Sphingosine Phosphate Lyase Expression Is Essential for Normal Development in Caenorhabditis elegans

Sphingolipids are ubiquitous membrane constituents whose metabolites function as signaling molecules in eukaryotic cells. Sphingosine 1-phosphate, a key sphingolipid second messenger, regulates proliferation, motility, invasiveness, and programmed cell death. These effects of sphingosine 1-phosphate and similar phosphorylated sphingoid bases have been observed in organisms as diverse as yeast and humans. Intracellular levels of sphingosine 1-phosphate are tightly regulated by the actions of sphingosine kinase, which is responsible for its synthesis and sphingosine-1-phosphate phosphatase and sphingosine phosphate lyase, the two enzymes responsible for its catabolism. In this study, we describe the cloning of the Caenorhabditis elegans sphingosine phosphate lyase gene along with its functional expression in Saccharomyces cerevisiae. Promoter analysis indicates tissue-specific and developmental regulation of sphingosine phosphate lyase gene expression. Inhibition of C. elegans sphingosine phosphate lyase expression by RNA interference causes accumulation of phosphorylated and unphosphorylated long-chain bases and leads to poor feeding, delayed growth, reproductive abnormalities, and intestinal damage similar to the effects seen with exposure to Bacillus thuringiensis toxin. Our results show that sphingosine phosphate lyase is an essential gene in C. elegans and suggest that the sphingolipid degradative pathway plays a conserved role in regulating animal development

Rapid soft X-ray fluctuations in solar flares observed with the X-ray polychromator

Three flares observed by the Soft X-Ray Polychromator on the Solar Maximum Mission were studied. Flare light curves from the Flat Crystal Spectrometer and Bent Crystal Spectrometer were examined for rapid signal variations. Each flare was characterized by an initial fast (less than 1 min) burst, observed by the Hard X-Ray Burst Spectrometer (HXRBS), followed by softer gradual X-ray emission lasting several minutes. From an autocorrelation function analysis, evidence was found for quasi-periodic fluctuations with rise and decay times of 10 s in the Ca XIX and Fe XXV light curves. These variations were of small amplitude (less than 20%), often coincided with hard X-ray emissions, and were prominent during the onset of the gradual phase after the initial hard X-ray burst. It is speculated that these fluctuations were caused by repeated energy injections in a coronal loop that had already been heated and filled with dense plasma associated with the initial hard X-ray burst

Group Theory of Chiral Photonic Crystals with 4-fold Symmetry: Band Structure and S-Parameters of Eight-Fold Intergrown Gyroid Nets

The Single Gyroid, or srs, nanostructure has attracted interest as a circular-polarisation sensitive photonic material. We develop a group theoretical and scattering matrix method, applicable to any photonic crystal with symmetry I432, to demonstrate the remarkable chiral-optical properties of a generalised structure called 8-srs, obtained by intergrowth of eight equal-handed srs nets. Exploiting the presence of four-fold rotations, Bloch modes corresponding to the irreducible representations E- and E+ are identified as the sole and non-interacting transmission channels for right- and left-circularly polarised light, respectively. For plane waves incident on a finite slab of the 8-srs, the reflection rates for both circular polarisations are identical for all frequencies and transmission rates are identical up to a critical frequency below which scattering in the far field is restricted to zero grating order. Simulations show the optical activity of the lossless dielectric 8-srs to be large, comparable to metallic metamaterials, demonstrating its potential as a nanofabricated photonic material

Group Theory of Circular-Polarization Effects in Chiral Photonic Crystals with Four-Fold Rotation Axes, Applied to the Eight-Fold Intergrowth of Gyroid Nets

We use group or representation theory and scattering matrix calculations to derive analytical results for the band structure topology and the scattering parameters, applicable to any chiral photonic crystal with body-centered cubic symmetry I432 for circularly-polarised incident light. We demonstrate in particular that all bands along the cubic [100] direction can be identified with the irreducible representations E+/-,A and B of the C4 point group. E+ and E- modes represent the only transmission channels for plane waves with wave vector along the ? line, and can be identified as non-interacting transmission channels for right- (E-) and left-circularly polarised light (E+), respectively. Scattering matrix calculations provide explicit relationships for the transmission and reflectance amplitudes through a finite slab which guarantee equal transmission rates for both polarisations and vanishing ellipticity below a critical frequency, yet allowing for finite rotation of the polarisation plane. All results are verified numerically for the so-called 8-srs geometry, consisting of eight interwoven equal-handed dielectric Gyroid networks embedded in air. The combination of vanishing losses, vanishing ellipticity, near-perfect transmission and optical activity comparable to that of metallic meta-materials makes this geometry an attractive design for nanofabricated photonic materials

Atom interferometry with Bose-Einstein condensates in a double-well potential

A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein condensates coherently split by deforming an optical single-well potential into a double-well potential. The relative phase between the two condensates was determined from the spatial phase of the matter wave interference pattern formed upon releasing the condensates from the separated potential wells. Coherent phase evolution was observed for condensates held separated by 13 $\mu$m for up to 5 ms and was controlled by applying ac Stark shift potentials to either of the two separated condensates.Comment: 4 pages, 4 figure

Regulation of Sphingosine-1-phosphate Lyase Gene Expression by Members of the GATA Family of Transcription Factors

Sphingosine-1-phosphate is a bioactive sphingolipid that regulates proliferation, differentiation, migration, and apoptosis. Sphingosine-1-phosphate is irreversibly degraded by the highly conserved enzyme sphingosine-1-phosphate lyase. Recent studies have suggested that sphingosine-1-phosphate lyase expression affects animal development and cell fate decisions. Despite its crucial role, mechanisms affecting expression of sphingosine-1-phosphate lyase remain poorly understood. In this study, regulation of sphingosine-1-phosphate lyase gene expression was investigated in Caenorhabditis elegans, where lyase expression is spatially restricted to cells of the developing and adult gut and is essential for normal development. Deletion analysis and generation of transgenic worms combined with fluorescence microscopy identified a 350-nucleotide sequence upstream of the ATG start site necessary for maximal lyase expression in adult worms. Site-specific mutagenesis of a GATA transcription factor-binding motif in the promoter led to loss of reporter expression. Knockdown of the gut-specific GATA transcription factor ELT-2 by RNA interference similarly led to loss of reporter expression. ELT-2 interacted with the GATA factor-binding motif in vitro and was also capable of driving expression of a Caenorhabditis elegans lyase promoter-{beta}-galactosidase reporter in a heterologous yeast system. These studies demonstrate that ELT-2 regulates sphingosine-1-phosphate lyase expression in vivo. Additionally, we demonstrate that the human sphingosine-1-phosphate lyase gene is regulated by a GATA transcription factor. Overexpression of GATA-4 led to both an increase in activity of a reporter gene as well as an increase in endogenous sphingosine-1-phosphate lyase protein

The Cathodoluminescence Mode of the Scanning Electron Microscope: A Powerful Microcharacterization Technique

By detecting cathodoluminescence (CL) in a scanning electron microscope (SEM), pan and monochromatic micrographs and CL spectral analyses analogous to x-ray mode point analyses can be obtained. Complete microcharacterization requires alternate examination of both micrographs and spectra. New techniques for near infra-red CL and low-temperatures to produce sharp spectra are of increasing importance. CL emission is due to electron transitions between quantum mechanical states so the radiative defects present can be unambiguously identified at liquid helium temperatures. Strongly luminescent impurities can be detected to below one part in 108. This is 104 times as sensitive as the x-ray mode (electron probe microanalysis). Only luminescent impurities can be detected and quantitative analyses by CL have not yet been attempted. There is a rapidly increasing use of the CL mode for the study of industrially important problems and for the study of the electronic effects of dislocations in semiconductors

Distillation of Bose-Einstein condensates in a double-well potential

Bose-Einstein condensates of sodium atoms, prepared in an optical dipole trap, were distilled into a second empty dipole trap adjacent to the first one. The distillation was driven by thermal atoms spilling over the potential barrier separating the two wells and then forming a new condensate. This process serves as a model system for metastability in condensates, provides a test for quantum kinetic theories of condensate formation, and also represents a novel technique for creating or replenishing condensates in new locations

Optical Weak Link between Two Spatially Separate Bose-Einstein Condensates

Two spatially separate Bose-Einstein condensates were prepared in an optical double-well potential. A bidirectional coupling between the two condensates was established by two pairs of Bragg beams which continuously outcoupled atoms in opposite directions. The atomic currents induced by the optical coupling depend on the relative phase of the two condensates and on an additional controllable coupling phase. This was observed through symmetric and antisymmetric correlations between the two outcoupled atom fluxes. A Josephson optical coupling of two condensates in a ring geometry is proposed. The continuous outcoupling method was used to monitor slow relative motions of two elongated condensates and characterize the trapping potential.Comment: 4 pages, 5 figure