Respiration kinetic of mango (Mangifera indica L.) as function of storage temperature

Respiration of cut mango (Mangifera Indica L.) cv. Tommy Atkins was studied using the closed system method at three temperatures (4, 20 and 35 °C). Two models were used to estimate the gas concentration, which were adjusted through non-lineal regression algorisms using Matlab R2011a software. Three mathematic models, a model based on Michaelis-Menten's enzymatic kinetics, and two models based on regression analysis, in one of which a saturation equation was included as a new proposal in this field, were set to predict the substrate respiration rate. Results made evident the positive effect of temperature on mango respiration rate. The model with the best adjustment to mango respiration rate was Michaelis-Menten's with an adjusted correlation coefficient of 0.9811 and 0.9747 for CO2 and O2 respectively, with a relative mean error lower than 10%.

The development of thermotolerance protects blowfly flight muscle mitochondrial function from heat damage

The LD50 of 10-day-old adult blowflies was determined to be 38.12±0.07 °C. A transitory increase in heat resistance occurred following the exposure of adult blowflies to a sublethal heat shock at 36 °C. This thermotolerance was apparent 1 h after the application of the shock, was maximal 2­3 h later and had disappeared 6 h after exposure. Oxidative phosphorylation by flight muscle mitochondria from control flies was impaired by an LD50 dose in vivo using both pyruvate+proline (P+P) and glycerol 3-phosphate (G3P) as substrates. Acceptor control (state III respiration/state IV respiration) was lost with G3P as substrate and so ADP:O ratios were not measurable. The effect of experimental temperature in vitro on respiratory performance of mitochondria isolated from control and thermotolerant flies was also determined between 19 and 39 °C. State III respiration was markedly temperature-dependent in mitochondria from control flies with both substrates; it was maximal at 24­29 °C and fell progressively at higher measuring temperatures. In mitochondria from thermotolerant flies, state III respiration was less temperature-dependent with both substrates but this was most marked for G3P. The effect of experimental temperature on state IV respiration was similar in mitochondria from control and thermotolerant flies with each substrate, but differed between the two substrates. With G3P as substrate, respiration rate rose with temperature with a Q10 of approximately 1.5; however, with P+P as substrate, the trend was for respiration rate to fall as experimental temperature rose. Using G3P as substrate, acceptor control was demonstrable at 34 °C in some preparations of mitochondria from thermotolerant flies but not in those from control flies at that temperature. With P+P as substrates, acceptor control was demonstrable in mitochondria from both control and thermotolerant flies at all experimental temperatures.

The Oxidation of Fatty-Acyl Derivatives by Mitochondria from Bovine Fetal and Calf Hearts

Functional activity of the "external" carnitine palmitoyltransferase in intact mitochondria, prepared from hearts from various sources, was estimated by measuring respiration by mitochondria in the presence of palmitoyl-CoA plus or minus l-carnitine. When palmitoyl-CoA alone was substrate, respiration was not increased above the basal rate under all conditions examined. Addition of l-carnitine increased respiration, provided the ionic strength of the incubation medium was sufficiently high. In the presence of palmitoyl-CoA plus l-carnitine, the rate of respiration increased as the ionic strength was increased to physiological levels. In contrast, the increase in rate of oxygen consumption by heart mitochondria which followed the addition of palmitoyl-l-carnitine was relatively independent of the ionic strength of the medium.Mitochondrial fractions prepared from fetal bovine hearts were shown to possess "external" carnitine palmitoyltransferase activity, as judged by the ability of l-carnitine to stimulate respiration by mitochondria incubated with palmitoyl-CoA under various conditions. These data were discussed in relation to information available concerning the functions of different carnitine acyltransferases in mitochondria.

The Metabolism During Starvation of Balanus Balanoides

There is some reduction in oxygen uptake of isolated bodies on starvation when carbohydrate is being utilized.There is a gross discrepancy between the oxygen demand as measured in isolated bodies and the available substrate; respiration is probably reduced during inanition.It is suggested that the moulting cycle is coupled to the metabolic activity in an obligatory fashion rather than being dominated by the kind of hormonal control found in decapods.

Fat deficiency and the calorigenic action of L-thyroxine

The influence of a fat-deficient diet on the calorigenic action of l-thyroxine was investigated. The BMR, endogenous and substrate respiration (succinate) of liver slices and hemidiaphragms were determined. The increase of BMR in fat-deficient animals was confirmed. Furthermore, both endogenous and ‘substrate’ respiration of liver and diaphragm were higher than in controls. When thyroxine was administered, the fat-deficient animals demonstrated a greater BMR response than did controls. Substrate respiration of liver and diaphragm indicated that both fat deficiency and thyroxine treatment increase succinate utilization and that these effects are additive in these tissues.

Metabolic characteristics of the isolated perfused rat liver

The use of the isolated perfused rat liver for quantitative biochemical studies of liver metabolism over an experimental period of as long as 4 hours is demonstrated. Respiration rates responded immediately to the addition of substrates and the liver could be restimulated by a second dose of substrate, respiration rates reflecting the nature of the substrate. Net amino nitrogen uptake was consistently exceeded by urea nitrogen production, the latter comparing favorably with in vivo rates. Fructose was rapidly removed from the perfusate by the liver, and the liver efficiently removed lactic acid formed by erythrocyte glycolysis. Ketone body production was continuous and within normal in vivo rates. Bile production declined gradually over a 4-hour period.

RESPIRATION AND INTENSITY DEPENDENCE OF PHOTOSYNTHESIS IN CHLORELLA

1. Respiration changes as a result of illumination. 2. In the absence of glucose or other supply of substrate, respiration decays in the dark showing at least two types—a fast decay in a few minutes and a slow decay lasting hours. 3. Respiratory response to illumination is delayed. 4. Intermittent illumination (in the absence of glucose, etc.) produces a periodic variation in respiration with a delay or phase lag. 5. Periodic variation of respiration may produce a higher average value in the dark than in the light due to the lag and depending upon the period of intermittent illumination. 6. Based upon average respiration values our data confirm the Kok effect. 7. Interpolated values of respiration, however, result in photosynthetic rates which are linearly dependent upon intensity of illumination. 8. Thus the quantum efficiency is found to be independent of intensity, over the wide range of intensities investigated.