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M Kano

Publications and source records attributed to M Kano.

At least 127 records · Page 7Linked to original sources
PubMed1995

Impaired synapse elimination during cerebellar development in PKC gamma mutant mice.

PKC gamma is highly expressed in Purkinje cells (PCs) but not in other types of neurons in the cerebellum. The expression of PKC gamma changes markedly during cerebellar development, being very low at birth and reaching a peak around the third postnatal week. This temporal pattern of PKC gamma expression coincides with the developmental transition from multiple to single climbing fiber innervation onto each PC. In adult mutant mice deficient in PKC gamma, we found that 41% of PCs are still innervated by multiple climbing fibers, while other aspects of the cerebellum including the morphology and excitatory synaptic transmission of PCs appear normal. Thus, elimination of multiple climbing fiber innervation appears to be specifically impaired in the mutant cerebellum. We suggest that the developmental role of PKC gamma may be to act as a downstream element in the signal cascade necessary for the elimination of surplus climbing fiber synapses.

Age Factors↗
PubMed1995

Impaired motor coordination correlates with persistent multiple climbing fiber innervation in PKC gamma mutant mice.

It is generally believed that a smooth execution of a compound movement, or motor coordination, requires learning of component movements as well as experience-based refinement of the motor program as a whole. PKC gamma mutant mice display impaired motor coordination but intact eyeblink conditioning, a form of component movement learning. Cerebellar long-term depression, a putative cellular mechanism for component motor learning, is also unimpaired. Thus, PKC gamma mutant mice are defective in refinement of the motor program. In the accompanying paper, we demonstrate that innervation of multiple climbing fibers onto Purkinje cells persists in adulthood in these mutant mice. We propose that this defective elimination of surplus climbing fibers underlies motor discoordination.

Animals↗
PubMed1995

Ryanodine receptor-mediated intracellular calcium release in rat cerebellar Purkinje neurones.

1. Ryanodine receptor-mediated Ca2+ release was investigated in Purkinje neurones of rat cerebellar slices by using whole-cell patch-clamp recordings combined with fluorometric digital imaging of cytoplasmic Ca2+ concentration ([Ca2+]i). 2. Caffeine caused a transient increase in [Ca2+]i in the somata and dendrites of Purkinje neurones. Caffeine-induced Ca2+ transients were not associated with a membrane inward current and persisted in Ca(2+)-free external solutions, indicating that they are caused by Ca2+ released from intracellular stores. The amplitudes of the caffeine-mediated elevations in [Ca2+]i were strongly dependent on the baseline level of [Ca2+]i. 3. Intracellular application of Ruthenium Red through the patch pipette blocked caffeine-induced Ca2+ transients in Purkinje neurones. Ryanodine when applied either intra- or extracellularly caused a use-dependent block of caffeine-induced Ca2+ release. 4. Depolarization-induced Ca2+ transients were strongly prolonged by caffeine. Several lines of evidence suggest that these prolongations reflect Ca(2+)-induced Ca2+ release. 5. Despite the presence of skeletal muscle type ryanodine receptors in Purkinje neurones, depolarizing pulses failed to induce any changes in [Ca2+]i when the influx of Ca2+ through voltage-gated channels was prevented by using Ca(2+)-free solution, or when applying blockers of voltage-gated Ca2+ channels. 6. Dendritic Ca2+ transients produced by stimulation of the excitatory climbing fibre synaptic input were also prolonged by caffeine, indicating that ryanodine receptor-mediated release of Ca2+ may be involved in synaptic signalling in cerebellar Purkinje neurones. 7. Ryanodine receptor-mediated release of Ca2+ in cerebellar Purkinje neurones can be explained by a model in which release of Ca2+ is strongly facilitated by the co-operative action of Ca2+, caffeine and/or ryanodine. Our results suggest that Ca2+ release in these central neurones becomes prominent only during episodes of intensive electrical activity associated with increased Ca2+ entry.

Animals↗
PubMed1995

Differential suppression of axoplasmic transport: effects of light irradiation to the growth cone of cultured dorsal root ganglion neurons.

1. Growth cones of cultured dorsal root ganglion neurons from mice were irradiated using a mercury lamp. 2. The flux of particles of fast retrograde axoplasmic transport decreased promptly after light irradiation without a change in velocity. 3. That of anterograde transport decreased as well, but with a significant latency. The decrease in anterograde flux was attributed to decreased velocity of particles. 4. Video-enhanced contrast microscopy of growth cones revealed transient swelling of growth cones and transient stagnation of particles in growth cones. 5. The longer the neurite, the larger the latency of the change of the anterograde transport; peripheral information was calculated to be conveyed to the cell body at a speed of 6 microns/min. 6. The mechanism of this information conveyance and the export of materials from the cell body are discussed.

Animals↗
PubMed1995

Plasticity of inhibitory synapses in the brain: a possible memory mechanism that has been overlooked.

Long-term modification of transmission efficacy at inhibitory synapses has recently been discovered in several regions of the vertebrate brain, i.e. Mauthner cells of the goldfish, cerebellar Purkinje cells, deep cerebellar nuclei and the visual cortex. Synaptic plasticity at inhibitory synapses has properties similar to that of excitatory synapses, such as dependency on intracellular Ca2+ levels, input specificity, saturation and associativity. Considering the ubiquitous distribution of inhibitory synapses and the receptors for inhibitory transmitters, GABA and glycine, plasticity of inhibitory synapses may exist widely throughout the brain. It may contribute to learning and development in concert with plasticity of excitatory synapses.

Animals↗
PubMed1995

Depolarization-induced calcium signals in the somata of cerebellar Purkinje neurons.

Cerebellar Purkinje neurons express voltage-gated Ca2+ channels that are located on their somata and dendrites. Previous reports, based on microelectrode recordings and fura-2 Ca2+ imaging, suggested that depolarization-mediated intracellular Ca2+ signaling is confined almost completely to the dendrites. We investigated the spatial distribution of depolarization-induced Ca2+ signals in Purkinje neurons by applying whole-cell patch-clamp recordings combined with fluorometric Ca2+ imaging to cerebellar slices. Under our recording conditions, depolarizing pulses produced the dendritic but also large somatic Ca2+ signals. By selective perfusion of the slice with a Ca(2+)-free EGTA-containing solution, we could isolate experimentally Ca2+ signals in somata and dendrites, respectively. Moreover, experiments performed on cerebellar slices from young rats (up to postnatal day 6), in which Purkinje neurons are almost completely devoid of dendrites, showed that Ca2+ currents produced by the activation of somatic Ca2+ channels are associated with Ca2+ transients similar to those seen in the somata of adult Purkinje neurons. Our results strongly indicate that the depolarization-induced somatic Ca2+ signals are caused by Ca2+ entry through voltage-gated channels located on the somatic membrane of Purkinje neurons.

Animals↗
PubMed1995

The traffic of particles in the axonic process of vertebrate cone-type photoreceptor cells.

Differential-interference-contrast microscopy with video enhancement displayed the movement of particles for the first time in the isolated axonic process of cone-type photoreceptor cells of Rana catesbiana. This movement was observed under visible light which visual pigments could absorb. The number of retrograde moving particles in an arbitrary area on the axonic process was twice that of those moving in the anterograde direction. The mean velocities were 1.03 +/- 0.55 microns/sec for anterograde particles and 0.41 +/- 0.30 microns/sec for retrograde particles, which are of the same order as those found in isolated neurons.

Animals↗
PubMed1995

[Long-term results of surgical treatment for renal pelvic and ureteral tumors].

Fifty eight cases of primary tumors in the renal pelvis and ureter were treated at Toranomon Hospital between 1983 and 1992. They consisted of 32 renal pelvic tumors, 21 ureteral tumors and 5 tumors at both sites. The age of the patients ranged from 30 to 84 years (mean 63.1). Surgery was performed in 56 cases. Radical nephroureterectomy with concomitant ipsilateral retroperitoneal lymph node dissection was performed in 38 cases. The other surgeries were radical nephroureterectomy without lymph node dissection in 9, nephrectomy in 4, resection of ureter and reanastomosis in 3, radical nephroureterectomy and cystectomy in 1 and partial nephrectomy in 1. Pathologically, 53 were transitional cell carcinoma (TCC), 2 were TCC plus squamous cell carcinoma and 1 was TCC plus adenocarcinoma. Over-all survival rates (Kaplan-Meier) of 56 surgical cases at 1, 3, 5 years were 92.2, 83.7 and 72.8%, respectively. Combination chemotherapy (M-VAC or CAP) was performed in 9 cases of metastatic disease and 1 case of bilateral disease. Of these 10 cases, one achieved complete remission, 2 no change and 7 had progressive disease. Adjuvant chemotherapy was performed in 21 cases after surgery. These 21 patients were of high risk in recurrence either Grade 3 or pT3. However, the 5-year survival rate was 77.3% in these patients. Thus we conclude that the adjuvant chemotherapy in high risk patients was effective in our cases.

Adult↗
PubMed1994

Deficient cerebellar long-term depression and impaired motor learning in mGluR1 mutant mice.

mGluR1 mutant mice are viable but show characteristic cerebellar symptoms such as ataxic gait and intention tremor. The anatomy of the cerebellum is not overtly disturbed. Excitatory synaptic transmission from parallel fibers (PFs) to Purkinje cells and that from climbing fibers (CFs) to Purkinje cells appear to be functional, and voltage-gated Ca2+ channels of Purkinje cells are normal. Both PF and CF synapses display normal short-term synaptic plasticity to paired stimuli. By marked contrast, long-term depression (LTD) is clearly deficient and conditioned eyeblink response is impaired. We conclude that mGluR1 is required for the induction of LTD and that the ataxic behavior and impaired eyeblink conditioning of the mGluR1 mutant mice are primarily due to deficient LTD.

Animals↗
PubMed1994

Mediation of renal cyst formation by hepatocyte growth factor.

Hepatocyte growth factor (HGF) is a potent mitogen for renal tubular cells, and HGF and its receptor (c-met proto-oncogene product, Met) can induce lumen formation in epithelial cells. We measured the concentration of HGF in cyst fluids from patients with renal cystic diseases. The concentration of HGF was high in proximal cyst fluid (mean 2.45 vs 0.42 ng/mL in distal cysts). Cyclic AMP concentration was higher in distal than in proximal cysts (663 vs 6.0 pmol/L). mRNA of HGF and Met were co-expressed in cyst walls from cases with polycystic kidney disease. These findings suggest that HGF is a growth factor that may mediate human renal cyst genesis.

Base Sequence↗
PubMed1994

Ca2+/calmodulin-dependent regulation of the density of Na+ channels in embryonic chick skeletal muscle cells during their development in culture.

Regulation of the density of voltage-dependent Na+ channels (VDNC) was studied in chick myotubes during their development in culture. The density of VDNC was assessed quantitatively in terms of the maximum rate of rise (M.R.R.) of Na+ spikes. Chronic treatment of myotubes, whose density of VDNC had reached a plateau level after 6 days in culture, with the calmodulin (CaM) inhibitor W-7 caused a further increase in the density. A derivative of W-7, known as W-5, which has a lower affinity for CaM than does W-7, was without effect. A selective inhibitor of Ca2+/CaM-dependent protein kinase II (CaM-KII), namely, KN-62, also caused an increase in the density of VDNC when its effect was examined in mature myotubes. A structural analogue of KN-62, namely, KN-04, which is a much less effective inhibitor of CaM-KII, was without effect. These results suggest that density of VDNC in developing myotubes is regulated by Ca2+/CaM and CaM-KII. However, the role of CaM-KII in this regulation is not straightforward since it appears to decrease the density of VDNC in mature myotubes, but to increase their density in immature myotubes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Bradykinin-responsive cells of dorsal root ganglia in culture: cell size, firing, cytosolic calcium, and substance P.

1. We analyze bradykinin-sensitive cells of the mouse dorsal root ganglion in culture from the viewpoints of cell size, electrical responses, and Ca2+ concentration change due to bradykinin and immunocytochemistry of substance P. 2. Sixteen percent of cells in the cell group 26-30 microns in diameter fired in response to 10 microM bradykinin. None of other cell groups showed a firing response to bradykinin. 3. We measured a cytosolic Ca2+ change due to bradykinin using a Ca(2+)-sensitive fluorescent dye, Fura 2. The rapid rise (peak time, 20 sec) in the Ca2+ concentration was ascribed to Ca2+ release from intracellular Ca2+ stores. The profound change in the Ca2+ concentration was observed again in the cell group 26-30 microns in diameter. Seventeen percent of cells in this group increased the Ca2+ concentration by approximately seven times that at resting level. 4. Among cells which increase Ca2+ concentration responding to bradykinin, 83% of them contain substance P (an immunocytochemical study). 5. We conclude that 16-17% of the cell group 26-30 microns in diameter of the dorsal root ganglia in culture are polymodal nociceptors and respond to bradykinin.

Animals↗
PubMed1994

Identification of asynergic but viable myocardium in patients with chronic coronary artery disease by gated blood pool scintigraphy during isosorbide dinitrate and low-dose dobutamine infusion: comparison with thallium-201 scintigraphy with reinjection.

To evaluate the ability of low-dose dobutamine and isosorbite dinitrate (ISDN) gated blood pool scintigraphy (GBPS) and thallium SPECT with reinjection to identify viability in asynergic myocardium, both procedures were performed in 38 consecutive patients with chronic coronary artery disease and left ventricular dysfunction. Twenty-two of the 38 patients with successful revascularization were analyzed. GBPS was performed at the baseline and during continuous infusion of low dose dobutamine (5 micrograms/kg/min) and ISDN (2 micrograms/kg/min). Cine mode GBPS wall motion was scored from normal (0) to dyskinesis (4) semiquantitatively. Forty-seven of 110 segments with severe asynergy at the baseline were analyzed. Viability determined by GBPS was defined as wall motion score improvement by more than 1 grade. Thallium viability was defined as the segment with redistribution or fill in with severe initial perfusion defect. GBPS was 76.7% sensitive and 70.6% specific for predicting post vascularization wall motion improvement (p < 0.005). Of 47 segments with severe asynergy, concordance of judgement was obtained in 40 segments (85.1%), and reversibility was correctly diagnosed in 34 of 40 patients (85.0%), but thallium with reinjection correctly identified tissue viability in 6 of 7 segments with discordance between 2 studies. These data suggest that most cases of reversible asynergy (hibernating myocardium) respond to ISDN and dobutamine, suggesting the possibility of predicting improvement by revascularization, although some underestimation of tissue viability remained to be resolved. Thallium with reinjection is superior to low-dose dobutamine + ISDN GBPS for the assessment of myocardial viability.

Adult↗
PubMed1994

Calcium-induced long-lasting potentiation of GABAergic currents in cerebellar Purkinje cells.

Activity-dependent long-term modification of transmission efficacy at synapses is thought to be a cellular basis of learning and memory [Kandel and Schwartz (1982) Science 229: 433-443]. Since the discovery of long-term potentiation (LTP) in the hippocampus [Bliss and Lomo (1973) J Physiol (Lond) 232: 331-356], synapses that undergo plastic change have been described in various parts of the brain [Kuba and Kumamoto (1990) Prog Neurobiol 34: 197-269; for review]. In the cerebellar cortex, long-term depression (LTD) of excitatory parallel fibers (PFs) was found, and this is thought to be a cellular basis of motor learning [Ito (1989) Annu Rev Neurosci 12: 85-102]. However, modifiable synapses discovered and studied to date are mostly glutamatergic excitatory synapses. In spite of the importance of inhibition in brain functions, plasticity at inhibitory synapses has not been demonstrated except some related to epilepsy [Stelzer et al. (1987) Nature 326: 698-701]. Recently, inhibitory synaptic currents (IPSCs) of cerebellar Purkinje cells are found to undergo a long-lasting (usually longer than 30 min) "rebound potentiation (RP)" following stimulation of excitatory climbing fibers (CFs) [Kano et al. (1992) Nature 356: 601-604]. Several lines of evidence indicate that RP is triggered by transient elevation of intracellular calcium concentration ([Ca2+]i). RP is mainly due to upregulation of postsynaptic GABAA receptor function, since PC responses to bath-applied exogenous GABA is also potentiated with a time course similar to RP.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗