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At least 1,279 records · Page 71Linked to original sources
PubMed2004

Histopathologic changes in dental and oral soft tissues in 2-butoxyethanol-induced hemolysis and thrombosis in rats*.

BACKGROUND: 2-Butoxyethanol (2-BE; ethylene glycol monobutyl ether) is extensively used as a solvent in surface coatings, such as lacquers, enamels, and varnishes in industrial and household cleaning products. Its major toxicity is manifested in the circulation, as it induces hemolytic anemia and thrombosis in various organs. While 2-BE has been implicated in the induction of anemia in different species, the rat has proven most sensitive, especially the female of this species. The purpose of this study was to document the effects of 2-BE on dentition, the periodontal ligament, the tongue, the salivary glands, and the oral mucosa in male and female Fischer 344 rats. METHODS: The experiment included 40 rats divided into five groups. Four groups were exposed to 2, 3, or 4 daily doses of 2-BE, and a fifth group served as control. The rats were killed on days 2, 3, 4, and 29. The teeth and soft oral tissues were prepared for histopathologic observation. RESULTS: The histopathologic analysis showed that the major effect of 2-BE was exerted on the odontoblasts of the incisors and on molars, with greater effect on the incisors. Foci of damaged muscle cells in the tongue were also observed. The blood vessels were dilated and congested, and a primary thrombosis was seen in the dental pulp. CONCLUSIONS: The results of this study revealed a resemblance between the dental injuries in this rat model and those seen in sickle cell anemia in humans. This 2-BE animal model holds potential to assist in the discovery of preventive measures and/or treatment for dental injuries that occur in human diseases with hemolytic anemia.

Anemia, Hemolytic↗
PubMed1976

Differentiation of odontogenic tissues in organ culture.

Molar tooth germs from 17-d-old mouse embryos were cultivated in a Trowell-type culture, and different culture media were tested for their ability to support enamel formation. The medium which allowed secretion of considerable amounts of enamel matrix by ameloblasts consisted of BGJb medium supplemented with 20% horse serum, 10% chick embryo extract and 0.9 mM ascorbic acid. At the onset of culture the teeth were in the early bell stage. After 2 weeks of cultivation both odontoblasts and ameloblasts had differentiated, and considerable amounts of predentin and enamel matrix had been secreted. Similar development was also seen in teeth which had been enzymatically separated into the mesenchymal dental papilla and epithelial enamal organ and subsequently recombined in vitro. This method allows good differentiation of odontogenic tissues, and is considered suitable for further studies of tissue interactions in the tooth rudiment.

Animals↗
PubMed1977

Evaluation of histologic criteria applied for description of pulp reactions in replanted human premolars.

To test the reproducibility of a scoring system prepared for the study of the tissue changes in replanted teeth, 30 teeth were allocated at random from a material comprising 70 replanted and control teeth. The scoring system elaborated was applied for description of the odontoblast layer, predentin, secondary dentin, circulatory alterations, resorption, Weil's zone, cellular infiltration and calcification. The registrations were performed twice with a time interval of approximately 2 months. The scores were subsequently compared. Generally speaking, the double determinations were in good agreement as only 4.7% of the pairs of registrations failed to correspond. The agreement was particularly good for secondary dentin, cellular infiltration, resorption, Weil's zone and calcification scores. These criteria are accessible for group comparisons when differences in pulp tissue characteristics are small. The remaining three criteria may prove not to be useful unless the tissue response is substantial.

Bicuspid↗
PubMed1977

Histologic and microradiographic observations on teeth during calcium deprivation in rats.

Adult female rats were subjected to severe calcium deprivation by feeding them a calcium-deficient diet containing oxalate (Group a). Furthermore, pregnant and lactating animals were subjected to the same diet (Group b). The mandibular teeth were examined by histologic, microradiographic and fluorescence microscopic techniques. The incisor enamel was found to be nearly unaffected by the experimental regimen; the dentin formed and mineralized during the experimental period was abnormal only in Group b. Characteristic features were reduced thickness, increased width of predentin and numerous globular defects. Both ameloblasts and odontoblasts were seemingly normal. No obvious differences could be observed between the molars from the controls and the test groups (a,b). "Cementolysis" seemed to be present to the same extent in all groups. In some of the animals of Group b some carious or erosional defects were observed in the molars. These may at least partially account for a small reduction in molar ash content observed in this group.

Animals↗
PubMed1979

Vincristine's effect on dentinogenesis in rat incisor.

Vincristine was administered to 60 rats in four groups in doses of 0.1, 0.3, 0.5 and 0.7 mg/kg. Histomorphologic investigation of the dentin and odontoblasts in the maxillary incisors after 1, 2 and 3 weeks revealed a moderate to severe disturbance of dentin production in some parts of the incisors. In some of the affected areas the effect seemed to be reversible in that normal-appearing dentin was found pulpal to the dentinal derangements after 2 and 3 weeks. The distribution and severity of the lesions were similar to those previously observed 3 days after injection of the same doses of vincristine.

Animals↗
PubMed1980

Long-term effects of colchicine on dentinogenesis in rat incisors.

Colchicine in doses of 0.5, 1.0 and 1.5 mg/kg was administered to 15 rats divided in three experimental groups. Histomorphologic investigation of the maxillary incisors after 2 weeks revealed; 1) alterations in the odontoblasts mainly related to size, shape, polarity and staining properties, and 2) presence of irregular dentin separated from normal dentin by one or two incremental lines. The dentinal irregularities were dose-dependent and consisted of twisting of the dentinal tubules, globular formations and cellular inclusions in addition to niche-like defects.

Animals↗
PubMed1984

Influence of doxorubicin on rat incisor mesenchymal cells.

Three groups of female Wistar rats were intravenously injected with the antineoplastic drug doxorubicin in a single dose of 5 mg/kg, 10 mg/kg and 20 mg/kg, respectively. The animals were killed 1 and 5 days after injection. Paraffin and Vestopal W embedded sections were prepared of the maxillary right and left incisors, respectively, and evaluated by light microscopy. Doxorubicin produced necrosis of single cells, of small groups of cells in the basal pulp and destroyed the preodontoblasts as evaluated 1 day after injection. On the 5th day of observation, the late preodontoblasts and basal pulp had regenerated, but the early preodontoblast zone remained absent, leading to an abnormal odontogenesis. This caused a marked reduction of dentin deposition in the apical part of the tooth and production of irregular predentin by cells in the pulp and by the young odontoblasts.

Animals↗
PubMed1985

Activity of gamma-glutamyl transferase in developing teeth of the rat.

gamma-Glutamyl transferase activity was studied with an enzyme histochemical technique in rat molar teeth at different stages of development. The odontoblasts showed an increasing activity during formation of the crown. The secretory ameloblasts did not show any activity, while activity was intense in the postsecretory ameloblasts. This activity was confined to the apical part of the cell. In the reduced ameloblasts at the enamel free cusp tips a similar activity was noted. Since gamma-glutamyl transferase has been shown to be involved in endocytosis and transport of amino acids, the localization of the enzyme in developing teeth suggests an active uptake of amino acids from the enamel matrix of the ameloblasts during enamel maturation.

Ameloblasts↗
PubMed1987

Scanning electron microscopic study of giant tubule content in bovine dentin.

Incisal segments of unerupted permanent incisors from 1/2-1 1/2-yr-old calves were fractured along an axiomesiodistal plane exposing the organic components within the giant tubule lumina situated in this plane. Along the lining wall of the pulpal vascularized giant tubule portion, large flattened cells and a few odontoblasts were situated in shallow depressions. Just incisal to the vascular loop numerous cells were seen, both along the giant tubule wall and enclosed within a loosely textured collagenous matrix. Further incisally, the number and size of the cells decreased, and they were embedded in a compact unmineralized collagenous matrix that completely filled out the giant tubule lumina. This matrix consisted of fibrils regularly arranged in separate bundles whose orientation was mainly longitudinal. The incisal origins of the giant tubules were filled with coarse fibrils being about three times thicker than those of the luminal matrix and those of the circumpulpal dentin proper.

Animals↗
PubMedDate not supplied

Inability of calcium hydroxide to induce reparative dentinogenesis at non-peripheral sites of dog dental pulp.

The ability of 2 calcium hydroxide-containing materials to induce initiation of reparative dentinogenesis was tested at sites remote from the dentinogenically-active regions of the pulp periphery. Pieces of the cements, Dycal and Life, were implanted in central parenchymal sites of dog dental pulps for periods of 6, 14 and 42 days, respectively. Similar pieces were placed in peripheral capping sites as controls. The responses were analyzed by light and transmission electron microscopy. Induction of tubular dentin matrix lined with elongated and polarized odontoblast-like cells was only seen at peripheral capping sites. In response to the centrally implanted cements, only atubular hard tissue with lining fibroblast-like cells was deposited.

Animals↗
PubMed1997

Expression of hsc 70, but not hsp 70, in human third molar dental pulp.

The constitutive (hsc 70) and inducible (hsp 70) isoforms of heat shock protein 70 are important members of the superfamily of stress related proteins that protect and promote the recovery of cells from physiological and pathologic stress. The goal of this study was to define the baseline expression of hsc 70 and hsp 70 in disease-free, minimally stressed human dental pulp of the adult 3rd molar. Immunolocalization demonstrated moderate to heavy staining intensity for hsc 70 in both the cytoplasm and nucleus of odontoblasts and fibroblasts comprising the human pulp. Endothelial and smooth muscle cells displayed weak to moderate immunoreactivity for hsc 70 in both the cytoplasm and nucleus. Schwann cells demonstrated only weak nuclear staining for hsc 70. No immunoreactivity for hsp 70 was observed in any cell type in human pulp. Western, northern, and RT-PCR analysis of pulp preparations confirmed the expression of hsc 70 mRNA and protein within components of the pulp. These results demonstrate that cells of the human pulp express, under conditions of minimal stimulation, a key component of the stress response protein superfamily. The expression of hsc 70 under conditions of minimal stress may provide pulp components an advantage in resisting cell injury when stress occurs.

Adult↗
PubMed1998

Expression of p21(WAF1/CIP1) during mouse odontogenesis.

p21(WAF1/CIP1) is a cyclin-dependent kinase (Cdk) inhibitor. This protein may function during development as an inducible growth inhibitor that contributes to cell cycle exit and differentiation. The expression pattern of p21 during mouse embryogenesis was correlated with terminal differentiation of multiple cell lineages including skeletal muscles, cartilage, skin and nasal epithelium. p21 expression was analyzed by in situ hybridization during odontogenesis as well as during in vitro tooth development in chemically defined medium with or without retinoic acid. p21 transcripts were detected in the restricted area of the inner dental epithelium during late cap and initial bell stages and then confined to the post-mitotic odontoblasts and ameloblasts. The replicating cells were devoid of any signal. The distribution of p21 mRNA in vitro, whatever the culture conditions, was similar to the in vivo pattern. p21 protein immunolocalization was superimposed on the transcripts distribution but more restricted in ameloblasts. TGFbeta1 is known to induce p21 expression. During dental cytodifferentiations, TGFbeta1 and p21 expressions overlap. Growth inhibition by TGFbeta1 may be associated with p21 induction.

Ameloblasts↗
PubMed1998

Sequential expression of an amelin gene in mesenchymal and epithelial cells during odontogenesis in rats.

Novel mRNA isoforms encoding the enamel matrix proteins amelin-1, amelin-2 and ameloblastin have been recently described. We have applied detailed immunohistochemical as well as non-radioactive in situ hybridization analyses to follow amelin-1 expression in developing rat incisors and molars. We constructed an expression vector, overproduced recombinant amelin in Escherichia coli and prepared an antibody. In addition to the previously reported amelin mRNA expression patterns in ameloblasts, the amelin message was also detected in pulpal mesenchymal cells including preodontoblasts and young odontoblasts. The signal in these cells persisted until deposition of mantle dentin became evident. The immunolocalization of amelin-1 in preodontoblasts and ameloblasts essentially followed the pattern of mRNA expression. The most intense staining was found in the enamel matrix adjacent to secretory ameloblasts. Focal accumulations of immunoreactive material were found at the dentinoenamel junction during the maturation stage. Also, using 5'-RACE (Rapid Amplification of cDNA Ends) we could confirm only amelin-1 and ameloblastin messages in the total RNA pool from rat molars and conclude that amelin-2 is a truncated form of ameloblastin. The sequential expression of amelin in mesenchymal and epithelial cells suggests it plays a role in cell differentiation during early tooth development.

Ameloblasts↗
PubMed2006

Immunohistochemical localization of transcription factor Sp3 during dental enamel development in rat tooth germ.

Sp3, a member of the Sp family of transcription factors, has previously been thought to be ubiquitously expressed, and its expression pattern in tooth development is not clear. This study was carried out to investigate the immunolocalization of Sp3 during the development of rat tooth germs. Sprague-Dawley rats at ages of 1, 3, 7, 10, and 14 d were used to represent different stages of tooth development. First mandibular molar tooth germs were sectioned and studied by immunohistochemistry. Sp3 was found to be localized within the nuclei of cells in developing tooth germs; however, ameloblast nuclei showed variable intensities at different developmental stages. At the same time, the positive signals in odontoblast nuclei remained stable. The results suggest that Sp3 may play a role in the development of teeth, specifically in the transcription of enamel-specific genes.

Ameloblasts↗
PubMed2006

Overexpression of transforming growth factor-beta1 in teeth results in detachment of ameloblasts and enamel defects.

Transforming growth factor-beta1 (TGF-beta1) is a key regulator of many cellular processes, including cell adhesion, the immune response and synthesis of extracellular matrix proteins. In the present study, we report the characterization of enamel defects in a transgenic mouse model overexpressing TGF-beta1 in odontoblasts and ameloblasts, its expression being driven by the promoter sequences of the dentin sialophosphoprotein gene. As reported earlier, these mice develop distinct dentin defects similar to those seen in human dentin dysplasia and dentinogenesis imperfecta. A further detailed examination of enamel in these mice revealed that from the early secretory stage, ameloblasts began to detach from dentin to form cyst-like structures. A soft X-ray analysis revealed that this cyst-like structure had a disorganized and partially mineralized matrix with an abnormal mineralization pattern and a globular appearance. In the molars, the enamel was not only pitted and hypoplastic, but enamel rods were completely lost. Thus, altered TGF-beta1 expression in the tooth seems to trigger detachment of ameloblasts and abnormal secretion and deposition of minerals in the cyst-like structures adjoining the dentin. We speculate that the altered expression of TGF-beta1 in teeth impacts the adhesion process of ameloblasts to dentin.

Ameloblasts↗
PubMed2006

Immunohistochemical study of small integrin-binding ligand, N-linked glycoproteins in reactionary dentin of rat molars at different ages.

Small integrin-binding ligand, N-linked glycoproteins (SIBLING) are believed to play key roles in the process of biomineralization. Reactionary dentin (RD), formed by odontoblasts in response to external stimuli, differs morphologically from primary dentin (PD). To test our hypothesis that the microscopic changes reflect variations in molecular mechanisms involved in formation of the two forms of dentin, and to characterize RD further, we compared the distributions of four SIBLING proteins [bone sialoprotein (BSP), osteopontin (OPN), dentin matrix protein 1 (DMP-1) and dentin sialophosphoprotein (DSPP)] in naturally occurring RD with those in PD. Molars of rats aged 12, 18, 24 and 36 wk were analyzed using immunohistochemistry with antibodies against BSP, OPN, DMP-1, and dentin sialoprotein (a fragment of DSPP). Differences in the distribution of the four SIBLING proteins were evident. Bone sialoprotein, not seen in PD, was consistently observed in RD. Osteopontin, almost absent from PD, was clearly observed in RD. The expression levels of DMP-1 and DSP in RD were lower than in PD. Elevated expression of BSP and OPN, along with a marked decrease of dentin sialoprotein and DMP-1 in RD, suggests a difference in the mechanism of formation of the two forms of dentin.

Age Factors↗
PubMed2006

The relationship between the termination of cell proliferation and expression of heat-shock protein-25 in the rat developing tooth germ.

Odontoblast- and ameloblast-lineage cells acquire heat-shock protein (HSP)-25 immunoreactivity after they complete cell division during postnatal odontogenesis in rat molars. However, there are no data available concerning the relationship between the termination of cell proliferation and HSP-25 immunoreactivity during tooth morphogenesis. We compared the expression of HSP-25 in tooth germs with their proliferative activity in the rat prenatal to perinatal molar and postnatal incisor to clarify the functional significance of HSP-25 during tooth morphogenesis by immunohistochemistry using anti-HSP-25 and anti-Ki67/5-bromo-2'-deoxyuridine (BrdU). Numerous proliferating cells in developing molars were distributed throughout the tooth germ and HSP-25 immunoreactivity was recognizable in the dental epithelial and mesenchymal cells after they completed cell division. However, both cell proliferation and immunoreaction for HSP-25 are absent in the enamel knots. The distribution pattern of the proliferating cells in the incisors was basically identical to that in the prenatal molars except for the lack of non-proliferating secondary enamel knots and the sparse distribution of proliferating cells in the apical bud. Thus, HSP-25 protein is suggested to act as a switch between cell proliferation and terminal cyto-differentiation during odontogenesis.

Ameloblasts↗
PubMed2004

In situ expression of RANKL, RANK, osteoprotegerin and cytokines in osteoclasts of rat periodontal tissue.

OBJECTIVES: This study examined the in situ expression of receptor activator of nuclear factor-kappaB ligand (RANKL), receptor activator of nuclear factor-kappaB (RANK), osteoprotegerin, interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) in the osteoclasts of rat periodontal tissue. BACKGROUND: In periodontal disease, osteoclasts cause resorption of the alveolar bone. The function of osteoclasts is regulated by interaction with periodontal ligament cells (PDLs). Furthermore, various kinds of molecules such as RANKL, RANK, osteoprotegerin, IL-1beta and TNFalpha are known to be related to the osteoclasts differentiation and function. It is therefore important to observe the expression of RANKL, RANK, osteoprotegerin and cytokines in osteoclasts and PDLs. METHODS: Four-week-old Wistar rats were used. Tooth movement was performed by the Waldo method, and the pathological bone resorption was induced. The demineralized maxillae and mandiblae were embedded with paraffin. In situ hybridization was performed to detect RANKL, RANK, osteoprotegerin, IL-1beta, and TNFalpha mRNAs in osteoclasts and other cells using the specific RNA probes, respectively. RESULTS: Both RANKL and RANK were concomitantly expressed in some osteoclasts. RANKL was also positive in osteoblasts and PDLs. No IL-1beta- and TNFalpha-positive osteoclast was noted. The positive signals of osteoprotegerin were detected in almost all osteoblasts, PDLs and odontoblasts. No osteoprotegerin-positive osteoclasts were observed. The number and the distribution pattern of RANKL- and RANK-expressing osteoclasts changed when orthodontic excessive force was applied to periodontal tissue. In addition, IL-1beta and TNFalpha were shown to be expressed in osteoclasts under pathological status. CONCLUSION: These findings suggest that an autocrine mechanism of RANKL-RANK exists in osteoclast, which is heightened in the pathological conditions. Furthermore, the autocrine mechanism of IL-1beta and TNFalpha is also provided in osteoclast under pathological condition. These autocrine mechanisms therefore seem to regulate the osteoclast function in both physiological and pathological conditions.

Animals↗