Natural selection on tail and bill morphology in Barn Swallows Hirundo rustica during severe weather

An unusual six-day period of cold, rainy weather caused mortality among Barn Swallows Hirundo rustica in southwestern Nebraska, USA, in May 1996. We compared birds that died during the cold to those still alive when the severe weather ended. Among males, survivors had significantly longer culmens and significantly less variance in outer-tail asymmetry than non-survivors. Among females, survivors had significantly longer outer tails and significantly less variance in outer-tail length, overall body size and outer-tail asymmetry than non-survivors. Larger birds in general and those with less asymmetry in wing and outer tail tended to be favoured during this weather event. Long tails may reflect condition in females and, along with high levels of symmetry in wing and outer tail, improve foraging efficiency during extreme conditions. Males with long tails did not appear to suffer survival costs. Larger size probably allows more fat to be stored and may confer thermal benefits to swallows during late spring cold snaps. Similar mortality events have apparently occurred in the study area on only one other occasion since 1875.     

The effect of environmental temperature and average dose rate of microwave radiation on the oxygen-consumption rate of mice

Summary The oxygen consumption rate of CF1 male mice was determined before, during, and after sham- and microwave-irradiation at environmental temperatures of 20° C, 24° C, 30° C, and 35° C, relative humidity of 55%, and air flow rate of 78 ml/min. Five forward power levels ranging from 0.09 to 3.3 W, which resulted in corresponding average dose rates ranging from 1.2 to 45.1 mW/g were used. The values of the oxygen consumption rate were converted to those of the specific metabolic rate (SMR). The result indicates that with high levels of microwave dosing (greater than 10 mW/g) the specific metabolic rate of mice decreased in some cases, in the environmental temperatures of 20° C and 24° C. However, the decreased SMR values were not lower than the SMR values of the sham-irradiated group in 30° C. In the case of 35° C, the high level dosing with microwave radiation caused increases in the SMR value over the sham value. A possible trend towards increased SMR value during and after irradiation with low level (1.6 mW/g) microwave radiation in the environmental temperatures of 24° C and 30° C suggests further experiments with low level microwave radiation to determine possible effects of low level microwave radiation in stimulating increases in specific metabolic rate.     

Measurement of blood flow and oxygen consumption in the pelvic limb of fetal sheep

In order to determine blood flow and oxygen consumption in the pelvic limb of fetal sheep, we applied the Fick principle of measurement of oxygen consumption in seven paired experiments in seven fetal sheep under normal conditions and after treatment with pancuronium bromide. Catheterization procedures, which minimized interference with the study limb circulation, avoided changes of catheter tip position during fetal movements,n and prevented collateral circulation to and from tissues not located in the pelvic limb, were utilized. Blood flow through the external iliac artery was measured by means of a transit time ultrasonic method. Six sample sets for oxygen content were drawn from the external iliac artery and vein during 45-min control period and repeated after neuromuscular blockade. Normal oxygen consumption under these experimental conditions was determined to be 20.7 +/- 1.9 (mean +/- SEM) mumole.min-1.100 g-1. Neuromuscular blockade caused oxygen consumption to decrease significantly (P less than 0.01) by 12% to 18.1 +/- 2.1 mumole.min-1.100 g-1 and decreased the average coefficient of variation from 15 to 8%. The data demonstrate that spontaneous skeletal muscle activity accounts for a significant amount of oxygen consumption, the level of which can vary widely over brief periods of time. These results suggest that such tissues with significant spontaneous changes in metabolic activity require repeated blood flow measurements with simultaneous determination of substrate arteriovenous differences to best describe metabolism under normal conditions.     

The effect of somatic and gonadal size on the rate of oxygen consumption in the subantarctic echinoid Abatus cordatus (Echinodermata) from Kerguelen

1. The rate of oxygen consumption of this burrowing spatangoid was measured for individuals ranging in size from 3-month old 2.5-mm long juveniles to 39-mm long adults. 2. The decrease in the rate of oxygen consumption/dry weight with increasing body size is greater among mature adults than among juveniles because the increase in aerobic tissue (primarily the test) with body size is less than the increase in anaerobic tissues (mainly the gonads). 3. The rate of oxygen consumption/ash-free dry weight decreased more slowly with increasing body size because of the increase in the level of inorganic material. 4. Replacement of the common fresh weight or dry weight specific oxygen consumption by a more synthetic value calculated from ash-free dry weight specific oxygen consumption measurements, to annulate the body-size effect, is proposed for interspecific comparison over a wide range of body size, taking into account parameters such as temperature.     

Functional evidence for nitric oxide production by skeletal-muscle mitochondria from lipopolysaccharide-treated mice

The possible existence of a mitochondrially localized nitric oxide (NO) synthase (mtNOS) is controversial. To clarify this, we studied the ability of intact mitochondria to generate NO and the effect of mitochondrial NO on respiration. Respiratory rates and oxygen kinetics (P(50) values) were determined by high-resolution respirometry in skeletal-muscle mitochondria from control mice and mice injected with Escherichia coli lipopolysaccharide (LPS). In the presence of the NOS substrate L-arginine, mitochondria from LPS-treated mice had lower respiration rates and higher P(50) values than control animals. These effects were prevented by the NOS inhibitor L-NMMA. Our results suggest that mitochondrially derived NO is generated by an LPS-inducible NOS protein other than iNOS and modulates oxygen consumption in mouse skeletal muscle.     

Ontogeny of total body oxygen stores and aerobic dive potential in Steller sea lions (Eumetopias jubatus)

Two key factors influence the diving and hence foraging ability of marine mammals: increased oxygen stores prolong aerobic metabolism and decreased metabolism slows rate of fuel consumption. In young animals, foraging ability may be physiologically limited due to low total body oxygen stores and high mass specific metabolic rates. To examine the development of dive physiology in Steller sea lions, total body oxygen stores were measured in animals from 1 to 29 months of age and used to estimate aerobic dive limit (ADL). Blood oxygen stores were determined by measuring hematocrit, hemoglobin, and plasma volume, while muscle oxygen stores were determined by measuring myoglobin concentration and total muscle mass. Around 2 years of age, juveniles attained mass specific total body oxygen stores that were similar to those of adult females; however, their estimated ADL remained less than that of adults, most likely due to their smaller size and higher mass specific metabolic rates. These findings indicate that juvenile Steller sea lion oxygen stores remain immature for more than a year, and therefore may constrain dive behavior during the transition to nutritional independence.     

Heritable variation in reaction norms of metabolism and activity across temperatures in a wild-derived population of white-footed mice (Peromyscus leucopus)

Heritable variation in metabolic traits is likely to affect fitness. In this study, white-footed mice from wild-derived photoresponsive [R, infertile in short day length (SD)] and non-photoresponsive (NR, fertile in SD) selection lines were maintained under short-day (SD 8Light:16Dark), sub-thermoneutral conditions (22 or 12 °C). Mice had significantly higher levels of food intake and resting metabolic rates (RMR) at low temperature. RMR differed significantly between lines (greater in NR mice). In contrast to previous work under thermoneutral conditions, there was no significant difference in overall activity or average daily metabolic rates (ADMR) of mice from the two lines. Reduced activity may reflect behavioral changes under cooler conditions (e.g., nest building) reducing the overall energetic cost of fertility (for NR mice). There was no significant difference in maximal rate of oxygen consumption ( $\dot V \text{O}_{\text {2max}} $ ) between lines. R mice had significantly greater brown adipose tissue and white abdominal fat mass due to both line and temperature. Reaction norms for intake, resting metabolism (RMR/BMR) and level of activity from current (12 and 22 °C) and previously published data (28 °C) demonstrate independent effects of genetics (line) and environment (temperature) for resting metabolism, but a clear interaction between these for activity. The results suggest that fertility under winter conditions imposes metabolic costs that are related to the level of reproductive development. Under the coldest conditions tested, however, mice that remained fertile in SD reduced activity, ADMR and food requirements, decreasing the differential between selection lines. Heritable variation in reaction norms suggests a genetic by environment effect that could be subject to selection.     

Aerobic metabolism of American alligators, Alligator mississippiensis, under standard conditions and during voluntary activity

We measured the rate of consumption of oxygen by alligators in a dry metabolic chamber and in a tank of water where they were free to dive and surface at will at 10-35 degrees C, a range spanning most of the body temperatures experienced by alligators in nature. Neither the standard metabolic rate nor the rate of oxygen consumption during one hour of sustained, voluntary activity varied with body mass, month of the year, duration of fasting before measurement, or experimental condition (terrestrial vs aquatic). Voluntary diving is not accompanied by any reduction in standard metabolic rate; these results and those of others suggest that the "diving reflex" of alligators is probably employed only in emergencies. Spontaneous activity for one hour is accompanied by a 1.9-4.4 fold rise in oxygen consumption; this factorial increase is less than that for other reptiles induced to maximal activity for brief intervals. Both standard and active oxygen consumption rise significantly with body temperature.     

Detection of Ophthalmic Acid in Serum from Acetaminophen-Induced Acute Liver Failure Patients Is More Frequent in Non-Survivors

Background/Aim

Acetaminophen (APAP) hepatotoxicity is related to the formation of N-acetyl-p-benzoquinone imine (NAPQI), which is detoxified through conjugation with reduced glutathione (GSH). Ophthalmic acid (OA) is an analogue of GSH in which cysteine is replaced with 2-aminobutyrate. Metabolomics studies of mice with APAP-induced acute liver failure (APAP-ALF) identified OA as a marker of oxidative stress and hepatic GSH consumption. The aim of the current study was to determine whether OA is detectable in APAP-ALF human patients either early (day 2) or late (day 4) and whether OA levels were associated with in-hospital survival in the absence of liver transplant.

Methods

Serum samples from 130 APAP-ALF patients (82 survivors, 48 non-survivors) were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and correlated with clinical data from the United States Acute Liver Failure Study Group (US ALFSG) Registry (2004–2011).

Results

Survivors had significantly lower admission bilirubin (4.2 vs. 5.7 mg/dl) and lactate levels (3.3 vs. 6.5 μmol/l, p<0.05 for all). During the first 7 days of the study, survivors were less likely to require mechanical ventilation (55% vs. 88%), vasopressor support (9.8% vs. 67%) or renal replacement therapy (26% vs. 63%, p< 0.001 for all). Non-survivors were more likely to have detectable OA levels early (31% vs. 15%, p = 0.034) and late (27% vs. 11%, p = 0.02). However there were no significant differences in mean OA levels between non-survivors and survivors (early 0.48 vs. 0.36, late 0.43 vs. 0.37, P > 0.5 for all).

Conclusion

OA was detectable more frequently in APAP-ALF non-survivors but mean OA levels were not associated with survival. The routine clinical administration of N-acetyl cysteine could replenish GSH levels and prevent OA production.     

Influence of respirometry methods on intraspecific variation in standard metabolic rates in newts

Standard metabolic rate (SMR) is both a highly informative and variable trait. Variation in SMR stems not only from diverse intrinsic and extrinsic factors, but also from the use of diverse methods for metabolic measurements. We measured CO(2) production (VCO(2)) and oxygen consumption rates (VO(2)) using two flow-through respirometry modes, continuous and intermittent (stop-flow), to evaluate their potential contribution to SMR variation in Alpine newts, Ichthyosaura alpestris. Both respirometry modes yielded similar and repeatable VCO(2) values. Although VO(2) was highly repeatable, continuous respirometry produced lower VO(2) than the intermittent method. During intermittent measurements, the total number of activity bouts was higher than during continuous respirometry trials. Statistical correction for disparate activity levels minimized variation in oxygen consumption between respirometry modes. We conclude that use of either method of flow-through respirometry, if properly applied, introduced less noise to SMR estimates than a variation in activity levels.     

Strain differences in response to acute hypoxia: CD-1 versus C57BL/6J mice.

Some mammals respond to hypoxia by lowering metabolic demand for oxygen and others by maximizing efficiency of oxygen usage: the former strategy is generally held to be the more effective. We describe within the same species one outbred strain (CD-1) that lowers demand and another inbred strain (C57BL/6J) that maximizes oxygen efficiency to markedly extend hypoxic tolerance. Unanesthetized adult male mice (Mus musculus, CD-1 and C57BL/6J) between 20 and 35 g were used. Sham-conditioned (SC) C57BL/6J mice survived severe hypoxia (4.5% O(2), balance N(2)) roughly twice as long as SC CD-1 mice (median 211 and 93.5 s, respectively; P < 0.0001). Following acute hypoxic conditioning (HC), C57BL/6J mice survived subsequent hypoxia 10 times longer than HC CD-1 mice (median 2,198 and 238 s respectively; P < 0.0001). Therefore, C57BL/6J mice are both naturally more tolerant to hypoxia and show a greater increase in hypoxic tolerance in response to hypoxic conditioning. Indirect calorimetry indicates that CD-1 mice lower mass-specific oxygen consumption (V'o(2) in ml O(2).kg(-1).min(-1)) and carbon dioxide production (V'co(2) in ml CO(2).kg(-1).min(-1)) in response to HC (P = 0.002 and P < 0.0001, respectively), but C57BL/6J mice maintain V'o(2) and V'co(2) after HC. Respiratory exchange ratio and fluorometric assay of plasma ketones suggest that C57BL/6J mice rapidly switch to ketone metabolism, a more efficient substrate, while CD-1 mice reduce overall metabolic activity. We conclude that under severe hypoxia in mice, switching fuel, possibly to ketones, while maintaining V'o(2), may confer a greater survival advantage than simply lowering demand.     

Cerebral oxidative metabolism during sustained hypoxaemia in fetal sheep

Cerebral oxidative metabolism was determined in 9 unanaesthetized fetal sheep near term, during a normoxic control period and during sustained hypoxaemia induced by lowering maternal inspired O2 concentration to 11-8% with 3% CO2 added. Preductal arterial and sagittal vein blood samples were analyzed for oxygen content, blood gas tensions and pH. Cerebral blood flow was measured with a radioactively-labelled microsphere technique. Induced fetal hypoxaemia resulted in a metabolic acidaemia which was progressive over several h. Cerebral oxygen consumption was initially marginally decreased in response to induced hypoxaemia with cerebral blood flow increased thus maintaining O2 delivery coupled to cerebral oxygen consumption. With a worsening metabolic acidemia, pHa below 7.15, cerebral blood flow fell as mean arterial pressure fell, but cerebral oxygen consumption was little changed as fractional O2 extraction now increased. With sustained hypoxaemia and profound metabolic acidaemia, pHa below 7.00, fractional O2 extraction also fell resulting in a terminal fall in cerebral oxygen consumption to less than 50% of control values. Although the initial marginal decrease in cerebral oxygen consumption in response to induced hypoxia may represent a protective mechanism whereby the fetal brain decreases nonessential functions thus lowering oxidative needs, the terminal fall in cerebral oxygen consumption suggests pathological alterations within the brain at this time.     

The effects of two levels of caffeine ingestion on excess postexercise oxygen consumption in untrained women

The effects of two levels of caffeine ingestion (5 mg.kg-1, CAF1, and 10 mg.kg-1, CAF2) on postexercise oxygen consumption was investigated in six untrained women aged 20.5 (SEM 0.5) years. After a test to determine maximal oxygen consumption (VO2max) each subject underwent three test sessions at 55% VO2max either in a control condition (CON) or with the CAF1 or CAF2 dose of caffeine. During exercise, oxygen consumption was found to be significantly higher in the CAF1 and CAF2 trials, compared to CON (P < 0.05). During the hour postexercise, oxygen consumption in CAF1 and CAF2 remained significantly higher than in CON (P < 0.05). At all times throughout the exercise, free fatty acid (FFA) concentrations were significantly higher in the caffeine trials than in CON. The FFA concentrations 1 h postexercise (+60 min) were further elevated above resting values for all three trials. Caffeine ingestion caused the greatest elevation above resting levels being 1.89 (SEM 0.19) mmol.l-1 and 1.96 (SEM 0.22) mmol.l-1 for the CAF1 and CAF2 trials, respectively. This was significantly higher (P < 0.0001) than the CON level which was 0.97 (SEM 0.19) mmol.l-1. Respiratory exchange ratio (R) values became significantly lower (P < 0.05) in CAF1 and CAF2 compared to CON at the onset of exercise and continued to decrease during the activity. Throughout the recovery period, R values were significantly lower for both caffeine trials compared to CON. The results of this study would suggest that caffeine is useful in significantly increasing metabolic rate above normal levels in untrained women during, as well as after, exercising at 55% VO2max.     

Influence of body size and gender on control of ventilation

Hypoxic (HVR) and hypercapnic (HCVR) ventilatory responses are influenced by both metabolic activity and hormonal factors. By studying 67 subjects of both sexes, including those at the extremes of stature, we examined the influence of gender, CO2 production (VCO2), O2 consumption (VO2), body surface area (BSA), and vital capacity (VC) on resting ventilation (VE), HVR, and HCVR. We measured resting VE, VO2, and VCO2 and then performed isocapnic progressive hypoxic and hypercapnic ventilatory responses. The effect of stature was reflected in higher VE and metabolic rate (both P less than 0.001) in tall men compared with short men that was ablated by correction for BSA. Perhaps because their heights vary less than those of the men, tall women were not statistically distinguishable from short women in any of these measured parameters. Tall men tended to have greater hypoxic chemosensitivity than short men but this was not significantly different (P = 0.07). Gender affected the control of ventilation in a number of ways. Men had higher VE (P less than 0.05) and metabolic rate (P less than 0.001) than women. Even after correction for BSA men still had higher metabolic rates. Women had higher VE/VCO2 than men (P less than 0.05) and lower resting end-tidal Pco2 (PETCO2) values (P less than 0.05). Both A, the shape parameter of the hyperbolic HVR curve, and HVR determined from mouth occlusion pressure (AP) were greater in women than in men, although only AP reached statistical significance. However, corrections of A for BSA (P less than 0.05), VCO2 (P less than 0.01), and VC (P less than 0.001) amplified these differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of temperature changes on the oxygen consumption of juvenile Chinese shrimp Fenneropenaeus chinensis Osbeck

The effects of temperature changes on oxygen consumption of Chinese shrimp (Fenneropenaeus chinensis Osbeck) were studied. The response of oxygen consumption to a temperature rise was conformed to partial metabolic compensation. No compensatory response was observed at lower temperature. A sudden temperature increase by 12 °C resulted an overshoot in oxygen consumption in shrimp adapted to 19 °C, while a sudden decrease by 12 °C in shrimp adapted to 19 °C resulted in an undershoot in oxygen consumption. The shrimp adapted to 31 °C responded with an undershoot in oxygen consumption when a sudden temperature drop by 12 °C occurred. But overshoot in oxygen consumption did not occur when the shrimps were transferred back from 19 to 31 °C. The amplitude of oxygen consumption was reduced in shrimp during the process of acclimation to the temperature diel fluctuation. After the shrimp had adapted to the temperature fluctuation, the daily mean oxygen consumption of shrimp at diel temperature fluctuation from 24 to 30 °C was significantly lower than those adapted to the constant temperature at 27 °C (P<0.05). The decrease in metabolic rate may account for the increase in the growth rate of shrimp at a diel fluctuating thermal regime.     

Tissue Inhibitor of Metalloproteinase-3 Knockout Mice Exhibit Enhanced Energy Expenditure through Thermogenesis

Tissue inhibitors of metalloproteinases (TIMPs) regulate matrix metalloproteinase activity and maintain extracellular matrix homeostasis. Although TIMP-3 has multiple functions (e.g., apoptosis, inhibition of VEGF binding to VEGF receptor, and inhibition of TNFα converting enzyme), its roles in thermogenesis and metabolism, which influence energy expenditure and can lead to the development of metabolic disorders when dysregulated, are poorly understood. This study aimed to determine whether TIMP-3 is implicated in metabolism by analyzing TIMP-3 knockout (KO) mice. TIMP-3 KO mice had higher body temperature, oxygen consumption, and carbon dioxide production than wild-type (WT) mice, although there were no differences in food intake and locomotor activity. These results suggest that metabolism is enhanced in TIMP-3 KO mice. Real-time PCR analysis showed that the expression of PPAR-δ, UCP-2, NRF-1 and NRF-2 in soleus muscle, and PGC-1α and UCP-2 in gastrocnemius muscle, was higher in TIMP-3 KO mice than in WT mice, suggesting that TIMP-3 deficiency may increase mitochondrial activity. When exposed to cold for 8 hours to induce thermogenesis, TIMP-3 KO mice had a higher body temperature than WT mice. In the treadmill test, oxygen consumption and carbon dioxide production were higher in TIMP-3 KO mice both before and after starting exercise, and the difference was more pronounced after starting exercise. Our findings suggest that TIMP-3 KO mice exhibit enhanced metabolism, as reflected by a higher body temperature than WT mice, possibly due to increased mitochondrial activity. Given that TIMP-3 deficiency increases energy expenditure, TIMP-3 may present a novel therapeutic target for preventing metabolic disorders.     

The effects of meal size on postprandial metabolic response and post-exercise metabolic recovery process in juvenile black carp (Mylopharyngodon piceus)

The effects of meal size on the postprandial metabolic response and of digestion on the post-exercise metabolic recovery process were investigated in juvenile black carp (Mylopharyngodon piceus) . Experimental fish were forcedly fed with compound feed (meal sizes: 0.5%, 1% and 2% body weight). Then, the postprandial oxygen consumption rate and excess post-exercise oxygen consumption (EPOC) of the experimental fish were measured. Both the duration and the peak of oxygen consumption rate (PMR) increased with increasing meal size. The peak post-exercise metabolic rate of digesting fish were significantly higher, whereas EPOC magnitude and its duration were significantly smaller or (shorter) than those in the fasting fish. It is suggested that (1) this fish fulfills the increased energy demand during the digestive process by increasing PMR and by prolonging SDA duration with increasing meal size and (2) digesting fish might decrease their anaerobic exhaustive activity but increase the post-exercise recovery capacity.     

Skeletal muscle respiratory uncoupling prevents diet-induced obesity and insulin resistance in mice

To determine whether uncoupling respiration from oxidative phosphorylation in skeletal muscle is a suitable treatment for obesity and type 2 diabetes, we generated transgenic mice expressing the mitochondrial uncoupling protein (Ucp) in skeletal muscle. Skeletal muscle oxygen consumption was 98% higher in Ucp-L mice (with low expression) and 246% higher in Ucp-H mice (with high expression) than in wild-type mice. Ucp mice fed a chow diet had the same food intake as wild-type mice, but weighed less and had lower levels of glucose and triglycerides and better glucose tolerance than did control mice. Ucp-L mice were resistant to obesity induced by two different high-fat diets. Ucp-L mice fed a high-fat diet had less adiposity, lower levels of glucose, insulin and cholesterol, and an increased metabolic rate at rest and with exercise. They were also more responsive to insulin, and had enhanced glucose transport in skeletal muscle in the setting of increased muscle triglyceride content. These data suggest that manipulating respiratory uncoupling in muscle is a viable treatment for obesity and its metabolic sequelae.     

Thyroid status is a key modulator of tumor oxygenation: implication for radiation therapy

In normal tissues, thyroid hormones play a major role in the metabolic activity and oxygen consumption of cells. Because the rate of oxygen consumption is a key factor in the response of tumors to radiation, we hypothesized that thyroid hormones may affect the metabolic activity of tumor cells and hence modulate the response to cytotoxic treatments. We measured the influence of thyroid status on the tumor microenvironment in experimental tumors. Hypothyroidism and hyperthyroidism were generated in mice by chronic treatment with propyl thiouracil and l-thyroxine. Thyroid status significantly modified tumor pO(2) as measured with EPR oximetry. Mechanistically, this was the result of the profound changes in oxygen consumption rates. Thyroid status was associated with a significant change in tumor radiosensitivity since the regrowth delay was increased in hypothyroid mice compared to euthyroid mice, an effect that was abolished when temporarily clamped tumors were irradiated. This study provides unique insights into the impact of modulating tumor oxygen consumption and could have implications in the management of cancer patients with thyroid disorders.     

Oxygen transport properties of blood in two different bovine breeds

1. The whole oxygen dissociation curve of oxyhemoglobin has been determined in double-muscled cattle of the Belgian White Blue breed and in Friesian cattle of different body weight. 2. In calves, P50 values are low and DPG level is high (4-20 mumol/g Hb). 3. P50 values of 25 +/- 1.4 mm Hg (mean +/- SD) and a level of DPG less than 1.5 mumol/g Hb have been found in animals weighing more than 80 kg. 4. Effects of temperature and pH on the oxygen dissociation curve have been measured at all levels of saturation. The temperature coefficient (dlog P50/dT) and the Bohr effect expressed as dlog P50/dpH were 0.017 and -0.40, respectively. 5. Hematocrit, hemoglobin concentrations and oxygen capacity of hemoglobin have been measured. 6. No difference between both breeds has been observed. 7. These data can be used to correct measured values of oxygen tension for temperature and pH and to measure oxygen content of blood in cattle.