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T Hamaguchi

Publications and source records attributed to T Hamaguchi.

At least 55 records · Page 3Linked to original sources
PubMed1998

The delta isoform of protein phosphatase type 1 is localized in nucleolus and dephosphorylates nucleolar phosphoproteins.

The immunolocalization and substrates of protein phosphatases present in nucleolus were investigated using Swiss 3T3 cells and Novikoff hepatoma ascites cells. The protein phosphatase activity was detected in the extract of the isolated nucleoli and its activity was inhibited by okadaic acid with IC50 value of 160 nM. Immunoblotting assay indicated that PP1c delta but not PP1c alpha, PP1c gamma 1, and PP2Ac was localized in the isolated nucleoli. Confocal microscopy showed that PP1c delta was localized in nucleoli, nuclei, and cytosol, though the intensity of fluorescence at the nucleoli was stronger than that of the cytosol or nuclei. PP1c delta was co-localized with the major nucleolar phosphoprotein B23 at nucleoli. The phosphatase was capable of dephosphorylating several proteins in the nucleolus, including B23. The Km of PP1 for the recombinant B23.1, phosphorylated by endogenous kinase(s), was 3.5 microM. These results indicate that PP1c delta is the major serine/threonine phosphatase present in nucleolus and it dephosphorylates nucleolar phosphoproteins, including B23.

3T3 Cells↗
PubMed1998

Mutation/polymorphism scanning of glucose-6-phosphatase gene promoter in noninsulin-dependent diabetes mellitus patients.

Glucose-6-phosphatase (G6Pase) catalyzes the rate-limiting step of gluconeogenesis, and hepatic G6Pase activity is increased in diabetes. We have cloned and analyzed the human G6Pase gene promoter region and identified putative regulatory sequences for insulin, cAMP, glucocorticoid, and hepatocyte nuclear factors. The promoter region of the G6Pase gene was analyzed in 154 noninsulin-dependent diabetes mellitus patients and 90 control subjects by PCR-single strand conformation polymorphism and direct sequencing methods. Polymorphisms were not found in any subjects. The results suggested that in noninsulin-dependent diabetic patients, the major cause of the hepatic glucose overproduction was not attributed to dysregulation of the G6Pase gene due to mutation/polymorphism of its promoter region.

Adolescent↗
PubMed1998

[Two cases of dermatophytosis of the external auditory meatus].

We report two cases of dermatophytosis of the external auditory meatus. Case 1: A 44-year-old man suffered from severe itching in the right external auditory meatus for a year, and had also had tinea unguium for several years. He visited our outpatient clinic because of scaly erythema which had developed on the auricle. Otoscopic examination revealed yellow-brown dry cerumen and redness from the cartilaginous to the bony portion of the external auditory meatus. Case 2: A 14-year-old boy, the son of Case 1, suffered from severe itching in the left external auditory meatus. He scratched the auditory meatus with an earpick which his father had used. Otoscopic examination revealed a similar lesion as in the father's case, although he had no history of dermatophytosis elsewhere on his body, including the auricle. Direct examination using a KOH method of the cerumen from both cases demonstrated numerous fungal elements. Fungal culture identified Trichophyton rubrum. Both cases were successfully treated with oral itraconazole. We suggest that infection from father to son was transferred by the earpick.

Adolescent↗
PubMed1997

Stevastelins, a novel group of immunosuppressants, inhibit dual-specificity protein phosphatases.

BACKGROUND: Since the molecular target of the immunosuppressive reagents FK506 and cyclosporin A was revealed to be protein phosphatase PP2B (calcineurin), many researchers have been screening the protein phosphatase inhibitors from microbial metabolites to develop new immunosuppressive reagents. We isolated stevastelin B, which is composed of valine, threonine, serine and 3,5-dihydroxy-2,4-dimethyl stearic acid, and stevastelin A, which is a sulphonylated derivative of stevastelin B. To understand the action mechanism of stevastelins A and B, we synthesized a series of stevastelin derivatives and investigated their structure-activity relationships. RESULTS: A series of stevastelin derivatives have been systematically synthesized. Stevastelin B inhibited gene expression that is dependent on interleukin-2 (IL-2) or IL-6 promoters in situ, but it had no inhibitory activity against any protein phosphatases in vitro. In contrast, stevastelin A, which is a sulphonylated derivative of stevastelin B, inhibited the phosphatase activity of a dual-specificity phosphatase, VH1-related human protein (VHR), in vitro, but it had no inhibitory activity against gene expression or cell-cycle progression in situ. CONCLUSIONS: Stevastelin B is a novel immunosuppressant. It inhibited IL-2 or IL-6 dependent gene expression but did not inhibit the phosphatase activity of calcineurin. The structure-activity relationships show that the acidic functional group on the threonine residue and the stearic acid moiety in the stevastelin molecule are important for inhibitory effects on the dephosphorylation activity of VHR in vitro. Stevastelin B might be sulphonylated or phosphorylated after incorporation into the target cell, and then it interacts with protein tyrosine phosphatases and regulates cell-cycle progression.

Anti-Bacterial Agents↗
PubMed1996

Pneumatosis intestinalis and necrotizing enterocolitis associated with liver cirrhosis.

We report a 58-year-old woman with pneumatosis intestinalis and necrotizing enterocolitis associated with liver cirrhosis. She was receiving treatment for liver cirrhosis and hepatic failure when sudden severe right upper abdominal pain and fever developed. Abdominal radiograph disclosed pneumatosis intestinalis, involving the ascending colon, and small collections of free air along the right hemidiaphragm. The pneumatosis intestinalis appeared in both cystic and linear form. Autopsy revealed necrosis and multiple gas-filled mural cysts in the ascending colon. To our knowledge, this is the first case to be reported of pneumatosis intestinalis and necrotizing enterocolitis associated with liver cirrhosis.

Colon↗
PubMed1996

Dominant TCR alpha-chain clonotypes and interferon-gamma are expressed in the pancreas of patients with recent-onset insulin-dependent diabetes mellitus.

In order to clarify the nature of T lymphocytes infiltrating the pancreatic islets of patients with insulin-dependent diabetes mellitus (IDDM), we analysed T cell receptor (TCR) gene transcripts expressed in pancreatic biopsy specimens of patients with recent-onset IDDM. We also investigated the expression of cytokines (interferon-gamma: IFN-gamma; tumour necrosis factor-alpha: TNF-alpha; interleukin-4: IL-4; interleukin-6: IL-6) in the same specimens. The TCR V beta repertoire was not restricted either in the pancreas or the peripheral lymphocytes of IDDM patients. In contrast, the TCR V alpha repertoire was restricted in the pancreas, but not in the peripheral blood lymphocytes, of IDDM patients. The sequence analysis of the complementarity-determining region 3 (CDR3) of the TCR alpha revealed the presence of dominant clonality in alpha chains of T cells in the patients. IFN-gamma mRNA was highly expressed in the pancreas of IDDM patients, while IL-4 mRNA was deficient. A lower level of expression of IL-6 mRNA was detected in the IDDM pancreas than in the control tissue. These results indicate that T cells bearing a distinct TCR alpha chain are selectively retained and activated within the pancreas of recent-onset IDDM.

Adolescent↗
PubMed1996

IL-6 mRNA synthesis by peripheral blood mononuclear cells (PBMC) in patients with chronic renal failure.

We measured levels of IL-6 mRNA in PBMC obtained from patients with chronic renal failure, using polymerase chain reaction (PCR). PBMC were isolated from 45 patients on haemodialysis (HD) at the start of HD. PBMC were also isolated from 35 patients on HD at the end of HD, 23 patients on continuous ambulatory peritoneal dialysis (CAPD), 24 undialysed patients with chronic renal failure (CRF), and 19 healthy controls. Total RNA was extracted from PBMC with RNA zol and reverse transcribed into cDNA. To prepare samples containing identical amounts of beta-actin cDNA, we performed competitive PCR by co-amplifying serial dilutions of mutant templates containing a single point mutation which generated a unique Eco RI site. Next, to measure IL-6 cDNA semiquantitatively in the samples containing identical amounts of beta-actin (100 pg), we performed PCR amplification using 2 fg of the IL-6 mutant template containing a unique Eco RI site. Higher levels of IL-6 mRNA in the PBMC were observed in the HD patients than in the CAPD patients and healthy controls. The levels of IL-6 mRNA in the PBMC at the end of HD were not significantly higher than those at the start of HD. These results suggest that the dialysis session itself did not significantly affect IL-6 mRNA levels in the PBMC, but that chronic stimulation by maintenance HD may be associated with higher levels of IL-6 mRNA observed in HD patients.

Adult↗
PubMed1996

Expression and distribution of glucose-6-phosphatase catalytic subunit messenger RNA and its changes in the diabetic state.

Glucose-6-phosphatase (G6Pase) plays a major role in gluconeogenic pathway. To analyze its regulation, we have cloned a full-length cDNA for G6Pase catalytic subunit from the rat liver. In the cloned cDNA, a 492 base insertion, respective to the previously reported sequence, was found in the 3'-noncoding region. In both ends of this insertion, 5'- and 3' 2' splice site motifs were identified. However, spliced mRNA was hardly observed in the rat RNA. Abundant expression was observed in the liver and the kidney by Northern analysis. Expression was also observed in the spleen, adrenal gland and small intestines. Reverse-transcription (RT) polymerase chain reaction (PCR) analysis revealed that G6Pase mRNA was also expressed in a variety of tissues including pancreatic islets. Its expression was increased in the ketotic diabetic mice livers and was corrected by insulin treatment. However, no appreciable changes were observed in kidneys. Broad tissue distribution in expression and the tissue specificity in regulation were thus considered to be the important features of G6Pase gene.

Amino Acid Sequence↗
PubMed1996

[Myogenic hyperuricemia].

Myogenic hyperuricemia is caused by over-production of uric acid, which based on the excessive degradation of purine derivatives in exercising muscle. This phenomenon is frequently observed in the patients of muscle glycogen storage disease (GSD) types III, V and VII. In these patients, impairment of muscle ATP production leads to over-production of AMP, followed by excessive release of inosine and hypoxanthine from the muscle. The molecular lesions of muscle GSDs have been well analyzed. Recent repertoire of these mutations were referred in respect of myogenic hyperuricemia.

Adenosine Monophosphate↗
PubMed1996

[Trial of home infusion therapy for near-terminal stage patients with lung cancer].

To improve the quality of life in patients with malignant diseases at the near-terminal stage, we established a system for home infusion therapy (HIT) in Osaka Prefectural Habikino Hospital in 1994. Thirty-three patients were taken care of at home using the HIT system from January, 1995 to May, 1996. Their average age was 70 years old. The duration of HIT varied from 1 to 105 days (mean:25.5 days). Twenty-four cases received parenteral nutrition. The others received agents for brain edema (4 cases), morphine hydrochloride (2 cases), and anti-fungal agents (3 case). Additionally, 63% of these patients required home oxygen therapy (HOT) with HIT. Questionnaires to their families revealed that they were afraid of the progress of the disease in patients and their physical burden became heavier after the start of HIT. However, they were quite satisfied with the results of HIT.

Adolescent↗
PubMed1996

Hepatocyte nuclear factor-4 alpha gene mutations in Japanese non-insulin dependent diabetes mellitus (NIDDM) patients.

A mutation in the hepatocyte nuclear factor-4 alpha (HNF-4 alpha) gene has been recently reported to cause maturity-onset diabetes of the young (MODY) (Yamagata, Furuta, et al., 1996). The mutation can also be a good candidate for the responsible gene of non-insulin dependent diabetes mellitus (NIDDM). The existence of the mutated allele of Q268X (C to T substitution within the exon 7 of HNF-4 alpha gene) was searched in 514 alleles of Japanese NIDDM patients by polymerase chain reaction-restriction fragment length polymorphism analysis. No mutation was found in these patients. The result showed that the Q268X mutation of HNF-4 alpha gene was not frequent among general NIDDM patients and that it cannot serve as the major diabetogenic gene in the Japanese ethnic group.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗
PubMed1995

RK-682, a potent inhibitor of tyrosine phosphatase, arrested the mammalian cell cycle progression at G1phase.

A specific inhibitor of protein tyrosine phosphatase (PTPase), RK-682 (3-hexadecanoyl-5-hydroxymethyl-tetronic acid) was isolated from microbial metabolites. In vitro, RK-682 inhibited dephosphorylation activity of CD45 and VHR with IC50 54 and 2.0 microM, respectively. In situ, sodium orthovanadate and RK-682 enhanced the phosphotyrosine level of Ball-1 cells, a human B cell leukemia, but not the phosphoserine/threonine level. The PTPase inhibitors, however, had the different arrest point on the cell cycle progression. Sodium orthovanadate inhibited the cell cycle progression at G2/M boundary phase, on the other hand, RK-682 inhibited the G1/S transition.

Aniline Compounds↗
PubMed1995

Compound heterozygous mutations affecting both hepatic and erythrocyte isozymes of pyruvate kinase.

Novel erythrocyte pyruvate kinase gene defects were found in a patient without a family history of consanguinity. The polymerase chain reaction products of the R-type pyruvate kinase cDNA from the propositus contained two point mutations of Ser80 (TCC)-->Pro (CCC) and Arg490 (CGG)-->Trp (TGG). Allele-specific polymerase chain reaction of the genomic DNA revealed that this patient was a compound heterozygote. The mobilities of the patient's L- and R-type pyruvate kinase by thin-layer polyacrylamide gel electrophoresis were abnormal. The results are consistent with the fact that these mutations are within exons common to the hepatic and erythrocyte isozymes.

Adult↗
PubMed1995

Extracellular phosphorylation of membrane protein modifies theta burst-induced long-term potentiation in CA1 neurons of guinea-pig hippocampal slices.

The involvement of ecto-protein kinase activity in activity-dependent long-term potentiation (LTP) was studied in CA1 neurons of guinea-pig hippocampal slices. Application of 5 microM K-252b, an ecto-protein kinase inhibitor, blocked LTP induced by a theta-burst stimulation (3 bursts composed of 5 pulses at 100 Hz with inter-burst intervals of 200 ms). On the other hand, under 10 microM RK682, an ecto-phosphatase inhibitor, a robust LTP was induced by a weak theta-burst stimulation (3 bursts composed of 3 pulses) which was just at the threshold for the induction of LTP in the control perfusate. These findings suggest that ATP released from presynaptic terminals during the burst stimulation plays an important role in the induction of LTP through phosphorylation of extracellular domains of synaptic membrane proteins, as the substrate for ecto-protein kinase.

Animals↗
PubMed1995

The mechanism of ATP-induced long-term potentiation involves extracellular phosphorylation of membrane proteins in guinea-pig hippocampal CA1 neurons.

The mechanism of ATP-induced long-term potentiation was studied pharmacologically using guinea-pig hippocampal slices. Application of 1-10 microM ATP for 10 min transiently depressed and then slowly augmented the synaptic transmission in CA1 neurons leading to long-term potentiation (LTP). This ATP-induced LTP was blocked by the addition of K-252b, an ecto-protein kinase inhibitor, but was enhanced by the addition of RK682, an ecto-phosphatase inhibitor, both of which do not permeate the cell membrane. These results suggest that ATP applied to the perfusate provides enough substrate for ecto-protein kinase to induce LTP through phosphorylation of extracellular domains of membrane proteins in CA1 neurons.

Adenosine Triphosphate↗
PubMed1995

Phosphofructokinase deficiency: recent advances in molecular biology.

Phosphofructokinase (PFK) plays a major role in glycolysis. Deficiency of PFK-M is characterized by muscle weakness due to fuel crisis in exercising muscles. To elucidate the gene defect of PFK-deficient patients, we have cloned and determined the complete structure and transcription mechanism of human PFK-M mRNA and gene. Molecular defects were investigated in three unrelated Japanese family cases. The first case was characterized by a point mutation at the donor site of intron 15 of the PFK-M gene. Cryptic splicing resulted in a 25 amino acid truncation in the patient's PFK-M. The second case possessed a point mutation at the donor site of intron 19, resulting in the skipping of exon 19 and the truncation of 55 amino acids. In the third case, a missense mutation was identified in the coding region. The review of an updated mutation repertoire indicates the heterogeneity of the molecular mechanism of the disease.

Animals↗