Fogorvosi szemle, 2005 (98. évfolyam, 1-6. szám)
2005-04-01 / 2. szám
74 FOGORVOSI SZEMLE ■ 98. évf. 2. sz. 2005. el epithelium, the stellate reticulum, the stratum intermedium and ameloblasts. These cells formed cluster like structures, of which boundaries did not show the localization. The cluster cells played to form the ameloblast grouping and the boundary ameloblasts formed the junctional zone of H-S bands. The actin of ameloblast layers showed groups of same as H-S band pattern. Some Tomes’ processes showed the actin reaction, but others lacked it. This suggested Tomes’ process dancing each other, which formed the arrangement of enamel prisms. The keratin localized in all Tomes’ process, which played the maintenance of the forms to produce the shape of enamel prisms. It is concluded that these localization showed it changed rhythmically in the enamel organ. Key words: Ameloblast dancing and grouping, Enamel structure References: Hanaizumi.Y et al (1992) Anat. Rec. 252:355-368. Kozawa,Y et al (2001) in Dental Morphology 2001, 69-73. Nishikawa.S (1992) Anat.Rec. 232:466-478. H. LESOT , P. KRISTENOVA*, A. HAZE **, D. DEUTSCH**, M. PETERKA*, R. PETERKOVA* INSERMU595, Faculty of Medicine, 11, rue Humann, 67085 Strasbourg Cedex, France. *Academy of Sciences CR, Institute of Experimental Medicine, Prague, Czech Republic “Hebrew University, Hadassah, Faculty of Dental Medicine, Jerusalem, Israel MISSING INCISORS IN TABBY MICE The tabby (Ta) syndrome in the mouse is homologous to the X-linked hypohidrotic ectodermal dysplasia (XLHED) in humans. The syndrome includes alterations of the dentition with teeth of modified size, shape and number. Although prenatally two lower incisors always started to develop, incisors were missing on one side (15%) or even on both sides (3%) in the functional dentition. The effects of the Ta mutation on the development of the lower incisor was investigated using histology, computer aided 3D-reconstructions, and X-ray micro computed tomography (micro-CT). From the bud stage, the lowers incisors show alterations in their size and shape. At the cap stage, changes in the shape interfered with the medial-lateral asymmetry, and alteration in the posterior growth led to a loss of the labial-lingual asymmetry of the cervical loop. At the bell stage, the incisor germ in Ta showed an abnormal shape and size (decrease in the length and diameter). The balance between prospective crown- and rootanalogue tissues was also altered. The surface of the dental papilla covered by the root analogue was strongly reduced, which might lead to a decrease in tooth anchoring. However, this cannot explain the absence of incisors in some cases. Micro-CT was performed on Ta with unilateral incisor. On the side where an incisor is present, a strong decrease in its length was observed as already detected prenatally. On the contra-lateral side where the incisor was missing, an associated hypoplastic mandibular bone was observed. Histological observations and 3D reconstructions of the enamel organ, shortly after birth, showed an abnormal shaped cervical loop. This precisely included the posterior epithelial proliferative region, which allows the permanent growth of the incisor in rodents. The incisor development thus involves a distal growth during the pre-eruptive period and a mesial growth later. These observations show that the distal growth is affected in all Ta incisors while the mesial growth is inhibited in about 18% of incisors, which might result from the malformation of the posterior proliferative region of the enamel organ. Acknowledgement: The support of COSTB23 is gratefully acknowledged. H. LOVSCHALL, M.TUMMERS*, I. THESLEFF*, E.-M. FÜCHTBAUER“, K. POULSEN*** Department of Dental Pathology, Operative Dentistry and Endodontics, Royal Dental College, University of Aarhus, Denmark. ‘Research Program in Developmental Biology, Institute of Biotechnology, Viikki Biocenter, University of Helsinki, Finland. “Department of Molecular Biology, Faculty of Sciences, ‘“Department of Medical Microbiology and Immunology, Faculty of Health Sciences, University of Aarhus, Denmark. ACTIVATION OF NOTCH SIGNALING PATHWAY DURING PULP REGENERATION Notch signaling regulates developmental choices made by stem cells. In this study we explored Notch signaling after pulp capping of adult first upper rat molars. The wound was capped with calcium hydroxide. In situ hybridization revealed increased expression of Notch signaling genes on day 1 with a tendency of decrease on day 3. Notchl increased in the subodontoblast zone and close to the lesion limited to few cells. Notch2 increased in pulp stroma surrounded by coronal odontoblasts. Notchl and especially Notch3 expression increased corresponding to perivascular cell groups. Low increase of ligand expression was observed near the injury with Deltái expression along the dentin wall and Jaggedl in the stroma. Expression of the downstream target Hes1 was observed along the lesion and adjacent dentin walls. Hes5 expression was not observed. In conclusion, the findings suggest Notch signaling is activated and affect differentiation of stem cells and odontoblasts during pulp repair. Key words: pulp injury, stem cells, hybridization, wound, odontoblasts Acknowledgemet: The support of COSTB23 program is acknowledged.
