Active Mars: A Dynamic World.

Mars exhibits diverse surface changes at all latitudes and all seasons. Active processes include impact cratering, aeolian sand and dust transport, a variety of slope processes, changes in polar ices, and diverse effects of seasonal CO2 frost. The extent of surface change has been surprising and indicates that the present climate is capable of reshaping the surface. Activity has important implications for the Amazonian history of Mars: understanding processes is a necessary step before we can understand their implications and variations over time.

A Survey of Small-Scale Waves and Wave-Like Phenomena in Jupiter's Atmosphere Detected by JunoCam.

In the first 20 orbits of the Juno spacecraft around Jupiter, we have identified a variety of wave-like features in images made by its public-outreach camera, JunoCam. Because of Juno's unprecedented and repeated proximity to Jupiter's cloud tops during its close approaches, JunoCam has detected more wave structures than any previous surveys. Most of the waves appear in long wave packets, oriented east-west and populated by narrow wave crests. Spacing between crests were measured as small as ~30 km, shorter than any previously measured. Some waves are associated with atmospheric features, but others are not ostensibly associated with any visible cloud phenomena and thus may be generated by dynamical forcing below the visible cloud tops. Some waves also appear to be converging, and others appear to be overlapping, possibly at different atmospheric levels. Another type of wave has a series of fronts that appear to be radiating outward from the center of a cyclone. Most of these waves appear within 5° of latitude from the equator, but we have detected waves covering planetocentric latitudes between 20°S and 45°N. The great majority of the waves appear in regions associated with prograde motions of the mean zonal flow. Juno was unable to measure the velocity of wave features to diagnose the wave types due to its close and rapid flybys. However, both by our own upper limits on wave motions and by analogy with previous measurements, we expect that the waves JunoCam detected near the equator are inertia-gravity waves.

Functional Characterization of Abicipar-Pegol, an Anti-VEGF DARPin Therapeutic That Potently Inhibits Angiogenesis and Vascular Permeability.

Purpose: DARPin molecules are a novel class of small proteins that contain engineered ankyrin repeat domain(s) and bind to target proteins with high specificity and affinity. Abicipar-pegol (abicipar), a DARPin molecule targeting vascular endothelial growth factor-A (VEGF-A), is currently under evaluation in patients with age-related macular degeneration. The pharmacodynamic properties of abicipar were characterized using in vivo and in vitro assays. Methods: The binding affinity of abicipar was assessed using a kinetic exclusion assay (KinExA). In vitro assays evaluated abicipar effects on VEGF-A165-induced calcium mobilization and tube formation in human umbilical vein endothelial cells. Abicipar was tested in vivo in a mouse model of corneal neovascularization and a rabbit model of chronic retinal neovascularization. The efficacies of abicipar and ranibizumab were compared in a rabbit model of VEGF-A165-induced retinal vasculopathy. Results: Abicipar has a high affinity for the soluble isoforms of VEGF-A; binding affinities for human VEGF-A165 are approximately 100-fold greater than those of ranibizumab and bevacizumab and are similar for rat VEGF-A164 but approximately 20-fold lower for rabbit VEGF-A165. Abicipar was effective in cell-based and in vivo models of angiogenesis and vascular leak, blocking neovascularization in a mouse model of corneal neovascularization and vascular permeability in a rabbit model of chronic neovascularization. In a rabbit model of VEGF-A165-induced vasculopathy, the duration of effect of abicipar was longer than ranibizumab when the two compounds were administered at molar-equivalent doses. Conclusions: These data support the testing of abicipar as a treatment for retinal diseases characterized by neovascularization and vascular leak.

Enceladus Plume Structure and Time Variability: Comparison of Cassini Observations.

During three low-altitude (99, 66, 66 km) flybys through the Enceladus plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Science Subsystem (ISS) imaging observations of the plume's icy component have been reported, which constrain the locations and orientations of the numerous gas/grain jets. In the present study, we used these ISS imaging results, together with ultraviolet imaging spectrograph stellar and solar occultation measurements and modeling of the three-dimensional structure of the vapor cloud, to constrain the magnitudes, velocities, and time variability of the plume gas sources from the INMS data. Our results confirm a mixture of both low and high Mach gas emission from Enceladus' surface tiger stripes, with gas accelerated as fast as Mach 10 before escaping the surface. The vapor source fluxes and jet intensities/densities vary dramatically and stochastically, up to a factor 10, both spatially along the tiger stripes and over time between flyby observations. This complex spatial variability and dynamics may result from time-variable tidal stress fields interacting with subsurface fissure geometry and tortuosity beyond detectability, including changing gas pathways to the surface, and fluid flow and boiling in response evolving lithostatic stress conditions. The total plume gas source has 30% uncertainty depending on the contributions assumed for adiabatic and nonadiabatic gas expansion/acceleration to the high Mach emission. The overall vapor plume source rate exhibits stochastic time variability up to a factor ∼5 between observations, reflecting that found in the individual gas sources/jets. Key Words: Cassini at Saturn-Geysers-Enceladus-Gas dynamics-Icy satellites. Astrobiology 17, 926-940.

Dune-slope activity due to frost and wind throughout the north polar erg, Mars.

Repeat, high-resolution imaging of dunes within the Martian north polar erg have shown that these dune slopes are very active, with alcoves forming along the dune brink each Mars year. In some areas, a few hundred cubic metres of downslope sand movement have been observed, sometimes moving the dune brink 'backwards'. Based on morphological and activity-timing similarities of these north polar features to southern dune gullies, identifying the processes forming these features is likely to have relevance for understanding the general evolution/modification of dune gullies. To determine alcove-formation model constraints, we have surveyed seven dune fields, each over 1-4 Mars winters. Consistent with earlier reports, we found that alcove-formation activity occurs during the autumn-winter seasons, before or while the stable seasonal frost layer is deposited. We propose a new model in which alcove formation occurs during the autumn, and springtime sublimation activity then enhances the feature. Summertime winds blow sand into the new alcoves, erasing small alcoves over a few Mars years. Based on the observed rate of alcove erasure, we estimated the effective aeolian sand transport flux. From this, we proposed that alcove formation may account for 2-20% of the total sand movement within these dune fields.

Retinal gene expression and visually evoked behavior in diabetic long evans rats.

PURPOSE: Patients with diabetic retinopathy may experience severe vision loss due to macular edema and neovascularization secondary to vascular abnormalities. However, before these abnormalities become apparent, there are functional deficits in contrast sensitivity, color perception, and dark adaptation. The goals of this study are to evaluate early changes (up to 3 months) in retinal gene expression, selected visual cycle proteins, and optokinetic tracking (OKT) in streptozotocin (STZ)-induced diabetic rats. METHODS: Retinal gene expression in diabetic Long Evans rats was measured by whole genome microarray 7 days, 4 weeks, and 3 months after the onset of hyperglycemia. Select gene and protein changes were probed by polymerase chain reaction (PCR) and immunohistochemistry, respectively, and OKT thresholds were measured using a virtual optokinetics system. RESULTS: Microarray analysis showed that the most consistently affected molecular and cellular functions were cell-to-cell signaling and interaction, cell death, cellular growth and proliferation, molecular transport, and cellular movement. Further analysis revealed reduced expression of several genes encoding visual cycle proteins including lecithin/retinol acyltransferase (LRAT), retinal pigment epithelium (RPE)-specific protein 65 kDa (RPE65), and RPE retinal G protein-coupled receptor (RGR). These molecular changes occurred simultaneously with a decrease in OKT thresholds by 4 weeks of diabetes. Immunohistochemistry revealed a decrease in RPE65 in the RPE layer of diabetic rats after 3 months of hyperglycemia. CONCLUSIONS: The data presented here are further evidence that inner retinal cells are affected by hyperglycemia simultaneously with blood retinal barrier breakdown, suggesting that glial and neuronal dysfunction may underlie some of the early visual deficits in persons with diabetes.

Enceladus' water vapor plume.

The Cassini spacecraft flew close to Saturn's small moon Enceladus three times in 2005. Cassini's UltraViolet Imaging Spectrograph observed stellar occultations on two flybys and confirmed the existence, composition, and regionally confined nature of a water vapor plume in the south polar region of Enceladus. This plume provides an adequate amount of water to resupply losses from Saturn's E ring and to be the dominant source of the neutral OH and atomic oxygen that fill the Saturnian system.

Ultraviolet imaging spectroscopy shows an active saturnian system.

Neutral oxygen in the saturnian system shows variability, and the total number of oxygen atoms peaks at 4 x 10(34). Saturn's aurora brightens in response to solar-wind forcing, and the auroral spectrum resembles Jupiter's. Phoebe's surface shows variable water-ice content, and the data indicate it originated in the outer solar system. Saturn's rings also show variable water abundance, with the purest ice in the outermost A ring. This radial variation is consistent with initially pure water ice bombarded by meteors, but smaller radial structures may indicate collisional transport and recent renewal events in the past 10(7) to 10(8) years.