On-line continuous measurement of the oxygen consumption rate in mammalian cell culture

A method for on-line, continuous measurement of the oxygen consumption rate (Io₂) by mammalian cells on a microcarrier was developed and its reliability investigated. Utilizing the periodic dissolved oxygen (DO) fluctuation in the normal on-off control of DO, on-line, continuous measurement of Io₂ was carried out in which real-time estimation of the DO saturation concentration was made by measuring the gas-phase pressure and the gas-phase oxygen concentration. It was found that the continuously measured Io₂ value was quantitatively exact and could be applied commercially using the oxidation reaction of glucose by glucose oxidase.     

Membrane open-system cell for oxygen consumption measurement

A membrane-diffusion cell for oxygen uptake measurements in an open system is described. Polarographic oxygen measurements with a Clark electrode are combined with simultaneous pH and absorbance or fluorescence determinations. Examples of its use are given and discussed, including experiments on mitochondrial respiration. Advantages of this cell are analyzed and comparisons are made with other open-system respirographs.     

Detection of wood boring insects by measurement of oxygen consumption

A possible method for detection of wood-boring insects in wood is the measurement of oxygen consumption. In order to develop such a method, several parameters have to be determined first. The most important one is to determine the respiration rate of possible pest species. To obtain the data for establishing the method mentioned above, the respiration rates of the following species were determined: the old house borer, Hylotrupes bajulus, common furniture beetle, Anobium punctatum and subterranean termite, Reticulitermes lucifugus. We compared the O₂ consumption between different species as well as between adults and larvae of one species in different environmental conditions (temperature, day/night and light/dark regime). The most intensive respiration rates were found for the larvae of Hylotrupes bajulus (4.0 ml/g h O₂) and Anobium punctatum (3.9 ml/g h O₂). Less intensive breathing was measured by Reticulitermes lucifugus (workers 2.9 ml/g h, nymphs 2.6 ml/g.h and soldiers 2.0 ml/g h O₂). These results indicate that it is possible to detect the presence of wood-boring insects respirometrically. To detect the presence of an individual insect in the wood by means of respirometry, the sensitivity of the instrument for oxygen measurement at the optimal conditions must be around 0.2 ml/h.     

Continuous measurement of oxygen consumption in small laboratory animals]

A technique for measuring the oxygen consumption of small laboratory animals suitable for pharmacological and toxicological studies is described. The oxygen consumption of the animal in the respiratory chamber is compensated by means of a photoelectrically operating servo mechanism from an oxygen reservoir. The oxygen supplied is directly recorded via a transducer by an X-Y recorder. The carbon dioxide exhaled by the animal is entirely absorbed. Composition and pressure of air in the respiratory chamber correspond to the physiological medium. The usefulness of this technique is demonstrated by investigations on the effects of epinephrine and morphine on the oxygen consumption of rats.     

An inexpensive instrument for sediment erosion-accumulation rate measurement in intertidal environments

A low-cost instrument to determine elevation changes in intertidal environments is presented. The instrument consists of two small PVC pipes driven into the soil and a ruler attached to a bar sustained by two rods that are inserted into the pipes during the measurement. This method cost only a fraction of similar ones described in the literature. Furthermore, because large numbers can be deployed in an area, statistically significant sedimentation-erosion rates can be obtained for places where spatial variances are very large.     

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 pyrene fluorescence technique and microchamber for measurement of oxygen consumption of single isolated axons

Pyrene fluorescence is quenched by oxygen in an inverse and linear manner related to the partial pressure of O2 in solution. We have developed a microchamber for measuring QO2 of a single isolated axon, monitoring the change in fluorescence of a pyrene probe. The probe consists of a Spectra/Por dialysis hollow fiber filled with 2.5 mM pyrene in paraffin oil. The probe is inserted into a 1-mm-i.d. 2-cm-long quartz capillary tube with a freshly isolated crayfish medial giant axon. The capillary is mounted in an apparatus that forms an air- and water-tight seal except for a 0.2-mm-i.d. stainless steel tube at both ends permitting the exchange of solutions. An Olympus inverted microscope, equipped with epifluorescence optics and a 150-W xenon lamp, is used to view the preparation, generate the excitation light, and monitor the emitted fluorescence with a photomultiplier tube placed in the microscope TV port. A dichroic filter unit is utilized to select an excitation wavelength of 350 nm and collect emitted light above 420 nm. The signal is amplified with a Keithley 480 picoammeter and recorded on a strip chart. QO2 of isolated axons was 552 +/- 70 X 10(-6) mol O2/liter tissue X min. Following sequential treatment with 2 mM ouabain and 2 mM NaCN, QO2 decreased by 22 and 82%, respectively. These data are consistent with QO2 measurements of whole nerve cord made with a Clark electrode O2 monitor.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetic studies of biodegradation of insoluble compounds by continuous determination of oxygen consumption

Continuous determination of oxygen consumption by electrolytic respirometry has been experimented as a means to study the biodegradation kinetics of scarcely soluble environmental pollutants. The substrates used were the polycyclic aromatic hydrocarbons (PAH), naphthalene, phenanthrene, anthracene, fluoranthene and pyrene. The definition of an appropriate mode of PAH supply, either as crystals or more generally as a solution in a water non-miscible solvent, was found essential for yielding reproducible biodegradation kinetics. In these conditions, for all compounds tested, oxygen determination was found suitable for quantitative evaluation of PAH biodegradation and formation of biomass and soluble metabolites. The study of biodegradation kinetics with this methodology showed that a first phase of exponential growth could be characterized in most cases, followed by a phase of limited growth. Possible mechanisms involved in insoluble substrate uptake are discussed. During exponential growth, the bacteria utilized (although not necessarily exclusively) the PAH solubilized in the aqueous medium.     

Dynamic measurement of oxidase activity based on oxygen consumption in open systems

Oxidases catalyze the oxidation of a variety of substrates with the concomitant reduction of molecular oxygen as a final electron acceptor. UV‐visible spectrophotometry is a simple and high‐throughput method commonly used to measure oxidase activities. However, drawbacks such as light scattering exist especially concerning the activity assessment of enzymes immobilized on supports. Monitoring of the universal cosubstrate O₂ circumvents these drawbacks. This study aimed at developing a methodology that allows activity measurement of many types of oxidases based on O₂ consumption applicable to various open systems. Dissolved oxygen in the reaction medium was monitored by an O₂ sensor and the reaction rate was deduced from the O₂ mass balance equation correcting for atmospheric diffusion. Common activity units (μM_product min^?1 or U/L) could be subsequently derived using calibration curves. The sensitivity of the method toward temperature, atmospheric pressure, and ionic strength variations was evaluated, and made it possible to define operating windows for the simplification of the proposed methodology.     

An automated continuous determination of oxygen with high sensitivity

A sensitive, rapid, and precise method is described for the continuous determination of oxygen in gases. The principle of the method is based on the reaction of O₂ with an alkaline catechol or pyrogallol solution, which is combined with a Fe²⁺ solution to increase the sensitivity of the color reaction. The development of the color takes place in a tube system provided with a proportioning pump and is read automatically on a recorder after passing a flow cell of a photometer. The lower limit of sensitivity of this method is 0.05 μl of O₂ min^?1. Thus, in a gas flow of ≈0.5 ml min^?1, an oxygen concentration of ≥0.01% (v/v) can be determined. If the gas flow is increased to ≈2.5 ml min^?1, this limit of sensitivity is lowered to ≥0.002% (v/v). Since a 2-min period is necessary for the measurement, the volume of the sample has to be 1 ml in the first case and 5 ml in the second.