Is there an oxidative cost of acute stress? Characterization, implication of glucocorticoids and modulation by prior stress experience

Acute rises in glucocorticoid hormones allow individuals to adaptively respond to environmental challenges but may also have negative consequences, including oxidative stress. While the effects of chronic glucocorticoid exposure on oxidative stress have been well characterized, those of acute stress or glucocorticoid exposure have mostly been overlooked. We examined the relationship between acute stress exposure, glucocorticoids and oxidative stress in Japanese quail (Coturnix japonica). We (i) characterized the pattern of oxidative stress during an acute stressor in two phenotypically distinct breeds; (ii) determined whether corticosterone ingestion, in the absence of acute stress, increased oxidative stress, which we call glucocorticoid-induced oxidative stress (GiOS); and (iii) explored how prior experience to stressful events affected GiOS. Both breeds exhibited an increase in oxidative stress in response to an acute stressor. Importantly, in the absence of acute stress, ingesting corticosterone caused an acute rise in plasma corticosterone and oxidative stress. Lastly, birds exposed to no previous acute stress or numerous stressful events had high levels of GiOS in response to acute stress, while birds with moderate prior exposure did not. Together, these findings suggest that an acute stress response results in GiOS, but prior experience to stressors may modulate that oxidative cost

Electrodeposition of Ordered Bi2Te3 Nanowire Arrays

2 páginas, 3 figuras.-- Communications to the Editor.Funding for this work was provided by the Department of Defense ONR-MURI on Thermoelectrics, N00014-97-1- 0516. A.L.P. thanks Lucent Technologies, Bell Labs for funding.Peer reviewe

Electrodeposition of Bi1-xSbx Films and 200-nm Wire Arrays from a Nonaqueous Solvent

6 páginas, 6 figuras, 1 tabla.Films and 200-nm wire arrays of Bi1-xSbx alloys, one of the best known low-temperature thermoelectric materials, have been obtained by electrodeposition without the need for complexing the Sb cations in solution or further thermal treatment after deposition. The process consists of reduction of Bi1-xSbx directly from a solution of Bi(NO3)3· 5H2O and SbCl3 in dimethyl sulfoxide at 25 °C on Pt electrodes. The electrodeposited films are polycrystalline and single phase under slow growth conditions, but two phases are observed under rapid growth conditions (more negative potentials) and for films with roughly equal amounts of Bi and Sb. 200-nm wire arrays of Bi1-xSbx were grown under similar conditions using porous alumina as a template. Arrays of dense, continuous, and highly crystalline Bi0.84Sb0.16 wires (close to the predicted optimum composition for thermoelectric applications) have been fabricated successfully at deposition potentials of −0.28 V vs Ag/AgCl from a solution of 0.050 M Bi and 0.030 M Sb in DMSO.This work was funded by the Office of Naval Research (ONR N00014-01-1-1058). Additional support was provided by the Department of Defense ONR-MURI on Thermoelectrics, N00014-97-1- 0516. M.S.M.G thanks the MEC/Fulbright Postdoctoral Fellowship program and A.L.P. thanks Lucent Technologies, Bell Labs for funding.Peer reviewe

Structure and properties of nanophase TiO/sub 2/

Ultrafine-grained, nanophase samples of TiO/sub 2/ (rutile) were synthesized by the gas-condensation method and subsequent in-situ compaction, and then studied by transmission electron microscopy, Vickers hardness measurements, and positron annihilation spectroscopy as a function of sintering temperature. The nanophase compacts densified rapidly above 500/sup 0/C, with only a small increase in grain size. The hardness values obtained by this method are comparable to or greater than coarser-grained compacts, but at temperatures 400 to 600/sup 0/C lower than conventional sintering temperatures and without the need for sintering aids. 11 refs., 3 figs

STRUCTURE AND PROPERTIES OF NANOPHASE TiO2

Echantillons, de TiO2 (rutile) nanophasé de grains ultrafins ont été synthétisés par la méthode de condensation dans un gaz, suivie ensuite par compaction en-situ, et étudiés par microscopie électronique en transmission, par microdureté de Vickers, et par spectroscopie d'annihilation positronique en fonction de température de frittage. La densité des échantillons augmente rapidement au-dessus de 500°C avec seulement une légère croissance de grains. La dureté obtenue par cette méthode, effectuée aux températures 400-600°C plus basses que la température de frittage conventionnel et sans avoir besoin des additives de frittage, est comparable on supérieure à celle des échantillons de gros grains.Ultrafine-grained, nanophase samples of TiO2 (rutile) were synthesized by the gas-condensation method and subsequent in-situ compaction, and then studied by transmission electron microscopy, Vickers hardness measurements, and positron annihilation spectroscopy as a function of sintering temperature. The nanophase compacts densified rapidly above 500°C, with only a small increase in grain size. The hardness values obtained by this method are comparable to or greater than coarser-grained compacts, but at temperatures 400 to 600°C lower than conventional sintering temperatures and without the need for sintering aids