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Title	Ultrastructural changes in the secretory organelles of endocardium and endocardial cushion tissue of embryonic rat heart after teratogenic treatment
Author	Mills, William Palmer, Jr.
Date	1974
Affiliation/College	College of Graduate Studies
Department	Anatomy
Extent	87 leaves : ill.; 29 cm
Subject.MeSH	Endocardium--ultrastructure Organelles--ultrastructure Endocardial Cushion Defects--etiology Academic Dissertations
Collection	MUSC Theses and Dissertations
Contributing Institution	Waring Historical Library (MUSC)
Rights	Copyright is held by the author.
Language	English
Type	Text
Format	application/pdf
Media Type	Manuscripts
Resource Identifier	mtd1974_mills_wp
Abstract	Endocardium and endocardial cushion tissue from 12.5 and 14.5 day embryonic rat hearts exposed to sodium salicylate or 6-aminonicotinamide were compared electron microscopically with non-injected or parahydroxybenzoic acid-treated control tissue. The purpose of these comparisons was to test a working hypothesis which purports that cardiac septal defects are causally related to an inhibition of acid mucopolysaccharide synthesis within endocardium and the subjacent cushion tissue. Emphasis in this study was placed on the ultrastructural morphology of the secretory organelles of these cell types. The endocardium was found to undergo a biphasic pattern of cytodifferentiation in which endocardium associated with myocardial trabeculae displayed atrophy of secretory organelles and attenuation of cytoplasm. Conversely, endocardium overlying cushion tissue exhibited hypertrophy of the secretory organelles and associated cytoplasm resulting in a scalloped appearance. Ultrastructural similarities between endocardial cells and subjacent cushion tissue cells suggest the latter are of endocardial origin. The two teratogens apparently inhibited secretory potential by inducing regressions or alterations of the secretory organelles of endocardium and the associated cushion tissue. These alterations took the form of "honeycombl distensions within the otherwise non-dilated cisternae of rough endoplasmic reticulum (RER) of endocardium overlying cushion tissue, a feature normally seen only in control trabeculated endocardium. In addition, there was a reduction in the number of non-coated secretory vesicles associated with Golgi lamellae. Localization of acid mucopolysaccharides was attempted through the use of Mowry's and Rinehart and Abul-Haj's dialyzed iron preparations. Polyanionic material was localized in control tissue within non-coated vesicles associated with Golgi lamellae as well as along cell surfaces. No stain was associated with the "honeycomb" distensions of the RER. Therefore, these distensions appeared to be focalized accumulations of proteinaceous material associated with mucopolysaccharide synthetic inhibition. Localization of dialyzed iron in experimental tissue was reduced apparently due to the teratogenically-induced regression of the secretory organelles. Finally, it was found that both teratogens had an epitheliolytic effect on cushion tissue cells. Sodium salicylate and 6-aminonicotinamide are both established inhibitors of acid mucopolysaccharide synthesis, and it appears that this induced cellular degeneration may play a part in the reduction of synthetic potential.

Ultrastructural changes in the secretory organelles of endocardium and endocardial cushion tissue of embryonic rat heart after teratogenic treatment

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