共查询到20条相似文献,搜索用时 15 毫秒
1.
Christian-Serge Degoute M.-P. Preckel Christian Dubreuil Vincent Banssillon Roland Duclaux 《European journal of applied physiology and occupational physiology》1997,75(4):326-332
The purpose of this work was to show that regulation of the blood flow to the cochlea by the sympathetic nervous system occurs
in humans at the level of the cochlear microcirculation during increases in blood pressure and that its involvement depends
on the pressure level. Eight anaesthetized patients undergoing tympanoplasty for hearing disease took part in a pharmacological
protocol of stimulation and inhibition of the autonomic nervous system (ANS) to provide variations in systolic blood pressure
(BPS) and cochlear blood flow (CBF). The CBF was measured by laser-Doppler flowmetry. Changes in autonomic nerve activity were
brought about by changes in baroreceptor activity (BR) initiated by the injection of an α adrenergic agent before and after
sympathetic and parasympathetic blockade. The CBF variations (δCBF) were plotted against BPS increases at each stage of the ANS inhibition. The BR diminished significantly after α blockade, after α and β blockade,
and after α and β blockade and atropine, by 50% (P < 0.01), 29% (P < 0.05), and 95% (P < 0.001) respectively. The BPS increased significantly (P < 0.01) by 36 (SD 9)%, 47 (SD 1)%, and 67 (SD 16)% respectively. The CBF response to an increase in BPS exhibited two opposing variations in the patients: CBF decreased significantly in one group, and increased significantly
in the other group. In both groups, δCBF decrease and δCBF increase, respectively, were significant after ANS blockade; even
so the decrease and increase, respectively, levelled off at BPS around 160 mmHg before ANS blockade. For BPS below 160 mmHg, correlations between δCBF and BPS were significant before inhibition and after inhibition of ANS. For BPS above 160 mmHg, BPS and δCBF were not correlated before inhibition of ANS, and were significantly correlated after inhibition of ANS. For BPS below 160 mmHg, CBF response to the BPS increase was the same before and after ANS blockade, i.e. ANS control did not predominate; even so, for BPS above 160 mmHg, the CBF response to BPS increase was different before and after ANS blockade: CBF varied significantly after ANS blockade as it varied for BPS below 160 mmHg, while it remained constant before ANS blockade that elicited ANS control of CBF. In conclusion, sympathetic
nerve regulation via its vasomotor tone at the level of cochlear microcirculation occurred markedly when the blood pressure
was above 160 mmHg; the autonomic nervous system would appear to control the cochlear blood flow against large variations
in blood flow in response to hypertensive phenomena.
Accepted: 7 October 1996 相似文献
2.
K?re B. Hagen Jostein Hallen Karin Harms-Ringdahl 《European journal of applied physiology and occupational physiology》1993,67(4):291-297
To establish safe levels for physical strain in occupational repetitive lifting, it is of interest to know the specific maximal working capacity. Power output, O2 consumption, heart rate and ventilation were measured in ten experienced forestry workers during maximal squat and stoop repetitive lifting. The two modes of repetitive lifting were also compared with maximal treadmill running. In addition, electromyogram (EMG) activity in four muscles was recorded and perceived central, local low-back and thigh exertion were assessed during the lifting modes. No significant difference was found in power output between the two lifting techniques. Despite this the mean O2 consumption was significantly greater during maximal squat lifting [38.7 (SD 5.8) ml·kg–1-·min–1] than maximal stoop lifting [32.9 (SD 5.7) ml·kg–1·min–1] (P<0.001). No significant correlation was found between O2 consumption (in millilitres per kilogram per minute) during maximal treadmill running and maximal stoop lifting, while O2 consumption during maximal squat lifting correlated highly with that of maximal treadmill running (r=0.928, P<0.001) and maximal stoop lifting (r=0.808, P<0.01). While maximal heart rates were significantly different among the three types of exercise, no such differences were found in the central rated perceived exertions. Perceived low-back exertion was rated significantly lower during squat lifting than during stoop lifting. The EMG recordings showed a higher activity for the vastus lateralis muscle and lower activity for the biceps femoris muscle during squat lifting than during stoop lifting. Related to the maximal voluntary contraction, the erector spinae muscle showed the highest activity irrespective of lifting technique. 相似文献
3.
The purpose of this study was to investigate the role of brain α1-adrenergic receptor binding in the rat model of pancreatic regeneration using 60–70% pancreatectomy. The α1-adrenergic receptors kinetics was studied in the cerebral cortex and brain stem of sham operated, 72 h pancreatectomised and 7 days pancreatectomised rats. Scatchard analysis with [3H]prazosin in cerebral cortex and brain stem showed a significant decrease (P < 0.01), (P < 0.05) in maximal binding (B
max) with a significant decrease (P < 0.001), (P < 0.01) in the K
d in 72 h pancreatectomised rats compared with sham respectively. Competition analysis in cerebral cortex and brain stem showed a shift in affinity during pancreatic regeneration. The sympathetic activity was decreased as indicated by the significantly decreased norepinephrine level in the plasma (P < 0.001), cerebral cortex (P < 0.01) and brain stem (P < 0.001) of 72 h pancreatectomised rats compared to sham. Thus, from our results it is suggested that the central α1-adrenergic receptors have a functional role in the pancreatic regeneration mediated through the sympathetic pathway. 相似文献
4.
K. H?kkinen A. Pakarinen R. U. Newton W. J. Kraemer 《European journal of applied physiology and occupational physiology》1998,77(4):312-319
Acute hormone responses of growth hormone (GH), total and free testosterone (TT and FT) and cortisol (C) to heavy resistance
isometric exercise were examined in ten young men [YM 26.5 (SD 4.8) years] and ten old men [OM 70.0 (SD 3.7) years]. Loading
conditions of the same relative intensity were created for the lower and upper extremity actions separately as well as for
both of them together – lower extremity exercise (LE; knee extension), upper extremity exercise (UE; bench press extension),
and lower and upper extremity exercise (LUE) performed simultaneously in a seated position. Single voluntary maximal isometric
actions lasting for 5 s were performed repeatedly for ten repetitions (with a recovery of 5 s) for a total of four sets. The
recovery time between the sets was 1 min. Each exercise led to large acute decreases in maximal isometric force in both YM
(P < 0.001) and OM (P < 0.001) ranging from 41% to 26% with no significant differences between the groups. Serum GH concentrations increased in
both YM (P < 0.05–0.01) and OM (P < 0.05) but the postexercise value in YM during LE was greater (P < 0.05) than for OM. The TT increased (P < 0.01–0.001) in YM in all three exercises, while in OM the increase occurred only during LE (P < 0.01). The exercises led to increases in FT in YM (P < 0.05 for LE and LUE), while in OM the increase occurred only during LUE (P < 0.05). The pre and postexercise FT were greater in YM (P < 0.001) than in OM. No significant changes occurred in C either in YM or in OM. The blood lactate concentrations increased
during the exercises in both YM (P < 0.001) and OM (P < 0.05–0.001) but the postexercise values during LE and LUE in YM were greater (P < 0.05) than in OM. The present data would indicate that the responses of GH, TT and FT to heavy resistance isometric exercise
are lowered with increasing age. The reduced acute hormone response together with the lowered basal values in FT in the older
men compared to the young men may indicate decreased anabolic effects on muscles and may explain in part the loss of muscle
mass and strength associated with aging.
Accepted: 18 August 1997 相似文献
5.
Tatsuhisa Takahashi Yoshimi Miyamoto 《European journal of applied physiology and occupational physiology》1998,77(4):305-311
To examine the influence of light exercise on cardiac responses during recovery from exercise, we measured heart rate (HR),
stroke volume (SV), and cardiac output (Q˙
c) in five healthy untrained male subjects in an upright position before, during, and after 10-min steady-state cycle exercise
at an exercise intensity of 170 W, corresponding to a mean of 68 (SD 4)% of maximal oxygen uptake. The recovery phase was
evaluated separately for three different conditions: 10 min of complete rest (passive recovery), 7 min of pedalling at 20-W
exercise intensity followed by 3 min of rest (partially active recovery), and 7 min of pedalling at 40-W exercise intensity
followed by 3 min of rest (partially active recovery), on an upright cycle ergometer. The time courses of decreases in HR
in the two active recovery phases at different exercise intensities were almost identical to those in the passive recovery
phase. However, the subsequent HR reductions during the rest after active recovery at 20 W and at 40 W were mean 7.5 (SD 4.4)
and mean 10.0 (SD 3.1) beats · min−1, respectively, both of which were significantly larger (P<0.05 and P<0.005) than the corresponding reduction [1.4 (SD 2.5) beats · min−1] for passive recovery. The SV values at the two exercise intensities during the active recovery periods were maintained at
levels similar to that during 170-W steady-state exercise. In contrast, the SV during passive recovery decreased gradually
to a level significantly below the initial baseline level at rest before exercise (P<0.05). The resultant time courses of CO values during active recovery were significantly higher (each P<0.05) than that during passive recovery. It was concluded from these findings that light post-exercise physical activity
plays an important role in facilitating the venous return from the muscles and in restoring the elevated HR to the pre-exercise
resting level.
Accepted: 17 September 1997 相似文献
6.
Tomasz Kostka Marc Bonnefoy Laurent M. Arsac Sophie E. Berthouze Alain Belli Jean-René Lacour 《European journal of applied physiology and occupational physiology》1997,76(1):81-87
The aim of this study was to investigate the relationship between maximal anaerobic power (P
max) and corresponding optimal velocity (V
opt) and habitual physical activity (PA) on the one hand and with maximal oxygen consumption (V˙O2max) on the other hand, in elderly women. Twenty-nine community dwelling, healthy women aged 66–82 years participated in the
study. PA was evaluated using the Questionnaire d'Activite Physique Saint-Etienne (QAPSE) and expressed using two QAPSE activity
indices: mean habitual daily energy expenditure (MHDEE) and daily energy expenditure corresponding to leisure time sports
activities (sports activity). The subjects' P
max and V
opt were measured while they cycled on a friction-loaded non-isokinetic cycle ergometer. P
max was expressed relative to body mass [P
max/kg(W · kg−1)], and relative to the mass of two quadriceps muscles [P
max
/Quadr(W·kgQuadr
−1)]. A negative relationship between P
max/kg (Spearman's r = −0.56; P < 0.01), P
max/Quadr (r = −0.53; P < 0.01) and V
opt (r = −0.45; P < 0.05) and age was found. P
max/kg was positively associated with MHDEE (r = 0.51; P < 0.01) and sports activity (r = 0.58; P < 0.01), as were P
max/Quadr and V
opt (r = 0.55; P < 0.01 and r = 0.54; P < 0.01, respectively). P
max/kg, P
max/Quadr and V
opt correlated positively with V˙O2max. The positive relationship between ergometer measurements and PA indices was similar to that between V˙O2max and PA. P
max/kg was, moreover, closely related to V
opt (r = 0.77; P < 0.001). When a multiple stepwise regression analysis was used to select the variables influencing ergometer measurements,
MHDEE contributed significantly to P
max/kg variance, whereas sports activity contributed to P
max/Quadr and V
opt variances. In conclusion, the data from this cross-sectional study suggest that in healthy elderly women habitual PA, and
especially leisure time PA, alleviates the decline of the P
max of the quadriceps muscles.
Accepted: 30 January 1997 相似文献
7.
Bailliart Olivier; Capderou Andre; Cholley Bernard P.; Kays Christian; Riviere Daniel; Techoueyres Pierre; Lachaud Jean-Luc; Vaida Pierre 《Journal of applied physiology》1998,85(6):2100-2105
Variations in gravity [head-to-footacceleration (Gz)] inducehemodynamic alterations as a consequence of changes in hydrostatic pressure gradients. To estimate the contribution of the lower limbs toblood pooling or shifting during the different gravity phases of aparabolic flight, we measured instantaneous thigh and calf girths byusing strain-gauge plethysmography in five healthy volunteers. Fromthese circumferential measurements, segmental leg volumes werecalculated at 1, 1.7, and 0 Gz.During hypergravity, leg segment volumes increased by 0.9% for thethigh (P < 0.001) and 0.5% for thecalf (P < 0.001) relative to1-Gz conditions. After suddenexposure to microgravity following hypergravity, leg segment volumeswere reduced by 3.5% for the thigh (P < 0.001) and 2.5% for the calf (P < 0.001) relative to 1.7-Gzconditions. Changes were more pronounced at the upper part of the leg.Extrapolation to the whole lower limb yielded an estimated 60-mlincrease in leg volume at the end of the hypergravity phase and asubsequent 225-ml decrease during microgravity. Although quantitativelyless than previous estimations, these blood shifts may participate inthe hemodynamic alterations observed during hypergravity and weightlessness. 相似文献
8.
Juha E. Peltonen Heikki K. Rusko Jari Rantam?ki Kai Sweins Seppo Niittym?ki Jukka T. Viitasalo 《European journal of applied physiology and occupational physiology》1997,76(6):495-503
Six male rowers rowed maximally for 2500 m in ergometer tests during normoxia (fractional concentration of oxygen in inspired
air, F
IO2 0.209), in hyperoxia (F
IO2 0.622) and in hypoxia (F
IO2 0.158) in a randomized single-blind fashion. Oxygen consumption (V˙O2), force production of strokes as well as integrated electromyographs (iEMG) and mean power frequency (MPF) from seven muscles
were measured in 500-m intervals. The iEMG signals from individual muscles were summed to represent overall electrical activity
of these muscles (sum-iEMG). Maximal force of a stroke (F
max) decreased from the 100% pre-exercise maximal value to 67 (SD 12)%, 63 (SD 15)% and 76 (SD 13)% (P<0.05 to normoxia, ANOVA) and impulse to 78 (SD 4)%, 75 (SD 14)% and 84 (SD 7)% (P<0.05) in normoxia, hypoxia and hyperoxia, respectively. A strong correlation between F
max and V˙O2 was found in normoxia but not in hypoxia and hyperoxia. The mean sum-iEMG tended to be lower (P<0.05) in hypoxia than in normoxia but hyperoxia had no significant effect on it. In general, F
IO2 did not affect MPF of individual muscles. In conclusion, it was found that force output during ergometer rowing was impaired
during hypoxia and improved during hyperoxia when compared with normoxia. Moreover, the changes in force output were only
partly accompanied by changes in muscle electrical activity as sum-iEMG was affected by hypoxic but not by hyperoxic gas.
The lack of a significant correlation between F
max and V˙O2 during hypoxia and hyperoxia may suggest a partial uncoupling of these processes and the existence of other limiting factors
in addition to V˙O2.
Accepted: 2 June 1997 相似文献
9.
Said Ahmaidi Janick Masse-Biron Brigitte Adam Dominique Choquet Michel Freville Jean-Pierre Libert Christian Prefaut 《European journal of applied physiology and occupational physiology》1998,78(2):170-176
This study assessed clinical and cardiorespiratory responses after an interval training programme in sedentary elderly adults
using the ventilatory threshold (V
th) as the index of exercise training intensity. A selection of 22 subjects were randomized into two groups: 11 subjects served
as the training group (TG) and the others as controls (CG). Maximal exercise tests were performed on a treadmill before (T0), each month (T1, T2) and after the 3-month interval training programme period (T3). The TG subjects were individually trained at the heart rate corresponding to V
th measured at T0, T1 and T2 as the breakpoint in the oxygen uptake-carbon dioxide production relationship. Their training programme consisted of walking/jogging
sessions on a running track twice a week. The sessions consisted of varying durations of exercise alternating with active
recovery in such a way that the subjects slowly increased their total exercise time from an initial duration of 30 min to
a final duration of 1 h. During training the heart rate was continuously monitored by a cardiofrequency meter. Compared with
the daily activities of the controls, no training programme-related injuries were observed in TG. Moreover, programme adherence
(73%) and attendance (97.3%) were high. The maximal oxygen uptake and V
th were increased in TG, by 20% (P<0.05) and 26% (P<0.01), respectively. Interval training at V
th also significantly increased maximal O2 pulse (P<0.05) and maximal ventilation (P<0.01). A significant decrease in submaximal ventilation (P<0.05) and heart rate (P<0.01) was also noted. These results would suggest that for untrained elderly adults, an interval training programme at the
intensity of V
th may be well-tolerated clinically and may significantly improve both maximal aerobic power and submaximal exercise tolerance.
Accepted: 6 January 1998 相似文献
10.
Pennycooke JC Cheng H Roberts SM Yang Q Rhee SY Stockinger EJ 《Plant molecular biology》2008,67(5):483-497
11.
A neuroimaging technique based on the saturation-recovery (SR)-T1 MRI method was applied for simultaneously imaging blood oxygenation level dependence (BOLD) contrast and cerebral blood flow change (ΔCBF), which is determined by CBF-sensitive T1 relaxation rate change (ΔR1
CBF). This technique was validated by quantitatively examining the relationships among ΔR1
CBF, ΔCBF, BOLD and relative CBF change (rCBF), which was simultaneously measured by laser Doppler flowmetry under global ischemia and hypercapnia conditions, respectively, in the rat brain. It was found that during ischemia, BOLD decreased 23.1±2.8% in the cortical area; ΔR1
CBF decreased 0.020±0.004s-1 corresponding to a ΔCBF decrease of 1.07±0.24 ml/g/min and 89.5±1.8% CBF reduction (n=5), resulting in a baseline CBF value (=1.18 ml/g/min) consistent with the literature reports. The CBF change quantification based on temperature corrected ΔR1
CBF had a better accuracy than apparent R1 change (ΔR1
app); nevertheless, ΔR1
app without temperature correction still provides a good approximation for quantifying CBF change since perfusion dominates the evolution of the longitudinal relaxation rate (R1
app). In contrast to the excellent consistency between ΔCBF and rCBF measured during and after ischemia, the BOLD change during the post-ischemia period was temporally disassociated with ΔCBF, indicating distinct CBF and BOLD responses. Similar results were also observed for the hypercapnia study. The overall results demonstrate that the SR-T1 MRI method is effective for noninvasive and quantitative imaging of both ΔCBF and BOLD associated with physiological and/or pathological changes. 相似文献
12.
S. Bermon M.-N. Magnié C. Dolisi J. Wolkiewiez M. Gastaud 《European journal of applied physiology and occupational physiology》1997,76(2):170-173
Non-smoking, male, professional firemen divers (n = 15) underwent two pulmonary function tests (PFT) separated by 6 years. Measured data were compared to European Coal Steel
Community recommended reference values to permit cross-sectional and then longitudinal study. Higher vital capacity (VC; P < 0.01) and forced expiratory volume in 1 s (FEV1; P < 0.05), and lower maximal mid-expiratory flow (MMEF) coefficient with VC (MMEF/VC; P < 0.05) were observed in both PFT. Diver's pulmonary diffusing capacity (DLCO) and the coefficient with alveolar volume (DLCO/V
A) showed significantly (P < 0.001) different evolution profiles than those expected from predicted values. In divers, DLCO and DLCO/V
A decreased from 104.0% to 91.4% and from 106.4% to 91.5% of predicted values respectively. Changes in DLCO and DLCO/V
A correlated positively with the initial measurement of DLCO (r = 0.67, P < 0.01) and DLCO/V
A (r = 0.74, P < 0.01) respectively, whereas no correlation between changes in pulmonary gas transfer function and age or diving history
parameters was found. Thus, it is suggested from our observations that hyperbaric atmosphere exposure increases the effects
of aging on pulmonary diffusing capacity and that pulmonary gas transfer function should be regularly tested in professional
and recreational divers.
Accepted: 22 February 1997 相似文献
13.
The modulation of the calmodulin-induced inhibition of the calcium release channel (ryanodine receptor) by two sulfhydryl
oxidizing compounds, 4-(chloromercuri)phenyl–sulfonic acid (4-CMPS) and 4,4′-dithiodipyridine (4,4′-DTDP) was determined by
single channel current recordings with the purified and reconstituted calcium release channel from rabbit skeletal muscle
sarcoplasmic reticulum (HSR) and [3H]ryanodine binding to HSR vesicles. 0.1 μm CaM reduced the open probability (P
o
) of the calcium release channel at maximally activating calcium concentrations (50–100 μm) from 0.502 ± 0.02 to 0.137 ± 0.022 (n= 28), with no effect on unitary conductance. 4-CMPS (10–40 μm) and 4,4′-DTDP (0.1–0.3 mm) induced a concentration dependent increase in P
o (> 0.9) and caused the appearance of longer open states. CaM shifted the activation of the calcium release channel by 4-CMPS
or 4,4′-DTDP to higher concentrations in single channel recordings and [3H]ryanodine binding. 40 μm 4-CMPS induced a near maximal (P
o
> 0.9) and 0.3 mm 4,4′-DTDP a submaximal (P
o
= 0.74) channel opening in the presence of CaM, which was reversed by the specific sulfhydryl reducing agent DTT. Neither
4-CMPS nor 4,4′-DTDP affected Ca-[125I]calmodulin binding to HSR. 1 mm MgCl2 reduced P
o
from 0.53 to 0.075 and 20–40 μm 4-CMPS induced a near maximal channel activation (P
o
> 0.9). These results demonstrate that the inhibitory effect of CaM or magnesium in a physiological concentration is diminished
or abolished at high concentrations of 4-CMPS or 4,4′-DTDP through oxidation of activating sulfhydryls on cysteine residues
of the calcium release channel.
Received: 22 July 1999/Revised: 15 November 1999 相似文献
14.
R. Candau A. Belli G. Y. Millet D. Georges B. Barbier J. D. Rouillon 《European journal of applied physiology and occupational physiology》1998,77(6):479-485
The aim of the present study was to examine the physiological and mechanical factors which may be concerned in the increase
in energy cost during running in a fatigued state. A group of 15 trained triathletes ran on a treadmill at velocities corresponding
to their personal records over 3000m [mean 4.53 (SD 0.28) m · s−1] until they felt exhausted. The energy cost of running (C
R) was quantified from the net O2 uptake and the elevation of blood lactate concentration. Gas exchange was measured over 1 min firstly during the 3rd–4th min
and secondly during the last minute of the run. Blood samples were collected before and after the completion of the run. Mechanical
changes of the centre of mass were quantified using a kinematic arm. A significant mean increase [6.9 (SD 3.5)%, P < 0.001] in C
R from a mean of 4.4 (SD 0.4) J · kg−1 · m−1 to a mean of 4.7 (SD 0.4) J · kg−1 · m−1 was observed. The increase in the O2 demand of the respiratory muscles estimated from the increase in ventilation accounted for a considerable proportion [mean
25.2 (SD 10.4)%] of the increase in CR. A mean increase [17.0 (SD 26.0)%, P < 0.05] in the mechanical cost (C
M) from a mean of 2.36 (SD 0.23) J · kg−1 · m−1 to a mean of 2.74 (SD 0.55) J · kg−1 · m−1 was also noted. A significant correlation was found between C
R and C
M in the non-fatigued state (r = 0.68, P < 0.01), but not in the fatigued state (r = 0.25, NS). Furthermore, no correlations were found between the changes (from non-fatigued to fatigued state) in C
R and the changes in C
M suggesting that the increase in C
R is not solely dependent on the external work done per unit of distance. Since step frequency decreased slightly in the fatigued
state, the internal work would have tended to decrease slightly which would not be compatible with an increase in C
R. A stepwise regressions showed that the changes in C
R were linked (r = 0.77, P < 0.01) to the changes in the variability of step frequency and in the variability of potential cost suggesting that a large
proportion of the increase in C
R was due to an increase in the step variability. The underlying mechanisms of the relationship between C
R and step variability remains unclear.
Accepted: 15 September 1997 相似文献
15.
M. De Angelis G. Vinciguerra A. Gasbarri C. Pacitti 《European journal of applied physiology and occupational physiology》1998,78(2):121-127
The aim of this research was to investigate the physiological responses and, in particular, the participation of lactic acid
anaerobic metabolism in aerobic dance, which is claimed to be pure aerobic exercise. In contrast to previous studies, that
have put subjects in very unfamiliar situations, the parameters were monitored in the familiar context of gymnasium, practice
routine and habitual instructor. A group of 30 skilled fairly well-trained women performed their usual routine,␣a combination
of the two styles: low (LI) and high impact (HI), and were continuously monitored for heart rate (HR) and every 8 min for
blood lactate concentration ([La−]b). Of the group, 15 were tested to determine their maximal aerobic power (V˙O2max) using a cycleergometer. They were also monitored during the routine for oxygen uptake (V˙O2) by a light telemetric apparatus. The oxygen pulses of the routine and of the corresponding exercise intensity in the incremental
test were not statistically different. The mean values in the exercise session were: peak HR 92.8 (SD 7.8)% of the subject's
maximal theoretical value, peak V˙O2 99.5 (SD 12.4)% of V˙O2max, maximal [La−]b 6.1 (SD 1.7) mmol · l−l, and mean 4.8 (SD 1.3) mmol · l−l. Repeated measures ANOVA found statistically significant differences between the increasing [La−]b values (P < 0.001). In particular, the difference between the [La−]b values at the end of the mainly LI phase and those of the LI-HI combination phase, and the difference between the samples
during the combination LI-HI phase were both statistically significant (both P= 0.002 and P= 0.002). The similar oxygen pulses confirmed the validity of the present experiment design and the reliability of HR monitoring
in this activity. The HR, V˙O2 and, above all, the increase of [La−]b to quite high values, showing a non steady state, demonstrated the high metabolic demand made by this activity that involved
lactic acid metabolism at a much higher level than expected.
Accepted: 23 September 1997 相似文献
16.
Jerzy A. Zoladz Krzysztof Duda Joanna Majerczak 《European journal of applied physiology and occupational physiology》1998,77(5):445-451
A group of 12 healthy non-smoking men [mean age 22.3 (SD 1.1) years], performed an incremental exercise test. The test started
at 30 W, followed by increases in power output (P) of 30 W every 3 min, until exhaustion. Blood samples were taken from an antecubital vein for determination of plasma concentration
lactate [La−]pl and acid-base balance variables. Below the lactate threshold (LT) defined in this study as the highest P above which a sustained increase in [La−]pl was observed (at least 0.5 mmol · l−1 within 3 min), the pulmonary oxygen uptake (V˙O2) measured breath-by-breath, showed a linear relationship with P. However, at P above LT [in this study 135 (SD 30) W] there was an additional accumulating increase in V˙O2 above that expected from the increase in P alone. The magnitude of this effect was illustrated by the difference in the final P observed at maximal oxygen uptake (V˙O2max) during the incremental exercise test (P
max,obs at V˙O2max) and the expected power output at V˙O2max(P
max,exp at V˙O2max) predicted from the linear V˙O2-P relationship derived from the data collected below LT. The P
max,obs at V˙O2max amounting to 270 (SD 19) W was 65.1 (SD 35) W (19%) lower (P<0.01) than the P
max,exp at V˙O2max
. The mean value of V˙O2max reached at P
max,obs amounted to 3555 (SD 226) ml · min−1 which was 572 (SD 269) ml · min−1 higher (P<0.01) than the V˙O2 expected at this P, calculated from the linear relationship between V˙O2 and P derived from the data collected below LT. This fall in locomotory efficiency expressed by the additional increase in V˙O2, amounting to 572 (SD 269) ml O2 · min−1, was accompanied by a significant increase in [La−]pl amounting to 7.04 (SD 2.2) mmol · l−1, a significant increase in blood hydrogen ion concentration ([H+]b) to 7.4 (SD 3) nmol · l−1 and a significant fall in blood bicarbonate concentration to 5.78 (SD 1.7) mmol · l−1, in relation to the values measured at the P of the LT. We also correlated the individual values of the additional V˙O2 with the increases (Δ) in variables [La−]pl and Δ[H+]b. The Δ values for [La−]pl and Δ[H+]b were expressed as the differences between values reached at the P
max,obs at V˙O2max and the values at LT. No significant correlations between the additional V˙O2 and Δ[La−]pl on [H+]b were found. In conclusion, when performing an incremental exercise test, exceeding P corresponding to LT was accompanied by a significant additional increase in V˙O2 above that expected from the linear relationship between V˙O2 and P occurring at lower P. However, the magnitude of the additional increase in V˙O2 did not correlate with the magnitude of the increases in [La−]pl and [H+]b reached in the final stages of the incremental test.
Accepted: 30 October 1997 相似文献
17.
Nilakantan V Hilton G Maenpaa C Van Why SK Pieper GM Johnson CP Shames BD 《Molecular and cellular biochemistry》2007,304(1-2):1-11
Oxidative stress is important in the pathogenesis of renal ischemia-reperfusion (IR) injury; however whether imbalances in
reactive oxygen production and disposal account for susceptibility to injury is unclear. The purpose of this study was to
compare necrosis, apoptosis, and oxidative stress in IR-resistant Brown Norway rats vs. IR-susceptible Sprague-Dawley (SD)
rats in an in vivo model of renal IR injury. As superoxide (O2·−) interacts with nitric oxide (NO) to form peroxynitrite, inducible NO synthase (iNOS) and nitrotyrosine were also examined.
Renal IR was induced in SD and BN rats by bilateral clamping of renal arteries for 45 min followed by reperfusion for 24 h
(SD 24 and BN 24, respectively). BN rats were resistant to renal IR injury as evidenced by lower plasma creatinine and decreased
acute tubular necrosis. TUNEL staining analysis demonstrated significantly decreased apoptosis in the BN rats vs. SD rats
after IR. Following IR, O2·− levels were also significantly lower in renal tissue of BN rats vs. SD rats (P < 0.05) in conjunction with a preservation of the O2·− dismutating protein, CuZn superoxide dismutase (CuZn SOD) (P < 0.05). This was accompanied by an overall decrease in 4-hydroxynonenal adducts in the BN but not SD rats after IR. BN rats
also displayed lower iNOS expression (P < 0.05) resulting in lower tissue NO levels and decreased nitrotyrosine formation (P < 0.01) following IR. Collectively these results show that the resistance of the BN rat to renal IR injury is associated
with a favorable balance of oxidant production vs. oxidant removal.
This work was supported in part by a Medical College of Wisconsin-Research Affairs Committee Grant to V. Nilakantan, and by
divisional funds to V. Nilakantan and B.D. Shames. 相似文献
18.
A.-W. Pan J. He Y. Kinouchi Hisao Yamaguchi Hiroshi Miyamoto 《European journal of applied physiology and occupational physiology》1997,75(5):388-395
The present study investigated the mechanism of diving bradycardia. A group of 14 healthy untrained male subjects were examined
during breath-holding either out of the water (30–33°C), in head-out immersion, or in whole-body submersion (27–29°C) in a
diving pool. Blood velocity, blood volume flow in the carotid artery, diastolic blood pressure and electrocardiogram were
measured and recorded during the experiments. The peak blood velocity increased by 13.6% (P < 0.01) and R-wave amplitude increased by 57.1% (P < 0.005) when the subjects entered water from air. End-diastolic blood velocity in the carotid artery increased significantly during breath-holding, e.g. increased from 0.20 (SD 0.02) m · s−1 at rest to 0.33 (SD 0.04) m · s−1 (P < 0.001) at 50.0 s in breath-hold submersion to a 2.0-m depth. Blood volume flow in the carotid artery increased by 26.6%
(P < 0.05) at 30 s and 36.6% (P < 0.001) at 40 s in breath-hold submersion to a 2.0-m depth. Diastolic blood pressure increased by 15.4% (P < 0.01) at 60 s during breath-holding in head-out immersion. Blood volume flow, and diastolic blood pressure increased significantly more and faster during breath-holding in submersion than out of the
water. There was a good negative correlation with the heart rate: the root mean square correlation coefficient r was 0.73 (P < 0.001). It was concluded that an increased accumulation of blood in the aorta and arteries at end-diastole and decreased
venous return, caused by an increase in systemic peripheral resistance during breath-holding, underlies diving bradycardia.
Accepted: 22 November 1996 相似文献
19.
目的 本研究旨在观察不同持续时间的模拟失重对大鼠抑郁样行为和海马超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的影响,以探究其影响及可能的作用机制。方法 采用后肢悬挂(HLS)尾吊法模拟大鼠失重状态。将大鼠分为对照组和不同模拟失重时间尾吊组(尾吊时长分别为1、2、3、4周)。采用旷场实验(OFT)、新物体识别实验(NORT)、强迫游泳实验(FST)观察大鼠抑郁样行为,采用酶联免疫吸附试验(ELISA)法测定海马SOD和CAT活性。结果 OFT结果显示,与对照组相比,HLS不同时间大鼠的僵滞时间增加(P<0.05,P<0.01)。在NORT中,与对照组相比,HLS不同时间大鼠对新物体的探索潜伏期增加,探索次数和时间减少(P<0.05,P<0.01)。在FST中,与对照组相比,HLS不同时间大鼠在FST中的不动时间增加,攀爬次数减少(P<0.05,P<0.01)。与对照组相比,HLS不同时间组大鼠海马组织中SOD和CAT水平均下降(P<0.05,P<0.01)。结论 短时间或长时间的失重都会导致大鼠产生类抑郁样行为。 相似文献
20.
The effect of a 120-day 6° head-down tilt (HDT) bed rest with and without countermeasures on the mechanical properties of
the human triceps surae muscle was studied in eight healthy young women subjects. One group [n = 4, mean age 31.5 (SEM 1.7) years] underwent a 120-day HDT only and a second group [n = 4; mean age 28.0 (SEM 1.1) years] underwent HDT with countermeasures (physical training). The results showed that the contractile
properties of the skeletal muscle studied changed considerably. After HDT without countermeasures the maximal voluntary contraction
(MVC) had decreased by 36% (P < 0.05), and the electrically evoked tetanic tension at 150 Hz (P
o) and isometric twitch contraction (P
t) had decreased by 24% (P < 0.02) and 12% (P < 0.05), respectively. Time- to-peak tension (TPT) of the twitch had significantly increased by 14% (P<0.05), but half-relaxation time (1/2RT), and total contraction time (TCT) had decreased by 19% (P<0.05) and 18% (P<0.05), respectively. The difference between P
o and MVC expressed as a percentage of P
o and referred to as force deficiency (FD), was also calculated. The FD had increased by 40% (P<0.001). The rate of increase of voluntary contractions calculated according to a relative scale had significantly reduced,
but for the electrically evoked contraction no substantial changes were observed. After HDT with countermeasures TPT, 1/2RT
and TCT of the twitch had decreased by 4%, 7%, 19%, respectively in relation to the control condition. Training had caused
a decrease of 3% (P>0.05) in MVC, and P
t, and in P
o of 14%, and of 9% (P>0.05), respectively. The FD had decreased significantly by 10% (P<0.02). The rate of increase of electrically evoked tetanic tension did not change significantly during HDT with countermeasures
but the rate of increase in isometric voluntary tension development was increased. Physical training provided a reserve of
neuromuscular function, which attenuated the effect of bed rest. The experimental findings indicated that neural as well as
muscle adaptation occurred in response to HDT with countermeasures.
Accepted: 7 November 1997 相似文献