Displaying publications 1 - 20 of 140 in total

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  1. Tan NH, Yahya A, Adeeb N
    J Obstet Gynaecol (Tokyo 1995), 1995 Aug;21(4):313-8.
    PMID: 8775898
    OBJECTIVE: To evaluate the risk factors of spontaneous abortion.

    METHODS: A case-control study was conducted by interviewing 350 women who were admitted to the university gynaecological unit for spontaneous abortion and 350 women who delivered normally at the university obstetric unit. Odds ratios, as the estimators of relative risks, were calculated.

    RESULTS: The relative risk for spontaneous abortion among women in the age-group 30 to 39 years was 1.61 and among women above 40 years of age was 3.68 when compared to those below 30 years of age. In relation to career women, the relative risk of spontaneous abortion for housewives was 0.45. Ethnic group, parity, subfertility, previous induced abortion, ectopic pregnancy, contraception and menarcheal age did not influence the risk of spontaneous abortion.

    CONCLUSION: Increasing age and a woman's career are significant risk factors of spontaneous abortion.

  2. Tan NH, Fung SY, Sim SM, Marinello E, Guerranti R, Aguiyi JC
    J Ethnopharmacol, 2009 Jun 22;123(2):356-8.
    PMID: 19429384 DOI: 10.1016/j.jep.2009.03.025
    The seed, leaf and root of Mucuna pruriens have been used in traditional medicine for treatments of various diseases. In Nigeria, the seed is used as oral prophylactics for snakebite.
  3. Fung SY, Tan NH, Liew SH, Sim SM, Aguiyi JC
    Trop Biomed, 2009 Apr;26(1):80-4.
    PMID: 19696731
    Seed of Mucuna pruriens (Velvet beans) has been prescribed by traditional medicine practitioners in Nigeria as a prophylactic oral antisnake remedy. In the present studies, we investigated the protective effects of M. pruriens seed extract (MPE) against histopathological changes induced by intravenous injection of Naja sputatrix (Malayan cobra) venom in rats pretreated with the seed extract. Examination by light microscope revealed that the venom induced histopathological changes in heart and blood vessels in liver, but no effect on brain, lung, kidney and spleen. The induced changes were prevented by pretreatment of the rats with MPE. Our results suggest that MPE pretreatment protects rat heart and liver blood vessels against cobra venom-induced damages.
  4. Fung SY, Tan NH, Sim SM, Marinello E, Guerranti R, Aguiyi JC
    Indian J Exp Biol, 2011 Apr;49(4):254-9.
    PMID: 21614888
    Mucuna pruriens has been used by native Nigerians as a prophylactic for snakebite. The protective effects of M. pruriens seed extract (MPE) were investigated against the pharmacological actions of N. sputatrix (Javan spitting cobra) venom in rats. The results showed that MPE-pretreatment protected against cardiorespiratory and, to a lesser extent, neuromuscular depressant effects of N. sputatrix venom. These may be explained at least in part by the neutralisation of the cobra venom toxins by anti-MPE antibodies elicited by the MPE pretreatment.
  5. Fung SY, Tan NH, Sim SM, Aguiyi JC
    PMID: 21785646 DOI: 10.1155/2012/486390
    Mucuna pruriens Linn. (velvet bean) has been used by native Nigerians as a prophylactic for snakebite. Rats pretreated with M. pruriens seed extract (MPE) have been shown to protect against the lethal and cardiovascular depressant effects of Naja sputatrix (Javan spitting cobra) venoms, and the protective effect involved immunological neutralization of the venom toxins. To investigate further the mechanism of the protective effect of MPE pretreatment against cobra venom toxicity, the actions of Naja sputatrix venom on spontaneously beating rat atria and aortic rings isolated from both MPE pretreated and untreated rats were studied. Our results showed that the MPE pretreatment conferred protection against cobra venom-induced depression of atrial contractility and atrial rate in the isolated atrial preparations, but it had no effect on the venom-induced contractile response of aortic ring preparation. These observations suggested that the protective effect of MPE pretreatment against cobra venom toxicity involves a direct protective action of MPE on the heart function, in addition to the known immunological neutralization mechanism, and that the protective effect does not involve action on blood vessel contraction. The results also suggest that M. pruriens seed may contain novel cardioprotective agent with potential therapeutic value.
  6. Tan NH, Armugam A
    Toxicon, 1990;28(10):1193-8.
    PMID: 2264068
    The in vivo interactions between alpha-neurotoxin, cardiotoxin and two phospholipases A2 (sputa-phospholipase A2-1 and 3) isolated from Malayan cobra venom were assessed by examining the effects of simultaneous injection of sub-LD50 dose of one toxin on (i) i.v. LD50 S of the other toxins in mice; and (ii) mean survival times of mice injected with lethal doses of the other toxins. While LD50 measurements did not reveal any interaction between the toxins in vivo, survival time measurements suggest a synergy between the neurotoxin and sputa-phospholipase A2-1 and between sputa-phospholipase A2-1 and sputa-phospholipase A2-3. Our results also suggest that both sputa-phospholipases A2 interfere with the lethal action of the cardiotoxin, resulting in prolongation of the mean survival time of mice injected with a lethal dose of cardiotoxin. The patterns of in vivo interactions between phospholipase A2 and other venom toxins appear to depend on the nature and mode of pharmacological action of the phospholipase A2.
  7. Tan NH, Arunmozhiarasi A
    Biochem. Int., 1989 Oct;19(4):803-10.
    PMID: 2619749
    Malayan cobra (Naja naja sputatrix) venom was found to exhibit an in vitro anticoagulant activity that was much stronger than most common cobra (genus Naja) venoms. The most potent anticoagulants of the venom are two lethal phospholipase A2 enzymes with pI's of 6.15 and 6.20, respectively. The anticoagulant activity of the venom is due to the synergistic effect of the venom phospholipase A2 enzymes and polypeptide anticoagulants. Bromophenacylation of the two phospholipase A2 enzymes reduced their enzymatic activity with a concomitant drop in both the lethal and anticoagulant activities.
  8. Tan NH, Arunmozhiarasi A
    Biochem. Int., 1989 Apr;18(4):785-92.
    PMID: 2764979
    An acidic, lethal phospholipase Az was purified to electrophoretic homogeneity from the venom of the Malayan cobra (Naja naja sputatrix). The enzyme has an isoelectric point of 5.58, a molecular weight of 12000, and a medium lethal dose (LD50) of 0.86 micrograms/g in mice by intravenous injection. The enzyme also exhibited weak anticoagulant and edema-forming activities. The amino acid composition of the enzyme is similar to those of other cobra venom phospholipases Az.
  9. Yap HY, Muria-Gonzalez MJ, Kong BH, Stubbs KA, Tan CS, Ng ST, et al.
    Microb Cell Fact, 2017 Jun 12;16(1):103.
    PMID: 28606152 DOI: 10.1186/s12934-017-0713-x
    BACKGROUND: Genome mining facilitated by heterologous systems is an emerging approach to access the chemical diversity encoded in basidiomycete genomes. In this study, three sesquiterpene synthase genes, GME3634, GME3638, and GME9210, which were highly expressed in the sclerotium of the medicinal mushroom Lignosus rhinocerotis, were cloned and heterologously expressed in a yeast system.

    RESULTS: Metabolite profile analysis of the yeast culture extracts by GC-MS showed the production of several sesquiterpene alcohols (C15H26O), including cadinols and germacrene D-4-ol as major products. Other detected sesquiterpenes include selina-6-en-4-ol, β-elemene, β-cubebene, and cedrene. Two purified major compounds namely (+)-torreyol and α-cadinol synthesised by GME3638 and GME3634 respectively, are stereoisomers and their chemical structures were confirmed by 1H and 13C NMR. Phylogenetic analysis revealed that GME3638 and GME3634 are a pair of orthologues, and are grouped together with terpene synthases that synthesise cadinenes and related sesquiterpenes. (+)-Torreyol and α-cadinol were tested against a panel of human cancer cell lines and the latter was found to exhibit selective potent cytotoxicity in breast adenocarcinoma cells (MCF7) with IC50 value of 3.5 ± 0.58 μg/ml while α-cadinol is less active (IC50 = 18.0 ± 3.27 μg/ml).

    CONCLUSIONS: This demonstrates that yeast-based genome mining, guided by transcriptomics, is a promising approach for uncovering bioactive compounds from medicinal mushrooms.

  10. Tan NH, Ponnudurai G, Chung MC
    Toxicon, 1997 Jun;35(6):979-84.
    PMID: 9241791
    The proteolytic specificity of rhodostoxin, the major hemorrhagin from Calloselasma rhodostoma (Malayan pit viper) venom was investigated using oxidized B-chain of bovine insulin as substrate. Six peptide bonds were cleaved: Ser9-Hist10, His10-Leu11, Ala14-Leu15, Tyr16-Leu17, Gly20-Glu21 and Phe24-Phe25. Deglycosylated rhodostoxin, however, cleaved primarily at Arg22-Gly23.
  11. Kong BH, Teoh KH, Tan NH, Tan CS, Ng ST, Fung SY
    PeerJ, 2020;8:e9650.
    PMID: 32832273 DOI: 10.7717/peerj.9650
    Background: Lignosus tigris, a recently discovered species of the unique Lignosus family, has been traditionally used by the indigenous communities in Peninsular Malaysia to treat various ailments and as an alternative medicine for cancer treatment. The L. tigris cultivar sclerotia (Ligno TG-K) was found to contain numerous bioactive compounds with beneficial biomedicinal properties and the sclerotial extract exhibited potent antioxidant activity. However, the anticancer property of the Ligno TG-K including in vitro and in vivo antitumor effects as well as its anticancer active compounds and the mechanisms has yet to be investigated.

    Methods: The cytotoxicity of the Ligno TG-K against human breast (MCF7), prostate (PC3) and lung (A549) adenocarcinoma cell lines was evaluated using MTT cytotoxicity assay. The cytotoxic mechanisms of the active high molecular weight proteins (HMWp) fraction were investigated through detection of caspases activity and apoptotic-related proteins expression by Western blotting. The in vivo antitumor activity of the isolated HMWp was examined using MCF7 mouse xenograft model. Shotgun LC-MS/MS analysis was performed to identify the proteins in the HMWp.

    Results and Discussion: Cold water extract of the sclerotia inhibited proliferation of MCF7, A549 and PC3 cells with IC50 ranged from 28.9 to 95.0 µg/mL. Bioassay guided fractionation of the extract revealed that HMWp exhibited selective cytotoxicity against MCF7 cells via induction of cellular apoptosis by the activation of extrinsic and intrinsic signaling pathways. HMWp activated expression of caspase-8 and -9 enzymes, and pro-apoptotic Bax protein whilst inhibiting expression of tumor survivor protein, Bcl-2. HMWp induced tumor-cell apoptosis and suppressed growth of tumor in MCF-7 xenograft mice. Lectins, serine proteases, RNase Gf29 and a 230NA deoxyribonuclease are the major cytotoxic proteins that accounted for 55.93% of the HMWp.

    Conclusion: The findings from this study provided scientific evidences to support the traditional use of the L. tigris sclerotia for treatment of breast cancer. Several cytotoxic proteins with high abundance have been identified in the HMWp of the sclerotial extract and these proteins have potential to be developed into new anticancer agents or as adjunct cancer therapy.

  12. Yap MK, Tan NH, Sim SM, Fung SY
    Toxicon, 2013 Jun;68:18-23.
    PMID: 23537711 DOI: 10.1016/j.toxicon.2013.02.017
    Existing protocols for antivenom treatment of snake envenomations are generally not well optimized due partly to inadequate knowledge of the toxicokinetics of venoms. The toxicokinetics of Naja sputatrix (Javan spitting cobra) venom was investigated following intravenous and intramuscular injections of the venom into rabbits using double-sandwich ELISA. The toxicokinetics of the venom injected intravenously fitted a two-compartment model. When the venom was injected intramuscularly, the serum concentration-time profile exhibited a more complex absorption and/or distribution pattern. Nevertheless, the terminal half-life, volume of distribution by area and systemic clearance of the venom injected intramuscularly were not significantly different (p > 0.05) from that of the venom injected intravenously. The systemic bioavailability of the venom antigens injected by intramuscular route was 41.7%. Our toxicokinetic finding is consistent with other reports, and may indicate that some cobra venom toxins have high affinity for the tissues at the site of injection. Our results suggest that the intramuscular route of administration doesn't significantly alter the toxicokinetics of N. sputatrix venom although it significantly reduces the systemic bioavailability of the venom.
  13. Yap HYY, Tan NH, Ng ST, Tan CS, Fung SY
    PeerJ, 2018;6:e4940.
    PMID: 29888137 DOI: 10.7717/peerj.4940
    Background: The highly valued medicinal tiger milk mushroom (also known as Lignosus rhinocerus) has the ability to cure numerous ailments. Its anticancer activities are well explored, and recently a partially purified cytotoxic protein fraction termed F5 from the mushroom's sclerotial cold water extract consisting mainly of fungal serine proteases was found to exhibit potent selective cytotoxicity against a human breast adenocarcinoma cell line (MCF7) with IC50 value of 3.00 μg/ml. However, characterization of its cell death-inducing activity has yet to be established.

    Methods: The mechanism involved in the cytotoxic activities of F5 against MCF7 cells was elucidated by flow cytometry-based apoptosis detection, caspases activity measurement, and expression profiling of apoptosis markers by western blotting. Molecular attributes of F5 were further mined from L. rhinocerus's published genome and transcriptome for future exploration.

    Results and Discussion: Apoptosis induction in MCF7 cells by F5 may involve a cross-talk between the extrinsic and intrinsic apoptotic pathways with upregulation of caspase-8 and -9 activities and a marked decrease of Bcl-2. On the other hand, the levels of pro-apoptotic Bax, BID, and cleaved BID were increased accompanied by observable actin cleavage. At gene level, F5 composed of three predicted non-synonymous single nucleotide polymorphisms (T > C) and an alternative 5' splice site.

    Conclusions: Findings from this study provide an advanced framework for further investigations on cancer therapeutics development from L. rhinocerus.

  14. Cheong PCH, Yong YS, Fatima A, Ng ST, Tan CS, Kong BH, et al.
    IUBMB Life, 2019 10;71(10):1579-1594.
    PMID: 31190445 DOI: 10.1002/iub.2101
    A lectin gene from the Tiger Milk Mushroom Lignosus rhinocerus TM02® was successfully cloned and expressed via vector pET28a in Escherichia coli BL21(DE3). The recombinant lectin, Rhinocelectin, with a predicted molecular mass of 22.8 kDa, was overexpressed in water-soluble form without signal peptide and purified via native affinity chromatography Ni-NTA agarose. Blast protein analysis indicated the lectin to be homologous to jacalin-related plant lectin. In its native form, Rhinocelectin exists as a homo-tetramer predicted with four chains of identical proteins consisting of 11 beta-sheet structures with only one alpha-helix structure. The antiproliferative activity of the Rhinocelectin against human cancer cell lines was concentration dependent and selective. The IC50 values against triple negative breast cancer cell lines MDA-MB-231 and breast cancer MCF-7 are 36.52 ± 13.55 μg mL-1 and 53.11 ± 22.30 μg mL-1 , respectively. Rhinocelectin is only mildly cytotoxic against the corresponding human nontumorigenic breast cell line 184B5 with IC50 value at 142.19 ± 36.34 μg mL-1 . The IC50 against human lung cancer cell line A549 cells is 46.14 ± 7.42 μg mL-1 while against nontumorigenic lung cell line NL20 is 41.33 ± 7.43 μg mL-1 . The standard anticancer drug, Doxorubicin exhibited IC50 values mostly below 1 μg mL-1 for the cell lines tested. Flow cytometry analysis showed the treated breast cancer cells were arrested at G0/G1 phase and apoptosis induced. Rhinocelectin agglutinated rat and rabbit erythrocytes at a minimal concentration of 3.125 μg mL-1 and 6.250 μg mL-1 , respectively.
  15. Lee SS, Tan NH, Pailoor J, Fung SY
    Front Pharmacol, 2017;8:594.
    PMID: 28919858 DOI: 10.3389/fphar.2017.00594
    Twenty-eight days subacute toxicity studies performed in rats using sclerotial powder of Lignosus cameronensis cultivar was conducted to assess its safety for consumption prior to other scientific investigations on its medicinal benefits, nutraceutical or pharmaceutical application of the mushroom. The study was conducted at 250, 500, and 1000 mg/kg sclerotial powder of L. cameronensis cultivar (n = 5 for each respective dose, on both male and female groups) while control groups received only distilled water. At the end of the study (29th day), the animals were sacrificed followed by blood and organs collection for analysis. Subacute toxicity studies done shows that sclerotial powder of L. cameronensis cultivar at 250, 500, and 1000 mg/kg did not induce treatment related changes on behavioral patterns, gross physical appearance, growth pattern, body weight gain, values of hematological and clinical biochemical panels as well as histopathological findings on kidney, spleen, heart, lung and liver of the experimental rats. The no-observed-adverse-effect level dose for sclerotial powder of L. cameronensis cultivar in 28-days sub-acute toxicity study is determined to be 1000 mg/kg.
  16. Yap HY, Tan NH, Ng ST, Tan CS, Fung SY
    Front Pharmacol, 2018;9:103.
    PMID: 29491836 DOI: 10.3389/fphar.2018.00103
    Naturally occurring anti-glycation compounds have drawn much interest in recent years as they show potential in reducing or preventing the risk of chronic complications for diabetic patients. In this study, annotation of the genome-transcriptome data from tiger milk mushroom (Lignosus rhinocerus, syn.Lignosus rhinocerotis) to PlantCyc enzymes database identified transcripts that are related to anti-diabetic properties, and these include genes that are involved in carotenoid and abscisic acid biosynthesis as well as genes that code for glyoxalase I, catalase-peroxidases, and superoxide dismutases. The existence of these genes suggests thatL. rhinocerusmay contain bioactive compound(s) with anti-glycation properties that can be exploited for management of diabetic complications. A medium-molecular-weight (MMW) fraction which was obtained from a combination of cold water extraction and Sephadex®G-50 (fine) gel filtration chromatography ofL. rhinocerussclerotia powder was demonstrated to exhibit potent anti-glycation activity. The fraction specifically inhibited the formation of N𝜀-(carboxymethyl)lysine, pentosidine, and other advanced glycation end-product (AGE) structures in a human serum albumin-glucose system, with an IC50value of 0.001 mg/ml, almost 520 times lower than that of the positive control, aminoguanidine hydrochloride (IC50= 0.52 mg/ml). Its ability to suppress protein glycation may be partly associated with its strong superoxide anion radical scavenging activity (10.16 ± 0.12 mmol TE/g). Our results suggest that the MMW fraction ofL. rhinocerusshows potential to be developed into a potent glycation inhibitor for preventing AGE-mediated diabetic complications.
  17. Tan CH, Tan NH, Sim SM, Fung SY, Gnanathasan CA
    Acta Trop, 2012 Jun;122(3):267-75.
    PMID: 22322247 DOI: 10.1016/j.actatropica.2012.01.016
    Envenomation by hump-nosed pit viper (Hypnale hypnale, Hh) in Sri Lanka has caused significant morbidity and mortality, attributed to 35% of total venomous snakebites. In Southwestern India (Kerala), H. hypnale was increasingly identified as a dangerous and common source of envenomation, second to the Russell's viper but ahead of the cobra bites. Unfortunately, there is still no specific antivenom to date. This study aims to investigate the immunological properties of the venom and to assess the feasibility of specific Hh antivenom production as well as the development of a diagnostic assay. Hh venom elicited satisfactory titers of anti-Hh IgG in rabbits after 3rd immunization. The anti-Hh IgG, isolated with caprylic acid precipitation method, was effective in neutralizing the venom lethality (potency=48 LD(50) per ml IgG) as well as its procoagulant, hemorrhagic and necrotic effects, indicating the possibility to produce the specific antivenom using the common immunization regime. Cross-reactivity studies using indirect ELISA showed that anti-Hh IgG cross-reacted extensively with several Asiatic crotalid venoms, particularly that of Calloselasma rhodostoma (73.6%), presumably due to the presence of venom antigens common to both snakes. Levels of immunological cross-reactivity were vastly reduced with double-sandwich ELISA. Further work demonstrated that the assay was able to distinguish and quantify venoms of H. hypnale, Daboia russelii and Echis carinatus sinhaleyus (three common local viperid) used to spike human sera at various concentrations. The assay hence may be a useful investigating tool for diagnosing biting species and studying the time course profile of venom concentrations in blood.
  18. Tan CH, Tan NH, Sim SM, Fung SY, Gnanathasan CA
    Toxicon, 2015 Jan;93:164-70.
    PMID: 25451538 DOI: 10.1016/j.toxicon.2014.11.231
    The hump-nosed pit viper, Hypanle hypnale, contributes to snakebite mortality and morbidity in Sri Lanka. Studies showed that the venom is hemotoxic and nephrotoxic, with some biochemical and antigenic properties similar to the venom of Calloselasma rhodostoma (Malayan pit viper). To further characterize the complexity composition of the venom, we investigated the proteome of a pooled venom sample from >10 Sri Lankan H. hypnale with reverse-phase high performance liquid chromatography (rp-HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and peptide sequencing (tandem mass-spectrometry and/or N-terminal sequencing). The findings ascertained that two phospholipase A2 subtypes (E6-PLA2, W6-PLA2) dominate the toxin composition by 40.1%, followed by snake venom metalloproteases (36.9%), l-amino acid oxidase (11.9%), C-type lectins (5.5%), serine proteases (3.3%) and others (2.3%). The presence of the major toxins correlates with the venom's major pathogenic effects, indicating these to be the principal target toxins for antivenom neutralization. This study supports the previous finding of PLA2 dominance in the venom but diverges from the view that H. hypnale venom has low expression of large enzymatic toxins. The knowledge of the composition and abundance of toxins is essential to elucidate the pathophysiology of H. hypnale envenomation and to optimize antivenom formulation in the future.
  19. Tan CH, Tan NH, Sim SM, Fung SY, Jayalakshmi P, Gnanathasan CA
    Toxicon, 2012 Dec 1;60(7):1259-62.
    PMID: 22975088 DOI: 10.1016/j.toxicon.2012.08.012
    Mice experimentally envenomed with Hypnale hypnale venom (1× and 1.5×LD₅₀) developed acute kidney injury (AKI) principally characterized by raised blood urea and creatinine. Prolonged blood clotting time and hemorrhage in lungs implied bleeding tendency. Pallor noted in most renal cortices was suggestive of renal ischemia secondary to consumptive coagulopathy. Intravenous infusion of Hemato polyvalent antivenom following experimental envenoming effectively prevented death and AKI in all mice, supporting its potential therapeutic use in envenoming cases.
  20. Tan NH, Hj MN
    Toxicon, 1989;27(6):689-95.
    PMID: 2749765
    Some enzymatic activities and toxic properties of four samples of Ophiophagus hannah (king cobra) venom were investigated. There is little intraspecific variation in enzyme contents, protein composition and toxic properties of the venom. The venom does not exhibit hemolytic or edema-inducing activity but is characterized by an exceptionally high alkaline phosphomonoesterase activity. DEAE-Sephacel ion exchange chromatography and Sephadex G-75 gel filtration chromatography of the venom indicate that the major lethal toxins are the low mol.wt, non-enzymatic basic proteins. Venom fractions exhibiting high enzymatic activities apparently do not play an important role in the lethality in mice of Ophiophagus hannah venom.
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