Relation between embryotoxicity of adenine in mice and day of prenatal treatment

Testing the vulnerability of the phylotypic stage: on modularity and evolutionary conservation

The phylotypic stage is the developmental stage at which vertebrates most resemble each other. In this study we test the plausibility of the hypotheses of Sander [1983, Development and Evolution, Cambridge University Press] and Raff [1994, Early Life on Earth, Columbia University Press; 1996, The Shape of Life, University of Chicago Press] that the phylotypic stage is conserved due to the intense and global interactivity occurring during that stage. First, we test the prediction that the phylotypic stage is much more vulnerable than any other stage. A search of the teratological literature shows that disturbances at this stage lead to a much higher mortality than in other stages, in accordance with the prediction. Second, we test whether that vulnerability is indeed caused by the interactiveness and lack of modularity of the inductions or, alternatively, is caused by some particularly vulnerable process going on at that time. From the pattern of multiple induced anomalies we conclude that it is indeed the interactiveness that is the root cause of the vulnerability. Together these results support the hypotheses of Sander and Raff. We end by presenting an argument on why the absence of modularity in the inductive interactions may also be the root cause of the conservation of the much discussed temporal and spatial colinearity of the Hox genes. J. Exp. Zool. (Mol. Dev. Evol.) 291:195-204, 2001.

Review of drug-induced limb defects in mammals

The objective of this paper was to illustrate the spectrum of possible limb malformations in mammals resulting from drug exposure. A bibliography of 171 papers from 20 journals was generated from which pertinent data (drug used, limb defects reported, predominant defect location) were tabulated. These data should provide a basis for predictions about types of defects that might be expected in further studies and for judging postulated drug-induced human limb defects. However, direct extrapolation to humans is inappropriate. The following trends were observed: 1) Distal limb defects (autopod) are almost twice as common as proximal limb defects (stylopod and zygopod). 2) Ectrodactyly is the single most common type of limb defect, accounting for over half of the autopod defects. 3) Ectrodactyly is almost twice as common in the hindlimb as in the forelimb. 4) Postaxial ectrodactyly is over twice as common as preaxial ectrodactyly in the forelimb, but preaxial ectrodactyly is four times more common in the hindlimbs. 5) Polydactyly occurs with approximately equal frequency in forelimbs and hindlimbs, and preaxial polydactyly is most common in both fore and hindlimbs. 6) Polymelia (supernumerary limbs) occurred in one case, and may have been a spurious result. 7) Either transverse hemimelia is greatly underreported in teratology studies or it essentially does not occur. We have concluded that, at least in some cases, acetazolamide, adenine, 1,7-dimethylxanthine, and xanthine derivative aminophylline, retinoic acid, acetoxy-methyl-methylnitrosamine, aspirin, and cadmium can all cause unilateral defects.

External examination of limb positions in near-term mouse fetuses: an experimental study and review of the literature published in Teratology

The accidental finding of near-term mouse fetuses exhibiting limb positions that could have been interpreted as malformations but that were, in fact, spurious, led us to study the posture of the limbs in the offspring of 100 CD-1 mouse dams. A total of 1,015 fetuses (18 days-old, vaginal plug: day 0), was examined. Fifteen of these fetuses presented positions that deviated markedly from the norm and were therefore considered to be "unusual," although the usual position was recovered in 6 of the 15 by placing the affected limb in a standard position and eventually eliciting locomotion. A broad review of the literature was made in order to evaluate our results fully. This review included 43 reports published in Teratology that recorded abnormal limb positions in near-term mouse and rat fetuses, and another 9 reports where these were not referred to but that included photographs showing such abnormalities. The data obtained from our experimental study and review led us to conclude that for a correct record of abnormal positions in near-term mouse and rat fetuses, authors must follow appropriate, clearly described technical procedures, including maneuvers to rule out spurious displacements; give adequate information in the legends of the photographs; use unequivocal terminology; and carry out further research to determine accurately the range in variation of normal limb positions.

Mitigation of caffeine-induced fetopathy in mice by pretreatment with beta-adrenergic blocking agents

In a previous experiment, fetopathic effects of caffeine were significantly reduced by pretreatment with propranolol at dosage levels of 2.5 to 10 mg/kg. The present experiments were undertaeken to investigate the relation between time intervals of propranolol pretreatment and its effect on reducing fetopathy. Furthermore, the effect of timolol, another beta-adrenergic blocking agent, on reducing fetopathy was compared with that of propranolol. Propranolol (5 mg/kg) administered 15, 30 or 60 minutes before caffeine treatment significantly reduced the caffeine-induced fetopathy. The optimal effect was found when propranolol was given 30 minutes before caffine. The reduction in fetopathy by timolol pretreatment was comparable to that of propranolol. The results lend support to the hypothesis that the fetopathic effect of caffeine is linked with released catecholamines in material or fetal issues of mice.