University of Guelph

About: University of Guelph is a education organization based out in Guelph, Ontario, Canada. It is known for research contribution in the topics: Population & Gene. The organization has 26542 authors who have published 50553 publications receiving 1715255 citations. The organization is also known as: U of G & Guelph University.

The membrane lipid environment modulates drug interactions with the P-glycoprotein multidrug transporter.

Abstract: The P-glycoprotein multidrug transporter functions as an ATP-driven efflux pump for a large number of structurally unrelated hydrophobic compounds. Substrates are believed to gain access to the transporter after partitioning into the membrane, rather than from the extracellular aqueous phase. The binding of drug substrates to P-glycoprotein may thus be modulated by the properties of the lipid bilayer. The interactions with P-glycoprotein of two drugs (vinblastine and daunorubicin) and a chemosensitizer (verapamil) were characterized by quenching of purified fluorescently labeled protein in the presence of various phospholipids. Biphasic quench curves were observed for vinblastine and verapamil, suggesting that more than one molecule of these compounds may bind to the transporter simultaneously. All three drugs bound to P-glycoprotein with substantially higher affinity in egg phosphatidylcholine (PC), compared to brain phosphatidylserine (PS) and egg phosphatidylethanolamine (PE). The nature of the lipid a...

Resuspension of sediment-associated Escherichia coli in a natural stream.

Abstract: In this study, a tracer bacteria was used to investigate the resuspension and persistence of sediment-associated bacteria in a small alluvial stream The study was conducted in Swan Creek, located within the Grand River watershed of Ontario, Canada A 11-m2 section of the bed was seeded with a strain of Escherichia coli resistant to nalidixic acid (E coli NAR) The survival, transport, and redistribution of the tracer bacteria within a 17-km river section downstream of the source cell was assessed for a 2-mo period following the introduction of the tracer bacteria This study has illustrated that enteric bacteria can survive in bed sediments for up 6 wk and that inactivation of the tracer bacteria resembled typical first-order decay Critical conditions for resuspension, as well as resuspension rates, of sediment-associated bacteria were determined for several storm events The critical shear stress for E coli NAR resuspension in Swan Creek ranged from 15 to 17 N m(-2), which is comparable with literature values for critical shear stresses for erosion of cohesive sediments Bacteria resuspension was primarily limited to the rising limb of storm hydrographs implying that a finite supply of sediment-associated bacteria are available for resuspension during individual storm events The information presented in this paper will further the development of representative microbial water quality models

Genome duplication and the evolution of physiological responses to water stress.

Abstract: Whole-genome multiplication, or polyploidy, is common in angiosperms and many species consist of multiple cytotypes that have different physiological tolerances. However, the relative importance of genome duplication vs post-duplication evolutionary change in causing differentiation between cytotypes is not known. We examined the water relations of Chamerion angustifolium, a herbaceous perennial in which diploid and tetraploid cytotypes occupy different niches. To differentiate between the effects of genome duplication and evolutionary changes that followed polyploidization, we compared extant diploids and tetraploids with experimentally synthesized neotetraploids. Tetraploids had 32% higher xylem hydraulic conductivity (K(H)) than neotetraploids and 87% higher K(H) than diploids, but vulnerability to water stress induced cavitation and gas exchange sensitivity to water potential did not differ among cytotypes. Nevertheless, tetraploids took 22% and 30% longer to wilt than neotetraploids and diploids. A simple hydraulic model suggested that tetraploids deplete soil moisture to a greater degree than neotetraploids and diploids before reaching leaf water potentials that cause stomatal closure. We conclude that the different physiological tolerances and distribution of diploid and tetraploid C. angustifolium are unlikely to be caused solely by genome duplication. The enhanced ability of tetraploids to survive water stress likely evolved after polyploidization.