3,252 research outputs found
Intravital imaging of metastasis in adult Zebrafish
Background
Metastasis is a major clinical problem whose biology is not yet fully understood. This lack of understanding is especially true for the events at the metastatic site, which include arrest, extravasation, and growth into macrometastases. Intravital imaging is a powerful technique that has shown great promise in increasing our understanding of these events. To date, most intravital imaging studies have been performed in mice, which has limited its adoption. Zebrafish are also a common system for the intravital imaging of metastasis. However, as imaging in embryos is technically simpler, relatively few studies have used adult zebrafish to study metastasis and none have followed individual cells at the metastatic site over time. The aim of this study was to demonstrate that adult casper zebrafish offer a convenient model system for performing intravital imaging of the metastatic site over time with single-cell resolution.
Methods
ZMEL1 zebrafish melanoma cells were injected into 6 to 10-week-old casper fish using an intravenous injection protocol. Because casper fish are transparent even as adults, they could be imaged without surgical intervention. Individual cells were followed over the course of 2Â weeks as they arrested, extravasated, and formed macroscopic metastases. Results
Our injection method reliably delivered cells into circulation and led to the formation of tumors in multiple organs. Cells in the skin and sub-dermal muscle could be imaged at high resolution over 2 weeks using confocal microscopy. Arrest was visualized and determined to be primarily due to size restriction. Following arrest, extravasation was seen to occur between 1 and 6Â days post-injection. Once outside of the vasculature, cells were observed migrating as well as forming protrusions.
Conclusions
Casper fish are a useful model for studying the events at the metastatic site using intravital imaging. The protocols described in this study are relatively simple. Combined with the reasonably low cost of zebrafish, they offer to increase access to intravital imaging.National Cancer Institute (U.S.) (Grant P30-CA14051)National Institutes of Health (U.S.) (Grant 5-T32-GM007287
Dynamic clay microstructures emerge via ion complexation waves
Clays control carbon, water and nutrient transport in the lithosphere,
promote cloud formation5 and lubricate fault slip through interactions among
hydrated mineral interfaces. Clay mineral properties are difficult to model
because their structures are disordered, curved and dynamic. Consequently,
interactions at the clay mineral-aqueous interface have been approximated using
electric double layer models based on single crystals of mica and atomistic
simulations. We discover that waves of complexation dipoles at dynamically
curving interfaces create an emergent long-range force that drives exfoliation
and restacking over time- and length-scales that are not captured in existing
models. Curvature delocalizes electrostatic interactions in ways that
fundamentally differ from planar surfaces, altering the ratio of ions bound to
the convex and concave sides of a layer. Multiple-scattering reconstruction of
low-dose energy-filtered cryo electron tomography enabled direct imaging of ion
complexes and electrolyte distributions at hydrated and curved mineral
interfaces with {\aa}ngstrom resolution over micron length scales. Layers
exfoliate and restack abruptly and repeatedly over timescales that depend
strongly on the counterion identity, demonstrating that the strong coupling
between elastic, electrostatic and hydration forces in clays promote collective
reorganization previously thought to be a feature only of active matter
Genetic and pharmacological relationship between P-Glycoprotein and increased cardiovascular risk associated with clarithromycin prescription:An Epidemiological and Genomic Population-Based Cohort Study in Scotland, UK
BackgroundThere are conflicting reports regarding the association of the macrolide antibiotic clarithromycin with cardiovascular (CV) events. A possible explanation may be that this risk is partly mediated through drug-drug interactions and only evident in at-risk populations. To the best of our knowledge, no studies have examined whether this association might be mediated via P-glycoprotein (P-gp), a major pathway for clarithromycin metabolism. The aim of this study was to examine CV risk following prescription of clarithromycin versus amoxicillin and in particular, the association with P-gp, a major pathway for clarithromycin metabolism.Methods and findingsWe conducted an observational cohort study of patients prescribed clarithromycin or amoxicillin in the community in Tayside, Scotland (population approximately 400,000) between 1 January 2004 and 31 December 2014 and a genomic observational cohort study evaluating genotyped patients from the Genetics of Diabetes Audit and Research Tayside Scotland (GoDARTS) study, a longitudinal cohort study of 18,306 individuals with and without type 2 diabetes recruited between 1 December 1988 and 31 December 2015. Two single-nucleotide polymorphisms associated with P-gp activity were evaluated (rs1045642 and rs1128503 -AA genotype associated with lowest P-gp activity). The primary outcome for both analyses was CV hospitalization following prescription of clarithromycin versus amoxicillin at 0-14 days, 15-30 days, and 30 days to 1 year. In the observational cohort study, we calculated hazard ratios (HRs) adjusted for likelihood of receiving clarithromycin using inverse proportion of treatment weighting as a covariate, whereas in the pharmacogenomic study, HRs were adjusted for age, sex, history of myocardial infarction, and history of chronic obstructive pulmonary disease. The observational cohort study included 48,026 individuals with 205,227 discrete antibiotic prescribing episodes (34,074 clarithromycin, mean age 73 years, 42% male; 171,153 amoxicillin, mean age 74 years, 45% male). Clarithromycin use was significantly associated with increased risk of CV hospitalization compared with amoxicillin at both 0-14 days (HR 1.31; 95% CI 1.17-1.46, p ConclusionsIn this study, we observed that the increased risk of CV events with clarithromycin compared with amoxicillin was associated with an interaction with P-glycoprotein
Inflamed neutrophils sequestered at entrapped tumor cells via chemotactic confinement promote tumor cell extravasation
Systemic inflammation occurring around the course of tumor progression and treatment are often correlated with adverse oncological outcomes. As such, it is suspected that neutrophils, the first line of defense against infection, may play important roles in linking inflammation and metastatic seeding. To decipher the dynamic roles of inflamed neutrophils during hematogenous dissemination, we employ a multiplexed microfluidic model of the human microvasculature enabling physiologically relevant transport of circulating cells combined with real-time, high spatial resolution observation of heterotypic cellâcell interactions. LPS-stimulated neutrophils (PMNs) and tumor cells (TCs) form heterotypic aggregates under flow, and arrest due to both mechanical trapping and neutrophilâendothelial adhesions. Surprisingly, PMNs are not static following aggregation, but exhibit a confined migration pattern near TCâPMN clusters. We discover that PMNs are chemotactically confined by self-secreted IL-8 and tumor-derived CXCL-1, which are immobilized by the endothelial glycocalyx. This results in significant neutrophil sequestration with arrested tumor cells, leading to the spatial localization of neutrophil-derived IL-8, which also contributes to increasing the extravasation potential of adjacent tumor cells through modulation of the endothelial barrier. Strikingly similar migration patterns and extravasation behaviors were also observed in an in vivo zebrafish model upon PMNâtumor cell coinjection into the embryo vasculature. These insights into the temporal dynamics of intravascular tumorâPMN interactions elucidate the mechanisms through which inflamed neutrophils can exert proextravasation effects at the distant metastatic site. Keywords: metastasis; inflammation; neutrophils; extravasation; cell migratio
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A Veritable Menagerie of Heritable Bacteria from Ants, Butterflies, and Beyond: Broad Molecular Surveys and a Systematic Review
Maternally transmitted bacteria have been important players in the evolution of insects and other arthropods, affecting their nutrition, defense, development, and reproduction. Wolbachia are the best studied among these and typically the most prevalent. While several other bacteria have independently evolved a heritable lifestyle, less is known about their host ranges. Moreover, most groups of insects have not had their heritable microflora systematically surveyed across a broad range of their taxonomic diversity. To help remedy these shortcomings we used diagnostic PCR to screen for five groups of heritable symbiontsâArsenophonus spp., Cardinium hertigii, Hamiltonella defensa, Spiroplasma spp., and Wolbachia spp.âacross the ants and lepidopterans (focusing, in the latter case, on two butterfly familiesâthe Lycaenidae and Nymphalidae). We did not detect Cardinium or Hamiltonella in any host. Wolbachia were the most widespread, while Spiroplasma (ants and lepidopterans) and Arsenophonus (ants only) were present at low levels. Co-infections with different Wolbachia strains appeared especially common in ants and less so in lepidopterans. While no additional facultative heritable symbionts were found among ants using universal bacterial primers, microbes related to heritable enteric bacteria were detected in several hosts. In summary, our findings show that Wolbachia are the dominant heritable symbionts of ants and at least some lepidopterans. However, a systematic review of symbiont frequencies across host taxa revealed that this is not always the case across other arthropods. Furthermore, comparisons of symbiont frequencies revealed that the prevalence of Wolbachia and other heritable symbionts varies substantially across lower-level arthropod taxa. We discuss the correlates, potential causes, and implications of these patterns, providing hypotheses on host attributes that may shape the distributions of these influential bacteria.Organismic and Evolutionary Biolog
The Third wave in globalization theory
This essay examines a proposition made in the literature that there are three waves in globalization theoryâthe globalist, skeptical, and postskeptical or transformational wavesâand argues that this division requires a new look. The essay is a critique of the third of these waves and its relationship with the second wave. Contributors to the third wave not only defend the idea of globalization from criticism by the skeptics but also try to construct a more complex and qualified theory of globalization than provided by first-wave accounts. The argument made here is that third-wave authors come to conclusions that try to defend globalization yet include qualifications that in practice reaffirm skeptical claims. This feature of the literature has been overlooked in debates and the aim of this essay is to revisit the literature and identify as well as discuss this problem. Such a presentation has political implications. Third wavers propose globalist cosmopolitan democracy when the substance of their arguments does more in practice to bolster the skeptical view of politics based on inequality and conflict, nation-states and regional blocs, and alliances of common interest or ideology rather than cosmopolitan global structures
Correlative analysis of structure and chemistry of LixFePO4 platelets using 4D-STEM and X-ray ptychography
Lithium iron phosphate (LixFePO4), a cathode material used in rechargeable
Li-ion batteries, phase separates upon de/lithiation under equilibrium. The
interfacial structure and chemistry within these cathode materials affects
Li-ion transport, and therefore battery performance. Correlative imaging of
LixFePO4 was performed using four-dimensional scanning transmission electron
microscopy (4D-STEM), scanning transmission X-ray microscopy (STXM), and X-ray
ptychography in order to analyze the local structure and chemistry of the same
particle set. Over 50,000 diffraction patterns from 10 particles provided
measurements of both structure and chemistry at a nanoscale spatial resolution
(16.6-49.5 nm) over wide (several micron) fields-of-view with statistical
robustness.LixFePO4 particles at varying stages of delithiation were measured
to examine the evolution of structure and chemistry as a function of
delithiation. In lithiated and delithiated particles, local variations were
observed in the degree of lithiation even while local lattice structures
remained comparatively constant, and calculation of linear coefficients of
chemical expansion suggest pinning of the lattice structures in these
populations. Partially delithiated particles displayed broadly core-shell-like
structures, however, with highly variable behavior both locally and per
individual particle that exhibited distinctive intermediate regions at the
interface between phases, and pockets within the lithiated core that correspond
to FePO4 in structure and chemistry.The results provide insight into the
LixFePO4 system, subtleties in the scope and applicability of Vegards law
(linear lattice parameter-composition behavior) under local versus global
measurements, and demonstrate a powerful new combination of experimental and
analytical modalities for bridging the crucial gap between local and
statistical characterization.Comment: 17 pages, 4 figure
Dielectric breakdown of alumina thin films produced by pulsed direct current magnetron sputtering
Alumina films (~2âŻÎŒm thick) were deposited with a mixed Cu/Al interlayer onto copper. Direct current (DC)/Pulsed DC (PDC) magnetron sputtering techniques were independently compared for reactive alumina sputtering. In DC sputtered films, elemental aluminium of 9.2 at.% and nano-crystallites were present within the x-ray amorphous matrix, resulting from target arcing. Defects lead to premature dielectric breakdown/increased current leakage. PDC sputtering improved film quality by removing crystallites, metallic clusters and through thickness cracking. Time dependent dielectric breakdown (TDDB) measurements were carried out using conductive atomic force microscopy identified an improvement in dielectric strength (166 to 310âŻVâŻÎŒmâ1) when switching from DC to PDC deposition power. TDDB suggested that at high applied field the dominant pre-breakdown conduction mechanism was Fowler-Nordheim tunnelling in DC films. Tensile pull-off adhesion ranged from 56 to 72âŻMPa and was highest following incorporation of an Cu/Al blended interfacial layer. Scratch testing indicated various cracking/buckling failures
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