Novel measurements of periaortic adipose tissue in comparison to anthropometric measures of obesity, and abdominal adipose tissue.

BACKGROUND: Perivascular adipose tissue may be associated with the amount of local atherosclerosis. We developed a novel and reproducible method to standardize volumetric quantification of periaortic adipose tissue by computed tomography (CT) and determined the association with anthropometric measures of obesity, and abdominal adipose tissue. METHODS: Measurements of adipose tissue were performed in a random subset of participants from the Framingham Heart Study (n=100) who underwent multidetector CT of the thorax (ECG triggering, 2.5 mm slice thickness) and the abdomen (helical CT acquisition, 2.5 mm slice thickness). Abdominal periaortic adipose tissue (AAT) was defined by a 5 mm cylindrical region of interest around the aortic wall; thoracic periaortic adipose tissue (TAT) was defined by anatomic landmarks. TAT and AAT were defined as any voxel between -195 and -45 HU and volumes were measured using dedicated semiautomatic software. Measurement reproducibility and association with anthropometric measures of obesity, and abdominal adipose tissue were determined. RESULTS: The intra- and inter-observer reproducibility for both AAT and TAT was excellent (ICC: 0.97 and 0.97; 0.99 and 0.98, respectively). Similarly, the relative intra- and inter-observer difference was small for both AAT (-1.85+/-1.28% and 7.85+/-6.08%; respectively) and TAT (3.56+/-0.83% and -4.56+/-0.85%, respectively). Both AAT and TAT were highly correlated with visceral abdominal fat (r=0.65 and 0.77, P<0.0001 for both) and moderately correlated with subcutaneous abdominal fat (r=0.39 and 0.42, P<0.0001 and P=0.009), waist circumference (r=0.49 and 0.57, P<0.0001 for both) and body mass index (r=0.47 and 0.58, P<0.0001 for both). CONCLUSION: Standardized semiautomatic CT-based volumetric quantification of periaortic adipose tissue is feasible and highly reproducible. Further investigation is warranted regarding associations of periaortic adipose tissue with other body fat deposits, cardiovascular risk factors and clinical outcomes.

Mid-depth circulation of the subpolar north atlantic during the last glacial maximum.

Holocene and glacial carbon isotope data of benthic foraminifera from shallow to mid-depth cores from the northeastern subpolar Atlantic show that this region was strongly stratified, with carbon-13-enriched glacial North Atlantic intermediate water (GNAIW) overlying carbon-13-depleted Southern Ocean water (SOW). The data suggest that GNAIW originated north of the polar front and define GNAIW end-member carbon isotope values for studies of water-mass mixing in the open Atlantic. Identical carbon isotope values in the core of GNAIW and below the subtropical thermocline are consistent with rapid cycling of GNAIW through the northern Atlantic. The high carbon isotope values below the thermocline indicate that enhanced nutrient leakage in response to increased ventilation may have extended into intermediate waters. Geochemical box models show that the atmospheric carbon dioxide response to nutrient leakage that results from an increase in ventilation rate may be greater than the response to nutrient redistribution by conversion of North Atlantic deep water into GNAIW. These results underscore the potential rule of Atlantic Ocean circulation changes in influencing past atmospheric carbon dioxide values.

Glacial surface temperatures of the southeast Atlantic Ocean.

A detailed record of sea surface temperature from sediments of the Cape Basin in the subtropical South Atlantic indicates a previously undocumented progression of marine climate change between 41 and 18 thousand years before the present (ky B.P.), during the last glacial period. Whereas marine records typically indicate a long-term cooling into the Last Glacial Maximum (around 21 ky B.P.) consistent with gradually increasing global ice volume, the Cape Basin record documents an interval of substantial temperate ocean warming from 41 to 25 ky B.P. The pattern is similar to that expected in response to changes in insolation owing to variations in Earth's tilt.

Synchronous radiocarbon and climate shifts during the last deglaciation.

Radiocarbon data from the Cariaco Basin provide calibration of the carbon-14 time scale across the period of deglaciation (15,000 to 10, 000 years ago) with resolution available previously only from Holocene tree rings. Reconstructed changes in atmospheric carbon-14 are larger than previously thought, with the largest change occurring simultaneously with the sudden climatic cooling of the Younger Dryas event. Carbon-14 and published beryllium-10 data together suggest that concurrent climate and carbon-14 changes were predominantly the result of abrupt shifts in deep ocean ventilation.