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R Baumal

Publications and source records attributed to R Baumal.

At least 145 records · Page 8Linked to original sources
PubMed1976

Casein-induced murine amyloidosis: amyloid and immunoglobulin production and proliferative capacity of splenocytes.

We have examined some aspects of lymphocyte and macrophage function in experimental murine amyloidosis. Casein-induced murine amyloidosis is a good model for studying secondary human amyloidosis while myeloma-associated murine amyloidosis is a poor model for human myeloma-associated amyloidosis. The amyloid of casein-induced and myeloma-associated murine amyloidosis cross-reacted immunologically. Neither form of amyloidosis was associated with L chain fragments or excess L chain production. Cellular immunologic reactivity of casein-induced amyloidotic mice, as assessed by lymphocyte transformation with mitogens, was abnormal using spleen lymphocytes but completely normal when thymus and peripheral blood lymphocytes were examined. The depressed activity could be attributed to splenic amyloid deposits. Intracellular amyloid was detected in the spleens of casein-injected mice prior to extracellular amyloid deposits. Amyloid containing cells could also be cultured from the spleen in a much higher proportion than that found in vivo. These cells may represent a subpopulation committed to amyloid synthesis.

Amyloid↗
PubMed1976

Covalent assembly of mouse immunoglobulin G subclasses in vitro: application of a theoretical model for interchain disulfide bond formation.

The pathways and kinetics of interchain disulfide bond formation have been determined in vitro for purified myeloma proteins representing the three major subclasses of mouse immunoglobulin G(IgG) using the reoxidation system described previously (Petersen, J.G.L. & Dorrington, K.J. (1974) J. Biol. Chem. 249, 5633-5641). Mixtures of oxidized and reduced glutathione were added to act as a disulfide interchange catalyst. The pathways of covalent assembly observed in vitro were qualitatively and quantitatively similar to those followed by the various subclasses in vivo. HH and HHL were the principle covalent intermediates seen with IgG1 (MOPC 31C) and IgG2a (MOPC 173 and clone 19). With IgG2b( MPC 11C), HL, HH and HHL were all prominant intermediates. The time courses of reoxidation were simulated using a theoretical model based on second-order reaction kinetics (Percy, J.R., Percy, M.E. & Dorrington, K.J. (1974) J. Biol. Chem. 250, 2398-2400). Two distinct phases were apparent in the reoxidation sequence. The first, which lasted for the initial 5-15 min, did not confirm to the theoretical model. The second phase could be accounted for by the model and represented the remainder of the covalent assembly process. The physico-chemical basis for this biphasic phenomenon was explored. Sedimentation velocity studies showed that noncovalent association was incomplete at the beginning of the reoxidation step for all proteins except IgG2b (MOPC 11C). No dissociation was apparent in the reduced and alkylated proteins at pH 5 in the absence of prior exposure to acid conditions. Thus, exposure to acid appears to affect the affinity between the subunits in the native proteins. Transfer of the proteins from pH 5 to pH 8.2 (the pH at which reoxidation proceeds) is accompanied by the generation of an absorption difference spectrum over an 8-10 min period. These data suggest that a pH-dependent conformational relaxation process may influence the early stages of reoxidation.

Binding Sites↗
PubMed1976

Assembly of three major subclasses of mouse immunoglobulin G: a theoretical model for covalent assembly in vivo.

A mathematical model, based on second-order reaction kinetics, has been used to describe the covalent assembly of immunoglobulin G(IgG) in vitro from its heavy (H) and light (L) chains (Percy, M.E., Baumal, R., Dorrington, K.J. & Percy, J. (1976) Can. J. Biochem. 54, 675-687). In the present paper, the same model has now been applied to the steady-state assembly of IgG in vivo. This mathematical approach permits a quantitative comparison of the pathways of covalent assembly used by given immunoglobulins in vivo and in vitro. The assumptions in the model are: the species L, H, HL, HH, HHL and LHHL belong to a common pool; incompleted IgG intermediates may freely assemble to form HL, HH, HHL and LHHL; the reaction rate for covalent linkage between any two reacting species is proportional to the products of the number densities of the reactants and to a parameter P which takes the value PHH if the reaction joins two H chains, and PHL if it joins an H and L chain. In vivo values of PHH/PHL were determined for the 18 mouse myeloma tumours and cell lines studied by Baumal et al. (Baumal, R., Potter, M. & Scharff, M. (1971) J. Exp. Med. 134, 1316-1334). From these analyses, we have arrived at the following conclusions: (1) the three major IgG subclasses have distinctive values of PHH/PHL (mean value 53 for IgG1, 12 for IgG2a and 2.8 for IgG2b); (2) for IgGs of the same subclass, the values of PHH/PHL are similar; (3) the mean in vivo values of PHH/PHL are very close to those determined from in vitro assembly experiments. Finally, the individual values of PHH/PHL have been used to simulate pulse-chase experiments in the various tumours and cell lines. Considering the sources and magnitude of experimental error, the theoretical pathways of assembly agree with those determined qualitatively from the pulse-chase experiments.

Cell Line↗
PubMed1976

Inhibition of anaphylactic histamine release by Forssman antiserum. I. Characteristics of the reaction and inhibitor.

Forssman antiserum produced in rabbits immunized with sheep erythrocyte stromata was found to contain an IgG antibody which inhibited both passive anaphylactic sensitization of guinea-pig lung and also histamine-releasing activity of soluble immune complexes. This Forssman antibody did not itself cause histamine release or depletion of lung histamine stores. The IgM haemolysin component of the Forssman antiserum was not associated with inhibitory activity. The inhibition by the IgG Forssman antibody differed from that of normal rabbit gammaglobulin both in its irreversible character and in being absorbed by sheep erythrocytes. The inhibitory antibody had no effect on the histamine-releasing activity of compound 48/80, anaphylatoxin or reversed anaphylaxis. It was concluded that IgG Forssman antibody probably blocks the tissue receptor(s) for anaphylactic antibody in guinea-pig lung.

Anaphylaxis↗
PubMed1976

Immunoglobulin biosynthesis by the MOPC 173 mouse myeloma tumor and a variant spleen clone.

The IgG2a producing MOPC 173 tumor synthesizes heavy (H) and light (L) chains and assembles them into H2L2 utilizing heavy chain dimers (H2) and H2L as the major precursors. Although the tumor cells secrete only H2L2, they synthesize excess L chains which appear to be degraded and are not secreted. A L chain-producing variant arising spontaneously from the MOPC 173 tumor also failed to secrete any L chains. MOPC 173 tumor cells were cloned in the spleens of normal BALB/c mice and 1 of 23 spleen clones appeared to differ from the parent tumor in demonstrating a) a transient block in the assembly of H2L2 at the H2 level, leading to delayed formation and secretion of H2L2, b) appreciable amounts of non-covalently bonded H2L, c) an abnormal intracellular immunoglobulin species, H4, d) production of equimolar amounts of H and L chains. The patterns of immunoglobulin synthesis and assembly demonstrable in the above studies were also observed when tumor cells were studied in situ. Tryptic peptide mapping of the H and L chains produced by the MOPC 173 tumor and the variant spleen clone failed to demonstrate any differences in the H chains, but there were definite chemical differences in the L chains. These studies indicate that variant myeloma cells producing structurally altered immunoglobulins may continually be arising in myeloma tumors.

Animals↗
PubMed1975

Experimental murine amyloidosis: a model system for studying amyloid formation.

Myeloma-associated and casein-induced murine amyloidosis were used as models to study the role of lymphocytes and macrophages in amyloid formation. Amyloidosis occurred rarely and in small amounts in Balb/C mice with immunoglobulin (Ig)-producing myeloma tumours but large amounts could be induced by injections of casein. Fluorescent staining of both forms of amyloid deposits by means of anti-casein- and anti-myeloma-amyloid antibodies indicated that they either crossreacted or coexisted. Nor abnormality of Ig biosynthesis was detected in amyloidosis, suggesting that abnormal degradation was responsible for production of the Ig form of amyloid. Although spleen lymphocytes of casein-injected mice with amyloidosis demonstrated diminished cellular immunologic responses, this did not indicate generalized immunologic incompetence. The non-Ig form of amyloid in casein-injected mice was shown to be produced by macrophages, and a technique was developed for increasing the yield of amyloid-containing cells.

Amyloid↗
PubMed1975

Immunoglobulin biosynthesis in myeloma-associated and casein- and endotoxin-induced murine amyloidosis.

Amyloidosis was induced in C57BL mice by daily injections of casein and in BALB/c mice by daily injections of endotoxin. There was no obvious disorder of immunoglobulin biosynthesis by spleen lymphocytes in these mice either before, during the development of, or in the amyloidotic stage. The pattern of immunoglobulin synthesis, assembly, and secretion was unaltered, the relative amount of heavy and light chains produced was normal, and there was an absence of immunoglobulin polypeptide chain fragments. Small amounts of amyloid were present in only 1 of 19 BALB/c and C3H mice (the IgG2a producing MOPC 173 tumor) bearing immunoglobulin-producing myeloma tumors and variants of these tumors. There was no relationship between excess light chain production by tumor plasma cells or spleen lymphocytes and the development of amyloidosis and there were no light chain fragments demonstrable. Antiserum prepared against casein-induced amyloid cross-reacted by immunofluorescence with the amyloid present in the MOPC 173 tumor-bearing mice, indicating the presence of common antigenic determinants in these two forms of amyloid. Attempts to study the biosynthesis of amyloid with incorporation of radioactively labeled amino acids were unsucessful.

Amyloid↗
PubMed1975

Synthesis but not secretion of J chain by variant mouse myeloma cells which lose alpha-chain-synthesizing ability.

We have devised a rapid method for obtaining large amounts of J chain from IgA in the ascitic fluid of mice bearing the MOPC 315 tumor. The J chain was released by reduction from the MOPC 315 IgA adsorbed onto a DNP-lysyl-Sepharose column, and was further purified by DEAE Sephadex chromatography. The mouse J chain was characterized as to its electrophoretic mobility, amino acid composition, apparent size, presence in different immunoglobulin classes, and reactivity with an antiserum containing anti-J chain activity. Variant cell lines have been selected from the IgA-producing mouse myeloma cell line MOPC 315. The variants did not synthesize detectable quantities of alpha heavy chains but continued to synthesize and secrete light chains. J chain was synthesized by both parent and variant cell lines but only secreted by the parent cells. It is postulated that J chain synthesis is not dependent on alpha heavy chain synthesis, but that secretion of J chain by MOPC 315 cells occurs only because of its attachment to the Ig1 molecule.

Amino Acids↗
PubMed1973

Mutations in immunoglobulin-producing mouse myeloma cells.

Three mouse myeloma cell lines were cloned in soft agar and screened by an antiserum overlay method for variants defective in secretion of the myeloma protein. Variants that had lost the capacity to synthesize heavy chains arose spontaneously at a high rate of about 10(-3) per cell per generation. Such variants lost the capacity to produce light chains at a similarly high rate. After cells were treated with the acridine half mustard ICR-191, variants occurred with an even higher incidence, and some of these synthesized heavy chains differing from that of the parent.

Acridines↗