DETERMINATION OF SENSORY OIL-WATER PARTITION COEFFICIENTS OF SINGLE AROMA COMPOUNDS COMBINING PANELIST FREE INTENSITY RATING AND THEORETICAL MODELING OF ODOR INTENSITY

Using an intensity rating with no external calibration, experiments were designed to measure the sensory oil-water partition coefficients of four aroma molecules (benzaldehyde, ethyl butyrate, linalool and acetophenone) as the ratios of concentration producing stimuli of equivalent intensities. Flavored water and oil phases were successively assessed for odor intensity by 24 panelists who were given total freedom regarding scaling strategy. Each session combined five concentration levels of three out of the four studied aromas in a solvent (water or oil). A predominant concentration effect was found for each aroma in both solvents and concentration dependencies of perceived intensity above water and oil were similar. Experimental data were modeled with Fechner, Stevens and Hill equations. Combining results above water and oil solutions to feed a common model led to the evaluation of an overall sensory oil-water partition coefficient for each aroma compound. All three models produced similar partition coefficient values for each aroma that were lower than the related instrumental partition coefficients. Biases previously detected when external calibration had been used were reduced in a large proportion while suggested enhancement of odor intensity by water vapor could not be excluded.     

Acclimation of isoprene emission and photosynthesis to growth temperature in hybrid aspen: resolving structural and physiological controls

Acclimation of foliage to growth temperature involves both structural and physiological modifications, but the relative importance of these two mechanisms of acclimation is poorly known, especially for isoprene emission responses. We grew hybrid aspen (Populus tremula x P. tremuloides) under control (day/night temperature of 25/20 °C) and high temperature conditions (35/27 °C) to gain insight into the structural and physiological acclimation controls. Growth at high temperature resulted in larger and thinner leaves with smaller and more densely packed chloroplasts and with lower leaf dry mass per area (M_A). High growth temperature also led to lower photosynthetic and respiration rates, isoprene emission rate and leaf pigment content and isoprene substrate dimethylallyl diphosphate pool size per unit area, but to greater stomatal conductance. However, all physiological characteristics were similar when expressed per unit dry mass, indicating that the area‐based differences were primarily driven by M_A. Acclimation to high temperature further increased heat stability of photosynthesis and increased activation energies for isoprene emission and isoprene synthase rate constant. This study demonstrates that temperature acclimation of photosynthetic and isoprene emission characteristics per unit leaf area were primarily driven by structural modifications, and we argue that future studies investigating acclimation to growth temperature must consider structural modifications.     

Different stomatal responses of maize leaves after blue or red illumination under anoxia

Abstract In normal air, illumination with a low level of blue or red light (40 μmol m^?2 s^?1) did not induce stomatal opening in maize plantlets. In CO₂-free air, 40 μmol m^?2 s^?1 of blue or red light promoted an enhancement in stomatal opening. At the same quantum flux, blue light was more efficient than red light and stomatal closure occurred more rapidly with a significantly shorter lag phase after blue light. Anoxia inhibited light-dependent stomatal opening, even under 320 μmol m^?2 s^?1 illumination. However, after 60 min of illumination with 40 μmol m^?2 s^?1 of blue light in anoxia, transient stomatal opening was observed when the plant was returned to darkness and normal air. This transient stomatal opening was weaker after pretreatment with red light. We conclude that a blue-light-dependent process induced under anoxia leads to stomatal opening provided oxygen is present. Possible mechanisms associated with blue-light-effect and the nature of the oxygen-consuming processes are discussed.     

Mating systems and territory in Lapwings Vanellus vanellus

In a population of Lapwings Vanellus vanellus studied for 5 years near Bergen, southwester Norway, 23–41% of the males were polygynous, having two and sometimes three mates, whereas 50–77% were monogamous and 0–21% remained unmated. Bachelors held territories in or immediately adjacent to the study area each of the years. As predicted from the Polygyny Threshold model, primary females generally laid eggs earlier than monogamous females, but the overlap in laying dates was substantial between these two classes. The number of females and start of breeding on the territories were analysed in relation to nine variables pertaining to safety from predation and to food. Of these, territory size correlated most consistently with number of females (positively) and the laying of first egg (negatively). Numbers of females observed were not significantly different from numbers expected from territory size in 4 out of 5 years; however, earlier start of breeding on large territories indicated that females did not settle according to the Neutral Mate Choice model. The Female-biased Sex Ratio hypothesis was refuted, unmated territorial males being available throughout the breeding seasons.     

Bacteria and algae in stream periphyton along a nutrient gradient

1. Stream riffles in southern Ontario and western Quèbec were sampled for biomass (58 stations from 51 streams) and production (22 stations from 21 streams) of algae and bacteria in periphyton to test the hypothesis that bacteria in benthic biofilms compete with algae for nutrients. 2. Algal and bacterial biomass were positively correlated, as were algal and bacterial production. Bacterial production was also positively correlated to algal and bacterial biomass, but the relationship was not significant. The ratio of algal to bacterial biomass did not vary with nutrients whereas algal production tended to increase with nutrients more rapidly than bacterial production. 3. Instream nitrogen concentrations explained 38–58% of the variability in algal biomass and production. Bacterial abundance explained an additional 9–29% of the residual variance in algal production and biomass. However, the relationship between bacterial abundance and algal production and biomass, once nutrients were taken into account, was positive, in contrast to the predicted effect of competition. 4. Hence, we reject our original hypothesis that bacteria in biofilms compete with algae for nutrients and instead suggest that bacteria and algae in biofilms coexist in an association that offers space and resources to sustain production of both groups of organisms.     

Overexpression of progesterone receptor B increases sensitivity of human colon muscle cells to progesterone

Colon muscle strips and cells from female patients with slow-transit constipation (STC) exhibit impaired motility, signal transduction abnormalities characterized by downregulation of Gq/11 and upregulation of Gs proteins, decreased cyclooxygenase (COX)-1 and thromboxane (Tx)B2 levels, increased COX-2 and PGE2 levels, and overexpression of progesterone receptors (PGR). Progesterone (P4) treatment of normal cells reproduced these motility and signal transduction abnormalities. The purpose of the study was to examine whether overexpression of PGR-B reproduces these abnormalities by rendering the cells more sensitive to physiological concentrations of P4. Cultured human colon muscle was transfected with a plasmid DNA expressing PGR-B. The mRNAs of PGR, COX-1, COX-2, and Gq/11 were determined by quantitative real-time PCR. Their protein expression was determined by Western blot, and prostaglandins were measured by radioimmunoassay. Cultured muscle cells maintained their phenotypic features determined with myosin light chain (MLC) and h-caldesmon antibodies. Control and transfected muscle cells responded to 10(-6) M P4. In contrast, muscle cells transfected with PGR-B responded to lower P4 concentration (10(-7) M). This P4 concentration reduced MLC phosphorylation induced by CCK-8 (10(-8) M), downregulated Gq/11, and decreased COX-1 and TxB2 levels. It upregulated Gs proteins. It also increased COX-2 and PGE2 levels. We conclude that overexpression of PGR-B renders the cells more sensitive to physiological concentrations of P4. These results are consistent with the hypothesis that overexpression of PGR-B contributes to the motility and signal transduction abnormalities observed in female patients with STC and normal serum levels of P4.     

Adipokinetic hormone counteracts oxidative stress elicited in insects by hydrogen peroxide: in vivo and in vitro study

The role of adipokinetic hormone (AKH) in counteracting oxidative stress elicited in the insect body is studied in response to exogenously applied hydrogen peroxide, an important metabolite of oxidative processes. In vivo experiments reveal that the injection of hydrogen peroxide (8 µmol) into the haemocoel of the firebug, Pyrrhocoris apterus L. (Heteroptera: Pyrrhocoridae) increases the level of AKH by 2.8‐fold in the central nervous system (CNS) and by 3.8‐fold in the haemolymph. The injection of hydrogen peroxide also increases the mortality of experimental insects, whereas co‐injection of hydrogen peroxide with Pyrap‐AKH (40 pmol) reduces mortality to almost control levels. Importantly, an increase in haemolymph protein carbonyl levels (i.e. an oxidative stress biomarker) elicited by hydrogen peroxide is decreased by 3.6‐fold to control levels when hydrogen peroxide is co‐injected with Pyrap‐AKH. Similar results are obtained using in vitro experiments. Oxidative stress biomarkers such as malondialdehyde and protein carbonyls are significantly enhanced upon exposure of the isolated CNS to hydrogen peroxide in vitro, whereas co‐treatment of the CNS with hydrogen peroxide and Pyrap‐AKH reduces levels significantly. Moreover, a marked decrease in catalase activity compared with controls is recorded when the CNS is incubated with hydrogen peroxide. Incubation of the CNS with hydrogen peroxide and Pyrap‐AKH together curbs the negative effect on catalase activity. Taken together, the results of the present study provide strong support for the recently published data on the feedback regulation between oxidative stressors and AKH action, and implicate AKH in counteracting oxidative stress. The in vitro experiments should facilitate research on the mode of action of AKH in relation to oxidative stress, and could help clarify the key pathways involved in this process.