Accumulation et excrétion de substances organiques par les cellules à chlorure de la branchie d'Anguilla anguilla L. adaptée à l'eau de mer

Résumé Les sites branchiaux d'accumulation de certaines substances (bleu de méthylène, urée, paraaminohippurate et inuline) injectées dans la circulation générale ont été localisés sur des anguilles adaptées à l'eau de mer. Le bleu de méthylène est accumulé et excrété par les cellules à chlorure. Les autoradiographies des corps marqués au ¹⁴C: inuline, PAH et urée, faites après cryodessication montrent que les cellules à chlorure accumulent ces substances. La signification de ces résultats est discutée.

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Accumulation and excretion of organic substances by the branchial chloride cells in sea-water adapted eel (anguilla anguilla L.)

Summary The branchial site of accumulation of various organic substances (methylene blue, urea, inulin and paraaminohippurate) following intracardiac injection has been localised in sea-water adapted eels. Methylene blue is concentrated and excreted by chloride cells. By combining freeze-drying and radioautographic technique it was possible to demonstrate that chloride cells concentrate urea, inulin and paraaminohippurate. The signification of these results is discussed in relation with the branchial excretion of organic substances.

     

Sodium and calcium balance in Mozambique tilapia, Oreochromis mossambicus, raised at different salinities

Mozambique tilapia, Oreochromis mossambicus, born and raised in five salinities, viz. (relatively soft) fresh water, 25, 50, 75% and full-strength sea-water, were analyzed for ionoregulatory performance (in particular sodium and calcium handling) and growth. This tilapia regulates its blood serum mineral composition rather effectively; however, in sea-water serum concentrations of sodium, chloride and calcium (in males only) were increased, as was the serum osmolarity. In sea-water, the total body sodium pool was significantly enlarged. With increasing salinity, sodium turnover increased. Serum calcium levels and the total body calcium pool were more strictly controlled than those of sodium. The lowest density of chloride cells in opercular epithelium and the lowest branchial Na+-K+-ATPase activity were observed in 50% sea-water; these values were higher in fish kept in waters of lower or higher salinities. Fish grew more rapidly in brackish water. Fish kept in brackish water appeared to depend on food-related calcium for growth as branchial calcium uptake provides no more than 20% of growth related Ca-accumulation.     

Calcitonin induces hypercalcemia in grey mullet and immature freshwater and sea-water adapted rainbow trout

1. Changes in plasma calcium levels, in response to salmon calcitonin injections, were studied in freshwater and sea-water adapted trout (Salmo gairdnerii) and in grey mullet (Chelon labrosus). 2. Low doses (0.1 ng sCT/100 g body weight) elicited hypercalcemia in the two species studied. 3. High doses (0.5 microgram) provoked hypocalcemia only in freshwater and sea-water adapted trout. 4. An hypercalcemic response appears as the primordial effects of CT injections, higher doses of CT leading to hypocalcemic effects.     

The effects of osmotic experiments and prolactin on the mucous cells in the skin and the ionocytes in the gills of the teleost Cichlasoma biocellatum

Summary Adult Cichlasoma biocellatum were kept in deionized water, 25% sea-water and tap-water. The mucous cells in the epithelium of the gills and the buccal floor were not affected by the osmotic experiments. In animals kept in deionized water the mucous cells in the skin remained unaffected, but the ionocytes (chloride cells) in the gills were strongly stimulated. Keeping the animals in salt water led to a strong regression of the epidermis including the mucous cells, and of the ionocytes. The regression could be counteracted by prolactin injections. The changes in the skin and the ionocytes could be correlated with the activity of the prolactin producing cells in the adenohypophysis. It is suggested that the epidermis and its mucous cells as well as the ionocytes are under prolactin control.The authors gratefully acknowledge the interest and helpful suggestions of Prof. Dr. P. G. W. J. van Oordt. Thanks are also due to Mr. H. van Kooten for making the photographs, to Dr. L. Boomgaart for correcting the english, and to the N. I. H., Bethesda, Maryland (U.S.A.) for presenting the ovine prolactin.     

Metabolic effects in rats drinking increasing concentrations of sea-water

Research on laboratory rats confirmed that drinking sea-water when dehydrated, was not beneficial and caused impaired renal function. When the concentration of sea-water in the drinking water is gradually increased there is a gradual increase in water uptake and corresponding urine excretion. At 50% sea-water the maximum uptake and excretion is reached. Following this there is a decline in appetite, water uptake and urine secretion. When on 100% sea-water, the creatinine clearances were greater than on tap water, while urine/plasma osmolalities (U/P) averaged 7. The only higher U/P was found in animals drinking sea-water when dehydrated, i.e. a U/P of 11. The urea metabolism appears to be suited to either the need to conserve body water, up to 50% sea-water, or to guarantee an adequate urine production, from 50% sea-water to pure sea-water. It is suggested that when a man is stranded at sea it is not advisable to drink all the fresh water and then be compelled to drink sea-water when dehydrated. It is better to slowly increase the sea-water uptake. This will prolong the time before sea-water needs to be drunk and result in only minor metabolic changes. Return to fresh water will be followed by an immediate return to normal homeostasis.     

Heat-induced activation of reducing properties of of sea water

It was shown using the Ellman's reagent that chloride and bicarbonate anions are the heat-induced reducing agents of sea-water, and their combined action is more than additive. Sulfate anions do not exhibit these properties. The influence of sea-water anions on the heat-induced production of hydrogen peroxide was studied by enhanced chemiluminescence in a peroxidase-luminol-p-iodophenol system. In NaCl and NaHCO3 solutions, at concentration and pH values equal to those of sea-water, the production of H2O2 upon heating increased, as compared with water, whereas sulfate anions depressed its formation. By using coumarin-3-carboxylic acid as a fluorescent detector of OH radicals, a substantial increase in the production of radicals in the presence of chloride and bicarbonate anions upon heating was shown. The effect is due to the electron donor properties of these anions, which lead to the decomposition of H2O2 with the formation of OH radicals. The results obtained were considered from the viewpoint of the equivalence of heat and electromagnetic radiation of an absolutely black body. It is supposed that the high-energy quanta of its spectrum lead to the dissociation of anions with the formation of a hydrated electron and radicals. Then a recombination of radicals with the formation of various molecular products takes place.     

Phosphatase activity in the larva of the euryhaline mosquito, Aëdes togoi Theobald,with special reference to sea-water adaptation

The alkaline and acid phosphatases in larvae of the euryhaline mosquito, Aëdes togoi Theobald, were measured and the distribution of alkaline phosphatase was examined histochemically. The optima pH for alkaline and acid phosphatases in the larvae were ≈9.0 and 3.2. respectively. The thorax region showed the highest activity of alkaline phosphatase. The enzyme activity of the thorax of seawater adapted larvae was about twice as high as that of freshwater larvae. When the larvae were transferred from fresh water to sea water, the alkaline phosphatase activity of the thorax increased greatly for 3 days, and thereafter decreased to the normal level of sea-water adapted larvae within seven days. In larvae transferred from sea water to fresh water, the activity of the thorax decreased gradually and after 7 days remained at the level of freshwater adapted larvae. No change in acid phosphatase activity was detected following transfer of the larvae from fresh water to sea water or vice versa. A strong alkaline phosphatase reaction was found only in the luminal border of the gastric caeca in the thorax region. The locality of this enzyme did not vary according to the salinity of environmental water.The activity change of alkaline phosphatase of the gastric caeca is discussed in relation to the absorption of the ingested medium from the gastric caeca.     

Crystal structures of the psychrophilic alpha-amylase from Alteromonas haloplanctis in its native form and complexed with an inhibitor.

Alteromonas haloplanctis is a bacterium that flourishes in Antarctic sea-water and it is considered as an extreme psychrophile. We have determined the crystal structures of the alpha-amylase (AHA) secreted by this bacterium, in its native state to 2.0 angstroms resolution as well as in complex with Tris to 1.85 angstroms resolution. The structure of AHA, which is the first experimentally determined three-dimensional structure of a psychrophilic enzyme, resembles those of other known alpha-amylases of various origins with a surprisingly greatest similarity to mammalian alpha-amylases. AHA contains a chloride ion which activates the hydrolytic cleavage of substrate alpha-1,4-glycosidic bonds. The chloride binding site is situated approximately 5 angstroms from the active site which is characterized by a triad of acid residues (Asp 174, Glu 200, Asp 264). These are all involved in firm binding of the Tris moiety. A reaction mechanism for substrate hydrolysis is proposed on the basis of the Tris inhibitor binding and the chloride activation. A trio of residues (Ser 303, His 337, Glu 19) having a striking spatial resemblance with serine-protease like catalytic triads was found approximately 22 angstroms from the active site. We found that this triad is equally present in other chloride dependent alpha-amylases, and suggest that it could be responsible for autoproteolytic events observed in solution for this cold adapted alpha-amylase.     

Spirulina culture in sea-water

Summary Laboratory experiments using small raceway ponds have shown that Spirulina maxima can be adapted easily to grow in sea-water supplemented with nitrate, phosphate, bicarbonate, and Fe-EDTA. To prevent precipitate formation, phosphate was supplied by diffusion through a dialysis membrane; the amount of Na-bicarbonate added was low (100 ppm) and the pH was kept in the range 8.6–8.8 by bubbling CO₂ into the culture.No significant differences have been noticed in productivity or in the chemical composition of the biomass between cultures in sea-water and in the standard bicarbonate medium. Cultures subjected to light/dark cycles of 12/12 h showed a higher respiration rate in sea-water than in the bicarbonate medium.The higher weight loss in the sea-water medium in the dark was counterbalanced by an increased synthesis of carbohydrates during the light period.     

Models for human porphyrias: Have animals in the wild been overlooked?

Humans accumulate porphyrins in the body mostly during the course of porphyrias, diseases caused by defects in the enzymes of the heme biosynthesis pathway and that produce acute attacks, skin lesions and liver cancer. In contrast, some wild mammals and birds are adapted to accumulate porphyrins without injurious consequences. Here we propose viewing such physiological adaptations as potential solutions to human porphyrias, and suggest certain wild animals as models. Given the enzymatic activity and/or the patterns of porphyrin excretion and accumulation, the fox squirrel, the great bustard and the Eurasian eagle owl may constitute overlooked models for different porphyrias. The Harderian gland of rodents, where large amounts of porphyrins are synthesized, presents an underexplored potential for understanding the carcinogenic/toxic effect of porphyrin accumulation. Investigating how these animals avoid porphyrin pathogenicity may complement the use of laboratory models for porphyrias and provide new insights into the treatment of these disorders.     

Branchial osmoregulatory response to salinity in the gilthead sea bream, Sparus auratus

The branchial osmoregulatory response of gilthead sea bream (Sparus auratus L.) to short-term (2-192 hr) and long-term (2 weeks) exposure to different environmental salinities (5 per thousand, 15 per thousand, 25 per thousand, 38 per thousand and 60 per thousand) was investigated. A "U-shaped" relationship was observed between environmental salinity and gill Na+,K+ -ATPase activity in both long- and short-term exposure to altered salinity, with the increase in activity occurring between 24 and 96 hr after the onset of exposure. Plasma osmolality and plasma ions (sodium, chloride, calcium and potassium) showed a tendency to increase in parallel with salinity. These variables only differed significantly (P<0.05) in fish adapted to 60 per thousand salinity with respect to fish adapted to full-strength sea-water (SW). Plasma glucose remained unchanged whereas plasma lactate was elevated at 5 per thousand and 60 per thousand. Muscle water content (MWC) was significantly lower in fish adapted to 60 per thousand. Chloride cells (CC) were only present on the surface of the gill filaments and absent from the secondary lamellae. CC distribution was not altered by external salinity. However, the number and size of CC were significantly increased at salinity extremes (5 per thousand and 60 per thousand), whereas fish exposed to intermediate salinities (15 per thousand and 25 per thousand) had fewer and smaller cells. Furthermore, the CC of fish exposed to diluted SW became rounder whereas they were more elongated in fish in full-strength and hypersaline SW. This is consistent with previous reports indicating the existence of two CC types in euryhaline fish. At likely environmental salinities, gilthead sea bream show minor changes in plasma variables and the effective regulation of gill Na+,K+ -ATPase. However, at very low salinities both haemodilution and up-regulation of gill Na+,K+ -ATPase predict a poor adaptation most likely related to deficiency or absence of specific components of the CC important for ion xuptake.     

Na transport and enzyme activities in the intestine of the freshwater and sea-water adapted trout (Salmo gairdnerii R.)

Unidirectional fluxes of Na+ obtained in perfused preparation and mucosal enzyme equipment (alkaline phosphatase, ouabain-sensitive Na+, K+-ATPase) have been determined in the middle and posterior intestine of freshwater (FW) and sea-water (SW) adapted trout. In FW, influxes and outfluxes were higher in the middle than in the posterior intestine, although net fluxes were similar. SW adaptation induced an increase of influxes and net fluxes mainly in the posterior intestine. SW adaptation decreased the alkaline phosphatase activity only in the posterior intestine. Na+,K+-ATPase activity was always higher in the middle than in the posterior intestine in FW and SW and increased in both parts by SW adaptation. Thus, it seems that SW adaptation of rainbow trout modifies Na intestinal absorption principally in its posterior part and in relation with the Na+, K+-ATPase activity.     

The effects of starvation and sexual maturation on Na+ transbranchial fluxes following direct transfer from fresh water to sea-water in rainbow trout (Salmo gairdneri)

1. The perfused isolated head technique has been used to measure sodium arterial fluxes following direct transfer from fresh water to sea-water. 2. A starvation-related decrease in net sodium flux is reported. 3. Sexual maturation slackens the decrement of this net flux. 4. In starved fish, the cytological modifications of chloride cells following such a transfer are delayed. 5. This effect of starvation is discussed in terms of lamella sodium imperviousness.     

The action of salt-solutions on the unfertilized and fertilized eggs of Arbacia,and of other animals

Summary The last two experiments show that after 4 1/2 hours in the solutions employed the unfertilized eggs divided excellently when returned to sea-water. The last experiment shows that potassium chloride, 1.5%, gives the same results as the other salts.     

Light optical and electron microscopic changes in striated muscle tissue under the effects of sea water and thymogen in experimental animals]

Effect of sea-water with t degrees +4 degrees to +8 degrees C with time of exposure from 30 minutes to 24 hours on pelvic extremities was studied in 200 rabbits, optical and ultrastructural studies were carried out. It was revealed that effect of sea-water causes damage of striated tissues' structure and death of animals. Prophylactic injections of thymogen stabilized ultrastructure and raised survival, if time of exposure did not exceed 12 hours.     

Sodium balance in adult atlantic salmon (Salmo salar L.) during migration into neutral and acid fresh water

• 1.1. In sea-water, adult salmon (S. salar) exchange an average of 12.6% of total body sodium/hr.
• 2.2. Following transfer to fresh water sodium uptake follows Michaelis-Menton kinetics. F_max = 2.40 mmol Na/1 ECF/hr, K_m = 0.26 mmol Na/1. The uptake system is fully activated immediately following transfer to fresh water.
• 3.3. Post smolts adapted to sea-water for 3 months take up sodium at only one third of the rate of adult fish following return to fresh water.
• 4.4. The concentration of prolactin in the plasma is low in sea-water adapted fish and does not rise during the first 8 hr in fresh water.
• 5.5. At pH 5 sodium uptake is reduced by almost 90%, even in the absence of aluminium, but recovers immediately on return to neutral water.
• 6.6. At pH 5 and 20 μmol Al/1 there is little further effect on sodium uptake but after 6 hr in aluminium the inhibition of sodium uptake continues after return to neutral aluminium fresh water and uptake is only 50% of normal 24 hr later.

     

The Mercury Content and Antioxidant System in Insectivorous Animals (Insectivora,Mammalia) and Rodents (Rodentia,Mammalia) of Various Ecogenesis Conditions

This study is aimed at analyzing the total mercury in the tissues of mammals adapted to a semiaquatic or subterranean lifestyle and at analyzing the possible role of their antioxidant system in heavy metal detoxication. The water shrew Neomis fodiens Pennant, 1771, European mole Talpa europaea Linnaeus, 1758, muskrat Ondatra zibethicus Linnaeus, 1766, and water vole Arvicola terrestris Linnaeus, 1758 were the species under study. Our results indicate that mercury accumulation in the tissue depends on the age, tissue type, and diet of the species. The highest mercury content was recorded in water shrew tissues compared to other species. Age-dependent accumulation of the toxicant in the animals is reported. A correlation between mercury accumulation and catalase activity in the kidneys of the animals studied was found.     

Activity Blockade and GABAA Receptor Blockade Produce Synaptic Scaling through Chloride Accumulation in Embryonic Spinal Motoneurons and Interneurons

Synaptic scaling represents a process whereby the distribution of a cell''s synaptic strengths are altered by a multiplicative scaling factor. Scaling is thought to be a compensatory response that homeostatically controls spiking activity levels in the cell or network. Previously, we observed GABAergic synaptic scaling in embryonic spinal motoneurons following in vivo blockade of either spiking activity or GABA_A receptors (GABA_ARs). We had determined that activity blockade triggered upward GABAergic scaling through chloride accumulation, thus increasing the driving force for these currents. To determine whether chloride accumulation also underlies GABAergic scaling following GABA_AR blockade we have developed a new technique. We expressed a genetically encoded chloride-indicator, Clomeleon, in the embryonic chick spinal cord, which provides a non-invasive fast measure of intracellular chloride. Using this technique we now show that chloride accumulation underlies GABAergic scaling following blockade of either spiking activity or the GABA_AR. The finding that GABA_AR blockade and activity blockade trigger scaling via a common mechanism supports our hypothesis that activity blockade reduces GABA_AR activation, which triggers synaptic scaling. In addition, Clomeleon imaging demonstrated the time course and widespread nature of GABAergic scaling through chloride accumulation, as it was also observed in spinal interneurons. This suggests that homeostatic scaling via chloride accumulation is a common feature in many neuronal classes within the embryonic spinal cord and opens the possibility that this process may occur throughout the nervous system at early stages of development.     

Osmoregulation of the cane toad, Bufo marinus, in salt water

Adult cane toads, B. marinus, survived in salinities up to 40% sea-water (SW). Pre-exposure to 30, then 40% SW, increased the survival time of toads in 50% SW. Plasma from toads acclimated to salt water is hyperosmotic to the environment--a result of increased plasma sodium, chloride and urea concentrations. When toads were placed in tap-water and 20% SW, all significant changes to plasma sodium, chloride, urea and osmotic pressure occurred within the first 2 days of exposure. When toads were placed in 30 and 40% SW environments, the increases in plasma sodium and chloride concentrations occurred within the first 2 days of exposure while urea and total osmotic pressure continued to rise until some time between 2 and 7 days exposure.