Early steps in insulin action.

The biological effects of insulin are initiated by the binding of insulin to the insulin receptor. Insulin binds to the extracellular domain of the insulin receptor and induces conformational changes in the receptor, leading to autophosphorylation of the receptor on intracellular tyrosine residues. These phosphorylated tyrosine residues act as binding sites for proteins which subsequently may be phosphorylated by the insulin receptor. As a result, yet other proteins can be recruited to form larger complexes and, in the case of enzymes, changes in their activity may take place. By a combination of these processes, the activated insulin receptor initiates cascades of biochemical events which are regulated mainly by specific phosphorylation or dephosphorylation reactions. Intermediates which are involved in the normal insulin signalling pathway are subjects of expanding research.

Affinity chromatography with the immobilized agonist N-0434 yields an active and highly purified preparation of the dopamine D-2 receptor from bovine striatum.

Partial purification of the dopamine D-2 receptor from bovine striatum, solubilized in the presence of 1% digitonin, was obtained by chromatography on wheat germ lectin agarose. The preparation was purified approximately 10-fold. The stability of the receptor preparation was considerably improved and non-specific protein absorption on the affinity gel used later was decreased. Further purification was achieved on a column containing a D-2-selective agonist, N-0434. Approximately 90% of the receptor activity was bound to the gel and 20-40% of the activity could be eluted by pH shock. The total purification factor after one affinity chromatography step was estimated to be at least 1500. An active preparation of at least 20% purity was obtained after a second cycle of affinity chromatography. This corresponds to an enrichment of more than 5000 times compared to the solubilized receptor preparation.

Natural antibodies in human sera cross-reactive with type C RNA tumor viral P 30.

Antibodies cross-reactive with type C viral p30 were concentrated from 105 samples of human plasma by affinity chromatography using Sepharose beads to which disrupted Simian sarcoma associated virus (SSAV) had been coupled. Eluates obtained from the affinity beads were tested for anti-p30 activity by performing radio-immunoprecipitations with 125I-labeled SSAV p30 and Rauscher murine leukemia viral (R-MuLV) p30. Forty six percent of the eluates were found positive when tested against SSAV p30. From 44 positive eluates for anti SSAV p30 activity, 20 (45%) were also found to be positive for anti-R-MuLV p30 activity. No significant difference was found in anti-p30 activity in eluates from normal controls and from patients with various kinds of malignancy.

The antigen spot test (AST): a highly sensitive assay for the detection of antibodies.

A method is described for detection of antibodies by means of nitrocellulose or diazobenzyloxymethyl (DBM) paper on which various antigens have been spotted. The sensitivity of this antigen spot test (AST) is comparable with that of RIA and ELISA. The method requires only nanogram amounts of antigen. Since a variety of antigens can be spotted on a single piece of nitrocellulose or DBM paper, this antigen spot test is especially useful for specificity controls on antibodies.