Salivary alpha-amylase stress reactivity in advanced-aged marmosets (Callithrix jacchus): Impacts of cognitive function and oral health status.

Salivary alpha-amylase (sAA) is an enzyme found in saliva and is considered a noninvasive biomarker for sympathetic nervous system activity. While a wide range of sAA activity in response to stress has been reported in nonhuman primates, the effects of stress on sAA activity in common marmosets are still unknown. We tested the hypothesis that advanced age and cognitive function may have an impact on stress-related sAA reactivity in marmosets. Thirteen marmosets (nine males and five females) had saliva samples collected during a stressful condition (manual restraint stress) at two different time points, with a 60-min interval. On the next day, the animals underwent the object recognition test (ORT, a type of cognitive test), and then oral examinations. The animals were categorized into two age groups: old (10-13 years), and very old (15-22 years). Irrespective of age, sAA levels showed a significant difference between T1 (mean 2.07 ± 0.86 U/mL) and T2 samples (mean 1.03 ± 0.67 U/mL), with higher values observed at T1 (p < 0.001). The intra-assay coefficients of variation (CV) for low and high sAA concentrations were 10.79% and 8.17%, respectively, while the interassay CVs for low and high sAA concentrations were 6.39% and 4.38%, respectively. Oral health issues were common but did not significantly impact sAA levels. The ORT indicated that the animals could recognize an object placed in the cage 6 h after familiarization. In conclusion, all marmosets showed a higher sAA concentration in the first saliva sample as compared to the second saliva sample collected 1 h later, indicating adaptation to stress. No significant differences in sAA levels were observed between sexes, ORT performance, or oral health. Our results indicate that autonomic responsivity and cognitive (memory) functions were preserved even in very old marmosets.

Anatomical, behavioural and physiological analyses of craniofacial development by cineradiographic imaging in marmosets.

BACKGROUND: Non-human primates are the closest animal models to humans regarding genetics, physiology and behaviour. Marmoset monkeys in particular are one of the most versatile species for biomedical research. OBJECTIVE: To assess the craniofacial growth and development of the masticatory function in the common marmoset (Callithrix jacchus), from birth to the fourth month of life through minimally invasive cineradiographic imaging. METHODS: Ten individuals were followed-up from 0 to 4 months of age regarding craniofacial growth and masticatory function assessed by cineradiography. For the experimental procedure, we used a microfocal X-ray source apparatus and a beryllium fast-response image-intensifier. RESULTS: The duration of the masticatory cycles was stable across age groups. Chewing a very soft Castella cake or the slightly harder Marshmallow did not change the masticatory cycle in the time domain. On the other hand, linear and angular measurements of the jaw-opening movement showed a tendency for bigger movements at the latter stages of craniofacial growth. Qualitative analysis showed that marmosets had a small preference for Castella over Marshmallow, that they most often bit off pieces of food to chew with their posterior teeth, that they manipulated the food with their hands, and that they chewed the food continuously. CONCLUSION: We observed critical developmental events during the first 3 months of life in marmosets. Cineradiographic imaging in marmosets may provide valuable information on craniofacial form and function for basic and preclinical research models.

Appetite, oral health and weight loss in community-dwelling older men: an observational study from the Concord Health and Ageing in Men Project (CHAMP).

BACKGROUND: Unintended weight loss and the reduction in appetite are common phenomenon among older people. Reduced appetite has been linked to medication related reductions in saliva production, reduced taste ability and poor oral health. Poor appetite can result in reduced nutrient intake ensuing weight loss. It is possible that poor appetite is a mediating step on the causal pathway between oral health and weight loss. This study investigates whether poor oral health and loss of appetite are related to weight loss. METHODS: This is an observational study where data were obtained from the Concord Health and Ageing in Men Project (CHAMP). Information on socio-demographics, appetite and health related behavior was collected by self-completed questionnaire. Intraoral assessment was conducted by calibrated oral health therapists. Height and weight were measured by trained staff. Regression analysis investigated associations between oral health and appetite as risk factors for weight loss. RESULTS: Participants included 542 community dwelling older males. 99 older men (18.3%) experienced 5% or more weight loss over 3 years. Men who lost weight from baseline had lower BMI and lower body weight, had higher prevalence of frailty and depression, reported poorer appetite, and had fewer teeth (13.8 ± 9.5) than those who did not lose weight (16.3 ± 9.3). Before adjustment, the prevalence ratio (PR) for weight loss was 1.76 (95% Confidence Interval (CI), 1.19-2.59) for participants with 0-19 natural teeth present compared to those with 20 or more teeth. When adding appetite and other variables to the model, the PR for number of teeth and weight loss was unchanged: 1.78 (95% CI, 1.06-3.00). The mediation analysis showed that the indirect effect of appetite on the association between number of natural teeth on weight loss was not found to be significant. CONCLUSION: This study found that number of natural teeth present and appetite are independently related to weight change among elderly men in Australia. Tooth loss can increase the risk of swallowing difficulty leading to change in food preference, avoidance of foods and a decrease in energy intake. Our study showed the importance of oral health interventions to encourage maintenance of 20 or more natural teeth in older people.

Oral health and cognitive status in the Concord Health and Ageing in Men Project: A cross-sectional study in community-dwelling older Australian men.

BACKGROUND: Several studies have examined the relationship between cognition and oral health in older populations. To further understand this relationship, we examined the associations between cognitive function, chewing capacity and the number of teeth present in community-dwelling older males in Australia. METHODS: Data were obtained from cross-sectional analysis of fourth wave of the Concord Health and Ageing in Men Project (CHAMP). Participants were 369 community-dwelling males aged 78 years or over. Cognitive function was measured utilising the Mini-Mental State Examination (MMSE). Chewing capacity was determined on ability to chew food items of different textures, and oral health data were collected. Ordinal regression was used to analyse associations between MMSE (four categories) and chewing capacity and number of natural teeth present. RESULTS: Overall, 67.5% of participants reported that they could chew all 11 listed food items. Participants with fewer than 20 teeth were statistically significantly more likely to have cognitive impairment (unadjusted odds ratio (OR) 1.87; 95% confidence interval (CI) 1.25-2.79, adjusted OR 1.62; 95% CI 1.07-2.43). Participants with limited chewing capacity were also more likely to have cognitive impairment (unadjusted OR 1.91; 95% CI 1.25-2.94, adjusted OR 1.61; 95% CI 1.03-2.49). CONCLUSIONS: This study suggests either that older men with fewer than 20 natural teeth and those with limited chewing capacity are more likely to have an associated cognitive impairment or that those with cognitive impairment are more likely to have fewer teeth and limited chewing capacity. Further longitudinal studies should clarify these relationships.

Prevalence and risk factors of halitosis in Japanese school children.

BACKGROUND: Little data are available regarding halitosis in Japanese children. The aim of the current study was to investigate the prevalence and risk factors associated with halitosis in Japanese elementary and junior high school children. METHODS: The subjects consisted of 520 elementary (1st-6th grade: boys, n = 284; girls, n = 236) and 248 junior high (7th-9th grade: boys, n = 136; girls, n = 112) school children aged 6-15 years in Saitama Prefecture, Japan. A self-administered questionnaire survey; halitosis measurement using an organoleptic assessment method; and clinical oral examination were conducted. RESULTS: Overall, 44.9% of subjects had halitosis. The proportion of boys with halitosis was 43.6% and that of girls was 46.6%. On logistic regression analysis, grade and tongue coating were significant predictors of halitosis. The 7th-9th graders were significantly more likely to have halitosis than 1st-3rd graders (OR, 1.83; P = 0.007). Subjects with area of tongue coating score 2 or 3 were 5.51-fold more likely to present with halitosis (P < 0.001) than those with area of tongue coating score 0 or 1. Similarly, subjects with thickness of tongue coating score 2 or 3 were 3.28-fold more likely to have halitosis than those with thickness of tongue coating score 0 or 1 (P < 0.001). CONCLUSIONS: Halitosis in the school children is not a rare condition; instead, its occurrence is relatively high. Therefore, inclusion of a halitosis prevention and management component in school oral health programs would lead to the promotion of overall oral health.

Saliva viscosity as a potential risk factor for oral malodor.

OBJECTIVES: The objective of this study was to assess whether saliva viscosity, measured by a viscometer, was a predictor of oral malodor. MATERIALS AND METHODS: The subjects were 617 patients who visited an oral malodor clinic. The organoleptic test (OT) was used for diagnosis of oral malodor. An oral examination assessed the numbers of teeth present and decayed teeth as well as the presence or absence of dentures. Further, periodontal pocket depths (PD), gingival bleeding, dental plaque and tongue coating were investigated. Unstimulated saliva were collected for 5 min. Saliva viscosity was measured with a viscometer. Logistic regression analysis with oral malodor status by OT as a dependent variable was performed. Possible confounders including age, gender, number of teeth present, number of decayed teeth, number of teeth with PD ≥ 4 mm, number of teeth with bleeding on probing, presence or absence of dentures, plaque index, area of tongue coating, saliva flow rate, saliva pH and saliva viscosity were used as independent variables. RESULTS: Saliva viscosity (p = 0.047) along with the number of teeth with PD ≥4 mm (p = 0.001), plaque index (p = 0.037) and area of tongue coating (p < 0.001) were significant variables for oral malodor. Subjects with a higher number of teeth with PD ≥ 4 mm (OR = 1.32), plaque index (OR = 2.13), area of tongue coating (OR = 3.17) and saliva viscosity (OR = 1.10) were more likely to have oral malodor compared to those with lower values. CONCLUSIONS: The results suggested that high saliva viscosity could be a potential risk factor for oral malodor.

Apnea behavior in early- and late-stage mouse models of Parkinson's disease: Cineradiographic analysis of spontaneous breathing, acute stress, and swallowing.

This study aimed to evaluate the timing and frequency of spontaneous apneas during breathing and swallowing by using cineradiography on mouse models of early/initial or late/advanced Parkinson's disease (PD). C57BL/6 J mice received either 6-OHDA or vehicle injections into their right striatum, followed by respiratory movement recordings during spontaneous breathing and swallowing, and a stress challenge, two weeks later. Experimental group animals showed a significantly lower respiratory rate (158.66 ± 32.88 breaths/minute in late PD, 173.16 ± 25.19 in early PD versus 185.27 ± 25.36 in controls; p<0.001) and a significantly higher frequency of apneas (median 1 apnea/minute in both groups versus 0 in controls; p<0.001). Other changes included reduced food intake and the absence of swallow apneas in experimental mice. 6-OHDA-induced nigrostriatal degeneration in mice disrupted respiratory control, swallowing, stress responsiveness, and feeding behaviors, potentially hindering airway protection and elevating the risk of aspiration.

The relationship between turbidity of mouth-rinsed water and oral health status.

OBJECTIVES: The purpose of this study was to examine the relationship between turbidity of mouth rinsed water and oral health status such as dental and periodontal conditions, oral hygiene status, flow rate of saliva and oral bacteria. MATERIALS AND METHODS: Subjects were 165 patients who visited the Dental Hospital, Tokyo Medical and Dental University. Oral health status, including dental and periodontal conditions, oral hygiene status and flow rate of saliva, was clinically examined. The turbidity was measured with a turbidimeter. Quantification of Fusobacterium spp, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola and total bacteria levels was performed using real-time PCR. The Pearson correlation and multiple regression analysis were used to explore the associations between the turbidity and oral health parameters. RESULTS: The turbidity showed significant correlations with the number of decayed teeth and deep pockets, the plaque index, extent of tongue coating and Fusobacterium spp, P. gingivalis, T. forsythia, T. denticola and total bacteria levels. In a multiple regression model, the turbidity was negatively associated with the flow rate of saliva and positively associated with the total number of bacteria (p < 0.001). CONCLUSION: Current findings suggested that turbidity of mouth rinsed water could be used as an indicator to evaluate oral health condition and the amount of bacteria in the oral cavity. In addition, the turbiditimeter appeared as a simple and objective device for screening abnormality of oral health condition at chair side as well as community-based research.

Maternal Factors in Relation to Early Childhood Caries Among Preschool Children in Myanmar.

A cross-sectional study was conducted among 3- to 5-year-old preschool children in Yangon City in 2016-2017 to investigate the association between their caries experience and maternal factors. Children's oral examination and questionnaire surveys to their mothers were conducted. Children's caries prevalence was 82.9% with mean dmft of 6.4 ± 4.9. Mean oral health knowledge score of their mothers was 8.5 ± 2.8. Mother's educational level and oral health knowledge were significant predictors of childhood caries. Third- or later-born children were twice more likely to have dental caries than first-born children (P = .022). Mother's regular dental check-up resulted in significantly lower odds ratios for caries development in her child. Children's caries experience was high and mother's oral health knowledge regarding the importance of primary teeth was unsatisfactory. It is, therefore, necessary to improve awareness and attentiveness for prevention of childhood caries among parents and guardians in Myanmar.

Socioeconomic, behavioral, and psychological factors related to oral health in Myanmar: A cross-sectional study.

OBJECTIVES: This study aims to evaluate the effects of socioeconomic, behavioral, and psychological factors on oral health status and oral health-related quality of life in Myanmar adults. METHODS: Data were from a convenience sample of Myanmar adults who are from a township health center in Yangon city. Face-to-face interviews using a paper-based questionnaire in the Myanmar language and clinical oral examinations were performed at the health center. Mann-Whitney U test and linear regressions were used to assess the association of socio-demographic, behavioral, and psychological variables with oral health outcomes. RESULTS: In socio-demographic variables, significant associations were observed in individual income with periodontal pocket and OHIP-14, and history of COVID-19 infection with OHIP-14. However, there were no associations between behavioral factors and oral health outcomes. After adjustment for sex, age, educational level, and individual income, the depression subscale was statistically significant with the number of present teeth, decayed teeth, decayed, missing, and filled teeth, and OHIP-14. The anxiety subscale remained significant with periodontal pocket, but no stress subscale was associated with oral health outcomes. CONCLUSION: The experiences of oral health status were high, and the oral health-related quality of life was unfavorable in Myanmar adults. A large proportion of them suffers from psychological distress. Additionally, individuals with lower income and who experienced a history of COVID-19 infection were susceptible to poor oral health-related quality of life. Psychological distress indicates a higher risk for oral health problems in Myanmar adults.

Oral Health Promotion under the 8020 Campaign in Japan-A Systematic Review.

(1) Background: The aim of this study is to review the benefits of the 8020 Campaign since its inception. (2) Methods: We followed the PRISMA guideline and collected information regarding the 8020 Campaign through online database searches. (3) Results: Twenty-five studies met the inclusion criteria and were eligible for analysis. The main outcomes of the 25 included studies were reviewed. The quality evaluation demonstrated a range of studies showing a credible relationship between masticatory function, number of teeth, salivary secretion, frequent dental check-ups, and general health concerns. Due to the risk of bias, publication bias, and indirectness, 22 studies were considered that only had "fair" quality. (4) Conclusions: The 8020 Foundation funded several of the studies, and other research papers noted the 8020 Campaign in their papers, however there were no clear explanations for any direct relationship between their findings and the 8020 Campaign. As a result, evidence for the direct effectiveness and benefits assessment of the 8020 Campaign positive outcomes were compromised by confounding social and economic variables over the 30-year period. To fully elucidate how improvement in Japan's oral health was directly related to the 8020 Campaign, a more informed and systematic explanation of the campaign's structure and activities is required.

A Cross-Sectional Study of Perceived Dental Treatment Needs and Oral Health Status in Community-Dwelling Older Australian Men: The Concord Health and Ageing in Men Project.

BACKGROUND: Assessing perceived needs for dental treatment is important in understanding and predicting people's health behaviours. The purpose of this study is to examine older men's perceptions regarding dental treatment needs, and to investigate the disparity between perceived needs and the actual oral health of a population of community-dwelling older Australians. METHODS: Using cross-sectional data from the 4th wave of the Concord Health and Ageing in Men Project, logistic regression analysis of perceived needs for dental treatment was conducted for 596 men aged 78 and over, with functional tooth units (FTUs), number of decayed tooth surfaces, and periodontitis as independent variables. RESULTS: Thirty-six percent (n = 216) of the participants believed they required some form of dental treatment. The remaining participants did not perceive a need for treatment, yet 65.3% objectively required prosthodontic or restorative care. The regression model showed men with lower FTUs were significantly more likely to report a perceived need for dental treatment than those with 12 FTUs [0-6 FTUs: adjusted odds ratio (OR) 2.58, 95% CI 1.28-5.20; 7-11 FTUs: adjusted OR 2.43, 95% CI 1.16-5.10]. However, neither the number of decayed tooth surfaces nor the existence of periodontitis was associated with perceived dental treatment needs. CONCLUSIONS: Most older men viewed their oral health positively, and the majority of those with objectively assessed needs, did not perceive themselves as requiring dental treatment. Loss of FTUs appears to alert participants to seek treatment, but not the presence of dental caries or periodontitis.

Relationship between oral malodor and glycosylated salivary proteins.

Volatile sulfur compounds (VSCs), which are major sources of oral malodor, are produced by putrefactive activities of bacteria. Saliva provides easily degradable protein substrates, and most proteins are glycosylated. We hypothesized that oral malodor would be associated with enhanced proteolysis or deglycosylation in saliva. The purpose of this study was to evaluate properties of glycoproteins in saliva and assess their association with VSC levels. Subjects were 88 patients who visited "the Fresh Breath Clinic", Dental Hospital, Tokyo Medical and Dental University. They were classified into malodor (n = 67) and non-malodor (n = 21) groups. After collecting saliva, the amounts of the total proteins and carbohydrate were determined. Molecular size distributions of salivary proteins/glycoproteins were analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The amount of the total salivary proteins was significantly higher in the malodor group. Major proteins/glycoproteins observed in SDS-PAGE analyses showed similar distributions between the two groups. In the malodor group, the salivary protein concentrations were positively correlated with the CH3SH levels (p < 0.05), and the carbohydrate contents were negatively correlated with the H2S levels (p < 0.05). These results indicated the possibility that salivary proteins/glycoproteins might be related to the malodor generation.

Ecological study on the penetration of induction heating cookers and birth outcomes in Japan.

In recent years, equipment that generates intermediate-frequency electromagnetic fields (IF-EMFs) has become increasingly prevalent, and the influence of IF-EMFs on human health is thus attracting increasing attention. The present study was conducted with the aim of analyzing whether there is a relationship between the penetration of induction heating cookers and birth outcomes using an ecological study design at the prefectural level. We created data sets for all 47 prefectures in Japan using previously published statistics. Spontaneous fetal death rate, fetal death rate after 22 weeks of pregnancy, perinatal mortality rate, and proportion of newborns weighing less than 2500 g were used as birth outcomes in correlation analysis. A weak positive association was observed between the penetration of induction heating cookers and the fetal death rate after the 22nd week of pregnancy (r = 0.27, p = 0.07), but it was not statistically significant. In addition, a weak negative association was observed between the penetration of induction heating cookers and the spontaneous fetal death rate (r = -0.27, p = 0.07), but it was not statistically significant. In the present ecological study, no statistically significant association were shown between the penetration of induction heating cookers and birth outcomes. To demonstrate further the safety of induction heating cooker use, observations in epidemiological studies of other designs should be considered.

Associations between oral health and depressive symptoms: Findings from the Concord Health and Ageing in Men Project.

OBJECTIVE: To investigate whether poorer oral health, tooth loss and lower usage of dental services are associated with depressive symptoms in older Australian men. METHODS: Cross-sectional study of data collected from participants of the Concord Health and Ageing in Men Project. Depressive symptoms were evaluated by the Geriatric Depression Scale. Chewing capacity was estimated by ability to chew 11 food items. RESULTS: The prevalence of depressive symptoms was 17.5%. Self-evaluated oral health, chewing capacity and the number of natural and decayed teeth were associated with depressive symptoms. After adjusting for multiple confounders, chewing capacity (PR 1.93; 95% CI 1.34-2.79) and decayed teeth (PR 1.68; 95% CI 1.03-2.75) maintained a significant association with depressive symptoms. CONCLUSION: The direction of causality between oral health and depression is unclear; however, oral health may contribute to depression in older Australian men and depressive symptoms may limit chewing capacity and be aggravated by untreated dental decay.

Factors affecting the motivation for dental check-ups and anxiety in the elderly in Tokyo.

OBJECTIVES: The purpose of this study was to identify factors influencing the motivation for regular dental check-ups and anxiety about future dental problems in the elderly. BACKGROUND: Regular dental check-ups are important to maintain oral health. Anxiety affects the quality of life of the elderly. However, few studies have investigated the factors influencing the motivation for regular dental check-ups and anxiety in the elderly. MATERIALS AND METHODS: Among 452 elderly persons, 215 participants provided useful answers to our questionnaire. The questionnaire consisted of items concerning oral and living conditions of the subjects. Logistic regression analysis was conducted. RESULTS: The mean age of the study sample was 75.7 +/- 5.8 years. The percentage of edentulous subjects was 12.1%. The motivation for regular dental check-ups was significantly positively correlated with the number of teeth present (p < 0.01), using inter-dental brushes (p < 0.01), being on regular prescribed medication (p < 0.05), and having experience of providing oral care for the bedridden (p < 0.05). Anxiety about future oral problems was significantly associated with self-rated health status (p < 0.01) and the presence of dentists who could be counted on to provide domiciliary visits (p < 0.05). CONCLUSION: The participants of this study had a high motivation for regular dental check-ups, but were concerned about the future, particularly if they became bedridden.

Characterization of oral microbiota in marmosets: Feasibility of using the marmoset as a human oral disease model.

With rapid aging of the world's population, the demand for research, for a better understanding of aging and aging-related disorders, is increasing. Ideally, such research should be conducted on human subjects. However, due to ethical considerations, animals such as rodents and monkeys are used as alternatives. Among these alternative models, non-human primates are preferred because of their similarities with humans. The small South American common marmoset (Callithrix jacchus) may offer several advantages over other non-human primates in terms of its smaller size, shorter life-span, and dental anatomy identical to humans. The purpose of this study was to determine the viability of using the marmoset as a human oral disease model. We collected saliva samples from eight marmosets and eight human subjects. Prokaryotic DNA was extracted from the saliva samples, and 16S bacterial rRNA gene sequencing was performed on each of the samples. Our results indicated that the types of oral microbiomes detected among human and marmoset samples were nearly indistinguishable. In contrast, the oral microbiomes of our human and marmoset subjects were distinctly different from those reported for rats and dogs, which are currently popular research animals. The oral microbiomes of marmosets showed greater diversity than those of humans. However, the oral microbiota of marmosets exhibited less variation than those of humans, which may be attributed to the fact that the marmoset subjects were kept in a controlled environment with identical lifestyles. The characteristics of its oral microbiota, combined with other technical advantages, suggest that the marmoset may provide the best animal model thus far for the study of oral health. This study characterized the oral microbes of the marmoset, thereby providing information to support future application of the marmoset as a model for age-related oral disease.

Relationships between occupational and behavioral parameters and oral health status.

The aim of the present study was to assess the influence of various workplace parameters and oral health behaviors on tooth decay, periodontal disease, and the number of teeth present in industrial workers. The study participants were 1,078 workers (808 males, 270 females, mean age 42.8 ± 11.4 yr) employed at 11 different workplaces. Oral examinations and a self-administered questionnaire were conducted for participants. A logistic regression analysis was conducted to identify factors related to their oral health status. Factors significantly associated with decayed teeth were smoking (OR=2.02), not having received tooth brushing instruction (OR=1.73), not having annual dental examinations (OR=1.64) and not brushing before sleeping (OR=0.55). The factors significantly associated with severe periodontal disease were employment with a company with fewer than 50 employees (OR=15.56) and not brushing teeth before bedtime (OR=2.41). The factors significantly associated with having 23 teeth or fewer were subjects in the education and learning support industry compared with manufacturing industry (OR=5.83) and transport industry (OR=12.01). The results of the present study showed that various occupational parameters and health behaviors are associated with oral health status including tooth decay, periodontal disease, and tooth loss.

Characteristics of undergraduate dental students in Japan: English competency and willingness to study abroad.

OBJECTIVE: This study was conducted to acquire a deeper understanding of Japanese students' motivation to study abroad and to provide baseline information for nurturing globally-minding dental students. MATERIALS AND METHODS: Students from the first to the sixth year (n = 332), at the Faculty of Dentistry, Tokyo Medical and Dental University, were invited to participate in the study and were asked to complete a self-administered questionnaire, written in Japanese. Self-reported English competency was assessed in four areas: reading; writing; speaking; and listening. Students were asked to score their competencies in these areas using a 10-point visual analogue scale (VAS). Of the total eligible students, 312 (94%) participated. RESULTS: The results of the study suggest that competency and confidence in the English language could be one of the biggest obstacles for students to study abroad. Students with an interest in studying abroad were highly motivated and studied English independently. DISCUSSION AND CONCLUSIONS: Japanese educational authorities and dental schools may need to consider a range of incentives and motivational strategies to nurture clinicians, educators and researchers who can function confidently in an increasingly borderless world. These could include increasing exposure to English language skills through mandatory lectures and seminars in English, increasing the range of inbound international students through student exchange programmes and encouraging students to develop and communicate with international colleagues. The Faculty of Dentistry at Tokyo Medical and Dental University has begun to increase exposure of students to English through the regular curriculum. Outcomes will be followed and evaluated.

Degradation of MUC7 and MUC5B in human saliva.

BACKGROUND: Two types of mucins, MUC7 and MUC5B constitute the major salivary glycoproteins, however their metabolic turnover has not been elucidated in detail to date. This study was conducted to examine turnover of MUC7 and MUC5B in saliva, by focusing on the relationship between their deglycosylation and proteolysis. METHODOLOGY/PRINCIPAL FINDINGS: Whole saliva samples were collected from healthy individuals and incubated at 37°C in the presence of various protease inhibitors, sialidase, or a sialidase inhibitor. General degradation patterns of salivary proteins and glycoproteins were examined by SDS-polyacrylamide-gel-electrophoresis. Furthermore, changes of molecular sizes of MUC7 and MUC5B were examined by Western blot analysis. A protein band was identified as MUC7 by Western blot analysis using an antibody recognizing an N-terminal epitope. The MUC7 signal disappeared rapidly after 20-minutes of incubation. In contrast, the band of MUC7 stained for its carbohydrate components remained visible near its original position for a longer time indicating that the rapid loss of Western blot signal was due to the specific removal of the N-termimal epitope. Pretreatment of saliva with sialidase facilitated MUC7 protein degradation when compared with samples without treatment. Furthermore, addition of sialidase inhibitor to saliva prevented proteolysis of N-terminus of MUC7, suggesting that the desialylation is a prerequisite for the degradation of the N-terminal region of MUC7. The protein band corresponding to MUC5B detected in both Western blotting and glycoprotein staining showed little sign of significant degradation upon incubation in saliva up to 9 hours. CONCLUSIONS/SIGNIFICANCE: MUC7 was highly susceptible to specific proteolysis in saliva, though major part of MUC5B was more resistant to degradation. The N-terminal region of MUC7, particularly sensitive to proteolytic degradation, has also been proposed to have distinct biological function such as antibacterial activities. Quick removal of this region may have biologically important implication.