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Biomedical subjects

J F Fallon

Publications and source records attributed to J F Fallon.

87 records · Page 5Linked to original sources
PubMed1977

Interdigital cell death during limb development of the turtle and lizard with an interpretation of evolutionary significance.

Cell death accompanies the formation of free digits in birds and mammals. However, in species with webbing between the adult digits, little or no cell death occurs in the prospectively webbed region of the developing interdigit. Cell death does not occur during the formation of free digits in amphibians. In this paper we report that cell death accompanies the formation of the digits in snapping and painted turtles and in the skink (a lizard). We conclude that cell death accompanying the formation of free digits had its origin at the point of amniote emergence during evolution.

Animals↗
PubMed1975

Normal development of the chick wing following removal of the polarizing zone.

The negative results of assays for polarizing activity along the posterior border of the chick wing 24 and 48 hours after removal of the polarizing zone demonstrate that this zone is not regenerated following removal. These results, and the fact that normal wing development can occur after polarizing zone removal from stages 15 through 24 wing buds, indicate that during these stages the polarizing zone has no direct role in normal development of the limb bud. It is speculated that the polarizing zone is effective only during limb induction and that after this time it exists in latent or residual form.

Animals↗
PubMed1975

The role of beta-adrenergic activity in the production of cardiac and aortic arch anomalies in chick embryos.

The sympathomimetic amines isoproterenol, epinephrine, norepinephrine, and phenylephrine are structural derivatives of beta-phenylethylamine and have proportionately different effects on alpha- and beta-adrenergic receptors. Chick embryos in ovo were each administered a single dose of one of these compounds at concentrations ranging from 0.4 times 10(-9) to 20 times 10(-9) mol/5 mul saline during Hamburger and Hamilton stages 20-27. In other experiments embryos were pretreated with the beta-antagonist propranolol and subsequently administered isoproterenol. 743 cardiovascular anomalies were produced. The production of cardiovascular anomalies was proportional to the degree of beta-adrenergic activity of each drug. The frequency of anomalies was significantly reduced by pretreatment with propranolol. At all concentrations tested the anomaly rate was greater in chick embryos receiving an experimental compound than in controls. The general types of anomalies included aortic arch defects, ventricular septal defect, double outlet right ventricle, aortic hypoplasia, and truncus arteriosus. These results demonstrate that activation of the beta-adrenergic receptor mechanism is directly related to the cardiovascular anomalies produced in the chick embryos.

Abnormalities, Drug-Induced↗