This chapter discusses the importance of tissue-specific biochemistry in determining the target organ for a toxic chemical. The tissue distribution of paraquat is so dramatically influenced by the fact that it is actively transported into the lung such that it becomes a lung-specific toxin. This is tissue-specific biochemistry, but it is relative only to tissue distribution of the toxin. Tissue-specific biochemistry would definitely determine the target organ for any toxin affecting a biochemical process which only occurred in that tissue. Toxicities resulting from tissue-specific biochemistry can be related to the two families of biochemicals involved in communication between cells: hormones and neurotransmitters. Blood-forming tissues require a high rate of proliferation to produce adequate quantities of blood cells. There are a number of chemicals which exhibit striking tissue-specific toxicity. J. H. Doroshow et al. have pointed out that cardiac tissue contained considerably less superoxide dismutase and catalase activity than does liver.

PURPOSE: To determine the local origin of hydroxyl radicals during phacoemulsification using an ultrasonic phacoemulsification device that includes longitudinal and torsional modalities.SETTING: Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA.DESIGN: Experimental study.METHODS: Experiments were conducted using the Infiniti Vision System and Ozil handpiece. Hydroxyl radical concentrations during longitudinal and torsional phacoemulsification were quantitated as malondialdehyde (MDA) determined spectrophotometrically using the deoxyribose assay. The difference between the total concentration found in the aspirated solution at steady-state concentrations and the pre-aspirate levels deductively determined the concentration of MDA formed along the interior of the sonicating tip. The time to reach 50% of steady state as a function of reaction vessel volume was determined.RESULTS: The mean maximum for torsional ultrasound at 100% amplitude was 7.70 nM +/- 0.38 (SD), 91.1% of which was generated outside the tip. During longitudinal ultrasound at 100% power, MDA concentration in the aspirated solution was 29.5 +/- 0.3 nM, 71.6% of which was generated outside the tip. The time (seconds) to reach 50% of maximum for longitudinal ultrasound using 5 mL, 10 mL, and 20 mL reaction vessels was 12.6 +/- 1.5, 21.0 +/- 1.5, and 25.3 +/- 3.4, respectively.CONCLUSION: Although a significantly greater proportion of the hydroxyl radicals generated during ultrasound modality were formed outside the phaco tip (91.1% torsional; 71.6% longitudinal), torsional ultrasound generated only about one-fourth the amount of MDA as longitudinal ultrasound in total and about one-third that generated outside the tip (7.02 nM versus 21.1 nM).

To quantitate free radical generation during phacoemulsification using an ultrasonic phacoemulsification device that includes a torsional mode and evaluate tip designs specific to the torsional mode.Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA.Experimental study.Experiments were performed using the Infiniti Vision System and OZil handpiece. Hydroxyl radical concentrations in the aspirated irrigation solution during torsional phacoemulsification were quantitated as nanomolar malondialdehyde (nM MDA) and determined spectrophotometrically using the deoxyribose assay.The mean free radical production during phacoemulsification with torsional modality at 100% amplitude was 30.1 nM MDA ± 5.1 (SD) using a 0.9 mm 45-degree Kelman tapered ABS tip. With other tip designs intended for use with the torsional modality, free radical production was further reduced when fitted with the 0.9 mm 45-degree Kelman mini-flared ABS tip (13.2 ± 5.6 nM MDA) or the 0.9 mm 45-degree OZil-12 mini-flared ABS tip (14.3 ± 6.7 nM MDA). Although the measurements resulting from the use of the latter 2 tips were not statistically significantly different (P ≈ .25), they were different from those of the tapered tip (P<.0001).The MDA concentration in the aspirated irrigation solution using the torsional modality was approximately one half that reported for the handpiece's longitudinal modality in a previous study using the same bent-tip design (Kelman tapered, P<.0001). The level of MDA was further reduced approximately one half with torsional-specific tips.

PURPOSE: To quantitate hydroxyl radicals produced during phacoemulsification with various irrigating solutions and conditions used in cataract surgery. SETTING: Chemistry and Biochemistry Department, Utah State University, Logan, Utah, USA. METHODS: All experiments were performed using an Infiniti Vision System phacoemulsifier with irrigation and aspiration. Hydroxyl radicals were quantitated using electron spin resonance spectroscopy and a spectrophotometric assay for malondialdehyde, which is formed by the oxidation of deoxyribose by the hydroxyl radical. RESULTS: Hydroxyl radical production increased during longitudinal-stroking phacoemulsification as power levels were increased in a nonlinear, nonexponential fashion. The detection of hydroxyl radical was reduced in irrigating solutions containing organic molecules (eg, citrate, acetate, glutathione, dextrose) and further reduced in Navstel, an irrigating solution containing a viscosity-modifying agent, hydroxypropyl methylcellulose. CONCLUSIONS: Hydroxyl radicals produced in settings representative of those used in phacoemulsification cataract surgery were quantitated using the deoxyribose method. Hydroxyl radical production was dependent on the level of ultrasound power applied and the irrigating solution used. Oxidative stress on the eye during phacoemulsification may be minimized by using irrigating solutions that contain organic molecules, including the viscosity-modifying agent hydroxypropyl methylcellulose, that can compete for reaction with hydroxyl radicals.

We demonstrated previously that loading iron into ferritin via its own ferroxidase activity resulted in damage to the ferritin while ferritin loaded by ceruloplasmin, a copper-containing ferroxidase, was not damaged and had similar characteristics to native ferritin (Welch et al. (2001) Free Radic Biol Med 31:999-1006). Interestingly, it has been suggested that the formation of hemosiderin, a proposed degradation product of ferritin, is increased in animals deficient in copper. In this study, groups of rats were fed normal diets, copper deficient diets, iron supplemented diets, or copper deficient-iron supplemented diets for 60 days. Rats fed copper-deficient diets had no detectable active serum ceruloplasmin, which indicates that they were functionally copper deficient. There was a significant increase in the amount of iron in isolated hemosiderin fractions from the livers of copper-deficient rats, even more than that found in rats fed only an iron-supplemented diet. Histological analysis showed that copper-deficient rats had iron deposits (which are indicative of hemosiderin) in their hepatocytes and Kupffer cells, whereas rats fed diets sufficient in copper only had iron deposits in their Kupffer cells. Histologic evidence of iron deposition was more pronounced in rats fed diets that were deficient in copper. Additionally, sucrose density-gradient sedimentation profiles of ferritin loaded with iron in vitro via its own ferroxidase activity was found to have similarities to that of the sedimentation profile of the hemosiderin fraction from rat livers. The implications of these data for the possible mechanism of hemosiderin formation are discussed.

Wheat straw is an abundantly available and potentially valuable biomass that is currently underexploited. In this study, the feasibility of using wheat straw as a filler in high-density polyethylene (HDPE)-based composites was explored. Straw was treated with the white-rot fungus Pleurotits ostreatus with the aim of improving adhesion between straw and plastic, and thereby the mechanical properties of the composite. Results indicate that the use of sterilized straw is necessary to inhibit the growth of indigeous organisms that preclude, likely through competition, removal of lignin, and hence, improved bonding between straw and plastic. Light and transmission electron microscopy revealed cell wall modification in sterilized, inoculated straw. Reduced thermal stability of treated straw did not negatively affect the production of injection-molded straw-plastic composites (SPC). Comparable interfacial adhesion, based on activation energies obtained in dynamic mechanical analysis, was observed in untreated and treated straw- and pine-based thermoplastic composites. The results of this study indicate that wheat straw represents a promising alternative to wood fillers in the production of thermoplastic composites. (c) 2006 Wiley Periodicals, Inc.

Vol. 113, No. 7 PerspectivesOpen AccessBioremediation Monitoring Steven D. Aust Steven D. Aust Search for more papers by this author Published:1 July 2005https://doi.org/10.1289/ehp.113-a444aAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit In their article published in the February issue of EHP, Ganey and Boyd (2005) made some excellent points about the potential pitfalls of simply assaying for the disappearance of an environmental pollutant during or as a result of bioremediation. This is important because it would be wrong to leave a metabolite that might pose as much or even more risk then the original chemical of interest.Ganey and Boyd (2005) used the bio-remediation of polychlorinated biphenyls (PCBs) as an example, which was an excellent choice. However, the subject of metabolism of the PCB bioremediation metabolites should also be considered. As chlorines are removed by bioremediation, the less-chlorinated products could be more readily metabolized by many species exposed to the bioremediated material. That is, less-heavily chlorinated products (or intermediates) of bioremediation may be less toxic because of shorter half-lives due to metabolism. This phenomenon can be exemplified by work we conducted years ago at Michigan State University. We showed that 3,4,3′,4′-tetrabromobiphenyl was less toxic than 3,4,5,3′,4′,5′-hexabromobiphenyl, even though it was bound at higher affinity by the dioxin receptors because it was more readily metabolized and eliminated (Millis et al. 1985).Commercial preparations contain few or no strictly coplanar PCB or polybrominated biphenyl congeners. This fact does not seem to be appreciated, and the impression is sometimes given that those very toxic congeners are in the environment. In fact, the coplanar polyhalogenated biphenyls probably receive way too much attention, most likely because they were used rather extensively in research; however, they were used only as model toxic congeners. The synthesis of strictly coplanar halogenated biphenyls (i.e., 3,4,3′,4′-PCB) is much different from that of the commercial preparations (which was by simple halogenation of biphenyl). Phenyl is strongly ortho-para directing, leading to non-coplanar halogenated biphenyls. The initial para and/or ortho halogenation makes for an even stronger ortho-para directive. Thus, the major components will be non-coplanar halobiphenyls. Only very small amounts of single ortho halobiphenyls can be found in commercial mixtures, and these mixtures are quite ineffective in eliciting effects associated with binding by the dioxin receptor.ReferencesGaney PE, Boyd SA. 2005. An approach to evaluation of the effect of bioremediation on biological activity of environmental contaminants: dechlorination of polychlorinated biphenyls. Environ Health Perspect 113:180-18515687055. Link, Google ScholarMillis CD, Mills RA, Sleight SD, Aust SD. 1985. Toxicity of 3,4,5,3′,4′,5′-hexabrominated biphenyl and 3,4,3′,4′-tetrabrominated biphenyl. Toxicol Appl Pharmacol 78:88-952994254. Crossref, Medline, Google ScholarFiguresReferencesRelatedDetails Vol. 113, No. 7 July 2005Metrics About Article Metrics Publication History Originally published1 July 2005Published in print1 July 2005 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

White-rot fungi can degrade a wide variety of environmental pollutants using a variety of extracellular enzymes and chemicals normally involved in lignin degradation. Examples of toxic chemicals shown to be degraded by white-rot fungi include pentachlorophenol, trinitrotoluene, trichloroethylene, cyanide and polyaromatic hydrocarbons. Pentachlorophenol is methylated by a transmembrane methyl transferase. Trinitrotoluene is reduced by a transmembrane redox potential associated with a proton pump that the fungus uses to establish a rather low (4.5) extracellular pH. Trichloroethylene is aerobically dechlorinated by peroxidases using the carboxylate anion radical. The peroxidases oxidize either veratryl alcohol or manganese which oxidize oxalic acid to form the carboxylate anion radical for reductive dechlorinations. Other chemicals can either be directly or indirectly oxidized to radicals by the peroxidases. In all cases the chemicals are detoxified such that relatively high concentrations of these chemicals can be degraded. In addition, sites contaminated with multiple chemicals, including these toxic chemicals, can be remediated.

Surfactants are frequently added to pesticide and herbicide formulations as adjuvants to improve handling, delivery and effectiveness. From a regulatory perspective such additives are generally considered to be inert, and their influence on co-contaminant fate and transport processes has been largely ignored. The objective of this chapter is to illustrate the potential effects of representative surfactant adjuvants on the phase distribution and availability of hydrophobic organic compounds (HOCs), soil water retention and water flow in unsaturated soils. Although the addition of surfactants at concentrations above the critical micelle concentration (CMC) is shown to enhance the total aqueous-phase concentration of HOCs, the free (non-micellar) aqueous phase HOC concentration decreases with increasing surfactant concentration. Results of pressure-saturation studies and one-dimensional column experiments demonstrate that surfactants can substantially reduce soil water retention and alter unsaturated water flow. These findings demonstrate the need to carefully consider the influence of surfactant adjuvants on both soil water characteristics and agrochemical fate and transport in the environment.

This research investigated electrochemical oxidation of triclosan using Ebonex((R)) and boron-doped diamond (BDD) film anodes. Oxidative destruction of triclosan was conducted in both high pH aqueous solutions and in ethanol. At current densities of 5 mA/cm(2) and above, oxidation of triclosan in water was rapid due to the action of hydroxyl radicals generated from water oxidation. However, at current densities below 5 mA/cm(2), the electrodes in aqueous solutions were rapidly inactivated by a film of polymerized byproducts. Oxidation of triclosan in ethanol solutions was much slower than in water. The primary mechanism of triclosan oxidation in ethanol was indirect, and involved ethoxy radicals produced from ethanol oxidation. Product analysis showed that breaking the ether linkage was easier than opening the aromatic rings. Microtox((R)) tests showed that residual triclosan was the major source of toxicity in the treated wastewater, despite byproduct concentrations that were significantly higher than triclosan concentrations.

The diverse array of naturally isolated microorganisms capable of degrading organophosphate pesticides has led to increased attention in using bioremediation as a method to treat these compounds. Combined with advancements in biotechnology, manipulation of natural systems for novel strategies in pesticide degradation has provided an environmentally-friendly in situ treatment method. The innovative use of bifunctional proteins with a catalytic domain and moieties for cell surface targeting, facilitated purification and immobilization are some of the recent strategies used to treat these chemical agents. This chapter will focus on the use of genetically engineered microorganisms and custom tailored enzymes as an altemative to current disposal methods for the treatment of organophosphate pesticides.

Fumigants are used for control of nematodes, fungi, weeds, and insects in high-cash-value crops. Because of their high volatility, a large fraction of the applied mass may be volatilized from the soil surface following application. Emission reduction strategies are needed to prevent adverse human or environmental health impacts. Some emission-reduction strategies, such as tarping the soil surface with impermeable plastic, increase containment of fumigants in the soil. The resulting fumigant residues could cause atmospheric contamination once the tarp is disrupted, groundwater contamination if leaching is allowed, or phytotoxicity to the crop planted following fumigation. Previous research has shown that thiosulfate compounds, including ammonium thiosulfate (ATS), abiotically react with and detoxify halogenated fumigants in soil and water. In these experiments, we investigated subsurface application of ATS to reduce fumigant concentrations in the root zone, preventing off-site transport following fumigation. Results indicated that halogenated fumigants were dissipated more rapidly in soil receiving ATS application compared to those receiving water only. First-order dissipation half-lives were less than or equal to1 day for the halogenated compounds 1,3-dichloropropene and propargyl bromide. For methyl isothiocyanate, a non-halogenated fumigant that does not undergo reaction with ATS, application of ATS had no impact on the rate of dissipation in soil. These results suggest that subsurface application of ATS may be useful for the root-zone remediation of halogenated compounds.

The electrochemistry of the ligninolytic redox enzymes, which include lignin peroxidase, manganese peroxidase and laccase and possibly also cellobiose dehydrogenase, is reviewed and discussed in conjunction with their basic biochemical characteristics. It is shown that long-range electron transfer between these enzymes and electrodes can be established and their ability to degrade lignin through a direct electron transfer mechanism is discussed.

An electrochemical adaptation of the Fenton treatment method has been successfully applied to the degradation of pesticides and other contaminants in aqueous solution. The results of this work have implications for fast and efficient treatment and pretreatment of aqueous wastes. The anodic Fenton treatment (AFT) system has been applied to the treatment of ethylene thiourea, trifluralin, atrazine, 2,4-D, diazinon, carbaryl, carbofuran, and other carbamate pesticides. The method was initially developed in a batch system that can be scaled up to a flow-through system as a convenient way to deliver Fenton reagents. Ferrous ion is produced at an iron anode while hydrogen peroxide is delivered via a peristaltic pump. Separation of the anode chamber from the inert cathode (where water is reduced), first by a salt bridge and then by an anion exchange membrane, improved the method considerably, making it as effective as traditional Fenton chemistry without the disadvantages. Development of a kinetic delivery model for the AFT method has made it an extremely useful probe to study hydroxyl radical reactions rates using competitive kinetics. These advances, coupled with the use of GC-MS to identify degradation products, has enabled the study of reaction mechanisms for degradation of these aqueous contaminants.

Iron is an essential metal for most biological organisms. However, if not tightly controlled, iron can mediate the deleterious oxidation of biomolecules. This review focuses on the current understanding of the role of iron in the deleterious oxidation of various biomolecules, including DNA, protein, lipid, and small molecules, e.g., ascorbate and biogenic amines. The effect of chelation on the reactivity of iron is also addressed, in addition to iron-associated toxicities. The roles of the iron storage protein ferritin as both a source of iron for iron-mediated oxidations and as a mechanism to safely store iron in cells is also addressed.

Iron is an essential metal for most biological organisms. However, if not tightly controlled, iron can mediate the deleterious oxidation of biomolecules. This review focuses on the current understanding of the role of iron in the deleterious oxidation of various biomolecules, including DNA, protein, lipid, and small molecules, e.g., ascorbate and biogenic amines. The effect of chelation on the reactivity of iron is also addressed, in addition to iron-associated toxicities. The roles of the iron storage protein ferritin as both a source of iron for iron-mediated oxidations and as a mechanism to safely store iron in cells is also addressed.