Development and application of consensus in silico models for advancing high-throughput toxicological predictions

Computational toxicology models have been successfully implemented to prioritize and screen chemicals. There are numerous in silico (quantitative) structure-activity relationship ([Q]SAR) models for the prediction of a range of human-relevant toxicological endpoints, but for a given endpoint and chemical, not all predictions are identical due to differences in their training sets, algorithms, and methodology. This poses an issue for high-throughput screening of a large chemical inventory as it necessitates several models to cover diverse chemistries but will then generate data conflicts. To address this challenge, we developed a consensus modeling strategy to combine predictions obtained from different existing in silico (Q)SAR models into a single predictive value while also expanding chemical space coverage. This study developed consensus models for nine toxicological endpoints relating to estrogen receptor (ER) and androgen receptor (AR) interactions (i.e., binding, agonism, and antagonism) and genotoxicity (i.e., bacterial mutation, in vitro chromosomal aberration, and in vivo micronucleus). Consensus models were created by combining different (Q)SAR models using various weighting schemes. As a multi-objective optimization problem, there is no single best consensus model, and therefore, Pareto fronts were determined for each endpoint to identify the consensus models that optimize the multiple-criterion decisions simultaneously. Accordingly, this work presents sets of solutions for each endpoint that contain the optimal combination, regardless of the trade-off, with the results demonstrating that the consensus models improved both the predictive power and chemical space coverage. These solutions were further analyzed to find trends between the best consensus models and their components. Here, we demonstrate the development of a flexible and adaptable approach for in silico consensus modeling and its application across nine toxicological endpoints related to ER activity, AR activity, and genotoxicity. These consensus models are developed to be integrated into a larger multi-tier NAM-based framework to prioritize chemicals for further investigation and support the transition to a non-animal approach to risk assessment in Canada.

In vitro transcriptomic analyses reveal pathway perturbations, estrogenic activities, and potencies of data-poor BPA alternative chemicals

Since initial regulatory action in 2010 in Canada, bisphenol A (BPA) has been progressively replaced by structurally related alternative chemicals. Unfortunately, many of these chemicals are data-poor, limiting toxicological risk assessment. We used high-throughput transcriptomics to evaluate potential hazards and compare potencies of BPA and 15 BPA alternative chemicals in cultured breast cancer cells. MCF-7 cells were exposed to BPA and 15 alternative chemicals (0.0005-100 µM) for 48 h. TempO-Seq (BioSpyder Inc) was used to examine global transcriptomic changes and estrogen receptor alpha (ERα)-associated transcriptional changes. Benchmark concentration (BMC) analysis was conducted to identify 2 global transcriptomic points of departure: (1) the lowest pathway median gene BMC and (2) the 25th lowest rank-ordered gene BMC. ERα activation was evaluated using a published transcriptomic biomarker and an ERα-specific transcriptomic point of departure was derived. Genes fitting BMC models were subjected to upstream regulator and canonical pathway analysis in Ingenuity Pathway Analysis. Biomarker analysis identified BPA and 8 alternative chemicals as ERα active. Global and ERα transcriptomic points of departure produced highly similar potency rankings with bisphenol AF as the most potent chemical tested, followed by BPA and bisphenol C. Further, BPA and transcriptionally active alternative chemicals enriched similar gene sets associated with increased cell division and cancer-related processes. These data provide support for future read-across applications of transcriptomic profiling for risk assessment of data-poor chemicals and suggest that several BPA alternative chemicals may cause hazards at similar concentrations to BPA.

Predicting estrogen receptor activation by a group of substituted phenols: An integrated approach to testing and assessment case study

Traditional approaches for chemical risk assessment cannot keep pace with the number of substances requiring assessment. Thus, in a global effort to expedite and modernize chemical risk assessment, New Approach Methodologies (NAMs) are being explored and developed. Included in this effort is the OECD Integrated Approaches for Testing and Assessment (IATA) program, which provides a forum for OECD member countries to develop and present case studies illustrating the application of NAM in various risk assessment contexts. Here, we present an IATA case study for the prediction of estrogenic potential of three target phenols: 4-tert-butylphenol, 2,4-di-tert-butylphenol and octabenzone. Key features of this IATA include the use of two computational approaches for analogue selection for read-across, data collected from traditional and NAM sources, and a workflow to generate predictions regarding the targets' ability to bind the estrogen receptor (ER). Endocrine disruption can occur when a chemical substance mimics the activity of natural estrogen by binding to the ER and, if potency and exposure are sufficient, alters the function of the endocrine system to cause adverse effects. The data indicated that of the three target substances that were considered herein, 4-tert-butylphenol is a potential endocrine disruptor. Further, this IATA illustrates that the NAM approach explored is health protective when compared to in vivo endpoints traditionally used for human health risk assessment.

Performance of predictive tools to identify individuals at risk of non-traumatic fracture: a systematic review, meta-analysis, and meta-regression

There is no consensus on which tool is the most accurate to assess fracture risk. The results of this systematic review suggest that QFracture, Fracture Risk Assessment Tool (FRAX) with BMD, and Garvan with BMD are the tools with the best discriminative ability. More studies assessing the comparative performance of current tools are needed.

INTRODUCTION

Many tools exist to assess fracture risk. This review aims to determine which tools have the best predictive accuracy to identify individuals at high risk of non-traumatic fracture.

METHODS

Studies assessing the accuracy of tools for prediction of fracture were searched in MEDLINE, EMBASE, Evidence-Based Medicine Reviews, and Global Health. Studies were eligible if discrimination was assessed in a population independent of the derivation cohort. Meta-analyses and meta-regressions were performed on areas under the ROC curve (AUCs). Gender, mean age, age range, and study quality were used as adjustment variables.

RESULTS

We identified 53 validation studies assessing the discriminative ability of 14 tools. Given the small number of studies on some tools, only FRAX, Garvan, and QFracture were compared using meta-regression models. In the unadjusted analyses, QFracture had the best discriminative ability to predict hip fracture (AUC = 0.88). In the adjusted analysis, FRAX with BMD (AUC = 0.81) and Garvan with BMD (AUC = 0.79) had the highest AUCs. For prediction of major osteoporotic fracture, QFracture had the best discriminative ability (AUC = 0.77). For prediction of osteoporotic or any fracture, FRAX with BMD and Garvan with BMD had higher discriminative ability than their versions without BMD (FRAX: AUC = 0.72 vs 0.69, Garvan: AUC = 0.72 vs 0.65). A significant amount of heterogeneity was present in the analyses.

CONCLUSIONS

QFracture, FRAX with BMD, and Garvan with BMD have the highest discriminative performance for predicting fracture. Additional studies in which the performance of current tools is assessed in the same individuals may be performed to confirm this conclusion.

Medication recommendation by physiotherapists: A survey of Québec physiotherapists' opinions regarding a new interprofessional model of care with pharmacists

BACKGROUND

To improve the efficiency of the health care system, new interprofessional models of care are emerging. In 2015, two provincial professional colleges, regulating the practice of physiotherapists and that of pharmacists in the province of Québec, Canada, developed a new interprofessional model of care. This model is designed to guide non-prescription medication recommendations by physiotherapists treating patients in primary care with neuromusculoskeletal disorders (NMSKD) with the collaboration of pharmacists.

PURPOSE

To assess Québec physiotherapists' interests to use this model and explore their opinions concerning their ability to recommend non-prescription medications to patients in primary care with NMSKD.

METHODS

An email invitation to complete an electronic survey was sent in February 2016 to all the Ordre professionnel de la physiothérapie du Québec's registered physiotherapists. The survey included a questionnaire with 31 questions divided into 5 sections. Descriptive analyses and Chi-square tests (χ² ) were performed to compare proportions (%) across demographic and clinical characteristics.

RESULTS

Two hundred twenty-five physiotherapists completed the full survey. Of these, 70% of respondents knew of the model of care, but only 15% had previously used it. Perceived workload increase was one major reason reported for this lack of use (51%). Most of the respondents had a positive perception of this model and interactions with pharmacists and were confident regarding their ability to safely recommend medication (63%). However, 63% believed that further training was necessary to enable physiotherapists to provide efficient and safe non-prescription medication recommendations to patients with NMSKD.

CONCLUSIONS

Overall, physiotherapists have a positive perception of this model, but there remain opportunities for increased integration into practice. Most respondents believe that additional training is required regarding non-prescription medication recommendations.

Sex-specific association between obesity and self-reported falls and injuries among community-dwelling Canadians aged 65 years and older

This study investigated the relationship between body mass index (BMI) and falls among community-dwelling elderly. Results indicate that obesity is associated with increased falls and there appears to be a sex-specific difference with obese men at higher risk of falling. Obesity is identified as a risk factor for falls in men.

INTRODUCTION

The prevalence of falls, fall-related injuries, and obesity has increased over the last decade. The objectives of this study were to investigate sex-specific association and dose-response relationship between BMI and falls (and related injuries) among community-dwelling elderly.

METHODS

Our study sample consisted of 15,860 adults aged 65 years or older (6399 men and 9461 women) from the 2008-2009 Canadian Community Health Survey-Healthy Aging (CCHS-HA). Falls, fall-related injuries, and BMI measures were self-reported. For both sex, dose-response curves presenting the relationship between BMI, falls, and fall-related injuries were first examined. Thereafter, multivariate logistic regression analyses were also performed to investigate these relationships after adjustment for potentially confounding variables.

RESULTS

Of women, 21.7 % reported a fall and 16.9 % of men. The dose-response relationship between BMI and prevalence of falls showed that underweight and obese individuals reported falling more than normal and overweight individuals; this being more apparent in men than women. Finally, the dose relationship between BMI and prevalence of fall-related injuries showed that only obese men seem more likely to have sustained a fall-related injury. Results from the multivariate analysis showed that obesity in men was significantly associated with higher odds of falling odds ratio (OR) 1.33 (1.04-1.70) and was not significantly associated with higher odds of fall-related injuries OR 1.10 (0.66-1.84) over a 12-month period compared to normal weight men. For women, obesity was not significantly associated with higher fall prevalence OR 0.99 (0.79-1.25) and fall-related injuries OR 0.71 (0.51-1.00).

CONCLUSION

Obesity is associated with self-reported falls, and there appears to be a sex-specific difference in elderly persons.

Impact of online visual feedback on motor acquisition and retention when learning to reach in a force field

When subjects learn a novel motor task, several sources of feedback (proprioceptive, visual or auditory) contribute to the performance. Over the past few years, several studies have investigated the role of visual feedback in motor learning, yet evidence remains conflicting. The aim of this study was therefore to investigate the role of online visual feedback (VFb) on the acquisition and retention stages of motor learning associated with training in a reaching task. Thirty healthy subjects made ballistic reaching movements with their dominant arm toward two targets, on 2 consecutive days using a robotized exoskeleton (KINARM). They were randomly assigned to a group with (VFb) or without (NoVFb) VFb of index position during movement. On day 1, the task was performed before (baseline) and during the application of a velocity-dependent resistive force field (adaptation). To assess retention, participants repeated the task with the force field on day 2. Motor learning was characterized by: (1) the final endpoint error (movement accuracy) and (2) the initial angle (iANG) of deviation (motor planning). Even though both groups showed motor adaptation, the NoVFb-group exhibited slower learning and higher final endpoint error than the VFb-group. In some condition, subjects trained without visual feedback used more curved initial trajectories to anticipate for the perturbation. This observation suggests that learning to reach targets in a velocity-dependent resistive force field is possible even when feedback is limited. However, the absence of VFb leads to different strategies that were only apparent when reaching toward the most challenging target.

Experimental tonic hand pain modulates the corticospinal plasticity induced by a subsequent hand deafferentation

Sensorimotor reorganization is believed to play an important role in the development and maintenance of phantom limb pain, but pain itself might modulate sensorimotor plasticity induced by deafferentation. Clinical and basic research support this idea, as pain prior to amputation increases the risk of developing post-amputation pain. The aim of this study was to examine the influence of experimental tonic cutaneous hand pain on the plasticity induced by temporary ischemic hand deafferentation. Sixteen healthy subjects participated in two experimental sessions (Pain, No Pain) in which transcranial magnetic stimulation was used to assess corticospinal excitability in two forearm muscles (flexor carpi radialis and flexor digitorum superficialis) before (T0, T10, T20, and T40) and after (T60 and T75) inflation of a cuff around the wrist. The cuff was inflated at T45 in both sessions and in the Pain session capsaicin cream was applied on the dorsum of the hand at T5. Corticospinal excitability was significantly greater during the Post-inflation phase (p=0.002) and increased similarly in both muscles (p=0.861). Importantly, the excitability increase in the Post-inflation phase was greater for the Pain than the No-Pain condition (p=0.006). Post-hoc analyses revealed a significant difference between the two conditions during the Post-inflation phase (p=0.030) but no difference during the Pre-inflation phase (p=0.601). In other words, the corticospinal facilitation was greater when pain was present prior to cuff inflation. These results indicate that pain can modulate the plasticity induced by another event, and could partially explain the sensorimotor reorganization often reported in chronic pain populations.

Changes in fall-related mortality in older adults in Quebec, 1981–2009

Introduction

Our purpose was to evaluate changes in fall-related mortality in adults aged 65 years and over in Quebec and to propose a case definition based on all the causes entered on Return of Death forms.

Methods

The analysis covers deaths between 1981 and 2009 recorded in the Quebec vital statistics data.

Results

While the number of fall-related deaths increased between 1981 and 2009, the adjusted falls-related mortality rate remained relatively stable. Since the early 2000s, this stability has masked opposing trends. The mortality rate associated with certified falls (W00–W19) has increased while the rate for presumed falls (exposure to an unspecified factor causing a fracture) has decreased.

Conclusion

For fall surveillance, analyses using indicators from the vital statistics data should include both certified falls and presumed falls. In addition, a possible shift in the coding of fall-related deaths toward secondary causes should be taken into account.

Changes in fall-related mortality in older adults in Quebec, 1981-2009

INTRODUCTION

Our purpose was to evaluate changes in fall-related mortality in adults aged 65 years and over in Quebec and to propose a case definition based on all the causes entered on Return of Death forms.

METHODS

The analysis covers deaths between 1981 and 2009 recorded in the Quebec vital statistics data.

RESULTS

While the number of fall-related deaths increased between 1981 and 2009, the adjusted falls-related mortality rate remained relatively stable. Since the early 2000s, this stability has masked opposing trends. The mortality rate associated with certified falls (W00-W19) has increased while the rate for presumed falls (exposure to an unspecified factor causing a fracture) has decreased.

CONCLUSION

For fall surveillance, analyses using indicators from the vital statistics data should include both certified falls and presumed falls. In addition, a possible shift in the coding of fall-related deaths toward secondary causes should be taken into account.

Short-term reliability of transcranial magnetic stimulation motor maps in upper limb amputees

The aim of this study was to verify the short-term reliability of transcranial magnetic stimulation (TMS) parameters for a damaged stump muscle in upper-limb amputees (n=6). The motor threshold, response latency and map center of gravity in the mediolateral plane showed good reliability, whereas the map volume measure was less stable. The stability of most TMS measures across time supports the use of TMS in studying cortical plasticity in amputees.

[The MRC (County Regional Municipality) team: new configuration of the team and mental health reform]

The concept of the équipe MRC (county regional municipality team) has developed as a result of the rapid transformation of mental health services. In most regions of Quebec, there has been a transition from an institutional model, where all services were provided by a single establishment, to a dispersed model where there are a whole range of services provided by a multitude of agencies. In this context, partnership becomes a necessity. The intention of the équipe MRC is thus to provide a structure that brings together under the same aegis all the public-sector and community-based personnel working with clients who suffer from severe and persistent mental health problems. This article seeks to define the concept of the équipe MRC and to assess the state of collaboration among the members of these teams, taking into account the fact that relations between community-based and public-sector agencies have not always been productive.

Use of bovine satellite sequences to increase transgene integration by homologous recombination in bovine embryos

Homologous recombination (HR) has proven to be functional in mammalian embryos. The efficiency of the HR process was tested in bovine zygotes in an attempt to increase the frequency of transgene integration using different lengths of a bovine satellite (BS) DNA flanking both ends of a neo gene marker (called BS500, BS250, and BS50) and neo alone as a control. Pronuclear microinjection at 16-19 hr post insemination (hpi) of the BS500, BS250, BS50 or neo fragments at a concentration of 1 ng/microl resulted in an increasingly negative effect on embryo development. Therefore all microinjections were performed at a single molecular concentration (320 x 10(6) molecules/ microl). After microinjection, the embryos were allowed to develop for 6 days followed by morphological and PCR analysis. The HR event was detected by PCR in 13 of the 26 embryos (43%) that developed beyond the 12-cell stage, 7/22 (31%), 9/27 (33%), and 0/25 (0%) with the BS500, BS250, BS50, and neo constructs respectively. The length of BS homology had no effect on transgene integration. However, embryos injected with BS neo constructs had significantly lower development rates than neo injected zygotes (17% more than 16 cells for BS500; 14% for BS250; 16% for BS50 compared to 32% for neo, P < 0.05, 6 replicates). These results demonstrate that BS sequences have a negative effect on embryo development and survival regardless of the amount of DNA injected. The use of HR with highly repetitive genomic sequences is therefore a feasible procedure to produce transgenic bovine embryos.

pi-Stacking interactions. Alive and well in proteins

A representative set of high resolution x-ray crystal structures of nonhomologous proteins have been examined to determine the preferred positions and orientations of noncovalent interactions between the aromatic side chains of the amino acids phenylalanine, tyrosine, histidine, and tryptophan. To study the primary interactions between aromatic amino acids, care has been taken to examine only isolated pairs (dimers) of amino acids because trimers and higher order clusters of aromatic amino acids behave differently than their dimer counterparts. We find that pairs (dimers) of aromatic side chain amino acids preferentially align their respective aromatic rings in an off-centered parallel orientation. Further, we find that this parallel-displaced structure is 0.5-0.75 kcal/mol more stable than a T-shaped structure for phenylalanine interactions and 1 kcal/mol more stable than a T-shaped structure for the full set of aromatic side chain amino acids. This experimentally determined structure and energy difference is consistent with ab initio and molecular mechanics calculations of benzene dimer, however, the results are not in agreement with previously published analyses of aromatic amino acids in proteins. The preferred orientation is referred to as parallel displaced pi-stacking.

Long-term bone loss in kidney transplant recipients: a cross-sectional and longitudinal study

Organ transplantation is associated with an early bone loss that subsequently increases the risk of osteopenia and bone fractures. It is not known whether bone loss continues in long-term survivors, but persistent bone demineralization could further jeopardize an already diminished bone mass. To better define long-term bone status of kidney transplant recipients (KTR), we conducted cross-sectional and longitudinal evaluations of bone mineral density (BMD) in 70 KTR with a mean posttransplantation time of 8.1 years. BMD was determined by dual-energy X-ray absorptiometry and was repeated in 55 of the patients after a mean follow-up period of 22 +/- 5 months. Lumbar and femoral osteopenia, defined as a BMD lower than 2 standard deviations from mean value of sex- and age-matched controls, was present in 28.6% and 10.5% of patients, respectively. There was a significant negative correlation between cumulative prednisone dose and adjusted lumbar as well as femoral BMD (R = 0.45, P < 0.001 and R = 0.29, P < 0.05, respectively). Five patients had a vertebral BMD below a fracture threshold of 0.777 g/cm2. Vertebral fractures (VF) were found in four men and were associated with higher prednisone dosage (P < 0.05), larger cumulative prednisone dose (P < 0.05), and significantly lower BMD values. According to World Health Organization recent criteria for women, prevalences of lumbar and femoral osteopenia and lumbar and femoral osteoporosis in female patients reach 75%, 65%, 33%, and 10%, respectively. The longitudinal part of the study showed a persistent pathological lumbar demineralization process. Over the study period, BMD, expressed as a percentage of that of controls, decreased from 89 +/- 14% to 86 +/- 14% (P < 0.001). Annual change of bone mass was -1.7 +/- 2.8% per year. Accelerated vertebral bone loss (defined as a decrease of BMD, expressed as a percentage of that of controls, of more than 1% per year) was present in 56% of patients and was associated with higher prednisone dosage (P < 0.01). In conclusion, although VF are relatively infrequent in long-term survivors of renal transplantation, osteopenia is a frequent finding, and a substantial proportion of women present lumbar osteoporosis. An ongoing demineralization process of the spine is also demonstrated and probably contributes to long-term spinal osteoporosis incidence. Prednisone dosage remains the most constantly isolated risk factor.

Airevac nurses in war zones

Since early 1993, the flight nurses and flight medical assistants of the Canadian Air Force (CAF) have been evacuating casualties from the war zones of Bosnia, Somalia and Rwanda. It's the first time since the Korean War that Canadian medical crews have done airevacs from a theatre of war, and the evacuations have been demanding--and eye-opening--experiences.

Effect of microinjection time during postfertilization S-phase on bovine embryonic development

Microinjection into bovine zygotes was performed to evaluate the effects of the timing of injection during the phase of DNA replication on the subsequent in vitro development of embryos and expression of injected chicken beta-actin promoter-lac Z gene construct. The period of DNA replication of bovine zygotes, determined by 3H-thymidine incorporation, begins between 12 hr and 13 hr postinsemination (hpi) of in vitro matured oocytes, reaches a maximum from 17 hpi to 19 hpi, and is complete by 21-22 hpi. Aphidicolin, an inhibitor of DNA polymerase alpha, was used to synchronize the pronuclei and the zygote population. Treatment with aphidicolin at 9-18 hpi arrested DNA replication without affecting formation of the pronuclei or embryo development. Cycloheximide, an inhibitor of protein synthesis, was used for nucleocytoplasmic resynchronization of the aphidicolin-treated zygotes. Microinjection was performed at 15 (early), 18 (mid), and 21 (late S phase) hpi. Embryonic development was affected following each of the three microinjection times. The development of zygotes injected at 18 hpi was significantly higher (P < 0.01) after 5 days of culture than those injected at 15 hpi or 21 hpi. Expression of the marker gene was observed in the higher stage of development (> 16 cells) only in the zygotes injected at 18 hpi. At the earlier stages of development, the proportions of embryos showing expression of the foreign gene were the same for all microinjection times. In aphidicolin- and cycloheximide-treated zygotes, expression of the marker gene followed the same curve as development, i.e., expression was low when injected early or late and higher (P < 0.005) when injected in the middle of zygotic S phase. The ability of the embryos to survive microinjection and to express the marker gene as a function of hpi seems to be influenced mostly in the cytoplasm processing stage rather than the pronuclei processing stage.

Stark-cell stabilized submillimeter wave laser at 393 mum

We report new Stark resonances in methylene fluoride on the R18 line of the 9.4-microm CO(2) laser transition. These resonances are used to stabilize an optically pumped formic acid laser at 393 microm.

Developmental potential of early bovine zygotes submitted to centrifugation and microinjection following in vitro maturation of oocytes

This study was designed to investigate the potential use of in vitro matured, in vitro fertilized bovine zygotes for producing transgenic calves by microinjection of foreign DNA. In Experiment 1, the effect of centrifugation (4 min, 15,000 x g, 20 degrees C) on in vitro derived bovine zygotes was evaluated. In vitro development from 2 to 8 cells was not affected (80 vs 78%) when control zygotes (n = 211) were compared with zygotes treated (n = 210) 18 h post insemination. In Experiment 2, the influence of the centrifugation alone on the developmental potential of embryos was evaluated in rabbit oviducts for 120 h. The percentage of control and treated zygotes that developed to 1, 2 to 8, 8 to 32 and more than 32 cells were 7, 54, 10 and 10% vs 7, 40, 11 and 10%, respectively. In Experiment 3, the effect of pronuclear injection with plasmid containing CRF (corticotropin releasing factor) gene or pOCAT 330 Delta 1 plasmids; 2 microg/ml in Tris 10 mM, EDTA 0.2 mM, 18 to 20 h post insemination was evaluated by in vivo development in the rabbit oviduct. The embryos submitted only to centrifugation and vortexing resulted in a morula-blastocyst (> 32 cells) rate of 25% (n = 226) compared with the injected zygotes of which only 5% (n = 206) achieved the same stage. We conclude that in vitro produced bovine zygotes have a reduced developmental potential following microinjection, and this effect is not due to the centrifugation process.

Relative leucopenia in the peripheral blood of asbestos miners: a epidemiologic analysis

The study examines differential leucocyte counts in blood of asbestos miners and quarriers identified during the course of a community health survey comprising 693 men over 25 years of age of all occupations. Subjects in the asbestos mining and quarrying occupational groups were present in the lowest total leucocyte quintile in significantly greater numbers than expected on the basis of a age-specific uniform leucocyte distribution based upon the total population of male workers. This relative leucopenia was not seen in their wives nor in any of the 22 other major occupational groups examined after their leucocyte counts were adjusted for age and sex variations.