Anaerobic metabolism of the common cockle,Cardium edule—IV. Time dependent changes of metabolites in the foot and gill tissue induced by anoxia and electrical stimulation

• 1.1. The levels of adenylates, arginine phosphate, arginine and various other metabolites related to anaerobic metabolism were determined in foot and gills of Cardium edule during anoxia (incubation in oxygen-free sea water) up to 48 hr and after electrical stimulation of the foot muscle.
• 2.2. In the foot the phosphagen was depleted quite rapidly in the first hours of anoxia. Free arginine levels rose while there was little octopine accumulation. d-Lactate appeared to be the predominant end product. Alanine and succinate were also produced and the concentration of aspartate decreased, suggesting this metabolite as precursor for succinate. In the gills, where no arginine phosphate was present, succinate production was higher than in the foot and exceeded lactate formation.
• 3.3. Only a small decline in ATP occurred during anoxia and consequently, only moderate changes in the energy charge were observed in both tissues.
• 4.4. Electrical stimulation of the foot also resulted in the breakdown of arginine phosphate and formation of mainly lactate and not octopine.
• 5.5. Total ATP consumption during anoxia has been calculated to be more rapid during the first hours. The ATP consumption rate was reduced by a factor of 7.8 during 48 hr of anoxia.
• 6.6. During the first 4 hr of anoxia about 60% of the total consumed energy (as ATP equivalents) was provided by the phosphagen, while later glycolysis contributed about 80%. During electrical stimulation about 75% of the energy supplied was derived from the phosphagen.
• 7.7. A comparison of the C. edule results with the data during anoxia and exercise of the jumping cockle is made.

     

Inhibition of tubifex pyruvate kinase by storage phosphagens and adenosine triphosphate

• 1.1. Within the first 6–12 hr of experimental anaerobiosis the concentration of Tubifex phosphagens, phospholombricine and phosphoarginine, decrease to 10–30% of the values under aerobic conditions (7.5 and 3. μM/g dry wt).
• 2.2. High concentrations of both phosphagens (5–25 mM) inhibit Tubifex pyruvate kinase (PK) activity, the inhibitory mechanisms seem to be different. The inhibition is not mediated by the corresponding phosphagen kinases. Inhibition by phosphoarginine obviously requires an additional factor, which chemical nature is still unknown.
• 3.3. Certain phosphocreatine preparations also inhibit Tubifex PK. This inhibition, however, is likely due to contaminants than to phosphocreatine.
• 4.4. Mg-ATP demonstrates the strongest inhibitory effect on PK activity with a mixed competitive inhibition vs PEP and a non competitive vs ADP.

     

Individual and sibling-group variation in metabolism of lizards: The aerobic capacity model for the origin of endothermy

• 1.1. We measured standard, resting and exercise metabolism of 28 Chaicides ocellatus (Scincidae). Individual lizards consistently showed statistically significant differences in mass-independent rates of standard and exercise metabolism during three replicates of the experiments at weekly intervals.
• 2.2. Metabolic differences were also detected among groups of siblings.
• 3.3. Mass-independent resting metabolic rates were closely correlated with standard rates, but there was no correlation of metabolic rates during forced activity with either standard or resting rates.
• 4.4. These data suggest a heritable component of metabolism for lizards, but they do not support the “aerobic capacity model” of the origin of endothermy, which proposes that initial selection for high resting metabolic rates operated via selection for high rates of aerobic metabolism during exercise.

     

Contribution of aerobic and anaerobic scope to the total metabolic scope of the desert skink,Chalcides ocellatus (Forskal)

• 1.1. Measurements of aerobic scope (resting and active oxygen consumption rates) and anaerobic scope (resting and active production of lactate rates in the whole body homogenates) were carried out on the desert skink, Chalcides ocellatus at temperatures between 10 and 40°C.
• 2.2. The aerobic scope was maximal around the preferred body temperature with a low thermal temperature dependence above the preferred levels.
• 3.3. During initial stages of forced activity, C. ocellatus employed anaerobic metabolism as its major energy source.

     

Sublethal effects of hypoxia in the abalone (Haliotis rufescens) as measured by in vivo31P NMR spectroscopy

• 1.1. Effects of hypoxia were investigated in red abalones (Haliotis rufescens) using a flow-through exposure system and in vivo³¹P NMR spectroscopy.
• 2.2. Following seawater acclimation, abalones were exposed to air for 1 hr, then seawater for 2.5 hr to check recovery; parallel controls were performed without air exposure.
• 3.3. In foot muscle, hypoxia produced a decrease in phosphoarginine concentration and intracellular pH, an increase in inorganic monophosphate concentration, and no change in that of ATP; upon resubmergence, all effects generally recovered.
• 4.4. The changes induced by hypoxia during normal tidal changes are consistent with the blockage of mitochondrial oxidative phosphorylation.
• 5.5. Use of in vivo NMR allows measurement of the biochemical effects of natural stress factors in live, intact aquatic organisms in the laboratory.

     

Ventilatory rate in the butterfish (Pholis gunnellus) as a consequence of temperature and previous emersion

• 1.1. Observation of ventilation in immersed Pholis gunnellus showed a linear relationship between ventilatory rate and temperature between 8 and 20°C.
• 2.2. At 13°C and after 30 min emersion, ventilatory rate was initially lower than prior to emersion, providing evidence of adequate uptake of O₂ for standard metabolism during the emersion period.
• 3.3. This species has a laterally elongate body form with reduced scales and extensive mucus secretion.
• 4.4. During emersion, gaping behaviour probably exposes the gills and extensively vascularised oesophageal regions to air.
• 5.5. These are considered to be morphological and behavioural adaptations by P. gunnellus, to aerial respiration in the intertidal habitats occupied by this species.

     

Anaerobic metabolism in sublittoral living Mytilus galloprovincialis in the mediterranean—IV. Role of amino acids in adaptation to low salinities during anaerobiosis and aerobiosis

• 1.1. When Mytilus galloprovincialis were transferred from 38 to 19%. sea water (S), the metabolism became anaerobic for at least 8 hr. After 24 hr the animals were entirely aerobic again.
• 2.2. Upon transfer to 19%. S, the total free amino acid concentration in haemolymph doubled within 4 hr, remaining nearly constant thereafter, up to 48 hr.
• 3.3. In the posterior adductor muscle a strong decrease of alanine and glycine occurred at 48 hr exposure to 19%. S, and a smaller decrease of glutamate; taurine remained relatively constant. When transferred again to 38%. S after 14 days, a strong overcompensation occurred in the concentrations of alanine and proline, and a smaller overcompensation in those of threonine and serine.
• 4.4. In the gill no distinct change in the amino acid pool occurred during 14 days of exposure, with the exception of a decrease in serine. When transferred again to 38%. S, a strong overcompensation occurred in alanine, proline, glycine and serine, and a smaller in glutamate and threonine.
• 5.5. No evidence for anaerobic metabolism in the decrease of the amino acid pool was found.
• 6.6. M. galloprovincialis is less able to adapt to low salinities than the more euryhaline M. edulis.

     

Adenosine effect on lactate and pyruvate production in the hypoxic guineapig heart

• 1.1. It has been shown that adenosine stimulates glycolysis in some cells and this ability of adenosine was tested in the hypoxic guineapig heart.
• 2.2. Adenosine (10 μM) activated lactate production in the isolated perfused guineapig heart under conditions of normoxia but did not under hypoxia.
• 3.3. Despite this, the nucleoside favorably influenced the energy metabolism of the hypoxic heart as revealed by the better posthypoxic functional recovery (98%) compared to the control without adenosine (78%).
• 4.4. Our findings suggest a role for the glycolytic pathway in this effect of the nucleoside as long as other cardiac energy-yielding pathways are strictly aerobic.

     

The effects of organic and inorganic pollutants on intracellular phosphate compounds in blue mussels (Mythus edulis)

• 1.1. The effects of sublethal concentrations of organic and inorganic pollutants on intracellular energy-rich phosphates in blue mussels, Mytilus edulis, were investigated by in vivo ³¹P-NMR.
• 2.2. Formaldehyde (30 and 10mg/l), phenol, pyridine, mercury and cadmium gave marked reductions in phosphoarginine and, in some cases, the ATP amounts. The reduction in high-energy phosphate was accompanied by an increase in inorganic phosphate in all groups.
• 3.3. A “phosphorus index”, the product of the ratios between phosphoarginine and inorganic phosphate, and ATP and inorganic phosphate, is suggested, which might serve as an early warning (“alarm”) parameter in environmental monitoring.
• 4.4. Diversity in the responses to different pollutants make phosphorus compounds in M. edulis also an interesting element in a finger print parameter system designed to distinguish between pollutants in the marine environment.

     

The energy burden of the bopyrid parasite Argeia pauperata (Crustacea,isopoda) on the grass shrimp Crangon franciscorum (Crustacea,crangonidae)

• 1.1. The relationship between host and parasite rates of energy metabolism was used to estimate the energy burden of Argeia pauperata on its host Crangon franciscorum.
• 2.2. Respiration rates of the host were not significantly affected by the parasite even though the caloric turnover rate of the parasite was more than three times that of the host.
• 3.3. The ratios of both energy expenditure and size of the parasite to those of the host were positively correlated with host size.

     

Active transport of d-glucose in intestinal segments,in vitro,of the scup,Stenotomus versicolor and the puffer,Spheroides maculatus

• 1.1. Active transport of d-glucose was shown using intestinal sac preparations, in vitro, made from two marine fish, the scup, Stenotomus versicolor and the puffer, Spheroides maculatus.
• 2.2. Differences in absorption characteristics were evident in populations from year to year.
• 3.3. Anaerobiotic conditions, i.e. 100 per cent nitrogen gassing of the incubation medium, inhibit the active transport of d-glucose in scup and puffer intestine.
• 4.4. Phlorizin, 5 × 10⁻⁴ M, inhibits the active transport of d-glucose in scup intestine.
• 5.5. Intestinal transmural glucose transport mechanisms operate well at incubation temperatures, 20°–27°C, i.e. temperatures close to habitat and holding tank temperatures, whereas movement of the sugar against a concentration gradient is interrupted at higher incubation temperatures, 29° and 30°C.
• 6.6. Detailed comparison of procedures and results with those used by other workers in the field of in vitro intestinal absorption of poikilotherms suggests that aerobic metabolism may not be a uniformly significant energy source in intestinal active transport.

     

Seasonal variation in the metabolic rates and Q10-values of the fingernail clam,Sphaerium striatinum lamarck

• 1.1. Metabolic rates were highest during periods of maximum reproduction.
• 2.2. The exponent of the metabolic rate-weight equation varied seasonally, rates of metabolism of small animals exhibited greater annual fluctuations than those of large animals.
• 3.3. Absolute and weight-specific Q₁₀s (determined at 5–10°C above field temperatures) for smaller clams were greatest in the winter; absolute values of Q₁₀ were highest for larger individuals in the summer.
• 4.4. Small clams had Q₁₀ < 1.0 in the summer; Q₁₀-values for larger clams were near 1.0 at this time.
• 5.5. 38.9% of the total energy assimilated by the population annually was allocated to metabolism, which is near the low end of the range of values reported for freshwater molluscs, suggesting that this species can partition a large amount of energy to growth and reproduction.

     

Glucose metabolism in a kangaroo (Macropus robustus erubescens) and a similar size eutherian herbivore,the feral goat

• 1.1. Glucose pool size, space, entry rate, and turnover time were estimated from the specific radioactivity vs time curves of [³H] and [¹⁴C]glucose administered as a single injection in the euro (Macropus robustus erubescens) and the sympatric feral goat (Capra hircus).
• 2.2. Digestible energy intake was greater (P < 0.05 ± SE) in the goat than in the euro (798 ± 64 vs 624 ± 31kJ/kg^0.75 × day).
• 3.3. However, there were no significant differences between the two species in parameters of glucose metabolism.
• 4.4. The use of an implantable osmotic infusion pump to deliver isotopic glucose showed promise as a means of avoiding the stress involved with the single injection technique.

     

Effects of temperature and metabolic inhibitors on contraction of anterior byssus retractor muscle of Mytilus

• 1.1. Anterior byssus retractor muscle of Mytilus (ABRM) was stimulated to contract by ACh (acetylcholine) and effects of temperature (5–30°C), FDNB (1-fluoro 2,4 dinitro-benzene) and IAA (iodoacetic acid) on tension response were examined.
• 2.2. Isometric tension was highest at the temperature range of 10–20°C and decreased at higher and lower temperature than that range.
• 3.3. The rate of tension decay after washing of ACh was accelerated by the increase of temperature.
• 4.4. Tension redevelopment after release of 1 % during contraction was much smaller at 5°C than at 20°C.
• 5.5. Tension development by ACh and the rate of tension decay after washing of ACh were remarkably decreased by the treatment of FDNB or IAA.
• 6.6. The above results were discussed from the viewpoint that energy metabolism might be related to catch.

     

Analysis of the circadian rhythm in energy metabolism of rat liver

• 1.1. To study the temporal organization of energy metabolism in rat liver the steady state concentrations of key intermediates of carbohydrate and phosphorus metabolism were determined during 24 hr.
• 2.2. The circadian rhythm in energy metabolism of rat liver has been analysed by four different approaches. It was shown that neither apparent PEP synthesis nor crossover theorem were acceptable for the elucidation of the temporal organization of multi-enzyme systems.
• 3.3. Correlations analysis explained the temporal organization of energy metabolism most satisfactorily.
• 4.4. Based on the results of this analysis it was suggested that circadian regulation of energy metabolism in liver was realized at the level of the citric acid cycle.

     

The energy costs of temperature regulation in birds: The influence of quick sinusoidal temperature fluctuations on the gaseous metabolism of the japanese quail (Coturnix coturnix japonica)

• 1.1. Quick sinusoidal temperature fluctuations (constant average 10°C) cause an increase in metabolism in comparison to an invariable constant ambient temperature of the same dimension.
• 2.2. At the observed mean value of 10°C metabolism is increased by 0.8% per 1 K/hr based on the values of resting metabolic rate (correlation: M = 53.5 + 0.445 T_a, M in J/K g hr, T_a = ambient temperature change in K/hr) and 0.6% based on the values of activity metabolism (M = 70.4 + 0.425 T_a).
• 3.3. The absolute augmentation of metabolism per 1 K/hr is, by comparison, the same for day and night. Its amount is 0.42 and 0.43 J/K g hr respectively.
• 4.4. In the response of metabolism to temperature fluctuations no differences could be found with respect to the amplitude and frequency modifications of temperature.
• 5.5. The increase of energy consumption is probably caused to a greater extent by “overshoot” of the feedback control system in the course of adjusting metabolism to new levels according to the ambient temperature conditions.
• 6.6. Short term ambient temperature changes (i.e. measuring different temperature levels in one night to test basic metabolism vs ambient temperature) cannot produce reasonable values for basic metabolic rate, since these artificially high values reflect the testing procedure.

     

Short-term regulation of food intake by the brown honeyeater,Lichmera indistincta

• 1.1. Regardless of nectar concentration, there are strong positive correlations between the durations of feeding bouts by Lichmera indistincta and subsequent inter-bout intervals, and energy intake during feeding bouts and energy expenditure during subsequent inter-bout intervals.
• 2.2. Energy utilization by L. indistincta conforms to an accumulation-depletion model, with a portion of the energy acquired during each feeding bout contributing to the gradual diurnal storage of energy that is subsequently used for maintenance during non-foraging periods.
• 3.3. L. indistincta compensates for a decrease in nectar concentration by increasing the frequency of feeding bouts and decreasing the duration of inter-bout intervals.
• 4.4. Changes in the duration of inter-bout intervals caused by alterations to the calorific value of nectar drunk can be explained in terms of the rate at which the stomach empties.

     

Occurrence of d-alanine in the eggs and the developing embryo of the sea urchin Paracentrotus lividus

• 1.1. d-Alanine has been found in appreciable amounts in the eggs and embryos of the sea urchin Paracentrotus lividus.
• 2.2. The content of d-alanine, expressed as pmol/egg or embryo, is 1.32 in the egg, 0.81 in the blastula, 0.54 in the gastrula and 0.60 in the pluteus.
• 3.3. The percentage of d-alanine with respect to the total alanine (d + l) decreases during embryonic development.
• 4.4. d-Amino acid oxidase, d-alanine transaminase and d-alanine racemase activities were found neither in eggs nor in embryos.
• 5.5. Therefore, it does not appear likely that d-alanine is subject to oxidative metabolism.
• 6.6. The decrease in this d-amino acid during development may be due to its utilization in the synthesis of a more complex molecule.

     

Effects of the nonsteroidal anti-inflammatory drug piroxicam on energy metabolism in the perfused rat liver

• 1.1. The actions of piroxicam, a nonsteroidal and noncarboxylic anti-inflammatory drug, on the metabolism of the isolated perfused rat liver were investigated. The main purpose was to verify if piroxicam is also active on glycogenolysis and energy metabolism, as demonstrated for several carboxylic nonsteroidal anti-inflammatories.
• 2.2. Piroxicam increased oxygen consumption in livers from both fed and fasted rats.
• 3.3. Piroxicam increased glucose release and glycolysis from endogenous glycogen (glycogenolysis).
• 4.4. Gluconeogenesis from lactate plus pyruvate was inhibited.
• 5.5. The action of piroxicam on oxygen consumption was blocked by antimycin A, but not by atractyloside.
• 6.6. The action of piroxicam in the perfused rat liver metabolism seems to be a consequence of its action on mitochondria.
• 7.7. It can be concluded that inhibition of energy metabolism and stimulation of glycogenolysis are not specific properties of carboxylic nonsteroidal anti-inflammatory drugs.

     

Phosphofructokinase from the anterior byssus retractor muscle of Mytilvs edulis: Modification of the enzyme in anoxia and by endogenous protein kinases

• 1.1. Anoxia exposure resulted in a stable modification of the kinetic properties of 6-phosphofructo-1-kinase (PFK) from the anterior byssus retractor muscle (ABRM) of the sea mussel Mytilus edulis L.
• 2.2. Compared to the aerobic enzyme, the anoxic form of PFK. showed a reduced affinity for both substrates, fructose-6-phosphate (F6P) and ATP, and an increased sensitivity to inhibition by phosphoenolpyruvate.
• 3.3. To analyze the involvement of protein kinases in the modification of PFK, extracts from aerobic or anoxic muscle were incubated with ATP and Mg²⁺ plus protein kinase second messengers cyclic 3',5'-adenosine monophosphate (cAMP), cyclic 3',5'-guanosine monophosphate (cGMP) or Ca²⁺ plus phorbol 12-myristate 13-acetate (PMA).
• 4.4. Both forms of the enzyme responded to the presence of cAMP with a strong increase in affinity for F6P.
• 5.5. In response to cGMP affinity of the aerobic enzyme for F6P decreased whereas that of the anoxic enzyme form was not affected (at 0.5 mM ATP) or increased (at 3 mM ATP).
• 6.6. Incubation with Ca²⁺ + PMA had only a limited effect on PFK kinetics but appeared to enhance the response to cGMP when the three compounds were given together.
• 7.7. Treatment of PFK-aerobic with alkaline phosphatase resulted in a strong decrease in enzyme activity and affinity for F6P; subsequent treatment with cAMP reversed the effect on S_0.5 F6P.
• 8.8. The data indicate that PFK activity is altered during the aerobic-anaerobic transition by a change in the phosphorylation state of the enzyme and that cAMP and cGMP act oppositely to regulate PFK activity, and thereby alter glycolytic rate, during this transition.