Uptake Kinetics of \({\text{NH}_{4}^{+} }\), \({\text{NO}_{3}^{-} }\) and \({\text{H}_{2}\text{PO}_{4}^{-} }\) by Typha orientalis, Acorus calamus L., Lythrum salicaria L., Sagittaria trifolia L. and Alisma plantago-aquatica Linn

The emergent plants may differ in their capacity to assimilate nutrients from eutrophic water bodies, so the utilization of suitable emergent plants is the key part for successful restoration of shallow eutrophic lakes and rivers. This research applied the depletion method to study the kinetics of uptake of nutrient (H2PO4−, NH4+, NO3−) in different nutrient stresses by the five emergent aquatic plants (Acorus calamus L., Typha orientalis, Lythrum salicaria L., Sagittaria trifolia L., Alisma plantago-aquatica Linn) in the riverine zones of Dashi River (39°30′–39°40′ N, 115°59′–116°5′ E), a shallow eutrophic river located in Fangshan District, Beijing. The results showed that at the three phosphorus levels, A. calamus and A. plantago-aquatica had the highest maximum uptake rate values for NH4+ under low to moderate phosphorus conditions, and high phosphorus, respectively. T. orientalis had the highest maximum uptake rate values for NO3− at all phosphorus concentrations, while the Michaelis-Menten constant values of L. salicaria and A. plantago-aquatica were smaller. At the three nitrogen levels, the maximum uptake rate values for H2PO4− were the greatest for A. plantago-aquatica at the low to moderate nitrogen levels and L. salicaria at high levels. Meanwhile, T. orientalis and L. salicaria had the smallest Michaelis-Menten constant values. In this study, nitrogen microbial transformations, such as nitrification, denitrification and their coupling were not measured and their role in measuring kinetics was not assessed. Thus, achieved results shall be considered as a synthesis of several processes mediated by plants, a theoretical guidance to the selection of plant species for phytoremediation of polluted water bodies with different nutrient stresses for quality improvement around the diverse rivers in Haihe River basin.

Initial evaluation of nitrogen uptake of Thalassia hemprichii in Nha Trang, Khanh Hoa

The uptake rate of nitrate by leaves and roots was simultaneously investigated in the seagrass T. hemprichii collected from Lo river, Nha Trang. The principle of nutrient uptake of seagrass was based on the approaches of the Michaelis-Menten model. The laboratory experiments of nitrate uptake were done the ranges of ambient nitrate concentrations in the separate water column of leaves and roots. The calculated results indicated that the nitrate uptake rate through the leaves was higher than that of the roots. The maximum uptake rate (Vmax) through the leaves and the roots was 1,777.0 mgN/g DW/h and 131.6 mgN/g DW/h, respectively. From these results, the nitrate uptake rate by the seagrass in Lo river was estimated at 52.2 mgNm-2h-1. The value plays an important role in developing and implementing plans for the protection and rehabilitation of seagrass beds in coastal areas.

Effects of Antiviral Drugs on Organic Anion Transport in Human Placental BeWo Cells

ABSTRACTPlacental drug transfer is important for achieving better pharmacotherapy in pregnant women and in fetuses. In the present study, we examined the effects of anti-hepatitis C virus (HCV) and anti-HIV drugs on organic anion transport in human placental BeWo cells. The cellular uptake of two fluorescence organic anions, 8-(2-[fluoresceinyl]aminoethylthio)adenosine-3′,5′-cyclic monophosphate (8-FcAMP) and fluorescein, was temperature and concentration dependent. The Michaelis constant (Km) and the maximum uptake rate (Vmax) for 8-FcAMP transport in BeWo cells were estimated to be 6.45 ± 0.75 μM and 25.55 ± 5.93 pmol/mg protein/10 min, respectively. TheKmandVmaxvalues for fluorescein uptake were estimated to be 31.2 ± 11.8 μM and 510.9 ± 90.6 pmol/mg protein/10 min, respectively. Several known substrates of organic anion transporters in human placenta, including atorvastatin, glibenclamide, estrone-3-sulfate, and rifampin, inhibited cellular uptake of 8-FcAMP and fluorescein in BeWo cells. Transport of 8-FcAMP and fluorescein was inhibited by the antiviral drugs boceprevir, telaprevir, elvitegravir, and maraviroc. These findings suggest that some antiviral drugs are sufficiently potent to influence placental drug transfer and cause drug-drug interactions.

Estimation of the Parameters in a Dynamical Marine Ecosystem Model Based on the Adjoint Assimilation

By utilizing spatial biological parameterizations, the adjoint variational method was applied to a 3D marine ecosystem model (NPZD-type) and its adjoint model which were built on global scale based on climatological environment and data. When the spatially varying Vm (maximum uptake rate of nutrient by phytoplankton) was estimated alone, we discussed how would the distribution schemes of spatial parameterization and influence radius affected the results. The reduced cost function (RCF), the mean absolute error (MAE) of phytoplankton in the surface layer, and the relative error (RE) of Vm between given and simulated values decreased obviously. The influence of time step was studied then and we found that the assimilation recovery would not be more successful with a smaller time step of 3 hours compared with 6 hours.

Application of ADM1 for the simulation of anaerobic digestion of olive pulp under mesophilic and thermophilic conditions

The management of the wastewater originating from olive oil producing industries poses a serious environmental problem. Recently, two-phase production of olive oil has been developed, leading to almost complete elimination of the bulk of the generated wastewater and, is thus regarded as an environmentally friendly technology. However, the main waste stream (olive pulp) is a slurry material characterized by high solids concentration (∼30%), requiring stabilisation before its final disposal. The anaerobic digestion of olive pulp is studied in this work under mesophilic and thermophilic conditions in CSTR-type digesters. The digesters were fed with water-diluted (1:4) olive pulp at an HRT of 20 days and an OLR of 3.94 kg COD m−3 d−1. In order to study the process kinetics, the digesters were subjected to impulse disturbances of different substrates. The IWA anaerobic digestion model was used to simulate the reactors' response. Some key process parameters, such as the specific maximum uptake rate constants and the saturation constants for the volatile fatty acids degradation were estimated and compared with the standard values suggested by the ADM1.

167 Nutrient Uptake and Growth Performance of OH87 and OH97 Pear Rootstocks

One-year-old (Old Home) OH87 and OH97 pear rootstocks were grown in 2-gallon containers under natural conditions at Corvallis, Ore., in in 1999. Uniform plants were harvested during August and September, and total leaf area, new shoot number and length, and root growth were measured. The kinetics of NH4+ and NO3- uptake by new roots of both rootstocks were determined with the ion-depletion technique. OH87 had larger total leaf area, and more and longer shoots than OH97. Total root biomass was similiar between the two rootstocks, but OH87 had a larger proportion of new roots and more extension roots than OH97. Both rootstocks had lower Km values for NH4+ absorption than for NO3- and therefore both had greater absorptive power for NH4+ than for NO3- at the low nutrient concentrations. The maximum uptake rates (Vmax) of OH97 were similiar for both NH4+ and NO3- absorption, but OH87 had a much higher maximum uptake rate for NO3- than for NH4+.

290 Nutrient Uptake by New Roots of Six Clonal Apple Rootstocks

The nutrient uptake kinetics by new roots of 1-year-old potted clonal apple rootstocks (M7, M9, M26, M27, MM106, and MM111) were determined by the ion depletion technique at the stable development stage of trees in August. The total roots of five of the rootstocks (except MM111) consisted of more than 60% feeder roots and less than 12% extension roots. MM111, the most vigorous rootstocks tested, had 60.7% feeder roots and 24.5% extension roots. Root: top ratio was negatively related to the growth inhibiting character of the rootstock. Nutrient uptake by excised new roots was found to fit into Michaelis-Menton kinetic model for all rootstocks tested. The kinetic characteristics (maximum uptake rate, Imax, apparent Michaelis-Menton constant, Km, and root absorption power, (α = Imax•1/Km) between rootstocks differed significantly. MM111 had the highest Imax for NH4+ absorption and M9 for NO3-. Root affinity to ions was highest with MM106 for NH4+ and with M26 for NO3-. Root absorption power (α = Imax•1/Km) was greatest in MM106 for NH4+ and M9 for NO3-. At this developmental stage the data suggest no relationship between nutrient uptake and dwarfing character of the rootstocks.

289 Ammonium Ion Uptake by Feeder and Extension Roots of MM106 Apple Rootstock

New roots of Malus domestica Borkh MM106 apple rootstock were divided into two categories, 1) feeder roots and 2) extension roots based on morphology and their ability to take up NH4+, were studied. The roots were harvested in August from 1-year-old potted plants growing under natural conditions in Corvallis, Ore. Extension roots were thicker and longer than feeder roots. Average diameter and length were 0.89 and 45.29 mm for extension roots and 0.27 and 5.36 mm for feeder roots. Root special length (cm/g FW) and surface area (cm2/g FW) were 11.94 and 33.17 for extension roots and 108.97 and 93.38 for feeder roots. Maximum uptake rate, Imax, Km, and root absorption power, α (α = Imax•1/Km), for NH4+ absorption were 6.875, 0.721, and 9.48 for extension roots and 4.32, 0.276, and 15.63 for feeder roots. Feeder roots had stronger affinity to NH4+ (low Km) and higher NH4+ absorption power (high α value) than extension roots. The feeder roots were better able to uptake NH4+ at lower external solution concentrations than extension roots according to the nutrient depletion curve, which indicates feeder roots being more efficient than extension roots in nutrient absorption when NH4+ availability was low.

Uptake of ammonium by four species of macroalgae in Port Phillip Bay, Victoria, Australia

The uptake rates of ammonium were determined for three species of native macroalgae and an exotic macroalga from Port Phillip Bay. All species exhibited rate-saturated mechanisms of uptake described by Michaelis–Menten uptake kinetics. At the highest concentration examined (28.6 µmol NH4-N) Hincksia sordida had a higher rate of uptake (435 µmol NH4 -N g dry wt–1 h–1) than Ulva sp. (108 µmol NH4-N g dry wt–1 h–1) or Polysiphonia decipiens (53 µmol NH4 -N g dry wt–1 h–1). Maximum surge uptake rate was highest for H. sordida and lowest for P. decipiens (802 and 57 µmol NH4 -N g dry wt–1 h–1 respectively). The introduced phaeophyte Undaria pinnatifida had an intermediate capacity for ammonium uptake which was dependent on blade maturity. Differences in the ratio of maximum uptake rate to half-saturation rate between surge and assimilation uptake phases suggest a propensity for some species to take up ammonium at low concentrations. The relationships between nutrient uptake and growth among species would afford mature U. pinnatifida, H. sordida and Ulva sp. a competitive advantage for ammonium uptake in winter during high N availability, whereas P. decipiens would be able to exploit low N concentrations in spring and summer.

Mechanisms of ferric citrate uptake by human hepatoma cells

The mechanisms of uptake of non-transferrin-bound iron by human hepatoma cells (HuH7) were investigated using 59Fe-citrate and [14C]citrate. The amount of iron associated with the cells increased linearly with time, whereas citrate uptake reached a plateau after 45 min, resulting in a cellular accumulation of iron over citrate. The cells displayed high-affinity membrane binding sites for citrate with maximum binding of 118 ± 17 pmol citrate/mg protein and a dissociation constant of 21 ± 2 μM ( n = 3). Iron uptake was saturable with a maximum uptake rate of 1.95 ± 0.43 pmol ⋅ mg protein−1 ⋅ min−1and an apparent Michaelis constant of 1.1 ± 0.1 μM. Nonradioactive ferric citrate and citrate inhibited59Fe uptake to a similar degree. This suggests that the uptake of citrate-bound iron is dependent on either binding to specific citrate binding sites or the concentration of unbound iron. The uptake of iron was inhibited by ferricyanide (>100 μM) and ferrous iron chelators but stimulated by ferrocyanide and ascorbate, suggesting that the iron is reduced from Fe3+ to Fe2+ and transported into the cell by an iron carrier-mediated step.