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1.
Gerhard Heldmaier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1975,102(2):115-122
Summary Djungarian hamsters,Phodopus sungorus (31.1 g body weight) were exposed to ambient temperatures (T
a
) between –35°C and +34°C. They tolerated severe cold stress but were less able to withstand heat. At –35° CT
a
, normal body temperature was maintained for several hours. Thereby maximum thermal insulation was calculated at 1.1 g·°C/mW, which is only slightly higher than expected from the hamsters body size. High levels of heat production (60 to 90 m W/g) were maintained for several hours, suggesting that well developed means of heat production are the main reason for cold tolerance of the Djungarian hamster. 相似文献
2.
Qing-Sheng Chi De-Hua Wang 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):91-103
The adjustments in thermal physiology and energetics were investigated in male desert hamsters (Phodopus roborovskii) which were acclimated to 5°C for 4 weeks. Mean core body temperature in cold acclimated animals decreased by 0.21°C compared
with controls. Further analysis revealed that the decrease mainly occurred in the scotophase, while in the photophase core
body temperature remained constant during the whole cold acclimation. Thermogenic capacity, represented by resting metabolic
rate and nonshivering thermogenesis increased in cold acclimated hamsters from initial values of 1.38 ± 0.05 and 5.32 ± 0.30
to 1.77 ± 0.08 and 8.79 ± 0.31 mlO2 g−1 h−1, respectively. After cold acclimation, desert hamsters maintained a relative stable body mass of 21.7 ± 0.1 g very similar
to the controls kept at 23°C (21.8 ± 0.1 g). The mean values of food intake and digestible energy (metabolisable energy) in
cold acclimated hamsters were 5.3 ± 0.1 g day−1 and 76.3 ± 0.9 kJ day−1 (74.8 ± 0.9), respectively, which were significantly elevated by 76.7 and 80.4% compared to that in control group. The apparent
digestibility was 81.0 ± 0.3% in cold acclimated animals which was also higher than the 79.7 ± 0.2% observed in controls.
This increase corresponded with adaptive adjustments in morphology of digestive tracts with 20.2 and 36.8% increases in total
length and wet mass, respectively. Body fat mass and serum leptin levels in cold acclimated hamsters decreased by 40.7 and
67.1%, respectively. The wheel running turns and the onset of wheel running remained unchanged. Our study indicated that desert
hamsters remained very active during cold acclimation and displayed adaptive changes in thermal physiology and energy metabolism,
such as enhanced thermogenic and energy processing capacities. 相似文献
3.
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
4.
Shawna A. Karpovich Øivind Tøien C. Loren Buck Brian M. Barnes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(6):691-700
Arctic ground squirrels overwintering in northern Alaska experience average soil temperature of −10°C. To examine energetic
costs of arousing from hibernation under arctic compared to temperate conditions, captive ground squirrels were maintained
in ambient temperatures (T
a) of 2, −5 and −12°C. Rates of oxygen consumption and carbon dioxide production were used to estimate metabolic rate and fuel
use during the three phases of arousal episodes: rewarming, euthermia, and recooling. Respiratory quotient comparisons suggest
exclusive use of lipid during rewarming and mixed fuel use during euthermia. Animals rewarming from torpor at T
a −12°C took longer, consumed more oxygen, and attained higher peak rates of oxygen consumption when compared to 2°C. T
a had no significant effect on cost or duration of the euthermic phase. Animals recooled faster at −12°C than at 2°C, but total
oxygen consumption was not different. T
a had no significant effect on the total cost of arousal episodes when all three phases are included. Arousal episodes account
for 86% of estimated costs of a complete hibernation cycle including torpor when at 2°C and only 23% at −12°C. Thus, due to
the higher costs of steady-state metabolism during torpor, proportional metabolic costs of arousal episodes at T
a characteristic of the Arctic are diminished compared to relative costs of arousals in more temperate conditions. 相似文献
5.
W. Bartels B. S. Law F. Geiser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(3):233-239
Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics
and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats
showed a large variation in body temperature (T
b) (33 to 37 °C) over a wide range of ambient temperatures (T
as) and a relatively low basal metabolic rate (1.29 ml O2 g−1 h−1). Bats entered torpor frequently in the laboratory at T
as between 14 and 25 °C. Entry into torpor always occurred when lights were switched on in the morning, independent of T
a. MRs during torpor were reduced to about 20–40% of normothermic bats and T
bs were regulated at a minimum of 23.1 ± 1.4 °C. The duration of torpor bouts increased with decreasing T
a in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum T
b and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the T
b was also about 5 °C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected
by T
a and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor.
Accepted: 22 September 1997 相似文献
6.
Six Angus steers (319 ± 8.5 kg) were assigned to one of two groups (hot or cold exposure) of three steers each, and placed
into two environmental chambers initially maintained at 16.5–18.8°C air temperature (T
a). Cold chamber T
a was lowered to 8.4°C, while T
a within the hot chamber was increased to 32.7°C over a 24-h time period. Measurements included respiration rate, and air and
body (rectal and skin) temperatures. Skin temperature was measured at shoulder and rump locations, with determination of sweat
rate using a calibrated moisture sensor. Rectal temperature did not change in cold or hot chambers. However, respiration rate
nearly doubled in the heat (P < 0.05), increasing when T
a was above 24°C. Skin temperatures at the two locations were highly correlated (P < 0.05) with each other and with T
a. In contrast, sweat rate showed differences at rump and shoulder sites. Sweat rate of the rump exhibited only a small increase
with T
a. However, sweat rate at the shoulder increased more than four-fold with increasing T
a. Increased sweat rate in this region is supported by an earlier report of a higher density of sweat glands in the shoulder
compared to rump regions. Sweat rate was correlated with several thermal measurements to determine the best predictor. Fourth-order
polynomial expressions of short-term rectal and skin temperature responses to hot and cold exposures produced r values of 0.60, 0.84, and 0.98, respectively. These results suggest that thermal inputs other than just rectal or skin temperature
drive the sweat response in cattle. 相似文献
7.
Johannes Rafael Pavel Vsiansky Gerhard Heldmaier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(4):521-528
Summary The composition and oxidative capacity of brown adipose tissue (BAT) were investigated in Djungarian hamsters kept under natural photoperiod, either indoors at neutralT
a (23°C) or under outdoor conditions. BAT comprises up to 5% of the body weight in summer/indoor hamster, with lipid representing 86% of the total tissue mass. Tissue mass and thermogenic capacity are inversely related during seasonal adaptation: 30% decrease of total DNA, accompanied by extensive lipid depletion, reduces the amount of BAT by almost 60% during acclimatization from summer/indoor to winter/outdoor conditions. Mitochondrial protein in BAT is increased by a factor of 2.6 concomitantly, and by a factor of 4 when related to body weight (body weight reduction 36%).Cytochrome oxidase activity in different brown fat deposits varies by up to 150% in summer/indoor hamsters; depending on the fat pad, the enzyme activity is increased 200%–700% during adaptation to winter/outdoor conditions.Natural photoperiod is decisive in determining the seasonal adaptation of DNA content in BAT and of body weight. Short photoperiod alone may lead to depletion of lipid content of BAT and thus decrease the tissue mass practically to the lowest seasonal level, even though both parameters may be also influenced byT
a. One third of the maximum adaptive increase of tissue mitochondria may be attributed to seasonal changes in photoperiod and up to two thirds toT
a. Photoperiod establishes a fixed fundament of slow-reacting functional adaptation of BAT, whereas the effect of decreasedT
a depends on the rate and duration of cold influence.Abbreviations
BAT
brown adipose tissue
-
NST
nonshivering thermogenesis
-
T
a
ambient temperature 相似文献
8.
Seasonal control of energy requirements for thermoregulation in the djungarian hamster (Phodopus sungorus), living in natural photoperiod 总被引:4,自引:4,他引:0
Gerhard Heldmaier Stephan Steinlechner 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,142(4):429-437
Summary Djungarian dwarf hamsters,Phodopus s. sungorus, were kept in natural photoperiodic conditions throughout the year, either inside at a constantT
a of 23°C or outside subjected to seasonally varyingT
a. Comparisons were made between hamsters from both conditions to evaluate the significance of seasonal changes in photoperiod and/orT
a as environmental cues for seasonal acclimatization inPhodopus. Basal metabolic rate was lowest in July (1.68 ml/g·h) and highest in January (2.06 ml/g·h inPhodopus living outside), combined with a decrease inT
1c from 26°C in July to 20°C in January. This was parallelled by seasonal changes in body weight (summer 42 g, winter 25g), fur colouration, fur depth and the occurrence of short daily torpor.AtT
a below thermoneutrality total energy requirements for thermoregulation in winter acclimatizedPhodopus were found 36% lower than summer values (e.g. at O°CT
a in summer 1,160 mW, in winter 760 mW), which were effected by a combined strategy of reducing body weight (19%) together with improvements of thermal insulation of the body surface (17%). All seasonal changes were similar inPhodopus living inside or outside, suggesting that seasonal changes in photoperiod and not seasonal changes inT
a is the overriding controller for the environmental cueing of seasonality in energy requirements for thermoregulation.This research was supported by the Deutsche Forschungsgemeinschaft (He 990) 相似文献
9.
Mariska Batavia George Nguyen Kristine Harman Irving Zucker 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2013,183(2):269-277
Turkish hamsters (Mesocricetus brandti) are a model organism for studies of hibernation, yet a detailed account of their torpor characteristics has not been undertaken. This study employed continuous telemetric monitoring of body temperature (T b) in hibernating male and female Turkish hamsters at ambient temperatures (T as) of 5 and 13 °C to precisely characterize torpor bout depth, duration, and frequency, as well as rates of entry into and arousal from torpor. Hamsters generated brief intervals of short (<12 h), shallow test bouts (T b > 20 °C), followed by deep torpor bouts lasting 4–6 days at T a = 5 °C and 2–3 days at T a = 13 °C. Females at T a = 5 °C had longer bouts than males, but maintained higher torpor T b; there were no sex differences at T a = 13 °C. Neither body mass loss nor food intake differed between the two T as. Hamsters entered torpor primarily during the scotophase (subjective night), but timing of arousals was highly variable. Hamsters at both T as generated short, shallow torpor bouts between deep bouts, suggesting that this species may be capable of both hibernation and daily torpor. 相似文献
10.
Weathers WW Gerhart KL Hodum PJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(8):561-572
We measured resting metabolic rates at air temperatures between ca. −5 and 30 °C in snow petrels (Pagodroma nivea), cape petrels (Daption capense), Antarctic petrels (Thalassoica antarctica), and Antarctic fulmars (Fulmarus glacialoides). We measured seven age classes for each species: adults, and nestlings that were 3, 8, 15, 28, 35, and 42 days old. Basal
metabolic rate (BMR) and thermal conductance (C) of adults averaged, respectively, 140% and 100% of values predicted allometrically
for nonpasserine birds. Minimum metabolic rates of unfasted nestlings aged 15–42 days averaged, respectively, 97% and 98%
of predicted adult BMR in Antarctic petrels and snow petrels, versus 119% and 126% of predicted in Antarctic fulmars and cape
petrels. Nestlings of the southerly breeding snow petrel and Antarctic petrel were relatively well insulated compared with
nestlings of other high-latitude seabirds. Adult lower critical temperature (Tlc) was inversely related to body mass and averaged 9 °C lower than predicted allometrically. As nestlings grew, their Tlc decreased with increasing body mass from ca. 14 to 22 °C (depending upon species) at 3 days of age, to −4 to 8 °C when nestlings
attained peak mass. Nestling Tlc subsequently increased as body mass decreased during pre-fledging weight recession. Nestling Tlc was close to mean air temperature from the end of brooding until fledging in the three surface nesting species.
Accepted: 12 July 2000 相似文献
11.
Studied was the effect of temperature in the range 12–46 °C on the rate of bacterial decolorization of the mono-azo dye Acid
Orange 7 by Alcaligenes faecalis 6132 and Rhodococcus erythropolis 24. With both strains the raise of temperature led to a corresponding raise of decolorization rate better manifested by R. erythropolis. The analysis of the Arrhenius plot revealed a break near the middle of the temperature range. The regression analysis showed
practically complete identity of the observed break point temperatures (T
BP): 20.7 °C for Alc. faecalis and 20.8 °C for R. erythropolis. The values of the activation energy of the decolorization reaction (E
a) were found to depend on both the organism and the temperature range. In the range below T
BP the estimated values of E
a were 138 ± 7 kJ mol−1 for Alc. faecalis and 160 ± 8 kJ mol−1 for R. erythropolis. In the range above T
BP they were 54.2 ± 1.8 kJ mol−1 for Alc. faecalis and 37.6 ± 4.1 kJ mol−1 for R. erythropolis. Discussed are the possible reasons for the observed abrupt change of the activation energy. 相似文献
12.
R. Arieli D. Kerem A. Gonen I. Goldenberg O. Shoshani Y. I. Daskalovic A. Shupak 《European journal of applied physiology and occupational physiology》1997,76(1):69-74
A wet suit may not provide adequate thermal protection when diving in moderately cold water (17–18°C), and any resultant
mild hypothermia may impair performance during prolonged diving. We studied heat exchange during a dive to a depth of 5 m
in sea water (17–18.5°C) in divers wearing a full wet suit and using closed-circuit oxygen breathing apparatus. Eight fin
swimmers dived for 3.1 h and six underwater scooter (UWS) divers propelled themselves through the water for 3.7 h. The measurements
taken throughout the dive were the oxygen pressure in the cylinder and skin and rectal temperatures (T
re). Each subject also completed a cold score questionnaire. The T
re decreased continuously in all subjects. Oxygen consumption in the fin divers (1.40 l · min−1) was higher than that of the UWS divers (1.05 l · min−1). The mean total insulation was 0.087°C · m2 · W−1 in both groups. Mean body insulation was 37% of the total insulation (suit insulation was 63%). The reduction in T
re over the 1st hour was related to subcutaneous fat thickness. There was a correlation between cold score and T
re at the end of 1 h, but not after that. A full wet suit does not appear to provide adequate thermal protection when diving
in moderately cold water.
Accepted: 21 January 1997 相似文献
13.
Temperature response curves of chlorophyll a fluorescence parameters were used to assess minimum sub-zero temperature assuring functioning of photosynthetic photochemical
processes in photosystem II (PS II) of Antarctic lichens. Umbilicaria Antarctica and Xanthoria elegans were measured within the temperature range from −20 to +10°C by a fluorometric imaging system. For potential (F
V/F
M) and actual (Φ
II) quantum yields of photochemical processes the minimum temperature was found to be between −10 and −20°C. Non-photochemical
quenching (NPQ) of absorbed excitation energy increased with temperature drop reaching maximum NPQ at −15°C. Image analysis
revealed intrathalline heterogeneity of chlorophyll a fluorescence parameters with temperature drop. Temperature response of Φ
II exhibited an S-curve with pronounced intrathalline differences in X. elegans. The same relation was linear with only limited intrathalline difference in U. antarctica. The results showed that Antarctic lichen species were well adapted to sub-zero temperatures and capable of performing primary
photosynthesis at −15°C. 相似文献
14.
Heterothermy in the southern African hedgehog, <Emphasis Type="Italic">Atelerix frontalis</Emphasis>
Hallam SL Mzilikazi N 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(3):437-445
Most research on mammalian heterothermic responses in southern Africa tends to be laboratory based and biased towards rodents
and smaller members of the Afrotheria. In this study, we continuously measured body temperature of southern African hedgehogs
(Atelerix frontalis) between April and August 2009 (−10°C < T
a < 43°C), kept under semi-captive conditions. A. frontalis showed a high propensity for torpor with animals spending up to 84% of the measurement period torpid. During this study,
A. frontalis displayed the lowest T
b min (ca 1°C) yet recorded in an Afrotropical placental heterotherm. Bout lengths of between 0.7 h (40 min) and 116.3 h (4.8 days)
were recorded. Differences in bout length were observed between lighter individuals compared with an individual exhibiting
a higher body mass at the onset of winter, with low M
b individuals exhibiting daily torpor whereas a heavier individual exhibited torpor bouts that were indicative of hibernation.
Our results suggest that heterothermic responses are an important feature in the energy balance equation of this species and
that body mass at the onset of winter may determine the patterns of heterothermy utilised in this species. 相似文献
15.
A. Ancel L. Petter R. Groscolas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):533-539
The triggering of transitory egg desertion in fasting and incubating blue petrels (Halobaena caerulea, nocturnal burrowing seabirds living in the subantarctic region) was investigated by continuously monitoring both body temperature
(T
sto) and egg temperature (T
egg) with a telemetry system, and by measuring body mass (BM) loss. The birds were kept captive in their burrow and incubated
day and night without any interruption; there was no day-night cycle in T
sto and T
egg, which averaged 39.9 °C and 32.0 °C, respectively. There was no evidence of hypothermia as a way to save energy in this fasting
situation. Egg desertion occurred at night and was an abrupt and definitive phenomenon reflected by a simultaneous fall in
T
egg and a peak in T
sto. After egg desertion, a distinct day-night cycle of body temperature was observed, T
sto being 0.6 °C higher during night-time (P < 0.05), probably reflecting increased nocturnal activity. BM at egg desertion averaged 166.7 ± 3.8 g in telemetered birds
and 164.4 ± 1.6 g in␣a group of free-living birds. Throughout fasting, the␣specific daily BM loss remained at 46 ± 1 g · kg−1 · day−1, but increased sharply below a critical BM of 160.0 ± 2.5 g. Thus, fasting incubating blue petrels spontaneously desert their
egg when reaching a BM threshold. This BM is very close to a critical value in fasting birds and mammals that corresponds
to a critical depletion of fat stores and to a shift from lipid to protein utilization. This strongly suggests that such a
metabolic shift triggers behavioural changes leading to egg desertion and refeeding, which is of great relevance to the understanding
of the long-term control of food intake and BM.
Accepted: 16 July 1998 相似文献
16.
Vanos JK Warland JS Gillespie TJ Kenny NA 《International journal of biometeorology》2012,56(6):1065-1074
The purpose of this paper is to implement current and novel research techniques in human energy budget estimations to give more accurate and efficient application of models by a variety of users. Using the COMFA model, the conditioning level of an individual is incorporated into overall energy budget predictions, giving more realistic estimations of the metabolism experienced at various fitness levels. Through the use of VO2 reserve estimates, errors are found when an elite athlete is modelled as an unconditioned or a conditioned individual, giving budgets underpredicted significantly by −173 and −123 W m−2, respectively. Such underprediction can result in critical errors regarding heat stress, particularly in highly motivated individuals; thus this revision is critical for athletic individuals. A further improvement in the COMFA model involves improved adaptation of clothing insulation (I cl), as well clothing non-uniformity, with changing air temperature (T a) and metabolic activity (M act). Equivalent T a values (for I cl estimation) are calculated in order to lower the I cl value with increasing M act at equal T a. Furthermore, threshold T a values are calculated to predict the point at which an individual will change from a uniform I cl to a segmented I cl (full ensemble to shorts and a T-shirt). Lastly, improved relative velocity (v r) estimates were found with a refined equation accounting for the degree angle of wind to body movement. Differences between the original and improved v r equations increased with higher wind and activity speeds, and as the wind to body angle moved away from 90°. Under moderate microclimate conditions, and wind from behind a person, the convective heat loss and skin temperature estimates were 47 W m−2 and 1.7°C higher when using the improved v r equation. These model revisions improve the applicability and usability of the COMFA energy budget model for subjects performing physical activity in outdoor environments. Application is possible for other similar energy budget models, and within various urban and rural environments. 相似文献
17.
Cold prevents the light induced inactivation of pineal N-acetyltransferase in the Djungarian hamster,Phodopus sungorus 总被引:1,自引:0,他引:1
Ariane Stieglitz Stephan Steinlechner Thomas Ruf Gerhard Heldmaier 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(5):599-603
Summary In the Djungarian hamster seasonal acclimatization is primarily controlled by photoperiod, but exposure to low ambient temperature amplifies the intensity and duration of short day-induced winter adaptations. The aim of this study was to test, whether the pineal gland is involved in integrating both environmental cues. Exposure of hamsters to cold (0 °C) reduces the sensitivity of the pineal gland to light at night and prevents inactivation of N-acetyltransferase (NAT). The parallel time course of NAT activity and plasma norepinephrine content suggests that circulating catecholamines may stimulate melatonin synthesis under cold load.Abbreviations
NAT
N-acetyltransferase
- NE
norepinephrine
-
T
a
ambient temperature 相似文献
18.
Chlorogenic acid, 3’-O-caffeoyl D-quinic acid, is an inherent ligand present inHelianthus annuus L. The effect of pH on chlorogenic acid binding to helianthinin suggests that maximum binding occurs at pH 6.0. The protein-polyphenol
complex precipitates as a function of time. The association constant of the binding of chlorogenic acid to helianthinin, determined
by equilibrium dialysis, at 31°C has a value of 3.5 ± 0.1 × 104M−-1 resulting in a ΔG value of − 6.32 ± 0.12 kcal /mol. The association constantK
ais 1.0 ± 0.1 × 104M−1 as determined by ultraviolet difference spectral titration at 25°C with ΔG° of -5.46 ± 0.06 kcal/mol. From fluorescence spectral
titration at 28°C, theK
avalue is 1.38 ± 0.1 × 1 0 4M−1 resulting in a ΔG of − 5.70 ± 0.05 kcal/mol. The total number of binding sites on the protein are 420 ± 50 as calculated
from equilibrium dialysis. Microcalorimetric data of the ligand-protein interaction at 23°C suggests mainly two classes of
binding. The thermal denaturation temperature,T
mof the protein decreases from 76°C to 72°C at 1 × 10−3M chlorogenic acid concentration upon complexation. This suggests that the complexation destabilizes the protein. The effect
of temperature onK
aof chlorogenic acid shows a nonlinear increase from 10.2°C to 45°C. Chemical modification of both lysyl and tryptophanyl residues
of the protein decreases the strength of binding of chlorogenic acid. Lysine, tryptophan and tyrosine of protein are shown
to be present at the binding site. Based on the above data, it is suggested that charge-transfer complexation and entropically
driven hydrophobic interaction are the predominant forces that are responsible for binding of chlorogenic acid to the multisubunit
protein, helianthinin.
Publication No. 324. 相似文献
19.
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
20.
H. A. M. Daanen F. J. G. Van de Linde T. T. Romet M. B. Ducharme 《European journal of applied physiology and occupational physiology》1997,76(6):538-543
The relationship between body temperature and the hunting response (intermittent supply of warm blood to cold exposed extremities)
was quantified for nine subjects by immersing one hand in 8°C water while their body was either warm, cool or comfortable.
Core and skin temperatures were manipulated by exposing the subjects to different ambient temperatures (30, 22, or 15°C),
by adjusting their clothing insulation (moderate, light, or none), and by drinking beverages at different temperatures (43,
37 and 0°C). The middle finger temperature (T
fi) response was recorded, together with ear canal (T
ear), rectal (T
re), and mean skin temperature (Tˉ
sk). The induced mean T
ear changes were −0.34 (0.08) and +0.29 (0.03)°C following consumption of the cold and hot beverage, respectively. Tˉ
sk ranged from 26.7 to 34.5°C during the tests. In the warm environment after a hot drink, the initial finger temperature (T
fi,base) was 35.3 (0.4)°C, the minimum finger temperature during immersion (T
fi,min) was 11.3 (0.5)°C, and 2.6 (0.4) hunting waves occurred in the 30-min immersion period. In the neutral condition (thermoneutral
room and beverage) T
fi,base was 32.1 (1.0)°C, T
fi,min was 9.6 (0.3)°C, and 1.6 (0.2) waves occurred. In the cold environment after a cold drink, these values were 19.3 (0.9)°C,
8.7 (0.2)°C, and 0.8 (0.2) waves, respectively. A colder body induced a decrease in the magnitude and frequency of the hunting
response. The total heat transferred from the hand to the water, as estimated by the area under the middle finger temperature
curve, was also dependent upon the induced increase or decrease in T
ear and Tˉ
sk. We conclude that the characteristics of the hunting temperature response curve of the finger are in part determined by core
temperature and Tˉ
sk. Both T
fi,min and the maximal finger temperature during immersion were higher when the core temperature was elevated; Tˉ
sk seemed to be an important determinant of the onset time of the cold-induced vasodilation response.
Accepted: 29 April 1997 相似文献