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  • 1
    Electronic Resource
    Electronic Resource
    Temperature-dependent changes in energy metabolism, intracellular pH and blood oxygen tension in the Atlantic cod (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of acute increase in temperature on oxygen partial pressure (Po2) was measured in the gill arches of Atlantic cod Gadus morhua between 10 and 19° C by use of oxygen microoptodes. Oxygen saturation of the gill blood under control conditions varied between 90 and 15% reflecting a variable percentage of arterial or venous blood in accordance with the position of each optode in the gill arch. The data obtained suggested that arterial Po2 remained more or less constant and arterial oxygen uptake did not become limiting during warming. A progressive drop in venous Po2, however, was observed at 〉10° C indicating that excessive oxygen uptake from the blood is not fully compensated for by circulatory performance, until finally, Po2 levels fully collapse. In a second set of experiments energy and acid–base status of white muscle of Atlantic cod in vivo was measured by magnetic resonance (31P-NMR) spectroscopy in unanaesthetized and unimmobilized fish in the temperature range between 13 and 21° C. A decrease in white muscle intracellular pH (pHi) with temperature occurred between 10 and 16° C (ΔpH per ° C = −0·025 per ° C). In white muscle temperature changes had no influence on high-energy phosphates such as phosphocreatine (PCr) or ATP except during exposure to high critical temperatures (〉16° C), indicating that white muscle energy status appears to be relatively insensitive to thermal stress if compared to the thermal sensitivity of the whole animal. The data were consistent with the hypothesis of an oxygen limitation of thermal tolerance in animals, which is set by limited capacity of oxygen supply mechanisms. In the case of Atlantic cod circulatory rather than ventilatory performance may be the first process to cause oxygen deficiency during heat stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1095-8649.2003.00099.x
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  • 2
    Electronic Resource
    Electronic Resource
    Hsp70 is not a sensitive indicator of thermal limitation in Gadus morhua (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 67 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The levels of heat-shock proteins of the 70 kDa family (Hsp70s) were measured in different soft tissues of Atlantic cod Gadus morhua from different locations and after exposure to various thermal conditions: acute temperature increments (1° C day−1), mid-term (73 days at 4–15° C) and long-term thermal acclimation (278 days at 8–15° C), and seasonal and latitudinal temperature variations (field samples). Tissue specific distribution patterns of Hsp70s were observed: liver 〉 gills 〉 red blood cells 〉 brain 〉 white muscle. Thus, different tissues may have required different levels of protection by Hsp70s, and possibly this was related to the rate of protein synthesis. There were no differences in tissue Hsp70s between Arctic cod populations (Arctic, i.e. Barents and White Seas, Norwegian coast, and North or Baltic Seas). No changes in Hsp70s levels were observed in response to temperature variation of any intensity (acute fluctuation or seasonal and latitudinal) within the range of physiological temperatures (4–15° C) in wild and laboratory Atlantic cod. This confirms previous observations that changes in Hsp70 caused by such temperature variation are often small in fishes. Probably, the constitutive level of Hsp70s in Atlantic cod was high enough to overcome potentially harmful effects of temperature variations within the physiological range. A suppressing effect of high temperature (15° C) has already been observed at a systematic level (as reduced rate of somatic growth), whereas it is not reflected in modified Hsp70s. Therefore, Hsp70s apparently played a secondary role in defining thermal tolerance limits in Atlantic cod. These conclusions are in line with a recent concept of thermal tolerance which indicated that the first line of thermal limitation in the cold and warm is a loss in aerobic scope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00778.x
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  • 3
    Electronic Resource
    Electronic Resource
    Metabolic adaptation of the intertidal worm Sipunculus nudus to functional and environmental hypoxia (1984)
    Springer
    Marine biology 79 (1984), S. 237-247 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The scope of anaerobic metabolism of Sipunculus nudus L. was assessed from the maximal activities of some enzymes of the intermediary metabolism and from the concentration of some metabolites accumulated during enhanced muscular activity and during prolonged experimental hypoxia. (1) Maximal enzyme activities demonstrate that the scope of anaerobic glycolysis, as indicated by maximal activities of glycogen phosphorylase (0.84 U g-1 fresh wt), far exceeds the aerobic capacity, which is assumed not to surpass the activity of succinate dehydrogenase (0.09 U g-1 fresh wt). Three pyruvate reductase activities (alanopine-, strombine- and octopine dehydrogenase) can possibly terminate anaerobic glycolysis. (2) During muscular activity, energy is provided by the degradation of phospho-L-arginine and by anaerobic glycolysis. Octopine is the major endproduct during functional anaerobiosis while the formation of strombine is less pronounced. (3) During exposure to a nitrogen atmosphere, several anaerobic endproducts are found to accumulate. Anaerobic glycolysis is terminated by strombine synthesis. This opine accumulates in concentrations much higher than octopine. In addition the concentrations of succinate, propionate and acetate are found to increase in tissues, and/or in the coelomic fluid and the incubation water. (4) The relative contribution of energy by the different anaerobic metabolic pathways are estimated during functional and environmental hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393255
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  • 4
    Electronic Resource
    Electronic Resource
    Intracellular pH and energy metabolism in the highly stenothermal Antarctic bivalve Limopsis marionensis as a function of ambient temperature (1999)
    Springer
    Polar biology 22 (1999), S. 17-30 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in oxygen consumption, ammonia excretion and in the acid-base and energy status of various tissues were investigated in the cold stenothermal Antarctic bivalve, Limopsis marionensis, and compared to similar data in the limpet, Nacella concinna, for an assessment of thermal sensitivity. Oxygen consumption of L. marionensis varied between −1.5 and 2°C with a Q 10 of 2.2. Ammonia excretion could only be detected in animals exposed to elevated temperature for periods in excess of 45 days and close to death and it is interpreted as the onset of protein and amino acid catabolism with starvation under temperature stress. In L. marionensis any change in temperature as well as starvation stress at constant temperature induced a decrease in phospho-l-arginine and ATP levels. However, only temperature stress resulted in a drop in the Gibb's free energy change of ATP hydrolysis. Intracellular pH rose in all tissues during upward or downward temperature changes of only 1.5 or 2°C for 24 h with a concomitant trend to accumulate succinate and acetate in the tissues. These changes are seen to reflect disturbances of the tissue acid-base and energy status with any under- or overshoot in aerobic metabolic rate during a temperature decrease or increase. Elevated temperature at 2°C during 2 weeks of incubation resulted in continued net ATP depletion, at low levels of ATP free energy. This indicates long-term stress, which was also mirrored in the inability to establish a new steady-state mean rate of oxygen consumption. Incubation at even higher temperatures of 4 and 7°C led to an aggravation of energetic stress and transition to an intracellular acidosis, as well as a fall in oxygen consumption. In N. concinna a drop in energy levels was also visible at 2°C but was compensated for during long-term incubation. In conclusion, L. marionensis will be able to compensate for a temperature change only in a very narrow range whereas the thermal tolerance window is much wider in N. concinna. The inability of the metabolic rate to rise continually and the concomitant transition to anaerobic metabolism and long-term energetic stress characterize the upper critical temperature. Stenothermality is discussed, not only as reflecting the permanent and very stable low temperature in the natural environment, but also regarding dif- ferences in the level of activity and aerobic scope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050386
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  • 5
    Electronic Resource
    Electronic Resource
    Extra- and intracellular acid-base balance and ionic regulation in cod (Gadus morhua ) during combined and isolated exposures to hypercapnia and copper (1997)
    Springer
    Marine biology 128 (1997), S. 337-346 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cod (Gadus morhua) were exposed to hypercapnia (water Pco2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO3 −]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na+] and [Cl−] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na+] and [Cl−] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances. The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia. Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma were significantly elevated only after 48 h, with liver showing the largest elevation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050099
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  • 6
    Electronic Resource
    Electronic Resource
    Temperature induced anaerobiosis in two populations of the polychaete worm Arenicola marina (L.) (1997)
    Springer
    Journal of comparative physiology 167 (1997), S. 25-35 
    Details
    ISSN: 1432-136X
    Keywords: Key words Acid-base status  ;  Alpha-stat regulation  ;  Anaerobic metabolism  ;  Cold adaptation  ;  Critical temperatures  ;  Intracellular pH  ;  Temperature adaptation  ;  Volatile fatty acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Temperature dependent changes in the mode of energy metabolism and in acid-base status were studied in the range from −1.7 to 26 °C in two populations of Arenicola marina collected in summer as well as in winter from intertidal flats of the North Sea (boreal) and the White Sea (subpolar). Extreme temperatures led to an accumulation of anaerobic end products, indicating the existence of both a low and a high critical temperature, beyond which anaerobic metabolism becomes involved in energy production. In summer animals from the North Sea the high critical temperature was found at temperatures above 20 °C, and the low critical temperature below 5 °C. Latitudinal or seasonal cold adaptation lead to a more or less parallel shift of both high and low critical temperature values to lower values. Between critical temperatures intracellular pH declined with rising temperature. Slopes varied between −0.012 and −0.022 pH- units/°C. In summer animals from the North Sea, the slope was slightly less than in White Sea animals, but differences appeared independent of the season. However, slopes were no longer linear beyond critical temperatures. A drop in intracellular pH at low temperatures coincided with the accumulation of volatile fatty acids in the body wall tissue of North Sea animals. A failure of active pHi adjustment is held responsible for the reduced ΔpHi/ΔT at temperatures above the high critical temperature. Extracellular pH was kept constant over the whole temperature range investigated. The ability of North Sea animals to adapt to temperatures beyond the critical temperature is poor compared to White Sea specimens. The larger range of temperature fluctuations at the White Sea is seen as a reason for the higher adaptational capacity of the subpolar animals. A hypothesis is proposed that among other mechanisms critical temperature values are set by an adjustment of mitochondrial density and thus, aerobic capacity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050044
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  • 7
    Electronic Resource
    Electronic Resource
    Anaerobiosis and acid-base status in marine invertebrates: effect of environmental hypoxia on extracellular and intracellular pH inSipunculus nudus L. (1984)
    Springer
    Journal of comparative physiology 155 (1984), S. 13-20 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intra- and extracellular acid-base status was investigated during prolonged experimental anaerobiosis inSipunculus nudus L. An acidosis could not be observed during the first 6–12 h of anaerobiosis, in contrast, a slight alkalosis developed in both extra- and intracellular body compartments. Extra- and intracellular pH only started to decrease gradually after 12 h of environmental hypoxia as an expression of a non-compensated non-respiratory acidosis. The initial alkalosis associated with a positive base excess is interpreted as being due to the concomitant degradation of phospho-l-arginine (Pörtner et al. 1984a). The amount of succinate, propionate, and acetate accumulated in the extracellular fluid (coelomic plasma) could not be correlated quantitatively with a concomitant negative base excess. This discrepancy suggests that protons and anionic metabolites are distributed between various body compartments according to different equilibria and kinetics. Comparison of the changes in the acid-base status with the concentration changes of characteristic anaerobic metabolites (Pörtner et al. 1984a) indicates that (at least inSipunculus nudus) pHi is not the crucial factor initiating the observed shift of the metabolite flux from the Embden-Meyerhofpathway towards the succinate-propionate pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688786
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  • 8
    Electronic Resource
    Electronic Resource
    Energy metabolism and ATP free-energy change of the intertidal worm Sipunculus nudus below a critical temperature (1996)
    Springer
    Journal of comparative physiology 166 (1996), S. 492-500 
    Details
    ISSN: 1432-136X
    Keywords: Key words Cold-induced anaerobiosis ; Acid-base status ; Blood gas parameters ; Gibb’s free-energy change of ATP hydrolysis ; Intracellular pH ; Critical temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The intertidal worm Sipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were incubated in sea water or maintained for up to 8 days at 4 and 0 °C while dwelling in the sediment. Cannulation of the animals prior to experimentation allowed the analysis of blood gas parameters (P O2, P CO2 and pH). P O2 fell to 0 torr within 8 days at 0 °C. A simultaneous reduction of ventilatory activity was derived from measurements of the pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in P CO2 and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates and the phosphagen, phospho-L-arginine, reflect a significant decrease in the Gibb’s free-energy change of ATP hydrolysis. These changes are interpreted to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12 °C after more than 2 days of exposure to 0 °C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist below 4 °C owing to the insufficient response of the ventilatory system to the developing hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050037
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  • 9
    Electronic Resource
    Electronic Resource
    Energy metabolism and ATP free-energy change of the intertidal wormSipunculus nudus below a critical temperature (1996)
    Springer
    Journal of comparative physiology 166 (1996), S. 492-500 
    Details
    ISSN: 1432-136X
    Keywords: Cold-induced anaerobiosis ; Acid-base status ; Blood gas parameters ; Gibb's free-energy change of ATP hydrolysis ; Intracellular pH ; Critical temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The intertidal wormSipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were incubated in sea water or maintained for up to 8 days at 4 and 0°C while dwelling in the sediment. Cannulation of the animals prior to experimentation allowed the analysis of blood gas parameters ( $$P_{O_2 } $$ , $$P_{CO_2 } $$ and pH). $$P_{O_2 } $$ fell to 0 torr within 8 days at 0°C. A simultaneous reduction of ventilatory activity was derived from measurements of the pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in $$P_{CO_2 } $$ and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates and the phosphagen, phospho-l-arginine, reflect a significant decrease in the Gibb's free-energy change of ATP hydrolysis. These changes are interpreted to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12°C after more than 2 days of exposure to 0°C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist below 4°C owing to the insufficient response of the ventilatory system to the developing hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02338292
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  • 10
    Electronic Resource
    Electronic Resource
    Anaerobiosis and acid-base status in marine invertebrates: a theoretical analysis of proton generation by anaerobic metabolism (1984)
    Springer
    Journal of comparative physiology 155 (1984), S. 1-12 
    Details
    ISSN: 1432-136X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary In animals, various organic acids are accumulated during hypoxia or anoxia as products of anaerobic energy metabolism. The diversity of such acids is largest in marine invertebrates where succinate, propionate, acetate, lactate, alanine, octopine, strombine, and alanopine, are produced mainly from glycogen and aspartate. The effect of these substances on the acid-base status was assessed by a theoretical analysis of the respective metabolic pathways. This resulted in a general rule which was applied to evaluate the proton balance of the reactions in energy metabolism: net changes in the number of carboxyl groups or changes in the degree of dissociation of other groups (e.g. phosphate or ammonia) determine the net amount of H+ ions released or bound by the substrates and the metabolic end products. For marine invertebrates the results of the analysis can be summarized as follows: In glycogenolysis one mol of protons per mol of end products is released during cytosolic glycolysis, independent of the type of metabolic end product (lactate, octopine, alanopine, strombine, or alanine). The same applies for mitochondrial production of propionate and acetate, whereas formation of succinate results in dissociation of two mol H+ per mol. Fermentation of aspartate, however, diminishes the amount of protons which is produced in the succinate-propionate pathway. Net metabolisation of Mg ATP2− yields extra protons, whereas the cleavage of phosphagens (e.g. creatine phosphate, arginine phosphate) consumes protons. Additionally the break-down of energy-rich phosphates to inorganic phosphate has to be taken into account because of the shift of the intracellular buffer curve caused by changes of the respective effective pK values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688785
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