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Tan K, Radloff SE, Li JJ, Hepburn HR, Yang MX, Zhang LJ, Neumann P. Bee-hawking by the wasp, Vespa velutina, on the honeybees Apis cerana and A. mellifera. Naturwissenschaften 2007; 94:469-72. [PMID: 17235596 DOI: 10.1007/s00114-006-0210-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2006] [Revised: 11/30/2006] [Accepted: 12/06/2006] [Indexed: 10/23/2022]
Abstract
The vespine wasps, Vespa velutina, specialise in hawking honeybee foragers returning to their nests. We studied their behaviour in China using native Apis cerana and introduced A. mellifera colonies. When the wasps are hawking, A. cerana recruits threefold more guard bees to stave off predation than A. mellifera. The former also utilises wing shimmering as a visual pattern disruption mechanism, which is not shown by A. mellifera. A. cerana foragers halve the time of normal flight needed to dart into the nest entrance, while A. mellifera actually slows down in sashaying flight manoeuvres. V. velutina preferentially hawks A. mellifera foragers when both A. mellifera and A. cerana occur in the same apiary. The pace of wasp-hawking was highest in mid-summer but the frequency of hawking wasps was three times higher at A. mellifera colonies than at the A. cerana colonies. The wasps were taking A. mellifera foragers at a frequency eightfold greater than A. cerana foragers. The final hawking success rates of the wasps were about three times higher for A. mellifera foragers than for A. cerana. The relative success of native A. cerana over European A. mellifera in thwarting predation by the wasp V. velutina is interpreted as the result of co-evolution between the Asian wasp and honeybee, respectively.
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Regier T, Paulsen J, Wright G, Coulthard I, Tan K, Sham TK, Blyth RIR. Commissioning of the Spherical Grating Monochromator Soft X-ray Spectroscopy Beamline at the Canadian Light Source. ACTA ACUST UNITED AC 2007. [DOI: 10.1063/1.2436101] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Lu J, Kong L, Loh K, Shakespeare T, Thiagarajan A, Tan K. 2430. Int J Radiat Oncol Biol Phys 2006. [DOI: 10.1016/j.ijrobp.2006.07.840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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154
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Tan K, Booth D, Newell SJ, Dear PRF, Hughes C, Richards M. Point-of-care testing of neonatal coagulation. ACTA ACUST UNITED AC 2006; 28:117-21. [PMID: 16630216 DOI: 10.1111/j.1365-2257.2006.00765.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The aim of this validation study was to compare prothrombin time (PT) and activated partial thromboplastin time (APTT) results from a point-of-care testing (POCT) device (Rapidpoint Coag) with those from standard laboratory tests. The subjects were newborn infants needing coagulation screen for any clinical indications within a regional neonatal intensive care unit. The level of agreement between POCT and laboratory measurements of PT and APTT was determined. For PT: the bias was from -7.6 to 12.4 s and precision was 5.0 s. For the detection of prolonged PT at a level of 16 s, the sensitivity was 0.70, specificity was 0.57 and the positive predictive value (PPV) was 0.62. For APTT: the bias was from -39.1 to 23.7 s, and precision was 15.7 s. For the detection of prolonged APTT at a level of 55 s, the sensitivity was 0.80, specificity was 0.95 and the PPV was 0.80. The POCT device tested has limited utility as a cot-side device for screening for a prolongation of the APTT in the newborn but is not sensitive for screening for prolongation of the PT.
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Koh Y, Kurup A, Tohid H, Lee L, Wong Y, Tan K, Lee W, Ling M. P14.01 A Review of Control Measures in Containing a Large Outbreak of Vancomycin-resistant enterococci (VRE) in a Non-endemic Setting. J Hosp Infect 2006. [DOI: 10.1016/s0195-6701(06)60245-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Obendorf SK, Lemley AT, Hedge A, Kline AA, Tan K, Dokuchayeva T. Distribution of pesticide residues within homes in central New York State. ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY 2006; 50:31-44. [PMID: 16237496 DOI: 10.1007/s00244-004-0185-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Accepted: 05/19/2005] [Indexed: 05/04/2023]
Abstract
Residues for 17 pesticides were analyzed in 41 households in central New York State that represented farm, rural, and urban houses. Samples were taken in both summer and winter of 2000-2001 from the same households from four locations; family room carpet; adjacent smooth floor; flat tabletop surface; and settled dust collected in a Petri dish on a tabletop. Pesticide residues were analyzed to identity factors that influence both the transport into and the redistribution of pesticides in the indoor environment. Differences were observed between the various pesticides and pesticide classifications relative to location within and between households as well as by season. Variations in the pesticide residues were related to a number of factors. Higher residues were observed in the farm households, particularly in summer, with the highest amount observed for chloropyrifos in carpet (33 microg/m2). For many pesticides, the frequency of detection and the amount of residues were higher in summer, which relates to usage patterns in agriculture and horticulture; however, larger amounts of insecticides such as mecoprop, resmethrin, and tetramethrin were found on flat surfaces in winter, indicating household use and possible redistribution within the home. Distribution patterns suggest that routines within a household may cause high variation in residues; these practices include indoor pets and treatment for fleas and ticks, use of termiticides, and fastidiousness of occupants. Frequency of pesticide detection was highest in carpet for both summer and winter for all households, indicating that carpets hold pesticides over time. Adsorbent fibrous materials such as textiles hold pesticides by macro- and micro-occlusion in their complex structures. Amounts of pesticide residue were higher in carpets than on smooth floors, particularly for rural farm households where the farmer was a certified pesticide applicator. The maximum amount of pesticide residue on a smooth floor surface was 13.6 microg/m2 malathion while the maxima on wiped surfaces and in settled dust were 1.8 microg/m2 2, 4 D and 3 microg/m2 pendimethalin, respectively. Physical properties of individual pesticides such as vapor pressure influenced the distribution of the pesticide within the households. Evidence of volatilization of pesticides and redeposition on surfaces was observed, indicating that this is a mechanism for contamination of surfaces in addition to adsorption on airborne particles and tracking. High residues in winter are evidence that closure of households in winter that reduces ventilation results in redistribution of pesticides within households.
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Tan E, Hsu A, Eng P, Tan K, Lee P, Raghuram J, Lo C, Loo C, Cheah F, Toh C, Leong S, Lim W, Lau J, Hui K. P-123 Molecular profiling of lung cancers: Can it be used as a clinicaltool? Lung Cancer 2005. [DOI: 10.1016/s0169-5002(05)80617-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Laserson KF, Binkin NJ, Thorpe LE, Laing R, Iademarco MF, Bloom A, Agerton TB, Nelson L, Cegielski JP, Ferroussier O, Holtz T, Vitek E, Gammino V, Tan K, Finlay A, Dewan P, Miranda A, Aquino G, Weyer K, Sy DN, Vernon A, Becerra J, Ershova J, Wells CD. Capacity building for international tuberculosis control through operations research training. Int J Tuberc Lung Dis 2005; 9:145-50. [PMID: 15732732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023] Open
Abstract
SETTING In resource-poor countries, few tuberculosis (TB) program staff at the national, provincial, and even district levels have the basic analytical and epidemiological skills necessary for collecting and analyzing quality data pertaining to national TB control program (NTP) improvements. This includes setting program priorities, operations planning, and implementing and evaluating program activities. OBJECTIVES To present a model course for building capacity in basic epidemiology and operations research (OR). DESIGN A combination of didactic lectures and applied field exercises were used to achieve the main objectives of the 6-day OR course. These were to increase the understanding of quantitative and qualitative research concepts, study design, and analytic methods, and to increase awareness of how these methods apply to the epidemiology and control of TB; and to demonstrate the potential uses of OR in answering practical questions on NTP effectiveness. As a final outcome, course participants develop OR proposals that are funded and later implemented. RESULTS Since 1997, this OR course has been conducted nine times in five countries; 149 key NTP and laboratory staff have been trained in OR methods, and 44 OR protocols have been completed or are underway. CONCLUSION This low-cost model course can be adapted to a wide range of public health issues.
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Abstract
The adsorption of 14 trivalent lanthanoid ions and yttrium ion (denoted by Ln3+) on calcite surfaces was investigated under various solution conditions of pH (pH = 6.8-7.8) and calcium ion concentration (pCa = -log[Ca2+]= 2.0 and 3.0), and different surface conditions of calcite crystals (well-developed and rough surfaces). The lanthanoid ions were equilibrated in a solution of ionic strength 0.1 mol dm-3(NaCl) saturated with calcite at 25.0 degrees C using excess (solid) calcite crystals suspended in solution. The concentrations of the lanthanoid ions on the calcite crystals (C(cry)/mol kg-1) and in solution (C(soln)/mol dm-3) were determined by means of inductively coupled plasma-mass spectrometry (ICP-MS). It is found that the distribution ratio (D=C(cry)/C(soln) decreases as the atomic number of the lanthanoid increases showing the so called Tetrad Effect. D values increase with increasing pH, whereas they are independent of the calcium ion concentration (i.e., carbonate ion concentration). These results indicate that lanthanoid ions are adsorbed on the calcite surface together with hydroxide ions, i.e., the adsorption of hydroxo-complexes. The heavy lanthanoid ions (Er3+ to Lu3+) are adsorbed as monohydroxo-complexes, (Ln(OH)2+), whereas those of the light lanthanoids are predominantly adsorbed as dihydroxo-complexes (Ln(OH)2+). Other lanthanoids show competitive adsorption reactions of mono- and dihydroxo complexes. Both successive adsorption constants of hydroxo complexes increase with decreasing atomic number of the lanthanoid. The rough surface of calcite is quite active and the distribution ratio of the lanthanoid ions on the rough surface is much higher than that on the well-developed crystalline surface. Rates of adsorption of lanthanide ions were measured and mechanisms are being discussed
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Tayebjee M, Tan K, Lip G, MacFadyen R. W01.82 Circulating neutrophil matrix metalloproteinase-9 is elevated in stable coronary artery disease and ischaemic cardiomyopathy. ATHEROSCLEROSIS SUPP 2004. [DOI: 10.1016/s1567-5688(04)90082-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Ramasamy I, Kennedy J, Tan K. Capillary electrophoresis for characterization of low molecular weight heparins. LABORATORY HEMATOLOGY : OFFICIAL PUBLICATION OF THE INTERNATIONAL SOCIETY FOR LABORATORY HEMATOLOGY 2004; 9:64-6. [PMID: 12828300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/03/2023]
Abstract
In many instances, low molecular weight heparins (LMWH) have replaced unfractionated heparins for prevention and treatment of venous thromboembolism. Each LMWH is a specific compound with its own physicochemical and pharmacological properties. These properties are critical in determining the therapeutic efficacy of the product. In recent times, capillary electrophoresis (CE) has emerged as a means of analytical separation of biological molecules. There are few reports, however, detailing the separation of whole heparins by capillary electrophoresis. This paper reports the use of CE to characterize LMWH without prior oligosaccharide release, labeling, or derivatization. The paper also focuses on the advantages of CE separation for the monitoring of product consistency.
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Tan K, Guibert C, Neaud V, Rosenbaum J. Hepatitis C virus proteins do not directly trigger fibrogenic events in cultured human liver myofibroblasts. J Viral Hepat 2003; 10:427-32. [PMID: 14633175 DOI: 10.1046/j.1365-2893.2003.00460.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Although liver fibrosis is the major complication of hepatitis C virus (HCV) infection, the mechanisms of fibrogenesis in this setting are not completely understood. The aim of this study was to test the direct effect of HCV proteins on signalling- and fibrosis-related events in cultured human liver myofibroblasts, the effector cells of liver fibrogenesis. Cultured myofibroblasts were exposed to recombinant HCV core, a structural protein, and nonstructural proteins (NS) 3, NS 4 and NS 5. HCV proteins did not significantly increase DNA synthesis in myofibroblasts. We then examined if these proteins affected early signalling events. None of the HCV proteins affected the phosphorylation of the mitogen activated protein kinases/extracellular regulated kinases 1 and 2, or of the phosphatidylinositol 3-kinase target, Akt. HCV proteins had also no effect on intracellular calcium concentration. In other experiments, fibrogenesis-related parameters were measured. None of the HCV proteins had any effect on the secretion of type I collagen, tissue inhibitor of matrix metalloproteinases type 1, gelatinase or urokinase. Alpha-smooth muscle actin expression was also not modified. In summary, our experiments do not support a direct effect of these HCV proteins on fibrogenic cells.
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Evans CJ, Smye SW, Snowden S, Tan K, Newell S, Dear PRF. A mathematical model of CO2 variation in the ventilated neonate. Physiol Meas 2003; 24:703-15. [PMID: 14509308 DOI: 10.1088/0967-3334/24/3/307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A mathematical model of the variation of partial pressure of carbon dioxide in the arterial blood of a ventilated neonate is developed. The model comprises alveolar, arterial, pulmonary, venous and tissue compartments, with gas exchange in the lung determined by inspiration and expiration terms. Gas exchange is modelled through diffusion and convective transfer. Carbon dioxide is produced in the tissue by a metabolic term. Shunting is modelled by allowing blood flow to bypass the pulmonary compartment in which diffusion takes place. The model predicts changes in the carbon dioxide partial pressures that occur following abrupt changes in the ventilation settings, and show broad agreement with actual data obtained from novel sensing technology.
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Baglin I, Mitaine-Offer AC, Nour M, Tan K, Cavé C, Lacaille-Dubois MA. A review of natural and modified betulinic, ursolic and echinocystic acid derivatives as potential antitumor and anti-HIV agents. Mini Rev Med Chem 2003; 3:525-39. [PMID: 12871156 DOI: 10.2174/1389557033487917] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this review is to update current knowledge on the betulinic, ursolic and echinocystic acids and their natural and semisynthetic analogs, focussing on their cytotoxic and anti-HIV activities. Then, the last results of the authors' team on unusual semisynthetic derivatives of these triterpenoids will be presented in order to establish structure/activity relationships.
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Tan K, Grigoriadis K, Wu F. H∞ and L2 - to - L∞ gain control of linear parameter-varying systems with parameter-varying delays. ACTA ACUST UNITED AC 2003. [DOI: 10.1049/ip-cta:20030708] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Ellington JK, Harris M, Webb L, Smith B, Smith T, Tan K, Hudson M. IntracellularStaphylococcus aureus. ACTA ACUST UNITED AC 2003. [DOI: 10.1302/0301-620x.85b6.13509] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Staphylococcus aureus is the bacterial pathogen which is responsible for approximately 80% of all cases of human osteomyelitis. It can invade and remain within osteoblasts. The fate of intracellular Staph. aureus after the death of the osteoblast has not been documented. We exposed human osteoblasts to Staph. aureus. After infection, the osteoblasts were either lysed with Triton X-100 or trypsinised. The bacteria released from both the trypsinised and lysed osteoblasts were cultured and counted. Colonies of the recovered bacteria were then introduced to additional cultures of human osteoblasts. The number of intracellular Staph. aureus recovered from the two techniques was equivalent. Staph. aureus recovered from time zero and 24 hours after infection, followed by lysis/trypsinisation, were capable of invading a second culture of human osteoblasts. Our findings indicate that dead or dying osteoblasts are capable of releasing viable Staph. aureus and that Staph. aureus released from dying or dead osteoblasts is capable of reinfecting human osteoblasts in culture.
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Ellington JK, Harris M, Webb L, Smith B, Smith T, Tan K, Hudson M. Intracellular Staphylococcus aureus. A mechanism for the indolence of osteomyelitis. THE JOURNAL OF BONE AND JOINT SURGERY. BRITISH VOLUME 2003; 85:918-21. [PMID: 12931819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Staphylococcus aureus is the bacterial pathogen which is responsible for approximately 80% of all cases of human osteomyelitis. It can invade and remain within osteoblasts. The fate of intracellular Staph. aureus after the death of the osteoblast has not been documented. We exposed human osteoblasts to Staph. aureus. After infection, the osteoblasts were either lysed with Triton X-100 or trypsinised. The bacteria released from both the trypsinised and lysed osteoblasts were cultured and counted. Colonies of the recovered bacteria were then introduced to additional cultures of human osteoblasts. The number of intracellular Staph. aureus recovered from the two techniques was equivalent. Staph. aureus recovered from time zero and 24 hours after infection, followed by lysis/trypsinisation, were capable of invading a second culture of human osteoblasts. Our findings indicate that dead or dying osteoblasts are capable of releasing viable Staph. aureus and that Staph. aureus released from dying or dead osteoblasts is capable of reinfecting human osteoblasts in culture.
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Baglin I, Poumaroux A, Nour M, Tan K, Mitaine-Offer AC, Lacaille-Dubois MA, Chauffert B, Cavé C. New ursolic and betulinic derivatives as potential cytotoxic agents. J Enzyme Inhib Med Chem 2003; 18:111-7. [PMID: 12943194 DOI: 10.1080/1475636031000093543] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Fifteen new ursolic and betulinic triterpenoids, bearing various functionalities at C-3 and C-28 were synthesized as potential cytotoxic agents. All compounds were obtained by a hemisynthetic route via ursolic and betulinic acids. Preliminary screening of these compounds on human HT 29 colon cancer cells revealed inhibitory activity for three of them. Beta-D-Glucopyranosyl-3beta-hydroxyurs-12(13)-en-28-oate 1c, 3beta-3-(3-pyridyl)-prop-2-enoyloxyurs-12(13)-en-28-oic acid 1i and the potassium salt of 3beta-cinnamoyloxylup-20(29)-en-28-oic acid 2d demonstrated cytotoxic activity in the micromolar range: 8.0, 45.0 and 8.0 microM, respectively.
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Tan K. 3WS20-4 Dyslipidaemia, inflammation and endothelial dysfunction in diabetes mellitus. ATHEROSCLEROSIS SUPP 2003. [DOI: 10.1016/s1567-5688(03)90816-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Tan K. Paediatric Respiratory Examination: C O'Callaghan, W Stannard. Leicester, UK: OCB Media, 2001, pound49.95 (students pound25.00). ISBN 190403906. Thorax 2002. [DOI: 10.1136/thorax.57.2.188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Demetzos C, Perdetzoglou D, Tan K. Chemical analysis and antimicrobial activity of Halimium voldii. Z NATURFORSCH C 2001; 56:979-82. [PMID: 11837687 DOI: 10.1515/znc-2001-11-1212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Volatile constituents and a hexane extract of the leaves of Halimium voldii Kit Tan, Perdetzoglou & Raus, sp. nova, were analyzed by GC and GC-MS. Thirty compounds were identified in the essential oil of Halimium representing 88.7% of the oil composition. The main components were nonanal (12.8%), dodecane (10.6%), Z-caryophyllene (8.2%), gamma-muurolene (10.9%), delta-cadidene (3.5%), caryophyllene oxide (5.1%), beta-eudesmol (3.6%) and manoyl oxide (5.5%). Thymol was identified in the hexane extract as the main compound. A labdane diterpene ent-labd-7, 13 (E)-dien, 15-ol was detected by its mass spectra fragmentation pattern and its structure was determined by spectroscopic methods and its optical rotation. The essential oil and the hexane extract were assayed for their antimicrobial activity against gram (+) and gram (-) bacteria.
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Tan K, Smyth A. Commentaries--read with caution! Arch Dis Child 2001; 85:268. [PMID: 11517951 PMCID: PMC1718905 DOI: 10.1136/adc.85.3.268b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Tan K, Bruce C, Birkhead A, Thomas PS. Nasal and exhaled nitric oxide in response to occupational latex exposure. Allergy 2001; 56:627-32. [PMID: 11421920 DOI: 10.1034/j.1398-9995.2001.00975.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Latex sensitivity is an increasing problem among health-care workers. Allergic responses are associated with changes in nitric oxide (NO) generation and the changes secondary to latex have not been described. METHODS A total of 22 subjects comprising equal numbers of control volunteers and subjects with self-reported latex sensitivity were recruited to undergo latex skin prick testing. Symptom scores, exhaled nitric oxide (eNO), and nasal nitric oxide (nNO) were studied 1) before and after a controlled latex challenge (n=16), and 2) at the beginning and end of the working week, during exposure to latex (n=18). RESULTS Latex challenge caused a significant fall in nNO levels in latex-sensitive subjects, compared to normal control subjects (P=0.04). eNO levels also decreased in the latex-sensitive subjects after latex challenge, but to a lesser degree. There were no significant differences between the beginning and end of the working week in terms of eNO or nNO in either group, although symptom scores showed a nonsignificant increase in latex-sensitive subjects. CONCLUSION Fall in nasal NO after latex challenge is associated with reported symptomatic latex sensitivity, and this corresponds to latex skin prick test positivity. Neither nNO nor eNO showed a clear relationship to routine workplace exposure.
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Liang T, Tan K, Chong K, Zhu Z, Pongor S, Simoncsits A. Selection and design of high affinity DNA ligands for mutant single-chain derivatives of the bacteriophage 434 repressor. SCIENCE IN CHINA. SERIES C, LIFE SCIENCES 2001; 44:274-286. [PMID: 18726407 DOI: 10.1007/bf02879334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2000] [Indexed: 05/26/2023]
Abstract
Single-chain repressor RR(Tres) is a derivative of bacteriophage 434 repressor, which contains covalently dimerized DNA-binding domains (amino acids 1-69) of the phage 434 repressor. In this single-chain molecule, the wild type domain R is connected to the mutant domain R(TRES) by a recombinant linker in a head-to-tail arrangement. The DNA-contacting amino acids of R(TRES) at the -1, 1, 2, and 5 positions of the a3 helix are T, R, E, S respectively. By using a randomized DNA pool containing the central sequence -CATACAAGAAAGNNNNNNTTT-, a cyclic,in vitro DNA-binding site selection was performed. The selected population was cloned and the individual members were characterized by determining their binding affinities to RR(Tres) The results showed that the optimal operators contained the TTAC or TTCC sequences in the underlined positions as above, and that the Kd values were in the 1 x 10(-12) mol/L-1 x 10(11) mol/L concentration range. Since the affinity of the natural 434 repressor to its natural operator sites is in the 1 x 10(-9) mol/L range, the observed binding affinity increase is remarkable. It was also found that binding affinity was strongly affected by the flanking bases of the optimal tetramer binding sites, especially by the base at the 5' position. We constructed a new homodimeric single-chain repressor R(TRES)R(TRES) and its DNA-binding specificity was tested by using a series of new operators designed according to the recognition properties previously determined for the R(TREs) domain. These operators containing the consensus sequenceGTAAGAAARNTTACN orGGAAGAAARNTTCCN (R is A or G) were recognized by R(TRES)R(TRES) specifically, and with high binding affinity. Thus, by using a combination of random selection and rational design principles, we have discovered novel, high affinity protein-DNA interactions with new specificity. This method can potentially be used to obtain new binding specificity for other DNA-binding proteins.
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