DNA synthesis inhibition, cytotoxicity and their relationship to teratogenesis following administration of a nicotinamide antagonist, aminothiadiazole, to pregnant rats

Four groups of Wistar rats were treated with 100 mg/kg aminothiadiazole (ATD) i.p. on day 12 of gestation. The first group was allowed to proceed to day 20, when they were sacrificed and the teratogenic effects analyzed in the surviving fetuses. A second group was given 100 mg/kg nicotinamide (NAM) i.p. simultaneously or at intervals of 4, 8 or 12 h following ATD. Third and fourth groups corresponded to the first and second except that [3H]thymidine was administered and one uterine horn removed for histological study or analysis of DNA synthesis rates. The following observations were made:

1. ATD proved teratogenic to 90% of the surviving fetuses, causing one or more malformations of organs such as limbs, tail, palate and heart.

2. Nicotinamide was capable of protecting the embryo against ATD teratogenicity. This effect diminished as the interval between ATD and NAM administration lengthened so that by 12 h little protection remained.

3. ATD produced a severe and prolonged inhibition of DNA synthesis, reaching a low of 12% of control level at 17 h and returning to near normal by 38 h.

4. NAM reversed this inhibition of DNA synthesis in proportion to the length of the interval between ATD and NAM administration.

5. ATD produces severe cytotoxicity especially in the limb buds and neural tube.

6. Based on this and earlier studies the hypothesis is proposed that the time of appearance of maximal cell death plays a major role in determining the degree and pattern of forelimb ectrodactyly.

Mass spectra of nitrogen heterocycles. II. Pyridyl Schiff bases

A number of anils of pyridine aldehydes and benzylideneaminopyridines were used to study positional effects of aromatic substituents and heteroatom placement on electron impact mass spectra. The simple fragmentation pattern of aromatic Schiff bases was obtained with all 3- and 4-pyridyl compounds when the other aromatic ring was unsubstituted phenyl, or in the case of anils, had a chloro or 3-methoxy substituent. Marked changes were brought about by a pyridyl ring at either end of the azomethine group when the heterocyclic nitrogen was adjacent to it. Displacement and rearrangement reactions then became dominant. Methoxy substitution para to the azomethine in all anils studied gave loss of methyl radical as the major reaction.

γ-Radiolysis of some 1,4-quinones in benzene

The γ-radiolysis of several 1,4-quinones in benzene solution has been studied.� 1,4-Benzoquinone, 1,4-naphthoquinone, and 2-phenylnaphthoquinone undergo nuclear phenylation in deaerated solution. In aerated solution 1,4-benzoquinone is exceptional in being converted into 4-hydroxydiphenyl ether (13). Possible mechanisms for the formation of the radiolysis products are discussed.

γ-Radiolysis of chloranil in benzene

Γ-Radiolysis of chloranil in benzene gave four products: the quinones 3,6-di-chloro-2,5-diphenyl-1,4-benzoquinone (11) and 2-chloro-3,5,6-triphenyl-1,4-benzo-quinone (12), and small amounts of 2,3,5-trichloro-6-phenylhydroquinone (10) and 1,3,4-trichloro-2-hydroxydibenzofuran (14; R = H). The last compound only was formed when radiolysis was carried out in the presence of oxygen. Syntheses of 2,3,5-trichloro-6-phenylhydroquinone (10), 2,3,6-trichloro-6-phenyl-1,4-benzoquinone (9), and 2-chloro-3,5,6-triphenyl-1,4-benzoquinone (12)are described.

A Technic Suppressing Development of Reproductive Function and Sensitivity to Estrogen in the Female Rat

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