The Japanese Journal of Physiology (Jpn J Physiol)

Publications in this journal

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  Available from: ccmu.edu.cn

  Article: Single-channel properties of volume-sensitive Cl- channel in ClC-3-deficient cardiomyocytes.

  Jun Wang, Hongtao Xu, Shigeru Morishima, Shigeru Tanabe, Kouichi Jishage, Shinichi Uchida, Sei Sasaki, Yasunobu Okada, Takahiro Shimizu
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  ABSTRACT: It is controversial whether the ClC-3 protein, which is one of the voltage-dependent chloride channel ClC family members, is a candidate for the volume-sensitive outwardly rectifying (VSOR) Cl(-) channel per se or its regulator. Here, for the first time, we examined the single-channel properties of the VSOR Cl(-) channel in ventricular myocytes isolated from ClC-3-deficient mice. The single-channel current induced by cell swelling exhibited Cl(-) selectivity, mild outward rectification, and an intermediate unitary conductance (around 38 pS). A Cl(-) channel blocker, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), reversibly inhibited the outward current. These single-channel properties were identical with those in ClC-3 expressing wild-type ventricular myocytes. These results indicate that the single-channel activity of the VSOR Cl(-) channel is independent of the expression of ClC-3 proteins in mouse ventricular myocytes.
  The Japanese Journal of Physiology 01/2006; 55(6):379-83.
• Article: Restoration by VIP of the carbachol-stimulated Cl- secretion in TTX-treated guinea pig distal colon.

  A Kokubo, Y Yasuoka, M Nishikitani, K Saigenji, K Kawahara
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  ABSTRACT: To determine if vasoactive intestinal peptide (VIP) restores neural activity from tetrodotoxin (TTX) blockade, we studied the effects of VIP and related agents on carbachol (Cch)-induced Cl(-) secretion in control-isolated guinea pig distal colon and in that treated with TTX. The short circuit current (I(sc)) increased dose-dependently after serosal applications of Cch (10(-6) - 2 x 10(-5) M) and VIP (5 x 10(-9) - 10(-7) M). But no additive or synergistic increase in I(sc) was observed. Cch- and VIP-induced I(sc) was completely abolished by a serosal application of TTX (10(-6) M). However, a serosal application, not mucosal, of VIP (10(-7) M) and 8-bromo-cAMP (10(-3) M) restored the Cch-stimulated, TTX-inhibited I(sc) by 113% and 75.8%, respectively. Furthermore, mucosal and serosal applications of forskolin (aden late cyclase activator) restored the I(sc) by 43.9% and 65.3%, respectively. The restored I(sc) was completely abolished by atropine (muscarinic receptor antagonist). These results suggest that VIP may restore the cholinergic activity by increasing the level of intracellular cAMP, and that cholinergic neuron is very likely to be responsible for the regulation of Cl(-) secretion at neuroepithelial junctions. The exact mechanism of VIP's effect on the TTX-inhibited epithelial Cl(-) secretion, and its possible usefulness in the treatment of TTX-induced pathophysiological conditions, remain to be determined.
  The Japanese Journal of Physiology 01/2006; 55(6):317-24.
• Article: Synthetic peptides of actin-tropomyosin binding region of troponin I and heat shock protein 20 modulate the relaxation process of skinned preparations of taenia caeci from guinea pig.

  Yasumasa Yoshino, Wataru Sakurai, Sachio Morimoto, Masaru Watanabe
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  ABSTRACT: To explore the possible role of the thin filament-linked regulation of cross-bridge cycling in living smooth muscle contraction, we studied the effects of TnIp and HSP20p, a synthetic peptide originating from an actin tropomyosin binding region of rabbit cardiac troponin I (residues 136-147; GKFKRPTLRRVR), and that of human heat shock protein 20 (residues 110-121; GFVAREFHRRYR) on the relaxation of skinned (cell membrane ilized) preparations from guinea pig taenia caeci. An active stress of the skinned preparations, resulting from actin-myosin interaction, rapidly decayed following Ca(2+) removal (relaxation). TnIp accelerated the initial rapid phase and slowed the following slow phase of the relaxation. On the other hand, HSP20p only slowed the whole process of the relaxation. The relaxation time courses were well fitted in a double exponential manner, and the double exponential decay of the stress could be explained as a portion of fast-detaching cross bridges not to dissociate rapidly by Ca(2+) removal, but to transfer to latch bridges dissociating very slowly. Our present results suggested that (i) TnIp and HSP20p accelerated transferring from fast-detaching cross bridges to slow-detaching (latch) bridges, and (ii) TnIp accelerated dissociation of the fast-detaching cross bridges and the latch bridges, while HSP20p slowed dissociation the fast-detaching cross bridges. Since TnIp and HSP20p are thought to bind to actin and tropomyosin, but not to myosin, we concluded that through thin-filament-dependent mechanisms these peptides regulated the formation and/or deformation of latch bridges in smooth muscle. The thin-filament-dependent regulation might physiologically control the stress maintenance and relaxation in smooth muscle cells.
  The Japanese Journal of Physiology 01/2006; 55(6):373-8.
• Article: Comparison of biomechanical and histological properties in dog carotid arteries injured by neointima or intimal thickening.

  Hirohisa Goto, Risuke Mizuno, Nobuyuki Ono, Masao Sakaguchi, Toshio Ohhashi
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  ABSTRACT: A general formula (Oka and Azuma's equation) has been rigorously derived for the circumferential wall tension in a hollow cylindrical tube in equilibrium. To evaluate the validity and usefulness of Oka and Azuma's equation, T = P(1) x r(1) - P(2) x r(2) (T, circumferential wall tension; P(1) and P(2), internal and external pressures of the tube; r(1) and r(2), the corresponding internal and external radii), we experimentally investigated changes in circumferential wall tension of noninjured (control) and injured dog common carotid arteries by using a newly developed apparatus with a photo- and X-ray-sensitive image sensor. We also studied histological features of the control and injured arteries with special reference to the relation of biomechanical properties. Two types of animal models with injured arteries--balloon-induced neointima or external collar-induced intimal thickening--were adopted in the present study. In the control arteries, the circumferential wall tension was experimentally confirmed to change from negative to positive by an increase in intraluminal pressure ranging from 50 to 180 mmHg. The critical intraluminal pressure that produced 0 dyne/cm of the circumferential wall tension was around 135 mmHg. The activation of arterial smooth muscles caused a significant increase in the critical pressure in the control arteries. In the arteries injured by neointima, the critical intraluminal pressure was significantly lower than that in the control. The activation of smooth muscles also significantly increased the critical pressure in the injured arteries. Histological examination demonstrated the existence of a circumferential neointimal formation along with a shortening of the internal diameter. In other arteries injured by intimal thickening, the circumferential wall tension was always negative at intraluminal pressure ranging from 50 to 180 mmHg. Newly developed structures consisted of elastic and collagen fibers, smooth muscles, and extracellular matrix in the intima and media of the injured arteries. These experimental findings suggest that the circumferential wall tension of dog common carotid arteries has been confirmed experimentally to become negative. We have also concluded that circumferential wall tension calculated with Oka-Azuma's equation may be one of the best parameters for evaluating changes in the biomechanical and histological properties of pathologically injured arteries.
  The Japanese Journal of Physiology 01/2006; 55(6):355-64.
• Article: Propionate modulates spontaneous contractions via enteric nerves and prostaglandin release in the rat distal colon.

  Retsu Mitsui, Shigeyuki Ono, Shin-ichiro Karaki, Atsukazu Kuwahara
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  ABSTRACT: Short-chain fatty acids, such as propionate and acetate, are produced by a bacterial fermentation of carbohydrates in the colonic lumen. We examined the effects of propionate on the frequency and mean amplitude of spontaneous giant contractions (GCs) in circular muscle strips of the rat distal colon with the mucosa attached. An addition of propionate increased the frequency of GCs for about 20 min (> or =1 mm), but the mean amplitude was decreased (> or =0.1 mm). The propionate-induced increase in the frequency of GCs was blocked by the muscarinic acetylcholine receptor antagonist, atropine. In contrast, the nicotinic receptor antagonist, hexamethonium, augmented the response. The propionate-induced decrease in the mean amplitude of GCs was prevented by the cyclooxygenase inhibitor, piroxicam. A pretreatment of the tissues with acetate prevented the propionate-induced modulations of the frequency and amplitude of GCs. These results suggest that propionate increases the frequency of GCs by an activation of cholinergic motor neurons and decreases the mean amplitude by a prostaglandin release. Propionate as well as acetate may be involved in the regulation of spontaneous circular muscle activity in the rat distal colon.
  The Japanese Journal of Physiology 01/2006; 55(6):331-8.
• Article: Role of TRPV4 in control of body temperature under heat radiation

  Modhizuki-Oda, Kusuno, Hanada, Tominaga M, TominagaT, Suzuki M, Yamada Hisao, Yamada Hironari
  The Japanese Journal of Physiology 01/2006; 56.
• Article: Wavelength dependence of optical action potentials in the isolated rat atrium.

  Tetsuro Sakai
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  ABSTRACT: The wavelength dependence of optical action potentials was studied using voltage-sensitive merocyanine-rhodanine, merocyanine-oxazolone, and oxonol dyes in the isolated rat atrium preparation. Most of the dyes had action spectra that were similar to those reported in other preparations. Species-to-species difference was observed with a merocyanine-oxazolone dye.
  The Japanese Journal of Physiology 01/2006; 55(6):389-93.
• Article: Establishment of a mouse macula densa cell line with an nNOS promoter driving EGFP expression.

  Yukiko Yasuoka, Hideaki Kawada, Yoshiro Suzuki, Masahiro Sato, Hitoshi Endou, Masuo Obinata, Katsumasa Kawahara
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  ABSTRACT: We describe a unique method for establishing a functionally intact macula densa cell line from immortalized renal cells in culture. The macula densa is involved in the tubuloglomerular feedback (TGF) system in the kidney and specifically expresses neuronal nitric oxide synthase (nNOS). A 347 bp portion of the nNOS promoter was used to drive the expression of enhanced green fluorescence protein (EGFP). An immortalized distal tubule (DT) cell line was derived from distal tubules microdissected from the kidneys of SV40 large T antigen transgenic mice. Immunofluorescence labeling using an antibody against nNOS revealed no specific EGFP expression in immunofluorescence-negative DT cells. The established cell line (NE-MD) showed a time-dependent increase in signals of the nNOS protein when they were incubated with 12 microM furosemide (an inhibitor of Na(+)-K(+)-2Cl(-) symporter) for 5 h. In conclusion, this newly developed macula densa cell line will be useful in studies of the TGF stem.
  The Japanese Journal of Physiology 01/2006; 55(6):365-72.
• Article: The medial amygdala controls the coital access of female rats: a possible involvement of emotional responsiveness.

  Yasuhiko Kondo, Yasuo Sakuma
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  ABSTRACT: Partner preference and paced mating tests were accomplished in ovariectomized female rats following bilateral radiofrequency lesions in the medial amygdala. Open field behavior and passive avoidance learning were also examined to investigate the underlying behavioral mechanism. Partner preference was determined in a chamber located between castrated and sexually active males. Airborne olfactory cues were presented to the female through small holes on the partition. The lesion diminished preference for the odor of sexually active males over that of castrated males, even after injection with a high-dose of estrogen. On the other hand, in a paced mating test the lesioned females without estrogen treatment showed a significantly shorter latency for entering the male's compartment in a two-compartment apparatus, which allowed the females, but not the males, to cross the barrier through a narrow opening at the bottom. However, an administration of estrogen and progesterone reduced the effect. The lesion had no effect on emotionality or exploratory behavior in an open field test, but it impaired passive avoidance learning capability. We suggest that a male poses an inherent threat to a female. The seemingly incompatible results of partner preference and paced mating tests can be compromised if the male is inherently aversive to the female; this emotional response can be removed by the medial amygdala lesion.
  The Japanese Journal of Physiology 01/2006; 55(6):345-53.
• Article: Analgesic effect of electroacupuncture on complete Freund's adjuvant-induced inflammatory pain in mice: a model of antipain treatment by acupuncture in mice.

  W M Li, K M Cui, N Li, Q B Gu, W Schwarz, G H Ding, G C Wu
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  ABSTRACT: Electroacupuncture (EA) was applied bilaterally to the acupoints of Zu-san-li (ST-36) and Kun-lun (BL-60) in the hindlimbs of mice. The therapeutic effect of EA on inflammatory pain induced by an ipsilateral injection of complete Freund's adjuvant (CFA) into the right paw of the mouse was investigated in this study. The time of paw-withdrawal latency (PWL) was used as an indicator for judging the intensity of the pain induced by the CFA injection. The EA effects were divided into immediate (PWL tests within 2 h after EA treatment) and cumulative (PWL tests during and after repetitive EA treatments for 3 weeks) effects. As immediate effects, PWL was significantly shortened in the CFA-injected paw, but was again prolonged 20 min after an EA treatment and lasted until 30 min after. As cumulative effects, PWL was significantly shortened in the CFA-injected paw, but recovered from the 2nd to the 8th day during repetitive EA treatments. No such effects could be observed after sham EA treatment, which resulted in behavior similar to that in untreated animals. These results demonstrate that the CFA-induced inflammatory pain in mice is an ideal model system for the investigation of EA effects and may serve as a valuable reference for the clinical treatment of inflammatory pain in human beings. Furthermore, the mouse pain model opens the possibility to apply the investigation also to transgenic mice.
  The Japanese Journal of Physiology 01/2006; 55(6):339-44.
• Article: Sprint-interval training-induced alterations of Myosin heavy chain isoforms and enzyme activities in rat diaphragm: effect of normobaric hypoxia.

  Yuji Ogura, Hisashi Naito, Junichiro Aoki, Jin Uchimaru, Takao Sugiura, Shizuo Katamoto
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  ABSTRACT: The purpose of this study was twofold: (i) to investigate if sprint-interval training (SIT) alters myosin heavy chain (MyHC) isoform composition and bioenergetic properties within the rat diaphragm, and (ii) to determine if mild normobaric hypoxia would enhance the effects of SIT-induced diaphragmatic adaptation. Male Wistar rats (8 weeks old) were randomly assigned to one of four groups (n = 7/group): (i) normoxic control (NC); (ii) normoxic training (NT); (iii) hypoxic control (HC); or (iv) hypoxic training (HT). The NT and HT groups were engaged in SIT (1 min sprint and 2-5 min rest, 6-10 sets/day, 5-6 days/week) on a treadmill for 9 weeks. Animals in the HC and HT groups were exposed to normobaric hypoxia (14.5% O(2)) during an SIT program from the 4th week of the training period. After completion of the training program, MyHC composition, citrate synthase (CS) activity, and lactate dehydrogenase (LDH) activity in the diaphragm and plantaris muscle were analyzed. An analysis of diaphragmatic MyHC composition demonstrated increased type IIa and decreased type IId/x for both training groups (P < 0.05), with the HT group producing greater changes than the NT group (P < 0.05). The plantaris muscle, however, showed increased Type IIa and IId/x and decreased Type IIb for both the NT and HT groups (P < 0.05). CS activity increased only for the training groups (P < 0.05), and this change was greater for the HT group in the diaphragm and for the NT group in the plantaris muscle (P < 0.05). Further, diaphragmatic LDH activity in HT was significantly lower (P < 0.05) than in HC and NT. These findings demonstrated that SIT could induce alterations in MyHC composition from fast to slow within type II isoforms and also improve the oxidative capacity in the diaphragm and plantaris muscles. It is of importance that our data revealed that SIT-induced diaphragmatic adaptations were enhanced when SIT was performed in normobaric hypoxia.
  The Japanese Journal of Physiology 12/2005; 55(6):309-16.
• Article: The underlying cellular mechanism in the effect of tetramethylpyrazine on the anion secretion of colonic mucosa.

  Wen-Chao Zhao, Dong-Xiao Duan, Zhi-Ju Wang, Ning Tang, Ming Yan, Gui-Hong Zhang, Ying Xing
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  ABSTRACT: The present study investigated the underlying cellular mechanism in the effect of ligustrazine (tetramethylpyrazine, TMP) on the anion secretion of colonic mucosa in rats using a short-circuit current (I(sc)) technique in conjunction with "tool drugs." (i) After a pretreatment of the tissues by bathing the bilateral surface with Cl(-)-free Krebs-Henseleit (K-H) solution for over an hour, a basolateral application of 1 mmol/l TMP produced an increase in I(sc), and the total charges transported for 30 min were about 8.7 +/- 1.4 mC/cm(2); an apical pretreatment of DPC and a basolateral addition of acetazolamide decreased the TMP-induced I(sc) by about 60% (P < 0.01) and 45% (P < 0.05), respectively; a basolateral application of 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), the inhibitor of Na(+)-HCO(3)(-) cotransporter (NBC), did not alter the TMP-induced I(sc). (ii) After the bilateral surface of mucosa was bathed with HCO(3)(-)-free K-H solution for over an hour, a basolateral application of 1 mmol/l TMP produced an increase in I(sc), and the total charges transported in 30 min were about 8.3 +/- 1.9 mC/cm(2); an apical pretreatment of DPC (1 mmol/l), the inhibitor of Cl(-) channels, decreased the TMP-induced Isc by about 84% (P < 0.01). The basolateral presence of bumetanide (0.1 mmol/l), the inhibitor of Na(+)-K(+)-Cl(-) cotransporter (NKCC), significantly reduced the TMP-evoked I(sc) by about 86% (P < 0.01). In conclusion, (i) ligustrazine could promote colonic mucosa secretion Cl(-) via apical Cl(-) channels and basolateral NKCC; (ii) ligustrazine could promote colonic mucosa secretion HCO(3)(-) via apical Cl(-) channels and the basolateral diffusion of CO(2).
  The Japanese Journal of Physiology 12/2005; 55(6):325-9.
• Article: Cardiac developmental biology: from flies to humans.

  Ichiro Shiojima, Issei Komuro
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  ABSTRACT: The heart is the first organ to form during embryogenesis, and heart formation is essential for subsequent embryonic development. Since the identification of a cardiac-restricted transcription factor Csx/Nkx-2.5 in the early 1990s, extensive studies on cardiac development have been done in various species ranging from flies to humans. Molecular dissection of regulatory pathways that control multiple steps of cardiogenesis will not only advance our understanding of cardiac development and congenital heart diseases, but will also provide an important clue to novel therapeutic strategies for heart diseases.
  The Japanese Journal of Physiology 11/2005; 55(5):245-54.
• Article: Overeating after restraint stress in cholecystokinin-a receptor-deficient mice.

  Kyoko Miyasaka, Setsuko Kanai, Minoru Ohta, Hiroko Hosoya, Saeko Takano, Ayako Sekime, Chihiro Sakurai, Takao Kaneko, Shoichi Tahara, Akihiro Funakoshi
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  ABSTRACT: In mammals, including humans, a brain-gut hormone, cholecystokinin (CCK) mediates the satiety effect via CCK-A receptor (R). We generated CCK-AR gene-deficient (-/-) mice and found that the daily food intake, energy expenditure, and gastric emptying of a liquid meal did not change compared with those of wild-type mice. Because CCK-AR(-/-) mice show anxiolytic status, we examined the effects of restraint stress. Seven hours of restraint stress was found to significantly decrease both body weight and food intake during the subsequent 3 days in all tested animals. On the fourth day after restraint stress, the CCK-AR(-/-) mice showed a significantly higher level of daily food intake than prior to stress, and food intake recovered to prestress levels in the wild-type mice. Since peripheral CCK-AR has been known to mediate gastric emptying, both gastric emptying and gastric acid secretion were determined to examine the mechanism of overeating in CCK-AR(-/-) mice. Neither gastric emptying nor gastric acid secretion differed between CCK-AR(-/-) and wild-type mice on the fourth day after stress. In contrast, however, the contents of dopamine and its metabolites in the cerebral cortex of CCK-AR(-/-) mice were increased by stress, but were rather decreased in wild-type mice. Changes in 5-hydroxytryptamine (5-HT) and its metabolite 5HIAA did not differ between the genotypes. In conclusion, CCK-AR(-/-) mice showed overeating after restraint stress, and dopaminergic hyperfunction in the brain of these mice was observed. The present evidence suggests that the CCK-AR function, possibly via altering the dopaminergic function, might be involved in overeating after stress.
  The Japanese Journal of Physiology 11/2005; 55(5):285-91.
• Article: Cutaneous Mechanical Stimulation Regulates Ovarian Blood Flow via Activation of Spinal and Supraspinal Reflex Pathways in Anesthetized Rats.

  Sae Uchida, Fusako Kagitani, Harumi Hotta, Tomoko Hanada, Yoshihiro Aikawa
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  ABSTRACT: The reflex effects of noxious mechanical stimulation of a hindpaw or abdominal skin on ovarian blood flow, and the reflex pathways involved in those responses were examined in anesthetized rats. Blood flow in the left ovary was measured using a laser Doppler flowmeter, and the activity of the left ovarian sympathetic nerve and mean arterial pressure (MAP) of the common carotid artery were recorded. Stimulation of the left or right hindpaw for 30 s produced marked increases in ovarian sympathetic nerve activity and MAP. Ovarian blood flow slightly decreased during the stimulation and then slightly increased after the stimulation. After the left ovarian sympathetic nerves were severed, the same stimulus produced a remarkable monophasic increase in ovarian blood flow that was explained by passive vasodilation due to a marked increase in MAP. After spinal transection at the third thoracic (T3) level, the responses of MAP, ovarian sympathetic nerve activity, and ovarian blood flow to hindpaw stimulation were nearly abolished. Stimulation of the abdomen at the right or left side for 30 s produced slight increases in ovarian sympathetic nerve activity and MAP. Ovarian blood flow slightly decreased during the stimulation and then slightly increased after the stimulation. After the ovarian sympathetic nerves were severed, the response of the ovarian blood flow changed to a monophasic increase due to an increase in MAP. After spinal transection, stimulation of the left abdomen produced a moderate increase in MAP, a remarkable increase in ovarian sympathetic nerve activity and a slight decrease in ovarian blood flow during the stimulation. In contrast, stimulation of the right abdomen produced a smaller response in ovarian sympathetic nerve activity during the stimulation while it increased the MAP to a similar degree. Ovarian blood flow slightly increased after the end of stimulation, which was explained as passive vasodilation due to the increase in MAP. In conclusion, stimulation of somatic afferents affects ovarian blood flow by inducing changes in ovarian sympathetic nerve activities and blood pressure. When stimulation was applied to a hindpaw whose segment of afferent input is far from the segment of the ovarian sympathetic nerves, it took a supraspinal reflex pathway. However, when stimulation was applied to the abdomen whose spinal segment of the afferent is close to the segment of the ovarian sympathetic nerve output, there are spinal segmental reflex pathways. The present results demonstrate that spinal reflexes depend on the laterality of the stimulus, while supraspinal reflexes do not depend on the laterality of the stimulus.
  The Japanese Journal of Physiology 11/2005; 55(5):265-77.
• Article: Hemodynamics under Hippocampal Functional Hyperemia in Anesthetized Rat: A Greater Contribution of Red Blood Cell Velocity Compared to Its Concentration.

  Takeshi Nishijima, Hideaki Soya
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  ABSTRACT: It remains controversial which of the two regulators, red blood cell velocity (RBC-V) or concentration (RBC-C), is a main contributor to increasing flow (RBC-F) during functional hyperemia in the rat hippocampus induced by N-methyl-D-aspartate (NMDA). To address this, we monitored these parameters simultaneously under NMDA-infusion via microdialysis in the hippocampus of urethane-anesthetized rats and found a greater elevation in RBC-V than in RBC-C. This suggests that an RBC-V-dependent increase in RBC-F occurs under NMDA-induced functional hyperemia in the hippocampus as well as in the cortex.
  The Japanese Journal of Physiology 11/2005; 55(5):303-7.
• Article: Variable Unstressed Volume Keeps Normal Distributions of Canine Left Ventricular Contractility and Total Mechanical Energy under Atrial Fibrillation.

  Satoshi Mohri, Juichiro Shimizu, Haruo Ito, Hiroki Yamaguchi, Shunji Sano, Miyako Takaki, Hiroyuki Suga
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  ABSTRACT: We have reported that the contractility index (E(max)) and the total mechanical energy (PVA) of arrhythmic beats of the left ventricle (LV) distribute normally in canine hearts under electrically induced atrial fibrillation (AF). Here, E(max) is the ventricular elastance as the slope of the end-systolic (ES) pressure-volume (P-V) relation (ESPVR), and PVA is the systolic P-V area as the sum of the external mechanical work within the P-V loop and the elastic potential energy under the ESPVR. To obtain E(max) and PVA, we had to assume the systolic unstressed volume (V(o)) as the V-axis intercept of the ESPVR to be constant despite the varying E(max), since there was no method to obtain V(o) directly in each arrhythmic beat. However, we know that in regular stable beats V(o) decreases by approximately 7 ml/100 g LV with approximately 100 times the increases in E(max) from ~0.2 mmHg/(ml/100 g LV) of almost arresting weak beats to approximately 20 mmHg/(ml/100 g LV) of strong beats with a highly enhanced contractility. In the present study, we investigated whether E(max) and PVA under AF could still distribute normally, despite such E(max)-dependent V(o) changes. The present analyses showed that the E(max) changes were only approximately 3 times at most from the weakest to the strongest arrhythmic beat under AF. These changes were not large enough to affect V(o) enough to distort the frequency distributions of E(max) and PVA from normality. We conclude that one could practically ignore the slight E(max) and PVA changes with the Emax-dependent V(o) changes under AF.
  The Japanese Journal of Physiology 11/2005; 55(5):255-64.
• Article: Arachidonic Acid-Induced COX-1 and COX-2-Mediated Vasodilation in Rat Gingival Arterioles In Vivo.

  Atsushi Nakatsuka, Risuke Mizuno, Nobuyuki Ono, Jun Nakayama, Toshio Ohhashi
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  ABSTRACT: The roles of cyclooxygenase (COX) and prostaglandins (PGs) in the regulation of vasoreactivity of rat gingival arterioles in vivo were evaluated by sing an intravital microscope. The superfusion of indomethacin (a nonselective COX inhibitor) or SC-560 (a selective COX-1 inhibitor) onto the gingiva significantly constricted the arterioles, though NS-398 (a selective COX-2 inhibitor) did not affect the diameter of the arterioles. The SC-560-mediated constriction of the arterioles was completely reversed by an additional treatment with arachidonic acid (AA). The superfusion of AA, beraprost-Na (an analogue of PGI2) or PGE2 onto the gingival significantly dilated the arterioles dose-dependently. The AA-induced dilation of the arterioles was significantly reduced by the treatment with SC-560 or NS-398. The expression of COX-1 and COX-2 were positive in the endothelium, but not the smooth muscles, of the arterioles. The expression of PGE synthase (PGES) was found only in the smooth muscles, but not the endothelium, of the arterioles. Neither the endothelium nor the smooth muscles of the arterioles expressed PGI synthase (PGIS). These findings suggest that the COX-2-mediated PG cascade may collaborate with the COX-1 pathway in the regulation of arteriolar myogenic activity in rat gingiva in the case of the supply of a large amount of AA.
  The Japanese Journal of Physiology 11/2005; 55(5):293-302.
• Article: Hormone and lipolytic responses to whole body vibration in young men.

  Kazushige Goto, Kaoru Takamatsu
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  ABSTRACT: This study examined the effects of whole-body vibration (WBV) on the hormone and lipolytic responses. Eight male subjects performed WBV and control (CON) trials on separate days. The WBV session consisted of 10 sets of vibration for a duration of 60 s with rest periods of 60 s between each set (frequency 26 Hz). The subjects maintained a static squat position with knees bent on the platform. In the CON trial, the WBV stimulation was not imposed. Blood samples were collected before both trials and during the recovery period. In the WBV trial, the concentrations of plasma epinephrine (Epi) and norepinephrine (NE) increased immediately after the session (P < 0.05). Serum free fatty acids (FFA) concentration increased significantly at the 150, 180, and 210 min points of the recovery period in the WBV trial (P < 0.01) with the interaction between trial and time (P < 0.01). Serum glycerol showed no significant change in either trial. These results suggest that the WBV session causes secretions of Epi and NE, and it subsequently increases FFA concentration during the recovery period. However, because the FFA response was inconsistent with that of glycerol, we were unable to clarify the effect of WBV exposure on lipolysis.
  The Japanese Journal of Physiology 10/2005; 55(5):279-84.