Regulation of neuronal excitability through pumilio-dependent control of a sodium channel gene

Dynamic changes in synaptic connectivity and strength, which occur during both embryonic development and learning, have the tendency to destabilize neural circuits. To overcome this, neurons have developed a diversity of homeostatic mechanisms to maintain firing within physiologically defined limits. In this study, we show that activity-dependent control of mRNA for a specific voltage-gated Na+ channel [encoded by paralytic (para)] contributes to the regulation of membrane excitability in Drosophila motoneurons. Quantification of para mRNA, by real-time reverse-transcription PCR, shows that levels are significantly decreased in CNSs in which synaptic excitation is elevated, whereas, conversely, they are significantly increased when synaptic vesicle release is blocked. Quantification of mRNA encoding the translational repressor pumilio (pum) reveals a reciprocal regulation to that seen for para. Pumilio is sufficient to influence para mRNA. Thus, para mRNA is significantly elevated in a loss-of-function allele of pum (pumbemused), whereas expression of a full-length pum transgene is sufficient to reduce para mRNA. In the absence of pum, increased synaptic excitation fails to reduce para mRNA, showing that Pum is also necessary for activity-dependent regulation of para mRNA. Analysis of voltage-gated Na+ current (INa) mediated by para in two identified motoneurons (termed aCC and RP2) reveals that removal of pum is sufficient to increase one of two separable INa components (persistent INa), whereas overexpression of a pum transgene is sufficient to suppress both components (transient and persistent). We show, through use of anemone toxin (ATX II), that alteration in persistent INa is sufficient to regulate membrane excitability in these two motoneurons

Pumilio binds para mRNA and requires nanos and brat to regulate sodium current in drosophila motoneurons

Homeostatic regulation of ionic currents is of paramount importance during periods of synaptic growth or remodeling. Our previous work has identified the translational repressor Pumilio (Pum) as a regulator of sodium current (INa) and excitability in Drosophila motoneurons. In this current study, we show that Pum is able to bind directly the mRNA encoding the Drosophila voltage-gated sodium channel paralytic (para). We identify a putative binding site for Pum in the 3' end of the para open reading frame (ORF). Characterization of the mechanism of action of Pum, using whole-cell patch clamp and real-time reverse transcription-PCR, reveals that the full-length protein is required for translational repression of para mRNA. Additionally, the cofactor Nanos is essential for Pum-dependent para repression, whereas the requirement for Brain Tumor (Brat) is cell type specific. Thus, Pum-dependent regulation of INa in motoneurons requires both Nanos and Brat, whereas regulation in other neuronal types seemingly requires only Nanos but not Brat. We also show that Pum is able to reduce the level of nanos mRNA and as such identify a potential negative-feedback mechanism to protect neurons from overactivity of Pum. Finally, we show coupling between INa (para) and IK (Shal) such that Pum-mediated change in para results in a compensatory change in Shal. The identification of para as a direct target of Pum represents the first ion channel to be translationally regulated by this repressor and the location of the binding motif is the first example in an ORF rather than in the canonical 3'-untranslated region of target transcripts

Characterization of the visit-to-visit Stability of the GR700XD Spectral Traces for NIRISS/SOSS Observations

In this report, we present the results of our analysis of trace position changes during NIRISS/SOSS observations. We examine the visit-to-visit impact of the GR700XD pupil wheel (PW) position alignment on trace positions for spectral orders 1 and 2 using the data obtained to date. Our goal is to improve the wavelength solution by correlating the trace positions on the detector with the PW position angle. We find that there is a one-to-one correspondence between PW position and spectral trace rotation for both orders. This allowed us in turn to find an analytic model that is able to predict a trace position/shape as a function of PW position with sub-pixel accuracy of about ~0.1 pixels. Such a function can be used to predict the trace position in low signal-to-noise ratio cases, and/or as a template to track trace position changes as function of time in Time Series Observations (TSOs).Comment: 9 pages, package to predict spectral traces for NIRISS/SOSS: https://github.com/spacetelescope/pastasos

Characterization of the visit-to-visit Stability of the GR700XD Wavelength Calibration for NIRISS/SOSS Observations

When utilizing the NIRISS/SOSS mode on JWST, the pupil wheel (tasked with orienting the GR700XD grism into the optical path) does not consistently settle into its commanded position resulting in a minor misalignment with deviations of a few fractions of a degree. These small offsets subsequently introduce noticeable changes in the trace positions of the NIRISS SOSS spectral orders between visits. This inconsistency, in turn, can lead to variations of the wavelength solution. In this report, we present the visit-to-visit characterization of the NIRISS GR700XD Wavelength Calibration for spectral orders 1 and 2. Employing data from Calibration Program 1512 (PI: Espinoza), which intentionally and randomly sampled assorted pupil wheel positions during observations of the A-star BD+60-1753, as well as data from preceding commissioning and calibration activities to model this effect, we demonstrate that the wavelength solution can fluctuate in a predictable fashion between visits by up to a few pixels. We show that via two independent polynomial regression models for spectral orders 1 and 2, respectively, using the measured x-pixel positions of known Hydrogen absorption features in the A-star spectra and pupil wheel positions as regressors, we can accurately predict the wavelength solution for a particular visit with an RMS error within a few tenths of a pixel. We incorporate these models in PASTASOSS, a Python package for predicting the GR700XD spectral traces, which now allows to accurately predict spectral trace positions and their associated wavelengths for any NIRISS/SOSS observation.Comment: 12 pages, package to predict wavelength solution for NIRISS/SOSS: https://github.com/spacetelescope/pastasos

Exploring Venus with Balloons - Science Objectives and Mission Architectures for Small and Medium-Class Missions

This presentation was part of the session : Current Planetary Probe Science and TechnologySixth International Planetary Probe WorkshopFollowing the trailblazing flights of the 1985 twin Soviet VEGA balloons, missions to fly in the skies of Venus have been proposed to both NASA's Discovery Program and ESA's Cosmic Visions amd are currently being planned for NASA's next Frontiers Mission opportunity. Such missions will answer fundamental science issues highlighted in a variety of high-level NASA-authorized science documents in recent years, including the Decadal Study, various NASA roadmaps, and recommendations coming out of the Venus Exploration Analysis Group (VEXAG). Such missions would in particular address key questions of Venus's origin, evolution, and current state, including detailed measurements of (1) trace gases associated with Venus's active photo- and thermo-chemistry and (2) measurements of vertical motions and local temperature which characterize convective and wave processes. As an example of what can be done with small and medium class missions (less than $900M and$500M, respectively), the Venus Aerostatic-Lift Observatories for in-situ Research (VALOR) Discovery and New Frontiers mission concepts will be discussed. Floating in Venus's rapid windstream near an altitude of 55 km, VALOR's twin balloon-borne aerostats will sample rare gases and trace chemicals and measure vertical and horizontal motions and cloud aerosols within Venus's dynamic middle cloud layer. Each balloon will explore a distinctive dynamical/meteorological region within Venus's energetic atmosphere as each circles the globe for over a week, with one drifting in the cloudy north polar region and the other flying in the less-cloudy but more convective temperate region. The New Frontiers concept would carry several drop sondes that would provide vertical profiles from 55 km down to the surface of temperature, pressure, winds, and the abundances of key reactive gases including SO2, CO, and H2O. In addition, each drop sonde would obtain stereoscopic images and spectra of the surface. Each of these VALOR missions would test a variety of scenarios for the origin, formation, and evolution of Venus by sampling all the noble gases and their isotopes, especially the heaviest elements never reliably measured previously, xenon and krypton. Riding the gravity and planetary waves of Venus a la the VEGA balloons in 1985, the VALOR balloons would sample in particular the chemistry and dynamics of Venus's sulfur-cloud meteorology. Tracked by an array of Earth-based telescopes, zonal, meridional, and vertical winds would be measured with unprecedented precision. Such measurements will help in developing our fundamental understanding of (1) the circulation of Venus, including the role of waves in powering the planet's poorly-understood super-rotation, (2) the nature of Venus's sulfur cycle, key to Venus's current climate, and (3) how Earth's neighbor formed and evolved over the aeons.NAS

Cassini atmospheric chemistry mapper. Volume 1. Investigation and technical plan

The Cassini Atmospheric Chemistry Mapper (ACM) enables a broad range of atmospheric science investigations for Saturn and Titan by providing high spectral and spatial resolution mapping and occultation capabilities at 3 and 5 microns. ACM can directly address the major atmospheric science objectives for Saturn and for Titan, as defined by the Announcement of Opportunity, with pivotal diagnostic measurements not accessible to any other proposed Cassini instrument. ACM determines mixing ratios for atmospheric molecules from spectral line profiles for an important and extensive volume of the atmosphere of Saturn (and Jupiter). Spatial and vertical profiles of disequilibrium species abundances define Saturn's deep atmosphere, its chemistry, and its vertical transport phenomena. ACM spectral maps provide a unique means to interpret atmospheric conditions in the deep (approximately 1000 bar) atmosphere of Saturn. Deep chemistry and vertical transport is inferred from the vertical and horizontal distribution of a series of disequilibrium species. Solar occultations provide a method to bridge the altitude range in Saturn's (and Titan's) atmosphere that is not accessible to radio science, thermal infrared, and UV spectroscopy with temperature measurements to plus or minus 2K from the analysis of molecular line ratios and to attain an high sensitivity for low-abundance chemical species in the very large column densities that may be achieved during occultations for Saturn. For Titan, ACM solar occultations yield very well resolved (1/6 scale height) vertical mixing ratios column abundances for atmospheric molecular constituents. Occultations also provide for detecting abundant species very high in the upper atmosphere, while at greater depths, detecting the isotopes of C and O, constraining the production mechanisms, and/or sources for the above species. ACM measures the vertical and horizontal distribution of aerosols via their opacity at 3 microns and, particularly, at 5 microns. ACM recovers spatially-resolved atmospheric temperatures in Titan's troposphere via 3- and 5-microns spectral transitions. Together, the mixing ratio profiles and the aerosol distributions are utilized to investigate the photochemistry of the stratosphere and consequent formation processes for aerosols. Finally, ring opacities, observed during solar occultations and in reflected sunlight, provide a measurement of the particle size and distribution of ring material. ACM will be the first high spectral resolution mapping spectrometer on an outer planet mission for atmospheric studies while retaining a high resolution spatial mapping capability. ACM, thus, opens an entirely new range of orbital scientific studies of the origin, physio-chemical evolution and structure of the Saturn and Titan atmospheres. ACM provides high angular resolution spectral maps, viewing nadir and near-limb thermal radiation and reflected sunlight; sounds planetary limbs, spatially resolving vertical profiles to several atmospheric scale heights; and measures solar occultations, mapping both atmospheres and rings. ACM's high spectral and spatial resolution mapping capability is achieved with a simplified Fourier Transform spectrometer with a no-moving parts, physically compact design. ACM's simplicity guarantees an inherent stability essential for reliable performance throughout the lengthy Cassini Orbiter mission

Infrared observations of planetary atmospheres

The goal of this research in to obtain infrared data on planetary atmospheres which provide information on several aspects of structure and composition. Observations include direct mission real-time support as well as baseline monitoring preceding mission encounters. Besides providing a broader information context for spacecraft experiment data analysis, observations will provide the quantitative data base required for designing optimum remote sensing sequences and evaluating competing science priorities. In the past year, thermal images of Jupiter and Saturn were made near their oppositions in order to monitor long-term changes in their atmospheres. Infrared images of the Jovian polar stratospheric hot spots were made with IUE observations of auroral emissions. An exploratory 5-micrometer spectrum of Uranus was reduced and accepted for publication. An analysis of time-variability of temperature and cloud properties of the Jovian atomsphere was made. Development of geometric reduction programs for imaging data was initiated for the sun workstation. Near-infrared imaging observations of Jupiter were reduced and a preliminary analysis of cloud properties made. The first images of the full disk of Jupiter with a near-infrared array camera were acquired. Narrow-band (10/cm) images of Jupiter and Saturn were obtained with acousto-optical filters

Carmody Groarke & Phil Baines: Three contemporary memorials in London

The exhibition documents the collaboration between architect and lettering designer in the design of three permanent memorials for London. Each of the completed memorials are testaments to the close conversations between the disciplines of these two art-practices – a close synthesis of architecture and lettering design. The exhibition shows the process and inspirations behind both architectural and lettering designs and how both practices worked to forge these ideas into a cohesive, sculptural whole in each unique memorial. The work describes the innate connection (and necessary tension) in a memorial between emotional and pragmatic, figurative and abstract, historic and contemporary, ephemeral and eternal, form and substance, lettering and materials that are required for such a unique public commission. This process illustrates not only the integration of the design of the memorials into their physical, historical, cultural and social context, but the consideration of the necessary integration of the experience of the visitor in the presence of this architecture. The collaborative process reinforces the intention of bringing meaning to the memorial through its making and illustrates an approach where the place, material and message are of equal measure. This approach reminds us of the responsibility of a memorial, as a permanent reminder for society to ‘stop one forgetting’ the unique circumstances that shattered the order of so many people’s lives

Assessing the Potential of Stratospheric Balloons for Planetary Science

Recent developments in high altitude balloon platform capabilities, specifically long duration flights in excess of 50 days at over 100,000 ft and precision pointing with performance at the arc sec level or better have raised the question whether this platform can be utilized for high-value planetary science observations. In January of 2012 a workshop was held at NASA Glenn Research Center in Cleveland, Ohio to explore what planetary science can be achieved utilizing such a platform. Over 40 science concepts were identified by the scientists and engineers attending the workshop. Those ideas were captured and then posted to a public website for all interested planetary scientists to review and give their comments. The results of the workshop, and subsequent community review, have demonstrated that this platform appears to have potential for high-value science at very competitive costs. Given these positive results, the assessment process was extended to include 1) examining, in more detail, the requirements for the gondola platform and the mission scenarios 2) identifying technical challenges and 3) developing one or more platform concepts in enough fidelity to enable accurate estimating of development and mission costs. This paper provides a review of the assessment, a summary of the achievable science and the challenges to make that science a reality with this platform