There are many interesting articles published in PLoS ONE, PLoS Medicine, PLoS Biology and PLoS Neglected Tropical Diseases today. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week - you go and look for your own favourites:
It has been assumed that the unusual tail club of ankylosaurid dinosaurs was used actively as a weapon, but the biological feasibility of this behaviour has not been examined in detail. Ankylosaurid tail clubs are composed of interlocking vertebrae, which form the handle, and large terminal osteoderms, which form the knob. Computed tomographic (CT) scans of several ankylosaurid tail clubs referred to Dyoplosaurus and Euoplocephalus, combined with measurements of free caudal vertebrae, provide information used to estimate the impact force of tail clubs of various sizes. Ankylosaurid tails are modeled as a series of segments for which mass, muscle cross-sectional area, torque, and angular acceleration are calculated. Free caudal vertebrae segments had limited vertical flexibility, but the tail could have swung through approximately 100Â° laterally. Muscle scars on the pelvis record the presence of a large M. longissimus caudae, and ossified tendons alongside the handle represent M. spinalis. CT scans showed that knob osteoderms were predominantly cancellous, which would have lowered the rotational inertia of the tail club and made it easier to wield as a weapon. Large knobs could generate sufficient force to break bone during impacts, but average and small knobs could not. Tail swinging behaviour is feasible in ankylosaurids, but it remains unknown whether the tail was used for interspecific defense, intraspecific combat, or both.
Shared decision making in health care can be defined as the process of "...defining problems, presenting options, and providing high-quality information so patients can participate more actively in care..." . This model of decision making is rooted in several core principles of medical ethics, but perhaps most strongly that of patient autonomy . Autonomy--the right to self-determination--entails a process of informed and meaningful consent to the care a patient is to receive . The idea of informed consent clearly goes beyond a simple procedure of form-filling, and requires that the nature of an intervention, the potential alternatives, the likely risks and benefits, and the implications are clearly laid out and mutually understood before a patient and clinician can agree on the course of action to be undertaken. In a Policy Forum published in PLoS Medicine, Michael Wilkes and Margaret Johns set out four key characteristics of the types of decisions that best lend themselves to shared decision making : those where "effectiveness of the outcome is uncertain; ...where the risks and benefits are sizeable or nearly equal; ...where the patient is able and willing to participate; ...[and] where the patient can understand the trade-offs." An obvious requirement for the fourth characteristic--the understanding of trade-offs--is that a patient interprets data regarding risk and can integrate that data into their own system of values--an issue we discuss within this Editorial.
In mammals, complex songs are uncommon and few studies have examined song composition or the order of elements in songs, particularly with respect to regional and individual variation. In this study we examine how syllables and phrases are ordered and combined, ie "syntax", of the song of Tadarida brasiliensis, the Brazilian free-tailed bat. Specifically, we test whether phrase and song composition differ among individuals and between two regions, we determine variability across renditions within individuals, and test whether phrases are randomly ordered and combined. We report three major findings. First, song phrases were highly stereotyped across two regions, so much so that some songs from the two colonies were almost indistinguishable. All males produced songs with the same four types of syllables and the same three types of phrases. Second, we found that although song construction was similar across regions, the number of syllables within phrases, and the number and order of phrases in songs varied greatly within and among individuals. Last, we determined that phrase order, although diverse, deviated from random models. We found broad scale phrase-order rules and certain higher order combinations that were highly preferred. We conclude that free-tailed bat songs are composed of highly stereotyped phrases hierarchically organized by a common set of syntactical rules. However, within global species-specific patterns, songs male free-tailed bats dynamically vary syllable number, phrase order, and phrase repetitions across song renditions.
As personal genetic information becomes an increasingly frequent component of the patient medical record, it is crucial that medical students be trained to use and interpret this information appropriately and responsibly. Here, I argue the need for medical education reform that equips physicians with the knowledge, skills, and attitudes required to practice personalized medicine.
In February 2009, The Washington Post reported that three South American countries, Bolivia, Ecuador, and Venezuela, have either launched or completed ambitious efforts to rewrite their constitutions in order to expand the social and economic rights guaranteed to its citizens . For the most part these new charters are considered populist documents, reflecting the leanings of newly elected leftist regimes and emphasizing the rights of poor and indigenous people, i.e., populations that have suffered decades or even centuries of neglect in previous regimes. In Venezuela, Hugo Chavez has ruled the longest--a decade--while both Bolivia's Evo Morales (who became the region's first indigenous leader) and Ecuador's Rafael Correa campaigned and won elections based on their pledges to reverse centuries of discrimination .
A condition vital for the consolidation and maintenance of sleep is generally reduced responsiveness to external stimuli. Despite this, the sleeper maintains a level of stimulus processing that allows to respond to potentially dangerous environmental signals. The mechanisms that subserve these contradictory functions are only incompletely understood. Using combined EEG/fMRI we investigated the neural substrate of sleep protection by applying an acoustic oddball paradigm during light NREM sleep. Further, we studied the role of evoked K-complexes (KCs), an electroencephalographic hallmark of NREM sleep with a still unknown role for sleep protection. Our main results were: (1) Other than in wakefulness, rare tones did not induce a blood oxygenation level dependent (BOLD) signal increase in the auditory pathway but a strong negative BOLD response in motor areas and the amygdala. (2) Stratification of rare tones by the presence of evoked KCs detected activation of the auditory cortex, hippocampus, superior and middle frontal gyri and posterior cingulate only for rare tones followed by a KC. (3) The typical high frontocentral EEG deflections of KCs were not paralleled by a BOLD equivalent. We observed that rare tones lead to transient disengagement of motor and amygdala responses during light NREM sleep. We interpret this as a sleep protective mechanism to delimit motor responses and to reduce the sensitivity of the amygdala towards further incoming stimuli. Evoked KCs are suggested to originate from a brain state with relatively increased stimulus processing, revealing an activity pattern resembling novelty processing as previously reported during wakefulness. The KC itself is not reflected by increased metabolic demand in BOLD based imaging, arguing that evoked KCs result from increased neural synchronicity without altered metabolic demand.
Humans rely on marine ecosystems for economic and nutritional sustenance--including about 16% of animal protein consumed by humans--making it especially important for natural scientists, economists, conservationists and long-term policy planners to understand how climate change is likely to affect oceanic food webs. Yet the general effects of warming on food web productivity are completely unknown. The productivity of consumers (such as zooplankton), in food webs is determined in large part by their metabolic rates and the availability and productivity of their limiting metabolic resources. A general theory relating food web dynamics to temperature suggests that fundamental differences between consumers and primary producers (such as phytoplankton) may lead to predictable shifts in their relative abundance and productivity with warming. We experimentally tested the effects of warming on food web structure and productivity under two resource supply scenarios. Our results show that warming alone can strengthen the role of consumers in the food web, increasing consumer biomass relative to producer biomass, and reducing the total biomass of the food web despite increases in primary productivity. In contrast, when resources were less available, food web production was constrained at all temperatures. These results demonstrate that small changes in water temperature could drive dramatic shifts in marine food web structure and productivity, and potentially provide a general, species-independent mechanism of ecological response to climate change.
While prepubertal nutritional influences appear to play a role in sexual maturation, there is a need to clarify the potential contributions of maternal and childhood influences in setting the tempo of reproductive maturation. In the present study we employed an established model of nutritional programming to evaluate the relative influences of prenatal and postnatal nutrition on growth and ovarian function in female offspring. Pregnant Wistar rats were fed either a calorie-restricted diet, a high fat diet, or a control diet during pregnancy and/or lactation. Offspring then were fed either a control or a high fat diet from the time of weaning to adulthood. Pubertal age was monitored and blood samples collected in adulthood for endocrine analyses. We report that in the female rat, pubertal timing and subsequent ovarian function is influenced by the animal's nutritional status in utero, with both maternal caloric restriction and maternal high fat nutrition resulting in early pubertal onset. Depending on the offspring's nutritional history during the prenatal and lactational periods, subsequent nutrition and body weight gain did not further influence offspring reproductive tempo, which was dominated by the effect of prenatal nutrition. Whereas maternal calorie restriction leads to early pubertal onset, it also leads to a reduction in adult progesterone levels later in life. In contrast, we found that maternal high fat feeding which also induces early maturation in offspring was associated with elevated progesterone concentrations. These observations are suggestive of two distinct developmental pathways leading to the acceleration of pubertal timing but with different consequences for ovarian function. We suggest different adaptive explanations for these pathways and for their relationship to altered metabolic homeostasis.
Herbivorous insects, such as the wasps that induce trees to make galls, and the parasitoids that attack (and ultimately kill) the wasps comprise about a third of all animal species, but it remains unclear what determines the structure of these complex coevolving communities. Here, we analyzed 48 parasitoid communities attacking different cynipid wasps that live and feed on oak trees. These communities are diverse and "closed," with each centered upon the characteristic gall induced by a given cynipid wasp species. The often spectacular and complex galls are extended phenotypes of gallwasp genes and have been suggested to evolve as gallwasp defenses against their parasitoid enemies--"the Enemy Hypothesis." Our analysis showed that similar parasitoid communities occurred on galls with similar structural traits (e.g., toughness, hairiness, stickiness), supporting the Enemy Hypothesis. We also found similar communities on galls that co-occur frequently in time and space; in particular, those occurring on the same oak species and same plant organ (e.g., leaf, bud, seed). Our results suggest that cynipid wasps might escape particular parasitoids via evolutionary shifts in the structure or location of their galls. However, escape may often be transient due to recruitment of new enemies already attacking other host galls with similar trait combinations.
Agri-environment schemes play an increasingly important role for the conservation of rare plants in intensively managed agricultural landscapes. However, little is known about their effects on gene flow via pollen dispersal between populations of these species. In a 2-year experiment, we observed effective pollen dispersal from source populations of Centaurea jacea in restored meadows, the most widespread Swiss agri-environment scheme, to potted plants in adjacent intensively managed meadows without other individuals of this species. Potted plants were put in replicated source populations at 25, 50, 100 m and where possible 200 m distance from these source populations. Pollen transfer among isolated plants was prevented by temporary bagging, such that only one isolated plant was accessible for flower visitors at any one time. Because C. jacea is self-incompatible, seed set in single-plant isolates indicated insect mediated effective pollen dispersal from the source population. Seed set was higher in source populations (35.7Â±4.4) than in isolates (4.8Â±1.0). Seed set declined from 18.9% of that in source populations at a distance of 25 m to 7.4% at 200 m. At a distance of 200 m seed set was still significantly higher in selfed plants, indicating long-distance effective pollen dispersal up to 200 m. Analyses of covariance suggested that bees contributed more than flies to this long-distance pollen dispersal. We found evidence that pollen dispersal to single-plant isolates was positively affected by the diversity and flower abundance of neighboring plant species in the intensively managed meadow. Furthermore, the decline of the dispersal was less steep when the source population of C. jacea was large. We conclude that insect pollinators can effectively transfer pollen from source populations of C. jacea over at least 200 m, even when "recipient populations" consisted of single-plant isolates, suggesting that gene flow by pollen over this distance is very likely. Source population size and flowering environment surrounding recipient plants appear to be important factors affecting pollen dispersal in C. jacea. It is conceivable that most insect-pollinated plants in a network of restored sites within intensively managed grassland can form metapopulations, if distances between sites are of similar magnitude as tested here.
As a developmental biologist with a passion for teaching, I enjoy explaining my work on cell rearrangements in the yolk sacs of killifish embryos to audiences ranging from first-year undergraduates to professional colleagues. Becoming a parent offered new opportunities. When my daughter entered our local elementary school, I wanted to find a way to share my professional life with her teachers. My modest desire to lend a helping hand evolved into a "Science Buddies" program, where undergraduate science majors are matched with elementary classrooms. Conceived as a way to help enrich the local science curriculum, the program has served as a training ground for young science educators, opening the eyes of college students to the joys and challenges of primary school teaching.
While politicians like United States Representative Michele Bachmann (R-Minn.) rail against efforts to curb human contributions to global warming--she thinks carbon dioxide, a "natural by-product of nature," could not possibly be harmful--scientists are documenting the damage. Numerous studies describe how climate change is threatening the persistence of a broad range of plant and animal species across diverse taxa, geographic regions, and trophic levels, from the polar bear at the top of the food chain to the shrimp-like krill at the bottom. As they catalog the ecological casualties of a rapidly warming world, researchers are also searching for general effects of climate change to help them predict and mitigate its consequences. The search has not been easy. Many of the documented impacts reflect species' life history--upset synchrony between the peak food needs of newly hatched birds and the peak availability of their traditional insect diet, for example--marked by idiosyncrasies that defy generalization. What's more, field studies have yielded conflicting results, with warming causing significant effects on food webs in some regions but not in others. Complicating matters, experiments that test how temperature affects food web dynamics--an approach that would help validate general predictions--are rarely done.
Amoebae that make fruiting bodies consisting of a stalk and spores and classified as closely related to the myxogastrids have classically been placed in the taxon Eumycetozoa. Traditionally, there are three groups comprising Eumycetozoa: myxogastrids, dictyostelids, and the so-called protostelids. Dictyostelids and myxogastrids both make multicellular fruiting bodies that may contain hundreds of spores. Protostelids are those amoebae that make simple fruiting bodies consisting of a stalk and one or a few spores. Protostelid-like organisms have been suggested as the progenitors of the myxogastrids and dictyostelids, and they have been used to formulate hypotheses on the evolution of fruiting within the group. Molecular phylogenies have been published for both myxogastrids and dictyostelids, but little molecular phylogenetic work has been done on the protostelids. Here we provide phylogenetic trees based on the small subunit ribosomal RNA gene (SSU) that include 21 protostelids along with publicly available sequences from a wide variety of amoebae and other eukaryotes. SSU trees recover seven well supported clades that contain protostelids but do not appear to be specifically related to one another and are often interspersed among established groups of amoebae that have never been reported to fruit. In fact, we show that at least two taxa unambiguously belong to amoebozoan lineages where fruiting has never been reported. These analyses indicate that we can reject a monophyletic Eumycetozoa, s.l. For this reason, we will hereafter refer to those slime molds with simple fruiting as protosteloid amoebae and/or protosteloid slime molds, not as protostelids. These results add to our understanding of amoebozoan biodiversity, and demonstrate that the paradigms for understanding both nonfruiting and sporulating amoebae must be integrated. Finally, we suggest strategies for future research on protosteloid amoebae and nonfruiting amoebae, and discuss the impact of this work for taxonomists and phylogenomicists.
Cell biology owes some of its greatest discoveries to the electron microscope, and few were more passionate about its power to "wrest from nature her closely guarded secrets" than Don Wayne Fawcett. A pioneer of electron microscopy and one of its greatest practitioners for studying the organization of cells and tissues, Fawcett died at his home in Missoula, Montana on May 7, 2009 at the age of 92.