Catching Element Formation In The Act

Gamma-ray astronomy explores the most energetic photons in nature to address some of the most pressing puzzles in contemporary astrophysics. It encompasses a wide range of objects and phenomena: stars, supernovae, novae, neutron stars, stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays and relativistic-particle acceleration, and the evolution of galaxies. MeV gamma-rays provide a unique probe of nuclear processes in astronomy, directly measuring radioactive decay, nuclear de-excitation, and positron annihilation. The substantial information carried by gamma-ray photons allows us to see deeper into these objects, the bulk of the power is often emitted at gamma-ray energies, and radioactivity provides a natural physical clock that adds unique information. New science will be driven by time-domain population studies at gamma-ray energies. This science is enabled by next-generation gamma-ray instruments with one to two orders of magnitude better sensitivity, larger sky coverage, and faster cadence than all previous gamma-ray instruments. This transformative capability permits: (a) the accurate identification of the gamma-ray emitting objects and correlations with observations taken at other wavelengths and with other messengers; (b) construction of new gamma-ray maps of the Milky Way and other nearby galaxies where extended regions are distinguished from point sources; and (c) considerable serendipitous science of scarce events -- nearby neutron star mergers, for example. Advances in technology push the performance of new gamma-ray instruments to address a wide set of astrophysical questions.Comment: 14 pages including 3 figure

Characterization of Meteorin-An Evolutionary Conserved Neurotrophic Factor

Growth factors control cellular growth, proliferation, and differentiation and may have therapeutic applications. In this study, we focus on Meteorin which is a member of a largely uncharacterized evolutionary conserved two-member growth factor family. Our analysis shows that Meteorin is expressed in the central nervous system both during development and in adult mice. Detailed immunohistological analysis of the adult mouse brain reveals that Meteorin is highly expressed in Bergmann glia and in a few discrete neuronal populations residing in the superior colliculus, the ocular motor nucleus, the raphe and pontine nuclei, and in various thalamic nuclei. In addition, low levels of Meteorin is found in astrocytes (S100 beta+, OX42-) distributed ubiquitously throughout the brain. Meteorin was cloned and recombinant protein purified allowing N-terminal sequencing and mass spectrometric analysis showing that Meteorin is secreted as an unmodified monomer. This form is bioactive as it induces neurite outgrowth from dorsal root ganglions in vitro. Intrastriatal protein injection and lentiviral studies in vivo showed that Meteorin is a highly diffusible molecule in the brain and cellular uptake is apparent in specific populations which may carry the receptor. In summary, we provide a comprehensive expression analysis and have made and thoroughly validated molecular tools to help investigate the therapeutic potential of Meteorin

Cometin is a novel neurotrophic factor that promotes neurite outgrowth and neuroblast migration in vitro and supports survival of spiral ganglion neurons in vivo

AbstractNeurotrophic factors are secreted proteins responsible for migration, growth and survival of neurons during development, and for maintenance and plasticity of adult neurons. Here we present a novel secreted protein named Cometin which together with Meteorin defines a new evolutionary conserved protein family. During early mouse development, Cometin is found exclusively in the floor plate and from E13.5 also in dorsal root ganglions and inner ear but apparently not in the adult nervous system. In vitro, Cometin promotes neurite outgrowth from dorsal root ganglion cells which can be blocked by inhibition of the Janus or MEK kinases. In this assay, additive effects of Cometin and Meteorin are observed indicating separate receptors. Furthermore, Cometin supports migration of neuroblasts from subventricular zone explants to the same extend as stromal cell derived factor 1a. Given the neurotrophic properties in vitro, combined with the restricted inner ear expression during development, we further investigated Cometin in relation to deafness. In neomycin deafened guinea pigs, two weeks intracochlear infusion of recombinant Cometin supports spiral ganglion neuron survival and function. In contrast to the control group receiving artificial perilymph, Cometin treated animals retain normal electrically-evoked brainstem response which is maintained several weeks after treatment cessation. Neuroprotection is also evident from stereological analysis of the spiral ganglion. Altogether, these studies show that Cometin is a potent new neurotrophic factor with therapeutic potential