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Equivalent Concentrations (equivalent + concentration)
Selected AbstractsUsing Biomonitoring Equivalents to interpret human biomonitoring data in a public health risk contextJOURNAL OF APPLIED TOXICOLOGY, Issue 4 2009Sean M. Hays Abstract Increasingly sensitive analytical tools allow measurement of trace concentrations of chemicals in human biological media in persons from the general population. Such data are being generated by biomonitoring programs conducted by the US Centers for Disease Control and other researchers. However, few screening tools are available for interpretation of such data in a health risk assessment context. This review describes the concept and implementation of Biomonitoring Equivalents (BEs), estimates of the concentration of a chemical or metabolite in a biological medium that is consistent with an existing exposure guidance value such as a tolerable daily intake or reference dose. The BE approach integrates available pharmacokinetic data to convert an existing exposure guidance value into an equivalent concentration in a biological medium. Key concepts regarding the derivation and communication of BE values resulting from an expert workshop held in 2007 are summarized. BE derivations for four case study chemicals (toluene, 2,4-dichlorophenoxyacetic acid, cadmium and acrylamide) are presented, and the interpretation of biomonitoring data for these chemicals is presented using the BE values. These case studies demonstrate that a range of pharmacokinetic data and approaches can be used to derive BE values; fully developed physiologically based pharmacokinetic models, while useful, are not required. The resulting screening level evaluation can be used to classify these compounds into relative categories of low, medium and high priority for risk assessment follow-up. Future challenges related to the derivation and use of BE values as tools in risk management are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Developmental toxicity of in ovo exposure to polychlorinated biphenyls: I. Immediate and subsequent effects on first-generation nestling American kestrels (Falco sparverius)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2003Kim Fernie Abstract We determined that in ovo exposure to polychlorinated biphenyls (PCBs) alters growth off first-generation nestlings during and one year after parental exposure. Captive American kestrels (Falco sparverius) laid eggs with environmentally relevant total PCB levels (34.1 ,g/g whole-egg wet wt) when fed PCB-spiked (Aroclor® 1248, 1254, and 1260) food (7 mg/kg body wt/d) for 100 d in 1998. In 1999, the same adults laid eggs with estimated total PCBs of 29.0 ,g/g. Nonsurviving PCB-exposed chicks were small (mass, bones) in 1998. Survivors showed a strong sex-specific growth response (mass, bones) compared to respective sex controls: Only female hatchlings were larger, and only male nestlings had longer feathers (1998); maximal growth and bone growth rates also differed (males were advanced, faster; females delayed, slower) (1999); and male nestlings fledged earlier and were smaller, while females were larger (1998, 1999). However, regardless of sex, PCB-exposed nestlings generally grew at faster rates in both years. In 1998, greater contaminant burdens and toxic equivalent concentrations in sibling eggs were associated with nestlings being lighter, having longer bones and feathers, and growing at faster rates (mass, bone) for females but slower rates (mass) for males. Both physiological-biochemical and behavioral changes are likely mechanisms. This study supports and expands on the Great Lakes embryo mortality, edema, and deformities syndrome: While PCB exposure alters nestling size, maximal growth and growth rates also change immediately, are sustained, and are sex specific. [source] Substances with estrogenic activity in effluents of sewage treatment plants in southwestern Germany.ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Abstract The proliferation test with human estrogen receptor-positive MCF-7 breast cancer cells (E-Screen assay) was applied for quantitative determination of total estrogenic activity in 24-h composite effluent samples from 16 municipal and two industrial sewage treatment plants (STPs) in the state of Baden-Württemberg, southwestern Germany. The estrogenic efficacy relative to the positive control, 17,-estradiol, was between 26 and 74% (median, 48%) for the 16 municipal STPs. Estradiol equivalent concentrations (EEQs) were between 0.2 and 7.8 ng/L (median, 1.6 ng/L) and, thereby, were lower than those found in a pilot study, which revealed EEQs of greater than 10 ng/L in the effluents of two other STPs. The EEQs in 14 of the 16 effluent samples were very similar (0.9,3.3 ng/L), indicating a rather constant input of estrogenic substances via STPs into rivers. Additional activated charcoal filtration turned out to be very efficient in further eliminating estrogenic activity from effluents. The EEQs of the E-Screen assay and those calculated from the results of extensive chemical analysis using the estradiol equivalency factors determined for 13 natural and synthetic estrogenic substances were comparable for most of the effluent samples. 17,-Estradiol, 17,-ethinylestradiol, and, to a lesser extent, estrone contributed to 90% or more of the EEQ value. [source] Response of bobwhite quail and gray-tailed voles to granular and flowable diazinon applicationsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2001Guiming Wang Abstract We used gray-tailed voles (Microtus canicaudus) and northern bobwhite quail (Colinus virginianus) as experimental model species to field test whether small mammals and birds respond differently to equivalent concentrations of a pesticide applied in granular and flowable formulations. In mid-May 1998, we placed voles into 15, 0.2-ha enclosures planted with a mixture of pasture grasses. In mid-July, we placed quail into the same enclosures with the voles. In late July, we applied the organophosphorus insecticide diazinon in five treatments; a control (all habitats sprayed with water), liquid formulation of diazinon at 0.55 kg/ha, liquid formulation of diazinon at 1.11 kg/ha, broadcast of granular diazinon at 1.11 kg/ha, and broadcast of granular diazinon at 2.22 kg/ha. The diazinon treatment in liquid and granular formulations did not depress population size or growth rate, or survival rate of voles. We found a significant difference in the survival rate of the quail between the controls and treatments; granular diazinon caused a measurable decline of quail survival, whereas the liquid application at an equivalent rate did not significantly affect quail survival. Analysis of our results suggests that ground-feeding birds are more susceptible to granular insecticides than flowable applications, but voles were not susceptible to either formulation at the rate we used. [source] The Application of Ultraviolet Irradiation to Exogenous Sources of DNA in Plasticware and Water for the Amplification of Low Copy Number DNAJOURNAL OF FORENSIC SCIENCES, Issue 4 2006Jeannie Tamariz B.S. ABSTRACT: Using high sensitivity forensic STR polymerase chain reaction (PCR) typing procedures, we have found low concentrations of DNA contamination in plasticware and water assumed to be sterile, which is not detected by standard DNA procedures. One technique commonly used to eliminate the presence of DNA is ultraviolet (UV) irradiation; we optimized such a protocol used in the treatment of water, tubes, plates, and tips for low copy number DNA (LCN) amplification. UV light from a Stratalinker® 2400 was administered to 0.2, 1.5 mL tubes, and PCR plates contaminated with up to 500 pg of DNA. They were subsequently quantified with an ALU-based real-time PCR method using the Rotorgene 3000. Overall, there was a decrease in concentration of DNA recovered as the duration of treatment increased. Nonetheless, following 45 min of irradiating a PCR plate with 500 pg of DNA, nearly 6 pg were still detected. However, when the plate was raised within an inch of the UV source, less than 0.2 pg of DNA was detected. Additionally, lining the area around the samples with aluminum foil further reduced the amount of time necessary for irradiation, as only 30 min eliminated the presence DNA in the raised PCR plate. Similar experiments were conducted using tubes filled with a solution of DNA and water in equivalent concentrations for 50, 15, and 1.5 mL tubes with comparative results. It is plausible that the aluminum foil increased the amount of reflection in the area thereby enhancing penetration of UV rays through the walls of the plasticware. This protocol was tested for the possibility of inhibitors produced from irradiation of plastic tubes. As our protocols require less irradiation time than previous studies, PCR sensitivity was not affected. Moreover, the lifespan of the UV lamps was extended. Our findings demonstrate that this method is useful as an additional precautionary measure to prevent amplification of extraneous DNA from plasticware and water without compromising the sensitivity of LCN DNA amplifications. [source] Triton-X-100-modified polymer and microspheres for reversal of multidrug resistanceJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2001Zhi Liu Triton X-100 is a non-ionic detergent capable of reversing multidrug resistance (MDR) due to its interaction with cell membranes. However, it interacts with cells in a non-specific way, causing cytotoxicity. This work aimed to develop polymeric chemosensitizers that possess the ability to reverse MDR and lower toxic side effects. When being delivered to tumours, the polymeric chemosensitizers may also have longer retention times in tumours than the free detergent. Triton-X-100-immobilized dextran microspheres (T-MS) and inulin (T-IN) were prepared and characterized. Their cytotoxicity against multidrug-resistant Chinese hamster ovary cells (CHRC5) was compared with that of free Triton X-100 solutions. The in-vitro effect of the products on 3H-vinblastine accumulation by CHRC5 cells was determined. Both T-MS and T-IN showed a marked decrease in the cytotoxicity, as compared with free Triton solutions at equivalent concentrations. Drug accumulation by CHRC5 cells was increased over two fold in the presence of T-MS or T-IN. These results suggest that polymeric drug carriers with MDR-reversing capability and lower cytotoxicity may be prepared by immobilization of chemosensitizers. [source] Technical advances in the sectioning of dental tissue and of on-section cross-linked collagen detection in mineralized teethMICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2010Sim K. Singhrao Abstract Immunohistochemical detection of cross-linked fibrillar collagens in mineralized tissues is much desired for exploring the mechanisms of biomineralization in health and disease. Mineralized teeth are impossible to section when embedded in conventional media, thus limiting on-section characterization of matrix proteins by immunohistochemistry. We hypothesized that by using an especially formulated acrylic resin suitable for mineralized dental tissues, not only sectioning of teeth would be possible, but also our recently developed immunofluorescence labeling technique would be amenable to fully calcified tissues for characterization of dentinal fibrillar collagens, which remains elusive. The hypothesis was tested on fixed rodent teeth embedded in Technovit 9100 New®. It was possible to cut thin (1 ,m) sections of mineralized teeth, and immunofluorescence characterization of cross-linked type I fibrillar collagen was selected due to its abundance in dentine. Decalcified samples of teeth embedded in paraffin wax were also used to compare immunolabeling from either method using the same immunoreagents in equivalent concentrations. In the decalcified tissue sections, type I collagen labeling in the dentine along the tubules was "patchy" and the signal in the predentine was very weak. However, enhanced signal in mineralized samples with type I collagen was detected not only in the predentine but also at the limit between intertubular dentine, within the elements of the enamel organ and subgingival stroma. This report offers advances in sectioning mineralized dental tissues and allows the application of immunofluorescence not only for on-section protein detection but importantly for detecting cross-linked fibrous collagens in both soft and mineralized tissue sections. Microsc. Res. Tech. 73:741,745, 2010. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||