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Biomedical subjects

P Sébert

Publications and source records attributed to P Sébert.

At least 19 recordsLinked to original sources
PubMed2001

Why can the eel, unlike the trout, migrate under pressure.

In order to elucidate the difference between pressure resistance in trout (Onchorhyncus mykiss) and eel (Anguilla anguilla), oxygen consumption of red muscle permeabilised cells and mitochondria were measured at 101 ATA hydrostatic pressure per se. Such an experiment involved the setting up of a special system allowing measurements under high pressure. The results show that hydrostatic pressure strongly alters the oxidative phosphorylation in trout but not in eel, which exhibits mitochondrial pressure resistance. It is hypothesised that the eel has a supranormal mitochondria functioning at atmospheric pressure in order to cope with the high pressure environment encountered during its migration.

Journal Article↗
PubMed2000

High pressure and glycolytic flux in the freshwater Chinese crab, Eriocheir sinensis.

The hexose part of glycolysis has been studied in the freshwater Chinese crab Eriocheir sinensis exposed to high pressure (101 ATA, i.e. 1000 m depth) at 14 degrees C and in normoxic conditions. Glycolytic fluxes (from glucose, JA and from Glucose 6 Phosphate, JB) have been determined using NADH depletion during the conversion of dihydroxy acetone phosphate into alpha-glycerol phosphate. Measurements have been performed at 14 and 19 degrees C. Pressure exposure induces an increase of glycolytic flux and a decrease of the time needed for the transition from aerobic to anaerobic glycolysis. As a consequence pressure-exposed crabs have a higher potential to increase glycolytic flux than control animals at atmospheric pressure. It is concluded that high pressure known to alter numerous enzymes individually, can also modify an overall metabolic pathway.

Analysis of Variance↗
PubMed2000

Improvement in the efficiency of oxidative phosphorylation in the freshwater eel acclimated to 10.1 MPa hydrostatic pressure.

Previous studies have suggested that the efficiency of oxidative phosphorylation in the freshwater eel (Anguilla anguilla) is increased after acclimation to high hydrostatic pressure. Analysis at atmospheric pressure of the respiratory chain complexes showed that, after 21 days at 10.1 MPa, the activity of complex II was decreased to approximately 50 % (P<0.01) of the control value and that cytochrome c oxidase (complex IV) activity was significantly increased to 149 % of the control value (P<0.05). ADP/O ratios calculated from mitochondrial respiration measurements were significantly increased after acclimation to high hydrostatic pressure (2.87 versus 2.52, P<0.001) when measured in the presence of pyruvate plus malate at atmospheric pressure. These results clearly show an increased oxidative phosphorylation efficiency in response to high-pressure acclimation.

Adaptation, Physiological↗
PubMed1995

Effects of a temperature increase on oxygen consumption of yellow freshwater eels exposed to high hydrostatic pressure.

Oxygen consumption was measured in yellow freshwater eels, Anguilla anguilla, during exposure to a hydrostatic pressure (HP) of 101 atmosphere absolute (ATA) for 3 h, either with or without a 5 degrees C increase in water temperature. It was found that concomitant increases in temperature and pressure resulted in an increase in oxygen consumption that was lower than when pressure alone was increased. When eels were acclimated to HP for 21 days and then submitted to a temperature increase of 5 degrees C, this induced a significant increase in oxygen consumption but only during the first hour. It is therefore concluded that raising the water temperature during the first hours under pressure could counterbalance the pressure effects on membrane fluidity in a thermodynamic manner and thus help shallow-water fish acclimate to high pressure. In contrast, when acclimation processes are ended, the temperature effect disappears within 1 h.

Acclimatization↗
PubMed1995

[Effects of hydrostatic pressure on malondialdehyde (MDA) determination in brain from yellow freshwater eels].

Malondialdehyde (MDA) content in a tissue can be an indicator of lipoperoxidation and thus of membrane alteration. MDA concentrations have been measured in the brain of yellow freshwater eels (Anguilla anguilla) submitted to 1.51 or 101 ATA of hydrostatic pressure. Exposure to pressure was performed for 6 h at constant water temperature and in normoxic conditions. The results thus obtained show a significant increase (P < 0.05 or better) of MDA brain concentrations at 51 ATA (+ 124%) and 101 ATA (+ 290%). These results mean that hydrostatic pressure is able to activate lipoperoxidation and can alter membrane functions together with the decrease in membrane fluidity it induces. Such a membrane alteration can explain, at least in part, the excitation periods which are observed during and after animal compression.

Anguilla↗
PubMed1992

[External resistances and dyspnea. Value of the study of flow-volume loops].

Breathlessness induced by external resistances (diaphragms with orifice size of 20, 15, 10, 7.5 and 5 mm) introduced in the ventilatory circuit of a spirometer and the corresponding parameters of a maximal flow-volume loop have been studied. 10 healthy subjects (5 men, 5 women), free from any acute or chronic cardiorespiratory disease, volunteered for this study. The results showed that the breathlessness (severe or moderate) was especially correlated with the decrease in peak flows, peak inspiratory flow (PIF) more than peak expiratory flow (PEF): when breathlessness was moderate, PIF was more decreased than PEF, -35% and -28% respectively; when breathlessness became severe, PIF also decreased more than PEF, -60% and -50% respectively; forced vital capacity (FVC) never changed and maximal expiratory flows at 50% and 25% of FVC were only slightly modified despite obvious breathlessness. The increase in diaphragmatic activity seemed more implicated than the activation of expiratory muscles in the genesis of breathlessness. PIF more than the commoner PEF could be a useful marker of the breathlessness perceived by the patient during acute bronchial obstruction (asthma).

Adult↗
PubMed1990

A simple device for measuring a vertical jump: description and results.

A simple and cheap device has been designed which makes it possible to quantify a vertical jump. The parameters which can be measured or calculated with this device include: height of the jump, duration of thrust, maximal velocity and thus the corresponding maximal power output. The device was tested on 22 young soccer players for whom the height of the jump (0.47 m, SEM 0.015) and maximal power output (34.9 W. kg-1, SEM 1.04) were considered. The device is proposed for assessing training methods and sports aptitude.

Adolescent↗
PubMed1989

Ventilatory responses to hypoxia in healthy subjects: a comparison between young children and adults.

Ventilatory responses and breathing patterns during acute hypoxia have been studied at sea level in healthy subjects (8 children, 8 adults). While breathing ambient air it appears that, compared to adults, children hyperventilate when ventilation is standardized to body mass unit. During hypoxia, ventilatory strategy differs with age: when adults essentially increase tidal volume (VT), children increase VT and ventilatory frequency (fr). The ventilatory steady-state response to hypoxia is lesser in children than in adults, that is to say, children have a lower O2 ventilatory sensitivity. These results, which show that adults and children have qualitatively and quantitatively different ventilatory responses to hypoxia, are interpreted in terms of the ability to displace gaseous volumes.

Adult↗
PubMed1989

Effects of maximal breath holding on maximal expiratory flows.

Effects of breath holdings (BH) on bronchomotor tone, maintained until their breaking points, have been studied using maximal expiratory flow volume curves (MEFVC). BHs have been performed either at high lung volume (total lung capacity, EIBH) or at low lung volume (residual volume +250 ml, EEBH), an inspiratory manoeuvre immediately preceding the MEFVC. The results show that: (1) EIBH induces a significant increase of expiratory flow at 25% of FVC; (2) EEBH induces a significant and constant decrease of expiratory flows at 50% and 25% of FVC. The same modifications were recorded after inhalation of 400 micrograms of Fenoterol or 80 micrograms of Ipratropium bromide. The observed results are suggestive of mechanical effects of BH on expiratory flows. After EIBH airway hysteresis dominates over lung hysteresis, with opposite effects after EEBH.

Administration, Inhalation↗
PubMed1988

Effects of hydrostatic pressure (HP = 101 ATA) on nucleotides and pyridine dinucleotides tissue contents in trout.

Tissue concentrations of energetic nucleotides and coenzymes, and oxygen consumption (MO2), have been measured in trout, exposed for 30 min in normoxic conditions (PwO2 congruent to 150 Torr), to 101 ATA (Atmosphere Absolute) of hydrostatic pressure (HP) and compared with results obtained at atmospheric pressure (1 ATA). The results show that in trout exposed to HP, there is an increase in MO2 accompanied by a decrease in ATP and energy charge (EC) in the three tissues explored (brain, liver, and muscle). Moreover, the fall of EC in muscle is accompanied by an increase in inosine 5' monophosphate (IMP). These results are in agreement with the hypothesis of an histotoxic hypoxia induced by HP, which can act at the Krebs cycle level and/or at the respiratory chain level, possibly by uncoupling the respiratory chain from oxidative phosphorylation processes.

Adenine Nucleotides↗
PubMed1983

Heart rate and breathing pattern: interactions and sex differences.

Ten subjects (five males, five females) were studied in resting conditions. Ventilation (VT, f, TI, TE), heart rate (HR) and RR interval were recorded or measured. Each subject voluntarily breathed with spontaneous frequency at different ratios of his spontaneous tidal volume (VrT). The results show that sinus arrhythmia increases with lung volume but without effect on mean heart rate. When VT is increased by two times its spontaneous value, the ventilatory drive (VT/TI) is raised in both sexes; the relative duration of inspiration (TI/Ttot) is modified (+20%) in females only. Thus with the cardiac effects of increasing lung volume being similar in both sexes, we conclude that sinus arrhythmia is not generated by sensory inputs from pulmonary structures, but that its origin is at the CNS level. Moreover, there may be a sex difference in the control of voluntary ventilation, a suggestion requiring further investigation.

Adult↗
PubMed1981

Sexual and postural differences in cardioventilatory responses during and after breath holding at rest.

Twelve subjects (six men, six women) were studied in resting conditions for simple breath holding (BH) in either the supine or upright position. Ventilation (VT, V, fr) heart rate (fc) and arterial blood pressure (ABP) were recorded or measured in steady state and then transiently during BH and its recovery. Each subject performed seven HB in the supine position and two in the upright position. Several criteria were used for fc data analysis. During BH, in either the supine or upright position, no change in heart rate was observed, but subjects taken individually may exhibit some significant cardiac responses (tachycardia or bradycardia) for all the tests. In contrast, an increase in mean ABP is always observed, with different patterns in males and females. The upright position allows the responses to be greater, more rapid and significant. As a general rule, males have larger and slower responses than females. After BH, there is a ventilatory cost of apnea which is more important in males. However the delay in repayment of the ventilatory deficit observed during BH is very short (about 40 s): ventilatory and cardiac recovery are complete within 120 s. The results support the ideas that, (1) cardiac responses during BH are dependent on pulmonary physical conditions and metabolic levels before BH, (2) cardiac changes during recovery are, at least in great part, due to the concomitant hyperventilation.

Adult↗
PubMed1981

Carotid chemoreceptor function in ventilatory and circulatory O2 convection of exercising dogs at low and high altitude.

Awake dogs were studied before (control) and after chronic bilateral carotid denervation (denervated) at rest and running for 3 min on a treadmill at 8 km . h-1 and at various grades, in an altitude chamber operated either at 140 m or at 4000 m for 3 h. Steady-state pulmonary ventilation (Vg) and breathing pattern (VT, fR), oxygen consumption (MO2), O2 concentrations (C) and pressures (P) in the arterial (a) and mixed venous blood (v), hematocrit (Ht) and acid-base status in arterial blood, and heart frequency (fH) were measured. From these data cardiac output (Vb) and stroke volume (Vs), ventilatory and circulatory requirements (Vg/Mo2, Vb/MO2), extraction of O2 from inspired gas (EairO2) and blood (EbO2), and capacitance coefficient of blood for oxygen (beta bO2) were calculated. Ventilatory responses to transient O2-inhalation were also studied and the aortic (AP) and pulmonary (PP) blood pressures measured in resting conditions. 1. After chronic carotid denervation the hypoxic chemoreflex drive of ventilation was reduced by about half, maximal MO2 remained unaffected at 140 m, but at 4000 m decreased 50% compared to 30% in controls. 2. In all experimental conditions, Vg/MO2, PaO2 and CaO2 were less in denervated animals than in controls, and EairO2, PaCO2 and H+ ion concentration were higher. 3. At 140 m, circulatory O2 convective transport was identical in the two groups of dogs. At 4000 m, beta bO2 increased similarly in both groups, but Vb and Vb/MO2 were higher in denervated dogs than in controls, in relation with reduced CaO2-CVO2 difference which contributed to restore PVO2 towards higher values. 4. At 140 m, mean resting AP and PP were similar in both groups of dogs. At 4000 m, AP increased not significantly in controls, and decreased in denervated animals; PP increased in controls, but not in denervated dogs. It is concluded that integrity of the arterial chemoreceptor drive is essential in determining the eupneic level of ventilation and normal acid-base status of the blood in both resting and exercising dogs, at low and at high altitude, and in reducing the O2 circulatory requirement at high altitude. At 4000 m, the lack of carotid chemosensitivity is accompanied by severe hypoxemia, in association with hypercapnia and acidosis, and by increased cardiac blood flow, most presumably due to decreased peripheral resistance and increased venous return; despite these compensatory changes in circulatory O2 convective transport, denervated animals reach a maximum O2 uptake at lower work load than controls.

Adaptation, Physiological↗
PubMed1979

O2-chemoreflex drive of ventilation in awake birds at rest.

Three varieties of birds (a non-flyer, the chicken; a diver, the duck; a flyer, the pigeon) were studied in resting conditions at neutral ambient temperature, while awake, either intact or sham operated, or after bilateral chronic carotid body denervation. Tidal volume (VT), ventilatory period (T) and minute volume (V = VT/T) measured plethysmographically, were recorded breath-by-breath in steady state at two levels of oxygenation, and in the course of transient pure O2 inhalation (60-sec O2-test). O2 partial pressures in the inspired and expired gases (PIO2 and PETO2), and in the arterial blood (PaO2) were also measured. In intact and sham operated birds, the abrupt switch from a normoxic gas mixture (FIO2 = 0.21) to pure O2 resulted shortly in rapid increases of PIO2, PETO2 and paO2, and in a fall of V which was completed within 20--30 sec and accounted for about 30% of the control minute volume. In the animals previously made hypoxic (FIO2 = 0.12) and hyperventilating, the O2-test provoked a 50--60% fall of V. In chickens, a decreased VT and an increased T contributed to the transient ventilatory changes; in ducks, mainly VT changed, and in the pigeon only T changed. In the birds with denervated carotid bodies, there were no ventilatory responses to hypoxia and to the O2-test. A few of these birds developed a tachypneic response to hypoxia with no apparent change in the effective pulmonary ventilation, which was partly overcome during the O2-test. It is concluded that in the three varieties of birds, the O2-chemoreflex drive from the carotid bodies controlled about 30% of the resting minute volume near sea level, and 50--60% in hypoxic conditions duplicating an altitude exposure to 4000 m.

Animals↗
PubMed1979

[Evidence for a central action of CO2 ventilatory stimulus in Pekin ducks (author's transl)].

Ventilatory responses to changes in PCO2 of the blood perfusing the central nervous system were studied breath by breath by pneumotachography in Pekin ducks under transient and steady condition. 1. Transients. In conscious birds, all the arteries to the cephalic region were tied or clamped, except the right internal carotid. The blood supply via the single remaining arterial pathway was transiently replaced, for about 15 sec, by injecting 2 ml of blood previously made either normocapnic (control PCO2 = 32 Torr) or hypercapnic (test; PCO2 = 76 Torr) from a syringe thermostated at 41 degrees C, under normal oxygenation (PO2 around 110 Torr) and mean endovascular pressure (107 mm Hg). During control injections, no significant ventilatory changes were observed. In contrast, test injections provoked an early and significant 20% increase in the minute volume of ventilation. 2. Steady conditions. Using cross-perfusion between pairs of anesthetized ducks, the head of a recipient animal (R) was vascularly isolated from the trunk and perfused by a donor (D), the nervous connections with the trunk remaining intact. When giving some CO2 to breathe to D (FICO2 = 0.05) while R breathed ambient air, arterial PCO2 increased in D and in the head of R, and hyperventilation occurred in both ducks. As a consequence of this hyperventilation, PCO2 decreased in the arterial blood and the end-tidal gas of R.

Animals↗
PubMedDate not supplied

Does hydrostatic pressure have an effect on reactive oxygen species in the eel?

Eels are submitted to hydrostatic pressure (HP) during their spawning migration (about 6000 Km). Before migration, they change from the yellow to the silver stage (silvering process). The effects of HP in relation to the silvering process have been studied on aerobic metabolism and more precisely on reactive oxygen species (ROS) metabolism. HP acclimatization of yellow eels improves oxidative phosphorylation together with supposed concomitant changes in electron leak and ROS production. Therefore hydroxyl radical (OH*) production, superoxyde dismutase and catalase activities, malondialdehyde content and in parallel oxygen consumption were measured in the red muscle of long-term pressure exposed and control group yellow and silver eels. At atmospheric pressure, yellow eels exhibited significantly higher oxygen consumption and OH* production than silver eels; and significantly lower malondialdehyde content. This could be due to the increase in membrane fluidity induced by the silvering process. Long-term HP exposure decreases yellow eel oxygen consumption which becomes similar to that of the silver stage. In parallel there is a decrease in OH* production and concomitantly antioxidant enzyme activities follow the same tendency. Thus the respiratory chain improvement in pressure acclimatized yellow eels is accompanied by a ROS production decrease which could mean an electron leak decrease.

Acclimatization↗
PubMedDate not supplied

A comparative study of reactive oxygen species in red muscle: pressure effects.

In ectotherms as well as in endotherms, the mitochondrial respiratory chain is the major source of reactive oxygen species (ROS) including the highly reactive, hydroxyl radical (OH*). It is known that the different steps involved in ROS production and the antioxidant systems are comparable in ectotherms and endotherms. But regulatory mechanisms in ROS production are less known especially in fish submitted to environmental changes. Firstly, we performed a ROS muscle metabolism interspecies study, using trout and eels as ectotherms and rats as endotherms, measuring OH* production, superoxide dismutase and catalase activities and in parallel oxygen consumption (MO2). Secondly, we studied the effects of an environmental factor (hydrostatic pressure) on ROS metabolism in both fish species. The results show that, at atmospheric pressure, fish have a higher OH*/MO2 ratio than rats which exhibit a higher superoxide dismutase activity. In fish exposed to hydrostatic pressure, this ratio is reversed so that for the same MO2 value, fish produce less OH* under hydrostatic pressure than at atmospheric pressure.

Animals↗