Initial phase and frequency modulations of pumping a playground swing.

The playground swing is a dynamic, coupled oscillator system consisting of the swing as an object and a human as the swinger. Here, we propose a model for capturing the effect of the initial phase of natural upper body motion on the continuous pumping of a swing and validate this model from the motion data of ten participants pumping swings of three different swing chain lengths. Our model predicts that the swing pumps the most if the phase of maximum lean back, which we call the initial phase, occurs when the swing is at a vertical (midpoint) position and moving forward when the amplitude is small. As the amplitude grows, the optimal initial phase gradually shifts towards an earlier phase of the cycle, the back extreme of the swing's trajectory. As predicted by our model, all participants shifted the initial phase of their upper body movements earlier as swing amplitude increased. This indicated that swingers adjust both the frequency and initial phase of their upper body movements to successfully pump a playground swing.

High Mobility Group Box 1 Expression in Oral Inflammation and Regeneration.

High mobility group box 1 (HMGB1) is a non-histone DNA-binding protein of about 30 kDa. It is released from a variety of cells into the extracellular milieu in response to inflammatory stimuli and acts on specific cell-surface receptors, such as receptors for advanced glycation end-products (RAGE), Toll-like receptor (TLR)2, TLR4, with or without forming a complex with other molecules. HMGB1 mediates various mechanisms such as inflammation, cell migration, proliferation, and differentiation. On the other hand, HMGB1 enhances chemotaxis acting through the C-X-C motif chemokine ligand (CXCL)12/C-X-C chemokine receptor (CXCR)4 axis and is involved in regeneration. In the oral cavity, high levels of HMGB1 have been detected in the gingival tissue from periodontitis and peri-implantitis patients, and it has been shown that secreted HMGB1 induces pro-inflammatory cytokine expression, such as interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF)-α, which prolong inflammation. In contrast, wound healing after tooth extraction or titanium dental implant osseointegration requires an initial acute inflammation, which is regulated by secreted HMGB1. This indicates that secreted HMGB1 regulates angiogenesis and bone remodeling by osteoclast and osteoblast activation and promotes bone healing in oral tissue repair. Therefore, HMGB1 can prolong inflammation in the periodontal tissue and, conversely, can regenerate or repair damaged tissues in the oral cavity. In this review, we highlight the role of HMGB1 in the oral cavity by comparing its function and regulation with its function in other diseases. We also discuss the necessity for further studies in this field to provide more specific scientific evidence for dentistry.

Acute Prevertebral Abscesses Caused by Bacterial-infected Traumatic Tooth Fractures.

We report a case of acute prevertebral abscess caused by traumatic tooth fractures in a 77-year-old Japanese man. After being transferred to our hospital the patient was initially diagnosed with a neck hematoma; however, blood culture showed Streptococcus parasanguinis, an oral bacterium, and an MRI examination suggested prevertebral abscesses. Tooth fractures, severe periodontitis, and peri-implantitis with Streptococcus parasanguinis were observed. Antibiotics were administered and fractured teeth were extracted. The patient's condition then gradually improved. We concluded that bacteremia caused by traumatic tooth fractures induced the acute prevertebral abscesses.

Molecular imaging assessment of periodontitis lesions in an experimental mouse model.

OBJECTIVE: We aimed to evaluate molecular imaging as a novel diagnostic tool for mice periodontitis model induced by ligature and Porphyromonas gingivalis (Pg) inoculation. MATERIALS AND METHODS: Twelve female mice were assigned to the following groups: no treatment as control group (n = 4); periodontitis group induced by ligature and Pg as Pg group (n = 4); and Pg group treated with glycyrrhizinic acid (GA) as Pg + GA group (n = 4). All mice were administered a myeloperoxidase (MPO) activity-specific luminescent probe and observed using a charge-coupled device camera on day 14. Image analysis on all mice was conducted using software to determine the signal intensity of inflammation. Additionally, histological and radiographic evaluation for periodontal inflammation and bone resorption at the site of periodontitis, and quantitative enzyme-linked immunosorbent assay (ELISA) were conducted on three mice for each group. Each experiment was performed three times. RESULTS: Levels of serum IgG antibody against P. gingivalis were significantly higher in the Pg than in the Pg + GA group. Histological analyses indicated that the number of osteoclasts and neutrophils were significantly lower in the Pg + GA than in the Pg group. Micro-CT image analysis indicated no difference in bone resorption between the Pg and Pg + GA groups. The signal intensity of MPO activity was detected on the complete craniofacial image; moreover, strong signal intensity was localized specifically at the periodontitis site in the ex vivo palate, with group-wise differences. CONCLUSIONS: Molecular imaging analysis based on MPO activity showed high sensitivity of detection of periodontal inflammation in mice. CLINICAL RELEVANCE: Molecular imaging analysis based on MPO activity has potential as a diagnostic tool for periodontitis.

Induction of migration of periodontal ligament cells by selective regulation of integrin subunits.

The recruitment of tissue-resident stem cells is important for wound regeneration. Periodontal ligament cells (PDL cells) are heterogeneous cell populations with stemness features that migrate into wound sites to regenerate periodontal fibres and neighbouring hard tissues. Cell migration is regulated by the local microenvironment, coordinated by growth factors and the extracellular matrix (ECM). Integrin-mediated cell adhesion to the ECM provides essential signals for migration. We hypothesized that PDL cell migration could be enhanced by selective expression of integrins. The migration of primary cultured PDL cells was induced by platelet-derived growth factor-BB (PDGF-BB). The effects of blocking specific integrins on migration and ECM adhesion were investigated based on the integrin expression profiles observed during migration. Up-regulation of integrins α3, α5, and fibronectin was identified at distinct localizations in migrating PDL cells. Treatment with anti-integrin α5 antibodies inhibited PDL cell migration. Treatment with anti-integrin α3, α3-blocking peptide, and α3 siRNA significantly enhanced cell migration, comparable to treatment with PDGF-BB. Furthermore, integrin α3 inhibition preferentially enhanced adhesion to fibronectin via integrin α5. These findings indicate that PDL cell migration is reciprocally regulated by integrin α3-mediated inhibition and α5-mediated promotion. Thus, targeting integrin expression is a possible therapeutic strategy for periodontal regeneration.

Anti-HMGB1 Neutralizing Antibody Attenuates Periodontal Inflammation and Bone Resorption in a Murine Periodontitis Model.

High mobility group box 1 (HMGB1) is a non-histone DNA-binding protein that is secreted into the extracellular milieu in response to inflammatory stimuli. The secreted HMGB1 mediates various inflammatory diseases, including periodontitis; however, the underlying mechanisms of HMGB1-induced periodontal inflammation are not completely understood. Here, we examined whether anti-HMGB1 neutralizing antibody inhibits periodontal progression and investigated the molecular pathology of HMGB1 in vitro and in vivo. In vitro analysis indicated that HMGB1, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-1ß (IL-1ß) were secreted in response to tumor necrosis factor-α (TNF-α) stimuli in human gingival epithelial cells (HGECs) and human monocytic leukemia cells (THP-1) treated with phorbol myristate acetate. Increased levels of GM-CSF and IL-1ß were observed in the conditioned media from TNF-α-stimulated HGECs and THP-1 in vitro Simultaneous stimulation with TNF-α and anti-HMGB1 antibody significantly decreased TNF-α-induced inflammatory cytokine secretion. Experimental periodontitis was induced in mice using Porphyromonas gingivalis-soaked ligatures. The extracellular translocation was confirmed in gingival epithelia in the periodontitis model mice by immunofluorescence analysis. Systemic administration of anti-HMGB1 neutralizing antibody significantly inhibited translocation of HMGB1. The anti-HMGB1 antibody inhibited periodontal inflammation, expression of IL-1ß and C-X-C motif chemokine ligand 1 (CXCL1), migration of neutrophils, and bone resorption, shown by bioluminescence imaging of myeloperoxidase activity, quantitative reverse transcription-PCR (RT-PCR), and micro-computed tomography analysis. These findings indicate that HMGB1 is secreted in response to inflammatory stimuli caused by periodontal infection, which is crucial for the initiation of periodontitis, and the anti-HMGB1 antibody attenuates the secretion of a series of inflammatory cytokines, consequently suppressing the progression of periodontitis.

Effect of metabolic syndrome components and their clustering on carotid atherosclerosis in a sample of the general Japanese population.

The objective of this study was to investigate the impact of metabolic syndrome (MS) on carotid atherosclerosis in a Japanese population. A total of 1727 subjects (805 males and 922 females) were included. Intima-media thickness (IMT) was measured using ultrasonography. To evaluate the independent determinants of IMT, a stepwise multiple regression analysis was employed that included age, current smoking habit, LDL-C, HbA1c and the MS components (SBP, DBP, TG, HDL-C, FBG, and WC) as independent variables. Multivariate regression analyses were performed to determine the independent associations of the MS components with IMT. In males, age (ß=0.383, P<0.001), SBP (ß=0.237, P<0.001), LDL-C (ß=0.188, P<0.001), current smoking habit (ß=0.124, P=0.007) and HbA1c (ß=0.110, P=0.014) were significantly associated with IMT. In females, age (ß=0.474, P<0.001), SBP (ß=0.130, P=0.003) and FBG (ß=0.110, P=0.038) were significantly associated with IMT. The present study demonstrated that an elevated number of MS components, with or without central obesity, is associated with higher IMT. Among the analyzed components, hypertension has the strongest association with higher IMT.

Relationship between blood pressure response during step exercise test and atherosclerotic markers.

Abstract The relationship between blood pressure (BP) response to exercise and atherosclerotic markers were evaluated in a population based sample of 426 normotensive subjects. The subjects with greater increase of SBP during exercise and delayed recovery of SBP after exercise showed higher hs-CRP and SBP2. Multiple regression analysis revealed that the greater BP response and delayed BP recovery were independently associated with SBP2 after adjusting for resting SBP, age, and gender. These results suggest that early atherosclerosis may contribute to greater BP responses to exercise, supporting the concept that exercise BP adds incremental information of cardiovascular risks to resting BP.