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.     

Aerobic metabolism of the lizardVaranus exanthematicus: Effects of activity, temperature, and size

Summary Oxygen consumption was measured at rest and during spontaneous activity at body temperatures of 25 and 35°C in 14 fasting Savanna monitor lizards,Varanus exanthematicus ranging in weight from 172 to 7500 g. The allometric relationship between metabolic rate at 25°C and body weight (W) is given by: (ml O₂ STPD·g^–1·hr^–1)=0.88W ^–0.43 (Fig. 2). Although statistical comparisons are equivocal, this intraspecific size dependence exceeds that reported for interspecific comparisons among reptiles and other vertebrate groups (Fig 3). A reproducible diurnal pattern of activity was observed in undisturbed animals with minimum values of between 2400 and 0800 h (Fig. 1). Spontaneous activity and generally reached peak values between 1200 and 2000 hrs. The average ratio of active aerobic metabolic rate (AMR) to minimum (standard) aerobic metabolic rate (SMR) was 8.2. This voluntary AMR/SMR inVaranus exceeds the AMR/SMR for most reptiles stimulated to exhaustion. The high aerobic capacity is consistent with other evidence for efficient exchange and transport of respiratory gases inV. exanthematicus; e.g., low or absent intracardiac shunt flow resulting in high arterial saturation and low ventilation and perfusion requirements.     

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     

Skeletal muscle [(V)\dot]O2 \dot V_{O_2 } in rat and lemming: Effect of blood flow rate

Summary The rate of oxygen consumption ( ) by skeletal muscle was investigated in isolated perfused hindlimbs of laboratory rats and lemmings (Lemmus). In both species, increased in proportion to blood flow rate, even at flow rates 4–5 times above resting level. The slope of the line relating to skeletal muscle blood flow was significantly greater in the lemming than in the rat. This may be related to the inverse relationship between body weight and metabolic rate. These data support the hypothesis that in small animals a dependent relationship exists between blood flow and skeletal muscle .     

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 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     

Energetics of vocalization by an anuran amphibian (Hyla versicolor)

Summary The metabolic demands of vocalization byHyla versicolor were determined by measuring oxygen consumption and whole body lactate content of calling animals. A stepwise multiple regression analysis identified both calling rate (calls/h) and call duration (s/call) as significant determinants of oxygen consumption during calling. These two variables accounted for 84% of the total variation in oxygen consumption observed in calling frogs. Aerobic metabolism increased linearly with calling rate and call duration, reaching a peak value of 1.7 ml O₂/(g·h) at the highest vocalization effort. For comparison, metabolic rates of the same individuals were also measured during short bouts of vigorous locomotor exercise induced by mechanical stimulation. The mean value of was only 62% of the peak , and 5 of 13 frogs had rates of oxygen consumption during calling that exceeded their . Whole body lactate levels were measured in two samples of calling frogs, one collected early in the evening (2100–2115 h) and the other 1.5 h later (2230–2245 h). The frogs in the second sample had significantly lower lactate levels (0.10 mg/g) than the frogs collected early in the evening (0.22 mg/g). Hence, vocalization does not entail the use of anaerobic metabolism, although lactate levels may be slightly elevated at the onset of an evening of calling. Calling rates of unrestrained frogs in a large chorus were measured at regular intervals during an evening. During the first half hour of calling, rates increased gradually from an initial mean value of 600 calls/h at 2030 h to nearly 1400 calls/h at 2100 h. These data indicate that acoustic advertisement byHyla versicolor is among the most energetically expensive activities regularly undertaken by any anuran, and indeed, is the most demanding yet measured in an ectothermic vertebrate.Abbreviations resting rate of oxygen consumption - maximum rate of oxygen consumption - rate of oxygen consumption during forced exercise - rate of oxygen consumption during calling     

Effects of wind on thermoregulation and energy balance in deer mice (Peromyscus maniculatus)

Summary The effects of various convective and temperature regimes on heat production, evaporative heat loss, and thermal resistance were studied in deer mice,Peromyscus maniculatus. Heat production (measured as oxygen consumption) increased with increasing wind speed (V) and decreasing ambient temperature (T _a), except atT _a=35°C which was thermoneutral for allV from 0.05 through 3.75 m/s. Evaporative water loss ( ) increased with increasingT _a, but wind had little effect on except at highT _a. In the absence of forced convection, the animals' total resistance to heat transfer (r _t) was high and stable atT _a below thermoneutrality. However, at highV ther _t increased steadily with decreasingT _a. Although deer mice rarely experience high wind speeds in natural microhabitats, the convective regime is nevertheless important in determining rates of heat loss, and must be considered in studies of ecological energetics.Symbols and Abbreviations A animal surface area - HP _n net metabolic heat production - EHL evaporative heat loss - MHP metabolic heat production - r _t total resistance to heat transfer - r _ext external resistance component of r_t - RQ respiratory quotient - pc _p volumetric specific heat of air - T _a ambient temperature - t _b body temperature - t _e operative, or equivalent blackbody temperature of the environment - T _sk skin temperature - T _es standard operative temperature - V wind speed - oxygen consumption - carbon dioxide production - evaporative water loss     

Effect of photoperiod and melatonin on cold resistance,thermoregulation and shivering/nonshivering thermogenesis in Japanese quail

Summary The effect of photoperiod and melatonin treatment on cold resistance and thermogenesis of quails was studied. The birds were acclimated for 8 weeks to short day (8L:16D) or long day (16L:8D) conditions, and 8 of 16 quails in each group were implanted with melatonin capsules. One group of quails was maintained outside in an aviary during winter. Oxygen consumption ( ) body temperature (T _b, recorded with temperature transmitters) and shivering (integrated pectoral EMG) were recorded continuously, and samples of heart rate and breathing rate were picked up when ambient temperature was decreased stepwise from 27 down to –75 °C. Heat production maximum (HP_max), cold limit, lower critical temperature, basal metabolic rate (BMR) and thermal conductance were determined.The results show that short day, cold and melatonin treatment improved cold resistance and thermal insulation of quils when compared with quails acclimated to long day conditions. An increase in HP_max was induced only by melatonin treatment. The results suggest that the acclimatization of quails is under control of the pineal gland.The linear increase of shivering intensity with at moderate cold load shows that shivering is the primary source for thermoregulatory heat production in the quail. AtT _a's below –40 °C shivering remained constant although , heart rate and breathing rate continued to increase with increasing cold load. This could indicate the existence of a nonshivering thermogenesis in birds. Unlike to mammals, this non-shivering thermogenesis in birds would serve as secondary source of heat supporting shivering thermogenesis in severe coldAbbreviations BMR basal metabolic rate - ECG electrocardiogram - EMG electromyogram - NST nonshivering thermogenesis - SMR standard metabolic rate     

Breathing pattern and growth: comparative aspects

Summary The resting oxygen consumption and breathing pattern of nine newborn and adult species (ranging in body size from mouse to human) have been compared on the basis of data collected from the literature. Minute ventilation is similarly linked to at both ages, the percent of extracted as O₂ about 2.2. Tidal volume/kg is an interspecies constant in newborns and adults, approximately 8 ml/kg. Breathing frequency decreases with the increase in size in a different way at the two ages: large species have newborns breathing at rates 2–3 times above the corresponding adults' values, while in the small species newborns and adults breathe at almost the same rate. Therefore the newborns of the smallest species have both and below the expected values, implying a greater inability to cope with the external demands than newborns of larger species. Several considerations indicate that in the smallest newborns the mechanical properties of the respiratory system could be a constraint to resting ventilations larger than observed. It is therefore possible that their low is the cause, and not the effect, of the relatively small .     

Seasonality of torpor and thermoregulation in three dasyurid marsupials

Summary Seasonal variation in the pattern of torpor and temperature regulation was investigated in the closely related arid zone dasyurid marsupialsSminthopsis crassicaudata (17 g),S. macroura (24 g), andDasyuroides byrnei (120 g). The tendency to enter torpor was greater, torpor commenced earlier, torpor duration was longer, and body temperatures (T _b) were lower inSminthopsis spp. than inD. byrnei. The minimum mass-specific rate of oxygen consumption ( ) of torpid animals was similar among the three species despite the differences in minimumT _b. The mass-specific oxygen consumption of normothermic animals was reduced during winter when compared with the summer values in all species, but there was no seasonal variation in normothermicT _b in any species. The tendency to enter torpor was incrased during winter. TorpidSminthopsis spp. had lower values ofT _b and during winter than during summer;D. byrnei did not show seasonal changes in these variables. These results suggest that seasonal changes in the pattern of thermoregulation and torpor in small dasyurids may be more distinct than in larger species.Abbreviations RMR resting metabolic rate - BMR basal metabolic rate     

Metabolism,temperature relations,maternal behavior,and reproductive energetics in the ball python (Python regius)

Summary Thermogenic incubation has been documented in two large species of pythons, but the phenomenon has not been studied in small species with concomitantly large heat transfer coefficients. We describe behavior, metabolic rates, mass changes, and temperature relations for adult ball pythons (Python regius), the smallest member of the genus, during the reproductive cycle. Egg and hatchling metabolism and hatchling growth rates were also examined.Rates of oxygen consumption ( ) of both gravid and non-gravid snakes showed typical ectothermic responses to changing ambient temperature (T _a). TheQ ₁₀ forT _a's of 20–35°C was 2.2–2.3. The of gravid females was significantly greater than that of non-gravid snakes at allT _a. Maximum oxygen consumption ( max) during forced exercise was about 12 times resting atT _a=30°C.Eggs (5–6 per female) were laid in April. Total clutch mass was approximately 32% of the females' pre-oviposition mass. After oviposition, mother snakes coiled tightly around their clutches and remained in close attendance until the eggs hatched in June. Sudden decreases inT _a elicited abrupt but transient 2- to 4-fold increases in the of incubating females. Similar responses were not observed in non-incubating snakes. The steady-state of incubating females was independent ofT _a. In no case was body temperature (T _b) elevated more than a few tenths of a degree aboveT _a in steady-state conditions.The of developing eggs increased sigmoidally through the 58–70 day incubation period. Total oxygen consumption during incubation atT _a=29.2°C was about 3.61 per egg. Young snakes quadrupled their mass during their first year of growth.Compared to larger python species which are endothermic during incubation, ball pythons have similar aerobic scopes and higher mass-specific max. However, effective endothermy in ball pythons is precluded by high thermal conductance and limited energy stores.     

Energy expenditure and cardiorespiratory responses at the transition between walking and running

We investigated whether the spontaneous transition between walking and running during moving with increasing speed corresponds to the speed at which walking becomes less economical than running. Seven active male subjects [mean age, 23.7 (SEM 0.7) years, mean maximal oxygen uptake ( ), 57.5 (SEM 3.3) ml·kg ^–1·min ^–1, mean ventilatory threshold (VTh), 37.5 (SEM 3) ml·kg ^–1 ·min ^–1] participated in this study. Each subject performed four exercise tests separated by 1-week intervals: test 1, and VTh were determined; test 2, the speed at which the transition between walking and running spontaneously occurs (ST) during increasing speed (increases of 0.5 km·h ^–1 every 4 min from 5 km·h ^–1) was determined; test 3, the subjects were constrained to walk for 4 min at ST, at ST ± 0.5 km·h ^–1 and at ST ± 1 km·h ^–1; and test 4, the subjects were constrained to run for 4 min at ST, at ST±0.5 km·-h ^–1 and at ST±1 km·h ^–1. During exercise, oxygen uptake ( ), heart rate (HR), ventilation ( ), ventilatory equivalents for oxygen and carbon dioxide (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaca% WaaSbaaSqaaiaabweaaeqaaOGaai4laiqadAfagaGaamaaBaaaleaa% caqGYaaabeaakiaacYcacaqGGaGaaeiiaiqadAfagaGaamaaBaaale% aacaqGfbaabeaakiaac+caceWGwbGbaiaacaqGdbGaae4tamaaBaaa% leaacaaIYaaabeaaaaa!4240!\[\dot V_{\text{E}} /\dot V_{\text{2}} ,{\text{ }}\dot V_{\text{E}} /\dot V{\text{CO}}_2 \]), respiratory exchange ratio (R), stride length (SL), and stride frequency (SF) were measured. The results showed that: ST occurred at 2.16 (SEM 0.04) m·s ^–1; , HR and speed at ST were significantly lower than the values measured at VTh (P< 0.001, P< 0.001 and P< 0.05, respectively); changed significantly with speed (P< 0.001) but was greater during running than walking below ST (ST minus 1 km·h ^–1, P< 0.001; ST minus 0.5 km·h ^–1, P< 0.05) with the converse above ST (ST.plus 1 km·h ^–1, P<0.05), whereas at ST the values of were very close [23.9 (SEM 1.1) vs 23.7 (SEM 0.8) ml·kg ^–1 · min ^–1 not significant, respectively, for walking and running]; SL was significantly greater during walking than running (P<0.001) and SF lower (P<0.001); and HR and were significantly greater during running than walking below ST (ST minus 1 km·h ^–1, P<0.01; ST minus 0.5 km·h ^–1, P{<0.05) with the converse above ST (ST plus 1 km·h ^–1, P·< 0.05), whereas no difference appeared for and R between the two types of locomotion. We concluded from this study that ST corresponded to the speed at which the energy expenditure of running became lower than the energy expenditure of walking but that the mechanism of the link needed further investigation.     

Gas exchange in the incubation mounds of megapode birds

Summary The brush turkey (Alectura lathami) and mallee fowl (Leipoa ocellata) are megapode birds that incubate their eggs by burying them in mounds. Respiratory gas exchange between the buried eggs and the atmosphere occurs mainly by diffusion through about 60 cm of decomposing forest litter (brush turkey) or sand (mallee fowl).Gas fluxes in the brush turkey mound are greatly influenced by the respiration of thermophilic microorganisms which consume O₂ at rates over eight times that of all of the eggs. The respiratory exchange ratio ( ) of the microorganisms is 0.75 and theQ ₁₀ for metabolism is 2.56. Fermentation and nitrogen fixation do not occur in the mounds.If the mound becomes too wet, gas tensions near the eggs can become critical because water increases rates of microbial respiration and impedes gas diffusion. However, field mounds are relatively dry, possibly because the adult bird modifies the shape of the mound and affects the entry of rain water. At egg level in field mounds, and are about 132 and 21 Torr, respectively, in both species. Embryonic respiration decreases and increases about 5 Torr in the immediate environment of individual eggs in late development. Due to a high eggshell gas conductance, which increases during incubation, the gas tensions within the shell of late embryos ( ca. 108 Torr, ca. 47 Torr) are not far from the mean values found in species that nest above ground.     

Resting metabolic rates in boid snakes: allometric relationships and temperature effects

Summary Resting metabolic rates (RMR) of 34 species from 18 genera of boas and pythons (Serpentes: Boidae), with body masses ranging from 2 to 67,800 g, were determined as oxygen consumption ( ) and carbon dioxide production ( ) at three ambient temperatures (T _a).The temperature coefficient of metabolism (Q₁₀) averaged 2.61 betweenT _a of 20–30°C and 2.65 between 30 and 34°C. The respiratory exchange ratio RE (= / ) increased slightly with increasingT _a (0.795 at 20°C, 0.819 at 30°C, and 0.834 at 34°C). Interspecific differences in Q₁₀ and RE were slight or insignificant.A multiple regression relating metabolism ( ) to mass andT _a explained 97% of the variance in the pooled interspecific data. The mass exponent was 0.806, which is approximately the same as reported for squamates and for all reptilian taxa combined. The mean within-species slope (0.732) was significantly less than the slope for pooled data, but did not differ significantly from 0.75. In 40 of 42 cases (14 species at 3T _a), within-species slopes did not differ from each other. Values of the adjusted mean Y, from covariance analysis, were significantly and positively correlated with mass, indicating that the mass coefficient increases with increasing mass.Considerable variation in metabolic rate is apparent both within and between ecological and taxonomic categories.Original metabolic data are available from the National Auxiliary Publications Services, c/o Microfiche Publication, P.O. Box 3153 Grand Central Station, New York, New York 10017, USA     

Cold thermoregulatory changes induced by sleep deprivation in men

The aim of this study was to evaluate the thermoregulatory changes induced by 27-h of sleep deprivation (SD) in men at rest both in a comfortable ambient temperature and in cold air. A group of 12 male subjects were placed in a comfortable ambient temperature (dry bulb temperature,T _db = 25° C, relative humidity, rh = 40%–50% , clothing insulation = 1 clo) for 1 h and then they were submitted to a standard cold air test in a climatic chamber for 2h (T _db=1° C, rh = 40%–50%, wind speed = 0.8 m·s^–1, nude), before and after 27 h of sleep deprivation. Thermoregulatory changes (rectal temperature,T _re; mean skin temperature, _sk; metabolic heat production ) were monitored continuously. At comfortable ambient temperature, no significant change was observed after SD forT _re, _sk and . During the cold test,T _re did not change but _sk and were higher after SD (P<0.05). Increased (+ 6%,P < 0.05) was related to earlier and higher shivering, with a possible increase in the sensitivity of the thermoregulatory system as shown by the shorter time to onset of continous shivering (d): 8.66 (SEM 1.33) min versus 28.20 (SEM 1.33) min (P < 0.001) and by a higher _sk observed at d: 27.60 (SEM 1.40)° C versus 21.40 (SEM 0.60)° C (P < 0.001). These results were associated with higher cold sensations and shivering following SD. They also suggested that SD modified thermoregulatory responses at a central level especially in a cold environment.     

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.     

Growth and product formation of actinomycetes cultivated at increased total pressure and oxygen partial pressure

Summary Influence of pressure (P) and oxygen partial pressure ( ) on cultivation of various Streptomyces spp. and Micromonospora purpurea was examined in pressurized air-lift and stirred tank fermenters. The maximum was 2100 mbar. Growth and product formation of all cultures tested were markedly influenced by higher than 1000 mbar. There is evidence that wild strains are more oxygen tolerant than production strains. At a certain the metabolic activities of all cultures were inhibited. However, results obtained with S. aureofaciens and S. rimosus indicated an increase in specific product formation rate at elevated pressure. With increase in oxygen tension incorporation of oxygen into tetracycline molecules was enhanced. Since elevated oxygen tension can either show inhibiting effects or may be used for regulation of product formation and selectivity, the influence of should be determined in an appropriate experimental set-up for each process.Offprint requests to: U. Onken