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Toxic Species (toxic + species)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Digital Imaging: A Promising Tool for Mushroom Identification

ACADEMIC EMERGENCY MEDICINE, Issue 7 2003
Connie B. Fischbein BA
Mushroom poisoning is a diagnostic and treatment dilemma for health care professionals. Decisions regarding treatment following ingestions are usually made without a firm identification of the fungus and tend to be more aggressive than necessary. The identification of mushrooms is beyond the scope of health care professionals, and a mycologist is essential to make an accurate identification. Telemedicine and digital imaging is an emerging technology that can assist in mushroom identification and facilitate patient care. The efficacy of using digital images sent over the Internet was tested in a pilot project. This article describes three cases in which digital images and verbal descriptions assisted in mushroom identification. When the actual specimen was sent to a mycologist, a definitive identification was obtained and compared with the presumptive identification. Digital images alone do not permit definitive identification; however, they often contain sufficient information to help the clinician rule out the possibility of a severely toxic species. Data accumulated to date indicate that digital imaging can be an important tool in the diagnosis and treatment of mushroom ingestion, and possibly other biologicals such as plants, insects, and reptiles. [source]

Inhibition of human squalene monooxygenase by selenium compounds

JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 1 2002
Nisha Gupta
Abstract Selenosis in animals is characterized by a variety of neurological abnormalities, but the chemical species of selenium and the molecular targets that mediate this neurotoxicity are unknown. We have previously shown that selenite is a potent inhibitor of squalene monooxygenase, the second enzyme in the committed pathway for cholesterol biosynthesis; inhibition of this enzyme by dimethyltellurium leads to a peripheral demyelinating neuropathy similar to that seen in selenosis. To evaluate the role methylation plays in selenium toxicity, we examined the ability of three methylselenium compounds, methylselenol, dimethylselenide, and trimethylselenonium iodide, to inhibit purified recombinant human squalene monooxygenase. IC50 values for methylselenol (95 ,M) and dimethylselenide (680 ,M) were greater than that previously obtained for selenite (37 ,M), and inhibition by trimethylselenonium iodide was evident only at concentrations above 3 mM. Inhibition by methylselenol as well as by selenite was slow and irreversible, suggestive of covalent binding to the enzyme, and thiol-containing compounds could prevent and reverse this inhibition, indicating that these compounds were reacting with sulfhydryl groups on the protein. Monothiols such as glutathione and ,-mercaptoethanol provided better protection than did dithiols, suggesting that these selenium compounds bind to only one of the two proposed vicinal cysteines on squalene monooxygenase. Unexpectedly, the inhibition by selenite was significantly enhanced by dithiols, indicating that a more toxic species, possibly selenide, was formed in the presence of these dithiol reductants. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:18,23, 2002; DOI 10.1002/jbt.10014 [source]

Soluble oligomers from a non-disease related protein mimic A,-induced tau hyperphosphorylation and neurodegeneration

JOURNAL OF NEUROCHEMISTRY, Issue 2 2007
Marcelo N. N. Vieira
Abstract Protein aggregation and amyloid accumulation in different tissues are associated with cellular dysfunction and toxicity in important human pathologies, including Alzheimer's disease and various forms of systemic amyloidosis. Soluble oligomers formed at the early stages of protein aggregation have been increasingly recognized as the main toxic species in amyloid diseases. To gain insight into the mechanisms of toxicity instigated by soluble protein oligomers, we have investigated the aggregation of hen egg white lysozyme (HEWL), a normally harmless protein. HEWL initially aggregates into ,-sheet rich, roughly spherical oligomers which appear to convert with time into protofibrils and mature amyloid fibrils. HEWL oligomers are potently neurotoxic to rat cortical neurons in culture, while mature amyloid fibrils are little or non-toxic. Interestingly, when added to cortical neuronal cultures HEWL oligomers induce tau hyperphosphorylation at epitopes that are characteristically phosphorylated in neurons exposed to soluble oligomers of the amyloid-, peptide. Furthermore, injection of HEWL oligomers in the cerebral cortices of adult rats induces extensive neurodegeneration in different brain areas. These results show that soluble oligomers from a non-disease related protein can mimic specific neuronal pathologies thought to be induced by soluble amyloid-, peptide oligomers in Alzheimer's disease and support the notion that amyloid oligomers from different proteins may share common structural determinants that would explain their generic cytotoxicities. [source]

Control of Oxidative Reactions of Hemoglobin in the Design of Blood Substitutes: Role of the Ascorbate,Glutathione Antioxidant System

ARTIFICIAL ORGANS, Issue 2 2009
Jan Simoni
Abstract Uncontrolled oxidative reactions of hemoglobin (Hb) are still the main unresolved problem for Hb-based blood substitute developers. Spontaneous oxidation of acellular ferrous Hb into a nonfunctional ferric Hb generates superoxide anion. Hydrogen peroxide, formed after superoxide anion dismutation, may react with ferrous/ferric Hb to produce toxic ferryl Hb, fluorescent heme degradation products, and/or protein-based free radicals. In the presence of free iron released from heme, superoxide anion and hydrogen peroxide might react via the Haber,Weiss and Fenton reactions to generate the hydroxyl radical. These highly reactive oxygen and heme species may not only be involved in shifting the cellular redox balance to the oxidized state that facilitates signal transduction and pro-inflammatory gene expression, but could also be involved in cellular and organ injury, and generation of vasoactive compounds such as isoprostanes and angiotensins. It is believed that these toxic species may be formed after administration of Hb-based blood substitutes, particularly in ischemic patients with a diminished ability to control oxidative reactions. Although varieties of antioxidant strategies have been suggested, this in vitro study examined the ability of the ascorbate,glutathione antioxidant system in preventing Hb oxidation and formation of its ferryl intermediate. The results suggest that although ascorbate is effective in reducing the formation of ferryl Hb, glutathione protects heme against excessive oxidation. Ascorbate without glutathione failed to protect the red blood cell membranes against Hb/hydrogen peroxide-mediated peroxidation. This study provides evidence that the ascorbate,glutathione antioxidant system is essential in attenuation of the pro-oxidant potential of redox active acellular Hbs, and superior to either ascorbate or glutathione alone. [source]