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Fulltext Molecular genetic approaches for the conservation of endangered orchids

Rodrigues, K. F., Yeoh, K. A., Kumar, S. V.

Buletin Persatuan Genetik Malaysia, 2006;12(1):13-14.
MyJurnal

Geographically isolated populations of endemic orchids have evolved and adapted to an existence within specifi c ecological niches. These populations are highly susceptible to anthropogenic
infl uences on their microhabitats. The primary objective of conservation programs is the restoration of endangered populations to their ecologically sustainable levels, and the fi rst stage in the process of conservation involves estimation of molecular diversity at the level of the population. The approach described in this article involves the application of RAPD, Microsatellites and Chloroplast DNA markers for the characterization of the genetic structure of Paphiopedilum rothschildianum and Phalaenopsis gigantea, two endangered and endemic orchids of Sabah. This study has isolated a total of 96 microsatellite loci in P. rothschildianum and P. gigantea, 42 specifi c primer pairs have been designed for amplifi cation of microsatellite loci and are currently being applied to screen the breeding pools. The Chloroplast DNA regions amplifi ed by the primer pairs trnH-psbA and trnL-trnF exhibit distinct polymorphisms and can be used to establish phylogenetic
relationships. The ability of microsatellite loci to cross-amplify selected varieties of orchids has been determined. The molecular markers developed will be applied to estimate population diversity
levels and to formulate long-term management strategies for the conservation of endangered species of orchids of Sabah.
Malaysian child psychiatric practice: a pragmatic and rational approach

Yeoh KL, Ong SB

Aust N Z J Psychiatry, 1982 Jun;16(2):61-6.
PMID: 6957184

A pragmatic and rational approach to the management of five child psychiatric cases in Malaysia is briefly reviewed. The significance of sociocultural factors in treating these cases within the context of a rapidly developing plural society is emphasized. The implications of overemphasis on educational and material achievements are noted.
Proceedings: Cultural conflict and transition: epidemic hysteria and social sanction

Teoh JI, Yeoh KL

Aust N Z J Psychiatry, 1973 Dec;7(4):283-95.
PMID: 4522945
A first-principles comparative study of lithium, sodium, potassium and calcium storage in two-dimensional Mg2C

Chu YZ, Yeoh KH, Chew KH

J Phys Condens Matter, 2021 Feb 17;33(7):075002.
PMID: 33152714 DOI: 10.1088/1361-648X/abc807

Two-dimensional (2D) materials have recently emerged as potential candidates for high-capacity lithium-ion batteries anode materials because of their compelling physicochemical and structural properties. In the present study, we use first-principles calculations to investigate the performance of 2D Mg2C as anode materials for Li, Na, K and Ca-ions batteries. The calculated average open-circuit voltage are 0.37, 0.50, 0.03 and 0.06 eV vs Li, Na, K, Ca. No significant structural deformations are observed on the 2D Mg2C upon the adsorption of Li, Na, K or Ca and the metallic characteristic of the 2D Mg2C is retained. The metallic behaviour of both pristine and adsorbed Mg2C ensures the desirable electric conductivity, implying the advantages of 2D Mg2C for batteries. The Na and K atoms show an extremely high diffusivity on the 2D Mg2C with a low energy barrier of 0.08 and 0.04 eV respectively, which is about an order of magnitude smaller than that of Li atom. For the Na and K atoms, the theoretical storage capacity can reach up to 1770 mAh g-1, nearly two times that of the Li atom of 885 mAh g-1. Our study suggests that the 2D Mg2C is a promising anode material which offers a fast ion diffusion and high storage capacity.
Sequence analysis and gene expression of putative oil palm chitinase and chitinase-like proteins in response to colonization of Ganoderma boninense and Trichoderma harzianum

Yeoh KA, Othman A, Meon S, Abdullah F, Ho CL

Mol Biol Rep, 2013 Jan;40(1):147-58.
PMID: 23065213 DOI: 10.1007/s11033-012-2043-8

Chitinases are glycosyl hydrolases that cleave the β-1,4-glycosidic linkages between N-acetylglucosamine residues in chitin which is a major component of fungal cell wall. Plant chitinases hydrolyze fungal chitin to chitin oligosaccharides that serve as elicitors of plant defense system against fungal pathogens. However, plants synthesize many chitinase isozymes and some of them are not pathogenesis-related. In this study, three full-length cDNA sequences encoding a putative chitinase (EgChit3-1) and two chitinase-like proteins (EgChit1-1 and EgChit5-1) have been cloned from oil palm (Elaeis guineensis) by polymerase chain reaction (PCR). The abundance of these transcripts in the roots and leaves of oil palm seedlings treated with Ganoderma boninense (a fungal pathogen) or Trichoderma harzianum (an avirulent symbiont), and a combination of both fungi at 3, 6 and 12 weeks post infection were profiled by real time quantitative reverse-transcription (qRT)-PCR. Our findings showed that the gene expression of EgChit3-1 increased significantly in the roots of oil palm seedlings treated with either G. boninense or T. harzianum and a combination of both; whereas the gene expression of EgChit1-1 in the treated roots of oil palm seedlings was not significantly higher compared to those of the untreated oil palm roots. The gene expression of EgChit5-1 was only higher in the roots of oil palm seedlings treated with T. harzianum compared to those of the untreated oil palm roots. In addition, the gene expression of EgChit1-1 and EgChit3-1 showed a significantly higher gene expression in the leaf samples of oil palm seedlings treated with either G. boninense or T. harzianum.
Evaluation of nasal cavity by acoustic rhinometry in Chinese, Malay and Indian ethnic groups

Huang ZL, Wang DY, Zhang PC, Dong F, Yeoh KH

Acta Otolaryngol, 2001 Oct;121(7):844-8.
PMID: 11718250

Acoustic rhinometry (AR) evaluates the geometry of the nasal cavity by measuring the minimum cross-sectional area (MCA) and nasal volume (V) by means of acoustic reflection. Understanding the normal and pathologic conditions of the internal nasal cavity using AR is important in the diagnosis of structural abnormalities in patients. The aim of this study was to investigate the normal range of AR parameters in healthy volunteers from three ethnic groups in Singapore: Chinese, Malay and Indian. We also attempted to evaluate the role of these measurements in the documentation of structural abnormalities in the nose. A total of 189 Singaporeans, aged > or = 18 years, were recruited from a nationwide survey study. They comprised 83 Chinese, 35 Malays and 71 Indians. Eighty-nine subjects had a rhinoscopically normal nose (Group 1), 77 had significant septal deviation (Group 2) and 23 had inferior turbinate hypertrophy (Group 3). AR was performed to measure the MCA at the anterior 1-5 cm from the nostril and the volume (V) between points at the nostril and 5 cm into the nose. A mean MCA (mMCA; equal to (L + R)/2) and a total volume (Vt; equal to L + R) were then calculated for each subject, where L and R refer to the measurements made for the left and right nostrils, respectively. The results showed that there was no statistically significant difference in mMCA (p = 0.80) and Vt (p = 0.60) among the three ethnic subgroups of Group 1. Statistically significant differences were found only between Groups 1 and 3 (p < 0.001 for both mMCA and Vt) and between Groups 2 and 3 (p = 0.001 for mMCA and p = 0.013 for Vt). Although there was no significant difference between Groups 1 and 2, significant differences in MCA (p = 0.001) and V (p = 0.040) were found between the narrower sides (smaller volume) and the wider sides in Group 2, indicating volume compensation between the nasal cavities. In conclusion, our study demonstrates that there is no significant difference in the normal range of AR measurements among Chinese, Malay and Indian ethnic groups. AR is able to determine the structural abnormality of the internal nasal cavity caused by septal deviation and inferior turbinate hypertrophy.
Fulltext The outcome of abdominal aortic aneurysm repair in northern Malaysia

Lakhwani MN, Yeoh KCB, Gooi BH, Lim SK

Med J Malaysia, 2003 Aug;58(3):420-8.
PMID: 14750383

A prospective study of all infrarenal abdominal aortic aneurysm (AAA) repairs both as electives and emergencies in Penang between January 1997 to December 2000 is presented. The objectives of the study were to determine the age, gender, racial distribution of the patients, the incidence, and risk factors and to summarize treatments undertaken and discuss the outcome. Among the races, the Malays were the most common presenting with infrarenal AAA. The mean age of patients operated was 68.5 years. Males were more commonly affected compared to females (12:1). Most infrarenal AAA repairs were performed as emergency operations, 33 cases (61.1%) compared to electives, 21 cases (38.9%). Total survival was 70.3% (elective 85.7%; emergency 57.6%). Mortality rate was 31.5% and the primary reason is the lack of operating time available for urgent operation and for treatment of concurrent disease states. Mycotic aneurysm with its triad of abdominal pain, fever and abdominal mass resulted in a significantly higher mortality (46.6%). Ninety six percent of the infrarenal AAA had transverse diameter greater than 6 cm. Morphologically 90.7% were fusiform AAA rather than saccular aneurysm (9.3%). Pulmonary complications (35.2%) were more common than cardiac complications (11.1%) possibly related to the urgent nature of the operation, smoking or history of pulmonary tuberculosis. Bleeding (14.8%) was the most common cause of mortality in ruptured mycotic infrarenal AAA.
Infectiousness of HBsAg carriers in Malaysia

Ton SH, Yeoh KS, Lim WC, Noriah R, Cheong SK, Thanaletchimy N

J Trop Med Hyg, 1995 Aug;98(4):277-80.
PMID: 7636926

HBV-DNA were analysed in 330 HBsAg-positive carriers in Malaysia by dot-blot hybridization and polymerase chain reaction. Seventy-three (22.12%) were positive for the virus. Of these, 65 (89%) were males and 8 (11%) were females. Statistically, there was no significant difference (P = 0.13). No significant decline in HBV-DNA with age in the Malay and Chinese males was observed (P = 0.2). Prevalence of HBV-DNA was higher in the Chinese carriers than in the Malay carriers for most age groups in both sexes. Sixty-one HBV-DNA-positive carriers were also positive for HBeAg. However, three individuals were positive only for anti-HBe, one was positive for both HBeAg and anti-HBe, and eight were negative for both HBeAg and anti-HBe. Fifty-seven were positive for HBeAg but negative for HBV-DNA. No relation was observed between raised alanine aminotransaminase and aspartate aminotransaminase levels and the presence of HBV-DNA (P = 0.4).
A first-principles study of two-dimensional NbSe2H/g-ZnO van der Waals heterostructures as a water splitting photocatalyst

Yeoh KH, Chew KH, Yoon TL, Chang YHR, Ong DS

Phys Chem Chem Phys, 2021 Nov 03;23(42):24222-24232.
PMID: 34668497 DOI: 10.1039/d1cp03565g

Based on first-principles calculations, we propose a new two-dimensional (2D) van der Waals (vdW) heterostructure that can be used as a photocatalyst for water splitting. The heterostructure consists of vertically stacked 2D NbSe2H and graphene-like ZnO (g-ZnO). Depending on the stacking orders, we identified two configurations that have high binding energies with an energy band gap of >2.6 eV. These 2D systems form a type-II heterostructure which enables the separation of photoexcited electrons and holes. The presence of a strong electrostatic potential difference across the 2D NbSe2H and g-ZnO interface is expected to suppress the electron-hole recombination leading to an enhancement in the efficiency of the photocatalytic activity. Our study also shows that the 2D NbSe2H/g-ZnO vdW heterostructure has good thermodynamic properties for water splitting. Furthermore, the optical absorption of the 2D NbSe2H/g-ZnO vdW heterostructure extends into the visible light region. Our results suggest that the 2D NbSe2H/g-ZnO vdW heterostructure is a promising photocatalytic material for water splitting.
The effect of vacancy defects on the electromechanical properties of monolayer NiTe2 from first principles calculations

Yeoh KH, Chew KH, Chang YHR, Yoon TL, Ong DS

Phys Chem Chem Phys, 2022 Dec 05.
PMID: 36468660 DOI: 10.1039/d2cp05102h

The electromechanical properties of monolayer 1-T NiTe2 under charge actuation were investigated using first-principles density functional theory (DFT) calculations. Monolayer 1-T NiTe2 in its pristine form has a work area density per cycle of up to 5.38 MJ m-3 nm upon charge injection and it can generate a strain and a stress of 1.51% and 0.96 N m-1, respectively. We found that defects in the form of vacancies can be exploited to modulate the electromechanical properties of this material. The presence of Ni-vacancies can further enhance the generated stress by 22.5%. On the other hand, with Te-vacancies, it is possible to improve the work area density per cycle by at least 145% and also to enhance the induced strain from 1.51% to 2.92%. The effect of charge polarity on the contraction and expansion of monolayer 1T-NiTe2 was investigated. Due to its excellent environmental stability and good electromechanical properties, monolayer NiTe2 is considered to be a promising electrode material for electroactive polymer (EAP) based actuators.
Computational Screening of a Single-Atom Catalyst Supported by Monolayer Nb2S2C for Oxygen Reduction Reaction

Yeoh KH, Chang YHR, Chew KH, Jiang J, Yoon TL, Ong DS, et al.

Langmuir, 2024 Feb 08.
PMID: 38329924 DOI: 10.1021/acs.langmuir.3c03188

The search for high-performance catalysts to improve the catalytic activity for an oxygen reduction reaction (ORR) is crucial for developing a proton exchange membrane fuel cell. Using the first-principles method, we have performed computational screening on a series of transition metal (TM) atoms embedded in monolayer Nb2S2C to enhance the ORR activity. Through the scaling relationship and volcano plot, our results reveal that the introduction of a single Ni or Rh atom through substitutional doping into monolayer Nb2S2C yields promising ORR catalysts with low overpotentials of 0.52 and 0.42 V, respectively. These doped atoms remain intact on the monolayer Nb2S2C even at elevated temperatures. Importantly, the catalytic activity of the Nb2S2C doped with a TM atom can be effectively correlated with an intrinsic descriptor, which can be computed based on the number of d orbital electrons and the electronegativity of TM and O atoms.
Racial differences in Helicobacter pylori seroprevalence in Singapore: correlation with differences in peptic ulcer frequency

Kang JY, Yeoh KG, Ho KY, Guan R, Lim TP, Quak SH, et al.

J Gastroenterol Hepatol, 1997 Oct;12(9-10):655-9.
PMID: 9407329

The aim of this study was to determine, first, whether racial differences exist in the seroprevalence of Helicobacter pylori infection in Singapore, and second, whether these differences correlate with racial differences in peptic ulcer frequency. A commercial serological test for immunoglobulin (Ig)G antibody to H. pylori which was 90% sensitive and 83% specific in our population was used to screen 403 adult blood donors of Chinese, Malay and Indian origin, aged between 15-60 years. Serum specimens from 84 paediatric patients admitted to the Paediatrics Department, National University of Singapore, with non-gastroenterological illnesses were also tested. In all three races, seroprevalence of H. pylori increased with age. Indians have the highest prevalence of infection followed by Chinese and Malays. Peptic ulcer prevalences are known to be highest in Chinese, followed by Indians and Malays. The Malays have the lowest prevalence of H. pylori and peptic ulcer among the three races in Singapore. Indians have a higher prevalence of H. pylori antibodies but a lower frequency of peptic ulcer than the Chinese. Racial differences in peptic ulcer frequency between Chinese and Indians are not explained by the prevalence of H. pylori infection; other environmental or genetic factors may be involved.
Hepatitis B virus infection among children of hepatitis B surface antigen positive mothers in a Malaysian hospital

Chan WK, Yeoh KY, Lim CY, Lai SM, Lee JL, Leow AHR, et al.

Med J Malaysia, 2018 06;73(3):137-140.
PMID: 29962496 MyJurnal

INTRODUCTION: There have been no published data on the transmission of hepatitis B virus (HBV) infection among children of hepatitis B surface antigen (HBsAg) positive mothers in Malaysia.
METHODS: This is a cross-sectional study of all the children of HBsAg-positive mothers who delivered at the University of Malaya Medical Centre between 1993 and 2000.
RESULTS: A total of 60 HBsAg-positive mothers and their 154 children participated in the study. HBsAg was detected in four children (2.6%) while IgG antibody to the hepatitis B core antigen (anti-HBc IgG) was detected in seventeen children (11.0%). The mother's age at childbirth was significantly lower in the children with detectable HBsAg (22.5±6.1 years vs. 29.7±4.5 years, p=0.043) and anti-HBc IgG (26.6±6.1 years vs. 30.0±4.3 years, p=0.004). Children born in the 1980s were significantly more likely to have detectable HBsAg (18.8% vs. 0.7%, p=0.004) and anti-HBc IgG (37.5% vs. 8.0%, p=0.000) compared with those born later. All children with detectable HBsAg were born via spontaneous vaginal delivery, and hepatitis B immunoglobulin was either not given or the administration status was unknown. The majority of mothers with chronic HBV infection (70.4%) were not under any regular follow-up for their chronic HBV infection and the main reason was the lack of awareness of the need to do so (47.4%).
CONCLUSION: Transmission of HBV infection among children of HBsAg-positive mothers in Malaysia is low. However, attention needs to be given to the high rate of HBsAgpositive mothers who are not on any regular follow-up.
Fulltext Exploring the natural products chemical space through a molecular search to discover potential inhibitors that target the hypoxia-inducible factor (HIF) prolyl hydroxylase domain (PHD)

Sayaf AM, Ullah Khalid S, Hameed JA, Alshammari A, Khan A, Mohammad A, et al.

Front Pharmacol, 2023;14:1202128.
PMID: 37670941 DOI: 10.3389/fphar.2023.1202128

Introduction: Hypoxia-inducible factor (HIF) prolyl hydroxylase domain (PHD) enzymes are major therapeutic targets of anemia and ischemic/hypoxia diseases. To overcome safety issues, liver failure, and problems associated with on-/off-targets, natural products due to their novel and unique structures offer promising alternatives as drug targets. Methods: In the current study, the Marine Natural Products, North African, South African, East African, and North-East African chemical space was explored for HIF-PHD inhibitors discovery through molecular search, and the final hits were validated using molecular simulation and free energy calculation approaches. Results: Our results revealed that CMNPD13808 with a docking score of -8.690 kcal/mol, CID15081178 with a docking score of -8.027 kcal/mol, CID71496944 with a docking score of -8.48 kcal/mol and CID11821407 with a docking score of -7.78 kcal/mol possess stronger activity than the control N-[(4-hydroxy-8-iodoisoquinolin-3-yl)carbonyl]glycine, 4HG (-6.87 kcal/mol). Interaction analysis revealed that the target compounds interact with Gln239, Tyr310, Tyr329, Arg383 and Trp389 residues, and chelate the active site iron in a bidentate manner in PHD2. Molecular simulation revealed that these target hits robustly block the PHD2 active site by demonstrating stable dynamics. Furthermore, the half-life of the Arg383 hydrogen bond with the target ligands, which is an important factor for PHD2 inhibition, remained almost constant in all the complexes during the simulation. Finally, the total binding free energy of each complex was calculated as CMNPD13808-PHD2 -72.91 kcal/mol, CID15081178-PHD2 -65.55 kcal/mol, CID71496944-PHD2 -68.47 kcal/mol, and CID11821407-PHD2 -62.06 kcal/mol, respectively. Conclusion: The results show the compounds possess good activity in contrast to the control drug (4HG) and need further in vitro and in vivo validation for possible usage as potential drugs against HIF-PHD2-associated diseases.
Fulltext Ministry of health clinical practice guidelines: cancer screening

Lee HP, Chew CT, Consigliere DT, Heng D, Huang DT, Khoo J, et al.

Singapore Med J, 2010 Feb;51(2):170-3; quiz 174-5.
PMID: 20358158

The Ministry of Health publishes national clinical practice guidelines to provide doctors and patients in Singapore with evidence-based guidance on managing important medical conditions. This article reproduces the introduction and executive summary (with key recommendations from the guidelines) from the Ministry of Health clinical practice guidelines on cancer screening, for the information of readers of the Singapore Medical Journal. Chapters and page numbers mentioned in the reproduced extract refer to the full text of the guidelines, which are available from the Ministry of Health website (http://www.moh.gov. sg/mohcorp/publications.aspx?id=24018). The recommendations should be used with reference to the full text of the guidelines. Following this article are multiple choice questions based on the full text of the guidelines.
An updated Asia Pacific Consensus Recommendations on colorectal cancer screening

Sung JJ, Ng SC, Chan FK, Chiu HM, Kim HS, Matsuda T, et al.

Gut, 2015 Jan;64(1):121-32.
PMID: 24647008 DOI: 10.1136/gutjnl-2013-306503

OBJECTIVE: Since the publication of the first Asia Pacific Consensus on Colorectal Cancer (CRC) in 2008, there are substantial advancements in the science and experience of implementing CRC screening. The Asia Pacific Working Group aimed to provide an updated set of consensus recommendations.
DESIGN: Members from 14 Asian regions gathered to seek consensus using other national and international guidelines, and recent relevant literature published from 2008 to 2013. A modified Delphi process was adopted to develop the statements.
RESULTS: Age range for CRC screening is defined as 50-75 years. Advancing age, male, family history of CRC, smoking and obesity are confirmed risk factors for CRC and advanced neoplasia. A risk-stratified scoring system is recommended for selecting high-risk patients for colonoscopy. Quantitative faecal immunochemical test (FIT) instead of guaiac-based faecal occult blood test (gFOBT) is preferred for average-risk subjects. Ancillary methods in colonoscopy, with the exception of chromoendoscopy, have not proven to be superior to high-definition white light endoscopy in identifying adenoma. Quality of colonoscopy should be upheld and quality assurance programme should be in place to audit every aspects of CRC screening. Serrated adenoma is recognised as a risk for interval cancer. There is no consensus on the recruitment of trained endoscopy nurses for CRC screening.
CONCLUSIONS: Based on recent data on CRC screening, an updated list of recommendations on CRC screening is prepared. These consensus statements will further enhance the implementation of CRC screening in the Asia Pacific region.

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