Intra-individual variation in Galium odoratum is affected by experimental drought and shading

BACKGROUND AND AIMS

Climate-change induced warmer spring temperatures advance tree leaf-out and result in earlier shading of the forest floor. Climate change also leads to more frequent droughts. Forest understorey herbs may respond to these environmental changes by varying traits at different hierarchical levels of organization. While trait mean variation at the inter-individual level in response to environmental changes is well-studied, little is known about how variation at the intra-individual level responds.

METHODS

We sampled genets of the forest understorey herb Galium odoratum from 21 populations in three regions in Germany, varying in microclimatic conditions. The genets were transplanted into a common garden, where we applied shading and drought treatments. We measured plant height and leaf length and width, and calculated the coefficient of variation (CV) at different hierarchical levels: intra-population, intra-genet, intra-ramet and intra-shoot.

KEY RESULTS

Variance partitioning showed that intra-shoot CV represented most of the total variation, followed by intra-ramet CV. We found significant variation in CV of plant height and leaf width among populations of origin, indicating that CV is at least partly genetically based. The soil temperature at populations' origins correlated negatively with CV in plant height, suggesting adaptation to local conditions. Furthermore, we observed that early shade led to increased intra-ramet CV in leaf length, while drought reduced intra-shoot CV in leaf width. Finally, intra-shoot leaf width mean and CV were independent under control conditions but correlated under drought.

CONCLUSIONS

Our experimental results reveal correlations of intra-individual variation with soil temperature, indicating that intra-individual variation can evolve and may be adaptive. Intra-individual variation responded plastically to drought and shading, suggesting functional changes to improve light capture and reduce evapotranspiration. In conclusion, intra-individual variation makes up the majority of total trait variation in this species and can play a key role in plant adaptation to climatic change.

MetaboVariation: Exploring Individual Variation in Metabolite Levels

To date, most metabolomics biomarker research has focused on identifying disease biomarkers. However, there is a need for biomarkers of early metabolic dysfunction to identify individuals who would benefit from lifestyle interventions. Concomitantly, there is a need to develop strategies to analyse metabolomics data at an individual level. We propose "MetaboVariation", a method that models repeated measurements on individuals to explore fluctuations in metabolite levels at an individual level. MetaboVariation employs a Bayesian generalised linear model to flag individuals with intra-individual variations in their metabolite levels across multiple measurements. MetaboVariation models repeated metabolite levels as a function of explanatory variables while accounting for intra-individual variation. The posterior predictive distribution of metabolite levels at the individual level is available, and is used to flag individuals with observed metabolite levels outside the 95% highest posterior density prediction interval at a given time point. MetaboVariation was applied to a dataset containing metabolite levels for 20 metabolites, measured once every four months, in 164 individuals. A total of 28% of individuals with intra-individual variations in three or more metabolites were flagged. An R package for MetaboVariation was developed with an embedded R Shiny web application. To summarize, MetaboVariation has made considerable progress in developing strategies for analysing metabolomics data at the individual level, thus paving the way toward personalised healthcare.

Single nucleotide polymorphism analysis of the ITS2 region of two sympatric malaria mosquito species in Sweden: Anopheles daciae and Anopheles messeae

Four species of the Anopheles maculipennis complex have previously been recorded in Sweden. A recent addition to the complex is Anopheles daciae, which is considered to be closely related to, but distinct from Anopheles messeae. The original designation of An. daciae was based on five genetic differences (161, 165, 167, 362 and 382) in the second internal transcribed spacer (ITS) 2 of the ribosomal RNA. Further studies have shown that only two nucleotide differences (362 and 382) robustly separate the species. Thirty-three An. maculipennis complex mosquitoes were collected in the province of Uppland, Sweden. All were An. daciae but showed double peaks for three variable positions (161, 165 and 167). When cloned, the intra-individual nucleotide variation was almost exclusively fixed with either TTC or AAT, originally diagnostic for An. messae and An. daciae, respectively. To further investigate the intra-individual variation, nine An. daciae and 11 An. messeae were collected in southern Sweden and their ITS2 fragments were amplified and sequenced using Illumina MiSeq sequencing (Illumina, Inc., San Diego, CA, USA). For the diagnostic nucleotide 382 no intra-individual variation could be detected. However, although each An. daciae specimen carried several ITS2 sequence variants for the four other nucleotides, there was no intra-individual variation in the An. messeae specimens.

Whole-plant reddening in Silene germana is due to anthocyanin accumulation in response to visible light

The phenology of anthocyanin accumulation in leaves has been widely studied in perennial plants; several hypotheses have been proposed to explain their adaptive significance. Here, we explored the photoprotection hypothesis in Silene germana, a Mediterranean annual plant with late-spring/summer flowering. We analysed the temporal patterns of anthocyanin accumulation in photosynthetic calyces, leaves and stems and throughout the reproductive season, and their relationship with flower abortion, florivory and plant mortality due to drought. In addition, the flavonoid production and the photoinhibitory response were measured in a shading experiment. The whole plant becomes red at the end of the flowering and remains red until fruiting and senescence. Calyces were redder on the side with more sun exposition. Aborted flowers showed redder calyces than those of fruiting flowers. No effect of plant redness on florivory or plant mortality was found. The shading experiment showed a positive relationship between anthocyanin accumulation and intensity of solar radiation, but plants growing in absence of UV showed similar redness than full sunlight plants. Plants growing in natural shade lack anthocyanins but produced the same amount of non-anthocyanin flavonoids. Anthocyanic and non-anthocyanic plants showed similar photochemical efficiency (F_v /F_m ) after sun exposition, but in early morning, the former showed lower F_v /F_m values. Plants growing in full sunlight produced more fruits than those of natural shade plants. Whole-plant reddening during fruiting and senescence appears to be a property of S. germana. Our results suggest that anthocyanin accumulation depends on sunlight intensity, but non-anthocyanin flavonoids are produced constitutively.

Effect of flower orientation on the male and female traits of Myrtillocactus geometrizans (Cactaceae)

Intra-individual variation in the production and size of reproductive traits has been documented in columnar cacti, being higher in equator-facing flowers. Such variation is attributed to the high amount of PAR intercepted by stems oriented towards the equator. Most studies focused on this phenomenon have documented the existence of intra-individual variation on traits associated with the female function; however, its impact on traits associated with the male function has been neglected. We tested the hypothesis that equator-facing flowers of Myrtillocactus geometrizans exhibit higher values on traits associated with both male and female functions than flowers facing against it. Number and size of anthers and ovaries, pollen:ovule ratio and number and quality of pollen grains (diameter, germinability, viability and pollen tube length) were estimated from reproductive structures facing north and south, and compared with t-tests between orientations. Number of anthers per flower, number of pollen grains per anther and per floral bud; pollen size, viability and germinability; pollen tube length; ovary length and pollen:ovule ratio were significantly higher in reproductive structures oriented towards the south (i.e. equator). These findings suggest that intra-individual variation in floral traits of M. geometrizans might be associated with different availability of resources in branches with contrasting orientation. Our results provide new evidence of the existence of a response to an orientation-dependent extrinsic gradient. To our knowledge, this is the first study documenting the existence of intra-individual variation on pollen quality and P:O ratio in Cactaceae species.

Intra-individual variation of miRNA expression levels in human plasma samples

BACKGROUND

Circulating miRNAs as potential non-invasive biomarkers for disease risk assessment and cancer early diagnosis have attracted increasing interest. Little information, however, is available regarding the intra-individual variation of circulating miRNA levels.

METHODS

We measured expression levels of a panel of 800 miRNAs in repeated plasma samples from 51 healthy individuals that were collected 6 to 12 months apart and evaluated the intra-individual variation by the intra-class correlation coefficient (ICC).

RESULTS

After background correction, a total of 185 miRNAs were detected in at least 10% of the plasma samples, with 69 and 28 miRNAs being detected in 50% and 90% of samples, respectively. The median ICC was 0.46 for these 185 miRNAs. Among them, 41% (75 miRNAs) had an ICC ≥ 0.5, and 23% (42 miRNAs) had an ICC ≥ 0.6. The ICC is higher for miRNAs with higher expression levels or higher detection rates, when compared to those with lower expression levels or lower detection rates.

CONCLUSIONS

These results suggest that common circulating miRNAs are stable over a relatively long period and can serve as reliable biomarkers for epidemiological and clinical research.

Technical and performance characteristics of anti-Müllerian hormone and antral follicle count as biomarkers of ovarian response

BACKGROUND

Stratified (individualized) medicine has been recognized as a key priority for policy makers and healthcare providers. The main principle of individualized care depends on utilizing patients' characteristics and biomarkers to predict prognosis, tailor intended treatment and predict treatment outcomes. In reproductive medicine a wide variety of biomarkers have been proposed as predictors of ovarian response; of these, anti-Müllerian hormone (AMH) and antral follicle count (AFC) are purported as exhibiting the most favourable analytical and performance characteristics. Previously AFC and AMH have been considered essentially interchangeable; however, recent trial data have questioned this postulation. The aim of this review is to present an analysis of the strengths and weaknesses of these biomarkers as predictors of ovarian response, using both physiological and technical perspectives.

METHODS

We have conducted a systematic search of the most recent (to May 2014) relevant literature and summarized the existing evidence. Articles written in a language other than English without an available English translation were excluded.

RESULTS

Both AMH values and AFC can be influenced by comparable technical, physiological and exogenous factors. AMH displays some variation within and between cycles, consistent with its physiological role in follicle development, and there are growing data on the impact of pharmacological treatments and pathological conditions but cycle-independent measurement is appropriate for clinical purposes. A range of issues with manual AMH assays may be resolving with the development of fully automated assays. Despite described standardization of its measurement technique, AFC is subject to marked inter- and intra-operator variability and the effects of external influences are likely to be comparable. Outwith some highly specialist centres, the intracyclic variation in AFC requires its measurement between Day 2 and 4 of the cycle. Observational studies suggest comparable performance characteristics for AMH and AFC in predicting poor and high ovarian response, but recent RCTs suggest markedly better performance for AMH.

CONCLUSIONS

The performance characteristics of both AMH and AFC for the prediction of ovarian response to exogenous gonadotrophins have been inflated by single site observational cohorts, resulting in the viewpoint that AMH and AFC exhibit equivalent performance characteristics. Large scale multicentre RCTs, with centralized assay performance, have demonstrated that AMH is substantially the more accurate and robust biomarker, probably reflecting difficulties with standardization of AFC determination. While AFC retains some advantages, particularly immediacy and accessibility, international standardization of AMH combined with a stable automated assay is likely to enhance its performance as the biomarker of choice in predicting the ovarian response in assisted conception.

Plastic proteans: reduced predictability in the face of predation risk in hermit crabs

Variation in behaviour occurs at multiple levels, including between individuals (personality) and between situations (plasticity). Behaviour also varies within individuals, and intra-individual variation (IIV) in behaviour describes within-individual residual variance in behaviour that remains after the effects of obvious external and internal influences on behaviour have been accounted for. IIV thus describes how predictable an individual's behaviour is. Differences in predictability, between individuals and between situations, might be biologically significant. For example, behaving unpredictably under predation threat might reduce the chance of capture. Here, we investigated the duration of startle responses in hermit crabs, in the presence and absence of a predator cue. Individuals differed in startle response duration (personality) and while individuals also varied in their sensitivity to risk, mean response time was greater in the presence of a predator (plasticity). Moreover, IIV was greater in the presence of a predator, providing some of the first evidence that the facultative injection of unpredictability into behaviour might represent a strategy for dealing with risk.

Daily urinary excretion of bisphenol A

OBJECTIVES

Concerns over dietary exposure to bisphenol A (BPA), an endocrine disruptor, have been raised because BPA is contained in resins and plastics commonly used for the preservation of food and beverages. The purpose of the present study was to assess daily intake levels of BPA in a group of male subjects by measuring total urinary BPA (free BPA plus BPA released by treatment with β-glucuronidase), as well as determining intra-individual variation in BPA excretion.

METHODS

Twenty-four-hour urine was collected from 5 subjects for 5 consecutive days for the evaluation of between-day variation in urinary BPA excretion and from 36 male subjects for the estimation of the level of daily BPA intake. BPA in the urine samples was measured by GC/MS/MS following enzymatic hydrolysis of BPA glucuronate, solid phase extraction, and derivatization.

RESULTS

A large between-day variation was found over 5 days for the daily excretion of urinary BPA in the 5 subjects. The daily excretion of urinary BPA was distributed log-normally in the 36 male subjects, with the median value being 1.2 μg/day (range: <0.21-14 μg/day), which was far below the Tolerable Daily Intake (0.01 mg/kg bw) recommended by a scientific committee in the European Commission in 2002. However, the maximum estimated intake per body weight (0.2 μg/kg/day) was only one order of magnitude lower than the reported lowest level for reproductive/behavioral effects in pregnant mice (2 μg/kg/day).

CONCLUSIONS

Measuring urinary BPA in urine is a suitable approach for estimating short-term BPA intake levels in individuals and/or estimating the average exposure level of populations. Urine analyses will be increasingly important in the human health risk assessment of BPA.

Can Colonoscopy Aspirates be a Substitute for Fecal Samples in Analyses of the Intestinal Microbiota?

There is a growing interest in the study of the human gut microbiota, as correlations between changes in bacterial profiles and diseases are increasingly discovered. Studies in this field generally use fecal samples, but it is often easier to obtain colon content aspirates during colonoscopy. This study used automated ribosomal internal spacer analysis (ARISA) to examine the extent to which the microbiota of colon aspirate samples obtained after bowel cleansing can reflect interindividual differences and serve as a proxy for fecal samples. Pre-bowel preparation fecal samples as well as colonoscopy aspirate samples from the cecum and rectum were obtained from 19 subjects. DNA was extracted from all samples, and comparative analysis was performed, including analysis of similarity (ANOSIM) and nonmetric multidimensional scaling. ANOSIM confirmed that samples from the same individual were well separated from samples from different individuals. Significantly larger differences were found between samples from different individuals than between samples of the same individual (R = 0.7605, p < 0.0001). These findings show that post-bowel preparation aspirates maintain a strong individual signature. Colonoscopy aspirates can therefore serve as a substitute for fecal samples in studies comparing the microbiota of different clinical study groups, especially when fecal samples are unavailable.

Intestinal absorption of strontium chloride in healthy volunteers: pharmacokinetics and reproducibility

1. The absorption kinetics of orally administered strontium chloride and its reproducibility were investigated in healthy volunteers after administering strontium either under fasting conditions (study I, n = 8) or in combination with a standardized meal (study II, n = 8). Each subject received strontium orally at day 0, 14, and 28 and intravenously at day 42. The study was performed as part of a project in which a simple clinical test for measuring intestinal calcium absorption is being developed, based on the use of stable strontium as a marker. 2. Plasma strontium concentration-time curves were analysed by noncompartment analysis and a four compartment disposition model. Within a volunteer each oral curve was fitted simultaneously with the intravenous curve, by which means a two segment model for absorption was revealed. 3. Mean absolute bioavailability of strontium was 25% without a meal and 19% with a meal, whereas the intraindividual variation was 24% and 20%, respectively. 4. Various limited sampling absorption parameters were determined in order to select a potential test parameter for measuring intestinal calcium absorption using strontium as a marker. Fractional absorption at 4 h (Fc240), obtained after co-ingestion of strontium with a meal, appeared to be the best test parameter, because it represented bioavailability well (r = 0.90).