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  • 1
    Electronic Resource
    Electronic Resource
    Effects of anoxia on the activities of pyruvate kinase and phosphoenolpyruvate carboxykinase, and the production of lactate and succinate in the intertidal pulmonate Onchidium tumidium (1993)
    Springer
    Marine biology 116 (1993), S. 103-107 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Onchidium tumidium, an intertidal pulmonate, has evolved to depend mainly on the formation of succinate, rather than lactate and opines, to survive in anoxia. For our study O. tumidum were collected from the mud flats of the mangrove swamp at Mandai, Singapore between 1988 and 1991. After 24 h of anoxic exposure, the lactate and succinate contents of the anoxic individuals were approximately 10 and 150 times, respectively, the corresponding values of the normoxic individuals. Alanine and acetate accumulations also occurred during anoxia, though to a much lesser extent. No propionate or octopine was detected. The depletion in aspartate content in O. tumidium could not account for the amount of succinate accumulated during anoxia. The succinate formed might have originated from glycogen involving the flow of carbon through the phosphoenolpyruvate (PEP) branch point of glycolysis. In support of such a hypothesis, results indicate that there was a decrease in the affinity of pyruvate kinase from O. tumidium exposed to 24h of anoxia to PEP to facilitate succinate formation through phosphoenolpyruvate carboxykinase (PEPCK). In comparison, the affinity of PEPCK from O. tumidium exposed to anoxia to PEP was apparently unaltered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350737
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  • 2
    Electronic Resource
    Electronic Resource
    Survival of the intertidal pulmonate Onchidium tumidium during short term and long term anoxic stress (1996)
    Springer
    Marine biology 125 (1996), S. 707-713 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Onchidium tumidium showed a triphasic response to anoxia. Twelve hours of anoxic exposure had no effect on the glycogen content in O. tumidium. However, there were significant increases in the alanine, lactate and succinate contents in the anoxic individuals. These were accompanied by a significant decrease in the ATP content. These results suggest that O. tumidium survived the first 12 h of anoxic exposure without increasing the glycolytic flux to compensate for the lower efficiency of ATP production through anaerobic pathways. Indeed, the fructose-2,6-bisphosphate (F-2,6-P2) content and the percentage of phosphofruc-tokinase (PFK) associated with the subcellular particles remain unchanged in O. tumidium exposed to 12 h of anoxia. Hence, a reduction in the metabolic rate of these individuals might have occurred during such a period of anoxia. In contrast, in between 12 and 24 h of anoxic exposure, the glycogen content O. tumidium decreased significantly, and levelled off thereafter. A significant increase in the percentage of PFK associated with the subcellular particles was observed in individuals exposed to 24 h of anoxia. In addition, the F-2,6-P2 content of these anoxic individuals increased significantly. Taken together, these two mechanisms could activate PFK and lead to a greater glycolytic flux. Beyond 24 h of anoxic exposure, survival of O. tumidium must have required considerable suppression of metabolism as accumulation of end products and depletions of glycogen and ATP had reached constant levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349253
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  • 3
    Electronic Resource
    Electronic Resource
    Biochemical adaptations of the mudskipper Boleophthalmus boddaerti to a lack of oxygen (1992)
    Springer
    Marine biology 112 (1992), S. 567-571 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Specimens of the mudskipper Boleophthalmus boddaerti, collected along the estuarine canal at Pasir Ris, Singapore between April 1987 and December 1989, were examined in the laboratory. After being exposed to environmental hypoxia for 6 h, no accumulation of lactate, alanine or succinate was observed in the muscle tissue of B. boddaerti. In addition, the blood lactate content and muscle creatine phosphate (CrP), adenosine triphosphate (ATP) and glycogen contents were not significantly different from those of the control. During normoxic recovery, oxygen debt repayment was only a small fraction of the oxygen deficit incurred during the 6 h of hypoxic exposure. Therefore, it would appear that B. boddaerti coped with environmental hypoxia by undergoing metabolic rate reduction. After anoxic exposure, the CrP, ATP and adenosine diphosphate (ADP) contents in the muscle tissue of B. boddaerti were significantly lower than the corresponding control values. Lactate accumulated in the blood and muscle tissue of the anoxic fish though the muscle energy charge and glycogen content remained constant. Hence, B. boddaerti was able to cope with such a period of anoxia without increasing its glycolytic rate. Succinate, which was not detected in the muscle tissue of the control and hypoxia-exposed fish, accumulated in significant quantities in the muscle tissue of B. boddaerti exposed to environmental anoxia and functional hypoxia. In the case of functional hypoxia, there was a significant decrease in the muscle glycogen content, and the muscle lactate content increased 17.3-fold, indicating that glycolysis was activated to provide the source of energy during muscular exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346174
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  • 4
    Electronic Resource
    Electronic Resource
    Ammonia production and kinetic properties of glutamate dehydrogenase in the sipinculid Phascolosoma arcuatum exposed to anoxia (1994)
    Springer
    Marine biology 119 (1994), S. 261-266 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amounts of total NH 4 + detected in the external media in which Phascolosoma arcuatum had been exposed to various periods of anoxia were significantly greater than those in which the worms were exposed to normoxia for a similar period. The increased NH 4 + production by P. arcuatum during anoxic exposure was unlikely to be due to an increased catabolism of adenine nucleotides or urea. In contrast, there were significant decreases in the concentrations of several free amino acids in the coelomic plasma and body tissues of individuals during the 48 h of anoxic exposure. The amount of NH 4 + produced by the anoxic P. arcuatum could be accounted for by the decreases in the concentrations of aspartate or glycine. Increases in the catabolism of free amino acids (FAA), leading to the increased production of NH 4 + , in P. arcuatum during anoxia were supported by the detection of significant changes in the kinetic properties of glutamate dehydrogenase (GDH), in the deaminating direction, from worms exposed to anoxia for 48 h. The apparent increase in the affinity of GDH from the anoxic worm to glutamate would bring about a greater deaminating activity at physiological concentrations of ths substrate. P. arcuatum used in these experiments were collected from the mangrove swamp at Mandai, Singapore between 1990 and 1993.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349565
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  • 5
    Electronic Resource
    Electronic Resource
    Free amino acids and osmoregulation in the intertidal pulmonate Onchidium tumidium (1999)
    Springer
    Marine biology 134 (1999), S. 735-741 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this study is to elucidate the osmoregulatory capabilities of the intertidal pulmonate Onchidium tumidium. Our results indicate that O. tumidium could tolerate hyperosmotic stress more effectively than hypoosmotic stress. In 10% seawater (SW), it was capable of maintaining its plasma hyperosmotic and hyperionic to the external medium. However, it rapidly gained weight in 10% SW, and no restoration of body weight was observed. In contrast, in 90% SW it was able to recover its body weight partially. In a hyperosmotic medium, accumulation of intracellular free amino acids (FAA) was responsible for cell volume regulation. The accumulated FAA might originate from protein catabolism, which occurred in the internal organs (IO). In contrast, the relatively smaller amination:deamination ratio of glutamate dehydrogenase in the body wall (BW) and IO of specimens exposed to hypoosmotic stress might lead to a higher rate of amino acid catabolism. This was supported by the greater ammonia contents in the BW and IO of, and higher rate of ammonia excretion by, specimens exposed to 10% SW.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050590
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of hypoxia on the mudskipper, Periophthalmus chrysospilos (Bleeker, 1853) (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 38 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb03148.x
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  • 7
    Electronic Resource
    Electronic Resource
    Differences in electrophoretic patterns of lactate dehydrogenases from the gills, hearts and muscles of three mudskippers (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 40 (1992), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1992.tb02644.x
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  • 8
    Electronic Resource
    Electronic Resource
    Metabolic adjustments in the common carp during prolonged hypoxia (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 57 (2000), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Biochemical and respiratory changes in the common carp Cyprinus carpio, were studied 6, 24, 96 and 168 h upon exposure to hypoxia (0·5 mgO2 l−1). Modification of kinetic properties of phosphofructokinase (PFK-1), coupled with a decreased in PFK-1 activities, were evident in muscle. No changes in kinetics and activities could be observed in muscle pyruvate kinase (PK) and lactate dehydrogenase (LDH). A decrease in muscle citrate synthase (CS) and an increase in muscle cytochrome c oxidase (CCO) were found. The common carp was able to maintain a constant level of muscle glycogen, muscle ATP, and liver CS throughout the 168-h experimental period. Changes in activities of liver LDH and muscle CCO were observed only at 168 h, which indicates that common carp may switch to alternative metabolic pathway to deal with prolonged hypoxia. A severe decrease in liver glycogen was accompanied by increases in lactate levels in both the muscle and liver. Oxygen consumption rate was reduced under hypoxia, but resumed to normoxic levels within 2 h upon return to normoxic condition. Overall, these results indicate that carp adopt different strategies in an attempt to deal with short term and long term hypoxia in the natural environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2000.tb00478.x
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  • 9
    Electronic Resource
    Electronic Resource
    Nitrogen metabolism and excretion in Allenbatrachus grunniens(L): effects of variable salinity, confinement, high pH and ammonia loading (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The nitrogen metabolism and excretion patterns of the grunting toadfish Allenbatrachus grunniens and the effects of salinity on these processes were examined. Individuals of A. grunniens were subjected to several experimental treatments, including variable salinity (2 to 30), high pH (8·5 compared to 7·0 for controls), high environmental ammonia (10 mM) and confinement to small water volumes, and measurements were made of activities of selected enzymes of nitrogen metabolism, ammonia and urea excretion rates, and tissue and plasma contents of ammonia, urea and amino acids. Activities of key ornithine-urea cycle enzymes were rather low (e.g. liver carbamoyl phosphate synthetase III activity was 0·001 μmols min−1 g−1), and A. grunniens consistently demonstrated a low capacity for urea excretion despite significant elevations of plasma and tissue ammonia contents by the high pH and high ammonia treatments. This species could thus be categorized as ammoniotelic. Total free amino acid contents in plasma and tissues were increased by the high pH and high ammonia treatments, but no patterns were discerned in individual amino acids that would indicate any preferential accumulation (e.g. alanine and glutamine) as has been noted previously in several semi-terrestrial fish species. Thus, it appeared that A. grunniens was not unusual in its patterns of nitrogen metabolism and excretion in comparison to other ‘typical’ teleosts. Furthermore, manipulation of salinity had no major effects on nitrogen excretion in either this species or in comparative studies with the ureotelic gulf toadfish Opsanus beta. The results are discussed in the context of the broader pattern of nitrogen metabolism and excretion in the Batrachoididae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2004.00538.x
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  • 10
    Electronic Resource
    Electronic Resource
    Changes in lactate content in the gills of the mudskippers Periophthalmus chrysospilos and Boleophthalmus boddaerti in response to environmental hypoxia (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 36 (1990), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The gills of Periophthalmus chrysospilos exhibited significantly greater pyruvate kinase and lactate dehydrogenase activities than those of Boleophthalmus boddaerti (P 〈0.01). Under the control normoxic condition, the branchial lactate content of the former mudskipper was also significantly greater (P 〈 0.01) than that of the latter. After hypoxic exposure, lactate and alanine accumulated in the gills of P. chrysospilos but not B. boddaerti. Succinate and propionate were not detected in the gills of these two mudskippers under the control and hypoxic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1990.tb03550.x
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