5,608 research outputs found
A tale of three kingdoms: Members of the Phylum Nematoda independently acquired the detoxifying enzyme cyanase through horizontal gene transfer from plants and bacteria
Horizontal gene transfer (HGT) has played an important role in the evolution of nematodes. Among candidate genes, cyanase, which is typically found only in plants, bacteria and fungi, is present in more than 35 members of the Phylum Nematoda, but absent from free-living and clade V organisms. Phylogenetic analyses showed that the cyanases of clade I organisms Trichinella spp., Trichuris spp. and Soboliphyme baturini (Subclass: Dorylaimia) represent a well-supported monophyletic clade with plant cyanases. In contrast, all cyanases found within the Subclass Chromadoria which encompasses filarioids, ascaridoids and strongyloids are homologous to those of bacteria. Western blots exhibited typical multimeric forms of the native molecule in protein extracts of Trichinella spiralis muscle larvae, where immunohisto- chemical staining localized the protein to the worm hypodermis and underlying muscle. Recombinant Trichinella cyanase was bioactive where gene transcription profiles support functional activity in vivo. Results suggest that: (1) independent HGT in parasitic nematodes originated from different Kingdoms; (2) cyanase acquired an active role in the biology of extant Trichinella; (3) acquisition occurred more than 400 million years ago (MYA), prior to the divergence of the Trichinellida and Dioctophymatida, and (4) early, free-living ances- tors of the genus Trichinella had an association with terrestrial plants
The Identification of Haemonchus Species and Diagnosis of Haemonchosis
Diagnosis is often equated with identification or detection when discussing parasitic diseases. Unfortunately, these are not necessarily mutually exclusive activities; diseases and infections are generally diagnosed and organisms are identified. Diagnosis is commonly predicated upon some clinical signs; in an effort to determine the causative agent, identification of genera and species is subsequently performed. Both identification and diagnosis play critical roles in managing an infection, and involve the interplay of direct and indirect methods of detection, particularly in light of the complex and expanding problem of drug-resistance in parasites. Accurate and authoritative identification that is cost- and time-effective, based on structural and molecular attributes of specimens, provides a foundation for defining parasite diversity and changing patterns of geographical distribution, host association and emergence of disease. Most techniques developed thus far have been grounded in assumptions based on strict host associations between Haemonchus contortus and small ruminants, that is, sheep and goats, and between Haemonchus placei and bovids. Current research and increasing empirical evidence of natural infections in the field demonstrates that this assumption misrepresents the host associations for these species of Haemonchus. Furthermore, the capacity of H. contortus to utilize a considerably broad spectrum of ungulate hosts is reflected in our understanding of the role of anthropogenic forcing, the ‘breakdown’ of ecological isolation, global introduction and host switching as determinants of dis- tribution. Nuanced insights about distribution, host association and epidemiology have emerged over the past 30 years, coincidently with the development of increasingly robust means for parasite identification. In this review and for the sake of argument, we would like to delineate the diagnosis of haemonchosis from the identification of the specific pathogen. As a foundation for exploring host and parasite biology, we will examine the evolution of methods for distinguishing H. contortus from other com- mon gastrointestinal nematodes of agriculturally significant and free-ranging wild ru- minants using morphological, molecular and/or immunological methods for studies at the species and genus level
Numerical Analysis of Space Effect on the Pile-Anchor Bracing Deep Foundation Pit
Volume 8 Issue 1 (January 201
Optimization of robustness of scale-free network to random and targeted attacks
The scale-fee networks, having connectivity distribution (where is the site connectivity), is very resilient to random
failures but fragile to intentional attack. The purpose of this paper is to
find the network design guideline which can make the robustness of the network
to both random failures and intentional attack maximum while keeping the
average connectivity per node constant. We find that when $=3$ the
robustness of the scale-free networks reach its maximum value if the minimal
connectivity $m=1$, but when is larger than four, the networks will
become more robust to random failures and targeted attacks as the minimal
connectivity gets larger
Multistage Random Growing Small-World Networks with Power-law degree Distribution
In this paper, a simply rule that generates scale-free networks with very
large clustering coefficient and very small average distance is presented.
These networks are called {\bf Multistage Random Growing Networks}(MRGN) as the
adding process of a new node to the network is composed of two stages. The
analytic results of power-law exponent and clustering coefficient
are obtained, which agree with the simulation results approximately.
In addition, the average distance of the networks increases logarithmical with
the number of the network vertices is proved analytically. Since many real-life
networks are both scale-free and small-world networks, MRGN may perform well in
mimicking reality.Comment: 3 figures, 4 page
Relation of cyclotron resonant energy and luminosity in a strongly magnetized neutron star GRO J1008-57 observed by Insight-HXMT
Cyclotron line scattering features are detected in a few tens of X-ray
pulsars (XRPs) and used as direct indicators of a strong magnetic field at the
surface of accreting neutron stars (NSs). In a few cases, cyclotron lines are
known to be variable with accretion luminosity of XRPs. It is accepted that the
observed variations of cyclotron line scattering features are related to
variations of geometry and dynamics of accretion flow above the magnetic poles
of a NS. A positive correlation between the line centroid energy and luminosity
is typical for sub-critical XRPs, where the accretion results in hot spots at
the magnetic poles. The negative correlation was proposed to be a specific
feature of bright super-critical XRPs, where radiation pressure supports
accretion columns above the stellar surface. Cyclotron line in spectra of
Be-transient X-ray pulsar GRO J1008-57 is detected at energies from keV, the highest observed energy of cyclotron line feature in XRPs. We
report the peculiar relation of cyclotron line centroid energies with
luminosity in GRO J1008-57 during the Type II outburst in August 2017 observed
by Insight-HXMT. The cyclotron line energy was detected to be negatively
correlated with the luminosity at 3.2\times 10^{37}\,\ergs, and positively correlated at L\gtrsim 5\times
10^{37}\,\ergs. We speculate that the observed peculiar behavior of a
cyclotron line would be due to variations of accretion channel geometry.Comment: 9 pages. 5 figures, 2 tables, accept for publication in Ap
Wnt signaling in age-related macular degeneration: human macular tissue and mouse model
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