Validation of a DNA methylation reference panel for the estimation of nucleated cells types in cord blood

Cord blood is widely used as surrogate tissue in epigenome-wide association studies of prenatal conditions. Cell type composition variation across samples can be an important confounder of epigenome-wide association studies in blood that constitute a mixture of cells. We evaluated a newly developed cord blood reference panel to impute cell type composition from DNA methylation levels, including nucleated red blood cells (nRBCs). We estimated cell type composition from 154 unique cord blood samples with available DNA methylation data as well as direct measurements of nucleated cell types. We observed high correlations between the estimated and measured composition for nRBCs (r = 0.92, R² = 0.85), lymphocytes (r = 0.77, R² = 0.58), and granulocytes (r = 0.72, R² = 0.52), and a moderate correlation for monocytes (r = 0.51, R² = 0.25) as well as relatively low root mean square errors from the residuals ranging from 1.4 to 5.4%. These results validate the use of the cord blood reference panel and highlight its utility and limitations for epidemiological studies.     

Species Richness and Patterns of Invasion in Plants, Birds, and Fishes in the United States*

We quantified broad-scale patterns of species richness and species density (mean # species/km²) for native and non-indigenous plants, birds, and fishes in the continental USA and Hawaii. We hypothesized that the species density of native and non-indigenous taxa would generally decrease in northern latitudes and higher elevations following declines in potential evapotranspiration, mean temperature, and precipitation. County data on plants (n = 3004 counties) and birds (n=3074 counties), and drainage (6 HUC) data on fishes (n = 328 drainages) showed that the densities of native and non-indigenous species were strongly positively correlated for plant species (r = 0.86, P < 0.0001), bird species (r = 0.93, P<0.0001), and fish species (r = 0.41, P<0.0001). Multiple regression models showed that the densities of native plant and bird species could be strongly predicted (adj. R² = 0.66 in both models) at county levels, but fish species densities were less predictable at drainage levels (adj. R² = 0.31, P<0.0001). Similarly, non-indigenous plant and bird species densities were strongly predictable (adj. R² = 0.84 and 0.91 respectively), but non-indigenous fish species density was less predictable (adj. R² = 0.38). County level hotspots of native and non-indigenous plants, birds, and fishes were located in low elevation areas close to the coast with high precipitation and productivity (vegetation carbon). We show that (1) native species richness can be moderately well predicted with abiotic factors; (2) human populations have tended to settle in areas rich in native species; and (3) the richness and density of non-indigenous plant, bird, and fish species can be accurately predicted from biotic and abiotic factors largely because they are positively correlated to native species densities. We conclude that while humans facilitate the initial establishment, invasions of non-indigenous species, the spread and subsequent distributions of non-indigenous species may be controlled largely by environmental factors. The U.S. Government’s right to retain a non-exclusive, royalty-free licence in and to any copyright is acknowledged.     

Ethnic Differences in Visceral Adipose Tissue and Type 2 Diabetes: Filipino,African‐American,and White Women

Objective: To compare ethnic differences in visceral adipose tissue (VAT), assessed by computed tomography, and type 2 diabetes risk among 55‐ to 80‐year‐old Filipino, African‐American, and white women without known cardiovascular disease. Research Methods and Procedures: Subjects were participants in the Rancho Bernardo Study (n = 196), the Filipino Women's Health Study (n = 181), and the Health Assessment Study of African‐American Women (n = 193). Glucose and anthropometric measurements were assessed between 1995 and 2002. Results: African‐American women had significantly higher age‐adjusted BMI (29.7 kg/m²) and waist girth (88.1 cm) compared with Filipino (BMI, 25.5 kg/m²; waist girth, 81.9 cm) or white (BMI: 26.0 kg/m²; waist girth: 80.7 cm) women. However, VAT was significantly higher among Filipino (69.1 cm³) compared with white (62.3 cm³; p = 0.037) or African‐American (57.5 cm³, p < 0.001) women. VAT correlated better with BMI (r = 0.69) and waist (r = 0.77) in whites, compared with Filipino (r = 0.42; r = 0.59) or African‐American (r = 0.50; r = 0.56) women. Age‐adjusted type 2 diabetes prevalence was significantly higher in Filipinas (32.1%) than in white (5.8%) or African‐American (12.1%) women. Filipinas had higher type 2 diabetes risk compared with African Americans [adjusted odds ratio, 2.30; 95% confidence interval (CI), 1.09 to 4.86] or whites (adjusted odds ratio, 7.51; 95% CI, 2.51 to 22.5) after adjusting for age, VAT, exercise, education, and alcohol intake. Discussion: VAT was highest among Filipinas despite similar BMI and waist circumference as whites. BMI and waist circumference were weaker estimates of VAT in Filipino and African‐American women than in whites. Type 2 diabetes prevalence was highest among Filipino women at every level of VAT, but VAT did not explain their elevated type 2 diabetes risk.     

Sentinel-2 Satellite Imagery Application to Monitor Soil Salinity and Calcium Carbonate Contents in Agricultural Fields

The estuary tides affect groundwater dynamics; these areas are susceptible to waterlogging and salinity issues. A study was conducted on two fields with a total area of 60 hectares under a center pivot irrigation system that works with solar energy and belong to a commercial farm located in Northern Sudan. To monitor soil salinity and calcium carbonate in the area and stop future degradation of soil resources, easy, non-intrusive, and practical procedures are required. The objective of this study was to use remote sensing-determined Sentinel-2 satellite imagery using various soil indices to develop prediction models for the estimation of soil electrical conductivity (EC) and soil calcium carbonate (CaCO₃). Geo-referenced soil samples were collected from 72 locations and analyzed in the laboratory for soil EC and CaCO₃. The electrical conductivity of the soil saturation paste extract was represented by average values in soil dataset samples from two fields collected from the topsoil layer (0 to 15 cm) characteristic of the local salinity gradient. The various soil indices, used in this study, were calculated from the Sentinel-2 satellite imagery. The prediction was determined using the root mean square error (RMSE) and cross validation was done using coefficient of determination. The results of regression analysis showed linear relationships with significant correlation between the EC analyzed in laboratory and the salinity index-2 “SI2” (Model-1: R² = 0.59, p = 0.00019 and root mean square error (RMSE = 1.32%) and the bare soil index “BSI” (Model-2: R² = 0.63, p = 0.00012 and RMSE = 6.42%). Model-1 demonstrated the best model for predicting soil EC, and validation R² and RMSE values of 0.48% and 1.32%, respectively. The regression analysis results for soil CaCO₃ determination showed linear relationships with data obtained in laboratory and the bare soil index “BSI” (Model- 3: R² = 0. 45, p = 0.00021 and RMSE = 1.29%) and the bare soil index “BSI” & Normalized difference salinity index “NDSI” (Model-4: R² = 0.53, p = 0.00015 and RMSE = 1.55%). The validation confirmed the Model-3 results for prediction of soil CaCO₃ with R² and RMSE values of 0.478% and 1.29%, respectively. Future soil monitoring programs might consider the use of remote sensing data for assessing soil salinity and CaCO₃ using soil indices results generated from satellite image (i.e., Sentinel-2).     

<Emphasis Type="Italic">Aeromonas salmonicida</Emphasis> infected fish transfer disease to healthy fish <Emphasis Type="Italic">via</Emphasis> water

Experimental studies of infection transmission via water from infected to healthy fish were conducted. The dark-brown bacterial colonies typical for Aeromonas salmonicida on tryptone soya agar (TSA) have been isolated and counted (from 3.0±0.6×10² to 3.5±0.5×10⁵ c.f.u. g⁻¹) from the internal organs of naturally infected (NI) and experimentally infected (EI) perch and sea trout. No significant differences in dark-brown bacterial counts were detected between EI perch and EI sea trout. The assessment and comparison of the alterations of the biological parameters of EI European perch and sea trout with bacterium Aeromonas salmonicida subsp. salmonicida with naturally infected perch were conducted. No mortality was recorded in groups of EI perch and sea trout. Whereas, the mortality of NI perch (collected from the main sites of outbreak of disease) was observed from the second day of the experiments. Changes in morphophysiological parameters of EI perch and sea trout were similar. Different alterations in blood cell parameters of EI fish were observed, and the most noticeable was the decrease (P≤0.01) in white blood cell count (WBC) of EI perch and sea trout. Based on these results it can be deduced that there is infection transmission of bacterium A. salmonicida from European perch via water to other fish species.     

Age,growth and reproduction in creole perch (Percichthys trucha) in the Negro River,Argentinean Patagonia

Age, growth and reproductive characteristics of creole perch, Percichthys trucha, were investigated in the Negro River, southern Argentina from samples collected seasonally, December 1994–December 1995. Age was estimated via scale and whole otolith reading methods. Total length (n = 413) ranged from 103 to 432 mm, and weight from 12 to 1042 g. Significant differences between the length‐weight relationships of males and females were detected (P < 0.05). Isometric growth was observed in juveniles and males, whereas total population and females exhibited positive allometric growth. The marking pattern in scales and otoliths followed an annual rhythm, with the formation of only one annulus in scales and only one hyaline band in otoliths during autumn‐winter. The oldest males were 5 years old whereas maximum age in females was 12 years from scales and 15 years from otoliths. Because scales were found to underestimate age in individuals older than 4 years, otoliths were considered to be the best structures for creole perch age determination. Gompertz growth parameters based on otolith data were L∞: 428.0 mm, k = 0.46 and t₀ = 0.43 for total population (r = 0.90), L∞: 410.7 mm, k = 0.42 and t₀ = 0.46 for males (r = 0.91), and L∞: 434.1 mm, and k = 0.49 and t₀ = 0.43 for females (r = 0.91). Lengths at first maturity (TL₅₀) were 260 and 241 mm in males and females, respectively, both of which corresponded to ages between 1 and 2 years. Macroscopic gonad inspection and the high percentage of juveniles captured during summer indicated that spawning begins at the end of spring.     

Manganese-54 accumulation by Chlorella spp., Daphnia magna and yellow perch (Perca flavescens)

Concentration factor and biological half-life of ⁵⁴Mn were determined in three species representing an ecologically and economically important food chain. Green algae (Chlorella spp.), Daphnia magna and yellow perch (Perca flavescens) were exposed to ⁵⁴Mn in water and assayed for ⁵⁴Mn uptake. Steady state concentration factors computed from the laboratory data for algae, Daphnia and perch were 4230, 17 000 and 11, respectively. Respective biological half-lives were 1.6, 1.2 and 8.3 days.     

Differential Effects of Abdominal Adipose Tissue Distribution on Insulin Sensitivity in Black and White South African Women

Black South African women are more insulin resistant than BMI‐matched white women. The objective of the study was to characterize the determinants of insulin sensitivity in black and white South African women matched for BMI. A total of 57 normal‐weight (BMI 18–25 kg/m²) and obese (BMI > 30 kg/m²) black and white premenopausal South African women underwent the following measurements: body composition (dual‐energy X‐ray absorptiometry), body fat distribution (computerized tomography (CT)), insulin sensitivity (S_I, frequently sampled intravenous glucose tolerance test), dietary intake (food frequency questionnaire), physical activity (Global Physical Activity Questionnaire), and socioeconomic status (SES, demographic questionnaire). Black women were less insulin sensitive (4.4 ± 0.8 vs. 9.5 ± 0.8 and 3.0 ± 0.8 vs. 6.0 ± 0.8 × 10^?5/min/(pmol/l), for normal‐weight and obese women, respectively, P < 0.001), but had less visceral adipose tissue (VAT) (P = 0.051), more abdominal superficial subcutaneous adipose tissue (SAT) (P = 0.003), lower SES (P < 0.001), and higher dietary fat intake (P = 0.001) than white women matched for BMI. S_I correlated with deep and superficial SAT in both black (R = ?0.594, P = 0.002 and R = 0.495, P = 0.012) and white women (R = ?0.554, P = 0.005 and R = ?0.546, P = 0.004), but with VAT in white women only (R = ?0.534, P = 0.005). In conclusion, body fat distribution is differentially associated with insulin sensitivity in black and white women. Therefore, the different abdominal fat depots may have varying metabolic consequences in women of different ethnic origins.     

THE SCALING OF PLANT AND ANIMAL BODY MASS,LENGTH, AND DIAMETER

The interspecific scaling exponents of body mass M and diameter D with respect to length L were determined to evaluate the predictions of three scaling hypotheses (geometric, stress, and elastic similitude). The relation between M and L was determined for data from a total of 133 aquatic and terrestrial species (66 plant and 67 animal species); the relation between D and L was determined independently for a total of 753 aquatic and terrestrial species (667 plant and 86 animal species). Organisms were crudely classified as to their geometry (spheres, spheroids, cylinders) and shape (defined as the body slenderness factor, L/D) to examine whether geometry and shape evinced size-dependent variations. Regression indicated M = 1.29L^2.95 (r² = 0.91, N = 133; α_RMA = 3.09 ± 0.088). The stress and elastic similitude (which respectively predict α_RMA = 5 and α_RMA = 4) were rejected; geometric similitude was not (α_RMA = 3). For animals and plants, α_RMA = 2.81 ± 0.061 (r² = 0.98), and α_RMA = 2.95 ± 0.093 (r² = 0.94), respectively. For aquatics and terrestrial organisms, α_RMA = 2.82 ±0.134 (r² = 0.97, N = 36), and α_RMA = 3.08 ±0.111 (r² = 0.89, N = 97), respectively. These results were interpreted to support the hypothesis of geometric similitude. For the pooled plant and animals data, D = 0.05L^1.00 (r² = 0.95; α_RMA = 1.03 ± 0.009), which was compatible with the hypothesis of geometric similitude. For plants, D = 0.05L^1.06 (r² = 0.95; α_RMA = 1.09). For animals, D = 0.29L^0.98 (r² = 0.95; α_RMA = 1.01 ± 0.025). Also, for aquatics, α_RMA = 0.951 ± 0.151, whereas for terrestrial plants and animals, α_RMA = 1.03 ± 0.089. Although the scaling exponent for D differed among individual groupings of animals and plants, the results of regression analyses were interpreted to indicate that, on the average, body diameter scaled isometrically with respect to length as predicted by geometric similitude. For the pooled data set, organic shape varied over 3 orders of magnitude; L varied over 9 orders of magnitude reflecting 22 orders of magnitude of M. In terms of body geometry and the absolute numbers of species in the total data set: spherical shaped species (L = D) < unassigned species < prolate spheroidal species < cylindrical (squat < slender) species. The largest organisms in the data set were slender (L/D > 20) cylindrical plants; the smallest organisms were spherical plants and animals. Although not subject to statistical inference, these data were interpreted to indicate that organic shape and geometry evince size-dependent variations. These variations as well as size-dependent changes in bulk density are hypothesized to account for the scaling exponents of M and D determined for individual plant and animal clades and grades.     

Regulatory Serotype Mutations in TETRAHYMENA PYRIFORMIS, Syngen 1

A method utilizing allelic exclusion has been developed to isolate mutants of Tetrahymena pyriformis, syngen 1, in which the normal pattern of expression of mutally exclusive surface antigens is altered. Cells homozygous for the recessive mutant allele R-1^r do not express the L, H and T serotypes when grown under conditions appropriate for their expression. Rather, a new immobilization antigen, r, is expressed. Cells homozygous for the recessive mutant allele R-3^r also express the r antigen instead of H serotypes, but are normal in their expression of T antigens. Genetic analyses show that R-1 and R-3 are not closely linked, that R-1 is linked to T by 9.3 units, and that R-3 may be loosely linked to the mt locus. Different linkage values were obtained, however, when different inbred laboratory strains were used, suggesting the possible existence of crossover modifying genes. The rates of assortment of R-1^R/R-1^r and R-3^R/R-3^r heterozygotes into pure sublines expressing either H or r serotypes are close to the values observed for the differentiation of heterozygotes at other loci. The data confirm the previous observation that genetic coupling relationships are not maintained in macronuclear phenotypes and are consistent with the hypothesis that the macronucleus contains 45 assorting subunits. The assortment of the double heterozygote R-1^R/R-1^r, R-3^R/R-3^r at R_f=0.0112 suggests that the units of assortment are not individual genetic loci or chromosome fragments, but that the units may be complete genomes.     

Proposed standard weight (Ws) equation for European perch (Perca fluviatilis Linnaeus, 1758)

Relative weight (W_r) is an important and commonly used condition index that provides a measure of the well‐being of a fish population by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and of the same length in good physiological condition, i.e. the standard weight (W_s). Two methods of calculating the standard weight are proposed in the literature: the RLP method and the EmP method. The aim of this study was to develop a standard weight equation for European perch by means of both methods, using length–weight data from 64 913 fish from 18 countries (across Europe and Oceania). The resulting equations were: log₁₀ (W_s) = ?3.1483 + 1.2663 log₁₀ (TL) + 0.4291 [log₁₀ (TL)]² for the EmP method and log₁₀ (W_s) = ?5.3493 + 3.2152 log₁₀ (TL) for the RLP method. The applicable length‐range of the two W_s equations was restricted to 80–460 mm. A further research aim was to compare the performances of RLP and EmP. The resulting quadratic EmP W_s equation did not exhibit length‐related biases, which suggests that it can be used to compute relative weight for European perch.     

Microsatellite mapping of the bovine roan locus: A major determinant of White Heifer Disease

In the Belgian Blue Cattle breed, coat color variation is mainly under the influence of a single autosomal locus, the roan locus, characterized by a pair of codominant alleles: r ⁺ (black) and R (white). Heterozygous r ⁺ R animals have intermingled black and white hairs, yielding the ``blue' phenotype typical of the breed. Major interest for the roan locus stems from its pleiotropic effect on fertility, owing to the critical role of the R allele in the determinism of White Heifer Disease. We describe the linkage mapping of the roan locus to bovine Chromosome (Chr) 5, in the interval between microsatellite markers BPI and AGLA293, with an associated lodscore of 11.2. Moreover, we map a candidate gene, the Steel locus coding for the mast cell growth factor, to bovine Chr 5. Received: 30 May 1995 / Accepted: 6 September 1995     

Root turnover in pasture species: chicory,lucerne, perennial ryegrass and white clover

For pastures, root turnover can have an important influence on nutrient and carbon cycling, and plant performance. Turnover was calculated from mini‐rhizotron observations for chicory (Cichorium intybus), lucerne (Medicago sativa), perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) grown in the Manawatu, New Zealand. The species were combined factorially with four earthworm species treatments and a no‐earthworm control. Split plots compared the effects of not cutting and cutting the shoots at intervals. Observations were made c. 18 days apart for 2.5 years. This article concentrates on differences between plant species in root turnover in the whole soil profile to 40 cm depth. At this scale, earthworm effects were generally small and short lived. For ryegrass and white clover, root length and mass were linearly related (R² = 0.82–0.99). For chicory and lucerne, the relationships were poorer (R² = 0.38–0.77), so for those species length turnover may be a poor indicator of mass turnover. Standing root length, total growth and death generally decreased in the sequence ryegrass > lucerne > chicory = white clover. In length terms, scaled turnover (growth divided by average standing root length) generally followed the sequence lucerne > white clover > perennial ryegrass = chicory. Across species the scaled turnover rate averaged 3.4 per year or 0.9% per day. Cutting shoots reduced standing root length, growth and death, but increased scaled turnover. These results indicate fast and prolonged root turnover. For ryegrass and white clover, at least there is need to reappraise how to measure and model shoot : root ratios, dry matter production and carbon cycling.     

Chronotype,social jetlag,and time perspective

ABSTRACT

The phase of entrainment (chronotype) is known to be associated with time perspective (TP), suggesting that the state of circadian system is involved in the long-term planning of human life. However, little is known regarding the influence of circadian misalignment on long-term planning ability. The aim of this study was to investigate the association between social jetlag (SJL) and TP. A total of 1064 schoolchildren and university students (mean age ± standard deviation, 19.2 ± 2.9 years; range, 15–25 years; females, 71.7%) from four cities in the Russian Federation located between 56.9 and 61.7 degrees North completed the Munich ChronoType Questionnaire, the Pittsburgh Sleep Quality Index, the Seasonal Pattern Assessment Questionnaire, and Zimbardo Time Perspective Inventory. Study participants also indicated personal data (age, sex, height weight, place of residence, and achievements). A multiple regression analysis with stepwise inclusion of predictors in the model was performed to evaluate associations between time perspective characteristics (dependent variables) and predictor variables. The change in R² was used as the measure of effect size. Chronotype was found to be a moderate predictor of future TP (B = 0.034; ΔR² = 0.037). In addition, sleep quality was found to be a moderate predictor of past negative (B = 0.043; ΔR² = 0.074), present fatalistic (B = 0.021; ΔR² = 0.035), and deviation from balanced TP (B = 0.034; ΔR² = 0.066). Mood seasonality was a moderate predictor of present hedonistic TP (B = 0.016; ΔR² = 0.038), and social jetlag was a weak predictor of present fatalistic (B = 0.052; ΔR² = 0.019), future (B = ?0.033; ΔR² = 0.004), and deviation from balanced TP (B = 0.047; ΔR² = 0.012). In conclusion, this study found a weak but significant association between social jetlag and TP in adolescents and young adults.     

Predation on fish eggs by white perch,Morone americana,in western Lake Erie

Synopsis The white perch,Morone americana, is an east coast estuarine species that invaded Lake Erie in the 1950's, but did not increase in abundance until the mid 1970's. We studied its distribution and feeding during spawning in the Sandusky River, Ohio in 1981–1983. White perch were present in the area from early April through May, but abundance was highest on bedrock riffles about 45 km upstream from Lake Erie. Spawning activity peaked in the last week of April when temperatures approached 18°C. White perch collected in early April had eaten walleye,Stizostedion vitreum vitreum, eggs. As spawning activity of white perch increased, feeding activity declined, and most fish collected during late April contained no food. Egg predation increased again in May, but the eggs eaten then were those of white bass,Morone chrysops, white perch, and possibly other species. We have no evidence that egg predation by white perch has affected walleye or white bass recruitment, but it could become a problem if white perch continue to increase in abundance.     

Multivariate Statistical Assessment of Predictors of Firefighters’ Muscular and Aerobic Work Capacity

Physical capacity has previously been deemed important for firefighters physical work capacity, and aerobic fitness, muscular strength, and muscular endurance are the most frequently investigated parameters of importance. Traditionally, bivariate and multivariate linear regression statistics have been used to study relationships between physical capacities and work capacities among firefighters. An alternative way to handle datasets consisting of numerous correlated variables is to use multivariate projection analyses, such as Orthogonal Projection to Latent Structures. The first aim of the present study was to evaluate the prediction and predictive power of field and laboratory tests, respectively, on firefighters’ physical work capacity on selected work tasks. Also, to study if valid predictions could be achieved without anthropometric data. The second aim was to externally validate selected models. The third aim was to validate selected models on firefighters’ and on civilians’. A total of 38 (26 men and 12 women) + 90 (38 men and 52 women) subjects were included in the models and the external validation, respectively. The best prediction (R²) and predictive power (Q²) of Stairs, Pulling, Demolition, Terrain, and Rescue work capacities included field tests (R² = 0.73 to 0.84, Q² = 0.68 to 0.82). The best external validation was for Stairs work capacity (R² = 0.80) and worst for Demolition work capacity (R² = 0.40). In conclusion, field and laboratory tests could equally well predict physical work capacities for firefighting work tasks, and models excluding anthropometric data were valid. The predictive power was satisfactory for all included work tasks except Demolition.     

Dual‐energy X‐ray Absorptiometry and Anthropometric Estimates of Visceral Fat in Black and White South African Women

Visceral adipose tissue (VAT) is associated with increased risk for cardiovascular disease, and therefore, accurate methods to estimate VAT have been investigated. Computerized tomography (CT) is the gold standard measure of VAT, but its use is limited. We therefore compared waist measures and two dual‐energy X‐ray absorptiometry (DXA) methods (Ley and Lunar) that quantify abdominal regions of interest (ROIs) to CT‐derived VAT in 166 black and 143 white South African women. Anthropometry, DXA ROI, and VAT (CT at L4–L5) were measured. Black women were younger (P < 0.001), shorter (P < 0.001), and had higher body fat (P < 0.05) than white women. There were no ethnic differences in waist (89.7 ± 18.2 cm vs. 90.1 ± 15.6 cm), waist:height ratio (WHtR, 0.56 ± 0.12 vs. 0.54 ± 0.09), or DXA ROI (Ley: 2.2 ± 1.5 vs. 2.1 ± 1.4; Lunar: 2.3 ± 1.4 vs. 2.3 ± 1.5), but black women had less VAT, after adjusting for age, height, weight, and fat mass (76 ± 34 cm² vs. 98 ± 35 cm²; P < 0.001). Ley ROI and Lunar ROI were correlated in black (r = 0.983) and white (r = 0.988) women. VAT correlated with DXA ROI (Ley: r = 0.729 and r = 0.838, P < 0.01; Lunar: r = 0.739 and r = 0.847, P < 0.01) in black and white women, but with increasing ROI android fatness, black women had less VAT. Similarly, VAT was associated with waist (r = 0.732 and r = 0.836, P < 0.01) and WHtR (r = 0.721 and r = 0.824, P < 0.01) in black and white women. In conclusion, although DXA‐derived ROIs correlate well with VAT as measured by CT, they are no better than waist or WHtR. Neither DXA nor anthropometric measures are able to accurately distinguish between high and low levels of VAT between population groups.     

Effects of root diameter and root nitrogen concentration on in situ root respiration among different seasons and tree species

Knowledge of root respiration is a prerequisite for a better understanding of ecosystem carbon budget and carbon allocation. However, there are not many relevant data in the literature on direct measurements of in situ root respiration by root chamber method. Furthermore, few studies have been focused on the effects of root diameter (D _r) and root nitrogen concentration (N _r) on in situ root respiration among different seasons and tree species. To address these goals, we used a simplified root-chamber system to measure in situ root respiration rates of Acacia crassicarpa and Eucalyptus urophylla in subtropical plantations of south China. We found that the species and season variation in root respiration were affected by D _r and N _r. Also, the root respiration per unit dry mass (R _r, nmol CO₂ g⁻¹ s⁻¹) and root respiration per unit N (R _n, nmol CO₂ g N⁻¹ s⁻¹) were affected by D _r and N _r. The R _r, R _n, N _r and soil temperature sensitivity (Q ₁₀) of R _r for the two species significantly decreased with an increase of D _r. The R _r of the two species showed significant an inter-seasonal and diurnal pattern, and this trend decreased with increasing D _r. Both the R _r and Q ₁₀ of the two species increased with increasing N _r. The D _r and N _r explained 54 and 52% of the observed variation in R _r for A. crassicarpa, and 65 and 70% for E. urophylla. The R _r, N _r, and Q ₁₀ of A. crassicarpa were significantly higher than those of E. urophylla. Our results indicated that root respiration was dependent on D _r and N _r, and this dependence varied with season and plant species.     

Accuracy of Optimized Chemical-exchange Parameters Derived by Fitting CPMG R 2 Dispersion Profiles when R 2 0a ≠ R 2 0b

The transverse relaxation rate, R₂, measured as a function of the effective field (R₂ dispersion) using a Carr-Purcell-Meiboom-Gill (CPMG) pulse train, is well suited to detect conformational exchange in proteins. The dispersion data are commonly fitted by a two-site (sites a and b) exchange model with four parameters: the relative population, p_a, the difference in chemical shifts of the two sites, δω, the correlation time for exchange, τ_ex, and the intrinsic relaxation rate (i.e., transverse relaxation rate in the absence of chemical exchange), R₂⁰. Although the intrinsic relaxation rates of the two sites, R₂^0a and R₂^0b, can differ, they are normally assumed to be the same (i.e., R₂^0a = R₂^0b = R₂⁰) when fitting dispersion data. The purpose of this investigation is to determine the magnitudes of the errors in the optimized exchange parameters that are introduced by the assumption that R₂^0a = R₂^0b. In order to accomplish this goal, we first generated synthetic constant-time CPMG R₂ dispersion data assuming two-site exchange with R₂^0a ≠ R₂^0b, and then fitted the synthetic data assuming two-site exchange with R₂⁰ = R₂^0a = R₂^0b. Although all the synthetic data generated assuming R₂^0a ≠ R₂^0b were well fitted (assuming R₂^0a = R₂^0b), the optimized values of p_a and τ _ex differed from their true values, whereas the optimized values of δω values did not. A theoretical analysis using the Carver–Richards equation explains these results, and yields simple, general equations for estimating the magnitudes of the errors in the optimized parameters, as a function of ( R₂^0a − R₂^0b).