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S Yabushita

Publications and source records attributed to S Yabushita.

6 recordsLinked to original sources
PubMed2000

Comparative evaluation of a 5-day Hershberger assay utilizing mature male rats and a pubertal male assay for detection of flutamide's antiandrogenic activity.

A 5-day Hershberger assay utilizing mature male rats and a pubertal male assay were evaluated for the ability to detect antiandrogenic compounds such as flutamide, an androgen receptor antagonist. Six days after the operation, implantation with two silicon capsules containing testosterone (T) (30 mg/capsule) in castrated rats provided the ventral prostate and seminal vesicle weights as well as serum T and luteinizing hormone (LH) levels equivalent to those of the controls (non-castrated, non-implanted rats). Castrated rats implanted with two T-capsules (6 rats/dose) were treated by gavage for 5 days with vehicle (0.5% carboxymethylcellulose) or flutamide (0.15, 0.6, 2.5, or 10 mg/kg/day). Flutamide produced significant decreases in weights of the seminal vesicles and the levator ani plus bulbocavernosus muscles (> or =0.6 mg/kg/day) and ventral prostate (> or =2.5 mg/kg/day), and an increase in serum LH levels (> or =2.5 mg/kg/day), but no changes in serum T levels. When age-matched intact male rats were treated with 10-mg/kg/day flutamide, a significant increase in serum T levels was observed concomitant with a tendency of increased LH. The organ weights were also decreased; however, the changes were less than those in the castrated, T-implanted rats. Immature intact male rats (10 rats/dose) were treated for 20 days with flutamide (0, 0.15, 0.6, 2.5, or 10 mg/kg/day). Flutamide produced significant decreases in weights of the seminal vesicles, ventral prostate, and levator ani plus bulbocavernosus muscles at 2.5 and 10 mg/kg/day. Serum LH levels, but not T levels, were increased at 10 mg/kg/day. Statistical significance of some of these changes was not observed in the 6 animals/dose examined. Our findings support that the Hershberger assay, in the current conditions, is the most sensitive among the assays examined and a useful short-term screening method for the detection of antiandrogenic compounds.

Androgen Antagonists↗
PubMed2000

Evaluation of a 5-day Hershberger assay using young mature male rats: methyltestosterone and p,p'-DDE, but not fenitrothion, exhibited androgenic or antiandrogenic activity in vivo.

A 5-day Hershberger assay using young mature male rats to detect compounds interfering with androgen receptor (AR)-mediated mechanisms was evaluated for ability to identify p,p'-DDE (a weak AR antagonist) and methyltestosterone (MT, an AR agonist). Fenitrothion, an organophosphate pesticide, was also evaluated in this validated assay. Castrated male Crj:CD(SD)IGS rats (1 week after castration, 11 weeks of age) were subjected to experiments. To determine a suitable value of testosterone propionate (TP) as a reference androgen for detection of antiandrogenic chemicals, castrated male rats were treated daily with TP (0, 0.06, 0.25, 1, 4, or 16 mg/kg/day, s.c.). TP produced increases in weights of ventral prostate, seminal vesicles and levator ani plus bulbocavernosus muscles. Serum androgen level measured by RIA kit (mostly TP) were elevated in a dose-related manner, while the weights of organs with 1 mg/kg/day of TP were nearly equivalent to the maximum responses (i.e., sub-maximal). One hundred mg/kg/day of p,p'-DDE significantly attenuated TP 0.1 mg/kg-induced increases in weights of seminal vesicles and muscles, and TP 1 mg/kg-induced increases in weights of ventral prostate, seminal vesicles and muscles, but did not affect the weight of these organs in either TP 16 mg/kg-treated or intact rats, demonstrating that the dose range of 0.1-1 mg/kg TP is suitable for reference androgen. Oral treatment with 100 mg/kg of MT increased the weights of ventral prostate, seminal vesicles and muscles as strongly as did subcutaneous injection of 1 mg/kg of TP. These findings demonstrate that the 5-day Hershberger assay using young mature as well as immature male rats is a sensitive and valid short-term screening method for the detection of chemicals interfering with AR-mediated mechanisms. To determine whether fenitrothion interferes with AR-mediated mechanisms in vivo, fenitrothion (0, 0.75, 1.5 or 3 mg/kg/day) was administered by gavage for 5 days to castrated rats for androgenicity, or to castrated rats treated with 1 mg/kg TP for antiandrogenicity. Treatment with fenitrothion had no adverse effects on clinical signs, body weight, or liver or kidney weights, but cholinesterase activities in the brain and erythrocytes were significantly suppressed by fenitrothion to, respectively, 77-81% and 66-67% of control levels. In the antiandrogenicity experiment, serum androgen levels of TP-treated, castrated rats did not differ among groups. Treatment with 100 mg/kg of p,p'-DDE as a positive control again significantly attenuated TP-induced increases in weights of the ventral prostate and seminal vesicles, while fenitrothion had no effect on the weights of any organs. In the androgenicity experiment, treatment with 100 mg/kg of MT significantly increased weights of ventral prostate, seminal vesicles and muscles, but fenitrothion had no effects on the weights of any of these organs. These findings yield no evidence that fenitrothion interferes with AR-mediated mechanisms in vivo, consistent with the result of several toxicological bioassays.

Androgen Antagonists↗
PubMed1994

Reduction of aluminium concentration in albumin products.

The aluminium concentration in albumin products has been reduced to < or = 100 ppb by an anion exchanger treatment. Furthermore, we have found that this low aluminium concentration in a albumin products has been maintained for extensive periods of time, when they are stored in de-alkalized soft glass containers.

Aluminum↗