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T Takigawa

Publications and source records attributed to T Takigawa.

At least 19 recordsLinked to original sources
PubMed2001

GABA-evoked chloride currents do not differ between dendrites and somata of rat neocortical neurons.

1. We performed patch-clamp recordings on acutely isolated somata and dendritic segments of rat neocortical neurons, in order to compare the reversal potential (E(GABA)) and relative density of GABA(A) receptor-mediated Cl(-) currents in these two cellular compartments. 2. Currents were recorded with the Cl(-)-impermeable pore former gramicidin (25--75 microg ml(-1)) in HCO(3)(-)-free bath solution. Voltage ramps (-110 to -30 mV) from a holding potential (V(h)) of -60 mV in the absence and presence of 2 microM GABA were used to construct instantaneous current-voltage relationships. Currents were abolished by co-application of GABA with the GABA(A) receptor antagonist bicuculline (40 microM). 3. GABA conductance, normalized to membrane surface area, was not different in somata and dendrites. In addition, E(GABA) was not different in the two compartments. 4. Replacement of intracellular K(+) with Cs(+) resulted in a significantly more depolarized E(GABA) in both somata and dendrites. These results suggest that the resting intracellular Cl(-) concentration ([Cl(-)](i)) is similar in somata and dendrites and that an outward Cl(-) transporter system maintains low [Cl(-)](i).

Animals↗
PubMed2001

Mechanical properties of artificial tracheas composed of a mesh cylinder and a spiral stent.

Much work has been done on the materials used for mesh-type artificial tracheas, but a precise mechanical evaluation of these structures has not yet been performed. In the present study, we determined the mechanical properties of typical mesh-type artificial tracheas and compared them with those of native trachea. Four types of artificial trachea were made and used for the mechanical tests. The basic frame of all the specimens was composed of a mesh cylinder and a spiral stent. The specimen whose mesh was sealed with collagen sponge showed almost the same behavior in the force-strain curve under compression, suggesting that collagen sealing has little effect on mechanical properties. Agreement between measured and estimated mechanical properties was good, especially in the low strain region, suggesting that artificial tracheas can be designed in terms of mechanical properties by mainly considering the basic frame structure.

Animals↗
PubMed2000

Increases in K+ conductance and Ca2+ influx under high glucose with suppressed Na+/K+-pump activity in rat myelinated nerve fibers.

To test the combined effect of high glucose and decreased Na+/K+-pump activity, a condition which closely mimics the diabetic state, on nerve ionic currents, changes in action potential and membrane current induced by high glucose in the presence of ouabain were investigated using voltage clamp analysis in rat single myelinated nerve fibers. In the presence of 0.1 mM ouabain, 30 mM glucose caused a progressive increase in the delayed K+ current as well as persistent decreases in action potential and Na+ current, suggesting that Na+/K+ pump plays an important role in preventing the increase in the K+ current. The latter increase was suppressed by a blocker of Ca2+-activated K+ channels. Two types of voltage-dependent Ca2+ channel blockers (L and N-type) as well as a Na+/Ca2+-exchange blocker diminished the ouabain-induced increase in K+ conductance. These results suggest that high glucose with suppressed Na+/K+ pump activity might induce an increase of Ca2+ influx through either Ca2+ channels or reverse Na+/Ca2+-exchange, possibly leading to the elevation of Ca2+-activated voltage-dependent K+ channels. Both a decrease in inward Na+ current and an increase in K+ conductance may result in decreased nerve conduction. In addition, a possible increase of axoplasmic Ca2+ concentration may lead to axonal degeneration. These results provide a clue for understanding the pathophysiologic mechanism of diabetic neuropathy.

Action Potentials↗
PubMed2000

The sera from GM1 ganglioside antibody positive patients with Guillain-Barré syndrome or chronic inflammatory demyelinating polyneuropathy blocks Na+ currents in rat single myelinated nerve fibers.

OBJECTIVE: To determine the possible role of anti-GM1 ganglioside antisera from patients with Gullain-Barr*e syndrome (GBS) or chronic inflammatory demyelinating polyneuropathy (CIDP) in the development of nerve dysfunction. METHODS: The effect of the anti-GM1 antibody positive antisera obtained from 4 GBS patients and 1 CIDP patient on membrane potential and ionic currents in rat single myelinated nerve fibers was investigated using the voltage clamp technique and compared with that of the anti-GM1 negative antisera obtained from 3 healthy controls and 2 GBS patients. RESULTS: In the presence of active complement, anti-GM1 positive antisera from 5 patients including 4 GBS patients and 1 CIDP patient significantly suppressed Na+ current more than anti-GM1 negative antisera. CONCLUSION: This study supports the notion that anti-GM1 antibody is one of the causative factors of conduction abnormality in GBS patients.

Adult↗
PubMed1999

G protein-activated inwardly rectifying K+ (GIRK) currents in dendrites of rat neocortical pyramidal cells.

1. We performed patch-clamp recordings on acutely isolated dendritic segments and cell somata of rat neocortical pyramidal neurons to determine and compare the relative density of G protein-activated K+ (GIRK) currents in the two cellular compartments. 2. Hyperpolarizing voltage ramps and elevation of extracellular K+ concentration to 40 mM served to identify inwardly rectifying K+ currents. Near-saturating concentrations of adenosine (100 microM), baclofen (20 microM) and serotonin (20 microM) all produced robust GIRK currents in cell somata as well as in dendritic segments that were completely abolished by Ba2+ (200 microM). In addition to agonist-activated GIRK currents, both somata and dendrites displayed a constitutive Ba2+-sensitive inward rectification. 3. In order to compare the relative strengths of GIRK current responses in the two compartments, GIRK conductance was normalized to surface area. In contrast to intrinsic, G protein-independent inward rectification, which was comparable in size in the two compartments, all three agonists evoked significantly larger GIRK conductances in dendrites than in somata. 4. Our data suggest that several neurotransmitters might employ GIRK currents as a tool to directly modulate the electrical properties of dendrites. In concert with voltage-dependent K+ currents and the hyperpolarization-activated cation current (Ih) of the dendrite, GIRK currents should dampen dendritic excitability and thus influence various aspects of dendritic signal integration.

Animals↗
PubMed1999

Confocal calcium imaging reveals an ionotropic P2 nucleotide receptor in the paranodal membrane of rat Schwann cells.

1. The paranodal Schwann cell region is of major importance for the function of a myelinated axon. In the present study we searched for a possible ionotropic effect of extracellular ATP in this Schwann cell compartment. 2. Whole-cell patch-clamp recordings from cultured rat Schwann cells revealed that ATP and 2'-3'-O-(4-benzoylbenzoyl)-adenosine 5'-triphosphate (BzATP) induced a non-specific cation current. The effect of ATP was much enhanced in a Ca2+- and Mg2+-free solution. ADP, UTP and alpha,beta-methylene adenosine 5'-triphosphate (alpha,beta-meATP) had no effect. 3. Confocal Ca2+ imaging of myelinating Schwann cells in isolated rat spinal roots showed a BzATP-induced rise in the free intracellular Ca2+ concentration in the paranodal Schwann cell cytoplasm whereas alpha,beta-meATP and 2-(methylthio)-adenosine 5'-triphosphate were without effect. In contrast to the known metabotropic effect of UTP on these Schwann cell regions, the BzATP-induced Ca2+ signal was not transient, was unaffected by depletion of intracellular Ca2+ stores and dependent on the presence of extracellular Ca2+. 4. These results suggest that an ionotropic ATP receptor with electrophysiological and pharmacological characteristics of the P2X7 subtype of nucleotide receptors is functionally active in myelinating Schwann cells of peripheral nerves. Such a receptor might contribute to Schwann cell reactions in nerve injury or neuropathy.

Adenosine Triphosphate↗
PubMed1999

Variance analysis of current fluctuations of adenosine- and baclofen-activated GIRK channels in dissociated neocortical pyramidal cells.

Whole cell recordings were obtained from pyramidal cell somata acutely isolated from rat neocortex. In voltage-clamp mode, adenosine (0.3-1000 microM), and the GABA(B) receptor agonist, baclofen (1-300 microM), induced K+ current responses mediated by G protein-activated inwardly rectifying K+ (GIRK) channels. In our preparation, adenosine activated GIRK currents with an average EC(50) of 2 microM. Baclofen had an average EC50 of 26 microM. To estimate and compare unitary conductance and density of GIRK channels activated by either adenosine or baclofen, we performed variance analysis of current fluctuations associated with the application of the two agonists at increasing concentrations. Irrespective of the agonist tested, GIRK channels displayed an average single-channel conductance of 25 pS at our recording conditions ([K+]o: 60 mM). Assuming that GIRK channel conductance increases in proportion to the square root of [K+]o, this would translate into 5-6 pS at physiological ion gradients. GIRK channels activated by adenosine or baclofen were not only identical in terms of unitary conductance, they also displayed the same average density of 0.5 channels micron(-2) for both agonists. Our data strongly suggest that the two compounds recruit the same type of channel and thus most likely share a common transduction and effector system.

Adenosine↗
PubMed1999

[Effects of message and personal involvement on risk perception and acceptance].

The present study analyzed people's risk perception regarding driving a car with studded or non-studded winter tires. Subjects were 252 residents of Sapporo, where a recent municipal ordinance prohibited studded tires, allowing only non-studded ones. Questionnaire data were examined concerning (1) the relationship between risk perception and its acceptance, (2) the effect of an inserted message, which was either positive or negative about the use of non-studded tires, and (3) the role of personal involvement, assessed with Personal Involvement Inventory (Zaichkowsky, 1985), regarding winter driving. Results were as follows: (1) The use of non-studded tires was favorably judged because of social benefit, but subjects hesitated to choose them because of a higher perceived possibility of an accident. (2) The inserted message had significant effects on benefit evaluation and perceived accident possibility. The effects were weaker for drivers who had experienced driving a car with studded tires. And (3) personal involvement had a weak correlation with risk judgements of the present study.

Adult↗
PubMed1999

Swelling and flow properties of tubular poly(vinyl alcohol) gels.

Swelling and flow properties of tubular poly(vinyl alcohol) (PVA) hydrogels prepared with the cooling method were investigated using an inflation testing method. When the tubular hydrogel in liquid paraffin was inflated by using liquid paraffin as a pressure transmitting medium, namely in the case that the liquids inside and outside the gel are both liquid paraffin (P/P combination), the gel showed a slight volume change determined by Poisson's ratio of the gel. When the gel in water was inflated by liquid paraffin (P/W combination), the gel swelled to large extent compared with the case of P/P. The hydrogel in W/W combination, namely in the situation that the gel was immersed in water and also inflated by water, showed a very large volume change if the comparison was done at the same pressure. The origin of the volume change in P/P, P/W and W/W combinations is discussed. The volume change in P/P was governed by the Poisson ratio as a material constant (mu 0) of the PVA gels, and the gels swelled by the change in the application of pressure (or deformation) in P/W. The volume change in W/W was closely related to the flow of solvent in the gel.

Gels↗
PubMed1998

Skeletal overgrowth in transgenic mice that overexpress brain natriuretic peptide.

Longitudinal bone growth is determined by the process of endochondral ossification in the cartilaginous growth plate, which is located at both ends of vertebrae and long bones and involves many systemic hormones and local regulators. Natriuretic peptides organize a family of three structurally related peptides: atrial natriuretic peptide, brain natriuretic peptide (BNP), and C-type natriuretic peptide. Atrial natriuretic peptide and BNP are cardiac hormones that are produced predominantly by the atrium and ventricle, respectively. C-type natriuretic peptide occurs in a wide variety of tissues, where it acts as a local regulator. These peptides can influence body fluid homeostasis and blood pressure control through the activation of two guanylyl cyclase (GC)-coupled natriuretic peptide receptor subtypes-GC-A and GC-B. We report here marked skeletal overgrowth in transgenic mice that overexpress BNP. Transgenic mice with elevated plasma BNP concentrations exhibited deformed bony skeletons characterized by kyphosis, elongated limbs and paws, and crooked tails. Bone abnormalities resulted from a high turnover of endochondral ossification accompanied by overgrowth of the growth plate. Studies using an in vitro organ culture of embryonic mouse tibias revealed that BNP increases the height of cartilaginous primordium directly, thereby stimulating the total longitudinal bone growth. The present study demonstrates that natriuretic peptides can affect the process of endochondral ossification.

Aging↗
PubMed1998

A special blocker reveals the presence and function of the hyperpolarization-activated cation current IH in peripheral mammalian nerve fibres.

Electrotonic responses recorded extra- or intracellularly from peripheral nerve preparations show a "sag" to hyperpolarizing current pulses. The biophysical nature of this "inward rectification" is still under discussion since the phenomenon has not been noted at voltage-clamped single nerve fibres, and since Cs+, which reduces inward rectification, is not a specific ion channel blocker. In this study, we found that low micromolar concentrations of ZD 7288, a specific blocker of the hyperpolarization-activated cationic current (Ih) in the soma of central mammalian neurons, result in a complete block of inward rectification in the electrotonic responses of isolated rat spinal dorsal roots. In addition, ZD 7288 enhanced the activity-dependent slowing of conduction seen in compound C fibre action potentials of isolated rat vagus nerves and augmented the post-tetanic hyperpolarization following trains of action potentials in unmyelinated and myelinated axons. The data suggest that ZD 7288 is a potent blocker and a useful research tool for the study of hyperpolarization-activated inward rectification (Ih) of peripheral nerve preparations.

Animals↗
PubMed1998

Cortical myoclonus: sensorimotor hyperexcitability.

Cortical or cortical reflex myoclonus is characterized by abnormally enlarged cortical somatosensory evoked potentials (giant SEPs), which most likely reflect pathologically hyperexcitable sensorimotor cortex. To clarify the pathogenesis of myoclonus of cortical origin, we simultaneously recorded SEPs and whole head somatosensory evoked magnetic fields (SEFs) following electric stimulation of the median nerve at the wrist in six patients with cortical myoclonus. N20m and enlarged P30m were observed in all patients and were localized at the posterior bank of the central sulcus (Brodmann area 3b of the primary somatosensory cortex). In addition, P25m and N35m components of SEFs were recognized in five and four patients, respectively. P25m component, that is, the magnetic counterpart of P25 in EEG, was the earliest cortical component showing enhancement in patients. Multidipole analysis combined with magnetic resonance imaging (MRI) coregistration revealed that the generators of P25m were in the precentral gyrus in four patients and in the postcentral gyrus in one patient. The second SEFs around 200 msec after the single stimulus were recorded in three patients at area 3b (repetitive SEFs); two of whom showed negative as well as positive myoclonus. The importance of motor cortex for the generation of cortical reflex myoclonus was thus demonstrated. The pathologic features of SEFs suggest abnormal excitability of primary sensorimotor cortex.

Adult↗
PubMed1998

Inhibition of S-warfarin metabolism by nonsteroidal antiinflammatory drugs in human liver microsomes in vitro.

We studied the inhibition of S-warfarin metabolism by nonsteroidal antiinflammatory drugs (NSAIDs) in human liver microsomes in vitro. After screening for potential inhibitors among ten NSAIDs using human recombinant cytochrome P450, inhibition kinetic parameters were estimated using human liver microsomes. Phenylbutazone and bucolome were suggested to increase the unbound steady-state level of S-warfarin about four- and five-fold, respectively, as estimated from these metabolic parameters.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Afferent mechanism of cortical myoclonus studied by proprioception-related SEPs.

Proprioception-related somatosensory evoked potentials (SEPs) to passive flexion movement of the middle finger at proximal interphalangeal joint were recorded in 7 patients with myoclonus of cortical origin who demonstrated enlarged electrical SEPs (giant SEPs). In 3 out of the 7 patients, the proprioception-related SEPs were also enlarged. The remaining 4 patients showed giant electrical SEPs without enhancement of proprioception-related SEPs. Long loop electromyographic response was recorded during the resting condition in all of the 3 patients with enlarged proprioception-related SEPs. We have previously reported that proprioception-related SEPs are mainly generated by muscle afferent inputs, though electrical SEPs are thought to reflect mostly cutaneous inputs with some contribution from muscle afferents. Therefore, it is concluded that hyperexcitability of the sensorimotor cortex in cortical myoclonus is modality-specific. Cortical excitability is exaggerated to both cutaneous and deep receptor inputs in some patients, but only to cutaneous input in others.

Adult↗
PubMed1997

Characteristic expression of high molecular mass heat shock protein HSP105 during mouse embryo development.

Expression of 105 k-Da heat shock protein (HSP105) during mouse embryo development was investigated. Although HSP105 was detected scarcely in mouse embryos at gestational day (GD) 8, its level of HSP105 increased markedly in the embryos from GD 9 to 11, and then decreased gradually by GD 14. In contrast, 70 k-Da heat shock cognate protein (HSC70) was detected at constantly high levels in embryo from GD 8 to 17 (before birth). The transient increase in level of HSP105 was observed in most embryonic tissues. Since the levels of HSP105 mRNA was detected at constantly high levels in the embryos between GD 8 and 12, the increased expression of HSP105 at GD 9 to 11 seemed to be regulated at posttranscriptional level. Immunohistochemically, HSP105 as well as HSC70 were localized in the cytoplasm and the nuclei of cells in various mouse embryonic tissues. After treatment of tissue sections with proteinase K, HSP105 but not HSC70 was also found to be localized in condensed cells and condensed bodies which showed the typical characteristics of apoptotic cells and apoptotic bodies at the interdigital regions of limbs. These findings suggest that HSP105 plays important roles during mouse embryo development.

Animals↗
PubMed1997

A case of hemangiopericytoma of the buccal mucosa.

We report a 46-year-old woman who presented with a hemangiopericytoma in the buccal mucosa. At the 2-year postoperative examination, there was no evidence of recurrence or metastasis. The findings in the present case are compared with previous reports in the Japanese literature, with regard to patient age and sex, and lesion size, location, malignancy, local recurrence and metastasis.

Endothelium, Vascular↗
PubMed1997

[A case of cortical reflex myoclonus manifesting tremor].

A 58-year-old woman developed slowly progressive tremulous myoclonus provoked mainly by action and posture. She had neither seizure nor dementia. No one in her family had similar symptoms. The presence of giant somatosensory evoked potentials (SEP) with enhanced long loop reflex and premovement cortical spikes demonstrated by the jerk-locked averaging method suggest that the involuntary movement is cortical reflex myoclonus. Magnetoencephalogram revealed that the generator sources of giant SEPs were the post-central somatosensory cortex and probably also the pre-central motor cortex. Symptoms improved after treatment with zonisamide, clonazepam and valpolate. This kind of involuntary movement might be called cortical myoclonic tremor.

Anticonvulsants↗