Cell Death and Developing Oral Structures

Sweney

1969

J Dent Res

Self Cite

Oral ectodermal cells that appear to be programmed to die as part of normal embryonic development were studied histochemically and electron microscopically. Cytochemical changes were noted in these and neighboring cells at about the time that key events in their differentiation have been said to occur. It was hypothesized that the transitory appearance of alkaline phosphatase in subjacent mesenchyme and decreased respiration in the ectoderm are crucial events in the differentiation of this cell type.

mentioning

confidence: 99%

Electron Microscopic and Histochemical Examination of Oral Epithelial-Mesenchymal Interaction (Programmed Cell Death)

Sweney

1969

J Dent Res

Self Cite

Enzyme histochemistry of embryonic nasal mucosa

1970

Anat. Rec.

The prenatal development of rodent nasal mucous membrane has been examined histochemically (lactate dehydrogenase, succinate dehydrogenase, glucose-6-phosphate dehydrogenase, alkaline phosphatase, PAS and PAS with diastase digestion). Localization and intensity of the enzyme systems studied were distinctly different in respiratory and olfactory areas. These differences were demonstrable by at least the second half of gestation in the animals studied. Findings i n Jacobson's organs were parallel to those in olfactory areas. Each of the pathways of carbohydrate metabolism examined was present in respiratory epithelium. However, intensity was less, appeared later and was more variable in intracellular localization than that found in olfactory areas. Based on enzyme staining olfactory epithelium seemed metabolically more active than respiratory mucosa. Apical portions of olfactory epithelium stained most intensely for oxidative enzyme systems, particularly the glucose-6-phosphate dehydrogenase system. These areas of high activity were thought to represent apices of supporting cells rather than receptor cells. This localization of a pentose phosphate shunt enzyme system was related speculatively to ion transport in these cells. Alkaline phosphatase was relatively slight in respiratory areas during the ages studied. The basal portions of olfactory epithelium stained positively for alkaline phosphatase. Since hydrolytic enzymes have been thought to be important in the mechanism of olfaction, its demonstration in these tissues suggests that this portion of the olfactory mechanism is present by midgestation in the rodents studied.

Histogenesis of Swiss white mouse secondary palate from nine and one‐half days to fifteen and one‐half days In utero. I. Epithelial‐mesenchymal relationships—light and electron microscopy

Sweney

1970

Journal of Morphology

Development of the secondary palate in Swiss white mouse embryos was studied from age nine-and-one-half days in utel-o to the stage of mesenchymal coalescence in the secondary palate (approximately fifteen-and-one-half days). The greatest changes observed occur in the mesenchyme. At early stages, mesenchymal cells underlying oral ectoderm of the head are few and only occasionally contact the ectoderm. Electron micrographs show large intercellular spaces between the ectodermal cells. As embryogenesis continues, the mesenchymal cells become more numerous, closer to each other and closer to the epithelium. Just prior to horizontal transposition of shelves, the mesen,chymal cells spread farther from each other and from the palatal epithelium and epithelium of the palatal tip becomes stretched. important to study earlier stages of secondary palate histogenesis. In this paper, we describe palatal development from a stage where neither tongue nor palate are present to the stage of mesenchymal coalescence in the secondary palate. METHODS AND MATERIALSSwiss white female mice were bred in the evening. If a plug was found the next morning, 2:OO AM of that morning was considered day 0 of gestation. Embryos were removed at various time intervals from 9 days, 6 hours to 15 days, 12 hours. They were fixed in 10% neutral formalin or Bouin's and embedded in paraplast, or fixed in 1% (phosphate buffered) OsOd and embedded in Epon (Luft, '61). With younger embryos, the entire body was fixed, while only the head of older embryos was used. Coronal and sagittal sections of