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1.
The cwlV gene, which encodes Bacillus polymyxa var. colistinus autolysin was cloned and sequenced. cwlV comprises a 1497-bp ORF and encodes a polypeptide of 499 amino acid (aa) residues (Mr of 53,707 Da). The N-terminal sequence of the mature 23-kDa CwlV protein is NSXGKKVVVIDAGXGAKD(X, undetermined aa); this processed form corresponds to the C-terminal portion (183?aa, Mr of 20,050?Da) of the cwlV ORF. Sequencing of the flanking region revealed that another putative autolysin gene, cwlU, is located upstream of cwlV. cwlU encodes a polypeptide of 524 aa and its deduced sequence is 34.9% identical to the full-length sequence of CwlV. Downstream of cwlV, the genes for a deduced lipoprotein (OrfW), an endonuclease III homolog (Nth), a non-homologous OrfX, a glutathione peroxidase homolog (Gpx), and the N-terminal region of OrfZ containing a ATP/GTP-binding site motif were found. Northern blotting and primer-extension analyses revealed that cwlU is transcribed as a single cistron, but cwlV is transcribed with orfW. The unprocessed forms of CwlV and CwlU (VΔS and UΔS, respectively) and their predicted mature forms (Vcat and Ucat, respectively) were expressed in, and purified from, Escherichia coli. Enzyme analysis indicated that VΔS and Vcat exhibit low and high cell wall hydrolase activities toward B. polymyxa cell wall, respectively, but UΔS and Ucat exhibit almost no and low cell wall hydrolase activities, respectively. 相似文献
2.
Hiroshi Takaki Kenji Sunagawa Masaru Sugimachi Yasushi Hara Toru Kawada Takashi Kurita Yoichi Goto 《European journal of applied physiology and occupational physiology》1998,78(4):333-339
The transient response of oxygen uptake (V˙O2) to submaximal exercise, known to be abnormal in patients with cardiovascular disorders, can be useful in assessing the functional
status of the cardiocirculatory system, however, a method for evaluating it accurately has not yet been established. As an
alternative approach to the conventional test at constant exercise intensity, we applied a random stimulus technique that
has been shown to provide relatively noise immune responses of system being investigated. In 27 patients with heart failure
and 24 age-matched control subjects, we imposed cycle exercise at 50 W intermittently according to a pseudo-random binary
(exercise-rest) sequence, while measuring breath-by-breath V˙O2. After determining the transfer function relating exercise intensity (W˙) to V˙O2 and attenuating the high frequency ranges (>6 exercise-rest cycles · min−1), we computed the high resolution band-limited (0–6 cycles · min−1) V˙O2 response (0–120 s) to a hypothetical step exercise. The V˙O2 response showed a longer time constant in the patients than in the control subjects [47 (SD 37) and 31 (SD 8) s, respectively,
P < 0.05]. Furthermore, the amplitude of the V˙O2 response after the initial response was shown to be significantly smaller in the patients than in the control subjects [176
(SD 50) and 267 (SD 54) ml · min−1 at 120 s]. The average amplitude over 120 s correlated well with peak V˙O2 (r = 0.73) and ΔV˙O2/ΔW˙ (r = 0.70), both of which are well-established indexes of exercise tolerance. The data indicated that our band-limited V˙O2
step response using random exercise was more markedly attenuated and delayed in the patients with heart failure than in the normal controls
and that it could be useful in quantifying the overall functional status of the cardiocirculatory system.
Accepted: 6 January 1998 相似文献
3.
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
4.
Ngoc-Phuong-Thao Nguyen Kyoung-Mi Lee Kyoung-Min Lee In-Won Kim Yeong-Suk Kim Marimuthu Jeya Jung-Kul Lee 《Applied microbiology and biotechnology》2010,87(6):2107-2116
A highly efficient β-1,4-glucosidase (BGL) secreting strain, Stereum hirsutum SKU512, was isolated and identified based on morphological features and sequence analysis of internal transcribed spacer
rDNA. A BGL containing a carbohydrate moiety was purified to homogeneity from S. hirsutum culture supernatants using only a single chromatography step on a gel filtration column. The relative molecular weight of
S. hirsutum BGL was determined as 98 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis or 780 kDa by size exclusion chromatography,
indicating that the enzyme is an octamer. S. hirsutum BGL showed the highest activity toward p-nitrophenyl-β-D-glucopyranoside (V
max = 3,028 U mg-protein−1, k
cat = 4,945 s−1) ever reported. The enzyme also showed good stability at an acidic pH ranging from 3.0 to 5.5. The BGL was able to promote
transglycosylation with an activity of 42.9 U mg-protein−1 using methanol as an acceptor and glucose as a donor. The internal amino acid sequences of the isolated enzyme showed significant
homology with hydrolases from glycoside hydrolase family 1 (GH1), indicating that the S. hirsutum BGL is a member of GH1 family. The characteristics of S. hirsutum BGL could prove to be of interest in several potential applications, especially in enhancing flavor release during the wine
fermentation process. 相似文献
5.
D. Habedank I. Reindl G. Vietzke U. Bauer A. Sperfeld S. Gl?ser K. D. Wernecke F. X. Kleber 《European journal of applied physiology and occupational physiology》1998,77(5):421-426
The ventilatory equivalent for CO2 defines ventilatory efficiency largely independent of metabolism. An impairment of ventilatory efficiency may be caused by
an increase in either anatomical or physiological dead space, the latter being the most important mechanism in the hyperpnoea
of heart failure, pulmonary embolism, pulmonary hypertension and the former in restrictive lung disease. However, normal values
for ventilatory efficiency have not yet been established. We investigated 101 (56 men) healthy volunteers, aged 16–75 years,
measuring ventilation and gas exchange at rest (n = 64) and on exercise (modified Naughton protocol, n = 101). Age and sex dependent normal values for ventilatory efficiency at rest defined as the ratio ventilation:carbon dioxide
output (V˙
E:V˙CO2), exercise ventilatory efficiency during exercise, defined as the slope of the linear relationship between ventilation and
carbon dioxide output (V˙
E vs V˙CO2 slope), oxygen uptake at the anaerobic threshold and at maximum (V˙O2AT,V˙O2max, respectively) and breathing reserve were established. Ventilatory efficiency at rest was largely independent of age, but
was smaller in the men than in the women [V˙
E:V˙CO2 50.5 (SD 8.8) vs 57.6 (SD 12.6) P<0.05]. Ventilatory efficiency during exercise declined significantly with age and was smaller in the men than in the women
(men: (V˙
E vs V˙CO2 slope = 0.13 × age + 19.9; women: V˙
E vs V˙CO2 slope = 0.12 × age + 24.4). The V˙O2AT and V˙O2max were 23 (SD 5) and 39 (SD 7) ml O2 · kg · min−1 in the men and 18 (SD 4) and 32 (SD 7) in the women, respectively, and declined significantly with age. The V˙O2AT was reached at 58 (SD 9)% V˙O2max. Breathing reserve at the end of exercise was 41% and was independent of sex and age. It was concluded from this study that
ventilatory efficiency as well as peak oxygen uptake are age and sex dependent in adults.
Accepted: 11 June 1997 相似文献
6.
This study investigated the effects on running economy (RE) of ingesting either no fluid or an electrolyte solution with
or without 6% carbohydrate (counterbalanced design) during 60-min running bouts at 80% maximal oxygen consumption (V˙O2max). Tests were undertaken in either a thermoneutral (22–23°C; 56–62% relative humidity, RH) or a hot and humid natural environment
(Singapore: 25–35°C; 66–77% RH). The subjects were 15 young adult male Singaporeans [V˙O2max = 55.5 (4.4 SD) ml kg−1 min−1]. The RE was measured at 3 m s−1 [65 (6)% V˙O2max] before (RE1) and after each prolonged run (RE2). Fluids were administered every 2 min, at an individual rate determined
from prior tests, to maintain body mass (group mean = 17.4 ml min−1). The V˙O2 during RE2 was higher (P < 0.05) than that during the RE1 test for all treatments, with no differences between treatments (ANOVA). The mean increase
in V˙O2 from RE1 to RE2 ranged from 3.4 to 4.7 ml kg−1 min−1 across treatments. In conclusion, the deterioration in RE at 3 m s−1 (65% V˙O2max) after 60 min of running at 80% V˙O2max appears to occur independently of whether fluid is ingested and regardless of whether the fluid contains carbohydrates or
electrolytes, in both a thermoneutral and in a hot, humid environment.
Accepted: 30 October 1997 相似文献
7.
M. Faina V. Billat R. Squadrone M. De Angelis J. P. Koralsztein A. Dal Monte 《European journal of applied physiology and occupational physiology》1997,76(1):13-20
Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to
the time to exhaustion (t
lim) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (V˙O2
max) occurs (I
V˙O2
max) was assessed by analysing the relationship between the t
lim and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of V˙O2
max, the exercise intensity was increased so that each subject reached his I
V˙O2max
in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min
steps for determining the I
V˙O2max
and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure
at I
V˙O2max
. The AOD for the t
lim exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage
value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9–24.1] with significant differences
between swimmers and kayakists (16.8% vs 11.5%, P≤0.05) and cyclists and kayakists (16.4% vs 11.5%, P≤0.05). Absolute AOD values ranged from 26.4 ml · kg−1 to 83.6 ml · kg−1 with a mean value of 45.9 (SD 18) ml · kg−1. Considering all the subjects, the t
lim was found to have a positive and significant correlation with AOD (r = 0.62, P≤0.05), and a negative and significant correlation with V˙O2
max (r = −0.46, P≤0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at I
V˙O2max
should not be ignored when t
lim is used as a supplementary parameter to evaluate specific adaptation of athletes.
Accepted: 17 December 1996 相似文献
8.
Carlo Capelli Dave R. Pendergast B. Termin 《European journal of applied physiology and occupational physiology》1998,78(5):385-393
The energy cost per unit of distance (C
s, kilojoules per metre) of the front-crawl, back, breast and butterfly strokes was assessed in 20 elite swimmers. At sub-maximal
speeds (v), C
s was measured dividing steady-state oxygen consumption (V˙O2) by the speed (v, metres per second). At supra-maximal v, C
s was calculated by dividing the total metabolic energy (E, kilojoules) spent in covering 45.7, 91.4 and 182.9 m by the distance. E was obtained as: E = E
an+V˙O2max
t
p−V˙O2max(1−e−(
t
p/)), where E
an was the amount of energy (kilojoules) derived from anaerobic sources, V˙O2max litres per second was the maximal oxygen uptake, α (=20.9 kJ · l O2
−1) was the energy equivalent of O2, τ (24 s) was the time constant assumed for the attainment of V˙O2max at muscle level at the onset of exercise, and t
p (seconds) was the performance time. The lactic acid component was assumed to increase exponentially with t
p to an asymptotic value of 0.418 kJ · kg−1 of body mass for t
p ≥ 120 s. The lactic acid component of E
an was obtained from the net increase of lactate concentration after exercise (Δ[La]b) assuming that, when Δ[La]b = 1 mmol · l−1 the net amount of metabolic energy released by lactate formation was 0.069 kJ · kg−1. Over the entire range of v, front crawl was the least costly stroke. For example at 1 m · s−1, C
s amounted, on average, to 0.70, 0.84, 0.82 and 0.124 kJ · m−1 in front crawl, backstroke, butterfly and breaststroke, respectively; at 1.5 m · s−1, C
s was 1.23, 1.47, 1.55 and 1.87 kJ · m−1 in the four strokes, respectively. The C
s was a continuous function of the speed in all of the four strokes. It increased exponentially in crawl and backstroke, whereas
in butterfly C
s attained a minimum at the two lowest v to increase exponentially at higher v. The C
s in breaststroke was a linear function of the v, probably because of the considerable amount of energy spent in this stroke for accelerating the body during the pushing
phase so as to compensate for the loss of v occurring in the non-propulsive phase.
Accepted: 14 April 1998 相似文献
9.
Patrick Mucci Jacques Prioux Maurice Hayot Michèle Ramonatxo Christian Préfaut 《European journal of applied physiology and occupational physiology》1998,77(4):343-351
Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyper- pnoea. The aim of this
study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation
of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7
(SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, V˙O2max), and during strenuous exercise (70% V˙O2max) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [ΔTh0–40: 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that ΔTh0–40 and Th during moderate exercise were negatively correlated with arterial O2 saturation during maximal exercise (r = 0.50, P<0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response
to CO2, but may be partly related to a greater increase in Th during moderate exercise.
Accepted: 18 August 1997 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.
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
12.
Jerzy A. Zoladz Zbigniew Szkutnik Joanna Majerczak Krzysztof Duda 《European journal of applied physiology and occupational physiology》1998,78(4):369-377
The purpose of this study was to develop a method to determine the power output at which oxygen uptake (V˙O2) during an incremental exercise test begins to rise non-linearly. A group of 26 healthy non-smoking men [mean age 22.1 (SD
1.4) years, body mass 73.6 (SD 7.4) kg, height 179.4 (SD 7.5) cm, maximal oxygen uptake (V˙O2max) 3.726 (SD 0.363) l · min−1], experienced in laboratory tests, were the subjects in this study. They performed an incremental exercise test on a cycle
ergometer at a pedalling rate of 70 rev · min−1. The test started at a power output of 30 W, followed by increases amounting to 30 W every 3 min. At 5 min prior to the first
exercise intensity, at the end of each stage of exercise protocol, blood samples (1 ml each) were taken from an antecubital
vein. The samples were analysed for plasma lactate concentration [La]pl, partial pressure of O2 and CO2 and hydrogen ion concentration [H+]b. The lactate threshold (LT) in this study was defined as the highest power output above which [La−]pl showed a sustained increase of more than 0.5 mmol · l−1 · step−1. The V˙O2 was measured breath-by-breath. In the analysis of the change point (CP) of V˙O2 during the incremental exercise test, a two-phase model was assumed for the 3rd-min-data of each step of the test: X
i
=at
i
+b+ɛ
i
for i=1,2,…,T, and E(X
i
)>at
i
+b for i =T+1,…,n, where X
1, … , X
n
are independent and ɛ
i
∼N(0,σ2). In the first phase, a linear relationship between V˙O2 and power output was assumed, whereas in the second phase an additional increase in V˙O2 above the values expected from the linear model was allowed. The power output at which the first phase ended was called the
change point in oxygen uptake (CP-V˙O2). The identification of the model consisted of two steps: testing for the existence of CP and estimating its location. Both
procedures were based on suitably normalised recursive residuals. We showed that in 25 out of 26 subjects it was possible
to determine the CP-O2 as described in our model. The power output at CP-V˙O2 amounted to 136.8 (SD 31.3) W. It was only 11 W – non significantly – higher than the power output corresponding to LT. The
V˙O2 at CP-V˙O2 amounted to 1.828 (SD 0.356) l · min−1 was [48.9 (SD 7.9)% V˙O2
max
]. The [La−]pl at CP-V˙O2, amounting to 2.57 (SD 0.69) mmol · l−1 was significantly elevated (P<0.01) above the resting level [1.85 (SD 0.46) mmol · l−1], however the [H+]b at CP-V˙O2 amounting to 45.1 (SD 3.0) nmol · l−1, was not significantly different from the values at rest which amounted to 44.14 (SD 2.79) nmol · l−1. An increase of power output of 30 W above CP-V˙O2 was accompanied by a significant increase in [H+]b above the resting level (P=0.03).
Accepted: 25 March 1998 相似文献
13.
H. Hebestreit O. Bar-Or 《European journal of applied physiology and occupational physiology》1998,78(1):7-12
Heart rate (HR) monitoring is commonly used to assess 24-h energy expenditure (EE) in children but it has been found to overestimate
the true values. One reason for this may be the effect of climatic heat stress on HR. An equation has been previously developed
to adjust HR measured during continuous exercise for the influence of climate. Since play in children is rarely of a continuous
pattern, one objective of this study was to compare the effects of climatic heat stress on the HR response to intermittent
and to continuous exercise. A second objective was to determine whether the previously developed equation is suitable for
intermittent exercise. A group of 12 boys and 8 girls (aged 8–11 years) cycled in a climatic chamber. The exercise consisted
of continuous cycling for 5 min at 35%, 55%, and 75% of peak oxygen up take (random order) followed by alternating cycling
at the same resistance and cadence (30 s) and rest (30 s) for 3 additional min. The oxygen uptake (V˙O2) and HR were determined for 2 min at the end of continuous cycling and for 2 min during intermittent cycling. Climatic conditions
(randomly assigned) were dry bulb temperature T
db 22°C, 50% relative humidity (rh); T
db 28°C, 55% rh; T
db 32°C, 52% rh; or T
db 35°C, 58% rh. The difference between HR measured at a given T
db (HRmeas) and HR at 22°C and at the same V˙O2 was then calculated (ΔHR). The ΔHR increased linearly with increasing temperature but was not related to V˙O2 or to exercise type. However, a small but significant difference was found if the published equation was used with data from
intermittent exercise. The accuracy of the existing equation adjusting HRmeas for the influence of T
db (HRcorr) could be improved to HRcorr= HRmeas · (1.18308−(0.0083218 · T
db)). In conclusion, the effects of climatic heat stress on HR were similar in continuous and intermittent exercise, and HR
can be adjusted for the influence of climate in groups of pre- and early pubertal children during rest, intermittent and continuous
exercise at ambient temperatures between 22°C and 35°C, thereby reducing the error in predicting EE from HR.
Accepted: 13 January 1998 相似文献
14.
David V. B. James Jonathan H. Doust 《European journal of applied physiology and occupational physiology》1998,77(6):551-555
Eight male endurance runners [mean ± (SD): age 25 (6) years; height 1.79 (0.06) m; body mass 70.5 (6.0) kg; % body fat 12.5
(3.2); maximal oxygen consumption (V˙O2max 62.9 (1.7) ml · kg−1 · min−1] performed an interval training session, preceded immediately by test 1, followed after 1 h by test 2, and after 72 h by
test 3. The training session was six 800-m intervals at 1 km · h−1 below the velocity achieved at V˙O2max with 3 min of recovery between each interval. Tests 1, 2 and 3 were identical, and included collection of expired gas, measurement
of ventilatory frequency (f
v
), heart rate (f
c), rate of perceived exertion (RPE), and blood lactate concentration ([La−]B) during the final 5 min of 15 min of running at 50% of the velocity achieved at V˙O2max (50% −V˙O2max).␣Oxygen uptake (V˙O2), ventilation (V˙
E
), and respiratory exchange ratio (R) were subsequently determined from duplicate expired gas collections. Body mass and plasma volume changes were measured preceding
and immediately following the training session, and before tests 1–3. Subjects ingested water immediately following the training
session, the volume of which was determined from the loss of body mass during the session. Repeated measures analysis of variance
with multiple comparison (Tukey) was used to test differences between results. No significant differences in body mass or
plasma volume existed between the three test stages, indicating that the differences recorded for the measured parameters
could not be attributed to changes in body mass or plasma volume between tests, and that rehydration after the interval training
session was successful. A significant (P < 0.05) increase was found from test 1 to test 2 [mean (SD)] for V˙O2 [2.128 (0.147) to 2.200 (0.140) 1 · min−1], f
c [125 (17) to 132 (16) beats · min−1], and RPE [9 (2) to 11 (2)]. A significant (P < 0.05) decrease was found for submaximal R [0.89 (0.03) to 0.85 (0.04)]. These results suggest that alterations in V˙O2 during moderate-intensity, constant-velocity running do occur following heavy-intensity endurance running training, and that
this is due to factors in addition to changed substrate metabolism towards greater fat utilisation, which could explain only
31% of the increase in V˙O2.
Accepted: 8 December 1997 相似文献
15.
For the first time, the purification has been achieved of the type II polyhydroxyalkanoate (PHA) synthases PhaC1 and PhaC2
from Pseudomonas aeruginosa applying N-terminal His6-tag fusions and metal chelate affinity chromatography. In vivo His6-tagged PHA synthase activity was confirmed by functional expression of the corresponding genes in Escherichia coli, and PHA synthase activity could also be measured in vitro with the enzymes. The specific enzyme activity of PHA synthases PhaC1 and PhaC2 was 0.039 U mg−1 and 0.035 U mg−1 protein, respectively. Kinetic studies showed a lag phase for both PHA synthases using (R,S)-3-hydroxydecanoyl-CoA as substrate. Specific enzyme activity was increased to 0.055 U mg−1 when the phasin GA24 from Ralstonia eutropha was added to the assay. CoA inhibited PHA synthase activity, and a K
i of 85 μM was determined. A two-enzyme system was established, employing commercially available acyl-CoA synthetase and PHA
synthase, which allowed the in vitro de novo PHA granule formation and the in vitro synthesis of poly(3-hydroxydecanoate) exhibiting a weight average molar mass of 9.8 × 104 g mol−1, and which occurred independently of pre-existing PHA granules.
Received: 3 December 1999 / Revision received: 10 January 2000 / Accepted: 14 January 2000 相似文献
16.
Fifteen young adult Singaporean male physical education students maximum oxygen consumption [(V˙O2max) = 56 (4.7) ml · kg−1 · min−1] performed three prolonged runs in a counterbalanced design. The running bouts varied in time (40 vs 60 min) and intensity
(70% vs 80% V˙O2
max
). Each prolonged run was separated by 7 days. The running economy (RE) at 10.8 km · h−1 during 10-min running bouts was measured before (RE1) and after (RE2) each prolonged run. A control study involved monitoring
RE at 10.8 km · h−1 before and after 60 min rest. There were no differences between RE1 and RE2 values during the control run. However, there
were differences between RE1 and RE2 values when separated by a prolonged run. For example, the mean (SD) changes in oxygen
consumption (ml · kg−1 · min−1) values were 38.2 (2.5) versus 40.1 (2.6) (40 min at 80% V˙O2
max
), 38.9 (2.8) versus 41.5 (2.6) (60 min at 70% V˙O2
max
), and 39.0 (3.1) versus 42.7 (2.9) (60 min at 80% V˙O2
max
; P < 0.01). The results of this investigation support the hypothesis that RE deteriorates during prolonged running, and that
the magnitude of the deterioration in RE increases with both increasing exercise intensity and duration.
Accepted: 14 July 1997 相似文献
17.
S. Morris J. Callaghan 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):377-388
The Australian Yabby, Cherax destructor, inhabits occasionally hypoxic water. The respiratory gas, acid-base, metabolite and energetic status of this crayfish was
assessed during progressive hypoxia and during 3 h at a water PO2 of 1.33 kPa. The O2 affinity of haemocyanin from C. destructor was increased by lactate (Δlog P
50/Δlog[lactate] = −0.111) and by Ca (Δlog P
50/Δlog[Ca] = −0.62) but not by urate. While the non-bicarbonate buffering capacity was low (Δ[HCO3
−]/ ΔpH=−4.89) the haemocyanin had a low sensitivity to pH changes (ϕ = −0.33). The crayfish showed a compensatory hyperventilation,
which induced a respiratory alkalosis, until the water O2 partial pressure declined below 2.67 kPa, after which the O2 uptake rate was approximately 10% of normoxic rates. The high haemocyanin-O2 affinity maintained haemolymph O2 content during progressive hypoxia despite the normally low arterial O2 partial pressure of C. destructor. During severe hypoxia, pH decreased but increased lactate aided in maintaining haemocyanin-O2 saturation. The importance of regulated haemocyanin-O2 affinity in hypoxic C. destructor was reduced by lowered metabolism, including reduced cardiac output, and the consequent reduction in O2 requirement. Anaerobiosis became important only at very low PO2 but thereafter proceeded rapidly, supported by a marked hyperglycaemia. There was no depletion of adenylates, even after
3 h of severe hypoxia. The tail muscle of C. destructor held small amounts of glycogen which would sustain anaerobiosis for a only a few hours. Hypometabolism seems an important
hypoxic response but severe hypoxia may encourage the crayfish to breathe air.
Accepted: 26 February 1998 相似文献
18.
Y. Bhambhani R. Maikala S. Buckley 《European journal of applied physiology and occupational physiology》1998,78(5):422-431
The purpose of this study was to compare the rates of muscle deoxygenation in the exercising muscles during incremental arm
cranking and leg cycling exercise in healthy men and women. Fifteen men and 10 women completed arm cranking and leg cycling
tests to exhaustion in separate sessions in a counterbalanced order. Cardiorespiratory measurements were monitored using an
automated metabolic cart interfaced with an electrocardiogram. Tissue absorbency was recorded continuously at 760 nm and 850 nm
during incremental exercise and 6 min of recovery, with a near infrared spectrometer interfaced with a computer. Muscle oxygenation
was calculated from the tissue absorbency measurements at 30%, 45%, 60%, 75% and 90% of peak oxygen uptake (V˙O2) during each exercise mode and is expressed as a percentage of the maximal range observed during exercise and recovery (%Mox).
Exponential regression analysis indicated significant inverse relationships (P < 0.01) between %Mox and absolute V˙O2 during arm cranking and leg cycling in men (multiple R = −0.96 and −0.99, respectively) and women (R =−0.94 and −0.99, respectively). No significant interaction was observed for the %Mox between the two exercise modes and
between the two genders. The rate of muscle deoxygenation per litre of V˙O2 was 31.1% and 26.4% during arm cranking and leg cycling, respectively, in men, and 26.3% and 37.4% respectively, in women.
It was concluded that the rate of decline in %Mox for a given increase in V˙O2 between 30% and 90% of the peak V˙O2 was independent of exercise mode and gender.
Accepted: 31 March 1998 相似文献
19.
Thierry Weissland P. Pelayo Jacques Vanvelcenaher Ga?lle Marais Jean-Marc Lavoie Hervé Robin 《European journal of applied physiology and occupational physiology》1997,76(5):428-433
The aims of the present study were: first, to assess the interindividual variations of a spontaneously chosen crank rate
(SCCR) in relation to the power developed during an incremental upper body exercise on an arm ergometer set at a constant
power regime, and second, to compare heart rate (HR) responses, expired minute ventilation (V˙
E) and oxygen consumption (V˙O2) when the pedal rates were chosen spontaneously (TSCCR) or set at ±10% of the freely chosen rates (T+10% and T−10%, respectively). The mean pedal rate values were linearly related (P < 0.01) with the power developed during arm cranking (r = 0.96), although large variations of pedalling rate strategies were observed between subjects. Maximal power (MP) and time
to exhaustion values were significantly higher (P < 0.05) during TSCCR than during T+10% and T−10%. Peak V˙O2 values were significantly higher (P < 0.05) in T+10% than in TSCCR and T−10%. The increase in HR, V˙
E, and V˙O2 mean values, in relation to the increase in the power developed, was significantly higher (P < 0.05) when the pedal rate was set at plus 10% of the SCCR (T±10%) than in the two other conditions. The findings of the present study suggest that the use of an electromagnetically braked
ergometer, which automatically adjusts the resistance component to maintain a constant work rate, should be used in order
to achieve the highest MP values during an incremental upper body exercise. A 10% increase of the SCCR should be used in order
to provide the highest peak V˙O2 value.
Accepted: 5 May 1997 相似文献
20.
Sanni P. Voutilainen Harry Boer Marika Alapuranen Janne J?nis Jari Vehmaanper? Anu Koivula 《Applied microbiology and biotechnology》2009,83(2):261-272
Two different types of approach were taken to improve the hydrolytic activity towards crystalline cellulose at elevated temperatures
of Melanocarpus albomyces Cel7B (Ma Cel7B), a single-module GH-7 family cellobiohydrolase. Structure-guided protein engineering was used to introduce an additional
tenth disulphide bridge to the Ma Cel7B catalytic module. In addition, a fusion protein was constructed by linking a cellulose-binding module (CBM) and a linker
from the Trichoderma reesei Cel7A to the C terminus of Ma Cel7B. Both approaches proved successful. The disulphide bridge mutation G4C/M70C located near the N terminus, close to the
entrance of the active site tunnel of Ma Cel7B, led to improved thermostability (ΔT
m = 2.5°C). By adding the earlier found thermostability-increasing mutation S290T (ΔT
m = 1.5°C) together with the disulphide bridge mutation, the unfolding temperature was increased by 4°C (mutant G4C/M70C/S290T)
compared to that of the wild-type enzyme, thus showing an additive effect on thermostability. Both disulphide mutants had
increased activity towards microcrystalline cellulose (Avicel) at 75°C, apparently solely because of their improved thermostability.
The addition of a CBM also improved the thermostability (ΔT
m = 2.5°C) and caused a clear (sevenfold) increase in the hydrolysis activity of Ma Cel7B towards Avicel at 70°C. 相似文献