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Biomedical subjects

M Le Poncin-Lafitte

Publications and source records attributed to M Le Poncin-Lafitte.

At least 19 recordsLinked to original sources
PubMed1986

[Protective effects of Ginkgo biloba extract on the early rupture of the hemato-encephalic barrier in the rat].

During the hours immediately following an hypertensive burst or a cerebral ischemia induced by the intracarotid administration of microspheres, damage to the blood brain barrier can be observed with molecules of low molecular weight, such as angiotensin, whereas albumin or large proteins will not yet have been able to cross over and there is virtually no edema. Gingko biloba extract causes the brain uptake index of angiotensin hypertensive animals. This effect is proportional to the dose of extract used (500-100 mg/kg). A similar effect can be observed in animals showing embolism in one hemisphere. The process can therefore doubtlessly be explained by the stabilizing effect of Ginkgo biloba on membranes.

Angiotensin II↗
PubMed1985

Multiparametric imaging of blood flow and metabolism after middle cerebral artery occlusion in cats.

In anesthetized adult cats, acute stroke was produced by transorbital occlusion of the left middle cerebral artery. A battery of imaging techniques was used for simultaneous evaluation of regional blood flow, glucose utilization, protein synthesis, pH, and the regional tissue content of glucose, ATP, and potassium. The electrophysiological impact of stroke was monitored by EEG frequency analysis and recording of somatosensory evoked potentials. Two hours after vascular occlusion, a close correlation existed between the degree of electrophysiological changes and biochemical alterations, in particular with the extent of tissue acidosis, ATP depletion, decrease of tissue potassium content, and suppression of protein synthesis. However, there was only a poor correlation with blood flow and glucose utilization. Both of these exhibited a greatly inhomogeneous pattern with regions of reduced, normal, or increased rates. In areas remote from the infarct, the content of biochemical substrates was normal but blood flow was reduced globally by approximately 50% and glucose utilization by approximately 20%. An anatomically defined regional pattern of cerebral or cerebellar diaschisis was not observed. It is concluded that during the acute phase of stroke, imaging of blood flow and glucose utilization does not provide an accurate estimate of the actual functional or metabolic disturbance. For the clinical evaluation of the development or treatment of stroke, in consequence, alternative noninvasive techniques such as imaging of protein synthesis and/or pH may be more relevant.

Adenosine Triphosphate↗
PubMed1985

Learning and cholinergic neurotransmission in old animals: the effect of Hydergine.

In the present work, a study of the number of functional receptors has been made with 3HQNB given to resting awaken animals during a learning process. Ageing leads to a decrease in the ability of learning associated with an increase in the number of large movements. The number of cholinergic receptors is also reducel if we compare 22 month old animals with 4 month old animals maintained under usual conditions. Learning conditioning leads to a stimulation of the cholinergic system with a release of acetylcholine. The mediator takes the 3HQNB out of its fixation areas which causes an apparent decrease in the number of receptors. This result is more significant in young animals than in aged ones because of the possibility of activation in the cholinergic system. The treatment by dihydroergotoxine partially re-establishes the learning abilities in animals and, at the same time, increases the number of cholinergic receptors This effect could explain the actions of this drug on the memory process in ageing persons.

Aging↗
PubMed1984

Iodoamphetamine as a new tracer for local cerebral blood flow in the rat: comparison with isopropyliodoamphetamine.

Rats were injected with iodoamphetamine synthesized and labeled with 125I or with 125I- isopropyliodoamphetamine , a molecule of established value for the determination of local cerebral blood flow. The blood kinetics, tissue distribution, and brain uptake index for each tracer exhibited practically no differences. Autoradiographic quantification of the local cerebral blood flow, calculated according to the microsphere model, produced identical results for both molecules. However, compared with the values reported for other tracers, our values constituted an underestimation of white matter blood flow and a more real estimation of hippocampal flow. It is concluded from the brain uptake of the derivatives of both amphetamines during the first minutes following their injection that these tracers can be used as a chemical microembolus for the measurement of local cerebral blood flow.

Amphetamines↗
PubMed1984

Simultaneous study of cerebral blood flow, vascular bed and deoxyglucose in aged rats. Effects of two dihydrogenated rye ergot alkaloids.

The influence of aging and the effects of treatment with dihydrogenated rye ergot alkaloid on cerebral hemodynamics and metabolism were studied in Long-Evans rats. Cerebral blood flow (CBF) was not affected by aging whereas the vascular bed and the uptake of deoxyglucose were significantly lower in aged than in young rats. 20 days after ligation of a carotid artery the blood flow on the same side of the brain, the vascular bed and the uptake of deoxyglucose were significantly lowered in aged rats as opposed to young rats. The second carotid artery was ligated 1 h before the animals were sacrificed: in the corresponding cerebral hemisphere the blood flow was found to be significantly lowered in young rats and even more so in aged rats. These results show that young rats are more likely to adapt to an acute or chronic circulatory deficiency than aged rats. Dihydroergocryptine ( DHEC , 0.1 mg/kg/day for 5 days, p.o.) reduces CBF and the vascular bed in aged rats, as opposed to dihydroergotoxine ( DHET , 5 X 0.1 mg/kg/day p.o.). The uptake of deoxyglucose was not influenced by the treatments. After ligation of the carotid arteries, treatment with DHEC and DHET induced an increase in CBF without any change in the vascular bed and, in the case of DHEC only, there was a significant increase in the uptake of deoxyglucose in the cerebral hemisphere submitted to acute circulatory deficiency. DHEC and DHET thus exerted significant effects on cerebral metabolism and hemodynamics in the aged rats after repeated oral treatment.

Aging↗
PubMed1984

Simultaneous study of haemodynamic, metabolic and behavioural sequelae in a model of cerebral ischaemia in aged rats: effects of nicergoline.

Unilateral cerebral ischaemia was induced in 18-month-old Long-Evans rats by injection of 2,000 labelled microspheres (phi 50 microns) into the carotid blood stream. This results in an ipsilateral decrease in cerebral blood flow, development of severe oedema and modifications of glucose uptake and consumption. Furthermore, this ischaemia led to a deterioration of the avoidance response in conditioned animals. All these disturbances, including the cerebral oedema, diminished with nicergoline pretreatment.

Aging↗
PubMed1983

[Learning, hemodynamic and metabolic attendant effects in aged animals after an acute ischemic accident].

The effects of ageing in normal and pathological rats were studied. Learning (spatio-temporal test) was measured simultaneously with the local cerebral blood flow, determined by a diffusible indicator (iodoantipyrine) and with the uptake and consumption of glucose, determined by the deoxyglucose. Normal ageing disturbs the learning with a decrease in acquisition speed and an increase in the number of errors. Furthermore, normal ageing induces a decrease in glucose uptake and in glucose consumption in the brain structures such as hippocampus or corpus striatum, with only a slight decrease in local cerebral blood flow. Dihydroergotoxine partially reestablishes the performances of the rats and increases the glucose consumption in the areas involved in learning. Pathological ageing, produced by the administration of microspheres and corresponding to the multi-infarct dementia, is correlated to a large decrease in glucose consumption and local blood flow. Dihydroergotoxine treatment partially suppresses the micro-infarct effects before the reestablishment of rat performance in behavioral tests.

Acute Disease↗
PubMed1983

[Chemical and pharmacological aspects of cerebral cellular tracers].

Among the iodophenylalkylamines studied and labelled with iodine 125 or iodine 123, N-isopropyl-iodo-amphetamin (IAMP) was selected and proposed as tracer for blood flow, a "chemical embolus" having almost 100% extraction in the brain. A new way of obtaining N-isopropyl-p-iodo-amphetamin is proposed and the easily-applied exchange reaction with iodine 125 or 123 gives a product with a radiochemical purity of more than 96% and an unexchanged radioactive iodine content of less than 1%. The pharmacokinetic study of this product in the Wistar rat showed distribution in three compartments and the appearance of a steady state by the fourth minute. The target organs are the lungs, liver and brain. The latter receives 3% of the radioactivity and the autoradiographic study shows that the early distribution in the brain for IAMP closely equals the blood flow as found by a diffusible indicator. In the first hour, the redistribution is very low and at this time although IAMP is proposed for the study of regional blood flow, it does not exactly determine the flow but rather mirrors cell activity.

Amphetamines↗
PubMed1983

Demonstration of vascular redistribution after carotid clamping in rats.

In Long Evans rats, the vertebral arteries supply only the brain stem. Simultaneous application of clamps to both carotid arteries results in a considerable fall of cerebral blood flow and eventually death. If an interval of about 4 days is allowed between the clamping of the 2 carotids, redistribution of blood flow takes place. Owing to this mechanism, 50% of the rats survive with a satisfactory restoration of cerebral blood flow.

Animals↗
PubMed1982

[Cerebral ischemia after ligature of both carotid arteries in rats: effect of ginkgo biloba extracts (author's transl)].

Simultaneous ligature of both carotid arteries in Long Evans rats results in death for all animals. 50% of the animals survive if the ligatures are separated by a four-day interval. Studies of variations in cerebral blood flow according to the time interval between the two ligatures show that alternative vascularization develops and that the balance between both hemibrains is restored. After giving L-dopa3H to animals with ligature of both carotids, increased synthesis of cerebral dopamine 3H and norepinephrine 3H can be demonstrated. When animals are given extracts of Ginkgo biloba leaves prior to carotid ligatures, survival rate is improved and dopamine synthesis increased, without marked changes in cerebral blood flow. This is related to increased brain cell activity in spite of hypoxia due to carotid ligature.

Animals↗
PubMed1982

[Cerebral blood flow metabolism and behavior following cerebral infarction in the awake rat (author's transl)].

In the awake rats, a cerebral ischemia was performed by means of 2,000 microspheres administered into the internal carotid via a chronic catheter. After a coma lasting for a few minutes and a 24-48 h palsy, the Long Evans rats gradually recover a normal behavior. The acquisition of an avoidance response is deeply disturbed by microembolization but the capacities of memorization reappeared with the regression of oedema. 7 days after embolization, the cerebral blood flow in ischemized hemisphere was still significantly decreased, and in spite the glucose consumption was identical in ischemized and non ischemized side. This latter parameter is a better index of the cell activity. This model in the awake rat was proposed for the study of molecules used in cerebral ischemia without interference of anesthetics drugs.

Animals↗
PubMed1982

Effects of naftidrofuryl on cerebral hemodynamics, metabolism and function after a retracted ischaemia.

Unilateral microemboli were formed in the brains of Long Evans rats by means of an intracarotid injection of microspheres (50 mu). This embolization resulted in a decrease in blood flow, severe cerebral oedema and a modification of glucose uptake. Furthermore, these microemboli affected a conditioned avoidance response. Naftidrofuryl enabled a better recovery of the processes involved in the expression of acquisition. This has been related to a decrease in the development of oedema on one side and to a better glucose uptake on the other. These data demonstrated that naftidrofuryl influences the sequelae of rapidly regressive ischaemia.

Animals↗