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Biomedical subjects

T Harayama

Publications and source records attributed to T Harayama.

At least 19 recordsLinked to original sources
PubMed2001

Diffusion of particles bouncing on a one-dimensional periodically corrugated floor.

We report on a class of spatially extended mechanical systems sustaining a transport process of diffusive type. These systems consist of a point particle subject to a constant vertical acceleration and bouncing on a one-dimensional periodically corrugated floor. We show that the deterministic dynamics of these systems is chaotic with small elliptic islands for many parameter values. The motion of particles perturbed by a small noise has a horizontal diffusion that is normal. In such a case, we show that the diffusion coefficient oscillates periodically as the energy of particles increases. In the absence of noise, there still exists an effective numerical value for the diffusion coefficient and this value has an irregular dependence on energy.

Journal Article↗
PubMed2001

Quantum-classical correspondences of the Berry-Robnik parameter through bifurcations in lemon billiard systems.

The quantum level statistics affected by bifurcations in classical dynamics is studied by using a one-parameter family of lemon billiard systems. The classical phase space of our system consists of regular and irregular regions. We determine an analytic solution of the phase volume for these regions as a function of the system parameter and show that the function reveals a cusp singularity at the bifurcation point. The function is compared with its quantum mechanical counterpart, the Berry-Robnik parameter. By estimating the semiclassical regime from the effective Planck constant that validates the quantum-classical correspondence of the Berry-Robnik parameter, we determine a region of the system parameter where the cusp can be reproduced by the statistical properties of the eigenenergy levels.

Journal Article↗
PubMed2001

Synthesis and antimalarial activity of febrifugine derivatives.

The regioisomers (2a,b) of the piperidine ring of febrifugine (1a) and isofebrifugine (1b) were synthesized from 4-allyl-3-piperidone (5). Reduction of 5 afforded a mixture of the trans and cis alcohols (6a,b) without diastereoselectivity; this result differentiated it from the reduction of 2-allyl-3-piperidone (14). The antimalarial activity of 2a,b and related compounds was tested.

Antimalarials↗
PubMed2000

Anomalous substituent effects in the bischler-napieralski reaction of 2-aryl aromatic formamides

Treatment of some 1-naphthylformamides (or formanilides) possessing a 2,4,5-trioxygenated phenyl substituent at the 2-position with POCl(3) caused an unprecedented carbon insertion reaction into a benzene ring, producing 7-5 ring (azaazulene) systems as valence isomers of isoquinoline skeletons. Precise examination of this abnormal Bischler-Napieralski reaction (BNR) using various substrates led to the following scope and limitations: (i) the 7-5 ring systems were constructed when either 2-alkoxy-4, 5-methylenedioxyphenyl- or 4,5-dialkoxy-2-hydroxyphenyl-substituted formamides were used as a starting substrate; (ii) in the former case the formyl carbon was inserted into the C(1)-C(6) bond of the 2-phenyl group, and normal isoquinoline cyclization competed with an abnormal carbon insertion reaction; (iii) the presence of a hydroxy group at the 2'-position as in the latter cases caused exclusive carbon insertion, in which alternative C(1)-C(2) insertion products were quantitatively formed; (iv) 3, 6-dimethoxy-2-hydroxyphenyl-substituted formanilide electronically equivalent to 4,5-dialkoxy-2-hydroxy derivatives produced an indole-pyrone as an abnormal BNR product. Theoretical approaches using the PM-3 method indicated that these abnormal BNRs could be triggered by ipso attack at the 1'-position yielding spiro intermediates. Ring cleavege of the six-membered ring in the spiro intermediates to a ketene function followed by recyclization was proposed for the 2'-hydroxy-directed abnormal BNRs leading to the C(1)-C(2) insertion product or the indole-pyrone derivative.

Journal Article↗
PubMed1999

Shedding of membrane type 1 matrix metalloproteinase in a human breast carcinoma cell line.

Membrane type 1 matrix metalloproteinase (MT1-MMP) with a transmembrane domain is a new member of the MMP gene family and is expressed on the cell surfaces of many carcinoma cells to activate the zymogen of MMP-2 (gelatinase A). We have previously reported that MT1-MMP is released into culture media in a complex form with tissue inhibitor of metalloproteinases 2 (TIMP-2) from a human breast carcinoma cell line, MDA-MB-231, treated with concanavalin A (Con A). In the present study, we further studied the release mechanism of MT1-MMP. Immunoblot analysis indicated that the amounts of MT1-MMP in culture media increase with the time of exposure and the concentration of Con A, and those in cell lysates conversely decrease in a similar way. Time- and dose-dependent release of MT1-MMP into the media was confirmed by a sandwich enzyme immunoassay specific to MT1-MMP. The molecular weight of the immunoreactive MTI-MMP in the media was Mr 56,000, which was 4,000-Mr smaller than that in the cell lysates. Northern blot analysis demonstrated that the mRNA expression level of MT1-MMP is about 3-fold enhanced after a 24 h-exposure to Con A and this is maintained up to 72-h exposure. The release of MT1-MMP from the Con A-treated cells was inhibited by metalloproteinase inhibitors such as EDTA and o-phenanthroline, but not by MMP inhibitors including TIMP-1, TIMP-2 and BB94 or other proteinase inhibitors of serine, cysteine and aspartic proteinases. During the Con A treatment of the cells, cell viability decreased time- and dose-dependently and dead cells reacted positively in the TdT-mediated dUTP Nick-End Labeling (TUNEL) method. Con A-treated MDA cells showed apoptotic morphology when stained with Hoechst dye and hematoxylin and eosin. DNA ladder formation was detected by electrophoresis of the DNA from Con A-treated MDA cells. These results suggest that MT1-MMP release from Con A-treated cells is due to shedding mediated by metalloproteinase(s) other than MMPs, and is associated with apoptosis.

Apoptosis↗
PubMed1999

[Baeyer-Villiger reaction of benzaldehydes possessing oxygen functions with SeO2-H2O2].

The Baeyer-Villiger (B. V.) reaction using SeO2-H2O2 was examined for various benzaldehydes possessing methoxy groups and/or a furan ring. When benzaldehydes have an electron-donating group (methoxy group) at the ortho or para position to a formyl group, the B. V. reaction proceeded rapidly and in a good yield. Since the reaction using SeO2-H2O2 is carried out under a neutral condition, this reaction are applicable to aldehyde derivatives with a furan ring which is unstable against acid.

Benzaldehydes↗
PubMed1998

Comparison of the structural characteristics of chromosome VI in Saccharomyces sensu stricto: the divergence, species-dependent features and uniqueness of saké yeasts.

Previous studies have revealed that chromosome VI of saké yeasts is much larger than that of the other strains of Saccharomyces cerevisiae. Southern analysis using segments of chromosome VI of a laboratory strain as probes suggested that the nucleotide sequence of a major portion of this chromosome is conserved, but considerable diversity was found in the distal parts in the other strains. Physical maps also indicated that differences in length of chromosome VI were mainly due to differences in its ends. NotI was found to generate 9 kb and/or 16 kb fragments from the left telomere of chromosome VI in most saké yeasts, but no fragment in the case of AB972. SfiI produced one or two 30-50 kb fragments from the right end of this chromosome in all saké yeasts tested, but produced a 20 kb fragment in the case of AB972. All S. cerevisiae strains not employed in saké brewing were the same as AB972 in these respects. S. paradoxus had one NotI site in chromosome VI, while S. bayanus had two, one of which is possibly common to both species. The SfiI site mentioned above was present in chromosome VI of all species, while that of S. bayanus and S. paradoxus each had a second site distinct from the other. Chromosome VI of S. pastorianus was not distinguishable from that of S. bayanus.

Blotting, Southern↗
PubMed1997

Syntheses and antifungal activity of dl-griseofulvin and its congeners. III.

Several congeners (1b-g), with novel substituents on the benzene ring of griseofulvin, were prepared by the application of a synthetic method developed by us. Antifungal activity of these congeners decreased in order of dl-griseofulvin (1a) = 1d > 1b, c >> 1e-f (inactive). The relationship between the antifungal activity and the position or kind of substituents on the benzene ring of griseofulvin is discussed.

Antifungal Agents↗
PubMed1997

Synthesis and antitumor activity of fused quinoline derivatives. V. Methylindolo[3,2-b]quinolines.

Indolo[3,2-b]quinoline derivatives (1b-i) with a methyl group at each possible position have been synthesized. The 1-methyl (1b) and 9-methyl (1i) derivatives were inactive, but the 3-methyl (1d), 4-methyl (1e), and 6-methyl (1f) derivatives exhibited high treatment/control (T/C) value and cure rates against leukemia P388 in mice. These results indicated that modification of indolo[3,2-b]quinoline derivatives at 3, 4, and 6 positions may be useful approach for lead optimization.

Animals↗
PubMed1997

Syntheses and antifungal activity of dl-griseofulvin and its congeners. II.

Griseofulvin derivatives, dl-6'-demethyl-6'-ethylgriseofulvin (dl-5) and dl-6'demethyl-6'phenylgriseofulvin (dl-6) were prepared by application of a synthetic method developed by us. Antifungal activity of these derivatives decreased in the order of dl-griseofulvin (dl-1) >> dl-6(inactive). The reaction of these derivatives with ethanethiol gave two types of compounds, 2'-(ethylthio)griseofulvin (15) and 4'-(ethylthio)isogriseofulvin (16). The relationship between the ratios of isolated yield of 15 and 16 and antifungal the activity of griseofulvin derivatives is discussed.

Antifungal Agents↗
PubMed1995

[Alkylation of gem-dibromocyclopropanes with higher-order organocuprates].

The reaction of gem-dibromocyclopropanes (1) with a higher-order organ-ocuprate prepared from CuCN and commercially available MeLi, followed by the addition of MeI in situ, afforded dimethylcyclopropanes (2) in good yields. The differential substitution reaction of dibromide (1a) in one pot with the higher-order organocuprate and allyl bromide gave a compound (8) in the moderate selectivity as shown in Table 3. Its stereochemistry was deduced by the reaction mechanism.

Alkylation↗
PubMed1991

On the conversion of thymidine phosphate bromohydrins to thymidine phosphates: a model reaction for the repair of oxidized nucleotides.

Bromohydrins (12, 13, and 14), which were oxidatively damaged products of thymidine nucleotides, were repaired by the action of sunlight (2700 lux) or heat via a radical mechanism to regenerate the original nucleotides (8,9, and 10). A significant effect of 3',5'-phosphate linkage on the repair reactions to natural type of thymidine nucleotide was proposed.

Alcohols↗