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1.
Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal
changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns
and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns
observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O2 g−1 h−1) than in winter (0.75 ± 0.11 ml O2 g−1 h−1). Body temperatures during torpor were regulated at 19.3 ± 1.0°C in summer and at 23.4 ± 2.0°C in winter. Torpor bout duration
was significantly longer in summer (7.3 ± 0.6 h) than in winter (5.5 ± 0.3 h), but in both seasons, bout duration was not
affected by ambient temperature. Consequently, average daily metabolic rates were also significantly lower in summer than
in winter. Body temperatures and metabolic rates in normothermic bats did not change with season. Our findings on seasonal
changes of torpor in this bat from the subtropics are opposite to those made for many species from cold climates which generally
show deeper and longer torpor in winter and are often entirely homeothermic in summer. More pronounced torpor in subtropical
S. australis in summer may be due to low or unpredictable nectar availability, short nights which limit the time available for foraging,
and long days without access to food. Thus, the reversed seasonal response of this subtropical bat in comparison to temperate
species may be an appropriate response to ecological constraints.
Received: 6 May 1997 / Accepted: 19 October 1997 相似文献
2.
Ronald Heus Alexander H. Wertheim George Havenith 《European journal of applied physiology and occupational physiology》1998,77(4):388-394
The assumption that working on board ship is more strenuous than comparable work ashore was investigated in this study. Various
physiological parameters (V˙O2, V˙CO2, V˙
E and HR) have been measured to determine the energy expenditure of subjects walking slowly on a moving platform (ship motion
simulator). Twelve subjects (eight men and four women) walked either freely on the floor or on a treadmill at a speed of 1 m · s−1. Platform motion was either in a heave, pitch or roll mode. These three conditions were compared with a control condition
in which the platform remained stationary. The results showed that during pitch and roll movements of the platform, the energy
expenditure for the same walking task was about 30% higher than under the stationary control condition (3.6 J · kg−1 · m−1 vs 2.5 J · kg−1 · m−1, P < 0.05) for both walking on a treadmill and free walking. The heart rate data supported the higher energy expenditure results
with an elevation of the heart rate (112 beats · min−1 vs 103 beats · min−1, P < 0.05). The heave condition did not differ significantly from the stationary control condition. Pitch and roll were not
significantly different from each other. During all experimental conditions free walking resulted in a higher energy cost
of walking than treadmill walking (3.5 J · kg−1 · m−1 vs 2.7 J · kg−1 · m−1, P < 0.05) at the same average speed. The results of this experiment were interpreted as indicating that the muscular effort,
needed for maintaining balance when walking on a pitching or rolling platform, resulted in a significantly higher work load
than similar walking on a stable or a heaving floor, independent of the mode of walking. These results explain in part the
increased fatigue observed when a task is performed on a moving platform.
Accepted: 3 October 1997 相似文献
3.
Fritz Geiser G. J. Kenagy John C. Wingfield 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):416-422
Dietary cholesterol can affect both body lipid composition and steroid hormone concentration. We investigated whether a diet
rich in cholesterol influences torpor patterns of hibernating chipmunks (Tamias amoenus) and, if so, whether these changes are better explained by diet-induced changes in body lipid composition or the concentration
of testosterone, which at high levels inhibits torpor. Two groups of chipmunks were maintained either on a cholesterol diet
(rodent chow containing 10% cholesterol) or a control diet (rodent chow) during pre-hibernation fattening and throughout the
hibernation season. Torpid chipmunks on the cholesterol diet had significantly lower minimum body temperatures (−0.2 ± 0.2
vs +0.6 ± 0.2 °C), lower metabolic rates (0.029 ± 0.002 ml O2 g−1h−1 vs 0.035 ± 0.001 ml O2 g−1h−1), and longer torpor bouts at −1 °C (6.8 ± 0.5 vs 4.1 ± 1.0 days) than chipmunks on the control diet. Dietary cholesterol
resulted in a significant increase in blood plasma cholesterol (sevenfold), liver cholesterol content (6.9-fold) and liver
triglyceride content (3.5-fold) in comparison to controls. In contrast, dietary cholesterol had no detectable effect on the
concentration of plasma testosterone, which was very low in both groups. Since torpor was deeper and longer in animals on
the cholesterol diet our study suggests that torpor patterns of chipmunks were either directly affected by the dietary cholesterol
or via changes in body lipid composition.
Accepted: 22 January 1997 相似文献
4.
Stiffler DF Talbot CR 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(7):505-509
Oxygen consumption was measured in five Dermophis mexicanus and averaged (±SEM) 0.047 ± 0.004 ml O2 g−1 h−1. Carbon dioxide production averaged 0.053 ± 0.005 ml CO2 g−1 h−1 in the same five animals 1 week later. This metabolic rate is similar to metabolic rates of other Gymnophionans but lower
than metabolic rates reported for Anurans and Urodeles. Total nitrogen excretion averaged 1.37 μmol N g−1 h−1 which is higher than that found for other amphibians. Of this, 82.5% (1.13 μmol N g−1 h−1) was in the form of urea while 17.5% (0.24 μmol N g−1 h−1) was in the form of NH3 + NH+
4. Such ureotelism is typical of terrestrial amphibians like D. mexicanus. Osmotic water flux averaged 0.0193 ml g−1 h−1 in control (sham injected) animals and was not significantly altered by injection of either arginine vasotocin or mesotocin.
This osmotic flux is similar to osmotic fluxes found for other terrestrial amphibians. The combined data suggest that metabolism
in D. mexicanus is, like most other Gymnophionans, lower than other amphibians. The high rates of nitrogen (especially urea) excretion suggests
that this fossorial animal accumulates urea like other burrowing amphibians.
Accepted: 27 June 2000 相似文献
5.
D. Audet D. W. Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):146-152
The present study questions whether hypothermia is an artifact due to captivity-induced stress or a thermoregulatory strategy
for bats of the neotropical family Phyllostomidae. In Guanacaste, Costa Rica, Carollia perspicillata and Sturnira lilium exhibited a bimodal distribution of body temperatures when submitted to an ambient temperature of 21 °C. Body temperature
was highly correlated with body mass in both species. C. perspicillata of mass ≥20 g and S. lilium of mass ≥17 g remained normothermic (body temperature >37 °C), whereas at masses below 18 g and 13 g, respectively, >80%
of individuals were hypothermic (body temperature ≤32 °C). In two treatment groups for each species, we restricted food intake
to ca. 20% of body mass on either night 1 or night 4 following capture. Hypothermia was significantly related to food-restriction,
but not time in captivity. Metabolic rate (ml O2 · g−1 h−1) at ambient temperature = 21 °C was MR = e
(–2.11 + 0.101 Tb) (r
2 = 0.7, P < 0.001) for C. perspicillata and MR = e
(−2.62 + 0.115 Tb) (r
2 = 0.89) for S. lilium. Free-ranging, radio tagged C. perspicillata exhibited daily depression of body temperature to 33–34 °C. We conclude that hypothermia is an thermoregulatory strategy
that allows phyllostomid bats to adjust metabolic rate to feeding success and the level of fat stores.
Accepted: 20 August 1996 相似文献
6.
Geiser F Brigham RM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):153-162
Previous studies have suggested that Australian long-eared bats (Nyctophilus) differ from northern-hemisphere bats with respect to their thermal physiology and patterns of torpor. To determine whether
this is a general trait of Australian bats, we characterised the temporal organisation of torpor and quantified metabolic
rates and body temperatures of normothermic and torpid Australian bats (Nyctophilus geoffroyi, 7 g and N. gouldi, 10 g) over a range of air temperatures and in different seasons. The basal metabolic rate of normothermic bats was 1.36 ± 0.17 ml g−1 h−1 (N. geoffroyi) and 1.22 ± 0.13 ml g−1 h−1 (N. gouldi), about 65% of that predicted by allometric equations, and the corresponding body temperature was about 36 °C. Below an air
temperature of about 25 °C bats usually remained normothermic for only brief periods and typically entered torpor. Arousal
from torpor usually occurred shortly after the beginning of the dark phase and torpor re-entry occurred almost always during
the dark phase after normothermic periods of only 111 ± 48 min (N. geoffroyi) and 115 ± 66 min (N. gouldi). At air temperatures below 10 °C, bats remained torpid for more than 1 day. Bats that were measured overnight had steady-state
torpor metabolic rates representing only 2.7% (N. geoffroyi) and 4.2% (N. gouldi) of the basal metabolic rate, and their body temperatures fell to minima of 1.4 and 2.3 °C, respectively. In contrast, bats
measured entirely during the day, as in previous studies, had torpor metabolic rates that were up to ten times higher than
those measured overnight. The steady-state torpor metabolic rate of thermoconforming torpid bats showed an exponential relationship
with body temperature (r
2 = 0.94), suggesting that temperature effects are important for reduction of metabolic rate below basal levels. However, the
75% reduction of metabolic rate between basal metabolic rate and torpor metabolic rate at a body temperature of 29.3 °C suggests
that metabolic inhibition also plays an important role. Torpor metabolic rate showed little or no seasonal change. Our study
suggests that Australian Nyctophilus bats have a low basal metabolic rate and that their patterns of torpor are similar to those measured in bats from the northern
hemisphere. The low basal metabolic rate and the high proclivity of these bats for using torpor suggest that they are constrained
by limited energy availability and that heterothermy plays a key role in their natural biology.
Accepted: 22 November 1999 相似文献
7.
M. Helanto K. Kiviharju T. Granström M. Leisola A. Nyyssölä 《Applied microbiology and biotechnology》2009,83(1):77-83
l-Ribose is a rare and expensive sugar that can be used as a precursor for the production of l-nucleoside analogues, which are used as antiviral drugs. In this work, we describe a novel way of producing l-ribose from the readily available raw material l-arabinose. This was achieved by introducing l-ribose isomerase activity into l-ribulokinase-deficient Escherichia coli UP1110 and Lactobacillus plantarum BPT197 strains. The process for l-ribose production by resting cells was investigated. The initial l-ribose production rates at 39°C and pH 8 were 0.46 ± 0.01 g g−1 h−1 (1.84 ± 0.03 g l−1 h−1) and 0.27 ± 0.01 g g−1 h−1 (1.91 ± 0.1 g l−1 h−1) for E. coli and for L. plantarum, respectively. Conversions were around 20% at their highest in the experiments. Also partially purified protein precipitates
having both l-arabinose isomerase and l-ribose isomerase activity were successfully used for converting l-arabinose to l-ribose. 相似文献
8.
J. Hall I. A. Macdonald P. J. Maddison J. P. O''Hare 《European journal of applied physiology and occupational physiology》1998,77(3):278-284
This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise
on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water
temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h−1. Oxygen consumption (V˙O2) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing
speed both in water and on land. At 3.5 km · h−1
V˙O2 was similar across procedures [χ = 0.6 (0.05) l · min−1]. At 4.5 and 5.5 km · h−1
V˙O2 was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm:
0.8 and 0.9 l · min−1, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at
4.5 and 5.5 km · h−1 (P ≤ 0.003). The HR-V˙O2 relationship showed that at a V˙O2 of 0.9 l · min−1, HR was higher in water at 36°C (115 beats · min−1) than either on land (100 beats · min−1) or in water at 28°C (99 beats · min−1). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h−1 was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was
27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data
has implications for therapists working in hydrotherapy pools.
Accepted: 3 September 1997 相似文献
9.
Bustard MT McEvoy EM Goodwin JA Burgess JG Wright PC 《Applied microbiology and biotechnology》2000,54(3):424-431
The aerobic biodegradation of high concentrations of 1-propanol and 2-propanol (IPA) by a mixed microbial consortium was
investigated. Solvent concentrations were one order of magnitude greater than any previously reported in the literature. The
consortium utilized these solvents as their sole carbon source to a maximum cell density of 2.4 × 109 cells ml−1. Enrichment experiments with propanol or IPA as carbon sources were carried out in batch culture and maximum specific growth
rates (μmax) calculated. At 20 °C, μ
max values were calculated to be 0.0305 h−1 and 0.1093 h−1 on 1% (v/v) IPA and 1-propanol, respectively. Growth on propanol and IPA was carried out between temperatures of 10 °C and
45 °C. Temperature shock responses by the microbial consortium at temperatures above 45 °C were demonstrated by considerable
cell flocculation. An increase in propanol substrate concentration from 1% (v/v) to 2% (v/v) decreased the μ
max from 0.1093 h−1 to 0.0715 h−1. Maximum achievable biodegradation rates of propanol and IPA were 6.11 × 10−3% (v/v) h−1 and 2.72 × 10−3% (v/v) h−1, respectively. Generation of acetone during IPA biodegradation commenced at 264 h and reached a maximum concentration of
0.4% (v/v). The results demonstrate the potential of mixed microbial consortia in the bioremediation of solvent-containing
waste streams.
Received: 14 December 1999 / Received revision: 3 April 2000 / Accepted: 7 April 2000 相似文献
10.
D. A. Gray S. K. Maloney 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(8):558-562
The relationship between body temperature (T
b) and the plasma concentrations of arginine vasotocin (AVT) and angiotensin II (AII) was examined in conscious, adult Pekin
ducks. Exposure of birds to an ambient temperature of 40 °C for 3 h increased T
b by about 1.5 °C and increased breathing rate five-fold. Plasma osmolality was elevated from the normothermic value of 294.9 ± 1.4
mosmol kg−1 by about 8 mosmol kg−1 Circulating AVT levels increased by about 2 pg ml−1 from a basal concentration of 4.98 ± 0.15 pg ml−1, a rise which could be accounted for by the change in osmotic status. Plasma AII concentrations were unchanged from the pre-heat
exposure value of 31.8 ± 3.4 pg ml−1. Time control birds, exposed only to an ambient temperature of 22 °C demonstrated no significant changes in any of the measured
variables. The results suggest that an increased T
b has no direct effect on the circulating concentrations of AVT or AII in ducks.
Accepted: 2 June 1997 相似文献
11.
Booth DT Thompson MB Herring S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):269-276
Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 °C and 30 °C. Incubation periods were significantly longer at 25 °C in both species, and
temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 °C; 23.1 days at 30 °C) than L. guichenoti (40.1 days at 25 °C; 27.7 days at 30 °C). Patterns of oxygen consumption were similar in both species at both temperatures,
being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature
resulted in higher peak and higher pre-hatch rates of oxygen consumption in both species. Total amount of oxygen consumed
during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 °C consumed significantly more (32.6 ml) than eggs incubated at 25 °C (28.5 ml). Hatchling mass was unaffected
by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic
production cost of hatchling B. duperreyi (3.52 kJ · g−1) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 °C (4.00 kJ · g−1) than at 25 °C (3.47 kJ · g−1). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 °C had longer tails (29.3 mm) than those from eggs incubated at 25 °C (26.2 mm). These results indicate that
incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling
morphology.
Accepted: 27 January 2000 相似文献
12.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
13.
C. M. Todd 《Polar Biology》1997,18(3):166-171
The influence of feeding state on cold-adapted metabolism was investigated in the adults of two carabid beetles, Trechisibus antarcticus and Oopterus soledadinus (Coleoptera: Carabidae), which have been introduced to sub-Antarctic South Georgia. The metabolic rates in both fed and starved
O. soledadinus and T. antarcticus were determined at eight temperatures ranging from 0 to 35°C, using a Servomex 570A oxygen analyser. There was no significant
difference in the metabolic rates between the fed and starved animals of each species. In T. antarcticus this ranged from 0.28 to 3.84 ml O2 g−1 h−1, and in O. soledadinus from 0.19 to 2.80 ml O2 g−1 h−1 at 0 and 35°C, respectively. In each of the four experimental groups there was a strong positive correlation between metabolic
rate and temperature, with the highest increase occurring between 0 and 5°C. In contrast, the metabolic rate was significantly
negatively correlated with initial live weight of the beetles at most temperatures. The results are discussed comparatively
with other species and against a background of the ecology of the two carabids at South Georgia.
Received: 26 August 1996 / Accepted: 3 February 1997 相似文献
14.
P. Pfeiffer B. M. Culik 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(2):143-148
We used a still-water swim channel in conjunction with open-flow oxygen and carbon dioxide respirometry to examine the energy
requirements of river-otters (Lutra lutra L.) swimming voluntarily underwater in Neumünster Zoo (Germany). While at rest on land (5 °C), river-otters had a respiratory
quotient of 0.77 and a resting metabolic rate of 4.1 W kg−1. This increased to an estimated 6.4 W kg−1 during rest in water (11–15 °C) and to 12.3 W kg−1 when the animals were feeding in the channel. River-otters swimming under water preferred a mean speed of 0.89 m s−1, and their energy requirements attained 11.6 W kg−1. Cost of transport, however, was minimal at 1.3 m s−1 and amounted to 0.95 J N−1 m−1.
Accepted: 3 November 1997 相似文献
15.
Yoshida A Nishimura T Kawaguchi H Inui M Yukawa H 《Applied microbiology and biotechnology》2007,74(4):754-760
A three-step biohydrogen production process characterized by efficient anaerobic induction of the formate hydrogen lyase (FHL)
of aerobically grown Escherichia coli was established. Using E. coli strain SR13 (fhlA
++, ΔhycA) at a cell density of 8.2 g/l medium in this process, a specific hydrogen productivity (28.0 ± 5.0 mmol h−1 g−1 dry cell) of one order of magnitude lower than we previously reported was realized after 8 h of anaerobic incubation. The
reduced productivity was attributed partly to the inhibitory effects of accumulated metabolites on FHL induction. To avoid
this inhibition, strain SR14 (SR13 ΔldhA ΔfrdBC) was constructed and used to the effect that specific hydrogen productivity increased 1.3-fold to 37.4 ± 6.9 mmol h−1 g−1. Furthermore, a maximum hydrogen production rate of 144.2 mmol h−1 g−1 was realized when a metabolite excretion system that achieved a dilution rate of 2.0 h−1 was implemented. These results demonstrate that by avoiding anaerobic cultivation altogether, more economical harvesting
of hydrogen-producing cells for use in our biohydrogen process was made possible. 相似文献
16.
Willis CK Turbill C Geiser F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(7):479-486
Data on thermal energetics for vespertilionid bats are under-represented in the literature relative to their abundance, as
are data for bats of very small body mass. Therefore, we studied torpor use and thermal energetics in one of the smallest
(4 g) Australian vespertilionids, Vespadelus vulturnus. We used open-flow respirometry to quantify temporal patterns of torpor use, upper and lower critical temperatures (T
uc and T
lc) of the thermoneutral zone (TNZ), basal metabolic rate (BMR), resting metabolic rate (RMR), torpid metabolic rate (TMR),
and wet thermal conductance (C
wet) over a range of ambient temperatures (T
a). We also measured body temperature (T
b) during torpor and normothermia. Bats showed a high proclivity for torpor and typically aroused only for brief periods. The
TNZ ranged from 27.6°C to 33.3°C. Within the TNZ T
b was 33.3±0.4°C and BMR was 1.02±0.29 mlO2 g−1 h−1 (5.60±1.65 mW g−1) at a mean body mass of 4.0±0.69 g, which is 55 % of that predicted for a 4 g bat. Minimum TMR of torpid bats was 0.014±0.006 mlO2 g−1 h−1 (0.079±0.032 mW g−1) at T
a=4.6±0.4°C and T
b=7.5±1.9. T
lc and C
wet of normothermic bats were both lower than that predicted for a 4 g bat, which indicates that V. vulturnus is adapted to minimising heat loss at low T
a. Our findings support the hypothesis that vespertilionid bats have evolved energy-conserving physiological traits, such as
low BMR and proclivity for torpor. 相似文献
17.
Nigel J. Adams Berry Pinshow Leonard Z. Gannes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):444-450
We used tritium-labeled water to measure total body water, water influx (which approximated oxidative water production) and
water efflux in free-flying tippler pigeons (Columba livia) during flights that lasted on average 4.2 h. At experimental air temperatures ranging from 18 to 27 °C, mean water efflux
by evaporation and excretion [6.3 ± 1.3 (SD) ml · h−1, n = 14] exceeded water influx from oxidative water and inspired air (1.4 ± 0.7 ml · h−1, n = 14), and the birds dehydrated at 4.9 ± 0.9 ml · h−1. This was not significantly different from gravimetrically measured mass loss of 6.2 ± 2.1 g · h−1 (t = 1.902, n = 14, P>0.05). This flight-induced dehydration resulted in an increase in plasma osmolality of 4.3 ± 3.0 mosmol · kg−1 · h−1 during flights of 3–4 h. At 27 °C, the increase in plasma osmolality above pre-flight levels (ΔP
osm = 7.6±4.29 mosmol · kg−1 · h−1, n = 6) was significantly higher than that at 18 °C (ΔP
osm = 0.83±2.23 mosmol · kg−1 · h−1, (t = 3.43, n = 6, P < 0.05). Post-flight haematocrit values were on average 1.1% lower than pre-flight levels, suggesting plasma expansion. Water
efflux values during free flight were within 9% of those in the one published field study (Gessaman et al. 1991), and within
the range of values for net water loss determined from mass balance during wind tunnel experiments (Biesel and Nachtigall
1987). Our net water loss rates were substantially higher than those estimated by a simulation model (Carmi et al. 1992) suggesting
some re-evaluation of the model assumptions is required.
Accepted: 8 April 1997 相似文献
18.
Titis Wijayanto Hitoshi Wakabayashi Joo-Young Lee Nobuko Hashiguchi Mohamed Saat Yutaka Tochihara 《International journal of biometeorology》2011,55(4):491-500
The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese)
natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages:
22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating
was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local
sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences
in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m−2 h−1) and Japanese (83.2 ± 6.4 g m−2 h−1) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese
(0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower
on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg
immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution
might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over
the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating
and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical
and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function. 相似文献
19.
H. E. M. Mc Mahon C. T. Kelly W. M. Fogarty 《Applied microbiology and biotechnology》1997,48(4):504-509
The α-amylase of Streptomyces sp. IMD 2679 was subject to catabolite repression. Four different growth rates were achieved when the organism was grown
at 40 °C and 55 °C in the presence and absence of cobalt, with an inverse relationship between α-amylase production and growth
rate. Highest α-amylase yields (520 units/ml) were obtained at the lowest growth rate (0.062 h−1), at 40 °C in the absence of cobalt, while at the highest growth rate (0.35 h−1), at 55 °C in the presence of cobalt, α-amylase production was decreased to 150 units/ml. As growth rate increased, the rate
of specific utilisation of the carbon source maltose also increased, from 46 to 123 μg maltose (mg biomass)−1 h−1. The pattern and levels of α-glucosidase (the enzyme degrading maltose) detected intracellularly in each case, indicate that
growth rate effectively controls the rate of feeding of glucose to the cell, and thus catabolite repression.
Received: 17 February 1997 / Received revision: 29 April 1997 / Accepted: 11 May 1997 相似文献
20.
S. Sánchez V. Bravo E. Castro A. J. Moya F. Camacho 《Applied microbiology and biotechnology》1998,50(5):608-611
We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation
of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature
was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth
of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone.
Thus, at an initial pH of 5.5, the maximum specific production rate (μm) was 0.41 h−1, the overall biomass yield (Y
x/s
G) was 0.12 g g−1, the specific d-xylose-consumption rate (q
s
) was 0.075 g g−1 h−1 (for t = 75 h), the specific xylitol-production rate (q
Xy
) was 0.31 g g−1 h−1 (for t = 30 h) and the overall yields of ethanol (Y
E/s
G) and xylitol (Y
Xy/s
G) were 0.017 and 0.61 g g−1 respectively. Both q
s
and q
Xy
decreased during the course of the experiments once the exponential growth phase had finished.
Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998 相似文献