Variable Influence (variable + influence)

Distribution by Scientific Domains


Selected Abstracts


Comparison of hardness- and chloride-regulated acute effects of sodium sulfate on two freshwater crustaceans

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2007
David John Soucek
Abstract Based on previous observations that hardness (and potentially chloride) influences sodium sulfate toxicity, the objective of the current study was to quantify the influence of both chloride and water hardness on acute toxicity to Hyalella azteca and Ceriodaphnia dubia. In addition, observed toxicity data from the present study were compared to toxicity predictions by the salinity/toxicity relationship (STR) model. Hardness had a strong influence on sulfate toxicity that was similar for both crustaceans, and nearly identical median lethal concentration (LC50)/hardness slopes were observed for the two species over the tested range. Chloride had a strong but variable influence on sulfate acute toxicity, depending on the species tested and the concentration range. At lower chloride concentrations, LC50s for H. azteca strongly were correlated positively with chloride concentration, although chloride did not affect the toxicity of sodium sulfate to C. dubia. The opposite trend was observed over the higher range of chloride concentrations where there was a negative correlation between chloride concentration and sulfate LC50 for both species. The widely ranging values for both species and a high correlation between LC50s in terms of sulfate and conductivity suggested that, whether based on sulfate, conductivity, or total dissolved solids (TDS), attempts at water quality standard development should incorporate the fact that water quality parameters such as hardness and chloride strongly influence the toxicity of high TDS solutions. The STR model predicted toxicity to C. dubia relatively well when chloride was variable and hardness fixed at approximately 100 mg/L; however, the model did not account for the protective effect of hardness on major ion/TDS toxicity. [source]


Using patterns of reef fish assemblages to refine a Habitat Classification System for marine parks in NSW, Australia

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2010
Hamish A. Malcolm
Abstract 1.The Solitary Islands Marine Park (SIMP) in New South Wales (NSW), Australia, is located in a tropical-temperate biotone, with variable influence of the tropical East Australian Current (EAC) from inshore to offshore. Marine communities on the extensive, subtidal, rocky reefs are poorly described. As a result, the current Habitat Classification System (HCS) used as part of the process to determine the marine park zoning arrangements, which places all shallow reef (<25,m) in the same category, is unlikely to represent real biotic patterns. 2.To evaluate the influence of five key factors (distance from shore, reef type, dominant benthos, latitude, and depth range) fish assemblages were widely surveyed, using 30-minute timed counts, at 68 sites across the extent of shallow reef within the park. Relationships between assemblage patterns and levels of the different factors were subsequently examined using multivariate analyses. 3.Patterns of reef fish assemblages were most strongly correlated with distance from shore. Three distinct assemblages occurred on inshore (<1.5,km), mid-shelf (1.5,6,km), and offshore (>6,km) reefs. Differences in assemblage structure by reef type were also apparent on inshore and offshore reefs, but not on mid-shelf reefs. Correlations with the other factors were weak. The cross-shelf pattern was persistent over the scale of years. 4.The results of the study provide strong support for incorporating distance-from-shore categories into a refined HCS. This will improve its ability to represent biological diversity as reflected by patterns of reef fish assemblages. Further research is required to determine the wider application of the HCS to other marine parks in NSW and to determine if it also, effectively, represents other components of biodiversity. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Landscape memory: the imprint of the past on contemporary landscape forms and processes

AREA, Issue 1 2010
Gary John Brierley
The imprint of the past upon contemporary landscape forms and processes is differentiated in terms of geologic, climatic and anthropogenic memory. Geologic memory refers to controls exerted upon relief, erodibility, erosivity and accommodation space (areas in landscapes where sediments are stored and reworked). These factors set the imposed boundary conditions within which contemporary landscape-forming processes operate. Climatic memory refers to the influence of past climatic conditions upon contemporary landscape forms and processes. Climatic controls exert a primary influence upon the nature of geomorphic processes, while the influence of climate upon ground cover affects the effectiveness of these processes. Climate change may induce profound alterations to the flux boundary conditions under which contemporary landscapes operate. This is exemplified by the variable imprint of glacial/interglacial cycles in differing parts of the world. Anthropogenic memory refers to the imprint of past human activities on contemporary landscapes, whereby human disturbance in the past altered landscape forms, processes and associated flow/sediment fluxes in a manner that continues to affect the way the contemporary landscape works. Contrasting examples from a tectonically stable landscape (Australia) and a tectonically uplifting landscape (New Zealand) are used to highlight the variable influence of geologic, climatic and anthropogenic memory upon the persistence and erasure of landscape forms and resulting implications for sediment flux in differing settings. [source]


Metabolic profiling as a tool for understanding defense response of Taxus Cuspidata cells to shear stress

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Pei-Pei Han
Abstract To obtain a better understanding of responsive mechanism of plant cells in response to hydrodynamic mechanical stress, a metabolic profiling approach was used to profile metabolite changes of Taxus cuspidata cells under laminar shear stress. A total of 65 intracellular metabolites were identified and quantified, using gas chromatography coupled to time-of-flight mass spectrometry. Potential biomarkers were found by the principal component analysis as well as partial least squares combined with variable influence in the projection. Trehalose, sorbitol, ascorbate, sucrose, and gluconic acid were mainly responsible for the discrimination between shear stress induced cells and control cells. Further analysis by mapping measured metabolite concentrations onto the metabolic network revealed that shear stress imposed restrictions on primary metabolic pathways by inhibiting tricarboxylic acid cycle, glycolysis, and N metabolism. To adapt to the shear condition, cells responded by starting defensive programs. These defensive programs included coinduction of glycolysis and sucrose metabolism, accumulation of compatible solutes, and antioxidative strategy. A strategy of defense mechanisms at the level of metabolites for T. cuspidata cells when challenged with the shear stress was proposed. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]


Differential effects of glucose on agonist-induced relaxations in human mesenteric and subcutaneous arteries

BRITISH JOURNAL OF PHARMACOLOGY, Issue 3 2008
A MacKenzie
Background and purpose: Acute periods of hyperglycaemia are strongly associated with vascular disorder, yet the specific effects of high glucose on human blood vessel function are not fully understood. In this study we (1) characterized the endothelial-dependent relaxation of two similarly sized but anatomically distinct human arteries to two different agonists and (2) determined how these responses are modified by acute exposure to high glucose. Experimental approach: Ring segments of human mesenteric and subcutaneous arteries were mounted in a wire myograph. Relaxations to acetylcholine and bradykinin were determined in a control (5 mM) and high glucose (20 mM) environment over a 2 and 6 h incubation period. Key results: Bradykinin-induced relaxation in both sets of vessels was mediated entirely by EDHF whilst that generated by acetylcholine, though principally generated by EDHF, also had contribution from prostacyclin and possibly nitric oxide in mesenteric and subcutaneous vessels, respectively. A 2-h incubation of high glucose impaired bradykinin-induced relaxation of subcutaneous vessels whilst, in contrast, the relaxation generated by bradykinin in mesenteric vessels was enhanced at the same time point. High glucose significantly augmented the relaxation generated by acetylcholine in mesenteric and subcutaneous vessels at a 2 and 6 h incubation point, respectively. Conclusions and implications: Short periods of high glucose exert a variable influence on endothelial function in human isolated blood vessels that is dependent on factors of time, agonist-used and vessel studied. This has implications for how we view the effects of acute hyperglycaemia found in patients with diabetes mellitus as well as other conditions. British Journal of Pharmacology (2008) 153, 480,487; doi:10.1038/sj.bjp.0707592; published online 26 November 2007 [source]


An assessment of consumer preference for fair trade coffee in Toronto and Vancouver

AGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2010
John Cranfield
In this article, the authors use conjoint analysis to elicit the views of coffee consumers on the attributes of Fair Trade coffee using data from the Greater Toronto Area and Vancouver collected through face-to-face interviews with consumers. The impact of socioeconomic and demographic factors on respondents' acceptance of Fair Trade coffee is evaluated using cluster analysis and multinomial logit models. The results suggest that, regardless of location, consumers place a strong premium on price and labeling claims. Three consumer segments are identified in each city; in Toronto, these segments are labeled Fair Trade-Focused, Price Conscious, and Balanced Buyers; for Vancouver these segments are labeled Organic and Fair Trade-Focused, Price Conscious, and Balanced Buyers. Although a broad spectrum of variables influences segment membership, no single variable explains membership in the same segment in each city. Such a result is rather telling; it suggests deeper constructs underlie segment membership, and presumably consumption behavior with respect to Fair Trade coffee. © 2010 Wiley Periodicals, Inc. [source]