The relationship between osmoregulation and nitrogen metabolism in the intertidal prawn,Palaemon elegans (Rathke)

• 1.1. The relationship between nitrogen metabolism and osmoregulation has been studied in the prawn Palaemon elegans (Rathke) following sudden exposure to hyper- and hyposaline conditions.
• 2.2. Animals acclimated to a salinity of 30‰ showed a pronounced increase in the rates of ammonia excretion during the first 2 hr after transfer to lower salinities. These gradually declined during the next 6 hr to rates that were significantly higher than that of control animals (30‰) and were maintained throughout the rest of the experiment.
• 3.3. Rates of ammonia excretion in animals transferred to hypersaline conditions (40‰) fluctuated considerably during the experiment. It was consistently observed, however, that there were two periods during the experiments when ammonia excretion rates had negative values indicating that NH⁺₄ ions were being taken up by the prawns.
• 4.4. Experiments in which small quantities of (NH₄)₂SO₄ containing the stable isotope ¹⁵N were added to the sea-water confirmed that P. elegans was able to take NH⁺₄ ions from the sea-water.
• 5.5. Changes in the Na⁺ ion concentration in the blood and the changes in free amino acid concentration in the blood and in the muscle after exposure to differing salinities were also determined. Their significance and relationship to the observed changes in the rates of ammonia excretion are discussed.

     

Electrolyte changes,cell volume regulation and hormonal influences during acclimation of rainbow trout (Salmo gairdnerii) to salt water

• 1.1. Rainbow trout were acclimated to salt water (1.5, 2.0 or 3.0%, which means 40, 60 or 85% concentrated sea-water) and the electrolyte, glucose and cortisol concentrations of the plasma as well as the extra- and intracellular muscle space, the muscle electrolyte concentrations and the ATPase activity were analysed.
• 2.2. Plasma osmolality, Na⁺, Ca²⁺ and Mg²⁺ concentrations of the plasma had a maximum at 24 hr after the start of acclimation when acclimated to 3.0% salt water. Plasma osmolality, Na⁺ and Mg²⁺ concentrations were significantly higher during the whole acclimation time when exposed to 3.0% salt water.
• 3.3. Variations and regulations of ECS and ICS were clearly demonstrated. The intracellular electrolyte concentrations were also maximal at 24 hr.
• 4.4. The plasma glucose level was just slightly elevated, but the cortisol level clearly indicated a stress response at 24 hr.
• 5.5. The activity of gill Na-K-ATPase increased during the acclimation time.
• 6.6. The regulatory processes in trout during acclimation to salt water are compared with those occurring in tilapia and carp.

     

In vivo responses in plasma osmolality,and intracellular water and solute concentrations in flounder (Platichthys flesus) heart ventricles under acclimation to fresh and sea water

• 1.1. Flounders transferred abruptly from sea to fresh water displayed a gradual decrease in plasma osmolality for 5–6 days (10–15 mOsm daily). When returned to sea water the osmolality increased to the original level within 1 day.
• 2.2. Heart ventricle cell water content remained unchanged during the acclimations, except for a temporary 1.4% reduction within the first 4 hr of sea water acclimation.
• 3.3. During acclimation to sea water intracellular K⁺ increased rapidly in parallel with plasma osmolality. During fresh water acclimation, however, cellular K⁺ decreased rapidly in the first day only, whereas plasma osmolality decreased further.
• 4.4. Cellular taurine remained unchanged during the initial 4 days of fresh water acclimation and then declined 32% within the next 3 days. Upon retransfer to sea water, cellular taurine increased gradually to its original level in the course of 7 days.

     

Genetic variation at the Lap locus and ammonia excretion following salinity transfer in an estuarine snail

• 1.1. Thais haemastoma were transferred from 30 to 15‰ and 15 to 30‰ S and ammonia excretion was measured for 72 hr.
• 2.2. Increased ammonia excretion following transfer from high to low salinity was significantly greater in snails with the rare Lap allele, Lap⁹⁴.
• 3.3. Increased rates of nitrogen loss induced by salinity reductions could be responsible for maintaining the Lap⁹⁴ allele at low frequency in estuarine populations of T. haemastoma.

     

Osmoregulatory responses to abrupt salinity changes in the euryhaline gilthead sea bream (Sparus aurata L.)

• 1.1. Gilthead sea breams (Sparus aurata L.) adapted to sea water (SW, 39‰ salinity) and brackish water (BW, 7‰) were submitted to abrupt osmotic stress by transferring the specimens to 7‰ and 39‰, respectively.
• 2.2. Plasma osmolality, Na,⁺ Cl, ⁻ K, ⁺ Ca, ²⁺ cortisol and glucose were measured before and after the transfers.
• 3.3. The transfer from SW to BW led to transitory hypomineralization and hyperglycemia. In long-term adapted fish cortisol level increased, and osmolality slightly decreased.
• 4.4. Conversely, the transfer from BW to SW provoked transitory hypermineralization. In adapted fish, cortisol levels strongly decreased, and osmolality slightly increased.

     

Protein digestion and ion concentrations in rainbow trout (Salmo gairdnerii Rich.) digestive tract in sea- and fresh water

• 1.1. Rainbow trout maintained in fresh water or Actapted to sea-water for 24 hr were fed casein-based dry diet. After feeding, fish were kept in fresh water (FW) or transferred to artificial sea-water (SW) and sacrificed after 10 or 20 hr.
• 2.2. The digestive tract was separated into five parts: stomach, pyloric caeca region, middle intestine and two equal lengths of rectum.
• 3.3. The content of these parts was analysed for ions Na⁺, K⁺, Cl⁻, Mg²⁺ and for free, peptide and total amino acids.
• 4.4. In the fish stomach all ions, with the exception of Ca²⁺, indicate drinking of sea-water. In the pyloric caeca region Na⁺ appears to be efficiently absorbed in SW fish but influxed in FW fish. In the rectum of SW fish K⁺ appears to be reabsorbed but Na⁺ concentrated in faeces.
• 5.5. Free amino acid concentrations were always higher in gut lumen of SW than in FW fish in respect to time after feeding and portion of intestinal content. Free amino acids constitute at most 7.4–8.7% of total amino acids in the content of pyloric caeca region.
• 6.6. Peptide amino acids, being mostly di-, tri- and tetra-peptides, increased in stomach content from 14.7 to 28.4% of the total, from 6 to 10 hr after a meal in SW fish. Peptide amino acids constituted 80.3–89.0% of total amino acids in intestinal content of the pyloric caeca region. These peptide portions decreased in the mid-intestine (47.5–52.5%) and increased again in the rectum (73.6–76.0%).
• 7.7. It was concluded that in rainbow trout fed in both sea- or fresh water, ion concentrations do not seem to interfere with protein digestion and nutrient absorption in alimentary tract.

     

Blood volume recovery in hemorrhaged japanese quail

• 1.1. Blood volume and plasma biochemical changes and feed and water consumption in response to a hemorrhage by phlebotomy of 30% of the calculated total blood volume with and without replacement of blood volume with physiological saline were determined in juvenile male Coturnix coturnix japonica.
• 2.2. Plasma protein and osmolality decreased rapidly posthemorrhage and did not recover by 72 hr posthemorrhage.
• 3.3. Plasma glucose, Na⁺ and K⁺ increased within Ihr postphlebotomy. Plasma Na⁺ returned to nonphlebotomized levels within 6 hr postphlebotomy.
• 4.4. Saline replacement of blood volume resulted in hypervolemia within 3–5 min postphlebotomy.
• 5.5. Phlebotomized quail receiving no saline recovered blood volume to 0 hr (nonphlebotomized) levels within l hr postphlebotomy.

     

Na+ regulation and (Na++ K+)ATPase activity in the euryhaline fiddler crab Uca minax (Le conte)

• 1.1. Specific activity and kinetic characteristics of the (Na⁺ + K⁺)ATPase have been investigated in the gill epithelium of the hyper-hypoosmoregulator crab Uca minax.
• 2.2. (Na⁺ +K⁺)ATPase activity is shown to be at least three times higher in the posterior gills.
• 3.3. The kinetic study supports the hypothesis of the existence of two different (Na⁺ + K⁺)ATPases: the enzyme activity in the posterior gills could be involved in the transepithelial transport of Na⁺ while the activity of the anterior gills could be responsible for the intracellular regulation of Na⁺ and K⁺.
• 4.4. Significant and specific changes in (Na⁺ +K⁺)ATPase activity occur upon acclimation to media of various salinities.

     

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.

     

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.

     

Sodium and potassium balance of captive meadow voles (Microtus pennsylvanicus) fed laboratory chow and vegetation diets

• 1.1. Mineral balance was studied in meadow voles (Microtus pennsylvanicus) maintained in the laboratory.
• 2.2. Urine and fecal Na⁺ contents of voles on low-Na⁺ diets were comparable to those reported for other herbivore species, but urine and fecal K levels were higher.
• 3.3. Voles approached Na⁺ balance (input = output) on diets with Na⁺ content as low as 56 ppm.
• 4.4. There was not a clearcut hypertrophy of the adrenal-gland zona glomerulosa in voles maintained on low-Na⁺ diets.
• 5.5. Plasma K content and bone water content were higher in voles maintained on high-Na ⁺ vegetation diets, suggesting expansion of extracellular fluid volume.

     

Purine metabolism in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) Seedlings

• 1.1. The metabolism of purine bases and nucleosides in cotyledons and embryonic axes of black gram (Phaseolus mungo L.) was studied.
• 2.2. A large portion of absorbed [8-¹⁴C]adenine, [8-¹⁴C]guanine and [8-¹⁴C]adenosine was salvaged in nucleotide and nucleic acid synthesis.
• 3.3. Most of the radioactivity of [8-¹⁴C]hypoxanthine and [8-¹⁴C]inosine was incorporated into allantoin and allantoic acid.
• 4.4. Activity of adenine phosphoribosyltransferase in enzyme extracts was much higher than that of hypoxanthme and guanine phosphoribosyltransferase(s).
• 5.5. Apparent activity of adenosine kinase was higher than that of inosine kinase. 6. NAD⁺-dependent xan thine dehydrogenase was detected in both cotyledons and embryonic axes of the seedlings.
• 6.7. The capacity of purine salvage was higher m 24 hr old cotyledons than 24 and 48 hr old embryonic axes. The reverse was observed concerning that of purine degradation.

     

Behaviour and haemolymphatic ionic composition of the intertidal crab Chasmagnathus granulata dana, 1851 (Crustacea: Decapoda) during emersion

• 1.1. Behavioural observations and haemolymphatic measurements of Na⁺ K⁺ and Ca⁺ were performed in Chasmagnalhus granulata during emersion.
• 2.2. Activity levels were found to be higher during voluntary emersion periods than when the animals were submerged. A lt₅₀ of 39.45 hr was observed when no access to water was allowed.
• 3.3. The Na⁺ and K⁺ and Ca⁺ levels increased during aerial exposure. The Na⁺ and K⁺ levels were restored prior the end of the experimental period. Mechanisms for such regulation are therefore discussed. The Ca²⁺ levels, remaining high during emersion, are probably a result of acid-base balance adjustments.

     

Serum ions concentration and atpase activity in gills,kidney and oesophagus of european sea bass (Dicentrarchus labrax,pisces, perciformes) during acclimation trials to fresh water

• 1.1. Kidney, oesophagus and gill Na⁺-K⁺ ATPase activity and serum Na⁺, K⁺ and Cl⁻ concentrations are evaluated in European sea bass during experimental acclimation to fresh water.
• 2.2. Kidney and oesophagus ATPase increase in low salinity and reach a maximum in fresh water.
• 3.3. Gill ATPase decreases during the acclimation trials and rises again to normal values after a 3-week stay in fresh water.
• 4.4. Na⁺ and K⁺ serum concentrations decrease during the trials and increase back after a 3-week stay in fresh water.
• 5.5. The correlations between enzymatic activities, serum ion concentrations, morphological changes and environmental salinity are discussed.

     

Na+-K+ ATPase and carbonic anhydrase activities in larvae,postlarvae and adults of the shrimp Penaeus japonicus (Decapoda,Penaeidea)

• 1.1. Activities of Na⁺-K⁺ ATPase and carbonic anhydrase were measured through the early post-embryonic development of Penaeusjaponicus. In adults, only the Na⁺-K⁺ ATPase activity was measured.
• 2.2. ATPase activity was variable in the successive development stages. From zero in nauplii, the activity slightly increased in zoeae, and rose sharply in mysis stages 2 and 3.
• 3.3. A further significant increase in activity was noted at the transition from late mysis to early postlarvae, concomitant with a change from the larval osmoconforming pattern of osmoregulation to the postlarval and adult hyper-hyporegulating pattern.
• 4.4. The activity of Na⁺-K⁺ ATPase, measured in isolated cephalothorax, increased from PL3 to PL4 to its maximum value in PL5; at this stage, osmoregulatory capacity was fully efficient.
• 5.5. In young stages of P. japonicus, the variations in Na⁺-K⁺ ATPase activity appear correlated with the development of osmoregulatory ultrastructures, and with osmoregulation and salinity tolerance.
• 6.6. These results are discussed with regard to their ecological and physiological implications.
• 7.7. In adults, the activity of Na⁺-K⁺ ATPase was high in gills and epipodites and no activity was detected in branchiostegites. These results are related to the ultrastructure of these organs.
• 8.8. The activity of carbonic anhydrase did not change significantly in larval and postlarval stages.
• 9.9. From these results, it is proposed that the effector sites of osmoregulation are located in branchiostegites, pleurae and epipodites in postlarvae, and in epipodites and mainly in gills in adults.

     

Acute toxicity and bioaccumulation of endosulfan in rotifer (Brachionus calyciflorus)

• 1.1. The acute toxicity of endosulfan was determined for the freshwater rotifer Brachionus calyciflorus.
• 2.2. The mean 24 hr lc₅₀ value for endosulfan was 5.15 ppm with a coefficient of variation of 14.7%.
• 3.3. Rotifers were exposed at two sublethal concentrations (1.5–2.0 ppm) of endosulfan for bioaccumulation experiments, for an exposure time of 24, 48, 72 and 96 hr. The rotifers were fed with Nannochloris oculata (5 × 10⁵cell/ml).
• 4.4. The highest accumulation of endosulfan was found 24 hr after the start of the exposure to 1.5 ppm of the toxicant. A steady-state concentration in rotifer was reached between 24–48 hr, followed by a gradual decrease until 96 hr.

     

The isolation of skeletal muscle plasma membranes from rainbow trout (Salmo gairdneri)

• 1.1. Plasma membranes were isolated from caudal flank skeletal musculature of rainbow trout by discontinuous sucrose gradient centrifugation.
• 2.2. Na⁺−K⁺-ATPase was enriched 8-fold and 5′-nucleotidase activities 4-fold in a fraction isolated at the 8–25% sucrose interface.
• 3.3. A cholesterol: phospholipid ratio of 0.37 in the plasma membrane fraction was 85% greater than that observed in adjacent subcellular fractions.
• 4.4. Electron microscopy provided morphological confirmation of enrichment and integrity of skeletal muscle plasma membranes at the 8–25% sucrose interface.

     

Sodium transport in red blood cells of lamprey LAmpetra fluviatilis

• 1.1. Unidirectional Na⁺ influx in lamprey red blood cells was determined using ²²Na as a tracer.
• 2.2. Total Na⁺ uptake and amiloride-inhibitable Na⁺ influx increased in a saturable fashion as a function of external Na⁺ concentration (Na_e).
• 3.3. At 141 mM Na_e, the average value of net Na⁺ influx was 13 ± 1.1 and the amiloride-sensitive Na⁺ influx was 5.3±1.1 mmol/l cells per hr (±SE).
• 4.4. The amiloride-sensitive component of Na⁺ influx was significantly activated by 10⁻⁵ M isoproterenol, by 2 × 10⁻⁵ M DNP, and by cell shrinkage.
• 5.5. Furosemide (1 mM) had no effect on the Na⁺ transport in red cells.
• 6.6. The residual amiloride-insensitive component of Na⁺ transport was a linear function of Na_e in the range of 5–141 mM. This transport seems to be accounted for by simple diffusion.

     

Effects of Na+ and/or K+ on the Mg2+-dependent ATPase activities in shrimp (Macrobrachium amazonicum) gill homogenates

• 1.1. Homogenates of gills from the freshwater shrimp M. amazonicum exhibit the following ATPase activities: (i) a basal, Mg²⁺-dependent ATPase; (ii) an ouabain-sensitive, Na⁺ + K⁺-stimulated ATPase; (iii) an ouabain-insensitive, Na⁺-stimulated ATPase; and (iv) an ouabain-insensitive, K⁺-stimulated ATPase.
• 2.2. K⁺ suppresses the Na⁺-stimulated ATPase activity in a mixed-type kind of inhibition, whereas Na⁺ does not exert any noticeable effect on the K⁺-stimulated ATPase activity.
• 3.3. The Na⁺- and the K⁺-stimulated ATPase activities are totally inhibited by 5 mM ethacrynic acid in the incubation medium.
• 4.4. The Na⁺- and the K⁺-stimulated ATPase activities are not expressions of the activation of a Ca-ATPase.
• 5.5. The possible localization and roles of the described ATPases within the gill epithelium are briefly discussed and evaluated.

     

Tetanus responses under rapid bath solution change: Electrotonic depolarization of transverse tubules may release Ca2+ from sarcoplasmic reticulum of Rana japonica skeletal muscle

• 1.1. Single skeletal muscle fibers were transferred from a normal Ringer solution to Na⁺ ion free solution, and vice versa, and tetanus responses were recorded immediately after the transfer.
• 2.2. Fractional tetanus tension recorded immediately after the displacement from the Na⁺ ion free solution to normal Ringer solution was dependent on fiber diameter.
• 3.3. Diffusion of Na⁺ ions along the transverse tubules was simulated [apparent diffusion constant was 3.11 × 10⁻⁶ (cm²/s)].
• 4.4. Our results suggest that the electrotonic spreading of membrane potential, caused by an action potential in the transverse tubules, could release Ca²⁺ ions from sarcoplasmic reticulum.