Improved basal medium for Y-1 mouse adrenal cortex tumor cells in culture

Summary An improved basal medium is presented that requires only minimal supplementation with dialyzed fetal bovine serum or bovine serum albumin and fetuin to be comparable to Ham's F-10, which requires 15% horse serum (HS) and 2.5% fetal bovine serum (FBS) for the growth and function of Y-1, mouse adrenal cortex tumor, cells. Cell monolayers maintained for up to 2 weeks without any protein supplementation have retained their steroid response to ACTH. The medium differs from Ham's F-10 in its buffer composition and higher calcium-ion concentration. This medium should be a useful adjunct to studies pertaining to steroid and lipid intermediary metabolism, the retention of a specialized physiological function in a chemically defined medium, and the mechanism of hormonal response. Supported by the Medical Research Service of the Veterans Administration.     

Radioimmune assay of tubulin applied to oligomers, synaptic membranes, and plants

A radioimmune assay for microtubule protein, tubulin, is described, in which unknown amounts of native or denatured tubulin can be quantitated by the ability to compete with pure [¹²⁵I]tubulin for rabbit antibodies produced against purified bovine brain tubulin. The assay is used to demonstrate that crude extracts of mouse brain contain negligible amounts of 30–36S tubulin oligomers under conditions where purified tubulin forms substantial amounts of such structures. Also, the particulate fraction of osmotically shocked and sonicated brain synaptosomes contains negligible tubulin antigenic activity. By contrast, soluble extracts of soybean, especially rapidly dividing regions of the plant, were found to contain significant amounts of cross-reacting material, providing further evidence for the conservative evolutionary nature of this ubiquitous and important protein.     

Cell surface component(s) involved in rat hepatocyte intercellular adhesion

Aggregation of rat hepatocytes was effectively inhibited by monovalent antibodies (Fab fragments) directed against hepatocyte plasma membranes, but monovalent antibodies against some distinct, known hepatocyte surface antigens had no effect. Surface antigens, which neutralized the Fab inhibiting effect on cell aggregation, could be solubilized from plasma membranes by limited proteolytic digestion. Thus, hepatocyte intercellular adhesion seems to involve specific cell surface components, which may be proteins or protein derivatives.     

Bromoacetylcholine as an affinity label of the acetylcholine receptor from Torpedo californica

Bromoacetyl[methyl-³H]choline is a highly specific label for the reduced acetylcholine binding site on the acetylcholine receptor from $\text{Torpedo californica}$. Only one of two binding sites per receptor monomer is susceptible to labeling. The labeled site is on the α chain of the receptor.