Continuous symmetry and chirality measures: approximate algorithms for large molecular structures

Quantifying imperfect symmetry of molecules can help explore the sources, roles and extent of structural distortion. Based on the established methodology of continuous symmetry and chirality measures, we develop a set of three-dimensional molecular descriptors to estimate distortion of large structures. These three-dimensional geometrical descriptors quantify the gap between the desirable symmetry (or chirality) and the actual one. They are global parameters of the molecular geometry, intuitively defined, and have the ability to detect even minute structural changes of a given molecule across chemistry, including organic, inorganic, and biochemical systems. Application of these methods to large structures is challenging due to countless permutations that are involved in the symmetry operations and have to be accounted for. Our approach focuses on iteratively finding the approximate direction of the symmetry element in the three-dimensional space, and the relevant permutation. Major algorithmic improvements over previous versions are described, showing increased accuracy, reliability and structure preservation. The new algorithms are tested for three sets of molecular structures including pillar[5]arene complexes with Li+, C100 fullerenes, and large unit cells of metal organic frameworks. These developments complement our recent algorithms for calculating continuous symmetry and chirality measures for small molecules as well as protein homomers, and simplify the usage of the full set of measures for various research goals, in molecular modeling, QSAR and cheminformatics.

A positive toxicology screen is a rare finding in sports-related sudden cardiac deaths

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): University of Copenhagen

Introduction

Sports-related sudden cardiac deaths (SrSCD) are rare events often occurring in healthy individuals. An underlying cardiac disease may, in combination with strenuous exercise, trigger lethal arrhythmias. Intake of drugs (legal and illicit) increases the risk of sudden cardiac death (SCD), but knowledge on toxicological findings in SrSCD remains sparse.

Purpose

This study aimed to characterize the SrSCD population in an international consortium by investigating the epidemiology and autopsy findings in SrSCD.

Methods

Participating centers of the consortium (Denmark, Australia, England, Spain) provided data on all forensically autopsied SCDs aged 12—49 years in their respective cohorts, spanning from 2000—2019. Demographics, autopsy findings, and toxicology screen were assessed. A toxicology screen was considered positive if any drug was detected, except drugs related to resuscitation.

Results

Of all 5,029 SCDs, we identified 435 (9%) SrSCD. The majority (88%) died during sports while the remaining 12% died within one hour from exercise. SrSCD occurred more often in males (91% vs 71%, p<0.001) who were younger (32 vs 36 years). In SrSCD, the autopsy more frequently revealed an underlying structural cardiac cause of death (64% vs 54%, p<0.001); the most frequent causes of death among SrSCDs were sudden unexpected death (SUD), ischemic heart disease (IHD), and arrhythmogenic cardiomyopathy (ACM). Toxicological screens were performed in approx. 90% of cases, regardless of relation to sport. Among SrSCD cases, the rate of a positive toxicology was less than half compared to other SCDs (18% vs 44%, p<0.001). The most frequent toxicological findings among SrSCDs were ethanol, central stimulants, cannabinoids, and non-opioid analgesics.

Conclusions

Sports-related SCD accounted for 9% of all SCDs in our population aged 12—49 years. The majority of sports-related deaths (88%) occurred during exercise activity. SrSCDs more often had an underlying structural cardiac disease, mainly IHD and ACM. Positive toxicology screens were half as frequent in SrSCDs compared with non-SrSCDs.

Usefulness of subcutaneous Implantable Loop Recorder in Brugada Syndrome. A single UK centre experience

Background

Experience with implantable loop recorder (ILR) in Brugada Syndrome (BrS) is limited.

Purpose

We sought to evaluate the usefulness of continuous monitoring in BrS patients in a UK based Inherited Cardiac Conditions centre.

Methods

Subjects with BrS were consecutively recruited and demographic, clinical, device and follow-up data acquired.

Results

Of 452 subjects with BrS recruited in our centre, 41 (9%) received an ILR. Twenty-one (51%) were males. Twenty-four subjects (59%) had a high probability of BrS based on the Shanghai score. Mean age at implantation was 45.3±15.5 years. The indications for the implantation were: syncope or pre-syncope in 28 subjects (68%), palpitations in 12 (29%), family history of SADS in 1 case. Sixteen subjects presented with a spontaneous type 1 pattern, of whom 12 (75%) underwent an electrophysiological study for risk stratification which was negative. During a mean follow-up of 82±46 months (range 4.0–182), 5 new diagnoses of atrial fibrillation (AF) or supraventricular tachycardia were made; 3 subjects had symptomatic pathological pauses (in one case associated with fast AF) and underwent permanent pacemaker or ICD implantation; one subject experienced an asymptomatic episode of fast, non-sustained monomorphic ventricular tachycardia. In 2 cases the device was explanted prematurely due to site infection. Patients who received an ECG diagnosis following interrogation of the ILR were older (mean age 55±11 vs 43±16m p=0.04), although there were no differences in sex or Shanghai score.

Conclusions

In a large UK cohort of BrS patients, the use of ILR was low. However, continuous subcutaneous monitoring yielded a diagnosis of tachy- or brady-arrhythmic episodes in 22% of cases, and therefore can be helpful in guiding the management of low/intermediate risk BrS patients.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Robert Lancaster Memorial Fund

Do we know how to set decision thresholds for diabetes?

The diagnosis of diabetes, based on measured fasting plasma glucose level, depends on choosing a threshold level for which the probability of failing to detect disease (missed diagnosis), as well as the probability of falsely diagnosing disease (false alarm), are both small. The Bayesian risk provides a tool for aggregating and evaluating the risks of missed diagnosis and false alarm. However, the underlying probability distributions are uncertain, which makes the choice of the decision threshold difficult. We discuss an hypothesis for choosing the threshold that can robustly achieve acceptable risk. Our analysis is based on info-gap decision theory, which is a non-probabilistic methodology for modelling and managing uncertainty. Our hypothesis is that the non-probabilistic method of info-gap robust decision making is able to select decision thresholds according to their probability of success. This hypothesis is motivated by the relationship between info-gap robustness and the probability of success, which has been observed in other disciplines (biology and economics). If true, it provides a valuable clinical tool, enabling the clinician to make reliable diagnostic decisions in the absence of extensive probabilistic information. Specifically, the hypothesis asserts that the physician is able to choose a diagnostic threshold that maximizes the probability of acceptably small Bayesian risk, without requiring accurate knowledge of the underlying probability distributions. The actual value of the Bayesian risk remains uncertain.

Vibrio coralliilyticus sp. nov., a temperature-dependent pathogen of the coral Pocillopora damicornis

Vibrio sp. YB1T (=ATCC BAA-450T =LMG 20984T), the aetiological agent of tissue lysis of the coral Pocillopora damicornis, was characterized as a novel Vibrio species on the basis of 16S rDNA sequence, DNA-DNA hybridization data (G + C content is 45.6 mol%), AFLP and GTG5-PCR genomic fingerprinting patterns and phenotypic properties, including the cellular fatty acid profile. The predominant fatty acids were 16:0 and 18:1 omega7c. The name Vibrio coralliilyticus sp. nov. is proposed for the novel coral-pathogenic species. In addition to strain YB1T, which was isolated from the Indian Ocean, five additional strains of V. coralliilyticus have been isolated, three from diseased P. damicornis in the Red Sea, one from diseased oyster larvae (Kent, UK) and one from bivalve larvae (Brazil). The six V. coralliilyticus strains showed high genotypic and phenotypic similarities and all were pathogenic to P. damicornis. The closest phylogenetic neighbours to V. coralliilyticus are Vibrio tubiashii, Vibrio nereis and Vibrio shilonii.

Inhibition of photosynthesis and bleaching of zooxanthellae by the coral pathogen Vibrio shiloi

Vibrio shiloi is the causative agent of bleaching (loss of endosymbiotic zooxanthellae) of the coral Oculina patagonica in the Mediterranean Sea. To obtain information on the mechanism of bleaching, we examined the effect of secreted material (AK1-S) produced by V. shiloi on zooxanthellae isolated from corals. AK1-S caused a rapid inhibition of photosynthesis of the algae, as measured with a Mini-PAM fluorometer. The inhibition of photosynthesis was caused by (i) ammonia produced during the growth of V. shiloi on protein-containing media and (ii) a non-dialysable heat-resistant factor. This latter material did not inhibit photosynthesis of the algae by itself but, when added to different concentrations of NH4Cl, enhanced the inhibition approximately two- to threefold. Ammonia and the enhancer were effective to different degrees on zooxanthellae isolated from four species of coral examined. In addition to the rapid inhibition of photosynthesis, AK1-S caused bleaching (loss of pigmentation) and lysis of zooxanthellae. Bleaching was more rapid than lysis, reaching a peak (25% bleached algae) after 6 h. The factors in AK1-S responsible for bleaching and lysis were different from those responsible for the inhibition of photosynthesis, because they were heat sensitive, non-dialysable and active in the dark. Thus, the coral pathogen V. shiloi produces an array of extracellular materials that can inhibit photosynthesis, bleach and lyse zooxanthellae.

Adaptive assay of radioactive pulmonary aerosols with an external detector

The accuracy of the assay of radioactive pulmonary aerosols is influenced by the spatial distribution of the aerosol in the lungs. In general, there is considerable uncertainty in the spatial distribution of the aerosol beginning a few months after inhalation. This paper develops an adaptive approach for optimizing the assay of non-uniform spatial distributions of pulmonary aerosols. An adaptive assay is one in which the design of the assay system is modified during operation in response to measurements obtained on-line. Experimental results are presented which compare the performance of an adaptive assay with that of the standard measurement procedure. We study the assay of 241Am distributed in the lungs of a Lawrence Livermore realistic phantom using a NaI-CsI Phoswich detector.