Search PubMed⌕ Search

Biomedical subjects

K Mitani

Publications and source records attributed to K Mitani.

At least 109 records · Page 6Linked to original sources
PubMed1997

Recent progress in molecular mechanisms of leukemogenesis: the cyclin-dependent kinase 4-inhibitor gene in human leukemias.

In order to clarify the significance of p16 gene (CDKN2) inactivation and its disease specificity among hematopoietic tumors, configurations of the p16 gene as well as those of the adjacent p15 and interferon alpha (IFN alpha) genes were examined in primary hematopoietic tumors. Loss of the p16 gene is frequent in and highly specific to lymphoid tumors among hematopoietic tumors. Gene deletions but not minute mutations should be the predominant mechanism of p16 gene inactivation in these types of tumors. The p16 gene is most frequently deleted among the p16, p15 and IFN alpha genes and thus should be the target of deletions in this locus. Deletions of the p16 gene were frequently observed in tumors carrying chromosome 9p abnormalities while a significant number of cases showed loss of the p16 gene without chromosome 9p abnormalities. So far inactivation of p53 and Rb tumor suppressors have also been found in lymphoid tumors. In our study, we detected homozygous deletions of p16 gene in 20%, loss of Rb protein in 28%, and p53 gene alterations in 8% of lymphoid tumors. Notably, 44% of lymphoid tumors showed inactivation of at least one of the three tumor suppressors, suggesting these tumor suppressors are important for lymphoid tumorigenesis. Inactivations of these tumor suppressors should independently occur in development of lymphoid tumors.

Carrier Proteins↗
PubMed1997

Molecular mechanism of blastic crisis in chronic myelocytic leukemia.

The t(3;21)(q26;q22), which is usually found in blastic crisis of chronic myelocytic leukemia or myelodysplastic syndrome-derived leukemia, produces an AML1/EVI-1 fusion protein of 180 kD containing amino-terminal half of AML1 including a runt homology domain which is fused to the entire of zinc finger EVI-1 protein. Thus, AML1/EVI-1 fusion protein is a chimeric transcription factor including a runt homology domain from AML1 and two zinc finger domains from EVI-1, totally three DNA binding domains, and an acidic domain from EVI-1. The AML1/EVI-1 fusion protein possesses the dual functions, namely, differentiation block and stimulation of proliferation. The ability of differentiation block depends on the runt homology domain in the AML1 part and the effect to stimulate proliferation depends on the second zinc finger domain in the EVI-1 portion. The AML1/EVI-1 could play an important role in leukemic progression of chronic myelocytic leukemia by these dual functions as a transcription factor.

Animals↗
PubMed1997

[Gait disturbance without motor and sensory involvement in cervical myelopathy--clinical course and radiological findings].

Among 100 patients with cervical myelopathy, we found 7 patients with gait disturbance in which motor or sensory involvements were absent (group A). In these patients, the gait was unsteady, but not ataxic nor spastic. Some of them showed mild hyperreflexia, but no one had Romberg's sign. We compared the effect of neck traction and radiological findings in group A with these in 25 patients who had gait disorders as well as other symptoms associated with cervical myelopathy (group B). Mean age in group A (mean 83.9 +/- 7.9 ys) was older than that in group B (mean 76.6 +/- 5.7 ys). Gait disorders improved in 6 cases of group A (86%), and 5 cases in group B (20%) by conservative therapy of Glisson's traction. On plain X-ray examination, the physiologic lordosis of cervical spine was preserved, the cervical canal diameters from C2 to C7 were more wide, and the number of intervertebral excessive mobility had tendency to be less in group A than in group B. Cervical MRI indicated that the number of intervertebral spinal compression was less in group A than in group B. In the cervical myelopathy, there was a type showing only gait disturbance which was characterized by the good response to Glisson's neck traction, and by the preserved physiological lordosis, relatively wide spinal canal, and slight intervertebral compression.

Aged↗
PubMed1997

[A case of osteopetrosis with an abnormal CK-MB/T-CK ratio].

Creatine kinase (CK)-MB subunit has been recognized as a useful marker for acute myocardial infarction (AMI). However, we recently experienced one case of osteopetrosis with moderately high CK-MB and an abnormal (more than 100%) CK-MB/total (T)-CK ratio without evidence of AMI in a medical examination. We have already experienced 17 cases with an abnormal CK-MB/T-CK ratios in addition to the present case. Those cases were patients with malignant tumor with metastasis (n = 13), leukemia (2), liver cirrhosis (1), and cerebral death (1), and thereby the band of macro-CK was found in the electrophoresis. However, we detected neither the band of macro-CK nor the abnormal levels of tumor markers such as CEA, alpha-fetoprotein, CA-19-9 in the present case. Instead of the macro CK, the high level of CK-BB was detected in electrophoresis. In the medical examination, especially in screening tests, the CK-MB was generally assayed with use of the immunoinhibition method in automated analyzers. The method principle was based on the absence of CK-BB in the patient serum. Since the patient had the past history of pathological fracture in his boyhood, this patient was diagnosed as osteopetrosis. These results suggest that we must consider the possibility of osteopetrosis when an abnormal CK-MB and CK-MB/T-CK ratio without evidence of serious diseases were found. This is simply because of the assay method of immunoinhibition for CK-MB activity.

Adult↗
PubMed1996

Growth and survival signals transmitted via two distinct NPXY motifs within leukocyte tyrosine kinase, an insulin receptor-related tyrosine kinase.

Leukocyte tyrosine kinase (LTK) is a receptor tyrosine kinase, which belongs to the insulin receptor family and is mainly expressed in pre-B cells and brain. In this study, we show that LTK utilizes insulin receptor substrate-1 (IRS-1) and Shc as major two substrates and possesses two NPXY motifs for them separately, tyrosine 485 of one NPXY motif at the juxtamembrane domain for IRS-1 and tyrosine 862 of another NPXY motif at the carboxyl-terminal domain for Shc. By using Ba/F3 cells expressing epidermal growth factor receptor-LTK chimeric receptors containing a mutation at each NPXY site, we showed that while both NPXY motifs equally contribute to activation of the Ras pathway and generation of mitogenic signals, only tyrosine 485 of LTK transmits cell survival signals. These data suggest that IRS-1 possesses anti-apoptotic function at least in LTK signaling. Moreover, our data indicate that the survival signaling pathway of LTK is distinct from the Ras pathway and the p70(S6) kinase pathway. Our results provide a useful insight in understanding the distinctive roles of Shc and IRS-1 in the signal transduction system of the insulin receptor family, and this anti-apoptotic function of IRS-1 may explain the survival effects of insulin, IGF-1, and interleukin 4.

Amino Acid Sequence↗
PubMed1996

A conserved cysteine residue in the runt homology domain of AML1 is required for the DNA binding ability and the transforming activity on fibroblasts.

The AML1 gene encodes DNA-binding proteins that contain the runt homology domain and is found at the breakpoints of t(8;21), t(3;21), and t(12;21) translocations associated with myelogenous leukemias. AML1 heterodimerizes with PEBP2beta/CBFbeta, resulting in the enhanced affinity with DNA. The runt homology domain is responsible for binding with DNA and heterodimerizing with PEBP2beta/CBFbeta. AML1 is suggested to perform a pivotal role in myeloid cell differentiation, whereas it can cause neoplastic transformation when overexpressed in fibroblasts. In this study, we demonstrated that the reducing reagent, dithiothreitol (DTT), markedly enhances the DNA binding of AML1 expressed in COS7 cells. Oxidation by diamide or modification by N-ethylmaleimide of the free sulfhydryl residues inhibited the interaction of AML1 with DNA. The diamide effect was reversible with excess of DTT, whereas DTT could not restore the DNA binding of AML1 treated with N-ethylmaleimide. Site-directed mutagenesis of the amino acid residue 72, a highly conserved cysteine in the runt homology domain of AML1, to serine almost completely abolished DNA binding without altering the interaction with PEBP2beta/CBFbeta. This substitution also impaired transactivation through the consensus DNA sequence and transformation of fibroblasts induced by AML1b. These data indicate an essential role of the conserved cysteine residue in DNA binding of AML1, and it is possible that the redox state of AML1 could contribute to the regulation of its function.

3T3 Cells↗
PubMed1996

Structurally altered Evi-1 protein generated in the 3q21q26 syndrome.

Overexpression of the Evi-1 gene appears to be a consistent feature of the 3q21q26 syndrome, an association of myeloid leukemias/myelodysplastic syndrome with a specific chromosomal aberration involving both 3q21 and 3q26, such as t(3;3)(q21;q26) or inv(3)(q21q26). The rearrangement in 3q26 has been reported to occur near the Evi-1 locus, implicating that it is the critical gene deregulated in the 3q21q26 syndrome. Here we present a structural abnormality of Evi-1 protein in a case with the 3q21q26 syndrome. In this case carrying typical inv(3)(q21q26), the 3q26 breakpoint is located within an intron of the Evi-1 gene, and resulted in overexpression of normally unexpressed, an aberrant form of Evi-1 protein, in which the C-terminal 44 amino acids of wild-type Evi-1 protein were truncated and replaced by five amino acids. The truncated Evi-1 protein is shown to increase AP1 activity when expressed in NIH3T3 cells as its wild-type counterpart. We also show that the origin of this peculiar type of rearrangement of the Evi-1 gene is not an artifact during establishment of the cell line, but is the event that occurred in the primary leukemic cells. Our results strongly support that the primary target for the 3q21q26 syndrome is the Evi-1 gene, and provide the first evidence that the structurally altered Evi-1 gene may be involved in the 3q21q26 syndrome.

3T3 Cells↗
PubMed1996

A new adenoviral vector: Replacement of all viral coding sequences with 28 kb of DNA independently expressing both full-length dystrophin and beta-galactosidase.

Adenoviral vector-mediated gene transfer offers significant potential for gene therapy of many human diseases. However, progress has been slowed by several limitations. First, the insert capacity of currently available adenoviral vectors is limited to 8 kb of foreign DNA. Second, the expression of viral proteins in infected cells is believed to trigger a cellular immune response that results in inflammation and in only transient expression of the transferred gene. We report the development of a new adenoviral vector that has all viral coding sequences removed. Thus, large inserts are accommodated and expression of all viral proteins is eliminated. The first application of this vector system carries a dual expression cassette comprising 28.2 kb of nonviral DNA that includes the full-length murine dystrophin cDNA under control of a large muscle-specific promoter and a lacZ reporter construct. Using this vector, we demonstrate independent expression of both genes in primary mdx (dystrophin-deficient) muscle cells.

Adenoviridae↗
PubMed1996

Overexpression of the AML1 proto-oncoprotein in NIH3T3 cells leads to neoplastic transformation depending on the DNA-binding and transactivational potencies.

The AML1 gene encodes DNA-binding proteins that contain the runt homology domain and is found at the breakpoints of t(8;21) and t(3;21) translocations associated with myelogenous leukemias. From the AML1 gene, two representative forms of proteins, AML1a and AML1b, are generated by alternative splicing. Both forms have the runt homology domain that possesses the DNA-binding ability but, unlike AML1b, AML1a lacks a putative transcriptional activation domain downstream of the runt homology domain. By using retroviral infection, we demonstrated that AML1b causes neoplastic transformation of NIH3T3 cells. AML1b-expressing cells form macroscopic colonies in soft agar and induce tumors in nude mice, indicating that AML1 can be a transforming gene when overexpressed in fibroblasts. Both the runt homology domain and the transactivational domain were required to transform NIH3T3 cells. By analysis of deletion mutants, it was shown that an element determining the transactivational potency exists between amino acids 288 and 396 within the region downstream of the runt homology domain. Furthermore, we demonstrated that this region was also required for fibroblast transformation, indicating that the transforming activity of AML1 is correlated with the transactivational potencies. These results suggest a role of AML1 in the regulation of cellular proliferation, as well as myeloid cell differentiation.

3T3 Cells↗
PubMed1996

Chromosomal abnormalities and oncogenes.

The alterations of transcription factor genes by chromosomal translocations play an important role in leukemogenesis and lymphomagenesis. The alterations are classified into two groups. One is the chimeric gene formation, and the other is the aberrant expression without structural changes. The former type is associated with the chromosomal translocations found in acute myeloid leukemia, such as the AML1/MTG8 in t(8;21) and PML/RAR alpha in t(15;17). The latter is the main mechanism in the gene activations observed in acute lymphoblastic leukemia and lymphoma. Many transcription factor genes are activated by the recombination with the immunoglobulin genes in B cell malignancies or T cell receptor genes in T cell malignancies. We isolated the AML1/EVI-1 fusion gene generated by the t(3;21) translocation, which is usually found in blastic crisis of chronic myelocytic leukemia. The chimeric transcription factor encoded by the fusion gene has dual functions, namely differentiation block and stimulation of proliferation. These findings provide new insight into the molecular mechanism in leukemogenesis by the chimeric transcription factors.

Chromosome Aberrations↗
PubMed1996

Elevated platelet count features the variant type of BCR/ABL junction in chronic myelogenous leukaemia.

A variant form of BCR/ABL junction was identified in a patient with chronic myelogenous leukaemia (CML). The BCR/ABL fusion mRNA of this patient showed in-frame junction between BCR exon c3 and ABL exon 2. Although the diagnosis of CML was made, the patient showed clinical features of essential thrombocythaemia (ET) rather than that of typical CML. Treatment with interferon-alpha showed no cytogenetic response. The c3-a2 type of BCR/ABL junction seems to be associated with elevated platelet count and thus could form a novel clinical entity different from typical CML.

Adolescent↗
PubMed1996

Macrolide susceptibility of Mycoplasma hyorhinis isolated from piglets.

Twenty strains of Mycoplasma hyorhinis were investigated for their in vitro susceptibilities to 15 antimicrobial agents by broth and agar dilution methods. Two of the 20 field strains showed low susceptibility to 14- and 16-membered macrolide antimicrobial agents tested. The two field strains were considered inducibly resistant to macrolides.

Animals↗
PubMed1996

A novel interferon regulatory factor family transcription factor, ICSAT/Pip/LSIRF, that negatively regulates the activity of interferon-regulated genes.

We have isolated a novel cDNA clone encoding interferon (IFN) consensus sequence-binding protein in adult T-cell leukemia cell line or activated T cells (ICSAT); this protein is the human homolog of the recently cloned Pip/LSIRF. ICSAT is structurally most closely related to the previously cloned ICSBP, a member of the IFN regulatory factor (IRF) family of proteins that binds to interferon consensus sequences (ICSs) found in many promoters of the IFN-regulated genes. Among T-cell lines investigated, ICSAT was abundantly expressed in human T-cell leukemia virus type 1 (HTLV-1)-infected T cells. When the HTLV-1 tax gene was expressed or phorbol myristake acetate-A23187 stimulation was used, ICSAT expression was induced in Jurkat cells which otherwise do not express ICSAT. When the binding of ICSAT to four different ICSs was tested, the relative differences in binding affinities for those ICSs were determined. To study the functional role of ICSAT, we performed cotransfection experiments with the human embryonal carcinoma cell line N-Tera2. ICSAT was demonstrated to possess repressive function over the gene activation induced by IFN stimulation or by IRF-1 cotransfection. Such repressive function is similar to that seen in IRF-2 or ICSBP. However, we have found that ICSAT has a different repressive effect from that of IRF-2 or ICSBP in some IFN-responsive reporter constructs. These results suggest that a novel mechanism of gene regulation by "differential repression" is used by multiple members of repressor proteins with different repressive effects on the IFN-responsive genes.

Amino Acid Sequence↗
PubMed1996

The extracellular signal-regulated kinase pathway phosphorylates AML1, an acute myeloid leukemia gene product, and potentially regulates its transactivation ability.

AML1 (also called PEBP2alphaB, CBFA2, or CBFalpha2) is one of the most frequently disrupted genes in chromosome abnormalities seen in human leukemias. It has been reported that AML1 plays several pivotal roles in myeloid hematopoietic differentiation and other biological phenomena, probably through the transcriptional regulation of various relevant genes. Here, we investigated the mechanism of regulation of AML1 functions through signal transduction pathways. The results showed that AML1 is phosphorylated in vivo on two serine residues within the proline-, serine-, and threonine-rich region, with dependence on the activation of extracellular signal-regulated kinase (ERK) and with interleukin-3 stimulation in a hematopoietic cell line. These in vivo phosphorylation sites of AML1 were phosphorylated directly in vitro by ERK. Although differences between wild-type AML1 and phosphorylation site mutants in DNA-binding affinity were not observed, we have shown that ERK-dependent phosphorylation potentiates the transactivation ability of AML1. Furthermore the phosphorylation site mutations reduced the transforming capacity of AML1 in fibroblast cells. These data indicate that AML1 functions are potentially regulated by ERK, which is activated by cytokine and growth factor stimuli. This study provides some important clues for clarifying unidentified facets of the regulatory mechanism of AML1 function.

Acute Disease↗
PubMed1996

Studies on quinolone antibacterials. IV. Structure-activity relationships of antibacterial activity and side effects for 5- or 8-substituted and 5,8-disubstituted-7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-1, 4-dihydro-4-oxoquinoline-3-carboxylic acids.

A series of 7-(3-amino-1-pyrrolidinyl)-1-cyclopropyl-1,4-dihydro-4- oxoquinoline-3-carboxylic acids bearing various substituents (H, F, C1, Me, OH, OMe, OEt, OCH2F, OCHF2, OCF3, SMe) at the C-8 position was prepared and evaluated for in vitro antibacterial activity against both standard laboratory strains and bacteria resistant to quinolones such as ciprofloxacin (CPFX, 1) and ofloxacin (OFLX, 2) from clinical isolates. The 8-methyl (8a), 8-fluoro (9a), 8-chloro (10a) and 8-methoxy (12a) compounds were 4 times more potent than CPFX (1) against both gram-positive and gram-negative bacteria. But these four compounds caused injury to the chromosomes of mammalian cells at a concentration of 100 micrograms/ml. Next, a series of quinolones having various substituents (H, C1, Me, NH2, NHMe, NMe2) at the C-5 position was prepared and evaluated for antibacterial activity and injurious effect on the chromosome. We found that the 5-amino-8-methyl compound (8d) showed strong antibacterial activity (in vitro antibacterial activity of 8d is 4 times more potent than that of CPFX (1) against both gram-positive and gram-negative bacteria), reduced injury to the chromosome, and reduced quinolone-type toxicity (free from both phototoxicity at a dosage of 30 mg/kg in guinea pigs (i.v.) and convulsion-inducing activity when coadministered with fenbufen at dosage of 100 mg/kg in mice (i.p.)).

4-Quinolones↗
PubMed1996

Mycoplasma hyorhinis infection levels in lungs of piglets with porcine reproductive and respiratory syndrome (PRRS).

The infection levels of Mycoplasma hyorhinis, M. hyopneumoniae and M. hyosynoviae in the lung of piglets were examined in relation to porcine reproductive and respiratory syndrome (PRRS). These animals consisted of 43 PRRS piglets with PRRS, 2 piglets infected with PRRS virus but symptom-free, and 10 control piglets free of PRRS virus and its antibody. M. hyorhinis was isolated from 40 of the 43 PRRS piglets, from 1 of the 2 latent infected piglets and from 3 of the 10 control piglets. The number of M. hyorhinis isolated from the lungs of PRRS piglets was more than 10(5) CFU/g, but those isolated from the latent infected piglets and the control piglets were less than 10(3) CFU/g. In addition to this, Haemophilus parasuis and Pasteurella spp. were frequently isolated from the piglets with PRRS (51.2% and 25.6%, respectively). On the other hand, M. hyopneumoniae was isolated from only 4 of 55 piglets tested, and M. hyosynoviae was not isolated. M. hyorhinis was also detected directly in the lung emulsion samples from almost all the PRRS piglets using a polymerase chain reaction-based method.

Animals↗
PubMed1996

In vitro susceptibility of Mycoplasma hyosynoviae and M. hyorhinis to antimicrobial agents.

Fifty-four Japanese strains of Mycoplasma hyosynoviae isolated from porkers during 1980 to 1995, and 107 Japanese strains of M. hyorhinis isolated from piglets with respiratory disease during 1991 to 1994 were investigated for the in vitro activities of 13 antimicrobial agents [josamycin, tylosin, spiramycin, kitasamycin, erythromycin, lincomycin (LCM), kanamycin (KM), chloramphenicol (CP), thiamphenicol (TP), tiamulin (TML), oxytetracycline (OTC), chlortetracycline (CTC), and enrofloxacin (ERFX)] by the agar dilution method. Of the drugs tested TML showed the highest activity with minimum inhibitory concentration (MIC) of 0.013 to 0.1 microgram/ m/ (MIC90; 0.05 microgram/ml) against strains of M. hyosynoviae, and 0.2 to 0.78 microgram/ml (MIC90; 0.39 microgram/ml) against strains of M. hyorhinis. ERFX, LCM, most of the 16-membered macrolide antibiotics and tetracyclines also showed low MICs against both mycoplasma species. The susceptibility of KM, CP and TP to the mycoplasmas was considered to be of a secondary grade. Two of 54 strains of M. hyosynoviae, and 11 of 107 strains of M. hyorhinis showed resistance to all 14- and 16-membered macrolide antibiotics tested. Tetracyclines (OTC and CTC) showed a relatively broad MIC distribution from 0.1 to 6.25 micrograms/ml against the M. hyosynoviae strains tested. All of the strains isolated during 1980 to 1984 were susceptible at the concentration of 0.78 microgram/ml or less (MIC90; 0.78 microgram/ml) to OTC and 1.56 micrograms/ml or less (MIC90; 1.56 micrograms/ml) to CTC, while the susceptibility of strains isolated recently, during 1994 to 1995, was more than 0.78 microgram/ml (MIC90; 3.13 micrograms/ml) to OTC, and more than 1.56 micrograms/ml (MIC90; 6.25 micrograms/ml) to CTC.

Animals↗