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Figure 3. Chalcides viridanus. Different steps of amelogenesis during replacement tooth development. Amelogenin gene (amelogenin) expression is revealed by in situ hybridization on sections (dark stippled regions in a,d,f,h,j), with 33P-labeled amelogenin probe. (c,e,g,i) One-µm-thick sections of stages of enamel formation in replacement teeth similar to those shown in d–j (toluidine blue staining). Labial to the right. (a) Low magnification showing 3 tooth positions in the left lower jaw arcade sectioned longitudinally. Anterior to the right. Amelogenin is not expressed in functional teeth, while numerous transcripts are detected in the enamel organ of the replacement teeth below. (b) Negative control for (a), with the sense probe. (c–j) Enamel matrix deposition in replacement teeth, from early deposition (c,d) to the end of enamel maturation (i,j). Transverse sections of the lower jaw. In situ hybridization reveals amelogenin transcripts in the enamel organ (ameloblasts). Transcripts are abundant in the ameloblasts facing the recently deposited immature enamel matrix; they are less numerous in the ameloblasts facing the maturing enamel, and are absent in ameloblasts facing the mature enamel. Scale bars: a,b = 100 µm; c–j = 50 µm. Abbreviations: am, ameloblasts; be, buccal epithelium; d, dentin; db, dentary bone; dej, dentin-enamel junction; e, enamel; eo, enamel organ; ft, functional tooth; od, odontoblasts; ode, outer dental epithelium; pd, predentin; rt, replacement tooth; sr, stellate reticulum.
