• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2000.11a
• /
• pp.76-100
• /
• 2000

A brief general discussion of the nature and function of biosensors is presented. While the primary motivator for biosensor development has been the health-care industries, recent research efforts have spread to problems in agriculture and biological production systems. To illustrate some of the research from our laboratory, three example biosensors and their corresponding applications are presented. The first of these is an immunosensor for measurement of the hormone progesterone during milking as a method to improve reproductive management of dairy herds. The second example is an enzyme sensor for measurement of urea in milk as a menas to determine the efficiency of conversion of input protein to milk protein and, thus, improve nutritional management of dairy herds. The third example is a DNA sensor using polymerase chain reaction to detect pathogenic bacteria in the wash water of fresh and minimally processed fruits and vegetables. The potential for application of biosensors in agriculture, agrobiotechnology, food processing, and environmental monitoring has barely been realized.

• Toxicological Research
• /
• v.34 no.4
• /
• pp.281-290
• /
• 2018

Exposure to chemical agents is an inevitable consequence of modern society; some of these agents are hazardous to human health. The effects of chemical carcinogens are of great concern in many countries, and international organizations, such as the World Health Organization, have established guidelines for the regulation of these chemicals. Carcinogens are currently categorized into two classes, genotoxic and non-genotoxic carcinogens, which are subject to different regulatory policies. Genotoxic carcinogens are chemicals that exert carcinogenicity via the induction of mutations. Owing to their DNA interaction properties, there is thought to be no safe exposure threshold or dose. Genotoxic carcinogens are regulated under the assumption that they pose a cancer risk for humans, even at very low doses. In contrast, non-genotoxic carcinogens, which induce cancer through mechanisms other than mutations, such as hormonal effects, cytotoxicity, cell proliferation, or epigenetic changes, are thought to have a safe exposure threshold or dose; thus, their use in society is permitted unless the exposure or intake level would exceed the threshold. Genotoxicity assays are an important method to distinguish the two classes of carcinogens. However, some carcinogens have negative results in in vitro bacterial mutation assays, but yield positive results in the in vivo transgenic rodent gene mutation assay. Non-DNA damage, such as spindle poison or topoisomerase inhibition, often leads to positive results in cytogenetic genotoxicity assays such as the chromosome aberration assay or the micronucleus assay. Therefore, mechanistic considerations of tumor induction, based on the results of the genotoxicity assays, are necessary to distinguish genotoxic and non-genotoxic carcinogens. In this review, the concept of threshold of toxicological concern is introduced and the potential risk from multiple exposures to low doses of genotoxic carcinogens is also discussed.

• Toxicological Research
• /
• v.3 no.1
• /
• pp.1-8
• /
• 1987

In vitro induction of cytochrome 450 associated monooxygenase activities by phenobarbital (PB) and 3-methylcholanthrene (MC) was investigated in primary cultures of adult rat hepatocytes. PB and MC were added to the culture 24 hr after the initial plating of hepatocytes. A signiftcant increase of the activities of 7-ethoxycoumarin 0-deethylase and aryl hydrocarbon hydroxylase were observed in MC and PB treated culture. MC caused about 500% induction of the initial oxidation rates of both enzymes in 48 hr. However the PB maintained both enzyme activities close to the level of freshly isolated hepatocytes. Biphenyl 4-hydroxylase and aminopyrine N-demethylase activities were also induced by MC and PB. But the level of induction was less than that occuring with 7-ethoxycoumarin 0-deethylase and aryl hydrocarbon hydroxylase. When aflatoxin $B_1$ was added to the hepatocyte cultures which have been treated with MC or PB, it caused a significant increase of the unscheduled DNA synthesis at higher dose of aflatoxin $B_1$ as compared to those of untreated control hepatocyte cultures. The results suggest that microsomal enzyme activities can be selectively controlled preferably in hepatocyte cultures by the in vitro induction method. This principle may be useful for studying the metabolism and other toxicological studies.

• Parasites, Hosts and Diseases
• /
• v.54 no.3
• /
• pp.329-334
• /
• 2016

Trichomoniasis caused by Trichomonas vaginalis is a common sexually transmitted disease. Its association with several health problems, including preterm birth, pelvic inflammatory disease, cervical cancer, and transmission of human immunodeficiency virus, emphasizes the importance of improved access to early and accurate detection of T. vaginalis. In this study, a rapid and efficient loop-mediated isothermal amplification-based method for the detection of T. vaginalis was developed and validated, using vaginal swab specimens from subjects suspected to have trichomoniasis. The LAMP assay targeting the actin gene was highly sensitive with detection limits of 1 trichomonad and 1 pg of T. vaginalis DNA per reaction, and specifically amplified the target gene only from T. vaginalis. Validation of this assay showed that it had the highest sensitivity and better agreement with PCR (used as the gold standard) compared to microscopy and multiplex PCR. This study showed that the LAMP assay, targeting the actin gene, could be used to diagnose early infections of T. vaginalis. Thus, we have provided an alternative molecular diagnostic tool and a point-of-care test that may help to prevent trichomoniasis transmission and associated complications.

• Molecular & Cellular Toxicology
• /
• v.1 no.1
• /
• pp.62-71
• /
• 2005

For toxicity model in the kidney, renal cell carcinoma (RCC) is one of the most important model to assess the structural and functional alterations. Most RCCs are sporadic, and environmental agents are suspected to play a role in the etiology of the disease. In this study, we discovered novel evidence for previously unknown gene expression patterns related to progression according to cancer stage in RCC. Four clear cell RCC tissue samples along with five corresponding patient-matched normal kidney tissue samples were obtained from patients undergoing partial or radical nephrectomy. To examine the difference of gene expression profile in clear cell RCC, radioactive cDNA microarrays were used to evaluate changes in the expression of 1,152 genes in a total. Using $^{33}P-labeled$ probes, this method provided highly sensitive gene expression profiles including drug metabolism, and cellular signaling. 29 genes were identified with expression levels that differed by more than 2.0 value of z-ratio, compared with that in control. Whereas expression of 38 genes were decreased by less than-2.0 value of z-ratio. In conclusion, this study has identified 67 gene expression alterations in clear-cell type of RCC. Most notably, genes involved in cell growth were up-regulated in stage I more than stage III whereas genes involved in signal transduction were down-regulated in which both stage I and stage III. The identified alteraions of gene expression will likely give in sight in to clear cell RCC and tumor progression.

• Journal of Microbiology
• /
• v.40 no.4
• /
• pp.274-281
• /
• 2002

The competitive quantitative PCR method targeting pcbC gene was developed for monitoring 4-chlorobiphenyl(4CB)-degrading bacteria, Pseudomonas sp. strain DJ-12, in soil microcosms. The method involves extraction of DNA from soil contaminated with 4CB, PCR amplification of a pcbC gene fragment from the introduced strain with a set of strain-specific primers, and quantification of the elec-trophoresed PCR product by densitometry. To test the adequacy of the method, Pseudomonas sp. strain DJ-12 was introduced into both contaminated and non-contaminated soil microcosms amended with 4CB. Pseudomonas sp. strain DJ-12 was monitored and quantified by a competitive quantitative PCR in comparison with 4CB degradation and the result was compared to those obtained by using the conventional cultivation method. We successfully detected and monitored 4CB-degrading bacteria in each microcosm and found a significant linear relationship between the number of 4CB-degrading bacteria and the capacity for 4CB biodegradation. The results of DNA spiking and cell-spreading experiments suggest that this competitive quantitative PCR method targeting the pcbC gene for monitoring 4CB- degrading bacteria appears to be rapid, sensitive and more suitable than the microbiological approach in estimating the capacity of 4CB biodegradation in environmental samples.

• Journal of Plant Biotechnology
• /
• v.31 no.3
• /
• pp.191-195
• /
• 2004

Arabidopsis NDPK2 (AtNDPK2) is a key singaling component that regulate cellular redox state and known to enhance multiple stress tolerance when over-expressed in Arabidopsis plant (Moon et al. 2003). In order to develop transgenic potato plants with enhanced tolerance to multiple stresses, we placed an AtNDPK2 cDNA under the control of a stress-inducible SWPA2 promoter or enhanced CaMV 35S promoter. Transgenic potato plants (cv. Superior and Atlantic) were generated using an Agrobacterium-mediated transformation system and selected on MS medium containing 100 mg/L kanamycin. Genomic Southern blot analysis confirmed the incorporation of AtNDPK2 cDNA into the potato genome. When potato leaf discs were treated with methyl viologen (MV) at 10 $\mu$M, transgenic plants showed higher tolerance to MV than non-transgenic or vector-transformed plants. The NDPK2 transgenic potato plants will be further used for analysis of stress-tolerance to multiple environmental stresses.

• Toxicological Research
• /
• v.17
• /
• pp.167-171
• /
• 2001

The introduction of genetically modified crops has raised concerns regarding safety issues over the insertion of foreign genes into plant genomes using recombinant DNA technology. Since 1991 in Japan, 29 foods and 6 food additives have been evaluated, based on the "Guideline for Safety Assessment", before these foods were marketed. The MHW, however, decided that safety assessment of such foods and food additives should be legally imposed. because soon such foods and food additives are expected to circulate globally and a new system for assessing safety of such foods and food additives at a pre-market stage is necessary, in order to avoid the distribution of any genetically modified foods that have had no safety assessment. The MHW published relevant announcements to amend existing regulations on 1 May 2000. "Standards for safety assessment of seed plant" is established based on a concept of substantial equivalence, and applicable to the products which are regarded as equivalent to the existing products used as foods and food additives. The characterization of the food products entails consideration of the molecular characterization. phenotypic and compositional characteristics, key nutrients and toxicants, and toxicity and allergenicity of the introduced proteins, and if there are indications of unintended effects of the modification, whether further safety testing (animal studies etc.) is needed should be considered. Safety and wholesomeness studies with whole foods should be care fully designed in order to avoid nutritional imbalances causing artifacts and uninterpretable results as was the case of Dr. Pusztaiis report. A case study of genetically modified soybeans (glyphosate-tolerant soybeans) on the immune system of rats and mice is shown. Chemical compositions were also compared with those of the non-GM soybeans. The studies failed to detect any differences in immuno-toxic activity.muno-toxic activity.

• Toxicological Research
• /
• v.19 no.2
• /
• pp.91-98
• /
• 2003

Alkylating agents form alkylated base adducts in the DNA and cause DNA lesions leading to cell killing. In this study, we investigated the mechanism of apoptosis induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in PC-3 and DU145 human prostate carcinoma cell lines. MNNG treatment resulted in the inhibition of cell proliferation in a concentration-dependent manner to a similar extent in both cell lines. This anti-proliferative effect of PC-3 and DU145 cells by MNNG was associated with morphological changed such as membrane shrinking, cell rounding up and formation of apoptotic bodies. MNNG treatment also induced a proteolytic cleavage of specific target proteins such as poly(ADP-ribose) polymerase (PARP) and $\beta$-catenin proteins in DU145 cells but in PC-3 cells. Furthermore, we observed an increase of proapoptotic protein Bax family expression and a decrease of antiapoptotic protein Bcl-2 family by MNNG treatment in a concentration-dependent manner MNNG also induced a proteolytic activation of caspase-3 and -9, which is believed to play a central role in the apoptotic signaling pathway.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.4
• /
• pp.734-739
• /
• 2005

Myxobacterium sp. HK1, isolated from Korean soil, degrades cellulose, differentiates to fruiting body, and its 16s rDNA has $95\%$ similarity to Polyangium sp. An anticancer molecule, CDMHK, was identified from culture broth of Myxobacterium sp. HK1, and purified by Diaion HP20, Silica gel, Sephadex LH-20 chromatography, and preparative HPLC using an YMC OSD-A C18 column. The molecular structure and formula were determined to be $C_{l2}H_{l9}N_3O_2$ (M.W 237) by MS spectrometry, 300 MHz $^{1}H\;and\;^{13}C$ NMR. The CDMHK was not active against Escherichia coli, Staphylococcus aureus, and Candida albicans. However, this molecule inhibited the growth of various cancer cell lines. The $ED_{50}$ values of CDMHK were determined to be 0.147, 0.086, 0.18, 0.166, and 0.142 $\mu$g/ml against A549, SK-OV-3, SK-MEL-2, VF498, and HCTl5 cancer cell lines, respectively. In addition, the CDMHK was able to induce apoptosis of the CCRF-CEM cancer cell line, evidenced by DNA fragmentation assay and DAPI staining.