The invention relates to proteins characterized in that they are proteins for communication between cells of a given type and the contiguous or proximal heterologous cells.

This involves an in vitro assay system to screen for mutagenic and/or carcinogenic agents based on alterations in the fidelity of DNA synthesis. In the system, chemicals will be tested for their mutagenicity or carcinogenicity by measuring increases in the number of mistakes incorporated by purified DNA polymerases using synthetic polynucleotide templates. This system offers the advantage of performing this analysis in the test tube so that all parameters in the reaction can be monitored. Agents that enhance misincorporation during DNA synthesis would be predicted to have a higher probability of being mutagens or carcinogens in the human population.

A method for determining in a patient the presence or absence of a pathological condition producing a specific immune response. The antigen associated with the pathological condition is labeled and added to a sample of the patient's lymphocytes and to a control sample. Comparison of the antigen-binding capacity of the patient's lymphocytes to that of the control sample is related to the presence or absence of the pathological condition.

Mutagenicity assay method involving exposing a population of an animal species to a suspected mutagen and then scoring the occurrence, in a subsequent generation, of animals of a size substantially different from that of the exposed population as a measure of the mutagenicity of the suspected mutagen.

The present invention relates to methods for detecting the presence of ribonuclease enzymes, more specifically to methods that provide for a visual detection assay. The methods entail contacting a test sample suspected of containing ribonuclease activity with a substrate containing a ribonuclease-sensitive internucleotide linkage flanked directly or indirectly by a fluorescence reporter group and a dark quencher, such that if a ribonuclease activity is present in the sample, the ribonuclease-sensitive internucleotide linkage is cleaved and the fluorescence reporter group emits a visually detectable signal. The present invention further provides novel nucleic acid compositions used as substrates for such assays and encompasses kits for performing the methods of the invention.