• Journal of Life Science
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• v.17 no.7 s.87
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• pp.923-930
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• 2007

Thymus can regenerate to its normal mass within 14 days after acute involution induced by cyclophosphamide (CY) in adult rat. Despite the established role of Wnt pathways in the process of thymus development, they have not yet been associated with the regeneration of adult thymus. The purpose of this study was to investigate whether Wnt7b, which is expressed in developing thymic epithelial cells rather than in thymocytes, is modulated during thymic regeneration in adult rat. Here, we show that Wnt7b expression was up-regulated in the regenerating thymus. Cells immunolabeled for the Wnt7b were identified as macrophages. Furthermore, Wnt7b gene expression was decreased by the treatment of receptor activator of NF-kappaB ligand (RANKL). Taken together, our results demonstrate that Wnt7b gene expression was increased in macrophages during thymic regeneration and negatively regulated by RANKL.

• Journal of Life Science
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• v.19 no.8
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• pp.1067-1072
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• 2009

Stromal derived factor-1 (SDF-1 or CXCL12), one of the CXC chemokines, is widely expressed in many tissues, including the thymus. The thymus can regenerate to its normal mass within 14 days after acute involution induced by cyclophosphamide (CY) in adult rats. Despite the established role of SDF-1 signaling in the development of T and B lymphocytes in the thymus, it has not yet been associated with the regeneration of the adult thymus. The purpose of this study was to investigate whether SDF-1, which is expressed in thymic stromal cells, is modulated during thymic regeneration in adult rats. Here, we showed that SDF-1 mRNAs were expressed in high levels in the thymocyte and thymic stromal cells at day 7 of the CY model. SDF-1 protein was shown to be present at the cortex-medulla junction, paraseptum and within the thymic medulla. Double-immunofluorescence for SDF-1 and ED-1 showed that strong SDF-1 expression was detected in the macrophages of the medulla region displaying immunoreactivity for ED-1 during thymus regeneration. Taken together, our results demonstrated that SDF-1 expression increased in regenerating thymic macrophages, suggesting the roles of SDF-1 as a chemo-attractant for damaged cells produced in the process of thymic regeneration after acute involution induced by CY.

• The Korean Journal of Zoology
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• v.14 no.4
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• pp.199-204
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• 1971

The effect of 400 R total-body X-irradiation on the rate of deoxycytidine-2-$^14 C$(CdR-2-$^14 C$) into DNA and on the degradation of DNA has been studied in the liver, spleen and thymus of the rat. The postirradiation period can be divided into a radiation reaction period followed by a regeneration period. During the period of radiation reaction, which consists of days 1-2, markdely decreased CdR-2-$^14 C$ incorporation into DNA of each organ is observed. Rate of incorporation of labeled precursor in the thymus shows the most profound decrease, whereas those in the liver and spleen show similar decrease when expressed as percent of normal. The change in the amount of DNA as percent of normal exhibits a similar pattern in all organs, but the rate of decrease is larger in the spleen and thymus compared to that in the liver. The period of regeneration as judged by the incorporation experiment appears day 4 to 5, which consists of the second phase of the regeneration period. The second phase is highlighted by a markedly increased rate of CdR-2-$^14 C$ incorporation and by a slow and continued increase in the amount of DNA in all organs. The regeneration occurs faster in the liver and spleen than in the thymus which is the most radiosensitive of the all. The findings of the present experiments are strongly suggestive of the fact that the radiation-induced loss of spleen and thymus DNA as well as the radiation-caused inhibition in the CdR incorporation into DNA of the thymus are the important factors in the elevated levels of CdR in the urine and plasma.

• Korean Journal of Veterinary Pathology
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• v.1 no.1
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• pp.1-6
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• 1997

The cellularity and composition of the spleen lymph node thymus and peripheral blood and tempo of regeneration were studied at various time points after syngeneic bone marrow transplantation(BMT) in C3H/Hen mice. Significant depression of absolute lymphocyte count was noted on week 1 after lethal whole-body irradiation and BMT. In comparison to the lymph node thymus and spleen had an rapid regeneration of cellularity. The distinct cell populations($CD4^+,\;CD8^+,\;CD28^+,\;B220^+) have determined in the lymphoid tissue of mice subjected to irradiation. The relative representation of these subpopulations was significantly different from that in nonirradiated control. $CD4^+\;and\;CD8^+$ cells were present in very low numbers whereas the $B220^+$ cells reached more than normal range at 2 weeks after BMT. The number of $CD4^+$ cells returned to normal relatively soon than $CD8^+$ cell. At week 4 after BMT, the cellularity and composition of spleen lymph node and peripheral blood lymphocyte reached about 50% of the normal range therefore we can choose this time point for the other tests of immune function after BMT.

• The Korean Journal of Zoology
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• v.15 no.1
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• pp.1-14
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• 1972

The effect of 400 R of whole-body X-irradiation on DNA synthesis, DNA degradation, CdR-aminohydrolase activity and oxygen uptake in the liver, spleen and thymus of the rat has been studied in connection with the radiosensitivity of these tissues. The rate of CdR-2-$^14 C$ incorporation has been followed during the postirradiation period and has been correlated with the increased levels of CdR-aminohydrolase activity druing this period. The postirradiation period comprises radiation reaction and tissue regeneration periods. During the period of radiation reaction, markedly decreased precursor incorporation, decreased tissue levels of DNA and decreased uptake of oxygen are noted as well as an increase in the CdR-aminohydrolase activity. The period of regeneration appears to consist in two discrete phases. The first phase reveals a return of CdR-aminohydrolase activity and the second phase is highlighted by a markedly increased rate of labeled CdR incorporation. Various events occurring during the radiation reaction period and the regeneration period in the three tissues studied can be considered qualitatively the same, differing only in the degree of acute cell death, in the duration of the delay of DNA synthesis in the sruviving cells, and in the rate of recovery resulting from accelerated cell replication during the period of regeneration. A possible biochemical mechanism involved in the DNA synthesis and degradation, in connection with the inreased levels of CdR-aminohydrolase after irradiation, has been briefly discussed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.17 no.3
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• pp.181-191
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• 2007

With the 2-Butanethiol, which is an unidentified inhalation toxic material, acute inhalation toxicity was tested with SD rats. The $LC_{50}$ was evaluated to be 2,500 ppm (9.22 mg/L) or higher which falls under the criteria of acute toxicity Category 3 (500<$LC_{50}$<2,500 ppm) in the Industrial Safety and Health Act. In the subchronical inhalation toxicity test by 0, 25, 100, and 400 ppm, 6 hours a day, 5 days a week, for 13 weeks repeated exposure, though no death or particular clinical presentation was observed, in the female 25 and 400 ppm group, including weight change, and in each concentration group including 400 ppm, change of feed rate, eye stimulation, motility change in male group, and lesions in blood and blood biochemical were observed. In the internal organs weight, 25, 100, and 400 ppm groups in male and 400 ppm group in female showed significant (p<0.05) changes in kidney, liver, thymus, and lung. In the pathological tissue test, severe cortical tubular hyaline droplets were observed in the male 400 ppm group, and all male rats of 400 ppm group and 2 female individuals showed tubular degeneration/regeneration accompanied with pigmentation, showing that the target organs of inhalation exposure of 2-Butanethiol are spleen, kidney, nasal cavity, and adrenal. Through the tests, the NOEL of 2-Butanethiol was evaluated to be 25 ppm (0.092 mg/L) or less for both male and female.

• Toxicological Research
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• v.14 no.2
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• pp.129-141
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• 1998

Toxic effects of 2-bromopropane (2-BP) on the hematopoietic system and testis were investigated in male Srague-Dawley (SD) rats. 80 male SD rats, 5 weeks old, were treated with 2-BP in corn oil at levels of 0, 100, 330 and 1,000 mg/kg/day for 4 weeks orally. 10 animals from each group were maintained for additional 8 weeks following the treatment. In addition, 60 male SD rats were divided into 2 groups and administered 2-BP in corn oil at levels of 0 and 1,000 mg/kg/day orally and sacrificed after 1. 2 and 3 weeks of treatment. Clinical observation. body weight changes, food consumption, organ weight changes. hematology, serum chemistry and histopathology of the testis were performed in the study. No clinical sign and mortality were observed in the study. The body weights were significantly reduced with the treatment but gradually recovered. The relative organ weights of the testis and thymus significantly decreased in both of the groups treated with 1,000 mg/kg/day for 3 and 4 weeks. In the recovery groups, organ weights of the testis and epididymis were significantly reduced in both of the groups treated with 330 and 1,000 mg/kg/day. Platelets and reticulocytes were significantly reduced in both of the group treated with 1.000 mg/kg/day for 3 and 4 weeks. While red blood cells were de-creased but mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were increased in the recovery group. Significant increase of chloride was observed in all of the treatment groups except the recovery groups, and calcium was significantly increased in both of the groups treated with 1,000 mg/kg/ day for 3 and 4 weeks. On the other hand. there were significant decreases in alanine aminotransferase (ALT) and aspatate aminotransferase (AST) in most of groups treated with 1.000 mg/kg/day. In the testis. the spermatogonia in stages I-VI were mostly depleted and the spermatocytes in stages VII-VIII were de-generated or necrotized at week 1 after treatment of 2-BP. The degeneration of germ cells and the a-trophy of seminiferous tubules became more severe in time-dependent and dose-dependent manners. The damaged tubules showed regeneration in part. however. they did not appear to be completely recovered within 8 weeks of the recovery period. On the basis of the results. it is suggested that 2-BP would cause toxicities in hematopoiesis by possibly interfering the production of red blood cells and platelets and in spermatogenesis by the destruction oj spermatogonia in SD male rats.