MODIFIED MOUSE LYMPHOMA CELL FORWARD MUTATION ASSAY

TO ENHANCE THE USEFULNESS OF THE MOUSE LYMPHOMA ASSAY (MLA) FOR PREDICTING THE POSSIBLE OUTCOMES OF EXPOSURE TO CHEMICALS, SOME MLA PROCEDURES WILL BE EXAMINED TO DETERMINEWHETHER A MODIFIED ASSAY WOULD PERMIT GREATER SENSITIVITY AND EASE OF PERFORMANCE. PHASE I RESEARCH WILL INCLUDE: (1) AUTORADIOGRAPHY STUDIES TO DETERMINE IF THE PROCEDURES USED TO CLEANSE THE CULTURES OF TK-/-CELLS RENDER THE CELLS MORE SUSCEPTIBLE TO THE EFFECTS OF MUTAGENS, INDUCE A SYNCHRONOUS POPULATION OF CELLS THAT MAY BE PRESENT AT THE TIME OF CHEMICAL EXPOSURE, AND/OR INDUCE MUTAGENESIS AND CHROMOSOMAL ABERRATIONS; (2) MUTAGENESIS ASSAYS TO EVALUATE THE IMPACT OF VARYING THE EXPOSURE TIME TO DIFFERENT CHEMICAL CONCENTRATIONS; (3) USE OF AN AUTOMATED SYSTEM TO DETERMINE THE MOST PRECISE AND EFFICIENT METHOD FOR COUNTINGCELLS IN SUSPENSION; AND (4) EXPERIMENTS TO INVESTIGATE ASSAY MODIFICATIONS FOR CLONING CELLS IMMEDIATELY AFTER THE CLONING PERIOD. BASED ON THE OUTCOME OF PHASE I EXPERIMEN- TATION, A MODIFIED MLA WILL BE RECOMMENDED. IT WILL BE EVALUATED IN PHASE II BY ADDITIONAL RESEARCH AND THE TESTINGOF CODED COMPOUNDS. AS A RESULT OF THIS RESEARCH, THE MLA SHOULD BE MORE SENSITIVE, ECONOMICAL, AND PREDICTIVE OF GENOTOXICITY, WHICH SHOULD LEAD TO GREATER ACCEPTABILITY ANDUSE OF THE ASSAY IN INDUSTRIAL AND COMMERCIAL LABORATORIES.