共查询到20条相似文献,搜索用时 15 毫秒
1.
F.-O. Lehmann 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):165-171
To gain insight into how temperature affects locomotor performance in insects, the limits of flight performance have been
estimated in freely flying fruit flies Drosophila melanogaster by determining the maximum load that a fly could carry following take-off. At a low ambient temperature of 15 °C, muscle
mechanical power output matches the minimum power requirements for hovering flight. Aerodynamic force production rises with
increasing temperature and eventually saturates at a flight force that is roughly equal to 2.1 times the body mass. Within
the two-fold range of different body sizes, maximum flight force production during free flight does not decrease with decreasing
body size as suggested by standard aerodynamic theories. Estimations of flight muscle mechanical power output yields a peak
performance of 110 W kg−1 muscle tissue for short-burst flight that was measured at an ambient temperature of 30 °C. With respect to the uncertainties
in estimating muscle mechanical power during free flight, the estimated values are similar to those that were published for
flight under tethered flight conditions.
Accepted: 5 January 1999 相似文献
2.
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
3.
Thermal acclimation of locomotor performance in tadpoles of the frog Limnodynastes peronii 总被引:3,自引:0,他引:3
R. S. Wilson C. E. Franklin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(6):445-451
Previous analyses of thermal acclimation of locomotor performance in amphibians have only examined the adult life history
stage and indicate that the locomotor system is unable to undergo acclimatory changes to temperature. In this study, we examined
the ability of tadpoles of the striped marsh frog (Limnodynastes peronii) to acclimate their locomotor system by exposing them to either 10 °C or 24 °C for 6 weeks and testing their burst swimming
performance at 10, 24, and 34 °C. At the test temperature of 10 °C, maximum velocity (Umax) of the 10 °C-acclimated tadpoles was 47% greater and maximum acceleration (Amax) 53% greater than the 24 °C-acclimated animals. At 24 °C, Umax was 16% greater in the 10 °C-acclimation group, while there was no significant difference in Amax or the time taken to reach Umax (T-Umax). At 34 °C, there was no difference between the acclimation groups in either Umax or Amax, however T-Umax was 36% faster in the 24 °C-acclimation group. This is the first study to report an amphibian (larva or adult) possessing
the capacity to compensate for cool temperatures by thermal acclimation of locomotor performance. To determine whether acclimation
period affected the magnitude of the acclimatory response, we also acclimated tadpoles of L. peronii to 10 °C for 8 months and compared their swimming performance with tadpoles acclimated to 10 °C for 6 weeks. At the test
temperatures of 24 °C and 34 °C, Umax and Amax were significantly slower in the tadpoles acclimated to 10 °C for 8 months. At 10 °C, T-Umax was 40% faster in the 8-month group, while there were no differences in either Umax or Amax. Although locomotor performance was enhanced at 10 °C by a longer acclimation period, this was at the expense of performance
at higher temperatures.
Accepted: 25 June 1999 相似文献
4.
B. Tatler D. C. O'Carroll S. B. Laughlin 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(4):399-407
A hot head gives an insect a clearer view of a moving world because warming reduces motion blur by accelerating photoreceptor
responses. Over a natural temperature range, 19–34 °C, the speed of response of blowfly (Calliphora vicina) photoreceptors more than doubles, to produce the fastest functional responses recorded from an ocular photoreceptor. This
acceleration increases temporal resolving power, as indicated by the corner frequency of the response power spectrum. When
light adapted, the corner frequency increases from 53 Hz to 119 Hz with a Q
10 of 1.9, and when dark adapted from 8 Hz to 32 Hz with a Q
10 of 3.0. Temperature sensitivity originates in the phototransduction cascade, and is associated with signal amplification.
The temperature sensitivity of photoreceptors must be taken into account when studying the mechanisms, function and ecology
of vision, and gives a distinct advantage to insects that thermoregulate.
Accepted: 2 February 2000 相似文献
5.
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
6.
Using the cell pressure probe, the effects of temperature on hydraulic conductivity (Lp; osmotic water permeability), solute
permeability (permeability coefficient, Ps), and reflection coefficients (σs) were measured on internodes of Chara corallina, Klein ex Willd., em R.D.W.. For the first time, complete sets of transport coefficients were obtained in the range between
10 and 35 °C which provided evidence about pathways of water and solutes as they move across the plasma membrane (water channel
and bilayer arrays). Test solutes used to check for the selectivity of water channels were monohydric alcohols of different
molecular size and shape (ethanol, n-propanol, iso-propanol, and tert-butanol) and heavy water (HDO). Within the limits of accuracy, Q10 values for Lp and for the diffusive water permeability (Pd) were identical (Q10 for Lp = 1.29 ± 0.17 (± SD; n = 15 cells) and Q10 for Pd = 1.25 ± 0.16 (n = 5 cells)). The Q10 values were equivalent to activation energies of Ea = 16.8 ± 6.4 and 16.6 ± 10.0 kJ · mol−1, respectively, which is similar to that of self-diffusion or of viscous flow of water. The Q10 values and activation energies for Ps of the alcohols were significantly larger (ethanol: Q10 = 1.68 ± 0.16, Ea = 37.1 ± 5.9 kJ · mol−1; n-propanol: Q10 = 1.75 ± 0.40, Ea = 43.1 ± 15.3 kJ · mol−1; iso-propanol: Q10 = 2.12 ± 0.42, Ea = 52.2 ± 14.6 kJ · mol−1; tert-butanol: Q10 = 2.13 ± 0.56, Ea = 51.6 ± 17.1 kJ · mol−1; ±SD; n = 5 to 6 cells). Effects of temperature on reflection coefficients were most pronounced. With increasing temperature, σs values of the alcohols decreased and those of HDO increased. The data indicate that water and solutes use different pathways
when crossing the membrane. Ordinary and isotopic water use water channels and the other test solutes use the bilayer array
(composite transport model of membrane). Changes in σs values with temperature were found to be a sensitive measure for the open/closed state of water channels. The decrease of
σs with temperature was theoretically predicted from the temperature dependence of Ps and Lp. Differences between predicted and measured values of σs allowed estimation of the bypass flow (slippage) of solutes through water channels which did not completely exclude test
solutes. The permeability of channels depended on the structure and size of test solutes. It is concluded that water channels
are much less selective than is usually thought. Since water channels represent single-file or no-pass pores, solutes drag
along considerable amounts of water as they diffuse across channels. This results in low overall values of σs. The σs of HDO was extremely low. Its response to temperature was opposite to that for the σs of the alcohols. This suggested a stronger effect of temperature on the hydraulic (osmotic) than on the diffusive water flow
across individual water channels, i.e. a differential sensitivity of different mechanisms to temperature.
Received: 10 October 1996 / Accepted: 2 December 1996 相似文献
7.
The escape swimming performance of the Antarctic scallop, Adamussium colbecki, was measured in animals acclimated for 6 weeks to –1, 0 or 2°C and tested at –1.5 to +1.5°C. Clap duration and swimming velocity were significantly related to temperature, but were not affected by acclimation, demonstrating no phenotypic plasticity. Comparisons of the mean swimming velocity of A. colbecki with the published data for temperate and tropical species showed little evidence for evolutionary compensation for temperature, with all data fitting to a single exponential relationship with a Q10 of 2.08 (0–20°C). The contraction kinetics of the isolated fast adductor muscle of A. colbecki were determined and the times to 50% peak tension and 50% relaxation had Q10s (0–4°C) of 3.6 and 4.7, respectively. The Q10 of the overall relationship for pooled time to peak twitch data for four scallop species was 2.05 (0–20°C). Field studies revealed low mobility and poor escape performance in wild A. colbecki. A combination of thermodynamic constraints, reduced food supply, and lower selective pressure probably explains the low levels of swimming performance seen in A. colbecki. 相似文献
8.
C. Traeholt 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):177-184
Five water monitor lizards, Varanus salvator salvator, and four clouded monitor lizards, Varanus bengalensis nebulosus, were caught on Tioman island in Malaysia. A radio-thermistor transmitter was implanted into the buccal cavity of each animal,
and they were released into an enclosure measuring 5.5 × 6.5 metres. The lizards were observed for 9 and 8 days, respectively,
before and after the parietal eye was covered with aluminium foil. With uncovered parietal eye, both species showed a clear
diurnal rhythm, being active only during day time. After covering the parietal eye, the mean locomotor activity of five V. s. salvator decreased from 791 to 107 min · day–1 but remained unchanged around 850 min · day–1 for V. b. nebulosus. The mean duration of locomotor activity decreased in V. s. salvator and V. b. nebulosus after the parietal eye was covered, but V. b. nebulosus maintained its locomotor activity by increasing the number of locomotor bouts. The water monitor spent very little time on
thermoregulation. Its body temperature ranged between 26.3 and 28.4 °C, which decreased after the parietal eye was covered.
The clouded monitor thermoregulated around 28.8–36.0 °C, which remained unchanged after the parietal eye was covered. In both
species, there was a strong correlation between body temperature and ambient temperature. Behavioural abnormalities were recorded
among V. s. salvator with covered parietal eye. They were often observed to be active by night and often slept outside a burrow. The circadian
rhythm of V. b. nebulosus appeared unaffected by shielding of its parietal eye. Captivity combined with shielded parietal eye induced agonistic behaviour
in both species.
Accepted: 11 September 1996 相似文献
9.
Thermal sensitivity of mitochondrial function in the Antarctic Notothenioid Lepidonotothen nudifrons 总被引:4,自引:0,他引:4
I. Hardewig H. O. Pörtner L. S. Peck 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):597-604
The thermal sensitivity of mitochondrial function was investigated in the stenothermal Antarctic fish Lepidonotothen nudifrons. State 3 respiration increases with increasing temperature between 0 °C and 18 °C with a Q
10 of 2.43–2.63. State 4 respiration in the presence of oligomycin, an inhibitor of mitochondrial ATP synthase, quantifies the
leakage of protons through the inner mitochondrial membrane, which causes oxygen consumption without concomitant ATP production.
This parameter shows an unusually high Q
10 of 4.21 ± 0.42 (0–18 °C), which indicates that proton leakage does not depend merely on ion diffusion but is an enzyme-catalysed
process. The differential thermal sensitivity of oxidative phosphorylation (=state 3) and proton leakage (=state 4 in the
presence of oligomycin) leads to progressive uncoupling of the mitochondria and decreased efficiency of oxidative phosphorylation
under in vivo conditions if the body temperature of L. nudifrons increases.
Accepted: 2 September 1999 相似文献
10.
J. B. K. Leonard J. F. Norieka B. Kynard S. D. McCormick 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):287-295
To assess the energetics of migration in an anadromous fish, adult American shad (Alosa sapidissima) were swum in a large respirometer at a range of speeds (1.0–2.3 body lengths (BL) s−1, 13–24 °C). Metabolic rate (MO2) was logarithmically related to swimming speed (Bl s−1; r
2 = 0.41, slope = 0.23 ± 0.037) and tailbeat frequency (beats × min−1; r
2 = 0.52, slope = 0.003 ± 0.0003). Temperature had a significant effect on metabolic rate (r
2 = 0.41) with a Q10 of 2.2. Standard metabolic rate (SMR), determined directly after immobilization with the neuroblocker gallamine triethiodide,
ranged from 2.2–6.2 mmolO2 kg−1 h−1 and scaled with mass (W) such that SMR = 4.0 (±0.03)W0.695(±0.15). Comparison of directly determined and extrapolated SMR suggests that swimming respirometry provides a good estimate of SMR
in this species, given the differences in basal activity monitored by the two methods. Overall, American shad metabolic rates
(MO2 and SMR) were intermediate between salmonids and fast-swimming perciforms, including tunas, and may be a result of evolutionary
adaptation to their active pelagic, schooling life history. This study demonstrates variability in metabolic strategy among
anadromous fishes that may be important to understanding the relative success of different migratory species under varying
environmental conditions.
Accepted: 3 March 1999 相似文献
11.
Brian Dawson Martin Fitzsimons Simon Green Carmél Goodman Michael Carey Keith Cole 《European journal of applied physiology and occupational physiology》1998,78(2):163-169
In contrast to endurance training, little research has been carried out to investigate the effects of short (<10 s) sprint
training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running
training sessions over 6 weeks. Distances sprinted were 30–80 m at 90–100% maximum speed and between 20 and 40 sprints were
performed in each session. Endurance (maximal oxygen consumption; V˙O2
max), sprint (10 m and 40 m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6 × 40 m sprints, 24 s
recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis)
were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements
were seen in 40 m time (P < 0.01), supramaximal treadmill run time (P < 0.05), repeated sprint performance (P < 0.05) and V˙O2
max (P < 0.01). Resting muscle concentrations of ATP and phosphocreatine did not change. Phosphorylase activity increased (P < 0.025), citrate synthase activity decreased (P < 0.01), but no significant changes were recorded in myokinase and phosphofructokinase activities. The proportion of type
II muscle fibres increased significantly (P < 0.05). These results demonstrate that 6 weeks of short sprint training can improve endurance, sprint and repeated sprint
ability in fit subjects. Increases in the proportion of type II muscle fibres are also possible with this type of training.
Accepted: 5 January 1998 相似文献
12.
K. E. Deaton C. M. Bishop P. J. Butler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(5):319-327
The role of thyroid hormones in the development of the locomotor and cardiac muscles of the barnacle goose (Branta leucopsis) was investigated. From 2 weeks of age, goslings were treated with thyroxine, triiodothyronine, or methimazole (a thyroid
inhibitor). Birds were killed at 6 weeks (n = 5) or 9 weeks (n = 4) and various locomotor and cardiac muscle masses recorded and tissue samples taken for analysis of citrate synthase activity.
The effects of thyroxine and triiodothyronine were not significantly different from each other, except in the case of the
iliofibularis at 9 weeks. The mass-specific citrate synthase activity of the iliofibularis, semimembranosus muscles and liver
were significantly increased by thyroid hormone treatment. Cardiac muscle showed a significant hypertrophy at 9 weeks of age
following treatment with thyroxine. Hypothyroidism induced by treatment with methimazole exhibited the greatest effect on
the pectoralis muscle, reducing citrate synthase activity by 33%. Mass-specific citrate synthase activity of the pectoralis
and pectoralis mass (% body wt.) were found to be highly correlated (r
2 = 0.74) at 6 weeks of age. It is suggested that thyroid hormones may be involved in controlling the tissue-specific timing
of the maturation of locomotor and cardiac muscles.
Accepted: 16 September 1996 相似文献
13.
P. C. Tiburcio F. C. F. Galvez L. J. Cruz V. C. Gavino 《Journal of applied phycology》2007,19(6):727-731
Gamma linolenic acid (GLA) degradation in Spirulina followed first-order reaction kinetics. At an accelerated temperature range of 45 to 55°C, the degradation rate constants
(k
r) of GLA obtained were 4.0 × 10−2 to 8.8 × 10−2 day−1. The energy of activation (E
a) was 16.53 kcal mol−1, and the Q10 was 2.22. Based on 20% GLA degradation, the shelf life of sun-dried Spirulina at 30°C is 263 days or 8.6 months using the Arrhenius plot, and 258 days or 8.5 months using the Q
10 approach.
Presented at the 6th Meeting of the Asia Pacific Society of Applied Phycology, Manila, Philippines. 相似文献
14.
Janne Avela Paavo V. Komi 《European journal of applied physiology and occupational physiology》1998,78(5):403-410
It has been suggested that during repeated long-term stretch-shortening cycle (SSC) exercise the decreased neuromuscular
function may result partly from alterations in stiffness regulation. Therefore, interaction between the short latency stretch-reflex
component (M1) and muscle stiffness and their influences on muscle performance were investigated before and after long lasting SSC exercise.
The test protocol included various jumps on a sledge ergometer. The interpretation of the sensitivity of the reflex was based
on the measurements of the patellar reflexes and the M1 reflex components. The peak muscle stiffness was measured indirectly and calculated as a coefficient of the changes in the
Achilles tendon force and the muscle length. The fatigue protocol induced a marked impairment of the neuromuscular function
in maximal SSC jumps. This was demonstrated by a 14.1%–17.7% (n.s. –P < 0.001) reduction in the mean eccentric forces and a 17.3%–31.8% (n.s. –P < 0.05) reduction in the corresponding M1 area under the electromyograms. Both of these methods of assessing the short latency reflex response showed a clear deterioration
in the sensitivity of the reflex after fatigue (P < 0.05–0.001). This was also the case for the eccentric peak stiffness of the soleus muscle which declined immediately after
fatigue by 5.4% to 7.1% (n.s. –P < 0.05) depending on the jump condition. The results observed would suggest that the modulation of neural input to the muscle
was at least partly of reflex origin from the contracting muscle, and furthermore, that the reduced muscle stiffness which
accompanied the decreased reflex sensitivity could have been partly responsible for the weakened muscle performance due to
impaired utilization of elastic energy.
Accepted: 28 April 1998 相似文献
15.
N. J. Bernier K. M. Gilmour Y. Takei S. F. Perry 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):237-248
The contributions of circulating angiotensin II (Ang II) and catecholamines to cardiovascular control in the spiny dogfish
were investigated by monitoring the effects of exogenous and endogenous dogfish [Asn1, Pro3, Ile5]-Ang II (dfAng II) on plasma catecholamine levels and blood pressure regulation. Bolus intravenous injections of dfAng II
(30–1200 pmol kg−1) elicited dose-dependent increases in plasma adrenaline and noradrenaline concentrations, caudal artery pressure (P
CA), and systemic vascular resistance (R
S), and a decrease in cardiac output (Q). Similar injections of Ang II in dogfish pre-treated with the α-adrenoceptor antagonist yohimbine (4 mg kg−1) also elicited dose-dependent increases in plasma catecholamine levels yet the cardiovascular effects were abolished. Dogfish
treated with yohimbine were hypotensive and had elevated levels of plasma Ang II and catecholamines. Intravenous injection
of the smooth muscle relaxant papaverine (10 mg kg−1) elicited a transient decrease in P
CA and R
S, and increases in plasma Ang II and catecholamine levels. In dogfish first treated with lisinopril (10−4 mol kg−1), an angiotensin converting enzyme inhibitor, papaverine treatment caused a more prolonged and greater decrease in P
CA and R
S, an attenuated increase in plasma catecholamines, and no change in plasma Ang II. By itself, lisinopril treatment had little
effect on P
CA, and no effect on R
S, plasma Ang II or catecholamines. In yohimbine-treated dogfish, papaverine treatment elicited marked decreases in P
CA, R
S, and Q, and increases in plasma Ang II and catecholamines. Among the three papaverine treatments, there was a positive linear relationship
between plasma Ang II and catecholamine concentrations, and the cardiovascular and hormonal changes were most pronounced in
the yohimbine + papaverine treatment. Therefore, under resting normotensive conditions, while Ang II does not appear to be
involved in cardiovascular control, catecholamines play an important role. However, during a hypotensive stress elicited by
vascular smooth muscle relaxation, Ang II indirectly contributes to cardiovascular control by dose-dependently stimulating
catecholamine release.
Accepted: 24 February 1999 相似文献
16.
Isabelle Sendowski Gustave Savourey Yves Besnard Jacques Bittel 《European journal of applied physiology and occupational physiology》1997,75(6):471-477
To study the physiological responses induced by immersing in cold water various areas of the upper limb, 20 subjects immersed
either the index finger (T1), hand (T2) or forearm and hand (T3) for 30 min in 5°C water followed by a 15-min recovery period.
Skin temperature of the index finger, skin blood flow (Qsk) measured by laser Doppler flowmetry, as well as heart rate (HR) and mean arterial blood pressure (ˉBPa) were all monitored during the test. Cutaneous vascular conductance (CVC) was calculated as Qsk / ˉBPa. Cold induced vasodilatation (CIVD) indices were calculated from index finger skin temperature and CVC time courses. The
results showed that no differences in temperature, CVC or cardiovascular changes were observed between T2 and T3. During T1,
CIVD appeared earlier compared to T2 and T3 [5.90 (SEM 0.32) min in T1 vs 7.95 (SEM 0.86) min in T2 and 9.26 (SEM 0.78) min
in T3, P < 0.01]. The HR was unchanged in T1 whereas it increased significantly at the beginning of T2 and T3 [+13 (SEM 2) beats · min−1 in T2 and +15 (SEM 3) beats · min−1 in T3, P < 0.01] and then decreased at the end of the immersion [−12 (SEM 3) beats · min−1 in T2, and −15 (SEM 3) beats · min−1 in T3, P < 0.01]. Moreover, ˉBPaincreased at the beginning of T1 but was lower than in T2 and T3 [+9.3 (SEM 2.5) mmHg in T1, P < 0.05; +20.6 (SEM 2.6) mmHg and 26.5 (SEM 2.8) mmHg in T2 and T3, respectively, P < 0.01]. The rewarming during recovery was faster and higher in T1 compared to T2 and T3. These results showed that general
and local physiological responses observed during an upper limb cold water test differed according to the area immersed. Index
finger cooling led to earlier and faster CIVD without significant cardiovascular changes, whereas hand or forearm immersion
led to a delayed and slower CIVD with a bradycardia at the end of the test.
Accepted: 26 November 1996 相似文献
17.
Novikov I Kalter-Leibovici O Chetrit A Stav N Epstein Y 《International journal of biometeorology》2012,56(1):121-127
Global climate changes affect health and present new challenges to healthcare systems. The aim of the present study was to
analyze the pattern of visits to the medical wing of emergency rooms (ERs) in public hospitals during warm seasons, and to
develop a predictive model that will forecast the number of visits to ERs 2 days ahead. Data on daily visits to the ERs of
the four largest medical centers in the Tel-Aviv metropolitan area during the warm months of the year (April–October, 2001–2004),
the corresponding daily meteorological data, daily electrical power consumption (a surrogate marker for air-conditioning),
air-pollution parameters, and calendar information were obtained and used in the analyses. The predictive model employed a
time series analysis with transitional Poisson regression. The concise multivariable model was highly accurate (r
2 = 0.819). The contribution of mean daily temperature was small but significant: an increase of 1°C in ambient temperature
was associated with a 1.47% increase in the number of ER visits (P < 0.001). An increase in electrical power consumption significantly attenuated the effect of weather conditions on ER visits
by 4% per 1,000 MWh (P < 0.001). Higher daily mean SO2 concentrations were associated with a greater number of ER visits (1% per 1 ppb increment; P = 0.017). Calendar data were the main predictors of ER visits (r
2 = 0.794). The predictive model was highly accurate in forecasting the number of visits to ERs 2 days ahead. The marginal
effect of temperature on the number of ER visits can be attributed to behavioral adaptations, including the use of air-conditioning. 相似文献
18.
B. Mercier P. Granier J. Mercier L. Foucat G. Bielicki J. Pradere J. P. Renou C. Prefaut 《European journal of applied physiology and occupational physiology》1998,78(1):20-27
We investigated whether localized 1H nuclear magnetic resonance spectroscopy (NMRS) using stimulated echoes (STEAM) with a long mixing time (t
m) allowed the suppression of the fat signal and detection of lactate in skeletal muscle. The 1H NMRS sequence was first validated in three isolated and perfused rabbit biceps brachii muscles. Spectra were obtained on a wide-bore spectrometer using a dual-tuned probe (1H and 31P). Death was simulated by ceasing the muscle perfusion, which allowed post-mortem changes to be followed. During and after the simulated death, changes in levels of pH and in content of energy-rich compounds
were observed with 31P NMRS. Our results showed an inverse linear relationship between pH and lactate in each of the three rabbits (r = 0.93, P < 0.001; r = 0.92, P < 0.01; r = 0.89, P < 0.01) and a decrease in phosphocreatine and concomitant increase in lactate. We then investigated whether this sequence
allowed repeated detection of lactate in human soleus muscle during the recovery between periods of intense exercise (force-velocity
test, F-v test). Seven subjects mean age 25.1 (SEM 0.8) years participated in this study. Soleus muscle lactate was detected at rest
and for 3 min 30 s of the 5-min recovery between periods using a 2.35-T 40-cm bore magnet spectrometer. Arm venous plasma
lactate concentration was measured at rest, during the F-v test when the subject stopped pedalling (S1), and at the end of each 5-min recovery between periods (S2). Results showed that the venous plasma lactate concentration at S1 and S2 increased significantly from the beginning of the F-v test to peak anaerobic power (W
an,peak) (P < 0.001). The spectra showed that muscle lactate resonance intensity rose markedly when W
an,peak was achieved. The muscle lactate resonance intensity plotted as a percentage of the resting value increased significantly
at W
an,peak compared with submaximal braking forces (P < 0.05). We concluded from these results that localized 1H NMRS using STEAM with a long t
m allows suppression of the fat signal and repeated detection of lactate on isolated perfused skeletal muscle in animals and
between periods of intense exercise in humans.
Accepted: 19 January 1998 相似文献
19.
Marco Bonifazi Eleni Bela Concetta Lupo Gilberto Martelli Bin Zhu Giancarlo Carli 《European journal of applied physiology and occupational physiology》1998,78(5):394-397
The aim of the present study was to evaluate the response of adrenocorticotropin ([ACTH]) and growth hormone ([GH]) concentrations
to a typical aerobic swimming set during a training season. Nine top-level male endurance swimmers (age range 17–23 years)
were tested during three training sessions occurring 6, 12 and 18 weeks after the beginning of the season. During each session,
after a standard warm-up, the swimmers performed a training set of 15 × 200-m freestyle, with 20 s of rest between repetitions,
at a predetermined individual speed. Blood samples were collected before warm-up and at the end of the training set. A few
days before each session, the individual swimming velocity corresponding to the 4 mmol · l−1 blood lactate concentration (v
4) was assessed as a standard of aerobic performance. Aerobic training affected v
4 levels, which were highest 18 weeks after the beginning of the season; at the same time, while [ACTH] response was attenuated,
[GH] response was enhanced. These results could be considered as adaptations to the exercise intensity. In our training programme,
these adaptations seemed to have occurred between the 12th and 18th weeks of the training season.
Accepted: 21 April 1998 相似文献
20.
Jerzy A. Zoladz Zbigniew Szkutnik Joanna Majerczak Krzysztof Duda 《European journal of applied physiology and occupational physiology》1998,78(4):369-377
The purpose of this study was to develop a method to determine the power output at which oxygen uptake (V˙O2) during an incremental exercise test begins to rise non-linearly. A group of 26 healthy non-smoking men [mean age 22.1 (SD
1.4) years, body mass 73.6 (SD 7.4) kg, height 179.4 (SD 7.5) cm, maximal oxygen uptake (V˙O2max) 3.726 (SD 0.363) l · min−1], experienced in laboratory tests, were the subjects in this study. They performed an incremental exercise test on a cycle
ergometer at a pedalling rate of 70 rev · min−1. The test started at a power output of 30 W, followed by increases amounting to 30 W every 3 min. At 5 min prior to the first
exercise intensity, at the end of each stage of exercise protocol, blood samples (1 ml each) were taken from an antecubital
vein. The samples were analysed for plasma lactate concentration [La]pl, partial pressure of O2 and CO2 and hydrogen ion concentration [H+]b. The lactate threshold (LT) in this study was defined as the highest power output above which [La−]pl showed a sustained increase of more than 0.5 mmol · l−1 · step−1. The V˙O2 was measured breath-by-breath. In the analysis of the change point (CP) of V˙O2 during the incremental exercise test, a two-phase model was assumed for the 3rd-min-data of each step of the test: X
i
=at
i
+b+ɛ
i
for i=1,2,…,T, and E(X
i
)>at
i
+b for i =T+1,…,n, where X
1, … , X
n
are independent and ɛ
i
∼N(0,σ2). In the first phase, a linear relationship between V˙O2 and power output was assumed, whereas in the second phase an additional increase in V˙O2 above the values expected from the linear model was allowed. The power output at which the first phase ended was called the
change point in oxygen uptake (CP-V˙O2). The identification of the model consisted of two steps: testing for the existence of CP and estimating its location. Both
procedures were based on suitably normalised recursive residuals. We showed that in 25 out of 26 subjects it was possible
to determine the CP-O2 as described in our model. The power output at CP-V˙O2 amounted to 136.8 (SD 31.3) W. It was only 11 W – non significantly – higher than the power output corresponding to LT. The
V˙O2 at CP-V˙O2 amounted to 1.828 (SD 0.356) l · min−1 was [48.9 (SD 7.9)% V˙O2
max
]. The [La−]pl at CP-V˙O2, amounting to 2.57 (SD 0.69) mmol · l−1 was significantly elevated (P<0.01) above the resting level [1.85 (SD 0.46) mmol · l−1], however the [H+]b at CP-V˙O2 amounting to 45.1 (SD 3.0) nmol · l−1, was not significantly different from the values at rest which amounted to 44.14 (SD 2.79) nmol · l−1. An increase of power output of 30 W above CP-V˙O2 was accompanied by a significant increase in [H+]b above the resting level (P=0.03).
Accepted: 25 March 1998 相似文献