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Biomedical subjects

K Hashimoto

Publications and source records attributed to K Hashimoto.

At least 721 records · Page 40Linked to original sources
PubMed1996

Antiarrhythmic effects of an aconitine-like compound, TJN-505, on canine arrhythmia models.

We examined the effects of an aconitine-like compound, TJN-505 (1alpha-16beta-dimethoxy-20-ethyl-14alpha-(4-methox ybenzoyloxy)-aconitan-8,13-diol hydrochloride), on canine arrhythmias provoked by digitalis, two-stage coronary ligation, adrenaline, programmed electrical stimulation, or aconitine. TJN-505 (2-2.5 mg/kg i.v.) suppressed digitalis-, two-stage coronary ligation- and adrenaline-induced ventricular arrhythmias. The antiarrhythmic plasma concentrations (IC50) of TJN-505 for these arrhythmia models were 1.26, 0.94 and 1.31 microg/ml, respectively. TJN-505 (2 mg/kg i.v. followed by the infusion of 0.1 mg/kg per min) prolonged PR, QRS, QTc and JTc intervals and the ventricular effective refractory period and reduced the incidence of programmed electrical stimulation-induced arrhythmias in dogs with 7-day-old myocardial infarction (P < 0.05). TJN-505 (2 mg/kg i.v.) also suppressed the aconitine-induced atrial arrhythmias. In conclusion, TJN-505 suppressed various canine ventricular and atrial arrhythmias and seems to act as a blocker of multiple channels.

Aconitine↗
PubMed1996

Antiarrhythmic effects of HOE642, a novel Na(+)-H+ exchange inhibitor, on ventricular arrhythmias in animal hearts.

HOE642 (4-isopropyl-3-methylsulphonylbenzoyl-guanidine methanesulphonate), a novel Na(+)-H+ exchange subtype 1 inhibitor, was investigated for its possible antiarrhythmic effects on coronary artery ligation/reperfusion and ouabain-induced arrhythmias in the canine heart which may occur after intracellular Ca2+ overload. Also, the effects of HOE642 on coronary artery ligation/reperfusion of the left coronary artery were tested in rat hearts. HOE642 (1 mg/kg) significantly suppressed the occurrence of fatal ventricular fibrillation during coronary artery ligation and after reperfusion in dogs (2 out of 8 dogs in the treated group compared to 7 out of 8 dogs in the control group, P < 0.05), but did not suppress ventricular premature contractions and ventricular tachycardia during ischemia in the canine hearts. HOE642 at the same dose markedly reduced the total duration and the incidence of reperfusion-induced ventricular tachycardia, and the incidence and mortality of reperfusion-induced ventricular fibrillation in rats (ventricular tachycardia duration, 159 +/- 12 s to 21 +/- 8 s, P < 0.01; ventricular tachycardia, 100% to 69%; ventricular fibrillation, 89% to 0%, P < 0.01; mortality, 89% to 11%, P < 0.01). The heart rate, blood pressure, QT interval and ST segment did not change in the canine and rat hearts. HOE642 slightly decreased the arrhythmic ratio of the ouabain-induced arrhythmia only at two time points (28 and 35 min after injection) in the canine hearts. In conclusion, HOE642 has obvious antifibrillatory effects on ischemia/reperfusion arrhythmias and, in addition, has a weak suppressing effect on the ouabain-induced arrhythmia.

Animals↗
PubMed1996

Structure and expression of the mouse oxytocin receptor gene.

To determine the structure of the mouse oxytocin receptor (OTR) gene, we have screened a mouse genomic library and confirmed cDNA sequence with rapid amplification of cDNA ends. Southern blot using human OTR cDNA probes indicated that the mouse genome has a single copy of the gene. The predicted amino acid sequence is 91% identical to human OTR. The gene contains 4 exons and 3 introns. Exons 1 and 2 contain the 5' untranslated region, with exons 3 and 4 encoding the amino acids of the receptor. Intron 3 interrupts the coding at the same location, after transmembrane domain 6, as in OTR genes of other species. The promoter region lacks an apparent TATA box but contains multiple putative interleukin-response elements and estrogen responsive elements. Expression of OTR gene in the uterus during pregnancy reached maximum at day 20 gestation. The information obtained from the mouse OTR gene facilitates further comparative and biochemical analysis for protein structure-function relationships and gene regulatory mechanisms.

Amino Acid Sequence↗
PubMed1996

Stereoselective action of (R*,R*)-(+/-)-methyl-4-[2-[2-hydroxy-2-(3-chlorophenyl)ethylamino] propyl]-phenoxyacetic acid (BRL37344) on beta-adrenoceptors and metabolic chiral inversion.

Stereoisomers of BRL37344 ((R*,R*)-(+/-)-methyl-4-[2-[2-hydroxy-2 -(3-chlorophenyl)ethylamino]propyl]-phenoxyacetic acid), a beta 3-adrenoceptor agonist, were synthesized and separated with good resolution by derivatization with 1-anthroyl cyanide prior to chiral HPLC. Agonist effects on rat right atria, guinea pig trachea, and rat brown adipocytes were due principally to the (RR) isomer, while other isomers (SS, RS, and SR) were much less potent or inactive. Since the racemate (RR +/- SS) was half as potent as the (RR) isomer in all specimens tested, the (SS) isomer does not appear to have antagonistic effects. When [14C](RR)BRL35135A ((R*,R*)-(+/-)-methyl-4-[2-[2-hydroxy-2-(3-chlorophenyl)ethylamino]propy l] -phenoxyacetate hydrobromide), the HBr salt of the methyl ester of BRL37344, was administered orally to male Wistar rats, both the (RR) and (SR) isomers of [14C]BRL37344 were detected in plasma, while only the (SS) isomer of [14C]BRL37344 was detected after [14C](SS)BRL35135A administration. These findings indicate that there is clear stereoselectivity in the effects of BRL37344 on beta-adrenoceptors, and that stereoselective chiral inversion from the RR isomer to the SR isomer occurs in rats.

Adipose Tissue, Brown↗
PubMed1996

Improvement of metabolic disorders and visceral fat obesity by the beta 3-adrenoceptor agonist (R*,R*)-(+/-)-methyl-4-[2-[2-hydroxy-2 -(3-chlorophenyl)ethylamino]propyl]-phenoxyacetate hydrobromide (BRL35135A) in genetically obese rodents.

The effects of BRL35135A ((R*,R*)-(+/-)-methyl-4-[2-[2-hydroxy-2 -(3-chlorophenyl)ethylamino]propyl]-phenoxyacetate hydrobromide), a beta 3-adrenoceptor agonist, on visceral and subcutaneous fat weight and metabolic disorders were studied in genetically obese C57BL/KsJ db/db mice and Zucker fa/fa rats. In db/db mice, four weeks of oral administration of BRL35135A (0.5 and 5 mg/kg/day) decreased body weight gain and reduced white fat weight. The rates of reduction of white fat weight were in the order mesenteric fat > retroperitoneal fat > subcutaneous fat. In fa/fa rats, daily administration of BRL35135A (0.05 mg/kg/day)) for 6 weeks reduced the visceral white fat weight/total energy intake ratio, particularly for mesenteric fat, without any clear effect on body weight gain. This tendency of the compound to exert effects on visceral fat was consistent with the findings that the effect of BRL37344 ((R*,R*)-(+/-) -methyl-4-[2-[2-hydroxy-2-(3-chlorophenyl)ethylamino]propyl]-phenoxyacet ic acid), an active metabolite of BRL35135A, on the lipolytic activity of isolated adipocytes and the tissue concentration of [14C]BRL37344 in male Wistar rats were each greater in visceral fat than in subcutaneous fat. Moreover, BRL35135A at 0.05 mg/kg/day elevated serum insulin levels and improved hyperglycemia in db/db mice without reducing body weight gain, whereas at doses of 0.5 and 5 mg/kg/day it ameliorated hyperglycemia and hyperlipidemia, and tended to decrease serum insulin levels. In fa/fa rats, BRL35135A (0.005 mg/kg/day) was also effective in improving hyperinsulinemia, glucose intolerance, and hypertriglyceridemia without any effect on body weight gain or fat distribution. These findings suggest that the improvement of metabolic disorders by BRL35135A may be due to improvement in insulin resistance as well as reduction of visceral fat weight.

Adipose Tissue↗
PubMed1996

Memantine induces heat shock protein HSP70 in the posterior cingulate cortex, retrosplenial cortex and dentate gyrus of rat brain.

High-affinity N-methyl-D-aspartate (NMDA) receptor antagonists like MK-801 are known to induce the heat shock protein, HSP70, in the posterior cingulate cortex and retrosplenial cortex of rat brain. Memantine, which is a low affinity uncompetitive NMDA receptor antagonist, has been used in the treatment of Parkinson's disease in Europe. The faster kinetics of memantine in blocking and unblocking the NMDA receptor-operated ion channel as opposed to high-affinity NMDA antagonists like MK-801 has been thought to account for the safety of memantine. The present study evaluated the neurotoxic potential of memantine and amantadine using the induction of HSP70 immunoreactivity in rat brain. Memantine (25, 50, 75 mg/kg) induced HSP70 in the posterior cingulate, retrosplenial cortex and dentate gyrus of rat brain. In contrast, amantadine (50, 100, 200 mg/kg) did not induce HSP70 in the rat brain. These results suggest that memantine has an antagonistic effect at NMDA receptor in vivo, and raises the possibility that high doses of memantine may cause neuronal damage similar to those observed with other high-affinity NMDA receptor antagonists.

Animals↗
PubMed1996

Paraoxonase gene polymorphism in Japanese subjects with coronary heart disease.

We investigated the association of paraoxonase (PON) gene polymorphism with both the occurrence of coronary heart disease (CHD) and the severity of coronary artery stenosis in Japanese subjects. PON is a protein associated with plasma HDL. It has been hypothesized an A/B (Gln 192-->Arg) polymorphism of PON may be involved in the pathogenesis of CHD, especially among subjects with non-insulin-dependent diabetes mellitus (NIDDM). The polymorphism was determined in 134 patients with myocardial infarction (MI) or angina pectoris, and in 252 healthy subjects as controls. The frequencies of the AA, AB, and BB genotypes in the patients were 15, 50 and 35%, respectively, and these frequencies did not differ from those in control subjects (14, 49, and 37%). The relative risk of CHD was not found to be associated with these genotypes. These data also were similar among selected subgroups (patients with MIs, those with a low-risk lipoprotein profile for CHD, and those with NIDDM). Neither the number of affected vessels nor Gensini's scores differed among the genotype groups. Our case-control study in Japanese subjects did not show that the PON A/B polymorphism is associated with a risk of CHD.

Aged↗
PubMed1996

Isolation and analysis of a novel gene, HXC-26, adjacent to the rab GDP dissociation inhibitor gene located at human chromosome Xq28 region.

We screened potential promoter regions from NotI-linking cosmid clones mapped on human chromosome Xq28 region with our constructed trapping vector and isolated six fragments containing transcription activity. Using one of the obtained fragments as a probe, a novel gene was isolated by screening a human skeletal muscle cDNA library. The isolated cDNA, termed HXC-26, contained an open reading frame of 975 nucleotides encoding 325 amino acids (38,848 Da). The HXC-26 gene was composed of 13 exons that span approximately 8 kb. Several potential GC boxes were found in the putative promoter region, but no typical TATA box. The HXC-26 gene associated with a CpG island was located adjacent to the rab GDP dissociation inhibitor (GDI) gene.

Amino Acid Sequence↗
PubMed1996

Human rasGTPase-activating protein (human counterpart of GAP1m): sequence of the cDNA, primary structure of the protein, production and chromosomal localization.

When cDNA encoding rat rasGTPase-activating protein (rat GAP1m) was used as a probe, two partial cDNA clones of a human counterpart of rat GAP1m were isolated from a cDNA library derived from growth-arrested normal human ectocervical epithelial cells. One clone was found to be a cDNA of premature mRNA with two introns. A complete cDNA of human GAP1m was constructed by a series of reverse transcription-polymerase chain reaction (RT-PCR) using total RNA from human epidermoid carcinoma A431 cells. Human GAP1m shows 87.7% nucleotide identity to rat GAP1m in open reading frame and encodes an 850-amino acid protein that shows 89.2% identity to rat GAP1m. A 100-kDa protein was detected in A431 cells by Western blotting with anti-rat GAP1m antibody. The human GAP1m gene was mapped to chromosome 3q24-q26.

Animals↗
PubMed1996

Regulation of mouse mast cell protease 6 gene expression by transcription factor encoded by the mi locus.

The mi locus of mice encodes a member of the basic-helix-loop-helix-leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF). Because the expression of the mouse mast cell protease 6 (MMCP-6) gene is remarkably reduced in mast cells of mi/mi mutant mice, we investigated the effect of MITF on the transcription of the MMCP-6 gene. First, we introduced the normal (+) MITF cDNA into mi/mi cultured mast cells using the retroviral vector. Overexpression of +-MITF but not mi-MITF normalized the expression of the MMCP-6 gene, indicating the involvement of +-MITF in the MMCP-6 gene transactivation. Second, we analyzed the promoter of the MMCP-6 gene by the transient cotransfection assay. The luciferase construct under the control of the MMCP-6 promoter and the cDNA encoding +-MITF or mi-MITF were cotransfected into NIH/ 3T3 fibroblasts. The coexpression of +-MITF but not mi-MITF increased the luciferase activity 10-fold. We found a CACATG and a CATCTG motif in the MMCP-6 promoter, both of which are generally recognized by bHLH-Zip-type transcription factors. We also found a GACCTG motif that was strongly bound by +-MITF. These three motifs were necessary for the 10-fold transactivation ability of the MMCP-6 promoter by +-MITF. Mutations of each motif significantly reduced the transactivation, suggesting that +-MITF directly transactivated the MMCP-6 gene through these three motifs.

3T3 Cells↗
PubMed1996

Prevention of methamphetamine-induced behavioral sensitization in rats by a cyclic AMP phosphodiesterase inhibitor, rolipram.

Effects of an interaction between rolipram, a cyclic adenosine 3', 5'-monophosphate (cyclic AMP) phosphodiesterase inhibitor, and methamphetamine on the development of behavioral sensitization were observed in rats. In vivo microdialysis showed that a single dose of 4 mg/kg methamphetamine (i.p.) significantly increased striatal dopamine levels while coadministration with 4 mg/kg rolipram (i.p.) did not affect these levels. Also, methamphetamine alone did not alter striatal cyclic AMP levels but coadministration with rolipram and rolipram alone significantly increased these levels. The administration of 4 mg/kg methamphetamine (i.p.) once a day for 5 days significantly enhanced hyperlocomotion and rearing induced by a 2-mg/kg methamphetamine challenge (i.p.) after a 1-week withdrawal period, compared with controls or coadministration with 4 mg/kg rolipram (i.p.). Striatal dopamine levels, detected by in vivo microdialysis, were increased following the challenge but were comparable between the groups. These findings suggest that rolipram prevents methamphetamine-induced behavioral sensitization by increasing cyclic AMP levels while not affecting dopamine-releasing processes.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1996

Significance of angiotensin I-converting enzyme and angiotensin II type 1 receptor gene polymorphisms as risk factors for coronary heart disease.

The D allele of an insertion/deletion (I/D) polymorphism in the angiotensin I-converting enzyme (ACE) gene is associated with a risk of myocardial infarction, and the relative risk associated with the ACE D allele is increased by the C allele of an angiotensin II type 1 receptor (AT1R) gene polymorphism (an A-->C transversion at nucleotide position 1166) [28]. The relation of the ACE and AT1R gene polymorphisms to coronary heart disease and the severity of coronary artery stenosis has now been investigated in 133 patients with myocardial infarction (MI) or angina pectoris who underwent coronary angiography and in 258 control subjects. The frequency of the ACE DD genotype as compared with non-DD was significantly higher in the patients who experienced an MI and in the low-risk patients than that in the controls (P < 0.05). The DD genotype showed a significantly increased risk of MI (odds ratio 1.85). The frequency of the AT1R A/C genotypes did not differ between the patients and the controls. The severity of coronary stenosis in the patients was estimated by the number of affected vessels (> 75% stenosis) and the coronary score of Gensini. Neither the number of affected vessels nor the coronary score differed among the ACE I/D genotypes. However, the number of affected vessels was significantly greater in patients with the AT1R AC genotype than in those with the 4A genotype (1.93 +/- 0.27 vs. 1.27 +/- 0.99; P < 0.05) (CC genotype was not found in the patients). After excluding patients with diabetes mellitus, the coronary score of those with the AC genotype was also significantly higher than in those with the AA genotype (51.7 +/- 34.4 vs. 18.2 +/- 23.3; P < 0.01). These results suggest that the ACE D allele is associated with the occurrence of myocardial infarction, while the AT1R C allele is involved in the development of the coronary artery stenosis.

Adult↗
PubMed1996

Genomic organization and promoter function of the human thyrotropin-releasing hormone receptor gene.

We isolated and characterized the gene for the human thyrotropin-releasing hormone receptor. The gene spanned more than 30 kilobases and contained three exons and two introns. Intron 1 exists in the 5'-untranslated region, and intron 2 is more than 25 kilobases in length which interrupts the coding region before the beginning of the putative sixth transmembrane domain. Exon 3 encodes the rest of the coding region and the entire 3'-untranslated region. The 3'-flanking region contains four potential polyadenylation signals, and 3'-rapid amplification of cDNA ends studies showed that only a signal at 2076 base pairs downstream of the stop codon was functional in the anterior pituitary. Primer extension and anchor-polymerase chain reaction studies indicated a transcriptional start site at 344 base pairs upstream of the translational start site. The promoter region does not contain either a TATA box or a CAAT box in the appropriate location. Transient transfection study revealed significant activity of the promoter in GH4C1 cells, and the region between -338 and -933 bp from the transcriptional start site worked as a negative regulator. Knowledge of the genomic organization and the promoter region of thyrotropin-releasing hormone (TRH) receptor gene will allow further studies of possible disorders of the TRH receptor, as well as facilitate elucidation of transcriptional control of the human TRH receptor gene.

Amino Acid Sequence↗
PubMed1996

Requirement for p56lck tyrosine kinase activation in T cell receptor-mediated thymic selection.

The nonreceptor protein tyrosine kinase p56lck (Lck) serves as a fundamental regulator of thymocyte development by delivering signals from the pre-T cell receptor (pre-TCR) that permit subsequent maturation. However, considerable evidence supports the view that Lck also participates in signal transduction from the mature TCR. We have tested this conjecture by expressing a dominant-negative form of Lck under the control of a promoter element (the distal lck promoter) that directs high expression in CD4+CD8+ thymocytes, mature thymocytes, and peripheral T cells, thereby avoiding, complications that result from the well-documented ability of dominant-negative Lck to block very early events in thymocyte maturation. Here we report that expression of the catalytically inactive Lck protein at twice normal concentrations inhibits thymocyte positive selection by as much as 80%, while leaving other aspects of cell maturation intact. This effect was studied in more detail in mice simultaneously bearing the male-specific H-Y alpha/beta TCR transgene and ovalbumin-specific DO10 alpha/beta TCR transgene, where even equimolar expression of the dominant-negative Lck protein substantially vitiated the positive selection process. Although deletion of H-Y alpha/beta thymocytes proceeded normally in male mice despite the presence of catalytically inactive Lck, modest inhibition of superantigen-mediated deletion was in some cases observed. These data further implicate Lck in the propagation of all TCR-derived signals, and indicate that even very modest deficiencies in the representation of functional Lck molecules could in humans, profoundly alter the character of the peripheral TCR repertoire.

Animals↗
PubMed1996

Narrowing the position of the Werner syndrome locus by homozygosity analysis-extension of homozygosity analysis.

Werner syndrome (WS) is an autosomal recessive disorder characterized by the premature occurrence of many age-related features. Previously, the WS gene (WRN) was mapped between D8S131 and D8S87, in an 8.3-cM interval. In this study, regions of homozygosity in 36 WS patients from inbred families were searched for by genotyping for 35 dinucleotide repeat polymorphic markers to narrow down the WRN critical region. The region most consistently homozygous in these patients was between the D8S1219/D8S1220 cluster and D8S278, within a 4.4-cM interval. For 16 markers mapped in this interval, 24 WS patients (22 Japanese patients and 2 Caucasian patients) in whom consanguinity failed to be proved were also genotyped, under the assumption that some of these patients might still be from consanguineous marriages. The data were analyzed by Fisher's exact test with a 2 x 2 contingency table for the 22 Japanese patients, excluding the 2 Caucasian patients. The frequencies of homozygosity in the 22 patients at 10 of 16 markers tested were significantly higher than those detected in the general population. Analysis of homozygosity patterns indicated that the region most consistently homozygous was between D8S1445 and D8S278. Thus the WRN locus is most likely between the two markers D8S1445 and D8S278, in a 1.6-cM interval.

Asian People↗
PubMed1996

Involvement of transcription factor encoded by the mi locus in the expression of c-kit receptor tyrosine kinase in cultured mast cells of mice.

The mi locus of mice encodes a member of the basic-helix-loop-helix-leucine zipper (bHLH-Zip) protein family of transcription factors (hereafter called MITF). Cultured mast cells of mi/mi genotype (mi/mi CMCs) did not normally respond to stem cell factor (SCF), a ligand for the c-kit receptor tyrosine kinase. The poor response of mi/mi CMCs to SCF was attributed to the deficient expression of c-kit both the mRNA and protein levels. The purpose of the present study is to investigate the effect of MITF on the transcription of the c-kit gene. First, we introduced cDNA encoding normal (+) MITF or mutant (mi) MITF into mi/mi CMCs using the retroviral vector. Overexpression of (+)-MITF but not mi-MITF normalized the expression of the c-kit and the poor response of mi/mi CMCs to SCF, indicating the involvement of (+)-MITF in the c-kit gene transactivation. Second, we analyzed the promoter of the c-kit gene. Three CANNTG motifs recognized by bHLH-Zip-type transcription factors were conserved between the mouse and human c-kit promoters. Among these three CANNTG motifs, only the CACCTG motif (nt -356 to -351) was specifically bound by (+)-MITF. When the luciferase gene under the control of the c-kit promoter was contransfected into NIH/3T3 fibroblasts with cDNA encoding (+)-MITF or mi-MITF, the luciferase activity significantly increased only when (+)-MITF cDNA was cotransfected. The deletion of the promoter region containing the CACCTG motif or the mutation of the CACCTG to CTCCAG abolished the transactivation effect of (+)-MITF, indicating that (+)-MITF transactivated the c-kit gene through the CACCTG motif. When the luciferase gene under the control of the c-kit promoter was introduced into the FMA3 mastocytoma and FEC-P1 myeloid cell lines, remarkable luciferase activity was observed only in FMA3 cells. Thus, the involvement of (+)-MITF in the c-kit transactivation appeared to be specific to the mast cell lineage.

Animals↗