Positional changes of pericentromeric heterochromatin and nucleoli in postmitotic Purkinje cells during murine cerebellum development

Previous studies revealed changes of pericentromeric heterochromatin arrangements in postmitotic Purkinje cells (PCs) during postnatal development in the mouse cerebellum (Manuelidis, 1985; Martou and De Boni, 2000). Here, we performed vibratome sections of mouse cerebellum (vermis) at P0 (day of birth), at various stages of the postnatal development (P2-P21), as well as in very young (P28) and 17-months-old adults. FISH was carried out on these sections with major mouse satellite DNA in combination with immunostaining of the nucleolar protein B23 (nucleophosmin). Laser confocal microscopy, 3D reconstructions and quantitative image analysis were employed to describe changes in the number and topology of chromocenters and nucleoli. At all stages of postnatal PC development heterochromatin clusters were typically associated either with nucleoli or with the nuclear periphery, while non-associated clusters were rare (<1% at P0 to P21 and about 3% in adult stages). At P0, about 2-4 nucleoli and 7-8 pericentromeric heterochromatin clusters were variably located within PC nuclei. The relative volume of heterochromatin clusters associated with the nucleoli (about 50%) was roughly equal to the volume of clusters associated with the nuclear periphery. Positional changes of both nucleoli and centromeres towards the nuclear center occurred between P0 and P6. At P6 the average number of chromocenters per PC nucleus had decreased to about five. In agreement with previous studies, one or occasionally two nucleoli were noted at the nuclear center surrounded by major perinucleolar heterochromatin clusters. The relative volume of these perinucleolar clusters increased to about 84%, while the volume of clusters in the nuclear periphery decreased to about 15%. At subsequent postnatal stages, the arrangement of most pericentromeric heterochromatin around a central nucleolus was maintained. In adult animals, however, we observed a partial redistribution of heterochromatin towards the nuclear periphery. The average total number of pericentromeric heterochromatin signals increased again to about ten. The volume of heterochromatin associated with the nuclear periphery roughly doubled (30%), while the volume of the perinucleolar heterochromatin decreased correspondingly. Copyright (C) 2004 S. Karger AG, Basel

Vortex solutions of the Lifshitz-Chern-Simons theory

We study vortex-like solutions to the Lifshitz-Chern-Simons theory. We find that such solutions exists and have a logarithmically divergent energy, which suggests that a Kostelitz-Thouless transition may occur, in which voxtex-antivortex pairs are created above a critical temperature. Following a suggestion made by Callan and Wilzcek for the global U(1) scalar field model, we study vortex solutions of the Lifshitz-Chern-Simons model formulated on the hyperbolic plane, finding that, as expected, the resulting configurations have finite energy. For completeness, we also explore Lifshitz-Chern-Simons vortex solutions on the sphere.Comment: Published version, added appendix on electromagnetic duality in Lifshitz system

Generalized Pomeranchuk instabilities in graphene

We study the presence of Pomeranchuk instabilities induced by interactions on a Fermi liquid description of a graphene layer. Using a recently developed generalization of Pomeranchuk method we present a phase diagram in the space of fillings versus on-site and nearest neighbors interactions. Interestingly, we find that for both interactions being repulsive an instability region exists near the Van Hove filling, in agreement with earlier theoretical work. In contrast, near half filling, the Fermi liquid behavior appears to be stable, in agreement with theoretical results and experimental findings using ARPES. The method allows for a description of the complete phase diagram for arbitrary filling.Comment: 9 pages, 3 figure

The Conserved G-Protein Coupled Receptor FSHR-1 Regulates Protective Host Responses to Infection and Oxidative Stress

The innate immune system’s ability to sense an infection is critical so that it can rapidly respond if pathogenic microorganisms threaten the host, but otherwise maintain a quiescent baseline state to avoid causing damage to the host or to commensal microorganisms. One important mechanism for discriminating between pathogenic and non-pathogenic bacteria is the recognition of cellular damage caused by a pathogen during the course of infection. InCaenorhabditis elegans, the conserved G-protein coupled receptor FSHR-1 is an important constituent of the innate immune response. FSHR-1 activates the expression of antimicrobial infection response genes in infected worms and delays accumulation of the ingested pathogenPseudomonas aeruginosa. FSHR-1 is central not only to the worm’s survival of infection by multiple pathogens, but also to the worm’s survival of xenobiotic cadmium and oxidative stresses. Infected worms produce reactive oxygen species to fight off the pathogens; FSHR-1 is required at the site of infection for the expression of detoxifying genes that protect the host from collateral damage caused by this defense response. Finally, the FSHR-1 pathway is important for the ability of worms to discriminate pathogenic from benign bacteria and subsequently initiate an aversive learning program that promotes selective pathogen avoidance

Dyons in Nonabelian Born-Infeld Theory

We analyze a nonabelian extension of Born--Infeld action for the SU(2) group. In the class of spherically symmetric solutions we find that, besides the Gal'tsov--Kerner glueballs, only the analytic dyons have finite energy. The presented analytic and numerical investigation excludes the existence of pure magnetic monopoles of 't Hooft--Polyakov type.Comment: 12 pages, 3 figure

Integration of SARS-CoV-2 RNA in infected human cells by retrotransposons: an unlikely hypothesis and old viral relationships

Zhang et al. (Proc Natl Acad Sci 118:e2105968118, 2021) recently reported that SARS-CoV-2 RNA can be retrotranscribed and integrated into the DNA of human cells by the L1 retrotransposon machinery. This phenomenon could cause persistence of viral sequences in patients and may explain the prolonged PCR-positivity of SARS-CoV-2 infected patients, even long after the phase of active virus replication has ended. This commentary does critically review the available data on this topic and discusses them in the context of findings made for other exogenous viruses and ancestral endogenous retroviral elements

Incidence of the boundary shape in the effective theory of fractional quantum Hall edges

Starting from a microscopic description of a system of strongly interacting electrons in a strong magnetic field in a finite geometry, we construct the boundary low energy effective theory for a fractional quantum Hall droplet taking into account the effects of a smooth edge. The effective theory obtained is the standard chiral boson theory (chiral Luttinger theory) with an additional self-interacting term which is induced by the boundary. As an example of the consequences of this model, we show that such modification leads to a non-universal reduction in the tunnelling exponent which is independent of the filling fraction. This is in qualitative agreement with experiments, that systematically found exponents smaller than those predicted by the ordinary chiral Luttinger liquid theory.Comment: 12 pages, minor changes, replaced by published versio