Refined Sea Salt Markers for Coastal Cities Facilitating Quantification of Aerosol Aging and PM2.5 Apportionment.

Sea salt (ss) aerosols in PM2.5 are often quantified through source apportionment by applying sodium (Na+) and chloride (Cl-) as the markers, but both markers can be substantially emitted from anthropogenic sources. In this study, we differentiate ss from nonss (nss) portions of Na+ and Cl- to better apportion PM2.5 in a coastal tropical urban environment. Size-resolved ionic profiles accounting for Cl- depletion of aged ss were applied to 162-day measurements during 2012 and 2018-2019. Results show that the nss (likely anthropogenic) portions, on average, account for 50-80% of total Na+ and Cl- in submicron aerosols (PM1). This corresponds to up to 2.5 µg/m3 of ss in submicron aerosols that can be ∼10 times overestimated if one attributes all Na+ and Cl- in PM1 to ss. Employing the newly speciated ss- and nss-portions of Na+ and Cl- to source apportionment of urban PM2.5 via positive matrix factorization uncovers a new source of transported anthropogenic emissions during the southwest monsoon, contributing to 12-15% of PM2.5. This increases anthropogenic PM2.5 by ≥19% and reduces ss-related PM2.5 by >30%. In addition to demonstrating Cl- depletion (aging) in submicron aerosols and quantifying ssNa+, nssNa+, ssCl-, as well as nssCl- therein, the refined PM2.5 apportionment resolves new insights on PM2.5 of anthropogenic origins in urban environments, useful to facilitate policy making.

Molecular mechanisms of experience-dependent maturation in cortical GABAergic inhibition.

Critical periods (CP) in early post-natal life are periods of plasticity during which the neuronal circuitry is most receptive to environmental stimuli. These early experiences translate to a more permanent and sophisticated neuronal connection in the adult brain systems. Multiple studies have pointed to the development of inhibitory circuitry as one of the central factors for the onset of critical periods. We discuss several molecular mechanisms regulating inhibitory circuit maturation and CP, from gene transcription level to protein signaling level. Also, beyond the level of gene sequences, we briefly consider recent information on dynamic epigenetic regulation of gene expression through histone methylation and acetylation and their implication on timed development of the inhibitory circuitry for the onset of CP.

Network-based characterization of the synaptic proteome reveals that removal of epigenetic regulator Prmt8 restricts proteins associated with synaptic maturation.

The brain adapts to dynamic environmental conditions by altering its epigenetic state, thereby influencing neuronal transcriptional programs. An example of an epigenetic modification is protein methylation, catalyzed by protein arginine methyltransferases (PRMT). One member, Prmt8, is selectively expressed in the central nervous system during a crucial phase of early development, but little else is known regarding its function. We hypothesize Prmt8 plays a role in synaptic maturation during development. To evaluate this, we used a proteome-wide approach to characterize the synaptic proteome of Prmt8 knockout versus wild-type mice. Through comparative network-based analyses, proteins and functional clusters related to neurite development were identified to be differentially regulated between the two genotypes. One interesting protein that was differentially regulated was tenascin-R (TNR). Chromatin immunoprecipitation demonstrated binding of PRMT8 to the tenascin-r (Tnr) promoter. TNR, a component of perineuronal nets, preserves structural integrity of synaptic connections within neuronal networks during the development of visual-somatosensory cortices. On closer inspection, Prmt8 removal increased net formation and decreased inhibitory parvalbumin-positive (PV+) puncta on pyramidal neurons, thereby hindering the maturation of circuits. Consequently, visual acuity of the knockout mice was reduced. Our results demonstrated Prmt8's involvement in synaptic maturation and its prospect as an epigenetic modulator of developmental neuroplasticity by regulating structural elements such as the perineuronal nets.

Using peer review to distribute group work marks equitably between medical students.

BACKGROUND: Although peer assessment has been used for evaluating performance of medical students and practicing doctors, it has not been studied as a method to distribute a common group work mark equitably to medical students working in large groups where tutors cannot observe all students constantly. METHODS: The authors developed and evaluated a mathematical formulation whereby a common group mark could be distributed among group members using peer assessment of individual contributions to group work, maintaining inter-group variation in group work scores. This was motivated by community health projects undertaken by large groups of year four medical students at the National University of Singapore, and the new and old formulations are presented via application to 263 students in seven groups of 36 to 40 during the academic year 2012/2013. RESULTS: This novel formulation produced a less clustered mark distribution that rewarded students who contributed more to their team. Although collusion among some members to form a voting alliance and 'personal vendettas' were potential problems, the former was not detected and the latter had little impact on the overall grade a student received when working in a large group. The majority of students thought the new formulation was fairer. CONCLUSIONS: The new formulation is easy to implement and arguably awards grades more equitably in modules where group work is a major component.

HDAC1 negatively regulates Bdnf and Pvalb required for parvalbumin interneuron maturation in an experience-dependent manner.

During early postnatal development, neuronal circuits are sculpted by sensory experience provided by the external environment. This experience-dependent regulation of circuitry development consolidates the balance of excitatory-inhibitory (E/I) neurons in the brain. The cortical barrel-column that innervates a single principal whisker is used to provide a clear reference frame for studying the consolidation of E/I circuitry. Sensory deprivation of S1 at birth disrupts the consolidation of excitatory-inhibitory balance by decreasing inhibitory transmission of parvalbumin interneurons. The molecular mechanisms underlying this decrease in inhibition are not completely understood. Our findings show that epigenetic mechanisms, in particular histone deacetylation by histone deacetylases, negatively regulate the expression of brain-derived neurotrophic factor (Bdnf) and parvalbumin (Pvalb) genes during development, which are required for the maturation of parvalbumin interneurons. After whisker deprivation, increased histone deacetylase 1 expression and activity led to increased histone deacetylase 1 binding and decreased histone acetylation at Bdnf promoters I-IV and Pvalb promoter, resulting in the repression of Bdnf and Pvalb gene transcription. The decrease in Bdnf expression further affected parvalbumin interneuron maturation at layer II/III in S1, demonstrated by decreased parvalbumin expression, a marker for parvalbumin interneuron maturation. Knockdown of HDAC1 recovered Bdnf and Pvalb gene transcription and also prevented the decrease of inhibitory synapses accompanying whisker deprivation.

Comparative network-based recovery analysis and proteomic profiling of neurological changes in valproic acid-treated mice.

Despite its prominence for characterization of complex mixtures, LC-MS/MS frequently fails to identify many proteins. Network-based analysis methods, based on protein-protein interaction networks (PPINs), biological pathways, and protein complexes, are useful for recovering non-detected proteins, thereby enhancing analytical resolution. However, network-based analysis methods do come in varied flavors for which the respective efficacies are largely unknown. We compare the recovery performance and functional insights from three distinct instances of PPIN-based approaches, viz., Proteomics Expansion Pipeline (PEP), Functional Class Scoring (FCS), and Maxlink, in a test scenario of valproic acid (VPA)-treated mice. We find that the most comprehensive functional insights, as well as best non-detected protein recovery performance, are derived from FCS utilizing real biological complexes. This outstrips other network-based methods such as Maxlink or Proteomics Expansion Pipeline (PEP). From FCS, we identified known biological complexes involved in epigenetic modifications, neuronal system development, and cytoskeletal rearrangements. This is congruent with the observed phenotype where adult mice showed an increase in dendritic branching to allow the rewiring of visual cortical circuitry and an improvement in their visual acuity when tested behaviorally. In addition, PEP also identified a novel complex, comprising YWHAB, NR1, NR2B, ACTB, and TJP1, which is functionally related to the observed phenotype. Although our results suggest different network analysis methods can produce different results, on the whole, the findings are mutually supportive. More critically, the non-overlapping information each provides can provide greater holistic understanding of complex phenotypes.

The role of miRNAs in complex formation and control.

UNLABELLED: microRibonucleic acid (miRNAs) are small regulatory molecules that act by mRNA degradation or via translational repression. Although many miRNAs are ubiquitously expressed, a small subset have differential expression patterns that may give rise to tissue-specific complexes. MOTIVATION: This work studies gene targeting patterns amongst miRNAs with differential expression profiles, and links this to control and regulation of protein complexes. RESULTS: We find that, when a pair of miRNAs are not expressed in the same tissues, there is a higher tendency for them to target the direct partners of the same hub proteins. At the same time, they also avoid targeting the same set of hub-spokes. Moreover, the complexes corresponding to these hub-spokes tend to be specific and nonoverlapping. This suggests that the effect of miRNAs on the formation of complexes is specific.

DNA methylation levels of RELN promoter region in ultra-high risk, first episode and chronic schizophrenia cohorts of schizophrenia.

The essential role of the Reelin gene (RELN) during brain development makes it a prominent candidate in human epigenetic studies of Schizophrenia. Previous literature has reported differing levels of DNA methylation (DNAm) in patients with psychosis. Therefore, this study aimed to (1) examine and compare RELN DNAm levels in subjects at different stages of psychosis cross-sectionally, (2) analyse the effect of antipsychotics (AP) on DNAm, and (3) evaluate the effectiveness and applicability of RELN promoter DNAm as a possible biological-based marker for symptom severity in psychosis.. The study cohort consisted of 56 healthy controls, 87 ultra-high risk (UHR) individuals, 26 first-episode (FE) psychosis individuals and 30 chronic schizophrenia (CS) individuals. The Positive and Negative Syndrome Scale (PANSS) was used to assess Schizophrenia severity. After pyrosequencing selected CpG sites of peripheral blood, the Average mean DNAm levels were compared amongst the 4 subgroups. Our results showed differing levels of DNAm, with UHR having the lowest (7.72 ± 0.19) while the CS had the highest levels (HC: 8.78 ± 0.35; FE: 7.75 ± 0.37; CS: 8.82 ± 0.48). Significantly higher Average mean DNAm levels were found in CS subjects on AP (9.12 ± 0.61) compared to UHR without medication (UHR(-)) (7.39 ± 0.18). A significant association was also observed between the Average mean DNAm of FE and PANSS Negative symptom factor (R2 = 0.237, ß = -0.401, *p = 0.033). In conclusion, our findings suggested different levels of DNAm for subjects at different stages of psychosis. Those subjects that took AP have different DNAm levels. There were significant associations between FE DNAm and Negative PANSS scores. With more future experiments and on larger cohorts, there may be potential use of DNAm of the RELN gene as one of the genes for the biological-based marker for symptom severity in psychosis.

Factors associated with self-reported burnout level in allied healthcare professionals in a tertiary hospital in Singapore.

BACKGROUND: Burnout has adverse implications in healthcare settings, compromising patient care. Allied health professionals (AHPs) are defined as individuals who work collaboratively to deliver routine and essential healthcare services, excluding physicians and nurses. There is a lack of studies on burnout among AHPs in Singapore. This study explored factors associated with a self-reported burnout level and barriers to seeking psychological help among AHPs in Singapore. METHODS: We conducted a cross-sectional study in a sample of AHPs in a tertiary hospital from October to December 2019. We emailed a four-component survey to 1127 eligible participants. The survey comprised four components: (1) sociodemographic characteristics, (2) Maslach Burnout Inventory (MBI-HSS), (3) Areas of Worklife Survey, and (4) Perceived Barriers to Psychological Treatment (PBPT). We performed a multiple logistic regression analysis to identify factors associated with burnout. Adjusted odds ratios (AORs) and associated 95% confidence intervals (CIs) were computed. RESULTS: In total, 328 participants completed the questionnaire. The self-reported burnout level (emotional exhaustion>27 and/or depersonalization>10) was 67.4%. The majority of the respondents were female (83.9%), Singaporean (73.5%), aged 40 years and below (84.2%), and Chinese ethnicity (79.9%). In the multiple logistic regression model, high burnout level was negatively associated with being in the age groups of 31 to 40 (AOR 0.39, 95% CI 0.16-0.93) and 40 years and older (AOR 0.30, 95% CI 0.10-0.87) and a low self-reported workload (AOR 0.35, 95% CI 0.23-0.52). High burnout level was positively associated with a work experience of three to five years (AOR 5.27, 95% CI 1.44-20.93) and more than five years (AOR 4.24; 95% CI 1.16-16.79. One hundred and ninety participants completed the PBPT component. The most frequently cited barriers to seeking psychological help by participants with burnout (n = 130) were 'negative evaluation of therapy' and 'time constraints.' CONCLUSIONS: This study shows a high self-reported burnout level and identifies its associated factors among AHPs in a tertiary hospital. The findings revealed the urgency of addressing burnout in AHPs and the need for effective interventions to reduce burnout. Concurrently, proper consideration of the barriers to seeking help is warranted to improve AHPs' mental well-being.

Factors influencing protective behaviours during haze episodes in Singapore: A population-based study.

INTRODUCTION: Haze is a recurrent problem in Southeast Asia. Exposure to haze is linked to ophthalmic, respiratory and cardiovascular diseases, and mortality. In this study, we investigated the role of demographic factors, knowledge and perceived risk in influencing protective behaviours during the 2013 haze in Singapore. METHODS: We evaluated 696 adults in a cross-sectional study. Participants were sampled via a 2-stage simple random sampling without replacement from a large residential district in Singapore in 2015. The questionnaire measured the participant's knowledge, perceived risk and behaviours during the Southeast Asian haze crisis in 2013. Reliability and validity of the questionnaire were assessed using comparative fit index (≥0.96) and root mean square error of approximation (≤0.05). We performed structural equation modelling to examine the relationship between the hypothesised factors and protective behaviours. RESULTS: More than 95% of the individuals engaged in at least 1 form of protective behaviour. Knowledge was strongly associated with protective behaviours via direct effect (ß=0.45, 95% CI 0.19-0.69, P<0.001) and indirect effect through perceived risk (ß=0.18, 95% CI 0.07-0.31, P=0.002). Perceived risk was associated with protective behaviours (ß=0.28, 95% CI:0.11-0.44, P=0.002). A lower household income and ethnic minority were associated with protective behaviours. A lower education level and smokers were associated with lower knowledge of haze. A higher education and ethnic minority were associated with a lower perceived risk. Wearing of N95 masks was associated with other haze-related protective behaviours (ß=0.24, 95% CI 0.08-0.37, P=0.001). CONCLUSION: Knowledge was associated with protective behaviours, suggesting the importance of public education. Efforts should target those of lower education level and smokers. The wearing of N95 masks correlates with uptake of other protective behaviours.

MEF2C and HDAC5 regulate Egr1 and Arc genes to increase dendritic spine density and complexity in early enriched environment.

We investigated the effects of environmental enrichment during critical period of early postnatal life and how it interplays with the epigenome to affect experience-dependent visual cortical plasticity. Mice raised in an EE from birth to during CP have increased spine density and dendritic complexity in the visual cortex. EE upregulates synaptic plasticity genes, Arc and Egr1, and a transcription factor MEF2C. We also observed an increase in MEF2C binding to the promoters of Arc and Egr1. In addition, pups raised in EE show a reduction in HDAC5 and its binding to promoters of Mef2c, Arc and Egr1 genes. With an overexpression of Mef2c, neurite outgrowth increased in complexity. Our results suggest a possible underlying molecular mechanism of EE, acting through MEF2C and HDAC5, which drive Arc and Egr1. This could lead to the observed increased dendritic spine density and complexity induced by early EE.

Responding to the COVID-19 pandemic: The role of occupational health services in a tertiary hospital in Singapore.

With coronavirus disease 2019 declared a Public Health Emergency of International Concern on 30 January 2020, occupational health services in a tertiary hospital in Singapore stepped up via a three-pronged approach, namely, protection of individual staff, protection of staff workforce, and prevention of nosocomial spread so as to support business continuity plans. Despite the multiple new challenges brought by the COVID-19 pandemic, the hospital's occupational health services were able to adapt and keep all employees and patients safe with strong support from senior management and close collaboration with various departments.

Plasticity of DNA methylation, functional brain connectivity and efficiency in cognitive remediation for schizophrenia.

Cognitive remediation (CR) is predicated on principles of neuroplasticity, but the actual molecular and neurocircuitry changes underlying cognitive change in individuals with impaired neuroplastic processes is poorly understood. The present study examined epigenetic-neurocircuitry-behavioral outcome measures in schizophrenia, before and after participating in a CR program that targeted higher-order cognitive functions. Outcome measures included DNA methylation of genes central to synaptic plasticity (CpG sites of Reelin promoter and BDNF promoter) from buccal swabs, resting-state functional brain connectivity and topological network efficiency, and global scores of a cognitive battery from 35 inpatients in a rehabilitative ward (18 CR, 17 non-CR) with similar premorbid IQ to 15 healthy controls. Baseline group differences between healthy controls and schizophrenia, group-by-time effects of CR in schizophrenia, and associations between the outcome measures were tested. Baseline functional connectivity abnormalities within the frontal, fronto-temporal and fronto-parietal regions, and trending decreases in global efficiency, but not DNA methylation, were found in schizophrenia; the frontal and fronto-temporal connectivity, and global efficiency correlated with global cognitive performance across all individuals. Notably, CR resulted in differential changes in Reelin promoter CpG methylation levels, altered within-frontal and fronto-temporal functional connectivity, increasing global efficiency and improving cognitive performance in schizophrenia, when compared to non-CR. In the CR inpatients, positive associations between the micro to macro measures: Reelin methylation changes, higher global efficiency and improving global cognitive performance were found. Present findings provide a neurobiological insight into potential CR-led epigenetics-neurocircuitry modifications driving cognitive plasticity.

Skin cancer trends among Asians living in Singapore from 1968 to 2006.

BACKGROUND: The incidence rates of skin cancers in Caucasian populations are increasing. There is little information on skin cancer trends in Asians, who have distinctly different skin types. OBJECTIVE: We sought to study skin cancer incidence rates and time trends among the 3 Asian ethnic groups in Singapore. METHODS: We analyzed skin cancer data from the Singapore Cancer Registry from 1968 to 2006 using the Poisson regression model. RESULTS: There were 4044 reported cases of basal cell carcinoma, 2064 of squamous cell carcinoma, and 415 of melanoma. Overall skin cancer incidence rates increased from 2.9/100,000 in 1968 to 1972 to 8.4/100,000 in 1998 to 2002, declining to 7.4/100,000 in 2003 to 2006. Among older persons (> or = 60 years), basal cell carcinoma rates increased the most, by 18.9/100,000 in Chinese, 6.0/100,000 in Malays, and 4.1/100,000 in Indians from 1968 to 1972 to 2003 to 2006. Squamous cell carcinoma rates among those aged 60 years and older increased by 2.3/100,000 in Chinese and by 1/100,000 in Malays and Indians. Melanoma rates were constant for all 3 races. Skin cancer rates among the fairer-skinned Chinese were approximately 3 times higher than in Malays and Indians, who generally have darker complexions. LIMITATIONS: Although appropriate population denominators were used, lack of data from 2007 could have affected the results for the last time period, which comprised 4 instead of 5 years. CONCLUSION: Incidence rates of skin cancer in Singapore increased from 1968 to 2006, especially among older Chinese.

Bridging the gap between occupational medicine and family medicine.

Family medicine and occupational medicine share close similarities in their focus on disease prevention and health promotion. The opportunities for mutual learning and collaboration in patient care abound, with far-reaching implications on the standard of patient care that can be offered. Unfortunately, a gap exists between family medicine and occupational medicine in dayto- day practice as well as in continuing medical education. It is important that we actively seek to bridge this gap. The workforce constitutes a significant part of the population and thus the patient load of a typical primary healthcare practice. Moreover, with an ageing population and rising retirement age, we can expect that there will be an increasing number of health issues to be addressed among older working people. Both occupational and non-occupational factors are important in determining an individual's health. Thus, family physicians need to adequately understand occupational medicine and vice versa.

Histone modifications in the brain.

Chromatin remodelling, including histone modifications has been recognized to play a central role in the regulation of gene expression. Histone modifications are mostly based on studies in cell culture systems in vitro. Recent evidence suggests that histone modifications are actively involved in activity-dependent neural plasticity via regulation of critical gene transcription necessary for the biological process in vivo. We have reviewed here the recent works studied on long-term memory formation, visual cortical plasticity during the critical period and drug-induced status epilepticus to elucidate a role for histone modifications in these biological processes. All of the studies indicate that chromatin structure, including histone modifications is highly dynamic within the nervous system and suggest the possibility that chromatin structure itself might be recruited as a target of plasticity-associated signal transduction mechanisms.

Defining a critical period for inhibitory circuits within the somatosensory cortex.

Although experience-dependent changes in brain inhibitory circuits are thought to play a key role during the "critical period" of brain development, the nature and timing of these changes are poorly understood. We examined the role of sensory experience in sculpting an inhibitory circuit in the primary somatosensory cortex (S1) of mice by using optogenetics to map the connections between parvalbumin (PV) expressing interneurons and layer 2/3 pyramidal cells. Unilateral whisker deprivation decreased the strength and spatial range of inhibitory input provided to pyramidal neurons by PV interneurons in layers 2/3, 4 and 5. By varying the time when sensory input was removed, we determined that the critical period closes around postnatal day 14. This yields the first precise time course of critical period plasticity for an inhibitory circuit.

Awareness and Attitudes of Community-Dwelling Individuals in Singapore towards Participating in Advance Care Planning.

INTRODUCTION: Advance care planning (ACP) is an important aspect of end-of-life care that has been shown to improve patient autonomy in decision-making and reduce stress for surviving family members. Given the rapidly ageing population in Singapore, a greater emphasis on end-of-life care planning is needed. This study therefore sought to examine the awareness and attitudes of the general Singaporean community towards participating in ACP, which are not known hitherto. MATERIALS AND METHODS: A 24-item interviewer-administered questionnaire was constructed and administered via door-to-door survey amongst community-dwelling residents living in Housing and Development Board (HDB) flats across Singapore, selected via a two-stage stratified random sampling. RESULTS: Of the 406 completed surveys, 14.4% of respondents had heard of ACP (n = 58), mostly through the media (67.9%), from family and friends (21.4%) and healthcare providers (21.4%). Only 26.8% of those who had previously heard of ACP knew how to begin an ACP discussion and 12.5% of them had a prior ACP discussion. After education, the majority of respondents were willing to begin an ACP discussion (n = 236, 60.1%). Being of an older age, having a life threatening illness, and having more knowledge about ACP were significant factors associated with willingness to have an ACP discussion. Barriers included perceiving oneself as still healthy and preferring the family to make decisions instead. CONCLUSION: There is a low awareness but high expressed willingness to engage in an ACP discussion amongst the Singaporean community. More efforts are needed to educate the public about ACP, engage the family unit and correct the present misconceptions.

Can Peripheral Blood-Derived Gene Expressions Characterize Individuals at Ultra-high Risk for Psychosis?

The ultra-high risk (UHR) state was originally conceived to identify individuals at imminent risk of developing psychosis. Although recent studies have suggested that most individuals designated UHR do not, they constitute a distinctive group, exhibiting cognitive and functional impairments alongside multiple psychiatric morbidities. UHR characterization using molecular markers may improve understanding, provide novel insight into pathophysiology, and perhaps improve psychosis prediction reliability. Whole-blood gene expressions from 56 UHR subjects and 28 healthy controls are checked for existence of a consistent gene expression profile (signature) underlying UHR, across a variety of normalization and heterogeneity-removal techniques, including simple log-conversion, quantile normalization, gene fuzzy scoring (GFS), and surrogate variable analysis. During functional analysis, consistent and reproducible identification of important genes depends largely on how data are normalized. Normalization techniques that address sample heterogeneity are superior. The best performer, the unsupervised GFS, produced a strong and concise 12-gene signature, enriched for psychosis-associated genes. Importantly, when applied on random subsets of data, classifiers built with GFS are "meaningful" in the sense that the classifier models built using genes selected after other forms of normalization do not outperform random ones, but GFS-derived classifiers do. Data normalization can present highly disparate interpretations on biological data. Comparative analysis has shown that GFS is efficient at preserving signals while eliminating noise. Using this, we demonstrate confidently that the UHR designation is well correlated with a distinct blood-based gene signature.