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Biomedical subjects

P Dejours

Publications and source records attributed to P Dejours.

At least 37 records · Page 2Linked to original sources
PubMed1980

Blood acid-base balance as a function of water oxygenation: a study at two different ambient CO2 levels in the dogfish, Scyliorhinus canicula.

In the unanesthetized dogfish, Scyliorhinus canicula, oxygen and carbon dioxide partial pressures and concentrations in inspired and expired water and the acid-base balance of arterial blood, pHa and PcCO2, were determined. Each dogfish was exposed to waters differing in oxygenation and in CO2 levels, which was controlled with a pH-CO2-stat device, for successive 2- to 3-h periods. The four ambient conditions were: normoxia-normocapnia (inspired PO2, PIO2 ca 160 Torr; PICO2 ca 0.3 Torr), hyperoxia-normocapnia (PIO2 ca 730 Torr), hyperoxia-hypercapnia (PICO2 ca 1.0 Torr); normoxia-hypercapnia. At both low and high ambient CO2, the inspired-expired O2 and CO2 concentration differences increased in hyperoxia. Ventilation was depressed, and concomitantly, PACO2 increased and the arterial plasma pH decreased. The hypercapnic acidosis was rapidly but only partially compensated by an increase of the plasma bicarbonate concentration. Due to the buffer action of carbonate in sea water, low and high ambient CO2 levels corresponded respectively to high and low values of the CO2 capacitance coefficient, betaWCO2. At both ambient oxygenation levels, the expired-inspired PCO2 difference was greater at low than at high betaWCO2. At a given ambient CO2 level, expired PCO2, PECO2, wash higher in hyperoxia than in normoxia; an effect more marked at low than at high betaWCO2. Thus, the water capacitance coeffcient betaWCO2 is an important factor determining PECO2 values and probably arterial blood acid-base balance. As a general conclusion, the acid-base balance of the arterial blood in the dogfish is very much dependent on the conditions of the oxygenation and acid-base balance of the ambient water which consequently should be carefully controlled.

Acid-Base Equilibrium↗
PubMed1980

Ventilatory CO2 drive in the tortoise Testudo horsfieldi.

1. Ventilation was recorded by pneumotachography, before and after bilateral vagotomy, in conscious tortoises (Testudo horsfieldi) (breathing 0, 2, 3 or 4% CO2 in air or oxygen). 2. Each breath consists of expiratory and inspiratory phases and an apneic plateau (absence of air flow). Inhalation of hypercapnic mixtures led to increased ventilatory flow, augmentation of tidal volume, and an increase in respiratory frequency through the shortening of the apneic plateau. 3. Intact tortoises breathing hypercapnic-hyperoxic mixtures hyperventilated less than with hypercapnic-normoxic mixtures. 4. In bivagotomized animals, the respiratory frequency decreased, the expiratory and inspiratory durations lengthened, and the apneic plateau was prolonged. The tidal volume was increased, but ventilation, nevertheless, decreased slightly. 5. Bivagotomized animals breathing hypercapnic-normoxic or hypercapnic-hyperoxic mixtures hyperventilated, but less than intact animals under the same conditions. 6. It is concluded that in tortoises there are: (1) peripheral chemoreceptors which are innervated by branches of the vagus nerves, and are sensitive to CO2; and (2) an extrathoracic, probably central, ventilatory CO2 drive.

Animals↗
PubMed1978

Carbon dioxide in water- and air-breathers.

Because water-breathers breathe much more water than air-breathers breathe air, and because in the two media the CO2 capacitance coefficients are similar, the difference in PCO2 between inspired and expired medium is much smaller in aquatic than in aerial animals, being generally inferior to 1 Torr. However, as regards CO2, water is a very complex medium, since the aquatic CO2 system varies with salinity, temperature, carbonation, photosynthesis and eventually ionic exchange in the gills. In no two waters is the pattern of CO2 exchange the same. In respiratory studies of aquatic animals it is very important to keep the carbon dioxide system of the water as constant as possible, or at least to be aware of its possible variation with many factors.

Acid-Base Equilibrium↗
PubMed1977

Crayfish respiration as a function of water oxygenation.

Crayfish, Astacus leptodactylus, for several hours breathed water equilibrated either with a hypoxic gas mixture, or air, or oxygen. The hydrostatic pressure in the right epibranchial cavity was recorded and the left epibranchial water sempled from time to time. The higher the water oxygenation, the less the duration of ventilation, the frequency of the scaphognathite beats which ensure water convection, the negative of the water hydrostatic pressure relative to ambient water pressure, and the respired water flow. The water convection per unit quantity of oxygen consumed decreased by a factor of about 20 when the animal passed from hypoxic water at PO2 of 72 torr to hyperoxic water at PO2 of 697 torr. Prolonged hyperoxia, up to 100 days, results in a hypercapnic acidosis of the prebranchial blood. pH decreased about 0.2 unit, PCO2 increased from 2.5 torr to a value of 6 torr, and [HCO-3] from 6 to a value of 9 meq-L-1. This hypercapnic acidosis remained uncompensated during several weeks exposure to hyperoxia. Observations on the fresh water crayfish, a marine crab, and several species of fish, suggest that in aquatic animals (1) the ventilatory activity depends greatly on the degree of water oxygenation: the higher the water oxygenation, the lower the ventilation; (2) the change of ventilation may be accompanied by a new equilibrium of the blood acid-base status, quite different from that observed in normoxia.

Acid-Base Equilibrium↗
PubMed1976

Breath-to-breath variations of alveolar Po2 and Pco2 at barometric pressures of 490, 745 and 1500 Toor in resting awake dogs.

Two awake, resting dogs born and raised at low altitude were studied, breathing air (1) at 745 torr, (2) during a 12 days sojourn at 490 torr in an altitude chamber, and (3) during 5 days sojourn at 1500 torr in a hyperbaric chamber. The respired gas was continuously sampled an end-tidal PCO2 and PO2 of sequences of thirty breaths were measured by fast analyzers. The mean value of alveolar PCO2 was 29 torr at high altitude; 35 torr at 745 torr; and 40 torr in hyperbary. The changes of PCO2 indicate different alveolar ventilations which result mainly from the changes of the chemoreceptor drive which is enhanced at high altitude and decreased in hyperbary. The scattering of PCO2 is about the same at the three pressures. The scattering of PO2 is less at high altitude than at sea level, and less at sea level than in hyperbary. On a PCO2 vs PO2 diagram end-tidal PCO2 and PO2 points form elliptical clouds whose mean slopes decrease with the increase of total pressure. The characteristics of the dispersion of the alveolar pressures and of the slopes of the alveolar clouds depend on several factors among which the relevant steepness (i.e. capacitance) of the O2 and CO2 blood abosrption curves at the three pressures presumably plays the major role.

Altitude↗
PubMed1975

[Control of respiration in teleostean fishes: existence of chemoreceptors, physiologically analogous to those of higher vertebrates].

Injection of NaCN or lobeline into the ventral aorta of the trout or carp provokes hyperventilation and bradycardia within 5 seconds, responses which are the weaker the higher the oxygen tension of the ambient water. The reactions, precisely similar to the chemoreflexes of higher vertebrates, suggest that these fish also possess arterial chemoreceptors.

Animals↗