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1998

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Articles 1 - 15 of 15

Full-Text Articles in Life Sciences

Evaluation Of A Methyl Anthranilate-Based Bird Repellent: Toxicity To Channel Catfish Ictalurus Punctatus And Effect On Great Blue Heron Ardea Herodias Feeding Behavior, Brian S. Dorr, Larry Clark, Igor Mezine Dec 1998

Evaluation Of A Methyl Anthranilate-Based Bird Repellent: Toxicity To Channel Catfish Ictalurus Punctatus And Effect On Great Blue Heron Ardea Herodias Feeding Behavior, Brian S. Dorr, Larry Clark, Igor Mezine

Brian S Dorr

No abstract provided.


A Kinetic Analysis Of The Conformational Flexibility Of Steroid Hormones, Steven P. Bradbury, Julian Ivanov, Ovanes Mekenyan, Gerritt Schüürmann Oct 1998

A Kinetic Analysis Of The Conformational Flexibility Of Steroid Hormones, Steven P. Bradbury, Julian Ivanov, Ovanes Mekenyan, Gerritt Schüürmann

Steven P. Bradbury

For a set of 10 androgen steroids and estradiol (E2), the kinetic feasibility of conformation flexibility of the cyclic moieties was studied under the constraint of maintaining the B/C trans and C/D trans ring fusion of the natural and biologically active enantiomer. To this end, the conformational energy surface was quantified using the semiempirical quantum chemical AM1 model. The computational analysis included the location of Conformational transition states with associated barriers, and intrinsic reaction coordinate (IRC) calculations to characterize the trajectories of the rotations and the relationships of the transition states to neighbouring chair and twist conformations. Conformational ...


Neurological Effects On Startle Response And Escape From Predation By Medaka Exposed To Organic Chemicals, Steven P. Bradbury, Richard W. Carlson, Robert A. Drummond, Dean E. Hammermeister Sep 1998

Neurological Effects On Startle Response And Escape From Predation By Medaka Exposed To Organic Chemicals, Steven P. Bradbury, Richard W. Carlson, Robert A. Drummond, Dean E. Hammermeister

Steven P. Bradbury

Simultaneous electrophysiological and behavioral studies were performed on 21–32 day old juvenile medaka (Oryzias latipes) exposed at sublethal concentrations to organic chemicals representing various modes of action. Non-invasive recordings were made of the electrical impulses generated within giant neuronal Mauthner cells, associated interneurons and motoneurons, and axial musculature, all of which initiate the startle or ‘escape’ response in fish. Timing in ms between these electrical sequelae was measured for each fish before and after 24 and 48 h exposure to a chemical. Carbaryl and phenol affected Mauthner cell to motoneuron transmission while chlorpyrifos, carbaryl, phenol and 2,4-dinitrophenol (DNP ...


A Comparative Study Of Molecular Similarity, Statistical, And Neural Methods For Predicting Toxic Modes Of Action, Steven P. Bradbury, Subhash C. Basak, Gregory D. Grunwald, George E. Host, Gerald J. Niemi Jun 1998

A Comparative Study Of Molecular Similarity, Statistical, And Neural Methods For Predicting Toxic Modes Of Action, Steven P. Bradbury, Subhash C. Basak, Gregory D. Grunwald, George E. Host, Gerald J. Niemi

Steven P. Bradbury

Quantitative structure–activity relationship (QSAR) models are routinely used in predicting toxicologic and ecotoxicologic effects of untested chemicals. One critical factor in QSAR-based risk assessment is the proper assignment of a chemical to a mode of action and associated QSAR. In this paper, we used molecular similarity, neural networks, and discriminant analysis methods to predict acute toxic modes of action for a set of 283 chemicals. The majority of these molecules had been previously determined through toxicodynamic studies in fish to be narcotics (two classes), electrophiles/proelectrophiles, uncouplers of oxidative phosphorylation, acetylcholinesterase inhibitors, and neurotoxicants. Nonempirical parameters, such as topological ...


A New Genetic Locus In Sinorhizobium Meliloti Is Involved In Stachydrine Utilization, Donald A. Phillips Dr., Eve S. Sandee Dr., Jan A.C. Vriezen Dr., Frans J. Debruijn Dr., Daniel Lerudulier Dr., Cecillia M. Joseph Dr. Jan 1998

A New Genetic Locus In Sinorhizobium Meliloti Is Involved In Stachydrine Utilization, Donald A. Phillips Dr., Eve S. Sandee Dr., Jan A.C. Vriezen Dr., Frans J. Debruijn Dr., Daniel Lerudulier Dr., Cecillia M. Joseph Dr.

Jan A.C. Vriezen Dr.

Stachydrine, a betaine released by germinating alfalfa seeds, functions as an inducer of nodulation genes, a catabolite, and an osmoprotectant in Sinorhizobium meliloti. Two stachydrine-inducible genes were found in S. meliloti 1021 by mutation with a Tn5-luxAB promoter probe. Both mutant strains (S10 and S11) formed effec- tive alfalfa root nodules, but neither grew on stachydrine as the sole carbon and nitrogen source. When grown in the absence or presence of salt stress, S10 and S11 took up [14C]stachydrine as well as wild-type cells did, but neither used stachydrine effectively as an osmoprotectant. In the absence of salt stress ...


Medical Students Development Of Empathic Understanding Of Their Patients, William T. Branch Jr. Md, Macp Jan 1998

Medical Students Development Of Empathic Understanding Of Their Patients, William T. Branch Jr. Md, Macp

William T.Branch Jr.MD

No abstract provided.


Professional And Moral Development In Medical Students: The Ethics Of Caring For Patients, William T. Branch Jr. Md, Macp Jan 1998

Professional And Moral Development In Medical Students: The Ethics Of Caring For Patients, William T. Branch Jr. Md, Macp

William T.Branch Jr.MD

The young physician-in-training faces arduous tasks. Knowledge must be absorbed, and skills must be mastered. But, becoming a physician is a moral as well as an intellectual task. The attitudes and values that a young physician adopts will determine the way he or she practices, and be equally as important as intellectual and technical proficiency. Physicians-in-training are young adults. They have emerged from adolescence into adulthood, hopefully with a firm image of themselves and a self-awareness of their values and inner feelings.


Intracellular Coexpression Of Epidermal Growth Factor Receptor, Her-2/Neu, And P21ras In Human Breast Cancers: Evidence For The Existence Of Distinctive Patterns Of Genetic Evolution That Are Common To Tumors From Different Patients, Stanley E. Shackney, Agnese A. Pollice, Charles A. Smith, Laura E. Janocko, Lillian Sweeney, Kathryn A. Brown, Sarita G. Singh, Lingping Gu, Robert Yakulis, Joseph F. Lucke Jan 1998

Intracellular Coexpression Of Epidermal Growth Factor Receptor, Her-2/Neu, And P21ras In Human Breast Cancers: Evidence For The Existence Of Distinctive Patterns Of Genetic Evolution That Are Common To Tumors From Different Patients, Stanley E. Shackney, Agnese A. Pollice, Charles A. Smith, Laura E. Janocko, Lillian Sweeney, Kathryn A. Brown, Sarita G. Singh, Lingping Gu, Robert Yakulis, Joseph F. Lucke

Joseph Lucke

Multiparameter flow cytometry studies were performed on cells from the primary tumors of 94 patients with breast cancer. Correlated cellular measurements of cell DNA content, Her-2/neu, epidermal growth factor receptor (EGFR), and p21ras levels were performed on each of 5,000 to 100,000 cells from each tumor. When criteria for positivity were matched with those in common use for immunohistochemical studies, 28 of 94 (30\%) breast cancers were classified as positive for Her-2/neu overexpression. When similar criteria were applied to the EGFR measurements, 23 of 94 (24\%) cases were classified as positive for EGFR overexpression. Similarly, 23 ...


Genetic Variation Among Populations Of River Otters In North America: Considerations For Reintroducing Projects, Thomas L. Serfass, Robert P. Brooks, James M. Novak, Paul E. Johns, Olin E. Rhodes Jr. Jan 1998

Genetic Variation Among Populations Of River Otters In North America: Considerations For Reintroducing Projects, Thomas L. Serfass, Robert P. Brooks, James M. Novak, Paul E. Johns, Olin E. Rhodes Jr.

James M. Novak

Horizontal starch gel electrophoresis was used to assess variability at 23 presumptive gene loci of 732 river otters obtained from fur-trappers in 18 states and three Canadian provinces. States and provinces providing otters were sorted into eight geographic regions for genetic comparisons. Multilocus heterozygosity and polymorphism ranged from 0.018 to 0.032 and 0.044 to 0.087, respectively. One locus, esterase-2, (EST-2) demonstrated a high level of polymorphism throughout all regions. Malate dehydrogenase-1 (MDH-1) was polymorphic throughout the Mississippi drainage but not elsewhere. Heterozygosity, occurrence of rare alleles, and mean number of alleles per locus were associated positively ...


Evaluation Of Molar Size As A Basis For Distinguishing Wild Boar From Domestic Swine: Employing The Present To Decipher The Past, John J. Mayer, James M. Novak, I. Lehr Brisbin Jr. Jan 1998

Evaluation Of Molar Size As A Basis For Distinguishing Wild Boar From Domestic Swine: Employing The Present To Decipher The Past, John J. Mayer, James M. Novak, I. Lehr Brisbin Jr.

James M. Novak

No abstract provided.


Species Delineation And The Identification Of Evolutionarily Significant Units: Lessons From The Freshwater Mussel Genus Potamilus (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard Jan 1998

Species Delineation And The Identification Of Evolutionarily Significant Units: Lessons From The Freshwater Mussel Genus Potamilus (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard

Kevin J. Roe

Accurate identification of biological entities is critical to the timely and efficient preservation of biodiversity. Concepts that define segments of biological diversity--species and evolutionarily significant units (ESUs)--should reflect our current knowledge of the biological world. Conflation of different hierarchical definitions of taxa has the potential to obscure distinct biological entities in need of protection. The concept of the ESU has been criticized because it includes within its definition distinct biological entities that otherwise would be recognized as species. Herein we evaluate several versions of the evolutionary significant unit concept and provide as a case study an analysis of geographic ...


The Role Of Ligand Flexibility In Predicting Biological Activity: Structure–Activity Relationships For Aryl Hydrocarbon, Estrogen, And Androgen Receptor Binding Affinity, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley Jan 1998

The Role Of Ligand Flexibility In Predicting Biological Activity: Structure–Activity Relationships For Aryl Hydrocarbon, Estrogen, And Androgen Receptor Binding Affinity, Steven P. Bradbury, Ovanes G. Mekenyan, Gerald T. Ankley

Steven P. Bradbury

Recent studies indicate that the potency and agonist or antagonist activity of steroid hormone ligands are dependent, in part, on ligand–receptor binding affinity as well as the conformation of the ligand–receptor complex. The binding of ligands to hormone receptors is thought to involve interactions by which shapes of both the receptor and ligand are modified in the formation of the ligand–receptor complex. As a consequence, it is essential to explore the significance of ligand flexibility in the development of screening-level structure–activity relationships. In this review, examples are provided of techniques used to generate and screen ligand ...


Leaf Fluctuating Assymetry Increases With Hybridization And Elevation In Tree-Line Birches, Brian J. Wilsey, Erkki Haukioja, Julia Koricheva, Matti Sulkinoja Jan 1998

Leaf Fluctuating Assymetry Increases With Hybridization And Elevation In Tree-Line Birches, Brian J. Wilsey, Erkki Haukioja, Julia Koricheva, Matti Sulkinoja

Brian J. Wilsey

Fluctuating asymmetry (FA), or random non-directional deviations from perfect symmetry in bilaterally or radially symmetrical traits, has recently been proposed to be a useful indicator of genetic and environmental stress. However, the factors underlying fluctuating asymmetry, especially in plants, remain poorly understood. We sampled leaf fluctuating asymmetry among and within three species of even-aged birch (Betula pubescens, B. nana, and B. pendula) and their interspecific hybrids growing in common gardens of northern Finland to determine whether hybridization and environmental stress are associated with increased developmental instability. Our predictions were that: (1) interspecific hybrids among B. pubescens, B. nana, and B ...


Molecular Systematics Of The Freshwater Mussel Genus Potamilu (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard Jan 1998

Molecular Systematics Of The Freshwater Mussel Genus Potamilu (Bivalvia: Unionidae), Kevin J. Roe, Charles Lydeard

Kevin J. Roe

Few explicit hypotheses for the relationships of unionid mussels exist. The absence of explicit phylogenetic hypotheses is problematic and is in part responsible for the lack of taxonomic stability seen in this group. In this paper we examine the relationships of mussels in the genus Potamilus, based upon the DNA sequences of a 600 base pair portion of the first subunit of the mitochondrial cytochrome c oxidase (COI) gene. We also examine the genetic distinctiveness of populations of the inflated heelsplitter P. inflatus. The molecular phylogeny indicates that Potamilus is paraphyletic with Leptodea fragilis and Lampsilis ornata nested between P ...


A Comparison Of Iron Absorption In Adults And Infants Consuming Identical Infant Formulas, Richard F. Hurrell, Lena Davidsson, Manju B. Reddy, Peter Kastenmayer, James D. Cook Jan 1998

A Comparison Of Iron Absorption In Adults And Infants Consuming Identical Infant Formulas, Richard F. Hurrell, Lena Davidsson, Manju B. Reddy, Peter Kastenmayer, James D. Cook

Manju B. Reddy

Fe absorption was estimated in adults and infants from the erythrocyte incorporation of Fe isotopes added to infant formula. Fe absorption was measured in adults using radioisotopes, and in infants with a stable-isotope technique. In adults, the geometric mean Fe absorption from a ready-to-feed soya formula with its native phytic acid content was 2.4%. This increased to 6.0 % (P < 0.05) after almost complete dephytinization. In infants, mean Fe absorption values were 3.9 and 8.7% respectively from the same products (P(O.05). In adults, mean Fe absorption from a spray-dried soya formula containing 110 mg ascorbic acid was 4.1 %, increasing to 5.3 % (P < 0.05) when ascorbic acid was doubled to 220 mgfl. In infants, mean Fe absorption values were 5.7 and 9.5 % (P < 0.05) from the same products. Mean Fe absorption from a milk-based formula was 6.5 % in adults compared with 6.7 % in infants. All meals in the adult and infant studies were fed using an identical meal size of 217 g. Increasing the meal size threefold in adults did not change fractional Fe absorption. Mean Fe absorption values for each meal were lower in adults than in infants, but the relative inhibitory effect of phytic acid and the enhancing effect of ascorbic acid were similar. We conclude that Fe absorption studies in adults can be used to assess the influence of enhancers and inhibitors of Fe absorption in infant formulas fed to infants. Further studies, however, are required to extend these findings to weaning foods and complete meals.