• Korean Journal of Animal Reproduction
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• v.9 no.2
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• pp.124-132
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• 1985

The work was conducted to clarify the development of testes and histological changes of the Seminiferous tubules that is the Surface area, diameter, length of the tubules and the process of Spermatic cells growth in Seminal epithelium in relation to Sexual maturity of the meat-type cockerels. In addition the present experiments were planned to gain some basic data helpful for the study of reproductive physiology in meat-type cockerels and also to compare the histological changes Seminiferous tubules between egg and general purpose type cockerels. 1. The growth pattern of body weight, testes and comb was classified into four phase according to age. Body weight increased up to about 2kg at 2nd stage and to 4.3kg at 4th stage while at 3rd stage the growth rate of body weight was slower. The tests developed slowly until 22 weeks of age with no correlation to the growth of body weight. However, it grew rapidly afterwards, reaching 27.79$\pm$9.26gm and 42.46$\pm$5.33 gm at 24 and 28 weeks of age, respectively. The spermatozoa was seen first at 24 weeks of age. On the other hand, comb grew at similar rate to the testes, weighing on the average 21.78$\pm$6.48gm and 41.42$\pm$1.25gm at 24 and 28 weeks of age, respectively. 2. The areal rate of the Seminiferous tubules to interstitial tissues was 66%:34% at 2 weeks of age and the rate of the former increased in comparison to that of the latter as they grew older, becoming 94%:7% between at 24 weeks of age, when the testes weight increased rapidly too. 3. Diameter of Seminiferous tubules at 2 weeks of age was 42.76$\pm$1.04$\mu$m and then it gradually increased as the testes grew until 22 weeks of age, when it grew rapidly, increasing about 2.9 times of those of 2 weeks and at last increased up to 5 times at 24 weeks. 4. Length of Seminiferous tubules was 4.5cm at 2 weeks and then it was gradually increased. At 22 weeks old the length of tubules was icnreased rapidly being 321 meter and increased more than double, being 658 meter at 24 weeks old. 5. The cells of Seminal epithelium developed poorly and the number of cells were relatively few until 16 weeks old. Afterwards the cells increased rapidly in number and at 18 weeks, the number became twice of those of 16 weeks, reaching 140.43$\pm$43.6. At 24 weeks the cells increased more rapidly, reaching to 10 layers and Spermatozoa were first time seen.

• Journal of Animal Reproduction and Biotechnology
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• v.35 no.2
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• pp.177-182
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• 2020

The present study aimed to investigate the conceptus-related changes during early pregnancy in the Black Bengal breed of goat. A total of 22 gravid genitalia of the Black Bengal goats were collected from local slaughterhouses. The crown-rump lengths (CRL) of the conceptuses were determined to estimate the gestational age (GA). The length and diameter of uterine horn and amniotic sac were measured, and volume of amniotic and allantoic fluid formed by individual conceptus were recorded. The results reveal that the CRL is positively correlated with GA of the conceptus (R² = 0.89, p < 0.05); however, CRL was not influenced by number of conceptus. Both the left and the right uterine horn gradually increased in size with the advancement of pregnancy irrespective of conceptus number present in the horn. The size of the amniotic sac of conceptus gradually increased with the conceptus age but maintained spherical shape from 5 to 7 weeks of pregnancy. The amniotic fluid formed by individual conceptus rapidly increased from 5 weeks (3.4 ± 0.3 mL) to 7 weeks (21.0 ± 2.0 mL) and 9 weeks (111.5 ± 4.0 mL). The volume of allantoic fluid formed by individual conceptus was steadily increased until 7 weeks (60.0 ± 5.0 mL) and began to decline slowly thereafter (50.0 ± 5.0 mL at 9 weeks). Notably, there was no effect of conceptus number per pregnancy on individual amniotic and allantoic fluid volume. The cotyledons have first appeared on the allanto-chorionic surface from 4 to 5 weeks of pregnancy. The closed eye, nostril and hooves of the conceptus became visible at 7 weeks of pregnancy. The present study has shown the basic information on conceptus-related developmental changes during early pregnancy up to 9 weeks in Black Bengal goat.

• Development and Reproduction
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• v.22 no.3
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• pp.225-234
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• 2018

A new embryonic cell line (OFEC-17FEN) derived from olive flounder Paralichthys olivaceus was developed. OFEC-17FEN cells were subcultured for <30 passages over ~200 days. OFEC-17FEN cells had a doubling time of 114.34 h and modal diploid chromosome number was 48. The pluripotency genes POU5f1 and NANOG were expressed in OFEC-17FEN cells. However, the lack of several pluripotency-related genes expression indicates that OFEC-17FEN cells are not stem cells. OFEC-17FEN cells transfected with plasmid pEGFP-c1 exhibited a strong green fluorescent signal at 48 h after transfection. Accordingly, OFEC-17FEN cells may be useful for both basic research and biotechnological application.

• Journal of Preventive Medicine and Public Health
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• v.53 no.5
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• pp.302-306
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• 2020

Objectives: In this paper, we aimed to investigate the evolving debate over border closure in Korea during the coronavirus disease 2019 (COVID-19) pandemic, to address the main themes associated with border closure, and to discuss the factors that need to be considered when making such decisions. Methods: We collated and reviewed previously conducted review studies on border closures during infectious disease outbreaks to derive relevant themes and factors. Results: According to our systematic review on border closures and travel restrictions, the effects of such containment efforts are limited. We suggest considering the following factors when determining whether to impose border closure measures: (1) disease characteristics, (2) timeliness of implementation, (3) transmission delay and the basic reproduction number, (4) globalization and pandemics, and (5) social and economic costs. Conclusions: Our assessment indicates that the effects of border closures are at best temporary and limited. Alternative measures must be contemplated and implemented to suppress the spread of COVID-19 in particular and infectious diseases more broadly.

• Development and Reproduction
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• v.19 no.4
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• pp.189-196
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• 2015

This study was examined the ovogenesis of Ussurian bullhead, Leiocassis ussuriensis and the morphological development of its larvae and juveniles and to use the results as basic information for the preservation of species and resource enhancement. For artificial egg collection, human chorionic gonadotropin (HCG) was injected at a rate of 10 IU per gram of fish weight. During breeding period, water temperature maintained at $24.5{\sim}26.5^{\circ}C$ (mean $25.0{\pm}0.05^{\circ}C$). The process of ovogenesis reached the two-cell stage in 50 minutes after fertilization. In 73 hours of fertilization the movement of the embryoid body became active state and the larvae began to hatch from the tail through the oolemma. Length of prelarvae were 6.33~6.50 mm long (mean $6.40{\pm}0.06mm$) just after hatching having yolk with their mouth not opened. After thirty eight days of hatching, juveniles were 30.6~32.5 mm long (mean $31.5{\pm}0.65mm$). The color was dark yellowish brown throughout the entire body, and the number of caudal fin rays developed to thirty six perfectly.

• Journal of the Korean housing association
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• v.18 no.4
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• pp.79-88
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• 2007

The purpose of the this study was to provide the basic information about the formation background of urban squatter and their housing state in Korea. This study was progressed on the basis of socio-historical point of view from after the Korean War to the present time. Therefore, this study considered the meaning of housing for urban squatter in the Korean housing history. For this study, the formation background of urban squatter was divided into five periods. The first one was the period of the policy on the mass migration (1955-1960) after the Korean War. The second period was the period of reproduction of deteriorated residential area (1960-1970) for the continuing mass migration policy. The third was the period of disbanding of deteriorated residential area (1970-1980) for redevelopment. The forth period was before the IMF (1980-1997) broke up the deteriorated residential area. The fifth period was after the IMF (1997-) produced the new poverty due to the unemployment and the business failure. Thus, such social change increased the number of urban squatter and created the new type urban poor.

• Journal of the Korean Mathematical Society
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• v.49 no.4
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• pp.779-794
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• 2012

In this paper, we study the global stability of two mathematical models for human immunodeficiency virus (HIV) infection with intra-cellular delays. The first model is a 5-dimensional nonlinear delay ODEs that describes the interaction of the HIV with two classes of target cells, $CD4^+$ T cells and macrophages taking into account the saturation infection rate. The second model generalizes the first one by assuming that the infection rate is given by Beddington-DeAngelis functional response. Two time delays are used to describe the time periods between viral entry the two classes of target cells and the production of new virus particles. Lyapunov functionals are constructed and LaSalle-type theorem for delay differential equation is used to establish the global asymptotic stability of the uninfected and infected steady states of the HIV infection models. We have proven that if the basic reproduction number $R_0$ is less than unity, then the uninfected steady state is globally asymptotically stable, and if the infected steady state exists, then it is globally asymptotically stable for all time delays.

• Development and Reproduction
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• v.24 no.4
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• pp.307-316
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• 2020

The purpose of this study is to observe the early life history of Korean Lefua costata and use the result as basic taxonomic research data for balitorid fish. The fertilized eggs were light green color with completely circle shape and mean size was 1.21±0.06 mm (n=30). Immediately after hatching, the size of the larvae was 2.81±0.11 mm (n=5) in mean length, with egg yolk. On the 3rd day after hatching, the preflexion larvae had a mean length of 4.64±0.09 mm (n=5), and their mouth was opened to start feeding. On the 8th day after hatching, a mean length of the postflexion larvae was 9.43±0.46 mm (n=5), the distal part of the notochord was bent to 45°, and 16 fin rays were developed on the caudal fin. On the 31st day after hatching, a mean length of juveniles was 22.3±0.85 mm (n=5), and the number of fin rays was the same as that of adult fish with (iv8) dorsal fins and (iii8) anal fins.

• Development and Reproduction
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• v.22 no.4
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• pp.379-391
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• 2018

Through the development of organic synthetic skill, chemicals that mimic signaling mediators such as steroid hormones have been exposed to the environment. Recently, it has become apparent that this circumstance should be further studied in the field of physiology. Estrogenic action of chronic low-dose nonylphenol (NP) and di-(2-ethylhexyl) phthalate (DEHP) in mouse uterus was assessed in this study. Ten to twelve-week-old female mice (CD-1) were fed drinking water containing NP (50 or $500{\mu}g/L$) or DEHP (133 or $1,330{\mu}g/L$) for 10 weeks. Uterine diameter, the thickness of myometrium and endometrium, and the height of luminal epithelial cells were measured and the number of glands were counted. The expression levels of the known $17{\beta}$-estradiol ($E_2$)-regulated genes were evaluated with real-time RT-PCR methodology. The ration of uterine weight to body weight increased in $133{\mu}g/L$ DEHP. Endometrial and myometrial thickness increased in 133 and $1,330{\mu}g/L$ DEHP treated groups, and in 50, $500{\mu}g/L$ NP and $133{\mu}g/L$ DEHP, respectively. The height of luminal epithelial cell decreased in NP groups. The numbers of luminal epithelial gland were decreased in NP groups but increased in $50{\mu}g/L$ DEHP group. The histological characters of glands were not different between groups. The mRNA expression profiles of the known $17{\beta}$-estradiol ($E_2$) downstream genes, Esr1, Esr2, Pgr, Lox, and Muc1, were also different between NP and DEHP groups. The expression levels dramatically increased in some genes by the NP or DEHP. Based on these results, it is suggested that the chronic low-dose NP or DEHP works as estrogen-like messengers in uterus with their own specific gene expression-regulation patterns.

• Korean Journal of Organic Agriculture
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• v.22 no.1
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• pp.197-208
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• 2014

The present study was conducted to provide basic data for efficient vermicomposting of swine manure by investigating the effect of sawdust mix on growth and reproduction of earthworms, amount of earthworm cast produced, and its chemical composition when mixing swine manure in different levels (0(SSD0), 10(SSD10), 20(SSD20), 30(SSD30), and 40%(SSD40)) with sawdust commonly used as moist control in manure composting. The C/N ratio of the feed and the survival rate of earthworms for the SSD0 treatment (10.19, 35.2%), The C/N ratio of the feed was 11.09-16.44 and increased with higher level of sawdust mixed, and the survival rate of earthworms during the experiment period was 35.2-100%. The number of earthworms was 16.6 in the SSD40 treatment, and young worms were not found in the SSD0 treatment or the treatment with less than 30% sawdust in the mix. The number and the weight of cocoons in SSD30 and SSD40 treatments were found to be in the ranges of 23.8-59.8 and 256-660 mg respectively. The production of earthworm cast and digested amount were higher with the higher level of mixed sawdust (p<0.05), and the C/N ratio of cast increased with the mixed sawdust ratio, being significantly higher ratio in SSD30 and SSD40 than other treatments (p<0.05). Heavy metals content tended to decrease with the mixed sawdust level. To summarize, the higher level of mixed sawdust was associated with improvement in growth and reproduction of earthworms, and 30-40% sawdust mix in particular could result in efficient vermicomposting.