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51.
Hydrolysis of a model nonionic surfactant, [1‐14C]methyl palmitate, was compared between porcine esterase and lipase using a new hydrolase assay. The assay incorporates acyl coenzyme A (CoA) synthetase to convert the hydrolytic product of methyl palmitate, palmitic acid, to its acyl CoA derivative; palmitoyl CoA is separated from unreacted substrate for quantitation by a highly efficient extraction. The assay achieves quantitative separation between product and substrate due to the high water solubility of the acyl CoA derivative, eliminating the need for time‐consuming chromatographic separations. After 60 min under optimal conditions, only 20 U/mL porcine hepatic esterase hydrolyzed 93.6+0.9% of 20μM methyl palmitate, while 100U/mL porcine pancreatic lipase was required to hydrolyze only 82.3 ±0.7% of the same substrate. While both enzymes detoxified the surfactant, esterase was more efficient, possibly indicating preferential specificity for simple monoesters; generally selective for endogenous triacylglycerols, lipase may be less specific for surfactants. However, together both enzymes may enable mammals to hydrolyze ingested nonionic surfactants from oil spill dispersants, reducing their toxicity. 相似文献
52.
Steven Kornguth Glenn Chambliss Kristine Gehring Lyman Wible Jack Anderson George Shalabi Louis Unversagt Bruce W. Brodman 《补救:环境净化治理成本、技术与工艺杂志》1997,8(1):7-17
This article describes the utility of Spizizen medium in effecting the release of 2,4 dinitrotoluene (DNT) from plasticized propellant in aged clay soil and of added Pseudomonas organisms in enhancing the rate of degradation of DNT in clay and sandy soils. DNT is an environmental problem because of its toxicity to mammals. It is proposed that the citrate in Spizizen medium chelates metals that form the aggregates of humin in aged clay soils, thereby releasing propellant components. Lack of awareness of DNT mobilization by citrate or other polyanions may lead to a potential underestimation of the 2,4 DNT present in aged contaminated soil and a potential increased release of DNT following exposure to solvents containing citrate or other polyanions. DNT in contaminated sandy soils was rapidly degraded when Pseudomonas and Spizizen medium were added (85% degraded in 20 days). Pseudomonas isolated/Torn soils at the Badger Plant have particular utility for the in situ degradation of 2,4 DNT in clay and sandy soils because they metabolize Spizizen medium, thrive in diverse climates, and have been selected for their ability to grow in soils contaminated with DNT. Mixture of either the contaminated clay soil or the contaminated sandy soil with uncontaminated prairie silt loam (20:80 ratio) facilitated management of the treatment process. This observation is important because of the widespread distribution, and hence low cost, of this soil type in the central United States. 相似文献
53.
There is growing evidence that the sex ratios of wild vertebrate populations are determined by mechanisms that are directly
influenced by environmental characteristics. The Trivers–Willard (TWH) and extrinsic modification (EMH) hypotheses postulate
differing determinants of mammalian offspring sex ratios. TWH states that mothers allocate resources according to their current
condition and sex-specific offspring costs. EMH states that environmental forces that affect maternal condition determine
offspring sex ratios, independently of maternal tactics of sex-biased allocation. We statistically assessed support for each
of these hypotheses using long-term life histories of the allied rock-wallaby, Petrogale assimilis; a continuously breeding, polygynous, weakly dimorphic marsupial. We showed that birth sex ratios were equal and independent
of maternal and environmental conditions. However, secondary sex ratios were male-biased under good environmental conditions
and for high quality mothers or mothers in good condition. Sex differences in offspring survival contributed to these biases:
(1) environmental conditions strongly influenced survival to pouch emergence (in support of EMH) and (2) maternal quality
affected survival to the end of maternal care (in support of TWH). Environmental effects on survival were more important than
maternal factors over the entire period of maternal care and contributed most to male-biased sex ratios at pouch emergence.
In contrast, maternal mass was the best predictor of sex ratios at the end of maternal care—the life history stage where offspring
body mass differed between the sexes. 相似文献
54.
Shahid Parvez Glenn E. Rice Linda K. Teuschler Jane Ellen Simmons Thomas F. Speth Susan D. Richardson Richard J. Miltner E. Sidney Hunter III Jonathan G. Pressman Lillian F. Strader Gary R. Klinefelter Jerome M. Goldman Michael G. Narotsky 《环境科学学报(英文版)》2017,29(8):311-321
A method based on regression modeling was developed to discern the contribution of component chemicals to the toxicity of highly complex, environmentally realistic mixtures of disinfection byproducts(DBPs). Chemical disinfection of drinking water forms DBP mixtures.Because of concerns about possible reproductive and developmental toxicity, a whole mixture(WM) of DBPs produced by chlorination of a water concentrate was administered as drinking water to Sprague–Dawley(S–D) rats in a multigenerational study. Age of puberty acquisition,i.e., preputial separation(PPS) and vaginal opening(VO), was examined in male and female offspring, respectively. When compared to controls, a slight, but statistically significant delay in puberty acquisition was observed in females but not in males. WM-induced differences in the age at puberty acquisition were compared to those reported in S–D rats administered either a defined mixture(DM) of nine regulated DBPs or individual DBPs. Regression models were developed using individual animal data on age at PPS or VO from the DM study. Puberty acquisition data reported in the WM and individual DBP studies were then compared with the DM models. The delay in puberty acquisition observed in the WM-treated female rats could not be distinguished from delays predicted by the DM regression model, suggesting that the nine regulated DBPs in the DM might account for much of the delay observed in the WM. This method is applicable to mixtures of other types of chemicals and other endpoints. 相似文献
55.
Jurgen Garbrecht Glenn P Fernandez 《Journal of the American Water Resources Association》1994,30(2):297-306
ABSTRACT: Small systematic changes in climatic records are often poorly visualized by standard time series plots because they are usually hidden by the magnitude and variability of the data values themselves. A visualization approach based on the rescaled adjusted partial sums (RAPS) which overcomes the above-stated shortcomings is presented. This visualization highlights trends, shifts, data clustering, irregular fluctuations, and periodicities in the record. Additional information on the number, magnitude, shape, frequency, and timing of fluctuations and trends can also be inferred. The visualization approach can be used for preliminary visual inspection of a time series, to gain a feel for the data, and/or to guide and focus subsequent statistical tests and analyses. It is not intended as a substitute for standard statistical analysis. Alternatively, the visualization approach can be used to display findings of a time series analysis. The capabilities and limitations of the approach are discussed and illustrated for two time series of annual rainfall values. 相似文献
56.
57.
This paper summarizes research evaluating nitrate levels in shallow groundwater of upstate New York, USA. Water from abandoned dug wells in six different land-use categories was analyzed for nitrate. Findings indicate that regardless of overlying land-use, shallow groundwater is susceptible to high levels of nitrate. Over 60 percent of the water samples tested, including at least one sample from each land-use category, had nitrate levels in excess of the United States drinking water standard of 10 mg 1–1. Due to the potential threat of elevated nitrate levels, efforts should be made to eliminate abandoned dug wells in shallow groundwater as a source of water supply.Glenn Harris is with the Environmental Studies Programme of St Lawrence University in Canton, New York. Brian Henry is with the Department of Entomology at the University of Georgia in Athens, Georgia. Jeffrey Deyette is with the joint International Relations and Resource and Environmental Management Programme at Boston University in Boston, Massachusetts. This research was performed as a Community Service Project sponsored by the Mergardt Fund while Mr Henry and Mr Deyette were students under the supervision of Dr Harris at St Lawrence University. 相似文献
58.
59.
Richard A Voldseth W Carter Johnson Tagir Gilmanov Glenn R Guntenspergen Bruce V Millett 《Ecological applications》2007,17(2):527-540
Wetlands of the Prairie Pothole Region exist in a matrix of grassland dominated by intensive pastoral and cultivation agriculture. Recent conservation management has emphasized the conversion of cultivated farmland and degraded pastures to intact grassland to improve upland nesting habitat. The consequences of changes in land-use cover that alter watershed processes have not been evaluated relative to their effect on the water budgets and vegetation dynamics of associated wetlands. We simulated the effect of upland agricultural practices on the water budget and vegetation of a semipermanent prairie wetland by modifying a previously published mathematical model (WETSIM). Watershed cover/land-use practices were categorized as unmanaged grassland (native grass, smooth brome), managed grassland (moderately heavily grazed, prescribed burned), cultivated crops (row crop, small grain), and alfalfa hayland. Model simulations showed that differing rates of evapotranspiration and runoff associated with different upland plant-cover categories in the surrounding catchment produced differences in wetland water budgets and linked ecological dynamics. Wetland water levels were highest and vegetation the most dynamic under the managed-grassland simulations, while water levels were the lowest and vegetation the least dynamic under the unmanaged-grassland simulations. The modeling results suggest that unmanaged grassland, often planted for waterfowl nesting, may produce the least favorable wetland conditions for birds, especially in drier regions of the Prairie Pothole Region. These results stand as hypotheses that urgently need to be verified with empirical data. 相似文献
60.
Summary This research concerned the relative potential for signaling and priming incompatibilities to promote reproductive isolation in rodents. Signaling is defined here as involving behavioral responses, while priming involves endocrine responses. Compatibility of both types of communications was tested between two widely separated and markedly diverging populations of deermice, and between equally separated but much less divergent populations of house mice. Signaling compatibility was assessed by comparing the amount of aggression toward young females by adult males when the two sexes were of the same vs the different stock of the same species. Priming compatibility was tested by measuring the relative amounts of uterine growth induced in young females by exposure to adult males.No signaling or priming incompatibilities were detected during cross-testing of the house mouse stocks. A degree of developing reproductive isolation was observed between the two deermouse populations, however, and this isolation was reinforced by independently occurring incompatibilities of both the signaling and the priming type. The signaling incompatibility was particularly dramatic, manifesting itself in the killing of young females by adult males.The present results provide the first demonstration of a priming incompatibility supporting reproductive isolation in diverging populations of a mammal. Furthermore, our results suggest that signaling and priming systems are independently subject to evolutionary change even when both systems probably operate through the same sensory modality. 相似文献