129 research outputs found
Evidence for a "Wattle and Daub" Model of the Cyst Wall of Entamoeba
No full textThe cyst wall of Entamoeba invadens (Ei), a model for the human pathogen Entamoeba histolytica, is composed of fibrils of chitin and three chitin-binding lectins called Jacob, Jessie3, and chitinase. Here we show chitin, which was detected with wheat germ agglutinin, is made in secretory vesicles prior to its deposition on the surface of encysting Ei. Jacob lectins, which have tandemly arrayed chitin-binding domains (CBDs), and chitinase, which has an N-terminal CBD, were each made early during encystation. These results are consistent with their hypothesized roles in cross-linking chitin fibrils (Jacob lectins) and remodeling the cyst wall (chitinase). Jessie3 lectins likely form the mortar or daub of the cyst wall, because 1) Jessie lectins were made late during encystation; 2) the addition to Jessie lectins to the cyst wall correlated with a marked decrease in the permeability of cysts to nucleic acid stains (DAPI) and actin-binding heptapeptide (phalloidin); and 3) recombinant Jessie lectins, expressed as a maltose-binding proteins in the periplasm of Escherichia coli, caused transformed bacteria to agglutinate in suspension and form a hard pellet that did not dissociate after centrifugation. Jessie3 appeared as linear forms and rosettes by negative staining of secreted recombinant proteins. These findings provide evidence for a "wattle and daub" model of the Entamoeba cyst wall, where the wattle or sticks (chitin fibrils likely cross-linked by Jacob lectins) is constructed prior to the addition of the mortar or daub (Jessie3 lectins). Author SummaryParasitic protists, which are spread by the fecal-oral route, have cyst walls that resist environmental insults (e.g. desiccation, stomach acids, bile, etc.). Entamoeba histolytica, the cause of amebic dysentery and liver abscess, is the only protist characterized to date that has chitin in its cyst wall. We have previously characterized Entamoeba chitin synthases, chitinases, and multivalent chitin-binding lectins called Jacob. Here we present evidence that the Entamoeba Jessie3 lectin contributes to the mortar or daub, which makes the cyst wall impenetrable to small molecules. First, the Jessie3 lectin was made after chitin and Jacob lectins had already been deposited onto the surface of encysting Entamoeba. Second, cysts became impenetrable to small molecules at the same time that Jessie3 was deposited into the wall. Third, recombinant Jessie3 lectins self-aggregated and caused transfected bacteria to agglutinate. These results suggest a "wattle and daub" model of the Ei cyst wall, where the wattle or sticks (chitin fibrils likely cross-linked by Jacob lectins) is constructed prior to the addition of the mortar or daub (Jessie3 lectins).National Institutes of Health (AI44070, GM31318); Council for Scientific and Industrial Research, Government of Indi
Detecting sub-MeV neutrons in solid plastic scintillator with gamma-ray discrimination
No full textWe report on recent efforts to design a solid plastic scintillation hodoscope to measure neutron production cross sections at low energies. Our program includes not only the development of the detector itself, but also a set of auxiliary measurements which will help characterize its low-energy response. A novel scintillation counter has been developed to detect sub-MeV neutrons while rejecting gamma-ray backgrounds with good efficiency. The detector uses multiple layers of thin solid scintillator, with optical isolation between the adjacent layers. Incident low-energy neutrons produce ionizing recoil particles which remain within just one of the scintillator layers, while background gamma rays create electrons which most often cross the boundary between layers. By observing the trigger pattern within the layers, most gamma-ray backgrounds can be distinguished from the low-energy neutrons of interest. We report on the results of our Monte Carlo studies of this design, as well as on the operation of a prototype detector unit. We also have undertaken a new measurement of the neutron-proton total cross section below 1 MeV. Calculations of the efficiency for detecting low energy neutrons in plastic scintillator rely on accurate low energy n-p cross sections, yet surprisingly few such data currently exist. New measurements which span the region from 150 to 800 keV neutron (lab) energy are reported and discussed. Additionally, we have measured the light response of BC 418 scintillator for recoil proton energies as low as 100 keV. Recoil protons are produced at a known energy in the scintillator by placing it in a neutron beam and detecting in coincidence the elastically scattered neutrons at fixed angle. Our new results extend the energy range of previous measurements of the light response of solid organic scintillators, and may indicate a significantly modified response at the lowest observed energies.United States. Dept. of Energy (Grant No. DE-FG52-10NA29651
Author Correction: Considerations in the search for epistasis
No full textFollowing publication of the original article [1], the authors identified that two author affiliations were incorrect. Joséphine Daub is affiliated with Utrecht University (21) and not affiliation 9. Sanne Abeln is affiliated with Utrecht University only (21) and not affiliation 1. The original article [1] has been corrected.</p
Videos of eMouseAtlas Models: Theiler Stage 17 (10-11.25 dpc)
No full textA number of videos for each of the eMouseAtlas 3D mouse embryo models to show the overall form and in some cases selected anatomy. Each video is identified by the unique EMA ID with annotation if required. The videos labelled as "watermovies" are captured using the OPT system with the embryo spun on a longitudinal axis with no tissue clearing
Videos of eMouseAtlas Models: Theiler Stage 22 (13.5-15 dpc)
No full textA number of videos for each of the eMouseAtlas 3D mouse embryo models to show the overall form and in some cases selected anatomy. Each video is identified by the unique EMA ID with annotation if required. The videos labelled as "watermovies" are captured using the OPT system with the embryo spun on a longitudinal axis with no tissue clearing
Videos of eMouseAtlas Models: Theiler Stage 15 (9-10.5 dpc)
No full textA number of videos for each of the eMouseAtlas 3D mouse embryo models to show the overall form and in some cases selected anatomy. Each video is identified by the unique EMA ID with annotation if required. The videos labelled as "watermovies" are captured using the OPT system with the embryo spun on a longitudinal axis with no tissue clearing
Videos of eMouseAtlas Models: Theiler Stage 18 (10.5-11.75 dpc)
No full textA number of videos for each of the eMouseAtlas 3D mouse embryo models to show the overall form and in some cases selected anatomy. Each video is identified by the unique EMA ID with annotation if required. The videos labelled as "watermovies" are captured using the OPT system with the embryo spun on a longitudinal axis with no tissue clearing
High Resolution sections of eMouseAtlas Models: EMA145, Theiler Stage 12 TS12(cultured) - Head
No full textHigh resolution images of each section used for the Mouse Atlas 3D models. Images are sub-sampled for the 3D models to provide approximately iso-tropic voxel dimensions, here the images are at the full resolution of the original digitisation
High Resolution sections of eMouseAtlas Models: EMA102, Theiler Stage 26 TS26(17.5 dpc)
No full textHigh resolution images of each section used for the Mouse Atlas 3D models. Images are sub-sampled for the 3D models to provide approximately iso-tropic voxel dimensions, here the images are at the full resolution of the original digitisation
Developing New Top-Down Mass Spectrometry Strategies for Studying Transient Protein-Protein Interactions
No full textDatasets related to the PhD Thesis of Maria Mateos Jimenez entitled 'Developing New Top-Down Mass Spectrometry Strategies for Studying Transient Protein-Protein Interactions'
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