Biomedical subjects

Joon-Ho Lee

Publications and source records attributed to Joon-Ho Lee.

7 recordsLinked to original sources

PubMed2006

Evaluation of resistance pattern to fenpyroximate and pyridaben in Tetranychus urticae collected from greenhouses and apple orchards using lethal concentration-slope relationship.

This study aimed to monitor the present and future developments of the resistance of Tetranychus urticae Koch to fenpyroximate and pyridaben, using the relationship of the LC(50) and slope of the concentration-mortality line in a probit model, for the provision of reliable resistance management tactics. Tetranychus urticae populations were collected from 16 commercial greenhouses, where various crops were cultivated, as well as from 10 apple orchards throughout Korea. The resistance to fenpyroximate and pyridaben of each population was estimated by calculating the median lethal concentration (LC(50)), resistance ratio (RR) and slope of the concentration-mortality regression. Most of the greenhouse populations exhibited moderate levels of resistance, whereas the apple orchard populations showed only low levels, indicating that T. urticae populations in greenhouses were more strongly selected than those in apple orchards. Four population groups were established based on either the habitats (greenhouse and apple orchard) or acaricides (fenpyroximate and pyridaben). To test the hypothesis, "the slope is greatest at low and high levels of resistance," the slopes were regressed as a function of the LC(50), and fitted to a polynomial regression. The polynomial regression model explained this relationship well for the four population groups (p < 0.05), indicating that the development of resistance toward fenpyroximate or pyridaben was consistent with the gradient. A laboratory selection study agreed with the results from both acaricide field populations. These results suggest that the gradient was a good indicator of the susceptibility of T. urticae to genetic variations, which was related to the LC(50). The application of these findings is also discussed in relation to the resistance management of T. urticae.

Animals↗

PubMed2006

An efficient forward solver in electrical impedance tomography by spectral element method.

In electrical impedance tomography (EIT), a forward solver capable of predicting the voltages on electrodes for a given conductivity distribution is essential for reconstruction. The EIT forward solver is normally based on the conventional finite element method (FEM). One of the major problems of three-dimensional (3-D) EIT is its high demand in computing power and memory since high precision is required for obtaining a small secondary field which is typical for a small anomaly. This accuracy requirement is also set by the level of noise in the real data; although currently the noise level is still an issue, future EIT systems should significantly reduce the noise level to be capable of detecting very small anomalies. To accurately simulate the forward solution with the FEM, a mesh with large number of nodes and elements is usually needed. To overcome this problem, we proposed the spectral element method (SEM) for EIT forward problem. With the introduction of SEM, a smaller number of nodes and hence less computational time and memory are needed to achieve the same or better accuracy in the forward solution than the FEM. Numerical results demonstrate the efficiency of the SEM in 3-D EIT simulation.

Algorithms↗

PubMed2005

Impact of twospotted spider mite (Acari: Tetranychidae) on growth and productivity of glasshouse cucumbers.

Experiments were conducted to assess the damage of the glasshouse cucumber by twospotted spider mite, Tetranychus urticae Koch, and to investigate when the economic yield begins to decrease after T. urticae infestations. To assess the damage, dry matter partitioning in the cucumber plant was quantified and plant growth analyses were conducted at four different T. urticae infestation levels. T. urticae infestations decreased leaf productivity by reducing the total number of leaves per plant. Approximately 14% reductions of total leaf areas could result in significant yield loss. The decreased leaf productivity by T. urticae feeding caused biomass reductions and altered the pattern of dry matter partitioning in the plant; damaged plants accumulated more dry matter in the leaf, and partitioning of dry matter to fruits was hindered. The economic yield of cucumber began to significantly decrease as early as 4 wk after heavy mite infestations. This study also showed the seasonal differences in T. urticae-cucumber damage interactions among mite infestation levels.

Agriculture↗

PubMed2004

Effects of advanced glycosylation endproducts on perlecan core protein of glomerular epithelium.

Perlecan is one of major heparan sulfate proteoglycans in the glomerular basement membrane and is reduced in the renal parenchyma of diabetic patients and animals with proteinuria. To examine the effects of glucose and advanced glycosylated end-products (AGE) on perlecan, we cultured rat glomerular epithelial cells (GEpC) on AGE- or bovine serum albumin (BSA)-coated plates under normal (NG, 5 mM) and high-glucose (HG, 30 mM) conditions and measured the change in perlecan core protein production by a sandwich ELISA and northern blot analysis. We observed significant decreases of perlecan core protein under HG conditions at 1 week incubation, specifically on the AGE-coated compared with the BSA-coated surface, by 22.2% and 4.7%, respectively. The expression of mRNA for perlecan promoter was decreased under HG conditions on AGE-coated surfaces by 19.7% at 2 days and 61.1% at 1 week. Even under NG condition, the expression of mRNA was reduced by 30% at 1 week if GEpC were grown on an AGE-coated surface. In conclusion, HG and AGE have an additive effect in reducing the production of perlecan core protein by GEpC in vitro. AGE had a greater effect than HG, implying that the inhibition of AGE formation may be more effective than short-term glucose control in the prevention of diabetic proteinuria.

Animals↗

PubMed2003

Inhibitory effect of Sejin-Eum I/II on nicotine- and cigarette extract-induced cytotoxicity in human lung fibroblast.

Nicotine is a major pharmacologically active component of cigarette smoke. Excessive cigarette smoking is harmful to lung. Sejin-Eum (SJE) I is composed of various Oriental medicines, and SJE II is SJE I plus seeds of Avena sativa (Gramineae) that reduces the craving for cigarette in man. In this study, we have examined whether an aqueous extract of SJE I/II inhibits nicotine- or cigarette extract (CE)-induced cytotoxicity in human embryonic lung fibroblast, MRC-9. Assessment of cell viability using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay indicated that SJE I/II (500 and 1000 microg/ml) not only inhibited nicotine-induced cytotoxicity but also had significantly proliferous effect on MRC-9. However, SJE I/II had little effect on inhibition of CE-induced cytotoxicity. These results suggest the possibility that the use of SJE I/II may be useful for improvement of many symptoms by nicotine.

Cell Survival↗

PubMed2003

Oviposition model of overwintered adult Tetranychus urticae (Acari: Tetranychidae) and mite phenology on the ground cover in apple orchards.

The phenology of overwintered Tetranychus urticae was studied on the ground cover in apple orchards in the early season, and an oviposition model of overwintered adults was developed. The movement of overwintered adults from trees to ground cover started from mid-March and continued until mid-April. One life cycle from eggs to new adults (the 1st generation adults) on the ground cover was from late March to early May. The longevity and fecundity of overwintered T. urticae were affected largely by temperature. The longevity ranged from 46.6 days at 10 degrees C to 6.5 days at 35 degrees C. The total fecundity was minimum (0.2 eggs) at 10 degrees C and maximum (45.5 eggs) at 25 degrees C. The relationship between total fecundity and temperature was described well by a nonlinear equation. The cumulative age-specific oviposition rate was described well by the two-parameter Weibull function. The overall adult survival exhibited a reverse logistic curve. Three temperature-dependent components, age-specific cumulative oviposition rate, temperature-dependent total fecundity and age-specific survival rate functions, were incorporated into an oviposition model. The oviposition model simulation described the occurrence pattern of eggs laid by overwintered T. urticae on the ground cover in apple orchards relatively well.

Animals↗

PubMed2002

Leaf cell and tissue damage of cucumber caused by twospotted spider mite (Acari: Tetranychidae).

To quantify the damage caused by twospotted spider mite, Tetranychus urticae Koch, feeding on cucumber, Cucumis sativus L., leaf-cell and -tissue damage was assessed. On the abaxial leaf surface, adult T. urticae could feed through the spongy parenchyma and part of the palisade parenchyma of the leaf, while immature T. urticae could feed only through the sponge parenchyma. T. urticae punctured individual epidermal cells and consumed the contents of the mesophyll cells. Injured leaves had more empty space in the spongy parenchyma and fewer chloroplasts per cell. Damage also occurred even in the adjacent uninjured parenchyma cells without additional T. urticae feeding injury. Net photosynthetic rate, total chlorophyll content, and greenness of the leaf were significantly affected by feeding as quantified by mite-days. The percent loss of these parameters increased linearly or nonlinearly as mite-days increased, regardless of mite developmental stages. At 1,000 mite-days per 6 cm2, net photosynthetic rate was reduced by approximately 50 and 95%, total chlorophyll content was reduced by approximately 55 and 80%, and greenness was reduced by approximately 50 and 80% by feeding by immature and adult T. urticae, respectively.

Animals↗