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This paper reports a close link between terrain ruggedness and forage availability for caribou during snowmelt. Indices of terrain ruggedness based on contour characteristics from topographical maps were related to field measures of cover, biomass, and live/dead ratio of graminoids within the Kuparuk Oilfield, Alaska. Terrain ruggedness was found to be the most significant factor affecting forage availability during snowmelt within the study area. Terrain ruggedness was positively correlated to 1) graminoid cover within wet, moist and dry herbaceous tundra, 2) cover of four individual graminoid species, 3) height of Salix planifolia, 4) amount of Eriophorum vaginatum flowers, and 5) live/dead ratio of plant material during early and late snowmelt. The live/dead ratio of plant material varied among vegetation types during snowmelt, causing rugged areas to have sprouting green plant material available for forage throughout this period. While annual differences in snow depths and snowmelt will affect forage availability in a given year, indices of terrain ruggedness combined with vegetation maps can substantially improve our understanding of how forage availability for caribou may vary across the landscape during snowmelt.

Six clones of RHODIOLA ROSEA, obtained from plants originating from widely different areas in Norway, were investigated for their IN VITRO inhibitory potential on CYP3A4-mediated metabolism and P-gp efflux transport activity. Presumed active constituents in the ethanol extracts of the different clones were quantified. C-DNA baculovirus expressed CYP3A4 and Caco-2 cells were used for inhibitory assays, and as positive control inhibitors ketoconazole and verapamil were applied, respectively. A validated HPLC methodology was used to quantify the formation of 6-beta-OH-testosterone and scintillation counting was used to quantify the transport of (3)H-digoxin in Caco-2 cells. All clones showed potent inhibition of CYP3A4 and P-gp activities, with IC (50) values ranging from 1.7 to 3.1 microg/mL and from 16.7 to 51.7 microg/mL, respectively, being below that reported for other herbs and some known classic drug inhibitors, such as St. John's wort and fluoxetine. RHODIOLA ROSEA might thus be a candidate for clinically relevant drug interactions. The concentration of presumed biologically active constituents in the different clones varied considerably, but this variation was not related to the clones' inhibitory potential on CYP3A4 or P-gp activities. Other constituents might thus be responsible for the observed inhibitory properties. The place of origin seemed to be of minor importance for CYP3A4 or P-gp inhibition.

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