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K Miyagawa

Publications and source records attributed to K Miyagawa.

At least 37 records · Page 2Linked to original sources
PubMed2001

Trichorzin HA V, a member of the peptaibol family, stimulates intracellular cAMP formation in cells expressing the calcitonin receptor.

By a cell-based screening of an in-house natural product library, trichorzin HA V, belonging to a peptaibol family, was isolated from a strain of fungus Trichoderma as a calcitonin (CT) agonist. Like CT, trichorzin HA V elevated cAMP levels in T47D cells which endogenously express the human CT receptor. It also stimulated cAMP formation in cells expressing recombinant human CT receptor, but not in those that do not express the receptor, suggesting that it selectively interacts with the CT receptor. In contrast to trichorzin HA V, alamethicin, another well-characterized peptaibol, showed no cAMP-elevating activity at all. These results suggest that, although there was little amino acid sequence similarity between trichorzin HA V and CT, the biological activity of trichorzin HA V can mimic that of CT, acting via the CT receptor.

Animals↗
PubMed2000

A novel human rad54 homologue, Rad54B, associates with Rad51.

Members of the SNF2/SWI2 family, characterized with sequence motifs similar to those found in DNA and RNA helicases, play roles in various aspects of cellular fundamental processes such as transcriptional regulation, chromosome stability, nucleotide excision repair, and recombination. We have isolated a novel member of the human SNF2/SWI2 family, RAD54B, which is highly homologous to mammalian RAD54. The RAD54 gene is a member of the RAD52 epistasis group which is involved in the recombinational repair of DNA damage. Here we demonstrate that human Rad54B (hRad54B), like human Rad54 (hRad54), associates with human Rad51 (hRad51). Both hRad54B and hRad54 associate with hRad51 through their NH(2)-terminal domains, but there are differences in their ways of association with hRad51. In contrast to Rad54, whose association with Rad51 is induced by ionizing radiation, Rad54B associates with Rad51 constitutively in immunoprecipitation experiments. Also, the failure to detect the interaction between hRad54B and hRad51 in the yeast two-hybrid assay suggests that their interaction, unlike that between hRad54 and hRad51, may be indirect. Immunofluorescence microscopy revealed that hRad54B formed nuclear foci that colocalized with hRad51, hRad54, and BRCA1. These findings suggest that Rad54B may be functionally distinct from Rad54, although it may play an active role in recombination processes in concert with other members of the RAD52 epistasis group.

Adenosine Triphosphatases↗
PubMed2000

Failure of L-arginine to induce hypotension in patients with a history of accelerated-malignant hypertension.

A profound elevation of blood pressure on exercises or after withdrawal of antihypertensive drugs has been reported in patients with a history of accelerated-malignant hypertension. We tested the hypothesis that severe endothelial dysfunction is responsible for the profound hypertensive response in these patients. Responses of blood pressure, heart rate and plasma cyclic guanosine monophosphate to intravenously infused L-arginine, a precursor of nitric oxide, was investigated in hypertensive patients with (group A) or without any history of accelerated-malignant hypertension (group B) in order to evaluate endothelial function. Casual blood pressure or severity of hypertension was not different between group A and B. Infusion of L-arginine decreased mean blood pressure in group B (97.4 +/- 8.7 to 81.7 +/- 6.9 mm Hg), but not in group A (99.0 +/- 10.2 to 101.5 +/- 8.7 mm Hg). Plasma levels of cyclic guanosine monophosphate were increased after infusion of L-arginine in group B (5.4 +/- 2.0 to 7. 7 +/- 1.7 pmol/ml, P< 0.01), while no significant changes were observed in group A (5.4 +/- 2.1 to 5.9 +/- 2.1 pmol/ml). There was a significant correlation between decrease in mean blood pressure and increase in plasma levels of cyclic guanosine monophosphate (r = 0.83, P < 0.001). The results indicated that much more severe endothelial dysfunction is present in hypertensive patients with a history of accelerated-malignant hypertension as compared to those without the history. The difference in the endothelial function may account for the different pressor responses to exercises or other stimuli observed in hypertensive patients with and without a history of accelerated-malignant hypertension. Journal of Human Hypertension (2000) 14, 485-488

Aged↗
PubMed2000

Older boys benefit from higher initial prednisolone therapy for nephrotic syndrome. The West Japan Cooperative Study of Kidney Disease in Children.

BACKGROUND: A long course of the initial prednisolone therapy has been shown to be more effective than standard-course therapy in reducing relapse rates in children with idiopathic nephrotic syndrome, but it is commonly accompanied by corticosteroid toxicities. There has been no study on prednisolone dosage for the effective treatment of nephrotic syndrome. METHODS: Sixty-eight children (42 boys and 26 girls) with an initial attack of nephrotic syndrome were randomly allocated into two different long-course treatment groups. Patients in Group 1 received a daily prednisolone dose of 60 mg/m2 for six weeks, followed by an alternate-day dose of 40 mg/m2 for six weeks. Patients in Group 2 had a daily dose of 40 mg/m2 instead of 60 mg/m2. RESULTS: Four children in each group did not respond within six weeks. Group 1 was associated with a significantly earlier response but more frequent corticosteroid toxicities than Group 2. Boys in Group 1 had a higher rate of sustained remission than boys in Group 2 (P = 0.0073), especially boys four years old or more (P = 0.0027), but girls did not show a significant difference (P = 0.863). Boys four years old or more in Group 1 had a course of frequent relapsing less often than those in Group 2 (2 of 13 vs. 6 of 8, P = 0.0075). CONCLUSION: These findings indicate that efficient prednisolone doses may vary between sexes and ages, and that a higher initial prednisolone therapy may be of greater benefit to older boys.

Adolescent↗
PubMed2000

Magnesium removal impairs the regulatory role of rat endothelium.

Vascular endothelium has been shown to play an important role in the regulation of vascular tone and, hence, impairment of the endothelium may induce hypertension. Although magnesium (Mg) deficiency could induce hypertension, the role of Mg on the endothelium is unclear. We examined the effects of Mg removal on endothelium-dependent and -independent responses using ring preparations of femoral arteries obtained from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Norepinephrine (10(-9)-10(-4) M) evoked concentration-dependent contractions in arteries with endothelium. The maximal response was greater in SHR than in WKY. Removal of external Mg augmented the contraction in WKY but not in SHR. As a result, the contraction obtained in arteries with endothelium was identical in the two groups. Removal of the endothelium enhanced the contraction in both strains, with a greater response occurring in WKY than in SHR in Krebs, but not in Mg-free, solution. As a result, in arteries without endothelium, the contractions were identical in WKY and SHR both in Krebs and Mg-free solutions. Acetylcholine (10(-9)-10(-4) M) evoked concentration-dependent relaxation in arteries with, but not in those without, endothelium obtained from WKY and SHR. The relaxation did not differ between the two strains, nor was it altered by Mg removal. Thus, Mg removal impairs inhibitory function of the endothelium against contraction induced by norepinephrine, without affecting endothelium-dependent relaxation in response to acetylcholine, in the rat femoral artery. The effect of Mg removal is not apparent in SHR. The fact that after removal of external Mg the contraction in response to norepinephrine in arteries with endothelium is identical in WKY and SHR suggests that a normotensive artery with Mg deficiency may mimic a hypertensive artery through endothelial impairment.

Acetylcholine↗
PubMed1999

Mutations of a novel human RAD54 homologue, RAD54B, in primary cancer.

Association of breast tumor susceptibility gene products BRCA1 and BRCA2 with the RAD51 recombination protein suggested that cancer could arise through defects in recombination. The identification of NBS1, responsible for Nijmegen breakage syndrome, from the MRE11/RAD50 recombination protein complex also supports this hypothesis. However, our mutation analysis revealed that known members of the RAD52 epistasis group are rarely mutated in human primary cancer. Here we describe the isolation of a novel member of the SNF2 superfamily, characterized with sequence motifs similar to those in DNA and RNA helicases. The gene, designated RAD54B, is significantly homologous to the RAD54 recombination gene. The expression of RAD54B was high in testis and spleen, which are active in meiotic and mitotic recombination. These findings suggest that RAD54B may play an active role in recombination processes in concert with other members of the RAD52 epistasis group. RAD54B maps to human chromosome 8q21.3-q22 in a region associated with cancer-related chromosomal abnormalities. Homozygous mutations at highly conserved positions of RAD54B were observed in human primary lymphoma and colon cancer. These findings suggest that some cancers arise through alterations of the RAD54B function.

Adenocarcinoma↗
PubMed1999

Mutations in the RAD54 recombination gene in primary cancers.

Association of a recombinational repair protein RAD51 with tumor suppressors BRCA1 and BRCA2 suggests that defects in homologous recombination are responsible for tumor formation. Also recent findings that a protein associated with the MRE11/RAD50 repair complex is mutated in Nijmegen breakage syndrome characterized by increased cancer incidence and ionizing radiation sensitivity strongly support this idea. However, the direct roles of BRCA proteins and the protein responsible for NBS in recombinational repair are not clear though they are associated with the recombinational repair complexes. Since RAD51 forms a complex with other members of the RAD52 epistasis group and with BRCA proteins, it is reasonable to ask if alterations of members of the RAD52 epistasis group lead to tumor development. Here we describe missense mutations at functional regions of RAD54 and the absence of the wild-type RAD54 expression resulting from aberrant splicing in primary cancers. Since RAD54 is a recombinational protein associated with RAD51, this is the first genetic evidence that cancer arises from a defect in repair processes involving homologous recombination.

Adenocarcinoma↗
PubMed1999

A zinc finger truncation of murine WT1 results in the characteristic urogenital abnormalities of Denys-Drash syndrome.

The Wilms tumor-suppressor gene, WT1, plays a key role in urogenital development, and WT1 dysfunction is implicated in both neoplastic (Wilms tumor, mesothelioma, leukemias, and breast cancer) and nonneoplastic (glomerulosclerosis) disease. The analysis of diseases linked specifically with WT1 mutations, such as Denys-Drash syndrome (DDS), can provide valuable insight concerning the role of WT1 in development and disease. DDS is a rare childhood disease characterized by a nephropathy involving mesangial sclerosis, XY pseudohermaphroditism, and/or Wilms tumor (WT). DDS patients are constitutionally heterozygous for exonic point mutations in WT1, which include mutations predicted to truncate the protein within the C-terminal zinc finger (ZF) region. We report that heterozygosity for a targeted murine Wt1 allele, Wt1(tmT396), which truncates ZF3 at codon 396, induces mesangial sclerosis characteristic of DDS in adult heterozygous and chimeric mice. Male genital defects also were evident and there was a single case of Wilms tumor in which the transcript of the nontargeted allele showed an exon 9 skipping event, implying a causal link between Wt1 dysfunction and Wilms tumorigenesis in mice. However, the mutant WT1(tmT396) protein accounted for only 5% of WT1 in both heterozygous embryonic stem cells and the WT. This has implications regarding the mechanism by which the mutant allele exerts its effect.

Animals↗
PubMed1999

Purification, characterization, and application of an acid urease from Arthrobacter mobilis.

It has been shown that urea in fermented beverages and foods can serve as a precursor of ethylcarbamate, a potential carcinogen, and acid urease is an effective agent for removing urea in such products. We describe herein the purification and characterization of a novel acid urease from Arthrobacter mobilis SAM 0752 and show its unique application for the removal of urea from fermented beverages using the Japanese rice wine, sake, as an example. The purified acid urease showed an optimum pH for activity at pH 4.2. The enzyme exhibited an apparent K(m) for urea of 3.0 mM and a Vmax of 2370 mumol of urea per mg and min at 37 degrees C and pH 4.2. Gel permeation chromatographic and sodium dodecyl sulfate gel electrophoretic analyses showed that the enzyme has an apparent native molecular weight (M(r)) of 290,000 and consisted of three types of subunit proteins (M(r), 67,000, 16,600, 14,100) denoted by alpha, beta, and gamma. The most probable stoichiometry of the subunits was estimated to be alpha: beta: gamma = 1:1:1, suggesting the enzyme subunit structure of (alpha beta gamma)3. The enzyme also existed as an aggregated form with an M(r) of 580,000. The purified enzyme contained 2 g-atom of nickel per alpha beta gamma unit of the enzyme. Enzyme activity was inhibited by acetohydroxamic acid, HgCl2, and CuCl2. The isoelectric point of the native enzyme was estimated by gel electrofocusing to be 6.8. Urea (50 ppm), which was exogenously added to sake (pH 4.4, 17 +/- 1% (v/v) ethanol), was completely decomposed by incubation with the enzyme (0.09 U ml-1) at 15 degrees C for 13 days. The enzyme was unstable at temperatures higher than 65 degrees C and pHs lower than 4, and was completely inactivated under the conditions of a pasteurization step involved in the traditional sake-making processes. These results indicate that the enzyme is applicable to the elimination of urea in fermented beverages with minimal modification to the conventional process.

Alcoholic Beverages↗
PubMed1999

Detection of WT1 mRNA in urine from patients with kidney diseases.

Detachment of glomerular epithelial cells (GEC) from glomerular basement membrane (GBM) could account for a part of the pathogenic mechanism of proteinuria seen in primary and secondary renal diseases. The Wilms' tumour suppresser gene (WT1) is strictly expressed in GEC in the adult kidney. Mutations of WT1 gene have been implicated in progressive renal damage. Utilizing nested RT-PCR we detected mRNA of WT1 in the urine of patients with renal diseases. Seven of 20 (35%) chronic glomerulonephritis (CGN), eight of 20 (40%) diabetes mellitus (DM) with proteinuria, and two of 24 (8.3%) rheumatic diseases were WT1 positive. Interestingly, only one of 51 (2%) DM without proteinuria was WT1 positive. None of the healthy volunteers or cystitis patients were WT1 positive. This is the first report describing the detection of endogenous WT1 mRNA, an important gene in progressive renal failure, from patients' urine. This technique could be a powerful tool in the search for information about glomerular damage in clinical settings as well as for WT1 mutations or isoform imbalance at the research level without renal biopsy.

Adult↗
PubMed1999

[Cilostazol increased heart rate with improvement of activity of daily living in an elderly patient with sick sinus syndrome].

An 86-year-old man had a history of hypertension and had been treated with calcium antagonist but no medications that could reduce heart rate. As a 12-lead electrocardiogram showed sinus bradycardia, complete right bundle branch block and left anterior fascicular hemiblock on his first visit to our hospital on January 1998, he was admitted to our hospital for further examination and treatment. A 24-hour Holter electrocardiogram demonstrated a total number of 74,182 heartbeats per day with pauses (> 2.0 sec) of 187/day. Overdrive atrial pacing study and His bundle electrogram revealed a prolonged corrected sinus node recovery time (5.820msec at a stimulation rate of 130/min) and H-V conduction time (80msec) with normal A-H conduction time, respectively. We diagnosed these abnormalities as sick sinus syndrome (Rubenstein II). His activity of daily living score was 30 points by the Barthel index on the day of admission. Oral administration of orciprenaline sulfate (30 mg/day), a beta-adrenoceptor agonist, was initially chosen rather than implantation of a cardiac pacemaker to increase his heart rate since he did not have any symptoms due to bradycardia and he did not give us an informed consent for the implantation. Orciprenaline sulfate, however, failed to increase total heartbeats (73,079/day). Then, oral cilostazol (100 mg/day), a phosphodiesterase III inhibitor, was administered. After two weeks of the regimen total heart beats were increased (85,642/day) with no pauses. The increase in heart rate resulted in the improvement of his activity of daily living (Barthel index: 55 points). Cilostazol could be the first line medication for elderly patients with bradyarrhythmia in whom implantation of cardiac pacemaker is not absolutely indicated.

Activities of Daily Living↗
PubMed1999

Mutations of the WT1 gene in childhood nonlymphoid hematological malignancies.

The Wilms' tumor gene WT1, whose loss of function accounts for the genesis of about 10% of Wilms' tumors, is expressed in hematopoietic stem cells and leukemia. By analogy with the relationship between the kidney stem cell and Wilms' tumor, it is probable that WT1 is mutated in leukemia. WT1 mutations have been found in only eight cases of primary leukemia, mainly in acute myeloid leukemia (AML) and rarely in acute lymphoblastic leukemia. However, two other studies have demonstrated the absence of WT1 mutations in leukemia. To determine if WT1 mutations are associated with leukemias, we screened childhood nonlymphoid malignancies for WT1 mutation. WT1 mutations were found in 6 of 46 (13%) AMLs, but not in other nonlymphoid hematological malignancies. In addition, the presence of WT1 mutations in AML caused by chromosomal translocations suggests that mutations of WT1 may lead to the progression of leukemia.

Child↗
PubMed1998

c-Cbl is tyrosine-phosphorylated by interleukin-4 and enhances mitogenic and survival signals of interleukin-4 receptor by linking with the phosphatidylinositol 3'-kinase pathway.

Interleukin-4 (IL-4) is a cytokine that induces both proliferation and differentiation and suppresses apoptosis of B cells. Although IL-4 has been shown to activate the phosphatidylinositol 3' (PI3)-kinase pathway, the role of PI3 kinase in the IL-4 receptor (IL-4R) signaling remains unclear. In this study, we demonstrated that c-Cbl proto-oncogene product is inducibly phosphorylated on tyrosine residues and is associated with the p85 subunit of PI3-kinase by IL-4 stimulation. Overexpression of c-Cbl enhances the PI3-kinase activity and, at the same time, mitogenic activity and survival of cells in the presence of IL-4. However, these effects of c-Cbl were abolished by wortmannin, a specific inhibitor for the PI3 kinase pathway, or by a point mutation at tyrosine 731 of c-Cbl, which is a major binding site for p85. These results indicate that c-Cbl plays a role in linking IL-4R with the PI3 kinase pathway and thus enhancing the mitogenic and survival signals.

Androstadienes↗
PubMed1998

Genetic instability and cancer.

It is well known that defects in some aspects of DNA metabolism including telomere maintenance, nucleotide excision repair and mismatch repair contribute to tumor development. However, to account for the multiple mutations observed in cancer cells, the new fields of DNA metabolism that maintain genome integrity must be determined. I will show four new aspects of genetic instability that have recently emerged which helps toward the understanding of the links between defects in genome integrity and tumor development. First, mutations in DNA helicase genes cause rare genetic instability syndromes, suggesting that defects in DNA helicase activities are responsible for predispositions to cancers. Second, mutations of the gene for ataxia-telangiectasia in sporadic leukemias suggest that genes involved in rare syndromes are paradigms for understanding the mechanism underlying the genesis of sporadic tumors. Third, since the emergence of a link between breast cancer susceptibility gene products and RAD51, great interest has been shown in recombinational repair. Finally, a mutator phenotype is conditional in some mismatch-repair deficient cells, proposing that cancer arises under restrictive conditions even though stability genes are mutated.

DNA Helicases↗
PubMed1998

In vitro modulation of primate coronary vascular muscle cell reactivity by ovarian steroid hormones.

Susceptibility to drug-induced coronary vasospasm in rhesus monkeys increases after removal of the ovaries and can be normalized by adding back physiological levels of estradiol-17ss (E2) and/or natural progesterone (P) in vivo as reported recently by our group. Furthermore, the reactivity status (Ca2+ and protein kinase C responses) of freshly isolated and primary culture coronary artery vascular muscle cells (VMC) mimic the intact coronary artery responses to 5-HT + U46619. Since coronary reactivity is maintained in the isolated VMC, we hypothesized that the reactivity state inherent in the VMC was modulated directly by ovarian steroids in vitro as in the whole animal. To test this hypothesis, we treated hyperreactive VMC from ovariectomized (ovx) monkeys in vitro with E2 or P and measured VMC reactivity to combined stimulation with 5-HT and U46619, as determined by the amplitude and especially the duration of intracellular Ca2+ signals, as well as protein kinase C (PKC) activation/translocation. VMC were treated for 12 96 h with 3 100 pg/ml E2 (10 365 pM) and/or 0.3 3 ng/ml P (0.95 9.5 nM). Hyperreactive responses to the combination of 5-HT and U46619 in untreated VMC were significantly and dose-dependently reduced by treatment in vitro with physiological levels of either E2 or P for at least 24 h. Both the early transient and late sustained increases in intracellular Ca2+ and PKC translocation were blunted, and the effects of 0.2 nM E2 and 3.2 nM P were specifically antagonized by the receptor blockers ICI 182,780 (200 nM) and RU486 (15 nM), respectively. Antibodies to the estrogen receptor and progesterone receptor labeled nuclei in VMC, which were also positively labeled by a smooth muscle myosin heavy chain monoclonal antibody. These data indicate that natural ovarian steroids directly reduce hyperreactive 5-HT and thromboxane A2-stimulated Ca2+ and PKC responses of coronary artery VMC from surgically menopausal rhesus macaques. We hypothesize that vascular hyperreactivity, which may be a critical factor involved in the increased incidence of coronary artery vasospasm and ischemic heart disease in postmenopausal women, can be normalized by E2 and/or P through direct actions on coronary artery vascular muscle cells.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗