The effect of unilateral phrenicectomy on the rate of protein synthesis in rat diaphragm in vivo

The fractional rate of protein synthesis (ks) in the denervated rat-diaphragm has been measured in vivo by the continuous amino acid infusion technique at 1, 3, 5 and 10 days after nerve section, and compared with the rate determined in normal rats. Similar rates of protein synthesis, 14% per day, were found for both the left and right hemidiaphragms in the control animals. In the denervated rats, the rates of protein synthesis in the contralateral control hemidiaphragms were significantly increased as soon as 1 day after nerve section. This is considered to be evidence of a compensatory synthesis in the control tissues. In the denervated hemidiaphragm, the rate of protein synthesis had doubled by the third day after nerve section, but by the fifth day had fallen slightly to a value some 50% greater than that of the controls, and remained at this level for a further 5 days. Based on these measured values of protein synthetic rate, calculated estimates have been made of the rate of protein degradation necessary to account for the reported (Turner, L.V. and Manchester, K.L. (1972) Biochem. J. 128, 789-801) changes in mass of the denervated tissue. During the first three days after nerve section, the rate constant for degradation increased to more than twice the normal rate for skeletal muscle, and remained at this value throughout the peak of the hypertrophy.     

Effects of denervation on the activities of some tricarboxylic acid-cycle-associated dehydrogenases and adenine-metabolizing enzymes in rat diaphragm muscle

1. The activity of several tricarboxylic acid-cycle-associated dehydrogenases, adenine-metabolizing enzymes and glutathione reductase and the content of myoglobin were measured in rat diaphragm muscle after unilateral nerve section. 2. Consistent with morphological disintegration of the mitochondria there was a rapid diminution in activity of NAD- and NADP-linked isocitrate dehydrogenase, malate dehydrogenase and glutamate dehydrogenase. 3. Creatine phosphokinase and adenylate kinase, by contrast, showed little change in activity; adenylate deaminase and glutathione reductase activities increased during the hypertrophic phase. The concentration of myoglobin at first declined, then increased again. 4. The distribution of enzymes between the left and right hemidiaphragms was found not to be uniform. 5. Activities of adenine-metabolizing enzymes in the diaphragm were as great as in white muscle. It is suggested that their reputedly lower activities in red muscle properly refer to muscle containing a high proportion of intermediate fibres, which is not the case with diaphragm. 6. The possible causes of the transient hypertrophy after nerve section are discussed.     

Variation in Plasma Calcium with Induced Changes in Plasma Specific Gravity,Total Protein,and Albumin

The relationship of plasma calcium levels to changes in plasma specific gravity, total protein, and albumin induced by venous stasis was investigated. Factors were derived for adjusting calcium results to offset the effects of variation in protein concentration and thus to make them of increased discriminatory value to the clinician. The validity of an existing specific gravity correction has been substantiated, but a more exact adjustment of 0·23 mg/100 ml of calcium for every 0·001 change in specific gravity is proposed. We recommend for automated laboratories that the factor based on albumin be used: 0·09 mg/100 ml of calcium should be subtracted from the total calcium value for every increase of 0·1 g in albumin above 4·6 g/100 ml, and a corresponding addition should be made for values of albumin below 4·6 g/100 ml.Using a calcium specific electrode, it has been shown that the ionized calcium concentration does not alter with prolonged venous stasis.