Protein synthesis in vitro after cryopreservation of rat skeletal muscle

Metabolic effects on growth and muscle of soya-bean protein feeding in cod (Gadus morhua)

The aim of the present study was to investigate the effect of soya-bean protein on growth and muscle metabolism in fish. Cod, Gadus morhua, were fed on a fish-feed formula with the high-quality fish-meal protein being replaced by 100, 200 or 300 g soya-bean protein/kg fish-meal protein. The feeding experiment lasted for 43 d at a water temperature of 7-8 degrees and a sea water salinity of 3.5%. At the 200 g/kg level of soya-bean protein, food intake and growth rate were similar to those of the controls. At the 300 g/kg level of soya-bean protein, food intake was diminished by 6% and growth by 67% relative to control levels. In muscle, sarcoplasmic protein (/g wet weight) was significantly decreased by 14%. Myofibrillar protein (/g wet weight) was unchanged. Levels of RNA in the myofibrillar fraction decreased at all three levels of soya-bean protein, and that of the sarcoplasmic fraction decreased at the highest level of legume-protein. With increased levels of soya-bean protein, RNA:DNA declined by 18% from 1.88 to 1.54. The contractile protein myosin heavy chain (/mg protein and /g wet weight) and myosin heavy chain-specific mRNA (/mg RNA) were not significantly affected by dietary conditions. Expressed per g wet weight, the decline by 21% of the specific mRNA depended on the total RNA content which decreased with the increase in soya-bean protein. Acid proteinase activity was lowest at the 200 g/kg level, showing a decrease of 23%.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of elongation factors in protein synthesis rate variation in white teleost muscle

Protein synthesis-stimulating activity was assayed in the cytosolic fraction of white muscle from teleost fish (rainbow trout, carp) and of rat liver. In vitro protein synthesis-stimulating activity in the cytosolic fraction is reduced by food deprivation. The addition of elongation factors EF1, EF2, or EF1 + EF2 compensates for the starvation-induced loss of protein synthesis-stimulating activity in trout muscle cytosol. The action of EF2 is stronger than that of EF1 in this respect. However, EF1 enhances in vitro protein synthesis-stimulating activity in rat liver cytosol more than EF2. The EF2 concentration in the cytosolic fraction of white muscle from starved trout is significantly lower than in fed specimens.

Dietary protein levels affect growth and protein metabolism in trunk muscle of cod, Gadus morhua

Cod (Gadus morhua) of 50 g body weight were kept at 14 degrees C. The fish were fed ad libitum during 80 days a diet containing protein levels which in terms of total energy corresponded to 25%, 45% or 65%. Growth increased in accordance with protein-energy levels. The protein content per gram of wet weight of white trunk muscle was unchanged, as was the myofibrillar protein myosin heavy chain determined by the antigen-antibody reaction of the enzyme-linked immunosorbent assay. The amount of messenger ribonucleic acid (mRNA) coding for myosin heavy chain was lower at 25% than at 45% or 65% protein-energy intake, the differences being significant per gram of wet weight of muscle. Acid proteinase activity was highest at the lowest protein-energy intake. Glycogen content in muscle increased with the protein-energy levels. It is concluded that the metabolic response of white trunk muscle to graded protein-energy intake included a change in the capacity to synthesize myosin heavy chain as judged by its mRNA content. The protein content per gram of wet weight was unaffected by dietary protein-energy levels of 25%, 45% and 65%, but protein accretion and thus growth of the animals increased with the protein intake. Dietary protein-energy restriction caused a rise in acid proteinase activity and a decrease in content of mRNA for myosin heavy chain, resulting in a diminished growth rate at an unchanged protein content per gram of wet weight of muscle.

Myosin heavy chain synthesis in white trunk muscle of cod (Gadus morhua) fed different ration sizes

In this study the expression of myosin heavy chain was investigated at the messenger RNA and protein level of the muscle ribosome. Cod (Gadus morhua) weighing 80 g were fed for 70 days eitherad libitum or with rations consisting of 75%, 50%, or 25% of thead libitum food intake. Protein and RNA contents of the ribosome from the white trunk muscle decreased with the diminished ration sizes. Myosin heavy chain content relative to total ribosome protein increased with the 50% ration size but fell again to thead libitum level at 25%. Expressed relative to RNA, a decrease in the protein content occurred in parallel with the decreasing ration size. The amount of protein/total muscle homogenate fell with diminished ration sizes, and that of myosin heavy chain/mg of protein remained unchanged with a slight increase at the 25% food energy intake. The messenger RNA for myosin heavy chain (relative to poly(A)(+) messenger (RNA) was increased in response to the decreased ration size but was decreased when calculated per g wet weight of the muscle. The changes in messenger RNA for myosin heavy chain were less pronounced than those of the protein itself. The levels of gene transcription and translation for myosin heavy chain were affected to a lesser extent by the low food intake than the synthesis of total RNA and protein. Immunological methods and messenger RNA hybridization to cloned DNA for myosin heavy chain permitted the precise determinations of the events taking place during a food-energy supply shortage. Translation appeared to diminish prior to changes in messenger RNA concentrations.

Protein synthesis in skeletal muscle of rats following starvation and refeeding

Determination of protein synthesis in individual tissues is important to understand the changes in protein metabolism during catabolic states. Three methods based on different underlying assumptions were compared in assessing muscle protein synthesis during nutritional manipulation. Rats were nonstarved, starved for 1 or 3 days, or refed for 2 days after 3 days of starvation. The extensor digitorum longus (EDL) muscles from the two hindlegs were used for analysis. In one EDL muscle the concentration and size distribution of ribosomes as well as the incorporation of [14C]leucine into protein in a cell-free system were determined. The other EDL muscle was incubated as such and the incorporation of [14C]phenylalanine into protein was measured. The total ribosome concentration per milligram of DNA decreased to 65% on the third day of starvation and remained low after refeeding. The amount of polyribosomes in the percentage of total ribosomes fell to 90% on the first day of starvation, regained the initial level on the third day, and reached 110% upon refeeding. During refeeding amino acid incorporation into protein in a cell-free system decreased to 40% and that in intact muscle to 64% of the prestarvation level. Upon refeeding, the activity increased to or above the original values. The use of several different techniques in parallel to assess protein synthesis in skeletal muscle is recommended since it gives information about the factors involved in regulation of the translational process in intact mammalian tissues.

Protein synthesis activity in vitro in mouse tissues in relation to methionine-cysteine deficiency and age

The objective of this study was to determine whether ageing in the mouse is associated with changes in protein synthesis activity and response to dietary methionine-cysteine deficiency. Growing subadult mice (30-day-old) and adult mice (70-day-old) were compared. The amino acid restricted diet contained methionine and cysteine at a level of 10% that of the control diet. After a feeding period of 6 days protein synthesis activity was measured in liver, kidney and lung. In control liver, the level of protein synthesis activity was the same for the two age groups; in kidney and lung, activity was diminished in the adult group. After methionine-cysteine deficiency protein synthesis activity was unchanged in the subadult and diminished in the adult liver. In kidney, both age groups responded with an increase in activity. In lung, the subadult group remained unchanged and activity in the adult group was elevated. The amount of DNA/g wet weight of tissue was higher in the subadult than the adult group throughout. Methionine-cysteine deficiency resulted in an increase in DNA/g tissue wet weight, while the total amount of DNA in liver decreased, but was unchanged in kidney and lung. Total liver activity was decreased less in subadult than adult mice. Total kidney and lung activities were diminished in subadult but not adult mice. The results suggest that the specific protein synthesis activity of the ribosomes in the kidney and lung tends to decrease with age more readily than in liver, and that subadult liver displays less sensitivity towards methionine-cysteine deficiency than does adult liver.

High mobility group proteins in skeletal muscle of pre- and postsmolt salmon (Salmo salar)

HMG proteins were extracted from whole skeletal muscle of pre- and postsmolt salmon (Salmo salar). The proteins were identified by SDS and acid-urea polyacrylamide gel electrophoresis. Semi-quantitative analysis revealed an increase in the ratio of HMG H6 to F protein and of HMG T to HMG H6 protein in the postsmolt as compared with the presmolt stage of the salmon. The results demonstrate a change in relative amounts of skeletal muscle HMG proteins which was dependent on the developmental stage of the fish.

Purification of fish muscle myosin heavy chain and quantification of the specific polyribosome-bound polypeptide

A purification procedure for fish myosin heavy chain is described. The protein was injected into rabbits for production of antibodies. The specificity of the antibodies was determined by immunoblotting. The enzyme-linked immunosorbent assay technique was applied to quantify myosin heavy chain bound to isolated polyribosomes of epaxial muscle from fish.

Size distribution of ribosomes in biopsy specimens of human skeletal muscle during starvation

The changes in the poly- and monoribosome distribution and in the total ribosome concentration in muscle during short term starvation were investigated. Transcutaneous muscle biopsies of 50 mg wet wt were taken from healthy human subjects, nonstarved and after one, two, and three days of total starvation. The percentage amount of polyribosomes was significantly lower (P less than 0.02) on days 2 and 3 of starvation than on day 0 (nonstarved). No significant sex-dependent differences were observed between the group of five females and six males. Ribosome concentration per g wet wt of muscle tissue was significantly lower on day 3 than on each preceding day (P less than 0.05). The reproducibility of the polyribosome analyses, together with the changes observed, suggest a future application of this method for evaluation of the effects of nutritional support in patients with posttraumatic and septic conditions.

The influence of the ratio of protein energy to total energy in the feed on the activity of protein synthesis in vitro, the level of ribosomal RNA and the RNA-DNA ratio in white trunk muscle of Atlantic cod (Gadus morhua)

Cod (Gadus morhua) were fed diets containing protein energy to total energy levels (PE/TE) of 10.0, 20.6, 29.6, 38.4, 56.2 and 74.1% for 21 days. Ribosomes were isolated from the white trunk muscle tissue, the capacity for protein synthesis in vitro determined and related to muscle tissue wet weight rRNA and DNA. Protein concentrations of less than 47.4% PE/TE in the diets reduce the ribosomal capacity for protein synthesis per g wet weight and per mg DNA, and the tissue contents of rRNA and ratio of rRNA/DNA. The capacity for muscle protein synthesis in vitro is a significant and sensitive parameter of protein inadequacy in fish diets.

A comparative study of protein synthesis in vitro by skeletal muscle ribosomes from livestock

Skeletal muscle was dissected from the forelimbs of animals and stored at -80 degrees C. Protein synthesis activity was determined in cell-free systems. Incorporation of amino acids into protein was expressed per milligramme of ribosomal RNA, per gramme wet weight of skeletal muscle and per milligramme of DNA. Species related differences in activity were observed in skeletal muscle obtained from pig, horse, lamb, sheep, calf and young steer. Intraspecies differences were seen in cattle of different breeds. The protein composition of the muscle tissue showed quantitative differences between the species. Using biopsy specimens, the system could be used to monitor the protein nutrition status of animals and the production of animal proteins.

Experimental studies on the quality of food proteins

1. This paper reviews chemical and biological assays for measuring the quality of food proteins. 2. The availability of amino acids in a protein is determined by digestability and the capacity of the recipient animal to absorb the amino acids. 3. Intracellularly amino acid concentration influences enzyme activities associated with amino acid and nitrogen metabolism. 4. Amino acids utilized for metabolism affect the cells at the gene level: transcription of DNA to RNA and translation of RNA to protein. 5. More accurate measurements of amino acid utilization for metabolism will follow from further understanding of basic cellular metabolic events.

Properties of white trunk muscle from saithe Pollachius virens, rainbow trout Salmo gairdneri and herring Clupea harengus: protein synthesis in vitro, electrophoretic study of proteins

1. Ribosomes were isolated from white trunk muscle of saithe (Pollachius virens), rainbow trout (Salmo gairdneri) and herring (Clupea harengus). 2. Incorporation of amino acids into protein by the ribosomes was determined in systems containing liver cell sap from rainbow trout. 3. Incorporation of phenylalanine into protein was as follows: saithe 163.19 +/- 7.64 pmol, rainbow trout 126.99 +/- 3.07 pmol, herring 29.34 +/- 1.28 pmol per g wet weight of tissue and 4 min of incubation at 28 degrees C. 4. Proteins associated with the ribosome fractions showed minor differences between the species as analysed by polyacrylamide gel electrophoresis in sodium dodecylsulfate. Proteins of myofibrillar origin were predominant in those fractions.

Protein synthesis in vitro by epaxial muscle polyribosomes from cod, gadus morhua

1. Ribosomes were isolated from epaxial muscle of cod (Godus morhua). 2. Incorporation of amino acids into protein was determined in systems containing liver cell sap from rat or rainbow trout (Salmo gairdneri R.). Maximal rates were at 35 degrees and 28 degrees C, respectively. The optimum pH was between 7.5 and 8.0. 3. Ribosomes isolated from muscle stored at -80 degrees C between 1 and 14 days retained 86% of the activity of ribosomes from fresh tissue. 4. Starvation of fish for 10 days reduced amino acid incorporating activity of isolated ribosomes to 15-20%. 5. All ribosome preparations used in the experiments were analysed by sucrose density gradient centrifugations.