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Advances in Micronucleus Analysis
by Flow Cytometry
Environmental Mutagen Society Workshop, 2007
An extremely well attended event, this workshop brought together noted experts to discuss micronucleus analysis by flow cytometry and present data based on their own research.
Dr. James MacGregor, Toxicology Consulting Services
Due to an unexpected circumstance, Dr. MacGregor was not able to attend this year's meeting. Instead, Dr. Steve Dertinger presented his data and conclusions concerning MicroFlow analysis in the peripheral blood of various species.
According to Dr. MacGregor, the data show the frequency of MN-RETs in peripheral blood determined by flow cytometric analysis: 1) accurately reflect increases in bone marrow for the species considered; 2) is minimally invasive and requires only µl quantities of blood; and 3) is easily determined during routine toxicology studies. This last point provides an index of in vivo cytogenetic damage in relevant species for which other toxicological, metabolic, and kinetic information are already available.
Dr. Leslie Recio, Integrated Laboratory Sciences
Flow Cytometry Based Micronucleus Assay as an Investigative Toxicology Tool
Dr. Recio presented data from studies designed to determine mechanism of micronucleus formation (clastogen vs. aneugen) and pathways of response to genotoxic stress. The results indicate that the MicroFlow method can be used to determine modes of action at several levels for studies in rats and mice.
Dr. Jack Bishop, National Institute of Environmental Health Sciences
Detection of Elevated % MN-RETs in Blood of Infants and Mothers Following Prenatal AZT
Dr. Bishop presented data that revealed 10-fold increases in % MN-RET in women and their infants who received AZT-containing antiretroviral therapy prenatally, while no increases were seen in those who did not receive AZT. This demonstrated that transplacental AZT exposure is genotoxic in humans. Results indicate that infants exposed to AZT need to be monitored for potential long-term effects.
Dr. Robert Heflich, National Center for Toxicological Research, US FDA
Using Flow Cytometry to Measure Micronuclei in Mice Exposed Transplacentally and Neonatally to AZT and Other Antiretroviral Agents
Dr. Heflich presented data that showed rapid analysis of micronuclei can be conducted in neonatal mice by employing the MicroFlow method. Micronuclei were evaluated in 1 to 16 day old mice treated neonatally and/or transplacentally with various drug and drug combinations used to prevent mother-to-child transmission of the HIV-1 virus. Generally, the highest % micronuclei were detected in 9 to 10 day-old mice and with drug regimens that included AZT.
Dr. Jeff Bemis, Litron Laboratories
Micronucleated Reticulocytes: Bridging Preclinical and Clinical Genetox Assessments
Dr. Bemis described how hydroxyurea (HU) therapy in adults with Sickle Cell Disease (SCD) has proven to be an effective means to manage symptoms and improve quality of life. The observed in vitro and in vivo genotoxic effects of HU raise concerns about its use in pediatric patients. Micronucleated reticulocyte data from a preliminary examination of young SCD patients, with and without HU therapy, were presented.
Dr. Ronald Fiedler, Pfizer
Flow Cytometric Analysis of Rat Bone Marrow for Micronuclei using the CD71 MicroFlow Technology
Dr. Fiedler demonstrated that the CD71 method, established in blood, can be reliably applied to fractionated bone marrow specimens with only slight modifications. He reported that the MicroFlow method has been incorporated into routine bone marrow analysis for Pfizer’s exploratory assays and those used for regulatory submission under Good Laboratory Practice (GLP) regulations.
Dr. Jeff Bemis, Litron Laboratories
In Vitro Micronucleus Analysis by Flow Cytometry
Dr. Bemis gave a brief introduction to the In Vitro MicroFlow method currently under development at Litron. This automated method takes advantage of the speed, objectivity and throughput capacity of flow cytometry and combines that with a robust cytotoxicity assessment system.
These excellent presentations illustrated how micronucleated reticulocyte measurements can serve a cross-species role, bridging pre-clinical safety assessments to human exposure scenarios. Overall, the session was considered an engaging and valuable event.
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