Date of Award

8-1-1980

Degree Type

Dissertation

University or Center

Atlanta University (AU)

Degree Name

Ph.D.

Department

Biology

First Advisor

Roy Hunter, Jr.

Abstract

The notochord, a characteristic vertebrate structure, has been the subject of investigation for many years; yet, the information is scant. This structure is important for it aids in the establishment of bilateral symmetry in the developing embryo. The amphibian and chick embryo notochords have been investigated recently, and a pattern of normal development was proposed. The notochord develops in phases: bilaminar; rod-like unvacuolated; rod-like and vacuolated. These phases encompass changes in shape, orientation and position of the cells, an increase in cell contacts, and the laying do\~ of a basal lamina. An increasing complexity within the cytoplasm also accompanies the morphogenetic changes.

This investigative report undertook the study of older amphibian larvae notochord, more specifically the effects of L-azetidine-2-carboxYlic acid (LACA) on the notochord in an in vitro system. LACA is a proline analog that becomes incorporated into polypeptides in place of proline. In this study, amphibian notochord was subjected to 100~g/ml of LACA and the cellular changes were noted.

Light microscopic analysis of hematoxylin-eosin staining provided information as to the general composition of notochord tissue. Two distinguishable cell types were observed -- an outer cell termed "peripheral." and an inner cell called "vacuolated." The peripheral cell is somewhat spherical in shape. contains a large nucleus. and the cytoplasm is without vacuoles. A layer of these cells forms a continuum around the outer area of the notochordal structure. The vacuolated cell contains a large vacuole. and a meager amount of cytoplasm with a smaller nucleus.

Electron microscopic analysis supports the findings of the two distinct cell types. It does not provide evidence for a peripheral cell continuum. These studies also suggest that LACA may interfere with the integrity of cellular organelles and moreover limit the existing number of intracellular entities. A moderate increase in vesicular and fibrillar cytoplasmic content is expressed in TEM. and a restriction of the extracellular material is shown in SEM.

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Biology Commons

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