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Masaki Ito

Publications and source records attributed to Masaki Ito.

At least 37 records · Page 2Linked to original sources
PubMed2003

Arabidopsis D-type cyclin CYCD4;1 is a novel cyclin partner of B2-type cyclin-dependent kinase.

B-type cyclin-dependent kinases (CDKs) are unique to plants and are assumed to be involved in the control of the G2-to-M phase progression and mitotic events. However, little is known about their cyclin partners. In Arabidopsis, we isolated cDNA encoding the D-type cyclin CYCD4;1 by a yeast (Saccharomyces cerevisiae) two-hybrid screening using CDKB2;1 as bait. In vitro pull-down assay showed that CYCD4;1 bound to CDKB2;1 and CDKA;1. Protein complexes of CYCD4;1-CDKA;1 and CYCD4;1-CDKB2;1 in insect cells exhibited histone H1-kinase activity. Promoter analysis using the luciferase reporter gene showed that CDKB2;1 was expressed from early G2 to M phase, whereas CYCD4;1 was expressed throughout the cell cycle. In situ hybridization of plant tissues revealed that both CDKB2;1 and CYCD4;1 transcripts accumulated in the shoot apical meristem, leaf primordia, vasculature of leaves, and tapetal cells in anthers. Our results suggest that CDKB2;1 and CYCD4;1 may form an active kinase complex during G2/M phase and control the development of particular tissues.

Arabidopsis↗
PubMed2003

[Difficulties in the treatment of tuberculosis in infants].

Nowadays, methods of the diagnosis in infants with suspected tuberculosis and of the treatment are definitely established in Japan, where a number of childhood tuberculosis has been falling down (the incidence is less than 2 per 100,000). Still, infants less than one year are considered to be at high risk against tuberculosis. Actually, the number of tuberculosis among them is three times larger than those of one or two years old children. One of major reasons of difficulties in the treatment is the rapid progress of the disease because of underdeveloped cell-mediated immunity among them. Alveolar macrophage and lymphocyte and their cooperation in immunological functions do not develop enough to kill or confine Mycobacterium tuberculosis. As a result, the infection may progress to disease quickly, and then may spread systemically before the starting treatment. Anatomical underdevelopment of cranial arteries and narrow cerebrospinal passages easily cause cerebral infarction and hydrocephalus following meningeal inflammation due to tuberculosis. These neurological disorders may result in poor prognosis despite of administration of effective anti-tuberculosis medicines. Delay in the diagnosis also makes the treatment difficult in some infants whose tuberculin skin test shows false negative and radiographic manifestation of chest is not clear. During the treatment, systemic and enteric viral infections occur frequently among infants with tuberculosis, and liver functional disorders caused by these infections sometimes disturbs the treatment for tuberculosis. Recurrence of tuberculosis is very rare among infants who complete the full treatment at the age of more than one year. Finally, it is important for the early start of treatment for tuberculosis to recognize both susceptibility to tuberculosis and difficulties in the diagnosis in some infants less than one year.

Humans↗
PubMed2003

[Usefulness of cranial and chest imaging in the diagnosis of tuberculous meningitis among infants and young children].

We retrospectively evaluated the clinical and laboratory data of children with tuberculous meningitis (TBM) treated at our hospital from 1990 to 1999 to determine the optimal method of diagnosing TBM. The evaluated diagnostic criteria for TBM were as follows: (1) fever and malaise as symptoms of acute/subacute inflammation, (2) positive cerebrospinal fluid and/or gastric aspirate cultures for Mycobacterium tuberculosis, (3) pleocytosis of cerebrospinal fluid, and (4) a good response to anti-tuberculous therapy. The data for eleven patients (6 boys, 5 girls) with TBM (mean age, 10.7 months) were reviewed. Three patients (27%) were previously vaccinated with BCG. A known contact with tuberculosis was established at the time of admission in four patients (36%). Symptoms related to tuberculosis appeared on the average 14.8 days before the diagnosis. Three patients (27%) were diagnosed as clinical stage I, three (27%) as stage II, and five (46%) as stage III; all patients had fever (100%). With regard to the cerebrospinal fluid examinations, pleocytosis with mononuclear predominance was noted in all patients but one (91%), and mycobacterial staining was positive in three patients (27%). Tuberculin skin test was positive in four out of 10 patients (40%). Mycobacterial staining of gastric aspirate was positive in four patients (36%). Chest radiological examinations showed a swelling of the mediastinal lymphonodes and/or parenchymal infiltration in all patients (100%). A cranial CT examination demonstrated a basal meningeal enhancement in all patients (100%), hydrocephalus in nine patients (82%), and infarction in eight patients (73%). These results suggest that chest and cranial CT examinations are useful adjunct methods for diagnosis of TBM in infants and young children suffering from meningitis with pleocytosis of the cerebrospinal fluid and mononuclear predominance, in addition to conventional methods such as the tuberculin skin test, plain chest radiography, and staining for mycobacteria in body fluids.

Brain↗
PubMed2003

[Predominant location of pulmonary parenchymal lesions of tuberculosis primary complex in infants aged less than one year].

It is useful to know the distribution of pulmonary lesions in the diagnosis of tuberculosis on radiological examination. The aim of this study was to investigate if there is predominant lung segment or lobe for tuberculous lesions in infants aged less than one year using contrast enhanced CT. We studied 57 infants (40 boys, 17 girls) who were diagnosed as tuberculosis by isolation of Mycobacterium tuberculosis or combination of family contact, radiographic findings suggesting tuberculosis, and positive reaction of 5 mm or more induration to PPD tuberculin. All the infants had lesions in mediastinal and/or hilar lymphonodes, and 54 out of 57 infants had parenchymal lesions as well. In the study of the segmental predominance of tuberculous lesions, each infant had a share of 100 points. If an infant had a single focus, all the points were distributed to the corresponding segment. If he or she had multiple foci, the 100 points were equally divided into affected lung segments. There was no significant difference between right (3385 points/10 segments) and left (2005 points/8 segments) lungs. The points in upper lobes (2224 points/5 segments) were significantly higher than the combined points of middle and lingual (896 points/4 segments) and lower (2270 points/9 segments) lobes (p < 0.05). The points in posterior lung segments (2839 points/7 segments) were significantly higher than the combined points of middle (436 points/3 segments) and anterior (2115 points/8 segments) lung segments (p < 0.05). These results suggest that upper lobes and posterior segments are predominant parenchymal regions of tuberculosis among infants less than one year, although tuberculous lesions may locate in any lung segment.

Age of Onset↗
PubMed2003

[Efficacy of tuberculosis contacts investigation and treatment, especially of preventive therapy in infants and young children].

BACKGROUND: Although large clinical trials reported in 1960s suggested that preventive therapy in subjects with tuberculosis (TB) infection reduces the risk of developing TB by 70-90%, the therapy in our TB clinic seems to be more effectiveness. OBJECTIVE: We retrospectively evaluated the efficacy of the present contacts investigation, especially of preventive therapy for further improvement of TB control for children. METHODS: We examined 273 asymptomatic infants and children younger than five years who had household contacts with active TB patients and visited our clinic for contact investigation. After the diagnosis at the first visit to our TB clinic, they were treated and/or observed for at least two years to assess whether contact investigations and following treatment are appropriate. Since infants less than a year are underdeveloped in cell-mediated immunity and their tuberculous lymphadenopathy can be overlooked on standard chest radiographs, chest CT scans were added. RESULTS: At their first visit, 60 (22%) out of 273 subjects were diagnosed as TB, and 37 (14%) were suspected as TB. We treated them by combinations of anti-TB medicines including isoniazid and rifampin for six to 12 months, and they did not relapse during the observation period. Twenty-six subjects (9%) were diagnosed uninfected. However, a three-year-old girl developed bilateral hilar lymphadenopathy two months later when the reexamination was done. A hundred and fifty subjects (55%) were diagnosed to have TB infection. They received preventive therapy with isoniazid (10 mg/kg/day) for six months. Among them, a four-month-old boy developed TB disease soon after starting to take isoniazid and was treated by the combination of anti-TB medicines. Other 149 subjects completed the therapy, and none of them developed disease during the observation period. There was no increase in serum GOT and/or GPT to > 100 IU/L within one month after starting to take isoniazid. CONCLUSION: The present contacts investigations and treatments in our TB clinic are useful ways to find out and control TB diseases and infections, and it might be suggested to start the six-months preventive therapy after active TB has been ruled out in all infants and children who had close contacts with active TB patients for preventing TB disease and latent TB infection in the future even their clinical and laboratory examinations do not suggest infection.

Child, Preschool↗
PubMed2003

[Infants and children who developed tuberculosis following contacts investigation].

OBJECT: Reevaluating the important points in tuberculosis contacts investigation. SUBJECT AND METHODS: We retrospectively examined the medical charts of 25 infants and children who developed tuberculosis following contacts investigation. RESULTS: In thirteen patients, diagnosis of infection was missed, and three of five infants less than one year old suffered from meningitis or military tuberculosis while they were waiting the next examination. Three patients were not indicated preventive treatment despite of induration of 5 mm or more in tuberculin skin test. Other twelve patients including five infants less than one year old were diagnosed to have tuberculosis infection and started preventive therapy, however, tuberculosis developed in 10 patients while taking the medicine, and in two patients probably because of defaulting from taking the medicine. CONCLUSION: These results suggest that the contacts investigation have to be done promptly and be flexible based on age of contacts, evaluation of tuberculin skin test results and radiographic findings in order to reduce the disease further.

Adolescent↗
PubMed2002

Inactivation of Apc perturbs mammary development, but only directly results in acanthoma in the context of Tcf-1 deficiency.

Apc (adenomatous polyposis coli) encodes a tumour suppressor gene that is mutated in the majority of colorectal cancers. Recent evidence has also implicated Apc mutations in the aetiology of breast tumours. Apc is a component of the canonical Wnt signal transduction pathway, of which one target is Tcf-1. In the mouse, mutations of both Apc and Tcf-1 have been implicated in mammary tumorigenesis. We have conditionally inactivated Apc in both the presence and absence of Tcf-1 to examine the function of these genes in both normal and neoplastic development. Mice harbouring mammary-specific mutations in Apc show markedly delayed development of the mammary ductal network. During lactation, the mice develop multiple metaplastic growths which, surprisingly, do not spontaneously progress to neoplasia up to a year following their induction. However, additional deficiency of Tcf-1 completely blocks normal mammary development and results in acanthoma.

Adenomatous Polyposis Coli Protein↗
PubMed2002

Control of plant cytokinesis by an NPK1-mediated mitogen-activated protein kinase cascade.

Cytokinesis is the last essential step in the distribution of genetic information to daughter cells and partition of the cytoplasm. In plant cells, various proteins have been found in the phragmoplast, which corresponds to the cytokinetic apparatus, and in the cell plate, which corresponds to a new cross wall, but our understanding of the functions of these proteins in cytokinesis remains incomplete. Reverse genetic analysis of NPK1 MAPKKK (nucleus- and phragmoplast-localized protein kinase 1 mitogen-activated protein kinase kinase kinase) and investigations of factors that might be functionally related to NPK1 have helped to clarify new aspects of the mechanisms of cytokinesis in plant cells. In this review, we summarize the evidence for the involvement of NPK1 in cytokinesis. We also describe the characteristics of a kinesin-like protein and the homologue of a mitogen-activated protein kinase that we identified recently, and we discuss possible relationships among these proteins in cytokinesis.

Cell Division↗
PubMed2002

Different accumulations of 3-ketoacyl-CoA thiolase precursor in peroxisomes of Chinese hamster ovary cells harboring a dysfunction in the PEX2 protein.

The peroxisomal localization of 3-ketoacyl-CoA thiolase (hereafter referred to as thiolase) was characterized in five Chinese hamster ovary (CHO) mutant cell lines each harboring a dysfunction in the PEX2 protein. PT54 (Pex2pN100) cells carry a nonsense mutation that results in the PEX2 protein truncated at amino acid position 100. SK24 (Pex2pC258Y) cells carry a missense mutation resulting in the amino acid substitution of a cysteine residue by a tyrosine residue at amino acid position 258 of the PEX2 protein. The WSK24 (Pex2pC258Y/+wild) cell line is a stable transformant of SK24 (Pex2pC258Y) cells transfected with wild-type rat PEX2 cDNA. The SPT54 (Pex2pN100/+Pex2pC258Y) and WPT54 (Pex2pN100/+wild) cell lines are stable transformants of PT54 (Pex2pN100) cells transfected with the mutant PEX2 cDNA from SK24 (Pex2pC258Y) cells and wild-type rat PEX2 cDNA, respectively. In these cell lines, except PT54 (Pex2pN100), thiolase appeared to be localized in peroxisomes, as it is in the wild-type cells. When the molecular size of the enzyme was examined on SDS-polyacrylamide gel electrophoresis, the peroxisome-localized enzyme exhibited a larger precursor form in these mutant cells. The characterizations with salt wash, sodium carbonate extraction and proteinase K digestion indicated that the precursor forms of the enzyme were accumulated at different states in peroxisomes of these mutant cells. The dispositions on the peroxisomal membrane were further sustained by differential permeabilization using digitonin, followed by immunocytochemical fluorescence. These results suggest that PEX2 protein functions differently on two processes of the maturation and the disposition in the import pathway of thiolase.

Acetyl-CoA C-Acyltransferase↗
PubMed2002

Fluorescent cytochemical detection of sialidase activity using 5-bromo-4-chloroindol-3-yl-alpha- D- N-acetylneuraminic acid as the substrate.

A novel fluorescent cytochemical method for sialidase activity was developed using 5-bromo-4-chloroindol-3-yl-alpha- D- N-acetylneuraminic acid (X-Neu5Ac) as the substrate. Intact nuclei were isolated from porcine liver and incubated at 37 degrees C for 3 h with 1 mM X-Neu5Ac at pH 4.8. The nuclei were stained with blue color that was derived from the oxidized compound of the reaction product X (5-bromo-4-chloro-3-hydroxyindole). A specific sialidase inhibitor, 2,3-dehydro-2-deoxy- N-acetylneuraminic acid, suppressed the staining in a dose-dependent manner. Despite the specificity of the cytochemical reaction, the staining was too weak to analyze the staining distribution and pattern of individual nuclei. To attain more sensitive detection of sialidase activity, the nuclei were incubated with X-Neu5Ac in the presence of Fast Red Violet LB. Individual nuclei of porcine liver were clearly stained with fluorescence that was produced by the conjugated compound of product X with Fast Red Violet LB. This fluorescent cytochemical method was also employed successfully for detection of sialidase activity of intact GOTO neuroblastoma cells in culture. The present method should provide a useful tool for investigating the localization and stage-specific expression of sialidase activity in tissues and cells.

Animals↗
PubMed2002

Effect of a conserved mutation in uridine diphosphate glucuronosyltransferase 1A1 and 1A6 on glucuronidation of a metabolite of flutamide.

OBJECTIVE: We investigated how the conserved mutation (Y486D) changed the kinetic parameters of uridine diphosphate glucuronosyltransferase 1A1 and 1A6 (UGT1A1 and 1A6) for 2-amino-5-nitro-4-trifluoromethylphenol, which is a major metabolite of flutamide, a nonsteroidal antiandrogenic agent. METHODS: The wild-type or mutant cDNA-expressed UGT was co-incubated with 2-amino-5-nitro-4-trifluoromethylphenol (aglycone) and uridine diphosphate-glucuronic acid (UDP-GA, donor substrate). The glucuronidation of the aglycone was determined. RESULTS: The maximum velocities of the mutant UGT1A1 and UGT1A6 were about 12% and less than 1% of the corresponding wild-type, respectively. The Michaelis constant (K(M)) for the aglycone of the wild-type UGT1A1 was double that of the mutant, but the K(M) for UDP-GA of the wild-type UGT1A1 was not significantly different from that of the mutant. CONCLUSION: Patients with Y486D may accumulate excessive 2-amino-5-nitro-4-trifluoromethylphenol, which might lead to unexpected toxicity.

Androgen Antagonists↗
PubMed2002

An improved fluorometric high-performance liquid chromatography method for sialic acid determination: an internal standard method and its application to sialic acid analysis of human apolipoprotein E.

An improved fluorometric HPLC method for sialic acid determination was developed by employing synthetic N-propionylneuraminic acid (NPNA) as an internal standard. A fixed amount of NPNA was added to a sialoglycoconjugate sample. After hydrolyzing sialioglycoconjugates with diluted sulfuric acid, the released sialic acids and NPNA were derivatized with a fluorogenic compound, 1,2-diamino-4,5-(methylenedioxy)benzene (DMB), followed by fluorometric HPLC. The fluorescent derivative of NPNA was separated from those of N-acetylneuraminic acid, N-glycolylneuraminic acid, 2-keto-3-deoxy-D-glycero-D-galacto-nonoic acid, and 2-keto-3-deoxyoctanoate on HPLC. The separation of NPNA derivative on HPLC was not interfered by components of biological samples such as human sera. Using this internal standard method, low amounts of NANA (0.15-1.0 ng) were quantified with the coefficient of variation values below 4%. Using this method, the sialic acid content of human apolipoprotein E was successfully determined. The present method is useful for sensitive and accurate quantification of sialic acids of different molecular species in biological samples.

Apolipoproteins E↗
PubMed2002

Age-dependent reduction in sialidase activity of nuclear membranes from mouse brain.

Sialidase is an enzyme that cleaves alpha-linked sialic acid residues from sialoglycoconjugates and participates in various cellular functions. In the present study, we characterized sialidase activity in nuclear membranes from mouse brain and examined its age-related changes. A highly purified nuclear membrane preparation from 4-week-old mouse brain contained sialidase activity that hydrolyzed both 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid (4MU-Neu5Ac) and ganglioside GM3. The specific activities directed toward both substrates were 6.33+/-0.77 and 13.4+/-1.1pmol/mgprotein/min, respectively. Nuclear localization of sialidase activity was confirmed by fluorescent cytochemistry of intact nuclei using 5-bromo-4-chloro-3-indolyl-alpha-D-N-acetylneuraminic acid (X-Neu5Ac) as the substrate. Age-related changes in nuclear sialidase activity in brain tissue were investigated using mice of different ages (i.e. 2-week-, 4-week-, 14-month-, and 26-month-old). Sialidase activity toward 4MU-Neu5Ac had almost identical levels at 2nd and 4th weeks, but thereafter decreased rapidly; the activity at 26 months was about one third of the young levels. Sialidase activity toward GM3 also showed a similar developmental pattern, though the reduction at advancing ages was less than that of activity toward 4MU-Neu5Ac. The present study demonstrates that the activity of nuclear sialidase decreases with aging. The reduced activity of nuclear sialidase may be implicated with alterations of neural cell function during aging.

Aging↗
PubMed2002

Identification of a novel gene HYS1/CPR5 that has a repressive role in the induction of leaf senescence and pathogen-defence responses in Arabidopsis thaliana.

We isolated two allelic mutants of Arabidopsis thaliana that showed an early senescence phenotype under light/dark and continuous dark photo regimes, and designated the mutant hypersenescence1 (hys1). The hys1 mutants decreased chlorophyll and protein content, lowered the efficiency of photosystem II, and accumulated several senescence upregulated gene transcripts earlier than the wild-type plants. In addition to these senescence features, the hys1 seedlings responded more intensely to exogenously applied sugars than did wild-type seedlings in sugar-induced growth inhibition and sugar-mediated transcript accumulation, both of which are known to be regulated by the sugar sensor hexokinase. The hys1 mutant also had abnormal trichomes. Map-based cloning of the HYS1 gene identified a novel gene that encodes a protein with a potential nuclear localization signal in the amino-terminal region, and five putative transmembrane domains in the carboxyl-terminal region. Furthermore, we found that the constitutive expressor of pathogenesis-related genes 5 (cpr5) mutant, which shows spontaneous pathogen-defence responses and abnormal trichomes, has a point mutation in the HYS1 gene, suggesting that these independently isolated mutants are allelic to each other. Although no definite conclusion can be drawn from these results, we suggest that altered sensitivity to sugars and/or enhanced efficiency of sugar signalling in the hys1/cpr5 mutant may have important roles in the initiation processes of leaf senescence and pathogen-defence responses in Arabidopsis.

Alleles↗
PubMed2002

A delayed leaf senescence mutant is defective in arginyl-tRNA:protein arginyltransferase, a component of the N-end rule pathway in Arabidopsis.

We have isolated a delayed-leaf-senescence mutant, designated dls1, from an Arabidopsis T-DNA line. Leaf senescence progresses more slowly in the dls1 mutant than in the wild-type plant in both age-dependent and dark-induced senescence. Genetic analysis revealed that the dls1 is a monogenic recessive mutation that cosegregated with the T-DNA insertion. Isolation of DNA flanking the T-DNA revealed that the T-DNA was inserted into the fourth intron of the AtATE1 gene, which encodes arginyl-tRNA:protein arginyltransferase (EC. 2.3.2.8, R-transferase), a component of the N-end rule proteolytic pathway in yeast and mammals that transfers arginine to the N-terminus of proteins with N-terminal glutamyl or aspartyl residues. AtATE1 transcripts were not detectable in the dls1 mutant by RT-PCR analysis. Introduction of a wild-type AtATE1 gene into the dls1 mutant complemented the dls1 phenotype. We also showed using a transient expression assay system, that the dls1 mutation results in a decreased degradation of proteins with Asp or Glu at their N-termini, and that the introduction of the wild-type AtATE1 gene reverses this deficiency. These results suggest that the normal progression of leaf senescence requires R-transferase activity, and that proteolysis by the N-end rule pathway has an important physiological function in the progress of leaf senescence in plants.

Aminoacyltransferases↗
PubMed2002

Activation of the promoters of Arabidopsis genes for the branched-chain alpha-keto acid dehydrogenase complex in transgenic tobacco BY-2 cells under sugar starvation.

Sugar starvation exerted by sub-10 mM levels of sucrose on Arabidopsis T87 suspension-cultured cells triggered marked accumulation of the transcripts of genes for E1beta and E2 subunit of the branched-chain alpha-keto acid dehydrogenase complex. Similar levels of sugar starvation increased the luciferase activity in transgenic tobacco BY-2 lines expressing the Arabidopsis E1beta- or E2-promoter-luciferase fusion gene. These results indicate that sugar levels tightly regulate the E1beta and E2 promoter activity in the heterologous plant system. We further showed in the transgenic tobacco BY-2 lines that sugar-starvation-induced activation of the E1beta and E2 promoters was prevented by K-252a, an inhibitor of Ser/Thr protein kinase, and was enhanced by okadaic acid, an inhibitor of protein phosphatases. By contrast, the cauliflower mosaic virus 35S promoter activity in sugar-starved BY-2 cells was not significantly affected by K-252a and only slightly enhanced by okadaic acid. Taken together, we propose that transcriptional activation of genes for the branched-chain alpha-keto acid dehydrogenase complex and its modulation by specific protein kinases/phosphatases are of critical importance in branched-chain amino acid catabolism in plant cells under sugar starvation.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed2002

[Successful treatment with combined anti-thymocyte globulin and methylprednisolone for bronchiolitis obliterans after allogeneic bone marrow transplantation in a child with chronic myelogenous leukemia].

A 9-year-old boy with secondary chronic myelogenous leukemia after treatment of acute lymphoblastic leukemia underwent allogeneic bone marrow transplantation (BMT) from an HLA-identical sibling in December 1998. Grade II acute GVHD developed on day 24 and chronic GVHD developed 5 months after BMT. Cough and dyspnea appeared 9 months after BMT. Despite administration of tacrolimus and methylprednisolone (m-PSL) pulse therapy, the dyspnea gradually increased in severity. Bronchiolitis obliterans was diagnosed on the basis of lung biopsy in January 1999. Because renal dysfunction made it difficult to continue the use of tacrolimus, we attempted antithymocyte globulin (ATG) + m-PSL therapy. Major BCR/ABL mRNA was transiently positive on RT-PCR after the ATG + m-PSL therapy, but no severe complications were observed. A decreasing V50/V25 level and increasing peak flow value were observed in respiratory function tests after ATG + m-PSL therapy, and the patient is currently free of dyspnea. Our findings suggest that ATG + m-PSL therapy is beneficIal for patients with drug-resistant bronchiolitis obliterans after BMT.

Anti-Inflammatory Agents↗