共查询到20条相似文献,搜索用时 15 毫秒
1.
M. E. Forster W. Davison M. Axelsson L. Sundin C. E. Franklin S. Gieseg 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):345-352
Two species of Antarctic fish were stressed by moving them from seawater at −1 °C to seawater at 10 °C and holding them for
a period of 10 min. The active cryopelagic species Pagothenia borchgrevinki maintained heart rate while in the benthic species Trematomus bernacchii there was an increase in heart rate. Blood pressure did not change in either species. Both species released catecholamines
into the circulation as a consequence of the stress. P. borchgrevinki released the greater amounts, having mean plasma concentrations of 177 ± 54 nmol · l−1 noradrenaline and 263 ± 131 nmol · l−1 adrenaline at 10 min. Plasma noradrenaline concentrations rose to 47 ± 14 nmol · l−1 and adrenaline to 73 ± 28 nmol · l−1 in T. bernacchii. Blood from P. borchgrevinki was tonometered in the presence of isoprenaline. A fall in extracellular pH suggests the presence of a Na+/H+ antiporter on the red cell membrane, the first demonstration of this in an Antarctic fish. Treatment with the β-adrenergic
antagonist drug sotalol inhibited swelling of red blood cells taken from temperature-stressed P. borchgrevinki, suggesting that the antiporter responds to endogenous catecholamines.
Accepted: 22 January 1998 相似文献
2.
Reed JZ Chambers C Hunter CJ Lockyer C Kastelein R Fedak MA Boutilier RG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):1-10
The respiratory physiology, heart rates and metabolic rates of two captive juvenile male harbour porpoises (both 28 kg) were
measured using a rapid-response respiratory gas analysis system in the laboratory. Breath-hold durations in the laboratory
(12 ± 0.3 s, mean ± SEM) were shorter than field observations, although a few breath-holds of over 40 s were recorded. The
mean percentage time spent submerged was 89 ± 0.4%. Relative to similarly-sized terrestrial mammals, the respiratory frequency
was low (4.9 ± 0.19 breaths · min−1) but with high tidal volumes (1.1 ± 0.01 l), enabling a comparatively high minute rate of gas exchange. Oxygen consumption
under these experimental conditions (247 ± 13.8 ml O2 · min−1) was 1.9-fold higher than predicted by standard scaling relations. These data together with an estimate of the total oxygen
stores predicted an aerobic dive limit of 5.4 min. The peak end-tidal O2 values were related to the length of the previous breath-hold, demonstrating the increased oxygen uptake from the lung for
the longer dives. Blood oxygen capacity was 23.5 ± 1.0 ml · 100 ml−1, and the oxygen affinity was high, enabling rapid oxygen loading during ventilation.
Accepted: 11 August 1999 相似文献
3.
S. J. Brown R. B. Child S. H. Day A. E. Donnelly 《European journal of applied physiology and occupational physiology》1997,75(4):369-374
Indirect indices of exercise-induced human skeletal muscle damage and connective tissue breakdown were studied following
a single bout of voluntary eccentric muscle contractions. Subjects (six female, two male), mean (SD) age 22 (2) years performed
a bout of 50 maximum voluntary eccentric contractions of the knee extensors of a single leg. The eccentric exercise protocol
induced muscle soreness (P < 0.05 Wilcoxon test), chronic force loss, and a decline in the 20:100 Hz percutaneous electrical myostimulation force ratio
[P < 0.01, repeated measures analysis of variance (ANOVA)]. Serum creatine kinase (CK) and lactate dehydrogenase (LDH) activities
were elevated (P < 0.01, repeated measures ANOVA) following the bout. The mean (SD) CK and LDH levels recorded 3 days post-exercise were 2815
(4144) IU · l–1 and 375 (198) IU · l–1, respectively. Serum alkaline phosphatase activity showed no changes throughout the study, and a non-significant increase
(P = 0.058, repeated measures ANOVA) in pyridinoline was recorded following the bout. Urinary hydroxyproline (HP) and hydroxylysine
(HL) excretion, expressed in terms of creatinine (Cr) concentration, increased after exercise (P < 0.05 and P < 0.01, respectively, repeated measures ANOVA). An increased HP:Cr was recorded 2 days post-exercise and HL:Cr was increased
above baseline on days 2, 5, and 9 post-exercise. This indirect evidence of exercise-induced muscle damage suggests that myofibre
disruption was caused by the eccentric muscle contractions. Elevated urine concentrations of indirect indices of collagen
breakdown following eccentric muscle contractions suggests an increased breakdown of connective tissue, possibly due to a
localised inflammatory response.
Accepted: 9 October 1996 相似文献
4.
Gray DA Ironside CS Maloney SK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):315-320
The objective of this study was to determine the effect of modulating the plasma concentrations of the avian antidiuretic
hormone, arginine vasotocin (AVT), upon the febrile response to lipopolysaccharide (LPS) in Pekin ducks. LPS, intravenously
administered into conscious control birds at a dose of 1 μg · kg−1, caused a monophasic increase in body temperature of 0.85 ± 0.12 °C associated with a Thermal Response Index of 2.5 ± 0.6 C° h.
Plasma AVT concentrations in the control birds also increased with the progression of the fever response, more than doubling
from their basal values. Ducks in which the circulating level of AVT had either been elevated by the intravenous infusion
of the peptide or dehydration, or reduced by the administration of a specific AVT antibody prior to LPS administration, produced
body temperature profiles and Thermal Response Index values that did not differ significantly from those of the control birds.
The lack of any direct effect of variations in plasma AVT concentrations upon the magnitude of the fever response indicates
that the LPS-induced elevation in plasma AVT is not associated with modulating the rise in body temperature obtained in avian
fever.
Accepted: 7 March 2000 相似文献
5.
Noren DP Williams TM Berry P Butler E 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):93-99
Heat transfer from the periphery is an important thermoregulatory response in exercising mammals. However, when marine mammals
submerge, peripheral vasoconstriction associated with the dive response may preclude heat dissipation at depth. To determine
the effects of exercise and diving on thermoregulation in cetaceans, we measured heat flow and skin temperatures of bottlenose
dolphins (Tursiops truncatus) trained to follow a boat and to dive to 15 m. The results demonstrated that skin temperatures usually remained within 1 °C
of the water after all exercise levels. Heat flow from peripheral sites (dorsal fin and flukes) increased over resting values
immediately after exercise at the water surface and remained elevated for up to 20 min. However, post-exercise values for
heat flow from the flukes and dorsal fin decreased by 30–67% when dolphins stationed at 15 m below the surface. The pattern
in heat flow was reversed during ascent. For example, mean heat flow from the flukes measured at 5 m depth, 40.10 ± 2.47 W · m−2, increased by 103.2% upon ascent. There is some flexibility in the balance between thermal and diving responses of dolphins.
During high heat loads, heat transfer may momentarily increase during submergence. However, the majority of excess heat in
dolphins appears to be dissipated upon resurfacing, thereby preserving the oxygen-conserving benefits of the dive response.
Accepted: 4 January 1999 相似文献
6.
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
7.
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
8.
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
9.
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
10.
The use of amiloride to uncouple branchial sodium and proton fluxes in the brown trout, Salmo trutta
I. D. Nelson W. T. W. Potts H. Huddart 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):123-128
Resting proton, ammonium and sodium fluxes in Salmo trutta were 492.6 ± 19.5 (n = 29); 122.9 ± 34.2 (n = 28) and 277.1 ± 18.5 (n = 50) μmol · kg−1 · h−1, respectively. The resting transepithelial potential was found to be composed of three successive potentials, the outermost
averaging −7.36 ± 0.19mV, the second, −14.3 ± 1.4 mV and the third −37 ± 1.7 mV. Amiloride inhibits the proton, ammonium and
sodium fluxes in a dose-dependent manner at concentrations of 0.5 mmol · 1−1 and 0.1 mmol · l−1, but at 0.01 mmol · l−1, proton and ammonium fluxes remained at control levels whilst the sodium was reduced to 70.59 ± 7.29 μmol · kg−1 · h−1. The trans-epithelial potential was effected in a bi-phasic manner by 0.5 mmol · l−1 amiloride. An initial hyperpolarisation of ca. 6 mV was followed by a sustained depolarisation of ca. 14 mV (towards zero)
which persisted until the amiloride was washed off the gill. The initial hyperpolarisation was thought to reflect a rapid
inhibition of a positive inward sodium current and the subsequent depolarisation was due to the inhibition of a positive outward
current (proton) which would abolish the transepithelial potential. However, at 0.01 mmol · l−1 only the hyperpolarisation was seen, due to the inhibition of only the inward sodium current. Acetazolamide (0.1 mmol · l−1) was found to have no significant effect on the proton, ammonium and sodium fluxes. These results indicate that the proton
and sodium fluxes across the gill of the freshwater trout are not tightly linked. While this suggests that the trout gill
resembles the model of Ehrenburg et al. (1985) of sodium uptake in frog skin, the apical potentials measured in the pavement
epithelial cell(s) are too low to account for sodium uptake unless the activity of the sodium in the cells is very low.
Accepted: 8 August 1996 相似文献
11.
Juan Fuentes F. B. Eddy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):438-443
Drinking in Atlantic salmon (Salmo salar) juveniles was investigated in fresh water and following transfer to sea water. There was a significant effect of fish size
on drinking, and smolts (20–30 g) imbibed about ten times less water than alevins of 0.2–0.3 g. Freshwater smolts drank at
a rate of 0.15 ± 0.03 ml · kg−1 · h−1 and administration of doses of 10 or 20 mg · kg−1 of papaverine (stimulator of the renin- angiotensin system RAS) or [Asn1, Val5]-Angiotensin II (0.4 μmol · kg−1) resulted in significant increases in drinking, while administration of the angiotensin converting enzyme inhibitor, enalapril
(50 mg · kg−1) had no effect on drinking. Transfer of Atlantic salmon smolts to 1/3, 2/3 and full strength sea water resulted in significant
increases in drinking to 1.06 ± 0.12, 1.24 ± 0.0.16 and 3.89 ± 0.28 ml · kg−1 · h−1, respectively. In sea water, stimulation of the endogenous RAS by administration of papaverine (20 mg · kg−1) resulted in a 20% increase in drinking, while administration of enalapril to doses of 50 and 200 mg · kg−1 lowered drinking to 1.99 ± 0.48 and 0.32 ± 0.06 ml · kg−1 · h−1, respectively. All treatments were without effect on blood plasma levels of Na+ and Cl− in fresh water, while in sea water smolts both stimulation and inhibition of drinking resulted in hemoconcentration of Na+ and Cl−. The role of the renin angiotensin system in control of drinking and hydromineral balance in Atlantic salmon is discussed.
Accepted: 27 February 1997 相似文献
12.
Smith RW Palmer RM Houlihan DF 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(2):135-144
Protein synthesis in fish has been previously correlated with RNA content. The present study investigates whether protein
and RNA synthesis rates are similarly related. Protein and RNA synthesis rates were determined from 3H-phenylalanine and 3H-uridine incorporation, respectively, and expressed as % · day−1 and half-lives, respectively. Three fibroblast cell lines were used: BF-2, RTP, CHSE 214, which are derived from the bluegill,
rainbow trout and Chinook salmon, respectively. These cells contained similar RNA concentrations (∼175 μg RNA · mg−1 cell protein). Therefore differences in protein synthesis rates, BF-2 (31.3 ± 1.8)>RTP (25.1 ± 1.7)>CHSE 214 (17.6 ± 1.1),
were attributable to RNA translational efficiency. The most translationally efficient RNA (BF-2 cells), 1.8 mg protein synthesised · μg−1 RNA · day−1, corresponded to the lowest RNA half-life, 75.4 ± 6.4 h. Translationally efficient RNA was also energetically efficient with
BF-2 cells exploiting the least costly route of nucleotide supply (i.e. exogenous salvage) 3.5–6.0 times more than the least
translationally efficient RNA (CHSE 214 cells). These data suggest that differential nucleotide supply, between intracellular
synthesis and exogenous salvage, constitutes the area of pre-translational flexibility exploited to maintain RNA synthesis
as a fixed energetic cost component of protein synthesis.
Accepted: 12 November 1999 相似文献
13.
N. P. Walsh A. K. Blannin A. M. Clark L. Cook P. J. Robson M. Gleeson 《European journal of applied physiology and occupational physiology》1998,77(5):434-438
Glutamine is an essential substrate for the proper functioning of cells of the immune system. Falls in plasma glutamine concentration
after exercise may have deleterious consequences for immune cell function and render the individual more susceptible to infection.
The purpose of the present study was to examine changes in plasma glutamine concentration (measured using a validated enzymatic
spectrophotometric method) following an acute bout of intermittent high-intensity exercise. Eight well-trained male games
players took part in the study. Subjects reported to the laboratory following an overnight fast and performed a 1-h cycle
exercise task consisting of 20 1-min periods at 100% maximal O2 consumption (V˙O2max) each separated by 2 min of recovery at 30% V˙O2max. Venous blood samples were taken before exercise and at 5 min, 1 h, 2.5 h, 5 h and 24 h post-exercise. Glutamine was measured
by enzymatic spectrophotometric determination of the ammonia concentration before and after treatment of the plasma with glutaminase
(EC 3.5.1.2). Plasma glutamine concentration did not fall in the immediate post-exercise period [pre-exercise 681 (23) μM
compared with 663 (46) μM at 5 min post-exercise, mean (SEM)], but fell to 572 (35) μM at 5 h post-exercise (P < 0.05 compared with pre-exercise). Plasma lactate concentration rose to 8.8 (1.0) mM at the end of exercise and fell to
1.8 (0.4) mM at 1 h post-exercise, but plasma concentrations of free fatty acids and β-hydroxybutyrate both rose substantially
in the post-exercise period (to 240% and 400% of pre-exercise levels, respectively). The circulating leucocyte count increased
significantly during exercise (P < 0.01), continued to increase in the hours following exercise and peaked at 2.5 h post-exercise (mainly due to a neutrophilia).
The fall in the plasma glutamine concentration at 5 h post-exercise could be due to increased renal uptake of glutamine, which
generally occurs in conditions of metabolic acidosis or due to a greater removal of glutamine from the plasma resulting from
the elevated circulating leucocyte count.
Accepted: 22 October 1997 相似文献
14.
Sugar beet shoot tips from cold-acclimated plants were successfully cryopreserved using a vitrification technique. Dissected
shoot tips were precultured for 1 day at 5 °C on solidified DGJ0 medium with 0.3 M sucrose. After loading for 20 min with
a mixture of 2 M glycerol and 0.4 M sucrose (20 °C), shoot tips were dehydrated with PVS2 (0 °C) for 20 min prior to immersion
in liquid nitrogen. Both cold acclimation and loading enhanced the dehydration tolerance of shoot tips to PVS2. After thawing,
shoot tips were deloaded for 15 min in liquid DGJ0 medium with 1.2 M sucrose (20 °C). The optimal exposure time to both loading
solution and PVS2 depended on the in vitro morphology of the clone. With tetraploid clones a higher sucrose concentration
during cold acclimation and preculture further enhanced survival after cryopreservation. Survival rates ranged between 60%
and 100% depending on the clone. Since only 10–50% of the surviving shoot tips developed into non-hyperhydric shoots, regrowth
was optimized.
Received: 13 September 1999 / Revision received: 2 March 2000 / Accepted: 16 March 2000 相似文献
15.
Masashi Shibata Mitsuko Shimura Shiori Shibata Tomoko Wakamura Toshio Moritani 《European journal of applied physiology and occupational physiology》1997,75(3):206-211
The purpose of this study was to determine the walking speed which has the greatest influence on neural relaxation in healthy
elderly women as determined by electromyogram (EMG) and electroencephalogram (EEG) analyses. Seven elderly female volunteers
[mean age 68.5 (SD 3.95) years] served as subjects for this study. The EMG signals were recorded from the gastrocnemius (MG),
soleus (SL) and tibialis anterior (TA) muscles while walking on a treadmill, starting at 40␣m · min−1 and increasing 6 m · min−1 incrementally for 10␣min. The turning point of muscle activities (by integrated EMG, iEMGtp) was determined as the walking speed at the point at which the mean rate of change of iEMG (MG + SL + TA) abruptly increased.
After the determination of iEMGtp, the treadmill was set at three constant speeds, one corresponding to the speed for the iEMGtp and two others 20% higher or lower than that for the iEMGtp. The subjects then walked for 20 min at each of these speeds on 3 separate days and their EEG power spectrum data were obtained
for frequencies from the 8 to 13 Hz (α-wave component, AWC). The mean of iEMGtp for our subjects was at a mean walking speed of 64.7 (SD 7.9) m · min−1. Considering the subjects' age and height, iEMGtp was somewhat faster than their expected self-paced normal walking speed. There were no differences between the mean AWC values
of the subjects prior to exercising at each of the three speeds. The mean AWC values after exercise were significantly (P < 0.01) greater than before. The extent of the increase in AWC at iEMGtp was greater than those at slower speeds. Our data would suggest that walking exercise at the speed which corresponds with
EMG evidence of iEMGtp may induce the most significant relaxing effects in elderly women.
Accepted: 11 September 1996 相似文献
16.
William J. Kraemer Keijo H?kkinen Robert U. Newton Matthew McCormick Bradley C. Nindl Jeff S. Volek Lincoln A. Gotshalk Steven J. Fleck Wayne W. Campbell Scott E. Gordon Peter A. Farrell William J. Evans 《European journal of applied physiology and occupational physiology》1998,77(3):206-211
The purpose of this investigation was to examine the acute responses of several hormones [total and free testosterone (TT
and FT, respectively), adrenocorticotropic hormone (ACTH), cortisol (C), growth hormone (GH), and insulin (INS)] to a single
bout of heavy resistance exercise (HRE). Eight younger [30-year (30y) group] and nine older [62-year (62y) group] men matched
for general physical characteristics and activity levels performed four sets of ten repetitions maximum (RM) squats with 90 s
rest between sets. Blood samples were obtained from each subject via an indwelling cannula with a saline lock pre-exercise,
immediately post-exercise (IP), and 5, 15 and 30 min post-exercise. Levels of TT, FT, ACTH, C and lactate significantly increased
after HRE for both groups. Pre-HRE pairwise differences between groups were noted only for FT, while post-HRE pairwise differences
were found for TT, FT, GH, glucose and lactate. Area under the curve analysis showed that the 30y group had a significantly
higher magnitude of increase over the entire recovery period (IP, 5, 15, and 30 min post-exercise) for TT, FT, ACTH and GH.
Few changes occurred in the INS response with the only change being that the 62y group demonstrated a decrease IP. Lactate
remained elevated at 30 min post-HRE. This investigation demonstrates that age-related differences occur in the endocrine
response to HRE, and the most striking changes appear evident in the FT response to HRE in physically active young and older
men.
Accepted: 11 June 1997 相似文献
17.
K. S. Lam S. W. Mamber E. J. Pack S. Forenza P. B. Fernandes D. M. Klaus 《Applied microbiology and biotechnology》1998,49(5):579-583
The effect of space flight on the production of the antibiotic monorden on two types of agar media, T8 and PG, by Humicola fuscoatra WC5157 was examined on board the US Space Shuttle mission STS-77 in May 1996. Paired space-flight and ground control samples
were prepared using identical hardware, protocol, media, and inoculum. Inoculation occurred simultaneously for both groups
2.5 h after launch. The flight and ground samples were allowed to grow for the entire 10-day mission in a dark, thermally
controlled (22 °C) environment. Post-flight HPLC analysis of the flight and ground sample extracts indicated that the production
of monorden by H. fuscoatra WC5157 in the flight samples was higher than in the ground samples in both agar media. In the T8 medium, the production of
monorden in the flight and ground samples was 11.6 ± 3.5 μg and 8.9 ± 1.1 μg respectively (30% increase). In the PG medium,
the production of monorden in the flight and ground samples was 23.8 ± 3.3 μg and 8.2 ± 2.2 μg respectively (190% increase).
The production of monorden in the flight and ground control samples was confirmed by HPLC-MS analysis.
Received: 30 September 1997 / Received revision: 23 December 1997 / Accepted: 2 January 1998 相似文献
18.
Carmel M. McEniery David G. Jenkins Christopher Barnett 《European journal of applied physiology and occupational physiology》1997,75(5):462-466
The present study investigated the relationship between plasma potassium ion concentration ([K+]) and skeletal muscle torque during three different 15-min recovery periods after fatigue induced by four 30-s sprints. Four
males and one female completed the multiple sprint exercise on three separate days; recovery was passive, i.e. no cycling
exercise (PRec), active cycling at 30% peak oxygen consumption O2peak (30% Rec) and active cycling at 60% O2peak (60% Rec). Plasma [K+] was measured from blood sampled from an antecubital vein of subjects at rest and at 0, 3, 5, 10 and 15 min into each recovery.
Isokinetic leg strength was measured at rest and at 1, 6, 11 and 16 min during each recovery. Following the exhaustive sprints,
[K+] increased significantly from an average mean (SEM) resting value of 3.81 (0.07) mmol · l−1 to 4.48 (0.19) mmol · l−1 (P < 0.01). In all recovery conditions, plasma [K+] returned to resting levels within 3 min following the fourth sprint. However, in the two active recovery conditions plasma
[K+] increased over the remainder of the recovery periods to 4.36 (0.12) mmol · l−1 in the 30% Rec condition and 4.62 (0.12) mmol · l−1 in the 60% Rec condition, the latter being significantly higher than the former (P < 0.01). The maximum torque measured following the sprints decreased significantly, on average, to 61.1 (8.36)% of peak levels
(P < 0.01). After 15 min of recovery, maximum torque was highest in the 30% Rec condition at 92.13 (3.06)% of peak levels (P < 0.01), compared to 85.23 (3.64)% and 85.71 (0.82)% for the PRec and 60% Rec conditions, respectively. In contrast to the
significant differences in plasma [K+] across all three recovery conditions, muscle torque recovery was significantly different in only the 30% Rec condition.
In summary, recovery of peak levels of muscle torque following fatiguing exercise does not appear to follow changes in plasma
[K+].
Accepted: 18 October 1996 相似文献
19.
Shoot tips from in vitro-grown, cold-hardened stock plants of white poplar (Populus alba L.) were successfully cryopreserved at –196 °C by one-step vitrification. After preculturing at 5 °C for 2 days on hormone-free
MS medium containing different sucrose concentrations, and loading for 20 min with 2 m glycerol and 0.4 m sucrose, shoot tips were treated with the PVS2 vitrification solution and plunged directly into liquid nitrogen. Best survival
rate (90%) was obtained when shoot tips were precultured on 0.09 m sucrose, hormone-free MS medium, vitrified by exposure to PVS2 solution for 60 min at 0 °C and, following cryopreservation,
rewarmed at 40 °C and washed in 1.2 m sucrose solution for 20 min. Regrowth was improved by plating shoot tips on a gelled MS medium containing 1.5 μm N6-benzyladenine plus 0.5 μm gibberellic acid, while shoot rooting was achieved on MS medium containing 3 μm indole-3-butyric acid. Following this procedure, almost 60% rooted shoots were obtained from cryopreserved shoot tips.
Received: 1 February 1999 / Revision received: 3 May 1999 · Accepted: 21 May 1999 相似文献
20.
John Ejnik Amalia Muñoz Tong Gan C. Frank Shaw III D. H. Petering 《Journal of biological inorganic chemistry》1999,4(6):784-790
− 1 s − 1 at 25 °C and pH 7.4 in Tris.HCl buffer and 0.1 M KCl. At 25 °C, Zn7-metallothionein also exchanged metal ions with Cd-carbonic anhydrase with a rate constant of 0.33 ± 0.02 M − 1 s − 1 to reconstitute enzymatically active protein. Cd-carbonic anhydrase reacted within the time of mixing with the peptide sequence
49–61 of rabbit metallothionein 2 which contains four cysteinyl residues, leading to the exchange of most of the Cd2+ into the peptide. At pH 7.4 and 25 °C, Cd2+ has higher affinity for apometallothionein than for the apo-peptide.
Received: 25 February 1999 / Accepted: 17 September 1999 相似文献