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Fulltext Should community pharmacies provide COVID-19 screening services?

Tan CS

Drugs Ther Perspect, 2020;36(10):463-465.
PMID: 32837196 DOI: 10.1007/s40267-020-00753-7
Prevalence of haemosporidia in Asian Glossy Starling with discovery of misbinding of Haemoproteus-specific primer to Plasmodium genera in Sarawak, Malaysian Borneo

Noni V, Tan CS

BMC Vet Res, 2023 Apr 20;19(1):66.
PMID: 37081458 DOI: 10.1186/s12917-023-03619-y

BACKGROUND: Plasmodium, Haemoproteus and Leucocytozoon are three mainly studied blood parasites known to cause malarial and pseudomalarial infections in avian worldwide. Although Sarawak is a biodiversity hotspot, molecular data on blood parasite diversity in birds are absent. The objective of the study is to determine the prevalence of blood parasite in Asian Glossy Starlings (AGS), an urban bird with high population density in Sarawak and to elucidate the phylogenetic relationship with other blood parasite.
METHODS: Twenty-nine carcasses of juvenile AGS that were succumbed to death due to window collision were collected around the vicinity of Universiti Malaysia Sarawak. Nested-multiplex and nested PCR targeting the Cytochrome B gene were used to detect Plasmodium and Haemoproteus, and Leucocytozoon respectively. Two primer sets were used for Haemoproteus detection to increase detection sensitivity, with one being a genus-specific primer.
RESULTS: Fourteen samples (prevalence rate: 48.28%) were found positive for avian Plasmodium. Phylogenetic analysis divided our sequences into five lineages, pFANTAIL01, pCOLL4, pACCBAD01, pALPSIS01 and pALPSIS02, with two lineages being novel. No Haemoproteus and Leucocytozoon was found in this study. However, Haemoproteus-specific primer used amplified our Plasmodium samples, making the primer non-specific to Haemoproteus only.
CONCLUSION: This is the first blood parasite detection study on AGS using carcasses and blood clot as sample source in Sarawak. Due to the scarcity of longer sequences from regions with high genetic plasticity, usage of genus-specific primers should be validated with sequencing to ensure correct prevalence interpretation.
High-titred neutralizing antibodies to human enterovirus 71 preferentially bind to the N-terminal portion of the capsid protein VP1

Tan CS, Cardosa MJ

Arch Virol, 2007;152(6):1069-73.
PMID: 17318736

Human enterovirus 71 has emerged as an important pathogen of children in the Asia Pacific region, and it may be important to consider the development of a vaccine against this virus. Human cord serum was used as a source of neutralizing antibodies to determine whether the N- or C-terminal half of the VP1 capsid protein was more likely to harbour neutralizing determinants. Cord sera from 205 individuals were tested for neutralizing antibodies against human enterovirus 71 in an indirect ELISA against recombinant VP1 antigen as well as the N- and C-terminal portions of VP1 antigen. High-titred human neutralizing antibodies were significantly more reactive with the N-terminal half of VP1 than weak or negative sera. The N-terminal half of human enterovirus 71 is likely to have important neutralizing antibody determinants and should be investigated further in vaccine development efforts.
A comparative study of cobra (Naja) venom enzymes

Tan NH, Tan CS

Comp. Biochem. Physiol., B, 1988;90(4):745-50.
PMID: 2854766

1. The L-amino acid oxidase, hyaluronidase, alkaline phosphomonoesterase, protease, phosphodiesterase, acetylcholinesterase, phospholipase A and 5'-nucleotidase activities of 47 samples of venoms from all the six species of cobra (Naja), including five subspecies of Naja naja, were examined. 2. The results demonstrated interspecific differences in the venom contents of phospholipase A, acetylcholinesterase, hyaluronidase and phosphodiesterase. These differences in venom enzyme contents can be used for the differentiation of species of the genus Naja. 3. Thus, our results revealed a correlation between the enzyme composition of venom and the taxonomic status of the snake at the species level for the genus Naja.
Acidimetric assay for phospholipase A using egg yolk suspension as substrate

Tan NH, Tan CS

Anal Biochem, 1988 May 1;170(2):282-8.
PMID: 3394929

A convenient acidimetric assay for phospholipase A using egg yolk suspension as substrate has been developed. The substrate mixture consists of 1 part egg yolk, 1 part 8.1 mM sodium deoxycholate, and 1 part 18 mM calcium chloride. Phospholipase A activity is measured by following the initial rate of pH change, which is linear between pH 8.0 and 7.75 and is proportional to enzyme concentration over a wide range. The assay is highly reproducible, with a coefficient of variation of 3%, and as sensitive as most established assays for phospholipase A. The assay uses inexpensive and easily available substrate and is simple to perform. It is particularly useful for monitoring phospholipase A activity in chromatography fractions.
The enzymatic activities and lethal toxins of Trimeresurus wagleri (speckled pit viper) venom

Tan NH, Tan CS

Toxicon, 1989;27(3):349-57.
PMID: 2543103

Trimeresurus wagleri (speckled pit viper) venom exhibited the usual set of enzyme activities occurring in pit viper venoms but the content of alkaline phosphomonoesterase was unusually high, whereas the proportions of protease and arginine ester hydrolase were very low. The venom also exhibited weak thrombin-like activity but did not exhibit hemorrhagic or anticoagulant activity. Analysis of the Sephadex G-200 gel filtration fractions of the venom indicated that the lethal fraction was a low mol.wt protein, and that fractions exhibiting phosphodiesterase, phosphomonoesterase, arginine ester hydrolase, thrombin-like enzyme, L-amino acid oxidase and phospholipase A activities were not lethal. Two lethal toxins, designated as wagleri toxins 1 and 2, were isolated from the venom using Sephadex G-50 gel filtration chromatography followed by SP-Sephadex C-25 ion exchange chromatography. The mol.wts of the two toxins were 8900 by gel filtration. The LD50 (i.v.) values in mice for wagleri toxins 1 and 2 are 0.17 microgram/g and 0.19 microgram/g, respectively.
Partial purification of acetylcholinesterase from the venom of the shore pit viper (Trimeresurus purpureomaculatus)

Tan NH, Tan CS

Toxicon, 1988;26(5):505-8.
PMID: 3188057

Trimeresurus purpureomaculatus venom acetylcholinesterase has been partially purified by Sephadex G-200 gel filtration chromatography and DEAE Sephacel ion exchange chromatography. The enzyme has a mol. wt of 58,600. It was strongly inhibited by physostigmine salicylate and edrophonium chloride and exhibited substrate inhibition at high substrate concentration. The content of acetylcholinesterase in Trimeresurus purpureomaculatus venom was estimated to be much less than 0.3%.
Enzymatic activities of Malayan cobra (Naja naja sputatrix) venoms

Tan NH, Tan CS

Toxicon, 1987;25(11):1249-53.
PMID: 3433296

The enzymatic activities of four samples of Malayan cobra venom were investigated. There was significant variation in the contents of L-amino acid oxidase, alkaline phosphomonoesterase, acetylcholinesterase, phospholipase A, 5'-nucleotidase and hyaluronidase. The phosphodiesterase content was, however, constant. Storage of the lyophilized venom powder at 25 degrees C for 1 month did not affect the enzymatic activities. The venom enzymatic activities were generally also stable at 4 degrees C in 0.85% saline solution. After incubation at 37 degrees C for 39 days in 0.85% saline solution, the venom still retained considerable amounts of enzymatic activities. SP-Sephadex C-25 ion-exchange chromatography of the venom showed that the phospholipase A, L-amino acid oxidase, 5'-nucleotidase, phosphodiesterase and alkaline phosphomonoesterase exist in multiple forms.
Fractionation of Sumatran pit viper (Trimeresurus sumatranus sumatranus) venom by DEAE-Sephacel ion exchange chromatography and some biological properties of the fractions

Tan NH, Tan CS

Toxicon, 1989;27(6):697-702.
PMID: 2749766

Sumatran pit viper (Trimeresurus sumatranus sumatranus) venom was fractionated by DEAE-Sephacel ion exchange chromatography into seven fractions. Fractions 4, 5 and 6 were lethal to mice and exhibited strong hemorrhagic activity, as well as some enzymatic activities. Fraction 6 also exhibited potent anticoagulant and thrombin-like activities. Analysis of the biological and enzymatic properties of the three lethal fractions suggests that the major lethal component of fractions 4 and 5 may be the hemorrhagic principle, and that the lethality of fraction 6 may be due to the hemorrhagic principle and/or the anticoagulant principle.
Mechanism of vasorelaxation induced by 3'-hydroxy-5,6,7,4'-tetramethoxyflavone in the rats aortic ring assay

Tan CS, Yam MF

Naunyn Schmiedebergs Arch Pharmacol, 2018 06;391(6):561-569.
PMID: 29552696 DOI: 10.1007/s00210-018-1481-9

Previous studies have demonstrated that 3'-hydroxy-5,6,7,4'-tetramethoxyflavone (TMF) content in Orthosiphon stamineus fractions correlate with its vasorelaxation activity. Even with the availability of previous studies, there is still very little information on the vasorelaxation effect of TMF, and few scientific studies have been carried out. Therefore, the present study was designed to investigate the vasorelaxation activity and mechanism of action of the TMF. The vasorelaxation activity and the underlying mechanisms of TMF were evaluated on thoracic aortic rings isolated from Sprague Dawley rats. TMF caused the relaxation of aortic rings with endothelium pre-contracted with phenylephrine. However, the vasorelaxant effect of TMF was significantly decreased in PE-primed endothelium-denuded and potassium chloride-primed endothelium-intact aortic rings. In the presence of Nω-nitro-L-arginine methyl ester, methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, indomethacin, tetraethylammonium, 4-aminopyridine, barium chloride, atropine and propranolol, the relaxation stimulated by TMF was significantly reduced. TMF was also found to reduce Ca2+ release from sarcoplasmic reticulum (via IP3R) and block calcium channels (VOCC). The present study demonstrates the vasorelaxant effect of TMF involves NO/sGC/cGMP and prostacyclin pathways, calcium and potassium channels and muscarinic and beta-adrenergic receptors.
A comparative study of the enzymatic and toxic properties of venoms of the Asian lance-headed pit viper (Genus Trimeresurus)

Tan NH, Armugam A, Tan CS

Comp. Biochem. Physiol., B, 1989;93(4):757-62.
PMID: 2553329

1. The lethalities, anticoagulant effects, hermorrhagic, thrombin-like enzyme, hyaluronidase, protease, arginine ester hydrolase, 5'-nucleotidase, L-amino acid oxidase, alkaline phosphomonoesterase, phosphodiesterase and phospholipase A activities of twenty-three samples of venoms from twelve species of Asian lance-headed pit vipers (genus Trimeresurus) were examined. 2. The results indicate that notwithstanding individual variations in venom properties, the differences in biological properties of the Trimeresurus venoms can be used for the differentiation of venoms from different species of Trimeresurus. 3. The results also suggest that differences in the biological properties of snake venoms are useful parameters in the classification of snake species. 4. Our results indicate that venoms from the species T. okinavensis exhibited biological properties markedly different from other Trimeresurus venoms examined. This observation supports the recently proposed reclassification of T. okinavensis as a member of the genus Ovophis, rather than the genus Trimeresurus.
Evaluation of different promoters driving the GFP reporter gene and selected target tissues for particle bombardment of Dendrobium Sonia 17

Tee CS, Marziah M, Tan CS, Abdullah MP

Plant Cell Rep, 2003 Jan;21(5):452-8.
PMID: 12789448

Three different morphological callus types, identified as type A, B and C, and tips of in vitro inflorescences were used as target tissues for genetic transformation. Five different DNA plasmids carrying a synthetic green fluorescent protein (gfp) gene driven by different promoters, CaMV 35S, HBT, and Ubi1 were tested for the genetic transformation of Dendrobium Sonia 17. 35S-sgfp-TYG-nos (p35S) with the CaMV 35S promoter showed the highest GFP transient expression rate, while the HBT and Ubi1 promoters showed a relatively lower expression rate in all of the target tissues tested. The highest number of GFP-expressing cells was observed on day 2 post-bombardment, and the number declined gradually over the course of the next 2 weeks. Type A and B callus were found to be the best potential target tissues for genetic transformation.
COVID-19: Critical Role of Angiotensin 1-7 in ACE2 Modulation

Tan CS, Yeoh SF, Long CM

Ann Acad Med Singap, 2020 06;49(6):398-400.
PMID: 32712639
Vasorelaxant effect of sinensetin via the NO/sGC/cGMP pathway and potassium and calcium channels

Yam MF, Tan CS, Shibao R

Hypertens Res, 2018 Oct;41(10):787-797.
PMID: 30111856 DOI: 10.1038/s41440-018-0083-8

Orthosiphon stamineus Benth. (Lambiaceae) is an important traditional plant for the treatment of hypertension. Previous studies have demonstrated that the sinensetin content in O. stamineus is correlated with its vasorelaxant activity. However, there is still very little information regarding the vasorelaxant effect of sinensetin due to a lack of scientific studies. Therefore, the present study was designed to investigate the underlying mechanism of action of sinensetin in vasorelaxation using an in vitro precontraction aortic ring assay. The changes in the tension of the aortic ring preparations were recorded using a force-displacement transducer and the PowerLab system. The mechanisms of the vasorelaxant effect of sinensetin were determined in the presence of antagonists. Sinensetin caused relaxation of the aortic ring precontracted with PE in the presence and absence of the endothelium and with potassium chloride in endothelium-intact aortic rings. In the presence of Nω-nitro-L-arginine methyl ester (nitric oxide synthase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), ODQ (selective soluble guanylate cyclase inhibitor), indomethacin (a nonselective cyclooxygenase inhibitor), tetraethylammonium (nonselective calcium activator K+ channel blocker), 4-aminopyridine (voltage-dependent K+ channel blocker), barium chloride (inwardly rectifying Kir channel blocker), glibenclamide (nonspecific ATP-sensitive K+ channel blocker), atropine (muscarinic receptor blocker), or propranolol (β-adrenergic receptor blocker), the relaxation stimulated by sinensetin was significantly reduced. Sinensetin was also active in reducing Ca2+ release from the sarcoplasmic reticulum (via IP3R) and in blocking calcium channels (VOCC). The present study demonstrates the vasorelaxant effect of sinensetin, which involves the NO/sGC/cGMP and indomethacin pathways, calcium and potassium channels, and muscarinic and beta-adrenergic receptors.
The lethal and biochemical properties of Bungarus candidus (Malayan krait) venom and venom fractions

Tan NH, Poh CH, Tan CS

Toxicon, 1989;27(9):1065-70.
PMID: 2799837

Bungarus candidus venom exhibited high hyaluronidase, acetylcholinesterase and phospholipase A activities; low proteinase, 5'-nucleotidase, alkaline phosphomonoesterase and phosphodiesterase activities and moderately high L-amino acid oxidase activity. SP-Sephadex C-50 ion exchange chromatographic fractionation of the venom and Sephadex G-50 chromatography of the major lethal venom fractions indicate that the venom contains at least two highly lethal, basic phospholipases A with LD50 (i.v.) values of 0.02 micrograms/g (F6A) and 0.18 micrograms/g (F4A), respectively; as well as two polypeptide toxins with LD50 (i.v.) values of 0.17 micrograms/g and 0.83 micrograms/g, respectively. The major lethal toxin is the basic lethal phospholipase A, F6A, which accounts for approximately 13% of the venom protein and has a mol. wt of 21,000.
Extraversion and happiness: The mediating role of social support and hope

Tan CS, Low SK, Viapude GN

Psych J, 2018 Sep;7(3):133-143.
PMID: 30015375 DOI: 10.1002/pchj.220

Studies have found that extraversion enhances happiness indirectly through social support. However, it is unclear how social support may be connected to happiness. On the basis of a literature review, we hypothesize that individual hope may play an important role in the relationship between social support and happiness. Using a serial mediation model, the present study attempted to investigate the hypothetical mediating role of hope in the relationship between extraversion and happiness and between social support and happiness. Analysis of responses of 360 undergraduate students showed that extraversion, social support, and hope were significantly linked with happiness. Moreover, hope was found to mediate the linkage of extraversion and happiness and of social support and happiness. The results also supported the view that extraversion enhances happiness through social support and then hope (serial mediating effect). Lastly, the serial mediating effect was found to be significantly lower than the other two indirect effects. The findings offer insights into the effect of social support on happiness and extend the understanding of the relationship between extraversion and happiness.
Fulltext The Executive Skills Questionnaire-Revised: Adaptation and Psychometric Properties in the Working Context of Malaysia

Nasir H, Tan CS, Pheh KS

Int J Environ Res Public Health, 2021 08 26;18(17).
PMID: 34501571 DOI: 10.3390/ijerph18178978

Executive functions (EFs) are a set of high-level cognitive and behavioral monitoring skills that are important to employees' work performance. The 25-item Executive Skills Questionnaire-Revised (ESQ-R) measures executive dysfunction in five dimensions (e.g., emotional regulation). Nevertheless, the usability of this newly developed scale for employees remains unclear. The present study evaluated the psychometric properties of the adopted ESQ-R for working adults in Malaysia. A total of 325 employees responded to an online survey consisted of the ESQ-R, Executive Function Index (EFI), self-rated creativity scale (SRCS), and 9-item Utretch Work Engagement Scale (UWES-9) and Employee Well-being Scale. Several CFAs were conducted to compare three competing models. While all models showed a good fit, the 5-factor second-order model that is in line with the theoretical structure is preferable. The ESQ-R showed excellent internal consistency. Moreover, the ESQ-R score was negatively correlated with EFI, creativity, and UWES-9 scores, supporting the convergent, discriminant, and concurrent validity. The ESQ-R score also explained incremental variance in well-being above and beyond scores of the UWES-9 and SRCS. Taken together, the ESQ-R is a useful tool for assessing employees' executive dysfunction and suggesting intervention programs helping employees with deficits in EFs.
Severe midface and maxillary hypoplasia in non-cleft and non-syndromic patients: A 2-stage surgical strategy using distraction osteogenesis and orthognathic surgery

Tan CS, Hariri F, Hassan MK

J Stomatol Oral Maxillofac Surg, 2023 Jul 04.
PMID: 37406736 DOI: 10.1016/j.jormas.2023.101552

Severe midface and maxillary hypoplasia can have an impact on an individual, either on the appearance, functions or psychologically. Based on literature review, severe maxillary hypoplasia with more than 25.0 mm reverse overjet in non-cleft and non-syndromic patients is very rare. It is more often seen in cleft lip and palate and syndromic patients. When the magnitude of correction exceeds the limit of what a single orthognathic surgery can achieve, multiple surgeries would be required, involving different surgical techniques. The authors report two rare cases of non-syndromic nor cleft severe hypoplastic midface and maxilla with 26.0 mm and 27.0 mm reverse overjet, respectively, treated with 2-stage surgery involving maxillary distraction osteogenesis and orthognathic surgery. Both cases recorded reasonably clinical and functional outcomes. The significance of both surgical interventions is further discussed.
Fulltext Critical state of sand matrix soils

Marto A, Tan CS, Makhtar AM, Kung Leong T

ScientificWorldJournal, 2014;2014:290207.
PMID: 24757417 DOI: 10.1155/2014/290207

The Critical State Soil Mechanic (CSSM) is a globally recognised framework while the critical states for sand and clay are both well established. Nevertheless, the development of the critical state of sand matrix soils is lacking. This paper discusses the development of critical state lines and corresponding critical state parameters for the investigated material, sand matrix soils using sand-kaolin mixtures. The output of this paper can be used as an interpretation framework for the research on liquefaction susceptibility of sand matrix soils in the future. The strain controlled triaxial test apparatus was used to provide the monotonic loading onto the reconstituted soil specimens. All tested soils were subjected to isotropic consolidation and sheared under undrained condition until critical state was ascertain. Based on the results of 32 test specimens, the critical state lines for eight different sand matrix soils were developed together with the corresponding values of critical state parameters, M, λ, and Γ. The range of the value of M, λ, and Γ is 0.803-0.998, 0.144-0.248, and 1.727-2.279, respectively. These values are comparable to the critical state parameters of river sand and kaolin clay. However, the relationship between fines percentages and these critical state parameters is too scattered to be correlated.
Immunogenic properties of recombinant ectodomain of Newcastle disease virus hemagglutinin-neuraminidase protein expressed in Escherichia coli

Wong SK, Tan WS, Omar AR, Tan CS, Yusoff K

Acta Virol., 2009;53(1):35-41.
PMID: 19301949

Hemagglutinin-neuraminidase (HN) protein of Newcastle disease virus (NDV) plays a vital role in the viral infectivity, host immunity, and disease diagnosis. A portion of the HN gene encoding the ectodomain (nt 142-1739) was cloned and expressed in Escherichia coli yielding an insoluble HN protein and a soluble NusA-HN protein containing N-utilization substance A (NusA) fusion component. Both recombinant proteins were purified and used for immunization of chickens. The recombinant HN protein induced higher antibody titers as compared to the recombinant NusA-HN protein. These antibodies were able to react in immunoblot analysis with the corresponding recombinant proteins as well as with the HN protein of NDV.

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