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Mohamad Noordin N, Tan JL, Chong CK, Chem YK, Tajudin N, Abu Bakar RS, Sengol S, Phoon HYP, Che Azid NAM, W Mohd Arifin WNA, Aziz ZA, Hussin H, Ibrahim NS, Omar A, Ravi U, Kamarul Zaman KH, Yamin MA, Ngeow YF. Genomic diversity of SARS-CoV-2 in Malaysia. PeerJ 2021; 9:e12449. [PMID: 34760404 PMCID: PMC8571957 DOI: 10.7717/peerj.12449] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 10/18/2021] [Indexed: 01/17/2023] Open
Abstract
Background More than a year after its first appearance in December 2019, the COVID-19 pandemic is still on a rampage in many parts of the world. Although several vaccines have been approved for emergency use, the emergence and rapid spread of new SARS-CoV-2 variants have sparked fears of vaccine failure due to immune evasion. Massive viral genome sequencing has been recommended to track the genetic changes that could lead to adverse consequences. Methods We sequenced SARS-CoV-2 respiratory isolates from the National Public Health Laboratory, Malaysia and examined them together with viral genomes deposited in GISAID by other Malaysian researchers, to understand the evolutionary trend of the virus circulating in the country. We studied the distribution of virus lineages and site-wise mutations, analysed genetic clustering with the goeBURST full Minimum Spanning Tree algorithm, examined the trend of viral nucleotide diversity over time and performed nucleotide substitution association analyses. Results We identified 22 sub-lineages, 13 clonal complexes, 178 sequence types and seven sites of linkage disequilibrium in 277 SARS-CoV-2 genomes sequenced between January and December 2020. B.1.524 was the largest lineage group. The number of mutations per genome ranged from 0 to 19. The mean genomic diversity value over 12 months was 3.26 × 10-4. Of 359 mutations detected, 60.5% of which were non-synonymous, the most frequent were in the ORF1ab (P4715L), S (D614G and A701V) and N (S194L) genes. Conclusion The SARS-CoV-2 virus accumulated an abundance of mutations in the first year of the COVID-19 pandemic in Malaysia. Its overall genetic diversity, however, is relatively low compared to other Asian countries with larger populations. Continuous genomic and epidemiological surveillance will help to clarify the evolutionary processes determining viral diversity and impacting on human health.
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Affiliation(s)
- Noorliza Mohamad Noordin
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Joon Liang Tan
- Faculty of Information Science and Technology, Multimedia University, Melaka, Melaka, Malaysia
| | | | - Yu Kie Chem
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Norazimah Tajudin
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Rehan Shuhada Abu Bakar
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Selvanesan Sengol
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Hannah Yik Phing Phoon
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | | | | | - Zirwatul Adilah Aziz
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Hani Hussin
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Nurul Syahida Ibrahim
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Aziyati Omar
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Ushananthiny Ravi
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | | | - Mohd Asri Yamin
- National Public Health Laboratory, Ministry of Health Malaysia, Sungai Buloh, Selangor, Malaysia
| | - Yun Fong Ngeow
- Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Bandar Sungai Long, Selangor, Malaysia.,Center for Research on Communincable Diseases, Universiti Tunku Abdul Rahman, Bandar Sungai Long, Selangor, Malaysia
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Dass S, Ngui R, Gill BS, Chan YF, Wan Sulaiman WY, Lim YAL, Mudin RN, Chong CK, Sulaiman LH, Sam IC. Spatiotemporal spread of chikungunya virus in Sarawak, Malaysia. Trans R Soc Trop Med Hyg 2021; 115:922-931. [PMID: 33783526 DOI: 10.1093/trstmh/trab053] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 12/11/2020] [Accepted: 03/10/2021] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND We studied the spatiotemporal spread of a chikungunya virus (CHIKV) outbreak in Sarawak state, Malaysia, during 2009-2010. METHODS The residential addresses of 3054 notified CHIKV cases in 2009-2010 were georeferenced onto a base map of Sarawak with spatial data of rivers and roads using R software. The spatiotemporal spread was determined and clusters were detected using the space-time scan statistic with SaTScan. RESULTS Overall CHIKV incidence was 127 per 100 000 population (range, 0-1125 within districts). The average speed of spread was 70.1 km/wk, with a peak of 228 cases/wk and the basic reproduction number (R0) was 3.1. The highest age-specific incidence rate was 228 per 100 000 in adults aged 50-54 y. Significantly more cases (79.4%) lived in rural areas compared with the general population (46.2%, p<0.0001). Five CHIKV clusters were detected. Likely spread was mostly by road, but a fifth of rural cases were spread by river travel. CONCLUSIONS CHIKV initially spread quickly in rural areas mainly via roads, with lesser involvement of urban areas. Delayed spread occurred via river networks to more isolated areas in the rural interior. Understanding the patterns and timings of arboviral outbreak spread may allow targeted vector control measures at key transport hubs or in large transport vehicles.
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Affiliation(s)
- Sarat Dass
- School of Mathematical & Computer Sciences, Heriot-Watt University Malaysia, 62200 Putrajaya, Malaysia
| | - Romano Ngui
- Department of Parasitology, Faculty of Medicine, University Malaya, 50603 Kuala Lumpur
| | | | - Yoke Fun Chan
- Department of Medical Microbiology, Faculty of Medicine, University Malaya, 50603 Kuala Lumpur, Malaysia
| | | | - Yvonne Ai Lian Lim
- Department of Parasitology, Faculty of Medicine, University Malaya, 50603 Kuala Lumpur
| | - Rose Nani Mudin
- Vector Borne Disease Sector, Disease Control Division, Ministry of Health Malaysia, Pusat Pentadbiran Kerajaan Persekutuan, 62590 Putrajaya, Malaysia
| | - Chee Kheong Chong
- Office of the Deputy Director General of Health (Public Health), Ministry of Health Malaysia, Pusat Pentadbiran Kerajaan Persekutuan, 62590 Putrajaya
| | - Lokman Hakim Sulaiman
- Department of Community Medicine, School of Medicine, International Medical University, Bukit Jalil, 57000 Kuala Lumpur, Malaysia.,Institute for Research, Development and Innovation, International Medical University, Bukit Jalil, 57000 Kuala Lumpur, Malaysia
| | - I-Ching Sam
- Department of Medical Microbiology, Faculty of Medicine, University Malaya, 50603 Kuala Lumpur, Malaysia
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Cicero A, Meyer D, Shearer MP, AbuBakar S, Bernard K, Carus WS, Chong CK, Fischer J, Hynes N, Inglesby T, Kwa CG, Makalinao I, Pangestu T, Sitompul R, Soebandrio A, Sudarmono P, Tjen D, Wibulpolprasert S, Yunus Z. Southeast Asia Strategic Multilateral Dialogue on Biosecurity. Emerg Infect Dis 2019; 25. [PMID: 31002062 PMCID: PMC6478199 DOI: 10.3201/eid2505.181659] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
A strategic multilateral dialogue related to biosecurity risks in Southeast Asia, established in 2014, now includes participants from Singapore, Malaysia, Indonesia, Thailand, Philippines, and the United States. This dialogue is conducted at the nonministerial level, enabling participants to engage without the constraints of operating in their official capacities. Participants reflect on mechanisms to detect, mitigate, and respond to biosecurity risks and highlight biosecurity issues for national leadership. Participants have also identified factors to improve regional and global biosecurity, including improved engagement and collaboration across relevant ministries and agencies, sustainable funding for biosecurity programs, enhanced information sharing for communicable diseases, and increased engagement in international biosecurity forums.
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Hassan N, Baharom N, Dawam ND, Ismail N, Festus CE, Mihat O, Chong CK. Strengthening quit smoking services in Malaysia through Malaysia Quit (mQuit) Program. Tob Induc Dis 2018. [DOI: 10.18332/tid/84344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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5
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Hong KW, Asmah Hani A, Nurul Aina Murni C, Pusparani R, Chong CK, Verasahib K, Yusoff WNW, Noordin NM, Tee KK, Yin WF, Yu CY, Ang GY, Chan KG. Comparative genomic and phylogenetic analysis of a toxigenic clinical isolate of Corynebacterium diphtheriae strain B-D-16-78 from Malaysia. Infection, Genetics and Evolution 2017; 54:263-270. [DOI: 10.1016/j.meegid.2017.07.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 06/11/2017] [Accepted: 07/11/2017] [Indexed: 11/24/2022]
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Nealon J, Taurel AF, Capeding MR, Tran NH, Hadinegoro SR, Chotpitayasunondh T, Chong CK, Wartel TA, Beucher S, Frago C, Moureau A, Simmerman M, Laot T, L’Azou M, Bouckenooghe A. Symptomatic Dengue Disease in Five Southeast Asian Countries: Epidemiological Evidence from a Dengue Vaccine Trial. PLoS Negl Trop Dis 2016; 10:e0004918. [PMID: 27532617 PMCID: PMC4988713 DOI: 10.1371/journal.pntd.0004918] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/22/2016] [Indexed: 12/03/2022] Open
Abstract
Dengue incidence has increased globally, but empirical burden estimates are scarce. Prospective methods are best-able to capture all severities of disease. CYD14 was an observer-blinded dengue vaccine study conducted in children 2-14 years of age in Indonesia, Malaysia, Thailand, the Philippines, and Vietnam. The control group received no vaccine and resembled a prospective, observational study. We calculated the rates of dengue according to different laboratory or clinical criteria to make inferences about dengue burden, and compared with rates reported in the passive surveillance systems to calculate expansion factors which describe under-reporting. Over 6,933 person-years of observation in the control group there were 319 virologically confirmed dengue cases, a crude attack rate of 4.6%/year. Of these, 92 cases (28.8%) were clinically diagnosed as dengue fever or dengue hemorrhagic fever by investigators and 227 were not, indicating that most symptomatic disease fails to satisfy existing case definitions. When examining different case definitions, there was an inverse relationship between clinical severity and observed incidence rates. CYD14's active surveillance system captured a greater proportion of symptomatic dengue than national passive surveillance systems, giving rise to expansion factors ranging from 0.5 to 31.7. This analysis showed substantial, unpredictable and variable under-reporting of symptomatic dengue, even within a controlled clinical trial environment, and emphasizes that burden estimates are highly sensitive to case definitions. These data will assist in generating disease burden estimates and have important policy implications when considering the introduction and health economics of dengue prevention and control interventions.
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Affiliation(s)
| | | | | | - Ngoc Huu Tran
- Pasteur Institute Ho Chi Minh City, Ho Chi Minh City, Vietnam
| | - Sri Rezeki Hadinegoro
- University of Indonesia Medical School, Cipto Mangunkusumo Hospital, Jakarta, Indonesia
| | | | - Chee Kheong Chong
- Disease Control Division, Malaysian Ministry of Health, Putrajaya, Malaysia
| | | | | | | | | | | | - Thelma Laot
- Sanofi Pasteur Asia & JPAC Region, Singapore
| | - Maïna L’Azou
- Sanofi Pasteur, Global Epidemiology, Lyon, France
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7
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Shridhar Iyer U, Fah KK, Chong CK, Macachor J, Chia N. Survey of medication errors among anaesthetists in Singapore. Anaesth Intensive Care 2011; 39:1151-1152. [PMID: 22165377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Lee GC, Chong CK, Lee CH, Lee ST. Cell-culture-based immunochromatography for rapid detection of group A human rotaviruses in aquatic environments. Environ Technol 2009; 30:37-43. [PMID: 19213464 DOI: 10.1080/09593330802422696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In an effort to detect rapidly and conveniently the infectious waterborne group A human rotaviruses that cause diarrhea in infants and children, the authors developed the first-ever cell-culture-based immunochromatography method. An immunochromatography kit interacted only with the human rotaviruses VP6 antigen, and the cell-culture-based immunochromatography detected group A human rotaviruses with a sensitivity as low as 1.99 TCID50 ml(-1). This detection sensitivity was similar to that of the cytopathic effect-based method. There were no actual differences between the sensitivity of this method and that of the real-time reverse transcription polymerase chain reaction method, which is known as a method with a relatively high sensitivity. Furthermore, while cell culture detection methods, that is total culturable virus assay, can determine only the presence of infectious waterborne viruses, the cell-culture-based immunochromatography is advantageous for the accurate detection of group A human rotaviruses. Compared with the real-time reverse transcription polymerase chain reaction method, the cell-culture-based immunochromatography is advantageous because it requires a relatively simple process that enables easy quality controls and low test costs. Thus, this study proposed a new method for the identification of group A human rotaviruses, and it is suggested that this cell-culture-based immunochromatography may be applied to detect group A human rotaviruses in aquatic environments.
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Affiliation(s)
- G C Lee
- Water Analysis and Research Center, Korea Institute of Water and Environment, Korea Water Resources Corporation, Daejeon, Republic of Korea.
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9
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Bockenhauer D, Cruwys M, Kleta R, Halperin LF, Wildgoose P, Souma T, Nukiwa N, Cheema-Dhadli S, Chong CK, Kamel KS, Davids MR, Halperin ML. Antenatal Bartter's syndrome: why is this not a lethal condition? QJM 2008; 101:927-42. [PMID: 18829713 DOI: 10.1093/qjmed/hcn119] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
There are four themes in this teaching exercise for Professor McCance. The first challenge was to explain how a premature infant with Bartter's syndrome could survive despite having such a severe degree of renal salt wasting. Second, the medical team wanted to know why there was such a dramatic decrease in the natriuresis in response to therapy, despite the presence of a permanent molecular defect that affected the loop of Henle. Third, Professor McCance was asked why this patient seemed to have a second rare disease, AQP2 deficiency type of nephrogenic diabetes insipidus. The fourth challenge was to develop a diagnostic test to help the parents of this baby titrate the dose of indomethacin to ensure an effective dose while minimizing the likelihood of developing nephrotoxicity. The missing links in this interesting story emerge during a discussion between the medical team and its mentor.
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Affiliation(s)
- D Bockenhauer
- Great Ormond Street Hospital for Children NHS Trust, Great Ormond Street, London WC1N 3JH, UK.
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10
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Xiong FL, Chong CK. A parametric numerical investigation on haemodynamics in distal coronary anastomoses. Med Eng Phys 2008; 30:311-20. [PMID: 17616426 DOI: 10.1016/j.medengphy.2007.04.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 01/23/2007] [Accepted: 04/19/2007] [Indexed: 11/20/2022]
Abstract
Anastomotic haemodynamics, which plays an important role in the performance of bypass graft, is known to be profoundly affected by the diameter ratio (Phi) and angle (alpha) between the graft and host artery in the peripheral region. We hypothesize that these geometric factors would play similar roles in distal coronary anastomoses and that they could be improved for clinical applications through parametric studies. Anastomotic models covering a range of Phi (1:1, 1.5:1 and 2:1) and alpha (15 degrees , 30 degrees , 45 degrees and 60 degrees ) were investigated numerically in physiological coronary flow conditions. The transient flow patterns, cycle-averaged wall shear stress (WSS), oscillatory shear index (OSI), spatial and temporal WSS gradients (SWSSG and TWSSG) were compared. Results show a stronger influence of Phi than alpha on haemodynamics in distal coronary artery anastomoses. Substantially higher SWSSG and TSSWG occur on the artery floor when Phi=1:1 compared to larger Phi. High levels of OSI occur in critical regions when Phi=1:1 and 2:1. The largest area of high OSI is found in the anastomotic region when alpha=15 degrees , whereas the highest level of SWSSG appears on the artery floor when alpha=60 degrees . The study suggests the clinical relevance of optimizing geometric parameters of coronary anastomoses to improve their haemodynamic performance. We speculate that for a distal coronary anastomosis with a 20:80 proximal-distal flow division ratio maintained in the host artery, Phi=1.5 and alpha=30-45 degrees would enhance its long-term performance.
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Affiliation(s)
- F L Xiong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore
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11
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Yang W, Fung TC, Chian KS, Chong CK. Three-dimensional finite element model of the two-layered oesophagus, including the effects of residual strains and buckling of mucosa. Proc Inst Mech Eng H 2007; 221:417-26. [PMID: 17605399 DOI: 10.1243/09544119jeim47] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study was carried out to develop a two-layered finite element model of the oesophagus. The outer muscle and inner mucosal layer were constructed individually with different mechanical properties and zero-stress opening angles. With the model, two simulations were performed. First, the distention of oesophageal wall under the pressurized state was investigated, from which the effects of residual strains on the stress distribution were evaluated. Second, the buckling modes were determined using a linear eigenvalue analysis. The self-contact capability in ABAQUS was applied to simulate the folding of mucosa under the muscle contraction. The first simulation indicated that, by taking the residual strains into account, the mucosa undertook a very small portion of stress and the luminal pressure almost transmitted completely to the outer muscle layer. On the other hand, the folding of mucosa was shown to be able to reduce the contractile force of circular muscle to maintain the lumen closure. In conclusion, the preliminary study demonstrated the feasibility of simulating the oesophageal peristaltic transport using finite element analysis.
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Affiliation(s)
- W Yang
- Biomedical Engineering Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
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Abstract
BACKGROUND The effect of traditional risk factors on the association between angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and stroke was rarely studied previously. We investigated such effect in Taiwanese type 2 diabetic patients. MATERIALS AND METHODS A total of 872 (422 men and 450 women) patients aged 63.5 (SD: 11.6) years were recruited. Among them, 92 cases (48 men and 44 women) had stroke. Polymerase chain reaction was used to classify the genotypes as II, ID and DD. Analyses were performed in separate sexes. RESULTS The adjusted odds ratios for stroke for ID vs. II and DD vs. II were 0.837 (0.413-1.697) and 1.778 (0.596-5.300), respectively, for men; but were 1.700 (0.824-3.505) and 3.706 (1.375-9.985), respectively, for women. In models assuming recessive (DD vs. II + ID), dominant (DD + ID vs. II) and additive (II = 0, ID = 1 and DD = 2) transmission, none of the odds ratios was significant for men; but were all significant for women: 2.784 (1.137-6.818), 1.996 (1.006-3.962) and 1.877 (1.155-3.050), respectively. In models using patients without risk factors (hypertension, obesity, smoking or dyslipidaemia ) as a referent group and comparing them to patients with the risk factor and with ID/II, and with DD genotypes, all models (except for smoking) favoured an increasing trend of risk with patients having the risk factor and DD genotype at the highest risk in women. Similar trends for hypertension and dyslipidaemia were also observed in men. CONCLUSION Traditional risk factors play an important role in the association between the ACE genotypes and stroke. Patients with DD genotype and having traditional risk factors are at the highest risk.
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Affiliation(s)
- C H Tseng
- National Taiwan University College of Medicine, Taipei, Taiwan.
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Hakim SL, Gan CC, Malkit K, Azian MN, Chong CK, Shaari N, Zainuddin W, Chin CN, Sara Y, Lye MS. Parasitic infections among Orang Asli (aborigine) in the Cameron Highlands, Malaysia. Southeast Asian J Trop Med Public Health 2007; 38:415-9. [PMID: 17877212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
In April 2004, an outbreak of acute diarrheal illness occurred among the Orang Asli (aborigine) in the Cameron Highlands, Pahang State, Peninsular Malaysia, where rotavirus was later implicated as the cause. In the course of the epidemic investigation, stool samples were collected and examined for infectious agents including parasites. Soil transmitted helminthes (STH), namely Ascaris lumbricoides (25.7%), Trichuris trichiura (31.1%) and hookworm (8.1%), and intestinal protozoa, which included Giardia lamblia (17.6%), Entamoeba histolytica/E. dispar (9.4%), Blastocystis hominis (8.1%) and Cryptosporidium parvum (2.7%), were detected. Forty-four (59.5%) were infected with at least one parasite, 24 (32.4%), 12 (16.2%) and 8 (10.8%) had single, double and triple parasitic infections, respectively. STH were prevalent with infections occurring as early as in infancy. Giardia lamblia, though the most commonly found parasite in samples from symptomatic subjects, was within the normally reported rate of giardiasis among the various communities in Malaysia, and was an unlikely cause of the outbreak. However, heavy pre-existing parasitic infections could have contributed to the severity of the rotavirus diarrheal outbreak.
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Affiliation(s)
- S Lokman Hakim
- Environmental Health Research Center, Institute for Medical Research, Kuala Lumpur, Malaysia.
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Abstract
The identification of a three dimensional constitutive model is useful for describing the complex mechanical behavior of a nonlinear and anisotropic biological tissue such as the esophagus. The inflation tests at the fixed axial extension of 1, 1.125, and 1.25 were conducted on the muscle and mucosa layer of a porcine esophagus separately and the pressure-radius-axial force was recorded. The experimental data were fitted with the constitutive model to obtain the structure-related parameters, including the collagen amount and fiber orientation. Results showed that a bilinear strain energy function (SEF) with four parameters could fit the inflation data at an individual extension very well while a six-parameter model had to be used to capture the inflation behaviors at all three extensions simultaneously. It was found that the collagen distribution was axial preferred in both layers and the mucosa contained more collagen, which were in agreement with the findings through a pair of uniaxial tensile test in our previous study. The model was expected to be used for the prediction of stress distribution within the esophageal wall under the physiological state and provide some useful information in the clinical studies of the esophageal diseases.
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Affiliation(s)
- W Yang
- School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, 639798 Singapore
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Yang W, Fung TC, Chian KS, Chong CK. Instability of the two-layered thick-walled esophageal model under the external pressure and circular outer boundary condition. J Biomech 2007; 40:481-90. [PMID: 16677658 DOI: 10.1016/j.jbiomech.2006.02.020] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 02/27/2006] [Indexed: 10/24/2022]
Abstract
The mucosal folding is a phenomenon observed for some biological tissues, including the pulmonary airway and gastrointestinal tract. In order to understand the mechanism of the formation of mucosal folding, a thick-walled two-layered cylindrical mathematical model was developed to investigate the buckling behavior under the external pressure and circular outer boundary condition. With the finite element method, the validity and accuracy of the proposed model was verified. The results showed that the fold number was in the range of 4-6, which was agreed with the experimental observation for the mucosal folding of a porcine esophagus. The fold number was found to decrease with the increase in the ratio of the inner to outer material stiffness. The increase in the thickness of inner layer also caused a slight declination of the fold number. Since the effects of both the material and geometrical nonlinearities have been accounted for, this model is more general to be used for the prediction of the buckling behavior of the layered structure with a wide range of thickness ratios and/or stiffness ratios.
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Affiliation(s)
- W Yang
- School of Civil and Environmental Engineering, Nanyang Technological University, Singapore.
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16
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Xiong FL, Chong CK. PIV-validated numerical modeling of pulsatile flows in distal coronary end-to-side anastomoses. J Biomech 2007; 40:2872-81. [PMID: 17466995 DOI: 10.1016/j.jbiomech.2007.03.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 03/09/2007] [Accepted: 03/09/2007] [Indexed: 10/23/2022]
Abstract
This study employed particle image velocimetry (PIV) to validate a numerical model in a complementary approach to quantify hemodynamic factors in distal coronary anastomoses and to gain more insights on their relationship with anastomotic geometry. Instantaneous flow fields and wall shear stresses (WSS) were obtained from PIV measurement in a modified life-size silastic anastomosis model adapted from a conventional geometry by incorporating a smooth graft-artery transition. The results were compared with those predicted by a concurrent numerical model. The numerical method was then used to calculate cycle-averaged WSS (WSS(cyc)) and spatial wall shear stress gradient (SWSSG), two critical hemodynamic factors in the pathogenesis of intimal thickening (IT), to compare the conventional and modified geometries. Excellent qualitative agreement and satisfactory quantitative agreement with averaged normalized error in WSS between 0.8% and 8.9% were achieved between the PIV experiment and numerical model. Compared to the conventional geometry, the modified geometry produces a more uniform WSS(cyc) distribution eliminating both high and low WSS(cyc) around the toe, critical in avoiding IT. Peak SWSSG on the artery floor of the modified model is less than one-half that in the conventional case, and high SWSSG at the toe is eliminated. The validated numerical model is useful for modeling unsteady coronary anastomotic flows and elucidating the significance of geometry regulated hemodynamics. The results suggest the clinical relevance of constructing smooth graft-artery transition in distal coronary anastomoses to improve their hemodynamic performance.
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Affiliation(s)
- F L Xiong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore
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Gan HN, Tan KY, Chong CK, Tay KH. Finding hepatic portal venous gas in an adult patient: its significance. Singapore Med J 2006; 47:814-6. [PMID: 16924366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Portal venous gas is a well-established radiological finding in neonates. With the advancement in diagnostic imaging, more cases are being reported in adults. We present a 55-year-old man with radiological findings of both portal venous gas and pneumatosis intestinalis secondary to ischaemic necrotising enterocolitis, with subsequent fatality. The significance of finding portal venous gas and its possible aetiology is discussed.
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Affiliation(s)
- H N Gan
- Department of General Surgery, Changi General Hospital, 2 Simei Street 3, Singapore 529889
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18
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Yang W, Fung TC, Chian KS, Chong CK. Directional, regional, and layer variations of mechanical properties of esophageal tissue and its interpretation using a structure-based constitutive model. J Biomech Eng 2006; 128:409-18. [PMID: 16706590 DOI: 10.1115/1.2187033] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The esophagus, like other soft tissues, exhibits nonlinear and anisotropic mechanical properties. As a composite structure, the properties of the outer muscle and inner mucosal layer are different. It is expected that the complex mechanical properties will induce nonhomogeneous stress distributions in the wall and nonuniform tissue remodeling. Both are important factors which influence the function of mechanosensitive receptor located in various layers of the wall. Hence, the characterization of the mechanical properties is essential to understand the neuromuscular motion of the esophagus. In this study, the uniaxial tensile tests were conducted along two mutually orthogonal directions of porcine esophageal tissue to identify the directional (circumferential and axial), regional (abdominal, thoracic, and cervical), and layer (muscle and mucosa) variations of the mechanical properties. A structure-based constitutive model, which took the architectures of the tissue's microstructures into account, was applied to describe the mechanical behavior of the esophagus. Results showed that the constitutive model successfully described the mechanical behavior and provided robust estimates of the material parameters. In conclusion, the model was demonstrated to be a good descriptor of the mechanical properties of the esophagus and it was able to facilitate the directional, layer, and regional comparisons of the mechanical properties in terms of the associated material parameters.
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Affiliation(s)
- W Yang
- School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, 639798, Singapore
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19
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Abstract
The time-dependent mechanical properties of the porcine esophagus were investigated experimentally and theoretically. It was hypothesized that the viscoelasticity was quasilinear, i.e., the time and strain effects were independent. In order to verify the separability of time and strain effects, the stress-relaxation test was conducted at various strains and the data were fitted with the Fung’s quasilinear viscoelastic (QLV) model. By using the material parameters obtained from the stress relaxation test, the cyclic peak stress and hysteresis were predicted. Results showed that the stress relaxed by 20–30% of the peak stress within the first 10s and stabilized at ∼50% at the time of 300s. The relative stress relaxation R2 (i.e., the difference of stress at a particular time to the final equilibrium stress normalized by the total difference of the peak and final stress) was not different significantly for various strains. It was also found that, by using the stress-time data during both the ramp and relaxation phases, the correlation between parameters was substantially reduced. The model could also predict the cyclic peak stress and hysteresis except for the underestimate of valley stress. We conclude that the QLV model could be used as the material characterization of the esophageal tissue.
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Affiliation(s)
- W Yang
- School of Civil and Environmental Engineering, Nanyang Technological University, Singapore
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20
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Abstract
We report a rare case of gastrointestinal tumor of the anus with an unusual presentation as a perianal lipoma. A 65-year-old man presented with a 2-month history of a painless perianal lump clinically resembling a perianal lipoma. Endoanal ultrasonography revealed a 3 x 3 cm2 mass in the intersphincteric plane. Following initial excision of the lesion, histological analysis revealed a stromal lesion comprising fascicles of spindle cells with a mitotic count of 4 per 50 x high power field. Immunohistochemical analysis displayed positive reactivity for CD34 with focal staining for CD117; S100, smooth muscle actin and desmin were not expressed. No evidence of local or distant metastatic disease was found on computed tomography of the abdomen and pelvis. The patient subsequently underwent abdominoperineal resection. The resected specimen contained a mural nodule measuring 0.7 cm, located 5 cm from the distal margin and 2 mm from the radial margin. Histological analysis confirmed a stromal tumor composed of spindle cells with mitoses up to 2 per 10 x high power field. The patient's recovery was uneventful and he was free of recurrence at the 1-year follow-up. Gastrointestinal stromal tumors of the anal canal are an extremely rare occurrence, and may mimic benign perianal lesions. Tumor size and mitotic count are the most important factors in prognosticating outcome. Oncologic resection and protracted follow-up must factor in their predilection for late recurrence and metastatic spread. The role of adjuvant therapy with STI571 here remains to be clearly defined.
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Affiliation(s)
- G Y M Tan
- Department of Colorectal Surgery, Singapore General Hospital, Singapore,
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21
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Abstract
Endovascular exclusion of the abdominal aortic aneurysm (AAA) has been carried out in selected patients during the past decade. The deployment of a complex multicomponent endovascular device in an aneurysmal aorta may alter the local haemodynamics and lead to thrombosis and intimal hyperplasia development. The aim of this in vitro study was to investigate the flow patterns using flow visualisation and laser Doppler anemometry in a commercial bifurcated stent-graft. Two configurations of the stent-graft, endo-stent and exo-stent, were investigated in an idealised planar AAA model. The flow structures in the main trunk in both configurations of the stent-graft are three-dimensional with complex secondary structures. However, these flow structures were not entirely caused by the stent-graft. The stent struts in the endo-stent configuration cause localised alteration in the flow pattern but the overall flow structures were not significantly affected. Low velocity regions in the main trunk and flow separation in the stump region and the curved segment of the iliac limbs were observed. These areas are associated with thrombosis in the clinical situation. Improvements in the design of endovascular devices may remove these areas of unfavourable flow patterns and lead to better clinical performance.
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Affiliation(s)
- C K Chong
- Department of Clinical Engineering, University of Liverpool, Duncan Building, Liverpool L69 3GA, UK
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22
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Abstract
BACKGROUND Endogenous endophthalmitis is an inflammation of ocular tissues that can lead to deterioration of and loss of vision. Rarely, this can complicate the course of a patient with pyogenic liver abscess. METHODS Over an 18-month period, 68 patients were treated for pyogenic liver abscesses. Three patients, all of whom were male and with diabetes, were diagnosed with a Klebsiella pneumoniae liver abscess complicated by endogenous endophthalmitis. Open surgical or percutaneous drainage of the liver abscess was undertaken and the symptomology and outcome of the endophthalmitis reviewed. RESULTS There was no mortality in our series. Two patients presented with simultaneous abdominal and ocular symptoms and one patient had ocular symptoms 3 days after surgical drainage of the liver abscess. Despite aggressive treatment, all patients had permanent deterioration of visual function with one patient becoming blind and requiring evisceration of the infected eye. CONCLUSION Ocular symptoms in patients treated for pyogenic abscesses must be dealt with urgently with an ophthalmologic consultation. Increased awareness of this complication and a high index of suspicion are paramount for salvage of visual function.
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Affiliation(s)
- Y M Tan
- Department of Surgery, Singapore General Hospital, 169608, Singapore.
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23
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Lin MH, Tseng CH, Tseng CC, Huang CH, Chong CK, Tseng CP. Real-time PCR for rapid genotyping of angiotensin-converting enzyme insertion/deletion polymorphism. Clin Biochem 2001; 34:661-6. [PMID: 11849627 DOI: 10.1016/s0009-9120(01)00281-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
OBJECTIVE To develop a real-time PCR technique for detection of the insertion/deletion (I/D) polymorphism of angiotensin-converting enzyme (ACE) gene. DESIGN AND METHODS Three primers were designed for performing real-time PCR in the presence of SYBR Green I as flurochrome followed by melting curve analysis. Forty human genomic DNA that have been genotyped by two-rounds of conventional PCR were used for evaluation of this technique. RESULTS Melting curve analysis indicated the melting peak at 73.9 degrees C and 76.2 degrees C corresponding to the presence of I and D alleles, respectively. Comparable genotyping results were obtained by both conventional and real-time PCR. Besides, the mistyping of ID allele individuals by the first run of conventional PCR were accurately genotyped by single-tube real time PCR. CONCLUSIONS The real-time PCR method presented in this study provides a rapid and sensitive way for genotyping of ACE gene that may be suitable for large-scale clinical and epidemiologic study.
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Affiliation(s)
- M H Lin
- School of Medical Technology, Chang Gung University, Taiwan, Republic of China
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24
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Chong CK, Xing J, Phillips DL, Corke H. Development of NMR and raman spectroscopic methods for the determination of the degree of substitution of maleate in modified starches. J Agric Food Chem 2001; 49:2702-2708. [PMID: 11409954 DOI: 10.1021/jf0102160] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this paper we report the application of NMR spectroscopy and Raman spectroscopy to determine the degree of maleate substitution in maleinated starches. Five kinds of maleinated starches were investigated and calibration sets were constructed to derive linear regression equations that may be used to predict the degree of maleate substitution for starch samples with unknown amounts of chemical modification. The calibration sets reported have very high linearity (r > 0.99) for both the NMR and Raman methods. The NMR and Raman calibration sets allow fast and nondestructive measurement of the degree of maleate substitution for different starches with little need of sample preparation.
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Affiliation(s)
- C K Chong
- Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong
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25
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Abstract
Acetolactate synthase (ALS) is the common enzyme in the biosynthetic pathways leading to valine, leucine, and isoleucine in plants and microorganisms. ALS is the target site of several classes of structurally unrelated herbicides including sulfonylureas, imidazolinones, and triazolopyrimidines. To identify the residues conferring herbicide tolerance in tobacco ALS, site-directed mutagenesis for three residues, Ala121, Pro187 and Ser652, was performed. Mutant A121T showed strong resistance to Londax (a sulfonylurea) and Cadre (an imidazolinone), while mutant S652T was resistant only to Cadre. The S652N mutation abolished the binding affinity of FAD, and inactivated the enzyme. Double mutation of Ala121 and Ser652 with Thr yielded a mutant highly tolerant to Londax, Cadre, and TP (a triazolopyrimidine sulfonamide), but has enzymatic properties similar to those of wild-type. Substitution of Pro187 with Ser resulted in the enzyme highly susceptible to oxidation and fragmentation. These results suggest that two residues Ala121 and Ser652 are potent residues conferring herbicide resistance in tobacco ALS, and that double mutation of Ala121 and Ser652 by Thr can confer stronger tolerance to Londax, Cadre, and TP.
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Affiliation(s)
- C K Chong
- School of Life Science, Cheongju, 361-763, Korea
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26
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Phillips DL, Xing J, Chong CK, Liu H, Corke H. Determination of the degree of succinylation in diverse modified starches by raman spectroscopy. J Agric Food Chem 2000; 48:5105-5108. [PMID: 11087444 DOI: 10.1021/jf9907790] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A method using Raman spectroscopy was recently developed for the determination of the degree of substitution of succinate in waxy maize starch. In this paper it is demonstrated that the method can be generalized to a wide range of starches of different amylose contents and botanical origins. Raman calibration sets were used to form regression equations for five types of succinylated starches, that is, waxy, regular, and two high-amylose maize samples (47 and 66% amylose, respectively) and wheat. The derived calibration curves can be used to find the degree of substitution in samples with unknown levels of succinylation. The Raman calibration lines had linear correlation coefficients of 0.995 or better and enable the fast and nondestructive determination of the degree of substitution of succinate for different types of starches with minimal sample preparation. Also discussed is the potential utility of Raman spectroscopy to simultaneously determine the degree of substitution of succinate and amylose content, using previously determined calibration curves developed for the amylose content of maize starches.
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Affiliation(s)
- D L Phillips
- Departments of Chemistry and Botany, The University of Hong Kong, Pokfulam Road, Hong Kong
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27
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Abstract
Currently, diabetes mellitus is the fifth leading cause of death in Taiwan. The trends of diabetes mortality is increasing steadily. Epidemiologic studies also showed increasing prevalence of diabetes mellitus over the past few decades. The incidence of diabetes mellitus in Taiwan has only been studied in recent 10 years. The areas that have been included as study areas for diabetes incidence are Kin-Chen (Kinmen), Chu-Dung, Pu-Tzu, Pu-Li and Pu-Tai. The reported incidence rates ranged from 1.0 to 4.0% per year for people with varying degrees of baseline plasma glucose levels not reaching the diagnosis of diabetes mellitus according to the criteria of the World Health Organization. Age, baseline glucose level, and obesity are important predictors for the development of diabetes mellitus. In the Pu-Tai study, which was aimed at following a group of people who had been living in the hyperendemic villages of blackfoot disease and had been exposed to arsenic from drinking artesian well water, the incidence of diabetes mellitus was calculated to be 27.4 per 1000 person years. The incidence of diabetes mellitus in these arseniasis-hyperendemic villages correlated with age, body mass index and cumulative arsenic exposure.
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Affiliation(s)
- C H Tseng
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan
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28
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Tseng CH, Tai TY, Chong CK, Tseng CP, Lai MS, Lin BJ, Chiou HY, Hsueh YM, Hsu KH, Chen CJ. Long-term arsenic exposure and incidence of non-insulin-dependent diabetes mellitus: a cohort study in arseniasis-hyperendemic villages in Taiwan. Environ Health Perspect 2000; 108:847-51. [PMID: 11017889 PMCID: PMC2556925 DOI: 10.1289/ehp.00108847] [Citation(s) in RCA: 229] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Diabetes prevalence in arseniasis-hyperendemic villages in Taiwan has been reported to be significantly higher than in the general population. The aim of this cohort study was to further evaluate the association between ingested inorganic arsenic and the incidence of non-insulin-dependent diabetes mellitus in these villages. A total of 446 nondiabetic residents in these villages were followed biannually by oral glucose tolerance test. Diabetes is defined as a fasting plasma glucose level > or = 7.8 mmol/L and/or a 2-hr post-load glucose level > or = 11.1 mmol/L. During the follow-up period of 1499.5 person-years, 41 cases developed diabetes, showing an overall incidence of 27.4/1,000 person-years. The incidence of diabetes correlated with age, body mass index, and cumulative arsenic exposure. The multivariate-adjusted relative risks were 1.6, 2.3, and 2.1 for age > or = 55 versus < 55 years, a body mass index ¿Greater/Equal to] 25 versus < 25 kg/m(2), and a cumulative arsenic exposure > or = 17 versus < 17 mg/L-years, respectively. The incidence density ratios (95% confidence intervals) between the hyperendemic villages and the two nonendemic control townships were 3.6 (3.5-3.6), 2.3 (1.1-4.9), 4.3 (2.4-7.7), and 5.5 (2.2-13.5), respectively, for the age groups of 35-44, 45-54, 55-64, and 65-74 years. The findings are consistent with our previous cross-sectional observation that ingested inorganic arsenic is diabetogenic in human beings.
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Affiliation(s)
- C H Tseng
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
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29
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Affiliation(s)
- C K Chong
- School of Life Science and Research Institute for Genetic Engineering, Chungbuk National University, Cheongju, 361-763, Korea
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30
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Abstract
Acetolactate synthase (ALS) is the common enzyme in the biosynthesis of valine, leucine, and isoleucine. The role of four cysteinyl residues in tobacco ALS was determined using site-directed mutagenesis and cysteine-specific cleavage. The C411A mutation abolished the enzymatic activity, as well as the binding affinity for the cofactor FAD. The activation constant of C411S for FAD is approximately 50-fold higher than that of wALS. The C607S mutation did not significantly affect the kinetic parameters. The IC(50) values of C411S and C607S for ALS-inhibiting herbicides are not much different from those of wALS. Two mutants, C163S and C309S, are labile and readily degraded to peptide fragments. The treatment of wALS with 2-nitro-5-thiocyanobenzoic acid, specific for cleavage of the N-terminal side of cysteine, yielded three peptides of 37.0, 22. 0, and 7.0 kDa. This fragmentation pattern is consistent with that deduced from the amino acid sequence of tobacco ALS, assuming the disulfide bond between Cys163 and Cys309. These results suggest that Cys411 is involved in the binding of FAD and that the intrachain disulfide bond between Cys163 and Cys309 plays a key role in maintaining the correct conformation of tobacco ALS.
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Affiliation(s)
- H J Shin
- School of Life Sciences, Chungbuk National University, Cheongju, 361-763, Korea
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31
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Melo LG, Veress AT, Chong CK, Ackermann U, Sonnenberg H. Salt-sensitive hypertension in ANP knockout mice is prevented by AT1 receptor antagonist losartan. Am J Physiol 1999; 277:R624-30. [PMID: 10484477 DOI: 10.1152/ajpregu.1999.277.3.r624] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mice harboring a functional deletion of the pro-atrial natriuretic peptide (ANP) gene (-/-) develop salt-sensitive hypertension relative to their wild-type (+/+) counterparts after prolonged (>1 wk) maintenance on high-salt (HS, 8% NaCl) diet. We reported recently that the sensitization of arterial blood pressure (ABP) to dietary salt in the -/- mice is associated with failure to downregulate plasma renin activity. To further characterize the role and mechanism of ANG II in the sensitization of ABP to salt in the ANP "knockout" mice, we measured ABP, heart rate (HR), and plasma catecholamine and aldosterone concentrations in -/- and +/+ mice maintained on HS for 4 wk and treated with daily injections of AT1 receptor antagonist DuP-753 (losartan) or distilled water (control). Daily food and water intake and fluid and electrolyte excretion were also measured during the first and last weeks of the dietary regimen. Cumulative urinary excretion of fluid and electrolytes did not differ significantly between genotypes and was not altered by chronic treatment with losartan. Basal ABP and HR were significantly elevated in control -/- mice compared with control +/+ mice. Losartan did not affect ABP or HR in +/+ mice, but reduced ABP and HR in the -/- mice to the levels in the +/+ mice. Total plasma catecholamine was elevated by approximately ten-fold in control -/- mice compared with control +/+ mice. Losartan reduced plasma catecholamine concentration significantly in -/- mice and abrogated the difference in plasma catecholamine between -/- and +/+ mice on HS diet. Plasma aldosterone did not differ significantly between genotypes and was not altered by losartan. We conclude that salt sensitivity of ABP in ANP knockout mice is mediated, at least in part, by a synergistic interaction between ANG II and sympathetic nerve activity.
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Affiliation(s)
- L G Melo
- Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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32
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Honrath U, Chong CK, Melo LG, Sonnenberg H. Effect of saline infusion on kidney and collecting duct function in atrial natriuretic peptide (ANP) gene "knockout" mice. Can J Physiol Pharmacol 1999. [DOI: 10.1139/y99-043] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Atrial natriuretic peptide (ANP) is thought to play a role in renal regulation of salt balance by reducing tubular reabsorption of sodium and chloride. Therefore, in the chronic absence of this hormone, a defect of salt excretion should be evident. We used an ANP gene deletion model to test this premise. F2 homozygous mutant mice (-/-) and their wild-type littermates (+/+) were fed an 8% NaCl diet prior to an acute infusion of isotonic saline. Arterial blood pressures, renal excretions of salt and water, as well as collecting duct transport of fluid and electrolytes were measured. Pressures were significantly higher in -/- compared with +/+ mice (139 ± 4 vs. 101 ± 2 mmHg; 1 mmHg = 133.3 Pa). There was no difference in glomerular filtration rate (-/- = 0.84 ± 0.06; +/+ = 0.81 ± 0.04 mL·min-1·g-1 kidney weight). In the collecting duct, sodium and chloride reabsorptions were significantly higher in the -/- group than in the +/+ group. As a result, natriuresis and chloruresis were relatively reduced (UNaV: -/- = 8.6 ± 1.1; +/+ = 14.0 ± 1.1; UClV: -/- = 10.1 ± 1.4; +/+ = 16.0 ± 1.1 µmol·min-1·g-1 kidney weight). We conclude that the absence of endogenous ANP activity in mice on a high-salt diet subjected to acute saline infusion causes inappropriately high reabsorption of sodium and chloride in the medullary collecting duct, resulting in a relative defect in renal excretory capacity for salt.Key words: high-salt diet; water, sodium, chloride, and potassium transport.
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33
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Honrath U, Chong CK, Melo LG, Sonnenberg H. Effect of saline infusion on kidney and collecting duct function in atrial natriuretic peptide (ANP) gene "knockout" mice. Can J Physiol Pharmacol 1999; 77:454-7. [PMID: 10537232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Atrial natriuretic peptide (ANP) is thought to play a role in renal regulation of salt balance by reducing tubular reabsorption of sodium and chloride. Therefore, in the chronic absence of this hormone, a defect of salt excretion should be evident. We used an ANP gene deletion model to test this premise. F2 homozygous mutant mice (-/-) and their wild-type littermates (+/+) were fed an 8% NaCl diet prior to an acute infusion of isotonic saline. Arterial blood pressures, renal excretions of salt and water, as well as collecting duct transport of fluid and electrolytes were measured. Pressures were significantly higher in -/- compared with +/+ mice (139 +/- 4 vs. 101 +/- 2 mmHg; 1 mmHg = 133.3 Pa). There was no difference in glomerular filtration rate (-/- = 0.84 +/- 0.06; +/+ = 0.81 +/- 0.04 mL x min(-1) x g(-1) kidney weight). In the collecting duct, sodium and chloride reabsorptions were significantly higher in the -/- group than in the +/+ group. As a result, natriuresis and chloruresis were relatively reduced (U(Na)V: -/- = 8.6 +/- 1.1; +/+ = 14.0 +/- 1.1; U(Cl)V: -/- = 10.1 +/- 1.4; +/+ = 16.0 +/- 1.1 micromol x min(-1) x g(-1) kidney weight). We conclude that the absence of endogenous ANP activity in mice on a high-salt diet subjected to acute saline infusion causes inappropriately high reabsorption of sodium and chloride in the medullary collecting duct, resulting in a relative defect in renal excretory capacity for salt.
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Affiliation(s)
- U Honrath
- Department of Physiology, University of Toronto, ON, Canada
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34
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Abstract
Acetolactate synthase (ALS) catalyzes the first common step in the biosynthesis of valine, leucine, and isoleucine. ALS is the target of three classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. Five mutants (W266F, W439F, W490F, W503F, and W573F) of the ALS gene from Nicotiana tabacum were constructed and expressed in Escherichia coli, and the enzymes were purified. The W490F mutation abolished the binding affinity for cofactor FAD and inactivated the enzyme. The replacement of Trp573 by Phe yielded a mutant ALS resistant to the three classes of herbicides. The other three mutations, W266F, W439F, and W503F, did not significantly affect the enzymatic properties and the sensitivity to the herbicides. These results indicate that the Trp490 residue is essential for the binding of FAD and that Trp573 is located at the herbicide binding site. The data also suggest that the three classes of herbicides bind ALS competitively.
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Affiliation(s)
- C K Chong
- Department of Biochemistry, Chungbuk National University, Cheongju, 361-763, Korea
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35
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Chong CK, Rowe CS, Sivanesan S, Rattray A, Black RA, Shortland AP, How TV. Computer aided design and fabrication of models for in vitro studies of vascular fluid dynamics. Proc Inst Mech Eng H 1999; 213:1-4. [PMID: 10087899 DOI: 10.1243/0954411991534753] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
An integrated computer aided design/computer aided manufacture system has been used to model the complex geometry of blood vessel anastomoses. Computer models are first constructed with key dimensions derived from radiological images of bypass grafts, and from casts of actual blood vessel anastomoses. Physical models are then fabricated in one of two ways: the surface geometry data can be used to control the movement of a three-axis milling machine; alternatively, the same data can be exported in a form that can be interpreted by a stereolithography apparatus. Both methods produce geometrically defined solid investments that can be used in a multistep casting process that yields high-quality physical models for vascular fluid dynamic studies. This technique is useful for parametric studies.
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Affiliation(s)
- C K Chong
- Department of Clinical Engineering, University of Liverpool, UK
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36
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Honrath U, Chong CK, Sonnenberg H. Body fluid volume status and the renal response to atrial natriuretic peptide in rats. Can J Physiol Pharmacol 1998; 76:1156-60. [PMID: 10326839 DOI: 10.1139/cjpp-76-12-1156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of altering the volumes of different body fluid compartments on the renal response to atrial natriuretic peptide (ANP) was studied in anesthetized rats before and during administration of the peptide at 170 ng/min. Four different groups were used. In the first (De), reduction of total body water content was induced by 48 h water deprivation. In the second (De+NaCl), an acute intravenous infusion after the same 48 h dehydration was used to restore the extracellular, but not the intracellular, fluid compartment. In the third (Eu+NaCl), euvolemic rats were infused with isotonic saline at the same rate as in group De+NaCl to expand both intravascular and interstitial components of extracellular fluid. In the fourth group (Eu+BSA) an infusion of hyperoncotic (6%) bovine serum albumin in isotonic saline was used to expand the intravascular volume while contracting the interstitial volume. Excretion of water and salt was predictably reduced in the De group compared with the others. This reduction was associated with increased tubular reabsorption, both upstream from the medullary collecting duct and in the duct itself. Administration of ANP did not significantly affect diuresis and saluresis, or tubular transport. By contrast, there were marked and similar diuretic and natriuretic responses to ANP in groups De+NaCl and Eu+NaCl, associated with transport inhibition primarily in the medullary collecting duct. Surprisingly, the rats infused with hyperoncotic solution (Eu+NaCl) also failed to show marked excretory or duct transport responses to ANP. According to the study design, the two nonresponding groups had, respectively, a decreased or a normal intracellular compartment, and a decreased or increased plasma volume. The common feature of both nonresponding groups was a decreased interstitial fluid compartment, whereas the two responding groups had normal or increased interstitial volume. We suggest, therefore, that a replete interstitial fluid compartment is essential for the renal response to ANP.
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Affiliation(s)
- U Honrath
- Department of Physiology, University of Toronto, Canada
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37
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Honrath U, Chong CK, Sonnenberg H. Body fluid volume status and the renal response to atrial natriuretic peptide in rats. Can J Physiol Pharmacol 1998. [DOI: 10.1139/y98-135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of altering the volumes of different body fluid compartments on the renal response to atrial natriuretic peptide (ANP) was studied in anesthetized rats before and during administration of the peptide at 170 ng/min. Four different groups were used. In the first (De), reduction of total body water content was induced by 48 h water deprivation. In the second (De+NaCl), an acute intravenous infusion after the same 48 h dehydration was used to restore the extracellular, but not the intracellular, fluid compartment. In the third (Eu+NaCl), euvolemic rats were infused with isotonic saline at the same rate as in group De+NaCl to expand both intravascular and interstitial components of extracellular fluid. In the fourth group (Eu+BSA) an infusion of hyperoncotic (6%) bovine serum albumin in isotonic saline was used to expand the intravascular volume while contracting the interstitial volume. Excretion of water and salt was predictably reduced in the De group compared with the others. This reduction was associated with increased tubular reabsorption, both upstream from the medullary collecting duct and in the duct itself. Administration of ANP did not significantly affect diuresis and saluresis, or tubular transport. By contrast, there were marked and similar diuretic and natriuretic responses to ANP in groups De+NaCl and Eu+NaCl, associated with transport inhibition primarily in the medullary collecting duct. Surprisingly, the rats infused with hyperoncotic solution (Eu+NaCl) also failed to show marked excretory or duct transport responses to ANP. According to the study design, the two nonresponding groups had, respectively, a decreased or a normal intracellular compartment, and a decreased or increased plasma volume. The common feature of both nonresponding groups was a decreased interstitial fluid compartment, whereas the two responding groups had normal or increased interstitial volume. We suggest, therefore, that a replete interstitial fluid compartment is essential for the renal response to ANP.Key words: water and sodium chloride excretion, collecting duct transport, plasma volume, interstitial fluid, intracellular compartment.
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Low CK, Chong CK, Wong HP, Low YP. Operative treatment of displaced talar neck fractures. Ann Acad Med Singap 1998; 27:763-6. [PMID: 10101545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Twenty-two displaced talar neck fractures were treated by open reduction and internal fixation. Four open fractures were operated within 8 hours and 18 closed injuries were treated at an average interval of 13.8 hours after injury. Fractures were classified according to Hawkins' classification into 14 type II, 7 type III and 1 type IV. At an average follow up of 4.4 years, 18 cases obtained excellent or good results. Result was fair in 2 cases of delayed union and 1 case of avascular necrosis. Another case of avascular necrosis developed osteoarthritis of the ankle and had poor result. The overall incidence of avascular necrosis of the body of the talus was 9%.
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Affiliation(s)
- C K Low
- Department of Orthopaedic Surgery, Tan Tock Seng Hospital, Singapore
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Chong CK, How TV, Black RA, Shortland AP, Harris PL. Development of a simulator for endovascular repair of abdominal aortic aneurysms. Ann Biomed Eng 1998; 26:798-802. [PMID: 9779952 DOI: 10.1114/1.66] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The design and development of a simulator for endovascular repair of abdominal aortic aneurysm (AAA) is described. The simulator consists of an interchangeable model of a human AAA based on computed tomography data and is produced by means of computer-aided design and manufacture (CAD/CAM) techniques. The model has renal, iliac, and femoral arteries, and is perfused with a temperature controlled blood-analog fluid under simulated physiological flow conditions. "Fluoroscopic imaging" is simulated by a computerized imaging system that uses visible light. A movable video camera relays images in the antero-posterior and lateral planes of the AAA to a monitor. The imaging system allows "arteriography" and "road-mapping" to be performed so as to facilitate accurate deployment of endovascular stent-grafts. The system has been used for teaching and demonstrating endovascular techniques to clinicians, as well as the evaluation of new stent-graft devices. Its successful incorporation into endovascular workshops has demonstrated its role in the training of clinicians in endovascular repair of AAA.
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Affiliation(s)
- C K Chong
- Department of Clinical Engineering, University of Liverpool, United Kingdom
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Yuen YH, Chang S, Chong CK, Lee SC, Critchley JA, Chan JC. Drug utilization in a hospital general medical outpatient clinic with particular reference to antihypertensive and antidiabetic drugs. J Clin Pharm Ther 1998; 23:287-94. [PMID: 9867312 DOI: 10.1046/j.1365-2710.1998.00161.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVES To examine the prescribing patterns, particularly antihypertensive and antidiabetic drugs, in a hospital outpatient clinic and to evaluate the expenditure incurred. METHODS Prescriptions from a general medical outpatient clinic in a teaching hospital were collected for 4 weeks. Drug expenditures were calculated. RESULTS A total of 622 prescriptions containing 1903 items were collected. Antihypertensive and antidiabetic drugs accounted for 25.9 and 9.1% usage, respectively. Calcium channel blocking agents, angiotensin converting enzyme inhibitors and beta-blocking agents were the most popular antihypertensive drugs used. Sulphonylureas were the most frequently prescribed antidiabetic agents. Amlodipine, doxazosin and sotalol accounted for 4.5% of all prescription items but 27.8% of the total drug expenditure. CONCLUSION The use of antihypertensive and antidiabetic drugs accounted for most of the drug usage in this study. Use of newer and more expensive agents has further increased drug expenditure. Monitoring drug usage and their correlations with clinical outcomes are warranted.
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Affiliation(s)
- Y H Yuen
- Department of Pharmacy, The Chinese University of Hong Kong, Shatin, New Territories
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Melo LG, Veress AT, Chong CK, Pang SC, Flynn TG, Sonnenberg H. Salt-sensitive hypertension in ANP knockout mice: potential role of abnormal plasma renin activity. Am J Physiol 1998; 274:R255-61. [PMID: 9458926 DOI: 10.1152/ajpregu.1998.274.1.r255] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Atrial natriuretic peptide (ANP), a peptide hormone produced by the heart, exerts a chronic hypotensive effect. Knockout mice with a homozygous disruption of the pro-ANP gene (-/-) are incapable of producing ANP and are hypertensive relative to their wild-type (+/+) siblings. Previous studies showed that arterial blood pressure (ABP) was further increased in conscious -/- mice kept for 2 wk on 2% salt, but not in anesthetized -/- mice after 1 wk on 8% salt. To determine whether inconsistencies in observed effects of salt on ABP of -/- mice are due to duration of increased salt intake and/or the state of consciousness of the animals, we measured ABP from an exteriorized carotid catheter during and after recovery from anesthesia with ketamine-xylazine in adult +/+ and -/- mice kept on low (LS; 0.008% NaCl)- or high (HS; 8% NaCl)-salt diets for 3-4 wk. Conscious ABP +/- SE (mmHg) of +/+ mice did not differ significantly on either diet (HS, 113 +/- 3; LS, 110 +/- 5). However, on HS diet -/- mice had significantly higher ABP (135 +/- 3; P < 0.001) than both -/- (115 +/- 2) and +/+ (110 +/- 5) mice on LS diet. Anesthesia decreased ABP in all groups, but the the genotype- and diet-related differences were preserved. Plasma renin activity (PRA, ng ANG I.ml-1.h-1) in blood collected at termination of experiment was appropriately different on the 2 diets in +/+ mice (HS, 4.9 +/- 1.9; LS, 21 +/- 2.8). However, PRA failed to decrease in -/- mice on HS diet (HS, 18 +/- 2.9; LS, 19 +/- 3.7). Independent of genotype, concentration of endothelin-1 (ET-1, pg/mg protein) and endothelial constitutive NOS (ecNOS, density/100 micrograms protein) was significantly elevated in kidneys of mice fed on HS diet (ET-1 -/-, 31 +/- 4.7 and +/+, 32 +/- 4.1; ecNOS -/-, 160 +/- 19 and +/+, 156 +/- 19) compared with mice fed on LS diet (ET-1 -/-, 19 +/- 1.9 and +/+, 21 +/- 1.8; ecNOS -/-, 109 +/- 13 and +/+, 112 +/- 18). We conclude that, regardless of the state of alertness, -/- mice develop salt-sensitive hypertension after prolonged feeding on HS, in part due to their inability to reduce PRA, whereas the specific renal upregulation of ecNOS and ET-1 in response to HS intake may be an ANP-independent adaptive adjustment aimed at improving kidney function and counteracting the pressor effect of salt.
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Affiliation(s)
- L G Melo
- Department of Physiology, University of Toronto, Ontario, Canada
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Abstract
BACKGROUND The injury resulting from postmortem ischemia is a critical deterrent to the availability of donor valves. Using the reduction of XTT-tetrazolium salt as a marker of metabolic sequelae, we assessed the injurious effect of ischemia and the metabolic sequelae in 156 porcine semilunar leaflets. METHODS The leaflets were randomly allocated to noncryoprocessed (n = 72) or cryoprocessed (n = 72) groups. At each preservation temperature of 4 degrees C, 24 degrees C, or 37 degrees C, 24 leaflets each were exposed to one of four storage periods of 9, 17, 30, or 60 hours. Twelve fresh aortic leaflets served as baseline reference samples. RESULTS There was a progressive loss in the metabolic functioning of valve leaflet cells in both noncryopreserved and cryopreserved tissue as the storage times increased. Cryopreserved tissue showed a greater loss of function than noncryopreserved tissue did. The metabolic injury was mainly a consequence of cryoprocessing. The greatest loss in metabolic functioning occurred in the valves stored for 60 hours. The least favorable combination of variables was cryopreservation and a precryopreservation storage time of 60 hours. CONCLUSIONS We conclude that 30- to 60-hour delays do not have a significant metabolic effect on cardiac leaflets. Thus it may be possible to safely extend the permissible ischemic periods after organ harvest.
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Affiliation(s)
- J H Lu
- Division of Pediatric Cardiology, Veterans General Hospital-Taipei, National Yang-Ming University, Taiwan, Republic of China
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Chong CK, Senan P, Kumar GV. Carbon monoxide poisoning from gas water heater installed and operated in the bathroom. Med J Malaysia 1997; 52:169-71. [PMID: 10968076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Two cases of carbon monoxide poisoning involving 3 victims occurred in Cameron Highlands in the months of August and September 1995. Two of the victims were found dead in the bathrooms where they were taking a bath while the other one survived. Blood toxicology from the post mortems revealed high levels of carbon monoxide. The only significant source of carbon monoxide in both cases were the gas water heaters which were installed in the bathrooms. A multigas detector was used to monitor the level of carbon monoxide in one of the bathrooms and carbon monoxide was found to be produced to 1200 ppm in 16 minutes during operation of the heater. Carbon monoxide poisoning from gas water heaters installed in bathroom is a significant hazard.
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Abstract
To examine whether lipid abnormalities contributed to the endemic peripheral vascular disease (PVD) in villages where arseniasis was hyperendemic in Taiwan, the authors studied 533 adults with Doppler ultrasound and lipid profiles including total cholesterol, triglyceride, high- and low-density lipoprotein cholesterol, apolipoprotein AI, and apolipoprotein B. Among them, 63 had PVD based on an ankle-brachial index < 0.90. Long-term arsenic exposure indices including cumulative arsenic exposure in mg/L-years, duration of drinking artesian well water in years, and duration of living in arseniasis-hyperendemic villages in years were calculated from detailed history obtained through standardized interviews based on a structured questionnaire and arsenic concentration in well water. Possible confounders including age, sex, body mass index, cigarette smoking, and disease status of diabetes mellitus and hypertension were considered in the analyses. None of the lipid profiles differed significantly between the presence and absence of PVD. The odds ratios for PVD did not differ among different quintiles of lipid profiles with the lowest quintile as the referent. However, a significant dose-response relation was found for the long-term arsenic exposure indices. The multivariate-adjusted odds ratios for cumulative arsenic exposure of 0.1 approximately 19.9 and > or = 20 mg/L-years were 2.77 and 4.68, respectively, compared with the unexposed. These results suggest that the PVD in arseniasis-hyperendemic villages is correlated with ingested inorganic arsenic and not with the lipid profiles.
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Affiliation(s)
- C H Tseng
- Department of Internal Medicine, National Taiwan University Hospital, Taipei
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Lu JH, Chiu YT, Sung HW, Hwang B, Chong CK, Chen SP, Mao SJ, Yang PZ, Chang Y. XTT-colorimetric assay as a marker of viability in cryoprocessed cardiac valve. J Mol Cell Cardiol 1997; 29:1189-94. [PMID: 9160870 DOI: 10.1006/jmcc.1996.0354] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This study sought to evaluate the use of tetrazolium salt XTT reduction as an indicator of valvular viability in a cryoprocessed porcine cardiac homograft model. The XTT tetrazolium assays was based on the metabolic reduction of Sodium 3'-[1-(phenylamino-carbonyl)-3,4-Tetrazolium]-bis(4-methoxy-6-nitro) benzene sulfonic acid hydrate. The relationship between XTT reduction and: (1) leaflet tissue with various weight (n = 24); (2) morphometric evaluation (n = 30); (3) cadaveric ischemic intervals (n = 30); (4) freeze-thawing (n = 30) has been studied. The measurement of XTT reduction were significantly correlated with the weight of cardiac leaflets, in the range of 30 to 180mg (y=0.015x-0.063; r=0.99). Compared to morphometry of valvular damage, the reduction of mitochondrial enzymatic activity in cardiac leaflets was correlated with matrix cells without irreversible damage (r=0.89, P<0.005). The depletion of XTT reduction occurred dependent of ischemic time intervals. In general, freeze-thawing reduced more than 20% activity of mitochondrial dehydrogenase. We concluded that XTT tetrazolium assay is highly sensitive to determine valvular injury. The study demonstrated its potential for testing of cryopreserved cardiac valve.
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Affiliation(s)
- J H Lu
- Homograft Laboratory, Veterans General Hospital-Taipei, Taiwan, R.O.C
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Honrath U, Veress AT, Chong CK, Sonnenberg H. Effect of sympathetic and angiotensin-aldosterone systems on renal salt conservation in the rat. Am J Physiol 1997; 272:F538-44. [PMID: 9140056 DOI: 10.1152/ajprenal.1997.272.4.f538] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
During dietary salt deprivation, the sympathetic nervous system and the angiotensin-aldosterone system are stimulated. Both systems are thought to be essential for maximal salt conservation by the kidney. To study their relative contributions, we produced negative salt balance in rats by intraperitoneal injection of furosemide, followed by a low-salt diet (<0.008% NaCl). In a 1-wk metabolic study, the animals were unable to replace the drug-induced salt deficit. Six groups of rats were studied. A control group established baseline function, a second group of 6-hydroxydopamine (OHDA) rats were treated with OHDA to destroy sympathetic efferent nerve terminals, and a third group (losartan) were treated with the angiotensin-receptor antagonist losartan. The influence of catecholamines and aldosterone released from the adrenal gland was studied in a further three groups. Rats were sham-adrenalectomized (sham), subjected to bilateral adrenal enucleation (Enuc) to eliminate catecholamine secretion, or were bilaterally adrenalectomized (Adx), eliminating both catecholamine and corticosteroid release. Dexamethasone was used as glucocorticoid replacement in this group. Steady-state urinary salt excretion was not different between control and OHDA rats. The losartan group showed significantly increased sodium but not chloride excretion. Surprisingly, there were no differences in salt excretion among sham, Enuc, and Adx groups. We conclude that, during a state of chronic salt depletion, renal mechanism(s) independent of neuronally released or systemically circulating catecholamines or of adrenally released aldosterone can ensure maximal salt conservation by the kidney. Although our data show that losartan increased sodium excretion under these conditions, we suggest that the losartan effect can be explained by a reduction of bicarbonate reabsorption, obligating simultaneous excretion of the cation.
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Affiliation(s)
- U Honrath
- Department of Physiology, University of Toronto, Ontario, Canada
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Veress AT, Honrath U, Chong CK, Sonnenberg H. Renal resistance to ANF in salt-depleted rats is independent of sympathetic or ANG-aldosterone systems. Am J Physiol 1997; 272:F545-50. [PMID: 9140057 DOI: 10.1152/ajprenal.1997.272.4.f545] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Chronic salt depletion was used as a model to study the mechanism of renal resistance to the natriuretic effect of atrial natriuretic factor (ANF). Rats were pretreated with furosemide and placed on a low-salt diet (<0.008% NaCl) for 1 wk before a clearance experiment. Compared with animals on a normal salt diet (0.4% NaCl), the natriuretic reponse to ANF administration was reduced by one order of magnitude and was quantitatively trivial. To assess the influence of the sympathoadrenergic system, different groups of rats were either subjected to acute unilateral renal denervation, to chronic adrenal enucleation to reduce circulating catecholamines, or to pretreatment with 6-hydroxydopamine (OHDA) to destroy sympathetic postganglionic nerve endings. None of these treatments was able to fully or even partially restore ANF natriuresis. To determine whether an effect of angiotensin on the kidney prevented the response, the specific receptor antagonist losartan (DuP-753) was administered during the week prior to the experiment. This treatment also did not influence ANF resistance. Similarly, bilateral adrenalectomy 2 wk before the experiment did not affect the renal ANF resistance in salt-depleted rats. The depressed excretory response could not be explained on the basis of reduced renal perfusion pressure or glomerular filtration rate. We conclude that undetermined compensatory mechanism(s) ensures renal salt conservation in this model in the face of even supraphysiological levels of ANF.
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Affiliation(s)
- A T Veress
- Department of Physiology, University of Toronto, Ontario, Canada
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Chong CK, Brennan J, How TV, Edwards R, Gilling-Smith GL, Harris PL. A prototype simulator for endovascular repair of abdominal aortic aneurysms. Eur J Vasc Endovasc Surg 1997; 13:330-3. [PMID: 9129609 DOI: 10.1016/s1078-5884(97)80107-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A prototype simulator for training in endovascular repair of abdominal aortic aneurysms (AAA) has been developed. Employing transparent models of human AAA complete with renal, iliac and femoral arteries, this system allows accurate simulation of aortography, road-mapping, catheter guidewire manipulation and stent-graft deployment while obviating the need for ionising radiation.
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Affiliation(s)
- C K Chong
- Department of Clinical Engineering, University of Liverpool, U.K
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John SW, Veress AT, Honrath U, Chong CK, Peng L, Smithies O, Sonnenberg H. Blood pressure and fluid-electrolyte balance in mice with reduced or absent ANP. Am J Physiol 1996; 271:R109-14. [PMID: 8760210 DOI: 10.1152/ajpregu.1996.271.1.r109] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Atrial natriuretic peptide (ANP)-gene knockout mice of three genotypes (+/+, +/-, and -/-) were maintained on a low-salt diet (0.008% NaCl). They were then fed either the same low-salt diet or a high-salt diet (8% NaCl) for 1 wk. No differences were found among genotypes in daily food and water intakes or in urinary volume and electrolyte excretions. Arterial blood pressures measured in anesthetized animals at the end of the dietary regimen were significantly and similarly increased in -/- compared with +/+ mice on each diet. Renal excretion of fluid and electrolytes was measured in anesthetized mice before and after acute blood volume expansion. No genotype differences were observed before volume expansion. After volume expansion the wild-type (+/+) mice had much greater saluretic responses than either the heterozygous (+/-) or the homozygous mutant (-/-) animals on the low-salt diet but not on the high-salt diet. We conclude that ANP lowers blood pressure in the absence of detected changes in renal function; ANP is not essential for normal salt balance, even on high-salt intake; and ANP is essential for the natriuretic response to acute blood volume expansion on a low-salt but not high-salt intake.
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Affiliation(s)
- S W John
- Department of Pathology, University of North Carolina, Chapel Hill 27599-7020, USA
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Tseng CH, Chong CK, Chen CJ, Tai TY. Dose-response relationship between peripheral vascular disease and ingested inorganic arsenic among residents in blackfoot disease endemic villages in Taiwan. Atherosclerosis 1996; 120:125-33. [PMID: 8645353 DOI: 10.1016/0021-9150(95)05693-9] [Citation(s) in RCA: 129] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The purpose of this study was to examine the correlation between previous arsenic exposure and peripheral vascular disease after stopping consumption of high-arsenic artesian well water for more than two decades in blackfoot disease endemic villages in Taiwan. A total of 582 adults (263 men and 319 women, aged 52.6 +/- 10.6 years) living in these villages underwent Doppler ultrasound measurement of systolic pressures on bilateral ankle (posterior tibial and dorsal pedal) and brachial arteries and estimation for long-term arsenic exposure. The diagnosis of peripheral vascular disease was based on an ankle-brachial index (the ratio between ankle and brachial systolic pressures) <0.90 on either side. Three indices of arsenic exposure were estimated: (1) duration of living in blackfoot disease endemic villages; (2) duration of artesian well water consumption; and (3) cumulative arsenic exposure in mg/l-years based on the detailed history of residential addresses and artesian well water consumption and the arsenic concentration in artesian well water. Multiple logistic regression analysis was used to assess the association between peripheral vascular disease and arsenic exposure. A dose-response relation was observed between the prevalence of peripheral vascular disease and the long-term arsenic exposure. The odds ratios (95% confidence intervals) after adjustment for age, sex, body mass index, cigarette smoking, serum cholesterol and triglyceride levels, diabetes mellitus and hypertension were 2.77 (0.84-9.14), and 4.28 (1.26-14.54) for those who had cumulative arsenic exposure of 0.1-19.9 and > or = 20.0 mg/l-years, respectively, compared with those who were not exposed. This study suggests a close relation between long-term arsenic exposure and peripheral vascular disease in blackfoot disease endemic villages in Taiwan after stopping consumption of artesian well water.
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Affiliation(s)
- C H Tseng
- Department of Internal Medicine, National Taiwan University Hospital, Taipei, ROC
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