Al and Fe Biogeochemistry in a floodplain forest: Implications for P retention

We examined spatial and temporal variationsin soil chemistry in a floodplain forest landscape todetermine the effects of flooding on aluminum (Al) andiron (Fe) oxide biogeochemistry and inorganicphosphorus (P_i) sorption capacity. Whenpreviously sorbed P_i was considered, the sorptioncapacities of floodplain and adjacent upland soilswere comparable, suggesting that floodplain soilsrepresent a second line of defense protectingdownstream aquatic ecosystems from agriculturalrun-off. P_i sorption capacity was highlycorrelated with oxalate-extractable Al (Al_o)(r_s = 0.78); Al_o and percent organic matter(OM) were also highly correlated (r_s = 0.72),suggesting the importance of OM-Al complexes in thesesoils. The correlation of oxalate-extractable Fe(Fe_o) with OM (r_s = 0.64) was improved(r_s = 0.80) by removing lower elevation (swale)soils, suggesting that flooding inhibits theassociation of Fe_o with OM. Fe oxidecrystallinity decreased during seasonal flooding, buttotal extractable Fe did not change significantly. Fesolubilized during flooding was either replaced bysediment deposition (252 ± 3 mmol kg^–1yr^–1), and/or reprecipitated locally. Al oxidecrystallinity also decreased during flooding due to asignificant decline in NaOH-extractable Al (Al_N). Al_N concentrations subsequently returned topre-flooding levels, but sediment Al inputs (57 ±3 mmol kg^–1 yr^–1), were insufficient to account for this recovery. Observed Fetransformations suggest the importance offlooding-induced declines in soil redox potential toFe biogeochemistry; observed Al transformationssuggest the importance of complexation reactions withsoil OM to Al biogeochemistry in this floodplainforest.     

Age and sex affect protein metabolism at protein intakes that span the range of adequacy: comparison of leucine kinetics and nitrogen balance data

Research suggests that changes in leucine oxidation (leu_ox) with feeding may reflect adult protein requirements. We evaluated this possibility by assessing the effects of age, sex, and different protein intakes on whole-body leucine kinetics and nitrogen balance. Thirty-four young (n= 18, 22–46 years) and old (n= 16, 63–81 years) men and women completed three 18-day trials with protein intakes of 0.50, 0.75 and 1.00 g protein·kg body weight^? 1·d^? 1. Fasting and fed-state leucine kinetics were quantified on day 12 of each trial using a primed, constant infusion of L-[1-13C]leucine. Protein requirement was estimated using classical nitrogen balance measurements and calculations. Leucine kinetics parameters were influenced by age and sex across all protein intakes. With feeding, leu_ox increased more in old vs. young adults. Independent of age, fasting and fed-state leu_ox were lower, and net leucine balance (fasting+fed-state) was higher in women vs. men. Among all subjects and protein intakes, nitrogen balance was correlated with fed-state leu_ox (r= 0.39), fed-state leucine balance (r= 0.60), net leucine balance (r= 0.49) and the change in leu_ox from the fasting to fed state (r= 0.49) (P<.05 for all results). At the highest protein intake, the change in leu_ox with feeding was inversely correlated with protein requirement (r=?0.39). These findings indicate that leucine kinetics, especially leu_ox, reflect nitrogen balance-based estimates of the need for dietary protein and generally support the view that protein requirement is comparable between young and old adults.     

Identification and Manipulation of Soil Properties To Improve the Biological Control Performance of Phenazine-Producing Pseudomonas fluorescens

Pseudomonas fluorescens 2-79RN₁₀ protects wheat against take-all disease caused by Gaeumannomyces graminis var. tritici; however, the level of protection in the field varies from site to site. Identification of soil factors that exert the greatest influence on disease suppression is essential to improving biocontrol. In order to assess the relative importance of 28 soil properties on take-all suppression, seeds were treated with strain 2-79RN₁₀ (which produces phenazine-1-carboxylate [PCA⁺]) or a series of mutants with PCA⁺ and PCA⁻ phenotypes. Bacterized seeds were planted in 10 soils, representative of the wheat-growing region in the Pacific Northwest. Sixteen soil properties were correlated with disease suppression. Biocontrol activity of PCA⁺ strains was positively correlated with ammonium-nitrogen, percent sand, soil pH, sodium (extractable and soluble), sulfate-sulfur, and zinc. In contrast, biocontrol was negatively correlated with cation-exchange capacity (CEC), exchangeable acidity, iron, manganese, percent clay, percent organic matter (OM), percent silt, total carbon, and total nitrogen. Principal component factor analysis of the 16 soil properties identified a three-component solution that accounted for 87 percent of the variance in disease rating (biocontrol). A model was identified with step-wise regression analysis (R² = 0.96; Cp statistic = 6.17) that included six key soil properties: ammonium-nitrogen, CEC, iron, percent silt, soil pH, and zinc. As predicted by our regression model, the biocontrol activity of 2-79RN₁₀ was improved by amending a soil low in Zn with 50 μg of zinc-EDTA/g of soil. We then investigated the negative correlation of OM with disease suppression and found that addition of OM (as wheat straw) at rates typical of high-OM soils significantly reduced biocontrol activity of 2-79RN₁₀.     

Effective Suppression of Methane Emission by 2-Bromoethanesulfonate during Rice Cultivation

2-bromoethanesulfonate (BES) is a structural analogue of coenzyme M (Co-M) and potent inhibitor of methanogenesis. Several studies confirmed, BES can inhibit CH₄ prodcution in rice soil, but the suppressing effectiveness of BES application on CH₄ emission under rice cultivation has not been studied. In this pot experiment, different levels of BES (0, 20, 40 and 80 mg kg^-1) were applied to study its effect on CH₄ emission and plant growth during rice cultivation. Application of BES effectively suppressed CH₄ emission when compared with control soil during rice cultivation. The CH₄ emission rates were significantly (P<0.001) decreased by BES application possibly due to significant (P<0.001) reduction of methnaogenic biomarkers like Co-M concentration and mcrA gene copy number (i.e. methanogenic abunadance). BES significantly (P<0.001) reduced methanogen activity, while it did not affect soil dehydrogenase activity during rice cultivation. A rice plant growth and yield parameters were not affected by BES application. The maximum CH₄ reduction (49% reduction over control) was found at 80 mg kg^-1 BES application during rice cultivation. It is, therefore, concluded that BES could be a suitable soil amendment for reducing CH₄ emission without affecting rice plant growth and productivity during rice cultivation.     

Response ofZea mays andLycopersicon esculentum to the ethylene precursors,L-methionine and L-ethionine applied to soil

Glasshouse experiments were conducted to evaluate the influence of L-methionine (L-MET) and L-ethionine (L-ETH) added to soil on the growth of corn (Zea mays L.) and tomato (Lycopersicon esculentum), respectively. The application of L-MET and L-ETH stimulated C₂H₄ production in soil by 299- and 313-fold, respectively, over an unamended control. An L-MET treatment of 1.85 mg kg⁻¹ soil was the most effective in increasing shoot height, shoot fresh weight, internodal distance, and stem diameter in two corn cultivars, Kandy Korn and Miracle, while shoot and root dry weights, leaf width, uppermost leaf collar base distance and resistance to stem breaking were increased in the case of Kandy Korn only. A significant epinastic response was observed in the second and third leaves of tomato plants when soil was treated with L-ETH. An L-ETH treatment of 0.2 mg kg⁻¹ soil resulted in the maximum fresh fruit yield, while 0.02 and 2.0 mg kg⁻¹ gave the most fruit and greater average weight of fresh fruit, respectively. Concentrations ranging from 0.002 to 2.0 mg L-ETH kg⁻¹ soil initiated early fruit formation. Early fruit ripening was observed with an application rate of 20 mg L-ETH kg⁻¹ soil. The mechanism of action of these chemicals could either be attributed to i) substrate-dependent C₂H₄ production in soil by the indigenous microflora, ii) uptake directly by plant roots followed by metabolism within the tissues, and/or iii) a change in the balance of rhizosphere microflora affecting plant growth.     

Effect of soil cadmium application and pH on growth and cadmium accumulation in roots, leaves and fruit of strawberry plants (Fragaria × ananassa Duch.)

Three strawberry (Fragaria × ananassa Duch.) cultivars Rainier, Totem and Selva were grown under greenhouse conditions in a Parkhill sandy loam soil with a background DTPA-extractable Cd concentration of 0.18 mg kg^-1 and a pH of 5.1. Experimental treatments included combinations of 4 Cd applications (0, 15, 30 and 60 mg Cd kg^-1 soil) applied as CdSO₄ and 2 soil pH values 5.1 and 6.8. Both the application of Cd and pH of the soil significantly affected plant growth, yield and Cd accumulation in plant tissue anf fruit. Although roots accumulated the highest concentrations of Cd of all plant parts investigated, increased soil Cd application reduced leaf weight more than root weight. In general, yield of strawberries was decreased by an increase in amount of soil-applied Cd, however the yield response varied among cultivars. At 60 mg Cd kg^-1 soil, yield of Rainier cultivar was reduced to 17.6% of control plants. Over 90% of total Cd taken up by plants grown in Cd-treated soil accumulated in roots, regardless of the Cd level in the soil. Root Cd concentrations ranged from 2.6 mg kg^-1 (control plants) to 505.7 mg kg^-1 (Totem plants grown in soil at highest Cd and a soil pH 5.1) and were directly related to soil Cd concentrations. Cd translocation from roots to leaves and fruit was very limited, resulting in a maximum Cd concentration in root leaf tissue of 10.2 mg kg^-1. Accumulation of Cd in fruit was found to correlate well with leaf Cd, although even at the highest amount of applied Cd, fruit Cd concentration did not exceed 700 g kg^-1 of fresh weight.Contribution no. 951     

Accumulation and excretion of pesticides used as insecticides or fungicides in agricultural products by the willow shiner Gnathopogon caerulescens

The average bioconcentration factors (BCF) in the whole body of willow shiner (Gnathopogon caerulescens) after 24–336 hr exposure were 810 for chlorpyriphosmethyl, 802 for vamidothion, 110 for edifenphos, 25 for ethoprophos, 83 for bendocarb, 39 for pirimicarb and 114 for methyl parathion. The correlations between a logarithm of 48 hr-Lc₅₀ to carp (log Lc₅₀ and the parameters (a logarithm of n-octanol-water partition coefficiens (log P_ow) and log BCF in willow shiner) were investigated for the pesticides studied here and already reported. The correlation factor (r) was −0.136 (N = 21) for log Lc₅₀ vs log P_ow and 0.039 (N = 24) for log Lc ₅₀ vs log BCF. The excretion rate constants (k) from the whole body of the fish were 0.01 hr⁻¹ for chlorpyriphosmethyl, 0.03 hr⁻¹ for vamidothion, 0.11 hr⁻¹ for edifenphos, 0.27 hr⁻¹ for ethoprophos, 0.18 hr⁻¹ for bendiocarb, 0.01 hr⁻¹ for pirimicarb and 0.08 hr⁻¹ for methyl parathion. The correlation between log k and log BCF was investigated for 22 pesticides already reported and studied here. The r value was not so high (−0.537, N = 22) but higher (−0.672, N = 2) in the case of excluding simetryne.     

Neutralizing a Surface Charge on the FMN Subdomain Increases the Activity of Neuronal Nitric-oxide Synthase by Enhancing the Oxygen Reactivity of the Enzyme Heme-Nitric Oxide Complex

Nitric-oxide synthases (NOSs) are calmodulin-dependent flavoheme enzymes that oxidize l-Arg to nitric oxide (NO) and l-citrulline. Their catalytic behaviors are complex and are determined by their rates of heme reduction (k_r), ferric heme-NO dissociation (k_d), and ferrous heme-NO oxidation (k_ox). We found that point mutation (E762N) of a conserved residue on the enzyme''s FMN subdomain caused the NO synthesis activity to double compared with wild type nNOS. However, in the absence of l-Arg, NADPH oxidation rates suggested that electron flux through the heme was slower in E762N nNOS, and this correlated with the mutant having a 60% slower k_r. During NO synthesis, little heme-NO complex accumulated in the mutant, compared with ∼50–70% of the wild-type nNOS accumulating as this complex. This suggested that the E762N nNOS is hyperactive because it minimizes buildup of an inactive ferrous heme-NO complex during NO synthesis. Indeed, we found that k_ox was 2 times faster in the E762N mutant than in wild-type nNOS. The mutational effect on k_ox was independent of calmodulin. Computer simulation and experimental measures both indicated that the slower k_r and faster k_ox of E762N nNOS combine to lower its apparent K_m,O2 for NO synthesis by at least 5-fold, which in turn increases its V/K_m value and enables it to be hyperactive in steady-state NO synthesis. Our work underscores how sensitive nNOS activity is to changes in the k_ox and reveals a novel means for the FMN module or protein-protein interactions to alter nNOS activity.Nitric oxide (NO)² is a biological mediator that is produced in animals by three NO synthase isozymes (NOS, EC 1.14.13.39): inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) (1, 2). The NOS are modular enzymes composed of an N-terminal oxygenase domain and a C-terminal flavoprotein domain, with a calmodulin (CaM)-binding site connecting the two domains (3). During NO synthesis, the flavoprotein domain transfers NADPH-derived electrons through its FAD and FMN cofactors to a heme located in the oxygenase domain. The FMN-to-heme electron transfer enables heme-dependent oxygen activation and a stepwise conversion of l-Arg to NO and citrulline (4, 5). Heme reduction also requires that CaM be bound to NOS and is rate-limiting for NO biosynthesis (6–9).NOS enzymes operate under the constraint of having their newly made NO bind to the ferric heme before it can exit the enzyme (10). How this intrinsic heme-NO binding event impacts NOS catalytic cycling is shown in Fig. 1 and has previously been discussed in detail (10–13). The l-Arg to NO biosynthetic reaction (Fe^III to Fe^IIINO in Fig. 1) is limited by the rate of ferric heme reduction (k_r), because all biosynthetic steps downstream are faster than k_r. However, once the ferric heme-NO complex forms at the end of each catalytic cycle, it can either dissociate to release NO into the medium (at a rate k_d as shown in Fig. 1) or become reduced by the flavoprotein domain (at a rate k′_r in Fig. 1; equal to k_r) to form the enzyme ferrous heme-NO species (Fe^IINO), which releases NO very slowly (11, 12). Consequently, two cycles compete during steady-state NO synthesis (Fig. 1); NO dissociation from the ferric heme (k_d) is part of a “productive cycle” that releases NO and is essential for NOS bioactivity, whereas reduction of the ferric heme-NO complex (k_r′) channels the enzyme into a “futile cycle” that actually represents a NO dioxygenase activity. The rate of futile cycling is also determined by the rate of O₂ reaction with the ferrous heme-NO complex (at a rate k_ox in Fig. 1), which regenerates the ferric enzyme. Surprisingly, NOS enzymes have evolved to have a broad range of k_r (varies 40×), k_ox (varies 15×), and k_d (varies 30×) values (Table S1) (12). This causes each NOS to distribute quite differently during steady-state NO synthesis and gives each NOS a unique catalytic profile (12).Open in a separate windowFIGURE 1.Global kinetic model for NOS catalysis. Ferric enzyme reduction (k_r) is rate-limiting for the biosynthetic reactions (central linear portion). k_cat1 and k_cat2 are the conversion rates of the enzyme Fe^IIO₂ species to products in the l-Arg and N^ω-hydroxy-l-arginine (NOHA) reactions, respectively. The ferric heme-NO product complex (Fe^IIINO) can either release NO (k_d) or become reduced (k′_r) to a ferrous heme-NO complex (Fe^IINO), which reacts with O₂ (k_ox) to regenerate ferric enzyme. Enzyme partitioning and NO release are determined by the relative rates of k_r, k_ox, and k_d. This figure is adapted from Ref. 12.The enzyme physical and electronic factors that may set and regulate each of the three kinetic parameters (k_r, k_ox, and k_d) in NOS enzymes remain to be fully described. At present, the composition of the NOS flavoprotein domain and CaM appear to be primarily responsible for determining the k_r (14–17), whereas the composition of the NOS oxygenase domain is presumed to determine the k_d and k_ox (18, 19). Indeed, our recent point mutagenesis study identified a patch of electronegative residues on the FMN subdomain that are required to maintain a normal k_r and NO synthesis activity in nNOS, suggesting that subdomain electrostatic interactions are important in the process (20). We found particularly large effects when the negative charge at Glu⁷⁶² was neutralized via mutation to Asn. Remarkably, the NO synthesis activity of E762N nNOS was double that of wild-type nNOS, despite the mutant displaying a slow k_r that was half of wild type. In the current report, we show that the E762N mutation has an additional, unsuspected effect on the k_ox kinetic parameter of nNOS. How this effect alters distribution of the nNOS enzyme during steady-state catalysis, impacts the apparent K_m,O2, and leads to hyperactive NO synthesis is described. Our finding that the nNOS flavoprotein domain can tune a key kinetic parameter that defines the rate of a heme-based reaction in the nNOS oxygenase domain is unusual and suggests a means by which protein-protein interactions could regulate the catalytic behavior of nNOS.     

Rare earth elements and relation between their potential bioavailability and soil properties, Nidda catchment (Central Germany)

Rare earth elements (REEs) are widely used in industry and the entry of REEs into the pedosphere is assumed. Data about REEs in soils are scarce since only a few studies discuss their ecologically relevant behavior. Hence, we investigated total contents (aqua regia digestion) and potentially bioavailable contents (EDTA extraction) of REEs in soils from the Nidda catchment in Hesse (Central Germany). The study site covers a 1,600 km² sized area and 232 soil samples from 63 soil profiles were examined. The total REE content varied considerably, ranging from 544 mg kg^?1 to 41 mg kg^?1 (mean 201.1 mg kg^?1) with a high proportion of light REEs. Highest REE contents were found in the soilscape VB, followed by LVB, WNE, T, WSW and BF with the smallest concentrations. With respect to the parent material the contents decreased in the following order: basalt > clay slate > loess > sandstone. On average 15.9% of the total REEs belong to the potentially bioavailable fraction. They range greatly by a factor of 100, between 1.3 and 171.3 mg kg^?1 (average 33.5 mg kg^?1). Remarkably, Yttrium has a maximum available proportion of 75%. In contrast, Ce showed the highest total contents with the smallest potentially bioavailable proportion of all elements. Regression analyses established relation between soil properties and the potential bioavailability of REEs. Around 53% (range from 29.9 to 76.8%) of the REE’s potential bioavailability variations could be explained by the chosen variables (pH, clay and C_org contents and the total element concentrations). Occurrence patterns and concentrations of REEs lie within the range of the results found in the available literature. Bioavailability is linked to soil properties and varies greatly according to the individual element. In comparison with the chosen soil properties the pH value shows the least impact on bioavailability.     

Ca2+ Influx via the Na+/Ca2+ Exchanger Is Enhanced in Malignant Hyperthermia Skeletal Muscle

Malignant hyperthermia (MH) is potentially fatal pharmacogenetic disorder of skeletal muscle caused by intracellular Ca²⁺ dysregulation. NCX is a bidirectional transporter that effluxes (forward mode) or influxes (reverse mode) Ca²⁺ depending on cellular activity. Resting intracellular calcium ([Ca²⁺]_r) and sodium ([Na⁺]_r) concentrations are elevated in MH susceptible (MHS) swine and murine muscles compared with their normal (MHN) counterparts, although the contribution of NCX is unclear. Lowering [Na⁺]_e elevates [Ca²⁺]_r in both MHN and MHS swine muscle fibers and it is prevented by removal of extracellular Ca²⁺ or reduced by t-tubule disruption, in both genotypes. KB-R7943, a nonselective NCX3 blocker, reduced [Ca²⁺]_r in both swine and murine MHN and MHS muscle fibers at rest and decreased the magnitude of the elevation of [Ca²⁺]_r observed in MHS fibers after exposure to halothane. YM-244769, a high affinity reverse mode NCX3 blocker, reduces [Ca²⁺]_r in MHS muscle fibers and decreases the amplitude of [Ca²⁺]_r rise triggered by halothane, but had no effect on [Ca²⁺]_r in MHN muscle. In addition, YM-244769 reduced the peak and area under the curve of the Ca²⁺ transient elicited by high [K⁺]_e and increased its rate of decay in MHS muscle fibers. siRNA knockdown of NCX3 in MHS myotubes reduced [Ca²⁺]_r and the Ca²⁺ transient area induced by high [K⁺]_e. These results demonstrate a functional NCX3 in skeletal muscle whose activity is enhanced in MHS. Moreover reverse mode NCX3 contributes to the Ca²⁺ transients associated with K⁺-induced depolarization and the halothane-triggered MH episode in MHS muscle fibers.     

Chiral spin crossover iron(II) complex, fac-Λ-[Fe(HL)3](ClO4)2·EtOH (HL = 2-methylimidazol-4-yl-methylideneamino-R-(+)-1-methylphenyl)

A chiral spin crossover iron(II) complex, fac-Λ-[Fe^II(HL^R)₃](ClO₄)₂·EtOH was synthesized and its crystal structures in both the high-spin (HS) and low-spin (LS) states were determined, where HL^R denotes 2-methylimidazol-4-yl-methylideneamino-R-(+)-1-methylphenyl. The complex assumes octahedral coordination geometry of N₆ donor atoms by three bidentate ligands HL^R. The complex exists as the facial-Λ-isomer of fac-Λ-[Fe^II(HL^R)₃]²⁺ of the possible geometrical fac- and mer-isomers and the Δ- and Λ-enantiomorphs. The X-ray structural analyses revealed that the R-form of the ligand (HL^R) induces the fac-Λ-isomer of fac-Λ-[Fe^II(HL^R)₃]²⁺ and the S-form of the ligand (HL^S) induces the fac-Δ-isomer of fac-Δ-[Fe(HL^S)₃]²⁺. The complex fac-Λ-[Fe^II(HL^R)₃](ClO₄)₂·EtOH shows a complete steep spin crossover between the HS and the LS states at T_1/2 = 195 K.     

Phosphorus Accumulation and Sorption in Calcareous Soil under Long-Term Fertilization

Application of phosphorus (P) fertilizers to P-deficient soils can also result in P accumulation. In this study, soil P status and P uptake by apple trees were investigated in 5-, 10-, and 15-year-old orchards in the semi-arid Loess Plateau, China, and subset soils with different soil P statuses (14–90 Olsen-P mg kg⁻¹) were selected to evaluate the characteristic P adsorption. Due to the low P-use efficiency (4–6%), total soil P increased from 540 mg kg⁻¹ to 904 mg kg⁻¹, Olsen-P ranged from 3.4 mg kg⁻¹ to 30.7 mg kg⁻¹, and CaCl₂-P increased from less than 0.1 mg kg⁻¹ to 0.66 mg kg⁻¹ under continuous P fertilization. The P sorption isotherms for each apple orchard were found to fit the Langmuir isotherm model (R ² = 0.91–0.98). K (binding energy) and Q _m (P sorption maximum) decreased, whereas DPS (degree of phosphorus sorption) increased with increasing P concentration. CaCl₂-P increased significantly with the increase of Olsen-P, especially above the change point of 46.1 mg kg⁻¹. Application of surplus P could result in P enrichment in P-deficient soil which has high P fixation capacity, thus posing a significant environmental risk.     

Synthesis and characterization of [Fe(III)(qsal)2][M(III)(pds)2] (M = Cu, Au)

Salts of the Fe(III) spin crossover cation [Fe^III(qsal)₂]⁺ (qsalH = N-(8-quinolyl)salicylaldimine) and monoanions [M^III(pds)₂]⁻ (M = Cu, Au; pds = pirazine-2,3-diselenolate) with formula [Fe^III(qsal)₂][M^III(pds)₂] were prepared and characterized by single crystal X-ray diffraction and magnetic measurements. These two salts present magnetic properties essentially due to the Fe^III centres in the high-spin state (S = 5/2), and do not have any spin transition.     

Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S) and Molybdenum (Mo) in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm) were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO₃, NaOH, HCl, and HClO₄–HNO₃. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg^?1, and 177 to 1509 mg kg^?1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg^?1, respectively. Average total Mo in Kelantan were 0.25 mg kg^?1 (surface layer) and 0.28 mg kg^?1 (subsoil). Cation exchange capacity (CEC) was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C) at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities.     

The kinetics of the complex formation between iron(III)-ethylenediaminetetraacetate and hydrogen peroxide in aqueous solution

The kinetics of the formation of the purple complex [Fe^III(EDTA)O₂]³⁻, between Fe^III-EDTA and hydrogen peroxide was studied as a function of pH (8.22-11.44) and temperature (10-40 °C) in aqueous solutions using a stopped-flow method. The reaction was first-order with respect to both reactants. The observed second-order rate constants decrease with an increase in pH and appear to be related to deprotonation of Fe^III-EDTA ([Fe(EDTA)H₂O]⁻ ⇔ Fe(EDTA)OH]²⁻ + H⁺). The rate law for the formation of the complex was found to be d[Fe^IIIEDTAO₂]³⁻/dt=[(k₄[H⁺]/([H⁺] + K₁)][Fe^III-EDTA][H₂O₂], where k₄=8.15±0.05×10⁴ M⁻¹ s⁻¹ and pK₁=7.3. The steps involved in the formation of [Fe(EDTA)O₂]³⁻ are briefly discussed.     

Background Intestinal 18F-FDG Uptake Is Related to Serum Lipid Profile and Obesity in Breast Cancer Patients

Background

This study investigated the relationships between background intestinal uptake on ¹⁸F–FDG PET and cardio-metabolic risk (CMR) factors.

Methods

A total of 326 female patients that underwent ¹⁸F–FDG PET to determine the initial stage of breast cancer were enrolled. None of the patients had history of diabetes or hypertension. The background intestinal uptake on PET was visually graded (low vs. high uptake group) and quantitatively measured using the maximal standardized uptake value (SUV_max). SUV_max of 7 bowel segments (duodenum, jejunum, ileum, cecum, hepatic flexure, splenic flexure, and descending colon-sigmoid junction) were averaged for the total bowel (TB SUV_max). Age, body mass index (BMI), fasting blood glucose level (BST), triglyceride (TG), cholesterol, high density lipoprotein (HDL), and low density lipoprotein (LDL) were the considered CMR factors. The relationships between background intestinal ¹⁸F–FDG uptake on PET and diverse CMR factors were analyzed.

Results

The visual grades based on background intestinal ¹⁸F–FDG uptake classified 100 (30.7%) patients into the low uptake group, while 226 (69.3%) were classified into the high uptake group. Among CMR factors, age (p = 0.004), BMI (p<0.001), and TG (p<0.001) were significantly different according to visual grade of background intestinal ¹⁸F–FDG uptake. Quantitative TB SUV_max showed significant positive correlation with age (r = 0.203, p<0.001), BMI (r = 0.373, p<0.001), TG (r = 0.338, p<0.001), cholesterol (r = 0.148, p = 0.008), and LDL (r = 0.143, p = 0.024) and significant negative correlation with HDL (r = -0.147, p = 0.022). Multivariate analysis indicated that BMI and TG were independent factors in both visually graded background intestinal ¹⁸F–FDG uptake (p = 0.027 and p = 0.023, respectively) and quantitatively measured TB SUV_max (p = 0.006 and p = 0.004, respectively).

Conclusion

Increased background intestinal ¹⁸F–FDG uptake on PET may suggest alteration of lipid metabolism and risk of cardio-metabolic disease in non-diabetic and non-hypertensive breast cancer patients.     

Remediation of Nitrobenzene Contaminated Soil by Combining Surfactant Enhanced Soil Washing and Effluent Oxidation with Persulfate

The combination of surfactant enhanced soil washing and degradation of nitrobenzene (NB) in effluent with persulfate was investigated to remediate NB contaminated soil. Aqueous solution of sodium dodecylbenzenesulfonate (SDBS, 24.0 mmol L^-1) was used at a given mass ratio of solution to soil (20:1) to extract NB contaminated soil (47.3 mg kg^-1), resulting in NB desorption removal efficient of 76.8%. The washing effluent was treated in Fe²⁺/persulfate and Fe²⁺/H₂O₂ systems successively. The degradation removal of NB was 97.9%, being much higher than that of SDBS (51.6%) with addition of 40.0 mmol L^-1 Fe²⁺ and 40.0 mmol L^-1 persulfate after 15 min reaction. The preferential degradation was related to the lone pair electron of generated SO₄•⁻, which preferably removes electrons from aromatic parts of NB over long alkyl chains of SDBS through hydrogen abstraction reactions. No preferential degradation was observed in •OH based oxidation because of its hydrogen abstraction or addition mechanism. The sustained SDBS could be reused for washing the contaminated soil. The combination of the effective surfactant-enhanced washing and the preferential degradation of NB with Fe²⁺/persulfate provide a useful option to remediate NB contaminated soil.     

Sedimentation-Diffusion Equilibrium of Monomer-Dimer Mixtures, Studied in the Analytical Ultracentrifuge

By generalizing the fundamental differential equation valid for a single ideal solute, it is usual to define, for a monomer-dimer nonideal mixture, an apparent molecular weight M_w,app = (2RT/[1 - ρV]ω²) (d lnc/dr²); RT has the usual meaning; ρ is the density of the solvent; V is the partial specific volume of the solute, assumed to be the same for the monomer and the dimer; w is the angular velocity of the rotor; c is the solute concentration at the radial position r in the cell. It is shown here that the above equation can be integrated in the case of a monomer-dimer nonideal mixture and that, after integration, we obtain the following relation between c and r: ([1 + 4Kc]^1/2 - 1)/([1 + 4Kc₀]^1/2 - 1]) exp (BM_m[c - c₀]) = exp ([σ_m/2] [r² - r₀²]); σ_m = M_m(1 - ρV)ω²/RT (M_m = molecular weight of the monomer); K is the monomer-dimer equilibrium constant; B is the second virial coefficient, assumed to be the same for the monomer and the dimer. As soon as M_m is known, the above equation permits the calculation of K and B, from the experimental curve c(r). Moreover, the reversibility of the monomer-dimer equilibrium can be tested from this equation: it is necessary and sufficient that the values of K corresponding to different loading concentrations in the cell are identical.     

Methane oxidation and methane driven redox process during sequential reduction of a flooded soil ecosystem

A laboratory incubation study conducted to assess the temporal variation of CH₄ oxidation during soil reduction processes in a flooded soil ecosystem. A classical sequence of microbial terminal electron accepting process observed following NO₃ ^? reduction, Fe³⁺ reduction, SO₄ ^2? reduction and CH₄ production in flooded soil incubated under initial aerobic and helium-flushed anaerobic conditions. CH₄ oxidation in the slurries was influenced by microbial redox process during slurry reduction. Under aerobic headspace condition, CH₄ oxidation rate (k) was stimulated by 29 % during 5 days (NO₃ ^? reduction) and 32 % during both 10 days (Fe³⁺) and 20 days (early SO₄ ^2? reduction) over unreduced slurry. CH₄ oxidation was inhibited at the later methanogenic period. Contrastingly, CH₄ oxidation activity in anaerobic incubated slurries was characterized with prolonged lag phase and lower CH₄ oxidation. Higher CH₄ oxidation rate in aerobically incubated flooded soil was related to high abundance of methanotrophs (r?=?0.994, p?<?0.01) and ammonium oxidizers population (r?=?0.184, p?<?0.05). Effect of electron donors NH₄ ⁺, Fe^2+, S^2? on CH₄ oxidation assayed to define the interaction between reduced inorganic species and methane oxidation. The electron donors stimulated CH₄ oxidation as well as increased the abundance of methanotrophic microbial population except S^2? which inhibited the methanotrophic activity by affecting methane oxidizing bacterial population. Our result confirmed the complex interaction between methane-oxidizing microbial groups and redox species during sequential reduction processes of a flooded soil ecosystem.     

EPR study of iron status in human body during intensive physical activity

The iron metabolism was studied in serum blood samples collected from 26 professional sportsmen undergoing intensive physical exercises using EPR combined with hematological and biochemical laboratory tests. Only 23% of EPR spectra (n = 6) were practically normal while in the rest spectra additional abnormal absorption lines were detected. Presumably, the significant portion of new signals may be caused by different cytochromes. Moreover, the anisotropic signals with g ₁ ? 2.02; g ₂ ? 1.94 and g ₃ ? 1.86 registered in some spectra pointed to the sulfur-iron centers. There was nearly linear correlation between the concentration of Fe³⁺ in transferrin (Fe³⁺-Tf) obtained from the EPR spectra and the serum iron concentration measured by absorption photometry both for sportsmen and controls (healthy individuals and patients with different diseases). At equal serum iron concentrations the Fe³⁺-Tf level was higher in sportsmen than that in controls. The Pearson correlation coefficient (r) for Fe³⁺-Tf and serum iron values was equal to 0.89 in sportsmen versus r = 0.97 in controls. Additional new lines in serum EPR spectra of professional sportsmen prove the suitability of EPR assay for scheduled medical exams since routine biochemical and hematological tests are insufficient to discover all abnormalities in iron metabolism under intensive physical exercises.