The effects of flooding for rice culture on soil chemical properties and subsequent maize growth

Summary The effects of flooding and lowland rice culture on soil chemical properties and subsequent maize growth were investigated in two contrasting rice soils of S.E. Australia. The effects of incorporating rice straw, either during or after flooding were also studied. The experiment was conducted in a glasshouse with the use of large intact soil cores.Previous flooding markedly reduced maize growth, leaf P concentration and P uptake, despite the application of a large quantity of P fertilizer after drainage. Soil analyses showed that previous flooding increased the Langmuir sorption terms for maximum P sorption and bonding energy. The availability of P was more closely related to the bonding energy between soil and P than to the capacity of the soils to sorb P. The increases, in the P sorption parameters, were associated with decreases in the crystallinity of the free iron oxides as determined by their oxalate solubility. It was concluded that depressed P supply to maize sown in previously flooded soils was due to stronger P sorption by the drained soils, rather than to P immobilization during flooding.Rice plants grown during flooding reduced the amount of N available to the subsequent maize crop, but did not significantly affect P availability. Rice straw added during flooding did not affect subsequent maize growth, but when added after flooding caused microbial immobilization of N.Salts, Fe or Mn from previous flooding did not affect maize growth.     

Changes in Al and Fe crystallinity and P sorption capacity in a flood-plain forest soil subjected to artificially manipulated flooding regimes in field mesocosms

Changes in noncrystalline Fe and P sorption capacity in soils subjected to flooding and draining for rice cultivation sparked interest in how periodic flooding in natural riparian wetlands influences soil chemistry and P retention. We examined monthly changes in soil oxalate-extractable Al and Fe, NaOH-extractable Al, DCB-extractable Fe, and P sorption capacity as a function of flooding regime in artificially manipulated field mesocosms installed in a floodplain forest along the Ogeechee River, near Savannah, GA. We hypothesized that: (1) flooding would cause increases in both oxalate-extractable (noncrystalline) Al and Fe concentrations and P sorption capacity, and, (2) this effect would be augmented by increased flooding duration and periodicity. Flooding resulted in increases in oxalate-extractable Al in flooded-drained and periodically flooded soils, decreases in crystalline Fe in all flooding treatments, and an increase in P sorption capacity in flooded-drained soils. However, consistent trends were not observed across all treatment regimes. Potential confounding factors include a lack of synchronicity of experimental and natural flooding cycles, spatial variability of soil chemistry, and increased soil wetness in the treatment field, variables that should be considered in future attempts at elucidating relationships between flooding, soil chemistry and wetland function.     

Effects of temperature and prior flooding on intensity and sorption of phosphorus in soil

Summary Effects of temperature and flooded-drained soil conditions on 0.01M CaCl₂ extractable phosphorus (soluble P) were investigated in four soils over the period of 42 days after fertilizer-P application. These soils show severe induced P deficiency problem in crops following flooded rice culture. The effects of temperature on the reaction rate constants were determined and activation energy was calculated. Increasing soil temperature as well as prior flooding of soil decreased soluble P concentration but the effect of the latter was dominant. The decrease in soluble P concentration in these soils with time followed a first order kinetics and the rate constant (K₁) increased as the temperature increased from 10°C to 30°C. The activation energy (Ea) for the kinetics of soluble P concentration in soil, as affected by temperature, was found to be 8.9 and 34.5 KJ mol⁻¹ for Meyers and Willows clay, respectively, over the temperature range studied.     

Phosphorus dynamics within agricultural drainage ditches in the lower Mississippi Alluvial Valley

Excessive phosphorus loading from fertilizers in agriculture results in enriched runoff and downstream aquatic system eutrophication. This study evaluated phosphorus dynamics in agricultural drainage ditches across eight sites within the Lower Mississippi Alluvial Valley (LMAV). The objective of the study was to examine the capacity of drainage ditches across the LMAV to sorb P. Spatially and temporally, all drainage ditch sediments had very low immediately bioavailable phosphorus (P_w), and a very low degree of phosphorus saturation (DPS < 20%) throughout the LMAV. Phosphorus binding energy (K) (0.34-0.60 L/mg) and P sorption maxima (17.8-26.6 L/mg) were low, with very little variation in space and time. Using these metrics, drainage ditches sampled within the LMAV could be described as P sinks, capable of sorbing varying degrees of P seasonally as a result to changes in the Fe-P pool. Sorption, however, will likely be low due to low P sorption maxima and low binding energies. These results will help in P management within primary aquatic systems (such as drainage ditches) within the agricultural landscape and enhance P mitigation strategies at the source, prior to runoff reaching downstream aquatic systems.     

Microbially Available Phosphorus in Boreal Forests: Effects of Aluminum and Iron Accumulation in the Humus Layer

Soil microorganisms play an important role in the mobilization of phosphorus (P), and these activities may be beneficial for plant P utilization. We investigated the effects on microbial P availability of different combinations of aluminum and iron (Al + Fe) concentrations and different P pools in humus soils from boreal forest ecosystems. We measured respiration rates in laboratory incubations before and after additions of glucose plus (NH₄)₂SO₄ (Glu+N), with or without a small dose of KH₂PO₄. Glu+N was added in excess so that the availability of the inherent soil P would be growth-limiting for the microorganisms. The exponential increases observed in microbial growth after substrate additions (Glu+N) was slower for humus soils with high Al+Fe concentrations than for humus soils with low Al+Fe concentrations. Adding a small dose of KH₂PO₄ to humus soils with high Al+Fe concentrations did, however, increase the exponential growth, measured as the slope of the log-transformed respiration rates, by more than 200%. By contrast, the average increase in exponential growth was only 6% in humus soils with low Al+Fe concentrations. Almost eight times more carbon dioxide (CO₂) was evolved between the substrate additions and the point at which the respiration rate reached 1 mg CO₂ h^–1 for soils with high Al+Fe concentrations compared to humus soils with low Al+Fe concentrations. The amount of CO₂ evolved was positively related to the Al+Fe concentration of the humus soils (r ² = 0.86, P < 0.001), whereas the slope was negatively related to Al+Fe concentration (r ² = 0.70, P < 0.001). Easily available P forms were negatively related to the Al+Fe concentration, whereas organic P showed a strong positive relationship to Al+Fe (r ² = 0.85, P < 0.001), suggesting that other forms of P, as well as inorganic P, are affected by the increased sorption capacity. The results indicate that P mobilization by microorganisms is affected by the presence of sorption sites in the humus layer, and that this capacity for sorption may relate not only to phosphate but also to organic P compounds.     

Phosphorus status of some saline and non-saline hydromorphic soils of the Niger Delta of Nigeria

Summary The phosphorus status of some mangrove and fresh-water hydromorphic soils of the Nigerian Niger Delta was evaluated by determining the relative abundance of various P forms and the P-sorption capacity indices. Total P was high in all soils ranging from 352 to 2055 mg/kg, with a mean of 1011 mg/kg. The saline mangrove-swamp soils had generally higher values than the fresh-water soils. Organic P formed about 34% of total P. The relative abundance of the inorganic P forms was in decreasing order, active P, occluded P and residual P. The relative distribution of active P followed the decreasing order, Fe–P, Al–P and Ca–P.The adsorption capacity was generally low in all soils. The amount of P sorbed from the addition of 150 mg/100g of soil ranged from zero to 13 mg/100g, giving an average of about 7% of added P sorbed.The abundance of active P and low content of occluded P were attributed to the poorly drained and unweathered nature of the soils. The low P adsorption suggests little capacity of the soils to fix P. The relatively high content of active P and the low P sorption capacity generally indicate high availability of P to plant in these soils.     

Vertical distribution of biological and geochemical phosphorus subcycles in two southern Appalachian forest soils

We measured Al, Fe, and P fractions by horizon in two southern Appalachian forest soil profiles, and compared solution PO₄ ^–1 removal in chloroform-sterilized and non-sterilized soils, to determine whether biological and geochemical P subcycles were vertically stratified in these soils. Because organic matter can inhibit Al and Fe oxide crystallization, we hypothesized that concentrations of non-crystalline (oxalate-extractable) Al (Al₀) and Fe (Fe₀), and concomitantly P sorption, would be greatest in near-surface mineral (A) horizons of these soils.Al₀ and Fe₀ reached maximum concentrations in forest floor and near-surface mineral horizons, declined significantly with depth in the mineral soil, and were highly correlated with P sorption capacity. Small pools of readily acid-soluble (AF-extractable) and readily-desorbable P suggested that PO₄ ^3– was tightly bound to Al and Fe hydroxide surfaces. P sorption in CHCl₃-sterilized mineral soils did not differ significantly from P sorption in non-sterilized soils, but CHCl₃ sterilization reduced P sorption 40–80% in the forest floor. CHCl₃ labile (microbial) P also reached maximum concentrations in forest floor and near-surface mineral horizons, comprising 31–35% of forest floor organic P. Combined with previous estimates of plant root distributions, data suggest that biological and geochemical P subcycles are not distinctly vertically stratified in these soils. Plant roots, soil microorganisms, and P sorbing minerals all reach maximum relative concentrations in near-surface mineral horizons, where they are likely to compete strongly for PO₄ ^3– available in solution.     

Reducing Copper Availability in Contaminated Soils Using Drinking Water Treatment Residuals

Copper mobility and availability in soil environments is largely controlled by Cu sorption reactions as well as its chemical forms. In this study, equilibrium, kinetic batch experiments, and a chemical fractionation scheme were carried out to evaluate effects of drinking water treatment residual (DWTR) application on sorption and bioavailability of Cu in three arid zone soils having different properties. Distinct differences in the amounts of Cu sorbed among the different soils were observed where highest sorption was associated with clay, OM, and CEC contents. The quantity of Cu sorbed on the three studied soils drastically increased as a result of increasing rates of DWTR application from 2% to 12% (w/w). Freundlich distribution coefficient (K_f) values indicate that Cu sorption affinities for the studied soils followed the trend Typic torrifluvent (TF) > Typic calciorthids (CO) > Typic torripsamment (TP) soils. The sorption of Cu was initially fast with 95, 92, and 73% of Cu sorbed on TF and CO and TP unamended soils, respectively, in the first 60 min. Following the initial fast reaction, the sorption reaction continued for 63 h, after which only a small amount of additional sorption occurred (2–6%). The parabolic diffusion law and the power function models described Cu sorption kinetics in all the sorbents studied equally well as the R² values were quite high and SE values were low. Addition of DWTR drastically reduced non-residual (NORS) Cu and simultaneously increased residual (RS) Cu fractions. At 12% application rate, DWTR decreased NORS-Cu in nonamended soils from 10.9 to 4.2, from 50.2 to 21.5, and from 78.6 to 33.3% in TF, CO, and TP soils, respectively. Our results suggest that as the application rate of DWTR to Cu-contaminated soils increased, more Cu was associated with the residual fractions, which decreased potential Cu mobility and bioavailability in these soils.     

Effect of soil flooding on photosynthesis,carbohydrate partitioning and nutrient uptake in the invasive exotic Lepidium latifolium

Lepidium latifolium L. is an invasive exotic crucifer that has spread explosively in wetlands and riparian areas of the western United States. To understand the ecophysiological characteristics of L. latifolium that affect its ability to invade riparian areas and wetlands, we examined photosynthesis, chlorophyll concentration, carbohydrate partitioning and nutrient uptake in L. latifolium in response to soil flooding. Photosynthesis of flooded plants was about 60–70% of the rate of unflooded controls. Chlorophyll concentrations of flooded plants were about 60–70% of the unflooded plants during 15–50 days of flooding. Flooding resulted in an increase in leaf starch concentration, but root starch concentration was not significantly affected. However, concentrations of soluble sugar were significantly higher in both leaves and roots of flooded plants than unflooded controls. On day 50 after initial flooding, the concentrations of N, P, K and Zn in leaves of flooded plants were lower than in control plants. The concentrations of Mn and Fe in leaves of flooded plants were eight and two times those of control plants, respectively. In contrast, N, P, K and Zn concentrations of roots of flooded plants were slightly higher than in unflooded plants. The concentrations of Fe and Mn in roots of flooded plants were 15 and 150 times those of the control plants, respectively. The transport of P, K, and Zn to shoots decreased and that of Mn increased under flooding. The accumulation of N, K and Zn in roots decreased and that of Mn increased in response to flooding. The results suggested that the maintenance of relatively high photosynthesis and the accumulation of soluble sugar in roots of flooded plants are important adaptations for this species in flooded environments. Despite a reduction in photosynthesis and disruption in nutrient and photosynthate allocation in response to flooding, L. latifolium was able to survive 50 days of flooding stress. Overall, L. latifolium performed like a facultative hydrophyte species under flooding.     

Legacy phosphorus in subtropical wetland soils: Influence of dairy, improved and unimproved pasture land use

Wetlands provide various ecosystem services. One of these services includes nutrient storage in soils. Soils retain and release nutrients such as phosphorus (P). This dynamic can be controlled by soil characteristics, overlying water quality, environmental conditions and historical nutrient loading. Historical nutrient loading contributes to a legacy of P stored in soils and this may influence present day P dynamics between soil and water. We quantified P characteristics of wetland soils and determined the availability and capacity of soils to retain additional P loadings. We sampled surface (0-10) and subsurface (10-30) wetland soils within dairy, improved and unimproved pastures. Surface soils had much greater concentrations of organic and inorganic P. Wetland soils in dairy had greatest concentrations of Ca and Mg, probably due to inputs of inorganic fertilizer. They also had much greater total P, inorganic P, and P sorption capacity; however, these soils were P saturated and had little capacity to retain additional P loading. Improved and unimproved pasture wetland soils had greatest amounts of organic P (>84%) and a capacity to store additional P loadings. Using multivariate statistics, we determined that rather than being different based on land use, wetland soils in improved and unimproved pasture were dissimilar based upon organic matter, organic P fractions, residual P, and soil metal (Fe and Al) content. The legacy of stored P in soils, particularly wetland soils from dairies, combined with best management practices (BMPs) to reduce nutrient loading to these systems, could contribute to a short-term release of soil-stored P to overlying wetland water.     

Phosphorus Transformations in an Oxisol under contrasting land-use systems: The role of the soil microbial biomass

It is generally assumed that phosphorus (P) availability for plant growth on highly weathered and P-deficient tropical soils may depend more on biologically mediated organic P (P_o) turnover processes than on the release of adsorbed inorganic P (P_i). However, experimental evidence showing the linkages between P_o, microbial activity, P cycling and soil P availability is scarce. To test whether land-use systems with higher soil P_o are characterized by greater soil biological activity and increased P mineralization, we analyzed the partitioning of P among various organic and inorganic P fractions in soils of contrasting agricultural land-use systems and related it to biological soil properties. Isotopic labeling was used to obtain information on the turnover of P held in the microbial biomass. Soil samples were taken from grass–legume pasture (GL), continuous rice (CR) and native savanna (SAV) which served as reference. In agreement with estimated P budgets (+277, +70 and 0 kg P ha^–1 for CR, GL and SAV, respectively), available P estimated using Bray-2 and resin extraction declined in the order CR > GL > SAV. Increases in Bray-2 and resin P_i were greater in CR than GL relative to total soil P increase. Organic P fractions were significantly less affected by P inputs than inorganic fractions, but were a more important sink in GL than CR soils. Extractable microbial P (P_chl) was slightly higher in GL (6.6 mg P kg^–1) than SAV soils (5.4 mg P kg^–1), and significantly lowest in CR (2.6 mg P kg^–1). Two days after labeling the soil with carrier free ³³P, 25, 10 and 2% of the added ³³P were found in P_chl in GL, SAV and CR soils, respectively, suggesting a high and rapid microbial P turnover that was highest in GL soils. Indicators of P mineralization were higher in GL than CR soils, suggesting a greater transformation potential to render P_o available. Legume-based pastures (GL) can be considered as an important land-use option as they stimulate P cycling. However, it remains to be investigated whether crops planted in pasture–crop rotations could benefit from the enhanced P_o cycling in grass–legume soils. Furthermore, there is need to develop and test a direct method to quantify P_o mineralization in these systems.     

Effects of Sterilization and Temperature on the Decrease Kinetic of Lead Bioavailability in Two Different Soil Groups

Sorption of metal ions by soil and clay minerals is a complex process involving different mechanisms, and controlled by different variables that can interact. The impacts of sterilization and incubation temperature on the decrease kinetic of Pb bioavailability in two different groups of soils were studied. Surface soils were sampled from Guilan and Hamadan provinces in the north and northwest of Iran with temperate and semiarid climates. The decrease kinetic of Pb bioavailability in the Pb(NO₃)₂ treated (400 μg Pb g^?1) soils has been studied in solid state incubation in sterile and unsterile conditions at 15, 27 and 37°C. The decrease of DTPA-extractable Pb in both groups of soils is often characterized by an initial rapid step followed by a slow step. The temperate soil with high affinity surface sites for Pb sorption compared to semiarid soils had a lower DTPA-extractable Pb in each time of extraction. Sterilization and soil incubation at lower temperature decreased the rate of Pb sorption/precipitation processes. Among the kinetic models the second order model and Elovich kinetic equation were the better choice to express the decrease kinetic of Pb bioavailability according to higher determined coefficient and the small standard error of the estimate. The determination coefficients of the mass transfer equation were increased and the standard errors of the estimates were decreased in sterile and unsterile conditions by increasing incubation temperature from 15 to 37°C.     

Effects of phosphate sorptivity on long-term plant recovery and effectiveness of fertilizer phosphate in soils

Summary A greenhouse experiment was carried out on 30 soils of eastern Australia in the first year and 15 soils in the following years to determine the effects of soil phosphate sorptivity and phosphate removal in harvested material on effectiveness and recovery of fertilizer phosphate by white clover during a four year period.Phosphate recovery by the clover and fertilizer effectiveness were primarily negative functions of phosphate sorptivity. After the first year there was a progressive decrease in the sorptivity effect such that the subsequent decreases in phosphate recovery and effectiveness were largest on weakly sorptive soils and smallest on strongly sorptive soils. In the long term the cumulative effects of the apparently slow immobilizing reactions on the weakly sorptive soils tended to equalize the effects of faster reactions on strongly sorptive soils so that the actual recovery and effectiveness in the final year were similar on all soils regardless of their sorptivities. The cumulative recovery and cumulative effectiveness in the long term, however, remained strongly negative functions of sorptivity. Phosphate removal in harvested material caused large decreases in phosphate effectiveness on all soils and particularly on weakly sorptive soils.     

On the tropical soils; The influence of organic matter (OM) on phosphate bioavailability

Application of organic manure (OM) and crop residues in agricultural soils can potentially influence positively or negatively the availability of soil phosphorus (P) through soil mineralization, sorption, or desorption of soil-bound P. Traditionally, the addition of OM can reduce the capacity of the soil colloids to adsorb P, thus increasing the release of P in soil solution, but also added OM can increase the adsorption site and increase the fixation or sorption of P to soil colloids, thus reducing the availability of P in soil solution and loss to the environment. The highly weathered tropical soils (HWTS) are susceptible to P insufficiency because HWTS have high P adsorption and fixation; this is mainly due to high concentration of P adsorbent. The main P adsorbents in HWTS include Al, Fe, Ca, and clay minerals, which are principally the same binding or adsorbent for OM compounds, but in excess, are toxic (Al and Fe) to crops. Thus, the presence of OM in HWTS can compromise the adsorption and availability of P in agricultural soils following phosphatic fertilizer applications. In this study, the influence of OM on P adsorption and availability was characterized to have a clear understanding of how OM influences P availability in agricultural soils, especially in highly weathered tropical soil. It is clearly outlined that the application of OM and crop residues can positively or negatively influence the availability of P in agricultural soils for plant uptake and dictate the P that is available for loss to the environment. Thus, the addition of organic matter as a strategy to increase P bioavailability for plant uptake must be treated with care because their contribution is not strait forward to be positive in many agricultural soils.     

Speciation and dynamics of phosphorus in some organically amended soils of southwestern Nigeria

Availability of soil phosphorus (P) is a function of its dynamics and can be improved by using organic amendments. Experiments were carried out to determine the effect of poultry manure (PM) on soil P fractions and bioavailability to soybean (Glycine max). Soils from ten farmers’ fields in Southwest Nigeria, were used for incubation and pot experiments. Treatments were five rates of PM (0, 2.5, 5.0, 7.5 and 10 t ha^?1). Triplicate units in incubation and pot experiments were arranged in Completely Randomised Design. Soybean was grown for three consecutive growth cycles of seven weeks each and soil samples were analysed for Saloid P, Al-P, Fe-P, Ca-P, occluded P, reductant soluble P, and residual P. Results indicated that Fe-P was the dominant active inorganic P in the soils while residual P was the dominant inactive inorganic-P in most of the soils. In the pot experiment, application of poultry manure significantly increased organic P in the soils in the first growth cycle, but decreased slightly in second growth cycle. Highest and lowest (P ≤ 0.05) organic P values were observed in soil samples from Ayetoro and Odeda, respectively. In the pot experiment, application of PM reduced P fixation and occluded P fraction in the soils. There was general increase in available P in most of the soils considered despite increase or decrease in other forms of P. Poultry manure reduced the fixation of P and release of occluded phosphorus. Generally, Poultry manure significantly improved soil P fractions and plant P tissue concentrations.     

Reversibility of phosphorus sorption by ferruginous nodules

Ferruginous nodules sorb significant amounts of available soil and fertiliser phosphate. The effect of this sorption on phosphorus availability of an agricultural soil was tested by sequential extraction and by exhaustive cropping with millet (Pennisetum typhoides) in a greenhouse trial following fertilisation of the original soil containing 70% nodules and of prepared samples containing various mixes of separated soil fines and nodules. Phosphorus sorption maxima by the soil fines and nodules were 190 mg kg⁻¹ and 380 mg kg⁻¹ respectively. Samples of fines and nodules which had sorbed 110 and 194 mg kg⁻¹ were submitted to 8 successive extractions with 0.01 M KCl, after which P desorption amounted to 117 mg kg⁻¹ and 103 mg kg⁻¹ respectively. Hysteresis between sorption and desorption was negligible for the soil fines and increased with increasing nodule content of the samples. In the greenhouse experiment, P uptake at the first cropping was highest in the soil fines at all levels of phosphorus applied. Subsequent croppings, however, showed higher P uptake in the concretionary soils. These results indicate a higher initial P release from the soil fines with cropping followed by an earlier exhaustion of phosphorus. At the end of the greenhouse experiment, yields were low in spite of the large quantities of P still remaining in the soils. Phosphorus fractionation showed that, of the P left in the soil after cropping 20% was in labile, 29% in Fe or Al-associated, and 51% in low-availability forms.     

Nitrogen, carbon and phosphorus mineralization in soils from semi-arid highlands of central Mexico amended with tannery sludge

Tannery sludge contains valuable nutrients and could be used as a fertilizer to pioneering vegetation in heavily eroded soils of the semi-arid highlands of central Mexico. Soil collected under and outside the canopy of mesquite (Prosopis laeviginata), huizache (Acacia tortuoso) and catclaw (Mimosa biuncifera), and cultivated with maize (Zea mays) and beans (Phaesolus vulgaris) was amended with 1.5 g tannery sludge kg-1 soil or 210 kg dry sludge ha-1 or left unamended. Amended and unamended soils were incubated aerobically for 70 days at 22 +/- 2 degrees C and CO2 production, available P, and inorganic N concentrations were monitored. The CO2 production rate, total C and P, available P, biomass C and P were larger under the canopy of the vegetation than outside of the canopy. The soils were depleted of N as more than 50 mg N kg-1 soil could not be accounted for in the first days of the incubation. Nitrification showed a lag, which lasted 28 days, and concentration of available P remained constant or increased slightly. Application of tannery sludge to soil increased CO2 production with 6.5 mg CO2 kg-1 soil d-1 and inorganic N with 30 mg N kg-1 soil after 70 days, but available P did not increase. Application of tannery sludge increased C and N mineralization and could thus provide valuable nutrients to a pioneer vegetation. Although no inhibitory effects on the biological functioning of the soil were found, further investigation into possible long-term environmental effects are necessary.     

Multifactorial risk factor intervention in patients with Type 2 diabetes improves arginine bioavailability ratios

Diabet. Med. 29, e365-e368 (2012) ABSTRACT: Aim Endothelial dysfunction is defined by reduced bioavailability of nitric oxide and has been shown to be associated with cardiovascular risk. The global arginine bioavailability ratio and the arginine to ornithine ratio have recently been shown to be associated with cardiovascular outcome in patients with coronary artery disease. The aim of our study was to investigate the impact of a multifactorial risk factor intervention in subjects with Type?2 diabetes on these two potential new cardiovascular surrogate parameters. Methods In a single-centre and prospective study, we investigated 41 patients with Type?2 diabetes not reaching treatment targets according to current local diabetes guidelines in two out of three of the following measurements: HbA(1c) LDL cholesterol 2.6 or blood pressure. Within 3?months, therapy was intensified according to current guidelines aiming to reach the treatment targets. At baseline and 3?months, arginine, ornithine and citrulline were chromatographically determined after pre-column-derivatization followed by fluorescent detection, and arginine bioavailability ratios were calculated. Results Intensified risk factor management significantly improved the global arginine bioavailability ratio (0.33?±?0.12 at baseline vs. 0.38?±?0.14 after 3?months; P?=?0.018). A significant improvement was only seen in patients with short diabetes duration (相似文献   

Anhydrobiosis in Pratylenchus penetrans

Anhydrobiotic survival of Pratylenchus penetrans was compared in several soil moisture regimes. Bodies of anhydrobiotic nematodes were coiled. In slow-dried soils, Vineland silt loam (VSL) and Fox loamy sand (FLS), 70 and 58% of the total P. penetrans populations were anhydrobiotic when soil moistures reached ca. 3% and water potential 15 kPa or greater. Coiling began at a much lower water potential in FLS than in VSL. In fast-dried soils, only 31 and 22% of the P. penetrans populations in the same two soil types had entered the anhydrobiotic state at comparable moistures. In the above soils, 76-96% of the P. penetrans were alive immediately after entering the anhydrobiotic state. In slow-dried VSL, some nematodes (1%) survived 770 days. In the other soils, all anhydrobiotic nematodes were dead after 438 days. Anhydrobiosis increased the ability of nematodes to survive subzero temperatures, but it did not increase their ability to survive temperatures above 40 C. Infectivity and reproductivity of rehydrated P. penetrans were not affected by anhydrobiosis.     

Decline in lung liquid volume before labor in fetal lambs

The volume of liquid in the fetal lung depends on the amount of liquid secreted across the pulmonary epithelium and the amount flowing through the trachea. Lung liquid volume (V1) and secretion rate Vs) were determined using an indicator-dilution technique, while tracheal flow rate (Vtr) was measured simultaneously with a bubble flowmeter. Least-squares regression analysis showed that in 10 chronically instrumented fetal lambs, V1 increased from 51.0 ml at 119 days to 104.6 ml at 135 days (V1 = -347.65 + 3.35 X days; 95% confidence limits on slope: 1.89-4.81) before declining to 70.2 ml at 142 days gestation (V1 = 768.8 - 4.92 X days; 95% confidence limits on slope: -2.55 to -7.30). Similarly Vs increased from 7.4 ml/h at 119 days to 16.8 ml/h at 133 days (Vs = -72.35 + 0.67 X days; 95% confidence limits on slope: 0.21-1.14), before declining to 7.1 ml/h at 142 days (Vs = 159.07 - 1.07 X days; 95% confidence limits on slope: -0.56 to -1.57). Vtr did not change significantly with gestation. We conclude that V1 increases until 135 days gestation, after which it falls substantially. This fall in volume, which occurs well before the onset of labor, results predominantly from the decline in Vs.