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Biomedical subjects

D Dormont

Publications and source records attributed to D Dormont.

At least 181 records · Page 10Linked to original sources
PubMed1997

Obtention and characterization of primary astrocyte and microglial cultures from adult monkey brains.

Simple methods for obtention of primary cultures of isolated astrocytes and microglia from adult simian brain have been developed. Characterization of these two glial cell populations were performed by morphological observations and by immunocytochemistry. The astroglial cultures were obtained by an indirect method. After L-leucine methyl-ester treatment and trypsinizations, more than 99% of cells expressed glial fibrillary acidic protein (GFAP), whereas no macrophages or microglia could be detected. Likely, the 1% remaining cells were immature astrocytes or cells that lost their GFAP expression. Cultured simian astrocytes expressed vimentin, laminin, and fibronectin. We also found a constitutively low expression of major histocompatibility complex (MHC) class II by cultured astrocytes which was significantly enhanced by lipopolysaccharide (LPS), interferon gamma (IFN-gamma), or tumor necrosis factor alpha (TNF-alpha) treatments. Microglial cultures were obtained by a direct method of isolation using Percoll gradient separations and compared to simian monocyte-derived macrophages or alveolar macrophages. Microglial cells differed from macrophages by their proliferation upon granulocyte-macrophage colony stimulating factor (GM-CSF) treatment and by their typical morphology when observed by scanning electron microscopy. As macrophages, they expressed in vitro CD68, CD64, CD14, CD11b, MHC class II, and fibronectin. However, contrary to macrophages, simian cultured microglia expressed laminin. This observation suggests that microglia represent a new potential source of this extracellular matrix protein in the brain.

Animals↗
PubMed1997

Production and characterization of monoclonal antibodies to simian immunodeficiency virus envelope glycoproteins.

Twelve monoclonal antibodies (MAbs), TB1 to TB12, were produced against a soluble vaccinia recombinant envelope glycoprotein (gp140) from simian immunodeficiency virus SIVmac251. These MAbs recognized SIV gp140 with a relatively high affinity (K0.5 from 6.7 x 10(-8) to 4 x 10(-9) M). All the MAbs except TB9, TB11, and TB12 cross-reacted with HIV-2 envelope glycoproteins, but none of the 12 MAbs recognized those from HIV-1. Using a panel of 87 overlapping synthetic peptides containing 20 amino acid residues, with an overlap of 10 amino acids and spanning the entire primary sequence of gp140, 3 linear epitopes were identified. The first mapped with a neutralizing MAb, TB12, which recognized a linear sequence around amino acids 28-31 within the N-terminal end of the external envelope glycoprotein. The two other new nonneutralizing MAbs recognized linear epitopes around amino acid sequence 380-381 by MAbs TB1, TB2, and TB3, and at the transmembrane glycoprotein amino acids 581-600 by MAb TB6. Seven of the 12 MAbs, TB4, TB5, TB7-9, TB10, and TB11, failed to bind the linear synthetic peptides in ELISA. Moreover, among these seven MAbs only MAbs TB4, TB5, TB9, and TB10 failed to recognize SIV envelope glycoproteins in Western blot (WB) or ELISA after reduction of disulfide bridges by dithiothreitol (DTT), suggesting that they are directed against conformational or discontinuous epitopes. It is of interest to note that MAb TB10 can block the binding of gp140 to the CD4 receptor when the MAb is previously incubated with gp140. Consistent with this result, MAb TB10 cannot bind to gp140 that has been previously complexed with the CD4 receptor. All these results suggest that MAb TB10 recognizes a conformational or discontinuous epitope overlapping or close to the CD4-binding site. These properties are probably implicated in the neutralizing activity observed with this MAb.

Amino Acid Sequence↗
PubMed1997

Lack of interleukin 10 expression in monocyte-derived macrophages in response to in vitro infection by HIV type 1 isolates.

Interleukin 10 is a pleiotropic cytokine that is overexpressed in HIV-infected patients. Here, we investigated IL-10 expression in primary cultures of monocyte-derived macrophages (MDMs) in response to in vitro infection by HIV-1/Ba-L or two macrophage-tropic HIV-1 primary isolates. Whatever the multiplicity of infection used, and in spite of high replication levels and an increase in HIV-infected cell frequency, neither significant IL-10 secretion nor IL-10 mRNA overexpression was induced in HIV-1-infected MDMs. Moreover, identical results were obtained with HIV-1-infected 1-day monocytes. These results show that MDM infection by HIV is not sufficient by itself for inducing IL-10 synthesis.

Cells, Cultured↗
PubMed1997

Expression of cell adhesion molecules at the surface of in vitro human immunodeficiency virus type 1-infected human monocytes: relationships with tumor necrosis factor alpha, interleukin 1beta, and interleukin 6 syntheses.

Further evidence suggests that cell adhesion molecules (CAMs) expressed on the surface of human immunodeficiency virus type 1 (HIV-1)-infected cells are regulated during lentiviral infection. To address this hypothesis we have investigated the kinetic pattern of CAM expression at the surface of HIV-1Ba.L-infected human monocytes during the first 72 hr of infection. A significantly lower expression of CD18 and CD54 as well as a decrease in CD44 expression level were observed at the surface of infected monocytes when compared with mock-infected cultures. No modification of CD11a, CD11b, CD11c, CD58, and CD62L expression was detected. Except for CD18, the expression of which at the cell surface is decreased, no modification of CD44 and CD54 expression was observed after heat-inactivated HIV-1 treatment of monocytes. Investigation of soluble forms of CAMs (sCAMs) and cytokine production in the culture supernatants of infected monocytes showed a peak of sCD44, TNF-alpha, IL-1beta, and IL-6 release between 2 and 24 hr after infection. Treatment of monocytes with monoclonal antibodies (MAbs) against CAMs showed that engagement of some CAMs may trigger TNF-alpha and IL-1beta production. In addition, pretreatment of infected monocytes with a TNF-alpha synthesis inhibitor, RP 55778, or with MAbs directed against IL-1beta, confirmed the role of TNF-alpha and IL-1beta in the regulation of CD18, CD44, and CD54 expression.

Antibodies, Monoclonal↗
PubMed1997

[Unconventional transmissible agents or prions].

UNLABELLED: NEUROGENERATIVE DISEASES: Unconventional transmissible agents or prions cause subacute transmissible spongiform encephalopathies (TSE) in man and animals. These rare neurological diseases have a long incubation period. The only clinical manifestations are signs of central nervous system deficits. HISTOPATHOLOGY: There are three characteristics features vacuolization of the cerebral cortex, neuronal loss and astrogliosis. A host protein, the PrP (prion protein) accumulates in the central nervous system of infected individuals in quantities proportional to the titer of the infectious agent. The gene coding for the PrP is the main factor determining genetic susceptibility to unconventional transmissible agents. THE TRANSMISSIBLE AGENT: The exact nature of these unconventional transmissible agents remains a question of debate. For certain authors, prions are proteins totally devoid of nucleic genomes, being composed entirely by a particular pathogenic form of the protease-resistant PrP protein. For others, the structure is more conventional, containing an independent genome, the PrP being the recepto and virulence factor.

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↗
PubMed1997

Mechanisms of downmodulation and release of tumour necrosis factor receptor induced by human immunodeficiency virus type 1 in human monocytes.

Infection of human monocytes with human immunodeficiency virus type (HIV-1 LAI) triggers the release of both the cytokine tumour necrosis factor alpha (TNF-alpha) and its soluble receptor (TNFsr). In the present study, the authors have investigated the cellular events implicated in the modulation of expression and shedding of the monocyte TNF receptor induced by HIV-1 LAI. Release of TNFsr75 was triggered at an early step of interaction of the virus particles with the monocyte, involving the envelope glycoprotein gp120. HIV-1 LAI induced an upregulation of TNFr75 mRNA, whereas TNFr55 mRNA was not detectable. TNFsr75 release required exocytosis, proteolytic cleavage by serine protease(s), but was independent of prior endocytosis of the receptor. Early shedding of TNFr75 accounted for the almost total but transient disappearance of the membrane TNF receptor P75, observed 60 min after activation with HIV-1 LAI, whereas internalization was minimal. Endogenous TNF-alpha had no role in the disappearance of its own receptor. Complete and stable restoration of TNFr expression at the cell membrane, dependent on de novo protein synthesis, occurred after 5 h, followed by massive TNFsr75 release. These results demonstrate that interaction of human monocytes with HIV-1 LAI triggers at an early stage a cascade of cellular events that lead to profound remodeling of the cell TNFr pool. Understanding the mechanisms of these receptor movements is of importance to document the central role of the TNF system in HIV infection.

Cells, Cultured↗
PubMed1997

Temporal lobe epilepsy with varying severity: MRI study of 222 patients.

MRI was performed in 222 consecutive adult patients with temporal lobe epilepsy of varying severity from January 1991 to May 1993. The diagnosis of hippocampal sclerosis was established visually by three independent observers. The accuracy of visual assessment of hippocampal asymmetry was compared with volumetric measurements. Neuropathological correlations were obtained in 63 patients with refractory seizures. Temporal lobe abnormalities were observed in 180 patients (81%) as follows: hippocampal sclerosis in 122 (55%); developmental abnormalities in 16 (7.2%); tumours in 15 (6.8%); scars in 11 (5%); cavernous angiomas in 10 (4.5%); miscellaneous lesions in 6. MRI was normal or showed unrelated changes in 42 patients (19%). Visual assessment correctly lateralised hippocampal sclerosis in 79 of the 84 patients measured (94%). Temporal lobectomy confirmed the MRI data (side and aetiology) in all 63 operated patients. Patients with normal MRI had an older age of seizure onset and were more often drug-responsive than patients with hippocampal sclerosis. MRI showed temporal lobe abnormalities in 81% of epileptic patients with varying severity with good neuropathological correlation. Patients with normal MRI had a less severe form of the disease.

Adolescent↗
PubMed1997

Probing the dynamics of prion diseases with amphotericin B.

Amphotericin B (AmB) is one of the rare drugs that affect the course of experimental prion diseases and modify the kinetics of abnormal prion protein accumulation in the central nervous system. Therefore, AmB could be used as a pharmacological tool to contribute to our understanding of the pathogenic mechanisms involved in these neurodegenerative disorders.

Amphotericin B↗
PubMed1997

Consequences of gamma-irradiation on inflammatory cytokine regulation in human monocytes/macrophages.

Inflammation is a frequent result of radiation damage, especially after therapeutic irradiation. Monocytes and macrophages play an important role in inflammatory cytokine secretion. However, knowledge of monocyte/ macrophage involvement in the pathogenesis of inflammation is still incomplete. In this study, we investigated the inflammatory cytokine regulation after in vitro gamma-irradiation of monocytes/macrophages. Semiquantitative RT-PCR after irradiation revealed no significant induction of interleukin 1 beta or tumour necrosis factor-alpha mRNA expression. When induction was observed, for only two donors out of seven, only interleukin 6 gene expression was affected by irradiation, with a 5-14-fold increase in level according to the donor, 2h after irradiation compared with sham-irradiated cells. For only one of seven donors tested, monocytes/macrophages responded to 10-Gy gamma-rays by releasing inflammatory cytokines.

Cell Separation↗
PubMed1997

Modulations of cytokine expression in pregnant women.

PROBLEM: Although the overall anti-infectious and anti-parasitic immunity of parous women appears normal, several aspects of maternal cell-mediated and humoral immunity are altered during pregnancy. This has been suggested to occur via preferential local and systemic secretion of Th-2 type cytokines, which down-regulate or prevent secretion/action of Th-1 type cytokines, in animals as well as in humans. METHOD: To evaluate the influence of gestation on the maternal immune system, we have measured, in pregnant women, the mRNAs coding for several cytokines (TNF alpha, IFN gamma, GM-CSF, IL-1 beta, IL-2, IL-4, IL-6, and IL-10) in peripheral blood mononuclear cells, by use of semi-quantitative RT-PCR. RESULTS: Our results show significant modulations of IFN gamma, IL-1 beta, IL-4, and IL-6 genes expression especially during the third trimester and near parturition. CONCLUSION: Cytokine expression is thus finely tuned in peripheral blood during pregnancy, in a previously unexpected complex pattern, related to gestational stage.

Cohort Studies↗
PubMed1997

Effects of RP 55778, a tumor necrosis factor alpha synthesis inhibitor, on antiviral activity of dideoxynucleosides.

Tumor necrosis factor alpha (TNF-alpha) is overexpressed during human immunodeficiency virus (HIV) infection. RP 55778, a TNF-alpha synthesis inhibitor, decreases HIV replication in monocytes/macrophages. Therapeutic use of RP 55778 in vivo, like that of other biological response modifiers, would theoretically require association with dideoxynucleosides. We have evaluated here the combinatory effects of zidovudine (AZT) or dideoxyinosine (ddI) and RP 55778. This TNF-alpha inhibitor antagonizes the antiviral effects of both dideoxynucleosides, especially AZT. The more favorable anti-HIV activity of ddI in resting cells may explain these unequal degrees of antagonism.

Anti-HIV Agents↗
PubMed1997

Late treatment with polyene antibiotics can prolong the survival time of scrapie-infected animals.

Amphotericin B (AmB) is one of the few drugs able to prolong survival times in experimental scrapie and delays the accumulation of PrPres, a specific marker of this disease in the brain in vivo. Previous reports showed that the AmB effect is observed only if the drug is administered around the time of infection. In the present study, intracerebrally infected mice were treated with AmB or one of its derivatives, MS-8209, between 80 and 140 days postinoculation. We observed an increased incubation time and a delay in PrPres accumulation and glial fibrillary acidic protein gene expression. Treatment starting at 80 days postinoculation was as efficient as long-term treatment starting the day of inoculation. Our results indicate that polyene antibiotics may interfere, throughout the course of the experimental disease, with the propagation of the scrapie agent.

Amino Acid Sequence↗
PubMed1997

Pallidal stimulation for Parkinson's disease. Two targets?

There has been renewed interest in functional surgery as treatment for Parkinson's disease (PD). Although pallidotomy and chronic pallidal stimulation are highly effective in suppressing levodopa-induced dyskinesia (LID), both methods also seem to be effective in reducing parkinsonian disability. However, the simultaneous improvement of LID and motor signs is hard to explain with the classic model of basal ganglia circuitry. Taking advantage of the fact that deep brain stimulation is reversible and that implanted electrodes contain four discrete stimulation sites, we investigated the effect of stimulation on different sites of the globus pallidus (GP) in five PD patients. Stimulation in the dorsal GP (upper contact) significantly improved gait, akinesia, and rigidity and could induce dyskinesia when patients were in the "off" state. In contrast, stimulation in the posteroventral GP (lower contact) significantly worsened gait and akinesia, although the reduction in rigidity remained. For patients in the "on" state, stimulation in the posteroventral GP dramatically reduced LID but, as in the "off" state, worsened gait and akinesia, thus canceling out the antiparkinsonian effect of levodopa. Our results indicate that stimulation had a striking different effect on parkinsonism and dyskinesia when applied at two different loci of the GP and that stimulation applied in the posteroventral GP produced opposite effects on rigidity and on akinesia. We conclude that parkinsonian signs and LID are a reflection of at least two different anatomofunctional systems within the GP and that this functional organization of the GP needs to be considered when determining the optimal target for surgical treatment of PD.

Adult↗
PubMed1997

Creutzfeldt-Jakob disease: therapeutic strategies.

Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative illness which belongs to the group of transmissible subacute spongiform encephalopathies (TSSE). Today, no treatment is available for TSSE. The appearance of a new variant of CJD, which affects young people and could be linked to so-called ;mad cow disease', has stimulated researchers to develop new therapies against CJD. A few drugs have already been shown to delay the onset of experimental TSSE. They could contribute to the understanding of the pathogenic mechanisms involved in TSSE and, therefore, could be the basis for therapeutic strategies against CJD.

Editorial↗