Nitrogen fixation in the High Arctic: a source of ‘new’ nitrogen?

Biological nitrogen (N₂) fixation performed by diazotrophs (N₂ fixing bacteria) is thought to be one of the main sources of plant available N in pristine ecosystems like arctic tundra. However, direct evidence of a transfer of fixed N₂ to non-diazotroph associated plants is lacking to date. Here, we present results from an in situ ¹⁵N–N₂ labelling study in the High Arctic. Three dominant vegetation types (organic crust composed of free-living cyanobacteria, mosses, cotton grass) were subjected to acetylene reduction assays (ARA) performed regularly throughout the growing season, as well as ¹⁵N–N₂ incubations. The ¹⁵N-label was followed into the dominant N₂ fixer associations, soil, soil microbial biomass and non-diazotroph associated plants three days and three weeks after labelling. Mosses contributed most to habitat N₂ fixation throughout the measuring campaigns, and N₂ fixation activity was highest at the beginning of the growing season in all plots. Fixed ¹⁵N–N₂ became quickly (within 3 days) available to non-diazotroph associated plants in all investigated vegetation types, proving that N₂ fixation is an actual source of available N in pristine ecosystems.     

Determinants of Change in Children’s Sedentary Time

Background

Understanding the determinants of sedentary time during childhood contributes to the development of effective intervention programmes.

Purpose

To examine family and home-environmental determinants of 1-year change in objectively measured sedentary time after-school and at the weekend.

Methods

Participants wore accelerometers at baseline and 1 year later. Longitudinal data for after-school and weekend analyses were available for 854 (41.5%male, mean±SD age 10.2±0.3years) and 718 (41.8%male, age 10.2±0.3years) participants. Information on 26 candidate determinants, including socioeconomic status (SES), availability of electronic media and parental rules for sedentary behaviours was self-reported by children or their parents at baseline. Change in the proportion of registered time spent sedentary was used as the outcome variable in multi-level linear regression models, adjusted for age, sex, body mass index and baseline sedentary time. Simple and multiple models were run and interactions with sex explored.

Results

Children from higher socioeconomic status families exhibited greater increases in after-school (beta; 95% CI for change in % time spent sedentary 1.02; 0.37, 1.66) and weekend (1.42; 0.65, 2.18) sedentary time. Smaller increases in after-school sedentary time were observed in children with more siblings (−1.00; −1.69, −0.30), greater availability of electronic media (−0.81; −1.29, −0.33) and, for boys, more frequent family visits to the park (−1.89; −3.28, −0.51) and family participation in sport (−1.28; −2.54, −0.02). Greater maternal weekend screen-time (0.45; 0.08, 0.83) and, in girls, greater parental restriction on playing outside (0.91; 0.08, 1.74) were associated with larger increases in weekend sedentary time. The analytical sample was younger, more likely to be female, had lower BMI and was of higher SES than the original baseline sample.

Conclusions

Intervention strategies aimed at reducing parents’ weekend screen-time, increasing family participation in sports or recreation (boys) and promoting freedom to play outside (girls) may contribute towards preventing the age-related increase in sedentary time.     

Revisiting the ‘cornerstone of Amazonian conservation’: a socioecological assessment of Brazil nut exploitation

The Brazil nut (the seeds of the rainforest tree Bertholletia excelsa) is the only globally traded seed collected from the wild by forest-based harvesters across the Amazon basin. The large geographic scale of Brazil nut exploitation and the significant contributions to local livelihoods, national economies, and forest-based development over the last decades, merit a review of the “conservation-through-use” paradigm. We use Elinor Ostrom’s framework for assessing sustainability in socioecological systems: (1) resource unit, (2) users, (3) governance system, and (4) resource system, to determine how different contexts and external developments generate specific conservation and development outcomes. We find that the resource unit reacts robustly to the type and level of extraction currently practiced; that resource users have built on a self-organized system that had defined boundaries and access to the resource; that linked production chains, market networks and informal financing work to supply global markets; and that local harvesters have used supporting alliances with NGOs and conservationists to formalize and secure their endogenous governance system and make it more equitable. As a result, the Brazil nut model represents a socioecological system that may not require major changes to sustain productivity. Yet since long-term Brazil nut production seems inextricably tied to a continuous forest cover, and because planted Brazil nut trees currently provide a minimal contribution to total nut production basin-wide, we call to preserve, diversify and intensify production in Brazil nut-rich forests that will inevitably become ever more integrated within human-modified landscapes over time.     

‘Time’ and the expression of temporality in eastern Sumba

In this article the author attempts to show the rationale behind the ideology of the Fijian political movement called Taukei, i.e. “owners of the land”. The fundamentalist current within the Fijian political scene in later years has made powerful use of indigenous concepts related to the land (vanua). In contrast to other ethnic groups in the country Fijians consider themselves to be upholders of indisputable moral principles also embraced by the concept vanua. On the one hand their preoccupation with everything that vanua stands for makes Fijians easy prey to political manipulation. On the other hand, the moral standards represented by vanua give them a sense of identity in a situation of rapid social and political change.     

Testing the Role of Climate Change in Species Decline: Is the Eastern Quoll a Victim of a Change in the Weather?

To conserve a declining species we first need to diagnose the causes of decline. This is one of the most challenging tasks faced by conservation practitioners. In this study, we used temporally explicit species distribution models (SDMs) to test whether shifting weather can explain the recent decline of a marsupial carnivore, the eastern quoll (Dasyurus viverrinus). We developed an SDM using weather variables matched to occurrence records of the eastern quoll over the last 60 years, and used the model to reconstruct variation through time in the distribution of climatically suitable range for the species. The weather model produced a meaningful prediction of the known distribution of the species. Abundance of quolls, indexed by transect counts, was positively related to the modelled area of suitable habitat between 1990 and 2004. In particular, a sharp decline in abundance from 2001 to 2003 coincided with a sustained period of unsuitable weather over much of the species’ distribution. Since 2004, abundance has not recovered despite a return to suitable weather conditions, and abundance and area of suitable habitat have been uncorrelated. We suggest that fluctuations in weather account for the species’ recent decline, but other unrelated factors have suppressed recovery.     

Aboriginal ‘Difference’ and ‘Autonomy’ Then and Now: Four Decades of Change in a Western Desert Society

In just a few decades, Aboriginal people living near Australia's Western Desert fringe have experienced an extraordinarily intense trajectory of change: from a highly autonomous nomadic existence, through ‘first contacts’, the pastoral and mission frontiers, the devastating impacts of alcohol and of Western lifestyle diseases, the outstation movement, resource exploration and mining, a long but largely successful struggle for native title, and much else. In this paper, notions of ‘difference’ and ‘autonomy’ are used to explore these transformations. The situation among the Mardu is here linked to the gulf between government policies and lived Aboriginal experience. If the self‐management thrust of 1970s policies achieved partial restoration of Aboriginal autonomy, recent Federal Government policies are intent on intervention to reduce difference and claw back some of that autonomy. Their determination to force Aboriginal people out of their ‘dysfunctional’ ‘cultural museums’ (homeland settlements) and into greater economic engagement ignores the crucial underpinnings of security and identity among remote Aborigines. The retention of difference, albeit at considerable social cost and entrenched disadvantage, is still strongly preferred by Mardu to the kinds of engagement with the dominant society that not only assault their sense of self but also threaten to overwhelm whatever autonomy remains to them.     

Spatial heterogeneity of the species composition of a clavarioid fungi’s compex in the Eurasian Arctic

Using the example of a model group of macromycete (clavarioid fungi), a large-scale investigation into the mycological complex of the Eurasian Arctic is conducted. The species composition of clavarioid fungi’s complex is revealed in all longitudinal sectors and latitudinal subzones, and a comparative analysis is carried out. It has been determined that, among groups of aphyllophoroid fungi, the clavarioid life form is the most adapted to the extremally psychrophilic conditions of the Arctic. It is shown that the near-oceanic sectors are the richest, whereas the continental sectors are much poorer. The distribution of the species composition of fungi conforms to the similar distribution of flowering plants, especially hemicryptophytes. The average annual quantity of atmospheric precipitation is the leading climatic factor. The differences make it possible to subdivide the Eurasian Arctic into four mycogeographical regions: Atlantic (European), Siberian, Chukotian (Beringian), and High Arctic.     

The ‘Psychic Surgeon’ and the schizophrenic patient: Crisis in a ‘Medicodrama’

This paper is concerned with a Filipino psychic surgeon confronted by a particularly challenging case of a kind perhaps unprecedented in his practice. The paper describes and analyzes how the practitioner modified his usual clinical performance and adapted his actions to demands of an extremely difficult situation. The case is viewed in wider perspective relative to the significance of performative acts of healing in a pluralistic medical setting.     

Tracing the shifting sands of ‘medical genetics’: what’s in a name?

This paper focuses on the structural development of institution-based interest in genetics in Anglo-North American medicine after 1930 concomitantly with an analysis of the changes through which ideas about heredity and the hereditary transmission of diseases in families have passed. It maintains that the unfolding relationship between medicine and genetics can best be understood against the background of the shift in emphasis in conceptualisations of recurring patterns of disease in families from ‘biological relatedness’ to ‘related to chromosomes and genes’. The paper begins with brief considerations of the historical confluences of, first, heredity and medicine and, second, genetics and medicine which, in a third section, leads to a discussion about a uniquely ‘genetics-based approach’ to medicine in the second half of the twentieth century.     

β Oscillation during Slow Wave Sleep and Rapid Eye Movement Sleep in the Electroencephalogram of a Transgenic Mouse Model of Huntington’s Disease

Study objectives

To search for early abnormalities in electroencephalogram (EEG) during sleep which may precede motor symptoms in a transgenic mouse model of hereditary neurodegenerative Huntington’s disease (HD).

Design

In the R6/1 transgenic mouse model of HD, rhythmic brain activity in EEG recordings was monitored longitudinally and across vigilance states through the onset and progression of disease.

Measurements and results

Mice with chronic electrode implants were recorded monthly over wake-sleep cycles (4 hours), beginning at 9–11 weeks (presymptomatic period) through 6–7 months (symptomatic period). Recording data revealed a unique β rhythm (20–35 Hz), present only in R6/1 transgenic mice, which evolves in close parallel with the disease. In addition, there was an unusual relationship between this β oscillation and vigilance states: while nearly absent during the active waking state, the β oscillation appeared with drowsiness and during slow wave sleep (SWS) and, interestingly, strengthened rather than dissipating when the brain returned to an activated state during rapid eye movement (REM) sleep.

Conclusions

In addition to providing a new in vivo biomarker and insight into Huntington''s disease pathophysiology, this serendipitous observation opens a window onto the rarely explored neurophysiology of the cortico-basal ganglia circuit during SWS and REM sleep.     

The Effectiveness of a ‘Train the Trainer’ Model of Resuscitation Education for Rural Peripheral Hospital Doctors in Sri Lanka

Background

Sri Lankan rural doctors based in isolated peripheral hospitals routinely resuscitate critically ill patients but have difficulty accessing training. We tested a train-the-trainer model that could be utilised in isolated rural hospitals.

Methods

Eight selected rural hospital non-specialist doctors attended a 2-day instructor course. These “trained trainers” educated their colleagues in advanced cardiac life support at peripheral hospital workshops and we tested their students in resuscitation knowledge and skills pre and post training, and at 6- and 12-weeks. Knowledge was assessed through 30 multiple choice questions (MCQ), and resuscitation skills were assessed by performance in a video recorded simulated scenario of a cardiac arrest using a Resuci Anne Skill Trainer mannequin.

Results/Discussion/Conclusion

Fifty seven doctors were trained. Pre and post training assessment was possible in 51 participants, and 6-week and 12-week follow up was possible for 43, and 38 participants respectively. Mean MCQ scores significantly improved over time (p<0.001), and a significant improvement was noted in “average ventilation volume”, “compression count”, and “compressions with no error”, “adequate depth”, “average depth”, and “compression rate” (p<0.01). The proportion of participants with compression depth ≥40mm increased post intervention (p<0.05) and at 12-week follow up (p<0.05), and proportion of ventilation volumes between 400-1000mls increased post intervention (p<0.001). A significant increase in the proportion of participants who “checked for responsiveness”, “opened the airway”, “performed a breathing check”, who used the “correct compression ratio”, and who used an “appropriate facemask technique” was also noted (p<0.001). A train-the-trainer model of resuscitation education was effective in improving resuscitation knowledge and skills in Sri Lankan rural peripheral hospital doctors. Improvement was sustained to 12 weeks for most components of resuscitation knowledge and skills. Further research is needed to identify which components of training are most effective in leading to sustained improvement in resuscitation.     

Time Evolution of the Macroscopic Characteristics of a Thin Current Sheet in the Course of Its Formation in the Earth’s Magnetotail

A numerical model is developed that allows tracing the time evolution of a current sheet from a relatively thick current configuration with isotropic distributions of the pressure and temperature in an extremely thin current sheet, which plays a key role in geomagnetic processes. Such a configuration is observed in the Earth’s magnetotail in the stage preceding a large-scale geomagnetic disturbance (substorm). Thin current sheets are reservoirs of the free energy released during geomagnetic disturbances. The time evolution of the components of the pressure tensor caused by changes in the structure of the current sheet is investigated. It is shown that the pressure tensor in the current sheet evolves in two stages. In the first stage, a current sheet with a thickness of eight to ten proton Larmor radii forms. This stage is characterized by the plasma drift toward the current sheet and the Earth and can be described in terms of the Chu–Goldberger–Low approximation. In the second stage, an extremely thin current sheet with an anisotropic plasma pressure tensor forms, due to which the system is maintained in an equilibrium state. Estimates of the characteristic time of the system evolution agree with available experimental data.     

A DNA ‘Barcode Blitz’: Rapid Digitization and Sequencing of a Natural History Collection

DNA barcoding protocols require the linkage of each sequence record to a voucher specimen that has, whenever possible, been authoritatively identified. Natural history collections would seem an ideal resource for barcode library construction, but they have never seen large-scale analysis because of concerns linked to DNA degradation. The present study examines the strength of this barrier, carrying out a comprehensive analysis of moth and butterfly (Lepidoptera) species in the Australian National Insect Collection. Protocols were developed that enabled tissue samples, specimen data, and images to be assembled rapidly. Using these methods, a five-person team processed 41,650 specimens representing 12,699 species in 14 weeks. Subsequent molecular analysis took about six months, reflecting the need for multiple rounds of PCR as sequence recovery was impacted by age, body size, and collection protocols. Despite these variables and the fact that specimens averaged 30.4 years old, barcode records were obtained from 86% of the species. In fact, one or more barcode compliant sequences (>487 bp) were recovered from virtually all species represented by five or more individuals, even when the youngest was 50 years old. By assembling specimen images, distributional data, and DNA barcode sequences on a web-accessible informatics platform, this study has greatly advanced accessibility to information on thousands of species. Moreover, much of the specimen data became publically accessible within days of its acquisition, while most sequence results saw release within three months. As such, this study reveals the speed with which DNA barcode workflows can mobilize biodiversity data, often providing the first web-accessible information for a species. These results further suggest that existing collections can enable the rapid development of a comprehensive DNA barcode library for the most diverse compartment of terrestrial biodiversity – insects.     

Hormonal correlates of individual quality in a long-lived bird: a test of the ‘corticosterone–fitness hypothesis’

Measuring individual quality in vertebrates is difficult. Focusing on allostasis mechanisms may be useful because they are functionally involved in the ability of an individual to survive and reproduce in its environment. Thus, a rise in stress hormones levels (corticosterone) occurs when an organism has to cope with challenging environmental conditions. This has recently led to the proposal of the ‘cort–fitness hypothesis’, which suggests that elevated baseline corticosterone levels should be found in individuals of poor quality that have difficulty coping with their environment. We tested this hypothesis by comparing an integrative measure of individual quality to baseline corticosterone in black-browed albatrosses (Thalassarche melanophrys). We found that individual baseline corticosterone levels were related to individual quality and highly repeatable from one breeding season to the next. Importantly, this relationship was found in males, but not in females. Therefore, we suggest that the relationship between quality and baseline corticosterone levels may depend on the environmental and energetic constraints that individuals have to cope with.     

Progress in deciphering the information content of the ‘glycome’ – a crescendo in the closing years of the millennium

The closing years of the second millennium have been uplifting for carbohydrate biology. Optimism that oligosaccharide sequences are bearers of crucial biological information has been borne out by the constellation of efforts of carbohydrate chemists, biochemists, immunochemists, and cell- and molecular biologists. The direct involvement of specific oligosaccharide sequences in protein targeting and folding, and in mechanisms of infection, inflammation and immunity is now unquestioned. With the emergence of families of proteins with carbohydrate-binding activities, assignments of information content for defined oligosaccharide sequences will become more common, but the pinpointing and elucidation of the bioactive domains on oligosaccharides will continue to pose challenges even to the most experienced carbohydrate biologists. The neoglycolipid technology incorporates some of the key requirements for this challenge: namely the resolution of complex glycan mixtures, and ligand binding coupled with sequence determination by mass spectrometry.     

Rapid ‘on-line’ Image Processing as a Tool in the Evaluation of Kinetic and Morphological Aspects of Receptor – induced Cell Activation

Abstract

Transmembrane signalling involves rapid and spatially well defined changes in cytosolic free Ca²⁺, [Ca²⁺]_i. Specific technologies involving image processing permit the analysis of kinetic and morphological aspects of [Ca²⁺]_i at the subcellular level with the fluorescent Ca²⁺ probe fura-2. Fluorescence excitation wavelengths (340 nm or 380 nm) are alternated in synchrony with the acquisition at video rate of images captured with an intensified CCD camera. Images are digitized, recursively filtered, divided, and displayed after calibration of the ‘ratio’ image into a numerical [Ca²⁺]_i scale. The image processor IMAGINE (Synoptics Ltd., UK) permits these operations at video rate. This produces ‘on-line’ [Ca²⁺]_i images in real time which are stored on video tapes for subsequent analysis. The present communication summarizes the rationale for the selection of our current technologies. A comparison with alternative solutions should highlight the particular advantages and drawbacks of our approach. The present text thus should serve as a help for investigators who try to assemble image processing tools for work in the receptor and cellular signalling field.