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Biomedical subjects

H Kasai

Publications and source records attributed to H Kasai.

At least 361 records · Page 20Linked to original sources
PubMed1978

Synthesis and antitumor activity of preactivated isophosphamide analogues bearing modified alkylating functionalities.

In search of cancer chemotherapeutic agents with greater efficacy than cyclophosphamide, 4-hydroperoxyisophosphamide analogues bearing modified alkylating functionalities such as 2-bromoethyl, 2-iodoethyl, 2-methyl-sulfonyloxyethyl, and 2-ethylsulfonyloxyethyl groups were prepared by ozonolytic cyclization reaction of N,N'-substituted 3-butenyl phosphorodiamidates. Comparative cytotoxicity against L1210 cells and antileukemic life-span activity against L1210 implanted BDF1 mice of the newly synthesized compounds were tabulated. The 4-hydroperoxyisophosphamide analogues which have different alkylating groups in a molecule showed slightly greater cytoxicity in vitro than those with the same alkylating groups. Most of the compounds having different alkylating groups also showed high antileukemic activity in vivo. Among them, the highest efficacy was found for 2-[N-methyl-n-(2-chlorethyl)]amino-3-(2-methylsulfonyloxyethyl)-4-hydroperoxy-1,3,2-oxazaphosphorinane 2-xoide (NSC 280122D) whos life-span activity was also greater than that of 4-hydroperoxyisophosphamide, cyclophosphamide, and isoposphamide. The superiority of this compound was especially apparent by oral administration.

Alkylating Agents↗
PubMed1976

Benzo(a)pyrene diol epoxides as intermediates in nucleic acid binding in vitro and in vivo.

Evidence has been obtained that a specific isomer of a diol epoxide derivative of benzo(a)pyrene, (+/-)-7 beta,8alpha-dihydroxy-9alpha, 10alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, is an intermediate in the binding of benzo(a)pyrene to RNA in cultured bovine bronchial mucosa. An adduct is formed between position 10 of this derivative and the 2-amino group of guanine.

Animals↗
PubMed1976

Structure of wye (Yt base) and wyosine (Yt) from Torulopsis utilis phenylalanine transfer ribonucleic acid.

A fluorescent base wye (Yt base) was isolated from Torulopsis utilis tRNAPhe. The structure was established as 4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazo[1,2-alpha]purine based on ultraviolet (uv), nuclear magnetic resonance (NMR), and mass spectra, and by direct comparison with synthetic material. The nucleoside, wyosine (Yt), was isolated from purified tRNAPhe by enzymatic degradations followed by column and thin-layer chromatographies. The structure of wyosine is proposed as 3-ribofuranosyl-4,9-dihydro-4,6-dimethyl-9-oxo-1H-imidazol[1,2-alpha]purine (the ribosyl group is attached to the N-9 position of guanine nucleus) on the basis of comparison with model compounds.

Candida↗
PubMed1976

Formation of 5alpha-reduced C19 steroids from progesterone in vivo by 5alpha-reduced pathway in older prepubertal rat testis.

Either [3H] progesterone (0.5 or 5 nmol/5 muCi), 5alpha-[3H] pregnane-3,20-dione (5 nmol/5 muCi) or [14C] progesterone (6.6 nmol/0.2 muCi) plus 5alpha-[3H]-pregnane-3,20-dione (1 or 6.6 nmol/0.6 muCi), suspended in 0.05 ml of physiological saline solution, was injected into each testis of 32- and 90-day-old rats. Following injection, radioactive metabolites in testis and spermatic vein blood were extracted, isolated, measured and identified by column and paper chromatographies, with derivative formation and recrystallization to constant specific activity. In the blood and testis of older prepubertal rats, major 17-OH-C21 and C19 metabolites of progesterone were 5alpha-reduced steroids such as 3alpha, 17alpha-dihydroxy-5alpha-pregnan-20-one, 5alpha-androstane-3alpha,17beta-diol and androsterone. Following injection of [14C] progesterone plus 5alpha-[3H] pregnane-3,20-dione into 32-day-old rat testis, no significant augmentation of the isotope from progesterone was observed in 5alpha-reduced C19 steroids as compared with 5alpha-reduced 17-OH-C21 steroids, indicating that 5alpha-reduced C19 steroids were mainly formed from 5alpha-reduced 17-OH-C21 steroids in older prepubertal testis. In the blood and testis of adult rats, small amounts of 5alpha-reduced metabolites were shown to be produced from progesterone, while active 17alpha-hydroxylation of 5alpha-pregnane-3,20-dione followed by C17-C20-lyase reaction was demonstrated. These findings seem to indicate that formation of 5alpha-reduced C19 steroids from progesterone by the 5alpha-reduced pathway is a major pathway of androgen biosynthesis in older prepubertal rat testis in vivo.

Animals↗
PubMed1976

Structure of 7,12-dimethylbenz(a)anthracene-guanosine adducts.

Arene oxides have been proposed as the reactive intermediates in the process of carcinogenesis induced by polycyclic aromatic hydrocarbons. The present study defines the structures of four guanosine adducts formed by the reaction of 7,12-dimethylbenz[a]anthracene-5,6-oxide with polyguanylic acid. The modified polymer was hydrolyzed to nucleotides and the hydrophobic guanosine adducts separated from unmodified guanosine by LH-20 column chromatograhy. The adducts were further resolved into four components (I-IV) by reverse phase high pressure liquid chromatography. Analysis of the ultraviolet, circular dichroism, mass, and proton magnetic resonance spectra of these compounds, or their acetate and free base derivatives, indicates that in all four compounds the aromatic hydrocarbon is present on the 2 amino group of guanine. Compounds I and IV, and II and III constitute diastereoisomeric pairs, respectively. In the I and IV pair, the adducts result from addition at the 6 position of the original dimethylbenz[a]anthracene oxide, whereas in the II and III pair, the addition occurs at the 5 position. Indirect evidence suggests that trans opening of the oxide occurred in all cases but this remains to be established.

9,10-Dimethyl-1,2-benzanthracene↗