Changes In Energy Status Research Articles

Glycolysis and energetics in organs of hibernating mice (Zapus hudsonius)

Hibernation-induced changes in the concentrations of glycolytic intermediates, creatine phosphate, and adenylates were monitored in brain and skeletal muscle of the meadow jumping mouse, Zapus hudsonius, after both short (24 h) and long (5 – 7 d) periods of hibernation. Levels of hexose phosphates were greatly reduced in both organs after 24 h of hibernation, suggesting strong suppression of carbohydrate catabolism early in hibernation and indicating enzymatic regulation at the level of carbohydrate input into glycolysis. Both organs showed large changes in energy status during hibernation. Creatine phosphate content declined progressively over time to levels in 5 – 7 d hibernating animals that were 50 and 60% of control values in brain and muscle, respectively. Total adenylates and ATP levels also fell sharply during hibernation, but the net effect of changing adenylate levels on energy charge was minimal; energy charge was 0.94 in both organs of control animals and fell to 0.88 –0.90 in hibernating animals. The overall reduction in the pool sizes of phosphagen and adenylates in organs of hibernating animals may be one factor involved in metabolic suppression during hibernation.

Energy Status and Radiobiological Hypoxia at Specified Oxygen Concentrations

The relationship between energy status and oxygen concentration was evaluated using Chinese hamster ovary cells over a gas-phase oxygen concentration ranging from 40 to 210,000 ppm O2. Energy status was examined in cells in complete medium equilibrated with specified gas-phase oxygen concentrations, in the presence and absence of glucose. The change in two parameters of energy status, adenylate energy charge, which is ([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]), and ATP/cell as a function of oxygen concentration, was compared with the radiation oxygen enhancement ratio. In the presence of glucose, neither parameter of energy status is substantially affected by oxygen at various concentrations. In the absence of glucose, energy status is affected over the oxygen concentration range which parallels the change in the radiation oxygen enhancement ratio. However, the magnitude of the changes in energy status is dependent upon the duration of oxygen deprivation. In addition, glucose deprivation alone results in a decrease in ATP/cell in the presence of 210,000 ppm O2.

Acute inhibition of rat heart protein synthesis in vitro during beta-adrenergic stimulation or hypoxia

In the anterogradely perfused rat heart with glucose as fuel, 1 microM isoproterenol (ISO) inhibited the insulin (INS) plus adenosine deaminase (AdoDA) stimulation of ventricular protein synthesis by 72%. ISO (1 microM) alone had no effect on ventricular protein synthesis but inhibited atrial protein synthesis by 20%. The concentration dependence of the ISO inhibition was similar to the stimulation of glucose uptake by ISO. Inhibition could not be overcome by increasing INS concentrations. The effects of ISO were diminished by propranolol and could be partially mimicked by forskolin (FSK) or 8-(4-chlorophenylthio-)adenosine 3',5'-cyclic monophosphate (CPT-cAMP). The stimulation of protein synthesis by noncarbohydrate fuels was antagonized by ISO. Hypoxia (PO2 = 50%) also antagonized the INS stimulation of ventricular protein synthesis but did not affect basal rates. ATP contents were decreased by ISO but not by a PO2 of 50%. Both manipulations increased lactate output. The inhibition of protein synthesis by ISO could possibly be explained by indirect effects of ISO on cardiac "energy status." Furthermore, inhibition may thus represent purely an in vitro phenomenon and may not occur in vivo. However, the possibility that there are more direct effects of ISO on the machinery of protein synthesis has not been excluded. The inhibition of protein synthesis by hypoxia cannot be explained by changes in energy status and may result from intracellular lactoacidosis.

Simulation of heat and moisture transfer through a surface residue—soil system

A simulation model suitable for describing the dynamic aspects of mass and energy transfer in a soil—residue—atmosphere system has been developed and used to determine soil heat and water budgets. The model has been programmed in BASIC and uses numerical methods suitable for microcomputer applications. It displays a fundamental coupling of the surface residue to the soil—atmosphere system, and uses network analysis to describe heat and moisture transfer. Short-wave and long-wave radiative transfer, changes in energy status, rainfall interception by the residue, infiltration, redistribution, evaporation, and drainage are all accounted for. Daily input requirements include global short-wave radiation, maximum and minimum air temperatures, average wind speed, precipitation, and temperature and water content deep within the soil. General site, residue, and soil characteristics are also needed. Surface residues are treated as a thin layer with uniform horizontal distribution and residue loading rate is 3000 kg ha −1. Application of the model to energy and water budget studies using environmental data recorded at Pullman, WA during 1981/82 is discussed. Simulation results indicate that for the Pullman conditions surface residues decreased evaporation by roughly 36% when compared with simulations of bare soil evaporation. Monthly trends, however, indicate that the effectiveness of residues in conserving soil moisture decreases as the length of rain-free periods increases.

Switch on and switch off phenomenon of liver gluconeogenic function in lamprey ( Lampetra fluviatilis L.) Under the influence of season and temperature

1. 1. The potential activity of pyruvate carboxylase in lamprey liver is the same as in mammals. However, at certain stages of the life cycle this reaction does not take place because of ATP deficiency in mitochondria. 2. 2. Energy charge potential of liver cells ranges from 0.76 to 0.11 throughout a year. 3. 3. Heat adaptation of lampreys leads to a rapid increase of the ATP level and of the NAD +/NADH ratio in liver. The intensity of gluconeogenesis and glycogen levels are also enhanced. Cold reacclimation reverses the effect. 4. 4. A scheme accounting for the temperature changes in energy status of hepatocytes has been proposed.

Effect of body condition on the intake of food by mature sheep

Mature Merino wethers were changed in liveweight by grazing treatments or by feeding in pens and their intake of food over the next 5 weeks was then measured at two levels of pasture availability or in pens. Of nine groups of six sheep with mean initial fleece-free liveweight of 33 kg, three groups were increased to 37 kg (389 MJ energy) in 6 weeks by grazing abundant pasture, another three were reduced to 28 kg (220 MJ) on sparse pasture, and those remaining were reduced to 30 kg (268 MJ) by restricted feeding in pens. The three groups from each treatment were then moved to abundant pasture, to sparse pasture or to pens where food was offered ad lib. Energy status, within the range imposed here, had no effect on the intake of pasture or on the time spent grazing; both of these variables depended solely on the herbage currently available. Nor did energy status affect food intake when sheep were removed from pasture and compared in pens with a standard food. Sheep moved from sparse pasture to abundant pasture gained at least as much liveweight, but only 20% as much energy as sheep in better condition because more of their gain was water. These results suggest that short-term changes in the body condition of mature grazing sheep will have no effect on their intake of food and that their subsequent changes in fasted liveweight may give a misleading impression of changes in energy status.