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Biomedical subjects

S Muller

Publications and source records attributed to S Muller.

At least 271 records · Page 15Linked to original sources
PubMed1991

Characterization of monoclonal antibodies against alpha-hemolysin of Escherichia coli.

Monoclonal antibodies (MAbs) were raised against native and denatured alpha-hemolysin (HlyA) of Escherichia coli. Binding of the MAbs to native, denatured, and erythrocyte-complexed active wild-type hemolysin and mutant derivatives was tested. All 15 MAbs analyzed bound to native hemolysin, even when the toxin was complexed with human erythrocytes. While some MAbs were unable to bind to a specific native mutant hemolysin, others could not even bind to mutant hemolysin carrying deletions remote from their actual binding sites. A rough determination of the binding sites of 15 MAbs on HlyA was performed by Western immunoblot analysis using CNBr fragments of HlyA and mutant hemolysin proteins. Interestingly, the binding sites of the MAbs against native hemolysin seem to be more randomly distributed on HlyA than are those of MAbs against denatured hemolysin. Three MAbs inhibited the hemolytic activity significantly. Two of these MAbs bound to the hydrophobic region, and the other one bound to the repeat domain of HlyA. The use of synthetic peptides from these regions allowed determination of the linear epitopes for two of these MAbs.

Animals↗
PubMed1991

[Catamenial pneumothorax].

Pulmonary endometriosis has been described as occurring in two forms: --bronchopulmonary with haemoptysis at the periods, --pleuropulmonary with pneumothorax at the periods. In 30-40% of cases it is associated with pelvic endometriosis. The pathways along which it can be disseminated are: --transdiaphragmatic peritoneal migration, --or metastatic migration through the veins and lymphatics. The treatment at present consists of hormone therapy together with surgery.

Adult↗
PubMed1991

[Hemorheology in clinical practice. Introduction to the notion of hemorheologic profile].

Although the non-Newtonian characteristics of blood have now been accurately defined, the influence and effect of a hyperviscosity syndrome at the onset of ischemia and in oxygen transport to the tissues remains within the realm of assumptions. Using a simple theoretical approach it can be shown that oxygen transport capacity to the tissues is proportional to the radio H/eta s (where H = hematocrit, eta s = blood viscosity), as long as vascular bed geometry remains constant (with no sign of compensatory vasodilation). With the help of examples, the authors show the changes in oxygen transport as a function of various rheological parameters (red cell aggregation ans deformability). Further, the authors introduce the concept of a hemorheological profile for taking all the hemorheological parameters into consideration and for standardising the presentation of the results for hyperviscosity syndromes.

Blood Viscosity↗
PubMed1991

[Erythrocyte aggregation in patients with monoclonal gammopathies: effect of plasma exchange treatment].

Analyses of erythrocyte aggregation have been carried out in 15 patients with multiple myeloma or Waldenström's macroglobulinemia before and after plasma exchange. The volume of exchanged plasma was about 1.2-1.5 plasmatic mass. It was replaced by the same volume of a 4% solution of human albumin. Each treatment included at least 3 plasma exchanges at 48 hours intervals. The kinetic (aggregation times) and rheological (dissociation threshold) parameters of erythrocyte aggregation were determined before and immediately after each plasma exchange using a device based on the analysis of the backscattered light by a blood suspension. Before the first plasma exchange, erythrocyte aggregation measurements revealed a pronounced reduction in time aggregation and high values of dissociation thresholds indicating an hyperaggregation of red cells. The successive plasma exchanges produced very different changes in erythrocyte aggregation. For some patients, the aggregation parameters presented normal values from the first plasma exchange when similar changes were only noted after the second plasma exchange in other patients. Finally, in some cases, an hyperaggregation state was maintained after a series of three plasma exchanges. The influence of the nature and the concentration of monoclonal immunoglobulin as well as plasmatic fibrinogen are discussed.

Blood Viscosity↗
PubMed1990

Selective in vivo inhibition of T cell activation by class II MHC-binding peptides administered in soluble form.

A synthetic peptide corresponding to residues 53-61 of hen egg white lysozyme, as well as its N-succinyl C-amide, inhibit in vivo priming for T cell responses when administered in soluble form, in osmotic minipumps implanted s.c., 1 day before immunization. The inhibition exhibits MHC selectivity that corresponds to the binding specificity of these peptides for class II MHC molecules in vitro. Approximately fourfold higher doses of soluble competitor are required than of competitor in CFA-depot, in order to achieve comparable levels of inhibition. The inhibition of priming to a nonimmunodominant T cell determinant requires lower doses of soluble competitor than the suppression of priming to a dominant T cell determinant. The soluble competitors do not appear to induce class II MHC-restricted T cell response against themselves.

Animals↗
PubMed1990

Expression and site-directed mutagenesis of the catalytic domain of human poly(ADP-ribose)polymerase in Escherichia coli. Lysine 893 is critical for activity.

Bacterially expressed fusion proteins containing the COOH-terminal domain of the human poly(ADP-ribose)polymerase were analyzed by means of a novel assay, the "activity blot," which allows the detection of transferred polypeptides involved in poly(ADP-ribose) synthesis. Deletion analysis demonstrated that the 40-kDa COOH-terminal region of the enzyme is an autonomous catalytic domain exhibiting both the polymerizing and branching activities in the absence of DNA. Site-directed mutagenesis demonstrated that lysine 893 is essential for these catalytic processes. In addition, sequence similarities obtained with the NAD(P)+ amino acid dehydrogenases suggest that (i) lysine 893 may interact with the substrates of poly(ADP-ribose)polymerase and (ii) the COOH-terminal part of the 40-kDa fragment may also contain a Rossman fold structure.

Amino Acid Sequence↗
PubMed1990

Acute lethal graft-versus-host reaction induced by major histocompatibility complex class II-reactive T helper cell clones.

T cell clones isolated from class II MHC-disparate MLR combinations, and specific for I-Ak and I-Ek molecules, respectively, are shown to induce acute lethal graft-vs-host disease in unirradiated recipients. Cytolytic and noncytolytic clones are equally efficient in this respect. The lethal disease is dependent on recognition of the stimulatory class II molecules in the host. The clones home to lungs and liver, and become activated in these organs as demonstrated by an in vivo thymidine incorporation assay. After activation, a severe vascular leak syndrome develops causing death of the recipients within 5 d after the injection of 5 x 10(6) to 10(7) cloned cells. The disease develops without the participation of secondary host-derived inflammatory mechanisms, such as mast cell degranulation, complement activation, and the release of prostaglandins, oxygen radicals, or proteolytic enzymes. The results raise the possibility that Th cells can directly influence vascular permeability, and control, thereby, the acute inflammatory reaction of blood vessels.

Alleles↗
PubMed1990

Flexibility of the T cell repertoire. Self tolerance causes a shift of T cell receptor gene usage in response to insulin.

Bovine insulin(BI)-specific I-Ab-restricted T cell clones have been characterized for fine specificity and TCR gene usage. We have demonstrated that mouse strains carrying H-2b on three different genetic backgrounds (C57BL, BALB, and 129) rearrange and express the V beta 6 gene in a large proportion (36%) of insulin-specific clones. In these strains, the non-MHC background did not seem to influence TCR gene usage in response to BI. The V beta 6+ clones appeared to be selected by the antigen. In contrast, no V beta 6+ clones could be isolated from (B6 x DBA/2)F1 mice, where V beta 6+ (and V beta 8.1+) T cells are deleted by self tolerance to Mls-1a. Thus, although a small proportion of residual V beta 6+ cells had been demonstrated in Mls-1a mice, these cells could not be retrieved in a response that uses V beta 6 predominantly. In functional terms, therefore, the deletion of V beta 6 by self tolerance appears to be complete. Instead of V beta 6, the majority (up to 60%) of I-Ab- as well as I-Ad-restricted insulin-specific clones from the (B6 x DBA/2)F1 mice expressed V beta 8.2 and V beta 8.3. This shift of gene usage was not accompanied by any detectable change in the fine specificity pattern of response. Thus, in the insulin-specific response, the flexibility of T cell repertoire fully compensates for deletions caused by self tolerance.

Animals↗
PubMed1990

Use of an immobilized enzyme and specific antibodies to analyse the accessibility and role of histone tails in chromatin structure.

Using limited proteolysis with subtilisin bound to collagen membranes, the degradation of the histone proteins revealed by specific antibodies was correlated to changes in chromatin conformation and condensation monitored by circular dichroism and electric birefringence. This new approach allows us to detect for the first time a hierarchy of histone tails cleavages. The terminal domains of H1, the NH2-terminal tail of H3 and the carboxy-terminal ends of histones H2A and H2B were found to be cleaved already at the early stages of proteolysis and this led to a decondensation of polynucleosomal chains. Thereafter the C-terminal part of H3 and both NH2-terminal regions of H2A and H2B became rapidly cleaved, resulting in relative reorientation of swinging nucleosomes or partially unfolded segments. Unexpectedly, this removal of tails of H1, H2B, H2A and H3 is not accompanied by significant changes in DNA-protein interactions resulting in free-oriented DNA. This might suggest that histone-histone interactions play a central role in stabilizing the solenoid.

Animals↗
PubMed1990

Polyclonal human rheumatoid factors cross-reacting with histone H3: characterization of an idiotope on the H3 binding site.

The development of highly sensitive immunoassays has made the detection of the multireactivity of antibodies a relatively common phenomenon. Polyreactivity is frequent in human auto antibodies, especially in rheumatoid factors (RFs), but the structural basis and the significance of this phenomenon remain substantially unknown. Recently, we showed that the double reactivity of a human monoclonal RF with histones was probably due to two distinct binding sites. However, cross-reactivity seems more frequent among polyclonal RFs occurring during autoimmune diseases than with monoclonal RFs. We studied double-reactive (IgG and histone H3) polyclonal RFs in a patient suffering from primary Sjögren's syndrome. We showed by means of affinity chromatographies that H3 cross-reactive RFs were only a small subset of the total patient's RFs and that this subset was enriched in IgA class. Competitive inhibition experiments suggested the existence of two distinct binding sites for IgG and H3. These results were confirmed by showing the selective sensitivity to acid treatment of the histone binding site and by producing a murine antiidiotope monoclonal antibody BII 2.1 defining an idiotope on bireactive RF apparently linked to the H3 binding site. This idiotope was absent in a panel of monoclonal RF, one of them cross-reacting with histone H3. This report extends previous results concerning a monoclonal RF to the polyclonal RFs which occur during autoimmune diseases.

Acids↗
PubMed1990

Rheological properties and membrane fluidity of red blood cells and platelets in primary hyperlipoproteinemia.

Lipid fluidity of the erythrocyte membrane and intact platelets was examined in 32 male patients affected by types IIA, IIB and IV primary hyperlipoproteinemia and 15 control subjects. Lipid fluidity was determined by fluorescence polarization using two probes: DPH and TMA-DPH which are localized in different lipid areas of the cell membrane. Classical haemorheological tests were also performed including plasma viscosity, whole blood viscosity and erythrocyte aggregation. As compared to a control group, plasma viscosity and whole blood viscosity at low shear rate was significantly increased in types IIB and IV, but not in type IIA patients. In contrast, the increase in erythrocyte aggregation was significant in all HLP types. Concerning lipid fluidity, the results recorded with red cells and platelets were not significantly different for type IIA HLP compared to the control group. In contrast, erythrocyte membranes from patients with types IIB and IV HLP had a significantly higher level of fluidity in lipid regions characterized by TMA-DPH. Using DPH as a fluorescent probe, identical results were only noted in type IIB patients. Regarding intact platelets of IIB and IV patients, an increase in lipid fluidity was noted for two fluorescent probes. These findings suggest that HLP associated erythrocyte and platelet fluidity alterations are not related to hypercholesterolemia but to the triglyceride level.

Adult↗
PubMed1990

Antigenic properties and protective capacity of a cyclic peptide corresponding to site A of influenza virus haemagglutinin.

Two cyclic peptide analogues corresponding to residues 139-146 (site A) of influenza A virus haemagglutinin (strain X31) were synthesized. The ability of these peptides to react with anti-influenza virus antibodies was found to depend on the conformation of the loop and on the orientation in which the peptide was presented to antibodies. Antibodies raised to the peptides were able to bind in ELISA with influenza virus antigen that had been allowed to dry on the microtitre plate. When OF1 mice were immunized with cyclic peptides, approximately 80% of the animals were protected against an intranasal challenge with influenza virus.

Amino Acid Sequence↗
PubMed1990

Recent advances in solid-phase peptide synthesis and preparation of antibodies to synthetic peptides.

Peptides prepared by the solid-phase peptide synthesis (SPPS) approach are used increasingly in biological research, for instance to elicit anti-peptide antibodies that will recognize the intact, cognate protein. Recent advances in SPPS are reviewed, including the use of new coupling reagents, new methods for evaluating peptide purity and new techniques of automated and multiple peptide synthesis. Methods for enhancing peptide immunogenicity are discussed such as the use of adjuvants and liposomes, and of synthetic branched polypeptides as carriers.

Adjuvants, Immunologic↗
PubMed1990

Accessibility and structural role of histone domains in chromatin. biophysical and immunochemical studies of progressive digestion with immobilized proteases.

The accessibility and role of histone regions in chromatin fibres were investigated using limited proteolysis with enzymes covalently bound to collagen membranes. The changes in chromatin conformation and condensation monitored by various biophysical methods, were correlated to the degradation of the histone proteins revealed by antibodies specific for histones and histone peptides. Upon digestion with trypsin and subtilisin, chromatin undergoes successive structural transitions. The cleavage of the C-terminal domains of H1, H2A and H2B, and of the N-terminal tail of H3 led to a decondensation of chromatin fibres, indicated by increases in electric birefringence and orientational relaxation times. It corresponds to a 15% increase in linear dimensions. The degradation of the other terminal regions of histones H3, H2A and H2B resulted in the appearance of hinge points between nucleosomes without alteration of the overall orientation of polynucleosome chains. Despite the loss of all the basic domains of H1, H3, H2A and H2B, no significant change in DNA-protein interactions occurred, suggesting that most of these protease-accessible regions interact weakly, if at all, with DNA in chromatin. Further proteolysis led to H4 degradation and other additional cleavages of H1, H2B and H3. This caused the relaxation of no more than 8% of the total DNA but resulted in changes in the ability of chromatin to condense at high ionic strength. More extensive digestion resulted in a total unravelling of nucleosomal chains which acquired properties similar to those of H1-depleted chromatin, although the globular part of H1 was still present. The data suggest that histone-histone interactions between H1 and core histone domains play a central role in stabilizing the chromatin fibres, and cuts in H3, H2A and H2B as well as H1, seem necessary for chromatin expansion. On the contrary, H4 might be involved in the stabilization of nucleosomes only.

Animals↗
PubMed1990

Recognition of synthetic peptides of Sm-D autoantigen by lupus sera.

The reactivity of autoantibodies present in the serum of patients with systemic lupus erythematosus (SLE) was investigated by ELISA using seven overlapping synthetic peptides representing the entire sequence of the polypeptide D component of 'Sm antigen'. Of the 165 SLE sera tested, 59% were found to contain IgG antibodies able to bind to peptide 1-20, while 37% of the sera reacted with peptide 44-67. All sera reacting with peptide 44-67 also reacted with peptide 1-20. These two peptides were only seldom recognized by the sera of 187 patients with other rheumatic autoimmune diseases or by 53 sera of normal individuals. In a parallel study using sera that reacted with the D band in immunoblotting, most of the sera recognized peptides 44-67 (89%) and 1-20 (67%), while 33% of them reacted with peptide 97-119. The use of these synthetic peptides in ELISA may be of considerable help for detecting anti Sm autoantibodies.

Amino Acid Sequence↗
PubMed1990

Testicular teratoma and peripheral neurofibromatosis.

Peripheral neurofibromatosis (Von Recklinghausen's disease) has been previously reported in association with a number of tumours and recently with aqueductal stenosis. We report a case which had both aqueductal stenosis and a testicular teratoma, which has not previously been reported in this condition.

Adult↗
PubMed1990

Antibodies from patients with rheumatoid arthritis and juvenile chronic arthritis analyzed with core histone synthetic peptides.

Antihistone antibodies were detected in the sera of a randomly selected group of patients with rheumatoid arthritis (RA) and juvenile chronic arthritis (JCA) by an enzyme-linked immunosorbent assay (ELISA) with the five individual histones and by immunoblotting. In ELISA, the overall frequency of antihistone antibodies in RA and JCA was 51 and 44%, respectively. Antibodies present in these serum samples were further studied by ELISA by means of 17 core histone synthetic peptides. The fragment 1-21 of H3 was recognized by 60% of RA sera and by 62% of JCA sera. In addition, at least four terminal or internal peptides of H3 and H4 were recognized by more than a third of JCA sera, while only two of these peptides reacted with 20% of RA sera. Many of the sera that did not show any reactivity with the whole histone reacted with various histone peptides. This finding demonstrates the usefulness of synthetic peptides for identifying autoantibodies.

Adolescent↗