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Biomedical subjects

K Hashimoto

Publications and source records attributed to K Hashimoto.

At least 739 records · Page 41Linked to original sources
PubMed1996

Angiotensin II-induced renal responses in anesthetized rabbits: effects of N omega-nitro-L-arginine methyl ester and losartan.

Intrarenal arterial infusion of angiotensin II (4 ng/kg/min) reduced renal blood flow, glomerular filtration rate and urinary Na+ excretion (UNaV) without affecting fractional Na+ excretion (FENa) in anesthetized rabbits. Losartan (10 micrograms/kg/min) abolished these angiotensin II-induced renal responses. The renal blood flow, glomerular filtration rate and UNaV responses were potentiated during intrarenal arterial infusion of N omega-nitro-L-arginine methyl ester (L-NAME, 10 micrograms/kg/min). A high dose of L-NAME (50 micrograms/kg/min) also potentiated the renal blood flow and UNaV responses but not the glomerular filtration rate response. Angiotensin II reduced FENa during L-NAME infusion at either dose. In L-NAME-pretreated rabbits, losartan abolished the angiotensin II-induced renal blood flow and glomerular filtration rate responses, but the reduction in FENa still remained. The present study suggests that in the rabbit kidney (1) nitric oxide attenuates the angiotensin II-induced (angiotensin AT1 receptor-mediated) vasoconstriction and (2) angiotensin II can evoke losartan-resistant tubular Na+ reabsorption, but the tubular action is concealed by nitric oxide.

Angiotensin II↗
PubMed1996

Duplication of chromosome 9 carrying a BCR/ABL chimeric gene in Philadelphia chromosome negative chronic myeloid leukemia.

We investigated a patient with Philadelphia chromosome (Ph) negative but BCR positive chronic myeloid leukemia (CML) by fluorescence in situ hybridization (FISH). In the chronic phase one chromosome 9 contained a BCR/ABL fusion gene instead of chromosome 22. Although in blast crisis, both chromosomes 9 had BCR/ABL fusion genes. This could be caused by duplication of the rearranged chromosome 9, which may have a significance similar to a double Ph chromosome. This may suggest that the critical event in CML is the formation of a BCR/ABL chimeric gene regardless of its locus in the genome.

Chromosome Aberrations↗
PubMed1996

Rfc5, a small subunit of replication factor C complex, couples DNA replication and mitosis in budding yeast.

The inhibition of DNA synthesis prevents mitotic entry through the action of the S phase checkpoint. In the yeast Saccharomyces cerevisiae, an essential protein kinase, Spk1/Mec2/Rad53/Sad1, controls the coupling of S phase to mitosis. In an attempt to identify genes that genetically interact with Spk1, we have isolated a temperature-sensitive mutation, rfc5-1, that can be suppressed by overexpression of SPK1. The RFC5 gene encodes a small subunit of replication factor C complex. At the restrictive temperature, rfc5-1 mutant cells entered mitosis with unevenly separated or fragmented chromosomes, resulting in loss of viability. Thus, the rfc5 mutation defective for DNA replication is also impaired in the S phase checkpoint. Overexpression of POL30, which encodes the proliferating cell nuclear antigen, suppressed the replication defect of the rfc5 mutant but not its checkpoint defect. Taken together, these results suggested that replication factor C has a direct role in sensing the state of DNA replication and transmitting the signal to the checkpoint machinery.

Amino Acid Sequence↗
PubMed1996

Interactions of selective serotonin reuptake inhibitors with subtypes of sigma receptors in rat brain.

The interactions of selective serotonin reuptake inhibitors and tricyclic antidepressants with subtypes of sigma receptors were investigated. The rank order of affinity (Ki values) from competition experiments of [3H](+)-pentazocine binding to sigma 1 sites was: fluvoxamine > sertraline > S(+)-fluoxetine > (+/-)-fluoxetine > citalopram > imipramine > paroxetine > desipramine > R(-)-fluoxetine > (+/-)-norfluoxetine. The Ki values of all drugs for sigma 2 sites were more than 1000 nM. Furthermore, all drugs were more potent at sigma 1 sites than at sigma 2 sites. These findings suggest that sigma receptors (sigma 1 site) may play, in some way, a role in the actions of selective serotonin reuptake inhibitors.

Animals↗
PubMed1996

Amelioration of insulin resistance in genetically obese rodents by M16209, a new antidiabetic agent.

Improvement of metabolic disorders by M16209 (1-(3-bromobenzofuran-2-ylsulfonyl)hydantoin), an antidiabetic agent, was studied in genetically obese Zucker fa/fa rats and C57BL/6J ob/ob mice. In fa/fa rats oral administration of M16209 (30 and 100 mg/kg/day) for 7 days dose dependently improved hyperinsulinemia without affecting body weight. Oral glucose loading (2 g glucose/kg body weight) after 10 days of administration to fa/fa rats revealed that M16209 significantly improved glucose tolerance both 30 and 60 min after glucose loading, but did not affect preload serum glucose levels. At one day after 13 days of administration of M16209, the serum levels of triglyceride, total cholesterol and free fatty acid were clearly lower in treated fa/fa rats than those in untreated rats. In C57BL/6J ob/ob mice, M16209 given for 28 days at doses of 30 and 100 mg/kg/day improved hyperinsulinemia, hyperglycemia and hypercholesterolemia without affecting body weight. In a hyperinsulinemic euglycemic clamp study in fa/fa rats, administration of M16209 for 7 days at a dose of 100 mg/kg/day significantly normalized the decreased metabolic clearance rate but did not show any effect on the augmented hepatic glucose output. These findings demonstrate that improvement of metabolic disorders in genetically obese rodents by M16209 is due to amelioration of insulin resistance in peripheral tissues.

Administration, Oral↗
PubMed1996

Photoinduced Magnetization of a Cobalt-Iron Cyanide

Photoinduced magnetization was observed in a Prussian blue analog, K0.2Co1.4- [Fe(CN)6]·6.9H2O. An increase in the critical temperature from 16 to 19 kelvin was observed as a result of red light illumination. Moreover, the magnetization in the ferrimagnetic region below 16 kelvin was substantially increased after illumination and could be restored almost to its original level by thermal treatment. These effects are thought to be caused by an internal photochemical redox reaction. Furthermore, blue light illumination could be used to partly remove the enhancement of the magnetization. Such control over magnetic properties by optical stimuli may have application in magneto-optical devices.

Journal Article↗
PubMed1996

Hypertrichosis, pigmentary retinopathy, and facial anomalies: a new syndrome?

We report on a 22-month-old male with congenital hypertrichosis of the face, arms, legs, shoulders, back, and buttocks, abnormal facial appearance, dolichocephaly, and pigmentary retinopathy. Symmetrical hyperpigmentation is present on the sideburn areas of his face, and hyperpigmented streaks are seen on arms and legs. Biopsy of the hyperpigmented' skin showed many separate bundles of smooth muscles in the dermis. No relative had hypertrichosis or other birth defects. To our knowledge, the syndrome of facial anomalies, pigmentary retinopathy, and congenital hypertrichosis has not been reported previously.

Abnormalities, Multiple↗
PubMed1996

Effects of zatebradine on ouabain-, two-stage coronary ligation- and epinephrine-induced ventricular tachyarrhythmias.

To determine whether a hyperpolarization-activated current (If) participates in ventricular tachyarrhythmias, we investigated the effects of zatebradine, an I(f) inhibitor, on the ventricular tachyarrhythmias induced by ouabain, two-stage coronary ligation and epinephrine infusion in the dog heart. We determined atrial rate, ectopic ventricular rate, total heart rate and arrhythmic ratio (the number of ectopic ventricular beats divided by total heart beats). Zatebradine (0.15, 0.5 and 1.5 mg/kg, i.v.) dose dependently decreased the arrhythmic ratio, ectopic ventricular rate and atrial rate of the ouabain-induced ventricular tachyarrhythmias in pentobarbital-anesthetized dogs. The inhibition by zatebradine of the ventricular arrhythmias needed larger doses than the inhibition of the atrial rate. Zatebradine weakly depressed the ectopic ventricular rate but not the arrhythmic ratio of the ventricular arrhythmias induced by two-stage coronary ligation 24 h after the ligation in conscious dogs. Although neither the ectopic ventricular rate nor the arrhythmic ratio of the epinephrine-induced ventricular arrhythmias was affected by zatebradine, after treatment with zatebradine, the arrhythmias elicited by epinephrine developed more slowly. Together with the previously reported spectra of the effects of the antiarrhythmic agents in three ventricular tachyarrhythmia models, our results suggest that zatebradine may improve automaticity-related ventricular tachyarrhythmias due to I(f) inhibition or to other undetermined mechanisms in the heart.

Animals↗
PubMed1996

Effects of MCI-154, a new cardiotonic Ca2+ sensitizer, on ventricular arrhythmias and membrane ionic currents.

We examined whether a new positive inotropic agent with Ca(2+)-sensitizing activity, MCI-154, 6-[4-(4-pyridylamino)phenyl]-4, 5-dihydro-3-(2H)-pyridazinone hydrochloride trihydrate, had deleterious effects on ventricular arrhythmias, since several phosphodiesterase III inhibitors have been shown to aggravate arrhythmias in our earlier studies. Continuous infusion of MCI-154 (1 microgram/kg/min for 15 min) did not suppress or aggravate the arrhythmias generated in the two-stage coronary ligation-, digitalis- and adrenaline-induced canine arrhythmia models studied. Also in the case of a bolus injection of 30 micrograms/kg, MCI-154 did not aggravate the adrenaline-induced arrhythmias. To explain these results in vivo, a whole-cell voltage-clamp experiment on guinea-pig ventricular cells was performed. MCI-154 (10-100 microM) did not increase the inward Ca2+ current under the condition where these currents were increased by isoprenaline. These results indicate that MCI-154 does not aggravate ventricular arrhythmias and does not act on membrane currents associated with arrhythmogenesis. Thus, MCI-154 may become a useful positive inotropic agent with little arrhythmogenic effect.

Animals↗
PubMed1996

Role of aspartic acid 814 in the function and expression of c-kit receptor tyrosine kinase.

The c-kit receptor tyrosine kinase (KIT) is constitutively activated in three different types of neoplastic mast cell lines by naturally occurring mutations that result in substitutions of Val or Tyr for Asp814 in the phosphotransferase domain. In an effort to characterize the role of the Asp814 residue, we have investigated the properties of mutant KITs in which the Asp814 residue was deleted or mutated to a series of other amino acids. With the exception of rare instances, mutant KITs with substitutions of Asp814 were found to be constitutively phosphorylated on tyrosine and activated in the absence of the ligand, stem cell factor (SCF), whereas a deletion mutant lacking Asp814 (KITDel-Asp-814) did not exhibit tyrosine phosphorylation and activation even after treatment with SCF. In addition to constitutive activation, furthermore, both highly activated substitution mutants (KITVal-814 and KITTyr-814) and modestly activated substitution mutants (KITGly-814 and KITHis-814) were continuously degraded in the absence of SCF, whereas wild-type KIT (KITWild) required SCF stimulation to undergo degradation. These results suggested that the Asp814 residue may play a crucial role in regulating enzymatic activity and expression of KIT and that various types of mutations at the Asp814 residue may generate oncogenic protein with constitutive activation and degradation.

Amino Acid Sequence↗
PubMed1996

Sequence analysis of the cDNA for the human casein kinase I delta (CSNK1D) gene and its chromosomal localization.

A cDNA clone coding for human casein kinase I (CK1) has been isolated and sequenced. The insert of 1911 bp contained an open reading frame of 415 amino acids. The entire amino acid sequence of human CK1 was 97% homologous to that of rat CK1 delta, and their sequences in the kinase domain (284 amino acid residues) were completely identical, predicting that the obtained cDNA is for a human homolog of the CK1 delta isoform (CSNKID). The considerable similarity in the amino acid sequence of the kinase domain of human CK1 delta to the Saccharomyces cerevisiae CK1, HRR25 (66%), and to the Saccharomyces pombe CK1, HHP1 (78%), which are involved in the repair of DNA strand break, supports the speculation that human CK1 delta might also act in DNA metabolism through excision and recombinational repair. The human CK1 delta gene was mapped to chromosome 17q25.2-q25.3 by fluorescence in situ hybridization and polymerase chain reaction analysis of the human/rodent hybrid cell panels.

Amino Acid Sequence↗
PubMed1996

Constitutive activation of c-kit in FMA3 murine mastocytoma cells caused by deletion of seven amino acids at the juxtamembrane domain.

A peculiar point mutation results in constitutive activation of c-kit receptor tyrosine kinase (KIT) in three different tumor mast cell lines; ie, the HMC-1, P-815, and RBL-2H3. Because constitutive activation of KIT was also observed in the FMA3 mouse mastocytoma cell line, we investigated the molecular mechanism. Sequencing of the whole coding region of the c-kit showed that the point mutation found in HMC-1, P-815, and RBL-2H3 cells was absent in FMA3 cells and that the c-kit cDNA of FMA3 cells carried an in-frame deletion of 21 base pairs (bp) encoding Thr-Gln-Leu-Pro-Tyr-Asp-His at codons 573 to 579 at the juxtamembrane domain. The FMA3-type c-kit cDNA with 21 bp deletion was introduced into the IC-2 cell line, which was derived from murine cultured mast cells. IC-2 cells were dependent on interleukin (IL)-3 and did not express KIT on the surface. In IC-2 cells introduced with the FMA3-type c-kit cDNA, KIT was constitutively phosphorylated on tyrosines and activated. Moreover, the FMA3-type KIT was dimerized without the stimulation by stem cell factor (SCF), a ligand for KIT. The spontaneously dimerized FMA3-type KIT without SCF binding was not internalized even after the activation. IC-2 cells expressing the FMA3-type KIT grew in suspension culture without IL-3 and SCF and became leukemic in nude athymic mice. The deletion of seven amino acids at the juxtamembrane domain appeared to be a new activating mutation of KIT that might be involved in neoplastic growth of mast cells.

Amino Acid Sequence↗
PubMed1996

11q23 aberration is an additional chromosomal change in de novo acute leukemia after treatment with etoposide and mitoxantrone.

We report on 2 patients with acute leukemia who had an 11q23 chromosomal aberration as an additional change after treatment with etoposide and mitoxantrone, agents that affect topoisomerase II (Topo II). One patient with Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (L2) received chemotherapy, including 1,000 mg of etoposide and 75 mg of mitoxantrone. She relapsed 10 months later. Analysis at time of relapse showed a chromosomal aberration of del(11)(q23) as an additional cytogenetic change. The other patient was diagnosed with acute monoblastic leukemia (M5a) and received two autologous peripheral blood stem-cell transplantations. Her cumulative doses of etoposide and mitoxantrone were 6,000 mg and 42 mg, respectively. She also relapsed, and analysis at that time revealed del(11)(q23) as an additional chromosomal aberration. The mixed lineage leukemia/myeloid-lymphoid leukemia (MLL) gene was not rearranged in either case, making these cases distinct from previously described therapy-related leukemias caused by Topo II inhibitors. Based on these two cases, it may be that Topo II inhibitors can cause clonal evolution affecting chromosome band 11q23.

Adult↗
PubMed1996

Detection of human T lymphotrophic virus type I (HTLV-I) DNA and mRNA in individual cells by polymerase chain reaction (PCR) in situ hybridization (ISH) and reverse transcription (RT)-PCR ISH.

Human T lymphotrophic virus type I (HTLV-I) proviral DNA and mRNA in the blood obtained directly from HTLV-I infected adult T cell leukemia (ATL) patients were amplified by the polymerase chain reaction (PCR), and reverse transcription (RT)-PCR, and then were hybridized to fluorescein-labelled probes by means of in situ hybridization (ISH). Before the cytospin samples were prepared, heterogenous cell populations were reproducibly resolved into HTLV-I-positive and -negative distributions. Immunohistochemical staining was performed, using anti-fluorescein monoclonal antibody. Microscopic observations demonstrated a preserved cellular morphology. The intranuclear localization of amplified DNA products of proviral HTLV-I by PCR/ISH, and intracytoplasmic localization of amplified DNA of HTLV-I tax/rex mRNA by RT-PCR/ISH were maintained. In this study, about one in 10 HTLV-I provirus integrated cells expressed low copies of tax/rex mRNA. In HTLV-I-negative cell lines, amplified DNA was not observed by either PCR/ISH or RT-PCR/ISH. With the use of this technique it is thus possible to detect single-copy DNA and a few copies of mRNA, and it is therefore possible to study, not only suspended materials, but also other tissue materials for further characterization, in association with the localization of the HTLV-I infected cells.

DNA, Viral↗