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J P Pennec

Publications and source records attributed to J P Pennec.

13 recordsLinked to original sources
PubMed1993

Detection of phosphodiester resonances in the perfused heart from vertebrate ectotherms with nuclear magnetic resonance.

In vivo 31P NMR has been used to characterize the phosphorylated compounds present in the heart from vertebrate ectotherms. The perfused hearts from all animals experimented showed prominent resonances between the inorganic phosphate and phosphocreatine peaks. The pattern of these compounds was found to be different in the heart of the different species. As shown by 31P and proton NMR of perchloric extracts, the chemical shift of some of the compounds was characteristic of glycerophosphorylcholine, glycerophosphorylinositol, phosphorylcholine, phosphorylserine, phosphorylethanolamine and phosphoenolpyruvate. The non-identified resonances were found to be phosphodiesters, as demonstrated by alkaline phosphatase hydrolysis. The physiological significance of these high levels of phosphodiesters in the heart from vertebrate ectotherms is discussed.

Alkaline Phosphatase↗
PubMed1988

Relationships between swimming speed, oxygen consumption, plasma catecholamines and heart performance in rainbow trout (S. gairdneri R.).

Rainbow trout swimming at controlled speeds in a tunnel respirometer have been used to measure oxygen consumption and plasma catecholamine levels, and systolic pressure/frequency relationships. Catecholamine (CA) levels evaluated in trout plasma at low swimming speed [0.5 bodylengths/second (bl/s)] were: adrenaline (A) 1.77 +/- 0.22 nM; noradrenaline (NA) 3.94 +/- 0.83 nM; dopamine (DA) 2.40 +/- 0.36 nM. No significant increase was observed during moderate exercise (1.5 bl/s): A 1.60 +/- 0.20 nM; NA 5.76 +/- 1.07 nM; DA 2.31 +/- 0.80 nM, or stronger exercise (2.0 and 2.5 bl/s-1): A 2.10 +/- 0.21 nM; NA 5.90 +/- 0.90 nM; DA 2.21 +/- 0.40 nM. A correlation was found between heart rate at these swimming speeds, and its position on the systolic pressure frequency curve of isolated hearts, which suggests that the heart functions at maximum systolic pressure at low (0.5 bl/s-1) swimming speeds and that this pressure decreases during exercise as cardiac frequency rises.

Animals↗
PubMed1988

Diel and seasonal rhythms of the heart rate in the common eel (Anguilla anguilla L.): role of cardiac innervation.

Using a computerized system, ECG recordings of eels were made during long-term experiments, to show circadian and circannual variations in the heart rate. The circadian variations synchronize with the photoperiod. The maximum frequency is observed during the dark phase, the peak values occurring just after sunset and before sunrise. By using specific blockers--atropine, propranolol, desmethylimipramine--the respective roles of neurotransmitters (acetylcholine and catecholamines) were evaluated. The results point to the existence of a dual nervous regulation of the cardiac function involving a permanent sympathetic tone, even in the resting eel.

Acetylcholine↗
PubMed1987

The effect of pressure on the lateral swimming muscle of the European eel Anguilla anguilla and the deep sea eel Histiobranchus bathybius; results of Challenger cruise 6B/85.

1. The viability of Histiobranchus lateral muscle was prolonged up to 7 times by recompression of the tissue. 2. The maximum twitch contraction force of both Anguilla and Histiobranchus was recorded at a pressure between 150 and 350 atm. At 1 atm Anguilla developed 60% maximum force and Histiobranchus 10-20% maximum force. 3. Twitch contraction time doubled for a pressure increase of 400 atm. This effect is predicted to halve the maximum swimming speed at 4000 m and is discussed in relation to muscle force and anaerobic support.

Anguilla↗
PubMed1987

Effects of adrenaline on the isolated heart of the trout (Salmo gairdneri R.) before and after transfer from fresh water to sea water.

1. Adrenaline induces positive inotropic and chronotropic effects on the isolated heart of the trout (Salmo gairdnerii) via the stimulation of beta adrenoreceptors. 2. The effects are relatively more marked in winter than in spring. But there is no seasonal variation as in the cel. The intrinsic reactivity of the heart is not basically modified after a transfer from fresh water to sea water. 3. However, after such a transfer, adrenaline induces an increase of the membrane resting potential which suggests that adrenaline can enhance the activity of the Na/K pump and/or modify the Ca/K balance and could improve the cardiac performances during the "crisis period" following the transfer.

Adenosine Triphosphatases↗
PubMed1984

Effects of aconitine and veratrine on the isolated perfused heart of the common eel (Anguilla anguilla L.).

The effects of two alkaloids: aconitine and veratrine have been investigated in isolated perfused heart of the common eel (Anguilla anguilla L.). Low concentrations (less than 10(-6)M) of aconitine induced a decrease of the heart rate where high concentrations (greater than 10(-6)M) produced a tachycardia and finally led to a depolarization of cardiac cells. Veratrine induced a decrease of the heart rate depending on the concentration. A cardiac arrest was observed with high concentrations (greater than 10(-4)M). Removal of aconitine or veratrine from perfusion medium did not reverse the effects of high concentrations. The tachycardia and arrhythmias were triggered or enhanced.

Aconitine↗
PubMed1984

Storage and release of catecholamines by nervous endings in the isolated heart of the eel (Anguilla anguilla L.).

Experiments performed on isolated perfused hearts of the eel (Anguilla anguilla L.) showed that the heart spontaneously released catecholamines (i.e. Adrenaline, Noradrenaline, Dopamine) suggesting that they take part in the cardiac regulation. Stimulation of cardiac vagus branches significantly increased catecholamines levels, measured in a perfusion medium and simultaneously the heart rate and the systolic pressure. The effect of Desmethylimipramine showed that the catecholamines were released from nervous endings and not from endothelial cells.

Action Potentials↗
PubMed1984

Biological activity of new phosphorylated analogues of oxotremorine.

A number of N-4 (4-dialkylamino-2-butynyl) phosphoramide derivatives related to the oxotremorine structure were prepared and evaluated for their muscarinic activity on isolated perfused rat hearts. A structure-activity relationship study revealed that among other factors, muscarinic activity is directly related to the environment of the phosphorus atom.

Action Potentials↗
PubMed1983

Effects of adrenaline on isolated heart of the eel (Anguilla anguilla L.) during winter.

1. The intrinsic effects of adrenaline on the myocardium of the eel in winter were investigated in the isolated perfused eel heart. 2. Adrenaline was ineffective both on the pacemaker activity and auricular action potentials but markedly increased ventricular action potential duration, thus leading to an auriculo-ventricular desynchronisation. 3. This effect was not reversed by propranolol but was by phentolamine and was attributed to the stimulation of alpha receptors. 4. Clonidine reproduced the effect of adrenaline but also decreased the cardiac rhythm, possibly via alpha 2 adrenoceptors. 5. No direct inotropic effect was observed.

Action Potentials↗
PubMedDate not supplied

Effects of excess free fatty acids on the electrophysiological properties of ventricular specialized conducting tissue: a comparative study between the sheep and the dog.

The effects of sodium palmitate were studied on the transmembrane potential properties of canine subendocardial Purkinje fibers and on the Purkinje fibers of the dog and the sheep false tendons with standard microelectrode technique. Following 4 h of superfusion with palmitate/albumin = 10, action potential duration in all preparations was prolonged (p less than 0.05), and resting membrane potential, action potential amplitude, and maximum rate of rise were slightly but significantly (p less than 0.05) diminished in the subendocardial preparation, but not in the false tendons. Action potential prolongation was reversible in the dog preparations but only partially reversible in the sheep Purkinje fibers. Following palmitate-induced prolongation of the action potential duration, rapid spontaneous diastolic depolarization was observed in the subendocardial Purkinje fibers. Palmitate enhanced spontaneous diastolic depolarization in the sheep but not in the dog Purkinje fibers (false tendons). Albumin alone had no effect on all action potential properties in both species. It is concluded that extended periods of exposure of the ventricular specialized conducting tissue to excess levels of palmitate can induce action potential abnormalities and subsequent rhythm disturbances both in the dog and the sheep.

Action Potentials↗
PubMedDate not supplied

Purification of a tumoral marker recognized by monoclonal antibody Po66 and associated with human lung squamous cell carcinoma.

Monoclonal antibody (MAb) Po66, a murine IgG1, was raised by immunization against human lung squamous cell carcinoma. When injected intravenously, Po66 showed prolonged retention in the tumor. It recognized an intracellular antigen. The human lung squamous carcinoma cell line SK-MES-1 expresses the antigen recognized by MAb Po66 and was used as a source of biological material for its purification. The SK-MES-1 cell line was labeled in culture with [35S]methionine and its lysate was immunoprecipitated with Po66 immobilized on Protein G-Sepharose. The precipitate contained three proteins (47, 50 and 69 kDa) absent in the controls. The 69 kDa polypeptide was further purified by anion exchange and immunoaffinity chromatographies. To date, no other tumor marker expressed in non-small cell lung cancer with these characteristics has been described and as such this marker is interesting for future use in immunotherapy and in diagnosis.

Animals↗
PubMedDate not supplied

Membrane bioelectrogenesis and ionic channel activity simulation under drug action.

The concept of the ionic channel, as a protein with more discrete ionic conductance levels, is analyzed and a computer program, aiming to simulate its dynamics under the action of a pharmacological agent, is presented. The binding of a pharmacological agent modifies the set of the possible configurations and the channel energy spectrum. Therefore it modifies the transition probabilities and the dwelling times in the excited (generally conductive) states. The program creates a library of simulations of the electric activity of some user designated hypothetical models. The simulations are then statistically compared to the recorded single channel events to select the most suitable model.

Cell Membrane↗