thiosemicarbazide and Bone-Diseases

In vitro reactivity for each of four osteolathyrogens with a model compound for the lysyl oxidase (LO) cofactor was evaluated and coupled with mixture toxicity testing to evaluate agent-cofactor reactivity as a potential mechanism of action for osteolathyrism. Reactivity of the model cofactor (mLTQ: 4-butylamino-5-methyl-o-quinone), with each of two ureides, semicarbazide (SC) and thiosemicarbazide (TSC), and each of two aminonitriles, aminoacetonitrile (AAN) and beta-aminopropionitrile (betaAPN), was assessed using UV-vis spectrophotometry; both in the absence and presence of Cu(II)-bipyridine (bipy) complex. Two sets of mixture toxicity experiments were conducted using a frog embryo assay that assessed the incidence of osteolathyrism in the notochord of tadpoles after 96-h exposure. The resulting concentration-response curves for each set were evaluated (chi(2) goodness-of-fit test) against theoretical curves for two combined effects models: dose-addition and independence, to determine the combined effect of each osteolathyrogen combination. The agents SC, TSC and AAN each showed rapid, irreversible reactivity with mLTQ, both in the absence and presence of Cu(II)-bipy complex, as indicated by bleaching of the mLTQ peak (504 nm) and formation of an adduct at 350 nm. betaAPN showed no apparent reactivity in the absence of prolonged incubation with mLTQ, whether Cu(II)-bipy complex was present or not. After prolonged incubation (24-144 h) a new peak formed at 350 nm, suggesting that betaAPN reacts weakly with the cofactor, but in a manner different from the other agents examined. The toxicity tests indicated a dose-additive combined effect for the SC:TSC, AAN:SC and AAN:SC:TSC mixtures (0.1

Topics: Abnormalities, Drug-Induced; Aminoacetonitrile; Aminopropionitrile; Animals; Bone Diseases; Collagen; Dose-Response Relationship, Drug; Lathyrism; Lysine; Protein-Lysine 6-Oxidase; Quinones; Semicarbazides; Xenopus

Eight substituted thiosemicarbazides were assayed for their toxicity and teratogenicity using early embryos of Xenopus laevis. Results of the 96-h static tests on seven 4-position alkyl substituents were used for quantitative structure-activity relationship (QSAR) analyses, with thiosemicarbazide as the parent compound. The compounds induced malformations via the connective tissue defect osteolathyrism. Teratogenicity (log EC50) was negatively correlated with molar refractivity, suggesting that steric inhibitions were important in explaining the variations in biological activity due to changes in the 4-position substituent. It appeared that there were two separate modes of lethal action, one associated with the ring-containing substituents and the other with straight-chain substituents. However, QSARs were not developed for embryolethality (log LC50) or for the mortality/malformation index (LC50/EC50) due to the limited number of chemicals eliciting each lethal mode of action.

Topics: Animals; Bone Diseases; Chemical Phenomena; Chemistry; Lathyrism; Semicarbazides; Structure-Activity Relationship; Teratogens; Xenopus laevis

Exposure of Xenopus laevis tadpoles to thiosemicarbazide (TSC), at concentrations from 10 to 75 mg/liter, causes an inhibition of metamorphosis and produces the classic manifestations of the experimental disease, osteolathyrism. Concentration-dependent effects of TSC exposure are observed in growth rate and in the severity of the osteolathyrogenic effect. Concentrations allowing the most rapid growth produce the more extreme osteolathyrogenic defects. Osteolathyrism in these animals is identical in characteristics to the condition described in a wide variety of vertebrate species. In Xenopus, osteolathyrism is expressed morphologically as anomalies in bone development, skeletal conformation, and abnormal connective tissue organization in the aorta wall. The underlying defect responsible for these observations is apparently a perturbation of collagen fiber formation and maturation, as evidenced ultrastructurally by aberrant distribution and packing of collagen fibers. It is suspected that TSC produces this effect by altering the availability of copper ion, a cofactor to lysyl oxidase, an essential enzyme for intermolecular cross-linking of procollagen. This step in collagen metabolism has been consistently implicated as the site of action of several osteolathyrogenic agents. Xenopus tadpoles present a classic response to this known osteolathyrogen and demonstrate a high degree of uniformity of response within the experimental groups. In view of the developmentally significant events accessible with this system and inherent logistic and economical advantages, the metamorphosing tadpole of Xenopus holds considerable potential for the experimental analysis of teratogenic agents and events.

Topics: Animals; Bone and Bones; Bone Diseases; Collagen; Copper; Lathyrism; Metamorphosis, Biological; Semicarbazides; Xenopus laevis