1873-1874, End of a Century?: Time and Space in Valera's Pepita Jiménez, Ros de Olano's Jornadas de retorno, and Alarcón's El sombrero de tres picos and La Alpujarra

This article argues for the existence of a literature of the first Spanish Republic in the early 1870s. Valera's Pepita Jimenez makes sense in relation to this literature, rather than in comparison with 'Realism'. The literature of the first republic is distinguished by two facets: an ongoing dialogue with Ros de Olano's experiments in simultaneous compression and extension of form; and a belief that the nineteenth-century revolutionary spirit of the age has reached a critical end point, and needs reinvention that leads to Restoration politics

Statistical Mechanics of Horizontal Gene Transfer in Evolutionary Ecology

The biological world, especially its majority microbial component, is strongly interacting and may be dominated by collective effects. In this review, we provide a brief introduction for statistical physicists of the way in which living cells communicate genetically through transferred genes, as well as the ways in which they can reorganize their genomes in response to environmental pressure. We discuss how genome evolution can be thought of as related to the physical phenomenon of annealing, and describe the sense in which genomes can be said to exhibit an analogue of information entropy. As a direct application of these ideas, we analyze the variation with ocean depth of transposons in marine microbial genomes, predicting trends that are consistent with recent observations using metagenomic surveys.Comment: Accepted by Journal of Statistical Physic

MODAL BISTABILITY IN A GaAlAs LEAKY WAVEGUIDE

We report the observation of power dependent mode changes leading to a nonlinear transmission response and optical bistability in a GaAlAs leaky slab waveguide. The dominant mechanism appears to be an optothermal nonlinearity

Productive CD4-dependent HIV-1 fusion, entry and infection dynamically studied by Total Internal Reflection Fluorescence Microscopy in living cells

Background: Membrane trafficking cooperates with HIV-1 fusion with plasma membrane of target cells independently of virus tropism. TIRFM is a tool that can dynamically study CD4- dependent HIV-1 fusion, entry, viral assembly and release from the surface of permissive cells. While regulation of early HIV-1 infection by Arf6 activity seems to be related to fusion and entry steps of the viral cycle we agreed to characterize by TIRFM the function of Arf6-mediated membrane dynamics on HIV-1 entry and infection. Observations: We observed that TZM-bl cells over-expressing the Arf6-Q67L and Arf6-T44N constructs exhibited accumula- tion of PIP2-associated structures on plasma membrane. TIRFM studies revealed that wt-Arf6-, Arf6-Q67L- and Arf6-T44N-ECFP constructs did not co-localize with cell-surface CD4-DsRed, and HIV-1 binding to CD4 did not promote co-distribution of CD4 with Arf6 constructs. Finally, we performed TIRFM studies from the CD4-dependent HIV-1 uptake process by using fluorescent HIV-1-Gag-EGFP viral particles in permissive TZM-bl (CD4+/ CXCR4+/CCR5+) cells transiently expressing fluorescent CD4-DsRed together with one of the different Arf6-HA construct and the PH-ECFP probe. Our results indicated that alteration of Arf6-mediated PIP2-membrane dynamics by over-express- ing Arf6-Q67L-HA or Arf6-T44-HA mutant prevented produc- tive CD4-dependent HIV-1 uptake. Moreover, endogenous Arf6 knock-down did not affect the first CD4-DsRed/HIV-1-Gag-EGFP interaction, but prevented CD4-dependent viral uptake. Blocking plasma membrane dynamics by Arf6-Q67L and Arf6-T44N over-expression or by specific Arf6 silencing did not inhibit cell infection by HIV-1 vectors pseudotyped with the VSV-G protein. Conclusions: Arf6-GTP/GDP cooperates with HIV-1-cell receptors interactions, by maintaining PIP2-associated membrane dynamics to promote viral fusion and entry. Arf6- coordinated plasma membrane dynamics is required for an efficient HIV-1 membrane fusion, viral entry and infection of permissive CD4+T lymphocytes

HIV-1 requires Arf6-mediated membrane dynamics to efficiently enter and infect T lymphocytes

Background: As the initial barrier to viral entry, the plasma membrane along with membrane trafficking machinery and cytoskeleton are of fundamental importance in the viral cycle. However little is known about the contribution of plasma membrane dynamics during early HIV-1 infection. ARF6 regulates cellular invasion via several microorganisms by coordi- nating membrane trafficking. Our aim was to study the function of ARF6-mediated membrane dynamics on HIV-1 entry and infection of T lymphocytes. Observations: We observed that an alteration of the ARF6-GTP/ GDP cycle, by expression of GDP-bound or GTP-bound inactive mutants or by specific ARF6 silencing, significantly inhibited HIV-1 infection of T lymphocytes and permissive cells, regard- less of viral tropism. Furthermore, cell-to-cell HIV-1 transmis- sion of primary human CD4+ T lymphocytes was inhibited by ARF6 knock-down. ARF6 silencing or its mutants did not affect the infection of VSV-G pseudotyped viruses or ligand-induced CXCR4 or CCR5 endocytosis, both clathrin-dependent processes. Conclusions: Our results show that ARF6 silencing inhibits HIV-1 infection, regardless of viral tropism and without affecting the membrane distribution of the HIV-1 co-receptors CXCR4/ CCR5. We therefore propose that efficient early HIV-1 infection requires an ARF6-coordinated plasma membrane dynamics