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Biomedical subjects

A Muto

Publications and source records attributed to A Muto.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Ten years experience of home parenteral nutrition or hydration in advanced cancer patients].

From April 1987 to May 1997, ninety-six advanced cancer patients including ninety-one among 159 home care patients and five outpatients were administered parenteral nutrition or hydration. Eventually, 67 patients died at home. We concluded through our experience that advanced cancer patients who were unable to eat or drink might live at home with the support of parenteral nutrition or hydration. But four conditions are needed for satisfactory home care of these patients. First, patients understanding their disease condition therefore together with their family hope for home care. Second, the home care support team is organized in an institution. Third, the home care support team is on call for emergencies. Fourth, the home care support team can not only manage home parenteral nutrition but also provide palliative care, including pain control.

Adult↗
PubMed1997

Escherichia coli tmRNA (10Sa RNA) in trans-translation.

Here we show that Escherichia coli tmRNA (10Sa RNA) has a dual function both as an mRNA and as a tRNA in vitro. The function as a tRNA is prerequisite for the function as an mRNA. These observations strongly support the trans-translation hypothesis.

Amino Acid Sequence↗
PubMed1997

Purification of a Mycoplasma capricolum MCS4 RNA binding protein and cloning its gene.

MCS4 RNA (125 nt in length) is one of the small stable RNAs found in Mycoplasma capricolum cells. Gel shift assay was performed with the 5' end-32P-labeled MCS4 RNA and the S100 fraction from M. capricolum to identify the RNA binding proteins. Several bands were detected above free MCS4 RNA, indicating that the RNA formed complexes with proteins and/or RNAs. One of the proteins which specifically binds to MCS4 RNA was purified. The amino acid sequence of the N-terminus revealed 60 to 80% identity to those of glyceraldehyde-3-phosphate dehydrogenases (GAPDH) from various sources.

Amino Acid Sequence↗
PubMed1996

Interaction of 10Sa RNA with ribosomes in Escherichia coli.

10Sa RNA is a bacterial small stable RNA, in which the 5'- and 3'-end sequences are folded into a tRNA-like structure. The RNA accepts alanine in vitro, and interacts with 70S ribosomes in the cells. In this study, we examined the ribosome-binding properties of Escherichia coli 10Sa RNA in vivo, and found that the aminoacylation ability of 10Sa RNA with alanine is necessary for the binding to 70S ribosomes. 10Sa RNA was also found to bind only to 70S monosomes and not to polysomes. Recently, E. coli 10Sa RNA was suggested to be used as mRNA for tag peptides, which were found to attach to the C-termini of truncated peptides synthesized in vivo. The present results are consistent with the 'trans-translation' model, which has been proposed for tag-peptide synthesis.

Escherichia coli↗
PubMed1996

Establishment and characterization of a novel acute promyelocytic leukemia cell line (UF-1) with retinoic acid-resistant features.

All-trans retinoic acid (RA) induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL). Nevertheless, most of these patients develop RA resistance and relapse. The mechanisms of RA resistance by APL cells are still unclear. To understand the characteristics of human leukemia, human leukemic cell lines are useful tools for study. APL cells have a strikingly low proliferation potential in vitro; thus, only one APL cell line has been established. We developed a novel APL cell line (UF-1) from a patient clinically resistant to all-trans RA. Cell surface markers in the UF-1 cells were positive for CD7, CD13, CD33, and CD38. Cytogenetic analyses revealed additional abnormalities, 46XX, add(1)(q44), add(6)(q12), add(7)(q36), t(15;17) (q21;q21). Molecular analyses showed a PML/RAR alpha fusion transcript. Sequence analysis of the RAR alpha gene in RA-resistant HL-60 cells disclosed a point mutation in codon 411 (C to T substitution), whereas UF-1 cells showed the normal sequence. All-trans RA did not change morphological features of the cell, NBT reduction activity, or their expression of CD11b antigens as determined by FACS analysis except at 10(-6) mol/L. RA also did not alter the growth curve of the cells as determined by the MTT assay. These findings suggest that the UF-1 cell is the first permanent cell line with spontaneous RA-resistant APL cells. This RA-resistant APL cell line may be a useful model for molecular studies on the block of leukemic cell differentiation and as a means to investigate the mechanisms of RA resistance.

Adult↗
PubMed1996

The beta subunit of human granulocyte-macrophage colony-stimulating factor receptor forms a homodimer and is activated via association with the alpha subunit.

Human granulocyte-macrophage colony-stimulating factor (hGM-CSF) receptor (hGMR) consists of alpha and beta subunits, and the precise stoichiometry of these subunits has remained to be determined. In this work, oligomerization of the beta subunit was studied using a chemical cross-linker. In Ba/F3, a mouse interleukin-3-dependent cell line expressing both subunits of hGMR (Ba/F3-alpha,beta), a protein with a molecular mass corresponding to that of a homodimer of the beta subunit (beta homodimer) was detected only when cells were treated with the cross-linker. Dimerization of the beta subunit was confirmed by coimmunoprecipitation of a tagged beta subunit with the wild type beta subunit COS7 cells. The beta homodimer had already formed in the absence of hGM-CSF, whereas stimulation with the ligand brought both alpha and beta subunits into a complex, the result being tyrosine phosphorylation of the beta homodimer. Tyrosine phosphorylation of the subunit was impaired by deletion of the cytoplasmic domain of the alpha subunit without interfering with the association of both subunits. These results indicate that the beta homodimer, which alone is insufficient for signaling, forms the functional hGMR with the alpha subunit in response to hGM-CSF.

Cross-Linking Reagents↗
PubMed1996

Granulocyte-macrophage colony-stimulating factor provokes RAS activation and transcription of c-fos through different modes of signaling.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) provokes a proliferative response and induction of early-response genes such as c-fos in target cells. It also induces rapid tyrosine phosphorylation of cellular proteins, including the beta subunit (betac) of its functional receptor. However, locations and functions of phosphorylated tyrosine residues within the betac are unclear. To elucidate the mechanism of the human GM-CSF receptor signal transduction, mutational analyses were made of the cytoplasmic domain of the beta-c, using murine BA/F3 cells. Deletion of the conserved box 1 motif resulted in loss of tyrosine phosphorylation of the betac, thereby indicating an essential role for this motif in activating the tyrosine kinase which phosphorylates betac. A C-terminal truncated mutant at position 589 activated the c-fos promoter, and this activation was diminished by a substitution at tyrosine 577 (Tyr577). However, the same substitution in the full-length betac did not completely abrogate the c-fos promoter activation, hence, redundant signaling pathways probably exist. When we analyzed signaling molecules functioning downstream of the beta-c we found that Tyr577 is essential for Shc phosphorylation, while tyrosine phosphorylation of PTP1D was mediated through Tyr577 as well as through other site(s). We suggest that GM-CSF stimulates at least two modes of signals leading to Ras activation, an event which ultimately gives rise to promoter activation of c-fos.

Amino Acid Sequence↗
PubMed1996

Mechanisms of retinoid resistance in leukemic cells: possible role of cytochrome P450 and P-glycoprotein.

Retinoic acid (RA) regulates the differentiation and proliferation of a wide variety of different cell types and all-trans RA induces complete remission in a high proportion of patients with acute promyelocytic leukemia (APL). However, clinical resistance to retinoids may develop and poses a serious problem for differentiation-inducing therapy. We studied the effects of RA in combination with a cytochrome P450 inhibitor (clotrimazole) and a P-glycoprotein antagonist (verapamil) on cell growth and differentiation of RA-resistant HL-60 cells and fresh RA-resistant leukemic cells from two APL patients. RA-resistant HL-60 cells and APL cells differentiated to mature granulocytes when cultured with all-trans RA and either clotrimazole and verapamil but not with either of the agents alone. These findings were confirmed in these cells by their increased expression of CD11b antigen and migration-inhibitory factor-related protein-8/14 mRNAs and decreased levels of c-myc mRNA. These combinations also markedly decreased the number of viable cells and inhibited cellular proliferation. After isolation of microsomes, measurements showed that levels of cytochrome P450 activities in both wild-type and RA-resistant HL-60 cells were almost comparable. Moreover, expression of the CYP1A1-type cytochrome P450 gene could not be detected in either cell type. However, RA-resistant HL-60 cells and APL cells, but not RA-sensitive HL-60 cells and APL cells, expressed multidrug-resistance-1 gene transcripts. Taken together, acquired resistance to RA may be explained in part by drug metabolism in leukemic cells. Possible mechanisms for accelerated clearance of RA include the induction of non-CYP1A1 cytochrome P450 enzymes and P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1996

All-trans and 9-cis retinoic acid enhance 1,25-dihydroxyvitamin D3-induced monocytic differentiation of U937 cells.

Retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (D3) are well known for inducing differentiation in many leukemic cell lines. The nuclear signalling pathways of RA and D3 are mediated through their cognate receptors, the retinoic acid receptor (RAR) and vitamin D3 receptor (VDR), respectively. Retinoid X receptor (RXR) is an auxiliary factor that forms a heterodimer with RAR and VDR, enabling their efficient transcriptional activation. 9-cis RA, a high-affinity ligand for RXR, greatly enhanced D3-induced CD14 expression in U937 cells, while RA alone did not induce CD14 expression. 9-cis RA also resulted in morphological changes of U937 cells to macrophage-like cells when combined with D3, while RA alone resulted in granulocyte-like cells. RA and D3 together enhanced c-fms expression, phagocytic activity, and acted synergistically to promote nitroblue tetrazolium reduction activity and inhibit proliferation. Northern analysis showed that U937 cells constitutively expressed RAR-alpha, VDR and RXR-alpha mRNAs. RA or D3 alone or in combination did not affect RAR-alpha and VDR expression, while 9-cis RA and 9-cis RA plus all-trans RA significantly reduced RXR-alpha expression. Interestingly, D3 could restore the down-regulation of RXR-alpha mRNA by 9-cis RA. These findings suggest that there is crossover of the nuclear signalling pathways of RA and D3. This may have clinical implications in that RA and D3 may be used in combination for differentiation-inducing therapy in acute myelogenous leukemia and myelodysplastic syndrome.

Antineoplastic Agents↗
PubMed1996

Structural organization of Escherichia coli tmRNA.

A secondary structure of Escherichia coli 10Sa RNA (tmRNA) recently proposed on the basis of a variety of chemical and enzymatic probing data combined with phylogenetic analysis (Felden et al, in press), indicates a highly folded structure. Several long-range interactions including pseudoknots are proposed based on comparative analysis of 10 tmRNA genes. Whereas most of the probing data support these predicted secondary structures, several atypical reactivities in specific domains of the molecule suggest structural dynamics, perhaps relating to the complex functions of the molecule as both tRNA and mRNA. The structure of tmRNA has three modular units; a tRNA-like domain, an mRNA-like domain and an intricate connecting unit probably responsible for correct orientation of the two functional parts of the molecule.

Base Sequence↗
PubMed1996

Structure and function of 10Sa RNA: trans-translation system.

10Sa RNA is a small stable bacterial RNA in which the 5'- and 3'-end sequences are folded into a tRNA-like structure. The RNA is aminoacylatable with alanine in vitro, and it interacts with 70S ribosomes in the cell. Recently, Escherichia coli 10Sa RNA has been shown to contain the sequence-encoding tag-peptides, which are found to attach to the C-termini of truncated peptides synthesized in vivo. We have found that the E coli 10Sa RNA stimulates incorporation of the tag-specific amino acids into proteins depending on the poly(U)-directed poly-phenylalanine synthesis in the in vitro translation system. Our finding supports the 'trans-translation' model proposed for the tag synthesis, in which alanyl-10Sa RNA enters the ribosome when translation stops at the 3'-end of the truncated mRNA lacking a stop codon, and translation of the tag-peptide occurs by switching the template from mRNA to 10Sa RNA. In this unique reaction, 10Sa RNA acts both as a tRNA and as an mRNA.

Amino Acid Sequence↗
PubMed1996

Serial quantification of minimal residual disease of t(8;21) acute myelogenous leukaemia with RT-competitive PCR assay.

The chromosomal translocation (8;21)(q22;q22) in the AML M2 subtype according to the FAB classification, results in the production of a novel fusion gene AML1/ETO. The chimaeric AML1/ETO transcript is useful for the detection of minimal residual disease (MRD). Recently, several studies on the detection of AML1/ETO transcripts in t(8;21) AML have been reported. However, the clinical significance of a small number of AML1/ETO transcripts by a reverse transcription-polymerase chain reaction (RT-PCR) remains to be elucidated. We have developed a novel quantitative RT-competitive PCR assay and evaluated the clinical usefulness of this method by the monitoring of MRD in eight patients with t(8;21) AML. In four patients in first continuous complete remission (CR) the value of MRD was always < 0.1 fg of the competitor dose throughout their courses, whereas in four relapsed patients there was an increase in the value of MRD to > 0.1 fg of the competitor dose before cytogenetic relapse. We conclude that the detection of the presence of cells with AML1/ETO fusion transcripts by our RT-competitive PCR assay may be useful to monitor disease progression and to predict subsequent relapse.

Aged↗
PubMed1996

Calcium waves along the cleavage furrows in cleavage-stage Xenopus embryos and its inhibition by heparin.

Calcium signaling is known to be associated with cytokinesis; however, the detailed spatio-temporal pattern of calcium dynamics has remained unclear. We have studied changes of intracellular free calcium in cleavage-stage Xenopus embryos using fluorescent calcium indicator dyes, mainly Calcium Green-1. Cleavage formation was followed by calcium transients that localized to cleavage furrows and propagated along the furrows as calcium waves. The calcium transients at the cleavage furrows were observed at each cleavage furrow at least until blastula stage. The velocity of the calcium waves at the first cleavage furrow was approximately 3 microns/s, which was much slower than that associated with fertilization/egg activation. These calcium waves traveled only along the cleavage furrows and not in the direction orthogonal to the furrows. These observations imply that there exists an intracellular calcium-releasing activity specifically associated with cleavage furrows. The calcium waves occurred in the absence of extracellular calcium and were inhibited in embryos injected with heparin an inositol 1,4,5-trisphosphate (InsP3) receptor antagonist. These results suggest that InsP3 receptor-mediated calcium mobilization plays an essential role in calcium wave formation at the cleavage furrows.

Animals↗
PubMed1996

[Trial of home anti-cancer chemotherapy with infusion of 5-FU and low-dose cisplatin].

We tried home anti-cancer chemotherapy for patients with advanced or recurrent cancer of the digestive system, using two disposable balloon pumps connected to an implantable drug delivery system via central venous line. There were 33 patients under 75 years old, including 20 cases of gastric cancer, 9 cases of colorectal cancer, 2 cases of cholangiocarcinoma and 2 cases of esophageal cancer enrolled in this study. The protocol was combined chemotherapy with continuous intravenous infusion of 5-FU (300 mg/body/day) and low-dose intravenous injection of cisplatin (5 mg/body/day) in 10-day courses for two weeks, and it was repeated 3 times for 6 weeks. Because of side effects such as nausea, vomiting and bone marrow suppression, treatment was discontinued in 12 cases with peritoneal cancer infiltration. In two of 10 with estimable disease, the reduction of the metastatic lymph node was observed, but no effect was shown in the colorectal metastatic liver tumor. Thanks to the portability of the pump with this method, the patient need not undergo hospitalization. Moreover, there is no renal dysfunction or other major side effects, quality of life is not compromised and a return to family and social life is possible. Thus, if the patient cannot take the oral nutrition, it is easy to start home hyper-alimentation.

Aged↗
PubMed1996

[How to palliate the symptoms of terminally ill patients at home].

We reported the kind of symptoms and how they could be palliated in terminally ill patients at home based on our experience of about 9 years. Cancer pain, which was the most frequent symptom, appeared in 67 among 126 patients receiving home care, and it could be effectively controlled with morphine; no patient returned to the hospital because of aggravation of pain. Very few patients stayed in the hospital and never returned home due to uncontrollable pain. Home parenteral infusion was done for 63 patients who were unable to eat or drink because of peritonitis carcinomatosa or cancer cachexia. High fever in the tumor mass was controlled by glucocorticoid hormone, and ascites was drained continuously when the patients suffered from abdominal distension. From analysis of the cases in which home care was interrupted or those in which patients were unable to transfer to home care, symptoms that were difficult to palliate at home were nausea caused by bowel obstruction, acute symptoms (bleeding, disturbance of consciousness, and so on), and dyspnea. But if the patients and family are eager for home care and an adequate medical support system is in place, home care may be possible despite these symptoms.

Hospice Care↗
PubMed1995

Novel small stable RNAs of Mycoplasma capricolum.

Two stable RNA species and their genes have been isolated from Mycoplasma capricolum, and the nucleotide sequences have been determined by partial RNA sequencing and sequencing of the genes. The RNAs are 92 and 105 nucleotides in length, respectively. The two RNAs reveal no sequence similarity to any stable RNA so far reported, indicating that these are novel RNA species. The RNAs, designated MCS2 and MCS3 RNA, exist in small amounts in the soluble fraction of the cell extract.

Base Sequence↗
PubMed1995

The neuroprotective effect of a potent and selective inhibitor of type I NOS (L-MIN) in a rat model of focal cerebral ischaemia.

Our newly synthesized delta-(S-methylisothioureido)-L-norvaline (L-MIN) was shown to have potent inhibitory effects on Ca(2+)-dependent and constitutively expressed neuronal nitric oxide synthase (type I NOS) when compared to other commonly recognized NOS inhibitors and produced an IC50 value of 5.7 nM. By contrast, this compound exhibited more than 40-fold weaker inhibitory effects on the other NOS isoforms. Administration of L-MIN (0.1, 0.3 and 1 mg kg-1, i.p.) to rats immediately after 2 h middle cerebral artery occlusion and 2 h reperfusion reduced infarct size in a dose-dependent manner. These results suggest that type I NOS activation has a crucial role in the pathogenic cellular mechanisms underlying cerebral ischaemia.

Analysis of Variance↗