Phenomics for photosynthesis, growth and reflectance in Arabidopsis thaliana reveals circadian and long-term fluctuations in heritability.

BACKGROUND: Recent advances in genome sequencing technologies have shifted the research bottleneck in plant sciences from genotyping to phenotyping. This shift has driven the development of phenomics, high-throughput non-invasive phenotyping technologies. RESULTS: We describe an automated high-throughput phenotyping platform, the Phenovator, capable of screening 1440 Arabidopsis plants multiple times per day for photosynthesis, growth and spectral reflectance at eight wavelengths. Using this unprecedented phenotyping capacity, we have been able to detect significant genetic differences between Arabidopsis accessions for all traits measured, across both temporal and environmental scales. The high frequency of measurement allowed us to observe that heritability was not only trait specific, but for some traits was also time specific. CONCLUSIONS: Such continuous real-time non-destructive phenotyping will allow detailed genetic and physiological investigations of the kinetics of plant homeostasis and development. The success and ultimate outcome of a breeding program will depend greatly on the genetic variance which is sampled. Our observation of temporal fluctuations in trait heritability shows that the moment of measurement can have lasting consequences. Ultimately such phenomic level technologies will provide more dynamic insights into plant physiology, and the necessary data for the omics revolution to reach its full potential.

The effect of caffeine on working memory load-related brain activation in middle-aged males.

Caffeine is commonly consumed in an effort to enhance cognitive performance. However, little is known about the usefulness of caffeine with regard to memory enhancement, with previous studies showing inconsistent effects on memory performance. We aimed to determine the effect of caffeine on working memory (WM) load-related activation during encoding, maintenance and retrieval phases of a WM maintenance task using functional magnetic resonance imaging (fMRI). 20 healthy, male, habitual caffeine consumers aged 40-61 years were administered 100 mg of caffeine in a double-blind placebo-controlled crossover design. Participants were scanned in a non-withdrawn state following a workday during which caffeinated products were consumed according to individual normal use (range = 145-595 mg). Acute caffeine administration was associated with increased load-related activation compared to placebo in the left and right dorsolateral prefrontal cortex during WM encoding, but decreased load-related activation in the left thalamus during WM maintenance. These findings are indicative of an effect of caffeine on the fronto-parietal network involved in the top-down cognitive control of WM processes during encoding and an effect on the prefrontal cortico-thalamic loop involved in the interaction between arousal and the top-down control of attention during maintenance. Therefore, the effects of caffeine on WM may be attributed to both a direct effect of caffeine on WM processes, as well as an indirect effect on WM via arousal modulation. Behavioural and fMRI results were more consistent with a detrimental effect of caffeine on WM at higher levels of WM load, than caffeine-related WM enhancement. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Effects of caffeine on sleep and cognition.

Caffeine can be used effectively to manipulate our mental state. It is beneficial in restoring low levels of wakefulness and in counteracting degraded cognitive task performance due to sleep deprivation. However, caffeine may produce detrimental effects on subsequent sleep, resulting in daytime sleepiness. This justifies a careful consideration of risks related to sleep deprivation in combination with caffeine consumption, especially in adolescents. The efficacy of caffeine to restore detrimental effects of sleep deprivation seems to be partly due to caffeine expectancy and to placebo effects. The claim that stimulant effects of caffeine are related to withdrawal or withdrawal reversal seems to be untenable.

Caffeine does not modulate inhibitory control.

The effects of a 3mg/kg body weight (BW) dose of caffeine were assessed on behavioral indices of response inhibition. To meet these aims, we selected a modified AX version of the Continuous Performance Test (CPT), the stop task, and the flanker task. In three double-blind, placebo-controlled, within-subjects experiments, these tasks were administered to healthy participants. While the results for the AX-CPT were indicative of improved response inhibition after caffeine, they might also reflect caffeine-induced changes in mechanisms other than response inhibition (e.g., attentional processes). The results for the stop task and flanker task were more straightforward. That is, the effects of caffeine on overall flanker performance and selective response suppression as revealed by distribution-analytical techniques were negligible. In the stop task a global effect of caffeine on processing speed was seen, rather than specific effects on response inhibition. Taken together, these experiments showed that both active and reactive inhibition were not significantly modulated by caffeine. The present results are linked to neural circuits that underlie inhibitory control and the role of caffeine-induced strategic changes.

Effects of caffeine on anticipatory control processes: evidence from a cued task-switch paradigm.

Effects of caffeine on task switching were studied using ERPs in a cued task-switch paradigm. The need for advance preparation was manipulated by varying the number of task-set aspects that required switching. In a double-blind, within-subjects experiment, caffeine reduced shift costs compared to placebo. ERPs revealed a negative deflection developing within the preparatory interval, which was larger for shift than for repeat trials. Caffeine increased this shift-induced difference. Furthermore, shift costs increased as a function of the number of task-set features to be switched, but this pattern was not modulated by caffeine. The results suggest that caffeine improves task-switching performance by increasing general effects on task switching, related to task-nonspecific (rather than task-specific) anticipatory processes. Caffeine's actions may be mediated by dopaminergic changes in the striatum or anterior cingulate cortex.

No evidence for substantial aerobic methane emission by terrestrial plants: a 13C-labelling approach.

* The results of a single publication stating that terrestrial plants emit methane has sparked a discussion in several scientific journals, but an independent test has not yet been performed. * Here it is shown, with the use of the stable isotope (13)C and a laser-based measuring technique, that there is no evidence for substantial aerobic methane emission by terrestrial plants, maximally 0.3% (0.4 ng g(-1) h(-1)) of the previously published values. * Data presented here indicate that the contribution of terrestrial plants to global methane emission is very small at best. * Therefore, a revision of carbon sequestration accounting practices based on the earlier reported contribution of methane from terrestrial vegetation is redundant.

Caffeine improves anticipatory processes in task switching.

We studied the effects of moderate amounts of caffeine on task switching and task maintenance using mixed-task (AABB) blocks, in which participants alternated predictably between two tasks, and single-task (AAAA, BBBB) blocks. Switch costs refer to longer reaction times (RT) on task switch trials (e.g. AB) compared to task-repeat trials (e.g. BB); mixing costs refer to longer RTs in task-repeat trials compared to single-task trials. In a double-blind, within-subjects experiment, two caffeine doses (3 and 5mg/kg body weight) and a placebo were administered to 18 coffee drinkers. Both caffeine doses reduced switch costs compared to placebo. Event-related brain potentials revealed a negative deflection developing within the preparatory interval, which was larger for switch than for repeat trials. Caffeine increased this switch-related difference. These results suggest that coffee consumption improves task-switching performance by enhancing anticipatory processing such as task set updating, presumably through the neurochemical effects of caffeine on the dopamine system.

In a prospective study in young people, associations between changes in smoking behavior and risk factors for cardiovascular disease were complex.

OBJECTIVE: This study investigates how voluntary changes in tobacco consumption are related to changes in biological risk factors for cardiovascular disease in 21- to 36-year-old men and women. STUDY DESIGN AND SETTING: Data of the Amsterdam Growth and Health Longitudinal Study (AGAHLS) were used to study the association between voluntary changes in tobacco consumption and changes in biological risk factors for cardiovascular disease (CVD) during 4-6 years of follow-up in 165 men and 195 women aged 21-36 years. We used multiple linear regression analyses with corrections for age and changes in other lifestyles. RESULTS: In both sexes, we found trends for a reduction in blood pressure, high-density lipoprotein cholesterol (HDL-C), body weight, and waist-to-hip ratio (WHR) and a rise in the ratio between total serum cholesterol (TC) and HDL-C (TC/HDL-C) with increasing tobacco consumption. Opposite trends were found with reducing tobacco consumption. In women, body weight, WHR, and waist circumference reduced significantly and independently with increasing tobacco consumption and increased significantly with decreasing tobacco consumption. CONCLUSION: These results suggest that voluntary changes in tobacco consumption go together with both healthy and unhealthy changes in biological risk factors for CVD.

Altered photosynthetic performance of a natural Arabidopsis accession is associated with atrazine resistance.

Natural variation for photosynthetic traits was studied by determining chlorophyll fluorescence parameters in a collection of Arabidopsis accessions. This screen revealed only one single accession (Ely), exhibiting photosynthetic characteristics markedly different from all others, while a few lines showed small but significant variation. Detailed genetic and physiological analyses showed reduced fitness for Ely compared with the standard laboratory strain Ler for various growth parameters. At low temperature (15 degrees C), Ely had a higher electron transport rate than Ler, indicating increased photosystem II efficiency under this condition, while at high temperature (30 degrees C) the opposite was observed. Ely had a high sensitivity to UV-B radiation compared with Ler and was atrazine resistant. This atrazine-resistance and related chlorophyll fluorescence traits were maternally inherited, pointing towards chloroplast-located gene(s). Definite proof that Ely is atrazine-resistant was obtained by sequencing the psbA gene, encoding the D1 protein of photosystem II, revealing a point mutation causing the same amino acid change as found in other atrazine-resistant species. Additional nuclear encoded genetic variation was also present, as was concluded from the small but significant differences in phenotype between Ely and its reciprocal crosses with Ler. It was concluded that the photosynthetic yield is highly conserved and that only severe selection pressure results in marked variations in photosynthetic performance.

Comparison between self-report and a dipstick method (NicCheck 1) to assess nicotine intake.

The purpose of this study was to investigate the agreement between self-reported tobacco consumption and NicCheck 1 (Dynagen Inc. Cambridge, Mass., USA) regarding smoking status and nicotine intake in a population of smokers (20.8%) and non-smokers. NicCheck 1 is a dipstick that changes colour in the presence of urinary nicotine metabolites. Smoking was assessed by self-report and NicCheck 1 in 169 males and 191 females (mean age 36.0 SD 0.7). Self-report and NicCheck 1 agreed highly on smoking status, especially in moderate to heavy smokers. With regard to nicotine intake, there was a large overlap in self-reported tobacco consumption between NicCheck 1 levels, despite a relatively high correlation coefficient between self-report and NicCheck 1 in smokers (i.e. 0.74). No effect modification by gender or BMI was found. When both methods were validated against two blood lipid parameters, self-report seemed to do equally well as NicCheck 1 in assessing nicotine intake.

Comparison of short questionnaires on alcohol drinking behavior in a nonclinical population of 36-year-old men and women.

Little is known on the diagnostic characteristics of brief questionnaires on alcohol drinking behaviors. This report investigates the determinants of three short alcohol questionnaires and investigates their diagnostic utility as screening tools for alcohol-related problems in a general population from The Netherlands. This report uses cross-sectional data obtained in the year 2000 from 36-year-old healthy male (N=166) and female (N=165) volunteers who reported to drink alcohol at least occasionally. Since they were 13-years-old these volunteers have been members of the Amsterdam Growth And Health Longitudinal Study, which started as a school-based study in 1977. Among many other variables, quantity-frequency questions (QF), the CAGE questionnaire, and a question on the highest number of alcoholic units consumed on one occasion during the previous month (MAX) were asked. The sensitivity, specificity, Cohen's kappa, and diagnostic odds ratio of QF, CAGE, MAX, and combinations of these three brief questionnaires were calculated using a 7-item questionnaire on alcohol-related problems as reference. Both in women and men, the prevalence of most alcohol-related problems and of a high QF, CAGE, and MAX was low. QF, CAGE, and MAX, as well as all possible combinations of the three questionnaires, were poor in detecting last-year alcohol-related problems. The CAGE appeared to perform worse than the even shorter and easier-to-interpret QF and MAX. In this healthy population of 36-year-old men and women, using the QF, MAX, and especially the CAGE questionnaire as screening instruments for alcohol-related problems resulted in many false positive and false negative classifications.

Caffeine strengthens action monitoring: evidence from the error-related negativity.

The medial frontal cortex, especially the anterior cingulate cortex (ACC), is involved in action monitoring. We studied the role of moderate amounts of caffeine in action monitoring as expressed by the error-related negativity (ERN), an event-related brain component that reflects ACC activity. In a double-blind, placebo-controlled, within-subjects experiment, two caffeine doses (3 and 5 mg/kg body weight) and a placebo were administered to habitual coffee drinkers. Compared with placebo, both caffeine doses enlarged the ERN. Amplitudes of the P2 and P3 components were not affected by caffeine. Thus, the enlarged ERN after caffeine reflects a specific effect on action monitoring. We conclude that consumption of a few cups of coffee strengthens central information processing, specifically the monitoring of ongoing cognitive processes for signs of erroneous outcomes. Brain areas related to action monitoring such as the ACC presumably mediate these caffeine effects.

Smoking and quantitative ultrasound parameters in the calcaneus in 36-year-old men and women.

Little is known regarding the association between smoking and quantitative ultrasound (QUS) parameters. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) are believed to provide information on bone quality besides information on bone mineral density (BMD). The aim of this study was to investigate (1) current tobacco smoking; (2) lifetime tobacco smoking; and (3) years since smoking cessation, in relation to QUS and BMD parameters in 36-year-old men and women. Data came from the ninth measurement of the Amsterdam Growth and Health Longitudinal Study (AGAHLS), in which 165 men (36 smokers and 129 nonsmokers) and 178 women (33 smokers and 145 nonsmokers) participated, with an average age of 36 years (SD = 0.7). BUA (dB/MHz) and SOS (m/s) of the calcaneus were assessed by using the CUBA Clinical instrument. BMD of the lumbar spine (L1-L4), total hip, and total body were measured with dual-energy X-ray absorptiometry (DXA). We used multiple linear regression analyses with correction for body weight, physical activity, calcium intake, and alcohol consumption. We found no significant associations between smoking and any of the BMD parameters in 36-year-old men and women. However, both current and lifetime tobacco smoking were significantly and negatively associated with BUA in women but not in men. Lifetime tobacco smoking was significantly and negatively associated with SOS in both sexes. The latter association was independent of body weight, calcium intake, physical activity, and alcohol consumption in women, but not in men. Our results suggest that both current and lifetime tobacco smoking are associated with a deterioration in bone quality but not with a reduction in BMD. However, since BMD parameters and QUS parameters were not measured at the same sites, our results may also simply suggest that the calcaneus is affected by smoking at an earlier stage than the lumbar spine, hip, and total body.

Impaired executive function in male MDMA ("ecstasy") users.

RATIONALE: Long-term users of ecstasy have shown impaired performance on a multitude of cognitive abilities (most notably memory, attention, executive function). Research into the pattern of MDMA effects on executive functions remains fragmented, however. OBJECTIVES: To determine more systematically what aspects of executive function are affected by a history of MDMA use, by using a model that divides executive functions into cognitive flexibility, information updating and monitoring, and inhibition of pre-potent responses. METHODS: MDMA users and controls who abstained from ecstasy and other substances for at least 2 weeks were tested with a computerized cognitive test battery to assess their abilities on tasks that measure the three submodalities of executive function, and their combined contribution on two more complex executive tasks. Because of sex-differential effects of MDMA reported in the literature, data from males and females were analyzed separately. RESULTS: Male MDMA users performed significantly worse on the tasks that tap on cognitive flexibility and on the combined executive function tasks; no differences were found on the other cognitive tasks. Female users showed no impairments on any of the tasks. CONCLUSIONS: The present data suggest that a history of MDMA use selectively impairs executive function. In male users, cognitive flexibility was impaired and increased perseverative behavior was observed. The inability to adjust behavior rapidly and flexibly may have repercussions for daily life activities.

A longitudinal study on smoking in relationship to fitness and heart rate response.

PURPOSE: Smoking has been shown to be associated with impaired cardiovascular fitness and reduced heart rate response to exercise. It is not known whether these associations are present in adolescence and young adults, and whether they change over time. METHODS: Maximal oxygen uptake ([OV0312]O(2max)), maximum treadmill slope (Slope(max)), resting heart rate (HR(rest)), heart rate at submaximal exercise (HR(submax)), heart rate reserve (HRR), and maximum heart rate (HR(max)) were measured one to nine times between ages 13 and 36 in 298 male and 334 female participants of the Amsterdam Growth and Health Longitudinal Study. Generalized estimating equation analyses were used to study the longitudinal relationship between smoking and cardiovascular fitness and heart rate response to exercise, whereas linear regression analyses were used to study the reversibility of smoking effects at age 36. RESULTS: Moderate to heavy smoking (>/=10 g of tobacco per day) was longitudinally and negatively related to [OV0312]O(2max), Slope(max), HR(submax), and HR(max). With increasing age, the negative relationship between smoking and [OV0312]O(2max), Slope(max), and HR(max) became stronger in males. Cross-sectional analyses suggested that the adverse effects of smoking were reversible in 36-yr-old males. CONCLUSION: Cardiovascular fitness and heart rate response to exercise are already reduced in young healthy smokers. In men, the adverse effects of smoking become stronger with increasing age but appear to be reversible at age 36.

Alcohol consumption impairs detection of performance errors in mediofrontal cortex.

The anterior cingulate cortex (ACC) is a critical component of the human mediofrontal neural circuit that monitors ongoing processing in the cognitive system for signs of erroneous outcomes. Here, we show that the consumption of alcohol in moderate doses induces a significant deterioration of the ability to detect the activation of erroneous responses as reflected in the amplitude of brain electrical activity associated with the ACC. This impairment was accompanied by failures to instigate performance adjustments after these errors. These findings offer insights into how the effects of alcohol on mediofrontal brain function may result in compromised performance.

Concurrent validity of alcohol consumption measurement in a 'healthy' population; quantity-frequency questionnaire v. dietary history interview.

Self-reports of alcohol consumption account for approximately 50 % of the reported sales of alcohol. In the absence of a gold standard, it is not known how accurately different methods of measurement reflect actual consumption and whether under-reporting varies among different populations. The objective of the present study was to compare the consumption reported by the widely used quantity-frequency questionnaire (QFQ) with that reported in a cross-check dietary history interview (DHI), which has higher face validity. In 171 male and 197 female subjects of the Amsterdam Growth and Health Longitudinal Study (mean age 36 years), alcohol consumption was assessed by both the QFQ and the DHI. Most subjects reported a moderate consumption of alcohol by both measures. Spearman correlation coefficients were high (0.77 and 0.87 in men and women respectively). Overall, greater alcohol consumption was reported using the DHI. The difference between the DHI and QFQ reports was usually greater for wine than for beer. Backward stepwise regression analysis showed that the difference in reporting was positively related to a more irregular drinking pattern, and in wine drinkers to the square of the QFQ report. Sex, drinking alone or with others and the CAGE (acronym for four questions on drinking behaviour) score were not related to the difference in reporting. The precision of DHI estimation from QFQ reports and other factors was low. Serious questions arise as to the validity and precision of alcohol consumption measurements based on the QFQ alone. QFQ information may be improved by incorporating questions on the type of beverage and drinking patterns.