Biomedical subjects

R Sakai

Publications and source records attributed to R Sakai.

At least 91 records · Page 5Linked to original sources

PubMed1995

A new polyether acid from a cold water marine sponge, a Phakellia species.

A new polyether acid, 14, 15-dihydrodinophysistoxin-1 [1], was isolated along with dinophysistoxin-1 [2] and okadaic acid [3], from an unidentified species of the sponge genus Phakellia. The structure of 1 was assigned by comparison of its 1H- and 13C-nmr and fabms spectral data to those of 2 and 3, as well as interpretation of homonuclear 2D nmr data. Compounds 1-3 showed cytotoxicity against L-1210 leukemia cells with IC50 values of 3 ng/ml. The isolation, structure determination, and biological activities of these compounds are described (1).

Animals↗

PubMed1995

Kinetics of frequency-dependent conduction delay by class I antiarrhythmic drugs in human atrium.

We investigated use-dependent prolongation of interatrial conduction time (IACT) by class I antiarrhythmic drugs in 16 patients. Changes in IACT at the initiation of atrial pacing were used to evaluate the onset kinetics. We examined recovery kinetics by giving a single extra stimulus with a varying coupling interval after discontinuing train stimulation. Time constants of the onset kinetics were 1.52 +/- 0.15/n(fast) and 0.087 +/- 0.031/n(slow) for mexiletine, 0.075 +/- 0.015/n for aprindine, 0.078 +/- 0.019/n for disopyramide, and 0.050 +/- 0.006/n for pilsicainide. The recovery time constants were 203 +/- 66 ms for mexiletine, 1,021 +/- 162 ms for aprindine, 993 +/- 101 ms for disopyramide, and 2,930 +/- 569 ms for pilsicainide. Class I antiarrhythmic drugs produced use-dependent IACT prolongation in humans, with characteristic kinetics for each agent similar to that of depression of the maximum upstroke velocity of cardiac action potential (Vmax) reported in in vitro studies.

Anti-Arrhythmia Agents↗

PubMed1995

Frequent loss of the cyclin-dependent kinase-4 inhibitor gene in human gliomas.

Studies have shown that homozygous deletion of the cyclin-dependent kinase-4 inhibitor (CDK4I) gene, which is mapped to chromosome 9p21, is frequently observed in various types of human cancers. Here we report that the CDK4I gene was deleted in gliomas. Eight cell lines derived from glioblastomas and samples from 14 patients with various grades of gliomas were examined by Southern blot analysis. We found that the CDK4I gene was deleted in 7 of 8 (87.5%) cell lines and 7 of 9 (78%) samples from high-grade glioma patients, whereas it was deleted in 1 of 5 (20%) low-grade glioma samples. These results suggested that inactivation of the CDK4I gene may play an important role in the progression of human glioma.

Adolescent↗

PubMed1995

Occurrence of acute megakaryoblastic leukemia in a patient with idiopathic growth hormone deficiency.

We describe a case of a 15 year old boy who developed acute megakaryoblastic leukemia (AMKL) while receiving treatment with human growth hormone (hGH) for idiopathic growth hormone deficiency (GHD). He was diagnosed as having idiopathic GHD and given hGH from December 1991. The examination of his peripheral blood showed mild pancytopenia 2 months before the start of the hGH therapy. Since January 1992, paleness of the skin, general fatigue and fervescence progressed gradually. In February 1992, because of the occurrence of acute leukemia, administration of hGH was discontinued. Judging from the results of surface marker analysis of the blast cells, the patient was diagnosed as having AMKL. He was treated with chemotherapy for acute non-lymphoblastic leukemia from March 1992. A complete remission was obtained after 4 weeks of treatment. The chemotherapy was completed in July 1993. He remains in complete remission 26 months after diagnosis. This case suggests the importance of hematological examination and, when there is any abnormality which is not caused by GHD, such as pancytopenia, more detailed medical examinations (for example bone marrow examination) are necessary.

Child↗

PubMed1995

Of the GATA-binding proteins, only GATA-4 selectively regulates the human interleukin-5 gene promoter in interleukin-5-producing cells which express multiple GATA-binding proteins.

Interleukin-5 (IL-5) is produced by T lymphocytes and known to support B-cell growth and eosinophilic differentiation of the progenitor cells. Using ATL-16T cells which express IL-5 mRNA, we have identified a region within the human IL-5 gene promoter that regulates IL-5 gene transcription. This cis-acting sequence contains the core binding motif, (A/T)GATA(A/G), for GATA-binding family proteins and thus suggests the involvement of this family members. In this report, we describe the cloning of human GATA-4 (hGATA-4) and show that hGATA-4 selectively interacts with the -70 GATA site within the IL-5 proximal promoter region. By promoter deletion and mutation analyses, we established this region as a positive regulatory element. Cotransfection experiments revealed that both hGATA-4 and phorbol-12-myristate-13-acetate (PMA)-A23187 stimulation are necessary for IL-5 promoter activation. The requirement for another regulatory element called CLE0, which lies downstream of the -70 GATA site, was also demonstrated. ATL-16T cells express mRNAs of three GATA-binding proteins, hGATA-2, hGATA-3, and hGATA-4, and each of them has a potential to bind to the consensus (A/T)GATA(G/A) motif. However, using ATL-16T nuclear extract, we demonstrated that GATA-4 is the only GATA-binding protein that forms a specific DNA-protein complex with the -70 GATA site. An electrophoretic mobility shift assay with extracts of COS cells expressing GATA-binding proteins showed that GATA-4 has the highest binding affinity for the -70 GATA site among the three GATA-binding proteins. When the transactivation abilities were compared among the three, GATA-4 showed the highest activity. These results demonstrate the selective role of GATA-4 in the transcriptional regulation of the IL-5 gene in a circumstance where multiple members of the GATA-binding proteins are expressed.

Amino Acid Sequence↗

PubMed1995

Effects of alkyl substituents of xanthine on phosphodiesterase isoenzymes.

The structure-activity relationships of a series of alkylxanthine derivatives were investigated. The partition coefficient of alkylxanthines enlarged with an elongation of the alkyl chain at the 1-, 3-, or 7-position of xanthine. There was a mild correlation between the apparent partition coefficient and the tracheal relaxant activity or the inhibitory activity on phosphodiesterase (PDE) IV isoenzyme, while the tracheal relaxant activity closely correlated with the PDE IV inhibitory activity. Regarding substituents at different positions, the alkylation at the 3-position increased the inhibitory activity on every PDE isoenzyme. The alkylation at the 1-position potentiated the inhibitory activity on PDE IV with the alkyl chain length, but decreased the activities on other PDE isoenzymes. The alkylation at the 7-position was characteristic in its decrease in inhibitory activity on PDE III. These results suggested that the potency of the inhibitory activity of xanthine derivatives on PDE isoenzymes is not dependent simply upon their hydrophobicity but upon change in the affinity for the active sites on PDE isoenzymes by the introduction of the alkyl group at particular positions of the xanthine skeleton.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1995

Evaluation of repeated balloon inflation in angioplasty as a clinical model of ischemic preconditioning.

Reevaluation of repeated balloon angioplasty as a model of ischemic preconditioning and of the role of collateral circulation and high-frequency electrocardiograms in repeated inflations was carried out. There have been few studies using angioplasty as a model of ischemic preconditioning of the collateral circulation during repeated inflations or of the use of high-frequency electrocardiograms during angioplasty. Twenty patients underwent 3 repeated balloon inflations, each with a duration of more than 138 seconds. During inflation, ipsilateral and contralateral coronary angiography and signal-averaged electrocardiography were performed. At the 1st inflation, the ST segment gradually increased as the inflation time elapsed. During the 2nd and 3rd inflations, in which ST elevation was nearly equal, the ST segment gradually increased, but it was not as prominent as that at the 1st inflation; thus, the concept that ischemia is gradually ameliorated (adaptation to ischemia) was not documented. Comparison of the maximal ST elevation and ipsilateral and contralateral circulation at each inflation revealed that the ST segment became elevated and the contralateral collateral circulation increased significantly at the 1st inflation compared with those in the control. ST elevation, however decreased significantly and collateral circulation remained unchanged at the 2nd inflation; thus, collateral circulation did not cause the ST elevation decrease. The total root mean square voltage detected by signal averaging decreased significantly only at the 1st inflation. Balloon angioplasty is not always suitable as a model of ischemic preconditioning and collateral circulation is not the cause of ischemic preconditioning.

Aged↗

PubMed1995

[Autopsy cases of cytomegalovirus interstitial pneumonitis following bone marrow transplantation].

We investigated the relevance of cytomegalovirus (CMV) to interstitial pneumonitis (IP) using formalin-fixed and paraffin-embedded lung tissues obtained from 12 autopsy cases who died following bone marrow transplantation (BMT) from May 1985 to March in 1992. The lung tissues were examined by hematoxylin and eosin (H.E.) staining, immunohistochemistry with monoclonal antibodies (DDG9, CCH2) and polymerase chain reaction (PCR) for amplifying human CMV DNA. Eight of 12 cases were clinically diagnosed as IP. The 4 cases showed no signs of IP, and their tissues were used as controls. H.E. staining revealed inclusion bodies in two of the eight and only severe fibrosis in the other six. In 4 of the 6 cases, however, CMV was identified by immunohistochemistry or PCR. We concluded that the relevance of CMV in the genesis of IP is often overlooked by H.E. staining alone. Immunohistochemistry and PCR are useful in examining tissues which are suspected of CMV-IP.

Adolescent↗

PubMed1995

Successful pregnancy after allogeneic bone marrow transplantation following conditioning with total body irradiation.

A 23-year-old woman had a normal full-term delivery 78 months after BMT for ALL. Conditioning therapy was Ara C 1.4 g/m2 x 4, CY 60 mg/kg x 2 and TBI 2.5 Gy x 5 at a dose rate of 3.5 cGy/min. Despite GVHD prophylaxis with short-term MTX and CsA, she developed grade I acute GVHD, but showed no evidence of chronic GVHD. Following amenorrhea for 4 years, menstruation recommenced spontaneously. She had a normal pregnancy 6 years after BMT resulting in a healthy infant with simple hypospadias. This and previous reports indicate that normal pregnancy is possible after BMT with TBI in excess of 10 Gy.

Acute Disease↗

PubMed1995

[Hypoplastic leukemia achieved long-term remission with low-dose cytosine arabinoside].

A 74-year-old woman was admitted in October 1988 with anemia and leukocytopenia. Hematologic investigations established a diagnosis of hypoplastic acute leukemia. She received a low dose of cytosine arabinoside (LDAC: 10 mg/m2 every 12 hours) subcutaneously for 21 days and achieved complete remission (CR) one month later. After one course of LDAC of 14 days, she received LDAC of 21 days every 5 to 6 months as maintenance therapy till April 1993. She has been in remission for 6 years. Intensification therapy with LDAC every 5 to 6 months might be useful in maintaining remission for hypoplastic acute leukemia.

Aged↗

PubMed1995

[Treatment for elderly patients with acute non-lymphocytic leukemia].

A retrospective analysis was performed on forty nine elderly (34 males and 15 females) patients aged 65 years or more (median age 73, range 65-82) with acute non-lymphocytic leukemia (ANLL). Patients were studied to examine factors according to age group (65-69 years, 70-74, 75-79 and 80 or over), respectively. Patients were treated with either low dose Ara-C therapy or BHAC-DMP therapy according of the choice of their attending physicians. Complete remission (CR) was obtained in 20 of 49 patients (43%), and in 6 of 14 patients (43%) aged 65-69, in 8 of 18 (44%) aged 70-74, in 5 of 12 (42%) aged 75-79 years and in 1 of 3 (33%) aged 80 or over, respectively. The median survivals of these groups were 263, 298, 260, 168.5 and 38.5 days, respectively. Multivariate analysis revealed that the achievement of CR was associated with normal karyotype, and serum GOT level < or = 30 mu/ml and GPT < or = 40 mu/ml. Prolonged survival was related to the achievement of CR. The results indicated that liver function before chemotherapy was an important prognostic factor.

Age Factors↗

PubMed1995

[Therapy related leukemia].

Eleven therapy related leukemias (TRL) who were hospitalized in the Department of Hematology and Chemotherapy, Kanagawa Cancer Center between October 1983 and December 1993 were identified. Six of the patients were males and five were females. Their median age was 62 years (range from 14 to 75). Three patients had previously received treatment for breast cancer and two patients for malignant lymphoma. The other patients had received treatment for lung cancer, urinary bladder cancer, gastric cancer, brain tumor, maxillary sinus cancer and macroglobulinemia, respectively. Seven patients had been treated with chemotherapy and four patients had been treated with chemotherapy and irradiation for the primary tumor. The TRL cases consisted of 8 acute non-lymphoid leukemias, two acute lymphoid leukemias and one hypoplastic leukemia, respectively. The status of primary tumors at the development of TRL was complete remission in ten patients and partial remission in one patient. Three of the 10 patients who received anti-leukemic therapy entered complete remission and the median survival time was 36 days (from 7 days to 489 days). One patient expired of pneumonia before he received anti-leukemic therapy. TRL patients showed poor response to chemotherapy and had poor prognosis. These data suggest that the use of reduced doses of carcinogenic drugs for primary tumors might be required to prevent the development of TRL.

Adolescent↗

PubMed1994

Characterization, partial purification, and peptide sequencing of p130,the main phosphoprotein associated with v-Crk oncoprotein.

The transforming gene v-crk found in CT10 and ASV-1 avian sarcoma viruses induces marked phosphorylation of several proteins in cells expressing p47v-crk (v-Crk). In this work, the main tyrosine-phosphorylated proteins in ASV-1-infected chicken cells and v-crk-transfected rat cells were characterized biochemically. Both these proteins have a molecular mass of about 130 kDa and are tightly associated with v-Crk in vivo. Two-dimensional gel electrophoresis revealed that they are both essentially single proteins (p130) with modifications that result in a broad spot in an acidic region. The broad band of semi-purified p130 became sharp at an elevated position in the gel upon treatment with orthovanadate in vivo or with c-Src kinase produced using a baculovirus vector in vitro, whereas it shifted at a lower position upon treatment with alkaline phosphatase in vitro. These results suggest multiple phosphorylation states of p130, which result in a broad band of p130. Two procedures of immunoaffinity purification were used to purify p130 from 3Y1 cells transfected with v-crk. Approximately 30 pmol of purified p130 was obtained in an immobilized form on a filter starting from 3 x 10(10) cells. Peptide mapping of p130 digested in situ by peptidase revealed that the purity and quantity of the final material were enough for peptide sequencing. Several stretches of partial amino acid sequences were determined, and they indicated that p130 is a novel protein.

Amino Acid Sequence↗

PubMed1994

Molecular cloning and characterization of a cDNA for bovine phospholipase C-alpha: proposal of redesignation of phospholipase C-alpha.

We have isolated bovine phospholipase C (PLC)-alpha cDNA from bovine thymus. Sequence analysis showed that PLC-alpha is highly conserved among rat, mouse, and calf and that it has two Trp-Cys-Gly-His-Cys-Lys motifs completely conserved in the mammals. Southern blot analysis revealed that bovine PLC-alpha is derived from a single gene. When PLC-alpha cDNA was stably transfected in NIH3T3 cells, there was no increase in PLC activity. PLC-alpha is supposed to be a member not of PLC superfamily but of Trp-Cys-Gly-His-Cys-Lys motif-containing proteins consisting of protein disulfide isomerase, P5, ERp72, and thioredoxin. PLC-alpha should be redesignated ERp57 (ER-resided p57).

3T3 Cells↗

PubMed1994

Cyclic nucleotide phosphodiesterase isoenzymes in guinea-pig tracheal muscle and bronchorelaxation by alkylxanthines.

In this study the phosphodiesterase (PDE) isoenzymes in guinea-pig trachealis smooth muscle were separated by DEAE-Sepharose anion exchange chromatography, identified, and characterized. Furthermore the effect of theophylline and 1-n-butyl-3-n-propylxanthine (BPX) on the isolated PDE isoenzymes and on their tracheal relaxant effect were investigated and compared with the nonxanthine PDE inhibitors amrinone and Ro 20-1724. We identified five distinct isoenzymes in guinea-pig tracheal muscle; calcium/calmodulin-stimulated cyclic AMP PDE (PDE I), cyclic GMP-stimulated cyclic AMP PDE (PDE II), cyclic GMP-inhibited and amrinone-sensitive cyclic AMP PDE (PDE III), cyclic AMP-specific and Ro 20-1724-sensitive PDE (PDE IV), and cyclic GMP-specific PDE (PDE V). BPX strongly inhibited the PDE IV isoenzyme with high selectivity, while the inhibitory effect of theophylline was weak. The PDE IV inhibitors BPX and Ro 20-1724 synergistically increased the relaxant effect of the beta 2-adrenoceptor agonist salbutamol in carbachol-contracted trachea much more strongly than theophylline. In contrast, amrinone, a PDE III inhibitor, hardly influenced the relaxant effect of salbutamol, suggesting that the PDE IV isoenzyme is functionally associated with beta 2-adrenoceptors in guinea-pig trachea and that inhibition of this enzyme potentiates the ability of salbutamol to increase the intracellular cyclic AMP content. These results indicate that the PDE IV isoenzyme plays a significant role in alkylxanthine-mediated relaxation of guinea-pig trachea.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1994

A novel signaling molecule, p130, forms stable complexes in vivo with v-Crk and v-Src in a tyrosine phosphorylation-dependent manner.

p47v-crk (v-Crk), a transforming gene product containing Src homology (SH)-2 and -3 domains, induces an elevated level of tyrosine phosphorylation of several cellular proteins. Among these proteins, a 125-135 kDa protein (p130) shows marked phosphorylation at tyrosines and tight association with v-Crk, suggesting a direct signal mediator of v-Crk. Here we report the molecular cloning of rat p130 by immunoaffinity purification. The p130 is a novel SH3-containing signaling molecule with a cluster of multiple putative SH2-binding motifs of v-Crk. Immunochemical analyses revealed that p130 is highly phosphorylated at tyrosines during transformation by p60v-src (v-Src), as well as by v-Crk, forming stable complexes with these oncoproteins. The p130 behaves as an extremely potent substrate of kinase activity included in the complexes and it is a major v-Src-associated substrate of the Src kinase by partial peptidase mapping. Subcellular fractionation demonstrated that the cytoplasmic p130 could move to the membrane upon tyrosine phosphorylation. The p130 (designated Cas for Crk-associated substrate) is a common cellular target of phosphorylation signal via v-Crk and v-Src oncoproteins, and its unique structure indicates the possible role of p130Cas in assembling signals from multiple SH2-containing molecules.

Amino Acid Sequence↗

PubMed1994

Selective tracheal relaxation and phosphodiesterase-IV inhibition by xanthine derivatives.

The effects of substitutions in the xanthine nucleus on tracheal relaxant activity, atrium chronotropic activity, adenosine A1 affinity, and inhibitory activities on cyclic AMP-phosphodiesterase isoenzymes in guinea pigs were studied. Substitution with a long alkyl chain at the N1-position of xanthine nucleus increased the tracheal relaxant activity without leading to positive chronotropic action, and long alkyl chains at the N3-position increased both activities. N7-substitutions with n-propyl and 2'-oxopropyl groups, such as in denbufylline, increased bronchoselectivity. N7-substitution decreased the adenosine A1 affinity, but substitution at either the N1- or N3-position increased it. The bronchorelaxant activity of xanthine derivatives was closely correlated with their inhibition of phosphodiesterase-IV, but not with their adenosine A1 affinity; the positive chronotropic effects were related to their inhibition of phosphodiesterase-III. This study confirms that the bronchorelaxation of xanthine derivatives is mediated by inhibition of the isoenzyme phosphodiesterase-IV. The results of structure-activity analysis suggest that substitutions at the N1- and N7-positions should be tried in the development of xanthine derivatives that are selective bronchodilators and phosphodiesterase-IV inhibitors.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1994

Effects of E-4031 on atrial fibrillation threshold in guinea pig atria: comparative study with class I antiarrhythmic drugs.

The effects of E-4031, a new class III antiarrhythmic agent, on atrial fibrillation threshold (AFT), atrial effective refractory period (ERP), and interatrial conduction time (ACT) were investigated in Langendorff-perfused guinea pig hearts; the results were then compared with those of the class I agents disopyramide, procainamide, lidocaine, and flecainide. Whole guinea pig hearts were perfused with Tyrode's solution containing acetylcholine (ACh 3 x 10(-7) M). The three indexes were measured before and after administration of the test drugs, using right atrial extrastimulus and 50-Hz continuous stimulation. Disopyramide, procainamide, and flecainide (> or = 10(-6) M) significantly increased AFT. Although E-4031 (> or = 3 x 10(-6) M) also increased AFT, this effect was less potent than that observed with the other drugs. E-4031 (> or = 10(-6) M) significantly prolonged ERP, and this prolongation was less pronounced than that observed with disopyramide but similar to that observed with procainamide or flecainide. E-4031 did not affect ACT, and the greatest prolongation of ACT was observed with flecainide. Lidocaine had no effect on any of the indexes. These findings suggest that in guinea pig hearts E-4031 exerts an antifibrillatory effect by prolonging atrial ERP alone, but this effect is less pronounced than that observed with class I drugs, because AFT measured by 50-Hz continuous stimulation is influenced by both ERP and ACT.

Acetylcholine↗