Cellular Inclusion Bodies of Mutant Huntingtin Exon 1 Obscure Small Fibrillar Aggregate Species

The identities of toxic aggregate species in Huntington's disease pathogenesis remain ambiguous. While polyQ-expanded huntingtin (Htt) is known to accumulate in compact inclusion bodies inside neurons, this is widely thought to be a protective coping response that sequesters misfolded conformations or aggregated states of the mutated protein. To define the spatial distributions of fluorescently-labeled Htt-exon1 species in the cell model PC12m, we employed highly sensitive single-molecule super-resolution fluorescence imaging. In addition to inclusion bodies and the diffuse pool of monomers and oligomers, fibrillar aggregates ~100 nm in diameter and up to ~1–2 µm in length were observed for pathogenic polyQ tracts (46 and 97 repeats) after targeted photo-bleaching of the inclusion bodies. These short structures bear a striking resemblance to fibers described in vitro. Definition of the diverse Htt structures in cells will provide an avenue to link the impact of therapeutic agents to aggregate populations and morphologies

Fluorescence Microscopy with Nanometer Resolution

Throughout the twentieth century, it was widely accepted that a light microscope relying on propagating light waves and conventional optical lenses could not discern details that were much finer than about half the wavelength of light, or 200−400nm, due to diffraction. However, in the 1990s, the potential for overcoming the diffraction barrier was realized, and microscopy concepts were defined that now resolve fluorescent features down to molecular dimensions. This chapter discusses the simple yet powerful principles that make it possible to neutralize the resolution-limiting role of diffraction in far-field fluorescence nanoscopy methods such as STED, RESOLFT, PALM/"​"​STORM, or PAINT. In a nutshell, feature molecules residing closer than the diffraction barrier are transferred to different (quantum) states, usually a bright fluorescent state and a dark state, so that they become discernible for a brief period of detection. With nanoscopy, the interior of transparent samples, such as living cells and tissues, can be imaged at the nanoscale. A fresh look at the foundations shows that an in-depth description of the basic principles spawns powerful new concepts. Although they differ in some aspects, these concepts harness a local intensity minimum (of a doughnut-shaped or a standing wave pattern) for determining the coordinate of the fluorophore(s) to be registered. Most strikingly, by using an intensity minimum of the excitation light to establish the fluorophore position, MINFLUX nanoscopy has obtained the ultimate (super)resolution: the size of a molecule (≈1nm)

The Family Campylobacteraceae

The Campylobacteraceae is the largest and most diverse family in the phylogenetically distinct Epsilonproteobacteria, presently comprising the genera Campylobacter (30 taxa), Arcobacter (17 taxa), and Sulfurospirillum (7 taxa). Individual species may be able to grow in microaerobic, anaerobic, and/or aerobic conditions, in temperatures from 25°C to 42°C; free-living, commensal, or pathogenic; motile or aflagellate; and able to colonize the oral cavity, intestine, stomach, or reproductive tracts of humans, large production animals (such as sheep, cattle, and deer), birds, and reptiles. Some species are known to be among the most frequent causes of human gastroenteritis, others are significant threats to bovine and ovine fertility, and many pose an as-yet unknown, or no, role in human or animal diseases. The taxonomy of the Campylobacteraceae has evolved extensively since its beginnings in 1963. This chapter outlines key events in the family's taxonomic history; reviews general phenotypic traits of each genus, including their isolation; outlines the clinical (including pathogenicity studies and antimicrobial resistance traits) and/or ecological significance of constituent species; and describes current approaches and challenges for species identification and epidemiological subtyping

The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3

Abstract The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of  ℒ = 2 × 1034 cm-2 s-1 was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of  ℒ = 2 × 1034 cm-2 s-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector.</jats:p