• Journal of Food Hygiene and Safety
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• v.8 no.4
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• pp.215-223
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• 1993

Chloramphenicol (CAP) is a very effective broad-spectrum antibiotic which had been widely used in animal production. However, the drug is not approved in many countries for use in food-producing animals because of its potential toxicity and the possibility of residues in food products. In this study, a modified microbiological assay was developed for the sensitive detection of CAP residues in meat and milk. The method was characterized by the extraction of CAP with ethyl acetate, addition of $0.15\;\mu\textrm{g}$ oxytetracycline/ml in the phosphate buffer diluent (pH 6.0), a luteus ATCC 9341. The lowest levels of CAP detected in muscle tissues and milk were $0.025\;\mu\textrm{g}/ml\;and\;0.05\;\mu\textrm{g}/g$, respectively. Recovery rates free CAP from milk were 68.5%, from bovine muscle 65.1%, from swine muscle 63.8%, and from chicken muscle 59.4%, respectively, and the coefficients of variation were 1.8~15.1%. The results showed that the detection limits of CAP residues in animal products could significantly be improved by the modified microbiological assay than the conventional ones.

• Korean Journal of Veterinary Service
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• v.45 no.1
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• pp.1-11
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• 2022

A novel porcine circovirus 4 (PCV4) was recently identified in Chinese and Korean pig herds. Although several conventional polymerase chain reaction (cPCR) and real-time PCR (qPCR) assays were used for PCV4 detection, more sensitive and reliable qPCR assay is needed that can simultaneously detect PCV4 and internal positive control (IPC) to avoid false-negative results. In the present study, a duplex qPCR (dqPCR) assay was developed using primers/probe sets targeting the PCV4 Cap gene and pig (glyceraldehyde-3-phosphate dehydrogenase) GAPDH gene as an IPC. The developed dqPCR assay was specifically detected PCV4 but not other PCVs and porcine pathogens, indicating that the newly designed primers/probe set is specific to the PCV4 Cap gene. Furthermore, GAPDH was stably amplified by the dqPCR in all tested viral and clinical samples containing pig cellular materials, indicating the high reliability of the dqPCR assay. The limit of detection of the assay 5 copies of the target PCV4 genes, but the sensitivity of the assay was higher than that of the previously described assays. The assay demonstrated high repeatability and reproducibility, with coefficients of intra-assay and inter-assay variation of less than 1.0%. Clinical evaluation using 102 diseased pig samples from 18 pig farms showed that PCV4 circulated in the Korean pig population. The detection rate of PCV4 obtained using the newly developed dqPCR was 26.5% (27/102), which was higher than that obtained using the previously described cPCR and TaqMan probe-based qPCR and similar to that obtained using the previously described SYBR Green-based qPCR. The dqPCR assay with IPC is highly specific, sensitive, and reliable for detecting PCV4 from clinical samples, and it will be useful for etiological diagnosis, epidemiological study, and control of the PCV4 infections.

• Applied Microscopy
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• v.27 no.2
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• pp.189-196
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• 1997

The ultrastrucures of Xenopus otic vesicle from normal embryo (st. 43) and induced otic vesicle from animal cap assay with Activin A were compared. Activin A was applied to the presumptive ectoderm at various concentrations for three days at $20^{\circ}C$. The results were almost identical to the reference studies, but it was found that the otic vesicle was induced at the concentration of 10 ng/ml in to)v rate. This otic vesicle may be secondarily induced by the neural tissue showed commonly at the concentration of 10 ng/ml. Otoliths were observed as three or four-axis crystaline bodies in the lumen of otic vesicle. In electron micrograph of the normal embryo, two kinds of microvilli were observed on the apical position of hair cells. One was small and common, the other was large-sized and sparsely distributed. In both cell of otic vesicle, mitochondria, golgi apparatus and multivesicular body were rich, so, they showed a lot of similarities in ultrastructure. However, the otolith was not found and microvilli were overexpressed in the otic vesicle induced by Activin A.

• Journal of Life Science
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• v.8 no.5
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• pp.479-485
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• 1998

The induction of nephric duct from Xenopus presumptive ectoderm(animal cap) was studied and the high-dose ef-fect of IGF-1 was investigated. Activin A induce various organs from cultured animal cap explants and the effects are time and dose-dependent. On the induction of nephric duct, the combined-dose of activin A and retinoic acid was very efficient method in reference study. In present study, we used IGF-1 as well as activin A as a combined growth factor. The concentration ranges of growth factors were activin A l00ng/ml an IGF-1 0-500ng/m1. Explants were cultured in combined solution for 3days to the normal embryo arrives at st. 43. In general, when the explant was cultured in high concentration(l00ng/ml) of activin A, it was destroyed, however, nephric duct and other tis-sues were differentiated by adding IGF-1. In addition, eye induction by adding IGF-1 500ng/ml to activin A 1- 100 ng/ml solution was studied. The low concentration of activin A(1ng/ml) have blood-like cell inducing effect and the explant was balloon-shaped, however, the high dose combination with IGF-1 extended the range of eye inductive concentration of activin A.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1221-1232
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• 2011

We investigated the toxic effects of difenoconazole on the development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of difenoconazole (0-30 ${\mu}M$). $LC_{100}$ for difenoconazole was 30 ${\mu}M$, and the $LC_{50}$ determined by probit analysis was 27.19 ${\mu}M$. Exposure to difenoconazole concentrations ${\geq}$5 ${\mu}M$ resulted in 10 different types of severe external malformation. Histological examinations revealed dysplasia of the eye, heart, liver, somatic muscle, and swelling of the pronephric ducts. The tissue-specific toxic effects were investigated with an animal cap assay. Blood cells were normally induced at a high frequency by mSCF and activin A. However, the induction of blood cells was strongly inhibited by the addition of difenoconazole. Electron micrographs of tested embryos showed the degeneration of somatic muscle and the shrinkage of microvilli on pronephric duct. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction (RT-PCR). It revealed that the expression of the blood-specific marker(${\beta}$-globin II) and muscle-specific marker (XMA) were more strongly inhibited than the neural-specific marker(XEn2) by the addition of difenoconazole.

• Journal of Environmental Science International
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• v.19 no.8
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• pp.1001-1012
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• 2010

We investigated the toxic effects of tebuconazole on development in the African clawed frog, Xenopus laevis. To test the toxic effects, frog embryo teratogenesis assays using Xenopus were performed. Embryos were exposed to various concentrations of tebuconazole($0-100\;{\mu}M$). $LC_{100}$ for tebuconazole was $100\;{\mu}M$, and the $LC_{50}$ determined by probit analysis was $82.35\;{\mu}M$. The exposure to tebuconazole concentrations ${\geq}40\;{\mu}M$ resulted in 11 different types of severe external malformations including gut dysplasia. Histological examinations revealed various dysplasia in the eye, heart, liver, intestine, somatic muscle, and in the pronephric ducts. The tissue-specific toxic effects were investigated with an animal cap assay. Blood cells are generally induced at a high frequency by the combination of mSCF and activin A, however, the induction of blood cells was strongly inhibited by the addition of tebuconazole. Electron micrographs of tested embryos showed many of multivesicular bodies and dysplasia of photo-receptive cell, however, the somatic muscle degeneration was not severe. The gene expression of cultivated animal cap explants was investigated by reverse transcriptase-polymerase chain reaction and revealed that expression of the blood-specific marker, $\beta$ globin II and muscle-specific marker, muscle actin were more strongly inhibited than the neural-specific marker, XEn2.

• Molecules and Cells
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• v.44 no.10
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• pp.723-735
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• 2021

Spemann organizer is a center of dorsal mesoderm and itself retains the mesoderm character, but it has a stimulatory role for neighboring ectoderm cells in becoming neuroectoderm in gastrula embryos. Goosecoid (Gsc) overexpression in ventral region promotes secondary axis formation including neural tissues, but the role of gsc in neural specification could be indirect. We examined the neural inhibitory and stimulatory roles of gsc in the same cell and neighboring cells contexts. In the animal cap explant system, Gsc overexpression inhibited expression of neural specific genes including foxd4l1.1, zic3, ncam, and neurod. Genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) and promoter analysis of early neural genes of foxd4l1.1 and zic3 were performed to show that the neural inhibitory mode of gsc was direct. Site-directed mutagenesis and serially deleted construct studies of foxd4l1.1 promoter revealed that Gsc directly binds within the foxd4l1.1 promoter to repress its expression. Conjugation assay of animal cap explants was also performed to demonstrate an indirect neural stimulatory role for gsc. The genes for secretory molecules, Chordin and Noggin, were up-regulated in gsc injected cells with the neural fate only achieved in gsc uninjected neighboring cells. These experiments suggested that gsc regulates neuroectoderm formation negatively when expressed in the same cell and positively in neighboring cells via soluble factors. One is a direct suppressive circuit of neural genes in gsc expressing mesoderm cells and the other is an indirect stimulatory circuit for neurogenesis in neighboring ectoderm cells via secreted BMP antagonizers.

• Korean Journal of Animal Reproduction
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• v.7 no.2
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• pp.8-26
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• 1983

Various early pregnancy diagnostic methods have been developed in order to improve the reproductive efficiency in cow, mare, mule, sow, sheep, goat, dog, cat, rabbit, buffalo, camel, elephant, monkey, deer, lion, coipus and guinea pig. These methods include abdominal swelling, abdominal palpation, esturs cylce detection, Lupin test, gonadotropin assay, colostrum injection test, sperm motility assessment, cervical mucus viscosity test, Kaber chromagens method, estrogen test, A Scheim-Zond다 test, spectrophotometric detection of estrogen in urine and feces, boric acid crystraline formation test in urine, oxytocin injection test, diamino-oxidase test, PMSG HA test, behaviour test, Simolus iodine detection test, detection of tryptophane in urine, x-ray method, Cuboni and Lunaas method, vaginal biopsy method, Friedmann Schneider diagnostic method, electrode method, barium chloride detection method, ECG, Doptone method, ultrasound method, ultrasound scanning method, LDH method, rectal palpation method, CL palpation method, radioautography, serum creatine test, serum globulin test, chlormadine method, CAP method, Medata Do, pp.ers method, body fluid test, Plasma oCS detection method, ERIA, LHRH method, negative latex cogulation test and oestrone sulphate detection method. The most reliable methods with high a, pp.icability to farm animals such as sheep, mare, sow and cow are rectal palpation, ultrasound method and hormonal assay in blood and milk. However, they require complicated laboratory works for the early diagnosis of pregnancy and in most cases, the simple and economical methods which are described up to now need a long period of time after conception. Generally, it is possible to detect pregnancy after one estrus cycle, even though it varies depending on the species of animals. For improvement of the reproductive efficiency, it is required to develop a more accurate, economical, simple and early detectable method. It is anticipated that the result of a study on the detection method of EPF(early pregnancy factor) would be a, pp.icable to various animals within 6 hours after conception.

• Journal of Life Science
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• v.14 no.3
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• pp.375-384
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• 2004

Fibroblast growth factors (FGFs) are known to induce multiple functions in early development, including mesoderm formation, gastrulation movement and antero-posterior patterning. The induction of mesoderm from Xenopus presumptive ectoderm and the combination effect on inducing organs of bFGF(basic FGF) and HGF (Hepatocyte Growth Factor) were studied. Explants were cultured in the combined solution for 3 days to normal embryo arrive at St. 43. These effects on combined dose were examined by histological experiment and by immunohistochemical method. The concentrations of growth factors were tested in 0, 0.5, 1, 10 and also tested in 50 ng/ml of bFGF, and 0, 1, 10, 50 and 100ng/ml of HGF respectively. The synergistic effects were seen in the combined-dose of bFGF and HGF rather than in single dose. Various organs were differentiated and highest inducing effects were seen at the combined concentration of 1 ng/ml of bFGF and 10ng/ml of HGF, and at the concentration 10ng/ml of bFGF and 1 ng/ml of HGF. The bFGF induces various organs from cultured animal cap explants and the effects are time and dose-dependent. HGF is also a potent mitogen for renal tubular cells and for mature hepatocytes in primary culture. Eyes were developed in high percentage at the combined concentration of 1 and 10ng/ml of bFGF, and 1 and 10 ng/ml of HGF. From the induced eye and normal embryonic eye, RPE65 was commonly detected by monoclonal antibodies 40All and 25F5 and the localization of RPE65 was seen by AP reaction.