Bovine retinal outer segment fragments were isolated by density gradient centrifugation in a high centrifugal field. Assays of the final preparation for enzymes of the mitochondrial respiratory chain indicated mitochondrial contamination not in excess of 1 per cent. Glucose-6-phosphatase and TPNH-cytochrome c reductase activities, presumably diagnostic for microsomes, were also absent. Electron micrographs did not disclose the presence of significant numbers of particles other than fragments of the outer segment discs. The red fragments were characterized by an ascorbate-oxidizing system and a high lipid content.

Adenosine Triphosphatases↗

PubMedDate not supplied

Normal and dystrophic embryonic chicken pectoralis muscle cultures: I. Cell differentiation, protein synthesis, and enzyme levels.

Normal (line 200) and dystrophic (line 307) embryonic chicken pectoralis muscle cells were studied in cell culture over a period of 2 weeks. During the first 4 days, normal and dystrophic cultures exhibited similar developmental increases in the number of nuclei within multinucleated myotubes, however, dystrophic muscle cells degenerated approximately twice as fast as normal cells once the initial burst of myoblast fusion was complete. The apparent synthesis rate of nonmyofibrillar proteins was similar in normal aand dystrophic cells throughout development, but the apparent synthesis rates of myosin heavy chain and the myofibrillar protein fraction were 50%--90% higher in dystrophic muscle cultures once maturity had been reached (days 6--14). The specific activities of creatine kinase and phosphofructokinase were not affected by the dystrophic condition; however, specific activity of AMP-deaminase was depressed 25%--40% in the dystrophic muscle cultures.

AMP Deaminase↗

PubMedDate not supplied

Normal and dystrophic embryonic chicken pectoralis muscle cultures: II. Ultrastructural comparison.

Ultrastructural comparison was made between dystrophic and normal chicken breast muscle cells which had been isolated from 12-day-old embryos and cultured for up to 14 days. All electron microscopic examinations were conducted in the absence of any knowledge as to the dystrophic or normal origin of the cells, or the day on which the cells had been harvested from culture. The same blind procedures were applied to attempts to reconstruct from electron micrographs the correct sequence of days for a particular experiment and to identify the origin of the cells as normal or dystrophic. No consistent differences between normal and dystrophic cells were apparent either in extent of differentiation, such as the formation of mature sarcomeres, or in degenerative properties, such as disintegrating mitochondria, lipid aggregations, or extracellular debris. In light of metabolic and developmental differences in these cultures, the absence of ultrastructural differences was attributed in part to the presence of cells with widely different degrees of integrity, differentiation, and degeneration in both normal and dystrophic cultures.

Animals↗