Neuronal nicotinic receptors: the role of β3 and α5 subunits

Using a reporter mutation approach and the two-electrode voltage clamp technique, Groot-Komielink et al (1998) have shown that the 'orphan' α3 subunit can be incorporated into a functional 'triplet' α3β4α3 neuronal nicotinic acetylcholine receptor, when expressed in Xenopus oocytes. Based on the observation that in α3β4 receptors the EC50 value decreases with the number of 9'T mutations, we used the same reporter mutation approach to determine the stoichiometry of 'triplet' receptors. When either α3 or β4 carried the 9'T mutation in 'triplet' α3β4α3 or α3β4α5 receptors, the observed decreases in EC50 values were similar and larger than if only α3 or α5 were mutated. This suggests α3 and β4 are present in equal copy number, greater than that of α3 or α5, namely; 2 copies of β, 2 copies of β and 1 copy of α3 or α5. Potency ratio data for α3β4 and α3β4α3 receptors demonstrated that the incorporation of α3 reduced the potency of lobeline (relative to ACh) from 23.0 to 7.14 (p 0.01). However, the rank order of the seven nicotinic agonists tested was unchanged. Schild analysis showed that the Kd for the competitive antagonist trimetaphan was not affected by α3 incorporation (75.5 and 66.0 nM for α3β4 and α3β4α3, respectively), suggesting that α3 may not contribute to the properties of the agonist binding site. Calcium permeability data failed to detect differences in calcium permeability for α3β4 and α3β4α3 receptors, with mean shifts in reversal potential of 7.68 mV for α3β4 and 5.20 mV for α3β4α3 (for a 10 times increase in external calcium concentration)

Transformers:Intrusion Detection Data In Disguise

IoT cyber security deficiencies are an increasing concern for users, operators, and developers. With no immediate and holistic devicelevel fixes in sight, alternative wraparound defensive measures are required. Intrusion Detection Systems (IDS) present one such option, and represent an active field of research within the IoT space. IoT environments offer rich contextual and situational information from their interaction with the physical processes they control, which may be of use to such IDS. This paper uses a comprehensive analysis of the current stateof-the-art in context and situationally aware IoT IDS to define the often misunderstood concepts of context and situational awareness in relation to their use within IoT IDS. Building on this, a unified approach to transforming and exploiting such a rich additional data set is proposed to enhance the efficacy of current IDS approaches

Incomplete Incorporation of Tandem Subunits in Recombinant Neuronal Nicotinic Receptors

Tandem constructs are increasingly being used to restrict the composition of recombinant multimeric channels. It is therefore important to assess not only whether such approaches give functional channels, but also whether such channels completely incorporate the subunit tandems. We have addressed this question for neuronal nicotinic acetylcholine receptors, using a channel mutation as a reporter for subunit incorporation. We prepared tandem constructs of nicotinic receptors by linking α (α2–α4, α6) and β (β2, β4) subunits by a short linker of eight glutamine residues. Robust functional expression in oocytes was observed for several tandems (β4_α2, β4_α3, β4_α4, and β2_α4) when coexpressed with the corresponding β monomer subunit. All tandems expressed when injected alone, except for β4_α3, which produced functional channels only together with β4 monomer and was chosen for further characterization. These channels produced from β4_α3 tandem constructs plus β4 monomer were identical with receptors expressed from monomer α3 and β4 constructs in acetylcholine sensitivity and in the number of α and β subunits incorporated in the channel gate. However, separately mutating the β subunit in either the monomer or the tandem revealed that tandem-expressed channels are heterogeneous. Only a proportion of these channels contained as expected two copies of β subunits from the tandem and one from the β monomer construct, whereas the rest incorporated two or three β monomers. Such inaccuracies in concatameric receptor assembly would not have been apparent with a standard functional characterization of the receptor. Extensive validation is needed for tandem-expressed receptors in the nicotinic superfamily

Debris-Collecting Vacuum Machine with Grounded Safety System and Associated Methods

A debris collection machine includes a vacuum system (including a suction source operable to provide suction for pulling debris into a receptacle), a ground reference portion, a ground test portion, and a ground-checking module. The ground reference portion is electrically coupled with an electrically grounded reference point, and the ground test portion is electrically coupled with a portion of the vacuum system. The ground-checking module determines a resistance between from the ground reference portion and the ground test portion and prevents or terminates operation of the suction source of the vacuum system when the resistance exceeds a predetermined threshold value, e.g., which may correspond to a risk condition of spark generation that could ignite material in the receptacle

ICS Testbed Tetris:Practical Building Blocks Towards a Cyber Security Resource

Cyber attacks on Critical National Infrastructure (CNI) can be hugely detrimental to society, notably via compromising Industrial Control Systems (ICS) that underpin core CNI functions. In order to explore in-depth ICS Cyber Security challenges, testbeds are an essential tool, avoiding the need to experiment exclusively on live systems. However, ICS testbed creation is a complex multidisciplinary challenge, with a plethora of conflicting requirements. This paper, based on over six years of ICS testbed research and development that spans multiple diverse applications, proposes a flexible high-level model that can be adopted to support ICS testbed development. This is complemented by a baseline set of practical implementation guidance incorporating related and emerging technologies. As a collective, the model and implementation guidance offers a go-to guide for a wide range of end-users. Furthermore, it provides a coherent foundational structure towards establishing an online "living" resource, which can be expanded over time through broader community engagement

Floor determination in the operation of a lift by a mobile guide robot

Robotic assistants operating in multi-floor buildings are required to use lifts to transition between floors. To reduce the need for environments to be tailored to suit robots, and to make robot assistants more applicable, it is desirable that they should make use of existing navigational cues and interfaces designed for human users. In this paper, we examine the scenario whereby a guide robot uses a lift to transition between floors in a building. We describe an experiment into combining multiple data sources, available to a typical robot with simple sensors, to determine which floor of the building it is on. We show the robustness of this approach to realistic scenarios in a busy working environment

Cavity BPM System Tests for the ILC Spectrometer

The main physics programme of the International Linear Collider (ILC) requires a measurement of the beam energy at the interaction point with an accuracy of $10^{-4}$ or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPMs) has been proposed. This paper reports on the cavity BPM system that was deployed to test this proposal. We demonstrate sub-micron resolution and micron level stability over 20 hours for a 1\m long BPM triplet. We find micron-level stability over 1 hour for 3 BPM stations distributed over a 30\m long baseline. The understanding of the behaviour and response of the BPMs gained from this work has allowed full spectrometer tests to be carried out.Comment: Paper submitted to Nuclear Instruments and Methods. 35 pages, 23 figure

Phenotypic Anchoring of Acetaminophen-Induced Oxidative Stress with Gene Expression Profiles in Rat Liver

Toxicogenomics provides the ability to examine in greater detail the underlying molecular events that precede and accompany toxicity, thus allowing prediction of adverse events at much earlier times compared to classical toxicological endpoints. Acetaminophen (APAP) is a pharmaceutical that has similar metabolic and toxic responses in rodents and humans. Recent gene expression profiling studies with APAP found an oxidative stress signature at a sub-toxic dose that we hypothesized can be phenotypically anchored to conventional biomarkers of oxidative stress. Liver tissue was obtained from experimental animals used to generate microarray data where male rats were given APAP at sub-toxic (150 mg/kg), or overtly toxic (1500 and 2000 mg/kg) doses and sacrificed at 6, 24, or 48 hrs. Oxidative stress in liver was evaluated by a diverse panel of markers that included assessing expression of base excision repair (BER) genes, quantifying oxidative lesions in genomic DNA, and evaluating protein and lipid oxidation. A sub-toxic dose of APAP produced significant accumulation of nitrotyrosine protein adducts, while both sub-toxic and toxic doses caused a significant increase in 8-hydroxy-deoxyguanosine. Only toxic doses of APAP significantly induced expression levels of BER genes. None of the doses examined resulted in a significant increase in the number of abasic sites, or in the amount of lipid peroxidation. The accumulation of nitrotyrosine and 8-hydroxy-deoxyguanosine adducts phenotypically anchors the oxidative stress gene expression signature observed with a sub-toxic dose of APAP, lending support to the validity of gene expression studies as a sensitive and biologically-meaningful endpoint in toxicology

X-ray absorption spectroscopy systematics at the tungsten L-edge

A series of mononuclear six-coordinate tungsten compounds spanning formal oxidation states from 0 to +VI, largely in a ligand environment of inert chloride and/or phosphine, has been interrogated by tungsten L-edge X-ray absorption spectroscopy. The L-edge spectra of this compound set, comprised of [W<sup>0</sup>(PMe<sub>3</sub>)<sub>6</sub>], [W<sup>II</sup>Cl<sub>2</sub>(PMePh<sub>2</sub>)<sub>4</sub>], [W<sup>III</sup>Cl<sub>2</sub>(dppe)<sub>2</sub>][PF<sub>6</sub>] (dppe = 1,2-bis(diphenylphosphino)ethane), [W<sup>IV</sup>Cl<sub>4</sub>(PMePh<sub>2</sub>)<sub>2</sub>], [W<sup>V</sup>(NPh)Cl<sub>3</sub>(PMe<sub>3</sub>)<sub>2</sub>], and [W<sup>VI</sup>Cl<sub>6</sub>] correlate with formal oxidation state and have usefulness as references for the interpretation of the L-edge spectra of tungsten compounds with redox-active ligands and ambiguous electronic structure descriptions. The utility of these spectra arises from the combined correlation of the estimated branching ratio (EBR) of the L<sub>3,2</sub>-edges and the L<sub>1</sub> rising-edge energy with metal Z<sub>eff</sub>, thereby permitting an assessment of effective metal oxidation state. An application of these reference spectra is illustrated by their use as backdrop for the L-edge X-ray absorption spectra of [W<sup>IV</sup>(mdt)<sub>2</sub>(CO)<sub>2</sub>] and [W<sup>IV</sup>(mdt)<sub>2</sub>(CN)<sub>2</sub>]<sup>2–</sup> (mdt<sup>2–</sup> = 1,2-dimethylethene-1,2-dithiolate), which shows that both compounds are effectively W<sup>IV</sup> species. Use of metal L-edge XAS to assess a compound of uncertain formulation requires: 1) Placement of that data within the context of spectra offered by unambiguous calibrant compounds, preferably with the same coordination number and similar metal ligand distances. Such spectra assist in defining upper and/or lower limits for metal Z<sub>eff</sub> in the species of interest; 2) Evaluation of that data in conjunction with information from other physical methods, especially ligand K-edge XAS; 3) Increased care in interpretation if strong π-acceptor ligands, particularly CO, or π-donor ligands are present. The electron-withdrawing/donating nature of these ligand types, combined with relatively short metal-ligand distances, exaggerate the difference between formal oxidation state and metal Z<sub>eff</sub> or, as in the case of [W<sup>IV</sup>(mdt)<sub>2</sub>(CO)<sub>2</sub>], add other subtlety by modulating the redox level of other ligands in the coordination sphere