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This chapter de-mystifies respirometry equations, showing how they can be derived using a simple mental trick: concentrating the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases, are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.

By using modern gas analyzers and variations of constant volume techniques described in Chapter 2, simple and high-throughput measurement of the metabolic rates of organisms ranging in size from bacteria to large insects and even small vertebrates are easily implemented. It is even possible to measure water loss rate and carbon dioxide production using only an oxygen analyzer. The techniques can be deployed in the field as well as the laboratory. Both manual and automated, computerized implementations of constant volume techniques are covered in full step-by-step detail, and appropriate analytical protocols for oxygen, carbon dioxide, or both oxygen and carbon dioxide analysis systems are also described in detail.

This chapter describes constant pressure (Gilson) and constant volume (Warburg) respirometry — long-established techniques that are still capable of accurate results. These are useful for measuring the metabolic rates of small organisms, cell cultures, and biochemical preparations. In Gilson respirometry, oxygen consumption is measured by reducing the volume of a sealed system to maintain a constant pressure. In Warburg respirometry, oxygen consumption is measured by quantifying the accompanying drop in the pressure of a sealed system, the volume of which is known. The theory and practical details of implementing both techniques are described in detail. Finally, a more modern, computerized alternative to Warburg respirometry is introduced that can be implemented at low cost.

This chapter describes the theory and practical applications of coulometric respirometry. Coulometric respirometry is probably the most accurate method for measuring oxygen consumption rates. It is ideal for small animals and has the dual advantages of high sensitivity and the fact that the oxygen in the organism's environment is not depleted, allowing measurements to continue for long periods in many cases. The technique works by maintaining a constant pressure in a sealed system by electrolytically producing oxygen at the same rate at which an enclosed organism consumes it.

This chapter focuses on potential confounding factors in the interpretation of the blood oxygen level dependent (BOLD) signal in fMRI studies of cognitive aging. Studies generally attribute age-related changes in BOLD signal to age-related changes in neural activity, thereby assuming that the coupling between BOLD signal and neural activity is the same for young and older adults. However, this coupling may be altered by age-related changes in the neurovascular system and by comorbidities associated with aging. Age-related changes of the neurovascular system likely to affect the BOLD signal include changes in ultrastructure (e.g., sclerosis), resting cerebral blood flow (CBF), vascular reactivity, and cerebral metabolic rate of oxygen consumption. The BOLD signal may also be affected by comorbidities associated with aging, such as leukoariosis and small strokes, and by medications.

This chapter describes the setup, the plumbing, and the equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull-mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.

This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push-mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.

Metabolism is driven by redox reactions, in which part of the difference in potential energy between the electron donor and acceptor is used by the organism for its life processes (with the remainder being dissipated as heat). The key process is intermediary metabolism, by which the energy stored in reserves (glycogen, starch, lipid, protein) is transferred to ATP. In aerobic respiration the electrons released from reserves are passed to oxygen, which is thereby reduced to water. Not all ATP regeneration involves oxygen as the final electron acceptor, and not all oxygen is used for ATP regeneration, but oxygen consumption is often the simplest and most practical way to measure the rate of intermediary metabolism and the errors in doing so are believed to be small. The costs of existence, as estimated by resting metabolism, represent only a part (~ 25%) of the daily energy expenditure of organisms. The costs of the organism’s ecology (growth, reproduction, movement and so on) are additional to existence costs. Resting metabolic rate increases with cell temperature, indicating that it costs more energy to maintain a warm cell than it does a cool or cold cell. The temperature sensitivity of resting metabolism is highly conserved across organisms.

This chapter discusses the cardiovascular responses of diving seals during metabolic activity. Responses of the heart and circulation feature prominently in the protective reactions of marine mammals during long dives. Reduced cardiac output and constricted peripheral blood flow impose major alterations on the circulatory system. Their combined reactions result in a lowering of overall oxygen consumption by reduced blood flow, sometimes apparently eliminating it from the kidneys, intestines, skin, and other organs that can better tolerate temporary circulatory arrest. This results in an abrupt decline of metabolism in the blood-deprived organs. Along with the diving seal's reduced circulation, its heart rate slows, sometimes drastically to no more than a few beats per minute. This bradycardia is initiated by neural reflex activation and occurs in coordination with the lessened demand on the heart's pumping action for supplying the consequently reduced output of blood. The demand for cardiovascular supporting reactions is variable depending on whether the diving seal is swimming or quietly resting.

This chapter describes the theory and practical applications of coulometric respirometry. Coulometric respirometry is probably the most accurate method for measuring oxygen consumption rates. It is ideal for small animals and has the dual advantages of high sensitivity and the fact that the oxygen in the organism’s environment is not depleted, allowing measurements to continue for long periods in many cases. The technique works by maintaining a constant pressure in a sealed system by electrolytically producing oxygen at the same rate at which an enclosed organism consumes it.

The original claims of cognitive neuroscience, an offshoot of computer science and psychology, were of a logical brain in which mental concepts could be identified and localized. Reviews of the imaging studies of two popular cognitive neuroscience concepts, “working memory” and “willed action,” show that these expectations are not fulfilled, while in a Pragmatist understanding of such generalizations they cannot be found. Instead, neuroimages are shown to determine the values of cerebral blood flow and energy consumption, which can create a neurophysiological, bottom-up basis of brain function.

By using modern gas analyzers and variations of constant volume techniques described in Chapter 2, simple and high-throughput measurement of the metabolic rates of organisms ranging in size from bacteria to large insects and even small vertebrates are easily implemented. It is also possible to measure water loss rate and carbon dioxide production using only an oxygen analyzer. These respirometry techniques can be deployed in the field as well as the laboratory. Both manual and automated, computerized implementations of constant volume techniques for metabolic rate measurement are covered in full step-by-step detail, and appropriate analytical protocols for oxygen, carbon dioxide, or both oxygen and carbon dioxide analysis systems are also described in detail.

This chapter describes constant pressure (Gilson) and constant volume (Warburg) respirometry—long-established techniques that are still capable of accurate results. These are useful for measuring the metabolic rates of small organisms, cell cultures, and biochemical preparations. In Gilson respirometry, oxygen consumption is measured by reducing the volume of a sealed system to maintain a constant pressure. In Warburg respirometry, oxygen consumption is measured by quantifying the accompanying drop in the pressure of a sealed system, the volume of which is known. The theory and practical details of implementing both techniques are described in detail. Finally, a more modern, computerized alternative to Warburg respirometry is introduced that can be implemented at low cost.

This chapter demystifies respirometry equations, showing how they can be derived using a simple mental trick: focusing the analysis on the principal gas that is neither consumed nor produced by animals. The effect of dilution of oxygen by carbon dioxide, the enrichment of carbon dioxide by the consumption of oxygen, and the effects of water vapor on the concentrations of both gases are described and quantified. A system of eight equations is derived that allow oxygen consumption and carbon dioxide production to be calculated in practically any feasible flow-through respirometry system.

This chapter describes the setup, plumbing, and equations for implementing a respirometry system wherein the flow rate of the air leaving the animal chamber is known. Such systems are usually referred to as pull systems, because the air is usually pulled from a chamber or mask at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Such systems are often the only practical way of measuring the metabolic rates of large animals. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal pull mode respirometry systems, for compensating flow rate, and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are discussed.

The ocean and the atmosphere exchange massive amounts of carbon dioxide (CO2). The pre-industrial influx from the ocean to the atmosphere was 70.6 Gt C yr –1 , while the flux in the opposite direction was 70 Gt C yr –1 ( IPCC 2007 ). Since the Industrial Revolution an anthropogenic flux has been superimposed on the natural flux. The concentration of CO2 in the atmosphere, which remained in the range of 172–300 parts per million by volume (ppmv) over the past 800 000 years ( Lüthi et al. 2008 ), has increased during the industrial era to reach 387 ppmv in 2009. The rate of increase was about 1.0% yr –1 in the 1990s and reached 3.4% yr –1 between 2000 and 2008 ( Le Quéré et al. 2009 ). Future levels of atmospheric CO2 mostly depend on socio-economic parameters, and may reach 1071 ppmv in the year 2100 ( Plattner et al. 2001 ), corresponding to a fourfold increase since 1750. As pointed out over 50 years ago, ‘human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future’ ( Revelle and Suess 1957 ). Anthropogenic CO2 has three fates. In the years 2000 to 2008, about 29% was absorbed by the terrestrial biosphere and 26% by the ocean, while the remaining 45% remained in the atmosphere ( Le Quéré et al. 2009 ). The accumulation of CO2 in the atmosphere increases the natural greenhouse effect and generates climate changes ( IPCC 2007 ). It is estimated that the surface waters of the oceans have taken up 118 Pg C, or about 25% of the carbon generated by human activities since 1800 ( Sabine et al. 2004 ). By taking CO2 away from the atmosphere, the oceanic and terrestrial sinks mitigate climatic changes. Should their efficiency decrease, more CO2 would remain in the atmosphere, generating larger climate perturbations. This book has four main groups of chapters.

The average surface-ocean pH is reported to have declined by more than 0.1 units from the pre-industrial level ( Orr et al. 2005 ), and is projected to decrease by another 0.14 to 0.35 units by the end of this century, due to anthropogenic CO2 emissions (Caldeira and Wickett 2005 ; see also Chapters 3 and 14). These global-scale predictions deal with average surface-ocean values, but coastal regions are not well represented because of a lack of data, complexities of nearshore circulation processes, and spatially coarse model resolution (Fabry et al. 2008 ; Chapter 3 ). The carbonate chemistry of coastal waters and of deeper water layers can be substantially different from that in surface water of offshore regions. For instance, Frankignoulle et al. ( 1998 ) reported pCO2 (note 1) levels ranging from 500 to 9400 μatm in estuarine embayments (inner estuaries) and up to 1330 μatm in river plumes at sea (outer estuaries) in Europe. Zhai et al. (2005) reported pCO2 values of > 4000 μatm in the Pearl River Estuary, which drains into the South China Sea. Similarly, oxygen minimum layers show elevated pCO2 levels, associated with the degree of hypoxia (Millero 1996). These findings suggest that some coastal and mid-water animals, both pelagic and benthic, are regularly experiencing hypercapnic hypercapnic conditions (i.e. elevated pCO2 levels), that reach beyond those projected in the offshore surface ocean. These organisms might, therefore, be preadapted to relatively high ambient pCO2 levels. The anthropogenic signal will nonetheless be superimposed on the pre-existing natural variability. These phenomena lead to the question of whether future changes in the ocean’s carbonate chemistry pose a serious problem for marine organisms. Those with calcareous skeletons or shells, such as corals and some plankton, have been at the centre of scientific interest. However, elevated CO2 levels may also have detrimental effects on the survival, growth, and physiology of marine animals more generally (Pörtner and Reipschläger 1996; Seibel and Fabry 2003; Fabry et al. 2008; Pörtner 2008; Melzner et al. 2009a).

This chapter describes the setup, plumbing, and equations required for applying a respirometry system wherein the flow rate of the air entering the animal chamber is known. Such systems are usually referred to as push systems, because the air is usually pushed into a sealed respirometer chamber at a known rate, and the concentrations of incurrent and excurrent gases are alternately measured. Setups and equations for oxygen-only, carbon dioxide-only, and combined oxygen and carbon dioxide systems are described. Methods for creating multiple-animal push mode respirometry systems and for the automatic baselining (that is to say, measuring incurrent gas concentrations) of respirometry systems are also discussed.