Low-dose Gamma-irradiation Effect on Early Stage Development and Lifespan in Various Strains of Drosophila melanogaster / 대한산업의학회지

OBJECTIVES: Although ionizing radiation is recognized as being harmful to humans, debate continues regarding the effects of low doses of ionizing radiation. Some studies have reported that low doses of ionizing radiation have a bio-positive effect, namely hormesis, and many researchers have attempted to find concrete and scientific evidence to prove this. To determine whether the discrepancy in effects of low doses of ionizing radiation arises from genetic differences, a study with a multicellular organism system such as fruit flies is needed. METHODS: After irradiation at a low-dose rate of gamma radiation with chronic (0.2 Gy) and acute (0.2, 0.75 and 4 Gy), the pupa rate, eclosion rate and life span were examined with various wild type strains of Drosophila melanogaster such as W1118, Oregon-R, and Canton-S. RESULTS: The life span of Oregon-R exposed to both acute and chronic, low-dose radiation (0.2 Gy) was increased. Although there was some difference in the longevity between the acute and chronic radiation rate, no other differences were found. In Canton-S, only acute dose (0.75 Gy) increased the life span, but it did not in W1118. CONCLUSIONS: Although there were some differences between wild type fruit fly strains in longevity, the low doses of ionizing radiation extended the life span of D. melanogaster. Further studies need to be carried out to explain the difference according to dose and dose rate of radiation in the tested strains.

Effects of Epidermal growth factor (EGF) on the suppression of GH3 cell growth / 대한해부학회지

Some of the pituitary prolactinomas were reported that they don't have active dopamine receptors and do not respond to bromocriptine which is a dopamine agonist. GH3 cell line which is derived from the rat pituitary tumor cells lacks affinity of dopamine receptors and secrete prolactin as well as small amount of growth hormone. Although it has been reported that epidermal growth factor (EGF) induces functional expression of dopamine receptors on GH3 cells in vitro, there has been a contradictory result. In the present study, EGF effect on the GH3 cell response to the bromocriptine was observed in order to investigate whether EGF induces dopamine receptor expression on dopamine resistant tumors in the absence of serum. GH3 cells were cultured for 4 days in the serum-supplemented medium (SSM) followed by culture in serum-free medium (SFM) with or without EGF. Additionally, effect of tamoxifen was also observed. EGF decreased the cell number and the ratio of cell division of GH3 cells while the ratio of prolactin-immunoreac-tive cells was increased. However, EGF did not show any significant effect on the GH3 cell response to bromocriptine treatment. Although tamoxifen decreased the GH3 cell number by increasing apoptosis, it did not influence GH3 cell response to bromocriptine. Our results indicate that EGF does not increase the affinity of dopamine receptors on GH3 cells and is not useful for the treatment of the dopamine-resistant prolactinoma.

EGF Enhances the Differentiation Effect of the Extracellular Matrix Components on the GH3 Pituitary Tumor Cell / 대한해부학회지

This study was performed in order to establish the culture system optimal for the study on pituitary prolactin cells using growth factor and extra cellular matrix components as the culture substrate. The effect of epidermal growth factor (EGF) alone or along with extracellular marix components on GH3 cell growth and PRL expression was assessed using cell count, BrdU-immunocytochemistry and PRL-immunocytochemistry in in vitro cultures on plastic, laminin and Matrigel. EGF decreased the cell growth, BrdU-labeling and increased the PRL-immunoreactive cells regardless of the culture substrate by day 3 of the culture. Matrigel was the best culture substrate to decrease the cell growth and to increase the PRL expression. EGF treatment in the Matrigel culture showed about 80.5% of PRL-immunoreactive cells by day 6 of the culture. These results indicated that Matrigel is the better culture substrate than plastic or laminin to inhibit the overgrowth and to increase the prolactin expression of the GH3 cell and that EGF and Matrigel causes very effective culture environment for the long-term culture of the GH3 cell by synergistic mechanism.