Direct Toxic Effects (direct + toxic_effects)

Distribution by Scientific Domains


Selected Abstracts


Effects of lambda-cyhalothrln in two ditch microcosm systems of different trophic status

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005
Ivo Roessink
Abstract The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (,0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher. [source]


Responses of biofilms to combined nutrient and metal exposure

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2002
Núria Ivorra
Abstract Numerous studies have reported marked sensitivities of diatom species to phosphate and organic pollution but have ignored interactions with other common contaminants. The aim of the present study was to investigate the single and joint effects of increased phosphate and metal (cadmium, zinc) concentrations on benthic diatom communities. Microalgal biofilms from a relatively unpolluted stream were exposed in the laboratory to Zn, Cd, and P, separately and in combination, in concentrations found at a polluted stream in the same catchment. The Zn concentration reduced algal growth in biofilms more than the Cd concentration. Phosphate compensated for the single effect of each metal but not for their combined effects. Diatom community changes were evaluated using water quality indices based on the empirical sensitivities of taxa to nutrients (TDI) and organic pollution (%PTV). Phosphate exposure resulted in an increase of the eutrophy rank and presumed pollution-tolerant taxa. In contrast, exposure to Zn, Zn + Cd, and Zn + Cd + P caused a marked reduction of the TDI and %PTV community values. The successional trends in the laboratory matched the observed differences in microphyte communities in the reference and polluted river stations. However, the autoecology of the species present also revealed that the resulting composition of diatom communities cannot be attributed solely to the direct toxic effects of metal and nutrients and their interaction. Observed changes in the relative abundance of species are also determined by their growth form and microdistribution in biofilms. [source]


Haematological toxicity of drugs used in psychiatry,

HUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue S1 2008
Robert J. Flanagan
Abstract Almost all classes of psychotropic agents have been reported to cause blood dyscrasias. Mechanisms include direct toxic effects upon the bone marrow, the formation of antibodies against haematopoietic precursors or involve peripheral destruction of cells. Agranulocytosis is probably the most important drug-related blood dyscrasia. The mortality from drug-induced agranulocytosis is 5,10% in Western countries. The manifestations of agranulocytosis are secondary to infection. Aggressive treatment with intravenous broad-spectrum antimicrobials and bone marrow stimulants may be required. Of drugs encountered in psychiatry, antipsychotics including clozapine (risk of agranulocytosis approximately 0.8%, predominantly in the first year of treatment) and phenothiazines (chlorpromazine agranulocytosis risk approximately 0.13%), and antiepileptics (notably carbamazepine, neutropenia risk approximately 0.5%) are the most common causes of drug-related neutropenia/agranulocytosis. Drugs known to cause neutropenia should not be used concomitantly with other drugs known to cause this problem. High temperature and other indicators of possible infection should be looked for routinely during treatment. Clozapine is well known as a drug that can cause blood dyscrasias, but olanzapine and other atypicals may also cause similar problems. In addition to genetic factors, there are likely to be dose-related and immunological components to these phenomena. Important lessons have been learnt from the haematological monitoring that is necessary with clozapine and the monitoring has been very successful in preventing deaths related to clozapine-induced agranulocytosis. Continuing research into the mechanisms of drug-induced neutropenia and agranulocytosis may serve to further enhance the safe use not only of clozapine, but also of other agents. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Downregulation of cell survival signalling pathways and increased cell damage in hydrogen peroxide-treated human renal proximal tubular cells by alpha-erythropoietin

CELL PROLIFERATION, Issue 4 2009
M. Andreucci
Objective:, Erythropoietin has been shown to have a protective effect in certain models of ischaemia-reperfusion, and in some cases the protection has been correlated with activation of signalling pathways known to play a role in cell survival and proliferation. We have studied whether erythropoietin would overcome direct toxic effects of hydrogen peroxide (H2O2) treatment to human renal proximal tubular (HK-2) cells. Materials and methods:, HK-2 cells were incubated with H2O2 (2 mm) for 2 h with or without erythropoietin at concentrations of 100 and 400 U/ml, and cell viability/proliferation was assessed by chemical reduction of MTT. Changes in phosphorylation state of the kinases Akt, glycogen synthase kinase-3, (GSK-3,), mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase 1 and 2 (ERK1/ERK2) were also analysed. Results:, Cells incubated with H2O2 alone showed a significant decrease in viability, which did not significantly change by addition of erythropoietin at concentration of 100 U/ml, but was further reduced when concentration of erythropoietin was increased to 400 U/ml. Phosphorylation state of the kinases Akt, GSK-3,, mTOR and ERK1/ERK2 of H2O2 -treated HK-2 cells was slightly altered in the presence of erythropoietin at concentration of 100 U/ml, but was significantly less in the presence of erythropoietin at a concentration of 400 U/ml. Phosphorylation of forkhead transcription factor FKHRL1 was diminished in cells incubated with H2O2 and erythropoietin at a concentration of 400 U/ml. Conclusions:, Erythropoietin, at high concentrations, may significantly increase cellular damage in HK-2 cells subjected to oxidative stress, which may be due in part to decrease in activation of important signalling pathways involved in cell survival and/or cell proliferation. [source]