Daytime Variations Research Articles

Usefulness of Blood Pressure Variability Indices Derived From 24-Hour Ambulatory Blood Pressure Monitoring in Detecting Autonomic Failure.

BackgroundIncreased blood pressure (BP) variability and nondipping status seen on 24‐hour ambulatory BP monitoring are often observed in autonomic failure (ATF).Methods and ResultsWe assessed BP variability and nocturnal BP dipping in 273 patients undergoing ambulatory BP monitoring at Southwestern Medical Center between 2010 and 2017. SD, average real variability, and variation independent of mean were calculated from ambulatory BP monitoring. Patients were divided into a discovery cohort (n=201) and a validation cohort (n=72). ATF was confirmed by formal autonomic function test. In the discovery cohort, 24‐hour and nighttime average real variability, SD, and variation independent of mean did not differ significantly between ATF (n=25) and controls (n=176, all P>0.05). However, daytime SD, daytime coefficient of variation, and daytime variation independent of mean of systolic BP (SBP) were all significantly higher in patients with ATF than in controls in both discovery and validation cohorts. Nocturnal BP dipping was more blunted in ATF patients than controls in both cohorts (both P<0.01). Using the threshold of 16 mm Hg, daytime SD SBP yielded a sensitivity of 77% and specificity of 82% in detecting ATF in the validation cohort, whereas nondipping status had a sensitivity of 80% and specificity of 44%. The area under the receiver operator characteristic of daytime SD SBP was greater than the area under the receiver operator characteristic of nocturnal SBP dipping (0.79 [0.66‐0.91] versus 0.73 [0.58‐0.87], respectively).ConclusionsDaytime SD of SBP is a better screening tool than nondipping status in detecting autonomic dysfunction.

Evaluating the effect of 3D urban form on neighborhood land surface temperature using Google Street View and geographically weighted regression

Land surface temperature (LST) directly responds to incoming solar radiation and is strongly influenced by vertical urban structures, such as trees and buildings that provide shade. Conventional LST-planar land-cover assessments do not explicitly address the vertical dimension of the “urbanscape” and therefore do not capture the heterogeneity of solar radiation exposure of planar surfaces adequately. To fill this gap, this study compares and integrates novel spherical land-cover fractions derived from Google Street View (GSV) with the conventional planar land-cover fractions in estimating daytime and nighttime LST variations in the Phoenix metropolitan area, AZ. The GSV spherical dataset was created using big data and machine learning techniques. The planar land cover was classified from 1 m NAIP imagery. Ordinal least square (OLS) and geographically weighted regression (GWR) were used to assess the relationship between LST and urban form (spherical and planar fractions) at the block group level. Social-demographic variables were also added provide the most comprehensive assessment of LST. The GSV spherical fractions provide better LST estimates than the planar land-cover fractions, because they capture the multi-layer tree crown and vertical wall influences that are missing from the bird-eye view imagery. The GWR regression further improves model fit versus the OLS regression (R2 increased from 0.6 to 0.8). GSV and spatial regression (GWR) approaches improve the specificity of LST identified by neighborhoods in Phoenix metro-area by accounting for shading. This place-specific information is critical for optimizing diverse cooling strategies to combat heat in desert cities.

Abstract P409: Mortality in Subarachnoid Hemorrhage Varies by Day and Month Within the USA

Introduction: High mortality is associated with aneurysmal subarachnoid hemorrhage (SAH). Despite years of studies and translational research, only a few health and lifestyle factors have been found to definitively associate with an increased risk of SAH incidence and mortality. Prior studies have provided some evidence that environmental factors play a role in the incidence of SAH, but the available data is not often consistent or applicable to the United States of America (USA). Here we provide support that there is a temporal differences in SAH mortality by month of the year and day of the week. Methods: The Centers for Disease Control (CDC) and Prevention public health database (wonder.cdc.gov) was accessed. Mortality events for the years 1999-2016 were obtained for deaths attributed to SAH from a named vessel distribution with accounting for day of week and month of year as well as gender from year to year. ANOVA was used to test for differences by week or month. Results: Mortality for week day variations found no significant differences (p = 0.13) in women, while men demonstrated a significant difference (p = 0.003) with the most common day of death being Monday. Mortality for monthly variation found a significant difference (p = 0.01) in total with January being the most common month of SAH mortality. However, divided by gender women (p = 0.06) and men (p = 0.10) did not meet predefined statistical significance. Conclusion: Mortality from SAH appears to have a variation in time of day of week in men and by month for both genders but this has unclear significance at this time.

Serum albumin-fatty acid saturation test

Circulating non-esterified fatty acids (NEFA) are toxic to mammalian cells. They increase in diseases such as diabetes and sepsis. Herein we propose a serum albumin-fatty acid saturation test.•We based our test on three methodologies: isoelectric focusing (IF) of human plasma albumin, staining proteins after isoelectric focusing in gels with Coomassie Brilliant Blue, and serum albumin measurement with bromocresol green.•The test consists in the determination of albumin IF and staining with bromocresol green. If albumin is saturated with NEFA, it focuses on lower pH, meaning it is the threshold to bind to them. Excessive NEFA is free and toxic. Many other tests are available for NEFA quantification as NEFA kit assay. All colorimetric assays are used for quantification of NEFA and other tests need expensive equipment to read out the results, and they do not measure albumin levels.•Our method focused on albumin-NEFA saturation instead of just NEFA quantification. Critically ill patients have an alteration in both albumin and NEFA. Therefore, our test undergoes less daytime variation compared to assays that measure absolute NEFA values, allowing a more reliable use as an indicator of albumin-fatty acid saturation and NEFA toxicity.

Mid-Luteal 17-OH Progesterone Levels in 614 Women Undergoing IVF-Treatment and Fresh Embryo Transfer-Daytime Variation and Impact on Live Birth Rates.

Introduction: Corpus luteum (CL) produces progesterone (P4) and 17-OH progesterone (17-OH P4) during the luteal phase. Contrary to P4, 17-OH P4 is not supplied as part of the luteal phase support following IVF-treatment. Therefore, measuring endogenous serum 17-OH P4 levels may more accurately reflect the CL function compared to monitoring serum P4 concentrations.Objective: To explore the correlation between mid-luteal serum 17-OH P4 levels and live birth rates and to explore the possible daytime variations in mid-luteal serum 17-OH P4.Design: Prospective cohort study.Patients: 614 women undergoing IVF-treatment and fresh embryo transfer.Intervention: All patients had serum 17-OH P4 measured 7 days after oocyte pick-up (OPU+7). Furthermore, on OPU+7, seven patients underwent repeated blood sampling during daytime to clarify the endogenous daytime secretory pattern of 17-OH P4.Outcome measure: Live birth rate.Secondary outcome measure: Daytime variation in serum 17-OH P4 levels.Results: The highest chance of a live birth was seen with mid-luteal 17-OH P4 between 6.0 and 14.0 nmol/l. The chance of a live birth was reduced below (RD −10%, p = 0.07), but also above the optimal range for 17-OH P4 (RD −12%, p = 0.04). Patients with diminished CL-function (17-OH P4 < 6 nmol/l) displayed clinically stable 17-OH P4 values, whereas patients with 17-OH P4 levels >6 nmol/l showed random 17-OH P4 fluctuations during daytime.Conclusion: The association between 17-OH P4 and reproductive outcomes is non-linear, and the negative effect of excessive CL-secretion seems to be just as strong as the negative effect of a reduced CL-function during the peri-implantation period.

Daytime variation in hepatitis C virus replication kinetics following liver transplant.

Background: There is a growing interest in the role of circadian regulated pathways in disease pathogenesis. Methods: In a cohort of hepatitis C virus (HCV) infected patients undergoing liver transplantation, we observed differences in early viral infection kinetics of the allograft that associated with the time of liver transplant. Results: A higher frequency of subjects transplanted in the morning showed a rebound in viral RNA levels (n=4/6) during the first week post-surgery. In contrast, no viral rebound was observed in seven subjects transplanted in the afternoon. None of the other parameters previously reported to influence viral replication in the post-transplant setting, such as donor age, cold-ischemia time and length of surgery associated with viral rebound. Conclusions: These observation highlights a role for circadian processes to regulate HCV infection of the liver and warrants further investigation.

Daytime variation in hepatitis C virus replication kinetics following liver transplant

Background: There is a growing interest in the role of circadian regulated pathways in disease pathogenesis. Methods: In a cohort of hepatitis C virus (HCV) infected patients undergoing liver transplantation, we observed differences in early viral infection kinetics of the allograft that associated with the time of liver transplant. Results: A higher frequency of subjects transplanted in the morning showed a rebound in viral RNA levels (n=4/6) during the first week post-surgery. In contrast, no viral rebound was observed in seven subjects transplanted in the afternoon. None of the other parameters previously reported to influence viral replication in the post-transplant setting, such as donor age, cold-ischemia time and length of surgery associated with viral rebound. Conclusions: These observation highlights a role for circadian processes to regulate HCV infection of the liver and warrants further investigation.

Daytime variation in hepatitis C virus replication kinetics following liver transplant.

Background: There is a growing interest in the role of circadian regulated pathways in disease pathogenesis. Methods: In a cohort of hepatitis C virus (HCV) infected patients undergoing liver transplantation, we observed differences in early viral infection kinetics of the allograft that associated with the time of liver transplant. Results: A higher frequency of subjects transplanted in the morning showed a rebound in viral RNA levels (n=4/6) during the first week post-surgery. In contrast, no viral rebound was observed in seven subjects transplanted in the afternoon. None of the other parameters previously reported to influence viral replication in the post-transplant setting, such as donor age, cold-ischemia time and length of surgery associated with viral rebound. Conclusions: These observation highlights a role for circadian processes to regulate HCV infection of the liver and warrants further investigation.

The utility of saliva testing in the estimation of uremic toxin levels in serum.

Background p-Cresol sulfate (pCS) and indoxyl sulfate (IS) are uremic toxins, high concentrations of which are related to renal failure progression. Saliva could become the first-line diagnostic sample of choice, especially for monitoring purposes. Recently, a method for determination of pCS and IS in saliva was developed. Since no data exist on correlations between the levels of toxins in saliva and serum, the applicability of saliva as a diagnostic material is yet to be established. Here, we present a study on the assessment of the utility of saliva testing in the estimation of uremic toxin levels in serum. Methods The study material included serum and unstimulated, fasting saliva obtained from healthy volunteers (n=26) and patients at all stages of chronic kidney diseases (CKD, n=93). The concentration of pCS and IS in saliva and serum (total and unbound fractions) was determined. The daytime variation of the toxins was studied. Results A correlation was found between pCS and IS in saliva and biological active fractions in serum (0.74; 0.81). The variation of the serum/saliva ratio during the day was negligible, with a median of 10% for pCS and 6% for IS, making saliva a reliable material for the estimation of the uremic toxins in circulation at any time of the day. Significant correlations were observed between salivary toxin levels and estimated glomerular filtration rate (pCS: -0.61; IS: -0.70) as well as significant differences in toxin levels between the stages of CKD. Conclusions Saliva could be a valuable diagnostic material for the estimation of toxin levels in circulation.

Resting Motor Threshold, MEP and TEP Variability During Daytime

Humans show a variation in physiological processes during the day. To reliably assess (changes in) cortical excitability with transcranial magnetic stimulation (TMS), it is relevant to know the natural variation in TMS readouts during the day. In case of significant daytime variations, this should be taken into account when scheduling (follow-up) measurements. This study aims to evaluate the influence of the time of day on the resting motor threshold (RMT), motor evoked potential (MEP) and TMS evoked potential (TEP) in healthy controls. TMS–EMG–EEG was recorded in 16 healthy subjects. At both motor cortices, we administered 75 pulses at an intensity of 110% RMT. Subjects were stimulated during five sessions in one day (8:00 AM, 10:30 AM, 1:00 PM, 3:30 PM and 6:00 PM) while keeping the stimulation intensity constant. We compared the TEP waveforms between the five sessions with a cluster-based permutation analysis, and the RMT and MEP amplitude with rmANOVA. In general there were no significant differences between the five sessions in the RMT, MEP amplitude or TEP. Only for the left side, N100 amplitude was larger at 3:30 PM than 10:30 AM. The standard deviation of the P30 and N100 amplitude was significantly higher between subjects within one session than within single subjects during the day. The TEP is highly reproducible during the day, with a low intra-individual variation compared to the inter-individual variation. In addition, we found no significant variation of the RMT and MEP amplitude between multiple sessions on one day.

Investigation and Analysis of All-Day Atmospheric Water Vapor Content over Xi’an Using Raman Lidar and Sunphotometer Measurements

All-day atmospheric water vapor content measurements determined by Raman lidar and a sunphotometer were combined to investigate the all-day variation characteristics in the water vapor distribution in Xi’an, China (34.233°N, 108.911°E). To enhance the daytime lidar performance, the wavelet threshold de-noising method is used to filter out the strong solar background light, and effective denoised results are demonstrated with the following optimization: wavelet sym6, the improved threshold function, and the improved threshold selection. The denoised system signal-to-noise ratio (SNR) for the water vapor daytime measurement is validated, with an enhancement of ~3.4 times up to a height of 3 km compared to that of the original signal. The time series of the atmospheric water vapor mixing ratio profiles and the obtained precipitable water vapor (PWV) measured by Raman lidar are used to reveal the temporal and spatial variations in water vapor, and the comparisons with the total column water vapor content (TCWV) measured by a sunphotometer validate the daytime variation trend of the water vapor. All-day continuous observations clearly present a consistent variation trend in the water vapor between the sunphotometer and Raman lidar measurements. The correlation analysis between TCWV and PWV at the layers below 850 hPa and below 700 hPa yields a good positive correlation coefficient (&gt;0.75), indicating that PWV determination in the bottom layer by Raman lidar can directly reflect the variations in the total water vapor content. Moreover, different diurnal variation trends in water vapor are also observed, that is, a downward trend from the afternoon to the night, or a tendency of being high in the morning and afternoon and low at noon, demonstrating the high temporal-spatial variation characteristics of water vapor and close correlation with weather changes. The results reflected and validated that the diurnal variation in water vapor is complicated and can be an indicator of the weather to a certain extent.

Comparing methane emissions estimated using a backward-Lagrangian stochastic model and the eddy covariance technique in a beef cattle feedlot

Accurate methodologies to measure emissions of greenhouse gases (GHG) from livestock systems are necessary to improve the emission coefficients used in national GHG inventories and to evaluate mitigation strategies. The objective of this study was to compare methane (CH4) emissions estimated using the eddy covariance (EC) technique and a backward-Lagrangian stochastic (bLS) model. A closed-path EC system was used to measure CH4 fluxes in a commercial beef cattle feedlot. The EC fluxes were scaled from the feedlot to the animal scale using a footprint analysis. The EC measurements of CH4 concentration and wind data were used with the bLS model to infer CH4 emissions. The average CH4 emissions (±standard deviation) during the experiment were 87 (±30) g animal−1 d−1 and 85 (± 27) g animal−1 d−1 for EC and bLS techniques, respectively. These values are consistent with the results from previous studies with similar animal and feed characteristics. Both techniques were able to capture a pronounced daytime and nighttime variation in CH4 emissions, with higher CH4 emissions during the day and lower emissions at night. Our results indicate that the eddy covariance technique combined with footprint models can be successfully used to accurately measure enteric CH4 from cattle.

T47. IS THERE A DIURNAL VARIATION IN PSYCHIATRIC SYMPTOMS IN SCHIZOPHRENIA?

BackgroundAnecdotally we have observed subgroups of schizophrenic patients who experienced a diurnal variation in a wide range of psychiatric symptomology. Such a pattern could have substantial ramifications in both clinical care and clinical trials. For example, two commonly used measures of symptom severity in clinical trials, the Positive and Negative Symptom Scale (PANSS) and the Negative Symptom Assessment Scale (NSA-16) contain numerous items that are rated based entirely or in part on observations of the subject during the interview. We hypothesized that inconsistency in the time of day of assessment in subjects whose symptoms were influenced by circadian rhythms could introduce an erratic “noise” element in the longitudinal measure of their symptoms.To investigate this hypothesis we compared the change in PANSS total score and individual PANSS items across consecutive visits by whether the assessments had been conducted at consistent vs. inconsistent times of day.Methods2109 individual subject visits from multiple schizophrenia clinical trials for which PANSS interview start time was available were included in the analysis. 1,764 pairs of consecutive PANSS interviews within individual subjects were identified and the time difference between the start times of the interviews were calculated. The absolute time difference was divided into quartiles and the first quartile (assessments least disparate in time) and the fourth quartile (assessments most disparate in time) were compared in the analyses. The mean absolute change in PANSS total and PANSS individual items between the consecutive visits was compared between the 2 groups using a t-test. Given the exploratory and hypothesis driven nature of the analysis we did not correct for multiple comparisons.ResultsThe average absolute difference in interview start times was 79.5 minutes. The group with assessments closest in time (N = 446) had their interviews start no later than 30 minutes apart while the group with assessments most disparate in time (N = 445) had their interview start with at least 170 minutes difference. Of the 30 PANSS items, items P4 (Excitement 0.33 vs. 0.44, p =0.0077), P7 (Hostility 0.31 vs. 0.47, p < 0.001), N5 (Difficulty in abstract thinking 0.28 vs. 0.35, p = 0.043), N7 (Stereotyped thinking0.26 vs. 0.35, p = 0.021) G1 (Somatic concern 0.34. vs. 0.43, p = 0.041), G2 (Anxiety 0.42 vs. 0.53, p = 0.019), G6 (Depression 0.38 vs.0.52, p = 0.0044), G7 (Motor retardation 0.28 vs. 0.37, p = 0.025), and G8 (Uncooperativeness 0.29 vs. 0.39, p = 0.02) had an absolute difference significantly higher in the disparate group than in the close group. The mean absolute difference in the PANSS total was 5.1(+/-5.8) in the close group and 5.9(+/-5.4) in the disparate group, (p = 0.08).DiscussionThe results demonstrate a statistically significant effect of variation in time of day on symptom severity. These findings underscore the risk of potential noise (erratic changes) in longitudinal assessment of symptom severity when ratings are done at different times of day. Moreover, it suggests that symptom severity assessed in a standard PANSS interview may not generalize over the entire day, much less over the standard one week rating period. This is important because many PANSS items are rated partially or entirely on the interview which may not be a representative “biopsy” of the subject’s mental state or behavior during the one week rating period. This highlights the potential remedies of more frequent or ecological measurements.Hufford et al (2014) demonstrated a statistically significant effect of variation in the time of day on signal from the MCCB cognitive battery. Our results confirm our anecdotal observations that severity of non-cognitive schizophrenic symptoms are impacted by circadian rhythms as well.

Daytime Variation in Serum Progesterone During the Mid-Luteal Phase in Women Undergoing In Vitro Fertilization Treatment.

To investigate whether mid-luteal serum progesterone (P4) exhibits significant fluctuations during a 12-h daytime period in women undergoing in vitro fertilization (IVF) and to explore whether the extent of these fluctuations could impact the interpretation of luteal progesterone levels in a clinical setting. Explorative pilot study. Public hospital-based fertility unit. Ten women undergoing IVF treatment. Seven days after oocyte pick-up, patients underwent frequent repeated blood sampling (every 60 min for 12 h and during two of these hours, every 15 min). Serum samples were analyzed for progesterone, estradiol, and luteinizing hormone (LH). Daytime fluctuations in s-progesterone and s-estradiol. There was a significant positive correlation between median P4 levels and the magnitude of P4 variations-women with median P4 < 60 nmol/l had clinically stable P4 levels throughout the day, while patients with median P4 > 250 nmol/l exhibited periodic P4 peaks of several hundred nanomoles per liter. These endogenous P4 fluctuations were observed irrespective of the type of stimulation protocol or mode of triggering of final oocyte maturation and despite the fact that LH was under the detection limit at the time of measurement. Simultaneously, large fluctuations were seen in s-estradiol. Monitoring of early to mid-luteal P4 levels in IVF cycles may be valuable in the planning of individualized luteal phase support in the attempt to increase reproductive outcomes. The prerequisite for luteal phase monitoring is, however, that the validity of a single measured P4 value is reliable. We show for the first time, that a single P4 measurement in the low progesterone patient quite accurately reflects the corpus luteum function and that the measurement can be used to detect IVF patients with a need of additional exogenous luteal P4 administration.

Daytime variation of aerosol optical depth in North China and its impact on aerosol direct radiative effects

Daytime cycles of aerosol optical depth (AOD) and Angstrom exponent (AE) climatology were analyzed based on long-term (5–15 years) measurements at 18 stations of the China Aerosol Remote Sensing Network (CARSNET) in North China. AOD in Northwest China (NWC) exhibits a daytime trend with negative departures in the early morning and later afternoon while positive departures at midday. Daytime AOD relative departure in different sites and seasons varies from −30.26% to 30.28%. AE in NWC shows an opposite pattern to daytime variation of AOD. Daytime variation of AE is negligible in North China Plain (NCP), AOD increases steadily throughout the day. This trend is consistent and repeatable in four seasons. Such pronounced variability in AOD and AE should be taken accounted for in the estimation of diurnal aerosol direct radiative effects (ADRE), as suggested by the radiative transfer model simulations. The replacement of the observed daytime variation of AOD and AE by daytime mean values in NWC results in ADRE differences of 0.31 Wm−2 at the surface and 0.05 Wm−2 at the top of the atmosphere (TOA). ADRE in NWC will be underestimated by −0.47 Wm-2 and -0.25 Wm-2 at the surface and TOA, respectively, if instantaneous AOD and AE during the overpass time of Terra and Aqua are taken as the daytime mean values. The annual mean ADRE at the surface and TOA will be underestimated by −0.17 Wm-2 and -0.03 Wm-2 if daytime variations of AOD and AE are replaced by daytime mean values in NCP. ADRE will be underestimated by −0.07 Wm-2 at the surface and −0.06 Wm-2 at the TOA if instantaneous AOD and AE during the overpass time of Terra and Aqua other than daytime variation of AOD and AE are used in the calculations.

Variation of hmF2 and NmF2 deduced from DPS-4 over Multan (Pakistan) and their comparisons with IRI-2012 [formula omitted] IRI-2016 during the deep solar minimum between cycles 23 & 24

We report the results of ionospheric measurements from DPS-4 installed at Multan (Geog coord. 30.18°N, 71.48°E, dip 47.4°). The variations in F2-layer maximum electron density NmF2 and its peak height hmF2 are studied during the deep solar minimum between cycles 23 & 24 i.e 2008–2009 with comparisons conducted with the International Reference Ionosphere (IRI) versions 2012 & 2016. We find that the hmF2 observations peak around the pre-sunrise and sunrise hours depending on the month. Seasonally, the daytime variation of NmF2 is higher in the Equinox and Summer, while daytime hmF2 are slightly higher in the Equinox and Winter. High values of hmF2 around midnight are caused by an increase of upward drifts produced by meridional winds. The ionosphere over Multan, which lies at the verge of low and mid latitude, is affected by both E×B drifts and thermospheric winds as evident from mid-night peaks and near-sunrise dips in hmF2. The results of the comparison of the observed NmF2 and hmF2 for the year 2008–2009 with the IRI-2012 (both NmF2 and hmF2) and IRI-2016 (only hmF2) estimates indicate that for NmF2, IRI-2012 with Consultative Committee International Radio (CCIR) option produces values in better agreement with observed data. Whereas, for hmF2, IRI-2016 with both International Union of Radio Science (URSI) and CCIR SHU-2015 options, predicts well for nighttime hours throughout the year. However, the IRI-2012 with CCIR option produces better agreement with data during daytime hours. Furthermore, IRI-2012 with CCIR option gives better results during Equinox months, whereas, IRI-2016 with both URSI and CCIR SHU-2015 options predict well for Winter and Summer.

The effect of time-of-day and chest physiotherapy on multiple breath washout measures in children with clinically stable cystic fibrosis.

BackgroundIn this pilot study we investigated daytime variation of multiple breath nitrogen washout (N2MBW) measures in children with clinically stable cystic fibrosis. To our knowledge the effect of time-of-day on multiple breath washout measures in patients with cystic fibrosis has not previously been reported. Furthermore, we assessed the influence of chest physiotherapy on N2MBW measures.MethodsTen school children with cystic fibrosis performed N2MBW followed by spirometry and plethysmography in the morning and afternoon at three visits that were one month apart. Chest physiotherapy was performed immediately before the afternoon measurements at visit 2 and immediately before morning and afternoon measurements at visit 3. The influence of time-of-day and chest physiotherapy on the measures was evaluated using linear mixed models.ResultsThere were adequate quality data from 8 children with median age (range) 9.6 (6.0; 15.1) years. Baseline lung clearance index (LCI) (range) was 9.0 (7.1; 13.0) and baseline FEV1% predicted was 97.5 (78.5; 117.9). No N2MBW measures were significantly influenced by time-of-day or chest physiotherapy. LCI (95% confidence interval) decreased non-significantly 0.05 (-0.32; 0.22) during the day and increased non-significantly 0.08 (-0.26; 0.42) after chest physiotherapy. All spirometric measures were unaffected by time-of-day and chest physiotherapy. For plethysmographic measures FRCpleth decreased significantly (p<0.01) 110 mL during the day, whereas a borderline significant (p = 0.046) decrease in ΔFRCpleth-MBW during the day and a borderline significant (p = 0.03) increase in TLC after CPT were observed.ConclusionThis study demonstrated that the time-of-day as well as chest physiotherapy performed immediately prior to N2MBW had no consistent or significant influence on N2MBW measures. However, we emphasize that further studies of the effect of both daytime variation and the effect of chest physiotherapy on multiple breath washout measures are warranted.

Numerical research on the effects the skyglow could have in phytochromes and RQE photoreceptors of plants

The increase of artificial light at night has a terrible impact on organisms with nightlife patterns such as a migration, nutrition, reproduction and collective interaction. Plants are not free from this issue as they have life cycle events occurring not only yearly but also daily. Such events relate to daytime variations with seasons in which the flowers of deciduous trees bloom and the leaves of certain trees fall off and change color. A response of plants to artificial light at night still remains poorly quantified; but recent scientific research suggest that skyglow can disturb plants processes. For instance, low levels of light affect deciduous plants, which shed their leaves as days grow short in the fall.In this paper we model skyglow considering the features of artificial light that can affect natural processes of plants during the night. A case-study was conducted to mimic skyglow effects in real location for which experimental data exist. In our numerical simulations we found that some lighting systems can have an effect on plant photoreceptors and affect the phenology of plants. Specifically, the lamps that emit the electromagnetic energy in a wide spectral range can have greater effect on the photosensitivity of the plants. We believe the results obtained here will motivate botanists to make a targeted experiment to verify or challenge our findings. If the night light can change plant behavior under some conditions, it can have significant implications in botany, biology, or even agriculture.

Daytime variation of perioperative myocardial injury in cardiac surgery and its prevention by Rev-Erbα antagonism: a single-centre propensity-matched cohort study and a randomised study

On-pump cardiac surgery provokes a predictable perioperative myocardial ischaemia-reperfusion injury which is associated with poor clinical outcomes. We determined the occurrence of time-of-the-day variation in perioperative myocardial injury in patients undergoing aortic valve replacement and its molecular mechanisms. We studied the incidence of major adverse cardiac events in a prospective observational single-centre cohort study of patients with severe aortic stenosis and preserved left ventricular ejection fraction (>50%) who were referred to our cardiovascular surgery department at Lille University Hospital (Lille, France) for aortic valve replacement and underwent surgery in the morning or afternoon. Patients were matched into pairs by propensity score. We also did a randomised study, in which we evaluated perioperative myocardial injury and myocardial samples of patients randomly assigned (1:1) via permuted block randomisation (block size of eight) to undergo isolated aortic valve replacement surgery either in the morning or afternoon. We also evaluated human and rodent myocardium in ex-vivo hypoxia-reoxygenation models and did a transcriptomic analysis in myocardial samples from the randomised patients to identify the signalling pathway(s) involved. The primary objective of the study was to assess whether myocardial tolerance of ischaemia-reperfusion differed depending on the timing of aortic valve replacement surgery (morning vs afternoon), as measured by the occurrence of major adverse cardiovascular events (cardiovascular death, myocardial infarction, and admission to hospital for acute heart failure). The randomised study is registered with ClinicalTrials.gov, number NCT02812901. In the cohort study (n=596 patients in matched pairs who underwent either morning surgery [n=298] or afternoon surgery [n=298]), during the 500 days following aortic valve replacement, the incidence of major adverse cardiac events was lower in the afternoon surgery group than in the morning group: hazard ratio 0·50 (95% CI 0·32-0·77; p=0·0021). In the randomised study, 88 patients were randomly assigned to undergo surgery in the morning (n=44) or afternoon (n=44); perioperative myocardial injury assessed with the geometric mean of perioperative cardiac troponin T release was significantly lower in the afternoon group than in the morning group (estimated ratio of geometric means for afternoon to morning of 0·79 [95% CI 0·68-0·93; p=0·0045]). Ex-vivo analysis of human myocardium revealed an intrinsic morning-afternoon variation in hypoxia-reoxygenation tolerance, concomitant with transcriptional alterations in circadian gene expression with the nuclear receptor Rev-Erbα being highest in the morning. In a mouse Langendorff model of hypoxia-reoxygenation myocardial injury, Rev-Erbα gene deletion or antagonist treatment reduced injury at the time of sleep-to-wake transition, through an increase in the expression of the ischaemia-reperfusion injury modulator CDKN1a/p21. Perioperative myocardial injury is transcriptionally orchestrated by the circadian clock in patients undergoing aortic valve replacement, and Rev-Erbα antagonism seems to be a pharmacological strategy for cardioprotection. Afternoon surgery might provide perioperative myocardial protection and lead to improved patient outcomes compared with morning surgery. Fondation de France, Fédération Française de Cardiologie, EU-FP7-Eurhythdia, Agence Nationale pour la Recherche ANR-10-LABX-46, and CPER-Centre Transdisciplinaire de Recherche sur la Longévité.

Abstract P486: Effects of Isometric Leg Training on Ambulatory Blood Pressure and Morning Blood Pressure Surge in Young Normotensive Men and Women

Introduction: Cardiovascular disease (CVD) is a major cause of death globally with hypertension reported to be a leading modifiable risk factor. Ambulatory blood pressure (BP), in particular diurnal BP variability, is considered to be associated with CVD risk. In addition, the morning BP surge (MBPS) is thought to be associated with increased stroke risk and to be a destabilizing factor for atherosclerotic plaque. Isometric resistance training (IRT) is an effective method of lowering BP and has been recommended by the American Heart Association as an alternative treatment for reducing BP. To date, few studies have investigated the effects of IRT on ambulatory BP and particularly the morning surge in BP. Therefore, the purpose of this study was to determine whether (i) IRT causes reductions in ambulatory BP and the MBPS, in young normotensives and (ii) there are any sex differences in these changes. Methods: Ambulatory BP was measured prior to, and after, 10 weeks of bilateral leg IRT using an isokinetic dynamometer (4 x 2 minute contractions at 20% MVC, with 2 minute rest periods on 3 days per week). Twenty normotensive individuals (10 men, age=21 ± 4 years; 10 women, age=23 ± 5 years) were recruited. A two-way repeated measures ANOVA was used to assess the within and between groups ambulatory (mean 24-h, daytime, night time and diurnal variation) BP and MBPS. MBPS was calculated as: mean systolic BP 2 hours after waking minus the lowest sleeping 1 hour mean systolic BP. Results: There were significant reductions in 24-h ambulatory (4 ± 2 mmHg, p=0.0001; 4 ± 2 mmHg, p=0.0001) systolic BP in both men and women following IRT. This comprised significant reductions in day time (5 ± 5 mmHg, p=0.019; 5 ± 4 mmHg, p=0.002) but not night time (1 ± 5 mmHg, p=0.75; 1 ± 3 mmHg, p=0.3) systolic BP. Additionally, there were significant reductions in the MBPS (6 ± 8 mmHg, p=0.044; 6 ± 7 mmHg, p=0.019). There were no significant differences between men and women in these changes (p&gt;0.05). Conclusion: These results support previous research showing that IRT is effective in lowering ambulatory BP. Furthermore, the significant reductions in the MBPS offer the potential for clinically meaningful CVD and stroke risk reduction, provided these effects can be demonstrated in those who are at risk.