Oxygen uptake of growth hormone transgenic coho salmon during starvation and feeding

Oxygen uptake of growth hormone transgenic coho salmon Oncorhynchus kisutch was measured in individual fish with a closed-system respirometer and was compared with that of similar-sized non-transgenic control coho salmon during starvation and when fed a fixed ration or to satiation. Transgenic and control fish did not differ in their standard oxygen uptake after 4 days of starvation, although control fish had a higher routine oxygen uptake, scope for spontaneous activity and initial acclimation oxygen uptake. During feeding, transgenic fish ate significantly more than control fish, and had an overall oxygen uptake that was 1·7 times greater than control fish. When fish that had eaten the same per cent body mass were compared, transgenic fish had an oxygen uptake that was 1·4 times greater than control fish. Differences in oxygen uptake in growth hormone transgenic coho salmon and non-transgenic fish appear to be due to the effects of feeding, acclimation and activity level, and not to a difference in basal metabolism.     

Effect of trazodone on oxidative metabolism of rat brain in vitro

Oxygen uptake of rat brain homogenate was reduced by 1 mM trazodone, a new atypical antidepressant. Na,K-ATPase activity and the associated oxygen consumption of rat brain slices were also reduced. Oxygen consumption of rat brain slices was enhanced by dopamine and this effect was blocked by 0.0001 mM trazodone. This drug uncoupled oxidative phosphorylation.     

Allometric relationship between oxygen consumption and body weight of mosquitofish,Gambusia affinis

Synopsis The allometric relationship between body size and oxygen consumption of Gambusia affinis at 28° C was determined under controlled experimental conditions, using a manometric respirometer. The allometric exponent (b-value) was 0.64 ± 0.02 S.E. (n = 51). Oxygen consumption was not influenced by any time-related factors during the 17 days of measurements. Variance between replicated oxygen consumption trials on individual fish was negligible. Specific oxygen consumption rates of several G. affinis at 28° C that were determined by using a sealed vessel and O₂ electrode respirometry method were similar to the rates measured by the manometric respirometry method in similar-sized G. affinis.     

Effect of mexiletine on glucose and oxygen uptake in rat brain, liver and myocardial tissue in vitro (author's transl)

The effect of mexiletine on oxygen and glucose consumption was studied both in homogenate and slices of brain, liver and myocardium of Wistar rats. Oxygen consumption was detected by means of Warburg's manometric techniques, and glucose utilization by the enzymatic method of glucose oxidase. Whilst glucose uptake was not modified in any of the studied preparations, mexiletine promoted a significant increase of oxygen consumption in the homogenized slices, and an inhibition in the intact tissue.     

Oxygen consumption during embryonic development of the annual fish Nothobranchius korthausae with special reference to diapause

The oxygen consumption of Nothobranchius korthausae eggs in different developmental stages, including diapause II and III, was measured. Oxygen consumption increases exponentially during embryonic development. In diapause II and III there is a drop in oxygen consumption, which attains a minimal level in diapause II after 3 weeks and in diapause III after 2 weeks. During early development the embryos can escape from hypoxic stress by entering diapause I and II. During late embryogenesis embryos in diapause III can escape from hypoxic stress by hatching. We conclude that survival of annual fish embryos is enhanced during conditions of low oxygen concentration by reduced oxygen consumption rates during diapause.     

Increases in human sperm oxygen consumption at low cell concentrations

Human spermatozoan oxygen consumption was measured in semen serially diluted with its own plasma, and shortly after serial dilution of washed spermatozoa in an artificial medium. In both media, per-sperm oxygen uptake rose significantly when sperm concentration fell below the range of 15-25 X 10(6) cells/ml. Oxygen uptake was higher in the artificial medium, regardless of sperm concentration. Sperm oxygen consumption in the artificial medium declined over times short enough that no change in the percentage of motile spermatozoa was detected.     

Oxygen consumption of mammalian myocardial cells in culture: measurements in beating cells attached to the substrate of the culture dish

A Lucite attachment which permitted the measurement of oxygen consumption in cells in culture without manipulating the cells was constructed. The attachment fit over commercially available dishes for cell culture and had an oxygen electrode built into it. Oxygen uptake of cells in culture was thus measured. Cells were attached to the substrate of the culture dish during the measurements and could be observed in an inverted phase microscope. Cells did not show any morphological changes, e.g., cell shapes or beating rate in case of myocardial cells, before and after the measurements of oxygen consumption. Using this method the rate of oxygen consumption was determined in rat myocardial and heart non-muscle cells in culture and also in HeLa and L6 cell lines. Myocardial cells in culture had an approximately four times higher rate of oxygen uptake compared with heart non-muscle, HeLa, and L6 cells. The oxygen uptake of beating myocardial cells was higher by about 50% compared with quiescent myocardial cells.     

Kinetics of oxygen consumption by phagocytosing human neutrophils

Oxygen consumption by phagocytosing human neutrophils commences after a lag of ～ 25 secs after particle uptake, reaches a maximal rate of ～ 35 nmols/10⁷ cells/min and remains linear for ～ 60 secs. A strict temporal and stoichiometric relationship exists between particle uptake and oxygen consumption. For each particle taken up, 0.2 fmols of oxygen is consumed in a very brief and self limiting process.     

Development of a telemetry system for measuring oxygen uptake during sports activities

A new system for continuous measurement of oxygen uptake by means of a telemeter has been developed. Oxygen uptake and pulmonary ventilation during rest and exercise were determined using a portable oxygen consumption meter (Oxylog). A small interface circuit between the Oxylog and the transmitter of a frequency modulated bio-telemeter system was designed and installed inside the Oxylog. Data from the transmitter were passed to a receiver and were fed into a microcomputer system. The microcomputer system displayed and printed out minute values of ventilation and oxygen uptake. The accuracy and reliability of the new system were checked by comparison with the traditional (Douglas bag) method. In the range less than 80 l.min-1 of ventilation and less than 2 l.min-1 of oxygen uptake, the system was not inferior to the Douglas bag method. The new system was applied for field continuous measurement of oxygen uptake during a doubles tennis game. The results of the application indicate that the telemetry system developed here is a very practical and useful way of measuring oxygen uptake during sports activities.     

Effects of salinity on physiological conditions in juvenile common snook Centropomus undecimalis

This study describes the effects of different salinities on oxygen consumption, ammonia excretion, osmotic pressure, apparent heat increment, postprandial nitrogen excretion, and oxygen:nitrogen ratio in juvenile common snook Centropomus undecimalis. Oxygen consumption of fish fasting and fish feeding was statistically different in relation with salinity. Fish maintained at 0, 25, and 35 ppt invested more energy processing feed than fish maintained at 12 ppt. Fasting fish had lower ammonia excretion than feeding fish and excretion was reduced at high salinities. Snook can change the energetic substrate in function with salinity, from a mixture of protein and lipids and carbohydrates at 35 ppt to a more acute preference for proteins at lower salinities. This species changes osmotic plasma concentrations at extreme experimental salinities. The different salinities were the snook inhabits (0-36 ppt), have a direct effect on the physiology, inducing changes on the oxygen consumption, nitrogen excretion, changes on the energetic substrate and plasma osmotic pressure.     

Bimodal oxygen uptake in juveniles and adults amphibious fish,Channa (= Ophiocephalus) marulius

Oxygen uptake of Channa marulius was studied under water with and without access to air. There was a significant increase in the oxygen uptake through the gills when access to air was prevented. However, this value (0.863 ± 0.058 mlO₂/indiv./h) was quite low in comparison to the total bimodal oxygen uptake (2.04 ± 0.14 mlO₂/indiv./h) in juveniles. In adult fish the oxygen uptake per unit time increased appreciably (4.673 ± 0.404 mlO₂/indiv./h). In juveniles as well as in adults the air breathing dominated over aquatic breathing. This fish showed a definite circadian rhythm in the bimodal oxygen uptake during different hours of the day.This work was performed in the Ichthyology Laboratory, P. G. Dept. of Zoology, Bhagalpur University, and was supported by a research grant from Bhagalpur University     

Respiration and nitrogen fixation in nodulated roots of soya bean and pea

Summary Oxygen uptake, carbon dioxide evolution and nitrogenase activity, measured either as hydrogen evolution (under argon 80%, oxygen 20%) or as the reduction of acetylene to ethylene, were assayed over the same time period by a direct mass-spectrometric method. When carbon dioxide evolution was used to estimate carbohydrate consumption, the results agreed with other work on whole plants. The RQ values obtained in these experiments were always less than 1.0 and thus the carbohydrate consumption calculated from oxygen uptake suggests that previous estimates, using carbon dioxide evolution as a measure of the cost of nitrogen fixation may be underestimates. Lag periods observed in the reduction of acetylene to ethylene suggest that there is a resistance to diffusion of gases in the root nodules.     

A novel oxyconforming response in the freshwater fish Galaxias maculatus

How fish oxygen consumption is modulated by external PO₂ has long been a matter of interest, yet is an experimentally complicated question to answer. In this study closed and semi-closed respirometry were used to evaluate the oxygen consumption rate of the scaleless galaxiid fish, inanga (Galaxias maculatus) as a function of decreasing external PO₂. Both respirometry techniques showed that as environmental oxygen levels declined, oxygen consumption rates also decreased. At no point did inanga regulate oxygen consumption. This is strong evidence that inanga is an oxyconformer. Partitioned respirometry experiments showed that skin plays an important role in oxygen uptake in this fish species, and cutaneous oxygen uptake may have an important role in shaping the oxygen consumption response to hypoxia.     

Diversity of juvenile fish assemblages in the pelagic waters of Lebanon (eastern Mediterranean)

Oxygen consumption rates of nauplii of the brine shrimp Artemia franciscana Kellogg 1906 were determined over a range of salinities from 10 to 110 ppm, in temperatures from 0 to 30°C, using a multi-factorial design. The oxygen micro-sensors employed have a fast response time and are capable of accurately measuring oxygen concentrations at temperatures well below 0°C. Oxygen uptake rate ranged from 0.03 to 0.66 μmol O₂ mg⁻¹ h⁻¹ and was sensitive to changes in both salinity and temperature. Temperature was the dominant factor affecting oxygen consumption rates, which showed a significant increase with increasing temperature. A slight decrease was measured in oxygen consumption with increasing salinity related to differential solubility of oxygen in waters of different salinities. Thermal sensitivity of oxygen consumption determined from calculations of Q ₁₀, indicated physiological adaptation of Artemia nauplii to the ranges of temperatures tested. Handling editor: A. van Kerchove     

Balancing the competing requirements of air-breathing and display behaviour during male–male interactions in Siamese fighting fish Betta splendens

Air-breathing fish of the Anabantoidei group meet their metabolic requirements for oxygen through both aerial and aquatic gas exchange. Siamese fighting fish Betta splendens are anabantoids that frequently engage in aggressive male–male interactions which cause significant increases in metabolic rate and oxygen requirements. These interactions involve opercular flaring behaviour that is thought to limit aquatic oxygen uptake, and combines with the increase in metabolic rate to cause an increase in air-breathing behaviour. Air-breathing events interrupt display behaviour and increase risk of predation, raising the question of how Siamese fighting fish manage their oxygen requirements during agonistic encounters. Using open-flow respirometry, we measured rate of oxygen consumption in displaying fish to determine if males increase oxygen uptake per breath to minimise visits to the surface, or increase their reliance on aquatic oxygen uptake. We found that the increased oxygen requirements of Siamese fighting fish during display behaviour were met by increased oxygen uptake from the air with no significant changes in aquatic oxygen uptake. The increased aerial oxygen uptake was achieved almost entirely by an increase in air-breathing frequency. We conclude that limitations imposed by the reduced gill surface area of air-breathing fish restrict the ability of Siamese fighting fish to increase aquatic uptake, and limitations of the air-breathing organ of anabantoids largely restrict their capacity to increase oxygen uptake per breath. The resulting need to increase surfacing frequency during metabolically demanding agonistic encounters has presumably contributed to the evolution of the stereotyped surfacing behaviour seen during male–male interactions, during which one of the fish will lead the other to the surface, and each will take a breath of air.     

Microgradients of Microbial Oxygen Consumption in a Barley Rhizosphere Model System

A microelectrode technique was used to map the radial distribution of oxygen concentrations and oxygen consumption rates around single roots of 7-day-old barley seedlings. The seedlings were grown in gel-stabilized medium containing a nutrient solution, a soil extract, and an inert polymer. Oxygen consumption by microbial respiration in the rhizosphere (<5 mm from the root) and in bulk medium (>30 mm from the root) was determined by using Fick's laws of diffusion and an analytical approach with curve fitting to measured microprofiles of oxygen concentration. A marked increase of microbial respiration was observed in the inner 0- to 3-mm-thick, concentric zone around the root (rhizosphere). The volume-specific oxygen consumption rate (specific activity) was thus 30 to 60 times higher in the innermost 0 to 0.01 mm (rhizoplane) than in the bulk medium. The oxygen consumption rate in the root tissue was in turn 10 to 30 times higher than that in the rhizoplane. Both microbial respiration and oxygen uptake by the root varied between different roots. This was probably due to a between-root variation of the exudation rate for easily degradable carbon compounds supporting the microbial oxygen consumption.     

The effect of temperature and mass on routine metabolism in Sarotherodon (Tilapia)mossambicus (Peters)

A reappraisal of oxygen uptake by Sarotherodon mossambicus was undertaken using a continuous flow respirometer. Measurements were obtained over the temperature range 16°C–37°C for fish weighing between 10 g and 150 g. Oxygen uptake was converted to energy equivalents ( Q _ox) using the value 13.68 J mg O₂^–1and the routine metabolic energy expenditure can be described by the equation E =0.0086 t ^{2 0783} M ^{0 652} where E is the energy requirement for routine metabolism expressed in J h^-1, t the temperature in °C and M the mass in g.     

In situ study of the effect of oyster biomass on benthic metabolic exchange rates

Oxygen consumption and dissolved nitrogen fluxes at the water-sediment interface of an oyster-bed were measured in situ using transparent enclosures inserted on undisturbed sediment. Experiments were performed in summer, under dark and light conditions, with various densities of the oyster Crassostrea gigas (0–150 animals m ^{– 2}). The influence of oyster biomass on oxygen and ammonia exchange rates was similar in both lighting conditions. Oxygen consumption increased with increasing biomass, though not at the level of prediction for the highest biomasses, suggesting a depressed respiration rate. Ammonia release never matched the rates predicted by adding sediment efflux to oyster excretion, when biomass exceeded 100 g DW m ^{– 2}. The coupling between oxygen consumption and ammonia release (O : N ratio) was thus influenced by oyster biomass. Stabilization of nitrogen release was related to enhanced nitrification in the presence of oyster and/or sediment uptake of ammonia against the molecular gradient. Urea release was erratic but appeared uninfluenced by oyster biomass. Fluxes of oxygen and of each nitrogen compound displayed thus a specific response to modifications of the oyster biomass. Both the organisms and the sediment are involved in regulation processes of metabolic exchange rates at the water-sediment interface.     

The use of opercular muscle electromyograms as an indicator of the metabolic costs of fish activity in rainbow trout, Salmo gairdneri Richardson, as determined by radiotelemetry

Averages of electromyogram (EMG) signals emanating from the levator arcus palatini , a small muscle involved in the operation of the operculum in rainbow trout, Salmo gairdneri , were analysed in terms of their relationship to the fish's oxygen consumption rates under various activity levels. The EMG signals were detected and transmitted with a radio-telemetry system. The EMG values showed a good correlation with corresponding oxygen consumption rates for fish under forced-swimming conditions but not when the fish was swimming spontaneously; this is attributed to an ability to regulate oxygen uptake at the gill surfaces by other means than increasing the ventilation volume, including alterations in the gill blood flow dynamics (e.g. secondary lamellar recruitment), and changes in the cardiac output. Under forced-swim conditions, where the oxygen demands by the respiring muscles were higher, increased ventilation volume, as indicated by increased opercular muscle activity, was directly related to swimming speed and oxygen uptake.     

Forearm oxygen uptake during maximal forearm dynamic exercise

This study was undertaken in an attempt to determine the maximal oxygen uptake in a small muscle group by measuring directly the oxygen expenditure of the forearm. Five healthy medical students volunteered. The subjects' maximal forearm work capacity was determined on a spring-loaded hand ergometer. Exercise was continued until exhaustion by pain or fatigue. Two weeks later intra-arterial and intravenous catheters were placed in the dominant arm. Blood samples for measurement of oxygen concentration were collected via the catheters. Forearm blood flow was measured by means of the indicator dilution technique. Oxygen uptake was determined according to the Fick principle. The forearm oxygen uptake attained at maximal work loads was a mean of 201 (SD +/- 56) mumol.min-1.100 ml-1. It was impossible at maximal exercise to discern a plateau of the oxygen uptake curve in relation to work output. It is suggested that a plateau in the oxygen uptake curve is not a useful criterion for maximal oxygen uptake in a small muscle group. Skeletal muscle may have an unused capacity for oxygen consumption even at maximal exercise intensity where muscle work cannot be continued due to muscle pain and fatigue.