Coupled anaerobic methane oxidation and metal reduction in soil under elevated CO2.

Continued current emissions of carbon dioxide (CO2 ) and methane (CH4 ) by human activities will increase global atmospheric CO2 and CH4 concentrations and surface temperature significantly. Fields of paddy rice, the most important form of anthropogenic wetlands, account for about 9% of anthropogenic sources of CH4 . Elevated atmospheric CO2 may enhance CH4 production in rice paddies, potentially reinforcing the increase in atmospheric CH4 . However, what is not known is whether and how elevated CO2 influences CH4 consumption under anoxic soil conditions in rice paddies, as the net emission of CH4 is a balance of methanogenesis and methanotrophy. In this study, we used a long-term free-air CO2 enrichment experiment to examine the impact of elevated CO2 on the transformation of CH4 in a paddy rice agroecosystem. We demonstrate that elevated CO2 substantially increased anaerobic oxidation of methane (AOM) coupled to manganese and/or iron oxides reduction in the calcareous paddy soil. We further show that elevated CO2 may stimulate the growth and metabolism of Candidatus Methanoperedens nitroreducens, which is actively involved in catalyzing AOM when coupled to metal reduction, mainly through enhancing the availability of soil CH4 . These findings suggest that a thorough evaluation of climate-carbon cycle feedbacks may need to consider the coupling of methane and metal cycles in natural and agricultural wetlands under future climate change scenarios.

Correlation of thyroid dysfunction and cognitive impairments induced by subcortical ischemic vascular disease.

BACKGROUND: To date, the relationship between thyroid dysfunction and subcortical ischemic vascular disease (SIVD)-induced cognitive impairments still remains elusive. METHODS: Cognitive performances were examined in 215 participants, including 54 healthy participants, 52 SIVD patients with no dementia (SIVDND), 55 patients with mild cognitive impairment (SVMCI), and 54 patients with vascular dementia (VD). Serum thyroid-stimulating hormone (TSH), total triiodothyronine (TT3), free triiodothyronine (FT3), total thyroxine (TT4) and free thyroxine (FT4), thyroglobulin antibody (TGA), and antithyroid peroxidase antibody (TPO-Abs) were quantified by radioimmunoassay or ELISA. RESULTS: A close correlation between thyroid status and cognitive dysfunction in SIVD was observed. Serum TT3 and FT3 levels decreased, whereas serum TSH level increased, with the decline in cognitive functions. Furthermore, TT3 levels showed a positive correlation, whereas TSH level showed a negative correlation, with the Mini-Mental State Examination (MMSE) scores. Our results suggested that thyroid function was associated with cognitive impairments induced by SIVD. Also, thyroid function and thyroid hormone level could be a risk factor in the development of SIVD. Serum TT3 and TSH levels might also be used as biomarkers for cognitive dysfunction. CONCLUSIONS: These findings might contribute to a more accurate clinical diagnosis and differentiation among normal controls, SIVDND, SVMCI, and VD patients, in order to develop appropriate intervention approaches for SIVD therapeutic treatment.

[Root activity and nitrogen assimilation of rice (Oryza sativa) under free-air CO2 enrichment].

With Free-Air CO2 Enrichment(FACE) technique, this paper studied the root activity and amino acid(aa) synthesis of rice (Oryza sativa )at low N(LN, 150 kgN x hm(-2)) and normal N(NN, 250 kgN x hm(-2)) under ambient air and elevated atmospheric CO2 (Ambient + 200 micromol x mol(-1)). Under elevated CO2, the xylem exudates per hill changed little, while the xylem exudates per stem declined by 1.4% - 21.7% as the result of greater tiller numbers. At tillering and heading stages, elevated CO2 increased aa N/inorganic N in xylem exudates by 11.1% - 143.1%, but did not affect the aa concentration in xylem exudates and the total amount of aa in roots significantly. However, at 35 days after heading, the aa N/inorganic N ratio decreased by 38.1% (LN) and 29.2% (NN) under elevated CO2. FACE also declined the aa concentration in xylem exudates by 34.0% (LN) and 44.7% (NN), and the total amount of aa by 50.8% (LN) and 40.0% (NN), which meant the retarded capability of aa synthesis in roots. N amendment led to a decrease of aa N/inorganic N in xylem exudates by 19.5% (Ambient) and 36.8% (FACE) at heading stage, as the result of unaffected aa and increased inorganic N concentration. There existed a significantly antagonistical CO2 x N interaction on aa N/inorganic N at heading stage.