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R J Genco

Publications and source records attributed to R J Genco.

At least 73 records · Page 4Linked to original sources
PubMed1996

Exploratory case-control analysis of psychosocial factors and adult periodontitis.

We explored the association between social factors and adult periodontitis by comparing self-reported information for daily strains and symptoms of depression in 71 cases and 77 controls. Cases and controls were selected from among 1,426 participants in the Erie County Risk Factor Study. We found differences among those who scored higher than their peers on measures of social strain. The odds ratio (OR) and 95% confidence interval (95% CI) for the association between case status and Role Strain score of 2.27 or more was 2.84, 95% CI = 1.08 to 7.46. We also examined serum antibody, dichotomized at the median, for three periodontal pathogens (Bacteroides forsythus [IgG Bf], Porphyromonas gingivalis [IgG Pg], Actinobacillus actinomycetemcomitans [IgG Aa]), and assessed interaction between antibody levels and a Depression score derived from the Brief Symptom Inventory. IgG Pg and IgG Aa were both strongly associated with case status (OR = 4.52, 95% CI = 1.99 to 10.3 and OR = 5.29, 95% CI = 2.34 to 12.0, respectively). IgG Bf was associated with periodontal disease but only among individuals who had higher scores for Depression (OR = 6.75, 95% CI = 1.25 to 36.5). Smoking status was associated with case status (OR = 4.95, 95% CI = 1.86 to 13.2). We assessed these findings prospectively by examining factors associated with more extensive disease among the 71 case subjects after 1 year of follow-up. We found baseline smoking status and IgG Bf among individuals scoring high on Depression at baseline to be associated with more extensive disease (8.1% or more of the sites showing further breakdown). In this population an elevated Depression score may be a marker for social isolation, which could play a role in immune function during periods of social strain. This exploratory analysis has served to identify specific lines of inquiry concerning psychosocial measures as important environmental factors in adult periodontitis.

Adult↗
PubMed1996

The role of osteopenia in oral bone loss and periodontal disease.

Osteoporosis and periodontitis are diseases which affect a large number of women and men, with incidence increasing with advancing age. Osteopenia is a reduction in bone mass due to an imbalance between bone resorption and formation, favoring resorption, resulting in demineralization and leading to osteoporosis. Osteoporosis is a disease characterized by low bone mass and fragility and a consequent increase in fracture risk. Periodontitis is characterized by inflammation of the supporting tissues of the teeth, resulting in resorption of the alveolar bone as well as loss of the soft tissue attachment to the tooth and is a major cause of tooth loss and edentulousness in adults. The relationship of osteopenia to oral bone loss and periodontal disease has been addressed in a limited number of studies. A review of current knowledge regarding this relationship is presented. Interpretation of the literature is complicated by the variety of methods used to assess osteopenia, oral bone mass, and periodontitis, as well as varying definitions of outcomes of interest. Results of a previously unpublished study are presented which suggest that severity of osteopenia is related to loss of alveolar crestal height and tooth loss in post-menopausal women. The literature on the relationship among these disorders is limited and points to the need for additional studies which thoroughly evaluate the influence of potential confounding factors to further define the relationship between low bone mineral density and periodontal disease in larger populations. Clearer understanding of this relationship may aid health care providers in their efforts to detect and prevent osteoporosis and periodontal disease. Increased dialogue among medical and dental professional will be increasingly important in achieving and maintaining patients' optimal health.

Adult↗
PubMed1996

Severe periodontitis and risk for poor glycemic control in patients with non-insulin-dependent diabetes mellitus.

This study tested the hypothesis that severe periodontitis in persons with non-insulin-dependent diabetes mellitus (NIDDM) increases the risk of poor glycemic control. Data from the longitudinal study of residents of the Gila River Indian Community were analyzed for dentate subjects aged 18 to 67, comprising all those: 1) diagnosed at baseline with NIDDM (at least 200 mg/dL plasma glucose after a 2-hour oral glucose tolerance test); 2) with baseline glycosylated hemoglobin (HbA1) less than 9%; and 3) who remained dentate during the 2-year follow-up period. Medical and dental examinations were conducted at 2-year intervals. Severe periodontitis was specified two ways for separate analyses: 1) as baseline periodontal attachment loss of 6 mm or more on at least one index tooth; and 2) baseline radiographic bone loss of 50% or more on at least one tooth. Clinical data for loss of periodontal attachment were available for 80 subjects who had at least one follow-up examination, 9 of whom had two follow-up examinations at 2-year intervals after baseline. Radiographic bone loss data were available for 88 subjects who had at least one follow-up examination, 17 of whom had two follow-up examinations. Poor glycemic control was specified as the presence of HbA, of 9% or more at follow-up. To increase the sample size, observations from baseline to second examination and from second to third examinations were combined. To control for non-independence of observations, generalized estimating equations (GEE) were used for regression modeling. Severe periodontitis at baseline was associated with increased risk of poor glycemic control at follow-up. Other statistically significant covariates in the GEE models were: 1) baseline age; 2) level of glycemic control at baseline; 3) having more severe NIDDM at baseline; 4) duration of NIDDM; and 5) smoking at baseline. These results support considering severe periodontitis as a risk factor for poor glycemic control and suggest that physicians treating patients with NIDDM should be alert to the signs of severe periodontitis in managing NIDDM.

Adolescent↗
PubMed1996

Response to periodontal therapy in diabetics and smokers.

Diabetics and smokers are two patient groups at high risk for periodontal disease who also exhibit impaired wound healing and, therefore, constitute two different groups in whom the relationship between host-parasite interaction, outcome of periodontal therapy, and systemic factors is best represented. The results of two independent clinical trials involving treatment of periodontal disease in diabetics and smokers are presented. A new treatment regimen for the management of periodontal disease associated with diabetes mellitus is proposed. This treatment approach incorporates both antimicrobial agents and pharmacological modulation of the host response. Elimination of periodontal infection and reduction of periodontal inflammation in diabetic patients resulted in a significant short-term reduction in the concentration of glycosylated hemoglobin (HbA1c). Control of chronic infections and modulation of the host response offer a new therapeutic approach in the management of patients with both diabetes and periodontal disease. The effect of smoking on periodontal healing is also discussed. The clinical and microbiological response of smokers to non-surgical periodontal therapy is compared to non-smokers. In addition, possible mechanisms whereby diabetes mellitus and cigarette smoking increase the severity of periodontal disease are discussed.

Adjuvants, Immunologic↗
PubMed1996

Analytical performance of an immunologic-based periodontal bacterial test for simultaneous detection and differentiation of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia.

The analytical performance of a membrane-based immunoassay for the simultaneous detection and differentiation of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia (including Prevotella nigrescens) was investigated. Positive reactions were observed for 71 of 71 reference strains and recent oral isolates of A. actinomycetemcomitans, P. gingivalis, and P. intermedia. No cross-reactivity was observed with 39 other common oral and environmental species. The specificity of the test was unaffected by the presence of potential oral interferents including whole blood, white blood cells, mucin, saliva, toothpastes, and oral rinses. A proficiency test by dental professionals using a standardized set of unknown simulated samples yielded a sensitivity of 97% (116/120) and a 100% specificity (240/ 240). An additional group including dental professionals and high school students was shown to be 99% proficient (1385/1397) in distinguishing proper from improper test function when processing control samples with normal test devices and devices with simulated error conditions. Comparisons to a culture standard for 104 subgingival plaque samples collected from 26 adult periodontitis patients yielded > 98% specificity for each of the test bacteria. In addition, the detection threshold for the test was determined to be equivalent to 10(4) cultivable test bacteria when compared to the culture standard. The data indicate that this membrane immunoassay is a valid and easy-to-use method for the detection of A. actinomycetemcomitans, P. gingivalis, and P. intermedia in subgingival plaque, at levels above the detection threshold of the test.

Adult↗
PubMed1996

Long-term stability of Class II furcation defects treated with barrier membranes.

The present longitudinal study was designed to explore the long-term efficacy of guided tissue regeneration (GTR) in Class II furcation defects and establish the factors that might be responsible for modifying this response. Subjects with two or more mandibular molars, one of which had Class II furcation defects, received the hygienic phase of therapy followed by baseline clinical measurements and subgingival plaque sampling. GTR procedure was performed in furcation defect sites using expanded polytetrafluoroethylene (ePTFE) membranes, while the other non-furcated molars received only scaling and root planning. Twenty-eight subjects (13 females, 15 males) aged 27 to 66 were included in this longitudinal analysis. Post-surgical treatment included routine home care supplemented with daily chlohexidine rinse and systemic tetracycline. Membranes were retrieved 4 to 6 weeks after surgery. During the first year, patients were initially seen bi-weekly and subsequently monthly for professional prophylaxis. At the end of this year, clinical measurements and samples were obtained. For the next 2 years, patients were seen bi-annually for maintenance visits. Clinical measurements and microbiological samples were then repeated. Next, a tighter maintenance protocol was established and patients were seen quarterly for scaling and oral hygiene reinforcement. Final measurements and samples were taken again 1 year later (4 years postoperative). Significant probing reduction (3.00 mm) and gain in horizontal attachment (2.59 mm) were obtained 1 year postsurgery for the GTR sites. These changes were maintained over 4 years with a slight decline at the end of year 3. Changes in probing depth (PD) from year 1 to 4 served to dichotomize the sites into stable (delta PD < or = 0.9 mm), and unstable (PD increase > or = 1 mm). Of the 54 sites available for this analysis only 5 (9.3%) were unstable while 49 (90.7%) were stable or even further improved. Sites which exhibited minimal or no plaque (plaque index [PI] < or = 1) over the tight maintenance period had a further decrease in mean probing depth (0.43 mm) compared with a slight increase (-0.06 mm) in mean probing depth in sites with PI > or = 2 mm (P = 0.0235). The same phenomenon was observed for changes in relative attachment level (RAL): mean gain in RAL was 0.61 mm compared to 0.25 mm for the 2 groups, respectively (P = 0.07). Actinobacillus actinomycetemcomitans was only isolated from 2 sites at year 3, and none at year 4, compared to 21.45% of the sites at baseline. Porphyromonas gingivalis positive sites showed a continual decline over the years: 14.28% at baseline, 10.71% at year 1, and 5.1% at year 4. On the contrary, Prevotella intermedia (Pi) and Bacteroides forsythus (Bf) infected sites remained at approximately the same rate throughout the 4 years of the study (40% to 50% and 30% to 40% for Pi and Bf, respectively). Of these, Pi-infected sites exhibited less favorable clinical results compared to sites which were not infected with this microorganism. In summary, furcation defects treated with membrane barriers can be maintained in health for at least 4 years; however, good oral hygiene and frequent recall visits as part of a complete anti-infective therapy are essential. Finally, once treated, these teeth are comparable to similar molar teeth with no previous history of furcation pathosis.

Adult↗
PubMed1995

Fibronectin binding domain of P. gingivalis fimbriae.

P. gingivalis fimbriae play an important role in attachment of bacteria to various salivary components as well as to host cells and matrix proteins including fibronectin. In the present study, we investigated the binding domain of P. gingivalis fimbriae to fibronectin using synthetic peptides. A series of 20 mer fimbrillin peptides were used. Binding of fibronectin to purified fimbriae and synthetic peptides was assayed using polyclonal fibronectin antibodies as well as iodinated fibronectin. Purified fimbriae and peptide 126-146 (RMAFTEIKVQMSAAYDNIYTF) showed high levels of binding to fibronectin, while peptide 318-337(HLNVQCTVAEWVLVGQNATW) showed low but statistically significant binding. Our results suggest V-Q-X-X-X-A or V-X-X-X A common domain/domains present in both peptides might be involved in protein-protein interaction between P. gingivalis fimbriae and fibronectin.

Amino Acid Sequence↗
PubMed1995

Purification of major fimbrial proteins of Porphyromonas gingivalis.

Binding of Porphyromonas gingivalis to pellicle-coated teeth is mediated to a large extent by fimbrillin, a major structural subunit of fimbriae. A simple and efficient method for purifying the major fimbrial proteins from various strains of P. gingivalis was developed. The sonic extracts of crude fimbriae were prepared from P. gingivalis strains 2561, A7A1-28, EM-3, and 9-14K-1, which are representatives of different fimbrial groups. The crude fimbriae were precipitated from the extracts with 40% saturated ammonium sulfate. The dialyzed crude fimbriae were dissolved in 8 M guanidine HCl and loaded onto a Sepharose CL-6B column equilibrated with 6 M guanidine HCl. The major fimbrial protein-enriched fractions were obtained and further purified to homogeneity by repetitive gel filtration on the same column. The purity and intactness of the purified fimbrial proteins were ascertained by SDS-polyacrylamide gel electrophoresis followed by silver nitrate staining and immunoblot analysis using rabbit antisera raised against the purified fimbrial proteins. The result demonstrates the usefulness of guanidine HCl as a reliable reagent for purifying various fimbrial proteins of P. gingivalis, which are often associated strongly with other outer membrane proteins and show different physicochemical and antigenic characteristics.

Ammonium Sulfate↗
PubMed1995

Identification of linear antigenic sites on the Porphyromonas gingivalis 43-kDa fimbrillin subunit.

The fimbrillin of Porphyromonas gingivalis is thought to be an important virulence factor that mediates adherence to host surfaces. The linear immunogenic and antigenic structure of P. gingivalis fimbrillin was investigated with synthetic peptides corresponding to the amino acid sequence predicted from the cloned fimbrillin gene for P. gingivalis 2561. A series of continuous and overlapping peptides corresponding to the entire sequence of P. gingivalis fimbrillin was used to immunize Wistar rats. The resulting polyclonal antibodies were used to test the antigenicity of the 43-kDa fimbrillin protein by enzyme-linked immunosorbent assay and Western blot analysis. All the peptides elicited specific antibodies directed to the corresponding peptides but differed in their ability to elicit antisera that cross-reacted with either native or denatured fimbrillin. Antisera to various C-terminal one-third peptides were more reactive to the denatured monomeric form of fimbrillin by Western blot analysis. Antisera to peptide 99-110 was by far the most reactive against the native form of the oligomeric fimbrillin as well as the partially denatured oligomeric form of fimbrillin. The results indicate that amino acid residues 99-110 on the native fimbrillin protein are accessible to antibody binding and that the immunogen 99-110, when conjugated to thyroglobulin, is able to mimic an epitope on the 43-kDa fimbrillin.

Amino Acid Sequence↗
PubMed1995

Assessment of risk for periodontal disease. II. Risk indicators for alveolar bone loss.

This study examined the risk indicators for alveolar bone loss associated with periodontal infection. A cross-section of 1,361 subjects aged 25 to 74 years, from Erie County, NY were evaluated for interproximal alveolar bone loss and potential explanatory variables including age, gender, history of systemic diseases, smoking, and presence of 8 subgingival bacteria. Interproximal alveolar bone loss was measured from the alveolar crest to the CEJ and a mean computed for each subject. The mean bone loss per subject (BL) ranged from 0.4 to 8.8 mm, and this outcome variable was grouped into 4 ordered categories. The degree of association between the explanatory variables and BL was examined utilizing an ordinal stepwise logistic regression model. Factors which were positively associated with more severe bone loss included subgingival colonization with B. forsythus (O.R. 2.52; 95% CI: 1.98 to 3.17) or P. gingivalis (O.R. 1.73; 95% CI: 1.27 to 2.37), race (Native American, Asian, or Pacific Islanders) with an O.R. 2.40 (95% CI: 1.21 to 4.79), and gender with males having higher odds than females. Smokers had greater odds for more severe bone loss compared to non-smokers ranging from 3.25 (95% CI: 2.33 to 4.54) to 7.28 (95% CI: 5.09 to 10.31) for light and heavy smokers, respectively. Individuals at older ages also showed more severe levels of bone loss. History of kidney disease (O.R. 0.55; 95% CI: 0.35 to 0.89) and history of allergies (O.R. 0.76; 95% CI: 0.59 to 0.98) were inversely associated with severity of bone loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Periodontal regeneration in class III furcation defects of beagle dogs using guided tissue regenerative therapy with platelet-derived growth factor.

We developed an effective regenerative therapy, referred to as platelet-derived growth factor-BB (PDGF-BB)-modulated guided tissue regenerative (GTR) therapy (P-GTR), capable of achieving periodontal regeneration of horizontal (Class III) furcation defects in the beagle dog. To determine its efficacy, repair and regeneration of horizontal furcation defects by P-GTR therapy and GTR therapy were compared. Chronically inflamed horizontal furcation defects were created around the second (P2) and fourth mandibular premolars (P4). After demineralization of the root surfaces with citric acid, the surfaces of left P2 and P4 were treated with PDGF-BB (P-GTR therapy) and those of contralateral teeth were treated with vehicle only (GTR therapy). Periodontal membranes were placed and retained 0.5 mm above the cemento-enamel junction for both groups. The mucoperiosteal flap was sutured in a coronal position and plaque control was achieved by daily irrigation with 2% chlorhexidine gluconate. At 5, 8, and 11 weeks, two animals each were sacrificed by perfusion with 2.5% glutaraldehyde through the carotid arteries, and the lesions were sliced mesio-distally, demineralized, dehydrated, and embedded. Periodontal healing and regeneration after GTR and P-GTR therapy were compared by histomorphometric as well as morphological analysis. Morphometric analysis for each time period was performed on the pooled samples of P2 and P4. Five weeks after both therapies, the lesions were filled primarily by tissue-free area, epithelium, inflamed tissue, and a small amount of newly formed fibrous connective tissue. At 8 and 11 weeks after P-GTR therapy, there was a statistically greater amount of bone and periodontal ligament formed in the lesions. The newly formed bone filled 80% of the lesion at 8 weeks and 87% at 11 weeks with P-GTR therapy, compared to 14% of the lesion at 8 weeks and 60% at 11 weeks with GTR therapy. Also, with P-GTR therapy there was less epithelium and tissue-free area, less inflamed tissue, and less connective tissue. Morphological analysis indicated that the defects around P2 revealed faster periodontal repair and regeneration than those around P4. While the lesions around P2 were effectively regenerated by 11 weeks even after GTR therapy, those around P4 failed to regenerate. On the other hand, P-GTR therapy further promoted periodontal repair and regeneration so that at 8 weeks the lesions around P2 and P4 demonstrated complete and nearly complete regeneration, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Alveolar Process↗
PubMed1995

Platelet-derived growth factor-modulated guided tissue regenerative therapy.

The goal of this study was to develop an effective regenerative therapy capable of achieving periodontal regeneration of Class III furcation defects. We attempted to achieve this goal by combining three therapeutic approaches. First, the lesion was protected by an expanded polytetrafluoroethylene barrier membrane that prevents migration of gingival fibroblasts as well as osteogenic cells from the mucoperiosteal flaps. Second, platelet-derived growth factor-BB (PDGF-BB), which has potent chemotactic and mitogenic effects on periodontal ligament fibroblasts (PDL), was used to promote migration of fibroblasts and their proliferation on the root surface. Third, the root surface, demineralized by citric acid conditioning, was chosen as the primary site for PDGF-BB application. The demineralized root surface appeared to have the capability of providing a sustained release of the applied growth factor. This seemed to facilitate rapid repopulation of PDL fibroblasts on the root surface and new PDL formation in the early stages of repair, which contributed to complete periodontal regeneration without root resorption and ankylosis in later stages. Combining these approaches, we developed a therapy referred to as "PDGF-modulated guided tissue regenerative therapy." Unlike guided tissue regenerative therapy alone (without PDGF-BB), this therapy effectively promoted periodontal regeneration of Class III furcation defects in the beagle dog without significant ankylosis or root resorption.

Animals↗
PubMed1995

Immunohistochemical expression of extracellular matrix components of normal and healing periodontal tissues in the beagle dog.

Periodontal regeneration requires formation of periodontal tissues lost due to periodontal disease. To better understand the formation of new periodontal tissues during periodontal repair and regeneration, immunohistochemical expression of extracellular matrix components of normal as well as healing periodontal tissues was evaluated and compared using the avidin-biotin complex immunohistochemical technique. For this purpose, horizontal furcation defects were created around mandibular P2 and P4 of 6 dogs after extraction of P1 and P3. The root surfaces were conditioned with citric acid and expanded polytetrafluoroethylene (ePTFE) membranes were placed and retained 0.5 mm above the cemento-enamel junction. The mucoperiosteal flaps were sutured in a coronal position. Two animals were sacrificed at 2, 4, and 8 weeks, and mesio-distal tissue slices containing normal or healing periodontal tissues were demineralized, dehydrated, and embedded in paraffin. Immunohistochemical localization of type I collagen (CI), fibronectin (FN), secreted protein, acidic and rich in cysteine (SPARC), vitronectin (VN), and bone sialoprotein (BSP) was performed on 6 microns thick sections. Morphological results demonstrated that at 2 weeks after defect creation, lesions were filled primarily with granulation tissue which was gradually replaced by newly-formed fibrous connective tissue, periodontal ligament (PDL), cementum, and bone between 4 and 8 weeks. The results of immunohistochemical study revealed that at 2 weeks the granulation tissue, especially in the intercellular spaces of inflammatory cells, was intensively stained for FN and VN. At 4 and 8 weeks, staining for CI, FN, and VN was found in fibrous connective tissue, the newly-formed PDL, cementum, and osteoid. Further the attachment zone of the PDL collagen fibers to cementum showed intense staining for FN. Immunostaining for SPARC was positive in the new PDL, cementum, and bone, while staining for BSP was restricted to the new cementum and bone. Interestingly, the PDL, especially in areas adjacent to active bone formation, demonstrated intense staining for BSP. However, fibrous connective tissue and PDL proper were unstained for BSP. These results indicate that FN and VN are involved in the early stages of periodontal repair, and periodontal regeneration is achieved through formation of periodontal tissues that are composed of different matrix components specific to different types of periodontal tissues.

Acid Etching, Dental↗
PubMed1995

The origin of fibroblasts and their role in the early stages of horizontal furcation defect healing in the beagle dog.

The origin of fibroblasts, their proliferative activity and roles in the early stages of periodontal repair were investigated in order to better understand the periodontal healing process in furcation defects of the beagle dog after guided tissue regenerative therapy. Newly divided cells were identified by immunolocalization of bromodeoxyuridine (BrdU) injected 1 hour prior to sacrificing the animals. At 1 and 2 weeks after creation of the defects, the lesions were occupied primarily by granulation tissue. Under this condition, periodontal ligaments (PDL) fibroblasts in a coronal portion of the remaining PDL close to wounds proliferated actively, migrated along the root surface and formed fibrous connective tissue on the surface. Similarly, the fibroblasts adjacent to the bone surface also showed proliferative activity and engaged in active formation of fibrous connective tissue on the bone surface. The majority of labeled cells in both areas were located in the extravascular area. At 3 and 4 weeks, the defects were filled with an increased amount of new connective tissue and bone. The labeled fibroblasts were preferentially found in the most coronal portion of connective tissue formed on the root surface that was in direct contact with inflamed tissue, and the collagen fibers projected into granulation tissue. In areas of active bone formation, numerous labeled fibroblasts were located in connective tissue adjacent to the newly-formed bone. However, fibroblasts in the endosteum of new bone were rarely labeled These results indicate that fibroblasts involved in periodontal repair originate primarily from both the remaining PDL and alveolar bone, and actively engage in fibrous connective tissue formation in the early stages of periodontal repair The ability of PDL fibroblasts to proliferate, migrate, and form connective tissue on the root surfaces in the early repair stages appears to play a crucial role in the formation of the PDL and cementum, and consequently, in periodontal regeneration in the absence of root resorption and ankylosis. As the formation of new connective tissue and bone continues, the precursor cells for fibroblasts and osteoblasts are supplied locally through the continued divisions of the fibroblastic cells in association with the newly-formed connective tissue. Paravascular and endosteal cells appear to be minor contributors to new cell population during furcation defect repair in the beagle dog.

Alveolar Process↗
PubMed1995

Gingival recession and exposure of barrier membrane: effect on guided tissue regeneration of Class II furcation defects.

The purpose of the present study was to evaluate the effect of barrier membrane exposure on the success of guided tissue regeneration in Class II furcation defects. Twenty-six subjects with mandibular Class II furcation defects received initial periodontal therapy followed by guided tissue regeneration surgery. The membrane was placed and the flaps were repositioned so that the membrane was totally submerged. Membranes were removed 4 to 6 weeks later, at which time the extent of their exposure was recorded. An overall improvement in all clinical parameters was observed for all subjects 1 year after surgery. Half of the patients had experienced no membrane exposure, while the other 13 subjects had experienced mild to pronounced exposure; both groups showed similar improvement in all clinical and surgical parameters. In light of the comparable results obtained in exposed sites, and the anatomic difficulties sometimes encountered in covering a membrane completely, in some of these cases the membrane may be left only partially submerged. This approach will allow for tighter occlusal "seal" of the tooth-membrane interface and preservation of the keratinized gingiva.

Adult↗
PubMed1994

Effects of temperature stress on expression of fimbriae and superoxide dismutase by Porphyromonas gingivalis.

We examined the biosynthesis of fimbriae and superoxide dismutase (SOD) produced by the periodontopathic bacterium Porphyromonas gingivalis in response to elevated temperature. P. gingivalis 2561, grown at 37 degrees C to mid-logarithmic phase, was subsequently incubated at 39, 41, and 43 degrees C, respectively, to stationary phase. There was no difference in the growth of cells at 37 and 39 degrees C. However, at 39 degrees C there was a 54% reduction in the amount of fimbrillin (fimbriae) as well as decreased expression of mRNA for fimA. On the other hand, under the same conditions, a more than twofold increase in the amount of SOD activity, as well as in the levels of SOD mRNA, was observed. Moreover, cells cultured for 20 h at 39 degrees C showed an 86% decrease of fimbrillin protein and a threefold increase in SOD activity. These observations suggest that P. gingivalis may undergo alterations in its virulence and susceptibility to host immune responses as a result of the elevated temperatures found in inflamed periodontal pockets.

Bacterial Proteins↗
PubMed1994

Structural and functional characterization of the human formyl peptide receptor ligand-binding region.

The formyl peptide (N-formyl-1-methionyl-1-leucyl-1-phenylalanine [FMLP]) receptor is involved in the activation of neutrophils and their subsequent response to chemotactic N-formylated peptides. Recently, we found that the first extracellular loop closest to the N-terminal end of the FMLP receptor exhibited the strongest ligand binding compared with that shown by other extracellular regions. By constructing amino acid substitutional variants of this domain, we have determined that residues Arg-84 and Lys-85 on this loop play major roles in ligand-binding activity. Furthermore, random rearrangement of the residues of this receptor region demonstrated that the position of these charged amino acids did not affect their involvement in ligand binding, although their presence was essential for this binding to occur. We propose that the portion of the first N-terminal extracellular loop of the FMLP receptor containing residues Arg-84 and Lys-85 contributes significantly to the active site in ligand-receptor binding. We further propose that this binding is not dependent on defined structure but rather that these charged moieties may function as important "contacts" in receptor-ligand interactions.

Amino Acid Sequence↗