Efficacy of Er:YAG laser for the peri-implantitis treatment and microbiological changes: a randomized controlled trial.

The aims of this study were to identify the microbiological changes in the periodontal pockets following an Er:YAG laser (ERL) irradiation and mechanical debridement to compare the effectiveness of ERL irradiation to mechanical debridement for peri-implantitis treatment through randomized controlled trials. Twenty-three patients with peri-implantitis lesions were treated in either a test group, ERL set at energy level of 100 mJ/pulse, frequency of 10 Hz, pulse duration was 100 µs, and irradiated by three passages, or a control group, with mechanical debridement using an ultrasonic scaler. An examiner measured the following clinical parameters at different stages (a baseline and at 3- and 6-month post-treatment): probing depth (PD), bleeding on probing (BOP), marginal bone loss (MBL), and anaerobic bacteria counts. Linear regression, with generalized estimation equations, was used to compare the clinical parameters and anaerobic bacterial counts at different stages and between groups. The anaerobic bacterial counts significantly decreased within the control group during the follow-ups. At the 6-month follow-up, both groups showed a significant reduction in PD (test group: mean difference of 0.84 mm; control group: mean difference of 0.41 mm), and the test group showed a significantly higher PD reduction on the buccal site (1.31 mm) compared to that of the control group (0.25 mm). Both ERL and mechanical debridement treatments led to significant improvements in PD. When mechanical debridement therapy was used, significant anaerobic bacterial count reductions were observed. Future treatment of peri-implantitis should involve a combination of both of these therapies.

Sub-3 Å Cryo-EM Structures of Necrosis Virus Particles via the Use of Multipurpose TEM with Electron Counting Camera.

During this global pandemic, cryo-EM has made a great impact on the structure determination of COVID-19 proteins. However, nearly all high-resolution results are based on data acquired on state-of-the-art microscopes where their availability is restricted to a number of centers across the globe with the studies on infectious viruses being further regulated or forbidden. One potential remedy is to employ multipurpose microscopes. Here, we investigated the capability of 200 kV multipurpose microscopes equipped with a direct electron camera in determining the structures of infectious particles. We used 30 nm particles of the grouper nerve necrosis virus as a test sample and obtained the cryo-EM structure with a resolution as high as ∼2.7 Šfrom a setting that used electron counting. For comparison, we tested a high-end cryo-EM (Talos Arctica) using a similar virus (Macrobrachium rosenbergii nodavirus) to obtain virtually the same resolution. Those results revealed that the resolution is ultimately limited by the depth of field. Our work updates the density maps of these viruses at the sub-3Šlevel to allow for building accurate atomic models from de novo to provide structural insights into the assembly of the capsids. Importantly, this study demonstrated that multipurpose TEMs are capable of the high-resolution cryo-EM structure determination of infectious particles and is thus germane to the research on pandemics.

Roles of TREM2 in degeneration of human nucleus pulposus cells via NF-κB p65.

Nuclear factor (NF)-κB p65 plays a key role in the development of intervertebral disc degeneration (IDD). Herein, we found that messenger RNA levels of human triggering receptor expressed on myeloid cells-2 (TREM2) and NF-κB p65 were upregulated and strongly positive correlated (r2 = 0.299, P = 0.0126) in nucleus pulposus (NP) tissues of patients with IDD. To investigate the role of TREM2 in the development of IDD and whether NF-κB p65 was the underlying mechanism, whereby TREM2 played its role, we established TREM2-siRNA-transfected human degenerative NP cells and TREM2-overexpression vector-transfected human normal NP cells. Degeneration of human NP cells was assessed by measuring cell apoptosis, cell proliferation, and the secretion of tumor necrosis factor-α, interleukin (IL)-1ß, and IL-6. Protein levels of Bcl2, Bax, total NF-κB p65 in whole cell lysates, cytoplasm NF-κB p65, and nuclear NF-κB p65 were determined to evaluate underlying mechanisms. Our data elucidated that TREM2 silencing was a therapy for human degenerative NP cells through inhibiting cell apoptosis, promoting cell proliferation, suppressing production of tumor necrosis factor-α, IL 1ß, and IL-6, and the mechanisms included decreasing Bax while enhancing Bcl2, downregulating total NF-κB p65, and retarding NF-κB p65 nuclear translocation. On the contrary, upregulated TREM2 showed the opposite effects, accelerating the degeneration of human normal NP cells. Downregulating TREM2 and total NF-κB p65 and inhibiting NF-κB p65 nucleus translocation were also confirmed in NP tissue samples of four IDD rats. We concluded that TREM2 functioned as a promoter in the degeneration of human NP cells. Downregulating TREM2 may be a novel therapeutic strategy for human IDD.

Regulation of mammalian transcription by Gdown1 through a novel steric crosstalk revealed by cryo-EM.

In mammals, a distinct RNA polymerase II form, RNAPII(G) contains a novel subunit Gdown1 (encoded by POLR2M), which represses gene activation, only to be reversed by the multisubunit Mediator co-activator. Here, we employed single-particle cryo-electron microscopy (cryo-EM) to disclose the architectures of RNAPII(G), RNAPII and RNAPII in complex with the transcription initiation factor TFIIF, all to ~19 Å. Difference analysis mapped Gdown1 mostly to the RNAPII Rpb5 shelf-Rpb1 jaw, supported by antibody labelling experiments. These structural features correlate with the moderate increase in the efficiency of RNA chain elongation by RNAP II(G). In addition, our updated RNAPII-TFIIF map showed that TFIIF tethers multiple regions surrounding the DNA-binding cleft, in agreement with cross-linking and biochemical mapping. Gdown1's binding sites overlap extensively with those of TFIIF, with Gdown1 sterically excluding TFIIF from RNAPII, herein demonstrated by competition assays using size exclusion chromatography. In summary, our work establishes a structural basis for Gdown1 impeding initiation at promoters, by obstruction of TFIIF, accounting for an additional dependent role of Mediator in activated transcription.

Impact of removable dentures on oral health-related quality of life among elderly adults in Taiwan.

BACKGROUND: Although the use of removable dentures can improve oral function and esthetics for elderly people, compared to those who do not wear removable dentures, those wearing removable dentures could have worse oral health related-quality of life (OHRQoL). Additional information is required to assess which factors related to denture wearing influence the OHRQoL of elderly individuals. The purpose of this study is to evaluate the association between denture wearing and OHRQoL in a sample of elderly individuals in Taiwan. METHODS: The study population included 277 elderly people wearing removable dentures (mean age = 76.0 years). Using face-to-face interviews, we collected data on the participants' socio-demographic characteristics, dental care service usage (regular dental checkups, treatment during toothache, dental visits in the last year), and factors related to denture wearing (perceived oral pain, perceived loose denture, perceived oral ulcer, perceived halitosis, perceived dry mouth, and perceived total denture satisfaction scores). OHRQoL was measured using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The location and number of remaining natural teeth and the type of denture were also recorded. Hierarchical multiple regression analysis was performed using GOHAI-T scores as the dependent variable. RESULTS: All the predictors together accounted for 50% of the variance in GOHAI-T scores. Further, education level, number of natural teeth, denture status, perceived loose denture, perceived oral ulcer, and perceived total denture satisfaction scores had statistically significant influences on OHRQoL. When compared with other variables, factors related to denture wearing, especially perceived total denture satisfaction scores, had the greatest impact on GOHAI-T scores. CONCLUSIONS: Of the factors analyzed in this study, denture satisfaction was the strongest predictor of OHRQoL. This suggests that denture satisfaction is useful for assessing the effect of denture treatment on the OHRQoL of elderly individuals wearing removable dentures.

Masticatory factors as predictors of oral health-related quality of life among elderly people in Kaohsiung City, Taiwan.

OBJECTIVE: This study aimed to evaluate which masticatory factor is the best predictor of oral health-related quality of life (OHRQoL) in elderly Taiwanese individuals aged 65 years and older. METHODS: Subjects were 332 community-dwelling, independently living elderly adults (mean age, 76.0 ± 0.4 years) in Kaohsiung City, Taiwan. Information concerning age, gender, and socioeconomic status was collected via face-to-face interview questionnaires; the number of food groups rated 'easy to chew' was determined by using food intake questionnaires; and OHRQoL data were obtained by using the Taiwanese version of the Geriatric Oral Health Assessment Index (GOHAI-T). The number of natural teeth, functional tooth units, and posterior occlusal contacts according to Eichner Index was assessed by dental examination. Multiple regression analysis was conducted to determine the best masticatory factor that could serve as a predictor of GOHAI scores. RESULTS: The number of food groups rated 'easy to chew' was found to be the only masticatory factor affecting GOHAI-T scores, after adjustment for age, gender, socioeconomic status, and other masticatory variables. As compared to subjects who listed less food groups as 'easy to chew,' subjects who rated more food groups as 'easy to chew' were less likely to have low GOHAI-T scores. CONCLUSIONS: Of the masticatory predictors analyzed in this study, perceived masticatory ability, as measured using a food intake questionnaire, could be the best masticatory predictor of OHRQoL in the elderly.

Use of phase plate cryo-EM reveals conformation diversity of therapeutic IgG with 50 kDa Fab fragment resolved below 6 Å.

While cryogenic electron microscopy (cryo-EM) is fruitfully used for harvesting high-resolution structures of sizable macromolecules, its application to small or flexible proteins composed of small domains like immunoglobulin (IgG) remain challenging. Here, we applied single particle cryo-EM to Rituximab, a therapeutic IgG mediating anti-tumor toxicity, to explore its solution conformations. We found Rituximab molecules exhibited aggregates in cryo-EM specimens contrary to its solution behavior, and utilized a non-ionic detergent to successfully disperse them as isolated particles amenable to single particle analysis. As the detergent adversely reduced the protein-to-solvent contrast, we employed phase plate contrast to mitigate the impaired protein visibility. Assisted by phase plate imaging, we obtained a canonical three-arm IgG structure with other structures displaying variable arm densities co-existing in solution, affirming high flexibility of arm-connecting linkers. Furthermore, we showed phase plate imaging enables reliable structure determination of Fab to sub-nanometer resolution from ab initio, yielding a characteristic two-lobe structure that could be unambiguously docked with crystal structure. Our findings revealed conformation diversity of IgG and demonstrated phase plate was viable for cryo-EM analysis of small proteins without symmetry. This work helps extend cryo-EM boundaries, providing a valuable imaging and structural analysis framework for macromolecules with similar challenging features.

Hybrid electron microscopy-FRET imaging localizes the dynamical C-terminus of Tfg2 in RNA polymerase II-TFIIF with nanometer precision.

TFIIF-a general transcription factor comprising two conserved subunits can associate with RNA polymerase II (RNAPII) tightly to regulate the synthesis of messenger RNA in eukaryotes. Herein, a hybrid method that combines electron microscopy (EM) and Förster resonance energy transfer (FRET) is described and used to localize the C-terminus of the second TFIIF subunit (Tfg2) in the architecture of RNAPII-TFIIF. In the first stage, a poly-histidine tag appended to the Tfg2 C-terminus was labeled with nickel-NTA nanogold and a seven-step single particle EM protocol was devised to obtain the region accessible by the nanogold in 3D, suggesting the Tfg2 C-terminus is proximal to the clamp of RNAPII. Next, the C-termini of the Rpb2 and the Rpb4 subunits of RNAPII, adjacent to the clamp, were selected for placing FRET satellites to enable the nano-positioning (NP) analysis, by which the localization precision was improved such that the Tfg2 C-terminus was found to dwell on the clamp ridge but could move to the clamp top during transcription. Because the tag receptive to the EM or FRET probes can be readily introduced to any protein subunit, this hybrid approach is generally applicable to complement cryo-EM study of many protein complexes to nanometer precision.

Impact of oral health behaviours and oral habits on the number of remaining teeth in older Taiwanese dentate adults.

PURPOSE: To evaluate the impact of oral health behaviours and oral habits on the number of remaining teeth in older Taiwanese dentate adults. SUBJECTS AND METHODS: Subjects comprised dentate patients (mean age, 60.0 ± 9.9 years) in Taiwan. Information on demographic data, oral health behaviours, oral habits and self-perceived health status was collected via self-administered questionnaires and dentition status was assessed by oral examination. Multiple logistic regression analyses were used to determine variables correlated with the low dentition group (subjects with less than 20 natural teeth or 8 functional tooth units). RESULTS: The analysis showed that the low dentition group was more likely to be older and to exhibit low educational levels, less frequent use of dental floss, more common smoking habits, poor self-perceived dental health and to be exbetel- nut chewers. In addition, the low dentition group was less likely to be current betel-nut chewers. CONCLUSIONS: These results underscore the importance of the use of dental floss and confirm the adverse effects of smoking on dental health. Hence, the dental profession should continue to encourage proper oral health behaviours and oral habits.

Structural convergence endows nuclear transport receptor Kap114p with a transcriptional repressor function toward TATA-binding protein.

The transcription factor TATA-box binding protein (TBP) modulates gene expression in nuclei. This process requires the involvement of nuclear transport receptors, collectively termed karyopherin-ß (Kap-ß) in yeast, and various regulatory factors. In previous studies we showed that Kap114p, a Kap-ß that mediates nuclear import of yeast TBP (yTBP), modulates yTBP-dependent transcription. However, how Kap114p associates with yTBP to exert its multifaceted functions has remained elusive. Here, we employ single-particle cryo-electron microscopy to determine the structure of Kap114p in complex with the core domain of yTBP (yTBPC). Remarkably, Kap114p wraps around the yTBPC N-terminal lobe, revealing a structure resembling transcriptional regulators in complex with TBP, suggesting convergent evolution of the two protein groups for a common function. We further demonstrate that Kap114p sequesters yTBP away from promoters, preventing a collapse of yTBP dynamics required for yeast responses to environmental stress. Hence, we demonstrate that nuclear transport receptors represent critical elements of the transcriptional regulatory network.

Structural basis for a conserved neutralization epitope on the receptor-binding domain of SARS-CoV-2.

Antibody-mediated immunity plays a crucial role in protection against SARS-CoV-2 infection. We isolated a panel of neutralizing anti-receptor-binding domain (RBD) antibodies elicited upon natural infection and vaccination and showed that they recognize an immunogenic patch on the internal surface of the core RBD, which faces inwards and is hidden in the "down" state. These antibodies broadly neutralize wild type (Wuhan-Hu-1) SARS-CoV-2, Beta and Delta variants and some are effective against other sarbecoviruses. We observed a continuum of partially overlapping antibody epitopes from lower to upper part of the inner face of the RBD and some antibodies extend towards the receptor-binding motif. The majority of antibodies are substantially compromised by three mutational hotspots (S371L/F, S373P and S375F) in the lower part of the Omicron BA.1, BA.2 and BA.4/5 RBD. By contrast, antibody IY-2A induces a partial unfolding of this variable region and interacts with a conserved conformational epitope to tolerate all antigenic variations and neutralize diverse sarbecoviruses as well. This finding establishes that antibody recognition is not limited to the normal surface structures on the RBD. In conclusion, the delineation of functionally and structurally conserved RBD epitopes highlights potential vaccine and therapeutic candidates for COVID-19.

In situ structure and dynamics of an alphacoronavirus spike protein by cryo-ET and cryo-EM.

Porcine epidemic diarrhea (PED) is a highly contagious swine disease caused by porcine epidemic diarrhea virus (PEDV). PED causes enteric disorders with an exceptionally high fatality in neonates, bringing substantial economic losses in the pork industry. The trimeric spike (S) glycoprotein of PEDV is responsible for virus-host recognition, membrane fusion, and is the main target for vaccine development and antigenic analysis. The atomic structures of the recombinant PEDV S proteins of two different strains have been reported, but they reveal distinct N-terminal domain 0 (D0) architectures that may correspond to different functional states. The existence of the D0 is a unique feature of alphacoronavirus. Here we combined cryo-electron tomography (cryo-ET) and cryo-electron microscopy (cryo-EM) to demonstrate in situ the asynchronous S protein D0 motions on intact viral particles of a highly virulent PEDV Pintung 52 strain. We further determined the cryo-EM structure of the recombinant S protein derived from a porcine cell line, which revealed additional domain motions likely associated with receptor binding. By integrating mass spectrometry and cryo-EM, we delineated the complex compositions and spatial distribution of the PEDV S protein N-glycans, and demonstrated the functional role of a key N-glycan in modulating the D0 conformation.

Vaccination with SARS-CoV-2 spike protein lacking glycan shields elicits enhanced protective responses in animal models.

A major challenge to end the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is to develop a broadly protective vaccine that elicits long-term immunity. As the key immunogen, the viral surface spike (S) protein is frequently mutated, and conserved epitopes are shielded by glycans. Here, we revealed that S protein glycosylation has site-differential effects on viral infectivity. We found that S protein generated by lung epithelial cells has glycoforms associated with increased infectivity. Compared to the fully glycosylated S protein, immunization of S protein with N-glycans trimmed to the mono-GlcNAc-decorated state (SMG) elicited stronger immune responses and better protection for human angiotensin-converting enzyme 2 (hACE2) transgenic mice against variants of concern (VOCs). In addition, a broadly neutralizing monoclonal antibody was identified from SMG-immunized mice that could neutralize wild-type SARS-CoV-2 and VOCs with subpicomolar potency. Together, these results demonstrate that removal of glycan shields to better expose the conserved sequences has the potential to be an effective and simple approach for developing a broadly protective SARS-CoV-2 vaccine.

MMP-8 -799 C>T genetic polymorphism is associated with the susceptibility to chronic and aggressive periodontitis in Taiwanese.

AIM: Matrix metalloproteinase (MMP)-8 is a protease that degrades numerous extracellular molecules and has been implicated in the pathogenesis of periodontitis. Polymorphism in the MMP-8 could affect the susceptibility to disease. Our aim was to evaluate the association between periodontitis and MMP-8 -799 C>T polymorphism. MATERIAL AND METHODS: Genomic DNA was obtained from 361 chronic periodontitis patients (CP), 96 aggressive periodontitis patients (AgP), and 106 periodontally healthy controls (HC). MMP-8 -799 C>T polymorphism was determined using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: The frequencies of genotypes in diseased groups were similar but were significantly different from those in the HC. Multivariate logistic regression analysis with adjustment for age, gender and smoking indicated that increased risks of AgP and CP were associated with the -799 T allele (in AgP, adjusted OR = 1.99, p = 0.04; in CP, adjusted OR = 1.87, p = 0.007). To avoid the confounded effect of smoking on MMP-8 polymorphism to periodontitis, the analysis was conducted on non-smokers and the associations were significant. CONCLUSIONS: These results suggested that non-smoking Taiwanese with the MMP-8 -799 T allele were associated with the risks of both CP and AgP. Further studies in other ethnic populations are necessary.

Identification of fidelity-governing factors in human recombinases DMC1 and RAD51 from cryo-EM structures.

Both high-fidelity and mismatch-tolerant recombination, catalyzed by RAD51 and DMC1 recombinases, respectively, are indispensable for genomic integrity. Here, we use cryo-EM, MD simulation and functional analysis to elucidate the structural basis for the mismatch tolerance of DMC1. Structural analysis of DMC1 presynaptic and postsynaptic complexes suggested that the lineage-specific Loop 1 Gln244 (Met243 in RAD51) may help stabilize DNA backbone, whereas Loop 2 Pro274 and Gly275 (Val273/Asp274 in RAD51) may provide an open "triplet gate" for mismatch tolerance. In support, DMC1-Q244M displayed marked increase in DNA dynamics, leading to unobservable DNA map. MD simulation showed highly dispersive mismatched DNA ensemble in RAD51 but well-converged DNA in DMC1 and RAD51-V273P/D274G. Replacing Loop 1 or Loop 2 residues in DMC1 with RAD51 counterparts enhanced DMC1 fidelity, while reciprocal mutations in RAD51 attenuated its fidelity. Our results show that three Loop 1/Loop 2 residues jointly enact contrasting fidelities of DNA recombinases.

Roles of cysteines Cys115 and Cys201 in the assembly and thermostability of grouper betanodavirus particles.

The virus-like particle (VLP) assembled from capsid subunits of the dragon grouper nervous necrosis virus (DGNNV) is very similar to its native T = 3 virion. In order to investigate the effects of four cysteine residues in the capsid polypeptide on the assembly/dissociation pathways of DGNNV virions, we recombinantly cloned mutant VLPs by mutating each cysteine to destroy the specific disulfide linkage as compared with thiol reduction to destroy all S-S bonds. The mutant VLPs of C187A and C331A mutations were similar to wild-type VLPs (WT-VLPs); hence, the effects of Cys187 and Cys331 on the particle formation and thermostability were presumably negligible. Electron microscopy showed that either C115A or C201A mutation disrupted de novo VLP formation significantly. As shown in micrographs and thermal decay curves, beta-mercaptoethanol-treated WT-VLPs remained intact, merely resulting in lower tolerance to thermal disruption than native WT-VLPs. This thiol reduction broke disulfide linkages inside the pre-fabricated VLPs, but it did not disrupt the appearance of icosahedrons. Small dissociated capsomers from EGTA-treated VLPs were able to reassemble back to icosahedrons in the presence of calcium ions, but additional treatment with beta-mercaptoethanol during EGTA dissociation resulted in inability of the capsomers to reassemble into the icosahedral form. These results indicated that Cys115 and Cys201 were essential for capsid formation of DGNNV icosahedron structure in de novo assembly and reassembly pathways, as well as for the thermal stability of pre-fabricated particles.

The association of Fcgamma receptor IIIb genetic polymorphism and susceptibility to periodontitis in Taiwanese individuals.

AIM: The allelic polymorphism of FcgammaRIIIb, the neutrophil-specific receptor involved in the phagocytosis of immunoglobulin G-opsonized bacteria, has functionally distinct capacities that are important in host defence mediated by neutrophils. The aim of this study was to identify whether the polymorphism of FcgammaRIIIb is associated with periodontitis in Taiwanese individuals. MATERIALS AND METHODS: This case-control study included of 93 aggressive periodontitis (AgP) patients, 372 chronic periodontitis (CP) patients and 158 healthy controls (HC). The FcgammaRIIIb genotypes were determined by PCR using allele-specific primers. The risk for periodontitis associated with genotypes was calculated as the odds ratio (OR). RESULTS: A significant difference was observed in the distribution of the FcgammaRIIIb genotype between either AgP and HC, or AgP and CP, but not between CP and HC. The OR for carriage of the NA2 allele (NA1NA2+NA2NA2 versus NA1NA1) in AgP was 3.27 [95% confidence interval (CI)=1.57-7.51, p=0.0027] and 2.94 (95% CI=1.49-6.48, p=0.0037), as compared with HC and CP. After adjusting for possible confounding factors, the association was still significant. CONCLUSIONS: The results of the present study suggest that subjects carrying at least one copy of the FcgammaRIIIb-NA2 allele might be associated with susceptibility to AgP. However, the clinical implications of the FcgammaRIIIb allelic polymorphism should be determined by further studies.

A Carbohydrate-Binding Protein from the Edible Lablab Beans Effectively Blocks the Infections of Influenza Viruses and SARS-CoV-2.

The influenza virus hemagglutinin (HA) and coronavirus spike (S) protein mediate virus entry. HA and S proteins are heavily glycosylated, making them potential targets for carbohydrate binding agents such as lectins. Here, we show that the lectin FRIL, isolated from hyacinth beans (Lablab purpureus), has anti-influenza and anti-SARS-CoV-2 activity. FRIL can neutralize 11 representative human and avian influenza strains at low nanomolar concentrations, and intranasal administration of FRIL is protective against lethal H1N1 infection in mice. FRIL binds preferentially to complex-type N-glycans and neutralizes viruses that possess complex-type N-glycans on their envelopes. As a homotetramer, FRIL is capable of aggregating influenza particles through multivalent binding and trapping influenza virions in cytoplasmic late endosomes, preventing their nuclear entry. Remarkably, FRIL also effectively neutralizes SARS-CoV-2, preventing viral protein production and cytopathic effect in host cells. These findings suggest a potential application of FRIL for the prevention and/or treatment of influenza and COVID-19.

Phase TEM for biological imaging utilizing a Boersch electrostatic phase plate: theory and practice.

A Boersch electrostatic phase plate (BEPP) used in a transmission electron microscope (TEM) system can provide tuneable phase shifts and overcome the low contrast problem for biological imaging. Theoretically, a pure phase image with a high phase contrast can be obtained using a BEPP. However, a currently available TEM system utilizing a BEPP cannot achieve sufficiently high phase efficiency for biological imaging, owing to the practical conditions. The low phase efficiency is a result of the blocking of partial unscattered electrons by BEPP, and the contribution of absorption contrast. The fraction of blocked unscattered beam is related to BEPP dimensions and to divergence of the illumination system of the TEM. These practical issues are discussed in this paper. Phase images of biological samples (negatively stained ferritin) obtained by utilizing a BEPP are reported, and the phase contrast was found to be enhanced by a factor of approximately 1.5, based on the calculation using the Rose contrast criterion. The low gain in phase contrast is consistent with the expectation from the current TEM/BEPP system. A new generation of phase TEM utilizing BEPP and designed for biological imaging with a high phase efficiency is proposed.

Cyclooxygenase-2 Gene-765 single nucleotide polymorphism as a protective factor against periodontitis in Taiwanese.

AIM: Prostaglandin E(2) (PGE(2)) is considered to be an important mediator of tissue destruction in periodontitis. The cyclooxygenase (COX) catalyses the production of PGs. COX-2, which is induced in an inflammatory response, is responsible for PGs synthesis at sites of inflammation. A single nucleotide polymorphism of COX-2(-765) has been shown to alter the expression of the COX-2 gene. The purpose of the present study was to evaluate the association of the COX-2(-765) polymorphism and susceptibility to periodontitis in Taiwanese. MATERIAL AND METHODS: Eighty-five cases of aggressive periodontitis (AgP), 343 cases of chronic periodontitis (CP) and 153 cases of healthy controls (HC) were recruited for the study. Genotypes of COX-2(-765) were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The distribution of genotypes among groups was compared by logistic regression analyses. The risk for periodontitis associated with genotypes was calculated as the odds ratio (OR). RESULTS: The prevalence of the GC and CC genotypes was significantly lower in AgP (5%) and in CP (29%) compared with the HC (42%). The ORs for carriage of the -765C allele (GC+CC versus GG) in AgP and CP were 0.068 (95% CI=0.020-0.173, p<0.0001) and 0.571 (95% CI=0.385-0.849, p=0.006), respectively. After adjustment for age, gender and smoking status, the OR was 0.071 (95% CI=0.017-0.219) and 0.552 (95% CI=0.367-0.829) for AgP and CP, respectively. CONCLUSIONS: The results of the study suggest that the -765G to C polymorphism of the COX-2 gene is associated with a decreased risk for periodontitis in Taiwanese, especially in AgP. However, the biological meaning needs further investigation.