Redox heterogeneity in MORB as a function of mantle source

The oxidation state of Earth’s upper mantle both influences and records mantle evolution, but systematic fine-scale variations in upper mantle oxidation state have not previously been recognized in mantle-derived lavas from mid-ocean ridges. Through a global survey of mid-ocean ridge basalt glasses, we show that mantle oxidation state varies systematically as a function of mantle source composition. Negative correlations between Fe3+/ΣFe ratios and indices of mantle enrichment such as 87Sr/86Sr, 208Pb/204Pb, Ba/La, and Nb/Zr ratios reveal that enriched mantle is more reduced than depleted mantle. Because upper mantle carbon may act to simultaneously reduce iron and generate melts that share geochemical traits with our reduced samples, we propose that carbon creates magmas at ridges that are reduced and enriched

Prenatal Stress, Glucocorticoids and the Programming of Adult Disease

Numerous clinical studies associate an adverse prenatal environment with the development of cardio-metabolic disorders and neuroendocrine dysfunction, as well as an increased risk of psychiatric diseases in later life. Experimentally, prenatal exposure to stress or excess glucocorticoids in a variety of animal models can malprogram offspring physiology, resulting in a reduction in birth weight and subsequently increasing the likelihood of disorders of cardiovascular function, glucose homeostasis, hypothalamic–pituitary–adrenal (HPA) axis activity and anxiety-related behaviours in adulthood. During fetal development, placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) provides a barrier to maternal glucocorticoids. Reduced placental 11β-HSD2 in human pregnancy correlates with lower birth weight and higher blood pressure in later life. Similarly, in animal models, inhibition or knockout of placental 11β-HSD2 lowers offspring birth weight, in part by reducing glucose delivery to the developing fetus in late gestation. Molecular mechanisms thought to underlie the programming effects of early life stress and glucocorticoids include epigenetic changes in target chromatin, notably affecting tissue-specific expression of the intracellular glucocorticoid receptor (GR). As such, excess glucocorticoids in early life can permanently alter tissue glucocorticoid signalling, effects which may have short-term adaptive benefits but increase the risk of later disease

General practitioners’ attitudes, beliefs and behaviours regarding exercise for chronic knee pain

Patients with chronic knee pain (CKP) frequently present to general practitioners (GPs). Exercise, a core management approach for CKP, reduces pain and improves functioning. To maximise patient outcomes, GPs should practise in line with best evidence recommendations. Using an underpinning model (developed using behavioural theory), this thesis describes the attitudes, beliefs and behaviours of GPs regarding the use of exercise for patients with CKP. A systematic review revealed a paucity of published studies specifically examining this topic. Available data suggested that GPs’ attitudes and beliefs about exercise for CKP varied widely, exercise appeared to be underused and its implementation by GPs was unclear. The need to concurrently and specifically investigate the attitudes, beliefs and behaviours of GPs regarding exercise for CKP was identified. A vignette-based pilot questionnaire survey of 800 UK GPs was undertaken to refine the survey tool and methods and to inform the required sample size for the main survey. The subsequent main survey of 5000 UK GPs revealed that exercise was used by most GPs for CKP. However, methods employed to initiate exercise within an individual patient’s management plan were variable and imperfectly aligned with evidence-based recommendations. Attitudes and beliefs about exercise for CKP were generally positive; however GPs expressed some uncertainty about safety and efficacy, particularly regarding local exercise (e.g. strengthening, range-of-movement, stretching). Although some elements of the underpinning model (e.g. role and identity) predicted GPs’ behaviour, others (e.g. beliefs about capabilities) performed less well. To maximise the clinical outcomes of patients with CKP, recommendations from this research include: development of educational, organisational change and/or behaviour change strategies to improve initiation of individualised exercise, and clarification of GPs’ role, in this context. Approaches to better understand the key influences on GPs’ behaviour are required; a greater focus on decision-making theory may be valuable

Comparative Healthcare: Sexual Health

This month two general practitioners (GPs) describe their approach to sexual health consultations. The issue of a sexually active adolescent demonstrates some differences in legislation pertaining to the requirement to involve the authorities, although in essence the young person can expect the same response from these practitioners in two different health care systems. On the other hand a patient at risk of sexually transmitted infections is more likely to be referred to a specialist Genitourinary clinic in the UK although the protocols for screening and education are largely similar. Equally patients who are HIV positive can expect to receive the bulk of their care from specialist clinics in both countries. Midwives are the main stay of antenatal services in Australia and the UK with general practitioners minimally involved in routine cases. Also home births are a negigible proportion of all deliveries in either country. When patients opt for a home birth our authors expressed the view that GPs generally do not have the skills or experience to be the main health professional in attendance. Therefore such births are primarily managed by midwives as the key health care professional. The focus of General practitioners is primarily to ensure that the patient is making an informed decision about delivering her baby at home. The GP is therefore still in an influential position to assist the woman in making a decision about where to give birth. As a point of difference in Australia a home birth would result in out of pocket expences for the mother. The views expressed below are those of the authors and do not necessarily reflect health policy or practice elsewhere in their countries. However we believe they offer an interesting perspective on their health care systems and commend the article to our readers

Variation of parasite burden within the European badger (Meles meles): the effect of season, habitat, body condition, gender & age on the prevalence of Eimeria melis and Capillaria

1. Parasites, although naturally occurring can have severe impacts on both an individual host and on the wider population and ecosystem. 2. This study investigates the relationship of parasite burden within the European badger (N=175) with several life history characteristics such as age, condition, gender and co-infection of bovine tuberculosis and with the environmental factors of habitat and season. 3. Using two general linear mixed models results showed significant positive relationships between Eimeria melis burden and age and gender, and between Capillaria spp., age and month of sampling. A significant negative correlation was also observed between Capillaria spp. and badger body condition index. No significant results were found for habitat type or in the further GLMM’s (N=124) run to investigate co-infection of bovine tuberculosis. 4. The opportunity to investigate complex parasite interactions in a wild population of known individuals is rare and a valuable opportunity. Parasite burdens in Meles meles were found to be extremely variable with some exhibiting very high faecal egg/oocyst output. Results suggest that such burdens of gastro-intestinal parasites do have a relationship with life history characteristics and condition and therefore should be taken into account when wildlife disease management protocols or ecological studies are carried out.Food and Environment Research Agenc

Comparative Healthcare: Mental Health

AbstractIn the fourth in this series of ‘comparative healthcare’ medical practitioners explore the approach to mental illness in Bangladesh and the UK respectively. Differences and similarities in treatment regimens are illustrated with reference to patients with varying degrees of mental illness. Mental illness poses the greatest challenge in health care as national investment in services often reflects cultural attitudes and norms.  While the authors describe very similar approaches to the diagnosis and management of severe psychotic illness there are striking differences in the availability of support services for people with substance abuse and those with relapsing conditions. The involvement and co-operation of the family is particularly important in Bangladesh where comprehensive access to mental health services is very limited.  Private alcohol and drug detoxification centres are available although many are expensive and such treatment may effectively be denied to all but the wealthiest people. In the UK all people with serious and enduring mental illness are entered onto a register and therefore flagged for follow up at least once a year. General Practitioners, working within the nationally funded health service have been remunerated since 2003 for maintaining the register. In contrast in the absence of a case-management based psychiatric follow-up framework in Bangladesh, a general practitioner and treating psychiatrist would need to formulate a management plan involving recognition of clinical warning signs by the family. Indeed the co-operation and support of the patient’s family is of paramount importance in maintaining outpatient appointments when supporting people with mental health problems in Bangladesh. Finally we emphasise that the views expressed are those of the authors and do not necessarily reflect health policy or practice in their respective countries. Nonetheless we believe they offer a valuable perspective on mental health issues and commend the article to our readers

The influence of magmatic differentiation on the oxidation state of Fe in a basaltic arc magma

Subduction zone basalts are more oxidized than basalts from other tectonic settings (e.g., higher Fe 3 + /∑Fe), and this contrast may play a central role in the unique geochemical processes that generate arc and continental crust. The processes generating oxidized arc magmas, however, are poorly constrained, although they appear inherently linked to subduction. Near-surface differentiation processes unique to arc settings might drive oxidation of magmas that originate in equilibrium with a relatively reduced mantle source. Alternatively, arc magmas could record the oxidation conditions of a relatively oxidized mantle source. Here, we present new measurements of olivine-hosted melt inclusions from a single eruption of Agrigan volcano, Marianas, in order to test the influence of differentiation processes vs. source conditions on the Fe 3 + /∑Fe ratio, a proxy for system oxygen fugacity (fO 2 ). We determined Fe 3 + /∑Fe ratios in glass inclusions using μ-XANES and couple these data with major elements, dissolved volatiles, and trace elements. After correcting for post-entrapment crystallization, Fe 3+ /∑Fe ratios in the Agrigan melt inclusions (0.219 to 0.282), and their modeled fO 2 s (ΔQFM +1.0 to +1.8), are uniformly more oxidized than MORB, and preserve a portion of the evolution of this magma from 5.7 to 3.2 wt.% MgO. Fractionation of olivine ±clinopyroxene ±plagioclase should increase Fe 3+ /∑Fe as MgO decreases in the melt, but the data show Fe 3+ /∑Fe ratios decreasing as MgO decreases below 5 wt.% MgO. The major element trajectories, taken in combination with this strong reduction trend, are inconsistent with crystallization of common ferromagnesian phases found in the bulk Agrigan sample, including magnetite. Rather, decreasing Fe 3+ /∑Fe ratios correlate with decreasing S concentrations, suggesting that electronic exchanges associated with SO 2 degassing may dominate Fe 3+ /∑Fe variations in the melt during differentiation. In the case of this magma, the dominant effect of differentiation on magmatic fO 2 is reduction rather than oxidation. Tracing back Agrigan melts with MgO>5 wt.% (i.e., minimally degassed for S) along a modeled olivine fractionation trend to primary melts in equilibrium with Fo 90 olivine reveals melts in equilibrium with the mantle beneath Agrigan at fO 2 s of ΔQFM +1 to +1.6, significantly more oxidized than current constraints for the mantle beneath midocean ridges

The oxidation state of Fe in MORB glasses and the oxygen fugacity of the upper mantle.

Micro-analytical determination of Fe3+/ΣFe ratios in mid-ocean ridge basalt (MORB) glasses using micro X-ray absorption near edge structure (μ-XANES) spectroscopy reveals a substantially more oxidized upper mantle than determined by previous studies. Here, we show that global MORBs yield average Fe3+/ΣFe ratios of 0.16±0.01 (n=103), which trace back to primary MORB melts equilibrated at the conditions of the quartz-fayalite-magnetite (QFM) buffer. Our results necessitate an upward revision of the Fe3+/ΣFe ratios of MORBs, mantle oxygen fugacity, and the ferric iron content of the mantle relative to previous wet chemical determinations. We show that only 0.01 (absolute, or \u3c10%) of the difference between Fe3+/ΣFe ratios determined by micro-colorimety and XANES can be attributed to the Mössbauer-based XANES calibration. The difference must instead derive from a bias between micro-colorimetry performed on experimental vs. natural basalts. Co-variations of Fe3+/ΣFe ratios in global MORB with indices of low-pressure fractional crystallization are consistent with Fe3+ behaving incompatibly in shallow MORB magma chambers. MORB Fe3+/ΣFe ratios do not, however, vary with indices of the extent of mantle melting (e.g., Na2O(8)) or water concentration. We offer two hypotheses to explain these observations: The bulk partition coefficient of Fe3+ may be higher during peridotite melting than previously thought, and may vary with temperature, or redox exchange between sulfide and sulfate species could buffer mantle melting at ~QFM. Both explanations, in combination with the measured MORB Fe3+/ΣFe ratios, point to a fertile MORB source with greater than 0.3wt.% Fe2O3. © 2011