The influence of various sugars on the respiratory quotient

Cathcart, E. P.; Markowitz, Jacob

doi:10.1113/jphysiol.1927.sp002406

Cited by 38 publications

(6 citation statements)

References 7 publications

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“…Furthermore, partial oxidation of fatty acids to ketones or acetate in the liver is associated with an 0, consumption, but without CO, production. This would lower R. A conversion of carbohydates to fat which can also occur in the liver will increase R due to the smaller amount of 0, (in relation to hydrogen and carbon) in fat than in carbohydrates (Cathcart & Markowitz 1927). Accordingly, at rest after extreme diets, R is an uncertain indicator of the proportions of fat and carbohydrate oxidation in muscles.…”

Section: Discussionmentioning

confidence: 99%

On the significance of the respiratory exchange ratio after different diets during exercise in man

Jansson

1982

Acta Physiologica Scandinavica

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Total respiratory exchange ratio (R) was compared to the respiratory exchange ratio over the legs (RQL) during exercise after different diets, to evaluate if R (which represents a mean for the whole body) can be used to estimate the relative proportions of fat and carbohydrate oxidation in exercising muscle. One important prerequisite for this is a steady state acid base balance, 7 subjects were studied at rest and during the later part of a 25 min exercise (65% of Vo2 max) on two occasions, the first preceded by a fat rich diet and the second by a carbohydrate rich diet. Oxygen uptake, R and arterial-femoral venous differences for [O2], [CO2], PCO2 and pH and arterial concentrations for lactate and beta-hydroxybutyrate were measured. Respiratory exchange ratio over the exercising legs (RQL) and ventilation/oxygen uptake were calculated. Arterial pH, PCO2, lactate and beta-hydroxybutyrate as well as specific ventilation attained steady levels during the later part of exercise after both diets. Although arterial lactate and beta-hydroxybutyrate differed between the diets, the arterial pH and specific ventilation were the same. Both R and RQL were higher after the carbohydrate than after the fat diet and there was no systematic difference between R and RQL. Therefore, it seems likely that R estimates the proportion of fat and carbohydrate oxidation in skeletal muscle during submaximal exercise after extreme diets.

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Section: Discussionmentioning

confidence: 99%

On the significance of the respiratory exchange ratio after different diets during exercise in man

Jansson

1982

Acta Physiologica Scandinavica

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“…In addition to this changing level of the quotient with increasing metabolic rate, we wish to call attention to the quotients DIsCUSSION. There has been a widespread opinion that the respiratory quotient cannot be taken as an indication of combustion processes in the body unless it is obtained by the chamber method or unless the experiments are conducted for a long period of time (3). If experimental conditions are not properly controlled, and account taken of the capacity of the subject to do the work set for him to do, there is no doubt that the quotients obtained by indirect methods are valueless.…”

Section: The "Steady State"mentioning

confidence: 99%

Studies in muscular activity

Bock¹,

Vancaulaert²,

Dill³

et al. 1928

The Journal of Physiology

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“…In practice, the protein metabolism is often assumed to be negligible, especially under basal conditions, and the total RQ is used to estimate the heat production. Possible confounding sources of variation in RQ have been described, and the dangers inherent in an over-simplified interpretation of the RQ pointed out (Cathcart and Markowitz, 1927;Richardson, 1929;Mitchell, 1935). Nevertheless, as Mitchell (1935) has stated, accurate estimates of heat production can be obtained from measurements of the gaseous exchange, "at least within the RQ limits of 0.707 and 1.000."…”

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confidence: 96%

Studies of the Avian Respiratory Quotient

Mellen

Hill

1955

Poultry Science

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T HE time-honored and still useful methods of indirect animal calorimetry are based on measurement of the respiratory exchange and urinary nitrogen excretion, followed by conversion of oxygen consumption values to Calories. This procedure involves determination of the non-protein respiratory quotient (RQ), followed by reference to the classical Zuntz-Schumberg table of heat values of oxygen at various RQ's. In practice, the protein metabolism is often assumed to be negligible, especially under basal conditions, and the total RQ is used to estimate the heat production. Possible confounding sources of variation in RQ have been described, and the dangers inherent in an over-simplified interpretation of the RQ pointed out (Cathcart and Markowitz, 1927;Richardson, 1929;Mitchell, 1935). Nevertheless, as Mitchell (1935) has stated, accurate estimates of heat production can be obtained from measurements of the gaseous exchange, "at least within the RQ limits of 0.707 and 1.000." Except for hibernants, normal fasted mammals apparently rarely have RQ's of less than 0.70, the theoretical RQ for the oxidation of fat. For example, Benedict and Fox (1934) fasted rats until death, but in no case was an RQ less than 0.70 recorded. In contrast, many fasting RQ values of less than 0.70 have been reported in the literature on respiratory exchange in birds. These have occurred with both gravimetric methods (Mitchell et al.

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The influence of various sugars on the respiratory quotient

Cited by 38 publications

References 7 publications

On the significance of the respiratory exchange ratio after different diets during exercise in man

On the significance of the respiratory exchange ratio after different diets during exercise in man

Studies in muscular activity

Studies of the Avian Respiratory Quotient

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