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  • 1
    ISSN: 1432-0738
    Keywords: Methylnitrosourea ; Teratogenicity ; Mice ; Dose-response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The teratogenic potency of the directly acting alkylating agent methylnitrosourea (MNU) was analysed in mice. Skeletal abnormalities were evaluated after treatment on either day 11 or 12 of pregnancy. Ectrodactyly was the predominant effect after treatment on day 11. Treatment on day 12 triggered especially double-sided microdactyly (method of analysis: measuring digit lengths). Litter variabilities were analysed using a new biometrical procedure. Using probit analysis, dose-response curves were computed from the experimental data obtained and the effective doses were calculated and compared with maternal toxicity. Low dose extrapolation was performed by use of various mathematical models which yielded very similar EDI/100 and EDI/1000 values.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 60 (1987), S. 238-245 
    ISSN: 1432-0738
    Keywords: Dose-response-relationship ; Pharmacokinetics ; Prenatal toxicity ; Teratogenic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract (1) The terminology to be used in reproductive (or in prenatal) toxicology has to be in accord with other fields and principles of toxicology; the reasons are briefly discussed. In addition it is essential to assess prenatal toxicity in comparison to adult (maternal) toxicity. (2) Since pharmacokinetics in laboratory animals (e. g. rodents) usually differ considerably from that in man, this fact has to be considered when planning and evaluating studies on prenatal toxicity. Up till now this aspect has seldom been taken into account. (3) A special problem in prenatal toxicity is the inter- and intralitter variability of the toxic manifestation (especially in polytocal animals). This problem has to be recognized by the investigators and means of dealing with it have to be developed. (4) Like all other toxic effects, embryo-/fetotoxic manifestations occur dose dependently. Little information is available in the literature on clean dose-response-curves for teratogenic effects. Some data from our laboratory are presented. (5) Risk assessment of teratogenic effects up till now represents a major problem. While qualitative risk assessment for man on the basis of animal data is possible, quantitative extrapolation from such data to the situation possibly existing in man is still difficult, because basic principles and strategies are largely lacking (e. g. may a “threshold” be assumed or not?). The results of some activities towards this goal are presented from our laboratory.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0738
    Keywords: Acetoxymethyl-methylnitrosamine ; Teratogen ; Sidepreference ; Limb bud culture ; DNA alkylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1. The alkylating agent acetoxymethyl-methylnitro-samine (DMN-OAc) triggers preferential left-sided paw defects in mice following IP administration on either day 11 or 12 of pregnancy. Predominantly, ectrodactyly and hypoplasia of the left paws were found. 2. In an organ culture system, using limb buds of 11-day-old mouse embryos, differentiation is severly impaired following addition of 2 μM DMN-OAc to the culture medium. Left and right limbs are equally affected. In contrast, when DMN-OAc is administered in vivo to the dams with subsequent culturing of the limb buds, growth and differentiation of the left limb buds is more affected when compared to the right. 3. Furthermore, DNA alkylation experiments were performed: in vitro, following addition of (14C)-DMN-OAc (2.3 μM) to the culture medium, the DNA alkylation rate of the limb bud DNA is determined. In vivo, following IP administration of 10 mg/kg DMN-OAc to the dams on day 11 of pregnancy, the extent of DNA alkylation of whole-embryo DNA is similar. However, the DNA alkylation rate of separately pooled left and right limb buds exhibits a two-fold difference according to the different teratogenic susceptibility. The results obtained with both in vivo and in vitro systems are consistent with the thesis that a certain amount of DNA alkylation in the tissue of the embryos is the initial step of alkylating agent-induced teratogenicity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0738
    Keywords: Methylnitrosourea ; DNA adduct formation ; Mice ; Embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Formation of DNA adducts in 11-day-old mouse embryos was studied by measuring the initial alkylation rates of the methylated purine bases 7-methylguanine, O6-methylguanine, and 3-methyladenine. In the first part of the studies the adduct rates were measured in the teratogenic dose range (ED10-ED90, 2.7–5.6 mg/kg). These results were compared with similar data obtained from studies with ethylmethanesulfonate and acetoxymethyl-methylnitrosamine. For the three investigated substances a correlation was found between the initial adduct rate of O6-alkylguanine in the DNA of the embryos and the teratogenic potency. In the second part of the study the rate of adduct formation was measured in the sub-teratogenic dose range. These data will be used for molecular dosimetry in a risk assessment of low doses.
    Type of Medium: Electronic Resource
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