Accessory gland as a site for prothoracicotropic hormone controlled ecdysone synthesis in adult male insects

Insect steroid hormones (ecdysteroids) are important for female reproduction in many insect species and are required for the initiation and coordination of vital developmental processes. Ecdysteroids are also important for adult male physiology and behavior, but their exact function and site of synthesis remains unclear, although previous studies suggest that the reproductive system may be their source. We have examined expression profiles of the ecdysteroidogenic Halloween genes, during development and in adults of the flour beetle Tribolium castaneum. Genes required for the biosynthesis of ecdysone (E), the precursor of the molting hormone 20-hydroxyecdysone (20E), are expressed in the tubular accessory glands (TAGs) of adult males. In contrast, expression of the gene encoding the enzyme mediating 20E synthesis was detected in the ovaries of females. Further, Spookiest (Spot), an enzyme presumably required for endowing tissues with competence to produce ecdysteroids, is male specific and predominantly expressed in the TAGs. We also show that prothoracicotropic hormone (PTTH), a regulator of E synthesis during larval development, regulates ecdysteroid levels in the adult stage in Drosophila melanogaster and the gene for its receptor Torso seems to be expressed specifically in the accessory glands of males. The composite results suggest strongly that the accessory glands of adult male insects are the main source of E, but not 20E. The finding of a possible male-specific source of E raises the possibility that E and 20E have sex-specific roles analogous to the vertebrate sex steroids, where males produce primarily testosterone, the precursor of estradiol. Furthermore this study provides the first evidence that PTTH regulates ecdysteroid synthesis in the adult stage and could explain the original finding that some adult insects are a rich source of PTTH

Influence of laser energy density on the plasma expansion dynamics and film stoichiometry during laser ablation of BiSrCaCuO

The plasma expansion dynamics and the composition of films deposited during laser ablation of BiSrCaCuO at laser energy densities in a broad interval (1-6 J/cm2) have been studied by means of spatially resolved real time optical emission spectroscopy and Rutherford backscattering and nuclear reactive analysis, respectively. In vacuum, the velocity of the ejected species is found to increase as the energy density increases whereas the compositional and angular distribution of the deposited films remain unchanged. When an oxygen pressure of 10-1 mbar is applied, the film composition and angular distribution depend on the laser energy density. The results are analyzed in the frame of a collisional mechanism between the ejected and gas species, the effect of increasing the laser energy density being similar to that of decreasing the oxygen pressure. Finally, this competitive influence of the oxygen pressure and the energy density is discussed within the adiabatic expansion model. © 1996 American Institute of Physics.This work was partially supported under SCIENCE Project No. SCT-910753 and the CNRS (France) GDR No. 86. Dr. J. Solís (I. de Optica, Spain) is thanked for helpful discussions. One of us (J.G.) acknowledges a FPI grant from the Spanish Ministry of Educación y CienciaPeer Reviewe

The role of film re-emission and gas scattering processes on the stoichiometry of laser deposited films

Laser ablation of a BiSrCaCuO target is performed both in vacuum and in an oxygen pressure of 0.1 mbar. Two substrates are located in the chamber in order to study the role of re-emission processes from the growing film and/or the scattering of the ablated species by an oxygen atmosphere. The results indicate that re-emission processes from the growing film are very weak (they may affect up to 1% of the deposited material at most) and are not related to the re-sputtering of the growing film. Films grown in vacuum are found to have the correct cation composition, whereas those grown in an oxygen environment show significant variations which are clearly related to gas scattering processes.© 1995 American Institute of Physics.Peer Reviewe

Angular distribution of oxide films deposited by multi- or single-component laser ablation

The angular distribution of Bi-Ge-O and Ge-O films prepared by pulsed laser deposition in an oxygen pressure has been studied for different target-substrate distances using two configurations: ablation of multi-component (Bi12GeO20 (BGO) and GeO2) and single-component (Bi and Ge) targets. The results show that the angular distribution of Bi-Ge-O films obtained by alternate ablation of single-component targets is narrower than the one obtained by ablation of the multi-component target. In the case of Ge-O films, in which the multi-component target contains only one cation (Ge), no significant dependence of the angular distribution on the ablation configuration was observed. The results are discussed in terms of the existence of intraplume effects which enhance the broadening effect due to the atmosphere when ablating multi-component targets with two or more cations.This work has been partially supported by CICYT (Spain) and GDR 86 (CNRS, France).Peer Reviewe

The importance of gas scattering processes on the stoichiometry deviations of laser deposited films

Laser ablation of a BiSrCaCuO (2212) target is performed in vacuum, both in reactive (O2) and inert (Ar) atmospheres (0.1 mbar). Two substrates are properly located in the chamber in order to collect material from the scattering of the ablated species by the foreign atmosphere and from the re-emission and/or re-sputtering processes occurring in the growing films. The results show that the latter processes are very weak and may affect to 3% of the deposited material at the most. Whereas films deposited in vacuum are nearly stoichiometric, significant deviations are observed in the composition of films grown in the presence of a foreign gas, that are qualitatively similar in Ar and in O2 environments. The results show clearly that these deviations are related to scattering processes prior to deposition and not to chemical reactions in the gas phase or re-emission processes from the growing film. These scattering processes are more important for the lighter species, thus explaining the Bi enrichment of the films in the presence of a foreign gas.This work was partially supported under SCI- ENCE project SCT-910753 and the CNRS (France) GDR No. 86. We would like to thank to J.M. Ballesteros for experimental assistance. One of us (J.G) acknowledges a FPI grant from the Spanish Ministry of EducaciBn y Ciencia.Peer Reviewe

Growth of stoichiometric and textured LiNbO3 films on Si by pulsed laser deposition

Laser ablation of single-crystal LiNbO3 in a gas environment is used to grow films on (100) Si substrates heated to 650 °C. The film composition and crystallinity are studied as a function of the nature (reactive, O2, or inert, Ar) and pressure of the gas environment applied during deposition and cooling-down processes, the laser energy density and the target-substrate distance. Experimental results show that a gas pressure close to 1 mbar is required to produce stoichiometric films in either O2 or Ar. The modification of the laser energy density and the target-substrate distance allows us to improve the crystallinity of the films that become textured along the (006) direction. The influence of the experimental parameters on the film properties is discussed in the frame of the formation of a blast wave, that leads to the focusing of the expanding Li species and thus, to the increase of the Li content in the films.This work has been partially funded by CICYT (Spain) under the TIC96-0467 and TIC99-0866 projects. J.A.C. acknowledges a grant from the Ministerio de Educacion y Cultura (Spain).Peer Reviewe

Growth of Nd:potassium gadolinium tungstate (KGW) thin-film waveguides by pulsed laser deposition

Thin Nd-doped potassium gadolinium tungstate [KGW or KGd(WO4)2] films are grown by pulsed laser deposition by ablation of a stoichiometric monocrystal target. Rutherford backscattering, x-ray diffraction, atomic force microscopy, and waveguide propagation analyses are performed. The as-grown films are optically active, as evidenced by the photoluminescence spectra centered at 1.068 µm. In some of the films, fine photoluminescence spectra between Stark levels are observed