The effect of salinity on coelomic fluid osmolyte concentration and intracellular water content in Luidia clathrata (Say) (Echinodermata: Asteroidea)

• 1.1. The concentrations (mM) of osmolytes in the coelomic fluid of Luidia clathrata kept at 25‰S seawater (control individuals) were: 345, Na⁺; 10, K⁺; 10, Ca²⁺; 44, Mg²⁺; 387, Cl⁻; 0.67, amino acids; 0.09, NH₄⁺.
• 2.2. When individuals were transferred from 25‰S to 15‰S or 35‰S, the concentrations of inorganic ions in the coelomic fluid usually equilibrated within 24hr and became the same as those in the medium.
• 3.3. The intracellular water content (g intracellular H₂O/g solute-free dry tissue) of the pyloric caeca and tube feet of control individuals throughout the experiment was 2.13 and 5.40, respectively.
• 4.4. In tissues of individuals transferred to 15‰S, the intracellular water content increased by an average 50% in 12 hr but returned to 19% above control levels during 1 week.
• 5.5. In tissues of individuals transferred to 35‰S, the intracellular water content decreased by an average 17% in 12 hr and did not change during 1 week.
• 6.6. Luidia clathrata is an osmoconformer and partial cell volume regulator within the seasonal salinity range it encounters.

     

The influence of anaerobiosis on the levels of adenosine nucleotides and some glycolytic metabolites in tubifex sp. (annelida,oligochaeta)

• 1.1. In Tubifex sp. the amounts of ATP, ADP and AMP, and of glucose, glucose-1-P, glucose-1-P, glucose-6-P, fructose-6-P and fructose-1, 6-P were measured after experimental anaerobiosis.
• 2.2. The energy charge decreased from 0.84 to 0.07/0.69 within 6–9 hr of anaerobiosis.
• 3.3. During long term anaerobiosis there was no change from 0.70/0.69.
• 4.4. The concentrations of glucose, glucose-6-P and fructose-1,6-P increased somewhat during an initial phase of anaerobiosis.
• 5.5. The data are discussed with respect to the regulation of energy metabolism, especially during the transition of aerobic to anaerobic metabolism.
• 6.6. It is concluded that this transition is accomplished within 6–12 hours.

     

Temperature and salinity tolerance of the mole crab,Emerita talpoida (Say) (Crustacea,Anomura)

• 1.1. Adult Emerita talpoida were subjected to 25 temperature-salinity combinations within the range of 5–35°C and 15–65‰.
• 2.2. E. talpoida tolerated 15–65‰ salinity at 20°C and below.
• 3.3. Optimum salinity for survival at stressful temperatures was 40‰.
• 4.4. Crabs transferred directly from one salinity to another experienced changes in osmoconcentration toward that of the new salinity.
• 5.5. Temperature modified the rate of change toward the experimental salinity. Q values averaged 1.2.

     

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.

     

Anaerobic metabolism in the lugworm Arenicola Marina L.: The transition from aerobic to anaerobic metabolism

After onset of anaerobic conditions Arenicola Marina does not switch immediately to typical anaerobiosis. The adaptation occurs in three steps.

• 1.1. In the first 3 hr the phosphagen stores are mobilized, glycogen is degraded to alanine, aspartate is metabolized to succinate and volatile fatty acids (transition period).
• 2.2. Starting approximately after 3 hr, the route of glycogen degradation at the phosphoenolpyruvate-branchpoint is changed gradually from metabolizing via pyruvate kinase to phosphoenolpyruvate carboxykinase. At the same time the metabolic rate is reduced significantly (switching period).
• 3.3. After more than 12 hr the energy supply occurs exclusively via the known pathways typical for long-term anaerobiosis.

     

Metabolic responses of the mussels Perna viridis and Perna indica to declining oxygen tension at different salinities

• 1.1. Oxygen uptake and ammonia loss were monitored during responses to reductions of both salinity and oxygen tension (PO₂) in the marine mussels Perna viridis and Perna indica from southern India.
• 2.2. The proportional contribution of protein to total catabolic substrates under natural environmental conditions was as much as 96% in P. viridis, relative to only 19% in P. indica.
• 3.3. Normoxic oxygen consumption remained statistically unchanged in P. viridis conditioned to salinities between 32 and 15‰, with no obvious signs of distress. Although equally unaffected at salinities between 32 and 20‰, P. indica showed significantly reduced oxygen uptake following transfer from 32 to 15‰, and had died within the next 7 days.
• 4.4. At salinities greater than 20‰, P. viridis was better able than P. indica to regulate oxygen consumption independent of PO₂.
• 5.5. P. indica showed a compensatory increase in oxyregulatory capacity at 15‰. This exceeded unstressed abilities, helping to maintain albeit reduced oxygen uptake throughout wider ranges of PO₂.
• 6.6. Different responses recorded in each of these tropical and often intertidal species were in accordance with their natural distributions. Nevertheless, the oxyregulatory capacity in both species was higher than in bivalves from temperate and/or subtidally restricted habitats.

     

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.

     

Synthesis of reserved polysaccharide from wax esters accumulated as the result of anaerobic energy generation in Euglena gracilis returned from anaerobic to aerobic conditions

• 1.1. Euglena gracilis SM-ZK (a non-photosynthetic mutant), cultured in Koren-Hutner medium, containing glucose, malate and glutamate as the main nutrients, were incubated anaerobiosis for 24 hr, and then returned to aerobic conditions. Wax esters, which were synthesized from paramylon (the reserved polysaccharide) for ATP generation under anaerobiosis (wax ester fermentation) were promptly degraded immediately after the cells were replenished with sufficient O₂. A large part (about 70%) of the decomposed wax esters were converted back to paramylon.
• 2.2. When cells were fed with [1–14C]acetate or [U-¹⁴C]acetate immediately after transfer from anaerobic to aerobic conditions, radioactivity incorporated into paramylon in the cells fed with [U-¹⁴C]acetate was about 1.5-times as high as that with [1-¹⁴C]acetate, proposing that glyoxylate cycle participates in the conversion from wax esters to paramylon.
• 3.3. Paramylon synthesis from [1-¹⁴C]acetate was considerably activated by anaerobic preincubation of cells for several hours.
• 4.4. Isocitrate lyase and malate synthase occurred in cells cultured in Koren-Hutner medium, but the activities were obviously lower than those in cells grown on ethanol. These enzymes were not induced by the anaerobic preincubation.

     

Modulation of the ATP induced [Ca2+]c increase in as-30D hepatoma cells

• 1.1. The regulation of the increase in the cytosolic calcium concentration ([Ca²⁺]c) induced by extracellular ATP in AS-30D hepatoma cells was studied.
• 2.2. Homologous desensitization involving the refilling of intracellular calcium pools and the participation of protein kinase C was found.
• 3.3. Isoproterenol, forskolin and dibutyril-cyclic AMP also induced an increase in [Ca²⁺]c.
• 4.4. Interestingly, synergism was found for isoproterenol or forskolin and ATP.
• 5.5. The results suggest that there are two pathways for mobilizing [Ca²⁺] in AS-30D hepatoma cells; one is activated by ATP receptors and the other by cyclic AMP.

     

Possible involvement of adenylylation in the modification of a 26 kDa protein in rat parotid acinar cells

• 1.1. Adenylylation, a posttranslational modification of proteins, was investigated in saponin-permeabilized acinar cells of the rat parotid gland.
• 2.2. When cells were incubated with [2,8-³H]ATP, several proteins, including a 26 kDa protein in the particulate fraction, were labeled.
• 3.3. Upon incubation of cells with [α-³²P]ATP in the presence of cAMP and 3-isobutyl-lmethylxanthine, ³²P-labeling of the 26 kDa protein was observed.
• 4.4. After treatment with snake venom phosphodiesterase, [³²P]AMP was released from the 26kDa protein. Such release was not observed when cells were labeled with [γ-³²P]ATP.
• 5.5. The ³²P-labeling pattern of proteins with [α-³²P]ATP was clearly different from that with [adenylate-³²P]NAD⁺.
• 6.6. The results suggest that the 26 kDa protein is one of the adenylylation substrates in rat parotid acinar cells.

     

Amino acid synthesis during hyperosmotic stress in penaeus aztecus postlarvae

• 1.1. Glycine, proline, and taurine are the quantitatively most important amino acid osmolytes in Penaeus aztecus postlarvae.
• 2.2. Taurine dominates the amino acid pool in low salinity, while proline dominates the amino acid pool at higher salinities.
• 3.3. Although not major contributors to the pool, glutamate and alanine are constitutively synthesized from [¹⁴C]glucose and [¹⁴C]glutamate under constant salinity and under hyperosmotic stress treatments.
• 4.4. Proline synthesis from [¹⁴C]-precursors is apparent under constant high (but not low) salinity and is significantly induced by hyperosmotic stress.
• 5.5. No appreciable glycine synthesis was observed from [¹⁴C]glucose or [¹⁴C]glutamate under any experimental conditions.

     

Cooperative atp inhibition and fructose-1,6-biphosphate activation of rat liver pyruvate kinase

• 1.1. For the determination of relationship between FDP and ATP in the rat liver pyruvate kinase regulation, kinelic studies have been carried out at several ATP and FDP concentrations.
• 2.2. The results obtained on FDP activation show a great cooperativity for FDP saturation with a Hill coefficient of h = 2.79.
• 3.3. Kinetic studies on ATP inhibition also show a great cooperativity for ATP saturation (h = 2.84) at high FDP concentrations.
• 4.4. These results may contribute to explain the regulation of rat liver pyruvate kinase accounting for the activity of this enzyme at high FDP concentrations modulated by small changes in ATP concentrations.

     

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.

     

Characterization of NaK ATPase from the gills of the freshwater prawn Macrobrachium rosenbergii (de Man)

• 1.1. The specific activity of Na-K ATPase was determined from the microsomal preparation of gills dissected from adult Macrobrachium rosenbergii.
• 2.2. Maximal ATPase activity was achieved at a substrate concentration of 0.5 mM ATP.
• 3.3. Optimal enzyme activity was obtained at pH of 7.5.
• 4.4. The Arrhenius plot of Na-K ATPase activity revealed a marked discontinuity at 30°C. “Mg” ATPase activity did not exhibit a marked discontinuity.
• 5.5. The E_a for Na-K ATPase and “Mg” ATPase was 14.6 kCal/mole and 9.31 kCal/mole respectively. Q₁₀ values for Na-K ATPase was 2.34 and for “Mg” ATPase 1.65.
• 6.6. ATPase activity and gill homogenate protein concentration exhibited a linear relationship up to 130 μg protein/ml.
• 7.7. Na-K ATPase activity was inhibited by 10⁻³ M ouabain. It was equally inhibited by the removal of K⁺ from the reaction medium.

     

Reabsorption and accumulation of α-amino-iso-butyric acid in the nephridia of Sabella pavonina Sa vigny (Annelida polychaeta)

• 1.l. High amino acid concentrations were found in the anterior coelomic fluid of a Polychaeta (Sabella pavonina Savigny).
• 2.2. The concentrations being much higher in the fluid which penetrates the nephrostomia into the nephridia lumen than in the final urine indicates that the nephridia reabsorbs large amounts of amino acids.
• 3.3. Nephridial perfusion experiments showed that an amino acid analogue (α-amino-iso-butyric acid, AIB) is transported by the nephidia.
• 4.4. The transport took place across the nephridial wall owing to the presence of a carrier-mediated transport system and a diffusion system.
• 5.5. For the carrier-mediated transport, the V_max was 0.234 ± 0.025 nmol·min⁻ and the K_m 3.715 ± 0.315mmol·l⁻.
• 6.6. AIB accumulated in the nephridial cells up to a maximum rate of 01.17 nmol·min⁻.
• 7.7. Intracellular accumulation stopped increasing when the V_max for reabsorption was reached.
• 8.8. These results indicate that the carrier-mediated transport of AIB is located at the apical membrane of the nephridial cell, and that AIB transport by simple diffusion takes place through the paracellular pathway.

     

Phosphorylation in crayfish (Procambarus clarkii) eggs during hatching

• 1.1.|The high-energy phosphorylation metabolism in crayfish, Procambarus clarkii eggs during brooding and juvenile crayfish after hatching was studied by in vivo³¹P nuclear magnetic resonance (³¹P NMR) spectroscopy.
• 2.2.|Inorganic phosphoric acid (Pi) and adenosine-5′-triphosphate ATP(γ-,α-,β-) were detected in the dark brownish red eggs after oviposition.
• 3.3.|In orange unhatched eggs, only sugar phosphate (SP), Pi and resolved phosphometabolite from ATP were observed.
• 4.4.|Peaks of SP, Pi, arginine phosphate (Arg-P), and ATP (γ,α,β) appeared in larvae of crayfish after hatching (nauplius, zoea and juvenile crayfish).
• 5.5.|The high-energy phosphorylation metabolism changed to an anaerobic condition along with a decrease in the concentration of dissolved oxygen in fresh water.

     

Some kinetic properties of pyruvate kinase from Phycomyces blakesleeanus

• 1.1. Pyruvate kinase from mycelium of Phycomyces blakesleeanus NRRL 1555(−) has been partially purified and some kinetic properties has been investigated at pH 7.5.
• 2.2. Positive homotropic interactions were observed with phosphoenolpyruvate and Mg²⁺, showing Hill coefficient values of 2.8 and 2.5, respectively, whereas hyperbolic kinetics are found when ADP was the variable substrate.
• 3.3. Fructose 1,6-bisphosphate acts as a heterotropic allosteric activator, markedly decreasing the S_0.5 value for phosphoenolpyruvate saturation curve from a sigmoidal to a hyperbolic form.
• 4.4. ATP inhibits pyruvate kinase from mycelium of Phycomyces blakesleeanus. ATP appears to be a non-competitive inhibitor with respect PEP and competitive inhibitor with respect ADP.

     

Changes in the EEL intestine during seawater adaptation

• 1.1. Rate of fluid absorption by eel (Anguilla rostrata) intestinal sacs in vitro reached seawater adapted values 3 days after transfer from freshwater to seawater.
• 2.2. After 3 days in seawater oxygen consumption and Na-K-ATPase activity of intestinal mucosa had not increased over freshwater values.
• 3.3. The weight of intestinal mucosa increased 32% during seawater adaptation as a result of an increase in the number of mucosal cells (hyperplasia).
• 4.4. The rate of intestinal fluid absorption was reduced by 10⁻⁴ M ouabain and was not affected by 10⁻⁴ M acetazolamide.

     

Human GMP synthetase

• 1.1. The specific activity of GMP synthetase was measured in several human tissues and found to be highest in cultured skin fibroblasts, followed by bone marrow, leukocytes, erythrocytes. placenta, and liver.
• 2.2. The enzyme from fibroblasts was purified approximately 50-fold by ammonium sulfate fractionation and gel filtration.
• 3.3. The K_m values were determined to be 4.9μM for XMP, 270μM for ATP. and 340 μM for glutamine.
• 4.4. Ammonium sulfate could replace glutamine as the amino donor but was much less efficient.
• 5.5. The enzyme was specific for ATP as the energy source.
• 6.6. Unlike the calf thymus enzyme, the human enzyme has no requirement for a reduced sulfhydryl compound.
• 7.7. Human GMP synthetase is inhibited by ATP, dATP, azaserine, and hydroxylamine.

     

Inhibitors of active Ca2+ uptake by fragments of the sarcoplasmic reticulum of lobster muscle

• 1.1. Vesicles from the sarcoplasmic reticulum of lobster muscle accumulate Ca²⁺ if supplied with ATP as an energy source. A search was undertaken for inhibitors of Ca²⁺ transport.
• 2.2. p-Hydroxymercuribenzoate can completely inhibit Ca²⁺ transport and ATP hydrolysis. 2–4 Dinitrophenol inhibits uptake but not hydrolysis.
• 3.3. Sr²⁺, Ba²⁺ and Zn²⁺ inhibit uptake, perhaps by competing with Ca²⁺ for a carrier.
• 4.4. The vesicles contain acetylcholinesterase. Anticholinesterases can reduce —but not abolish—Ca²⁺ uptake. Acetylcholine has no effect on the activity of the vesicles.
• 5.5. Ca²⁺ uptake is not affected by Mn²⁺, glutamate, pilocarpine, carnosine, caffeine, strophanthidin or tetraethylammonium.
• 6.6. K⁺ is needed for maximal activity of the uptake system but not for ATP hydrolysis. Apparently K⁺ enhances the coupling between the energy supply and the carrier mechanism.