Survival time analysis of remaining teeth following replacement of unilateral free-end missing teeth: A comparison between fixed implant-supported prostheses and removable partial dentures.

OBJECTIVES: This retrospective study aimed to investigate the differences in tooth loss rate between fixed implant-supported prostheses (FISPs) and removable partial dentures (RPDs) in cases of unilateral free-end missing teeth. MATERIALS AND METHODS: The data of 324 patients who underwent treatment with FISPs or RPDs for unilateral free-end missing teeth and satisfied the applicable criteria, were evaluated (47 in the FISPs group and 277 in the RPDs group). After propensity score (PS) matching, which was used to extract patients with similar background factors related to prosthetic selection at baseline, survival time analyses were performed with tooth loss as the endpoint. The adjusted variables were age, sex, number of restored teeth, periodontal status, and the practicing dentist's experience in years. The remaining teeth were classified into subcategories in relation to the missing molars. RESULTS: Overall, 58 patients (29 in each group) selected by PS matching were evaluated in the final analysis. The total number of lost teeth was 35 (FISPs group: n = 10; RPDs group: n = 25). The mean (±SD) period to tooth loss and the 10-year survival rates in the FISPs and RPDs groups were 51.6 (±30.1) months and 42.3 (±29.7) months, 70.5% and 16.4%, respectively. The log-rank test showed that significantly longer survival time in FISPs compared with RPDs. CONCLUSIONS: After adjustments for confounding factors using PS matching, replacing unilateral free-end missing teeth with FISPs may exhibit a lower tooth loss rate in adjacent and contralateral teeth compared to replacing with RPDs.

Factors related to subjective evaluation of difficulty in chewing among community-dwelling older adults.

AIM: Awareness of difficulty chewing may limit the diversity of food intake in older adults. However, few studies have clarified which factors are related to subjective difficulty in chewing. The aim was to identify factors related to subjective difficulty in chewing in 70- and 80-year-old Japanese older adults. METHODS: A total of 1680 participants (792 men, 888 women) were surveyed. Difficulty in chewing was assessed with questionnaires regarding food intake, such as rice, apples, beef, and hard rice crackers. The participants were classified into two groups, the "with difficulty" group (participants who answered "cannot eat," "can eat with difficulty," and "can eat if small") and the "without difficulty" group (participants who answered "can eat without problems"), according to their answers to questionnaires for each food. A logistic regression analysis with subjective difficulty in chewing as the dependent variable was performed for each food. RESULTS: Subjective difficulty in chewing was associated with age, occlusal force, and depression for rice; age, number of remaining teeth, occlusal force, and depression for apples; number of remaining teeth, occlusal force, and depression for beef; and number of remaining teeth and occlusal force for hard rice crackers. CONCLUSIONS: Age, number of remaining teeth, and occlusal force, as well as depression, might be related to subjective evaluation of difficulty chewing in community-dwelling Japanese older adults. Geriatr Gerontol Int 2024; 24: 327-333.

The relationship between changes in occlusal support and masticatory performance using 6-year longitudinal data from the SONIC study.

OBJECTIVES: Reduced occlusal support is thought to be related to a decline in masticatory performance. However, previous research in this field was based on cross-sectional studies. In this study, we conducted a 6-year longitudinal observation of older adults living in the community and examined the associations of changes in occlusal support with masticatory performance. METHODS: Of the 864 participants aged 72-74 years in the SONIC study, 488 who were followed up (median follow-up period 5.92 years) and had no missing data were included in this study. Participants were divided into three groups according to the number of occlusal support zones in the posterior area: Complete occlusion (four zones), Reduced occlusion (one to three zones), and Collapsed occlusion (no occlusal support zone). Longitudinal analysis of the relationship between occlusal support and masticatory performance was undertaken with linear mixed-effects models. RESULTS: Sex, occlusal force, number of unreplaced missing teeth, aging, and occlusal support change were significantly related to masticatory performance. Furthermore, the interaction term between change in occlusal support and aging was a significant explanatory variable for the decline in masticatory performance. The interaction was strongest in the group that changed from Complete or Reduced occlusion to Collapsed occlusion. This result indicates that the loss of occlusal support is a major factor contributing to declining masticatory performance. CONCLUSIONS: The decline of occlusal support was greatly associated with the deterioration of masticatory performance. Our results suggest that older adults need to prevent the collapse of posterior occlusal support to maintain their masticatory performance. CLINICAL SIGNIFICANCE: Occlusal support is important for preserving masticatory performance in older adults. Preventing the loss of molars and retaining occlusal support may contribute to maintaining food intake diversity and nutritional status, thereby improving quality of life. Dental professionals need to carefully examine dental status to assess the risk of occlusal collapse.

Tolerance of bitter stimuli and attenuation/accumulation of their bitterness in humans.

Some components of bitterness make key flavor contributions to promote the palatability of foods, whereas other components are recognized as aversive signals to avoid consuming harmful substances. These contradictory behaviors suggest that humans tolerate tastes of bitterants based on certain criteria. Here, we investigated human taste tolerance and sensory cues leading to diverse taste tolerance of bitter compounds. Tolerance of eight bitter compounds, which are typically contained in foods, was evaluated by measuring detection and rejection thresholds. The results revealed that the level of tolerance of each compound was variable, and some compounds showed an acceptable concentration regarding the suprathreshold intensity. Tolerance did not depend on the nutritive value or attenuation and accumulation characteristics of bitterness and bitter taste receptors. These results suggest that the criteria controlling tolerance of bitter compounds may be derived from a complex relationship between the taste quality and cognitive process.

Inhibition of autolysosome formation in host autophagy by Trypanosoma cruzi infection.

Autophagy has emerged as an essential component of the defense system against intracellular pathogens. We demonstrated that Trypanosoma cruzi, an intracellular protozoan parasite, was not eliminated by the host's autophagic machinery despite exposure to the host cell cytoplasm. Puncta of microtubule-associated protein 1 light chain 3 (LC3), an autophagy marker, and LC3-II, a lipidated form of LC3, were significantly increased after infection with T. cruzi, indicating that the parasite activated the early steps of host autophagy and induced autophagosome formation. However, autolysosomes were not observed in the infected cells. In addition, T. cruzi was not enwrapped by autophagosomes, suggesting that the parasite has mechanisms to allow it to evade autophagic capture. The results of this study indicate that host autophagy is incomplete following T. cruzi infection.

Host cytoplasmic processing bodies assembled by Trypanosoma cruzi during infection exert anti-parasitic activity.

Processing bodies (PBs) are cytoplasmic granules containing mRNAs and proteins involved in translation and degradation of mRNAs. PBs are constitutively present in cells and are induced to accumulate when external stressors including microbial infection are applied to cells, followed by a rapid translational arrest. We have examined the impact of Trypanosoma cruzi (T. cruzi, Tc) infection on host cytoplasmic PB assembly. Within 24h post-infection, we found the average number of PB foci per cell increased by more than 2-fold. Protein levels of PB components were unaltered during infection. These results indicated that Tc infection caused accumulation of PBs by changing the localization pattern of PB protein components. To elucidate the role of the accumulated PBs on Tc infection, we knocked down PBs using a siRNA specific for PB components EDC4 and Lsm14A, which are involved in mRNA decapping and translational repression, respectively. We observed that the inhibition of PB accumulation significantly enhanced the infectivity and growth of intracellular amastigotes. Depletion of PBs did not affect nitric oxide (NO) production during Tc infection, indicating that the growth promotion was not caused by modulation of NO-mediated killing of Tc. Our results suggest that the accumulated PBs partially contribute to anti-parasitic responses by manipulating the host's mRNA metabolism.

The Assembly of EDC4 and Dcp1a into Processing Bodies Is Critical for the Translational Regulation of IL-6.

Macrophages play critical roles in the onset of various diseases and in maintaining homeostasis. There are several functional subsets, of which M1 and M2 macrophages are of particular interest because they are differentially involved in inflammation and its resolution. Here, we investigated the differences in regulatory mechanisms between M1- and M2-polarized macrophages by examining mRNA metabolic machineries such as stress granules (SGs) and processing bodies (P-bodies). Human monocytic leukemia THP-1 cells cultured under M1-polarizing conditions (M1-THPs) had less ability to assemble oxidative-stress-induced SGs than those cultured under M2-polarizing conditions (M2-THPs). In contrast, P-body assembly in response to oxidative stress or TLR4 stimulation was increased in M1-THPs as compared to M2-THPs. These results suggest that mRNA metabolism is controlled differently in M1-THPs and M2-THPs. Interestingly, knocking down EDC4 or Dcp1a, which are components of P-bodies, severely reduced the production of IL-6, but not TNF-α in M1-THPs without decreasing the amount of IL-6 mRNA. This is the first report to demonstrate that the assembly of EDC4 and Dcp1a into P-bodies is critical in the posttranscriptional regulation of IL-6. Thus, improving our understanding of the mechanisms governing mRNA metabolism by examining macrophage subtypes may lead to new therapeutic targets.

Processing bodies accumulate in human cytomegalovirus-infected cells and do not affect viral replication at high multiplicity of infection.

Translationally silenced mRNAs are recruited to two major classes of RNA granules in the cytoplasm, processing bodies (PBs) and stress granules (SGs). We show that PBs accumulated after human cytomegalovirus (HCMV) infection. PB assembly after HCMV infection was also detected in the presence of the protein synthesis inhibitor, cycloheximide, but required active RNA synthesis. UV-inactivated HCMV virions were sufficient to induce PB accumulation in HFF cells treated with cycloheximide. Viral IE1 RNA did not colocalize with PBs, and we could not detect an effect of PB accumulation on viral growth. These results may indicate that HCMV inhibits the colocalization of IE1 mRNA with PBs, preventing IE1 mRNA decay and translational inhibition.

Micro RNAs of Epstein-Barr virus promote cell cycle progression and prevent apoptosis of primary human B cells.

Cellular and viral microRNAs (miRNAs) are involved in many different processes of key importance and more than 10,000 miRNAs have been identified so far. In general, relatively little is known about their biological functions in mammalian cells because their phenotypic effects are often mild and many of their targets still await identification. The recent discovery that Epstein-Barr virus (EBV) and other herpesviruses produce their own, barely conserved sets of miRNAs suggests that these viruses usurp the host RNA silencing machinery to their advantage in contrast to the antiviral roles of RNA silencing in plants and insects. We have systematically introduced mutations in EBV's precursor miRNA transcripts to prevent their subsequent processing into mature viral miRNAs. Phenotypic analyses of these mutant derivatives of EBV revealed that the viral miRNAs of the BHRF1 locus inhibit apoptosis and favor cell cycle progression and proliferation during the early phase of infected human primary B cells. Our findings also indicate that EBV's miRNAs are not needed to control the exit from latency. The phenotypes of viral miRNAs uncovered by this genetic analysis indicate that they contribute to EBV-associated cellular transformation rather than regulate viral genes of EBV's lytic phase.

Epstein-Barr virus infection in immortalized nasopharyngeal epithelial cells: regulation of infection and phenotypic characterization.

Epstein-Barr virus (EBV) infection has been postulated to be an early event involved in the pathogenesis of nasopharyngeal carcinomas (NPC). The lack of representative premalignant nasopharyngeal epithelial cell system for EBV infection has hampered research investigation into the regulation and involvement of EBV infection in NPC pathogenesis. We have compared the efficiency of EBV infection in nasopharyngeal epithelial cells with different biological properties including immortalized, primary and cancerous nasopharyngeal epithelial cells. EBV infection could be achieved in all the nasopharyngeal epithelial cells examined with variable infection rate. TGF-beta effectively enhanced EBV infection into nasopharyngeal epithelial cells both in the immortalized and primary nasopharyngeal epithelial cells. Stable infection of EBV was achieved in a telomerase-immortalized nasopharyngeal epithelial cell line, NP460hTert. The expression pattern of EBV-encoded genes and biological properties of this EBV infected cell line on long-term propagation were monitored. The EBV-infected nasopharyngeal epithelial cells acquired anchorage-independent growth and exhibited invasive growth properties on prolonged propagation. A distinguished feature of this EBV-infected nasopharyngeal epithelial cell model was its enhanced ability to survive under growth factor and nutrient starvation. This was evidenced by the suppressed activation of apoptotic markers and sustained activation of pAkt of EBV-infected cells compared to control cells under nutrient starvation. Examination of cytokine profiles of EBV-infected NP460hTert cells to nutrient and growth factor deprivation revealed upregulation of expression of MCP-1 and GRO-alpha. The establishment of a stable EBV infection model of premalignant nasopharyngeal epithelial cells will facilitate research investigation into the pathogenic role of EBV in NPC development.

Reconstitution of nasopharyngeal carcinoma-type EBV infection induces tumorigenicity.

Several reports have shown that the EBV-encoded BARF1 gene has oncogenic activity. We have recently reported that BARF1 is expressed as a latent gene in most nasopharyngeal carcinomas (NPC), suggesting that BARF1 may have an important role in NPC oncogenesis. However, we found that when the NPC-derived EBV-negative cell lines, HONE-1 and CNE-1, were infected with EBV in vitro, BARF1 was not expressed, although the expression of other latent genes was identical to that of NPC tumors. Therefore, we generated a recombinant EBV (rEBV) carrying the BARF1 gene (BARF1-rEBV) under the SV40 promoter to reconstitute the NPC-type EBV infection. NPC-derived EBV-negative cell lines were stably infected with either a wild-type rEBV (wild-rEBV) or BARF1-rEBV. The resultant BARF1-rEBV-infected NPC cell clones represented NPC-type EBV expression, and BARF1 expression was similar to that observed in NPC tissues. BARF1-rEBV-infected cell clones grew to a higher cell density and were more resistant to apoptosis than wild-rEBV-infected counterparts. BARF1 protein was quickly secreted into the culture medium, and secreted BARF1 contributed to the increase of cell densities in NPC cells, but it had no effect on resistance to apoptosis. Furthermore, BARF1-rEBV-infected cell clones became tumorigenic in nude mice. These results suggest that BARF1 plays an important role in NPC development.

G-protein-dependent and -independent pathways in denatonium signal transduction.

To clarify the involvement of G protein in denatonium signal transduction, we carried out a whole-cell patch-clamp analysis with isolated taste cells in mice. Two different responses were observed by applying GDP-beta-S, a G-protein inhibitor. One response to denatonium was reduced by GDP-beta-S (G-protein-dependent), whereas the other was not affected (G-protein-independent). These different patterns were also observed by concurrently inhibiting the phospholipase C beta2 and phosphodiesterase pathways via G protein. These data suggest dual, G-protein-dependent and -independent mechanisms for denatonium. Moreover, the denatonium responses were not attenuated by singly inhibiting the phospholipase C beta2 or phosphodiesterase pathway, implying that both pathways were involved in G-protein-dependent transduction. In the G-protein-independent cells, the response was abolished by the depletion of calcium ions within the intracellular store. These results suggest that Ca2+ release from the intracellular store is an important factor. Our data demonstrate multiple transduction pathways for denatonium in mammalian taste cells.

Epstein-Barr virus (EBV)-encoded BARF1 gene is expressed in nasopharyngeal carcinoma and EBV-associated gastric carcinoma tissues in the absence of lytic gene expression.

The BARF1 gene is located in the BamHI-A fragment of the Epstein-Barr virus (EBV) genome, encodes 221 amino acids, and has activity as an oncogene. Several reports have demonstrated that BARF1 is expressed in the tissues of various EBV-associated epithelioid malignancies. However,BARF1 is thought to be a lytic gene, since its expression is induced upon induction of the lytic cycle in Burkitt's lymphoma cell lines. Therefore, the possibility cannot be excluded that BARF1 expression in EBV-associated epithelioid malignancies reflects spontaneous induction of the lytic cycle in carcinoma cells. The present study aimed to clarify whether BARF1 was expressed as a latent gene or a lytic gene in epithelioid malignancies. Quantitative real-time RT-PCR assay revealed that BARF1 was highly expressed in nasopharyngeal carcinoma (NPC) and EBV-positive gastric carcinoma tissues in the absence of expression of lytic genes. On the other hand, BARF1 protein was detectable only in two of seven NPC tissue samples by immunoblot analysis. Analysis of BARF1-transfected CNE1 cells revealed that BARF1 was quickly secreted into culture medium and was hardly detectable in the cell lysate, which would account for why some NPC tissues were negative for BARF1 protein expression even though they were strongly positive forBARF1 expression at the transcriptional level. The present findings indicate that BARF1 is expressed in NPC and EBV-positive gastric carcinoma tissues as a latent gene and suggest that BARF1 plays a role in the pathogenesis of these malignancies.