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Biomedical subjects

I Kanazawa

Publications and source records attributed to I Kanazawa.

At least 91 records · Page 5Linked to original sources
PubMed1999

Caspase activation during apoptotic cell death induced by expanded polyglutamine in N2a cells.

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder. To investigate the mechanism of neurodegeneration induced by mutant huntingtin, we developed a stable neuro2a cell line expressing truncated N-terminal huntingtin (tNhtt) with EGFP using the ecdysone-inducible system. The formation of aggregates and the cell death induced by expression of tNhtt with expanded polyglutamine was repeat length- and dose-dependent. Caspases were activated, and the death substrates of caspases, lamin B and ICAD (an inhibitor of caspase-activated DNase), were cleaved in this cell death process. The cleavage of lamin B was inhibited by caspase inhibitors. These findings suggest that the cell death induced by tNhtt with expanded polyglutamine is mediated by caspases.

Animals↗
PubMed1999

Caveolin-3 upregulation activates beta-secretase-mediated cleavage of the amyloid precursor protein in Alzheimer's disease.

Here, we investigate the involvement of caveolins in the pathophysiology of Alzheimer's disease (AD). We show dramatic upregulation of caveolin-3 immunoreactivity in astroglial cells surrounding senile plaques in brain tissue sections from authentic AD patients and an established transgenic mouse model of AD. In addition, we find that caveolin-3 physically interacts and biochemically colocalizes with amyloid precursor protein (APP) both in vivo and in vitro. Interestingly, recombinant overexpression of caveolin-3 in cultured cells stimulated beta-secretase-mediated processing of APP. Immunoreactivities of APP and presenilins were concomitantly increased in caveolin-3-positive astrocytes. Because the presenilins also form a physical complex with caveolin-3, caveolin-3 may provide a common platform for APP and the presenilins to associate in astrocytes. In AD, augmented expression of caveolin-3 and presenilins in reactive astrocytes may alter APP processing, leading to the overproduction of its toxic amyloid metabolites.

Aged↗
PubMed1999

Molecular pathology of dentatorubral-pallidoluysian atrophy.

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant disorder characterized clinically by myoclonus, epilepsy, cerebellar ataxia, choreoathetosis and dementia. Cardinal pathological features of DRPLA are a combined degeneration of both the dentatorubral and the pallidoluysian systems. Although the early sporadic cases were reported by Western neuropathologists, a strong heritability and an age of onset-dependent variability of the clinical features were carefully deduced by Japanese clinicians. The disease is fairly common in Japan, but extremely rare in Caucasians. Since the gene was identified in 1994, DRPLA is known as one of the CAG repeat expansion diseases, in which the responsible gene is located on chromosome 12p and its product is called atrophin 1. DRPLA shows prominent 'anticipation', which is genetically clearly explained by a marked instability of the expanded CAG repeat length during spermatogenesis. Moreover, the instability of the CAG repeat length also seems to occur in the somatic cells, resulting in 'somatic mosaicism'. Possible mechanism(s) underlying the neuronal cell death in DRPLA are discussed in terms of molecular pathological points of view.

Atrophy↗
PubMed1999

Fulminant form of acute disseminated encephalomyelitis: successful treatment with hypothermia.

We described herein a case of the fulminant form of acute disseminated encephalomyelitis (ADEM) that developed after mycoplasma pneumonia. A 28-year-old man who presented with fever, headache, and writing difficulty was admitted to our hospital in August 1997. He developed hernia on the 3rd hospital day. Surgical decompression and intravenous prednisolone failed to halt his progressive deterioration. We introduced systemic hypothermia and he has shown marked recovery; despite having Broca's type aphasia, he could comprehend spoken language and communicate with others by gesture. Head MRI demonstrated diffuse high signals over the white matter on fluid attenuated inversion recovery (FLAIR) images, which suggested extensive demyelination. The clinical course, imaging studies and presence of polymorphonuclear dominant leucocytosis in the blood and CSF in the patient are somewhat similar to findings in acute hemorrhagic leukoencephalitis, however, the result of a brain biopsy was inconclusive. The fulminant form of ADEM is usually fatal. Treatments such as corticosteroids, intravenous immunoglobulin, and surgical decompression have been performed to improve the prognosis. Our case results indicate that hypothermia, which suppresses both brain edema and immune response, may be included in the repertoire of treatment for the fulminant form of ADEM.

Adult↗
PubMed1999

Rapid aggregate formation of the huntingtin N-terminal fragment carrying an expanded polyglutamine tract.

Huntington's disease (HD) is caused by an expansion of the CAG repeat in the HD gene. The repeat is translated to the polyglutamine tract as huntingtin, the product of HD gene. Several studies showed that the expansion of polyglutamine tract leads to formation of cytoplasminc and/or intranuclear aggregates in vivo or in vitro. To understand the molecular mechanism of the aggregate formation, we studied the transient expression of HD exon 1-GFP fusion proteins in COS-7 cells. The fusion protein carrying 77 glutamine repeats aggregated in a time-dependent manner, while the fusion protein carrying 25 glutamine tract remained to be distributed diffusely in the cytoplasm even 72 hours after transfection. Initially, fluorescent signals were diffusely distributed in the COS-7 cells that were transfected with the construct containing the 77 CAG repeats. Approximately 40 hours later after the transfection, large aggregates grew very rapidly in those cells and the diffuse cytoplasmic fluorescence faded out. This process was completed within 40 minutes from the appearance of small aggregates in the perinuclear regions. The addition of cycloheximide reduced the frequencies of aggregate formation. A possibility was discussed that the aggregate formation was via nucleation. The focal concentration of mutated proteins in neurons may trigger the aggregate formation.

Animals↗
PubMed1999

Rabbit experimental sensory ataxic neuropathy: anti-GD1b antibody-mediated trkC downregulation of dorsal root ganglia neurons.

We previously reported experimental sensory neuropathy in rabbit induced by the immunization of ganglioside GD1b. The major pathological change in diseased rabbits was degeneration of primary sensory neurons with central axons extending to the dorsal column of the spinal cord. The loss of primary sensory neurons that mediate proprioceptive sensation prompted us to investigate the expression of trkC in dorsal root ganglia (DRG) because this type of neuron is thought depend mainly on neurotrophin-3-mediated trkC signaling. Northern blotting analysis revealed markedly reduced expression of trkC in DRG of diseased rabbits in acute phase. This result together with the absence of lymphocytic infiltration in DRG of diseased rabbits at any stage suggests the anti-GD1b antibody-mediated downregulation of trkC expression could be one of the pathogenesis of this experimental sensory ataxic neuropathy.

Animals↗
PubMed1999

Positive symptoms in multiple sclerosis: their treatment with sodium channel blockers, lidocaine and mexiletine.

Patients with multiple sclerosis (MS) often show positive symptoms of painful tonic seizure and dysesthesia as well as negative symptoms of paralysis and hypesthesia. Positive manifestation is paroxysmal and/or persistent. These are considered to be mediated by ectopic impulses generated at the site of demyelination, whereas negative symptoms are caused by conduction block. Conduction block at a demyelinated segment should reduce positive symptoms, but worsen negative ones. As reported previously, lidocaine, an Na channel blocker unmasks silent negative symptoms presumably by further reducing the action current in demyelinated portions and blocking conduction. Furthermore, because it blocks Na channels in a voltage- and frequency dependent manner, fibers that mediate positive symptoms are preferentially blocked. We administered lidocaine to 30 MS patients with positive symptoms. Lidocaine (mean plasma level, 2.4 pg/ml) almost completely abolished the paroxysmal manifestation of painful tonic seizures, neuralgic attacks, paroxysmal itching, and Lhermitte's sign. It also markedly alleviated persistent symptoms, but less so than paroxysmal symptoms. Similar effects were obtained with orally-administered mexiletine (300-400 mg/day), a derivative of lidocaine, but to a lesser extent. Na channel blockers have a dual effect on symptoms in MS, depending on whether symptoms are positive or negative. The mechanism that produces positive symptoms and the effects of the drugs on these symptoms are discussed.

Adult↗
PubMed1999

Dorsal root ganglia neuron-specific promoter activity of the rabbit beta-galactoside alpha1,2-fucosyltransferase gene.

The rabbit H-blood type alpha1,2-fucosyltransferase (RFT-I), gene and its biosynthetic products, H antigens (Fucalpha1,2Galbeta), are abundantly expressed in a subset of dorsal root ganglia (DRG) neurons. To investigate the regulatory mechanisms for the RFT-I gene expression, we determined the genomic structure and promoter activity of this gene. PCR amplification of the 5' cDNA end analysis revealed two transcriptional start sites, 498 and 82 nucleotides upstream of the translational initiation codon, the latter site yielding a major 3.1-kb transcript specifically expressed in DRG, as revealed by Northern blotting. Promoter analysis of the 5'-flanking region of the RFT-I gene using a luciferase gene reporter system demonstrated strong promoter activity in PC12 cells, which express the rat H-type alpha1,2-fucosyltransferase gene, and Neuro2a mouse neuroblastoma cells. Deletion analysis revealed the 704-base pair minimal promoter region flanking the translational initiation codon, for which two distinct promoter activities were detected and differentially used in PC12 and Neuro2a cells. The minimal promoter region contained a GC-rich domain (GC content 80%), in which a Sp1 binding sequence and a GSG-like nerve growth factor-responsive element were found, but lacked TATA- and CAAT-boxes. Promoter analysis with a primary culture of DRG neurons demonstrated that the minimal promoter region of the RFT-I gene was sufficient for the expression of a reporter gene in DRG neurons. We conclude that the TATA-less GC-rich minimal promoter region of the RFT-I gene controls DRG small neuron-specific expression of the RFT-I gene.

Animals↗
PubMed1999

Anti-GQ1b IgG antibody is associated with ataxia as well as ophthalmoplegia.

Close association between the increase in anti-GQ1b immunoglobulin G (IgG) antibody and ophthalmoplegia in Miller Fisher syndrome (MFS) and Guillain-Barré syndrome (GBS) has been reported. We investigated whether anti-GQ1b IgG antibody also is associated with ataxia, another of the MFS triad. Of 149 patients who had anti-GQ1b IgG antibody without profound weakness, 144 showed ophthalmoplegia (120 showed both ophthalmoplegia and ataxia; 24, ophthalmoplegia without ataxia). In contrast, five showed ataxia without ophthalmoplegia. Some large neurons of the dorsal root ganglia were immunostained with anti-GQ1b monoclonal antibody. Anti-GQ1b IgG antibody may thus be associated with ataxia as well as ophthalmoplegia. Ataxia may be due to its binding to a subset of primary sensory neurons.

Antibodies↗
PubMed1999

Pelizaeus-Merzbacher disease: three novel mutations and implication for locus heterogeneity.

We report a mutational and polymorphic analysis of the proteolipid protein gene in members of 27 Japanese families with Pelizaeus-Merzbacher disease. We found causative mutations in 6 members of 27 families (22.2%); 5 of the 6 mutations, including two novel mutations, Leu45Arg and 231 + 2T --> G, resulted in the typically severe clinical symptoms. Paradoxically, the Cys219Tyr mutation, presumed to disrupt the tertiary structure of proteolipid protein by removing the disulfide bond between Cys200 and Cys219, was associated with a mild clinical presentation wherein the patient could walk with assistance and speak. It was inferred that the structural change prevented the toxicity associated with a gain of function mutation. Moreover, in one family 3 patients exhibited a intragenic polymorphism that did not segregate with the disease, suggesting a locus heterogeneity for Pelizaeus-Merzbacher disease.

Adult↗
PubMed1999

Ataxia with isolated vitamin E deficiency: a Japanese family carrying a novel mutation in the alpha-tocopherol transfer protein gene.

We report a Japanese family with ataxia with isolated vitamin E deficiency (AVED). Gene analysis revealed a single nucleotide substitution of T to C at nucleotide position 2 in the alpha-tocopherol transfer protein gene (TTPA). This substitution abolishes the start codon. The proband and his affected sister were homozygous for this mutation, and their serum alpha-tocopherol concentrations were remarkably reduced. Relations between the mutations and clinical features are discussed.

Adult↗
PubMed1999

Reduction of GluR2 RNA editing, a molecular change that increases calcium influx through AMPA receptors, selective in the spinal ventral gray of patients with amyotrophic lateral sclerosis.

Enhancement of calcium influx through the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptor is a plausible mechanism underlying selective neuronal death in amyotrophic lateral sclerosis (ALS). The calcium conductance of the AMPA receptor is regulated by the GluR2 subunit that is edited at the glutamine/arginine residue site in the subunit assembly. We investigated the molecular changes of GluR2 mRNA in the spinal cord of ALS cases, those of cases with other neurological diseases, and those of normal cases using reverse transcription-polymerase chain reaction combined with restriction enzyme cleavage. We found that the editing efficiency was significantly lower only in the ventral gray of ALS cases (virtually 0% in 2 cases) than in any spinal region of the disease controls and normal controls. In addition, expression of GluR2 mRNA is lower in the ventral gray of the ALS cases and disease controls than in that of the normal controls. The above molecular changes of GluR2 mRNA in the ventral gray of ALS cases may enhance calcium influx through AMPA receptors, thereby promoting neuronal vulnerability. The decrement of GluR2 mRNA editing efficiency is unique to the ventral gray of ALS cases and may be closely linked to the etiology of ALS.

Adult↗
PubMed1999

Bleeding risk in unruptured and residual cerebral aneurysms--angiographic annual growth rate in nineteen patients.

Whether and when unruptured aneurysms or aneurysmal rests following incomplete surgery result in subsequent bleeding are major concerns for neurosurgeons. By calculating the annual growth rate of aneurysms in long-term follow-up angiography (partly supplemented with MR-imaging and/or MR-angiography), we attempted to determine the surgical indications for these aneurysms. Long-term follow-up angiography ranging from one to 20 years was carried out on five patients whose ruptured aneurysms had been incompletely occluded, six patients with multiple aneurysms, of which the ruptured ones had been completely obliterated at operation and the small unruptured aneurysms, missed or misdiagnosed, and eight patients with unruptured aneurysms which were asymptomatic or symptomatic. The correlation of annual aneurysm growth rate to subsequent bleeding was investigated. Four out of six fast-growing aneurysms with high annual growth rates (more than 8% increase per year) resulted in subsequent bleeding whereas none of the fourteen slow-growing aneurysms with low annual growth rates (less than 8% increase per year) led to bleeding (Fisher's exact test; p < 0.01). Hypertension, patient age and aneurysmal location showed no significant correlation to the annual growth rate (Fisher's exact test; p > 0.05). This study suggests that aneurysmal rests after incomplete surgery and missed or misdiagnosed multiple or incidental aneurysms which are fast growing have a high possibility of subsequent bleeding and should be operated on as soon as possible.

Aneurysm, Ruptured↗
PubMed1999

Somatosensory evoked high-frequency oscillation in Parkinson's disease and myoclonus epilepsy.

AIM: A high-frequency oscillation in the range of 600-900 Hz has been shown to be a component of the somatosensory evoked potential (SEP) in humans. In the present communication, we studied these oscillation potentials in two neurological disorders. SUBJECTS AND METHODS: Subjects were 20 healthy volunteers, 17 patients with Parkinson's disease (PD) and 3 with myoclonus epilepsy (ME). Median nerve SEPs were recorded using filters set at 0.5 and 3000 Hz. Several peaks of oscillation were obtained by digitally filtering raw SEPs from 500 to 1000 Hz, and their amplitudes and onset latencies were measured. RESULTS: In normal subjects, several oscillation potentials were observed at the latency of 0 to 8 ms after the onset of N20. In PD patients, the oscillation potentials at normal latencies were significantly larger than those of normal subjects. Moreover, in 7 of 17 PD patients, they were extremely enlarged (>mean +/- 3 SD of normal values). In contrast, in patients with ME, abnormally enlarged oscillation potentials were seen at longer latencies (7-14 ms) in spite of normal-sized early oscillation potentials. Magnetoencephalographic analyses showed that any oscillation potentials originated from the primary sensory cortex. CONCLUSIONS: There are at least two mechanisms for producing the oscillation potentials of SEP. Those around N20 have some relation with the basal ganglia function and are enlarged in PD patients, the others around P25-N33 are enhanced in ME patients.

Adult↗
PubMed1999

Input-output organization of the foot motor area in humans.

OBJECTIVE: A well-organized input-output relation similar to that of the monkey motor cortex has been demonstrated in the human hand motor area (Terao Y, Ugawa Y, Uesaka Y, Hanajima R, Gemba-Shimizu K, Ohki Y, Kanazawa I. Input-output organization in the hand area of the human motor cortex, Electroenceph clin Neurophysiol 1995;97:375-381). The aim of this study is to investigate the input-output organization of the human foot motor area. METHODS: We studied the effect of tactile stimuli given to the toe tip on the sizes of following responses; motor evoked potentials (MEPs) elicited by transcranial magnetic or electrical stimulation (TMS or TES) over the motor cortex and magnetic stimulation at the foramen magnum level. RESULTS: Air stimuli applied to the toe tip facilitated magnetically evoked MEPs of mainly the muscle attached to that toe, although a less prominent facilitation was also noted in muscles attached to the adjacent toes. Neither responses evoked by TES, nor those by stimulation at the foramen magnum level, were affected by air stimuli. These results suggest that the observed facilitatory effect occurs at the cortical level. CONCLUSION: A fairly well-organized input-output relation is present also in the foot motor area in humans, although the facilitatory effect is not so topographically restricted as is noted for the hand motor area.

Adult↗
PubMed1999

Motor-evoked potentials: unusual findings.

OBJECTIVE: The aims of this study were to present rare findings of motor evoked potentials (MEPs) in 3 patients with spastic paraparesis and to show that careful interpretation is indispensable in experiments done with very high intensity stimulation. METHODS: The conduction along several segments of the descending tracts was studied by our previously published method in 3 patients with spastic paraparesis. RESULTS: The threshold for activation of descending tracts was markedly increased in all the patients. In one patient, both transcranial electrical and magnetic cortical stimulation elicited responses with 4 different latencies. They were compatible with the latencies of I1-, D(D1)-, D2- or D3-waves. Very high intensity stimulation elicited D2 waves (activation around the cerebral peduncle) or D3 waves (activation at the foramen magnum level). In the other two patients, unexpectedly, the latency of responses to foramen magnum level stimulation was longer than the cortical latency. Foramen magnum and spinal cord stimulation could not excite the corticospinal tract but activated other slowly conducting descending tracts (about 20 m/s), whereas cortical stimulation activated the corticospinal tract. CONCLUSIONS: The site of activation following cortical stimulation was variable when very high intensity stimulation is used. The descending tracts that contribute to the onset of electromyographic (EMG) responses may not be the same after cortical and spinal stimulation in patients with severely affected corticospinal tract, especially when using very high intensities of stimulation. Such factors complicate the interpretation of EMG responses obtained in patients with severely affected corticospinal tracts.

Adult↗
PubMed1999

Structural organization and expression of the mouse gene for Pur-1, a highly conserved homolog of the human MAZ gene.

We have characterized the genomic structure and expression of the mouse gene for Pur-1. The cloned Pur-1 gene spans a 5-kb region encompassing the promoter, five exons, four introns and the 3'-untranslated region. All exon-intron junction sequences conform to the GT/AG rule. The promoter region has typical features of a housekeeping gene: a high G + C content (77.5%); a high frequency of CpG dinucleotides, in particular within the region 0.5 kb upstream of the site of initiation of translation; and the absence of canonical TATA and CAAT boxes. S1 nuclease protection assay demonstrated the presence of multiple sites for initiation of transcription around a site 108 nucleotides upstream of the ATG codon. Comparison of Pur-1 with the human gene for MAZ (Myc-associated zinc finger protein) revealed a striking homology of both their nucleotide and deduced protein sequences, an identical genomic organization and high similarity in promoter architecture and mRNA expression pattern. Sequence analysis of the 5'-flanking region of Pur-1 revealed numerous potential binding sites for transcription factors Sp1, AP-2 and Pur-1/MAZ itself. An element required for basal Pur-1 expression was mapped from nucleotide -258 to +43. This region also mediated stimulation of basal transcription by ectopically expressed MAZ protein. We conclude that the Pur-1 gene is the murine homolog of human MAZ and, like it, belongs to the family of housekeeping genes.

Animals↗