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Extreme Sensitivity (extreme + sensitivity)
Selected AbstractsWhen does parameter drift decrease the uncertainty in extinction risk estimates?ECOLOGY LETTERS, Issue 12 2003Stephen P. Ellner Abstract Halley (2003) proposed that parameter drift decreases the uncertainty in long-range extinction risk estimates, because drift mitigates the extreme sensitivity of estimated risk to estimated mean growth rate. However, parameter drift has a second, opposing effect: it increases the uncertainty in parameter estimates from a given data set. When both effects are taken into account, parameter drift can increase, sometimes substantially, the uncertainty in risk estimates. The net effect depends sensitively on the type of drift and on which model parameters must be estimated from observational data on the population at risk. In general, unless many parameters are estimated from independent data, parameter drift increases the uncertainty in extinction risk. These findings suggest that more mechanistic PVA models, using long-term data on key environmental variables and experiments to quantify their demographic impacts, offer the best prospects for escaping the high data requirements when extinction risk is estimated from observational data. [source] Assessing the link between BACH1/FANCJ and MLH1 in DNA crosslink repairENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 6 2010Sharon B. Cantor Abstract FANCJ (also known as BRIP1 or BACH1) is a DNA helicase that was originally identified by its direct interaction with the hereditary breast cancer protein, BRCA1. Similar to BRCA1, FANCJ function is essential for DNA repair and breast cancer suppression. FANCJ is also mutated in the cancer prone syndrome Fanconi anemia, for which patient cells are characterized by extreme sensitivity to agents that generate DNA interstand crosslinks. Unexpectedly, correction of the interstrand crosslink sensitivity of FANCJ-null patient cells did not require the FANCJ/BRCA1 interaction. Instead, FANCJ binding to the mismatch repair protein, MLH1 was required. Given this finding, we address the role of FANCJ and MLH1 in DNA crosslink processing and how their functions could be linked in checkpoint and/or recombination pathways. We speculate that after DNA crosslink processing and repair, the FANCJ/MLH1 interaction is critical for recovery and restart of replication. These ideas are considered and summarized in this review. Environ. Mol. Mutagen., 2010. © 2010 Wiley-Liss, Inc. [source] Chronic toxicity of lead to three freshwater invertebrates,Brachionus calyciflorus, Chironomus tentans, and Lymnaea stagnalisENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006Martin Grosell Abstract Chronic lead (Pb) toxicity tests with Brachionus calyciflorus, Chironomus tentans, and Lymnaea stagnalis were performed in artificial freshwaters. The no-observable-effect concentration (NOEC), lowest-observable-effect concentration (LOEC), and calculated 20% effect concentration (EC20) for the rotifer B. calyciflorus were 194, 284, and 125 ,g dissolved Pb/L, respectively. The midge C. tentans was less sensitive, with NOEC and LOEC of 109 and 497 ,g dissolved Pb/L, respectively, and the snail L. stagnalis exhibited extreme sensitivity, evident by NOEC, LOEC, and EC20 of 12, 16, and <4 ,g dissolved Pb/L, respectively. Our findings are presented in the context of other reports on chronic Pb toxicity in freshwater organisms. The L. stagnalis results are in agreement with a previous report on pulmonate snails and should be viewed in the context of current U.S. Environmental Protection Agency (U.S. EPA) hardness adjusted water quality criteria of 8 ,g Pb/L. The present findings and earlier reports indicate that freshwater pulmonate snails may not be protected by current regulatory standards. Measurements of whole-snail Na+ and Ca2+ concentrations following chronic Pb exposure revealed that Na+ homeostasis is disturbed by Pb exposure in juvenile snails in a complicated pattern, suggesting two physiological modes of action depending on the Pb exposure concentration. Substantially reduced growth in the snails that exhibit very high Ca2+ requirements may be related to reduced Ca2+ uptake and thereby reduced shell formation. [source] Fluorescent Nanoprobes: Fluorescent Gold Nanoprobe Sensitive to Intracellular Reactive Oxygen Species (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 12 2009Mater. On page 1884, H. Lee and co-workers report fluorescent gold nanoprobes sensitive to reactive oxygen species (ROS). Using nanoparticle surface energy transfer between gold nanoparticles and end-dopamine modified fluorescein-hyaluronic acid conjugates, gold nanoprobes are created with extreme sensitivity to intracellular ROS. The cover image shows real time monitoring of intracellular ROS generation within macrophage cells via fluorescence recovery of the nanoprobes. [source] Attenuation of the Stimulant Response to Ethanol is Associated with Enhanced Ataxia for a GABAA, but not a GABAB, Receptor AgonistALCOHOLISM, Issue 1 2009Sarah E. Holstein Background:, The ,-aminobutyric acid (GABA) system is implicated in the neurobiological actions of ethanol, and pharmacological agents that increase the activity of this system have been proposed as potential treatments for alcohol use disorders. As ethanol has its own GABA mimetic properties, it is critical to determine the mechanism by which GABAergic drugs may reduce the response to ethanol (i.e., via an inhibition or an accentuation of the neurobiological effects of ethanol). Methods:, In this study, we examined the ability of 3 different types of GABAergic compounds, the GABA reuptake inhibitor NO-711, the GABAA receptor agonist muscimol, and the GABAB receptor agonist baclofen, to attenuate the locomotor stimulant response to ethanol in FAST mice, which were selectively bred for extreme sensitivity to ethanol-induced locomotor stimulation. To determine whether these compounds produced a specific reduction in stimulation, their effects on ethanol-induced motor incoordination were also examined. Results:, NO-711, muscimol, and baclofen were all found to potently attenuate the locomotor stimulant response to ethanol in FAST mice. However, both NO-711 and muscimol markedly increased ethanol-induced ataxia, whereas baclofen did not accentuate this response. Conclusions:, These results suggest that pharmacological agents that increase extracellular concentrations of GABA and GABAA receptor activity may attenuate the stimulant effects of ethanol by accentuating its intoxicating and sedative properties. However, selective activation of the GABAB receptor appears to produce a specific attenuation of ethanol-induced stimulation, suggesting that GABAB receptor agonists may hold greater promise as potential pharmacotherapies for alcohol use disorders. [source] Behaviour of polynuclear aryl sulphonatesLUBRICATION SCIENCE, Issue 3 2005A. K. Singh A series of hexadecyl polynuclear aromatic, decalin, and tetralin sulphonates have been synthesised. The critical micelle concentration (CMC) and surface and interfacial tension values at various concentrations above and below the CMC in both aqueous and non-aqueous media have been determined. The micellar size and shape, the average number of monomers constituting these micelles, and the thermodynamic properties have also been estimated. These studies show that the CMC value in both aqueous and heptane media decreases with an increase in the number of aromatic rings in the sulphonates. The size and shape of the micelles do not change appreciably in heptane, although the number of monomers constituting the micelles changes with a change of structure of the aromatic moiety. The thermodynamic parameters do not seem to affect the surface activity and solubilising properties even though the free energy, enthalpy, and entropy decrease with an increase in the size of the aromatic moiety. The surface and interfacial tension values are the lowest with aqueous and non-aqueous solutions of hexadecyl naphthalene sulphonate, but these values increase with an increase in the number of aromatic rings in the sulphonates. The sizes of the micelles of hexadecyl naphthalene sulphonate in aqueous solutions and the number of monomer molecules constituting the micelles are greater than for the other aromatic sulphonates. Although the sizes of micelles of hexadecyl benzanthracene sulphonate and hexadecyl pentacene sulphonate are comparable, the numbers of molecules constituting these micelles are the smallest. The solubilisation of alkanes in aqueous solutions of sodium naphthalene sulphonate containing electrolyte and isobutanol is the highest, but it falls off rapidly for all the other sulphonates. This shows the extreme sensitivity of solubilisation to the structure of the sulphonates. The detergency increases with an increase in the size of the aromatic moiety. The structure thus has a profound influence on the surface and micellar properties of these sulphonates. These studies are important from the point of view of the use of synthetic sulphonates as additives / surfactants in place of petroleum sulphonates. [source] Highly Sensitive and Selective Fluoride Ion Chemosensing, Fluoroalkylated Polysilane,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 20 2004Anubhav Saxena Abstract Summary: This paper reports a new and simple approach for the amplified detection of fluoride ions by a polymer-based chemosensor made of stiff fluoroalkylated polysilane, poly(3,3,3-trifluoropropylmethylsilane). This chemosensor exhibited extreme sensitivity and selectivity towards fluoride ions by a decrease in the photoluminescence (PL) intensity with parts per billion concentrations of fluoride ions in solution in tetrahydrofuran (THF). The quenching constant for fluoride ions (K,=,1.35,×,107M,1) was found to be exceptionally high. Schematic representation of the polymer amplification mechanism after addition of fluoride ion in tetrahydrofuran. [source] | |||||||||||||