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Curriculum vitae

IP Yuen Kwong Professor Contact Information: Dept of Biological Sciences National University of Singapore Science Drive 4 Singapore 117543 Tel: 65162702 Fax:67792486 email: dbsipyk@nus.edu.sg

Research interests 

Strategies adopted by air-breathing fishes to defend against ammonia toxicity during aerial exposure.

Fishes currently being studied include the mudskippers (Periophthalmodon schlosseri, Boleophthalmus boddaerti, and Periophthalmus chrysospilos), the marble goby (Oxyeleotris marmoratus), the four-eyed sleeper (Bostrichythes sinensis), the snakeheads (Channa asiatica and Channa micropeltes), the Oriental weather loach (Misgurnus anguillicaudatus), the African sharptooth catfish (Clarias gariepinus) and the swamp eel (Monopterus albus). Liver failure in mammals leads to hepatic encephalopathy manifested as comma followed by death. It is hoped that results obtained will reveal adaptations involved in conferring these air-breathing fishes high ammonia-tolerance, which can be of value for the formulation of treatments for patients with liver failure.  At present, efforts are focused on (1) the role of glutamine synthetase in ammonia detoxification and how it can be up-regulated in response to an ammonia surge, and (2) active transport of NH₄⁺ and H⁺ excretion via V-type H⁺-ATPase.

Urea synthesis and the ornithine-urea cycle.

Animals currently being studied include the giant African snail (Achatina fulica), the Asian freshwater stingray (Himantura signifer), the South American stingray (Potamotrygon motoro), the marine blue-spotted stingray (Taeniura lymma), the African lungfishes (Protopterus dolloi, Protopterus aethiopicus and Protopterus annectens), the Chinese fire-belly newt (Cynops orientalis), the crab-eating frog (Rana cancrivora), and the soft-shelled turtle (Amyda cartilaginea). Mammals detoxify ammonia to urea. However, whether the usurpation of the arginine synthetic pathway for urea production was directed to ammonia detoxification or osmotic retention of water is a moot point. Attempts are made in my laboratory to elucidate the role of urea synthesis in various animals during emersion, exposure to environmental ammonia, injection/infusion with ammonia or feeding. We aim to elucidate how the ornithine-urea cycle capacity of these animals can be up-regulated under certain environmental conditions.

Ammonia toxicity to brains of vertebrates.

Fish currently being studied are those which had extraordinary capacity to synthesize and accumulate glutamine and/or to tolerate high levels of ammonia in their brains. These include the mudskippers, the swamp eel and the African catfish. Specifically we focus on (1) the deleterious effects of glutamine synthesis and accumulation and (2) glutamate dysfunction leading to activation of the N-methyl-D-aspartate (NMDA) type glutamate receptor, using pharmacological agents like MK-801 and MSO. I am interested in finding out why, unlike mammals, some of these unique fishes have very high tolerance of ammonia in their brains, and how ammonia toxicity to mammalian brains can be ameliorated.

Metabolic rate reduction in aestivating African lungfishes and swamp eel.

Lungfishes (or dipnoans as they are 'dual breathers') are an archaic group of fishes, characterized by the possession of a lung opening off the ventral side of the oesophagus. The African lungfishes (Protopterus aethiopicus, Protopterus annectens, Protopterus amphibious and Protopterus dolloi) can aestivate in subterranean mud cocoons for long periods of time (up to 5 years). On the other hand, the swamp eel can aestivate in mud without forming a cocoon for months during drought. I am interested in (a) how dehydration is avoided, (b) how metabolic rate is reduced to prevent exhaustion of internal reserves, and (c) how the pollution of the internal environment is ameliorated. Answers to all these questions have important biomedical implications.

1. Wilkie, M P, T P Morgan, F Galvez, R Smith, M Kajimura, Y K Ip, and C M Wood, Ionic and osmotic regulation in the slender African lungfish on land occur across the ventral body surface. Physiological and Biochemical Zoology 80 (2007): 97-112. (USA).  

2. Lee, S M L, W P Wong, A M Loong, K C Hiong, S F Chew and Y K Ip, Postprandial increases in nitrogenous excretion and urea synthesis in the Malayan soft-shelled turtle, Pelodiscus sinensis. Journal of Comparative Physiology B 77 (2007): 19-29. (Germany).

3. Chew, S F, M Y Sim, Z C Phua, S M L Lee, W P Wong and Y K Ip, 'Active ammonia excretion in the giant mudskipper, Periophthalmodon schlosseri (Pallas), during emersion'. The Journal of Experimental Zoology, 307A (2007): 357-369. (United States). 

4. Wee, N L J, Y Y M Tng, H T Cheng, S M L Lee, S F Chew and Y K Ip, 'Ammonia toxicity and tolerance in the brain of the African sharptooth  catfish, Clarias gariepinus'. Aquatic Toxicology, 82 (2007): 204-213. (Ireland). 

5. Gilmour, K M, R M Euverman, A J Esbaugh, L Kenney, S F Chew, Y K Ip and S F Perry, 'Mechanisms of acid-base regulation in the African lungfish Protopterus annectens'. Journal of Experimental Biology, 210 (2007): 1944-1959. (United Kingdom). 

6. Loong, A M, J Y L Tan, K C Hiong, W P Wong, S F Chew and Y K Ip, 'Defense against environmental ammonia toxicity in the African lungfish, Protopterus aethiopicus: Bimodal breathing, skin ammonia permeability and urea synthesis'. Aquatic Toxicology, 85 (2007): 76-86. (Ireland). 

7. Chang, E W Y, A M Loong, W P Wong, S F Chew, J M Wilson and Y K Ip, 'Changes in tissue free amino acid contents, branchial Na⁺/K⁺-ATPase activity and bimodal breathing pattern in the freshwater climbing perch, Anabas testudineus (Bloch), during seawater acclimation. Journal of Experimental Zoology 307A (2007): 708-723.(United States) 

8. Ip, Y K, A M Loong, W P Wong, J M Wilson and S F Chew, 'Active ammonia excretion in two tropical air-breathing fishes during emersion'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 148 (2007): S47-S47. (United States). 

9. Iftika, F I, Y K Ip, M Patel, C M Wood, 'The influence of feeding on metabolic rate and nitrogenous waste excretion in the African lungfish Protopterus annectens'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 148 (2007): S124-S125. (United States). 

10. Chew S F, K C Hiong, Y K Ip, A M Loong, CY M Pang and W P Wong, 'From Homer-Smith to modern day comparative physiology A -The secrets of ammonia excretion'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 148 (2007): S125-S125. (United States). 

11. Bock C, C R Bridges, Y K Ip, A M Loong, H O Portner and A Wegener, 'Old question-new pictures: Advances in aestivation research with NMR'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 148 (2007): S125-S125. (United States)

12. Perry, S F, R Euverman, T Wang, A M Loong, S F Chew, Y K Ip* and K M Gilmour, 'Control of breathing in awake and aestivating African lungfish (Protopterus dolloi)'. Respiratory Physiology and Neurobiology, 160 (2008):8-17. (United States) 

13. Ip, Y K, S M L. Lee, W P Wong and S F Chew Mechanisms of and defense against acute ammonia toxicity in the aquatic Chinese soft-shelled turtle, Pelodiscus sinensis. Aquatic Toxicology, 86 (2008): 185-196. (Ireland).

14. Amelio, D, F Garofalo, A M Loong, W P Wong, Y K Ip, B Tota and M C Cerra, Differential NOS expression in the freshwater and aestivating lungfish Protopterus dolloi: heart versus kidney readjustments. Nitric Oxide:Biology and Chemistry 18 (2008): 1-10. (United States)

15. Loong A M, C Y M Pang, K C Hiong, W P Wong and S F Chew and Y. K. Ip, 'The African lungfish, Protopterus annectens, adopts different strategies to defend against ammonia toxicity during 40 days of aestivation in air or in mud'. The Journal of Comparative Physiology B. 178 (2008): 351-363. (Germany).

16. Speers-Roesch, B, Y K Ip and J S Ballantyne, 'Plasma non-esterified fatty acids of elasmobranchs: comparisons of freshwater, euryhaline, and temperate and tropical marine species'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology. 149 (2008):209-216 (United States).

17. Iftika, F I, M Patel, Y K Ip and C M Wood, 'The influence of feeding on aerial and aquatic oxygen consumption, nitrogenous waste excretion and fuel usage in the African lungfish Protopterus annectens'. Canadian Journal of Zoology, 86 (2006): 790-800. (Canada)

18. Loong, A M, S F Ang, W P Wong, H O Portner, C Bock. R Wittig, C R Bridges, S F Chew and Y K Ip, 'Effects of hypoxia on the energy status and nitrogen metabolism of African lungfish during aestivation in a mucus cocoon.' The Journal of Comparative Physiology B. 178 (2008): 853-865. (Germany).

19. Icardo, J M, D Amelio, F Garofalo, E Colvee, M C Cerra, W P Wong, B Tota and Y K Ip, 'The structural characteristics of the ventricle of the African Protopterus dolloi: Freshwater and aestivation'. Journal of Morphology 213 (2008): 106-119. (United States)

20. Ojeda, J L, W P Wong, Y K Ip and J M Icardo, 'The renal corpuscle of the African lungfish Protopterus dolloi: Structural, histochemical and immunofluorescence modification during aestivation.'Anatomical Record Part A - Discoveries in Molecular, Cellular and Evolutionary Biology, 291 (2008): 1156-1172. (United States)

21. Staples, J F, M Kajimura, C M Wood, M Patel, Y K Ip, G. B. and McClelland, 'Enzymatic and Mitochondrial Responses to Five Months of Aerial Exposure in the Slender Lungfish (Protopterus dolloi)'. Journal of Fish Physiology 73 (2008): 608-622. (England).

22. Tng, Y Y M, N L J Wee, Y K Ip and S F Chew, 'Postprandial nitrogen metabolism and excretion in juvenile marble goby, Oxyeleotris marmorata (Bleeker, 1852)' Aquaculture284 (2008): 260-267. (United States). 

23. Frick, N T, J S Bystriansky, Y K Ip, S F Chew and J S Ballantyne, 'Carbohydrate and amino acid metabolism in fasting and aestivating African lungfish (Protopterus dolloi)'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 151 (2008): 85-92. (United States). 

24. Frick, N T, J S Bystriansky, Y K Ip, S F Chew and J S Ballantyne, 'Lipid, ketone body and oxidative metabolism in the African lungfish, Protopterus dolloi, following 60 days of fasting and aestivation'. Comparative Biochemistry and Physiology A-Molecular and Integrative Physiology, 151 (2008): 93-101. (United States). 

25. Tng, Y Y M, N L J Wee, F K Wong, W P Wong, S F Chew and Y K Ip, 'Acute ammonia toxicity and the protective effects of methionine sulfoximine on the swamp eel, Monopterus albus'. Journal of Experimental Zoology Submitted (United States) 

26. Patel, M, F I Iftikar, R Smith, Y K Ip and C M Wood. Water balance and renal function in two species of African lungfish Protopterus dolloi and Protopterus annectens. Journal of Experimental Zoology Submitted (United States) 

27. Patel, M, F I Iftikar, Y K Ip and C M Wood. Ionoregulatory physiology of two species of African lungfish Protopterus dolloi and Protopterus annectens. Journal of Fish Physiology Submitted (England). 

28. Chew S F, Y Y M Tng, N L J Wee and Y K Ip. Nitrogen metabolism and branchial osmoregulatory acclimation in the juvenile marble goby, Oxyeleostris marmorata, exposed to seawater. Aquaculture Submitted (United States). 

29. Hung, C Y C, F Galvez, Y K Ip and C M Wood. A facilitated diffusion urea transporter in the skin of the African lungfish, Protopterus annectens. Journal of Experimental Biology, Submitted. (United Kingdom). 

30. Tok, C Y, S F Chew, W Y X Peh, A M Long, W P Wong and Y K Ip. Increases in tissue glutamine contents and glutamine synthetase activity in the swamp eel, Monopterus albus (Zuiew), exposed to brackish water. Journal of Experimental Biology, Submitted. (United Kingdom). 

31. Peh, W Y X, S F Chew, Z Y Gong and Y K Ip, Branchial and intestinal osmoregulatory acclimation in the four-eyed sleeper, Bostrychus sinensis, exposed to seawater. Marine Biology Submitted. (Germany)