共查询到20条相似文献,搜索用时 15 毫秒
1.
Hans Gesser William R. Driedzic Francisco Tadeu Rantin José Carlos de Freitas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(7):474-480
Isometric force development of electrically paced preparations isolated from the systemic heart of Octopus vulgaris were utilized to examine the regulation of contractility by Ca2+. Increases in extracellular Ca2+, to the physiological level, resulted in enhancement of twitch force. For instance, at 36 beats · min−1 an increase in Ca2+ from 3 to 9 mmol · l−1 resulted in a threefold increase in twitch force development. When steady-state contraction at 12 beats · min−1 was followed by a rest period of either 5 or 10 min, the first contraction always exhibited either an increase in twitch
force or stayed unchanged such that post-rest twitch force was about 133% of the last value in the steady-state train. Ryanodine
(12.5 μmol · l−1), which is considered to be a specific inhibitor of the Ca2+ storage and release capabilities of the sarcoplasmic reticulum (SR), was applied to further assess Ca2+ handling. Twitch force fell to about 22% of the preteatment level in preparations paced at either 12 or 36 beats · min−1. In all preparations the frequency transition from 12 to 36 beats · min−1 was associated with an increase in resting tension. The␣increase␣was 37 ± 14% prior to ryanodine treatment and was significantly
elevated to 127 ± 33% following treatment. When steady-state contraction at 36 beats · min−1 was followed by a rest period of 10 s, the first contraction was not significantly different from the last beat in the train
prior to ryanodine; however, with ryanodine treatment, post-rest twitch force development significantly decreased. Twitch
force development was regular at pacing rates of up to 300 beats · min−1. Twitch force was maintained up to rates of 84 beats · min−1 but␣decreased thereafter and reached a value of about 10% at 300 beats · min−1. Resting tension increased substantially as frequency was elevated from 12 to 36 beats · min−1 and then gradually increased as frequency was further elevated to 180 beats · min−1. In conclusion, the Octopus ventricle is dependent upon extracellular Ca2+ for contraction. A post-rest potentiation of force development, the negative impact of ryanodine, and the ability to respond
regularly at high pacing rates imply a strong reliance on the SR in Ca2+ cycling based on criteria established for vertebrate hearts.
Accepted: 19 January 1997 相似文献
2.
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
3.
H. J. Bogaard H. H. Woltjer B. M. Dekker A. R. J. van Keimpema P. E. Postmus P. M. J. M. de Vries 《European journal of applied physiology and occupational physiology》1997,75(5):435-442
Whereas with advancing age, peak heart rate (HR) and cardiac index (CI) are clearly reduced, peak stroke index (SI) may decrease,
remain constant or even increase. The aim of this study was to describe the patterns of HR, SI, CI, arteriovenous difference
in oxygen concentration (C
a-vO2), mean arterial pressure (MAP), systemic vascular resistance index (SVRI), stroke work index (SWI) and mean systolic ejection
rate index (MSERI) in two age groups (A: 20–30 years, n = 20; B: 50–60 years n = 20. After determination of pulmonary function, an incremental bicycle exercise test was performed, with standard gas-exchange
measurements and SI assessment using electrical impedance cardiography. The following age-related changes were found: similar
submaximal HR response to exercise in both groups and a higher peak HR in A than in B[185 (SD 9) vs 167 (SD 14) beats · min−1, P < 0.0005]; increase in SI with exercise up to 60–90 W and subsequent stabilization in both groups. As SI decreased towards
the end of exercise in B, a higher peak SI was found in A [57.5 (SD 14.0) vs 43.6 (SD 7.7) ml · m−2, P < 0.0005]; similar submaximal CI response to exercise, higher peak CI in A [10.6 (SD 2.5) vs 7.2 (SD 1.3) l · min−1 · m−2, P < 0.0005]; no differences in C
a-vO2 during exercise; higher MAP at all levels of exercise in B; higher SVRI at all levels of exercise in B; lower SWI in B after
recovery; higher MSERI at all levels of exercise in A. The decrease in SI with advancing age would seem to be related to a
decrease in myocardial contractility, which can no longer be compensated for by an increase in preload (as during submaximal
exercise). Increases in systemic blood pressure may also compromise ventricular function but would seem to be of minor importance.
Accepted: 24 September 1996 相似文献
4.
S. E. Mathiassen T. Aminoff 《European journal of applied physiology and occupational physiology》1997,76(5):434-444
Ten females (25–50 years of age) performed isometric shoulder flexions, holding the right arm straight and in a horizontal
position. The subjects were able to see the rectified surface electromyogram (EMG) from either one of two electrode pairs
above the upper trapezius muscle and were instructed to keep its amplitude constant for 15 min while gradually unloading the
arm against a support. The EMG electrodes were placed at positions representing a “cranial” and a “caudal” region of the muscle
suggested previously to possess different functional properties. During the two contractions, recordings were made of: (1)
EMG root mean square-amplitude and zero crossing (ZC) frequency from both electrode pairs on the trapezius as well as from
the anterior part of the deltoideus, (2) supportive force, (3) heart rate (HR) and mean arterial blood pressure (MAP), and
(4) perceived fatigue. The median responses during the cranial isoelectric contraction were small as compared to those reported
previously in the literature: changes in exerted glenohumeral torque and ZC rate of the isoelectric EMG signal of −2.81% · min−1 (P = 0.003) and 0.03% · min−1 (P= 0.54), respectively, and increases in HR and MAP of 0.14 beats · min−2 (P= 0.10) and 0.06 mmHg · min−1 (P= 0.33), respectively. During the contraction with constant caudal EMG amplitude, the corresponding median responses were
−2.51% · min−1 (torque), 0.01% · min−1 (ZC rate), 0.31 beats · min−2 (HR), and 0.93 mmHg · min−1 (MAP); P=0.001, 0.69, 0.005, and 0.003, respectively. Considerable deviations from the “isoelectric” target amplitude were common
for both contractions. Individuals differed markedly in response, and three distinct subgroups of subjects were identified
using cluster analysis. These groups are suggested to represent different motor control scenarios, including differential
engagement of subdivisions of the upper trapezius, alternating motor unit recruitment and, in one group, a gradual transition
towards a greater involvement of type II motor units. The results indicate that prolonged low-level contractions of the shoulder
muscles may in general be accomplished with a moderate metabolic stress, but also that neuromuscular adaptation strategies
differ significantly between individuals. These results may help to explain why occupational shoulder-neck loads of long duration
cause musculoskeletal disorders in some subjects but not in others.
Accepted: 1 March 1997 相似文献
5.
J. Hall I. A. Macdonald P. J. Maddison J. P. O''Hare 《European journal of applied physiology and occupational physiology》1998,77(3):278-284
This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise
on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water
temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h−1. Oxygen consumption (V˙O2) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing
speed both in water and on land. At 3.5 km · h−1
V˙O2 was similar across procedures [χ = 0.6 (0.05) l · min−1]. At 4.5 and 5.5 km · h−1
V˙O2 was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm:
0.8 and 0.9 l · min−1, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at
4.5 and 5.5 km · h−1 (P ≤ 0.003). The HR-V˙O2 relationship showed that at a V˙O2 of 0.9 l · min−1, HR was higher in water at 36°C (115 beats · min−1) than either on land (100 beats · min−1) or in water at 28°C (99 beats · min−1). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h−1 was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was
27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data
has implications for therapists working in hydrotherapy pools.
Accepted: 3 September 1997 相似文献
6.
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
7.
C. Schirlo A. Bub C. Reize A. Bührer J. Kohl E. A. Koller 《European journal of applied physiology and occupational physiology》1997,75(2):124-131
To investigate the role of fluid shifts during the short-term adjustment to acute hypobaric hypoxia (AHH), the changes in
lower limb (LV) and forearm volumes (FV) were measured using a strain-gauge plethysmograph technique in ten healthy volunteers
exposed to different altitudes (450 m, 2500 m, 3500 m, 4500 m) in a hypobaric chamber. Arterial blood pressure, heart rate,
arterial oxygen saturation (S
aO2), endtidal gases, minute ventilation and urine flow were also determined. A control experiment was performed with an analogous
protocol under normobaric normoxic conditions. The results showed mean decreases both in LV and FV of −0.52 (SD 0.39) ml · 100
ml−1 and −0.65 (SD 0.32) ml · 100 ml−1, respectively, in the hypoxia experiments [controls: LV −0.28 (SD 0.37), FV −0.41 (SD 0.47) ml · 100 ml−1]. Descent to normoxia resulted in further small but not significant decreases in mean LV [−0.02 (SD 0.11) ml · 100 ml−1], whereas mean FV tended to increase slightly [ + 0.02 (SD 0.14) ml · 100 ml−1]; in the control experiments mean LV and FV decreased continuously during the corresponding times [−0.19 (SD 0.31), −0.18
(SD 0.10) ml · 100 ml−1, respectively]. During the whole AHH, mean urine flow increased significantly from 0.84 (SD 0.41) ml · min−1 to 3.29 (SD 1.43) ml · min−1 in contrast to the control conditions. We concluded that peripheral fluid volume shifts form a part of the hypoxia-induced
acute cardiovascular changes at high altitude. In contrast to the often reported formation of peripheral oedema after prolonged
exposure to hypobaric hypoxia, the results provided no evidence for the development of peripheral oedema during acute induction
to high altitude. However, the marked increase in interindividual variance in S
aO2 and urine flow points to the appearance of the first differences in the short-term adjustment even after 2 h of acute hypobaric
hypoxia.
Accepted: 27 August 1996 相似文献
8.
Gerald S. Zavorsky David L. Montgomery David J. Pearsall 《European journal of applied physiology and occupational physiology》1998,77(3):224-230
The purposes of this study were to determine whether running economy (RE) is adversely affected following intense interval
bouts of 10 × 400-m running, and whether there is an interaction effect between RE and recovery duration during the workouts.
Twelve highly trained male endurance athletes [maximal oxygen consumption; V˙O2
max
=72.5 (4.3) ml·kg−1·min−1; mean (SD)] performed three interval running workouts of 10 × 400 m with a minimum of 4 days between runs. Recovery duration
between the repetitions was randomly assigned at 60, 120 or 180 s. The velocity for each 400-m run was determined from a treadmill
V˙O2
max
test. The average running velocity was 357.9 (9.0) m · min−1. Following the workout, the rating of perceived exertion (RPE) increased significantly (P < 0.01) as recovery duration between the 400-m repetitions decreased (14.4, 16.1, and 17.7 at 180s, 120s, and 60 s recovery,
respectively). Prior to and following each workout, RE was measured at speeds of 200 and 268 m · min−1. Changes in RE from pre- to post-workout, as well as heart rate (HR) and respiratory exchange ratio (R) were similar for the three recovery conditions. When averaged across conditions, oxygen consumption (V˙O2) increased significantly (P < 0.01) from pre- to post-test (from 38.5 to 40.5 ml · kg−1 · min−1 at 200 m · min−1, and from 53.1 to 54.5 ml · kg−1 · min−1 at 268 m · min−1, respectively). HR increased (from 124 to 138, and from 151 to 157 beats · min−1 respectively) and R decreased (from 0.90 to 0.78, and from 0.93 to 0.89, respectively) at 200 and 268 m · min−1, respectively (P < 0.01). This study showed that RE can be perturbed after a high-intensity interval workout and that the changes in V˙O2, HR and R were independent of the recovery duration between the repetitions.
Accepted: 23 June 1997 相似文献
9.
Tazawa H Akiyama R Moriya K 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2002,132(4):675-689
Heart rate (HR) in avian embryos developing inside an eggshell has been measured by various means while maintaining adequate gas exchange through the eggshell. This is an important requirement in order to avoid adverse effects of impeding gas exchange on the cardiac rhythms of developing embryos. The present report is a review of our ontogenetic study on embryonic HR, which was measured with fulfillment of the above requirement and also hatchling HR measured non-invasively. Firstly, we reviewed measurements of daily changes (developmental patterns) in embryonic mean heart rate (MHR), which were determined from a short-term measurement of HR once a day, in 34 species of altricial and precocial birds. The allometric relationship between the MHR during pipping in altricial birds and their fresh egg masses was the same as that between the MHR at 80% of incubation duration and fresh egg masses in pre-cocial birds. Secondly, we presented the developmental patterns of MHR in chick embryos and hatchlings, which were determined from long-term, continuous measurement of HR before, during and after hatching. The ultradian and circadian rhythms of HR were clearly shown in embryos and hatchlings, respectively. Thirdly, we summarized instantaneous HR fluctuations: HR variability and HR irregularities, in chick embryos and hatchlings. The distinctive patterns were shown in pre-pipped and pipped embryos and newly hatched chicks, individually, which were partly related to autonomic nervous functions and physiological functions. 相似文献
10.
H. Arabi H. Vandewalle P. Pitor J. de Lattre H. Monod 《European journal of applied physiology and occupational physiology》1997,76(2):122-127
The present experiment was designed to study the importance of strength and muscle mass as factors limiting maximal oxygen
uptake (V˙O2
max
) in wheelchair subjects. Thirteen paraplegic subjects [mean age 29.8 (8.7) years] were studied during continuous incremental
exercises until exhaustion on an arm-cranking ergometer (AC), a wheelchair ergometer (WE) and motor-driven treadmill (TM).
Lean arm volume (LAV) was estimated using an anthropometric method based upon the measurement of various circumferences of
the arm and forearm. Maximal strength (MVF) was measured while pushing on the rim of the wheelchair for three positions of
the hand on the rim (−30°, 0° and +30°). The results indicate that paraplegic subjects reached a similar V˙O2
max
[1.23 (0.34) l · min−1, 1.25 (0.38) l · min−1, 1.22 (0.18) l · min−1 for AC, TM and WE, respectively] and V˙O2
max
/body mass [19.7 (5.2) ml · min−1 · kg−1, 19.5 (6.14) ml · min−1 · kg−1, 19.18 (4.27) ml · min−1 · kg−1 for AC, TM and WE, respectively on the three ergometers. Maximal heart rate f
c
max
during the last minute of AC (173 (17) beats · min−1], TM [168 (14) beats · min−1], and WE [165 (16) beats · min−1], were correlated, but f
c
max
was significantly higher for AC than for TM (P<0.03). There were significant correlations between MVF and LAV (P<0.001) and between the MVF data obtained at different angles of the hand on the rim [311.9 (90.1) N, 313.2 (81.2) N, 257.1
(71) N, at −30°, 0° and +30°, respectively]. There was no correlation between V˙O2
max
and LAV or MVF. The relatively low values of f
c
max
suggest that V˙O2
max
was, at least in part, limited by local aerobic factors instead of central cardiovascular factors. On the other hand, the
lack of a significant correlation between V˙O2
max
and MVF or muscle mass was not in favour of muscle strength being the main factor limiting V˙O2
max
in our subjects.
Accepted: 31 January 1997 相似文献
11.
Moriya K Kato K Matsumura M Dzialowski E Burggren WW Tazawa H 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2002,131(4):787-795
Six emu hatchlings were non-invasively measured for electrocardiogram (ECG) from their chest wall using flexible electrodes, and the instantaneous heart rate (IHR) was determined from ECG throughout the first week of post-hatching life. Although the baseline heart rate (HR) was low, approximately 100-200 beats per min (bpm), compared with chick hatchlings, the IHR fluctuated markedly. The fluctuation of IHR comprised HR variability and irregularities that were designated as types I, II and III in chick hatchlings and additional large accelerations distinctive of emu hatchlings. Type I was HR oscillation with a mean frequency of 0.37 Hz (range 0.2-0.7 Hz), i.e. respiratory sinus arrhythmia (RSA). From RSA, breathing frequency in emu hatchlings was estimated to be approximately half of that in chickens. Type II HR oscillation was also found in the emu; the frequency ranged from approximately 0.04 to 0.1 with a mean of 0.06 Hz, and the magnitude tended to be large compared with that of chickens. In addition to type III HRI, which was designated in chickens, large, irregular HR accelerations were characteristic of emu hatchlings. From IHR data, developmental patterns of mean heart rate (MHR) were constructed and plotted on a single graph to inspect the diurnal rhythm of MHR by visual inspection and power spectrum analysis. A circadian rhythm was not clear in the emu hatchlings, in contrast to chick hatchlings, which showed a dominant diurnal rhythm. 相似文献
12.
Ronald Heus Alexander H. Wertheim George Havenith 《European journal of applied physiology and occupational physiology》1998,77(4):388-394
The assumption that working on board ship is more strenuous than comparable work ashore was investigated in this study. Various
physiological parameters (V˙O2, V˙CO2, V˙
E and HR) have been measured to determine the energy expenditure of subjects walking slowly on a moving platform (ship motion
simulator). Twelve subjects (eight men and four women) walked either freely on the floor or on a treadmill at a speed of 1 m · s−1. Platform motion was either in a heave, pitch or roll mode. These three conditions were compared with a control condition
in which the platform remained stationary. The results showed that during pitch and roll movements of the platform, the energy
expenditure for the same walking task was about 30% higher than under the stationary control condition (3.6 J · kg−1 · m−1 vs 2.5 J · kg−1 · m−1, P < 0.05) for both walking on a treadmill and free walking. The heart rate data supported the higher energy expenditure results
with an elevation of the heart rate (112 beats · min−1 vs 103 beats · min−1, P < 0.05). The heave condition did not differ significantly from the stationary control condition. Pitch and roll were not
significantly different from each other. During all experimental conditions free walking resulted in a higher energy cost
of walking than treadmill walking (3.5 J · kg−1 · m−1 vs 2.7 J · kg−1 · m−1, P < 0.05) at the same average speed. The results of this experiment were interpreted as indicating that the muscular effort,
needed for maintaining balance when walking on a pitching or rolling platform, resulted in a significantly higher work load
than similar walking on a stable or a heaving floor, independent of the mode of walking. These results explain in part the
increased fatigue observed when a task is performed on a moving platform.
Accepted: 3 October 1997 相似文献
13.
Greg J. Wilson Andrew D. Walshe Mark R. Fisher 《European journal of applied physiology and occupational physiology》1997,75(5):455-461
The aims of the present study were: (1) to assess aerobic metabolism in paraplegic (P) athletes (spinal lesion level, T4–L3)
by means of peak oxygen uptake (V˙O2peak) and ventilatory threshold (VT), and (2) to determine the nature of exercise limitation in these athletes by means of cardioventilatory
responses at peak exercise. Eight P athletes underwent conventional spirographic measurements and then performed an incremental
wheelchair exercise on an adapted treadmill. Ventilatory data were collected every minute using an automated metabolic system:
ventilation (l · min−1), oxygen uptake (V˙O2, l · min−1, ml · min−1 · kg−1), carbon dioxide production (V˙CO2, ml · min−1), respiratory exchange ratio, breathing frequency and tidal volume. Heart rate (HR, beats · min−1) was collected with the aid of a standard electrocardiogram. V˙O2peak was determined using conventional criteria. VT was determined by the breakpoint in the V˙CO2−V˙O2 relationship, and is expressed as the absolute VT (V˙O2, ml · min−1 · kg−1) and relative VT (percentage of V˙O2peak). Spirometric values and cardioventilatory responses at rest and at peak exercise allowed the measurement of ventilatory
reserve (VR), heart rate reserve (HRr), heart rate response (HRR), and O2 pulse (O2 P). Results showed a V˙O2peak value of 40.6 (2.5) ml · min−1 · kg−1, an absolute VT detected at 23.1 (1.5) ml · min−1 · kg−1
V˙O2 and a relative VT at 56.4 (2.2)% V˙O2peak. HRr [15.8 (3.2) beats · min−1], HRR [48.6 (4.3) beat · l−1], and O2 P [0.23 (0.02) ml · kg−1 · beat−1] were normal, whereas VR at peak exercise [42.7 (2.4)%] was increased. As wheelchair exercise excluded the use of an able-bodied
(AB) control group, we compared our V˙O2peak and VT results with those for other P subjects and AB controls reported in the literature, and we compared our cardioventilatory
responses with those for respiratory and cardiac patients. The low V˙O2peak values obtained compared with subject values obtained during an arm-crank exercise may be due to a reduced active muscle
mass. Absolute VT was somewhat comparable to that of AB subjects, mainly due to the similar muscle mass involved in wheelchair
and arm-crank exercise by P and AB subjects, respectively. The increased VR, as reported in patients with chronic heart failure,
suggested that P athletes exhibited cardiac limitation at peak exercise, and this contributed to the lower V˙O2peak measured in these subjects.
Accepted: 22 April 1997 相似文献
14.
Theodore J. Angelopoulos Robert J. Robertson F. L. Goss Allan Utter 《European journal of applied physiology and occupational physiology》1997,75(2):132-135
Eight fit men [maximum oxygen consumption (O2max) 64.6 (1.9) ml · kg−1 · min−1, aged 28.3 (1.7) years (SE in parentheses) were studied during two treadmill exercise trials to determine the effect of endogenous
opioids on insulin and glucagon immunoreactivity during intense exercise (80% O2max). A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order.
Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration
of naloxone (N; 1.2 mg; 3 ml) and the other after receiving a placebo (P; 0.9% NaCl saline; 3 ml). Prior to each experimental
trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately after,
each subject received either a N or P bolus injection. Blood samples were also collected after 20 min of continuous exercise
(running). Glucagon was higher (P < 0.05), while insulin was lower (P < 0.05), during exercise compared with pre-exercise values in both trials. However, glucagon was higher (P < 0.05) in the P than in the N exercise trial [141.4 (8.3) ng · l−1 vs 127.2 (7.6) ng · l−1]. There were no differences in insulin during exercise between the P and N trials [50.2 (4.3) pmol · l−1 vs 43.8 (5) pmol · l−1]. These data suggest that endogenous opioids may augment the glucagon response during intense exercise.
Accepted: 15 June 1996 相似文献
15.
Kato K Moriya K Dzialowski E Burggren WW Tazawa H 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2002,131(4):775-785
Emu eggs weigh approximately 600 g and have an incubation duration (ID) of approximately 50 days. The egg mass is approximately 10-fold heavier than the chicken egg and the ID is approximately 2.5-fold longer. Daily changes in mean heart rate (MHR) of emu embryos were previously determined, but further measurement was needed to investigate the species-specific behavior of cardiac rhythm for comparison with other species. In the present study, we continuously measured the electrocardiogram of emu embryos while maintaining adequate gas exchange through the eggshell and determined instantaneous heart rate (IHR) during the last 2-7 days of incubation until hatching or death. The MHR over 1-min intervals was calculated from IHR data in order to present continuous developmental patterns of heart rate (HR) in a single graph and 24-h recordings of HR in a single panel, showing the HR trend over a prolonged period. However, neither circadian nor ultradian rhythms of HR were shown in these figures or by power spectrum analysis. The IHR distinctively fluctuated and the fluctuations were mainly comprised of three patterns of irregular HR accelerations in embryos that hatched. Respiratory sinus arrhythmia also occurred in perinatal embryos. During the final stages of the perinatal period, short-term, repeated, large accelerations of IHR appeared, which signaled imminent hatching and has been reported for chick embryos. IHR fluctuations in embryos that failed to hatch tended to become inactive towards death. 相似文献
16.
Koji Ishida Tatsuya Hayashi Toshio Moritani Miharu Miyamura 《European journal of applied physiology and occupational physiology》1997,76(3):230-235
To elucidate whether combined adrenergic and parasympathetic blockade would affect the ventilatory response to exercise,
especially at the initial stage (phase I), six healthy subjects performed a brief and light voluntary bilateral leg extension
exercise and passive movements under the conditions of control (before the blockade) and after intravenous administration
of combined β-adrenergic (propranolol, 0.2 mg · kg−1) and muscarinic (atropine, 0.04 mg · kg−1) receptor antagonists. The movements were continued only within two breaths after the onset of the motion. Ventilation increased
immediately and significantly (P<0.05) within the first breath at the onset of voluntary exercise in all conditions as compared with at rest. However, the
magnitude of increase in mean ventilation within two breaths at the start of exercise as against the resting value (delta
ventilation) was significantly less (P<0.05) after the combined blockades (2.5 l · min−1) than in the control condition (3.7 l · min−1). Passive movements showed a similar but smaller change as compared with voluntary exercise. The heart rate response to exercise
was attenuated by the combined blockade while cardiac output showed a slight change at the onset of exercise. It is concluded
that phase I should occur despite the inhibited activity of the β-adrenergic and the cholinergic systems; nevertheless, the
response was attenuated by the combined blockade. These results suggest a possible role of the β-adrenergic and/or cholinergic
systems in the rapid increase in ventilation that occurs at the start of exercise.
Accepted: 2 March 1997 相似文献
17.
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
18.
Aldegunde M Andrés MD Soengas JL 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(3):237-243
The influx of glucose into the brain and plasma glucose disappearance were estimated in rainbow trout (Oncorhynchus mykiss) intravenously injected (1 ml · kg−1 body weight) with a single dose (15 μCi · kg−1 body weight) of 3-O-methyl-D-[U-14C]glucose ([U-14C]-3-OMG) at different times (2–160 min), and after intravenous injection at 15 min of increased doses (10–60 μCi · kg−1 body weight) of [U-14C]-3-OMG. Brain and plasma radiotracer concentrations were measured, and several kinetic parameters were calculated. The apparent
brain glucose influx showed a maximum after 15–20 min of injection then decreased to a plateau after 80 min. Brain distribution
space of 3-OMG increased from 2 min to 20 min reaching equilibrium from that time onwards at a value of 0.14 ml · g−1. The unidirectional clearance of glucose from blood to brain (k1) and the fractional clearance of glucose from brain to blood (k2) were estimated to be 0.093 ml · min−1 · g−1, and 0.867 min−1, respectively. A linear increase was observed in brain and plasma radiotracer concentrations when increased doses of [U-14C]-3-OMG were used. All these findings support a facilitative transport of glucose through the blood-brain barrier of rainbow
trout with characteristics similar to those observed in mammals. The injection of different doses of melatonin (0.25–1.0 mg · kg−1) significantly increased brain glucose influx suggesting a possible role for melatonin in the regulation of glucose transport
into the brain.
Accepted: 26 January 2000 相似文献
19.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
20.
J.-J. Janvier 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(7):517-526
Prostaglandin E2 (PGE2) injection caused an initial decrease in heart rate (HR) (55%), cardiac output (QC) (55%), ventral (VAP, 40%) and dorsal
(DAP, 60%) aortic pressures, associated with a marked gill vasoconstriction (100%) and a systemic vasodilation (30%) while
cardiac stroke volume (CSV) remained unchanged. It was followed by a progressive recovery of HR, DAP, and vascular resistances
to control values while VAP, QC, and CSV significantly increased (20%, 40%, and 40%, respectively). Bradycardia was abolished
either by atropine treatment or bilateral section of the cardiac vagus, suggesting that bradycardia could be the consequence
of a vagal mechanism triggered by a central action of PGE2. The increase in QC is due to the increase in CSV, which suggests a positive inotropic action of PGE2. Infusion with PGE2 (10−9 to 10−5 mol · l−1) did not cause any significant effect on the branchial vasculature in vitro, but when the preparation was pre-treated with
adrenaline (10−8 mol · l−4), a dose-related vasoconstrictory response to PGE2 (10−9 to 10−5 mol · l−1) occurred. A significant rise (25%) in gill vascular resistance was observed in vivo after treatment with the β-blocker propranolol
(2.0 mg · kg−1), suggesting the existence of a vasodilatory β-adrenergic control of the branchial vasculature. PGE2 caused an apnea followed by a simultaneous tachypnea (50%) and decrease in ventilatory amplitude (40%). The resulting decrease
in ventilatory water flow (Qw) was accompanied by a fall in arterial O2 tension (Pa O
2). Under steady Qw in curarized eels, an initial fall in Pa O
2 was still observed during the PGE2-induced gill vasoconstriction. It is concluded that PGE2 could play a role in the regulation of gas exchanges and blood circulation in particular environmental conditions which require
an impairment of gill respiration and a redistribution of blood to the benefit of the systemic vascular bed.
Accepted: 3 June 1997 相似文献