Adaptive significance of play: Are we getting closer?

Life history theory predicts that animals whose activities impose time, energy or survivorship costs at one stage of their lives will subsequently suffer incremental decreases in fitness unless there are compensatory benefits. Play, a widespread activity among juvenile mammals and several orders of birds' appears costly, yet its adaptive significance is poorly understood despite over 15 years of detailed study. Four issues have plagued understanding of the function of play: lack of a consensus on its definition, difficulties in selectively depriving animals of play opportunities and in meeting the challenge of interpreting negative results, paucity of empirical data on the costs of play, and failure to pay sufficient attention to field and naturalistic studies. Despite these problems, sex differences in play and partner preferences of participants now suggest that play serves to improve future adult motor skills in a number of species.     

Understanding variation in human fertility: what can we learn from evolutionary demography?

Decades of research on human fertility has presented a clear picture of how fertility varies, including its dramatic decline over the last two centuries in most parts of the world. Why fertility varies, both between and within populations, is not nearly so well understood. Fertility is a complex phenomenon, partly physiologically and partly behaviourally determined, thus an interdisciplinary approach is required to understand it. Evolutionary demographers have focused on human fertility since the 1980s. The first wave of evolutionary demographic research made major theoretical and empirical advances, investigating variation in fertility primarily in terms of fitness maximization. Research focused particularly on variation within high-fertility populations and small-scale subsistence societies and also yielded a number of hypotheses for why fitness maximization seems to break down as fertility declines during the demographic transition. A second wave of evolutionary demography research on fertility is now underway, paying much more attention to the cultural and psychological mechanisms underpinning fertility. It is also engaging with the complex, multi-causal nature of fertility variation, and with understanding fertility in complex modern and transitioning societies. Here, we summarize the history of evolutionary demographic work on human fertility, describe the current state of the field, and suggest future directions.     

Are we sure we know how to measure 8-oxo-7,8-dihydroguanine in DNA from human cells?

The most commonly measured marker of oxidative DNA damage is 8-oxo-7,8-dihydroguanine (8-oxoGua) or its deoxyribonucleoside (8-oxodGuo). Published estimates of the concentration of 8-oxoGua/8-oxodGuo in DNA of normal human cells vary over a range of three orders of magnitude. Analysis by chromatographic methods (GC-MS, HPLC with electrochemical detection (ECD) or HPLC-MS/MS) is beset by the problem of adventitious oxidation of guanine during sample preparation. An alternative approach, based on the use of the DNA repair enzyme formamidopyrimidine DNA N-glycosylase (FPG) to make breaks in the DNA at sites of the oxidised base, gives much lower values. ESCODD, the European Standards Committee on Oxidative DNA Damage, has been testing the ability of different laboratories using a variety of methods to measure 8-oxoGua in standard samples of 8-oxodGuo, calf thymus DNA, pig liver, oligonucleotides, and HeLa cells, and in lymphocytes isolated from blood of volunteers. HPLC-ECD is capable of measuring 8-oxodGuo induced experimentally in calf thymus DNA or HeLa cells with high accuracy. However, there is no sign of consensus over the background level of this damage, suggesting that, even though standard extraction procedures were used, variable oxidation of Gua is still occurring. GC-MS failed to detect a dose response of induced 8-oxoGua and cannot be regarded as a reliable method for measuring low levels of damage. HPLC-MS/MS as yet has not proved capable of measuring low levels of oxidative DNA damage. FPG-based methods seem to be less prone to the artefact of additional oxidation. Although they can be used quantitatively, they require careful calibration and standardisation if they are to be used in human biomonitoring. The background level of DNA oxidation in normal human cells is likely to be around 0.3-4.2 8-oxoGua per 10(6) Gua. An effort should be made to develop alternative, validated methods for estimating oxidative DNA damage.     

Is it best to cryopreserve human cumulus-free immature oocytes before or after in vitro maturation?

Freezing unfertilized oocytes is an option for females without a partner, either to preserve their fertility prior to sterilizing cancer treatment or for social reasons. Our study considered whether it is best to freeze immature human oocytes at the germinal vesicle (GV) stage, prior to in vitro maturation (IVM) or at metaphase-II (M-II), after IVM. Sibling GV-stage oocytes from stimulated ICSI cycles were allocated to freezing either prior to (n = 109) or after (n = 107) IVM. Cumulus-free oocytes were cryopreserved using a choline-substituted slow-freezing protocol and matured in a defined medium, with analysis of chromatin, microtubules, and microfilaments by three-dimensional imaging. Cryopreserved oocytes were compared with oocytes matured in vitro but never frozen (n = 114). Survival was similar between oocytes frozen before or after IVM (69.7% vs. 70.5%). Polar body extrusion after IVM was lower in oocytes frozen at the GV stage versus those matured and then frozen (51.3% vs. 75.7%) or not frozen (75.4%). Stratification by patient age (<36 and ?36 year) showed no difference in oocyte survival or maturation. Oocytes frozen as GVs showed elevated proportions of spontaneous activation (with or without polar body), an effect augmented by patient age. Spindle and chromosome configurations were disrupted to similar extents in both groups of frozen oocytes, with no further detrimental effect of patient age. The length, width, and volume of bipolar M-II spindles were comparable in all three groups. When frozen as GVs, oocytes exhibited decreased maturation and increased spontaneous activation, suggesting that it is best to freeze oocytes at M-II.     

Understanding breast cancer risk ‐ where do we stand in 2005?

Breast cancer is the most frequent cancer in women and represents the second leading cause of cancer death among women (after lung cancer). The etiology of breast cancer is still poorly understood with known breast cancer risk factors explaining only a small proportion of cases. Risk factors that modulate the development of breast cancer discussed in this review include: age, geographic location (country of origin) and socioeconomic status, reproductive events, exogenous hormones, lifestyle risk factors (alcohol, diet, obesity and physical activity), familial history of breast cancer, mammographic density, history of benign breast disease, ionizing radiation, bone density, height, IGF- 1 and prolactin levels, chemopreventive agents. Additionally, we summarized breast cancer risk associated with the following genetic factors: breast cancer susceptibility high-penetrance genes (BRCA1, BRCA2, p53, PTEN, ATM, NBS1 or LKB1) and low-penetrance genes such as cytochrome P450 genes (CYP1A1, CYP2D6, CYP19), glutathione S-transferase family (GSTM1, GSTP1), alcohol and one-carbon metabolism genes (ADH1C and MTHFR), DNA repair genes (XRCC1, XRCC3, ERCC4/XPF) and genes encoding cell signaling molecules (PR, ER, TNFalpha or HSP70). All these factors contribute to a better understanding of breast cancer risk. Nonetheless, in order to evaluate more accurately the overall risk of breast tumorigenesis, novel genetic and phenotypic traits need to be identified.     

ADARs: allies or enemies? The importance of A‐to‐I RNA editing in human disease: from cancer to HIV‐1

Adenosine deaminases acting on RNA (ADARs) are enzymes that convert adenosine (A) to inosine (I) in nuclear‐encoded RNAs and viral RNAs. The activity of ADARs has been demonstrated to be essential in mammals and serves to fine‐tune different proteins and modulate many molecular pathways. Recent findings have shown that ADAR activity is altered in many pathological tissues. Moreover, it has been shown that modulation of RNA editing is important for cell proliferation and migration, and has a protective effect on ischaemic insults. This review summarises available recent knowledge on A‐to‐I RNA editing and ADAR enzymes, with particular attention given to the emerging role played by these enzymes in cancer, some infectious diseases and immune‐mediated disorders.     

Sex‐biased migration in humans: what should we expect from genetic data?

Different patterns of mitochondrial and Y-chromosome diversity have been cited as evidence of long-term patrilocality in human populations. However, what patterns are expected depends on the nature of the sampling scheme. Samples from a local region reveal only the recent demographic history of that region, whereas sampling over larger geographic scales accesses older demographic processes. A historical change in migration becomes evident first at local geographic scales, and alters global patterns of genetic diversity only after sufficient time has passed. Analysis of forager populations in the ethnographic record suggests that patrilocality may not have predominated among pre-agricultural humans. The higher female migration rate inferred by some genetic studies may reflect a shift to patrilocality in association with the emergence of agriculture. A recent global survey does not show the expected effects of higher female migration, possibly because the sampling scheme used for this study is accessing pre-agricultural human migration patterns. In this paper, we show how the demographic shift associated with agriculture might affect genetic diversity over different spatial scales. We also consider the prospects for studying sex-biased migration using the X-linked and autosomal markers. These multi-locus comparisons have the potential of providing more robust estimates of sex differences than Y-linked and mitochondrial data, but only if a very large number of loci are included in the analysis.     

Survey‐gap analysis in expeditionary research: where do we go from here?

Research expeditions into remote areas to collect biological specimens provide vital information for understanding biodiversity. However, major expeditions to little‐known areas are expensive and time consuming, time is short, and well‐trained people are difficult to find. In addition, processing the collections and obtaining accurate identifications takes time and money. In order to get the maximum return for the investment, we need to determine the location of the collecting expeditions carefully. In this study we used environmental variables and information on existing collecting localities to help determine the sites of future expeditions. Results from other studies were used to aid in the selection of the environmental variables, including variables relating to temperature, rainfall, lithology and distance between sites. A survey gap analysis tool based on ‘ED complementarity’ was employed to select the sites that would most likely contribute the most new taxa. The tool does not evaluate how well collected a previously visited site survey site might be; however, collecting effort was estimated based on species accumulation curves. We used the number of collections and/or number of species at each collecting site to eliminate those we deemed poorly collected. Plants, birds, and insects from Guyana were examined using the survey gap analysis tool, and sites for future collecting expeditions were determined. The south‐east section of Guyana had virtually no collecting information available. It has been inaccessible for many years for political reasons and as a result, eight of the first ten sites selected were in that area. In order to evaluate the remainder of the country, and because there are no immediate plans by the Government of Guyana to open that area to exploration, that section of the country was not included in the remainder of the study. The range of the ED complementarity values dropped sharply after the first ten sites were selected. For plants, the group for which we had the most records, areas selected included several localities in the Pakaraima Mountains, the border with the south‐east, and one site in the north‐west. For birds, a moderately collected group, the strongest need was in the north‐west followed by the east. Insects had the smallest data set and the largest range of ED complementarity values; the results gave strong emphasis to the southern parts of the country, but most of the locations appeared to be equidistant from one another, most likely because of insufficient data. Results demonstrate that the use of a survey gap analysis tool designed to solve a locational problem using continuous environmental data can help maximize our resources for gathering new information on biodiversity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85 , 549–567.     

First evidence of RNA interference mechanism induced in human: Getting closer to a cure?

Knocking down a human gene by -RNA silencing has been the focus of a number of laboratories since the discovery of the RNAi mechanism more than ten years ago. In their remarkable work, M. Davis and collaborators show for the first time the induction of an RNAi pathway in humans following systemic administration of nanoparticles.² In a clinical trial, they demonstrate the accumulation of the particles in the tumor, as well as the downregulation of mRNA and protein expression of the target gene. Moreover, they successfully linked these observations to the induction of mRNA cleavage by the delivered siRNA in the tumor.Key words: RNAi, nanoparticles, melanoma, clinical trial, systemic administration     

Plant‐insect interactions: what can we learn from plant lectins?

Many plant lectins have high anti‐insect potential. Although the effects of most lectins are only moderately influencing development or population growth of the insect, some lectins have strong insecticidal properties. In addition, some studies report a deterrent activity towards feeding and oviposition behavior. Transmission of plant lectins to the next trophic level has been investigated for several tritrophic interactions. Effects of lectins with different sugar specificities can vary substantially with the insect species under investigation and with the experimental setup. Lectin binding in the insect is an essential step in exerting a toxic effect. Attempts have been made to study the interactions of lectins in several insect tissues and to identify lectin‐binding receptors. Ingested lectins generally bind to parts of the insect gut. Furthermore, some lectins such as the Galanthus nivalus agglutinin (GNA) cross the gut epithelium into the hemolymph and other tissues. Recently, several candidate lectin‐binding receptors have been isolated from midgut extracts. To date little is known about the exact mechanism for insecticidal activity of plant lectins. However, insect glycobiology is an emerging research field and the recent technological advances in the analysis of lectin carbohydrate specificities and insect glycobiology will certainly lead to new insights in the interactions between plant lectins and insects, and to a better understanding of the molecular mechanisms involved. © 2010 Wiley Periodicals, Inc.     

Models for truth‐telling in physician‐patient encounters: What can we learn from Yoruba concept of Ooto?

Empirical studies have now established that many patients make clinical decisions based on models other than Anglo American model of truth‐telling and patient autonomy. Some scholars also add that current medical ethics frameworks and recent proposals for enhancing communication in health professional‐patient relationship have not adequately accommodated these models. In certain clinical contexts where health professional and patients are motivated by significant cultural and religious values, these current frameworks cannot prevent communication breakdown, which can, in turn, jeopardize patient care, cause undue distress to a patient in certain clinical contexts or negatively impact his/her relationship with the community. These empirical studies have now recommended that additional frameworks developed around other models of truth‐telling; and which take very seriously significant value‐differences which sometimes exist between health professional and patients, as well as patient's cultural/religious values or relational capacities, must be developed. This paper contributes towards the development of one. Specifically, this study proposes a framework for truth‐telling developed around African model of truth‐telling by drawing insights from the communitarian concept of oot?? amongst the Yoruba people of south west Nigeria. I am optimistic that if this model is incorporated into current medical ethics codes and curricula, it will significantly enhance health professional‐patient communication.     

Chronic stress in superb fairy‐wrens occupying remnant woodlands: Are noisy miners to blame?

Interactions between competing species may be intensified when they are restricted to small patches of remnant habitat, potentially increasing physiological stress in individuals. The effects of interspecific competition on stress in wildlife remain largely unexplored. In Australia, remnant woodlands are often dominated by aggressive honeyeaters, especially the noisy miner (Manorina melanocephala). Harassment of smaller birds by miners may result in their exclusion from suitable woodland habitat. We tested whether the presence of noisy miners is also associated with elevated stress in a model species of small passerine bird, the superb fairy‐wren (Malurus cyaneus). We sampled wrens from six sites, three remnant woodlands with noisy miners and three larger fragments of reserved habitat without noisy miners. Differential white blood cell counts were used to infer levels of chronic stress. We also assessed variation in body condition and the prevalence of blood parasites (Haemoproteus spp.) to test for associations between stress and parasitemia. The mean heterophil‐to‐lymphocyte (H:L) ratio was 1.8 × higher among superb fairy‐wrens living in miner‐dominated woodlands, suggesting higher levels of chronic stress. Individuals with higher stress appeared to be in poorer condition, as indicated by fat scores and residual body mass. Prevalence of blood parasites was generally high and was highest in reserved habitat (59%) where miners were absent. Birds with blood parasites living in these habitats had higher H:L ratios but the intensity of infection and H:L ratio was inversely related. Our results suggest that birds persisting in the presence of noisy miners might experience chronic stress, but further study is necessary to separate the relative importance of noisy miner aggression from other potential stressors in small patches of degraded woodland. Stress induced by interspecific aggression should be considered in future studies of wildlife living in remnant vegetation.     

“Ryanopathies” and RyR2 dysfunctions: can we further decipher them using in vitro human disease models?

The regulation of intracellular calcium (Ca²⁺) homeostasis is fundamental to maintain normal functions in many cell types. The ryanodine receptor (RyR), the largest intracellular calcium release channel located on the sarco/endoplasmic reticulum (SR/ER), plays a key role in the intracellular Ca²⁺ handling. Abnormal type 2 ryanodine receptor (RyR2) function, associated to mutations (ryanopathies) or pathological remodeling, has been reported, not only in cardiac diseases, but also in neuronal and pancreatic disorders. While animal models and in vitro studies provided valuable contributions to our knowledge on RyR2 dysfunctions, the human cell models derived from patients’ cells offer new hope for improving our understanding of human clinical diseases and enrich the development of great medical advances. We here discuss the current knowledge on RyR2 dysfunctions associated with mutations and post-translational remodeling. We then reviewed the novel human cellular technologies allowing the correlation of patient’s genome with their cellular environment and providing approaches for personalized RyR-targeted therapeutics.Subject terms: Ventricular tachycardia, Ventricular tachycardia     

Are vocal characteristics related to leadership patterns in mixed‐species bird flocks?

What structures the organization of mixed‐species bird flocks, so that some ‘nuclear’ species lead the flocks, and others follow? Previous research has shown that species actively listen to each other, and that leaders are gregarious; such gregarious species tend to make contact calls and hence may be vocally conspicuous. Here we investigated whether vocal characteristics are associated with leadership, using a global dataset of mixed‐species flock studies and recordings from sound archives. We first asked whether leaders are different from following or occasional species in flocks in the proportion of the recordings that contain calls (n = 58 flock studies, 145 species), and especially alarm calls (n = 111 species). We found that leaders tended to have a higher proportion of their vocalizations that were classified as calls than occasional species, and both leaders and following species had a significantly higher proportion of their calls rated as alarms compared to occasional species. Next, we investigated the acoustic characteristics of flock participants’ calls, hypothesizing that leaders would make more calls, and have less silence on the recordings. We also hypothesized that leaders’ calls would be simple acoustically, as contact calls tend to be, and thus similar to each other, as well as being detectable, in being low frequency and with high frequence bandwidth. The analysis (n = 45 species, 169 recordings) found that only one of these predictions was supported: leading species were less often silent than following or occasional species. Unexpectedly, leaders’ calls were less similar to each other than occasional species. The greater amount of information available and the greater variety of that information support the hypothesis that leadership in flocks is related to vocal communication. We highlight the use of sound archives to ask questions about behavioral and community ecology, while acknowledging some limitations of such studies.     

Understanding the assembly of phytoplankton in relation to the trophic spectrum: where are we now?

An overview of the eleventh IAP Workshop is presented. Although significant progress has been made in the recognition of the factors governing species selection at differing trophic levels, it is recognised that the ultimate influences of species composition are precedent and stochasticity. No individual species is selected uniquely by a given combination of environmental conditions, although there are functional and morphological traits which pre-adapt some species above others to function preferentially in either oligotrophic or eutrophic conditions. With this in mind, a new set of rules of community assembly is offered.