Thyrotroph Embryonic Factor Regulates Light-Induced Transcription of Repair Genes in Zebrafish Embryonic Cells

Numerous responses are triggered by light in the cell. How the light signal is detected and transduced into a cellular response is still an enigma. Each zebrafish cell has the capacity to directly detect light, making this organism particularly suitable for the study of light dependent transcription. To gain insight into the light signalling mechanism we identified genes that are activated by light exposure at an early embryonic stage, when specialised light sensing organs have not yet formed. We screened over 14,900 genes using micro-array GeneChips, and identified 19 light-induced genes that function primarily in light signalling, stress response, and DNA repair. Here we reveal that PAR Response Elements are present in all promoters of the light-induced genes, and demonstrate a pivotal role for the PAR bZip transcription factor Thyrotroph embryonic factor (Tef) in regulating the majority of light-induced genes. We show that tefβ transcription is directly regulated by light while transcription of tefα is under circadian clock control at later stages of development. These data leads us to propose their involvement in light-induced UV tolerance in the zebrafish embryo

Formation and spectral characterisation of Bragg gratings in standard single-mode optical fibers

Permanent Bragg gratings in monomode optical fibers are obtained by irradiation through an interference pattern of an ultraviolet laser. The main parameters of such gratings, in particular the index modulation amplitude and their length, are precisely determined by a fine adjustment between the measured reflectivity and a theoretical curve. Gratings have been formed in a standard monomode telecommunication fiber, with reflectivities above 90% and with bandwidths on the order of 1 to 3 nm. Their reflectivity spectra are symmetric and comparable with theoretical curves. Index modulations up to 1.2 10-3 have been determined, which is more than one order of magnitude greater than earlier reported. A precise knowledge of the maximal index change allows one to know the formation possibilities of gratings with regard to reflectivity and bandwidt

Bragg gratings with directional, efficient, and wavelength-selective fiber outcoupling

Wavelength demultiplexing is a very promising application of photoinduced fiber gratings. In this paper efficient outcoupling of a very narrow wavelength band, in addition to the usual guided Bragg reflection, is presented. The selective outcoupling gratings were fabricated by focusing the irradiation beam to a dimension smaller than the core diameter of a standard fiber. The highly selective outcoupling of such devices might increase the multiplexing densit

All Optical Up-Conversion of WLAN signal in 60 GHz Range with Side-Band Suppression

International audienc

Correlation of index changes with stress changes in fibers containing UV-written Bragg gratings

Strong correlation between index change and stress change in irradiated optical fibers is reported. The stress increases with fluence. Stress changes and hence index changes seem to be due to a compaction of the fiber cor

Nondestructive method for measuring the degree of cluster-induced quenching in Er3+-doped waveguides and fibers

Ion clustering is one of the major dissipative processes in the operation of Er3+-doped planar waveguide amplifiers and heavily doped fiber amplifiers. We propose and demonstrate a nondestructive method for measuring the fraction of erbium ions in doped planar waveguides and fibers that are quenched by ultrafast parasitic energy transfer in ion pairs or clusters. The method is based on unsaturable absorption measurements in the 980-nm absorption band. By combining transmission data at resonance with the corresponding data for radiation outside the absorption band, the influence of background and coupling losses can be eliminated. (C) 1998 Optical Society of America

Fiber grating characterization by OLCR measurements

Fiber gratings are investigated with optical low coherence reflectometry. This novel method allows to measure accurately the location and the length of the gratings and to evaluate their coupling constant with a precision of up to 2