Kyu-Seung Lee

Effect of Amino Acid Fertilization on Nitrate Assimilation of Leafy Radish and Soil Chemical Properties in High Nitrate Soil

Abstract The objective of the present work was to investigate the corresponding uptake and assimilation of nitrate (NO3 −) in leafy radish and effects on soil chemical properties by foliar application of amino acid fertilizer (AAF). The activity of the enzymes related to the process of NO3 − reduction (NR: nitrate reductase; NiR: nitrite reductase; GS: glutamine synthetase) and the content of NO3 −, total N, and the end products of this process (amino acids and proteins) were analyzed. The soils were sampled twice, and some chemical properties were analyzed. The results of this study showed that application of AAF increased biomass production, and nitrogen (N) utilization in the treatment of a low rate of AAF increased 55% over the control. In addition, the activities of the enzymes were affected differently depending on applied rate of AAF. Furthermore, the NO3 − content was reduced 4–24%, and total N content was increased 14–32% by AAF treatments. Finally, application of AAF improved uptake efficiency of N from soil and prevented N loss by leaching.

Comparison of Analytical Methods and Residue Patterns of Pymetrozine in Aster scaber

Residues of the polar pesticide pymetrozine were compared using two methods: hydromatrix and liquid–liquid extraction (LLE). The biological half-life and the final residue level were investigated using Aster scaber over a 10-days cultivation period. The respective biological half-lives of the pesticide were 4.2 and 3.5xa0days at the recommended and double dose. The final residue levels were 1.28 and 1.98xa0mgxa0kg−1, respectively, at the same application rate of pymetrozine according to the GAP standard of the United Kingdom. Average recovery was higher with LLE than with the hydromatrix method. Dissipation curves of pymetrozine were influenced by the application amount and growth rate of A. scaber. The final residue level of pymetrozine could be predicted to be lower than the UK maximum residue limit for lettuce applying the GAP standard.

Enhancement of nitrate uptake and reduction by treatment with mixed amino acids in red pepper (Capsicum annuum L.)

Abstract The objective of the present work was to determine the corresponding uptake and assimilation of in roots and leaves by the application of mixed amino acids in red pepper. The amino acids used in this experiment were alanine, β-alanine, aspartic acid, asparagines, glutamic acid, glutamine, and glycine. The 42-day-old seedlings were treated with 0, 0.3, and 3.0 mM of mixed amino acids containing 10 mM in growth medium. Nitrate uptake was determined by following depletion from the uptake solution. The activity of the enzymes related to the process of reduction and the content of , , and the end-products of this process (amino acids and proteins) were analyzsed in leaves and roots. The results of this study indicate that the application of mixed amino acids increased uptake in red pepper, and the highest uptake was found in the treatment with 3.0 mM mixed amino acids that was nearly seven times higher than the control. In addition, the enzymatic activities of nitrate reductase and nitrite reductase were positively affected by the treatments of mixed amino acids in the roots. The results presented here are in contrast to recent studies, which have shown that the single amino acid treatments inhibited uptake and nitrate reductase activity. Finally, the content was decreased both in leaves and roots by the mixed amino acids treatments.

Inhibitory effects of coronary vasodilator papaverine on heterologously-expressed HERG currents in Xenopus oocytes

AbstractAim:To characterize the effects of papaverine on HERG channels expressed in Xenopus oocytes as well as cardiac action potential in rabbit ventricular myocytes.Methods:Conventional microelectrodes were used to record action potential in rabbit ventricular myocytes. HERG currents were recorded by 2-electrode voltage clamp technique in Xenopus oocytes injected with HERG cRNA.Results:Papaverine increased the cardiac action potential duration in rabbit ventricular myocytes. It blocked heterologously-expressed HERG currents in a concentration-dependent manner (IC50 71.03±4.75 μmol/L, NH 0.80, n=6), whereas another phosphodiesterase inhibitor, theophylline (500 μmol/L), did not. The blockade of papaverine on HERG currents was not voltage-dependent. The slope conductance measured as a slope of the fully activated HERG current-voltage curves decreased from 78.03±4.25 μS of the control to 56.84±5.33, 36.06±6.53, and 27.09±5.50 μS (n=4) by 30, 100, and 300 μmol/L of papaverine, respectively. Papaverine (100 μmol/L) caused a 9 mV hyperpolarizing shift in the voltage-dependence of steady-state inactivation, but there were no changes in the voltage-dependence of HERG current activation. Papaverine blocked HERG channels in the closed, open, and inactivated states.Conclusion:These results showed that papaverine blocked HERG channels in a voltage- and state-independent manner, which may most likely be the major mechanism of papaverine-induced cardiac arrhythmia reported in humans.

Modulating effect of ginseng saponins on heterologously expressed HERG currents in Xenopus oocytes

AbstractAim:To examine the effects of ginseng saponins on the heterologously expressed human ether-a-go-go related gene (HERG) that encodes the rapid component of the delayed rectifier K+ channel.Methods:A two-electrode voltage clamp technique was used. HERG currents were recorded in Xenopus oocytes injected with HERG cRNA.Results:Crude saponins of Korean red ginseng (GS) induced a minimal increase of the maximal HERG conductance without changes in the voltage-dependent HERG current activation and inactivation curves. GS, however, decelerated HERG current deactivation in a concentration-dependent manner, which was more noticeable with panaxitriol (PT) than panaxidiol (PD). Consistently, ginseng saponins increased the HERG deactivation time constants with the order of potency of Rg1 (a major component of PT)>Rf 1>Rb1 (a major component of PD). Re had little effect on HERG deactivation. During a cardiac action potential, GS increased the outward HERG current.Conclusion:Ginseng saponins enhance HERG currents, which could be in part a possible mechanism of the shortening cardiac action potential of ginseng saponins.

Characteristics of the Absorption of Cherry Tomato by the Application of Chelated Calcium and Germanium

Bloods from slaughtered Korean native cattle (Hanwoo : Bos taurus coreanae) can be used in agriculture with various beneficial effects on the environment. This study was performed to find out the effect of the application of calcium and germanium, which are chelated with peptides made of cattle bloods on the absorption of them by cherry tomato (Lycopersicon esculentum Mill.). Peptide was purified by enzymatic hydrolysis and ultrafiltration from serum protein, which is composed of Asp, Glu, Lue etc. Chelated Ca and Ge were produced by reacting the peptide with and Ge-. Then, they were applied to cherry tomato during cultivation period at the rate of (10 days interval) for each tomato tree. Application of chelated-Ca increased the Ca contents in leaves and fruits of cherry tomato showing as 19.9% and 23.4% in newerly prepared chelated-Ca-200 (), 8.1% and 6.8% in commecrial Calciolid Ca-300 () compared to 3152.6 and in control, respectively. Application of chelated-Ge showed the increase in the germanium contents in both leaves and fruits of cherry tomato by over 6 times than those of control and over 4 times than Ge -20 application. As a result of this study, it seemed that the application of chelated-Ca and chelated-Ge would be more effective than the existing commertial one in the absorption of calcium and germanium by cherry tomato.

Determination of Abamectin Residue in Paprika by High-Performance Liquid Chromatography

Reversed-phase high-performance liquid chromatography (HPLC) techniques were developed to quantify abamectin (ABM) in paprika ( Capsicum annum ). Separation was achieved on a C 18 ODS column with a mobile phase of acetonitrile/water (96/4 v/v) mixture in an isocratic elution at the flow rate of 1.2 , ,, , mL/min for avermectins (AVMs). The retention times were 8.0 and 9.7mins for AVM B 1b and AVM B 1a , respectively. Residual AVMs (sum of AVM B 1a , AVM B 1b and 8,9-Z-AVM B 1a ) in the vegetable were ext- racted with acetonitrile, and the silica solid-phase extraction cartridges were used to purify the extracts. AVMs were derivatized using trifluoroacetic acid and 1-methylimidazole, and the derivatives were determined with a fluorescence detector (excitation at 365 nm and emission at 470 nm). High and consistent recoveries, ranging from 93% to 115%, were obtained for AVM B 1a and 8, 9-Z-AVM B 1a at fortified levels of 20 g/kg and μμ μ 200 g/kg for paprika. The limit of quantitation (LOQ) was 2 g/kg. The residual levels of AVMs in pap μ μ μ μ μ μ μ μ - rika in a field experiment from one day to seven days after the last application decreased from 18.40 to 7.59 g/kg. The half-life (T μμ μ 1/2 ) of AVMs in paprika was 1.47 days.

Onion (Allium cepa L.) peel extract (OPE) regulates human sperm motility via protein kinase C-mediated activation of the human voltage-gated proton channel

Onion (Allium cepa L.) and quercetin protect against oxidative damage and have positive effects on multiple functional parameters of spermatozoa, including viability and motility. However, the associated underlying mechanisms of action have not yet been identified. The aim of this study was to investigate the effect of onion peel extract (OPE) on voltage‐gated proton (Hv1) channels, which play a critical role in rapid proton extrusion. This process underlies a wide range of physiological processes, particularly male fertility. The whole‐cell patch‐clamp technique was used to record the changes in Hv1 currents in HEK293 cells transiently transfected with human Hv1 (HVCN1). The effects of OPE on human sperm motility were also analyzed. OPE significantly activated the outward‐rectifying proton currents in a concentration‐dependent manner, with an EC50 value of 30 μg/mL. This effect was largely reversible upon washout. Moreover, OPE induced an increase in the proton current amplitude and decreased the time constant of activation at 0 mV from 4.9 ± 1.7 to 0.6 ± 0.1 sec (n = 6). In the presence of OPE, the half‐activation voltage (V1/2) shifted in the negative direction, from 20.1 ± 5.8 to 5.2 ± 8.7 mV (n = 6), but the slope was not significantly altered. The OPE‐induced current was profoundly inhibited by 10 μm Zn2+, the most potent Hv1 channel inhibitor, and was also inhibited by treatment with GF109203X, a specific protein kinase C (PKC) inhibitor. Furthermore, sperm motility was significantly increased in the OPE‐treated groups. OPE exhibits protective effects on sperm motility, at least partially via regulation of the proton channel. Moreover, similar effects were exerted by quercetin, the major flavonoid in OPE. These results suggest OPE, which is rich in the potent Hv1 channel activator quercetin, as a possible new candidate treatment for human infertility.

Low Molecular Weight Organic Acids in Brassica pekinensis Rupr. and Growing soil Influenced by Simulated Nitrate Deposition

We investigated whether carboxylate exudation of Brassica pekinensis Rupr. was affected by nitrate deposition from simulated acid rain. A gas chromatographic (GC) analysis was employed for the determination of low molecular weight organic acids (LOA) in rhizosphere soils, bulk soil, roots and leaves of Brassica pekinensis Rupr.. Rhizosphere soils were collected after 8 weeks of plant growth by first removing the bulk soil from the root system and then by mechanical move off the rhizosphere soil that adhered to the root surface with soft brush. Soil and plant materials were simultaneously extracted with the mixture of methanol and sulfuric acid (100:7, v/v). Seven organic acids, oxalic, malonic, fumaric, succinic, maleic, L-malic and citric acid were identified and quantified by GC equipped with FID. Oxalic, L-malic, and citric acids were found in both the bulk and rhizosphere soils, while most LOAs were not detected in the control treatment. On the contrary, except maleic acid, all other organic acids were detected in the leaves and roots of cabbages treated with nitrate deposition.

Researches using radio-labelled Herbicide in Korea

The research results using radio-labelled herbicides performed by Korean researchers were reviewed. All the research works were used 14 C-labelled chemicals and generally carried out to know the behavior of herbicides in soils and plants. The degradation, mineralization and bound-residues formation are the major concerning area in soil studies, and uptake, translocation, metabolism, selectivity and resistance are in plant studies. Also few papers covered synthesis, formulation and animal metabolism.