Association between low skeletal muscle mass and subclinical coronary atherosclerosis in asymptomatic individuals evaluated by CT.

AIM: To investigate the associations of skeletal muscle area and density with coronary atherosclerotic plaques and significant stenosis in asymptomatic adults. MATERIALS AND METHODS: A total of 243 consecutive subjects who had voluntarily undergone abdominal unenhanced computed tomography (CT) and coronary CT angiography (CCTA) as part of a general health examination were investigated retrospectively. Skeletal muscle area index (SMI) and skeletal muscle density (SMD) was assessed using CT. Coronary atherosclerotic plaques and stenosis on CCTA were evaluated. The associations of low SMI and low SMD with coronary atherosclerotic plaques and significant stenosis were determined by logistic regression analysis. RESULTS: After adjustment for cardiovascular risk factors, there were significant associations of low SMI or low SMD with atherosclerotic plaque, total significant stenosis, and significant stenosis caused by calcified or mixed plaques (for all p<0.05). In addition, multivariate regression analysis also showed that low SMI was independently associated with calcified plaque (p=0.038) and non-calcified plaque (p=0.006), and individuals with low SMD were more likely to have mixed plaque (p=0.001). CONCLUSION: Assessment of the skeletal muscle on CT help to identify asymptomatic adults at risk for coronary atherosclerosis.

Phosphorus release from ash and remaining tissues of two wetland species after a prescribed fire.

Dead plant tissues and ash from a prescribed fire play an important role in nutrient balance and cycling in the Florida Everglades ecosystem. The objective of this study was to assess the dynamic changes in total phosphorus release (TPr) from ash or tissues of either cattail (Typha domingensis Pers.) or sawgrass (Cladium jamaicense Crantz) to water. Natural-dead (senesced-dead) and burning-dead (standing-dead due to a prescribed fire) cattail and sawgrass were collected from highly (H) and moderately (M) impacted zones in the Florida Everglades. This experiment was conducted by incubation and water-extraction of the materials in plastic bottles for 65 d at room temperature (24 +/- 1 degrees C). Results showed that 63 to 88%, 17 to 48%, 9 to 20%, and 13 to 28% of total P (TPp) were released as TPr from cattail and sawgrass ash, cattail tissues from the H zone, cattail tissues, and sawgrass tissues from the M zone, respectively. TPp means total P of plant tissues, whereas TPr is total P release from the tissues or ash. Most of the TPr was released within 24 h after burning. The quick release of TPr observed in this experiment may help explain the P surge in the surface water immediately following a fire in the marsh. These findings suggest that prescribed burning accelerates P release from cattail and sawgrass. They also imply that it is very important to keep the water stagnant in the first 24 h to maximize the benefits of a prescribed fire in the Everglades.

Effects of burn temperature on ash nutrient forms and availability from cattail (Typha domingensis) and sawgrass (Cladium jamaicense) in the Florida Everglades.

Plant ash derived from fire plays an important role in nutrient balance and cycling in ecosystems. Factors that determine the composition and availability of ash nutrients include fire intensity (burn temperature and duration), plant species, habitat nutrient enrichment, and leaf type (live or dead leaf). We used laboratory simulation methods to evaluate temperature effects on nutrient composition and metals in the residual ash of sawgrass (Cladium jamaicense) and cattail (Typha domingensis), particularly on post-fire phosphorus (P) availability in plant ash. Live and dead leaf samples were collected from Water Conservation Area 2A in the northern Everglades along a soil P gradient, where prescribed fire may be used to accelerate recovery of this unique ecosystem. Significant decreases in total carbon and total nitrogen were detected with increasing fire temperature. Organic matter combustion was nearly complete at temperatures > or = 450 degrees C. HCl-extractable P (average, 50% of total P in the ash) and NH(4)Cl-extractable P (average, 33% of total P in the ash) were the predominant P fractions for laboratory-burned ash. Although a low-intensity fire could induce an elevation of P availability, an intense fire generally resulted in decreased water-soluble P. Significant differences in nutrient compositions were observed between species, habitat nutrient status, and leaf types. More labile inorganic P remained in sawgrass ash than in cattail ash; hence, sawgrass ash has a greater potential to release available P than cattail. Fire intensity affected plant ash nutrient composition, particularly P availability, and the effects varied with plant species and leaf type. Therefore, it is important to consider fire intensity and vegetation community when using a prescribed fire for ecosystem management.

Estimation of postfire nutrient loss in the Florida everglades.

Postfire nutrient release into ecosystem via plant ash is critical to the understanding of fire impacts on the environment. Factors determining a postfire nutrient budget are prefire nutrient content in the combustible biomass, burn temperature, and the amount of combustible biomass. Our objective was to quantitatively describe the relationships between nutrient losses (or concentrations in ash) and burning temperature in laboratory controlled combustion and to further predict nutrient losses in field fire by applying predictive models established based on laboratory data. The percentage losses of total nitrogen (TN), total carbon (TC), and material mass showed a significant linear correlation with a slope close to 1, indicating that TN or TC loss occurred predominantly through volatilization during combustion. Data obtained in laboratory experiments suggest that the losses of TN, TC, as well as the ratio of ash total phosphorus (TP) concentration to leaf TP concentration have strong relationships with burning temperature and these relationships can be quantitatively described by nonlinear equations. The potential use of these nonlinear models relating nutrient loss (or concentration) to temperature in predicting nutrient concentrations in field ash appear to be promising. During a prescribed fire in the northern Everglades, 73.1% of TP was estimated to be retained in ash while 26.9% was lost to the atmosphere, agreeing well with the distribution of TP during previously reported wild fires. The use of predictive models would greatly reduce the cost associated with measuring field ash nutrient concentrations.

Overexpression of the PDCD2-like gene results in inhibited TNF-alpha production in activated Daudi cells.

Both PDCD2 and PDCD2-like proteins have PDCD2_C terminal domains, but their functions are still unclear. After analysis of their expression in Gene Expression Omnibus, we hypothesized that they played a role in inflammation. In Daudi cells exposed to lipopolysaccharides, PDCD2-like RNA was upregulated, whereas PDCD2 was downregulated. Overexpression of PDCD2-like gene effectively attenuated tumor necrosis factor (TNF)-alpha release but elevated interleukin (IL)-6 and PDCD2 expression induced by lipopolysaccharide (LPS). It is possible that both proteins have anti-inflammatory effects like IL-6. The results have implications for understanding the function of PDCD2/PDCD2-like proteins and may help in the development of novel anti-inflammatory drugs.

Effects of simulated root herbivory and fertilizer application on growth and biomass allocation in the clonal perennialSolidago canadensis.

Compensatory growth in response to simulated belowground herbivory was studied in the old-field clonal perennialSolidago canadensis. We grew rootpruned plants and plants with intact root systems in soil with or without fertilizer. For individual current shoots (aerial shoot with rhizome and roots) and for whole clones the following predictions were tested: a) root removal is compensated by increased root growth, b) fertilizer application leads to increased allocation to aboveground plant organs and increased leaf turnover, c) effects of fertilizer application are reduced in rootpruned plants. When most roots (90%) were removed current shoots quickly restored equilibrium between above-and belowground parts by compensatory belowground growth whereas the whole clone responded with reduced aboveground growth. This suggests that parts of a clone which are shared by actively growing shoots act as a buffer that can be used as source of material for compensatory growth in response to herbivory. Current shoots increased aboveground mass and whole clones reduced belowground mass in response to fertilizer application, both leading to increased allocation to aboverground parts. Also with fertilizer application both root-pruned and not root-pruned plants increased leaf and shoot turnover. Unfertilized plants, whether rootpruned or not, showed practically no aboveground growth and very little leaf and shoot turnover. Effects of root removal were as severe or more severe under conditions of high as under conditions of low nutrients, suggesting that negative effects of belowground herbivory are not ameliorated by abundant nutrients. Root removal may negate some effects of fertilizer application on the growth of current shoots and whole clones.

CO2-induced growth enhancements of co-occurring tree species decline at different rates.

To elucidate how enriched CO2 atmospheres, soil fertility, and light availability interact to influence the long-term growth of tree seedlings, six co-occurring members of temperate forest communities including ash (Fraxinus americana L.), gray birch (Betula populifolia), red maple (Acer rubrum), yellow birch (Betula alleghaniensis), striped maple (Acer pensylvanicum), and red oak (Quercus rubra L.) were raised in a glasshouse for three years in a complete factorial design. After three years of growth, plants growing in elevated CO2 atmospheres were generally larger than those in ambient CO2 atmospheres, however, magnitudes of CO2-induced growth enhancements were contingent on the availability of nitrogen and light, as well as species identity. For all species, magnitudes of CO2-induced growth enhancements after one year of growth were greater than after three years of growth, though species' growth enhancements over the three years declined at different rates. These results suggest that CO2-induced enhancements in forest productivity may not be sustained for long periods of time. Additionally, species' differential growth responses to elevated CO2 may indirectly influence forest productivity via long-term species compositional changes in forests.

Elevated CO2 and drought alter tissue water relations of birch (Betula populifolia Marsh.) seedlings.

The effect of increasing atmospheric CO2 concentrations on tissue water relations was examined in Betula populifolia, a common pioneer tree species of the northeastern U.S. deciduous forests. Components of tissue water relations were estimated from pressure volume curves of tree seedlings grown in either ambient (350 µl l-1) or elevated CO2 (700 µl l-1), and both mesic and xeric water regimes. Both CO2 and water treatment had significant effects on osmotic potential at full hydration, apoplasmic fractions, and tissue elastic moduli. Under xeric conditions and ambient CO2 concentrations, plants showed a decrease in osmotic potentials of 0.15 MPa and an increase in tissue elastic moduli at full hydration of 1.5 MPa. The decrease in elasticity may enable plants to improve the soil-plant water potential gradient given a small change in water content, while lower osmotic potentials shift the zero turgor loss point to lower water potentials. Under elevated CO2, plants in xeric conditions had osmotic potentials 0.2 MPa lower than mesic plants and decreased elastic moduli at full hydration. The increase in tissue elasticity at elevated CO2 enabled the xeric plants to maintain positive turgor pressures at lower water potentials and tissue water contents. Surprisingly, the elevated CO2 plants under mesic conditions had the most inelastic tissues. We propose that this inelasticity may enable plants to generate a favorable water potential gradient from the soil to the plant despite the low stomatal conductances observed under elevated CO2 conditions.

Elevated CO2 differentially alters the responses of coocurring birch and maple seedlings to a moisture gradient.

To determine the effects of elevated CO2 and soil moisture status on growth and niche characteristics of birch and maple seedlings, gray birch (Betula populifolia) and red maple (Acer rubrum) were experimentally raised along a soil moisture gradient ranging from extreme drought to flooded conditions at both ambient and elevated atmospheric CO2 levels. The magnitude of growth enhancement due to CO2 was largely contingent on soil moisture conditions, but differently so for maple than for birch seedlings. Red maple showed greatest CO2 enhancements under moderately moist soil conditions, whereas gray birch showed greatest enhancements under moderately dry soil conditions. Additionally, CO2 had a relatively greater ameliorating effect in flooded conditions for red maple than for gray birch, whereas the reverse pattern was true for these species under extreme drought conditions. For both species, elevated CO2 resulted in a reduction in niche breadths on the moisture gradient; 5% for gray birch and 23% for red maple. Species niche overlap (proportional overall) was also lower at elevated CO2 (0.98 to: 0.88: 11%). This study highlights the utility of of experiments crossing CO2 levels with gradients of other resources as effective tools for elucidating the potential consequences of elevated CO2 on species distributions and potential interactions in natural communities.