Molecular imaging of glycan chains couples cell-wall polysaccharide architecture to bacterial cell

Biopolymer composite cell walls maintain cell shape and resist forces in plants, fungi and bacteria. Peptidoglycan, a crucial antibiotic target and immunomodulator, performs this role in bacteria. The textbook structural model of peptidoglycan is a highly ordered, crystalline material. Here we use atomic force microscopy (AFM) to image individual glycan chains in peptidoglycan from Escherichia coli in unprecedented detail. We quantify and map the extent to which chains are oriented in a similar direction (orientational order), showing it is much less ordered than previously depicted. Combining AFM with size exclusion chromatography, we reveal glycan chains up to 200 nm long. We show that altered cell shape is associated with substantial changes in peptidoglycan biophysical properties. Glycans from E. coli in its normal rod shape are long and circumferentially oriented, but when a spheroid shape is induced (chemically or genetically) glycans become short and disordered

Cortisol in hair measured in young adults - a biomarker of major life stressors?

<p>Abstract</p> <p>Background</p> <p>Stress as a cause of illness has been firmly established. In public health and stress research a retrospective biomarker of extended stress would be an indispensible aid. The objective of this pilot study was to investigate whether concentrations of cortisol in hair correlate with perceived stress, experiences of serious life events, and perceived health in young adults.</p> <p>Methods</p> <p>Hair samples were cut from the posterior vertex area of (n = 99) university students who also answered a questionnaire covering experiences of serious life events, perceived Stress Scale and perceived health during the last three months. Cortisol was measured using a competitive radioimmunoassay in methanol extracts of hair samples frozen in liquid nitrogen and mechanically pulverised.</p> <p>Results</p> <p>Mean cortisol levels were significantly related to serious life events (p = 0.045), weakly negatively correlated to perceived stress (p = 0.025, r = -0.061) but nor affected by sex, coloured/permed hair, intake of pharmaceuticals or self-reported health. In a multiple regression model, only the indicator of serious life events had an independent (p = 0.041) explanation of increased levels of cortisol in hair. Out of four outliers with extremely high cortisol levels two could be contacted, both reported serious psychological problems.</p> <p>Conclusions</p> <p>These findings suggest that measurement of cortisol in hair could serve as a retrospective biomarker of increased cortisol production reflecting exposure to major life stressors and possibly extended psychological illness with important implications for research, clinical practice and public health. Experience of serious life events seems to be more important in raising cortisol levels in hair than perceived stress.</p

Soil bacterial and fungal communities across a pH gradient in an arable soil

Soils collected across a long-term liming experiment (pH 4.0-8.3), in which variation in factors other than pH have been minimized, were used to investigate the direct influence of pH on the abundance and composition of the two major soil microbial taxa, fungi and bacteria. We hypothesized that bacterial communities would be more strongly influenced by pH than fungal communities. To determine the relative abundance of bacteria and fungi, we used quantitative PCR (qPCR), and to analyze the composition and diversity of the bacterial and fungal communities, we used a bar-coded pyrosequencing technique. Both the relative abundance and diversity of bacteria were positively related to pH, the latter nearly doubling between pH 4 and 8. In contrast, the relative abundance of fungi was unaffected by pH and fungal diversity was only weakly related with pH. The composition of the bacterial communities was closely defined by soil pH; there was as much variability in bacterial community composition across the 180-m distance of this liming experiment as across soils collected from a wide range of biomes in North and South America, emphasizing the dominance of pH in structuring bacterial communities. The apparent direct influence of pH on bacterial community composition is probably due to the narrow pH ranges for optimal growth of bacteria. Fungal community composition was less strongly affected by pH, which is consistent with pure culture studies, demonstrating that fungi generally exhibit wider pH ranges for optimal growth. The ISME Journal (2010) 4, 1340-1351; doi: 10.1038/ismej.2010.58; published online 6 May 2010&nbsp

Cardiovascular effects of sub-daily levels of ambient fine particles: a systematic review

<p>Abstract</p> <p>Background</p> <p>While the effects of daily fine particulate exposure (PM) have been well reviewed, the epidemiological and physiological evidence of cardiovascular effects associated to sub-daily exposures has not. We performed a theoretical model-driven systematic non-meta-analytical literature review to document the association between PM sub-daily exposures (≤6 hours) and arrhythmia, ischemia and myocardial infarction (MI) as well as the likely mechanisms by which sub-daily PM exposures might induce these acute cardiovascular effects. This review was motivated by the assessment of the risk of exposure to elevated sub-daily levels of PM during fireworks displays.</p> <p>Methods</p> <p>Medline and Elsevier's EMBase were consulted for the years 1996-2008. Search keywords covered potential cardiovascular effects, the pollutant of interest and the short duration of the exposure. Only epidemiological and experimental studies of adult humans (age > 18 yrs) published in English were reviewed. Information on design, population and PM exposure characteristics, and presence of an association with selected cardiovascular effects or physiological assessments was extracted from retrieved articles.</p> <p>Results</p> <p>Of 231 articles identified, 49 were reviewed. Of these, 17 addressed the relationship between sub-daily exposures to PM and cardiovascular effects: five assessed ST-segment depression indicating ischemia, eight assessed arrhythmia or fibrillation and five considered MI. Epidemiologic studies suggest that exposure to sub-daily levels of PM is associated with MI and ischemic events in the elderly. Epidemiological studies of sub-daily exposures suggest a plausible biological mechanism involving the autonomic nervous system while experimental studies suggest that vasomotor dysfunction may also relate to the occurrence of MI and ischemic events.</p> <p>Conclusions</p> <p>Future studies should clarify associations between cardiovascular effects of sub-daily PM exposure with PM size fraction and concurrent gaseous pollutant exposures. Experimental studies appear more promising for elucidating the physiological mechanisms, time courses and causes than epidemiological studies which employ central pollution monitors for measuring effects and for assessing their time course. Although further studies are needed to strengthen the evidence, given that exposure to sub-daily high levels of PM (for a few hours) is frequent and given the suggestive evidence that sub-daily PM exposures are associated with the occurrence of cardiovascular effects, we recommend that persons with cardiovascular diseases avoid such situations.</p

Long Tract of Untranslated CAG Repeats Is Deleterious in Transgenic Mice

The most frequent trinucleotide repeat found in human disorders is the CAG sequence. Expansion of CAG repeats is mostly found in coding regions and is thought to cause diseases through a protein mechanism. Recently, expanded CAG repeats were shown to induce toxicity at the RNA level in Drosophila and C. elegans. These findings raise the possibility that CAG repeats may trigger RNA-mediated pathogenesis in mammals. Here, we demonstrate that transgenic mice expressing EGFP transcripts with long CAG repeats in the 3′ untranslated region develop pathogenic features. Expression of the transgene was directed to the muscle in order to compare the resulting phenotype to that caused by the CUG expansion, as occurs in myotonic dystrophy. Transgenic mice expressing 200, but not those expressing 0 or 23 CAG repeats, showed alterations in muscle morphology, histochemistry and electrophysiology, as well as abnormal behavioral phenotypes. Expression of the expanded CAG repeats in testes resulted in reduced fertility due to defective sperm motility. The production of EGFP protein was significantly reduced by the 200 CAG repeats, and no polyglutamine-containing product was detected, which argues against a protein mechanism. Moreover, nuclear RNA foci were detected for the long CAG repeats. These data support the notion that expanded CAG repeat RNA can cause deleterious effects in mammals. They also suggest the possible involvement of an RNA mechanism in human diseases with long CAG repeats

Intravascular Food Reward

Consumption of calorie-containing sugars elicits appetitive behavioral responses and dopamine release in the ventral striatum, even in the absence of sweet-taste transduction machinery. However, it is unclear if such reward-related postingestive effects reflect preabsorptive or postabsorptive events. In support of the importance of postabsorptive glucose detection, we found that, in rat behavioral tests, high concentration glucose solutions administered in the jugular vein were sufficient to condition a side-bias. Additionally, a lower concentration glucose solution conditioned robust behavioral responses when administered in the hepatic-portal, but not the jugular vein. Furthermore, enteric administration of glucose at a concentration that is sufficient to elicit behavioral conditioning resulted in a glycemic profile similar to that observed after administration of the low concentration glucose solution in the hepatic-portal, but not jugular vein. Finally using fast-scan cyclic voltammetry we found that, in accordance with behavioral findings, a low concentration glucose solution caused an increase in spontaneous dopamine release events in the nucleus accumbens shell when administered in the hepatic-portal, but not the jugular vein. These findings demonstrate that the postabsorptive effects of glucose are sufficient for the postingestive behavioral and dopaminergic reward-related responses that result from sugar consumption. Furthermore, glycemia levels in the hepatic-portal venous system contribute more significantly for this effect than systemic glycemia, arguing for the participation of an intra-abdominal visceral sensor for glucose

Twenty years of stereotype threat research: A review of psychological mediators

This systematic literature review appraises critically the mediating variables of stereotype threat. A bibliographic search was conducted across electronic databases between 1995 and 2015. The search identified 45 experiments from 38 articles and 17 unique proposed mediators that were categorized into affective/subjective (n = 6), cognitive (n = 7) and motivational mechanisms (n = 4). Empirical support was accrued for mediators such as anxiety, negative thinking, and mind-wandering, which are suggested to co-opt working memory resources under stereotype threat. Other research points to the assertion that stereotype threatened individuals may be motivated to disconfirm negative stereotypes, which can have a paradoxical effect of hampering performance. However, stereotype threat appears to affect diverse social groups in different ways, with no one mediator providing unequivocal empirical support. Underpinned by the multi-threat framework, the discussion postulates that different forms of stereotype threat may be mediated by distinct mechanisms

Dietary Protein and Blood Pressure: A Systematic Review

Background - Elevated blood pressure (BP), which is a major risk factor for cardiovascular disease, is highly prevalent worldwide. Recently, interest has grown in the role of dietary protein in human BP. We performed a systematic review of all published scientific literature on dietary protein, including protein from various sources, in relation to human BP. Methodology/Principal Findings - We performed a MEDLINE search and a manual search to identify English language studies on the association between protein and blood pressure, published before June 2010. A total of 46 papers met the inclusion criteria. Most observational studies showed no association or an inverse association between total dietary protein and BP or incident hypertension. Results of biomarker studies and randomized controlled trials indicated a beneficial effect of protein on BP. This beneficial effect may be mainly driven by plant protein, according to results in observational studies. Data on protein from specific sources (e.g. from fish, dairy, grain, soy, and nut) were scarce. There was some evidence that BP in people with elevated BP and/or older age could be more sensitive to dietary protein. Conclusions/Significance - In conclusion, evidence suggests a small beneficial effect of protein on BP, especially for plant protein. A blood pressure lowering effect of protein may have important public health implications. However, this warrants further investigation in randomized controlled trials. Furthermore, more data are needed on protein from specific sources in relation to BP, and on the protein-BP relation in population subgroup

Sense of Coherence and Gambling: Exploring the Relationship Between Sense of Coherence, Gambling Behaviour and Gambling-Related Harm

Understanding why some people experience problems with gambling whilst others are able to restrict gambling to recreational levels is still largely unexplained. One potential explanation is through salutogenesis, which is a health promotion approach of understanding factors which move people towards health rather than disease. An important aspect of salutogenesis is sense of coherence. Individuals with stronger sense of coherence perceive their environment as comprehensible, manageable and meaningful. The present study examined the relationship of individuals’ sense of coherence on their gambling behaviour and experience of gambling related harm. This exploratory study utilised an archival dataset (n = 1236) from an online, cross sectional survey of people who had experienced negative consequences from gambling. In general, a stronger sense of coherence was related to lower problem gambling severity. When gambling behaviour was controlled for, sense of coherence was significantly related to the experience of individual gambling harms. A strong sense of coherence can be seen as a protective factor against problematic gambling behaviour, and subsequent gambling related harms. These findings support the value of both primary and tertiary prevention strategies that strengthen sense of coherence as a harm minimisation strategy. The present study demonstrates the potential value of, and provides clear direction for, considering sense of coherence in order to understand gambling-related issues.This study was funded by the Victorian Responsible Gambling Foundation, Grant VRGF1-13