LINC complexes mediate the positioning of cone photoreceptor nuclei in mouse retina

It has long been observed that many neuronal types position their nuclei within restricted cytoplasmic boundaries. A striking example is the apical localization of cone photoreceptors nuclei at the outer edge of the outer nuclear layer of mammalian retinas. Yet, little is known about how such nuclear spatial confinement is achieved and further maintained. Linkers of the Nucleoskeleton to the Cytoskeleton (LINC complexes) consist of evolutionary-conserved macromolecular assemblies that span the nuclear envelope to connect the nucleus with the peripheral cytoskeleton. Here, we applied a new transgenic strategy to disrupt LINC complexes either in cones or rods. In adult cones, we observed a drastic nuclear mislocalization on the basal side of the ONL that affected cone terminals overall architecture. We further provide evidence that this phenotype may stem from the inability of cone precursor nuclei to migrate towards the apical side of the outer nuclear layer during early postnatal retinal development. By contrast, disruption of LINC complexes within rod photoreceptors, whose nuclei are scattered across the outer nuclear layer, had no effect on the positioning of their nuclei thereby emphasizing differential requirements for LINC complexes by different neuronal types. We further show that Sun1, a component of LINC complexes, but not A-type lamins, which interact with LINC complexes at the nuclear envelope, participate in cone nuclei positioning. This study provides key mechanistic aspects underlying the well-known spatia

Similar dissection of sets

In 1994, Martin Gardner stated a set of questions concerning the dissection of a square or an equilateral triangle in three similar parts. Meanwhile, Gardner's questions have been generalized and some of them are already solved. In the present paper, we solve more of his questions and treat them in a much more general context. Let $D\subset \mathbb{R}^d$ be a given set and let $f_1,...,f_k$ be injective continuous mappings. Does there exist a set $X$ such that $D = X \cup f_1(X) \cup ... \cup f_k(X)$ is satisfied with a non-overlapping union? We prove that such a set $X$ exists for certain choices of $D$ and $\{f_1,...,f_k\}$. The solutions $X$ often turn out to be attractors of iterated function systems with condensation in the sense of Barnsley. Coming back to Gardner's setting, we use our theory to prove that an equilateral triangle can be dissected in three similar copies whose areas have ratio $1:1:a$ for $a \ge (3+\sqrt{5})/2$

Disrupting the heritage of place: practising counter-archaeologies at Dumby, Scotland

The notion of counter-archaeology is echoed by the opposing faces of the volcanic plug of Dumbarton Rock, Scotland. On the one side is the ‘official’ heritage of Dumbarton Castle, with its upstanding seventeenth-century military remains and underlying occupation evidence dating back to at least the eighth centuryad. On the other side lies a landscape of climbing, bouldering and post-industrial abandonment. This paper develops counter-archaeology through the climbing traditions and boulder problems at Dumbarton Rock and brings to the surface marginalized forms of heritage. Climbers and archaeologists have co-authored the paper as part of a collaborative project, which challenges the binary trope of researcher and researched and provides a model for a collaborative, co-designed and co-produced counter-archaeology

Water at an electrochemical interface - a simulation study

The results of molecular dynamics simulations of the properties of water in an aqueous ionic solution close to an interface with a model metallic electrode are described. In the simulations the electrode behaves as an ideally polarizable hydrophilic metal, supporting image charge interactions with charged species, and it is maintained at a constant electrical potential with respect to the solution so that the model is a textbook representation of an electrochemical interface through which no current is passing. We show how water is strongly attracted to and ordered at the electrode surface. This ordering is different to the structure that might be imagined from continuum models of electrode interfaces. Further, this ordering significantly affects the probability of ions reaching the surface. We describe the concomitant motion and configurations of the water and ions as functions of the electrode potential, and we analyze the length scales over which ionic atmospheres fluctuate. The statistics of these fluctuations depend upon surface structure and ionic strength. The fluctuations are large, sufficiently so that the mean ionic atmosphere is a poor descriptor of the aqueous environment near a metal surface. The importance of this finding for a description of electrochemical reactions is examined by calculating, directly from the simulation, Marcus free energy profiles for transfer of charge between the electrode and a redox species in the solution and comparing the results with the predictions of continuum theories. Significant departures from the electrochemical textbook descriptions of the phenomenon are found and their physical origins are characterized from the atomistic perspective of the simulations.Comment: 29 pages, 15 figure

Nutrient levels and trade-offs control diversity in a serial dilution ecosystem

Microbial communities feature an immense diversity of species and this diversity is linked with outcomes ranging from ecosystem stability to medical prognoses. Yet the mechanisms underlying microbial diversity are under debate. While simple resource-competition models don't allow for coexistence of a large number of species, it was recently shown that metabolic trade-offs can allow unlimited diversity. Does this diversity persist with more realistic, intermittent nutrient supply? Here, we demonstrate theoretically that in serial dilution culture, metabolic trade-offs allow for high diversity. When a small amount of nutrient is supplied to each batch, the serial dilution dynamics mimic a chemostat-like steady state. If more nutrient is supplied, diversity depends on the amount of nutrient supplied due to an "early-bird" effect. The interplay of this effect with different environmental factors and diversity-supporting mechanisms leads to a variety of relationships between nutrient supply and diversity, suggesting that real ecosystems may not obey a universal nutrient-diversity relationship.Comment: Appendix follows main tex

Constitutive TRIM22 expression within the respiratory tract identifies tissue-specific and cell-type dependent intrinsic immune barriers to influenza A virus infection

We hypothesized that increased expression of antiviral host factors at portals of viral entry may protect exposed tissues from the constant threat of invading pathogens. Comparative transcriptomic analysis identified the broad-acting restriction factor TRIM22 (TRIpartite Motif 22) to be among the most abundantly expressed antiviral host factors in the lung, a major portal of entry for many respiratory pathogens. This was surprising, as TRIM22 is currently considered to be an interferon stimulated gene (ISG) product that confers protection following the activation of pathogen-induced cytokine-mediated innate immune defences. Using human respiratory cell lines and the airways of rhesus macaques, we experimentally confirmed high levels of constitutive TRIM22 expression in the lung. In contrast, TRIM22 expression in many widely used transformed cell lines could only be observed following immune stimulation. Endogenous levels of TRIM22 in non-transformed cells were sufficient to restrict human and avian influenza A virus (IAV) infection by inhibiting the onset of viral transcription independently of cytokine-mediated innate immune defences. Thus, TRIM22 confers a pre-existing (intrinsic) tissue-specific immune barrier to IAV infection in the respiratory tract. We investigated whether the constitutive expression of TRIM22 was a characteristic shared by other ISGs in human lung tissue. Transcriptomic analysis identified a large group of ISGs and IAV immuno-regulatory host factors that were similarly enriched in the lung relative to other mucosal tissues, but whose expression was downregulated in transformed cell-lines. We identify common networks of immune gene downregulation which correlated with enhanced permissivity of transformed cells to initiate IAV replication. Our data highlight the importance of tissue-specific and cell-type dependent patterns of pre-existing immune gene expression in the intrinsic intracellular restriction of IAV; findings highly relevant to the immune regulation of many clinically important respiratory pathogens

Risk Assessment of Impacts of Climate Change for Key Marine Species in South Eastern Australia. Part 2: species profiles

[Extract] Blacklip and greenlip abalone form the basis of valuable fisheries in Tasmania, Victoria, South Australia and New South Wales (Figure 1.1). The Tasmanian abalone fishery is the largest wild abalone fishery in the world, producing more than 25% of the global catch (Miller et al. 2009). In 2008, the fishery had a gross landed value of $ 90 million. Blacklip abalone (BA), Haliotis rubra, is the predominant species harvested in Tasmania with 2461 t landed in 2008, compared to only 122 t of greenlip abalone (GA), H. laevigata (Tarbath and Gardner 2009). Since 2003, the BA fishery has been divided into five zones: Eastern, Western, Northern, Bass Strait, and Central West (Tarbath and Gardner 2009). The GA fishery is restricted to the north of the state and is managed by regions and separately from the BA fishery. In Victoria, approximately 1,200 t was landed in 2007/08, however, the current TAC is 774 t (2010/11). Catches are dominated by BA (96%) and the fishery is structured into three zones: Western, Central and Eastern. The South Australian fishery harvests approximately 880 t of abalone each year, about 60% of this is BA with the remainder comprising GA. Like Victoria, the South Australian fishery is divided into the Southern, Central and Western zones. Current annual catches in NSW were less than 75 t in 2009/10 and consist exclusively of BA. The commercial fisheries are assessed on a variable combination of commercial catch, effort and size-composition data, fishery-independent surveys and length-structured models. In Tasmania, 105,500 abalone were taken by recreational fishers in 2006/07, weighing an estimated 49 t. The number of recreational licenses has tripled since 1995, with 12,500 recreational diving licenses issued in 2007/08 (Lyle 2008). Recreational catches in SA are small, probably less than 1% of the TACC (Jones, 2009)

The influence of the frequency of periodic disturbances on the maintenance of phytoplankton diversity

The influence of periodic disturbances of various frequency on the maintenance of the phytoplankton diversity was studied by semicontinuous competition experiments. Disturbances consisted of dilution events, which meant both addition of fresh nutrients and elimination of organisms. The intervals between dilution events varied from 1 to 14 days. Diversity was found to increase with increasing intervals between disturbances. coexisting species belonged to different strategy types: (a) species with rapid growth under enriched conditions, (b) species with good competitive abilities under impoverished conditions, (c) species with the ability to build up storage pools of the limiting nutrient. An increase of the number of coexisting species over the number that would have coexisted in steady state was only found when the interval exceeded one generation time