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Left/right asymmetry in the early avian embryo

Hoyle, Christine Irma; (1992) Left/right asymmetry in the early avian embryo. Doctoral thesis (Ph.D), UCL (University College London). Green open access


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Left/right asymmetry was investigated during the development of the early avian embryo with particular reference to the normal asymmetry of the heart, which loops to the embryo's right-hand side. The structure of the pre-looped and post-looped heart was studied using light and electron microscopy. In the pre-looped heart, the right and left myocardial wall were of equal thickness. In the looping heart the right wall had thinned in comparison to the left. The direction of rotation in right and left looped hearts was examined using fluorescent carbocyanine dyes and viewed with a confocal microscope. The direction of rotation was found to be the same as the direction of looping. The situs of multiple embryos was studied by dividing the unincubated quail blastoderm in ovo. Singles, twins and triplet embryos were formed. Twins and triplets showed great variation in their orientation to each other. The majority of embryos had normal situs of the heart and body but 14% showed left-hand looping of the heart. No universal mechanism controlling situs was found at this stage. Areas of precardiac mesoderm were exchanged in the stage 4-6 embryo, in order to form double-right and double-left sided embryos. At stage 6, double-left sided embryos and controls formed right-sided loops, whereas the situs of hearts in double-right sided embryos approximated randomness. Left-handed heart loops were formed by cutting the right splanchnopleure at stage 8-9. following the work of Lepori. Teratological agents were applied both in ovo and in vitro. Retinoic acid was applied systemically and locally to form a right/left gradient using formate beads. Retinoic acid gave a dose-dependent and stage-related spectrum of heart malformations, including altering the situs. No significant difference was found in heart shape resulting from a right or left gradient. Methoxamine, βFGF, heparininase and ultraviolet light caused malformations of the heart but no significant alteration in the situs of the heart.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Left/right asymmetry in the early avian embryo
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Health and environmental sciences; Left/right asymmetry
URI: https://discovery.ucl.ac.uk/id/eprint/10108324
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