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Biomedical subjects

J G Fournier

Publications and source records attributed to J G Fournier.

At least 19 recordsLinked to original sources
PubMed2002

The cellular prion protein: a new partner of the lectin CBP70 in the nucleus of NB4 human promyelocytic leukemia cells.

Prion diseases are characterized by the presence of an abnormal isoform of the cellular prion protein (PrPc) whose physiological role still remains elusive. To better understand the function of PrPc, it is important to identify the different subcellular localization(s) of the protein and the different partners with which it might be associated. In this context, the PrPc-lectins interactions are investigated because PrPc is a sialoglycoprotein which can react with lectins which are carbohydrate-binding proteins. We have previously characterized a nuclear lectin CBP70 able to recognize N-acetyl-beta-D-glucosamine residues in HL60 cells. Using confocal immunofluorescence, flow-cytofluorometry, and Western-blotting, we have found that PrPc is expressed in the nucleus of the NB4 human promyelocytic leukemia cell line. It was also found that the lectin CBP70 is localized in NB4 cell nuclei. Moreover, several approaches revealed that PrPc and CBP70 are colocalized in the nucleus. Immunoprecipitation experiments showed that these proteins are coprecipitated and interact via a sugar-dependent binding moiety. In conclusion, PrPc and CBP70 are colocalized in the nuclear compartment of NB4 cells and this interaction may be important to better understand the biological function and possibly the conversion process of PrPc into its pathological form (PrPsc).

Blotting, Western↗
PubMed2001

Adaptation of the bovine spongiform encephalopathy agent to primates and comparison with Creutzfeldt-- Jakob disease: implications for human health.

There is substantial scientific evidence to support the notion that bovine spongiform encephalopathy (BSE) has contaminated human beings, causing variant Creutzfeldt-Jakob disease (vCJD). This disease has raised concerns about the possibility of an iatrogenic secondary transmission to humans, because the biological properties of the primate-adapted BSE agent are unknown. We show that (i) BSE can be transmitted from primate to primate by intravenous route in 25 months, and (ii) an iatrogenic transmission of vCJD to humans could be readily recognized pathologically, whether it occurs by the central or peripheral route. Strain typing in mice demonstrates that the BSE agent adapts to macaques in the same way as it does to humans and confirms that the BSE agent is responsible for vCJD not only in the United Kingdom but also in France. The agent responsible for French iatrogenic growth hormone-linked CJD taken as a control is very different from vCJD but is similar to that found in one case of sporadic CJD and one sheep scrapie isolate. These data will be key in identifying the origin of human cases of prion disease, including accidental vCJD transmission, and could provide bases for vCJD risk assessment.

Adaptation, Biological↗
PubMed2001

Nonneuronal cellular prion protein.

The normal cellular prion protein (PrP(c)) is a membrane sialoglycoprotein of unknown function having the unique property of adopting an abnormal tertiary conformation. The pathological conformer PrP(sc) would be the agent of transmissible spongiform encephalopathies or prion diseases. They include scrapie and bovine spongiform encephalopathy in animals and Creutzfeldt-Jakob disease in humans. The conversion of PrP(c) into PrP(sc) in the brain governs the clinical phenotype of the disease. However, the three-dimensional structure change of PrP(c) can also take place outside the central nervous system, in nonneuronal cells particularly of lymphoid tissue where the agent replicates. In natural infection, PrP(c) in nonneuronal cells of peripheral extracerebral organs may play a key role as the receptor required to enable the entry of the infectious agent into the host. In the present review we have undertaken a first evaluation of compelling data concerning the PrP(c)-expressing cells of nonneuronal origin present in cerebral and extracerebral tissues. The analysis of tissue, cellular, and subcellular localization of PrP(c) may help us better understand the biological function of PrP(c) and provide some information on physiopathological processes underlying prion diseases.

Animals↗
PubMed2000

Ultrastructural localization of prion proteins: physiological and pathological implications.

The transmissible spongiform encephalopathies (TSE) or prion diseases are fatal neurodegenerative disorders in which the central event is the conversion of a normal host-encoded protein (PrP(c)) into an abnormal isoform (PrP(sc)) which accumulates as amyloid in TSE brain. The two PrP(c) and PrP(sc) prion protein isoforms are membrane sialoglycoproteins synthesized in the central nervous system and various peripheral organ tissues. In this review, we describe the ultrastructural localization of prion proteins in human and animal cerebral and non-cerebral tissues whether or not infected by TSE agents. In addition to the plasma membrane of several cells, PrP(c) was found in association with cytoplasmic organelles of central and nerve-muscle synapses, and secretory granules of epithelial cells. Fibrils of amyloid plaques, synaptic structures, and lysosome-like organelles constitute the subcellular sites harboring PrP(sc). These findings have led to discussions on the physiological role of PrP(c) and the pathological mechanisms underlying prion spongiform encephalopathies.

Animals↗
PubMed2000

Electron microsocopy of brain amyloid plaques from a patient with new variant Creutzfeldt-Jakob disease.

Cerebral cortex biopsy from a patient with new variant Creutzfeldt-Jakob disease (nvCJD) has been examined at the electron microscope level. Spongiform changes corresponded mostly to distended neurites scattered in the neuropil or surrounding amyloid plaques. These latter exhibited heterogeneous submicroscopic morphology including variable amount of loosely interwoven amyloid fibrils admixed in a cellular-rich environment constituted essentially by abnormal neuronal processes. By immunoelectron microscopy, fibrils and some membrane structures reacted with anti-prion protein (PrP) antibodies. One striking aspect was the presence of many small dystrophic neurites without paired helical filaments. Moreover, amyloid fibrils showed unexpected intimate association with abnormal membranes, suggesting a relationship between PrP fibrillogenesis and membrane alteration. These ultrastructural findings provide an additional criterion to distinguish nvCJD-from sporadic CJD-type plaques and reinforce the hypothesis that nvCJD brain is infected by a distinctive strain of the transmissible agent encephalopathy.

Adult↗
PubMed1999

New insight into abnormal prion protein using monoclonal antibodies.

Studies of abnormal prion protein (PrPres) are hindered by the lack of specific monoclonal antibodies (mAbs), and the relationships between PrPres, infectivity, and strain specificity in prion diseases are still subject to debate. We have studied PrPres with new mAbs produced against PrP in mice using various immunization strategies. PrPres was analyzed by Western blot with different prion strains in various hosts. Differences in the electrophoretic pattern of human PrPres revealed by these antibodies provide new insight into PrPres cleavage by proteases and interpretation of strain typing. This study confirms that the N-terminal extremity of PrPres is differentially sensitive to proteases. Conversely, the C-terminal extremity, which resists proteolysis, seems to be abnormally detectable by antibodies in ultrastructural studies. This work confirms the highly complex role of PrPres in prion diseases and provides new tools which will be made available to facilitate progress in qualitative and quantitative studies of PrP.

Amino Acid Sequence↗
PubMed1999

Submicroscopic immunodetection of PrP in the brain of a patient with a new-variant of Creutzfeldt-Jakob disease.

We analyzed the distribution and organization of the pathological prion protein isoform (PrPsc) in the brain of new variant Creutzfeldt-Jakob disease using a sensitive post-embedding immunogold electron microscopy method. On methacrylate semithin sections, silver-PrP staining showed florid plaques, containing microvacuoles. It also revealed scattered granular and perivacuolar deposits. At the electron microscope level, plaque PrP-gold labeling was associated with filaments and flocculent amorphous material sometimes observed inside microvacuoles, considered as degenerative neurites. Outside the plaques, PrP-gold labeling was predominantly found over flocculent amorphous material and the presynaptic domain of synapses. Some lysosome-like organelles seen in the neuron perikaryon, were also found to be PrP-immunoreactive. These results are consistent with the hypothesis that the synapse is a privileged target in prion disease.

Adult↗
PubMed1999

Ultrastructural localization of cellular prion protein (PrPc) at the neuromuscular junction.

We examined the localization of the normal cellular isoform of prion protein (PrPc) in mammalian skeletal muscle. Using two anti-PrP antibodies, the neuromuscular junction (NMJ) was preferentially stained after immunohistofluorescence. The mouse, hamster, and human NMJ displayed a fluorescent signal specific for PrPc. Postembedding immunoelectron microscopy analysis performed in the mouse muscle showed that the PrPc-specific colloidal gold immunolabelling was concentrated over the sarcoplasmic cytoplasm. The membrane of the postsynaptic domain was devoid of gold particles, while a weak signal was occasionally observed close to the presynaptic vesicles of the terminal axons. These results indicate that the PrP gene is expressed in mammalian muscle at the NMJ. The subsynaptic sarcoplasm of the NMJ appears to be the privileged site where PrPc presumably associated with endosome membrane may play a role in either physiological activity or maintenance of the morphological integrity of the synapse.

Animals↗
PubMed1999

Expression of matrix metalloproteinases 2 and 9 in regenerating skeletal muscle: a study in experimentally injured and mdx muscles.

Matrix metalloproteinases (MMPs) cooperatively degrade all components of the extracellular matrix (ECM). Remodeling of ECM during skeletal muscle degeneration and regeneration suggests a tight regulation of matrix-degrading activity during muscle regeneration. In this study, we investigated the expression of MMP-2 and MMP-9, in normal muscles and their regulation during regeneration process. We further investigated their secretion by C2C12 myogenic cell line. Two models of muscle degeneration-regeneration were used: (1) normal muscles in which necrosis was experimentally induced by cardiotoxin injection; (2) mdx muscles which exhibit recurrent signs of focal myofiber necrosis followed by successful regeneration. MMPs were studied by zymography; their free activity was quantified using 3H-labeled gelatin substrate and mRNA expression was followed by Northern hybridization. Muscle degeneration-regeneration was analyzed by conventional morphological methods and in situ hybridization was performed on muscle sections to identify the cells expressing these MMPs. Results show that MMP-2, but not MMP-9 expression, is constitutive in normal muscles. Upon injury, the active form of MMP-2 is transiently increased, whereas MMP-9 is induced within 24 h and remains present for several days. Quantitative assays of free gelatinolytic activity show a progressive and steady increase that culminates at 7 days postinjury and slowly returns to normal levels. In adult mdx mice, both pro and active forms of MMP-2 and MMP-9 are expressed. Northern blot results support these findings. Zymography of C2C12-conditioned medium shows that myogenic cells produce MMP-2. By in situ hybridization we localized MMP-9 mRNA in inflammatory cells and putative activated satellite cells in injured muscles. Our data allow the correlation of the differential expression of pro and/or active forms of MMP-2 and MMP-9 with different stages of the degeneration-regeneration process: MMP-9 expression is related to the inflammatory response and probably to the activation of satellite cells, whereas MMP-2 activation is concomitant with the regeneration of new myofibers.

Animals↗
PubMed1998

Distribution and submicroscopic immunogold localization of cellular prion protein (PrPc) in extracerebral tissues.

In transmissible spongiform encephalopathies (TSE), such as scrapie in animals and Creutzfeldt-Jakob disease in humans, the central event is the conversion of a host-encoded amyloidogenic protein (PrPc) into an abnormal isoform (PrPsc) that accumulates as amyloid in TSE brain. PrPc is a membrane sialoglycoprotein synthesized in the central nervous system and elsewhere. We have examined the ultrastructural localization of PrPc in numerous hamster and some human extracerebral tissues, by means of a post-embedding electron-microscopic method combined with immunogold labeling. In stomach, intestine, lung, and kidney from hamsters, and in stomach, kidney, and spleen from humans, immunogold labeling specific for PrPc is observed on various cellular substructures related to secretory pathways: Golgi apparatus, secretory globules, and plasma membrane. In mucous epithelial cells of stomach and intestine, PrPc appears to be concentrated in secretory globules, suggesting a role for PrPc in the secretory function of the digestive tract. The secretory aspect of PrPc may be a key to understanding the physiopathological mechanisms underlying TSE.

Animals↗
PubMed1997

Transmission of the BSE agent to mice in the absence of detectable abnormal prion protein.

The agent responsible for transmissible spongiform encephalopathies (TSEs) is thought to be a malfolded, protease-resistant version (PrPres) of the normal cellular prion protein (PrP). The interspecies transmission of bovine spongiform encephalopathy (BSE) to mice was studied. Although all of the mice injected with homogenate from BSE-infected cattle brain exhibited neurological symptoms and neuronal death, more than 55 percent had no detectable PrPres. During serial passage, PrPres appeared after the agent became adapted to the new host. Thus, PrPres may be involved in species adaptation, but a further unidentified agent may actually transmit BSE.

Animals↗
PubMed1996

Detection of human herpes virus 6 in AIDS-associated retinitis by means of in situ hybridization, polymerase chain reaction and immunohistochemistry.

The ubiquitous nature of HHV-6 and its genomic relationship with cytomegalovirus led us to evaluate an etiological link between HHV-6 and AIDS-associated retinitis in a prospective study. HHV-6 infection was studied in patients with AIDS-associated retinitis and in two control populations. Eye pairs were obtained at necropsy from nine patients with AIDS-associated retinitis, four human immunodeficiency virus (HIV)-sero-positive patients with normal fundus examination and three HIV-seronegative patients. HHV-6 infection was detected by polymerase chain reaction (PCR), in situ hybridization and immunohistochemistry. Human cytomegalovirus (CMV) and HIV-1 infections were detected in parallel by the same methods. HHV-6 infection was detected in three cases of AIDS-associated retinitis. In two of these patients, HHV-6 infection was detected both by immunohistochemistry and PCR while in the third case it was detected by in situ hybridization and PCR. In the three patients, fundus examination showed bilateral retinitis in two of them and unilateral retinitis in one of them. HHV-6 infection was not detected in the retina of the two control groups. CMV was also detected in the three cases positive for HHV-6 by all three methods. HIV DNA was detected by PCR in two of three cases and was confirmed in one of these cases by in situ hybridization. These results confirm that HHV-6 infects the retina but suggests that HHV-6 does not have an exclusive causative role in AIDS-associated retinitis, since CMV coinfection of the retina was detected in all three of the patients positive for HHV-6.

AIDS-Related Opportunistic Infections↗
PubMed1995

Ultrastructural localization of cellular prion protein (PrPc) in synaptic boutons of normal hamster hippocampus.

The cellular prion protein (PrPc) is a membrane sialoglycoprotein synthesized in the central nervous system and extraneural tissues. Its post-translational modification produces an accumulation of abnormal isoform PrPsc found in brains of transmissible neurodegenerative disorders in animals (scrapie and bovine spongiform encephalopathy) and humans (Kuru, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome). One major unanswered question relative to PrPc concerns its physiological role in brain neurons, depending largely on the limited knowledge of its subcellular localization. Using a highly-sensitive immunogold electron microscopy technique, we reported that in the hamster dentate gyrus, the synaptic boutons constituted the submicroscopic site where PrPc was observed. This detection was obtained with 2 highly-specific polyclonal antibodies for prion protein. PrPc localization was assigned, both on structural basis and on its co-localization with synaptophysin. The presence of PrPc in synaptic terminals should provide additional informations on its possible role in neuronal transmission and on the implication of synapses in the pathogenesis of spongiform encephalopathies.

Animals↗
PubMed1993

Detection by in situ hybridization of HIV and c-myc RNA in tumour cells of AIDS-related B-cell lymphomas.

The incidence of acquired immune deficiency syndrome (AIDS)-related malignant lymphoma has increased since the disease was first described, but its pathogenesis is still not understood. There have been numerous molecular studies addressing the clonality of these proliferations, the presence of Epstein-Barr virus genome in the tumor cells, and rearrangements of the c-myc oncogene. However, very few in situ hybridization studies have been carried out. We analysed 24 cases of high-grade B-cell malignant lymphomas and two cases of polymorphic B-cell proliferation associated with human immunodeficiency virus (HIV) infection. Human immunodeficiency virus ribonucleic acids were detected in some of the tumour cells in 19 of the 24 cases of malignant lymphomas and in both cases of polymorphic B-cell proliferation, with the in situ hybridization technique and using a specific tritiated copy deoxyribonucleic acid probe. With the same technique, c-myc ribonucleic acid was detected in most of the tumour cells from all the 21 cases of malignant lymphomas tested but not in the polymorphic B-cell proliferation.

Acquired Immunodeficiency Syndrome↗
PubMed1993

In situ hybridization of HIV-1 RNA in retinal vascular wall.

In situ hybridization of human immunodeficiency virus-1 (HIV-1) has been performed on eight eyes from eight distinct acquired immune deficiency syndrome patients (three cases had a normal fundus examination and five presented with cytomegalovirus retinitis). The eyes were removed at autopsy and frozen immediately. Contiguous 10-mu cryostat sections were obtained and tested with a HIV probe labeled by nick-translation with [35S]-ATP. HIV-1 RNA was detected in the retina of two acquired immune deficiency syndrome patients. The first positive case presented with typical ophthalmological and histopathological cytomegalovirus retinitis, the second one was not related to cytomegalovirus, according to clinical or histopathological classical criterias. HIV-1 was localized in retinal vascular walls. This shows that there is an active replication of HIV in retina of some acquired immune deficiency syndrome patients.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Thymic pseudotumorous enlargement due to follicular hyperplasia in a human immunodeficiency virus sero-positive patient. Immunohistochemical and molecular biological study of viral infected cells.

An enlargement of the thymus suggesting a tumor was discovered in a 28-year-old man who had early-stage acquired immune deficiency syndrome. A biopsy was performed. The adipose involuted thymus, with persistence of many Hassall's corpuscles, was judged to be a large lymphoid follicular hyperplasia. This follicular hyperplasia was similar to that previously described for lymph nodes, spleen, and other lymphoid tissues at earlier stages of human immunodeficiency virus infection, before the development of acquired immune deficiency syndrome. Human immunodeficiency virus RNA and p24 human immunodeficiency virus protein were detected in the hyperplastic germinal centers (lymphocytes and follicular dendritic infected cells), and also in many cells that may have been either lymphocytes and/or epithelial cells in the interfollicular areas. The tissue was negative for Epstein-Barr virus DNA sequences, as determined by the polymerase chain reaction. These observations identify the first state of infection of the thymus in a human immune deficiency virus-infected adult, preceding the severe involution with lymphoid depletion observed in all fatal cases of acquired immunodeficiency syndrome in which the thymus has been analyzed.

Acquired Immunodeficiency Syndrome↗