University of Nevada, Reno

About: University of Nevada, Reno is a education organization based out in Reno, Nevada, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 13561 authors who have published 28217 publications receiving 882002 citations. The organization is also known as: University of Nevada & Nevada State University.

Variations in normal color vision. II. Unique hues.

Abstract: We examined individual differences in the color appearance of nonspectral lights and asked how they might be related to individual differences in sensitivity to chromatic stimuli. Observers set unique hues for moderately saturated equiluminant stimuli by varying their hue angle within a plane defined by the LvsM and SvsLM cone-opponent axes that are thought to characterize early postreceptoral color coding. Unique red settings were close to the +L pole of the LvsM axis, while green, blue, and yellow settings clustered along directions intermediate to the LvsM and SvsLM axes and thus corresponded to particular ratios of LvsM to SvsLM activity. Interobserver differences in the unique hues were substantial. However, no relationship was found between hue settings and relative sensitivity to the LvsM and SvsLM axes. Moreover, interobserver variations in different unique hues were uncorrelated and were thus inconsistent with a common underlying factor such as relative sensitivity or changes in the spectral sensitivities of the cones. Thus for the moderately saturated lights we tested, the unique hues appear largely unconstrained by normal individual differences in the cone-opponent axes. In turn, this suggests that the perceived hue for these stimuli does not depend on fixed (common) physiological weightings of the cone-opponent axes or on fixed (common) color signals in the environment.

Competition and facilitation : Contrasting effects of Artemisia tridentata on desert vs. montane pines

Abstract: Circumstantial evidence suggests that Artemisia tridentata may out-compete Pinus ponderosa and P. jefferyi for water at ecotones between shrub steppe and montane forest vegetation in the Great Basin. Other studies indicate that within the shrub steppe Artemisia may act as a nurse plant for a third species of pine, P. monophylla. We used field experiments to study these contrasting effects of Artemisia on P. ponderosa and P. monophylla within the context of the distributional patterns in western Nevada of all three species on andesite, and on sites where hydrothermal activity has altered the andesite. At intermediate elevations in the Great Basin Artemisia and P. monophylla are restricted to unaltered desert soils, whereas P. ponderosa is restricted to acidic, nutrient-poor altered andesite. Although mature P. monophylla were virtually absent in our study plots on altered andesite, first- and second-year seedlings were common. On adjacent unaltered andesite, all size classes of P. monophylla occurred, and P. monophylla seedlings were associated with Artemisia shrubs. Pinus ponderosa and P. jefferyi adults and seedlings were rare on unaltered andesite, but a wide range of size classes was found on altered andesite. In experiments, all P. ponderosa seedlings on unaltered andesite were consumed by predators regardless of positive or negative spatial association with shrubs. Of the P. monophylla seedlings that germinated on unaltered andesite, all that were under shrubs survived, but only 6% of those that germinated in the intershrub spaces survived. On the open altered andesite the mortality of P. monophylla seedlings due to abiotic stress was high, with a final survival of only 3%, whereas 28% of P. ponderosa seedlings survived the first growing season on altered andesite. On unaltered andesite, survival and conductance of P. ponderosa saplings was enhanced by shrub removal, but P. monophylla survival was significantly higher under shrubs than in shrub-removal plots or in intershrub spaces. In Artemisia- removal experiments, we found that Artemisia competed with P. ponderosa seedlings and saplings for water. Removal of Artemisia decreased water use efficiency (WUE) of P. monophylla seedlings. The absence of Artemisia may restrict Pinus monophylla from out- crops of altered andesite in the Great Basin, but provide refuges for P. ponderosa.

Assessment of interrelationships among levels of intake and production, organ size and fasting heat production in growing animals.

Abstract: Although the concept of metabolic body size (kg075) has gained widespread use in the field of energy metabolism, its application to the growing animal has been questioned Fasting heat production, or maintenance, rather than being a constant function of body size, has been shown to vary because of breed, sex, condition, physiological state, production level, nutrition level and environmental conditions Data are presented to show that fasting heat production and maintenance vary with nutritional level or rate of growth in animals postweaning Variation in these energy expenditures are related to variation in weight of metabolically active internal organs Weights of liver and gut and fasting heat production are shown to be functions of body size and level of production More information is needed to ascertain the primary components of energy expenditures in animals and to quantitatively relate these components to animal energy metabolism

Factors controlling concentration, export, and decomposition of dissolved organic nutrients in the Everglades of Florida

Abstract: Water draining from the Everglades marshes of southern Florida containshigh concentrations of dissolved organic C (DOC), N (DON), and in somelocations, P (DOP). These dissolved organic nutrients carry over 90% of the Nand organic C, and about 25% of the P exported downstream in the Everglades.Ourobjectives were to describe the most important aspects of the origin and fateofdissolved organic matter (DOM) in the Everglades, and to describe the processescontrolling its concentration and export. Concentrations of dissolved organicnutrients are influenced by local plant production, decomposition, and sorptionequilibrium with peat. The drained peat soils of the Everglades AgriculturalArea and the more productive marshes of the northern Everglades produce some ofthe highest concentrations of DOC and DON in the Everglades watershed. Inportions of the marshes of the northern Everglades, P enrichment was correlatedwith higher local DOC and DON concentrations and greater production of solubleplant matter. Microbial degradation of Everglades DOM was very slow; less than10% of the DOC was lost after 6 months of incubation in the laboratory andsupplements of inorganic nutrients failed to speed the decomposition. Exposureto solar radiation increased the subsequent decay rate of the remaining DOC(25%in 6 mo.). Solar radiation alone mineralized 20.5% of the DOC, 7%of the DON, and degraded about 50% of the humic substances over 21 days insterile porewater samples and thus degraded DOM faster than microbialdegradation. The humic substances appeared to inhibit biodegradation of theother fractions of the DOC since hydrophilic organic acids decomposed fasterwhen isolated from the humic substances.The fate of DOC and DON is closely linked as indicated by a generally narrowrange of C/N ratios. In contrast, high concentrations of DOP were associatedwith P enrichment (at least in pore water). The DOC was composed of about 50%humic substances, 33% hydrophilic acids, and 15% hydrophilic neutralsubstances,typical of DOC from other environments, despite the fact that it originatesfroma neutral to slightly alkaline peatland. Despite high exports of DON (3.9g m−2 y−1 from one area), themarshes of the northern Everglades are a sink for DON on a landscape scale. Theagricultural fields of the Everglades Agricultural Area, however, exported netquantities of DON. High concentrations of DOC desorbed from the agriculturalsoils when water with no DOC was added. Sorption experiments indicated thathighconcentrations of dissolved organic matter flowing into the marshes from theEverglades Agricultural Area could suppress the further desorption ofadditionalsoluble organic matter through physicochemical mechanisms. While biologicalfactors, plant production and microbial decomposition are important inproducingpotentially soluble organic nutrients, physicochemical sorption equilibria,hydrology, and degradation by solar radiation are also likely to control theexport of this material on the landscape scale.

An efficient method for isolation of RNA from tissue cultured plant cells

Abstract: Total cellular RNA has commonly been prepared from plant material utilizing methods involving CTAB (cetyltrimethylammonium bromide), SDS (sodium dodecyl sulfate), phenol/chloroform, or guanidine hydrochloride (Logemann et al, 1987). Although very effective in the preparation of intact RNA from leaf tissue, when applied to cultured plant cells these methods all result in a low yield and a substantial contamination by polysaccharides. The procedure outlined in this report is a substantial modification of a published method developed for minipreparation of plant leaf RNA (Verwoerd et al, 1989). Our method is specifically designed to reduce the amount of insoluble polysaccharides associated with cultured cell material and to maintain an efficient yield of intact RNA suitable for poly (A) enrichment and analysis of less abundant transcripts.