著者

Takao Sugiura Naoko Ito Katsumasa Goto Hisashi Naito Toshitada Yoshioka Scott K. Powers

出版者

PHYSIOLOGICAL SOCIETY OF JAPAN

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.56, no.6, pp.393-399, 2006 (Released:2006-12-28)

参考文献数

43

被引用文献数

34 37

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We tested the hypothesis that estrogen administration would retard immobilization-induced muscle atrophy in adult male rats. The rats were injected for 24 days with either estrogen (40 μg/kg−1, β-estradiol 3-benzoate in olive oil vehicle), or vehicle alone. At day 14 of estrogen treatment, the hindlimb muscles of one leg were immobilized in plantar flexion position by the use of a plaster cast. Following 10 days of immobilzation, the atrophic and the contralateral soleus muscles were both removed and analyzed to determine the level of muscle atrophy along with the measurement of the protein levels of Cu-Zn-superoxide dismutase (Cu-Zn-SOD), heat shock protein 72 (HSP72), and selected proteases. Compared to placebo animals, estrogen treatment significantly reduced (–35%) muscle atrophy. Further, estrogen significantly abridged the expression of the calcium-activated protease, calpain, in the atrophied hindlimb muscle. In contrast, estrogen treatment did not alter the protein levels of HSP72 in the immobilized soleus muscle. These results support the postulate that estrogen attenuates the rate of disuse muscle atrophy, partly because of reductions in immobilization-induced calcium-activated protease levels.

著者

Lee Yukyung Choi Gaeun Jeon Hyongjun Kim Dongsoo Ryu Sun Koo Sungtae Ha Ki-Tae Kim Seungtae

出版者

Physiological Society of Japan

雑誌

The journal of physiological sciences (ISSN:18806546)

巻号頁・発行日

vol.68, no.4, pp.455-462, 2018-07

著者

Matsukawa Kanji Endo Kana Ishii Kei Ito Momoka Liang Nan

出版者

Physiological Society of Japan

雑誌

The journal of physiological sciences (ISSN:18806546)

巻号頁・発行日

vol.68, no.2, pp.175-190, 2018-03

著者

Shun Sato Chengzhu Yin Akira Teramoto Yasuo Sakuma Masakatsu Kato

出版者

PHYSIOLOGICAL SOCIETY OF JAPAN

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.58, no.5, pp.317-322, 2008 (Released:2008-10-29)

参考文献数

47

被引用文献数

7 16

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Gonadotropin-releasing hormone (GnRH) neurons represent the final output neurons in the central control of reproduction. γ-Amino butyric acid (GABA), one of the major regulators of GnRH neurons, depolarizes GnRH neurons isolated from adult rats via GABAA receptors. The presence of GABAA receptors in GnRH neurons has also been demonstrated morphologically. Furthermore, the pineal hormone melatonin is involved in the regulation of reproductive function, including the timing of the luteinizing hormone surge. The suprachiasmatic nucleus and the GABAergic system in the medial preoptic area are considered as possible sites of the action of melatonin. Until now, however, a direct action of melatonin on GnRH neurons has not been reported. Therefore we examined the effect of melatonin on GABAA receptor currents in GnRH neurons isolated from GnRH-EGFP transgenic rats by means of perforated patch-clamp experiments. The GABAA receptor currents were modulated by melatonin in a sex-specific manner. In GnRH neurons from adult males, melatonin augmented these currents in 67% of the neurons examined, but attenuated the currents in only 19% of them. These modulations were blocked by the melatonin receptor antagonist luzindole, suggesting an involvement of melatonin receptors. The modulation by melatonin was not observed in GnRH neurons isolated from infantile rats. These findings indicate that GABA affects the excitability of GnRH neurons in adult rats through GABAA receptors, and that melatonin modifies this excitability via melatonin receptors in a sex-specific manner.

著者

Kazushige Goto Kazumasa Takahashi Masato Yamamoto Kaoru Takamatsu

出版者

PHYSIOLOGICAL SOCIETY OF JAPAN

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.58, no.1, pp.7-14, 2008 (Released:2008-02-23)

参考文献数

33

被引用文献数

22 34

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This study examined acute hormone and recovery responses to resistance exercise with slow movements. Six men performed three types of exercise regimens (five sets of knee extension exercise): (1) high-intensity resistance exercise with normal movement (HN; 1 s for lifting action, 1 s for lowering action), (2) low-intensity resistance exercise with slow movement (LS; 3 s for lifting action, 3 s for lowering action), and (3) low-intensity resistance exercise with normal movement (LN; 1 s for lifting action, 1 s for lowering action). The intensity in the first set was set at approximately 80% of 1RM for HN and 40% of 1RM for LS and LN. In the HN and LS, the subjects performed each exercise set until exhaustion. In the LN, both intensity and number of repetitions were matched with those for LS. The total work volume in the HN showed approximately double the value of LS and LN (P < 0.05). Electromyography (EMG) data indicated that LS showed sustained EMG signals throughout the exercise. During the exercise, the HN and LS showed lower muscle oxygenation levels. After the exercise, LS caused significantly greater norepinephrine and free testosterone responses (delta value) than in the HN and LN (P < 0.05). However, no significant difference was observed in the recovery of maximal isometric strength, isokinetic strength, and jump performance between the HN and LS. These results indicate that slow movements during the resistance exercise are important for the enhancement of hormonal responses, especially catecholamine and free testosterone, but they do not affect muscle strength recovery.

著者

Gerlinger-Romero Frederico Guimaraes-Ferreira Lucas Yonamine Caio Yogi Salgueiro Rafael Barrera Nunes Maria Tereza

出版者

Physiological Society of Japan

雑誌

The journal of physiological sciences (ISSN:18806546)

巻号頁・発行日

vol.68, no.2, pp.165-174, 2018-03

著者

Yutaka Kano Kazumi Masuda Hirotaka Furukawa Mizuki Sudo Kazuyuki Mito Kazuyoshi Sakamoto

出版者

日本生理学会

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.58, no.5, pp.349-355, 2008 (Released:2008-10-29)

参考文献数

37

被引用文献数

8 20

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This study examined the effects of a different number of eccentric contractions (ECs) on histological characteristics, surface electromyogram (EMG) parameters (integral EMG, iEMG; muscle fiber conduction velocity, MFCV; and action potential waveform), and isometric peak torque using the rat EC model. Male Wistar rats (n = 40) were anesthetized, and ECs were initiated in the tibialis anterior muscle via electrical stimulation while the muscle was being stretched by electromotor. The rats were grouped according to the number of ECs (EC1, EC5, EC10, EC20, EC30, EC40, and EC100). Three days after the ECs, surface EMG signals and isometric peak torque were measured during evoked twitch contractions via electrical stimulation of the peroneal nerve. The muscle damage was evaluated from hematoxylin-eosin (HE) stained cross sections as a relative number of damaged fibers to intact fibers. Intense histological muscle damage (approximately 50% to 70% of the fiber), loss of isometric peak torque, disturbance of action potential waveform, and depression of iEMG (approximately −60% to −70%) were observed at EC20, EC30, EC40, and EC100. On the other hand, the MFCV did not change in any EC group. Although muscle damage and pathological surface EMG signals were not found at EC10, isometric peak torque was reduced significantly. In conclusion, the extent of histological muscle damage is not proportionally related to the number of ECs. Muscle damage was reflected by iEMG and action potential waveforms, but not by MFCV, which remained unaffected even though approximately 50% to 70% of the fiber demonstrated injury.

著者

Eisuke Ochi Koichi Nakazato Naokata Ishii

出版者

日本生理学会

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.57, no.1, pp.1-6, 2007 (Released:2007-02-24)

参考文献数

36

被引用文献数

15 26

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We investigated the effects of repeated eccentric exercise for rat medial gastrocnemius muscle on ankle joint stiffness and muscle connectin (titin) isoform composition (longer form, α-connectin; shorter form, β-connectin). Male Wistar rats were trained on a custom-made, isokinetic dynamometer (eccentric-exercise group, n = 6; sham-operated group, n = 6). The exercise session consisted of 20 eccentric contractions elicited by submaximal electric stimulations under anesthesia. The contracting muscle was forcibly lengthened by an isokinetic dorsi-flexion of the ankle joint (velocity, 30°/s; range of motion, 45°). Rats in the eccentric-exercise group were trained every two days for 20 days (10 sessions in total). The static passive resistive torque (PRT) of 45° at the ankle joint was used as a measure of the joint stiffness, and was determined before and after the experimental period. After 10 sessions of eccentric exercise, the wet weight of medial gastrocnemius muscle significantly increased (P < 0.05), whereas the static PRT significantly decreased (P < 0.05) in the eccentric-exercise group, when compared to the sham-operated group. Myosin-ATPase staining showed a decrease in the number of type IIb/IId fibers (P < 0.001) and an increase in the number of type IIa fibers (P < 0.05). However, no significant difference was seen in the connectin (titin) isoform composition between the eccentric-exercise group and the sham-operated group, suggesting that the reduction in PRT was not due to change in resting mechanical properties of muscle fibers.

著者

Nao Akiyama Yoshiki Ohnuki Yuki Kunioka Yasutake Saeki Takenori Yamada

出版者

日本生理学会

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.56, no.2, pp.145-151, 2006 (Released:2006-07-30)

参考文献数

28

被引用文献数

20 35

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The transverse stiffness of single myofibrils of skeletal and cardiac muscles was examined by atomic force microscopy. The microscopic images of both skeletal and cardiac myofibrils in a rigor state showed periodical striation patterns separated by Z-bands, which is characteristic of striated muscle fibers. However, sarcomere patterns were hardly distinguishable in the stiffness distributions of the relaxed myofibrils of skeletal and cardiac muscles. Myofibrils in a rigor state were significantly stiff compared with those in a relaxed state, and in each state, cardiac myofibrils were significantly stiffer compared with skeletal myofibrils. By proteolytic digestions of sarcomere components of myofibrils, it was suggested that cardiac myofibrils are laterally stiffer than skeletal myofibrils because Z-bands, connectin (titin) filament networks, and other components of sarcomere structures for the former myofibrils are stronger than those for the latter.

著者

Véronique L. Billat Eva Wesfreid Christian Kapfer Jean P. Koralsztein Yves Meyer

出版者

日本生理学会

雑誌

The Journal of Physiological Sciences (ISSN:18806546)

巻号頁・発行日

vol.56, no.1, pp.103-111, 2006 (Released:2006-07-14)

参考文献数

36

被引用文献数

17 33

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We hypothesized that a freely paced 10,000 m running race would induce a smaller physiological strain (heart rate and oxygen uptake) compared with one performed at the same average speed but with an imposed constant pace. Furthermore, we analyzed the scaling properties with a wavelet transform algorithm computed log2 (wavelet transform energy) vs. log2 (scale) to get slope a, which is the scaling exponent, a measure of the irregularity of a time series. HR was sampled beat by beat and VO2 breath by breath. The enforced constant pace run elicited a significantly higher mean VO2 value (53 ± 4 vs. 48 ± 5 ml kg−1 min−1, P < 0.001), HR (169 ± 13 vs. 165 ± 14 bpm, P < 0.01), and blood lactate concentration (6.6 ± 0.9 vs. 7.5 ± 1 mM, P < 0.001) than the freely paced run. HR and VO2 signals showed a scaling behavior, which means that the signals have a similar irregularity (a self-similarity) whatever the scale of analysis may be, in both constant and free-paced 10,000 m runs. The scaling exponent was not significantly different according to the type of run (free vs. constant, P > 0.05) and the signal (HR vs. VO2, P > 0.05). The higher metabolic cost of constant vs. free paced run did not affect the self-similarity of HR and VO2 in either run. The HR signal only kept its scaling behavior only with a distance run, no matter the type of run (free or constant).The results suggest that the larger degree of pace variation in freely paced races may be an intentionally chosen strategy designed to minimize the physiological strain during severe exercise and to prevent a premature termination of effort, even if the variability of the heart rate and VO2 are comparable in an enforced constant vs. a freely paced run and if HR keeps the same variability until the arrival.