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Biomedical subjects

P Lacombe

Publications and source records attributed to P Lacombe.

At least 91 records · Page 5Linked to original sources
PubMed1994

Widespread attenuation of the cerebrovascular reactivity to hypercapnia following inhibition of nitric oxide synthase in the conscious rat.

Despite the increasing number of publications devoted to the cerebrovascular role of NO, its precise influence in awake animals is still poorly characterized. The effect of nitric oxide synthase (NOS) inhibition on the cerebrovascular CO2 reactivity was therefore studied in conscious rats. Regional CBF was measured using the [14C]iodoantipyrine technique and brain tissue sampling. The CO2 reactivity was determined 60 min after administration of 30 mg kg-1 N omega-nitro-L-arginine methyl ester (L-NAME). Blockade of NOS by L-NAME significantly decreased CBF in all 11 brain regions studied (-17 to -49%) and increased arterial pressure from 117 +/- 12 to 147 +/- 11 mn Hg. In control conditions, CO2 responsiveness ranged from 1.3 +/- 0.4 in the hypophysis to 6.4 +/- 0.6 ml 100 g-1 min-1 mm Hg-1 in the parietal cortex. Following L-NAME injection, the reactivity to hypercapnia was significantly attenuated in all structures, the magnitude of the reduction ranging from 57% in the medulla to 74% in the cerebellum. This result shows that NO is an important mediator of the hypercapnic vasodilation in the conscious rat.

Amino Acid Oxidoreductases↗
PubMed1993

High flow coronary fistula closure by percutaneous coil packing.

Few cases of transcatheter coronary fistula closure have been reported. High flow coronary fistulae are usually treated by surgery. This case report presents a 5.4 liters/min flow coronary fistula percutaneously closed by steel coils. This large flow needed the packing of 25 coils, 10-15 cm long, for its total occlusion.

Arteriovenous Fistula↗
PubMed1993

The cerebrovascular effects of physostigmine are not mediated through the substantia innominata.

This study sought to determine whether the cortical cholinergic projections from Meynert's nucleus are actually the target of the cholinesterase inhibitor physostigmine, which presents the ability to increase cortical blood flow. To this aim, the multiregional cerebrovascular effects of physostigmine in rats with and without lesion of the substantia innominata (SI), the equivalent of Meynert's nucleus of primates, were investigated. Unilateral SI lesions were made using ibotenic acid in three groups of rats. Four to 11 days later, the cortical choline acetyltransferase (ChAT) activity was measured in one group to assess the efficacy of the lesion. In the two other groups, the regional cerebral blood flow was measured using the [14C]iodoantipyrine technique, under physostigmine (0.2 mg/kg/h iv) or control conditions. SI lesion induced 27-59% fall in cortical ChAT activity in the ipsilateral hemisphere with the frontal area most affected. Despite these large biochemical differences, the lesion had little cerebrovascular effects. Side-to-side blood flow differences did not exceed 11% and did not strictly overlap the ChAT depletion. Physostigmine increased flow (38-66%) in all cortical areas, with no frontal predominance. Despite these considerable vasodilations, there were no significant differences between the lesioned and the intact hemisphere, nor any significant interaction between physostigmine and SI lesion. Thus, physostigmine does not actually activate the SI neuron terminals. This result suggests that cholinesterase inhibitors cannot be used as presynaptic markers of the cholinergic activity of this nucleus and casts doubts on their specificity as enhancement therapeutic agents in Alzheimer's disease.

Animals↗
PubMed1993

Effects of dorsal raphe nucleus stimulation on cerebral blood flow and flow-metabolism coupling in the conscious rat.

In the present study, we have investigated the effects of an activation of the ascending serotonergic pathway on the cerebral blood supply to a number (63) of well-defined neuroanatomical structures. To this end, we have measured the local cerebral blood flow during electrical stimulation of the dorsal raphe nucleus. Measurement of regional blood flow was performed in the conscious rat through the use of the [14C]iodoantipyrine autoradiographic technique. Stimulation of the dorsal raphe nucleus induced increases (> 15% compared to control) in cerebral blood flow in 17 structures of which statistical significance (P < 0.05) was achieved in nine; raphe stimulation significantly decreased flow in three regions. The greatest increases (+71 and +46%) were found in the frontal sensorimotor and posterior parietal cortices. Other increases were noted in relay stations of the extrapyramidal and limbic systems. Stimulation induced a decrease in two regions of the primary auditory system and in the lateral habenular nucleus. These results show that activation of the serotonergic pathway in the conscious rat effects regional cerebral blood flow heterogeneously, differing from the widespread increase in glucose utilization that we previously observed using the same experimental paradigm. Statistical analyses indicated that activation of the dorsal raphe nucleus resulted in a global modification of the flow-metabolism ratio. Moreover, in 19 out of 31 regions analysed, this ratio is significantly altered as compared to control. The dichotomy between raphe-induced changes in flow and glucose-metabolism could be explained by one or both of two hypotheses; firstly there could be a direct serotonergic innervation of cerebral resistance vessels; secondly, during raphe stimulation it could be that glucose use is not the primary determinant of tissue perfusion.

Animals↗
PubMed1993

[Disclosure by neurologic signs of right subclavian aneurysm. Post-traumatic aneurysm?].

BACKGROUND: Aneurysms of the subclavian artery are rare in childhood and may be due to traumatic, infectious or congenital causes. CASE REPORT: A 15 year-old boy presented with a sudden left visual disturbance plus decreased muscle strength and paresthesias of the left arm; these manifestations disappeared within 15 minutes. His neurological examination on admission was normal. The right arm radial pulse was weak and the blood pressures of the right and left arms were significantly different. Doppler showed a right subclavian artery aneurysm containing several clots, that was confirmed by angiography. There were no signs of inflammation or indication of autoimmune disease. This aneurysm might have been caused by trauma as the patient had had a violent cervical traumatism after a diving accident 2 years earlier. The aneurysm was surgically removed and the right vertebral artery arising from it was reimplanted. Histological examination of the aneurysm gave no evidence of etiology. The post-surgical MRI showed no brain abnormaly. CONCLUSIONS: This aneurysm is probably of post-traumatic origin. The cerebral disturbance could be due to embolism or transient ischemia; the latter is more compatible with the normal NMR.

Adolescent↗
PubMed1992

Cerebrovascular nerve fibers immunoreactive for tryptophan-5-hydroxylase in the rat: distribution, putative origin and comparison with sympathetic noradrenergic nerves.

The distribution of serotonergic nerves in major basal and isolated small pial arteries (diameter > or = 50 microns) was investigated immunohistochemically using an antibody directed against tryptophan-5-hydroxylase (TPOH), the rate-limiting enzyme in the synthesis of 5-hydroxytryptamine (5-HT or serotonin), and compared to that of the noradrenergic system labeled for the selective noradrenaline (NA) synthesizing enzyme, dopamine-beta-hydroxylase (DBH). In addition, the possible peripheral and/or central origins of the cerebrovascular serotonergic (TPOH-positive) nerve fibers were examined. Strongly labeled TPOH-immunoreactive (TPOH-I) fiber bundles were observed in major basal arteries and gave rise to small varicose fibers organized in a meshwork pattern. The highest density of TPOH-I fibers was found in the middle cerebral artery followed by the anterior cerebral and the anterior communicating arteries, with a moderate to low density in the internal carotid and the vertebro-basilar trunk. Of the isolated pial arteries, only the larger ones (diameter > 75 microns) were significantly endowed with TPOH-I varicose fibers. However, free floating TPOH-I nerves were observed coursing through the pia-arachnoid membranes and reaching small pial vessels. In contrast, DBH-I nerve fibers were fine and were visualized primarily as numerous varicosities distributed in a circumferential manner around the vessel wall. A very high density of DBH-I varicosities was seen in the rostral part of the circle of Willis, with the internal carotid being the most richly supplied followed by the anterior cerebral and the anterior communicating arteries; comparatively, the middle cerebral artery was moderately innervated. The differences in distribution pattern and density between TPOH-I and DBH-I cerebrovascular fibers clearly suggest that these two innervation systems are not exactly superimposable. Superior cervical ganglionectomy caused an almost complete disappearance of TPOH-I nerves in all vascular segments, with some residual fibers in selected vessels. Lesion of the central serotonergic component with the neurotoxin 5,7-dihydroxytryptamine had virtually no effect on the TPOH-I fibers in the major basal and isolated pial arteries. These results strongly suggest that the serotonergic innervation of major cerebral as well as pial arteries has a prominent peripheral origin closely related to the sympathetic system. Processing of superior cervical ganglion slices for TPOH immunocytochemistry, however, failed to unequivocally detect TPOH-I neurons.

5,7-Dihydroxytryptamine↗
PubMed1992

Inoue balloon usefulness in case of failure to stabilize bifoil catheter balloons during percutaneous mitral valvotomy.

A new bifoil balloon catheter has been used in the last 120 percutaneous mitral valvotomies carried out in our institution. The shaft segment between the two balloons of the bifoil catheter has been adjusted to the guide-wire diameter, allowing its introduction through a 14F sheath. This thinner shaft does not always offer enough back up to the balloons during inflation. An Inoue balloon replaced an unstable bifoil balloon in 5 cases of mitral dilatation failure due to balloon instability, regularly providing firm stability until full balloon inflation.

Adult↗
PubMed1992

Spreading depression induces prolonged reduction of cortical blood flow reactivity in the rat.

The purpose of the present study was to examine the dynamic aspects of the cerebrovascular events occurring during and up to 2 h following cortical spreading depression (CSD) in the rat, using the mass spectrometry technique which enables continuous measurements of the cortical tissue PO2 and PCO2 and repeated blood flow measurements (CoBF) by helium clearance. We mostly sought to determine whether cortical perforation by a stimulation electrode induced long-lasting perturbation of the cortical vasoreactivity to hypercapnia and basal forebrain electrical stimulation. Cortical perforation in the animal under alpha-chloralose anesthesia, chronically implanted with mass spectrometry probes, was associated with biphasic changes in tissue gases. PO2 first briefly decreased (-7.8%) and then strongly increased (+79%) while PCO2 changed in the opposite direction (+7%, -13%) in the ipsilateral frontal cortex. Qualitatively similar changes occurred in the ipsilateral parietal cortex. The CoBF measurements showed a marked vasodilation (131 and 108% in the frontal and parietal cortex, respectively) in parallel with the PO2 increase, followed by a prolonged (60 min), moderate hypoperfusion (maximum -17% at 20 min after CSD). There was a pronounced reduction of vascular reactivity to both hypercapnia (20.3% of the control response) and substantia innominata stimulation (1/6 of the response obtained 80 min later) at 10 min after CSD. Both reactivities progressively recovered in approximately 2 h. Since the issue of CSD in human has become a popular hypothesis for migraine, the reduced cerebrovascular reactivity could constitute the basis of a test for the involvement of CSD in migraine.

Animals↗
PubMed1992

Percutaneous recanalization of a renal artery in aortic dissection.

Chronic renal failure acutely worsened in a patient with a type B aortic dissection. Aortography revealed an occlusion of the left renal artery without renal intimal tear. Percutaneous recanalization, performed with a self-expandable stent, resulted in improvement in the renal function. This technique offers a new therapeutic choice in patients with visceral complications of aortic dissection.

Aortic Dissection↗
PubMed1992

[Compression of the left renal artery by the diaphragm].

Investigation of hypertension in a 21 year old man detected the presence of stenosis of the left renal artery. The arteriographic appearance of this stenosis, associated with the presence of stenosis of the celiac trunk of identical morphology, was suggestive of extrinsic pressure by the diaphragm and excluded endoluminal dilatation. Section of the left diaphragmatic crus released the renal artery and celiac trunk with complete recovery from the hypertension.

Adult↗
PubMed1991

Effects of dorsal raphe stimulation on cerebral glucose utilization in the anaesthetized rat.

The aim of this study was to determine the effects of electrical stimulation of the dorsal raphe nucleus on local cerebral glucose utilization (LCGU) in the alpha-chloralose anaesthetized rat. Activation of the dorsal raphe nucleus effected significant increases in LCGU, ranging from 13 to 52% in 8 brain structures out of 33 investigated. Increases were restricted to extrapyramidal and limbic non-specific areas, and no modifications were observed in cortical areas. The comparison with our previous results, showing that a similar raphe activation induced a global decrease in local cerebral blood flow, suggests that the ascending serotonergic system may be of importance in the regulation of the cerebral circulation.

Anesthesia↗
PubMed1991

[Quantitative two-dimensional echocardiography in acute pulmonary embolism].

Emergency two-dimensional echocardiography was carried out in 61 patients admitted to an intensive care unit for suspected pulmonary embolism, in order to find out whether signs of acute cor pulmonale (ACP) were present or absent. Pulmonary angiography was subsequently performed to confirm or infirm the diagnosis of pulmonary embolism. Only 7 out of 13 patients with normal echocardiography had no pulmonary embolism. All other patients who showed echocardiographic signs of ACP had pulmonary embolism. Thus, the finding of normal echocardiographic results does not necessarily exclude a diagnosis of pulmonary embolism. Conversely, the presence of echocardiographic signs of ACP in a suggestive context provides a near-certain diagnosis of pulmonary embolism.

Acute Disease↗
PubMed1991

Hypercapnia and stimulation of the substantia innominata increase rat frontal cortical blood flow by different cholinergic mechanisms.

This study was designed to further investigate in the rat how the cerebrovascular response to excitation of the projections from the substantia innominata (SI) to the frontal cerebral cortex was mediated. Local cortical blood flow (CoBF) (by helium clearance) and tissue gas partial pressures (pO2, pCO2) (indices of energy metabolic activity) were measured in the frontal cortex in unanesthetized adult Fischer rats in response to electrical stimulation of the SI and, for comparison, in hypercapnic conditions. SI stimulation and hypercapnia increased CoBF to a similar extent (+92% and +106%, respectively). Differences between the changes in tissue gas partial pressures under hypercapnia and SI stimulation suggest that different patterns of flow-metabolism coupling prevail in the mechanisms underlying the two cerebrovascular responses. Cortical pCO2 increased under hypercapnia, but decreased during SI stimulation, indicating that a 'vascular' mechanism (i.e. independent of energy metabolism activation) is at least partly responsible for the flow increase in the latter condition. However, cortical pO2 rose more under hypercapnia than during SI stimulation, suggesting that oxygen consumption, and hence energy metabolism, was increased in the latter case. The ability of the acetylcholine esterase inhibitor physostigmine and the muscarinic receptor antagonist scopolamine to modulate the responses was quantified. In both experimental conditions, CoBF changes were potentiated by 0.15 mg/kg/h physostigmine (by factors of about 2). In contrast, 1 mg/kg scopolamine reduced by 65% the frontal CoBF response elicited by SI stimulation but was without effect on the response to hypercapnia. Thus, although a cholinergic mechanism may be implicated in both responses, activation of muscarinic receptors appears to occur when the stimulation originates from the SI but not from the hypercapnia.

Animals↗