Sex and asymmetry in humans: what is the role of developmental instability?

Because asymmetric individuals are less attractive and may suffer from reduced fitness, bilateral asymmetry is widely believed to affect human sexual selection. Its evolutionary significance is based on the presumed relationship with developmental instability (DI). Yet, relationships between DI and bilateral asymmetry are often weak and possibly confounded by asymmetric mechanical loadings because of handedness. We related asymmetry in hands and faces to degrees of handedness and sexual behaviour in 100 humans. Handedness correlated to levels of asymmetry, thereby likely invalidating the use of asymmetry to estimate DI. For facial asymmetry, applying existing theoretical models refuted a link between asymmetry and DI. Explicit statistical modelling at the level of DI confirmed the absence of a link between DI and aspects of sexual behaviour. Nevertheless, asymmetries in both hands and face correlated significantly with sexual behaviour. We conclude that bilateral asymmetry per se, rather than its presumed link with DI, more likely relates to measures of human sexual behaviour. Because lateralization of behaviour appears widespread, evaluating the role of DI in evolution and ecology relies on a very critical selection of traits whose asymmetry can reliably reflect DI.     

Head and neck cancer in the UK: what is expected of cytopathology?

Objective:  This review highlights the role of cytopathology in cancer management within UK Head and Neck Cancer Networks and informs on the issues raised by recent UK Department of Health documents and other UK professional guidance. UK guidance requires the formal involvement of cytopathologists within multidisciplinary cancer teams, with medical and non-medical cytopathology staff setting up and running rapid access lump clinics, and support for image-guided fine needle aspiration cytology (FNAC) services. UK guidance also makes recommendations for training, resources and quality control. This review also highlights the resource gap between best practice evidence-based guidance for head and neck (HN) cancer services and existing UK provision for cytopathology, as evidenced by lack of availability of experienced staff and adequacy of training and quality control (QC). Finally, it stresses the importance in the UK of the Royal College of Pathologists' guidance, which defines the need for training, the experience needed for new consultants, the requirements for audit and QC. The implications for the additional resources required for HN cancer cytopathology services are discussed. Recent professional guidance specifying the provision of HN cancer services in the UK includes a cytopathology service for cancer networks, such as rapid access FNAC clinics. Although these clinics already operate in some institutions, there are many institutions where they do not and where the provision of cytopathology services would have to be restructured. This would need the support of local cancer networks and their acceptance of the detailed requirements for cytopathology, including resources, training and QC. The standards are not defined locally, as Strategic Health Authorities and Primary Care Trusts have been instructed by the Department of Health to support, invest and implement them.     

Individual-based modelling in ecology: what makes the difference?

Is individual-based modelling really a new approach in ecology? A large part of the uncertainty surrounding this question is a consequence of imprecisely delimited boundaries between classical and individual-based modelling. Genuine 'individual-based' models describe a population made up of individuals that may differ from one another; they also describe changes in numbers of individuals rather than in the population density, and take resource dynamics explicitly into account. Individual-based models that fulfil these criteria will not characterize ecological systems as 'stable' systems in their ideal form, with equilibrium states represented by points in the phase space.     

Motor endplates in fast and slow muscles of the rat: what determines their difference?

Motor endplates in fast and slow skeletal muscles have different functional and morphological characteristics, and for brevity, are termed fast and slow respectively. We have examined the terminal arborization patterns of fast fibular and slow soleus axons 3-4 and 6 months after they reinnervated old preformed endplates or formed new ectopic endplates with denervated rat soleus muscles. Ectopic endplates formed by transplanted fibular and soleus nerves were fast and slow in appearance respectively. Both the fibular and the soleus nerves formed endplates of slow appearance when they reinnervated the original endplates. The fast appearance of ectopic fibular nerve endplates was unaffected by reinnervation of the original endplates by the slow soleus nerve. Dually innervated fibres had intermediate contraction speed compared to the fast fibres reinnervated only by the fibular nerve and the slow fibres reinnervated only by the soleus nerve. Continuous stimulation of the transplanted fibular nerve at 10 Hz for 3-4 months, starting just before the onset of ectopic endplate formation, prevented the increase in contraction speed seen without stimulation. The ectopic endplates of the stimulated axons were much smaller than usual and showed some signs of fast to slow transformation, but the transformation was incomplete and varied in degree between preparations. Transplanted soleus axons were less prone to growing along foreign pathways and to forming ectopic endplates than fibular axons.(ABSTRACT TRUNCATED AT 250 WORDS)     

What is signal and what is noise in the brain?

The response of a cortical neuron to a stimulus can show a very large variability when repeatedly stimulated by exactly the same stimulus. This has been quantified in terms of inter-spike-interval (ISI) statistics by several researchers (e.g., [Softky, W., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13(1), 334-350.]). The common view is that this variability reflects noisy information processing based on redundant representation in large neuron populations. This view has been challenged by the idea that the apparent noise inherent in brain activity that is not strictly related or temporally coupled to the experiment could be functionally significant. In this work we examine the ISI statistics and discuss these views in a recently published model of interacting cortical areas [Knoblauch, A., Palm, G., 2002. Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback. Biol. Cybernet. 87(3), 151-167.]. From the results of further single neuron simulations we can isolate temporally modulated synaptic input as a main contributor for high ISI variability in our model and possibly in real neurons. In contrast to alternative mechanisms, our model suggests a function of the temporal modulations for short-term binding and segmentation of figures from background. Moreover, we show that temporally modulated inputs lead to ISI statistics which fit better to the neurophysiological data than alternative mechanisms.     

Phylogeography of the capercaillie in Eurasia: what is the conservation status in the Pyrenees and Cantabrian Mounts?

The Western capercaillie (Tetrao urogallus) is a keystone species of Palearctic boreal and altitude coniferous forests. With the increase of mountain leisure activities and habitat loss, populations are declining in most mountain ranges in Western Europe. Recent work has shown that the populations from the Pyrenees and Cantabrian Mountains survived a severe bottleneck during the 19th century, and are still considered as threatened due to habitat fragmentation and isolation with other populations. We present an extensive phylogeographic study based on mitochondrial DNA sequence (control region) extracted non-invasively from faeces collected throughout the species range (from western European mountains to central and eastern Europe, Fenno-Scandia, Russia and Siberia). We also compared our results with DNA sequences of closely related black-billed capercaillie (T. parvirostris). We found that populations from Pyrenees and Cantabrians are closely related but are different from all other capercaillie populations that form a homogenous clade. Therefore, we consider that these South-Western populations should be considered as forming an Evolutionary Significant Unit that needs an appropriate management at a local scale. We also discuss the possible locations of glacial refugia and subsequent colonisation routes in Eurasia, with a Western “aquitanus” lineage from Iberia and Balkans, and an Eastern “urogallus” lineage from Southern Asia. This work might have important implication for capercaillie conservation strategies to define important areas for conservation, and to prevent possible exchange or introductions of individuals originated from other lineages. Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Cell and leaf size plasticity in Arabidopsis: what is the role of endoreduplication?

Leaf area expansion is affected by environmental conditions because of differences in cell number and/or cell size. Increases in the DNA content (ploidy) of a cell by endoreduplication are related to its size. The aim of this work was to determine how cell ploidy interacts with the regulation of cell size and with leaf area expansion. The approach used was to grow Arabidopsis thaliana plants performing increased or decreased rounds of endoreduplication under shading and water deficit. The shading and water deficit treatments reduced final leaf area and cell number; however, cell area was increased and decreased, respectively. These differences in cell size were unrelated to alterations of the endocycle, which was reduced by these treatments. The genetic modification of the extent of endoreduplication altered leaf growth responses to shading and water deficit. An increase in the extent of endoreduplication in a leaf rendered it more sensitive to the shade treatment but less sensitive to water deficit conditions. The link between the control of whole organ and individual cell expansion under different environmental conditions was demonstrated by the correlation between the plasticity of cell size and the changes in the duration of leaf expansion.     

Sex and death: what is the connection?

A cost of reproduction, where lifespan and fecundity are negatively correlated, is of widespread occurrence. Mutations in insulin/IGF signaling (IIS) pathways and dietary restriction (DR) can extend lifespan in model organisms but do not always reduce fecundity, suggesting that the link between lifespan and fecundity is not inevitable. Understanding the molecular basis of the cost of reproduction will be informed by elucidation of the mechanisms by which DR and IIS affect these two traits.     

Autophagy and apoptosis: what is the connection?

The therapeutic potential of autophagy for the treatment cancer and other diseases is beset by paradoxes stemming from the complexity of the interactions between the apoptotic and autophagic machinery. The simplest question of how autophagy acts as both a protector and executioner of cell death remains the subject of substantial controversy. Elucidating the molecular interactions between the processes will help us understand how autophagy can modulate cell death, whether autophagy is truly a cell death mechanism, and how these functions are regulated. We suggest that, despite many connections between autophagy and apoptosis, a strong causal relationship wherein one process controls the other, has not been demonstrated adequately. Knowing when and how to modulate autophagy therapeutically depends on understanding these connections.     

Developmental programming of reproduction and fertility: what is the evidence?

The concept of the foetal/developmental origins of adult disease has been around for ~20 years and from the original epidemiological studies in human populations much more evidence has accumulated from the many studies in animal models. The majority of these have focused upon the role of early dietary intake before conception, through gestation and/or lactation and subsequent interactions with the postnatal environment, e.g. dietary and physical activity exposures. Whilst a number of theoretical models have been proposed to place the experimental data into a biological context, the underlying phenomena remain the same; developmental deficits (of single (micro) nutrients) during critical or sensitive periods of tissue growth alter the developmental pathway to ultimately constrain later functional capacity when the individual is adult. Ageing, without exception, exacerbates any programmed sequelae. Thus, adult phenotypes that have been relatively easy to characterise (e.g. blood pressure, insulin sensitivity, body fat mass) have received most attention in the literature. To date, relatively few studies have considered the effect of differential early environmental exposures on reproductive function and fecundity in predominantly mono-ovular species such as the sheep, cow and human. The available evidence suggests that prenatal insults, undernutrition for example, have little effect on lifetime reproductive capacity despite subtle effects on the hypothalamic-pituitary-gonadal axis and gonadal progenitor cell complement. The postnatal environment is clearly important, however, since neonatal/adolescent growth acceleration (itself not independent from prenatal experience) has been shown to significantly influence fecundity in farm animals. The present paper will expand these interesting areas of investigation and review the available evidence regarding developmental programming of reproduction and fertility. However, it appears there is little strong evidence to indicate that offspring fertility and reproductive senescence in the human and in farm animal species are overtly affected by prenatal nutrient exposure. Nevertheless, it is clear that the developing gonad is sensitive to its immediate environment but more detailed investigation is required to specifically test the long-term consequences of nutritional perturbations during pregnancy on adult reproductive well-being.     

Where is the difference between the genomes of humans and annelids?

The first systematic investigation of an annelid genome has revealed that the genes of the marine worm Platynereis dumerilii are more closely related to those of vertebrates than to those of insects or nematodes. For hundreds of millions of years vertebrates have preserved exon-intron structures descended from their last common ancestor with the annelids.     

Where is the root of the universal tree of life?

The currently accepted universal tree of life based on molecular phylogenies is characterised by a prokaryotic root and the sisterhood of archaea and eukaryotes. The recent discovery that each domain (bacteria, archaea, and eucarya) represents a mosaic of the two others in terms of its gene content has suggested various alternatives in which eukaryotes were derived from the merging of bacteria and archaea. In all these scenarios, life evolved from simple prokaryotes to complex eukaryotes. We argue here that these models are biased by overconfidence in molecular phylogenies and prejudices regarding the primitive nature of prokaryotes. We propose instead a universal tree of life with the root in the eukaryotic branch and suggest that many prokaryotic features of the information processing mechanisms originated by simplification through gene loss and non-orthologous displacement.     

Structure and development of onychophoran eyes: what is the ancestral visual organ in arthropods?

Scarce and controversial information on visual organs and their innervation in Onychophora currently do not allow a thorough comparison with Euarthropoda. Therefore, this study sets out to provide additional data on the architecture and morphogenesis of the onychophoran visual system and to explore similarities and differences between the visual organs of onychophorans and other arthropods. Based on the new data for Epiperipatus biolleyi (Peripatidae) and Metaperipatus blainvillei (Peripatopsidae), it is suggested that the compound eyes represent an autapomorphy of Euarthropoda since similarities with the onychophoran eyes are weak or absent. Instead, the innervation from a central rather than lateral part of the brain, the presence of only one (paired or unpaired) visual center, and a similar ontogenetic origin from an ectodermal groove rather than a proliferation zone suggest homology between the onychophoran eyes and the median ocelli of euarthropods. In conclusion, I suggest that the last common ancestor of arthropods bore only one pair of ocellus-like visual organs that were modified in several arthropod lineages. This hypothesis is supported by recent paleontological data.     

Of bonds and boundaries: what is the modern role of anthropomorphism in primatological studies?

Anthropomorphism (and its obverse, zoomorphism) continues to shift and propel us toward changing perspectives on ourselves and other animals. Discussions of anthropomorphism in primate behavior are ostensibly about our use and definition of terms, but ultimately reflect our views of what is unique to humans or unknowable in other animals. Primatologists doing long-term fieldwork report on the bonds that are inevitably formed through familiarity with their study subjects and how anecdotes and anthropomorphism help them to gain a contextualized view of animal lives. This fuller view of animal society serves as an aid to understanding different rationalities and provides a more effective modern role for anthropomorphism than does seeking to demonstrate isomorphic capacities in alloprimates. Although most ordinary language terms are accepted among primatologists, "primate culture" serves as an example of a term and a concept that overreached acceptable anthropomorphic limits when defined to accord with definitions of modern human culture. Comparing similar behavioral forms as the product of similar selective pressures acting on specific early traits, producing homoplasies through convergent evolution, provides a nonanthropomorphic basis for seeking similarities in human and alloprimate behavior.