Kysa K. Gilkerson

Comparison of the proliferation and differentiation of myogenic satellite cells and embryonic myoblasts derived from the Turkey

Abstract 1. 1. Embryonic and posthatch turkey skeletal muscle development was compared in in vitro studies using clonal-derived embryonic myoblasts and satellite cells. 2. 2. Although population doubling times were similar between the two lines (25.4 hr for satellite cells and 26.4 hr for embryonic myoblasts), embryonic myoblasts consistently began log phase growth 24 hr earlier than satellite cells. 3. 3. Differentiation (fusion) of embryonic myoblasts was maximized by 36 hr in Dulbeccos Modified Eagles Medium containing 1% horse serum compared with 72 hr for satellite cells. 4. 4. When administered a serum-free medium which supports proliferation of turkey satellite cells, embryonic myoblasts differentiated to form myotubes.

Comparison of insulin-like growth factor interaction with satellite cells and embryonic myoblasts derived from the turkey

1. The interaction of insulin-like growth factors (IGFs) with receptors on clonal-derived turkey satellite cells and embryonic myoblasts was compared using competitive binding assays and affinity cross-linking analysis. 2. Although [125I]IGF-I and [125I]IGF-II were displaced similarly by IGF-I and IGF-II within cell lines (P greater than 0.05), displacement, and therefore dissociation constants, differed between cell lines (P less than 0.0001). 3. Receptor cross-linking analysis using iodinated IGFs suggests that both IGF-I and IGF-II interact with the type I receptor on turkey embryonic and posthatch myogenic cells.

Tissue distribution of insulin-like growth factor receptors in the turkey

1. The distribution and relative insulin-like growth factor (IGF) binding capacities of membranes derived from 14 tissues of the turkey were examined. 2. Affinity cross-linking analyses using [125I]IGF-I and [125I]IGF-II with membranes derived from the liver, pectoralis major muscle, gizzard, heart and brain indicated that both IGFs interact with only type-I IGF receptors on these tissues. 3. There was no evidence for the existence of a type-II IGF receptor in any tissue. 4. Although considerable variation was detected in the molecular weights of the IGF receptor alpha subunits between tissues (112.2-132.9 kDa), these differences did not appear to influence receptor-ligand affinities.

Comparison of protein metabolism and glucose uptake in turkey (Meleagris gallopavo) satellite cells and embryonic myoblasts in vitro

Protein synthesis, protein degradation, and glucose uptake were compared in clonal-derived turkey myogenic satellite cells (clone D5-SC) and embryonic myoblasts (EM) and between satellite cell cultures from Nicholas (DN) and Merriams (WM) turkeys. Protein synthesis rates were higher and degradation rates were lower in myotube cultures of D5-SC compared with EM (P < or = 0.05). Protein synthesis and degradation rates did not differ between cultures of DN and WM (P > or = 0.05). Glucose transport rates were significantly higher in EM than D5-SC cultures and did not differ between DN and WM cultures. Insulin-like growth factors and insulin stimulated protein synthesis, decreased protein degradation, and increased glucose uptake in all cell lines.

Comparison of the proliferation and differentiation of myogenic satellite cells derived from Merriam's and commercial varieties of turkeys

1. Myogenic satellite cells were isolated and cloned from the Pectoralis major muscles of 6-week-old Nicholas and Merriams tom turkeys to compare in vitro properties of muscle development between turkeys with markedly different growth rates. 2. Although only small differences (P < or = 0.05) were noted between proliferation rates of the two cell populations in McCoys 5A medium-15% chicken serum, satellite cells derived from the Nicholas variety were more responsive (P < or = 0.05) to mitogenic stimuli from serum at all levels tested. 3. When satellite cells were stimulated by low serum levels to differentiate into multinucleated myotubes, cells from the Merriams turkey fused more rapidly (P < or = 0.05).