Aspects of Lipid Metabolism in the Subcellular Fractions of the Embryo and Neonatal Chick

Bath, Helen Margaret (1993) Aspects of Lipid Metabolism in the Subcellular Fractions of the Embryo and Neonatal Chick. PhD thesis, University of Glasgow.

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The parental age of the broiler bird is known to exert a significant effect on embryo hatchability and early chick survival. In order to increase chick yield to the broiler industry, there is a need to procure hatching eggs at earlier stages of the hen's reproductive life. However reduced hatchability of eggs from young parents has affected the economics of such a move and has thus led to the eggs from young parents being discarded. Results to date have shown that there are extensive disturbances to yolk lipid uptake and the subsequent assimilation of lipid by the embryonic tissues. The present study was concerned with comparative changes in lipid and fatty acid compositions of the subcellular lipid, together with aspects of tissue lipid metabolism in embryos and neonatal chicks derived from mature and young parents. Fertile eggs were obtained from Ross 1 broiler-breeder parent stock at twenty-three to twenty-four and then again at thirty-seven to forty weeks of age. Embryos and chicks from each parental group were randomly selected at predetermined intervals during incubation and post-hatch development. Tissue organelles were separated by standard techniques following suitable modification. Preparations for electron microscopy were also made by standard techniques. Lipid extraction and subsequent analyses of lipid moieties and fatty acids were performed by a range of methodologies which included differential solvent extraction, Thin Layer chromatography. Gas Liquid chromatography and High Performance Liquid chromatography. As shown by electron microscopy, the mitochondria exhibited typical pleomorphism throughout the embryonic and post-hatch periods. Absolute amounts of lipid associated with the liver cytoplasm of embryos from mature parents increased dramatically over the last week of incubation. In embryos from young parents, the lipid accumulation was significantly less. There was a rapid diminution in the levels of cytoplasmic lipid in the livers of chicks of mature parents following hatching. By comparison, the rate of lipid loss was less in the livers of chicks from young parents. The levels of lipid associated within the membrane organelles were, throughout the embryonic and post-hatch periods, consistently higher than within the cellular supernatant. Within the subcellular fractions from embryos of young parents, the levels of lipid within the mitochondria of the liver, heart and brain were higher compared with those from mature parents. Phospholipids and free cholesterol were the major lipid fractions within the mitochondria and microsomes. The phospholipids of the liver mitochondria and microsomes from embryos of both parental groups, showed unique changes in their saturated to polyunsaturated fatty acid pairings during the final week of incubation, suggesting the differentiation in phospholipid turnover and associated changes in membrane organelle stability and function. Lipid and fatty acid changes in the heart organelles were very similar to those of the liver, suggesting similar relative metabolic changes in spite of proportional differences in both lipid and fatty acid compositions. The mitochondria of the brain were characterised by high levels of docosahexaenoic acid, whilst the levels of linoleic and linolenic acids were exceedingly low. Cholesteryl esters, in particular cholesterol oleate, comprised by far the bulk of the supernatant fractions of the liver and heart. A marked increase in the relative concentration of cholesteryl esters was observed within the liver during the final week of incubation. By comparison, the brain supernatant displayed an exceedingly low level of cholesteryl esters throughout the embryonic and post-hatch periods. The level of cholesteryl esters and of cholesterol oleate in particular, decreased following hatching. The triglycerides of the liver uniquely showed, during the final week of incubation, a very high concentration of docosahexaenoic acid, the level of which decreased rapidly during the early post-hatch period. In contrast, the concentration of docosahexaenoic acid within the triglycerides of the brain organelles was very low. A marked increase in the relative concentration of triglycerides occurred in both the subcellular fractions of the liver and heart following hatching, associated in particular with the rapid reduction in cholesterol ester level. A range of significant differences in both lipid and fatty acid compositions of the liver and its organelles between progeny from mature and young parents was observed, reflecting disturbances in lipid metabolism within the embryos from young parent stock. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: R C Noble
Keywords: Animal sciences, Physiology
Date of Award: 1993
Depositing User: Enlighten Team
Unique ID: glathesis:1993-74651
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 27 Sep 2019 17:22
Last Modified: 27 Sep 2019 17:22

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