Minimal Functional Unit of Lactate Dehydrogenase

The tetrameric heart isozyme of lactate dehydrogenase (H₄) is modified by p-chloromercuribenzoate (PCMB) to produce the inactive tetramer and then hybridized with native tetrameric muscle isozyme (M₄). The hybrid mixture was isolated by polyacrylamide gel electrophoresis (PAGE) and then stained for enzyme activity and with Coomassie brilliant blue. Only three bands were found on the gels in either case. The hybrid enzymes as isolated by PAGE have half the specific activity of the native muscle enzyme. The electrophoresis properties of HM₃ are very similar to those of HM₃, while the electrophoresis properties of are very similar to those of H₂M₂. The above results strongly suggest that the tetramer having enzymatic activity contains at least two native subunits, and the di-subunit in the tetrameric enzyme is the minimal functional unit.     

Changes in skeletal muscle oxygenation during incremental exercise measured with near infrared spectroscopy

To determine the change in muscle oxygenation in response to progressively increasing work rate exercise, muscle oxyhemoglobin + oxymyoglobin saturation was measured transcutaneously with near infrared spectroscopy in the vastus lateralis muscle during cycle ergometry. Studies were done in 11 subjects while gas exchange was measured breath-by-breath. As work rate was increased, tissue oxygenation initially either remained constant near resting levels or, more usually, decreased. Near the work rate and metabolic rate where significant lactic acidosis was detected by excess CO₂ production (lactic acidosis threshold, LAT), muscle oxygenation decreased more steeply. As maximum oxygen uptake ( ) was approached, the rate of desaturation slowed. In 8 of the 11 subjects, tissue O₂ saturation reached a minimum which was sustained for 1–3 min before was reached. The LAT correlated with both the (r = 0.95,P < 0.0001) and the work rate (r = 0.94,P < 0.0001) at which the rate of tissue O₂ desaturation accelerated. These results describe a consistent pattern in the rate of decrease in muscle oxygenation, slowly decreasing over the lower work rate range, decreasing more rapidly in the work rate range of the LAT and then slowing at about 80% of , approaching or reaching a minimum saturation at .     

Growth yields and saturation constant of Desulfovibrio vulgaris in chemostat culture

Desulfovibrio vulgaris (strain Marburg) was grown on H₂ and sulfate as sole energy source in a chemostat limited by the sulfate supply. The biomass concentration and the sulfate concentration in the culture were determined as a function of the dilution rate. From the data a K _S (saturation constant) for sulfate of 10 M, a _max of 0.23 h^–1, and a of 13 g/mol were calculated. The organism was also grown in chemostat culture on H₂ and sulfite, H₂ and thiosulfate, and pyruvate (without sulfate). was found to be 35 g/mol, 36 g/mol, and Y _pyr ^max 10 g/mol. The growth yields are discussed with respect to ATP gains in dissimilatory sulfate reduction.     

Energy requirements of Adélie penguin (Pygoscelis adeliae) chicks

Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O₂ consumption ( ) and CO₂ production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from in lying chicks to at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities ( ), and one for walking ( ). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as , whereas mass-specific O₂ consumption was related to walking speed (S, m·s^-1) as .Abbreviations bpm beats per minute - D distance walked (m) - ECG electrocardiogram - HR heart rate (bpm) - ns number of steps - RQ respiratory quotient - S walking speed (m·s^-1) - T time walked (s) - W body mass (kg)     

High groundwater nitrate concentrations inhibit eutrophication of sulphate-rich freshwater wetlands

During the last 60 years, pollution of the groundwater with has greatly increased in many parts of Europe, as a consequence of excessive use of manure and synthetic fertilisers. Monitoring of groundwater-fed wetlands indicated that sediments with high concentrations had the lowest Fe and concentrations in the pore water. A comparison of two restored open water fens, differing in supply via the groundwater, indicated that the redox potential and the sulphate ( ) reduction rate were lower when the groundwater contained not only but also high concentrations. The lower reduction rates in the -rich open water fen were associated with lower concentrations and the presence of plant species characteristic of clear water. In contrast, the higher reduction rates in the -poor open water fen were associated with very high concentrations and massive development of plant species characteristic of eutrophic environments. Investigations at -rich seepage sites in black alder carrs, showed that high concentrations in the pore water caused chlorosis in the alder carr vegetation, due to lower availability of Fe in the pore water and less Fe uptake by the plants. Experimental desiccation of sediments proved that the -rich seepage sites contained no oxidisable FeS _x , contrary to -poor locations, which became acidified and mobilised extremely high amounts of due to FeS _x oxidation. A laboratory experiment showed that addition to sediments led to reduced releases of Fe, and S^2–, very likely due to the oxidation of reduced Fe and S compounds. Overall, the results confirmed that is an energetically more favourable electron acceptor in anaerobic sediments than Fe and , and that high loads function as a redox buffer, preventing reduction of Fe and . Limited reduction prevents S^2– -mediated mobilisation of from Fe- complexes. At a higher redox potential, reduced Fe, including FeS _x , was oxidised, increasing the content of Fe(III) capable of binding . This prevented increased availability and the concomitant massive development of plant species characteristic of eutrophic environments.     

A comparative study of the mechanism of Na+ and Cl? excretion by the gill ofMugil capito andFundulus heteroclitus: Effects of Stress

Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na⁺ and of Cl^– and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not . InFundulus, is also decreased. Transfer of the two species from SW to fresh water (FW) reduces and by 75 to 85% and leads to a large inversion of P.D. When K⁺ is added to FW, a gill depolarization occurs, as well as a large increase of and .These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na⁺ ( ) being greater than that to Cl^– ( ), 2) a Cl^–/Cl^– exchange independent of P.D. is associated with the Cl^– pump; 3) Cl^– pump activity is linked to Na⁺/K⁺ exchange which in turn is associated to a Na⁺/Na⁺ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of and observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of which becomes equal to in both species.As a result of stress, the K⁺-activated Na⁺ and Cl^– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil.     

Association between heart rate variability and training response in sedentary middle-aged men

The effect of exercise training on heart rate variability (HRV) and improvements in peak oxygen consumption ( _peak) was examined in sedentary middle-aged men. The HRV and absolute and relative _peak of training (n = 19) and control (n = 15) subjects were assessed before and after a 24-session moderate intensity exercise training programme. Results indicated that with exercise training there was a significantly increased absolute and relative _peak (P < 0.005) for the training group (12% and 11% respectively) with no increase for the control group. The training group also displayed a significant reduction in resting heart rate; however, HRV remained unchanged. The trained subjects were further categorized into high (n = 5) and low (n = 5) HRV groups and changes in _peak were compared. Improvements in both absolute and relative _peak were significantly greater (P > 0.005) in the high HRV group (17% and 20% respectively) compared to the low HRV group (6% and 1% respectively). The groups did not differ in mean age, pretraining oxygen consumption, or resting heart rate. These results would seem to suggest that a short aerobic training programme does not alter HRV in middle-aged men. Individual differences in HRV, however, may be associated with _peak response to aerobic training.     

Energetics of the growth of Methanobacterium thermoautotrophicum and Methanococcus thermolithotrophicus on ammonium chloride and dinitrogen

Methanobacterium thermoautotrophicum was grown in continuous culture in a fermenter gassed with H₂ and CO₂ as sole carbon and energy sources, and in a medium which contained either NH₄Cl or gaseous N₂ as nitrogen source. Growth was possible with N₂. Steady states were obtained at various gas flow rates with NH₄Cl and with and the maintenance coefficient varied with the gas input and with the nitrogen source. Growth of Methanococcus thermolithotrophicus in continuous culture in a fermenter gassed with H₂, CO₂ as nitrogen, carbon and energy sources was also examined.Abbreviations molecular growth yield (g dry weight of cells per mol of CH₄ evolved) - growth rate (h^-1) - D dilution rate (h^-1) - rate (h_-1); relation of Neijssel and Tempest and of Stouthamer and Bettenhaussen - energy     

Are oxygen uptake kinetics at the onset of exercise speeded up by local metabolic status in active muscles?

To assess the rate-limiting factor of oxygen uptake ( ) kinetics at the onset of exercise, six healthy male sedentary subjects performed repeated one-legged constant-load cycle exercise. The one-legged constant-load exercise test consisted of two 5-min periods of pedalling at an exercise intensity of 50 W, with a 5-min rest between periods (these exercise periods, i.e. first and second exercises, were performed by the same leg). The exercise was then repeated using the other leg. In addition, two-legged incremental exercise was investigated to establish whether kinetics were affected by slower heart rate kinetics. The incremental exercise test consisted of two-legged pedalling first with the cycle unloaded as a warm-up for 5 min followed by 50-W exercise for 5 min. The exercise intensity was then increased to 100 W for 5 min. During exercise, gas exchange parameters were determined by the breath-by-breath method and cardiac output ( ) was determined continuously by an impedance technique with a computer-based automated system. To determine the kinetics of heart rate (HR), and , a best fit procedure was employed using least-squares criteria with a time delay, except during the initial increase. During the one-legged constant-load exercise test, kinetics were significantly accelerated by repeated exercise using the same leg. On the other hand, when the exercise was changed to the other leg, kinetics were significantly slower, although kinetics continued to be faster. During the incremental exercise test, although the HR response was slower at the transition from 50-W to 100-W exercise than at the transition from warm-up to 50-W exercise, there were no significant changes in kinetics. These findings suggest that kinetics may be affected by metabolic conditions in the muscle, but not by blood flow ( and/or HR) kinetics.     

Water relations of buried eggs of mound building birds

Summary Eggs of the brush turkey (BT) and mallee fowl (MF) are incubated in mounds of soil and plant litter. Humidity in BT mounds is always near saturation (>99% RH), but in MF mounds it drops to lower values in summer (x=77% RH). Despite these high humidities, the eggs lose an average of 9.5% (BT) and 12.0% (MF) of their initial mass by evaporation before hatching. The rate of evaporation increases during incubation several-fold due to large changes in water vapor conductance of the shell and embryonic heat production. Values of in fully incubated eggs in mound material are about 3–6 times higher than values obtained from unincubated eggs in desiccators. This effect depends on two factors: (1) increases with ambient humidity, especially above 80% RH, possibly because the effective site of evaporation moves out along the walls of the pores in the eggshell. (2) Structural changes of the pores due to calcium absorption by the embryo directly increase . The first factor is most important in BT eggs and the second is dominant in MF eggs. Production of metabolic heat by the embryo increases the vapor pressure difference across the shell and further increases , especially in mounds of high humidity. The changes in pore structure are adaptive because they produce high conductances to respiratory gases and cause normal gas tensions within the egg at the end of development, yet is low enough in early development to prevent excessive water loss. Water not lost by evaporation or taken up by the embryo is stored and released during hatching. A small amount of mass is lost during incubation by respiratory gas exchange.Abbreviations BT brush turkey - MF mallee fowl - RH relative humidity     

Gill function in an elasmobranch

Summary Highly efficient oxygen uptake in elasmobranchs, as indicated by frequent excess of over has previously been ascribed to the operation of multicapillary rather than counter-current gas exchange by the gills. Analysis of models shows that, at maximum efficiency, a multicapillary system cannot account for values of greater than . In Port Jackson sharks Heterodontus portusjacksoni) commonly exceeds , which indicates the operation of a functional counter-current at the respiratory surface. The anatomical basis of this counter-current is provided by the demonstration that a continuous flow of water passes between the secondary lamellae into septal canals and thence via the parabranchial cavities to the exterior.Queen Elizabeth II Fellow.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .     

Effect of oxygen on the growth (yield) of Chlorella vulgaris

The growth yield of Chlorella vulgaris, Y _kJ defined as g cells harvested per kJ of light energy absorbed by the cells, was assessed in a turbidostat culture by varying CO₂ and O₂ partial pressures ( and ). The value of Y _kJ ranged from 3.1×10^-3 to 5.0×10^-3 g cells/kJ under light-limited conditions [ = 1.02.4%, = 065%; total pressure of gas (composed of CO₂, O₂ and N₂)=1 atm]. In the light-limited environment, the algal specific growth rate deteriorated appreciably with the increase of . The deterioration accounts for the above range of Y _kJ observed. The growth inhibition due to oxygen that was defined by subtracting from 1.0 the ratio of at given values of to that at = 0% extended from 0.07–0.30 (7–30%). However, glycolate could not be detected in the turbidostat culture. Isotopic experiments on the specific rate of ¹⁴CO₂ uptake also revealed that the inhibition due to oxygen was from 22–38% when was varied from 0 to nearly 100%. These effects of oxygen were discussed, referring to the activity of ribulose-1,5-bisphosphate carboxylase that is inhibited competitively by oxygen.Non-Standard Abbreviations INH isonicotinic acid hydrazide - PPO 2,5-diphenyloxazole - DCMU 3-(-3,4-dichlorophenyl)-1,1-dimetylurea - CA carbonic anhydrase - RuP₂ ribulose-1,5-bisphosphate     

Prediction of individual oxygen uptake on-step transients from frequency responses

Power-oxygen uptake ( ) frequency responses can be used to predict responses to arbitrary exercise intensity patterns. It is still an open question for which range of exercise intensities such computed response patterns yield valid predictions. In the present study, we determined the power- frequency response of nine sports students by means of pseudo-randomised switching between 20 W and 80 W during upright and supine cycle exercise. Starting from a baseline of 20 W each subject also performed sustained step increases to 40 W, 80 W, 120 W, and 160 W in both positions. The individual step responses were then compared with the expected time-courses predicted on the basis of the individual frequency responses. The comparison showed a close agreement for the 20 W–40 W and 20 W–80 W steps in both positions. With larger step amplitudes the kinetics became increasingly slower than the predicted time course in both positions. During additional ramp tests (10 W · 30 s^–1) whole blood lactic acid concentration [1a^–]_b tended to be higher in the supine position at exercise intensities higher than 160 W. The mean power at 4 mmol · 1^–1 [la^–]_b amounted to 234 (SD 32) W and 253 (SD 44) W (P<5%) in the supine and the upright position, respectively. The maximal oxygen uptake relative to body mass was not found to be significantly different [upright, mean 57 (SD 10) ml · (min · kg)^–1;supine, mean 54 (SD 10) ml · (min · kg)]. These findings would suggest that for a range of mild exercise intensities kinetics are not appreciably influenced by the step amplitude or by cardiovascular changes associated with the upright and the supine position.     

Nitrate reductase in needles,roots and trunk wood of spruce trees [Picea abies (L.) Karst.]

Summary Nitrate reductase (EC 1.6.6.2) activity (NRA), as measured by an in vivo assay, is present in needle leaves and mycorrhizal fine root tips of adult Norway spruce [Picea abies (L.) Karst.] in at least equal amounts on a fresh weight basis, in both adult and 5-year-old trees. NRA could also be demonstrated in trunk wood of deroted trees after fertilization with 5 mM , exhibiting a longitudinal profile in the trunk. Inducibility in needles can more efficiently be achieved by NO₂ (100 g·m^-3) than by 5 mM nitrate, which is effective only in root-amputated trees. A remarkably high level of needle-NRA in unfertilized trees, which are characterized by a very low level of nitrate in the xylem sap, suggests that NRA in spruce needles may in part be constitutive. Organic-N is a major nitrogen source for the needles even in root-amputated trees, indicating pronounced exchange processes between ray parenchyma and trunk xylem, which in turn are modified by the nitrogen source fed to the trunk stump. Intact trees exhibit a very similar amino acid composition of the xylem sap, regardless of whether or has been fed. The amino acid pattern of the needles is not thrown out of balance by flooding with and , which occurs in fertilized derooted trees. This indicates a distinct potential for homoeostasis of nitrogen entrance-metabolism (i.e. NRA and glutamine synthetase activity) in the needles. In the ectomycorrhiza/fine root-system (EMC), marked differences in NRA were observed depending on root-tip diameter and along the longitudinal profile of the fine roots. EMC-nitrate reductase is strongly enhanced by . Needle-NRA exhibits a circannual rhythm. An early summer maximum is followed by a December minimum. This activity pattern matches well the transitory increase of soluble nitrogen in spring and the total protein maximum in winter. In an indirect way assimilatory NRA may well contribute to nitrogen overfertilization (by consumption of NO_X) as one possible cause of the contemporary decline of spruce populations.     

Thermoregulation,gas exchange,and ventilation in Adelie penguins (Pygoscelis adeliae)

Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT _a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both and were constant and minimal atT _a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT _a. Values of were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT _a to 6% atT _a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T _a ambient temperature - T _b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume     

Larmor frequency selective model free analysis of protein NMR relaxation

Summary The Lipari-Szabo dynamical formalism is extended by setting the time constants of the Lorentzian terms to and . This analysis is compared to the earlier proposed three-parameter extended model free formalism with regard to the range of equivalence and the advantages of the simplified two-parameter (S _inff ^sup2 ,S _infH ^sup2 ) and (S _inff ^sup2 ,S _infN ^sup2 ) representations. Spectral density components are calculated and compared to those obtained from the spectral density analysis formalism. Protein relaxation data, commonly analyzed in terms of the two-parameter representation, may correspond to a dynamically heterogeneous behaviour that is more appropriately represented in terms of a fast limit order parameter and a second, lower frequency order parameter.     

Determination of heteronuclear three-bond J-coupling constants in peptides by a simple heteronuclear relayed E.COSY experiment

Summary A simple heteronuclear relayed E.COSY pulse sequence with a minimum number of pulses is proposed for the quantitative determination of heteronuclear three-bond J-coupling constants in uniformly ¹³C-enriched polypeptide samples. Numerous heteronuclear three-bond coupling constants, including , , , and , can be determined for each residue from a single heteronuclear relayed E.COSY spectrum. Couplings relevant for stereospecific assignments as well as for the determination of dihedral angles in the amino acid backbone and in side chains are obtained. The method is demonstrated on the uniformly ¹³C-enriched decapeptide antamanide (-Val¹-Pro²-Pro³-Ala⁴-Phe⁵-Phe⁶-Pro⁷-Pro⁸-Phe⁹-Phe¹⁰-).     

Effects of variation in total and regional shell conductance on air cell gas tensions and regional gas exchange in chicken eggs

Summary Gas conductance of the shell, rates of O₂ consumption, CO₂ production and air cell gas tensions were measured in pre-internal pipping, 19 day-old chicken eggs that were selected for a wide range in shell conductance. Regional conductance was measured in eggs with partially waxed shells.Surface-specific shell conductance was not uniform over the egg; it was over 3-fold higher at the poles than at the equator. Conductance was about 59% higher over the air cell than over the chorioallantoic part of the egg. Surface-specific perfusion was 12% higher in the air cell. Therefore the in the air cell was higher, and the lower, than values calculated for the whole egg. The mean difference in between the air cell and the chorioallantoic part of the egg was 14.8 Torr, and that of , was 7.0 Torr. These differences were somewhat dependent on total conductance. Respiratory gas exchange ratio ( ) was higher in the air cell (R=0.82) and lower in the chorioallantoic region (R=0.67) than for the whole egg (R=0.70). Air cell R increased slightly in eggs of higher total conductance.Mismatching of regional shell conductance and chorioallantoic perfusion contributes to a functional venous shunt that is partly responsible for nonequilibrium between the air cell and the blood in the chorioallantoic veins.Symbols and abbreviations D gas diffusity - F _A fractional surface area - F _G fractional conductance - G conductance - G _diff diffusion conductance - G _perf perfusion conductance - PA average gas pressure (O₂ or CO₂) - Pac gas pressure in air cell - PE gas pressure in respiratory chamber - Pca gas pressure over chorioallantois - perfusion     

The effect of ambient temperature on the relationship between ventilation and metabolism in a small parrot (Agapornis roseicollis)

Summary Values for basal metabolism, standard tidal volume (V _T), standard minute volume ( ), and mean extraction efficiency (EO₂) in the thermal neutral zone (TNZ) inAgapornis roseicollis (1.84 ml·min^–1; 0.95 ml·br^–1, STPD; and 33.3 ml·min^–1, STPD; and 22.5%; respectively) were all very similar to values for these parameters previously measured inBolborhynchus lineola, a similarly sized, closely related species from a distinctly different habitat.Having both a lower critical temperature (T_lc) below and an upper critical temperature (T_uc) above those ofB. lineola, the TNZ ofA. roseicollis extended from 25° to at least 35°C. The thermal conductance below the TNZ ofA. roseicollis was 14% less than that ofB. lineola. Therefore, at 5°C the standard metabolic rate (SMR) of the former is 17% less than that of the latter, and at 35°C it is 20% less. At 5°CA. roseicollis has a lower EO₂ and at 35°C a higher EO₂ than that ofB. lineola. The patterns of resting energy metabolism and of ventilation ofA. roseicollis and ofB. lineola are consistent with the former species being better suited to living in a more variable thermal environment than the latter.MeanV _T has a weak positive correlation with the rate of oxygen consumption ( ) at a constant ambient temperature (T _a) but a much stronger correlation when resting increases in response to a decrease inT _a.V _t is the only ventilatory parameter which is linearly correlated toT _a from 35° to –25°C. The data suggest thatT _a may have a regulatory effect onV _T somewhat independent of or .