197 research outputs found
Phase diagram of mixtures of colloids and polymers in the thermal crossover from good to solvent
We determine the phase diagram of mixtures of spherical colloids and neutral
nonadsorbing polymers in the thermal crossover region between the
point and the good-solvent regime. We use the generalized free-volume theory
(GFVT), which turns out to be quite accurate as long as
( is the radius of gyration of the polymer and is the colloid
radius). Close to the point the phase diagram is not very sensitive to
solvent quality, while, close to the good-solvent region, changes of the
solvent quality modify significantly the position of the critical point and of
the binodals. We also analyze the phase behavior of aqueous solutions of
charged colloids and polymers, using the extension of GFVT proposed by Fortini
et al., J. Chem. Phys. 128, 024904 (2008)
Electric Field Controlled Columnar and Planar Patterning of Cholesteric Colloids
We study how dispersions of colloidal particles in a cholesteric liquid
crystal behave under a time-dependent electric field. By controlling the
amplitude and shape of the applied field wave, we show that the system can be
reproducibly driven out of equilibrium through different kinetic pathways and
navigated through a glassy-like free energy landscape encompassing many
competing metastable equilibria. Such states range from simple Saturn rings to
complex structures featuring amorphous defect networks, or stacks of
disclination loops. A non-equilibrium electric field can also trigger the
alignment of particles into columnar arrays, through defect-mediated force
impulses, or their repositioning within a plane. Our results are promising in
terms of providing new avenues towards controlled patterning and self-assembly
of soft colloid-liquid crystal composite materials.Comment: 5 pages, 4 figures. Phys. Rev. Lett., 2015, in pres
Migratory crustaceans as biomonitors of metal pollution in their nursery areas. The Lesina lagoon (SE Italy) as a case study
The Lesina lagoon is located on the
southern Adriatic coast of Italy; many marine species,
such as the shrimp M. kerathurus, use the Lesina
lagoon as a nursery, spending their initial growth
phase there. In order to assess the usefulness of
migratory species as biomonitors of the environmental
quality of this nursery area, we evaluated the metal
content of the M. kerathurus juveniles at the end of
their growth phase in the lagoon (October), when they
are assumed to have bioaccumulated the maximum
level of metals from the lagoon environment. The
concentrations of Cr, Cd, Pb, Zn, Mn and Cu were
measured in the muscle and exoskeleton of the
shrimp, and in the sediments and waters of three
areas of the Lesina Lagoon. Both the water and
sediment levels of the investigated metals tended to
fall within the ranges recorded for other lagoon
environments characterized by similar anthropic impact
and texturally similar sediment; the juveniles of
the shrimp M. kerathurus proved to be strong
bioaccumulators of heavy metals such as Zn and Cu
(biota-sediment accumulation factors – BSAFs – 6.01
and 25.0 respectively), which derive from agricultural
activities; therefore, at the end of their growing phase
in the lagoon they can be considered useful biomonitors
of metal contamination of agricultural origin in
their nursery area
Anti-trafficking in the time of FOSTA/SESTA : networked moral gentrification and sexual humanitarian creep
Globally, sex workers have highlighted the harms that accompany anti-prostitution efforts advanced via anti-trafficking policy, and there is a growing body of social science research that has emerged documenting how anti-trafficking efforts contribute to carceral and sexual humanitarian interventions. Yet mounting evidence on the harms of anti-trafficking policies has done little to quell the passage of more laws, including policies aimed at stopping sexual exploitation facilitated by technology. The 2018 passage of the Allow States and Victims to Fight Online Sex Trafficking Act (FOSTA) in the U.S. House of Representatives, and the corresponding Senate bill, the Stop Enabling Sex Traffickers Act (SESTA), is a case study in how efforts to curb sexual exploitation online actually heighten vulnerabilities for the people they purport to protect. Drawing on 34 months of ethnographic fieldwork and interviews with sex workers and trafficked persons (n = 58) and key informants (n = 20) in New York and Los Angeles, we analyze FOSTA/SESTA and its harmful effects as a launchpad to more broadly explore how technology, criminalization, shifting governance arrangements, and conservative moralities cohere to exacerbate sex workers’ vulnerability
Metabolic acetate therapy improves phenotype in the tremor rat model of Canavan disease
Genetic mutations that severely diminish the activity of aspartoacylase (ASPA) result in the fatal brain dysmyelinating disorder, Canavan disease. There is no effective treatment. ASPA produces free acetate from the concentrated brain metabolite, N-acetylaspartate (NAA). Because acetyl coenzyme A is a key building block for lipid synthesis, we postulated that the inability to catabolize NAA leads to a brain acetate deficiency during a critical period of CNS development, impairing myelination and possibly other aspects of brain development. We tested the hypothesis that acetate supplementation during postnatal myelination would ameliorate the severe phenotype associated with ASPA deficiency using the tremor rat model of Canavan disease. Glyceryltriacetate (GTA) was administered orally to tremor rats starting 7 days after birth, and was continued in food and water after weaning. Motor function, myelin lipids, and brain vacuolation were analyzed in GTA-treated and untreated tremor rats. Significant improvements were observed in motor performance and myelin galactocerebroside content in tremor rats treated with GTA. Further, brain vacuolation was modestly reduced, and these reductions were positively correlated with improved motor performance. We also examined the expression of the acetyl coenzyme A synthesizing enzyme acetyl coenzyme A synthase 1 and found upregulation of expression in tremor rats, with a return to near normal expression levels in GTA-treated tremor rats. These results confirm the critical role played by NAA-derived acetate in brain myelination and development, and demonstrate the potential usefulness of acetate therapy for the treatment of Canavan disease
Parent-of-origin-specific allelic associations among 106 genomic loci for age at menarche.
Age at menarche is a marker of timing of puberty in females. It varies widely between individuals, is a heritable trait and is associated with risks for obesity, type 2 diabetes, cardiovascular disease, breast cancer and all-cause mortality. Studies of rare human disorders of puberty and animal models point to a complex hypothalamic-pituitary-hormonal regulation, but the mechanisms that determine pubertal timing and underlie its links to disease risk remain unclear. Here, using genome-wide and custom-genotyping arrays in up to 182,416 women of European descent from 57 studies, we found robust evidence (P < 5 × 10(-8)) for 123 signals at 106 genomic loci associated with age at menarche. Many loci were associated with other pubertal traits in both sexes, and there was substantial overlap with genes implicated in body mass index and various diseases, including rare disorders of puberty. Menarche signals were enriched in imprinted regions, with three loci (DLK1-WDR25, MKRN3-MAGEL2 and KCNK9) demonstrating parent-of-origin-specific associations concordant with known parental expression patterns. Pathway analyses implicated nuclear hormone receptors, particularly retinoic acid and γ-aminobutyric acid-B2 receptor signalling, among novel mechanisms that regulate pubertal timing in humans. Our findings suggest a genetic architecture involving at least hundreds of common variants in the coordinated timing of the pubertal transition
Physical Links: Defining and detecting inter-chain entanglement
Fluctuating filaments, from densely-packed biopolymers to defect lines in structured fluids, are prone to become interlaced and form intricate architectures. Understanding the ensuing mechanical and relaxation properties depends critically on being able to capture such entanglement in quantitative terms. So far, this has been an elusive challenge. Here we introduce the first general characterization of non-ephemeral forms of entanglement in linear curves by introducing novel descriptors that extend topological measures of linking from close to open curves. We thus establish the concept of physical links. This general method is applied to diverse contexts: equilibrated ring polymers, mechanically-stretched links and concentrated solutions of linear chains. The abundance, complexity and space distribution of their physical links gives access to a whole new layer of understanding of such systems and open new perspectives for others, such as reconnection events and topological simplification in dissipative fields and defect lines
Rab proteins and Rab-associated proteins: major actors in the mechanism of protein-trafficking disorders
Ras-associated binding (Rab) proteins and Rab-associated proteins are key regulators of vesicle transport, which is essential for the delivery of proteins to specific intracellular locations. More than 60 human Rab proteins have been identified, and their function has been shown to depend on their interaction with different Rab-associated proteins regulating Rab activation, post-translational modification and intracellular localization. The number of known inherited disorders of vesicle trafficking due to Rab cycle defects has increased substantially during the past decade. This review describes the important role played by Rab proteins in a number of rare monogenic diseases as well as common multifactorial human ones. Although the clinical phenotype in these monogenic inherited diseases is highly variable and dependent on the type of tissue in which the defective Rab or its associated protein is expressed, frequent features are hypopigmentation (Griscelli syndrome), eye defects (Choroideremia, Warburg Micro syndrome and Martsolf syndrome), disturbed immune function (Griscelli syndrome and Charcot–Marie–Tooth disease) and neurological dysfunction (X-linked non-specific mental retardation, Charcot–Marie–Tooth disease, Warburg Micro syndrome and Martsolf syndrome). There is also evidence that alterations in Rab function play an important role in the progression of multifactorial human diseases, such as infectious diseases and type 2 diabetes. Rab proteins must not only be bound to GTP, but they need also to be ‘prenylated’—i.e. bound to the cell membranes by isoprenes, which are intermediaries in the synthesis of cholesterol (e.g. geranyl geranyl or farnesyl compounds). This means that isoprenylation can be influenced by drugs such as statins, which inhibit isoprenylation, or biphosphonates, which inhibit that farnesyl pyrophosphate synthase necessary for Rab GTPase activity. Conclusion: Although protein-trafficking disorders are clinically heterogeneous and represented in almost every subspeciality of pediatrics, the identification of common pathogenic mechanisms may provide a better diagnosis and management of patients with still unknown Rab cycle defects and stimulate the development of therapeutic agents
A sustained ocean observing system in the Indian Ocean for climate related scientific knowledge and societal needs
© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hermes, J. C., Masumoto, Y., Beal, L. M., Roxy, M. K., Vialard, J., Andres, M., Annamalai, H., Behera, S., D'Adamo, N., Doi, T., Peng, M., Han, W., Hardman-Mountford, N., Hendon, H., Hood, R., Kido, S., Lee, C., Lees, T., Lengaigne, M., Li, J., Lumpkin, R., Navaneeth, K. N., Milligan, B., McPhaden, M. J., Ravichandran, M., Shinoda, T., Singh, A., Sloyan, B., Strutton, P. G., Subramanian, A. C., Thurston, S., Tozuka, T., Ummenhofer, C. C., Unnikrishnan, A. S., Venkatesan, R., Wang, D., Wiggert, J., Yu, L., & Yu, W. (2019). A sustained ocean observing system in the Indian Ocean for climate related scientific knowledge and societal needs. Frontiers in Marine Science, 6, (2019): 355, doi: 10.3389/fmars.2019.00355.The Indian Ocean is warming faster than any of the global oceans and its climate is uniquely driven by the presence of a landmass at low latitudes, which causes monsoonal winds and reversing currents. The food, water, and energy security in the Indian Ocean rim countries and islands are intrinsically tied to its climate, with marine environmental goods and services, as well as trade within the basin, underpinning their economies. Hence, there are a range of societal needs for Indian Ocean observation arising from the influence of regional phenomena and climate change on, for instance, marine ecosystems, monsoon rains, and sea-level. The Indian Ocean Observing System (IndOOS), is a sustained observing system that monitors basin-scale ocean-atmosphere conditions, while providing flexibility in terms of emerging technologies and scientificand societal needs, and a framework for more regional and coastal monitoring. This paper reviews the societal and scientific motivations, current status, and future directions of IndOOS, while also discussing the need for enhanced coastal, shelf, and regional observations. The challenges of sustainability and implementation are also addressed, including capacity building, best practices, and integration of resources. The utility of IndOOS ultimately depends on the identification of, and engagement with, end-users and decision-makers and on the practical accessibility and transparency of data for a range of products and for decision-making processes. Therefore we highlight current progress, issues and challenges related to end user engagement with IndOOS, as well as the needs of the data assimilation and modeling communities. Knowledge of the status of the Indian Ocean climate and ecosystems and predictability of its future, depends on a wide range of socio-economic and environmental data, a significant part of which is provided by IndOOS.This work was supported by the PMEL contribution no. 4934
Oligodendrocytes Do Not Export NAA-Derived Aspartate In Vitro.
Oligodendroglial cells are known to de-acetylate the N-acetylaspartate (NAA) synthesized and released by neurons and use it for lipid synthesis. However, the role of NAA regarding their intermediary metabolism remains poorly understood. Two hypotheses were proposed regarding the fate of aspartate after being released by de-acetylation: (1) aspartate is metabolized in the mitochondria of oligodendrocyte lineage cells; (2) aspartate is released to the medium. We report here that aspartoacylase mRNA expression increases when primary rat oligodendrocyte progenitor cells (OPCs) differentiate into mature cells in culture. Moreover, characterising metabolic functions of acetyl coenzyme A and aspartate from NAA catabolism in mature oligodendrocyte cultures after 5 days using isotope-labelled glucose after 5-days of differentiation we found evidence of extensive NAA metabolism. Incubation with [1,6-13C]glucose followed by gas chromatography-mass spectrometry and high performance liquid chromatography analyses of cell extracts and media in the presence and absence of NAA established that the acetate moiety produced by hydrolysis of NAA does not enter mitochondrial metabolism in the form of acetyl coenzyme A. We also resolved the controversy concerning the possible release of aspartate to the medium: aspartate is not released to the medium by oligodendrocytes in amounts detectable by our methods. Therefore we propose that: aspartate released from NAA joins the cytosolic aspartate pool rapidly and takes part in the malate-aspartate shuttle, which transports reducing equivalents from glycolysis into the mitochondria for ATP production and enters the tricarboxylic acid cycle at a slow rate.This work was supported by grants from the
UK Multiple Sclerosis Society and from Qatar Foundation. The
work was further supported by core funding from the Wellcome
Trust and MRC to the Wellcome Trust-Medical Research Council
Cambridge Stem Cell Institute. The authors acknowledge the excellent
technical support in GC-MS and HPLC analysis from Lars Evje
(NTNU, Norway).This is the final version of the article. It first appeared from Springer at http://dx.doi.org/10.1007/s11064-016-1985-y
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