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M D Scharff

Publications and source records attributed to M D Scharff.

At least 163 records · Page 9Linked to original sources
PubMed1971

Synthesis, assembly, and secretion of gamma globulin by mouse myeloma cells. 3. Assembly of the three subclasses of IgG.

The synthesis, assembly, and secretion of the three major subclasses of mouse IgG has been examined in 14 myeloma tumors and two cultured cell lines as well as in the cells from the popliteal lymph nodes of immunized mice. The total amount of IgG synthesized was between 15 and 43% of the cytoplasmic proteins made during a 15 min period. H(2) and H(2)L were the major precursors of IgG(2a) and IgG(1) but, in all of the tumors, HL was also an intermediate. In contrast, HL was a major precursor of IgG(2b). Most of the noncovalent and covalent assembly of IgG occurred after release of the newly synthesized H and L chains from the polyribosomes and assembly was not completed until 10 min or more after the synthesis of the polypeptide chains.

Animals↗
PubMed1971

Synthesis and assembly of immunoglobulins by malignant human plasmacytes and lymphocytes. II. Heterogeneity of assembly in cells producing IgM proteins.

Bone marrow or lymph node cells from 10 patients whose sera contained large amounts of monoclonal IgM proteins were incubated with radioactive amino acids in short-term tissue culture. Samples of soluble cytoplasmic extracts and secreted material were examined by immunologic precipitation with specific antisera, acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, and sucrose gradient centrifugation. In all samples studied, 8S IgM was the major intracellular precursor of the fully assembled 19S protein. Cells obtained from some patients contained little or no fully assembled 19S protein intracellularly; however, cells from most patients seemed to accumulate fully assembled 19S molecules intracellularly before secretion. Secreted material from both groups contained large amounts of 19S IgM. The differentiation between accumulating and nonaccumulating cells did not correlate with heavy or light chain antigenic type. Synthesis and assembly appeared to be identical in cells obtained from different anatomic sites in the same patient Studies carried out in one patient before and after therapy revealed no qualitative differences in the pathway of assembly and reflected only a decrease in the total number of immunoglobulin-producing cells.

Blood Protein Electrophoresis↗
PubMed1971

Rate of somatic mutation in immunoglobulin production by mouse myeloma cells.

Cultures of mouse myeloma cells which secrete both heavy (H) and light (L) immunoglobulin chains were cloned in soft agar. Variants that synthesized neither chain, or only light chains, were detected by overlaying the growing colonies with antiserum specific for the individual immunoglobulin chains. The rate of conversion of heavy plus light chain producers to light chain producers was 1.1 x 10(-3) per cell per generation, as determined by fluctuation analysis.

Animals↗
PubMed1970

Synthesis and assembly of immunoglobulins by malignant human plasmacytes. I. Myelomas producing gamma-chains and light chains.

Three basic patterns of gamma-globulin synthesis are described in malignant human plasmacytes: extreme unbalanced synthesis where only L chains are synthesized; unbalanced synthesis in which intact gammaG globulin and an excess of free L chains are synthesized and secreted; and balanced synthesis where H and L chains appear to be synthesized in equimolar amounts. Studies of the cellular products appear to reflect the biosynthetic processes of the cells in a more reliable fashion than does analysis of serum or urinary proteins. The absence of Bence Jones proteins from the urine does not necessarily indicate that free L chains are not being synthesized and secreted at the cellular level. Similarly, the completed globulin molecule secreted by malignant plasma cells may not be demonstrable by examination of serum. Patterns of globulin synthesis in human myelomatous tissues vary as do patterns of globulin synthesis in mouse plasmacytomas. Pulse-chase studies of the cells from one patient showed that a gammaG myeloma protein was assembled via an HL (half molecule) intermediate.

Bence Jones Protein↗
PubMed1970

Synthesis, assembly, and secretion of gamma globulin by mouse myeloma cells. I. Adaptation of the Merwin plasma cell tumor-11 to culture, cloning, and characterization of gamma globulin subunits.

MPC-11 myeloma tumor cells were adapted to growth in continuous culture. The cultured cells resembled the parent tumor in that they produced the fully assembled gamma globulin molecules as well as six unassembled molecules. Although cultured and tumor cells synthesized excess light chains, the molar ratio of light (L) to heavy (H) chains was approximately 1.7:1 in the culture, and 3.5:1 in the tumor. The cultured cells also produced fewer half molecules and free light chains than the parent tumor. Peptide column analysis did not reveal differences in the primary structure of the H chains derived from the parent tumor and the culture. The L chains may have differed by a minor peptide. As much as 20% of the newly labeled cytoplasmic proteins and almost 100% of the proteins secreted by the cultured myeloma cells could be precipitated by specific antiserum. The immune precipitates contained seven different gamma globulin molecules, six of which were characterized according to their molecular size and H and L chain content as fully assembled molecules (H(2)L(2)), heavy chain dimers (H(2)), half molecules (HL), H, light chain dimers (L(2)), and L chains. All gamma globulin subunits as well as the complete H(2)L(2) molecule were produced and secreted by splenic clones of the parent MPC-11 tumor, and agar clones of the cultured cells. This indicates that the various gamma globulin subunits were produced by the same cell and did not reflect cellular heterogeneity with respect to gamma globulin synthesis.

Animals↗
PubMed1970

Immunoglobulin production: method for quantitatively detecting variant myeloma cells.

Mouse myeloma cells in continuous culture were cloned in soft agar. The clones were assayed for their ability to synthesize heavy and light chains of gamma globulin by immunoprecipitation directly in the agar. A minor population secreting only light chains was identified. The two cell types were recloned and a low incidence of conversion of 7S to light-chain production was demonstrated. This technique can be used to isolate rare variants of cells secreting specific macromolecules.

Animals↗
PubMed1970

Harry Eagle.

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Biology↗