8,045 research outputs found
Toxoplasma gondii major surface antigen (SAG1): in vitro analysis of host cell binding
Previous studies have indicated that SAG1, the major surface molecule of the protozoan parasite Toxoplasma gondii, is an important attachment ligand for the host cell. However, the research data that supports this claim comes largely from studies investigating tachyzoite binding, and not SAG1 binding per se.
In this study we successfully developed an in vitro attachment assay to directly evaluate the mechanism of SAG1-host cell binding. Competition experiments were then performed using SAG1 that had been pre-treated with the neoglycoprotein BSA-glucosamide or with antibody. Soluble BSA-glucosamide blocked SAG1 attachment to MDBK cells in a dose-dependent manner, implying that SAG1 binding is mediated, in part, via attachment to host cell surface glucosamine. Interestingly, pre-incubation of SAG1 in polyclonal sera from chronically infected mice failed to block binding. This challenges the assumption that anti-SAG1 antibodies block parasite attachment through the masking of SAG1 host cell binding domains. Taken together, this evidence presents new strategies for understanding SAG1-mediated attachment
Segregation of a microsporidian parasite during host cell mitosis
We investigated the segregation of an intracellular microsporidian parasite during host cell division. A time-course
experiment was carried out to examine the distribution of parasites relative to host chromosomal DNA via light and
electron microscopy. Fluorescent light microscopy and EM studies showed that the parasite lay in the perinuclear zone
of the host cell during interphase and segregated to daughter cells at mitosis. At metaphase, the parasite was frequently
closely associated with host microtubules and mitochondria. Electron-dense bridges were observed between the parasites
and the host microtubules and also between host mitochondria and microtubules. The study suggests that both the parasite
and the host cell organelles segregate in association with spindle microtubules
Cellular distribution of a feminizing microsporidian parasite: a strategy for transovarial transmission
The cellular distribution of a vertically transmitted, feminizing microsporidian was followed in its host Gammarus duebeni. In adult females the parasite was restricted to gonadal tissue, in particular primary and secondary follicle cells. Spores were diplokaryotic with a thin spore wall and a short polar filament, characteristics typical of ‘early’ spores involved in autoinfection. The diplokaryotic life-cycle, absence of spore groupings and of a pansporoblast membrane typify the genus Nosema. However, the unusual globular polaroplast of the spore and restriction of this stage to host ovarian tissue have not previously been described in Nosema. Sporogony occurred only in follicle cells adjacent to developing oocytes and was in synchrony with the process of vitellogenesis. Oocytes were infected after formation of intracellular connections with follicle cells but harboured only vegetative stages of the parasite. Parasites were associated with the perinuclear cytoplasm and, in developing embryos, segregated to daughter cells along the axis of the spindle. In juvenile animals there was no evidence of pathology linked with feminization and the parasite was found at low density in cells under the cuticle. The parasite is highly adapted to transovarial transmission with an efficient mechanism of oocyte infection and no evidence of pathology
Infection of Gammarus duebeni populations by two vertically transmitted microsporidia; parasite detection and discrimination by PCR–RFLP
We screened a population of the brackish water crustacean Gammarus duebeni from the Isle of Cumbrae for the presence of vertically transmitted microsporidia. We compared 2 screening techniques; light microscopy and PCR-based detection using generic 16S rDNA microsporidian primers. Fifty percent of females from this population tested positive for vertically transmitted microsporidia. The PCR screen was 100% efficient in comparison with existing LM based screening. In addition, the PCR screen produced bands of 2 sizes suggesting that more than 1 species of microsporidian was present. Sequencing revealed 2 distinct species of vertically transmitted microsporidia; 33% of females were infected with the feminizer Nosema granulosis and 17% were infected with a new species which we provisionally designate Microsporidium sp. On the basis of sequence information, we developed a discriminatory PCR–RFLP test based on MspI and HaeIII digests. This screen allows rapid detection and discrimination of vertically transmitted microsporidia in natural field populations. We applied the PCR–RFLP screen to a second G. duebeni population from the Isle of Man. This population also hosted these 2 parasite species. In total 45% of females harboured N. granulosis and 10% harboured Microsporidium sp. No dual-infected individuals were found in either population. The occurrence of 2 vertically transmitted parasites within a population has implications for our understanding of parasite–host relationships in the field and we discuss factors affecting the dynamics of parasite–parasite competition and coexistence
Meissner effect, Spin Meissner effect and charge expulsion in superconductors
The Meissner effect and the Spin Meissner effect are the spontaneous
generation of charge and spin current respectively near the surface of a metal
making a transition to the superconducting state. The Meissner effect is well
known but, I argue, not explained by the conventional theory, the Spin Meissner
effect has yet to be detected. I propose that both effects take place in all
superconductors, the first one in the presence of an applied magnetostatic
field, the second one even in the absence of applied external fields. Both
effects can be understood under the assumption that electrons expand their
orbits and thereby lower their quantum kinetic energy in the transition to
superconductivity. Associated with this process, the metal expels negative
charge from the interior to the surface and an electric field is generated in
the interior. The resulting charge current can be understood as arising from
the magnetic Lorentz force on radially outgoing electrons, and the resulting
spin current can be understood as arising from a spin Hall effect originating
in the Rashba-like coupling of the electron magnetic moment to the internal
electric field. The associated electrodynamics is qualitatively different from
London electrodynamics, yet can be described by a small modification of the
conventional London equations. The stability of the superconducting state and
its macroscopic phase coherence hinge on the fact that the orbital angular
momentum of the carriers of the spin current is found to be exactly ,
indicating a topological origin. The simplicity and universality of our theory
argue for its validity, and the occurrence of superconductivity in many classes
of materials can be understood within our theory.Comment: Submitted to SLAFES XX Proceeding
Recommended from our members
Hydrologic data for urban studies in the Austin, Texas, metropolitan area, 1981
This technical report includes maps of ground-water data-collection sites, rainfall for specific storms, storm rainfall-runoff for the 1981 water year, monthly water-level measurements of observation wells, water quality data, peak discharge, and daily rainfall summaries for specific gages.Waller Creek Working Grou
The development of spray-coated perovskite solar cells
Over the past six years, researchers have investigated the use of spray coating to fabricate perovskite solar cells (PSCs), with the aim of demonstrating its viability as an industrial manufacturing process. This spotlight on applications outlines the key benefits of this coating technology and summarizes progress made to date, with attention focused on varied efforts to control the crystallization and uniformity of the perovskite layer. The emerging understanding of processes required to create smooth, dense spray-cast perovskite films has recently led to the demonstration of fully spray-cast PSCs with a power conversion efficiency of 19.4%
The massive star population of Cygnus OB2
We have compiled a significantly updated and comprehensive census of massive stars in the nearby Cygnus OB2 association by gathering and homogenizing data from across the literature. The census contains 169 primary OB stars, including 52 O-type stars and 3 Wolf–Rayet stars. Spectral types and photometry are used to place the stars in a Hertzsprung–Russell diagram, which is compared to both non-rotating and rotating stellar evolution models, from which stellar masses and ages are calculated. The star formation history and mass function of the association are assessed, and both are found to be heavily influenced by the evolution of the most massive stars to their end states. We find that the mass function of the most massive stars is consistent with a ‘universal’ power-law slope of Γ = 1.3.Peer reviewedFinal Accepted Versio
Major incident triage: Derivation and comparative analysis of the Modified Physiological Triage Tool (MPTT).
BACKGROUND: Triage is a key principle in the effective management at a major incident. There are at least three different triage systems in use worldwide and previous attempts to validate them, have revealed limited sensitivity. Within a civilian adult population, there has been no work to develop an improved system. METHODS: A retrospective database review of the UK Joint Theatre Trauma Registry was performed for all adult patients (>18years) presenting to a deployed Military Treatment Facility between 2006 and 2013. Patients were defined as Priority One if they had received one or more life-saving interventions from a previously defined list. Using first recorded hospital physiological data (HR/RR/GCS), binary logistic regression models were used to derive optimum physiological ranges to predict need for life-saving intervention. This allowed for the derivation of the Modified Physiological Triage Tool-MPTT (GCS≥14, HR≥100, 12<RR≥22). A comparison of the MPTT and existing triage tools was then performed using sensitivities and specificities with 95% confidence intervals. Differences in performance were assessed for statistical significance using a McNemar test with Bonferroni correction. RESULTS: Of 6095 patients, 3654 (60.0%) had complete data and were included in the study, with 1738 (47.6%) identified as priority one. Existing triage tools had a maximum sensitivity of 50.9% (Modified Military Sieve) and specificity of 98.4% (Careflight). The MPTT (sensitivity 69.9%, 95% CI 0.677-0.720, specificity 65.3%, 95% CI 0.632-0.675) showed an absolute increase in sensitivity over existing tools ranging from 19.0% (Modified Military Sieve) to 45.1% (Triage Sieve). There was a statistically significant difference between the performance (p<0.001) between the MPTT and the Modified Military Sieve. DISCUSSION & CONCLUSION: The performance characteristics of the MPTT exceed existing major incident triage systems, whilst maintaining an appropriate rate of over-triage and minimising under-triage within the context of predicting the need for a life-saving intervention in a military setting. Further work is required to both prospectively validate this system and to identify its performance within a civilian environment, prior to recommending its use in the major incident setting
The Impact of Link Suggestions on User Navigation and User Perception
The study reported in this paper explores the effects of providing web users with link suggestions that are relevant to their tasks. Results indicate that link suggestions were positively received. Furthermore, users perceived sites with link suggestions as more usable and themselves as less disoriented. The average task execution time was significantly lower than in the control condition and users appeared to navigate in a more structured manner. Unexpectedly, men took more advantage from link suggestions than women
- …