In multiple sclerosis (MS), a chronic inflammatory relapsing demyelinating disease, failure to control or repair damage leads to progressive neurological dysfunction and neurodegeneration. Implantation of neural stem cells (NSCs) has been shown to promote repair and functional recovery in the acute experimental autoimmune encephalomyelitis (EAE) animal model for MS; the major therapeutic mechanism of these NSCs appeared to be immune regulation. In the present study, we examined the efficacy of intraventricularly injected NSCs in chronic relapsing experimental autoimmune encephalomyelitis (CREAE), the animal disease model that is widely accepted to mimic most closely recurrent inflammatory demyelination lesions as observed in relapsing-remitting MS. In addition, we assessed whether priming these NSCs to become oligodendrocyte precursor cells (OPCs) by transient overexpression of Olig2 would further promote functional recovery, for example, by contributing to actual remyelination. Upon injection at the onset of the acute phase or the relapse phase of CREAE, NSCs as well as Olig2-NSCs directly migrated toward active lesions in the spinal cord as visualized by in vivo bioluminescence and biofluorescence imaging, and once in the spinal cord, the majority of Olig2-NSCs, in contrast to NSCs, differentiated into OPCs. The survival of Olig2-NSCs was significantly higher than that of injected control NSCs, which remained undifferentiated. Nevertheless, both Olig2-NSCs and NSC significantly reduced the clinical signs of acute and relapsing disease and, in case of Olig2-NSCs, even completely abrogated relapsing disease when administered early after onset of acute disease. We provide the first evidence that NSCs and in particular NSC-derived OPCs (Olig2-NSCs) ameliorate established chronic relapsing EAE in mice. Our experimental data in established neurological disease in mice indicate that such therapy may be effective in relapsing-remitting MS preventing chronic progressive disease.
Small aperture telescopes provide the opportunity to conduct high frequency, targeted observations of near-Earth Asteroids that are not feasible with larger facilities due to highly competitive time allocation requirements. Observations of asteroids with these types of facilities often focus on rotational brightness variations rather than longer-term phase angle-dependent variations (phase curves) due to the difficulty of achieving high precision photometric calibration. We have developed an automated asteroid light curve extraction and calibration pipeline for images of moving objects from the 0.43 m Physics Innovations Robotic Telescope Explorer. This allows for the frequency and quality of observations required to construct asteroid phase curves. Optimizations in standard data reduction procedures are identified that may allow for similar small aperture facilities, constructed from commercially available/off-the-shelf components, to improve the image and subsequent data quality. A demonstration of the hardware and software capabilities is expressed through observation statistics from a 10 months observing campaign, and through the photometric characterization of near-Earth Asteroids 8014 (1990 MF) and 19764 (2000 NF5).
Phase curves of asteroids are typically considered to depend solely on the scattering properties of airless particulate surfaces and the size of the object being studied. In this study, we demonstrate the additional dependence of phase curves on object shape, rotation pole orientation, and viewing geometry over an apparition. Variations in the phase curve of near-Earth asteroid (159402) 1999 AP10 over its apparition from July 2020 - January 2021 are verified to be due to aspect changes over the apparition. This is achieved through shape modelling of the asteroid and simulation of the phase curve over the apparition. We present simulations of asteroid phase curves over a range of geometries to understand the potential magnitude of this aspect effect, and under which circumstances it can begin to dominate in the phase curves. This dependence on aspect may introduce significant additional uncertainty in the properties derived from phase curve data. We provide and demonstrate software code to estimate the aspect-related uncertainty in near-Earth asteroid phase curves through simulation and model fitting of a randomly generated sample of ellipsoidal asteroid models over the observed viewing geometry. We demonstrate how ignoring this effect may lead to misleading interpretations of the data and underestimation of uncertainties in further studies, such as those in the infrared that use phase curve derived parameters when fitting physical properties of an asteroid.
. BackgroundThe nature of asteroid phase curves is typically explained solely by the scattering properties of atmosphereless particulate surfaces. Models such as the H, G [1] and H, G1, G2 [2] systems aim to approximate the behaviour of these scattering properties without any assumption of the physical processes involved. However, these and other models are unable to account for changes in disk-integrated brightness of asteroids due to changing viewing aspect geometry during and between apparitions. If the viewing geometry of an asteroid changes rapidly, then the change in the cross-sectional area visible by the observer can impart modulations to the phase curve, becoming more significant for elongated asteroids [3]. These effects are likely to be significant for asteroids that undergo large changes to viewing aspect during apparitions, i.e. the near-Earth Asteroids (NEAs). Shape-induced modulations to phase curves limit the taxonomic information that can be extracted from parameters such as G, or G1 & G2. In this work we are aiming to characterise the magnitude of these shape effects, and investigate the potential error introduced into interpretation of individual phase curves.2. Modelling Phase Curve VariabilityTo study this effect, we have simulated asteroid phase curves for a variety of shapes over different geometries. Figure 1 describes one of these geometries that has the Earth kept fixed, with the asteroid sweeping past from south to north during a close approach with the Earth. We create ellipsoidal models, with a spherical model as a control, with differing pole orientations. The rotationally averaged reduced magnitudes for points along the orbit are simulated using a Hapke scattering model [4], using assumed S-type parameters based on (433) Eros [5].We note significant deviations from the spherical model for elongated objects over these geometries and observe clear separation of pre- and post-opposition phase curves for certain pole orientations (Figure 2). The large differences between these phase curves and the spherical model at high phase angles indicate that taxonomic information may be far more limited in individual phase curves of NEAs than previously thought. Using a single parameter taxonomic fitting method [6] we obtain a classification for the pre-opposition phase curve in Figure 2(c) as C-type, and for the post-opposition phase curve we obtain an E-type classification. The taxonomic classification using this method changes entirely based on when the asteroid is observed. The separation of the phase curve in Figure 2(c) is significantly larger at higher phase angles, underscoring the importance of this effect in NEA phase curves.3. Observational Detection of Phase Curve VariabilityPhase curve variability has been detected in rotationally averaged calibrated photometry from the PIRATE telescope of NEA (159402) 1999 AP10 over a single apparition from 2020-07-29 to 2021-01-24 (Figure 3). PIRATE is a 0.43m aperture telescope located at Observatorio del Teide, Tenerife. These observations were conducted as part of an ongoing NEA observation and facility characterisation project [7]. A convex shape model is constructed from the uncalibrated PIRATE photometric data and additional archival data from ALCDEF [8]. Using simulations of the phase curve over this apparition using the convex model and assumed S-type Hapke parameters we verify that the variability in the phase curve is a result of aspect changes during the apparition.4. Future WorkFurther work will investigate the potential impact of shape modulations to phase curves in the formulation and optimisation of the basis functions in phase curve models. Methods for extracting taxonomic information from phase curves with potential shape modifications will need to be developed to continue to aid the classification of NEAs from photometric data in existing and upcoming datasets (e.g. LSST).References[1] Bowell et al. 1989, in Asteroids II, 524[2] Muinonen et al. 2010, Icarus, 209, 542[3] Rozitis et al. 2020, Bulletin of the AAS, 52(6)[4] Hapke 1984, Icarus, 59, 41[5] Li et al. 2004, Icarus, 172, 415[6] Penttilä et al. 2016, Planetary and Space Science, 123, 117[7] Jackson et al. 2021, submitted to PASP[8] Stephens et al. 2018, AAS, DPS Meeting #50, id 417.03.
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