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PubMed2003

Mitochondrial DNA from pre-Columbian Ciboneys from Cuba and the prehistoric colonization of the Caribbean.

To assess the genetic affinities of extinct Ciboneys (also called Guanajuatabeys) from Cuba, 47 pre-Columbian skeletal samples belonging to this group were analyzed using ancient DNA techniques. At the time of European contact, the center and east of Cuba were occupied by agriculturalist Taino groups, while the west was mainly inhabited by Ciboneys, hunter-gatherers who have traditionally been considered a relic population descending from the initial colonization of the Caribbean. The mtDNA hypervariable region I (HVR-I) and haplogroup-specific markers were amplified and sequenced in 15 specimens using overlapping fragments; amplification from second extractions from the same sample, independent replication in different laboratories, and cloning of some PCR products support the authenticity of the sequences. Three of the five major mtDNA Amerindian lineages (A, C, and D) are present in the sample analyzed, in frequencies of 0.07, 0.60, and 0.33, respectively. Different phylogenetic analyses seem to suggest that the Caribbean most likely was populated from South America, although the data are still inconclusive, and Central American influences cannot be discarded. Our hypothesis is that the colonization of the Caribbean mainly took place in successive migration movements that emanated from the same area in South America, around the Lower Orinoco Valley: the first wave consisted of hunter-gatherer groups (ancestors of the Ciboneys), a subsequent wave of agriculturalists (ancestors of the Tainos), and a latter one of nomadic Carib warriors. However, further genetic studies are needed to confirm this scenario.

Bone and Bones↗

PubMedDate not supplied

Histomorphologic changes in the gingiva and pulp of overretained primary teeth.

This study examined the influence of overretention on the tissues of human primary teeth. The range of overretention was two to thirty-two years. Light microscopy and computerized morphometry were utilized for histologic assessment of twenty-five sites of twenty-one teeth. Dentinoclasts were found on the resorbing root surface of nine teeth; polymorphonuclear leucocytes were found in the pulp of fourteen teeth; and monocytes were present in all pulps. The apical and coronal ends of the junctional epithelium were apical to the cemento-enamel junction in eighteen and fourteen teeth, respectively. Significant correlations were found between the extent of overretention and gingival height, the length of the junctional epithelium and the extent of apical migration of the junctional epithelium. Present and previous findings indicate that odontoclastic activity in the pulp is reduced with overretention; and while at the beginning of overretention there is a lower percentage of pulps with polymorphonuclear leucocytes in the pulp, with an extended period of overretention an increase in this percentage takes place.

Adolescent↗

PubMed1993

Effect of root conditioning on periodontal wound healing with and without guided tissue regeneration: a pilot study. 1. Histologic evaluation.

Closed fenestration wounds in four mongrel dogs were used to study the source of fibroblast proliferation and extracellular matrix production during healing; the arrangement and attachment of newly formed collagenous fibers; and the cementogenesis and osteogenesis at healing sites. Fenestration wounds were made through the alveolar bone, periodontal ligament, cementum, and dentin, and citric acid, tetracycline, or sterile water was applied to the dentinal walls for 3 minutes. Nonresorbable membranes were randomly placed over half of the defects. Animals were killed at 1, 3, 7, or 21 days and routine histologic examinations with hematoxylin and eosin staining followed. Results of this pilot study suggest that the periodontal ligament and/or alveolar bone are the main source of fibroblast proliferation and migration as well as extracellular matrix formation at the initial stages of healing, and that at 21 days, citric acid stimulated more cementogenesis than tetracycline or sterile water. Also, while the tetracycline influenced the maximal deposition of alveolar bone, no differences in healing were found between the citric acid, tetracycline, and sterile water with and without the use of membrane barriers.

Acid Etching, Dental↗

PubMed1984

Alveolar ridge maintenance with solid nonporous hydroxylapatite root implants.

Animal studies were carried out to determine a simple technique of implantation of nonresorbable polycrystalline hydroxylapatite solid root forms and the biocompatibility of the material placed in fresh extraction sockets. An appropriately shaped root form was evaluated, and alveolar bone preservation was investigated in dogs and primates. It was found that bone and soft tissue would migrate across the HA root implant when placed 2 to 3 mm below the alveolar bone crest without soft-tissue closure. It was not necessary to use roots that fit the socket from the apex to the alveolar crest. An average of 2 mm more alveolar bone was preserved in fresh extraction sites as compared to control sites. The results of the animal studies indicated the appropriateness of a clinical trial in human beings.

Alveolar Process↗

PubMed2001

The AN2 protein is a novel marker for the Schwann cell lineage expressed by immature and nonmyelinating Schwann cells.

The expression of the 330 kDa AN2 glycoprotein was studied in the rodent peripheral nervous system. AN2 is expressed by immature Schwann cells in vitro and in vivo and downregulated as the cells upregulate myelin genes. A subpopulation of nonmyelinating Schwann cells in the adult sciatic nerve retains expression of AN2. In rat sciatic nerve crushes, where Schwann cell numbers increase after initial axonal loss and markers of immature Schwann cells show an upregulation, no increased expression of AN2 was observed. In contrast, AN2 expression was upregulated in nerves from peripheral myelin protein-22-transgenic rats, where immature Schwann cells expand without axonal loss. Furthermore, coculture with neurons upregulated AN2 expression on Schwann cells in vitro. Polyclonal antibodies against AN2 inhibited the migration of an immortalized Schwann cell clone in an in vitro migration assay, and the purified AN2 protein was shown to be neither inhibitory nor permissive for outgrowing dorsal root ganglion neurites. AN2 is thus a novel marker for the Schwann cell lineage. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of purified AN2 from early postnatal mouse brain demonstrated that AN2 is the murine homolog of the rat NG2 proteoglycan.

Animals↗

PubMed1977

Healing following simulated fiber retention procedures in rats.

Healing responses of a simulated fiber retention procedure in rats has been presented. In the area of attached, but severed supracrestal fibers, a loss of cells was observed in the initial stages of repair. Subsequently, connective tissue cells migrated into this area as did blood vessels. A very distinct interface was seen at about 1 week after surgery between the advancing soft tissues from the flap wound surface and the attached, but severed supracrestal fibers. By 4 weeks after surgery, such distinction was absent and supragingival fiber bundles appeared continuous from their cemental attachment over to the adjacent alveolar crest. However, no evidence of cementogenesis was seen at this site which suggests that these attached fibers were attached prior to surgery. The position of the new junctional epithelium appeared to be limited to the level of the retained supracrestal fiber fragments. However, in areas where cementum, and thereby attached fibers, had been removed during surgery, an altered epithelial adherence was usually seen. This altered adherence was in the form of a long junctional epithelium or a short junctional epithelium on top of parallel oriented collagen fibers. The latter also appeared to adhere to the tooth surfaces.

Animals↗

PubMed1992

Guided tissue regeneration--why, when and how?

Chronic periodontitis results in the destruction of the collagen fibre attachment to cementum, apical migration of the epithelial attachment, contamination of the exposed root surface by plaque and loss of alveolar bone. Regeneration can be defined as the restitution of lost tissues to a state which existed before destruction. As such, it is an ultimate and ideal goal and in most circumstances is currently beyond our capabilities. However, research in periodontology over the last 10 years or so has made considerable advances and is perhaps unique in proposing a new and fundamental treatment modality--guided tissue regeneration.

Alveolar Bone Loss↗

PubMed1983

Fibrin linkage: a precursor for new attachment.

Previous studies indicated that connective tissue attachment to the root surface appeared to be dependent upon a chronologic healing sequence related to fibrin and collagen interactions. It was the purpose of the present study to try and substantiate this hypothesis by using histologic techniques designed to differentiate between fibrin and collagen during healing at the root surface interface. In four squirrel monkeys, 24 normal teeth were extracted and reimplanted after either (i) surgically denuding the coronal root surface of connective tissue fibers and cementum by root planing or, (ii) surgical denudation followed by topical application of citric acid (pH = 1; 3 minutes). Three specimens were available for histological analysis 1, 3, 7 and 21 days after reimplantation. Mallory's phosphotungstic acid hematoxylin staining technique was used to differentiate between fibrin and collagen. Epithelium migrated rapidly along the denuded, non-acid-treated, root surfaces, had reached the alveolar crest at 3 days, and was within the ligament space to the level of root denudation at 21 days. Epithelium did not migrate apically along denuded root surfaces treated with citric acid. At 1 and 3 days, inflammatory cells were enmeshed in a fibrin network which appeared to be attached to the root surface by arcade-like structures. At 7 and 21 days, the region had repopulated with connective tissue cells, and collagen fibers had replaced the fibrin. It was concluded that collagen fiber attachment to the root surface was preceded by fibrin linkage, and that the linkage process occurred as an initial event in the wound healing response.

Animals↗

PubMed1984

In vivo crevicular leucocyte response in humans to a chemotactic challenge. Effects of periodontal diseases.

An in vivo assay was recently developed to monitor the crevicular leucocyte response to chemotactic agents, e.g., casein and N-formyl peptides. This method was used to monitor humans with little or no gingival disease (C group), gingivitis (G group), chronic periodontitis (CP group) and localized juvenile periodontitis (LJP group). Casein (0.2 microliters, 2 mg/ml) was placed into an isolated gingival crevice of each subject with a calibrated wire loop and the time recorded (t = 0). Leucocytes were counted in crevicular washes (10 microliters) 15 minutes later and every 5 minutes thereafter up to t = 50 minutes. This protocol was repeated for the crevice of an adjacent tooth except that the crevicular fluid flow response to the chemotactic challenge was monitored. The C, G and CP subjects showed a similar pattern of response to the chemoattractant with a single "peak" of leucocytes at approximately t = 25 minutes. However, the peak cell count was much greater in the G and CP groups than in the C group. LJPs showed an abnormal pattern with two leucocyte peaks, one at approximately 25 minutes and the other at 45 minutes. Both peaks tended to be higher than the single peak seen in Cs but were significantly lower than that in Gs or CPs, even at similar levels of inflammation. In addition, the peak leucocyte response (to casein) in LJPs did not increase with increasing leucocyte counts in the unchallenged (resting) crevice, whereas a positive relationship was seen in the other groups of subjects. These data suggest that this new assay may provide important diagnostic information on in vivo neutrophil migration in the gingival crevice and on susceptibility to periodontal disease.

Adolescent↗

PubMed1997

Ancient DNA from Polynesian rats: extraction, amplification and sequence from single small bones.

The human colonisation of Polynesia was a major event in world prehistory. It represents one of the last human population migrations, and one which required crossing major water barriers. Though the subject of Pacific population origins has been approached by scholars from numerous fields for nearly a century, recent years have seen the problem addressed by human geneticists. Since the initial report describing the recovery of DNA from skeletal remains, ancient DNA studies have also focused on the Pacific region. In this paper we present the results of ancient DNA analyses of Rattus exulans, an animal that was transported by ancestral Polynesians through the Pacific to the far reaches of the Polynesian triangle. Analysis of DNA of R. exulans skeletal remains has many advantages over studies of ancient human remains, yet the one drawback has been the recovery of ancient DNA from single bones of these very small rodents. We have successfully modified standard extraction protocols for ancient DNA and have consistently extracted, amplified and sequenced mitochondrial DNA (mtDNA) from less than 0.1 g of R. exulans bone and tooth samples recovered from archaeological sites throughout the Pacific, ranging from 400 to 2000 years old.

Animals↗

PubMed1984

The Papillon-Lefèvre syndrome: neutrophil dysfunction with severe periodontal disease.

Two cases of Papillon-LeF evre are described. Both siblings demonstrated neutrophil dysfunction and severe precocious periodontal disease. The neutrophil locomotion defect was characterized by a decreased migration toward a chemotactic factor and decreased random migration. Binding of the chemotactic factor, FMLP, to the neutrophil surface was unchanged. Both patients harbored Actinobacillus actinomycetemcomitans and showed elevated serum IgG levels. Both patients also demonstrated salivary and serum antibody to A. actinomycetemcomitans. The Papillon-LeF evre syndrome is compared with the more common localized juvenile periodontitis.

Actinobacillus↗

PubMed1995

Lectins--proteins with a sweet tooth: functions in cell recognition.

Lectins, non-enzymic proteins that bind mono- and oligosaccharides reversibly and with high specificity, occur widely in nature. They come in a variety of sizes and shapes, but can be grouped in families with similar structural features. The combining sites of lectins are also diverse, although they are similar in the same family. The specificities of lectins are determined by the exact shape of the binding sites and the nature of the amino acid residues to which the carbohydrate is linked. Small changes in the structure of the sites, such as the substitution of only one or two amino acids, may result in marked changes in specificity. The carbohydrate is linked to the protein mainly through hydrogen bonds, with added contributions from van der Waals contacts and hydrophobic interactions. Coordination with metal ions may occasionally play a role too. Microbial surface lectins serve as a means of adhesion to host cells of viruses (e.g. influenza virus), bacteria (e.g. E. coli) and protozoa (e.g. amoeba): a prerequisite for the initiation of infection. Blocking the adhesion by carbohydrates that mimic those to which the lectins bind prevents infection by these organisms. The way is thus open for the development of anti-adhesive therapy against microbial diseases. Lectin-carbohydrate mediated interactions between leucocytes and endothelial cells are the first step in the recirculation of lymphocytes and in the migration of neutrophils to sites of inflammation. Such interactions may also feature highly in the formation of metastases. Studies of these processes are expected to lead to the development of carbohydrate-based anti-adhesion drugs for the treatment of inflammatory diseases as well as cancer.

Animals↗

PubMed2000

Improved bone regeneration and root coverage using a resorbable membrane with physically assisted cell migration and DFDBA.

Twelve patients with 2 Miller Class I or II buccal recession defects measuring > or = 3.0 mm were treated using the principles of guided tissue regeneration and followed for 12 months. The effectiveness of a polylactide (Guidor) resorbable membrane (GA sites) was compared to a combination treatment of polylactide membrane plus polyglactin root-lining mesh (Vicryl) and demineralized freeze-dried bone allograft (DFDBA) (GVB sites) designed to enhance cell migration and bone regeneration. There was 90% mean soft tissue root coverage for the GVB sites and 78% for the GA sites. The mean osseous dehiscence area coverage with hard tissue was 75% for GVB sites and 30% for GA sites.

Absorbable Implants↗

PubMed1984

Potentials for root resorption during periodontal wound healing.

The present study was undertaken to examine whether (1) the process of resorption, which invariably affects periodontitis involved reimplanted roots facing bone or gingival connective tissue during healing, is a transient phenomenon and, (2) root resorption can be prevented by permitting downgrowth of epithelium along the root surface. A total of 24 teeth in 2 monkeys (Macaca cynomolgus) was subjected to experimental periodontal tissue breakdown by the placement of elastic ligatures around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following removal of the ligatures, the teeth were extracted and the denuded portions of the roots were scaled and planed. The crowns of the teeth were resected and the root canals filled with guttapercha. The roots were subsequently implanted into sockets prepared in the jaw bone in such a way that each root was embedded in bone except for a portion which was in contact with gingival connective tissue. 1 month prior to sacrifice of the animals, the cut surface of the coronal part of the roots was exposed by removal of the covering soft tissue. The epithelium was thereby allowed to migrate into the wound. Implantation of the roots was scheduled to provide healing periods of 1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks before exposure of the roots. The histologic examination of the implant specimens disclosed that replacement resorption was a progressive process which eventually resulted in the elimination of the transplanted roots. It was possible to prevent root resorption in this model by permitting apical downgrowth of epithelium along the root surface during the initial phase of healing. The results are discussed in relation to procedures used in periodontal therapy.

Animals↗

PubMed1993

Migration of a Streptococcus sanguis strain through the root dentinal tubules.

The persistent presence of bacteria in the root canal system often leads to the failure of treatment. The aim of this study was to study the in vitro penetration of root dentinal tubules by bacteria. Bovine dentin was inoculated with a strain of Streptococcus sanguis, NCTC 7863; samples were taken at 10, 20, and 28 days, and bacterial penetration of the tubules was demonstrated using two techniques, scanning electron microscopy and light microscopy after Brown and Brenn staining. The results showed that S. sanguis can penetrate deep inside the tubules (792 microns). The maturity of the dentin blocks seems to be a major factor in tubule penetration.

Animals↗

PubMed1986

Periodontal attachment responses to surgical injury in the cat. Removal of buccal bone with and without placement of foreign body at ligament periphery.

Recently, PDL progenitor cells were claimed essential for the establishment of new connective tissue attachment to root surface. To further test new periodontal attachment after surgical injury, portions of the buccal alveolar plate were removed from the canines of 4 cats. Removal of bone was carried out with or without removal of the underlying PDL, and in half of the experimental sites, dental amalgam was placed at ligament periphery. Tissue blocks were prepared for routine histologic evaluation (H & E) and specific collagen stains (Mallory Trichrome and Mallory PATH). Exfoliation of amalgam was noted in 6 experimental sites during the healing period. At all sites, plaque accumulation and marginal gingivitis were observed before sacrifice. Histologic observation demonstrated limited new connective tissue attachment to root surfaces at PDL periphery where bone, PDL and cementum had been removed. Where PDL was retained, connective tissue attachment was present which appeared to be the result of fiber interdigitation between root-inserted fiber ends and gingival wound edge fibers. "Blockage" of PDL cell migration by amalgam could not be well controlled. However, the placement of amalgam seems to have interfered with new connective tissue attachment and/or cementogenesis. In 5 specimens, root resorption had progressed into dentin. At these sites, collagen tufts appeared to arise from dentin. These tufts were in intimate contact with zones of dense inflammatory cellular infiltrate and connective tissue elements. We suggest that this observation may be a further tissue response to injury, namely: root resorption with the unmasking of dentinal collagen, which may finally lead to fiber interdigitation.

Alveolar Process↗

PubMed1989

[Histological study of cell attachment and proliferation of periodontal ligament cells on the tooth surface. Effect of the fibronectin application].

The purpose of this study was to examine the effect of fibronectin on cell attachment and the growth of cultured cells on the surface of the dentin. In the first experiment, dentin specimens were divided into following three groups: dentin surface polished with carborundum-point, carborundum-point and #150 sandpaper and carborundum-point, #150 sandpaper and #240 sandpaper. The roughness of the surface was measured with a profilometer (Surfcom e-st-sa) for the purpose of comparing differences among the three groups. The foregoing treated samples were added to cultures of periodontal ligament (PDL) cells and following fixation, the number of cells was counted under a light microscope and examination under a scanning electron microscope (SEM) was also performed. 1. Greater numbers of cells attached to the smooth surface (#240) than the rough surface. 2. SEM observations showed increased numbers of attached and proliferated cells on the smooth surface. In the second experiment, the dentin surfaces were polished with carborundum point, #150 and #240 sand paper. The dentin tube side was treated with fibronectin. MEM-treated samples not immersed in fibronectin were employed as controls. The foregoing treated root samples were cultured with PDL cells. Following fixation, the cells attached to the root surface were examined under the light microscope and using a SEM. 1. A significant increase in the number of the attached cells as observed after treatment with fibronectin. 2. SEM observation suggested PDL cells migrated more and proliferated more on the side treated with fibronectin. 3. Fibronectin application increased cell attachment and proliferation more on the smooth surface of dentin.

Cell Adhesion↗

PubMed1999

Expression of laminin-5 in ameloblastomas and human fetal teeth.

Extracellular matrix proteins have been shown to play important roles in the cell migration and differentiation in both normal and pathological conditions. In the present study, we used immunohistochemistry and in situ hybridization to determine the distribution of laminin-5 in ameloblastomas and developing human teeth. In ameloblastomas, the immunoreaction for the laminin-5 gamma2 chain was confined to the tumor cells of the peripheral area. The staining reaction was variable, being mostly weak and fragmented in the basement membrane structures surrounding the neoplastic islands. Some peripheral epithelial cells and some invading small ameloblastoma cell islands showed intense intracellular staining for the gamma2 chain. Tumor cells in the proliferating areas of ameloblastomas expressed gamma2 chain mRNA. The laminin-5 gamma2 chain was located beneath the dental lamina and in the outer, but not in the inner, enamel epithelium of the developing teeth. During the early hard tissue apposition stage, intense staining for the gamma2 chain was confined to ameloblasts, which also gave a strong signal for gamma2 chain mRNA. These results suggest that laminin-5 may contribute to the infiltrative and progressive growing potential of ameloblastomas. During human tooth development, however, laminin-5 may participate in the terminal differentiation of ameloblasts and in enamel matrix formation.

Ameloblastoma↗