| Abstract: | The neural basal lamina in hindbrain regions of exencephalic loop-tail (Lp/Lp) mice and of their normal (+/+; Lp/+) littermates was analyzed histochemically at the electron microscopic level by means of enzyme digestion and alcian blue staining with critical electrolyte concentrations (CEC) of MgCl2. At 9 days of gestation, the normal and abnormal embryos showed a similar pattern of alcian blue staining with a CEC of 0.00 M or 0.05 M MgCl2. However, with a CEC of 0.30 M MgCl2, the basal lamina in the abnormals stained more prominently, particularly the lamina rara externa, suggesting the presence of more sulfated glycosaminoglycans (GAG) in the abnormals. Moreover, predigestion of the tissues with Streptomyces hyaluronidase, which removes hyaluronic acid (HA), indicated that the abnormal basal lamina contained relatively less HA than in the normal embryos. By 10 days of gestation the normal basal lamina contained relatively more sulfated GAG and less HA and was thus more similar in appearance to that in the abnormal embryos. This apparently premature shift from HA predominance to sulfated GAG predominance in the abnormal basal lamina may be of significance in the etiology of dysraphism in this mutant. |
