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At least 19 recordsLinked to original sources
PubMed1981

Purification and characterization of bovine dental sac collagenase.

1. Active type collagenase was purified as much as 140-fold from the explant medium of bovine dental sacs and showed a single band on disc gel electrophoresis. Purified collagenase cleaved native collagen at only one locus under physiological conditions, but hydrolyzed neither gelatin nor alpha-casein. The optimal pH was about 7.8. 2. The molecular weight of active type enzyme was 35,000 by gel filtration and 34,000 by gel electrophoresis. The activation of latent type of collagenase resulted in the reduction of molecular weight from 45,000 to 38,000 by gel filtration. 3. A small but detectable amount of collagenase was directly extracted from frozen and thawed bovine dental sacs. In explant media of frozen and thawed tissue and fresh tissue with actinomycin D, some activity was detected for the first 2 days, but essentially no collagenase activity was detected in the explant medium after day 3. 4. The latent type collagenase was activated by trypsin, 4-aminophenylmercuric acetate (4-APMA), thiocyanate and deoxycholate (DOC). DOC showed irreversible dissociation of latent type enzyme in similar fashion to that exerted by 4-APMA. 5. The purified collagenase was inhibited by bovine serum, EDTA, o-phenanthroline, cysteine and dithiothreitol.

Animals↗
PubMed1990

[Dental sac and its role in periodontal development].

The present study examined the role of the innermost layer of dental sac tissue in periodontal development. Empty bony crypts were filled with Hydroxylapatite ceramic granules of porous consistency in 5-day-old rats. After 4.5 and 24 weeks the specimens were processed for light and transmission electron microscopy. Only 4 weeks later cement regeneration was seen on ceramic surfaces with bundles of oriented collagen fibers inserting in the cementoid matrix. Ultrastructurally the newly formed cementum-like tissue was in intimate contact to the synthetic hydroxylapatite crystals. A consistent finding was the presence of an interface between cementum and the ceramic surface. The present findings question the unique role of the "investing layer" in periodontal development and the existence of cement-inducting properties of dentin.

Animals↗
PubMed1986

The innermost layer of cementum in rat molars: its ultrastructure, development, and calcification.

The present study describes the ultrastructure of the innermost layer of cementum (ILC) in the rat molars and discusses its developmental process and calcification mechanisms. The following points are the main results of this study: The ILC is a thin layer, about 2.0 micron thick, intensely stained with hematoxylin but not stained by silver impregnation. Electron microscopically, it is composed of substances stained with ruthenium red and chronic phosphotungstic acid presumed to be proteoglycans and a few thin collagen fibrils. Periodontal fibers penetrate the ILC only a short distance, and do not reach the root dentin surface. The ILC begins to form on the root dentin surface, just after the disintegration of Hertwig's epithelial root sheath. At the same time, matrix vesicles and spherical bodies, which may be derived from the matrix vesicles, appear on the surface of the developing ILC. Dental sac cells show higher cell activities than the epithelial sheath cells. Observations support the view that the dental sac cells secrete the ruthenium red positive material. On the basis of the above findings, the ILC is suggested to be formed by the dental sac cells and calcified by the matrix vesicles derived from these cells. The ILC can be regarded as a specialized cementum between the root dentin and the cementum in the strict sense, serving the connection of the two tissues.

Animals↗
PubMed2002

Behavior of epithelial root sheath during tooth root formation in porcine molars: TUNEL, TEM, and immunohistochemical studies.

The behavior of epithelial cells during tooth root formation in porcine molars was investigated using TUNEL, immunohistochemical and transmission electron microscopic methods. Cells of Hertwig's epithelial root sheath (HERS) expressed bcl-2, but were TUNEL-negative. Epithelial cells of HERS were tightly connected and surrounded by a continuous basement membrane. When dental papilla cells were attached to the inner HERS, they became positive for osteopontin (OPN). The inner basement membrane was intermittent immediately after those cells started to synthesize dentin matrix, and the intercellular spaces of the HERS became wider. Dental sac cells then migrated between the fragmented HERS and were directly connected to epithelial cells by desmosome-like structures. After the cementum was synthesized by these mesenchymal cells, epithelial cells aggregated to form cell clusters, which were again surrounded by a continuous basement membrane. These results suggest that fragmentation of the HERS is due to the invasion of dental sac cells, but is not related to cell death. Furthermore, the differentiation of dental papilla cells into odontoblasts occurred following their connection to the HERS through the basement membrane. Moreover, it is suggested that the differentiation of dental sac cells into cementoblasts occurred upon their direct connection to epithelial cells of the HERS.

Animals↗
PubMed1989

[Immunoglobulins in periapical lesion with special reference to qualitative and quantitative analysis of IgG].

Immunoglobulins in periapical lesions (including 34 radicular cysts and 11 radicular granulomas) were investigated through extracts of the lesions and cystic fluids. The extracts of dental sacs and sera were used as a control. For a qualitative analysis, the immunoglobulins (especially IgG) of each sample were investigated by agarose gel electrophoresis and agarose gel isoelectric focusing. For quantitative analysis, single radial immunodiffusion was employed for determining the concentration of IgG, IgG subclasses, IgA and IgM in the extracts, cystic fluids and autologous sera, also IgE in cystic fluids. In agarose gel electrophoresis, homogeneous bands that were regarded as monoclonal or oligoclonal patterns in gamma region were identified with IgG by immunofixation. These bands were detected in 65% of the radicular cysts, 73% of the radicular cysts obtained cystic fluid, and 73% of the radicular granulomas, but were not detected in any of the autologous sera and dental sacs. In cases that these homogeneous bands were found in extract of cyst, the same bands were found in fluid of same radicular cyst. These results strongly suggested that a part of IgG in periapical lesions was locally produced. By agarose gel isoelectric focusing, immunoglobulins in the extract, cystic fluid and serum were investigated. Many clearly detectable bands were found in extracts of periapical lesions and cystic fluids in the range of pH 6-9 and identified with IgG by immunofixation. These findings revealed restricted heterogeneity of IgG. These IgG bands were found randomly in the range of pH 6-9 and no specific inclination of arrangement. These results suggested that IgG in periapical lesions seem to have different specificities in immunological reaction. Furthermore, in isoelectric focusing pattern of IgG, similar bands were identified in the extract of the cystic wall and fluid of same radicular cyst in 82% of the cases. These bands were detected in some of the dental sacs but not in the serum. Therefore it means that a quantities of IgG in periapical lesions and cystic fluids were locally produced. By quantitative analysis, no statistically significant differences were found in the concentration of IgG, IgG subclasses, IgA and IgM in sera between periapical lesion group and control group.

Immunoglobulin G↗
PubMed1993

Development of the murine periodontium. II. Role of the epithelial root sheath in formation of the periodontal attachment.

Experimental manipulation of the developing murine tooth germ has provided evidence that basement membrane components on the forming root surface are involved in early periodontal attachment formation. The purpose of this investigation was to determine the role of epithelial root sheath (ERS) cells in murine cementogenesis and periodontal ligament formation using tissue separation and recombination techniques. Root dentin specimens, with and without root-associated basement membrane components (D + RBM or D - RBM), were recombined with dental sac in the presence or absence of ERS. Recombinations were cultured for 2 weeks, harvested, and examined by light, electron, and immunofluorescence microscopy. Mineralized tissue formed in all tissue recombinations. However, when ERS was included in recombinations between D + RBM and dental sac, 25% of recombinations formed a periodontal ligament with fibrous attachment of the root specimen to adjacent bone. These results support the hypothesis that root and periodontal ligament formation is influenced by epithelio-mesenchymal interactions and further support a key role for ERS in these processes.

Alveolar Process↗
PubMedDate not supplied

[Histomorphometry of dentigerous cysts in children, associated or not with formocresol].

Literature reports appeared in the last years suggested that some type of dentigerous cyst (DC) in children would initiate by teh action of other factors than developmental and at different stages of dental sac growth. Periodontitis and pulp therapy with formocresol (FC) have been suggested as aeteological factors, both promoting DC in children by irritation of the underlaying dental sacs of premolar. The purpose of this study is to analyse the pathological changes in DC of patients aged 0 to 15 years, and to compare the findings according to the anatomical site of DC and the existence of previous FC therapy. Morphological changes observed in the epithelium and the connective wall did not show clear differences between both groups of DC. The histometric measurements of epithelial changes did not show significant statistical differences of various parameters in the DC walls. These facts would not support the hypotesis of DC initiation from FC effects.

Adolescent↗
PubMed1989

Ultrastructural and histochemical study on the morphogenesis of epithelial rests of Malassez.

The morphogenesis of the epithelial rests of Malassez in rat molars was studied by light and electron microscopy. The epithelial islands immediately after disintegration of the Hertwig's root sheath consisted of a few irregularly shaped cells with scanty rough endoplasmic reticulum, which were surrounded in portions by disrupted basal lamina. Close topographic relationships between the epithelial cells and mesenchymal cells of the dental sac were often observed in this period. After thirty days of age, the epithelial cells started to form ovally shaped epithelial islands consisting of four or five cells, but collagen fibrils still remained in the intercellular spaces. Vacuoles containing collagen fibrils were occasionally observed in the cytoplasm of the epithelial cells during this period in association with an acid phosphatase positive reaction. In more mature rat molars, the epithelial islands were characterized by an increased number of epithelial cells, only rarely observed collagen fibrils in the cytoplasm and the intercellular spaces, and an almost complete lining of basal lamina. The results indicate that the phagocytosis of collagen fibrils by the epithelial cells is a crucial step in the formation of the epithelial rests. The possibility is suggested that interactions with mesenchymal cells of the dental sac and regeneration of the basal lamina may also contribute to the epithelial rest formation.

Animals↗
PubMed1999

Expression of mRNA encoding tissue-nonspecific alkaline phosphatase in human dental tissues.

Tissue-nonspecific-type alkaline phosphatase (TNSALP) is found in the bone, liver, kidney, and other tissues, and its gene consists of 12 exons with the coding sequence beginning in the second exon. Recently, a noncoding first exon was identified in the liver message (liver type) which differed from that of the previously known osteoblast-derived cDNA sequence (bone type). Although these two mRNAs produce an identical protein, they have different promoter regions. It is known that ALPs in dental pulp and periodontal ligament are classified into TNSALP by their enzymatic and immunological properties, but little is known about the expression of ALP mRNAs and the transcriptional mechanisms. In order to examine the expression of their mRNA type, specific oligonucleotide primers corresponding to two types of mRNAs of human TNSALP were designed and amplified by reverse transcription-polymerase chain reaction (RT-PCR). It was found that bone-type mRNA was expressed in the human dental tissues such as dental pulp, periodontal ligament, and dental sac, whereas liver-type mRNA was not expressed. Thus, it was concluded that the human dental tissues express the bone-type isozymes and are regulated by the same transcriptional mechanism as in the bone.

Alkaline Phosphatase↗