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Articles 361 - 377 of 377
Full-Text Articles in Biology
Mortality And Behavior Of Prairie Falcons During The Fledging-Dependence Period, Mary E. Mcfadzen
Mortality And Behavior Of Prairie Falcons During The Fledging-Dependence Period, Mary E. Mcfadzen
Biology
The primary focus of my research was to determine the magnitude and causes of mortality of Prairie Falcons (Falco mexicanus) during the fledging-dependence period. In 1992 and 1993, I radio-tagged nestlings prior to fledging and monitored their survival until they emigrated from the study area. Additionally, I quantified parental behavior during the nesting period as well as other factors that have been shown to influence subsequent survivorship. Of the 152 radio-tagged nestlings, 47 died prior to dispersal from their natal territories. Mortality rates were consistent between years, 28% in 1992 and 34% in 1993. The magnitude of mortality …
The Indirect Effects Of Large-Scale Insecticide Spraying On Populations Of Echinacea Angustifolia Dc (Asteraceae) In The North Dakota Badlands, Heidi Kristine Leuszler
The Indirect Effects Of Large-Scale Insecticide Spraying On Populations Of Echinacea Angustifolia Dc (Asteraceae) In The North Dakota Badlands, Heidi Kristine Leuszler
Biology
Broad-spectrum insecticide spraying for the control of grasshoppers may have a detrimental effect of native pollinators of western rangelands. Many rangeland plants depend upon such pollinators for successful reproduction. Pollinators also transfer genes between plants via pollen, and pollinator movement between plants is related to pollinator density; thus insecticide application may alter gene movements in a plant population. This study uses a common forb, Echinacea angustifolia, to examine the potential negative effects of insecticide application on gene movements. I first determined the breeding system of E. angustifolia and specifically whether an insect vector is required for reproduction. Flowers set …
Migration Trend And Morphometric Characteristics Of Northern Harriers During Autumn Migration At Cape May Point, New Jersey, Christopher W. Schultz
Migration Trend And Morphometric Characteristics Of Northern Harriers During Autumn Migration At Cape May Point, New Jersey, Christopher W. Schultz
Biology
There were two primary objectives of this thesis. The first was to test the validity of sampling raptors during autumn migration for the purpose of monitoring trends in populations. The second was to describe morphometric characteristics of northern harriers (Circus cyaneus) during autumn migration in coastal New Jersey and revise the key for sexing and aging harriers captured on the east coast of North America. Harriers were concurrently, but independently, counted and captured during autumn migration at Cape May Point, New Jersey, from 1976 through 1995. All data were standardized to the same 83-day annual study period and …
The Effects Of Temperature And Rain On The Metabolism Of The American Kestrel (Falco Sparverius), Glenn R. Wilson
The Effects Of Temperature And Rain On The Metabolism Of The American Kestrel (Falco Sparverius), Glenn R. Wilson
Biology
The change in metabolism of birds exposed to rainfall is poorly understood. I measured the rate of oxygen consumption (VO2) using open-flow respirometry of four male and four female American kestrels (Falco sparverius) during the breeding season at ambient temperatures (Ta) of 5, 10, 15, and 25°C in air without rainfall and then at low (2.5 cm⋅h-1) rainfall and high (6.1 cm⋅h-1) rainfall. Trial order was analyzed as a covariate because kestrel responses appeared to decrease in intensity during the 14-wk study period. The VO2 increased 12.65% at low …
Clp-C3a, A New Cyclic Lipodepsipeptide From Pseudomonas Syringae, Kwang-Hee Kim
Clp-C3a, A New Cyclic Lipodepsipeptide From Pseudomonas Syringae, Kwang-Hee Kim
Biology
Cyclic lipodepsipeptides (CLPs), a new class of antifungal agents, are produced by Pseudomonas syringae pv. syringae. To find novel CLP members, bacterial fluorescent isolates from different plant sources were screened for CLP biosynthetic genes syrB and syrD using a polymerase chain reaction (PCR) and Southern blot analyses. A positive isolate, strain C3, isolated from a cherry tree was virulent on immature cherry fruits, possessed the hypersensitivity/pathogenicity gene, hrpZ, and was grown in supplemented potato broth. Purification of a CLP from strain C3 was performed by acetone extraction, XAD-2 column chromatography, and reversed-phase high performance liquid chromatography (HPLC). HPLC …
Reference Levels Of Plasma Cholinesterase Activity From Autumn Migrant Sharp-Shinned (Accipiter Striatus) And Cooper's (Accipiter Cooperii) Hawks, Daniel H. Kim
Biology
Detecting exposure to anticholinergic pesticides involves measuring levels of cholinesterase (ChE) activity. There are few published values for plasma ChE activity from wild avian species, yet reference levels of ChE activity are vital for nonlethal bioassays to determine exposure to carbamate or organophosphate pesticides. I used plasma samples from 102 sharp-shinned hawks (Accipiter striatus) and 45 Cooper's hawks (A. cooperii) captured during autumn migration to establish reference levels of cholinesterase activity. I evaluated the use of a spectrophotometer (SPEC) and 96-well optical microplate reader (MPR) for determining plasma cholinesterase activity from migrating hawks. The SPEC was …
Effects Of Insecticide Spraying For Grasshoppers On The Reproductive Success Of Three Prairie Plant Species In Western North Dakota, Suzanne Digiacomo
Effects Of Insecticide Spraying For Grasshoppers On The Reproductive Success Of Three Prairie Plant Species In Western North Dakota, Suzanne Digiacomo
Biology
Grasshopper control is often accomplished through application of broad-spectrum insecticides that may also affect many non-target arthropods. To assess whether these insecticides reduce pollinator numbers and hence plant reproductive success, three forb species were examined. Potentilla fruticosa and Calylophus serrulatus were sampled before, immediately after, and approximately one week after spraying. The seed number for both species declined marginally but significantly immediately after spraying. The average weight per achene was significantly lower in spray sites for Potentilla fruticosa, but no significant interaction of time by spray was found for either species. Also, for two germination characters there was no …
Coordinate Cell Cycle Control Of A Caulobacter Dna Methyltransferase And The Flagellar Genetic Hierarchy, Craig Stephens, Gary Zweiger, Lucy Shapiro
Coordinate Cell Cycle Control Of A Caulobacter Dna Methyltransferase And The Flagellar Genetic Hierarchy, Craig Stephens, Gary Zweiger, Lucy Shapiro
Biology
The expression of the Caulobacter ccrM gene and the activity of its product, the M.Ccr II DNA methyltransferase, are limited to a discrete portion of the cell cycle (G. Zweiger, G. Marczynski, and L. Shapiro, J. Mol. Biol. 235:472-485, 1994). Temporal control of DNA methylation has been shown to be critical for normal development in the dimorphic Caulobacter life cycle. To understand the mechanism by which ccrM expression is regulated during the cell cycle, we have identified and characterized the ccrM promoter region. We have found that it belongs to an unusual promoter family used by several Caulobacter class II …
A Cell Cycle-Regulated Bacterial Dna Methyltransferase Is Essential For Viability, Craig Stephens, Ann Reisenaur, Rachel Wright, Lucy Shapiro
A Cell Cycle-Regulated Bacterial Dna Methyltransferase Is Essential For Viability, Craig Stephens, Ann Reisenaur, Rachel Wright, Lucy Shapiro
Biology
The CcrM adenine DNA methyltransferase, which specifically modifies GANTC sequences, is necessary for viability in Caulobacter crescentus. To our knowledge, this is the first example of an essential prokaryotic DNA methyltransferase that is not part of a DNA restriction/modification system. Homologs of CcrM are widespread in the Cl subdivision of the Proteobacteria, suggesting that methylation at GANTC sites may have important functions in other members of this diverse group as well. Temporal control of DNA methylation state has an important role in Caulobacter development, and we show that this organism utilizes an unusual mechanism for control of remethylation of newly …
Caulobacter Lon Protease Has A Critical Role In Cell-Cvcle Cbntrol Of Dna I Methylation, Craig Stephens, Rachel Wright, Gary Zweiger, Lucy Shapiro, M.R.K. Alley
Caulobacter Lon Protease Has A Critical Role In Cell-Cvcle Cbntrol Of Dna I Methylation, Craig Stephens, Rachel Wright, Gary Zweiger, Lucy Shapiro, M.R.K. Alley
Biology
CcrM, an adenine DNA methyltransferase, is essential for viability in Caulobacter crescentus. The CcrM protein is present only in the predivisional stage of the cell cycle, resulting in cell-cycle-dependent variation of the DNA methylation state of the chromosome. The availability of CcrM is controlled in two ways: (1) the ccrM gene is transcribed only in the predivisional cell, and (2) the CcrM protein is rapidly degraded prior to cell division. We demonstrate here that CcrM is an important target of the Lon protease pathway in C. crescentus. In a lon null mutant, ccrM transcription is still temporally regulated, but the …
Reproduction Of The Rare, Riparian Orchid Spiranthes Diluvialis: Pollination Ecology, Variations In Reproductive Success, And Implications For Conservation, Sedonia D. Sipes
Reproduction Of The Rare, Riparian Orchid Spiranthes Diluvialis: Pollination Ecology, Variations In Reproductive Success, And Implications For Conservation, Sedonia D. Sipes
Biology
I examined the reproductive biology and pollination of Ute lady's tresses, Spiranthes diluvialis Sheviak, a rare orchid from Colorado and Utah. S. diluvialis exhibits a mixed-mating system. Outcrossing is promoted by protandrous flowers and by acropetal movement of long-tongued bees (predominantly bumblebees) on inflorescences. However, male and female phases overlap, and flowers are fully self-compatible. No autogamous or agamospermous seed set was observed, indicating a pollinator is required for reproduction. Fruit set and pollinia removal varied greatly within and between flowering seasons. I found evidence for both resource and pollinator limitation of fruit set, and suggest that the limiting factor …
Overlapping Transcription By Rna Polymerases Ii And Iii Of The Xenopus Tfiiia Gene In Somatic Cells, Ernest Martinez, Giorgio Lagna, Robert G. Roeder
Overlapping Transcription By Rna Polymerases Ii And Iii Of The Xenopus Tfiiia Gene In Somatic Cells, Ernest Martinez, Giorgio Lagna, Robert G. Roeder
Biology
Xenopus TFIIIA gene expression is developmentally regulated. The per cell level of steady-state TFIIIA mRNA present in oocytes is drastically reduced (10(6)-fold) in adult somatic cells, suggesting regulation at the transcriptional level. This is supported by the presence of TFIIIA mRNAs with different 5'-ends in oocytes and in somatic cells, which suggests the presence of distinct cell-/stage-specific promoters, i.e. a strong oocyte-specific and a weak somatic-specific promoter. Here, by mapping the 5'-ends of TFIIIA RNAs found in Xenopus somatic cells, we document the activity not only of an upstream somatic-specific promoter, but also of a down-stream “oocyte-specific” promoter that gives …
Two Mechanisms For Growth Inhibition By Elevated Transport Of Sugar Phosphates In Escherichia Coli, Robert J. Kadner, G. Patrick Murphy, Craig Stephens
Two Mechanisms For Growth Inhibition By Elevated Transport Of Sugar Phosphates In Escherichia Coli, Robert J. Kadner, G. Patrick Murphy, Craig Stephens
Biology
The Escherichia coli uhp T gene encodes an active transport system for sugar phosphates. When the uhp T gene was carried on a multicopy plasmid, amplified levels of transport activity occurred, and growth of these strains was inhibited upon the addition of various sugar phosphates. Two different mechanisms for this growth inhibition were distinguished. Exposure to glucose-6-phosphate, fructose-6-phosphate or mannose-6-phosphate, which enter directly into the glycolytic pathway, resulted in cessation of growth and substantial loss of viability. Cell killing was correlated with the production of the toxic metabolite, methylglyoxal. In contrast, addition of 2-deoxyglucose-6-phosphate, galactose-6-phosphate, glucosamine-6-phosphate or arabinose-5-phosphate, which do …
Essential Cysteines In 3-Deoxy-D-Arabino-Heptulosonate-7-Phosphate Synthase From Escherichia Coli., Craig Stephens, Ronald Bauerle
Essential Cysteines In 3-Deoxy-D-Arabino-Heptulosonate-7-Phosphate Synthase From Escherichia Coli., Craig Stephens, Ronald Bauerle
Biology
The phenylalanine-sensitive isozyme of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli was inactivated by the sulfhydryl modifying reagents 5,5-dithiobis-(2-nitrobenzoate), bromopyruvate, and N-ethylmaleimide and protected from inactivation by the presence of its metal activator, Mn2+, and substrate, phosphoenolpyruvate. Inactivation by 5,5-dithiobis-(2-nitrobenzoate) was correlated with modification of two of the seven cysteine sulfhydryls of the enzyme monomer. The kinetics of 5,5-dithiobis-(2-nitrobenzoate) modification were altered significantly and distinctively by both substrates (phosphoenolpyruvate and erythrose 4-phosphate), by Mn2+, and by L-phenylalanine, suggesting that ligand binding has significant effects on the conformation of the enzyme. Site-directed mutagenesis was used to create multiple substitutions at the two invariant …
Analysis Of The Metal Requirement Of 3-Deoxy-D-Arabino-Heptulosonate-7-Phosphate Synthase From Escherichia Coli., Craig Stephens, Ronald Bauerle
Analysis Of The Metal Requirement Of 3-Deoxy-D-Arabino-Heptulosonate-7-Phosphate Synthase From Escherichia Coli., Craig Stephens, Ronald Bauerle
Biology
The three isozymes of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli were overproduced, purified, and characterized with respect to their requirement for metal cofactor. The isolated isozymes contained 0.2-0.3 mol of iron/mol of enzyme monomer, variable amounts of zinc, and traces of copper. Enzymatic activity of the native enzymes was stimulated 3-4-fold by the addition of Fe2+ ions to the reaction mixture and was eliminated by treatment of the enzymes with EDTA. The chelated enzymes were reactivated by a variety of divalent metal ions, including Ca2+, Cd2+, Co2+, Cu2+, Fe2+, Mn2+, Ni2+, and Zn2+. The specific activities of the reactivated enzymes varied …
Hrpf, A Human Sequence-Specific Dna-Binding Protein Homologous To Xrpfl, A Xenopus Iaevis Oocyte Transcription Factor, Giorgio Lagna, Fabrizio Loreni, Elena Beccari, Francesca Carnevali
Hrpf, A Human Sequence-Specific Dna-Binding Protein Homologous To Xrpfl, A Xenopus Iaevis Oocyte Transcription Factor, Giorgio Lagna, Fabrizio Loreni, Elena Beccari, Francesca Carnevali
Biology
The identification in HeLa nuclei of a novel DNA-binding protein, designated HrpF, is presented. This factor recognizes and binds a sequence of the Xenopus Iaevis L14 ribosomal protein (r-p) gene promoter bound by the Xenopus r-p transcription factor I (XrpFl) (1). We show here that XrpFl and HrpF share a conserved DNA-binding domain. We also present evidences suggesting that the two factors perform similar functions in the cell. We discuss the hypothesis that closely related factors might be involved in the control of rp-gene transcription in vertebrates.
A New Braconid Genus (Hymenoptera) Parasitizing Webspinners (Embiidina) In Trinidad, Scott Shaw, Janice Edgerly-Rooks
A New Braconid Genus (Hymenoptera) Parasitizing Webspinners (Embiidina) In Trinidad, Scott Shaw, Janice Edgerly-Rooks
Biology
Early in 1984, while conducting field studies on embiid behavior in the Arima valley of northern Trinidad, the junior author ob- served a braconid wasp ovipositing into the silk webs of an embiid, Clothoda urichi (Saussure) [Clothodidae]. The wasp and a paralyzed embiid were collected, and another wasp was successfully reared from that host. Specimens were sent to the senior author, then stationed at the National Museum of Natural History (USNM), who determined it to be a new braconid genus. A search of the USNM collection yielded no comparable specimens; however, during a subsequent search of the Museum of Comparative …