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Biomedical subjects

J Poirier

Publications and source records attributed to J Poirier.

At least 127 records · Page 7Linked to original sources
PubMed1993

Apolipoprotein E polymorphism and Alzheimer's disease.

Apolipoprotein E (apoE) is associated with Alzheimer's neurofibrillary tangles and beta-amyloid protein in senile plaques. It also appears to play an important part in the redistribution of lipids that follows deafferentation and neurodegeneration in the brain. The gene for apoE is on chromosome 19, within the genomic region previously associated with late-onset familial Alzheimer's disease (AD). We have studied apoE phenotype expression and the corresponding allele frequencies (epsilon 2, epsilon 3, epsilon 4) in 91 patients with sporadic AD and 74 controls. There was a significant association between epsilon 4 and sporadic AD (epsilon 4 frequency 0.380 in AD and 0.122 in controls, p < 0.01). Analysis of epsilon 4 in whom AD develops this tended to happen earlier in life than in those with epsilon 3 or epsilon 2. The epsilon 4/AD association was more pronounced in women. Octogenarians with AD had an epsilon 4 allele frequency that was 3 times higher than one reported, in a different study, in healthy octogenarians. ApoE may be an important susceptibility factor in the aetiopathology of sporadic AD.

Age Factors↗
PubMed1993

[3H]phorbol ester binding sites and neuronal plasticity in the hippocampus following entorhinal cortex lesions.

Entorhinal cortex lesioning (ECL) produces a loss of more than 80% of the synapses in the outer molecular layer of the hippocampus. However, the loss of synapses is transient. Beginning a few days after denervation, new synapses are formed, virtually replacing the lost inputs within 2 months. Synaptic remodelling induced by ECL is associated with specific modifications of neurotransmitters, hormones and growth factors. Particularly, protein kinase C (PKC) plays important functional roles in receptor-mediated transmembrane signal transduction. PKC is also involved in various aspects of synaptic plasticity, such as cellular growth and differentiation. To investigate further the potential roles of PKC in synaptic plasticity observed in the ECL model, [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding, a putative marker of PKC, was examined at different times post-lesion. [3H]PDBu binding sites transiently decreased bilaterally at 2 and 8 days post-lesion (20%) in different laminae and sub-fields of the rostral hippocampus but returned to control values at 14 and 30 days post-lesion. In caudal portion of the hippocampus, [3H]PDBu binding was also decreased at 2 days post-lesion but only on the contralateral side. Interestingly, [3H]PDBu binding sites in the cortex increased by up to 30% in the contralateral side while no significant change was observed in the ipsilateral side at any time post-lesion. It is known that PKC can be regulated by different systems following alterations of neuronal and glial activity. We suggest that these could be involved in the response of PKC and [3H]PDBu binding sites following ECL. Moreover, PKC seemed to be modified in different brain areas in neuronal inputs from the entorhinal cortex and the subsequent reinnervation process.

Acetylcholinesterase↗
PubMed1993

Pseudotumoral neuro-Behçet's disease.

Pseudotumoral presentation of Neuro-Behçet's disease has been described before. The diagnosis may be difficult obtain in patients without mucosal, cutaneous, and ocular signs. We report the observation of a young patient suffering from a right hemiparesis with computed-tomographic (CT) features suggestive of a thalamocapsular expanding lesion. Histologic study of brain biopsy tissue ruled out a tumor but did not show any specific diagnosis. The patient improved with steroid therapy.

Adult↗
PubMed1993

Entorhinal cortex lesion induces differential responses in [125I]insulin-like growth factor I, [125I]insulin-like growth factor II and [125I]insulin receptor binding sites in the rat hippocampal formation.

The hippocampus can be induced by deafferentation to selectively reorganize its neuronal input. Entorhinal cortex lesion, which causes degeneration of the perforant pathway, evokes sprouting of septal afferents as well as glutamatergic commissural/associational fibers in the deafferentated zone of the molecular layer of the dentate gyrus. Although the process of reactive synaptogenesis that follows deafferentation has been extensively studied, at present little is known about its molecular basis and the mechanism of initiation. In this study, following unilateral lesion of the entorhinal cortex, the time-course of possible alterations of insulin-like growth factors I and II, and insulin binding sites were evaluated by in vitro quantitative receptor autoradiography. [125I]Insulin-like growth factor I receptor binding sites did not exhibit any significant variation between the contralateral and ipsilateral hippocampal formation at any time periods following lesion except in the molecular layer of the dentate gyrus (P < 0.05) at day 8. However, when compared with the unlesioned animals, a differential time-dependent response of [125I]insulin-like growth factor I binding sites was noted in selective layers of the hippocampus. [125I]Insulin-like growth factor II receptor binding sites showed a significant decrease (P < 0.05) in the ipsilateral granular cell layer of the dentate gyrus only at day 14 post lesion. Interestingly, compared to controls, a dramatic bilateral increase (P < 0.05) in [125I]insulin-like growth factor II binding was evident between days 1 and 8 in most layers of the hippocampal formation. A lesion-induced bilateral increase (P < 0.05) in [125I]insulin binding sites was evident in all layers of the hippocampus between two to eight days and at 30 days post lesion. In selective layers, however, a significant increase (P < 0.05) in [125I]insulin binding sites was also observed at days 1 and 14 after lesion. These results, which are compatible with the process of degeneration and/or sprouting of the terminal fibers, suggest possible involvement of insulin-like growth factors and insulin in the sequence of molecular events that occur to facilitate neuronal repair and to promote neuronal survival following entorhinal cortex lesion.

Afferent Pathways↗
PubMed1993

Cholesterol synthesis and lipoprotein reuptake during synaptic remodelling in hippocampus in adult rats.

Apolipoprotein E is synthesized and secreted by astrocytes in the hippocampus following lesions of the entorhinal cortex. It was proposed that apolipoprotein E, by analogy to its role in cholesterol transport in circulation, could be involved in the salvage and reutilization of non-esterified cholesterol released during terminal breakdown. The salvaged cholesterol could then be transported to neurons by apolipoprotein E-complexes and taken up via the apolipoprotein E/apolipoprotein B (low-density lipoprotein) receptor. To test this hypothesis, we have examined low-density lipoprotein receptor binding in brain sections of rats undergoing hippocampal reinnervation. The number of neuronal cells labelled by fluorescent Dil-low-density lipoprotein as well as the density of [125I]low-density lipoprotein binding sites in the dentate gyrus were found to increase in parallel with the extent of cholinergic reinnervation occurring in the deafferented hippocampus. In contrast, hippocampal cholesterol synthesis fell by more than 60% at eight days post-lesion, but eventually returned to control levels at 30 days post-lesion. The transient loss of cholesterol synthesis coincided with a peak in hippocampal apolipoprotein E expression. A concomitant accumulation of sudanophilic lipids (cholesterol esters and phospholipids) was detected in the outer molecular layer of the dentate gyrus and in the hilar region. The present findings suggest that non-esterified cholesterol released during terminal breakdown is esterified, transported via the apolipoprotein E transport system to neurons undergoing reinnervation, and take-up through the low-density lipoprotein receptor pathway where it is presumably used as a precursor molecule for the synthesis of new synapses and terminals.

Afferent Pathways↗
PubMed1993

Entorhinal cortex lesions transiently alter glucocorticoid but not mineralocorticoid receptor gene expression in the rat hippocampus.

Entorhinal cortex lesions destroy an important hippocampal input and lead to axonal sprouting in the dentate gyrus. Glucocorticoids are known to inhibit this reinnervation process. In the present study, we examined changes in hippocampal glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) mRNA expression using in situ hybridization following unilateral entorhinal cortex lesioning (ECL) in the rat. As early as 1 day postlesioning, a 33% bilateral decrease in GR mRNA expression was observed in the dentate gyrus. By contrast, a 36% bilateral increase in GR mRNA expression was detected in the CA1 cell field. GR mRNA levels in both regions returned to those of control animals 2 days postlesioning, indicating that these effects were transient. Adjacent sections hybridized with probes to MR mRNA revealed no changes in hippocampal MR gene expression as a result of ECL. The selective decrease in GR mRNA expression observed in the dentate gyrus following ECL is specific to the hippocampal subregion targeted for reactive synaptogenesis and thus may serve to attenuate the inhibitory actions of circulating glucocorticoids.

Animals↗
PubMed1993

Are free radicals involved in the pathogenesis of idiopathic Parkinson's disease?

Since the original description of Parkinson's disease (PD) more than 170 years ago, there have been major advances in the understanding and treatment of PD. This article reviews some current knowledge concerning the role of free radicals, especially superoxide, in the etiology of PD. Hypotheses regarding inhibition of mitochondrial respiration and free radicals generation in PD are discussed in relation to the mechanisms of action of the N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a neurotoxin known to produce parkinsonian syndromes.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1993

[Monotherapy using amoxicillin/clavulanic acid as treatment of first choice in community-acquired lung abscess. Apropos of 57 cases].

In a multicentre open prospective trial the effectiveness of AM-CA as first-line treatment of community-acquired lung abscess was evaluated in immunocompetent adult patients. AM-CA was administered intravenously in doses of 4 g/day for at least 7 days, then orally in doses of 2 g/day for at least 14 days. Radio-clinical and laboratory evaluations were made during treatment, and 30 and 60 days after it was discontinued. The results of this trial concerned 57 patients (48 men, 9 women; mean age 52 years). The facilitating factors were those usually found in lung abscess. Twenty-seven patients had previously received an antibiotic treatment which had failed. The clinical picture, built up gradually in 42/37 patients, consisted of infectious syndrome (52 cases), altered general condition (39 cases), purulent expectoration (47 cases), sometimes foetid (10 cases), and thoracic clinical abnormalities (57 cases. X-ray films of the chest showed round abscess images (44 cases) or looked like necrotizing pneumonia (13 cases) with pleural reaction (8 cases). Protecting bacteriological sampling by BFW brushing and transtracheal or transparietal sample collecting was performed in 41 of the 57 patients. The pathogens, isolated in 31 cases, were: S. pneumoniae 5; Streptococcus spp. 12; Staph. aureus 4; H. influenzae 7; Enterobacteriaceae 6; anaerobes 7. These organisms were associated in 8 cases. With the exception of Enterobacter cloacae, all were sensitive to AM-CA in-vitro. The outcome was satisfactory in 52 patients.

Adolescent↗
PubMed1992

Modulation of gamma-actin and alpha 1-tubulin expression by corticosterone during neuronal plasticity in the hippocampus.

Evidence is given for altered gene expression of gamma-actin in the hippocampus in response to entorhinal cortex lesion (ECL). Time course analysis reveals a progressive repression of gamma-actin expression between 4 and 14 days post-lesion, coinciding with the early and middle phases of the hippocampal reinnervation process. RNA prevalence returns to near control values at 30 days post-lesion. Corticosterone administration, which is known to impair the reinnervation process in ECL rats, prevents the lesion-induced reduction in gamma-actin expression and blocks the induction of alpha 1-tubulin in the deafferented hippocampus. The timing of response of gamma-actin to ECL and its modulation by glucocorticoid administration support suggestions that gamma-actin has an important role to play in neuronal cytoarchitecture remodelling during hippocampal reinnervation.

Actins↗
PubMed1992

Multiple vertebral hemangiomas with neurological signs. Case report.

A case of multiple vertebral hemangiomas with progressive neurological deficit is presented. Successful treatment was accomplished using preoperative embolization, palliative surgical decompression, and postoperative radiation therapy. The patient has remained asymptomatic for 6 years. The authors review the role of current imaging modalities and options for therapeutic intervention. Preoperative embolization, palliative surgical decompression, and postoperative radiotherapy appear to provide a satisfactory outcome in patients with multiple hemangiomas and may represent an effective alternative to more aggressive surgical intervention.

Adult↗
PubMed1991

Iron pigment deposits, small vessel vasculitis, and erythrophagocytosis in the muscle of human immunodeficiency virus-infected patients.

Hemosiderin deposition and vascular inflammation were evaluated in muscle specimens from 50 human immunodeficiency virus (HIV)-infected individuals with neuromuscular symptoms. Iron deposits were detected in 25 of 50 cases, and were found more frequently in the distal muscles of lower limbs than in proximal muscles (22 of 30 cases v three of 20 cases; P less than .001). The incidence was higher than in controls (P less than .01). Polyarteritis nodosa was observed in three cases and microvascular inflammation was observed in 27. Direct immunofluorescence showed deposits of both immunoglobulins (mainly immunoglobulin M) and complement in small vessel walls of 19 of 34 patients. The p17 and p24 HIV antigens were detected in three of 27 cases. Both T8 lymphocytes and macrophages were significantly more numerous in patients with Perls'-positive material; these patients also showed vascular inflammation more frequently. Other findings included noninflammatory microangiopathy (18 cases), tubuloreticular inclusions in endothelial cells (one case), and free and intracytoplasmic eosinophilic globules likely representing digested erythrocytes (seven cases). The present study shows that iron pigment deposition in skeletal muscle is a nonspecific finding, frequently observed in the lower extremities of HIV-infected individuals, where it reflects immunopathologic alterations of the microcirculation. Erythrophagocytosis, which may be observed in the muscle of some HIV-infected individuals, may also be implicated.

Adult↗
PubMed1991

Cloning of hippocampal poly(A) RNA sequences that increase after entorhinal cortex lesion in adult rat.

Evidence is given for altered gene expression in the hippocampus in response to entorhinal cortex lesioning. Three RNA markers encoding glial fibrillary acidic protein, apolipoprotein E and alpha-tubulin were isolated from a rat hippocampal cDNA library by differential screening with cDNA probes from entorhinal cortex lesioned and control rat hippocampus RNA. By Northern blot analysis, mRNA for apolipoprotein E and alpha-tubulin increased to peak around 6 days after the lesion and returned to near control level at 30 days. The increased synthesis of both mRNAs coincides with the acute phase of synaptogenesis, protein synthesis, and polyribosomes accumulation in the deafferented hippocampal area.

Animals↗
PubMed1991

Astrocytic apolipoprotein E mRNA and GFAP mRNA in hippocampus after entorhinal cortex lesioning.

Entorhinal cortex lesions (ECL) that damage the perforant path to the hippocampus induce rapid increases of apolipoprotein E (apo E) mRNA in the hippocampus. Apo E mRNA was localized in astrocytes by in situ hybridization in combination with immunocytochemistry for glial fibrillary acidic protein (GFAP). Unilateral ECL also increased hippocampal GFAP mRNA, with increases preceding those of apo E mRNA. The apo E mRNA and GFAP mRNA responses were transiently bilateral in non-denervated zones. The timing of response in apo E mRNA to deafferentation supports suggestions that apo E has roles in membrane remodelling during responses to neuron injury.

Animals↗
PubMed1991

Environment, genetics and idiopathic Parkinson's disease.

Since Idiopathic Parkinson's disease (IPD) was first described more than 170 years ago, there have been major advances in the understanding of the etiology of the disease as well as in its treatment. This article will review current knowledge concerning the role of the environment, genetic hypotheses and the aging factor in the etiology of IPD and proposes a complex interaction involving all these factors. Hypotheses regarding mitochondrial inhibition and free radical generation in IPD are discussed in relation to the mechanism of action of neurotoxins known to produce parkinsonian syndromes.

Aging↗
PubMed1991

Fulminating multiple sclerosis-like leukoencephalopathy revealing human immunodeficiency virus infection.

A 66-year-old French homosexual man and a 42-year-old Brazilian man with no known risk factors for HIV infection developed headaches, asthenia, and neurologic episodes of abrupt onset. CT showed multiple hypodense, nonenhancing lesions. Serology for HIV was positive. They died respectively 2 months and 1 month after onset of the illnesses. Autopsy in both cases showed multiple, well-demarcated, demyelinating foci in the white matter of the cerebral hemispheres, brainstem, and cerebellum with histologic features characteristic of recent plaques of multiple sclerosis. There were no multinucleated giant cells or microglial nodules. Immunostaining for HIV was negative. Although a random coincidence of MS and HIV infection cannot be ruled out, the close temporal relationship between the 2 disorders suggests a possible etiologic association.

Adult↗