34 results on '"Sturgess N"'
Search Results
2. The economic value of improved environmental health in Victorian rivers
- Author
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Bennett, J., Dumsday, R., Howell, G., Lloyd, C., Sturgess, N., and Van Raalte, L.
- Subjects
Victoria -- Environmental aspects ,Environmental health -- Evaluation ,Environmental health -- Models ,Environmental issues ,Environmental services industry ,Law - Abstract
To address the poor health of approximately one third of Victoria's rivers, current government targets include delivering significant improvements in river health by 2010. The quantification of benefits associated with improvements in river health arising from policy initiatives and projects enables the use of benefit-cost analysis to assess the viability of investment options. The non-market valuation technique known as choice modelling was used to generate benefit estimates for a selection of Victorian rivers. Monetary values were estimated for four attributes of environmental improvement: the percentage of pre-settlement fish species and populations; the percentage of the river's length with healthy vegetation on both banks; the number of native waterbird and animal species with sustainable populations; and the percentage of the river suitable for primary contact recreation without threat to public health. The relevance of the approach to management and policy issues is demonstrated. Keywords: choice modelling, river management, healthy rivers, environmental economics
- Published
- 2008
3. Oligopoly Pricing in the World Wheat Market: Reply
- Author
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Alaouze, Chris M., Watson, A. S., and Sturgess, N. H.
- Published
- 1979
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4. K-Channels in an Insulin-Secreting Cell Line: Effects of ATP and Sulphonylureas
- Author
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Ashford, M. L. J., Sturgess, N. C., Cook, D. L., Hales, C. N., Atwater, Illani, editor, Rojas, Eduardo, editor, and Soria, Bernat, editor
- Published
- 1986
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5. Calcium and ATP regulate the activity of a non-selective cation channel in a rat insulinoma cell line
- Author
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Sturgess, N. C., Hales, C. N., and Ashford, M. L. J.
- Published
- 1987
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6. Adenosine-5′-triphosphate-sensitive ion channels in neonatal rat cultured central neurones
- Author
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Ashford, M. L. J., Sturgess, N. C., Trout, N. J., Gardner, N. J., and Hales, C. N.
- Published
- 1988
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7. Letter to the Editor
- Author
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Cook A, Minnema D, Sturgess N, Botham P, Travis K, and Breckenridge C
- Subjects
Letter to the editor ,business.industry ,Host (biology) ,Health, Toxicology and Mutagenesis ,General Medicine ,Toxicology ,Biochemistry ,chemistry.chemical_compound ,Paraquat ,chemistry ,Immunology ,Molecular Medicine ,Medicine ,business ,Molecular Biology - Published
- 2014
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8. Expression of Seven Transmembrane Receptors in Mammalian cells
- Author
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Needham, M., primary, Cerillo, G., additional, McLaughlin, S., additional, Stacey, C., additional, McPheat, J., additional, Green, I., additional, Sturgess, N., additional, and Hollis, M., additional
- Published
- 1999
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9. Monocyte chemoattractant protein-1: receptor interactions and calcium signaling mechanisms
- Author
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Needham, M, primary, Sturgess, N, additional, Cerillo, G, additional, Green, I, additional, Warburton, H, additional, Wilson, R, additional, Martin, L, additional, Barratt, D, additional, Anderson, M, additional, Reilly, C, additional, and Hollis, M, additional
- Published
- 1996
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10. High Level Expression of Human MCP-1 Using the LCR/MEL Expression System
- Author
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Needham, M., primary, Barratt, D., additional, Cerillo, G., additional, Green, I., additional, Warburton, H., additional, Anderson, M., additional, Sturgess, N., additional, Rollins, B., additional, Reilly, C., additional, and Hollis, M., additional
- Published
- 1996
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11. Rice Harvesting: A View From the Theory of Common Property.
- Author
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Sturgess, N. H. and Wijaya, Hesti
- Published
- 1995
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12. Land Leasing in East Java.
- Author
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Wijaya, Hesti and Sturgess, N. H.
- Published
- 1979
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13. The Measurement of Technical Efficiency Using Frontier Production Functions of Rice Farms in West Java.
- Author
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Esparon, N. M. and Sturgess, N. H.
- Abstract
Information from the Patanas survey of 1983/84 was used to estimate frontier production functions for rice farmers from four villages in West Java. The results indicate that rice farmers in these regions were technically efficient in their rice production. 1 The authors gratefully acknowledge the financial assistance of the Australian Centre for International Agricultural Research and the Centre for Agro Economic Research, Indonesia. We are grateful to Dr. C. Alaouze, Dr. G. Lim and Dr. D. MacLaren for their helpful comments. [ABSTRACT FROM PUBLISHER]
- Published
- 1995
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14. Book Reviews.
- Author
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Glassburner, Bruce, Booth, Anne, Casino, Eric, White, B. N. F., Sturgess, N. H., Mackie, J. A. C., Hill, Hal, and Imansyah, M. Handry
- Abstract
Richard Robison, Indonesia: The Rise of Capital, Allen and Unwin, Sydney, 1986 pp. xxv + 425. Indexed. $19.95. W.L. Korthals Altes, Changing Economy in Indonesia: Volume 7: Balance of Payments, 1822–1939, Amsterdam: The Royal Tropical Institute. pp. 167. Trade Statistics, Java, 1823–73: Trade Statistics, Indonesia 1874–1937. Mededeelingen van het Centraal Kantoor voor de Statistiek nos 160 and 161 Om Prakash, The Dutch East India Company and the Economy of Bengal, 1630–1720, Princeton: Princeton University Press, 1985 pp. xii + 291, map, tables. graphs, glossary, index. Cloth $38.50. Sediono M.P. Tjondronegoro, Social Organization and Planned Development in Rural Java, Singapore, Oxford University Press for the Institute of Southeast Asian Studies, 1984, pp. xv + 326. A. Fujimoto and F. Matsuda (eds), An Economic Study of Rice Farming in West Java, Tokyo: NODAI Research Institute, Tokyo, University of Agriculture, 1986. A. Fujimoto and T. Matsuda (eds), A Comparative Study of the Structure of Rice Productivity and Rural Society in Southeast Asta Two Village Studies in Indonesta and Thailand, Tokyo: University of Agriculture, 1985. Reviewed by C.L J. van der Meer (1986) Bulletin of Indanesian Economic Studies, 22(2) pp. 124–27 David Jenkins, Suharto and His Generals: Indonesian Military Politics, 1975–1983, Ithaca: Cornell Modern Indonesia Project, Monograph Series No. 64, 1984, pp. xiii + 280. US$12.50. David Bourchier, Dynamics of Dissent in Indonesia Sawito and the Phantom Coup, Ithaca: Cornell Modern Indonesia Project, Interim Reports Series, 1984, pp. 128. US$9.00. Linda G. Martin (ed), The ASEAN Success Story: Social, Economic, and Political Dimensions, East-West Center, distributed by the University of Hawaii Press, Honolulu, 1987, pp. xviii + 253. $15.00. Mubyarto and Edy Suandy Hamid (eds), Kredit Pedesaan di Indonesia, Badan Penerbit Fakultas Ekonomi, U.G.M., 1986 pp, 160. Ron Hatley, et al., Other Javas Away from the Kraton, Melbourne: Monash University, 1984, pp. 60. K.S. Nathan and M. Pathmanathan (eds), Trilateralism in Asia: Problems and Prospects in US-Japan-ASEAN Relations, Antara Book Company, Kuala Lumpur, 1986, pp. xviii + 205. $18.00 (cloth): $12.00 (paper). [ABSTRACT FROM PUBLISHER]
- Published
- 1995
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15. 2-Halopropionic Acid-induced Cerebellar Granule Cell Necrosis in the Rat: In Vivo and In Vitro Studies
- Author
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Lock, E. A., Gyte, A., Sturgess, N. C., Duffell, S., and Wyatt, I.
- Published
- 2001
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16. The Measurement of Technical Efficiency Using Frontier Production Functions of Rice Farms in West Java
- Author
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Esparon, N. M. and Sturgess, N. H.
- Abstract
Information from the Patanas survey of 1983/84 was used to estimate frontier production functions for rice farmers from four villages in West Java. The results indicate that rice farmers in these regions were technically efficient in their rice production.
- Published
- 1989
- Full Text
- View/download PDF
17. Book Reviews
- Author
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Hardjono, Joan, Cremer, Georg, Gardiner, Peter, Dick, H. W., Cribb, Robert, Keyfitz, Nathan, Sturgess, N. H., and Hill, Hal
- Abstract
Colin Macandrews (Ed.), Central Government and Local Development in Indonesia, Singapore: Oxford University Press, East Asian Social Science Monographs, 1986, pp. 270, 36 Tables, 2 Figures, 4 Maps.Himpunan Peraturan Perundang-undangan Republik Indonesia di Bidang Ketenaga-kerjaan [Labour Legislation in Indonesia], Vols I-III, Jakarta: P.T. Twins, 1986.Michael A. Costello, Thomas R. Leinbach and Richard Ulack, with Marilou Palabrica-Costello and Bambang Suwarno, Mobility and Employment in Urban Southeast Asia: Examples From Indonesia and the Philippines, Boulder: Westview Press, 1987, pp. xvi + 191. $Us 26.50.Susan Abeyasekere, Jakarta: A History, Singapore: Oxford U.P., 1987, pp. xvii + 280. Cloth: $45.00.David P. Chandler and M.C. Ricklefs (Eds), Nineteenth and Twentieth Century Indonesia: Essays in Honour of Professor J.D. Legge, Clayton, Vic. : Monash University Centre of Southeast Asian Studies, 1986, pp. 281. $14.00.Graeme J. Hugo, Terence H. Hull, Valerie J. Hull, Gavin W. Jones, The Demographic Dimension in Indonesian Development, Singapore: Oxford University Press, 1987, pp. xxv + 417. $50.00.I Ketut Nehen and Ian R. Wills, Land Preparation in West Java: Benefits and Costs of Alternative Techniques, Agency For Agricultural Research and Development, Indonesia, and International Rice Research Institute, 1986, pp. xii + 159.Michael Smith et al., Asia's New Industrial World, London: Methuen, 1985, pp. vi + 136. £2.95.Australian Institute of Urban Studies, Review of Australian Assistance to the Indonesian Water Supply and Sanitation Sector, A Report for the Australian Development Assistance Bureau, 1986, pp. xxxiii + 305, $26.00 plus postage.
- Published
- 1988
- Full Text
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18. Book Reviews
- Author
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Glassburner, Bruce, Booth, Anne, Casino, Eric, White, B. N. F., Sturgess, N. H., Mackie, J. A. C., Hill, Hal, Imansyah, M. Handry, and Casino, Eric
- Abstract
Richard Robison, Indonesia: The Rise of Capital, Allen and Unwin, Sydney, 1986 pp. xxv + 425. Indexed. $19.95.W.L. Korthals Altes, Changing Economy in Indonesia: Volume 7: Balance of Payments, 1822-1939, Amsterdam: The Royal Tropical Institute. pp. 167.Trade Statistics, Java, 1823-73: Trade Statistics, Indonesia 1874-1937. Mededeelingen van het Centraal Kantoor voor de Statistiek nos 160 and 161Om Prakash, The Dutch East India Company and the Economy of Bengal, 1630-1720, Princeton: Princeton University Press, 1985 pp. xii + 291, map, tables. graphs, glossary, index. Cloth $38.50.Sediono M.P. Tjondronegoro, Social Organization and Planned Development in Rural Java, Singapore, Oxford University Press for the Institute of Southeast Asian Studies, 1984, pp. xv + 326.A. Fujimoto and F. Matsuda (eds), An Economic Study of Rice Farming in West Java, Tokyo: NODAI Research Institute, Tokyo, University of Agriculture, 1986.A. Fujimoto and T. Matsuda (eds), A Comparative Study of the Structure of Rice Productivity and Rural Society in Southeast Asta Two Village Studies in Indonesta and Thailand, Tokyo: University of Agriculture, 1985. Reviewed by C.L J. van der Meer (1986) Bulletin of Indanesian Economic Studies, 22(2) pp. 124-27David Jenkins, Suharto and His Generals: Indonesian Military Politics, 1975-1983, Ithaca: Cornell Modern Indonesia Project, Monograph Series No. 64, 1984, pp. xiii + 280. US$12.50. David Bourchier, Dynamics of Dissent in Indonesia Sawito and the Phantom Coup, Ithaca: Cornell Modern Indonesia Project, Interim Reports Series, 1984, pp. 128. US$9.00.Linda G. Martin (ed), The ASEAN Success Story: Social, Economic, and Political Dimensions, East-West Center, distributed by the University of Hawaii Press, Honolulu, 1987, pp. xviii + 253. $15.00.Mubyarto and Edy Suandy Hamid (eds), Kredit Pedesaan di Indonesia, Badan Penerbit Fakultas Ekonomi, U.G.M., 1986 pp, 160.Ron Hatley, et al., Other Javas Away from the Kraton, Melbourne: Monash University, 1984, pp. 60.K.S. Nathan and M. Pathmanathan (eds), Trilateralism in Asia: Problems and Prospects in US-Japan-ASEAN Relations, Antara Book Company, Kuala Lumpur, 1986, pp. xviii + 205. $18.00 (cloth): $12.00 (paper).
- Published
- 1987
- Full Text
- View/download PDF
19. Rice Harvesting: A View From the Theory of Common Property
- Author
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Sturgess, N. H. and Wijaya, Hesti
- Published
- 1983
- Full Text
- View/download PDF
20. Single channel recordings of potassium currents in an insulin-secreting cell line
- Author
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Sturgess, N. C., Ashford, M. L. J., Carrington, C. A., and Hales, C. N.
- Abstract
Using the patch-clamp technique we observed three distinct classes of K+channels which were spontaneously active in excised 'inside-out' membrane patches from an insulin-secreting rat pancreatic islet cell line (CRI-G1). Two of these occurred infrequently, one with a conductance of approximately 7 pS, and the other a conductance of 220 pS. The activation of the 220 pS K+channel was dependent upon the membrane voltage and was sensitive to the concentration of calcium ions at the cytoplasmic surface of the membrane. The third, and by far the most common class of K+channel, was characterized by its sensitivity to ATP. Application of ATP to the cytoplasmic side of the membrane reversibly inhibited this K+channel in a dose-dependent manner, but had no effect when applied to the external side. The properties of the ATP-sensitive K+channel appear to be indistinguishable from those of a channel found in rat neonatal β cells. Thus this insulin-secreting cell line should prove valuable in the investigation of the role of K+channels in the regulation of insulin secretion.J. Endocr.(1986) 109,201–207
- Published
- 1986
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21. Characterisation of kainate receptor mediated whole-cell currents in rat cultured cerebellar granule cells
- Author
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Savidge, J. R., Sturgess, N. C., Bristow, D. R., and Lock, E. A.
- Published
- 1999
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22. Planning for White Veal Production on Dairy Farms
- Author
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Sturgess, N. H.
- Subjects
Agricultural and Food Policy ,Livestock Production/Industries ,Farm Management - Published
- 1973
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23. Evidence for a separate mechanism of toxicity for the Type I and the Type II pyrethroid insecticides.
- Author
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Breckenridge CB, Holden L, Sturgess N, Weiner M, Sheets L, Sargent D, Soderlund DM, Choi JS, Symington S, Clark JM, Burr S, and Ray D
- Subjects
- Animals, Brain ultrastructure, Calcium metabolism, Cell Line, Tumor, Disease Models, Animal, Factor Analysis, Statistical, Glutamic Acid metabolism, Insecticides classification, Ion Channel Gating drug effects, Ion Channels classification, Ion Channels drug effects, Membrane Potentials drug effects, Membrane Potentials physiology, Mice, Neuroblastoma pathology, Neurotoxicity Syndromes physiopathology, Oocytes, Patch-Clamp Techniques, Principal Component Analysis, Rats, Synaptosomes drug effects, Synaptosomes physiology, Xenopus, Insecticides toxicity, Neurotoxicity Syndromes classification, Neurotoxicity Syndromes etiology, Pyrethrins classification, Pyrethrins toxicity
- Abstract
Neurotoxicity and mechanistic data were collected for six alpha-cyano pyrethroids (beta-cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin and lambda-cyhalothrin) and up to six non-cyano containing pyrethroids (bifenthrin, S-bioallethrin [or allethrin], permethrin, pyrethrins, resmethrin [or its cis-isomer, cismethrin] and tefluthrin under standard conditions. Factor analysis and multivariate dissimilarity analysis were employed to evaluate four independent data sets comprised of (1) fifty-six behavioral and physiological parameters from an acute neurotoxicity functional observatory battery (FOB), (2) eight electrophysiological parameters from voltage clamp experiments conducted on the Na(v)1.8 sodium channel expressed in Xenopus oocytes, (3) indices of efficacy, potency and binding calculated for calcium ion influx across neuronal membranes, membrane depolarization and glutamate released from rat brain synaptosomes and (4) changes in chloride channel open state probability using a patch voltage clamp technique for membranes isolated from mouse neuroblastoma cells. The pyrethroids segregated into Type I (T--syndrome-tremors) and Type II (CS syndrome--choreoathetosis with salivation) groups based on FOB data. Of the alpha-cyano pyrethroids, deltamethrin, lambda-cyhalothrin, cyfluthrin and cypermethrin arrayed themselves strongly in a dose-dependent manner along two factors that characterize the CS syndrome. Esfenvalerate and fenpropathrin displayed weaker response profiles compared to the non-cyano pyrethroids. Visual clustering on multidimensional scaling (MDS) maps based upon sodium ion channel and calcium influx and glutamate release dissimilarities gave similar groupings. The non-cyano containing pyrethroids were arrayed in a dose-dependent manner along two different factors that characterize the T-syndrome. Bifenthrin was an outlier when MDS maps of the non-cyano pyrethroids were based on sodium ion channel characteristics and permethrin was an outlier when the MDS maps were based on calcium influx/glutamate release potency. Four of six alpha-cyano pyrethroids (lambda-cyfluthrin, cypermethrin, deltamethrin and fenpropathrin) reduced open chloride channel probability. The R-isomers of lambda-l-cyhalothrin reduced open channel probability whereas the S-isomers, antagonized the action of the R-isomers. None of the non-cyano pyrethroids reduced open channel probability, except bioallethrin, which gave a weak response. Overall, based upon neurotoxicity data and the effect of pyrethroids on sodium, calcium and chloride ion channels, it is proposed that bioallethrin, cismethrin, tefluthrin, bifenthrin and permethrin belong to one common mechanism group and deltamethrin, lambda-cyhalothrin, cyfluthrin and cypermethrin belong to a second. Fenpropathrin and esfenvalerate occupy an intermediate position between these two groups.
- Published
- 2009
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24. Neurotoxic effect of L-2-chloropropionic acid on primary cultures of rat cerebellar granule cells.
- Author
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Sturgess NC, Rustad A, Fonnum F, and Lock EA
- Subjects
- Aging physiology, Animals, Animals, Newborn, Cell Survival drug effects, Cells, Cultured, Cyclic N-Oxides, Cytoplasmic Granules, Dizocilpine Maleate pharmacology, Dose-Response Relationship, Drug, Drug Interactions, Hydrocarbons, Chlorinated, Neurons pathology, Nitrogen Oxides pharmacology, Rats, Vitamin E pharmacology, Cerebellum drug effects, Neurons drug effects, Neurotoxins toxicity, Propionates toxicity
- Abstract
L-2-Chloropropionic acid (L-CPA), when administered orally to rats, produces selective necrosis to the granule cell layer of the rat cerebellum which is delayed in onset, not appearing until 36-48 h after exposure. The present study was conducted to characterise the toxic effect of L-CPA in primary cell cultures of rat cerebellar granule cells in vitro. Exposure to L-CPA produced a time and concentration dependent loss in cerebellar granule cell viability. Mean 50% effective concentration (EC50) values for L-CPA toxicity were 18.3 +/- 0.3, 7.4 +/- 0.1, and 3.5 +/- 0.1 mM for 24, 48 and 72 h exposure respectively. Exposure for 24 h followed by a return to L-CPA free medium for 24 h was more toxic than exposure for 24 h alone. Cells maintained in culture for a longer duration were more susceptible to L-CPA-induced toxicity. The toxic effects of L-CPA could be partially or fully prevented by concomitant exposure of the cells to putative neuroprotective compounds. The N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801 (3 microM), afforded partial protection against L-CPA induced toxicity, whilst other glutamate receptor antagonists including, D(-)-2-amino-5-phosphopentanoic acid (D-AP5; 300 microM), D(-)-3-(2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (D-CPP; 300 microM), 5,7-dichlorokynurenic acid (10 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 1 microM) were ineffective. The antioxidant, vitamin E (10 microM), afforded significant but incomplete protection from L-CPA toxicity. However when both MK-801 (3 microM) and vitamin E (10 microM) were present during L-CPA exposure, a greater degree of protection was observed than with either compound alone, although the combination failed to provide complete protection. Cyclosporin A, an inhibitor of the mitochondrial transition pore, also provided partial protection. By contrast, the free radical trapping agent, N-tert-butyl-alpha-(2-sulfophenyl)-nitrone (S-PBN) provided concentration (1-10 mM) dependent protection against the L-CPA-induced toxicity, which was complete at 10 mM. Our findings suggest that free radical production may be involved in the mechanism of L-CPA-induced toxicity.
- Published
- 2000
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25. Methyl iodide toxicity in rat cerebellar granule cells in vitro: the role of glutathione.
- Author
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Chamberlain MP, Sturgess NC, Lock EA, and Reed CJ
- Subjects
- Animals, Antioxidants pharmacology, Cell Survival drug effects, Cells, Cultured, Cerebellum cytology, Glutamic Acid toxicity, Glutathione Transferase metabolism, Hydrocarbons, Iodinated antagonists & inhibitors, Hydrocarbons, Iodinated metabolism, Oxidative Stress physiology, Rats, Rats, Wistar, Cerebellum drug effects, Glutathione physiology, Hydrocarbons, Iodinated toxicity
- Abstract
The monohalomethane methyl iodide (MeI) is toxic to a number of organ systems including the central nervous system. Clinical symptoms of neurotoxicity suggest that the cerebellum is the target within the brain, and we have now modelled the toxicity of MeI in cultured rat cerebellar granule cells. Cytotoxicity is maximal 24 h after a 5 min exposure to MeI, and the EC50 for MeI under these conditions was calculated to be 1.6 mM. The glutathione S-transferase (GST) dependent metabolism of MeI was investigated in these cultures. There was a marked decrease in intracellular glutathione (GSH) 15 min after exposure to MeI, and GSH concentrations then increased, reaching 130% of control levels 7 h after exposure. To investigate the role of conjugation with GSH in the toxicity of MeI, GSH levels were modulated prior to exposure. Depletion of GSH exacerbated the cytotoxicity of MeI while provision of a bioavailable source of GSH was protective. Inclusion of antioxidants [vitamin E, butylated hydroxytoluene (BHT) or desferrioxamine mesylate (DF)] also protected against the cytotoxicity of MeI. Our in vitro data suggest that MeI is conjugated with GSH in the cerebellum, and the resulting extensive depletion of GSH may be the first step en route to toxicity, rendering the tissue susceptible to methylation and/or oxidative stress.
- Published
- 1999
- Full Text
- View/download PDF
26. L-2-chloropropionic acid inhibits glutamate and aspartate release from rat cerebellar slices but does not activate cerebellar NMDA receptors: implications for L-2-chloropropionic acid-induced neurotoxicity.
- Author
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Widdowson PS, Briggs I, BoSmith RE, Sturgess NC, Rosbottom A, Smith JC, and Wyatt I
- Subjects
- Animals, Binding, Competitive, Cells, Cultured, Cerebellum metabolism, Drug Evaluation, Preclinical, Female, Hydrocarbons, Chlorinated, In Vitro Techniques, Male, Patch-Clamp Techniques, Radioligand Assay, Rats, Receptors, N-Methyl-D-Aspartate metabolism, Aspartic Acid metabolism, Cerebellum drug effects, Glutamic Acid metabolism, Neurotoxins toxicity, Propionates toxicity, Receptors, N-Methyl-D-Aspartate drug effects
- Abstract
L-2-Chloropropionic acid (L-CPA), when orally administered at single high dose to rats produces a selective lesion in the cerebellum involving destruction of a high proportion of granule cells by a mechanism which involves N-methyl-D-aspartate (NMDA) receptors. Receptor binding studies demonstrated that L-CPA a had low affinity at the glutamate and glycine binding sites at NMDA receptors (530-660 microM), respectively, whereas L-CPA did not displace [3H]AMPA, [3H]NBQX or [3H]kainate from AMPA or kainate receptors. Whole cell-patch clamp experiments using cultured granule cells failed to demonstrate changes in membrane potential of cultured granule cells when either L-CPA (0.25 or 1 microM) was added alone to the bathing solution, or in combination with glycine (10 microM). Furthermore L-CPA did not alter the magnitude of the inward current produced by application of NMDA (100 microM)) to cultured granule cells, in the presence of glycine, as measured by patch clamp techniques. Experiments were also performed to discover whether L-CPA may alter the release of the excitatory amino acids from the cerebellum, which may then indirectly alter activity at glutamate receptors, leading to neuronal cell death. L-CPA (2 mM) did not affect either basal or stimulated (electrical or high potassium) endogenous aspartate release from superfused cerebellar slices nor did it alter the basal or stimulated release of [3H]aspartate from preloaded slices when introduced into the superfusion medium over 30 min. However, when cerebellar slices were preincubated with 2 mM L-CPA for 2 h at concentrations that are known to be neurotoxic to the brain in vivo, but not in vitro, the stimulated endogenous glutamate and aspartate net release was significantly attenuated, as compared to controls. Basal release was not significantly affected by the introduction of L-CPA-induced cerebellar neurotoxicity may be related to the inhibition of excitatory amino acid release from the cerebellum. In conclusion, although L-CPA does not appear to directly alter NMDA receptor activity the L-CPA-induced cerebellar neurotoxicity may be related to the inhibition of excitatory amino acid release from the cerebellum.
- Published
- 1997
27. Inhibitory actions of ZENECA ZD7288 on whole-cell hyperpolarization activated inward current (If) in guinea-pig dissociated sinoatrial node cells.
- Author
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BoSmith RE, Briggs I, and Sturgess NC
- Subjects
- Action Potentials drug effects, Animals, Anti-Arrhythmia Agents pharmacology, Benzazepines pharmacology, Clonidine analogs & derivatives, Clonidine pharmacology, Electrophysiology, Guinea Pigs, In Vitro Techniques, Membrane Potentials drug effects, Sinoatrial Node cytology, Sinoatrial Node metabolism, Cardiovascular Agents pharmacology, Ion Channels drug effects, Pyrimidines pharmacology, Sinoatrial Node drug effects
- Abstract
1. ZENECA ZD7288 (4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyridinium chloride) is a sinoatrial node (SAN) modulating agent which produces a selective slowing of the heart rate. Its effects have been studied in single, freshly dissociated guinea-pig SAN cells, by standard patch clamp procedures. 2. Whole-cell inward currents were evoked by hyperpolarizing voltage clamp steps from a holding potential of -40 mV. ZD7288 inhibited the hyperpolarization activated cationic current (If) in a concentration-dependent manner. The 'selective bradycardic agents' alinidine and UL-FS 49 (zatebradine) both also inhibited If. 3. The activation of If was investigated by measuring tail current amplitudes at +20 mV after hyperpolarizing steps to different potentials to activate the current. The reduction in If resulted from both a shift in the If current activation curve in the negative direction on the voltage axis, and also a reduction in the activation curve amplitude. 4. ZD7288 did not affect the ion selectivity of the If channel, since the tail current reversal potential was unchanged in the presence of the drug. 5. With ZD7288 the inhibition of If was not use-dependent, whereas UL-FS 49 displayed use-dependence in the block of the If current. 6. Whereas ZD7288 had no significant effect on the delayed rectifier current (Ik) in these cells, both alinidine and UL-FS 49 significantly reduced Ik at the same concentrations which reduced If. 7. The data show that ZD7288 reduces If by affecting the activation characteristics of the If current; this inhibition may account for this agent's selective bradycardiac properties.
- Published
- 1993
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28. The actions of endogenous and synthetic pregnane steroids on GABAA receptors.
- Author
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Hill-Venning C, Lambert JJ, Peters JA, Hales TG, Gill C, Callachan H, and Sturgess NC
- Subjects
- Adrenal Medulla drug effects, Adrenal Medulla metabolism, Anesthetics pharmacology, Animals, Bridged Bicyclo Compounds metabolism, Cattle, Cells, Cultured, Cloning, Molecular, Electrophysiology, In Vitro Techniques, Membranes drug effects, Membranes metabolism, Neurons metabolism, Pregnanediones pharmacology, Radioligand Assay, Rats, Bridged Bicyclo Compounds, Heterocyclic, Pregnanes pharmacology, Receptors, GABA-A drug effects
- Published
- 1992
29. Voltage-activated currents in the CRI-G1 rat insulin-secreting cell-line.
- Author
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Kozlowski RZ, Sturgess NC, Hales CN, and Ashford ML
- Subjects
- Action Potentials physiology, Animals, Cell Line, Insulin Secretion, Islets of Langerhans cytology, Islets of Langerhans physiology, Membrane Potentials physiology, Models, Biological, Rats, Insulin metabolism, Islets of Langerhans metabolism
- Abstract
1. The whole-cell configuration of the patch-clamp recording technique was used to characterize the electrophysiological properties of CRI-G1 insulin-secreting cells. 2. Current-clamp recordings demonstrated the excitable nature of these cells. 3. Voltage-clamp recordings revealed the presence of an inward Na+ current, an inward Ca2+ current and a delayed outward K+ conductance. 4. The electrophysiological properties of CRI-G1 closely resemble those of pancreatic beta-cells, thereby rendering this cell-line as a useful alternative to freshly isolated cells for the study of pancreatic beta-cell electrophysiology and pharmacology.
- Published
- 1991
- Full Text
- View/download PDF
30. Steroid modulation of the GABAA receptor complex: electrophysiological studies.
- Author
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Lambert JJ, Peters JA, Sturgess NC, and Hales TG
- Subjects
- Anesthetics pharmacology, Animals, Cattle, Chromaffin System cytology, Chromaffin System physiology, Chromaffin System ultrastructure, Desoxycorticosterone analogs & derivatives, Desoxycorticosterone pharmacology, Electrophysiology, Hippocampus cytology, Hippocampus physiology, Hippocampus ultrastructure, Membrane Proteins drug effects, Membrane Proteins physiology, Pregnanediones pharmacology, Pregnanolone pharmacology, Rats, Receptors, GABA-A physiology, Receptors, GABA-A drug effects, Steroids pharmacology
- Abstract
The effect of some endogenous and synthetic steroids on the operation of inhibitory and excitatory amino acid neurotransmitter receptors was examined. Anaesthetic pregnane steroids (e.g. alphaxalone, 5 alpha-pregnan-3 alpha-ol-20-one, 5 alpha-pregnane-3 alpha,21-diol-20-one) potentiated GABAA receptor-mediated whole-cell currents recorded from bovine chromaffin cells. The threshold concentration for enhancement was 10-30 nM. Potentiation was stereoselective and was mediated by a steroid-induced prolongation of the burst duration of the GABA-activated channel. Additionally, the pregnane steroids directly activated the GABAA receptor. Both the potentiation and activation appear to be mediated through a site(s) distinct from the well-known barbiturate and benzodiazepine allosteric sites of the GABAA receptor. Intracellularly applied alphaxalone and 5 beta-pregnan-3 alpha-ol-20-one had no discernible effects on the GABAA receptor, suggesting that the steroid binding site can only be accessed extracellularly. Unlike behaviourally depressant barbiturates, which modulate GABAA receptor function in a manner similar to that of the pregnane steroids, alphaxalone and 5 beta-pregnan-3 alpha-ol-20-one show striking pharmacological selectivity. Voltage-clamp recordings from rat central neurons in culture indicate that pentobarbitone exerts its potentiating and GABA-mimetic effects over a range of concentrations which also depress currents mediated by glutamate receptor subtypes. In contrast, alphaxalone and several endogenous steroids greatly enhance responses to GABA, but have no direct effect on glutamate receptors. Such pharmacological selectivity, coupled with appropriate stereoselectivity of action, suggests that the GABAA receptor mediates some of the behavioural effects of synthetic and endogenous pregnane steroids.
- Published
- 1990
- Full Text
- View/download PDF
31. Effects of sulphonylureas and diazoxide on insulin secretion and nucleotide-sensitive channels in an insulin-secreting cell line.
- Author
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Sturgess NC, Kozlowski RZ, Carrington CA, Hales CN, and Ashford ML
- Subjects
- Adenosine Triphosphate pharmacology, Animals, Cell Line, Electrophysiology, Glucose pharmacology, Glyburide pharmacology, Insulin Secretion, Islets of Langerhans drug effects, Islets of Langerhans metabolism, Leucine pharmacology, Rats, Tolbutamide pharmacology, Diazoxide pharmacology, Insulin metabolism, Nucleotides pharmacology, Potassium Channels metabolism, Sulfonylurea Compounds pharmacology
- Abstract
1. The effects of various sulphonylureas and diazoxide on insulin secretion and the activity of various channels have been studied using tissue culture and patch-clamp methods in an insulin-secreting cell line derived from a rat islet cell tumour. 2. Tolbutamide, glibenclamide and HB699 increased the rate of insulin release by 2-5 fold. The concentrations of tolbutamide and glibenclamide giving half-maximum effects on insulin secretion were approximately 40 microM and 0.2 microM, respectively. 3. Diazoxide (0.6-1.0 mM) per se, had either no effect or produced a small increase in insulin secretion, whereas when secretion was maximally stimulated by the combination of glucose (3 mM) and leucine (20 mM), it produced inhibition. Tolbutamide-induced release was also inhibited by diazoxide. 4. Tolbutamide, glibenclamide, HB699 and HB985 reduced the open-state probability of the ATP-K+ channel in a dose-dependent manner. Tolbutamide and glibenclamide were shown to be effective regardless of which side of the membrane they were applied. 5. In whole cell recording, in which the total ATP-sensitive K+ conductance of the cell could be measured, dose-inhibition curves for tolbutamide and glibenclamide were constructed, resulting in Ki values of 17 microM and 27 nM, respectively. The value of Ki for tolbutamide was unchanged when ATP (0.1 mM) was present in the electrode. 6. Diazoxide (0.6 mM) activated the ATP-K+ channels only when they had first been inhibited by intracellular ATP (0.1 mM) or bath applied tolbutamide (3-30 microM). The inhibition produced by glibenclamide could not be reversed by diazoxide. 7. Neither tolbutamide (1.0 mM) nor glibenclamide (10 microM) altered the open-state probability of the Ca2+-activated K+ channel or the Ca2+-activated non-selective cation channel which are present in this cell line. 8. It is concluded that the sulphonylureas and related hypoglycaemic drugs and diazoxide regulate insulin secretion by direct effects on the ATP-K+ channel or a protein closely associated with this channel.
- Published
- 1988
- Full Text
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32. Nucleotide-sensitive ion channels in human insulin producing tumour cells.
- Author
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Sturgess NC, Carrington CA, Hales CN, and Ashford ML
- Subjects
- Adenosine Monophosphate pharmacology, Adenosine Triphosphate physiology, Adult, Animals, Calcium physiology, Female, Humans, In Vitro Techniques, Insulin Secretion, Potassium metabolism, Rats, Adenoma metabolism, Insulin metabolism, Ion Channels physiology, Pancreatic Neoplasms metabolism
- Abstract
Cells from a human insulin producing tumour have been studied and single channel currents recorded. We have observed three main cation-selective channels in excised patch experiments. An ATP-sensitive potassium channel is present the activity of which can be inhibited by the oral hypoglycaemic drug, tolbutamide. A calcium-activated non-selective cation channel, which is inhibited by AMP could also be seen. In addition a large conductance potassium selective channel, possibly the "maxi" calcium-activated potassium channel is present in these cells.
- Published
- 1987
- Full Text
- View/download PDF
33. The sulphonylurea receptor may be an ATP-sensitive potassium channel.
- Author
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Sturgess NC, Ashford ML, Cook DL, and Hales CN
- Subjects
- Animals, Cell Line, Cell Membrane metabolism, Glyburide metabolism, Insulin metabolism, Islets of Langerhans ultrastructure, Rats, Tolbutamide metabolism, Adenosine Triphosphate physiology, Ion Channels metabolism, Islets of Langerhans metabolism, Sulfonylurea Compounds metabolism
- Abstract
The stimulation of insulin secretion from the beta cells of the islets of Langerhans appears to be mediated by a decrease in the cell-membrane potassium-ion permeability. Tolbutamide reduced K+ movement through an ATP-sensitive K+ channel in patches of plasma membrane from an insulin-producing cell line when applied to the external surface of the membrane. The effect occurred at concentrations which exist in the serum of patients treated with tolbutamide and which stimulate insulin secretion from islets of Langerhans in vitro. Glibenclamide had a similar effect but, in keeping with its greater therapeutic potency, at concentrations one hundred times lower. These findings suggest that an ATP-sensitive K+ channel or a protein closely associated with it may be the receptor through which sulphonylureas act to stimulate insulin secretion in vitro.
- Published
- 1985
- Full Text
- View/download PDF
34. Inhibition of a calcium-activated, non-selective cation channel, in a rat insulinoma cell line, by adenine derivatives.
- Author
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Sturgess NC, Hales CN, and Ashford ML
- Subjects
- Animals, Cations, Cell Line, Cell Membrane physiology, Cytoplasm physiology, Rats, Adenine Nucleotides pharmacology, Adenoma, Islet Cell physiopathology, Adenosine pharmacology, Calcium physiology, Insulinoma physiopathology, Ion Channels drug effects
- Abstract
The effects of adenosine and adenine nucleotides on a calcium-activated non-selective cation channel, present in the plasma membrane of an insulin-secreting cell line CRI-Gl were investigated. Single-channel currents were recorded from inside-out membrane patches and the adenine derivatives applied to the solution bathing the cytoplasmic aspect of the membrane surface. The activity of this channel is shown to be inhibited by all the derivatives tested. The potency sequence for inhibition was found to be AMP greater than ADP greater than ATP greater than adenosine.
- Published
- 1986
- Full Text
- View/download PDF
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