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I Oota

Publications and source records attributed to I Oota.

At least 19 recordsLinked to original sources
PubMed2002

Differential gene expression of vascular endothelial growth factor isoforms and their receptors in the development of the rat masseter muscle.

The capillary network in the masseter muscle develops dramatically with the differentiation of muscle fibres after birth, especially around weaning. Here, developmental changes in mRNA expression for four splicing variants of vascular endothelial growth factor (VEGF) and for two distinct VEGF receptors (Fms-like tyrosine kinase (Flt-1) and kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/Flk-1)) were studied in rat masseter. The relative abundance of VEGF (120) mRNA was the highest, representing 35% of total VEGF mRNA on day 7 after birth and gradually decreased with age to become approximately 5% on day 37. In contrast, VEGF (188) mRNA was very low in the newborn rat, but increased sharply before weaning and reached 40-50% of the total on day 50. Neither VEGF (144) nor VEGF(164) mRNA showed any significant change in abundance after birth. The expression of KDR/Flk-1 mRNA was transiently high in the early postnatal stage and gradually decreased with age, Flt-1 mRNA was stably expressed at a constant level after birth. These findings suggest that different combinations of VEGF isoforms and their receptors regulate angiogenesis in the development of the masseter muscle.

Alternative Splicing↗
PubMed2001

Developmental expression of vascular endothelial growth factor in the masseter muscle of rats.

Developmental changes in vascular endothelial growth factor (VEGF) in rat masseter after birth were investigated. VEGF was extracted efficiently and reproducibly from muscle homogenate with low concentrations of non-ionic detergents, such as Triton X-100, Nonidet P-40, and Tween 20. The amount of VEGF measured by enzyme-linked immunosorbent assay (ELISA) increased markedly by approximately 9-fold, from day 8 to 35 after birth. The increase in VEGF was closely correlated with the development of the capillary network, as shown by the capillary to muscle fibre ratio (C/F ratio). Immunoblotting revealed that the predominant molecular species of VEGF concentrated with heparin-sepharose beads was VEGF(188). These results suggest that VEGF plays an important part in the development and maintenance of the capillary network in the rat masseter.

Animals↗
PubMed1999

Effects of bilobalide, a sesquiterpene in Ginkgo biloba leaves, on population spikes in rat hippocampal slices.

The effects of bilobalide, a sesquiterpene isolated from the leaves of Ginkgo biloba L., were investigated in a rat hippocampal slice preparation. Bilobalide (10-500 microM) significantly increased the amplitude of population spikes evoked by electrical stimulation of Schaffer collateral/commissural fibers in a concentration-dependent manner. Paired-pulse inhibition at interpulse intervals of 10-50 ms was significantly reduced in the presence of bilobalide (50 microM). The inhibitory action of muscimol (1 microM) was attenuated by bilobalide (100 microM). These results suggest that bilobalide induces an enhancement of excitability of CA1 pyramidal neurons, which involves, at least in part, a reduction in GABAergic inhibition in rat hippocampus.

Action Potentials↗
PubMed1993

Mechanosensitive afferent units in the lumbar intervertebral disc and adjacent muscle.

The purpose of this study was to characterize the somatosensory units of the lumbar intervertebral disc and adjacent muscle. A laminectomy was performed on the lumbar spine of adult male Japanese White rabbits. Receptive fields of mechanosensitive afferent units were investigated in the intervertebral disc and adjacent muscle, and electrophysiologic recordings were obtained from filaments of the dorsal root. Thirteen mechanosensitive units were identified: three units in the intervertebral disc area, and 10 units in the psoas muscle. Of the three units in the disc area, one was identified at the surface of the L5-6 anulus fibrosus and two at the insertion of the anulus fibrosus to the L5 and L6 vertebral bodies. These three units belonged to Group III and had very high mechanical thresholds, more than 160 g. The 10 units in the psoas muscle belonged to Groups II, III, and IV, and had mechanical thresholds ranging from 0.22 to 12.6 g. The units in the disc area may serve as nociceptors sensitive to strong noxious stimulation that could traumatize the tissue. The units in the psoas muscle may contribute to nociception and proprioception.

Animals↗
PubMed1992

Effect of muscle stretching on the activity of neuromuscular transmission.

The purpose of this study was to investigate how muscle stretching affects the activity of neuromuscular transmission. The magnitude of the post-tetanic potentiation (PTP) of miniature end-plate potential (m.e.p.p.) frequency was measured in the rat soleus muscle at resting length and stretched length. The parameters of the magnitude of PTP can be indicators of the kinetics of Ca2+ metabolism in the nerve terminal. One of the parameters, normalized initial post-tetanic frequency (f), was significantly increased by stretching muscle 10% (P less than 0.05) and 20% (P less than 0.01) of its resting length. Another parameter, the time constant of augmentation (tau a), was not significantly changed by muscle stretching. The time constant of potentiation (tau p) was significantly increased by 20% muscle stretching (P less than 0.05). These results indicate that the Ca2+ conductance, especially the voltage-dependent Ca2+ influx, of the nerve terminal could be increased by muscle stretching. Greater Ca2+ conductance of the nerve terminal would increase intracellular free Ca2+. Consequently, the probability of transmitter release would be increased, because Ca2+ is closely related to the activity of the transmitter release mechanism.

Action Potentials↗
PubMed1987

Post-tetanic potentiation of miniature end-plate potential frequency at neuromuscular junction of the rat soleus muscle.

1. Changes in miniature end-plate potential (m.e.p.p.) frequency by repetitive nerve stimulation were examined in the rat soleus muscle. 2. The increase of m.e.p.p. frequency was induced by repetitive stimulation and persisted for several minutes after the tetanus. That is, post-tetanic potentiation (PTP) of neuromuscular transmission was first demonstrated here in the rat soleus muscle. 3. The time course of the decay of m.e.p.p. frequency after the tetanus showed a double exponential curve which consisted of a fast decaying component (augmentation) and a slow decaying component (potentiation). 4. The magnitude of PTP depended on the stimulation frequency and its duration. It increased with the increase of duration and was at its maximum at a frequency of 100 Hz. 5. No PTP was elicited by repetitive stimulation under conditions in which end-plate potential (e.p.p.) was completely suppressed, and, moreover, m.e.p.p. frequency tended to decrease after the tetanus.

Action Potentials↗
PubMed1987

Changes in post-tetanic potentiation of neuromuscular transmission in chronically stretched muscle.

1. Changes in the parameters of the magnitude of PTP of m.e.p.p. frequency were examined in rat soleus muscles chronically stretched for a variety of durations (4-28 days) by leg-lengthening operations. 2. On day 4 after the operation, the magnitude of PTP in the stretched muscles obviously increased compared to the control muscles. This indicates that Ca2+-conductance in the nerve terminals increases in the stretched muscles at day 4. 3. On day 7 after the operation, there was no significant difference between the magnitudes of PTP in the control and stretched muscles. 4. After day 14 following the operation, the magnitude of PTP in the stretched muscles was smaller than that in the control muscles. This indicates that Ca2+-conductance in the nerve terminals decreases in the stretched muscles after day 14.

Action Potentials↗
PubMed1979

Effect of transverse tubule-disruption on 14C-caffeine influx in frog skeletal muscle.

Effect of transverse tubule-disruption (T-disruption) on 14C-caffeine influx was studied using small bundles, consisting of 40 to 50 fibers, of frog semitendinosus muscle. The peak tension of caffeine contracture was inhibited by about 69% at 5 mM caffeine and by about 31% at 7 mM caffeine by T-disruption. In addition, the amount of caffeine influx in a small bundle was inhibited by about 52% at 5 mM caffeine and by about 28% at 7 mM caffeine by T-disruption, corresponding to the inhibition of the peak tension of caffeine contracture by T-disruption. These findings support our previous suggestion that caffeine enters the muscle fibers through the surface membrane and transverse tubuler membrane (T-membrane), and that the T-membrane contributes to the entry of caffeine more greatly at 5 mM caffeine than at 7 mM caffeine. Moreover, at 5 mM caffeine it was noted that there is a slight difference between the extent of inhibition of the caffeine influx and that of the peak contracture tension. From these results, it could be concluded that the inhibition of peak tension of caffeine contracture by T-disruption is mainly due to the inhibition of caffeine influx which occurs through the T-membrane and is partly due to the functional disturbance of the sarcoplasmic reticulum which is probably induced by T-disruption.

Animals↗
PubMed1979

Effect of SCN on potassium contracture in twitch muscle fibers of the frog.

The effect of SCN on potassium contracture, especially the time course and the mechanical inactivation of the contracture, was investigated using frog twitch muscle fibers. SCN increased the magnitude and the rate of rise of the potassium contracture tension and prolonged its time course. These effects of SCN depended on the concentration of K+ in the external medium and on the duration of pretreatment of the fibers with SCN-Ringer solution. The potentiating effect of SCN on the potassium contracture tension was pronounced at lower and moderate concentrations of K+ and this effect attained a maximum within 1 min after the pretreatment. In the contracture induced by exposure of the fibers to K-SCN-solution without the pretreatment, the time course of the contracture, especially the retardation of the spontaneous relaxation, was marked at higher concentrations of K+. This retarding effect of SCN attained a maximum at more than 10 min after the pretreatment with SCN-Ringer solution. SCN shifted the mechanical inactivation curve of potassium contracture toward lower concentrations of K+, as in the case of the activation curve, and markedly increased the rate of the inactivation induced by conditioning with 15 mM K+. In addition, SCN delayed the recovery of potassium contracture from the mechanical inactivation induced by preceding K-SCN-contracture. On the basis of these results, the sites and the mechanism of action of SCN on potassium contracture are discussed.

Animals↗
PubMed1978

Caffeine contracture in transverse tubules-disrupted fiber and effect of anomalous anions on the contracture in frog twitch fiber.

Caffeine contracture in transverse tubules-disrupted (T-disrupted) muscle preparation and the effect of anomalous anions (SCN and NO3) on the contracture in single twitch fibers or thin bundles consisting of 2 or 3 fibers of frog were investigated. The magnitude and the rate of rise of caffeine contracture tension were decreased by T-disruption and the decrease was more marked at lower concentrations of caffeine. No seasonal difference between summer and winter frogs on the effect of T-disruption on caffeine contracture was observed. On the other hand, the magnitude and the rate of rise of caffeine contracture tension in the intact preparation was increased by anomalous anions, whereas the rate of spontaneous relaxation of the contracture was decreased. The effect of SCN on caffeine contracture appeared 5 min after the pre-exposure of muscle preparation of SCN-Ringer solution, with the maximal effect appearing after 10 min. The threshold curve of caffeine contracture was shifted toward the lower caffeine concentrations by anomalous anions and the extent of the shift in the curve was more pronounced with SCN than with NO2. In contrast, the potentiating effect of these anions on the caffeine contracture completely disappeared in T-disrupted muscle preparation. On the basis of these results, the caffeine pathway to the sarcoplasmic reticulum, and the sites and mechanism of the action of anomalous anions on caffeine contracture are discussed.

Animals↗
PubMed1977

Time- and Na-dependent effects of Ca depletion on potassium contracture in frog twitch muscle fiber.

The effect of the extracellular Ca depletion on potassium contracture was investigated in single fibers isolated from frog semitendinosus muscle mainly in relation to its time and Na dependency. The shortening of plateau duration and the increase in the rate of relaxation of the potassium contracture appeared within 3--5 sec and 15 sec, respectively, after the fiber was immersed in Ca-free Na Ringer solution containing 1 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) (EGTA-Na Ringer solution) or Ca-free choline Ringer solution containing 1 mM (EGTA (EGTA-choline Ringer solution). These effects were independent of the presence or absence of extracellular Na. In EGTA-Na Ringer solution, the potassium contracture tension was inhibited only by about 20% after 20--90 min and was abolished after 120 min. The inhibition of the peak tension was accelerated by the depletion of extracellular Na; in EGTA-choline Ringer solution, the tension was gradually inhibited by about 20% during the first 7 min and abolished after 10--12 min. When the peak tension of potassium contracture was abolished in EGTA-choline Ringer solution, the depolarization by Ca depletion was about 10 mV and the caffeine contracture was sufficiently produced. The results suggest that the inhibition of the potassium contracture tension in EGTA-choline Ringer solution is due to the dissociation of excitation-contraction coupling. On the basis of these results, an aspect of the inactivation of the potassium contracture was proposed.

Animals↗
PubMed1976

Role of superficially membrane-bound calcium on excitation-contraction coupling in frog skeletal muscle.

Single fibers isolated from frog semitendinosus muscle continued to twitch for 5-8 min in calcium-free Ringer solution containing 1 mM ethylene glycol bis (beta-aminoethyl ether)-N, N'-tetraacetic acid (EGTA). Even after twitching was completely abolished, the tension of potassium contracture was not depressed, although the time course was markedly shortened. The resting potential recorded from single fibers 10 min after immersion in EGTA-Ringer solution decreased slightly. These fibers failed to generate action potential, however, in a whole sartorius muscle the self-exchangeable calcium was not significantly reduced by 1mM EGTA, while it was reduced by about 27% during the potassium contracture induced in the EGTA solution. From these results, it is suggested that the calcium bound on the surface sites of the transverse tubular membrane and the sarcolemma can serve as a trigger for the release of calcium from the sarcoplasmic reticulum and can produce a resting potential and maintain relatively long duration excitability under the condition of extracellular calcium deficiency.

Action Potentials↗
PubMed1976

Radioactive calcium influx at rest and during potassium contracture in the T-disrupted, and the urea- or manganese-treated frog sartorius muscles.

45Ca influx in the intact, the T-disrupted, and the urea-treated or Mn++-treated frog sartorius muscles was measured at rest and during potassium contracture. In the intact muscle, Ca influx increased with the increasing of potassium concentration in the bathing solution, and the time course of the Ca influx showed considerable correspondence with that of the potassium contracture. This increased Ca influx was divided into two components: early rapid Ca influx and late slow Ca influx. The amount of early rapid Ca influx at higher concentrations of potassium occupied about 60% of the total Ca influx. The early rapid Ca influx markedly decreased in the T-disrupted and in the urea-treated or Mn++-treated muscles. On the other hand, the late slow Ca influx and the resting Ca influx in these muscles changed only slightly. These results suggest that the early rapid Ca influx occurs mainly through the membrane of the T-system, particularly at the triadic junctional area of muscle fiber, while the late slow Ca influx and the resting Ca influx occur mainly through the surface membrane.

Animals↗