Reliability of urine lactate as a novel biomarker of lactate production capacity in maximal swimming

Context: Postexercise urine lactate may be a novel biomarker of lactate production capacity during exercise.

Objective: To evaluate the reliability and utility of the urine lactate concentration after maximal swimming trials between different training protocols (6?×?50?m and 3?×?100?m) and training states (active and nonactive swimmers).

Materials and methods: Lactate and creatinine were determined by spectrophotometry in blood and urine.

Results: Blood and urine lactate concentrations were correlated in-between training protocols and in participants of different training states. The reliability of the urine lactate concentration was moderate for one of the training protocols and good or moderate for the two training states. Additionally, it was lower than that of the blood lactate concentration, and did not improve after normalizing to the urine creatinine concentration.

Discussion and conclusion: Although promising as a biomarker of lactate production capacity, urine lactate requires further research to improve its reliability.     

Test-Retest reliability of the internal shoulder rotator muscles' stretch reflex in healthy men

Until now the reproducibility of the short latency stretch reflex of the internal rotator muscles of the glenohumeral joint has not been identified. Twenty-three healthy male participants performed three sets of external shoulder rotation stretches with various pre-activation levels on two different dates of measurement to assess test–retest reliability. All stretches were applied with a dynamometer acceleration of 10⁴°/s² and a velocity of 150°/s. Electromyographical response was measured via surface EMG. Reflex latencies showed a pre-activation effect (ƞ² = 0,355). ICC ranged from 0,735 to 0,909 indicating an overall “good” relative reliability. SRD 95% lay between ±7,0 to ±12,3 ms. The reflex gain showed overall poor test–retest reproducibility. The chosen methodological approach presented a suitable test protocol for shoulder muscles stretch reflex latency evaluation. A proof-of-concept study to validate the presented methodical approach in shoulder involvement including subjects with clinically relevant conditions is recommended.     

Validity and reliability of the Slovene version of the Morningness-Eveningness Questionnaire

ABSTRACT

Morningness-eveningness (ME) can be defined as individual differences in sleep-wake patterns, and the time of day people feel and perform best. Various self-report instruments that measure ME have been developed. The Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) has most frequently been used for classifying ME types. The aim of this study was to investigate the validity and reliability of the Slovene version of the MEQ (Slovene MEQ). Two hundred and sixty-five participants (65.3% women, 34,7% men, mean age 38,1 years, range 19–67) took the Slovene MEQ twice, 2 weeks apart (MEQ test and retest). Internal consistency of the Slovene MEQ items was high, with Cronbach’s Alpha coefficients of 0.86. The test–retest reliability was also high, with intraclass correlation coefficient (ICC) of 0.96. The classification of chronotypes on middle-aged population offered a more balanced representation of the five chronotypes than those proposed by the authors Horne and Östberg . Age changes in chronotype could be confirmed in this study in the supposed direction with older adults being more morning-oriented. The criterion validity of the Slovene MEQ through the relationship of morningness and basic personality traits showed that conscientiousness and agreeableness demonstrated positive and significant correlations with morningness. A low negative correlation was observed between openness and morningness, with higher eveningness among more open participants.     

Improved reliability of the urine lactate concentration under controlled hydration after maximal exercise

Context: Urine lactate may be a novel biomarker of lactate production capacity but its reliability has been unsatisfactory so far.

Objective: To compare the reliability of urine lactate between controlled hydration and no hydration after maximal exercise.

Material and methods: Athletes performed swimming exercise four times: two followed by consumption of 1?L of water and two followed by no water intake. Blood and urine lactate was measured.

Results: The reliability of urine lactate was good and similar to that in blood only after controlled hydration. Blood and urine lactate were correlated under both hydration conditions.

Discussion and conclusion: Controlled hydration after exercise provides satisfactory reliability of urine lactate.     

Dunnock social status correlates with sperm speed,but fast sperm does not always equal high fitness

Sperm competition theory predicts that males should modulate sperm investment according to their social status. Sperm speed, one proxy of sperm quality, also influences the outcome of sperm competition because fast sperm cells may fertilize eggs before slow sperm cells. We evaluated whether the social status of males predicted their sperm speed in a wild population of dunnocks (Prunella modularis). In addition to the traditional analysis of the average speed of sperm cells per sample, we also analysed subsamples of the fastest sperm cells per sample. In other words, we systematically evaluated the effects of including different numbers of the fastest sperm in our analyses, ranging from the 5‐fastest sperm cells to the 100‐fastest sperm cells in a sample. We further evaluated whether fitness, defined here as the number of chicks sired per male per breeding season, relates to the sperm speed in the same population. We found that males in monogamous pairings (i.e. low levels of sperm competition), produced the slowest sperm cells, whereas subordinate males in polyandrous male–male coalitions (i.e. high levels of sperm competition) produced the fastest sperm cells. This result was consistent regardless of the number of fastest sperm included in our analyses, but statistical support was conditional on the number of sperm cells included in the analysis. Interestingly, we found no significant relationship between fitness and sperm speed, which suggests that it is possible that the differential mating opportunities across social status levelled out any possible difference. Our study also suggests that it is important to identify biologically meaningful subsets of fastest sperm and cut‐offs for inclusions for assessing sperm competition via sperm speed.     

A novel index of functional connectivity: phase lag based on Wilcoxon signed rank test

Phase synchronization has been an effective measurement of functional connectivity, detecting similar dynamics over time among distinct brain regions. However, traditional phase synchronization-based functional connectivity indices have been proved to have some drawbacks. For example, the phase locking value (PLV) index is sensitive to volume conduction, while the phase lag index (PLI) and the weighted phase lag index (wPLI) are easily affected by noise perturbations. In addition, thresholds need to be applied to these indices to obtain the binary adjacency matrix that determines the connections. However, the selection of the thresholds is generally arbitrary. To address these issues, in this paper we propose a novel index of functional connectivity, named the phase lag based on the Wilcoxon signed-rank test (PLWT). Specifically, it characterizes the functional connectivity based on the phase lag with a weighting procedure to reduce the influence of volume conduction and noise. Besides, it automatically identifies the important connections without relying on thresholds, by taking advantage of the framework of the Wilcoxon signed-rank test. The performance of the proposed PLWT index is evaluated on simulated electroencephalograph (EEG) datasets, as well as on two resting-state EEG datasets. The experimental results on the simulated EEG data show that the PLWT index is robust to volume conduction and noise. Furthermore, the brain functional networks derived by PLWT on the real EEG data exhibit a reasonable scale-free characteristic and high test–retest (TRT) reliability of graph measures. We believe that the proposed PLWT index provides a useful and reliable tool to identify the underlying neural interactions, while effectively diminishing the influence of volume conduction and noise.     

Resting‐state functional connectivity measured by diffuse correlation spectroscopy

Near‐infrared diffuse correlation spectroscopy (DCS) is used to record spontaneous cerebral blood flow fluctuations in the frontal cortex. Nine adult subjects participated in the experiments, in which 8‐minute spontaneous fluctuations were simultaneously recorded from the left and right dorsolateral and inferior frontal regions. Resting‐state functional connectivity (RSFC) was measured by the temporal correlation of the low frequency fluctuations. Our data shows the RSFC within the dorsolateral region is significantly stronger than that between the inferior and dorsolateral regions, in line with previous observations with functional near‐infrared spectroscopy. This indicates that DCS is capable of investigating brain functional connectivity in terms of cerebral blood flow.      

Assessing inter-rater reliability when the raters are fixed: Two concepts and two estimates

Intraclass correlation (ICC) is an established tool to assess inter-rater reliability. In a seminal paper published in 1979, Shrout and Fleiss considered three statistical models for inter-rater reliability data with a balanced design. In their first two models, an infinite population of raters was considered, whereas in their third model, the raters in the sample were considered to be the whole population of raters. In the present paper, we show that the two distinct estimates of ICC developed for the first two models can both be applied to the third model and we discuss their different interpretations in this context.     

A Generalized Concordance Correlation Coefficient Based on the Variance Components Generalized Linear Mixed Models for Overdispersed Count Data

Summary The classical concordance correlation coefficient (CCC) to measure agreement among a set of observers assumes data to be distributed as normal and a linear relationship between the mean and the subject and observer effects. Here, the CCC is generalized to afford any distribution from the exponential family by means of the generalized linear mixed models (GLMMs) theory and applied to the case of overdispersed count data. An example of CD34+ cell count data is provided to show the applicability of the procedure. In the latter case, different CCCs are defined and applied to the data by changing the GLMM that fits the data. A simulation study is carried out to explore the behavior of the procedure with a small and moderate sample size.     

基于空间ICA和时间相关方法的人脑视觉皮层V5区的功能连通性研究

利用功能磁共振成像技术,将空间ICA和时间相关方法相结合来研究不同活动状态下人脑视觉皮层V5区的功能连通性。首先利用空间ICA处理组块视觉运动刺激的数据,定位V5区;然后分别计算静息和连续视觉运动刺激两种稳态下V5区与其它脑区低频振荡的时间相关,检测出该区的功能连通网络。实验结果表明,静息时V5区的功能连通网络更广泛,且与已知的解剖连通一致;当被试接受连续视觉运动刺激时,与V5区连通的脑区网络局限在视觉皮层,此时的网络特定于处理视觉运动这一任务。     

The research of constructing dynamic cognition model based on brain network

Estimating the functional interactions and connections between brain regions to corresponding process in cognitive, behavioral and psychiatric domains is a central pursuit for understanding the human connectome. Few studies have examined the effects of dynamic evolution on cognitive processing and brain activation using brain network model in scalp electroencephalography (EEG) data. Aim of this study was to investigate the brain functional connectivity and construct dynamic programing model from EEG data and to evaluate a possible correlation between topological characteristics of the brain connectivity and cognitive evolution processing. Here, functional connectivity between brain regions is defined as the statistical dependence between EEG signals in different brain areas and is typically determined by calculating the relationship between regional time series using wavelet coherence. We present an accelerated dynamic programing algorithm to construct dynamic cognitive model that we found that spatially distributed regions coherence connection difference, the topologic characteristics with which they can transfer information, producing temporary network states. Our findings suggest that brain dynamics give rise to variations in complex network properties over time after variation audio stimulation, dynamic programing model gives the dynamic evolution processing at different time and frequency. In this paper, by applying a new construct approach to understand whole brain network dynamics, firstly, brain network is constructed by wavelet coherence, secondly, different time active brain regions are selected by network topological characteristics and minimum spanning tree. Finally, dynamic evolution model is constructed to understand cognitive process by dynamic programing algorithm, this model is applied to the auditory experiment, results showed that, quantitatively, more correlation was observed after variation audio stimulation, the EEG function connection dynamic evolution model on cognitive processing is feasible with wavelet coherence EEG recording.     

卧龙自然保护区三江珙桐群落种间关系的数量分析

应用2×2列联表的Fisher精确检验、Pearson相关系数和Spearman秩相关系数检验研究了卧龙自然保护区三江珙桐(Davidia involucrata)群落种间关系。测定了83种植物,共3 403个种对的种间关联(或相关)。结果表明,2×2列联表的Fisher精确检验共186个种对为正关联,100个种对为负关联(P<0.05或P<0.01);Pearson相关系数有295个种对为正关联,129个种对为负关联;Spearman秩相关系数有448个种对为正关联,244个种对为负关联。用2×2列联表的Fisher精确检验不能反映两个种对的数量关系,应用Pearson相关系数和Spearman秩相关系数刻化种对间的数量变化关系;与Pearson相关系数检验相比,Spearman秩相关系数检验具有较高的灵敏度。种对的正关联和正相关,主要是由于它们具有相近的生物学特性,对生境具有相似的生态适应性和相互分离的生态位所致;而种对间的负关联和负相关,则主要是由于它们具有不同的生物学特性,对生境具有不同的生态适应性和相互重叠的生态位所致。     

旅游干扰对历山亚高山草甸优势种群种间相关性的影响

基于2×2列联表,应用方差比率法、χ2检验、Pearson相关系数检验及Spearm an秩相关系数检验等数量分析方法研究了旅游干扰对山西历山舜王坪亚高山草甸种间关联程度的影响。结果表明:(1)不同旅游距离带的联结指数(VR)均大于1,但统计量W均界于χ2分布的上下临界值之间。群落总体呈正关联,但联结性较弱,种的分布相对独立。(2)随着距游径距离的增加,4条不同旅游距离带的联结指数(VR)呈下降趋势;正负关联比有所增加,2χ检验显著率、Pearson相关检验显著率和Spearm an秩相关检验显著率都明显下降,说明旅游干扰对舜王坪亚高山草甸种间关联程度产生了一定的影响,距离游径越远,种间关联越趋于随机性,但这种影响尚未引起种间联结性的改变。(3)χ2检验与Pearson相关系数检验、Spearm an秩相关系数检验结果用来刻划种间相关性具有一定的相似之处,但仍存在一定差异,结合使用效果更好。与Pearson相关检验相比,Spearm an秩相关检验更具灵敏性。4)本研究结果支持随着群落演替进程的发展,群落种群总体向着无关联发展的观点。     

基于双核酸频率分布特征的细菌亲缘关系定量分析

目的采用生物信息学方法定量分析细菌的亲缘关系。方法抽取全基因组核酸序列的双核苷酸频率特征向量,表征数字特征。采用Pearson相关系数分析特征向量之间的距离。结果以119个细菌的全基因组核酸序列为研究对象,两两比对的结果为:越是相近的物种,Pearson相关系数越大,PCC距离越小。结论该方法对细菌亲缘关系的定量描述做了有益的探索。     

基于图论的两栖类生物栖息地网络规划——以黑斑侧褶蛙为例

生物多样性保护和生物栖息地网络建设是目前我国国土空间规划的重要内容,提升生物栖息地网络的景观功能连接度对生物多样性保护具有重要作用.目前,已有研究对生物栖息地网络规划进行了探索,但在实际规划层面仍缺乏可操作性强的技术方法支撑.本研究采用图论方法,聚焦国土空间规划中生物多样性保护和生态网络建设涉及的进行生物栖息地斑块重要...     

Effects of the number of presences on reliability and stability of MARS species distribution models: the importance of regional niche variation and ecological heterogeneity

Question: What are the effects of the number of presences on models generated with multivariate adaptive regression splines (MARS)? Do these effects vary with data quality and quantity and species ecology? Location: Spain and Ecuador. Methods: We used two data sets: (1) two trees from Spain, representing high‐occurrence number data sets with real absences and unbalanced prevalence; (2) two herbs from Ecuador, representing low‐occurrence number data sets without real absences and balanced prevalence. For model quality, we used two different measures: reliability and stability. For each sample size, different replicates were generated at random and then used to generate a consensus model. Results: Model reliability and stability decrease with sample size. Optimal minimum sample size varies depending on many factors, many of which are unknown. Regional niche variation and ecological heterogeneity are critical. Conclusions: (1) Model predictive power improves greatly with more than 18‐20 presences. (2) Model reliability depends on data quantity and quality as well as species ecological characteristics. (3) Depending on the number of presences in the data set, investigators must carefully distinguish between models that should be treated with skepticism and those whose predictions can be applied with reasonable confidence. (4) For species combining few initial presences and wide environmental range variation, it is advisable to generate several replicate models that partition the initial data and generate a consensus model. (5) Models of species with a narrow environmental range variation can be highly stable and reliable, even when generated with few presences.     

A non-iterative confidence interval estimating procedure for the intraclass kappa statistic with multinomial outcomes

We obtain the asymptotic sample variance of the intraclass kappa statistic for multinomial outcome data. A modified Wald type procedure based on this theory is then used for confidence interval construction. The results of a simulation study show that the proposed non-iterative approach performs very well in terms of confidence interval coverage and width for samples as small as 50. The procedure is illustrated with two examples from previously published medical studies.