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 (H2L2), heavy chain dimers (H2), half molecules (HL), H, light chain dimers (L2), and L chains. All gamma globulin subunits as well as the complete H2L2 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

INDEPENDENT SYNTHESIS OF LIGHT AND HEAVY CHAINS : Quantitation of Light-Chain Production by Mouse Myeloma Variants

The rates of immunoglobulin synthesis have been examined in two MFC-11 cell lines which were independently adapted to tissue culture and in light-chain-producing variants derived from each of them. One cell line synthesized 2.5 pg immunoglobulin/cell/h, while the other synthesized 3.6 pg immunoglobulin/cell/h. The ratio of heavy and light chains in the two cell lines was approximately the same, and the size of the intracellular pool of immunoglobulin was proportioned to the rate of synthesis. Variants which had spontaneously lost the ability to produce heavy chains continued to synthesize light chains at approximately the same rate as their parent cell line

SYNTHESIS, ASSEMBLY, AND SECRETION OF GAMMA GLOBULIN BY MOUSE MYELOMA CELLS : III. 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. H2 and H2L were the major precursors of IgG2a and IgG1 but, in all of the tumors, HL was also an intermediate. In contrast, HL was a major precursor of IgG2b. 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

Targeted Neuronal Death Affects Neuronal Replacement and Vocal Behavior in Adult Songbirds

AbstractIn the high vocal center (HVC) of adult songbirds, increases in spontaneous neuronal replacement correlate with song changes and with cell death. We experimentally induced death of specific HVC neuron types in adult male zebra finches using targeted photolysis. Induced death of a projection neuron type that normally turns over resulted in compensatory replacement of the same type. Induced death of the normally nonreplaced type did not stimulate their replacement. In juveniles, death of the latter type increased recruitment of the replaceable kind. We infer that neuronal death regulates the recruitment of replaceable neurons. Song deteriorated in some birds only after elimination of replaceable neurons. Behavioral deficits were transient and followed by variable degrees of recovery. This raises the possibility that induced neuronal replacement can restore a learned behavior