RESUMEN
PURPOSE: Previous studies have evaluated the presence of serotonin in the dental epithelia and mesenchyme during odontogenesis, suggesting its participation in tooth development. MATERIALS AND METHODS: Here, we used fluoxetine, a selective serotonin re-uptake inhibitor, at a dose of 10 mg/kg, administered for 20 days during pregnancy in 12 Wistar rats to examine the influence of this drug on the development of the enamel organ of the upper first molars of rat fetuses at 17 days of intra-uterine life (i.u.l.), and at one, five and ten days postpartum. The pregnant rats were anesthetized with xylazine at 10 mg/kg and ketamine at 25 mg/kg. The fetuses were removed and beheaded; their jaws were removed, and the upper jaws were exposed. The tissues were fixed in Bouin's fixative, decalcified in 5% nitric acid for 4 - 12 h, conventionally processed for microscopy, and embedded in paraffin. Serial sections of approximately 5 mum were obtained and stained with hematoxylin and eosin, as well as periodic acid-Schiff. RESULTS AND CONCLUSION: Morphological analysis showed no structural changes in the experimental group compared to the controls, suggesting that, at the dose used, fluoxetine does not interfere with serotonin-mediated development of the enamel organ or the process of amelogenesis.
Asunto(s)
Órgano del Esmalte/anatomía & histología , Órgano del Esmalte/efectos de los fármacos , Fluoxetina/administración & dosificación , Inhibidores Selectivos de la Recaptación de Serotonina/administración & dosificación , Amelogénesis/efectos de los fármacos , Amelogénesis/fisiología , Animales , Órgano del Esmalte/crecimiento & desarrollo , Femenino , Modelos Animales , Embarazo , Distribución Aleatoria , Ratas , Ratas WistarRESUMEN
Purpose: Previous studies have evaluated the presence of serotonin in the dental epithelia and mesenchyme during odontogenesis, suggesting its participation in tooth development. Materials and methods: Here, we used fluoxetine, a selective serotonin re-uptake inhibitor, at a dose of 10 mg/kg, administered for 20 days during pregnancy in 12 Wistar rats to examine the influence of this drug on the development of the enamel organ of the upper first molars of rat fetuses at 17 days of intra-uterine life (i.u.l.), and at one, five and ten days postpartum. The pregnant rats were anesthetized with xylazine at 10 mg/kg and ketamine at 25 mg/kg. The fetuses were removed and beheaded; their jaws were removed, and the upper jaws were exposed. The tissues were fixed in Bouin's fixative, decalcified in 5 percent nitric acid for 4 - 12 h, conventionally processed for microscopy, and embedded in paraffin. Serial sections of approximately 5 mm were obtained and stained with hematoxylin and eosin, as well as periodic acid-Schiff. Results and conclusion: Morphological analysis showed no structural changes in the experimental group compared to the controls, suggesting that, at the dose used, fluoxetine does not interfere with serotonin-mediated development of the enamel organ or the process of amelogenesis.
Asunto(s)
Animales , Femenino , Embarazo , Ratas , Órgano del Esmalte/anatomía & histología , Órgano del Esmalte/efectos de los fármacos , Fluoxetina/administración & dosificación , Inhibidores Selectivos de la Recaptación de Serotonina/administración & dosificación , Amelogénesis/efectos de los fármacos , Amelogénesis/fisiología , Órgano del Esmalte/crecimiento & desarrollo , Modelos Animales , Distribución Aleatoria , Ratas WistarRESUMEN
The process of vascularization of the enamel organ, a unique epithelial structure, occurs when the tooth germ is fully developed, i.e., at the onset of dentinogenesis. Although the three-dimensional organization of the capillaries has been previously investigated, the structural features underlying the formation of the new capillaries remains poorly understood. Thus, in the hope of better understanding the mechanism of formation of the stellate reticulum capillaries, upper first molar tooth germs of newborn and 3-day-old rats were fixed in glutaraldehyde-formaldehyde and processed for light and electron microscopy. Our results showed that blood capillaries are initially in close proximity to the outer enamel epithelium. Between and intercalated with the capillaries are round/ovoid clusters of cells, some of which are vacuolated, closely apposed to the outer enamel epithelium. The outer enamel epithelium is not a continuous layer, but exhibits gaps between the cells. This suggests that the capillaries penetrate the enamel organ through these gaps, since no invagination of the epithelium was observed. The presence of a cluster of cells containing vacuoles suggests that vasculogenesis is taking place. Images showing loss of the basal lamina, proliferation of endothelial cells, presence of filopodia and lateral sprouting suggests that angiogenesis is also occurring. Thus, neoformation of capillaries of the molar enamel organ of rat seems to occur simultaneously by mechanisms of vasculogenesis and angiogenesis.
Asunto(s)
Capilares/anatomía & histología , Órgano del Esmalte/irrigación sanguínea , Órgano del Esmalte/ultraestructura , Diente Molar , Germen Dentario/irrigación sanguínea , Animales , Animales Recién Nacidos , Órgano del Esmalte/crecimiento & desarrollo , Femenino , Masculino , Ratas , Ratas WistarRESUMEN
When the enamel organ of the rat tooth germ is fully developed at the tip of the prospective cusp, amelogenesis begins, and at this site the overlaying stellate reticulum begins its involution. During the involution process, there is a gradual decrease in intercellular spaces, invasion by blood vessels, appearance of macrophage-like cells and reduction in the number of stellate reticulum cells. Since reduction or disappearance of cells during embryonic development in organs and tissues has been shown to occur by apoptosis, we decided to examine early involuting regions of the stellate reticulum in the hope of detecting apoptosis. For this purpose, upper first molars of Wistar newborn rats aged 1 and 3 days were fixed in formaldehyde for the TUNEL method and in glutaraldehyde-formaldehyde for light and electron microscopy. Paraffin sections revealed TUNEL-positive structures, i.e. brown-yellow-stained bodies, in the central portion of the stellate reticulum, and next to the outer enamel epithelium and stratum intermedium. Examination of ultrathin sections confirmed the TUNEL findings: some stellate reticulum cells showed nuclei containing crescent-like electron-opaque condensed masses of peripheral chromatin, typical of apoptosis. Also, apoptotic bodies of various sizes and appearances were frequently observed within stellate reticulum cells. We should like to suggest that apoptosis is associated with the reduction in the number of cells during regression of the reticulum.
Asunto(s)
Amelogénesis/fisiología , Apoptosis , Órgano del Esmalte/crecimiento & desarrollo , Diente Molar/crecimiento & desarrollo , Animales , Animales Recién Nacidos , Órgano del Esmalte/ultraestructura , Epitelio/crecimiento & desarrollo , Epitelio/ultraestructura , Femenino , Etiquetado Corte-Fin in Situ , Masculino , Ratas , Ratas WistarRESUMEN
Com a finalidade de estudar a histoarquitetura das células componentes do órgäo do esmalte dos primeiros molares superiores de camundongos, foram utilizados animais desde o nascimento até a idade de 18 dias, quando o dente emergiu na cavidade bucal. Após a anestesia por inalaçäo de éter etílico, os animais, foram decapitados e a regiäo correspondente aos primeiros molares superiores foi cuidadosamente dissecada e removida, as peças foram imediatamente imersas em glutaraldeído a 6 por cento em soluçäo tampäo fosfato, ph 7,2 após a descalcificaçäo em EDTA, as peças foram fixadas em tetróxido de ósmio a 1 por cento, desidratadas em acetona em concentraçöes crescentes e finalmente incluídas em EPON. Cortes em 1m de espessura foram obtidos em ultramicrótomo, utilizando-se navalhas de vidro, e posteriormente, coradas com uma soluçäo de Azur II + Azul de metileno em partes iguais. Através do microscópio óptico, observou-se que: antes da formaçäo do esmalte, o órgäo do esmalte é invadido por capilares sangüíneos vindos do saco dental. Os ameloblastos näo formadores, situados sobre as áreas destituídas de esmalte, näo possuem processos de Tomes, seus núcleos säo situados centralmente e as células säo menores do que as formadoras, situadas nas outras regiöes da coroa. As células do extrato intermédio, situadas adjacentes aos ameloblastos näo formadoras, apresentam a forma achatada. As células do extrato intermédio, situadas adjacentes aos ameloblastos formadores, possuem a forma cubóide. Após o término da formaçäo do esmalte, o epitélio externo e o retículo estrelado parecem estar ausentes e o órgäo do esmalte fica reduzido a duas camadas de células: a camada do extrato e a camada ameloblástica. O diafragma radicular é a primeira porçäo da bainha de Hertwig a se formar. A bainha radicular de Hertwig é formada por somente duas camadas de células do órgäo do esmalte: o epitélio interno e o epitélio externo do órgäo do esmalte