共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Lovegrove G Körtner G Geiser F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(1):11-18
The costs of arousal from induced torpor were measured in the striped-faced dunnart (Sminthopsis macroura; ca. 25 g) under two experimental ambient temperature cycles. The sinusoidal-type temperature cycles were designed to evaluate
the effects of passive, ambient temperature heating during arousal from torpor in these insectivorous marsupials. It was hypothesised
that diel ambient temperature cycles may offer significant energy savings during arousal in animals that employ daily torpor
in summer as a response to unpredictable food availability. The cost of arousal in animals in which passive, exogenous heating
occurred was significantly lower than that in animals not exposed to an ambient temperature cycle. The total cost of all three
phases of torpor (entry, maintenance and arousal) was almost halved when animals were exposed to an ambient heating cycle
from 15 °C to 25 °C over a 24-h period. In all animals, irrespective of the experimental ambient temperature cycle employed,
the minimum torpor body temperature was 17–18 °C. The body temperature (Tb) of animals exposed to exogenous heating increased from the torpor Tb minimum to a mean value of 22.59 °C before endogenous heat production commenced. This relatively small increase in Tb of ca. 5 °C through `free' passive heating was sufficient to account for the significant ca. three-fold decrease in the cost
of arousal and may represent an important energetic aid to free-ranging animals.
Accepted: 4 October 1998 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.
Energetic cost of hovering flight in nectar-feeding bats (Phyllostomidae: Glossophaginae) and its scaling in moths, birds and bats 总被引:2,自引:0,他引:2
Voigt CC Winter Y 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(1):38-48
Three groups of specialist nectar-feeders covering a continuous size range from insects, birds and bats have evolved the
ability for hovering flight. Among birds and bats these groups generally comprise small species, suggesting a relationship
between hovering ability and size. In this study we established the scaling relationship of hovering power with body mass
for nectar-feeding glossophagine bats (Phyllostomidae). Employing both standard and fast-response respirometry, we determined
rates of gas exchange in Hylonycteris underwoodi (7 g) and Choeronycteris mexicana (13–18 g) during hover-feeding flights at an artificial flower that served as a respirometric mask to estimate metabolic
power input. The O2 uptake rate (V˙
o2) in ml g−1 h−1 (and derived power input) was 27.3 (1.12 W or 160 W kg−1) in 7-g Hylonycteris and 27.3 (2.63 W or 160 W kg−1) in 16.5-g Choeronycteris and thus consistent with measurements in 11.9-g Glossophagasoricina (158 W kg−1, Winter 1998). V˙
o2 at the onset of hovering was also used to estimate power during forward flight, because after a transition from level forward
to hovering flight gas exchange rates initially still reflect forward flight rates. V˙
o2 during short hovering events (<1.5 s) was 19.0 ml g−1 h−1 (1.8 W) in 16-g Choeronycteris, which was not significantly different from a previous, indirect estimate of the cost of level forward flight (2.1 W, Winter
and von Helversen 1998). Our estimates suggest that power input during hovering flight P
h
(W) increased with body mass M (kg) within 13–18-g Choeronycteris (n = 4) as P
h
= 3544 (±2057 SE) M
1.76 (±0.21 SE) and between different glossophagine bat species (n = 3) as P
h
= 128 (±2.4 SE) M
0.95 (±0.034 SE). The slopes of three scaling functions for flight power (hovering, level forward flight at intermediate speed and submaximal
flight power) indicate that: 1. The relationship between flight power to flight speed may change with body mass in the 6–30-g
bats from a J- towards a U-shaped curve. 2. A metabolic constraint (hovering flight power equal maximal flight power) may
influence the upper size limit of 30–35 g for this group of flower specialists.
Mass-specific power input (W kg−1) during hovering flight appeared constant with regard to body size (for the mass ranges considered), but differed significantly
(P < 0.001) between groups. Group means were 393 W kg−1 (sphingid moths), 261 W kg−1 (hummingbirds) and 159 W kg−1 (glossophagine bats). Thus, glossophagine bats expend the least metabolic power per unit of body mass supported during hovering
flight. At a metabolic power input of 1.1 W a glossophagine bat can generate the lift forces necessary for balancing 7 g against
gravitation, whereas a hummingbird can support 4 g and a sphingid moth only 3 g of body mass with the same amount of metabolic
energy. These differences in power input were not fully explained by differences in induced power output estimated from Rankine-Froude
momentum-jet theory.
Accepted: 10 November 1998 相似文献
5.
Brown CR Everitt VJ Baxter RM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(1):19-24
The Hogsback (32°33S 26°57E) and Alice (32°47S 26°50E), Eastern Cape, South Africa, are separated by only 24 km but by 1000 m
in altitude and fall into different climatic regions. Thermal responses (energy expenditure and body temperature) to ambient
temperature were measured in a population of vlei rats (Otomys irroratus) from each of the two localities. We predicted that animals from the colder Hogsback would show differences in their thermal
physiology and morphology consistent with better cold-resistance. Basal metabolic rates of the Hogsback population were slightly,
but not significantly, higher than the Alice population (23.9 J g−1 h−1 vs 22.3 J g−1 h−1), but the slope of the regression between energy expenditure and ambient temperature below the thermal neutral zone was significantly
lower (−1.28 vs −1.60). Body temperature, although quite variable in both populations, was not significantly influenced by
ambient temperature in the Hogsback population, whereas that of Alice animals was. Fur length was longer and relative size
of the ears and tail was smaller in the Hogsback population, which probably accounted for the slightly lower minimum thermal
conductance (1.79 J g−1 h−1 °C−1 vs 1.91 J g−1 h−1 °C−1) in the Hogsback population. Vlei rats from the two sites also have different karyotypes that correlate with climate but
there is insufficient evidence at present to suggest that the different karyotypes and the physiological parameters measured
are adaptive.
Accepted: 15 October 1998 相似文献
6.
Wilson RS James RS Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):117-124
Among amphibians, the ability to compensate for the effects of temperature on the locomotor system by thermal acclimation
has only been reported in larvae of a single species of anuran. All other analyses have examined predominantly terrestrial
adult life stages of amphibians and found no evidence of thermal acclimatory capacity. We examined the ability of both tadpoles
and adults of the fully aquatic amphibian Xenopus laevis to acclimate their locomotor system to different temperatures. Tadpoles were acclimated to either 12 °C or 30 °C for 4 weeks
and their burst swimming performance was assessed at four temperatures between 5 °C and 30 °C. Adult X. laevis were acclimated to either 10 °C or 25 °C for 6 weeks and their burst swimming performance and isolated muscle performance
was determined at six temperatures between 5 °C and 30 °C. Maximum swimming performance of cold-acclimated X. laevis tadpoles was greater at cool temperatures and lower at the highest temperature in comparison with the warm-acclimated animals.
At the test temperature of 12 °C, maximum swimming velocity of tadpoles acclimated to 12 °C was 38% higher than the 30 °C-acclimation
group, while at 30 °C, maximum swimming velocity of the 30 °C-acclimation group was 41% faster than the 12 °C-acclimation
group. Maximum swimming performance of adult X. laevis acclimated to 10 °C was also higher at the lower temperatures than the 25 °C acclimated animals, but there was no difference
between the treatment groups at higher temperatures. When tested at 10 °C, maximum swimming velocity of the 10 °C-acclimation
group was 67% faster than the 25 °C group. Isolated gastrocnemius muscle fibres from adult X. laevis acclimated to 10 °C produced higher relative tetanic tensions and decreased relaxation times at 10 °C in comparison with
animals acclimated to 25 °C. This is only the second species of amphibian, and the first adult life stage, reported to have
the capacity to thermally acclimate locomotor performance.
Accepted: 28 October 1999 相似文献
7.
Navas CA James RS Wakeling JM Kemp KM Johnston IA 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):588-596
The aims of this study were: (1) to analyze individual variation in frog locomotor performance, (2) to compare the thermal
sensitivity of jumping and swimming, and (3) to contrast whole animal versus muscle fiber performance at different temperatures.
The jumping and swimming performance of Rana temporaria was analyzed at 5, 10, 15 and 20 °C. Muscle fiber bundles were isolated from lateral gastrocnemius and subjected to the length
and activation patterns thought to occur in vivo. As temperature increased, locomotor performance in R. temporaria improved with a Q
10 of 1.2 for both jump take-off velocity and mean swimming velocity. The slope of the relationship between performance and
temperature (TE) was similar for both locomotor parameters and was described by the equation z-scores of locomotor performance = 0.127 × TE − 1.585. Although some frogs performed better than others relative performance was affected by locomotor type and temperature.
Locomotor performance improved with temperature as the power required during take-off and the mean muscle power output increased
with Q
10 values of 1.7 and 1.6 respectively. The mean muscle power output during take-off was only 34% of the calculated requirements
for the whole animal, suggesting the involvement of elastic strain energy storage mechanisms.
Accepted: 2 September 1999 相似文献
8.
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
9.
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
10.
D. J. Hosken P. C. Withers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(1):71-80
The thermal and metabolic physiology of Chalinolobus gouldii, an Australian vespertilionid bat, was studied in the laboratory using flow-through respirometry. Chalinolobus gouldii exhibits a clear pattern of euthermic thermoregulation, typical of endotherms with respect to body temperature and rate of
oxygen consumption. The basal metabolic rate of euthermic Chalinolobus gouldii is approximately 86% of that predicted for a 17.5-g mammal and falls into the range of mass-specific basal metabolic rates
ascribed to vespertilionid bats. However, like most vespertilionid bats, Chalinolobus gouldii displays extreme thermolability. It is able to enter into torpor and spontaneously arouse at ambient temperatures as low
as 5 °C. Torpid bats thermoconform at moderate ambient temperature, with body temperature ≈ ambient temperature, and have
a low rate of oxygen consumption determined primarily by Q
10 effects. At low ambient temperature (< 10 °C), torpid C. gouldii begin to regulate their body temperature by increased metabolic heat production; they tend to maintain a higher body temperature
at low ambient temperature than do many northern hemisphere hibernating bats. Use of torpor leads to significant energy savings.
The evaporative water loss of euthermic bats is relatively high, which seems unusual for a bat whose range includes extremely
arid areas of Australia, and is reduced during torpor. The thermal conductance of euthermic C. gouldii is less than that predicted for a mammal of its size. The thermal conductance is considerably lower for torpid bats at intermediate
body temperature and ambient temperature, but increases to euthermic values for torpid bats when thermoregulating at low ambient
temperature.
Accepted: 22 August 1996 相似文献
11.
Facial heat exchange convection coefficients were estimated from experimental data in cold and windy ambient conditions applicable to wind chill calculations. Measured facial temperature datasets, that were made available to this study, originated from 3 separate studies involving 18 male and 6 female subjects. Most of these data were for a −10°C ambient environment and wind speeds in the range of 0.2 to 6 m s−1. Additional single experiments were for −5°C, 0°C and 10°C environments and wind speeds in the same range. Convection coefficients were estimated for all these conditions by means of a numerical facial heat exchange model, applying properties of biological tissues and a typical facial diameter of 0.18 m. Estimation was performed by adjusting the guessed convection coefficients in the computed facial temperatures, while comparing them to measured data, to obtain a satisfactory fit (r 2 > 0.98, in most cases). In one of the studies, heat flux meters were additionally used. Convection coefficients derived from these meters closely approached the estimated values for only the male subjects. They differed significantly, by about 50%, when compared to the estimated female subjects' data. Regression analysis was performed for just the −10°C ambient temperature, and the range of experimental wind speeds, due to the limited availability of data for other ambient temperatures. The regressed equation was assumed in the form of the equation underlying the “new” wind chill chart. Regressed convection coefficients, which closely duplicated the measured data, were consistently higher than those calculated by this equation, except for one single case. The estimated and currently used convection coefficients are shown to diverge exponentially from each other, as wind speed increases. This finding casts considerable doubts on the validity of the convection coefficients that are used in the computation of the "new" wind chill chart and their applicability to humans in cold and windy environments. 相似文献
12.
G. F. Birchard C. L. Reiber 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(8):461-466
Growth and development can occur over a wide range of physical conditions in reptiles. Cardiovascular function must be critical
to this ability. However, information on cardiovascular function in developing reptiles is lacking. Previous work indicated
that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. This study
examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in
amniotic vertebrates are correlated with cardiovascular function. Embryonic and hatchling carcass mass, heart mass and heart
rate (HR) were compared for snapping turtle eggs (Chelydra serpentina) incubated at 24 ° and 29 °C. Incubation time was shorter at 29 °C (56.2 days) than at 24 °C (71.1 days). Carcass and heart
growth showed a sigmoidal pattern at both temperatures. However, cardiac growth showed a relative decrease as incubation proceeded.
Incubation temperature significantly affected the HR pattern during development. The HR of embryos incubated at 24 °C was
constant for most of incubation (51.8±4.8 min-1). A small decrease was observed just prior to and a large decrease immediately following hatching (posthatch, 22.3±4.1 min-1). At 29 °C embryonic HR was greater than at 24 °C early in development (72.3±3 min-1). The HR steadily decreased to values equivalent to those at 24 °C. The HRs of 24 °C and 29 °C hatchlings were not different.
Cardiac output (estimated as the product of heart mass and HR) increased rapidly during early development and then slowed
dramatically at both temperatures. These data are consistent with the suggestion that temperature exerts its effects primarily
early in development. Furthermore, the changes in cardiovascular function are correlated with metabolic changes in hatching
vertebrates.
Accepted:12 June 1996 相似文献
13.
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
14.
Y. Winter O. von Helversen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(2):105-111
Flapping flight is one of the most expensive activities in terms of metabolic cost and this cost has previously been considered
equal for the two extant vertebrate groups which evolved flapping flight. Owing to the difficulty of obtaining accurate measurements
without disturbing flight performance, current estimates of flight cost within the group of small birds and bats differ by
more than a factor of five for given body masses. To minimize the potential problem that flight behaviour may be affected
by the measurements, we developed an indirect method of measuring flight energy expenditure based on time budget analysis
in which small nectar-feeding bats (Glossophaginae) could continue their natural rhythm of flying and resting entirely undisturbed.
Estimates of metabolic flight power based on 172 24-h time and energy budget measurements were obtained for nine individual
bats from six species (mass 7–28 g). Metabolic flight power (PF) of small bats was found to increase with body mass following the relation PF = 50.2 M0.771 (r2 = 0.96, n = 13, PF in W, M in kg). This is about 20–25% below the majority of current predictions of metabolic flight cost for small birds.
Thus, either the flight cost of small birds is significantly lower than has previously been thought or, contrary to current
opinion, small bats require less energy to fly than birds.
Accepted: 29 September 1997 相似文献
15.
Schmid J Ruf T Heldmaier G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):59-68
Thermoregulation, energetics and patterns of torpor in the pygmy mouse lemur, Microcebus myoxinus, were investigated under natural conditions of photoperiod and temperature in the Kirindy/CFPF Forest in western Madagascar.
M. myoxinus entered torpor spontaneously during the cool dry season. Torpor only occurred on a daily basis and torpor bout duration was
on average 9.6 h, and ranged from 4.6 h to 19.2 h. Metabolic rates during torpor were reduced to about 86% of the normothermic
value. Minimum body temperature during daily torpor was 6.8 °C at an ambient temperature of 6.3 °C. Entry into torpor occurred
randomly between 2000 and 0620 hours, whereas arousals from torpor were clustered around 1300 hours within a narrow time window
of less than 4 h. Arousal from torpor was a two-step process with a first passive climb of body temperature to a mean of 27 °C,
carried by the daily increase of ambient temperature when oxygen consumption remained more or less constant, followed by a
second active increase of oxygen consumption to further raise the body temperature to normothermic values. In conclusion,
daily body temperature rhythms in M. myoxinus further reduce the energetic costs of daily torpor seen in other species: they extend to unusually low body temperatures
and consequently low metabolic rates in torpor, and they employ passive warming to reduce the energetic costs of arousal.
Thus, these energy-conserving adaptations may represent an important energetic aid to the pygmy mouse lemur and help to promote
their individual fitness.
Accepted: 2 November 1999 相似文献
16.
The muscle I2 is a smooth muscle from the buccal mass of the marine mollusc Aplysia californica whose neural control, in vivo kinematics, and behavioral role have been extensively analyzed. In this study, we measured
the activation and contractile dynamics of the muscle in order to construct a Hill-type kinetic model of the muscle. This
is the first study to our knowledge, of Aplysia muscle contractile dynamics. The isometric force-frequency relationship of I2 had a frequency threshold of about 6–8 Hz,
and its force output saturated at 20–25 Hz, properties that match the high frequency (20 Hz) bursts generated by the B31/B32
neurons that innervate it. Peak isometric force was generated at about 118% of the in situ relaxed length. These results and
I2's estimated in vivo kinematics suggest that it generates maximum force at the onset of protraction. The muscle tension
during iso-velocity lengthening and shortening was an asymmetric function of velocity. Short range stiffness and yielding
responses were observed in lengthening, whereas muscle tension decreased smoothly in shortening. These visco-elastic properties
suggest that the I2 muscle can serve to brake forceful retraction movements. A Hill-type model, parameterized from the measurements,
captured many of the mechanical properties of I2. Our results provide a quantitative understanding of the biomechanical significance
of the muscle's neural control and provide a basis for simulation studies of the control of feeding behavior.
Received: 5 February 1999 / Accepted in revised form: 18 May 1999 相似文献
17.
E. Kellis V. Baltzopoulos 《European journal of applied physiology and occupational physiology》1997,76(3):253-259
The purpose of this study was to examine the effects of moment of antagonistic muscle on the resultant joint moment during
isokinetic eccentric and concentric efforts of the knee extensors. Ten males performed maximum eccentric and concentric knee
extension and flexion efforts on a Biodex dynamometer at 0.52 rad · s−1 (30° · s−1). Electromyographic (EMG) activity of vastus medialis and biceps femoris (hamstrings) was also recorded. The antagonistic
moment of the hamstrings was determined by recording the integrated EMG (iEMG)/moment relationship at different levels of
muscle effort. The iEMG/moment curves were fitted using second-degree polynomials. The polynomials were then used to predict
the antagonistic moment exerted by the hamstrings from the antagonist iEMG. The antagonistic moment had a maximum of 42.92
Nm and 28.97 Nm under concentric and eccentric conditions respectively; paired t-tests indicated that this was a significant difference (P < 0.05). These results indicate that the resultant joint moment of knee extensors is the result of both agonist and antagonist
muscle activation. The greater antagonist muscle activity under concentric activation conditions may be partly responsible
for the lower resultant joint concentric moment of knee extensors compared with the corresponding eccentric activation. The
antagonist moment significantly affects comparisons between the isokinetic moments and agonist EMG and in vitro force measurements
under different testing (muscle action and angular velocity) conditions.
Accepted: 25 February 1997 相似文献
18.
Nigel J. Adams Berry Pinshow Leonard Z. Gannes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):444-450
We used tritium-labeled water to measure total body water, water influx (which approximated oxidative water production) and
water efflux in free-flying tippler pigeons (Columba livia) during flights that lasted on average 4.2 h. At experimental air temperatures ranging from 18 to 27 °C, mean water efflux
by evaporation and excretion [6.3 ± 1.3 (SD) ml · h−1, n = 14] exceeded water influx from oxidative water and inspired air (1.4 ± 0.7 ml · h−1, n = 14), and the birds dehydrated at 4.9 ± 0.9 ml · h−1. This was not significantly different from gravimetrically measured mass loss of 6.2 ± 2.1 g · h−1 (t = 1.902, n = 14, P>0.05). This flight-induced dehydration resulted in an increase in plasma osmolality of 4.3 ± 3.0 mosmol · kg−1 · h−1 during flights of 3–4 h. At 27 °C, the increase in plasma osmolality above pre-flight levels (ΔP
osm = 7.6±4.29 mosmol · kg−1 · h−1, n = 6) was significantly higher than that at 18 °C (ΔP
osm = 0.83±2.23 mosmol · kg−1 · h−1, (t = 3.43, n = 6, P < 0.05). Post-flight haematocrit values were on average 1.1% lower than pre-flight levels, suggesting plasma expansion. Water
efflux values during free flight were within 9% of those in the one published field study (Gessaman et al. 1991), and within
the range of values for net water loss determined from mass balance during wind tunnel experiments (Biesel and Nachtigall
1987). Our net water loss rates were substantially higher than those estimated by a simulation model (Carmi et al. 1992) suggesting
some re-evaluation of the model assumptions is required.
Accepted: 8 April 1997 相似文献
19.
Water spray cooling during handling of feedlot cattle 总被引:1,自引:0,他引:1
Tami M. Brown-Brandl Roger A. Eigenberg John A. Nienaber 《International journal of biometeorology》2010,54(6):609-616
Activities involved in receiving or working (e.g., sorting, dehorning, castration, weighing, implanting, etc.) of feedlot
cattle cause an increase in body temperature. During hot weather the increased body temperature may disrupt normal behaviors
including eating, which can be especially detrimental to the well-being and performance of the animals. Sprinkle cooling of
animals has been successfully employed within the pen; however, added moisture to the pens’ surface increases odor generation
from the pen. A study was conducted to investigate the effectiveness of a single instance of wetting an animal within the
working facility instead of in the pen, which could potentially provide extra evaporative cooling to offset the added heat
produced by activity. Sixty-four cross-bred heifers were assigned to one of eight pens on the basis of weight. On four separate
occasions during hot conditions (average temperature 28.2 ± 1.9°C, 29.1 ± 2.0°C, 28.9 ± 3.0°C, and 26.8 ± 1.6°C; with the
temperature ranging from 22.6 to 32.5°C during the trials), the heifers were moved from their pens to and from the working
facility (a building with a scale and squeeze chute located 160–200 m away). While in the squeeze chute, four of the pens
of heifers were sprinkle cooled and the remaining four pens were worked as normal. The heifers that were treated had a body
temperature that peaked sooner (31.9 ± 0.63 min compared to 37.6 ± 0.62) with a lower peak body temperature (39.55 ± 0.03°C
compared to 39.74 ± 0.03°C), and recovered sooner (70.5 ± 2.4 min compared to 83.2 ± 2.4 min). The treated animals also had
a lower panting score, a visual assessment of level of cattle heat stress (1.1 ± 0.2 compared to 1.16 ± 0.2). The behavior
measurements that were taken did not indicate a change in behavior. It was concluded that while a single instance of wetting
an animal within the working facility did not completely offset the increase in body temperature, it was beneficial to the
animals without needing to add water to the pen surface, thus reducing the potential for odor generation. 相似文献
20.
Soria F Ellenrieder G Oliveira GB Cabrera M Carvalho LB 《Applied microbiology and biotechnology》2012,93(3):1127-1134
α-l-Rhamnosidase from Aspergillus terreus was covalently immobilized on the following ferromagnetic supports: polyethylene terephthalate (Dacron-hydrazide), polysiloxane/polyvinyl
alcohol (POS/PVA), and chitosan. The powdered supports were magnetized by thermal coprecipitation method using ferric and
ferrous chlorides, and the immobilization was carried out via glutaraldehyde. The activity of the Dacron-hydrazide (0.53 nkat/μg
of protein) and POS/PVA (0.59 nkat/μg of protein) immobilized enzyme was significantly higher than that found for the chitosan
derivative (0.06 nkat/μg of protein). The activity–pH and activity–temperature profiles for all immobilized enzymes did not
show difference compared to the free enzyme, except the chitosan derivative that presented higher maximum temperature at 65 °C.
The Dacron-hydrazide derivative thermal stability showed a similar behavior of the free enzyme in the temperature range of
40–70 °C. The POS/PVA and chitosan derivatives were stable up to 60 °C, but were completely inactivated at 70 °C. The activity
of the preparations did not appreciably decrease after ten successive reuses. Apparent K
m of α-l-rhamnosidase immobilized on magnetized Dacron-hydrazide (1.05 ± 0.22 mM), POS/PVA (0.57 ± 0.09 mM), and chitosan (1.78 ± 0.24 mM)
were higher than that estimated for the soluble enzyme (0.30 ± 0.03 mM). The Dacron-hydrazide enzyme derivative showed better
performance than the free enzyme to hydrolyze 0.3% narigin (91% and 73% after 1 h, respectively) and synthesize rhamnosides
(0.116 and 0.014 mg narirutin after 1 h, respectively). 相似文献