title: Absolute numbers versus proportions in the assessment of differentiation of beta-cells in the embryonic avian pancreas.
abstract: Environmental factors may influence the proliferation and differentiation of embryonic pancreatic endocrine cells, creating a need for the quantification of such effects. The explanted dorsal pancreatic bud (DPB) of the 5-day chick embryo is a useful in vitro model. Since all explants cannot be assumed to have the same number of endocrine cells at the start of culture, the proportion of beta-cells with respect to alpha-cells may be a more meaningful measure than absolute numbers. This study aimed to establish baseline values for the proportion of beta-cells in both intact and mesoderm-depleted DPBs before culture. Buds were excised from 12 chick embryos and the surrounding mesoderm was removed from 6 buds following collagenase treatment. All the buds were freeze-dried, fixed in parabenzoquinone vapour, embedded in resin and sectioned at 1 micro m. alpha- and beta-cells were detected by an indirect immunoenzyme method. alpha-cells outnumbered beta-cells in 9 of the 12 buds. The proportion of beta-cells in the intact buds varied from 16% to 64% (mean 39.5%) and in the mesoderm-depleted buds from 17% to 66% (mean 39%). There was no significant difference between the absolute numbers or the proportions of cells in either case. The proportions of beta-cells in the 5-day DPBs were higher than those in buds cultured in previous studies for 7 days under various conditions. This result may reflect the role of apoptosis in response to the culture conditions.
authors.affiliation: Embryonic Differentiation and Development Research Programme, School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. kramerb@anatomy.wits.ac.za
authors.forename: Beverley
authors.initials: B
authors.lastname: Kramer
authors.forename: Dianne
authors.initials: D
authors.lastname: Manning
authors.forename: Clem
authors.initials: C
authors.lastname: Penny
mesh_terms: D000818:Animals; D002452:Cell Count / Q000379:methods*; D002454:Cell Differentiation; D002642:Chick Embryo; D002645:Chickens; D007150:Immunohistochemistry; D007515:Islets of Langerhans / Q000166:cytology* / Q000196:embryology*; D008648:Mesoderm / Q000166:cytology