The detailed mechanistic aspects for the final starch digestion process leading to effective a-gl... more The detailed mechanistic aspects for the final starch digestion process leading to effective a-glucogenesis by the 2 mucosal a-glucosidases, human sucrase-isomaltase complex (SI) and human maltase-glucoamylase (MGAM), are poorly understood. This is due to the structural complexity and vast variety of starches and their intermediate digestion products, the poorly understood enzyme-substrate interactions occurring during the digestive process, and the limited knowledge of the structure-function properties of SI and MGAM. Here we analyzed the basic catalytic properties of the N-terminal subunit of MGAM (ntMGAM) on the hydrolysis of glucan substrates and compared it with those of human native MGAM isolated by immunochemical methods. In relation to native MGAM, ntMGAM displayed slower activity against maltose to maltopentose (G5) series glucose oligomers, as well as maltodextrins and a-limit dextrins, and failed to show the strong substrate inhibitory ''brake'' effect caused by maltotriose, maltotetrose, and G5 on the native enzyme. In addition, the inhibitory constant for acarbose was 2 orders of magnitude higher for ntMGAM than for native MGAM, suggesting lower affinity and/or fewer binding configurations of the active site in the recombinant enzyme. The results strongly suggested that the C-terminal subunit of MGAM has a greater catalytic efficiency due to a higher affinity for glucan substrates and larger number of binding configurations to its active site. Our results show for the first time, to our knowledge, that the C-terminal subunit of MGAM is responsible for the MGAM peptide's ''glucoamylase'' activity and is the location of the substrate inhibitory brake. In contrast, the membrane-bound ntMGAM subunit contains the poorly inhibitable ''maltase'' activity of the internally duplicated enzyme. J. Nutr. 138: 685-692, 2008.
A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the ... more A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the bioluminescence output from marine dinoflagellates has been developed and tested over the course of 16 years. The toxicity system, QwikLite, was developed for the sole purpose of evaluating the potential toxicity of various materials used in bay sediments, storm water discharges, industrial discharges from Naval facilities, and antifoulant paints. Bioluminescence inhibition was observed in the following dinoflagellates: Lingulodinium polyedrum (formerly known as Gonyaulax polyedra), Ceratocorys horrida, Pyrocystis noctiluca, Pyrocystis lunula, Pyrocystis fusiformis, and Pyrophacus steinii. Cultured cells were exposed to various concentrations of contaminants from hours through 10 days. Further application with bioluminescent dinoflagellates in a variety of toxicity testing schemes have shown that these species can be used as a screening assay organism in lieu of the more costly, labor intensive bioassays presently in use.
The Arc Hydro geographic data model for representing water resources features of the landscape is... more The Arc Hydro geographic data model for representing water resources features of the landscape is a customization of ArcGIS for representation of water resources features of the landscape. Arc Hydro is used here to integrate the HEC-HMS and HEC-RAS flood simulation models so as to transform Nexrad radar rainfall data into flood inundation maps through the HEC models. An automated workflow sequence is established using Map2Map: an ArcGIS version 9 toolbox and Model Builder that accomplishes all the desired data transformations between the GIS and the two hydrologic models including time series data exchange for rainfall, flows and water surface elevations. An example application is presented for Salado and Rosillo Creeks in San Antonio.
Archives of Environmental Contamination and Toxicology, 2008
This study compared the sensitivity of two rapid toxicity tests, QwikLite and Microtox, to seven ... more This study compared the sensitivity of two rapid toxicity tests, QwikLite and Microtox, to seven metals and ammonia. Both of these tests measure a reduction in light production from bioluminescent microorganisms (dinoflagellates and marine bacteria, respectively) as a means of toxicity detection and are simple and inexpensive to conduct compared to many standardized acute toxicity tests. For QwikLite tests, three marine dinoflagellate species (Lingulodinium polyedrum, Ceratocorys horrida, and Pyrocystis noctiluca) were separately evaluated following a 24-h exposure period. The marine bacterium, Vibrio fischeri, was used in the Microtox tests, in 15-min exposures to the same metal preparations as those used for the QwikLite tests. The QwikLite tests were generally one to two orders of magnitude more sensitive than the Microtox tests, as indicated by lower median effects concentrations (EC50). Both QwikLite and Microtox, however, resulted in similar toxicity rankings for the metals tested. The dinoflagellate species used in the QwikLite tests responded similarly for most compounds tested, with L. polyedrum appearing to be somewhat more sensitive than the other two species for most metals evaluated. QwikLite was also more comparable in sensitivity to several commonly used standardized toxicity tests. As with all toxicity tests, species selection for QwikLite should take into account study-specific factors, including the potential for sensitivity to confounding factors, such as ammonia.
An application integrating the Hydrologic Engineering Center's ͑HEC͒-Hydrologic Modeling System h... more An application integrating the Hydrologic Engineering Center's ͑HEC͒-Hydrologic Modeling System hydrologic simulation model and the HEC-River Analysis System hydraulic simulation model into a seamless floodplain mapping application is presented. The application is implemented with an ArcGIS 9 workflow model called Map to Map, which converts a map of rainfall data to a flood inundation map. The simulation models are integrated into the application by establishing information exchange points at which time series of information are passed to a model or returned from a model. Communication between simulation models and the Geographic Information System ͑GIS͒ is made possible by interface data models, which provide a one-to-one mapping between data structures within the simulation model and the GIS. A case study is presented for Rosillo Creek in Texas, in which the Map-to-Map model computes flood inundation polygons from rainfall data. Map to Map gives the user a powerful floodplain mapping and real-time flood forecasting tool.
Saber: Identificar los proyectos mutuamente excluyentes e independientes; identificar los ciclos ... more Saber: Identificar los proyectos mutuamente excluyentes e independientes; identificar los ciclos de vida de los proyectos, comprender el calculo del valor presente neto (VPN), y del valor anual (VA) así como, los requisitos para la utilización de modelos computacionales y la utilización de criterios para la definición de proyectos viables. Hacer: Evaluar las alternativas a través de calcular el VPN y el VA.
The detailed mechanistic aspects for the final starch digestion process leading to effective a-gl... more The detailed mechanistic aspects for the final starch digestion process leading to effective a-glucogenesis by the 2 mucosal a-glucosidases, human sucrase-isomaltase complex (SI) and human maltase-glucoamylase (MGAM), are poorly understood. This is due to the structural complexity and vast variety of starches and their intermediate digestion products, the poorly understood enzyme-substrate interactions occurring during the digestive process, and the limited knowledge of the structure-function properties of SI and MGAM. Here we analyzed the basic catalytic properties of the N-terminal subunit of MGAM (ntMGAM) on the hydrolysis of glucan substrates and compared it with those of human native MGAM isolated by immunochemical methods. In relation to native MGAM, ntMGAM displayed slower activity against maltose to maltopentose (G5) series glucose oligomers, as well as maltodextrins and a-limit dextrins, and failed to show the strong substrate inhibitory ''brake'' effect caused by maltotriose, maltotetrose, and G5 on the native enzyme. In addition, the inhibitory constant for acarbose was 2 orders of magnitude higher for ntMGAM than for native MGAM, suggesting lower affinity and/or fewer binding configurations of the active site in the recombinant enzyme. The results strongly suggested that the C-terminal subunit of MGAM has a greater catalytic efficiency due to a higher affinity for glucan substrates and larger number of binding configurations to its active site. Our results show for the first time, to our knowledge, that the C-terminal subunit of MGAM is responsible for the MGAM peptide's ''glucoamylase'' activity and is the location of the substrate inhibitory brake. In contrast, the membrane-bound ntMGAM subunit contains the poorly inhibitable ''maltase'' activity of the internally duplicated enzyme. J. Nutr. 138: 685-692, 2008.
A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the ... more A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the bioluminescence output from marine dinoflagellates has been developed and tested over the course of 16 years. The toxicity system, QwikLite, was developed for the sole purpose of evaluating the potential toxicity of various materials used in bay sediments, storm water discharges, industrial discharges from Naval facilities, and antifoulant paints. Bioluminescence inhibition was observed in the following dinoflagellates: Lingulodinium polyedrum (formerly known as Gonyaulax polyedra), Ceratocorys horrida, Pyrocystis noctiluca, Pyrocystis lunula, Pyrocystis fusiformis, and Pyrophacus steinii. Cultured cells were exposed to various concentrations of contaminants from hours through 10 days. Further application with bioluminescent dinoflagellates in a variety of toxicity testing schemes have shown that these species can be used as a screening assay organism in lieu of the more costly, labor intensive bioassays presently in use.
The Arc Hydro geographic data model for representing water resources features of the landscape is... more The Arc Hydro geographic data model for representing water resources features of the landscape is a customization of ArcGIS for representation of water resources features of the landscape. Arc Hydro is used here to integrate the HEC-HMS and HEC-RAS flood simulation models so as to transform Nexrad radar rainfall data into flood inundation maps through the HEC models. An automated workflow sequence is established using Map2Map: an ArcGIS version 9 toolbox and Model Builder that accomplishes all the desired data transformations between the GIS and the two hydrologic models including time series data exchange for rainfall, flows and water surface elevations. An example application is presented for Salado and Rosillo Creeks in San Antonio.
Archives of Environmental Contamination and Toxicology, 2008
This study compared the sensitivity of two rapid toxicity tests, QwikLite and Microtox, to seven ... more This study compared the sensitivity of two rapid toxicity tests, QwikLite and Microtox, to seven metals and ammonia. Both of these tests measure a reduction in light production from bioluminescent microorganisms (dinoflagellates and marine bacteria, respectively) as a means of toxicity detection and are simple and inexpensive to conduct compared to many standardized acute toxicity tests. For QwikLite tests, three marine dinoflagellate species (Lingulodinium polyedrum, Ceratocorys horrida, and Pyrocystis noctiluca) were separately evaluated following a 24-h exposure period. The marine bacterium, Vibrio fischeri, was used in the Microtox tests, in 15-min exposures to the same metal preparations as those used for the QwikLite tests. The QwikLite tests were generally one to two orders of magnitude more sensitive than the Microtox tests, as indicated by lower median effects concentrations (EC50). Both QwikLite and Microtox, however, resulted in similar toxicity rankings for the metals tested. The dinoflagellate species used in the QwikLite tests responded similarly for most compounds tested, with L. polyedrum appearing to be somewhat more sensitive than the other two species for most metals evaluated. QwikLite was also more comparable in sensitivity to several commonly used standardized toxicity tests. As with all toxicity tests, species selection for QwikLite should take into account study-specific factors, including the potential for sensitivity to confounding factors, such as ammonia.
An application integrating the Hydrologic Engineering Center's ͑HEC͒-Hydrologic Modeling System h... more An application integrating the Hydrologic Engineering Center's ͑HEC͒-Hydrologic Modeling System hydrologic simulation model and the HEC-River Analysis System hydraulic simulation model into a seamless floodplain mapping application is presented. The application is implemented with an ArcGIS 9 workflow model called Map to Map, which converts a map of rainfall data to a flood inundation map. The simulation models are integrated into the application by establishing information exchange points at which time series of information are passed to a model or returned from a model. Communication between simulation models and the Geographic Information System ͑GIS͒ is made possible by interface data models, which provide a one-to-one mapping between data structures within the simulation model and the GIS. A case study is presented for Rosillo Creek in Texas, in which the Map-to-Map model computes flood inundation polygons from rainfall data. Map to Map gives the user a powerful floodplain mapping and real-time flood forecasting tool.
Saber: Identificar los proyectos mutuamente excluyentes e independientes; identificar los ciclos ... more Saber: Identificar los proyectos mutuamente excluyentes e independientes; identificar los ciclos de vida de los proyectos, comprender el calculo del valor presente neto (VPN), y del valor anual (VA) así como, los requisitos para la utilización de modelos computacionales y la utilización de criterios para la definición de proyectos viables. Hacer: Evaluar las alternativas a través de calcular el VPN y el VA.
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