Invasive Behaviour of Hamster Trophoblast Transplanted to Chick Intraembryonic Coelom

Babawale, Michael Oluwagbemiga (1992) Invasive Behaviour of Hamster Trophoblast Transplanted to Chick Intraembryonic Coelom. PhD thesis, University of Glasgow.

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Abstract

1. Previous studies of the invasive and destructive behaviour of trophoblast when transplanted to a variety of ectopic sites have yielded conflicting results. Some workers (e.g. Kirby, 1965; Billington, 1966) have reported ectopic trophoblast as highly destructive, either by phagocytosis or cytolysis or both. Others (e.g. Fawcett, 1950; Porter, 1967) found trophoblast to be much less aggressive, with limited or absent powers of phagocytosis or cytolysis. 2. Interpretation of previous studies is complicated by two factors: (i) the possibility of species differences in behaviour of trophoblast and (ii) the fact that all ectopic sites previously used involve some damage to host tissues by the operative procedure. 3. For this study, the ectopic site chosen was the 3.5d chick's intraembryonic coelom (Dossel, 1954), in which grafts can be placed without causing any operative damage. The grafts used were: (a) 7-d hamster egg cylinder, or ectoplacental cone, chosen because hamster's trophoblast is generally regarded as highly invasive. The grafts, 37 in all, were studied, in situ, in wax serial sections at intervals of 8h, 12h, 16h and 24h. (b) Control grafts of 5.5d chick limb bud and 7-d hamster decidual tissue were studied at 48h and 72h (limb bud) and at 8h and 16h (decidua). 4. Grafts of egg cylinder/ectoplacental cone. At 8 hours, all 15 grafts were attached to host tissue, by 'erosion' of coelomic mesothelium by trophoblastic giant cells. The preferred site was the dorsal coelomic wall; this was thought to be a matter of chance in placement of the graft. The site of erosion was localized; adjacent mesothelium appeared normal. Mesothelium was undamaged by the close proximity of trophoblast (short of actual contact) and of yolk sac endoderm, (even when in contact). Spread of giant cells was mostly local, into the dorsal coelomic wall, and caused erosion of the aortic wall and bleeding in a few embryos. More distant spread of a very few individual giant cells, was seen in 4/15 embryos. At 12 hours there was modest progress of invasion, mostly local, with tongues of giant cells eroding the aortic wall (9/10) and ductus venosus (1/10). Despite erosion of major vessels, bleeding was temporarily limited by plugging of the vascular defect by giant cells. Each of 5/10 embryos showed more distant migration of small numbers of individual giant cells, mostly periaortic. At 16 hours, local invasion was again (6/9) most frequently into the dorsal coelomic wall and around the aorta, but with increased involvement of other tissues bounding the coelom. More distant migration of a few individual giant cells was limited to 4/9 embryos. 4. Grafts of egg cylinder/ectoplacental cone. At 8 hours, all 15 grafts were attached to host tissue, by 'erosion' of coelomic mesothelium by trophoblastic giant cells. The preferred site was the dorsal coelomic wall; this was thought to be a matter of chance in placement of the graft. The site of erosion was localized; adjacent mesothelium appeared normal. Mesothelium was undamaged by the close proximity of trophoblast (short of actual contact) and of yolk sac endoderm, (even when in contact). Spread of giant cells was mostly local, into the dorsal coelomic wall, and caused erosion of the aortic wall and bleeding in a few embryos. More distant spread of a very few individual giant cells, was seen in 4/15 embryos. At 12 hours there was modest progress of invasion, mostly local, with tongues of giant cells eroding the aortic wall (9/10) and ductus venosus (1/10). Despite erosion of major vessels, bleeding was temporarily limited by plugging of the vascular defect by giant cells. Each of 5/10 embryos showed more distant migration of small numbers of individual giant cells, mostly periaortic. At 16 hours, local invasion was again (6/9) most frequently into the dorsal coelomic wall and around the aorta, but with increased involvement of other tissues bounding the coelom. More distant migration of a few individual giant cells was limited to 4/9 embryos. (ii) More distant (active) migration was surprisingly limited. Most cells seemed to have followed the outer aortic wall, possibly using the basement membrane as a migratory "cue". Distant migration was more commonly passive, by dissemination in veins. (iii) The mechanisms of trophoblastic invasion remain unclear. Tongues of giant cells had clearly 'eroded' chick tissues, coelomic mesothelium, mesenchyme and aortic endothelium more readily than epithelial tissues such as liver and mesonephric duct. Individual giant cells had traversed chick mesenchyme without leaving traces of damage, and where they came into contact with surface ectoderm, notochord, hepatic sheets and sympathetic ganglion cells, these all appeared normal. No consistent evidence was seen of phagocytosis of healthy chick cells, nor of histolysis or cytolysis. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: R J Emeritus
Keywords: Developmental biology, Morphology
Date of Award: 1992
Depositing User: Enlighten Team
Unique ID: glathesis:1992-75326
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 21:02
Last Modified: 19 Nov 2019 21:02
URI: http://theses.gla.ac.uk/id/eprint/75326

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