| Budget Amount *help |
¥14,900,000 (Direct Cost: ¥14,900,000)
Fiscal Year 1999: ¥5,700,000 (Direct Cost: ¥5,700,000)
Fiscal Year 1998: ¥9,200,000 (Direct Cost: ¥9,200,000)
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| Research Abstract |
1. E. coli clones which expressing recombinant Shiga toxin (Stx)1-A and Stx-1-B subunits, were established. Culture supernatant of the clone expressing Stx1-A, nut not Stx1-B showed the inhibitory activity on in vitro protein synthesis. Neither recombinant Stx1-A nor Stx1-B showed Vero cell cytotoxicity. For reconstitution of biologically active toxin, the culture supernatants were mixed. The reconstituted recombinant Stx1 showed both Vero cell cyotoxicity and inhibition in vitro protein synthesis.
2. The therapeutic effect of fosfomycin (FOM), microcycline (MINO), kanamycin (KM) and norfloxacin (NFLX) was evaluated using the EHEC infected mouse model which we established previously. Each of the antimicrobial agents, 1/16 LD50, was given to the mice per os (p.o.) or intraperitoneally (i.p.). For 3 days after bacterial inoculation and then we observed their mortality rate for 2 weeks. The mortality rates of mice administered with MINO (p.o./i.p.), KM (p.o.), NFLX(p.o./i.p) were significantly lower than those of the control group. In an in vitro experiment, each of the four drugs in combination with mitomycin (MMC) caused a more significant decrease in the bacterial number and the release of VT2c than sole MMV.
3. The study was aimed to evaluate the effects of Stx2 on (I) maternal lethality, (ii) fetuses, (iii) delivery period, and (iv) maternal behavior after delivery. Timed pregnant ICR mice were injected intravenously with Stx2 on day 5 of the pregnancy (early stage) or on day 15 (late stage). In early-stage experiments, the number of normal fetuses of mic injected with Stx2 was significantly lower than that of control mice. In late-stage experiments, mothers injected with Stx2 delivered normal numbers of neonates, but could not take care of them. The lethal dose of Stx2 were not difficult for pregnant and nonpregnant female mice at either stage.
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