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1.
Ø. Tøien J. B. Mercer 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(2):73-80
Hypothalamic temperature (T
hypo) and metabolic heat production (M) were measured in seven conscious rabbits injected intravenously with either saline or
with Staphylococcus aureus, (8 · 107 cell walls · kg−1) while being subjected to a 3-h period of ramp-like total body cooling using a chronically implanted intravascular heat exchanger.
In pyrogen-injected animals cooling started (1) at the time of injection or (2) 70 min after injection. In (1) the fall in
T
hypo induced by heat extraction was similar (1.0 °C) in afebrile and febrile animals. In (2) there was a transient increase in
T
hypo of about 0.5 °C at a time corresponding to the start of fever resulting in a significantly smaller fall in T
hypo at the end of the 3-h cooling period (0.5 °C vs 0.9 °C, P < 0.05, n = 5). At this time in both (1) and (2) M was lower than theoretically expected from the increase in shivering threshold during
fever. However, most of this effect can be explained when available data showing a decrease in thermosensitivity during S. aureus-induced fever are taken into account. After cessation of cooling in both groups of febrile animals T
hypo rose to about 1 °C higher than the precooling level, which is comparable to the fever level in a separate series of experiments
with S. aureus injection without cooling (1.2 °C).
Accepted: 23 September 1997 相似文献
2.
N. J. Adams B. Pinshow L. Z. Gannes H. Biebach 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):195-199
We examined the relationship between body temperature (Tb) of free flying pigeons and ambient water vapor pressure and temperature. Core or near core Tb of pigeons were measured using thermistors inserted into the cloaca and connected to small transmitters mounted on the tail
feathers of free flying tippler pigeons (Columba livia). Wet and dry bulb temperatures were measured using modified transmitters mounted onto free-flying pigeons. These allowed
calculation of relative humidity and hence water vapor pressure at flight altitudes. Mean Tb during flight was 42.0 ± 1.3 °C (n = 16). Paired comparisons of a subset of this data indicated that average in-flight Tb increased significantly by 1.2 ± 0.7 °C (n = 7) over that of birds at rest (t = −4.22, P < 0.05, n = 7) within the first 15 min of takeoff. In addition, there was a small but significant increase in Tb with increasing ambient air (Ta) when individuals on replicate flights (n = 35) were considered. Inclusion of water vapor pressure into the regression model did not improve the correlation between
body temperature and ambient conditions. Flight Tb also increased a small (0.5 °C) but significant amount (t = 2.827, P < 0.05, n = 8) from the beginning to the end of a flight. The small response of Tb to changing flight conditions presumably reflects the efficiency of convection as a heat loss mechanism during sustained
regular flight. The increase in Tb on landing that occurred in some birds was a probable consequence of a sudden reduction in convective heat loss.
Accepted: 2 February 1999 相似文献
3.
Follicle-stimulating hormone (FSH) was produced in Chinese hamster ovary (CHO) cells using a perfusion bioreactor. Perfusion
culture at 37°C yielded a high cell density but a low FSH production. To investigate the effect of culture temperature in
the range of 26–37°C on cell growth and FSH production, batch cultures were performed. Lowering culture temperature below
32°C resulted in growth suppression. However, specific productivity of FSH, q
FSH, increased as culture temperature decreased, and the maximum q
FSH of 43.4 ng/106 cells/h was obtained at 28°C, which is 13-fold higher than that at 37°C. Based on the results obtained from batch cultures,
we performed perfusion cultures with two consecutive temperatures. CHO cells were grown up to 3.2 × 107 cells/ml at 37°C and culture temperature shifted down to 28°C to obtain a high FSH titer. Soon after the maximum FSH titer
of 21 μg/ml was achieved, a rapid loss of not only viable cell concentration but also cell viability was observed, probably
due to the low activities of enzymes related to cell growth. Thus, the extension of production period at 28°C is critical
for the enhancement of FSH production, and the use of antiapoptotic genes seems to be promising. 相似文献
4.
Brain temperature and limits on transcranial cooling in humans: quantitative modeling results 总被引:3,自引:0,他引:3
D. A. Nelson S. A. Nunneley 《European journal of applied physiology and occupational physiology》1998,78(4):353-359
Selective brain cooling (SBC) of varying strengths has been demonstrated in a number of mammals and appears to play a role
in systemic thermoregulation. Although primates lack obvious specialization for SBC, the possibility of brain cooling in humans
has been debated for many years. This paper reports on the use of mathematical modeling to explore whether surface cooling
can control effectively the temperature of the human cerebrum. The brain was modeled as a hemisphere with a volume of 1.33 1
and overlying layers of cerebrospinal fluid, skull, and scalp. Each component was assigned appropriate dimensions, physical
properties and physiological characteristics that were determined from the literature. The effects of blood flow and of thermal
conduction were modeled using the steady-state form of the bio-heat equation. Input parameters included core (arterial) temperature:
normal (37°C) or hyperthermic (40°C), air temperature: warm (30°C) or hot (40°C), and sweat evaporation rate: 0, 0.25, or
0.50 l · m−2 · h−1. The resulting skin temperatures of the model ranged from 31.8°C to 40.2°C, values which are consistent with data obtained
from the literature. Cerebral temperatures were generally insensitive to surface conditions (air temperature and evaporation
rate), which affected only the most superficial level of the cerebrum (≤1.5 mm) The remaining parenchymal temperatures were
0.2–0.3°C above arterial temperatures, regardless of surface conditions. This held true even for the worst-case conditions
combining core hyperthermia in a hot environment with zero evaporative cooling. Modeling showed that the low surface-to-volume
ratio, low tissue conductivity, and high rate of cerebral perfusion combine to minimize the potential impact of surface cooling,
whether by transcranial venous flow or by conduction through intervening layers to the skin or mucosal surfaces. The dense
capillary network in the brain assures that its temperature closely follows arterial temperature and is controlled through
systemic thermoregulation independent of head surface temperature. A review of the literature reveals several independent
lines of evidence which support these findings and indicate the absence of functionally significant transcranial venous flow
in either direction. Given the fact that humans sometimes work under conditions which produce face and scalp temperatures
that are above core temperature, a transcranial thermal link would not necessarily protect the brain, but might instead increase
its vulnerability to environmentally induced thermal injury.
Accepted: 11 March 1998 相似文献
5.
Sanni P. Voutilainen Harry Boer Marika Alapuranen Janne J?nis Jari Vehmaanper? Anu Koivula 《Applied microbiology and biotechnology》2009,83(2):261-272
Two different types of approach were taken to improve the hydrolytic activity towards crystalline cellulose at elevated temperatures
of Melanocarpus albomyces Cel7B (Ma Cel7B), a single-module GH-7 family cellobiohydrolase. Structure-guided protein engineering was used to introduce an additional
tenth disulphide bridge to the Ma Cel7B catalytic module. In addition, a fusion protein was constructed by linking a cellulose-binding module (CBM) and a linker
from the Trichoderma reesei Cel7A to the C terminus of Ma Cel7B. Both approaches proved successful. The disulphide bridge mutation G4C/M70C located near the N terminus, close to the
entrance of the active site tunnel of Ma Cel7B, led to improved thermostability (ΔT
m = 2.5°C). By adding the earlier found thermostability-increasing mutation S290T (ΔT
m = 1.5°C) together with the disulphide bridge mutation, the unfolding temperature was increased by 4°C (mutant G4C/M70C/S290T)
compared to that of the wild-type enzyme, thus showing an additive effect on thermostability. Both disulphide mutants had
increased activity towards microcrystalline cellulose (Avicel) at 75°C, apparently solely because of their improved thermostability.
The addition of a CBM also improved the thermostability (ΔT
m = 2.5°C) and caused a clear (sevenfold) increase in the hydrolysis activity of Ma Cel7B towards Avicel at 70°C. 相似文献
6.
This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994–1995) and autumn (1995). Seasonal patterns of body temperature
(T
b) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To
quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those
estimated for a thermoconforming lizard. The study lizards' field T
bs varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available
operative temperatures (summer: GDM T
max 42.1 ± 1.7°C, T
min 32.2 ± 1.0°C, autumn: GDM T
max 31.7 ± 1.2°C, T
min 26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change
seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting
heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field T
bs from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference
was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative
temperatures rarely precluded lizards from attaining field T
bs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior
appear to have had an important influence on seasonal levels of thermoregulatory effort.
Received: 28 April 1997 / Accepted: 29 December 1997 相似文献
7.
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
8.
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
9.
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
10.
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
11.
Viability and thermal stability of a strain of Saccharomyces cerevisiae freeze-dried in different sugar and polymer matrices 总被引:1,自引:0,他引:1
P. Lodato M. Segovia de Huergo M. P. Buera 《Applied microbiology and biotechnology》1999,52(2):215-220
The viability and thermal stability of a freeze-dried yeast strain were studied in relation to some physical properties of
the matrices in which the cells were freeze-dried. Samples of inoculum with solutions of the matrix components [polyvinylpyrrolidone
(PVP), maltose, trehalose, maltodextrins, or mixtures of maltodextrin and trehalose] and controls without matrices were freeze-dried
and then equilibrated at several relative humidities. Viability was determined before and after freeze-drying and after heat
treatment (100 min at 70 °C). Freeze-drying with trehalose, PVP, maltose or 1.8-kDa maltodextrin, and mixtures of maltodextrin/trehalose
increased viability in comparison with controls. The 3.6-kDa maltodextrin was ineffective at protecting the cells during freeze-drying.
The glass transition temperature (T
g), which depends on moisture content, was indicated as a possible factor to determine the stability of labile materials. Protective
effects of the excipients during thermal treatment were analysed in relation to the physical changes (collapse or structural
shrinkage) which were dependent on the T
g of the systems. The presence of a certain amount of amorphous disaccharides during freeze-drying and heating was found to
be a critical factor for ensuring cell viability, which was protected even in rubbery (above T
g) matrices.
Received: 4 December 1998 / Received last revision: 2 March 1999 / Accepted: 14 March 1999 相似文献
12.
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
13.
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
14.
Human thermal comfort assessments pertaining to exercise while in outdoor environments can improve urban and recreational
planning. The current study applied a simple four-segment skin temperature approach to the COMFA (COMfort FormulA) outdoor
energy balance model. Comparative results of measured mean skin temperature (
[`(T)]\nolimitsMsk \mathop{{\bar{T}}}\nolimits_{{Msk}} ) with predicted
[`(T)]\nolimitssk \mathop{{\bar{T}}}\nolimits_{{sk}} indicate that the model accurately predicted
[`(T)]\nolimitssk \mathop{{\bar{T}}}\nolimits_{{sk}} , showing significantly strong agreement (r = 0.859, P < 0.01) during outdoor exercise (cycling and running). The combined 5-min mean variation of the
[`(T)]\nolimitssk \mathop{{\bar{T}}}\nolimits_{{sk}} RMSE was 1.5°C, with separate cycling and running giving RMSE of 1.4°C and 1.6°C, respectively, and no significant difference
in residuals. Subjects’ actual thermal sensation (ATS) votes displayed significant strong rank correlation with budget scores
calculated using both measured and predicted
[`(T)]\nolimitssk \mathop{{\bar{T}}}\nolimits_{{sk}} (r
s
= 0.507 and 0.517, respectively, P < 0.01). These results show improved predictive strength of ATS of subjects as compared to the original and updated COMFA
models. This psychological improvement, plus
[`(T)]\nolimitssk \mathop{{\bar{T}}}\nolimits_{{sk}} and T
c validations, enables better application to a variety of outdoor spaces. This model can be used in future research studying
linkages between thermal discomfort, subsequent decreases in physical activity, and negative health trends. 相似文献
15.
Tarek S. Awad Thrandur Helgason Kristberg Kristbergsson Eric A. Decker Jochen Weiss D. Julian McClements 《Food biophysics》2008,3(2):155-162
Solid lipid nanoparticle (SLN) suspensions undergo a phase transition from the α- to β-polymorphic forms, which is accompanied
by particle aggregation and gel formation. These processes are both time and temperature dependent, and so it is important
to study the impact of cooling rates (CRs) and heating rates (HRs) on polymorphic transformations, particle aggregation, and
gelation. Rheology measurements indicated that the temperature where gelation was first observed during cooling (T
gel) decreased with increasing CRs, with SLN suspensions remaining fluid at HR ≥ 5 °C/min. On the other hand, the temperature
where gelation was first observed during heating of stable SLN suspensions increased with increasing HRs: 18, 24, 31, and
45 °C at 2, 5, 10, and 20 °C/min, respectively. When the melted SLN suspensions were cooled again, two exothermic peaks were
observed in the differential scanning calorimetry scans at 39 (which was attributed to coalesced oil) and 19 °C (which was
attributed to stable SLN). With increasing CR, the enthalpy of the coalescence peak (ΔH
CO) decreased, while that of the supercooled SLN (ΔH
SLN) increased. With increasing HR, ΔH
CO decreased and ΔH
SLN increased, with no coalescence being observed at HR ≥ 10 °C/min. These results show that increasing the CRs or HRs retard
the α→β polymorphic transformation, which increased the stability of SLN against aggregation and retarded gelation. In addition,
this study shows that the careful selection of HRs and CRs is required to examine polymorphic transformations and the stability
of SLN suspensions. 相似文献
16.
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
17.
F. Aujard M. Perret G. Vannier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):540-548
The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food
availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal
rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in
ambient temperature, evaporative water loss (EWL), body temperature (T
b) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging
from 5 °C to 35 °C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions.
In both photoperiods, EWL, T
b and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 °C was associated
with a decrease in T
b and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in T
b and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed
according to daylength. Daily variations in T
b and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase
of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of T
b decrease with or without the occurrence of torpor (T
b < 33 °C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory
processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.
Accepted: 4 August 1998 相似文献
18.
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
19.
Rahman A Azad MA Hossain I Qusar MM Bari W Begum F Huq SM Hasnat A 《Biological trace element research》2009,127(2):102-108
The purpose of the study was to determine the concentration of trace elements present in scalp hair sample of schizophrenic
patients and to find out the relationship between trace elements level and nutritional status or socioeconomic factors. The
study was conducted among 30 schizophrenic male patients and 30 healthy male volunteers. Patients were recruited from Bangabandhu
Sheikh Mujib Medical University by random sampling. Hair trace element concentrations were determined by flame atomic absorption
spectroscopy and analyzed by independent t test, Pearson’s correlation analysis, regression analysis, and analysis of variance (ANOVA). Mn, Zn, Ca, Cu, and Cd concentrations
of schizophrenic patients were 3.8 ± 2.31 μg/gm, 171.6 ± 59.04 μg/gm, 396.23 ± 157.83 μg/gm, 15.40 ± 5.68 μg/gm, and 1.14 ± 0.89 μg/gm
of hair sample, while those of control subjects were 4.4 ± 2.32 μg/gm, 199.16 ± 27.85 μg/gm, 620.9 ± 181.55 μg/gm, 12.23 ± 4.56 μg/gm,
and 0.47 ± 0.32 μg/gm of hair sample, respectively. The hair concentration of Zn and Ca decreased significantly (p = 0.024; p = 0.000, respectively) and the concentration of Cu and Cd increased significantly (p = 0.021; p = 0.000, respectively) in schizophrenic patients while the concentration of Mn (p = 0.321) remain unchanged. Socioeconomic data reveals that most of the patients were poor, middle-aged and divorced. Mean
body mass indices (BMIs) of the control group (22.26 ± 1.91 kg/m2) and the patient group (20.42 ± 3.16 kg/m2) were within the normal range (18.5−25.0 kg/m2). Pearson’s correlation analysis suggested that only Ca concentration of patients had a significant positive correlation
with the BMI (r = 0.597; p = 0.000) which was further justified from the regression analysis (R
2 = 44%; t = 3.59; p = 0.002) and one-way ANOVA test (F = 3.62; p = 0.015). A significant decrease in the hair concentration of Zn and Ca as well as a significant increase in the hair concentration
of Cu and Cd in schizophrenic patients than that of its control group was observed which may provide prognostic tool for the
diagnosis and treatment of this disease. However, further work with larger population is suggested to examine the exact correlation
between trace element level and the degree of disorder. 相似文献
20.
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