Effects of nicotine on tongue development in the CD-1 mouse.

Fetuses of pregnant CD-1 mice, exposed to 0.1% nicotine sulfate at a dose of 1.67 mg/kg body weight from the 6th through the 15th gestational days were compared with control fetuses to assess the effects of nicotine on tongue development. Mothers were sacrificed on the 18th gestational day. The heads of a total of 130 nicotine-treated and 348 control fetuses were embedded in paraffin and sectioned in the frontal plane. 9.6% of the nicotine-treated fetuses had palatal clefts and their tongue development was much retarded compared to the controls. The tongues of the clefted fetuses were misshaped, reduced in size, had no filiform or fungiform papillae, and their myotubes were just in the process of formation. The circumvallate papilla of these fetuses were present but neither taste buds nor glands of von Ebner had as yet developed. Tongue development of nicotine-treated, non-clefted fetuses were closer to those of the controls. The anlagen of their filiform and fungiform papillae were developing, their myotubes were longer and better arranged, their circumvallate papilla was present but without taste buds, and their glands of von Ebner were not developed. It is suggested that nicotine interferes with both palatal and mesenchymal components of tongue development.

Teratogenic effects of nicotine on first molar odontogenesis in the mouse.

Fetuses of pregnant CD-1 Swiss albino mice, exposed to 0.1% nicotine sulphate at a dose of 1.67 mg/kg body weight from the 6th to the 15th gestational day, were compared with control fetuses to assess the effects of nicotine on first molar odontogenesis. Mothers were sacrificed on the 18th day of gestation. The 130 nicotine treated fetuses, as well as the 348 control fetuses were embedded in paraffin and sectioned in the frontal plane. The developing molars of the experimental fetuses were retarded, less differentiated, and reduced in breadth in comparison with controls. The developing molars of the control fetuses were in the bell stage of odontogenesis, whereas those of the experimental population were either in the late cap or early cap stage, depending on the absence or presence of palatal cleft, which occurred in 9.6% of the fetuses. It is suggested that nicotine, or its metabolic byproducts, interfere with normal interaction between the epithelial and mesenchymal components of the developing tooth.

Effects of nicotine on murine incisor development.

The effects of daily injections of nicotine sulfate on incisor development in CD-I mice were studied. Pregnant animals, injected with 0.1% nicotine sulfate at a dose of 1.67 mg/kg body weight from the 6th to the 15th day of gestation, were sacrificed on the 18th postcoital day. The 130 nicotine treated fetuses, as well as the 348 control fetuses were embedded in paraffin and sectioned in the frontal plane. The developing incisors of the experimental fetuses were retarded, less differentiated, and reduced in breadth and length. The developing incisors of the control fetuses were in the early appositional stage of odontogenesis, whereas those of the experimental population were either in the late cap or early bell stage, depending on the presence or absence of palatal cleft, which occurred in 9.6% of the fetuses.

Teratogenic effects of nicotine on palate formation in mice.

Fetuses of pregnant CD-1 mice, exposed to intraperitoneal injection of 0.1% nicotine sulfate at a dose of 1.67 mg/kg body weight/day on gestational days 6-15, were compared with control (saline injected and non-injected) fetuses to assess the effects of nicotine on fetal growth in general and palatogenesis in particular. A total of 59 pregnant females (18 experimental and 41 control) were sacrificed on the 18 th gestational day and their fetuses were examined gross morphologically and histologically (using serial sections through the head in the frontal plane). Data analysis revealed that maternal weight gain, crown-rump length, fetal weight and head dimensions were significantly reduced in nicoted treated animals when compared to those of the controls. Histological examination revealed that 9.6% of fetuses of nicotine injected mothers presented clefts of the palate, whereas none of the control fetuses had that anomaly. It was concluded that nicotine has a detrimental effect on general growth and development as well as on palatogenesis of mice.

SDH activity in the developing incisors or irradiated mouse fetuses.

Pregnant CD1 Swiss albino mice were irradiated with 400 rads of whole body X-irradiation on the twelfth gestational day. The animals were then sacrificed beginning on day 14 through 20 of gestation by chloroform inhalation. The fetuses were extirpated via laparotomy and decapitated. The severed heads were rapidly frozen and sectioned in a cryostat. The sections were affixed to glass slides and incubated for succinic dehydrogenase activity according to the method of Nachlas et al. (1957) and counterstained in Safranin 0, routinely dehydrated and mounted. Data from observations indicated that siccinic dehydrogenase activity appeared normal in the tissue layers of the developing tooth germ when compared to control animals. When the experimental procedure had invoked damage to the developing tooth, succinic dehydrogenase activity was lessened relative to the degree of damage. Presumably the X-irradiation had affected the cellular maturation process thereby reducing the functional competency of the cells as illustrated by the reduced enzyme activity.

Sensitivy of mouse molar tooth germs to x-ray irradiation in vitro.

Molar tooth germs, extirpated from 18-day mouse fetuses were cultured on Millipore filter strips in Falcon organ culture dishes. The tooth germs were exposed to 250 kVcp X-rays at 106 R/min. for a total exposure of 1 600 R. Tissues were harvested on a daily basis for a total period of 12 days and were examined microscopically, utilizing H and E stain. Severe disorganization of the tooth germs was evident within 24 hours of irradiation. The basement membrane became hyalinized; pyknotic nuclei and lysed cells were observed throughout the dental papilla, but mostly in the regions of the presumptive cusps. Although a thin layer of predentin was elaborated by the odontoblasts, the matrix failed to calcify and enamel matrix was not produced. Cultures older than 10 days demonstrated extensive cell death. The entire pulp was reduced to a mass of necrotic cells and the ameloblastic layer consisted of an epithelial remnant covering the cuspal tips.

Development of the squamosomandibular articulation in the Mongolian gerbil (Meriones unguiculatus). II. Succinate dehydrogenase activity.

Succinate dehydrogenase activity has been studied, according to the method of Nachlas et al. (1957), in the developing tissues forming the squamosomandibular articulation in the Mongolian gerbil from its inception through the sixty postnatal day. Increased activity was observed in the chondroblasts, osteoblasts and mesenchymal tissues of the developing articulation. The chondroclasts of the developing mandibular condyle displayed intense reaction as did the osteoclasts of the developing bony articulation. Succinate dehydrogenase activity appeared to be related to the functional maturity of the cellular elements of the developing joint.

Ultrastructural localization of adenosine triphosphatase in the stellate reticulum, stratum intermedium and ameloblasts of the mouse molar.

ATPase activity in the developing first mandibular molar of the mouse was demonstrated at the electron microscopic level with the method of Wachstein & Meisel (1957). It was localized along the cell surfaces of the ameloblast and stratum intermedium interface, the stratum intermedium and the stellate reticulum. The ATPase final reaction product was also present at the cell membranes of the proximal region of adjacent ameloblasts and extended to the level of the nuclei. The demonstration of ATPase mainly on the plasma membranes was similar to the observations by other investigators of various non-odontogenic cell types involved in the exchange of materials across plasma membranes.

A fine-structural analysis of mouse molar odontoblast maturation.

The first mandibular molars of the Swiss albino mice, 1 through 4 days of age, were fixed in glutaraldehyde or Karnovsky's fixative. The tissues were postfixed in OSO4, dehydrated and embedded in Epon. The prepolarizing, polarizing and secretory odontoblasts were described. The prepolarizing cells, located in the vicinity of the cervical loop, were mesenchymal-like in morphology. The cells of the polarizing stage possessed organelles indicative of protein synthesis. The nucleus was located proximally. Aperiodic fibers were evident in the wide basement membrane. The secretory odontoblasts were long, slender, polarized cells closely adjoining one another. Each odontoblast possessed six morphologically discernible regions: (1) an infranuclear region, limited in size and containing few cellular organelles; (2) a nuclear region, housing the oval nucleus and a few associated lamellae of rough endoplasmic reticulum as well as a limited number of mitochondria; (3) a supranuclear rough endoplasmic reticulum region, possessing an abundance of these organelles as well as some mitochondria and secretory vesicles; (4) a Golgi region, occupying the middle third of the cell, housing the elements of an extensive Golgi apparatus which was surrounded by peripherally located profiles of rough endoplasmic reticulum; additionally, this region contained smooth endoplasmic reticulum, mitochondria, numerous secretory granules and vesicles and occasional intracellular collagen fibers; (5) an apical rough endoplasmic reticulum region, containing a rough endoplasmic reticulum component that was less extensive than its supranuclear counterpart; in addition, this region was the one richest in mitochondria and contained a plethora of secretory vesicles and granules; (6) the odontoblastic process, a region mostly void of organelles, containing various secretory products, some of which appeared to be in the process of being released extracellularly into the surrounding dentin matrix.

Electron microscopic localization of 5'-nucleotidase in the stratum intermedium and ameloblasts.

5'-nucleotidase was demonstrated at the fine structural level in the stratum intermedium and ameloblasts of the first mandibular molars of CD-1 mice. The enzyme was localized with the Wachstein & Meisel (1957) method along the plasma membranes of the cells of the stratum intermedium and ameloblasts. While 5'- nucleotidase was present throughout the stratum intermedium, only the proximal region of the plasma membranes of ameloblasts was demonstrably active for this enzyme. 5'-Nucleotidase has been implicated in transport of metabolites across cell membranes, and its localization in the present study supports this implication as well as the transport functions of the stratum intermedium and the stratum intermedium--ameloblastic interface.

Palatal shelf epithelium: a morphologic and histochemical study in X-irradiated and normal mice.

The palatal shelf epithelium of normal and irradiated mice was examined morphologically and histochemically, utilizing the periodic acid-Schiff (PAS) technique for the demonstration of the basement membrane and the Nitro BT method for succinate dehydrogenase activity in order to demonstrate the metabolic competence of its cells. The 'programmed cell death theory' was not supported by the present investigation, since the cells of the medial ridge epithelium retained their structural and metabolic integrity even subsequent to the formation of cell nests. Additionally, the medial ridge epithelium of mice with radiation-induced cleft palates demonstrated normal structural and metabolic integrity long past the prospective time of fusion.

Succinic dehydrogenase activity during palate formation in the Mongolian gerbil.

The palatal shelf epithelium of the Mongolian gerbil was examined for succinic dehydrogenase activity prior to, during and the after palatal fusion (days 18-20 post coitus). Enzyme activity was present during all stages examined, and was noted even in the epithelial pearls of fused palates. The presence of SDH activity in these epithelial pearls lends support to the theory 'epithelial stretching', and questions the theory of 'programmed cell death' in relation to the loss of the epithelium along the plane of fusion.

Histochemical evaluation of thiamine pyrophosphatase activity during first molar odontogenesis of the neonatal hairless mouse.

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.

Molar odontogenesis in the hairless mouse.

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.

Effects of ionizing radiation on incisor development of the prenatal mouse.

The effects of 100 rad of X-irradiation of incisor development in CD1 mice were studied. 24 pregnant mice were irradiated on the 12th day post coitum and sacrificed from the 14th through the 20th gestational days. The 191 irradiated fetuses were smaller than those not irradiated, their crania and necks were malformed and their lower extremities were poorly developed. The developing incisors of the irradiated animals were retarded, the pulpal vessels were enlarged and the vessels walls did not maintain their structural integrity. The cells of the future pulp were necrotic, and the basement membranes appeared hyalinized. Ameloblasts and odontoblasts were abnormal in morphology and the formation of dental hard tissue was inhibited in places. Complete absence of incisor tooth germ was noted in three of the fetuses.

Succinate dehydrogenase activity in the developing molar of the Mongolian gerbil Meriones unguiculatus.

The distribution of succinate dehydrogenase in the odontogenic tissues in the Mongolian gerbil, ranging in age from 18 days prenatal to 8 days postnatal, was studied. Activity levels were designated negative, trace, slight, moderate, strong and very, dependent upon visual observations. The results indicated increased levels of activity as the tissue layers differentiated from the lamina stage through early apposition. The cell layer displaying the most succinate dehydrogenase activity was the ameloblastic layer while the stratum intermedium layer was the next most active cell layer. Succinate dehydrogenase activity appeared to be related to the degree of differentiation and functional competency of the odontogenic tissues in the Mongolian gerbil.