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Biomedical subjects

S Muller

Publications and source records attributed to S Muller.

At least 127 records · Page 7Linked to original sources
PubMed1999

MHC class II gene associations with autoantibodies to U1A and SmD1 proteins.

Autoantibodies against U small nuclear ribonucleoproteins (snRNP) are frequently present in the serum of patients with systemic rheumatic diseases, and have been reported to be associated with HLA-DR and -DQ genes. To better define the role of HLA genes in the production of such antibodies, we studied immunogenetic associations with autoantibodies reacting with U1 RNP, U1A and SmD1 proteins, and synthetic peptides containing immunodominant linear epitopes of these proteins. Only two out of the 15 overlapping peptides of U1A (i.e. peptides 35-58 and 257-282) and three of 11 peptides of SmD1 (i.e. peptides 1-20, 44-67 and 97-119) were significantly recognized by patients' sera selected on the basis of their antibody positivity with RNP in immunodiffusion. The distribution of DRB1, DQB1 and DPB1 alleles among the anti-RNP antibody-positive patients (n = 28) and healthy control subjects was similar. Antibodies against U1A (tested in Western immunoblotting with HeLa cell extracts) were positively associated to DRB1*06 allele; antibodies reacting with SmD1 peptide 44-67 were negatively associated to DRB1*02 and DQB1*0602 alleles. No association was found between DPB1 alleles and antibodies reacting with U1A and SmD1 antigens. This first study reporting an association between autoantibodies reacting with U1A and SmD1 proteins (and peptides of these proteins), and immunogenetic markers suggest that the production of antibody subsets directed against different components (or regions of these proteins) bound to the same snRNP particle is associated with distinct MHC class II alleles.

Alleles↗
PubMed1999

An improved nonisotopic test to screen a large series of new inhibitor molecules of poly(ADP-ribose) polymerase activity for therapeutic applications.

A reliable ELISA for screening large numbers of poly(ADP-ribose) polymerase (PARP) inhibitors is described. The test is based upon the drop in PARP activity estimated by the decrease in poly(ADP-ribose) synthesis in the presence of inhibitor. This ELISA is easy to perform, rapid, and specific. It is extremely sensitive because a clear inhibition of the total reaction could be visualized with molecules used in the nanomolar range. The assay uses no radioactivity, and automation is possible with robots for large-scale investigations. This test is of great interest for the screening of chemical libraries and the discovery of new inhibitors (and possibly activators) of PARP. Such molecules have important applications in all abnormal situations involving DNA damage and oxidative stress, such as cancer, autoimmunity, diabetes, myocardial dysfunctions, certain infections, aging, and radiation/chemical exposure.

Apoptosis↗
PubMed1999

[Hemorheology and vascular endothelial cells].

The vascular endothelium is a biologically active monolayer of cells providing an interface between the blood flow and tissues. Vascular Endothelial Cells (VEC) have two functional states. The endothelium is normally anti-thrombotic and anti-adhesive to ensure blood fluidity. During aggressions, such as atherosclerosis, inflammation states, metabolic diseases (through chemical or mechanical stimuli), VEC can reverse its functions by expressing stored material or by slower involvement of previously are repressed genes. Endothelial cells have three types of anti-thrombotic properties: vaso regulating properties: VEC release vasomotor components, such as endothelin (vasoconstriction), prostacyclin and nitric oxide, (vasodilatation). Endothelial cells also have antithrombotic and hemostatic properties. They express proteoglycans on their surface, including some negative-charge, plasminogen, sulfate glycosaminoglycans (heparan-sulfate), and secrete plasminogen tissular activator (t-PA) and tissular factor inhibitor. One fundamental action of the endothelium in that area is the production and expression of thrombomodulin, a thrombin receptor. This function has a major anticoagulation effect, controlling continual thrombin generation at the sub-endothelium and blood cell interface. Moreover, endothelial cells show anti-adhesion properties. During cardio-vascular diseases, all of these properties may be reversed. Thus the VEC have a determinant role in hemodynamic control through these various metabolic activities, such as control of homeostasis, vascular tone, blood fluidity, coagulating properties, cellular adhesion. Otherwise, many studies have demonstrated that local blood flow conditions have a crucial role on the VEC properties (mechanoactivation and mechanotransduction concept). In conclusion, knowledge of all the properties of the endothelial cells and control of the phenomena which define their functions is a key element in understanding cardiovascular diseases.

Animals↗
PubMed1999

Hemorheology and vascular endothelial cells.

The vascular endothelium is a biologically active monolayer of cells provided an interface between blood and tissues. Vascular endothelial cells (ECs) have two functional states, which are allowed by their different properties: (i) vaso regulating properties: ECs releases vasomotor components, as endothelin (vaso constriction), prostacyclin and nitrite oxide (vaso dilatation); (ii) antithrombotic and hemostatic properties; and (iii) anti-adhesion properties. The endothelium is normally antithrombotic and anti-adhesive to ensure blood fluidity. During many cardio-vascular diseases, these properties may be reversed. Thus, the ECs have a determinant role in hemodynamic control through these various metabolic activities. Otherwise, many studies have demonstrated that local blood flow conditions have a crucial role on the EC properties (mechanotransduction concept). The knowledge of the properties of ECs and the control of the phenomena which define their functions is a key element in the cardiovascular diseases understanding.

Animals↗
PubMed1999

Clinical dose ranging studies with finasteride, a type 2 5alpha-reductase inhibitor, in men with male pattern hair loss.

BACKGROUND: Androgenetic alopecia is a common condition of adult men. Finasteride, a type 2 5alpha-reductase inhibitor, decreases the formation of dihydrotestosterone from testosterone. OBJECTIVE: Two separate clinical studies were conducted to establish the optimal dose of finasteride in men with this condition. METHODS: Men from 18 to 36 years of age with moderate vertex male pattern hair loss received finasteride 5, 1, 0.2, or 0.01 mg/day or placebo based on random assignment. Efficacy was determined by scalp hair counts, patient self-assessment, investigator assessment, and assessment of clinical photographs. Safety was assessed by clinical and laboratory measurements and by analysis of adverse experiences. RESULTS: Efficacy was demonstrated for all end points for finasteride at doses of 0.2 mg/day or higher, with 1 and 5 mg demonstrating similar efficacy that was superior to lower doses. Efficacy of the 0.01 mg dose was similar to placebo. No significant safety issues were identified in the trials. CONCLUSION: Finasteride 1 mg/day is the optimal dose for the treatment of men with male pattern hair loss and was subsequently identified for further clinical development.

5-alpha Reductase Inhibitors↗
PubMed1999

Influence of a calcium antagonist on blood rheology and arterial compliance in hypertension: comparison with a thiazide diuretic.

Beyond their effects on blood pressure, antihypertensive agents may produce additional effects on blood rheology and arterial compliance abnormalities which may play a role in the target organ damage. These effects may depend only on their specific pharmacological properties. We compared the effects of nitrendipine to hydrochlorothiazide in 33 mild to moderate hypertensives in a double blind parallel group trial. Blood rheology and radial artery diameter and compliance were measured at t=0 and t=2 months. Both drugs produced blood pressure lowering. Blood viscosity decreased in the nitrendipine group and increased in the hydrochlorothiazide patients. Red blood cells deformability increased only in the nitrendipine group. Radial artery diameter and compliance were not different between the two groups but there was a trend to an increase of the cross-sectional compliance in hydrochlorothiazide group and to a decrease in nitrendipine group. Our data show that a calcium antagonist (Nitrendipine) could improve rheological parameters.

Antihypertensive Agents↗
PubMed1999

Modelisation of leukocyte adhesion on a fibrinogen coated surface in static conditions.

The adhesion of polymorphonuclear leukocytes (PMNs) on the vascular endothelium is a complex process that occurs during biological and pathological events and involves a large family of molecules. This phenomenom could be approached by a modelisation study of the adhesion of PMNs on a biological substrate, fibrinogen. Two different physiological conditions were tested such as the activated state of PMNs with a synthetic pro-inflammatory activator (N-Formyl-Methionyl-Leucyl-Phenylalanine, FMLP). The activated state of PMNs was both quantified by flow cytometry and controlled by fluorescence microscopy. The results suggest that quiescent PMNs deposit in accordance with the ballistic deposition model. The preliminary results obtained with FMLP-stimulated PMNs show a different deposit process compared to quiescent PMNs but do not allow to determine exactly a deposition model.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed1998

[Soluble tumor necrosis factor receptors in patients with systemic lupus erythematosus].

OBJECTIVE: To study the variations of type II soluble receptors for tumor necrosis factor (sR-TNF) in patients with systemic lupus erythematosus and investigate their use in the clinical setting. PATIENTS AND METHODS: Twenty-six patients with systemic lupus were followed for a mean 3 years. sR-TNF and other immunological parameters (C reactive protein, anti-DNA antibodies, C3 and C4 complement fractions, soluble receptors for interleukin 2) were measured in sera at different points of the disease course. The systemic lupus activity measure (SLAM) was determined at each point, and confronted with the biology results. The study was cross sectional for the group and longitudinal for the patients. RESULTS: sR-TNF was the immunological parameter which correlated best with SLAM. It also correlated with sedimentation rate, C reactive protein, thrombopenia, anemia, creatinine level, anti-DNA antibodies and sR-IL2. The longitudinal study pointed out however that this finding is not consistent for each patient. CONCLUSION: A rise in sR-TNF related to systemic lupus activity but is of limited practical interest for individual patient follow-up.

C-Reactive Protein↗
PubMed1998

At least three linear regions but not the zinc-finger domain of U1C protein are exposed at the surface of the protein in solution and on the human spliceosomal U1 snRNP particle.

No structural information on U1C protein either in its free state or bound to the spliceosomal U1 small nuclear ribonucleoprotein (snRNP) particle is currently available. Using rabbit antibodies raised against a complete set of 15 U1C overlapping synthetic peptides (16-30 residues long) in different immunochemical tests, linear regions exposed at the surface of free and U1 snRNP-bound U1C were identified. Epitopes within at least three regions spanning residues 31-62, 85-103 and 116-159 were recognized on free and plastic-immobilized recombinant human U1C expressed in Escherichia coli, on in vitro translated U1C protein and on U1C bound to the U1 snRNP particle present in HeLa S100 extract. Using a zinc affinity labeling method, we further showed that the N-terminal U1C peptide containing a zinc-finger motif (peptide 5-34) effectively binds65Zn2+. The N-terminal region of U1C, which is functional in U1 snRNP assembly, is apparently not located at the surface of the U1 snRNP particle.

Amino Acid Sequence↗
PubMed1998

Substituting selenocysteine for active site cysteine 149 of phosphorylating glyceraldehyde 3-phosphate dehydrogenase reveals a peroxidase activity.

Replacing the essential Cys-149 by a selenocysteine into the active site of phosphorylating glyceraldehyde 3-phosphate dehydrogenase (GAPDH) from Bacillus stearothermophilus leads to a selenoGAPDH that mimics a selenoperoxidase activity. Saturation kinetics were observed with cumenyl and tert-butyl hydroperoxides, with a better catalytic efficiency for the aromatic compound. The enzymatic mechanism fits a sequential model where the formation of a ternary complex between the holoselenoenzyme, the 3-carboxy 4-nitrobenzenethiol used as the reductant and the hydroperoxide precedes product release. The fact that the selenoGAPDH is NAD-saturated supports a binding of hydroperoxide and reductant in the substrate binding site. The catalytic efficiency is similar to selenosubtilisins but remains low compared to selenoglutathione peroxidase. This is discussed in relation to what is known from the X-ray crystal structures of selenoglutathione peroxidase and GAPDHs.

Binding Sites↗
PubMed1998

All-D peptides recognized by an anti-carbohydrate antibody identified from a positional scanning library.

Monoclonal antibodies recognize antigens with high affinity and specificity, but the structural basis for molecular mimicry remains unclear. It is often assumed that cross-reactive antigens share some structural similarity that is specifically recognized by a monoclonal antibody. Recent studies using combinatorial libraries, which are composed of millions of sequences, have examined antibody cross-reactivity in a manner entirely different from traditional epitope mapping approaches. Here, peptide libraries were screened against an anti-carbohydrate monoclonal antibody for the identification of peptide mimics. Positional scanning libraries composed of all-l or all-d hexapeptides were screened for inhibition of monoclonal antibody HGAC 39.G3 binding to an antigen displaying N-acetyl-d-glucosamine (GlcNAc) residues on a polyrhamnose backbone. Inhibitory activity by mixtures from the all-d hexapeptide library was greater than the activity from the all-l libraries. The most active d-amino acid residues defined in each of the six positions of the library were selected to prepare 27 different individual hexapeptides. The sequence Ac-yryygl-NH2 was specifically recognized by mAb HGAC 39.G3 with a relative affinity of 300 nM when measured in a competitive binding assay. The contributions to overall specificity of the residues of the all-d peptide (Ac-yryygl-NH2) in binding to mAb HGAC 39.G3 were examined with a series of truncation, l and d-amino acid substitution, and retro analogs. Dimeric forms of the all-d peptide were recognized with tenfold to 100-fold greater affinities relative to the monomer. The all-d peptide was found to inhibit mAb HGAC 39.G3 binding to an anti-idiotype antibody with approximately 1000-fold greater affinity than GlcNAc. As demonstrated here, the study of immune recognition using combinatorial chemistry may offer new insights into the molecular basis of cross-reactivity.

Amino Acid Sequence↗
PubMed1998

Multicentric infantile myofibromatosis.

Infantile myofibromatosis (IM) is a rare tumor of infancy and childhood, typically presenting as a firm, nodular mass involving soft tissue, bone or viscera. Approximately one-third of cases involve the head and neck. These tumors can be solitary or multicentric. Biopsy reveals tumor cells that resemble myofibroblasts. Spontaneous regression may occur. A high degree of suspicion is necessary to differentiate this entity from other more aggressive processes histiocytosis, fibrosarcoma, rhabdomyosarcoma. We describe the case of a male infant with multicentric myofibromatosis, presenting with multiple thoraco-abdominal subcutaneous nodules and lytic mass lesions of the temporal bone and calvarium. The characteristic clinical, radiologic and histopathologic features of this process are reviewed along with diagnostic and therapeutic options.

Humans↗
PubMed1998

Nonviral interferon alpha gene therapy inhibits growth of established tumors by eliciting a systemic immune response.

A plasmid expression system encoding murine IFN-alpha4 and complexed with a protective interactive noncondensing polymeric (PINC) delivery system was used for in vivo immunotherapy treatment of an immunogenic murine renal cell carcinoma, Renca, and a nonimmunogenic mammary adenocarcinoma, TS/A. Mice bearing established tumors were treated with IFN-alpha/polyvinylpyrrolidone (PVP) expression complexes via direct intratumoral injection. Up to 100% inhibition of tumor growth was observed in the treated mice. By using an optimal dose of 96 and 48 microg of formulated IFN-alpha plasmid for the treatment of Renca and TS/A, respectively, 30% (Renca) and 10% (TS/A) of the treated animals remained tumor free. Inhibition of tumor growth was dependent on activation of the immune system. The antitumor activity elicited by IFN-alpha gene therapy was abrogated when mice were selectively depleted of CD8+ T cells. By contrast, depletion of CD4+ T cells resulted in enhanced tumor rejection following IFN-alpha/PVP treatments. Finally, mice that remained tumor free following IFN-alpha gene therapy displayed immune resistance to a subsequent tumor challenge. These data provide evidence that IFN-alpha gene therapy can be used to induce an efficient antitumor response in vivo.

Adenocarcinoma↗
PubMed1998

Identification of V3 loop-binding proteins as potential receptors implicated in the binding of HIV particles to CD4(+) cells.

The binding of human immunodeficiency virus (HIV) type 1 particles to CD4(+) cells could be blocked either by antibodies against the V3 loop domain of the viral external envelope glycoprotein gp120, or by the V3 loop mimicking pseudopeptide 5[Kpsi(CH2N)PR]-TASP, which forms a stable complex with a cell-surface-expressed 95-kDa protein. Here, by using an affinity matrix containing 5[Kpsi(CH2N)PR]-TASP and cytoplasmic extracts from human CEM cells, we purified three V3 loop-binding proteins of 95, 40, and 30 kDa, which after microsequencing were revealed to be as nucleolin, putative HLA class II-associated protein (PHAP) II, and PHAP I, respectively. The 95-kDa cell-surface protein was also isolated and found to be nucleolin. We show that recombinant preparations of gp120 bind the purified preparations containing the V3 loop-binding proteins with a high affinity, comparable to the binding of gp120 to soluble CD4. Such binding is inhibited either by 5[Kpsi(CH2N)PR]-TASP or antibodies against the V3 loop. Moreover, these purified preparations inhibit HIV entry into CD4(+) cells as efficiently as soluble CD4. Taken together, our results suggest that nucleolin, PHAP II, and PHAP I appear to be functional as potential receptors in the HIV binding process by virtue of their capacity to interact with the V3 loop of gp120.

Amino Acid Sequence↗
PubMed1998

Histones and DNA ultrastructural distribution in plant cell nucleus: a combination of immunogold and cytochemical methods.

In this work we report for the first time the ultrastructural distribution of histones and DNA in the nuclear compartments in two different plant cell types: Allium cepa L. root meristems and Capsicum annuum L. microspores and pollen grains, by using antibodies against histones H2B and H4 and anti-DNA. Immunolocalizations were combined with ultrastructural cytochemistry for nucleic acids (methylation-acetylation method), DNA (NAMA-Ur) and RNPs (EDTA), to relate the subcellular location of histones and DNA with the chemical subcompartmentalization of the cell nucleus. This is particularly interesting concerning the presence of histones or not on fibers of the interchromatin region and on the fibrillar components of the nucleolus, nuclear subcompartments where transcription has been shown to take place at some regions. Our methodological approach permitted to define precisely the structures where histones were detected in relation to the ultrastructural localization of chromatin in various structural condensation levels. Concerning the localization of DNA and histones on the different components of the nucleolus, the combination of immunogold labeling with the methylation-acetylation cytochemical method, developed in our laboratory, was very useful, thus permitting a clear recognition of the nucleolar components and a correct assignment of labeling, which is not always evident on uranyl-lead-stained Lowicryl sections. Double immunogold assays were also done for a simultaneous visualization of histones and DNA. Our results show a coincident distribution of histones and DNA on the same nuclear compartments revealing the presence of both antigens on condensed chromatin, fibers of the interchromatin region, principally located at the periphery of the condensed chromatin, and in the fibrillar components of the nucleolus.

Acetic Anhydrides↗
PubMed1998

A partially modified retro-inverso pseudopeptide modulates the cytokine profile of CTL specific for an influenza virus epitope.

There is considerable evidence that peptides corresponding to MHC class I-restricted epitopes can be used as immunogens or immunomodulators. Pseudopeptides containing isosteric replacements of the amide bond provide more stable analogues, which may even have enhanced biologic activity. But there have been very few studies on the use of pseudopeptides to initiate or modulate the cellular immune response. This study describes the immunogenicity of a partially modified retro-inverso pseudopeptide of an influenza virus epitope and shows that this pseudopeptide modulates the cytokine profile expressed by CD8+ CTL generated from primed precursors. Moreover, the pseudopeptide is much more efficient at low concentration than the wild-type epitope to stimulate IFN-gamma secretion by CD8+ T effector cells. These results are analyzed with reference to changes in the conformation of the MHC molecule/peptide complex deduced from molecular modeling. The findings support the idea that partially modified retro-inverso analogues can be used as altered peptide ligands to enhance the stimulation of natural epitope-specific CTL and to modify their functional properties. Hence, pseudopeptide ligands might be promising tools for use in immunotherapy.

Cell Line↗
PubMed1998

Hypoxia/reoxygenation induces apoptosis through biphasic induction of protein synthesis in cultured rat brain neurons.

To investigate biochemical events accounting for the outcome of central neurons following hypoxia/reoxygenation, cultured neurons from fetal rat forebrain were exposed to hypoxia (95% N2/5% CO2) for 6 h, and then reoxygenated for up to 96 h. Time-dependent changes in macromolecular biosynthesis were analysed by incorporation of [3H]uridine and [3H]leucine and were coupled to cell viability and lactate dehydrogenase leakage. Morphological features of necrosis and apoptosis were scored following nuclear incorporation of the fluorescent dye 4,6-diamidino-2-phenylindole. Hypoxia led to a 36% reduction of cell viability at the end of the reoxygenation period, while 23% of the neurons exhibited apoptosis. A biphasic increase in the rates of protein synthesis was measured 1 h after the onset of hypoxia (77% above controls) and by 48-h postreoxygenation (72%). The presence of cycloheximide during hypoxia inhibited both peaks of synthesis and prevented the development of apoptosis. Protein electrophoresis outlined specific alterations in constitutive proteins, and immunohistochemistry revealed an overexpression of the pro-apoptotic gene products Bax and ICE. Therefore, hypoxia followed by reoxygenation would trigger sequential changes in synthesis of specific proteins, leading to delayed and mainly apoptotic neuronal death.

Animals↗