bluuebunny/crossref_metadata_2025 huggingface dataset:
Exotic plant species invade diversity hot spots: the alien flora of northwestern Kenya
Authors: Stadler J. , Trefflich A. , Klotz S. , Brandl R.
Published: October 2008

We analysed the distribution of native and alien plant species across 20 ecogeographic zones of northwestern Kenya. The source pool for the majority of aliens was Europe and America. Thus, the source pool has a biogeographic bias which explains the low proportion of aliens in the tropics: most species in the European or American source pool are not well adapted to tropical conditions. As expected, native and alien plant species showed an area effect. Correcting for this area effect. species rich zones showed a higher proportion of alien plant species in their flora. At the analysed scale, species richness of native plant communities does not increase the resistance to invasions and alien plant species invade diversity hotspots. Compared to the other ecogeographic zone, the urban area around Nairobi showed an increased richness in alien and native plant species. This is very similar to findings in Europe, although the history of urbanisation is much shorter in Kenya. The species turnover between zones (β‐diversity) shows a similar pattern in native and alien plant species. Within a very short time scale the alien plant species mapped the biogeographic patterns of natives, although the geography of human activities influences the propagule pressure.
Fragments are not islands: patch vs landscape perspectives on songbird presence and abundance in a harvested boreal forest
Authors: Norton Michael R. , Hannon Susan J. , Schmiegelow Fiona K. A.
Published: October 2008

The boreal mixed‐wood forest of northern Alberta. Canada is characterized by a mosaic of deciduous and coniferous forest patches. Recently, the deciduous portion of the forest was allocated for industrial logging. Widespread habitat loss and fragmentation may negatively affect birds and other wildlife. Most research on the effects of habitat loss on bird abundance has focussed on the forest as a patch or island in a matrix of non‐habitat, but some species of songbird may use both the forest patch and the matrix. We hypothesized that some species of songbird might be able to compensate for a loss of deciduous forest by moving into other habitat types (termed “habitat compensation”). We report on a replicated field investigation in which we assessed the response of songbirds to commercial timber harvest by first examining their abundance within deciduous forest only, and then adding the clearcuts and coniferous forest in the surrounding areas to the analysis for a broader, landscape view of the system. Bird communities in deciduous and coniferous habitats had significant overlap in species composition: there was less overlap between forest and clearcuts. The shift from patch‐centred to landscape sampling altered our interpretation of over half of the most common species' responses to logging in at least one year, suggesting that habitat compensation may have been occurring. However, significant variation in responses of species was observed between the two study areas. Our past reliance on island biogeographic and other single habitat approaches may be inappropriate for this system, and we stress that a broad, landscape view is required to properly assess and interpret species' responses to habitat loss and fragmentation.
Aboveground dry‐matter allocation in ungrazed and grazed stands of Indigofera spinosa in the arid zone of Turkana, Kenya
Authors: Oba Gufu , Mengistu Zelalem , Stenseth Nils C.
Published: October 2008

The dwarf shrub Indigofera spinosa, indigenous to arid and semi‐arid rangelands of northeastern Africa, is an important food source for livestock. Proper management of the shrub requires improved understanding of the effects of grazing and climatic variability on aboveground dry‐matter allocation. Between 1986 and 1990, we compared the temporal variability of aboveground dry‐matter allocation to different plant biomass compartments. We also compared dry‐matter transfers between components; total live biomass to litter, standing dead to litter and live biomass to standing dead between continuously grazed and an ungrazed treatments. Partitioning of combined total dry‐matter production among different structural organs (called allocation ratio) is influenced by phenological changes, episodic rainfall and her‐bivory. Dry‐matter production in the grazed treatment responded more markedly to episodic rainfall events more than in the ungrazed treatment. Exclusion of grazers failed to improve the relative growth rate (RGR) of shrub biomass, while grazing improved it. RGR declined in the ungrazed treatment following the accumulation of standing dead dry‐matter, while m the grazed treatment it declined following the shedding of leaves. The shrub allocated more to total live biomass than to standing dead. Greater reduction of total live allocation ratio in the grazed than in the ungrazed treatment occurred during a dry year. The ungrazed treatment had higher standing dead allocation ratio than did the grazed treatment. Plants transferred more dry‐matter from total live biomass compartment to litter, than from standing dead to or from total live biomass to standing dead independent of treatment. The rates of transfer were higher in the ungrazed than in the grazed treatment. The results suggest that I spinosa has evolved to respond to climatic variability and grazmgbyallocating dry allocating dry‐matter differently between various compartments.
Environmental heterogeneity and the spatial structure of fern species diversity in one hectare of old‐growth forest
Authors: Richard Monique , Bernhardt Torsten , Bell Graham
Published: October 2008

The precise relationship between species diversity and spatial heterogeneity has not often been investigated using quantitative and repeatable measures of environmental variation. In this study, we map the metre‐level distribution of fern species in one hectare of old‐growth forest and test for a relationship between diversity and heterogeneity of physical features and soil conditions. The nineteen species recorded in the hectare were non‐randomly distributed and varied greatly in abundance and spatial aggregation. Different. Species distributions were not independent of one another: three groups were formed with species which occurred together significantly more often than random expectation. Physical and soil conditions were highly variable and spatially auto correlated from the 5 m scale up to the extent of the whole hectare. Based on the sites where they grew, species differed in their references for soil moisture, fertility and pH. Fern diversity was highest at sites with high soil moisture and low soil fertility: however, there was no relationship between diversity and the environmental variance within quadrats. Unpredictable spatial distribution patterns produced by processes of dispersal and immigration may obscure any relationship between diversity and spatial heterogeneity at this fine scale.
Geographical separation of two Ulex species at three spatial scales: does competition limit species' ranges?
Authors: Bullock James M. , Edwards Rebecca J. , Carey Peter D. , Rose Rob J.
Published: October 2008

It is a common assumption that species' ranges are limited by their physiological tolerances to climatic factors, Biotic factors, such as competition, are rarely considered. We investigated the distributions of Ulex minor and U. gallii at three spatial scales from geographic ranges to individual heaths ‐ to examine whether the species are negatively associated, as predicted by the hypothesis that the ranges of the species are limited by competition with each other. Distribution maps for the British Isles and France (100 400 km2 survey units) show the two species have largely separated, but slightly overlapping ranges. A region of range overlap on the heaths of Dorset, southern England was mapped using 4 ha survey squares. There was strong negative association between the species, and the heaths could be divided into zones where one species was dominant. There was some indication of edaphic differences between the U. minor‐dominated zones and the U. gallii zones. The few heaths where the species co‐occurred were surveyed using 4 m2 quadrats placed along transects. Usually one species was widespread over the heath, while the other occurred in patches. The species were strongly negatively associated in all transects. Therefore, the two species showed strong negative associations at three mapping scales. Apparent co‐occurrences detected at one spatial scale largely disappeared when species were mapped at finer scales, emphasising the fractal nature of distributions. This provides evidence that the distributions of the two species are not independent and that they cannot coexist, and therefore that their ranges are limited by competition. Over their ranges, competitive superiority is probably determined by the climate. At the range boundaries in the region of overlap, climate is not important, but other physical factors such as edaphic conditions may determine the outcome of competition.
Expression and bioactivities of endothelin‐1 in gingiva during cyclosporine A treatment
Authors: Chin Y‐T. , Tu H‐P. , Chen Y‐T. , Dai N‐T. , Shen E‐C. , Chiang C‐Y. , Fu M. M‐J. , Fu E.
Published: October 2008

Background and Objective: This study aimed to evaluate the expression and bioactivities of endothelin‐1 (ET‐1) in gingiva during cyclosporine A (CsA) treatment.

Material and Methods: After establishing edentulous ridges, experimental rats were fed 30 mg/kg/day CsA while control animals received mineral oil for 4 weeks, after which a reverse transcription‐polymerase chain reaction (RT‐PCR) and/or immunohistochemistry was used to examine the expression of ET‐1, its receptors, proliferating cell nuclear antigen (PCNA) and inducible nitric oxide synthase (iNOS) in gingivae. The roles of the endothelin receptors A and B (ETAand ETB) in CsA‐enhanced expression of PCNA and iNOS were examined in cultured human gingival fibroblasts pretreated with receptor antagonists, by immunocytochemistry and RT‐PCR, respectively.

Results: The mRNA expression of ET‐1, ETAand ETB, as well as of PCNA and iNOS, was significantly greater in edentulous gingiva that received CsA compared with control gingiva. Immunohistochemistry revealed more cells positively stained for ET‐1 and its receptors in the tissues of CsA‐treated rats than in those of control rats. In fibroblast cultures, enhanced mRNA expression of ET‐1, ETAand ETBwas observed after CsA treatment at the concentrations of 10 and 100 ng/mL. Cyclosporine A‐enhanced PCNA expression was somewhat reduced by blockade of ETA, but not ETB, whereas iNOS expression was somewhat reduced by blockade of ETB.

Conclusion: Based on the present findings, we suggest that: (1) CsA upregulates the gingival expression of ET‐1 and its receptors; and (2) ETAand ETBhave different bioactivities, ETAbeing involved in cell proliferation and ETBbeing associated with iNOS expression.
Effects of heparin‐binding epidermal growth factor‐like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro
Authors: Lee J. S. , Kim J. M. , Hong E. K. , Kim S.‐O. , Yoo Y.‐J. , Cha J.‐H.
Published: October 2008

Background and Objective:  A growing amount of attention has been placed on periodontal regeneration and wound healing for periodontal therapy. This study was conducted in an effort to determine the effects of heparin‐binding epidermal growth factor‐like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro.

Material and Methods:  Human periodontal ligament cells were acquired from explant tissue of human healthy periodontal ligament. After the wounding of periodontal ligament cells, the change in expression of heparin‐binding epidermal growth factor‐like growth factor and epidermal growth factor receptors 1–4 mRNA was assessed. The effects of heparin‐binding epidermal growth factor‐like growth factor on periodontal ligament cell proliferation and repopulation were assessed in vitro via the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and by photographing the injuries, respectively. Extracellular signal‐regulated kinase (Erk)1/2, p38 and Akt phosphorylation was characterized via western blotting.

Results:  Scratch wounding resulted in a significant up‐regulation of heparin‐binding epidermal growth factor‐like growth factor mRNA expression, whereas wounding had no effect on the expression levels of epidermal growth factor receptors 1–4. Interestingly, no expression of epidermal growth factor receptors 2 and 4 was detectable prior to or after wounding. Heparin‐binding epidermal growth factor‐like growth factor treatment promoted the proliferation and repopulation of periodontal ligament cells. The scratch wounding also stimulated the phosphorylation of Erk1/2 and p38, but not of Akt, in periodontal ligament cells, and heparin‐binding epidermal growth factor‐like growth factor treatment applied after wounding amplified and extended the activations of Erk1/2 and p38, but not of Akt. Furthermore, Erk1/2 inhibition blocked the process of cell repopulation induced by heparin‐binding epidermal growth factor‐like growth factor, whereas the inhibition of p38 delayed the process.

Conclusion:  These results indicate that heparin‐binding epidermal growth factor‐like growth factor may constitute a critical factor in the wound healing of human periodontal ligament cells by a mechanism that requires the activation of Erk1/2 via specific interaction with epidermal growth factor receptor 1.
Elevation of collagen type I in fibroblast–keratinocyte cocultures emphasizes the decisive role of fibroblasts in the manifestation of the phenotype of cyclosporin A‐induced gingival overgrowth
Authors: Dannewitz B. , Tomakidi P. , Syagailo Y. , Kohl A. , Staehle H. J. , Eickholz P. , Komposch G. , Steinberg T.
Published: October 2008

Background and Objective: Collagen type I elevation in cyclosporin A‐induced gingival overgrowth supports evidence that gingival fibroblasts play a decisive role in the manifestation of the phenotype. To analyze the role of gingival fibroblasts under morein vivo‐like conditions, we evaluated the effect of cyclosporin A on collagen type I gene and protein expression in gingival overgrowth‐derived gingival fibroblasts established as cocultures with gingival keratinocytes as well as in matched gingival fibroblast monolayers.

Material and methods: Monolayers and cocultures of primary gingival fibroblasts were treated with cyclosporin A for 6 and 72 h. The expression of collagen type I mRNA was analyzed by quantitative real time polymerase chain reaction, while expression and secretion of collagen type I protein was analyzed by indirect immunofluorescence and western blotting.

Results: Compared with controls, significant elevation of collagen type I mRNA was restricted to cocultures after 6 and 72 h of treatment with cyclosporin A. In keratinocytes, collagen type I remained undetectable. In monolayers and cocultures, indirect immunofluorescence showed a slightly higher level of collagen type I protein in gingival fibroblasts in response to stimulation with cyclosporin A. Semiquantitative detection of collagen type I by western blotting demonstrated a nonsignificant increase for cell extracts in monolayers and cocultures. For secreted collagen type I, western blot analysis of the supernatants revealed elevated protein levels in cultures stimulated with cyclosporin A. Compared with the corresponding monolayers, the stimulatory effect of cyclosporin A on protein secretion was significant only in coculture.

Conclusion: Our results indicate that collagen type I is a target of cyclosporin A and that gingival fibroblasts are decisive for the manifestation of the gingival overgrowth‐phenotype. Furthermore, the results suggest that cocultures of gingival overgrowth‐derived gingival fibroblasts and gingival keratinocytes permit analysis of cyclosporin A‐induced effects under morein vivo‐like conditions.
E‐selectin and L‐selectin polymorphisms in patients with periodontitis
Authors: Houshmand B. , Rafiei A. , Hajilooi M. , Mani‐Kashani K. , Gholami L.
Published: October 2008

Background amd Objective:  Periodontitis is a multifactorial disease in which environmental and genetic determinant factors contribute to individual subject’s susceptibility. A DNA polymorphism in the regulating region of adhesion molecule genes is suggested to modulate the molecule’s physiological effects. The aim of this study was to investigate the genetic association between the E‐selectin Ser128Arg and L‐selectin Phe206Leu polymorphisms and periodontitis.

Material and Methods:  DNA was isolated from the whole blood of 88 patients with periodontitis and 139 healthy individuals. All samples were genotyped for the E‐selectin Ser128Arg and L‐selectin Phe206Leu polymorphisms using the polymerase chain reaction with sequence specific primers.

Results:  Our findings revealed a significant difference in the Ser128Arg polymorphism of E‐selectin, but not in the L‐selectin polymorphism, between periodontal patients and controls. The 128Arg allele was present more frequently in patients than in healthy individuals (31.25% vs. 12.2%, p < 0.0001). In addition, there was an association between the presence of the 128Arg allele and periodontitis (odds ratio 2.9; 95% confidence interval: 1.75–4.4, p < 0.0001). No significant association was found between the polymorphisms tested and the subgroups of periodontal disease (i.e. chronic periodontitis and aggressive periodontitis).

Conclusion:  The findings of this study showed that the Ser128Arg polymorphism of E‐selectin might contribute to the susceptibility of Iranian individuals to periodontitis.
Nicotinic acetylcholine receptor activation mediates nicotine‐induced enhancement of experimental periodontitis
Authors: Breivik T. , Gundersen Y. , Gjermo P. , Von Hörsten S. , Opstad P. K.
Published: October 2008

Background and Objective:  Smokers have an increased risk of developing periodontitis as well as showing more rapid progression and resistance to treatment of the disease, but the biological mechanisms are poorly understood. Our objective was to investigate putative biological mechanisms by which nicotine may enhance the susceptibility and thus the course of periodontitis in an animal model.

Material and Methods:  Ligature‐induced periodontitis was applied in periodontitis‐susceptible Fischer 344 rats. The animals were given daily intraperiotonal (i.p.) injections of the nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine (1 mg/kg) 45 min before subcutaneous (s.c.) injections in the neck skin with nicotine (0.8 mg/kg), or treated with the same amount of saline i.p. and nicotine s.c., or with mecamylamine and saline. Control rats received i.p. and s.c. injections of saline only. Periodontal bone loss was assessed when the ligatures had been in place for 3 weeks. Two hours before decapitation, all rats received lipopolysaccharide (LPS; 100 μg/kg, i.p.) to induce a robust immune and stress response.

Results:  Compared with saline/saline‐treated control rats, saline/nicotine‐treated rats developed significantly more periodontal bone loss, and LPS provoked a significantly smaller increase in circulating levels of the cytokines tumour necrosis factor α (TNF‐α), transforming growth factor 1β (TGF‐1β) and interleukin‐10 (IL‐10). Mecamylamine pretreatment of nicotine‐treated rats abrogated the increased periodontal bone loss and the LPS‐induced TNF‐α decrease, but had no significant effects on the levels of TGF‐1β and IL‐10, or the stress hormone corticosterone.

Conclusion:  The results indicate that nicotine enhances susceptibility to periodontitis via nAChRs, which may act via suppressing protective immune responses through the cholinergic anti‐inflammatory pathway.
In vivodetermination of multiple indices of periodontal inflammation by optical spectroscopy
Authors: Liu K. Z. , Xiang X. M. , Man A. , Sowa M. G. , Cholakis A. , Ghiabi E. , Singer D. L. , Scott D. A.
Published: October 2008

Background and Objective: Visible, near‐infrared (optical) spectroscopy can be used to measure regional tissue hemodynamics and edema and therefore may represent an ideal tool with which to study periodontal inflammation in a noninvasive manner. The study objective was to evaluate the ability of optical spectroscopy to determine simultaneously multiple inflammatory indices (tissue oxygenation, total tissue hemoglobin, deoxyhemoglobin, oxygenated hemoglobin and tissue edema) in periodontal tissuesin vivo.

Material and Methods: Spectra were obtained, processed and evaluated from healthy, gingivitis and periodontitis sites (n = 133) using a portable optical, near‐infrared spectrometer. A modified Beer–Lambert unmixing model that incorporates a nonparametric scattering loss function was used to determine the relative contribution of each inflammatory component to the overall spectrum.

Results: Optical spectroscopy was harnessed to generate complex inflammatory profiles of periodontal tissues. Tissue oxygenation at periodontitis sites was significantly decreased (p < 0.05) compared to sites with gingivitis and healthy controls. This was largely the result of an increase in deoxyhemoglobin in the periodontitis sites compared with healthy (p < 0.01) and gingivitis (p = 0.05) sites. Tissue water contentper seshowed no significant difference between the sites, but a water index associated with tissue electrolyte levels and temperature differed significantly between periodontitis sites and both healthy and gingivitis sites (p < 0.03).

Conclusion: This study established that optical spectroscopy can simultaneously determine multiple inflammatory indices directly in the periodontal tissuesin vivo. Visible, near‐infrared spectroscopy has the potential to be developed into a simple, reagent‐free, user‐friendly, chairside, site‐specific, diagnostic and prognostic test for periodontitis.
Periodontal disease in patients with familial Mediterranean fever: from inflammation to amyloidosis
Authors: Cengiz M. I. , Bagci H. , Cengiz S. , Yigit S. , Cengiz K.
Published: October 2008

Background and Objective:  Familial Mediterranean fever stimulates a very intense acute‐phase reactants response and if left untreated eventually leads to amyloidosis. The aim of this study was to determine the prevalence of periodontal disease among patients with familial Mediterranean fever in the Black Sea region in Turkey and to evaluate whether periodontitis is related to amyloidosis in patients with familial Mediterranean fever.

Material and Methods:  One‐hundred and thirty three patients with familial Mediterranean fever and 50 healthy subjects were included in this study. Periodontal health and disease were evaluated using the gingival index, papillary bleeding index, plaque index and periodontal disease index. The concentrations of serum acute‐phase reactants were measured at baseline and at 4–6 wk after completion of the nonsurgical periodontal therapy. Genetic testing for familial Mediterranean fever was performed using the familial Mediterranean fever StripAssay. Kidney biopsy was carried out on all proteinuric patients.

Results:  The prevalence of moderate to severe periodontitis in familial Mediterranean fever patients with amyloidosis (80.6%) was significantly greater (p < 0.01) than in familial Mediterranean fever patients without amyloidosis (38%) and in controls (20%). Serum levels of acute‐phase reactants in familial Mediterranean fever patients were reduced significantly following nonsurgical periodontal therapy (p < 0.01).

Conclusion:  Periodontal therapy seems to reduce the serum levels of acute‐phase reactants in patients with familial Mediterranean fever. Therefore, treating periodontitis might help to alleviate the disease burden in patients with familial Mediterranean fever.
Association between lactoferrin gene polymorphisms and aggressive periodontitis among Taiwanese patients
Authors: Wu Y‐M. , Juo S‐H. , Ho Y‐P. , Ho K‐Y. , Yang Y‐H. , Tsai C‐C.
Published: October 2008

Background and Objective:  A dramatic difference in the frequencies of the Lys/Arg single nucleotide polymorphism in the lactoferrin genotype between a small population of patients with localized juvenile periodontitis and healthy subjects has been reported. As the single nucleotide polymorphism could be associated with ethnicity, the present study aimed to investigate the association between polymorphisms of the lactoferrin gene and periodontitis.

Material and Methods:  Sixty‐five patients with aggressive periodontitis, 278 with chronic periodontitis and 88 healthy controls were genotyped for the Lys/Arg polymorphism of the lactoferrin gene at position 29 [reference sequence (rs) 1126478] in the N‐terminal alpha‐helical region.

Results:  The frequencies of the GG genotype and the G allele were highest in the aggressive periodontitis group, followed by the chronic periodontitis group and then the healthy controls. The frequency of the G allele was significantly higher in aggressive periodontitis and chronic periodontitis groups than in healthy controls (p = 0.0037 and 0.0212). Although the difference of the GG genotype distribution between subjects with chronic periodontitis and healthy controls did not reach significance, the distribution of genotypes between aggressive periodontitis and healthy controls was significantly different. The association of the gene polymorphism and aggressive periodontitis still existed, even after adjusting for age, gender and smoking status by logistic regression analysis (GG/AG+AA: odds ratio = 2.16, 95% confidence interval = 1.09–4.35, p = 0.0287). After the study, subjects were further stratified by their smoking status; the GG genotype was still significantly associated with the risk of aggressive periodontitis in the nonsmoking group (odds ratio = 2.69, p = 0.018). However, there were no statistical differences between chronic periodontitis vs. healthy controls and aggressive periodontitis vs. healthy controls in the smoking group.

Conclusion:  The present study revealed that the A/G polymorphism in the lactoferrin gene might be associated with aggressive periodontitis. The A allele might reduce the risk of development of aggressive periodontitis in a Taiwanese population. Our results also support the hypothesis that lactoferrin genetic polymorphisms could play a role in the risk for periodontitis separate from the smoking factor. The functionality of this gene’s polymorphisms has to be further elucidated.
Identifying early osteoclastic resorptive lesions in feline teeth: a model for understanding the origin of multiple idiopathic root resorption
Authors: DeLaurier A. , Boyde A. , Jackson B. , Horton M. A. , Price J. S.
Published: October 2008

Background and Objective: Domestic cats commonly suffer from external osteoclastic tooth resorption, a disease with many similarities to human multiple idiopathic root resorption. In both diseases, it is unclear whether anatomical features of the tooth surface are associated with a predisposition for resorptive lesions. The aim of the present study was to investigate the origin and progression of early feline osteoclastic resorptive lesions in teeth exhibiting no clinical signs of disease.

Material and Methods: The entire surfaces of 138 teeth from 13 adult cats were analysed using back‐scattered electron microscopy. The distribution of lesions was assessed by tooth type, location and between individuals.

Results: Seventy‐three (53%) teeth showed at least one resorptive lesion. Eleven (85%) cats had lesions, and there was a significant association between increasing age and incidence of resorptive lesions. The highest frequency occurred in mandibular molars (82%). On average, there were 3.5 lesions per tooth. Fifty‐two (38%) teeth featured resorptive lesions at the cemento–enamel junction. Twenty‐three per cent of teeth with resorptive lesions showed evidence of repair of lesions that was limited to the root surface. There was no evidence of repair of resorptive lesions at the cemento–enamel junction.

Conclusion: Resorption is prevalent without evidence of clinical disease, and occured at younger ages than previously reported. It can initiate anywhere on the root surface, but lack of repair of lesions at the cemento–enamel junction indicates that mechanisms of replacement are absent or compromised in this region. Whereas resorption of the root may undergo repair, resorption at the cervix may progress to clinically evident lesions.
Matrix metalloproteinase inhibitors reduce collagen gel contraction and α‐smooth muscle actin expression by periodontal ligament cells
Authors: Bildt M. M. , Bloemen M. , Kuijpers‐Jagtman A. M. , Von den Hoff J. W.
Published: October 2008

Background and Objective:  Orthodontic tooth movement requires remodeling of the periodontal tissues. The matrix metalloproteinases (MMPs) degrade the extracellular matrix components of the periodontal ligament, while the tissue inhibitors of metalloproteinases (TIMPs) control their activity. Synthetic MMP inhibitors have been developed to inhibit MMP activity. In this study, periodontal ligament cells in contracting collagen gels served as a model for enhanced periodontal remodeling. The effect of MMP inhibitors on gel contraction and on MMP and TIMP expression was analyzed.

Material and Methods:  Human periodontal ligament cells were cultured in three‐dimensional collagen gels and incubated with the MMP inhibitors BB94, CMT‐3, doxycycline and Ilomastat. Gel contraction was determined using consecutive photographs. The relative amounts of MMPs and TIMPs were analyzed using substrate zymography and mRNA expression using quantitative polyermase chain reaction.

Results:  All MMP inhibitors reduced MMP activity to about 20% of the control activity. They all reduced contraction, but CMT‐3 and doxycycline had the strongest effect. These inhibitors also reduced MMP‐2, MMP‐3 and α‐smooth muscle actin mRNA expression. The expression of MMP‐1 mRNA seemed to be increased by CMT‐3. No effects were found on the amounts of MMPs and TIMPs.

Conclusion:  Synthetic MMP inhibitors strongly reduced gel contraction by periodontal ligament cells. This was primarily caused by an inhibitory effect on MMP activity, which reduces matrix remodeling. In addition, α‐smooth muscle actin expression was reduced by CMT‐3 and doxycycline, which limits the contractile activity of the fibroblasts.
Gingipain enzymes from Porphyromonas gingivalis preferentially bind immobilized extracellular proteins: a mechanism favouring colonization?
Authors: McAlister A. D. , Sroka A. , Fitzpatrick R. E. , Quinsey N. S. , Travis J. , Potempa J. , Pike R. N.
Published: October 2008

Background and Objective:  Porphyromonas gingivalis, an anaerobic bacterium associated with adult periodontal disease, employs a number of pathogenic mechanisms, including protease/adhesin complexes (gingipains), fimbriae and hemagglutinins, to maintain attachment within colonized hosts. Here we examined the binding of gingipains and whole, live P. gingivalis cells to immobilized extracellular matrix proteins in the presence of soluble forms of the same proteins, to investigate whether this may constitute a colonization mechanism in the oral environment.

Material and Methods:  Binding of purified gingipain molecules and whole bacterial cells to immobilized matrix proteins was examined in the presence and absence of soluble competitors using enzyme‐linked immunosorbent assays.

Results:  Purified gingipains or whole, live bacteria preferentially bound immobilized forms of matrix proteins, even in the presence of soluble forms of the same proteins. Fimbriae appeared to be redundant for adhesion to immobilized proteins in the presence of the gingipains, indicating that the protease/adhesins and hemagglutinins may be more important for adhesion under these conditions.

Conclusion:  The data presented here provide evidence for a model of adhesion for P. gingivalis within the fluid environment of the oral cavity, where preferential binding of matrix‐located proteins over soluble forms facilitates colonization of the host.
Experimental periodontitis in mice selected for maximal or minimal inflammatory reactions: increased inflammatory immune responsiveness drives increased alveolar bone loss without enhancing the control of periodontal infection
Authors: Trombone A. P. F. , Ferreira Jr S. B. , Raimundo F. M. , De Moura K. C. R. , Avila‐Campos M. J. , Silva J. S. , Campanelli A. P. , De Franco M. , Garlet G. P.
Published: October 2008

Background and Objective:  Inflammatory immune reactions that occur in response to periodontopathogens are thought to protect the host against infection, but may trigger periodontal destruction. However, the molecular and genetic mechanisms underlying host susceptibility to periodontal infection and to periodontitis development have still not been established in detail.

Material and Methods:  In this study, we examined the mechanisms that modulate the outcome of Aggregatibacter (Actinobacillus) actinomycetemcomitans‐induced periodontal disease in mice mouse strains selected for maximal (AIRmax) or minimal (AIRmin) inflammatory reactions.

Results:  Our results showed that AIRmax mice developed a more severe periodontitis than AIRmin mice in response to A. actinomycetemcomitans infection, and this periodontitis was characterized by increased alveolar bone loss and inflammatory cell migration to periodontal tissues. In addition, enzyme‐linked immunosorbent assays demonstrated that the levels of the cytokines interleukin‐1β, tumor necrosis factor‐α and interleukin‐17 were higher in AIRmax mice, as were the levels of matrix metalloproteinase (MMP)‐2, MMP‐13 and receptor activator of nuclear factor‐κB ligand (RANKL) mRNA levels. However, the more intense inflammatory immune reaction raised by the AIRmax strain, in spite of the higher levels of antimicrobial mediators myeloperoxidase and inducible nitric oxide synthase, did not enhance the protective immunity to A. actinomycetemcomitans infection, because both AIRmax and AIRmin strains presented similar bacterial loads in periodontal tissues. In addition, the AIRmax strain presented a trend towards higher levels of serum C‐reactive protein during the course of disease.

Conclusion:  Our results demonstrate that the intensity of the inflammatory immune reaction is associated with the severity of experimental periodontitis, but not with the control of A. actinomycetemcomitans periodontal infection, suggesting that the occurrence of hyperinflammatory genotypes may not be an evolutionary advantage in the complex host–pathogen interaction observed in periodontal diseases.
Granulocyte chemotactic protein 2 (gcp‐2/cxcl6) complements interleukin‐8 in periodontal disease
Authors: Kebschull M. , Demmer R. , Behle J. H. , Pollreisz A. , Heidemann J. , Belusko P. B. , Celenti R. , Pavlidis P. , Papapanou P. N.
Published: October 2008

Background and Objective:  Mucosal inflammatory responses are orchestrated largely by pro‐inflammatory chemokines. The chemokine granulocyte chemotactic protein 2 (CXCL6) is involved in neutrophil recruitment and migration. Previous studies have shown that granulocyte chemotactic protein 2 is up‐regulated during mucosal inflammation (e.g. in inflammatory bowel disease), similarly to the functionally and structurally related chemokine interleukin‐8. Nevertheless, unlike interleukin‐8, a role of granulocyte chemotactic protein 2 in gingival inflammation has not been yet demonstrated. In this study we aimed to evaluate the expression of the chemokine granulocyte chemotactic protein 2 in clinically healthy vs. diseased gingival tissues and to explore possible correlations with clinical and microbiological markers of periodontitis.

Material and Methods:  Gene expression in 184 ‘diseased’ and 63 ‘healthy’ gingival tissue specimens from 90 patients with periodontitis was analyzed using Affymetrix U133Plus2.0 arrays. The expression of granulocyte chemotactic protein 2 was further confirmed by real‐time reverse transcription–polymerase chain reaction, western blotting and enzyme‐linked immunosorbent assay, while the localization of granulocyte chemotactic protein 2 in gingival tissues was analyzed by immunohistochemistry. Plaque samples from the adjacent periodontal pockets were collected and evaluated for 11 species of periodontal bacteria using checkerboard DNA–DNA hybridizations.

Results:  Among all known chemokines, GCP‐2 expression was the most up‐regulated (3.8‐fold, p < 1.1 × 10−16), in ‘diseased’ vs. ‘healthy’ tissue as compared to a 2.6‐fold increased expression of interleukin‐8 mRNA (p < 1.2 × 10−15). Increased expression of granulocyte chemotactic protein 2 correlated with higher levels of ‘red’ and ‘orange’ complex pathogens and with increased probing depth, but not with attachment loss. Immunohistochemistry showed that granulocyte chemotactic protein 2 was expressed in gingival vascular endothelium.

Conclusion:  The level of expression of granulocyte chemotactic protein 2 correlates with the severity of periodontitis and appears to act as a hitherto unrecognized functional adjunct to interleukin‐8 in diseased gingival tissues.
Surface components of Porphyromonas gingivalis
Authors: Yoshimura F. , Murakami Y. , Nishikawa K. , Hasegawa Y. , Kawaminami S.
Published: October 2008

Background and Objective:  Research on Porphyromonas gingivalis, a periodontopathogen, has provided a tremendous amount of information over the last 20 years, which may exceed in part than that on other closely related members in terms of phylogenetic as well as proteomic criteria, including Bacteroides fragilis and B. thetaiotaomicron as major anaerobic, opportunistic pathogens in the medical field. In this minireview, we focused on recent research findings concerning surface components such as outer membrane proteins and fimbriae, of P. gingivalis.

Material and Methods:  Elucidation of the surface components in P. gingivalis was especially difficult because outer membrane proteins are tightly bound to lipopolysaccharide and they are resistant to dissociation and separation from each other, even during sodium dodecyl sulfate–polyacrylamide gel electrophoresis, unless samples are appropriately heated. In addition, P. gingivalis is asaccharolytic and therefore a potent proteolytic bacterium, another factor causing difficulty in research. The study of the surface components was carefully carried out considering these unique features in P. gingivalis when compared with other gram‐negative bacteria, including Escherichia coli and Pseudomonas aeruginosa.

Results:  Separation of outer membrane proteins, and characterization of OmpA‐like proteins and RagAB as major proteins, is described herein. Our recent findings on FimA and Mfa1 fimbriae, two unique appendages in this organism, and on their regulation of expression are also described briefly.

Conclusion:  Surface components of P. gingivalis somehow have contact with host tissues and cells because of the outermost cell elements. Therefore, such bacterial components are potentially important in the occurrence of periodontal diseases.
Relationship between the gingival sulcus depth and interleukin‐1 isoform concentrations within the adjacent gingival tissue
Authors: Lester S. R. , Bain J. L. , Serio F. G. , Johnson R. B.
Published: October 2008

Background and Objective:  While there is substantial information concerning the concentrations of interleukin‐1 isoforms within gingival crevicular fluid, there is little information concerning their concentrations within either normal or diseased gingival tissues. Therefore, the aim of this study was to evaluate the relationship between the concentrations of gingival interleukin‐1 isoforms and the adjacent sulcular depth.

Material and Methods:  Interdental gingival papillae were excised and grouped based on adjacent pocket depth and the presence of bleeding on probing. Gingiva adjacent to a sulcus of ≤ 3 mm without bleeding on probing were classified as ‘normal’; gingiva adjacent to a 3‐mm sulcus with bleeding on probing were classified as ‘diseased‐slight’; gingiva adjacent to a 4–6‐mm sulcus featuring bleeding on probing were classified as ‘diseased‐moderate’; and gingiva adjacent to a sulcus of > 6 mm featuring bleeding on probing were classified as ‘diseased‐severe’. Tissues were solublized and the concentrations of interleukin‐1β, interleukin‐1α, interleukin‐1 receptor antagonist and interleukin‐6 were assessed by enzyme‐linked immunosorbent assay. Data were compared by factorial analysis of variance, the post‐hoc Tukey test and the Pearson’s correlation test.

Results:  Gingival concentrations of interleukin‐6, interleukin‐1 receptor antagonist, interleukin‐1α‐ and interleukin‐1β were significantly greater at diseased‐severe sites than at normal, diseased‐slight, or diseased‐moderate sites (p < 0.05); the gingival concentrations of interleukin‐1 receptor antagonist and interleukin‐1α were significantly greater at diseased‐severe than at diseased‐moderate sites (p < 0.05). Interleukin‐1 receptor antagonist concentrations were significantly correlated with both interleukin‐1α and interleukin‐1β concentrations. The ratios of concentrations of the interleukin‐1 isoforms were different at the various stages of inflammation.

Conclusion:  Our data indicated a progressive increase in gingival concentrations of interleukin‐1 isoforms with increased adjacent sulcular depth. However, within ‘diseased’ tissues, the proportional concentrations of interleukin‐1α and ‐β to interleukin‐1 receptor antagonist were lowest within diseased‐severe tissues.
Gingival crevicular fluid and plasma levels of neuropeptide Substance‐P in periodontal health, disease and after nonsurgical therapy
Authors: Pradeep A. R. , Raj S. , Aruna G. , Chowdhry S.
Published: October 2008

Background and Objective:  The level of Substance‐P in gingival crevicular fluid has been found to correlate with clinical measures of periodontal disease. The present study was designed to assess the relationship between clinical parameters and levels of Substance‐P in the gingival crevicular fluid from inflamed gingiva, periodontitis sites and after treatment of periodontitis sites, and to correlate them to the Substance‐P levels of plasma.

Material and Methods:  Thirty, age‐ and gender‐matched subjects were divided into three groups (healthy, gingivitis and chronic periodontitis) based on modified gingival index scores and clinical attachment loss. A fourth group consisted of 10 subjects from the periodontitis group, 6–8 wk after initial therapy. Plasma and gingival crevicular fluid samples were collected and quantified for Substance‐P using an enzyme immunoassay.

Results:  The mean concentration of Substance‐P, both in gingival crevicular fluid and plasma, was observed to be highest in the periodontitis group (45.13 pg/mL in gingival crevicular fluid and 67.8 pg/mL in plasma) and lowest in the healthy group (6.07 pg/mL in gingival crevicular fluid and below the detection level in plasma). The mean Substance‐P concentration in the gingivitis group (11.42 pg/mL in gingival crevicular fluid and 38.8 pg/mL in plasma) and in the after‐treatment group (7.58 pg/mL in gingival crevicular fluid and 39.7 pg/mL in plasma) lay between the highest and lowest values. In all groups the gingival crevicular fluid levels showed a statistically significant positive correlation with that of plasma and clinical attachment loss.

Conclusion:  Substance‐P levels were highest in the gingival crevicular fluid from sites with periodontal destruction; however, periodontal treatment resulted in the reduction of Substance‐P levels. Gingival crevicular fluid and plasma Substance‐P levels showed a positive correlation in all of the groups.
Porphyromonas gingivalis fimbriae induce unique dendritic cell subsets via Toll‐like receptor 2
Authors: Kanaya S. , Nemoto E. , Ogawa T. , Shimauchi H.
Published: October 2008

Backgound and Objective:  Dendritic cells (DCs) play a critical role in the activation of T cells as well as in shaping immune responses. We have reported previously that Porphyromonas gingivalis lipopolysaccharides (Pg LPS) induced a CD14+CD16+ DC subset with a weak immuno‐stimulatory activity. In contrast, Escherichia coli LPS (Ec LPS) induced fully matured DCs with strong immunostimulatory activities. Since Pg LPS as well as Pg fimbriae have been indicated to work as Toll‐like receptor (TLR) 2 ligands, we speculate that the TLR usage of bacterial antigens may be critical for DC maturation.

Material and Methods:  We investigated the effect of Pg fimbriae on the phenotype and function of human peripheral blood DCs in comparison with a TLR2 ligand, peptidoglycan, and a TLR4 ligand, Ec LPS.

Results:  Flow cytometry revealed that Pg fimbriae and peptidoglycan but not Ec LPS induced CD14 and CD16 expression on peripheral blood DCs (CD14−CD16−). A monoclonal antibody against TLR2 abrogated this induction, but an antibody against TLR4 had no effect. Dendritic cells stimulated with Pg fimbriae had a weaker capability to induce allogenic T cell proliferation and exhibited a weaker production of interleukin‐8 and regulated upon activation, normal T cell expressed and secreted (RANTES) than DCs stimulated with Ec LPS.

Conclusion:  These results indicate that different TLR usage affects mature DC phenotype and function and is thus crucial to the regulation of immunity to the pathogen.
Gender differences in systemic inflammation and atheroma formation following Porphyromonas gingivalis infection in heterozygous apolipoprotein E‐deficient mice
Authors: Champagne C. , Yoshinari N. , Oetjen J. A. , Riché E. L. , Beck J. D. , Offenbacher S.
Published: October 2008

Background and Objective:  Men are at higher risk for periodontal and cardiovascular diseases compared with women, although they have lower serum levels of risk markers, including lipids and acute phase proteins. In this study, we investigated whether infection with a major periodontal pathogen, Porphyromonas gingivalis, affected the inflammatory and atherosclerotic response of male and female mice differently.

Material and Methods:  Forty‐eight heterozygous apolipoprotein E‐deficient mice (24 males and 24 females), maintained on normal diet, were infected twice by intrasubcutaneous chamber injections of P. gingivalis or vehicle at weeks 11 and 14 of age. Serum samples were collected before the first infection and bi‐weekly thereafter, to quantify levels of high‐density lipoprotein (HDL) cholesterol and the murine acute phase protein, serum amyloid A (SAA). Mice were killed at week 17 to evaluate aortic atheroma lesion score.

Results:  Males had significantly higher baseline HDL cholesterol levels (p < 0.01, factorial ANOVA). Following P. gingivalis infection, HDL cholesterol levels decreased over time in infected males only [p < 0.05, generalized estimating equation (GEE)], whereas SAA levels increased and remained elevated over time in both male and female infected mice (p < 0.01, GEE). Lesion scores were significantly higher in infected mice (3‐fold, p < 0.01, factorial ANOVA), and lesion scores of all mice were positively correlated with SAA levels at the time of killing (Spearman correlation coefficient = 0.40, p < 0.01).

Conclusion:  In these young mice, P. gingivalis infection induced sex‐specific changes in serum lipids but no gender differences in acute phase proteins and atheroma lesion score.