223 research outputs found
Connectivity between marine reserves and exploited areas in the philopatric reef fish Chrysoblephus laticeps (Teleostei: Sparidae)
"No-take‟ Marine Protected Areas (MPAs) are successful in protecting populations of many exploited fish species, but it is often unclear whether networks of MPAs are adequately spaced to ensure connectivity among reserves, and whether spillover occurs into adjacent exploited areas. Such issues are particularly important in species with low dispersal potential, many of which exist as genetically distinct regional stocks.The roman, Chrysoblephus laticeps, is an overexploited, commercially important fishery species endemic to South Africa. Post-recruits display resident behavior and occupy small home ranges, making C. laticeps a suitable model species to investigate connectivity in marine teleosts with potentially low dispersal ability. We used multilocus data from two types of highly variable genetic markers (mitochondrial DNA control region and microsatellites) to clarify patterns of genetic connectivity and population structure in C. laticeps using samples from two MPAs and several moderately or severely exploited regions. Despite using analytical tools that are sensitive to detect even subtle genetic structure, we found that this species exists as a single, well-mixed stock throughout its core distribution. This finding lends supports to the status of MPAs as an adequate tool for managing overexploited marine teleosts. Even though adult dispersal out of MPAs is limited, the fact that the large adults in these reserves produce exponentially more offspring than their smaller counterparts in exploited areas makes MPAs a rich source of recruits. We nonetheless caution against concluding that the lack of structure identified in C. laticeps and several other southern African teleosts can be considered to be representative of marine teleosts in this region in general. Many such species are represented in more than one marine biogeographic province and may be comprised of regionally-adapted stocks that need to be managed individually
A 'Multiple Lenses' Approach to Policy Change: the Case of Tobacco Policy in the UK
This article examines a period of rapid policy change following decades of stability in UK tobacco. It seeks to account for such a long period of policy stability, to analyse and qualify the extent of change, and to explain change using a 'multiple lenses' approach. It compares the explanatory value of policy network models such as punctuated equilibrium and the advocacy coalition framework, with models stressing change from 'above and below' such as multi-level governance and policy transfer. A key finding is that the value of these models varies according to the narrative of policy change that we select. The article challenges researchers to be careful about assuming the nature of policy change before embarking on explanation. While the findings of the case study may vary with other policy areas in British politics, the call for clarity and lessons from multiple approaches are widely applicable
On the X-ray fast-time variability of Sco X-2 (GX 349+2)
We have analysed archived Ginga data on the Z source Sco X-2 (GX349+2). We
present the first detailed investigation of its X-ray fast-time variability, as
a function of position in the Z track. During the two-day observation over the
period 5-7 March 1989, the source was in the so-called flaring branch, and the
lower part of the so-called normal branch. We found broad peaked noise with a
centroid frequency and width of ~4-7 Hz and ~6-12 Hz respectively. The peaked
noise was strongest in the lower flaring branch, with a maximum fractional rms
amplitude of ~3 %. We conclude that it is not a manifestation of atoll source
high frequency noise, as had been suggested, and compare it with the power
spectral features seen in other Z sources. We find that the peaked noise is
markedly different to the quasi-periodic oscillations found in the normal and
flaring branches of Sco X-1; however it bears some resemblance to that seen in
the flaring branch of Cyg X-2 at low overall intensities.Comment: 9 pages, 7 figues, accepted for publication in A&
Assessing the authority of political office-holders: the leadership capital index
This article argues that the extent to which political office-holders can effectively attain and wield authority is a function of the stock of ‘leadership capital.’ Drawing on the concept of political capital, we define leadership capital as aggregate authority composed of three dimensions: skills; relations; and reputation of a leader. Leadership capital ebbs and flows over time within a trajectory of acquisition, expenditure and inevitable depreciation. We present a Leadership Capital Index (LCI) that systematically maps out the three broad areas combining concrete measures with interpretive aspects. This can be used as a tool for systematically tracking and comparing the political fortunes of leaders in a way that is both more nuanced and robust than exclusive reliance on the latest approval ratings. We offer an illustrative case study of Tony Blair demonstrating the LCI. We conclude by discerning several promising paths for future development of the LCI
Tissue-resident macrophages regulate lymphatic vessel growth and patterning in the developing heart.
Macrophages are components of the innate immune system with key roles in tissue inflammation and repair. It is now evident that macrophages also support organogenesis, but few studies have characterized their identity, ontogeny and function during heart development. Here, we show that the distribution and prevalence of resident macrophages in the subepicardial compartment of the developing heart coincides with the emergence of new lymphatics, and that macrophages interact closely with the nascent lymphatic capillaries. Consequently, global macrophage deficiency led to extensive vessel disruption, with mutant hearts exhibiting shortened and mis-patterned lymphatics. The origin of cardiac macrophages was linked to the yolk sac and foetal liver. Moreover, the Cx3cr1 + myeloid lineage was found to play essential functions in the remodelling of the lymphatic endothelium. Mechanistically, macrophage hyaluronan was required for lymphatic sprouting by mediating direct macrophage-lymphatic endothelial cell interactions. Together, these findings reveal insight into the role of macrophages as indispensable mediators of lymphatic growth during the development of the mammalian cardiac vasculature.This work was funded by the British Heart Foundation (chair award CH/11/1/28798 and programme grant RG/08/003/25264 to PRR) and supported by the BHF Oxbridge Centre of Regenerative Medicine (RM/13/3/30159); a Wellcome Trust Doctoral Training Fellowship 106334/Z/14/Z to TJC; a Wellcome Trust Four year PhD Studentship 215103/Z/18/Z to KK; a BHF Intermediate Basic Science Research Fellowship FS/19/31/34158 to JMV; a British Israel Research and Academic Exchange Partnership (BIRAX) Grant 13BX14PRET; a Leducq Foundation Transatlantic Network of Excellence Program 14CVD04 and MRC Unit funding to DGJ.S
Magnetic trapping of ultracold neutrons
Three-dimensional magnetic confinement of neutrons is reported. Neutrons are
loaded into an Ioffe-type superconducting magnetic trap through inelastic
scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low
energy and in the appropriate spin state are confined by the magnetic field
until they decay. The electron resulting from neutron decay produces
scintillations in the liquid helium bath that results in a pulse of extreme
ultraviolet light. This light is frequency downconverted to the visible and
detected. Results are presented in which 500 +/- 155 neutrons are magnetically
trapped in each loading cycle, consistent with theoretical predictions. The
lifetime of the observed signal, 660 s +290/-170 s, is consistent with the
neutron beta-decay lifetime.Comment: 17 pages, 18 figures, accepted for publication in Physical Review
BeppoSAX spectroscopy of the luminous X-ray sources in M33
The nearby galaxy M33 was observed by the imaging X-ray instruments on-board
BeppoSAX. Two observations at different phases of the 105.9 day intensity cycle
of the luminous central source X-8 failed to reveal the expected modulation,
suggesting that it is probably transitory. Similar behavior has been observed
from several X-ray binary sources. This strengthens somewhat the idea that M33
X-8 is a black hole accreting from a binary companion. The 0.2-10 keV spectrum
of M33 X-8 can best be modeled by an absorbed power-law with a photon index of
1.89 +0.40 -0.79 and a disk-blackbody with a temperature, kT, of 1.10 +/0 0.05
keV and a projected inner-disk radius of 55.4 +6.0 -7.7 km. This spectral shape
is in good agreement with earlier ASCA results. The 2-10 keV spectra of M33
X-4, X-5, X-7, X-9 and X-10 are all consistent with power-law or bremsstrahlung
models, whilst that of X-6 appears to be significantly more complex and may be
reasonably well modeled with a disk-blackbody with kT = 1.7 +/- 0.2 keV and a
projected inner-disk radius of 7 +/- 2 km. The spectrum of M33 X-9 is rather
hard with a photon index of 1.3. Compared to earlier Einstein and ROSAT
observations, M33 X-7 and X-9 varied in intensity, M33 X-4, X-6, and X-10 may
have varied and M33 X-5 remained constant.Comment: 11 pages. To appear in A&
Global trends in aquatic animal tracking with acoustic telemetry
Acoustic telemetry (AT) is a rapidly evolving technique used to track the movements of aquatic animals. As the capacity of AT research expands it is important to optimize its relevance to management while still pursuing key ecological questions. A global review of AT literature revealed region-specific research priorities underscoring the breadth of how AT is applied, but collectively demonstrated a lack of management-driven objectives, particularly relating to fisheries, climate change, and protection of species. In addition to the need for more research with direct pertinence to management, AT research should prioritize ongoing efforts to create collaborative opportunities, establish long-term and ecosystem-based monitoring, and utilize technological advancements to bolster aquatic policy and ecological understanding worldwide
Use of genome sequencing to investigate the molecular basis of bacteriaphage interaction of the Escherichia coli O157 typing phages and the elucidation of the biological and public health significance of phage type
Background
Shiga toxin producing Escherichia coli (STEC) O157 causes severe gastrointestinal
disease and haemolytic uremic syndrome, and has a major impact on public health
worldwide with regular outbreaks and sporadic infection. Phage typing, i.e. the
susceptibility of STEC O157 strains to a bank of 16 bacteriophages, has been used in the UK to differentiate STEC O157 for the past 25 years and the phage type (PT)
can be an epidemiological marker of strains associated with severe disease or
associated with cases that occur from foreign travel. However, little is known
about the molecular interactions between the typing phages (TP) and STEC O157.
The aims of this thesis were to use whole genome sequencing to elucidate the
genetic basis for phage typing of STEC O157 and through this understand genetic
differences between strains relevant to disease severity and epidemiology.
Results
Sequencing the STEC O157 TPs revealed that they were clustered into 4 groups
based on sequence similarity that corresponded with their infectivity. Long read
sequencing revealed microevolutionary events occuring in STEC O157 genomes
over a short time period (approximately 1 year), evidenced by the loss and gain of
prophage regions and plasmids. An IncHI2 plasmid was found responsible for a
change in Phage Type (PT) from PT8 to PT54 during two related outbreaks at the
same restaurant. These changes resulted in a strain (PT54) that was fitter under
certain growth conditions and associated with a much larger outbreak (140 as
opposed to 4 cases). TraDIS (Transposon directed Insertion site sequencing) was
used to identify 114 genes associated with phage sensitivity and 44 genes involved
in phage resistance, emphasising the complex nature of identifying specific
genetic markers of phage susceptibility or resistance. Further work is required to
prove their phage-related functions but several are likely to encode novel phage
receptors. Deletion of a Stx2a prophage from a PT21/28 strain led to a strain that
typed as PT32, supporting the concept that the highly pathogenic PT21/28 lineage
I strains emerged from Stx2c+ PT32 strains in the last two decades by acquisition
of Stx2a-encoding prophages.
Conclusions
This body of work has highlighted the complexity of bacteriophage interaction and
investigated the genetic basis for susceptibility and resistance in E. coli. The
grouping of the TPs showed that resistance or susceptibility to all members of a
typing group was likely to be caused by one mechanism. IncHI2 was identified as
one of the markers for the PT54 phenotype. The Stx2a prophage region was
associated with the switch from PT32 to PT21/28, although PT32 strains
containing both Stx2a and Stx2c-encoding prophages have been isolated and can
provide insights into phage variation underpinning the susceptibility to the
relevant typing phages. The TraDIS results indicated that susceptibility or
resistance was governed by multiple genetic factors and not controlled by a single
gene. The significance of LPS for initial protection from phage adsorption was
evident and a number of novel genes controlling phage susceptibility and
resistance identified including the Sap operon and stringent starvation protein A
respectively. While SNP-based typing provides an excellent indication of the
evolution and relatedness of strains, phage typing can provide real insights into
short term evolution of the bacteria as PTs can be altered by mobile elements
such as prophages and plasmids. This study has shown that, although complex,
genetic determinants for PT can be mined from the genome and allow us to
understand the evolution of this zoonotic pathogen between host species and
during outbreaks
Assessing similarity to primary tissue and cortical layer identity in induced pluripotent stem cell-derived cortical neurons through single-cell transcriptomics
Induced pluripotent stem cell (iPSC)-derived cortical neurons potentially present a powerful new model to understand corticogenesis and neurological disease. Previous work has established that differentiation protocols can produce cortical neurons, but little has been done to characterize these at cellular resolution. In particular, it is unclear to what extent in vitro two-dimensional, relatively disordered culture conditions recapitulate the development of in vivo cortical layer identity. Single-cell multiplex reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to interrogate the expression of genes previously implicated in cortical layer or phenotypic identity in individual cells. Totally, 93.6% of single cells derived from iPSCs expressed genes indicative of neuronal identity. High proportions of single neurons derived from iPSCs expressed glutamatergic receptors and synaptic genes. And, 68.4% of iPSC-derived neurons expressing at least one layer marker could be assigned to a laminar identity using canonical cortical layer marker genes. We compared single-cell RNA-seq of our iPSC-derived neurons to available single-cell RNA-seq data from human fetal and adult brain and found that iPSC-derived cortical neurons closely resembled primary fetal brain cells. Unexpectedly, a subpopulation of iPSC-derived neurons co-expressed canonical fetal deep and upper cortical layer markers. However, this appeared to be concordant with data from primary cells. Our results therefore provide reassurance that iPSC-derived cortical neurons are highly similar to primary cortical neurons at the level of single cells but suggest that current layer markers, although effective, may not be able to disambiguate cortical layer identity in all cells
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