The Cuisinart food processor efficiently disaggregates tissues.

The Cuisinart Model DLC-7 PRO food processor efficiently disaggregates plant and animal tissues resulting in time savings and often increased yields in the isolated material.

Activity of alkylated prolactin and human growth hormone in receptor and cell assays.

The disulfide bonds of two lactogenic hormones, ovine prolactin (oPRL) and human growth hormone (hGH), were reduced with dithiothreitol under denaturing conditions and alkylated with iodoacetic acid. The modified hormones were assayed for their ability to bind the plasma membrane-bound receptor for lactogenic hormone found in the rabbit mammary gland. S-Carboxymethylated ovine prolactin (SCM-oPRL) with all six cysteine residues modified had a nearly 300-fold decrease in binding as compared to native oPRL in a competitive binding assay using [125I]ovine prolactin. The S-carboxymethylated human growth hormone (SCM-hGH) had all four of its cysteine residues modified. It showed only a slightly reduced ability to bind the rabbit mammary gland prolactin receptor in a competitive binding assay with [125I]ovine prolactin. The two modified hormones were assayed for their ability to stimulate proliferation of the lactogen-dependent Nb 2 lymphoma cell line. SCM-oPRL required concentrations greater than 1 X 10(5) that of native oPRL to stimulate 50% of the maximum cell growth. SCM-hGH retained a significant amount of its ability to stimulate the Nb 2 lymphoma cells.

Purification of rabbit mammary prolactin receptor by acidic elution from a prolactin affinity column.

Membrane-bound prolactin receptors from the mammary gland of 6-7-day postpartum lactating rabbits were solubilized using the zwitterionic detergent, Zwittergent 3-12 (3- dodecyldimethylammonio )-1-propanesulfonate). The solubilized receptor from one rabbit was bound to an ovine prolactin-agarose affinity gel and eluted at pH 4.2. The receptor appeared as a single band upon staining sodium dodecyl sulfate-polyacrylamide gels with Coomassie blue. The protein yield from one rabbit was about 8 micrograms and the overall yield of receptor was over 50%. The apparent molecular weight was 42,000 on sodium dodecyl sulfate gels but varied on molecular weight columns due to the type of detergent. Receptor inactivated by iodination had an apparent molecular weight of 21,000 on sodium dodecyl sulfate gels. The purified receptor did not bind to concanavalin A-agarose or Lens culinaris-agarose.

pH dependence of dissociation of the ovine prolactin rabbit mammary receptor complex.

Ovine prolactin specifically bound to rabbit mammary membrane prolactin receptor was rapidly dissociated in a pH dependent manner with 0.1M ammonium acetate. Up to 75% of the bound hormone was dissociated at pH 4.0 or lower in less than 5 minutes. The pK of the dissociation was 4.7, implicating one or more critical carboxyl groups. Exposure of the membrane bound receptor to the dissociating buffer for up to one hour did not reduce its ability to bind hormone. The dissociated hormone was characterized as intact ovine prolactin by Bio-Gel P-150 gel chromatography and by its ability to bind to fresh rabbit prolactin receptor with the same binding affinity as native hormone.