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Biomedical subjects

Y Ohkawa

Publications and source records attributed to Y Ohkawa.

At least 73 records · Page 4Linked to original sources
PubMed1988

Anticoagulant therapy in recurrent cerebral embolism: a retrospective study in non-valvular atrial fibrillation.

For the prevention of recurrent embolic stroke, 23 elderly patients with non-valvular atrial fibrillation (NVAF) were treated with oral anticoagulants (warfarin) during a mean period of 3.8 years. Only one patient suffered recurrent embolism, and another had acute myocardial infarction. There was no cerebral haemorrhage during the treatment. In an untreated control group (from an autopsy series), recurrent embolic strokes occurred in 18 of 70 NVAF patients (26%) during a mean period of 1.3 years. Long-term anticoagulant therapy appears to be effective in the prevention of recurrent embolic stroke in elderly patients with NVAF.

Aged↗
PubMed1988

Screening for skin-tumor promoters.

Since attention has been drawn to the role of oxygen radicals in tumor promotion, we investigated whether or not the nitroblue tetrazolium (NBT) reduction test using mouse peritoneal macrophages was useful as a rapid screening method for skin-tumor promoters. On the basis of our results, we concluded that this test system was appropriate for the screening of 12-0-tetradecanoylphorbol-13-acetate (TPA)-type tumor promoters and bore comparison with other screening methods for tumor promoters. A large number of skin-tumor promoters, such as active phorbol esters, teleocidin and aplysiatoxin, appear to act indirectly through a free radical mechanism by binding to a membrane receptor.

Animals↗
PubMed1987

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-enhanced transformation in vitro by radical scavengers.

The inhibitory effects of some scavengers of oxygen radicals were studied, using a two-stage transformation assay system in vitro 3-methylcholanthrene (3-MC)-initiation and 12-O-tetradecanoylphorbol-13-acetate-(TPA)-promotion in Balb 3T3 cells. Mannitol, a scavenger for hydroxyl radicals, strongly inhibited the TPA-enhanced transformation in a dose-dependent manner. Superoxide dismutase (SOD) and catalase, which are specific scavengers for O2-. and H2O2, respectively, also inhibited the transformation. These results suggest that oxygen radicals may play an important role in the TPA-enhanced transformation in Balb 3T3 cells.

Animals↗
PubMed1986

Retinoic acid and butylated hydroxyanisole inhibit promoter-enhanced transformation in vitro.

The inhibitory effects of some antipromoters were studied using a two-stage transformation assay system in vitro with 3-methylcholanthrene (3-MC)-initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promotion in BALB 3T3 cells. Butylated hydroxyanisole (BHA), a phenolic antioxidant, inhibited TPA-enhanced transformation in a dose-dependent manner, but butylated hydroxytoluene (BHT) did not. Among the three antipromoters tested, retinoic acid (RA) was the most effective inhibitor.

Butylated Hydroxyanisole↗
PubMed1986

Surgical treatment of congenital distal tracheal stenosis involving the carina.

Untreated congenital stenosis of the distal trachea frequently results in lethal airway obstruction. A 3-year-old boy with segmental stenosis of the distal trachea and a 2-year-old girl with segmental stenosis involving the carina and the right main bronchus were treated successfully with resection and reanastomosis. Operative techniques, anesthetic management, postoperative care, and tracheal growth after anastomosis are discussed.

Child, Preschool↗
PubMed1986

Establishment of lung fibroblastic cell lines from a non-human primate Tupaia belangeri and their use in a forward gene mutation assay at the hypoxanthine-guanine phosphoribosyl transferase locus.

The cells obtained from a lung of a new-born male Tupaia belangeri were maintained in mass culture for greater than 400 days. After 55 population doubling levels (100 days in culture), three cell lines were separately established; these lines showed constant growth properties. One line, designated as T-23, was used for a mutation assay. The T-23 cells showed an absolute plating efficiency of 30-50%, and a population doubling time of 18-19 h in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum. The cells had a modal chromosome number of 62 (pseudodiploid) with the loss of a chromosome and the gain of an unidentified one. T-23 cells, like human cells, were much more susceptible to ouabain than mouse cells but relatively less susceptible to 8-azaguanine, while, unlike human cells, they were less sensitive to 6-thioguanine (6TG). N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) was less, but 4-nitroquinoline-1-oxide (4NQO) was more toxic to T-23 cells than to human or mouse cells. Benzo[a]pyrene-induced toxicity was almost comparable among the cell types. For the mutation assay, we chose 6TG-resistance (100 microM) as a marker. The optimal expression time (8-13 days) and cell density at selection to eliminate metabolic cooperation (2 x 10(4) cells/60-mm dish) were determined. Some of the cells selected with 6TG showed less than 0.4% of the total incorporation of [14C]hypoxanthine into wild-type cells, suggesting the mutants under selection were affected at the hypoxanthine-guanine phosphoribosyl transferase locus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Modified inverse square sensitometry for the determination of the characteristic curve of radiographic screen/film systems.

To determine the characteristic curve of the radiographic screen/film systems in a short focal spot-film distance, the inverse square sensitometric method was modified by changing the radiation intensity with two kinds of filters. The characteristic curves obtained in the two exposure series with these two kinds of filters were overlapped to obtain a complete one. The characteristic curve thus obtained was almost the same as the one obtained by the original inverse square sensitometric method. The accuracy of the characteristic curves obtained by the modified method was well-reflected in the clinical radiographs.

Humans↗
PubMed1986

Mouse peritoneal lymphocytes, a new target for analyzing induction of sister chromatid exchanges on in vivo exposure to a genotoxic agent.

The availability of use of mouse peritoneal lymphocytes as target cells for analyzing sister chromatid exchanges (SCE) upon exposure to a genotoxic drug, cyclophosphamide, was investigated using female ICR mice. Use of these cells overcame the difficulty in use of mouse lymphocyte cultures, recovering sufficient metaphase cells. The greatest advantage of use of peritoneal lymphocytes was that about 1-2 X 10(6) lymphocytes/mouse could easily be recovered from the peritoneal cavity in high purity. Their mitogenic responses were good when Escherichia coli lipopolysaccharide, in combination with 2-mercaptoethanol, was used as mitogens, but they were less when purified phytohemagglutinin was used. In the presence of lipopolysaccharide (60 micrograms/ml) and 2-mercaptoethanol (22-88 microM), the maximum incidence of second division metaphases (greater than 50%) and the highest mitotic index (greater than 4%) were observed 36-40 h after stimulation. Under these conditions, the base-line SCE showed the constant level. The range of intrastrain variations in the base-line SCE was 0.24-0.36/chromosome. The distribution histograms of SCE/chromosome did not fit a single Poisson model, suggesting that these cells are heterogeneous with respect to the base-line SCE. Single s.c. injections 1 h before harvest of doses of 0.75-3.0 mg of cyclophosphamide per kg evoked positive responses, and injections of over 0.375 mg/kg had linear dose-dependent effects. On harvest of cells for up to 192 h after the injection, the maximal induction of SCE attained 1 h after exposure was found to return time dependently to the control level at 192 h. After the initial rapid reduction in the cell number, cellular recovery, measured as the mitotic index and the number of peritoneal exudate cells recovered, returned to the control level within 48 h, without a significant increase thereafter. After maintaining cells under the liquid-holding experiment for various times in vitro following a single exposure to cyclophosphamide for 1 h in vivo, the reduction of their SCE and recovery of their mitotic index were more rapid than those of cells in the time-course experiment. These findings suggest that the association of the recruitment of less- and/or nondamaged cells from their precursors with reduction of the SCE is slight. Repair(s) and, to a lesser extent, selective loss of more damaged cells may be the main factors contributing to the early reduction response of the SCE frequency. The relations of these factors are discussed.

Animals↗
PubMed1985

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced nitroblue tetrazolium reduction in mouse peritoneal macrophages by various tumor promotion inhibitors.

The effects of various inhibitors on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced reduction of nitroblue tetrazolium (NBT) in mouse peritoneal macrophages were investigated. The reduction was inhibited by phospholipase A2 inhibitors, such as dibromoacetophenone, the lipoxygenase inhibitor nordihydroguaiaretic acid, an NADH-dehydrogenase inhibitor, the microfilament inhibitor cytochalasin B, oxygen radical scavengers such as superoxide dismutase, antioxidants such as butyl hydroxyanisole and non-specific inhibitors such as retinoic acid. The reduction was not affected by the cyclooxygenase inhibitor indomethacin or the H2O2 scavenger catalase.

Animals↗
PubMed1985

Induction of nitroblue tetrazolium reduction in mouse peritoneal macrophages by tumour promoters and inhibition of the induced nitroblue tetrazolium reduction by some inhibitors.

Two polyacetates, aplysiatoxin and debromoaplysiatoxin, as well as 12-O-tetradecanoylphorbol-13-acetate (TPA), mezerein and teleocidin enhance nitroblue tetrazolium (NBT) reduction in mouse peritoneal macrophages in vitro. The ED50 values for NBT reduction of these 5 TPA-type tumor promoters were 4.2 ng/ml for TPA, 36 ng/ml for mezerein, 0.53 ng/ml for teleocidin, 1.5 ng/ml for aplysiatoxin and 108 ng/ml for debromoaplysiatoxin. The NBT reduction induced by the 5 tumor promoters is inhibited by 2 inhibitors of tumor promotion, retinoic acid and dibromoacetophenone. The possibility that tumor promotion by TPA-type tumor promoters involves similar mechanisms such as superoxide anion radicals release in cell membranes is discussed.

Acetophenones↗
PubMed1985

Histidine increases the frequency of chromosomal aberrations induced by the xanthine oxidase-hypoxanthine system in V79 cells.

The combined effects of the xanthine oxidase (XO)-hypoxanthine (HX) system and the various kinds of amino acids in Eagle's minimum essential medium on chromosomal aberrations were studied in Chinese hamster V79 cells. Among 13 amino acids tested, only histidine significantly increased the number of aberrant chromosomes and cytotoxicity in combination with the XO-HX system. This enhancing effect of histidine on chromosomal aberrations was dose-dependent at 0.063% - 0.25%; it was not affected by superoxide dismutase, but was strongly inhibited by catalase.

Animals↗