Comparison of Two Software Versions for Assessment of Body‐Composition Analysis by DXA

Objective: To compare two software versions provided by Lunar Co. for assessment of body composition analysis by DXA. Research Methods and Procedures: Soft‐tissue phantoms for lean tissue (water) and fat tissue (methanol) were repeatedly scanned using DXA machines (DPX‐L; Lunar Co., Madison, WI) and analyzed using software version 1.33 and the updated year 2000‐compatible version 1.35. For the intersoftware comparison, the phantoms were scanned 10 times (each scan was analyzed once) with both software versions using all three scanning modes (slow, medium, and fast) for a total of 60 scans and analyses. For the intermachine comparison, the same phantoms were scanned three times (each scan was analyzed once) with a second machine from the same manufacturer using all three scanning modes and version 1.35 only. Percentage of fat was the variable of interest. Results: For version 1.33, fat was 9.9 ± 0.4%, 10.0 ± 0.5%, and 11.0 ± 0.5% (mean ± SD) for the lean‐tissue phantom and 50.8 ± 0.3%, 50.9 ± 0.5%, and 51.1 ± 0.6% for the fat‐tissue phantom using the slow, medium, and fast scanning modes, respectively. For version 1.35, the respective fat values were 9.8 ± 0.7%, 9.9 ± 0.4%, and 10.3 ± 0.7%, and 50.6 ± 0.5%, 50.9 ± 0.6%, and 50.8 ± 0.8%, respectively. For the lean‐tissue phantom, the estimation of percentage of fat was significantly (p < 0.05) affected by scanning mode but not by software version. For the fat‐tissue phantom, the estimation of percentage of fat was not affected by either scanning mode or software version. The use of version 1.35 did not effect intermachine variability. Discussion: Versions 1.33 and 1.35 of the Lunar body composition software appear to be comparable. Soft‐tissue phantoms, such as the ones described in this paper, may be useful in monitoring the reproducibility of body composition analyses within and between DXA machines, particularly in longitudinal studies.     

Oxidation of iron-nitrosyl-hemoglobin by dehydroascorbic acid releases nitric oxide to form nitrite in human erythrocytes

The reaction of deoxyhemoglobin with nitric oxide (NO) or nitrite ions (NO 2 (-)) produces iron-nitrosyl-hemoglobin (HbNO) in contrast to the reaction with oxyhemoglobin, which produces methemoglobin and nitrate (NO 3 (-)). HbNO has not been associated with the known bioactivities of NO. We hypothesized that HbNO in erythrocytes could be an important source of bioactive NO/nitrite if its oxidation was coupled to the ascorbic acid (ASC) cycle. Studied by absorption and electron paramagnetic resonance (EPR) spectroscopy, DHA oxidized HbNO to methemoglobin and liberated NO from HbNO as determined by chemiluminescence. Both DHA and ascorbate free radical (AFR), the intermediate between ASC and DHA, enhanced NO oxidation to nitrite, but not nitrate; nor did either oxidize nitrite to nitrate. DHA increased the basal levels of nitrite in erythrocytes, while the reactions of nitrite with hemoglobin are slow. In erythrocytes loaded with HbNO, HbNO disappeared after DHA addition, and the AFR signal was detected by EPR. We suggest that the ASC-AFR-DHA cycle may be coupled to that of HbNO-nitrite and provide a mechanism for the endocrine transport of NO via hemoglobin within erythrocytes, resulting in the production of intracellular nitrite. Additionally, intracellular nitrite and nitrate seem to be largely generated by independent pathways within the erythrocyte. These data provide a physiologically robust mechanism for erythrocytic transport of NO bioactivity allowing for hormone-like properties.     

Sorption of anionic polysaccharides by cellulose

The sorption of anionic polysaccharides pectin, alginate, and xanthan with cellulose were investigated in presence of calcium. Calcium sorption to cellulose was limited by the carboxyl group content in fibers. Atomic Absorption Spectroscopy (AAS) analysis was used to measure the calcium in cellulose fibers and chemical oxygen demand (COD) analysis reveals that the divalent ions calcium can bind the polysaccharide onto cellulose fibers. The amount of calcium and polysaccharide bound in Ca²⁺/polysaccharide modified cellulose fibers was 5.8-12.5 mM Ca²⁺/kg fibers and 1500-2400 mg polysaccharide/kg fibers, respectively. Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) analysis confirmed the presence of polysaccharide on calcium containing cellulose fibers. The results of alizarin dyeing experiments at the end of polysaccharide sorption further confirmed the presence of calcium in Ca²⁺/polysaccharide modified cellulose fibers. The basic phenomenon of interaction of soluble ionic polysaccharide and cellulosic fibers in presence of divalent cations such as calcium is a key to understand biological functions and technological applications.     

Global and Site-Specific Effect of Phosphorylation on Protein Turnover

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Plasma Adiponectin Levels Are Not Associated with Fat Oxidation in Humans

Objective: To test the hypothesis that low adiponectin is associated with low fat oxidation in humans. Research Methods and Procedures: We measured plasma adiponectin concentrations in 75 healthy, nondiabetic Pima Indians (age, 28 ± 7 years; 55 men and 20 women; body fat, 29.7 ± 7.5%) and 18 whites [(age, 33 ± 8 years; 14 men and 4 women; body fat, 28.2 ± 10.8% (means ± SD)] whose body composition was measured by DXA and 24-hour energy expenditure (24-hour EE) by a respiratory chamber. Respiratory quotient (an estimate of whole-body carbohydrate/lipid oxidation rate) was calculated over 24 hours (24-hour RQ). Results: Before correlational analyses, waist-to-thigh ratio (WTR) and percentage of body fat (PFAT) were adjusted for age, sex, and race; 24-hour EE was adjusted for fat mass and fat-free mass, and 24-hour RQ were adjusted for energy balance. Plasma adiponectin concentrations were negatively correlated with WTR (r = −0.42, p < 0.0001) and PFAT (r = −0.46, p < 0.0001). There was no correlation between plasma adiponectin concentrations and 24-hour RQ, (r = 0.09, p = 0.36) before or after adjustment for PFAT (r = 0.001, p = 0.99, respectively, partial correlation), and no correlation was found between plasma adiponectin concentrations and 24-hour EE (r = −0.12, p = 0.27). Discussion: Our cross-sectional data do not suggest physiological concentrations of fasting plasma adiponectin play a role in the regulation of whole-body fat oxidation or energy expenditure in resting conditions. Whether administration of adiponectin to individuals with low levels of this hormone will increase their fat oxidation rates/energy expenditure remains to be established.