A latent ability to persist: differentiation in Toxoplasma gondii

A critical factor in the transmission and pathogenesis of Toxoplasma gondii is the ability to convert from an acute disease-causing, proliferative stage (tachyzoite), to a chronic, dormant stage (bradyzoite). The conversion of the tachyzoite-containing parasitophorous vacuole membrane into the less permeable bradyzoite cyst wall allows the parasite to persist for years within the host to maximize transmissibility to both primary (felids) and secondary (virtually all other warm-blooded vertebrates) hosts. This review presents our current understanding of the latent stage, including the factors that are important in bradyzoite induction and maintenance. Also discussed are the recent studies that have begun to unravel the mechanisms behind stage switching

Deflectable beam linear strip cesium contact ion thruster system

Deflectable dual beam, linear strip cesium contact, ion thruster system design and performance testin

Advanced electrostatic ion thruster for space propulsion

The suitability of the baseline 30 cm thruster for future space missions was examined. Preliminary design concepts for several advanced thrusters were developed to assess the potential practical difficulties of a new design. Useful methodologies were produced for assessing both planetary and earth orbit missions. Payload performance as a function of propulsion system technology level and cost sensitivity to propulsion system technology level are among the topics assessed. A 50 cm diameter thruster designed to operate with a beam voltage of about 2400 V is suggested to satisfy most of the requirements of future space missions

Coherence in laser-induced Compton scattering

The concept of the electron mass dressing by a powerful laser pulse is discussed. It is shown, by considering the coherent frequency combs generated out of the Compton radiation, how the electron dressed mass can be determined experimentally. This also opens a possibility to measure properties of extremely intense pulses for which the previously developed methods, working at moderate intensities, are not applicable. Namely, one can determine these properties from the properties of coherent Compton radiation

Daphnia as an Emerging Epigenetic Model Organism

Daphnia offer a variety of benefits for the study of epigenetics. Daphnia's parthenogenetic life cycle allows the study of epigenetic effects in the absence of confounding genetic differences. Sex determination and sexual reproduction are epigenetically determined as are several other well-studied alternate phenotypes that arise in response to environmental stressors. Additionally, there is a large body of ecological literature available, recently complemented by the genome sequence of one species and transgenic technology. DNA methylation has been shown to be altered in response to toxicants and heavy metals, although investigation of other epigenetic mechanisms is only beginning. More thorough studies on DNA methylation as well as investigation of histone modifications and RNAi in sex determination and predator-induced defenses using this ecologically and evolutionarily important organism will contribute to our understanding of epigenetics

Coherence in laser-induced Compton scattering

The concept of the electron mass dressing by a powerful laser pulse is discussed. It is shown, by considering the coherent frequency combs generated out of the Compton radiation, how the electron dressed mass can be determined experimentally. This also opens a possibility to measure properties of extremely intense pulses for which the previously developed methods, working at moderate intensities, are not applicable. Namely, one can determine these properties from the properties of coherent Compton radiation

Identification and characterization in common bean of a putative homologue to the Arabidopsis Indehiscent gene.

Pod shattering represents a key component of the domestication syndrome in common bean, because it makes this species dependent upon the farmer for seed dispersal. Attempts to elucidate the genetic control of this process have led to the identification of a major gene(St) linked to the presence of pod suture fibers involved in pod shattering. Although St has been placed on the common bean genetic map, the sequence and the specific functions of this gene remain unknown. The purpose of the current study was to identify a candidate gene for St. Arabidopsis thaliana INDEHISCENT gene (IND) is the primary factory required for silique shattering. A sequence homologous to IND was successfully amplified in Phaseolus vulgaris and mapped on the common bean map using two recombinant inbred population (BAT93 x Jalo EEP558; Midas x G12873). Although PvIND maps near the St locus, the lack of complete co-segregation between PvIND and St and the lack of polymorphisms at the PvIND locus correlating with the dehiscent/indehiscent phenotype suggests that PvIND may be not directly involved in pod shattering and may not be the gene underlying the St locus. Alternatively, a more precise phenotyping method needs to be developed to more accurately map the St locus

Canonical histone H2Ba and H2A.X dimerize in an opposite genomic localization to H2A.Z/H2B.Z dimers in Toxoplasma gondii

Histone H2Ba of Toxoplasma gondii was expressed as recombinant protein (rH2Ba) and used to generate antibody in mouse that is highly specific. Antibody recognizing rH2Ba detects a single band in tachyzoite lysate of the expected molecular weight (12kDa). By indirect immunofluorescence (IFA) in in vitro grown tachyzoites and bradyzoites, the signal was detected only in the parasite nucleus. The nucleosome composition of H2Ba was determined through co-immunoprecipitation assays. H2Ba was detected in the same immunocomplex as H2A.X, but not with H2A.Z. Through chromatin immunoprecipitation (ChIP) assays and qPCR, it was observed that H2Ba is preferentially located at promoters of inactive genes and silent regions, accompanying H2A.X and opposed to H2A.Z/H2B.Z dimers

Giardia assemblage A: human genotype in muskoxen in the Canadian Arctic

As part of an ongoing program assessing the biodiversity and impacts of parasites in Arctic ungulates we examined 72 fecal samples from muskoxen on Banks Island, Northwest Territories, Canada for Giardia and Cryptosporidium. Cryptosporidium spp. were not detected, but 21% of the samples were positive for Giardia. Sequencing of four isolates of Giardia demonstrated G. duodenalis, Assemblage A, a zoonotic genotype

EPIC-DB: a proteomics database for studying Apicomplexan organisms

<p>Abstract</p> <p>Background</p> <p>High throughput proteomics experiments are useful for analyzing the protein expression of an organism, identifying the correct gene structure of a genome, or locating possible post-translational modifications within proteins. High throughput methods necessitate publicly accessible and easily queried databases for efficiently and logically storing, displaying, and analyzing the large volume of data.</p> <p>Description</p> <p>EPICDB is a publicly accessible, queryable, relational database that organizes and displays experimental, high throughput proteomics data for <it>Toxoplasma gondii </it>and <it>Cryptosporidium parvum</it>. Along with detailed information on mass spectrometry experiments, the database also provides antibody experimental results and analysis of functional annotations, comparative genomics, and aligned expressed sequence tag (EST) and genomic open reading frame (ORF) sequences. The database contains all available alternative gene datasets for each organism, which comprises a complete theoretical proteome for the respective organism, and all data is referenced to these sequences. The database is structured around clusters of protein sequences, which allows for the evaluation of redundancy, protein prediction discrepancies, and possible splice variants. The database can be expanded to include genomes of other organisms for which proteome-wide experimental data are available.</p> <p>Conclusion</p> <p>EPICDB is a comprehensive database of genome-wide <it>T. gondii </it>and <it>C. parvum </it>proteomics data and incorporates many features that allow for the analysis of the entire proteomes and/or annotation of specific protein sequences. EPICDB is complementary to other -genomics- databases of these organisms by offering complete mass spectrometry analysis on a comprehensive set of all available protein sequences.</p