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Biomedical subjects

P Sebert

Publications and source records attributed to P Sebert.

29 records · Page 2Linked to original sources
PubMed1986

Brain and plasma biogenic amines analysis by the EC-HPLC technique: application to fish.

A HPLC technique has been developed for the analysis of biogenic amines (noradrenaline, NA; dopamine, DA; adrenaline, A; serotonin, 5-HT) in tissues and blood and then applied to fish. It appears that when compared to classical methods, HPLC is more rapid and reliable with a lower variation in the results. This technique showed that in eel blood, 5-HT and DA (and their metabolites) are missing or at least are present at very low concentrations.

Anguilla↗
PubMed1986

Catecholamine content (as measured by the HPLC method) in brain and blood plasma of the eel: effects of 101 ATA hydrostatic pressure.

The catecholamine content (noradrenaline, NA; adrenaline, A; dopamine, DA, and its metabolite, DOPAC) was measured, by the HPLC method, in brain and blood plasma of eels studied at atmospheric pressure (1 ATA) or at 101 ATA of hydrostatic pressure (HP). In the brain, HP induces a slight but significant increase (P less than 0.05) in A and DA contents but NA and DOPAC levels are not modified at 101 ATA when compared to 1 ATA. In the plasma, only A and NA are detected, adrenaline being the predominant amine. In eels exposed to 101 ATA HP, A and NA are strongly increased (+100%; P less than 0.01). The significance of the catecholamine increase in brain and plasma of the eels under HP is discussed.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Effects of high hydrostatic pressure per se, 101 atm on eel metabolism.

Oxygen consumption (MO2) of confined eels was measured at atmospheric pressure, 1 atm, and at 101 atm of hydrostatic pressure per se (HP). The tolerance of the eels to hypoxia was studied at the two experimental pressures. At atmospheric pressure, when oxygen partial pressure (PWO2) fell below the critical pressure, Pc = 22.4 +/- 1.95 Torr, there was a linear PWO2-related decrease in MO2. At maximal hypoxia, the eels survived for several hours by their efficient anaerobic metabolism. At 101 atm of HP, as soon as the experimental pressure was attained, a linear PWO2-related decrease in MO2 was observed at PWO2 levels much higher than those considered as critical at atmospheric pressure. The relation MO2 = f (PWO2) was similar to that observed at 1 atm when PWO2 less than Pc, that is, when aerobic metabolism was insufficient to ensure the eels' energetic requirement. Moreover, the eels tolerated hypoxia much less well at 101 atm of HP than at 1 atm. In conclusion, the exposure of eels to 101 atm of HP induced a sharp decrease in aerobic metabolism; then, at 101 atm, the energetic requirements must be ensured by anaerobic processes which produced lactates in plasma whose values were similar to those observed at 1 atm when PWO2 less than Pc.

Anaerobiosis↗
PubMed1985

Hydrostatic pressure and adrenergic drugs (agonists and antagonists): effects and interactions in fish.

Cardiac responses to alpha and beta adrenergic drugs have been studied in the eel firstly at atmospheric pressure (1 ATA), secondly at 101 ATA per se hydrostatic pressure. The exposure of treated eels for 1 hr at 101 ATA cancels the propranolol effect, increases the clonidine effect and induces paradoxal effects (reversal effect) of isoproterenol, phentolamine and phenylephrine. The highly significant interaction (P less than 0.001) between drugs and HP at 101 ATA is discussed and interpreted as effects of hydrostatic pressure inducing a change in receptor function.

Animals↗
PubMed1984

Ventilatory and occlusion pressure responses to hypercapnia in patients with chronic renal failure.

Little is known of the effect of chronic renal failure (CRF) on ventilatory regulation. In 38 subjects (19 healthy, 19 with CRF before and after dialysis), we performed measurements of ventilation (VE) and occlusion pressure (P0.1) while the subjects were breathing air and hypercapnic gas mixtures. The results have shown that (1) during air ventilation, CRF patients exhibited lower values of VE and P0.1, which returned to normal after dialysis; (2) during hypercapnic ventilation, CRF patients had the same response as healthy subjects for VE but higher P0.1; hemodialysis induced an upward shift of the CO2 response curve in CRF patients. A twofold mechanism is probably involved: pulmonary edema, which reduces lung elasticity, and neuromuscular hypoexcitability, both implying a stronger central command.

Adult↗
PubMed1984

Effects of high hydrostatic pressure on catecholamine contents in tissues of the eel acclimatized at two temperatures.

Catecholamines (CA) are involved in many adaptative mechanisms of an organism to its environment. In fish, pressure is an environmental factor able to modify these mechanisms of adaptation, and some of the physiological perturbations observed under pressure can be compared to CA unloading. Moreover, the metabolic rate, and probably the CA metabolism of fish, are modified by the ambient temperature. This study has been conducted to measure tissue (brain and heart) CA contents (dopamine, norepinephrine, epinephrine) of eels acclimatized for 15 d at two temperatures, Tw, (15 degrees C or 25 degrees C). The measurements have been made either at atmospheric pressure (1 ATA) or after 60 min at 101 ATA of hydrostatic pressure "per se." The results show that 1) at a given Tw, pressure has no significant effect on tissue CA contents; and 2) there seems to exist a pressure-temperature antagonism concerning dopamine and epinephrine in the brain. It is suggested that this antagonism acts on enzymatic systems involved in the metabolism of these two amines.

Acclimatization↗
PubMed1982

Sex differences in cardiac responses to successive apnea periods.

Cardiac response to breath-holding is generally described as a bradycardia, which is explained by a two-fold mechanism involving the pulmonary mechanoreceptors and the arterial chemoreceptors. This study was conducted to determine the cardiac effects of five successive apnea periods separated by 1 min of free ventilation (FV). Heart rate (HR) and ventilation (V, VT, f) were measured during this protocol in 12 young subjects (6 men, 6 women). Ventilatory responses during FV periods were similar in both sexes, but HR responses were different during the apnea periods. The mean exhibited a bradycardia and the women a tachycardia. Although the statistical significance of the results was weak, they showed a clear tendency which was interpreted as differences in central cardioventilatory interactions. Sex difference in the cardiac consequences of static work from respiratory muscle is also evoked.

Adult↗
PubMed1977

Relative estimation of ventilatory fow rate in the eel (Anguilla anguilla L.)

Freshwater eels (Anguilla anguilla L.) were experimented on in order to measure ventilatory flow rate (by means of a direct method of collecting expired water), and simultaneously, to record sub-opercular pressure changes and opercular displacements (operculogram). Significant correlations (p less than 0.01) were found between the ventilatory flow rate (V) and various characteristics of operculiogram records. The relationships which are significant in each fish experimented on are; V = a(f.lo) + b; V = a(f.Ao) % b and V = a(f.Ao2) + b(f: ventilatory frequency: Ao and lo: mean amplitude and result of integration of opercular tracings). Considering the technical difficulties in measuring the ventilation flow rate of the eel, the easier operculographic recording methods lead to a correct estimation of relative changes in ventilatory flow rate, by using the refined relationship: V = a(Ao1.63).

Animals↗
PubMed1976

[Cardiorespiratory effects of exogenous hypercapnia in eels].

The study of electrocardiogram and opercular movement records, from eels exposed for prolonged periods to hypercarbic water (saturation by the gaseous mixture 2% CO2, 98% air) shows that 1) heart rate is not significantly changed; 2) the duration of spontaneous apnea phases and the magnitude of opercular movements during ventilatory phases are increased under hypercapnic conditions. Because the integrated records of opercular movements only give an arbitrary estimate of changes in ventilation rate, direct measurements of the ventilation volume were performed in order to state the way of the dominant action of CO2. This method allows us to conclude that exogenous hypercapnia significantly decreases the ventilatory rate in eels.

Animals↗
PubMedDate not supplied

Hydrostatic pressure effects on eel mitochondrial functioning and membrane fluidity.

Aerobic metabolism which is required for long swimming activities during the eel's spawning migration at depth, is a potential target for pressure effects due to its components located in the inner mitochondrial membrane (respiratory chain and oxidative phosphorylation). Previous studies have evidenced that eels are able to acclimatize to pressure through membrane fluidity adjustment. However these studies were performed on the premigratory stage (yellow stage), which never encounters high pressure. Metamorphosis (silvering) seems to preadapt eels (at the silver stage) to most of the environmental changes they will encounter during migration. Is it also true for pressure resistance? This study shows that yellow eels exhibit a higher pressure sensitivity than silver eels (compression effects). The acclimatization period (21 days at 10.1 MPa) cancels the differences in pressure sensitivity and in aerobic metabolism observed at 0.1 MPa between the two stages. The mechanisms, which take place in yellow eels during acclimatization to high pressure, appear to be already present in silver eels before pressure exposure. Indeed at 0.1 MPa, silver eels exhibit higher membrane fluidity and proportions of membrane polyunsaturated fatty acids. Metamorphosis, by improving membrane fluidity, seems to allow silver eels to cope with hydrostatic pressure without spending energy in acclimatization processes.

Acclimatization↗