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Biomedical subjects

H Hosoya

Publications and source records attributed to H Hosoya.

79 records · Page 5Linked to original sources
PubMedDate not supplied

Graph-theoretical analysis of tunneling electron transfer in large polycyclic aromatic hydrocarbon networks.

Effect of a single nitrogen atom substitution to a number of large polycyclic aromatic hydrocarbon (PAH) molecules was calculated systematically, and it was found that especially in parallelogram-type PAH abnormal electron transfer (called tunneling electron transfer, TET) was observed. That is, fairly large amount of pi-electron is withdrawn to an electronegative nitrogen atom from almost the farthest end of a conjugated aromatic hydrocarbon molecule, leaving almost no change in the interior of the molecule. This change can be simulated by the Kekulé structure counting for subgraphs of the parent molecule.

Journal Article↗
PubMedDate not supplied

Development of neural network simulator for structure--activity correlation of molecules (NECO). Prediction of endo/exo substitution of norbornane derivatives and of carcinogenic activity of PAHs from 13C-NMR shifts.

A perceptron type neural network simulator for structure--activity correlation of molecules has been developed with two different learning methods, i.e., back-propagation and reconstruction methods. First by use of the back-propagation method the exo/endo branching of norbornane and norbornene derivatives was correctly predicted from the set of 13C NMR chemical shifts for various ring carbon atoms. Then the obtained correlation was analyzed by the reconstruction learning method. It was shown in this case that the NMR shifts for two carbon atoms out of seven have strong correlation with the exo/endo branching. Further, structure--activity correlation between the 13C NMR chemical shifts and carcinogenicity of 11 polycyclic aromatic hydrocarbons was also analyzed using the reconstruction method. It was demonstrated that neural network analysis is suitable for the elucidation of complicated structure--activity problems where many factors are nonlinearly entangled.

Animals↗
PubMedDate not supplied

Effects of anticancer drugs, metals and antioxidants on cytotoxic activity of benzothiepins/benzoxepins.

Among 11 benzothiepins/benzoxepins, 4-chloro-3,4-dihydro-2-(2-oxo-2-phenylethyl)-1-benzothiepin-5-(2H)-one [1] showed the highest cytotoxicity against human oral squamous cell carcinoma HSC-2 cells, followed by 2,3-dihydro-2-(2-oxopropyl)-2-phenyl-1-benzoxepin [2]. Popular antioxidants, such as N-acetyl-L-cysteine and sodium ascorbate significantly reduced the cytotoxic activity of [1] but not that of [2]. Compound [1] induced internucleosomal DNA fragmentation in human promyelocytic leukemic HL-60 cell line, but produced large DNA fragmentation in human oral tumor cell lines (HSC-2, HSG). Compounds [1] and doxorubicin additively reduced the viable cell number of HSC-2 cells. These data, taken together with their tumor specific action, demonstrate for the first time, the medicinal efficacy of benzothiepins/benzoxepins.

Antineoplastic Agents↗
PubMedDate not supplied

Cytotoxic activity of benzothiepins against human oral tumor cell lines.

A total of 11 newly synthesized benzothiepins and structurally-related compounds were investigated for cytotoxic activity against both normal and tumor cells. All these compounds showed higher cytotoxic activity against three human oral tumor cell lines (HSC-2, HSC-3, HSG) than against normal human gingival fibroblast (HGF), suggesting tumor-specific cytotoxic action. In general, 3,4-dihydro-1-benzothiepin-5(2H)-ones [1-6] showed higher cytotoxic activity than 2,3-dihydro-1-benzothiepins [7-11]. Compounds 4 (4-bromo-3,4-dihydro-2-(2-oxo-2-phenylethyl)-1-benzothiepin-5(2H)-one), 5 (4-bromo-3,4-dihydro-2-(2-oxopropyl)-1-benzothiepin-5(2H)-one) and 6 (4-bromo-3,4-dihydro-2-[1-(methoxycarbonyl)-1-methylethyl]-1-benzothiepin-5(2H)-one), showed higher cytotoxic activity than compounds 1, 2 and 3, respectively, which had Cl instead of Br at C-4 position. Agarose gel electrophoresis demonstrated that these compounds induced large DNA fragments in oral tumor cells, whereas they produced smear pattern of smaller DNA fragments in human promyelocytic leukemia cells HL-60. These data suggest the medicinal efficacy of benzothiepins.

Antineoplastic Agents↗