A Practical Approach, Second Edition=Ronald D. Ho.pdf

IN VITRO METHODS FOR THE STUDY OF MECHANISMS OF DEVELOPMENTAL TOXICOLOGY 667(A)cfmhfChABffCcDcFigure 16.6(A) The TUNEL method was used on tissue sections of control embryos and embryos exposedto 50 µg/ml N-Ac-AAF, at the 10-h time point. Methyl green was used as a counterstain. A: Nearlymidsagittal section through a control embryo. Three regions of the brain are shown: forebrain (f),midbrain (m) and hindbrain (h). Between the heart (c) and brain a small portion of one of thevisceral arches can be seen (arrowhead). B: Sagittal section of treated embryo. C: Highermagnification of head of embryo shown in A. Arrow indicates DAB-positive (brown-stained) cellsor cellular particles. D: Higher magnification of section shown in B. (B) Transmission electronmicroscopy (TEM) of tissues from a control embryo and an embryo exposed to N-Ac-AAF, 5 hafter exposure. A: Typical appearance of mesenchymal cells in a control embryo. Cellular processeswere abundant, but there were no obvious apoptotic cells or debris. B: Embryo exposedto 50 µg/ml N-Ac-AAF. Occasional apoptotic bodies were noted (arrowhead), and electron-dense,intracellular inclusions were common (arrows). C: Cell from embryo shown in B, clearly undergoingapoptosis (arrowheads). D: Embryo exposed to 200 µg/ml N-Ac-AAF. Occasional apoptotic cells(arrowheads) were observed, and extracellular, heterogeneous, electron-dense bodies werecommon (open arrows). E: Section from embryo shown in D. In addition to apoptotic cells(arrowhead), some cells had discontinuous cell membranes and small electron-dense nuclei(large arrows), suggestive of necrosis. (Thayer, J.M. and Mirkes, P.E., Teratology, 51, 418, 1995.With permission.)© 2006 by Taylor & Francis Group, LLC