[Apropos of a text of Antoine Laurent de Lavoisier].
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Animal Population Groups↗
Biomedical subjects
P Dejours
Publications and source records attributed to P Dejours.
Acid-base balance in plasmatic, pericardial and peritoneal fluids in 2 species of amphibians.
The carbonic acid-base balance and the concentrations of Na and Cl were studied in 3 fluids, plasmatic, pericardial and peritoneal, sampled from 2 species of amphibians: Pleurodeles waltl and Xenopus laevis. In Pleurodeles the pericardial and peritoneal fluids are in a state of marked metabolic alkalosis, the carbonate alkalinity being up to 10 times higher in the serosal fluids than in the plasma, whereas PCO2's are very close in the 3 fluids. The Cl concentration is markedly lower in the serosal fluids than in the plasma. In Xenopus, the metabolic alkalosis of the serosal fluids also exists, but to a much lower extent than in Pleurodeles. These observations lead to further researches in the field of morphometry, physicochemistry and physiology.
Acid-Base Equilibrium↗
The effects of barometric pressure according to Paul Bert: the question today.
The scientific activity of Paul Bert was very diverse, but his main achievements concern the effects of barometric pressure upon life. The fundamental physiological effect of decreasing barometric pressure is due to the concomitant fall of the O2 partial pressure. The effects of lowering or raising the barometric pressure can be countered by increasing or decreasing the O2 fraction in the air. Extreme hyperoxia modifies cellular metabolism of all living beings: this is O2 poisoning, the Paul Bert effect. Rapid decompressions from several atmospheres, or even from sea level to high altitude, can entail the formation of bubbles of N2 dissolved under the high pressure in the tissues and blood. Decompression accidents may be prevented by decompressing slowly. Immediate recompression is the only way to overcome decompression accidents, as the N2 is forced back into solution. These main discoveries were not universally accepted before about 1915. However, since Paul Bert's time, some additional effects of changes of the barometric pressure, for example related to the variation of gas diffusivity and density, have been pointed out. It is also clear that some factors other than low barometric pressure, for instance radiation, temperature, humidity etc. may play important roles in the mechanism of mountain sickness. However, it remains that the main factor is hypoxia, since oxygen inhalation or recompression lead to a quick recovery.
Atmospheric Pressure↗
[Study in the anuran amphibian Xenopus laevis, some blood characteristics and nitrogen excretion based on changes in the water osmolarity].
The pH, the osmolality and the urea and ammonia concentrations in blood, as well as the net urea and ammonia excretions, were studied in the amphibian Xenopus laevis exposed for several weeks to increased osmotic pressure (OP) of the ambient water, as a result of the addition of either NaCl or mannitol to the water. The pH and the ammonia concentration of the blood were independent of the variations of the ambient osmolarity. On the contrary, the blood osmolality and its urea concentration increased markedly when the ambient OP was augmented. The increase of ambient OP by NaCl addition to the medium augmented the urea net excretion and slightly decreased the ammonia excretion. When the increase of ambient OP resulted from the addition of mannitol in the water, excretions of urea and ammonia became negligible.
Ammonia↗
[Excretion of urea and ammonia and its effect on the acid-base balance of water in the habitat of the anuran amphibian Xenopus laevis. Action of metabolic alkalosis].
We studied in Xenopus laevis the effect of changing the salinity and the acid-base status of the ambient water on the total nitrogen catabolism and the nature of the nitrogen end products, urea and ammonia. Increase of the ambient osmolarity by addition of NaCl led to a rise in protein catabolism and to a predominant ureotelism which can approach 95% of the excreted nitrogen. The osmolarity can reach 500 mosmol. L-1 without obvious harmful effects. NaCl can then be replaced by NaHCO3 without injury to the animal as long as water alkalosis is avoided by an appropriate increase of the ambient CO2 tension, PCO2. However, if PCO2 is kept low, the resulting water metabolic alkalosis causes death within a few hours.
Acid-Base Equilibrium↗
[Life and environment: from aquatic animals to terrestrial animals and to man].
Whether animals are vertebrates or invertebrates, the problems raised by the invasion of land are common to all who have succeeded--terrestrial worms, mollusks and crustaceans, arachnids, insects, terrestrial vertebrates. Many physiological traits, although supported by quite different morphological structures, are convergent and related to the environmental characteristics. Thus one is led to put terrestrial animals and aquatic animals belonging to very distantly related phyla, and then suggest an ecophysiological transphyletic division of the animal kingdom.
Animal Population Groups↗
[The spleen is more than a reservoir].
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Animals↗
[Do the variations in water carbon dioxide pressure and PH have an effect on the nature of end products of protein catabolism, ammonia and urea, in the clawed frog Xenopus laevis?].
The effects of PCO2 and pH changes in the ambient water on the nitrogen catabolism and the proportions of the excreted nitrogenous end products, ammonia and urea, were studied in the clawed frog, Xenopus laevis, at 24 degrees C. In animals living in artificial fresh water, the exposure to a hypocapnic alkalosis (PCO2 = 0.7 Torr instead of 10 Torr) did not entail any change in the nitrogen catabolism. In animals who lived in a water loaded with NaCl and had therefore a higher oxygen consumption, an intense nitrogen catabolism and a marked ureotelism, the hypocapnic alkalosis seems to have increased the intensity of the nitrogen catabolism. In neither group were there signs of ammonia toxicity.
Ammonia↗
Oxygen-sensitive chemoreceptors in the branchio-cardiac veins of the crayfish, Astacus leptodactylus.
Oxygen-sensitive activity was recorded from the branchial nerve of the crayfish Astacus leptodactylus in vitro. After the podobranchial and arthrobranchial nerves branch off to the gill, the branchial nerve terminates in the branchio-cardiac vein wall and its surroundings. When the former 2 branches were cut, irregular spontaneous activity could be recorded from a few fiber preparations innervating the branchio-cardiac vein. The branchio-cardiac vein was superfused or perfused with hypoxic or hyperoxic Ringer solution. Impulse frequency increased in response to hypoxia and decreased in hyperoxia. NaCN and almitrine strongly stimulated nerve activity. Baroreceptor activity was also observed. These response characteristics demonstrate that these receptors are Heymans-type chemoreceptors.
Animals↗
From comparative physiology of respiration to several problems of environmental adaptations and to evolution.
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Air↗
Oxygen consumption of the chick embryo's respiratory organ, the chorioallantoic membrane.
A new technique based on stopping the chick embryo's blood circulation in the intact egg was used to measure in situ the chorioallantoic (CA) oxygen consumption, MCAO2, from incubation day 12 to 20. Total egg MO2, MTOTO2, and wet and dry masses of embryo and CA were also measured daily. Embryo MO2, MEMBO2, was calculated. Mean MCAO2 decreased from 71 mumol X h-1 (17% of MTOTO2, 24% of MEMBO2) at 12 days to 62 mumol X h-1 (5% of MTOTO2) at 20 days. Dry mass of CA did not change significantly. Water remained at a high level in CA (88-94%), but embryo water decreased from 93% to 82% between days 12 and 20. The fairly high level of MCAO2, more marked at young stages, calls for corrections in respiratory and circulatory embryonic variables derived from MTOTO2, such as CA blood flow, CA diffusive capacity for O2, and CA arterio-venous shunt. Mass specific values and intra-specific allometric relations in bird embryos should be recalculated on the basis of MEMBO2 instead of MTOTO2.
Allantois↗
Ventilatory regulation of extracellular pH in crayfish exposed to changes in water titration alkalinity and NaCl concentration.
The mechanisms of extracellular pH regulation were studied in normoxic crayfish Astacus leptodactylus during changes in water ionic composition at 13 degrees C. In artificial waters all ambient physico-chemical properties were controlled. Ventilatory changes and the time course of hemolymph acid-base balance, ABB, were followed after a decrease of water titration alkalinity, TAw, from 4 to 2 meq X L-1 simultaneously associated with either an increase of NaCl concentration, [NaCl]w, from 0.5 to 5 mmol X L-1, or a decrease of [NaCl]w, from 0.5 to 0.15 mmol X L-1. The ABB changes were characterized by a hypercapnic acidosis attributable to the decrease of TAw. Depending on the simultaneous change of [NaCl]w, two different mechanisms of compensation were observed. When [NaCl]w increased, the compensation was metabolic: the ventilatory requirement, VW X MO2-1, did not vary. When [NaCl]w decreased, the compensation was ventilatory: VW X MO2-1 doubled. It is concluded that in water-breathers ventilation, contrary to what is generally accepted, can play a role in extracellular ABB regulation.
Acid-Base Equilibrium↗
Activity of vagal afferent fibers innervating CO2-sensitive receptors in the tortoise, Testudo hermanni.
Experiments were done on the tortoise, Testudo hermanni (anesthetized), or on its lung-vagus preparation in which all other internal organs had been removed. By recording the afferent impulse patterns in fine strands of the vagus, three kinds of CO2-sensitive receptors were demonstrated. Heymans-type chemoreceptors: Afferents originating from thoracic arterial chemoreceptors fired randomly at amplitudes below 100 microV. Firing frequency increased when the animal was ventilated with CO2-enriched, nitrogen or hypoxic mixtures, or was given NaCN. Intrapulmonary CO2 receptors (IPC). In an artificially ventilated tortoise and in lung-vagus preparations where the lung CO2-fraction (FCO2) was below 2.5%, single units with a spike amplitude above 200 microV fired regularly. When CO2-enriched air was inspired, impulse frequency decreased markedly, and when the lung was washed with air, it returned to the control frequency following the initial excitation. In lung-vagus preparations the impulse frequency did not change with lung inflation, was null for FCO2 greater than 2.5-3.5%, and was inversely proportional to lower FCO2's. Intrapulmonary CO2-sensitive mechanoreceptors: In anesthetized artificially ventilated tortoises, impulse bursts synchronized with inspiration decreased when the animal inspired 5 or 10% CO2 in air. In lung-vagus preparations, slowly adapting mechanoreceptor responses provoked by lung inflation were reduced when the lung was inflated with CO2-enriched air.
Afferent Pathways↗
Blood oxygen consumption and erythrocyte types in embryonic and postnatal chicken.
In an extension of previous work showing that oxygen consumption (MO2) of chick blood cells declines from 5 to 14-15 days incubation age, declines more steeply to hatching, rises abruptly up to 4-6 posthatch days, and declines thereafter, we investigated the succession of embryonic and posthatch erythrocytic types by performing differential erythrocyte (RBC) counts. MO2 of RBC groups separated by density gradients and fractionation into younger and older RBC populations were measured in 1- to 22-day-old posthatch chicks. The embryonic MO2 decline can be attributed to the appearance of erythrocytic types with successively lower metabolism. The MO2 slope change at 14-15 days incubation coincides with the predominance of definitive erythrocytes with oval nuclei over other cell types. The posthatch MO2 rise is due to a temporary invasion of immature RBC, especially postnatal polychromatic erythroblasts. MO2 then decreases as these cells mature.
Animals↗
The effect of ambient chloride concentration changes on branchial chloride-bicarbonate exchanges and hemolymph acid-base balance of crayfish.
In crayfish Astacus leptodactylus maintained in 13 degrees C ambient water of constant oxygenation and acid-base balance, water chloride concentration was varied while the concentration of other ions, except sulfate, were maintained at constant values. The effects of wide variations of the ambient Cl- concentration, CCl, on the branchial titration alkalinity, delta TA, on delta CCl, delta CCO2, delta CO2 between inspired and expired water, and on the prebranchial hemolymph CCl and pH were studied. The branchial changes of TA, CCl and CCO2 were dependent on the ambient CCl, and a decrease of CCl led to a fall of CO2 excretion. Hemolymph acid-base balance closely depended on ambient CCl, particularly when CCl was less than 1 meq . L-1; when ambient CCl fell from 1 meq . L-1 to 0.1 meq . L -1, pH increased from 7.87 to 8.30. Since hemolymph PCO2 was not affected by the variations of CCl, the changes of pH are mainly explained by the concomitant changes of the hemolymph HCO3- and CO32- concentrations. During an 18-day exposure of crayfish to dechlorinated water, hemolymph CCl decreased progressively whereas its pH increased. The extreme values for CCl were 193 meq . L-1 at day 1 and 96 meq . L -1 at day 18, and the corresponding pH extremes were 7.87 and 8.65. Since the observed modifications of the branchial exchanges and the hemolymph acid-base balance were not related to the small changes of ambient osmolarity or of the SO42- or Na+ concentrations, it is inferred that they depended on a modified Cl-/HCO3- exchange mechanism in the gills.
Acid-Base Equilibrium↗
Cutaneous O2 and CO2 exchanges in the dogfish, Scyliorhinus canicula.
Total and cutaneous O2 and CO2 exchanges were studied in the unanesthetized, spinalectomized dogfish, Scyliorhinus canicula. Total oxygen uptake and carbon dioxide output were measured with an open flow respirometer. Cutaneous fluxes of O2 and CO2 were determined on the tail, confined in the posterior compartment of a two-chambered respirometer, in normoxic conditions but under three different values of the transcutaneous Pco2 difference. Oxygen consumption and CO2 production were measured on excised skin patches confined in known volumes of normoxic, normocapnic sea water. The cutaneous CO2 flux varied almost linearly with the transcutaneous Pco2 difference. In dogfish kept in normoxic, normocapnic sea water, extrabranchial exchanges of O2 and CO2 across the body surface amounted to less than 5% (O2) and 4% (CO2) of the total exchanges, and practically represented the intrinsic O2 consumption and CO2 production of the skin itself. Consequently, the net transcutaneous fluxes of O2 and CO2 can be considered as negligible in the normoxic, normocapnic dogfish. Transcutaneous CO2 losses do not explain low values of Paco2 and gill exchange ratios previously observed in hyperoxic dogfish.
Animals↗
The compressibility and the capacitance coefficient of helium-oxygen atmospheres.
The capacitance coefficient beta of an ideal gas mixture depends only on its temperature T, and its value is derived from the ideal gas law (i.e., beta = 1/RT, R being the ideal gas constant). But real gases behave as ideal gases only at low pressures, and this would not be the case in deep diving. High pressures of helium-oxygen are used in human and animal experimental dives (up to 7 or 12 MPa or more, respectively). At such pressures deviations from the ideal gas law cannot be neglected in hyperbaric atmospheres with respect to current accuracy of measuring instruments. As shown both theoretically and experimentally by this study, the non-ideal nature of helium-oxygen has a significant effect on the capacitance coefficient of hyperbaric atmospheres. The theoretical study is based on interaction energy in either homogeneous (He-He and O2-O2) or heterogeneous (He-O2) molecular pairs, and on the virial equation of state for gas mixtures. The experimental study is based on weight determination of samples of known volume of binary helium-oxygen mixtures, which are prepared in well-controlled pressure and temperature conditions. Our experimental results are in good agreement with theoretical predictions. 1) The helium compressibility factor ZHe increases linearly with pressure [ZHe = 1 + 0.0045 P (in MPa) at 30 degrees C]; and 2) in same temperature and pressure conditions (T = 303 K and P = 0.1 to 15 MPa), the same value for Z is valid for a helium-oxygen binary mixture and for pure helium. As derived from the equation of state of real gases, the capacitance coefficient is inversely related to Z (beta = 1/ZRT); therefore, for helium-oxygen mixtures, this coefficient would decrease with increasing pressure. A table is given for theoretical values of helium-oxygen capacitance coefficient, at pressures ranging from 0.1 to 15.0 MPa and at temperatures ranging from 25 degrees C to 37 degrees C.
Atmospheric Pressure↗
Hemolymph acid-base balance of the crayfish Astacus leptodactylus as a function of the oxygenation and the acid-base balance of the ambient water.
The acid-base balance of the prebranchial hemolymph of the crayfish Astacus leptodactylus was studied at various acid-base balances and levels of oxygenation of the ambient water at 13 degrees C. The water acid-base balance was controlled automatically by a pH-CO2-stat. Into water of constant titration alkalinity, TA, this device intermittenly injects carbon dioxide to maintain the pH at a preset value. Water pH was reduced to the same value either by hypercapnia (at constant TA) or by adding HCl or H2SO4 to decrease the TA (at constant CO2 tension). Decrease of hemolymph pH and increase of hemolymph PCO2 were similar for the three acidic waters. Water oxygenation changes strongly affected hemolymph ABB. In crayfish living in hyperoxic water (PO2 congruent to 600 Torr) compared to those in hypoxic water (PO2 congruent to 40 Torr), hemolymph pH was 0.3 to 0.4 unit lower and hemolymph PCO2 several times higher, the exact values of pH and PCO2 depending on the controlled ambient acid-base balance. In any study of the hemolymph acid-base balance of the crayfish, it is an important to control ambient water's acid-base balance and oxygenation as it is to control its temperature, a conclusion which probably holds true for studies on all water breathers.
Acid-Base Equilibrium↗