The purpose of the present study was to examine whether the level of oxygen uptake (V.o2) at the onset of decrement-load exercise (DLE) is lower than that at the onset of constant-load exercise (CLE), since power output, which is the target of V.o2 response, is decreased in DLE. CLE and DLE were performed under the conditions of moderate and heavy exercise intensities. Before and after these main exercises, previous exercise and post exercise were performed at 20 watts. DEL was started at the same power output as that for CLE and power output was decreased at a rate of 15 watts per min. V.o2 in moderate CLE increased at a fast rate and showed a steady state, while V.o2 in moderate DLE increased and decreased linearly. V.o2 at the increasing phase in DLE was at the same level as that in moderate CLE. V.o2 immediately after moderate DLE was higher than that in the previous exercise by 98±77.5 ml/min. V.o2 in heavy CLE increased rapidly at first and then slowly increased, while V.o2 in heavy DLE increased rapidly, showing a temporal convexity change, and decreased linearly. V.o2 at the increasing phase of heavy DLE was the same level as that in heavy CLE. V.o2 immediately after heavy DLE was significantly higher than that in the previous exercise by 156±131.8 ml/min. Thus, despite the different modes of exercise, V.o2 at the increasing phase in DLE was at the same level as that in CLE due to the effect of the oxygen debt expressed by the higher level of V.o2 at the end of DLE than that in the previous exercise., T. Yano, H. Ogata, R. Matsuura, T. Arimitsu, T. Yunoki., and Obsahuje bibliografii a bibliografické odkazy
Diapause fixation and development were studied in females of a Czech population of Aquarius paludum by monitoring changes in oxygen uptake, weight and reproduction potential in field adults between August and February. The fall in oxygen uptake related to fresh weight (from > 1000 µl O2 per g per h to around 500 µl O2 per g per h) in field adults during early diapause was similar in two age cohorts, although the time of adult ecdysis differed by 50 days and thus occurred at markedly different temperatures and photoperiods of late August vs. early October. The different conditions affected the weight of females and thus also the absolute value of oxygen consumption: both parameters were much lower in the October females. The seasonal time of diapause termination in A. paludum did not differ from findings in other cold temperate insects: diapause and the photoperiodic response ended in the winter, as was shown by the possibility of insects' reactivation by 26°C in spite of a diapause promoting daylength of 12L : 12D. In most females (78.6%) ovaries matured after transfer to these conditions in mid-February, while ovarian maturation occurred in only 16.7% of females transferred in early January and no ovarian maturation was observed in females transferred in early December. Ovarian maturation was preceded by a transient increase in oxygen consumption from 600 µl O2 per g per h to 1400 µl O2 per g per h.
The protein secondary structure and pigments' microenvironment in photosystem 1 (PS1) complexes were studied in the temperature range of 25-80 °C using Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy, respectively. Quantitative analysis of the component bands of the amide I band (1 700-1 600 cm-1) showed no significant change below 50 °C. However, apparent conformational changes occurred at 60 °C and further continued at 70 and 80 °C accompanied with transitions of secondary structure mainly from α-helix to the β-sheet structures. CD analysis demonstrated that the regular arrangement, viz. protein microenvironment of pigments of PS1 complexes, was destroyed by heat treatment which might come from the changes of protein secondary structure of PS1. The CD signals at 645 nm contributed by chlorophyll (Chl) b of light-harvesting complex 1 (LHC1) were easily destroyed at the beginning of heat treatment (25-60 °C). When temperature reached 70 and 80 °C, the CD signals at 478 nm contributed mainly by Chl b of LHC1 and 498 nm contributed by carotenoids decreased most rapidly, indicating that LHC1 was more sensitive to high temperature than core complexes. In addition, the oxygen uptake rate decreased by 90.81 % at 70 °C and was lost completely at 80 °C showing that heat treatment damaged the regular function of PS1 complexes. This may be attributed to heat-induced changes of pigment microenvironment and protein secondary structure, especially transmembrane α-helix located in PsaA/B of PS1. and Z.-H. Hu ... [et al.].
The purpose of this study was to examine how oxygen uptake (V.o2) in decrement-load exercise (DLE) is affected by changing rate of decrease in power output. DLE was performed at three different rates of decrease in power output (10, 20 and 30 watts ・min-1: DLE10, DLE20 and DLE30, respectively) from power output corresponding to 90 % of peak V.o2. V.o2 exponentially increased and then decreased, and the rate of its decrease was reduced at low power output. The values of V.o2 in the three DLE tests were not different for the first 2 min despite the difference in power output. The relationship between V.o2 and power output below 50 watts was obtained as a slope to estimate excessive V.o2 (ex-V.o2) above 50 watts. The slopes were 10.0±0.9 for DLE10, 9.9±0.7 for DLE20 and 10.2±1.0 ml ・min-1 ・ watt-1 for DLE30. The difference between V.o2 estimated from the slope and measured V.o2 was defined as ex-V.o2. The peak value of ex-V.o2 for DLE10 (189±116 ml ・min-1) was significantly greater than those for DLE20 and for DLE30 (93±97 and 88±34 ml ・min-1). The difference between V.o2 in DLE and that in incremental-load exercise (ILE) below 50 watts (ΔV.o2) was greater in DLE 30 and smallest in DLE10. There were significant differences in ΔV.o2 among the three DLE tests. The values of ΔV.o2 at 30 watts were 283±152 for DLE10, 413±136 for DLE20 and 483±187 ml ・min-1 for DLE30. Thus, a faster rate of decrease in power output resulted in no change of V.o2 at the onset of DLE, smaller ex-V.o2 and greater ΔV.o2. These results suggest that V.o2 is disposed in parallel in each motor unit released from power output or recruited in DLE., T. Yano, T. Yunoki, R. Matsuura, T. Arimitsu, T. Kimura., and Obsahuje bibliografii a bibliografické odkazy
The kinetics of post-exercise heart rate (HR) and oxygen consumption (EPOC) was studied in 10 elite cyclists subjected to four laboratory cycle ergometer maximal exercises lasting 30, 90, 180 or 360 s. Heart rate and oxygen uptake (VO2) were recorded over a period of 6 min after the exercise. By applying the logit transformation to the recorded variables and relating them to the decimal logarithm of the recovery time, uniform single-phase courses of changes were shown for both variables in all subjects and exercises. This enabled computing half-recovery times (t½) for both variables. Half-time for VO2 negatively correlated with square root of exercise duration (within-subject r=-0.629, p<0.001), the total post-exercise oxygen uptake till t½ was thus constant irrespectively of exercise intensity. The method is simple and enables reliable comparisons of various modes of exercise with respect to the rate of recovery., R. Stupnicki ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We investigated the differential expression of AOX1 multi-gene family and the regulation of alternative respiratory pathway during initial greening development in leaves of rice (Oryza sativa L.) seedlings. After exposing the dark-grown rice seedlings to continuous irradiation, total respiration (Vt), capacity of alternative pathway (Valt), and their ratio (Valt/Vt) increased with the greening of leaves. In this process, AOX1c transcript increased under constant irradiation, while AOX1a and AOX1b transcripts were hardly detected. Thus AOX1c in rice presents a similar expression pattern as AOX2 does in many dicotyledonous species during greening development. Compared with the rapid increase of cyanideresistant respiration in the presence of photon energy, CO2 fixation was not observed until 8 h after the onset of irradiation. The AOX inhibitor salicylhydroxamic acid (SHAM; 1 mM) inhibited 67.3 % of cyanide-insensitive oxygen uptake in dark-grown leaves and 69.4 % of it in leaves grown under irradiation. Dark-grown plants pre-treated with SHAM were then irradiated for 12 h. SHAM did not obviously modify photosynthetic CO2 fixation rate on a chlorophyll (Chl) content basis in both leaves and simultaneously isolated chloroplasts. Hence during initial greening steps of the plants, the induction of alternative pathway and AOX1 expression by irradiation is not directly linked with carbon assimilation of photosynthesis. The application of SHAM partially limited Chl production in rapidly greening leaves, indicating that Chl synthesis in the process of greening might be medicated to some extent by alternative respiratory pathway. and H. Q. Feng ... [et al.].
The aim of this study was to evaluate the influence of exercise with the intensity progressively increasing from rest until maximal oxygen uptake (VCbmax) on 2,3-DPG levels in red blood cells (RBC) in relation to the changes in the acid-base balance and plasma lactate concentration. Six healthy young men (age 22.5 ±1.5 years, V02max 3.48 ±0.20 1/min) participated in this study. The subjects performed an incremental exercise test on a cycloergometer until exhaustion. Blood samples were tested for acid-base balance indices (pH, HCO3-, BE), plasma lactate and RBC 2,3-DPG concentration. Gas exchange variables were measured continuously breath-bybreath. In this paper we present data concerning 2,3-DPG, plasma lactate, pH, HCO3" and BE measured at rest, at the power output corresponding to the lactate threshold (PO LT), at the power output at maximal oxygen uptake (PO VCbmax), as well as 5, 15 and 30 min after finishing the incremental test. Increase of power output above the lactate threshold to the PO V02max was accompanied by a significant (p<0.01) increase of plasma lactate from 2.58±0.78 mmol/1 to 10.22±3.04 mmol/1. This was also accompanied by a significant drop (p<0.01) in blood pH value from 7.352 ± 0.025 at the PO LT to 7.294 ±0.041 at the PO V02max- No significant changes of the RBC
2,3-DPG level were observed at any of the analysed stages of the exercise. The RBC 2,3-DPG level expressed in relation to the changes of haematocrit showed only minor changes during the exercise period and after 15 min of recovery vs. resting value (3.21 ±1.19). However, after 30 min of recovery, RBC 2,3-DPG decreased to the value of 2.32±1.19 /rmol/ml. We conclude that, during an incremental test, no increase in RBC 2,3-DPG concentration is required to reach the maximal oxygen uptake level. Moreover, a rapid decrease in blood pH, developing during a single bout of exercise, is not a stimulus powerful enough to cause significant changes in the RBC 2,3-DPG level during short-term exercise.