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B Bellon

Publications and source records attributed to B Bellon.

At least 19 recordsLinked to original sources
PubMed1992

Separation and characterization of the precursor and activated forms of porcine and human pancreatic colipase by reversed-phase liquid chromatography.

Reversed-phase liquid chromatography was used as an alternative method for the characterization of the precursor and activated forms of porcine and human pancreatic colipase. Using a Beckman Ultrasphere column with an increasing acetonitrile gradient in 0.1% trifluoroacetic acid, it was possible to obtain well-resolved separation of the precursor form of colipase (procolipase) from its trypsin-activated derivative. This protocol was used (1) to study the activation of porcine procolipase by trypsin or thrombin in vitro, (2) to assess the homogeneity of porcine colipase preparations used in tridimensional structure studies and in combination with immunoaffinity chromatography, (3) to identify the form of colipase present in samples of human pancreatic juice.

Animals↗
PubMed1992

Susceptibility and resistance to autoimmunity following neonatal injection of semi-allogeneic spleen cells in rats.

A model of neonatal allotolerance was developed in rats. Brown-Norway (BN) neonates injected with semi-allogeneic (BN x Lewis) F1 hybrid spleen cells express a long-lasting chimerism and exhibit polyclonal B cell activation demonstrated by hyperimmunoglobulinemia affecting mainly IgE and IgG1, anti-laminin and anti-DNA autoantibodies as well as glomerulonephritis and anti-hapten antibodies. These abnormalities are autoregulated although the chimerism persists. In contrast, Lewis (LEW) neonates injected with semi-allogeneic (BN x LEW) F1 hybrid spleen cells exhibit a very short-lasting chimerism and transient activation of B cells, as reflected by increased allo-class II antigen expression, but do not develop an autoimmune disease. The autoimmune syndrome observed in BN rats is similar to that reported in mice during host-versus-graft reaction. Similarities between the drug-induced models of autoimmunity and allogeneic reactions in BN rats are also striking. The susceptibility of BN rats and the resistance of LEW rats to these autoimmune diseases might respectively reflect the involvement of TH2-like or of TH1-like subsets.

Animals↗
PubMed1992

The yemanuclein-alpha: a new Drosophila DNA binding protein specific for the oocyte nucleus.

The Drosophila yG 4.5 gene (now called yemanuclein-alpha gene), which maps at 98F, is a member of the yema gene cluster isolated in a search for differentially expressed maternal genes. The yemanuclein-alpha transcript (formerly yT 4.5) is specifically expressed in the female germ cells at early oogenic stages and displays a graded distribution along the antero-posterior axis of the oocyte. These provocative features are reminiscent of that of K10, bicoid and Bicaudal-D gene transcripts and lead us to hypothesize that the yemanuclein-alpha gene plays a key role in egg organization. We show in the present work that the yemanuclein-alpha is a nuclear protein highly specific for the oocyte nucleus. The sequence analysis of the 5696 bp EcoRI fragment containing the yemanuclein-alpha gene, and of 5 overlapping cDNAs, reveals a 3006 nucleotides long open reading frame (ORF) flanked by long untranslated 5' and 3' sequences. This ORF predicts a 109,215 kDa protein which is basic (pHi: 8.57), and serine rich (12.08%). It contains a 40 amino acid acidic domain in the first third of the protein with a potential alpha-helix organization; this domain has some similarity with the nucleolin acidic domain. Parts of the yemanuclein-alpha sequence are likely to form secondary structures known to interact with DNA. We demonstrate the DNA binding activity of the yemanuclein-alpha by affinity chromatography experiments. Our data indicate that the yemanuclein-alpha shares some of the features which are characteristic of genuine transcriptional activators.

Amino Acid Sequence↗
PubMed1992

Adoptive transfer of experimental autoimmune uveoretinitis in HgCl2 injected rats.

We previously demonstrated that mercuric chloride (HgCl2) injected-(Lewis x Brown-Norway) F1 rats are protected against experimental autoimmune uveoretinitis (EAU) induced by active immunization with the retinal S-antigen (S-Ag). To better understand the mechanisms of the protection promoted by HgCl2, we studied the effect of HgCl2-induced autoimmune disease on transferred EAU. We demonstrate herein that HgCl2 has no effect on adoptively transferred EAU. Therefore, the HgCl2-induced autoimmune disease does not affect effector S-Ag specific T cells activated in vitro but acts at an earlier stage.

Animals↗
PubMed1991

Antigen specificity of anticolipase monoclonal antibodies: characterization of colipase-Fab complexes using gel filtration high-performance liquid chromatography.

The epitope specificity of eight mouse monoclonal antiporcine procolipase antibodies (MAbs) was characterized on the basis of their competitive binding with antigen. Binary and ternary Fab-colipase complexes formed between antibody and porcine procolipase or its trypsin activated derivative were identified using gel filtration HPLC. The eight MAbs were divided in two groups that recognized overlapping epitopes located in distinct antigenic regions on procolipase. The gel filtration HPLC technique allowed to characterize two MAbs which did not react with solid-phase coupled antigen. Three MAbs formed Fab-antigen complexes with procolipase and not with activated colipase which suggests that epitopes recognized by these MAbs involve residues of the N-terminal pentapeptide of procolipase.

Animals↗
PubMed1991

Antigen specificity and cross-species reactivity of a monoclonal antibody (mAb 72.11) against porcine pancreatic procolipase.

We have studied the antigen specificity and cross-reactivity of a monoclonal antibody (mAb 72.11) of subclass IgG1, raised against the precursor form of porcine colipase (procolipase), whose epitope lies near the amino terminal region of the polypeptide. mAb 72.11 cross-reacts with native porcine, equine and human procolipase, as shown by immuno-inactivation and ELISA titration studies carried out on pure proteins, pancreatic tissue homogenate or pancreatic juice. The epitope site recognized by mAb 72.11 was further characterized by studying antibody binding to denatured procolipase. Reduced carboxymethylated procolipase reacted with mAb 72.11 in ELISA. Heat inactivated or reduced carboxymethylated porcine procolipase displaced antigen from the complex formed between antibody and native procolipase. The lack of sensitivity of epitope recognized by mAb 72.11 on procolipase to heat denaturation or reduction of the disulfide bridges is indicative that antigen specificity of mAb 72.11 is not dependent on the conformation of the antigenic site. Cross-reactivity of mAb 72.11 with procolipase from the three species demonstrates that substitution of amino acid at positions 1 and 3 causes no loss of antigenicity. Finally, mAb 72.11 was coupled to sepharose to isolate human procolipase from human pancreatic juice and to separate the precursor form from activated colipase non-adsorbed on the column.

Amino Acid Sequence↗
PubMed1991

Increased expression of class II major histocompatibility complex molecules on B cells in rats susceptible or resistant to HgCl2-induced autoimmunity.

Administration of HgCl2 to the susceptible Brown-Norway (BN) rats induces an autoimmune disease characterized by a T-dependent polyclonal activation of B cells responsible for a dramatic increase in serum IgE concentration. The resistant Lewis (LEW) rats injected with HgCl2 do not exhibit such autoimmune manifestations. We show here that, upon HgCl2 injections, major histocompatibility complex (MHC) class II molecule expression is increased very early in lymph nodes and spleen B cells from both strains. So far, it is the earliest marker (day 3) of the effect of HgCl2 on the immune system. In both strains this enhancement is transient, but regulatory mechanisms are much more efficient in the resistant LEW strain than in the susceptible BN strain. In addition, we observed that MHC class II molecule expression on B cells differs according to the organ and the rat strain tested. All these findings are discussed in an attempt to underline the role of MHC class II molecule expression in the occurrence of mercury-induced autoimmunity.

Animals↗
PubMed1991

Beneficial effect of human therapeutic intravenous immunoglobulins (IVIg) in mercuric-chloride-induced autoimmune disease of Brown-Norway rats.

Administration of HgCl2 to the susceptible Brown-Norway (BN) strain of rats induces an autoimmune disease characterized by polyclonal B cell activation, increased serum levels of IgE and the occurrence of anti-glomerular basement membrane antibody-mediated glomerulonephritis. We have observed that the simultaneous administration to BN rats of normal human polyspecific immunoglobulins for therapeutic use (IVIg) with HgCl2 significantly decreased the occurrence and severity of proteinuria, and reduced serum IgE levels in diseased animals. Hypergammaglobulinaemia was potentiated in animals receiving HgCl2 and IVIg, compared with animals receiving HgCl2 alone. In vitro experiments indicated that F(ab')2 fragments from IVIg inhibited the binding to laminin of pathogenic anti-laminin antibodies from diseased rats, as did antibodies from the resistant Lewis strain of rats but not antibodies from susceptible BN rats. These observations suggest that IVIg may interfere with the immune regulatory mechanisms involved in mercury-induced autoimmune disease in an analogous fashion to the ability of IVIg to suppress the expression of certain pathological autoimmune responses in humans.

Animals↗
PubMed1991

Conformational prediction studies on pancreatic colipase.

Comparison of the primary structures of pancreatic colipases from man, pig, horse and rat shows a high degree of homology between proteins. Fifty-two out of the 95 residues of the polypeptide are identical. All colipases contain 10 half-cystines which are located at invariant positions. The secondary structure of colipases has been predicted from the sequence using the statistical method of Chou and Fasman and the method of Gibrat, Garnier and Robson based on information theory. Predictions indicate that colipases have a low content of alpha-helix and beta-strand structure. The two segments at positions 7-10 and 56-59, assumed to be part of the lipid binding domain, have predicted beta-sheet conformation and should be in close spatial vicinity to each other in the proteins. Four beta-turns are predicted in all colipases at positions 3-6, 46-49, 61-64, and 81-84. They might contribute, with the five disulfide bridges, to a tight packing of the protein molecule. Surface residues and major sequential antigenic determinants of mammalian colipases have been predicted using methods based either on hydrophilicity/hydropathy scales or amino acid mutability. From these studies, it appears that colipases exhibit large conformational homologies. In the absence of data on the tertiary structure of colipase, predictive methods, together with physico-chemical and immunological studies, provide valuable information on the conformation of the protein in relation to the topology of residues involved in the functional and antigenic sites.

Amino Acid Sequence↗
PubMed1991

Prevention of experimental autoimmune uveoretinitis and experimental autoimmune pinealitis in (Lewis x Brown-Norway) F1 rats by HgCl2 injections.

Mercuric chloride (HgCl2) induces in Brown-Norway (BN) and (Lewis x Brown-Norway) F1 hybrid rats a transient autoimmune disease characterized by the production of various antibodies to self and non-self antigens and by a dramatic increase of serum IgE. Experimental autoimmune uveoretinitis (EAU) can be induced in Lewis (LEW) and (LEW x BN) F1 hybrid rats by a single immunization with retinal S-antigen (S-Ag). Besides uveoretinitis, animals immunized with S-Ag develop an autoimmune pinealitis (EAP). We demonstrate in this study that (LEW x BN) F1 hybrid rats, injected with HgCl2 7 days before S-Ag immunization, are quite efficiently protected against EAU and EAP. We also show that HgCl2-induced protection is neither due to a cytotoxic effect of HgCl2 nor to CD8+ T-cell dependent mechanisms nor to the HgCl2-induced increase of serum IgE concentration. The role of other hypothetical mechanisms, such as anti-S-Ag anti-idiotypic antibodies and/or HgCl2-induced unbalance between T-helper cell subsets, is discussed.

Animals↗
PubMed1990

Permeability of the normal rat brain, spinal cord and dorsal root ganglia microcirculations to immunoglobulins G.

The distribution of blood-borne immunoglobulins G (IgG) was studied in the cerebral cortex, pineal gland, spinal cord and dorsal root ganglia of normal Lewis rats using the detection of autologous anti-horseradish peroxidase (HRP) antibodies. This detection was performed by means of light and electron microscopy. This study demonstrated that, in the cerebral cortex and the spinal cord microcirculations, endothelial cells are a restrictive barrier against IgG while IgG are able to diffuse into the perivascular parenchyma of the pineal gland and spinal ganglia.

Animals↗
PubMed1990

Inhibition of experimental autoimmune uveoretinitis by mercuric chloride injections in (Lewis x Brown Norway) F1 hybrid rats.

Experimental autoimmune uveoretinitis (EAU), induced in (LEW X BN) F1 rats by immunization with S antigen (S-Ag) is T cell and antibody (ab) mediated and anti-S-Ag IgE ab have been involved in the occurrence of ocular lesions. (LEW X BN) F1 rats repeatedly injected with HgCl2 develop an autoimmune disease characterized by numerous auto-ab and a high increase of serum IgE level. We hypothesize that large amounts of non anti-S-Ag IgE induced by HgCl2 would compete with anti-S-Ag induced by S-Ag immunization so as to prevent EAU to occur. Indeed (LEW X BN) F1 rats immunized with S-Ag 7 days after the first HgCl2 injection are strongly protected against EAU. The putative role of the different mercury-induced autoimmune phenomena in the protection against EAU are discussed.

Animals↗
PubMed1989

Inhibitory properties and antigenic specificity of monoclonal antibodies to pancreatic colipase.

To understand the mechanism by which colipase acts as a protein cofactor for anchoring pancreatic lipase at triacylglycerol/water interface, we have used an immunochemical approach. Ten monoclonal antibodies (Mabs) against porcine pancreatic procolipase were produced. Purified immunoglobulins and Fab fragments were studied for their capacity to inhibit colipase-dependent lipase activity. These studies were carried out by using procolipase, the secretory form of the cofactor, and its trypsin-treated form obtained by removal of the amino terminal pentapeptide by trypsin. Reactivities of Mabs with both forms of the cofactor were also studied by immunoenzymatic methods. Mabs 6.1, 49.20. 75.8, 270.13 and 419.1 were found to inhibit lipolysis by preventing the binding of procolipase or trypsin-treated colipase to the lipid substrate. Mab 72.11 inhibited procolipase binding but had no effect on trypsin-treated colipase. Mab 72.11 reacted with procolipase in ELISA but showed no reactivity with trypsin-treated colipase. Finally, preincubation of Mab 72.11 with porcine procolipase prevented specific cleavage at the Arg5-Gly6 bond by trypsin. It could be concluded, that the five first residues of procolipase are structural elements of the antigenic determinant recognized by Mab 72.11. Results of ELISA additivity tests (cotitrations) further indicated that epitopes for Mabs 6.1, 72.11, 270.13 and 419.1 and for Mabs 49.20 and 75.8 are located in two distinct antigenic regions of the procolipase molecule. It appears then that the lipid binding domain of the pancreatic lipase protein cofactor comprises two regions. The first region corresponds to the amino terminal fragment of the protein. The second region is likely identical with the peptide segment at position 51-59 as previously hypothesized from NMR and spectrophotometric studies. Studies carried out on procolipase chemically modified at tyrosine residues provided evidence that epitopes for Mabs 49.20 and 75.8 are in or close to the region which contains tyrosines at positions 55 and 59, and that the two peptide regions essential for interfacial binding are spatially adjacent in the procolipase and the trypsin-treated form of the cofactor. General conclusions are in accordance with the location of antigenic regions of procolipase determined by predictive methods.

Animals↗
PubMed1988

Apple Macintosh programs for nucleic and protein sequence analyses.

This paper describes a package of programs for handling and analyzing nucleic acid and protein sequences using the Apple Macintosh microcomputer. There are three important features of these programs: first, because of the now classical Macintosh interface the programs can be easily used by persons with little or no computer experience. Second, it is possible to save all the data, written in an editable scrolling text window or drawn in a graphic window, as files that can be directly used either as word processing documents or as picture documents. Third, sequences can be easily exchanged with any other computer. The package is composed of thirteen programs, written in Pascal programming language.

Amino Acid Sequence↗
PubMed1988

Construction of restriction maps.

A computer program is described, which constructs maps of restriction endonuclease cleavage sites in linear or circular DNA molecules, given the fragment lengths in single and double digestions with two enzymes. The algorithm is based upon a partition method and a very simple rule to chain fragments. The program is written in Prolog II.

Algorithms↗
PubMed1987

High frequency of autoantibodies bearing cross-reactive idiotopes among hybridomas using VH7183 genes prepared from normal and autoimmune murine strains.

Hybridomas obtained by in vitro stimulation with lipopolysaccharides (LPS) of BALB/c, MRL/lpr, and NZB splenocytes were selected for expression of VH7183 by hybridization using slot blotting. Northern blot analysis showed that the majority of hybrids produce a full length message complementary to the VH7183 probe. The frequency of VH7183 hybridomas was significantly higher in NZB mice as compared with BALB/c mice. Using multiple binding assays, 60% of the total antibodies encoded by VH7183 were specific for self-epitopes. Finally, the vast majority express cross-reactive idiotypes borne by autoantibodies of various specificities.

Animals↗