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Iowa State University

1996

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Articles 1 - 13 of 13

Full-Text Articles in Life Sciences

Quantitative Structure-Activity Relationships For Polychlorinated Hydroxybiphenyl Estrogen Receptor Binding Affinity: An Assessment Of Conformer Flexibility, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley Nov 1996

Quantitative Structure-Activity Relationships For Polychlorinated Hydroxybiphenyl Estrogen Receptor Binding Affinity: An Assessment Of Conformer Flexibility, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley

Steven P. Bradbury

A diverse group of xenobiotics has a high binding affinity to the estrogen receptor (ER), suggesting that it can accommodate large variability in ligand structure. Relationships between xenobiotic structure, binding affinity, and estrogenic response have been suggested to be dependent on the conformational structures of the ligands. To explore the influence of conformational flexibility on ER binding affinity, a quantitative structure—activity relationship (QSAR) study was undertaken with estradiol, diethylstilbestrol, and a set of polychlorinated hydroxybiphenyls (PCHBs) of environmental concern. Although the low-energy minima of the PCHB congeners suggested that interconversions among conformers were likely, the electronic parameters associated with the …


The Effect Of Postruminal Amino Acid Flow On Muscle Cell Proliferation And Protein Turnover, James M. Reecy, James E. Williams, Monty S. Kerley, Ruth S. Macdonald, William H. Thornton, Julie L. Davis Sep 1996

The Effect Of Postruminal Amino Acid Flow On Muscle Cell Proliferation And Protein Turnover, James M. Reecy, James E. Williams, Monty S. Kerley, Ruth S. Macdonald, William H. Thornton, Julie L. Davis

Ruth S. MacDonald

An experiment was conducted to characterize the effects of postruminal administration of casein, glutamine, cornstarch, and water on protein turnover and in vitro muscle cell proliferation. Four MARC III steers (205 kg) were fed a protein-restricted bromegrass hay-based diet (2.86 Mcal of DE/kg and 13.6 g of N/kg). Using a 4 x 5 Latin square arrangement balanced for residual effects, casein and glutamine, equal to 50% of basal dietary nitrogen intake, cornstarch, isocaloric with casein infusion, or an equal volume of water was continuously infused into the abomasum of steers. Blood samples, collected every 2 h for 24 h after …


Comparison Of Sensors And Techniques For Crop Yield Mapping, Stuart J. Birrell, Kenneth A. Sudduth, Steven C. Borgett Feb 1996

Comparison Of Sensors And Techniques For Crop Yield Mapping, Stuart J. Birrell, Kenneth A. Sudduth, Steven C. Borgett

Stuart J. Birrell

The implementation of site-specific crop management is dependent on the variations in yield and yield potential within a field. Crop yield maps are important for both the implementation and evaluation of site-specific crop management strategies. Management decisions and evaluations based on yield maps must take into consideration the accuracy and resolution of the maps.

An impact-based yield monitor and a volumetric yield monitor were compared. The effect of different dynamic models of combine grain flow on the calculated instantaneous yields were investigated. Both simple time delay models and first order models could be used to model the grain flow. In …


Variation In Cell Dimensions And Fibril Angle For Two Fertilized Even-Aged Loblolly Pine Plantations, Douglas D. Stokke, Todd F. Shupe, Elvin T. Choong, Mark D. Gibson Jan 1996

Variation In Cell Dimensions And Fibril Angle For Two Fertilized Even-Aged Loblolly Pine Plantations, Douglas D. Stokke, Todd F. Shupe, Elvin T. Choong, Mark D. Gibson

Douglas D. Stokke

Increment core samples were obtained from randomly selected, nine-year-old lohlolly pine (Pinus faeda L.) in two even-aged plantations in Louisiana in order to determine the variation in cell dimensions and fibril angle of the sites. The Homer site is representative of the growing conditions in north Louisiana, and the Bogalusa site is typical of the conditions in southeastern Louisiana. Both sites were subjected to similar site preparation and weed control and were fertilized in the juvenile period. The anatomical properties that were measured include: fiber length, cell-wall thickness, and microfibril angle (MFA). Observations were made in order to compare corewood …


Estimating One-Electron Reduction Potentials Of Quinones, Steven P. Bradbury, Ovanes G. Mekenyan, V. B. Kamenska Jan 1996

Estimating One-Electron Reduction Potentials Of Quinones, Steven P. Bradbury, Ovanes G. Mekenyan, V. B. Kamenska

Steven P. Bradbury

The one-electron reduction potential ∗ E1 7 of benzo-, naphtho-and anthracenequinones is related to their ability to undergo redox cycling and elicit cytotoxicity through oxidative stress. To evaluate a general approach to estimate the E1 7 of benzo-, naphtho-and anthracenequinones, QSAR approaches based on gas phase and solvation based methods were employed. Stereoelectronic descriptors of ground state quinones, respective intermediates of the redox cycle, and the di erences in parameters for the transition between intermediates were evaluated. The variation of E1 7 was correlated with descriptors of the parent quinones and speci c transition parameters. The energy of the highest …


Presettlement Vegetation Of The Lower Chippewa River Valley, Lisa A. Schulte-Moore, William J. Barnes Jan 1996

Presettlement Vegetation Of The Lower Chippewa River Valley, Lisa A. Schulte-Moore, William J. Barnes

Lisa A. Schulte Moore

The lower Chippewa River of west-central Wisconsin is the portion that flows southwest from the city of Eau Claire to the Mississippi River at Nelson. The river has a gentle gradient of about 0.8 m/km and highly erodible banks of sand and gravel. The river valley occurs between 35 m to 70 m below the surrounding upland, is between 1 and 5 km wide, and was formed primarily by glacial meltwaters. The floodplain is defined by annual high water levels and is generally below the 25 year flood recurrence interval, which on this part of the Chippewa River is >5m …


2,3, 7,8-Tetrachlorodibenzo-P-Dioxin, Steven P. Bradbury Jan 1996

2,3, 7,8-Tetrachlorodibenzo-P-Dioxin, Steven P. Bradbury

Steven P. Bradbury

Since 1985, the United States Environmental Protection Agency (USEPA) has classified 2,3,7,8-tetrachloro-p-dioxin (TCDD) as a probable human carcinogen; subsequently, sources of TCDD in the environment have been regulated on the basis of animal cancer rates extrapolated to doses associated with human exposures. Two major activities have prompted the decision to reassess this approach for evaluating TCDD toxicity and its associated risks. First, an epidemiological study of cancer mortality in U.S. chemical workers by the National Institute of Occupational Safety and Health provided evidence of TCDD-mediated human carcinogenicity (Fingerhut et al. 1991 ). Second, at a 1990 Banbury conference a consensus …


Comparison Of The Effect Of Different Opsonins On The Phagocytosis Of Fluorescein-Labeled Staphylococcal Bacteria By Chicken Heterophils, Claire B. Andreasen, James R. Andreasen Jr., Anita E. Sonn, Julie A. Oughton Jan 1996

Comparison Of The Effect Of Different Opsonins On The Phagocytosis Of Fluorescein-Labeled Staphylococcal Bacteria By Chicken Heterophils, Claire B. Andreasen, James R. Andreasen Jr., Anita E. Sonn, Julie A. Oughton

Claire B. Andreasen

Heterophil phagocytosis of fluorescein-labeled staphylococcal bacteria was analyzed by flow cytometry. Opsonization with two types of normal pooled sera and staphylococcal antisera significantly increased bacterial phagocytosis compared to samples without an opsonin. The staphylococcal antisera did not significantly increase bacterial phagocytosis compared to the normal pooled sera. Opsonization appears to increase bacterial phagocytosis but specific antisera may not increase phagocytosis beyond that caused by pooled normal sera.


Development Of An Enzyme-Linked Immunosorbent Assay (Elisa) For Quantification Of Skeletal Muscle Calpastatin, M. E. Doumit, Steven M. Lonergan, J. R. Arbona, J. Killefer, M. Koohmaraie Jan 1996

Development Of An Enzyme-Linked Immunosorbent Assay (Elisa) For Quantification Of Skeletal Muscle Calpastatin, M. E. Doumit, Steven M. Lonergan, J. R. Arbona, J. Killefer, M. Koohmaraie

Steven M. Lonergan

An indirect antibody ELISA was developed for rapid and sensitive quantification of skeletal muscle calpastatin. Polyclonal antibodies were raised in rabbits against recombinant calpastatin, corresponding to domains 2, 3, and 4 of bovine skeletal muscle calpastatin. Western blot analysis revealed that these antibodies specifically recognize an immunoreactive calpastatin protein of approximately 130 kDa in prerigor skeletal muscle extracts. The intensity of the immunoreactive bands corresponds qualitatively with assayable calpastatin activity. For ELISA development, optimum dilutions of sample, primary anti-calpastatin antibody, and peroxidase-conjugated secondary antibody were determined by titration. A dilution optimum for coating of Immulonâ 4 (Dynatech) plates was observed …


Evaluation Of Gps For Applications In Precision Agriculture, Steven C. Borgelt, John D. Harrison, Kenneth A. Sudduth, Stuart J. Birrell Jan 1996

Evaluation Of Gps For Applications In Precision Agriculture, Steven C. Borgelt, John D. Harrison, Kenneth A. Sudduth, Stuart J. Birrell

Stuart J. Birrell

Location coordinate information is needed in precision agriculture to map in-field variability, and to serve as a control input for variable rate application. Differential global positioning system (DGPS) measurement techniques were compared with other independent data sources for sample point location and combine yield mapping operations. Sample point location could be determined to within 1 m (3 ft) 2dRMS using C/A code processing techniques and data from a high-performance GPS receiver. Higher accuracies could be obtained with carrier phase kinematic positioning methods, but this required more time and was a less robust technique with a greater potential for data acquisition …


Nutrient Mapping Implications Of Short-Range Variability, Stuart J. Birrell Jan 1996

Nutrient Mapping Implications Of Short-Range Variability, Stuart J. Birrell

Stuart J. Birrell

Successful site specific nutrient application depends on accurate soil nutrient maps, which are generally developed from grid samples. The implication of short range variability for soil nutrient mapping is investigated. Interpretation of soil nutrient maps must consider the level of confidence associated with estimated values.


Analysis Of Spatial Factors Influencing Crop Yield, K. A. Sudduth, S. T. Drummond, Stuart J. Birrell, N. R. Kitchen Jan 1996

Analysis Of Spatial Factors Influencing Crop Yield, K. A. Sudduth, S. T. Drummond, Stuart J. Birrell, N. R. Kitchen

Stuart J. Birrell

The spatial relationship between crop yields and soil and site parameters was modeled using several methods. Yield maps estimated by projection pursuit regression and neural network analysis agreed well with measured yields. These methods also allowed generation of response curves for estimated yield as a function of each of the input parameters. These response curves were useful for investigating the relationship between yields and individual soil and site parameters.


Missouri Precision Agriculture, N. R. Kitchen, K. A. Sudduth, Stuart J. Birrell, S. C. Borgelt Jan 1996

Missouri Precision Agriculture, N. R. Kitchen, K. A. Sudduth, Stuart J. Birrell, S. C. Borgelt

Stuart J. Birrell

A number of projects related to different facets of precision agriculture are being carried out by an interdisciplinary team of scientists and engineers with the University of Missouri and the USDA Agricultural Research Service. This paper provides an overview of those projects.