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Fulltext Porphyromonas gingivalis: An Overview of Periodontopathic Pathogen below the Gum Line

How KY, Song KP, Chan KG

Front Microbiol, 2016;7:53.
PMID: 26903954 DOI: 10.3389/fmicb.2016.00053

Periodontal disease represents a group of oral inflammatory infections initiated by oral pathogens which exist as a complex biofilms on the tooth surface and cause destruction to tooth supporting tissues. The severity of this disease ranges from mild and reversible inflammation of the gingiva (gingivitis) to chronic destruction of connective tissues, the formation of periodontal pocket and ultimately result in loss of teeth. While human subgingival plaque harbors more than 500 bacterial species, considerable research has shown that Porphyromonas gingivalis, a Gram-negative anaerobic bacterium, is the major etiologic agent which contributes to chronic periodontitis. This black-pigmented bacterium produces a myriad of virulence factors that cause destruction to periodontal tissues either directly or indirectly by modulating the host inflammatory response. Here, this review provides an overview of P. gingivalis and how its virulence factors contribute to the pathogenesis with other microbiome consortium in oral cavity.
Early-life citalopram-induced impairments in sexual behavior and the role of androgen receptor

Soga T, Wong DW, Putteeraj M, Song KP, Parhar IS

Neuroscience, 2012 Dec 6;225:172-84.
PMID: 22960312 DOI: 10.1016/j.neuroscience.2012.08.061

Postnatal treatment with selective serotonin reuptake inhibitors (SSRIs) has been found to affect brain development and the regulation of reproduction in rodent models. The normal masculinization process in the brain requires a transient decrease in serotonin (5-HT) levels in the brain during the second postnatal week. Strict regulation of androgen receptor (AR) and gonadotropin-releasing hormone (GnRH) expression is important to control male reproductive activity. Therefore, this study was designed to examine the effects of a potent SSRI (citalopram) on male sexual behavior and expression levels of AR and GnRH in adult male mice receiving either vehicle or citalopram (10mg/kg) daily during postnatal days 8-21. The citalopram-treated male mice showed altered sexual behavior, specifically a significant reduction in the number of intromissions preceding ejaculation compared with the vehicle-treated mice. The citalopram-treated male mice displayed elevated anxiety-like behavior in an open field test and lower locomotor activity in their home cage during the subjective night. Although there was no change in GnRH and AR mRNA levels in the preoptic area (POA), quantified by real-time polymerase chain reaction, immunostained AR cell numbers in the medial POA were decreased in the citalopram-treated male mice. These results suggest that the early-life inhibition of 5-HT transporters alters the regulation of AR expression in the medial POA, likely causing decreased sexual behavior and altered home cage activity in the subjective night.
Characterization and identification of antimicrobial compounds from endophytic Fusarium incarnatum isolated from Cymbidium orchids

Chua RW, Song KP, Ting ASY

Int Microbiol, 2023 Nov 17.
PMID: 37975992 DOI: 10.1007/s10123-023-00442-1

This study characterized and identified the antimicrobial compounds from an endophytic fungus (Fusarium incarnatum (C4)) isolated from the orchid, Cymbidium sp. Chromatographic techniques were employed to separate the bioactive compounds from the crude extracts of F. incarnatum (C4). Following bio-guided fractionation, two fractionated extracts (fractions 1 and 2) of F. incarnatum (C4) exhibited antibacterial and antifungal activities against Bacillus cereus (MIC: 0.156 mg/mL) and Ganoderma boninense (MIC: 0.3125 mg/mL), respectively. The active fractions were discovered to comprise of a variety of bioactive compounds with pharmacological importance (alkaloids, flavonoids, phenolic compounds, terpenoids, peptides and fatty acids). Liquid chromatography mass-spectrometry (LCMS) analysis detected the presence of antibacterial (kanzonol N, rifaximin, linoleic acid (d4), cannabisativine, docosanedioic acid, and stearamide) and antifungal components (3-methyl-quinolin-2-ol, prothiocarb, kanzonol N, peganine, 5Z-tridecene, and tetronasin) in fractions 1 and 2, respectively, which may have contributed to the antimicrobial effects. Findings from this study highlighted the important potential of fungal endophytes from medicinal hosts as producers of antimicrobials and antibiotics.
Comparative analysis of antimicrobial compounds from endophytic Buergenerula spartinae from orchid

Chua RW, Song KP, Ting ASY

Antonie Van Leeuwenhoek, 2023 Oct;116(10):1057-1072.
PMID: 37597137 DOI: 10.1007/s10482-023-01870-9

A rare fungal endophyte, identified as Buergenerula spartinae (C28), was isolated from the roots of Cymbidium orchids and was characterised and evaluated for its antimicrobial activities. Bio-guided fractionation revealed 4 fractions from B. spartinae (C28) having antibacterial activities against at least one bacterial pathogen tested (Bacillus cereus and Staphylococcus aureus). However, inhibitory activities were absent against pathogenic fungi (Ganoderma boninense, Pythium ultimum and Fusarium solani). Fraction 2 and fraction 4 of B. spartinae (C28) exhibited potent antibacterial activities against S. aureus (MIC: 0.078 mg/mL) and B. cereus (MIC: 0.313 mg/mL), respectively. LCMS analysis revealed the presence of antibacterial agents and antibiotics in fraction 2 (benoxinate, pyropheophorbide A, (-)-ormosanine and N-undecylbenzenesulfonic acid) and fraction 4 (kaempferol 3-p-coumarate, 6-methoxy naphthalene acetic acid, levofuraltadone, hinokitiol glucoside, 3-α(S)-strictosidine, pyropheophorbide A, 5'-hydroxystreptomycin, kanzonol N and 3-butylidene-7-hydroxyphthalide), which may be responsible for the antibacterial activities observed. Most of the bioactive compounds profiled from the antibacterial fractions were discovered for the first time from endophytic isolates (i.e. from B. spartinae (C28)). Buergenerula spartinae (C28) from Cymbidium sp. is therefore, an untapped resource of bioactive compounds for potential applications in healthcare and commercial industries.
Antioxidant properties and L-asparaginase activities of endophytic fungi from Cymbidium orchids

Chua RW, Song KP, Ting ASY

Folia Microbiol (Praha), 2023 Nov 23.
PMID: 37995083 DOI: 10.1007/s12223-023-01112-5

This study profiled the various endophytic fungi isolated from the orchid Cymbidium sp. and their L-asparaginase production and antioxidant potential. The L-asparaginase production was first screened through qualitative plate screening then quantified by the Nesslerization method. The antioxidant potential was quantified via the 2,2-diphenyl-1-picrylhydrazyl assay. A total of 30 endophytic fungi were isolated and all fungal isolates exhibited various degrees of radical scavenging activities (45.28% to 76.4%). Isolate Lasiodiplodia theobromae (C11) had the highest antioxidant capacity, represented by the lowest IC50 value (5.75 mg/mL) and highest ascorbic acid equivalent antioxidant capacity value (12.17 mg/g). Additionally, 16 isolates produced L-asparaginase (53.33%), which includes primarily species of Fusarium proliferatum, Fusarium fujikuroi, Fusarium incarnatum, and Fusarium oxysporum. A new isolate has also been discovered from Cymbidium orchid, Buergenerula spartinae (C28), which showed the highest L-asparaginase activity (1.736 unit/mL). These findings supported the postulation that medicinal species of Orchidaceae such as Cymbidium sp. harbor endophytes that are producers of L-asparaginase and antioxidants with various potential applications.
Antioxidant and L-asparaginase activities of culturable endophytic fungi from ornamental Dendrobium orchids

Chua RW, Song KP, Ting ASY

Lett Appl Microbiol, 2024 Mar 01;77(3).
PMID: 37563083 DOI: 10.1093/lambio/ovad096

This study reports the antioxidant potential and L-asparaginase production of culturable fungal endophytes from Dendrobium orchids in Malaysia. Twenty-nine isolates were screened using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay to determine their free radical scavenging activities and antioxidant capacity (IC50 and AEAC). L-asparaginase production of fungal endophytes was detected by the qualitative plate assay, and the enzyme activities estimated via the Nesslerization method. All 29 endophytic isolates exhibited various degrees of radical scavenging activities (35.37%-77.23%), with Fusarium fujikuroi (D1) identified as having the highest antioxidant capacity (IC50 6.097 mg/mL) and the highest AEAC value (11.55 mg/g). For L-asparaginase production, the majority of the isolates (89.66%) showed positive results, especially among the culturable species of Fusarium, Trichoderma, and Daldinia. Most Fusarium spp. were able to produce L-asparaginase (80.77%), but the highest L-asparaginase activity was detected in Daldinia eschscholtzii (D14) with 2.128 units/mL. Results from this study highlighted the potential of endophytic fungi from medicinal orchids (Dendrobium sp.) as natural sources of bioactive compounds to be developed into novel antioxidants and anticancer drugs.
To reduce or to cease: A systematic review and meta-analysis of quantitative studies on self-regulation of driving

Ang BH, Oxley JA, Chen WS, Yap KK, Song KP, Lee SWH

J Safety Res, 2019 09;70:243-251.
PMID: 31848001 DOI: 10.1016/j.jsr.2019.07.004

INTRODUCTION: The ability to remain safe behind the wheels can become arduous with aging, yet important for sustaining local travel needs. This review aimed to explore safe mobility issues involving older adults and gain a broad understanding of older drivers' self-regulatory driving practices and motivators behind such behavioral changes, including strategies adopted to reduce or cease driving while maintaining safe mobility.
METHODS: A systematic literature search was performed on 11 online databases for quantitative studies describing self-regulation of driving amongst older adults aged 60 years and above from database inception until December 2018. Data were described narratively and, where possible, data were pooled using random-effects meta-analysis.
RESULTS: Of the 1556 studies identified, 54 studies met the inclusion criteria and 46 studies were included in the meta-analyses. All included studies examined car drivers only. Older adults who were single or female were found to be at higher odds of driving cessation. Physical fitness, mental health, social influence, and support systems received by older adults were important driving forces influencing mobility and adjustments made in their travel patterns.
CONCLUSIONS: Driving self-regulation amongst older adults is a multifaceted decision, impacting mobility and mental health. Therefore, future interventions and support systems should not only create opportunities for retaining mobility for those who have ceased driving, but also promote better psychological and social well-being for regulators and for those who are transitioning from driving to non-driving status. Practical applications: (a) Engage and educate older adults about self-regulation, including strategies that can be adopted and non-car mobility options available. (b) Expand the research focus to explore potential interactions of factors facilitating or hindering the transition process to develop a more comprehensive framework of self-regulation. (c) Encourage ongoing research to formulate, monitor, and evaluate the effectiveness of policies and interventions implemented. (d) Expand the research horizon to explore and understand the perspectives of older adults from developing countries.
Fulltext The influence of spouses and their driving roles in self-regulation: A qualitative exploration of driving reduction and cessation practices amongst married older adults

Ang BH, Oxley JA, Chen WS, Yap MKK, Song KP, Lee SWH

PLoS One, 2020;15(5):e0232795.
PMID: 32413053 DOI: 10.1371/journal.pone.0232795

INTRODUCTION: There is growing evidence to suggest the importance of self-regulatory practices amongst older adults to sustain mobility. However, the decision to self-regulate driving is a complex interplay between an individual's preference and the influence of their social networks including spouse. To our best knowledge, the influence of an older adult's spouse on their decisions during driving transition has not been explored.
MATERIALS AND METHODS: This qualitative descriptive study was conducted amongst married older adults aged 60 years and above. All interview responses were transcribed verbatim and examined using thematic approach and interpretative description method.
RESULTS: A total of 11 married couples were interviewed. Three major themes emerged: [1] Our roles in driving; [2] Challenges to continue driving; and, [3] Our driving strategies to ensure continued driving. Older couples adopted driving strategies and regulated their driving patterns to ensure they continued to drive safely. Male partners often took the active driving role as the principal drivers, while the females adopted a more passive role, including being the passenger to accompany the principal drivers or becoming the co-driver to help in navigation. Other coping strategies include sharing the driving duties as well as using public transportation or mixed mode transportation.
DISCUSSION: Our findings suggest spouse play a significant role in their partners' decision to self-regulate driving. This underscores a need to recognise the importance of interdependency amongst couples and its impact on their driving decisions and outcomes.