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Biomedical subjects

K Toyoshima

Publications and source records attributed to K Toyoshima.

At least 91 records · Page 5Linked to original sources
PubMed1996

The tumor suppressor protein APC colocalizes with beta-catenin in the colon epithelial cells.

The APC gene is mutated in familial adenomatous polyposis and sporadic colorectal tumors. The product of this gene is a 300 kDa cytoplasmic protein associated with catenin. In the present study, we examined the subcellular localization of the APC protein and beta-catenin in the mouse colon by double-labeling immunocytochemistry. While the APC protein was localized in the lateral and apical cytoplasm and in microvilli of the epithelial cells, beta-catenin was present exclusively in the lateral cytoplasm. Double-labeling-immunoelectron microscopy demonstrated precise colocalization of the APC protein and beta-catenin along the lateral plasma membrane. These results suggest that the APC protein functions in cooperation with beta-catenin in the lateral cytoplasm but has other functions independent of beta-catenin in the apical cytoplasm and in microvilli.

Adenomatous Polyposis Coli Protein↗
PubMed1996

Binding of APC to the human homolog of the Drosophila discs large tumor suppressor protein.

The adenomatous polyposis coli gene (APC) is mutated in familial adenomatous polyposis and in sporadic colorectal tumors, and its product binds to the adherens junction protein beta-catenin. Overexpression of APC blocks cell cycle progression. The APC-beta-catenin complex was shown to bind to DLG, the human homolog of the Drosophila discs large tumor suppressor protein. This interaction required the carboxyl-terminal region of APC and the DLG homology repeat region of DLG. APC colocalized with DLG at the lateral cytoplasm in rat colon epithelial cells and at the synapse in cultured hippocampal neurons. These results suggest that the APC-DLG complex may participate in regulation of both cell cycle progression and neuronal function.

Adenomatous Polyposis Coli Protein↗
PubMed1996

MCC, a cytoplasmic protein that blocks cell cycle progression from the G0/G1 to S phase.

The MCC gene was isolated from the human chromosome 5q21 by positional cloning and was found to be mutated in several colorectal tumors. In this study, we prepared specific antibodies and detected the MCC gene product as a cytoplasmic 100-kDa phosphoprotein in mouse NIH3T3 cells. Immunoelectron microscopic analysis showed that the MCC protein is associated with the plasma membrane and membrane organelles in mouse intestinal epithelial cells and neuronal cells. The amount of the MCC protein remained constant during the cell cycle progression of NIH3T3 cells, while its phosphorylation state changed markedly in a cell cycle-dependent manner, being weakly phosphorylated in the G0/G1 and highly phosphorylated during the G1 to S transition. Overexpression of the MCC protein blocked the serum-induced cell cycle transition from the G1 to S phase, whereas a mutant MCC, initially identified in a colorectal tumor, did not exhibit this activity. These results suggest that the MCC protein may play a role in the signaling pathway negatively regulating cell cycle progression.

3T3 Cells↗
PubMed1996

Persistent activation of CDK4 during neuronal differentiation of rat pheochromocytoma PC12 cells.

It has been shown that suppression of cyclin-dependent kinase 4 (CDK4) expression or its kinase activity is a critical event for the differentiation of hematopoietic and myoblastic cells. To investigate the role of CDK4 during NGF-mediated neuronal differentiation of PC12 cells, we examined the changes in the expression and kinase activity of CDK4. Unexpectedly, both the expression of CDK4 and its kinase activity remained high throughout 10 days of exposure to NGF. Furthermore, constitutive overexpression of the human CDK4 did not inhibit the differentiation. These results suggest that suppression of CDK4 is not required for the NGF-induced neuronal differentiation of PC12 cells.

Animals↗
PubMed1996

The tumor suppressor gene product APC is hyperphosphorylated during the M phase.

The APC gene is mutated in familial adenomatous polyposis and sporadic colorectal tumors. The product of this gene is a 300 kDa cytoplasmic protein and its overexpression results in the block of cell cycle progression from the G0/G1 to the S phase. In the present study, we studied the expression and phosphorylation of the APC protein through the cell cycle. The APC protein was found to be constantly expressed and phosphorylated at serine and threonine residues. Moreover, the APC protein immunoprecipitated from cells arrested in the M phase by nocodazole treatment migrated in SDS-PAGE more slowly than those from the G1 and S phases. Phosphatase treatment abolished this M phase-specific retarded migration, suggesting that APC is transiently hyperphosphorylated in the M phase.

Adenomatous Polyposis Coli Protein↗
PubMed1996

Idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) in childhood.

Idiopathic bronchiolitis obliterans organizing pneumonia (idiopathic BOOP) is a clinicopathological entity of unknown origin first described by Epler and colleagues in 1985. We report our findings from a study of two Japanese boys aged 12 and 13 years with idiopathic BOOP. The patients showed no respiratory symptoms nor signs of infection. There was no history of exposure to noxious agents or medications in either case. Laboratory data, including hematological, biochemical, and immunological tests, were normal, and pulmonary function tests showed only a slight nonprogressive decrease from normal predicted values in vital capacity and diffusing capacity. Serial radiographs in both cases showed migration of patchy infiltrates. Fiberoptic bronchoscopy was performed for evaluation of eosinophilic pneumonia, but the bronchoalveolar lavage (BAL) revealed no increase in eosinophils and a decrease in CD4/CD8 ratio in the BAL fluid. Histopathological findings of transbronchial lung biopsy (TBLB) specimens were compatible with a diagnosis of BOOP. As neither case has shown clinical abnormalities apart from migratory patchy infiltrates on chest radiographs, both patients have been observed without drug therapy for 3-4 years.

Adolescent↗
PubMed1996

CD4 T-lymphocyte activation is associated with peak expiratory flow variability in childhood asthma.

BACKGROUND: Asthma has been recognized as a chronic inflammatory disorder of the airway. We have investigated the relationships among the activation markers on lymphocytes, eosinophils, their serum products in the peripheral blood, and the variability of airway obstruction in childhood asthma. METHODS: Twenty-two patients with atopic asthma (mean age, 12 years) were treated regularly and asked to measure their peak expiratory flow (PEF) twice daily for 7 days, Peripheral venous blood was obtained on day 8. RESULTS: The absolute counts of CD4 T lymphocytes expressing the activation marker CD25 in the peripheral blood on day 8 correlated significantly with the values of the coefficient of variation (CV) of both morning PEF (p < 0.01) and night PEF (p < 0.05) obtained over 7 days, but those of CD8+/CD25+ T lymphocytes, those of CD23+ B lymphocytes, and the serum concentrations of soluble CD25 did not. The absolute counts of peripheral blood eosinophils also demonstrated a significant correlation with the CV values of both morning PEF (p < 0.01) and night PEF (p <0.05). CONCLUSION: CD4 T-lymphocyte activation and increased counts of eosinophils in peripheral blood correlate with CV of PEF in patients with asthma, suggesting that CV of PEF is a good marker for assessing not only the variability of airway obstruction but also the degree of airway inflammation.

Adolescent↗
PubMed1996

Functional disturbance of naive T lymphocytes in very high IgE producers: depletion of interleukin-4-induced interleukin-4-producing cells.

We examined the capacity of T cells from normal individuals and allergic patients with very high IgE to differentiate into interleukin-4(IL-4)-producing cells in vitro. T cells incubated with anti-CD3 monoclonal antibody plus IL-4 or plus anti-IL-4 antibody in the presence of antigen-presenting cells for 7 days were restimulated and their capacity to express IL-4 mRNA was examined by RT-PCR. In T cells from normal individuals, there was a marked increase in the expression of IL-4 mRNA following the addition of IL-4. After fractionation of normal T cells into naive T (CD45RA+) and memory T (CD45RO+) cells, induction of the increase of IL-4 mRNA was restricted to the naive T cell population. In contrast, in T cells from allergic patients, the stimulation of whole or naive T cells with anti-CD 3 monoclonal antibody in the presence of IL-4 induced much less IL-4 mRNA. These findings suggest the presence of a functional abnormality in IL-4-dependent development of IL-4-producing T cells in the peripheral-blood naive T cells from allergic patients.

Adjuvants, Immunologic↗
PubMed1996

Peripheral blood T lymphocytes and basophils, freshly isolated from house-dust-mite-sensitive patients, produce interleukin-4 in response to allergen-specific stimulation.

We examined the capacity of interleukin-4 (IL) production from lymphocytes and basophils, isolated from the peripheral blood of allergic patients sensitive to house dust mite, after stimulation with mite extract. IL-4 production was measured by a sensitive bioassay based on coculture with CT.h4S (a human IL-4-responsive cell line). Lymphocytes and basophils from patients with elevated serum IgE specific to mite allergen [radioallergosorbent test (RAST) score > 3] could produce detectable levels of IL-4 in response to mite extract, whereas those from patients with a RAST score of less than 2 or normal volunteers could not. The sensitivity of basophils to mite extract was high, so that a lower concentration of mite extract (1-10 ng/ml) could induce maximal IL-4 production. On the other hand, a higher concentration (10 micrograms/ml) was required for maximal IL-4 production from the lymphocytes. These findings demonstrate that allergen-specific IL-4-producing cells, lymphocytes and basophils, are generated in vivo in allergic patients and also that there exist characteristic differences between lymphocytes and basophils related to the in vivo source of IL-4.

Allergens↗
PubMed1996

[Difference of lung deposition rate of disodium cromoglycate (DSCG) among three kinds of electric nebulizer].

We examined the lung deposition rate of DSCG with three kinds of electric nebulizer (NE-U03, Pari-Master, Nisshou) on 5 pediatrician skilled with inhalation therapy (31-54 years of age). Excretion of DSCG for 4 hours after inhalation in urine were highest in NE-U03 group, second in Pari-Master group and least in Nisshou group. And then we studied bronchodilating effect of sulbutamol on 18 children (7-17 years of age) with acute exacerbation of bronchial asthma with NE-U03 and Pari-Master. Asthmatic symptom score, SaO2 and pulmonary function were examined before and after inhalation. The delta %FVC, delta %FEV1.0, delta %PEF, delta %V50 and delta %V25 using NE-U03 were 10.3%, 19.1%, 25.5%, 32.5%, and 29.3% in NE-U03 group and 10.6%, 15.9%, 24.1%, 25.4% and 21.3% in Pari-Master group. The data of pulmonary obstraction in NE-03 group were better than that in Pari-Master group. From our data it is obvious that 3 kinds of electric nebulizers have different efficacy in regard to the lung deposition dose of inhaled drugs. When we compare the efficacy of drugs. When we compare the efficacy of drugs for nebulizer inhalation therapy, we should use the drug dose attained to lung and not nominal drug dose in principle.

Adolescent↗
PubMed1996

[Problems of inhaled steroid therapy in children with asthma].

Inhaled steroid therapy has become a most popular anti-inflammatory medication in asthmatic children. However, overreliance on inhaled steroids should not mislead the treatment of asthma because the best way to prevent asthmatic symptoms is the identification and control of triggers such as allergens and non-specific irritants. We should weigh the merits against adverse effects and make a correct decision to use inhaled steroids in each asthmatic child. Since the effectiveness of inhaled steroids mainly depends on the correct performance of inhalation therapy, we must educate patients and their family to develop a good partnership in asthma management as emphasized in every guideline.

Administration, Inhalation↗
PubMed1995

The tumour suppressor gene product APC blocks cell cycle progression from G0/G1 to S phase.

The APC gene is mutated in familial adenomatous polyposis (FAP) as well as in sporadic colorectal tumours. The product of the APC gene is a 300 kDa cytoplasmic protein associated with the adherence junction protein catenin. Here we show that overexpression of APC blocks serum-induced cell cycle progression from G0/G1 to the S phase. Mutant APCs identified in FAP and/or colorectal tumours were less inhibitory and partially obstructed the activity of the normal APC. The cell-cycle blocking activity of APC was alleviated by the overexpression of cyclin E/CDK2 or cyclin D1/CDK4. Consistent with this result, kinase activity of CDK2 was significantly down-regulated in cells overexpressing APC although its synthesis remained unchanged, while CDK4 activity was barely affected. These results suggest that APC may play a role in the regulation of the cell cycle by negatively modulating the activity of cyclin-CDK complexes.

3T3 Cells↗
PubMed1995

Constitutive overexpression of CDK2 inhibits neuronal differentiation of rat pheochromocytoma PC12 cells.

Changes in the levels of cyclins A, D, and E, p21, and cyclin-dependent kinase 2 (CDK2) were examined in rat pheochromocytoma PC12 cells during neuronal differentiation induced by nerve growth factor (NGF). Expression of cyclin A decreased to an undetectable level after 5 days of exposure to NGF, while expression of CDK2 decreased gradually after day 3. In contrast, the levels of cyclins D1 and E increased gradually through day 10, yet the amount of cyclin E associated with CDK2 decreased concomitant with a decrease in the CDK2 protein level. p21 expression increased gradually after day 7, while the level of CDK2-associated p21 remained unchanged. When human cDNAs encoding cyclins and CDK2 were introduced into PC12 cells, only CDK2 overexpression inhibited NGF-induced differentiation. The cell lines overexpressing CDK2 showed stable and high levels of CDK2 kinase activity during differentiation, whereas parental and vector-transfected cell lines displayed a marked decline in CDK2 kinase activity 1 day after NGF treatment. In cell lines overexpressing cyclins A, D, and E, this reduction of the kinase activity was not apparent until day 3. These results suggest that down-regulation of CDK2 activity is a crucial event for the neuronal differentiation of PC12 cells.

Adrenal Gland Neoplasms↗
PubMed1995

Dual transcriptional control by Ear3/COUP: negative regulation through the DR1 direct repeat and positive regulation through a sequence downstream of the transcriptional start site of the mouse mammary tumor virus promoter.

Ear3/COUP is an orphan member of the steroid/thyroid hormone receptor superfamily of transcription factors and binds most tightly to a direct repeat of AGGTCA with 1 nucleotide in between (DR1). Ear3/COUP also binds with a similar affinity to the palindromic thyroid hormone response element (TRE). This binding preference of Ear3/COUP is same as that of the retinoid X receptor (RXR), which is another member of the superfamily. In the present study, we identified a sequence responsible for Ear3/COUP-mediated transactivation in the region downstream of the transcription start site of the mouse mammary tumor virus promoter. This cis-acting sequence was unresponsive to RXR. When the DR1 or TRE sequence was added upstream of the promoter, transactivation by Ear3/COUP was completely abolished, whereas RXR enhanced transcription from the promoter. The mode of action of Ear3/COUP could be utilized to control complex gene expressions in morphogenesis, homeostasis, and development.

Animals↗
PubMed1995

G1 phase arrest induced by Wilms tumor protein WT1 is abrogated by cyclin/CDK complexes.

WT1, the Wilms tumor-suppressor gene, maps to the human chromosomal region 11p13 and encodes a transcriptional repressor, WT1, implicated in controlling normal urogenital development. Microinjection of the WT1 cDNA into quiescent cells or cells in early to mid G1 phase blocked serum-induced cell cycle progression into S phase. The activity of WT1 varied significantly depending on the presence or absence of an alternatively spliced region located upstream of the zinc finger domain. The inhibitory activity of WT1 was abrogated by the overexpression of cyclin E/CDK2 as well as cyclin D1/CDK4. Furthermore, both CDK4- and CDK2-associated kinase activities were downregulated in cells overexpressing WT1, whereas the levels of CDK4, CDK2, and cyclin D1 expression were unchanged. These findings suggest that inhibition of the activity of cyclin/CDK complexes may be involved in mediating the WT1-induced cell cycle block.

3T3 Cells↗
PubMed1995

Three-dimensional structure of the gustatory cell in the mouse fungiform taste buds: a computer-assisted reconstruction from serial ultrathin sections.

Taste buds in fungiform papillae of the mouse were examined with transmission electron microscopy and computer-assisted, three-dimensional reconstruction from serial ultrathin sections. In accord with observation by Murray (1971), four distinct cell types, type I, II, III and basal cells, were identified. Of these, only the type III cell made synaptic contacts with nerve terminals and contained both small, clear vesicles and dense-cored granules. The former vesicles were synaptic-type and accumulated in the cytoplasm just below the synaptic in membrane thickenings. This finding clearly indicates a sensory function for the type III cell. One to three type III cells were identified within a taste bud. The type III cell had at most eight synapses with nerve terminals. One nerve fiber making two synapses with the type III cell was occasionally observed in its terminal region.

Animals↗