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Author

Sangsoo Sun

Document Type

Dissertation - University Access Only

Award Date

1992

Degree Name

Doctor of Philosophy (PhD)

Department

Animal Science

First Advisor

Douglas C. McFarland

Abstract

The interaction of growth factors with receptors, and the biological effects of growth factors were examined with clonal-derived muscle cells at two distinct developmental stages, and in animals with markedly different propensities for muscle accretion. Embryonic myoblasts (EM) and satellite cells (D5-SC) were used in these studies, since these cells are responsible for embryonic and posthatch skeletal muscle development, respectively. Commercial Nicholas turkeys (DN) and Merriam's turkeys (WM) SC were used as models to compare muscle development in animals which have been either selected or unselected for growth, respectively. WM are included among the native North American varieties and have not been selected for enhanced growth. Clonal cultures were developed in order to minimize interferences from non-myogenic cells in the cultures. The interaction of insulin-like growth factors (IGFs) with receptors on embryonic and postnatal muscle cells were compared using competitive binding assays and receptor affinity cross-linking analysis. Although [125l]IGF-I and [125I]IGF-II were displaced similarly by IGF-I and IGF-II within cell lines, displacement, and therefore dissociation constants, differed between cell lines. Both IGF-I and IGF-II interact with the type I receptor in turkey embryonic myoblasts and postnatal myogenic cells. The interaction of fibroblast growth factor (FGF) with receptors on EM and D5-SC were compared using saturation isotherms. At least two binding sites, including a high affinity receptor and sites of low affinity, which are likely heparin sulfate proteoglycans, were observed on both EM and SC. The FGF binding affinities (Kds) were similar between SC and EM. Receptor Kds were also similar between DN and WM SC. Protein synthesis rates and glucose uptake were compared in the four cell lines using myotubes and confluent proliferating cultures, respectively. Protein synthesis was significantly higher in EM than D5-SC, and higher in WM than DN, respectively, and correlated with the extent of differentiation. Glucose uptake was significantly higher in EM than D5-SC, and higher in DN than WM, respectively. Within cell lines, high levels of either IGFs or insulin stimulated protein synthesis and glucose uptake.

Library of Congress Subject Headings

Turkeys -- Physiology
Growth factors
Musculoskeletal system -- Metabolism

Format

application/pdf

Publisher

South Dakota State University

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