Variations In Respiratory Quotient Research Articles

Differential energy expenditure is involved in the difference in activity levels between the Djungarian hamster (Phodopus sungorus) and the Roborovskii hamster (P. roborovskii)

The Djungarian hamster (Phodopus sungorus) shows calm behavior, while the Roborovskii hamster (P. roborovskii) exhibits hyperactivity. Even though they belong to the same genus, Phodopus, these two species are quite different. The current study investigated the relationship between energy expenditure and the markedly different levels of activity shown by these hamsters. Roborovskii hamsters showed significantly higher energy expenditure than Djungarian hamsters under both feeding and fasting conditions during darkness. Roborovskii hamsters showed a repeated increase and decrease in energy expenditure under the feeding condition; however, this changed under the fasting condition, during which the repeated increase and decrease in energy expenditure corresponded to the repeated active and sleeping conditions. Djungarian hamsters had a tendency to keep their energy expenditure constant during the fasting condition, while Roborovskii hamsters moved around a lot to find food. The respiratory quotient (RQ) values in Djungarian hamsters were relatively constant. However, Roborovskii hamsters showed a wide variation in RQ. In particular, the RQ value declined immediately before a dark phase commenced, indicating a switchover from the utilization of glucose to that of lipids as a substrate for energy production. In conclusion, Djungarian hamsters and Roborovskii hamsters showed different behavioral patterns that were related to differences in energy metabolism.

Comparison of seasonal variation in the fasting respiratory quotient of young Japanese, Polish and Thai women in relation to seasonal change in their percent body fat

BackgroundFrom the viewpoint of human physiological adaptability, we previously investigated seasonal variation in the amount of unabsorbed dietary carbohydrates from the intestine after breakfast in Japanese, Polish and Thai participants. In this investigation we found that there were significant seasonal variations in the amount of unabsorbed dietary carbohydrates in Japanese and Polish participants, while we could not find significant seasonal variation in Thai participants. These facts prompted us to examine seasonal variations in the respiratory quotient after an overnight fast (an indicator of the ratio of carbohydrate and fat oxidized after the last meal) with female university students living in Osaka (Japan), Poznan (Poland) and Chiang Mai (Thailand).MethodsWe enrolled 30, 33 and 32 paid participants in Japan, Poland and Thailand, respectively, and measurements were taken over the course of one full year. Fasting respiratory quotient was measured with the participants in their postabsorptive state (after 12 hours or more fasting before respiratory quotient measurement). Respiratory quotient measurements were carried out by means of indirect calorimetry using the mixing chamber method. The percent body fat was measured using an electric bioelectrical impedance analysis scale. Food intake of the participants in Osaka and Poznan were carried out by the Food Frequency Questionnaire method.ResultsThere were different seasonal variations in the fasting respiratory quotient values in the three different populations; with a significant seasonal variation in the fasting respiratory quotient values in Japanese participants, while those in Polish and Thai participants were non-significant. We found that there were significant seasonal changes in the percent body fat in the three populations but we could not find any significant correlation between the fasting respiratory quotient values and the percent body fat.ConclusionsThere were different seasonal variations in the fasting respiratory quotient values in the three different populations. There were significant seasonal changes in the percent body fat in the three populations but no significant correlation between the fasting respiratory quotient values and the percent body fat.

The relationship between lipoprotein lipase activity and respiratory quotient of rats in circadian rhythms.

Plasma lipid levels and lipoprotein lipase (LPL) are known to follow circadian rhythms in rats. However, very little information is available on the variations in respiratory quotient (RQ) during the 24-h period in rats. The aims of this study were to provide an overall view of the effects of circadian rhythm on RQ and to determine the relationship of LPL and RQ with metabolic parameters in these animals. Male rats were fed ad libitum and were kept under a 12 :12-h light-dark cycle. Rats were killed every 2 h over a 24-h period for measurement of metabolic parameters and tissue LPL activity. The RQ was measured every 4 h over the same 24-h period. The gastric contents increased during the dark phase and decreased during the light phase. For the metabolic parameters, circadian rhythms were detected for plasma glucose, triglycerides, high-density lipoprotein cholesterol and non esterified free fatty acids, but not for plasma total cholesterol or phospholipids. The RQ and adipose tissue LPL activity increased during the dark phase, while skeletal muscle LPL activity decreased during this phase. The RQ was inversely correlated with skeletal muscle LPL activity (r = -0.880) and positively correlated with adipose tissue LPL activity (r = 0.937). These results appear to show that rats tend toward consumption of fat by accelerating fat oxidation, resulting in suppression of fat accumulation in the light phase, while tending toward fat accumulation by the suppression of fat oxidation in the dark phase.

Circadian variation in heat production and respiratory quotient in growing broilers maintained at different food intakes and ambient temperatures

1. Circadian variations in heat production (HP) rate and respiratory quotient (RQ) were measured in growing broilers maintained at 5 ambient temperatures (14 degrees, 17 degrees, 22 degrees, 27 degrees and 32 degrees C) and at 5 rates of feeding [ad libitum intake and 75%, 50%, 25% and 0% (fasting) of ad libitum intake]. 2. In most cases, the HP rate decreased from 10 30 h (just after food was given) until 00 30 h (the 1-h dark period), showed an overshoot just after the 1-h dark period and then changed little. 3. Circadian variation in RQ , except in the fasted group, showed a similar pattern, which consisted of increase, decrease and constant phases. 4. Food intake affected the pattern of circadian variation in RQ , although ambient temperature had little effect. Possible effects of food intake on the pattern of circadian variation in HP rate were discussed.

Studies of the Avian Respiratory Quotient

THE 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 …

MICROBIOLOGICAL STUDIES OF SOME SUBANTARCTIC SOILS

SummaryA study has been made of the rhizosphere effect of four subantarctic plant associations at Macquarie Island. A stimulation occurred in each case in the rhizosphere, even in the more primitive Azorella selago and Dicranoweisia antarctica associations.No qualitative differences were found between rhizosphere and non‐rhizosphere isolates. The temperature range of most isolates was 10° to 25°C. with a high proportion giving maximum growth at 25° C.Respiration measurements were made on I I soils using the Warburg respirometer and a marked correlation was found between total carbon content of the soil and respiration. The variations in respiratory quotient which occurred were not related to carbon content and were probably due to differences in chemical constitution of the organic‐matter fractions and soil aeration.