Rapid growth of granulation tissue was induced in rats by injection of croton oil into a subcutaneous air pocket. Growth characteristics of the granulation tissue were evaluated by histopathologic techniques and measurement of ³H-thymidine incorporation into DNA. The DNA of cells growing in the granuloma was labeled with ³H-thymidine. Subsequently, 4 classes of test chemicals (monofunctional and polyfunctional alkylating agents, DNA intercalating agents and chemicals not known to interact with DNA) were injected intraperitoneally. The presence of single-strand breaks was assayed in DNA of granuloma tissue using the alkaline elution technique. DNA breaks were primarily induced by monofunctional alkylating agents and were characteristic for each compound. DNA from animals treated with polyfunctional alkylating agents and DNA-intercalating agents showed a variable degree of resistance to methylmethane sulfonate-induced DNA breakage.

The present report describes a simple and rapid procedure to isolate highly purified sperm heads from mouse, rat and rabbit. The isolation procedure involves mincing of the caput epididymidis (CPE) of mice and rats to obtain a crude CPE suspension. This suspension is filtered to remove tubular fragments. The filtrate containing sperms and cellular contaminants is trypsinized, followed by sonication. To obtain rabbit sperm head suspension, ejaculated spermatozoa are briefly exposed to the cationic detergent CTAB-D, followed by trypsinization. Trypsin treatment of the suspension yields sperm heads and tails. The suspension containing sperm heads and tails is separated by discontinuous sucrose density gradient centrifugation. Highly purified and enriched sperm heads are recovered from the bottom of 2.5 M sucrose of the gradient. Enriched sperm heads contain less than 1% sperm tails.