Displaying publications 1 - 20 of 410 in total

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  1. Tan SK, Tang ATH, Leung WK, Zwahlen RA
    J Stomatol Oral Maxillofac Surg, 2018 Dec;119(6):461-468.
    PMID: 30099221 DOI: 10.1016/j.jormas.2018.07.004
    PURPOSE: To investigate short- and long-term post-surgical three-dimensional changes of pharyngeal airway morphology and hyoid bone position in dento-skeletal class II deformity patients after two-jaw surgery with segmentation.

    METHODS: Relations between skeletal movement, hyoid bone position and three-dimensional pharyngeal airway changes were retrospectively analyzed on pre- and post-surgical CBCTs in dento-skeletal class II patients who underwent orthognathic two-jaw surgery with segmentation.

    RESULTS: While long-term significant reductions in length (P= 0.003), surface area (P= 0.042) and volume (P= 0.004) were found in the nasopharynx, the highly significant increases in oropharyngeal airway length, surface area, volume and the minimal cross-sectional area (P 

  2. Mariana A, Santana Raj AS, Ho TM, Tan SN, Zuhaizam H
    Trop Biomed, 2008 Dec;25(3):217-24.
    PMID: 19287360
    Scanning electron microscope (SEM) images of two dust mites, Sturnophagoides brasiliensis and Sturnophagoides halterophilus, are presented to provide an improved visualization of the taxonomic characters of these mites. Sturnophagoides halterophilus can be differentiated from S. brasiliensis by their expanded genu and femur of leg I. The differences in morphology of male and female S. brasiliensis are also discussed.
  3. Wills C, Wang B, Fang S, Wang Y, Jin Y, Lutz J, et al.
    PLoS Comput Biol, 2021 Apr;17(4):e1008853.
    PMID: 33914731 DOI: 10.1371/journal.pcbi.1008853
    When Darwin visited the Galapagos archipelago, he observed that, in spite of the islands' physical similarity, members of species that had dispersed to them recently were beginning to diverge from each other. He postulated that these divergences must have resulted primarily from interactions with sets of other species that had also diverged across these otherwise similar islands. By extrapolation, if Darwin is correct, such complex interactions must be driving species divergences across all ecosystems. However, many current general ecological theories that predict observed distributions of species in ecosystems do not take the details of between-species interactions into account. Here we quantify, in sixteen forest diversity plots (FDPs) worldwide, highly significant negative density-dependent (NDD) components of both conspecific and heterospecific between-tree interactions that affect the trees' distributions, growth, recruitment, and mortality. These interactions decline smoothly in significance with increasing physical distance between trees. They also tend to decline in significance with increasing phylogenetic distance between the trees, but each FDP exhibits its own unique pattern of exceptions to this overall decline. Unique patterns of between-species interactions in ecosystems, of the general type that Darwin postulated, are likely to have contributed to the exceptions. We test the power of our null-model method by using a deliberately modified data set, and show that the method easily identifies the modifications. We examine how some of the exceptions, at the Wind River (USA) FDP, reveal new details of a known allelopathic effect of one of the Wind River gymnosperm species. Finally, we explore how similar analyses can be used to investigate details of many types of interactions in these complex ecosystems, and can provide clues to the evolution of these interactions.
  4. Russo SE, McMahon SM, Detto M, Ledder G, Wright SJ, Condit RS, et al.
    Nat Ecol Evol, 2021 Feb;5(2):174-183.
    PMID: 33199870 DOI: 10.1038/s41559-020-01340-9
    Resource allocation within trees is a zero-sum game. Unavoidable trade-offs dictate that allocation to growth-promoting functions curtails other functions, generating a gradient of investment in growth versus survival along which tree species align, known as the interspecific growth-mortality trade-off. This paradigm is widely accepted but not well established. Using demographic data for 1,111 tree species across ten tropical forests, we tested the generality of the growth-mortality trade-off and evaluated its underlying drivers using two species-specific parameters describing resource allocation strategies: tolerance of resource limitation and responsiveness of allocation to resource access. Globally, a canonical growth-mortality trade-off emerged, but the trade-off was strongly observed only in less disturbance-prone forests, which contained diverse resource allocation strategies. Only half of disturbance-prone forests, which lacked tolerant species, exhibited the trade-off. Supported by a theoretical model, our findings raise questions about whether the growth-mortality trade-off is a universally applicable organizing framework for understanding tropical forest community structure.
  5. Fung T, Chisholm RA, Anderson-Teixeira K, Bourg N, Brockelman WY, Bunyavejchewin S, et al.
    Ecol Lett, 2020 Jan;23(1):160-171.
    PMID: 31698546 DOI: 10.1111/ele.13412
    Among the local processes that determine species diversity in ecological communities, fluctuation-dependent mechanisms that are mediated by temporal variability in the abundances of species populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness.
  6. Sullivan MJ, Talbot J, Lewis SL, Phillips OL, Qie L, Begne SK, et al.
    Sci Rep, 2017 01 17;7:39102.
    PMID: 28094794 DOI: 10.1038/srep39102
    Tropical forests are global centres of biodiversity and carbon storage. Many tropical countries aspire to protect forest to fulfil biodiversity and climate mitigation policy targets, but the conservation strategies needed to achieve these two functions depend critically on the tropical forest tree diversity-carbon storage relationship. Assessing this relationship is challenging due to the scarcity of inventories where carbon stocks in aboveground biomass and species identifications have been simultaneously and robustly quantified. Here, we compile a unique pan-tropical dataset of 360 plots located in structurally intact old-growth closed-canopy forest, surveyed using standardised methods, allowing a multi-scale evaluation of diversity-carbon relationships in tropical forests. Diversity-carbon relationships among all plots at 1 ha scale across the tropics are absent, and within continents are either weak (Asia) or absent (Amazonia, Africa). A weak positive relationship is detectable within 1 ha plots, indicating that diversity effects in tropical forests may be scale dependent. The absence of clear diversity-carbon relationships at scales relevant to conservation planning means that carbon-centred conservation strategies will inevitably miss many high diversity ecosystems. As tropical forests can have any combination of tree diversity and carbon stocks both require explicit consideration when optimising policies to manage tropical carbon and biodiversity.
  7. Stephenson NL, Das AJ, Condit R, Russo SE, Baker PJ, Beckman NG, et al.
    Nature, 2014 Mar 6;507(7490):90-3.
    PMID: 24429523 DOI: 10.1038/nature12914
    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.
  8. Tan S, Suraya A, Sa'don S, Ruzi A, Zahiah M
    Biomed Imaging Interv J, 2010 Apr-Jun;6(2):e16.
    PMID: 21611037 MyJurnal DOI: 10.2349/biij.6.2.e16
    The authors propose a musculoskeletal (MSK) magnetic resonance imaging (MRI) protocol using selected sequences for common orthopaedic indications. Selected sequences allow optimal visualisation of the indicated pathology while screening for other common conditions. The authors emphasise the need for standard positioning of the patient and standard orientation of scan planes to facilitate comparison with follow-up scans.
  9. Nagaya D, Zahari Z, Saleem M, Yahaya BH, Tan SC, Yusoff NM
    J Clin Pharm Ther, 2018 Feb;43(1):80-86.
    PMID: 28656735 DOI: 10.1111/jcpt.12585
    WHAT IS KNOWN: Drug addiction is a novelty-seeking personality trait that is associated with the candidate genes OPRD1 (opioid delta receptors), OPRK1 (opioid kappa receptors) and PDYN (prodynorphin). However, associations between single nucleotide polymorphisms (SNPs) rs1042114 (80G>T) of the OPRD1 gene, rs702764 (843 A>G) of the OPRK1 gene, and rs910080 (3' UTR _743T>C), rs1997794 (5' UTR -381A>G) and rs1022563 (3' UTR) of the PDYN gene and novelty seeking remain controversial as reported results have not been reproducible.

    OBJECTIVE: The goal of this study was to determine the frequencies of SNPs rs1042114, rs702764, rs1997794, rs1022563 and rs910080 in the Malaysian population and to study their association with opioid dependence in Malaysian Malays.

    METHODS: A total of 459 Malay male with opioid dependence and 543 healthy male (controls) subjects were included in this study. SNPs were genotyped using the TaqMan SNP genotyping assay. Statistical analysis was performed using Golden Helix SVS software suite to identify the distribution of allele and genotype frequencies, and SNP-SNP interactions were also analysed in this study.

    RESULTS AND DISCUSSION: SNP rs1042114 in the OPRD1 gene is strongly associated with opiate addiction (P=.0001). In individuals homozygous for this risk allele, the likelihood of opiate addiction is increased by a factor 1.62 (95% confidence interval (CI) 1.412-1.875). Polymorphic alleles at SNP rs702764 of OPRK1 were not associated with opioid dependence. A significant association between opioid dependence and SNP rs910080 of PDYN (P=.0217) was detected, but there was no association for SNPs rs199774 and rs1022563. A significant interaction was also identified between homozygous wild-type genotype TT of rs702764 with the risk genotypes TG/GG of rs1042114 (odds ratio (OR)=2.111 (95% CI 1.227-3.631), P=.0069) and with the risk genotypes GA/AA of rs910080 (OR=1.415 (95% CI 1.04-1.912), P=.0239).

    WHAT IS NEW AND CONCLUSION: The results indicate that SNPs rs1042114 and rs910080 contribute to vulnerability to opioid dependence in the Malaysian Malay population. These results will help us to understand the effect of the SNPs and the SNP-SNP interaction on opioid dependence and may assist in efforts to screen vulnerable individuals and match them with individually tailored prevention and treatment strategies.

  10. Hoh BP, Siraj SS, Tan SG, Yusoff K
    Genetika, 2008 Mar;44(3):427-9.
    PMID: 18664151
    Twelve single locus trinucleotide microsatellite markers were developed to characterize the Asian river catfish, Mystus nemurus, an important food fish in South East Asia. They were obtained by using a rapid method namely the 5' anchored PCR enrichment protocol. The specific primers were designed to flank the repeat sequences and these were subsequently used to characterize 90 unrelated fish from Malaysia. The number of alleles per locus ranged from 2 (MnVj2-281) to 12 (MnBp8-4-43b) while the levels of heterozygosity ranged from 0.0444 (MnVj2-1-19) to 0.7458 (MnVj2-291).
  11. Hoh BP, Siraj SS, Tan SG, Yusoff K
    Genet. Mol. Res., 2013;12(3):2578-93.
    PMID: 23479146 DOI: 10.4238/2013.February.28.1
    The river catfish Mystus nemurus is an important fresh water species for aquaculture in Malaysia. We report the first genetic linkage map of M. nemurus based on segregation analysis and a linkage map using newly developed microsatellite markers of M. nemurus. A total of 70 of the newly developed polymorphic DNA microsatellite markers were analyzed on pedigrees generated using a pseudo-testcross strategy from 2 mapping families. In the first mapping family, 100 offspring were produced from randomly selected dams of the same populations; dams of the second family were selected from 2 different populations, and this family had 50 offspring. Thirty-one of the 70 markers segregated according to the Mendelian segregation ratio. Linkage analysis revealed that 17 microsatellite markers belonging to 7 linkage groups were obtained at a logarithm of the odds score of 1.2 spanning 584 cM by the Kosambi mapping function, whereas the other 14 remained unlinked. The results from this study will act as primer to a more extensive genetic mapping study aimed towards identifying genetic loci involved in determining economically important traits.
  12. Usmani S, Tan SG, Siraj SS, Yusoff K
    Anim. Genet., 2003 Dec;34(6):462-4.
    PMID: 14687079
    A total of 143 microsatellites were isolated from Mystus nemurus using a 5' anchored polymerase chain reaction technique or the random amplified hybridization microsatellite method, the first set of microsatellite markers developed for the Southeast Asian river catfish. Twenty polymorphic microsatellite loci were used as markers for population characterization of M. nemurus from six different geographical locations in Malaysia (Perak, Kedah, Johor, UPM, Sarawak and Terengganu). The number of alleles per locus ranged from 2 to 11 with 6.3 as the average number of alleles per locus. Characterization of the populations showed relatively high levels of genetic variation compared with previous studies using allozyme markers. The highest genetic similarity was found between Perak and Kedah, while the highest genetic distance was found between Terengganu and Kedah. The majority of clustering was in accordance with geographical locations and the histories of the populations. Microsatellite analysis indicated that the Sarawak population might be genetically closer to the Peninsular Malaysian populations than has been previously shown by other molecular marker studies.
  13. Chang CT, Ang JY, Wong JM, Tan SS, Chin SK, Lim AB, et al.
    Med J Malaysia, 2020 05;75(3):286-291.
    PMID: 32467546
    AIM: This study is conducted to compare the pharmacokinetic profiles of two fixed dose combination of metformin/glibenclamide tablets (500mg/5 mg per tablet).

    MATERIALS AND METHODS: This is a single-center, single-dose, open-label, randomized, 2-treatment, 2-sequence and 2- period crossover study with a washout period of 7 days. All 28 adult male subjects were required to fast for at least 10 hours prior to drug administration and they were given access to water ad libitum during this period. Thirty minutes prior to dosing, all subjects were served with a standardized high-fat and high-calorie breakfast with a total calorie of 1000 kcal which was in accordance to the EMA Guideline on the Investigation of Bioequivalence. Subsequently, subjects were administered either the test or reference preparation with 240mL of plain water in the first trial period. During the second trial period, they received the alternate preparation. Plasma levels of glibenclamide and metformin were analysed separately using two different high performance liquid chromatography methods.

    RESULTS: The 90% confidence interval (CI) for the ratio of the AUC0-t, AUC0-∞, and Cmax of the test preparation over those of the reference preparation were 0.9693-1.0739, 0.9598- 1.0561 and 0.9220 - 1.0642 respectively. Throughout the study period, no serious drug reaction was observed. However, a total of 26 adverse events (AE)/side effects were reported, including 24 that were definitely related to the study drugs, namely giddiness (n=17), while diarrheoa (n=3), headache (n=2) and excessive hunger (n=2) were less commonly reported by the subjects.

    CONCLUSION: It can be concluded that the test preparation is bioequivalent to the reference preparation.

  14. Jamaludin A, Mohamad M, Navaratnam V, Selliah K, Tan SC, Wernsdorfer WH, et al.
    Br J Clin Pharmacol, 1988 Feb;25(2):261-3.
    PMID: 3358888
    The hydrochloride, sulphate and ethylcarbonate salts of quinine were given in single oral doses (600 mg base equivalent) to nine healthy male subjects according to a cross-over design. No statistically significant differences were noted in the plasma drug concentration-time profiles although inter- and intra-subject variation in AUC, Cmax and tmax values was appreciable. The ethylcarbonate salt may be preferred for use in paediatric patients because of its neutral taste.
  15. Tan ST, Yoong BK
    Med J Malaysia, 2020 11;75(6):734-735.
    PMID: 33219186
    Tacrolimus, which bonds to an immunophilin, FK506 binding protein (FKBP) has emerged as one of the most widely used immunosuppressant post solid organ transplantation. It offers excellent patient survival rates post-transplantation and a lesser number of acute rejections as compared to cyclosporine. Tacrolimus has a narrow therapeutic window with overexposure leading to acute and chronic forms of nephrotoxicity. Remarkably few data have been published on the overexposure to tacrolimus following mild diarrhoea in post-transplant patients who received treatment with tacrolimus. We observed a post-liver transplant patient with increased trough level of tacrolimus during severe diarrhoea with no complications following a timely adjustment on the dose of tacrolimus.
  16. Chang W, Ee-Uli J, Ng WL, Rovie-Ryan JJ, Tan SG, Yong CSY
    Sci Rep, 2019 06 11;9(1):8504.
    PMID: 31186469 DOI: 10.1038/s41598-019-44870-4
    Macaca fascicularis, also known as the cynomolgus macaque, is an important non-human primate animal model used in biomedical research. It is an Old-World primate widely distributed in Southeast Asia and is one of the most abundant macaque species in Malaysia. However, the genetic structure of wild cynomolgus macaque populations in Malaysia has not been thoroughly elucidated. In this study, we developed genic-simple sequence repeat (genic-SSR) markers from an in-house transcriptome dataset generated from the Malaysian cynomolgus macaque via RNA sequencing, and applied these markers on 26 cynomolgus macaque individuals. A collection of 14,751 genic-SSRs were identified, where 13,709 were perfect SSRs. Dinucleotide repeats were the most common repeat motifs with a frequency of 65.05%, followed by trinucleotide repeats (20.55%). Subsequently, we designed 300 pairs of primers based on perfect di- and trinucleotide SSRs, in which 105 SSRs were associated with functional genes. A subset of 30 SSR markers were randomly selected and validated, yielding 19 polymorphic markers with an average polymorphism information content value of 0.431. The development of genic-SSR markers in this study is indeed timely to provide useful markers for functional and population genetic studies of the cynomolgus macaque and other related non-human primate species.
  17. Tan SC, Matzen P, Yeo LN
    Value Health, 2014 Nov;17(7):A743.
    PMID: 27202679 DOI: 10.1016/j.jval.2014.08.151
    Objectives
    Budget impact analysis (BIA) is a useful tool for reimbursement decision-makers in health technology assessments by authorities across different countries. This study aimed to evaluate the financial impact from the Ministry of Health (MOH) perspective of different adoption rates of Biphasic Insulin Aspart (BIAsp) versus Biphasic Human Insulin (BHI) in treating type 2 diabetes mellitus.
    Methods
    An Excel basfed 5-year budget impact model was built to estimate insulin treated patients by public providers using local prevalence data. The published demographic, efficacy and adverse event data for ASEAN subgroup analyses of A1chieve study was applied. Both insulin acquisition costs and other medical costs for complications e.g. major hypoglycaemia, myocardial infarction, stroke, end-stage renal disease, blindness and amputation were included at a discount rate of 3%. The incidence rates of these complications were derived from the established UKPDS equations. The adoption rates were assumed and projected from the 2013 utilisation volume data of BIAsp and BHI by public providers. Sensitivity analyses were conducted.
    Results
    The adoption rates of BIAsp were assumed to increase from 1.8% in 2013 to 4.5% or 6.9% in 2018 for base case and upside scenario, respectively. Compared to the base case, upside scenario of wider BIAsp adoption was associated with an increased insulin cost up to RM 8.2M which was offset by avoided complication costs resulting in an overall net budget saving of approximately RM 5.5M over 5 years, primarily driven by estimated reduction in major hypoglycaemia events for patients treated with BIAsp.
    Conclusions
    The higher and wider adoption of BIAsp would likely be associated with cost savings in Malaysia from the MOH perspective attributed to its superiority in H1Ac reduction and lower major hypoglycemia risk in comparison to BHI. More cost saving would be concluded if productivity loss is included from a societal perspective.
  18. Hii JL, Chew M, Sang VY, Munstermann LE, Tan SG, Panyim S, et al.
    J Med Entomol, 1991 Sep;28(5):675-84.
    PMID: 1682492
    During the intermonsoon period from mid-September to mid-October 1986, wild-caught Anopheles balabacensis Baisas females were marked and released in a host-choice experiment. Association between capture and recapture of marked mosquitoes from human and bovid hosts and blood meal host identification of recaptured females were determined on a daily basis. Although the mark-recapture and blood meal data indicated behavioral heterogeneity between buffalo and human biters, restriction endonuclease fragment length polymorphism analysis revealed no differences in repeat sequence profiles. Doubly-marked recaptures strongly indicated a "learning" component involved in a separate host preference experiment. In a "habitat loyalty" experiment conducted in January 1987, females of An. balabacensis preferentially returned to the resting sites (indoor surfaces and exit traps) where they were first caught. Of nine isozyme loci found to be polymorphic, the genotypic frequencies of Esterase-3 and Isocitrate dehydrogenase-3 were different in "faithfully" endophilic and exophilic subpopulations. Genetic heterozygosity, as determined by polyacrylamide gel electrophoresis, was greater in exophilic than endophilic population components. These results confirm that genetic and learning components can significantly influence house resting and host seeking behavior and may contribute to local epidemiological patterns of malaria transmission observed in Sabah, Malaysia.
  19. Ong CC, Teh CH, Tan SG, Yusoff K, Yap CK
    Genetika, 2008 Apr;44(4):574-6.
    PMID: 18666563
    We report on the characterization of 11 polymorphic microsatellite loci in P. viridis, the first set of such markers developed and characterized for this species. The number of alleles per locus ranged from 2 to 7, whereas the observed heterozygosity ranged from 0.0447 to 0.4837. These markers should prove useful as powerful genetic markers for this species.
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