title: Mouse lymphoma thymidine kinase gene mutation assay: follow-up International Workshop on Genotoxicity Test Procedures, New Orleans, Louisiana, April 2000.
abstract: The Mouse Lymphoma Assay (MLA) Workgroup of the International Workshop on Genotoxicity Test Procedures held a second harmonization meeting just prior to the U.S. Environmental Mutagen Society Meeting in New Orleans, LA, in April 2000. The discussion focused on several important aspects of the MLA, including: 1) cytotoxicity measures and their determination, 2) use of a 24-hr treatment, 3) the ability of the assay to detect aneugens, and 4) concentration selection. Prior to the meeting the group developed Microsoft Excel Workbooks for data entry. Ten laboratories entered their data into the workbooks (primarily as coded chemicals). The Excel Workbooks were used to facilitate data analysis by generating an extensive set of graphs that were evaluated by the meeting participants. Based on the Workgroup's previous agreement that a single cytotoxicity measure should be established for both the microwell and soft agar versions of the assay, the Workgroup analyzed the submitted data and unanimously agreed that the relative total growth (RTG) should be used as the cytotoxicity measure for concentration selection and data evaluation. The Workgroup also agreed that the various cytotoxicity measures should be calculated using the same methods regardless of whether the soft agar or microwell version of the assay was used. In the absence of sufficient data to make a definitive determination, the Workgroup continued to endorse the International Committee on Harmonization recommendation for the use of 24-hr treatment and made some specific 24-hr treatment protocol recommendations. The Workgroup recognized the ability of the MLA to detect at least some aneugens and also developed general guidance and requirements for appropriate concentration selection.
authors.affiliation: National Center for Toxicological Research, Food and Drug Administration, Jefferson, AR, USA.
authors.forename: Martha M
authors.initials: MM
authors.lastname: Moore
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Honma
authors.forename: Julie
authors.initials: J
authors.lastname: Clements
authors.forename: Karen
authors.initials: K
authors.lastname: Harrington-Brock
authors.forename: Takumi
authors.initials: T
authors.lastname: Awogi
authors.forename: George
authors.initials: G
authors.lastname: Bolcsfoldi
authors.forename: Maria
authors.initials: M
authors.lastname: Cifone
authors.forename: Deborah
authors.initials: D
authors.lastname: Collard
authors.forename: Michael
authors.initials: M
authors.lastname: Fellows
authors.forename: Kathryn
authors.initials: K
authors.lastname: Flanders
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Gollapudi
authors.forename: Peter
authors.initials: P
authors.lastname: Jenkinson
authors.forename: Paul
authors.initials: P
authors.lastname: Kirby
authors.forename: Stephan
authors.initials: S
authors.lastname: Kirchner
authors.forename: Joann
authors.initials: J
authors.lastname: Kraycer
authors.forename: Stephen
authors.initials: S
authors.lastname: McEnaney
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Muster
authors.forename: Brian
authors.initials: B
authors.lastname: Myhr
authors.forename: Michael
authors.initials: M
authors.lastname: O'Donovan
authors.forename: Jo
authors.initials: J
authors.lastname: Oliver
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Ouldelhkim
authors.forename: Kamala
authors.initials: K
authors.lastname: Pant
authors.forename: Robert
authors.initials: R
authors.lastname: Preston
authors.forename: Colin
authors.initials: C
authors.lastname: Riach
authors.forename: Richard
authors.initials: R
authors.lastname: San
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Shimada
authors.forename: Leon F
authors.initials: LF
authors.lastname: Stankowski
mesh_terms: D000818:Animals; D004493:Education; D017408:Guidelines as Topic; D008223:Lymphoma / Q000201:enzymology*; D051379:Mice; D009152:Mutagenicity Tests / Q000379:methods*; D009154:Mutation; D013937:Thymidine Kinase / Q000235:genetics*; D013997:Time Factors
chemical_list: D013937:Thymidine Kinase