The AMeX method: a multipurpose tissue-processing and paraffin-embedding method. II. Extraction of spooled DNA and its application to Southern blot hybridization analysis.

In our previous report, we described a new fixation and paraffin-embedding method (the AMeX method) that preserves many of the antigens that are normally destroyed by routine formalin fixation. The current study was conducted to examine the preservation of high-molecular-weight DNA in tissues processed by this method. DNA was extracted from AMeX-processed tissue sections after deparaffinization by the same method as that used to extract DNA from fresh tissues. The total amounts of DNA extracted from 10 mg each in wet weight of AMeX-processed and fresh mouse liver tissues were identical. In tissues of malignant lymphoma, the total amount of spooled DNA extracted from 50 sections, each 20 microns thick, was about 8 micrograms/mm2. The electrophoretic pattern of DNA digested with restriction endonucleases on agarose gel from AMeX-processed tissue sections did not differ from that of fresh materials. Southern blot hybridization analysis also revealed that the mobility of specific DNA fragments was identical for AMeX-processed and fresh tissues. The AMeX method was thus proved to be a versatile multipurpose tissue-processing procedure, which is expected to provide important information regarding the correlation between morphology, phenotypic expression, and gene alteration.