• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.219-224
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• 1987

A strain of Leptospira interrogans(UM-19) was isolated in 1984 from a patient with epidemic pulmonary hemorrhagic fever. The bacteria has been characterized morphologically by a polymorphism showing spiral forms, short and long rods in culture. In order to study the biological relatedness among these forms of the bacteria, the short rods were separated from others by means of continuous sucrose density gradient centrifugation, and cultured at various temperatures such as $10^{\circ}C$, $15^{\circ}C$, $30^{\circ}C$ and $37^{\circ}C$. It was revealed that cultivation or subcultivation of the short rods has resulted in morphological changes observed by darkfield examination, silver stain, and scanning electron microscope showing spiral forms as well as short and long rods.

• Proceedings of the Korean Society of Life Science Conference
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• 2008.10a
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• pp.78.2-78.2
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• 2008

• The Korean Journal of Zoology
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• v.37 no.4
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• pp.597-604
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• 1994

Membranes obtained from the normal human RBC population were separated by continuous sucrose density gradient centrifugation and the density-fractionated membranes were then examined for changes in molecular markers. This study focuses on changes of (i) the membrane protein profile, (ii) differences in membrane-associsted enzyme activities, and (iii) the amount of autologous IgG bound. The following observations were made: (i) ratios for band 4. la over the sum of bands (4. la + 4.Ib) ranged from 0.58 to 0.79 for membranes of lowest density; (ii) significant changes in bound glyceraldehyde-3-phosphate dehydrogenase and acetvlcholinesterase activities were found; (iii) the amounts of autolosous IgG's attached to the red blood cells was highest in the membrane fraction of lowest density.

• Korean Journal of Food Science and Technology
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• v.11 no.2
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• pp.112-117
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• 1979

By using the existing caustic refining system with a minimum modification and by using a combination of various emulsifiers(0.2 % sodium hexametaphosphate. 0.05 % sodium lauryl sulfate and 0.001 % dioctyl sodium sulfosuccinate), a new economical dewaxing process for sunflower seed oil was developed in order to reduce the cost of the dewaxing process. The results indicate that the waxes can be removed satisfactorily from the sunflower seed oil by emulsifying. batchwise or continuously, the oil with the aqueous surfactant solution, followed by centrifugation at ambient temperatures $(16{\sim}27^{\circ}C)$. Dewaxing loss for the batch process was satisfactory for both low wax-and high wax-crude oil, whereas dewaxing loss for the continuous process needs to be improved. The results indicate that initial level of wax content (low wax vs. high wax) did not affect the loss for batch process (0.82 % vs. 0.62 %), but affected the loss for continuous processes, regardless of the type of mixing mode (2.28 % and 5.68 % for low wax-and high wax-oil, respectively). It was also noted that the type of mixing mode (centactor vs. static mixer) for the continuous process affected the loss, regardless of the wax content (5.2 % and 2.8 % for contactor and static mixer, respectively).

• Animal cells and systems
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• v.2 no.4
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• pp.483-488
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• 1998

We previously found that a potent gonadotropin-releasing hormone (GnRH) agonist, buserelin, decreases GnRH promoter activity together with GnRH mRNA level, providing evidence for an autoregulatory mechanism operating at the level of GnRH gene transcription in immortalized GT1-1 neuronal cells. To examine whether agonist-induced decrease in GnRH mRNA level requires the continuous presence of buserelin, we performed a pulse-chase experiment of buserelin treatment. Short-term exposure (15 min) of GT1-1 neuronal cells to buserelin ($10{\mu}M$) was able to decrease GnRH mRNA levels when determined 24 h later. When GT1-1 cells were treated with buserelin ( $10{\mu}M$) for 30 min and then incubated for 1, 3, 6, 12, 24, and 48 h after buserelin removal, a significant decrease in GnRH mRNA levels was observed after the 12 h incubation period. These data indicate that inhibitory signaling upon buserelin treatment may occur rapidly, but requires a long time (at least 12 h) to significantly decrease the GnRH mRNA level. To examine the possible involvement of de novo synthesis and/or mRNA stability in buserelin-induced decrease in GnRH gene expression, actinomycin D ($5{\mu}m/ml$), a potent RNA synthesis blocker, was co-treated with buserelin. Actinomycin D alone failed to alter basal GnRH mRNA Revel, but blocked the buserelin-induced decrease in GnRH mRNA level at 12 h of post-treatment. These data suggest that buserelin may exert its inhibitory action by altering the stability of GnRH mRNA. Moreover, a polvsomal RNA separation by sucrose gradient centrifugation demonstrated that buserelin decreased the translational efficiency of the transcribed GnRH mRNA. Taken together, these results clearly indicate that GnRH agonist buserelin acts as an inhibitory signal at multiple levels such as transcription mRNA stability, and translation.

• Proceedings of the Korean Society of Toxicology Conference
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• 2006.11a
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• pp.65-74
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• 2006

Modem drug discovery requires rapid pharmacokinetic evaluation of chemically diverse compounds for early candidate selection. This demands the development of analytical methods that offer high-throughput of samples. Naturally, liquid chromatography / tandem mass spectrometry (LC-MS/MS) is choice of the analytical method because of its superior sensitivity and selectivity. As a result of the short analysis time(typically 3-5min) by LC-MS/MS, sample preparation has become the rate- determining step in the whole analytical cycle. Consequently tremendous efforts are being made to speed up and automate this step. In a typical automated 96-well SPE(solid-phase extraction) procedure, plasma samples are transferred to the 96-well SPE plate, internal standard and aqueous buffer solutions are added and then vacuum is applied using the robotic liquid handling system. It takes only 20-90 min to process 96 samples by automated SPE and the analyst is physically occupied for only approximately 10 min. Recently, the ultra-high flow rate liquid chromatography (turbulent-flow chromatography)has sparked a huge interest for rapid and direct quantitation of drugs in plasma. There is no sample preparation except for sample aliquotting, internal standard addition and centrifugation. This type of analysis is achieved by using a small diameter column with a large particle size(30-5O ${\mu}$m) and a high flow rate, typically between 3-5 ml/min. Silica-based monolithic HPLC columns contain a novel chromatographic support in which the traditional particulate packing has been replaced with a single, continuous network (monolith) of pcrous silica. The main advantage of such a network is decreased backpressure due to macropores (2 ${\mu}$m) throughout the network. This allows high flow rates, and hence fast analyses that are unattainable with traditional particulate columns. The reduction of particle diameter in HPLC results in increased column efficiency. use of small particles (<2 urn), however, requires p.essu.es beyond the traditional 6,000 psi of conventional pumping devices. Instrumental development in recent years has resulted in pumping devices capable of handling the requirements of columns packed with small particles. The staggered parallel HPLC system consists of four fully independent binary HPLC pumps, a modified auto sampler, and a series of switching and selector valves all controlled by a single computer program. The system improves sample throughput without sacrificing chromatographic separation or data quality. Sample throughput can be increased nearly four-fold without requiring significant changes in current analytical procedures. The process of Bioanalytical Method Validation is required by the FDA to assess and verify the performance of a chronlatographic method prior to its application in sample analysis. The validation should address the selectivity, linearity, accuracy, precision and stability of the method. This presentation will provide all overview of the work required to accomplish a full validation and show how a chromatographic method is suitable for toxirokinetic sample analysis. A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method developed to quantitate drug levels in dog plasma will be used as an example of tile process.

• Natural Product Sciences
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• v.22 no.1
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• pp.46-52
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• 2016

Erectile dysfunction (ED) is a highly prevalent disorder that affects millions of men and considered to be an early symptom of atherosclerosis and a precursor of various systemic vascular disorders. The aim of the present study was to prepare ginsenoside Re enriched fraction (GS-F3K1, ginsenoside Re 10%, w/w) from ginseng berries flesh and to investigate the enhanced activities of GS-F3K1 on alcohol-induced ED. GS-F3K1 was prepared by the continuous liquid and solid separating centrifugation and circulatory ultrafiltration from ginseng berries flesh. GS-F3K1 was administered for 5 weeks in ethanol-induced ED rat by oral administration of 20% ethanol. To investigate the effects of GS-F3K1 on ED model, the levels of nitrite expression, cyclic guanosine monophosphate (cGMP) and erectile response of the penile corpus cavernosum of rat were measured. The erectile response of the corpus cavernosum was restored after GS-F3K1 administration, to a level similar to the normal group. The level of nitrite and cGMP expression in the corpus cavernosum of GS-F3K1-administered male rats was increased significantly compared to positive control group. GS-F3K1 from ginseng berries should effectively restore ethanol-induced ED in male rats and could be developed as a new functional food for the elderly men.