Browsing by Author "Tokach, Rebecca J."
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Item Chromium propionate enhances adipogenic differentiation of bovine intramuscular adipocytes(2015) Tokach, Rebecca J.; Ribeiro, Flavio R.B.; Chung, Ki Yong; Rounds, Whitney; Johnson, Bradley J.In vitro experiments were performed to determine the effects of increasing concentrations of chromium propionate (CrPro) on mRNA and protein abundance of different enzymes and receptors. Intramuscular (IM) and subcutaneous (SC) preadipocytes and bovine satellite cells were isolated from the longissimus muscle to determine the effect of treatment on glucose transporter type 4 (GLUT4) and peroxisome proliferator-activated receptor γ mRNA and GLUT4 protein abundance. Preadipocyte cultures were treated with differentiation media plus either sodium propionate or different concentrations of CrPro for 96, 120, and 144 h before harvest. This study indicated that adipogenesis of the bovine IM adipocytes were more sensitive to the treatment of CrPro as compared to SC adipocytes. Enhancement of adenosine monophosphate-activated protein kinase and GLUT4 mRNA by CrPro treatment may enhance glucose uptake in IM adipocytes. CrPro decreased GLUT4 protein levels in muscle cell cultures suggesting that those cells have increased efficiency of glucose uptake due to exposure to increased levels of CrPro. In contrast, each of the two adipogenic lines had opposing responses to the CrPro. It appeared that CrPro had the most stimulative effect of GLUT4 response in the IM adipocytes as compared to SC adipocytes. These findings indicated opportunities to potentially augment marbling in beef cattle fed CrPro during the finishing phase.Item The effects of zilpaterol hydrochloride and chromium propionate on bovine muscle satellite cells and preadipocytes(2011-05) Tokach, Rebecca J.; Johnson, Bradley J.; Miller, Markus F.; Starkey, Jessica D.Numerous feed additives have been used in the beef industry for enhancing muscle growth, improving immune efficiency, and increasing carcass quality. Zilpaterol hydrochloride (ZH), a beta-2 adrenergic agonist, has been used for enhancing muscle growth in feedlot cattle. Chromium propionate has shown to increase immune efficiency in all livestock species, increase pork quality, and increase milk yield in dairy cattle. The objectives of these in vitro experiments were to determine the effects of each compound on enzymes and/or growth factors in bovine muscle satellite cells (BSC) and/or intramuscular and subcutaneous preadipocytes. In the ZH experiments, insulin-like growth factor I (IGF-I) mRNA abundance increased in cells treated with ZH for 48 h and 120 h. A β2-adrenergic receptor antagonist (ICI) was used to block the effects of ZH. The addition of ICI attenuated the effect of ZH on IGF-I mRNA abundance. Myosin heavy chain (MHC) isoform I and MHC IIX mRNA expression was increased in cells treated with ZH for 120 h. This effect was ameliorated when ICI was added to the media. When cells were treated with ZH for 48 h there was no effect of ZH on MHC I or MHC IIX mRNA abundance. Indicating that MHC isoform abundance may be affected by duration of treatment. In the chromium propionate experiments, glucose transporter type 4 (GLUT4) mRNA abundance tended to increase after 144 h of treatment of 1 µM or 10 µM chromium propionate in intramuscular preadipocytes and increased in subcutaneous preadipocytes. Relative mRNA abundance for PPARγ increased when differentiation media was added for intramuscular and subcutaneous preadipocytes. In BSC, GLUT4/GAPDH protein abundance decreased in a dose-dependent matter when chromium propionate was added to the cultures. Results indicated that ZH and chromium propionate affect enzymes and growth factors important to muscle and adipose tissue growth.