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1.
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
2.
Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons 总被引:4,自引:0,他引:4
I. Hardewig H. O. Pörtner L. S. Peck 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):597-604
The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q
10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the
leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production.
This parameter shows an unusually high Q
10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed
process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the
presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation
under in vivo conditions if the body temperature of L. nudifrons increases.
Accepted: 2 September 1999 相似文献
3.
D. T. Booth 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):399-404
Incubation temperature and the amount of water taken up by eggs from the substrate during incubation affects hatchling size
and morphology in many oviparous reptiles. The Brisbane river turtle Emydura signata lays hard-shelled eggs and hatchling mass was unaffected by the amount of water gained or lost during incubation. Constant
temperature incubation of eggs at 24 °C, 26 °C, 28 °C and 31 °C had no effect on hatchling mass, yolk-free hatchling mass,
residual yolk mass, carapace length, carapace width, plastron length or plastron width. However, hatchlings incubated at 26 °C
and 28 °C had wider heads than hatchlings incubated at 24 °C and 31 °C. Incubation period varied inversely with incubation
temperature, while the rate of increase in oxygen consumption during the first part of incubation and the peak rate of oxygen
consumption varied directly with incubation temperature. The total amount of oxygen consumed during development and hatchling
production cost was significantly greater at 24 °C than at 26 °C, 28 °C and 31 °C. Hatchling mass and dimensions and total
embryonic energy expenditure was directly proportional to initial egg mass.
Accepted: 18 March 1998 相似文献
4.
R. B. Weinstein G. N. Somero 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(3):190-196
Effects of temperature on O2 consumption by mitochondria of the Antarctic fish Trematomus bernacchii were compared with effects obtained with mitochondria from tropical (Sarotheridon mossambica) and temperate zone fishes (Sebastes carnatus and Sebastes mystinus). Arrhenius plots of O2 consumption versus temperature exhibited slope discontinuities (“breaks”) at temperatures (Arrhenius break temperatures:
ABTs) reflective of the species' adaptation temperatures. The ABT for mitochondria of T. bernacchii is the lowest reported for any animal and is ∼12 °C below the value predicted by a regression equation based on ABT data
for several invertebrates and fishes. The temperature at which the acceptor control ratio (ACR), an index of efficiency of
coupling of electron transport to synthesis of ATP, began to decrease with rising temperature also reflected adaptation temperature.
The decrease in ACR with rising temperature began at ∼18 °C for mitochondria of T. bernacchii, in contrast to ∼35 °C for mitochondria of Sarotheridon mossambica. Maintaining T. bernacchii at 4 °C for 2 weeks led to no changes in ABT or in the response of ACR to temperature. The thermal sensitivities of mitochondria
of T. bernacchii reflect the high level of cold adaptation and stenothermy that is characteristic of Antarctic Notothenioid fishes.
Accepted: 5 January 1998 相似文献
5.
Effects of hypothermic hypoxia on anaerobic energy metabolism in isolated anuran livers 总被引:1,自引:0,他引:1
C. A. Fedorow T. A. Churchill N. M. Kneteman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(8):555-561
Many lower vertebrates (reptilian and amphibian species) are capable of surviving natural episodes of hypoxia and hypothermia.
It is by specific metabolic adaptations that anurans are able to tolerate prolonged exposure to harsh environmental stresses.
In this study, it was hypothesized that livers from an aquatic frog would possess an inherent metabolic ability to sustain
high levels of ATP in an isolated organ system, providing insight into a metabolic system that is well-adapted for low temperature
in vitro organ storage. Frogs of the species, R. pipiens were acclimated at 20 °C and at 5 °C. Livers were preserved using a clinical preservation solution after flushing. Livers
from 20 °C-acclimated frogs were stored at 20 °C and 5 °C and livers from 5 °C-acclimated frogs were stored at 5 °C. The results
indicated that hepatic adenylate status was maintained for 96 h during 5 °C storage, but not longer than 4–10 h during 20 °C
storage. In livers from 5 °C-acclimated animals subjected to 5 °C storage, ATP was maintained at 100% throughout the 96-h
period. Warm acclimation (20 °C) and 20 °C storage resulted in poorer maintenance of ATP; energy charge values dropped to
0.50 within 2 h and by 24 h, only 24% of control ATP remained. Lactate levels remained less than 25 μ mol/g dry weight in
all 5 °C-stored livers; 20 °C-stored livers exhibited greater accumulation of this anaerobic end-product (lactate reached
45–50 μ mol/g by 10 h). The data imply that hepatic adenylate status is largely dependent on exposure to hypothermic hypoxia
and although small amounts of ATP were accounted for by anaerobic glycolysis, there must have been either a substantial reduction
in cellular energy-utilization or an efficient use of low oxygen tensions.
Accepted: 24 August 1998 相似文献
6.
Vincourt V Escriou V Largeau C Bessodes M Scherman D Chaumeil JC Dumortier G 《Cell biology and toxicology》2011,27(5):363-370
Energetic failure which occurs in both ischemia/reperfusion and acute drug-induced hepatotoxicity is frequently associated
with oxidative stress. This study displays the setting of a new cell culture model for hepatic energetic failure, i.e., HepG2
models modified by etomoxir [ETO] addition [0.1 mM to 1 mM] and compares the cell impact versus tert-butylhydroperoxide [TBOOH; 0.2 mM], an oxidative stress inducer. As it was observed with Minimum Essential Medium (MEM) without
any interfering agent, decreasing temperature drastically lowered adenosine triphosphate (ATP) levels, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl
tetrazolium bromide (MTT) viability test, and protein content, compared to 37°C (p = 0.02, p < 0.001 and p < 0.001, respectively), but to a larger extent in the presence of ETO or TBOOH. The alteration was generally highly dependent
on the ETO concentration, time, and temperature. At 37°C 24 h after (T24h), regarding ETO concentration, R2 correlation ratio was 0.65 (p < 0.001), 0.70 (p < 0.001), and 0.89 (p < 0.001) for ATP levels, protein content, and viability, respectively. The lowest ETO concentration producing a significant
effect was 0.25 mM. Concerning time dependency (i.e., T24h versus after 5 h (T5h)), at 37°C with ETO, ATP level continued
to significantly decrease between T5h and T24h. In a similar way, at 37°C, the MTT viability test decrease was accelerated
only between T5h and T24h for ETO concentrations higher than 0.5 mM (p = 0.016 and p = 0.0001 for 0.75 and 1 mM, respectively). On the contrary, with TBOOH, comparing T24h versus T5h, cellular indicators were
improved but generally remained lower than MEM without any interfering agent at T24h, suggesting that TBOOH action was time
limited probably in relation with its oxidation in cell medium. This study confirms the interest of altered ETO cell model
to screen agents (or formulation) prone to prevent or treat energetic depletion in relation with oxidative stress. 相似文献
7.
Wilson RS James RS Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):117-124
Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation
has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial
adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles
and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 °C or 30 °C for 4 weeks
and their burst swimming performance was assessed at four temperatures between 5 °C and 30 °C. Adult X. laevis were acclimated to either 10 °C or 25 °C for 6 weeks and their burst swimming performance and isolated muscle performance
was determined at six temperatures between 5 °C and 30 °C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals.
At the test temperature of 12 °C, maximum swimming velocity of tadpoles acclimated to 12 °C was 38% higher than the 30 °C-acclimation
group, while at 30 °C, maximum swimming velocity of the 30 °C-acclimation group was 41% faster than the 12 °C-acclimation
group. Maximum swimming performance of adult X. laevis acclimated to 10 °C was also higher at the lower temperatures than the 25 °C acclimated animals, but there was no difference
between the treatment groups at higher temperatures. When tested at 10 °C, maximum swimming velocity of the 10 °C-acclimation
group was 67% faster than the 25 °C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 °C produced higher relative tetanic tensions and decreased relaxation times at 10 °C in comparison with
animals acclimated to 25 °C. This is only the second species of amphibian, and the first adult life stage, reported to have
the capacity to thermally acclimate locomotor performance.
Accepted: 28 October 1999 相似文献
8.
Schmid J Ruf T Heldmaier G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):59-68
Thermoregulation, energetics and patterns of torpor in the pygmy mouse lemur, Microcebus myoxinus, were investigated under natural conditions of photoperiod and temperature in the Kirindy/CFPF Forest in western Madagascar.
M. myoxinus entered torpor spontaneously during the cool dry season. Torpor only occurred on a daily basis and torpor bout duration was
on average 9.6 h, and ranged from 4.6 h to 19.2 h. Metabolic rates during torpor were reduced to about 86% of the normothermic
value. Minimum body temperature during daily torpor was 6.8 °C at an ambient temperature of 6.3 °C. Entry into torpor occurred
randomly between 2000 and 0620 hours, whereas arousals from torpor were clustered around 1300 hours within a narrow time window
of less than 4 h. Arousal from torpor was a two-step process with a first passive climb of body temperature to a mean of 27 °C,
carried by the daily increase of ambient temperature when oxygen consumption remained more or less constant, followed by a
second active increase of oxygen consumption to further raise the body temperature to normothermic values. In conclusion,
daily body temperature rhythms in M. myoxinus further reduce the energetic costs of daily torpor seen in other species: they extend to unusually low body temperatures
and consequently low metabolic rates in torpor, and they employ passive warming to reduce the energetic costs of arousal.
Thus, these energy-conserving adaptations may represent an important energetic aid to the pygmy mouse lemur and help to promote
their individual fitness.
Accepted: 2 November 1999 相似文献
9.
Adaptation and acclimation of growth and photosynthesis of five Antarctic red algae to low temperatures 总被引:2,自引:0,他引:2
Temperature requirements for growth, photosynthesis and dark respiration were determined for five Antarctic red algal species.
After acclimation, the stenothermal species Gigartina skottsbergii and Ballia callitricha grew at 0 or up to 5 °C, respectively; the eurythermal species Kallymenia antarctica, Gymnogongrus antarcticus and Phyllophora ahnfeltioides grew up to 10 °C. The temperature optima of photosynthesis were between 10 and 15 °C in the stenothermal species and between
15 and 25 °C in the eurythermal species, irrespective of the growth temperature. This shows that the temperature optima for
photosynthesis are located well below the optima from species of other biogeographical regions, even from the Arctic. Respiratory
rates rose with increasing temperatures. In contrast to photosynthesis, no temperature optimum was evident between 0 and 25 °C.
Partial acclimation of photosynthetic capacity to growth temperature was found in two species. B. callitricha and Gymnogongrus antarcticus acclimate to 0 °C, and 5 and 0 °C, respectively. But acclimation did in no case lead to an overall shift in the temperature
optimum of photosynthesis. B. callitricha and Gymnogongrus antarcticus showed acclimation of respiration to 5 °C, and P. ahnfeltioides to 5 and 10 °C, resulting in a temperature independence of respiration when measured at growth temperature. With respect
to the acclimation potential of the species, no distinction can be made between the stenothermal versus the eurythermal group.
(Net)photosynthetic capacity:respiration (P:R) ratios showed in all species highest values at 0 °C and decreased continuously to values lower than 1.0 at 25 °C. In turn,
the low P:R ratios at higher temperatures are assumed to determine the upper temperature growth limit of the studied species. Estimated
daily carbon balance reached values between 4.1 and 30.7 mg C g−1 FW day−1 at 0 °C, 16:8 h light/dark cycle, 12–40 μmol m−2 s−1.
Received: 4 November 1999 / Accepted: 7 March 2000 相似文献
10.
The effects of light and elevated temperatures on the efficiency of energy conversion in PSII [?PSII = (Fm′−Fs)/Fm′], pigment composition and heat tolerance of shade-acclimated Alocasia macrorrhiza were investigated. Leaf discs were exposed for 3 h to high light (HL; 1600 μmol photons · m−2 · s−1) or low light (LL; 20 μmol photons · m−2 · s−1) and a series of constant temperatures ranging from 30 to 49 °C. All HL treatments led to rapid and severe decreases in ?PSII. During the 2-h recovery period (LL, 25 °C) following the HL treatments, fast and slow recovery phases could be distinguished.
Leaf discs that had experienced HL and 30 °C recovered completely while no recovery of ?PSII was seen after a 3-h exposure to HL and 45 °C. A 3-h exposure to 45 °C at LL led to a less severe decrease in ?PSII and complete recovery was accomplished after less than 1 h. Under LL conditions a temperature of 49 °C was necessary to cause
an irreversible decrease in ?PSII, followed by necrosis the next day. Streptomycin had no effect on the degree of reduction and recovery in ?PSII discs exposed to HL and 35–45 °C, but partially inhibited recovery in discs exposed to HL and 30 °C. Streptomycin led to
a more severe decrease in ?PSII at LL and 49 °C and completely inhibited recovery. Streptomycin had no effect on the conversion of the xanthophyll-cycle
pigments during the treatment or the recovery. The epoxidation state was roughly the same in all leaf discs after a 3-h HL
treatment (0.270–0.346) irrespective of the exposure temperature. The back-conversion of zeaxanthin into violaxanthin after
a 2-h recovery period was only seen in leaf discs that had been exposed to HL and 30 °C. The thermotolerance of shade A. macrorrhiza leaves of 49.0 ± 0.7 °C (determined by fluorescence) coincided with the temperature at which damage occurred in leaf discs
exposed to LL. However, under HL the critical temperature under which necrosis occurred was much lower (42 °C). The thermotolerance
of A. macrorrhiza shade leaves could be increased by a short exposure (<20 min) to slightly elevated temperatures.
Received: 11 June 1997 / Accepted: 9 September 1997 相似文献
11.
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
12.
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
13.
The hypothesis that the Ajime-loach, Niwaella delicata, is guided to groundwater seepages by a positive thermotaxis in autumn, was tested by a field investigation and aquarium-based
experiments. A total of 763 individuals of N. delicata were captured from October to November in a groundwater trap in the Yasu River, Shiga Prefecture. Niwaella delicata began to be captured as the temperature of the surface water fell to 15.8° ± 1.1°C (mean ± SD) and that of the groundwater
to 15.5° ± 0.9°C. Groundwater was often warmer than surface water at night or occasionally all day, and the difference in
temperature reached a maximum of 1.3°C at the night on 5 November. For the diel pattern of captures, nocturnal capture was
higher than diurnal capture when the groundwater was warmer at night and colder during the daytime, whereas both diurnal and
nocturnal captures were high when the groundwater was always warmer than the surface water. The aquarium-based experiments
showed that N. delicata choose warmer water, ranging from 18.4° to 22.2°C, just before the capture period in the Yasu River, and are sensitive to
differences in water temperature of 1.3° ± 0.1°C. Although the present results broadly support the hypothesis, a part of the
results indicates that water temperature gradients may not be the only factor involved in the groundwater selection of N. delicata. 相似文献
14.
A Saccharomyces-cerevisiae-based simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass is limited to an operating temperature
of about 37 °C, and even a small increase in temperature can have a deleterious effect. This points to a need for a more thermotolerant
yeast. To this end, S. cerevisiae D5A and a thermotolerant yeast, Candida acidothermophilum, were tested at 37 °C, 40 °C, and 42 °C using dilute-acid-pretreated poplar as substrate. At 40 °C, C. acidothermophilum produced 80% of the theoretical ethanol yield, which was higher than the yield from S.cerevisiae D5A at either 37 °C or 40 °C. At 42 °C, C. acidothermophilum showed a slight drop in performance. On the basis of preliminary estimates, SSF with C. acidothermophilum at 40 °C can reduce cellulase costs by about 16%. Proportionately greater savings can be realized at higher temperatures
if such a high-temperature SSF is feasible. This demonstrates the advantage of using thermophilic or thermotolerant yeasts.
Received: 20 February 1997 / Received revision: 24 June 1997 / Accepted: 4 July 1997 相似文献
15.
D. J. Hosken P. C. Withers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):71-80
The thermal and metabolic physiology of Chalinolobus gouldii, an Australian vespertilionid bat, was studied in the laboratory using flow-through respirometry. Chalinolobus gouldii exhibits a clear pattern of euthermic thermoregulation, typical of endotherms with respect to body temperature and rate of
oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal metabolic rates
ascribed to vespertilionid bats. However, like most vespertilionid bats, Chalinolobus gouldii displays extreme thermolability. It is able to enter into torpor and spontaneously arouse at ambient temperatures as low
as 5 °C. Torpid bats thermoconform at moderate ambient temperature, with body temperature ≈ ambient temperature, and have
a low rate of oxygen consumption determined primarily by Q
10 effects. At low ambient temperature (< 10 °C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a higher body temperature
at low ambient temperature than do many northern hemisphere hibernating bats. Use of torpor leads to significant energy savings.
The evaporative water loss of euthermic bats is relatively high, which seems unusual for a bat whose range includes extremely
arid areas of Australia, and is reduced during torpor. The thermal conductance of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid bats at intermediate
body temperature and ambient temperature, but increases to euthermic values for torpid bats when thermoregulating at low ambient
temperature.
Accepted: 22 August 1996 相似文献
16.
The influence of low temperature (5–29 °C) on the methanogenic activity of non-adapted digested sewage sludge and on temperature/leachate-adapted
biomass was assayed by using municipal landfill leachate, intermediates of anaerobic degradation (propionate) and methane
precursors (acetate, H2/CO2) as substrates. The temperature dependence of methanogenic activity could be described by Arrhenius-derived models. However,
both substrate and adaptation affected the temperature dependence. The adaptation of biomass in a leachate-fed upflow anaerobic
sludge-blanket reactor at approximately 20 °C for 4 months resulted in a sevenfold and fivefold increase of methanogenic activity
at 11 °C and 22 °C respectively. Both acetate and H2/CO2 were methanized even at 5 °C. At 22 °C, methanogenic activities (acetate 4.8–84 mM) were 1.6–5.2 times higher than those
at 11 °C. The half-velocity constant (K
s) of acetate utilization at 11 °C was one-third of that at 22 °C while a similar K
i was obtained at both temperatures. With propionate (1.1–5.5 mM) as substrate, meth‐anogenic activities at 11 °C were half
those at 22 °C. Furthermore, the residual concentration of the substrates was not dependent on temperature. The results suggest
that the adaptation of biomass enables the achievement of a high treatment capacity in the anaerobic process even under psychrophilic
conditions.
Received: 23 December 1996 / Received last revision: 18 June 1997 / Accepted: 23 June 1997 相似文献
17.
H. Hebestreit O. Bar-Or 《European journal of applied physiology and occupational physiology》1998,78(1):7-12
Heart rate (HR) monitoring is commonly used to assess 24-h energy expenditure (EE) in children but it has been found to overestimate
the true values. One reason for this may be the effect of climatic heat stress on HR. An equation has been previously developed
to adjust HR measured during continuous exercise for the influence of climate. Since play in children is rarely of a continuous
pattern, one objective of this study was to compare the effects of climatic heat stress on the HR response to intermittent
and to continuous exercise. A second objective was to determine whether the previously developed equation is suitable for
intermittent exercise. A group of 12 boys and 8 girls (aged 8–11 years) cycled in a climatic chamber. The exercise consisted
of continuous cycling for 5 min at 35%, 55%, and 75% of peak oxygen up take (random order) followed by alternating cycling
at the same resistance and cadence (30 s) and rest (30 s) for 3 additional min. The oxygen uptake (V˙O2) and HR were determined for 2 min at the end of continuous cycling and for 2 min during intermittent cycling. Climatic conditions
(randomly assigned) were dry bulb temperature T
db 22°C, 50% relative humidity (rh); T
db 28°C, 55% rh; T
db 32°C, 52% rh; or T
db 35°C, 58% rh. The difference between HR measured at a given T
db (HRmeas) and HR at 22°C and at the same V˙O2 was then calculated (ΔHR). The ΔHR increased linearly with increasing temperature but was not related to V˙O2 or to exercise type. However, a small but significant difference was found if the published equation was used with data from
intermittent exercise. The accuracy of the existing equation adjusting HRmeas for the influence of T
db (HRcorr) could be improved to HRcorr= HRmeas · (1.18308−(0.0083218 · T
db)). In conclusion, the effects of climatic heat stress on HR were similar in continuous and intermittent exercise, and HR
can be adjusted for the influence of climate in groups of pre- and early pubertal children during rest, intermittent and continuous
exercise at ambient temperatures between 22°C and 35°C, thereby reducing the error in predicting EE from HR.
Accepted: 13 January 1998 相似文献
18.
In our previous studies, the yeast Endomyces fibuliger LU677 was found to degrade amygdalin in bitter apricot seeds. The present investigation shows that E. fibuliger LU677 produces extracellular β-glycosidase activity when grown in malt extract broth (MEB). Growth was very good at 25 °C
and 30 °C and slightly less at 35 °C. When grown in MEB of pH 5 and pH 6 with addition of 0, 10 or 100 ppm amygdalin, E. fibuliger produced only slightly more biomass at pH 5, and was only slightly inhibited in the presence of amygdalin. Approximately,
60% of the added amygdalin was degraded (fastest at 35 °C) during an incubation period of 5 days. Supernatants of cultures
grown at 25 °C and pH 6 for 5 days were tested for the effects of pH and temperature on activity (using amygdalin, linamarin
and prunasin as substrates). Prunase activity had two pH optima (pH 4 and pH 6), amygdalase and linamarase only one each at
pH 6 and pH 4–5 respectively. The linamarase activity evolved earlier than amygdalase (2 days and 4 days respectively). The
data thus indicate the presence of at least two different glycosidases having different pH optima and kinetics of excretion.
In the presence of amygdalin, lower glycosidase activities were generally produced. However, the amygdalin was degraded from
the start of the growth, strongly indicating an uptake of amygdalin by the cells. The temperature optimum for all activities
was at 40 °C. Activities of amygdalase (assayed at pH 4) and linamarase (at pH 6) evolving during the growth of E. fibuliger were generally higher in cultures grown at 25 °C and 30 °C. TLC analysis of amygdalin degradation products show a two-stage
sequential mechanism as follows: (1) amygdalin to prunasin and (2) prunasin to cyanohydrin.
Received: 16 September 1997 / Received revision: 6 October 1997 / Accepted: 14 October 1997 相似文献
19.
J. A. MacDonald K. B. Storey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):513-525
Arousal from hibernation requires thermogenesis in brown adipose tissue, a process that is stimulated by β-adrenergic signals,
leading to a rise in intracellular 3′,5′-cyclic adenosine monophosphate AMP (cAMP) and activating cAMP-dependent protein kinase
A (PKA) to phosphorylate a suite of target proteins and activate lipolysis and uncoupled respiration. To determine whether
specific adaptations (perhaps temperature-dependent) facilitate PKA kinetic properties or protein-phosphorylating ability,
the catalytic subunit of PKA (PKAc) from interscapular brown adipose of the ground squirrel Spermophilus richardsonii, was purified (final specific activity = 279 nmol phosphate transferred per min per mg protein) and characterized. Physical
properties of PKAc included a molecular weight of 41 kDa and an isoelectric point of 7.8 ± 0.08. A change in assay temperature
from a euthermic value (37 °C) to one typical of hibernating body temperature (5 °C) had numerous significant effects on ground
squirrel PKAc including: (a) pH optimum rose from 6.8 at 37 °C to 8.7 at 5 °C, (b) Km values at 37 °C for Mg.ATP (49.2±3.4 M) and for two phosphate acceptors, Kemptide (50.0±5.5 M) and Histone IIA (0.41 ± 0.05 mg/ml)
decreased by 53%, 80% and 51%, respectively, at 5 °C, and (c) inhibition by KCl, NaCl and NH4Cl was reduced. However, temperature change had little or no effect on Km values of rabbit PKAc, suggesting a specific positive thermal modulation of the hibernator enzyme. Arrhenius plots also differed
for the two enzymes; ground squirrel PKAc showed a break in the Arrhenius relationship at 9 °C and activation energies that
were 29.1 ± 1.0 kJ/mol for temperatures >9 °C and 2.3-fold higher at 68.1 ± 2.1 kJ/mol for temperatures <9 °C, whereas the
rabbit enzyme showed a breakpoint at 17 °C with a 13-fold higher activation energy over the lower temperature range. However,
fluorescence analysis of PKAc in the absence of substrates, showed a linear change in fluorescence intensity and wavelength
of maximal fluorescence over the entire temperature range; this suggested that the protein conformational change indicated
by the break in the Arrhenius plot was substrate-related. Temperature change also affected the Hill coefficient for cAMP dissociation
of the ground squirrel PKA holoenzyme which rose from 1.12 ± 0.18 at 37 °C to 2.19 ± 0.07 at 5 °C, making the release of catalytic
subunits at low temperature much more responsive to small changes in cAMP levels. Analysis of PKAc function via in vitro incubations
of extracts of ground squirrel brown adipose with 32P-ATP + cAMP in the presence versus absence of a PKA inhibitor, also revealed major differences in the patterns of phosphoproteins,
both between euthermic and hibernating animals as well as between 37 and 5 °C incubation temperatures; this suggests that
there are both different targets of PKAc phosphorylation in the hibernating animal and that temperature affects the capacity
of PKAc to phosphorylate different targets. Both of these observations, plus the species-specific and temperature-dependent
changes in ground squirrel PKAc kinetic properties, suggest differential control of the enzyme in vivo at euthermic versus
hibernating body temperatures in a manner that would facilitate a rapid and large activation of the enzyme during arousal
from torpor.
Accepted: 10 July 1998 相似文献
20.
Summary. Heat shock proteins (HSPs) are synthesised by cells subsequent to a stress exposure and are known to confer protection to
the cell in response to a second challenge. HSP induction and decay are correlated to thermotolerance and may therefore be
used as a biomarker of thermal history. The current study tested the temperature-dependent nature of the heat shock response
and characterised its time profile of induction. Whole blood from 6 healthy males (Age: 26 ± (SD) 2 yrs; Body mass 74.2 ±
3.8 kgs; VO2max: 49.1 ± 4.0 ml·kg−1·min−1) were isolated and exposed to in vitro heat shock (HS) at 37, 38, 39, 40, and 41 °C for a period of 90 min. After HS the
temperature was returned to 37 °C and intracellular HSP70 was quantified from the leukocytes at 0, 2, 4, and 6 h after heat
treatment. The concentration of HSP70 was not different between temperatures (P > 0.05), but the time-profile of HSP70 synthesis appeared temperature-dependent. At control (37 °C) and lower temperatures
(38–39 °C) the mean HSP70 concentration increased up to 4 h post HS (P < 0.05) and then returned towards baseline values by 6 h post HS. With in vitro hyperthermic conditions (40–41 °C), the time-profile
was characterised by a sharp rise in HSP70 levels immediately after treatment (P < 0.05 for 40 °C at 0 h), followed by a progressive decline over time. The results suggest a temperature-dependent time-profile
of HSP70 synthesis. In addition, the temperature at which HSP70 is inducted might be lower than 37 °C. 相似文献