{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/41625"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/41625","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Extrathyroidal thyroid hormone activation in ring doves","abstract":"The characteristics of 5’deiodinase (5’D) were studied in the postmitochondrial fraction (PMF) of liver homogenates from adult and developing ring doves (Streptopelia risoria). The 5’D assays were performed in the presence of abundant substrate, reverse triiodothyronine (rT3), cofactor (dithiothreitol) and trace amounts of I¹²⁵-rT3. 5’D activity was measured as I¹²⁵ released from the labelled rT3 during the assay incubation time. The 5’D assay was validated for all ages studied to assure that the initial reaction velocity of the enzyme was measured. Using the validated assay conditions the following characteristics were found in adult doves: the apparent K<sub>m</sub> was 0.44 μM rT3, V<sub>max</sub> was 255 pmol rT3 degraded/min-mg PMF protein. The 5’D activity was completely inhibited by 1.0 mM PTU and 50% inhibited by the addition of 18.0 μM thyroxine (T4) in the presence of 4.0 μM rT3. Activity was maximal at pH 8.04 and at 37.5 C. The K<sub>m</sub> of the enzyme did not change throughout development (1 day prehatch to adult). The 5’D specific activity (rT3 degraded/min-mg PMF protein) was highest during early development (1 day prehatch to 7 days post-hatch), after which it gradually decreased with increasing age. The liver 5’D activity/gram of body weight was highest during the first seven days posthatch. This period of high potential triiodothyronine (T3) production corresponds with the observed period of greatest increase in plasma thyroid hormone concentrations during the first 6-8 days posthatch in ring doves. These results are the first demonstration of initial velocity 5’D activity during development in an altricial bird species and demonstrate a correlation between hepatic 5’D activity and plasma thyroid hormone concentrations during development in ring doves.","abstract_html":"The characteristics of 5’deiodinase (5’D) were studied in the postmitochondrial fraction (PMF) of liver homogenates from adult and developing ring doves (Streptopelia risoria). The 5’D assays were performed in the presence of abundant substrate, reverse triiodothyronine (rT3), cofactor (dithiothreitol) and trace amounts of I¹²⁵-rT3. 5’D activity was measured as I¹²⁵ released from the labelled rT3 during the assay incubation time. The 5’D assay was validated for all ages studied to assure that the initial reaction velocity of the enzyme was measured. Using the validated assay conditions the following characteristics were found in adult doves: the apparent K&lt;sub&gt;m&lt;/sub&gt; was 0.44 μM rT3, V&lt;sub&gt;max&lt;/sub&gt; was 255 pmol rT3 degraded/min-mg PMF protein. The 5’D activity was completely inhibited by 1.0 mM PTU and 50% inhibited by the addition of 18.0 μM thyroxine (T4) in the presence of 4.0 μM rT3. Activity was maximal at pH 8.04 and at 37.5 C. The K&lt;sub&gt;m&lt;/sub&gt; of the enzyme did not change throughout development (1 day prehatch to adult). The 5’D specific activity (rT3 degraded/min-mg PMF protein) was highest during early development (1 day prehatch to 7 days post-hatch), after which it gradually decreased with increasing age. The liver 5’D activity/gram of body weight was highest during the first seven days posthatch. This period of high potential triiodothyronine (T3) production corresponds with the observed period of greatest increase in plasma thyroid hormone concentrations during the first 6-8 days posthatch in ring doves. These results are the first demonstration of initial velocity 5’D activity during development in an altricial bird species and demonstrate a correlation between hepatic 5’D activity and plasma thyroid hormone concentrations during development in ring doves.","abstract_has_math":false,"creators":["Rieman, James Davis"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Biology","degree_department":"Biology","school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1990,"date_issued":"1990","date_published":"1990","updated_at":"2026-07-22T22:19:27Z","subjects":[],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03142009-040750"],"render_values":[{"text":"etd-03142009-040750","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/41625","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.department","label":"Department","values":["Biology"]},{"key":"dc:creator","label":"Author","values":["Rieman, James Davis"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T21:31:46Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T21:31:46Z","2009-03-14"]},{"key":"dc:date.issued","label":"Date","values":["1990"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.dcmitype","label":"Dc Type Dcmitype","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-03142009-040750"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/41625"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The characteristics of 5’deiodinase (5’D) were studied in the postmitochondrial fraction (PMF) of liver homogenates from adult and developing ring doves (Streptopelia risoria). The 5’D assays were performed in the presence of abundant substrate, reverse triiodothyronine (rT3), cofactor (dithiothreitol) and trace amounts of I¹²⁵-rT3. 5’D activity was measured as I¹²⁵ released from the labelled rT3 during the assay incubation time. The 5’D assay was validated for all ages studied to assure that the initial reaction velocity of the enzyme was measured. Using the validated assay conditions the following characteristics were found in adult doves: the apparent K<sub>m</sub> was 0.44 μM rT3, V<sub>max</sub> was 255 pmol rT3 degraded/min-mg PMF protein. The 5’D activity was completely inhibited by 1.0 mM PTU and 50% inhibited by the addition of 18.0 μM thyroxine (T4) in the presence of 4.0 μM rT3. Activity was maximal at pH 8.04 and at 37.5 C. The K<sub>m</sub> of the enzyme did not change throughout development (1 day prehatch to adult). The 5’D specific activity (rT3 degraded/min-mg PMF protein) was highest during early development (1 day prehatch to 7 days post-hatch), after which it gradually decreased with increasing age. The liver 5’D activity/gram of body weight was highest during the first seven days posthatch. This period of high potential triiodothyronine (T3) production corresponds with the observed period of greatest increase in plasma thyroid hormone concentrations during the first 6-8 days posthatch in ring doves. These results are the first demonstration of initial velocity 5’D activity during development in an altricial bird species and demonstrate a correlation between hepatic 5’D activity and plasma thyroid hormone concentrations during development in ring doves."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["BTD"]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Extrathyroidal thyroid hormone activation in ring doves"]}]}],"canonical_facts":{"dc:contributor.department":["Biology"],"dc:creator":["Rieman, James Davis"],"dc:date.accessioned":["2014-03-14T21:31:46Z"],"dc:date.available":["2014-03-14T21:31:46Z","2009-03-14"],"dc:date.issued":["1990"],"dc:description.abstract":["The characteristics of 5’deiodinase (5’D) were studied in the postmitochondrial fraction (PMF) of liver homogenates from adult and developing ring doves (Streptopelia risoria). The 5’D assays were performed in the presence of abundant substrate, reverse triiodothyronine (rT3), cofactor (dithiothreitol) and trace amounts of I¹²⁵-rT3. 5’D activity was measured as I¹²⁵ released from the labelled rT3 during the assay incubation time. The 5’D assay was validated for all ages studied to assure that the initial reaction velocity of the enzyme was measured. Using the validated assay conditions the following characteristics were found in adult doves: the apparent K<sub>m</sub> was 0.44 μM rT3, V<sub>max</sub> was 255 pmol rT3 degraded/min-mg PMF protein. The 5’D activity was completely inhibited by 1.0 mM PTU and 50% inhibited by the addition of 18.0 μM thyroxine (T4) in the presence of 4.0 μM rT3. Activity was maximal at pH 8.04 and at 37.5 C. The K<sub>m</sub> of the enzyme did not change throughout development (1 day prehatch to adult). The 5’D specific activity (rT3 degraded/min-mg PMF protein) was highest during early development (1 day prehatch to 7 days post-hatch), after which it gradually decreased with increasing age. The liver 5’D activity/gram of body weight was highest during the first seven days posthatch. This period of high potential triiodothyronine (T3) production corresponds with the observed period of greatest increase in plasma thyroid hormone concentrations during the first 6-8 days posthatch in ring doves. These results are the first demonstration of initial velocity 5’D activity during development in an altricial bird species and demonstrate a correlation between hepatic 5’D activity and plasma thyroid hormone concentrations during development in ring doves."],"dc:description.degree":["Master of Science"],"dc:format.medium":["BTD"],"dc:format.mimetype":["application/pdf"],"dc:identifier.other":["etd-03142009-040750"],"dc:identifier.uri":["http://hdl.handle.net/10919/41625"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:title":["Extrathyroidal thyroid hormone activation in ring doves"],"dc:type":["Thesis"],"dc:type.dcmitype":["Text"],"thesis:degree_discipline":["Biology"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:27Z"}