azaserine and Abnormalities--Drug-Induced

Administration of azaserine (250 micrograms) to day-4 chick embryos in ovo was shown to induce micromelial limbs. In the present study, biosynthesis of cartilage-characteristic proteoglycan H (PG-H) as an index of limb chondrogenesis was examined in normal and micromelial hind limbs from day-7 chick embryos by biochemical and immunological methods. (1) Metabolic labelling of the micromelial limbs with [6-3H]-glucose and [35S]sulphate, followed by analysis of labelled proteoglycans by glycerol-density-gradient centrifugation under dissociative conditions, showed a marked reduction in PG-H synthesis. (2) PG-H synthesized by micromelial limbs differed from that synthesized by normal limbs in possessing a slower sedimenting velocity and much lower amounts of chondroitin sulphates. (3) The amount of PG-H core protein in micromelial limbs was significantly decreased to about 19% on a per limb basis and about 42% on a per DNA basis of that in normal limbs, as determined by e.l.i.s.a. (4) The transition from PG-M to PG-H during limb formation was retarded in micromelial limbs as judged by an indirect immunofluorescence technique using antibodies against PG-M and PG-H. (5) The deficiency of incorporation of labelled glucose into chondroitin sulphate chains of PG-H in micromelial limbs was partially restored by using [6-3H]-glucosamine as a precursor, suggesting that the synthesis of UDP-N-acetylhexosamine, required for chondroitin sulphate chain synthesis of PG-H in micromelial limbs, was decreased. These results suggest that the reduction in the synthesis of PG-H as well as the production of an abnormal form of PG-H during a critical period of limb morphogenesis may be important factors in explaining the micromelia induced by azaserine.

Topics: Abnormalities, Drug-Induced; Animals; Azaserine; Cartilage; Chick Embryo; Hindlimb; Proteoglycans

Topics: Abnormalities, Drug-Induced; Animals; Azaserine; Cricetinae; Female; Fetal Growth Retardation; Limb Deformities, Congenital; Mesocricetus; Pregnancy; Rats

The capabilities of investigators in the fields of teratology and toxicology are greatly enhanced by the use of tissue culture procedures in unraveling the mechanisms of drug action. Techniques currently available for the culture of postimplantation mammalian embryos permit evaluation of their metabolic responses to potential teratogens even when the length of time embryos survive and develop in culture is too short to allow a conventional teratologic survey of malformations. A simple procedure for culturing mouse embryos during early organogenetic stages is described in this report that will be of value to teratologists; it avoids the requirements of special glassware and equipment by using ordinary capped test tubes which are rotated tomaintain and efficient nutritional and gaseous evnironment. Some studies concucted with this procedure to monitor the metabolism of embryo during the first 24 h of culture are summarized. Another aspect of tissue culture, organ culture, provides further manipulative capability by which embryonic organs can be maintained for long periods of time during which they develop and differentiate to an extent that their morphological and biochemical responses to a teratogen can usually be made. Comparative effects of several teratogenic agents and the relative concentration of each that produces a similar degree of response are summarized. It is concluded that organs are more sensitive to teratogens in culture than they are in vivo, and that different teratogens possess enough specificity to isolate their simple growth-retarding effect from the role they play in distrubing other specific developmental events.

Topics: Abnormalities, Drug-Induced; Aminopropionitrile; Aminopterin; Animals; Azaserine; Bromodeoxyuridine; Culture Media; Culture Techniques; Diazooxonorleucine; DNA; Dose-Response Relationship, Drug; Embryo, Mammalian; Embryo, Nonmammalian; Embryology; Extremities; Female; Gestational Age; Limb Deformities, Congenital; Niacinamide; Protein Biosynthesis; Teratogens; Thalidomide; Vitamin A; Vitelline Membrane

Topics: Abnormalities, Drug-Induced; Animals; Azaserine; Carcinoma, Ehrlich Tumor; DNA, Neoplasm; Female; Glucosyltransferases; Leukemia L1210; Mammary Neoplasms, Experimental; Mercaptopurine; Mice; Nucleosides; Oxidoreductases; Phosphotransferases; Pregnancy; Pregnancy, Animal; Sarcoma 180; Sarcoma, Experimental