• Journal of Food Hygiene and Safety
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• v.28 no.1
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• pp.75-82
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• 2013

The simultaneous analysis and monitoring of aflatoxin $B_1$, $G_1$, $B_2$, $G_2$ and ochratoxin A in foods were carried out by HPLC with fluorescence detection. The samples were extracted with methanol/water mixture. The extract was centrifuged, diluted with phosphate buffer saline (PBS), filtered, and applied to an immunoaffinity column containing antibodies specific to both aflatoxins and ochratoxin A. After washing the column with PBS and water, the toxins were eluted from the column with methanol, and quantified by HPLC, with a run time of approximately 30 min. The recoveries for aflatoxin $B_1$, $G_1$, $B_2$, $G_2$ and ochratoxin A in foods were 78.4~101.5%, 73.3~102.1%, 81.7~106.7%, 67.0~104.6% and 78.7~120.8%, respectively. The limits of detection of aflatoxins and ochratoxin A ranged from 0.05 to $0.18{\mu}g/kg$. According to monitoring result with the established method, aflatoxin $B_1$ and ochratoxin A were found in 13 of 151 domestic commercial foods. The contamination levels were $0.32{\sim}1.80{\mu}g/kg$ for aflatoxin $B_1$ and $0.97{\mu}g/kg$ for ochratoxin A. Therefore, this study showed all commercial foods monitored were safe under the Korean standards for aflatoxins and ochratoxin A.

• Applied Microscopy
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• v.30 no.4
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• pp.347-355
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• 2000

Zinc is one of the most abundant oligoelements in the living cell. It appears tightly bound to some metalloproteins and nucleic acids, loosely bound to some metallothioneins or even as free ion. Small amounts of zinc ions (in the nanomolar range) regulate a plentitude of enzymatic proteins, receptors and transcription factors, thus rolls need accurate homeostasis of zinc ions. Zinc is an essential catalytic or structural element of many proteins, and a signaling messenger that is released by neural activity at many central excitatory synapses. Growing evidences suggest that zinc may also be a key mediator and modulator of the neuronal death associated with transient global ischemia and sustained seizures, as well as perhaps other neurological disease stoles. Some neurons have developed mechanisms to accumulate zinc in specific membrane compartment ('vesicular zinc') which can be evidenced using histochemical techniques. Substances giving a bright colour or emitting fluorescence when in contact with divalent metal ions are currently used to detect them inside cells; their use leads to the so called 'direct' methods. The fixation and precipitation of metal ions as insoluble salt precipitates, their maintenance along the histological process and, finally, their demonstration after autometallographic development are essential steps for other methods, the so called 'indirect methods'. This study is a short report on the autometallograhical approaches for zinc detection in the central nervous system (CNS) by means of a modified selenium method.

• Korean Journal of Animal Reproduction
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• v.26 no.3
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• pp.215-221
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• 2002

Antioxidants(N-acetyl-1-cysteine, ebselen and glutathione) and growth factors(EGF, PDGF) were studied as a mean of increasing the development of porcine embryos produced by in vitro maturation (IVM) and in vitro fertilization(IVF). Porcine embryos developed to the 2~8 cell stage after IVF were cultured fer 6 to 7 days at 38.5$^{\circ}C$ in NCSU 23 medium containing antioxidants plus growth factors. Cell numbers of blastocysts were counted by fluorescence staining method. The developmental rate beyond morula stages in NCSU 23 containing NAC(1nm) or NAC(1nm) plus EGF(100ng/$m\ell$) or PDGF(5ng/$m\ell$) were 28.1, 32.3 and 35.3%, respectively. NAC plus PDGF group was slightly higher than control group(P>0.05). The developmental capacity in NCSU 23 containing ebselen(10 $\mu$M) or ebselen(10 $\mu$M) plus EGF(100ng/$m\ell$) or PDGF(5ng/$m\ell$) were 17.8, 36.9 and 40.3%, respectively Ebselen plus growth factor groups were significantly higher than control group(P<0.05). The developmental capacity in NCSU 23 containing glutathione(100 $\mu$M) or glutathione(100 $\mu$M) plus EGF (100ng/$m\ell$) or PDGF(5ng/$m\ell$) were 24.1, 30.5 and 27.7%, respectively. There were not difference in all experimental groups(P>0.05). In all experimental groups, there was no significantly differences on the cell number of blastocysts, but ebselen plus growth factor groups were significantly higher than control group. These studies indicate that antioxidants plus growth factors can increase the proportion of embryos that developed beyond morulae stage.

• Korean Journal of Food Science and Technology
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• v.42 no.3
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• pp.263-268
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• 2010

This research was conducted to evaluate the occurrence of ochratoxin A (OTA) in coffee and fruit products in Korea. A total of 388 coffee and fruit product samples were collected from retail or outlet markets; 177 samples were coffee and 211 were fruits or their products. Analytical methods including AOAC and Comit$\acute{e}$ Europ$\acute{e}$en de Normalisation (CEN) were selected and modified by method validation to detect and quantify the OTA in samples. All samples were analyzed by liquid chromatography with fluorescence detection. OTA was detected in 3.9% of 177 kinds of coffee and 0% of 211 kinds of fruit products. The levels of OTA were $0.7-4.6\;{\mu}g/kg$ in green coffee, $0.3-4.8\;{\mu}g/kg$ in roasted coffee, $1.4\;{\mu}g/kg$ in mixed coffee, and $0.4-0.6\;{\mu}g/kg$ in instant coffee. However, OTA was not detected in liquid coffee, dried fruits, or grape juice. OTA levels of all samples detected were less than the European Union legislation of $5.0\;{\mu}g/kg$ in coffee, $10.0\;{\mu}g/kg$ in raisins and $2.0\;{\mu}g/kg$ in grape juice. Therefore, the risk of OTA in coffee and fruit products in Korea is relatively low at safe levels.

• Journal of Food Hygiene and Safety
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• v.35 no.3
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• pp.243-251
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• 2020

In this study, we investigated pesticide residues in 207 agricultural products distributed by direct trade in the northern area of Gyeonggi Province. A total of 94 general agricultural products and 113 eco-friendly agricultural products collected from local grocers and cooperative stores were analyzed by multiresidue method for 263 pesticides using GC (gas chromatography)/ECD (electron capture detector), GC/NPD (nitrogen phosphorus detector), GC-MS/MS (tandem mass spectrometry), LC (liquid chromatography)/PDA (photodiode array detector), LC/FLD (fluorescence detector), LC-MS/MS. All samples showing pesticide residues were general agricultural products collected from local food stores. The pesticide residue levels of 14 samples (6.8%) were below the maximum residue limits (MRLs) and one of them (0.5%) exceeded the MRLs. Sixteen pesticides were detected from samples of the following produce items: spinach, young cabbage, perilla leaves, mallow, cucumber, chives and water dropwort. The safety of the detected pesticides was assessed by monitoring the daily intake estimate (EDI) and the daily intake allowance (ADI) based on the amount of pesticides detected. The ADI percentage range (the ratio of EDI to ADI) was 0.0134-61.6259% and there was no health risk connected with consuming agricultural products in which pesticide residues were detected.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.10
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• pp.1353-1360
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• 2011

This study was performed to investigate the antimicrobial effects against food-borne pathogens and antioxidant activity of Rhododendron brachycarpum ethanol-extract. The antimicrobial activity of the extract was determined using a paper disc-diffusion method, and the diameter of the clear zone was measured. The diameter of the clear zone in the presence of 10 mg of extract was maximal against Bacillus cereus among the three tested Gram-positive bacteria and against Escherichia coli O157:H7 among the five tested Gram-negative bacteria. Analysis of the minimum inhibitory concentration (MIC) showed that the extract exhibited a similar efficacy as that of sorbic acid, a well-known chemical preservative. The growth inhibitory effects of the extract at concentrations of 250, 500, 1,000, and 2,000 mg/L on food-borne pathogens were determined against Staphylococcus aureus, Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7. Growth of the microorganisms was not affected by the extract at concentrations up to 250 mg/L, but it was significantly (p<0.05) inhibited by the extract at concentrations higher than 1,000 mg/L. The antioxidant effects of the extract were examined via measurement of DPPH radical scavenging activity, inhibition of reactive oxygen species (ROS) generation using fluorescent dichlorofluorescien (DCF) assay, and prevention of peroxyl radical- and hydroxyl radical-induced supercoiled DNA breakage. The $IC_{50}$ of the extract for DPPH radical scavenging activity was about half that of ${\alpha}$-tocopherol, which was used as a positive control. DCF fluorescence intensity decreased as the concentration of the extract increased, demonstrating that ROS generation was inhibited in a concentration-dependent manner. The ROS inhibitory effect of the extract was higher than that of ascorbic acid. The extract prevented supercoiled DNA strand breakage induced by peroxyl radical and hydroxyl radical. Thus, the results of the present study demonstrate that the extract exhibits antimicrobial effects against food-borne pathogens as well as potent antioxidant capacity, suggesting that R. brachycarpum could be used as a natural antibacterial agent and effective antioxidant in food.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.19 no.2
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• pp.109-124
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• 2014

In order to understand the carbon cycle in the Amundsen Sea of the Southern Ocean, the export fluxes of particulate organic carbon from the euphotic zone to deep water estimated using ${\psi}$/${\psi}$ disequilibrium method. Seawaters in 14 water columns were collected during February and March 2012, and analyzed for total and dissolved ${\psi}$, and particulate organic carbon. Total ${\psi}$ activities in the water column showed deficiency and excess relative to those of ${\psi}$ depending on the water depth. Deficiency of total ${\psi}$ in the euphotic zone showed mirror images both with chlorophyll-a and fluorescence, and was consistent with the loss of nitrate, which indicated the effect of biological activity. In addition, deficiency of total ${\psi}$ from deep water was associated with the increase of total dissolvable Fe/Mn concentration. Excess total ${\psi}$ activity presented below the euphotic zone might be related to particulate ${\psi}$ concentrated in this water depth. Mean export flux of ${\psi}$ estimated using the steady state model was $867{\pm}246dpmm^{-2}day^{-1}$. Mean export flux of particulate organic carbon, which were estimated by the product of total ${\psi}$ flux and ratio of POC/${\psi}$ ($7.08{\pm}4.27{\mu}molCdpm^{-1}$) in the sinking particles, was $5.9{\pm}3.9mmolCm^{-2}day^{-1}$. These fluxes were similar levels to those in the Weddell Sea during February and March 2008. Export ratios (ThE) relative to the primary production in the euphotic zone were in the range of 3-54% (av. 28%).

• Journal of radiological science and technology
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• v.37 no.3
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• pp.187-193
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• 2014

The purpose of this study was to analyze the effect on the selectivity on of high-voltage rectification device that measured the performance of the grid, and the contrast improvement ability (K factor) by measuring the scattered radiation content of the transmitted X-rays. The scattered radiation generated when the X-ray flux comes from the diagnostic X-ray generator that passes through an object. Targeting four different rectifications of X-ray generators, the mean value of the tube voltage and the tube current was measured in order to maximize the accuracy of the generating power dose within the same exposure condition. Using fluorescence meter, the content of the scattered rays that are transmitted through the acrylic was measured depending on the grid usage. When grid is not used, the content of the scattered rays was the lowest (34.158%) with the single-phase rectifier, was increased with the inverter rectifier (37.043%) and the three-phase 24-peak rectification method (37.447%). The difference of the scattered radiation content of each device was significant from the lowest 0.404% to the highest 3.289% while using 8:1 grid, the content of the scattered ray was the lowest with the single content of the scattered ray was the lowest with the single-phase rectifier (18.258%), was increased with the rectifier (25.502%) and the 24-peaks rectification (24.217%). Furthermore, there was difference up to content 7.244% to the lowest content 1.285% within three-phase 24-peaks rectification, inverter rectifications, and single-phase rectifier depending on the selectivity of the grid. Drawn from the statistical analysis, there was a similar relationship between the contrast improvement factor and the K factor. As a result, the grid selectivity and the contrast were increased within the single-phase rectifier rather than the constant voltage rectifier.

• Progress in Medical Physics
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• v.15 no.1
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• pp.1-8
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• 2004

Patient dose verification is one of the most Important responsibilities of the physician in the treatment delivery of radiation therapy. For the task, it is necessary to use an accurate dosimeter that can verify the patient dose profile, and it is also necessary to determine the physical characteristics of beams used in intensity modulated radiation therapy (IMRT) The Beam Intensity Scanner (BInS) System is presented for the dosimetric verification of the two dimensional photon beam. The BInS has a scintillator, made of phosphor Terbium-doped Gadolinium Oxysulphide (Gd$_2$O$_2$S:Tb), to produce fluorescence from the irradiation of photon and electron beams. These fluoroscopic signals are collected and digitized by a digital video camera (DVC) and then processed by custom made software to express the relative dose profile in a 3 dimensional (3D) plot. As an application of the BInS, measurements related to IWRT are made and presented in this work. Using a static multileaf collimator (SMLC) technique, the intensity modulated beam (IMB) is delivered via a sequence of static portals made by controlled leaves. Thus, when static subfields are generated by a sequence of abutting portals, the penumbras and scattered photons of the delivered beams overlap in abutting field regions and this results in the creation of “hot spots”. Using the BInS, inter-step “hot spots” inherent in SMLC are measured and an empirical method to remove them is proposed. Another major MLC technique in IMRT, the dynamic multileaf collimator (DMLC) technique, has different characteristics from SMLC due to a different leaf operation mechanism during the irradiation of photon and electron beams. By using the BInS, the actual delivered doses by SMLC and DMLC techniques are measured and compared. Even if the planned dose to a target volume is equal in our experimental setting, the actual delivered dose by DMLC technique is measured to be larger by 14.8% than that by SMLC, and this is due to scattered photons and contaminant electrons at d$_{max}$.

• Korean Journal of Poultry Science
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• v.39 no.4
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• pp.291-295
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• 2012

The use of methylacetamide (MA) as a cryoprotective agent for freezing Korean Native Black rooster Ogye semen was examined with artificial insemination. The diluted Ogye semen with HS-1 was subjected for 2 step dilution method of cryopreservation in which the final concentration of MA was adjusted to 7.5%. The sperm viability after thawing was reduced from $95.17{\pm}0.93%$ to $55.93{\pm}1.38%$ which was confirmed by live-death analysis based on Fluorescence-Activated Cell Sorting (FACS). The rates of fertilized eggs with fresh or frozen-thawed semen were reduced from $94.98{\pm}3.93%$ to $66.36{\pm}8.43%$ at day 7 with significant difference. However, the hatching rates of experiments at day 21 did not shown difference between $92.64{\pm}2.33%$ and $90.45{\pm}8.05%$ (P<0.05). With these results, the utilization of MA for freezing of Ogye spermatozoa could affect on viability of frozen-thawed semen but not on the fertility of lain eggs and hatchability of fertilized eggs and also provide possible tools of freezing for poultry genetic resource conservation.