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  • 1
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 38 (1991), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 40 (1992), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    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.
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  • 5
    ISSN: 1573-5168
    Keywords: respiration ; airbreathing teleost ; hypoxia ; oxygen debt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mudskipper P. chrysospilos became inert at 0.76 μl O2.ml−1 when it was allowed to respire in a ‘closed respiratory chamber’. No ethanol was detected although it excreted three times more total carbon dioxide into the surrounding sea water than the amount of oxygen consumed. However, P. chrysospilos could survive environmental hypoxic exposure (0.8 μl O2.ml−1) for at least 6 h. Upon normoxic recovery, the oxygen debt repayment was only a small fraction of the oxygen deficit incurred during the 6 h of hypoxic exposure. It would therefore appear that P. chrysospilos was able to cope with environmental hypoxia by suppressing its metabolic rate.
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  • 6
    ISSN: 1573-5168
    Keywords: Boleophthalmus boddaerti ; mudskipper ; osmoregulation ; Na+ ; K+-ATPase ; HCO3 − ; Cl−-ATPase ; carbonic anhydrase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mudskipperB. boddaerti, was able to survive in waters of intermediate salinities (4–27‰). Fish submerged in dechlorinated tap water suffered 60% mortality by the fifth day while 60% of those in 100% sea-water (sw) died after the third day of exposure. After being submerged in 50% or 80% sw for 7 days, the plasma osmolality, plasma Na+ and Cl− concentrations and the branchial Na+ and K+ activated adenosine triphosphatase (Na+,K+-ATPase) activity were significantly higher than those of fish submerged in 10% sw for the same period. However, the activities of the branchial HCO3 − and Cl− stimulated adenosine triphosphatase (HCO3 −,Cl−-ATPase) and carbonic anhydrase of the latter fish were significantly greater than those of the former. Such correlation suggests that Na+,K+-ATPase is important for hyperosmotic adaptation in this fish while HCO3 −-Cl−-ATPase and carbonic anhydrase may be involved in hypoosmotic survival.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 165 (1996), S. 558-564 
    ISSN: 1432-136X
    Keywords: Alanine ; Amino acid ; Racemase ; Sipunculid ; Phascolosoma arcuatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Free D- and L-alanine contents were comparable in the body wall and introvert cum retractor muscles of Phascolosoma arcuatum. In contrast, the content of free D-alanine in the internal organs was twice that of free L-alanine. Since alanine aminotrans-ferase from P. arcuatum was L-alanine specific, D-alanine appeared to be synthesized from L-alanine through the action of alanine racemase. Alanine racemase activity was higher in the D-alanine-forming direction in the three body parts of P. arcuatum. In addition, the ratio of D→L/L→D racemase activity in the internal organs was the lowest among the body parts studied. These results indicate that free D-alanine might be of lesser importance than the free D-isomer to the internal organs as compared to the body wall and introvert cum retractor muscles. Indeed, L-alanine inhibited pyruvate kinase from the body wall and introvert cum retractor muscles but had no effect on the pyruvate kinase from the internal organs. Furthermore, the activity of alanopine dehydrogenase present in the internal organs was significantly lower than those of the body wall and introvert cum retractor muscles. L-Alanine was an essential substrate for alanopine formation in the body wall and introvert cum retractor muscles during hypoxia since alanopine dehydrogenases from these body parts were L-alanine specific. When P. arcuatum was confronted with hypo-osmotic stress, the free D-alanine/total free alanine ratio in the internal organs increased approximately from 0.6 to 0.8 as the total free alanine content decreased. In comparison, those ratios in the body wall and introvert cum retractor muscles remained relatively constant. It was concluded that D- and D-alanine had different physiological functions in the three body parts of P. arcuatum.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 163 (1993), S. 487-494 
    ISSN: 1432-136X
    Keywords: Glycogen ; Lactate ; Pasteur effect ; Boleophthalmus boddaerti ; Periophthalmodon schlosseri
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A comparison of branchial enzyme profiles indicates that the gills of Periophthalmodon schlosseri would have a greater capacity for energy metabolism through glycolysis than those of Boleophthalmus boddaerti. Indeed, after exposure to hypoxia, or anoxia, there were significant increases in the lactate content in the gills of P. schlosseri. In addition, exposure to hypoxia or anoxia significantly lowered the glycogen level in the gills of this mudskipper. It can be deduced from these results that the glycolytic flux was increased to compensate for the decrease in ATP production through anaerobic glycolysis. Different from P. schlosseri, although there was an increase in lactate production in the gills of B. boddaerti exposed to hypoxia, there was no significant change in the branchial glycogen content, indicating that a reversed Pasteur effect might have occurred under such conditions. In contrast, anoxia induced an accumulation of lactate and a decrease in glycogen in the gills of B. boddaerti. Although lactate production in the gills of these mudskippers during hypoxia was inhibited by iodoacetate, the decreases in branchial glycogen contents could not account for the amounts of lactate formed. The branchial fructose-2,6-bisphosphate contents of these mudskippers exposed to hypoxia or anoxia decreased significantly, leaving phosphofructokinase and glycolytic rate responsive to cellular energy requirements under such conditions. The differences in response in the gills of B. boddaerti and P. schlosseri to hypoxia were possibly related to the distribution of phosphofructokinase between the free and bound states.
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  • 9
    Publication Date: 1996-06-01
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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