الفهرس | Only 14 pages are availabe for public view |
Abstract The present study has dealt with investigating the ontogenetic development of the gastrointestinal tract (GIT) of the Egyptian toad, Bufo regularis using four-fold different and integrative approaches, namely, morphological, histological, ultrastructural and molecular. The two former approaches were employed as a guide when conducting the latter. 1-1- Morphological investigation: This involved illustration and description for the developing GIT using light microscopy. Seven developmental stages were mainly considered including larval, i.e. 42, premetamorphic, i.e. 50, prometamorphic, i.e. 55, metamorphic, i.e. 60, post-metamorphic, i.e. 66, juvenile and adult stages. Morphometric parameters were employed for tracing the developmental changes in the length of both GIT and the body of the stages under consideration. The investigation revealed that the length of the GIT had the same attitude as the body length and exhibited progressive increase until stage 55, decreased sharply at stages 60 and 66, then increased progressively at juvenile and adult stages.2- Histological investigation: The developmental changes in the histology of the GIT were traced and described for certain stages namely 42, 50, 55, 60, 66, juvenile and adult stages. HistoSummary - 100 - morphometric parameters were employed for determining the developmental changes in the GIT histology including the length, diameter, wall thickness and height of mucosal folds.3- Ultrastructural investigation: This has been done using the transmission electron microscope. The ultrastructure of the anterior portion of the developing anterior part of the small intestine was investigated for the developmental stages 42, 50, 55, 60, 63 and 66. The results of this investigation was in accordance with the histological observations where the developmental changes at the ultrastructural level were correlated with the developmental phases in relation to the metamorphic state. The most prominent ultrastructural features were the appearance of apoptotic bodies/nuclei within the larval epithelium at the metamorphic stages 60 & 63.4- Molecular investigation: This involved two parts: A- Determination of DNA fragmentation: This has been done for different GIT segments of the developmental stages 50, 55, 60, 63 & 66 where the presence of deoxyribonucleic acid (DNA) ladder was determined. This molecular investigation revealed that the metamorphic stages 60 & 63 displayed extensive DNA laddering compared with the other larval 50 & 55 and post-metamorphic 66 developmental stages where the DNA appeared intact with no sign of fragmentation. However, the prometamorphic stage 55 exhibited some DNA fragmentation. B- Detection of DNA damage and measurement of cell cycle analysis: This has been done using flow cytometry and applied on the whole small intestine of the developmental stages 50, 55, 60, 63 & 66 |