The physiology of protein metabolism

Cathcart, E. P.

doi:10.5962/bhl.title.25108

Cited by 18 publications

(8 citation statements)

References 68 publications

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“…8, in which the number of meals of a fixed diet were varied from 8 to 2 without seriously affecting the level of N output (Table X). This is consistent with the results of other workers, as reviewed by Cathcart [1921]. It may be further noted that this change in the number of meals in Exp.…”

Section: Discussionsupporting

confidence: 93%

The relationship of carbohydrate metabolism to protein metabolism

Cuthbertson

Munro

1939

Biochemical Journal

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EARLIER observations showed that the provision of excess of energy in the human diet is attended by a storage of N and S, the storage being more marked when the surfeit is in the form of carbohydrate than when in the form of fat [Cuthbertson & Munro, 1937]. Simultaneously with these observations, it was demonstrated by Larson & Chaikoff [1937] in one-day superimposition experiments on dogs, that this storage was only provoked by carbohydrate ingested within 4 hr. before or after the protein meal. Moreover, the closer the proximity in time of the surfeit carbohydrate to the meal, the greater was the quantity of N stored. These effects of surfeit carbohydrate on protein metabolism prompted us to investigate the function of the total carbohydrate of the ordinary adequate diet, as it affects N metabolism, especially with regard to the relative times of ingestion of the protein and the carbohydrate. The present investigation of protein metabolism is divided into four sections: (I) The effect of complete separation as regards time of ingestion of all, or practically all, the carbohydrate and the protein of an adequate diet (Exps. 1-5). (II) The effect of separation of only a part of the protein from the carbohydrate in such a diet (Exp. 6). (III) The effect of taking surfeit carbohydrate at a time separated from that of the ingestion of the protein (Exp. 7). (IV) The effect on N balance of varying the number of meals in a fixed diet (Exp. 8). (This is intended as a control for certain aspects of the other experiments.) EXPERIMENTAL The analytical procedures were similar to those referred to in a previous paper [Cuthbertson & Munro, 1937]. The fluid intake was kept as constant as possible throughout these experiments. I. Separate ingestion of dietary protein and carbohydrate Exps. 1 and 2. In preliminary experiments, two adults, A. H. S. and H. B. C. (Table I), were put on diets adequate for maintenance, containing 80 g. protein and 2740 cal. in the case of the former, and 97 g. and 3400 cal. in the case of the latter. During Period I this food was divided for both subjects into four equal mixed meals, taken at 8.30 a.m., 1 p.m., 4.30 p.m. and 10 p.m. respectively (Tables II and III). Their bodyweights remained constant under this regime.

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Section: Discussionsupporting

confidence: 93%

The relationship of carbohydrate metabolism to protein metabolism

Cuthbertson

Munro

1939

Biochemical Journal

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“…Falta and others (7,4,14) have found that in normal individuals considerable lag in the excretion of nitrogen may follow the superposition of certain proteins on a standard diet. Lag has been attributed to the manufacture of deposit protein and its subsequent utilization in metabolism when the supplementary protein feeding was stopped.…”

Section: Discussionmentioning

confidence: 99%

“…Edema fluid, when present, was considered to contain 90 per cent water (17). 4 The consideration of all of the nitrogen of the stools as catabolic is probably not correct in all instances. For calculating the biological values of proteins the method of Mitchell (15) which involves the deduction of unabsorbed nitrogen from the intake is more accurate.…”

Section: Methodsmentioning

confidence: 99%

Dietary Protein in Hemorrhagic Bright's Disease

Keutmann¹,

Bassett²,

Julian³

et al. 1935

J. Clin. Invest.

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The comparatively few accurate studies of the nitrogen balance which have been made during the chronic active stage of nephritis have been concerned chiefly with the quantitative aspect of the protein requirement (17). Little attention has been given to the kind of protein fed and its effect upon hypoproteinemia, proteinuria and the storage of protein in the tissues.2 The problem of hypoproteinemia is of especial interest, since no satisfactory means of increasing the concentration of the serum proteins of the nephritic has been discovered. Recently a systematic attempt has been made by Whipple and collaborators (10,20) to ascertain factors governing the regeneration of plasma proteins. By repeated plasmapheresis of the dog they have shown the existence of a reserve depot containing precursors of the serum proteins. The quantity of protein released by the depot under the stimulus of depletion was often two or three times greater than the total amount of plasma protein originally present in the circulation. When the reserve had been exhausted the effect of different food proteins on the rate of regeneration was measured. The most satisfactory responses in order of decreasing potency were given by beef serum, smooth muscle, lactalbumin, boiled white of egg, skeletal muscle and liver. Owing to the excellent response of the experimental animal it seemed logical to test the effect of some of these 1Aided by a grant from the Subjects. The major part of the report is devoted to an investigation of two patients. The first was in the degenerative stage of chronic hemorrhagic Bright's disease. The second was a man whose illness was of shorter duration, and closely resembled a true nephrosis. Both patients were studied in the metabolism division of the hospital, where their diets were prepared and sampled in a manner previously described (1).The third patient, also in the degenerative stage of chronic active hemorrhagic Bright's disease, was studied on the general medical division. His diets were prepared in the special diet kitchen of the hospital but were not sampled or analyzed.Diets. The plan of varying the constituents of the diet differed with each subject, which necessitates a separate discussion of each case. In general the plan was to keep each patient on a control (basal) diet, from time to time superimposing the protein to be tested or additional calories in the form of carbohydrate and fat.To provide some variety three menus were prepared for each diet. These varied slightly but had the same caloric and protein content, and were fed consecutively during each three day period. The patients thus ate the same food every third day. All of the diets were prepared without salt.Protein supplements. With one exception, which is discussed under the case of L. R., the protein supplements 871

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“…probably heals as well as one whose labile protein pool overflows with an intake of more than 100 g/day. However, we must agree with Clark (1967) that there is no evidence as yet to show whether moderate protein depletion affects the convalescence of a patient.…”

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confidence: 82%

The control of haemoglobin synthesis: factors controlling the output of α and β chains

1969

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Analysis of the effects of amino acid starvation in reticulocytes is comparatively simple compared with similar analysis in other tissues of whole organisms. This is mainly because of the absence of RNA synthesis in reticulocytes, but also because the bulk of the protein being synthesized is haemoglobin, a protein whose structure is completely known. The absence of RNA synthesis eliminates complications that would otherwise arise through RNA-mediated control mechanisms which in turn might mask the effects of amino acid starvation on the protein synthetic machinery in the cells (Munro, 1969). Consequently reticulocytes have been used to study the effect of amino acid starvation on the actual process of protein synthesis and assembly.

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The physiology of protein metabolism

Cited by 18 publications

References 68 publications

The relationship of carbohydrate metabolism to protein metabolism

The relationship of carbohydrate metabolism to protein metabolism

Dietary Protein in Hemorrhagic Bright's Disease

The control of haemoglobin synthesis: factors controlling the output of α and β chains

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