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Full-Text Articles in Life Sciences
A Buried Spruce Forest Provides Evidence At The Stand And Landscape Scale For The Effects Of Environment On Vegetation At The Pleistocene/Holocene Boundary, Douglas D. Stokke
A Buried Spruce Forest Provides Evidence At The Stand And Landscape Scale For The Effects Of Environment On Vegetation At The Pleistocene/Holocene Boundary, Douglas D. Stokke
Douglas D. Stokke
Due to a unique set of circumstances, we were able to excavate an entire spruce (Picea) forest in Michigan's Upper Peninsula, USA, which was buried in the early Holocene (9928 ± 133 uncalibrated 14C years bp). Trees ranged from < 5 cm to > 50 cm in diameter, and dominants were approximately 9 m tall. The stand was multi-aged, with a maximum tree age of 145 years. Well-preserved stem cross-sections (n = 140) were recovered and the entire stand was mapped. Stand reconstruction combined with pollen and sediment analysis revealed a pure spruce forest in the sandy lowlands surrounded by hills dominated by pine, oak …
A Computationally Based Identification Algorithm For Estrogen Receptor Ligands: Part 2. Evaluation Of A Herα Binding Affinity Model, Steven P. Bradbury, O. G. Mekenyan, V. Kamenska, P. K. Schmieder, G. T. Ankley
A Computationally Based Identification Algorithm For Estrogen Receptor Ligands: Part 2. Evaluation Of A Herα Binding Affinity Model, Steven P. Bradbury, O. G. Mekenyan, V. Kamenska, P. K. Schmieder, G. T. Ankley
Steven P. Bradbury
The objective of this study was to evaluate the capability of an expert system described in the previous paper (S. Bradbury et al., Toxicol. Sci. 58, 253–269) to identify the potential for chemicals to act as ligands of mammalian estrogen receptors (ERs). The basis of the expert system was a structure activity relationship (SAR) model, based on relative binding affinity (RBA) values for steroidal and nonsteroidal chemicals derived from human ERa (hERa) competitive binding assays. The expert system enables categorization of chemicals into (RBA ranges of < 0.1, 0.1 to 1, 1 to 10, 10 to 100, and >150% relative to 17b-estradiol. In the current analysis, the algorithm was evaluated with respect …
A Computationally Based Identification Algorithm For Estrogen Receptor Ligands: Part 1. Predicting Herα Binding Affinity, Steven P. Bradbury, V. Kamenska, P. Schmieder, G. Ankley, O. Mekenyan
A Computationally Based Identification Algorithm For Estrogen Receptor Ligands: Part 1. Predicting Herα Binding Affinity, Steven P. Bradbury, V. Kamenska, P. Schmieder, G. Ankley, O. Mekenyan
Steven P. Bradbury
The common reactivity pattern (COREPA) approach is a 3-dimensional, quantitative structure activity relationship (3-D QSAR) technique that permits identification and quantification of specific global and local stereoelectronic characteristics associated with a chemical’s biological activity. It goes beyond conventional 3-D QSAR approaches by incorporating dynamic chemical conformational flexibility in ligand-receptor interactions. The approach provides flexibility in screening chemical data sets in that it helps establish criteria for identifying false positives and false negatives, and is not dependent upon a predetermined and specified toxicophore or an alignment of conformers to a lead compound. The algorithm was recently used to screen chemical data …