An automatic, closed-circuit oxygen consumption apparatus for small animals.

An apparatus suitable for the continuous measurement of oxygen consumption of rats and mice is described. The system uses a motorized syringe dispenser to deliver fixed volumes of oxygen to a closed animal chamber. The dispenser is controlled by a micro-differential pressure switch to maintain chamber pressure slightly above ambient. The rate of oxygen consumption is determined by timing the interval between successive operations of the dispenser. The system has proved suitable for a range of experimental conditions and treatments.     

A lab-built respirometer for plant and animal cell culture

A very simple off-line respirometer was developed to measure oxygen consumption rates of low respiring and shear-sensitive cell suspensions. The respirometer is composed of a 10 mL glass syringe in which the plunger was substituted with a polarographic dissolved oxygen probe. Mechanical agitation is provided by means of a magnetic stirring bar inside the measuring chamber and a stir plate placed below the respirometer. Abiotic oxygen fluxes occurring in the measurement chamber such as oxygen diffusion and probe oxygen consumption were investigated. The apparent oxygen uptake rate was then corrected for abiotic oxygen fluxes, leading to accurate measurements of respiration rates ranging from 0.5 to 25.0 mM x h(-1). Additionally, the effect of the stirring bar shape and of the test length on the integrity of plant (Eschschzoltzia californica) and animal (NS0) cells was evaluated. Animal cells showed a higher resistance to mechanical stirring inside the respirometer compared to plant cells (0% of broken cells and 78.1% respectively for a polygonal stirring bar and a 15 min test). For plant cells, cell damage inside the measurement chamber was reduced by optimizing the stirring bar shape and reducing the test length to 5 min or less. This very simple design was shown to provide reliable and low-cost quantification of the oxygen uptake rate of plant and animal cells and can be use even for more demanding measurements such as oxygen affinity studies.     

Direct measurement of oxygen consumption rate on the nematode Caenorhabditis elegans by using an optical technique

It is well known that aging and longevity strongly correlate with energy metabolism. The nematode Caenorhabditis elegans is widely used as an ultimate model of experimental animals. Thus, we developed a novel tool, which is constructed from an optical detector, using an indirect method that can measure simply the energy metabolism of C. elegans. If we measure the oxygen consumption rate using this optical tool, we can easily evaluate the activity of mitochondria as an index in the aging process. However, a direct measurement of the oxygen consumption rate of C. elegans exposed in air is thought to be impossible because of the high concentration of atmospheric oxygen and the small size of the animals. We demonstrate here that we can directly detect the oxygen consumption with a small number of animals (相似文献   

Lung oxygen consumption and mitochondria of alveolar epithelial and endothelial cells.

We examined oxygen consumption by lung slices and measured the volume density of mitochondria of granular pneumocytes, alveolar type I cells, and alveolar capillary endothelial cells in several species. We found that lung oxygen consumption (mu-1 02 times h-1 times mg DNA-1) varies inversely with the log of animal body weight and with the species alveolar diameter and directly with the species respiratory rate. The volume density of granular pneumocyte mitochondria show a direct linear correlation with the lung's oxygen consumption and the species respiratory rate, and an inverse linear correlation with the species alveolar diameter. The volume density of mitochondria in type I alveolar epithelial cells and capillary endothelial cells, considered together, did not differ in the two species studied (mouse and rat). We conclude that there are interspecies differences in oxygen consumption by lung cells and that granular pneumocytes contribute to these differences. We suggest that, at least part of these differences, are related to interspecies differences in surfactant secretory activity.     

Respiratory activity of bacteria Acinetobacter calcoaceticus TM-31 during assimilation of alkane hydrocarbons

The respiratory activity of Acinetobacter calcoaceticus TM-31 with resect to alkane hydrocarbons was studied. The dynamics of oxygen consumption by the cells while assimilating n-hexadecane was assayed by a modified technique using an oxygen electrode. The dependence of cell respiratory activity on the amount of n-hexadecane within the concentration range of 0.03-0.66% was determined. It was demonstrated that the cells also displayed respiratory activity towards other medium-chain n-alkanes: hexane, octane, decane, tridecane, and heptadecane. Thus, we demonstrated the possibility of determining alkanes by measuring the respiratory activities of microorganisms.     

Water fleas (Daphnia magna) provide a separate ventilatory mechanism for their brood

The planktonic filter feeder Daphnia magna depends on a steady oxygen supply by convection. In the ventral carapace chamber, this convection is established by the feeding current which is generated by the movement of the thoracic limbs. The present study revealed that this movement can cause an additional flow of medium which passes through the brood chamber of the animal. To visualise this current, ink or fluorescent microspheres were released by a microcapillary near the posterior opening of the brood chamber. The tracks of these probes were monitored by video microscopy. Digital motion analysis was used for the determination of flow velocity and flow rate. Ambient medium entered the brood chamber at the abdomen of the animal and moved then to the anterior end of the brood chamber before entering the ventral carapace chamber. Two horizontal lamellae, which are attached at both sides of the trunk and project laterally to contact the carapace walls, almost completely separate the dorsal brood chamber from the ventral carapace chamber. Water can only pass these barriers through small depressions in these lamellae at the level of the 3rd and 4th appendages. Female daphnids with embryos at late developmental stages showed more rapid water currents in the brood chamber than those with younger embryos. Moreover, animals showed higher flow rates when exposed to hypoxic conditions. As the oxygen uptake rate of older embryos is approximately three times higher than that of younger embryos, the enhanced brood chamber current could improve the oxygen availability for both the mother and its brood under conditions of reduced oxygen availability.List of symbols:a specific oxygen consumption rate (nmol mm-³ h-¹), K Krogh constant for oxygen diffusion (nmol mm-¹ h-¹ kPa-¹, P_c critical oxygen partial pressure (kPa), P o₂ oxygen partial pressure (kPa), r radius (mm), s distance (mm), t time (ms)     

Respiratory activity of the bacteriumAcinetobacter calcoaceticus TM-31 during assimilation of alkane hydrocarbons

The respiratory activity ofAcinetobacter calcoaceticus TM-31 with resect to alkane hydrocarbons was studied. The dynamics of oxygen consumption by the cells while assimilatingn-hexadecane was assayed by a modified technique using an oxygen electrode. The dependence of cell respiratory activity on the amount ofn-hexadecane within the concentration range of 0.03–0.66% was determined. It was demonstrated that the cells also displayed respiratory activity towards other medium-chainn-alkanes: hexane, octane, decane, tridecane, and heptadecane. Thus, we demonstrated the possibility of determining alkanes by measuring the respiratory activities of microorganisms.     

Water fleas (Daphnia magna) provide a separate ventilatory mechanism for their brood

The planktonic filter feeder Daphnia magna depends on a steady oxygen supply by convection. In the ventral carapace chamber, this convection is established by the feeding current which is generated by the movement of the thoracic limbs. The present study revealed that this movement can cause an additional flow of medium which passes through the brood chamber of the animal. To visualise this current, ink or fluorescent microspheres were released by a microcapillary near the posterior opening of the brood chamber. The tracks of these probes were monitored by video microscopy. Digital motion analysis was used for the determination of flow velocity and flow rate. Ambient medium entered the brood chamber at the abdomen of the animal and moved then to the anterior end of the brood chamber before entering the ventral carapace chamber. Two horizontal lamellae, which are attached at both sides of the trunk and project laterally to contact the carapace walls, almost completely separate the dorsal brood chamber from the ventral carapace chamber. Water can only pass these barriers through small depressions in these lamellae at the level of the 3rd and 4th appendages. Female daphnids with embryos at late developmental stages showed more rapid water currents in the brood chamber than those with younger embryos. Moreover, animals showed higher flow rates when exposed to hypoxic conditions. As the oxygen uptake rate of older embryos is approximately three times higher than that of younger embryos, the enhanced brood chamber current could improve the oxygen availability for both the mother and its brood under conditions of reduced oxygen availability.     

Oxygen metabolism and catecholamine secretion during chloralose anesthesia in lambs.

Anesthetic agents are required when restraining animals in most forms of animal research. In particular, alpha-chloralose is a widely used anesthetic for respiratory and cardiovascular research despite limited controlled studies investigating whether chloralose could represent a variable influencing cardiorespiratory reflexes in acute animal studies. We previously used a chronically-instrumented neonatal lamb model to determine that chloralose had important effects on oxygen delivery and on basal hemodynamics. To investigate the influence of chloralose on oxygen metabolism and catecholamine secretion in relation to these hemodynamic changes, we studied 12 lambs before and after infusion of chloralose (30 mg/kg, i.v.) or control saline vehicle. Chloralose caused no differences in arterial or mixed venous oxygen contents, arterio-venous oxygen difference, or oxygen delivery, consumption, or extraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nomograms for Calculation of Oxygen Consumption and Respiratory Exchange Ratio

Nomograms have been prepared whereby the respiratory exchange ratio may be derived from the concentrations of carbon dioxide and oxygen in expired gas and oxygen consumption from the volume and oxygen concentration of expired gas; they apply only to patients breathing room air. The nomogram for the respiratory exchange ratio has an error of less than 0·01, which is the limit of visual discrimination on the nomogram. The nomogram for oxygen consumption has an error of standard deviation 7·73 ml/min. This error may be substantially reduced by excluding cases with a respiratory exchange ratio outside the range 0·70-0·93. Under these conditions the maximum error was 10 ml/min, which is acceptable for a wide range of clinical purposes.     

Influence des conditions expérimentales sur le taux respiratoire des copépodes planctoniques

Measurements of oxygen consumption were carried out on two planktonic copepods, Temora stylifera Dana and Centropages typicus Kröyer under two experimental conditions, namely, degree of confinement and length of time spent in the laboratory. The effect of population density was studied for concentrations between 0.1 animal/ml to 2 animals/ml; the highest rate of respiration was observed in both species for a concentration of 0.5 animal/ml. Concentrations higher (1 or 2 animals/ml) and lower one (0.2 to 0.4 animal/ml) caused a decrease in the respiratory rate. Single animals have respiratory rates similar to those found with a concentration of 0.5 animal/ml. The observed effect of population densities did not depend on the absolute experimental volumes.     

A combined sensor suitable for telemetering respiratory functions.

A system for measuring oxygen consumption from momentary respiratory values of free moving person is described. The main part presented here is a sensor consisting of a flowmeter based on the impeller principle, called 'Wirbelrespirometer', joint with a polarographic electrode sensitive to oxygen, and a very fast reacting thermistor. First comparative studies in computation of respiratory volume and oxygen consumption yielded average deviations against comparison methods of less than +/- 1% for computation of volume, and +/- 4% for computation of oxygen consumption.     

The effects of location and design on the diffusion of respiratory gases in mammal burrows

To investigate the constraints placed on the location and design of mammal burrows by the resident mammal's need for an adequate exchange of respiratory gases with the free atmosphere, we constructed several simple mathematical models for the steady-state diffusion of these gases in sterile burrow-soil systems. In this exchange, diffusion through the soil is of prime importance. Openings of narrow tunnels further than three body lengths from a mammal have a negligible effect on its respiratory microenvironment. Since only a short length of a narrow tunnel around the mammal is of importance in this exchange we may confine attention to design and siting criteria for a discrete chamber containing the mammal.The porosity of the soil in which a burrow chamber is sited and the volume of the burrow chamber have strong and moderate effects respectively on the rate of gas exchange between a resident mammal and the free atmosphere. The depth of the burrow chamber, beyond two chamber diameters, has only a weak effect on this transfer. Soil temperature within the thermoneutral zone of the resident mammal has a weak effect on this transfer, but below the thermoneutral zone, where temperature modifies the rate of consumption (production) of respiratory gas, the effect is strong. Concentrations of respiratory gas in the burrow chamber approach free-atmosphere values when soil porosity, soil temperature, and chamber volume increase and burrow depth decreases.Large mammals are more restricted in the design and siting of burrows than small mammals. Our models indicate that normothermic eutherian mammals with masses much in excess of 0·5 kg are precluded from an indefinite occupation of deep burrows in most field situations. In considering the limitations to our models, several avenues for expanding a mammal's respiratory space are suggested.     

Using Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory Measurements

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-by-step instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.     

Respiration,temperature regulation and energetics of thermogenic inflorescences of the dragon lily Dracunculus vulgaris (Araceae)

Dracunculus vulgaris is a protogynous arum lily with thermogenic inflorescences consisting of male and female florets on a spadix within a floral chamber. Above the chamber, an odour-producing appendix and a carrion-coloured spathe attract flying insects. The inflorescence shows a triphasic warming pattern. The floral chamber warms weakly on the first night as the spathe opens. Then the appendix produces a large amount of heat and a powerful scent during the first day. As the appendix cools on the second night, scent production ceases and the floral chamber rewarms. Warming ceases when the pollen is shed on the second day. The heating pattern is associated with attraction of pollinating insects by the appendix on the first day, entrapment in the warm chamber at night and release after pollen shedding. The temperature in the floral chamber is regulated at around 18 °C during the second night. The oxygen consumption rate of the florets is inversely related to the ambient temperature as in other thermoregulatory flowers. Conversely, the oxygen consumption rate of the appendix is directly related to the ambient temperature, indicating that it does not thermoregulate. Thus, temperature regulation is not associated with scent production, but with some activity inside the floral chamber.     

Low Mitochondrial Free Radical Production Per Unit O2 Consumption Can Explain the Simultaneous Presence of High Longevity and High Aerobic Metabolic Rate in Birds

Birds are unique since they can combine a high rate of oxygen consumption at rest with a high maximum life span (MLSP). The reasons for this capacity are unknown. A similar situation is present in primates including humans which show MLSPs higher than predicted from their rates of O₂ consumption. In this work rates of oxygen radical production and O₂ consumption by mitochondria were compared between adult male rats (MLSP = 4 years) and adult pigeons (MLSP = 35 years), animals of similar body size. Both the O₂ consumption of the whole animal at rest and the O₂ consumption of brain, lung and liver mitochondria were higher in the pigeon than in the rat. Nevertheless, mitochondrial free radical production was 2-4 times lower in pigeon than in rat tissues. This is possible because pigeon mitochondria show a rate of free radical production per unit O₂ consumed one order of magnitude lower than rat mitochondria: bird mitochondria show a lower free radical leak at the respiratory chain. This result, described here for the first time, can possibly explain the capacity of birds to simultaneously increase maximum longevity and basal metabolic rate. It also suggests that the main factor relating oxidative stress to aging and longevity is not the rate of oxygen consumption but the rate of oxygen radical production. Previous inconsistencies of the rate of living theory of aging can be explained by a free radical theory of aging which focuses on the rate of oxygen radical production and on local damage to targets relevant for aging situated near the places where free radicals are continuously generated.     

Exchange of oxygen across the epicardial surface distorts estimates of myocardial oxygen consumption

The rate of oxygen consumption of isolated, Langendorff-circulated, saline-perfused hearts of guinea pigs, rats, and rabbits was measured using the classical Fick Principle method. The heart was suspended in a glass chamber the oxygen partial pressure, PO2, of which could be varied. The measured rate of oxygen consumption was found to vary inversely with the ambient (heart chamber) PO2. This result prevailed whether the chamber was filled with air, saline, or oil, and whether the pericardium was present or the heart was wrapped in Saran. The effect varied inversely with heart size both within and across species. It is concluded that the epicardial surface is permeable to oxygen which will diffuse either into or out of the heart as the PO2 gradient dictates. In either case the classically measured rate of oxygen consumption will be in error. The error can be large in studies of cardiac basal metabolism. A simple model is developed to describe the observed rate of oxygen consumption as classically measured. The measured rate is partitioned into two components: the true rate of oxygen consumption of the heart, and the rate of loss of oxygen by diffusive exchange across the epicardial surface. The latter component is proportional to the gradient of oxygen partial pressure from myocardium to environment and to the diffusive oxygen conductance of myocardial tissue. Application of the model allows the true rate of oxygen consumption of the heart to be recovered from measured values which may be considerably in error.     

Reversibility of oxygen switch-off effect on Bacillus polymyxa nitrogenase.

The objective of this study was to analyse in vivo the effect of oxygen on the nitrogenase of Bacillus polymyxa. The culture technique employed in this study prevented spore formation by B. polymyxa during the entire period of exposure to acetylene. Under these conditions the acetylene-reduction assay allowed quantification of nitrogenase activity over long incubation periods (44 h). Nitrogenase activity was highest in cells harvested in the late logarithmic phase. At PO2 of 0.19 and 0.37 kPa, acetylene reduction was inhibited by 80 and 100%, respectively. This switch-off effect could be reversed through oxygen exhaustion, either by flushing the culture with N2 or by cellular respiration, suggesting a respiratory protection mechanism for the nitrogenase complex in B. polymyxa. Oxygen consumption measured by a closed-chamber respirometer showed a linear increase up to a PO2 of 0.2 kPa. Above 0.3 kPa a saturation in oxygen consumption was observed. Exposure to high oxygen pressures resulted in an irreversible loss of nitrogenase activity. The oxygen inhibition pattern was shown to be similar to that in other microaerophilic and anaerobic nitrogen-fixing microorganisms.     

Effect of chronic insecticide, phosalone, toxicity on haem synthesis and blood gas composition in the rat.

The influence of multiple sublethal concentrations of phosalone on whole animal and kidney oxygen consumption, haem synthesis and blood gases of rat, were carried out over a 90 day dosed period. The results indicate the existence of hypoventilation and a hypoxic condition in the animals which lead to the disruption of neuromuscular transmission in respiratory muscles and increase of erythropoiesis and haemoglobin synthesis. The changes were most pronounced when animals were exposed for the 90 day dosed period.     

Carbon metabolism and bacteroid respiration in nodules of chick-pea (Cicer arietinum L.) plants grown under saline conditions

ABSTRACT

The present work investigates the relationships between nitrogen fixation, carbon metabolism and oxygen consumption by bacteroids of Mesorhizobium ciceri in root nodules of chick-pea plants. Its aim was to establish whether some of the compounds which accumulate under salt stress may be used as respiratory substrates by bacteroids to fuel their own metabolism and nitrogenase activity. Plants were grown in a growth chamber, and salt stress was induced by adding 50 mM NaCl to the nutrient solution at sowing. The data presented here show a rise in fermentative metabolism in nodules of chick-pea plants exposed to high salinity, and suggest that proline, lactate or ethanol, may play an important role as energy-yielding substrates for bacteroids in this plant species. The bacteroids could utilize glucose as a respiratory substrate both under control and saline conditions, while malate did not appear to be the preferred substrate in the presence of salt.