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Biomedical subjects

D J Millward

Publications and source records attributed to D J Millward.

At least 127 records · Page 7Linked to original sources
PubMed1976

The relative importance of muscle protein synthesis and breakdown in the regulation of muscle mass.

The effects of growth-suppressing and muscle-wasting treatments on muscle protein turnover and amino acid concentrations were determined in vivo. All treatments depressed protein synthesis and some treatments depressed protein breakdown. Only prolonged starvation increased protein breakdown. Muscle protein mass is regulated primarily through alterations in protein synthesis in all except emergency conditions. The increased concentrations of the branched-chain amino acids indicate that they are unlikely to be involved in this regulation.

Animals↗
PubMed1975

The effect of protein deprivation and starvation on the rate of protein synthesis in tissues of the rat.

1. The fractional rate of protein synthesis was measured in tissues of rats in vivo by continuous infusion of [14C]tyrosine. In growing animals proteins of liver and kidney were renewed at a rate greater than 50% per day, those in skeletal muscle, brain and heart at a rate between 13 and 23% per day. 2. Protein synthesis was also measured in liver, kidney, heart, brain and skeletal muscle of rats either given a protein-free diet for 21 days or starved for 2 days. During the first 2 days no clear differences between the effects of these two regimes could be detected. 3. Gastrocnemius muscle did not lose tissue protein till after 9 days without protein in the diet. The rate of protein synthesis was halved after 1 day and halved again after 21 days without protein. It was deduced that the rate of protein breakdown in muscle had declined also. 4. In liver the loss of protein was immediate without any apparent change in the fractional rate of protein synthesis. Between 2 and 21 days of dietary protein deprivation the liver lost protein slowly but the fractional rate of protein synthesis was increased. It is proposed that lack of protein in the diet also causes an increase in the rate of liver protein breakdown.

Animals↗
PubMed1975

Skeletal-muscle growth and protein turnover.

Because of turnover, protein synthesis and breakdown can each be involved in the regulation of the growth of tissue protein. To investigate the regulation of skeletal-muscle-protein growth we measured rates of protein synthesis and breakdown in growing rats during development on a good diet, during development on a marginally low-protein diet and during rehabilitation on a good diet after a period of severe protein deficiency. Rates of protein synthesis were measured in vivo with a constant intravenous infusion of [14C]tyrosine. The growth rate of muscle protein was measured and the rate of breakdown calculated as breakdown rate=synthesis rate-growth rate. These measurements showed that during development on a good diet there was a fall with age in the rate of protein synthesis resulting from a fall in capacity (RNA concentration) and activity (synthesis rate per unit of RNA). There was a fall with age in the breakdown rate so that the rate was highest in the weaning rats, with a half-life of 3 days. There was a direct correlation between the fractional growth and breakdown rates. During rehabilitation on the good diet, rapid growth was also accompanied by high rates of protein breakdown. During growth on the inadequate diet protein synthesis rates were lesss than in controls, but growth occurred because of decreased rates of protein breakdown. This compression was not complete, however, since ultimate muscle size was only one-half that of controls. It is suggested that increased rates of protein breakdown are a necessary accompaniment to muscle growth and may result from the way in which myofibrils proliferate.

Aging↗