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Biomedical subjects

H Kawai

Publications and source records attributed to H Kawai.

At least 145 records · Page 8Linked to original sources
PubMed2000

Kinetic stabilization of the [1.1]paracyclophane system: isolation and X-ray structural analysis of a [1.1]paracyclophane derivative and its interconversion with the transannular adduct.

Intentionally designed kinetic stabilization of the [1.1]paracyclophane skeleton has been achieved by multiple substitution of the aromatic rings with trimethylsilylmethyl and N,N-dimethyl-carbamoyl groups, which serve to shield the proximate bridgehead carbon atoms sterically from access by other reagents. The bis(Dewar benzene) precursor (1a) has been prepared in essentially the same manner as previous derivatives--starting from the photocycloaddition of 1,4-bis(trimethylsilyl)-2-butyne to octa-hydroindacene-1,5-dione--except for a few critical modifications described in the text. Substituted [1.1]paracyclophane (2a), photochemically generated from the precursor, is indefinitely stable at 50 degrees C and suffers decomposition only by 8 % after 2 h at 100 degrees C in degassed n-decane, demonstrating its greatly improved kinetic stability compared to previous [1.1]paracyclophanes. Since 2a undergoes efficient photochemical transformation into the transannular addition product 3a, irradiation of la tends to produce a mixture of products consisting mainly of 3a. Compound 3a, however, reverts thermally to 2a in a process of half life 40 min at 55 degrees C; the activation parameters for this process are deltaH(not equal to)= 21.1 +/- 0.8 kcalmol(-1) and deltaS(not equal to) = -10.5 +/- 2.6 cal K(-1)mol(-1). Thus, on heating 3a in benzene and cooling the resultant solution, 2a is obtained as orange-red crystals. X-ray crystallographic analysis of 2a reveals benzene rings bent to the highest degree ever reported for a paracyclophane, with their face-to-face arrangement in unusually close proximity. The shortest nonbonding interatomic distance is 2.376 A; less than the sum of the van der Waals radii by more than 1.0A. The generation of related substituted [1.1]paracyclophanes and their kinetic stabilities are also reported.

Journal Article↗
PubMed2000

Characterization and identification of (CT)n microsatellites in soybean using sheared genomic libraries.

Three small insert (300 to approximately 600 bp) sheared genomic libraries were constructed by pipetting and DNase I treatment of soybean DNA. About 15,000 clones from each library were screened for CT- simple sequence repeats (CT-SSRs). The CT-SSRs were abundant in the soybean genome at an estimated frequency of approximately one SSR per 110 kb of genomic DNA. Following the sequencing of 129 positive clones, the repeat types and frequency of CT repeats among the positive clones were characterized. Forty-nine primer pairs were designed and preliminarily evaluated for their ability to amplify genomic DNA from a set of six varieties, including parents of a mapping family. Amplified products were analyzed by 10% PAGE. Eighty-eight percent of the designed primers were able to amplify all these genomic DNAs using a single PCR profile of 53 degrees C annealing temperature, of which 22 (45%) were polymorphic in the six varieties, and 14 of them were polymorphic in the parents of the mapping family. The polymorphic primer sets were further assessed for allelic information using DNA from 16 soybean cultivars. The average number of alleles was 4, ranging from 2 to 7 with the highest polymorphism information content value 0.84. Fourteen of these SSRs were mapped, using an existing soybean RFLP map. The findings presented here will advance our understanding of the soybean genome, and assist in the mapping genome and discrimination of closely related varieties of this species.

Chromosome Mapping↗
PubMed2000

Nitric oxide spares myocardial oxygen consumption through attenuation of contractile response to beta-adrenergic stimulation in patients with idiopathic dilated cardiomyopathy.

BACKGROUND: The results of recent studies suggest that NO synthase may increase in the failing myocardium and that NO modulates the myocardial contractile response to beta-adrenergic stimulation. However, there are few data regarding the physiological role of NO in patients with heart failure. The aim of the present study was to address the role of NO in left ventricular (LV) contractile response to beta-adrenergic stimulation and corresponding oxygen expenditure in human heart failure. METHODS AND RESULTS: We studied 15 patients with heart failure due to idiopathic dilated cardiomyopathy (mean ejection fraction 0.33). We examined LV contractility (E(max), the slope of end-systolic pressure-volume relation), LV external work (EW), myocardial oxygen consumption (MVO(2)), and mechanical efficiency (measured as EW/MVO(2)) with the use of conductance and coronary sinus thermodilution catheters before and during dobutamine (DOB) infusion via a peripheral vein (4. 8+/-0.3 microg. kg(-1). min(-1) IV). Heart rate was kept constant with atrial pacing. We carried out a similar protocol during the intracoronary infusion of the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA; 200 micromol). DOB increased E(max), EW, and MVO(2) (by 77+/-17%, 39+/-5%, and 21+/-5%, respectively), leading to an increase in mechanical efficiency (25.4+/-3.1% to 29.6+/-4.1%). L-NMMA alone did not significantly change these variables. Although the concurrent infusion of DOB with L-NMMA increased E(max), EW, and MVO(2) (by 140+/-21%, 64+/-9%, and 35+/-5%, respectively) more than DOB alone, mechanical efficiency did not increase further (24.3+/-3.3% to 29.5+/-4.5%) because EW and MVO(2) increased in parallel. Conclusions-These data suggest that in patients with idiopathic dilated cardiomyopathy, endogenous NO spares MVO(2) through attenuation of LV contractile response to beta-adrenergic stimulation while maintaining LV energy-converting efficiency.

Adrenergic beta-Agonists↗
PubMed2000

Interaction of a semirigid agonist with Torpedo acetylcholine receptor.

The binding of the semirigid agonist [(3)H]arecolone methiodide to the Torpedo nicotinic acetylcholine receptor has been correlated with its functional properties measured both in flux studies with Torpedo membrane vesicles and by single-channel analysis after reconstitution in giant liposomes. Under both equilibrium and preequilibrium conditions, the binding of arecolone methiodide is similar to that of other agonists such as acetylcholine. At equilibrium, it binds to two sites per receptor with high affinity (K(d) = 99 +/- 12 nM), and studies of its dissociation kinetics suggest that each of these sites is made up of two subsites that are mutually exclusive at equilibrium. The kinetics of arecolone methiodide binding were monitored by the changes in the receptor intrinsic fluorescence, and the data are consistent with a model in which the initial binding event is followed by sequential conformational transitions of the receptor-ligand complex. In flux studies, arecolone methiodide was approximately 3-fold more potent (EC(50) = 31 +/- 5 microM) than acetylcholine but its maximum flux rate was 4-10-fold lower. This phenomenon has been studied further by single-channel analysis of Torpedo receptors reconstituted in giant liposomes. Whereas the flexible agonist carbamylcholine (5 microM) was shown to induce channels with conductances of 56 and 34 pS with approximately equal frequency, arecolone methiodide (2 microM) preferentially induced the channel of lower conductance. These results are interpreted in terms of a simple model in which the rigidity of arecolone methiodide restrains the conformation that the receptor-ligand complex can adopt, thus favoring the lower conductance state.

Animals↗
PubMed2000

Molecular cloning of mouse thioredoxin reductases.

We screened clones for thioredoxin reductase genes with a degenerate PCR-based strategy and have isolated two novel cDNA clones from a mouse thymocyte cDNA library. These encode two distinct thioredoxin reductases (TrxR1 and TrxR2) with 499 and 527 amino acid (aa) residues and calculated molecular masses of 54.5 kDa and 56.8 kDa respectively. These proteins share 90% and 50% aa sequence identity with those of previously cloned human TrxR, containing the redox-active cysteines, FAD binding domain, and the selenocysteine (SeCys) insertion sequence, which is composed of a putative stem-loop sequence located in the 3'-untranslated region (UTR). TrxR2 showing less homology to human TrxR has a mitochondrial translocation signal and a mitochondrial prepeptide protease cleavage site in the N-terminal domain. Transient expression experiments of each gene as fusion proteins with Xpress-tagged protein in NIH 3T3 cells indicated that TrxR1 was localized in the nucleus and cytoplasm and TrxR2 in the mitochondria. Furthermore, we mapped the TrxR1 gene to chromosome 10 (placed 1.71 cR from D10Mit42, lod>3.0) and the TrxR2 gene to chromosome 16 (placed 22.56 cR from D16Mit34, lod>3.0). Thus, the mouse has at least two distinct nuclear genes for TrxR that have different translocation sites in the cell.

3T3 Cells↗
PubMed2000

Dopamine transporter and catechol-O-methyltransferase activities are required for the toxicity of 1-(3',4'-dihydroxybenzyl)-1,2,3, 4-tetrahydroisoquinoline.

1-(3',4'-Dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline [3', 4'DHBnTIQ (1)] is an endogenous parkinsonism-inducing substance. It is taken up into dopaminergic neurons via the dopamine transporter, inhibits mitochondrial respiration, and induces parkinsonism in mice. We synthesized four derivatives [aromatized, N-methylated, N-methyl-aromatized, and O-methylated (2-5, respectively)] and studied the cellular uptake and cytotoxicity of 1-5, as well as the metabolism of 1. All except the O-methyl derivative (5) were specifically taken up by the dopamine transporter, but 1 was taken up most efficiently. Relative to 1, oxidation reduced v(max), N-methylation markedly increased K(m), and O-methylation eliminated the uptake activity. The cytotoxicity of 1-5 was examined in a mesencephalic cell primary culture. Compound 1 reduced cell viability by nearly 80% at 100 microM, but the other compounds had little or no effect on cell viability. In vivo and in vitro studies revealed that 1 was O-methylated by soluble catechol-O-methyltransferase (COMT). Aromatization and N-methylation of 1 were not observed. We found that dopamine transporter inhibitors and a COMT inhibitor each blocked the cytotoxicity of 1, indicating that uptake and O-methylation are both necessary for neurotoxicity. Thus, we consider that 1 is taken up into dopaminergic neurons via the dopamine transporter and then converted by COMT to 5, which has cytotoxic and parkinsonism-inducing activities.

Animals↗
PubMed2000

Quantitative evaluation of genomic instability as a possible predictor for development of hepatocellular carcinoma: comparison of loss of heterozygosity and replication error.

Both loss of heterozygosity (LOH) and replication error (RER) are considered to be phenotypes of genomic instability. To unveil the role of the genomic instability in hepatocarcinogenesis, frequencies of LOH and RER were simultaneously determined in 15 hepatocellular carcinomas (HCCs), surrounding nontumorous liver tissues (SL), and 13 liver tissues with chronic viral hepatitis void of cancer (NC) by referencing peripheral blood leukocytes (PBLs) from the corresponding donor using 18 microsatellite markers spread throughout the genome. LOH was significantly frequent in HCC compared with that in SL or NC (P =.005, P =.0003, respectively) and observed preferentially at particular microsatellite loci, D1S204, D2S123, D8S1106, D9S266, D16S748, and D19S601. Although the higher prevalence of RER was also significant in HCC compared with that in NC (P =.03), in most cases the errors were detected at very low frequencies and random loci. Both LOH and RER tended to appear more prevalently in SL than in NC. The occurrence rate of LOH was higher in the tissues associated with hepatitis B virus (HBV) than with hepatitis C virus (HCV) infection especially in HCC (P =.03). When referencing SL instead of PBLs, the prevalence of LOH and RER in HCC significantly decreased (P =.02 and P =.03, respectively). These results suggest that LOH is closely associated with multistep hepatocarcinogenesis especially under HBV infection, but RER is imperceptibly associated. The quantitative evaluation of the frequency of LOH by referencing PBLs may be a useful predictor for HCC development in chronic liver diseases.

Blood Cells↗
PubMed2000

Scaling behaviors of branched polymers

We study the thermodynamic behavior of branched polymers. We first study random walks in order to clarify the thermodynamic relation between the canonical ensemble and the grand canonical ensemble. We then show that correlation functions for branched polymers are given by those for straight phi(3) theory with a single mass insertion, not those for the straight phi(3) theory themselves. In particular, the two-point function behaves as 1/p(4), not as 1/p(2), in the scaling region. This behavior is consistent with the fact that the Hausdorff dimension of the branched polymer is 4. In the appendixes we derive the exact two-point correlation function at finite (but large) system size N, which is consistent with the analysis in the body of the paper.

Journal Article↗
PubMed2000

Alterations in cardiac adrenergic terminal function and beta-adrenoceptor density in pacing-induced heart failure.

Congestive heart failure is associated with cardiac adrenergic nerve terminal changes and beta-adrenoceptor density downregulation. To study the temporal sequence of these changes, we performed studies in rabbits at 2, 4, and 8 wk of cardiac pacing (360 beats/min) and at 1, 2, and 4 wk after cessation of pacing. Rapid pacing produced left ventricular (LV) dysfunction and an increase in plasma norepinephrine (NE) in 1-2 wk. At week 2, NE uptake activity, NE uptake-1 density, and adenylyl cyclase responses to isoproterenol, 5'-guanylyl imidodiphosphate [Gpp(NH)p], and forskolin reduced. However, immunostained tyrosine hydroxylase profile, beta-adrenoceptor density, and NE histofluorescence did not reduce until 4-8 wk of pacing. After cessation of cardiac pacing, LV function normalized quickly, followed by return of tyrosine hydroxylase and NE profiles in 1 wk and adenylyl cyclase responses to agonists and NE uptake activity in 2 wk. Myocardial beta-adrenoceptor density returned to normal by 4 wk after cessation of pacing. Our results suggest that there is no permanent structural neuronal damage in the myocardium within the first 8 wk of rapid cardiac pacing. Abnormal myocardial NE reuptake mechanism may play an important pathophysiological role in heart failure.

Adenylyl Cyclases↗
PubMed2000

Selegiline improves cardiac sympathetic terminal function and beta-adrenergic responsiveness in heart failure.

Selegiline is a centrally acting sympatholytic agent with neuroprotective properties. It also has been shown to promote sympathetic reinnervation after sympathectomy. These actions of selegiline may be beneficial in heart failure that is characterized by increased sympathetic nervous activity and functional sympathetic denervation. Twenty-seven rabbits with rapid cardiac pacing (360 beats/min, 8 wk) and twenty-three rabbits without pacing were randomly assigned to receive selegiline (1 mg/day, 8 wk) or placebo. Rapid pacing increased plasma norepinephrine (NE) and decreased left ventricular fractional shortening, baroreflex sensitivity, cardiac sympathetic nerve terminal profiles, cardiac NE uptake activity, and myocardial beta-adrenoceptor density. Selegiline administration to animals with rapid ventricular pacing attenuated the increase in plasma NE and decreases in fractional shortening, baroreflex sensitivity, sympathetic nerve profiles, NE uptake activity and beta-adrenoceptor density. Thus selegiline appears to exert a sympatholytic and cardiac neuroprotective effect in pacing-induced cardiomyopathy. The effects are potentially beneficial because selegiline not only improves cardiac function but also increases baroreflex sensitivity in heart failure.

Analysis of Variance↗
PubMed2000

Renin-angiotensin system inhibition on noradrenergic nerve terminal function in pacing-induced heart failure.

Chronic angiotensin-converting enzyme (ACE) inhibition has been shown to improve cardiac sympathetic nerve terminal function in heart failure. To determine whether similar effects could be produced by angiotensin II AT(1) receptor blockade, we administered the ACE inhibitor quinapril, angiotensin II AT(1) receptor blocker losartan, or both agents together, to rabbits with pacing-induced heart failure. Chronic rapid pacing produced left ventricular dilation and decline of fractional shortening, increased plasma norepinephrine (NE), and caused reductions of myocardial NE uptake activity, NE histofluorescence profile, and tyrosine hydroxylase immunostained profile. Administration of quinapril or losartan retarded the progression of left ventricular dysfunction and attenuated cardiac sympathetic nerve terminal abnormalities in heart failure. Quinapril and losartan together produced greater effects than either agent alone. The effect of renin-angiotensin system inhibition on improvement of left ventricular function and remodeling, however, was not sustained. Our results suggest that the effects of ACE inhibitors are mediated via the reduction of angiotensin II and that angiotensin II plays a pivotal role in modulating cardiac sympathetic nerve terminal function during development of heart failure. The combined effect of ACE inhibition and angiotensin II AT(1) receptor blockade on cardiac sympathetic nerve terminal dysfunction may contribute to the beneficial effects on cardiac function in heart failure.

Angiotensin Receptor Antagonists↗
PubMed2000

Cisplatin induces fas expression in esophageal cancer cell lines and enhanced cytotoxicity in combination with LAK cells.

OBJECTIVE: To establish a new therapeutic approach for the treatment of esophageal cancer, we investigated an alternative mechanism of immunotherapy for sensitizing target cells to effector cells. METHODS: Six human esophageal cancer cell lines were used. The expression of Fas antigen on tumor cells was determined by flow cytometry. The cytotoxic effect of cis-dichlorodiammineplatinum (CDDP) and anti-Fas antibody was evaluated using an MTT assay. The cytotoxic activity of LAK cells was measured by a (51)Cr release assay. RESULTS: Five out of six esophageal cancer cell lines expressed Fas antigen at various levels (26.2-61.5%), and Fas expression increased after CDDP treatment. The antitumor effect of anti-Fas antibody on the esophageal cancer cell line and the antitumor effect of LAK cells activated by IL-2 were enhanced by pretreatment with CDDP. After concanamycin A treatment to specifically evaluate Fas-dependent cytotoxicity, LAK cells expressing Fas ligand killed only Fas-positive cells, but not Fas-negative cells. An anti-Fas neutralizing antibody inhibited this cytotoxicity. DNA fragmentation was shown in a cell line that was treated with CDDP and anti-Fas antibody, and also in the targeted esophageal cancer cell line cocultured with LAK cells. CONCLUSION: Our results suggest a potential clinical application of CDDP as a Fas inducer to make esophageal tumors susceptible to Fas antigen and LAK cytotoxicity.

Antineoplastic Agents↗
PubMed2000

Effect of beta-blocker therapy on severe ventricular arrhythmias in patients with idiopathic dilated cardiomyopathy.

Beta-blocker therapy has been shown to improve cardiac function and prognosis in patients with idiopathic dilated cardiomyopathy (DCM). However, whether beta-blockers reduce severe ventricular arrhythmias and sudden cardiac death has not been clarified. The present study was designed to investigate the effects of beta-blockers on non-sustained ventricular tachycardia (VT) and sudden cardiac death in patients with DCM. Sixty-five patients with DCM treated with diuretics, digitalis and angiotensin-converting enzyme inhibitors were assigned to receive beta-blockers (n = 33) or not (n = 32). Mean follow-up was 53+/-30 months. The echocardiographic indices of cardiac function, the incidence of non-sustained VT on Holter monitoring electrocardiograms, and sudden cardiac death rate were compared between the 2 groups. Comparable improvement in cardiac function on echocardiograms was found in the 2 treatment groups. The patient group treated with beta-blockers showed a significant reduction in the prevalence of VT (from 43 to 15%, p<0.05) and the development of new episodes of VT (5 vs. 16%) compared to the group without beta-blockers. The sudden cardiac death rate did not differ between the 2 groups. The results of the present study suggest that beta-blockers are effective in reducing severe ventricular arrhythmias in patients with DCM.

Adrenergic beta-Antagonists↗
PubMed2000

Methionine-induced phytoalexin production in rice leaves.

The application of methionine on wounded rice leaves induced the production of rice phytoalexins, sakuranetin and momilactone A. This induction resulted from stimulation of phenylalanine ammonia-lyase and naringenin 7-O-methyltransferase activity. Jasmonic acid, ethylene, and active oxygen species are important as signal transducers in disease resistance mechanisms. However, although the endogenous level of jasmonic acid rapidly increased in reaction to wound, methionine treatment could not induced endogenous JA production. Ethylene induced the production of the flavonoid phytoalexin, sakuranetin, but did not induce the production of a terpenoid phytoalexin, momilactone A. On the other hand, a free radical scavenger, Tiron, counteracted the induction of both sakuranetin and momilactone A production in methionine-treated leaves. Active oxygen species may be important in methionine-induced production of phytoalexins.

Cyclopentanes↗
PubMed2000

Usefulness and safety of theophylline injection form (Theodrip) for the treatment of acute asthma.

The effects of the speed of intravenous infusion on the pharmacokinetics of theophylline were studied in 9 healthy volunteers (Ex I). Subjects were intravenously administered either six 4.8 mg/kg theophylline (Theodrip, Nikken Chemicals Co., Ltd., Japan) or three matching placebo injections (4.8 ml/kg physiological saline) for 30 min (Step I) or for 15 min (Step II). In Steps I and II, Cmax was 10.8 +/- 1.1 and 10.8 +/- 0.8 micrograms/ml, respectively. These Cmaxs were concentrations yielding therapeutic effects in patients with acute asthma. Next, comparative pharmacokinetics between theophylline (Theodrip) and aminophylline were examined by a crossover method in 16 healthy volunteers (Ex II). The 90% confidence limits of the differences of mean values were within 80-120% and were 92.8-100.1% for Cmax, 99.7-105.3% for t1/2 and 100.2-104.4% for AUC. Thus, we concluded that the pharmacokinetics of the plasma theophylline after intravenous administration of Theodrip (theophylline at 4.8 mg/kg) were bioequivalent to those of aminophylline (6.0 mg/kg) for 30 min. In Ex I and II, no subjects had adverse effects and in Ex I no influence on ECG was seen. In addition, the convenience of Theodrip was compared with that of ampules of aminophylline among nurse volunteers (Ex III). The times required for set-up of Theodrip were significantly shorter than those of aminophylline ampules. On the other hand, the adverse reactions to aminophylline resulting from hypersensitivity reactions to its ethylenediamine component have been reported. Theodrip consists of 200 mg theophylline and 200 ml physiological saline in a plastic bag. Therefore, Theodrip, which does not contain ethylenediamine, is expected to have less adverse effects and be easier to handle than aminophylline.

Acute Disease↗