Y K Ip

Summary

Affiliation: National University of Singapore
Country: Singapore

Publications

  1. ncbi request reprint Defences against ammonia toxicity in tropical air-breathing fishes exposed to high concentrations of environmental ammonia: a review
    Y K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, 117543 Singapore, Republic of Singapore
    J Comp Physiol B 174:565-75. 2004
  2. pmc Properties and expression of Na+/K+-ATPase α-subunit isoforms in the brain of the swamp eel, Monopterus albus, which has unusually high brain ammonia tolerance
    Xiu L Chen
    Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
    PLoS ONE 8:e84298. 2013
  3. pmc Ammonia production, excretion, toxicity, and defense in fish: a review
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore Singapore, Republic of Singapore
    Front Physiol 1:134. 2010
  4. pmc Gene Cloning and mRNA Expression of Glutamate Dehydrogenase in the Liver, Brain, and Intestine of the Swamp Eel, Monopterus albus (Zuiew), Exposed to Freshwater, Terrestrial Conditions, Environmental Ammonia, or Salinity Stress
    Chia Y Tok
    Department of Biological Science, National University of Singapore Singapore
    Front Physiol 2:100. 2011
  5. pmc High brain ammonia tolerance and down-regulation of Na+:K+:2Cl(-) Cotransporter 1b mRNA and protein expression in the brain of the Swamp Eel, Monopterus albus, exposed to environmental ammonia or terrestrial conditions
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
    PLoS ONE 8:e69512. 2013
  6. pmc Increases in apoptosis, caspase activity and expression of p53 and bax, and the transition between two types of mitochondrion-rich cells, in the gills of the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater
    Biyun Ching
    Department of Biological Science, National University of Singapore Kent Ridge, Singapore, Singapore
    Front Physiol 4:135. 2013
  7. pmc Aestivation and hypoxia-related events share common silent neuron trafficking processes
    Giuseppina Giusi
    Comparative Neuroanatomy Laboratory, University of Calabria, 87030 Arcavacata di Rende Cs, Italy
    BMC Neurosci 13:39. 2012
  8. pmc Molecular characterization of branchial aquaporin 1aa and effects of seawater acclimation, emersion or ammonia exposure on its mRNA expression in the gills, gut, kidney and skin of the freshwater climbing perch, Anabas testudineus
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    PLoS ONE 8:e61163. 2013
  9. doi request reprint The Chinese soft-shelled turtle, Pelodiscus sinensis, decreases nitrogenous excretion, reduces urea synthesis and suppresses ammonia production during emersion
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 216:1650-7. 2013
  10. doi request reprint The Chinese soft-shelled turtle, Pelodiscus sinensis, excretes urea mainly through the mouth instead of the kidney
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    J Exp Biol 215:3723-33. 2012

Collaborators

  • Shit F Chew
  • D J Randall
  • J S Ballantyne
  • C R Bridges
  • Patricia A Wright
  • H O Portner
  • Maria Carmela Cerra
  • B Tota
  • Elvira Brunelli
  • J M Wilson
  • Wai P Wong
  • A M Loong
  • Ai M Loong
  • Kum C Hiong
  • W P Wong
  • Biyun Ching
  • Chia Y Tok
  • Ai May Loong
  • Wai Peng Wong
  • Natasha Therese Frick
  • Yvonne Y M Tng
  • Xiu L Chen
  • Nicklaus L J Wee
  • Serene M L Lee
  • Kum Chew Hiong
  • Serene Min Lin Lee
  • Giuseppina Giusi
  • W Y X Peh
  • Jason Scott Bystriansky
  • Daniela Amelio
  • Esther Wei Yin Chang
  • Wendy Y X Peh
  • Yi L Tay
  • B Scott Nunez
  • Chiat Koo Lim
  • L Weng
  • C K Lim
  • Angeline S L Tay
  • Wai L Tam
  • T K N Tsui
  • Jing H A Yong
  • You R Chng
  • Jasmine L Y Ong
  • Eugene W L Sim
  • Siew H Lam
  • Nicklaus L J E Wee
  • Rosa Maria Facciolo
  • Y R Chng
  • Merylin Zizza
  • K C Hiong
  • C B Lim
  • Marcello Canonaco
  • B Y Ching
  • Fung K Wong
  • C Bock
  • S F Ang
  • Cheryl Y M Pang
  • R Wittig
  • Filippo Garofalo
  • J Y L Tan
  • Hin T Cheng
  • Shi J Lee
  • Andrew N Evans
  • Matthew A Simpson
  • Angeline Su Ling Tay
  • S M L Lee
  • Y Jin
  • P M Anderson

Detail Information

Publications67

  1. ncbi request reprint Defences against ammonia toxicity in tropical air-breathing fishes exposed to high concentrations of environmental ammonia: a review
    Y K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, 117543 Singapore, Republic of Singapore
    J Comp Physiol B 174:565-75. 2004
    ..The responses of tropical air-breathing fishes to high environmental ammonia are determined apparently by behavioural adaptations and the nature of their natural environments...
  2. pmc Properties and expression of Na+/K+-ATPase α-subunit isoforms in the brain of the swamp eel, Monopterus albus, which has unusually high brain ammonia tolerance
    Xiu L Chen
    Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
    PLoS ONE 8:e84298. 2013
    ..albus...
  3. pmc Ammonia production, excretion, toxicity, and defense in fish: a review
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore Singapore, Republic of Singapore
    Front Physiol 1:134. 2010
    ....
  4. pmc Gene Cloning and mRNA Expression of Glutamate Dehydrogenase in the Liver, Brain, and Intestine of the Swamp Eel, Monopterus albus (Zuiew), Exposed to Freshwater, Terrestrial Conditions, Environmental Ammonia, or Salinity Stress
    Chia Y Tok
    Department of Biological Science, National University of Singapore Singapore
    Front Physiol 2:100. 2011
    ....
  5. pmc High brain ammonia tolerance and down-regulation of Na+:K+:2Cl(-) Cotransporter 1b mRNA and protein expression in the brain of the Swamp Eel, Monopterus albus, exposed to environmental ammonia or terrestrial conditions
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
    PLoS ONE 8:e69512. 2013
    ..albus is able to down-regulate the mRNA and protein expression of nkcc1b/Nkcc1b in the brain when confronted with ammonia toxicity, which could be one of the contributing factors to its extraordinarily high brain ammonia tolerance. ..
  6. pmc Increases in apoptosis, caspase activity and expression of p53 and bax, and the transition between two types of mitochondrion-rich cells, in the gills of the climbing perch, Anabas testudineus, during a progressive acclimation from freshwater to seawater
    Biyun Ching
    Department of Biological Science, National University of Singapore Kent Ridge, Singapore, Singapore
    Front Physiol 4:135. 2013
    ..testudineus during seawater acclimation...
  7. pmc Aestivation and hypoxia-related events share common silent neuron trafficking processes
    Giuseppina Giusi
    Comparative Neuroanatomy Laboratory, University of Calabria, 87030 Arcavacata di Rende Cs, Italy
    BMC Neurosci 13:39. 2012
    ..e. the lungfish (Protopterus annectens)...
  8. pmc Molecular characterization of branchial aquaporin 1aa and effects of seawater acclimation, emersion or ammonia exposure on its mRNA expression in the gills, gut, kidney and skin of the freshwater climbing perch, Anabas testudineus
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    PLoS ONE 8:e61163. 2013
    ..Taken together, our results indicate that Aqp1aa might have a greater physiological role in ammonia excretion than in osmoregulation in A. testudineus...
  9. doi request reprint The Chinese soft-shelled turtle, Pelodiscus sinensis, decreases nitrogenous excretion, reduces urea synthesis and suppresses ammonia production during emersion
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 216:1650-7. 2013
    ..sinensis adopted a reduction in ammonia production, instead of increased urea synthesis, as the major strategy to ameliorate ammonia toxicity and problems associated with dehydration during terrestrial exposure...
  10. doi request reprint The Chinese soft-shelled turtle, Pelodiscus sinensis, excretes urea mainly through the mouth instead of the kidney
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    J Exp Biol 215:3723-33. 2012
    ..The ability to excrete urea through the mouth instead of the kidney might have facilitated the ability of P. sinensis and other soft-shelled turtles to successfully invade the brackish and/or marine environment...
  11. doi request reprint Hepatic carbamoyl phosphate synthetase (CPS) I and urea contents in the hylid tree frog, Litoria caerulea: transition from CPS III to CPS I
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    J Comp Physiol B 182:1081-94. 2012
    ....
  12. doi request reprint Cystic fibrosis transmembrane conductance regulator in the gills of the climbing perch, Anabas testudineus, is involved in both hypoosmotic regulation during seawater acclimation and active ammonia excretion during ammonia exposure
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Comp Physiol B 182:793-812. 2012
    ..testudineus uniquely responded to ammonia exposure by increasing the ambient pH and decreasing the branchial bafilomycin-sensitive V-type H⁺-ATPase activity, which suggests that its gills might have low NH₃ permeability...
  13. doi request reprint Roles of three branchial Na(+)-K(+)-ATPase α-subunit isoforms in freshwater adaptation, seawater acclimation, and active ammonia excretion in Anabas testudineus
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    Am J Physiol Regul Integr Comp Physiol 303:R112-25. 2012
    ....
  14. ncbi request reprint Changes in salinity and ionic compositions can act as environmental signals to induce a reduction in ammonia production in the African lungfish Protopterus dolloi
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Singapore 117543, Republic of Singapore
    J Exp Zool A Comp Exp Biol 303:456-63. 2005
    ..In conclusion, our results suggest that P. dolloi could respond to increases in salinity and changes in ionic composition in the external medium by suppressing ammonia production in preparation for aestivation when the water dries up...
  15. ncbi request reprint Marine (Taeniura lymma) and freshwater (Himantura signifer) elasmobranchs synthesize urea for osmotic water retention
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 78:610-9. 2005
    ..signifer. Taken together, these results suggest that the primary function of the ornithine-urea cycle in ureogenic marine and freshwater elasmobranchs is to synthesize urea for osmotic water retention and not for ammonia detoxification...
  16. ncbi request reprint The African sharptooth catfish Clarias gariepinus can tolerate high levels of ammonia in its tissues and organs during four days of aerial exposure
    Y K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 78:630-40. 2005
    ..gariepinus does not detoxify ammonia to urea or free amino acids on land...
  17. ncbi request reprint The interplay of increased urea synthesis and reduced ammonia production in the African lungfish Protopterus aethiopicus during 46 days of aestivation in a mucus cocoon
    Yuen Kwong Ip
    Department of Biological Sciences, National University of Singapore, Republic of Singapore
    J Exp Zool A Comp Exp Biol 303:1054-65. 2005
    ....
  18. ncbi request reprint Light induces an increase in the pH of and a decrease in the ammonia concentration in the extrapallial fluid of the giant clam Tridacna squamosa
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, Republic of Singapore
    Physiol Biochem Zool 79:656-64. 2006
    ..squamosa...
  19. ncbi request reprint Mechanisms of and defense against acute ammonia toxicity in the aquatic Chinese soft-shelled turtle, Pelodiscus sinensis
    Y K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Aquat Toxicol 86:185-96. 2008
    ....
  20. doi request reprint The freshwater Amazonian stingray, Potamotrygon motoro, up-regulates glutamine synthetase activity and protein abundance, and accumulates glutamine when exposed to brackish (15 per thousand) water
    Y K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 212:3828-36. 2009
    ..In contrast, P. motoro became N limited when exposed to 10 per thousand water with fasting and could not survive well in 15 per thousand water without food...
  21. doi request reprint Nitrogen metabolism and excretion during aestivation
    Y K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore, 117543, Republic of Singapore
    Prog Mol Subcell Biol 49:63-94. 2010
    ..Therefore, future efforts should be made to identify adaptive responses particular to each of the three phases of aestivation in various aestivators...
  22. ncbi request reprint Chronic and acute ammonia toxicity in mudskippers, Periophthalmodon schlosseri and Boleophthalmus boddaerti: brain ammonia and glutamine contents, and effects of methionine sulfoximine and MK801
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 208:1993-2004. 2005
    ..Thus, it can be concluded that there are major differences in mechanisms of chronic and acute ammonia toxicity between brains of these two mudskippers and mammalian brains...
  23. ncbi request reprint Postprandial increases in nitrogenous excretion and urea synthesis in the giant mudskipper Periophthalmodon schlosseri
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 207:3015-23. 2004
    ..schlosseri throughout the 24 h period post-feeding, accompanied by a significant decrease in brain glutamine content between 12 h and 24 h...
  24. ncbi request reprint The giant mudskipper Periophthalmodon schlosseri facilitates active NH(4)(+) excretion by increasing acid excretion and decreasing NH(3) permeability in the skin
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    J Exp Biol 207:787-801. 2004
    ..0) for 6 days. These changes might lead to an even lower permeability to NH(3) in the skin, and reduced back diffusion of the actively excreted NH(4)(+) as NH(3) or the net influx of exogenous NH(3), under such conditions...
  25. ncbi request reprint A comparison of the effects of environmental ammonia exposure on the Asian freshwater stingray Himantura signifer and the Amazonian freshwater stingray Potamotrygon motoro
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 206:3625-33. 2003
    ..Our results suggest that such a strategy began to develop in those elasmobranchs, e.g. H. signifer, that migrate into a freshwater environment from the sea but not in those permanently adapted to a freshwater environment...
  26. ncbi request reprint African sharptooth catfish Clarias gariepinus does not detoxify ammonia to urea or amino acids but actively excretes ammonia during exposure to environmental ammonia
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 77:242-54. 2004
    ..These results represent the first report on a freshwater fish (C. gariepinus) adopting active excretion of ammonia (probably NH4+) as a major strategy to defend against ammonia toxicity when exposed to environmental ammonia...
  27. ncbi request reprint Partial amino acid catabolism leading to the formation of alanine in Periophthalmodon schlosseri (mudskipper): a strategy that facilitates the use of amino acids as an energy source during locomotory activity on land
    Y K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 204:1615-24. 2001
    ..It is possible that such a strategy may be widely adopted, especially by obligatory air-breathing fishes, to avoid ammonia intoxication during aerial exposure...
  28. ncbi request reprint The sleeper Bostrichthys sinensis (family Eleotridae) stores glutamine and reduces ammonia production during aerial exposure
    Y K Ip
    Department of Biological Sciences, National University of Singapore, Republic of Singapore
    J Comp Physiol B 171:357-67. 2001
    ..After 72 h of aerial exposure, B. sinensis reduced internal ammonia production, possibly through reductions in proteolysis and amino acid catabolism, to avoid excessive accumulation of ammonia...
  29. ncbi request reprint Five tropical air-breathing fishes, six different strategies to defend against ammonia toxicity on land
    Y K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 77:768-82. 2004
    ....
  30. ncbi request reprint Strategies adopted by the mudskipper Boleophthalmus boddaerti to survive sulfide exposure in normoxia or hypoxia
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 77:824-37. 2004
    ..boddaerti detoxified sulfide mainly to sulfane sulfur in hypoxia. In conclusion, B. boddaerti was able to activate different mechanisms to detoxify sulfide, producing different types of detoxification products in normoxia and hypoxia...
  31. ncbi request reprint Strategies for surviving high concentrations of environmental ammonia in the swamp eel Monopterus albus
    Yuen K Ip
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 77:390-405. 2004
    ..albus was suppressed in order to prevent the newly established internal steady state concentration of ammonia from rising to an intolerable level after an extended period of exposure to HEA...
  32. ncbi request reprint Reduction in the rates of protein and amino acid catabolism to slow down the accumulation of endogenous ammonia: a strategy potentially adopted by mudskippers (Periophthalmodon schlosseri snd Boleophthalmus boddaerti) during aerial exposure in constant da
    C B Lim
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 204:1605-14. 2001
    ..This finding may be the first report of a teleost fish showing a reduction in proteolysis and amino acid catabolism in response to aerial exposure...
  33. doi request reprint Roles of intestinal glutamate dehydrogenase and glutamine synthetase in environmental ammonia detoxification in the euryhaline four-eyed sleeper, Bostrychus sinensis
    W Y X Peh
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Aquat Toxicol 98:91-8. 2010
    ..Therefore, it can be concluded that the intestine of B. sinensis was involved in the defense against ammonia toxicity during exposure to ammonia in a hyperosmotic medium...
  34. doi request reprint Effects of hypoxia on the energy status and nitrogen metabolism of African lungfish during aestivation in a mucus cocoon
    A M Loong
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Singapore
    J Comp Physiol B 178:853-65. 2008
    ..They also indicate that reduction in nitrogen metabolism, and probably metabolic rate, did not occur simply in association with aestivation (in normoxia) but responded more effectively to a combined effect of aestivation and hypoxia...
  35. ncbi request reprint Accumulation of ammonia in the body and NH(3) volatilization from alkaline regions of the body surface during ammonia loading and exposure to air in the weather loach Misgurnus anguillicaudatus
    T K N Tsui
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    J Exp Biol 205:651-9. 2002
    ..During periods of elevated tissue ammonia levels, some ammonia is lost by volatilization via air-breathing using the gut. In addition, some ammonia may be lost across the skin during air exposure...
  36. doi request reprint Molecular characterization and mRNA expression of carbamoyl phosphate synthetase III in the liver of the African lungfish, Protopterus annectens, during aestivation or exposure to ammonia
    A M Loong
    Department of Biological Sciences, National University of Singapore, Kent Ridge, 117543, Republic of Singapore
    J Comp Physiol B 182:367-79. 2012
    ..annectens, alluding to the important functional role of urea not only as a product of ammonia detoxification but also as a putative internal cue for aestivation...
  37. ncbi request reprint Defense against environmental ammonia toxicity in the African lungfish, Protopterus aethiopicus: Bimodal breathing, skin ammonia permeability and urea synthesis
    A M Loong
    Department of Biological Sciences, National University of Singapore, Singapore, Republic of Singapore
    Aquat Toxicol 85:76-86. 2007
    ..Therefore, unlike other fishes, glutamine and alanine contents did not increase in the muscle and liver, and there was no accumulation of glutamine in the brain, even when the fish was immersed in water containing 100 mmoll(-1) NH(4)Cl...
  38. ncbi request reprint Ammoniagenesis in mudskippers Boleophthalmus boddaerti and Periophthalmodon schlosseri
    S F Chew
    Department of Zoology, National University of Singapore, Kent Ridge
    Comp Biochem Physiol B 87:941-8. 1987
    ..4. Aspartate was the major substrate of ammoniagenesis in the mudskippers, though glutamate and glutamine were also oxidised. 5. Transdeamination was the major pathway for ammoniagenesis in the mudskippers studied...
  39. doi request reprint Glutamine accumulation and up-regulation of glutamine synthetase activity in the swamp eel, Monopterus albus (Zuiew), exposed to brackish water
    Chia Y Tok
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 212:1248-58. 2009
    ..In addition, exposure to 25 per thousand water for 4 days led to significant increases in GS protein abundance in both muscle and liver, indicating that increases in the expression of GS mRNA could have occurred...
  40. ncbi request reprint Exposure to air, but not seawater, increases the glutamine content and the glutamine synthetase activity in the marsh clam Polymesoda expansa
    Kum C Hiong
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    J Exp Biol 207:4605-14. 2004
    ....
  41. ncbi request reprint The osmotic response of the Asian freshwater stingray (Himantura signifer) to increased salinity: a comparison with marine (Taeniura lymma) and Amazonian freshwater (Potamotrygon motoro) stingrays
    Wai L Tam
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 206:2931-40. 2003
    ..signifier in 20 per thousand water. Therefore, H. signifer appears to have reduced its capacity to retain urea in order to survive in the freshwater environment and, consequently, it could not survive well in full-strength seawater...
  42. doi request reprint Differential gene expression in the liver of the African lungfish, Protopterus annectens, after 6 days of estivation in air
    A M Loong
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, 117543, Republic of Singapore
    J Comp Physiol B 182:231-45. 2012
    ....
  43. ncbi request reprint Excretory nitrogen metabolism in the Chinese fire-belly newt Cynops orientalis in water, on land, or in high concentrations of environmental ammonia
    L Weng
    Department of Biological Sciences, National University of Singapore, Kent Ridge, 117543 Singapore, Republic of Singapore
    J Comp Physiol B 174:113-20. 2004
    ..Under such experimental conditions, the ornithine-urea cycle may be operating close to its limit; glutamine began to accumulate in the body, and endogenous ammonia production via amino acid catabolism was reduced...
  44. ncbi request reprint Cyanide exposure affects the production and excretion of ammonia by the mudskipper Boleophthalmus boddaerti
    S F Chew
    Biology Division, School of Science, National Institute of Education, Nanyang Technological University, Singapore, Singapore
    Comp Biochem Physiol C Pharmacol Toxicol Endocrinol 120:441-8. 1998
    ..boddaerti during the early phase of cyanide exposure...
  45. ncbi request reprint The ammonotelic African lungfish, Protopterus dolloi, increases the rate of urea synthesis and becomes ureotelic after feeding
    C K Lim
    Department of Biological Science, National University of Singapore, Kent Ridge, 117543 Singapore, Republic of Singapore
    J Comp Physiol B 174:555-64. 2004
    ..However, there was a significant increase in the glutamine content in the brain at hour 24, indicating that the brain had to defend against ammonia toxicity after feeding...
  46. ncbi request reprint Acute ammonia toxicity and the protective effects of methionine sulfoximine on the swamp eel, Monopterus albus
    Yvonne Y M Tng
    Department of Biological Sciences, National University of Singapore, Singapore, Singapore
    J Exp Zool A Ecol Genet Physiol 311:676-88. 2009
    ..Instead, MSO suppressed the rate of ammonia buildup in the brain, possibly through its effects on glutamate dehydrogenase therein...
  47. ncbi request reprint The swamp eel Monopterus albus reduces endogenous ammonia production and detoxifies ammonia to glutamine during 144 h of aerial exposure
    Angeline S L Tay
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 206:2473-86. 2003
    ..albus in the mud for longer periods during drought because ammonia and glutamine concentrations had already built up to high levels in the body of specimens exposed to air for 144 h...
  48. ncbi request reprint Postprandial increases in nitrogenous excretion and urea synthesis in the Chinese soft-shelled turtle, Pelodiscus sinensis
    Serene M L Lee
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Comp Physiol B 177:19-29. 2007
    ..sinensis. After feeding, a slight but significant increase in the glutamine content occurred in the brain at hour 24, indicating that the brain might experience a transient increase in ammonia and ammonia was detoxified to glutamine...
  49. ncbi request reprint Active ammonia transport and excretory nitrogen metabolism in the climbing perch, Anabas testudineus, during 4 days of emersion or 10 minutes of forced exercise on land
    Yi L Tay
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Biol 209:4475-89. 2006
    ..testudineus as an energy source to support locomotor activity during emersion. As a result, it is capable of wandering long distance on land from one water body to another as reported in the literature...
  50. ncbi request reprint Excretory nitrogen metabolism in the juvenile axolotl Ambystoma mexicanum: differences in aquatic and terrestrial environments
    Ai M Loong
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Physiol Biochem Zool 75:459-68. 2002
    ..Hence, it can be concluded that the juvenile axolotl acquired ureotelism while submerged in water, and its hepatic capacity of urea synthesis was more than adequate to handle the toxicity of endogenous ammonia during migration to land...
  51. ncbi request reprint Effects of intra-peritoneal injection with NH4Cl, urea, or NH4Cl+urea on nitrogen excretion and metabolism in the African lungfish Protopterus dolloi
    Yuen K Ip
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    J Exp Zool A Comp Exp Biol 303:272-82. 2005
    ..These results suggest that urea excretion in P. dolloi is likely to be regulated by the level of internal ammonia in its body...
  52. ncbi request reprint Ammonia toxicity and tolerance in the brain of the African sharptooth catfish, Clarias gariepinus
    Nicklaus L J Wee
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    Aquat Toxicol 82:204-13. 2007
    ..Instead, MSO affected activities of glutamate dehydrogenase and alanine aminotransferase and suppressed the rate of ammonia build up in the brain of fish injected with a lethal dose of CH(3)COONH(4)...
  53. ncbi request reprint Increased urea synthesis and/or suppressed ammonia production in the African lungfish, Protopterus annectens, during aestivation in air or mud
    Ai M Loong
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore, 117543, Republic of Singapore
    J Comp Physiol B 178:351-63. 2008
    ..Consequently, fish aestivating in mud had a lower dependency on increased urea synthesis to detoxify ammonia, which is energy intensive, than fish aestivating in air...
  54. ncbi request reprint Active ammonia excretion in the giant mudskipper, Periophthalmodon schlosseri (Pallas), during emersion
    Shit F Chew
    Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore, Republic of Singapore
    J Exp Zool A Ecol Genet Physiol 307:357-69. 2007
    ..Only 4.6% of the exogenous ammonia was detoxified to urea. The glutamate contents in the muscle and liver also increased significantly, but the glutamine contents remained unchanged...
  55. doi request reprint Environmental ammonia exposure induces oxidative stress in gills and brain of Boleophthalmus boddarti (mudskipper)
    Biyun Ching
    Department of Biological Science, National University of Singapore, Republic of Singapore
    Aquat Toxicol 95:203-12. 2009
    ..boddarti. Overall, our results indicate that there could be multiple routes through which ammonia induced oxidative stress in and outside the brain...
  56. ncbi request reprint Differential NOS expression in freshwater and aestivating Protopterus dolloi (lungfish): heart vs kidney readjustments
    Daniela Amelio
    Department of Cellular Biology, University of Calabria, 87030 Arcavacata di Rende, CS, Italy
    Nitric Oxide 18:1-10. 2008
    ..Our findings are of evolutionary interest, since they document for the first time the presence of a NOS system in a ancestral fish, indicative of deep phylogenetic roots of NO bio-synthesis...
  57. doi request reprint Carbohydrate and amino acid metabolism in fasting and aestivating African lungfish (Protopterus dolloi)
    Natasha Therese Frick
    Department of Integrative Biology, University of Guelph, Guelph, Ont N1G2W1, Canada
    Comp Biochem Physiol A Mol Integr Physiol 151:85-92. 2008
    ..These findings indicate the importance of both carbohydrate and amino acid fuel stores during aestivation in aphylogenetically ancient, air-breathing fish...
  58. ncbi request reprint Increases in urea synthesis and the ornithine-urea cycle capacity in the giant African snail, Achatina fulica, during fasting or aestivation, or after the injection with ammonium chloride
    Kum Chew Hiong
    Department of Biological Sciences, National University of Singapore, Republic of Singapore
    J Exp Zool A Comp Exp Biol 303:1040-53. 2005
    ..fulica is to defend against ammonia toxicity, but suggest that urea may have more than an excretory role in terrestrial pulmonates capable of aestivation...
  59. doi request reprint Lipid, ketone body and oxidative metabolism in the African lungfish, Protopterus dolloi following 60 days of fasting and aestivation
    Natasha Therese Frick
    Department of Integrative Biology, University of Guelph, Guelph, Ont N1G2W1, Canada
    Comp Biochem Physiol A Mol Integr Physiol 151:93-101. 2008
    ....
  60. ncbi request reprint 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
    Esther Wei Yin Chang
    Department of Biological Science, National University of Singapore, Kent Ridge, Singapore, Republic of Singapore
    J Exp Zool A Ecol Genet Physiol 307:708-23. 2007
    ..This suggests for the first time that A. testudineus could alter its bimodal breathing pattern to facilitate the functioning of branchial Na+/K+ -ATPase for osmoregulatory purposes...
  61. ncbi request reprint Effects of peritoneal injection of NH4HCO3 on nitrogen excretion and metabolism in the swamp eel Monopterus albus-- increased ammonia excretion with an induction of glutamine synthetase activity
    Chiat Koo Lim
    Department of Biological Sciences, National University of Singapore, 10 Kent Ridge Road, Singapore 117543, Republic of Singapore
    J Exp Zool A Comp Exp Biol 301:324-33. 2004
    ..Overall, injection of NH4HCO3 had only minor effects on the contents of FAAs, other than glutamine, in tissues of M. albus because the majority (70%) of the injected ammonia was excreted within the 24-h period...
  62. ncbi request reprint The crab-eating frog, Rana cancrivora, up-regulates hepatic carbamoyl phosphate synthetase I activity and tissue osmolyte levels in response to increased salinity
    Patricia Wright
    Department of Zoology, University of Guelph, Guelph, Ontario, Canada N1G 2W1
    J Exp Zool A Comp Exp Biol 301:559-68. 2004
    ..Also, amino acid accumulation may contribute to an overall rise in the osmolarity of the muscle tissue, but relative to urea, the contribution is small...
  63. ncbi request reprint Ornithine-urea cycle and urea synthesis in African lungfishes, Protopterus aethiopicus and Protopterus annectens, exposed to terrestrial conditions for six days
    Ai May Loong
    Department of Biological Sciences, National University of Singapore, Singapore 117543, Republic of Singapore
    J Exp Zool A Comp Exp Biol 303:354-65. 2005
    ..aethiopicus and P. annectens depended more on reductions in ammonia production than on increases in urea synthesis to ameliorate ammonia toxicity when exposed to terrestrial conditions...
  64. ncbi request reprint Nitrogen metabolism and excretion in the aquatic chinese soft-shelled turtle, Pelodiscus sinensis, exposed to a progressive increase in ambient salinity
    Serene Min Lin Lee
    Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
    J Exp Zool A Comp Exp Biol 305:995-1009. 2006
    ....
  65. ncbi request reprint Characterization of cDNAs encoding cholesterol side chain cleavage and 3beta-hydroxysteroid dehydrogenase in the freshwater stingray Potamotrygon motoro
    B Scott Nunez
    Department of Marine Science, The University of Texas Marine Science Institute, Port Aransas, TX 78373, USA
    Comp Biochem Physiol B Biochem Mol Biol 145:306-17. 2006
    ..This study is the first to isolate full length cDNAs encoding elasmobranch CYP11A and HSD3 and the first to examine the regulation of steroidogenic genes in elasmobranch interrenal cells...