Basal laminar thinning in branching morphogenesis of the chick lung as demonstrated by lectin probes

Three lectins, wheat germ agglutinin (WGA), soybean agglutinin (SBA) and Ricinis communis agglutinin I (RCA), were used to study the basement membrane of developing chick lungs. Thinning of the basement membrane at the tips of newly formed bronchi was visualized with all three lectins, but was particularly evident using SBA. Control sections established the ability of the lectins to stain hyaluronic acid and chondroitin sulphate. Neuraminidase, bovine testes hyaluronidase and Streptomyces hyaluronidase removed some of the staining, but none were able to affect the staining of the basement membrane. Possible explanations for this are discussed in the text. Incorporation of [3H]thymidine is enhanced at the tips relative to the interbud area in stage-30 lungs, extending previous studies on stage-26 lungs. Evidence has been presented here which demonstrates that mechanisms of morphogenesis used in avian embryos are similar to those already elucidated in work on mammalian embryos.