Supernumerary rib

Pregnant females given toxaphene on days 6-15 of gestation at 32 mg/kg BW daily Maternal survival was 87% on day 8 and 50% on day 16. Survivors had weight loss in whole body, thymus, and spleen. Adverse developmental effect (supernumerary ribs) in litters 5... 

FIGURE 8.6. Effect of litter size (live fetuses per litter) on incidence of supernumerary rib in 1379 control rat litters. Between 1978 and 1988, fetal skeletons from 1379 litters of control rats were stained with alizarin red and examined for supernumerary rib. 

Beyer, P.E. and Chemoff, N. (1986). The induction of supernumerary ribs in rodents The role of maternal stress. Teratog. Carcinog. Mutag. 6 149-429. 

Wickramaratne, G.A. de S. (1988). The post-natal fate of supernumerary ribs in rat teratogenicity studies. J. Appl. Toxicol. 8 91-94. 

Diethyl phthalate administered in the diet to rats during major organogenesis increased the incidence of fetal lumbar ribs only at 3200mg/kg/day, a maternally toxic dose. In another report, there also was an increased incidence of supernumerary ribs, but no other embryo/fetal effects, in the offspring of rats fed 5% DEP on gestational days 6-15 maternal toxicity was evident as reduced body weight gain. ... 

Interpretation Using Historical Control Data to Understand Supernumerary Ribs, a Common Skeletal Variation... 

Supernumerary rib is an expected morphological observation in developmental toxicity studies and one of the most common skeletal variants in rodents and rabbits with highly variable incidence between species and strain. The interpretation of supernumerary rib data can be complex because not only is this a spontaneously occurring variant in normal fetuses but it is also induced in rats and mice by various experimental conditions, including increased maternal stress (27) or high dosages of xenobiotics (14, 28, 29). 

The phenotype is quite different in the rat and rabbit short supernumerary rib is much more common than full supernumerary rib in the rat whereas both short and full supernumerary rib are much more common in the rabbit, as illustrated in Table 3 using historical... 

Historical control data for supernumerary rib in the thoracolumbar region in the rat (14th rib) and Rabbit (13th rib) ... 

ChernoffN et al (1991) Significance of supernumerary ribs in rodent developmental toxicity studies Postnatal persistence in rats and mice. Fundam Appl Toxicol 17 448 53... 

Sprague-Dawley rats and Swiss CD-I mice were exposed by inhalation to 0, 280, 1400 or 7000 ppm [800-19 530 mg/m ] isoprene for 6 h per day on seven days per week on gestational days 6-19 (rats) or 6-17 (mice) (lARC, 1994). There was no adverse effect on rat dams or other reproductive index at any dose level. The only fetal malformation observed in rats was reduced ossification of the vertebral centra, which occurred at 7000 ppm isoprene. In mice, there was reduced fetal body weight at all dose levels and decreased maternal weight gain in the 7000-ppm group. Also in the 7000-ppm group, there was an increased incidence of supernumerary ribs but no increase in fetal malformations. 

Hackett et al. (1987) and by ORNL), 46%, and 69%, respectively, were reported. In addition, gastric lesions (mucosal inflammation, edema, necrosis, and mucosal sloughing) were found at all doses, and teratogenic effects (fetal stunting and supernumerary ribs) were observed at the highest dose. On the basis of gastric lesions and mortality, the lowest-observed-adverse-effect level (LOAEL) for this study was 0.07 mg/kg per day. 

F (decrease in ossification of skeleton, bent tails, and increase in supernumerary ribs, increase in stillborn litters)... 

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