Testing semiochemicals from aphid, plant and conspecific: attraction of Harmonia axyridis (Pallas)

in Insect Science (2012), 19

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an invasive specie affecting the dynamics and composition of several guilds. Nowadays, no biological control method is available to reduce the ... [more ▼]

Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is an invasive specie affecting the dynamics and composition of several guilds. Nowadays, no biological control method is available to reduce the populations of this harmful coccinellid. Attractants and semiochemicals seem to be the best alternative but only few studies have tested the impact of semiochemicals on this Asian lady beetle. In this work, through wind-tunnel experiments, semiochemicals from aphids [Z,E-nepetalactone, (E)-β-farnesene, α-pinene and β-pinene], from coccinellids [(-)-β-caryophyllene] and from the nettle Urtica dioica L. were envisaged as potential attractants. The nettle volatile compounds [(Z)-3-hexenol and (E)-2-hexenal] were extracted using a Clevenger Apparatus® and identified by headspace-GC-MS. The main components of the aphid alarm pheromone as well as a component of the aphid sexual pheromone strongly attracted both sexes of the Asian lady beetle while (-)-β-caryophyllene only attracted few individuals and had no impact on the males. The nettle extract as well as the (Z)-3-hexenol oriented both males and females to the odour source. The (E)-2-hexenal was showed to have no effect on females even if this green leaf volatile attracted males. This study highlighted that some semiochemicals from aphids and from nettle extracts orientated the harlequin ladybird H. axyridis. These volatile compounds could certainly help for an efficient biological control approach against this invasive specie. [less ▲]

Testing the direct effect of CO2 concentration on a bloom of the coccolithophorid Emiliania huxleyi in mesocosm experiments

in Limnology and Oceanography (2005), 50(2), 493-507

We studied the direct effects of CO, and related changes in seawater carbonate chemistry on marine planktonic organisms in a mesocosm experiment. In nine outdoor enclosures (similar to 11 m(3) each), the ... [more ▼]

We studied the direct effects of CO, and related changes in seawater carbonate chemistry on marine planktonic organisms in a mesocosm experiment. In nine outdoor enclosures (similar to 11 m(3) each), the partial pressure of CO2 (pCO(2)) in the seawater was modified by an aeration system. The triplicate mesocosm treatments represented low (similar to 190 parts per million by volume (ppmV) CO2), present (similar to 410 ppmV CO2), and high (similar to 710 ppmV CO2) pCO(2) conditions. After initial fertilization with nitrate and phosphate a bloom dominated by the coccolithophorid Emiliania huxleyi occurred simultaneously in all of the nine mesocosms; it was monitored over a 19-day period, The three CO2 treatments assimilated nitrate and phosphate similarly. The concentration of particulate constituents was highly variable among the replicate mesocosms, disguising direct CO2-related effects. Normalization of production rates within each treatment, however, indicated that the net specific growth rate of E. huxleyi, the rate of calcification per cell, and the elemental stoichiometry of uptake and production processes were sensitive to changes in pCO(2). This broad influence of CO2 on the E huxleyi bloom suggests that changes in CO2 concentration directly affect cell physiology with likely effects on the marine biogeochemistry. [less ▲]

Testing the effects of opacity and the chemical mixture on the excitation of pulsations in B stars of the Magellanic Clouds

in Monthly Notices of the Royal Astronomical Society (2012), 422

The B-type pulsators known as β Cephei and slowly pulsating B (SPB) stars present pulsations driven by the κ mechanism, which operates thanks to an opacity bump due to the iron-group elements. In low ... [more ▼]

The B-type pulsators known as β Cephei and slowly pulsating B (SPB) stars present pulsations driven by the κ mechanism, which operates thanks to an opacity bump due to the iron-group elements. In low-metallicity environments such as the Magellanic Clouds, β Cep and SPB pulsations are not expected. Nevertheless, recent observations show evidence for the presence of B-type pulsator candidates in both galaxies. We seek an explanation for the excitation of β Cep and SPB modes in those galaxies by examining basic input physics in stellar modelling: (i) the specific metal mixture of B-type stars in the Magellanic Clouds and (ii) the role of a potential underestimation of stellar opacities. We first derive the present-day chemical mixtures of B-type stars in the Magellanic Clouds. Then, we compute stellar models for that metal mixture and perform a non-adiabatic analysis of these models. In the second approach, we simulate parametric enhancements of stellar opacities due to different iron-group elements. We then study their effects in models of B stars and their stability. We find that adopting a representative chemical mixture of B stars in the Small Magellanic Cloud cannot explain the presence of B-type pulsators there. An increase of the opacity in the region of the iron-group bump could drive B-type pulsations, but only if this increase occurs at the temperature corresponding to the maximum contribution of Ni to this opacity bump. We recommend an accurate computation of the Ni opacity to understand B-type pulsators in the Small Magellanic Cloud, as well as the frequency domain observed in some Galactic hybrid β Cep–SPB stars. [less ▲]

Testing the forward modeling approach in asteroseismology. I. Seismic solutions for the hot B subdwarf Balloon 090100001 with and without a priori mode identification

in Astronomy and Astrophysics (2008), 488

Context: Balloon 090100001, the brightest of the known pulsating hot B subdwarfs, exhibits simultaneoulsy both short- and long-period pulsation modes, and shows relatively large amplitudes for its ... [more ▼]

Context: Balloon 090100001, the brightest of the known pulsating hot B subdwarfs, exhibits simultaneoulsy both short- and long-period pulsation modes, and shows relatively large amplitudes for its dominant modes. For these reasons, it has been studied extensively over the past few years, including a successful experiment carried out at the Canada-France-Hawaii Telescope to pin down or constrain the value of the degree index ℓ of several pulsation modes through multicolor photometry. Aims: The primary goal of this paper is to take advantage of such partial mode identification to test the robustness of our standard approach to the asteroseismology of pulsating subdwarf B stars. The latter is based on the forward approach whereby a model that best matches the observed periods is searched for in parameter space with no a priori assumption about mode identification. When successful, this method leads to the determination of the global structural parameters of the pulsator. As a bonus, it also leads, after the fact, to complete mode identification. For the first time, with the availability of partial mode identification for Balloon 090100001, we are able to evaluate the sensitivity of the inferred seismic model to possible uncertainty in mode identification. Methods: We carry out a number of exercises based on the double optimization technique that we developed within the framework of the forward modeling approach in asteroseismology. We use the set of ten periods corresponding to the independent pulsation modes for which values of ℓ have been either formally identified or constrained through multicolor photometry in Balloon 090100001. These exercises differ in that they assume different a priori mode identification. Results: Our primary result is that the asteroseismic solution stands very robust, whether or not external constraints on the values of the degree ℓ are used. Although this may come as a small surprise, the test proves to be conclusive, and small differences in mode identification among the ten modes do not affect in any significant way, at the typical accuracy presently achieved, the final emergent seismic model. This is due to the structure of the p-mode pulsation spectra in sdB stars. In all cases, the inferred structural parameters of Balloon 090100001 remain practically unchanged. They correspond, and this constitutes our second important result, to a star beyond the TAEHB with T_eff = 28 000 ± 1 200 K, log g = 5.383 ± 0.004, M⋆/Msun = 0.432 ± 0.015, and log{M_env/M⋆} = -4.89 ± 0.14. Other structural parameters are also derived. [less ▲]

Testing the value of six taxonomic groups as biodiversity indicators at a local scale

in Conservation Biology (2004), 18(3), 667-675

We examined six groups of taxa - woody plants, aquatic and terrestrial herpetofauna, small terrestrial birds, orchids, and Orthoptera - to determine their efficiency as biodiversity indicators in the ... [more ▼]

We examined six groups of taxa - woody plants, aquatic and terrestrial herpetofauna, small terrestrial birds, orchids, and Orthoptera - to determine their efficiency as biodiversity indicators in the Dadia Reserve in northern Greece. We investigated the indicator value of each group by examining the degree of congruence of its species-richness pattern with that of the other groups and the efficiency of its complementary network in conserving the other groups and biodiversity. The two techniques differed in many respects in their outputs, but they both showed woody plants as the best biodiversity indicator. There was in general low congruence in the species richness patterns across the different groups. Significant relationships were found between woody plants and birds, Orthoptera and terrestrial herpetofauna, and birds and aquatic herpetofauna. None of the optimal complementary networks of the groups we examined protected all species of the other groups. Nevertheless, the complementary network of woody plants adequately conserved all groups except orchids. We conclude that the principle of complementarity must be integrated into the methodology of evaluating an indicator. In an applied context, our results provide a scientific background on which to base a biomonitoring program for the Dadia Reserve. In a wider scope, if the group of woody plants prove an adequate biodiversity indicator for other Mediterranean areas as well, this will be important because it will facilitate conservation-related decisions for the entire Mediterranean region. [less ▲]

Testosterone Effects on Neurotensin-Immunoreactive Cells in the Quail Preoptic Area

in Neuroreport (1994), 5(9), 1129-32

In the quail preoptic area (POA), neurotensin-immunoreactive (NT-ir) cells are mostly located in the sexually dimorphic medial preoptic nucleus (POM). They are more numerous in females than in males and ... [more ▼]

In the quail preoptic area (POA), neurotensin-immunoreactive (NT-ir) cells are mostly located in the sexually dimorphic medial preoptic nucleus (POM). They are more numerous in females than in males and, in females, their number varies during the ovulatory cycle. This suggests a control by steroids of NT expression in the POA. This idea was tested by comparing the NT-ir populations in gonadectomized males and females treated or not with testosterone. No sex differences in the NT-ir cell number was present in gonadectomized birds. Testosterone treatment increased the number of immunoreactive perikarya. This effect was anatomically specific and the increase was observed in the area caudal to the anterior commissure but not in POM itself. [less ▲]

Testostérone en cas de dysfonction érectile

in Louvain Medical (2010), 129 (2)

Pour une bonne érection, il faut surtout de l’oxygène et le taux de testostérone est le plus souvent suffisant. Néanmoins, malgré le mérite clinique peu intéressant de l’effet thérapeutique isolé de la ... [more ▼]

Pour une bonne érection, il faut surtout de l’oxygène et le taux de testostérone est le plus souvent suffisant. Néanmoins, malgré le mérite clinique peu intéressant de l’effet thérapeutique isolé de la testostérone chez le patient en dysfonction érectile, la recherche et le traitement d’un hypogonadisme reste vivement recommandé pour d’autres importantes raisons. [less ▲]

Testostérone et troubles de l'humeur

Conference (2007)

Testosterone metabolism and sexual behavior in the chick.

in Hormones and Behavior (1979), 12(3), 253-63

Testosterone Metabolism in the Avian Hypothalamus

in Journal of Steroid Biochemistry & Molecular Biology (1991), 40(4-6), 557-70

Many central actions of testosterone (T) require the transformation of T into several metabolites including 5 alpha-dihydrotestosterone (5 alpha-DHT) and estradiol (E2). In birds as in mammals, 5 alpha ... [more ▼]

Many central actions of testosterone (T) require the transformation of T into several metabolites including 5 alpha-dihydrotestosterone (5 alpha-DHT) and estradiol (E2). In birds as in mammals, 5 alpha-DHT and E2, alone or in combination, mimic most behavioral effects of T. The avian brain is, in addition, able to transform T into 5 beta-DHT, a metabolite which seems to be devoid of any behavioral or physiological effects, at least in the context of reproduction. By in vitro product-formation assays, we have analyzed the distribution, sex differences and regulation by steroids of the 3 main T metabolizing enzymes (aromatase, 5 alpha- and 5 beta-reductases) in the brain of the Japanese quail (Coturnix c. japonica) and the zebra finch (Taeniopygia guttata castanotis). In the hypothalamus of quail and finches, aromatase activity is higher in males than in females. It is also decreased by castration and increased by T. The activity of the 5 alpha-reductase is not sexually differentiated nor controlled by T. The 5 beta-reductase activity is often higher in females than in males but this difference disappears in gonadectomized birds and no clear effect of T can be observed at this level. The zebra finch brain also contains a number of steroid-sensitive telencephalic nuclei [e.g. hyperstriatum ventrale, pars caudale (HVc) and robustus archistriatalis (RA)] which play a key role in the control of vocalizations. These nuclei also contain T-metabolizing enzymes but the regulation of their activity is substantially different from what has been observed in the hypothalamus. Aromatase activity is for example higher in females than in males in HVc and RA and the enzyme in these nuclei is not affected by castration nor T treatment. In these nuclei, the 5 alpha-reductase activity is higher in males than in females and the reverse is true for the 5 beta-reductase. These sex differences in activity are not sensitive to gonadectomy and T treatment and might therefore be organized by neonatal steroids. We have been recently able to localize aromatase-immunoreactive (AR-ir) neurons by ICC in the brain of the quail and zebra finch. Positive cells are found in the preoptic area, ventromedial and tuberal hypothalamus. AR-ir material is found in the perikarya of cells and fills the entire cellular processes including axons. At the electron microscope level, immunoreactive material can clearly be observed in the synaptic boutons. This observation raises questions concerning the mode of action of estrogens produced by central aromatization of T. [less ▲]