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81.
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Julie C Robidart Christina M Preston Ryan W Paerl Kendra A Turk Annika C Mosier Christopher A Francis Christopher A Scholin Jonathan P Zehr 《The ISME journal》2012,6(3):513-523
Monterey Bay, CA is an Eastern boundary upwelling system that is nitrogen limited much of the year. In order to resolve population dynamics of microorganisms important for nutrient cycling in this region, we deployed the Environmental Sample Processor with quantitative PCR assays targeting both ribosomal RNA genes and functional genes for subclades of cyanobacteria (Synechococcus) and ammonia-oxidizing Archaea (Thaumarchaeota) populations. Results showed a strong correlation between Thaumarchaea abundances and nitrate during the spring upwelling but not the fall sampling period. In relatively stratified fall waters, the Thaumarchaeota community reached higher numbers than in the spring, and an unexpected positive correlation with chlorophyll concentration was observed. Further, we detected drops in Synechococcus abundance that occurred on short (that is, daily) time scales. Upwelling intensity and blooms of eukaryotic phytoplankton strongly influenced Synechococcus distributions in the spring and fall, revealing what appear to be the environmental limitations of Synechococcus populations in this region. Each of these findings has implications for Monterey Bay biogeochemistry. High-resolution sampling provides a better-resolved framework within which to observe changes in the plankton community. We conclude that controls on these ecosystems change on smaller scales than are routinely assessed, and that more predictable trends will be uncovered if they are evaluated within seasonal (monthly), rather than on annual or interannual scales. 相似文献
83.
Alexandria A. Oviatt Jissy A. Kuriappan Elirosa Minniti Kendra R. Vann Princess Onuorah Anna Minarini Marco De Vivo Neil Osheroff 《Bioorganic & medicinal chemistry letters》2018,28(17):2961-2968
Etoposide is an anticancer drug that acts by inducing topoisomerase II-mediated DNA cleavage. Despite its wide use, etoposide is associated with some very serious side-effects including the development of treatment-related acute myelogenous leukemias. Etoposide targets both human topoisomerase IIα and IIβ. However, the contributions of the two enzyme isoforms to the therapeutic vs. leukemogenic properties of the drug are unclear. In order to develop an etoposide-based drug with specificity for cancer cells that express an active polyamine transport system, the sugar moiety of the drug has been replaced with a polyamine tail. To analyze the effects of this substitution on the specificity of hybrid molecules toward the two enzyme isoforms, we analyzed the activity of a series of etoposide-polyamine hybrids toward human topoisomerase IIα and IIβ. All of the compounds displayed an ability to induce enzyme-mediated DNA cleavage that was comparable to or higher than that of etoposide. Relative to the parent drug, the hybrid compounds displayed substantially higher activity toward topoisomerase IIβ than IIα. Modeling studies suggest that the enhanced specificity may result from interactions with Gln778 in topoisomerase IIβ. The corresponding residue in the α isoform is a methionine. 相似文献
84.
Bryan R. Helm Scott Payne Joseph P. Rinehart George D. Yocum Julia H. Bowsher Kendra J. Greenlee 《Arthropod Structure & Development》2018,47(5):521-528
Insect metamorphosis involves a complex change in form and function. In this study, we examined the development of the solitary bee, Megachile rotundata, using micro-computed tomography (μCT) and volume analysis. We describe volumetric changes of brain, tracheae, flight muscles, gut, and fat bodies in prepupal, pupal, and adult M. rotundata. We observed that individual organ systems have distinct patterns of developmental progression, which vary in their timing and duration. This has important implications for commercial management of this agriculturally relevant pollinator. 相似文献
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86.
Closed‐reference metatranscriptomics enables in planta profiling of putative virulence activities in the grapevine trunk disease complex
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Michele L. Markwardt Kendra M. Seckinger Mark A. Rizzo 《The Journal of biological chemistry》2016,291(6):3000-3009
Glucokinase (GCK) controls the rate of glucose metabolism in pancreatic β cells, and its activity is rate-limiting for insulin secretion. Posttranslational GCK activation can be stimulated through either G protein-coupled receptors or receptor tyrosine kinase signaling pathways, suggesting a common mechanism. Here we show that inhibiting Ca2+ release from the endoplasmic reticulum (ER) decouples GCK activation from receptor stimulation. Furthermore, pharmacological release of ER Ca2+ stimulates activation of a GCK optical biosensor and potentiates glucose metabolism, implicating rises in cytoplasmic Ca2+ as a critical regulatory mechanism. To explore the potential for glucose-stimulated GCK activation, the GCK biosensor was optimized using circularly permuted mCerulean3 proteins. This new sensor sensitively reports activation in response to insulin, glucagon-like peptide 1, and agents that raise cAMP levels. Transient, glucose-stimulated GCK activation was observed in βTC3 and MIN6 cells. An ER-localized channelrhodopsin was used to manipulate the cytoplasmic Ca2+ concentration in cells expressing the optimized FRET-GCK sensor. This permitted quantification of the relationship between cytoplasmic Ca2+ concentrations and GCK activation. Half-maximal activation of the FRET-GCK sensor was estimated to occur at ∼400 nm Ca2+. When expressed in islets, fluctuations in GCK activation were observed in response to glucose, and we estimated that posttranslational activation of GCK enhances glucose metabolism by ∼35%. These results suggest a mechanism for integrative control over GCK activation and, therefore, glucose metabolism and insulin secretion through regulation of cytoplasmic Ca2+ levels. 相似文献
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Zachary D. Nightingale Jeffrey B. Blumberg Garry J. Handelman 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,732(2):526
The determination by gas chromatography (GC) of fatty acid methyl esters (FAMEs) prepared from complex biological samples is subject to interference from cholesterol. During sample injection on the GC system of FAMEs prepared from tissues that contain cholesterol, we observed a major contaminant that co-eluted with docosahexaenoic acid (DHA, 22:6n-3). To address this problem, FAMEs were purified on an amino-phase high-performance liquid chromatography (HPLC) column using a hexane–isopropanol gradient. The HPLC retention times for both the FAME fraction and cholesterol were stable and reproducible when the amino column was used for sample purification. The purified extracts were analyzed by GC without artifacts or impurity peaks after 50 analytical runs. The method described here will be useful for measurement of 22:6n-3 and other fatty acids important for studies of nutrition or pathology. 相似文献