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Biomedical subjects

H Okayama

Publications and source records attributed to H Okayama.

At least 73 records · Page 4Linked to original sources
PubMed1996

Role of a signal transduction pathway which controls disassembly of microfilament bundles and suppression of high-molecular-weight tropomyosin expression in oncogenic transformation of NRK cells.

Role of disassembly of microfilament bundles and suppression of high-molecular-weight tropomyosin (TM) expression in growth factor- and various oncogene-induced transformation was studied by using NRK cells and its transformation-deficient mutants. In NRK cells which show a transformed phenotype by treatment with EGF and TGF-beta, cellular stress fibers became dissociated by EGF or EGF and TGF-beta combination, whereas TGF-beta alone caused thicker appearance of stress fibers. Accompanying these changes, the expression of TM isoforms 1 and 2 was suppressed by treatment with EGF or EGF and TGF-beta, but elevated by TGF-beta with similar time courses. On the other hand, the transformation-deficient mutant cell lines, 39-1 and 39-3, did not show the transformed phenotypes by treatment with EGF and TGF-beta. Neither EGF nor EGF and TGF-beta combination affected cellular stress fibers and expression of TM isoforms 1 and 2 in both mutant lines. The relationship between the formation of stress fibers and the expression of TM isoforms was consistent in NRK cells, the mutant lines and their various oncogene-expressing sublines under various culture conditions. NRK cells overexpressing exogenous mouse TM isoform 2 showed markedly decreased susceptibility to EGF-induced dissociation of stress fibers and decreased anchorage-independent growth potential in the presence of EGF and TGF-beta. These results indicate that the transformation-deficient NRK mutant lines, 39-1 and 39-3 have defects in an EGF signal transduction pathway which induces suppression of high-molecular-weight TM expression and disassembly of microfilament bundles and suggested that the activation of the pathway is important for morphological transformation and oncogenic growth in growth factors- and various oncogene-induced transformation of NRK cells.

Actin Cytoskeleton↗
PubMed1996

Stress signal, mediated by a Hog1-like MAP kinase, controls sexual development in fission yeast.

We identified the phh1+ gene that encodes a MAP kinase as the effector of Wis1 MAP kinase kinase in fission yeast, which is highly homologous with HOG1 of S. cerevisiae. Heterothalic phh1 dsiruptant is phenotypically indistinguishable from wis1 deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a variety of stress. In phh1 disruptant, nitrogen starvation-induced expression of ste11+, a key controller of sexual differentiation, is markedly diminished. Ectopic expression of ste11+ effectively restores fertility, but not stress resistance, to the phh1 disruptant. These data show that stress signal, mediated by a MAP kinase, is required for efficient start of sexual differentiation.

Amino Acid Sequence↗
PubMed1996

Alteration of atrial natriuretic peptide and brain natriuretic peptide gene expression associated with progression and regression of cardiac hypertrophy in renovascular hypertensive rats.

1. We assessed the changes of atrial natriuretic peptide and brain natriuretic peptide gene expression associated with progression and regression of cardiac hypertrophy in renovascular hypertensive rats (RHR). 2. Two-kidney, one-clip hypertensive rats (6-week-old male Wistar) were made and studied 6 (RHR-1) and 10 weeks (RHR-2) after the procedure. Regression of cardiac hypertrophy was induced by nephrectomy at 6 weeks after constriction, and the nephrectomized rats were maintained further for 4 weeks (nephrectomized rat: NEP). Sham operation was performed, and the rats were studied after 6 (Sham-1) and 10 weeks (Sham-2). Atrial natriuretic peptide and brain natriuretic peptide gene expression in the left ventricle was analysed by Northern blotting. 3. Plasma atrial natriuretic peptide and brain natriuretic peptide were significantly higher in RHR-1 and RHR-2 than in Sham-1, Sham-2 and NEP. Atrial natriuretic peptide and brain natriuretic peptide mRNA levels in RHR-1 were approximately 7.2-fold and 1.8-fold higher than those in Sham-1, respectively, and the corresponding levels in RHR-2 were 13.0-fold and 2.4-fold higher than those in Sham-2, respectively. Atrial natriuretic peptide and brain natriuretic peptide mRNA levels of NEP were normalized. Levels of atrial natriuretic peptide and brain natriuretic peptide mRNA were well correlated positively with left ventricular weight/body weight ratios. There was a significant positive correlation between the levels of atrial natriuretic peptide and brain natriuretic peptide mRNA (r = 0.86, P < 0.01). 4. We conclude that the expression of atrial natriuretic peptide and brain natriuretic peptide genes is regulated in accordance with the degree of myocardial hypertrophy and that the augmented expression of these two natriuretic peptides may play an important role in the maintenance of cardiovascular haemodynamics in renovascular hypertension.

Animals↗
PubMed1996

Domains determining the functional distinction of the fission yeast cell cycle "start" molecules Res1 and Res2.

In Schizosaccharomyces pombe the "start" of the cell cycle is regulated by two parallel, functionally overlapping complexes composed of Res1-Cdc10 and Res2-Cdc10. Res1 and Res2 are structurally very homologous and are required for the start of the mitotic and meiotic cycle, respectively. We have addressed the question which parts of the proteins are essential for function and determine the functional specificity. Several discrete domains in the nonconserved C-terminal region are essential for the mitotic and meiotic start function and determine the functional specificity independently of the structurally conserved motifs at the N-terminal end and in the center. One of these domains in Res2 restricts Res2 to interact only with Rep2. Res2 without this domain behaves like a functional chimera having the properties of Res2 and Res1. Likewise, internally truncated forms of Res1 lacking the centrally located ankyrin repeats and adjacent sequences can partially suppress the meiotic defect in res2- cells. These truncated Res1 molecules behave like functional chimeras with the properties of Res1 and Res2.

Amino Acid Sequence↗
PubMed1996

[Familial hypertrophic cardiomyopathy generating a marked left ventricular pressure gradient in an 82-year-old woman].

Familial nonobstructive hypertrophic cardiomyopathy in 78-year-old woman was diagnosed in 1988. Since then she has been treated with a beta-blocking drug and a calcium antagonist. Her clinical condition was NYHA I or II for several years. Echocardiography revealed asymmetric septal hypertrophy in 1988 (interventricular septal thickness = 21 mm, posterior wall thickness = 10 mm). Systolic anterior motion of the mitral valve was first observed at the end of 1992. The left ventricular pressure gradient also gradually increased; it was about 138 mmHg in 1993 (age 82 yrs). The left ventricular ejection time index increased from 376 msec in May, 1992 to 459 msec in May, 1994. In September, 1994, the patient's condition gradually deteriorated (NYHA IV), and she was admitted to our hospital. To attenuate the left ventricular pressure gradient, 150 mg of disopyramide was administered. Her condition markedly improved: the left ventricular pressure gradient decreased from 180 mmHg to 76 mmHg, and the left ventricular ejection time index decreased from 485 msec to 419 msec. These results indicate that a left ventricular pressure gradient can be generated rapidly even in a very old patient, and that disopyramide may be useful to attenuate the left ventricular pressure gradient.

Aged↗
PubMed1996

[A 66-year-old woman with a patent ductus arteriosus and no significant progression of pulmonary arterial pressure over 17 years].

We report the case of a 66-year-old woman with a patent ductus arteriosus and no significant progression of pulmonary arterial pressure over 17 years. She was admitted to our hospital in 1978 because of palpitations on exertion and chest discomfort. Cardiac catheterization was done, and she was given a diagnosis of patent ductus arteriosus. Because the left-to-right shunt was small (15%) and because there was no evidence of pulmonary hypertension (38/18 mmHg), she was treated medically. In 1995 she was admitted again, to determine the cause of a cerebral infarction. The cerebral infarction was believed to have been caused by an embolism due to atrial fibrillation. She underwent cardiac catheterization again. The left-to-right shunt had increased to 41%, but the pulmonary artery pressure had not changed (27/14 mmHg). Intravascular ultrasound imaging was used to evaluate the ductus arteriosus. The diameter of the ductus was 4.4 mm and calcification was not observed. During the 17 years of follow-up, heart size increased slightly, but pulmonary artery pressure did not change. In addition, intravascular ultrasound was very useful for evaluating the condition of the ductus arteriosus.

Aged↗
PubMed1996

[Genotypes of cystic fibrosis (CF) reported in the world and polymorphisms of cystic fibrosis transmembrane conductance regulator (CFTR) gene in Japanese].

Cystic fibrosis (CF) is a common autosomal recessive genetic disorder in Caucasians. Since identification of the gene responsible for CF in 1989, over 400 sequential alterations of the CFTR gene have been tabulated by the CF Genetic Analysis Consortium. However, except for the delta F508 mutation, which occurs in approximately 70% of CF chromosomes, the worldwide frequency of most mutations in this gene is less than 1%. In Orientals and African blacks, CF is very rare. In Japanese only 100 cases have been reported. A few genotypes of these cases have been analyzed but no delta F508 or other mutations were found. We have analyzed mutations of the CFTR gene in Japanese with diffuse panbronchiolitis (DPB), which is found only in Orientals and shares pathologic and clinical characteristics with mild adult CF. However, no significant mutation of the CFTR gene was identified in this series. This suggests a different etiological background from that of CF.

Asian People↗
PubMed1995

Cloning of cDNA for rat eosinophil major basic protein.

We have determined the complete nucleotide sequence for the cDNA encoding rat eosinophil major basic protein (MBP) using the rapid amplification of cDNA ends (RACE) procedure. The deduced amino acid sequence revealed that the rat prepro-MBP has three functional domains, namely the signal peptide, the acidic peptide that contains numerous acidic amino acids, and the mature MBP, as in human and guinea pig MBP.

Amino Acid Sequence↗
PubMed1995

Fission yeast Rep2 is a putative transcriptional activator subunit for the cell cycle 'start' function of Res2-Cdc10.

In the yeast cell cycle 'start' requires sets of the Cdc10/ SWI family of transcriptional factors which activate the MCB cis elements contained in genes essential for S phase progression. Fission yeast possess two such overlapping systems, Res1-Cdc10 and Res2-Cdc10, both of which act to start the mitotic and meiotic cycles. We have recently isolated rep2+ as a multicopy suppressor of a temperature-sensitive cdc10 mutant which encodes a zinc finger protein. Here we show that the Rep2 zinc finger protein is an essential component of the active Res2-Cdc10 transcriptional regulator complex and likely to play a role in the control of cell cycle 'start'. Our data suggest that Rep2 is a transcriptional activator subunit which interacts with the MCB binding subunit complex formed by Res2 and Cdc10.

Amino Acid Sequence↗
PubMed1995

Requirement for tyrosine phosphorylation of Cdk4 in G1 arrest induced by ultraviolet irradiation.

Exposure to ultraviolet light arrests the function of mammalian fibroblasts in the G1 phase of the cell cycle, as well as the S and G2 phases. Although p21, an inhibitor of cyclin-dependent kinase (Cdk) that is induced by DNA damage may partly account for the arrest in G1 (ref. 1), the mechanism is little understood. Here we show that tyrosine phosphorylation of Cdk4 is required for this arrest. In rat fibroblast, Cdk4 is tyrosine-phosphorylated during G1 progression, and its dephosphorylation is required for S phase. When cells are ultraviolet-irradiated, their arrest in G1 is accompanied by an increase in phosphorylation level. Conversely, cells expressing unphosphorylatable Cdk4F17 fail to arrest in G1, and suffer significantly elevated chromosomal aberrations and cell death.

Animals↗
PubMed1995

A kinase from fission yeast responsible for blocking mitosis in S phase.

In virtually all eukaryotes, mitosis starts after the completion of DNA synthesis. This orderly process is ensured by the checkpoint mechanism that blocks the onset of mitosis while DNA is being synthesized or is damaged. In the fission yeast Schizosaccharomyces pombe, this mechanism involves some rad+ and hus+ genes. However, it is not known how the checkpoint system monitors these events. Recently a multicopy suppressor of a temperature-sensitive DNA polymerase-alpha mutant was isolated. This gene, named cds1+ (checking DNA synthesis), encodes a typical protein kinase. Here we report that this protein kinase is a key component of the DNA replication-monitoring S/G2 checkpoint system. Our data suggest that its primary role is to monitor DNA synthesis by interacting with DNA polymerase alpha and send a signal to block the onset of mitosis while DNA synthesis is in progress.

Amino Acid Sequence↗
PubMed1995

Localization of histamine N-methyltransferase messenger RNA in human nasal mucosa.

BACKGROUND: Histamine is metabolized mainly by histamine N-methyltransferase (HMT) to N tau-methylhistamine in human nasal mucosa. Human HMT cDNA has been cloned and expressed in COS cells. The purpose of this study was to determine the localization of HMT METHODS: The fragment (nucleotide residues 430-1055) of human HMT cDNA was subcloned in a Bluescript vector (Stratagene, La Jolla, Calif.), and HMT sense anti-sense RNA probes were made with T7 and T3 RNA polymerases. In situ hybridization with digoxigenin-labeled RNA probes was performed on surgical specimens of human nasal turbinates. RESULTS: HMT mRNA was localized in cells in the epithelium and submucosa, and densely in endothelial cells of vessels. No HMT mRNA was identified in the submucosal glands. The presence of HMT mRNA was confirmed by Northern blot analysis, and HMT activities were also detected in nasal mucosa. CONCLUSION: Our study indicates that endothelium expresses HMT mRNA, whereas cells in the epithelium and submucosa, which remain unidentified, are an additional source of HMT mRNA.

Blotting, Northern↗
PubMed1995

Liver fructose-1,6-bisphosphatase cDNA: trans-complementation of fission yeast and characterization of two human transcripts.

The SV40 early promoter is active both in mammalian cells and in the fission yeast Schizosaccharomyces pombe, and is used to drive full-length cDNA in polyvalent pcD-libraries. Two such liver libraries, of human and rat origin, were used to trans-complement a S. pombe mutant deficient in fructose-1,6-bisphosphatase (Fru-1,6-Pase) activity, a key gluconeogenic enzyme restricted to liver, kidney and intestine in mammals. A rat liver Fru-1,6-Pase cDNA was readily cloned and sequenced. Complementary PCR experiments revealed full-length Fru-1,6-Pase cDNA also present in the human liver library, however at a low abundance. Two human liver transcripts were thus characterized. Contrary to expectation, they were not differentially spliced products. They both encoded the same protein and were generated by a polyadenylation choice mechanism. The longest transcript comprised two polyadenylation signals and a consensus GT-rich element for the 3' processing of the upstream site. Rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) analysis of 3' ends from hepatic, renal and intestinal mRNA disclosed that both Fru-1,6-Pase transcripts are expressed in the three main gluconeogenic cell types and are subject to insulin differential modulation. On the other hand, overcoming liver cell heterogeneity problems, sequence analysis of 16 independent clones of 3' end-cDNA demonstrated that, in addition to a monocytic type corresponding to a previously described lambda gt11 clone, human liver does not contain a hepatic type Fru-1,6-Pase comprising a liver-specific carboxyl-terminal extension like its rat counterpart. This liver-specific extension is involved in enzyme up-regulation and appears to give a conclusive advantage to the rat hepatic enzyme over the human one when trans-complementing mutant yeast.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

The G1/S boundary-specific enhancer of the rat cdc2 promoter.

Multiple species of G1 cyclins and cyclin-dependent kinases are induced sequentially during G1 phase, and the expression of cyclin A and cdc2 genes is subsequently induced at the G1/S boundary. To analyze the mechanism of cdc2 promoter activation, the 5'-flanking region of the rat cdc2 gene was isolated and its structural features were characterized. The highly conserved sequence between human and rat cdc2 genes is present in the basal promoter region from positions -183 to -122, which contains the E box, SpI, and E2F motifs. The expression of 5' sequential deletion derivatives of the promoter fused to luciferase cDNA in rat 3Y1 cells revealed the presence of the enhancer element. The presumed enhancer region was further analyzed by the introduction of base substitutions and by the formation of DNA-protein complexes with cell extracts prepared at various times during the G1-to-S-phase progression. These analyses revealed that the enhancer sequence, AAGTTACAAATA, located from -276 to -265, confers strong inducibility on the basal promoter at the G1/S boundary. The base substitutions introduced into the motifs of transcription factors indicated that the E2F motif is essential for the enhancer-dependent activation of the cdc2 promoter at the G1/S boundary. Electrophoretic mobility shift assays and DNase I footprinting showed that a factor which interacts with the enhancer element is induced late in G1 phase.

Animals↗
PubMed1995

Relation between postpacing T wave changes and myocardial scintigraphic characteristics in patients with ventricular demand pacemaker.

The aim of this study was to elucidate the cause of T wave changes after ventricular pacing using thallium 201 single photon emission computed tomography (Tl-SPECT). Tl-SPECT was performed in 20 patients with sick sinus syndrome who had negative T wave after ventricular pacing and had had a ventricular demand pacemaker (VVI) implanted. Patients who have stenotic coronary arteries were excluded from the study. From the analysis of Tl-SPECT, extent score was calculated as the ischemic region. Data in patients with SSS were compared with those in 20 normal controls (NC). Thallium perfusion defects in patients with VVI were observed and distributed mainly in apex and inferior regions on the polar map. The extent score in patients with VVI was significantly higher than that in NC (56.4 +/- 21.6% vs 3.2 +/- 6.4%, P < 0.01). The washout rate of thallium 201 in the defect area was significantly lower in patients with VVI than in NC (27.4 +/- 10.2% vs 46.8 +/- 12.3%, P < 0.01). These results suggest that T wave changes after ventricular pacing are closely related to myocardial ischemia.

Aged↗
PubMed1995

[Influence of aging upon changes in symptoms and cardiac size associated with surgical repair of atrial septal defect in adults].

To elucidate the influence of aging upon the improvement of symptoms and cardiac size associated with surgical repair of atrial septal defect, clinical symptoms, cardiothoracic ratio and hemodynamic variables in older patients (group A; age at operation > or = 50 years old, n = 11) were compared with those in younger patients (group B; age at operation < 50 years old, n = 8). There were no differences in hemodynamic variables, i.e., peak systolic pulmonary pressure, pulmonary to systolic flow ratio (Qp/Qs), pulmonary to systolic vascular resistance ratio (Rp/Rs) and left to right shunt ratio between the two groups. Symptomatic benefits occurred in all patients, although 3 patients in group A who had atrial fibrillation preoperatively still displayed symptoms such as exertional dyspnea. The postoperative (after 3 months) cardiothoracic ratio improved in all patients except for 3 patients in group A who were operated at over 60 years of age. Although there was no significant difference in preoperative cardiothoracic ratio between the two groups, the postoperative cardiothoracic ratio in group B was significantly smaller than that in group A. These results indicate that operative closure of atrial septal defect is recommended for all patients aged 50 years old or older, but early improvement of symptoms and cardiomegaly in older patients is lower than that in younger patients.

Adult↗