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The disturbances in odontogenesis in a case of epidermolysis bullosa hereditaria letalis are described, with particular emphasis on the morphologic alterations in the ameloblasts and on the nature of vesicles in the enamel organ. These latter structures are compared to those found in the skin.
Molar odontogenesis was studied in the hairless mouse from the initiation of the dental lamina through apposition. The dental lamina stage of the first molar was recognized on the 13th day, the bud on day 14th, cap on the 16th, bell on the 18th and apposition on the 20th day after conception. The morphology of the various stages and their temporal sequence were compared with those of other rodents.
Acidic and basic fibroblast growth factors (aFGF and bFGF), are both known to bind to extracellular matrix components, particularly proteoheparin sulfates, and to regulate in vitro proliferation, differentiation and morphology of cells of neuroectodermal and mesodermal origins. Their patterns of distribution were studied during mouse odontogenesis by means of indirect immunofluorescence and immunoperoxidase histochemistry on frozen fixed sections and after Bouin's fixative and paraffin embedding. Localization of aFGF on frozen fixed sections was observed in the oral epithelium, dental lamina and oral mesenchyme (day-12 of gestation), the stellate reticulum and oral epithelium (day-14), the stratum intermedium and at the basal and apical poles of preameloblasts at bell stage. After birth aFGF epitopes were localized within the predentin-dentin area, the stratum intermedium and at the secretory pole of ameloblasts. There was no staining with anti-aFGF antibodies after Bouin's fixative and paraffin embedding. In contrast, using this protocol, intense stainings were found with anti-bFGF antibodies predominantly within dental and peridental basement membranes and mesenchyme: staining of the dental basement membranes was transient (bud and cap stage) and discontinuous; a preferential concentration of bFGF epitopes in the condensed dental mesenchyme of incisors (cap stage) and the dental papillae mesenchymal cells of molars (bell stage) was observed in the posterior and the cervical part of tooth germs. An intense immunostaining of the stellate reticulum with anti-bFGF antibodies was also found on paraffin sections from bud to bell stage.(ABSTRACT TRUNCATED AT 250 WORDS)
Two experimental embryological problems concerning odontogenesis are investigated using the technique of intracameral transplants in mice: --the presence of odontogenetic material in the mandibular arches of the 9 day mouse embryo, --the degree of specificity of the epitheliomesenchymatous interact-ons in the region of the tooth of the mouse and the rabbit. The tolerance of the recipient eye has been studied: --in the case of homografts, --in the case of heterografts. The indications and limiting factors of the method are specified within the framework of the chosen experimental conditions, taking into account the rejection phenomena manifested in the case of the heterografts.
Cryosurgery, with temperatures ranging from -40 C to -140 C, was performed on 32 developing mandibular third and fourth premolar buds of dogs. Evaluations were made on clinical, radiographic, and histologic bases at prescribed time intervals. There was complete inhibition of odontogenesis in 62.5% of third premolars and 25% of fourth premolars. There was 25% partial inhibition of third premolars and a 56.25% inhibition of fourth premolars. The adjacent developing tooth buds and bone were not affected.
Odontogenesis in mouse is characterized by progressive morphogenesis and cytodifferentiation. Temporal dispacing was observed between the cusps of the same tooth and between lower and upper homologous teeth. These phenomenons underlined the importance of epithelial-mesenchymal interactions and the role of the stage of differentiation reached by the different cells before overt differentiation could be initiated.
The study of odontogenesis in teratomas, leads to the following observations. Conspicuous odontogenic fields are present in the vicinity of pluri-differentiated cystic structures. Tooth germs are connected to the walls of the cysts by an anastomosed dental laminar. The teeth developing in teratoma are not comparable to the normal process which is harmonized when the formation and the distribution of the various parts are concerned. They are deformed in appearance but not in the same way as the classic genetic malformations. The origin of both epithelial and mesenchymal parts is still not completely understood.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
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Arylsulfatase activity has been studied in the developing molar of the Swiss albino mouse from the lamina stage to the appositional stage. Timed-pregnant Swiss albino mice were utilized in this study. Females were sacrificed by ether anesthesia and fetuses extirpated or newborns anesthetized and decapitated. Frozen sections were fixed and incubated for arylsulfatase activity according to a modification of the method of PEARSE (1972). The tissue was dehydrated, cleared and covered. Phase light microscopy was utilized in evaluating arylsulfatase activity in the developing molar. Arylsulfatase activity was evaluated for each stage of development and the results presented in tabular form. The present investigation represents the first known effort to describe arylsulfatase activity in odontogenic tissues from the initiation of the dental lamina through the appositional stage. Arylsulfatase activity appeared to be related to the degree of vascularization of the developing enamel organ and adnexa and the beginning of hard tissue elaboration.
Localization of thiamine pyrophosphatase activity has been evaluated in the developing first molar of the neonatal hairless mouse. Postnatal animals from parturition to five days of age were decapitated and the severed heads frozen and sectioned in a frontal plane on a cryostat. 14 micron thick sections were fixed and subsequently incubated for thiamine pyrophosphatase activity according to the method of GOLDFISCHER et al. (1971). The tissue was visualized, dehydrated, cleared and mounted. Light microscopy was utilized in evaluating thiamine pyrophosphatase activity. Thiamine pyrophosphatase activity in the first molar of the hairless mouse is presented in tabular form and compared to similar data for the Swiss albino mouse. Enzyme activity increased as the metabolic activities of various cell layers increased. Thus, thiamine pyrophosphatase activity appeared to be related to the degree of differentiation and functional completency of the odontogenic tissues in the hairless mouse.
Epithelial-mesenchyme interactions during mouse molar tooth morphogenesis were observed by electron microscopy. The basal lamina was intact from day 10 to day 18. Aperiodic, later also periodic fibrils were deposited on the basal lamina. Ectomesenchymal cell processes were always in close relation with the basal lamina or with the fibrillar material. On day 19 some direct heterotypic cell contacts between odontoblasts and preameloblasts were observed. At all stages, especially the preodontoblasts but also preameloblasts, gave rise to aggregated vesicles, which were extruded in the epithelial-mesenchymal space.
Autoradiographic methods were used to analyze cell kinetics of mouse tooth germs during days 11, 14 and 16 of gestation. Cell cycle determination estimated from the labeled metaphases curves showed a lengthening of the cell cycle time during development, resulting from lengthening of G1 and S phases. These changes were also function of the histological localization of the analyzed cells.
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Differentiation of the cells of the dental bud which produce the hard tissues of teeth was studied at the ultrastructural level; the activity of these cells (odontoblasts and ameloblasts), the laying down of organic matrices elaborated by them, the mineralization of these matrices, and the maturation of dentine and enamel are described. Injections of tritiated proline enabled us by the autoradiographic method, to confirm and to indicate more precisely the activity of these cells. Dental calcified tissues of Rana exhibit the general properties of these tissues among Vertebrates: high content of apatite, low content of organic materials (collagenous in dentine, non-collagenous in enamel), precise orientation of crystals, and true but non-prismatic enamel. The enamel of Anura as well as enamel of Urodela is a true enamel of epithelial origin.
Using the technique of 3 dimensional reconstruction, the various steps involved in the formation and growth of the crown of a tooth primordium observed in a complex ovarian teratoma have been compared with that occurring in dermoid cysts and in the normal dental system. Inside dermoid cysts, the characteristic form of the tooth is established during the production of the dentine and enamel and the process is often similar to that occurring during normal tooth development. In teratomas, however, organogenesis and morphogenesis take place within a system undergoing multidirectional development. They are dissociated during both the embryonic stage and that of a structural formation. Morphogenesis is the most disturbed and the role of the environment is presumably therefore very important.