Taking the Monte-Carlo gamble: How not to buckle under the pressure!

Consistent buckling distortions of a large membrane patch (200 × 200 Å) are observed during molecular dynamics (MD) simulations using the Monte-Carlo (MC) barostat in combination with a hard Lennard-Jones (LJ) cutoff. The buckling behavior is independent of both the simulation engine and the force field but requires the MC barostat-hard LJ cutoff combination. Similar simulations of a smaller patch (90 × 90 Å) do not show buckling, but do show a small, systematic reduction in the surface area accompanied by ~1 Å thickening suggestive of compression. We show that a mismatch in the way potentials and forces are handled in the dynamical equations versus the MC barostat results in a compressive load on the membrane. Moreover, a straightforward application of elasticity theory reveals that a minimal compression of the linear dimensions of the membrane, inversely proportional to the edge length, is required for buckling, explaining this differential behavior. We recommend always using LJ force or potential-switching when the MC barostat is employed to avoid undesirable membrane deformations.

Sleep-disordered breathing in high-risk pregnancies is associated with elevated arterial stiffness and increased risk for preeclampsia.

BACKGROUND: Impaired vascular function is a central feature of pathologic processes preceding the onset of preeclampsia. Arterial stiffness, a composite indicator of vascular health and an important vascular biomarker, has been found to be increased throughout pregnancy in those who develop preeclampsia and at the time of preeclampsia diagnosis. Although sleep-disordered breathing in pregnancy has been associated with increased risk for preeclampsia, it is unknown if sleep-disordered breathing is associated with elevated arterial stiffness in pregnancy. OBJECTIVE: This prospective observational cohort study aimed to evaluate arterial stiffness in pregnant women, with and without sleep-disordered breathing and assess the interaction between arterial stiffness, sleep-disordered breathing, and preeclampsia risk. STUDY DESIGN: Women with high-risk singleton pregnancies were enrolled at 10 to 13 weeks' gestation and completed the Epworth Sleepiness Score, Pittsburgh Sleep Quality Index, and Restless Legs Syndrome questionnaires at each trimester. Sleep-disordered breathing was defined as loud snoring or witnessed apneas (≥3 times per week). Central arterial stiffness (carotid-femoral pulse wave velocity, the gold standard measure of arterial stiffness), peripheral arterial stiffness (carotid-radial pulse wave velocity), wave reflection (augmentation index, time to wave reflection), and hemodynamics (central blood pressures, pulse pressure amplification) were assessed noninvasively using applanation tonometry at recruitment and every 4 weeks from recruitment until delivery. RESULTS: High-risk pregnant women (n=181) were included in the study. Women with sleep-disordered breathing (n=41; 23%) had increased carotid-femoral pulse wave velocity throughout gestation independent of blood pressure and body mass index (P=.042). Differences observed in other vascular measures were not maintained after adjustment for confounders. Excessive daytime sleepiness, defined by Epworth Sleepiness Score >10, was associated with increased carotid-femoral pulse wave velocity only in women with sleep-disordered breathing (Pinteraction=.001). Midgestation (first or second trimester) sleep-disordered breathing was associated with an odds ratio of 3.4 (0.9-12.9) for preeclampsia, which increased to 5.7 (1.1-26.0) in women with sleep-disordered breathing and hypersomnolence, whereas late (third-trimester) sleep-disordered breathing was associated with an odds ratio of 8.2 (1.5-39.5) for preeclampsia. CONCLUSION: High-risk pregnant women with midgestational sleep-disordered breathing had greater arterial stiffness throughout gestation than those without. Sleep-disordered breathing at any time during pregnancy was also associated with increased preeclampsia risk, and this effect was amplified by hypersomnolence.

Awareness and Use of Heated Tobacco Products Among Middle School and High School Students, United States, 2019-2020.

PURPOSE: Heated tobacco products (HTP) heat-processed tobacco leaf into an aerosol inhaled by the user. This study assessed prevalence and correlates of HTP awareness, ever use, and current use among US middle and high school students. METHODS: Data came from the 2019 and 2020 National Youth Tobacco Survey, a cross-sectional survey of US public and private, middle and high school students. HTP awareness, ever use, and current (past 30-day) use were assessed. Weighted prevalence estimates and adjusted prevalence ratios (aPR) were assessed overall and by sex, school level, race/ethnicity, and current other tobacco product use. RESULTS: In 2019, 12.8% (3.44 million) of all students reported HTP awareness, increasing to 19.3% (5.29 million) in 2020 (p < .01). Ever [2019: 2.6% (630 000); 2020: 2.4% (620 000)] and current [2019: 1.6% (420 000); 2020: 1.4% (370 000)] HTP use did not significantly change from 2019 to 2020. Current e-cigarette users were more likely to report ever (2020 aPR = 1.79, 95% CI:1.23, 2.62) or current HTP use (2019 aPR = 5.16, 95% CI: 3.48, 7.67; 2020 aPR = 3.39, 95% CI: 2.10, 5.47) than nonusers. In both years, ever and current HTP use was more likely among current combustible (aPR range = 3.59-8.17) and smokeless tobacco product (aPR range = 2.99-4.09) users than nonusers. CONCLUSIONS: HTP awareness increased 51% among US students during 2019-2020; however, HTP use did not significantly change during this period. Students who used other tobacco products were more likely to currently use HTPs. Estimates of HTP awareness and use provided serve as a baseline as future monitoring of these products is warranted. IMPLICATIONS: Awareness of heated tobacco products (HTPs) increased among US youth from 2019 to 2020; however, HTP use did not change. These estimates of HTP awareness and use serve as a baseline for future surveillance of these products as their availability in the US increases.

Patterns of tobacco use and nicotine dependence among youth, United States, 2017-2018.

This study examined patterns of tobacco product use and their association with nicotine dependence among U.S. youth. Combined data from the 2017-2018 National Youth Tobacco Surveys were analyzed for students that reported current (past-30-day) use of e-cigarettes, cigarettes, cigars, smokeless tobacco, or hookah (n = 6106). Analyses assessed multiple product use (≥2 tobacco products) overall and by sex, school level, race/ethnicity, current use, and frequent use (use of a product for ≥20 of the preceding 30 days). Multivariable logistic regression was used to identify correlates of nicotine dependence. During 2017-2018, 40.8% of tobacco product users reported use of multiple products. Multiple product use ranged from 47.0% among e-cigarette users to 80.7% among cigarette smokers. Among frequent users of each respective product, 80.0% of cigarette smokers, 74.9% of cigar smokers, 73.6% of smokeless tobacco users, 70.7% of hookah smokers, and 40.3% of e-cigarette users reported use of multiple products. Most youth who reported nicotine dependence (64.0%) were multiple product users. E-cigarettes were the most common single product used (36.3%) and the product most commonly used in combination with other products; e-cigarettes plus cigarettes (6.7%) was the most common product combination. Combustible product use, smokeless tobacco use, multiple product use and frequent use were associated with greater odds of nicotine dependence. Nicotine dependence among youth is especially influenced by cigarette use, smokeless tobacco use, frequent use of any tobacco product, and multiple product use. Proven tobacco control interventions in coordination with regulatory efforts can reduce youth tobacco product use.

E-cigarette advertising expenditures in the USA, 2014-2018.

BACKGROUND: Tobacco product advertising has been shown to reach youth and promote initiation. This study assessed trends in e-cigarette advertising expenditures in the USA during 2014-2018, overall and by manufacturer and media type. METHODS: Data came from Kantar Media, which provides information on US advertising expenditures, including for e-cigarettes. Advertising expenditures were estimated as the dollar amount spent by e-cigarette companies to purchase advertising space in print, television, Internet, radio and outdoors. Dollar amounts were adjusted to 2017 dollars. Trends in e-cigarette advertising expenditures during 2014-2018 were analysed using Joinpoint regression overall, by media type, and by manufacturers based on 2017-2018 national sales. RESULTS: Total e-cigarette advertising expenditures in print, radio, television, Internet and outdoors decreased substantially from US$133 million in 2014 to US$48 million in 2017, followed by an increase to US$110 million in 2018. By media type, expenditures were highest for print advertising, irrespective of year. By manufacturer, Altria had the highest e-cigarette advertising expenditures, totalling over US$134 million during 2014-2018. Imperial Tobacco had the second highest, totalling over US$85 million during 2014-2018, while JUUL Labs had the highest single-year expenditures, spending over US$73 million in 2018 alone. CONCLUSIONS: E-cigarette advertising expenditures have been volatile in the USA, with declines in traditional advertising venues during 2014-2017 that may reflect a shift towards social media. However, an increase occurred in 2018 that is likely reflective of advertising by newer manufacturers. Continued monitoring of e-cigarette advertising is important to inform tobacco control strategies.

Harmonizing Experimental Data with Modeling to Predict Membrane Protein Insertion in Yeast.

Membrane proteins must adopt their proper topologies within biological membranes, but achieving the correct topology is compromised by the presence of marginally hydrophobic transmembrane helices (TMHs). In this study, we report on a new model membrane protein in yeast that harbors two TMHs fused to an unstable nucleotide-binding domain. Because the second helix (TMH2) in this reporter has an unfavorable predicted free energy of insertion, we employed established methods to generate variants that alter TMH2 insertion free energy. We first found that altering TMH2 did not significantly affect the extent of protein degradation by the cellular quality control machinery. Next, we correlated predicted insertion free energies from a knowledge-based energy scale with the measured apparent free energies of TMH2 insertion. Although the predicted and apparent insertion energies showed a similar trend, the predicted free-energy changes spanned an unanticipated narrow range. By instead using a physics-based model, we obtained a broader range of free energies that agreed considerably better with the magnitude of the experimentally derived values. Nevertheless, some variants still inserted better in yeast than predicted from energy-based scales. Therefore, molecular dynamics simulations were performed and indicated that the corresponding mutations induced conformational changes within TMH2, which altered the number of stabilizing hydrogen bonds. Together, our results offer insight into the ability of the cellular quality control machinery to recognize conformationally distinct misfolded topomers, provide a model to assess TMH insertion in vivo, and indicate that TMH insertion energy scales may be limited depending on the specific protein and the mutation present.

Ensemble simulations: folding, unfolding and misfolding of a high-efficiency frameshifting RNA pseudoknot.

Massive all-atom molecular dynamics simulations were conducted across a distributed computing network to study the folding, unfolding, misfolding and conformational plasticity of the high-efficiency frameshifting double mutant of the 26 nt potato leaf roll virus RNA pseudoknot. Our robust sampling, which included over 40 starting structures spanning the spectrum from the extended unfolded state to the native fold, yielded nearly 120 µs of cumulative sampling time. Conformational microstate transitions on the 1.0 ns to 10.0 µs timescales were observed, with post-equilibration sampling providing detailed representations of the conformational free energy landscape and the complex folding mechanism inherent to the pseudoknot motif. Herein, we identify and characterize two alternative native structures, three intermediate states, and numerous misfolded states, the latter of which have not previously been characterized via atomistic simulation techniques. While in line with previous thermodynamics-based models of a general RNA folding mechanism, our observations indicate that stem-strand-sequence-separation may serve as an alternative predictor of the order of stem formation during pseudoknot folding. Our results contradict a model of frameshifting based on structural rigidity and resistance to mechanical unfolding, and instead strongly support more recent studies in which conformational plasticity is identified as a determining factor in frameshifting efficiency.

State-Specific Patterns of Cigarette Smoking, Smokeless Tobacco Use, and E-Cigarette Use Among Adults - United States, 2016.

INTRODUCTION: State-level monitoring of changes in tobacco product use can help inform tobacco control policy and practice. This study examined state-specific prevalence of cigarette, smokeless tobacco, and e-cigarette use among US adults. METHODS: Data came from the 2016 Behavioral Risk Factor Surveillance System (BRFSS), a state-based telephone survey of US adults aged 18 years or older (N = 477,665). Prevalence estimates for current (every day or some days) cigarette smoking, smokeless tobacco use, and e-cigarette use were calculated for all 50 states and the District of Columbia (DC) and stratified by sex and race/ethnicity. Because the 2016 BRFSS measured e-cigarette use for the first time, estimates of ever e-cigarette use and concurrent use of cigarettes and e-cigarettes were also calculated. We assessed subgroup differences with χ2 tests. RESULTS: In 2016, prevalence of current cigarette smoking among US adults ranged from 8.8% (Utah) to 24.8% (West Virginia), while prevalence of current smokeless tobacco use ranged from 1.3% (DC) to 9.8% (Wyoming). For e-cigarettes, ever use ranged from 16.2% (DC) to 28.4% (Arkansas), and current use ranged from 2.4% (DC) to 6.7% (Oklahoma). Across all states, current e-cigarette use was significantly higher among current cigarette smokers than among former or never cigarette smokers. States with the highest prevalence of cigarette smoking generally had a high prevalence of current e-cigarette use. CONCLUSION: Prevalence of adult cigarette smoking, smokeless tobacco use, and e-cigarette use varies across states. These findings underscore the importance of comprehensive statewide tobacco control and use prevention efforts that address the diverse tobacco products used among adults.

Rules to prohibit the use of electronic vapor products inside homes and personal vehicles among adults in the U.S., 2017.

Most U.S. adults have voluntary rules prohibiting the use of smoked tobacco products in their homes and vehicles. However, the prevalence of similar rules for electronic vapor products (EVPs) is uncertain. This study assessed the prevalence and correlates of rules prohibiting EVP use inside homes and vehicles. Data from a 2017 Internet-based panel survey of U.S. adults aged ≥18 years (n = 4107) were analyzed. For homes and vehicles, prevalence of reporting that EVP use was not allowed, partially allowed, fully allowed, or unknown was assessed overall and by covariates. Correlates of prohibiting EVP use was assessed by multivariable logistic regression. In homes, 58.6% of adults did not allow EVP use, 7.7% partially allowed use, 10.1% fully allowed use, and 23.6% were unsure of the rules. In vehicles, 63.8% of respondents did not allow EVP use, 6.0% partially allowed use, 8.9% fully allowed use, and 21.4% were unsure of the rules. Following multivariable adjustment, prohibiting EVP use inside homes and vehicles was more likely among respondents with higher income and education, and with a child aged <18 years. Users of EVPs and other tobacco products, and respondents living with users of EVPs and other tobacco products, were less likely to prohibit EVP use in these locations. These findings show that about 6 in 10 U.S. adults have rules prohibiting EVP use inside homes and vehicles, but variations exist by population subgroups. Voluntary smoke-free rules in homes and vehicles that include EVPs can help protect children and non-users from secondhand EVP aerosol exposure.

MEthods of ASsessing blood pressUre: identifying thReshold and target valuEs (MeasureBP): a review & study protocol.

Despite progress in automated blood pressure measurement (BPM) technology, there is limited research linking hard outcomes to automated office BPM (OBPM) treatment targets and thresholds. Equivalences for automated BPM devices have been estimated from approximations of standardized manual measurements of 140/90 mmHg. Until outcome-driven targets and thresholds become available for automated measurement methods, deriving evidence-based equivalences between automated methods and standardized manual OBPM is the next best solution. The MeasureBP study group was initiated by the Canadian Hypertension Education Program to close this critical knowledge gap. MeasureBP aims to define evidence-based equivalent values between standardized manual OBPM and automated BPM methods by synthesizing available evidence using a systematic review and individual subject-level data meta-analyses. This manuscript provides a review of the literature and MeasureBP study protocol. These results will lay the evidenced-based foundation to resolve uncertainties within blood pressure guidelines which, in turn, will improve the management of hypertension.

SARS-CoV-2 vaccine uptake and reasons for hesitancy among Canadian pregnant people: a prospective cohort study.

BACKGROUND: Several vaccines against SARS-CoV-2 have been developed and approved at an unparalleled speed. Given that SARS-CoV-2 vaccines are recommended to pregnant people, our aim was to quantify vaccination uptake, and describe vaccination hesitancy and behavioural attitudes surrounding SARS-CoV-2 vaccination in pregnancy in Canada. METHODS: The CONCEPTION study is an ongoing international study started in June 2020, evaluating the impact of the COVID-19 pandemic on the health of pregnant people and their children. For this study, pregnant people recruited from Apr. 20, 2021, to Feb. 8, 2022, and residing in Canada were invited to complete a Web-based survey. In addition to all CONCEPTION variables, data on vaccine uptake as well as personal knowledge of COVID-19 severity in pregnancy and of SARS-CoV-2 vaccine safety and efficacy were collected. Marginal risk differences and adjusted odds ratios (ORs) were calculated to assess determinants of SARS-CoV-2 vaccination during pregnancy. RESULTS: From Apr. 20, 2021, to Feb. 8, 2022, 603 pregnant people were recruited and gave consent, of which 83.7% (n = 505) were vaccinated and 16.3% (n = 98) were not vaccinated against SARS-CoV-2. Uptake of the influenza vaccine in 2020/21 was a significant predictor of being vaccinated against SARS-CoV-2 or intention to be vaccinated (marginal risk difference 3.2%, 95% confidence interval [CI] 3.0% to 3.3%, adjusted OR 4.43, 95% CI 2.32 to 9.25), and being employed (marginal risk difference 11.2%, 95% CI 10.6% to 11.9%, adjusted OR 2.17, 95% CI 1.03 to 4.35) increased the likelihood of being vaccinated against SARS-CoV-2. Self-assessed knowledge of COVID-19 severity and vaccine efficacy was not associated with vaccine uptake. INTERPRETATION: Among the Canadian pregnant people who responded to this study, vaccine uptake against SARS-CoV-2 was high. However, our results underscore the importance of improving knowledge transfer about the efficacy of SARS-CoV-2 vaccines in pregnancy to guide vaccination efforts.

Is in-utero exposure to cannabis associated with the risk of attention deficit with or without hyperactivity disorder? A cohort study within the Quebec Pregnancy Cohort.

IMPORTANCE AND OBJECTIVE: Prenatal cannabis effect on attention deficit with or without hyperactivity disorder (ADHD) remains to be determined. Our aim is to quantify the impact of in-utero exposure to cannabis on the risk of ADHD. DESIGN: Cohort study. SETTING: Questionnaires were mailed to women sampled from the Quebec Pregnancy Cohort (QPC). Data from questionnaires were then linked with their QPC (built with administrative health databases, hospital patient charts and birth certificate databases). PARTICIPANTS: Respondents who gave birth to a singleton live born between January 1998 and December 2003 and were continuously enrolled in the Régie de l'assurance maladie du Québec (RAMQ) medication insurance plan for at least 12 months before the first day of gestation and during pregnancy. EXPOSURE: In-utero cannabis exposure was based on mothers' answers to the question on cannabis use during pregnancy (yes/no) and categorised as occasionally, regularly exposed and unexposed if they chose one of these categories. OUTCOMES: ADHD was defined by a diagnosis of ADHD through the RAMQ medical services or MedEcho databases or a prescription filled for ADHD medication through RAMQ pharmaceutical services between birth and the end of the follow-up period. Follow-up started at the birth and ended at the index date (first diagnosis or prescription filled for ADHD), child death (censoring), end of public coverage for medications (censoring) or the end of study period, which was December 2015 (censoring), whichever event came first. RESULTS: A total of 2408 children met the inclusion criteria. Of these children, 86 (3.6%) were exposed to cannabis in-utero and 241 (10.0%) had an ADHD diagnosis or medication filled. After adjustments for potential confounders, no significant association was found between in-utero cannabis exposure (occasional (1.22 (95% CI 0.63 to 2.19)) or regular (1.22 (95% CI 0.42 to 2.79))) and the risk of ADHD in children. CONCLUSIONS: In-utero exposure to cannabis seemed to not be associated with the risk ADHD in children.

The Canadian Mother-Child Cohort Active Surveillance Initiative (CAMCCO): Comparisons between Quebec, Manitoba, Saskatchewan, and Alberta.

BACKGROUND: Given that pregnant women taking medications are excluded from clinical trials, real-world evidence is essential. We aimed to build a Canadian Mother-Child Cohort Active Surveillance Initiative (CAMCCO) and compare frequency of prematurity, low-birth-weight (LBW), major malformations, multiplicity, and gestational medication use across four provinces. METHODS: CAMCCO is a collaborative research infrastructure that uses real-world data from large provincial health care databases in Canada; developed with standardized methods to similarly construct population-based pregnancy/child cohorts with longitudinal follow-up by linking administrative/hospital/birth databases. CAMCCO also includes a common repository to i) share algorithms and case definitions based on diagnostic and procedural codes for research/training purpose, and ii) download aggregate data relevant to primary care providers, researchers, and decision makers. For this study, data from Quebec (1998-2015), Manitoba (1995-2019), Saskatchewan (1996-2020), and Alberta (2005-2018) are compared (Chi-square tests, p-values), and trends are calculated using Cochran-Armitage trend tests. RESULTS: Almost two-thirds (61%) of women took medications during pregnancy, mostly antibiotics (26%), asthma drugs (8%), and antidepressants (4%). Differences in the prevalence of prematurity (5.9-6.8%), LBW (4.0-5.2%), and multiplicity (1.0-2.5%) were statistically significant between provinces (p<0.001). Frequency of major malformations increased over time in Quebec (7-11%; p<0.001), Saskatchewan (5-11%; p<0.001), and Alberta (from 7-8%; p<0.001), and decreased in Manitoba (5-3%; p<0.001). Cardiovascular and musculoskeletal malformations were the most prevalent. INTERPRETATION: Medications are often used among Canadian pregnancies but adverse pregnancy outcomes vary across provinces. Digitized health data may help researchers and care providers understand the risk-benefit ratios related to gestational medication use, as well as province-specific trends.

The COVID-19 Pandemic Impacted Maternal Mental Health Differently Depending on Pregnancy Status and Trimester of Gestation.

Introduction: We aimed to measure the impact of the COVID-19 pandemic on maternal mental health, stratifying on pregnancy status, trimester of gestation, and pandemic period/wave. Methods: Pregnant persons and persons who delivered in Canada during the pandemic, >18 years, were recruited, and data were collected using a web-based strategy. The current analysis includes data on persons enrolled between 06/2020−08/2021. Maternal sociodemographic indicators, mental health measures (Edinburgh Perinatal Depression Scale (EPDS), Generalized Anxiety Disorders (GAD-7), stress) were self-reported. Maternal mental health in pregnant women (stratified by trimester, and pandemic period/wave at recruitment) was compared with the mental health of women who had delivered; determinants of severe depression were identified with multivariate logistic regression models. Results: 2574 persons were pregnant and 626 had already delivered at recruitment. Participants who had delivered had significantly higher mean depressive symptom scores compared to those pregnant at recruitment (9.1 (SD, 5.7) vs. 8.4 (SD, 5.3), p = 0.009). Maternal anxiety (aOR 1.51; 95%CI 1.44−1.59) and stress (aOR 1.35; 95%CI 1.24−1.48) were the most significant predictors of severe maternal depression (EDPS ˃ 13) in pregnancy. Conclusion: The COVID-19 pandemic had a significant impact on maternal depression during pregnancy and in the post-partum period. Given that gestational depression/anxiety/stress has been associated with preterm birth and childhood cognitive problems, it is essential to continue following women/children, and develop strategies to reduce COVID-19's longer-term impact.

A longitudinal analysis of arterial stiffness and wave reflection in preeclampsia: Identification of changepoints.

PURPOSE: Preeclampsia (PrE) is a leading complication of pregnancy characterized by vascular dysfunction. Characterizing the longitudinal changes in vascular function prior to PrE onset is critical to the identification of optimal timepoints for vascular assessment and the development of effective early screening strategies. METHODS: In this prospective longitudinal study of women with singleton high-risk pregnancies, arterial stiffness and wave reflection parameters were assessed using applanation tonometry at 10-13 weeks' gestation and repeated every 4 weeks throughout pregnancy. Changepoints in carotid-femoral pulse wave velocity (cfPWV), carotid-radial PWV (crPWV), augmentation index (AIx), time to wave reflection (T1R), pulse pressure amplification (PPA), and subendocardial viability ratio (SEVR) were compared between women who did and did not subsequently develop PrE. RESULTS: A changepoint in cfPWV and crPWV was detected at 14-17 weeks' gestation. cfPWV then increased in women who went on to develop PrE but decreased in women who did not; a 1.2 m/s difference in cfPWV between the groups was observed at 22-25 weeks' gestation. Conversely, crPWV converged in the two groups from a baseline difference of 1.05 m/s (95% credible interval: 0.37, 1.72). Women who subsequently developed PrE demonstrated an increase in AIx at 18-21 weeks' gestation that was not seen in women who did not develop PrE until 30-33 weeks. No differences in T1R, PPA, or SEVR were observed between the groups. CONCLUSIONS: Altered vascular adaptations were detected using measures of arterial stiffness and wave reflection in the early second trimester of pregnant women who developed PrE compared to those who did not. These findings demonstrate the potential clinical utility of arterial stiffness and wave reflection parameters as an early screening tool for PrE, which can be used to inform clinical management of high-risk pregnancies.

Robust Sequence Determinants of α-Synuclein Toxicity in Yeast Implicate Membrane Binding.

Protein conformations are shaped by cellular environments, but how environmental changes alter the conformational landscapes of specific proteins in vivo remains largely uncharacterized, in part due to the challenge of probing protein structures in living cells. Here, we use deep mutational scanning to investigate how a toxic conformation of α-synuclein, a dynamic protein linked to Parkinson's disease, responds to perturbations of cellular proteostasis. In the context of a course for graduate students in the UCSF Integrative Program in Quantitative Biology, we screened a comprehensive library of α-synuclein missense mutants in yeast cells treated with a variety of small molecules that perturb cellular processes linked to α-synuclein biology and pathobiology. We found that the conformation of α-synuclein previously shown to drive yeast toxicity-an extended, membrane-bound helix-is largely unaffected by these chemical perturbations, underscoring the importance of this conformational state as a driver of cellular toxicity. On the other hand, the chemical perturbations have a significant effect on the ability of mutations to suppress α-synuclein toxicity. Moreover, we find that sequence determinants of α-synuclein toxicity are well described by a simple structural model of the membrane-bound helix. This model predicts that α-synuclein penetrates the membrane to constant depth across its length but that membrane affinity decreases toward the C terminus, which is consistent with orthogonal biophysical measurements. Finally, we discuss how parallelized chemical genetics experiments can provide a robust framework for inquiry-based graduate coursework.

The Impact of Intradialytic Pedaling Exercise on Arterial Stiffness: A Pilot Randomized Controlled Trial in a Hemodialysis Population.

OBJECTIVES: Regular exercise is known to reduce arterial stiffness (AS) in hemodialysis patients. However, the impact of a more realistic intradialytic form of exercise, such as pedaling, is unclear. We aimed to examine (i) the effect of intradialytic pedaling exercise on AS over 4 months and (ii) the longer term effect of pedaling on AS 4 months after exercise cessation. METHODS: Patients on stable in-center hemodialysis (3 x/week) were randomly assigned 1:1 to either intradialytic pedaling exercise (EX) or to a control group receiving usual hemodialysis (nonEX) for 4 months. At baseline and 4 months, peripheral and central blood pressure (BP) indices, heart rate (HR), augmentation index HR corrected (AIx75), and carotid-femoral pulse wave velocity (cfPWV) were assessed (applanation tonometry). Measurements were repeated in the EX group 4 months postexercise cessation. RESULTS: As per protocol analysis was completed in 10 EX group participants (58 ± 17 years, body mass index 26 ± 4 kg/m2) and 10 nonEX group participants (53 ± 15 years, body mass index 27 ± 6 kg/m2). Peripheral and central BP was unchanged in both groups. AIx75 was unchanged in the EX group, however, a significant median increase of 3.5% [interquartile range, IQR 1.0, 8.5] was noted in the nonEX group (P = 0.009). We noted a significantly greater absolute decrease in cfPWV in the EX group compared to controls: -1.00 [IQR -1.95, 0.05] vs. 0.20 [IQR -0.10, 0.90] (P = 0.033). Interestingly, the decrease in cfPWV observed in the EX group was partially reversed 4 months after exercise cessation. CONCLUSION: Intradialytic pedaling exercise has a beneficial impact on AS. This relationship warrants further investigation. CLINICAL TRIALS REGISTRATION: Trial Number #NCT03027778 (clinicaltrials.gov).

A systematic review on the effect of acute aerobic exercise on arterial stiffness reveals a differential response in the upper and lower arterial segments.

The objective of this systematic review was to provide insight into the controversy that still abounds as to the impact of acute aerobic exercise on immediate changes in arterial stiffness. Electronic databases were searched to identify articles assessing the effects of acute aerobic exercise on parameters of arterial stiffness. Eligible studies included arterial stiffness measurements before and after acute aerobic exercise in healthy human subjects. Forty-three studies were included. The effect of acute aerobic exercise on arterial stiffness was found to be dependent on the anatomical segment assessed, and on the timing of the measurement post-exercise. Arterial stiffness of the central and upper body peripheral arterial segments was found to be increased relative to resting values immediately post-exercise (0-5 min), whereas, thereafter (>5 min), decreased to a level at or below resting values. In the lower limbs, proximal to the primary working muscles, arterial stiffness decreased immediately post-exercise (0-5 min), which persisted into the recovery period post-exercise (>5 min). This systematic review reveals a differential response to acute exercise in the lower and upper/central arterial segments in healthy adult subjects. We further showed that the effect of acute aerobic exercise on arterial stiffness is dependent on the timing of the measurements post-exercise. Therefore, when assessing the overall impact of exercise on arterial stiffness, it is important to consider the arterial segment being analyzed and measurement time point, as failure to contextualize the measurement can lead to conflicting results and misleading clinical inferences.

Tobacco Use, Secondhand Smoke, and Smoke-Free Home Rules in Multiunit Housing.

INTRODUCTION: Multiunit housing (MUH) residents are particularly susceptible to involuntary secondhand smoke (SHS) exposure in their home, which can enter their living units from nearby units and shared areas where smoking occurs. To date, no study has assessed non-cigarette tobacco use among MUH residents. This study assessed the prevalence and sociodemographic correlates of tobacco use (combustible, noncombustible, any tobacco use including electronic cigarettes), smoke-free home rules, and SHS incursions among U.S. MUH residents. METHODS: Data came from the 2013-2014 National Adult Tobacco Survey, a telephone survey of U.S. adults aged ≥18 years. Analyses were conducted in 2015. Prevalence of current tobacco use and smoke-free home rules were assessed overall and by sociodemographics, stratified by housing type (single family versus MUH). Prevalence and adjusted odds of SHS incursions among MUH residents with smoke-free home rules were assessed. RESULTS: Tobacco use was higher among adults living in MUH (24.7%) than those in single-family housing (18.9%, p<0.05). Smoke-free home rules were higher among adults living in single-family housing (86.7%) than those in MUH (80.9%, p<0.05). Among MUH residents with smoke-free homes, 34.4% experienced SHS incursions. Adjusted odds of SHS incursions were greater among women, younger adults, non-Hispanic blacks, Hispanics, and those with lower income. CONCLUSIONS: One quarter of MUH residents use tobacco, and one third of MUH residents with smoke-free rules experience SHS incursions. Interventions are warranted to promote tobacco cessation and smoke-free building policies to protect all MUH residents, employees, and visitors from the dangers of tobacco use and SHS.

From rest to stressed: endothelin-1 levels in young healthy smokers and non-smokers.

INTRODUCTION: Endothelin-1 (ET-1) is a potent vasoconstrictor produced by vascular endothelial cells, and a known marker of endothelial dysfunction. However, the acute and chronic effects of smoking and nicotine gum on the ET-1 response to acute physical stress in young healthy smokers have not been investigated. METHODS: Healthy smokers (n=35) and non-smokers (n=35) underwent an exercise test to exhaustion (maximal oxygen consumption) on a treadmill. Smokers were assessed a) after 12h smoking abstinence (termed chronic smoking), b) immediately after smoking one cigarette (termed acute smoking), and c) immediately after chewing nicotine gum. Blood was drawn immediately pre-exercise, and 3 minutes post-exercise. During exercise, cardiorespiratory parameters were obtained breath-by-breath using an automated metabolic cart. Plasma ET-1 levels were quantified using enzyme-linked immunosorbent-assay. The above protocol was designed to incorporate exercise as a vascular stressor to reveal changes that would not be detected at rest. RESULTS: Mean age was 28.6±7.2 years and body mass index (BMI) was 23.6±3.2 kg/m(2). Post-exercise ET-1 levels were significantly lower than pre-exercise levels in non-smokers (P<0.001) and smokers under all three conditions (P=0.005, P<0.001, P=0.001, respectively). There were no differences in post-exercise ET-1 levels between non-smokers and smokers under all three conditions, however the absolute and relative decrease in ET-1 levels was significantly smaller in chronic smokers compared with non-smokers (P=0.007 and P=0.004). Chronic smokers had a significantly lower exercise-induced change in tidal volume (P=0.050), fraction of expired CO2 (P=0.021), oxygen consumption (P=0.005), carbon dioxide elimination (P=0.004) and peak expiratory flow (P=0.003) compared with non-smokers. Furthermore, the decrease in ET-1 observed in non-smokers in response to exercise was significantly associated with exercise induced-changes in inspiratory time, time for a tidal volume cycle, respiratory frequency, inspired minute ventilation and peak inspiratory flow. CONCLUSIONS: An acute decrease of circulating ET-1 in response to acute maximal exercise in young healthy individuals was noted. Chronic smokers had a significantly diminished decrease in ET-1 compared with non-smokers, however there were no significant differences in the ET-1 response between smokers under the three smoking conditions. Smokers were not able to achieve the same exercise-induced changes in cardiorespiratory parameters as non-smokers. By incorporating exercise as a vascular stressor in our study, we have taken a novel approach to provide evidence of an altered ET-1 and cardiorespiratory response that would not otherwise be observed at rest in young active healthy smokers.