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https://hdl.handle.net/2142/71734
Description
Title
Studies on Fertilization in Vitro in Mammals
Author(s)
Didion, Bradley Arlen
Issue Date
1988
Doctoral Committee Chair(s)
Graves, Charles N.
Department of Study
Animal Science
Discipline
Dairy Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Animal Culture and Nutrition
Abstract
The objective of this thesis was to examine, using light and electron microscopy, the behavior of the sperm-egg interaction: (a) during the normal fertilization process; and (b) when the fertilization process was modified chemically and physically. Chemical modification of the fertilization process entailed artificially fusing the sperm to the egg, whereas physical modification entailed microinjecting a single sperm cell into the egg. The rationale of the study was that by modifying the fertilization process we could enhance the inefficient methodology of fertilization in vitro currently used to treat certain infertility problems in humans and animals including exotic species. Our results showed that when rabbit sperm (uncapacitated, capacitated and sperm nuclei) were artificially fused to zona pellucida free mouse eggs, sperm chromatin was observed within the egg cytoplasm yet the egg remained unactivated. In these eggs the sperm appeared to be embedded into the egg vitelline membrane however total incorporation of the sperm into the egg was not observed. Mouse thymocytes underwent premature chromosome condensation when artificially fused to unactivated mouse eggs. When sperm and thymocytes were fused to artificially activated eggs, normal appearing pronuclear eggs were generated. Therefore it appears that artificial sperm-egg fusion does not induce egg activation which occurs as a result of normal sperm-egg fusion. When sperm were microinjected into unfertilized eggs a large percentage of the eggs were destroyed however two normal appearing pronuclear eggs were generated (2/129, 1.5%). When sperm were injected into eggs which remained unactivated, the sperm heads became swollen (decondensed) but did not form pronuclei. Therefore it appears that it is the state of the egg cytoplasm which governs the fate of the sperm i.e. in an unactivated egg the sperm nucleus can decondense however only until the egg is fully activated will the sperm nucleus transform into a pronucleus. Although the chemical and physical modifications of the fertilization process used in the present study did not enhance sperm penetration, many future studies are discussed which would include the use of these methodologies.
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