Activity and oxygen consumption during hypoxic exposure in high altitude and lowland sceloporine lizards

Summary Resting rates of O₂ consumption against , exercise endurance times and during recovery from vigorous exercise were measured inSceloporus occidentalis captured near sea level and inS. graciosus captured above 2850 m. Oxygen consumption against was also measured inS. occidentalis captured above 2850 m. When was recorded continuously, as ambient was slowly reduced from 155 Torr, it became directly dependent upon ambient between 110 and 120 Torr. The critical for the high altitude lizards was lower than that for the lowland lizards, which enabled the former to maintain relatively higher 's when ambient was reduced below 120 Torr. The high altitude lizards also had significantly greater endurance when stimulated to exercise at 1600 m ( 130 Torr). Both the higher under hypoxia and the greater endurance roughly parallel a significantly greater maximum in the high altitude lizards. At a simulated altitude of 3600 m ( 100 Torr), maximum and rate of recovery of the O₂ debt calculated from post active were significantly reduced in the lowland but not the high altitude lizards. The effects of simulated altitude conditions on the lowland but not the mountaine animals indicate adaptations to altitude in these sceloporine lizards. We did not find any consistent relationship between organ/body weight ratios or hematocrit and our measures of endurance or the altitude at which the lizards were captured.     

Estimating the Recombination frequency for the PTC-Kell linkage

Summary Two data sets are analyzed for linkage between the PTC and Kell blood group loci. The original report of close linkage for these loci was that of Conneally et al. (1976), where the maximum likelihood estimate of was 0.05. These two new data sets give a combined maximum likelihood estimate of _m=f =0.28. Estimating the recombination frequency for the sexes separately gave _m =0.29, _f =0.23. The combined maximum likelihood estimate over all published data sets including this report is _m=f =0.14, _max=8.94. There is statistically significant evidence of heterogeneity among the published studies.     

Relationship between the octanol-water partition coefficient of tertiary amines and their effect of ‘selective’ uncoupling of photophosphorylation

A series of tertiary amines was investigated for effects on the transmembrane proton potential difference ( H), on photophosphorylation and on electron-flux control related to the intrathylakoid proton potential ( H_I), using isolated chloroplasts ofSpinacia oleracea L. As indicated by 9-aminoacridine fluorescence and [14C]methylamine uptake, all amines studied inhibited a build-up of H and, in parallel, ATP synthesis. Even when H was low, strong H₁-dependent electron-flux control was observed under the influence of tertiary amines. The strength of flux control in the presence of low H and the effectiveness of inhibition of ATP synthesis linearly increased with the lipophilicity of the amines. The most effective of the amines tested caused 50% inhibition of ATP synthesis at a concentration of 6 M, which is about 1000-fold lower than the concentration required for inhibition by methylamine. The data presented indicate the existence of two proton domains in the thylakoid vesicles, one of them feeding the ATP-synthase, the other the sites of pH-dependent electron-flux control. It is concluded that tertiary amines develop their action in a lipophilic domain of the thylakoid membrane, in the vicinity of the ATP-synthase complex. A mechanism for selective uncoupling and for the maintenance of H_I-dependent electron flux control in the presence of low H is discussed.Abbreviations and symbols coefficient for pH-dependent electron flux control - 9-AA 9-aminoacridine - Chl chlorophyll - I₅₀ amine concentration producing 50% inhibition of ATP-synthesis - J_e flux of photosynthetic electron transport - k _H apparent rate constant for proton efflux - H₁ proton potential in the thylakoid lumen - H₁ transthylakoid proton potential difference - p partition coefficient - q _AA coefficient for 9-aminoacridine fluorescence quenching - PS photosystem - Q quantum flux of photosynthetically active light Dedicated to Professor Wilhelm Simonis, on the occasion of his 80th birthday     

Aerobic and anaerobic contribution to Wingate test performance in sprint and middle-distance runners

We investigated the aerobic and anaerobic contributions to performance during the Wingate test in sprint and middle-distance runners and whether they were related to the peak aerobic and anaerobic performances determined by two commonly used tests: the force-velocity test and an incremental aerobic exercise test. A group of 14 male competitive runners participated: 7 sprinters, aged 20.7 (SEM 1.3) years, competing in 50, 100 and 200-m events and 7 middle-distance runners, aged 20.0 (SEM 1.0) years, competing in 800, 1,000 and 1,500 m-events. The oxygen uptake ( ) was recorded breath-by-breath during the test (30 s) and during the first 20 s of recovery. Blood samples for venous plasma lactate concentrations were drawn at rest before the start of the test and during the 20-min recovery period. During the Wingate test mean power ( ) was determined and three values of mechanical efficiency, one individual and two arbitrary, 16% and 25%, were used to calculate the contributions of work by aerobic ( _{aer,ind,16%,25%}) and anaerobic ( _{an,ind,16%,25%}) processes. Peak anaerobic power ( _an,peak) was estimated by the force-velocity test and maximal aerobic energy expenditure ( _aer,peak) was determined during an incremental aerobic exercise test. During the Wingate test, the middle-distance runners had a significantly greater than the sprinters (P < 0.001), who had significantly greater venous plasma lactate concentrations (P < 0.001). Moreover, _{aer,ind,16%,25%} were also significantly higher (P < 0.05) in the middle-distance runners [ _aer,ind 45 (SEM 4) % vs 28 (SEM 2) %; _aer,16% 30 (SEM 3) % vs 19 (SEM 2) %; _aer,25% 46 (SEM 3) % vs 29 (SEM 2)%]; _{an,ind,16%,25%} in the sprint runners (P < 0.05) [ _an,ind 72 (SEM 3) % vs 55 (SEM 4) %; _an,16% 81 (SEM 2) % vs 70 (SEM 3) %; _an,25% 71 (SEM 2) % vs 54 (SEM 3) %]. The _aer,ind/ _aer,peak and × _an,ind/ _an,peak ratios, however, were not significantly different between the two groups of athletes. These results would indicate that the sprinters and middle-distance runners used preferentially a metabolic system according to their speciality. Nevertheless, under the conditions of its experiment, they seemed to rely on the same percentage of both peak anaerobic and peak aerobic performance for a given exercise task.     

Effects of root temperature on uptake of nitrate and ammonium ions by barley grown in flowing-solution culture

Summary Barley plants (Hordeum vulgare L.) grown from seed for 28 days in flowing solution culture were subjected to different root temperatures (3, 5, 7, 9, 11, 13, 17, 25°C) for 14 days with a common air temperature of 25/15°C (day/night). Uptake of NH₄ and NO₃ ions was monitored separately and continuously from solutions maintained at 10 M NH₄NO₃ and pH 6.0. Effects of root temperature on unit absorption rate , flux and inflow were compared. After 5 days , and increased with temperature over the range 3–11°C for NH₄ ions and over the range 3–13°C for NO₃ ions, with little change for either ion above these temperatures. Q₁₀ temperature coefficients for NH₄ ions (3–13°C) were 1.9, 1.7 and 1.6 for , and respectively, the corresponding values for NO₃ ions being 5.0, 4.5 and 4.6. For both ions, , and changed with time as did their temperature dependence over the range 3–25°C, suggesting that rates of ontogenetic development and the extent of adaptation to temperature may have varied among treatments.     

Dependency as a measure to estimate the order and the values of Markov processes

To evaluate the order and the values of Markov properties of the time series of events, we have proposed a statistical measure dependency:D _m = (H ₀ –H _m )/H ₀ , whereH ₀ andH _m are Shannon's entropy and them-th order conditional entropy, respectively. It is indicated that is a better point estimator ofD _m, giving a total value of them-th order Markov process. Here and are the estimate ofD _m and the arithmetic mean of when them-th order shuffling is made many times for a given observed series, respectively. The value represents Markov value of the orderm. Under the assumption that the series has continuous variables and the normal distribution, simplified dependency is defined by, where |S _m | is the determinant of serial correlation coefficients. It is shown that is practically useful for the estimation of the order and the values of Markov processes with small sample size. It is also indicated that analysis is basically equivalent to the least mean-square analysis of autoregressive models.     

Influence of lifting technique on perceptual and cardiovascular responses to submaximal repetitive lifting

Oxygen consumption ( O₂), heart rate, ventilation and central rating of perceived exertion (RPE) in repetitive lifting while executing squat and stoop techniques were investigated in ten male forestry workers. In all five mass/frequency combinations studied, O₂ was significantly higher for the squat than for the stoop technique. No differences were found in RPE between the techniques. The O₂ and RPE recordings were also related to those obtained during maximal repetitive lifting (same lifting technique) and maximal treadmill running. The O₂ expressed as a percentage of that obtained during maximal repetitive lifting with the same lifting technique was defined as relative aerobic intensity (% O_{2max, lifting}). The % O_{2max, lifting} was not significantly different between the techniques except for the lowest mass lifted (1 kg). This study therefore would support the hypothesis that RPE is more closely related to % O_{2max, lifting} than to absolute aerobic intensity. Related to maximal treadmill running, it was demonstrated for both lifting techniques that relative RPE (percentage of the RPE during maximal running) was more accurate than relative O₂ (percentage of maximal O₂ during maximal running) for determining the % O_{2max, lifting} in repetitive lifting. The study showed that the higher O₂ during squat. lifting compared to stoop lifting was caused by the O₂ expended in lifting and lowering the body rather than the O₂ expended lifting and lowering the external mass. It was concluded that the stoop technique was not superior to the squat technique in terms of central RPE. Based on % O_{2max, lifting}, there may be a rationale for choosing the stoop technique during repetitive lifting with light masses, but not with heavy masses.     

Laser light scattering determination of size and dispersity of synaptosomes and synaptic vesicles isolated from squid (Loligo pealei) optic lobes

Quasi-elastic laser light scattering has been used to investigate the size and dispersity of synaptosomes and synaptic vesicles isolated from optic lobes of the squid Loligo pealei. Synaptosomal fractions were highly polydisperse ( ) and the mean diameter ( ) ranged from 0.5–2.0 m. Size distribution histograms yielded two major components — smaller particles ( ) and a larger group of particles ( ). The heterogeneity of the synaptosomal particles detected in solution is in agreement with published data obtained using electron microscopy. Purified synaptic vesicle fractions also yielded complex particle size distribution data. A component with a mean diameter in the range 150–250 nm was detected, though a smaller particle ( ) dominated the scattering signal. This smaller particle closely resembles in size the electron lucent vesicles seen in the majority of squid optic lobe nerve terminals when examined by electron microscopy. Osmotically-induced shirnkage and swelling of the synptosomes was detected. Depolarization by veratridine (1.0×10^–4 M) did not result in a detectable change in the size of synaptosomal particles.     

A comparison of sweating responses during exercise and recovery in terms of sweating rate and body temperature

Based on the hypothesis that the relation between sweating rate and body temperature should be different during exercise and rest after exercise, we compared the sweating response during exercise and recovery at a similar body temperature. Healthy male subjects performed submaximal exercise (Experiment 1) and maximal exercise (Experiment 2) in a room at 27° C and 35% relative humidity. During exercise and recovery of 20 min after exercise, esophageal temperature (Tes), mean skin temperature, mean body temperature ( ), chest sweating rate ( ), and the frequency of sweat expulsion (F _SW) were measured. In both experiments, andF _SW were clearly higher during exercise than recovery at a similar body temperature (Tes, ). was similar during exercise and recovery, or a little less during the former, at a similarF _SW. It is concluded that the sweating rate during exercise is greater than that during recovery at the same body temperature, due to greater central sudomotor activity during exercise. The difference between the two values is thought to be related to non-thermal factors and the rate of change in mean skin temperature.     

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) .     

Evidence for linkage of the gene causing familial Mediterranean fever to chromosome 17q in non-Ashkenazi Jewish families: second locus or type I error?

Familial Mediterranean fever (FMF) is an autosomal recessive disorder of unknown pathogenesis, characterized by recurrent, selflimited attacks of fever with synovitis, peritonitis, or pleurisy. Using DNAs from affected Israeli families, we have recently mapped the gene causing FMF (designated MEF) to the short arm of chromosome 16, with two-point lod scores in excess of 20. In this report we consider the possibility of a second FMF susceptibility locus. Before discovering linkage to markers on chromosome 16, we had found suggestive evidence for linkage to chromosome 17q, with the following maximal two-point lod scores: D17S74 (pCMM86), = 2.47, ( = 0.20); D17S40 (pLEW101), = 2.15( = 0.15); D17S35 (CRI-pP3-1), = 1.78 ( = 0.15); D17S46 (pLEW108), = 1.69 ( = 0.18), D17S254, = 2.30 ( = 0.20). Moreover, multipoint linkage analysis using D17S74 and D17S40 as fixed loci gave = 3.27 approximately 10 centimorgans (cM) telomeric to D17S40. Data with the chromosome 17 markers alone in our families suggested locus heterogeneity. Nevertheless, our families were not separable into complementary subsets showing linkage either to chromosome 16 or to chromosome 17. We also examined the possibility that the positive lod scores for chromosome 17 might reflect a secondary, modifying locus. By several measures of disease severity, families with positive lod scores for chromosome 17 loci had no worse disease than those with negative lod scores for these loci. We conclude that chromosome 17 does not encode a major FMF susceptibility gene for some of the families, nor does it encode a disease-modifying gene. Rather, it would appear that linkage to chromosome 17 is a false positive (type I) error. These results reemphasize the fact that a lod score of 3.0 corresponds to a posterior probability of linkage of 95%, with an attendant 1 in 20 chance of observing a false positive.     

The nucleotide sequence ofBeneckea harveyi 5S rRNA

Summary The complete sequence of the 5S rRNA from the bioluminescent bacterium,Beneckea harveyi has been determined to be p U G C U U G G C G C C A U A G C G A U U-G G A C C C A C U G A (U) C U U C A U U C C-G A A C C A G A A G U G A A C G A A U U A-G G C C G A U G G U G U G U G G G G C U-C C C C A U G U A G A G U A G G A A U C G-C C A G G U (U)_OH.Two sites of sensitivity to ribonuclease T₂ cleavage were identified; at A₄₁ and either A₅₄ or A₅₅. Comparison with existing sequence information fromEscherichia coli andPhotobacterium phosphoreum clarifies the amount of diversity among the bioluminescent bacteria and provides further insight into their phylogenetic position. Sequence heterogeneities were encountered and the importance of these in interpreting 5S rRNA data is discussed.     

Two-substrates packed-bed bioreactors: inhibition of enzyme and competitive binding of substrate and product to a ligand

An analytical model is developed to describe the performance of a packed-bed immobilized enzyme reactor in which parallel processes take place. In particular, two-substrate reaction, inhibition of the enzyme by one of the reaction products, and binding of one substrate and/or one product to an added ligand are taken into account. In addition, substrates and product diffusion into the porous catalyst are also considered. Using this model, numerical simulations were performed. The results point to the fact that, when all the above processes occur concomitantly, a variety of performance characteristics can be obtained, depending on the particular values of the related parameters. Moreover, under certain conditions, the reactor performance can be improved by controlled addition of ligand.List of Symbols A total concentration of ligand - C _1,i concentration of Substrate-1 in the pores of stage i - C _2,i concentration of Substrate-2 in its free form in the pores of stage i - _2,i concentration of the Substrate-2-Ligand Complex in the pores of stage i - total concentration of Substrate-2 in the pores of stage i - _i concentration of the Product-Ligand Complex in the pores of stage i - concentration of the free Product in the pores of stage i - total concentration of the Product in the pores of stage i - internal (pore) diffusion coefficient for the Substrate-Ligand Complex - D ₁ internal (pore) diffusion coefficient of Substrate-1 - D ₂ internal (pore) diffusion coefficient of Substrate-2 - effective (pore) diffusion coefficient for Substrate-2 - internal (pore) diffusion coefficient for the Product - internal (pore) diffusion coefficient for the Product-Ligand Complex - effective (pore) diffusion coefficient for the Product - K thermodynamic equilibrium constant for binding Substrate-2 to Ligand - K _m,1,K _m,2 Michaelis constants for Substrates-1 and 2, respectively - effective Michaelis constant for Substrate-2 - K _p thermodynamic equilibrium constant for binding the reaction Product to Ligand - effective equilibrium constant for binding Substrate-2 to Ligand - effective equilibrium constant for binding the reaction Product to Ligand. - K _b inhibition constant - K _q inhibition constant - effective inhibition constant - effective inhibition constant - k _a, k _d association and dissociation rate constants for Substrate-2 — Ligand complex - association and dissociation constants for Product —Ligand complex - n total number of elementary stages in the reactor - Q volumetric flow rate throughout the reactor - R _j,i reaction rate of Substrate-j in stage i, in terms of volumetric units - S _1,0 concentration of Substrate-1 in the reactor feed - total concentration of Substrate-2 in the reactor feed - S _1,i–1,S _1,i concentration of Substrate-1 in the bulk phase leaving stages i–1 and i, respectively - S _2,i concentration of Substrate-2 in its free form, in the bulk phase leaving stage i - _2,i–1, _2,i concentration of Substrate-2 in the bulk phase leaving stage i–1 and i, respectively - total concentration of Substrate-2 in the bulk phase leaving stages i–1 and i, respectively - _i concentration of the Product-Ligand Complex in the bulk phase of stage i - concentration of free Product in the bulk phase of stage i - total concentration of Product in the bulk phase of stage i - V total volume of the reactor - V _m maximal reaction rate in terms of volumetric units - y axial coordinate of the pores - y ₀ depth of the pores Greek Symbols ₁ dimensionless parameter - dimensionless parameter - dimensionless parameter - ₁ dimensionless parameter - dimensionless parameter - _1,i dimensionless concentration of Substrate-1 in pores of stage i - dimensionless total concentration of Substrate-2 (in both free and bound form) in pores of stage i - dimensionless total concentration of the reaction product in the pores of stage i - ₁ dimensionless parameter - dimensionless parameter - dimensionless parameter - dimensionless parameter - dimensionless parameter - dimensionless position along the pore - volumetric packing density of catalytic particles (dimensionless) - porosity of the catalytic particles (dimensionless) - _1,i dimensionless concentration of Substrate-1 in the bulk phase of stage i - dimensionless total concentration of Substrate-2 (in both free and bound form) in the bulk phase of stage i     

A method for determining the maximal steady state of blood lactate concentration from two levels of submaximal exercise

The aim of this study was to estimate the characteristic exercise intensity _CL which produces the maximal steady state of blood lactate concentration (MLSS) from submaximal intensities of 20 min carried out on the same day and separated by 40 min. Ten fit male adults [maximal oxygen uptake _max 62 (SD 7) ml · min^–1 · kg^–1] exercisOed for two 30-min periods on a cycle ergometer at 67% (test 1.1) and 82% of _max (test 1.2) separated by 40 min. They exercised 4 days later for 30 min at 82% of _max without prior exercise (test 2). Blood lactate was collected for determination of lactic acid concentration every 5 min and heart rate and O₂ uptake were measured every 30 s. There were no significant differences at the 5th, 10th, 15th, 20th, 25th, or 30th min between , lactacidaemia, and heart rate during tests 1.2 and 2. Moreover, we compared the exercise intensities _CL which produced the MLSS obtained during tests 1.1 and 1.2 or during tests 1.1 and 2 calculated from differential values of lactic acid blood concentration ([1a^–]_b) between the 30th and the 5th min or between the 20th and the 5th min. There was no significant difference between the different values of _CL [68 (SD 9), 71 (SD 7), 73 (SD 6),71 (SD 11) % of _max (ANOVA test,P<0.05). Four subjects ran for 60 min at their _CL determined from periods performed on the same day (test 1.1 and 1.2) and the difference between the [la^–]_b at 5 min and at 20 min ( ([la^–]_b)) was computed. The [la^–]_b remained constant during exercise and ranged from 2.2 to 6.7 mmol · l^–1 [mean value equal to 3.9 (SD 1) mmol · l^–1]. These data suggest that the _CL protocol did not overestimate the exercise intensity corresponding to the maximal fractional utilization of _max at MLSS. For half of the subjects the _CL was very close to the higher stage (82% of _max where an accumulation of lactate in the blood with time was observed. It can be hypothesized that _CL was very close to the real MLSS considering the level of accuracy of [la^–]_b measurement. This study showed that exercise at only two intensities, performed at 65% and 80% of _max and separated by 40 min of complete rest, can be used to determine the intensity yielding a steady state of [la^–1]_b near the real MLSS workload value.     

The effect of short-term fasting and a single meal on protein synthesis and oxygen consumption in cod,Gadus morhua

Summary Rates of protein synthesis and oxygen consumption ( O₂) in cod were compared in both fasted and refed animals. During a 14-day fast both protein synthesis and respiration rates fell to stable values after 6 days. When a meal of whole sandeel at 6% body weight was fed to fish fasted for 6 days, protein synthesis and ( O₂) increased to a maximum at between 12 and 18 h after feeding. Peak ( O₂) was about twice the pre-feeding values, while whole animal protein synthesis increased four-fold. There were differences between tissues in the timing of maximum protein synthesis; the liver and stomach responded faster than the remainder of the body. Maximum protein synthesis rates in the liver and stomach occurred at 6 h after feeding, at which time their calculated contribution to total ( O₂) was 11%. Similar calculations suggested that the integrated increment in whole animal protein synthesis contributed between 23% and 44% of the post-prandial increase in ( O₂). It was concluded that protein synthesis is an important contributor to increased ( O₂) after feeding in cod.Abbreviations A _s absolute rate of protein synthesis - ASDA apparent specific dynamic action - ATP adenosine triphosphate - k _s fractional rate of protein synthesis - k _s/RNA amount of protein synthesized per unit RNA - ( O₂) oxygen consumption - PCA perchloric acid - RNA ribonucleic acid     

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle

Summary In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL>1 (where K is the scattering vector), the average characteristic linewidth ( ) increased with the addition of Ca²⁺ or with the depletion of ATP. The increase in the with the addition of Ca²⁺ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca²⁺. The increase in which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in following the addition of Ca²⁺ was found to be seasonal, i.e., values of obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in was also different. The increase showed a maximum at about 35°C during the summer and at about 25°C at other times. However, the percentage increase in developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca²⁺ per myosin molecule was 1 during the summer and 2 at other times.Abbreviations DLS dynamic light scattering - L length - K scattering vector - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis - average characteristic line width Deceased     

Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus)

Summary The effects of different ambient temperatures (T _a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).At both low and high altitude, oxygen consumption ( ) decreased with increasingT _a atT _a from –10 to 30 °C. The was 15–20% smaller at high altitude than at low altitude atT _a below 30 °C.Increased atT _a below thermoneutrality was supported by increased minute volume ( ) at both low and high altitude. At mostT _a, the change in was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V _T) or oxygen extraction efficiency (O₂EE). AtT _a=0 °C and below at high altitude, was constant due to decliningV _T and O₂EE increased in order to maintain high .At high altitude, (BTP) was 30–40% higher at a givenT _a than at low altitude, except atT _a below 10 °C. The increased at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT _a below 0 °C. The (STP) was equivalent at high and low altitude atT _a of 10 °C and above. At lowerT _a, (STPD) was larger at low altitude.At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT _a (20–30 °C).Abbreviations EHL evaporative heat loss - f respiration frequency - HL _a heat loss from warming tidal air - HL _e evaporative heat loss in tidal air - HL total respiratory heat loss - MHP metabolic heat production - O ₂ EE oxygen extraction efficiency - RQ respiratory quotient - T _a ambient temperature - T _b body temperatureT _lc lower critical temperature - carbon dioxide production - evaporative water loss - oxygen consumption - minute volume - V _T tidal volume     

Theoretical basis of single breath gas absorption tests

Absorption of gas from alveoli is examined in a simplified model of the respiratory system during a stylized single breath consisting of constant inspiratory flow, constant expiratory flow, and breathholding. The equations describing gas behavior are general since they are based upon conservation of mass. The equations simplify considerably when gases that are not soluble in pulmonary tissue and/or blood are utilized. In a three-compartment model, diffusing capacity of the lung for carbon monoxide (D _CO ) will be underestimated except when both uneven distribution of lung volume andD _CO are present; under most circumstances, the standard clinical 10-s method [9] is at least as accurate as any other. When pulmonary capillary blood flow is calculated by the one point method [2] in a one-compartment lung, it is underestimated; in the three-compartment model, it is underestimated except when both uneven distribution of . and lung volume are present. The multiple single breath method [2] accurately measuresD _CO and . Measurement of pulmonary tissue volume is improved by correcting the value of the intercept of acetylene absorption to the time when carbon monoxide apparently began rather than utilizing the beginning of inspiration.Nomenclature D _CO diffusing capacity of the lung for CO (ml CO, STPD/min/mm Hg) - pulmonary capillary blood flow rate (L/min) - V _t pulmonary tissue volume (L) - V _A alveolar compartment volume (L) - V _Ao alveolar compartment volume at conclusion of inspiratory flow (L) - inspiratory flow rate (L/sec) - expiratory flow rate (L/sec) - Bunsen coefficient of pulmonary tissue for test gas (ml test gas/ml tissue/atm) - Bunsen coefficient of pulmonary tissue for test gas (ml test gas/ml blood/atm) - F _A fractional pressure of test gas in the alveolar compartment (atm)     

Altitudinal and seasonal effects on aerobic metabolism of deer mice

Summary I compared the maximal aerobic metabolic rates ( ), field metabolic rates (FMR), aerobic reserves ( -FMR), and basal metabolic rates (BMR) of wild and recently captured deer mice from low (440 m) and high (3800 m) altitudes. To separate the effects of the thermal environment from other altitudinal effects, I examined mice from different altitudes, but similar thermal environments (i.e., summer mice from high altitude and winter mice from low altitude). When the thermal environment was similar, , FMR, and aerobic reserve of low and high altitude mice did not differ, but BMR was significantly higher at high altitude. Thus, in the absence of thermal differences, altitude had only minor effects on the aerobic metabolism of wild or recently captured deer mice.At low altitude, there was significant seasonal variation in , FMR, and aerobic reserve, but not BMR. BMR was correlated with , but not with FMR. The significant positive correlation of BMR with indicates a cost of high , because higher BMR increases food requirements and energy use during periods of thermoneutral conditions.Abbreviations BMR basal metabolic rate - FMR field metabolic rate - partial pressure of oxygen - T _a ambient temperature - T _b body temperature - T _e operative temperature - maximal aerobic metabolic rate     

Effects of ambient and local cutaneous temperatures on hand blood flow

The hand blood flow ( ) was investigated in response to a wide range of general and local cutaneous thermal stimuli (0–36°C and 4–42°C respectively), the local stimulus consisting of a thermostatically controlled water bath for the right hand (T_w), and the general stimulus, the ambient room temperature (T_a). was measured at the right wrist by strain gauge plethysmography; it was seen to respond more significantly to variations in T_w than to those in T_a at cold to comfortable ambient temperatures (T_a<22°C). A paradoxical vasodilatation was observed at T_w=4°C (Lewis' hunting phenomenon). The graphs of versus T at average to high local cutaneous temperatures (T_w > 33°C) are remarkably similar, except for an upward shift at successively higher values of T_w. The slope (or vasomotor reactivity) is interpreted as being controlled by variations in T_a. The curves exhibited maximum values at T_a = 31°C. Their subsequent decrease could represent a thermoregulatory adaptation to environment-organism heat transfer, the relative vasoconstriction tending to reduce the transfer. Although the qualitative response was the same for both sexes, the absolute value of was generally greater in male than in female subjects.