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1.
Migration and reproduction of the Caspian Lamprey, Caspiomyzon wagneri, in the Shirud River were investigated during late-March to early-May at water temperatures ranging from 11 to 21.25°C. We
examined the effect of water temperature on timing of spawning migrations. There was a significant negative relationship between
temperature and intensive migration of Caspian Lamprey (p < 0.05). The most intensive migration of lampreys was at night (21:00–3:00 h) and when the water temperatures averaged 16°C
(34.43%). The overall sex ratio (male to female) was 1.07 to 1. The individual absolute fecundity was 31 ‘758–51’ 198 eggs
(mean±SD—41,924 ± 5,382). The egg diameter was 0.780–1.151 (0.92 ± 0.081) mm. The individual relative fecundity varies from
80.3 to 148.1 (107.2 ± 15.1) eggs per 1 mm of length and from 260.8 to 677.4 (397.6 ± 93) eggs per 1 g of weight. The gonadosomatic
index (GSI) of females was 5.83–31.44 (11.22 ± 4.30). 相似文献
2.
Dimitris G. Sfakianakis Ioannis Leris Maroudio Kentouri 《Environmental Biology of Fishes》2011,90(4):421-427
It is widely known that water temperature affects the swimming capacity of fish. But the effect of the rearing temperature
on the swimming ability of the fish at later stages, has not had similar attention. In this study, four populations of zebrafish,
were reared in different water temperatures (22, 25, 28 and 31°C) and after being acclimatized in a common temperature (26.5°C)
for over a month, they were subjected to swimming trials in order to evaluate the maximum relative critical velocity (RU
crit
) in each case. Fish that were reared in 22°C showed statistically significant lower performance than the ones reared in 31°C
(7.72 ± 0.17 vs. 8.79 ± 0.28, means ± S.E.). Possible explanations for the observed differentiation could be the effect of
early life temperature on fish muscle ontogeny or on body shape. 相似文献
3.
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
4.
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
5.
Satoshi Suzuki Kazushige Furuya Tadashi Kawai Ichiro Takeuchi 《Journal of applied phycology》2008,20(5):833-844
Recent studies on global climate change report that increase in seawater temperature leads to coastal ecosystem change, including
coral bleaching in the tropic. In order to assess the effect of increased seawater temperature on a temperate coastal ecosystem,
we studied the inter-annual variation in productivity of Laminaria japonica using long-term oceanographic observations for the Uwa Sea, southern Japan. The annual productivity estimates for L. japonica were 2.7 ± 2.5 (mean ± SD) kg wet wt. m−1 (length of rope) (2003/2004), 1.0 ± 0.6 kg wet wt. m−1 (2004/2005) and 12.1 ± 12.5 kg wet wt. m−1 (2005/2006). Our previous study using the same methodology at the same locality reported that the productivity was estimated
for the 2001/2002 (33.3 ± 15.2 kg wet wt. m−1) and 2002/2003 (34.0 ± 8.7 kg wet wt. m−1) seasons. Productivity in 2003/2004 and 2004/2005 was significantly lower than in years 2001/2002, 2002/2003 and 2005/2006.
A comparison of oceanographic conditions among the 5 years revealed the presence of threshold seawater temperature effects.
When the average seawater temperature during the first 45 days of each experiment exceeded 15.5°C, productivity was reduced
to about 10 % of that in cooler years. Moreover the analysis of growth and erosion rates indicates that when the seawater
temperature was over 17.5°C, erosion rate exceeded growth rate. Thus, an increase of seawater temperature of just 1°C during
winter drastically reduces the productivity of L. japonica in the Uwa Sea. 相似文献
6.
Little is known about how animals from tropical and subtropical climates adjust their energy expenditure to cope with seasonal
changes of climate and food availability. To provide such information, we studied the thermal physiology, torpor patterns
and energetics of the nocturnal blossom-bat (Syconycteris australis 18 g) from a subtropical habitat in both summer and winter. In both seasons, S. australis frequently entered daily torpor at ambient temperatures between 12 and 25°C when food and water were withheld. Unlike patterns
observed in temperate animals, mean minimum metabolic rates during torpor were lower in summer (0.47 ± 0.07 ml O2 g−1 h−1) than in winter (0.75 ± 0.11 ml O2 g−1 h−1). Body temperatures during torpor were regulated at 19.3 ± 1.0°C in summer and at 23.4 ± 2.0°C in winter. Torpor bout duration
was significantly longer in summer (7.3 ± 0.6 h) than in winter (5.5 ± 0.3 h), but in both seasons, bout duration was not
affected by ambient temperature. Consequently, average daily metabolic rates were also significantly lower in summer than
in winter. Body temperatures and metabolic rates in normothermic bats did not change with season. Our findings on seasonal
changes of torpor in this bat from the subtropics are opposite to those made for many species from cold climates which generally
show deeper and longer torpor in winter and are often entirely homeothermic in summer. More pronounced torpor in subtropical
S. australis in summer may be due to low or unpredictable nectar availability, short nights which limit the time available for foraging,
and long days without access to food. Thus, the reversed seasonal response of this subtropical bat in comparison to temperate
species may be an appropriate response to ecological constraints.
Received: 6 May 1997 / Accepted: 19 October 1997 相似文献
7.
Acinetobacter sp. XMZ-26 (ACCC 05422) was isolated from soil samples obtained from glaciers in Xinjiang Province, China. The partial nucleotide
sequence of a lipase gene was obtained by touchdown PCR using degenerate primers designed based on the conserved domains of
cold-adapted lipases. Subsequently, a complete gene sequence encoding a 317 amino acid polypeptide was identified. Our novel
lipase gene, lipA, was overexpressed in Escherichia coli. The recombinant protein (LipA) was purified by Ni-affinity chromatography, and then deeply characterised. The LipA resulted
to hydrolyse pNP esters of fatty acids with acyl chain length from C2 to C16, and the preferred substrate was pNP octanoate showing a k
cat = 560.52 ± 28.32 s−1, K
m = 0.075 ± 0.008 mM, and a k
cat/K
m = 7,377.29 ± 118.88 s−1 mM−1. Maximal LipA activity was observed at a temperature of 15°C and pH 10.0 using pNP decanoate as substrate. That LipA peaked at such a low temperature and remained most activity between 5°C and 35°C indicated
that it was a cold-adapted enzyme. Remarkably, this lipase retained much of its activity in the presence of commercial detergents
and organic solvents, including Ninol, Triton X-100, methanol, PEG-600, and DMSO. This cold-adapted lipase may find applications
in the detergent industry and organic synthesis. 相似文献
8.
Jeffrey R. Ziegeweid Cecil A. Jennings Douglas L. Peterson 《Environmental Biology of Fishes》2008,82(3):299-307
Many populations of shortnose sturgeon, Acipenser brevirostrum, in the southeastern United States continue to suffer from poor juvenile recruitment. High summer water temperatures, which
may be exacerbated by anthropogenic activities, are thought to affect recruitment by limiting available summer habitat. However,
information regarding temperature thresholds of shortnose sturgeon is limited. In this study, the thermal maximum method and
a heating rate of 0.1°C min−1 was used to determine critical and lethal thermal maxima for young-of-the-year (YOY) shortnose sturgeon acclimated to temperatures
of 19.5 and 24.1°C. Fish used in the experiment were 0.6 to 35.0 g in weight and 64 to 140 days post hatch (dph) in age. Critical
thermal maxima were 33.7°C (±0.3) and 35.1°C (±0.2) for fish acclimated to 19.5 and 24.1°C, respectively. Critical thermal
maxima significantly increased with an increase in acclimation temperature (p < 0.0001). Lethal thermal maxima were 34.8°C (±0.1) and 36.1°C (±0.1) for fish acclimated to 19.5 and 24.1°C, respectively.
Lethal thermal maxima were significantly affected by acclimation temperature, the log10 (fish weight), and the interaction between log10(fish weight) and acclimation temperature (p < 0.0001). Thermal maxima were used to estimate upper limits of safe temperature, thermal preferences, and optimal growth
temperatures of YOY shortnose sturgeon. Upper limits of safe temperature were similar to previous temperature tolerance information
and indicate that summer temperatures in southeastern rivers may be lethal to YOY shortnose sturgeon if suitable thermal refuge
cannot be found. 相似文献
9.
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
10.
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
11.
Booth DT Thompson MB Herring S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):269-276
Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 °C and 30 °C. Incubation periods were significantly longer at 25 °C in both species, and
temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 °C; 23.1 days at 30 °C) than L. guichenoti (40.1 days at 25 °C; 27.7 days at 30 °C). Patterns of oxygen consumption were similar in both species at both temperatures,
being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature
resulted in higher peak and higher pre-hatch rates of oxygen consumption in both species. Total amount of oxygen consumed
during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 °C consumed significantly more (32.6 ml) than eggs incubated at 25 °C (28.5 ml). Hatchling mass was unaffected
by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic
production cost of hatchling B. duperreyi (3.52 kJ · g−1) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 °C (4.00 kJ · g−1) than at 25 °C (3.47 kJ · g−1). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 °C had longer tails (29.3 mm) than those from eggs incubated at 25 °C (26.2 mm). These results indicate that
incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling
morphology.
Accepted: 27 January 2000 相似文献
12.
Daisuke Sugimori 《Applied microbiology and biotechnology》2009,82(2):351-357
To develop a microbial treatment of edible oil-contaminated wastewater, microorganisms capable of rapidly degrading edible
oil were screened. The screening study yielded a yeast coculture comprising Rhodotorula pacifica strain ST3411 and Cryptococcus laurentii strain ST3412. The coculture was able to degrade efficiently even at low contents of nitrogen ([NH4–N] = 240 mg/L) and phosphorus sources ([PO4–P] = 90 mg/L). The 24-h degradation rate of 3,000 ppm mixed oils (salad oil/lard/beef tallow, 1:1 w/w) at 20°C was 39.8% ± 9.9% (means ± standard deviations of eight replicates). The highest degradation rate was observed at
20°C and pH 8. In a scaled-up experiment, the salad oil was rapidly degraded by the coculture from 671 ± 52.0 to 143 ± 96.7 ppm
in 24 h, and the degradation rate was 79.4% ± 13.8% (means ± standard deviations of three replicates). In addition, a repetitive
degradation was observed with the cell growth by only pH adjustment without addition of the cells. 相似文献
13.
Water conductance of the cuticular membrane (CM) of mature sweet cherry fruit (Prunus avium L. cv. Sam) was investigated by monitoring water loss from segments of the outer pericarp excised from the cheek of the fruit.
Segments consisted of epidermis, hypodermis and several cell layers of the mesocarp. Segments were mounted in stainless-steel
diffusion cells with the mesocarp surface in contact with water, while the outer cuticular surface was exposed to dry silica
(22 ± 1 °C). Conductance was calculated by dividing the amount of water transpired per unit area and time by the difference
in water vapour concentration across the segment. Conductance values had a log normal distribution with a median of 1.15 × 10−4 m s−1 (n=357). Transpiration increased linearly with time. Conductance remained constant and was not affected by metabolic inhibitors
(1 mM NaN3 or 0.1 mM carbonylcyanide m-chlorophenylhydrazone) or thickness of segments (range 0.8–2.8 mm). Storing fruit (up to 42 d, 1 °C) used as a source of
segments had no consistent effect on conductance. Conductance of the CM increased from cheek (1.16 ± 0.10 × 10−4 m s−1) to ventral suture (1.32 ± 0.07 × 10−4 m s−1) and to stylar end (2.53 ± 0.17 × 10−4 m s−1). There was a positive relationship (r2=0.066**; n=108) between conductance and stomatal density. From this relationship the cuticular conductance of a hypothetical astomatous
CM was estimated to be 0.97 ± 0.09 × 10−4 m s−1. Removal of epicuticular wax by stripping with cellulose acetate or extracting epicuticular plus cuticular wax by dipping
in CHCl3/methanol increased conductance 3.6- and 48.6-fold, respectively. Water fluxes increased with increasing temperature (range
10–39 °C) and energies of activation, calculated for the temperature range from 10 to 30 °C, were 64.8 ± 5.8 and 22.2 ± 5.0 kJ
mol−1 for flux and vapour-concentration-based conductance, respectively.
Received: 23 March 2000 / Accepted: 28 July 2000 相似文献
14.
Ethanol production by recombinant Escherichia coli strain FBR5 from dilute acid pretreated wheat straw (WS) by separate hydrolysis and fermentation (SHF) and simultaneous saccharification
and fermentation (SSF) was studied. The yield of total sugars from dilute acid (0.5% H2SO4) pretreated (160 °C, 10 min) and enzymatically saccharified (pH 5.0, 45 °C, 72 h) WS (86 g/l) was 50.0 ± 1.4 g/l. The hydrolyzate
contained 1,184 ± 19 mg furfural and 161 ± 1 mg hydroxymethyl furfural per liter. The recombinant E. coli FBR5 could not grow at all at pH controlled at 4.5 to 6.5 in the non-abated wheat straw hydrolyzate (WSH) at 35 °C. However,
it produced 21.9 ± 0.3 g ethanol from non-abated WSH (total sugars, 44.1 ± 0.4 g/l) in 90 h including the lag time of 24 h
at controlled pH 7.0 and 35 °C. The bioabatement of WS was performed by growing Coniochaeta ligniaria NRRL 30616 in the liquid portion of the pretreated WS aerobically at pH 6.5 and 30 °C for 15 h. The bacterium produced 21.6 ± 0.5 g
ethanol per liter in 40 h from the bioabated enzymatically saccharified WSH (total sugars, 44.1 ± 0.4 g) at pH 6.0. It produced
24.9 ± 0.3 g ethanol in 96 h and 26.7 ± 0.0 g ethanol in 72 h per liter from bioabated WSH by batch SSF and fed-batch SSF,
respectively. SSF offered a distinct advantage over SHF with respect to reducing total time required to produce ethanol from
the bioabated WS. Also, fed-batch SSF performed better than the batch SSF with respect to shortening the time requirement
and increase in ethanol yield. 相似文献
15.
Duncan Mitchell Shane K. Maloney Helen P. Laburn Michael H. Knight Gernot Kuhnen Claus Jessen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):335-343
We used miniature data loggers to record temperature and activity in free-ranging springbok (Antidorcas marsupialis) naturally exposed to severe nocturnal cold and moderate diurnal heat. The animals were active throughout the day and night,
with short rests; the intensity of activity increased during daylight. Arterial blood temperature, averaged over many days,
exhibited a circadian rhythm with amplitude <1 °C, but with a wide range which resulted from sporadic rapid deviations of
body temperature. Peak blood temperature occurred after sunset. Environmental thermal loads had no detectable effect on blood
temperature, even though globe temperature varied by >10 °C from day to day and >20 °C within a day. Brain temperature increased
approximately linearly with blood temperature but with a slope <1, so that selective brain cooling tended to be activated
at high body temperature, but without a precise threshold for the onset of brain cooling. Low activity attenuated selective
brain cooling and high activity abolished it, even at high brain temperature. Our results support the concept that selective
brain cooling serves to modulate thermoregulation rather than to protect the brain against heat injury.
Accepted: 7 January 1997 相似文献
16.
Bokas D Uy D Grattepanche F Duportail G Guedon E Delaunay S Goergen JL 《Applied microbiology and biotechnology》2007,76(4):773-781
1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) was used to assess the cell envelope fluidity of Corynebacterium glutamicum 2262 during a temperature-triggered glutamate producing process. Because the fluorescence lifetime of TMA-DPH was shown to
be constant all over the process, fluorescence anisotropy can be considered as a good index of cell envelope fluidity. When
the temperature of the fed-batch culture was increased from 33 to 39°C to induce glutamate excretion, the fluorescence anisotropy
values decreased from 0.212 ± 0.002 to 0.186 ± 0.002 (corresponding to an increase in the cell fluidity), while the specific
glutamate production rate reached its maximal value. The increase in fluidity of the C. glutamicum cell envelope was not due to a physical effect related to the temperature elevation, but rather to an alteration of the composition
of the cell envelope. Using a mutant devoid of corynomycolates, significant differences in fluorescence anisotropy values
were obtained compared to the wild-type strain, suggesting that TMA-DPH is mainly anchored into the corynomycomembrane. Differences
in fluorescence anisotropy were also observed when the bacteria were cultivated at 33, 36, 38, and 39°C in batch cultures,
and a linear relationship was obtained between the maximum specific glutamate production rate and the measured fluidity. When
using the glutamate non-producing variant of C. glutamicum 2262, the fluorescence anisotropy remained constant at 0.207 ± 0.003 whatever the applied temperature shift. This suggests
that the fluidity of the Corynebacteria mycomembrane plays an important role in glutamate excretion during the temperature-triggered
process. 相似文献
17.
Hikaru Nakagawa 《Ichthyological Research》2018,65(1):172-174
The gastric evacuation rate (GER) of the delicate loach Niwaella delicata was estimated experimentally under four temperature conditions (10, 15, 20, and 25 °C). The GER was relatively high under the ≥20 °C condition and was nearly zero under the ≤15 °C condition. The relationship between GER and water temperature was estimated following the method of Elliot (1972) as follows: GER = exp (0.436 × temperature ? 10.59). This physical characteristic might affect the seasonal activity of this species. 相似文献
18.
M. J. Tipton F. S. C. Golden C. Higenbottam I. B. Mekjavic C. M. Eglin 《European journal of applied physiology and occupational physiology》1998,78(3):253-257
The initial responses to cold-water immersion, evoked by stimulation of peripheral cold receptors, include tachycardia, a
reflex inspiratory gasp and uncontrollable hyperventilation. When immersed naked, the maximum responses are initiated in water
at 10°C, with smaller responses being observed following immersion in water at 15°C. Habituation of the initial responses
can be achieved following repeated immersions, but the specificity of this response with regard to water temperature is not
known. Thirteen healthy male volunteers were divided into a control (C) group (n = 5) and a habituation (H) group (n = 8). Each subject undertook two 3-min head-out immersions in water at 10°C wearing swimming trunks. These immersions took
place at a corresponding time of day with 4 days separating the two immersions. In the intervening period the C group were
not exposed to cold water, while the H group undertook another six, 3-min, head-out immersions in water at 15°C. Respiratory
rate (f
R), inspiratory minute volume (V˙
I) and heart rate (f
H) were measured continuously throughout each immersion. Following repeated immersions in water at 15°C, the f
R, V˙
I and f
H responses of the H group over the first 30 s of immersion were reduced (P < 0.01) from 33.3 breaths · min−1, 50.5 l · min−1 and 114 beats · min−1 respectively, to 19.8 breaths · min−1, 26.4 l · min−1 and 98 beats · min−1, respectively. In water at 10°C these responses were reduced (P < 0.01) from 47.3 breaths · min−1, 67.6 l · min−1 and 128 beats · min−1 to 24.0 breaths · min−1, 29.5 l · min−1 and 109 beats · min−1, respectively over a corresponding period of immersion. Similar reductions were observed during the last 2.5 min of immersions.
The initial responses of the C group were unchanged. It is concluded that habituation of the cold shock response can be achieved
by immersion in warmer water than that for which protection is required. This suggests that repeated submaximal stimulation
of the cutaneous cold receptors is sufficient to attenuate the responses to more maximal stimulation.
Accepted: 6 February 1998 相似文献
19.
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
20.
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