Relatively enriched housing conditions delay binge onset but do not attenuate binge size.

Housing and enrichment conditions are essential factors to consider when using animal models of behavior, as they can alter the behavior that is under investigation. The goal of this study was to determine the impact of the relatively enriched environment recommended by current animal care guidelines on development and maintenance of binge-type behavior in rats, using the limited access (LA) binge model. Non-food-deprived rats were divided into two groups, enriched and nonenriched, with all rats housed in shoebox cages. Bedding, nesting material, toys, and a solid floor were provided only to the enriched group to create a state of relative enrichment, or RE, compared to the nonenriched conditions historically used in the LA model. Enriched and nonenriched groups were further divided into control and experimental groups. Control rats received access to an optional source of fat (vegetable shortening) for 30min each day (daily access) while experimental rats received 30-min optional fat access on Monday, Wednesday, and Friday only (intermittent access). The four groups were designated C-E (Control-Enriched), C-NE (Control-Nonenriched), I-E (Intermittent-Enriched), and I-NE (Intermittent-Nonenriched). Bingeing in the LA model is established when a group with intermittent access (i.e., the I-E or I-NE group) consumes significantly more vegetable shortening during the limited access period than a group with daily access (i.e., the C-E or C-NE group). Access sessions continued for 8weeks under these conditions, at which time the housing conditions of the I-E and I-NE groups were reversed for an additional 8weeks of access sessions. Intakes of the C-E and C-NE groups were similar and data from these two groups were combined. Relative to this Combined Control Group (CCG), the I-NE group began bingeing in week 3 while the I-E group binged during weeks 6 and 8. Following the reversal at the beginning of week 9, the newly enriched I-NE group ceased bingeing in week 9 but resumed bingeing in weeks 10-16. The newly nonenriched I-E group continued bingeing through the remainder of the study. Intakes of the I-E and I-NE groups were not significantly different at any time during the study. These results indicate that RE delays binge onset; that is, RE increases the time between the first fat access session and the first occurrence of bingeing. However, RE does not significantly alter the amount of fat consumed during binge sessions. Furthermore, addition of RE to a nonenriched group of animals (I-NE) does not reverse established binge behavior. Thus it appears that regardless of enrichment condition, intermittent access to vegetable shortening induces greater consumption of fat than does daily access. However, it is clear that a certain level of austerity in housing conditions is required for rapid development of lasting binge-type eating to occur. In addition, results suggest that it is unlikely that enrichment, to the degree provided in this study, can prevent or reverse binge-type eating in rats.

Improvements of the fluoride reactivation method for the verification of nerve agent exposure.

One of the most appropriate biomarkers for the verification of organophosphorus nerve agent exposure is the conjugate of the nerve agent to butyrylcholinesterase (BuChE). The phosphyl moiety of the nerve agent can be released from the BuChE enzyme by incubation with fluoride ions, after which the resulting organophosphonofluoridate can be analyzed with gas chromatography-mass spectrometry (GC-MS). This paper describes recent improvements of the fluoride-induced reactivation in human plasma or serum samples by enhancing the sample preparation with new solid-phase extraction cartridges and the MS analysis with large volume injections. Analysis is performed with thermal desorption GC with either mass selective detection with ammonia chemical ionization or high-resolution MS with electron impact ionization. The organophosphorus chemical warfare agents analyzed in this study are O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate, ethyl methylphosphonofluoridate, isopropyl methylphosphonofluoridate (sarin, GB), O-ethyl N,N-dimethylphosphoramidocyanidate, ethyl N,N-dimethylphosphoramidofluoridate, and cyclohexyl methylphosphonfluoridate. Detection limits of approximately 10 pg/mL plasma were achieved for all analytes, which corresponds to 0.09% inhibition with GB on a sample with normal BuChE levels.

Quantitation of the sulfur mustard metabolites 1,1'-sulfonylbis[2-(methylthio)ethane] and thiodiglycol in urine using isotope-dilution Gas chromatography-tandem mass spectrometry.

Sulfur mustard (HD), or bis(2-chloroethyl)sulfide, has several urinary metabolites that can be measured to assess human exposure. These metabolites include the simple hydrolysis product thiodiglycol (TDG) and its oxidative analogue, TDG-sulfoxide, as well as metabolites of the glutathione/b-lyase pathway 1,1'-sulfonylbis[2-(methyl-sulfinyl)ethane] (SBMSE) and 1-methyl-sulfinyl-2-[(methylthio)ethyl-sulfonyl]ethane (MSMTESE). Current methods focus on either the TDG or the b-lyase metabolites. We have developed a single method that measures products of both metabolic branches, with the reduced compound of SBMSE and MSMTESE, 1,1'-sulfonylbis [2(methylthio)ethane] (SBMTE), as the definitive analyte and TDG as a confirmation analyte. Sample preparation included b-glucuronidase hydrolysis for TDG-glucuronide conjugates, titanium trichloride reduction of sulfoxides to SBMTE and TDG, solid-phase extraction, and a chemical derivatization. We analyzed samples using gas chromatography-tandem mass spectrometry with quantitation using isotope-dilution calibration. The method limits of detection for TDG and SBMTE were 0.5 ng/mL and 0.25 ng/mL, respectively, with relative standard deviations of less than 10%. Urine samples from individuals with no known exposure to mustard agent HD had measurable concentrations of TDG, but no SBMTE was detected. The geometric mean concentration of TDG was 3.43 ng/mL, with concentrations ranging from < 0.5 ng/mL to 20 ng/mL.

Comprehensive solid-phase extraction method for persistent organic pollutants. Validation and application to the analysis of persistent chlorinated pesticides.

The Centers for Disease Control and Prevention (CDC) is involved in many epidemiological studies regarding the measurement of chlorinated pesticides and polychlorinated biphenyls in specimens obtained from humans. In addition to these commonly determined analytes, there is a need to include additional persistent organic pollutants (POPs) in our analyses, which further stresses the analyses because sample volumes remain small. Thus, a single method of analysis for all POPs in human serum is needed. CDC has recently developed a semiautomated and comprehensive solid-phase extraction method for POPs. The method is comprehensive since it was optimized for the extraction of many different POP compound classes. We then developed a purification and fractionation scheme that allows (a) separation of different compound classes by particular functionalities and (b) purification of those fractions to remove coextracted interferences. This paper describes the first step in the semiautomated comprehensive extraction and multiple fractionation method developed by CDC for monitoring POPs. In this paper, we validate the analysis of the persistent chlorinated pesticides, a compound class difficult to examine because of their structural diversity, in human plasma. The method was validated against an existing CDC method by using a spiked quality-control serum pool. The concentrations determined for all analytes using both methods were within 2%-14% relative standard deviations. A multilevel (i.e., 3-4 point) matrix spike showed good linearity for the analytes tested (r2 = 0.978-0.999). The method was then applied to 40-year-old archived plasma samples for the quantitative analysis of selected chlorinated pesticides. Mean recoveries of the 13C-labeled internal quantification standards ranged from 64% to 123% for the 11 monitored pesticides. The overall method proved to be robust by handling old coagulated plasma samples. It allowed faster throughput of samples than our previous methods and provided cleaner samples with less frequent interferences or background as analyzed by high-resolution mass spectrometry. The method represents a preliminary step in establishing an automated, comprehensive multiresidue analysis method for POPs in human serum.