Tuesday night – time for four PLoS journals to publish new articles and for me to check them out and pick a few I consider most bloggable. 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:
Natural selection can shape specific cognitive abilities and the extent to which a given species relies on various cues when learning associations between stimuli and rewards. Because the flower bat Glossophaga soricina feeds primarily on nectar, and the locations of nectar-producing flowers remain constant, G. soricina might be predisposed to learn to associate food with locations. Indeed, G. soricina has been observed to rely far more heavily on spatial cues than on shape cues when relocating food, and to learn poorly when shape alone provides a reliable cue to the presence of food. Here we determined whether G. soricina would learn to use scent cues as indicators of the presence of food when such cues were also available. Nectar-producing plants fed upon by G. soricina often produce distinct, intense odors. We therefore expected G. soricina to relocate food sources using scent cues, particularly the flower-produced compound, dimethyl disulfide, which is attractive even to G. soricina with no previous experience of it. We also compared the learning of associations between cues and food sources by G. soricina with that of a related fruit-eating bat, Carollia perspicillata. We found that (1) G. soricina did not learn to associate scent cues, including dimethyl disulfide, with feeding sites when the previously rewarded spatial cues were also available, and (2) both the fruit-eating C. perspicillata and the flower-feeding G. soricina were significantly more reliant on spatial cues than associated sensory cues for relocating food. These findings, taken together with past results, provide evidence of a powerful, experience-independent predilection of both species to rely on spatial cues when attempting to relocate food.
Classical theory of species dynamics in ecosystems is built on the concept of homogeneous, reciprocal interaction. The concept is borrowed from that branch of physics and chemistry dealing with reaction kinetics of molecules in well-mixed gases and liquids. It idealizes individual entities–no longer molecules but now individuals of a species–as interacting with each other or with their predators or competitors in such a way that each individual has an equal likelihood of interacting with every other individual in the system. There is no spatial structure in the system; in fact, space is assumed to be immaterial to system dynamics.
Accelerated leukocyte telomere shortening has been previously associated to self-perceived stress and psychiatric disorders, including schizophrenia and mood disorders. We set out to investigate whether telomere length is affected in patients with anxiety disorders in which stress is a known risk factor. We also studied the effects of childhood and recent psychological distress on telomere length. We utilized samples from the nationally representative population-based Health 2000 Survey that was carried out between 2000-2001 in Finland to assess major public health problems and their determinants. We measured the relative telomere length of the peripheral blood cells by quantitative real-time PCR from 321 individuals with DSM-IV anxiety disorder or subthreshold diagnosis and 653 matched controls aged 30-87 years, who all had undergone the Composite International Diagnostic Interview. While telomere length did not differ significantly between cases and controls in the entire cohort, the older half of the anxiety disorder patients (48-87 years) exhibited significantly shorter telomeres than healthy controls of the same age (P = 0.013). Interestingly, shorter telomere length was also associated with a greater number of reported childhood adverse life events, among both the anxiety disorder cases and controls (P = 0.005). Childhood chronic or serious illness was the most significantly associated single event affecting telomere length at the adult age (P = 0.004). Self-reported current psychological distress did not affect telomere length. Our results suggest that childhood stress might lead to accelerated telomere shortening seen at the adult age. This finding has potentially important implications supporting the view that childhood adversities might have a considerable impact on well being later in life.
Neglected tropical diseases (NTDs) are the most common infections of the world’s poorest people and the leading causes of chronic disability and poverty in low- and middle-income countries -. NTDs (Table 1) especially affect children and young women of reproductive age , and consequently deprive them of their health and economic potential . NTDs also impair agricultural productivity and are an important reason why the world’s poorest 1.4 billion people who live below the poverty line cannot escape destitution and despair . Despite the devastating effect of these diseases on health and development, with evidence that their global burden is as great as that of any other serious disease -, financial support for control and elimination efforts, as well as research and development (R&D), have been inadequate , . Indeed, in Millennium Development Goal 6 (to “combat HIV/AIDS, malaria and other diseases”), NTDs were not even specifically mentioned but merely considered as part of the “other diseases” . However, policy makers are slowly beginning to appreciate the importance of NTDs.
Evolutionary genetics is a mature field of endeavour, and some of biology’s greatest minds have contributed to the theory of population genetics. Initially, they faced a problem, in that following the rediscovery of Mendel’s results in the early years of the 20th century, some saw an unbridgeable gulf between the sudden changes in appearance seen in the mutant forms of peas studied by Mendel, and the gradual and subtle changes to evolving populations envisaged by Darwin. The so-called Neo-Darwinian synthesis linked these ideas by considering the likely effect of Darwinian natural selection on variations in Mendelian genes, variations which would not necessarily have major effects on organisms’ phenotypes. Unusually, for biology, this theory was developed, primarily by Fisher, Haldane and Wright, prior to the existence of data sets to which it could realistically be applied. As a result, the second half of the 20th century saw evolutionary geneticists’ struggle to produce data to test theory. They were especially interested in polymorphisms–discrete genetic variations where the rarer type still has an appreciable frequency in the population. So they studied visible polymorphisms, such as the colours and banding patterns of snails, and polymorphisms in the charges of soluble enzymes, until, finally, abundant DNA sequence data became available in the last years of the century.
The recent announcement that WHO has approved the use of a combination of nifurtimox and eflornithine to treat chronic Gambian sleeping sickness, caused by Trypanosoma brucei gambiense, is a welcome step in the seemingly interminable process of searching for less toxic drugs to treat this devastating disease . Arsenical drugs were first used in 1905; melarsoprol remains the drug most frequently used for late stage disease and is a drug for which resistance is now a major problem .
Biology is rapidly changing from a descriptive to a data-driven discipline in which the discovery of novel findings depends on the comparison and integration of massive data sets. As a consequence, ontologies–systematic descriptions of specific biological attributes–are becoming more and more important for describing the existing biological knowledge. Despite an increasing awareness about ontologies among biologists, much work remains to be done before many research fields in biology can benefit from capturing the knowledge in such a way. We explore, here, the use of biological ontologies, illustrate how ontologies can be used to make discoveries, and discuss some of the challenges to using ontologies for more than descriptive purposes.
The ability to travel mentally through time sets humans apart from many other species, yet little is known about this core cognitive capacity. In particular, what shapes the passage of the mind’s journey through time? Guided by the viewpoint that higher cognitive activity can have a sensory-motor grounding, we explored the possibility that mental time travel is influenced by apparent movement through space. Participants performed a mundane vigilance task, during which they were expected to daydream, while viewing a display that elicited an illusion of self-motion (i.e., vection). Afterwards, the contents of their mind wandering experiences were probed. The results revealed that the direction of apparent motion influenced the temporal focus of mental time travel. While backward vection prompted thinking about the past, forward vection triggered a preponderance of future-oriented thoughts. Consistent with recent evidence that traveling mentally through time entails associated movements in space, the current results demonstrate the converse relationship–apparent movement through space influenced the temporal locus of mental activity. Together, these findings corroborate the viewpoint that mental time travel may be grounded in the embodiment of spatiotemporal information in a bidirectional manner.
Local interactions between organisms in nature can scale up to produce strikingly regular patterns across entire landscapes. With improvements in satellite imagery, such patterns are increasingly reported in the ecological literature. It remains unclear, however, whether the existence of such patterns actually matters for key ecosystem processes such as productivity. In semi-arid East Africa, below-ground mounds built by Odontotermes termites frequently occur in uniform, “polka-dot” arrangements. We show that, due to the ways in which termites modify the soil, these mounds are hotspots of plant and animal productivity: close to termite mounds, plants grow more quickly, herbivorous and predatory animals are more abundant, and reproductive output is greater than is true farther away from mounds. Moreover, the evenly spaced distribution of termite mounds means that all points in the landscape are relatively close to the nearest mound–with the result that ecosystem-wide productivity is greater under the actual distribution of mounds than it would be if the same number of mounds were randomly situated. Thus, although subterranean termites may be less visible and charismatic than the large mammals of African savannas, they are nonetheless critically important engineers of structures and patterns that underpin ecosystem function.
Cyanobacteria account for 20-30% of Earth’s primary photosynthetic productivity and convert solar energy into biomass-stored chemical energy at the rate of ~450 TW . These single-cell microorganisms are resilient predecessors of all higher oxygenic phototrophs and can be found in self-sustaining, nitrogen-fixing communities the world over, from Antarctic glaciers to the Sahara desert . Here we show that diverse genera of cyanobacteria including biofilm-forming and pelagic strains have a conserved light-dependent electrogenic activity, i.e. the ability to transfer electrons to their surroundings in response to illumination. Naturally-growing biofilm-forming photosynthetic consortia also displayed light-dependent electrogenic activity, demonstrating that this phenomenon is not limited to individual cultures. Treatment with site-specific inhibitors revealed the electrons originate at the photosynthetic electron transfer chain (P-ETC). Moreover, electrogenic activity was observed upon illumination only with blue or red but not green light confirming that P-ETC is the source of electrons. The yield of electrons harvested by extracellular electron acceptor to photons available for photosynthesis ranged from 0.05% to 0.3%, although the efficiency of electron harvesting likely varies depending on terminal electron acceptor. The current study illustrates that cyanobacterial electrogenic activity is an important microbiological conduit of solar energy into the biosphere. The mechanism responsible for electrogenic activity in cyanobacteria appears to be fundamentally different from the one exploited in previously discovered electrogenic bacteria, such as Geobacter, where electrons are derived from oxidation of organic compounds and transported via a respiratory electron transfer chain (R-ETC) , . The electrogenic pathway of cyanobacteria might be exploited to develop light-sensitive devices or future technologies that convert solar energy into limited amounts of electricity in a self-sustainable, CO2-free manner.
The developmental time of vector insects is important to their population dynamics, evolutionary biology, epidemiology of the diseases they transmit, and to their responses to global climatic change. In various triatomine species vectors of Chagas disease (Triatominae, Reduviidae), a delay in the molt of a small proportion of individuals has been observed, and from an evolutionary ecology approach, we propose the hypothesis that the developmental delay is an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) diapause strategy. We confirmed, by means of a survey among specialists, the existence of the developmental delay in triatomines. Statistical descriptions of the developmental time of 11 species of triatomines showed some degree of bi-modality in nine of them. We predicted by means of an optimization model which genotype, coding for a given frequency of developmental diapause, is expected to evolve. We identified a series of parameters that can be measured in the field and in the laboratory to test the hypothesis of an optimal diapause frequency. We also discuss the importance of these findings for triatomines in terms of global climatic change and epidemiological consequences such as their resistance to insecticides.
Two articles published recently in PLoS Medicine highlight the problem of how to effectively share information in the wake of a rapidly spreading disease, and prompted us to ask the question “How well are journals doing?” with regard to this important goal. The answer, sadly, seems to be “not well enough.” Although the potential of the Internet for improving the dissemination of information is now taken for granted, it would seem that the attitudes of those involved in sharing this information have not kept pace with the technology. Accordingly, it is fair to ask whether the flow of information in the face of a crisis is truly enabled by publication in medical journals (even online journals) or whether we need new avenues for rapid data sharing.
The Great Recession is making the hard writing on the wall for research libraries easy to read. In the United States, drastic decreases in endowment income at private universities have been well-publicized. Most public universities and research institutions that rely upon public funding are now experiencing reductions of a similar scale . As university income has declined, reductions have been assigned to library collections funds . This has a downstream effect on the scholarly society and commercial publishers who rely upon institutional subscriptions and licenses for revenue. Statements have been issued by library coalitions pleading for journal publishers to respond by issuing price reductions ,. Some publishers have responded by keeping journal prices flat. However, the signs are clear: more and more publishers are likely to find themselves challenged to survive through maintaining the still dominant funding model. That model is characterized by institutional subscriptions to a set of articles tied to a single journal’s brand or an entire publisher’s brand (in the case of the so-called “big deal”) providing the institution’s researchers with entrée to the content behind walls.
What kind of mental objects are letters? Research on letter perception has mainly focussed on the visual properties of letters, showing that orthographic representations are abstract and size/shape invariant. But given that letters are, by definition, mappings between symbols and sounds, what is the role of sound in orthographic representation? We present two experiments suggesting that letters are fundamentally sound-based representations. To examine the role of sound in orthographic representation, we took advantage of the multiple scripts of Japanese. We show two types of evidence that if a Japanese word is presented in a script it never appears in, this presentation immediately activates the (“actual”) visual word form of that lexical item. First, equal amounts of masked repetition priming are observed for full repetition and when the prime appears in an atypical script. Second, visual word form frequency affects neuromagnetic measures already at 100-130 ms whether the word is presented in its conventional script or in a script it never otherwise appears in. This suggests that Japanese orthographic codes are not only shape-invariant, but also script invariant. The finding that two characters belonging to different writing systems can activate the same form representation suggests that sound identity is what determines orthographic identity: as long as two symbols express the same sound, our minds represent them as part of the same character/letter.
What constitutes non-suicidal self-injury (NSSI) is a matter of some debate, but its growing presence in mainstream and popular media as well as the growing number of anecdotal reports by physicians, therapists, and junior and senior high school counselors suggest that it may be, as some have called it, “the next teen disorder” . Referred to in the literature and media as “self-injurious behavior,” “self-injury,” “self-harm,” “self-mutilation,” or “cutting,” self-injury is typically defined as the deliberate, self-inflicted destruction of body tissue without suicidal intent and for purposes not socially sanctioned . Although most often not a suicidal gesture, it is statistically associated with suicide and can result in unanticipated severe harm or fatality ,,.