Biomedical subjects

P Gourmelon

Publications and source records attributed to P Gourmelon.

9 recordsLinked to original sources

PubMed1991

Rapid postmortem decrease in the ectocellular acetylcholinesterase activity in rat striatum as assessed by in vivo microspectrophotometry.

The acetylcholinesterase (AChE) activity in striatum rat was determined before and shortly after death using the in vivo microspectrophotometric method. This technique allowed us to monitor the Ellman colorimetric reaction directly inside the brain using an optical probe implanted in a live animal and to determine locally the AChE activity. Whatever the cause of the animals death, we observed a drastic postmortem decrease of the AChE activity of about 35-50%, 10 min after death. We have verified that the postmortem decrease of brain temperature or pH and postmortem optical properties changes could only explain a fraction of the AChE activity fall (16%). This phenomenon seems to be related to events strictly localized at the cellular level, since local injection of cyanide at the measuring site promotes a decrease of the enzymatic activity (40%) close to the levels observed after death. The origin of this rapid postmortem fall of the AChE activity is discussed. The technical properties of the microspectrophotometric method exclude a decrease of the ectocellular pool of enzyme after death. Our results allow us to envisage the existence of an in vivo endogenous regulation of the AChE activity which disappears shortly after death.

Acetylcholinesterase↗

PubMed1991

Sleep alterations in experimental street rabies virus infection occur in the absence of major EEG abnormalities.

Brain electrical activity and sleep organization were investigated in chronically implanted mice during street rabies virus infection. Continuous EEG recordings showed no gross electrical abnormalities until a few hours before the fatal issue. In contrast, alterations of sleep stages were observed at an early stage during the course of rabies virus infection, at a time when clinical signs were absent. Quantification by spectral analysis showed that the main feature was the early decrease of REM-sleep stages and the increase of the duration of waking stages. Neuromuscular disorders which could occur early were also observed during the disease. Comparison of these data with those obtained from fixed rabies virus infection shows that in the latter the EEG recordings demonstrated early alterations and a progressive deterioration with disappearance of both sleep and waking stages, which were replaced by a pathological sleep stage. In order to evaluate the potential role of the host-specific immune response in promoting brain electrophysiological alterations, EEG recordings and spectral analysis were also performed in cyclophosphamide-treated mice. Street rabies virus-infected and immunosuppressed mice showed identical physiopathological changes as those observed in immunocompetent mice. The implication of these viral-induced electrophysiological alterations in the context of the pathogenic mechanisms of rabies virus is discussed.

Animals↗

PubMed1991

[Effects of neutron-gamma or gamma irradiation on plasma coagulation factors. Effect of a substitution treatment].

Neutron-gamma irradiation of the baboon at lethal dose altered the plasma clotting factors and induced a fibrinoformation alteration which occurred shortly before death. These disturbances, which were not found after gamma irradiation, could explain the importance of the haemorrhagic syndrome. Treatment by P.P.S.B. (factors II, VII, X and IX) counteracted the alterations of the plasma clotting factors, but had no influence on the lethality nor on the fibrinoformation alteration which seems to be an important cause of death.

Animals↗

PubMed1990

In vivo spectrophotometric determination of striatal acetylcholinesterase activity: the modulation induced by the antidepressant amitriptyline.

A new technology called in vivo spectrophotometry was applied to the quantitative determination of the variations in local acetylcholinesterase (AChE) activities. Repeated measurements of the enzyme activities in the same live animal allowed the study of the in vivo inhibition of AChE by amitriptyline. Interactions between AChE and this tricyclic antidepressant were investigated at the striatal level in anesthetized rats. In this anesthetized model, AChE assays were shown to be stable for approximately 8 h. The dose-effect relationship was explored in the 2.5- to 50-mg/kg amitriptyline range. A reversible inhibition was observed after acute amitriptyline administration. The maximum of inhibition appeared between 90 and 210 min after the intoxication and reached up to 22% for the 50-mg/kg dose. The threshold dose was established as 8 mg/kg. Evidence for an indirect interaction between tricyclic antidepressant and AChE was demonstrated when the total integrity of the biological system was preserved.

Acetylcholinesterase↗

PubMed1989

HIV-2 in rhesus monkeys: serological, virological and clinical results.

Diseases induced by animal retroviruses are not considered to be good models for the human acquired immunodeficiency syndrome (AIDS) at present. The lack of an animal model for the human immunodeficiency virus (HIV) infection presents a main problem in the complete understanding of the pathogenesis of HIV-mediated diseases. Because of the homologies between simian immunodeficiency virus (SIV) and HIV-2, we inoculated rhesus monkeys with HIV-2 and HIV-2 adapted in vitro to monkey cells. One of the ten animals inoculated developed clinical symptoms that might be related to the infection with HIV-2.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Sleep abnormalities with REM disorder in experimental Creutzfeldt-Jakob disease in cats: a new pathological feature.

Alterations in sleep organization were studied during the clinical phase of experimental Creutzfeldt-Jakob disease (CJD) in cats. Twenty months after intracerebral inoculation of a CJD agent, cats developed clinical signs including behavioral changes, diminished grooming activity, dysmetria, startle reflex, myoclonus, and unusual sleep abnormalities. Rapid eye movement (REM) sleep displayed a new and irreversible organization, with a continuous and constant pseudoperiodic pattern of rapid eye movements, synchronous with diffuse bursts of cortical abnormalities and with ponto-geniculo-occipital (PGO) wave activity. Computer analysis revealed a constant morphology of cortical bursts and their temporal relationship with ocular episodes. Induction of PGO wave activity with benzoquinolizine derivative Ro 4-1284 demonstrated the PGO-dependent nature of the cortical alterations. Abnormal unresponsive states were observed during REM sleep phases and arousal thresholds were increased in CJD cats during REM sleep. The percentages of wakefulness and slow-wave sleep were reversed in these animals. Preliminary neuropathological observations included discrete to minimal spongiosis of cerebral gray matter and a remarkably focalized intracytoplasmic vacuolation in neurons of the raphé system. Our findings suggest that particular neuronal systems involved in sleep regulation are impaired in CJD cats.

2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-↗

PubMed1987

Spectrophotometry in vivo, a technique for local and direct enzymatic assays: application to brain acetylcholinesterase.

In vivo enzymology is not widely studied due to the lack of a well-adapted technology. We have developed a system that allows local and long-term spectrophotometric assays in brain tissue of live animals. It utilizes a miniaturized optical probe consisting of a multibarrel micropipette for reagent injections and optical fibers for light absorption measurements. We have applied this system to the colorimetric determination of brain acetylcholinesterase activity in rats. The reproducibility of the assay was demonstrated by repetitive assays over 24 hr, its specificity was established through the use of a highly specific organophosphorus inhibitor, and the activities measured in different brain areas agreed with the known distribution of acetylcholinesterase. No electroencephalographic abnormalities and no change in vigilance level were observed in the experimental animals. This methodology should prove to be useful for the colorimetric measurement of different enzymes or metabolites in various organs.

Acetylcholinesterase↗

PubMed1986

Electrophysiological and sleep alterations in experimental mouse rabies.

Changes in the spontaneous brain electrical activity and sleep organization were investigated in 5 mice strains during the evolution of experimental fixed rabies infection. Cortical electrodes were chronically implanted for continuous EEG recording and spectral analysis until death. Three evolutionary phases were individualized. The initial phase exhibited alterations of sleep stages, REM sleep disappearance, pseudoperiodic facial myoclonus and first clinical signs. The mature phase was characterized by a generalized EEG slowing (2-4 cycles/s). The terminal phase occurring with extinction of hippocampal rhythmic slow activity showed a flattening of cortical activity. The brain electrical activity ceased about 30 min before the cardiac arrest. Paroxysmal activities appeared during the course of the disease as bursts of rhythmic slow waves, pseudoperiodic spikes or occasionally ictal epileptic discharges. Spectral analysis revealed a progressive and characteristic clustering of the EEG frequency band power values. The spread of infection in the CNS was monitored by specific immunofluorescence studies which revealed the presence of rabies virus antigen in the pons, the cerebellum, the thalamus and the cortex during the initial phase. The pyramidal field of the hippocampus was infected during the mature phase but the gyrus dentatus was never infected even at the terminal phase. These studies show that particular neuronal functions are impaired during rabies virus infection suggesting that neuronal alterations may be involved in the pathogenic mechanisms leading to lethality.

Animals↗

PubMed1986

New findings on sleep stage organization in squirrel monkeys.

The EEGs of 11 squirrel monkeys were studied during nocturnal sleep under conditions maintaining relative freedom of movement and minimal social intercourse. For the amount and partition of the different sleep stages, the present findings markedly differ from previous observations in experimental restrained conditions. Six sleep stages were defined by both EEG and spectral analysis criteria. Wakefulness, which occurred during the first period of the night, was more abundant (45%) and deep sleep (SIII) and REM sleep were less abundant (SIII: 5.1%; REM: 3.1%) in unrestrained squirrel monkeys. With predominant light sleep (85%), less abundant deep sleep and a REM sleep organization in short episodes, the sleep pattern in this New World monkey appeared fragmented and close to African monkey sleep.

Animals↗