• Radiation Oncology Journal
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• v.19 no.2
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• pp.153-162
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• 2001

Purpose : The mechanical insights of death of cancer cells by ionizing radiation are not of yet clearly defined. Recent evidences have demonstrated that radiation therapy may induce cell death via activation of signaling pathway for apoptosis in target cells. This study is designed whether ionizing radiation may activate the signaling cascades of apoptosis including caspase family cysteine pretenses, $Bcl_2/Bax$, cytochrome c and Fas/Fas-L in target cells. Materials and Methods : HL-60 cells were irradiated in vitro with 6 MV X-ray at dose ranges from 2 Gy to 32 Gy. The cell viability was tested by M assay and the extent of apoptosis was determined using agarose gel electrophoresis. The activities of caspase proteases were measured by proteolytic cleavages of substrates. Western blot analysis was used to monitor PARP, Caspase-3, Cytochrome-c, Bcl-2, Bax, Fas and Fas-L. Results : Ionizing radiation decreases the viability of HL-60 cells in a time and dose dependent manner. Ionizing radiation-induced death in HL-60 cells is an apoptotic death which is revealed as characteristic ladder-pattern fragmentation of genomic DNA over 16 Gy at 4 hours. ionizing radiation induces the activation of caspase-2, 3, 6, 8 and 9 of HL-60 cells in a time-dependent manner. The activation of caspase-3 pretense is also evidenced by the digestion of poly (ADP-ribose) polymerase and procaspase 3 with 16Gy ionizing irradiation. Anti-apoptotic Bcl2 expression is decreased but apoptotic Bax expression is increased with mitochondrial cytochrome c release in a time- dependent manner. In addiiton, expression of Fas and Fas-L is also increased in a time dependent manner. Conclusion : These data suggest that ionizing radiation-induced apoptosis is mediated by the activation of various signaling pathways including caspase family cysteine proteases, $Bcl_2/Bax$, Fas and Fas-L in a time and dose dependent manner.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.2
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• pp.120-128
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• 1976

Two experiments were conducted to study the nature of protein degradation in fish muscle postmortem, first one with English sole (Paraphyrus vetulus) followed by another with rockfish (Sebastodes spp.). In the first one, proteolysis was measured by the increase of amino-N in gutted fish during storage in ice and in the homogenates prepared from fish of different ice storage during $20^{\circ}C-incubation$. In order to test the possible involvement of fish muscle a cathepsin, a portion of each homogenate sample was exposed to 0.5 Mrad of gamma radiation to destroy viable microorganisms prior to the incubation. Proteolysis was not detected until viable count reached a level above $10^7$ cells per gm fish flesh, corresponding to 31 days of ice storage. Even if fish flesh were mechanically disrupted by means of homogenization and subsequently incubated at $20^{\circ}C$, proteloysis attributable to muscle cathepsin was not detected. In the second with rockfish muscle aseptically prepared from freshly killed fish, the samples were inoculated with a proteolytic strain of fish spoilage Pseudomonad or irradiated at 0, 0.5 and 3.0 Mrad. The four samle groups were stored at $0-2^{\circ}C$ to compare the spoilage pattern of sterile and non-sterile muscle. In sterile muscle both total-N (extracted in 0.5M KCl) and amino-N $(soluble\;in\;70\%\;ethanol)$ declined slightly while the inoculated muscle showing increase in parallel with the increase of number of inoculated bacterium. The results indicate that proteolysis is a part of normal fish spoilage and the onset of proteolysis is delayed until viable count reaches its maximum level. Contribution of fish muscle cathepsin to protein degradation in white flesh fish muscle post-mortem is nil.