Regulation of fructose diphosphate aldolase concentrations in skeletal muscles of normal and dystrophic chickens

Muscle growth and composition in heavy and light breed chickens adapted to intermittent feeding

1. The effect of intermittent feeding in chickens of heavy breed (HB; meat type) and light breed (LB; egg type) on skeletal muscle growth and composition was studied in adapted and non-adapted chickens. 2. Food intake, relative to body-weight, was similar in both breeds but was higher in ad lib.-fed than in intermittently fed birds. 3. On repletion days the relative growth rate was similar in both breeds, while on depletion the LB chickens lost more weight than the HB chickens. In both breeds, the relative growth was higher in the intermittently fed birds during days of food restoration than in those fed ad lib. 4. The relative weight of the breast muscle was higher in HB birds than in LB birds, but deposition rate on the day of food restoration was similar in both breeds. This growth was more pronounced in chickens adapted to alternate feeding than in chickens exposed to this feeding regimen for one cycle. 5. Protein concentration in breast muscle was not affected by age and was slightly higher in LB chickens than in HB chickens. Soluble protein was markedly reduced on days of repletion, and more at 46 d than at 18 d of age. 6. The RNA:DNA ratio was higher in HB than in LB chickens, and lower on days of food deprivation than on days of food restoration. After repletion this ratio returned to the level of the ad lib.-fed chickens. While in LB chickens cell size (as estimated by DNA concentration) remained constant on repletion and depletion days, in the HB chickens it decreased. 7. The rapid growth of breast muscle in HB chickens was attributed to the higher rate of protein synthesis (estimated by RNA:DNA ratio) compared with LB chickens. This may also explain why the breast muscle of LB chickens was less sensitive to intermittent feeding than that of HB chickens.

Additional biochemical criteria in the differential diagnosis of myositis

Thirty-six biopsy specimens of human biceps and vastus lateralis muscles were examined by histometric analysis and determination of enzyme activities (phosphorylase, triosephosphate dehydrogenase, 3-hydroxacyl-CoA-dehydrogenase, lactate dehydrogenase, hexose isomerase, citrate synthetase, 6-phosphogluconate dehydrogenase). The series included 13 specimens from patients suffering from a benign form of muscular dystrophy (limb girdle and Becker type of muscular dystrophy) and 12 specimens from patients with an acute (n = 5) or chronic (n = 7) form of myositis. Muscle fibres were atrophic in myositis and hypertrophic (with an increased variation of fibre diameters) in muscular dystrophies, as has been shown previously. When myositis samples were compared with either normal or dystrophic muscles, a highly significant lowering of glycolytic enzyme activity was found in chronic myositis, while the activity of 6-phosphogluconate dehydrogenase was elevated to highly significant levels. Measurements of the latter enzyme's activity might be of additional value in differentiating chronic forms of myositis from benign muscular dystrophies.

The effect of the myotoxic agent iodoacetate on dystrophic mice 129/Re

Three groups of dystrophic and non-dystrophic mice 129/Re were used for studying the effect of the myotoxic agent iodoacetate on dystrophic muscle. The mice of the first group were given intramuscular injections of iodoacetate. The mice of the second group were injected with normal saline and the third group was maintained as untreated controls. The most severe histopathological changes were found in the dystrophic mice treated with iodoacetate. The non-dystrophic mice of the same group showed a significant increase in the number of internal nuclei. Moderate changes were observed in saline-treated dystrophic controls. There was no significant decrease in the life expectancy in any of the groups. The body weight of dystrophic mice was reduced throughout the experiment. On the contrary the non-dystrophic group showed an increased in weight, regardless of the treatment. The aggravation of the histopathological changes of dystrophic mice by iodoacetate would probably give support to the cyclical necrosis/abnormal regeneration theory of pathogenesis of muscular dystrophy.

Glyceraldehyde-3-phosphate dehydrogenase mRNA. Activity and amount in dystrophic hamster muscle

The activity and amount of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in muscle of young dystrophic hamsters was reduced to approximately half the level found in control animals. No changes in brain or liver enzyme activity were found. Several other glycolytic enzyme activities and creatine kinase activity in muscle were unchanged, except for modest decreases in aldolase and pyruvate kinase. To assess the synthesis of glyceraldehyde-3-phosphate dehydrogenase, the poly(A)+ RNA was isolated from muscle polysomes of dystrophic and control animals and its activity was assessed in an mRNA-dependent translation system. The translatability of the mRNA for GAPDH found in the dystrophic muscle preparations also was half of that found in the control muscle preparations. Decreases were also found in the translatability of mRNA for tropomyosin.

Developmental regulation of the hepatocyte receptor for galactose-terminated glycoproteins

The receptor which recognizes glycoproteins that have had their terminal sialic acids removed, thus exposing penultimate galactose residues (asialoglycoproteins), was examined for expression in rat liver during development. The level of asialoglycoprotein receptor binding activity in fetal rat livers was present in very low amounts but rose dramatically at the time of birth and reached adult levels by the second day after birth. Using immunoquantitation methods, it was found that the increased binding capacity of rat liver for asialoglycoproteins during development reflected accumulation of receptor molecules rather than activation of previously existing ones. The relative rates of synthesis of the predominant polypeptide of Mr 42,000 and the lesser abundant polypeptides of Mr 50,000 and 58,000 which comprise asialoglycoprotein receptor were found to increase in livers of fetuses near term and attain adult synthesis rates around birth. Thus, the accumulation of receptor protein molecules during development reflected increased synthesis of receptor polypeptides. These results suggest that the different gene products which code for the three forms of the receptor are coordinately expressed during development. Copurifying with asialoglycoprotein receptor during ligand affinity chromatography were polypeptides of Mr 25,000 and 27,000. These polypeptides display several characteristics similar to hepatic mannose binding lectin described by others. Onset of synthesis of the mannose binding lectin during development was analogous to asialoglycoprotein receptor but, in contrast, did not reach adult synthesis rates immediately after birth.

Content and synthesis of glycolytic enzymes and creatine kinase in skeletal muscles and normal and dystrophic chickens

A number of workers have reported that avian muscular dystrophy causes alterations in the levels of certain enzyme activities in "fast-twitch" muscle fibers but has little effect on enzyme activities in "slow-twitch" muscle fibers. In the present work, the effects of this disease on the content and relative rates of synthesis of a number of glycolytic enzymes and the skeletal muscle-specific MM isoenzyme of creatine kinase in chicken muscles was investigated. It was shown that (i) the approximate 50% reductions in steady-state concentrations of three glycolytic enzymes (aldolase, enolase, and glyceraldehyde-3-P dehydrogenase) in dystrophic breast (fast-twitch) muscle result predominantly from decreases in relative rates of synthesis, rather than accelerations in relative rates of degradation, of these proteins in the diseased tissue; (ii) in contrast to the situation with the glycolytic enzymes, muscular dystrophy has only minor effects (25% or less) on the content and relative rate of synthesis of MM creatine kinase in breast muscle fibers; (iii) the muscular dystrophy-associated alterations in content and synthesis of the glycolytic enzymes in breast muscle fibers become apparent only during postembryonic maturation of this tissue; and (iv) as expected, muscular dystrophy has no significant effect on the content or relative rates of synthesis of glycolytic enzymes in slow-twitch lateral adductor muscles of the chicken. These results are discussed in terms of the apparent similarities between the effects of muscular dystrophy and surgical denervation on the protein synthetic programs expressed by mature fast-twitch muscle fibers.

Increase in the amount of elongation factor 2 in chicken muscular dystrophy

The amount of elongation factor 2 (EF2) in the cytoplasm and ribosome of breast muscle cell from normal and dystrophic strains of chicken was measured. Concentration in the cytoplasm of 20-day-old embryonic dystrophic muscle was higher than that in normal muscle, but no difference in content was found in muscles of 15-day-old embryos. The amount of EF2 bound to ribosomes was identical in normal and dystrophic muscles during all stages of development. Peptide mapping patterns of partial proteolytic fragments of EF2 from normal and dystrophic chicken breast muscles were similar. The increase in cytoplasmic protein synthetic activity of dystrophic breast muscles reported previously seems to be due to the corresponding increase in the number of EF2 molecules rather than to their modification in dystrophic muscle.

Content and synthesis of several abundant glycolytic enzymes in skeletal muscles of normal and dystrophic mice

In both 2- and 3-month-old 129 ReJ mice, the catalytic activity levels of three enzymes involved in glycogen breakdown (phosphorylase, enolase, and aldolase) were found to be 35-50% lower in hind limb muscles of dystrophic mice as compared with normal mice. The reduced activities of these enzymes in the diseased tissue was directly due to corresponding reductions in the number of enzyme molecules rather than being due to inactivation of the enzymes in the dystrophic muscle. Results of short term double isotope incorporation experiments conducted with muscle explants in vitro suggested that the rates of synthesis of these enzymes, and of most other abundant cytosolic proteins, relative to each other, were similar in hind limb muscles of normal and dystrophic mice. The present work on murine muscular dystrophy is discussed in terms of our previous studies into the influence of avian muscular dystrophy on the content and synthesis of abundant glycolytic enzymes in chicken skeletal muscles.

Similarities in properties, content, and relative rates of synthesis of fructose-P2 aldolase in livers of fed and starved rats

The present work gives evidence that, in contrast to the situation reported by Pontremoli et al. for the rabbit (Proc, Natl. Acad. Sci. U.S.A. 76, 6323-6325, 1979; Arch. Biochem. Biophys. 203, 390-394, 1980; Proc. Natl. Acad. Sci. U.S.A, 79, 5194-5196, 1982), starvation for as long as 3 days does not cause intracellular covalent modification and inactivation of fructose-P2 aldolase molecules in rat liver cells. This conclusion is based on our observations that liver aldolase molecules isolated from fed and starved rats in the presence of proteolytic inhibitors were not distinguished on the basis of specific catalytic activity, electrophoretic mobility, subunit molecular weight, NH2-terminal structure, or COOH-terminal structure. Further, the approximate 40% loss in rat liver mass which occurred during the 3-day fast was not associated with appreciable changes in the content of aldolase and most other abundant cytosolic proteins per gram of rat liver, as judged by electrophoretic analysis of 100 000-g soluble fractions of liver extracts. Finally, a 3-day fast had no appreciable effect on the relative rates of synthesis of aldolase and most other abundant cytosolic proteins in rat liver. Our findings suggest that nutrient deprivation has no preferential effect on the concentration or metabolism of aldolase in rat liver cells.

A simple procedure for the isolation of seven abundant muscle enzymes

The present work describes procedures in which seven major muscle enzymes and serum albumin can be simultaneously isolated from chicken skeletal muscles. The seven enzymes isolated were: phosphorylase, enolase, creatine-P kinase, aldolase, glyceraldehyde-3-P dehydrogenase, phosphoglycerate mutase, and triose-P isomerase. The proteins isolated by these methods were judged to be greater than 97% pure on the basis of electrophoretic analysis in sodium dodecyl sulfate polyacrylamide gels. The procedure is applicable for isolation of the enzymes from large (greater than 100 g) or small (less than 0.5 g) amounts of muscle tissue and the entire procedure can be completed within two days. Particularly useful features of the procedures are: (1) preferential solubilization of the enzymes from myofibrils by extraction of muscle specimens in solutions of different ionic strength; (2) specific precipitation of phosphorylase, creatine-P kinase, and glyceraldehyde 3-Phosphate dehydrogenase from solutions of specified pH and degrees of ammonium sulfate saturation; and (3) an alternate method for isolation of glyceraldehyde-3-P dehydrogenase by specific elution of the enzyme from phosphocellulose columns with ATP. Because of the ease, rapidity, and reproducibility of the procedures, these methods may be useful for the routine isolation of the muscle enzymes in studies on biochemical regulation, as well as for obtaining large quantitites of the enzymes for structural analysis.