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1.
Polymorphonuclear neutrophils (PMN) respond to a variety of stimuli with a sequence of reactions that lead to the production of "active oxygen" species, including H2O2, free radicals, such as superoxide (O2-.) and hydroxyl (HO.), and singlet molecular oxygen (1O2). Some of these can oxidize (5-amino-2,3-dihydrophthalazine 1,4-dione) (luminol) to the ground state aminophthalate ion; this reaction sequence is accompanied by the generation of a photon and forms the basis for the chemiluminescence (CL) response. In this work we used a dedicated photon counting instrument to record CL from PMN incubated with bacterial lipopolysaccharide (LPS). We have studied the CL response to the LPS from Escherichia coli strains 026:B6 and 055:B5, as well as Salmonella minnesota RE 595 and have determined that CL requires heat-labile serum factors, these most likely being intact components of the complement system. 相似文献
2.
Sergio D. Catz Maria C. Carreras Juan J. Poderoso 《Free radical biology & medicine》1995,19(6):741-748
Nitric oxide synthase (NOS) inhibitors have been reported to modulate luminol-dependent chemiluminescence (CL) in rat macrophages, whereas the potent oxidant peroxynitrite (ONOO-) was shown to react with luminol to yield CL in a cellfree system. We evaluated the role of the
-arginine/NOS pathway in luminol CL by phorbol ester-activated human polymorpho-nuclear (PMN) leukocytes using the NOS inhibitors NG-monomethyl-
-arginine (
-NMMA) and N-iminoethyl-
-omithine (
-NIO). Nitric oxide (·NO) release was determined by oxidation of oxymyoglobin. In addition, the effect of NOS inhibitors on superoxide anion O2-) production was measured. Luminol CL was notably diminished by
-NMMA in a dose-dependent manner. Superoxide dismutase (SOD) also decreased luminol CL and
-NMMA potentiated light emission decrease produced by SOD. Nitric oxide and O2·- production was significantly decreased by
-NMMA; moreover, luminol-dependent CL but not O2·- production was attenuated by
-NIO. These data suggest that products of catalytic activity of both ·NO synthase and NADPH oxidase are required to elicit maximal luminol CL in this system. These studies demonstrate that the NOS synthase pathway is involved in luminol CL by human PMN, and they suggest that ONOO would be an unrecognized mediator in this phenomenon. 相似文献
3.
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
4.
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
5.
The goal of this research was to measure in vitro the inhibitory constants of the antioxidants ascorbic and uric acid in urine, with lucigenin enhanced chemiluminescence (CL)
in Fenton’s system. Maximum CL emission is registered in urine containing H2O2 (5·10−4 M), Fe2+ (5·10−5 M), EDTA (5·10−5 M), and chemical enhancer lucigenin (10−4 M) at pH 5.5 and 36°C. Ascorbic acid exhibits up to 4-fold stronger antioxidant effect than uric acid. The constants of antioxidant
inhibition in urine were measured at concentrations 10−3 and 10−4 M: for ascorbic acid, 5.92 ± 0.04 and 24.05 ± 1.82 μmol·sec−1; for uric acid, 1.60 ± 0.02 and 21.45 ± 0.97 μmol·sec−1, respectively. Three phases of CL kinetics of urine are well observed: spontaneous CL (0–10 sec), fast flash of CL (10–50
sec), and latent period (50–300 sec). The antioxidant efficiency of ascorbic and uric acids in the final stage of catabolic
processes in the body is discussed.
Published in Russian in Biokhimiya, 2006, Vol. 71, No. 8, pp. 1062–1065. 相似文献
6.
Mühling J Nickolaus KA Halabi M Fuchs M Krüll M Engel J Wolff M Matejec R Langefeld TW Welters ID Menges T Dehne MG Sablotzki A Hempelmann G 《Amino acids》2005,29(3):289-300
Summary. The objective of this study was to determine the dose as well as duration of exposure-dependent effects of L-alanyl-L-glutamine,
arginine or taurine on polymorphonuclear neutrophil (PMN) free α-keto acid profiles and, in a parallel study, on PMN immune
functions. Exogenous L-alanyl-L-glutamine significantly increased PMN α-ketoglutarate, pyruvate PMN superoxide anion (O2−) generation, hydrogen peroxide (H2O2) formation and released myeloperoxidase (MPO) activity. Arginine also led to significant increases in α-ketoglutarate, pyruvate,
MPO release and H2O2 generation. Formation of O2− on the other hand was decreased by arginine. Incubation with taurine resulted in lower intracellular pyruvate and α-ketobutyrate
levels, decreased O2− and H2O2 formation and a concomitant significantly increased MPO activity. We therefore believe that considerable changes in PMN free-α-keto-acid
profiles, induced for example by L-alanyl-L-glutamine, arginine or taurine, may be one of the determinants in cell nutrition
that considerably modulates the immunological competence of PMN. 相似文献
7.
Yu. A. Vladimirov E. M. Demin E. V. Proskurnina A. N. Osipov 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2009,3(4):467-477
The key stage of apoptosis is lipid peroxidation which causes cytochrome c efflux from mitochondria. Cardiolipin-bound cytochrome c on the surface of the inner mitochondrial membrane is supposed to be a main lipoperoxidation catalyst. In this work, lipoperoxide
radical (LOO·) production in the complex of cytochrome c (Cyt C) with bovine heart cardiolipin (BCL) was investigated with the method of chemiluminescence (CL) in the presence of
a physical activator, coumarin dye C-525. It was shown that a CL flash with a half quenching time of 1.12 min was observed
after the addition of Cyt C to a BCL+C-525 solution in the absence of hydrogen peroxide. At H2O2 concentrations of 0.1–0.5 mM, quenching time reduced at constant CL flash amplitude and at H2O2 concentrations of 1–5 mM, the amplitude of CL increased with the growth of peroxide concentration. It testifies to different
mechanisms of BCL oxidation: the lipoxygenase mechanism in the absence of H2O2 and at low H2O2 concentrations, and the peroxidase mechanism at higher H2O2 concentrations. When small H2O2 amounts were added, another CL flash was observed in the course of a lipoxygenase reaction whose light sum increased with
time in parallel with the extent of the following inhibition of CL. Iron chelators EDTA and o-phenanthroline made no significant effect on the CL associated with cytochrome c lipoxygenase action, while desferal, a well-known peroxidase and lipoxygenase inhibitor, inhibited CL by half in a concentration
of 18 μM. A scheme of reactions resulting in LOO· radical production on BCL oxidation by the Cyt C-cardiolipin complex in
the absence and in the presence of H2O2 was suggested. 相似文献
8.
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
9.
Djordje Malenčić Slavko Kevrešan Milan Popović Dubravka Štajner Boris Popović Biljana Kiprovski Simonida Djurić 《Central European Journal of Biology》2012,7(1):132-137
The oxidative stress and antioxidant systems in soybean leaves and roots infected with plant pathogen Aspergillus niger were studied following treatment with different concentrations of cholic acid. Several oxidative stress parameters were analyzed:
production of superoxide (O2
·−) and hydroxyl radicals (·OH), lipid peroxidation (LP), and superoxide dismutase (SOD; EC 1.15.1.1) activity, as well as the content of reduced glutathione
(GSH). Results showed that inoculation with A. niger led to the increase of O2
·− production and GSH quantities in leaves and ·OH in roots. The highest activity of SOD occured in infected plants treated with cholic acid in concentrations of 40 and 60
mg L−1 which ultimately led to a decrease in O2
·− production. Inoculation with Aspergillus in combination with elevated cholic acid concentrations also increased ·OH production which is correlated with increased LP. These results may support the idea of using cholic acid as an elicitor
to trigger hypersensitive response in plant cells. Use of cholic acid may also actively contribute to soybean plants defense
response against pathogen attack. 相似文献
10.
NADH-stimulated, cyanide-resistant superoxide production in maize coleoptiles analyzed with a tetrazolium-based assay 总被引:9,自引:0,他引:9
Using the tetrazolium salt XTT (Na,3′-[(phenylamino)-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro)benzenesulfonic acid
hydrate) as a sensitive and physiologically compatible probe for the determination of superoxide (O2
·−) production in vivo, we have shown that maize (Zea mays L.) coleoptiles possess the capacity of generating O2
·− in the apoplastic space. Our results are in agreement with the notion that this activity is localized at the plasma membrane
and can be attributed to an O2
·−-synthesizing enzyme with catalytic and kinetic properties similar to that of the NADPH oxidase of mammalian phagocytes, with
the important exception that it utilizes NADH instead of NADPH as electron donor. When applied to the apoplastic space, NADH
strongly increased the O2
·−-producing activity of coleoptiles. The maize NADH-dependent O2
·−-synthase activity could clearly be differentiated from peroxidase-mediated O2
·−-synthesizing activity by its insensitivity to cyanide and azide, as well as by its much higher affinity to O2. Formation of O2
·−, and concomitantly appearing H2O2, was preferentially localized in the outer epidermis of the coleoptile. The physiological significance of O2
·− and H2O2 production in relation to the growth-controlling function of the epidermal cell wall is discussed.
Received: 14 January 2000 / Accepted: 2 May 2000 相似文献
11.
《Luminescence》2003,18(1):19-24
Using a highly sensitive single photon counter, a spontaneous chemiluminescence (CL) study on rice (Oryza sativa L.) seeds stored in different years was carried out. We first observed that the degree of ageing in rice seeds was related to the intensity of spontaneous CL during early imbibition (0–30 min). Rice seeds stored for a shorter time had a stronger intensity of CL in early imbibition. The germination rate of rice seeds showed an obvious positive correlation with the intensity of spontaneous CL. Singlet oxygen (1O2) in rice seeds during early imbibition was investigated by a CL method using a cypridina luciferin analogue, 2‐methyl‐6‐(p‐methoxyphenyl)‐3,7‐dihydroimidazo [1,2α] pyrazin‐3‐one (MCLA), as a selective CL probe. Additional experimental evidence for the formation of 1O2 came from the quenching effect of sodium azide (NaN3) on MCLA‐mediated rice seeds' CL. Analysis based on the experimental results demonstrated that spontaneous CL in rice seeds during early imbibition was mainly contributed by singlet oxygen (1O2). Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
12.
Bioenergetics and RNA/DNA ratios in the common carp (Cyprinus carpio ) under hypoxia 总被引:2,自引:0,他引:2
Zhou BS Wu RS Randall DJ Lam PK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2001,171(1):49-57
Hypoxia caused by eutrophication occurs over large areas in aquatic systems worldwide. Common carp (Cyprinus carpio) exposed to hypoxia (1 mg · O2 · l−1 and 2 mg · O2 · l−1) for 1 week showed a significant reduction in feeding rate, respiration rate, faecal production and nitrogenous excretion
compared to those maintained at normoxia (7 mg · O2 · l−1). Fish exposed to hypoxia showed negative scope for growth (SfG), but no significant difference in the specific growth rate
was revealed after 1 week in both hypoxic groups. A significant reduction in RNA/DNA ratio was, however, clearly evident in
the white muscle of the 1 mg · O2 · l−1 treatment group, but not in the 2 mg · O2 · l−1 treatment group. Both specific growth rate and RNA/DNA ratio were significantly reduced when fish were exposed to severe
hypoxia (0.5 mg · O2 · l−1) for 4 weeks. At all levels of hypoxia, growth reduction was accompanied by a significant decrease in RNA/DNA ratio in white
muscle. Covariance analysis showed no significant difference between the slope of RNA/DNA ratio and growth rate under normoxic
conditions and 0.5 mg · O2 · l−1 for 4 weeks (F=1.036, P > 0.326), as well as 1.0 mg · O2 · l−1 and 2.0 mg · O2 · l−1 for 1 week (F = 0.457, P > 0.5), indicating that the RNA/DNA ratio serves as a biomarker of growth under all oxygen levels, at least under controlled
experimental conditions. SfG also appears to be more sensitive than the RNA/DNA ratio in responding to hypoxia in fish.
Accepted: 15 September 2000 相似文献
13.
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
14.
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
15.
Senescence is a developmentally regulated and highly ordered sequence of events. Senescence leads to abscission of plant organs
and eventually leads to death of a plant or part of it. Present study revealed that Phalaenopsis flower undergo senescence due to over activation of O2
·−generating xanthine oxidase (XO), which consequently increases the concentrations of O2
·− leading to enhanced oxidative damage and disturbed cellular redox environment as indicated by increased lipid peroxidation
and DHA/AsA + DHA ratio, respectively. While activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and non-specific
peroxidase (POD) were enhanced in sepals and petals of old flower, activities of catalase (CAT) and glutathione reductase
(GR) were decreased. Exogenous application of nitric oxide (NO) retarded H2O2-induced senescence of Phalaenopsis flower by downregulating activity of XO and concentrations of O2
·−, H2O2 and malondialdehyde (MDA, an index of lipid peroxidation). Exogenous application of NO also downregulated SOD activity and
upregulated antioxidant enzymes involved in the detoxification of H2O2 (CAT and APX), and in the regulation of redox couples viz, monodehydroascorbate reductase (MDHAR) and GR, together with the
modulation in non-protein thiol status and DHA/AsA + DHA ratio. 相似文献
16.
Olas B Wachowicz B Saluk-Juszczak J Zieliński T Kaca W Buczyński A 《Cell biology and toxicology》2001,17(2):117-125
Resveratrol (3,4′,5-trihydroxystilbene) is a natural molecule with antioxidant action. It is also considered to be a molecule
with antiplatelet, anticancer and anti-inflammatory action. The effects of trans-resveratrol on the reactive oxygen species (ROS) generation and thiobarbituric acid-reactive substances (TBARS) in blood
platelets induced by endotoxin (lipopolysaccharide, LPS) or thrombin were studiedin vitro. The production of superoxide radicals (O2
.–) and other reactive oxygen species (H2O2, singlet oxygen, and organic radicals) in the presence of resveratrol was measured by a chemiluminescence method in resting
blood platelets and platelets stimulated by LPS (0.3 μg/108 platelets) or thrombin (2.5 U/108 platelets). We have shown that resveratrol (6.25–100 μg/ml) inhibits chemiluminescence and generation of O2
.– in blood platelets. It has an inhibitory effect on the production of ROS and TBARS in platelets caused by LPS or thrombin.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
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
18.
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
19.
R. K. Sairam K. Dharmar V. Chinnusamy S. Lekshmy R. Joshi P. Bhattacharya 《Biologia Plantarum》2011,55(4):741-746
The objective of this study was to examine the role of NADPH oxidase on superoxide radical production under waterlogging in
mung bean (Vigna radiata) cvs. T 44 (tolerant) and Pusa Baisakhi (PB) (susceptible), and wild species Vigna luteola. Two days of waterlogging caused decline in superoxide radical (O2
·−) contents in all the genotypes, however, further waterlogging up to 8 d caused significant increase in O2
·− contents. In control and revived plants O2
·− contents were higher in PB, while under waterlogging stress T 44 and V. luteola showed greater increases in the O2
·− contents. During waterlogging the increase in O2
·− content was found to be due to the diphenylene iodonium chloridesensitive NADPH oxidase (NOX). This was further confirmed
by the waterlogging induced increase in NOX activity, which was higher in tolerant genotypes T 44 and V. luteola compared with PB. Gene expression studies showed enhanced expression of NOX in the roots of waterlogged V. luteola and T 44, while little expression was observed in control or treated plants of PB. PCR band products were cloned and sequenced,
and partial cDNAs of NOX was obtained. Results suggest that increase in O2
·− content during waterlogging could be due to the induction of membrane linked NOX. 相似文献
20.
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