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Volume 52 (2002)
- Issue 6 Pages 507-
- Issue 5 Pages 403-
- Issue 4 Pages 327-
- Issue 3 Pages 235-
- Issue 2 Pages 135-
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Volume 52, Issue 2
Displaying 1-11 of 11 articles from this issue
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Regular Papers
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Hajime Imai, Tomoya Hayashi, Tsuneo Negawa, Koji Nakamura, Mihoko Tomi ...2002 Volume 52 Issue 2 Pages 135-140
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSA high-performance liquid chromatographic (HPLC) analysis of human serum albumin (HSA) using an ion-exchange (DEAE-form) column shows three components: The principal component corresponds to human mercaptalbumin (HMA); the secondary to nonmercaptalbumin (HNA), having mixed disulfide with cystine (HNA[Cys]), or oxidized glutathione (HNA[Glut]); and the tertiary to HNA, oxidized more highly than mixed disulfide. The purpose of the present study is to clarify the effects of strenuous exercise load on HMA↔HNA; conversion (i.e., dynamic change in redox state) of HSA from elite kendo athletes (n = 30; 20.0±1.1 years old). They participated in an intensive kendo training camp for 5 d. The mean value for the HMA fraction (f−[HMA]) of kendo athletes after camp (62.8±2.4%) was significantly lower than before camp (71.9±3.7%) (p<0.0005). In contrast, the mean value for f−(HNA-1) (i.e., f−[HNA(Cys) and HNA(Glut)]) after camp (34.2±2.1%) was significantly higher than before camp (25.7±3.7%) (p<0.0005). These results suggested that strenuous physical exercise markedly increased the oxidized albumin level in extracellular fluids during the intensive training camp.
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Masaru Watanabe, Hiromi Takano-Ohmuro2002 Volume 52 Issue 2 Pages 141-147
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSThe influences of cell membrane permeabilization (skinning) on the okadaic acid-induced inhibition of vascular smooth muscle contraction were studied in guinea pig hepatic portal vein. Pretreatment by 1 μM okadaic acid in the absence of Ca2+ suppressed subsequent submaximal Ca2+-induced contraction in preparations permeabilized with Staphylococcus aureus α-toxin or β-escin, but not in those treated with saponin or Triton X-100. The SDS-PAGE of elutants from the preparation suggests that the loss of the inhibitory effect of okadaic acid in preparations skinned with saponin or Triton X-100 results from the leakage of some cellular components with a molecular mass of 67 to 200 kDa.
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Masao Yamasaki, Tsuyoshi Shimizu2002 Volume 52 Issue 2 Pages 149-161
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSTo clarify the effects of the head-down tilt (HDT) posture on the postnatal development of the aortic baroreflex, we raised rabbits from 3-4 weeks of age for 34-36 d in this posture, which simulates the headward shift of body fluid in space, and examined the structural and functional characteristics of the aortic nerves and baroreflex responses. The rabbits were divided into 3 different groups: 20° HDT, environmental control (EC), and vivarium control (VIV). Left aortic nerve activity (ANA) at basal arterial pressure was defined as 100%, and the maximum ANA at maximal increase in arterial pressure was 265±103% (mean±SD, n=5) in the HDT, 482±170% (n=4) in the EC, and 677±491% (n=4) in the VIV groups. The minimum ANA at maximal decrease in arterial pressure was 67.3±13.8% in the HDT, 40.1±10.2% in the EC, and 38.6±13.8% in the VIV groups. The maximal change of ANA in response to maximal change in arterial pressure in the HDT group was significantly less than that of either the EC or VIV group (p<0.05). The average baroreflex gain in the HDT group was significantly less than in the VIV group (p<0.05). The number of unmyelinated fibers in the left aortic nerve in the HDT group was significantly less than that of each control group (p<0.05). Thus the development of the aortic baroreflex system is apparently depressed by the HDT posture, suggesting that similar consequences will be observed in mammals that develop in space.
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Nobuoki Tabayashi, Takehisa Abe, Shuichi Kobayashi, Yoshiro Yoshikawa, ...2002 Volume 52 Issue 2 Pages 163-171
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSThe aim of the present study was to compare the oxygen (O2) cost of left ventricular (LV) contractility (equivalent maximal elastance; eEmax, an index for contractility) for dobutamine (a β-receptor stimulant) with that for calcium (Ca2+) in normal rat hearts and to assess the O2 cost of LV eEmax for dobutamine in Ca2+ overload-induced failing rat hearts. The mean O2 cost of LV eEmax (×10−4 μl O2·beat−1·mmHg−1·ml·g−2) for Ca2+ was 1.30±0.37 in 12 normal hearts, and for dobutamine it was 1.26±0.30 in eight different normal hearts. In the same five normal hearts, the mean O2 cost of LV eEmax for dobutamine was 1.15±0.27, and for Ca2+ it was 0.81±0.36. These mean values showed no significant differences between Ca2+ and dobutamine. In five Ca2+ overload-induced failing hearts, the mean O2 cost of LV eEmax for Ca2+ could not be assessed, but the mean O2 cost of LV eEmax for dobutamine was 1.04±0.40. This mean value for dobutamine did not differ significantly from those (see above 1.26±0.30 or 1.15±0.27) in the normal hearts. The present results indicate, in terms of the coupling of mechanical work and energetics of the heart, that the total Ca2+ handling VO2 in excitation-contraction coupling against unit LV contractility change for dobutamine in the contractile failing hearts does not differ from that in the normal hearts. This suggests that in the Ca2+ overload-induced contractile failing hearts, there were no changes in the sensitivity of the contractile machinery for Ca2+, in the Ca2+/ATP in the total Ca2+ handling, and in the ATP/VO2 in the mitochondria.
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Kazunori Itoh, Kenji Kawakita2002 Volume 52 Issue 2 Pages 173-180
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSThe effect of indomethacin on the development of delayed onset muscle soreness (DOMS) and localized sensitive region produced by eccentric exercise was examined in lightly anesthetized rabbits (n=12, 2.0-3.3 kg). Repeated eccentric contractions of the gastrocnemius (GS) muscle were made by manual extensions during the tetanic contractions induced by electrical stimulation of the tibial nerve. The development of DOMS was confirmed by evoked reflex EMG in the biceps femoris (BF) muscle elicited by a quantitative manual extension of the GS muscle. The distribution of thresholds for the evoked BF EMG was measured by focal electrical stimulations of the GS muscle. Indomethacin (5 mg/kg in 2% sodium bicarbonate) or a vehicle was injected subcutaneously before, during, and after the exercise (a total of 60 mg/kg in 12 doses). A clear ropy taut band was palpated at the GS muscle on the second day after the exercise and a localized sensitive region for evoked BF EMG was detected at the depth of the fascia of the band in the exercise and vehicle groups, whereas no such phenomena appeared in the control and indomethacin groups. The palpable band and sensitive region disappeared on the seventh day after the exercise. That indomethacin inhibits the development of DOMS and the localized sensitive region suggests that a sensitization of polymodal-type nociceptors in the fascia mediated by prostaglandins is a possible mechanism for the development of DOMS and the localized sensitive region.
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C. Petibois, M. Paiva, G. Cazorla, G. Déléris2002 Volume 52 Issue 2 Pages 181-190
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSBlood chemical parameters were analyzed by Fourier-transform infrared spectrometry (notably for determining the concentrations of glucose, lactate, urea, glycerol, triglycerides, and proteins) in 14 top-class marathon runners (133.7±4.1 min at marathon, 10.1% difference between extremes) who performed a 10-km run at their individual marathon velocity. Marathon performance level was correlated to glycemia increase during exercise (9% difference between extremes; r=0.93; p<0.005). The best marathon runners presented longer and/or less unsaturated blood fatty acids during exercise (17% difference between extremes; r=0.89; p<0.01), suggesting an improved fatty acid selectivity for muscular metabolism. The marathon performance level was also found correlated to a decrease of blood triglycerides during exercise (r=20.95; p<0.003) and to a proportional glycerol concentration increase (11% difference between extremes; r=0.94; p<0.005). The best marathon runners presented higher amino acid blood delivery (r=0.88; p<0.01), which was correlated to an apparent protein catabolism. These results show that the best runners have enhanced both carbohydrate, lipid, and amino acid metabolisms to improve energetic supply to skeletal muscle during exercise.
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Tsuneo Negawa, Shinji Mizuno, Tomoya Hahashi, Hiromi Kuwata, Mihoko To ...2002 Volume 52 Issue 2 Pages 191-198
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSWe characterized the visual pathways involved in the stereoscopic recognition of the random dot stereogram based on the binocular disparity employing a functional magnetic resonance imaging (fMRI). The V2, V3, V4, V5, intraparietal sulcus (IPS) and the superior temporal sulcus (STS) were significantly activated during the binocular stereopsis, but the inferotemporal gyrus (ITG) was not activated. Thus a human M pathway may be part of a network involved in the stereoscopic processing based on the binocular disparity. It is intriguing that areas 44 (Broca's area) and 45 in the left hemisphere were also active during the binocular stereopsis. However, it was reported that these regions were inactive during the monocular stereopsis. To separate the specific responses directly caused by the stereoscopic recognition process from the nonspecific ones caused by the memory load or the intention, we designed a novel frequency labeled tasks (FLT) sequence. The functional MRI using the FLT indicated that the activation of areas 44 and 45 is correlated with the stereoscopic recognition based on the binocular disparity but not with the intention artifacts, suggesting that areas 44 and 45 play an essential role in the binocular disparity.
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Yasuhiro Suzuki, Osamu Ito, Naoki Mukai, Hideyuki Takahashi, Kaoru Tak ...2002 Volume 52 Issue 2 Pages 199-205
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSThe histidine-containing dipeptide carnosine (β-alanyl-L-histidine) has been shown to significantly contribute to the physicochemical buffering in skeletal muscles, which maintains acid-base balance when a large quantity of H+ is produced in association with lactic acid accumulation during high-intensity exercise. The purpose of the present study was to examine the relations among the skeletal muscle carnosine concentration, fiber-type distribution, and high-intensity exercise performance. The subjects were 11 healthy men. Muscle biopsy samples were taken from the vastus lateralis at rest. The carnosine concentration was determined by the use of an amino acid autoanalyzer. The fiber-type distribution was determined by the staining intensity of myosin adenosinetriphosphatase. The high-intensity exercise performance was assessed by the use of 30-s maximal cycle ergometer sprinting. A significant correlation was demonstrated between the carnosine concentration and the type IIX fiber composition (r=0.646, p<0.05). The carnosine concentration was significantly correlated with the mean power per body mass (r=0.785, p<0.01) during the 30-s sprinting. When dividing the sprinting into 6 phases (0-5, 6-10, 11-15, 16-20, 21-25, 26-30 s), significant correlations were observed between the carnosine concentration and the mean power per body mass of the final 2 phases (21-25 s: r=0.694, p<0.05; 26-30 s: r=0.660, p<0.05). These results indicated that the carnosine concentration could be an important factor in determining the high-intensity exercise performance.
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Koh Takeuchi, Elena Simplaceanu, Francis X. McGowan Jr., Takao Tsushim ...2002 Volume 52 Issue 2 Pages 207-215
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSRecently, cytokines have been proposed to cause cellular injury by nitric oxide (NO·) mediated pathway and L-arginine has been proposed to impair intracellular pH (pHi) regulation via vacuolar type H+-ATPase in macrophage. We conducted this investigation on Langendorff perfused hearts of rabbits to elucidate the mechanisms involving the NO· precursor L-arginine on myocardial contractile function, glycolysis, mitochondrial respiration, and intracellular alkalinization and tested the effects of amiloride. L-Arginine caused a significant loss of contractile function (96±4 mmHg in control, 53±16 during L-arginine perfusion, p<0.01) and a significant increase of pHi (7.01±0.02 prearginine infusion, 7.08±0.03 at the end of L-arginine infusion, p<0.01) along with decreased oxygen consumption (MVO2) (0.94±0.32 ml/min/g dry wt.), increased lactate release, and a loss of creatine phosphate (15% loss). Amiloride could prevent the cell alkalinization and contractile dysfunction, but not the derangement of oxidative metabolism caused by L-arginine in myocytes. We conclude that L-arginine has two distinct effects upon the myocardium: (1) an amiloride-sensitive loss of contractile function associated with intracellular alkalinization; and (2) an amiloride-insensitive inhibition of oxidative metabolism, possibly because of increased myocardial NO· production.
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Shinsuke Nakayama, Shigeko Torihashi2002 Volume 52 Issue 2 Pages 217-227
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSTo investigate spontaneous rhythmicity in smooth muscle tissue, we have developed a cell cluster preparation. Cell clusters were enzymatically isolated from the muscle layer of mouse small intestine and cultured for several days. They included smooth muscle, neurones, and c-Kit-immunopositive interstitial cells. c-Kit-immunopositive cells in myenteric plexus, showing a networklike structure, are putative pacemaker cells. The cultured cell clusters routinely show spontaneous contraction and preserve characteristic features in this tissue: (1) high temperature dependency of contractile frequency; (2) spontaneous electrical activities measured with patch clamp techniques are insensitive to tetradotoxin (TTX) and dihydropyridine Ca2+ antagonists. This preparation could therefore be used as a good model system to investigate the underlying mechanisms of intestinal motility and pacemaker function. The relationship between the frequency of electrical activity and cluster size suggests that the minimum unit of small intestine tissue to yield normal pacemaker activity is approximately 100 μm in diameter, or less. The applications of 100-120 μM Cd2+ and Ni2+ significantly suppressed the spontaneous activity. Ca2+ influx pathways other than L-type and "classical" T-type voltage-sensitive Ca2+ channels seem very likely to play an important role, such as nonselective cation channels and capacitative Ca2+ entry. Furthermore, applications of heptanol reduced the amplitude and the frequency of the oscillating inward currents and eventually terminated them, suggesting that electrical cell-to-cell coupling may also make some contribution to the generation of spontaneous activity.
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Short Communication
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Narihiko Kondo, Shuji Yanagimoto, Ken Aoki, Shunsaku Koga, Yoshimitsu ...2002 Volume 52 Issue 2 Pages 229-233
Published: 2002
Released on J-STAGE: June 19, 2004
JOURNAL FREE ACCESSChanges in the number of activated sweat glands (ASGs) and sweat output per gland (SGO) with increased exercise intensity during sustained static exercise were investigated. Fourteen male subjects performed 20, 35, and 50% maximal voluntary contraction (MVC) for 60 s with the right hand (exercised arm) at an ambient temperature of 35°C and 50% relative humidity. Although sublingual, local skin, and mean skin temperatures remained essentially constant throughout the exercise at each intensity, the sweating rate (SR) of nonglabrous skin on the nonexercised left forearm increased significantly with a rise in exercise intensity (p<0.05). Changes in the number of ASGs with rising exercise intensity paralleled changes in the SR, but the SGO did not change markedly with altered exercise intensity. These results suggest that in mildly heated humans, at less than 50% MVC, the increase in the SR from nonglabrous skin with rising exercise intensity during sustained static exercise is dependent on changes in the number of ASGs and not on SGO.
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