Biomedical subjects

M Kato

Publications and source records attributed to M Kato.

At least 127 records · Page 7Linked to original sources

PubMed2001

Chlorinated alkaloids in Menispermum dauricum DC: root culture.

Feeding experiments using (36)Cl showed that Menispermum dauricum root culture produces four alkaloids containing chlorine. They included the novel alkaloids dauricumine and dauricumidine as well as the known alkaloids acutumine and acutumidine. The structures of novel alkaloids were established by spectroscopic, crystallographic, and chemical methods. These four alkaloids were labeled with (36)Cl, isolated, and fed independently to root cultures. Mutual conversion between acutumine and acutumidine, and between dauricumine and dauricumidine by N-methylation and N-demethylation, was demonstrated. Moreover, dauricumine was converted to acutumine and acutumidine. Epimerization of acutumidine to dauricumidine or vice versa was not observed. These results suggest that dauricumine is the first chlorinated alkaloid formed in cultured M. dauricum roots. Skewed distribution of radioactivity derived from labeled dauricumine is proof that epimerization at C-1 proceeds at a lower rate than N-demethylation.

Alkaloids↗

PubMed2001

Effects of aluminum on the neurotoxicity of primary cultured neurons and on the aggregation of beta-amyloid protein.

Recent epidemiological, neuropathological, and biochemical studies have suggested a possible link between the neurotoxicity of aluminum and the pathogenesis of Alzheimer's disease. However, this relationship remains controversial. To investigate detailed characteristics of neurotoxicity of aluminum, we used primary cultured neurons of rat cerebral cortex as an in vitro model system for the observation of morphological changes induced by chronic exposure to aluminum. Although the exposure to aluminum chloride (10-100 microM) for 1 week did not cause marked neuronal death, degeneration of neuritic processes and accumulation of tau protein and beta-amyloid protein appeared after chronic exposure to 50 microM aluminum chloride for more than 3 weeks. We also investigated the polymerization of beta-amyloid protein in vitro using the immunoblotting technique. We thus found that aluminum induced conformational changes in beta-amyloid protein and enhanced its aggregation in vitro. The aggregated beta-amyloid protein was dissolved by the addition of desferrioxamine, a chelator of aluminum. The aggregated beta-amyloid protein pre-incubated with aluminum formed fibrillar deposits on the surface of cultured neurons.

Aluminum Chloride↗

PubMed2001

Requirement for etoposide in the treatment of Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis.

PURPOSE: We sought to identify the clinical variables most critical to successful treatment of Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (HLH). PATIENTS AND METHODS: Among the factors tested were age at diagnosis (< 2 years or > or = 2 years), time from diagnosis to initiation of treatment with or without etoposide-containing regimens, timing of cyclosporin A (CSA) administration during induction therapy, and the presence or absence of etoposide. RESULTS: By Kaplan-Meier analysis, the overall survival rate for the entire cohort of 47 patients, most of whom had moderately severe to severe disease, was 78.3% +/- 6.7% (SE) at 4 years. The probability of long-term survival was significantly higher when etoposide treatment was begun less than 4 weeks from diagnosis (90.2% +/- 6.9% v 56.5% +/- 12.6% for patients receiving this agent later or not at all; P <.01, log-rank test). Multivariate analysis with the Cox proportional hazards model demonstrated the independent prognostic significance of a short interval from EBV-HLH diagnosis to etoposide administration (relative risk of death for patients lacking this feature, 14.1; 95% confidence interval, 1.16 to 166.7; P =.04). None of the competing variables analyzed had significant predictive strength in the Cox model. However, concomitant use of CSA with etoposide in a subset of patients appears to have prevented serious complications from neutropenia during the first year of treatment. CONCLUSION: We conclude that early administration of etoposide, preferably with CSA, is the treatment of choice for patients with EBV-HLH.

Adolescent↗

PubMed2001

Novel actin-related proteins in vertebrates: similarities of structure and expression pattern to Arp6 localized on Drosophila heterochromatin.

Actin-related proteins (Arps), which share a basal structure with actin isoforms but possess different functions, have been identified in a wide variety of organisms. The Arps are classified into subfamilies based on the relatedness of their sequences and functions. Recently, several Arp subfamilies have been shown to be localized in the nucleus and included in protein complexes involved in the organization of chromatin structure, for example, in chromatin remodeling and histone acetyltransferase complexes. A member of the Arp6 subfamily in Drosophila, dArp6, is localized on centric heterochromatin together with heterochromatin protein 1 (HP1). We have identified the first examples of the Arp6 subfamily in vertebrates, novel human and chicken Arps, hArp6 and gArp6, respectively. They are closely related to each other (98% similar) and show apparent similarity to dArp6 (70%). In addition, the hArp6 gene possesses evolutionarily conserved exon/intron structures compared with genes for members of the Arp6 subfamily in invertebrates. Like Drosophila dArp6, gArp6 is expressed abundantly in the early developmental stages, when heterochromatin condensation and nuclear maturation occur. The finding of a conserved Arp6 subfamily in vertebrates will contribute to the understanding of molecular mechanisms of heterochromatin organization.

Actins↗

PubMed2001

beta-Phenylethylamine modulates acetylcholine release in the rat striatum: involvement of a dopamine D(2) receptor mechanism.

We examined the effects of beta-phenylethylamine on striatal acetylcholine release in freely moving rats using in vivo microdialysis. beta-Phenylethylamine at 12.5 mg/kg, i.p. did not affect acetylcholine release in the striatum, whereas 25 and 50 mg/kg, i.p. immediately induced an increase in acetylcholine release in the striatum at 15-45 min. This increase following intraperitoneal administration of beta-phenylethylamine (25 mg/kg) was not affected by locally applied SCH-23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine, 10 microM), a dopamine D(1) receptor antagonist, nor by raclopride (10 microM), a dopamine D(2) receptor antagonist. The increased release of acetylcholine induced by beta-phenylethylamine was suppressed by local infusion of tetrodotoxin (1 microM). In contrast, the extracellular acetylcholine level in the striatum was significantly decreased by local application of beta-phenylethylamine (10 and 100 microM) in the striatum via a microdialysis probe. The decrease was completely blocked by local co-application of raclopride (10 microM). The beta-phenylethylamine-induced decrease in striatal acetylcholine release was not affected by co-perfusion with SCH-23390 (10 microM). These results indicate that systemic administration of beta-phenylethylamine increases acetylcholine release, whereas locally applied beta-phenylethylamine decreases striatal acetylcholine release in freely moving rats. Furthermore, the dopaminergic system, through the dopamine D(2) receptor, is involved in the locally applied beta-phenylethylamine-induced decrease in acetylcholine in the striatum.

Acetylcholine↗

PubMed2001

A neuropathological study of the disturbance of the nigro-amygdaloid connections in brains from patients with dementia with Lewy bodies.

We neuropathologically and immunohistochemically investigated characteristics of the central amygdaloid nucleus lesion and its relationship with the substantia nigra lesion in dementia with Lewy bodies (DLB) brains. Nine DLB, four Parkinson's disease (PD) and four Alzheimer-type dementia (ATD) cases were examined. The degree of neuronal loss in the substantia nigra was (+)-(+++) in DLB cases, (+++) in PD cases and (+) in ATD cases. All DLB cases showed spongy change and ubiquitin-positive spheroids in the central nucleus. The degree of spongy change was (+)-(+++) in DLB cases, (+) in PD cases and (-)-(+) in ATD cases, which was correlated with the degree of neuronal loss in the substantia nigra in DLB cases. The number of ubiquitin-positive spheroids was parallel to the degree of spongy change. The central nucleus receives dense dopaminergic fibers from the substantia nigra. Many ubiquitin-positive spheroids were also positive to alpha-synuclein and tyrosine-hydroxylase, suggesting that they derive from the degeneration of terminal or distal axons of Lewy body-bearing dopaminergic neurons in the substantia nigra. The disturbance of the dopaminergic connections from the substantia nigra to the central nucleus may be responsible for psychotic symptoms in DLB patients.

Aged↗

PubMed2001

A complex of the bacteriophage T7 primase-helicase and DNA polymerase directs primer utilization.

The lagging strand of the replication fork is initially copied as short Okazaki fragments produced by the coupled activities of two template-dependent enzymes, a primase that synthesizes RNA primers and a DNA polymerase that elongates them. Gene 4 of bacteriophage T7 encodes a bifunctional primase-helicase that assembles into a ring-shaped hexamer with both DNA unwinding and primer synthesis activities. The primase is also required for the utilization of RNA primers by T7 DNA polymerase. It is not known how many subunits of the primase-helicase hexamer participate directly in the priming of DNA synthesis. In order to determine the minimal requirements for RNA primer utilization by T7 DNA polymerase, we created an altered gene 4 protein that does not form functional hexamers and consequently lacks detectable DNA unwinding activity. Remarkably, this monomeric primase readily primes DNA synthesis by T7 DNA polymerase on single-stranded templates. The monomeric gene 4 protein forms a specific and stable complex with T7 DNA polymerase and thereby delivers the RNA primer to the polymerase for the onset of DNA synthesis. These results show that a single subunit of the primase-helicase hexamer contains all of the residues required for primer synthesis and for utilization of primers by T7 DNA polymerase.

Amino Acid Sequence↗

PubMed2001

Serum levels of HCV RNA and core protein before and after incubation at 37 degrees C for 24 h.

The kinetics of HCV during interferon (IFN) therapy have recently been described and the estimated virion half-life is an average of 2.7 h, suggesting that HCV infection is highly dynamic. The aim of this study was to evaluate serum levels of HCV-RNA and HCV core protein (HCV-Ag) before and after incubation at 37 degrees C for 24 h. We also evaluated the viral kinetics during IFN treatment by determining their serum levels at 0, 24 and 48 h, and day 8 after the start of treatment. The decay slope was calculated as the logarithm of the ratio of HCV-RNA levels at 0 and 24 h of incubation: log(virus load) 24 h-log(virus load) 0 h and the estimated half-life was also calculated. The decay slope was -1.66+/-0.75 (-4.12 to -0.18) (mean+/-S.D. (range)) and the estimated virion half-life was 6.2+/-6.9 h (1.8-39.3). The HCV-RNA level was rapidly decreased to 6.8+/-13.1% of the initial load after incubation independently of the serotype. In contrast, the HCV-Ag level after incubation for 24 h was 98.7+/-12.2% of the initial level. The synthesized naked HCV-RNA (equivalent to 10(7) copy/ml) was not detected after 1-min incubation. These data suggested that HCV virions are very unstable and collapsed rapidly and that HCV-RNA, existing outside of virions, is immediately degraded in serum, whereas HCV-Ag remains stable. IFN treatment caused a rapid decrease in the levels of both HCV-RNA and HCV-Ag. The HCV-RNA decay slope was -1.95+/-0.96 (range: -3.48 to -0.50) and was similar to that seen in the incubation study. Our result suggested the significance of measuring HCV-Ag during clinical management independently of HCV-RNA, especially because of its high stability.

Journal Article↗

PubMed2001

Magnetic circular dichroism at transition metal L2,3 edges in D03-type (Fe(1-x)Mn(x))3Al alloys.

We have measured magnetic circular dichroism (MCD) spectra at the transition-metal L2,3 edges in D03-type (Fe(1-x)Mn(x))3Al in order to investigate their local magnetic moments. The analysis of the spectra shows that Fe has moments much larger than Mn, whose moment is ferromagnetically coupled with the Fe one. This does not lend support to the antiferromagnetic mechanism proposed for the reduction in magnetization as well as a large Mn moment predicted for x = 1/3. The evolution of satellites found in the Mn spectrum with x increased suggests that the change in the electronic state may result in the magnetization reduction.

Journal Article↗

PubMed2001

Magnetic circular dichroism at transition metal L2,3 edges in D03-type (Fe(1-x)Vx)3Al alloys.

Magnetic circular dichroism (MCD) spectra have been measured at the Fe and V L2,3 edges of DO3-type (Fe(1-x)Vx)3Al in order to investigate their local magnetic moments and electronic structures. Large MCD is observed at the Fe L2,3 edges, while the V L2,3 MCD shows relatively small intensity with complicated features. Signs of these MCD spectra indicate an antiferromagnetic coupling between the magnetic moments on Fe and V. According to the analysis based on the magneto-optical sum rules, the magnetic moment decreases with x, but remains fairly large for Fe2VAl, which might arise from its marginally magnetic nature.

Journal Article↗

PubMed2001

Detection of truncated midkine in Wilms' tumor by a monoclonal antibody against human recombinant truncated midkine.

Although the expression of a truncated midkine (tMK) mRNA has been detected in many cancer cells, the tMK protein itself has not yet been identified. The expression, purification and characterization of human recombinant tMK were described in the former report. A mouse hybridoma cell line producing an IgG2b monoclonal antibody (mab) against purified recombinant tMK was established. This anti-tMK mab did not cross react with synthetic full length (or c-half) human midkine. A putative native tMK was identified in G401 cells using this mab, and showed the same apparent Mw as the recombinant tMK in SDS-PAGE. This mab was also used in an immunohistochemical study to evaluate the expression of tMK in Wilms' tumor cell line, G401 cells, as well as in Wilms' tumor patient specimens. G401 cells and all Wilms' tumor patient specimens immunoreacted with this anti-tMK mab. We conclude that Wilms' tumor cells express tMK and that this mab is useful for the detection of tMK in the Wilms' tumor.

Antibodies, Monoclonal↗

PubMed2001

Corticobasal degeneration presenting with nonfluent primary progressive aphasia: a clinicopathological study.

A 62-year-old woman initially presented with slowly progressive nonfluent aphasia with minimal intellectual involvement. Echolalia and personality change were prominent whereas parkinsonian features and signs suggesting parietal lobe dysfunctions were not present. The patient's language deficit was consistent with transcortical motor aphasia. She did not manifest extrapyramidal signs. The patient was diagnosed as having Pick's disease or frontal lobe dementia. She died at age 65, 2 years and 9 months following disease onset. Neuropathological findings including cytoskeletal abnormalities, however, were clearly distinct from those of classical Pick's disease and were consistent with those reported in corticobasal degeneration (CBD). The distribution of her cortical lesions was accentuated in the frontal language-related area. The clinical manifestations in CBD are diverse, and primary progressive nonfluent aphasia should be considered as an initial symptom of CBD. Neuropathological examination of such patients should include cytoskeletal abnormality studies.

Aphasia, Primary Progressive↗

PubMed2001

Immunohistochemical localization of plasminogen activator inhibitor-1 in rat and human brain tissues.

We investigated immunohistochemically the localization of type 1 plasminogen activator inhibitor (PAI-1) in rat and human brain tissues. In rat, neurons and astrocytes were stained positively for PAI-1 after colchicine treatment. In post-mortem human brain, neurons were stained for PAI-1 but the number of positive neurons varied greatly from case to case. PAI-1 positive astrocytes occurred in the white matter lesions of some patients. In Alzheimer's disease, weak PAI-1 labeling was seen in association with senile plaques and ghost tangles. The present results support a notion that PAI-1 and its target proteases such as plasminogen activators and thrombin are involved in a variety of physiological and pathological processes in brain.

Aged↗

PubMed2001

FTIR study on heat-induced and pressure-assisted cold-induced changes in structure of bovine alpha-lactalbumin: stabilizing role of calcium ion.

The second derivative FTIR study of heat-induced and pressure-assisted cold-induced changes in the secondary structure of bovine alpha-lactalbumin was carried out for native holoprotein and calcium ion depleted apoprotein. The secondary structure and compactness of alpha-lactalbumin were examined in a temperature range from 20 to 80 degrees C during the heat treatment and 20 to -15 degrees C during the pressure-assisted cold treatment. This was the first FTIR study on the pressure-assisted cold denaturation of a protein. Because protein solutions had close to neutral pD and low ionic strength, the apoprotein remained in the molten globule state and the holoform maintained its native tertiary structure. In order to distinguish between unfolding-related and partially deuterated exchange-related spectral changes, we examined both the fully deuterated holoform and the partially deuterated holoform. The quantitative analysis of the spectral changes in the amide I/I' vibrational band revealed that the 3(10) helices were more prone to thermal unfolding than the alpha helices. We observed that the protein's compactness and secondary structure were both considerably stabilized against an increase and decrease in temperature by the presence of a calcium ion. Under the conditions of this study, only the apoprotein was susceptible to the cold denaturation. In contrast to this, an unexpected linear increase of the alpha-helical content was observed upon the cooling of the holoprotein under high pressure. The results were discussed in reference to the existing crystallographic data for crystals of human alpha-lactalbumin grown at two different temperatures.

Animals↗

PubMed2001

Mutation of the doublecortin gene in male patients with double cortex syndrome: somatic mosaicism detected by hair root analysis.

The molecular basis of double cortex syndrome was investigated in 2 male patients. Magnetic resonance imaging of the patients' heads showed diffuse subcortical band heterotopia, as is seen in female patients. We found a heterozygous mutation for Asp50Lys or Arg39Stop in both patients. Microsatellite polymorphism analysis revealed that both patients had inherited a single X chromosome from their mothers. Restriction enzyme analysis using DNA extracted from the hair roots of each patient showed four different patterns in the combination of cells carrying wild and mutant alleles, which strongly suggest somatic mosaicism. We conclude that somatic mosaic mutations in the doublecortin gene in male patients can cause subcortical band heterotopia, and that molecular analysis using hair roots is a useful method for detecting somatic mosaicism.

Cerebral Cortex↗

PubMed2001

Determination of catecholamines and their 3-O-methyl metabolites in mouse plasma.

The determination of catecholamines and their 3-O-methyl metabolites in a single mouse plasma is necessary to understand the role of the sympathetic nervous activity, while the inactivation of catecholamines by catechol-O-methyltransferase indicates the activity of blood pressure regulation in animals. Here we report the basal catecholamines and their 3-O-methyl metabolite concentrations obtained from 15 microL of mouse plasma utilizing semi-microcolumn high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence detection system. The concentrations were 6.63 +/- 1.37 pmol/mL plasma, 0.49 +/- 0.10 pmol/mL plasma, 5.25 +/- 2.30 pmol/mL plasma, 3.23 +/- 0.84 pmol/mL plasma, 0.44 +/- 0.11 pmol/mL plasma, and 3.39 +/- 1.67 pmol/mL plasma for norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine and 3-methoxytyramine, respectively (n = 5-7). Further, when blood pressure was reduced by minoxidil, plasma catecholamines were found to be significantly increased by the baroreflex-mediated response in mouse.

Animals↗

PubMed2001

A fluorimetric, column-switching HPLC and its application to an elimination study of LLU-alpha enantiomers in rat plasma.

A method for the enantiomeric determination of 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (LLU-alpha, gamma-CEHC) in rat plasma was developed using high-performance liquid chromatography (HPLC) with a fluorimetric derivatization with 4-N, N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) followed by O-acetylation with acetyl chloride. The proposed HPLC system used two non-chiral columns (phenyl and octadecylsilica) and a chiral column (a modified cellulose type), which were connected via two column-switching valves. A derivatized sample prepared from rat plasma was first separated on the phenyl column, and the fraction including LLU-alpha derivative was introduced to the octadecylsilica column to quantify the concentration of the mixture of S- and R-LLU-alpha. Finally, the LLU-alpha derivative was directly injected into the chiral column to obtain the ratio of the enantiomers. The proposed HPLC system was applied to the enantiomeric determination of LLU-alpha in plasma after intravenous administration of racemic LLU-alpha. S-LLU-alpha was eliminated faster than R-LLU-alpha, and its concentration in plasma decreased to one-third at 2 min after dosing.

Animals↗

PubMed2001

A study of chiral recognition for NBD-derivatives on a Pirkle-type chiral stationary phase.

A chiral stationary phase (CSP 1) derived from an (S)-N-3,5-dinitrobenzoyl-1-naphthylglycine showed excellent enantiomeric separation for amino acid derivatives with a fluorogenic reagent, 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), in high-performance liquid chromatography (HPLC). We compared elution profiles (separation factor and elution order) of NBD-amino acids and their analogs on HPLC, to determine the diastereomeric complex between the chiral moiety of CSP 1 and NBD-amino acid, which is responsible for the chiral recognition. (1)H-NMR studies of a mixture of model compound of CSP 1 and NBD-Ala suggest that the diastereomeric complex is composed of two hydrogen bonding sites at the amino proton and oxygen atom, and a pi-pi interaction by the benzofurazan structure (2,1,3-benzoxadiazole) of NBD-amino acid. Furthermore CSP 1 was able to separate esters, amides and alpha-methyl amino acids derivatized with NBD-F.

4-Chloro-7-nitrobenzofurazan↗