Description: The Kronian moon Enceladus is constantly feeding its surrounding with new gas and dust, from cryovolcanoes located in its south polar region. Through photoionization and impact ionization of these neutrals a plasma disk is created, which mainly contains hydrogen ions and water group ions. This paper investigates the importance of ion loss by outward radial transport and ion loss by dissociative recombination, which is the dominant chemical loss process in the inner plasma disk. We use plasma densities derived from several years of measurements by the Cassini Radio and Plasma Wave Science (RPWS) electric field power spectral density and Langmuir probe (LP), to calculate the total flux tube content N L 2 . Our calculation shows that N L 2 agrees well with earlier estimates within dipole L shell 8. We also show that loss by transport dominates chemical loss in between L shells 4 and 10. Using extrapolation of available measurements we extend the study to include L shells 2.5 to 4. The results indicate that loss by transport dominates chemical loss also in between L shells 2.5 and 4. The loss rate by transport is ∼5 times larger at L shell 5 and the difference increase as L 7.7 beyond L = 5, for the net ion population. Chemical loss may still be important for the structure of the plasma disk in the region closest to Enceladus (around ±0.5 R S ) at 3.95 R S (1 R S = Saturn's equatorial radius = 60,268 km), since the transport and chemical loss rates only differ by a factor of ∼2 in this region. We also derive the total plasma content of the plasma disk in between L shells 4 and 10 to be 1.9×10 33 ions, and the total ion source rate for the same region to be 5.8×10 27 s −1 . The equatorial ion production rate P , ranges from 2.6×10 −5 cm −3 s −1 (at L = 10) to 1.1×10 −4 cm −3 s −1 (at L = 4.8). The net mass loading rate is derived to be 123 kg/s for L shells 4 to 10.

Description: Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene that result in loss of the dystrophin–glycoprotein complex, a laminin receptor that connects the myofiber to its surrounding extracellular matrix. Utrophin, a dystrophin ortholog that is normally localized to the neuromuscular junction, is naturally upregulated in DMD muscle, which partially compensates for the loss of dystrophin. Transgenic overexpression of utrophin causes broad sarcolemma localization of utrophin, restoration of laminin binding and amelioration of disease in the mdx mouse model of DMD. We previously demonstrated that overexpression of sarcospan, a dystrophin- and utrophin-binding protein, ameliorates mdx muscular dystrophy. Sarcospan boosts levels of utrophin to therapeutic levels at the sarcolemma, where attachment to laminin is restored. However, understanding the compensatory mechanism is complicated by concomitant upregulation of α7β1 integrin, which also binds laminin. Similar to the effects of utrophin, transgenic overexpression of α7 integrin prevents DMD disease in mice and is accompanied by increased abundance of utrophin around the extra-synaptic sarcolemma. In order to investigate the mechanisms underlying sarcospan ‘rescue’ of muscular dystrophy, we created double-knockout mice to test the contributions of utrophin or α7 integrin. We show that sarcospan-mediated amelioration of muscular dystrophy in DMD mice is dependent on the presence of both utrophin and α7β1 integrin, even when they are individually expressed at therapeutic levels. Furthermore, we found that association of sarcospan into laminin-binding complexes is dependent on utrophin and α7β1 integrin.

Description: We recently identified pathogenic KIF1B β mutations in sympathetic nervous system malignancies that are defective in developmental apoptosis. Here we deleted KIF1B β in the mouse sympathetic nervous system and observed impaired sympathetic nervous function and misexpression of genes required for sympathoadrenal lineage differentiation. We discovered that KIF1Bβ is required for nerve growth factor (NGF)-dependent neuronal differentiation through anterograde transport of the NGF receptor TRKA. Moreover, pathogenic KIF1B β mutations identified in neuroblastoma impair TRKA transport. Expression of neuronal differentiation markers is ablated in both KIF1B β-deficient mouse neuroblasts and human neuroblastomas that lack KIF1Bβ. Transcriptomic analyses show that unfavorable neuroblastomas resemble mouse sympathetic neuroblasts lacking KIF1Bβ independent of MYCN amplification and the loss of genes neighboring KIF1B on chromosome 1p36. Thus, defective precursor cell differentiation, a common trait of aggressive childhood malignancies, is a pathogenic effect of KIF1Bβ loss in neuroblastomas. Furthermore, neuropathy-associated KIF1Bβ mutations impede cargo transport, providing a direct link between neuroblastomas and neurodegeneration.

Description: Photoelectron peaks in the 20-30 e V energy range are commonly observed in the planetary atmospheres, produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons are known to escape the planet down its tail, making them tracers for the atmospheric escape. Furthermore, their presence or absence allow to define the so-called PhotoElectron Boundary (PEB), that separates the photoelectron dominated ionosphere from the external environment. We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile Evolution (MAVEN) electron and magnetic field data obtained from September 2014 until May 2016 (including 1696 PEB crossings). The PEB appears as mostly sensitive to the solar wind dynamic and crustal fields pressures. Its variable altitude thus leads to a variable wake cross section for escape (up to ∼+50 % ), which is important for deriving escape rates. The PEB is not always sharp, and is characterized on average by : a magnetic field topology typical for the end of Magnetic Pile Up Region above it, more field aligned fluxes above than below, and a clear change of the altitude slopes of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and fields configurations determined by the draping topology of the interplanetary magnetic field around Mars and much influenced by the crustal field sources below, whose dynamics also impacts the estimated escape rate of ionospheric plasma.