Pressure adaptation of Na+/K+-ATPase in gills of marine teleosts

The effects of hydrostatic pressure on pertussis toxin-catalyzed ribosylation of G proteins from deep-living macrourid fishes

To test the effects of hydrostatic pressure on the coupling of receptors to guanyl nucleotide binding reglatory proteins (G proteins) in transmembrane signaling, pertussis toxin (PTX)-catalyzed [32P]ADP-ribosylation was used to probe the guanyl nucleotide-binding proteins Gi and G(o) in brain membranes from four marine teleosts. These macrourids, Coryphaenoides pectoralis, Coryphaenoides cinereus, Coryphaenoides filifer and Coryphaenoides armatus, span depths from 200 to 5400 m. Pertussis toxin specifically labelled proteins of 39-41 kDa. The PTX-catalyzed [32P]ADP-ribosylation reaction was linear for 7 h. Added guanyl nucleotides (guanosine 5'-diphosphate (GDP) and guanosine 5'-O-(3-thiotriphosphate)(GTP[S])) at concentrations up to 1000 microM did not affect ribosylation at atmospheric pressure. Under basal conditions the Gi/G(o) protein population appears to be uncoupled from receptors and bound with GDP. Pressures up to 476 atm were tested in the absence and presence of added guanyl nucleotides, 100 microM GDP and 100 microM GTP[S]. [32P]ADP-ribosylation in brain membranes from the deeper-occurring C. cinereus, C. filifer and C. armatus was not inhibited by increased pressure in the presence of 100 microM GDP. Increasing pressure decreased ribosylation in brain membranes of C. pectoralis. In the presence of 100 microM GTP[S], increased pressure inhibited ribosylation in all species. Pressure appears to enhance the efficacy of GTP[S] in dissociating the heterotrimeric holoprotein.

Leptocephalus energetics: metabolism and excretion

Leptocephali are the unusual transparent larvae that are typical of eels, bonefish, tarpon and ladyfish. Unlike the larvae of all other fishes, leptocephali may remain in the plankton as larvae for several months before metamorphosing into the juvenile form. During their planktonic phase, leptocephali accumulate energy reserves in the form of glycosaminoglycans, which are then expended to fuel metamorphosis. The leptocephalus developmental strategy is thus fundamentally different from that exhibited in all other fishes in two respects: it is far longer in duration and energy reserves are accumulated. It was anticipated that the unusual character of leptocephalus development would be reflected in the energy budget of the larva. This study describes the allocation of energy to metabolism and excretion, two important elements of the energy budget. Metabolic rates were measured directly in four species of leptocephali, Paraconger caudilimbatus, Ariosoma balearicum, Gymnothorax saxicola and Ophichthus gomesii, using sealed-jar respirometry at sea. Direct measurements of metabolic rates were corroborated by measuring activities of lactate dehydrogenase and citrate synthase, two key enzymes of intermediary metabolism, in addition to that of Na(+)/K(+)-ATPase, a ubiquitous ion pump important in osmotic regulation. Excretion rates were determined by subsampling the sea water used in the respiratory incubations. The entire premetamorphic size range for each species was used in all assays. Mass-specific oxygen consumption rate, excretion rate and all enzyme activities (y) declined precipitously with increasing mass (M) according to the equation y=aM(b), where a is a species-specific constant and −1.74<b<-0.44. In leptocephali, the highly negative slope of the familiar allometric equation describing the relationship between mass-specific metabolic rate and mass, normally between −0.33 and 0, showed that a massive decline in metabolic rate occurs with increasing size. The result suggests that the proportion of actively metabolizing tissue also declines with size, being replaced in large measure by the metabolically inert energy depot, the glycosaminoglycans. Leptocephali can thus grow to a large size with minimal metabolic penalty, which is an unusual and successful developmental strategy.

In vivo effects of deltamethrin on some biochemical parameters of carp (Cyprinus carpio L.)

Thein vivo effects of deltamethrin (DM) on the blood sugar level, the acetylcholinesterase (AChE, EC 3.1.1.7) activities of the blood serum and various organs (heart, liver and intestine), the lactate dehydrogenase (LDH, EC 1.1.2.3), glutamic-oxaloacetic transaminase (GOT, EC 2.6.1.1), and glutamic-pyruvic transaminase (GPT, EC 2.6.1.2) activities of the blood serum, the adenosine triphosphatases (EC 3.6.1.3; Na(+)/K(+)-ATPase and Mg(2+)-ATPase) activities of the erythrocyte plasma membrane and the catalase (EC 1.11.1.6) activity of the liver were examined throughout 96 h in adult carp (Cyprinus carpio L.) Two sublethal concentrations, 1.0 and 1.5 µg/l of deltamethrin, were used. All fish survived the experiment except one, in an aquarium containing 1.5 ppb of DM, which died after 72 h.The AChE specific activity was significantly inhibited in the heart and intestine after 96 h at both concentrations compared to that in the control animals (P<0.05, Student'st-test), while there was no detectable difference between the two treatment. At the same time there was no detectable change in the liver. In the serum, the AChE activity almost remained unchanged; the only significant decrease could be measured after 96 h at 1.5 µg/l deltamethrin concentration. The blood glucose content exhibited interesting changes: after 24 h fish exposed at 1 µg/l DM seemed to be stressed, although this increase was not significant. When these fish became used to the new conditions (in practice this meant the presence of DM), the glucose level decreased, especially after 72 h. At the same time the control animals kept in similar circumstances showed a small insignificant decrease. Meanwhile fish in aquaria containing 1.5 µg/l DM reacted to the treatment with an increased blood glucose level after 48 h, and this did not change until the end of the treatment. The Na(+)/K(+)-ATPase activity decreased in a dose-dependant manner, while Mg(2+)-ATPase was less affected. A small increase in LDH level was observed, indicating damage of different muscle tissues. However, this phenomenon appeared only with the small dosage after 24 h (P<0.05). It has to be mentioned that the individual values varied to a large extent among of the eight fish.The GOT activities of the serum increased during the treatment. However, significant changes were only expressed after 72 and 96 h at 1 µg/l DM concentrations (P<0.01 andP<0.05), and after a similar long treatment at the high dosage (P<0.05, 72 and 96 h). The GPT did not change significantly in aquaria containing 1 µg/l DM. The only larger increase was measured after 96 h at 1.5 µg/l DM concentration (P<0.05). The catalase activity in the liver of treated carp remained practically at the same level compared to that in control fish.All these changes (concerning the primary effects of this compound) demonstrate the effect of DM on different fish enzymes, at low concentrations under laboratory conditions, which might be useful in practice for biomonitoring using fish.

Biochemical ecology of deep-sea animals

Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.