Suppressing peatland methane production by electron snorkeling through pyrogenic carbon in controlled laboratory incubations.

Northern peatlands are experiencing more frequent and severe fire events as a result of changing climate conditions. Recent studies show that such a fire-regime change imposes a direct climate-warming impact by emitting large amounts of carbon into the atmosphere. However, the fires also convert parts of the burnt biomass into pyrogenic carbon. Here, we show a potential climate-cooling impact induced by fire-derived pyrogenic carbon in laboratory incubations. We found that the accumulation of pyrogenic carbon reduced post-fire methane production from warm (32 °C) incubated peatland soils by 13-24%. The redox-cycling, capacitive, and conductive electron transfer mechanisms in pyrogenic carbon functioned as an electron snorkel, which facilitated extracellular electron transfer and stimulated soil alternative microbial respiration to suppress methane production. Our results highlight an important, but overlooked, function of pyrogenic carbon in neutralizing forest fire emissions and call for its consideration in the global carbon budget estimation.

Beyond the usual suspects: methanogenic communities in eastern North American peatlands are also influenced by nickel and copper concentrations.

Peatlands both accumulate carbon and release methane, but their broad range in environmental conditions means that the diversity of microorganisms responsible for carbon cycling is still uncertain. Here, we describe a community analysis of methanogenic archaea responsible for methane production in 17 peatlands from 36 to 53 N latitude across the eastern half of North America, including three metal-contaminated sites. Methanogenic community structure was analysed through Illumina amplicon sequencing of the mcrA gene. Whether metal-contaminated sites were included or not, metal concentrations in peat were a primary driver of methanogenic community composition, particularly nickel, a trace element required in the F430 cofactor in methyl-coenzyme M reductase that is also toxic at high concentrations. Copper was also a strong predictor, likely due to inhibition at toxic levels and/or to cooccurrence with nickel, since copper enzymes are not known to be present in anaerobic archaea. The methanogenic groups Methanocellales and Methanosarcinales were prevalent in peatlands with low nickel concentrations, while Methanomicrobiales and Methanomassiliicoccales were abundant in peatlands with higher nickel concentrations. Results suggest that peat-associated trace metals are predictors of methanogenic communities in peatlands.

Amyloid beta peptides in human plasma and tissues and their significance for Alzheimer's disease.

BACKGROUND: We evaluated the amounts of amyloid beta (Abeta)) peptides in the central nervous system (CNS) and in reservoirs outside the CNS and their potential impact on Abeta plasma levels and Alzheimer's disease (AD) pathology. METHODS: Amyloid beta levels were measured in (1) the plasma of AD and nondemented (ND) controls in a longitudinal study, (2) the plasma of a cohort of AD patients receiving a cholinesterase inhibitor, and (3) the skeletal muscle, liver, aorta, platelets, leptomeningeal arteries, and in gray and white matter of AD and ND control subjects. RESULTS: Plasma Abeta levels fluctuated over time and among individuals, suggesting continuous contributions from brain and peripheral tissues and associations with reactive circulating proteins. Arteries with atherosclerosis had larger amounts of Abeta40 than disease-free vessels. Inactivated platelets contained more Abeta peptides than activated ones. Substantially more Abeta was present in liver samples from ND patients. Overall, AD brain and skeletal muscle contained increased levels of Abeta. CONCLUSIONS: Efforts to use plasma levels of Abeta peptides as AD biomarkers or disease-staging scales have failed. Peripheral tissues might contribute to both the circulating amyloid pool and AD pathology within the brain and its vasculature. The wide spread of plasma Abeta values is also due in part to the ability of Abeta to bind to a variety of plasma and membrane proteins. Sources outside the CNS must be accounted for because pharmacologic interventions to reduce cerebral amyloid are assessed by monitoring Abeta plasma levels. Furthermore, the long-range impact of Abeta immunotherapy on peripheral Abeta sources should also be considered.

Circle of willis atherosclerosis is a risk factor for sporadic Alzheimer's disease.

OBJECTIVE: We conducted a quantitative investigation of brain arterial atherosclerotic damage and its relationship to sporadic Alzheimer's disease (AD). METHODS AND RESULTS: Fifty-four consecutive autopsy cases, 32 AD and 22 nondemented control subjects, were examined to establish the degree of arterial stenosis. Vessel external and lumenal area measurements were taken from 3-mm arterial cross-sections to calculate a stenosis index. AD patient circle of Willis arteries possessed a significant degree of stenosis as a consequence of multiple and severe atherosclerotic lesions. These lesions were significantly more severe in AD cases than in age-matched controls (P<0.0001), and the number of stenoses and the index of occlusion (R=0.67; P<0.00001) were positively correlated. In addition, the index of stenosis significantly correlated with the following measures of AD neuropathological lesions: total plaque score, neuritic plaque score, neurofibrillary tangle score, Braak stage score, and white matter rarefaction score. CONCLUSIONS: Our study reveals an association between severe circle of Willis atherosclerosis and sporadic AD that should be considered a risk factor for this dementia. These observations strongly suggest that atherosclerosis-induced brain hypoperfusion contributes to the clinical and pathological manifestations of AD.

Performance of three clock scoring systems across different ranges of dementia severity.

The ability of three different Clock Drawing Test (CDT) scoring systems to detect Dementia of the Alzheimer Type (DAT) was investigated. As part of a neuropsychological battery, fifty DAT Type patients and fifty matched controls drew a clock. Each drawing was scored by three independent raters according to three different scoring systems: the 3-Factor system, the Template system, and the Abbreviated system. The CDT scoring systems were able to detect Dementia of the Alzheimer Type when the disease was moderate to severe, but lacked sensitivity in milder dementia. Animal Fluency was a better single predictor of dementia. Clinicians are advised to interpret the results of the Clock Drawing Test cautiously in an outpatient setting, where milder forms of dementia and low base rates are likely.

Case series of clinically probable dementia with Lewy bodies in two Native Americans.

While incidence and prevalence of dementias have been assessed in some tribes, little is known about whether the different types of dementias that affect whites also affect Native Americans. Here, we report 2 cases of clinically probable dementia with Lewy bodies (DLB) that fulfill McKeith Consensus Criteria in an 84-year-old full-blooded Navajo woman and a 78-year-old full-blooded Navajo male assessed in a neurology clinic.