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M Kano

Publications and source records attributed to M Kano.

At least 19 recordsLinked to original sources
PubMed1992

Calcium channels in embryonic chick skeletal muscle cells after cultivation with calcium channel blocker.

The effects of chronic treatment with calcium channel blockers were studied on the expression of voltage-dependent calcium channels (VDCCs) in chick skeletal muscle cells developing in culture. Myotubes were treated after 2 days in culture with either 20 microM D600 or 10 microM nifedipine, and measurements were made of the maximum rate of rise (M.R.R.) of the two components of action potential, operated by T- and L-type VDCCs, respectively. Treatment with either blocker reduced the M.R.R. of the action potential component operated by the L-type VDCC throughout the culture period examined. The M.R.R. of the T-type VDCC component, on the other hand, was unaffected by either treatment. The reduction in the M.R.R. of the L-type component in blocker-treated cells is thought to be due to the down-regulation of the expression of L-type VDCC. Thus, it appears that the expression of L-type VDCC in the chick skeletal muscle cells can be regulated by a function of L-type VDCC, which mediate the entry of Ca2+ into the cells. The physiological significance of the L-type VDCC, which expressed prominently early in the development of skeletal muscle cells, for the differentiation of excitability is discussed.

Action Potentials↗
PubMed1992

Augmentation of transient low-threshold Ca2+ current induced by GTP-binding protein signal transduction system in GH3 pituitary cells.

We characterized the effects of thyrotropin-releasing hormone (TRH; 500 nM) and guanosine 5'-0-3-thiotriphosphate (GTP gamma S; 50 microM) on two types of Ca2+ currents in pituitary-hormone-secretory GH3 cells and were surprised to find marked increases in transient, low-threshold Ca2+ currents (T currents) induced by extracellularly applied TRH or intracellularly applied GTP gamma S. The effect of TRH was blocked by intracellularly applied guanosine 5'-0-2-thiodiphosphate (GDP beta S; 100 microM). The increase in the T current was found to be accompanied by a decrease in long-lasting, high-threshold Ca2+ current (L-current), in response to both TRH or GTP gamma S. These indicate that the enhancement of Ca2+ influx by TRH (500 nM) is largely conferred by T currents in GH3 cells. A reduced concentration of TRH (5 nM) still markedly increased the T current, but failed to decrease the L current. These data suggest that the augmentation of the T currents as well as depression of the L currents by TRH (500 nM), through the activation of a GTP-binding protein, may constitute an important regulatory mechanism of sustained pituitary hormone secretion in GH3 cells.

Animals↗
PubMed1992

Chronic treatment with D600 enhances development of sodium channels in cultured chick skeletal muscle cells.

We have studied the long-term effects of D600, a blocker of L-type voltage-dependent Ca channels (VDCC), on the development of voltage-dependent Na channels (VDNC) that are sensitive to tetrodotoxin (TTX), by electrophysiological measurements of the maximum rate of rise of the TTX-sensitive Na spike in cultured chick skeletal muscle cells. Chronic treatment with D600 (2-20 microM) caused a dose-dependent increase in the density of VDNC. The density of VDNC was increased by 150-250% when D600 was added to the cultures at 20 microM from the second day of culture onward. Co-treatment with an inhibitor of the transcription of RNA from DNA, alpha-amanitin, or with cycloheximide, an inhibitor of protein synthesis, prevented the up-regulation by D600. Nifedipine, a different type of blocker of L-type VDCC, was also effective in increasing the density of VDNC, and BAY K 8644, an agonist of L-type VDCC, had the opposite effect. It is suggested that the effect of D600 was mediated via a mechanism specific for L-type VDCC that involves regulation of cytosolic levels of Ca2+ and protein synthesis de novo.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1992

Synaptic excitation produces a long-lasting rebound potentiation of inhibitory synaptic signals in cerebellar Purkinje cells.

Persistent changes in synaptic efficacy are thought to underlie the formation of learning and memory in the brain. High-frequency activation of an afferent excitatory fibre system can induce long-term potentiation, and conjunctive activation of two distinct excitatory synaptic inputs to the cerebellar Purkinje cells can lead to long-term depression of the synaptic activity of one of the inputs. Here we report a new form of neural plasticity in which activation of an excitatory synaptic input can induce a potentiation of inhibitory synaptic signals to the same cell. In cerebellar Purkinje cells stimulation of the excitatory climbing fibre synapses is followed by a long-lasting (up to 75 min) potentiation of gamma-aminobutyric acid A (GABAA) receptor-mediated inhibitory postsynaptic currents (i.p.s.cs), a phenomenon that we term rebound potentiation. Using whole-cell patch-clamp recordings in combination with fluorometric video imaging of intracellular calcium ion concentration, we find that a climbing fibre-induced transient increase in postsynaptic calcium concentration triggers the induction of rebound potentiation. Because the response of Purkinje cells to bath-applied exogenous GABA is also potentiated after climbing fibre-stimulation with a time course similar to that of the rebound potentiation of i.p.s.cs, we conclude that the potentiation is caused by a calcium-dependent upregulation of postsynaptic GABAA receptor function. We propose that rebound potentiation is a mechanism by which in vivo block of climbing fibre activity induces an increase in excitability in Purkinje cells. Moreover, rebound potentiation of i.p.s.cs is a cellular mechanism which, in addition to the long-term depression of parallel fibre synaptic activity, may have an important role for motor learning in the cerebellum.

Animals↗
PubMed1992

Identification of TaqI polymorphism in the mitochondrial acetoacetyl-CoA thiolase gene and familial analysis of 3-ketothiolase deficiency.

We analyzed the mitochondrial acetoacetyl-CoA thiolase gene (T2) by Southern blotting. Fifteen unrelated healthy individuals and members of five families with 3-ketothiolase deficiency (3KTD) were analyzed. We found a TaqI polymorphism, the heterozygosity of which was calculated to be 0.5 among healthy Japanese individuals. This restriction fragment length polymorphism (RFLP) proved to be useful for detecting 3KTD patients and its obligatory carriers, at the DNA level and in two out of five 3KTD families. This polymorphism was found to be generated by the presence/absence of a TaqI site in intron 9 of the T2 gene. With in vitro amplification of the genomic region around the TaqI site, this RFLP can be detected within 2 days.

Acetyl-CoA C-Acetyltransferase↗
PubMed1992

Potentiation of GABA-mediated currents by cAMP-dependent protein kinase.

Recent reports described a down-regulation of gamma-aminobutyric acid (GABA)-receptor function in several types of central neurones by cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA). Surprisingly, we found that in cerebellar Purkinje cells (PCs) the membrane permeable-compound 8-bromo-cAMP (500 microM) induced a long-lasting potentiation of both, whole-cell current responses to bath-applied GABA and amplitudes of miniature inhibitory synaptic currents (mIPSCs). When dialyzing the PCs with the specific protein kinase inhibitor peptide (PKIP, 400 micrograms ml-1), the same manipulation failed to induce a potentiation. These results strongly suggest that, in contrast to its action in other types of neurones, activation of PKA up-regulates the GABAA receptor function in cerebellar PCs.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1992

Further analysis of mutant thiolase protein in fibroblasts from a Japanese boy with 3-ketothiolase deficiency.

We examined the mutant protein of mitochondrial acetoacetyl-CoA thiolase (mutant T2) in fibroblasts from a Japanese boy with 3-ketothiolase deficiency. The molecular size of the mutant T2 protein, determined by pulse labeling and SDS/PAGE, was intermediate between the mature subunit and the precursor of T2. To characterize the mutant T2 protein, pulse-labeling and rhodamine 6G inhibition of mitochondrial transport in fibroblasts, cell-free translation experiments, and family studies by thiolase assay, immunoblotting, and pulse-labeling were carried out. The mutant T2 was detectable as early as a 10-min pulse. The probable precursor of the mutant T2 was not detectable in either the rhodamine 6G inhibition or cell-free translation experiments. In the parents, the K+ ion dependency of acetoacetyl-CoA thiolase activity was low and the T2 bands in immunoblots were faint. It would thus appear that the parents are heterozygotes of this disease. In pulse-labeling, only a band for the mutant T2 was detected in the patient and a single band for the normal mature subunit of T2 in the father; both bands were detected in the mother. These findings suggested that the mutant T2 in the patient was inherited from the mother, and that the expression of another mutant allele of the father may be either abolished or scanty.

Acetyl-CoA C-Acetyltransferase↗
PubMed1992

Mesenchymal hamartoma of the liver: report of an adult case and review of the literature.

A case of mesenchymal hamartoma of the liver incidentally found to be a hyperechoic mass by abdominal ultrasonography in a 62-year-old male is described. Computed tomography and magnetic resonance imaging of the liver confirmed the presence of a well-demarcated inhomogeneous mass in the left medial segment. Hepatic arteriography revealed the mass to be generally hypovascular. Histopathologic diagnosis of the resected specimen was a solid form of benign mesenchymal hamartoma, a rather rare lesion for the patient's age. Fifteen adult cases of hepatic mesenchymal hamartoma in the literature including the present case are reviewed.

Diagnosis, Differential↗
PubMed1992

[Laparoscopic nephrectomy. Animal experiment and clinical application].

Laparoscopic nephrectomy was carried out on 6 sows in order to develop the procedures of clinical laparoscopic nephrectomy and the equipment necessary for this operation. Based on the animal experiments, it was shown that (1) retroperitoneal approach was difficult due to narrow space. (2) there must be at least 5 cm distance between each trocar and 4 or 5 trocar 1 cm in diameter were basically required. (3) The procedure consisted of incision and dissection of the peritoneum around the kidney, cutting and ligation of the ureter, dissection along the medial side of the ureter to approach the renal pedicle and clipping and cutting of the renal vessels. (4) The equipment required for this surgery must be functionally equivalent to those used in the open surgery. (5) In addition, the specifically designed equipment, such as a morcellator and an instrument to ligate renal vessels are necessary. The first clinical case of laparoscopic nephrectomy was a 34 years old man with a right non-functioning hydronephrosis due to ureteropelvic junction stricture. The surgery was successfully performed with a 110 ml blood loss. It took 7 and half hours because of abundant peri-renal fatty tissue and large extra-renal pelvis. The convalescence was uneventful. Laparoscopic nephrectomy can be applied on selected cases and the development of equipment will make the surgery more popular.

Animals↗
PubMed1992

[The value and limitation of resting 201Tl reinjection after stress-redistribution imaging for the assessment of myocardial viability: comparison with wall motion improvement by revascularization].

Clinical value and limitation of resting reinjection of small dose of thallium (37 MBq) for the assessment of myocardial viability were evaluated. The results were compared with the degree of wall motion improvement by revascularization to infarcted myocardium supplied by chronic total vessels in 12 patients with old myocardial infarction. Thallium uptake was visually scored and judged as normal, reversible defect (Group 1), new fill in after reinjection (Group 2A), and no fill in even after reinjection (Group 2B). Among 53 segments with initial perfusion abnormality, 21 segments reverted to almost normal, while 32 segments remained abnormal on redistribution images. New fill in after reinjection was observed in 11 segments of 32 segments showing persisting defect on stress and delayed image (37%). Wall motion score index of Group 2A improved significantly higher than Group 2B (p less than 0.01) and almost equal to Group 1, suggesting the utility of reinjection for the assessment of tissue viability which may be underestimated by conventional imaging. But significant wall motion improvement (greater than or equal to 0.6 mean SD/chords) was observed in 6 segments (29%) of 21 segments showing neither redistribution nor fill in after reinjection. These data indicate that small dose of thallium reinjection may enhance detection of viable but jeopardized myocardium, although some underestimation of viability remained to be resolved.

Aged↗
PubMed1991

Structure and expression of the human mitochondrial acetoacetyl-CoA thiolase-encoding gene.

To examine 3-ketothiolase deficiency at the gene level, we analyzed the structure of the human mitochondrial acetoacetyl-CoA thiolase (MAT; EC 2.3.1.9)-encoding gene (MAT). From the genomic library of a normal subject in lambda EMBL3, we isolated seven overlapping clones covering the entire length of MAT and the structural organization was determined. The gene spans approx. 27 kb and contains twelve exons interrupted by eleven introns. The 5'-flanking region of the gene lacks a conventional TATA box, but is G + C-rich and contains two CAAT boxes. Included are a putative binding site for the transcription factor, Sp1, and sequences resembling the binding sites of several other transcription factors, all features characteristic of housekeeping genes. A CAT assay revealed that a 101-bp DNA fragment immediately upstream from the cap site has promoter activity, and suggested that a DNA fragment from bp -888 to -102 probably contains a negative regulatory element(s).

Acetyl-CoA C-Acetyltransferase↗
PubMed1991

Simple spike modulation of Purkinje cells in the cerebellar nodulus of the pigmented rabbit to optokinetic stimulation.

In immobilized pigmented rabbit anesthetized with N2O (70%) and halothane (2-4%), simple and complex spike responses of Purkinje cells in the cerebellar nodulus to large field optokinetic stimulation (OKS) was studied. About half of the cells showed significant simple spike modulation to OKS delivered to ipsilateral (25/57) or contralateral (18/31) eye. The preferred direction and the amplitude of modulation of simple spike responses did not necessarily correlate with those of complex spike responses, suggesting that the simple spike modulation is not secondary to complex spike modulation but due to modulation of mossy fiber activity to OKS.

Action Potentials↗
PubMed1991

Pharmacological properties of two types of calcium channel in embryonic chick skeletal muscle cells in culture.

We have studied the effects of organic and inorganic Ca channel blockers on the two-component action potentials (low- and high-threshold components) in cultured chick skeletal muscle cells, which are generated by the T- and L-type voltage-dependent Ca channels (VDCCs), respectively. Nifedipine and D600 effectively blocked the high-threshold component of the action potential, whereas omega-conotoxin and phenytoin had no effect on this component. By contrast, the low-threshold component was insensitive to all of these organic Ca channel blockers. Blocking effects of polyvalent cations were observed with the following rank order of relative potency (mean apparent dissociation constant in microM): La3+ (14.7) greater than Ni2+ (20.7) greater than Cd2+ (51.2) greater than Co2+ (912) for the low-threshold component, and Cd2+ (0.7) greater than La3+ (29.2) greater than Co2+ (431) greater than Ni2+ (1241) for the high-threshold component. Taken together, these findings suggest that the pharmacological properties of the T- and L-type VDCCs in cultured chick skeletal muscle cells may differ from those in other preparations.

Action Potentials↗
PubMed1991

Optokinetic response of simple spikes of Purkinje cells in the cerebellar flocculus and nodulus of the pigmented rabbit.

Under anesthesia with N2O (70%) and halothane (2-4%), Purkinje cell activities were extracellularly recorded in the flocculus and nodulus of immobilized pigmented rabbits. Large field (60 degrees x 60 degrees) optokinetic stimulation (OKS) was delivered to the central visual field of one eye with a constant velocity (0.1-4.0 degrees/s) at 0 degrees, 45 degrees, 90 degrees or 135 degrees to the horizontal plane of the eye. Most of the Purkinje cells in the flocculus and the nodulus showed significant simple spike modulations to OKS delivered to either eye. As a whole, the preferred directions of simple spike responses in the flocculus had the same orientation as those of complex spike responses. However, the preferred directions and amplitudes of modulation of simple spike responses did not necessarily correlate with those of complex spike responses in individual flocculus Purkinje cells. On the other hand, the preferred directions of simple and complex spike responses were not necessarily in the same orientation in the nodulus. The optimum velocity for simple spike responses was in the range 0.1-2.0 degrees/s for Purkinje cells in both the flocculus and the nodulus. The amplitude and time to peak of the simple spike responses of nodulus Purkinje cells were significantly smaller and longer, respectively, than those of flocculus Purkinje cells. In both the flocculus and the nodulus, Purkinje cells whose simple spikes preferred the horizontal orientation (H cells) and the vertical orientation (V cells) showed clustering. In particular, zonal organization was noted in the flocculus. H cells were localized in a dorso-ventral zone in the rostral one third of the flocculus, and V cells were in two distinct zones rostral and caudal to the H cell zone. The locations of H and V cells in the flocculus correspond to the H zone and V zones, respectively, determined on the basis of the preferred directions of complex spike responses to OKS. This indicates that the same subdivisions of the flocculus are supplied with optokinetic signals with the same orientation selectively through both mossy and climbing fibers, and suggest that such subdivisions of the flocculus are functional units which control horizontal and vertical components of optokinetic eye movements. The present results indicate that the flocculus and the nodulus are supplied with distinct optokinetic signals through mossy fibers and play different roles in controlling optokinetic eye movements.

Animals↗
PubMed1991

Optokinetic response of cells in the nucleus reticularis tegmenti pontis of the pigmented rabbit.

In immobilized pigmented rabbits anesthetized with N2O (70%) and halothane (2-4%), extracellular spikes were recorded from neurons in the nucleus reticularis tegmenti pontks (NRTP) and their responses to optokinetic stimulation (OKS) were examined. OKS was delivered using constant-velocity (0.1-4.0 degrees/s) movements of a random dot pattern (60 degrees x 60 degrees) at 0 degree, 45 degrees, 90 degrees or 135 degrees to the horizon. With OKS delivered to the contralateral eye (n = 43), the preferred directions of NRTP cells were forward (F, n = 10), backward (B, n = 7), downward (D, n = 5), and the remaining cells showed no response (N, n = 21). With OKS delivered to the ipsilateral eye (n = 43), the preferred directions were F (n = 8), B (n = 8), upward (U, n = 2), D (n = 1) and N (n = 24). The majority of cells which responded to OKS (17/22 for contralateral, and 16/19 for ipsilateral OKS) preferred the horizontal orientation. The optimum velocity ranged from 0.2 to 1 degree/s. The results suggest that the NRTP cells mainly transfer horizontal optikinetic signals to the flocculus and control horizontal optokinetic eye movements.

Animals↗