Hovering Performance of Hummingbirds in Hyperoxic Gas Mixtures

2001 ◽  
Vol 204 (11) ◽  
pp. 2021-2027 ◽  
Author(s):  
Douglas L. Altshuler ◽  
Peng Chai ◽  
Jeff S. P. Chen
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Atmospheric Oxygen ◽  
Supplemental Oxygen ◽  
Hovering Flight ◽  
Density Reduction ◽  
Air Density ◽  
Reduction Experiment ◽  
Elevational Distribution ◽  
Rate Of Oxygen Consumption

SUMMARY Hummingbirds evolved during a period of decline in atmospheric oxygen concentration and currently encounter varying levels of oxygen availability along their elevational distribution. We tested the hypothesis that inspiration of hyperoxic gas increases hummingbird hovering performance when birds are simultaneously challenged aerodynamically. We measured the maximum duration of hovering flight while simultaneously monitoring the rate of oxygen consumption of ruby-throated hummingbirds (Archilochus colubris) in low-density heliox that was either normoxic (21% O2) or hyperoxic (35% O2). As air density decreased below 0.85kgm−3, hummingbirds hovered significantly longer in hyperoxia than in normoxia, but the air density at which the birds could no longer sustain hovering flight was independent of oxygen concentration. At low air densities in hyperoxia flight trials, hummingbirds appeared to increase their rate of oxygen consumption relative to flight sequences at equivalent densities in normoxia trials, but these differences were not significant. We tested the hypothesis that hummingbirds can discriminate between environments that differ in oxygen concentration. In another density-reduction experiment, hummingbirds were allowed to choose between artificial feeders infused with either normoxic or hyperoxic gases. The hypothesis was not supported because birds failed to associate oxygen concentration with a particular feeder independently of air density. Supplemental oxygen thus yields increased hovering duration at intermediate air densities, but the minimum density at which birds can fly is limited exclusively by aerodynamic considerations.

The Respiratory Physiology of the Marine Nematodes Enoplus Brevis (Bastian) and E. Communis (Bastian)

1973 ◽  
Vol 59 (1) ◽  
pp. 267-274
Author(s):  
H. J. ATKINSON
Keyword(s):  
Oxygen Consumption ◽  
Sea Water ◽  
Atmospheric Oxygen ◽  
Respiratory Physiology ◽  
Marine Nematodes ◽  
Oxygen Regime ◽  
Lower Oxygen ◽  
Rate Of Oxygen Consumption ◽  
Oxygen Tensions ◽  
Oxygen Requirements

1. The rate of oxygen consumption of individual male Enoplus brevis and E. communis was measured at 15 °C, after altering the oxygen regime experienced since the animals were collected. 2. When both E. brevis and E. communis were transferred to 35 Torr from atmospheric oxygen tensions, their oxygen consumption was only two-thirds of that of individuals maintained at this lower oxygen tension. 3. The rate of oxygen consumption of the two species at 135 Torr was unaltered by exposure for 2 h to oxygen-free sea water. 4. The results are discussed in relation to the overall influence of fluctuating oxygen regimes on the oxygen requirements of nematodes.

Permeance to oxygen of detached Capsicum annuum fruit

2000 ◽  
Vol 40 (3) ◽  
pp. 457 ◽  
Author(s):  
J. Bower ◽  
B. D. Patterson ◽  
J. J. Jobling
Keyword(s):  
Oxygen Consumption ◽  
Gas Exchange ◽  
Capsicum Annuum ◽  
Oxygen Concentration ◽  
Concentration Gradient ◽  
Gas Diffusion ◽  
Major Barrier ◽  
Capsicum Annuum L ◽  
Rate Of Oxygen Consumption ◽  
Low Rate

The internal oxygen concentration and rate of oxygen consumption of detached capsicum fruits (Capsicum annuum L.) were monitored over several days. From this their overall permeance to oxygen was calculated. When wax was applied to the pedicel and its scar, permeance was reduced by 80–90%, indicating that most gas exchange occurred through this area. Readings from O2 sensors attached to the skins of the fruits were compared to those from O2 sensors inserted into the fruit cavity. These indicated that the cuticle was the major barrier to gas diffusion and that there was a concentration gradient through the capsicum flesh. Permeance of the cuticle was found to be about 0.64 x 10–4 mol O2/Pa.m2.s, while permeance to CO2 was 2–3 times higher. This suggests that the cuticle is composed of a coherent film. The low rate of gas diffusion through capsicum cuticle may allow recycling of respired CO2 by photosynthesis in the flesh before harvest.

scholarly journals THE RESPIRATION OF LUMINOUS BACTERIA AND THE EFFECT OF OXYGEN TENSION UPON OXYGEN CONSUMPTION

1929 ◽  
Vol 13 (1) ◽  
pp. 27-45 ◽  
Author(s):  
Charles S. Shoup
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Oxygen Tension ◽  
Small Cells ◽  
Pure Oxygen ◽  
Catalytic Surfaces ◽  
Rate Of Oxygen Consumption ◽  
Luminous Bacteria ◽  
Effect Of Oxygen

1. The respiration of luminous bacteria has been studied by colorimetric and manometric methods. 2. Limulus oxyhaemocyanin has been used as a colorimetric indicator of oxygen consumption and indicator dyes were used for colorimetric determination of carbon dioxide production. 3. The Thunberg-Winterstein microrespirometer has been used for the measurement of the rate of oxygen consumption by luminous bacteria at different partial pressures of oxygen. 4. The effect of oxygen concentration upon oxygen consumption has been followed from equilibrium with air to low pressures of oxygen. 5. Luminous bacteria consume oxygen and produce carbon dioxide independent of oxygen pressures from equilibrium with air (152 mm.) to approximately 22.80 mm. oxygen or 0.03 atmosphere. 6. Dimming of a suspension of luminous bacteria occurs when oxygen tension is lowered to approximately 2 mm. Hg (0.0026 atmosphere) and when the rate of respiration becomes diminished one-half. 7. Pure nitrogen stops respiratory activity and pure oxygen irreversibly inhibits oxygen consumption. 8. The curve for rate of oxygen consumption with oxygen concentration is similar to curves for adsorption of gasses at catalytic surfaces, and agrees with the Langmuir equation for the expression of the amount of gas adsorbed in unimolecular layer at catalytic surfaces with gas pressure. 9. A constant and maximum rate of oxygen consumption occurs in small cells when oxygen concentration becomes sufficient to entirely saturate the surface of the oxidative catalyst of the cell.

Cardiac effects of hypoxia in the neotenous tiger salamanderAmbystoma tigrinum

2002 ◽  
Vol 205 (12) ◽  
pp. 1725-1734 ◽  
Author(s):  
Tom McKean ◽  
Guolian Li ◽  
Kong Wei
Keyword(s):  
Cardiac Output ◽  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Mechanical Performance ◽  
Cardiac Mass ◽  
Differentially Expressed ◽  
Representational Difference Analysis ◽  
Ambystoma Tigrinum ◽  
Rate Of Oxygen Consumption ◽  
Aquatic Salamanders

SUMMARYThe aquatic form of the tiger salamander Ambystoma tigrinum lives in high-altitude ponds and is exposed to a hypoxic environment that may be either chronic or intermittent. In many animal species, exposure to hypoxia stimulates cardiac output and is followed by an increase in cardiac mass. The working hypothesis of the present study was that the hearts of these aquatic salamanders exposed to 10-14 days of 5 % oxygen in a laboratory setting would become larger and would differentially express proteins that would help confer tolerance to hypoxia. During exposure to hypoxia, cardiac output increased, as did hematocrit. Cardiac mass also increased, but mitotic figures were not detected in the cardiac myocytes of colchicine-injected animals. The mass increase was probably due to hypertrophy, although a very slow rate of hyperplasia cannot be ruled out. Representational difference analysis indicated that at least 14 mRNAs were expressed in hearts from the hypoxic animals that were not expressed in hearts from normoxic animals. The differentially expressed genes were cloned and sequenced and confirmed as coming from the ventricles of the hypoxic salamanders. Genes differentially expressed include mitochondrial genes and genes for elongation factor 2, a protein synthesis gene. The mechanical performance of buffer-perfused hearts isolated from normoxic and hypoxic animals did not differ. Acute responses to hypoxia were also measured. The rate of oxygen consumption of unanesthetized salamanders in metabolism chambers decreased when chamber oxygen concentration was reduced below 12 % oxygen. At a chamber oxygen concentration of 4-6 %, the rate of oxygen consumption of the salamanders was reduced to approximately one-third of the normoxic rate.

scholarly journals Relative sensitivity of soluble guanylate cyclase and mitochondrial respiration to endogenous nitric oxide at physiological oxygen concentration

2007 ◽  
Vol 405 (2) ◽  
pp. 223-231 ◽  
Author(s):  
Félix Rodríguez-Juárez ◽  
Enara Aguirre ◽  
Susana Cadenas
Keyword(s):  
Nitric Oxide ◽  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Guanylate Cyclase ◽  
Mitochondrial Respiration ◽  
Soluble Guanylate Cyclase ◽  
Atmospheric Oxygen ◽  
Cellular Respiration ◽  
Cell Physiology ◽  
Experimental Conditions

Nitric oxide (NO) is a widespread biological messenger that has many physiological and pathophysiological roles. Most of the physiological actions of NO are mediated through the activation of sGC (soluble guanylate cyclase) and the subsequent production of cGMP. NO also binds to the binuclear centre of COX (cytochrome c oxidase) and inhibits mitochondrial respiration in competition with oxygen and in a reversible manner. Although sGC is more sensitive to endogenous NO than COX at atmospheric oxygen tension, the more relevant question is which enzyme is more sensitive at physiological oxygen concentration. Using a system in which NO is generated inside the cells in a finely controlled manner, we determined cGMP accumulation by immunoassay and mitochondrial oxygen consumption by high-resolution respirometry at 30 μM oxygen. In the present paper, we report that the NO EC50 of sGC was approx. 2.9 nM, whereas that required to achieve IC50 of respiration was 141 nM (the basal oxygen consumption in the absence of NO was 14±0.8 pmol of O2/s per 106 cells). In accordance with this, the NO–cGMP signalling transduction pathway was activated at lower NO concentrations than the AMPKs (AMP-activated protein kinase) pathway. We conclude that sGC is approx. 50-fold more sensitive than cellular respiration to endogenous NO under our experimental conditions. The implications of these results for cell physiology are discussed.

The Respiration of Pteroides Griseum (Bohadsch) a Pennatulid Coelenterate

1967 ◽  
Vol 46 (1) ◽  
pp. 97-104
Author(s):  
A. E. BRAFIELD ◽  
G. CHAPMAN
Keyword(s):  
Body Weight ◽  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Continuous Flow ◽  
Strip Chart Recorder ◽  
Total Oxygen ◽  
Strip Chart ◽  
Chart Recorder ◽  
Rate Of Oxygen Consumption ◽  
Exponential Relation

1. The respiration of the pennatulid Pteroides griseum has been investigated by means of a continuous-flow polarographic respirometer and a strip-chart recorder. 2. The rate of oxygen consumption bears the same exponential relation to body weight as in more advanced phyla, and is markedly greater in expanded specimens than in contracted ones. 3. It is suggested that contracted specimens consume oxygen almost exclusively through the ectoderm but that in expanded specimens at least two-thirds of the total oxygen consumed enters through the endoderm. 4. Several sources of evidence confirm that the water within the enteron is poorly oxygenated. Rhythmically fluctuating records of the oxygen concentration of water which has flowed past expanded specimens are the result of periodic expulsions of some of this relatively deoxygenated enteric water. 5. The irrigation of the enteron is very probably brought about by peristaltic waves of contraction which pass along the length of the animal.

scholarly journals THE CATALYTIC EFFECT OF DYES ON THE OXYGEN CONSUMPTION OF LIVING CELLS

1930 ◽  
Vol 13 (4) ◽  
pp. 483-494 ◽  
Author(s):  
E. S. Guzman Barron ◽  
L. A. Hoffman
Keyword(s):  
Oxygen Consumption ◽  
Catalytic Effect ◽  
Reduction Potential ◽  
Atmospheric Oxygen ◽  
Neutral Red ◽  
Living Cells ◽  
Positive Side ◽  
Rate Of Oxygen Consumption ◽  
Oxidative Processes ◽  
Catalytic Power

From the experiments described in this paper and in those previously published it can be concluded that dyes which can be reversibly oxidized and reduced, act as catalysts for some oxidative processes taking place in the living cells, as is manifested by an increase in their oxygen consumption. It has been found that the catalytic power of the dyes on the oxygen consumption of starfish eggs (mature, unfertilized) is conditioned by two factors: the reduction potential of the dye and the permeability of the cell surface. Dyes whose E'o is towards the positive side of the aerobic reduction potential of the starfish eggs have a maximum catalytic effect. This catalytic power decreases as the E'o becomes more negative than the reduction potential of the cell and becomes nil beyond certain limits. When a dye cannot penetrate into the cell, its effect is greatly diminished as in this case only those oxidative processes taking place at the outer surface of the cell can be activated. Whether a dye can act as a catalyst or not is dependent on whether the normal consumption of oxygen by the cell is slower or quicker than the oxidation activated by the dye. The speed of this activation is correlated to (1) the speed at which the dye is reduced by the cell, and (2) the speed at which the leuco-dye is oxidized by the atmospheric oxygen. If one of these two processes is slower than the normal respiration, the dye cannot increase the rate of oxygen consumption (phenol indophenol at low concentrations which is kept reduced by the cell is very slowly reoxidized by atmospheric oxygen, on the other hand safranin and neutral red which are not reduced by the cell or at least too slowly reduced, though rapidly reoxidized by air). It will depend on these two reactions velocities whether a dye will act as catalyst (methylene blue and dyes with similar E'o which are quickly reduced by the cell and the leuco-dyes of which are relatively quickly reoxidized). Though this relationship between the reduction potential of the dyes and its catalytic power would seem in contradiction with the well known thermodynamic assumption that there is in general no distinct relationship between the potential and velocity of the reaction, we have pointed out from the literature some of the various experiments where one does recognize this connection.

Simple Method of Measuring Seston Respiration in Oligotrophic Lakes

1986 ◽  
Vol 43 (8) ◽  
pp. 1660-1663 ◽  
Author(s):  
R. J. Cornett ◽  
F. H. Rigler
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Concentration ◽  
Water Samples ◽  
Simple Technique ◽  
Oxygen Demand ◽  
Simple Method ◽  
Rate Of Oxygen Consumption ◽  
The Difference ◽  
Abiotic Influences ◽  
And Control

A simple technique for measuring the oxygen consumption of seston in oligotrophic waters was developed and tested. Water samples were filtered through 0.45-μm filters. The filters were suspended in biological oxygen demand bottles containing lake water. NaN3 added to one bottle stopped respiration and served as a control to eliminate abiotic influences during the experiments. The difference in oxygen concentration between the respiring and control samples increased linearly over the 1-d experiments. Filtration of hypolimnetic water samples did not significantly alter the rate of oxygen consumption of the seston. Concentrating the seston increased the change in oxygen concentration so that respiration rates from 2 to 80 mg O2∙m−3∙d−1 could be measured. This method is simple, precise, and can measure very low rates of respiration directly.

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