species only with this caution on its relative insensitivity.

Evaluating acute toxicity of methyl parathion application in constructed wetland mesocosms.

Wetland ecosystems have reduced ambient levels of various organic and metallic compounds, although their effectiveness on agricultural pesticides is not well documented. Five stations within each of two 10 x 50 m constructed wetlands (two vegetated, two nonvegetated) were selected to measure the fate and effects of methyl parathion (MeP). Following a simulated storm event (0.64 cm of rainfall), aqueous, sediment, and plant samples were collected and analyzed spatially (5, 10, 20, and 40 m from the inlet) and temporally (after 3-10 days) for MeP concentrations and for the impact of those concentrations on the aquatic fauna. Aqueous toxicity to fish decreased spatially and temporally in the vegetated mesocosm. Pimephales promelas survival was significantly reduced, to 68%, at the 10-m station of the nonvegetated wetlands (3 h postapplication), with pesticide concentrations averaging 9.6 microg MeP/L. Ceriodaphnia in both the vegetated and nonvegetated wetlands was sensitive (i.e., a significant acute response to MeP occurred) to pesticide concentrations through 10 days postapplication. Mean MeP concentrations in water ranged from 0.5 to 15.4 microg/L and from 0.1 to 27.0 microg/L in the vegetated and nonvegetated wetlands, respectively. Hyalella azteca aqueous tests resulted in significant mortality in the 5-m vegetated segment 10 days after exposure to MeP (2.2 microg/L). Solid-phase (10-day) sediment toxicity tests showed no significant reduction in Chironomus tentans survival or growth, except for the sediments sampled 3 h postapplication in the nonvegetated wetland (65% survival). Thereafter, midge survival averaged >87% in sediments sampled from both wetlands. These data suggest that wetlands play a significant role in mitigating the effect of MeP exposure in sensitive aquatic biota.

Evaluating toxicity of Asana XL (esfenvalerate) amendments in agricultural ditch mesocosms.

Agricultural ditches primarily serve to remove and store excess water associated with irrigation and storm events. The ability of these ecosystems to mitigate potential contaminants is not well understood. Five sites along a 650-m agricultural ditch located in the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were used to measure fate and effects of an esfenvalerate (insecticide) exposure. Following a 0.64-cm simulated storm event, samples were collected from water and sediments and analyzed spatially from five sites and temporally from 0.5 h to 56 d. Results of aqueous toxicity bioassays indicated that lethality progressed downstream throughout all sampling intervals, while sediment toxicity bioassays only elicited biological responses at the point of pesticide application to the ditch (0 m). Significant reductions in survival of Ceriodaphnia dubia and Pimephales promelas in water were measured at the 0-, 20-, and 80-m sites following application. Ten-day solid phase sediment testing of Chironomus tentans indicated persistent toxicity only at the point of application (0 m) and throughout 56 d (mean=14.4% survival). No lethality or significant reduction in midge growth was measured for remaining downstream sites. These measurements were used to evaluate the potential of agricultural ditches to reduce potential deleterious effects of contaminants in agricultural drainage systems that precede receiving streams.

Innovative uses of vegetated drainage ditches for reducing agricultural runoff.

Vegetated agricultural ditches play an important role in mitigation of pesticides following irrigation and storm runoff events. In a simulated runoff event in the Mississippi (USA) Delta, the mitigation capacity of a drainage ditch using the pyrethroid esfenvalerate (Asana XL) was evaluated. The pesticide was amended to soil prior to the runoff event to simulate actual runoff, ensuring the presence of esfenvalerate in both water and suspended particulate phases. Water, sediment, and plant samples were collected temporally and spatially along the drainage ditch. Even with mixing of the pesticide with soil before application, approximately 99% of measured esfenvalerate was associated with ditch vegetation (Ludwigia peploides, Polygonum amphibium, and Leersia oryzoides) three hours following event initiation. This trend continued for the 112 d study duration. Simple modeling results also suggest that aqueous concentrations of esfenvalerate could be mitigated to 0.1% of the initial exposure concentration within 510 m of a vegetated ditch. Observed field half-lives in water, sediment, and plant were 0.12 d, 9 d, and 1.3 d, respectively. These results validate the role vegetation plays in the mitigation of pesticides, and that ditches are an indispensable component of the agricultural production landscape.

Acute toxicity of methyl-parathion in wetland mesocosms: assessing the influence of aquatic plants using laboratory testing with Hyalella azteca.

Methyl-parathion (MeP) was introduced into constructed wetlands for the purpose of assessing the importance of distance from the source of contamination and the role of emergent vegetation on the acute toxicity to Hyalella azteca (Crustacea: Amphipoda). A vegetated (90% cover: mainly Juncus effuses) and a nonvegetated wetland (each with a water body of 50 x 5.5 x 0.2 m) were each exposed to a simulated MeP storm runoff event. H. azteca was exposed for 48 h in the laboratory to water samples taken from the wetlands at a distance of 5, 10, 20, and 40 m from the pesticide inlet 3 h, 24 h, 96 h, and 10 days following application. Methyl-parathion was detected throughout the nonvegetated wetland, whereas the pesticide was only transported halfway through the vegetated wetland. A repeated-measure three-way analysis of variance (ANOVA) using time, location, and vegetation indicated significantly lower toxicity in the vegetated wetland. Furthermore, the mortality decreased significantly with both increasing distance from the inlet and time (48-h LC50 +/- 95% CI: 9.0 +/- 0.3 microg/L). A significant three-way interaction of time x vegetation x location confirmed higher toxicity at the inlet area of the nonvegetated wetland immediately after contamination. Significant linear regressions of maximum mortality (independent of time) versus distance from the pesticide inlet indicated that 44 m of vegetated and 111 m of nonvegetated wetland would reduce H. azteca mortality to < or = 5%. These results suggest that vegetation contributes to reduced MeP effects in constructed wetlands.

Evaluating mosquito control pesticides for effect on target and nontarget organisms.

Recent requirements for biomonitoring of urban stormwater runoff have raised the issue of toxic contributions from mosquito control products. A comparison of seven pesticides for their toxicity to target and nontarget organisms was conducted in field and laboratory trials to determine relative impacts in and around Craighead County, Arkansas. Twenty-four and forty-eight-hour acute toxicity tests using Ceriodaphnia dubia, Daphnia magna, Daphnia pulex, and Pimephales promelas were employed with U.S. Environmental Protection Agency (U.S. EPA) suggested procedures as standard test organisms. Additional tests with resident mosquito fish, Gambusia affinis, and mosquito larvae, Anopheles quadrimaculatus, included ditch-receiving waters to compare the somewhat sterile laboratory exposures to actual field conditions. Exposure to as much as 31.4 microg/L of the pesticides Dursban(R), malathion, Permanone(R), Abate(R), Scourge(R), B.t.i, and Biomist(R) were required for effective control of An. quadrimaculatus, whereas as little as 2.7 microg/L resulted in substantial mortality of some nontarget organisms. These data suggest that prevailing application rates for effective mosquito control not only affect nontarget organisms but may also confound stormwater and nonpoint toxicity evaluations that utilize sensitive indicator species.

Reversible renal insufficiency due to angiotensin converting enzyme inhibitors in hypertensive nephrosclerosis.

OBJECTIVE: To review the incidence of reversible renal insufficiency in patients with hypertensive nephrosclerosis undergoing antihypertensive therapy. DESIGN: Retrospective analysis of 73 patients in a long-term blood pressure control study that compared the effects of an angiotensin converting enzyme (ACE) inhibitor plus conventional antihypertensive agents compared with placebo plus antihypertensive agents. SETTING: Hospital-based outpatient treatment center. INTERVENTIONS: Patients were divided into group 1, which received enalapril plus conventional antihypertensives, and group 2, which received placebo plus conventional antihypertensives. MEASUREMENTS: Blood pressure and serum creatinine levels were measured, and imaging studies of the main renal arteries were done. MAIN RESULTS: In group 1, eight of 42 patients (19%, 95% CI, 9% to 34%) developed reversible renal insufficiency, defined as an unexpected increase in serum creatinine of 88 mumol/L or higher. Six episodes of reversible renal insufficiency occurred during July and August when temperatures were 32.2 degrees C to 37.8 degrees C (90 degrees F to 100 degrees F). Renal artery stenosis was excluded by renal arteriogram or ultrasonic duplex scanning. All eight group-1 patients had a significant decrease in mean arterial pressure below their baseline level during reversible renal insufficiency (mean change, -28 +/- 10 mm Hg, P less than 0.001). The increase in the serum creatinine level was inversely correlated with the decrease in the mean arterial pressure (r = -0.68, P less than 0.01). Reversible renal insufficiency was successfully managed by withdrawing or reducing enalapril as well as other antihypertensive agents. Subsequently, enalapril was tolerated by seven of the eight patients without recurrence of renal insufficiency. In contrast, none of 31 (CI, 0% to 11%) patients in group 2 developed reversible renal insufficiency despite the fact that both the incidence of decreases in mean arterial pressure in 6 of 31 patients (19%) and the magnitude of the decreases in mean arterial pressure (mean change, -33 +/- 16 mm Hg) were similar to those observed in group 1. CONCLUSIONS: Reversible renal insufficiency in hypertensive nephrosclerosis associated with ACE inhibitor therapy correlates with relative hypotension, is not dependent on renal artery stenosis, and can usually be managed by dose reduction.

Chromoblastomycosis.

Chromoblastomycosis, together with phaeohyphomycosis and mycetoma, makes up the disease entities caused by the dematiaceous fungi. Most cases of chromoblastomycosis are caused by five genera of fungi: Fonsecaea compactum, Fonsecaea pedrosoi, Phialophora verrucosa, Cladosporium carrionii, and Rhino-cladiella aquaspersa. The disease has a cosmopolitan distribution but predominates in rural, agricultural settings. Clinically, chromoblastomycosis is hallmarked by verrucous nodules at the site of fungal implantation. Treatment involves surgical excision of the affected area, antimycotic agents, physical modalities such as temperature manipulation, or a combination of these.

Scleromyxedema: therapeutic response to isotretinoin in three patients.

Scleromyxedema is a rare type of papular mucinosis that exhibits a generalized lichenoid pattern. A wide variety of clinical manifestations can occur in patients with this disease. Cutaneous involvement is characteristic, but neurologic, cardiovascular, renal, neoplastic, and other systemic manifestations have been described. A monoclonal gammopathy may be present. Many treatment modalities have been used in the past for scleromyxedema. None, however, have shown consistently favorable results. This report concerns the cases of three patients with scleromyxedema who were treated with isotretinoin.