From our ongoing in vitro studies using the Fisher Rat Thyroid cell line-5 (FRTL-5) we recorded accelerated growth, reduced follicularization and reduction in thyroxin release that occurred as the cells were repeatedly sub-cultured. We also recorded that these changes occurred earlier and more rapidly following radiation exposure. We determined that TGF-β1 production increased under both conditions. We hypothesized that alteration in the TGF-β1 signaling pathway contributed to the changes observed in the cellular properties of FRTL-5 cells. Our objective was to examine some of the players in the TGF-β1 signaling pathway to determine whether radiation and/or repeated subculturing promoted changes in their levels and/or activity.
We quantified changes in cellular growth rate using the MTS cell proliferation assay. TGF-β1 ligand and receptor levels were quantified via ELISA, immunocytochemistry and western blot analysis respectively. The levels and activity of Smads 2, 3, 4 and 7, downstream effectors in the TGF-β1 signaling pathway were also measured via western blotting. Lastly, we examined whether TGF-β1 was correctly regulating the expression of its response genes; cyclin A and plasminogen activator inhibitor-1 (PAI-1) under our experimental conditions. To determine this we used luciferase reporter constructs containing promoters for cyclin A and PAI introduced to the cultures by transfection. PAI-1 production in response to exogenously added TGF-β was also tested using a PAI-1 specific ELISA.
We observed an acceleration of growth that occurred earlier in irradiated cells than it did in cells subjected to repeat sub-culturing (p < 0.05). The TGF-β1 receptor levels remained unchanged as a result of radiation and continual passage. We, however, observed decreases in the TGF-β1 induced phosphorylation levels of Smads2 (p < 0.05) and 3 (p < 0.05) after radiation and repeated subculturing. However, no differences in the inherent un-activated levels of Smads2, 3, 4 and 7 were observed. Alterations were observed in TGF-β1 ability to control the expression of cyclin A and PAI-1.
Collectively, these results support that alterations in the TGF-β1 signaling pathway were contributing to the changes in cellular properties that we measured in our cell line, FRTL-5. These alterations were evident at the level of Smad signaling and transcription initiation.
","abstract_html":"<p>From our ongoing <em>in vitro</em> studies using the Fisher Rat Thyroid cell line-5 (FRTL-5) we recorded accelerated growth, reduced follicularization and reduction in thyroxin release that occurred as the cells were repeatedly sub-cultured. We also recorded that these changes occurred earlier and more rapidly following radiation exposure. We determined that TGF-β1 production increased under both conditions. We hypothesized that alteration in the TGF-β1 signaling pathway contributed to the changes observed in the cellular properties of FRTL-5 cells. Our objective was to examine some of the players in the TGF-β1 signaling pathway to determine whether radiation and/or repeated subculturing promoted changes in their levels and/or activity.</p> <p>We quantified changes in cellular growth rate using the MTS cell proliferation assay. TGF-β1 ligand and receptor levels were quantified via ELISA, immunocytochemistry and western blot analysis respectively. The levels and activity of Smads 2, 3, 4 and 7, downstream effectors in the TGF-β1 signaling pathway were also measured via western blotting. Lastly, we examined whether TGF-β1 was correctly regulating the expression of its response genes; cyclin A and plasminogen activator inhibitor-1 (PAI-1) under our experimental conditions. To determine this we used luciferase reporter constructs containing promoters for cyclin A and PAI introduced to the cultures by transfection. PAI-1 production in response to exogenously added TGF-β was also tested using a PAI-1 specific ELISA.</p> <p>We observed an acceleration of growth that occurred earlier in irradiated cells than it did in cells subjected to repeat sub-culturing (p < 0.05). The TGF-β1 receptor levels remained unchanged as a result of radiation and continual passage. We, however, observed decreases in the TGF-β1 induced phosphorylation levels of Smads2 (p < 0.05) and 3 (p < 0.05) after radiation and repeated subculturing. However, no differences in the inherent un-activated levels of Smads2, 3, 4 and 7 were observed. Alterations were observed in TGF-β1 ability to control the expression of cyclin A and PAI-1.</p> <p>Collectively, these results support that alterations in the TGF-β1 signaling pathway were contributing to the changes in cellular properties that we measured in our cell line, FRTL-5. These alterations were evident at the level of Smad signaling and transcription initiation.</p>","abstract_has_math":false,"creators":["Burrell, Cheryl G."],"institution":null,"degree_name":"Doctor of Philosophy (PhD)","degree_level":"Dissertation","degree_discipline":"Microbiology","degree_department":null,"school":null,"contributors":["Lora M. Green","Daila S. Gridley","Thomas A. Linkhart","Richard A. Luben","Nathan R. Wall"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007-05-01T07:00:00Z","date_published":"2007-05-01T07:00:00Z","updated_at":"2026-07-24T02:54:01Z","subjects":["Animal Experimentation and Research","Hormones, Hormone Substitutes, and Hormone Antagonists","Laboratory and Basic Science Research","Microbiology","Molecular Genetics","Radiochemistry","Thyroid Gland -- microbiology; Thyroid Gland -- radiation effects; Transforming Growth Factor Beta 1; Thyroxine."],"languages":["English"],"rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsrepository.llu.edu/etd/1507","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Lora M. Green","Daila S. Gridley","Thomas A. Linkhart","Richard A. Luben","Nathan R. 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The author retains all other copyrights."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsrepository.llu.edu/etd/1507"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["From our ongoing in vitro studies using the Fisher Rat Thyroid cell line-5 (FRTL-5) we recorded accelerated growth, reduced follicularization and reduction in thyroxin release that occurred as the cells were repeatedly sub-cultured. We also recorded that these changes occurred earlier and more rapidly following radiation exposure. We determined that TGF-β1 production increased under both conditions. We hypothesized that alteration in the TGF-β1 signaling pathway contributed to the changes observed in the cellular properties of FRTL-5 cells. Our objective was to examine some of the players in the TGF-β1 signaling pathway to determine whether radiation and/or repeated subculturing promoted changes in their levels and/or activity.
We quantified changes in cellular growth rate using the MTS cell proliferation assay. TGF-β1 ligand and receptor levels were quantified via ELISA, immunocytochemistry and western blot analysis respectively. The levels and activity of Smads 2, 3, 4 and 7, downstream effectors in the TGF-β1 signaling pathway were also measured via western blotting. Lastly, we examined whether TGF-β1 was correctly regulating the expression of its response genes; cyclin A and plasminogen activator inhibitor-1 (PAI-1) under our experimental conditions. To determine this we used luciferase reporter constructs containing promoters for cyclin A and PAI introduced to the cultures by transfection. PAI-1 production in response to exogenously added TGF-β was also tested using a PAI-1 specific ELISA.
We observed an acceleration of growth that occurred earlier in irradiated cells than it did in cells subjected to repeat sub-culturing (p < 0.05). The TGF-β1 receptor levels remained unchanged as a result of radiation and continual passage. We, however, observed decreases in the TGF-β1 induced phosphorylation levels of Smads2 (p < 0.05) and 3 (p < 0.05) after radiation and repeated subculturing. However, no differences in the inherent un-activated levels of Smads2, 3, 4 and 7 were observed. Alterations were observed in TGF-β1 ability to control the expression of cyclin A and PAI-1.
Collectively, these results support that alterations in the TGF-β1 signaling pathway were contributing to the changes in cellular properties that we measured in our cell line, FRTL-5. These alterations were evident at the level of Smad signaling and transcription initiation.
"]},{"key":"dc:title","label":"Title","values":["The Effect of Radiation and Repeated Sub-culturing on TGF-β1 Signaling in FRTL-5 Cells"]}]}],"canonical_facts":{"dc:contributor":["Lora M. Green","Daila S. Gridley","Thomas A. Linkhart","Richard A. Luben","Nathan R. Wall"],"dc:creator":["Burrell, Cheryl G."],"dc:description.abstract":["From our ongoing in vitro studies using the Fisher Rat Thyroid cell line-5 (FRTL-5) we recorded accelerated growth, reduced follicularization and reduction in thyroxin release that occurred as the cells were repeatedly sub-cultured. We also recorded that these changes occurred earlier and more rapidly following radiation exposure. We determined that TGF-β1 production increased under both conditions. We hypothesized that alteration in the TGF-β1 signaling pathway contributed to the changes observed in the cellular properties of FRTL-5 cells. Our objective was to examine some of the players in the TGF-β1 signaling pathway to determine whether radiation and/or repeated subculturing promoted changes in their levels and/or activity.
We quantified changes in cellular growth rate using the MTS cell proliferation assay. TGF-β1 ligand and receptor levels were quantified via ELISA, immunocytochemistry and western blot analysis respectively. The levels and activity of Smads 2, 3, 4 and 7, downstream effectors in the TGF-β1 signaling pathway were also measured via western blotting. Lastly, we examined whether TGF-β1 was correctly regulating the expression of its response genes; cyclin A and plasminogen activator inhibitor-1 (PAI-1) under our experimental conditions. To determine this we used luciferase reporter constructs containing promoters for cyclin A and PAI introduced to the cultures by transfection. PAI-1 production in response to exogenously added TGF-β was also tested using a PAI-1 specific ELISA.
We observed an acceleration of growth that occurred earlier in irradiated cells than it did in cells subjected to repeat sub-culturing (p < 0.05). The TGF-β1 receptor levels remained unchanged as a result of radiation and continual passage. We, however, observed decreases in the TGF-β1 induced phosphorylation levels of Smads2 (p < 0.05) and 3 (p < 0.05) after radiation and repeated subculturing. However, no differences in the inherent un-activated levels of Smads2, 3, 4 and 7 were observed. Alterations were observed in TGF-β1 ability to control the expression of cyclin A and PAI-1.
Collectively, these results support that alterations in the TGF-β1 signaling pathway were contributing to the changes in cellular properties that we measured in our cell line, FRTL-5. These alterations were evident at the level of Smad signaling and transcription initiation.
"],"dc:identifier":["https://scholarsrepository.llu.edu/etd/1507"],"dc:language":["English"],"dc:rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"dc:subject":["Animal Experimentation and Research","Hormones, Hormone Substitutes, and Hormone Antagonists","Laboratory and Basic Science Research","Microbiology","Molecular Genetics","Radiochemistry","Thyroid Gland -- microbiology; Thyroid Gland -- radiation effects; Transforming Growth Factor Beta 1; Thyroxine."],"dc:title":["The Effect of Radiation and Repeated Sub-culturing on TGF-β1 Signaling in FRTL-5 Cells"],"thesis:degree_discipline":["Microbiology"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Doctor of Philosophy (PhD)"]},"updated_at":"2026-07-24T02:54:01Z"}