Magnesium isotope fractionation during microbially enhanced forsterite dissolution

Bacillus subtilis endospore‐mediated forsterite dissolution experiments were performed to assess the effects of cell surface reactivity on Mg isotope fractionation during chemical weathering. Endospores present a unique opportunity to study the isolated impact of cell surface reactivity because they exhibit extremely low metabolic activity. In abiotic control assays, ²⁴Mg was preferentially released into solution during forsterite dissolution, producing an isotopically light liquid phase (δ²⁶Mg = ?0.39 ± 0.06 to ?0.26 ± 0.09‰) relative to the initial mineral composition (δ²⁶Mg = ?0.24 ± 0.03‰). The presence of endospores did not have an apparent effect on Mg isotope fractionation associated with the release of Mg from the solid into the aqueous phase. However, the endospore surfaces preferentially adsorbed ²⁴Mg from the dissolution products, which resulted in relatively heavy aqueous Mg isotope compositions. These aqueous Mg isotope compositions increased proportional to the fraction of dissolved Mg that was adsorbed, with the highest measured δ²⁶Mg (?0.08 ± 0.07‰) corresponding to the highest degree of adsorption (~76%). The Mg isotope composition of the adsorbed fraction was correspondingly light, at an average δ²⁶Mg of ?0.49‰. Secondary mineral precipitation and Mg adsorption onto secondary minerals had a minimal effect on Mg isotopes at these experimental conditions. Results demonstrate the isolated effects of cell surface reactivity on Mg isotope fractionation separate from other common biological processes, such as metabolism and organic acid production. With further study, Mg isotopes could be used to elucidate the role of the biosphere on Mg cycling in the environment.     

Individual severity of dietary obesity in unselected Wistar rats: relationship with hyperphagia

We investigated the relative importance of overeating, thermogenesis, and uncoupling protein (UCP) expression in determining the severity of obesity in male Wistar rats fed a highly palatable diet. After 2 wk of feeding, body weight did not differ significantly from controls (248 +/- 4 vs. 229 +/- 3 g; P > 0.3), but rectal temperature, brown adipose tissue (BAT) mass, UCP3 expression in gastrocnemius muscle, and UCP2 expression in white adipose tissue (WAT) were all elevated in diet-fed animals. In a further study, rats fed a palatable diet for 8 wk exhibited higher energy intake and rectal temperature than controls. Dietary-obese rats were divided into high (427-490 g; n = 8) and low (313-410 g; n = 10) weight gainers. The high gainers ate significantly more than the low gainers, and energy intake was positively correlated with weight gain (r(2) = 0.72, P < 0.01). UCP2 and UCP3 mRNA levels in gastrocnemius muscle were significantly increased above lean controls in all diet-fed animals, whereas UCPs in WAT and BAT did not differ significantly from controls. Whereas rats fed palatable food exhibited a thermogenic response, there was no significant difference in core temperature between high and low gain groups (37. 5 +/- 0.1 vs. 37.6 +/- 0.1 degrees C; P > 0.5). We conclude that a higher energy intake is the critical factor determining susceptibility to dietary obesity in unselected Wistar rats.     

Leptin leads hypothalamic feeding circuits in a new direction

A decade ago, leptin (from the greek lepto meaning 'thin') was identified as the product of the ob gene.1 This adipocyte-derived hormone was found to suppress feeding and stimulate thermogenesis, and was thus proposed as a mediator in a negative feedback loop that controls body adiposity. This discovery led to a rapid revolution in the understanding of neurobiological mechanisms regulating obesity. However, while leptin's first life was as an adipostat, it is now known to have a wide range of additional neuroendocrine, metabolic and behavioural functions in the CNS and periphery. Remarkably, the pleiotropic nature of the hormone continues to be extended with the recent publication of two papers that expand on leptin's neurobiological actions in the CNS.2,3 They indicate novel regulatory roles for the hormone in both synaptic plasticity and axon guidance. Crucially, in light of the rising incidence of obesity in modern society, both of the studies reveal leptin-mediated links between nutrition and neurodevelopment, findings that have further implications for leptin's role in the regulation of energy homeostasis.     

An approximately 400 kDa membrane-associated complex that contains one molecule of the resistance protein Cf-4

Despite sharing more than 91% sequence identity, the tomato Cf-4 and Cf-9 proteins discriminate between two Cladosporium-encoded avirulence determinants, Avr4 and Avr9. Comparative studies between Cf-4 and Cf-9 are thus of particular interest. To investigate Cf-4 protein function in initiating defence signalling, we established transgenic tobacco lines and derived cell suspension cultures expressing c-myc-tagged Cf-4. Cf-4:myc encodes a membrane-localized glycoprotein of approximately 145 kDa, which confers recognition of Avr4. Elicitation of Cf-4:myc and Cf-9:myc tobacco cell cultures with Avr4 and Avr9, respectively, triggered the synthesis of active oxygen species and MAP kinase activation. Additionally, an Agrobacterium-mediated transient assay was used to express Cf-4:myc and a newly engineered fusion protein Cf-4:TAP. Both transiently expressed proteins were found to be functional in an in vivo assay, conferring a hypersensitive response (HR) to Avr4. Consistent with previous observations that Cf-9 is present in a protein complex, gel filtration analysis of microsomal fractions solubilized with octylglucoside revealed that epitope-tagged Cf-4 proteins migrated at a molecular mass of 350-475 kDa. Using blue native gel electrophoresis, the molecular size was confirmed to be approximately 400 kDa. Significantly, this complex appeared to contain only one Cf-4 molecule, supporting the idea that, as previously described for Cf-9, additional glycoprotein partners participate with Cf-4 in the perception of the Avr4 protein. Intriguingly, Cf proteins and Clavata2 (CLV2) of Arabidopsis are highly similar in structure, and the molecular mass of Cf-4 and CLV complexes is also very similar (400 and 450 kDa, respectively). However, extensive characterization of the Cf-4 complex revealed essentially identical characteristics to the Cf-9 complex and significant differences from the CLV2 complex.     

A novel real-time driving fatigue detection system based on wireless dry EEG

Development of techniques for detection of mental fatigue has varied applications in areas where sustaining attention is of critical importance like security and transportation. The objective of this study is to develop a novel real-time driving fatigue detection methodology based on dry Electroencephalographic (EEG) signals. The study has employed two methods in the online detection of mental fatigue: power spectrum density (PSD) and sample entropy (SE). The wavelet packets transform (WPT) method was utilized to obtain the \(\theta \) (4–7 Hz), \(\alpha \) (8–12 Hz) and \(\beta \) (13–30 Hz) bands frequency components for calculating corresponding PSD of the selected channels. In order to improve the fatigue detection performance, the system was individually calibrated for each subject in terms of fatigue-sensitive channels selection. Two fatigue-related indexes: (\(\theta +\alpha \))/\(\beta \) and \(\theta \)/\(\beta \) were computed and then fused into an integrated metric to predict the degree of driving fatigue. In the case of SE extraction, the mean of SE averaged across two EEG channels (‘O1h’ and ‘O2h’) was used for fatigue detection. Ten healthy subjects participated in our study and each of them performed two sessions of simulated driving. In each session, subjects were required to drive simulated car for 90 min without any break. The results demonstrate that our proposed methods are effective for fatigue detection. The prediction of fatigue is consistent with the observation of reaction time that was recorded during simulated driving, which is considered as an objective behavioral measure.     

The Contribution of Geography to Disparities in Preventable Hospitalisations between Indigenous and Non-Indigenous Australians

Objectives

To quantify the independent roles of geography and Indigenous status in explaining disparities in Potentially Preventable Hospital (PPH) admissions between Indigenous and non-Indigenous Australians.

Design, setting and participants

Analysis of linked hospital admission data for New South Wales (NSW), Australia, for the period July 1 2003 to June 30 2008.

Main outcome measures

Age-standardised admission rates, and rate ratios adjusted for age, sex and Statistical Local Area (SLA) of residence using multilevel models.

Results

PPH diagnoses accounted for 987,604 admissions in NSW over the study period, of which 3.7% were for Indigenous people. The age-standardised PPH admission rate was 76.5 and 27.3 per 1,000 for Indigenous and non-Indigenous people respectively. PPH admission rates in Indigenous people were 2.16 times higher than in non-Indigenous people of the same age group and sex who lived in the same SLA. The largest disparities in PPH admission rates were seen for diabetes complications, chronic obstructive pulmonary disease and rheumatic heart disease. Both rates of PPH admission in Indigenous people, and the disparity in rates between Indigenous than non-Indigenous people, varied significantly by SLA, with greater disparities seen in regional and remote areas than in major cities.

Conclusions

Higher rates of PPH admission among Indigenous people are not simply a function of their greater likelihood of living in rural and remote areas. The very considerable geographic variation in the disparity in rates of PPH admission between Indigenous and non-Indigenous people indicates that there is potential to reduce unwarranted variation by characterising outlying areas which contribute the most to this disparity.     

Allocation of pyloric caecum reserves in FED and starved sea stars, Pisaster giganteus (Stimpson): somatic maintenance comes before reproduction

Pyloric caeca were removed through the raytips of sea stars, Pisaster giganteus (Stimpson), beginning their seasonal period of gonad growth. Four months later their feeding rate, gonad growth, and gametogenic activity were lower than those of intact animals, while body growth rate remained the same. Removal of only the raytips also depressed feeding rate and gonad growth. When sea stars were starved, gonad growth and gametogenic activity were lower in animals without pyloric caeca, but body weight loss was the same as in intact animals. We conclude that when food is abundant, materials are utilized to enhance somatic and gonad growth. With decreasing reserves, due either to reduced food intake and/or pyloric caecum removal, somatic maintenance and growth have priority over gonad growth in material and energy allocation. Such a pattern of resource allocation is appropriate for long-lived iteroparous animals, such as these sea stars.