Varying levels of difficulty index of skills-test items randomly selected by examinees on the Korean emergency medical technician licensing examination.

PURPOSE: The goal of this study was to characterize the difficulty index of the items in the skills test components of the class I and II Korean emergency medical technician licensing examination (KEMTLE), which requires examinees to select items randomly. METHODS: The results of 1,309 class I KEMTLE examinations and 1,801 class II KEMTLE examinations in 2013 were subjected to analysis. Items from the basic and advanced skills test sections of the KEMTLE were compared to determine whether some were significantly more difficult than others. RESULTS: In the class I KEMTLE, all 4 of the items on the basic skills test showed significant variation in difficulty index (P<0.01), as well as 4 of the 5 items on the advanced skills test (P<0.05). In the class II KEMTLE, 4 of the 5 items on the basic skills test showed significantly different difficulty index (P<0.01), as well as all 3 of the advanced skills test items (P<0.01). CONCLUSION: In the skills test components of the class I and II KEMTLE, the procedure in which examinees randomly select questions should be revised to require examinees to respond to a set of fixed items in order to improve the reliability of the national licensing examination.

Texture analyses show synergetic effects of biomechanical and biochemical stimulation on mesenchymal stem cell differentiation into early phase osteoblasts.

We investigated the structural complexity and texture of the cytoskeleton and nucleus in human mesenchymal stem cells during early phase differentiation into osteoblasts according to the differentiation-induction method: mechanical and/or chemical stimuli. For this, fractal dimension and a number of parameters utilizing the gray-level co-occurrence matrix (GLCM) were calculated based on single-cell images after confirmation of differentiation by immunofluorescence staining. The F-actin and nuclear fractal dimensions were greater in both stimulus groups compared with the control group. The GLCM values for energy and homogeneity were lower in fibers of the F-actin cytoskeleton, indicating a dispersed F-actin arrangement during differentiation. In the nuclei of both stimulus groups, higher values for energy and homogeneity were calculated, indicating that the chromatin arrangement was chaotic during the early phase of differentiation. It was shown and confirmed that combined stimulation with mechanical and chemical factors accelerated differentiation, even in the early phase. Fractal dimension analysis and GLCM methods have the potential to provide a framework for further investigation of stem cell differentiation.

Combined effects of flow-induced shear stress and micropatterned surface morphology on neuronal differentiation of human mesenchymal stem cells.

This study investigated the combined effects of surface morphology and flow-induced shear stress on the neuronal differentiation of human mesenchymal stem cells. First, to examine the effect of surface morphology, three patterns were fabricated using photolithography and compared to the flat substrate. After selecting the most effective surface pattern, flow-induced shear stresses (0.10 and 0.25 Pa) were engaged parallel to the direction of the grooves. The degrees of alignment and neurite outgrowth were measured using digital image processing techniques for up to 10 days. Functional evaluations were also performed by monitoring the intracellular calcium concentration and the expression of synaptophysin, ß-tubulin III, and MAP2. Based on these analyses, the pattern of 5 µm/5 µm/3 µm for groove/ridge/depth, respectively, was selected. Next, shear stresses (0.00, 0.10, 0.25 Pa) were applied to the cells on the selected substrate. The shear stresses affected the expression of those markers. The outgrowth measurements indicated that the shear stresses were effective at day 7. However, the effect of shear stresses tended to decrease at day 10. More cells showed higher calcium concentrations under 0.10 Pa. The alignment was also confirmed. Taken together, these results indicated that a shear stress of 0.10 Pa on the substrate of 5 µm was most effective. Therefore, such combination of mechanical stimuli and surface pattern is expected to promote neuronal differentiation with regard to functional and morphological changes.

Mechanical stimulation and the presence of neighboring cells greatly affect migration of human mesenchymal stem cells.

There are few studies regarding the effects of mechanical stimulation on cell migration although biochemical factors have been widely studied. We have investigated the effects of intermittent hydrostatic pressure (IHP) on mesenchymal stem cell migration with or without neighboring endothelial cells (EC). IHP promoted MSCs migration and the neighboring ECs helped with this. However, when IHP was applied to MSCs cultured with ECs, the opposite effect was observed. The concentration of stromal-derived factor-1 culture in medium was measured to explain the obtained results. SDF-1 concentration increased as IHP increased when MSCs were cultured alone. However, it decreased as IHP increased when MSCs and ECs were co-cultured. These results indicate that the mechanical environment should be considered when studying the migration of a cell type along with its biochemical environment.

Effects of repeated silver nanoparticles exposure on the histological structure and mucins of nasal respiratory mucosa in rats.

To investigate the effects of repeated silver nanoparticle exposure on the nasal septum respiratory mucosa, 6-week-old SD rats were exposed to silver nanoparticles at concentrations of fresh air control, low-dose (1.73 x 10(4)/cm, 0.5 microg/m(3)), middle-dose (1.27 x 10(5)/cm(3), 3.5 microg/m(3)) and high-dose (1.32 x 10(6)particles/cm(3), 61 microg/m(3)) in an inhalation chamber for 6h per day, 5 times a week for 28 days. The animals were sacrificed after the 28 days of exposure period. Histochemical staining, including periodic acid Schiff (PAS), alcian blue (AB) pH 2.5, and high iron diamine-alcian blue (HID-AB) pH 2.5, was used to evaluate changes in the mucosubstance properties of the goblet cells in the respiratory epithelium. In a histopathological study, the nasal cavity and lungs from the exposed groups exhibited no remarkable changes compared to the control group. However, a slight increase in the neutral mucins was noted for all the silver nanoparticle-exposed groups when compared to the control group, although without statistical significance. Nonetheless, the size and number of goblet cells containing neutral mucins increased significantly in the groups exposed to silver nanoparticle at middle- and high-dose (P<0.05). While the densities of the stained mucosubstances showed no difference among the exposed groups, the amount of neutral mucins did tend to increase slightly, although acid mucins including sulfomucins and sialomucins showed no change in any of the exposed groups. Therefore, the present results did indicate that silver nanoparticles have an influence on the neutral mucins in the respiratory mucosa, yet without toxicological significance.

Effect of dietary epigallocatechin-3-gallate on cytochrome P450 2E1-dependent alcoholic liver damage: enhancement of fatty acid oxidation.

This study was designed to determine whether dietary epigallocatechin-3-gallate (EGCG), the most abundant catechin polyphenol in green tea, can protect the liver from cytochrome P450 2E1 (CYP2E1)-dependent alcoholic liver damage. Compared with an ethanol group, when EGCG was present in the ethanol diet, the formation of a fatty liver was significantly reduced and the serum aspartate transaminase (AST) and alanine transaminase (ALT) levels were much lower. Ethanol treatment significantly elevated hepatic CYP2E1 expression while simultaneously reducing hepatic phospho-acetyl CoA carboxylase (p-ACC) and carnitine palmitoyl-transferase 1 (CPT-1) levels. While EGCG markedly reversed the effect of ethanol on hepatic p-ACC and CPT-1 levels, it had no effect on the ethanol-induced elevation in CYP2E1 expression. EGCG prevents ethanol-induced hepatotoxicity and inhibits the development of a fatty liver. These effects were associated with improvements in p-ACC and CPT-1 levels. The use of EGCG might be useful in treating patients with an alcoholic fatty liver.

Inflammatory and genotoxic responses during 30-day welding-fume exposure period.

Welder's pneumoconiosis has generally been determined to be benign and unassociated with respiratory symptoms based on the absence of pulmonary-function abnormalities in welders with marked radiographic abnormalities. In previous studies, the current authors suggested a three-phase lung fibrosis process to study the pathological process of lung fibrosis and found that the critical point for recovery was after 30 days of welding-fume exposure at a high dose, at which point early and delicate fibrosis was observed in the perivascular and peribronchiolar regions. Accordingly, the current study investigated the inflammatory and genotoxic responses during a 30-day period of welding-fume exposure to elucidate the process of fibrosis. As such, rats were exposed to manual metal arc-stainless steel (MMA-SS) welding fumes at concentrations of 65.6 +/- 2.9 (low dose) and 116.8 +/- 3.9 mg/m3 (high dose) total suspended particulate for 2 h per day in an inhalation chamber for 30 days. Animals were sacrificed after the initial 2 h exposure, and after 15 and 30 days of exposure. The rats exposed to the welding fumes exhibited a statistically significant (P < 0.05) decrease in body weight when compared to the control during the 30-day exposure period, yet an elevated cellular differential count and higher levels of albumin, LDH, and beta-NAG, but not elevated TNF-alpha, and IL-1beta in the acellular bronchoalveolar lavage fluid. In addition, the DNA damage resulting from 30 days of welding-fume exposure was confirmed by a comet assay and the inmmunohistochemistry for 8-hydroxydeoxyguanine (8-OH-dG). Consequently, the elevated inflammatory and genotoxic indicators confirmed the lung injury and inflammation caused by the MMA-SS welding-fume exposure.