Within-day Variability Research Articles

Low within- and between-day variability in exposure to new insulin glargine 300 U/ml.

AimsTo characterize the variability in exposure and metabolic effect of insulin glargine 300 U/ml (Gla-300) at steady state in people with type 1 diabetes (T1DM).MethodsA total of 50 participants with T1DM underwent two 24-h euglycaemic clamps in steady-state conditions after six once-daily administrations of 0.4 U/kg Gla-300 in a double-blind, randomized, two-treatment, two-period, crossover clamp study. Participants were randomized to receive Gla-300 as a standard cartridge formulation in the first treatment period, and as a formulation with enhanced stability through polysorbate-20 addition in the second treatment period, or vice versa. This design allowed the assessment of bioequivalence between formulations and, subsequently, within- and between-day variability.ResultsThe cumulative exposure and effect of Gla-300 developed linearly over 24 h, and were evenly distributed across 6- and 12-h intervals. Diurnal fluctuation in exposure (within-day variability) was low; the peak-to-trough ratio of insulin concentration profiles was <2, and both the swing and peak-to-trough fluctuation were <1. Day-to-day reproducibility of exposure was high: the between-day within-subject coefficients of variation for total systemic exposure (area under the serum insulin glargine concentration time curve from time 0 to 24 h after dosing) and maximum insulin concentration were 17.4% [95% confidence interval (CI) 15–21] and 33.4% (95% CI 28–41), respectively. Reproducibility of the metabolic effect was lower than that of exposure.ConclusionsGla-300 provides predictable, evenly distributed 24-h coverage as a result of low fluctuation and high reproducibility in insulin exposure, and appears suitable for effective basal insulin use.

The Use of Continuous Glucose Monitoring System in Combination with Individualized Lifestyle and Therapeutic Recommandations on Glycemic Control of Type 2 Diabetes Patients

Abstract Background and aims. The aim of our research was to evaluate the impact of short-time continuous glucose monitoring (CGM) on glycemic control evaluated by HbA1c and within-day glucose variability. We also assessed if the initiation of insulin therapy in conjunction with lifestyle recommendations may prevent the weight gain. Materials and method. We included 28 patients with type 2 diabetes with 2 consecutive CGMS recordings available (baseline and follow-up) and for which were collected data on weight, body mass index (BMI), percentage (%) of body fat, visceral fat area, HbA1c and glycemic variability. Results. The HbA1c decreased significantly from 8.8% at baseline to 7.3% at follow-up (p &lt;0.0001) in the whole group, and from 10.5% to 7.5% in the subgroup for which the insulin therapy was initiated at baseline (p=0.011). The BMI, % body fat and visceral fat area decreased significantly from 29.2 kg/m2 to 28.4 kg/m2; from 32.3% to 30.4%; and from 141.6 to 129.3 (cm2), respectively. No increase of these parameters was observed in the subgroup for which the insulin therapy was initiated at baseline. Conclusion. The use of CGMS in combination with individualized lifestyle and therapeutic recommendations may have a beneficial effect on glycemic control and may prevent the weight gain associated with insulin initiation.

Quantification of malondialdehyde by HPLC-FL - application to various biological samples.

Malondialdehyde (MDA) is stabile product of lipid peroxidation (LPO), and therefore MDA is frequently used as a biomarker of LPO. To determine MDA level in various biological samples (human plasma, fish liver tissue and cells in culture), we used an HPLC method with fluorescent detection based on 2-thiobarbituric acid (TBA) assay. The method was validated by the use of spiked pooled plasma samples. In tested concentration range (0.15-3.0 µmol/L) the method was linear (R(2) = 0.9963), the between-day variability (coefficient of variations, CVs) was between 4.7 and 7.6%, the within-day variability CVs was between 2.6 and 6.4% and recovery was between 91.2 and 107.6%. The level of MDA in human plasma (healthy male, non-smokers, 46.3 ± 4.7 years; N = 38) was 2.2 ± 1.4 µmol/L; that in liver tissue of common carp (Cyprinus carpio; N = 12) was 0.02 ± 0.004 µmol/g tissue, and in cultured cells (human laryngeal carcinoma cells; N = 10) it was 0.18 ± 0.02 nmol/mg proteins. The HPLC-FL method is rapid, accurate and reliable to follow the extent of LPO in various biological samples, particularly in samples in which a low level of MDA is expected, such as cells in culture. Owing to the rapid analytical process and run time, it can be used for routine analysis of MDA in clinical laboratory.

Electrical activity of the diaphragm during progressive cycling exercise in endurance-trained men

The study aimed to investigate diaphragm respiratory drive modulation through electrical activity of the diaphragm (EADi) during progressive cycling in endurance-trained men (N=7) and to test day-to-day measurement reliability. Normalized EADi increased at exercise intensities from 40% workload (WL) to 70% and 85%WL but plateaued from 70% to 85% (p<0.05). V˙O2, V˙CO2, V˙E, increased at all exercise intensities, where Vt and BF increased from 40% to 55% WL and from 70% to 85% and RER increased at 70% and 85% (p<0.05). Bland–Altman plots of normalized EADi showed bias of 0.9% and −6.4% and limits of agreement of ±36.0% and ±30.4% for absolute measurements and relative changes from 40% WL, respectively. Within-day variability appeared constant indicating that measurements within a trial are reliable. Results suggest that diaphragm respiratory drive increases at moderate exercise intensities, but plateaus at high intensities where other respiratory muscles might contribute significantly to the breathing effort, perhaps to “protect” against diaphragm fatigue.

Effects of Cr2O3 labelling dose, and of faeces sampling schedule, on faecal Cr concentration and on digestibility estimation in cattle fed high-concentrate diets

Chromic oxide (Cr2O3) is used as digestibility marker with ruminants, although there are concerns about diurnal excretion patterns, irregular excretion over days and optimal concentration in the feed. This study aimed to assess the between- and within-day variability of faecal Cr concentration ([Cr]) in intensively fed cattle given concentrates spiked with 2000 or 4000mg/kg Cr2O3. Repercussions on digestibility estimations were also studied. Sixteen calves were given concentrates labelled with 4000mg/kg (period 1-Ph1) or 2000mg/kg (period 2-Ph2) Cr2O3. After four days of marker consumption, spot samples were taken from the rectum at 9:00h and 17:00h, during four (Ph1) or five (Ph2) consecutive days. Measured Cr in concentrate varied less in Ph1 than in Ph2 (2820±30.1 vs 1690±46.3mg/kg dry matter). Increasing sampling days from 1 to 4 in Ph1, and from 1 to 5 in Ph2, decreased the coefficient of variation of estimated dry matter digestibility from 5.17% to 3.37% in Ph1, and from 6.87% to 3.58% in Ph2, respectively. In conclusion, four days of adaptation to Cr2O3-labelled feed allows a steady [Cr] in intensively reared cattle. Labelling with 4000mg/kg Cr2O3 guarantees the homogeneity of the marker in the diet, and a low time-dependent variability of [Cr].

Phytoplankton photosynthetic activity dynamics in a temperate macrotidal ecosystem (the Strait of Dover, eastern English Channel): Time scales of variability and environmental control

The temporal variability in phytoplankton photosynthetic activity was studied in the coastal waters of the Strait of Dover and related to environmental conditions. Phytoplankton photosynthetic activity data collected from October 2008 and August 2010 at different time scales (hourly to interannual) using a nested sampling design are presented. Photosynthetic parameters including the maximum quantum yield (Fv/Fm), maximal light utilization efficiency (α), maximum electron transport rate (ETRm) and light saturation coefficient (Ek) were measured using Pulse Amplitude Modulation (PAM) fluorometry. Information on the taxonomic composition of phytoplankton assemblages and physicochemical parameters were also collected. Marked changes in photosynthetic parameters were observed at the different time scales investigated. The variability of photosynthetic parameters at sub-seasonal scale (hourly to monthly) could be of the same order of magnitude as at seasonal scale. At short time scale (hour to week), there was no consistent pattern of diel periodicity in photosynthetic parameters. There was a decline of ETRm and α during the day as often as there was a peak at the maximum of irradiance. Light conditions were the main influencing factor on photosynthetic parameters at these time scales. The optimal use of incident irradiance seemed focused on between-day rather than within-day variability. At longer time scale (seasonal to interannual), close interplays between shifts in community taxonomic composition and changes in the physicochemical characteristics of the environment controlled the variability in photosynthetic parameters. Whatever the time scale and period of year considered, variability in photosynthetic parameters was “Ek-independent”. In well-mixed macrotidal ecosystems, such as the Strait of Dover, a nested sampling design allowing to characterize the short- (intraday and daily) as well as long-term variability (within months, monthly, seasonal, annual and interannual) in photosynthetic parameters is required to get a suitable picture of phytoplankton photosynthesis and avoid potential problems of aliasing.

Quantitative determination and confirmatory analysis of N-acetylneuraminic and N-glycolylneuraminic acids in serum and urine by solid-phase extraction on-line coupled to liquid chromatography–tandem mass spectrometry

N-acetylneuraminic acid (Neu5Ac) and N-acetylglycolylneuraminic acid (Neu5Gc), two acylated derivatives of 9-C carboxylated monosaccharides, are involved in a number of biological processes as modulators of glycoconjugates. A partially automated method is here presented for determination of these sialic acids in the two most important biofluids for clinical analysis: serum and urine. For this purpose, a solid-phase extraction (SPE) workstation was on-line connected to an LC–MS/MS triple quadrupole mass detector. Hydrolysis to release sialic acids bound to glycoconjugates and derivatization were the two steps implemented as sample preparation prior to SPE–LC–MS/MS analysis. Following thorough optimization of the SPE and LC–MS/MS conditions, the analytical method was validated using the standard addition approach to assess the presence of matrix effects. The proposed method affords detection limits of 0.03ng/mL and 0.04ng/mL for Neu5Ac and Neu5Gc, respectively. The precision (expressed as relative standard deviation) was 1.7 and 4.6% for within-day variability, and 4.8 and 7.2% for between-days variability. Accuracy, estimated using spiked (between 1 and 50ng/mL) and non-spiked samples of both biofluids, ranged from 95.2 to 99.6%. The method was applied to human serum and urine of healthy volunteers, thus showing its suitability for application in both clinical and research laboratories.

Prediction of faecal output and hay intake by cattle from NIRS estimates of faecal concentrations of orally-dosed polyethyleneglycol

Polyethyleneglycol 6000 (PEG) was selected as a potential indigestible estimator of faecal output in cattle. NIRS-calibration equations of faecal PEG content were obtained with faeces from hay-fed cows added with 0.00–0.10g PEG content/g faeces. A digestibility trial was conducted with 8 dry cows in digestibility cages for two 3-week periods, during which half the cows received either a Low (9kg hay, as fed) or High (12kg hay) feeding level (FL), and were dosed daily during the last 10 days either 175 (Low) or 235 (High FL) g PEG/d. In the last 4 days total faeces were collected, and on the last day rectal samples were grabbed every 4h during 24h. Samples were NIRS-scanned to determine faecal PEG content. Using data from total faecal collection, PEG recovery was not complete (0.957g/g, s.e. 0.010), therefore faecal output was slightly overestimated with PEG data from total faeces (+0.052g/g, s.e. 0.089), and so was calculated feed intake, although only significantly in the High FL (+0.060g/g, s.e. 0.021), while estimates were accurate in the Low FL. Recovery was also incomplete in grab samples (0.928g/g, s.e. 0.039), and faecal PEG content had a large per cow within-day variability (0.40), and the bias of estimation of faecal output was high at any sampling time. The use of a daily composite of all grab samples per-cow reduced the variability of faecal PEG contents, and bias of estimations was below 0.10. It is concluded that dosing PEG and analysing PEG faecal contents with NIRS provides reasonably accurate estimates of faecal output and forage intake in cattle, provided faecal samples are representative of total faeces produced. This implies frequent faecal grab sampling, including nocturnal collection, which may limit the practical use of this technique under field conditions.

Within-day variability on short and long walking tests in persons with multiple sclerosis

ObjectiveTo compare within-day variability of short (10m walking test at usual and fastest speed; 10MWT) and long (2 and 6-minute walking test; 2MWT/6MWT) tests in persons with multiple sclerosis. DesignObservational study. SettingMS rehabilitation and research centers in Europe and US within RIMS (European network for best practice and research in MS rehabilitation). SubjectsAmbulatory persons with MS (Expanded Disability Status Scale 0–6.5). InterventionSubjects of different centers performed walking tests at 3 time points during a single day. Main measures10MWT, 2MWT and 6MWT at fastest speed and 10MWT at usual speed.Ninety-five percent limits of agreement were computed using a random effects model with individual pwMS as random effect. Following this model, retest scores are with 95% certainty within these limits of baseline scores. ResultsIn 102 subjects, within-day variability was constant in absolute units for the 10MWT, 2MWT and 6MWT at fastest speed (+/−0.26, 0.16 and 0.15m/s respectively, corresponding to +/−19.2m and +/−54m for the 2MWT and 6MWT) independent on the severity of ambulatory dysfunction. This implies a greater relative variability with increasing disability level, often above 20% depending on the applied test. The relative within-day variability of the 10MWT at usual speed was +/−31% independent of ambulatory function. ConclusionsAbsolute values of within-day variability on walking tests at fastest speed were independent of disability level and greater with short compared to long walking tests. Relative within-day variability remained overall constant when measured at usual speed.

Within-day variability of particulate organic carbon and remote-sensing reflectance during a bloom of Phaeocystis antarctica in the Ross Sea, Antarctica

We examined the within-day variability in seawater optical properties and biogeochemical constituents for a high-latitude location in the Ross Sea, Antarctica, during development of the annual spring phytoplankton bloom. Measurements of particulate organic carbon concentration (POC), chlorophyll-a concentration (Chl), and particle size distribution were conducted at 4–6 hour intervals in parallel with determinations of the spectral absorption and attenuation coefficients of particles, and the spectral remote-sensing reflectance of the surface ocean (Rrs). Surface POC and Chl exhibited more than a twofold variation throughout the day in the continuous presence of natural light. A minimum occurred near local noon coinciding with peak solar irradiance, a maximum in the evening, and a subsequent decrease throughout the night-time hours. These patterns were accompanied by large changes in the magnitude and spectral shape of Rrs, including the blue-to-green spectral band ratios used in ocean colour algorithms for estimating POC and Chl. The variability in Rrs could not be explained by changes in solar zenith angle, but was consistent with observations of within-day variations in spectral absorption and scattering by particles which were influenced by changes in the particle concentration and size distribution. The accuracy of an empirical ocean colour algorithm for estimating POC from Rrs was unaffected by within-day variability, implying that short-term variations in surface POC can be potentially monitored by multiple within-day measurements of Rrs, through means of in situ and remote sensing observations if available. Our findings also suggest that within-day changes in POC can be significant compared with the variability observed on meso-scale spatial scales, potentially confounding the interpretation of remote-sensing data obtained from temporal and spatial compositing of images measured at different times within a single day.

LC-MS-MS Analysis of Dietary Supplements for N-ethyl- -ethyl-phenethylamine (ETH), N, N-diethylphenethylamine and Phenethylamine

There has been a recent rise in the number of cases of athletes being banned from competition because of positive tests for prohibited substances in their biological specimens. Most of these substances are on the World Anti-Doping Agency (WADA) prohibited list, while others are not specifically named on the list. N-Ethyl-α-ethyl-phenethylamine (ETH), a derivative of phenethylamine (PEA), is one of these unlisted substances and shares chemical and biological effects to the amphetamines, which are listed on the WADA prohibited substances list. It is classified as Category 6B stimulant on the list. This study was directed toward the development of an liquid chromatography tandem mass spectrometry (LC-MS-MS) method for the analysis of ETH in performance-enhancing dietary supplement. A standard was prepared and confirmed by spectroscopic analysis, which was then used to develop the analytical procedure. The procedure was validated and found to have an limit of detection of 2.5 ng/mL, limit of quantification of 5 ng/mL and upper limit of linearity of 500 ng/mL, with within-day variability at the 10-ng/mL level range of 3.88-7.89% (n = 6) and 1.39-3.36% (n = 6) for the 100-ng/mL level. The day-to-day variability was 9.8% for the low control and 3.1% for the high control. The method was used to analyze a variety of dietary supplements for ETH as well as PEA and its N, N-diethyl derivative (NDP).

Diurnal variability of ocean optical properties during a coastal algal bloom: implications for ocean colour remote sensing

Understanding the diurnal variability of ocean optical properties is critical for better interpretation of satellite ocean colour data and characterizing biogeochemical processes. The daytime variability of ocean optical properties throughout an algal bloom event is analysed in this article based on in situ observations from dawn to dusk at a fixed coastal site in the South China Sea. Diurnal variability during the sunlit period of the ocean optical properties is found to be significant. During the 6 hours around noon, the temporal variability (defined by the coefficient of variation) of phytoplankton absorption, coloured dissolved organic matter and non-algal particle absorption, and particle backscattering at 443 nm can reach 21% ± 15%, 12% ± 9%, and 17% ± 9%, respectively. The diurnal variability during the bloom is much more pronounced than that of the non-bloom phase. With atmospheric radiative transfer modelling, it is further demonstrated that the geostationary satellite detection of within-day optical variability in algae-dominated waters depends on the reliability of the aerosol retrieval. The implications of the diurnal bio-optical variability for the retrieval, validation, and interpretation of satellite ocean colour products are also discussed.

Measurement of pulmonary transit time in healthy cats by use of ultrasound contrast media “Sonovue®”: Feasibility, reproducibility, and values in 42 cats

ObjectiveTo evaluate the feasibility of measuring pulmonary transit time (PTT) in healthy cats by transthoracic echocardiography using the ultrasound contrast agent Sonovue®. To determine normalized PTT (nPTT) values in 42 healthy cats and to estimate the interobserver variability and the within-day repeatability of nPTT measurements. AnimalsForty-two privately owned healthy cats of different breeds, gender and age presented for cardiac examination. MethodsA bolus injection of contrast agent (Sonovue®) was administered intravenously. The right parasternal short axis echocardiographic view was used to record the contrast agent's transit time from the pulmonary artery to the left atrium. Pulmonary transit time and nPTT were determined independently by three examiners with different levels of experience. ResultsNormalized PTT was 4.12 ± 1.0 (mean ± SD) in our population. The median interobserver variability across our population was 6.8%, the median within-day variability for the three observers were 13.1%, 12.7% and 13%. No effect of the observer's experience on nPTT measurement was identified. Age, sex and body weight did not significantly influence nPTT. ConclusionsThis study demonstrates that nPTT measurement is feasible in cats using ultrasound and the blood pool contrast media Sonovue®. Measurements of nPTT can be performed in a clinical setting. Normalized PTT values in healthy cats are comparable with those reported in healthy dogs.

Monitoring PM10 and Ultrafine Particles in Urban Environments Using Mobile Measurements

Mobile platforms are increasingly used to acquire air quality data at a high spatial and temporal resolution in complex urban environments. As such, mobile measurements provide a solution for short-term studies to acquire a spatially spread data set that would not be feasible if using stationary measurements. Mobile monitoring campaigns were carried out with a bicycle platform at two different urban locations, consisting of 20 and 24 repeated runs along a fixed route over a three-week period. The measurement runs were carried out on different days and at different times of the day, without systematical temporal coverage. Significant differences in UFP concentration were found within the day and between days, and also between several streets along the measurement route. These differences were related to traffic intensity and street characteristics. In contrast, PM10 concentrations differed between measurement days, but the within-day variability of PM10 was mostly non-significant. Additionally, the spatial variability was limited and the PM10 concentrations were only significantly different between busy streets, with high concentrations, and quiet background streets, with low ones. The results indicate that for most streets the number of runs was sufficient to give a good approximation of median daytime UFP concentration levels for the measurement period, and for some streets this number could even be reduced to less than 10. However, for PM10 a higher number of runs is needed, and this may be attributed to the significant background contribution to the roadside PM10 concentration, and the high variability of this. We conclude that a limited set of mobile measurements makes it possible to map locations with systematically higher or lower UFP and PM10 concentrations in urban environments.

Erratum: Variability of urinary concentrations of polycyclic aromatic hydrocarbon metabolite in general population and comparison of spot, first-morning, and 24-h void sampling

Urinary mono-hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) are commonly used in biomonitoring to assess exposure to polycyclic aromatic hydrocarbons (PAHs). Similar to other biologically non-persistent chemicals, OH-PAHs have relatively short biological half-lives (4.4–35 h). Little information is available on their variability in urinary concentrations over time in non-occupationally exposed subjects. This study was designed to (i) examine the variability of nine urinary OH-PAH metabolite concentrations over time and (ii) calculate sample size requirements for future epidemiological studies on the basis of spot urine, first-morning void, and 24-h void sampling. Individual urine samples (n=427) were collected during 1 week from 8 non-occupationally exposed adults. We recorded the time and volume of each urine excretion, dietary details, and driving activities of the participants. Within subjects, the coefficients of variation (CVs) for the wet-weight concentration of OH-PAHs in all samples ranged from 45% to 297%; creatinine adjustment reduced the CV to 19–288% (P<0.001; paired t-test). The simulated 24-h void concentrations were the least variable measure, with CVs ranging from 13% to 182% for the 9 OH-PAHs. Within-day variability contributed on average 84%, and between-day variability accounted for 16% of the total variance of 1-hydroxypyrene (1-PYR). Intraclass correlation coefficients of 1-PYR levels were 0.55 for spot urine samples, 0.60 for first-morning voids, and 0.76 for 24-h voids, indicating a high degree of correlation between urine measurements collected from the same subject over time. Sample size calculations were performed to estimate the number of subjects required for detecting differences in the geometric mean at a statistical power of 80% for spot urine, first-morning, and 24-h void sampling. These data will aid in the design of future studies of PAHs and possibly other biologically non-persistent chemicals and in the interpretation of their analytical results.

Impact of PCA strategies on pain intensity and functional assessment measures in adults with sickle cell disease during hospitalized vaso‐occlusive episodes

Clinical trials of sickle cell disease (SCD) pain treatment usually observe only small decrements in pain intensity during the course of hospitalization. Sub-optimal analgesic management and inadequate pain assessment methods are possible explanations for these findings. In a search for better methods for assessing inpatient SCD pain in adults, we examined several pain intensity and interference measures in both arms of a randomized controlled trial comparing two different opioid PCA therapies. Based upon longitudinal analysis of pain episodes, we found that scores from daily average Visual Analogue Scales (VAS) and several other measures, especially the Brief Pain Inventory (BPI), were sensitive to change in daily improvements in pain intensity associated with resolution of vaso-occlusive pain. In this preliminary trial, the low demand, high basal infusion (LDHI) strategy demonstrated faster, larger improvements in various measures of pain than the high demand, low basal infusion (HDLI) strategy for opioid PCA dosing, however, verification in larger studies is required. The measures and statistical approaches used in this analysis may facilitate design, reduce sample size, and improve analyses of treatment response in future SCD clinical trials of vaso-occlusive episodes.

Reliability of gait parameters during treadmill walking in community-dwelling healthy seniors

The present study aimed at assessing the between- and within-day-variability of temporal and spatial gait characteristics during treadmill walking in community-dwelling seniors. In 20 active, healthy seniors (10 women, 10 men, age: 64.8 (SD 3.2) years, height: 1.70 (0.10)m, weight: 69.7 (10.9)kg, physical activity: 11 (6)hweek−1) gait characteristics were assessed on three days in weekly intervals (between-day variability). Either on days two or three, testing was repeated 30min after the initial trial (within-day variability). We determined routine spatio-temporal gait parameters as well as gait variability during 400 steps at a normal walking speed (5.0 (0.4)kmh−1) on a one-dimensional ground reaction force measuring treadmill. No significant mean differences occurred in any parameter for between- and within-day comparisons. Between-day ICC were high (ICC≥0.86) for most parameters except for temporal (ICC=0.44) and spatial (ICC=0.22) gait variability. Coefficients of variation (CoV) were also high in the latter parameters (CoV=30.2–36.1%), whereas all other variables showed clearly lower values (CoV<7%). CoV were still lower between days 2 and 3 (CoV<5%). Compared to between-day comparisons, within-day variability was comparable in spatio-temporal gait parameters (CoV<5%, ICC≥0.97) and lower in gait variability parameters (CoV<18%, ICC≥0.72–0.74). In conclusion, most gait parameters were highly reliable during treadmill walking. Changes of less than 10% can be detected with sufficient confidence. Gait variability parameters were less reliable and, thus, should be carefully interpreted.

Does microphytobenthos resuspension influence phytoplankton in shallow systems? A comparison through a Fourier series analysis

Shallow coastal lagoons, especially the ones with clear waters and lighted substrata, are likely to have large microphytobenthos (MPB) communities. MPB is an important component of these systems, representing up to 99% of the chlorophyll concentration when compared to phytoplankton. It is therefore expected that MPB resuspension play a key role in the dynamics of phytoplankton due to the tide and wind action.Water samples were collected twice per month inside and outside Ria Formosa lagoon (Portugal), for nutrients and chlorophyll a (chl a). Sediment samples were also collected for MPB chl a. Chl a was also analysed in water and sediment samples from Venice lagoon (Italy), at least once per month. A truncated Fourier series was fitted to the data to investigate the seasonal and high-frequency components of the time-series. In the Ria Formosa, the best significant fit for MPB was obtained considering the sum of 26 wave-pairs (sin and cosine), which explained 31% of the variability. The seasonal cycle (1–3 waves) explained approximately 5% of the total variability. Within-day variability which includes spatial heterogeneity explained 61% of the variability. The best fit for phytoplankton inside Ria Formosa was obtained considering the sum of 23 wave-pairs. Outside the lagoon the best fit was obtained using only the sum of 16 wave-pairs. For both cases, the sum of waves explained more than 64% of the variability and the seasonal cycle explained more than 31% of the variability. It is expected that primary producers in the water column have a strong seasonal factor due to the direct effect of the solar cycle, which is the case of other clear waters. In the Venice lagoon, which is microtidal, the best fit for MPB was obtained using 10 wave-pairs. However, the best fit for phytoplankton was obtained with only 3 wave-pairs, indicating the importance of the seasonal cycle. Significant relationships were found between phytoplankton inside and outside the Ria Formosa, as well as between microphytobenthos and phytoplankton in the lagoons of Venice and Ria Formosa. These results suggest the influence of MPB resuspension in the phytoplankton community of shallow coastal lagoons and the importance of phytoplankton exportation to the coastal zone.

Reproducibility of different methods to measure the endothelial function

This study compares the reliability and reproducibility of flow-mediated dilatation (FMD) and peripheral arterial tonometry (PAT) to assess endothelial function. Eighteen volunteers with coronary heart disease underwent simultaneous testing of FMD by means of brachial artery ultrasound scanning and PAT with the EndoPAT 2000. The subjects underwent both tests twice with an interval of 30 minutes and the same protocol was repeated 2 days later. The within-day variability was lower for the FMD measurements than for the PAT measurements (10% versus 18%; p < 0.05). The between-day variability was similar (11%). A significant correlation was found between PAT and FMD (r = 0.57, p < 0.001). The typical errors of measurements for FMD were lower than those for PAT. In conclusion, in this study, FMD demonstrated the best reliability for the within- and between-day and separate day measurements when compared to PAT.

Long-term and within-day variability of working memory performance and EEG in individuals

ObjectiveAssess individual-subject long-term and within-day variability of a combined behavioral and EEG test of working memory. MethodsEEGs were recorded from 16 adults performing n-back working memory tasks, with 10 tested in morning and afternoon sessions over several years. Participants were also tested after ingesting non-prescription medications or recreational substances. Performance and EEG measures were analyzed to derive an Overall score and three constituent sub-scores characterizing changes in performance, cortical activation, and alertness from each individual’s baseline. Long-term and within-day variability were determined for each score; medication effects were assessed by reference to each individual’s normal day-to-day variability. ResultsOver the several year period, the mean Overall score and sub-scores were approximately zero with standard deviations less than one. Overall scores were lower and their variability higher in afternoon relative to morning sessions. At the group level, alcohol, diphenhydramine and marijuana produced significant effects, but there were large individual differences. ConclusionsObjective working memory measures incorporating performance and EEG are stable over time and sensitive at the level of individual subjects to interventions that affect neurocognitive function. SignificanceWith further research these measures may be suitable for use in individualized medical care by providing a sensitive assessment of incipient illness and response to treatment.